Laser welding method for high-carbon-equivalent strip steel

Abstract

The invention relates to a high-carbon-equivalent strip steel laser welding method, and belongs to the technical field of strip steel welding. The carbon equivalent of the high-carbon-equivalent strip steel is gt; the method comprises the steps that at least two pieces of to-be-welded high-carbon-equivalent strip steel with set chemical components are subjected to laser welding including first pre-welding induction heating, welding and first post-welding induction heating, so that a welding seam and a heat affected zone are formed; and heat treatment including second pre-welding induction heating and second post-welding induction heating is conducted on the welding seam and the heat affected zone, so that the hardness of the welding seam and the heat affected zone is reduced, and a welded plate is obtained. For the problem of high hardness of a laser welding seam and a heat affected zone, the welding seam is subjected to heat treatment by adopting a mode of increasing laser postweld heat treatment, so that the effect of reducing the hardness of the welding seam and the heat affected zone is achieved, and the toughness of the welding seam formed by welding the high-carbon-equivalent strip steel and the surrounding heat affected zone is improved.

Description

Technical Field

[0001] The present application relates to the technical field of strip steel welding, and in particular to a method for laser welding of high carbon equivalent strip steel. Background Art

[0002] In the continuous pickling and continuous pickling production lines, in order to ensure the continuity of the operation, the strip steel needs to be welded at the entrance of the production line. Laser welding is currently widely used in strip steel welding in continuous production lines due to its high welding efficiency, narrow heat-affected zone, and small welding deformation. Since the welded strip steel needs to withstand a certain tension when running on the continuous production line, and needs to undergo multiple bending deformations and withstand a certain bending moment, in order to avoid economic losses caused by broken strips during operation, high requirements are placed on the strength and toughness of the weld.

[0003] At present, high carbon equivalent strip steel, especially strip steel with a carbon content greater than 0.6%, has high hardness and poor plasticity in the laser welded weld seam and surrounding heat-affected zone of high carbon equivalent strip steel, which is prone to breakage during continuous production. Summary of the invention

[0004] The present application provides a method for laser welding of high carbon equivalent strip steel to solve the following technical problem: how to improve the toughness of a weld formed by welding high carbon equivalent strip steel and a surrounding heat affected zone.

[0005] In a first aspect, an embodiment of the present application provides a method for laser welding of a high carbon equivalent steel strip, wherein the carbon equivalent of the high carbon equivalent steel strip is greater than 0.80, and the method comprises:

[0006] Laser welding of at least two high carbon equivalent steel strips to be welded having a set chemical composition, including first pre-welding induction heating, welding, and first post-welding induction heating, to form a weld and a heat-affected zone;

[0007] The weld and the heat-affected zone are subjected to a heat treatment including a second pre-welding induction heating and a second post-welding induction heating to reduce the hardness of the weld and the heat-affected zone, thereby obtaining a welded plate.

[0008] Optionally, the laser welding method includes laser wire filling welding.

[0009] Optionally, the power of the second pre-welding induction heating is 24.0KW to 36.0KW; and / or,

[0010] The power of the second post-welding induction heating is 28.0 KW to 38.0 KW.

[0011] Optionally, the heat treatment speed is 4.0 m / min to 8.4 m / min.

[0012] Optionally, the interval time between the end point of the laser welding and the start point of the heat treatment is 10s to 60s.

[0013] Optionally, the chemical composition of the welding wire in the laser wire welding method includes:

[0014] C, Si, Mn, Ni, Cr, Mo, Cu, Al, V, Ti, P, S, and Fe; among which, in terms of mass fraction,

[0015] The C content is 0.05% to 0.15%, the Si content is 0.50% to 1.50%, the Mn content is 1.0% to 2.0%, the Ni content is 0.1% to 0.3%, the Cr content is 0.1% to 0.3%, the Mo content is 0.1% to 0.3%, the Cu content is 0.10% to 0.35%, the Al content is 0.01% to 0.03%, the V content is 0.01% to 0.05%, the Ti content is 0.10% to 0.20%, the P content is 0.02% to 0.03%, and the S content is 0.02% to 0.03%.

[0016] Optionally, the wire feeding speed of the laser wire-filling welding method is 1.2 m / min to 4.8 m / min.

