Production and preparation method of steel bar for heavy-load automobile axle

Abstract

The invention discloses a production and preparation method of a steel bar for a heavy-load automobile axle, and the steel bar comprises the following chemical components in percentage by mass: 0.33%-0.38% of C, 0.20%-0.35% of Si, 0.42%-0.60% of Mn, less than or equal to 0.015% of P, less than or equal to 0.006% of S, 0.80%-1.00% of Cr, less than or equal to 0.25% of Ni, 0.16%-0.23% of Mo, less than or equal to 0.15% of Cu and the balance of iron and inevitable impurities. Comprising the steps of ecological electric furnace smelting, LF refining, RH refining, continuous casting, heating, rolling and heat preservation. The steel bar for the heavy-load automobile axle meets the mechanical property requirement, and the steel purity is guaranteed.

Description

Technical Field

[0001] The present invention relates to the field of special steel, and specifically relates to a production preparation method for steel bars used in heavy-duty vehicle axles. Background Art

[0002] In the structure of an automobile, the axle plays a crucial role. It is like a bridge that tightly connects the suspension and the vehicle frame, ensuring the stability and load-bearing capacity of the vehicle during driving. The structure and functions of axles are diverse. According to the design requirements of the automobile, they can be divided into types such as steering axles, drive axles, steering drive axles, and support axles. The axles of heavy-duty vehicles are subjected to additional loads caused by the weight of the vehicle body, the weight of the loaded goods, etc., and also need to withstand the mechanical properties under high and low temperature conditions of the weather, as well as fatigue loads. Therefore, very high requirements are imposed on the high temperature resistance, low temperature resistance, mechanical properties, fatigue life, and steel purity of the steel used for heavy-duty vehicle axles to ensure the normal and safe operation of heavy-duty vehicles during operation.

[0003] Therefore, it is necessary to develop a steel bar for heavy-duty vehicle axles with excellent mechanical properties and high steel purity to meet the requirements of high-end products. Summary of the Invention

[0004] The purpose of the present invention is to provide a production process preparation method for steel bars used in heavy-duty vehicle axles. This method uses an ecological electric furnace + LF + RH + continuous casting smelting process for smelting and a rolling process to produce steel bars for heavy-duty vehicle axles. It not only ensures the mechanical properties and high steel purity and other indicators of the finished steel of the steel bars for heavy-duty vehicle axles, but also ensures the surface quality level of the steel bars for heavy-duty vehicle axles, meets the high-end use requirements, and realizes a breakthrough in the batch production of steel bars for heavy-duty vehicle axles in the ecological electric furnace continuous casting process.

[0005] To achieve the above-mentioned invention purpose, the present invention provides a production process preparation method for steel bars used in heavy-duty vehicle axles, including composition design and process design. The specific steps are: ecological electric furnace + LF refining + RH refining + continuous casting → heating → rolling process → heat preservation process, which meets the quality requirements of steel bars for heavy-duty vehicle axles, and the mechanical properties and high steel purity and other indicators can also meet the standard requirements.

[0006] For a steel bar used in a heavy-duty vehicle axle, its chemical composition, by mass percentage, is C: 0.33% - 0.38%, Si: 0.20% - 0.35%, Mn: 0.42% - 0.60%, P: ≤0.015%, S: ≤0.006%, Cr: 0.80% - 1.00%, Ni: ≤0.25%, Mo: 0.16% - 0.23%, Cu: ≤0.15%, and the balance is iron and unavoidable impurities.

[0007] The specification of the steel bar for heavy-duty truck axles of the present invention is Φ170mm.

[0008] The preparation method of the above-mentioned production process of steel bars for heavy-duty truck axles, the process route: ecological electric furnace smelting + LF refining + RH refining + continuous casting → heating furnace heating process → rolling process → heat preservation process;

[0009] Among them, the ecological electric furnace smelting is: adopting 100% scrap steel smelting process, tapping temperature 1615 - 1620 °C, C is 0.06 - 0.10% when tapping, P ≤ 0.010%, adding auxiliary materials and alloys when 1 / 4 - 1 / 3 of the tapping is completed, smelting cycle 40 - 45min, furnace oxygen consumption 26 - 27m 3 / t steel. Alloy addition per ton of steel: silicomanganese alloy 5.5 - 5.6 Kg / t, high-carbon ferrochrome 14.0 - 14.2 Kg / t, aluminum wire segment (Φ10 - 16mm) 0.8 - 0.9 Kg / t. Auxiliary material addition per ton of steel: coke particles 30 - 31 Kg / t, ladle ash 5.8 - 6.2 Kg / t, active lime (Φ10 - 70mm) 40 - 41 Kg / t, magnesite (Φ10 - 60mm) 15 - 16 Kg / t.

