Stainless steel composite plate for thick bridge and preparation method of stainless steel composite plate

Abstract

The invention relates to the technical field of stainless steel composite plates, in particular to a stainless steel composite plate for a thick bridge and a preparation method of the stainless steel composite plate for the thick bridge, and the method comprises the following steps: carrying out single assembly treatment to obtain a composite blank, carrying out primary heating and rolling on the composite blank, carrying out secondary heating, controlled rolling and controlled cooling treatment to obtain the composite plate, tempering and straightening; wherein the single-time assembly treatment specifically comprises the steps that beveling and drilling are conducted on the four edges of the to-be-compounded side of the base material to form air exhaust holes, the to-be-compounded face of the clad stainless steel is attached to the base material, then welding sealing is conducted, and vacuumizing treatment is conducted. The problems that the stainless steel composite plate for the high-performance thick-specification bridge is difficult to produce through symmetric assembly rolling and rolling is difficult to achieve through a conventional single assembly are solved, the produced stainless steel composite plate for the bridge is excellent in interface bonding, the shear strength is larger than or equal to 380 MPa, the yield ratio is smaller than or equal to 0.83, the impact Akv of a base material at the temperature of-40 DEG C is larger than or equal to 250 J, and the intergranular corrosion resistance of a covering material is excellent; and the steel plate has good comprehensive performance and plate shape.

Description

Technical Field

[0001] The invention relates to the technical field of stainless steel composite plates, in particular to a stainless steel composite plate for thick-gauge bridges and a preparation method thereof. Background Art

[0002] With the continuous improvement of steel bridge construction level and the increasing requirements for safety and reliability, bridges are gradually developing towards high speed, heavy load, large span, and paint-free, which also has higher requirements for bridge steel: high strength and toughness, low yield ratio, high corrosion resistance, etc. The composite plate composed of bridge steel and stainless steel has both high strength and toughness of the base layer and corrosion resistance of the coating, which can better meet the requirements of lightweight, high corrosion resistance and long service life of the bridge deck structure.

[0003] Common production methods for stainless steel composite plates for bridges include explosion method and rolling method. The explosion method is more suitable for the production of thick composite plates, but its production size is still limited. If the finished product is wide, the covering materials need to be welded before the explosion. After the explosion, defects are prone to appear at the welding of the covering materials, and the detonation point cannot be combined. This method is also easily affected by climate and environment, and there are problems such as noise and environmental pollution, which makes it difficult to produce in batches. The plate width produced by the rolling method can be flexibly adjusted and can be mass-produced efficiently. It is a green, environmentally friendly and sustainable production process, which is divided into symmetrical billet rolling and asymmetrical billet rolling. Symmetrical billet rolling can maintain a good plate shape throughout the production process because the upper and lower materials of the composite billet are consistent. However, when producing thick-gauge composite plates (finished product thickness ≥ 50mm), the rolling thickness can reach more than 100mm, and the billet thickness of the symmetrical billet needs to be more than 500mm, which places high demands on the billet assembly and rolling equipment; the greater the rolling thickness, the greater the difference in cooling rate in the thickness direction, and the smaller the rolling compression ratio, the insufficient deformation of the base and cladding material interface and the core of the base material, affecting the organizational properties of the final product. Asymmetric billet rolling is a combination of a single carbon steel and a single stainless steel, which can increase the rolling compression ratio and reduce the difference in cooling rate in the thickness direction, thereby improving the performance of the composite plate. However, due to the different thermal expansion coefficients and deformation resistance of carbon steel and stainless steel, warping and buckling are very likely to occur during the rolling process, and in severe cases, rolling may even fail to be completed. Summary of the invention

[0004] In view of the above technical problems, the present invention overcomes the shortcomings of the prior art and provides a thick-gauge stainless steel composite plate for bridges and a preparation method thereof, which solves the problem that symmetrical billet rolling is difficult to produce high-performance thick-gauge stainless steel composite plates for bridges and the problem that conventional single billet rolling is difficult to achieve rolling. The produced stainless steel composite plate for bridges has excellent interface bonding, shear strength ≥380MPa, yield strength ratio ≤0.83, substrate -40℃ impact Akv ≥250J, no cracking is found in 180° internal and external bending, the covering material has excellent intergranular corrosion resistance, and has good comprehensive performance and plate shape.

