Acid rolling process preparation method of low-cost 590MPa-grade continuous annealing reinforced plastic dual-phase steel

Abstract

The invention relates to an acid rolling process preparation method of low-cost 590MPa-grade continuous annealing reinforced plastic dual-phase steel, and belongs to the technical field of cold-rolled sheet production. The method comprises the following steps: S1, selecting hot rolling raw materials; s2, hot-rolled raw materials are treated; S3, welding wires are selected; s4, welding parameters including laser power, welding speed, wire feeding speed, welding seam heat treatment power and welding seam heat treatment frequency are determined; s5, weld joints are treated and checked; s6, straightening; s7, pickling and drying; and S8, cold rolling. Good welding seam quality is obtained by regulating and controlling the material quality, the plate shape, specification transition, the surface quality, the shearing process and the key welding process of the connecting material, the cold rolling reduction rate is regulated according to the product thickness, stable and efficient production of the acid rolling process is ensured, and the plasticity of a finished product is improved. The problems that existing 590MPa-grade cold-rolled dual-phase steel is poor in plastic and difficult to meet the requirements of complex parts, and the plastic lifting cost is high are solved.

Description

TECHNICAL FIELD

[0001] The application relates to a low-cost preparation method of a 590MPa-grade enhanced plastic dual-phase steel for continuous annealing by pickling and cold rolling, and belongs to the technical field of cold-rolled plate production. BACKGROUND

[0002] With the increasing prominence of energy and environmental problems, energy saving and environmental protection have become inevitable problems in the development of the automobile industry. Reducing the thickness of automobile steel through high strengthening to achieve weight reduction of the vehicle body is considered to be the most scientific and effective method to promote the sustainable development of the automobile industry. Dual-phase steel has good strength and plasticity and processing and preparation performance, and has become the most widely used advanced high-strength steel, but the problem of draw cracking easily occurs in the stamping process of complex (super complex) parts. The plastic elongation A 80 of the current 590MPa-grade cold-rolled dual-phase steel is required to be greater than or equal to 21%, which is difficult to meet the needs of relatively complex (super complex) parts, and it is necessary to introduce a certain amount of residual austenite to realize high plasticity (elongation A 80 value greater than or equal to 26%) through TRIP effect (DH steel) to meet the stamping needs of complex (super complex) parts. Some parts need high yield strength to resist deformation (such as seat rails), and the market demand for high-yield 590MPa-grade continuous annealing dual-phase steel is broad.

[0003] The domestic patent CN 107557684 B discloses a DH590 pickling production process control method, and the chemical components are as follows in percentage by weight: C: 0.130%-0.148%, Mn: 1.60%-2.05%, Si: 0.37%-0.43%, P: 0.014%-0.015%, S: 0.003%-0.005%, and Alt: 0.45%-0.55%. The plate roll welding adopts a laser welding process, the welding power is 10000-12000w, the welding speed is 2-6m / min, the wire feeding speed is 2-7m / min, the annealing current is 100-180A, the annealing temperature is 700-800℃, in the plate roll straightening process, the tensile bending straightening elongation is 0.5-2.0%, the insertion amount of the 1# bending unit is 20-40mm, the insertion amount of the 2# bending unit is 16-36mm, the insertion amount of the 3# straightening unit is 8-20mm, in the pickling process, the pickling temperature is 75-90℃, the pickling speed is 40-220m / min, in the cold continuous rolling process, the reduction distribution rate is as follows: the reduction distribution rates of F1-F5 racks are 25-35%, 25-35%, 25-33%, 20-27% and 0.3-1% from the inlet to the outlet of the rolling mill, and the unit tension between the five racks is 40-70N / mm 2 , 130-170N / mm 2 , 150-190N / mm2 150-210 N / mm 2 160-230 N / mm 2 40-70 N / mm 2 The rolling mill entrance speed is 30-200 m / min, and the bending forces of the working rolls F1-F5 of the rolling mill are 400-500 kN, 400-500 kN, 400-500 kN, 400-500 kN, and 100-300 kN, respectively. The thickness deviation of the cold hard coiling line plate is 0.5% or less, and the average value of the flatness of the cold hard coiling line plate is 1.5 IU-1.6 IU. The patent describes the DH590 pickling process, but the content of Al element is relatively high (0.45%-0.55%), which increases the smelting difficulty. The material, size specification, and product strength of the transition material are not described, which is not conducive to obtaining good welding effect.