[0010] The LF furnace refining is: LF inlet temperature 1510 - 1515 °C, large current of 35000 - 36000A for heating and slag melting. When the slag surface fluctuates and the molten steel and electric arc are not exposed, add active lime. Take the first sample for chemical composition analysis after 5 - 6min, add alloys and silicon carbide according to the chemical composition target value, and add coke particles for carbon increase. The alloys, silicon carbide and coke particles should be added onto the argon flow to promote the rapid melting and homogenization of the alloys and carbon powder. When the molten steel temperature reaches 1610 - 1620 °C, add 1.5 - 1.6 kg / t of steel of diffusion deoxidizer (aluminum pellets) for diffusion deoxidation, close the furnace door for 10 - 13min. When the molten steel temperature reaches 1640 - 1650 °C, take the second sample for chemical composition analysis to confirm the deviation value of the content of each chemical element from the target value requirement. After the second sample is taken away, when the molten steel temperature reaches 1660 - 1670 °C, leave the station. The LF smelting cycle is 60min - 70min, and the clear height is 440 - 460mm. Alloy addition for supplementary addition per ton of steel: ferrosilicon 0.3 - 0.35 kg / t, high-carbon ferromanganese 0.6 - 0.7 kg / t, high-carbon ferrochrome 0.8 - 0.9 kg / t, ferromolybdenum 2.8 - 2.9 kg / t, aluminum wire segment (Φ10 - 16mm) 0.3 - 0.35 Kg / t. Auxiliary material addition for supplementary addition per ton of steel: coke particles 0.2 - 0.25 Kg / t, silicon carbide 2.1 - 2.2 kg / t, active lime (Φ10 - 70mm) 4 - 4.2 Kg / t.

[0011] The RH refining process is as follows: the tapping temperature is 1655 - 1665 °C, the operation time is 40 - 50 min, the argon pressure is controlled at 0.1 - 0.3 MPa before the vacuum pump is started, with the slag surface slightly moving and the molten steel not exposed. When the vacuum degree reaches 100 - 110 Pa, timing starts, and the holding time is 10 - 15 min. Meanwhile, the argon pressure is adjusted to 0.3 - 0.5 MPa, and 0.84 - 0.86 kg / t of steel of calcium-silicon alloy cored wire (Φ14 - 15 mm) is added. After the static argon blowing ends, 0.6 - 0.7 kg / t of steel of covering agent (carbonized rice husk) is added, the clear height is 440 - 460 mm, the temperature of refining recompression is 1620 - 1630 °C, and the tapping temperature is 1600 - 1610 °C.

[0012] The continuous casting process is as follows: the ladle arrival temperature is 1590 - 1600 °C, the H content in the tundish is controlled ≤ 2 ppm, the casting time is 55 - 65 min, the superheat is 20 - 25 °C, the casting speed is 0.42 - 0.44 m / min, and the whole process is carried out under protective casting. The mold powder used is medium carbon steel mold powder at 3.6 - 3.7 kg / t of steel.

[0013] The heating process is as follows: the temperature entering the heating furnace is 500 - 550 °C, the temperature requirement in the preheating section is 600 - 650 °C, and the time is 1.4 - 1.5 h; the temperature requirement in the heating section 2 is 850 - 870 °C, and the time is 1.3 - 1.5 h; the temperature requirement in the heating section 1 is 1210 - 1230 °C, and the time is 1.4 - 1.5 h; the temperature requirement in the soaking section is 1200 - 1220 °C, and the time is 1.4 - 1.5 h; the tapping temperature is 1190 - 1210 °C.

