CN114571083A - 780 MPa-grade high-reaming cold-rolled dual-phase steel and welding method in acid rolling process thereof - Google Patents

780 MPa-grade high-reaming cold-rolled dual-phase steel and welding method in acid rolling process thereof Download PDF

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CN114571083A
CN114571083A CN202210361671.5A CN202210361671A CN114571083A CN 114571083 A CN114571083 A CN 114571083A CN 202210361671 A CN202210361671 A CN 202210361671A CN 114571083 A CN114571083 A CN 114571083A
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steel
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余灿生
苏冠侨
常智渊
郑之旺
刘庆春
王敏莉
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Pangang Group Panzhihua Iron and Steel Research Institute Co Ltd
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    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
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    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
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Abstract

The invention discloses 780MPa grade high-hole-expansion cold-rolled dual-phase steel and a welding method of an acid rolling process thereof, wherein the 780MPa grade high-hole-expansion cold-rolled dual-phase steel comprises the following components in percentage by weight: 0.05 to 0.163%, Si: 0.40-0.90%, Mn: 1.50-2.30%, P is less than or equal to 0.017%, S is less than or equal to 0.008%, Als: 0.010-0.080%, N not more than 0.008%, Cr: 0.10 to 0.40%, Nb: 0.01-0.05%; the rest elements are Fe and inevitable impurities for control. And (3) welding, namely, 780 MPa-grade high-reaming cold-rolled dual-phase steel is selected as a connecting material, the connecting material and the raw material steel coil are cut, welding wires are added to the connecting material and the raw material steel coil after the welding surface of the connecting material and the raw material steel coil are aligned and positioned on the same horizontal plane for welding, the welded seam is subjected to post-welding annealing and polishing treatment after welding, and the quality of the welded seam is checked through measuring the thickness of the welded seam and a cupping test. Therefore, the technical problems of instability and low production efficiency in the production process in the prior art are effectively solved, and the purpose of ensuring stable and high-efficiency production of the 780 MPa-grade high-reaming cold-rolled dual-phase steel acid rolling process is achieved.

Description

780 MPa-grade high-reaming cold-rolled dual-phase steel and welding method in acid rolling process thereof
Technical Field
The invention relates to the technical field of steel rolling production processes, in particular to 780MPa grade high-reaming cold-rolled dual-phase steel and a welding method for an acid rolling process of the 780MPa grade high-reaming cold-rolled dual-phase steel.
Background
The welding equipment is used for welding the front steel coil and the rear steel coil to realize the continuous production of steel enterprises, and the method is an important technological means for improving the production efficiency and reducing the production cost. Is widely applied to an acid rolling combined unit, a continuous annealing/galvanizing unit and the like to realize continuous and efficient production. Laser welding is a method of welding by the heat generated by a focused laser beam as an energy source to bombard a weldment. Because the laser has optical properties of refraction, focusing and the like, the laser welding has the characteristics of low heat input, small welding deformation, no electromagnetic field influence and the like, and is widely applied to welding raw materials of the acid rolling combined unit. If the welding effect is not added, the strip breakage accident along the welding line is easy to happen in the pickling and cold rolling processes, the continuous production is not facilitated, the production efficiency and the production safety are seriously affected, and the production rhythm, transition materials, welding key processes and the like of the strip breakage accident need to be studied in detail so as to obtain good welding quality and promote continuous and efficient production.
Patent document CN 112025081a discloses a method for welding QP980 and above ultra-high strength steel by a laser welder, which comprises the following steps: 1) adjusting the working process of the laser welding machine, namely adjusting the inlet section, the outlet section and the middle section; 2) adjusting the position of a protective gas nozzle; 3) adjusting the transverse blowing air pressure; 4) selecting a transition material; 5) cooling by a water cooling device;
6) optimizing welding parameters; 7) monitoring the quality of the welding seam in real time by adopting a QCDS welding seam detection system; 8) optimizing a preheating and annealing device; 9) equipment maintenance before production welding realizes QP980 production with carbon equivalent of more than 0.575% and poor weldability, but the technical scheme introduces production rhythm, transition material selection basis, raw material requirements, strip head/tail treatment, gas protection, weld joint quality evaluation and the like, is not beneficial to guidance of the whole welding process, and is not beneficial to popularization of 780 MPa-grade high-reaming cold-rolled dual-phase steel produced by the same type of equipment at home and abroad.
