Stainless steel clad sheet with excellent plate shape and method for manufacturing the same

Abstract

The present invention discloses a stainless steel clad steel plate excellent in plate shape and a manufacturing method thereof. The method includes three steps: manufacturing of the clad material, rolling of the clad material, and separation and leveling of the clad steel plate. In the step of manufacturing the clad material, three vacuum extractions and two vacuum breakages are performed on the clad material through a seamless steel pipe, and finally the vacuum degree is made 10 -2 Pa or less. In the step of rolling the clad material, intermittent cooling, leveling, and deposition cooling with two steel plates at T f -150°C to T f +150°C are performed. In the step of separating and leveling the clad steel plate, flattening is performed on a leveler, and the lateral flattening force F1 = ν × a × b × c w × σ w / (d × (ν - c w / a)), and the longitudinal flattening force F2 = a × b × c L × σ L / (d + c L ). The clad steel plate of the present invention has excellent shape and interface bonding quality, the flatness is ≤ 3 mm / m, the bonding rate of the bonding interface is 100%, the shear strength is ≥ 300 MPa, and the yield and production efficiency are high.

Description

[Technical Field]

[0001] This invention belongs to the field of steel material manufacturing technology and relates to stainless clad steel sheets with excellent sheet shape and a method for manufacturing the same. [Background technology]

[0002] With the continuous development of science, technology, and industry, ordinary alloys and single metals have become insufficient to meet the comprehensive performance requirements of materials in industrial development, leading to the application of clad steel sheets. Stainless steel clad steel sheets are composite materials in which stainless steel is used as the clad layer and carbon steel or low-alloy steel as the base layer, bonded together using a specific process method. They combine the corrosion resistance of the clad layer with the excellent mechanical properties of the base layer. By reducing the consumption of precious metals, significantly lowering construction costs, saving resources without compromising usability (mechanical strength, corrosion resistance, etc.), and reducing costs, they achieve a perfect combination of low cost and high performance, resulting in excellent economic and social benefits. They are widely applied in industries such as petrochemicals, pressure vessels, pharmaceutical equipment, papermaking, water conservancy, and bridges.

[0003] Chinese patent application, publication number CN110064835A, discloses an explosive welding method for manufacturing TMCP-type stainless steel clad steel sheets for bridges. This patent application describes an explosive cladding method between stainless steel and bridge steel. Explosive cladding causes vibration, noise, and dust pollution to the environment, and the resulting stainless steel clad sheets have poor shape and inferior interfacial bonding quality. [Overview of the Initiative]

[0004] The object of the present invention is to provide a stainless clad steel sheet having excellent plate shape and interfacial bonding quality, and a method for manufacturing the same.

[0005] To achieve the object of the above invention, one embodiment of the present invention is a method for manufacturing a stainless steel clad sheet, This includes a manufacturing process for clad material, a rolling process for clad material, and a separation and straightening process for clad sheets. 1) In the manufacturing process of the clad material, Prepare two carbon steel plates with thickness T1, length L1, and width W1 as the base materials, and prepare two stainless steel plates with thickness T2, length L2 < L1, and width W2 < W1 as the clad materials. Perform surface treatment on at least one surface of each of the two base materials and the two clad materials. Apply a release agent to one surface of one clad material. Stack them in the order of base material, clad material, clad material, base material. The clad materials are arranged in the center with respect to the base materials. All the surfaces in contact between the base materials and the clad materials are the surfaces that have undergone the surface treatment. The surface to which the release agent is applied faces the other clad material. Prepare four sealing materials with width W3 = 2T2 - 1 to 2 mm. Make the sealing materials abut on the four sides of the two clad materials, and perform gas shielded welding between adjacent sealing materials and between the sealing materials and the base materials to integrate the two base materials and the sealing materials to obtain a clad material body. Drill circular holes in the sealing materials in the groove part on the side surface of the clad material body, and weld a seamless steel pipe to the circular hole part. Perform build-up welding on the groove parts on the four sides of the clad material body. Perform three vacuum extractions and two vacuum breakages on the clad material through the seamless steel pipe, and finally make the vacuum degree 10 -2 , , , , , Pa or less, and then seal the seamless steel pipe to obtain a clad material. 2) In the rolling process of the clad material, After heating the obtained clad material, perform two-stage controlled rolling of rough rolling and finish rolling. Perform cooling after rolling, introduce the clad large plate into an ultra-rapid cooling system for intermittent cooling. Here, the ultra-rapid cooling system has 24 sets of cooling headers arranged at intervals of 1 m in the roll line direction, and the cooling distance of each set of cooling headers is 1 m. When the clad large plate passes through the ultra-rapid cooling system, control the opening and closing states of all 24 sets of cooling headers in the method of opening N sets of cooling headers and then not opening M sets of cooling headers. The cooling water pressure is 0.15 to 0.30 MPa, the cooling rate is 3 to 15 °C / s, and the final cooling temperature is 380 to 590 °C. Here, N takes a value of 2, 3, or 4, and M takes a value of 2, 3, or 4. After the clad large plate exits the ultra-rapid cooling system, it is directly introduced into the straightening machine for straightening. After straightening, the clad large plate is placed between two steel plates with a temperature of T f -150 °C to T f +150 °C for deposition cooling. The deposition cooling time is 0.4 min / mm × t0 ± 5 min, where t0 is the thickness of the clad large plate. After the deposition cooling is completed, the clad large plate is naturally cooled on the cooling bed. Here, T f = 550 + 30Si - 20Mn + 15Cr - 15Ni + 10Mo. In this formula, the elemental symbols represent 100 times the mass percentage of each element in the base material. 3) In the separation straightening of the clad plate, Cut the edge of the clad large plate to remove the part other than the sealing material, and separate the clad large plate into two upper and lower clad small plates. After determining the dimensions, place the clad layer of the clad small plate upward on the leveler for flattening. Here, when flattening in the horizontal direction (width direction W), the flattening force F1 of the leveler = ν × a × b × c w × σ w / (d × (ν - c w / a)) is controlled. When flattening in the vertical direction (length direction L), the flattening force F2 of the leveler = a × b × c L × σ L / (d + c L ) is controlled. Here, a is the width of the clad small plate, b is the thickness of the clad small plate, c w is the flatness per unit meter in the horizontal direction of the clad small plate, with the unit of mm, c L is the flatness per unit meter in the vertical direction of the clad small plate, with the unit of mm, d is the operating distance of the leveler, σ w is the tensile yield strength in the horizontal direction of the clad small plate, σ L is the tensile yield strength in the vertical direction of the clad small plate, and ν is the Poisson's ratio. Finally, perform cold straightening on the clad small plate to obtain a one-sided stainless steel clad steel plate product. Provide a manufacturing method for a stainless steel clad steel plate.

[0006] Preferably, "Perform three vacuum evacuations and two vacuum breaks on the clad material through the seamless steel pipe, and finally the vacuum degree is 10-2 In the step of "making it 10 Pa or less", First, connect the seamless steel pipe to a vacuum pump, evacuate the clad material, make the degree of vacuum 10 -2 Pa or less, then maintain the pressure for 4 hours or more. Subsequently, connect the seamless steel pipe to a nitrogen gas device, perform vacuum breakage on the clad material, and fill it with nitrogen gas. After that, connect the seamless steel pipe to the vacuum pump again, evacuate the clad material, make the degree of vacuum 10 -1 Pa or less, without maintaining the pressure. Subsequently, connect the seamless steel pipe to the nitrogen gas device again, perform vacuum breakage on the clad material, and fill it with nitrogen gas. Finally, connect the seamless steel pipe to the vacuum pump for the third time, evacuate the clad material, and make the degree of vacuum 10 -2 Pa or less.

[0007] Preferably, in the step of "heating the obtained clad material and then performing two-stage controlled rolling of rough rolling and finish rolling", Heat the obtained clad material. Here, the soaking temperature is 1150 - 1220 °C, the total heating time is ≥ 1.2 min / mm × t (where t is the thickness of the clad material), and the holding time in the soaking stage is 30 min - 50 min. Perform two-stage controlled rolling of rough rolling and finish rolling. In the rough rolling stage, the rolling start temperature is ≤ 1050 °C, the rolling end temperature is ≥ 980 °C. First, perform transverse rolling and then longitudinal rolling. When performing longitudinal rolling, the reduction per pass is at least ≥ 35 mm, the total reduction of rough rolling is 40 - 60%. End the rough rolling stage when the thickness of the intermediate material becomes 2.5 - 3.5 times the target thickness of the clad large plate, and then wait. During that time, perform spray cooling. Start the finish rolling stage when the surface temperature of the intermediate material drops to 860 °C or less. The rolling end temperature of the finish rolling stage is ≥ 780 °C, and the total reduction of finish rolling is 55 - 75% to obtain the clad large plate.

[0008] Preferably, in the step of "heating the obtained clad material and then performing two-stage controlled rolling of rough rolling and finish rolling", The obtained clad material was subjected to five heating stages: preheating, first heating, second heating, third heating, and soaking. Here, the preheating temperature was ≤850°C with a residence time of (0.45~0.55) min / mm × t, the first heating temperature was 1030~1090°C with a residence time of (0.35~0.45) min / mm × t, the second heating temperature was 1100~1160°C with a residence time of (0.25~0.35) min / mm × t, the third heating temperature was 1140~1180°C with a residence time of (0.15~0.25) min / mm × t, and the soaking temperature was 1170~1210°C with a residence time of (0.10~0.20) min / mm × t, where t is the thickness of the clad material. Two-stage controlled rolling is performed, consisting of rough rolling and finish rolling. In the first pass, longitudinal rolling is performed, with a rolling reduction of ≥46 mm. From the second pass onward, transverse rolling is performed, and the clad material is rolled to the target width of the final clad large plate up to the nth pass, with a rolling reduction of ≥25 mm in the second pass. From the (n+1)th pass onward, longitudinal rolling is performed, with a rolling reduction of ≥30 mm in the (n+1)th pass. Throughout the rough rolling stage, the rolling temperature of the first pass is ≥ The initial rolling temperature is 1060°C, the starting temperature for the remaining passes is ≤1050°C, and the ending temperature is ≥1000°C. The rough rolling stage is terminated when the thickness of the intermediate material reaches 2.5 to 3.5 times the target thickness of the clad large plate. A waiting period is then observed during which water cooling is performed. The finish rolling stage is started when the surface temperature of the intermediate material drops to 840°C or below. The starting temperature for the finish rolling stage is 810°C to 840°C, and the ending temperature is 780°C to 810°C.

[0009] Preferably, in the process of "heating the obtained clad material and then performing a two-stage controlled rolling process consisting of rough rolling and finish rolling," The obtained clad material was subjected to a four-stage heating process: preheating, first heating, second heating, and soaking. The preheating temperature was 950-1000°C, the residence time was 0.3 min / mm × t, the first heating temperature was 1050-1100°C, the second heating temperature was 1120-1180°C, the soaking temperature was 1150-1200°C, and the total residence time for the first, second, and soaking stages was 1.5 min / mm × t + 20-40 min, where t is the thickness of the clad material. After the clad material is removed from the heating furnace, high-pressure water descaling is performed first, followed by rolling. During the rolling process, transverse rolling is carried out from the first pass, and the clad material is rolled to a width of Wt+0 to 40 mm by the nth pass, where Wt is the target width of the clad sheet. The total reduction ratio up to this point is ≥30%. Longitudinal rolling is carried out from the (n+1)th pass, with a rolling reduction ratio of ≥20% for the (n+1)th pass. When the thickness of the intermediate material reaches 2.5 to 3.5 times the target thickness of the clad sheet, a pause is initiated. Rolling is resumed when the surface temperature of the intermediate material drops below 880°C and continues until the end of rolling. The rolling end temperature is T r The temperature range is ±20℃, and the total reduction ratio for the entire rolling process is ≥75%.

number

[0010] Preferably, in the intermittent cooling, When the thickness of the clad plate is 54 mm or less, the roll line speed of the ultra-rapid cooling system is 0.4 to 0.8 m / s, and the first to fourth sets of cooling collection tubes are opened, the fifth to sixth sets of cooling collection tubes are not opened, the seventh to eighth sets of cooling collection tubes are opened, the ninth to tenth sets of cooling collection tubes are not opened, the eleventh to twelfth sets of cooling collection tubes are opened, the thirteenth to fourteenth sets of cooling collection tubes are not opened, the fifteenth to sixteenth sets of cooling collection tubes are opened, the seventeenth to eighteenth sets of cooling collection tubes are not opened, the nineteenth to twentyth sets of cooling collection tubes are opened, the twenty-first to twenty-second sets of cooling collection tubes are not opened, and the twenty-third to twenty-fourth sets of cooling collection tubes are opened, completing intermittent cooling as the clad plate passes through the ultra-rapid cooling system once. When the thickness of the clad plate is >54 mm, the roll line speed of the ultra-rapid cooling system is 0.2 m / s or more and less than 0.6 m / s, and the first to fourth sets of cooling collection tubes are opened, the fifth to eighth sets of cooling collection tubes are not opened, the ninth to twelfth sets of cooling collection tubes are opened, the thirteenth to sixteenth sets of cooling collection tubes are not opened, the seventeenth to twentyth sets of cooling collection tubes are opened, the twenty-first to twenty-second sets of cooling collection tubes are not opened, and the twenty-third to twenty-fourth sets of cooling collection tubes are opened, completing intermittent cooling as the clad plate passes through the ultra-rapid cooling system once.

