Low-cost 980MPa-grade hot-dip galvanized dual-phase steel hot-dip galvanizing process narrow lap welding method

Abstract

The invention discloses a low-cost 980MPa-grade hot-dip galvanized dual-phase steel hot-dip galvanizing process narrow lap welding method, which comprises the following steps of: shearing a joining material and a raw material steel coil selected for welding, aligning the welding surfaces of the joining material and the raw material steel coil, and performing welding on the joining material and the raw material steel coil on the same horizontal plane, after welding, the welding seam quality is checked by measuring the thickness of the welding seam and performing a cup convex test; wherein welding is conducted according to the welding current, the welding speed, the welding pressure, the overlap amount and the welding compensation amount obtained through formula calculation. According to the low-cost 980MPa-grade hot-dip galvanized dual-phase steel hot-dip galvanizing process narrow lap welding method, a welding seam with good quality is obtained, and stable and efficient production of the hot-dip galvanizing process is ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of cold-rolled strip production, and in particular relates to a low-cost 980MPa grade hot-dip galvanized duplex steel hot-dip galvanizing process narrow lap welding method. Background Art

[0002] 980MPa grade hot-dip galvanized duplex steel is a high-strength steel. "980MPa grade" means that the yield strength of this steel reaches about 980 MPa, which has very high strength. Hot-dip galvanizing is a surface treatment process that immerses the steel in molten zinc liquid to form a layer of zinc-iron alloy and pure zinc on the surface of the steel. This galvanized layer can effectively prevent the steel from rusting and improve the corrosion resistance of the steel. Duplex steel refers to the microstructure of steel mainly composed of ferrite and martensite. This dual-phase structure makes the steel have both high strength and good toughness. Duplex steel is the most widely used advanced high-strength steel at present. 980MPa grade products have become one of the most important products used in the automotive manufacturing industry. At the same time, with the continuous improvement of corrosion resistance requirements, the proportion of galvanized sheets used is increasing. The hot-dip galvanizing process requires 460°C galvanizing (in the bainite transformation zone). In the composition design, more alloy elements need to be added to ensure hardenability and inhibit bainite phase transformation, resulting in reduced welding performance, which is not conducive to the continuous and stable production of the hot-dip galvanizing process.

[0003] The existing narrow lap welding method for hot-dip galvanizing of duplex steel lacks requirements on material quality, specifications and surface quality, and strip head / tail processing methods, which is not conducive to guiding large-scale industrial production, or the welding process is relatively general without detailed division, which is not conducive to efficient production and obtaining good quality welds.

[0004] Therefore, how to describe the welding process in detail and efficiently produce and obtain good quality welds in the narrow lap welding method of hot-dip galvanized duplex steel of 980MPa grade has become a problem that urgently needs to be solved. Summary of the invention

[0005] Based on this, and in view of the above-mentioned deficiencies in the prior art, a low-cost 980MPa grade hot-dip galvanized duplex steel hot-dip galvanizing process narrow lap welding method is provided.

[0006] In order to achieve the above purpose, the following technical solutions are adopted: The present invention provides a low-cost 980MPa grade hot-dip galvanized dual-phase steel hot-dip galvanizing process narrow lap welding method, wherein the welding connection material and the raw steel coil are sheared, and the welding surfaces of the connection material and the raw steel coil are aligned and placed on the same horizontal plane for welding, and the weld quality is checked by measuring the weld thickness and cupping test after welding; Wherein, welding is performed according to the welding current, welding speed, welding pressure, overlap amount and welding compensation amount calculated by the following formulas (1)-(5); I = T + 9.3 (1) V = -4 / 3T + 41.8 / 3 (2) P=5 / 3T+26.5 / 3(3) L=0.5T+0.25(4) Y=2 / 15T+7.6 / 15(5) Among them, T is the thickness of welding material, in mm; L is the overlap amount, in mm; Y is the welding compensation amount, in mm; V is the welding speed, in m / min; P is the welding pressure, in kN; I is the welding current, in kA.