[0014] Furthermore, the rolling process includes the blooming process and the continuous rolling process, specifically:

[0015] Primary rolling process: 11 rolling passes, steel turning → Pass 1: width 405.2 - 405.21 mm, height 435 - 435.01 mm, reduction 51 - 51.01 mm, rolling speed 2.3 - 2.31 m / s → Pass 2: width 416.45 - 416.46 mm, height 390 - 390.01 mm, reduction 45 - 45.01 mm, rolling speed 2.5 - 2.51 m / s → steel turning → Pass 3: width 400.94 - 400.95 mm, height 380 - 380.01 mm, reduction 36.45 - 36.46 mm, rolling speed 2.5 - 2.51 m / s → Pass 4: width 408.44 - 408.45 mm, height 355 - 355.01 mm, reduction 25 - 25.01 mm, rolling speed 2.5 - 2.51 m / s → steel turning → Pass 5: width 372.53 - 372.54 mm, height 350 - 350.01 mm, reduction 58.44 - 58.45 mm, rolling speed 2.5 - 2.51 m / s → Pass 6: width 387.53 - 387.54 mm, height 300 - 300.01 mm, reduction 50 - 50.01 mm, rolling speed 2.5 - 2.51 m / s → steel turning → Pass 7: width 317.26 - 317.27 mm, height 330 - 330.01 mm, reduction 57.53 - 57.54 mm, rolling speed 2.5 - 2.51 m / s → Pass 8: width 332.86 - 332.87 mm, height 278 - 278.01 mm, reduction 52 - 52.01 mm, rolling speed 2.5 - 2.51 m / s → steel turning → Pass 9: width 290.86 - 290.87 mm, height 290 - 290.01 mm, reduction 42.86 - 42.87 mm, rolling speed 2.5 - 2.51 m / s → Pass 10: width 304.06 - 304.07 mm, height 246 - 246.01 mm, reduction 44 - 44.01 mm, rolling speed 2.5 - 2.51 m / s → steel turning → Pass 11: width 267.62 - 267.63 mm, height 232 - 232.01 mm, reduction 72.06 - 72.07 mm, rolling speed 2.5 - 2.51 m / s; Pass through 3 sets of 850 mm rolling mills and 1 set of 735 mm rolling mill, and then enter the continuous rolling mill for rolling.

[0016] Continuous rolling process for producing steel bars: Five rolling passes are carried out. In the first pass, the height is 229 - 229.01 mm, the width is 245 - 245.01 mm, and the rolling speed is 0.27 - 0.271 m / s; in the second pass, the height is 192 - 192.01 mm, the width is 235 - 235.01 mm, and the rolling speed is 0.31 - 0.311 m / s; in the third pass, the height is 200 - 200.01 mm, the width is 195 - 195.01 mm, and the rolling speed is 0.35 - 0.351 m / s; in the fourth pass, the height is 159 - 159.01 mm, the width is 198 - 198.01 mm, and the rolling speed is 0.461 - 0.462 m / s; in the fifth pass, the height is 172.29 - 172.30 mm, the width is 172.29 - 172.30 mm, and the rolling speed is 0.572 - 0.573 m / s; the finished product is obtained after five passes.

[0017] Furthermore, the heat preservation process is as follows: The steel is heat-preserved. The temperature of the lower heat-preservation pit is ≥560 °C, the heat preservation time is 50 - 55 h, and the temperature when taken out of the pit is ≤150 °C.

[0018] Furthermore, samples are taken from the heat-preserved steel for heat treatment, and the heat treatment includes the following steps:

[0019] 1) Quenching: At 840 - 860 °C, heat preservation for 0.8 - 1.2 h, and oil cooling;

[0020] 2) Tempering: At 540 - 560 °C, heat preservation for 1.8 - 2.2 h, and oil cooling.

[0021] Advantages of the present invention:

[0022] (1) The heavy-duty truck axle steel bars are produced by using an ecological electric furnace + LF refining + RH refining + continuous casting smelting process and rolling process, meeting the mechanical property requirements and ensuring the steel purity.

[0023] (2) The reasonable composition design and production process ensure the surface quality and mechanical properties.

[0024] (3) The macrostructure and non-metallic inclusions of the finished steel bars meet the requirements of high-end products. Specific embodiments

[0025] The following non-limiting embodiments can enable those of ordinary skill in the art to more comprehensively understand the present invention, but do not limit the present invention in any way.

[0026] Example 1

[0027] 1 Chemical composition of the heavy-duty truck axle steel bars

[0028] By mass percentage: C: 0.35%, Si: 0.26%, Mn: 0.47%, P: 0.012%, S: 0.005%, Cr: 0.88%, Ni: 0.06%, Mo: 0.19%, Cu: 0.05%, the balance being iron and unavoidable impurities.

