Low-cost and high-efficiency steel for gas shielded welding wires and production method of low-cost and high-efficiency steel

Abstract

The invention discloses steel for a low-cost efficient gas shielded welding wire and a production method of the steel. The steel comprises the following chemical components in percentage by mass: 0.03-0.10% of C, 0.80-1.60% of Mn, less than or equal to 0.020% of S, less than or equal to 0.020% of P, 0.50-1.00% of Si, less than or equal to 0.010% of V, Ti, Nb and Alt, less than or equal to 0.030% of Cr, Ni and Cu, less than or equal to 0.0010% of Ca, less than or equal to 0.0045% of N and the balance of Fe and inevitable impurities. The production method comprises the steps of converter smelting, LF external refining, square billet continuous casting, straight roller way conveying, hot rolling spinning and air cooling packaging. The crystallizer adopts electric stirring and final stirring, the central shrinkage cavity and central segregation of a continuous casting billet are eliminated, a wire product with the specification of phi 5.0-7.0 mm is produced by adopting a heating-free direct rolling technology, and the steel for the gas shield welding wire is efficiently produced at low cost.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to low-cost and high-efficiency steel for gas shielded welding wire and a production method thereof. Background Art

[0002] With the gradual increase in demand for mechanical equipment and the large-scale application of engineering machinery, gas shielded welding wire has been increasingly widely used in my country's heavy machinery, engineering machinery, mining, bridges, construction, vehicles and other manufacturing industries. Gas shielded welding is an arc welding that uses external gas as an arc medium to protect the arc and welding area. Gas shielded solid welding is a high-quality, efficient and energy-saving welding method. When CO2 is used as a shielding gas for welding, gas shielded welding wire has excellent welding process performance, stable arc combustion, less spatter, beautiful weld formation, low weld metal porosity sensitivity, good all-position welding process, and can be suitable for a wider welding current range. According to the different uses of machinery, to ensure the welding performance of the welding wire, appropriate chemical composition and product organization are required to ensure the mechanical properties of the weld and the deposited metal.

[0003] Currently, carbon steel and 500MPa low-alloy steel are the mainstream steels for equipment and facilities in heavy machinery, engineering machinery, mining, bridges, construction, and vehicle industries. In recent years, my country's gas shielded welding has developed rapidly, the use of gas shielded welding wire has increased, and the market demand for welding steel wire rods used to process gas shielded welding wire is increasing rapidly. ER70S-6 is a commonly used gas shielded welding wire variety abroad, which is used for the welding process of carbon steel and 500MPa low-alloy steel. There are corresponding grade standards in China, but the composition and process flow are relatively complex, the production cost is high, and the control of impurity elements is relatively wide. Therefore, from the perspective of the whole process, the development of a steel with pure and simple steel composition, low impurity element content, advanced production process, low cost and high efficiency for gas shielded welding wire has positive significance for energy conservation and emission reduction and achieving carbon neutrality goals. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a low-cost and high-efficiency steel for gas shielded welding wire and a production method thereof.

[0005] The present invention adopts the process of continuous casting of square billets and high-speed direct rolling to produce steel for gas shielded welding wire. The product adopts Si and Mn as strengthening elements, controls impurity elements such as S, P, and N, manages strengthening elements such as Nb, V, and Ti, and residual elements such as Cr, Ni, and Cu, and controls strong reducing elements such as Al and Ca that are easy to produce inclusions. The present invention adopts the crystallizer electric stirring + end stirring technology, which can effectively eliminate the central shrinkage and central segregation of the continuous casting billet; adopts the heating-free direct rolling technology to avoid the energy consumption and metal iron burning during the heating and cooling process of the casting billet, and successfully produces φ5-7mm steel for gas shielded welding wire. The production method of the present invention has the characteristics of short process, low cost and good quality.

