A method of producing a wire rod for an alloy welding wire

Abstract

The application is a production method of wire rod for alloy welding wire, and belongs to the technical field of steel manufacturing. The wire rod is alloyed by Mn, Cr and Ni, strengthened by V and Ti, and added with certain B, so as to meet the requirements of 60 kg grade alloy welding wire. The process route is designed as follows: hot metal pretreatment + converter smelting + LF external refining + 150 mm / 180 mm square billet continuous casting + heating furnace + rolling + roller slow cooling + heat preservation corridor heat preservation. The stable composition, good castability and gas content meeting the requirements of molten steel are obtained by adopting the processes of hot metal pretreatment, converter smelting and LF external refining, the molten steel is poured into continuous casting billet, and then 24 hours of stack cooling or hot charging is carried out, high line rolling adopts high temperature rolling + high temperature wire feeding + roller slow cooling + heat preservation corridor process. The abnormal structure such as martensite and bainite affecting drawing of the wire rod can be prevented by adopting the process, the wire rod with the specification of Φ5.5 mm for high-strength alloy welding wire, which is stable in composition and can be drawn to Φ1.2 mm thin wire without annealing, is obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of steel manufacturing, and relates to a production method of high-strength alloy welding wire rod. BACKGROUND

[0002] The steel industry is an energy resource consumption industry, and a higher alloy content can cause consumption of mineral resources and increase of steel cost. The alloy welding wire with a weight of 60 kg or above produced by the prior art generally contains certain Cr, Mo, Ti and other alloys, and 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 leads to more difficult control of the structure of the wire rod, and martensite and bainite structures are easily formed, thereby affecting the drawing performance. SUMMARY

[0003] The application aims to provide a production method of high-strength alloy welding wire rod, and the produced wire rod can be directly drawn into welding wire with a minimum diameter of 1.2 mm without annealing; meanwhile, the deposited metal has a tensile strength of 690 MPa or above and good welding metal fluidity.

[0004] The technical scheme of the application is as follows:

[0005] A production method of alloy welding wire steel adopts a process route of molten iron pretreatment + converter smelting + LF furnace external refining + 150 mm / 180 mm square billet continuous casting + heating + rolling + roller slow cooling + heat preservation in a heat preservation corridor. The chemical composition of the steel contains, in mass percentage, 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 is Fe and inevitable impurities; and the key process steps include:

[0006] (1) Molten iron pretreatment: KR method is used to pretreat and desulfurize the molten iron entering the furnace, and the desulfurizing slag is removed clean after desulfurization; the sulfur content of the molten iron entering the furnace is controlled to be ≤0.015%, and the residual elements Cu and As of the molten iron are ≤0.10% and ≤0.007%, respectively;

[0007] (2) Converter smelting: end point control oxygen content [O]≤450ppm, carbon content [C]≤0.05%, [P]≤0.008%, [S]≤0.015%; 200kg±5kg lime+150kg±5kg synthetic slag slag washing is added during tapping process, and argon blowing stirring is carried out;

[0008] (3) LF refining: add 700-900kg of lime and appropriate amount of fluorite to make white slag, and keep white slag for more than 15 minutes. Refining slag is added in batches 50kg ferrosilicon powder and 50kg silicon carbide for diffusion deoxidation, 200kg±30kg titanium iron is used for precipitated deoxidation of molten steel, and sulfur wire is fed to adjust sulfur according to sulfur content. The soft blowing time after LF refining is not less than 10min;

[0009] (4) Heating and rolling: preheating temperature≤850℃, heating temperature 1050~1100℃, soaking temperature 1080~1120℃, heating time 90~180min, discharge temperature 1050±20℃; high pressure water phosphorus removal pressure 20~35Mpa, entry finishing temperature 970±20℃, entry reducing temperature 950±20℃, wire drawing temperature 920±10℃;

