Single-sided stainless steel clad plate and method of making same

Abstract

This invention discloses a single-sided stainless steel composite plate and its preparation method. The method involves preparing a composite billet with carbon steel substrates on the top and bottom and a stainless steel composite in the middle; heating and two-stage controlled rolling of the obtained composite billet, followed by cooling; after cooling, placing the straightened composite plate at a temperature T... f -150℃~T f Two steel plates at +150℃ are stacked for cooling for 0.4 min / mm×t ± 5 min. After stacking, the composite plate is naturally cooled on a cooling bed. The composite plate is then trimmed and cut to length. The smaller composite plates, with the cladding layer facing upwards, are placed on a flattening machine for flattening. During transverse flattening, the flattening force F1 of the flattening machine is controlled as follows: F1 = 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 This process yields a single-sided stainless steel composite panel.

Description

Technical Field

[0001] This invention belongs to the field of steel material preparation technology, and relates to a single-sided stainless steel composite plate and its preparation method. Background Technology

[0002] With the continuous development of science and industry, ordinary alloys or single metals are no longer sufficient to meet the comprehensive performance requirements of materials in industrial development, leading to the emergence of composite plates. Stainless steel composite plates use carbon steel or low-alloy steel as the base layer and stainless steel as the cladding layer. Metallurgical bonding at the composite interface is achieved through methods such as explosive bonding and rolling bonding, resulting in resource conservation and cost reduction without compromising performance (mechanical strength, corrosion resistance, etc.). Stainless steel composite plates are widely used in industries such as petrochemicals, pressure vessels, power equipment, medical equipment, water conservancy, papermaking, and bridge construction.

[0003] In recent years, with the increasing demands for safety and long service life of steel bridges, the problem of rust and corrosion prevention in steel bridge structures has become increasingly prominent. Applying a corrosion-resistant protective material to the surface of the bridge steel, replacing the single steel plate, can achieve long-term corrosion protection that cannot be achieved through spraying. Therefore, stainless steel composite plates have become a relatively ideal choice.

[0004] Existing stainless steel composite panels suffer from problems such as difficulty in controlling panel shape and poor uniformity. Summary of the Invention

[0005] The purpose of this invention is to provide a single-sided stainless steel composite plate and its preparation method, wherein the stainless steel composite plate has excellent plate shape and uniformity.

[0006] To achieve the above-mentioned objective, one embodiment of the present invention provides a method for preparing a single-sided stainless steel composite plate, which includes three steps performed sequentially: composite billet preparation, composite billet rolling, and composite plate separation and straightening.

[0007] In the composite billet preparation step, a composite billet with carbon steel substrates on the top and bottom and stainless steel composite material in the middle is prepared.

[0008] The composite billet rolling step includes:

[0009] The resulting composite billet is heated to a homogenization temperature of 1150~1220℃, and the total heating time is ≥1.2×t min / mm, where t is the thickness of the composite billet.

[0010] The rolling process is controlled by two stages: roughing and finishing. In the roughing stage, the final rolling temperature is ≥980℃, and the roughing stage ends when the thickness of the intermediate billet is 2.5 to 3.5 times the target thickness of the composite plate. After that, the billet is allowed to cool down by water. When the surface temperature of the intermediate billet drops below 860℃, the finishing stage begins, and the final rolling temperature of the finishing stage is ≥780℃.

[0011] After rolling, it enters an ultra-fast cooling system for cooling;

[0012] After the composite panel leaves the ultra-fast cooling system, it directly enters the straightening machine for straightening. The straightened composite panel is then placed at a temperature of T. f -150℃~T f Two steel plates at +150℃ were subjected to stack cooling between them for a time of 0.4 min / mm×t ± 5 min; after stack cooling, the composite plate was naturally cooled on a cooling bed; where T f =550+30[Si]-20[Mn]+15[Cr]-15[Ni]+10[Mo], where [Si], [Mn], [Mo], [Cr], and [Ni] are 100 times the mass percentage of each element in the substrate;

[0013] The composite plate separation and straightening step includes:

[0014] Cut the four sides of the large composite board to remove the part other than the seal strip, and separate the large composite board into two small composite board panels.

[0015] The composite board panels, after being cut to length, are placed with the cladding layer facing upwards on a flattening machine for flattening. When flattening laterally, the flattening force of the flattening machine is controlled as F1 = 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 by a×b×c longitudinal×σ 纵 / (d+c 纵 ); where a is the width of the composite panel, b is the thickness of the composite panel, and c 横 The flatness per meter in the transverse direction of the composite panel is expressed in mm, c. 纵 σ represents the unevenness per meter of the composite panel in the longitudinal direction, expressed 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 longitudinal tensile yield strength of the composite panel slab, and ν is Poisson's ratio.

[0016] Finally, the composite panel slabs are cold-straightened to obtain the finished single-sided stainless steel composite panel.

[0017] Preferably, the composite billet rolling step specifically includes:

[0018] When heating the obtained composite billet, a five-stage heating process is adopted, consisting of preheating, first heating, second heating, third heating, and homogenization. The preheating temperature is ≤850℃, and the residence time is (0.45~0.55)t min / mm. The first heating temperature is 1030~1090℃, and the residence time is (0.35~0.45)t min / mm. The second heating temperature is 1100~1160℃, and the residence time is (0.25~0.35)t min / mm. The third heating temperature is 1140~1180℃, and the residence time is (0.15~0.25)t min / mm. The homogenization temperature is 1170~1210℃, and the residence time is (0.10~0.20)t min / mm.

[0019] In the "two-stage controlled rolling process of roughing and finishing", during the roughing stage, the first pass uses longitudinal rolling with a rolling reduction of ≥46mm; the second pass begins transverse rolling until the nth pass rolls the composite billet to the target width of the final composite plate, with a rolling reduction of ≥25mm; the (n+1)th pass begins longitudinal rolling, ending when the thickness of the intermediate billet is 2.5 to 3.5 times the target thickness of the composite plate, with a rolling reduction of ≥30mm; throughout the roughing stage, the rolling temperature of the first pass is ≥1060℃, the initial rolling temperature of the remaining passes is ≤1050℃, and the final rolling temperature is ≥1000℃; after the roughing stage, the billet is allowed to cool down by water, and when the surface temperature of the intermediate billet drops below 840℃, the finishing stage begins, with an initial rolling temperature of 810℃ to 840℃ and a final rolling temperature of ≥780℃.

[0020] Preferably, the composite billet rolling step specifically includes:

[0021] When heating the obtained composite blank, the holding time in the heat soaking section is 30 min to 50 min;

[0022] When using a two-stage controlled rolling process of roughing and finishing, the initial rolling temperature in the roughing stage is ≤1050℃, and the final rolling temperature is ≥1000℃. Rolling is performed first in the transverse direction and then in the longitudinal direction. During the longitudinal rolling, at least one pass requires a reduction of ≥35mm. The total reduction in roughing is 40~60%. The roughing stage ends when the intermediate billet thickness is 2.5~3.5 times the target thickness of the composite plate. Afterward, the billet is allowed to cool to a suitable temperature, during which water cooling is applied. When the surface temperature of the intermediate billet drops below 830℃, the finishing stage begins. The final rolling temperature in the finishing stage is ≥800℃, and the total reduction in finishing is 55~75%.

[0023] Preferably, the composite billet rolling step specifically includes:

[0024] In the section "cooling after rolling in an ultra-rapid cooling system", after rolling, the composite plate enters the ultra-rapid cooling system for intermittent cooling.

[0025] The ultra-fast cooling system has 24 sets of cooling manifolds arranged along the roller conveyor. The cooling distance of each set of cooling manifolds is 1m. When the composite board passes through the ultra-fast cooling system, the opening and closing status of all 24 sets of cooling manifolds is controlled in a manner that N sets of cooling manifolds are opened and then M sets of cooling manifolds are not opened. The cooling water pressure is 0.2MPa, the cooling rate is 3~15℃ / s, and the final cooling temperature is 380~450℃. N takes the value of 2, 3 or 4, and M takes the value of 2, 3 or 4.

[0026] Preferably, the composite billet rolling step specifically includes:

[0027] In the section "cooling after rolling", after rolling, the composite plate enters the ultra-fast cooling system for cooling. The initial cooling temperature is ≥730℃, the cooling rate is 6~20℃ / s, and the final cooling temperature is 480~590℃. After leaving the ultra-fast cooling system, the composite plate directly enters the straightening machine for straightening 1~3 times. After straightening, it is naturally cooled on the cooling bed. When the surface temperature drops below 200℃, it is cold straightened using a cold straightening machine.

[0028] The specific steps for preparing the composite preform include:

[0029] Prepare two carbon steel billets with thickness T1, length L1, and width W1 as the base material for forming the base layer of the composite plate; and prepare two stainless steel billets with thickness T2, length L2, and width W2 as the composite material for forming the cladding layer of the composite plate; L2 < L1, W2 < W1.