[0006] The present invention adopts the process of continuous casting of square billets and high-speed direct rolling to produce steel for gas shielded welding wire. The product adopts Si and Mn as strengthening elements, controls impurity elements such as S, P, and N, manages strengthening elements such as Nb, V, and Ti, and residual elements such as Cr, Ni, and Cu, and controls strong reducing elements such as Al and Ca that are easy to produce inclusions. The present invention adopts the crystallizer electric stirring + end stirring technology, which can effectively eliminate the central shrinkage and central segregation of the continuous casting billet; adopts the heating-free direct rolling technology to avoid the energy consumption and metal iron burning during the heating and cooling process of the casting billet, and successfully produces φ5-7mm steel for gas shielded welding wire. The production method of the present invention has the characteristics of short process, low cost and good quality.

[0007] To solve the above technical problems, the technical solution adopted by the present invention is: a low-cost and high-efficiency steel for gas shielded welding wire, the chemical composition of the steel for gas shielded welding wire and its mass percentage are: C: 0.03-0.10%, Mn: 0.80-1.60%, S≤0.020%, P≤0.020%, Si: 0.50-1.00%, V≤0.010%, Ti≤0.010%, Nb≤0.010%, Alt≤0.010%, Cr≤0.030%, Ni≤0.030%, Cu≤0.030%, Ca≤0.0010%, N≤0.0045%, and the balance is Fe and unavoidable impurities.

[0008] The steel for the gas shielded welding wire of the present invention has a diameter of φ5-7mm and a structure of ferrite+pearlite.

[0009] The mechanical properties of the steel for gas shielded welding wire of the present invention are as follows: tensile strength Rm≤550MPa, elongation A≥35%, and section shrinkage Z≥70%.

[0010] Another object of the present invention is to provide a low-cost and high-efficiency production method for gas shielded welding wire steel, the production method comprising converter smelting, LF refining outside the furnace, billet continuous casting, direct rolling roller conveying, hot rolling wire laying and air cooling packaging processes; in the billet continuous casting process, the superheat of the molten steel in the tundish is 18-33°C, the casting speed of the continuous casting machine is controlled at 3.3-3.8m / min, the melting point of the protective slag used in the crystallizer is 1070-1150°C, the basicity is 0.90-1.10, the viscosity is 0.50-0.70P·S, the secondary cooling adopts intermediate cooling, and the specific water volume is 1.1-1.4L / kg steel.

[0011] The square billet continuous casting process of the present invention adopts electromagnetic stirring + end electromagnetic stirring in the crystallizer, and the electromagnetic stirring parameters are: current 380-450A, frequency 2-5Hz; end electromagnetic stirring parameters are: current 420-480A, frequency 5-10Hz. The crystallizer electric stirring + end stirring technology can effectively eliminate the central shrinkage and central segregation of the continuous casting billet.

[0012] The hot rolling wire laying process of the present invention adopts the heating-free direct rolling technology, has no billet heating link, avoids the energy consumption and metal iron burning in the process of billet heating and cooling; the billet is quickly transported to the rolling mill entrance by a direct rolling climbing roller with a heat preservation cover, and the direct rolling roller conveying speed is 2.2-3.6m / s; the rough rolling start temperature is 960-1010℃, and the head-tail temperature difference is ≤50℃; the square billet is rolled by a 6+6+6 arranged rough-medium-finishing rolling mill, the final rolling wire laying speed is 80-110m / s, the wire laying temperature is 860-920℃, and the wire products with a diameter of φ5-7mm are obtained by air-cooling rollers.

[0013] According to the converter smelting process of the present invention, S≤0.025% and P≤0.120% are contained in the molten iron fed into the converter; high-quality scrap steel is used, and the contents of Mo, Cr, Ni and Cu are controlled to be less than 0.040%; lime and light-burned dolomite are used for slag making, and 30-50kg / t of lime and 20-30kg / t of light-burned dolomite are added; the converter end point has a carbon content of 0.02-0.05%, a phosphorus content of P≤0.010%, and a sulfur content of S≤0.015%; and low-carbon and low-phosphorus silicon-manganese alloy, low-aluminum ferrosilicon, and silicon-barium-aluminum deoxidizer are added after the furnace.

[0014] The LF off-furnace refining process of the present invention controls the amount of refined lime added, the total amount of refined lime (converter + refining) is controlled to a target value of 6-8 kg / t steel (refined lime here refers to the refining slag material), the fluorite target range is 0.8-2 kg / t steel, SiC is used for slag making, wollastonite is added to control the basicity of the refined slag, the basicity of the final refined slag is controlled to a target of 1.3-1.7, and the FeO of the refined slag is controlled to a target of 0.5-1.5%; the refined outlet active oxygen [O] is controlled to 15-30 ppm; the soft blowing time is 15-30 min, and the outlet temperature is 1570-1600° C.