[0010] (5) Roller slow cooling: the first heat preservation cover of air cooling roller is opened, and the rest are all closed; The roller speed is 0.07-0.17m / s; The roller cooling fan is all closed, the air door is all closed, the gap between the heat preservation cover and the roller is ≤5mm, and all the gaps are filled or blocked with heat preservation materials;

[0011] (6) Heat preservation corridor heat preservation: after vertical coil core frame coiling, quickly enter the heat preservation corridor for heat preservation, the temperature of entering the heat preservation corridor is 500-700℃, after the coil enters the heat preservation corridor, immediately close the corridor door for airtight heat preservation; The slow cooling steel grade is used to preheat the heat preservation corridor, and the heat preservation corridor is full of steel before starting to exit, one coil is put in one coil, and the corridor is full of steel at all times. Get 5.5mm specification high strength alloy welding wire coil which can be drawn to Φ1.2mm without annealing.

[0012] Further, in step (5), the roller is preheated with slow cooling steel before rolling for not less than 60 coils, the roller 1 is 4.5m long, the speed is 0.07m / s; The roller 2~9 is 6.086m long each, the roller speed is 0.08-0.15m / s, each increases by 0.01m / s; The roller 10 is 3.8m long, the speed is 0.16m / s; The roller 11 is 5.28m long, the speed is 0.17m / s.

[0013] The beneficial effects of the present application: the present application adopts Mn, Cr, Ni alloying, and V, Ti micro-alloy strengthening, and adds certain B, to meet the performance requirements of 60 kg grade alloy welding wire, and reduce the alloy cost. And by adopting high temperature rolling + high temperature wire feeding + roller bed slow cooling after rolling + heat preservation corridor heat preservation process, the martensite and bainite organizations affecting drawing in the hot rolled wire rod are prevented. By controlling the S content, the welding fluidity of the welding wire is increased. Through this technology, the hot rolled wire rod produced has a cross-sectional shrinkage rate of more than 65% and a tensile strength of less than 650 Mpa, and the wire rod can be continuously drawn to a diameter of 1.2 mm or less without annealing from a 5.5 mm specification. After the gas shielded welding wire is made, the welding fluidity is good, and the tensile strength of the deposited metal reaches more than 690 Mpa. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The metallographic structure diagram of the wire rod produced for example 1.

[0015] Figure 2 The metallographic structure diagram of the wire rod produced for example 2. DETAILED DESCRIPTION Example 1

[0016] A production method of an alloy welding wire steel, the converter enters the molten iron for molten iron pretreatment, the phosphorus content of the molten iron before pretreatment is 0.129%, the sulfur content is 0.0456%, the carbon content is 4.15%, the Si content is 0.38%, and the temperature is 1299℃, the converter smelting adds 79 tons of molten iron, and 21 tons of scrap steel.

[0017] (1) The molten iron entering the furnace is pretreated by KR method for desulfurization operation, and the sulfur content of the molten iron after pretreatment is 0.0064%.

[0018] (2) The converter smelting end point is: oxygen content: 444ppm, [C]: 0.039%, [P]: 0.0065%, [S]: 0.0056%, end point temperature: 1592℃; During tapping, 1789kg of high-silicon silicon manganese and 304kg of metal manganese ball are added for deoxidation and alloying operation, 203kg of lime and 147kg of pre-melted slag are added for slag washing, and argon blowing stirring is carried out, and the requirement for the thickness of the slag during tapping is ≤20mm.

[0019] (3) Add 808kg of lime and 270kg of fluorite to form white slag, and keep the white slag for 20 minutes. Diffusion deoxidation is carried out by adding 50kg of ferrosilicon powder and 50kg of silicon carbide in batches, 210kg of titanium iron is used for sedimentation deoxidation of the molten steel, and aluminum-containing alloy is not allowed to be used for deoxidation of the molten steel. After deoxidation, the composition of the molten steel is adjusted, 20kg of sulfur wire is fed, and the soft blowing time after LF refining is 14min.