[0030] At least one surface of each of the two substrates and the two composites is surface treated;

[0031] Apply a release agent to one surface of a composite material;

[0032] The preforms are assembled in the following stacking order: substrate, composite, composite, and substrate; wherein the composite is placed in the center relative to the substrate, the surfaces of the substrate and composite that come into contact with each other are the surfaces that have undergone the aforementioned surface treatment, and the surface coated with the release agent faces the other composite.

[0033] Prepare four sealing strips with a width of W3, W3=2T2-1~2mm. Attach the sealing strips to the four sides of the two composite materials. Perform gas shielded welding between adjacent sealing strips and between the sealing strips and the substrate, so that the two substrates and the sealing strips form a whole, and obtain the composite blank base blank.

[0034] A round hole is machined on the seal at the groove on the side of the composite billet base, and a seamless steel pipe is welded at the round hole;

[0035] The grooves on the four sides of the composite billet base are welded together.

[0036] A vacuum pump is used to evacuate the composite billet through the seamless steel pipe, with a vacuum level ≤10. -1 The pressure is increased to Pa, then maintained for more than 4 hours; finally, the seamless steel pipe is sealed.

[0037] Preferably, the step "surface treating at least one surface of each of the two substrates and the two composites" includes:

[0038] One surface of each composite material is ground and polished to remove the surface oxide scale; and,

[0039] According to the complementary relative shapes, one surface of the two substrates is milled to form a transversely inclined surface with length L11=L1 and width W11>W1, and the substrate is a non-uniform thickness blank with varying thickness in the transverse direction; or the surface is milled to form a longitudinally inclined surface with length L11>L1 and width W11=W1, and the substrate is a non-uniform thickness blank with varying thickness in the longitudinal direction.

[0040] Preferably, the step "surface treating at least one surface of each of the two substrates and the two composites" includes:

[0041] According to the complementary relative shapes, one surface of two substrates is milled to form an irregular concave-convex surface containing n planes connected sequentially in the transverse direction, and the substrate is a non-uniform thickness blank with non-monotonic thickness variation in the transverse direction. The length L12 of the irregular concave-convex surface is L1 and the total width W12 is greater than W1; or, the surface is milled to form an irregular concave-convex surface containing n planes connected sequentially in the longitudinal direction, and the substrate is a non-uniform thickness blank with non-monotonic thickness variation in the longitudinal direction. The total length L12 of the irregular concave-convex surface is greater than L1 and the width W12 is W1; n≥2;

[0042] One surface of each composite material is polished to remove the surface oxide scale; then each composite material is bent to match the corresponding irregular uneven surface.

[0043] To achieve the above-mentioned objective, one embodiment of the present invention provides a single-sided stainless steel composite plate, characterized in that the composite plate is prepared using the aforementioned preparation method.

[0044] Preferably, the composite plate has an impact energy of ≥120J at 0℃, ≥120J at -20℃, and ≥120J at -40℃.

[0045] The unevenness of the composite board is ≤3mm / m.

[0046] Preferably, the Vickers hardness difference of the base layer of the composite board is ≤10 in the thickness direction, the strength difference between the head, middle and tail is ≤40MPa, and the strength difference at all parts of the whole board is ≤40MPa.

[0047] Compared with the prior art, the beneficial effects of the present invention are as follows: the composite board prepared by the preparation method of the present invention has the advantages of excellent surface quality, excellent board shape, and excellent uniformity. For example, it does not have obvious surface defects such as pits and side scratches that exist in existing composite boards. For example, the unevenness of the composite board is ≤3mm / m. Furthermore, the Vickers hardness difference in the thickness direction of the base layer of the composite board is ≤10, the strength difference at the head, middle and tail is ≤40MPa, and the strength difference at all parts of the whole board is ≤40MPa. Attached Figure Description

[0048] 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.

[0049] Figure 1a This is a cross-sectional schematic diagram of a steel billet according to the first embodiment of the billet surface treatment step in this invention;

[0050] Figure 1b This is a schematic diagram of the transverse cross section of a steel billet according to the second embodiment of the billet surface treatment step in this invention, wherein the surface shape change after surface treatment is indicated by a dashed line.

[0051] Figure 1c This is a longitudinal cross-sectional view of a steel billet according to the third embodiment of the billet surface treatment step in this invention, wherein the surface shape change after surface treatment is indicated by a dashed line.

[0052] Figure 1d This is a schematic diagram of the transverse cross section of a steel billet according to the fourth embodiment of the billet surface treatment step in this invention, and it shows the changes in surface shape before (A) and after (B) the surface treatment.

[0053] Figure 1e This is a longitudinal cross-sectional schematic diagram of a steel billet according to the fifth embodiment of the billet surface treatment step in this invention, and it illustrates the changes in surface shape before (A) and after (B) the surface treatment.

[0054] Figure 2a It corresponds to Figure 1a A schematic diagram of the cross-section of the composite blank;

[0055] Figure 2b It corresponds to Figure 1b A schematic diagram of the transverse cross section of the composite billet;

[0056] Figure 2c It corresponds to Figure 1c A schematic diagram of the longitudinal section of the composite billet;

[0057] Figure 2d It corresponds to Figure 1d A schematic diagram of the transverse cross section of the composite billet;

[0058] Figure 2e It corresponds to Figure 1e A schematic diagram of the longitudinal section of the composite billet;

[0059] Figure 3 This is a flowchart of the composite billet rolling process and the composite plate separation and straightening process of the present invention.

[0060] Figure 4a yes Figure 2a A schematic diagram of the cross-section of two composite plates rolled from a composite billet;

[0061] Figure 4b yes Figure 2b A schematic diagram of the transverse cross section of two composite plates rolled from a composite billet;

[0062] Figure 4c yes Figure 2c A schematic diagram of the longitudinal section of two composite plates rolled from a composite billet;

[0063] Figure 4d yes Figure 2d A schematic diagram of the transverse cross section of two composite plates rolled from a composite billet;

[0064] Figure 4e yes Figure 2e A schematic diagram of the longitudinal section of two composite plates rolled from a composite billet. Detailed Implementation

[0065] This invention provides a method for preparing a single-sided stainless steel composite plate, and a composite plate prepared based on this method.

[0066] Compared with existing technologies, such as explosive bonding, non-vacuum composite preparation, and vacuum electron beam welding mentioned in the background art, the composite plate prepared by the method of the present invention has advantages such as superior surface quality, superior plate shape, and excellent uniformity.

[0067] Specifically, the preparation method includes three main steps: composite billet preparation, composite billet rolling, and composite plate separation and straightening.

[0068] The overall steps for preparing the composite preform include the following sub-steps:

[0069] Prepare two carbon steel billets with thickness T1, length L1, and width W1 as base materials; and prepare two stainless steel billets with thickness T2, length L2, and width W2 as composite materials.

[0070] At least one surface of each of the two substrates and the two composites is surface treated;

[0071] Apply a release agent to one surface of a composite material;

[0072] The blanks are assembled in the following order: substrate, composite material, composite material, substrate.

[0073] Prepare four sealing strips with a width of W3, W3=2T2-1~2mm. Attach the sealing strips to the four sides of the two composite materials. Perform gas shielded welding between adjacent sealing strips and between the sealing strips and the substrate, so that the two substrates and the sealing strips form a whole, and obtain the composite blank base blank.

[0074] A round hole is machined on the seal at the groove on the side of the composite billet base, and a seamless steel pipe is welded at the round hole;

[0075] The grooves on the four sides of the composite billet base are welded together.

[0076] A vacuum pump is used to evacuate the composite billet through the seamless steel pipe, with a vacuum level ≤10. -1 The pressure is increased to Pa, then maintained for more than 4 hours; finally, the seamless steel pipe is sealed.

[0077] Furthermore, the above steps are explained in detail below.

[0078] The steps “Prepare two carbon steel billets with length L1 and width W1 as base materials; and prepare two stainless steel billets with length L2 and width W2 as composite materials”, which are the billet preparation steps.

[0079] The carbon steel billet used as the base material has a thickness of T1, a length of L1, and a width of W1, which is a rectangular billet. Similarly, the stainless steel billet used as the composite material has a thickness of T2, a length of L2, and a width of W2, which is also a rectangular billet. Furthermore, L2 < L1 and W2 < W1, meaning that the length and width dimensions of the composite material are smaller than those of the base material.

[0080] As a preferred embodiment, the surface oxide scale indentation depth and surface pit depth of the carbon steel billet are both ≤0.3mm, and the flatness is ≤3mm / m; the surface of the stainless steel billet is free of scratches, and the flatness is ≤2mm / m. This avoids billets with obvious surface defects or shape defects from entering the composite plate production line.

[0081] Next, regarding the step of "surface treatment of at least one surface of each of the two substrates and the two composite materials", that is, the blank surface treatment step. The present invention provides five preferred embodiments, and these five embodiments will be introduced separately below.

[0082] <The first embodiment of the blank surface treatment step>

[0083] In this embodiment, one surface of each substrate and each composite material is ground and polished to remove the surface oxide scale and expose the metallic luster.