[0005] In a first aspect, the present invention provides a method for preparing a thick stainless steel composite plate for a bridge, which specifically comprises the following steps:

[0006] Performing single-component assembly processing to obtain a composite billet;

[0007] The composite billet is heated and rolled once;

[0008] The rolled composite billet is subjected to secondary heating, controlled rolling and controlled cooling treatment to obtain a composite plate;

[0009] Tempering:

[0010] and straightening;

[0011] Wherein, the single batch processing specifically includes:

[0012] a) Beveling the four sides of the substrate to be composited;

[0013] b) drilling holes in the substrate to form air extraction holes;

[0014] c) Laminating the surface of the stainless steel to be laminated to the substrate;

[0015] d) Weld and seal and perform vacuum treatment.

[0016] Optionally, in the single-bill assembly process: the chamfer angle of the groove is 30-60°, and the groove height is 15-70 mm; a hole is drilled downward at 50-70 mm from the center of the short side edge of the substrate, and the hole depth is the groove height plus 15-40 mm; and a hole is drilled inward at 15-40 mm from the groove on the side wall of the short side of the substrate, and the hole depth is 50-70 mm, which is connected to the hole on the upper surface of the substrate to form an L-shaped exhaust hole. The exhaust hole is designed at the short side of the substrate, and less area needs to be cut off after rolling, which can improve product yield and save costs.

[0017] Optionally, welding sealing and vacuuming specifically include: firstly welding the connection between the base material and the covering material by gas shielded welding, pre-vacuuming the exhaust hole on one side, and sealing the exhaust hole when the vacuum value reaches below 20Pa; then fully welding the remaining part of the groove by submerged arc welding, and vacuuming for the second time so that the final vacuum value is not more than 10Pa, so as to obtain a composite billet of a single layer of stainless steel + a single layer of carbon steel in a high interface vacuum state.

[0018] Optionally, the one-time heating and rolling specifically includes:

[0019] The composite billet is sent to the heating furnace, with the cladding stainless steel surface facing upward and the base carbon steel surface facing downward. The heating temperature is 1150-1250°C, and the upper surface temperature is 20-50°C higher than the lower surface temperature. The total heating time is 9-18 min / cm;

[0020] After taking out of the furnace, single-stage rolling is adopted, and the reduction rate of multiple passes is not more than 5%, and the total reduction rate is 18% to 30%. When the composite billet is bitten, the sled coefficient is adjusted to a negative value to reduce the degree of warping. During the rolling process, only the descaling water on the lower side is opened to descale the carbon steel on the lower surface.

[0021] Optionally, the secondary heating, controlled rolling and controlled cooling treatment specifically include:

[0022] After the first rolling, the composite billet is turned over to ensure that the stainless steel surface of the cladding material faces downward and the carbon steel surface of the substrate faces upward. The composite billet is heated to 1180-1250°C, and the lower surface temperature is 20-50°C higher than the upper surface temperature. The total heating time is 10-18 min / cm;

[0023] Two-stage rolling is adopted, and the sled coefficient is adjusted to a positive value to reduce the buckling degree. The starting rolling temperature in the finishing rolling stage is not higher than 860℃, and the final rolling temperature is 720~850℃. During the rolling process, only the upper side descaling water is turned on and the lower side descaling is turned off.

[0024] The thickness of the intermediate billet to be heated is controlled to be no less than 1.6 times the thickness of the finished product, and the intermediate billet is cooled by natural air;

[0025] Pre-straightening is carried out before entering the water, the water entry temperature is controlled at 700-800℃, the red-returning temperature is 380-640℃, and the cooling lower and upper water ratio is 1.0-1.3.

[0026] Optionally, the tempering includes: turning over the composite plate so that the cladding stainless steel surface faces upward and the base carbon steel surface faces downward, the tempering temperature is 400-550° C., and the tempering time is 100-250 min.

[0027] Optionally, the straightening includes: performing straightening treatment for more than 3 times, with an unevenness of ≤5 mm / m, grinding and cleaning the surface of the composite plate to obtain a stainless steel composite plate product.

[0028] Optionally, before performing the single-assembly process, it also includes providing a substrate blank and a cladding blank, the cladding blank has the same width and length as the substrate blank, removing the oxidized iron scale, drill cuttings, dust and oil stains on the surface to be composited, placing the cladding blank with the stainless steel surface to be composited facing down on the substrate blank, and aligning and centering them.

