A processing method for a high-strength and tough stainless steel / carbon steel composite plate

Abstract

The present invention discloses a processing method for a high-strength and tough stainless steel / carbon steel composite plate. Through a rolling composite process under the action of laser-assisted heating, a high-strength carbon steel plate and a stainless steel plate are composite; subsequently, a temperature-controlled and on-line periodic laser surface annealing treatment is carried out on the stainless steel / carbon steel composite thin plate, and a corrosion-resistant structure with a non-uniform structure of coarse grains (soft zones) - fine grains (hard zones) arranged alternately can be obtained on the stainless steel surface layer, improving the corrosion resistance of the composite plate. At the same time, the stress relief effect induced by the laser surface annealing treatment, the tempering softening of partial martensite structure on the carbon steel side at the bonding interface, and the heterogeneous structure induced by the laser surface annealing treatment will simultaneously improve the strength and toughness of the stainless steel / carbon steel composite plate.

Description

Technical Field

[0001] The present invention relates to the technical field of stainless steel composite plate processing, and specifically relates to a processing method for high-strength and tough stainless steel / carbon steel composite plates. Background Art

[0002] Heterogeneous metal composite materials effectively utilize the performance advantages of each constituent metal, while significantly reducing material costs, and have broad application prospects. For example, stainless steel / carbon steel composite plates have a carbon steel base layer and a stainless steel cladding layer, and achieve metallurgical bonding through methods such as rolling compounding and explosive compounding, and are widely used in industries such as nuclear power, hydropower, pressure vessels, petrochemicals, etc.

[0003] Therefore, the invention patent with the application number CN201410823984.3 proposes a rolling method for pipeline steel and stainless steel composite plates. This method prepares stainless steel / carbon steel composite plates with relatively high strength by regulating processes such as heating, rolling, and controlled cooling. The tensile strength of the stainless steel / carbon steel composite plates prepared by this method is 590 MPa. The invention patent with the application number CN202410752115.X proposes a production method for stainless steel-bridge steel composite plates. This method prepares stainless steel / carbon steel composite plates through processes such as surface treatment of raw material slabs, assembling composite slabs, sectional heating, rough rolling of composite slabs, finish rolling, post-rolling cooling, and annealing heat treatment of post-rolled composite plates. However, similarly, due to the low strength of the base material (Q345) and multiple high-temperature annealing processes, the strength of the prepared stainless steel / carbon steel composite plates is still not high, only 545 MPa. It can be found that the stainless steel / carbon steel composite plates prepared by existing processes generally have the problem of low strength and cannot meet the requirements of specific industrial environments for high-strength stainless steel / carbon steel composite plates. How to improve the strength of stainless steel / carbon steel composite plates while maintaining excellent toughness and achieving short process flow is an urgent problem to be solved.

[0004] Therefore, this patent proposes a processing method for high-strength and tough stainless steel / carbon steel composite plates, that is, using a one-step forming rolling compounding process under the action of laser-assisted heating + online periodic laser surface annealing treatment to simultaneously improve the strength, toughness, and corrosion resistance to meet the urgent needs of the current industrial field for high-strength and tough stainless steel / carbon steel composite plates. Summary of the Invention

[0005] In order to solve the problems existing in the above background art, the present invention provides a processing method for high-strength and tough stainless steel / carbon steel composite plates, which realizes the lamination of stainless steel and high-strength carbon steel by the synergistic action of laser-induced thermal effect and rolling force, and then uses periodic laser surface annealing technology to simultaneously achieve surface tissue isomerization, improvement of corrosion resistance, and reduction of residual stress.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a processing method for a high-strength and high-toughness stainless steel / carbon steel composite plate, comprising the following steps:

[0008] S1. Machining and surface treatment:

[0009] The high-strength carbon steel plate and the stainless steel plate are processed into plates with the same width, and then the surfaces to be compounded of the high-strength carbon steel plate and the stainless steel plate are polished for surface roughening treatment. After the treatment is completed, the surfaces to be compounded are cleaned to remove surface stains.