[0015] In the LF refining process outside the furnace of the present invention, the chemical composition and mass percentage of the molten steel out of the argon blowing station are controlled to be: C: 0.03-0.10%, Mn: 0.80-1.60%, S≤0.020%, P≤0.020%, Si: 0.50-1.00%, V≤0.010%, Ti≤0.010%, Nb≤0.010%, Alt≤0.010%, Cr≤0.030%, Ni≤0.030%, Cu≤0.030%, Ca≤0.0010%, N≤0.0045%, and the balance is Fe and unavoidable impurities.

[0016] The beneficial effects of adopting the above technical scheme are: 1. The present invention is aimed at the 70 kg grade gas shielded welding wire steel with the largest application volume in the current market, and the composition design is aimed at the wire products with a specification of φ5-7mm. 2. The present invention uses converter smelting without adding strengthening elements such as V, Ti, and Nb, simplifying the material composition. 3. The present invention controls the content of residual elements such as Cr, Ni, and Cu by inspecting the quality of scrap steel to ensure the drawing performance of the welding wire and the final welding performance. 4. The present invention controls the content of strong reducing elements such as Alt and Ca to ensure the active oxygen content at the refined exit, control the level of inclusions, and ensure the drawing performance of the welding wire. 5. The present invention adopts the crystallizer electric stirring + end stirring technology, which can effectively eliminate the central shrinkage cavity and segregation of the ingot. 6. The present invention adopts the square billet continuous casting-hot rolling process, adopts the heating-free direct rolling technology, and has no ingot heating link, which avoids the energy consumption and metal iron burning during the ingot heating and cooling process. 7. The present invention ensures uniform pearlite + ferrite structure by controlling the final rolling speed, wire laying temperature, roller air cooling and other technologies, thereby achieving low-cost and high-efficiency production of wire for welding wire. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a macrostructure diagram of the ingot in Example 1; Figure 2 This is the metallographic structure diagram of the steel used for welding wire in Example 1 (200×). DETAILED DESCRIPTION

[0018] The scheme of the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. Example 1

[0019] The diameter of the steel product for gas shielded welding wire in this embodiment is φ5.0 mm, and its chemical composition and mass percentage are shown in Table 1.

[0020] The production method of the steel product for gas shielded welding wire in this embodiment includes converter smelting, LF refining outside the furnace, billet continuous casting, direct rolling roller conveying, hot rolling wire laying and air cooling packaging processes. The specific production process steps are as follows: (1) Converter smelting: S: 0.005%, P: 0.115% in the hot metal; use high-quality scrap steel, and control the content of Mo, Cr, Ni, and Cu to less than 0.040%; use lime and light-burned dolomite to make slag, add 30kg / t of lime and 20kg / t of light-burned dolomite; converter end point: C: 0.023%, P: 0.010%, end point S: 0.014%; add 0.2kg / t of silicon, barium, and aluminum during tapping, and add 14.5kg / t of low-carbon and low-phosphorus silicon-manganese alloy, 3.5kg / t of low-aluminum ferrosilicon, and 2kg / t of refined lime.

[0021] (2) LF refining: deoxidation slag making materials include 4 kg / t steel of refined lime, 0.8 kg / t steel of fluorite, 1.3 kg / t steel of silicon carbide, final slag basicity of 1.7, final slag FeO: 0.5%, active oxygen [O]: 15 ppm, soft blowing time of 30 min, and outlet temperature of 1595 °C. The chemical composition and mass percentage of the molten steel outlet from LF refining are shown in Table 1.

[0022] (3) Billet continuous casting process: The superheat of the molten steel in the tundish is 20-26°C, the casting speed of the continuous casting machine is controlled at 3.5m / min, the melting point of the protective slag used in the crystallizer is 1100°C, the basicity is 0.98, the viscosity is 0.55P·S, the secondary cooling adopts intercooling, and the specific water volume is 1.1L / kg steel. The crystallizer electromagnetic stirring + end stirring technology is used to stir the inside of the billet (electromagnetic stirring parameters: current 380A, frequency 3Hz; end electromagnetic stirring parameters: current 420A, frequency 7Hz).