[0004] The patent CN 104842056 A discloses a kind of super high strength dual-phase steel laser welding plate weld plasticizing device and process, by the weld of super high strength dual-phase steel welding plate is placed between heat-conducting material and cooling plate, guaranteeing the flatness of the welding plate material at the same time using electromagnetic chuck precise positioning to assemble the material;Connect high-frequency heating coil to adjust output power, ensure output temperature 800-850℃, holding time 3-5min, austenitize the weld structure;Using cooling plate filled with cooling liquid to quickly cool the weld of super high strength dual-phase steel welding plate;Adjust the output power of high-frequency heating coil to ensure the output temperature of 250-300℃, holding time 5-30s;Reduce the flow rate of cooling liquid, increase the output power of high-frequency heating coil to ensure the output temperature of 300-380℃, holding time 10-90s, to carry out local partition process on the weld;Reduce the output power of high-frequency heating coil to zero;Using cooling plate filled with cooling liquid to quickly cool the weld of super high strength dual-phase steel welding plate to room temperature. The average grain size of the obtained weld is 1.5 μm-4.0 μm, and the Erichsen value of the super high strength steel dual-phase steel welding plate is 7.3-9.9 mm, which is increased by 43%. It only describes the treatment of weld quality, but does not describe the production rhythm, transition material selection, raw material requirements, strip head / tail processing, and key welding process parameters (welding wire, laser power, welding speed, etc.), and the equipment is specially modified, which is not conducive to using conventional units to complete the welding of pickling raw materials.

[0005] The domestic patent CN 113118630 A discloses a preparation method of a differential thickness laser welding plate. Two DP steel plates with different thicknesses (thickness difference ≤0.5mm, C content difference ≤0.03%, Mn content difference ≤0.4%) are subjected to purification treatment, and then placed on a welding workbench after cooling and drying. The horizontal gap of the DP steel plates is 0mm, and the vertical gap is 0.05-0.08mm. During welding, the defocusing amount is 0.2-1.0mm; the laser power is 3.7-4.2kW; the welding speed is 5.0-8.0m / min; the laser offset is 0.4-0.7mm; the protective gas blowing device is used for blowing, and the blowing port is 20-28mm away from the weld; the blowing port of the blowing device and the to-be-welded DP steel plate form an angle of 30-60°; the protective gas is argon, and the gas flow is 900-1000L / H. The welding between 590DP and 780DP finished products is realized, the thickness of the welding material is relatively thin, and the production rhythm, transition material, etc. are not clearly described, which cannot provide guidance for the production of the low-cost 590MPa grade enhanced plastic dual-phase steel pickling process for continuous annealing. SUMMARY

[0006] The technical problem to be solved by the present application is that the plasticity of the existing 590MPa grade cold rolled dual-phase steel is difficult to meet the needs of complex parts, and the cost of improving plasticity is high.

[0007] The technical solution adopted by the present application to solve the technical problem is: a low-cost 590MPa grade enhanced plastic dual-phase steel pickling process preparation method, comprising the following steps: S1. The chemical composition is C: 0.09%-0.15%, Si: 0.40%-0.80%, Mn: 1.30%-1.80%, P≤0.020%, S≤0.010%, Ti: 0.010%-0.045%, B: 0.0010%-0.0035%, Als: 0.020%-0.070%, N≤0.0060%, the rest is Fe and inevitable impurities. Select a hot-rolled raw material, and the thickness range of the hot-rolled raw material is 2.50mm-5.00mm, and the width range is 800mm-1250mm; S2. The raw material is cut to a certain length to ensure the plate shape and surface quality before welding by using a double cutting shear. When the thickness of the raw material is <3.50mm, the cutting amount is 7.0±1.0m; when the thickness of the raw material is 3.30mm≤thickness of the raw material<4.25mm, the cutting amount is 5.5±1.0m; S3. The welding wire material is YGW12, and the chemical composition is C: 0.02-0.15%, Si: 0.50-1.0%, Mn: 1.25-2.00%, P≤0.030%, S≤0.030%, Cu≤0.50%, Ti+Zr: 0.02-0.30%; S4. The welding key process parameters, laser power, welding speed, weld heat treatment power and weld heat treatment frequency are respectively: 13.0±0.5 KW, 2.5~4.0±0.5 m / min, the welding speed is 4.0±0.5 m / min when the raw material thickness is less than or equal to 3.50 mm, and the speed decreases by 0.5 m / min for each 0.5 mm increase in thickness; the welding speed compensation range is 0~15%; after welding, the weld is cleaned by a rolling wheel, the rolling wheel pressure is less than or equal to 50 KN, the rolling wheel height is 0~6.5 mm, and the weld is heat treated by a thermal cycle, the power is 45±5 kW, the frequency is 35±5 kHz, the weld heat treatment current compensation is 0~15%, the weld heat treatment heating speed is less than or equal to 20 ℃ / s, and the cooling speed is less than or equal to 15 ℃ / s when cooling to below 280 ℃, and the weld is air cooled; S5. The weld is treated and the weld quality is checked by weld thickness and cup convexity test; S6. The strip shape is straightened by a tension leveling machine, the tension is built by a tension machine, the strip position is adjusted by a deviation correction roller, and the strip is adjusted by a pre-pickling loop; S7. The i-Box type pickling tank is used for pickling and drying; S8. The finished product is obtained by cold rolling.