[0010] S2. Laser-assisted rolling compounding:

[0011] The high-strength carbon steel plate and the stainless steel plate are stacked relatively and aligned at the four sides for combination. One end of the combined plate is fed into a rolling mill for cold rolling and pressing. The rolling mill presses down to bite the two plates together, and an opening is formed at the un-pressed part of the two plates. The laser processing head outputs a flat-top line-shaped light spot, and the laser is irradiated from the opening onto the bonding interface of the two plates. Subsequently, the rolling mill is started, and the laser processing head emits light to heat the surfaces to be compounded of the stainless steel plate and the high-strength carbon steel plate. Under the action of the rolling force, the two metals achieve metallurgical bonding at the interface, and the stainless steel plate and the high-strength carbon steel plate are compounded into one body to form a stainless steel / carbon steel composite plate.

[0012] S3. Periodic laser surface annealing:

[0013] The stainless steel surface of the stainless steel / carbon steel composite plate is subjected to temperature-controlled and periodic laser surface annealing treatment by using a homogenized light spot, and a non-uniform structure with alternating coarse grains and fine grains is constructed in the stainless steel surface layer region.

[0014] Adopting the above technical solutions:

[0015] In the present invention, by the synergistic action of the laser-induced thermal effect and the rolling force, the high-strength carbon steel plate and the stainless steel plate are compounded; subsequently, the stainless steel / carbon steel composite plate is subjected to temperature-controlled and periodic laser surface annealing. On the basis of realizing the metallurgical bonding of the heterogeneous metal surfaces, a corrosion-resistant and high-strength and high-toughness structure with alternating soft zones and hard zones is constructed, significantly improving the service performance of the stainless steel / carbon steel composite plate. At the same time, the periodic laser surface annealing treatment is directly carried out after the compounding process. This on-line post-treatment method greatly improves the processing efficiency and reduces the winding difficulty of the composite material.

[0016] Further, in the step S2, the angle formed by the opening at the un-pressed part of the two plates is 40-80°.

[0017] Specifically, in step S2, an opening with a certain angle is formed by opening the unbonded part of the two plates (high-strength carbon steel plate and stainless steel plate), so as to irradiate the laser on the interface to be compounded between the high-strength carbon steel plate and the stainless steel plate. Since the laser energy will be reflected when the laser irradiates on a material with a certain reflectivity, and the angles of the formed openings are different, the number of reflections of the laser is different, and finally the energy converging at the bonding interface is also different. After many experiments, preferably, the angle formed by opening the unbonded part of the two plates is controlled to be 40-80°, and more preferably, the angle of the formed opening is controlled to be 60°.

[0018] Further, in the step S2, the length of the line-shaped light spot is the same as the width of the plate, the width of the line-shaped light spot is 0.7-2 times the sum of the thicknesses of the two plates, and the angle between the line-shaped light spot and the horizontal direction is 0-17°.

[0019] During operation, the laser turns on the red light indicator light to make the laser line-shaped light spot pass through the opening and irradiate on the bonding interface of the two plates. In order to irradiate the entire interface to be compounded, the length of the line-shaped light spot is the same as the width dimension of the material bonding interface; at the same time, in order to ensure the deformation coordination of dissimilar metals in the micro-region of the bonding interface, the width of the line-shaped light spot is 0.7-2 times the sum of the thicknesses of the two plates.

[0020] When the thickness specification of the high-strength carbon steel plate ≤ 3.5 mm and the tensile strength of the high-strength carbon steel plate ≤ 800 MPa, the area ratio of the laser irradiation areas of the high-strength carbon steel plate and the stainless steel plate is approximately equal to the strength ratio of the two, and at the same time, the highest heating temperature of the laser-induced bonding interface is lower than the solidus line. If the thickness specification of the high-strength carbon steel plate exceeds 3.5 mm, regardless of whether its strength exceeds 800 MPa, the laser power will be increased and the laser irradiation area of the high-strength carbon steel plate will be increased (the area ratio of the laser irradiation areas of the stainless steel plate / high-strength carbon steel plate is 0.7-0.4), resulting in the highest heating temperature at the position to be bonded of the high-strength carbon steel plate reaching above the melting point. If the tensile strength of the high-strength carbon steel plate exceeds 800 MPa but the thickness specification ≤ 3.5 mm, the rolling force will be increased and the highest heating temperature of the bonding interface will be ensured to be lower than the melting point.

[0021] Further, in the step S2, the rolling speed of the rolling mill is 0.5-3 m / min, and the rolling reduction rate is 25-60%.

