CN114571083B - 780 MPa-level high-reaming cold-rolled dual-phase steel and welding method for acid rolling process thereof - Google Patents
780 MPa-level high-reaming cold-rolled dual-phase steel and welding method for acid rolling process thereof Download PDFInfo
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Abstract
The invention discloses 780 MPa-grade high-reaming cold-rolled dual-phase steel and a welding method of an acid rolling procedure thereof, wherein components of 780 MPa-grade high-reaming cold-rolled dual-phase steel are controlled according to C：0.05～0.163％、Si：0.40～0.90％、Mn：1.50～2.30％、P≤0.017％、S≤0.008％、Als：0.010～0.080％、N≤0.008％、Cr：0.10～0.40％、Nb：0.01～0.05％;, and the other elements are Fe and unavoidable impurities. And (3) welding, namely, 780 MPa-grade high-reaming cold-rolled dual-phase steel is selected as a connecting material, after shearing the connecting material and a raw steel coil, enabling the welding surfaces of the connecting material and the raw steel coil to be aligned and positioned on the same horizontal plane, adding welding wires for welding, and after welding, carrying out post-welding annealing and polishing treatment on a welding seam, and checking the quality of the welding seam through measuring the thickness of the welding seam and a cupping test. Thereby effectively solving the technical problems of unstable production process and low production efficiency in the prior art and achieving the purpose of ensuring stable and efficient production of 780 MPa-grade high-reaming cold-rolled dual-phase steel acid rolling process.
Description
Technical Field
The invention relates to the technical field of steel rolling production processes, in particular to 780 MPa-level high-reaming cold-rolled dual-phase steel and a welding method for 780 MPa-level high-reaming cold-rolled dual-phase steel acid rolling procedures.
Background
The welding equipment is used for welding the front steel coil and the rear steel coil to realize continuous production of steel enterprises, and the method is an important technological means for improving production efficiency and reducing production cost. Is widely applied to acid rolling combination generating units, continuous annealing/galvanization units and the like to realize continuous and efficient production. Laser welding is a method of welding by heat generated by a focused laser beam as an energy source to bombard a weldment. Because the laser has optical properties such as refraction and focusing, the laser welding has the characteristics of low heat input, small welding deformation, no influence of electromagnetic field and the like, and is widely applied to welding of raw materials of an acid-rolling combined unit. If the welding effect is not added, the strip breakage accident along the welding line is easy to occur in the pickling and cold rolling processes, the continuous production is unfavorable to seriously influence the production efficiency and the production safety, and detailed researches on the production rhythm, transition materials, welding key processes and the like are required to obtain good welding quality so as to promote continuous and efficient production.
Patent document with publication number CN 112025081a discloses a welding method of ultra-high strength steel of QP980 and above by a laser welder, comprising the following steps: 1) Adjusting the working flow of the laser welder, firstly adjusting the inlet section, then adjusting the outlet section, and finally adjusting 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 adopting a water cooling device;
6) Optimizing welding parameters; 7) Adopting QCDS welding line detection system to monitor welding line quality in real time; 8) Optimizing a preheating and annealing device; 9) The equipment maintenance before production and welding realizes the production of QP980 with poor weldability and carbon equivalent of more than 0.575%, but the technical scheme introduces production rhythm, transition material selection basis, raw material requirement, head/tail treatment, gas protection, weld quality evaluation and the like, is not beneficial to the guidance of the whole welding process, and is not beneficial to the popularization of 780 MPa-level high-reaming cold-rolled dual-phase steel produced by the same type of equipment at home and abroad.