[0017] Optionally, the power of the first pre-welding induction heating is 0-20.0KW; and / or,

[0018] The welding speed is 3.2m / min to 6.6m / min, and the welding laser power is 9.6KW to 12.0KW;

[0019] and / or,

[0020] The power of the first post-welding induction heating is 20.0 KW to 34.0 KW.

[0021] Optionally, the set chemical composition includes: C, Si, Mn, P, S, Al, Cu, Cr, and Fe; wherein, in terms of mass fraction,

[0022] The C content is 0.60% to 0.70%, the Si content is 0.20% to 0.30%, the Mn content is 0.50% to 1.5%, the P content is ≤0.0015%, the S content is ≤0.0025%, the Al content is 0.02% to 0.05%, the Cu content is 0.005% to 0.012%, and the Cr content is 0.10% to 0.20%.

[0023] Optionally, the hardness of the weld of the welding plate is ≤450 HV, and the hardness of the heat-affected zone of the welding plate is ≤400 HV.

[0024] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0025] The method for laser welding of high carbon equivalent steel strips provided in an embodiment of the present application, wherein the carbon equivalent of the high carbon equivalent steel strips is>0.80, and the method comprises: subjecting at least two pieces of high carbon equivalent steel strips to be welded with set chemical composition to laser welding including first pre-welding induction heating, welding, and first post-welding induction heating to form a weld and a heat-affected zone; subjecting the weld and the heat-affected zone to heat treatment including second pre-welding induction heating and second post-welding induction heating to reduce the hardness of the weld and the heat-affected zone to obtain a welded plate. At least two pieces of high carbon equivalent steel strips to be welded with set chemical composition are laser welded, wherein the first pre-welding induction heating can reduce the temperature gradient during the welding process. For high carbon equivalent steel strips, the first pre-welding induction heating can reduce the cooling rate to prevent excessive cooling from forming brittle and hard structures. Through the first induction heating before welding, the strip steel can reach a certain temperature before welding, so that the impact of heat input during welding is relatively reduced, which is beneficial to prevent the occurrence of welding cracks in the weld and heat-affected zone; laser welding has the advantages of concentrated energy and relatively small heat-affected zone, but for high-carbon equivalent strip steel, even if the heat-affected zone is small, its structural changes may still lead to toughness problems. Therefore, the induction heating after the first welding can temper the weld and heat-affected zone to improve the toughness; the weld is heat treated, among which the second induction heating before welding can further evenly soften the structure of the weld and the heat-affected zone, and the induction heating after the second welding can further stabilize the structure of the weld and the heat-affected zone, thereby improving the toughness of the weld formed by the welding of high-carbon equivalent strip steel and the surrounding heat-affected zone. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0028] Figure 1 A schematic flow chart of a method for laser welding of high carbon equivalent strip steel provided in an embodiment of the present application. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0030] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0031] In the present application, unless otherwise specified, the directional words used, such as "upper" and "lower", refer specifically to the directions of the drawings in the accompanying drawings. In addition, in the description of the specification of the present application, the terms "include", "comprise", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: the existence of A alone, the existence of A and B at the same time, and the existence of B alone. Among them, A and B can be singular or plural.

[0032] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0033] In a first aspect, an embodiment of the present application provides a method for laser welding of high carbon equivalent strip steel. Figure 1 A schematic diagram of a process for laser welding of high carbon equivalent strip steel provided in an embodiment of the present application; see Figure 1 , the carbon equivalent of the high carbon equivalent strip steel is>0.80, and the method comprises:

[0034] S1. Laser welding at least two high carbon equivalent steel strips to be welded with set chemical composition, including first pre-welding induction heating, welding, and first post-welding induction heating, to form a weld and a heat affected zone;

[0035] At least two pieces of high carbon equivalent steel strips to be welded with set chemical composition are laser welded, wherein the first induction heating before welding can reduce the temperature gradient during welding. For high carbon equivalent steel strips, the first induction heating before welding can reduce the cooling rate and prevent the formation of brittle and hard structures due to excessive cooling. Through the first induction heating before welding, the steel strip can reach a certain temperature before welding, so that the impact of heat input during welding is relatively reduced, which is conducive to preventing the generation of welding cracks in the weld and heat-affected zone.