[0022] Because the rolling of the stainless steel plate and the high-strength carbon steel plate can only be realized under the environment of large pressure and high temperature, the laser provides heat, the rolling mill provides a large rolling force, the rolling speed is slow, and the laser can continuously heat the interface to be compounded after the heat input, and the compounding effect is good. After many experimental verifications, in order to ensure both the processing efficiency and the compounding effect, the rolling reduction rate is controlled to be 25-60%, and the rolling speed of the rolling mill is controlled to be 0.5-3 m / min.

[0023] Further, in the step S3, the length of the homogenized light spot is consistent with the width of the stainless steel / carbon steel composite plate. High-power laser and low-power laser are alternately irradiated onto the surface of the stainless steel, and a pyrometer is used to monitor the heating temperature of the laser surface annealing area in real time.

[0024] Specifically, the maximum heating temperature in the high-power laser irradiation area is controlled at 850-1100 °C, and the maximum heating temperature in the low-power laser irradiation area is controlled at 500-680 °C. The width of a single high-power laser irradiation area or low-power laser irradiation area is 0.5-2 mm.

[0025] The stainless steel / carbon steel composite plate is subjected to periodic laser surface annealing treatment using the homogenized light spot to synergistically improve its strength, toughness and corrosion resistance. Specifically, the surface of the stainless steel is subjected to temperature-controlled periodic irradiation using a homogenized light spot with a length consistent with the width of the stainless steel / carbon steel composite plate. Temperature control means that a pyrometer is used to monitor the heating temperature of the laser surface annealing area in real time, and the heating temperature of the laser irradiation area is made controllable through closed-loop regulation of the laser power; periodicity means that high-power laser irradiation and low-power laser irradiation are alternately carried out, that is, high-power laser irradiation promotes grain coarsening on the surface layer of the stainless steel, high-temperature tempering of the martensite structure on the carbon steel side near the bonding interface, and only stress relief annealing of the carbon steel plate far from the bonding interface. Low-power laser irradiation only induces stress relief and other phenomena in the surface layer area of the stainless steel, thereby constructing a non-uniform structure with alternating coarse grains (soft zones) and fine grains (hard zones) in the surface layer area of the stainless steel. By utilizing the interaction between the soft zones and hard zones, the corrosion resistance of the stainless steel is further improved. At the same time, due to the high-temperature tempering softening of part of the martensite structure on the carbon steel plate side at the bonding interface, combined with the effects of transformation-induced strengthening and work hardening, the strength and toughness of the stainless steel / high-strength carbon steel plate composite plate are improved.

[0026] Further, the material of the high-strength carbon steel plate is low-alloy steel with a tensile strength ≥ 600 MPa, such as: Q690 steel, Q890 steel, Q960 steel, etc.

[0027] Further, in the step S1, after being ground with sandpaper, polished with a wire brush or ground with a sanding belt, the surface roughness Ra of the surfaces to be bonded of the high-strength carbon steel plate and the stainless steel plate is 3.2-6.3 μm. Mechanical grinding is used to increase the surface roughness of the material, so as to increase mechanical locking when the stainless steel and the carbon steel surfaces come into contact and improve the subsequent laser rolling bonding effect. After grinding treatment, the stainless steel and carbon steel need to be cleaned of the particles remaining on the surface using a dust adsorption system.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] In the present invention, by utilizing the synergistic effect of laser-induced thermal effect and rolling force, high-strength carbon steel plates and stainless steel plates are compounded; subsequently, the stainless steel / carbon steel composite plates are subjected to temperature-controlled and periodic laser surface annealing. On the basis of achieving metallurgical bonding of heterogeneous metals, a corrosion-resistant and high-strength and toughness structure with alternating soft and hard zones is constructed, significantly improving the service performance of the stainless steel / carbon steel composite plates. At the same time, the periodic laser surface annealing treatment is directly carried out after the compounding process. This on-line post-treatment method greatly improves the processing efficiency and reduces the coiling difficulty of the composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0031] Figure 1 It is a microstructure distribution diagram of the stainless steel / carbon steel composite plate after periodic laser surface annealing in the present invention.