[0007] In some embodiments, the chemical composition of the dual-phase steel includes, by mass percentage: C: 0.05%~0.12%, Si: 0.25%~0.50%, Mn: 2.00%~2.40%, P≤0.018%, S≤0.009%, Als: 0.010%~0.065%, N≤0.0065%, Cr: 0.30%~0.70%, Nb: 0.015%~0.040%, Ti: 0.025%~0.050%, B: 0.0010%~0.0050%, and the balance is Fe and unavoidable impurities.

[0008] In some embodiments, the chemical composition of the dual-phase steel includes, by mass percentage, C: 0.07%~0.10%, Si: 0.30%~0.45%, Mn: 2.05%~2.35%, P≤0.012%, S≤0.006%, Als: 0.025%~0.060%, N≤0.0045%, Cr: 0.33%~0.58%, Nb: 0.018%~0.033%, Ti: 0.028%~0.048%, B: 0.0025%~0.0045%, and the balance is Fe and unavoidable impurities.

[0009] In some embodiments, the overlap amount is 0.60 mm to 1.35 mm, the compensation amount is 0.60 mm to 0.80 mm, the welding speed is 11.0 to 13.0 m / min, the welding pressure is 10.0 to 12.5 kN, and the welding current is 10.0 to 11.5 kA.

[0010] In some embodiments, the carbon equivalent of the selected connection material and raw steel coil needs to be controlled by a carbon equivalent formula, which is: Ceq=C+Si / 30+Mn / 20+2×P+4×S(%); The tensile strength of the higher strength steel before and after welding shall not exceed 3.0 times the tensile strength of the lower strength steel.

[0011] In some embodiments, the carbon equivalent of the connecting material and the raw steel coil is controlled in the range of 0.35% to 0.90%.

[0012] In some embodiments, the step of "cutting the welding selected connecting material and the raw steel coil" includes: when cutting, the cutting length of the steel coil is controlled according to the following requirements, and welding is performed after ensuring the plate shape and surface quality; Use double shears to cut off a certain length of the steel strip to ensure the plate shape and surface quality before welding. When the raw material thickness t<1.2mm, the strip tail resection amount is 18.0m, and the strip head resection amount is 9.0m; when 1.2mm≤raw material thickness t<2.0mm, the strip tail resection amount is 16.0m, and the strip head resection amount is 7.5m; when the raw material thickness t≥2.0mm, the strip tail resection amount is 13.0m, and the strip head resection amount is 5.0m; and ensure that the defects of the strip head and tail can be completely removed without deteriorating the welding quality.

[0013] In some embodiments, the measured weld thickness needs to be 0.85 to 1.50 times the thickness of the weld material.

[0014] In some embodiments, when the weld is sampled for the cupping test, at least three points are inspected. If the crack is in the heat affected zone and the crack is perpendicular to the weld direction, the weld is judged to be qualified; if the crack coincides with the weld, the weld quality is judged to be unqualified.

[0015] In some embodiments, the plate shape of the connecting material and the raw steel coil is ≤18IU, and the curvature is ≤30mm2 / 10m; the thickness range of the welded chilled coil is 0.70mm~2.20mm, wherein the thickness ratio of the two steel coils is ≤1.5, and the width range of the welded chilled coil is 850~1350mm, wherein the width transition of the two steel coils is ≤160mm, that is, the single-side width transition is ≤80mm.

[0016] The present invention has the following beneficial technical effects: The low-cost 980MPa grade hot-dip galvanized duplex steel hot-dip galvanizing process narrow lap welding method of the present invention obtains a weld with good quality by controlling the material (carbon equivalent, plate shape, curvature) of the raw materials, thickness / width transition, surface quality, shearing process and quality, and key welding processes (welding current, welding speed, welding machine pressure, overlap amount, welding compensation amount, etc.), thereby ensuring stable and efficient production of the hot-dip galvanizing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 This is a strip welding effect diagram of a narrow lap welding method using a low-cost 980 MPa grade hot-dip galvanized dual-phase steel hot-dip galvanizing process according to an embodiment of the present invention. DETAILED DESCRIPTION

[0019] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0020] It should be understood that the embodiments of the present invention shown in the exemplary embodiments are only illustrative. Although only a few embodiments are described in detail in the present invention, it is easy for those skilled in the art to appreciate that multiple modifications are feasible without actually departing from the teaching of the subject matter of the present invention. Accordingly, all such modifications should be included within the scope of the present invention. Without departing from the gist of the present invention, other replacements, modifications, changes and deletions may be made to the design, operating conditions and parameters of the following exemplary embodiments.