[0036] In some embodiments, the power of the first pre-welding induction heating is 0 to 20.0 KW; and / or,

[0037] The welding speed is 3.2m / min to 6.6m / min, and the welding laser power is 9.6KW to 12.0KW; and / or,

[0038] The power of the first post-welding induction heating is 20.0 KW to 34.0 KW.

[0039] In the embodiment of the present application, the power of the induction heating before the first welding can be 0-20.0KW, and the strip steel is moderately preheated. For high carbon equivalent strip steel, the lower preheating power can play a role in reducing the temperature gradient. During the welding process, a large temperature gradient will lead to uneven cooling rate, which will produce uneven structure, affecting the toughness of the weld and the heat affected zone. Preheating can make the heat transfer more gentle during welding, which helps to obtain welds and heat affected zones with uniform structure. The welding speed and laser power determine the size of the welding heat input, which directly affects the quality of the weld. The welding speed can be 3.2m / min~6.6m / min, and the welding laser power can be 9.6KW~12.0KW, which can enable the weld and the heat affected zone to form a structure with good toughness under appropriate heat input and cooling conditions. The power of the induction heating after the first welding can be 20.0KW~34.0KW, which fully tempers the weld and the heat affected zone, helps to eliminate welding residual stress, and improves the toughness of the weld and the heat affected zone. The synergistic effect of the induction heating power of 0-20.0KW before the first welding and the induction heating power of 20.0KW-34.0KW after the first welding can improve the joint structure and hardness to a certain extent, reduce the degree of joint hardening, and reduce the risk of cracking caused by the hardness and brittleness of the joint. Exemplarily, the power of the induction heating before the first welding can be 1.0KW, 2.0KW, 4.0KW, 6.0KW, 8.0KW, 10.0KW, 12.0KW, 14.0KW, 16.0KW, 18.0KW, 20.0KW, etc.; the welding speed can be 3.2m / min, 3.4m / min, 3.6m / min, 3.8m / min, 4.0m / min, 4.2m / min, 4.4m / min, 4.6 m / min, 4.8m / min, 5.0m / min, 5.2m / min, 5.4m / min, 5.6m / min, 5.8m / min, 6.0m / min, 6.2m / min, 6.4m / min, 6.6m / min, etc.; the power of induction heating after the first welding can be 20.0KW, 22.0KW, 24.0KW, 26.0KW, 28.0KW, 30.0KW, 320KW, 34.0KW, etc. In addition, the above laser welding process parameters also include: defocusing amount is -4mm~-1mm, butt gap is: 0~0.2mm, secondary shear is 0.1~1.0, and shielding gas flow rate is 18L / min~25L / min.

[0040] In some embodiments, the set chemical composition includes: C, Si, Mn, P, S, Al, Cu, Cr, and Fe; wherein, in terms of mass fraction,

[0041] The C content is 0.60% to 0.70%, the Si content is 0.20% to 0.30%, the Mn content is 0.50% to 1.5%, the P content is ≤0.0015%, the S content is ≤0.0025%, the Al content is 0.02% to 0.05%, the Cu content is 0.005% to 0.012%, and the Cr content is 0.10% to 0.20%.

[0042] In the embodiments of the present application, the chemical composition of the high carbon equivalent strip steel to be welded is reasonably designed to ensure the mechanical properties (strength and toughness) of the welded plate. The carbon equivalent is calculated according to the following carbon equivalent calculation formula: Ceq(IIW)=C+Mn / 6+(Cu+Ni) / 15+(Cr+Mo+V) / 5, and the carbon equivalent is 0.82-0.89. Exemplarily, the C content can be 0.60%, 0.62%, 0.64%, 0.66%, 0.68%, 0.70%; the Si content can be 0.20%, 0.22%, 0.24%, 0.26%, 0.28%, 0.30%, etc.; the Mn content can be 0.50%, 0.70%, 0.90%, 1.1%, 1.3%, 1.5%, etc.; the P content can be 0.0015%, 0.0014%, 0.0013% and so on. %, 0.0012%, etc.; the S content can be 0.0025%, 0.0024%, 0.0023%, etc.; the Al content can be 0.02%, 0.03%, 0.04%, 0.05%, etc.; the Cu content can be 0.005%, 0.007%, 0.009%, 0.01%, 0.012%, etc.; the Cr content can be 0.10%, 0.12%, 0.14%, 0.16%, 0.18%, 0.20%, etc.