[0084] Refer Figure 1a As shown, for example, for the surface p1a of the substrate 11a, a grinding machine, a belt grinder or a milling machine is used for grinding and polishing to remove the surface oxide scale and expose the metallic luster; similarly, for the surface p2a of the prepared substrate 12a, a grinding machine, a belt grinder or a milling machine is used for grinding and polishing to remove the surface oxide scale and expose the metallic luster.

[0085] For the surface p3a of the prepared composite material 21a, a wire wheel is used for grinding and polishing to remove the surface oxide scale and expose the metallic luster; similarly, for the surface p4a of the prepared composite material 22a, a wire wheel is used for grinding and polishing to remove the surface oxide scale and expose the metallic luster.

[0086] Combined with the following text, it can be seen that when assembling the blank, the surface treated (in this embodiment, grinding and polishing) is used as the surface where the substrate and the composite material contact each other. For example, the surface p1a and the surface p3a contact each other, and the surface p4a and the surface p2a contact each other, so as to ensure the interface bonding quality.

[0087] <The second embodiment of the blank surface treatment step>

[0088] In this embodiment, the same as the foregoing first embodiment, one surface of each composite material (such as Figure 1b the surfaces p3b and p4b) is ground and polished to remove the surface oxide scale and expose the metallic luster, which will not be elaborated.

[0089] In this embodiment, different from the foregoing first embodiment, it is the surface treatment of the substrate:

[0090] Refer Figure 1b , the surface p1b of the substrate 11b is milled to process the surface p1b into a surface p1b0, which is a transverse inclined surface with a length L11 = L1 and a width W11 > W1. Correspondingly, the substrate 11b is processed into a non-uniform thickness blank with a gradually changing thickness in the transverse direction (that is, the width direction), that is, after the substrate 11b is milled, the height gradually increases from one side to the other side in the width direction.

[0091] Similarly, the surface p2b of the base material 12b is milled to process the surface p2b into a surface p2b0, which is a laterally inclined surface with a length L11 = L1 and a width W11 > W1. Correspondingly, the base material 12b is processed into a non-uniform-thickness blank with a gradually changing thickness in the lateral direction.

[0092] Among them, when milling the surface p2b of the base material 12b and the surface p1b of the base material 11b, it is carried out in a manner of relative shape complementarity, that is, the processed surfaces p2b0 and p1b0 are shape-complementary when facing each other. For example, the lateral inclination angle of the surface p2b0 (such as the angle with the original surface p2b) is equal to the lateral inclination angle of the surface p1b0 (such as the angle with the original surface p1b), thereby ensuring that the upper and lower surfaces of the composite blank are parallel when assembling the blanks later.

[0093] It can be understood that through the above milling process, the surface oxide scale on the surface p1b of the base material 11b and the surface p2b of the base material 12b can also be removed, revealing a metallic luster.

[0094] Combined with the following text, when assembling the blanks, by using the surfaces after surface treatment (milling in this embodiment) as the surfaces where the base material and the composite material contact each other. For example, the surface p1b0 and the surface p3b contact each other, and the surface p4b and the surface p2b0 contact each other. Similarly, it can ensure the interface bonding quality as in the aforementioned first embodiment, and this embodiment can further be used to prepare a non-uniform-thickness composite board with a gradually changing thickness in the lateral direction to expand the applicable scenarios and scope of the composite board.

[0095] <The third embodiment of the blank surface treatment step>

[0096] This embodiment is basically the same as the aforementioned second embodiment (including the surface treatment of the surfaces p3c and p4c), with the only difference being that: in the second embodiment, the thickness of the base material gradually changes in the lateral direction, while in this embodiment, the thickness of the base material gradually changes in the longitudinal direction (i.e., the length direction). The following introduces the differences, and for the other similarities, refer to the introduction of the second embodiment and will not be elaborated here.

[0097] Refer to Figure 1c , the surface p1c of the base material 11c is milled to process the surface p1c into a surface p1c0, which is a longitudinally inclined surface with a length L11 > L1 and a width W11 = W1. Correspondingly, the base material 11c is processed into a non-uniform-thickness blank with a gradually changing thickness in the longitudinal direction.

[0098] Similarly, the surface p2c of the base material 12c is milled to process the surface p2c into a surface p2c0, which is a longitudinally inclined surface with a length L11 > L1 and a width W11 = W1. Correspondingly, the base material 12c is processed into a non-uniform thickness blank with a gradually changing thickness in the longitudinal direction.

[0099] Among them, when milling the surface p2c of the base material 12c and the surface p1c of the base material 11c, it is carried out in a way that the relative shapes are complementary, that is, the processed surfaces p2c0 and p1c0 are complementary in shape when facing each other. For example, the longitudinal inclination angle of the surface p2c0 (such as the angle with the original surface p2c) is equal to the longitudinal inclination angle of the surface p1c0 (such as the angle with the original surface p1c), so as to ensure that the upper and lower surfaces of the composite blank are parallel during subsequent blank assembly.

[0100] It can be understood that through the above milling process, the surface oxide scale on the surface p1c of the base material 11c and the surface p2c of the base material 12c can also be removed, revealing a metallic luster.

[0101] <The fourth implementation mode of the blank surface treatment step>

[0102] In this implementation mode, one surface of each base material is milled to process the said surface into an irregular concave-convex surface containing n planes connected in sequence along the transverse direction, and the base material is a non-uniform thickness blank with a non-monotonic change in thickness in the transverse direction, and the length L12 of the irregular surface = L1 and the total width W12 > W1.

[0103] For example, refer Figure 1d , the surface p1d of the base material 11d is milled to process the surface p1d from Figure 1d the horizontal surface in (A) into Figure 1d the irregular concave-convex surface p1d0 shown in (B). The irregular concave-convex surface p1d0 specifically contains n planes connected in sequence along the transverse direction, where n ≥ 2, and is exemplified as 8 planes in the figure. It can be seen from the figure that the 1st, 3rd, 5th, and 7th of these 8 planes in the direction from the left side to the right side of the figure are all transversely inclined surfaces, while the 2nd, 4th, 6th, and 8th are all horizontal planes. Of course, this is only an example, and it can also be implemented with n taking other numbers, or only containing transversely inclined surfaces without horizontal planes, etc.

[0104] Refer Figure 1d , through the milling process of the surface p1d, the base material 11d is processed into a non-uniform thickness blank with a non-monotonic change in thickness in the transverse direction.

[0105] The length L12 of the irregular concave-convex surface p1d0 is L1, that is, it does not change due to milling; and the total width W12 of the irregular concave-convex surface p1d0 is greater than W1. It can be understood that the total width W12 is the sum of the widths of n planes.

[0106] Correspondingly, refer to Figure 1d , the surface p2d of the substrate 12d is also milled, and the surface p2d is changed from Figure 1d the horizontal surface in (A) to Figure 1d the irregular concave-convex surface p2d0 shown in (B). Among them, when milling the surface p2d of the substrate 12d and the surface p1d of the substrate 11d, it is carried out in a complementary relative shape manner, that is, the processed surface p2d0 and the surface p1d0 are complementary in shape when they face each other.

[0107] According to the complementary relative shape, the irregular concave-convex surface p2d0 also specifically includes n planes connected in sequence along the transverse direction, which is exemplified as 8 planes in the figure. The length L12 of the irregular concave-convex surface p2d0 is L1, that is, it does not change due to milling; and the total width W12 of the irregular concave-convex surface p2d0 is greater than W1. It can be understood that the total width W12 is the sum of the widths of n planes of the irregular concave-convex surface p2d0.

[0108] Refer to Figure 1d , through the milling of the surface p2d, the substrate 12d is processed into a non-uniform thickness blank with non-monotonic thickness change in the transverse direction. Based on the complementary relative shape of the irregular concave-convex surface p2d0 and the irregular concave-convex surface p1d0, if the milled substrates 12d and 11d are placed opposite to each other, the sum of the thicknesses at each place is constant. Thus, when assembling the blanks later, the upper and lower surfaces of the composite blank are parallel.

[0109] The above introduces the surface treatment of two substrates in this embodiment. Next, the surface treatment of two composite materials will be introduced.

[0110] In this embodiment, for the surface p3d of the prepared composite material 21d, a wire wheel is used for grinding and polishing to remove the surface oxide scale and expose the metallic luster; similarly, for the surface p4d of the prepared composite material 22d, a wire wheel is used for grinding and polishing to remove the surface oxide scale and expose the metallic luster.

[0111] Furthermore, matching the surface shapes of the base materials 11d and 12d, after removing the surface scale, in this embodiment, each composite material is bent so that each composite material matches the corresponding irregular concave-convex surface. For example, for the composite material 21d, it is bent to match the corresponding irregular concave-convex surface p1d0 to facilitate the fitting contact during subsequent blank assembly; for another example, for the composite material 22d, it is bent to match the corresponding irregular concave-convex surface p2d0 to facilitate the fitting contact during subsequent blank assembly.