The patent document with publication number CN 104842056a discloses a weld joint plasticizing device and process for an ultrahigh-strength dual-phase steel laser tailor-welded blank, wherein the weld joint of the ultrahigh-strength dual-phase steel tailor-welded blank is arranged between a heat conduction material and a cooling plate, so that the flatness of a welded plate is ensured, and meanwhile, an electromagnetic chuck is adopted for accurately positioning to assemble the material; switching on a high-frequency heating coil to adjust the output power, ensuring the output temperature to be 800-850 ℃, keeping the temperature for 3-5 min, and austenitizing the welded joint structure; rapidly cooling the welding line of the ultrahigh-strength dual-phase steel tailor-welded blank by adopting a cooling plate filled with cooling liquid; adjusting the output power of the high-frequency heating coil, ensuring the output temperature to be 250-300 ℃, and preserving the heat for 5-30 s; reducing the flow rate of the cooling liquid, improving the output power of the high-frequency heating coil, ensuring the output temperature to be 300-380 ℃, keeping the temperature for 10-90 s, and performing a local distribution process on the weld joint; reducing the output power of the high-frequency heating coil to zero; and (3) rapidly cooling the welding line of the ultrahigh-strength dual-phase steel tailor-welded blank to room temperature by adopting the cooling plate filled with cooling liquid. The average size of the obtained weld grains is 1.5-4.0 mu m, the cupping value of the dual-phase steel tailor-welded blank with the ultra-high strength steel is 7.3-9.9 mm, and the cupping value of the tailor-welded blank is improved by 43%. However, the technical scheme does not detail production rhythm, transition material selection basis, raw material requirements, strip head/tail treatment, welding key process parameters and the like, and equipment is specially modified, so that the conventional machine set is not favorable for completing welding of the acid rolling raw materials.
Patent document CN 113118630A discloses a method for preparing a laser tailor-welded blank with different thicknesses, which comprises the steps of purifying two DP steel plates with different thicknesses (the thickness difference is less than or equal to 0.5mm, the C content difference is less than or equal to 0.03%, and the Mn content difference is less than or equal to 0.4%), cooling, air-drying and placing on a welding workbench. The horizontal gap of the DP steel plate is 0mm, the gap in the vertical direction is 0.05-0.08 mm, and the defocusing amount is 0.2-1.0 mm in the welding process; the laser power is 3.7-4.2 kW; the welding speed is 5.0-8.0 m/min; the laser offset is 0.4-0.7 mm, a protective gas blowing device is adopted to blow gas, and the distance between a gas blowing port and a welding line is 20-28 mm; a 30-60-degree protective gas between the blowing opening of the blowing measuring device and the DP steel plate to be welded is argon, and the gas flow is 900-1000L/H; the 590DP and 780DP finished products are welded. However, the welding thickness of the finished product of the technical scheme is thin, no basis is provided for production rhythm and transition material selection, and guidance cannot be provided for the welding method of the 780 MPa-grade high-reaming cold-rolled dual-phase steel acid rolling process.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: provides 780MPa grade high-reaming cold-rolled dual-phase steel which can ensure stable and efficient production of an acid rolling process.
In order to solve the technical problems, the invention adopts the technical scheme that: 780MPa grade high-reaming cold-rolled dual-phase steel comprises the following components in percentage by weight: 0.05 to 0.163%, Si: 0.40-0.90%, Mn: 1.50-2.30%, P is less than or equal to 0.017%, S is less than or equal to 0.008%, Als: 0.010-0.080%, N is not more than 0.008%, Cr: 0.10 to 0.40%, Nb: 0.01-0.05%; the rest elements are Fe and inevitable impurities.
Further, the method comprises the following steps: comprises the following components in percentage by weight: 0.07 to 0.13%, Si: 0.40-0.70%, Mn: 1.90-2.25%, P is less than or equal to 0.012%, S is less than or equal to 0.006%, Al: 0.025-0.065%, N is less than or equal to 0.004%, Cr: 0.10 to 0.30%, Nb: 0.010-0.35%; the rest elements are Fe and inevitable impurities.
The invention also discloses a welding method for the 780 MPa-grade high-reaming cold-rolled dual-phase steel acid rolling process, which adopts the technical scheme that: the welding method comprises the following steps of selecting 780 MPa-grade high-reaming cold-rolled dual-phase steel as a connecting material, shearing the connecting material and a raw material steel coil, aligning the welding surfaces of the connecting material and the raw material steel coil, placing the welding surfaces on the same horizontal plane, adding a welding wire for welding, carrying out post-welding annealing and polishing treatment on a welding seam after welding, and checking the quality of the welding seam through measuring the thickness of the welding seam and a cupping test;
wherein, the steel coils need to be cooled to less than or equal to 80 ℃ before welding, and the yield strength of the steel strips with higher strength in the two steel coils before and after welding is not higher than 1.5 times of the yield strength of the steel strips with lower strength;
controlling the carbon equivalent of a connecting material selected for welding to be in a range of 0.25-0.65 according to a numerical value calculated by the following formula, wherein the carbon equivalent formula is Ceq ═ C + Mn/6+ Si/24+ Ni/40+ Cr/5+ Mo/4+ V/14 (%);
the chemical components of the welding wire are C: 0.02 to 0.15%, Si: 0.50 to 1.0%, Mn: 1.25-2.00%, P is less than or equal to 0.030%, S is less than or equal to 0.030%, Cu is less than or equal to 0.50%, Ti + Zr: 0.02-0.30%;
and (3) carrying out heat treatment on the welding seam through heat circulation after welding, wherein the power is 40kW, the frequency is 30kHz, the current compensation amount of the welding seam heat treatment is 0-15%, the heating speed is required to be less than or equal to 20 ℃/s in the heating process of the welding seam heat treatment, and the welding seam is cooled to below 300 ℃ at the cooling speed of less than or equal to 15 ℃/s during cooling.