[0011] Preferably, in the intermittent cooling, When the thickness of the clad plate is ≥ 70 mm, the roll line speed of the ultra-rapid cooling system is 0.4 to 0.9 m / s. The clad plate first enters the ultra-rapid cooling system in the forward direction from the inlet, and when its leading edge reaches the 24th set of cooling collection tubes, the roll line reverses, and the clad plate passes through the ultra-rapid cooling system in the reverse direction and exits the ultra-rapid cooling system from the inlet, completing intermittent cooling. Open the first to fourth sets of cooling pipes, keep the fifth to eighth sets of cooling pipes closed, open the ninth to twelfth sets of cooling pipes, keep the thirteenth to sixteenth sets of cooling pipes closed, open the seventeenth to twentyth sets of cooling pipes, keep the twenty-first to twenty-second sets of cooling pipes closed, and open the twenty-third to twenty-fourth sets of cooling pipes.

[0012] Preferably, the temperature of the clad plate after correction is T f -150℃~T f In the process of "placing the material between two steel plates at +150℃ and performing deposition cooling," the length and width of the steel plates used are both greater than the length and width of the clad plate, and the thickness of the steel plates used is twice the thickness of the clad plate.

[0013] Preferably, in the step of "applying a separating agent to one surface of a single clad material," the separating agent used is a coating solution containing silicon dioxide and magnesium oxide, with a mass ratio of silicon dioxide to magnesium oxide of 3:1. The amount of separating agent to be applied is 20 mg / m². 2 And y is the thickness ratio of the clad material to the clad plate. Before the process of "laminating in the order of base material, clad material, clad material, base material," the clad material coated with a separating agent is heated and dried in a trolley furnace, where the drying temperature is 340-360°C and the drying time is 35-45 minutes.

[0014] Preferably, in the step of "applying a separating agent to one surface of a single clad material," the components of the separating agent used are silicon nitride 25-35%, thermosetting amino resin 5-10%, and water 55-70% by mass ratio. The coating thickness of the separating agent is 0.2 to 0.5 mm. Before the process of "laminating in the order of base material, clad material, clad material, base material," the clad material coated with a separating agent is heated and dried, with a drying temperature of 100-250°C and a drying time of 20-40 minutes.

[0015] Preferably, in the step of "applying a surface treatment to at least one surface of each of the two base materials and the two clad materials", The surface of one of two base materials is milled and ground so that their shapes are complementary, and the surface is processed into an irregular uneven surface containing X planes sequentially connected along the transverse direction, making the base material an uneven thickness material in which the thickness does not change monotonically in the transverse direction, and the length of the irregular uneven surface is L12 = L1 and the total width is W12 > W1, or the surface is processed into an irregular uneven surface containing X planes sequentially connected along the longitudinal direction, making the base material an uneven thickness material in which the thickness does not change monotonically in the longitudinal direction, and the total length of the irregular uneven surface is L12 > L1 and the width is W12 = W1, and X ≥ 2. One surface of each clad material is polished to remove surface oxide scale, and then each clad material is bent to conform to the corresponding irregular uneven surface.

[0016] Preferably, in the step of "applying a surface treatment to at least one surface of each of the two base materials and the two clad materials", One surface of each cladding material is polished to remove surface oxide scale. To ensure that the shapes of the two base materials are complementary, one surface of the base material is milled and ground to create a lateral inclined surface with length L11 = L1 and width W11 > W1, thereby creating a base material with unequal thickness where the thickness gradually changes in the lateral direction; or the surface is processed to create a vertical inclined surface with length L11 > L1 and width W11 = W1, thereby creating a base material with unequal thickness where the thickness gradually changes in the vertical direction.

[0017] Preferably, in the step of "applying a surface treatment to at least one surface of each of the two base materials and the two clad materials", One surface of each base material and each cladding material is polished to remove surface oxide scale, and after polishing, both the base material and cladding material are of equal thickness.

[0018] Preferably, in the case where "the clad material is positioned centrally with respect to the base material," the distance from the lateral side end of the clad material to the corresponding side end of the base material is half the difference in width of the contact surface between the clad material and the base material, and the distance from the longitudinal side end of the clad material to the corresponding side end of the base material is half the difference in length of the contact surface between the clad material and the base material.

[0019] To achieve the objective of the above invention, one embodiment of the present invention provides a stainless clad steel sheet with excellent plate shape produced by the manufacturing method described above.

[0020] Preferably, the flatness of the clad steel sheet is ≤3 mm / m, the bonding ratio of the joint interface is 100%, and the shear strength is ≥300 MPa.

[0021] Preferably, the flatness of the clad steel plate is ≤2 mm / m and the shear strength is ≥360 MPa.

[0022] Preferably, the impact value at 0°C is ≥240J, the impact value at -20°C is ≥200J, and the impact value at -40°C is ≥150J.

[0023] Preferably, the Vickers hardness difference in the thickness direction of the base material layer of the clad steel sheet is ≤10, the strength difference between the front, middle, and rear is ≤40 MPa, and the strength difference between each part of the entire sheet is ≤40 MPa.

[0024] Compared to conventional technology, the advantages of the present invention are as follows: On the one hand, the corrosion resistance and mechanical strength of the stainless steel clad sheet are ensured through specific process control throughout the entire manufacturing method, and the corrosion resistance and mechanical performance are prevented from deteriorating during the rolling process of the clad material. On the other hand, the problems of shape defects, poor interface bonding quality, and poor surface quality in conventional thick stainless steel clad sheets are solved, and the stainless steel clad sheet can be given excellent plate shape and interface bonding quality. The flatness of the clad sheet is ≤3mm / m, the bonding rate of the bonding interface is 100%, and the shear strength is ≥300MPa. Furthermore, obvious surface defects such as dents and scratches caused by conventional explosion clad technology are avoided. On the other hand, the yield in the production process is high and the production efficiency is high. [Brief explanation of the drawing]

[0025] For clear representation and explanation, in each drawing of the present invention, the dimensions of some structures or parts are enlarged relative to other structures or parts and are therefore used solely to illustrate the basic structure of the subject matter of the present invention. [Figure 1a] Figure 1a is a schematic cross-sectional view of a steel plate according to the first embodiment of the material surface treatment process in the present invention. [Figure 1b] Figure 1b is a schematic cross-sectional view of a steel sheet according to the second embodiment of the material surface treatment process in the present invention, with the dashed line indicating the change in surface shape after surface treatment. [Figure 1c] Figure 1c is a schematic longitudinal cross-sectional view of a steel sheet according to the third embodiment of the material surface treatment process in the present invention, with the dashed line indicating the change in surface shape after surface treatment. [Figure 1d] Figure 1d is a schematic cross-sectional view of a steel sheet according to the fourth embodiment of the material surface treatment process in the present invention, showing the change in surface shape before (A) and after (B) surface treatment. [Figure 1e] Figure 1e is a schematic longitudinal cross-sectional view of a steel sheet according to the fifth embodiment of the material surface treatment process in the present invention, showing the change in surface shape before (A) and after (B) surface treatment. [Figure 2a] Figure 2a is a schematic cross-sectional view of the clad material corresponding to Figure 1a. [Figure 2b]Figure 2b is a schematic cross-sectional view of the cladding material corresponding to Figure 1b. [Figure 2c] Figure 2c is a schematic longitudinal cross-section of the clad material corresponding to Figure 1c. [Figure 2d] Figure 2d is a schematic cross-sectional view of the cladding material corresponding to Figure 1d. [Figure 2e] Figure 2e is a schematic longitudinal cross-sectional view of the clad material corresponding to Figure 1e. [Figure 3a] Figure 3a is a flowchart of the first embodiment of the clad material rolling process of the present invention. [Figure 3b] Figure 3b is a flowchart of a second embodiment of the clad material rolling process of the present invention. [Figure 3c] Figure 3c is a flowchart of the third embodiment of the clad material rolling process of the present invention. [Figure 4a] Figure 4a is a schematic cross-sectional view of two clad steel plates obtained by rolling the clad material shown in Figure 2a. [Figure 4b] Figure 4b is a schematic cross-sectional view of two clad steel sheets obtained by rolling the clad material shown in Figure 2b. [Figure 4c] Figure 4c is a schematic longitudinal cross-sectional view of two clad steel sheets obtained by rolling the clad material shown in Figure 2c. [Figure 4d] Figure 4d is a schematic cross-sectional view of two clad steel sheets obtained by rolling the clad material shown in Figure 2d. [Figure 4e] Figure 4e is a schematic longitudinal cross-sectional view of two clad steel sheets obtained by rolling the clad material shown in Figure 2e. [Modes for carrying out the invention]

[0026] As described in the background technology section, conventional stainless steel clad sheets suffer from problems such as shape defects and poor interfacial bonding quality due to the manufacturing process. To solve these technical problems, the present invention provides a method for manufacturing a single-sided stainless steel clad sheet with excellent sheet shape, and a single-sided stainless steel clad sheet manufactured by this method.

[0027] Specifically, the manufacturing method described above includes three main processes: the production of the clad material, the rolling of the clad material, and the separation and straightening of the clad steel sheet. These three processes will be described in order below.

[0028] The process for manufacturing the clad material includes the following individual steps.

[0029] Two carbon steel plates with thickness T1, length L1, and width W1 are prepared as the base material, and two stainless steel plates with thickness T2, length L2, and width W2 are prepared as the cladding material. The surface treatment is applied to at least one surface of each of the two base materials and the two cladding materials. A separating agent is applied to one surface of a single clad material. The layers are stacked in the order of base material, clad material, clad material, and base material. Four sealing materials with a width of W3 are prepared, where W3 = 2T2 - 1 to 2 mm. These sealing materials are brought into contact with the four sides of two clad materials, and adjacent sealing materials are gas-shielded together, as well as between the sealing materials and the base material. The two base materials and the sealing materials are then integrated to obtain the clad material body. A circular hole is machined into the sealing material in the groove on the side of the clad material body, and a seamless steel pipe is welded to the circular hole. Welding is applied to the grooves on all four sides of the clad material body. The clad material was subjected to three vacuum pumping and two vacuum breaking processes through the seamless steel pipe, and the final vacuum level was 10 -2 The pressure is set to Pa or less, and then the seamless steel pipe is sealed to obtain the clad material.

[0030] Furthermore, the individual processes described above will be explained in detail.

[0031] The following describes the process of "preparing two carbon steel plates of length L1 and width W1 as base materials, and preparing two stainless steel plates of length L2 and width W2 as cladding materials," that is, the material preparation process.

[0032] Here, the carbon steel plate used as the base material has a thickness T1, a length L1, and a width W1, that is, it is a rectangular steel plate. Similarly, the stainless steel plate used as the clad material has a thickness T2, a length L2, and a width W2, and this is also a rectangular steel plate.

[0033] Also, L2 < L1 and W2 < W1, and both the length and width dimensions of the clad material are smaller than those of the base material. Preferably, L2 = L1 - L0 and W2 = W1 - W0, and the preferred value ranges of L0 and W0 are 90 to 150 mm respectively.

[0034] As a preferred embodiment, both the indentation depth of the surface oxide scale and the surface depression depth of the carbon steel plate are ≤ 0.3 mm, and the flatness is ≤ 3 mm / m. The surface of the stainless steel plate has no scratches, and the flatness is ≤ 2 mm / m. This prevents steel plates with obvious surface defects or shape defects from entering the production line of the clad steel plate.