[0043] The laser welding device includes: a laser welding head, a pre-welding induction heater, and a post-welding induction heater. Step S1 may be: butt-welding the first steel strip to be welded with the second steel strip to be welded, butt-welding the two steel strips by laser welding to form a weld; after welding, the laser welding device returns to its original position. The pre-welding induction heater performs the first pre-welding induction heating, and the post-welding induction heater performs the first post-welding induction heating.

[0044] In some embodiments, the laser welding method includes laser wire welding.

[0045] In an embodiment of the present application, the laser welding method includes a laser wire-filling welding method, and the above-mentioned laser welding device also includes: a wire feeding device. For high-carbon equivalent strip steel, the established chemical composition plays a key role in the performance. During laser wire-filling welding, by selecting welding wire with adapted chemical composition, the element content at the weld can be accurately controlled to compensate for the element burnout during the welding process, further ensure the consistency of the weld and the parent material in composition, and stabilize the weld quality. In actual welding, it is difficult to ensure a completely gapless fit between the high-carbon equivalent strip steels to be welded. Laser wire-filling welding allows a certain gap to exist, and the welding wire can fill these gaps to ensure that the weld is complete and continuous, and avoid welding defects such as lack of fusion.

[0046] In some embodiments, the chemical composition of the welding wire includes:

[0047] C, Si, Mn, Ni, Cr, Mo, Cu, Al, V, Ti, P, S, and Fe; among which, in terms of mass fraction,

[0048] The C content is 0.05% to 0.15%, the Si content is 0.50% to 1.50%, the Mn content is 1.0% to 2.0%, the Ni content is 0.1% to 0.3%, the Cr content is 0.1% to 0.3%, the Mo content is 0.1% to 0.3%, the Cu content is 0.10% to 0.35%, the Al content is 0.01% to 0.03%, the V content is 0.01% to 0.05%, the Ti content is 0.10% to 0.20%, the P content is 0.02% to 0.03%, and the S content is 0.02% to 0.03%.

[0049] In the embodiment of the present application, by using low carbon equivalent welding wire for laser wire welding, the alloy content in the weld is diluted to achieve the effect of reducing the hardness of the weld; at the same time, in conjunction with the heat treatment process after laser welding, the hardness of the weld and the heat affected zone is further reduced by heat treatment. For example, the chemical composition of the welding wire is:

[0050] The content of C can be 0.05%, 0.07%, 0.09%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, etc.; the content of Si can be 0.50%, 0.70%, 0.90%, 1.1%, 1.2%, 1.3%, 1.4%, 1.50%, etc., the content of Mn can be 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, etc.; the content of Ni can be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, etc.; the content of Cr can be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, etc.; the content of Mo can be 0.1%, 0.15%, 0.2%, 0.25%, 0.3% etc.; the content of Cu can be 0.10%, 0.20%, 0.30%, 0.35%, etc.; the content of Al can be 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, etc.; the content of V can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, etc.; the content of Ti can be 0.10%, 0.12%, 0.14%, 0.16%, 0.18%, 0.20%, etc.; the content of P can be 0.02%, 0.022%, 0.024%, 0.026%, 0.028%, 0.03%, etc.; the content of S can be 0.02%, 0.022%, 0.024%, 0.026%, 0.028%, 0.03%, etc.

[0051] In some embodiments, the wire feeding speed of the laser wire welding method is 1.2 m / min to 4.8 m / min.

[0052] In an embodiment of the present application, the wire feeding speed of the laser wire welding method can be 1.2m / min to 4.8m / min, ensuring that the weld has a basic speed with sufficient filler metal. An appropriate wire feeding speed helps to maintain the stability of the molten pool, avoid instability in the solidification process of the molten pool, and produce defects such as pores and slag inclusions. Exemplarily, the wire feeding speed of the laser wire welding method can be 1.2m / min, 1.4m / min, 1.6m / min, 1.8m / min, 2.0m / min, 2.2m / min, 2.4m / min, 2.6m / min, 2.8m / min, 3.0m / min, 3.2m / min, 3.4m / min, 3.6m / min, 3.8m / min, 4.0m / min, 4.2m / min, 4.4m / min, 4.6m / min, 4.8m / min, etc.