Further, the method comprises the following steps: the shearing adopts double-shearing, the inclination angle between the shearing edge and the steel strip in the shearing process is 2 degrees, and the clearance range of the shearing edge is controlled to be 0.30-0.65 mm.
Further, the method comprises the following steps: the control of the shear blade gap is determined according to the steel strip thickness according to the following requirements, when the steel strip thickness is less than or equal to 2.5mm, the shear blade gap is 0.30mm, and when the steel strip thickness is increased by 0.5mm, the shear blade gap is increased by 0.05 mm; the shearing edge is replaced according to the period of less than or equal to 7800t or the shearing frequency of less than or equal to 13500 times, the side gap of the shearing edge is calibrated after the shearing edge is replaced every time, the shearing cross section and the longitudinal direction of the strip steel form 90 degrees, and the shearing end face is required to be ensured to be smooth and straight without the defects of burrs, layering and the like.
Further, the method comprises the following steps: during shearing, the cutting length of the steel coil is controlled according to the following requirements, and welding is carried out after the plate shape and the surface quality are ensured;
the control requirements for the resection length are as follows: the cutting length is 5.2mm when the thickness t of the strip steel is less than 2.75mm, the cutting length is 4.3mm when the thickness t of the strip steel is less than or equal to 2.75mm and less than 4.0mm, and the cutting length is 3.5mm when the thickness t of the strip steel is more than or equal to 4.0mm, thereby ensuring that the defects of the head and the tail of the strip can be completely cut without deteriorating the welding quality.
Further, the method comprises the following steps: the surface flatness of the strip steel is required to be less than or equal to 245umit, the camber is required to be less than or equal to 25mm/10m, hc-h40The convexity requirement is less than or equal to 150 μm.
Further, the method comprises the following steps: the welding is carried out by adopting a laser welding machine, the jumping range of the thickness of the welding machine is less than or equal to 1.5H1, the jumping range of the width is less than or equal to 330mm, and each side is less than or equal to 165mm, wherein H1 is the thickness of the thinner strip steel, and the unit is mm; in the laser welding process, a focusing position or a light spot position is utilized to focus a laser beam into a welding light spot, the height adjusting range of the focusing position is 0-9.0 mm, the Z-axis control precision is +/-0.05 mm, the adjusting range of the light spot position is +/-1.5 mm, and the X-axis control precision is +/-0.05 mm.
Further, the method comprises the following steps: the power of the laser welding is 12 +/-0.8 KW, the welding speed is controlled to be 2.5-4.8 +/-0.3 m/min according to the thickness of the strip steel, and the wire feeding speed is controlled to be 1.5-3.6 +/-0.3 m/min according to the thickness of the strip steel; introducing gas protection in the whole welding process, wherein the protection gas is He and N2And CO, wherein the auxiliary gas during welding is He; cleaning a weld joint by using a rolling wheel after welding is finished, wherein the pressure of the rolling wheel is less than or equal to 60KN, and the height of the rolling wheel is 0-7.5 mm;
wherein the welding speed is 4.8 +/-0.3 m/min when the thickness of the strip steel is less than or equal to 2.5mm, the welding speed is reduced by 0.3m/min when the thickness of the strip steel is increased by 0.5mm, and the compensation range of the welding speed is 0-15%; when the thickness of the strip steel is less than or equal to 2.5mm, the wire feeding speed is 1.5 +/-0.3 m/min, the welding speed is increased by 0.3m/min when the thickness of the strip steel is increased by 0.5mm, and the compensation range of the wire feeding speed is 0-15%;
the flow rate of He in the welding protective gas is 45-51 NL/h, and N2The flow rate of the mixed gas is 8.0-12.0 NL/h, the flow rate of the CO is 1.8-2.3 NL/h, the dew point of the mixed gas is less than or equal to minus 50 ℃, the pressure is 0.4-0.7 MPa, and the temperature is 5-50 ℃;
the flow rate of the auxiliary gas He is 90-160 NL/min, the pressure is 0.4-0.7 MPa, and the temperature is 5-50 ℃.
Further, the method comprises the following steps: in the welding process, the thickness of a welding seam is 1.02-1.20 times of that of the raw material steel strip; when the weld seam is sampled and the cupping test is carried out, the number of sampling points is at least 3, the left point and the right point are taken within a range of 100-200 mm from the edge part, the third point is taken in the middle of the steel strip, the hole diameter of a punching hole of the sampling point is 15mm, and the punching hole is 100mm away from the weld seam;
the requirement of the cupping test is that if the crack is vertical to the direction of the weld seam in the heat affected zone and the crack is vertical to the direction of the weld seam, the weld seam is judged to be qualified; if the crack is coincident with the welding seam, determining that the welding seam quality is unqualified; two welding seams are not allowed in one large coil, otherwise, the coil is judged to be unqualified;
when the welding is carried out with width jump connection, a crescent bay punching experiment is required,
(1) punching at the welding seam, wherein the punching amount is 30mm relative to the width of the narrow strip steel,
(2) in the case of narrow and wide, punching was performed twice at a position deviated from the wide side toward the inlet side by 240mm from the weld and at the weld,
(3) in the case of narrowing the width, punching was performed twice at a position deviated from the wider side by 240mm from the weld toward the exit side and at the weld,
after the experiment, the transition of the width jumping steel coil can be carried out without problems.