[0008] In the above method step S1, the chemical composition of the hot-rolled raw material is as follows in terms of weight percentage: C: 0.11%~0.13%, Si: 0.55%~0.75%, Mn: 1.40%~1.65%, Ti: 0.020%~0.040%, B: 0.0015%~0.0025%, P≤0.010%, S≤0.005%, Als: 0.025%~0.060%, N≤0.003%, and the balance is Fe and unavoidable impurities.

[0009] In step S1, the carbon equivalent formula of the connecting material is: Ceq=C+Mn / 6+Si / 24+Ni / 40+Cr / 5+Mo / 4+V / 14 (%), and the yield strength difference between the two steel coils before and after welding is within 1.7 times.

[0010] Further, in the above method step S3, the carbon equivalent of the connecting material is in the range of 0.25%~0.75%, the flatness of the strip surface is less than or equal to 210 umit, the sickle bend is less than or equal to 16 mm / 10 m, the crown (hc-h40) is less than or equal to 120 μm; the thickness jump range of the welding machine is less than or equal to 1.8, the thickness and width jump of the thinner steel strip is less than or equal to 300 mm and less than or equal to 150 mm on each side.

[0011] Wherein, the blade gap range in the step S2 is 0.30mm-0.45mm, the blade gap is 0.25mm when the raw material thickness is less than or equal to 3.50mm, and the blade gap increases by 0.05mm for each 0.5mm increase in the raw material thickness; the blade cycle is required to be less than or equal to 7000t or the shearing frequency is required to be less than or equal to 9500 times, and the blade side gap is calibrated after each replacement of the blade.

[0012] Wherein, the welding wire diameter in the step S3 is 0.9mm, and the welding seam thickness is 1.05-1.35 times of the raw material thickness.

[0013] Wherein, at least 3 points are tested when the welding seam is sampled for the cupping test in the step S5, and the crescent bending test is required to be performed when the width jump is connected.

[0014] Wherein, the acid liquid concentration of the 1# acid tank is 45g / l-70g / l, the acid liquid concentration of the 2# acid tank is 75g / l-100g / l, the acid liquid concentration of the 3# acid tank is 105g / l-140g / l, the acid liquid temperature is 60-80℃, the pickling speed is 65-210m / min, the pickling speed is 210m / min when the thickness is 2.50mm, the pickling speed decreases by 15m / min for each 0.25mm increase in the thickness, and the residual on the strip surface is removed by the rinsing unit, and the rinsing tank pH value is greater than or equal to 5.0.

[0015] Wherein, the strip surface is dried by the drying machine in the step S7, and the drying temperature is 85-160℃.

[0016] Wherein, the cold rolling is performed to become a thin strip steel with a thickness of 0.7-2.5mm in the step S8, the cold rolling reduction is 51%-75%, the cold rolling reduction gradually decreases with the increase in the material cold rolling product thickness, the cold rolling reduction decreases by about 4% for each 0.3mm increase in the cold rolling thin strip steel thickness, the raw material thickness is adjusted accordingly, the cold rolling is performed by 7 racks, and the reduction of the last pass is kept at 4-10%.