[0035] As a preferred embodiment, the stainless steel plate is preferably austenitic stainless steel. Its chemical composition in mass percentage is C ≤ 0.15%, Si ≤ 1.00%, Mn ≤ 2.00%, P ≤ 0.045%, S ≤ 0.030%, Ni: 6.0 - 22.0%, Cr: 16.0 - 26.0%, Mo ≤ 3.0%, and the balance is Fe and inevitable impurities. By using a stainless steel plate with this chemical composition, in addition to the above-mentioned technical effects, the performance of the clad steel plate, especially the corrosion resistance of the clad layer, can be further ensured. For example, the clad layer of the obtained clad steel plate (that is, the layer obtained by rolling the clad material) will not cause intergranular corrosion cracking even after a 20-hour boiling test in a sulfuric acid - copper sulfate solution followed by a 180° bending test.

[0036] It should be noted here that the chemical compositions of the two stainless steel plates may be the same or different. Only one of them may adopt the chemical composition provided in the above preferred embodiment, both may adopt it, or neither may adopt it.

[0037] In a preferred embodiment, the chemical composition of the carbon steel sheet is, by mass percentage: C: 0.03~0.16%, Si: 0.11~0.29%, Mn: 1.31~1.54%, P ≤ 0.018%, S ≤ 0.0030%, Cr: 0.06~0.29%, Nb: 0.011~0.034%, Ti: 0.011~0.019%, Al: 0.030~0.040%, with the remainder being Fe and unavoidable impurities.

[0038] More preferably, the chemical composition of the carbon steel sheet is, by mass percentage, C: 0.08~0.12%, Si: 0.16~0.24%, Mn: 1.36~1.44%, P ≤ 0.015%, S ≤ 0.0025%, Cr: 0.11~0.19%, Ni: 0.06~0.14%, Nb: 0.016~0.024%, Ti: 0.011~0.019%, Al: 0.030~0.040%, with the remainder being Fe and unavoidable impurities.

[0039] More preferably, the chemical composition of the carbon steel sheet is, by mass percentage, C: 0.05~0.09%, Si: 0.14~0.22%, Mn: 1.41~1.49%, P ≤ 0.012%, S ≤ 0.0020%, Cr: 0.16~0.24%, Ni: 0.11~0.19%, Mo: 0.11~0.19%, Nb: 0.021~0.029%, Ti: 0.011~0.019%, Al: 0.030~0.040%, with the remainder being Fe and unavoidable impurities.

[0040] More preferably, the chemical composition of the carbon steel sheet is, by mass percentage, C: 0.03~0.07%, Si: 0.11~0.19%, Mn: 1.46~1.54%, P ≤ 0.010%, S ≤ 0.0015%, Cr: 0.21~0.29%, Ni: 0.16~0.24%, Cu: 0.16~0.24%, Mo: 0.16~0.24%, Nb: 0.026~0.034%, Ti: 0.011~0.019%, Al: 0.030~0.040%, with the remainder being Fe and unavoidable impurities.

[0041] Similar to the description of the stainless steel sheet above, the chemical compositions of the two carbon steel sheets may be the same or different, and only one of the two carbon steel sheets may adopt the chemical composition provided in the preferred embodiment above, both may adopt it, or neither may adopt it.

[0042] Next, we will describe the process of "applying a surface treatment to at least one surface of each of the two base materials and the two cladding materials," that is, the material surface treatment process. The present invention provides five preferred embodiments, and these five embodiments will be described sequentially below.

[0043] <First embodiment of the material surface treatment process> In this embodiment, one surface of each base material and each cladding material is polished to remove surface oxide scale and expose the metallic luster. After polishing, both the base material and the cladding material become materials of equal thickness.

[0044] As shown in Figure 1a, for example, the surface p1a of the base material 11a and the surface p2a of the base material 12a are polished using a grinder, belt sander, or milling machine to remove the oxide scale on the surface and expose the metallic luster. The surface p3a of the prepared clad material 21a and the surface p4a of the clad material 22a are polished using a wire wheel to remove the oxide scale on the surface and expose the metallic luster.

[0045] Related to the content described later, by making the surface treated (polished in this embodiment) during lamination the surface that comes into contact with the base material and the cladding material, for example, surface p1a and surface p3a come into contact with each other, and surface p4a and surface p2a come into contact with each other, thereby ensuring interfacial bonding quality.

[0046] <Second embodiment of the material surface treatment process> In this embodiment, similar to the first embodiment described above, one surface of each clad material (for example, surface p3b of clad material 21b and surface p4b of clad material 22b in Figure 1b) is polished to remove the oxide scale on the surface and expose the metallic luster. A redundant explanation of this is omitted.

[0047] In this embodiment, the difference from the first embodiment described above is the surface treatment of the base material. Referring to Figure 1b, the surface p1b of the base material 11b is milled to process it into surface p1b0. Surface p1b0 is a lateral inclined surface with length L11=L1 and width W11>W1, and accordingly, the base material 11b is processed into a material with unequal thickness in the lateral direction (i.e., width direction). In other words, after milling, the height of the base material 11b gradually increases from one end to the other in the width direction. Similarly, the surface p2b of the base material 12b is milled to process it into surface p2b0. Surface p2b0 is a lateral inclined surface with length L11=L1 and width W11>W1, and accordingly, the base material 12b is processed into a material with unequal thickness in the lateral direction.

[0048] Here, when milling and grinding the surface p2b of the base material 12b and the surface p1b of the base material 11b, the machining is performed so that their shapes are complementary. That is, the shapes of the machined surfaces p2b0 and p1b0 are complementary when they face each other. For example, the lateral inclination angle of surface p2b0 (for example, the angle with respect to the original surface p2b) is equal to the lateral inclination angle of surface p1b0 (for example, the angle with respect to the original surface p1b), thereby ensuring that the upper and lower surfaces of the clad material are parallel during subsequent lamination.

[0049] To make it easier to understand, the above milling and grinding process also removes the surface oxide scale from surface p1b of the base material 11b and surface p2b of the base material 12b, exposing the metallic luster.

[0050] In relation to the content described later, by making the surface treated during lamination (milling and grinding in this embodiment) the surface that comes into contact with the base material and the cladding material, for example, surface p1b0 and surface p3b come into contact with each other, and surface p4b and surface p2b0 come into contact with each other. Not only can the interfacial bonding quality be ensured in the same way as in the first embodiment described above, but in this embodiment it can also be used to manufacture unequal thickness cladding steel sheets in which the lateral thickness gradually changes, thereby expanding the application scenes and range of cladding steel sheets.

[0051] <Third embodiment of the material surface treatment process> This embodiment is almost identical to the second embodiment described above (including the surface treatment of surfaces p3c and p4c), the only difference being that the lateral thickness change of the base material in the second embodiment becomes a longitudinal (i.e., lengthwise) thickness change in this embodiment. The differences will be explained below, and for other similarities, please refer to the description of the second embodiment, and redundant explanations will be omitted.

[0052] Referring to Figure 1c, the surface p1c of the base material 11c is milled to form surface p1c0. Surface p1c0 is a vertically inclined surface with length L11 > L1 and width W11 = W1, and accordingly, the base material 11c is processed into a material with unequal thickness where the thickness gradually changes in the vertical direction. Similarly, the surface p2c of the base material 12c is milled to form surface p2c0. Surface p2c0 is a vertically inclined surface with length L11 > L1 and width W11 = W1, and accordingly, the base material 12c is processed into a material with unequal thickness where the thickness gradually changes in the vertical direction.

[0053] Here, when milling and grinding the surface p2c of the base material 12c and the surface p1c of the base material 11c, the machining is performed so that their shapes are complementary. For example, the vertical inclination angle of surface p2c0 (for example, the angle with respect to the original surface p2c) is equal to the vertical inclination angle of surface p1c0 (for example, the angle with respect to the original surface p1c), thereby ensuring that the upper and lower surfaces of the cladding material are parallel during subsequent lamination.

[0054] <Fourth embodiment of the material surface treatment process> In this embodiment, one surface of each base material is subjected to milling and grinding to process the surface into an irregular uneven surface containing X planes sequentially connected along the transverse direction, thereby making the base material an uneven thickness material in which the thickness does not change monotonically in the transverse direction, and the length of the irregular surface L12 = L1 and the total width W12 > W1.

[0055] For example, referring to Figure 1d, the surface p1d of the base material 11d is subjected to milling and grinding to process the surface p1d from a horizontal surface in Figure 1d(A) to an irregular uneven surface p1d0 shown in Figure 1d(B). This irregular uneven surface p1d0 specifically includes X planes sequentially connected along the transverse direction, where X ≥ 2. In the figure, eight planes are shown as an example, and from left to right in the figure, the 1st, 3rd, 5th, and 7th planes are all transversely inclined surfaces, while the 2nd, 4th, 6th, and 8th planes are all horizontal surfaces. Of course, this is merely an example, and variations can be implemented, such as changing X to another number or omitting horizontal planes and consisting only of transversely inclined surfaces.

[0056] Referring to Figure 1d, by milling and grinding the surface p1d, the base material 11d is processed into a material with unequal thickness in which the thickness does not change monotonically in the lateral direction.

[0057] The length L12 = L1 of the irregular uneven surface p1d0, which does not change due to milling and grinding, and the total width W12 > W1 of the irregular uneven surface p1d0, so as can be understood, the total width W12 is the sum of the widths of X planes.

[0058] Accordingly, referring to Figure 1d, the surface p2d of the base material 12d is also milled and ground to change the surface p2d from the horizontal plane shown in Figure 1d(A) to the irregular uneven surface p2d0 shown in Figure 1d(B). Here, when milling and grinding the surface p2d of the base material 12d and the surface p1d of the base material 11d, the machining is performed so that their shapes are complementary. That is, the shapes of the machined surfaces p2d0 and p1d0 are complementary when they face each other.

[0059] The irregular uneven surface p2d0 also includes X planes that are sequentially connected along the lateral direction, with eight planes shown in the figure as an example, so that their shapes are complementary. The length L12 = L1 of the irregular uneven surface p2d0 does not change due to milling and grinding, and the total width W12 > W1 of the irregular uneven surface p2d0 is such that, as can be understood, the total width W12 is the sum of the widths of the X planes of the irregular uneven surface p2d0.

[0060] Referring to Figure 1d, by milling the surface p2d, the base material 12d is processed into an uneven-thickness material in which the thickness does not change monotonically in the lateral direction. Based on the fact that the irregular uneven surfaces p2d0 and p1d0 have complementary shapes, when the milled and ground base materials 12d and 11d are placed facing each other, the sum of the thicknesses of each part of both is constant. As a result, the upper and lower surfaces of the cladding material become parallel during subsequent lamination.

[0061] The surface treatment of the two base materials in this embodiment has been described above. The surface treatment of the two cladding materials will now be described.

[0062] In this embodiment, the surface p3d of the prepared clad material 21d is polished using a wire wheel to remove the oxide scale on the surface and expose the metallic luster. Similarly, the surface p4d of the prepared clad material 22d is polished using a wire wheel to remove the oxide scale on the surface and expose the metallic luster.

[0063] Furthermore, in order to conform to the surface shape of the base materials 11d and 12d, after removing the surface oxide scale, each clad material is bent in this embodiment to conform to the corresponding irregular uneven surface. For example, clad material 21d is bent to conform to the corresponding irregular uneven surface p1d0 to facilitate close contact during subsequent lamination. Similarly, clad material 22d is bent to conform to the corresponding irregular uneven surface p2d0 to facilitate close contact during subsequent lamination.

[0064] The surface treatment of this embodiment not only ensures interfacial bonding quality, similar to the first embodiment described above, but can also be used in the manufacture of unequal-thickness clad steel sheets where the lateral thickness does not change monotonically. This expands the application scenarios and range of clad steel sheets, improves corrosion resistance compared to conventional steel sheets, and avoids frequent welding between clad steel sheets of different thicknesses and dissimilar welding.

[0065] <Fifth embodiment of the material surface treatment process> This embodiment differs from the fourth embodiment described above in the following respects. Specifically, while the lateral thickness of the base material in the fourth embodiment does not change monotonically, in this embodiment the thickness in the longitudinal direction does not change monotonically.

[0066] For example, referring to Figure 1e, the surface p1e of the base material 11e is subjected to milling and grinding to process the surface p1e from a horizontal surface in Figure 1e(A) to an irregular uneven surface p1e0 shown in Figure 1e(B). This irregular uneven surface p1e0 specifically includes X planes sequentially connected along the vertical direction, where X ≥ 2. In the figure, eight planes are shown as an example, with the 1st, 3rd, 5th, and 7th planes being vertically inclined surfaces from left to right, and the 2nd, 4th, 6th, and 8th planes being horizontal surfaces. Of course, this is merely an example, and variations can be implemented, such as changing X to another number or omitting horizontal planes and consisting only of vertically inclined surfaces.