The invention has the beneficial effects that: the 780 MPa-grade high-reaming cold-rolled dual-phase steel comprises the following components in percentage by weight: 0.05 to 0.163%, Si: 0.40-0.90%, Mn: 1.50-2.30%, P is less than or equal to 0.017%, S is less than or equal to 0.008%, Als: 0.010-0.080%, N not more than 0.008%, Cr: 0.10 to 0.40%, Nb: 0.01-0.05%; controlling the other elements to be Fe and inevitable impurities, and welding before acid rolling according to the following method, namely selecting 780MPa high-reaming cold-rolled dual-phase steel as a connecting material, shearing the connecting material and a raw material steel coil to enable the welding surfaces of the connecting material and the raw material steel coil to be aligned and to be positioned on the same horizontal plane for welding, carrying out post-welding annealing and polishing treatment on a welding seam after welding, and checking the quality of the welding seam through measuring the thickness of the welding seam and a cupping test; the steel coils need to be cooled to be less than or equal to 80 ℃ before being welded, and the yield strength of the steel strips with higher strength in the two steel coils before and after being welded is not higher than 1.5 times of the yield strength of the steel strips with lower strength; the carbon equivalent of the connecting material selected for welding is controlled within the range of 0.25-0.65 according to the following formula, wherein Ceq is C + Mn/6+ Si/24+ Ni/40+ Cr/5+ Mo/4+ V/14 (%). Therefore, the technical problems of instability and low production efficiency in the production process in the prior art are effectively solved, and the purpose of ensuring stable and high-efficiency production of the 780 MPa-grade high-reaming cold-rolled dual-phase steel acid rolling process is achieved.
Drawings
FIG. 1 is a schematic representation of the quality of the weld after welding according to the present invention.
Detailed Description
In order to facilitate understanding of the present invention, the present invention will be further described with reference to the accompanying drawings and examples.
The invention discloses 780MPa grade high-reaming cold-rolled dual-phase steel which comprises the following components in percentage by weight: 0.05 to 0.163%, Si: 0.40-0.90%, Mn: 1.50-2.30%, P is less than or equal to 0.017%, S is less than or equal to 0.008%, Als: 0.010-0.080%, N not more than 0.008%, Cr: 0.10 to 0.40%, Nb: 0.01-0.05%; the rest elements are Fe and inevitable impurities. The welding method for the 780 MPa-grade high-reaming cold-rolled dual-phase steel acid rolling process comprises the steps of selecting 780 MPa-grade high-reaming cold-rolled dual-phase steel as a connecting material for welding, shearing the connecting material and a raw material steel coil, aligning the welding surfaces of the connecting material and the raw material steel coil and keeping the welding surfaces at the same horizontal plane for welding, carrying out post-welding annealing and polishing treatment on a welding seam after welding, and checking the quality of the welding seam through measuring the thickness of the welding seam and a cupping test; the steel coils need to be cooled to be less than or equal to 80 ℃ before being welded, and the yield strength of the steel strips with higher strength in the two steel coils before and after being welded is not higher than 1.5 times of the yield strength of the steel strips with lower strength; the carbon equivalent of the connecting material selected for welding is controlled within the range of 0.25-0.65 according to the following formula, and the adopted carbon equivalent formula is Ceq ═ C + Mn/6+ Si/24+ Ni/40+ Cr/5+ Mo/4+ V/14 (%). According to the welding method for the 780 MPa-grade high-reaming cold-rolled dual-phase steel acid rolling process, disclosed by the invention, the material parameters including temperature, straightness, camber and convexity, thickness/width transition, good surface quality, shearing process and quality of a connecting material, and key welding processes including welding wire selection, laser power, welding speed and the like are regulated, as shown in figure 1, a welding seam with a smooth surface and no crack is obtained, no defects such as inclusion, incomplete penetration, misalignment and the like exist in a welding seam area, the stable and efficient production of the acid hydrolysis process is ensured, and guidance can be provided for producing the 780 MPa-grade high-reaming cold-rolled dual-phase steel by using similar units at home and abroad.
According to actual needs, the components of 780MPa grade high-reaming cold-rolled dual-phase steel can be further optimized, and the components comprise the following components in percentage by weight: 0.07 to 0.13%, Si: 0.40-0.70%, Mn: 1.90-2.25%, P is less than or equal to 0.012%, S is less than or equal to 0.006%, Al: 0.025-0.065%, N is less than or equal to 0.004%, Cr: 0.10 to 0.30%, Nb: 0.010-0.35%; the rest elements are Fe and inevitable impurities.