[0029] 2 Electric furnace continuous casting production processes for steel bars used in heavy-duty vehicle axles

[0030] Process route: Ecological electric furnace smelting + LF refining + RH refining + continuous casting → heating furnace heating process → rolling process → heat preservation process → heat treatment process. Among them:

[0031] (1) Ecological electric furnace smelting

[0032] Adopt 100% scrap steel smelting process, tapping temperature 1618°C, C is 0.08% and P is 0.009% at tapping. Add auxiliary alloy when 1 / 4 of the steel is tapped. The smelting cycle is 42 min, and the furnace oxygen consumption is 26 m 3 / t of steel. Alloy addition per ton of steel: silicomanganese alloy 5.5 Kg / t, high-carbon ferrochrome 14.0 Kg / t, aluminum wire segment (Φ13mm) 0.8 Kg / t. Auxiliary addition per ton of steel: coke particles 30 Kg / t, ladle ash 6 Kg / t, activated lime (Φ30mm) 40 Kg / t, magnesite (Φ40mm) 15 Kg / t.

[0033] (2) LF furnace refining

[0034] The LF tapping temperature is 1513°C. Raise the temperature and melt the slag with a large current of 35500 A. When the slag surface fluctuates and the molten steel and electric arc are not exposed, add activated lime. Take the first sample for chemical composition analysis after 5 min. Add alloy and silicon carbide according to the chemical composition target value, and add coke particles to increase carbon. The alloy, silicon carbide and coke particles should be added onto the argon flow to promote the rapid melting and homogenization of the alloy, silicon carbide and coke particles. When the molten steel temperature reaches 1615°C, add 1.6 kg / t of diffusion deoxidizer (aluminum pellets) for diffusion deoxidation, close the furnace door for 12 min. When the molten steel temperature reaches 1645°C, take the second sample for chemical composition analysis to confirm the deviation value of the content of each chemical element from the composition target value. After the second sample is taken away, when the molten steel temperature reaches 1665°C, leave the station. The LF smelting cycle is 67 min, and the free space is 450 mm. Alloy addition per ton of steel for supplementary addition: ferrosilicon 0.32 kg / t, high-carbon ferromanganese 0.7 kg / t, high-carbon ferrochrome 0.8 kg / t, ferromolybdenum 2.9 kg / t, aluminum wire segment (Φ13mm) 0.32 Kg / t. Auxiliary addition per ton of steel for supplementary addition: coke particles 0.23 Kg / t, silicon carbide 2.1 kg / t, activated lime (Φ30mm) 4.1 Kg / t.

[0035] (3) RH refining

[0036] The inlet temperature is 1658 °C, the operation time is 45 min. Before starting the vacuum pump, the argon pressure is controlled at 0.1 MPa to keep the molten steel from being exposed while the slag surface is slightly moving. When the vacuum degree reaches 103 Pa, timing starts, and the holding time is 14 min. At the same time, the argon pressure is adjusted to 0.3 MPa, and 0.85 kg / t of calcium silicate cored wire (Φ14 mm) is added. After the static argon blowing ends, 0.7 kg / t of covering agent (carbonized rice husk) is added, the free space is 455 mm, the refining recompression temperature is 1627 °C, and the outlet temperature is 1604 °C. (4) Continuous casting

[0037] The ladle arrival temperature is 1596 °C, the middle package H is controlled at 1.5 ppm, the casting time is 59 min, the superheat is 22 °C, the casting speed is 0.43 m / min, and the whole process is protected by casting. The mold powder used is medium carbon steel mold powder at 3.7 kg / t.

[0038] (5) Heating process

[0039] Heating process: The temperature entering the heating furnace is 530 °C, the temperature requirement for the preheating section is 620 °C, and the time is 1.5 h; the temperature requirement for the second heating section is 860 °C, and the time is 1.5 h; the temperature requirement for the first heating section is 1220 °C, and the time is 1.4 h; the temperature requirement for the soaking section is 1210 °C, and the time is 1.4 h; the tapping temperature is 1196 °C.

