Method for producing stainless steel clad plate having excellent interface bonding

Abstract

The application discloses a preparation method of a stainless steel composite plate with excellent interface combination. The method comprises the following technological procedures: blank preparation, blank surface treatment, blank assembly, sealing welding, vacuum extraction, sealing, heating, rolling, cooling, plate separation and flattening; the blank assembly step: a circular through hole is formed in the sealing strip at at least one side edge of a composite base blank, and a circular tube with an outer diameter of r is welded in the through hole; the sealing welding step: a hole with a radius of R>r concentric with the circular tube is reserved around the circular tube; when the groove at the side edge where the circular tube is located is built up to a penetration depth of 2 / 3D, and the grooves at the other side edges are built up to a penetration depth of more than 2 / 3D, the sealing welding step is ended; the sealing step: after the vacuum extraction step of the composite base blank is completed, the circular tube is heated by a flame gun, pinched, and then folded into the reserved hole; full welding of the hole is carried out by using gas shielded welding, the circular tube is sealed in the hole; and the build-up welding is continuously carried out until the groove is filled.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of steel material preparation, and relates to a preparation method of a stainless steel clad plate with excellent interface bonding. BACKGROUND

[0002] The stainless steel clad plate for bridge steel has corrosion resistance of stainless steel, outstanding mechanical properties of bridge steel and price advantage, and is an important development direction of steel materials. At present, the methods for producing the clad plate mainly include explosion method, diffusion method, explosion-rolling method and rolling method. The explosion method and the diffusion method have a tendency to be eliminated gradually due to high pollution and high energy consumption, and the rolling method has become a mainstream method for producing the clad plate due to high efficiency and low cost.

[0003] The basic process for producing the clad plate by the hot rolling method includes billet preparation, billet surface treatment, billet assembly, sizing, sealing, composite billet heating, rolling, cooling, plate separation and straightening.

[0004] In one embodiment of the sealing process, a round pipe is welded at a hole reserved after sealing of the four sides of the composite billet, so as to perform vacuum extraction or inert gas filling on the composite billet, and then the round pipe is heated and crimped to be welded. In this way, the round pipe cannot be completely crimped and welded, and the round pipe is prone to falling off during subsequent handling, lifting and rolling, which leads to air leakage and affects the interface bonding quality of the clad plate.

[0005] In another embodiment of the sealing process, the four sides of the composite billet are sealed and a hole is reserved, vacuum extraction or inert gas filling is performed on the composite billet through the hole, and then the hole is simply blocked by an aluminum strip. In this way, on the one hand, the aluminum strip is expensive, which increases the production cost, and on the other hand, the aluminum strip is prone to falling off due to collision during subsequent handling and lifting, and the aluminum strip will melt at high temperature during heating, which leads to air leakage and affects the interface bonding quality of the clad plate. SUMMARY

[0006] The present application provides a preparation method of a stainless steel clad plate with excellent interface bonding.

[0007] To achieve the above-mentioned application purpose, one embodiment of the present application provides a preparation method of a stainless steel clad plate with excellent interface bonding, which includes the process flow of billet preparation, billet surface treatment, billet assembly, sealing, vacuum extraction, sealing, heating, rolling, cooling, plate separation and flattening; wherein,

[0008] The composite blank is formed by stacking the composite A and the composite B in the middle, the base material A on the top, the base material B on the bottom, and the sealing strip surrounding the four sides of the composite A and the composite B, and then performing gas shield welding between the sealing strip and the base material A and between the sealing strip and the base material B. The composite blank has a groove with a depth D formed by the base material A, the sealing strip and the base material B on the four sides, and a circular through hole is formed in the sealing strip on one side of the composite blank, and a circular tube with an outer diameter r is welded in the through hole.

[0009] The groove on the four sides of the composite blank is surfacing welded, and a hole with a radius R>r concentric with the circular tube is reserved around the circular tube during the surfacing welding. When the groove on the side where the circular tube is located is surfacing welded to a penetration depth of 2 / 3D, and the grooves on the other sides are surfacing welded to a penetration depth of more than 2 / 3D, the sealing step is completed.

[0010] After the vacuumizing step is completed, the circular tube is heated, pinched and then folded into the reserved hole by a flame gun, and then the hole is fully welded by gas shield welding to seal the circular tube in the hole. Next, the surfacing welding is continued until the groove is filled, and finally the surface welding is performed to obtain the composite blank.

[0011] Preferably, in the sealing step, when the groove on the side where the circular tube is located is surfacing welded to a penetration depth of 2 / 3D, and the grooves on the other sides are surfacing welded to a penetration depth of D, the sealing step is completed.

[0012] Preferably, during the surfacing welding, the multi-layer and multi-pass welding is performed in the order of the upper edge and the lower edge first and the middle region last, each layer is welded for more than 4 passes, the inter-pass temperature is 140-160℃, the total number of layers is 6-8, and the inter-layer temperature is 150-250℃.

[0013] Preferably, in the stacking step, the welding current during the gas shield welding is 220-240A, the welding voltage is 28-32V, the welding speed is 300-360mm / min, and the inter-pass temperature is controlled at 140-160℃.

[0014] Preferably, in the stacking step, the base material A and the base material B are preheated and baked by a flame gun before the gas shield welding, and the baking temperature is 150-250℃.

[0015] Preferably, in the stacking step, the through hole is formed in the sealing strip on one short side of the composite blank, and the through hole is centered at a position 1 / 3 of the length and 1 / 2 of the width of the sealing strip.

[0016] The end face of the circular tube is flush with the inner surface of the sealing strip.

[0017] Preferably, in the assembling step, the upper edge and the lower edge of the outer surface of the sealing strip are both provided with a bevel, and the angle of the bevel is 10-20°.

[0018] Preferably, the heating step is a four-stage heating process of preheating, first heating, second heating and soaking for the obtained composite blank, the preheating temperature is 950-1000℃, the residence time is 0.3t min / mm, the first heating temperature is 1050-1100℃, the second heating temperature is 1120-1180℃, the soaking temperature is 1150-1200℃, and the total residence time of the first heating, the second heating and the soaking is 1.5t min / mm+20-40min, t being the thickness of the composite blank.