[0067] Referring to Figure 1e, by milling and grinding the surface p1e, the base material 11e is processed into a material with unequal thickness in which the thickness does not change monotonically in the longitudinal direction.

[0068] The width W12 = W1 of the irregular uneven surface p1e0, i.e., it does not change due to milling and grinding, and the total length L12 > L1 of the irregular uneven surface p1e0, and as can be understood, this total length L12 is the sum of the lengths of X planes.

[0069] Correspondingly, referring to Figure 1e, the surface p2e of the base material 12e is also milled and ground to change the surface p2e from the horizontal plane shown in Figure 1e(A) to the irregular uneven surface p2e0 shown in Figure 1e(B). Here, when milling and grinding the surface p2e of the base material 12e and the surface p1e of the base material 11e, the machining is performed so that their shapes are complementary. That is, the shapes of the machined surfaces p2e0 and p1e0 are complementary when they face each other.

[0070] The irregular uneven surface p2e0 also includes X planes that are sequentially connected along the vertical direction, such that their shapes are complementary; in the figure, eight planes are shown as an example. The width W12 = W1 and total length L12 > L1 of the irregular uneven surface p2e0.

[0071] Referring to Figure 1e, by milling the surface p2e, the base material 12e is processed into an uneven-thickness material in which the thickness does not change monotonically in the longitudinal direction. Based on the fact that the irregular uneven surfaces p2e0 and p1e0 have complementary shapes, when the milled and ground base materials 12e and 11e are placed facing each other, the sum of the thicknesses of each part of both is constant. As a result, the upper and lower surfaces of the cladding material become parallel during subsequent lamination.

[0072] The surface treatment of the two base materials in this embodiment has been described above. The surface treatment of the two cladding materials will now be described.

[0073] In this embodiment, the surface p3e of the prepared clad material 21e is polished using a wire wheel to remove the oxide scale on the surface and expose the metallic luster. Similarly, the surface p4e of the prepared clad material 22e is polished using a wire wheel to remove the oxide scale on the surface and expose the metallic luster.

[0074] Furthermore, in order to conform to the surface shape of the base materials 11e and 12e, after removing the surface oxide scale, each clad material is bent in this embodiment to conform to the corresponding irregular uneven surface. For example, clad material 21e is bent to conform to the corresponding irregular uneven surface p1e0 to facilitate close contact during subsequent lamination. Similarly, clad material 22e is bent to conform to the corresponding irregular uneven surface p2e0 to facilitate close contact during subsequent lamination.

[0075] Similar to the fourth embodiment described above, this embodiment also expands the application scenarios and scope of clad steel sheets, improves corrosion resistance compared to conventional steel sheets, and avoids frequent welding between clad steel sheets of different thicknesses and dissimilar welding.

[0076] The above describes five preferred embodiments of the individual surface treatment steps for the clad material manufacturing process. Here, only the application of surface treatment to one surface of each of the base material and clad material has been described, but it is necessary to explain that in any of the above five embodiments, oxide scale removal treatment can also be applied to other surfaces of each base material and clad material. Such additional oxide scale removal treatment is not essential to realizing the technical effects of the present invention, but may be preferable. For example, in addition to oxide scale removal from the surface of the base material facing the clad material, oxide scale removal treatment can also be applied to the surface of the base material away from the clad material (i.e., the surface of the clad steel sheet).

[0077] The following describes the other individual processes involved in the manufacturing of the clad material.

[0078] This section describes the process of "applying a separating agent to one surface of a single clad material," i.e., the separating agent application process.

[0079] Here, in relation to the above, in the material surface treatment process, surface treatment such as polishing is applied to the surface that comes into contact with the base material during the lamination of the clad material, in order to ensure the quality of the interfacial bonding of the clad steel sheet. On the other hand, the purpose of this separation agent application process is to use a separation agent to prevent the surfaces that come into contact between one clad material and the other during lamination from bonding during the subsequent clad material rolling process, which would make separation difficult in the end.

[0080] Based on this, one of the two clad materials is selected and the separating agent is applied to it. If, in the previous material surface treatment step, one surface of the selected clad material is surface-treated and the other surface is not, the separating agent is applied to the "untreated" surface in this separating agent application step. On the other hand, as mentioned above, if, in the previous material surface treatment step, both surfaces of the selected clad material are surface-treated, the separating agent is applied to the surface that is intended to face the other clad material during lamination in this separating agent application step. For example, taking Figure 1a as an example, the separating agent can be applied to surface p6a of clad material 22a or surface p5a of clad material 21a.

[0081] Two preferred embodiments of the separating agent are provided here, and each will be described below.

[0082] <First embodiment of the separating agent> In this embodiment, the separating agent is a coating solution containing silicon dioxide and magnesium oxide, with a mass ratio of silicon dioxide to magnesium oxide of 3:1. The separating agent of this embodiment can achieve excellent separation effects and ensure the separation of the two subsequent cladding plates.

[0083] Herein, we provide a method for producing the separating agent. A separating agent powder, a binder powder, and water are mixed in a mass ratio of 27:3:70 to obtain a fluid separating agent coating solution. Here, the separating agent powder is a mixture of silicon dioxide and magnesium oxide in a mass ratio of 3:1. The binder powder is a mixture of polyvinyl alcohol and thermosetting phenolic resin in a mass ratio of 1:1.

[0084] When using the aforementioned separating agent and applying it to the surface of the cladding material, the amount of separating agent to be applied is 20 mg / m². 2 That is, the weight of the separating agent per unit area of ​​the surface of the clad material is 20ymg. Here, y is the ratio of the thickness of the clad material produced in the clad material manufacturing process to the thickness of the clad plate obtained in the subsequent rolling process, and this ratio is also called the clad material rolling reduction ratio.

[0085] Furthermore, based on this embodiment, after the separation agent has been applied and before the subsequent lamination (i.e., before the process of "laminating in the order of base material, clad material, clad material, base material"), the clad material to which the separation agent has been applied is heated and dried in a trolley furnace, with a drying temperature of 340-360°C and a drying time of 35-45 minutes.

[0086] <Second embodiment of the separating agent> In this embodiment, the components of the separating agent are silicon nitride 25-35% by mass, thermosetting amino resin 5-10%, and water 55-70%. Compared with conventional separating agents, and even with the first embodiment of the separating agent described above, the separating agent of this embodiment achieves a superior separation effect and can reliably separate the two subsequent cladding plates. Furthermore, the active ingredient silicon nitride has high chemical stability, high temperature resistance, and thermal shock resistance, and the thermosetting amino resin used as a binder can be cured at low temperatures, is non-toxic, and can obtain a strong bonding effect with the use of a small amount. Therefore, the overall cost is low, the operation is simple, and the separation and adhesion effects are good.

[0087] Herein, we provide one preferred method for producing the aforementioned separating agent. First, 5-10% silicon nitride (by mass) is placed in a container such as a beaker, and then 15-25% water is poured in and stirred. Once the silicon nitride is free of particles and there are no more bubbles, 2-3% thermosetting amino resin is poured in and stirring continues. When it becomes viscous, the remaining silicon nitride and water are added and stirred for 3-5 minutes, after which the remaining thermosetting amino resin is added. Stirring continues until it becomes viscous to obtain the separating agent.

[0088] When using the aforementioned separating agent and applying it to the surface of the cladding material, the thickness of the separating agent application should be 0.2 to 0.5 mm.

[0089] Furthermore, according to this embodiment, after the separation agent has been applied and before subsequent lamination, the clad material coated with the separation agent is heated and dried, with a drying temperature of 100 to 250°C and a drying time of 20 to 40 minutes.

[0090] Next, we will explain the process of "laminating the base material, cladding material, cladding material, and base material in that order" after the separation agent coating process is completed.

[0091] The process of "laminating in the order of base material, clad material, clad material, base material," i.e., the lamination process, will be explained. Here, in addition to the lamination order of base material, clad material, clad material, base material, the following conditions must be met.

[0092] 1) All surfaces that come into contact with each other between the base material and the cladding material must be surfaces that have undergone the aforementioned surface treatment. For example, In the first embodiment of the material surface treatment process described above, referring to Figure 2a, the surface p2a of the base material 12a and the surface p4a of the cladding material 22a are in contact with each other, and the surface p1a of the base material 11a and the surface p3a of the cladding material 21a are in contact with each other.

[0093] In the second embodiment, referring to Figure 2b, surfaces p1b0 and p3b are in contact with each other, and surfaces p4b and p2b0 are in contact with each other.

[0094] In the third embodiment, referring to Figure 2c, the surface p1c of the base material 11c and the surface p3c of the cladding material 21c are in contact with each other, and the surface p2c of the base material 12c and the surface p4c of the cladding material 22c are in contact with each other.

[0095] In the fourth embodiment, referring to Figure 2d, the irregular uneven surface p1d0 and the surface p3d of the cladding material 21d are in contact with each other, and the irregular uneven surface p2d0 and the surface p4d of the cladding material 22d are in contact with each other.

[0096] In the fifth embodiment, referring to Figure 2e, the irregular uneven surface p1e0 and the surface p3e of the clad material 21e are in contact with each other, and the irregular uneven surface p2e0 and the surface p4e of the clad material 22e are in contact with each other.

[0097] 2) The surface coated with the separating agent should be facing the other cladding material. For example, Referring to Figure 2a, the separating agent 30a is applied to either surface p6a or surface p5a.

[0098] Referring to FIG. 2b, a separating agent 30b is applied to either the surface p6b or the surface p5b.

[0099] Referring to FIG. 2c, a separating agent 30c is applied to either the surface p6c or the surface p5c.

[0100] Referring to FIG. 2d, a separating agent 30d is applied to either the surface p6d or the surface p5d.

[0101] Referring to FIG. 2e, a separating agent 30e is applied to either the surface p6e or the surface p5e.

[0102] It should be noted here that in FIGS. 2a to 2e, for the sake of easy understanding and explanation, the thickness dimension of the separating agent (for example, reference numerals 30a, 30b, 30c, 30d, 30e in FIGS. 2a to 2e) between the two clad materials is enlarged, that is, the ratio of the thickness of the separating agent shown in the figure to the thickness of the base material, the thickness of the clad material, and the width of the sealing material to be described later is enlarged.

[0103] 3) The clad material is arranged centrally with respect to the base material. In this regard, as described above, both the length and width dimensions of the clad material are smaller than those of the base material, that is, L2 < L1 and W2 < W1. During lamination, the distances from both lateral ends of the clad material in the lateral direction to the corresponding both lateral ends of the base material are equal, and the distances from both longitudinal ends of the clad material to the corresponding both longitudinal ends of the base material are also equal.

[0104] Hereinafter, regarding each of the five embodiments of the above-described material surface treatment process, the third point here will be described. Also, considering that the clad materials are arranged approximately symmetrically up and down, a set of base material + clad material in the clad materials, for example, only the upper set will be described as an example.

[0105] <Regarding the first embodiment of the above-described material surface treatment process> Referring to Figure 2a, the length L1 and width W1 of the surface p1a of the base material 11a, and the length L2 and width W2 of the surface p3a of the clad material 21a, where L2 = L1 - L0, W2 = W1 - W0, and the preferred range of L0 and W0 is 90 to 150 mm, respectively. In the laminated state, the distance from the lateral side edge of the clad material 21a (corresponding to the long side of surface p3a) to the lateral side edge of the base material 11a (corresponding to the long side of surface p1a) is half W0, and the distance from the vertical side edge of the clad material 21a (corresponding to the short side of surface p3a) to the vertical side edge of the base material 11a (corresponding to the short side of surface p1a) is half L0.

[0106] <Regarding the second embodiment of the aforementioned material surface treatment process> Referring to Figure 2b, the length L11 and width W11 are of the surface p1b0 of the base material 11b, and the length L2 and width W2 are of the surface p3b of the clad material 21b, where L2 = L11 - L0 and W2 = W11 - W0. The preferred ranges for L0 and W0 are 90 to 150 mm, respectively. In the laminated state, the distance from the lateral side edge of the clad material 21b (corresponding to the long side of surface p3b) to the lateral side edge of the base material 11b (corresponding to the long side of surface p1b0) is half W0, and the distance from the vertical side edge of the clad material 21b (corresponding to the short side of surface p3b) to the vertical side edge of the base material 11b (corresponding to the short side of surface p1b0) is half L0.