[0040] (6) Rolling process

[0041] Blooming process: Rolling is carried out for 11 passes. Steel turning → In the first pass, the width is 405.2 mm, the height is 435.01 mm, the reduction is 51.01 mm, and the rolling speed is 2.3 m / s → In the second pass, the width is 416.46 mm, the height is 390 mm, the reduction is 45.01 mm, and the rolling speed is 2.51 m / s → Steel turning → In the third pass, the width is 400.95 mm, the height is 380 mm, the reduction is 36.46 mm, and the rolling speed is 2.51 m / s → In the fourth pass, the width is 408.44 mm, the height is 355.01 mm, the reduction is 25 mm, and the rolling speed is 2.51 m / s → Steel turning → In the fifth pass, the width is 372.53 mm, the height is 350.01 mm, the reduction is 58.45 mm, and the rolling speed is 2.5 m / s → In the sixth pass, the width is 387.54 mm, the height is 300 mm, the reduction is 50.01 mm, and the rolling speed is 2.5 m / s → Steel turning → In the seventh pass, the width is 317.27 mm, the height is 330.01 mm, the reduction is 57.53 mm, and the rolling speed is 2.51 m / s → In the eighth pass, the width is 332.87 mm, the height is 278 mm, the reduction is 52.01 mm, and the rolling speed is 2.5 m / s → Steel turning → In the ninth pass, the width is 290.87 mm, the height is 290.01 mm, the reduction is 42.86 mm, and the rolling speed is 2.5 m / s → In the tenth pass, the width is 304.07 mm, the height is 246 mm, the reduction is 44.01 mm, and the rolling speed is 2.5 m / s → Steel turning → In the eleventh pass, the width is 267.63 mm, the height is 232 mm, the reduction is 72.07 mm, and the rolling speed is 2.5 m / s; It passes through 3 850-mm rolling mills and 1 735-mm rolling mill, and then enters the continuous rolling mill for rolling.

[0042] Continuous rolling product rolling process: Rolling is carried out for 5 passes. In the first pass, the height is 229.01 mm, the width is 245 mm, and the rolling speed is 0.271 m / s; In the second pass, the height is 192.01 mm, the width is 235 mm, and the rolling speed is 0.31 m / s; In the third pass, the height is 200.01 mm, the width is 195 mm, and the rolling speed is 0.351 m / s; In the fourth pass, the height is 159 mm, the width is 198.01 mm, and the rolling speed is 0.462 m / s; In the fifth pass, the height is 172.29 mm, the width is 172.30 mm, and the rolling speed is 0.573 m / s; The finished product comes out after 5 passes.

[0043] (7) Heat preservation process

[0044] Heat preservation process: The steel is heat-preserved. The temperature in the lower heat-preservation pit is 590 °C, the heat preservation time is 53 h, and the temperature when coming out of the pit is 120 °C.

[0045] (8) Heat treatment process

[0046] The heat-preserved steel is sampled for heat treatment, and the heat treatment includes the following steps:

[0047] 1) Quenching: 850 °C, holding for 1.0 h, oil cooling;

[0048] 2) Tempering: 550 °C, holding for 2.0 h, oil cooling.

[0049] Example 2

[0050] 1 Chemical composition of steel bars for heavy-duty truck axles

[0051] By mass percentage: C: 0.35%, Si: 0.25%, Mn: 0.48%, P: 0.010%, S: 0.004%, Cr: 0.90%, Ni: 0.05%, Mo: 0.18%, Cu: 0.04%, and the balance is iron and inevitable impurities.

[0052] 2 Electric furnace continuous casting production processes of steel bars for heavy-duty truck axles

[0053] Process route: Ecological electric furnace smelting + LF refining + RH refining + continuous casting → heating furnace heating process → rolling process → heat preservation process → heat treatment process. Among them:

[0054] (1) Ecological electric furnace smelting

[0055] Adopt 100% scrap steel smelting process, tapping temperature 1617 °C, C is 0.08% and P is 0.008% at tapping. Add auxiliary materials and alloys 1 / 4 of the way during tapping, smelting cycle 43 min, furnace oxygen consumption 26 m 3 / t of steel. Alloy addition per ton of steel: silicomanganese alloy 5.6 Kg / t, high-carbon ferrochrome 14.2 Kg / t, aluminum wire segment (Φ13 mm) 0.9 Kg / t. Auxiliary material addition per ton of steel: coke granules 30 Kg / t, ladle ash 6.1 Kg / t, active lime (Φ30 mm) 41 Kg / t, magnesite (Φ40 mm) 16 Kg / t.