[0112] The surface treatment of this embodiment can ensure the interface bonding quality as in the previous first embodiment, and can further be used to prepare non-uniform-thickness composite plates with non-monotonic changes in transverse thickness, so as to expand the applicable scenarios and scope of the composite plates, enhance the corrosion resistance compared with existing steel plates, and avoid frequent welding and dissimilar welding between composite plates of different thicknesses.

[0113] <The fifth embodiment of the blank surface treatment step>

[0114] The difference between this embodiment and the previous fourth embodiment is that: in the fourth embodiment, the thickness of the base material changes non-monotonically in the transverse direction, while in this embodiment, the thickness of the base material changes non-monotonically in the longitudinal direction.

[0115] For example, referring to Figure 1e , the surface p1e of the base material 11e is milled, and the surface p1e is processed from the Figure 1e horizontal surface in (A) to the Figure 1e irregular concave-convex surface p1e0 shown in (B). The irregular concave-convex surface p1e0 specifically includes n planes connected in sequence along the longitudinal direction, where n≥2, and is exemplified as 8 planes in the figure. It can be seen from the figure that the 1st, 3rd, 5th, and 7th of these 8 planes from the left to the right in the figure are longitudinally inclined surfaces, while the 2nd, 4th, 6th, and 8th are horizontal planes. Of course, this is only an example, and it can also be implemented with other values of n, or only including longitudinally inclined surfaces without horizontal planes, etc.

[0116] Referring to Figure 1e , through the milling of the surface p1e, the base material 11e is processed into a non-uniform-thickness blank with non-monotonic changes in longitudinal thickness.

[0117] The width W12 of the irregular concave-convex surface p1e0 = W1, that is, it does not change due to the milling process; and the total length L12 of the irregular concave-convex surface p1e0 > L1. It can be understood that the total length L12 is the sum of the lengths of n planes.

[0118] Correspondingly, referring to Figure 1e , the surface p2e of the base material 12e is also milled, and the surface p2e is processed from the Figure 1eThe horizontal surface in (A) is processed into Figure 1e the irregular concave-convex surface p2e0 shown in (B). When milling the surfaces p2e of the substrate 12e and the surface p1e of the substrate 11e, it is carried out in a manner of relative shape complementarity, that is, when the processed surfaces p2e0 and the surface p1e0 face each other, they are shape-complementary.

[0119] According to the relative shape complementarity, the irregular concave-convex surface p2e0 also specifically includes n planes connected in sequence along the longitudinal direction, which is exemplified as 8 planes in the figure. The width W12 of the irregular concave-convex surface p2e0 = W1, and the total length L12 > L1.

[0120] Refer Figure 1e , through the milling of the surface p2e, the substrate 12e is processed into a non-uniform-thickness blank with non-monotonic thickness change in the longitudinal direction. Based on the relative shape complementarity of the irregular concave-convex surface p2e0 and the irregular concave-convex surface p1e0, if the milled substrates 12e and 11e are placed opposite to each other, the sum of the thicknesses at each place is constant. Thus, when assembling the blanks subsequently, the upper and lower surfaces of the composite blank are parallel.

[0121] The surface treatment of the two substrates in this embodiment is introduced above. Next, the surface treatment of the two composite materials will be introduced.

[0122] In this embodiment, for the surface p3e of the prepared composite material 21e, a wire wheel is used for grinding and polishing to remove the surface scale and expose the metallic luster; similarly, for the surface p4e of the prepared composite material 22e, a wire wheel is used for grinding and polishing to remove the surface scale and expose the metallic luster.

[0123] And further, matching the surface shapes of the substrates 11e and 12e, after removing the surface scale, each composite material in this embodiment is also bent so that each composite material matches the corresponding irregular concave-convex surface. For example, for the composite material 21e, it is bent to match the corresponding irregular concave-convex surface p1e0 for easy fitting contact during subsequent blank assembly; for another example, for the composite material 22e, it is bent to match the corresponding irregular concave-convex surface p2e0 for easy fitting contact during subsequent blank assembly.

[0124] Same as the aforementioned fourth embodiment, this embodiment can also improve the applicable scenarios and scope of the composite board, enhance the corrosion resistance compared with the existing steel plate, and avoid frequent welding and dissimilar welding between composite boards with different thicknesses.

[0125] The above describes five preferred embodiments of the surface treatment step in the composite blank preparation process. Although only one surface of the substrate and the composite material is described, it should be noted that, regardless of which of the five embodiments is described, the oxide scale can be further removed from the other surfaces of the substrate and the composite material. Although this additional oxide scale removal is not necessary to achieve the technical effect of the present invention, it may be more advantageous. For example, in addition to removing the oxide scale from the surface of the substrate facing the composite material, the oxide scale can also be removed from the surface of the substrate facing away from the composite material (i.e., the surface of the composite board).

[0126] The other steps in the composite preform preparation process will be described below.

[0127] The step "apply release agent to one surface of a composite material" is also known as the release agent application step.

[0128] As mentioned above, the surface treatment of the composite material in the previous billet surface treatment steps, such as grinding and polishing, is performed on the surface that will be in contact with the substrate during billet assembly in order to ensure the interface bonding quality of the composite plate. The purpose of this step of applying the release agent is to prevent the surfaces of the composite material that are in contact with each other during billet assembly from bonding together in the subsequent composite billet rolling step, which would make them difficult to separate in the end.

[0129] Based on this, a release agent is applied to either of the two composite materials. If, in the previous blank surface treatment step, one surface of the selected composite material was treated while the other was not, then in this release agent application step, the release agent is applied to the "untreated" surface. However, if, as mentioned above, both surfaces of the selected composite material were treated in the previous blank surface treatment step, then in this release agent application step, the release agent is applied to the surface that is planned to face the other composite material during blank assembly.

[0130] For example, with Figure 1a For example, a release agent can be applied to the surface p6a of composite 22a or the surface p5a of composite 21a.

[0131] Regarding the separating agent, two preferred embodiments are provided here, which are described below.

[0132] <First Implementation Method of the Separating Agent>

[0133] In this embodiment, the separating agent is a coating liquid containing silicon oxide and magnesium oxide, wherein the mass ratio of silicon oxide to magnesium oxide is 3:1. The separating agent in this embodiment can achieve a good separating effect, ensuring the separation of the two subsequent composite board panels.

[0134] When applying the release agent to the surface of the composite material, the amount of release agent applied is 20 μmg / m³. 2 That is, the weight of the release agent per unit area on the surface of the composite material is 20 μmg. Wherein, y is the ratio of the thickness of the composite billet obtained in the composite billet preparation step to the thickness of the composite plate subsequently rolled, which is also called the composite billet rolling compression ratio.

[0135] Furthermore, based on this embodiment, after the release agent is applied and before subsequent preform assembly, the composite material coated with the release agent is placed in a trolley furnace for heating and drying at a temperature of 340~360℃ for 35~45 minutes.

[0136] <Second Implementation Method of the Separating Agent>

[0137] In this embodiment, the composition of the release agent by weight is: 25-35% silicon nitride, 5-10% thermosetting amino resin, and 55-70% water. Compared with existing release agents, and even compared with the first embodiment of the aforementioned release agent, the release agent of this embodiment not only achieves a good release effect, ensuring the separation of the two subsequent composite board panels, but also features strong chemical stability and high temperature and thermal shock resistance of the active ingredient silicon nitride. The thermosetting amino resin, as the adhesive, can be cured at low temperatures, is non-toxic, and achieves strong adhesion with a small dosage. Therefore, the overall cost is low, the operation is simple, and the release and adhesion effects are good.

[0138] Hereinafter, a preferred preparation method for the release agent is provided, comprising: first, placing 5-10% silicon nitride (by weight) in a beaker or other container, then adding 15-25% water and stirring; after the silicon nitride is free of particles and bubbles, adding 2-3% thermosetting amino resin and continuing to stir; when it becomes viscous, adding the remaining silicon nitride and water, stirring for 3-5 minutes, and then adding the remaining thermosetting amino resin; when it becomes viscous, the release agent is prepared.

[0139] When the release agent is applied to the surface of the composite material, the thickness of the release agent is 0.2~0.5mm.

[0140] Furthermore, based on this embodiment, after the release agent is applied and before subsequent preform assembly, the composite material coated with the release agent is heated and dried at a temperature of 100~250℃ for 20~40 minutes.

[0141] Next, after completing the step of applying the release agent, the step of "assembling the blank according to the stacking order of substrate, composite material, composite material, and substrate" will be introduced.