[0019] Preferably, the rolling step is as follows: after the composite blank leaves the heating furnace, the composite blank is first subjected to high-pressure water descaling, and then is subjected to rolling; during the rolling, transverse rolling is adopted from the first pass, and the rolling is continued until the composite blank is rolled to a width of Wt+0-40mm in the nth pass, wherein Wt is the target width of the composite plate large plate, and the total reduction ratio before the nth pass is ≥30%; longitudinal rolling is adopted from the n+1th pass, and the rolling reduction ratio in the n+1th pass is ≥20%; when the thickness of the intermediate blank is 2.5-3.5 times the target thickness of the composite plate large plate, the rolling is stopped for temperature holding, and when the surface temperature of the intermediate blank decreases to below 880℃, the rolling is resumed until the rolling is completed, and the finish rolling temperature is T r ±20℃, and the total reduction ratio in the whole rolling process is ≥75%; In the formula, the element symbols represent 100 times the mass percentage of each element in the base material.

[0020] Preferably, the cooling step is as follows: the composite plate large plate is subjected to ultrafast cooling in a cooling system, the start cooling temperature is T c -30℃~T c +30℃, the cooling speed is 5-8℃ / s, and the final cooling temperature is T f -40℃~T f +40℃; then, the composite plate large plate is placed between two steel plates with a temperature of T f -150℃~T f +150℃ for stack cooling, and the stack cooling time is 0.4min / mm×t0±5min, t0 being the thickness of the composite plate large plate; after the stack cooling is completed, the composite plate large plate is naturally cooled to room temperature on a cooling bed.

[0021] In the formula, T c =750+29Si-20Mn+17Cr-17Ni, and T f =550+30Si-20Mn+15Cr-15Ni+10Mo, and in the formula, the element symbols represent 100 times the mass percentage of each element in the base material.

[0022] Preferably, the flattening step involves placing the single-sided composite board small panels obtained in the slitting step, with the cladding layer facing upwards, onto a flattening machine for flattening. Specifically, during transverse flattening, the flattening force F1 of the flattening machine is controlled to be ν × a × b × c. 横 ×σ 横 / (d×(ν-c 横 / a)); When flattening longitudinally, the flattening force F2 of the flattening machine is controlled as a × b × c longitudinal × σ 纵 / (d+c 纵 ); where a is the width of the composite panel (in mm), b is the thickness of the composite panel (in mm), and c is the width of the composite panel (in mm). 横 The flatness per meter in the transverse direction of the composite panel is expressed in mm, c. 纵 σ represents the unevenness of the composite panel per meter in the longitudinal direction, in mm, where d is the working distance of the flattening machine, and σ is the flatness of the small panel. 横 σ represents the tensile yield strength of the composite panel in the transverse direction. 纵 ν represents the tensile yield strength of the composite panel in the longitudinal direction, and ν is Poisson's ratio.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: the pre-reserved through holes at the weld seam in the billet assembly, sealing and welding steps increase the handling space of the round tube, reduce the difficulty of sealing and welding, improve the sealing and welding efficiency, avoid air leakage at the sealing, prevent the round tube from falling off due to collision, and thus ensure the overall sealing of the composite billet. As a result, cracking and air leakage will not occur during rolling. Furthermore, the composite plate prepared has excellent interface bonding and reduces production costs. Attached Figure Description

[0024] For clarity of illustration and explanation, certain dimensions of structures or parts in the various figures of this invention are enlarged relative to other structures or parts. Therefore, only the basic structure of the subject matter of this invention is used to illustrate the invention.

[0025] Figure 1 This is a cross-sectional schematic diagram of the steel billet in the billet preparation step of this invention;

[0026] Figure 2 This is a cross-sectional schematic diagram of the composite billet base after the sealing welding step and before the sealing step in this invention. The cross-section passes through the central axis of the circular tube and is perpendicular to the width direction of the composite billet base.

[0027] Figure 3 yes Figure 2 A magnified view of the area within the dashed box;

[0028] Figure 4 This is another cross-sectional schematic diagram of the composite billet base after the sealing welding step and before the sealing step in this invention. This cross-section is perpendicular to the central axis of the circular tube and perpendicular to the thickness direction of the composite billet base.

[0029] Figure 5 Figure 1 is a schematic diagram of a cross section of a composite plate obtained by the preparation method of the present application. DETAILED DESCRIPTION

[0030] Referring to Figure 1 The present application provides a preparation method of a stainless steel composite plate, which is used to prepare a single-sided stainless steel composite plate composed of a carbon steel base layer and a stainless steel composite layer. The composite blank obtained in the preparation method has good sealing performance of the sealing portion, does not fall off, saves cost, and does not crack or leak during rolling, thereby achieving excellent interface bonding of the prepared composite plate.

[0031] Specifically, the preparation method of the present application includes the process flow of blank preparation, blank surface treatment, blank assembly, sealing welding, vacuum extraction, sealing, heating, rolling, cooling, plate separation, and flattening. That is, the single-sided stainless steel composite plate is prepared by the process route of blank preparation, blank surface treatment, blank assembly, sealing welding, vacuum extraction, sealing, heating, rolling, cooling, plate separation, and flattening. The preferred embodiments of each step are introduced one by one as follows.

[0032] <Blank preparation step>

[0033] In this step, two carbon steel blanks with thickness T1, length L1, and width W1 are prepared as base materials, which are distinguished as base material A and base material B; and two stainless steel blanks with thickness T2, length L2, and width W2 are prepared as composite materials, which are distinguished as composite material A and composite material B.

[0034] Preferably, L2 < L1 and W2 < W1, that is, the length and width dimensions of the composite material are smaller than those of the base material. More preferably, L1 ≥ 2500 mm, W2 ≥ 1600 mm, and T1 ≥ 60 mm; the value range of L1-L2 is 100-140 mm, and the value range of W1-W2 is also 100-140 mm.

[0035] <Blank surface treatment step>

[0036] This step generally includes two sub-steps of surface grinding treatment and coating of release agent.

[0037] In the surface grinding treatment, the surface to be combined of each base material and each composite material is polished to remove the surface oxide scale and expose the metal luster. After the surface grinding treatment, the roughness Ra of the surface to be combined is less than 5 μm. In this way, the interface bonding quality of the composite plate can be ensured, and the poor interface bonding caused by the surface oxide scale can be avoided.

[0038] Here, the "surface to be combined" refers to the surface of the base material and the composite material that needs to be bonded in the formation of the composite plate.