[0023] (4) Hot rolling wire laying process: The non-heating direct rolling technology is adopted, and there is no billet heating process. The billet is quickly transported to the rolling mill entrance through a direct rolling climbing roller with a heat preservation cover. The direct rolling roller conveying speed is 3.6m / s. The head temperature of the rough rolling billet is 970℃, and the tail temperature is 935℃. 2 The square billet is rolled by a rough-medium-finishing rolling mill arranged in 6+6+6, with a final rolling speed of 105m / s and a spinning temperature of 868℃, and the wire product is obtained by an air-cooled roller.

[0024] The properties of the steel used for the gas shielded welding wire in this embodiment are: Rm: 496MPa, A: 42%, Z: 81%.

[0025] Figure 1 The macrostructure diagram of the ingot obtained in Example 1 is shown in FIG. Figure 1 It can be seen that the quality of the ingot is good, with central shrinkage and no central segregation; Figure 2 The metallographic structure diagram (200×) of the steel for gas shielded welding wire obtained in Example 1 is shown in FIG. Figure 2 It can be seen that the structure is ferrite + pearlite, and the structure is fine and uniform. (The drawings of Examples 2-5 are similar to those of Example 1, so they are omitted.) Example 2

[0026] The diameter of the steel product for gas shielded welding wire in this embodiment is φ7mm, and its chemical composition and mass percentage are shown in Table 1.

[0027] The production method of the steel product for gas shielded welding wire in this embodiment includes converter smelting, LF refining outside the furnace, billet continuous casting, direct rolling roller conveying, hot rolling wire laying and air cooling packaging processes. The specific production process steps are as follows: (1) Converter smelting: S: 0.025%, P: 0.120% in the molten iron; use high-quality scrap steel, and control the content of Mo, Cr, Ni, and Cu to less than 0.040%; use lime and light-burned dolomite to make slag, add 48kg / t of lime and 30kg / t of light-burned dolomite; converter end point: C: 0.05%, P: 0.006%, end point S: 0.010%; add 0.10kg / t of silicon, barium, and aluminum during the steel tapping process, and add 22kg / t of low-carbon and low-phosphorus silicon-manganese alloy, 9kg / t of low-aluminum ferrosilicon, 6.4kg / t of high-carbon ferromanganese, and 2kg / t of refined lime.

[0028] (2) LF refining: deoxidized slag-making materials include 6 kg / t steel of refined lime, 2.0 kg / t steel of fluorite, and 0.7 kg / t steel of silicon carbide. Final slag basicity is 1.3, final slag FeO: 1.4%, active oxygen [O]: 28 ppm, soft blowing time is 16 min, and outlet temperature is 1586 °C. The chemical composition and mass percentage of the molten steel outlet from LF refining are shown in Table 1.

[0029] (3) Billet continuous casting process: The superheat of the molten steel in the tundish is 22-27°C, the casting speed of the continuous casting machine is controlled at 3.8m / min, the melting point of the protective slag used in the crystallizer is 1070°C, the basicity is 0.90, the viscosity is 0.50P·S, the secondary cooling adopts intercooling, and the specific water volume is 1.4L / kg steel. The crystallizer electromagnetic stirring + end stirring technology is used to stir the inside of the billet (electromagnetic stirring parameters: current 400A, frequency 3Hz; end electromagnetic stirring parameters: current 480A, frequency 8Hz).

[0030] (4) Hot rolling wire laying process: The heat-free direct rolling technology is adopted, and there is no billet heating process. The billet is quickly transported to the mill entrance through a direct rolling climbing roller with a heat preservation cover. The direct rolling roller conveying speed is 3.3m / s. The head temperature of the rough rolling billet is 1000℃, and the tail temperature is 950℃. 2 The square billet is rolled by a rough-medium-finishing rolling mill arranged in 6+6+6, with a final rolling speed of 80m / s and a spinning temperature of 920℃, and the wire product is obtained by an air-cooled roller.