[0032] Specific reference numerals are as follows:

[0033] High-power laser irradiation area 1, low-power laser irradiation area 2, coarse-grained area 11, tempered martensite 12, fine-grained area 21. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0035] The present invention discloses a processing method for a high-strength and toughness stainless steel / carbon steel composite plate, including the following steps:

[0036] S1. Machining and surface treatment:

[0037] The high-strength carbon steel plate and the stainless steel plate are processed into plates with the same width. By using methods such as sandpaper grinding, wire brush polishing, and sand belt grinding, the stainless steel and carbon steel with the same width are subjected to single-sided grinding treatment to obtain a bonding surface with a surface roughness Ra of 3.2 - 6.3 μm. By mechanically grinding, the surface roughness of the material is increased, so as to increase the mechanical interlocking when the stainless steel and carbon steel surfaces come into contact and improve the subsequent laser rolling compounding effect. After the grinding treatment, the stainless steel and carbon steel need to use a dust adsorption system to remove the particulate matter remaining on the surface.

[0038] The material of the high-strength carbon steel plate is a low-alloy steel with a tensile strength ≥ 600 MPa, such as: Q690 steel, Q890 steel, Q960 steel, etc.

[0039] S2. Laser-assisted rolling composite:

[0040] Stack the high-strength carbon steel plate and the stainless steel plate relative to each other and align them around the perimeter for combination. Feed one end of the combined plates into the rolling mill for cold rolling and pressing. The rolling mill presses down to bite the two plates together. An opening is formed at the un-pressed area of the two plates. The laser processing head outputs a flat-top line-shaped light spot, and irradiates the laser from the opening onto the bonding interface of the two plates. Subsequently, start the rolling mill. The laser processing head emits light to heat the interface to be compounded between the stainless steel plate and the high-strength carbon steel plate. Under the action of the rolling force, the two metals achieve metallurgical bonding at the interface, and the stainless steel plate and the high-strength carbon steel plate are compounded into one body to form a stainless steel / carbon steel composite plate.

[0041] The angle formed by the opening at the un-pressed area of the two plates is 40 - 80°, and at the same time, the line-shaped light spot irradiates directly on the surfaces to be bonded of the two metals at an angle of 0 - 17° with the horizontal direction.

[0042] When the thickness specification of the high-strength carbon steel plate ≤ 3.5 mm and the tensile strength of the high-strength carbon steel plate ≤ 800 MPa, the area ratio of the laser irradiation areas of the high-strength carbon steel plate and the stainless steel plate is approximately equal to the strength ratio of the two, and at the same time, the maximum heating temperature of the bonding interface induced by the laser is lower than the solidus line. If the thickness specification of the high-strength carbon steel plate exceeds 3.5 mm, regardless of whether its strength exceeds 800 MPa, the laser power will be increased and the laser irradiation area of the high-strength carbon steel plate will be increased (the area ratio of the laser irradiation area of the stainless steel plate / high-strength carbon steel plate is 0.7 - 0.4), resulting in the maximum heating temperature at the position to be bonded of the high-strength carbon steel plate reaching above the melting point. If the tensile strength of the high-strength carbon steel plate exceeds 800 MPa but the thickness specification ≤ 3.5 mm, the rolling force will be increased and the maximum heating temperature of the bonding interface will be ensured to be lower than the melting point.

[0043] The length of the line-shaped light spot is the same as the width of the plate, and the width of the line-shaped light spot is 0.7 - 2 times the sum of the thicknesses of the two plates.

[0044] The rolling speed of the rolling mill is 0.5 - 3 m / min, and the rolling reduction rate is 25 - 60%.

[0045] S3. Periodic laser surface annealing:

[0046] Periodic laser surface annealing treatment is carried out on a stainless steel / carbon steel composite plate using a homogenized light spot to synergistically improve its strength, toughness and corrosion resistance. Specifically, a homogenized light spot with a length equal to the width of the stainless steel / carbon steel composite plate is used for temperature-controlled periodic irradiation of the stainless steel surface. Temperature-controlled means that a pyrometer is used to monitor the heating temperature of the laser surface annealing area in real time, and the heating temperature of the laser irradiation area is made controllable through closed-loop regulation of the laser power; periodic means that high-power laser irradiation and low-power laser irradiation are carried out alternately, that is, high-power laser irradiation is used to promote grain coarsening in the stainless steel surface layer, tempering of the martensite structure on the carbon steel side near the bonding interface at high temperature, and only stress relief annealing occurs in the carbon steel far from the bonding interface. Low-power laser irradiation is used to only induce stress relief and other phenomena in the stainless steel surface layer area, so as to construct a non-uniform structure with alternating coarse grains (soft areas) - fine grains (hard areas) in the stainless steel surface layer area. By using the interaction between the soft areas and the hard areas, the corrosion resistance of the stainless steel is further improved. At the same time, due to the tempering softening of part of the martensite structure on the carbon steel side at the bonding interface, combined with the effects of transformation-induced strengthening and work hardening, the strength and toughness of the stainless steel / carbon steel composite plate are improved.