The patent document with the publication number of CN 104842056A discloses a device and a process for plasticizing a welding line of an ultra-high-strength dual-phase steel laser welding plate, wherein the welding line of the ultra-high-strength dual-phase steel welding plate is arranged between a heat conducting material and a cooling plate, so that the flatness of a welding plate is ensured, and meanwhile, the material is assembled by adopting an electromagnetic chuck for accurate positioning; switching on a high-frequency heating coil to adjust output power, ensuring output temperature to be 800-850 ℃, and keeping the temperature for 3-5 min to austenitize a weld joint tissue; adopting a cooling plate filled with cooling liquid to rapidly cool the welding line of the ultra-high strength dual-phase steel tailor-welded blank; 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 ℃, and keeping the temperature for 10-90 s, and carrying out a local distribution process on the welding seam; reducing the output power of the high-frequency heating coil to zero; and (3) adopting a cooling plate filled with cooling liquid to rapidly cool the welding line of the ultra-high strength dual-phase steel tailor-welded blank to the room temperature. The average value of the obtained weld grain size is 1.5-4.0 mu m, the cup burst value of the ultra-high strength steel dual-phase steel splice welding plate is 7.3-9.9 mm, and the cup burst value of the splice welding plate is improved by 43%. However, the technical scheme does not detail production rhythm, transition material selection basis, raw material requirements, head/tail treatment, welding key process parameters and the like, and equipment is specially modified, so that welding of acid rolling raw materials is not facilitated to be completed by using a conventional unit.
Patent document with publication number CN 113118630A discloses a preparation method of a laser splice welding plate with different thickness, 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 percent, and the Mn content difference is less than or equal to 0.4 percent), cooling, air drying and then placing the DP steel plates on a welding workbench. The horizontal clearance of the DP steel plate is 0mm, the clearance 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, the protective gas is adopted to measure and blow, and the distance between the blowing port and the welding line is 20-28 mm; the protective gas of 30-60 degrees between the gas blowing port of the measuring and blowing device and the DP steel plate to be welded is argon, and the gas flow is 900-1000L/H; it is achieved that 590DP and 780DP finished products are soldered. However, the welding thickness of the finished product of the technical scheme is thinner, no basis is provided for production rhythm and transition material selection, and guidance cannot be provided for the welding method of 780 MPa-level high-reaming cold-rolled dual-phase steel acid rolling procedure.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: the 780 MPa-grade high-reaming cold-rolled dual-phase steel can ensure stable and efficient production of the acid rolling process.
The technical scheme adopted by the invention for solving the technical problems is as follows: 780MPa grade high-reaming cold-rolled dual-phase steel comprises C：0.05～0.163％、Si：0.40～0.90％、Mn：1.50～2.30％、P≤0.017％、S≤0.008％、Als：0.010～0.080％、N≤0.008％、Cr：0.10～0.40％、Nb：0.01～0.05％; parts by weight of Fe and unavoidable impurities as the rest elements.
Further is: the alloy comprises C：0.07～0.13％、Si：0.40～0.70％、Mn：1.90～2.25％、P≤0.012％、S≤0.006％、Al：0.025～0.065％、N≤0.004％、Cr：0.10～0.30％、Nb：0.010～0.35％; weight percent of Fe and unavoidable impurities as the rest elements.
The invention also discloses a welding method for the 780 MPa-level high-reaming cold-rolled dual-phase steel acid rolling procedure, which adopts the following technical scheme: the welding adopts 780 MPa-grade high-reaming cold-rolled dual-phase steel as a connecting material, the connecting material and a raw steel coil are sheared, the welding surfaces of the connecting material and the raw steel coil are aligned and positioned on the same horizontal plane, welding wires are added for welding, after welding, annealing and polishing treatment are carried out on the welded seam, and the quality of the welded seam is checked through measuring the thickness of the welded seam and a cupping test;
The steel coils are cooled to be less than or equal to 80 ℃ before welding, and the yield strength of the band steel 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 band steel with lower strength;
the carbon equivalent of the jointing material used for welding is controlled within the range of 0.25-0.65 according to the 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 percent of Si:0.50 to 1.0 percent of Mn:1.25 to 2.00 percent, P is less than or equal to 0.030 percent, S is less than or equal to 0.030 percent, cu is less than or equal to 0.50 percent, 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 heat treatment of the welding seam is 0-15%, the heating speed is required to be less than or equal to 20 ℃/s in the heating process of the heat treatment of the welding seam, and cooling to below 300 ℃ at the cooling speed of less than or equal to 15 ℃/s during cooling.