[0021] Based on the above objectives, a first aspect of an embodiment of the present invention provides a low-cost 980MPa grade hot-dip galvanized duplex steel narrow lap welding method in a hot-dip galvanizing process.

[0022] Narrow lap welding is a type of resistance welding. In this welding method, the edges of two metal sheets are overlapped, and the width of the overlapped part is narrow. Then pressure is applied through electrodes and current is passed through. The resistance heat of the metal under the action of the current is used to heat and melt the metal in the overlapping part under pressure to form a welded joint.

[0023] In the embodiment of the present invention, after the connecting material and the raw steel coil are sheared, the welding surfaces of the connecting material and the raw steel coil are aligned and placed on the same horizontal plane for welding. After welding, the weld needs to be cleaned; after welding, the weld quality is checked by measuring the weld thickness and the cupping test; after welding, the weld cannot have defects such as inclusions, incomplete penetration, and misalignment. In addition, the weld quality needs to be further checked by weld thickness, cupping test, etc.

[0024] Welding is performed using the welding current, welding speed, welding pressure, overlap amount and welding compensation amount calculated according to the following formulas 1)-5); I = T + 9.3 (1) V = -4 / 3T + 41.8 / 3 (2) P=5 / 3T+26.5 / 3(3) L=0.5T+0.25(4) Y=2 / 15T+7.6 / 15(5) Among them, T is the thickness of welding material, in mm; L is the overlap amount, in mm; Y is the welding compensation amount, in mm; V is the welding speed, in m / min; P is the welding pressure, in kN; I is the welding current, in kA.

[0025] Specifically, the overlap amount is 0.60mm~1.35mm (when the thickness of the welding material is 0.70mm, the overlap amount is 0.6mm, and the overlap amount increases by 0.15mm for every 0.3mm increase in the thickness of the welding material); the welding compensation amount is 0.60mm~0.80mm (when the thickness of the welding material is 0.70mm, the compensation amount is 0.60mm, and the compensation amount increases by 0.1mm for every 0.75mm increase in the thickness of the welding material); the welding speed is 11.0~13.0m / m in (when the thickness of the welding material is 0.70mm, the welding speed is 13.0m / min, and the welding speed decreases by 0.4m / min for every 0.3mm increase in the thickness of the welding material); the welding pressure is 10.0~12.5kN (when the thickness of the welding material is 0.70mm, the welding pressure is 10.0kN, and the welding pressure increases by 0.5kN for every 0.3mm increase in the thickness of the welding material); and the welding current is 10.0~11.5kA (when the thickness of the welding material is 0.70mm, the welding current is 10.0kA, and the welding current increases by 0.3kA for every 0.3mm increase in the thickness of the welding material).

[0026] In some embodiments, the chemical composition of the dual-phase steel includes, by mass percentage, C: 0.05%-0.12%, Si: 0.25%-0.50%, Mn: 2.00%-2.40%, P≤0.018%, S≤0.009%, Als: 0.010%-0.065%, N≤0.0065%, Cr: 0.30%-0.70%, Nb: 0.015%-0.040%, Ti: 0.025%-0.050%, B: 0.0010%-0.0050%, and the balance is Fe and unavoidable impurities.

[0027] Preferably, the chemical composition of the dual-phase steel includes, by mass percentage, C: 0.07%~0.10%, Si: 0.30%~0.45%, Mn: 2.05%~2.35%, P≤0.012%, S≤0.006%, Als: 0.025%~0.060%, N≤0.0045%, Cr: 0.33%~0.58%, Nb: 0.018%~0.033%, Ti: 0.028%~0.048%, B: 0.0025%~0.0045%, and the balance is Fe and unavoidable impurities.