[0053] S2. Performing a heat treatment including a second pre-welding induction heating and a second post-welding induction heating on the weld and the heat-affected zone to reduce the hardness of the weld and the heat-affected zone, thereby obtaining a welded plate.

[0054] Laser welding has the advantages of concentrated energy and relatively small heat-affected zone, but for high carbon equivalent strip steel, even if the heat-affected zone is small, its structural changes may still lead to toughness problems. Therefore, the first post-welding induction heating can temper the weld and the heat-affected zone, thereby improving toughness; the weld is heat treated, wherein the second pre-welding induction heating can further uniformly soften the structure of the weld and the heat-affected zone, and the second post-welding induction heating can further stabilize the structure of the weld and the heat-affected zone to reduce the hardness of the weld and the heat-affected zone, thereby improving the toughness of the weld formed by the high carbon equivalent strip steel welding and the surrounding heat-affected zone. Step S2 implements the heat treatment by the pre-welding induction heater and the post-welding induction heater in the laser welding device.

[0055] In some embodiments, the power of the second pre-welding induction heating is 24.0 KW to 36.0 KW; and / or the power of the second post-welding induction heating is 28.0 KW to 38.0 KW.

[0056] In the embodiment of the present application, the power of the induction heating before the second welding can be 24.0KW~36.0KW, which can provide enough heat to start adjusting the organization of the weld and the heat-affected zone, which can not only make the organization undergo favorable changes, such as promoting the precipitation of carbides and eliminating residual stress, but also will not destroy the original favorable organization or produce new defects due to excessive temperature. The power of the induction heating after the second welding can be 28.0KW~38.0KW, which can provide enough heat for further tempering or other heat treatment of the weld and the heat-affected zone, and prevent overheating. Overheating may cause the adjusted organization to change again, such as grain growth, thereby reducing the performance of the material. Within this power range, the organization of the weld and the heat-affected zone can be stabilized in a state that is conducive to toughness. Exemplarily, the power of the second induction heating before welding can be 24.0KW, 25.0KW, 26.0KW, 27.0KW, 28.0KW, 29.0KW, 30.0KW, 30.0KW, 31.0KW, 32.0KW, 34.0KW, 35.0KW, 36.0KW, etc.; the power of the second induction heating after welding can be 28.0KW, 29.0KW, 30.0KW, 31.0KW, 32.0KW, 33.0KW, 34.0KW, 35.0KW, 36.0KW, 37.0KW, 38.0KW, etc.

[0057] In some embodiments, the heat treatment speed is 4.0 m / min to 8.4 m / min.

[0058] In the embodiment of the present application, the heat treatment speed can be 4.0m / min to 8.4m / min, and the strip has enough time to be fully heated during the heat treatment process, so that the desired changes occur in the structure of the weld and the heat affected zone. This speed can ensure that the heat of induction heating can be effectively transferred to the inside of the material and the structure can be deeply adjusted. For materials such as high carbon equivalent strip steel that are sensitive to structural changes, a suitable heat treatment speed can ensure that the toughness of the weld and the heat affected zone is effectively improved without generating new defects. Exemplarily, the heat treatment speed can be 4.0m / min, 5.0m / min, 6.0m / min, 7.0m / min, 8.0m / min, 8.4m / min, etc.

[0059] Therefore, under the synergistic effect of the induction heating power of 24.0KW~36.0KW before the second welding, the induction heating power of 28.0KW~38.0KW after the second welding and the heat treatment speed of 4.0m / min~8.4m / min, the weld can be fully heat treated, thereby reducing the hardness of the weld and the heat affected zone, and will not reduce the quality of strip steel production.

[0060] In some embodiments, the interval time between the end point of the laser welding and the start point of the heat treatment is 10s to 60s.