[0107] <Regarding the third embodiment of the aforementioned material surface treatment process> Referring to Figure 2c, the length L11 and width W11 are those of the surface p1c0 of the base material 11c, and the length L2 and width W2 are those of the surface p3c of the clad material 21c, where L2 = L11 - L0 and W2 = W11 - W0. The preferred ranges for L0 and W0 are 90 to 150 mm, respectively. In the laminated state, the distance from the lateral side edge of the clad material 21c (corresponding to the long side of surface p3c) to the lateral side edge of the base material 11c (corresponding to the long side of surface p1c0) is half of W0, and the distance from the vertical side edge of the clad material 21c (corresponding to the short side of surface p3c) to the vertical side edge of the base material 11c (corresponding to the short side of surface p1c0) is half of L0.

[0108] <Regarding the fourth embodiment of the aforementioned material surface treatment process> Referring to Figure 2d, the length L12 and width W12 of the irregular uneven surface p1d0 of the base material 11d, and the length L2 and width W2 of the surface p3d of the cladding material 21d, where L2 = L12 - L0 and W2 = W12 - W0, and the preferred range of values ​​for L0 and W0 is 90 to 150 mm, respectively. In the laminated state, the distance from the lateral side edge of the cladding material 21d (corresponding to the long side of the surface p3d) to the lateral side edge of the base material 11d (corresponding to the long side of the irregular uneven surface p1d0) is half W0, and the distance from the longitudinal side edge of the cladding material 21d (corresponding to the short side of the surface p3d) to the longitudinal side edge of the base material 11d (corresponding to the short side of the irregular uneven surface p1d0) is half L0.

[0109] <Regarding the fifth embodiment of the aforementioned material surface treatment process> Referring to Figure 2e, the length L12 and width W12 of the irregular uneven surface p1e0 of the base material 11e, and the length L2 and width W2 of the surface p3e of the clad material 21e, where L2 = L12 - L0 and W2 = W12 - W0, and the preferred range of values ​​for L0 and W0 is 90 to 150 mm, respectively. In the laminated state, the distance from the lateral side edge of the clad material 21e (corresponding to the long side of the surface p3e) to the lateral side edge of the base material 11e (corresponding to the long side of the irregular uneven surface p1e0) is half W0, and the distance from the longitudinal side edge of the clad material 21e (corresponding to the short side of the surface p3e) to the longitudinal side edge of the base material 11e (corresponding to the short side of the irregular uneven surface p1e0) is half L0.

[0110] The lamination process has been described above. In a preferred embodiment, after the lamination process, the entire set of four laminated steel plates is placed under a four-column hydraulic press, and pressure is applied to the opposing surfaces of the two base materials (i.e., the upper surface of the upper base material and the lower surface of the lower base material) to a pressure of ≥ 500 tons. This makes the contact between adjacent steel plates more tight.

[0111] Furthermore, in the process of "preparing four sealing materials with a width of W3, placing the sealing materials against the four sides of two clad materials, gas-shielded welding adjacent sealing materials together and between the sealing materials and the base material, and integrating the two base materials and the sealing materials to obtain the clad material body," the four stacked steel plates are joined together based on the placement of the sealing materials to form a single clad material body. Specifically, referring to Figures 2a to 2e, the clad material body consists of two base materials forming the upper and lower surfaces, two clad materials located in the middle, and four sealing materials surrounding the two clad materials in a four-sided frame shape and connecting the two base materials. Here, in Figures 2a to 2e, the sealing materials are labeled 40a, 40b, 40c, 40d, and 40e, respectively.

[0112] The width of the sealing material W3 = 2T2 - 1~2 mm. By using a sealing material of this width to simultaneously enclose the two cladding materials, the enclosing effect is improved. It is necessary to explain here that, as mentioned above, in order to facilitate understanding and explanation, the thickness dimensions of the separating agent (symbols 30a, 30b, 30c, 30d, 30e) are shown enlarged in Figures 2a~2e. Accordingly, the width of the sealing material shown in Figures 2a~2e is shown to be larger than the sum of the thicknesses of the two cladding materials. However, this is simply because the thickness dimensions of the separating agent have been enlarged, and in reality, the width of the sealing material W3 = 2T2 - 1~2 mm, i.e., the width of the sealing material is 1~2 mm smaller than the sum of the thicknesses of the two cladding materials.

[0113] Furthermore, of the four sealing materials, two are in contact with the lateral ends of the two cladding materials, with a length L31 = L2 - 1 to 2 mm, and the other two are in contact with the longitudinal ends of the two cladding materials, with a length L32 = W2 - 1 to 2 mm.

[0114] Preferably, the thickness T3 of the sealing material is 12 to 15 mm.

[0115] Regarding the forming method for each sealing material, it can be obtained without welding by directly cutting it from a single steel plate according to a thickness T3, width W3, and length L31 or L32, or it can be obtained by welding and joining sealing materials of different lengths. For example, the sealing materials at both ends in the longitudinal direction of the two clad materials in the fourth embodiment of the material surface treatment process described above, and the sealing materials at both ends in the transverse direction of the two clad materials in the fifth embodiment of the material surface treatment process described above.

[0116] In a preferred embodiment, this process may involve polishing both ends and sides of each seal material to remove surface oxide scale before performing gas shield welding between adjacent seal materials or between a seal material and the base material, thereby improving the welding effect, and / or beveling both ends and sides of each seal material.

[0117] Furthermore, in a preferred embodiment, in the process of "gas-shielded welding adjacent sealing materials together, and between a sealing material and a base material," the welding speed is controlled to 300-360 mm / min, and the interpass temperature during the welding process is controlled to 135-165°C.

[0118] In gas shielded welding, the protective gas is 75-80% Ar + 20-25% CO2 by volume.

[0119] Next, in the step of "machining a circular hole in the sealing material of the groove on the side of the clad material body and welding a seamless steel pipe to the circular hole," the groove is a groove formed between two base materials on the outside of the sealing material. In this step, a circular hole is machined and a seamless steel pipe is welded in place, enabling subsequent vacuuming of the inside of the clad material.

[0120] In a preferred embodiment, the circular hole is machined in the center of the short side (i.e., the vertical side edge) of the clad material body, but the invention is not limited thereto.

[0121] In a preferred embodiment, the diameter of the circular hole is 8 to 12 mm. Accordingly, the outer diameter of the seamless steel pipe is the same as the diameter of the circular hole, 8 to 12 mm, the wall thickness is 1.2 to 2 mm, and the length is 200 to 400 mm.

[0122] Next, in the step of "applying build-up welding to the grooves on all four sides of the clad material body," specifically, submerged arc build-up welding is performed. To make it easier to understand, a four-sided frame-shaped filling layer is formed on the outside of the four-sided frame made of sealing material by the build-up welding in this step. Referring to Figures 2a to 2e, the filling layers formed by the build-up welding are labeled 50a, 50b, 50c, 50d, and 50e, respectively.

[0123] In a preferred embodiment, the flux is fired at 350°C for 2 hours before overlay welding, and then kept warm at 150°C for 1 hour. During the overlay welding process, the interpass temperature is controlled to 135-165°C, and the welding speed is 420-480 mm / min. Thus, this submerged arc overlay welding technique, in combination with the aforementioned sealing material encasing and gas shielding welding, achieves stable joining of four steel plates, ensures joint strength, prevents the occurrence of cracking abnormalities in the subsequent clad material rolling process, and further improves the interfacial joining effect on top of realizing the aforementioned quality advantages of clad steel plates.

[0124] Furthermore, during the build-up welding process, it is necessary to clean off any deposits adhering to the weld bead before each welding pass to keep the weld bead clean. After welding is complete, the weld should be covered with insulating material to maintain heat retention.

[0125] Next, "Three vacuum pumps and two vacuum breaks are performed on the clad material through the seamless steel pipe, and finally the vacuum level is 10%." -2 The step of "making it Pa or less" is specifically preferably: First, the seamless steel pipe is connected to a vacuum pump, and the spaces inside the clad material (for example, the gap between the clad material and the base material, the gap between the clad materials themselves, the gap between the end faces of the clad material and the sealing material, etc.) are connected to the seamless steel pipe, and a vacuum is created around the clad material, with the vacuum level set to 10. -2 After reducing the pressure to below Pa, the pressure is maintained for at least 4 hours. Subsequently, the seamless steel pipe is connected to a nitrogen gas device (e.g., a nitrogen gas generator or nitrogen gas cylinder), thereby breaking the vacuum in the cladding material and filling the space inside the cladding material with nitrogen gas.

[0126] Afterward, the seamless steel pipe is connected to the vacuum pump again, and the clad material is evacuated to a vacuum level of 10. -1 The pressure is kept below Pa and no holding pressure is applied. Subsequently, the seamless steel pipe is connected to the nitrogen gas apparatus again, the vacuum is broken against the clad material, and nitrogen gas is filled in.

[0127] Finally, the seamless steel pipe is connected to the vacuum pump for the third time, and the clad material is vacuumed to a vacuum level of 10. -2 It should be Pa or less.

[0128] In this way, the air in the space prevents surface oxidation at the joint interface during subsequent cladding material rolling, thereby ensuring the quality of the joint at the joint interface.

[0129] Furthermore, in this process, the sealing of the seamless steel pipe can be carried out using existing, viable methods in the steel industry. For example, the seamless steel pipe can be heated with a torch burner and flattened to achieve sealing.

[0130] The above describes in detail the process for manufacturing the clad material. Here, specific settings such as surface treatment, three vacuum evacuations and two vacuum breaks, welding, and sealing were established to lay the foundation for the clad material to obtain excellent interfacial bonding quality and surface quality in subsequent rolling. In addition, the setting of the separating agent facilitates the smooth separation of the two clad plates.

[0131] The process for manufacturing the clad material has been described in detail above. As mentioned above, the manufacturing method of the present invention includes a clad material rolling step after the clad material manufacturing step. The present invention provides three embodiments of the clad material rolling step, each of which will be described in detail below.

[0132] <First embodiment of the clad material rolling process> In this embodiment, referring to Figure 3a, the clad material rolling process includes the following individual steps.

[0133] The resulting clad material is heated, with a soaking temperature of 1150-1220°C, a total heating time of ≥1.2 min / mm × t, where t is the thickness of the clad material, and a holding time of 30-50 min during the soaking stage.

[0134] Two-stage controlled rolling is performed: rough rolling and finish rolling. In the rough rolling stage, the rolling start temperature is ≤1050°C and the rolling end temperature is ≥980°C. First, transverse rolling is performed, followed by longitudinal rolling. During longitudinal rolling, the reduction amount in at least one pass is ≥35 mm, the total reduction amount in rough rolling is 40-60%, and the rough rolling stage is terminated when the thickness of the intermediate material is 2.5-3.5 times the target thickness of the clad sheet. After that, the material is left to wait, during which water cooling is performed, and the finish rolling stage is started when the surface temperature of the intermediate material drops to 860°C or below. In the finish rolling stage, the rolling end temperature is ≥780°C, and the total reduction amount in finish rolling is 55-75%, obtaining a clad sheet.

[0135] After rolling is complete, the clad plate is cooled and then introduced into an ultra-rapid cooling system for intermittent cooling. The ultra-rapid cooling system has 24 sets of cooling collection tubes arranged at 1m intervals in the direction of the roll line, with a cooling distance of 1m for each set of cooling collection tubes. When the clad plate passes through the ultra-rapid cooling system, the opening and closing states of all 24 sets of cooling collection tubes are controlled by opening N sets of cooling collection tubes and not opening M sets of cooling collection tubes. The cooling water pressure is 0.15~0.30 MPa, the cooling rate is 3~15°C / s, and the final cooling temperature is 380~590°C. Here, N can take values ​​of 2, 3, or 4, and M can take values ​​of 2, 3, or 4.

[0136] After the clad plate exits the ultra-rapid cooling system, it is directly introduced into the orthodontic machine for orthodontic treatment, and the temperature of the clad plate after orthodontic treatment is reduced to T f -150℃~T f The clad plate is cooled by deposition between two steel plates at +150°C, with a deposition cooling time of 0.4 min / mm × t0 ± 5 min, where t0 is the thickness of the clad plate. After deposition cooling is complete, the clad plate is allowed to cool naturally to room temperature on a cooling bed. Here T f= 550 + 30Si - 20Mn + 15Cr - 15Ni + 10Mo, and the element symbols in this formula represent 100 times the mass percentage of each element in the base material.

[0137] At this point, the clad material rolling process is completed, and the clad material separation and straightening process begins.