In the welding method disclosed by the invention, when the raw material steel coil is selected, the surface of the raw material is required not to have serious concave-convex printing, scratching and wrinkling, the normal hot-rolled iron scale is observed visually, the defect exceeding the standard is avoided, and the wave shape, the warping and the like of the steel coil needing to be welded are not too large. The thickness range of the welded raw material steel coil is 1.8-6.0 mm, and the width range is 850-1650 mm. When 780MPa grade high-reaming cold-rolled dual-phase steel is selected as the connecting material, the surface flatness of the connecting material is required to be less than or equal to 245um, the camber is required to be less than or equal to 25mm/10m, hc-h40The convexity requirement is less than or equal to 150 μm.
According to the welding method, the first connecting material and the raw material steel coil are required to be sheared before welding, double-shearing is adopted for shearing, the inclination angle between the shearing edge and the steel strip in the shearing process is 2 degrees, the tail part of the former steel coil and the head part of the latter steel coil are required to be subjected to double-shearing to remove a certain length before welding so as to ensure the shape of the steel strip and weld after the quality is indicated, and the clearance range of the shearing edge is controlled to be 0.30-0.65 mm; the control of the shear blade clearance is determined according to the steel strip thickness according to the following requirements, when the steel strip thickness is less than or equal to 2.5mm, the shear blade clearance is 0.30mm, and when the steel strip thickness is increased by 0.5mm, the shear blade clearance is increased by 0.05 mm; the shearing edge is replaced according to the period of less than or equal to 7800t or the shearing frequency of less than or equal to 13500 times, the side gap of the shearing edge is calibrated after the shearing edge is replaced every time, the shearing cross section and the longitudinal direction of the strip steel form 90 degrees, and the shearing end face is required to be ensured to be smooth and straight without the defects of burrs, layering and the like.
In addition, during shearing, the cutting length of the steel coil is controlled according to the following requirements, and welding is carried out after the plate shape and the surface quality are ensured; the control requirements for the resection length are as follows: the cutting length is 5.2mm when the thickness t of the strip steel is less than 2.75mm, the cutting length is 4.3mm when the thickness t of the strip steel is less than or equal to 2.75mm and less than 4.0mm, and the cutting length is 3.5mm when the thickness t of the strip steel is more than or equal to 4.0mm, thereby ensuring that the defects of the head and the tail of the strip can be completely cut without deteriorating the welding quality.
The welding method adopts laser welding to carry out welding, the jumping range of the thickness of the welding machine is less than or equal to 1.5H1, the jumping range of the width is less than or equal to 330mm, and each side is less than or equal to 165mm, wherein H1 is the thickness of the thinner strip steel, and the unit is mm; in the laser welding process, a focusing position or a light spot position is utilized to focus a laser beam into a welding light spot, the height adjusting range of the focusing position is 0-9.0 mm, the Z-axis control precision is +/-0.05 mm, the adjusting range of the light spot position is +/-1.5 mm, and the X-axis control precision is +/-0.05 mm. The laser welding power is 12 +/-0.8 KW, and the welding speed is controlled to be 2.5-4.8 +/-0.3 m/min according to the thickness of the strip steel; introducing gas for protection in the whole welding process, wherein the protective gas is He and N2And CO, and the auxiliary gas during welding is He.
Because 780MPa level high reaming cold-rolled dual phase steel's alloy content is higher and welding property is bad, need to add welding wire auxiliary welding in the welding process, the chemical composition of welding wire is C: 0.02 to 0.15%, Si: 0.50 to 1.0%, Mn: 1.25-2.00%, P is less than or equal to 0.030%, S is less than or equal to 0.030%, Cu is less than or equal to 0.50%, Ti + Zr: 0.02-0.30%; the diameter of the welding wire is 0.9mm,after welding is assisted by the welding wire, the part of the welding seam lower than the strip steel can be filled to improve the performance of the special steel welding seam area and eliminate blank areas among gaps. Cleaning a weld joint by using a rolling wheel after welding is finished, wherein the pressure of the rolling wheel is less than or equal to 60KN, and the height of the rolling wheel is 0-7.5 mm; wherein the welding speed is 4.8 +/-0.3 m/min when the thickness of the strip steel is less than or equal to 2.5mm, the welding speed is reduced by 0.3m/min when the thickness of the strip steel is increased by 0.5mm, and the compensation range of the welding speed is 0-15%; when the thickness of the strip steel is less than or equal to 2.5mm, the wire feeding speed is 1.5 +/-0.3 m/min, the welding speed is increased by 0.3m/min when the thickness of the strip steel is increased by 0.5mm, and the compensation range of the wire feeding speed is 0-15%; the flow rate of He in the welding protective gas is 45-51 NL/h, and N2The flow rate of the mixed gas is 8.0-12.0 NL/h, the flow rate of the CO is 1.8-2.3 NL/h, the dew point of the mixed gas is less than or equal to minus 50 ℃, the pressure is 0.4-0.7 MPa, and the temperature is 5-50 ℃; the flow rate of the auxiliary gas He is 90-160 NL/min, the pressure is 0.4-0.7 MPa, and the temperature is 5-50 ℃. In the welding process, the thickness of the welding seam is 1.02-1.20 times of that of the raw material steel strip.