[0017] The method has the advantages that the straightening process, material quality, plate shape, surface quality, and shearing effect of the strip head and tail, the setting of the key welding parameters (welding wire selection, laser power, welding speed, etc.), and the evaluation of the welding effect are described in detail, the subsequent loop control method and pickling process requirements are also clearly required, the reduction is adjusted according to the strip thickness, batch, continuous, and stable production is realized, the batch stable supply capacity of the 590MPa grade continuous annealing enhanced plastic dual-phase steel is realized at low cost, the market competition ability is improved, remarkable economic benefits are obtained, and the method can also be applied to the production of the 590MPa grade continuous annealing enhanced plastic dual-phase steel by the same type of units at home and abroad, and has reference and guidance significance. Attached Figure Description

[0018] Figure 1 This is a photograph of the actual weld seam of the strip steel of this invention. Detailed Implementation

[0019] The present invention will be further described below with reference to embodiments.

[0020] The present invention provides a low-cost method for preparing 590MPa continuously annealed reinforced duplex steel through pickling and rolling, comprising the following steps: S1. By weight percentage, its chemical composition is: C: 0.09%~0.15%, Si: 0.40%~0.80%, Mn: 1.30%~1.80%, P≤0.020%, S≤0.010%, Ti: 0.010%~0.045%, B: 0.0010%~0.0035%, Als: 0.020%~0.070%, N≤0.0060%, with the remaining elements being Fe and unavoidable impurities. Hot-rolled raw materials are selected, and the thickness of the hot-rolled raw materials ranges from 2.50mm to 5.00mm, and the width ranges from 800mm to 1250mm. S2. Welding can only proceed after the raw material is cut to a certain length using double shears to ensure the plate shape and surface quality. The cutting length is 7.0±1.0m when the raw material thickness is <3.50mm and 5.5±1.0m when the raw material thickness is 3.30mm≤4.25mm. S3. The welding wire material is YGW12, with the following chemical composition: C: 0.02-0.15%, Si: 0.50-1.0%, Mn: 1.25-2.00%, P≤0.030%, S≤0.030%, Cu≤0.50%, Ti+Zr: 0.02-0.30%; S4. Key welding process parameters: laser power, welding speed, weld heat treatment power, and weld heat treatment frequency are 13.0±0.5KW, 2.5~4.0±0.5 m / min, and when the raw material thickness is ≤3.50mm, the welding speed is 4.0±0.5m / min. For every 0.5mm increase in thickness, the speed decreases by 0.5m / min. The welding speed compensation range is 0~15%. After welding, the weld is cleaned by a rolling wheel with a rolling wheel pressure ≤50KN and a rolling wheel height of 0~6.5mm. The weld is then heat-treated by a thermal cycle with a power of 45kW, a frequency of 35kHz, and a weld heat treatment current compensation of 0~15%. The heating rate of the weld heat treatment is ≤20℃ / s, and during cooling, it is cooled to below 280℃ at a cooling rate of ≤15℃ / s and then air-cooled. S5. Process the weld and inspect the weld quality through weld thickness and cupping tests; S6. Straightening the strip shape using a tension leveler, building tension using a tension machine, adjusting the strip position using a deviation correction roller, and adjusting the strip using a pre-pickling loop; S7. Pickling using an i-Box type acid tank and drying; S8. Cold rolling to obtain the finished product. Those skilled in the art can understand that the present scheme describes in detail the straightening process, material quality, strip shape, surface quality, and the shearing effect of the strip head and tail, the setting of the key welding parameters (welding wire selection, laser power, welding speed), the evaluation of the welding effect, and makes clear requirements for the subsequent loop control method and pickling process requirements. The reduction rate is adjusted according to the thickness of the strip, realizing batch, continuous and stable production, realizing the batch stable supply capacity of low-cost 590MPa grade enhanced plastic dual-phase steel for continuous annealing, improving market competitiveness, and will produce significant economic benefits. In step S1, select a hot-rolled raw material with appropriate chemical composition, width and length, the hot-rolled raw material here is a strip. And the surface of the hot-rolled raw material requires visual normal hot-rolled iron oxide scale, no over-standard defects and no water accumulation, and also needs to have good strip shape. In step S2, the hot-rolled raw material is subjected to head and tail shearing treatment. And the operator needs to detect each incoming material to determine whether the head and tail defects have been completely removed to ensure the welding quality. In step S3, the appropriate welding wire is selected, and the weld needs to be supplemented with welding wire to ensure the welding quality. And the YGW12 welding wire can not only fill the part of the weld below the strip, but also improve the performance of the weld area of special steel and eliminate the blank area between the gaps. In step S4, the welding parameters and heat treatment parameters are determined to ensure the weld quality. This step specifically welds the hot-rolled raw material with the adapter material, which is the base material welded together, such as 590DH, 780DH, etc. And because of the high alloy content of the 590MPa grade enhanced plastic dual-phase steel for continuous annealing, the weld needs to be heat treated to improve its weld quality. In step S5, the weld is treated and the weld quality is checked. After welding, the weld is subjected to post-weld annealing and polishing, and the surface requires smoothness, no cracks, and the weld area cannot have defects such as inclusions, incomplete penetration, and misalignment. In addition, the weld quality is checked through weld thickness and cup convexity test. In step S6, the welded strip is straightened. Specifically, the strip shape is straightened using a tension leveler, tension is built using a tension machine, the strip position is adjusted using a deviation correction roller (to keep the strip in the center of the equipment), to avoid damage and downtime accidents caused by warping and other strip shape problems and strip deviation. The strip is adjusted using a pre-pickling loop to ensure the smooth progress of the pickling process. In step S7, the strip is further pickled using an i-Box type acid tank and dried. In step S8, the finished product is obtained by cold rolling.