[0138] <Comparison of this embodiment with the prior art> Firstly, the heating and rolling techniques employed not only ensure the mechanical performance of the final clad steel sheet by controlling parameters such as heating temperature, heating time, holding time, temperatures during rolling, reduction amount, cooling temperature, and cooling rate, but also prevent the corrosion resistance of the clad layer from deteriorating during the manufacturing process of the clad steel sheet.

[0139] Furthermore, by implementing the intermittent cooling method, as the clad plate passes through the ultra-rapid cooling system, it moves between alternately open and closed cooling collection tubes. This causes each part of the clad plate to cycle through cooling and reheating, continuing until the clad plate exits the ultra-rapid cooling system. In this way, within the cooling-reheating cycle, the carbon steel base material continuously undergoes phase transformation and self-tempering effects, and the phase transformation reaction gradually penetrates to the core, ultimately completing the phase transformation of the entire carbon steel base material. This intermittent cooling process differs from conventional reciprocating cooling. In reciprocating cooling, reheating and self-tempering occur after the phase transformation is completed at or near the surface, resulting in large temperature differences and cooling rate differences between the surface and the core, leading to significant differences in microstructure and mechanical performance. On the other hand, in the intermittent cooling process of this embodiment, a portion of the clad sheet is in a cooling state at the same time, while other portions are in a reheating / self-tempering state. Furthermore, since each part of the clad sheet alternately undergoes cooling and reheating / self-tempering over time, differences in temperature, cooling rate, structure, and performance between the surface and core of the clad sheet are reduced. For example, the Vickers hardness difference in the thickness direction of the base material layer of the final clad steel sheet is ≤10, the strength difference between the front, middle, and rear is ≤40 MPa, and the strength difference between each part of the entire sheet is ≤40 MPa. At the same time, the shape of the clad steel sheet can be further improved by intermittent cooling; that is, even if the flatness is low and the sheet is cooled directly on a cooling bed without straightening after the cooling is complete, an excellent shape can be obtained.

[0140] Furthermore, the temperature of the two steel plates and the cooling time during deposition cooling can further improve the structure, performance, and shape of the final clad steel plate compared to the first embodiment described above.

[0141] Furthermore, in the intermittent cooling described above, if the thickness of the clad plate is 54 mm or less, for example, 10 to 54 mm, the roll line speed of the ultra-rapid cooling system is set to 0.4 to 0.8 m / s, the first to fourth sets of cooling collection tubes are opened, the fifth to sixth sets of cooling collection tubes are not opened, the seventh to eighth sets of cooling collection tubes are opened, the ninth to tenth sets of cooling collection tubes are not opened, the eleventh to twelfth sets of cooling collection tubes are opened, the thirteenth to fourteenth sets of cooling collection tubes are not opened, the fifteenth to sixteenth sets of cooling collection tubes are opened, the seventeenth to eighteenth sets of cooling collection tubes are not opened, the nineteenth to twentyth sets of cooling collection tubes are opened, the twenty-first to twenty-second sets of cooling collection tubes are not opened, and the twenty-third to twenty-fourth sets of cooling collection tubes are opened, completing the intermittent cooling by having the clad plate pass through the ultra-rapid cooling system once.

[0142] More preferably, in the intermittent cooling, if the thickness of the clad plate is >54 mm, for example, >54 mm and <70 mm, the roll line speed of the ultra-rapid cooling system is set to 0.2 m / s or more and less than 0.6 m / s, the first to fourth sets of cooling collection tubes are opened, the fifth to eighth sets of cooling collection tubes are not opened, the ninth to twelfth sets of cooling collection tubes are opened, the thirteenth to sixteenth sets of cooling collection tubes are not opened, the seventeenth to twentyth sets of cooling collection tubes are opened, the twenty-first to twenty-second sets of cooling collection tubes are not opened, and the twenty-third to twenty-fourth sets of cooling collection tubes are opened, completing the intermittent cooling by having the clad plate pass through the ultra-rapid cooling system once. This achieves shape control and uniformity control of stainless steel clad plates, overcoming the production challenges of conventional stainless steel clad plates.

[0143] Preferably, in the intermittent cooling, if the thickness of the clad plate is ≥ 70 mm, for example, 70 mm to 110 mm, the roll line speed of the ultra-rapid cooling system is set to 0.4 to 0.9 m / s, the clad plate first enters the ultra-rapid cooling system in the forward direction from the inlet, and when its leading edge reaches the 24th set of cooling collection tubes, the roll line is reversed, the clad plate passes through the ultra-rapid cooling system in the reverse direction and exits the ultra-rapid cooling system from the inlet, completing the intermittent cooling. More preferably, the 1st to 4th sets of cooling collection tubes are opened, the 5th to 8th sets of cooling collection tubes are not opened, the 9th to 12th sets of cooling collection tubes are opened, the 13th to 16th sets of cooling collection tubes are not opened, the 17th to 20th sets of cooling collection tubes are opened, the 21st to 22nd sets of cooling collection tubes are not opened, and the 23rd to 24th sets of cooling collection tubes are opened. This enables shape control and uniformity control of extra-thick stainless steel clad sheets, overcoming the production challenges of conventional extra-thick stainless steel clad sheets.

[0144] Furthermore, in this embodiment, "the temperature of the clad plate after correction is T f -150℃~T f In the process of "placing the material between two steel plates at +150℃ and performing deposition cooling," the length and width of the steel plates used are both greater than the length and width of the clad plate, and the thickness of the steel plates used is twice the thickness of the clad plate.

[0145] <Second embodiment of the clad material rolling process> This embodiment differs from the first embodiment of the clad material rolling process described above, with reference to Figure 3b, in terms of heating and rolling. On the other hand, the processes after the completion of rolling (including intermittent cooling, straightening, deposition cooling, and natural cooling on the cooling bed) are the same as those of the first embodiment of the clad material rolling process described above, and these will not be explained again. Below, only the processes that differ between this embodiment and the first embodiment of the clad material rolling process (i.e., the heating process and the rolling process) will be described.

[0146] Specifically, in this embodiment, in the heating step of the clad material rolling process, The obtained clad material was subjected to five heating stages: preheating, first heating, second heating, third heating, and soaking. The preheating temperature was ≤850°C with a residence time of (0.45~0.55) min / mm × t, the first heating temperature was 1030~1090°C with a residence time of (0.35~0.45) min / mm × t, the second heating temperature was 1100~1160°C with a residence time of (0.25~0.35) min / mm × t, the third heating temperature was 1140~1180°C with a residence time of (0.15~0.25) min / mm × t, and the soaking temperature was 1170~1210°C with a residence time of (0.10~0.20) min / mm × t, where t is the thickness of the clad material.

[0147] In the rolling process of the clad material rolling process, Two-stage controlled rolling is performed: rough rolling and finish rolling. The first pass is longitudinal rolling with a reduction of ≥46 mm. From the second pass onwards, transverse rolling is performed, and the clad material is rolled to the target width of the final clad plate up to the nth pass, with a reduction of ≥25 mm in the second pass. From the (n+1)th pass onwards, longitudinal rolling is performed, with a reduction of ≥30 mm in the (n+1)th pass. Throughout the rough rolling process, the rolling temperature of the first pass is ≥1060°C, the rolling start temperature of the remaining passes is ≤1050°C, and the rolling end temperature is ≥1000°C. The rough rolling stage is terminated when the thickness of the intermediate material reaches 2.5 to 3.5 times the target thickness of the clad sheet. A waiting period is then observed during which water cooling is performed. The finish rolling stage is started when the surface temperature of the intermediate material drops below 840°C. The starting temperature for the finish rolling stage is 810°C to 840°C, and the ending temperature is 780°C to 810°C.

[0148] Compared to the conventional technology, this embodiment also implements intermittent cooling and deposition cooling, and accordingly has beneficial effects brought about by the intermittent cooling process and the deposition cooling process, and the description of the first embodiment of the clad material rolling process described above can be referenced. Furthermore, compared to the conventional technology, the heating process of this embodiment effectively controls the heating rate at each stage of the clad material, ensuring uniform heating of the material, preventing cracking and gas leakage of the clad material due to differences in the thermal properties of the base material and the clad material, thereby ensuring the interfacial bonding effect. In addition, the rolling process of this embodiment ensures the realization of large reduction rolling by performing longitudinal rolling first in rough rolling, then transverse rolling, and then longitudinal rolling, obtaining effective penetration into the core of the clad material, promoting deformation of the core, and ensuring the bonding rate of the bonding interface. By performing cooling with an immediate cooling device during waiting time, the waiting time is shortened, the rolling efficiency is improved, and at the same time, grain growth of the carbon steel base material due to excessively long waiting time is prevented. By controlling the temperature during the finishing rolling stage, the crystal grains can be refined, ensuring good low-temperature impact toughness of the clad plate.

[0149] <Third embodiment of the clad material rolling process> This embodiment differs from the first embodiment of the clad material rolling process described above, with reference to Figure 3c, in terms of heating and rolling. On the other hand, the processes after the completion of rolling (including intermittent cooling, straightening, deposition cooling, and natural cooling on the cooling bed) are the same as those of the first embodiment of the clad material rolling process described above, and these will not be explained again. Below, only the processes that differ between this embodiment and the first embodiment of the clad material rolling process (i.e., the heating process and the rolling process) will be described.

[0150] Specifically, in this embodiment, the heating step of the clad material rolling process is as follows:

[0151] The obtained clad material was subjected to a four-stage heating process: preheating, first heating, second heating, and soaking. The preheating temperature was 950-1000°C, the residence time was 0.3 min / mm × t, the first heating temperature was 1050-1100°C, the second heating temperature was 1120-1180°C, the soaking temperature was 1150-1200°C, and the total residence time for the first heating, second heating, and soaking was 1.5 min / mm × t + 20-40 min, where t is the thickness of the clad material.

[0152] The rolling process for clad material is as follows:

[0153] After the clad material is removed from the heating furnace, it is first subjected to high-pressure water descaling, followed by rolling. During the rolling process, transverse rolling is performed from the first pass, and the clad material is rolled to a width of Wt+0 to 40 mm by the nth pass, where Wt is the target width of the clad sheet, and the total reduction ratio up to this point is ≥30%. Longitudinal rolling is performed from the (n+1)th pass, and the rolling reduction ratio for the (n+1)th pass is ≥20%. When the thickness of the intermediate material reaches 2.5 to 3.5 times the target thickness of the clad sheet, a pause is initiated, and rolling is resumed when the surface temperature of the intermediate material drops below 880°C and continues until the end of rolling, with the rolling completion temperature being T r The temperature range is ±20℃, and the total reduction ratio for the entire rolling process is ≥75%.

number

[0154] Compared to the conventional technology, this embodiment also implements intermittent cooling and deposition cooling, and accordingly has beneficial effects brought about by the intermittent cooling process and the deposition cooling process, and the description of the first embodiment of the clad material rolling process described above can be referenced. Furthermore, compared to the conventional technology, the heating process of this embodiment can ensure sufficient heating of the clad material and reduce deformation resistance during rolling. In addition, the rolling process of this embodiment can not only reduce deformation resistance during widening, but also achieve good metallurgical bonding between the clad material and the base material, effectively ensure the interfacial bonding strength of the clad steel sheet, and further impart good performance to the clad steel sheet.

[0155] The process of rolling the clad material has been described in detail above. As mentioned above, the manufacturing method of the present invention further includes a clad steel sheet separation and straightening process. Specifically, the clad steel sheet separation and straightening process includes the following individual steps.

[0156] In the aforementioned clad material rolling process, the edges of the large clad plate are cut using a plasma cutter to remove the parts other than the sealing material, separating the large clad plate into two smaller clad plates, one above the other.

[0157] After determining the dimensions, the clad plate is placed on a leveler with the clad layer facing upwards and flattened. During lateral flattening, the leveler's flattening force F1 = ν × a × b × c w ×σ w / (d×(ν-c w / a)) is controlled, and during vertical flattening, the leveler's flattening force F2 = a × b × c L ×σ L / (d+c L ) controls the width of the cladding board, b is the thickness of the cladding board, c w This is the flatness per unit meter in the lateral direction of the clad plate, in units of mm, c L is the flatness per unit meter in the longitudinal direction of the clad plate, in units of mm, d is the working distance of the leveler, σ w σ is the lateral tensile yield strength of the clad plate. L ν is the longitudinal tensile yield strength of the clad plate, and ν is Poisson's ratio.

[0158] Finally, the clad plates are cold-formed to obtain single-sided stainless steel clad sheet products.

[0159] Thus, by controlling the flattening force of the leveler, the present invention can achieve shape control of clad steel sheets, and is easy to operate and extremely effective.