[0142] This step, "assembling the blank according to the stacking order of substrate, composite, composite, and substrate," is also known as the blank assembly step. In addition to following the stacking order of substrate, composite, composite, and substrate, the following conditions must also be met:

[0143] 1) The surfaces of the substrate and composite material that come into contact with each other are all surfaces that have undergone the aforementioned surface treatment; for example, in the first embodiment of the blank surface treatment step described above, the reference... Figure 2a The surfaces p2a of the substrate 12a and p4a of the composite 22a are in contact with each other, and the surfaces p1a of the substrate 11a and p3a of the composite 21a are in contact with each other; in the second embodiment of the blank surface treatment step described above, refer to Figure 2b Surfaces p1b0 and p3b are in contact with each other, and surfaces p4b and p2b0 are in contact with each other; in the third embodiment of the blank surface treatment steps described above, refer to Figure 2c The surfaces p1c of the substrate 11c and p3c of the composite 21c are in contact with each other, and the surfaces p2c of the substrate 12c and p4c of the composite 22c are in contact with each other; in the fourth embodiment of the blank surface treatment step described above, refer to Figure 2d The irregular uneven surface p1d0 is in contact with the surface p3d of the composite material 21d, and the irregular uneven surface p2d0 is in contact with the surface p4d of the composite material 22d; in the fifth embodiment of the blank surface treatment step described above, refer to Figure 2e The irregular uneven surface p1e0 is in contact with the surface p3e of the composite material 21e, and the irregular uneven surface p2e0 is in contact with the surface p4e of the composite material 22e.

[0144] 2) The surface coated with the release agent faces the other composite material; for example, refer to Figure 2a One of surfaces p6a and p5a is coated with release agent 30a; Figure 2b One of surfaces p6b and p5b is coated with release agent 30b; Figure 2c One of surfaces p6c ​​and p5c is coated with a release agent 30c; (Refer to...) Figure 2d One of the surfaces p6d and p5d is coated with a 30d release agent; Figure 2e One of the surfaces p6e and p5e is coated with release agent 30e;

[0145] 3) The composite material is placed in the center relative to the substrate. As mentioned earlier, the length and width of the composite material are smaller than those of the substrate, L2 < L1, W2 < W1. During the assembly process, the distances from the two sides of the composite material in the transverse direction to the corresponding two sides of the substrate are equal, and the distances from the two sides of the composite material in the longitudinal direction to the corresponding two sides of the substrate are also equal.

[0146] The third point here will be explained below for each of the five implementation methods of the blank surface treatment steps described above. Furthermore, since the composite blanks are roughly symmetrically arranged vertically, only one set of base material + composite material in the composite blank will be used as an example, such as the set on top.

[0147] Regarding the first embodiment of the blank surface treatment steps described above, see... Figure 2a The length L1 and width W1 of surface p1a of substrate 11a, the length L2 and width W2 of surface p3a of composite material 21a, L2=L1-L0, W2=W1-W0, and the preferred values ​​of L0 and W0 are 90~150mm respectively; in the assembled state, the distance from the side edge of composite material 21a in the transverse direction (corresponding to the long side edge of surface p3a) to the side edge of substrate 11a in the transverse direction (corresponding to the long side edge of surface p1a) is half of W0, and the distance from the side edge of composite material 21a in the longitudinal direction (corresponding to the short side edge of surface p3a) to the side edge of substrate 11a in the longitudinal direction (corresponding to the short side edge of surface p1a) is half of L0.

[0148] Regarding the second implementation method of the blank surface treatment step described above, see... Figure 2b The length L11 and width W11 of the surface p1b0 of the substrate 11b, and the length L2 and width W2 of the surface p3b of the composite material 21b, where L2 = L11 - L0 and W2 = W11 - W0, and the preferred values ​​of L0 and W0 are 90~150mm respectively; in the preform state, the distance from the side edge of the composite material 21b in the transverse direction (corresponding to the long side edge of the surface p3b) to the side edge of the substrate 11b in the transverse direction (corresponding to the long side edge of the surface p1b0) is half of W0, and the distance from the side edge of the composite material 21b in the longitudinal direction (corresponding to the short side edge of the surface p3b) to the side edge of the substrate 11b in the longitudinal direction (corresponding to the short side edge of the surface p1b0) is half of L0.

[0149] Regarding the third implementation method of the blank surface treatment step described above, see... Figure 2c The length L11 and width W11 of the surface p1c0 of the substrate 11c, and the length L2 and width W2 of the surface p3c of the composite material 21c, where L2 = L11 - L0 and W2 = W11 - W0, and the preferred values ​​of L0 and W0 are 90~150mm respectively; in the preform state, the distance from the side edge of the composite material 21c in the transverse direction (corresponding to the long side edge of the surface p3c) to the side edge of the substrate 11c in the transverse direction (corresponding to the long side edge of the surface p1c0) is half of W0, and the distance from the side edge of the composite material 21c in the longitudinal direction (corresponding to the short side edge of the surface p3c) to the side edge of the substrate 11c in the longitudinal direction (corresponding to the short side edge of the surface p1c0) is half of L0.

[0150] Regarding the fourth implementation method of the blank surface treatment step described above, see... Figure 2dThe length L12 and width W12 of the irregular uneven surface p1d0 of the substrate 11d, and the length L2 and width W2 of the surface p3d of the composite material 21d, where L2 = L12 - L0 and W2 = W12 - W0, and the preferred values ​​of L0 and W0 are 90~150mm respectively; in the assembled state, the distance from the side edge of the composite material 21d in the transverse direction (corresponding to the long side of the surface p3d) to the side edge of the substrate 11d in the transverse direction (corresponding to the long side of the irregular uneven surface p1d0) is half of W0, and the distance from the side edge of the composite material 21d in the longitudinal direction (corresponding to the short side of the surface p3d) to the side edge of the substrate 11d in the longitudinal direction (corresponding to the short side of the irregular uneven surface p1d0) is half of L0.

[0151] Regarding the fifth implementation method of the blank surface treatment step described above, see... Figure 2e The length L12 and width W12 of the irregular uneven surface p1e0 of the substrate 11e, and the length L2 and width W2 of the surface p3e of the composite material 21e, where L2 = L12 - L0 and W2 = W12 - W0, and the preferred values ​​of L0 and W0 are 90~150mm respectively; in the assembled state, the distance from the side edge of the composite material 21e in the transverse direction (corresponding to the long side of the surface p3e) to the side edge of the substrate 11e in the transverse direction (corresponding to the long side of the irregular uneven surface p1e0) is half of W0, and the distance from the side edge of the composite material 21e in the longitudinal direction (corresponding to the short side of the surface p3e) to the side edge of the substrate 11e in the longitudinal direction (corresponding to the short side of the irregular uneven surface p1e0) is half of L0.

[0152] The billet assembly steps have been described above. In a preferred embodiment, after the billet assembly step, the four stacked billets are placed under a four-column hydraulic press, and pressure is applied to the opposing surfaces of the two substrates (i.e., the upper surface of the upper substrate and the lower surface of the lower substrate) at a pressure of ≥500 tons. This allows for a closer contact between adjacent billets.

[0153] Furthermore, in the step "preparing four sealing strips of width W3, attaching the sealing strips to the four sides of the two composite materials, and performing gas shielded welding between adjacent sealing strips and between the sealing strips and the substrate, so that the two substrates and the sealing strips form a whole, obtaining a composite billet base blank," the sealing strips, based on their arrangement, allow the four stacked steel billets to be connected into a single composite billet base blank. Specifically, this composite billet base blank has the following characteristics: two substrates forming the upper and lower surfaces, two composite materials located in the middle, and four sealing strips forming a four-sided frame surrounding the two composite materials and connecting the two substrates. Here, Figures 2a-2e The seals are marked as 40a, 40b, 40c, 40d and 40e respectively.

[0154] The width of the seal, W3, is 2T2 - 1~2mm, meaning the width of the seal is slightly smaller than the sum of the thicknesses of the two composite materials by 1~2mm. Using a seal of this width to wrap both the upper and lower composite materials simultaneously improves the wrapping effect.

[0155] Furthermore, of the four seals, two seals are respectively attached to the two sides of the two composite materials in the horizontal direction, with a length L31=L2-1~2mm; the other two seals are respectively attached to the two sides of the two composite materials in the vertical direction, with a length L32=W2-1~2mm.

[0156] Preferably, the thickness T3 of the seal is 12~15mm.

[0157] Regarding the forming method of each seal, it can be directly cut from a steel plate according to thickness T3, width W3, and length L31 or L32 without welding, or it can be spliced ​​from multiple seals of different lengths by welding. For example, the seals on both sides of the longitudinal direction of the two composite materials in the fourth embodiment of the blank surface treatment step described above, and the seals on both sides of the transverse direction of the two composite materials in the fifth embodiment of the blank surface treatment step described above.

[0158] Furthermore, the seal uses the same type of steel as the base material; preferably, the seal material and the base material are the same.

[0159] In a preferred embodiment, before performing gas shielded welding between adjacent seals and between the seal and the substrate, the seals are preheated using a heating gun or electric heating cotton at a temperature of 120-200°C. The ends and sides of each seal can be polished to remove surface oxide scale and improve the welding effect; and / or, the ends and sides of each seal can be beveled.

[0160] Furthermore, as a preferred embodiment, in the step of "performing gas shielded welding between adjacent seals and between the seal and the substrate", the welding speed is 300~360mm / min, and the interpass temperature is controlled at 135~165℃ during the welding process.