[0056] (2) LF furnace refining

[0057] The LF tapping temperature is 1514°C. With a large current of 35600 A for heating and slag melting, when the slag surface fluctuates and the molten steel and arc are not exposed, add reactive lime. Take the first sample for chemical composition analysis after 6 minutes. Add alloys and silicon carbide according to the target values of chemical composition, and add coke particles for carbon enrichment. The alloys, silicon carbide, and coke particles should be added onto the argon flow to promote the rapid melting and homogenization of the alloys, silicon carbide, and coke particles. When the molten steel temperature reaches 1615°C, add 1.6 kg / t of diffusion deoxidizer (aluminum oxide pellets) for diffusion deoxidation. Close the furnace door for 11 minutes. When the molten steel temperature reaches 1646°C, take the second sample for chemical composition analysis to confirm the deviation of the content of each chemical element from the median value of the composition range. After the second sample is taken away, leave the station when the molten steel temperature reaches 1665°C. The LF smelting cycle is 65 minutes, and the freeboard is 450 mm. The addition amount of alloys per ton of steel: ferrosilicon 0.32 kg / t, high-carbon ferromanganese 0.6 kg / t, high-carbon ferrochrome 0.9 kg / t, ferromolybdenum 2.9 kg / t, aluminum wire segment (Φ13 mm) 0.3 Kg / t. The addition amount of auxiliary materials per ton of steel: coke particles 0.22 Kg / t, silicon carbide 2.1 kg / t, reactive lime (Φ30 mm) 4.2 Kg / t.

[0058] (3) RH refining

[0059] The tapping temperature is 1658°C, and the operation time is 44 minutes. Before starting the vacuum pump, control the argon pressure at 0.1 MPa to keep the slag surface slightly moving and the molten steel not exposed. Start timing when the vacuum degree reaches 107 Pa, maintain for 11 minutes, and at the same time adjust the argon pressure to 0.3 MPa. Add 0.84 kg / t of calcium-silicon alloy cored wire (Φ14 mm). After the static argon blowing ends, add 0.7 kg / t of covering agent. The freeboard is 450 mm. The refining recompression temperature is 1626°C, and the leaving station temperature is 1607°C. (4) Continuous casting

[0060] The ladle arrival temperature is 1598°C, the middle package H is controlled at 1.4 ppm, the casting time is 58 minutes, the superheat is 22°C, the casting speed is 0.43 m / min, and the whole process is protected by casting. Use 3.6 kg / t of medium-carbon steel protective slag for the mold powder.

[0061] (5) Heating process

[0062] Heating process: The temperature entering the heating furnace is 540°C, the temperature requirement for the preheating section is 630°C, and the time is 1.5 h; the temperature requirement for the second heating section is 854°C, and the time is 1.4 h; the temperature requirement for the first heating section is 1225°C, and the time is 1.4 h; the temperature requirement for the soaking section is 1215°C, and the time is 1.4 h; the tapping temperature is 1202°C.

[0063] (6) Rolling process

[0064] Primary rolling process: 11 rolling passes, steel turning → Pass 1: width 405.21 mm, height 435 mm, reduction 51.01 mm, rolling speed 2.31 m / s → Pass 2: width 416.46 mm, height 390 mm, reduction 45.01 mm, rolling speed 2.51 m / s → steel turning → Pass 3: width 400.95 mm, height 380.01 mm, reduction 36.45 mm, rolling speed 2.51 m / s → Pass 4: width 408.45 mm, height 355 mm, reduction 25.01 mm, rolling speed 2.5 m / s → steel turning → Pass 5: width 372.53 mm, height 350.01 mm, reduction 58.44 mm, rolling speed 2.51 m / s → Pass 6: width 387.54 mm, height 300 mm, reduction 50.01 mm, rolling speed 2.5 m / s → steel turning → Pass 7: width 317.27 mm, height 330.01 mm, reduction 57.54 mm, rolling speed 2.51 m / s → Pass 8: width 332.87 mm, height 278 mm, reduction 52.01 mm, rolling speed 2.5 m / s → steel turning → Pass 9: width 290.87 mm, height 290 mm, reduction 42.87 mm, rolling speed 2.5 m / s → Pass 10: width 304.07 mm, height 246 mm, reduction 44.01 mm, rolling speed 2.51 m / s → steel turning → Pass 11: width 267.62 mm, height 232.01 mm, reduction 72.07 mm, rolling speed 2.5 m / s; Pass through 3 850 mm rolling mills and 1 735 mm rolling mill, and then enter the continuous rolling mill for rolling.