[0031] The properties of the steel used for the gas shielded welding wire in this embodiment are as follows: Rm: 542MPa, A: 38%, Z: 75%. The product has a good surface, a ferrite+pearlite structure, and a fine and uniform structure. Example 3

[0032] The diameter of the steel product for the gas shielded welding wire in this embodiment is φ5.5 mm, and its chemical composition and mass percentage are shown in Table 1.

[0033] The production method of the steel product for gas shielded welding wire in this embodiment includes converter smelting, LF refining outside the furnace, billet continuous casting, direct rolling roller conveying, hot rolling wire laying and air cooling packaging processes. The specific production process steps are as follows: (1) Converter smelting: S: 0.007%, P: 0.110% in the hot metal; use high-quality scrap steel, and control the content of Mo, Cr, Ni, and Cu to less than 0.040%; use lime and light-burned dolomite to make slag, add 35kg / t of lime and 23kg / t of light-burned dolomite; converter end point: C: 0.035%, P: 0.006%, end point S: 0.012%; add 0.15kg / t of silicon, barium, and aluminum during tapping, and add 18kg / t of low-carbon and low-phosphorus silicon-manganese alloy, 4kg / t of low-aluminum ferrosilicon, and 2kg / t of refined lime.

[0034] (2) LF refining: deoxidation slag-making materials include 4.5 kg / t steel of refined lime, 1.1 kg / t steel of fluorite, 1.0 kg / t steel of silicon carbide, final slag basicity of 1.4, final slag FeO: 0.8%, active oxygen [O]: 20 ppm, soft blowing time of 20 min, and outlet temperature of 1580 °C. The chemical composition and mass percentage of the molten steel outlet from LF refining are shown in Table 1.

[0035] (3) Billet continuous casting process: The superheat of the molten steel in the tundish is 21-26°C, the casting speed of the continuous casting machine is controlled at 3.5m / min, the melting point of the protective slag used in the crystallizer is 1100°C, the basicity is 0.98, the viscosity is 0.55P·S, the secondary cooling adopts intercooling, and the specific water volume is 1.3L / kg steel. The crystallizer electromagnetic stirring + end stirring technology is used to stir the inside of the billet (electromagnetic stirring parameters: current 390A, frequency 5Hz; end electromagnetic stirring parameters: current 440A, frequency 7Hz).

[0036] (4) Hot rolling wire laying process: The heating-free direct rolling technology is adopted, and there is no billet heating process. The billet is quickly transported to the rolling mill entrance through a direct rolling climbing roller with a heat preservation cover. The direct rolling roller conveying speed is 2.2m / s. The head temperature of the rough rolling billet is 960℃, and the tail temperature is 943℃. 2 The square billet is rolled by a rough-medium-finishing rolling mill arranged in 6+6+6, with a final rolling speed of 89m / s and a spinning temperature of 900℃, and the wire product is obtained by air-cooling rollers.

[0037] The properties of the steel used for the gas shielded welding wire in this embodiment are as follows: Rm: 516MPa, A: 44%, Z: 79%. The product has a good surface, a ferrite+pearlite structure, and a fine and uniform structure. Example 4

[0038] The diameter of the steel product for the gas shielded welding wire in this embodiment is φ5.5 mm, and its chemical composition and mass percentage are shown in Table 1.

[0039] The production method of the steel product for gas shielded welding wire in this embodiment includes converter smelting, LF refining outside the furnace, billet continuous casting, direct rolling roller conveying, hot rolling wire laying and air cooling packaging processes. The specific production process steps are as follows: (1) Converter smelting: S: 0.003%, P: 0.108% in the molten iron; use high-quality scrap steel, and control the content of Mo, Cr, Ni, and Cu to less than 0.040%; use lime and light-burned dolomite to make slag, add 40kg / t of lime and 25kg / t of light-burned dolomite; converter end point: C: 0.04%, P: 0.007%, end point S: 0.010%; add 0.15kg / t of silicon, barium, and aluminum during tapping, and add 24kg / t of low-carbon and low-phosphorus silicon-manganese alloy, 4.5kg / t of low-aluminum ferrosilicon, and 2kg / t of refined lime.