[0161] Next, for the step "machine a round hole on the seal at the groove on the side of the composite billet base, and weld a seamless steel pipe at the round hole", the groove is the groove formed between the two base materials and outside the seal; in this step, the round hole is machined to weld the seamless steel pipe so as to facilitate the subsequent vacuuming of the interior of the composite billet.

[0162] As a preferred embodiment, the circular hole is machined in the middle of the short side (i.e., the side in the longitudinal direction) of the composite billet base, but it is not limited to this.

[0163] As a preferred embodiment, the diameter of the circular hole is 8~12mm; correspondingly, the outer diameter of the seamless steel pipe is consistent with the diameter of the circular hole, which is 8~12mm, the wall thickness is 1.2~2mm, and the length is 200~400mm.

[0164] Next, for the step "surfacing the grooves on the four sides of the composite billet base," submerged arc welding is specifically employed. It can be understood that, outside the four-sided frame formed by the sealing strip, a four-sided frame-shaped filler layer is formed through this welding step. (See [link / reference]). Figures 2a-2e The filler layers formed by the welding are designated as 50a, 50b, 50c, 50d and 50e, respectively.

[0165] As a preferred method, before welding, the flux is baked at 350℃ for 2 hours, followed by a holding time at 150℃ for 1 hour. During welding, the interpass temperature is controlled at 135~165℃, and the welding speed is 420~480mm / min. Thus, this submerged arc welding technology, combined with the preceding sealing and gas-shielded welding, achieves a stable connection between the four steel billets, ensuring connection strength and preventing cracking abnormalities in the subsequent composite billet rolling process. Furthermore, in addition to achieving the quality advantages of the composite plate mentioned above, it can further improve the interface bonding effect.

[0166] In addition, during the welding process, before each welding operation, it is necessary to clean the weld bead to keep it clean; after welding, insulation cotton should be used to cover it for insulation.

[0167] Next, the step involves using a vacuum pump to evacuate the composite billet through the seamless steel pipe, with a vacuum level ≤10. -1 In the process of "holding pressure for more than 4 hours after reaching Pa, and finally sealing the seamless steel pipe", the suction port of the vacuum pump is connected to the seamless steel pipe, and the seamless steel pipe is connected to the space inside the composite billet (such as the surface gap between the composite and the base material, the surface gap between the composites, the end face gap between the composite and the seal, etc.) to expel the air in the space until the vacuum degree is ≤10. - 1 The pressure is maintained at 4 Pa, and a vacuum level can be guaranteed by holding the pressure for more than 4 hours. This avoids air in the space from causing surface oxidation at the composite interface during subsequent composite billet rolling, thus ensuring the bonding quality of the composite interface.

[0168] Furthermore, in this step, the seamless steel pipe is sealed, which can be carried out in a manner that is currently feasible in the steel industry, such as heating and flattening the seamless steel pipe with a flame gun to achieve sealing.

[0169] The above describes in detail the overall steps for preparing the composite billet. As mentioned above, the preparation method of the present invention also includes a composite billet rolling step after the overall composite billet preparation steps.

[0170] This invention provides two specific implementations of the overall steps of composite billet rolling, both of which can be combined with any of the preceding composite billet preparation steps and the subsequent composite plate separation and straightening steps.

[0171] <First Implementation Method of Composite Billet Rolling Step>

[0172] In this embodiment, the reference Figure 3 The composite billet rolling process specifically includes the following sub-steps:

[0173] The heating system employs a five-stage heating process: preheating, primary heating, secondary heating, tertiary heating, and homogenization. The preheating temperature is ≤850℃ with a residence time of (0.45~0.55) t min / mm; the primary heating temperature is 1030~1090℃ with a residence time of (0.35~0.45) t min / mm; the secondary heating temperature is 1100~1160℃ with a residence time of (0.25~0.35) t min / mm; the tertiary heating temperature is 1140~1180℃ with a residence time of (0.15~0.25) t min / mm; and the homogenization temperature is 1170~1210℃ with a residence time of (0.10~0.20) t min / mm.

[0174] A two-stage controlled rolling process of roughing and finishing is adopted. In the roughing stage, the first pass uses longitudinal rolling with a rolling reduction of ≥46mm; the second pass and subsequent passes use transverse rolling until the nth pass rolls the composite billet to the target width of the final composite plate, with a rolling reduction of ≥25mm; the (n+1)th pass and subsequent passes use longitudinal rolling until the intermediate billet thickness is 2.5 to 3.5 times the target thickness of the composite plate, ending the roughing stage with a rolling reduction of ≥30mm; throughout the roughing stage, the rolling temperature of the first pass is ≥1060℃, the initial rolling temperature of the remaining passes is ≤1050℃, and the final rolling temperature is ≥1000℃; after the roughing stage, the billet is allowed to cool down by water. When the surface temperature of the intermediate billet drops below 840℃, the finishing stage begins, with an initial rolling temperature of 810℃ to 840℃ and a final rolling temperature of ≥780℃;

[0175] After rolling, the composite plate enters an ultra-fast cooling system for intermittent cooling.

[0176] The ultra-fast cooling system has 24 sets of cooling manifolds arranged along the roller conveyor. The cooling distance of each set of cooling manifolds is 1m. When the composite board passes through the ultra-fast cooling system, the opening and closing status of all 24 sets of cooling manifolds is controlled in a manner that N sets of cooling manifolds are opened and then M sets of cooling manifolds are not opened. The cooling water pressure is 0.2MPa, the cooling rate is 3~15℃ / s, and the final cooling temperature is 380~450℃. N takes the value of 2, 3 or 4, and M takes the value of 2, 3 or 4. For example, when the large composite panel passes through the ultra-fast cooling system, it is controlled by opening 4 sets of cooling manifolds and then closing 3 sets of cooling manifolds. That is, the 1st to 4th sets of cooling manifolds are open, the 5th to 7th sets of cooling manifolds are closed, the 8th to 11th sets of cooling manifolds are open, the 12th to 14th sets of cooling manifolds are closed, the 15th to 18th sets of cooling manifolds are open, the 19th to 21st sets of cooling manifolds are closed, and the 22nd to 24th sets of cooling manifolds are open.

[0177] After the composite panel leaves the ultra-fast cooling system, it directly enters the straightening machine for straightening. The straightened composite panel is then placed at a temperature of T. f -150℃~T f The two steel plates are stacked for cooling at +150℃, with the preferred cooling temperature being 420±20℃ and the cooling time being 0.4min / mm×t±5min. After stacking, the composite plate is naturally cooled to room temperature on the cooling bed. T f =550+30[Si]-20[Mn]+15[Cr]-15[Ni]+10[Mo], where [Si], [Mn], [Mo], [Cr], and [Ni] are 100 times the mass percentage of each element in the substrate;

[0178] This completes step 2) of composite billet rolling and leads to step 3) composite plate separation and straightening.

[0179] The heating process in this embodiment can better control the heating rate of the composite billet in each section, ensuring uniform heating of the billet and avoiding cracking and air leakage of the composite billet due to the difference in thermal properties of the base material and composite material, thereby ensuring the interface bonding effect.

[0180] The rolling process in this embodiment employs a sequence of longitudinal rolling, transverse rolling, and then longitudinal rolling in the roughing stage. This ensures high reduction rolling, allowing for effective penetration of the composite billet core, promoting core deformation, and guaranteeing the bonding rate of the composite interface. During the warming stage, an instant cooling device is used to reduce the warming time and improve rolling efficiency. At the same time, it avoids excessively long warming times that could lead to grain growth in the carbon steel substrate. Temperature control during the finishing rolling stage refines the grains, ensuring that the thick composite plate has good low-temperature impact toughness.

[0181] This embodiment employs the intermittent cooling method described above. When the composite panel passes through the ultra-fast cooling system, it travels between alternating periods of opening and closing the cooling manifolds. In this way, each part of the composite panel undergoes a cooling-and-re-heating cycle, until it leaves the ultra-fast cooling system. During this cooling-and-re-heating cycle, the carbon steel substrate continuously undergoes phase transformation and self-tempering effects, with the phase transformation reaction gradually penetrating towards the core until the entire carbon steel substrate has completed the phase transformation. This intermittent cooling process differs from conventional reciprocating cooling. In reciprocating cooling, the re-heating and self-tempering occur after the surface or near-surface layer has completed its phase transformation, resulting in a significant temperature difference or cooling rate between the surface and the core, leading to substantial differences in microstructure and mechanical properties. In contrast, the intermittent cooling process in this embodiment involves some parts of the composite board being cooled while others are undergoing re-heating / self-tempering simultaneously. Furthermore, each part of the composite board alternates between cooling and re-heating / self-tempering over time, minimizing differences in temperature, cooling rate, microstructure, and properties between the surface and core. For example, the resulting composite board exhibits a Vickers hardness difference ≤10 in the thickness direction of the base layer, a strength difference ≤40 MPa between the head, middle, and tail, and a strength difference ≤40 MPa across the entire board. Moreover, it can further improve the shape of the composite board, resulting in lower unevenness.