Further is: the shearing adopts double shearing, the inclination angle between the shearing edge and the steel belt 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 is: the control of the cutting edge clearance is determined according to the following requirements of the thickness of the steel strip, when the thickness of the steel strip is less than or equal to 2.5mm, the cutting edge clearance is 0.30mm, and when the thickness of the steel strip is increased by 0.5mm, the cutting edge clearance is increased by 0.05mm; the shearing blade is replaced according to the period of less than or equal to 7800t or the shearing times of less than or equal to 13500 times, the side clearance of the shearing blade is calibrated after each shearing blade replacement, the shearing cross section and the longitudinal direction of strip steel are ensured to form 90 degrees, and the shearing end face is ensured to be smooth and straight, and the defects of burrs, layering and the like are avoided.
Further is: during shearing, the cutting length of the steel coil is controlled according to the following requirements, and welding is performed after the plate shape and the surface quality are ensured;
The excision length control requirement is: the cutting length is 5.2mm when the thickness t of the strip steel is less than 2.75mm, 4.3mm when the thickness t of the strip steel is less than or equal to 2.75mm and less than 4.0mm, and 3.5mm when the thickness t of the strip steel is more than or equal to 4.0mm, and the defect of the tail of the strip steel can be completely cut, so that the welding quality is not deteriorated.
Further is: the surface flatness requirement of the strip steel is less than or equal to 245umit, the camber requirement is less than or equal to 25mm/10m, and the convexity requirement of h c-h40 is less than or equal to 150 mu m.
Further is: the welding is performed by a laser welding machine, the jump range of the thickness of the welding machine is less than or equal to 1.5H1, the jump 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 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 adjustment range of the focusing position is 0-9.0 mm, the Z-axis control precision is +/-0.05 mm, the adjustment range of the spot position is +/-1.5 mm, and the X-axis control precision is +/-0.05 mm.
Further is: 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; the whole process of welding is filled with gas for protection, the shielding gas is mixed gas of He, N 2 and CO, and the auxiliary gas during welding is He; after welding, cleaning the welding line by adopting a rolling wheel, 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, when the thickness of the strip steel is less than or equal to 2.5mm, the welding speed is 4.8+/-0.3 m/min, and when the thickness of the strip steel is increased by 0.5mm, the welding speed is reduced by 0.3m/min, 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, and when the thickness of the strip steel is increased by 0.5mm, the welding speed is increased by 0.3m/min, 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, the flow rate of N 2 is 8.0-12.0 NL/h, the flow rate of CO is 1.8-2.3 NL/h, the dew point of the mixed gas is less than or equal to-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 is: in the welding process, the thickness of the welding seam is 1.02-1.20 times of the thickness of the raw material steel belt; when the weld sampling is performed for the cupping test, the number of sampling points is at least 3, two points on the left and right are taken in the range of 100-200 mm from the edge, the third point is taken in the middle of the steel strip, the punching aperture of the sampling point is 15mm, and the punching distance is 100mm from the weld;
the requirement of the cupping test is that if the split is perpendicular to the welding line direction in time in the heat affected zone and the split is perpendicular to the welding line direction, the welding line is judged to be qualified; if the split is coincident with the weld, judging that the weld quality is unqualified; and two welding seams are not allowed in one large roll, otherwise, judging that the welding seams are unqualified;
The crescent moon punching experiment is needed when the welding is carried out with the width jumping connection, the experiment requirement is,
(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 widening, 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 240mm away from the weld toward the outlet side from the wider side and at the weld,
After experiments, the transition of the width jump steel coil can be carried out.