[0021] Preferably, the chemical composition of the hot-rolled material in step S1 of the method is, by weight percentage: C: 0.11% to 0.13%, Si: 0.55% to 0.75%, Mn: 1.40% to 1.65%, Ti: 0.020% to 0.040%, B: 0.0015% to 0.0025%, P≤0.010%, S≤0.005%, Als: 0.025% to 0.060%, N≤0.003%, and the balance being Fe and unavoidable impurities. Those skilled in the art will understand that the chemical composition of the hot-rolled material is further limited in the method, specifically, the chemical composition of the hot-rolled material is, by weight percentage: C: 0.11% to 0.13%, Si: 0.55% to 0.75%, Mn: 1.40% to 1.65%, Ti: 0.020% to 0.040%, B: 0.0015% to 0.0025%, P≤0.010%, S≤0.005%, Als: 0.025% to 0.060%, N≤0.003%, and the balance being Fe and unavoidable impurities.

[0022] Preferably, the carbon equivalent formula of the adapter material in step S3 is: Ceq=C+Mn / 6+Si / 24+Ni / 40+Cr / 5+Mo / 4+V / 14 (%) and the difference in yield strength between the two steel coils before and after welding is within 1.7 times. Those skilled in the art will understand that the adapter material is the base material welded thereto, such as 590DH, 780DH, etc. In order to ensure the welding quality, the carbon equivalent formula of the adapter material is: Ceq=C+Mn / 6+Si / 24+Ni / 40+Cr / 5+Mo / 4+V / 14 (%) and the difference in yield strength between the two steel coils before and after welding is within 1.7 times.

[0023] Preferably, the carbon equivalent of the adapter material in step S3 of the method is in the range of 0.25% to 0.75%, the flatness of the strip surface is ≤210umit, the camber is ≤16mm / 10m, the convexity (hc-h40) is ≤120μm; the thickness jump range of the welding machine is ≤1.8 times the thickness of the thinner steel strip, the width jump is ≤300mm and ≤150mm on each side. Those skilled in the art will understand that, in order to ensure the welding quality, the carbon equivalent of the adapter material is further limited in the method to be in the range of 0.25% to 0.75%, the flatness of the strip surface is ≤210umit, the camber is ≤16mm / 10m, the convexity (hc-h40) is ≤120μm; the thickness jump range of the welding machine is ≤1.8 times the thickness of the thinner steel strip, the width jump is ≤300mm and ≤150mm on each side.