[0029] Optionally, the chemical composition mass percentage of the substrate is: C: ≤0.14%, Si: 0.15-0.50%, Mn: 1.00-1.70%, P≤0.025%, S≤0.020%, Nb: 0.010-0.060%, V: ≤0.050%, Ti: 0.006-0.020%, Alt: 0.015-0.050%, Cu: ≤0.40%, Cr: ≤0.60%, Ni: ≤0.50%, Mo: ≤0.30%, and the balance is Fe and a small amount of unavoidable impurities;

[0030] The chemical composition mass percentage of the covering material is: C: ≤0.08%, Si: ≤1.50%, Mn: ≤2.00%, P≤0.045%, S≤0.030%, Cr: 16.00-26.00%, Ni: 8.00-22.00%, Mo: ≤4.00%, Ti: ≤0.40%, N≤0.16%, and the balance is Fe and a small amount of inevitable impurities.

[0031] In a second aspect, the present invention further provides a thick-gauge stainless steel composite plate for bridges, which is prepared using the thick-gauge stainless steel composite plate for bridges preparation method described in any one of the first aspects.

[0032] The beneficial effects of the present invention are:

[0033] (1) The present invention adopts single-hole vacuuming to reduce the probability of the sealing rivet falling off at the vacuuming hole, thereby reducing the risk of air leakage. After the sealing welding, a pre-vacuuming treatment is performed to remove the air between the two sides of the substrate and the covering material to be composited, thereby reducing the problem of oxidation between the two sides of the composite blank to be composited, especially at the edges, during the subsequent welding process. The present invention further vacuums after submerged arc welding, and pre-vacuuming and secondary vacuuming are performed after gas shielded welding and submerged arc welding, respectively, thereby greatly ensuring a high vacuum state between the covering material and the substrate, which is beneficial to improving the bonding quality.

[0034] (2) The present invention adopts a method of heating and rolling twice in different furnace feeding modes, which effectively adjusts the performance and plate shape of the thick-gauge composite plate. The temperature of the stainless steel side is set higher than that of the carbon steel side during the two heatings. This is because the thermal expansion coefficients of stainless steel and carbon steel are different and the ductility is greatly different. Increasing the temperature of the stainless steel side can make it deform more harmoniously with the carbon steel.

[0035] (3) In the present invention, during the first rolling, the stainless steel surface faces upward, and the interface between the stainless steel and the carbon steel is subjected to greater compression, which promotes the bonding of the interface. The flaw detection results show that the stainless steel and the carbon steel are completely bonded at this time, which avoids the situation in which the stainless steel and the carbon steel are delaminated and the stainless steel is rolled into the roll gap if buckling occurs during the second rolling; during the second rolling, if the stainless steel is on the upper side, there is no roller restraint and the temperature drop is faster than the lower side, making it easier to warp; and when the stainless steel surface faces downward, combined with adjusting the sled coefficient to be positive, the buckling can be reduced, and closing the stainless steel side descaling can reduce the temperature drop and thus reduce shrinkage, which is conducive to a good plate shape;

[0036] (4) The composite plate prepared by the present invention has excellent interface bonding, shear strength ≥ 380 MPa, yield strength ratio ≤ 0.83, substrate -40°C impact Akv ≥ 250 J, no cracking was found in 180° internal and external bending, and the cladding material has excellent intergranular corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of a comparison of two composite plates (the air extraction holes are located on the short side and the long side of the plate) cut out in a specific embodiment of the present invention;

[0038] In the figure: 100, finished composite board; 101, air extraction holes on the upper surface of the substrate; 102, cut-away area. DETAILED DESCRIPTION

[0039] The thick stainless steel composite plate for bridges and the preparation method thereof of the present invention will be described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not limit the present invention.

[0040] The thick stainless steel composite plates for bridges provided in Examples 1-6 of the present invention have a base layer (substrate) of bridge steel and a cladding layer (covering material) of austenitic stainless steel.

[0041] Table 1 and Table 2 respectively show the chemical composition weight percentages of the substrate and the covering material in Examples 1-6 of the present invention, with the remainder being Fe and a small amount of unavoidable impurities.

[0042] In the following table, atmospheric corrosion resistance index I = 26.01 (%Cu) + 3.88 (%Ni) + 1.20 (%Cr) + 1.49 (%Si) + 17.28 (%P) - 7.29 (%Cu) (%Ni) - 9.10 (%Ni) (%P) - 33.39 (%Cu) 2

[0043] Table 1 Chemical composition of the substrate of the present invention in percent by weight (wt%)

[0044]

[0045] Table 2 Chemical composition mass percentage (wt%) of the covering material of the present invention

[0046]

[0047] Example 1

[0048] In this embodiment, the base material is selected as bridge steel with a trace amount of Nb+Ti added, and the specific compositions of the base and cladding materials are shown in Table 1 and Table 2. The thickness of the composite blank is 300 mm, and the thickness of the final stainless steel composite plate is 50 mm, of which the thickness of the cladding material is 2 mm and the thickness of the base material is 48 mm.