The beneficial effects of the invention are as follows: the components of 780 MPa-grade high-reaming cold-rolled dual-phase steel are controlled according to C：0.05～0.163％、Si：0.40～0.90％、Mn：1.50～2.30％、P≤0.017％、S≤0.008％、Als：0.010～0.080％、N≤0.008％、Cr：0.10～0.40％、Nb：0.01～0.05％; and other elements of Fe and unavoidable impurities, and welding is carried out according to the following method before acid rolling, namely 780 MPa-grade high-reaming cold-rolled dual-phase steel is selected as a connecting material, after shearing the connecting material and a raw steel coil, the welding surface of the connecting material and the raw steel coil is aligned and positioned on the same horizontal plane, welding is carried out, after welding, annealing and polishing treatment are carried out on a welding seam, and the quality of the welding seam is checked through measuring the thickness of the welding seam and a cupping test; the steel coil is required to be cooled to be less than or equal to 80 ℃ before welding, and the yield strength of the steel strip 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 strip with lower strength; the carbon equivalent of the jointing material used for welding is controlled within the range of 0.25-0.65 according to the following formula, wherein the carbon equivalent formula is Ceq=C+Mn/6+Si/24+Ni/40+Cr/5+Mo/4+V/14 (%). Thereby effectively solving the technical problems of unstable production process and low production efficiency in the prior art and achieving the purpose of ensuring stable and efficient production of 780 MPa-grade high-reaming cold-rolled dual-phase steel acid rolling process.
Drawings
FIG. 1 is a schematic illustration of weld quality after welding in accordance with the present invention.
Detailed Description
In order to facilitate the understanding of the present invention, the present invention will be further described with reference to the accompanying drawings and examples.
The 780 MPa-grade high-reaming cold-rolled dual-phase steel comprises C：0.05～0.163％、Si：0.40～0.90％、Mn：1.50～2.30％、P≤0.017％、S≤0.008％、Als：0.010～0.080％、N≤0.008％、Cr：0.10～0.40％、Nb：0.01～0.05％; parts by weight of Fe and unavoidable impurities as the rest elements. The welding method for the 780MPa high-reaming cold-rolled dual-phase steel acid rolling procedure disclosed by the invention is that 780MPa high-reaming cold-rolled dual-phase steel is used as a connecting material in the welding process, after shearing the connecting material and a raw steel coil, the welding surface of the connecting material and the raw steel coil is aligned on the same horizontal plane, then welding is carried out, after welding, the welding seam is subjected to annealing and polishing treatment after welding, and the welding seam quality is checked through measuring the thickness of the welding seam and a cupping test; the steel coil is required to be cooled to be less than or equal to 80 ℃ before welding, and the yield strength of the steel strip 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 strip with lower strength; the carbon equivalent of the jointing material used for welding is controlled within the range of 0.25-0.65 according to the numerical value calculated by 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 780MPa grade high-reaming cold-rolled dual-phase steel acid rolling working procedure, disclosed by the invention, the key welding processes including temperature, flatness, camber and convexity of a joint material, thickness/width transition, good surface quality, shearing process and quality, welding wire selection, laser power, welding speed and the like are regulated and controlled, as shown in figure 1, a welding seam with smooth surface and no crack and no defects such as inclusion, incomplete penetration and edge staggering in a welding seam area is obtained, stable and efficient production of an acidolysis working procedure is ensured, and guidance can be provided for producing 780MPa grade high-reaming cold-rolled dual-phase steel by similar units at home and abroad.
The components of 780 MPa-level high-reaming cold-rolled dual-phase steel can be further optimized according to actual needs, and the components comprise C：0.07～0.13％、Si：0.40～0.70％、Mn：1.90～2.25％、P≤0.012％、S≤0.006％、Al：0.025～0.065％、N≤0.004％、Cr：0.10～0.30％、Nb：0.010～0.35％; weight percent of Fe and unavoidable impurities as the rest elements.
In the welding method disclosed by the invention, when a raw material steel coil is selected, the surface of the raw material is required to be required to have serious concave-convex marks, scratches and wrinkles, normal hot rolling iron scales are visually observed, the defect exceeding the standard cannot be caused, and meanwhile, the waveform, the warping and the like of the steel coil to be welded are not suitable to be excessively large. The thickness range of the welded raw steel coil is 1.8-6.0 mm, and the width range is 850-1650 mm. When 780 MPa-grade high-reaming cold-rolled dual-phase steel is used as a connecting material, the surface flatness requirement of the connecting material is less than or equal to 245umit, the camber requirement is less than or equal to 25mm/10m, and the convexity requirement of h c-h40 is less than or equal to 150 mu m.