[0028] The carbon equivalent of the selected connection material and raw steel coil needs to be controlled by the carbon equivalent formula, which is: Ceq=C+Si / 30+Mn / 20+2×P+4×S(%); The tensile strength of the higher strength steel before and after welding shall not exceed 3.0 times the tensile strength of the lower strength steel.

[0029] The plate shape of the connecting material and the raw steel coil is ≤18IU, and the curvature is ≤30mm2 / 10m; the thickness range of the welded chilled coil is 0.70mm~2.20mm, of which the thickness ratio of the two steel coils is ≤1.5, and the width range of the welded chilled coil is 850~1350mm, of which the width transition of the two steel coils is ≤160mm, that is, the single-side width transition is ≤80mm.

[0030] In some embodiments, the carbon equivalent of the connecting material and the raw steel coil is controlled in the range of 0.35% to 0.90%.

[0031] The step of "cutting the welding selected connecting material and the raw steel coil" includes: when cutting, the cutting length of the steel coil is controlled according to the following requirements, and welding is performed after ensuring the plate shape and surface quality; Use double shears to cut the steel strip to a certain length to ensure the plate shape and surface quality before welding. When the raw material thickness t<1.2mm, the tail of the strip is cut off 18.0m, and the head of the strip is cut off 9.0m; when 1.2mm≤raw material thickness t<2.0mm, the tail of the strip is cut off 16.0m, and the head of the strip is cut off 7.5m; when the raw material thickness t≥2.0mm, the tail of the strip is cut off 13.0m, and the head of the strip is cut off 5.0m; at the same time, the operator should determine the cutting length according to the actual situation of the incoming material to ensure that the defects of the head and tail of the strip can be completely removed and will not deteriorate the welding quality.

[0032] In some embodiments, the measured weld thickness needs to be 0.85 to 1.50 times the thickness of the welding material (0.85t≤t1≤1.50t, where t is the material thickness).

[0033] In some embodiments, when the weld is sampled for the cupping test, at least 3 points are inspected. If the crack is in the heat-affected zone and the crack is perpendicular to the weld direction, the weld is judged to be qualified; if the crack coincides with the weld, the weld quality is judged to be unqualified. In addition, two welds are not allowed in a large coil, otherwise it is judged to be unqualified. When performing width jump connection, a crescent bend test is required. Only after the test is found to be problem-free can the transition of the width jump steel coil be carried out.

[0034] The cupping test (also known as the Erichsen cupping test or the Erichsen cupping test) is a test method used to evaluate the ductility and formability of metal sheets and strips. The test measures the maximum deformation that the sheet can withstand by pressing a hemispherical punch into a metal sheet specimen fixed in a die at a certain speed until the specimen breaks.

[0035] Test equipment and devices The cupping test equipment mainly includes a punch, a die and a blank holder. The punch is generally hemispherical with a specific radius (such as 20mm), the die has a circular opening for placing the sample, and the blank holder is used to fix the edge of the sample during the test to prevent the edge material from excessively flowing during the test and affecting the test results. The entire test equipment is usually powered by a hydraulic or mechanical drive system, which enables the punch to punch the sample at a stable speed (such as 0.05 - 0.2mm / s).

[0036] Material performance evaluation For metal sheets, the cupping test is an important means of evaluating the quality of the sheet. Through this test, the forming limit of the sheet can be understood, providing a reference for subsequent processing techniques (such as stamping, deep drawing, etc.). For example, in automobile manufacturing, the stamping parts of the car body need to have good ductility, and the cupping test can be used to screen out metal sheets suitable for body stamping.

