Production method of wire rod for alloy welding wire

Abstract

The invention relates to a production method of a wire rod for an alloy welding wire, and belongs to the technical field of steel manufacturing. Mn, Cr and Ni alloying and V and Ti microalloy strengthening are adopted, and a certain amount of B is added, so that the requirement of a 60-kilogram-level alloy welding wire is met. The process route is designed as follows: molten iron pretreatment, converter smelting, LF furnace external refining, 150mm / 180mm square billet continuous casting, heating furnace heating, rolling, roller way slow cooling and heat preservation vestibule heat preservation. Molten steel with stable components, good castability and gas content meeting the requirement is obtained through the technologies of molten iron pretreatment, converter smelting, LF furnace external refining and the like, after the molten steel is poured into a continuous casting blank, stack cooling or hot delivery and hot charging are conducted for 24 hours, and the technologies of high-temperature rolling, high-temperature spinning, roller way slow cooling and heat preservation vestibule are adopted for high-speed wire rolling. By adopting the process of the scheme, the wire rod can be prevented from generating abnormal structures such as martensite and bainite which influence drawing, and the wire rod for the high-strength alloy welding wire with the specification of phi 5.5 mm, which has stable components and can be drawn into filaments with the specification of phi 1.2 mm without annealing, is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of steel manufacturing and relates to a method for producing a wire rod for high-strength alloy welding wire. Background Art

[0002] The steel industry is an energy and resource consuming industry. A high alloy content will cause the consumption of mineral resources and increase the cost of steel. The alloy welding wires of 60 kg and above produced by existing technology generally contain certain alloys such as Cr, Mo, and Ti. The alloy cost of Mo is much higher than that of other alloys. The addition of Mo leads to high alloy cost and reduced product competitiveness. In addition, the addition of Mo makes the wire rod structure more difficult to control, and it is easy to form martensite and bainite structures, which affects the drawing performance. Summary of the invention

[0003] The object of the present invention is to provide a method for producing a wire rod for high-strength alloy welding wire, wherein the produced wire rod can be directly drawn to a welding wire with a minimum diameter of 1.2 mm without annealing; at the same time, the tensile strength of the deposited metal is above 690 MPa, and the weld metal has good fluidity.

[0004] The technical solution of the present invention: A production method for alloy welding wire steel adopts a process route of molten iron pretreatment + converter smelting + LF refining outside the furnace + 150mm / 180mm square billet continuous casting + heating + rolling + roller slow cooling + insulation in an insulation corridor. The chemical composition of the steel is as follows: C = 0.06% ~ 0.08%, Si = 0.50% ~ 0.65%, Mn = 1.60% ~ 1.70%, P ≤ 0.015%, S = 0.008% ~ 0.012%, Cr = 0.30% ~ 0.40%, Ni = 0.05% ~ 0.10%, V = 0.03% ~ 0.05%, Ti = 0.08% ~ 0.12%, B = 0.003% ~ 0.005%, Al ≤ 0.010%, Ca ≤ 0.0010%, As ≤ 0.005%, O ≤ 0.003%, N ≤ 0.005%, and the rest are Fe and unavoidable impurities; the key process steps include: (1) Hot metal pretreatment: The hot metal entering the furnace is pretreated and desulfurized by the KR method. After desulfurization, the desulfurization slag is scraped off. The sulfur content of the hot metal entering the furnace is controlled at ≤0.015%, and the residual elements Cu and As in the hot metal are ≤0.10% and ≤0.007% respectively. (2) Converter smelting: endpoint control oxygen content [O] ≤ 450ppm, carbon content [C] ≤ 0.05%, [P] ≤ 0.008%, [S] ≤ 0.015%; during the steel tapping process, add 200kg ± 5kg lime + 150kg ± 5kg synthetic slag for slag washing, and perform argon blowing and stirring; (3) LF refining: add 700-900kg lime and appropriate amount of fluorite to make white slag, and keep the white slag for more than 15 minutes. Add 50kg ferrosilicon powder and 50kg silicon carbide in batches for diffusion deoxidation during refining and slag making, use 200kg±30kg ferrotitanium to precipitate deoxidize the molten steel, and adjust the sulfur content according to the sulfur feed line. The soft blowing time after LF refining is not less than 10 minutes; (4) Heating and rolling: preheating temperature ≤ 850℃, heating temperature 1050~1100℃, soaking temperature 1080~1120℃, heating time 90~180 minutes, furnace temperature 1050±20℃; high-pressure water dephosphorization pressure 20~35Mpa, finishing rolling temperature 970±20℃, sizing temperature 950±20℃, spinning temperature 920±10℃; (5) Slow cooling of rollers: The first insulation cover of the air-cooled roller is opened, and the others are all closed; the roller speed is 0.07-0.17 m / s; the roller cooling fans are all closed, the air doors are all closed, the gap between the insulation cover and each section of the roller is ≤5 mm, and all gaps are filled or blocked with insulation materials; (6) Insulation in the insulation corridor: After the vertical coiling core rack collects the coils, they are quickly put into the insulation corridor for insulation. The temperature of the insulation corridor is 500-700℃. After the wire rod enters the insulation corridor, the corridor door is immediately closed for airtight insulation. The insulation corridor is preheated with slow-cooling steel. After the insulation corridor is full of steel, the corridor is started to be discharged. One coil is taken out and one coil is put in, ensuring that the corridor is full of steel at all times. The wire rod for high-strength alloy welding wire with a specification of 5.5mm and can be drawn to Φ1.2mm without annealing is obtained.