[0049] (1) Preparation of base and cladding material blanks: Cut the base material into the required size, and make the cladding material blank consistent with the base material blank in width and length. Remove the iron oxide scale on the base and cladding material surfaces to be composited, and check the surface for defects.

[0050] (2) Single assembly: Bevel the four sides of the substrate to be composited, with a chamfer angle of 30° and a chamfer height of 16 mm. Drill a hole 50 mm downward from the center of the short side of the substrate, with a hole depth of 51 mm; then drill a hole 35 mm inward from the chamfer in the thickness direction of the short side of the substrate, with a hole depth of 50 mm, connected to the hole on the upper surface of the substrate, thereby forming an exhaust hole. After removing the drilling chips, dust and oil stains on the surface of the substrate, place the stainless steel to be composited surface of the cladding material facing down on the substrate, and align and center it. Use gas shielded welding to weld and seal the chamfered part of the substrate and the cladding material, and then perform single-sided pre-vacuuming at the exhaust hole. When the vacuum value reaches below 20 Pa, the exhaust hole is blocked. Finally, submerged arc welding is used to fully weld the remaining chamfered part, and then vacuuming is performed for the second time, with the final vacuum value of 0.20 Pa, thereby obtaining a composite blank of single-layer stainless steel + single-layer carbon steel in a high interface vacuum state.

[0051] It is understandable that the blocking described in this application refers to temporary or permanent sealing of the exhaust hole. Specifically, a rivet may be welded at the exhaust hole, vacuum is drawn through the rivet, and then the rivet is heated to block the exhaust hole. Before the second vacuum drawing, the rivet is removed to release the blocked state of the exhaust hole. Of course, in some other embodiments, other methods may also be used to block the exhaust hole. It should also be noted that the exhaust holes in this application are all opened at the short side of the substrate. The main reason is that a large amount of steel can be saved. See Figure 1 , both are finished composite plates 100. The exhaust holes 101 on the upper surface of the substrate of the finished composite plate 100 on the left are opened at the short side of the substrate, while those on the composite plate 100 on the right are opened at the long side of the substrate. The specific difference is that after the stainless steel composite plate is rolled, the position where the exhaust holes are drilled needs to be cut off. In comparison, when the exhaust holes 101 on the upper surface of the substrate are opened at the short side of the substrate, the range of the cut-off area 102 is smaller, which can greatly improve the product yield and save costs.

[0052] (3) One-time heating and rolling: Send the composite billet to the heating furnace. When loading the furnace, the stainless steel surface of the cladding material faces upward and the carbon steel surface of the base material faces downward. The heating temperature is 1200°C, and the upper surface temperature is adjusted to be 30°C higher than the lower surface temperature. The total heating time is 15min / cm. After leaving the furnace, single-stage rolling is adopted. The reduction rate of multiple passes is ≤5%, and the total reduction rate is 18%. When the composite billet is bitten, the sled coefficient is adjusted to a negative value to reduce the degree of warping. During the rolling process, only the descaling water on the lower side is turned on to descale the carbon steel on the lower surface.

[0053] (4) Secondary heating, controlled rolling and controlled cooling: After the first rolling, the composite billet is turned over to ensure that the stainless steel surface of the cladding material faces downward and the carbon steel surface of the substrate faces upward. The heating temperature is 1210℃, and the lower surface temperature is adjusted to be 30℃ higher than the upper surface temperature. The total heating time is 16min / cm. Two-stage rolling is adopted, and the sled coefficient is adjusted to a positive value to reduce the degree of buckling. The thickness of the intermediate billet to be warmed is ≥1.6h (h is the thickness of the finished product, unit: mm), the water spray cooling device of the intermediate billet is turned off, and the intermediate billet is cooled by natural air. The starting rolling temperature of the finishing rolling stage is 850℃, and the final rolling temperature is 830℃. During the rolling process, only the upper side descaling water is turned on and the lower side descaling is turned off. Pre-straightening is performed before entering the water, and the water temperature is controlled to be 800℃. The red-returning temperature is 640℃, and the cooling lower and upper water ratio is controlled to be 1.2. Then, according to the plate shape, multiple straightening processes are performed.