[0040] (2) LF refining: deoxidation slag making materials include 5 kg / t steel of refined lime, 1.3 kg / t steel of fluorite, 1.1 kg / t steel of silicon carbide, final slag basicity of 1.55, final slag FeO: 0.98%, active oxygen [O]: 23 ppm, soft blowing time of 25 min, and outlet temperature of 1578 °C. The chemical composition and mass percentage of the molten steel outlet from LF refining are shown in Table 1.

[0041] (3) Billet continuous casting process: The superheat of the molten steel in the tundish is 18-23°C, the casting speed of the continuous casting machine is controlled at 3.6m / min, the melting point of the protective slag used in the crystallizer is 1150°C, the basicity is 1.10, the viscosity is 0.70P·S, the secondary cooling adopts intercooling, and the specific water volume is 1.3L / kg steel. The crystallizer electromagnetic stirring + end stirring technology is used to stir the inside of the billet (electromagnetic stirring parameters: current 450A, frequency 2Hz; end electromagnetic stirring parameters: current 450A, frequency 6Hz).

[0042] (4) Hot rolling wire laying process: The heat-free direct rolling technology is adopted, and there is no billet heating process. The billet is quickly transported to the rolling mill entrance through a direct rolling climbing roller with a heat preservation cover. The direct rolling roller conveying speed is 3.1m / s. The head temperature of the rough rolling billet is 965℃, and the tail temperature is 915℃. 2The square billet is rolled by a rough-medium-finishing rolling mill arranged in 6+6+6, with a final rolling speed of 97m / s and a spinning temperature of 902℃, and the wire product is obtained by an air-cooled roller.

[0043] The properties of the steel used for the gas shielded welding wire in this embodiment are as follows: Rm: 520 MPa, A: 43.5%, Z: 83%. The product has a good surface, a ferrite + pearlite structure, and a fine and uniform structure. Example 5

[0044] The diameter of the steel product for the gas shielded welding wire in this embodiment is φ6.5 mm, and its chemical composition and mass percentage are shown in Table 1.

[0045] The production method of the steel product for gas shielded welding wire in this embodiment includes converter smelting, LF refining outside the furnace, billet continuous casting, direct rolling roller conveying, hot rolling wire laying and air cooling packaging processes. The specific production process steps are as follows: (1) Converter smelting: S: 0.007%, P: 0.112% in the hot metal; use high-quality scrap steel, and control the content of Mo, Cr, Ni, and Cu to less than 0.040%; use lime and light-burned dolomite to make slag, add 42kg / t of lime and 26kg / t of light-burned dolomite; converter end point: C: 0.02%, P: 0.008%, end point S: 0.013%; add 0.12kg / t of silicon, barium, and aluminum during tapping, and add 26kg / t of low-carbon and low-phosphorus silicon-manganese alloy, 5kg / t of low-aluminum ferrosilicon, and 2kg / t of refined lime.

[0046] (2) LF refining: deoxidation slag making materials include 5.5 kg / t steel of refined lime, 1.6 kg / t steel of fluorite, 1.3 kg / t steel of silicon carbide, final slag basicity 1.60, final slag FeO: 1.5%, active oxygen [O]: 30 ppm, soft blowing time 15 min, and outlet temperature 1600 °C. The chemical composition and mass percentage of the molten steel outlet from LF refining are shown in Table 1.

[0047] (3) Billet continuous casting process: The superheat of the molten steel in the tundish is 22-33°C, the casting speed of the continuous casting machine is controlled at 3.7m / min, the melting point of the protective slag used in the crystallizer is 1100°C, the basicity is 0.98, the viscosity is 0.55P·S, the secondary cooling adopts intercooling, and the specific water volume is 1.1L / kg steel. The crystallizer electromagnetic stirring + end stirring technology is used to stir the inside of the billet (electromagnetic stirring parameters: current 400A, frequency 3Hz; end electromagnetic stirring parameters: current 450A, frequency 10Hz).