[0182] The stacking cooling in this embodiment, especially the temperature of the two steel plates and the stacking cooling time, can further improve the microstructure, properties and shape of the final composite plate compared to the first embodiment described above.

[0183] <Second Implementation Method of Composite Billet Rolling Step>

[0184] This implementation differs from the first implementation of the aforementioned composite billet rolling steps in that: heating and two-stage controlled rolling are divided into steps, while cooling on the ultra-fast cooling system and subsequent steps are the same.

[0185] Specifically:

[0186] When heating the obtained composite billet, the soaking temperature is 1150~1220℃, the total heating time is ≥1.2×tmin / mm, where t is the thickness of the composite billet, and the soaking time is 30min~50min.

[0187] When using a two-stage controlled rolling process of roughing and finishing, the initial rolling temperature in the roughing stage is ≤1050℃, and the final rolling temperature is ≥1000℃. Rolling is performed first in the transverse direction and then in the longitudinal direction. During the longitudinal rolling, at least one pass requires a reduction of ≥35mm. The total reduction in roughing is 40~60%. The roughing stage ends when the intermediate billet thickness is 2.5~3.5 times the target thickness of the composite plate. Afterward, the billet is allowed to cool to a suitable temperature, during which water cooling is applied. When the surface temperature of the intermediate billet drops below 830℃, the finishing stage begins. The final rolling temperature in the finishing stage is ≥800℃, and the total reduction in finishing is 55~75%.

[0188] The overall steps of the composite billet rolling process have been described in detail above. As mentioned earlier, the preparation method of the present invention also includes a composite plate separation and straightening step. Specifically, the composite plate separation and straightening step includes the following sub-steps:

[0189] Cut the four sides of the large composite board to remove the part other than the seal strip, and separate the large composite board into two small composite board panels.

[0190] The composite board panels, after being cut to length, are placed with the cladding layer facing upwards on a flattening machine for flattening. When flattening laterally, the flattening force of the flattening machine is controlled as F1 = 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 by a×b×c longitudinal×σ 纵 / (d+c 纵 ); where a is the width of the composite panel, b is the thickness of the composite panel, and c 横 The flatness per meter in the transverse direction of the composite panel is expressed in mm, c. 纵 σ represents the unevenness per meter of the composite panel in the longitudinal direction, expressed 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 longitudinal tensile yield strength of the composite panel slab, and ν is Poisson's ratio.

[0191] Finally, the composite panel slabs are cold-straightened to obtain the finished single-sided stainless steel composite panel.

[0192] Specifically, the part outside the seal in the step "cutting its four sides to remove the portion other than the seal" refers to the edge portion of the large composite plate formed by the seal and filler layer in the composite billet mentioned earlier, after the preceding composite billet rolling step. Removing this portion exposes the stainless steel cladding layer, and without its connecting function, the large composite plate separates into two smaller composite plates. See also... Figures 4a-4eThis corresponds to the five implementation methods of the blank surface treatment steps described above. Figures 4a-4e The cross-sectional shapes of the two corresponding single-sided composite panels (i.e., the final composite panels) are shown respectively.

[0193] Each composite panel consists of a lamellae and a base layer. The lamellae are obtained from the original composite material through rolling, and the base layer is obtained from the original substrate through rolling. Therefore, in Figures 4a-4e The original composite material number is still marked for the multilayer layer, and the original substrate number is still marked for the base layer.

[0194] Thus, by adjusting the flattening force of the flattening machine, the present invention can achieve control over the shape of the composite board, which is convenient to operate and has excellent results.

[0195] Furthermore, the present invention provides a single-sided stainless steel composite plate prepared by the preparation method described above, which has excellent mechanical properties, good interfacial bonding quality, plate shape, uniformity and surface quality, and strong impact toughness and excellent corrosion resistance.

[0196] In a preferred embodiment, the total thickness of the composite board is 15-39 mm, the thickness of the base layer is 12-36 mm, and the thickness of the cladding layer is 3 mm.

[0197] In a preferred embodiment, the cladding layer of the composite plate is preferably austenitic stainless steel. Specifically, the chemical composition of the cladding layer, by mass percentage, is: C≤0.15%, Si≤1.00%, Mn≤2.00%, P≤0.045%, S≤0.030%, Ni: 6.0~22.0%, Cr: 16.0~26.0%, Mo≤3.0%, with the balance being Fe and unavoidable impurities. It is understood that the cladding layer is obtained by rolling the composite material, and its chemical composition is consistent with that of the composite material. Using this chemical composition can further guarantee the performance of the composite plate, especially the corrosion resistance of the cladding layer, while maintaining the aforementioned technical effects. For example, the cladding layer of the obtained composite plate (i.e., made of stainless steel) shows no intergranular corrosion cracks after being boiled in a sulfuric acid-copper sulfate solution for 20 hours and then bent at 180°.

[0198] In a preferred embodiment, the chemical composition of the base layer of the composite board, by mass percentage, is as follows: C: 0.03~0.16%, Si: 0.11~0.29%, Mn: 1.31~1.54%, P≤0.018%, S≤0.0030%, Cr: 0.06~0.29%, Ni≤0.24%, Cu≤0.24%, Mo≤0.24%, Nb: 0.011~0.034%, Ti: 0.011~0.019%, Al: 0.030~0.040%, with the balance being Fe and unavoidable impurities. More preferably, the chemical composition, by mass percentage, is: C: 0.03~0.07%, Si: 0.11~0.19%, Mn: 1.46~1.54%, P≤0.010%, S≤0.0015%, Cr: 0.21~0.29%, Ni: 0.16~0.24%, Cu: 0.16~0.24%, Mo: 0.16~0.24%, Nb: 0.026~0.034%, Ti: 0.011~0.019%, Al: 0.030~0.040%, with the remainder being Fe and unavoidable impurities. It is understood that this base layer is obtained by rolling the substrate, and its chemical composition is consistent with that of the composite material. Using this chemical composition, combined with the various processes in the preparation of the composite panel, can further improve the mechanical properties of the composite panel while ensuring the aforementioned technical effects, as well as its toughness, uniformity, and panel shape.

[0199] For example, in a preferred embodiment, the composite board has an impact energy of ≥120J at 0℃, ≥120J at -20℃, and ≥120J at -40℃; the composite board has no cracks when bent outwards by 180° and no cracks when bent inwards by 180°.

[0200] In a preferred embodiment, the yield strength is ≥345MPa, the tensile strength is ≥490MPa, the elongation after fracture is ≥18%, and the yield strength ratio is ≤0.86.

[0201] In a preferred embodiment, the Vickers hardness difference of the base layer of the composite board in the thickness direction is ≤10, the strength difference between the head, middle and tail is ≤40MPa, and the strength difference at all points of the board is ≤40MPa.

[0202] In a preferred embodiment, the composite plate has a 100% composite interface bonding rate and a shear strength ≥300MPa.

[0203] In a preferred embodiment, the unevenness of the composite board is ≤3mm / m, or even more preferably, the unevenness of the thicker part of the composite board is ≤2mm / m.

[0204] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

[0205] The beneficial effects of the present invention will be further illustrated below through two embodiments. Of course, these embodiments are only a part of the many variations contained in the present invention, and not all of them.

[0206] In these two embodiments, Q500q steel is selected as the base material and 316 stainless steel is selected as the composite material.

[0207] Here, two embodiments are provided to prepare composite blanks with a thickness of 378 mm according to the embodiments provided by the present invention. Each embodiment is further implemented according to two embodiments of surface treatment steps for the blanks: composite blanks with a constant substrate thickness and composite blanks with a variable substrate thickness.

[0208] Further, Example 1 was implemented according to the first embodiment of the composite billet rolling step of the present invention, and Example 2 was implemented according to the second embodiment of the composite billet rolling step of the present invention. A large composite plate with a thickness of 54 mm and a cladding thickness of 3 mm was obtained. Specifically: for the single-sided stainless steel composite plate made from a composite billet with a "constant thickness" base material, the thickness was 27 mm and the base layer thickness was 24 mm; while for the single-sided stainless steel composite plate made from a composite billet with a "variable thickness" base material, the thickness was 23-31 mm and the base layer thickness was 20-28 mm, which falls within the thickness range from minimum to maximum.

[0209] Sampling and testing of the composite panels from these embodiments revealed the following:

[0210] 1) The bonding rate of the composite interfaces is 100%;

[0211] 2) Inner bend 180° is qualified (no cracks), outer bend 180° is qualified (no cracks);

[0212] 3) After boiling in a sulfuric acid-copper sulfate solution for 20 hours and bending at 180°, the strata showed no intergranular corrosion cracks.

[0213] 4) The composite panels with constant base thickness in the two embodiments were subjected to performance tests, and the results are shown in Table 1.