[0047] Specifically, as Figure 1 shown, under temperature-controlled periodic irradiation of the stainless steel surface using a homogenized light spot with a length equal to the width of the stainless steel / carbon steel composite plate, the irradiated areas on the stainless steel side are alternately high-power laser irradiation area 1 and low-power laser irradiation area 2, and the width of a single high-power laser irradiation area 1 or low-power laser irradiation area 2 is 0.5 - 2 mm. The maximum heating temperature of the high-power laser irradiation area 1 is controlled at 850 - 1100 °C, and the maximum heating temperature of the low-power laser irradiation area 2 is controlled at 500 - 680 °C. The grain size of the stainless steel surface layer changes periodically, and a structure of coarse grain area 11 - fine grain area 21 - coarse grain area 11 - fine grain area 21 is obtained on the stainless steel surface layer, so as to construct a non-uniform structure with alternating coarse grains (soft areas) - fine grains (hard areas) in the stainless steel surface layer area. By using the interaction between the soft areas and the hard areas, the corrosion resistance of the stainless steel is further improved. At the same time, in the high-power irradiation area, the martensite structure on the carbon steel side near the stainless steel / carbon steel bonding interface undergoes high-temperature tempering to form tempered martensite 12, and only stress relief annealing occurs in the carbon steel far from the bonding interface to eliminate the stress generated during the processing.

[0048] Example 1

[0049] A processing method for a high-strength and high-toughness stainless steel / carbon steel composite plate includes the following steps:

[0050] S1. Roughing treatment of the surface to be bonded:

[0051] The Q690 high-strength carbon steel plate (tensile strength 813 MPa) and the 304 stainless steel plate were polished with sandpaper. The stainless steel and carbon steel with the same width were subjected to single-sided grinding treatment to obtain a bonding surface with a surface roughness Ra of 3.3 μm, and a dust adsorption system was used to remove the particulate matter remaining on the surface.

[0052] S2. Laser-assisted rolling composite:

[0053] The stainless steel and Q690 high-strength carbon steel were bitten into the rolling mill at a spatial angle of 60°, and at the same time, the laser beam was directly irradiated on the bonding surfaces of the two metals at an angle of 8° with the horizontal direction. The tensile strength of the Q690 high-strength steel is 813 MPa, the thickness specification is 1.5 mm, the rolling reduction rate is 50%, and the maximum heating temperature of the bonding interface is 1200 °C. At the same time, the width of the laser beam spot is 1.5 times the total thickness of the blank, and the length of the laser beam spot is the same as the width of the blank. The area ratio of the laser irradiation area of stainless steel / carbon steel is 0.6; the rolling composite speed is 3 m / min. Under the coupling action of the rolling force and the laser, the two materials achieve metallurgical bonding at the interface, and the 304 stainless steel plate and the Q690 high-strength carbon steel plate are combined into one to form a stainless steel / carbon steel composite plate.

[0054] S3. Periodic laser surface annealing:

[0055] The stainless steel / carbon steel composite plate was subjected to periodic laser surface annealing treatment using a homogenized light spot. The maximum heating temperature in the high-power laser irradiation area was controlled at 1000 °C, and the maximum heating temperature in the low-power laser irradiation area was controlled at 620 °C. The widths of the high-power laser irradiation area and the low-power laser irradiation area were 1.5 mm.

[0056] Finally, a stainless steel / carbon steel composite plate with a tensile strength of 934 MPa, an elongation after fracture of 21%, and a corrosion rate of 0.08 mm / a (fully corrosion-resistant) was prepared.

[0057] The tensile strength test method was as follows: According to the "GB / T 228-2002 Metallic materials-Tensile testing at ambient temperature", the stainless steel / carbon steel composite thin plate prepared by the present invention was subjected to a tensile test on a universal material testing machine to measure its tensile strength.

[0058] The corrosion rate test method was as follows: According to the "GB / T 4334-2020 Corrosion of metals and alloys - Intergranular corrosion test for austenitic and ferritic-austenitic (duplex) stainless steels", the stainless steel / carbon steel composite plate was placed in a 50 wt% sulfuric acid-ferric sulfate solution and subjected to a boiling test, and the corrosion resistance was evaluated by the corrosion rate.