[0054] (5) After rolling, the composite plate is turned over so that the stainless steel surface of the cladding material faces upward and the carbon steel surface of the substrate faces downward, and then sent to the tempering furnace. The tempering temperature is 550℃ and the tempering time is 100min. After tempering, it is straightened for more than 3 times, and the unevenness reaches 2mm / m. Then the surface of the composite plate is polished and cleaned to obtain a 50mm thick high-performance stainless steel composite plate product.

[0055] Example 2

[0056] In this embodiment, the base material is selected from bridge steel with a trace amount of Nb and an appropriate amount of Cr added. The specific compositions of the base and cladding materials are shown in Table 1 and Table 2. The thickness of the composite blank is 400 mm, and the thickness of the final stainless steel composite plate is 80 mm, of which the thickness of the cladding material is 2 mm and the thickness of the base material is 78 mm.

[0057] Preparation of base and cladding material blanks: Cut the base material into required sizes, make the cladding material blanks consistent with the base material blanks in width and length, remove the iron oxide scale on the base and cladding material surfaces to be composited, and check the surface for defects.

[0058] Single-fold assembly: Bevel the four sides of the substrate to be composited, with a chamfer angle of 60° and a height of 68mm. Drill a hole downward at 65mm from the center of the short side of the substrate, with a hole depth of 90mm; then drill a hole inward at 22mm from the chamfer in the thickness direction of the short side of the substrate, with a hole depth of 65mm, connected to the hole on the upper surface of the substrate, thereby forming an exhaust hole. After removing the drilling chips, dust and oil stains on the surface of the substrate, place the stainless steel to be composited surface of the cladding material facing down on the substrate, and align and center it. Use gas shielded welding to weld and seal the chamfered part of the substrate and the cladding material, and then perform single-sided pre-vacuuming at the exhaust hole, and block the exhaust hole when the vacuum value reaches below 20Pa. Finally, use submerged arc welding to fully weld the remaining chamfered part, and then perform a second vacuuming, with a final vacuum value of 0.05Pa, so as to obtain a composite blank of single-layer stainless steel + single-layer carbon steel in a high interface vacuum state.

[0059] The heating and rolling production steps of the composite plate are the same as those in Example 1, and the rolling parameters of the two times are shown in Table 3.

[0060] After rolling, the composite plate is turned over so that the stainless steel surface of the cladding material faces upward and the carbon steel surface of the substrate faces downward, and then sent to the tempering furnace. The tempering temperature is 520℃ and the tempering time is 240min. After tempering, it is straightened for more than 3 times, and the unevenness reaches 1mm / m. Then the surface of the composite plate is polished and cleaned to obtain a 80mm thick high-performance stainless steel composite plate product.

[0061] Example 3

[0062] In this embodiment, the base material is selected from bridge steel with trace amounts of Nb+V+Ti and appropriate amounts of Cr+Ni added. The specific compositions of the base and cladding materials are shown in Table 1 and Table 2. The thickness of the composite blank is 350 mm, and the thickness of the final stainless steel composite plate is 70 mm, of which the thickness of the cladding material is 3 mm and the thickness of the base material is 67 mm.

[0063] Preparation of base and cladding material blanks: Cut the base material into required sizes, make the cladding material blanks consistent with the base material blanks in width and length, remove the iron oxide scale on the base and cladding material surfaces to be composited, and check the surface for defects.

[0064] Single-fold assembly: Bevel the four sides of the substrate to be composited, with a chamfer angle of 45° and a height of 40mm. Drill a hole downward at 60mm from the center of the short side of the substrate, with a hole depth of 56mm; then drill a hole inward at 16mm from the chamfer in the thickness direction of the short side of the substrate, with a hole depth of 60mm, connected to the hole on the upper surface of the substrate, thereby forming an exhaust hole. After removing the drilling chips, dust and oil stains on the surface of the substrate, place the stainless steel to be composited face down on the substrate, and align and center it. Use gas shielded welding to weld and seal the chamfered part of the substrate and the covering material, and then perform single-sided pre-vacuuming at the exhaust hole, and block the exhaust hole when the vacuum value reaches below 20Pa. Finally, use submerged arc welding to fully weld the remaining chamfered part, and then perform a second vacuuming, with a final vacuum value of 0.08Pa, so as to obtain a composite blank of a single layer of stainless steel + a single layer of carbon steel in a high interface vacuum state.