And (3) carrying out heat treatment on the welding seam through heat circulation after welding, wherein the power is 40kW, the frequency is 30kHz, the current compensation amount of the welding seam heat treatment is 0-15%, the heating speed is required to be less than or equal to 20 ℃/s in the heating process of the welding seam heat treatment, and the welding seam is cooled to below 300 ℃ at the cooling speed of less than or equal to 15 ℃/s during cooling. After the welded seam is annealed and polished after welding, the surface of the welded seam is required to be smooth and free of cracks, the welded seam area cannot have the defects of inclusion, incomplete penetration, misalignment and the like, and the quality of the welded seam needs to be checked through measuring the thickness of the welded seam and a cupping test.
When the weld seam is sampled and the cupping test is carried out, the number of sampling points is at least 3, the left point and the right point are taken within a range of 100-200 mm from the edge part, the third point is taken in the middle of the steel strip, the hole diameter of a punching hole of the sampling point is 15mm, and the punching hole is 100mm away from the weld seam; the requirement of the cupping test is that if the crack is vertical to the direction of the weld seam in the heat affected zone and the crack is vertical to the direction of the weld seam, the weld seam is judged to be qualified; if the crack is coincident with the welding seam, determining that the welding seam quality is unqualified; two welding seams are not allowed in one large coil, otherwise, the coil is judged to be unqualified; need carry out when the welding carries out width jump to link up towards crescent gulf experiment, the experiment requirement is as follows:
(1) punching at the welding seam, wherein the punching amount is 30mm relative to the width of the narrow strip steel,
(2) in the case of narrow and wide, punching was performed twice at a position deviated from the wide side toward the inlet side by 240mm from the weld and at the weld,
(3) in the case of narrowing the width, punching was performed twice at a position deviated from the wider side by 240mm from the weld toward the exit side and at the weld,
after the experiment, the transition of the width jumping steel coil can be carried out without problems.
Examples
Example 1
After 4.1mm of tail shearing of a 780 MPa-high-reaming cold-rolled dual-phase steel coil (chemical components of 0.09% C, 0.56% Si, 2.05% Mn, 0.009% P, 0.005% S, 0.041% Als, 0.22% Cr, 0.021% Nb, and a carbon equivalent of 0.50) having a coil temperature of 53 ℃, a dimensional plan of 3.75 × 1250mm, a steel coil head shearing of 4.2mm of a 780 MPa-high-reaming cold-rolled dual-phase steel (chemical components of 0.085% C, 0.50% Si, 2.08% Mn, 0.011% P, 0.003% S, 0.036% Als, 0.18% Cr, 0.019% Nb, and a carbon equivalent of 0.49) having a coil temperature of 49 ℃, and a dimensional specification of 3.60 × 1280mm was welded at a wire feeding speed of 2.2m/min (chemical components of 0.008% Si, 0.010% S, 0.025%, 0.60% Cu, and 0.025% Cu) with a welding current of 12.5% Ti and a wire feeding speed of 2.2 m/min. The welding seam welded by the welding process is flat and smooth, has no nodules, craters and welding penetration, has no cracks along the welding seam and good effect of punching crescent in a cupping test, and has no strip breakage accident caused by the welding seam in the pickling and cold rolling processes.
Example 2
After cutting 4.0mm from a tail of a 780 MPa-grade high-hole-expansion cold-rolled dual-phase steel (chemical composition of 0.10% C, 0.56% Si, 2.08% Mn, 0.010% P, 0.002% S, 0.047% Als, 0.025% Nb, and carbon equivalent of 0.52) having a steel coil temperature of 45 ℃ and a size of 4.20 × 1310mm, a hot-dip galvanized 590DP (chemical composition of 0.81% C, 0.22% Si, 1.75% Mn, 0.010% P, 0.004% S, 0.030% Als, 0.33% Cr, 0.14% Mo, and carbon equivalent of 0.469) having a steel coil temperature of 47 ℃ and a size of 4.10 × 1275.0 mm was subjected to a tape head cutting of 5.0mm, and a welding current of 12.3kW was used in combination with a wire feeding speed of 2.7m/min (chemical composition of 0.09% C, 0.15% Si, 0.007% P, 0.85% S, 0.012/0.0% S) and a welding speed of Cu. The welding seam welded by the welding process is flat and smooth, has no nodules, craters and welding penetration, has no cracks along the welding seam and good effect of punching crescent in a cupping test, and has no strip breakage accident caused by the welding seam in the pickling and cold rolling processes.
Comparative example 1
After cutting 4.0mm of a tail of a 780 MPa-grade high-hole-expansion cold-rolled dual-phase steel (chemical components of 0.093% C, 0.58% Si, 2.15% Mn, 0.005% P, 0.002% S, 0.043% Als, 0.022% Nb, and a carbon equivalent of 0.52) coil of which the coil temperature is 55 ℃ and the size is 3.50 × 1280mm, a welding wire (chemical components of 0.11% C, 0.62% Si, 1.008% Si, 0.008% Si, 0.010% P, 0.010% S, 0.025% Si, 0.010% P, 0.010% S, and 0.5% S) was fed at a wire feeding speed of 3.5m/min by using a welding current of 12.5kW in cooperation with a welding current of 62.5 kW and a head of a DC06 (chemical components of 0.0015% C, 0.01% Si, 0.007% Mn, 0.05% Mn, 0.2% P, 0.004% S, 0.011) coil of which is 5 × 1550mm, and a carbon equivalent of 0.52. The welding seam welded by the welding process has poor quality, no crack is generated along the welding seam in a cupping test, and production is carried out after a connecting material is changed.