[0005] Furthermore, in step (5), the rollers are preheated with slow-cooled steel for not less than 60 turns before rolling. The length of roller section 1 is 4.5 m, and the speed is 0.07 m / s; the length of roller sections 2 to 9 is 6.086 m each, and the roller speed is 0.08 to 0.15 m / s, with an increase of 0.01 m / s for each section; the length of roller section 10 is 3.8 m, and the speed is 0.16 m / s; the length of roller section 11 is 5.28 m, and the speed is 0.17 m / s.

[0006] Beneficial effects of the present invention: Aiming at the use requirements of high-strength alloy welding wire, the present invention adopts Mn, Cr, Ni alloying, V, Ti micro-alloy strengthening, and adds a certain amount of B, which meets the performance requirements of 60 kg alloy welding wire and reduces the alloy cost. And by adopting high-temperature rolling + high-temperature wire drawing + slow cooling of rollers after rolling + insulation corridor insulation process, the martensite and bainite structures that affect drawing are prevented from being produced in the hot-rolled wire rod. By controlling the S content, the welding fluidity of the welding wire is increased. Through this technology, the cross-sectional shrinkage rate of the hot-rolled wire rod produced is more than 65%, and the tensile strength is less than 650Mpa. The wire rod can be continuously drawn from a specification of 5.5mm to a welding wire with a diameter of 1.2mm or less without annealing. After being made into gas-shielded welding wire, the welding fluidity is good, and the tensile strength of the deposited metal reaches more than 690Mpa. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 This is the metallographic structure diagram of the wire rod produced in Example 1.

[0008] Figure 2 This is the metallographic structure diagram of the wire rod produced in Example 2. DETAILED DESCRIPTION Example 1

[0009] A method for producing steel for alloy welding wire, comprising: pre-treating molten iron before entering a converter, wherein the molten iron has a phosphorus content of 0.129%, a sulfur content of 0.0456%, a carbon content of 4.15%, and a Si content of 0.38% before pre-treatment, and a temperature of 1299°C. 79 tons of molten iron and 21 tons of scrap steel are added during converter smelting.

[0010] (1) The KR method is used to pre-treat and desulfurize the molten iron. The sulfur content of the molten iron after pre-treatment is 0.0064%.

[0011] (2) The end point of converter smelting is: oxygen content: 444ppm, [C]: 0.039%, [P]: 0.0065%, [S]: 0.0056%, and end point temperature: 1592℃. During the steel-making process, 1789kg of high-silicon silicomanganese and 304kg of metallic manganese balls are added for deoxidation and alloying operations. At the same time, 203kg of lime and 147kg of pre-melted slag are added for slag washing, and argon blowing and stirring are performed. The slag thickness during the steel-making process is required to be ≤20mm.