[0020] (4) The temperature of the preheating section of the heating furnace is 650-660°C, the temperature of the heating section is 1070-1080°C, the temperature of the soaking section is 1100-1110°C, the heating time is 134 min, the temperature of the discharged steel is 1030-1040°C, and the residual oxygen content is 1.5; the pressure of the high-pressure water phosphorus removal is 30 MPa, the temperature of the entry into the finishing rolling is 978-982°C, the temperature of the entry into the reducing section is 954-960°C, and the temperature of the wire drawing is 919-925°C.

[0021] (5) The first heat-insulating cover of the air-cooling roller is opened, and the other heat-insulating covers are all closed, the roller speed is 0.07-0.15 m / s, and the speed is increased by 0.01 m / s for each section.

[0022] (6) After the steel is collected, the steel is quickly put into the heat-insulating corridor for heat-insulating slow cooling, the roller and the heat-insulating corridor are preheated by 100 industrial pure iron, the corridor door is closed after the steel is put into the heat-insulating corridor for heat insulation, so as to prevent heat loss. There is no empty position in the corridor, and one coil is put into the corridor after another. The lap joint point of the entry into the heat-insulating corridor is 683°C, and the non-lap joint point is 565°C.

[0023] The actual finished product chemical composition control of the steel produced in Example 1 is shown in Table 1, the metallographic structure of the hot-rolled wire rod is shown in Figure 1 , and the head-to-tail and circle performance of the hot-rolled wire rod is shown in Table 2. Example 2

[0024] The molten iron is pretreated by the KR method before the molten iron is put into the converter, the sulfur content of the pretreated molten iron is 0.006%, the carbon content is 4.17%, the Si content is 0.31%, and the temperature is 1310°C.

[0025] (1) The molten iron is pretreated by the KR method before the molten iron is put into the converter, the sulfur content of the pretreated molten iron is 0.006%, the carbon content is 4.17%, the Si content is 0.31%, and the temperature is 1310°C.

[0026] (2) The end point of the converter smelting: the oxygen content is 534 ppm, the carbon content is 0.051%, the phosphorus content is 0.0067%, the sulfur content is 0.0052%, and the end point temperature is 1598°C; 1750 kg of high-silicon silicon-manganese and 290 kg of metal manganese ball are added during the tapping process for deoxidation and alloying operation, 200 kg of lime and 150 kg of pre-melted slag are added for slag washing, and argon blowing stirring is performed, and the thickness of the slag during the tapping process is required to be ≤20 mm.

[0027] (3) Add 780 kg lime and 238 kg fluorite to make white slag, keep the white slag for 22 minutes. Add 50 kg ferrosilicon and 50 kg silicon carbide powder in batches to make the refining slag for diffusion deoxidation, use 230 kg ferrotitanium to precipitate deoxidation, do not allow to use aluminum alloy to deoxidize the molten steel, adjust the composition of the molten steel after deoxidation, feed 15 kg sulfur wire, and the soft blowing time after LF refining is 14 min.

[0028] (4) The temperature of the preheating section of the heating furnace is 650-665℃, the temperature of the heating section is 1075-1080℃, the soaking temperature is 1090-1110℃, the heating time is 120 min, the out-of-furnace temperature is 1035-1040℃, the residual oxygen content is 1.4; the entry temperature of the finishing mill is 982-989℃, the entry temperature of the reducing mill is 954-961℃, and the wire drawing temperature is 921-926℃.

[0029] (5) The first heat preservation cover of the air cooling roller is opened, and the other heat preservation covers are all closed, the roller speed is 0.07-0.15 m / s, and the speed is increased by 0.01 m / s for each section.

[0030] (6) After the coil is collected, it is quickly sent to the heat preservation corridor for heat preservation and slow cooling, the corridor door is immediately closed after the steel enters the heat preservation corridor to prevent heat loss. The corridor is full of steel without empty space, and one coil is put in and one coil is put out. The lap joint point of the heat preservation corridor is 680℃, and the non-lap joint point is 567℃.