[0039] As shown in Figure 1 Figure 1 For example, the surface p1 of the base material 11 (i.e., base material A) and the surface p3 of the composite material 21 (i.e., composite material A) need to be interfacially bonded in subsequent steps, and the surface p2 of the base material 12 (i.e., base material B) and the surface p4 of the composite material 22 (i.e., composite material B) need to be interfacially bonded in subsequent steps. Therefore, the surfaces p1, p2, p3, and p4 are all the so-called "surfaces to be composite-bonded".

[0040] In this surface grinding treatment, for the surfaces p1 and p2, a grinding wheel, a belt grinder or a milling machine is respectively used for grinding and polishing to remove the surface oxide scale and expose the metallic luster. For the surfaces p3 and p4, a wire wheel is respectively used for grinding and polishing to remove the surface oxide scale and expose the metallic luster. After this surface grinding treatment, the roughness Ra of the surfaces p1, p2, p3, and p4 is less than 5 μm.

[0041] It can be understood that after this surface grinding treatment, each base material and each composite material are all equal-thickness blanks.

[0042] Here only the surface grinding treatment of the surfaces to be composite-bonded of each base material and each composite material is described. It should be noted that the other surfaces of each base material and each composite material can also be further subjected to surface grinding treatment. Although this additional surface grinding treatment of the other surfaces is not necessary to achieve the technical effects of the present invention, it may be more preferable.

[0043] Furthermore, in the coating of the release agent, the release agent is applied on the non-surfaces to be composite-bonded of at least one composite material. Specifically, the release agent can be applied on the non-surfaces to be composite-bonded of each composite material, or one of the two composite materials can be selected for applying the release agent. Thus, the release agent is used to prevent the two composite materials from being bonded in the subsequent composite blank rolling step, resulting in difficulty in separating the final plates.

[0044] Here, corresponding to the "surfaces to be composite-bonded" described above, the so-called "non-surfaces to be composite-bonded" refer to the surfaces that do not need to be interfacially bonded when forming the composite plate. For example, the surface p5 of the composite material 21 (i.e., composite material A) and the surface p6 of the composite material 22 (i.e., composite material B) are both the so-called "non-surfaces to be composite-bonded".

[0045] The first embodiment of the release agent is: a coating solution containing silicon oxide and magnesium oxide, where the mass ratio of silicon oxide to magnesium oxide is 3:1. The release agent of this embodiment can achieve a good release effect and ensure the separation of the two subsequent small composite plates. Using this release agent, the total amount of the release agent 30 (as shown in Figure 2 Figure 2 ) between the two composite materials is 20 ymg / m 2, y is the ratio of the thickness of the composite blank prepared in the composite blank preparation step to the thickness of the composite plate after subsequent rolling, which is also referred to as the composite blank rolling compression ratio. After the completion of the brushing of the release agent, and before the subsequent grouping step, the composite material brushed with the release agent is placed in a trolley furnace for heating and drying, the drying temperature is 340-360°C, and the drying time is 35-45 min.

[0046] The second embodiment of the release agent is: the components are 25-35% silicon nitride

[0047] +5-10% thermosetting amino resin +55-70% water. Compared with the existing release agent, and even compared with the first embodiment of the aforementioned release agent, the release agent of this embodiment not only can achieve good isolation effect and ensure the separation of the two composite plate small plates, but also the chemical stability of the effective component silicon nitride is strong and resistant to high temperature and thermal shock, the thermosetting amino resin as the binder can be cured at low temperature, is non-toxic, and can achieve strong bonding effect with a small amount, so the overall price is low, the operation is simple, and the isolation and adhesion effects are good.

[0048] Here, a preferred preparation method of the release agent of the second embodiment is provided, which comprises: first, 5-10% silicon nitride (by weight percentage) is placed in a beaker or other container, then 15-25% water is poured and stirred; after the silicon nitride has no particles and no bubbles, 2-3% thermosetting amino resin is poured and continues to be stirred; when it becomes viscous, the remaining silicon nitride and water are continuously poured, and after stirring for 3-5 min, the remaining thermosetting amino resin is poured; when it is stirred to be viscous, the release agent is prepared.

[0049] For the release agent of the second embodiment, the total amount of the release agent 30 (see Figure 2 ) between the two composite materials is brushed according to the thickness of 0.2-0.5 mm; after the completion of the brushing of the release agent, and before the subsequent grouping step, the composite material brushed with the release agent is heated and dried, the drying temperature is 100-250°C, and the drying time is 20-40 min. Here, it should be noted that in the attached Figure 2 and Figure 3 , in order to facilitate understanding and description, the thickness of the release agent 30 between the two composite materials is enlarged, that is, the thickness of the release agent 30 in the figure is enlarged relative to the thickness of the base material, the thickness of the composite material, and the width of the seal mentioned later.

[0050] In the first embodiment and the second embodiment of the release agent, if the release agent is applied to both the surface p5 and the surface p6, the amount of the release agent applied to each of the surface p5 and the surface p6 can be half of the total amount, and if the release agent is applied to only one of the surface p5 and the surface p6, the release agent is applied in the total amount.

[0051] <grouping step>

[0052] In this step, the composite 21 and the composite 22 are grouped in a manner that the composite 21 and the composite 22 are arranged in the middle, the substrate 11 is arranged above, the substrate 12 is arranged below, and the sealant is arranged around the four sides of the composite 21 and the composite 22, and the sealant (see reference numeral 40) and the substrate 11 and the sealant and the substrate 12 are subjected to the gas shield welding to form a composite group base. Figure 2

[0053] In this step, the composite 21 and the composite 22 are grouped in a manner that the composite 21 and the composite 22 are arranged in the middle, the substrate 11 is arranged above, the substrate 12 is arranged below, and the sealant is arranged around the four sides of the composite 21 and the composite 22, and the sealant (see reference numeral 40) and the substrate 11 and the sealant and the substrate 12 are subjected to the gas shield welding to form a composite group base. Figure 2 In this step, the composite 21 and the composite 22 are grouped in a manner that the composite 21 and the composite 22 are arranged in the middle, the substrate 11 is arranged above, the substrate 12 is arranged below, and the sealant is arranged around the four sides of the composite 21 and the composite 22, and the sealant (see reference numeral 40) and the substrate 11 and the sealant and the substrate 12 are subjected to the gas shield welding to form a composite group base.