[0160] Here, the "parts other than the sealant" in the step of "cutting the edges of the clad plate to remove the parts other than the sealant" refers to the edges on the clad plate that have changed from the sealant and filling layer in the clad material after the clad material rolling process described above. By removing these parts, the stainless steel clad layer is exposed, and the clad plate is separated into two clad plates, upper and lower, without any bonding action in these parts.

[0161] Referring to Figures 4a to 4e, corresponding to the five embodiments of the material surface treatment process described above, Figures 4a to 4e show the cross-sectional shapes of two corresponding single-sided clad plates (i.e., final clad steel plates). Each obtained clad plate consists of a clad layer and a base material layer. The clad layer is obtained from the original clad material by rolling, and the base material layer is obtained from the original base material by rolling. Based on this, in Figures 4a to 4e, the clad layer still displays the symbol of the original clad material, and the base material layer still displays the symbol of the original base material. Referring to Figure 4a, the single-sided stainless steel clad steel plate manufactured based on the first embodiment of the material surface treatment process described above is a uniform-thickness plate with a total thickness of 5 to 55 mm, a base material layer thickness of 4 to 45 mm, and a clad layer thickness of 1 to 10 mm. Referring to Figures 4b to 4e, the single-sided stainless clad steel sheets manufactured based on the second to fifth embodiments of the material surface treatment process described above are of unequal thickness, with a maximum total thickness of 7 to 55 mm (corresponding to the thickest part of the clad steel sheet) and a minimum total thickness of 5 to 47 mm (corresponding to the thinnest part of the clad steel sheet), a maximum base material layer thickness of 6 to 45 mm (corresponding to the thickest part of the clad steel sheet) and a minimum total thickness of 4 to 37 mm (corresponding to the thinnest part of the clad steel sheet), and a clad layer thickness of 1 to 10 mm.

[0162] Furthermore, the present invention provides a single-sided stainless clad steel sheet, which is manufactured by the manufacturing method of any of the embodiments described above, possesses excellent mechanical properties and corrosion resistance, and has superior shape, interfacial bonding quality, uniformity, impact toughness, and surface quality compared to the prior art.

[0163] Specifically, sampling was performed from a single-sided stainless-clad steel sheet of one embodiment of the present invention in accordance with GB / T 2975 - Steel and Steel Products - "Sampling Location and Specimen Preparation for Mechanical Performance Tests," and also, In terms of shape, inspections are conducted according to GB / T 709 - "Dimensions, shape, weight and tolerances of hot-rolled steel sheets and strips," and the flatness of the clad steel sheet is ≤3 mm / m, and furthermore, flatness ≤2 mm / m.

[0164] In terms of interfacial bonding quality, tensile tests were performed on the clad steel sheets in accordance with GB / T 6396 - "Methods for Testing the Mechanical and Process Performance of Clad Steel Sheets". The bonding ratio of the interfacial bonding of the clad steel sheets was 100%, the shear strength was ≥300 MPa, and furthermore, the shear strength was ≥360 MPa.

[0165] In terms of mechanical performance, tensile tests were performed in accordance with GB / T 6396 - "Methods for testing the mechanical and industrial performance of clad steel sheets" and GB / T 228.1 - "Tensile tests for metallic materials, Part 1: Room temperature test methods". The yield strength of the clad steel sheet was ≥345 MPa, the tensile strength was ≥490 MPa, the elongation at break was ≥18%, and the yield ratio was ≤0.85. The Vickers hardness difference in the thickness direction of the base material layer of the clad steel sheet was ≤10, the strength difference between the front, middle, and rear sections was ≤40 MPa, and the strength difference between each part of the entire sheet was ≤40 MPa.

[0166] Tests were conducted in accordance with GB / T 6396 - "Methods for testing the mechanical and process performance of clad steel sheets" and GB / T 229 - "Charpy impact test methods for metallic materials," and the impact values ​​of the clad steel sheets were found to be ≥120J at 0°C, ≥120J at -20°C, ≥120J at -40°C, and furthermore, ≥240J at 0°C, ≥200J at -20°C, and ≥150J at -40°C.

[0167] Sampling was performed in accordance with GB / T 2975 - Steel and Steel Products - "Sampling Location and Specimen Preparation for Mechanical Performance Tests," and testing was performed in accordance with GB / T 6396 - "Methods for Testing Mechanical and Process Performance of Clad Steel Sheets." The clad steel sheet showed no cracks when bent 180° on the outside and no cracks when bent 180° on the inside.

[0168] Sampling was performed according to GB / T 6396 - "Methods for Testing the Mechanical and Process Performance of Clad Steel Sheets," and testing was performed according to GB / T 4334 - "Corrosion of Metals and Alloys: Test Methods for Intergranular Corrosion of Austenitic and Ferritic-Austenitic (Duplex) Stainless Steels." Even after boiling the clad steel sheets in a sulfuric acid-copper sulfate solution for 20 hours and then performing a 180° bending test, no intergranular corrosion cracking occurred in the clad layer.

[0169] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention and do not limit the scope of protection of the present invention. All equivalent embodiments or modifications that do not depart from the technical spirit of the present invention should be included within the scope of protection of the present invention.

[0170] The beneficial effects of the present invention will be further explained below through several examples. Of course, these examples are only a part of, and not all, of, the many variations included in the present invention.

[0171] In these examples, the steel grades / chemical compositions of the selected clad material and base material are shown in Table 1, respectively. Here, "-" indicates that the corresponding element was not intentionally added during the steel manufacturing process (content is zero or nearly zero).

[0172] [Table 1]

[0173] Using the base material and cladding material shown in Table 1 above, the cladding material was manufactured according to the cladding material manufacturing process of the manufacturing method of the present invention. For each example of cladding material, the base material, cladding material, cladding material thickness, and cladding material type are shown in Table 2. Here, "(1)", "(2)", "(3)", "(4)", and "(5)" in the "Clading Material Type" column of Table 2 indicate that the cladding material was manufactured according to the first, second, third, fourth, and fifth embodiments of the material surface treatment process described above, respectively.

[0174] [Table 2]

[0175] Furthermore, each embodiment was carried out according to the clad material rolling process of the manufacturing method of the present invention, and the specific parameters are shown in Tables 3 and 4. Here, "I", "II", and "III" in the "Embodiment of Heating + Rolling" column of Table 3 indicate that the corresponding embodiment was carried out according to the first, second, and third embodiments of the clad material rolling process described above.

[0176] [Table 3]

[0177] [Table 4]

[0178] Furthermore, each of the above embodiments was carried out according to the clad steel sheet separation and straightening process of the present invention to obtain single-sided stainless steel clad steel sheet products. The total thickness, base material layer thickness, clad layer thickness, and microstructure of the base material layer of the clad steel sheet products of these embodiments are shown in Table 5. Here, the ranges in the two columns for clad steel sheet thickness and base material layer thickness in Table 5 indicate the minimum thickness to the maximum thickness.

[0179] [Table 5]

[0180] Furthermore, the clad steel sheets of each example were sampled and tested using the previously disclosed sampling and testing standards. The interfacial bonding rate for each example was 100%, both the inner and outer 180° bend tests passed (no cracking), and no intergranular corrosion cracking occurred in the clad layer even after boiling in a sulfuric acid-copper sulfate solution for 20 hours followed by a 180° bend test. Other performance test results are shown in Table 6.

[0181] [Table 6]

[0182] In summary, compared to the prior art, the present invention ensures, on the one hand, the corrosion resistance and mechanical strength of stainless clad steel sheets through specific process control throughout the entire manufacturing method, and prevents deterioration of corrosion resistance and mechanical performance during the rolling process of the clad material. On the other hand, it solves the problems of shape defects, poor interfacial bonding quality, and poor surface quality of conventional stainless clad thick plates, giving stainless clad steel sheets superior shape and interfacial bonding quality, and avoids obvious surface defects such as dents and scratches caused by conventional explosion cladding technology. Furthermore, it achieves high yield and high production efficiency in the production process.

Claims

1. A method for manufacturing stainless steel clad steel sheets, This includes a manufacturing process for clad material, a rolling process for clad material, and a separation and straightening process for clad sheets. 1) In the manufacturing process of clad materials, Two carbon steel plates with thickness T1, length L1, and width W1 are prepared as the base material, and two stainless steel plates with thickness T2, length L2 < L1, and width W2 < W1 are prepared as the cladding material. The surface treatment is applied to at least one surface of each of the two base materials and the two cladding materials. A separating agent is applied to one surface of a single clad material. The layers are stacked in the order of base material, clad material, clad material, base material, with the clad material positioned in the center relative to the base material, and all surfaces of the base material and clad material that come into contact with each other are surfaces that have undergone the aforementioned surface treatment, with the surface to which the separating agent is applied facing the other clad material. Four sealing materials with a width W3 = 2T2 - 1 to 2 mm are prepared, and these sealing materials are brought into contact with the four sides of two clad materials. Gas shield welding is performed on adjacent sealing materials and between the sealing materials and the base material, and the two base materials and sealing materials are integrated to obtain the clad material body. A circular hole is machined into the sealing material in the groove on the side of the clad material body, and a seamless steel pipe is welded to the circular hole. Welding is applied to the grooves on all four sides of the clad material body. The clad material was subjected to three vacuum pumping and two vacuum breaking processes through the seamless steel pipe, and the final vacuum level was 10 －２ The pressure is set to Pa or less, and then the seamless steel pipe is sealed to obtain clad material. 2) In the rolling process of clad material, After heating the obtained clad material, a two-stage controlled rolling process consisting of rough rolling and finish rolling is performed. After rolling is complete, the clad plate is cooled and introduced into an ultra-rapid cooling system for intermittent cooling. This ultra-rapid cooling system has 24 sets of cooling collection tubes arranged at 1m intervals in the roll line direction, with a cooling distance of 1m for each set of cooling collection tubes. When the clad plate passes through the ultra-rapid cooling system, the opening and closing states of all 24 sets of cooling collection tubes are controlled in such a manner that N sets of cooling collection tubes are opened, while M sets of cooling collection tubes are not opened. The cooling water pressure is 0.15 to 0.30 MPa, the cooling rate is 3 to 15°C / s, and the final cooling temperature is 380 to 590°C, where N takes the value of 2, 3, or 4, and M takes the value of 2, 3, or 4. After the clad plate exits the ultra-rapid cooling system, it is directly introduced into the orthodontic machine for orthodontic treatment, and the clad plate after orthodontic treatment is cooled to a temperature of T ｆ -150℃ to T ｆ The cladding was cooled by placing it between two steel plates at +150°C, with a deposition cooling time of 0.4 min / mm × t0 ± 5 min, where t0 is the thickness of the cladding plate. After deposition cooling was completed, the cladding plate was allowed to cool naturally on a cooling bed, and then T ｆ = 550 + 30Si - 20Mn + 15Cr - 15Ni + 10Mo, where the element symbols represent 100 times the mass percentage of each element in the base material. 3) In the separation orthodontics of clad plates, The edges of the large clad board are cut to remove the parts other than the sealant, separating the large clad board into two smaller clad boards, one above the other. After determining the dimensions, place the clad layer of the clad small plate facing upward on a leveller and perform flattening. When flattening in the lateral direction here, the flattening force F1 of the leveller = ν × a × b × c ｗ × σ ｗ / (d × (ν - c ｗ / a)) is controlled. When flattening in the longitudinal direction, the flattening force F2 of the leveller = a × b × c Ｌ × σ Ｌ / (d + c Ｌ ) is controlled. Here, a is the width of the clad small plate, b is the thickness of the clad small plate, c ｗ is the flatness per unit meter in the lateral direction of the clad small plate, with the unit being mm, c Ｌ is the flatness per unit meter in the longitudinal direction of the clad small plate, with the unit being mm, d is the operating distance of the leveller, σ ｗ is the tensile yield strength in the lateral direction of the clad small plate, σ Ｌ is the tensile yield strength in the longitudinal direction of the clad small plate, and ν is the Poisson's ratio, Finally, the clad plates are cold-formed to obtain single-sided stainless steel clad sheet products. A method for manufacturing stainless steel clad sheets.