[0037] Example The tail of a low-cost 980MPa grade hot-dip galvanized duplex steel coil (chemical composition: 0.088%C, 0.42%Si, 2.33%Mn, 0.010%P, 0.003%S, 0.045%Als, 0.028%Nb, 0.55%Cr, 0.043%Ti, 0.0031%B, 0.0027%N, carbon equivalent: 0.249%) with a specification of 1.20mm×1150mm was cut to 15.0m and then connected with a low-cost 780MPa grade hot-dip galvanized duplex steel coil with a specification of 1.00mm×1150mm. Grade hot-dip galvanized duplex steel (chemical composition is 0.0.92%C, 0.28%Si, 2.22%Mn, 0.011%P, 0.002%S, 0.043%Als, 0.026%Nb, 0.61%Cr, 0.0024%N, and its carbon equivalent is 0.237%). The steel coil is cut to 6.0m, and the welding current is 10.5kA, with a speed of 12.5m / min, an overlap of 0.90mm, a compensation of 1.00mm, and a welding pressure of 12.5kN. Figure 1 As shown in the figure, the weld after welding with the above welding process is flat and smooth, without nodules, weld scars, weld penetration and other defects. The cupping test did not show cracking along the weld, and the crescent bend effect was good. No belt breakage accidents caused by the weld occurred during the hot-dip galvanizing annealing and finishing processes.

[0038] Comparative Example The tail of a low-cost 980MPa grade hot-dip galvanized duplex steel coil with a specification of 2.00mm×1350mm (chemical composition: 0.092%C, 0.40%Si, 2.28%Mn, 0.010%P, 0.002%S, 0.045%Als, 0.55%Cr, 0.031%Nb, 0.042%Ti, 0.0030%B, 0.0023%N, and carbon equivalent of 0.247%) was cut to 10.0m and then cut into a 3.50×1180 The DC06 (chemical composition is 0.0015%C, 0.01%Si, 0.03%Mn, 0.008%P, 0.002%S, 0.038%Als, 0.075%Ti, 0.0026%N, and its carbon equivalent is 0.0273%) steel coil is cut to 4.5m, and the welding current is 11.0kA, the speed is 11.5m / min, the overlap is 1.10mm, the compensation is 1.00mm, and the welding pressure is 14.0kN. The weld quality after welding by the above welding process is not good, and cracks appear along the weld after the cupping test. The connecting material should be changed before production.

[0039] The above are exemplary embodiments disclosed in the present invention, but it should be noted that various changes and modifications may be made without departing from the scope of the embodiments disclosed in the claims. Although the elements disclosed in the embodiments of the present invention may be described or required in individual form, they may also be understood as multiple unless explicitly limited to the singular.

[0040] A person skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples; under the concept of the embodiments of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the above embodiments of the present invention, which are not provided in detail for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the protection scope of the embodiments of the present invention.

Claims

1. A low-cost 980MPa grade hot-dip galvanized duplex steel hot-dip galvanizing process narrow lap welding method, characterized in that: After the welding connection material and the raw steel coil are sheared, the welding surfaces of the connection material and the raw steel coil are aligned and placed on the same horizontal plane for welding, and after welding, the weld quality is checked by measuring the weld thickness and cupping test; Wherein, welding is performed according to the welding current, welding speed, welding pressure, overlap amount and welding compensation amount calculated by the following formulas (1)-(5); I = T + 9.3 (1) V = -4 / 3T + 41.8 / 3 (2) P=5 / 3T+26.5 / 3(3) L=0.5T+0.25(4) Y=2 / 15T+7.6 / 15(5) Among them, T is the thickness of welding material, in mm; L is the overlap amount, in mm; Y is the welding compensation amount, in mm; V is the welding speed, in m / min; P is the welding pressure, in kN; I is the welding current, in kA.

2. The low-cost 980MPa grade hot-dip galvanized dual-phase steel hot-dip galvanizing process narrow lap welding method according to claim 1, characterized in that: The chemical composition of the dual-phase steel includes, by mass percentage, C: 0.05%~0.12%, Si: 0.25%~0.50%, Mn: 2.00%~2.40%, P≤0.018%, S≤0.009%, Als: 0.010%~0.065%, N≤0.0065%, Cr: 0.30%~0.70%, Nb: 0.015%~0.040%, Ti: 0.025%~0.050%, B: 0.0010%~0.0050%, and the balance is Fe and unavoidable impurities.