[0054] In one embodiment, the substrate 11, the composite 21, the composite 22, and the substrate 12 can be stacked first, and then the sealant 40 can be arranged around the four sides of the composite 21 and the composite 22, and finally the upper edge of the sealant 40 and the surface p1 of the substrate 11 and the lower edge of the sealant 40 and the surface p2 of the substrate 12 can be subjected to the gas shield welding. Of course, in a variant embodiment, the lower edge of the sealant 40 and the surface p2 of the substrate 12 can be subjected to the gas shield welding first, and then the composite 22 and the composite 21 can be arranged in the quadrangle frame formed by the sealant 40 on the surface p2 of the substrate 12, and then the substrate 11 can be arranged above the composite 21 and the frame, and finally the upper edge of the sealant 40 and the surface p1 of the substrate 11 can be subjected to the gas shield welding. In another variant embodiment, the upper edge of the sealant 40 and the surface p1 of the substrate 11 can be subjected to the gas shield welding first, and then the substrate 12, the composite 22, and the composite 21 can be stacked from bottom to top, and then the sealant 40 and the substrate 11 combined together can be arranged above and around the composite 21 and the composite 22, and finally the lower edge of the sealant 40 and the surface p2 of the substrate 12 can be subjected to the gas shield welding. These embodiments do not deviate from the spirit of the present application.

[0055] Preferably, the welding current during the gas shield welding is 220-240 A, the welding voltage is 28-32 V, the welding speed is 300-360 mm / min, and the interpass temperature is controlled at 140-160 °C.

[0056] In addition, before the gas shield welding, the substrate 11 and the substrate 12 are preferably preheated and baked by a flame gun, and the baking temperature is 150-250 °C.​

[0057] Preferably, the upper edge and the lower edge of the outer surface of the sealing strip 40 are both beveled, and the bevel angle is 10-20°, and the vertical depth of the bevel is 10-15 mm. Here, the "outer surface of the sealing strip 40" refers to the surface of the sealing strip 40 facing away from the composite 21 and the composite 22. In other words, the upper edge and the lower edge of one surface of the sealing strip 40 are both beveled, and in the assembly step, the sealing strip 40 and the base material 11, the base material 12, the composite 22, and the composite 21 are combined in a manner that the beveled "one surface" of the sealing strip 40 faces outward. By beveling, not only is the spot welding process on the inner side of the sealing strip avoided, but the heat-affected zone of the base material caused by multiple welding passes is also avoided, and subsequent sealing and welding of the bevel is facilitated, ensuring firmness.

[0058] Referring to FIG. 1, the composite blank 1 includes a base material 11, a base material 12, a composite 21, and a composite 22. The base material 11 and the base material 12 are made of a metal material, and the composite 21 and the composite 22 are made of a composite material. The base material 11 and the base material 12 are connected by a sealing strip 40, and the composite 21 and the composite 22 are connected by a sealing strip 40. Figure 3 Preferably, the bevel angle α1 of the upper edge and the bevel angle α2 of the lower edge of the outer surface of the sealing strip 40 are both 10-20°, and they can be the same or different.

[0059] In addition, regarding the size of the sealing strip 40, at the long side of the composite blank, the length L31 of the sealing strip 40 is the length L2 of the composite 21 / 22, and at the short side of the composite blank, the length L32 of the sealing strip 40 is the width W2 of the composite 21 / 22; the width W3 of the sealing strip 40 is the sum of the thicknesses of the composite 21 and the composite 22 or slightly less than the sum of the thicknesses of the composite 21 and the composite 22 within 2 mm, and the thickness T3 is 10-15 mm. Preferably, the width W3 of the sealing strip 40 on the four sides of the composite blank is the same, and the thickness T3 is also the same. Of course, it is not limited to this. It should be noted that, as mentioned above, in order to facilitate understanding and description, the thickness of the release agent 30 is exaggerated in FIG. 2, and accordingly, the width of the sealing strip 40 shown in FIGS. 3 and 4 is shown to be greater than the sum of the thicknesses of the two composites, but this is only because the thickness of the release agent 30 is exaggerated, and in fact, the width W3 of the sealing strip 40 is the sum of the thicknesses of the composite 21 and the composite 22 or slightly less than the sum of the thicknesses of the composite 21 and the composite 22 within 2 mm. Figure 2 Figure 2 Figure 3

[0060] Further, the four sides of the obtained composite blank have a recess with a depth D enclosed by the base material 11, the sealing strip 40, and the base material 12.

[0061] ​​​In a preferred embodiment, the depth D is in the range of 40-60 mm. It can be understood that the depth D depends on the difference between the length and width of the composite and the base material, and the thickness of the seal 40. By controlling the depth D, not only can the occurrence of weld cracking during the rolling of the composite blank be effectively avoided, but also the formation of weld heat cracks due to the deep penetration during the subsequent sealing and welding can be avoided, thereby affecting the sealing and welding quality of the composite blank.

[0062] Preferably, the depths of the grooves of the four sides of the composite blank base are preferably set to be the same, and during the assembly of the blank, the composite is placed centrally relative to the base material, and the distances from the two sides (i.e. long sides) of the composite in the transverse direction (i.e. width direction) to the corresponding two sides (i.e. long sides) of the base material are equal, and the distances from the two sides (i.e. short sides) of the composite in the longitudinal direction (i.e. length direction) to the corresponding two sides (i.e. short sides) of the base material are also equal.

[0063] For example, the groove depth D of the long side of the composite blank base is (W1-W2-2T3) / 2, and the groove depth D of the short side is (L1-L2-2T3) / 2.

[0064] Further, the seal at one side of the composite blank base is provided with a circular through hole, and during the assembly of the blank, a circular tube 60 with an outer diameter of r is welded in the through hole.

[0065] The through hole can be machined before the formation of the seal 30 and the argon shield welding of the base materials 11 and 12, or it can be machined after the argon shield welding is completed and the composite blank base is formed. These do not deviate from the technical purpose of the present application.

[0066] Preferably, the diameter of the through hole is consistent with the outer diameter of the circular tube 60, both being r.