According to the welding method, the steel coils which are connected with the raw materials first are required to be sheared before welding, double shearing is adopted for shearing, the inclination angle between the shearing edge and the steel belt is 2 degrees in the shearing process, the tail part of the steel coil and the head part of the steel coil are required to be sheared by double shearing before welding to ensure the shape of the plate and the quality of the plate, and the gap range of the shearing edge is controlled to be 0.30-0.65 mm; the specific control of the cutting edge clearance is determined according to the following requirements of the thickness of the steel strip, when the thickness of the steel strip is less than or equal to 2.5mm, the cutting edge clearance is 0.30mm, and when the thickness of the steel strip is increased by 0.5mm, the cutting edge clearance is increased by 0.05mm; the shearing blade is replaced according to the period of less than or equal to 7800t or the shearing times of less than or equal to 13500 times, the side clearance of the shearing blade is calibrated after each shearing blade replacement, the shearing cross section and the longitudinal direction of strip steel are ensured to form 90 degrees, and the shearing end face is ensured to be smooth and straight, and the defects of burrs, layering and the like are avoided.
In addition, during shearing, the cutting length of the steel coil is controlled according to the following requirements, and the welding is performed after the plate shape and the surface quality are ensured; the excision length control requirement is: the cutting length is 5.2mm when the thickness t of the strip steel is less than 2.75mm, 4.3mm when the thickness t of the strip steel is less than or equal to 2.75mm and less than 4.0mm, and 3.5mm when the thickness t of the strip steel is more than or equal to 4.0mm, and the defect of the tail of the strip steel can be completely cut, so that the welding quality is not deteriorated.
In the welding method, laser welding is adopted for welding, the jump range of the thickness of a welding machine is less than or equal to 1.5H1, the jump 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 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 adjustment range of the focusing position is 0-9.0 mm, the Z-axis control precision is +/-0.05 mm, the adjustment range of the spot position is +/-1.5 mm, and the X-axis control precision is +/-0.05 mm. The power of laser welding 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; and (3) introducing gas for protection in the whole welding process, wherein the protective gas is mixed gas of He, N 2 and CO, and the auxiliary gas in the welding process is He.
Because 780MPa high-hole-expansion cold-rolled dual-phase steel has higher alloy content and poor welding performance, welding wires are required to be added for auxiliary welding in the welding process, and the chemical components of the welding wires are C:0.02 to 0.15 percent of Si:0.50 to 1.0 percent of Mn:1.25 to 2.00 percent, P is less than or equal to 0.030 percent, S is less than or equal to 0.030 percent, cu is less than or equal to 0.50 percent, ti+Zr: 0.02-0.30%; the diameter of the welding wire is 0.9mm, and the welding wire can be used for filling the part of the welding seam lower than the strip steel after auxiliary welding so as to improve the performance of a special steel welding seam region and eliminate a blank region between gaps. After welding, cleaning the welding line by adopting a rolling wheel, 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, when the thickness of the strip steel is less than or equal to 2.5mm, the welding speed is 4.8+/-0.3 m/min, and when the thickness of the strip steel is increased by 0.5mm, the welding speed is reduced by 0.3m/min, 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, and when the thickness of the strip steel is increased by 0.5mm, the welding speed is increased by 0.3m/min, 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, the flow rate of N 2 is 8.0-12.0 NL/h, the flow rate of CO is 1.8-2.3 NL/h, the dew point of the mixed gas is less than or equal to-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 the thickness of the raw material steel belt.
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 heat treatment of the welding seam is 0-15%, the heating speed is required to be less than or equal to 20 ℃/s in the heating process of the heat treatment of the welding seam, and cooling 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 being welded, the surface of the welded seam is required to be smooth and free of cracks, defects such as inclusions, incomplete welding, misplacement and the like cannot exist in a welded seam area, and in addition, the quality of the welded seam is required to be checked through a weld seam thickness measurement and cup burst test.