[0065] The heating and rolling production steps of the composite plate are the same as those in Example 1, and the rolling parameters of the two times are shown in Table 3.

[0066] After rolling, the composite plate is turned over so that the stainless steel surface of the cladding material faces upward and the carbon steel surface of the base material faces downward, and then sent to the tempering furnace. The tempering temperature is 500℃ and the tempering time is 175min. After tempering, it is straightened for more than 3 times, and the unevenness reaches 2mm / m. Then the surface of the composite plate is polished and cleaned to obtain a 70mm thick high-performance stainless steel composite plate product.

[0067] Example 4

[0068] In this embodiment, the base material is selected from bridge steel with trace amounts of Nb+Ti and appropriate amounts of Cu+Cr+Ni+Mo added. The specific compositions of the base and cladding materials are shown in Table 1 and Table 2. The thickness of the composite blank is 346 mm, and the thickness of the final stainless steel composite plate is 65 mm, of which the thickness of the cladding material is 3 mm and the thickness of the base material is 62 mm.

[0069] Preparation of base and cladding material blanks: Cut the base material into required sizes, make the cladding material blanks consistent with the base material blanks in width and length, remove the iron oxide scale on the base and cladding material surfaces to be composited, and check the surface for defects.

[0070] Single-fold assembly: Bevel the four sides of the substrate to be composited, with a chamfer angle of 50° and a height of 46mm. Drill a hole downward at 55mm from the center of the short side of the substrate, with a hole depth of 64mm; then drill a hole inward at 18mm from the chamfer in the thickness direction of the short side of the substrate, with a hole depth of 55mm, connected to the hole on the upper surface of the substrate, thereby forming an exhaust hole. After removing the drilling chips, dust and oil stains on the surface of the substrate, place the stainless steel to be composited face down on the substrate, and align and center it. Use gas shielded welding to weld and seal the chamfered part of the substrate and the covering material, and then perform single-sided pre-vacuuming at the exhaust hole, and block the exhaust hole when the vacuum value reaches below 20Pa. Finally, use submerged arc welding to fully weld the remaining chamfered part, and then perform a second vacuuming, with a final vacuum value of 0.10Pa, so as to obtain a composite blank of single-layer stainless steel + single-layer carbon steel in a high interface vacuum state.

[0071] The heating and rolling production steps of the composite plate are the same as those in Example 1, and the rolling parameters of the two times are shown in Table 3.

[0072] After rolling, the composite plate is turned over so that the stainless steel surface of the cladding material faces upward and the carbon steel surface of the base material faces downward, and then sent to the tempering furnace. The tempering temperature is 480℃ and the tempering time is 165min. After tempering, it is straightened for more than 3 times, and the unevenness reaches 2mm / m. Then the surface of the composite plate is polished and cleaned to obtain a 65mm thick high-performance stainless steel composite plate product.

[0073] Example 5

[0074] In this embodiment, the base material is selected from bridge steel with trace amounts of Nb+Ti and appropriate amounts of Cu+Cr+Ni+Mo added. The specific compositions of the base and cladding materials are shown in Table 1 and Table 2. The thickness of the composite blank is 354 mm, and the thickness of the final stainless steel composite plate is 59 mm, of which the thickness of the cladding material is 1 mm and the thickness of the base material is 58 mm.

[0075] Preparation of base and cladding material blanks: Cut the base material into required sizes, make the cladding material blanks consistent with the base material blanks in width and length, remove the iron oxide scale on the base and cladding material surfaces to be composited, and check the surface for defects.

[0076] Single-fold assembly: Bevel the four sides of the substrate to be composited, with a chamfer angle of 40° and a height of 32mm. Drill a hole downward at 68mm from the center of the short side of the substrate, with a hole depth of 57mm; then drill a hole inward at 25mm from the chamfer in the thickness direction of the short side of the substrate, with a hole depth of 68mm, connected to the hole on the upper surface of the substrate, thereby forming an exhaust hole. After removing the drilling chips, dust and oil stains on the surface of the substrate, place the stainless steel to be composited surface of the cladding material facing down on the substrate, and align and center it. Use gas shielded welding to weld and seal the chamfered part of the substrate and the cladding material, and then perform single-sided pre-vacuuming at the exhaust hole, and block the exhaust hole when the vacuum value reaches below 20Pa. Finally, use submerged arc welding to fully weld the remaining chamfered part, and then perform a second vacuuming, with a final vacuum value of 0.04Pa, so as to obtain a composite blank of single-layer stainless steel + single-layer carbon steel in a high interface vacuum state.