[0048] (4) Hot rolling wire laying process: The heat-free direct rolling technology is adopted, and there is no billet heating process. The billet is quickly transported to the rolling mill entrance through a direct rolling climbing roller with a heat preservation cover. The direct rolling roller conveying speed is 2.8m / s. The head temperature of the rough rolling billet is 1010℃, and the tail temperature is 965℃. 2 The square billet is rolled by a rough-medium-finishing rolling mill arranged in 6+6+6, with a final rolling speed of 89m / s and a spinning temperature of 915℃, and the wire product is obtained by an air-cooled roller.

[0049] The properties of the steel used for the gas shielded welding wire in this embodiment are as follows: Rm: 526MPa, A: 42%, Z: 81%. The product has a good surface, a ferrite+pearlite structure, and a fine and uniform structure. Example 6

[0050] The diameter of the steel product for the gas shielded welding wire in this embodiment is φ6.5 mm, and its chemical composition and mass percentage are shown in Table 1.

[0051] The production method of the steel product for gas shielded welding wire in this embodiment includes converter smelting, LF refining outside the furnace, billet continuous casting, direct rolling roller conveying, hot rolling wire laying and air cooling packaging processes. The specific production process steps are as follows: (1) Converter smelting: S: 0.004%, P: 0.105% in the hot metal; use high-quality scrap steel, and control the content of Mo, Cr, Ni, and Cu to less than 0.040%; use lime and light-burned dolomite to make slag, add 50kg / t of lime and 28kg / t of light-burned dolomite; converter end point: C: 0.04%, P: 0.008%, end point S: 0.015%; add 0.10kg / t of silicon, barium, and aluminum during tapping, and add 28kg / t of low-carbon and low-phosphorus silicon-manganese alloy, 6kg / t of low-aluminum ferrosilicon, and 2kg / t of refined lime.

[0052] (2) LF refining: deoxidation slag making materials include 5 kg / t steel of refined lime, 1.5 kg / t steel of fluorite, 1.1 kg / t steel of silicon carbide, final slag basicity 1.5, final slag FeO: 1.2%, active oxygen [O]: 26 ppm, soft blowing time 23 min, outlet temperature 1570 °C; the chemical composition and mass percentage of molten steel outlet from LF refining are shown in Table 1.

[0053] (3) Billet continuous casting process: The superheat of the molten steel in the tundish is 20-25°C, the casting speed of the continuous casting machine is controlled at 3.3m / min, the melting point of the protective slag used in the crystallizer is 1100°C, the basicity is 0.98, the viscosity is 0.55P·S, the secondary cooling adopts intercooling, and the specific water volume is 1.2L / kg steel. The crystallizer electromagnetic stirring + end stirring technology is used to stir the inside of the billet (electromagnetic stirring parameters: current 380A, frequency 3Hz; end electromagnetic stirring parameters: current 420A, frequency 5Hz).

[0054] (4) Hot rolling wire laying process: The heating-free direct rolling technology is adopted, and there is no billet heating process. The billet is quickly transported to the mill entrance through a direct rolling climbing roller with a heat preservation cover. The direct rolling roller conveying speed is 2.5m / s. The head temperature of the rough rolling billet is 990℃, and the tail temperature is 952℃. 2 The square billet is rolled by a rough-medium-finishing rolling mill arranged in 6+6+6, with a final rolling speed of 110m / s and a spinning temperature of 860℃, and the wire product is obtained by an air-cooled roller.

[0055] The properties of the steel used for the gas shielded welding wire in this embodiment are as follows: Rm: 535MPa, A: 45%, Z: 82%. The product has a good surface, a ferrite+pearlite structure, and a fine and uniform structure.

[0056] Table 1 Chemical composition and mass percentage of steel used for welding wire in each embodiment (%)

[0057] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A low-cost and high-efficiency steel for gas shielded welding wire, characterized in that: The chemical composition and mass percentage of the steel for gas shielded welding wire are: C: 0.03-0.10%, Mn: 0.80-1.60%, S≤0.020%, P≤0.020%, Si: 0.50-1.00%, V, Ti, Nb, Alt≤0.010%, Cr, Ni, Cu≤0.030%, Ca≤0.0010%, N≤0.0045%, and the balance is Fe and unavoidable impurities.

2. The low-cost and high-efficiency steel for gas shielded welding wire according to claim 1, characterized in that: The steel used for the gas shielded welding wire has a diameter of φ5-7mm and a structure of ferrite+pearlite.