[0031] The actual finished product chemical composition of the steel is shown in Table 3. The metallographic structure of the hot rolled coil is shown in Figure 2 . The head-to-tail performance of the hot rolled coil is shown in Table 4.

[0032] Table 1 Actual finished product chemical composition of the steel of Example 1 (wt. %)

[0033] .

[0034] Table 2 Head-to-tail performance of the hot rolled coil of Example 1

[0035] .

[0036] Table 3 Actual finished product chemical composition of the steel of Example 2 (wt. %)

[0037] .

[0038] Table 4 Head-to-tail performance of the hot rolled coil of Example 2

[0039] .

Claims

1. A method for producing steel for alloy welding wire, comprising a process route of molten iron pretreatment + converter smelting + LF ladle refining + 150mm / 180mm square billet continuous casting + heating + rolling + roller table slow cooling + heat preservation corridor, characterized in that: The chemical composition of the steel, by mass percentage, is 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%, with the remainder being Fe and unavoidable impurities; Key process steps include: (1) Hot metal pretreatment: The hot metal entering the furnace is pretreated and desulfurized using the KR method. After desulfurization, the desulfurization slag is removed. The sulfur content of the molten iron fed into the furnace shall be controlled at ≤0.015%, and the residual elements in the molten iron shall be ≤0.10% Cu and ≤0.007% As. (2) Converter smelting: The final control oxygen content [O] ≤ 450 ppm, carbon content [C] ≤ 0.05%, [P] ≤ 0.008%, [S] ≤ 0.015%; during the tapping process, 200 kg ± 5 kg lime + 150 kg ± 5 kg synthetic slag are added for washing, and argon blowing and stirring are carried out; (3) LF refining: Add 700-900 kg of lime and an appropriate amount of fluorite to make white slag, keep the white slag for more than 15 minutes, add 50 kg of ferrosilicon powder and 50 kg of silicon carbide in batches for diffusion deoxidation during refining slag making, use 200 kg ± 30 kg of ferrotitanium to precipitate and deoxidize the molten steel, adjust the sulfur content according to the sulfur feeding line, and the soft blowing time after the LF refining is not less than 10 minutes; (4) Heating and rolling: Preheating section temperature ≤850℃, heating section temperature 1050~1100℃, soaking temperature 1080~1120℃, heating time 90~180 minutes, furnace exit temperature 1050±20℃; high pressure water descaling pressure 20~35Mpa, finishing mill entry temperature 970±20℃, sizing and reducing temperature 950±20℃, wire drawing temperature 920±10℃; (5) Slow cooling of roller conveyor: the first heat insulation cover of the air-cooled roller conveyor is opened and the rest are all closed; the roller conveyor speed is 0.07~0.17m / s; all cooling fans below the roller conveyor are closed and all dampers are closed; the gap between the heat insulation cover and each section of the roller conveyor is ≤5mm; all gaps are filled or covered with heat insulation material. (6) Insulation of the insulation corridor: After the coil is collected by the vertical core frame, it is quickly put into the insulation corridor for insulation. The temperature of the insulation corridor is 500-700℃. After the coil enters the insulation corridor, the corridor door is immediately closed for airtight insulation. The insulation corridor is filled with steel before it starts to leave the corridor. One coil is put in and one coil is put out, and the corridor is always kept full of steel. The result is Φ1.2mm high-strength alloy welding wire coil with a specification of 5.5mm. It 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 no less than 60 rolls before rolling. The first section of the roller is 4.5m long and has a speed of 0.07m / s; the second to ninth sections of the roller are each 6.086m long and have a speed of 0.08 to 0.15m / s, with each section increasing by 0.01m / s; the tenth section of the roller is 3.8m long and has a speed of 0.16m / s; and the eleventh section of the roller is 5.28m long and has a speed of 0.17m / s.

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