[0061] In an embodiment of the present application, after the laser welding is completed, the weld and the heat-affected zone are in a state that has just undergone rapid cooling (although there is induction heating after the first welding, it is still cooled relative to the high temperature during the welding process). The interval time between the end point of laser welding and the start point of heat treatment can be 10s to 60s, which allows the weld and the heat-affected zone to have a short stable stage. This stage can allow the metal crystal structure in the weld to self-adjust to a certain extent. Within this time range, a relatively suitable starting state can be provided for heat treatment while ensuring that the state of the weld and the heat-affected zone does not deteriorate. Exemplarily, the interval time between the end point of the laser welding and the start point of the heat treatment can be 10s, 20s, 30s, 40s, 50s, 60s, etc.

[0062] In some embodiments, the hardness of the weld of the welding plate is ≤450 HV, and the hardness of the heat-affected zone of the welding plate is ≤400 HV.

[0063] The method for laser welding of high carbon equivalent strip steel provided in the embodiment of the present application has the following advantages:

[0064] 1. For the problem of high hardness of laser welding seams and heat-affected zones, heat treatment is performed on the weld seams and heat-affected zones after laser welding to reduce the hardness of the weld seams and heat-affected zones.

[0065] 2. By using low-carbon equivalent welding wire for laser wire welding, the alloy content in the weld is diluted to achieve the effect of reducing the hardness of the weld; at the same time, in conjunction with the heat treatment process after laser welding, the hardness of the weld and the heat-affected zone is further reduced through the heat treatment process, and the toughness of the weld formed by high-carbon equivalent strip welding and the surrounding heat-affected zone is improved.

[0066] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for the unrecorded specific conditions in the following examples are usually measured according to national standards. If there is no corresponding national standard, then carry out according to general international standards, normal conditions or according to the conditions recommended by the manufacturer.

[0067] The high carbon equivalent strip steels to be welded in Examples 1 to 3 and Comparative Example 1 are shown in Table 1, and the welding parameters are shown in Table 2. Examples 1 and 2 use laser welding with wire filling combined with a post-welding heat treatment process, Example 3 only uses a post-welding heat treatment process, and Comparative Example 1 uses a laser welding process without wire filling. The maximum hardness, cupping results, and bending results of the welds of Examples 1 to 3 and Comparative Example 1 are shown in Table 3. [0] in Table 3 represents a qualified result, and [×] represents an unqualified result. The results show that for this material combination, Examples 1 to 3 can effectively reduce the weld hardness and provide high weld quality.

[0068] Table 1 Chemical composition (wt%) of high carbon equivalent strip steel to be welded in Examples 1 to 3 and Comparative Example 1, the remainder being Fe and unavoidable impurities

[0069] Plate thickness C Si Mn Cu Cr P S Ceq(IIW) 2.5mm 0.67 0.27 1.0 0.01 0.15 0.01 0.002 0.86 2.5mm 0.67 0.27 1.0 0.01 0.15 0.01 0.002 0.86

[0070] Table 2 Welding parameters of Examples 1 to 3 and Comparative Example 1

[0071]

[0072]

[0073] Table 3 Test results of Examples 1 to 3 and Comparative Example 1

[0074]

[0075] The material combinations of Examples 4 to 6 and Comparative Example 2 are shown in Table 4, and the welding parameters are shown in Table 5. Examples 4 and 5 use laser welding with wire filling combined with a post-welding heat treatment process, Example 6 only uses a post-welding heat treatment process, and Comparative Example 2 uses a laser welding process without wire filling. The maximum hardness, cupping results, and bending results of the welds of Examples 4 to 6 and Comparative Example 2 are shown in Table 6. [0] in Table 6 represents a qualified result, and [×] represents an unqualified result. The results show that for this material combination, Examples 4 and 5 can effectively reduce the weld hardness and provide high weld quality, and the process of Example 6 can improve the weld quality to a certain extent, but the effect is poorer than that of Examples 4 and 5.