[0024] Preferably, the gap between the blades in step S2 of the above method is 0.30mm-0.45mm, the gap between the blades is 0.25mm when the thickness of the raw material is ≤3.50mm, the gap between the blades increases by 0.05mm for each 0.5mm increase in the thickness of the raw material; the blade cycle is ≤7000t or the number of shearing times is ≤9500, and the gap between the blades is calibrated after each replacement of the blades. Those skilled in the art will understand that, in order to ensure that the welded joint after shearing meets the welding requirements, the actual preferred gap between the blades in the method is 0.30mm-0.45mm, the gap between the blades is 0.25mm when the thickness of the raw material is ≤3.50mm, the gap between the blades increases by 0.05mm for each 0.5mm increase in the thickness of the raw material; the blade cycle is ≤7000t or the number of shearing times is ≤9500, and the gap between the blades is calibrated after each replacement of the blades, to ensure that the sheared end surface is smooth and flat, free of burrs, delamination and other defects.

[0025] Preferably, the diameter of the welding wire in step S3 of the above method is 0.9mm, and the thickness of the weld is 1.05-1.35 times the thickness of the raw material. Those skilled in the art will understand that, in order to ensure welding quality, the diameter of the welding wire in step S3 of the method is preferably 0.9mm, and the thickness of the weld is 1.05-1.35 times the thickness of the raw material, to ensure that the strip is fully penetrated.

[0026] Preferably, in step S5 of the above method, at least 3 points are tested when the weld is sampled for the cupping test; and a punching moon bend test is required when the width jumps. Those skilled in the art will understand that, in order to detect the quality of the weld, at least 3 points are tested when the cupping test is actually preferred, and a punching moon bend test is required when the width jumps, to ensure that the welded strip meets the requirements of subsequent processes. After testing without problems, the transition of the width jump steel coil can be carried out.

[0027] Preferably, in step S7 of the above method, the acid concentration of the 1# acid tank is 45g / l-70g / l, the acid concentration of the 2# acid tank is 75g / l-100g / l, the acid concentration of the 3# acid tank is 105g / l-140g / l, the temperature of the acid is 60°C-80°C, and the pickling speed is 65m / min-210m / min, wherein the pickling speed is 210m / min when the thickness is 2.50mm, and the pickling speed decreases by 15m / min for each 0.25mm increase in the thickness; the rinsing unit is used to remove residues on the surface of the strip, and the pH value of the rinsing tank is ≥5.0. Those skilled in the art will understand that, in order to ensure the quality of pickling, the acid concentration, temperature and pickling speed of each pickling tank are further limited.

[0028] Preferably, the strip surface is dried by the drying machine in step S7 of the above method, and the drying temperature is 85-160°C. Those skilled in the art can understand that the preferred drying temperature of the method ensures the cold-rolled feed quality, and the strip surface is dried by the drying machine, and the drying temperature is 85-160°C.

[0029] Preferably, the thin strip steel with a thickness of 0.7-2.5 mm is obtained by cold rolling in step S8 of the above method, and the cold rolling reduction is 51-75%, and the cold rolling reduction gradually decreases with the increase of the thickness of the cold-rolled product, and the cold rolling reduction decreases by about 4% for each 0.3 mm increase in the thickness of the cold-rolled strip steel, the raw material thickness is adjusted accordingly, and the cold rolling is performed by 7 stands, and the reduction of the last pass is kept at 4-10%. Those skilled in the art can understand that the cold rolling process parameters are further preferred in the method, specifically, after the hot-rolled coil is pickled, the thin strip steel with a thickness of 0.7-2.5 mm is obtained by cold rolling, and the cold rolling reduction is 51-75%, and the cold rolling reduction gradually decreases with the increase of the thickness of the cold-rolled product, and the cold rolling reduction decreases by about 4% for each 0.3 mm increase in the thickness of the cold-rolled strip steel, the raw material thickness is adjusted accordingly, and the cold rolling is performed by 7 stands, and in order to obtain good plate shape, the reduction of the last pass is kept at 4-10%, and the rest of the passes are independently allocated by the computer.

[0030] Example 1 A low-cost 590 MPa grade continuous annealing reinforcing plastic dual-phase steel with a specification of 4.30 mm x 1100 mm (chemical composition: 0.125% C, 0.70% Si, 1.53% Mn, 0.007% P, 0.003% S, 0.038% Als, 0.030% Ti, 0.0020% B) and a low-cost 590 MPa grade continuous annealing reinforcing plastic dual-phase steel with a specification of 4.3 mm x 1080 mm (0.118% C, 0.66% Si, 1.50% Mn, 0.08% P, 0.004% S, 0.053% Als, 0.033% Ti, 0.0018% B) are cut according to the specified strip head and tail, and then welded by using YGW12 welding wire, and the cold rolling reductions are 63% and 63% respectively, and the pickling process is stable and smooth.