When the weld sampling is performed for the cupping test, the number of sampling points is at least 3, two points on the left and right are taken in the range of 100-200 mm from the edge, the third point is taken in the middle of the steel strip, the punching aperture of the sampling point is 15mm, and the punching distance is 100mm from the weld; the requirement of the cupping test is that if the split is perpendicular to the welding line direction in time in the heat affected zone and the split is perpendicular to the welding line direction, the welding line is judged to be qualified; if the split is coincident with the weld, judging that the weld quality is unqualified; and two welding seams are not allowed in one large roll, otherwise, judging that the welding seams are unqualified; the welding needs to be subjected to a crescent moon punching experiment when in width jump connection, and the experiment requirements are 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 widening, 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 240mm away from the weld toward the outlet side from the wider side and at the weld,
After experiments, the transition of the width jump steel coil can be carried out.
Examples
Example 1
The strip head shear of a steel coil with a temperature of 53 ℃ and a size of 3.75 x 660 mm of 780MPa grade high-hole-expansion cold-rolled dual-phase steel (with chemical compositions 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) is performed by shearing the strip tail of the steel coil by 4.1mm, and then welding the strip head shear (with chemical compositions of 0.10% C, 0.50% Si, 2.08% Mn, 0.011% P, 0.003% S, 0.036% Als, 0.18% Cr and 0.019% Nb) with a wire feeding speed of 2.2m/min, which is matched with a welding current of 12.5kW, at a wire feeding speed of 2.2m/min, with a temperature of 49 ℃ and a size of 3.60 x 1280m (with chemical compositions of 0.10% C, 0.50% Si, 0.08% Mn, 0.08% P, 0.010% S, 0.010% Ti, and 0.010% Ti, 0.010% S. The welded seam welded by the welding process is flat and smooth, free of knots, free of weld scars and free of weld penetration, the cup-shaped experiment has good effect of cracking along the welded seam and punching crescent bending, and the strip breakage accident caused by the welded seam is avoided in the pickling and cold rolling processes.
Example 2
The steel coil was cut at 45 ℃ with the end of the steel coil cut at 4.0mm and sized to 4.20 x 1310mm 780MPa high-hole-expansion cold-rolled dual-phase steel (chemical composition 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), and then welded with hot dip 590DP (chemical composition 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) at 47 ℃ and a wire feed rate of 2.7m/min (chemical composition 0.09% c, 0.15% si, 1.85% mn, 0.012% p, 0.010% cu, 0.030% cu, and 3.007 at 3/min) using a welding current of 12.3 kW. The welded seam welded by the welding process is flat and smooth, free of knots, free of weld scars and free of weld penetration, the cup-shaped experiment has good effect of cracking along the welded seam and punching crescent bending, and the strip breakage accident caused by the welded seam is avoided in the pickling and cold rolling processes.
Comparative example 1
The steel coil was cut to a final strip length of 4.0mm at 55 c and 3.50 x 1280mm in 780MPa high-hole-expansion cold-rolled dual-phase steel (chemical composition 0.093% c, 0.58% si, 2.15% mn, 0.005% p, 0.002% s, 0.043% als, 0.022% nb, and carbon equivalent of 0.52), and then welded with DC06 (chemical composition 0.0015% c, 0.01% si, 0.05% mn, 0.007% p, 0.004% s, 0.039% als, 0.075% ti, and carbon equivalent of 0.011) at a final strip length of 5.50 x 1550mm at 62 c, 0.62% si, 1.85% mn, 0.015% p, 0.007% s, 0.010% cu, and 0.5% ti at a wire feed rate of 3.5m/min using a welding current of 12.5 kW. The welding seam welded by the welding process has poor quality, the cup process is free from cracking along the welding seam, and the production is carried out after the joint material is changed.