Claims (10)

1.780MPa grade high-hole-expansion cold-rolled dual-phase steel, which is characterized in that: comprises the following components in percentage by weight: 0.05 to 0.163%, Si: 0.40-0.90%, Mn: 1.50-2.30%, P is less than or equal to 0.017%, S is less than or equal to 0.008%, Als: 0.010-0.080%, N not more than 0.008%, Cr: 0.10 to 0.40%, Nb: 0.01-0.05%; the rest elements are Fe and inevitable impurities.
2. The 780MPa grade high-reaming cold-rolled dual phase steel according to claim 1, wherein: comprises the following components in percentage by weight: 0.07 to 0.13%, Si: 0.40-0.70%, Mn: 1.90-2.25%, P is less than or equal to 0.012%, S is less than or equal to 0.006%, Al: 0.025-0.065%, N is less than or equal to 0.004%, Cr: 0.10 to 0.30%, Nb: 0.010-0.35%; the rest elements are Fe and inevitable impurities.
3. The welding method for the 780MPa grade high-hole-expansion cold-rolled dual-phase steel acid-rolling process as set forth in claim 2, wherein: the welding method comprises the following steps of selecting 780 MPa-grade high-chambering cold-rolled dual-phase steel as a connecting material, shearing the connecting material and a raw material steel coil, aligning welding faces of the connecting material and the raw material steel coil, placing welding wires on the same horizontal plane for welding, carrying out post-welding annealing and polishing treatment on a welding seam after welding, and checking the quality of the welding seam through measuring the thickness of the welding seam and a cupping test;
wherein, the steel coils need to be cooled to less than or equal to 80 ℃ before welding, and the yield strength of the steel strips with higher strength in the two steel coils before and after welding is not higher than 1.5 times of the yield strength of the steel strips with lower strength;
controlling the carbon equivalent of a connecting material selected for welding to be in a range of 0.25-0.65 according to a numerical value calculated by the following formula, wherein the carbon equivalent formula is Ceq ═ C + Mn/6+ Si/24+ Ni/40+ Cr/5+ Mo/4+ V/14 (%);
the chemical components of the welding wire are C: 0.02 to 0.15%, Si: 0.50 to 1.0%, Mn: 1.25-2.00%, P is less than or equal to 0.030%, S is less than or equal to 0.030%, Cu is less than or equal to 0.50%, Ti + Zr: 0.02-0.30%;
and (3) carrying out heat treatment on the welding seam through heat circulation after welding, wherein the power is 40kW, the frequency is 30kHz, the current compensation amount of the welding seam heat treatment is 0-15%, the heating speed is required to be less than or equal to 20 ℃/s in the heating process of the welding seam heat treatment, and the welding seam is cooled to below 300 ℃ at the cooling speed of less than or equal to 15 ℃/s during cooling.
4. The welding method for the 780MPa high-reaming cold-rolled dual-phase steel acid-rolling process as set forth in claim 3, wherein: the shearing adopts double-shearing, the inclination angle between the shearing edge and the steel strip in the shearing process is 2 degrees, and the clearance range of the shearing edge is controlled to be 0.30-0.65 mm.
5. The welding method for the 780MPa high-reaming cold-rolled dual-phase steel acid-rolling process as set forth in claim 4, wherein: the control of the shear blade gap is determined according to the steel strip thickness according to the following requirements, when the steel strip thickness is less than or equal to 2.5mm, the shear blade gap is 0.30mm, and when the steel strip thickness is increased by 0.5mm, the shear blade gap is increased by 0.05 mm; the shearing edge is replaced according to the period of less than or equal to 7800t or the shearing frequency of less than or equal to 13500 times, the side gap of the shearing edge is calibrated after the shearing edge is replaced every time, the shearing cross section and the longitudinal direction of the strip steel form 90 degrees, and the shearing end face is required to be ensured to be smooth and straight without the defects of burrs, layering and the like.
6. The welding method for the 780MPa high-reaming cold-rolled dual-phase steel acid-rolling process as set forth in claim 3, wherein: during shearing, the cutting length of the steel coil is controlled according to the following requirements, and welding is carried out after the plate shape and the surface quality are ensured;
the control requirements for the resection length are as follows: the cutting length is 5.2mm when the thickness t of the strip steel is less than 2.75mm, the cutting length is 4.3mm when the thickness t of the strip steel is less than or equal to 2.75mm and less than 4.0mm, and the cutting length is 3.5mm when the thickness t of the strip steel is more than or equal to 4.0mm, thereby ensuring that the defects of the head and the tail of the strip can be completely cut without deteriorating the welding quality.