[0031] Example 2 A low-cost 590 MPa grade continuous annealing enhanced plasticity dual-phase steel (chemical composition: 0.120% C, 0.73% Si, 1.60% Mn, 0.010% P, 0.002% S, 0.040% Al, 0.038% Ti, 0.0019% B) with a size of 3.80 mm x 1150 mm and a hot-dip galvanized 590 DP (0.080% C, 0.20% Si, 1.73% Mn, 0.010% P, 0.003% S, 0.031% Al, 0.32% Cr, 0.13% Mo) with a size of 4.00 x 1275 are cut according to a predetermined rule after cutting off the head and tail, and are welded using a YGW12 welding wire, with a cold rolling reduction ratio of 66% and 68%, respectively, and the entire pickling process is stable and has good continuity.

[0032] Comparative Example A low-cost 590 MPa grade continuous annealing enhanced plasticity dual-phase steel (chemical composition: 0.115% C, 0.68% Si, 1.62% Mn, 0.006% P, 0.003% S, 0.044% Al, 0.031% Ti, 0.0021% B) with a size of 4.50 mm x 1030 mm and a DC05 (chemical composition: 0.0018% C, 0.01% Si, 0.04% Mn, 0.005% P, 0.002% S, 0.033% Al, 0.072% Ti) with a size of 5.5 mm x 1550 mm are welded. The weld quality after welding by the above welding process is poor, and the cup convex test does not crack along the weld. The bridging material is changed to a cold-rolled 590 DP steel strip (chemical composition: 0.09% C, 0.50% Si, 1.50% Mn, 0.010% P, 0.005% S, 0.040% Al, 0.25% Cr) with a size of 4.0 mm x 1000 mm, which is cut according to a predetermined rule after cutting off the head and tail, and is welded using a YGW12 welding wire, with a cold rolling reduction ratio of 55% and 60%, respectively, and the entire pickling process has good welding effect.

Claims

1. A low-cost 590 MPa grade enhanced plastic dual-phase steel production method for continuous annealing, characterized by Comprising the following steps: S1. The chemical composition is C: 0.09%~0.15%, Si: 0.40%~0.80%, Mn: 1.30%~1.80%, P≤0.020%, S≤0.010%, Ti: 0.010%~0.045%, B: 0.0010%~0.0035%, Als: 0.020%~0.070%, N≤0.0060%, the rest is Fe and inevitable impurities, and the hot-rolled raw material has a thickness of 2.50mm~5.00mm and a width of 800mm~1250mm; S2. The raw material is cut to a certain length to ensure the plate shape and surface quality before welding, wherein the cutting amount is 7.0±1.0m when the thickness of the raw material is <3.50mm, and the cutting amount is 5.5±1.0m when the thickness of the raw material is 3.30mm≤thickness<4.25mm; S3. The welding wire material is YGW12, and the chemical composition is C: 0.02-0.15%, Si: 0.50-1.0%, Mn: 1.25-2.00%, P≤0.030%, S≤0.030%, Cu≤0.50%, Ti+Zr: 0.02-0.30%; S4. The key process parameters of welding, such as laser power, welding speed, weld heat treatment power and weld heat treatment frequency, are respectively 13.0±0.5KW, 2.5~4.0±0.5m / min, the welding speed is 4.0±0.5m / min when the thickness of the raw material is ≤3.50mm, and the speed decreases by 0.5m / min for every 0.5mm increase in thickness; the welding speed compensation range is 0~15%; after welding, the roller is used to clean the weld, the roller pressure is ≤50KN, the roller height is 0~6.5mm, and the weld is heat treated by heat cycle, the power is 45±5kW, the frequency is 35±5kHz, the weld heat treatment current compensation amount is 0~15%, the heating speed of weld heat treatment is ≤20℃ / s, and the cooling speed is ≤15℃ / s when cooling to 280℃ below and air cooling; S5. The weld is treated and the weld quality is checked by weld thickness and cup convex test; S6. The strip shape is straightened by using a tension leveling machine, the tension is built by using a tension machine, the strip position is adjusted by using a deviation correction roller, and the strip is adjusted by using a pre-pickling loop; S7. i-Box type acid tank is used for pickling and drying; S8. The finished product is obtained by cold rolling.