[0067] Further preferably, the length of the circular tube 60 is in the range of T3+2D to T3+2D+R. Figure 4 As shown, the through hole is provided on the seal 40 at one short side of the composite blank base, and the through hole is centered at a position that is 1 / 3 of the length (i.e. 1 / 3 of L32) and 1 / 2 of the width (i.e. 1 / 2 of W3) of the seal 40; as shown, the end face of the circular tube 60 is flush with the inner surface p7 of the seal 40. Figure 3 As shown, the end face of the circular tube 60 is flush with the inner surface p7 of the seal 40.

[0068] Preferably, the length of the circular tube 60 is in the range of T3+2D to T3+2D+R.

[0069] <Sealing and welding step>

[0070] In the sealing and welding step, the grooves of the four sides of the composite blank base are surfacing, and submerged arc surfacing is used.

[0071] Further, during the surfacing, the circular tube 60 is used as a guide for the surfacing torch. Figure 3, a hole 51 with a radius R>r is reserved around the pipe 60; when the groove on the side where the pipe 60 is located is built up to a penetration depth of 2 / 3D, and the grooves on the other three sides are built up to a penetration depth of D, the sealing step is completed. It can be understood that outside the frame formed by the seal 40, a filling layer in the shape of a four-sided frame is formed by the build-up welding, see Figure 4 , where the filling layer formed by the build-up welding is indicated as 50.

[0072] More preferably, when the groove on the side where the pipe 60 is located is built up to a penetration depth of 2 / 3D, and the grooves on the other three sides are built up to a penetration depth of D, the sealing step is completed. In this way, the penetration depth of the other three sides is D, so that the groove is completely filled by the build-up welding.

[0073] Further, during the build-up welding, the multi-layer and multi-pass welding is performed in the order of the upper edge first and the lower edge later, and the middle region last, which not only enables the heat generated during the welding to be fully diffused, but also avoids the welding through the seal; each layer is welded for more than 4 passes, the inter-pass temperature is 140-160℃, the total number of layers is 6-8, and the inter-layer temperature is 150-250℃, which not only effectively improves the strength of the welded joint, but also reduces the influence of the welding on the microstructure and performance of the base material and the composite material.

[0074] In addition, before the build-up welding, the welding flux used is pre-baked and kept warm for standby, the baking temperature is 300-350℃, the baking time is 90-120min, and the keeping warm temperature is 100-150℃.

[0075] Preferably, during the build-up welding, the welding current is 550-650A, the welding voltage is 28-32V, and the welding speed is 400-500mm / min.

[0076] <evacuation step>

[0077] The composite base blank is evacuated through the pipe 60 by a vacuum pump, and the vacuum degree is ≤10 -2 Pa, and then kept for more than 4h, preferably 5-8h.

[0078] <sealing step>

[0079] In this sealing step, the pipe 60 is heated by a flame gun, clamped, and then folded into the reserved hole 51; then the hole is fully welded by gas shielded welding, and the pipe is sealed in the hole 51; next, the build-up welding is continued until the groove on the side where the pipe 60 is located is filled (i.e. the groove on this side is welded from a penetration depth of 2 / 3D in the sealing step to a penetration depth of D), and finally, the surface welding is performed to obtain the composite blank.

[0080] Thus, by the blank assembling, sealing and sealing steps of the present application, the through hole 51 is reserved at the weld, the disposal space of the round pipe 60 is increased, the sealing difficulty is reduced, the sealing efficiency is improved, the sealing leakage is avoided, the round pipe 60 is prevented from falling off due to collision, and thus the sealing of the composite blank is ensured as a whole, so that the cracking and leakage phenomenon does not occur during rolling; and further, the interface bonding of the prepared composite plate is excellent, and the production cost is reduced.

[0081] <heating step>

[0082] The obtained composite blank is subjected to four-stage heating of preheating, first heating, second heating and soaking, the preheating temperature is 950-1000℃, the residence time is 0.3t min / mm, the first heating temperature is 1050-1100℃, the second heating temperature is 1120-1180℃, and the soaking temperature is 1150-1200℃, the total residence time of the first heating, the second heating and the soaking is 1.5t min / mm+20-40min, and t is the thickness of the composite blank.

[0083] <rolling step>

[0084] After the composite blank exits the heating furnace, high-pressure water descaling is performed first, and then rolling is performed.

[0085] During rolling, transverse rolling is adopted from the first pass, and the composite blank is rolled to a width of Wt+0-40mm in the nth pass, wherein Wt is the target width of the composite plate large plate, and the total reduction rate before the nth pass is ≥30%; longitudinal rolling is adopted from the n+1th pass, the rolling reduction rate in the n+1th pass is ≥20%; when the intermediate blank thickness is 2.5-3.5 times the target thickness of the composite plate large plate, the temperature is allowed to stand; when the surface temperature of the intermediate blank is reduced to below 880℃, the rolling is resumed until the rolling is completed, and the finish rolling temperature is T r ±20℃, and the total reduction rate in the whole rolling process is ≥75%; The element symbol in the formula represents 100 times the mass percentage of each element in the base material.

[0086] <cooling step>

[0087] The composite plate large plate enters the ultra-fast cooling system, the open cooling temperature is T c -30℃~T c +30℃, the cooling speed is 5-8℃ / s, and the final cooling temperature is T f -40℃~T f +40℃; then, the composite plate large plate is placed at a temperature of T f -150℃~T fThe two steel plates at 150℃ are stacked and cooled for 0.4min / mmxt0±5min, t0 being the thickness of the large clad plate; after the stacking and cooling, the large clad plate is naturally cooled on a cooling bed to room temperature.

[0088] wherein T c = 750 + 29Si - 20Mn + 17Cr - 17Ni, T f = 550 + 30Si - 20Mn + 15Cr - 15Ni + 10Mo, the element symbols in the formula representing 100 times the mass percentage of each element in the base material.

[0089] <Plate separating step>

[0090] The large clad plate cooled to room temperature is cut on four sides by a plasma cutting machine to remove the part outside the seal, and the large clad plate is separated into two small clad plates, thus realizing plate separation.

[0091] The part outside the seal is the edge part on the large clad plate transformed from the seal 60 and the filler layer 50 in the clad blank mentioned above after the preceding rolling step. Thus, this part is removed to expose the stainless steel clad layer, and the large clad plate is automatically separated into two small clad plates without the connecting effect of this part.