[0059] Example 2

[0060] A processing method for a high-strength and high-toughness stainless steel / carbon steel composite plate, comprising the following steps:

[0061] S1. Roughening the surfaces to be joined:

[0062] The Q960 high-strength carbon steel plate (tensile strength 1066 MPa) and the 304 stainless steel plate are polished with a sanding wheel. The stainless steel and carbon steel with the same width are polished on one side to obtain the surfaces to be joined with a surface roughness Ra of 6.3 μm, and the particulate matter remaining on the surfaces is removed by a dust adsorption system.

[0063] S2. Laser-assisted rolling compounding:

[0064] The stainless steel and Q960 high-strength carbon steel are bitten into the rolling rolls at a spatial angle of 40°, and at the same time, the laser beam irradiates directly on the surfaces to be joined of the two metals in a form with an angle of 0° to the horizontal direction. The tensile strength of the Q960 high-strength carbon steel is 1066 MPa, the thickness specification is 1.5 mm, the rolling reduction rate is 60%, and the maximum heating temperature at the bonding interface is 1300 °C. At the same time, the width of the laser beam spot is 2 times the total thickness of the blank, and the length of the laser beam spot is the same as the width of the blank. The area ratio of the laser irradiation area of the stainless steel / carbon steel is 0.4; the rolling compounding speed is 0.5 m / min. Under the coupled action of the rolling force and the laser heat, the two materials achieve metallurgical bonding at the interface, and the 304 stainless steel plate and the Q960 high-strength carbon steel plate are compounded into one to form a stainless steel / carbon steel composite plate.

[0065] S3. Periodic laser surface annealing:

[0066] The stainless steel / carbon steel composite plate is subjected to periodic laser surface annealing treatment with a homogenized light spot. The maximum heating temperature in the high-power laser irradiation area is controlled at 1100 °C, the maximum heating temperature in the low-power laser irradiation area is controlled at 680 °C, and the widths of the high-power laser irradiation area and the low-power laser irradiation area are 2 mm.

[0067] Finally, a stainless steel / carbon steel composite plate with a tensile strength of 1197 MPa, an elongation after fracture of 14%, and a corrosion rate of 0.091 mm / a (fully corrosion-resistant) is obtained.

[0068] Example 3

[0069] A processing method for a high-strength and high-toughness stainless steel / carbon steel composite plate, comprising the following steps:

[0070] S1. Roughening the surfaces to be joined:

[0071] The Q890 high-strength carbon steel plate (tensile strength 994 MPa) and the 316 stainless steel plate are polished with a wire brush. The stainless steel and carbon steel with the same width are polished on one side to obtain a bonding surface with a surface roughness Ra of 4.7 μm. The particulate matter remaining on the surface is removed using a dust adsorption system.

[0072] S2. Laser-assisted rolling composite:

[0073] The stainless steel and Q890 high-strength carbon steel are bitten into the rolling mill at a spatial angle of 80°. At the same time, the laser beam irradiates directly on the bonding surfaces of the two metals at an angle of 0° with the horizontal direction. The tensile strength of the Q890 high-strength carbon steel is 994 MPa, the thickness specification is 4 mm, the rolling reduction rate is 40%, and the maximum heating temperature at the bonding interface is about 1200 °C. At the same time, the spot width is 0.7 times the total thickness of the blank, and the spot length is the same as the width of the blank. The area ratio of the laser irradiation area of stainless steel / carbon steel is 0.7; the rolling composite speed is 1 m / min. Under the coupled action of the rolling force and the laser, the two materials achieve metallurgical bonding at the interface, and the 316 stainless steel plate and the Q890 high-strength carbon steel plate are combined into one to form a stainless steel / carbon steel composite plate.

[0074] S3. Periodic laser surface annealing:

[0075] The stainless steel / carbon steel composite plate is subjected to periodic laser surface annealing treatment using a homogenized light spot. The maximum heating temperature in the high-power laser irradiation area is controlled at 850 °C, and the maximum heating temperature in the low-power laser irradiation area is controlled at 500 °C. The widths of the high-power laser irradiation area and the low-power laser irradiation area are 0.5 mm.