[0077] The heating and rolling production steps of the composite plate are the same as those in Example 1, and the rolling parameters of the two times are shown in Table 3.

[0078] After rolling, the composite plate is turned over so that the stainless steel surface of the cladding material faces upward and the carbon steel surface of the base material faces downward, and then sent to the tempering furnace. The tempering temperature is 450℃ and the tempering time is 148min. After tempering, it is straightened for more than 3 times, and the unevenness reaches 1mm / m. Then the surface of the composite plate is polished and cleaned to obtain a 59mm thick high-performance stainless steel composite plate product.

[0079] Example 6

[0080] In this embodiment, the base material is selected from bridge steel with trace amounts of Nb+V+Ti and appropriate amounts of Cu+Cr+Ni+Mo added. The specific compositions of the base and cladding materials are shown in Table 1 and Table 2. The thickness of the composite blank is 360 mm, and the thickness of the final stainless steel composite plate is 75 mm, of which the thickness of the cladding material is 5 mm and the thickness of the base material is 70 mm.

[0081] Preparation of base and cladding material blanks: Cut the base material into required sizes, make the cladding material blanks consistent with the base material blanks in width and length, remove the iron oxide scale on the base and cladding material surfaces to be composited, and check the surface for defects.

[0082] Single-fold assembly: Bevel the four sides of the substrate to be composited, with a chamfer angle of 50° and a height of 48mm. Drill a hole downward at 58mm from the center of the short side of the substrate, with a hole depth of 68mm; then drill a hole inward at 20mm from the chamfer in the thickness direction of the short side of the substrate, with a hole depth of 58mm, connected to the hole on the upper surface of the substrate, thereby forming an exhaust hole. After removing the drilling chips, dust and oil stains on the surface of the substrate, place the stainless steel to be composited face down on the substrate, and align and center it. Use gas shielded welding to weld and seal the chamfered part of the substrate and the covering material, and then perform single-sided pre-vacuuming at the exhaust hole, and block the exhaust hole when the vacuum value reaches below 20Pa. Finally, use submerged arc welding to fully weld the remaining chamfered part, and then perform a second vacuuming, with a final vacuum value of 0.01Pa, so as to obtain a composite blank of single-layer stainless steel + single-layer carbon steel in a high interface vacuum state.

[0083] The heating and rolling production steps of the composite plate are the same as those in Example 1, and the rolling parameters of the two times are shown in Table 3.

[0084] After rolling, the composite plate is turned over so that the stainless steel surface of the cladding material faces upward and the carbon steel surface of the base material faces downward, and then sent to the tempering furnace. The tempering temperature is 400℃ and the tempering time is 220min. After tempering, it is straightened for more than 3 times, and the unevenness reaches 2mm / m. Then the surface of the composite plate is polished and cleaned to obtain a 75mm thick high-performance stainless steel composite plate product.

[0085] Table 3 Rolling parameters of the embodiment of the present invention

[0086]

[0087] The various properties of Examples 1-6 are shown in Table 4. It can be seen that the thick-gauge stainless steel composite plate for bridges produced by the present invention has excellent comprehensive properties, the interface achieves good metallurgical bonding, the shear strength is ≥380Mpa, the yield strength ratio is ≤0.83, -40℃Akv ≥250J and the fiber cross-section rate is ≥85%, the 180° internal and external bending are qualified, and the covering material has excellent intergranular corrosion resistance.

[0088] Table 4 Various properties of Examples 1-6 of the present invention

[0089]

[0090] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A method for preparing a thick stainless steel composite plate for bridges, characterized in that: The following steps are involved: Performing single-component assembly processing to obtain a composite billet; The composite billet is heated and rolled once; The rolled composite billet is subjected to secondary heating, controlled rolling and controlled cooling treatment to obtain a composite plate; Tempering: and straightening; Wherein, the single batch processing specifically includes: a) Beveling the four sides of the substrate to be composited; b) drilling holes in the substrate to form air extraction holes; c) Laminating the surface of the stainless steel to be laminated to the substrate; d) Weld and seal and perform vacuum treatment.