[0214]

Claims

1. A method for preparing a single-sided stainless steel composite plate, characterized in that, It includes three steps carried out in sequence: composite billet preparation, composite billet rolling, and composite plate separation and straightening; In the composite billet preparation step, a composite billet with carbon steel substrates on the top and bottom and stainless steel composite material in the middle is prepared. The composite billet rolling step includes: The resulting composite billet is heated to a homogenization temperature of 1150~1220℃, and the total heating time is ≥1.2min / mm×t, where t is the thickness of the composite billet. The rolling process is controlled by two stages: roughing and finishing. In the roughing stage, the final rolling temperature is ≥980℃, and the roughing stage ends when the thickness of the intermediate billet is 2.5 to 3.5 times the target thickness of the composite plate. After that, the billet is allowed to cool down by water. When the surface temperature of the intermediate billet drops below 860℃, the finishing stage begins, and the final rolling temperature of the finishing stage is ≥780℃. After rolling, it enters an ultra-fast cooling system for cooling; After the composite panel leaves the ultra-fast cooling system, it directly enters the straightening machine for straightening. The straightened composite panel is then placed at a temperature of T. f -150℃~T f Two steel plates at +150℃ were subjected to stack cooling between them for a time of 0.4 min / mm×t ± 5 min; after stack cooling, the composite plate was naturally cooled on a cooling bed; where T f =550+30[Si]-20[Mn]+15[Cr]-15[Ni]+10[Mo], where [Si], [Mn], [Mo], [Cr], and [Ni] are 100 times the mass percentage of each element in the substrate; The composite plate separation and straightening step includes: Cut the four sides of the large composite board to remove the part other than the seal strip, and separate the large composite board into two small composite board panels. The composite board panels, after being cut to length, are placed with the cladding layer facing upwards on a flattening machine for flattening. When flattening laterally, the flattening force of the flattening machine is controlled as F1 = 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 by a×b×c longitudinal×σ 纵 / (d+c 纵 ); where a is the width of the composite panel, b is the thickness of the composite panel, and c 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 is the longitudinal tensile yield strength of the small composite panel, and ν is Poisson's ratio. Finally, the composite panel slabs are cold-straightened to obtain the finished single-sided stainless steel composite panel.

2. The method for preparing a single-sided stainless steel composite plate according to claim 1, characterized in that, The composite billet rolling step specifically includes: When heating the obtained composite billet, a five-stage heating process is adopted, consisting of preheating, first heating, second heating, third heating, and homogenization. The preheating temperature is ≤850℃, and the residence time is (0.45~0.55)min / mm×t. The first heating temperature is 1030~1090℃, and the residence time is (0.35~0.45)min / mm×t. The second heating temperature is 1100~1160℃, and the residence time is (0.25~0.35)min / mm×t. The third heating temperature is 1140~1180℃, and the residence time is (0.15~0.25)min / mm×t. The homogenization temperature is 1170~1210℃, and the residence time is (0.10~0.20)min / mm×t. In the "two-stage controlled rolling process of roughing and finishing", during the roughing stage, the first pass uses longitudinal rolling with a rolling reduction of ≥46mm; the second pass begins transverse rolling until the nth pass rolls the composite billet to the target width of the final composite plate, with a rolling reduction of ≥25mm; the (n+1)th pass begins longitudinal rolling, ending when the thickness of the intermediate billet is 2.5 to 3.5 times the target thickness of the composite plate, with a rolling reduction of ≥30mm; throughout the roughing stage, the rolling temperature of the first pass is ≥1060℃, the initial rolling temperature of the remaining passes is ≤1050℃, and the final rolling temperature is ≥1000℃; after the roughing stage, the billet is allowed to cool down by water, and when the surface temperature of the intermediate billet drops below 840℃, the finishing stage begins, with an initial rolling temperature of 810℃ to 840℃ and a final rolling temperature of ≥780℃.

3. The method for preparing a single-sided stainless steel composite plate according to claim 1, characterized in that, The composite billet rolling step specifically includes: When heating the obtained composite blank, the holding time in the heat soaking section is 30 min to 50 min; When using a two-stage controlled rolling process of roughing and finishing, the initial rolling temperature is ≤1050℃ and the final rolling temperature is ≥1000℃. Rolling is performed first in the transverse direction and then in the longitudinal direction. During longitudinal rolling, at least one pass requires a reduction of ≥35mm. The total reduction during roughing is 40~60%. The roughing stage ends when the intermediate billet thickness is 2.5~3.5 times the target thickness of the composite plate. Afterwards, the billet is allowed to cool to a suitable temperature, with water cooling applied. When the surface temperature of the intermediate billet drops below 830℃, the finishing stage begins. The final rolling temperature during the finishing stage is ≥800℃, and the total reduction during finishing is 55~75%.

4. The method for preparing a single-sided stainless steel composite plate according to claim 1, characterized in that, The composite billet rolling step specifically includes: In the section "cooling after rolling in an ultra-rapid cooling system", after rolling, the composite plate enters the ultra-rapid cooling system for intermittent cooling. The ultra-fast cooling system has 24 sets of cooling manifolds arranged along the roller conveyor. The cooling distance of each set of cooling manifolds is 1m. When the composite board passes through the ultra-fast cooling system, the opening and closing status of all 24 sets of cooling manifolds is controlled in a manner that N sets of cooling manifolds are opened and then M sets of cooling manifolds are not opened. The cooling water pressure is 0.2MPa, the cooling rate is 3~15℃ / s, and the final cooling temperature is 380~450℃. N takes the value of 2, 3 or 4, and M takes the value of 2, 3 or 4.

5. The method for preparing a single-sided stainless steel composite plate according to claim 1, characterized in that, The specific steps for preparing the composite preform include: Prepare two carbon steel billets with thickness T1, length L1, and width W1 as the base material for forming the base layer of the composite plate; and prepare two stainless steel billets with thickness T2, length L2, and width W2 as the composite material for forming the cladding layer of the composite plate; L2 < L1, W2 < W1. At least one surface of each of the two substrates and the two composites is surface treated; Apply a release agent to one surface of a composite material; The preforms are assembled in the following stacking order: substrate, composite, composite, and substrate; wherein the composite is placed in the center relative to the substrate, the surfaces of the substrate and composite that come into contact with each other are the surfaces that have undergone the aforementioned surface treatment, and the surface coated with the release agent faces the other composite. Prepare four sealing strips with a width of W3, W3=2T2-1~2mm. Attach the sealing strips to the four sides of the two composite materials. Perform gas shielded welding between adjacent sealing strips and between the sealing strips and the substrate, so that the two substrates and the sealing strips form a whole, and obtain the composite blank base blank. A round hole is machined on the seal at the groove on the side of the composite billet base, and a seamless steel pipe is welded at the round hole; The grooves on the four sides of the composite billet base are welded together. A vacuum pump is used to evacuate the composite billet through the seamless steel pipe, with a vacuum level ≤10. -1 The pressure is increased to Pa, then maintained for more than 4 hours; finally, the seamless steel pipe is sealed.

6. The method for preparing a single-sided stainless steel composite plate according to claim 5, characterized in that, The step "surface treating at least one surface of each of the two substrates and the two composites" includes: One surface of each composite material is ground and polished to remove the surface oxide scale; and, According to the complementary relative shapes, one surface of the two substrates is milled to form a transversely inclined surface with length L11=L1 and width W11>W1, and the substrate is a non-uniform thickness blank with varying thickness in the transverse direction; or the surface is milled to form a longitudinally inclined surface with length L11>L1 and width W11=W1, and the substrate is a non-uniform thickness blank with varying thickness in the longitudinal direction.

7. The method for preparing a single-sided stainless steel composite plate according to claim 5, characterized in that, The step "surface treating at least one surface of each of the two substrates and the two composites" includes: According to the complementary relative shapes, one surface of two substrates is milled to form an irregular concave-convex surface containing n planes connected sequentially in the transverse direction, and the substrate is a non-uniform thickness blank with non-monotonic thickness variation in the transverse direction. The length L12 of the irregular concave-convex surface is L1 and the total width W12 is greater than W1; or, the surface is milled to form an irregular concave-convex surface containing n planes connected sequentially in the longitudinal direction, and the substrate is a non-uniform thickness blank with non-monotonic thickness variation in the longitudinal direction. The total length L12 of the irregular concave-convex surface is greater than L1 and the width W12 is W1; n≥2; One surface of each composite material is polished to remove the surface oxide scale; then each composite material is bent to match the corresponding irregular uneven surface.

8. A single-sided stainless steel composite plate, characterized in that, The composite board is prepared by any one of claims 1 to 7.

9. The single-sided stainless steel composite plate according to claim 8, characterized in that, The composite plate has an impact energy of ≥120J at 0℃, ≥120J at -20℃, and ≥120J at -40℃. The unevenness of the composite board is ≤3mm / m.

10. The single-sided stainless steel composite plate according to claim 8, characterized in that, The Vickers hardness difference of the base layer of the composite board is ≤10 in the thickness direction, the strength difference between the head, middle and tail is ≤40MPa, and the strength difference at all parts of the whole board is ≤40MPa.

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