3. The low-cost 980MPa grade hot-dip galvanized dual-phase steel hot-dip galvanizing process narrow lap welding method according to claim 2, characterized in that: The chemical composition of the dual-phase steel includes, by mass percentage, C: 0.07%~0.10%, Si: 0.30%~0.45%, Mn: 2.05%~2.35%, P≤0.012%, S≤0.006%, Als: 0.025%~0.060%, N≤0.0045%, Cr: 0.33%~0.58%, Nb: 0.018%~0.033%, Ti: 0.028%~0.048%, B: 0.0025%~0.0045%, and the balance is Fe and unavoidable impurities.

4. The low-cost 980MPa grade hot-dip galvanized dual-phase steel hot-dip galvanizing process narrow lap welding method according to claim 1, characterized in that: The overlap amount is 0.60mm~1.35mm, the compensation amount is 0.60mm~0.80mm, the welding speed is 11.0~13.0m / min, the welding pressure is 10.0~12.5kN and the welding current is 10.0~11.5kA.

5. The low-cost 980MPa grade hot-dip galvanized dual-phase steel hot-dip galvanizing process narrow lap welding method according to claim 3, characterized in that: The carbon equivalent of the selected connection material and raw steel coil needs to be controlled by the carbon equivalent formula, which is: Ceq=C+Si / 30+Mn / 20+2×P+4×S(%); The tensile strength of the higher strength steel before and after welding shall not exceed 3.0 times the tensile strength of the lower strength steel.

6. The low-cost 980MPa grade hot-dip galvanized dual-phase steel hot-dip galvanizing process narrow lap welding method according to claim 5, characterized in that: The carbon equivalent of the connecting material and raw steel coil is controlled in the range of 0.35%~0.90%.

7. The low-cost 980MPa grade hot-dip galvanized dual-phase steel hot-dip galvanizing process narrow lap welding method according to claim 1, characterized in that: The step of "cutting the welding selected connecting material and the raw steel coil" includes: when cutting, the cutting length of the steel coil is controlled according to the following requirements, and welding is performed after ensuring the plate shape and surface quality; Use double shears to cut off a certain length of the steel strip to ensure the plate shape and surface quality before welding. When the raw material thickness t<1.2mm, the strip tail is cut off 18.0m and the strip head is cut off 9.0m; when 1.2mm≤raw material thickness t<2.0mm, the strip tail is cut off 16.0m and the strip head is cut off 7.5m; when the raw material thickness t≥2.0mm, the strip tail is cut off 13.0m and the strip head is cut off 5.0m; and ensure that the defects of the strip head and tail can be completely removed without deteriorating the welding quality.

8. The low-cost 980MPa grade hot-dip galvanized dual-phase steel hot-dip galvanizing process narrow lap welding method according to claim 1, characterized in that: The measured weld thickness needs to be 0.85~1.50 times the thickness of the welding material.

9. The low-cost 980MPa grade hot-dip galvanized dual-phase steel hot-dip galvanizing process narrow lap welding method according to claim 1, characterized in that: When taking weld samples for cupping test, at least 3 points shall be inspected. If the crack is in the heat affected zone and the crack is perpendicular to the weld direction, the weld is judged to be qualified; if the crack coincides with the weld, the weld quality is judged to be unqualified.

10. The low-cost 980MPa grade hot-dip galvanized dual-phase steel hot-dip galvanizing process narrow lap welding method according to claim 1, characterized in that: The plate shape of the connecting material and the raw steel coil is ≤18IU, and the curvature is ≤30mm2 / 10m; the thickness range of the welded chilled coil is 0.70mm~2.20mm, of which the thickness ratio of the two steel coils is ≤1.5, and the width range of the welded chilled coil is 850~1350mm, of which the width transition of the two steel coils is ≤160mm, that is, the single-side width transition is ≤80mm.

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