[0092] Referring to Figure 5 , two single-sided clad small plates (i.e. final stainless clad plates) are shown. Each clad small plate is composed of a clad layer and a base layer, the clad layer being obtained from the original clad material through rolling, and the base layer being obtained from the original base material through rolling, and therefore, in Figure 5 , the original clad material is still marked with the original clad material code, and the original base material is still marked with the original base material code.

[0093] <Flattening step>

[0094] The clad layer of the single-sided clad small plate obtained in the plate separating step is placed on a flattening machine with the clad layer facing up, and is flattened, wherein: when transverse flattening, the flattening force F1 of the flattening machine is controlled to be ν×a×b×c 横 ×σ 横 / (d×(ν-c 横 / a)); when longitudinal flattening, the flattening force F2 of the flattening machine is controlled to be a×b×c 纵 ×σ 纵 / (d+c 横 ); wherein a is the width of the clad small plate, in mm, b is the thickness of the clad small plate, in mm, c 纵for the unevenness of the composite sheet in the longitudinal direction per meter, unit: mm, d is the working distance of the flattening machine, σ 横 for the tensile yield strength of the composite sheet in the transverse direction, σ 纵 for the tensile yield strength of the composite sheet in the longitudinal direction, v is the Poisson's ratio.

[0095] Thus, in a further preferred embodiment of the present application, through the heating, rolling, cooling and flattening steps, on the basis of achieving the excellent effect of the interfacial bonding of the present application, further, the comprehensive performance of the obtained stainless steel composite sheet can be improved compared to the prior art, especially the plate shape, specifically including: on the one hand, through heating parameter control, rolling control and cooling control, especially cooling speed control and stack cooling, the temperature of the composite sheet in the thickness direction of the whole plate can be uniform, avoiding the situation that the temperature of the base material is low and the temperature of the composite material is high, so that the base material and the composite material maintain a small difference in expansion, thereby ensuring the plate shape of the composite sheet; on the other hand, by adjusting the flattening force and the flattening direction, a better plate shape can be obtained; on the other hand, the heating process can ensure that the composite blank can be fully heated, reducing the deformation resistance during rolling, and the rolling process not only reduces the deformation resistance during spreading, but also the composite material and the base material can achieve good metallurgical bonding, which can further improve the interfacial bonding strength.

[0096] Next, a specific embodiment is provided, which prepares a stainless steel composite sheet by using the preparation method of a preferred embodiment of the present application, and the specific steps are as follows.

[0097] <Blank preparation step>

[0098] Two Q370qE blanks are selected as the base material, and the chemical composition is as follows: C: 0.10%, Si: 0.20%, Mn: 1.50%, Cr: 0.20%, Ni: 0.10%, Nb: 0.02%, Ti: 0.02%, Al: 0.04%, and the rest is Fe and unavoidable impurities.

[0099] The sizes of the two base materials are the same, the length L1 is 2600 mm, the width W1 is 1600 mm, and the thickness T1 is 100 mm.

[0100] Two pieces of 316L stainless steel are selected as the composite material, the length L2 is 2480 mm, the width W2 is 1480 mm, and the thickness T2 is 15 mm.

[0101] <Blank surface treatment step>

[0102] The surface of each base material to be compounded is polished to remove the surface oxide scale and expose the metal luster; after polishing, the roughness of the surface of each base material to be compounded is 3 μm.

[0103] The whole surface of each composite material is polished to remove the surface oxide and expose the metal gloss. After polishing, the roughness of the surface to be bonded of each substrate is 3 μm.

[0104] The non-bonding surface of one composite material (hereinafter referred to as composite material B, and the other composite material is referred to as composite material A) is coated with 0.3 mm thick release agent. The release agent used is: the composition is 25-35% silicon nitride + 5-10% thermosetting amino resin + 55-70% water by weight. The preparation method of the release agent is: first put 5-10% silicon nitride (by weight percentage) into a beaker or other container, then pour 15-25% water and stir; after the silicon nitride has no particles and no bubbles, pour 2-3% thermosetting amino resin and continue to stir; when it becomes viscous, continue to pour the remaining silicon nitride and water, stir for 3-5 min, and then pour the remaining thermosetting amino resin; when it is stirred to a viscous state, the release agent is prepared.

[0105] After the release agent is coated, the composite material B is dried at 150°C for 30 min.

[0106] <grouping step>

[0107] Four sealing strips of the same material as the substrate are prepared, wherein: two long sealing strips have dimensions of length L31 = 2480 mm, width W3 = 30 mm, and thickness T3 = 10 mm; two short sealing strips have dimensions of length L32 = 1480 mm, width W3 = 30 mm, and thickness T3 = 10 mm.

[0108] The ends of the four sealing strips are spot-welded to form a rectangular frame along the outer side. The upper and lower edges of the outer surface of the sealing strip are beveled, with a vertical depth of 12 mm and an angle of 10°.

[0109] A flame gun is used to preheat and bake a substrate (hereinafter referred to as substrate A) and the sealing strips, with a baking temperature of 150°C.

[0110] After baking, the frame is welded to the bonding surface of substrate A along the bevel of the sealing strip by one pass of gas shielded welding, with a welding current of 220 A, a welding voltage of 28 V, a welding speed of 300 mm / min, and a interpass temperature of 140-160°C.

[0111] Then, substrate B, composite material B, composite material A, substrate A + the frame are stacked from bottom to top in the following order: substrate B with its bonding surface facing up, composite material B with its release agent-coated surface facing up, the frame facing down and surrounding composite material A and composite material B, with composite material B and composite material A being centrally arranged relative to substrate A and substrate B.

[0112] The base material B and the seal are preheated and baked by a flame gun, and the baking temperature is 150°C. Then, the frame is gas shielded welded to the surface of the base material B to be combined along the bevel of the seal.

[0113] A through hole with a diameter of 10 mm is opened in the short seal at a position with a length of 1 / 3 and a width of 1 / 2 of the seal as the center. A round pipe with a diameter of 10 mm and a length of 120 mm is seal welded in the through hole.

[0114] <Sealing step>

[0115] The four sides of the composite blank have grooves with a depth D of 50 mm, and the grooves are built up. Before the build-up, the flux is baked at a baking temperature of 300°C for 90 min, and then is kept at a temperature of 100°C. During welding, the current is 550 A, the welding voltage is 28 V, and the welding speed is 400 mm / min. During the build-up, the upper edge and the lower edge are welded first, and the middle region is welded last. Each layer is welded 5 times, the inter-pass temperature is 140-160°C, the total number of layers is 8, and the inter-layer temperature is 200°C.