2. "Three vacuum pumping and two vacuum breaking procedures were performed on the clad material through the seamless steel pipe, and the final vacuum level was 10%. －２ In the process of "making it Pa or less", First, connect the seamless steel pipe to a vacuum pump and create a vacuum around the clad material, setting the vacuum level to 10. －２ After reducing the pressure to below Pa, the pressure is maintained for more than 4 hours, then the seamless steel pipe is connected to a nitrogen gas apparatus, the clad material is subjected to vacuum breaking, and nitrogen gas is filled in. Afterward, the seamless steel pipe is connected to the vacuum pump again, and the clad material is evacuated to a vacuum level of 10. －１ The pressure is kept below Pa, no holding pressure is applied, and then the seamless steel pipe is connected to the nitrogen gas apparatus again, the vacuum is broken against the cladding material, and nitrogen gas is filled in. Finally, the seamless steel pipe is connected to the vacuum pump for the third time, and the clad material is evacuated to a vacuum level of 10. －２ Let it be less than or equal to Pa. A method for manufacturing stainless steel clad steel sheets according to claim 1.

3. In the process of "heating the obtained clad material and then performing two-stage controlled rolling, consisting of rough rolling and finish rolling," The obtained clad material is heated, with a soaking temperature of 1150–1220°C, a total heating time of ≥1.2 min / mm × t, where t is the thickness of the clad material, and a holding time of 30–50 min during the soaking stage. Two-stage controlled rolling is performed: rough rolling and finish rolling. In the rough rolling stage, the rolling start temperature is ≤1050°C and the rolling end temperature is ≥980°C. First, transverse rolling is performed, followed by longitudinal rolling. During longitudinal rolling, the reduction amount in at least one pass is ≥35 mm, and the total reduction amount in rough rolling is 40-60%. The rough rolling stage is terminated when the thickness of the intermediate material is 2.5-3.5 times the target thickness of the clad sheet. After that, the material is left to wait, during which water cooling is performed. When the surface temperature of the intermediate material drops to 860°C or below, the finish rolling stage is started. The rolling end temperature in the finish rolling stage is ≥780°C, and the total reduction amount in finish rolling is 55-75%, resulting in a clad sheet. A method for manufacturing stainless steel clad steel sheets according to claim 1.

4. In the process of "heating the obtained clad material and then performing two-stage controlled rolling, consisting of rough rolling and finish rolling," The obtained clad material was subjected to five heating stages: preheating, first heating, second heating, third heating, and soaking. Here, the preheating temperature was ≤850°C with a residence time of (0.45–0.55) min / mm × t, the first heating temperature was 1030–1090°C with a residence time of (0.35–0.45) min / mm × t, the second heating temperature was 1100–1160°C with a residence time of (0.25–0.35) min / mm × t, the third heating temperature was 1140–1180°C with a residence time of (0.15–0.25) min / mm × t, and the soaking temperature was 1170–1210°C with a residence time of (0.10–0.20) min / mm × t, where t is the thickness of the clad material. Two-stage controlled rolling is performed, consisting of rough rolling and finish rolling. In the first pass, longitudinal rolling is performed, with a rolling reduction of ≥46 mm. From the second pass onwards, transverse rolling is performed, and the clad material is rolled to the target width of the final clad plate up to the nth pass, with a rolling reduction of ≥25 mm in the second pass. From the (n+1)th pass onwards, longitudinal rolling is performed, with a rolling reduction of ≥30 mm in the (n+1)th pass. Throughout the rough rolling stage, the rolling temperature of the first pass is ≥ The initial rolling temperature is 1060°C, the starting temperature for the remaining passes is ≤1050°C, and the ending temperature is ≥1000°C. The rough rolling stage is terminated when the thickness of the intermediate material reaches 2.5 to 3.5 times the target thickness of the clad sheet, followed by a waiting period during which water cooling is performed. The finish rolling stage is started when the surface temperature of the intermediate material drops below 840°C. The starting temperature for the finish rolling stage is 810°C to 840°C, and the ending temperature is 780°C to 810°C. A method for manufacturing stainless steel clad steel sheets according to claim 1.

5. In the process of "heating the obtained clad material and then performing two-stage controlled rolling, consisting of rough rolling and finish rolling," The obtained clad material was subjected to a four-stage heating process: preheating, first heating, second heating, and soaking. The preheating temperature was 950–1000°C, the residence time was 0.3 min / mm × t, the first heating temperature was 1050–1100°C, the second heating temperature was 1120–1180°C, the soaking temperature was 1150–1200°C, and the total residence time for the first heating, second heating, and soaking was 1.5 min / mm × t + 20–40 min, where t is the thickness of the clad material. After the clad material is removed from the heating furnace, high-pressure water descaling is performed first, followed by rolling. During the rolling process, transverse rolling is carried out from the first pass, and the clad material is rolled to a width of Wt + 0 to 40 mm by the nth pass, where Wt is the target width of the clad sheet. The total reduction ratio up to this point is ≥ 30%. Longitudinal rolling is carried out from the (n+1)th pass, with a rolling reduction ratio of ≥ 20% for the (n+1)th pass. When the thickness of the intermediate material reaches 2.5 to 3.5 times the target thickness of the clad sheet, a pause is initiated. Rolling is resumed when the surface temperature of the intermediate material drops below 880°C and continues until the end of rolling. The rolling end temperature is T ｒ The temperature range is ±20°C, and the total reduction ratio for the entire rolling process is ≥75%. [Math 1] In this formula, the element symbols represent 100 times the mass percentage of each element in the base material. A method for manufacturing stainless steel clad steel sheets according to claim 1.

6. In the aforementioned intermittent cooling, When the thickness of the clad plate is 54 mm or less, the roll line speed of the ultra-rapid cooling system is 0.4 to 0.8 m / s, and the first to fourth sets of cooling collection tubes are opened, the fifth to sixth sets of cooling collection tubes are not opened, the seventh to eighth sets of cooling collection tubes are opened, the ninth to tenth sets of cooling collection tubes are not opened, the eleventh to twelfth sets of cooling collection tubes are opened, the thirteenth to fourteenth sets of cooling collection tubes are not opened, the fifteenth to sixteenth sets of cooling collection tubes are opened, the seventeenth to eighteenth sets of cooling collection tubes are not opened, the nineteenth to twentyth sets of cooling collection tubes are opened, the twenty-first to twenty-second sets of cooling collection tubes are not opened, and the twenty-third to twenty-fourth sets of cooling collection tubes are opened, completing intermittent cooling as the clad plate passes through the ultra-rapid cooling system once. When the thickness of the clad plate is >54 mm, the roll line speed of the ultra-rapid cooling system is 0.2 m / s or more and less than 0.6 m / s, and the first to fourth sets of cooling collection tubes are opened, the fifth to eighth sets of cooling collection tubes are not opened, the ninth to twelfth sets of cooling collection tubes are opened, the thirteenth to sixteenth sets of cooling collection tubes are not opened, the seventeenth to twentyth sets of cooling collection tubes are opened, the twenty-first to twenty-second sets of cooling collection tubes are not opened, and the twenty-third to twenty-fourth sets of cooling collection tubes are opened, completing intermittent cooling as the clad plate passes through the ultra-rapid cooling system once. A method for manufacturing stainless steel clad steel sheets according to claim 1.

7. In the aforementioned intermittent cooling, When the thickness of the clad plate is ≥ 70 mm, the roll line speed of the ultra-rapid cooling system is 0.4 to 0.9 m / s. The clad plate first enters the ultra-rapid cooling system in the forward direction from the inlet, and when its leading edge reaches the 24th set of cooling collection tubes, the roll line reverses, and the clad plate passes through the ultra-rapid cooling system in the reverse direction and exits the ultra-rapid cooling system from the inlet, completing intermittent cooling. A method for manufacturing stainless steel clad steel sheets according to claim 1.

8. "The temperature of the clad plate after orthodontic treatment is T ｆ -150℃ to T ｆ In the process of "placing the material between two steel plates at +150°C and performing deposition cooling," the length and width of the steel plates used are both greater than the length and width of the clad plate, and the thickness of the steel plates used is twice the thickness of the clad plate. A method for manufacturing stainless steel clad steel sheets according to claim 1.

9. In the process of "applying a separating agent to one surface of a single clad material," the separating agent used is a coating solution containing silicon dioxide and magnesium oxide, with a mass ratio of silicon dioxide to magnesium oxide of 3:

1. The amount of separating agent to be applied is 20 mg / m². ２ Here, y is the thickness ratio of the clad material to the clad plate, Before the process of "laminating in the order of base material, clad material, clad material, base material," the clad material coated with a separating agent is heated and dried in a trolley furnace, with a drying temperature of 340-360°C and a drying time of 35-45 minutes. A method for manufacturing stainless steel clad steel sheets according to claim 1.

10. In the process of "applying a separating agent to one surface of a single clad material," the components of the separating agent used are, by mass ratio: silicon nitride 25-35%, thermosetting amino resin 5-10%, and water 55-70%. The coating thickness of the separating agent is 0.2 to 0.5 mm. Before the process of "laminating in the order of base material, clad material, clad material, base material," the clad material coated with a separating agent is heated and dried, with a drying temperature of 100-250°C and a drying time of 20-40 minutes. A method for manufacturing stainless steel clad steel sheets according to claim 1.

11. In the process of "applying surface treatment to at least one surface of each of the two base materials and the two cladding materials," The surfaces of two base materials are milled and ground so that their shapes are complementary, and the surface is processed into an irregular uneven surface containing X planes sequentially connected along the transverse direction, making the base material an uneven thickness material in which the thickness does not change monotonically in the transverse direction, and the length of the irregular uneven surface is L12 = L1 and the total width is W12 > W1, or the surface is processed into an irregular uneven surface containing X planes sequentially connected along the longitudinal direction, making the base material an uneven thickness material in which the thickness does not change monotonically in the longitudinal direction, and the total length of the irregular uneven surface is L12 > L1 and the width is W12 = W1, and X ≥ 2. One surface of each clad material is polished to remove surface oxide scale, and then each clad material is bent to conform to the corresponding irregular uneven surface. A method for manufacturing stainless steel clad steel sheets according to claim 1.

12. In the process of "applying surface treatment to at least one surface of each of the two base materials and the two cladding materials," One surface of each cladding material is polished to remove surface oxide scale. To make the shapes of the two base materials complementary, one surface of the base material is milled and ground to create a lateral inclined surface with length L11 = L1 and width W11 > W1, thereby creating a base material with unequal thickness where the thickness gradually changes in the lateral direction, or the surface is milled and ground to create a vertical inclined surface with length L11 > L1 and width W11 = W1, thereby creating a base material with unequal thickness where the thickness gradually changes in the vertical direction. A method for manufacturing stainless steel clad steel sheets according to claim 1.

13. In the process of "applying surface treatment to at least one surface of each of the two base materials and the two cladding materials," The surface of each base material and one cladding material is polished to remove surface oxide scale, and after polishing, both the base material and the cladding material are of equal thickness. A method for manufacturing stainless steel clad steel sheets according to claim 1.

14. In the aforementioned statement "the clad material is positioned at the center of the base material," the distance from the lateral side edge of the clad material to the corresponding side edge of the base material is half the difference in width of the contact surface between the clad material and the base material, and the distance from the longitudinal side edge of the clad material to the corresponding side edge of the base material is half the difference in length of the contact surface between the clad material and the base material. A method for manufacturing stainless steel clad steel sheets according to claim 1.

15. Stainless steel clad sheet, The flatness of the clad steel plate is ≤3 mm / m, the bonding ratio at the joint interface is 100%, and the shear strength is ≥300 MPa. Stainless steel clad sheet metal.

16. The flatness of the clad steel plate is ≤2 mm / m, and the shear strength is ≥360 MPa. Stainless steel clad sheet according to claim 15.

17. The impact force at 0°C is ≥240J, at -20°C it is ≥200J, and at -40°C it is ≥150J. Stainless steel clad sheet according to claim 15.

18. The Vickers hardness difference in the thickness direction of the base material layer of the clad steel sheet is ≤10, the strength difference between the front, middle, and rear sections is ≤40 MPa, and the strength difference between each part of the entire sheet is ≤40 MPa. Stainless steel clad sheet according to claim 15.

19. The aforementioned clad steel plate is a uniform thickness plate with a total thickness of 5 to 55 mm, and includes a base layer of 4 to 45 mm in thickness and a clad layer of 1 to 10 mm in thickness. Stainless steel clad sheet according to claim 15.

20. The clad steel sheet comprises a clad layer of equal thickness and a base material layer of unequal thickness, and the thickness of the clad layer is 1 to 10 mm. The base material layer has a thickness that does not change monotonically in the lateral or longitudinal direction, and its joint surface is an irregular uneven surface containing X planes sequentially connected along the lateral direction, or the base material layer has a thickness that changes monotonically and gradually in the lateral or longitudinal direction, and its joint surface is an inclined surface. Stainless steel clad sheet according to claim 15.

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