2. A method for preparing a low-cost 590 MPa grade continuous annealing reinforced plastic dual-phase steel according to claim 1, characterized by: In step S1, the chemical composition of the hot-rolled raw material is C: 0.11%~0.13%, Si: 0.55%~0.75%, Mn: 1.40%~1.65%, Ti: 0.020%~0.040%, B: 0.0015%~0.0025%, P≤0.010%, S≤0.005%, Als: 0.025%~0.060%, N≤0.003%, and the rest is Fe and inevitable impurities.

3. A method for preparing a low-cost 590 MPa grade continuous annealing reinforced plastic dual-phase steel according to claim 1, characterized by: The carbon equivalent formula of the adapter in step S1 is: Ceq=C+Mn / 6+Si / 24+Ni / 40+Cr / 5+Mo / 4+V / 14 (%) and the difference of yield strength between the two steel coils before and after welding is within 1.7 times.

4. A method for preparing a low-cost 590 MPa grade continuous annealing reinforced plastic dual-phase steel according to claim 1, characterized by: The carbon equivalent of the adapter in step S3 is in the range of 0.25% to 0.75%, the surface flatness of the strip steel is ≤210umit, the sickle bend is ≤16mm / 10m, the convexity (hc-h40) is ≤120μm; the thickness jump range of the welding machine is ≤1.8 times the thickness of the thinner steel strip, the width jump is ≤300mm and ≤150mm on each side.

5. The method according to claim 1, wherein the acid pickling process for preparing a low-cost 590 MPa grade enhanced plastic dual-phase steel for continuous annealing is characterized by: The shear blade gap in step S2 is in the range of 0.30mm to 0.45mm, the shear blade gap is 0.25mm when the raw material thickness is ≤3.50mm, the shear blade gap increases by 0.05mm for each 0.5mm increase in the raw material thickness; the shear blade cycle is required to be ≤7000t or the shear number is ≤9500 times, and the shear blade side gap is calibrated after each replacement of the shear blade.

6. A method for preparing a low-cost 590 MPa grade continuous-annealing reinforced plastic dual-phase steel according to claim 1, characterized by: The welding wire diameter in step S3 is 0.9mm and the welding seam thickness is 1.05 to 1.35 times the raw material thickness.

7. A method for preparing a low-cost 590 MPa grade continuous-annealing reinforced plastic dual-phase steel according to claim 1, characterized by: In step S5, at least 3 points are tested when the welding seam is sampled for cupping test; and the crescent bend test is required when the width jump adapter is used.

8. A method for preparing a low-cost 590 MPa grade continuous annealing reinforced plastic dual-phase steel according to claim 1, characterized by: In step S7, the acid concentration of the 1# acid tank is 45g / L to 70g / L, the acid concentration of the 2# acid tank is 75g / L to 100g / L, the acid concentration of the 3# acid tank is 105g / L to 140g / L, the acid temperature is 60℃ to 80℃, the pickling speed is 65m / min to 210m / min, the pickling speed is 210m / min when the thickness is 2.50mm, the pickling speed decreases by 15m / min for each 0.25mm increase in thickness; the rinsing machine group is used to remove the residues on the surface of the strip steel, and the pH value of the rinsing tank is ≥5.

0.

9. A method for preparing a low-cost 590 MPa grade continuous-annealing reinforced plastic dual-phase steel according to claim 1, characterized by: In step S7, the strip steel surface is dried by the drying machine, and the drying temperature is 85 to 160℃.

10. A method for preparing a low-cost 590 MPa grade continuous annealing reinforced plastic dual-phase steel according to claim 1, characterized by: In step S8, the cold rolling becomes a thin strip steel with a thickness of 0.7mm to 2.5mm, the cold rolling reduction is 51% to 75%, the cold rolling reduction gradually decreases as the material cold rolled product thickness increases, the cold rolling reduction decreases by about 4% for each 0.3mm increase in the cold rolled thin strip steel thickness, the raw material thickness is adjusted accordingly, 7 racks are used for cold rolling, and the reduction of the last pass is kept at 4 to 10%.

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