[0116] For the two long sides and the short side without the round pipe of the composite blank, the build-up is performed to a penetration depth of 50 mm. For the short side with the round pipe, the build-up is performed to a penetration depth of 35 mm, and then the build-up is ended. During the build-up, a hole with a radius of 12 mm concentric with the round pipe is reserved around the round pipe when each pass is welded to the vicinity of the round pipe. Thus, the sealing step is ended and the next step is entered.

[0117] <Evacuation step>

[0118] The composite blank is evacuated by a vacuum pump through the round pipe until the vacuum degree is ≤10 -2 Pa, and the pressure is maintained for 5 h.

[0119] <Sealing step>

[0120] The round pipe is heated by a flame gun, is pinched, and then is folded into the reserved hole. The hole is fully welded by gas shielded welding to seal the round pipe in the hole. Next, the build-up is continued until the penetration depth of the side with the round pipe is 50 mm, and then the surface welding is performed to obtain the composite blank.

[0121] <Heating step>

[0122] After the weld is slowly cooled to room temperature, the composite blank is sent into a heating furnace for four-stage heating of preheating, first heating, second heating, and soaking. The preheating temperature is 950°C, the residence time is 70 min, the first heating temperature is 1050°C, the second heating temperature is 1150°C, the soaking temperature is 1200°C, and the total residence time of the first heating, the second heating, and the soaking is 370 min.

[0123] <rolling step>

[0124] After the composite blank leaves the heating furnace, high-pressure water descaling is performed first, and then rolling is performed.

[0125] During rolling, transverse rolling is adopted in the first pass until the composite blank is rolled to a width of 2000 mm, at which point the total reduction is 35%; longitudinal rolling is then adopted, with a rolling reduction of 25% in the first pass; when the intermediate blank thickness is 120 mm, warm waiting is performed, and when the surface temperature of the intermediate blank decreases to 850℃, rolling is resumed until the end of rolling, with a finish rolling temperature of 825℃; the obtained composite plate has a large plate thickness of 46 mm, and the total reduction during the entire rolling process is 80%.

[0126] <cooling step>

[0127] The rolled composite plate is fed into a straightening machine for straightening, and then into an ultra-fast cooling system, with an open cooling temperature of 710℃, a cooling speed of 6℃ / s, and a final cooling temperature of 480℃.

[0128] After the water is discharged, the composite plate is directly fed into a straightening machine for straightening, and after straightening, the composite plate is placed between two steel plates with a temperature of 600℃ for stack cooling, with the steel plates having a length of 2700 mm, a width of 1650 mm, and a thickness of 25 mm, and the stack cooling time is 15 min; after stack cooling, the composite plate is naturally cooled to room temperature on a cooling bed.

[0129] <plate separation step>

[0130] The composite plate is cooled to room temperature, and the four sides are cut to remove the part outside the seal using a plasma cutting machine, and the composite plate is separated into two composite plate small plates, thus achieving plate separation.

[0131] <flattening step>

[0132] The composite layer of the single-sided composite plate small plate obtained in the plate separation step is placed on the flattening machine with the composite layer facing up for flattening, wherein: when transverse flattening is performed, the flattening force of the flattening machine is controlled to be 251 KN; when longitudinal flattening is performed, the flattening force of the flattening machine is controlled to be 316 KN.

[0133] Finally, a cold straightening machine is used for supplementary straightening, and a single-sided stainless steel composite plate with a total thickness of 23 mm, a base layer thickness of 20 mm, and a composite layer thickness of 3 mm is obtained.

[0134] The performance of the stainless steel composite plate was tested. The interface bonding strength was 393 MPa, the transverse and longitudinal unevenness was 3 mm / m, the transverse tensile strength was 553 MPa and the yield strength was 449 MPa, the longitudinal tensile strength was 551 MPa and the yield strength was 437 MPa, the longitudinal impact energy at -40℃ was 313 J, 319 J and 315 J, there were no cracks in the intergranular corrosion of the strata, and the overall cold bending performance of the composite plate was qualified.

[0135] In summary, the preparation method of a preferred embodiment of the present invention has the following advantages compared with the prior art:

[0136] Beneficial effects:

[0137] 1) The sealing performance is good and it will not fall off, which saves costs and prevents opening during rolling.

[0138] The cracking and air leakage phenomena result in excellent interfacial bonding of the prepared composite plate.

[0139] 2) Through heating parameter control, rolling control, cooling control, especially cooling rate control and stacking...

[0140] Cooling can ensure uniform temperature throughout the thickness of the composite board while maintaining its performance, avoiding situations where the substrate temperature is low and the composite material temperature is high. This allows the substrate and composite material to maintain a similar amount of expansion, thereby ensuring the shape of the composite board.

[0141] 3) By adjusting the flattening force and flattening direction, a better plate shape can be obtained;

[0142] 4) The heating process can ensure that the composite billet can be fully heated, reducing the deformation resistance during rolling. The rolling process can not only reduce the deformation resistance during widening, but also achieve good metallurgical bonding between the composite material and the substrate, which can further improve the interfacial bonding strength.

[0143] 5) The release agent has good chemical stability, is resistant to high temperature and thermal shock, and can form a protective film at high temperature to prevent oxidation of the steel plate surface and ensure the surface quality of the composite plate; it also has strong adhesion, is not only inexpensive, but also has good isolation and adhesion effects, avoiding accidental bonding of non-composite interfaces due to rolling.