[0076] Finally, a stainless steel / carbon steel composite plate with a tensile strength of 1103 MPa, an elongation after fracture of 17%, and a corrosion rate of 0.088 mm / a (fully corrosion-resistant) is prepared.

[0077] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for processing a high-strength and tough stainless steel / carbon steel composite plate, characterized in that: The following steps are involved: S1. Machining and surface treatment: The high-strength carbon steel plate and the stainless steel plate are processed into plates of the same width, and then the surfaces to be composited of the high-strength carbon steel plate and the stainless steel plate are polished to perform surface roughening treatment. After the treatment is completed, the surfaces to be composited are cleaned to remove surface stains; S2, Laser-assisted rolling composite: The high-strength carbon steel plate and the stainless steel plate are stacked relative to each other and aligned on all sides for combination. One end of the combined plate is sent to the rolling mill for cold rolling and pressing. The rolling mill is pressed down to bite the two plates together. The unpressed parts of the two plates are opened to form an opening. The laser processing head outputs a flat-top line spot and irradiates the laser from the opening to the bonding interface of the two plates. Subsequently, the rolling mill is started, and the laser processing head emits light to heat the interface to be composited between the stainless steel plate and the high-strength carbon steel plate. Under the action of the rolling force, the two metals are metallurgically bonded at the interface, and the stainless steel plate and the high-strength carbon steel plate are composited into one to form a stainless steel / carbon steel composite plate. The length of the line spot is consistent with the width of the plate, and the width of the line spot is 0.7 to 2 times the sum of the thickness of the two plates. When the thickness of the high-strength carbon steel plate is ≤3.5mm and the tensile strength of the high-strength carbon steel plate is ≤800MPa, the area ratio of the laser irradiation area of ​​the high-strength carbon steel plate and the stainless steel plate is approximately equal to the strength ratio of the two, and the maximum heating temperature of the laser-induced bonding interface is lower than the solidus; when the thickness of the high-strength carbon steel plate exceeds 3.5mm, regardless of whether its strength exceeds 800MPa, the area ratio of the laser irradiation area of ​​the stainless steel plate and the high-strength carbon steel plate is 0.7-0.4, and the maximum heating temperature of the laser-induced high-strength carbon steel plate at the position to be bonded reaches above the melting point; when the tensile strength of the high-strength carbon steel plate exceeds 800MPa, but the thickness is ≤3.5mm, the rolling force is increased, and the maximum heating temperature of the bonding interface is ensured to be lower than the melting point; S3, periodic laser surface annealing: The stainless steel surface of the stainless steel / carbon steel composite plate is subjected to temperature-controlled, periodic laser surface annealing treatment using a homogenized light spot, and a non-uniform structure of alternating coarse-fine grains is constructed in the stainless steel surface area; The length of the homogenized spot is consistent with the width of the stainless steel / carbon steel composite plate. High-power laser and low-power laser are alternately irradiated to the stainless steel surface. The heating temperature of the laser surface annealing area is monitored in real time using a pyrometer. The maximum heating temperature of the high-power laser irradiation area on the stainless steel surface is controlled at 850-1100°C, and the maximum heating temperature of the low-power laser irradiation area is controlled at 500-680°C. The width of a single high-power laser irradiation area or a low-power laser irradiation area is 0.5-2 mm.

2. The method for processing a high-strength and tough stainless steel / carbon steel composite plate according to claim 1, characterized in that: In step S2, the angle of the opening formed by the two plates not pressed together is 40-80°.

3. The processing method of the high-strength and toughness stainless steel / carbon steel composite plate according to claim 1 or 2, characterized in that: In the step S2, the angle between the line spot and the horizontal direction is 0-17°.

4. The method for processing a high-strength and tough stainless steel / carbon steel composite plate according to claim 1, characterized in that: In the step S2, the rolling rate of the rolling mill is 0.5 to 3 m / min, and the rolling reduction ratio is 25 to 60%.

5. The method for processing a high-strength and tough stainless steel / carbon steel composite plate according to claim 1, characterized in that: The material of high-strength carbon steel plate is low-alloy steel with a tensile strength ≥ 600MPa.

6. The method for processing a high-strength and tough stainless steel / carbon steel composite plate according to claim 1, characterized in that: In the step S1, after being polished with sandpaper, wire brush or abrasive belt, the roughness Ra of the surface to be composited of the high-strength carbon steel plate and the stainless steel plate is 3.2-6.3 μm.

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