[0065] Continuous rolling process for finished products: 5 rolling passes, Pass 1: height 229.01 mm, width 245 mm, rolling speed 0.271 m / s; Pass 2: height 192.01 mm, width 235 mm, rolling speed 0.311 m / s; Pass 3: height 200.01 mm, width 195 mm, rolling speed 0.351 m / s; Pass 4: height 159 mm, width 198 mm, rolling speed 0.462 m / s; Pass 5: height 172.29 mm, width 172.30 mm, rolling speed 0.573 m / s; The finished product is obtained after 5 passes.

[0066] (7) Heat preservation process

[0067] Heat preservation process: The steel is heat-preserved, the temperature in the lower heat-preservation pit is 580 °C, the heat preservation time is 54 h, and the temperature when leaving the pit is 120 °C.

[0068] (8) Heat treatment process

[0069] The heat-preserved steel is sampled for heat treatment, and the heat treatment includes the following steps:

[0070] 1) Quenching: 850 °C, holding for 1.0 h, oil cooling;

[0071] 2) Tempering: 550 °C, holding for 2.0 h, oil cooling.

[0072] Example 3

[0073] 1 Chemical composition of steel bars for heavy-duty truck axles

[0074] By mass percentage: C: 0.36%, Si: 0.26%, Mn: 0.48%, P: 0.013%, S: 0.005%, Cr: 0.87%, Ni: 0.06%, Mo: 0.18%, Cu: 0.05%, and the balance is iron and inevitable impurities.

[0075] 2 Electric furnace continuous casting production processes of steel bars for heavy-duty truck axles

[0076] Process route: Ecological electric furnace smelting + LF refining + RH refining + continuous casting → heating furnace heating process → rolling process → heat preservation process → heat treatment process.

[0077] (1) Ecological electric furnace smelting

[0078] Adopt 100% scrap steel smelting process, tapping temperature 1618 °C, C is 0.08% and P is 0.009% at tapping. Add auxiliary materials and alloys when 1 / 4 of the steel is tapped. The smelting cycle is 42 min, and the furnace oxygen consumption is 27 m 3 / t of steel. Alloy addition per ton of steel: silicomanganese alloy 5.6 Kg / t, high-carbon ferrochrome 14.2 Kg / t, aluminum wire segment (Φ13 mm) 0.9 Kg / t. Auxiliary material addition per ton of steel: coke particles 30 Kg / t, ladle ash 5.9 Kg / t, active lime (Φ30 mm) 41 Kg / t, magnesite (Φ40 mm) 16 Kg / t.

[0079] (2) LF furnace refining

[0080] The LF tapping temperature is 1514°C. With a large current of 35500A, the temperature is raised to melt the slag. When the slag surface fluctuates and the molten steel and arc are not exposed, reactive lime is added. After 6 minutes, the first sample is taken for chemical composition analysis. Alloys and silicon carbide are added according to the chemical composition target values, and coke particles are added to increase carbon content. The alloys, silicon carbide, and coke particles should be added onto the argon flow to promote their rapid melting and homogenization. When the molten steel temperature reaches 1616°C, 1.6 kg / t of diffusion deoxidizer (aluminum oxide pellets) is added for diffusion deoxidation. The furnace door is closed for 11 minutes. When the molten steel temperature reaches 1645°C, the second sample is taken for chemical composition analysis to confirm the deviation of the content of each chemical element from the composition target value. After the second sample is taken away, when the molten steel temperature reaches 1666°C, it leaves the station. The LF smelting cycle is 66 minutes, and the freeboard is 450 mm. The addition amount of alloys per ton of steel: ferrosilicon 0.32 kg / t, high-carbon ferromanganese 0.7 kg / t, high-carbon ferrochrome 0.9 kg / t, ferromolybdenum 2.9 kg / t, aluminum wire segment (Φ13 mm) 0.32 Kg / t. The addition amount of auxiliary materials per ton of steel: coke particles 0.23 Kg / t, silicon carbide 2.2 kg / t, reactive lime (Φ30 mm) 4.1 Kg / t.

[0081] (3) RH refining

[0082] The tapping temperature is 1659°C, and the operation time is 44 minutes. Before starting the vacuum pump, the argon pressure is controlled at 0.1 MPa to keep the slag surface slightly moving and the molten steel not exposed. When the vacuum degree reaches 106 Pa, the timing starts and the holding time is 13 minutes. At the same time, the argon pressure is adjusted to 0.4 MPa. 0.85 kg / t of calcium-silicon alloy cored wire (Φ14 mm) is added. After the static argon blowing ends, 0.6 kg / t of covering agent is added. The freeboard is 450 mm. The refining recompression temperature is 1627°C, and the leaving station temperature is 1604°C. (4) Continuous casting

[0083] The ladle arrival temperature is 1598°C, the middle package H is controlled at 1.6 ppm, the casting time is 60 minutes, the superheat is 22°C, the drawing speed is 0.43 m / min, and the whole process is protected by casting. The mold powder used is medium-carbon steel mold powder at 3.6 kg / t.