Claims

1. A method for producing a stainless steel clad plate having excellent interface bonding, characterized by, The method comprises the process flow of blank preparation, blank surface treatment, blank assembly, sealing welding, vacuumizing, sealing, heating, rolling, cooling, plate separation and flattening, wherein The blank assembly step is performed in the manner that composite material A and composite material B are in the middle, base material A is stacked above, base material B is stacked below, and the sealing strip is surrounded on the four sides of composite material A and composite material B, and the sealing strip and base material A and the sealing strip and base material B are subjected to gas shield welding to form a composite blank base blank; the four side edges of the composite blank base blank have a groove with a depth D surrounded by base material A, the sealing strip and base material B, and the sealing strip at one side edge of the composite blank base blank is provided with a circular through hole, and a circular pipe with an outer diameter of r is welded in the through hole; the through hole is provided on the sealing strip at one short side edge of the composite blank base blank, and the through hole is centered at a position of 1 / 3 of the length and 1 / 2 of the width of the sealing strip at the short side edge; the end face of the circular pipe is flush with the inner surface of the sealing strip; The sealing step: welding the groove of the four sides of the composite base blank, and reserving a hole with a radius of R>r concentric with the round tube during the welding process; when the groove of the side where the round tube is located is welded to a penetration depth of D, and the groove of the other side is welded to a penetration depth of D, the sealing step is completed. The sealing step is performed after the vacuumizing step of the composite blank base blank is completed, the circular pipe is heated and pinched by a flame gun, and then folded into the reserved hole; full welding is performed on the hole by gas shield welding to seal the circular pipe in the hole; then, the surfacing is continuously performed until the groove at the side edge of the circular pipe is filled, and finally, the surface welding is performed to obtain a composite blank.

2. The method of producing a stainless steel clad plate having excellent interface bonding according to claim 1, characterized by, In the sealing step, when the groove of the side where the circular pipe is located is built up to a penetration depth of D D, and the groove of the other side is built up to a penetration depth of D, the sealing step is ended.

3. The method for preparing a stainless steel composite plate with excellent interfacial bonding according to claim 1, characterized in that, In the surfacing process, the multi-layer and multi-pass welding is performed in the manner that the upper edge and the lower edge are in the front and the middle region is in the rear, each layer is welded for more than 4 passes, the inter-pass temperature is 140-160℃, the total number of layers is 6-8, and the inter-layer temperature is 150-250℃.

4. The method for preparing a stainless steel composite plate with excellent interfacial bonding according to claim 1, characterized in that, In the blank assembly step, the welding current during the gas shield welding is 220-240A, the welding voltage is 28-32V, the welding speed is 300-360mm / min, and the inter-pass temperature is controlled at 140-160℃.

5. The method of claim 1, wherein the stainless steel clad plate having excellent interface is prepared by the steps of: preparing a stainless steel clad plate by cladding a stainless steel plate with a low carbon steel plate; and performing a heat treatment on the stainless steel clad plate. In the blank assembly step, the base material A and the base material B are respectively preheated and roasted by a flame gun before the gas shield welding, and the roasting temperature is 150-250℃.

6. The method of claim 1, wherein the stainless steel clad plate having excellent interface is prepared by the steps of: preparing a stainless steel plate; preparing a carbon steel plate; and joining the stainless steel plate and the carbon steel plate. In the blank assembly step, the upper edge and the lower edge of the outer surface of the sealing strip are both provided with a bevel, and the bevel angle is 10-20°.

7. The method of producing a stainless steel clad plate having excellent interface bonding according to claim 1, characterized by, The heating step is performed in the four-stage heating of preheating, first heating, second heating and soaking on the obtained composite blank, the preheating temperature is 950-1000℃, the residence time is 0.3t min / mm, the first heating temperature is 1050-1100℃, the second heating temperature is 1120-1180℃, the soaking temperature is 1150-1200℃, the total residence time of the first heating, the second heating and the soaking is 1.5t min / mm+20-40min, and t is the thickness of the composite blank.

8. The method of claim 1, wherein the stainless steel clad plate having excellent interface is prepared by the steps of: preparing a stainless steel plate; preparing a carbon steel plate; and joining the stainless steel plate and the carbon steel plate. Rolling step: after the composite blank leaves the heating furnace, high-pressure water descaling is first performed, and then rolling is performed; during rolling, transverse rolling is adopted from the first pass, and until the composite blank is rolled to a width of Wt+0~40mm, wherein Wt is the target width of the composite plate large plate, and the total reduction rate up to this point is ≥30%; longitudinal rolling is adopted from the n+1 pass, and the n+1 pass rolling reduction rate is ≥20%; when the intermediate blank thickness is 2.5~3.5 times the target thickness of the composite plate large plate, warm waiting is started, when the surface temperature of the intermediate blank decreases to below 880℃, rolling is resumed until the end of rolling, and the finish rolling temperature is T r ±20℃, the total reduction rate of the entire rolling process is ≥75%; T r =855-150 +45Si-15Ni+31Mo+106Nb+100Ti+70Al, wherein the element symbol in the formula represents 100 times the mass percentage of each element in the base material.

9. The method of claim 1, wherein the stainless steel clad plate having excellent interface is prepared by the steps of: preparing a stainless steel plate; preparing a carbon steel plate; and joining the stainless steel plate and the carbon steel plate. Cooling step: the composite plate enters the ultra-fast cooling system, the open cooling temperature is T c -30℃~T c +30℃, the cooling speed is 5~8℃ / s, and the final cooling temperature is T f -40℃~T f +40℃; then, the composite plate is placed between two steel plates with a temperature of T f -150℃~T f +150℃ for stack cooling, the stack cooling time is (0.4min / mm)xt0±5min, t0 is the thickness of the composite plate; after the stack cooling is completed, the composite plate is naturally cooled to room temperature on the cooling bed. Among them, T c =750+29Si-20Mn+17Cr-17Ni, T f =550+30Si-20Mn+15Cr-15Ni+10Mo, where the element symbols in the formula represent 100 times the mass percentage of each element in the substrate.

10. The method of producing a stainless steel clad plate having excellent interface bonding according to claim 1, characterized by, The flattened step: the single-sided composite board plate obtained by the splitting step is placed on the flattening machine with the composite layer upwards, wherein: when transverse flattening, the flattening force F1 of the flattening machine is controlled as F1 = ν × a × b × c 横 × σ 横 / (d × (ν - c 横 / a) ); when longitudinal flattening, the flattening force F2 of the flattening machine is controlled as F2 = a × b × c longitudinal × σ 纵 / (d + c 纵 ); wherein, a is the width of the composite board plate, unit: mm, b is the thickness of the composite board plate, unit: mm, c 横 is the unevenness per meter of the composite board plate in the transverse direction, unit: mm, c 纵 is the unevenness per meter of the composite board plate in the longitudinal direction, unit: mm, d is the working distance of the flattening machine, σ 横 is the tensile yield strength of the composite board plate in the transverse direction, σ 纵 is the tensile yield strength of the composite board plate in the longitudinal direction, and ν is the Poisson's ratio.

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