[0012] (3) Add 808kg lime and 270kg fluorite to make white slag, and keep the white slag for 20 minutes. Add 50kg ferrosilicon powder and 50kg silicon carbide in batches for diffusion deoxidation during refining and slag making, use 210kg ferrotitanium to precipitate deoxidize the molten steel, and do not allow aluminum alloy to deoxidize the molten steel. After deoxidation, adjust the composition of the molten steel, feed 20kg sulfur line, and the soft blowing time after LF refining is 14 minutes.

[0013] (4) The preheating section temperature of the heating furnace is 650-660°C, the heating section temperature is 1070-1080°C, the soaking temperature is 1100-1110°C, the heating time is 134 min, the furnace outlet temperature is 1030-1040°C, and the residual oxygen content is 1.5; the high-pressure water dephosphorization pressure is 30 MPa, the finishing rolling temperature is 978-982°C, the sizing temperature is 954-960°C, and the spinning temperature is 919-925°C.

[0014] (5) The first insulation cover of the air-cooled roller is opened, and all other insulation covers are closed. The roller speed is 0.07~0.15m / s, increasing by 0.01m / s in each section.

[0015] (6) After the rolls are collected, they are quickly put into the insulation corridor for insulation and slow cooling. The rollers and insulation corridor are preheated with 100 pieces of industrial pure iron. After entering the insulation corridor, the corridor door is closed for insulation to prevent heat loss. The corridor is full of steel with no empty space, and one roll is taken out and one roll is put in. The overlap point of entering the insulation corridor is 683℃, and the non-overlap point is 565℃.

[0016] The actual finished product chemical composition of the steel produced in Example 1 is shown in Table 1, and the metallographic structure of the hot rolled wire rod is shown in Table 1. Figure 1 The performance of the hot rolled wire rod head and tail in the same circle is shown in Table 2. Example 2

[0017] The molten iron entering the converter is pretreated. Before pretreatment, the phosphorus content [P] of the molten iron is 0.1308%, the sulfur content [S] is 0.0469%, the carbon content is 4.17%, the Si content is 0.31%, the temperature is 1310℃, and 76 tons of molten iron and 20 tons of scrap steel are added to the converter.

[0018] (1) The KR method is used to pre-treat and desulfurize the molten iron. The sulfur content of the molten iron after pre-treatment is 0.006%.

[0019] (2) End point of converter smelting: oxygen content [O] 534ppm, [C] 0.051%, [P] 0.0067%, [S] 0.0052%, end point temperature 1598℃; during the steel tapping process, 1750kg of high silicon silicon manganese and 290kg of metal manganese balls are added for deoxidation and alloying operations, and 200kg of lime and 150kg of pre-melted slag are added for slag washing, and argon blowing and stirring are performed. The slag thickness during the steel tapping process is required to be ≤20mm.

[0020] (3) Add 780kg lime and 238kg fluorite to make white slag, and keep the white slag for 22 minutes. Add 50kg ferrosilicon and 50kg silicon carbide powder in batches for diffusion deoxidation during refining and slag making. Use 230kg ferrotitanium to precipitate deoxidize the molten steel. It is not allowed to use aluminum-containing alloy to deoxidize the molten steel. After deoxidation, adjust the composition of the molten steel, feed 15kg sulfur line, and the soft blowing time after LF refining is 14 minutes.

[0021] (4) The preheating section temperature of the heating furnace is 650-665°C, the heating section temperature is 1075-1080°C, the soaking temperature is 1090-1110°C, the heating time is 120 min, the furnace discharge temperature is 1035-1040°C, and the residual oxygen content is 1.4; the finishing rolling temperature is 982-989°C, the sizing temperature is 954-961°C, and the spinning temperature is 921-926°C.

[0022] (5) The first insulation cover of the air-cooled roller is opened, and all other insulation covers are closed. The roller speed is 0.07~0.15m / s, increasing by 0.01m / s in each section.

[0023] (6) After the steel rolls are assembled, they are quickly put into the insulation corridor for insulation and slow cooling. The corridor door is closed immediately after the steel enters the insulation corridor to prevent heat loss. The corridor is full of steel with no empty spaces. One roll is taken out and one roll is put in. The overlap point of the steel rolls entering the insulation corridor is 680℃, and the non-overlap point is 567℃.

[0024] The actual chemical composition of the finished steel is shown in Table 3. The metallographic structure of the hot-rolled wire rod is shown in Figure 2 The performance of the hot rolled wire rod head and tail in the same circle is shown in Table 4.