2. The method for preparing thick stainless steel composite plates for bridges according to claim 1, characterized in that: In the single-blanket assembly process, the chamfer angle of the groove is 30-60°, and the groove height is 15-70 mm; a hole is drilled downward at 50-70 mm from the center of the short side edge of the substrate, and the hole depth is the groove height plus 15-40 mm; and a hole is drilled inward at 15-40 mm from the groove on the side wall of the short side of the substrate, and the hole depth is 50-70 mm, which is connected to the hole on the upper surface of the substrate to form an exhaust hole.

3. The method for preparing thick stainless steel composite plates for bridges according to claim 1, characterized in that: The welding sealing and vacuuming treatment specifically include: firstly, welding the connection between the base material and the covering material by gas shielded welding, pre-vacuuming the exhaust hole on one side, and sealing the exhaust hole when the vacuum value reaches below 20Pa; then, fully welding the remaining part of the groove by submerged arc welding, and vacuuming for the second time, so that the final vacuum value is not more than 10Pa, to obtain a composite billet of a single layer of stainless steel + a single layer of carbon steel in a high interface vacuum state.

4. The method for preparing thick stainless steel composite plates for bridges according to claim 1, characterized in that: The one-step heating and rolling specifically includes: The composite blank is heated to 1150-1250°C, and the upper surface temperature is 20-50°C higher than the lower surface temperature, and the total heating time is 9-18 min / cm; Single-stage rolling is adopted, and the reduction rate of multiple passes is no more than 5%, and the total reduction rate is 18% to 30%. When the composite billet is bitten, the sled coefficient is adjusted to a negative value. During the rolling process, only the descaling water on the lower side is turned on to descale the carbon steel on the lower surface.

5. The method for preparing thick stainless steel composite plates for bridges according to claim 1, characterized in that: The secondary heating, controlled rolling and controlled cooling treatment specifically include: After the first rolling, the composite billet is turned over to ensure that the stainless steel surface of the cladding material faces downward and the carbon steel surface of the substrate faces upward. The composite billet is heated to 1180-1250°C, and the lower surface temperature is 20-50°C higher than the upper surface temperature. The total heating time is 10-18 min / cm; Two-stage rolling is adopted, and the sled coefficient is adjusted to a positive value to reduce the buckling degree. The starting rolling temperature in the finishing rolling stage is not higher than 860℃, and the final rolling temperature is 720~850℃. During the rolling process, only the upper side descaling water is turned on and the lower side descaling is turned off. Control the thickness of the intermediate warm billet to be no less than 1.6 times the thickness of the finished product; Pre-straightening is carried out before entering the water, the water entry temperature is controlled at 700-800℃, the red-returning temperature is 380-640℃, and the cooling lower and upper water ratio is 1.0-1.

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6. The method for preparing thick stainless steel composite plates for bridges according to claim 1, characterized in that: The tempering comprises: turning over the composite plate so that the cladding stainless steel surface faces upward and the base carbon steel surface faces downward, the tempering temperature is 400-550° C., and the tempering time is 100-250 minutes.

7. The method for preparing thick stainless steel composite plates for bridges according to claim 1, characterized in that: The straightening includes: performing straightening treatment for more than 3 times, with the unevenness ≤ 5 mm / m, grinding and cleaning the surface of the composite plate to obtain a stainless steel composite plate product.

8. The method for preparing thick stainless steel composite plates for bridges according to claim 1, characterized in that: Before the single-assembly process is carried out, a base material blank and a cladding material blank are provided, the cladding material blank has the same width and length as the base material blank, and the iron oxide scale on the surface to be composited is removed.

9. The method for preparing thick stainless steel composite plates for bridges according to claim 1, characterized in that: The chemical composition mass percentage of the substrate is: C: ≤0.14%, Si: 0.15-0.50%, Mn: 1.00-1.70%, P≤0.025%, S≤0.020%, Nb: 0.010-0.060%, V: ≤0.050%, Ti: 0.006-0.020%, Alt: 0.015-0.050%, Cu: ≤0.40%, Cr: ≤0.60%, Ni: ≤0.50%, Mo: ≤0.30%, and the balance is Fe and a small amount of unavoidable impurities; The chemical composition mass percentage of the covering material is: C: ≤0.08%, Si: ≤1.50%, Mn: ≤2.00%, P≤0.045%, S≤0.030%, Cr: 16.00-26.00%, Ni: 8.00-22.00%, Mo: ≤4.00%, Ti: ≤0.40%, N≤0.16%, and the balance is Fe and a small amount of inevitable impurities.

10. A thick stainless steel composite plate for bridges, characterized in that: The thick-gauge stainless steel composite plate for bridges is prepared using the preparation method of any one of claims 1-9.

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