Claims (6)
1. The welding method for 780MPa high-reaming cold-rolling dual-phase steel acid rolling process is characterized by comprising the following steps: the welding adopts 780 MPa-grade high-reaming cold-rolled dual-phase steel as a connecting material, the connecting material and a raw steel coil are sheared, the welding surfaces of the connecting material and the raw steel coil are aligned and positioned on the same horizontal plane, welding wires are added for welding, after welding, annealing and polishing treatment are carried out on the welded seam, and the quality of the welded seam is checked through measuring the thickness of the welded seam and a cupping test;
780MPa grade high-reaming cold-rolled dual-phase steel comprises C：0.07～0.13％、Si：0.40～0.70％、Mn：1.90～2.25％、P≤0.012％、S≤0.006％、Als：0.025～0.065％、N≤0.004％、Cr：0.10～0.30％、Nb：0.010～0.35％, balance elements of Fe and unavoidable impurities in percentage by weight;
The steel coil is cooled to the temperature less than or equal to 80 ℃ before welding, and the yield strength of the steel strip 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 strip with lower strength;
the carbon equivalent of the jointing material used for welding is controlled within the range of 0.25-0.65 according to the 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 percent of Si:0.50 to 1.0 percent of Mn:1.25 to 2.00 percent, P is less than or equal to 0.030 percent, S is less than or equal to 0.030 percent, cu is less than or equal to 0.50 percent, 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 heat treatment of the welding seam is 0-15%, the heating speed is required to be less than or equal to 20 ℃/s in the heating process of the heat treatment of the welding seam, and cooling to below 300 ℃ at the cooling speed of less than or equal to 15 ℃/s during cooling.
2. The welding method for 780MPa high-hole-expansion cold-rolled dual-phase steel acid rolling process according to claim 1, wherein: the shearing adopts double shearing, the inclination angle between the shearing edge and the steel belt in the shearing process is 2 degrees, and the clearance range of the shearing edge is controlled to be 0.30-0.65 mm.
3. The welding method for 780 MPa-stage high-hole-expansion cold-rolled dual-phase steel acid rolling process according to claim 2, characterized in that: the control of the cutting edge clearance is determined according to the following requirements of the thickness of the steel strip, when the thickness of the steel strip is less than or equal to 2.5mm, the cutting edge clearance is 0.30mm, and when the thickness of the steel strip is increased by 0.5mm, the cutting edge clearance is increased by 0.05mm; the shearing blade is replaced according to the period of less than or equal to 7800t or the shearing times of less than or equal to 13500 times, the side clearance of the shearing blade is calibrated after each shearing blade replacement, the shearing cross section and the longitudinal direction of strip steel are ensured to form 90 degrees, and the shearing end face is ensured to be smooth and straight, and no burrs and layering are ensured.
4. The welding method for 780MPa high-hole-expansion cold-rolled dual-phase steel acid rolling process according to claim 1, wherein: during shearing, the cutting length of the steel coil is controlled according to the following requirements, and welding is performed after the plate shape and the surface quality are ensured;
The excision length control requirement is: the cutting length is 5.2mm when the thickness t of the strip steel is less than 2.75mm, 4.3mm when the thickness t of the strip steel is less than or equal to 2.75mm and less than 4.0mm, and 3.5mm when the thickness t of the strip steel is more than or equal to 4.0mm, and the defect of the tail of the strip steel can be completely cut, so that the welding quality is not deteriorated.
5. The welding method for 780MPa high-hole-expansion cold-rolled dual-phase steel acid rolling process according to claim 1, wherein: the welding is performed by a laser welding machine, the jump range of the thickness of the welding machine is less than or equal to 1.5H1, the jump 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 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 adjustment range of the focusing position is 0-9.0 mm, the Z-axis control precision is +/-0.05 mm, the adjustment range of the spot position is +/-1.5 mm, and the X-axis control precision is +/-0.05 mm.
6. The welding method for 780MPa high-hole-expansion cold-rolled dual-phase steel acid rolling process according to claim 5, wherein: in the welding process, the thickness of the welding seam is 1.02-1.20 times of the thickness of the raw material steel belt; when the weld sampling is performed for the cupping test, the number of sampling points is at least 3, two points on the left and right are taken in the range of 100-200 mm from the edge, the third point is taken in the middle of the steel strip, the punching aperture of the sampling point is 15mm, and the punching distance is 100mm from the weld;
The requirement of the cup process test is that if the split is perpendicular to the welding line direction, the welding line is judged to be qualified; if the split is coincident with the weld, judging that the weld quality is unqualified; and two welding seams are not allowed in one large roll, otherwise, judging that the welding seams are unqualified;
The crescent moon punching experiment is needed when the welding is carried out with the width jumping connection, the experiment requirement is,
(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 widening, 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 240mm away from the weld toward the outlet side from the wider side and at the weld,
After experiments, the transition of the width jump steel coil can be carried out.
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