7. The welding method for the 780MPa high-reaming cold-rolled dual-phase steel acid-rolling process as set forth in claim 3, wherein: the surface flatness of the strip steel is required to be less than or equal to 245umit, the camber is required to be less than or equal to 25mm/10m, hc-h40The convexity requirement is less than or equal to 150 μm.
8. The welding method for the 780MPa high-reaming cold-rolled dual-phase steel acid-rolling process as set forth in claim 3, wherein: the welding is carried out by adopting a laser welding machine, the jumping range of the thickness of the welding machine is less than or equal to 1.5H1, the jumping range of the width is less than or equal to 330mm, and each side is less than or equal to 165mm, wherein H1 is the thickness of the thinner strip steel, and the unit is mm; in the laser welding process, a laser beam is focused into a welding spot by utilizing a focusing position or a spot position, the height adjusting range of the focusing position is 0-9.0 mm, the Z-axis control precision is +/-0.05 mm, the adjusting range of the spot position is +/-1.5 mm, and the X-axis control precision is +/-0.05 mm.
9. The welding method for the 780MPa high-reaming cold-rolled dual-phase steel acid-rolling process as set forth in claim 8, wherein: the power of the laser welding is 12 +/-0.8 KW, the welding speed is controlled to be 2.5-4.8 +/-0.3 m/min according to the thickness of the strip steel, and the wire feeding speed is controlled to be 1.5-3.6 +/-0.3 m/min according to the thickness of the strip steel; introducing gas for protection in the whole welding process, wherein the protective gas is He and N2And CO, and the auxiliary gas during welding is He; cleaning a weld joint by using a rolling wheel after welding is finished, wherein the pressure of the rolling wheel is less than or equal to 60KN, and the height of the rolling wheel is 0-7.5 mm;
wherein the welding speed is 4.8 +/-0.3 m/min when the thickness of the strip steel is less than or equal to 2.5mm, the welding speed is reduced by 0.3m/min when the thickness of the strip steel is increased by 0.5mm, and the compensation range of the welding speed is 0-15%; when the thickness of the strip steel is less than or equal to 2.5mm, the wire feeding speed is 1.5 +/-0.3 m/min, the welding speed is increased by 0.3m/min when the thickness of the strip steel is increased by 0.5mm, and the compensation range of the wire feeding speed is 0-15%;
the flow rate of He in the welding protective gas is 45-51 NL/h, and N2The flow rate of the mixed gas is 8.0-12.0 NL/h, the flow rate of the CO is 1.8-2.3 NL/h, the dew point of the mixed gas is less than or equal to minus 50 ℃, the pressure is 0.4-0.7 MPa, and the temperature is 5-50 ℃;
the flow rate of the auxiliary gas He is 90-160 NL/min, the pressure is 0.4-0.7 MPa, and the temperature is 5-50 ℃.
10. The welding method for the 780MPa high-reaming cold-rolled dual-phase steel acid-rolling process as set forth in claim 8, wherein: in the welding process, the thickness of a welding seam is 1.02-1.20 times of that of the raw material steel strip; when the weld seam is sampled and the cupping test is carried out, the number of sampling points is at least 3, the left point and the right point are taken within a range of 100-200 mm from the edge part, the third point is taken in the middle of the steel strip, the hole diameter of a punching hole of the sampling point is 15mm, and the punching hole is 100mm away from the weld seam;
the requirement of the cupping test is that if the crack is vertical to the direction of the weld seam in the heat affected zone and the crack is vertical to the direction of the weld seam, the weld seam is judged to be qualified; if the crack is coincident with the welding seam, determining that the welding seam quality is unqualified; two welding seams are not allowed in one large coil, otherwise, the coil is judged to be unqualified;
when the welding is carried out with width jump connection, a crescent bay punching experiment is required,
(1) punching at the welding seam, wherein the punching amount is 30mm relative to the width of the narrow strip steel,
(2) in the case of narrow and wide, punching was performed twice at a position 240mm away from the wider side from the weld toward the inlet side and at the weld,
(3) in the case of narrowing the width, punching was performed twice at a position deviated from the wider side by 240mm from the weld toward the exit side and at the weld,
after experiments show that no problem exists, the transition of the width jump steel coil can be carried out.
CN202210361671.5A 2022-04-07 2022-04-07 780 MPa-grade high-reaming cold-rolled dual-phase steel and welding method in acid rolling process thereof Pending CN114571083A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115091125A (en) * 2022-06-17 2022-09-23 攀钢集团攀枝花钢铁研究院有限公司 780 MPa-grade high-reaming cold-rolled dual-phase steel and welding method for acid rolling process thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115091125A (en) * 2022-06-17 2022-09-23 攀钢集团攀枝花钢铁研究院有限公司 780 MPa-grade high-reaming cold-rolled dual-phase steel and welding method for acid rolling process thereof
CN115091125B (en) * 2022-06-17 2023-10-03 攀钢集团攀枝花钢铁研究院有限公司 780 MPa-grade high-reaming cold-rolled dual-phase steel and welding method for acid rolling process thereof

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