3. The low-cost and high-efficiency steel for gas shielded welding wire according to claim 1, characterized in that: The mechanical properties of the steel for gas shielded welding wire are as follows: tensile strength Rm≤550MPa, elongation A≥35%, and section shrinkage Z≥70%.

4. A method for producing low-cost and high-efficiency steel for gas shielded welding wire according to any one of claims 1 to 3, characterized in that: The production method comprises converter smelting, LF refining outside the furnace, billet continuous casting, direct rolling roller conveying, hot rolling wire laying and air cooling packaging process; in the billet continuous casting process, the superheat degree of molten steel in the tundish is 18-33°C, the casting speed of the continuous casting machine is controlled at 3.3-3.8m / min, the melting point of the protective slag used in the crystallizer is 1070-1150°C, the basicity is 0.90-1.10, the viscosity is 0.50-0.70P·S, the secondary cooling adopts intermediate cooling, and the specific water volume is 1.1-1.4L / kg steel.

5. A low-cost and high-efficiency steel for gas shielded welding wire and a production method thereof according to claim 4, characterized in that: The square billet continuous casting process adopts electromagnetic stirring + terminal electromagnetic stirring in the crystallizer, and the electromagnetic stirring parameters are: current 380-450A, frequency 2-5Hz; terminal electromagnetic stirring parameters are: current 420-480A, frequency 5-10Hz.

6. A low-cost and high-efficiency steel for gas shielded welding wire and a production method thereof according to claim 4, characterized in that: The hot rolling spinning process adopts the heating-free direct rolling technology, without the billet heating link, and the billet is quickly transported to the rolling mill entrance through the direct rolling climbing roller with a heat preservation cover, and the direct rolling roller conveying speed is: 2.2-3.6m / s; the rough rolling start temperature is 960-1010℃, and the head and tail temperature difference is ≤50℃; the square billet is rolled by a 6+6+6 arranged rough-medium-finishing rolling mill, the final rolling spinning speed is 80-110m / s, the spinning temperature is 860-920℃, and the wire product with a diameter of φ5-7mm is obtained through an air-cooled roller.

7. A low-cost and high-efficiency steel for gas shielded welding wire and a production method thereof according to claim 4, characterized in that: In the converter smelting process, S≤0.025%, P≤0.120% in the molten iron fed into the furnace; high-quality scrap steel is used, and the contents of Mo, Cr, Ni, and Cu are controlled to be less than 0.040%; lime and light-burned dolomite are used for slag making, and 30-50kg / t of lime and 20-30kg / t of light-burned dolomite are added; the converter end point: carbon content 0.02-0.05%, phosphorus content P≤0.010%, sulfur content S≤0.015%; low-carbon and low-phosphorus silicon-manganese alloy, low-aluminum ferrosilicon, and silicon-barium-aluminum deoxidizer are added after the furnace.

8. A low-cost and high-efficiency steel for gas shielded welding wire and a production method thereof according to any one of claims 4 to 7, characterized in that: In the LF off-furnace refining process, the amount of refining lime added is controlled, the total amount of lime is controlled to a target value of 6-8kg / t steel, the fluorite target range is 0.8-2kg / t steel, SiC is used for slag making, wollastonite is added to control the basicity of the refining slag, the basicity of the final refining slag is controlled to a target of 1.3-1.7, and the FeO of the refining slag is controlled to a target of 0.5-1.5%; the active oxygen [O] at the refining outlet is controlled to 15-30ppm; the soft blowing time is 15-30min, and the outlet temperature is 1570-1600°C.

9. A low-cost and high-efficiency steel for gas shielded welding wire and a production method thereof according to any one of claims 4 to 7, characterized in that: In the LF refining process outside the furnace, the chemical composition and mass percentage of the molten steel leaving the argon blowing station are controlled as follows: C: 0.03-0.10%, Mn: 0.80-1.60%, S≤0.020%, P≤0.020%, Si: 0.50-1.00%, V, Ti, Nb, Alt≤0.010%, Cr, Ni, Cu≤0.030%, Ca≤0.0010%, N≤0.0045%, and the remainder is Fe and unavoidable impurities.

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