[0025] Table 1 Chemical composition of the actual finished steel of Example 1 (wt.%) .

[0026] Table 2 Performance of the head and tail of hot rolled wire rod in Example 1 .

[0027] Table 3 Chemical composition of the actual finished product of Example 2 steel (wt.%) .

[0028] Table 4 Performance of the head and tail of the hot rolled wire rod in Example 2 .

Claims

1. A method for producing alloy welding wire steel, adopting a process route of molten iron pretreatment + converter smelting + LF refining outside the furnace + 150mm / 180mm square billet continuous casting + heating + rolling + roller slow cooling + insulation corridor insulation, characterized in that: The chemical composition of steel is in percentage by mass: C = 0.06% ~ 0.08%, Si = 0.50% ~ 0.65%, Mn = 1.60% ~ 1.70%, P ≤ 0.015%, S = 0.008% ~ 0.012%, Cr = 0.30% ~ 0.40%, Ni = 0.05% ~ 0.10%, V = 0.03% ~ 0.05%, Ti = 0.08% ~ 0.12%, B = 0.003% ~ 0.005%, Al ≤ 0.010%, Ca ≤ 0.0010%, As ≤ 0.005%, O ≤ 0.003%, N ≤ 0.005%, and the rest are Fe and unavoidable impurities; The key process steps include: (1) Hot metal pretreatment: The hot metal entering the furnace is pretreated and desulfurized using the KR method, and the desulfurization slag is removed after desulfurization; The sulfur content of hot metal entering the furnace is controlled at ≤0.015%, and the residual elements Cu and As in hot metal are ≤0.10% and ≤0.007% respectively; (2) Converter smelting: endpoint control oxygen content [O] ≤ 450ppm, carbon content [C] ≤ 0.05%, [P] ≤ 0.008%, [S] ≤ 0.015%; during the steel tapping process, add 200kg ± 5kg lime + 150kg ± 5kg synthetic slag for slag washing, and perform argon blowing and stirring; (3) LF refining: add 700-900kg lime and appropriate amount of fluorite to make white slag, and keep the white slag for more than 15 minutes. Add 50kg ferrosilicon powder and 50kg silicon carbide in batches for diffusion deoxidation during refining and slag making, use 200kg±30kg ferrotitanium to precipitate deoxidize the molten steel, and adjust the sulfur content according to the sulfur feed line. The soft blowing time after LF refining is not less than 10 minutes; (4) Heating and rolling: preheating temperature ≤ 850℃, heating temperature 1050~1100℃, soaking temperature 1080~1120℃, heating time 90~180 minutes, furnace temperature 1050±20℃; high-pressure water dephosphorization pressure 20~35Mpa, finishing rolling temperature 970±20℃, sizing temperature 950±20℃, spinning temperature 920±10℃; (5) Slow cooling of rollers: The first insulation cover of the air-cooled roller is opened, and the rest are all closed; the roller speed is 0.07-0.17 m / s; the cooling fans under the roller are all closed, the air doors are all closed, the gap between the insulation cover and each section of the roller is ≤5 mm, and all gaps are filled or blocked with insulation materials; (6) Insulation in insulation corridor: After the coils are collected on the vertical coiling core rack, they are quickly put into the insulation corridor for insulation. The temperature entering the insulation corridor is 500-700℃. After the wire rods enter the insulation corridor, the corridor door is immediately closed for airtight insulation. After the insulation corridor is full of steel, the corridor is started to be unloaded, and one coil is taken out and put in one coil at a time to ensure that the corridor is full of steel at all times. The obtained wire rods for high-strength alloy welding wires with a diameter of Φ1.2mm and a size of 5.5mm can be drawn without annealing.

2. The method for producing alloy welding wire steel according to claim 1, characterized in that: In step (5), the rollers are preheated with slow-cooled steel for not less than 60 turns before rolling. The length of roller section 1 is 4.5 m, and the speed is 0.07 m / s; the length of roller sections 2 to 9 is 6.086 m each, and the roller speed is 0.08-0.15 m / s, with an increase of 0.01 m / s for each section; the length of roller section 10 is 3.8 m, and the speed is 0.16 m / s; the length of roller section 11 is 5.28 m, and the speed is 0.17 m / s.

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