[0076] Table 4 Chemical composition (wt%) of high carbon equivalent strip steel to be welded in Examples 4 to 6 and Comparative Example 2, the remainder being Fe and unavoidable impurities

[0077] Plate thickness C Si Mn Cu Cr P S Ceq(IIW) 4.0mm 0.68 0.26 1.0 0.01 0.20 0.01 0.002 0.89 4.0mm 0.68 0.26 1.0 0.01 0.20 0.01 0.002 0.89

[0078] Table 5 Welding parameters of Examples 4 to 6 and Comparative Example 2

[0079]

[0080]

[0081] Table 6 Test results of Examples 4 to 6 and Comparative Example 2

[0082]

[0083] One or more technical solutions in the embodiments of the present application also have at least the following technical effects or advantages:

[0084] (1) The embodiment of the present application uses a low-carbon equivalent welding wire for laser wire welding to dilute the alloy content at the weld, thereby achieving the effect of reducing the hardness of the weld; at the same time, in conjunction with the heat treatment process after laser welding, the technical solution of further reducing the hardness of the weld and the heat-affected zone through the heat treatment process reduces the hardness and brittleness of the laser weld and the heat-affected zone of the same material of high-carbon equivalent strip steel, and improves the toughness and deformation resistance of the weld joint;

[0085] (2) The embodiment of the present application realizes the stable and efficient production of the same material of high carbon equivalent strip steel in a continuous pickling or pickling production line. At the same time, the embodiment of the present application omits the requirement of transition material for welding high carbon equivalent strip steel in a continuous production line, thereby simplifying the production process and reducing production costs.

[0086] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for laser welding of high carbon equivalent steel strip, wherein the carbon equivalent of the high carbon equivalent steel strip is greater than 0.80, the method comprising: Laser welding of at least two high carbon equivalent steel strips to be welded having a set chemical composition, including first pre-welding induction heating, welding, and first post-welding induction heating, to form a weld and a heat-affected zone; The weld and the heat-affected zone are subjected to a heat treatment including a second pre-welding induction heating and a second post-welding induction heating to reduce the hardness of the weld and the heat-affected zone, thereby obtaining a welded plate.

2. The method according to claim 1, characterized in that The laser welding method includes a laser wire-filling welding method.

3. The method according to claim 1, characterized in that The power of the second pre-welding induction heating is 24.0KW to 36.0KW; and / or, The power of the second post-welding induction heating is 28.0 KW to 38.0 KW.

4. The method according to claim 1 or 3, characterized in that: The speed of the heat treatment is 4.0 m / min to 8.4 m / min.

5. The method according to claim 1, characterized in that The interval time between the end point of the laser welding and the start point of the heat treatment is 10s to 60s.

6. The method according to claim 2, characterized in that The chemical composition of the welding wire of the laser wire welding method includes: C, Si, Mn, Ni, Cr, Mo, Cu, Al, V, Ti, P, S, and Fe; among which, in terms of mass fraction, The C content is 0.05% to 0.15%, the Si content is 0.50% to 1.50%, the Mn content is 1.0% to 2.0%, the Ni content is 0.1% to 0.3%, the Cr content is 0.1% to 0.3%, the Mo content is 0.1% to 0.3%, the Cu content is 0.10% to 0.35%, the Al content is 0.01% to 0.03%, the V content is 0.01% to 0.05%, the Ti content is 0.10% to 0.20%, the P content is 0.02% to 0.03%, and the S content is 0.02% to 0.03%.

7. The method according to claim 2, characterized in that The wire feeding speed of the laser wire-filling welding method is 1.2 m / min to 4.8 m / min.

8. The method according to claim 1, characterized in that The power of the first pre-welding induction heating is 0-20.0KW; and / or, The welding speed is 3.2m / min to 6.6m / min, and the welding laser power is 9.6KW to 12.0KW; and / or, The power of the first post-welding induction heating is 20.0 KW to 34.0 KW.

9. The method according to claim 1, characterized in that: The set chemical composition includes: C, Si, Mn, P, S, Al, Cu, Cr, and Fe; wherein, in terms of mass fraction, The C content is 0.60% to 0.70%, the Si content is 0.20% to 0.30%, the Mn content is 0.50% to 1.5%, the P content is ≤0.0015%, the S content is ≤0.0025%, the Al content is 0.02% to 0.05%, the Cu content is 0.005% to 0.012%, and the Cr content is 0.10% to 0.20%.

10. The method according to claim 1, characterized in that The hardness of the weld of the welding plate is ≤450HV, and the hardness of the heat affected zone of the welding plate is ≤400HV.

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