[0084] (5) Heating process

[0085] Heating process: The temperature entering the heating furnace is 530°C, the temperature requirement for the preheating section is 630°C, and the time is 1.5 h; the temperature requirement for the heating section 2 is 860°C, and the time is 1.5 h; the temperature requirement for the heating section 1 is 1225°C, and the time is 1.4 h; the temperature requirement for the soaking section is 1215°C, and the time is 1.4 h; the tapping temperature is 1198°C.

[0086] (6) Rolling process

[0087] Primary rolling process: 11 rolling passes, steel turning → For the 1st pass, width is 405.21 mm, height is 435 mm, reduction is 51.01 mm, rolling speed is 2.31 m / s → For the 2nd pass, width is 416.46 mm, height is 390 mm, reduction is 45.01 mm, rolling speed is 2.51 m / s → Steel turning → For the 3rd pass, width is 400.95 mm, height is 380 mm, reduction is 36.46 mm, rolling speed is 2.51 m / s → For the 4th pass, width is 408.44 mm, height is 355.01 mm, reduction is 25.01 mm, rolling speed is 2.5 m / s → Steel turning → For the 5th pass, width is 372.53 mm, height is 350.01 mm, reduction is 58.45 mm, rolling speed is 2.5 m / s → For the 6th pass, width is 387.54 mm, height is 300 mm, reduction is 50.01 mm, rolling speed is 2.51 m / s → Steel turning → For the 7th pass, width is 317.27 mm, height is 330.01 mm, reduction is 57.53 mm, rolling speed is 2.51 m / s → For the 8th pass, width is 332.86 mm, height is 278.01 mm, reduction is 52.01 mm, rolling speed is 2.51 m / s → Steel turning → For the 9th pass, width is 290.87 mm, height is 290.01 mm, reduction is 42.87 mm, rolling speed is 2.51 m / s → For the 10th pass, width is 304.07 mm, height is 246 mm, reduction is 44.01 mm, rolling speed is 2.5 m / s → Steel turning → For the 11th pass, width is 267.63 mm, height is 232 mm, reduction is 72.07 mm, rolling speed is 2.51 m / s; Pass through 3 850-mm rolling mills and 1 735-mm rolling mill, and then enter the continuous rolling mill for rolling.

[0088] Continuous rolling product rolling process: 5 rolling passes, for the 1st pass, height is 229 mm, width is 245 mm, rolling speed is 0.271 m / s; for the 2nd pass, height is 192 mm, width is 235.01 mm, rolling speed is 0.311 m / s; for the 3rd pass, height is 200 mm, width is 195.01 mm, rolling speed is 0.35 m / s; for the 4th pass, height is 159.01 mm, width is 198 mm, rolling speed is 0.462 m / s; for the 5th pass, height is 172.30 mm, width is 172.30 mm, rolling speed is 0.572 m / s; After 5 passes, the finished product is produced.

[0089] (7) Heat preservation process

[0090] Heat preservation process: The steel is heat-preserved, the temperature in the lower heat-preservation pit is 590 °C, the heat preservation time is 54 h, and the temperature when leaving the pit is 130 °C.

[0091] (8) Heat treatment process

[0092] The heat-preserved steel is sampled for heat treatment, and the heat treatment includes the following steps:

[0093] 1) Quenching: 850°C, holding for 1.0 h, oil cooling;

[0094] 2) Tempering: 550°C, holding for 2.0 h, oil cooling.

[0095] Example 4

[0096] 1 Chemical composition of steel bars for heavy-duty truck axles

[0097] By mass percentage: C: 0.34%, Si: 0.25%, Mn: 0.48%, P: 0.012%, S: 0.004%, Cr: 0.88%, Ni: 0.05%, Mo: 0.19%, Cu: 0.05%, the balance being iron and unavoidable impurities.

[0098] 2 Electric furnace continuous casting production processes of steel bars for heavy-duty truck axles

[0099] Process route: Ecological electric furnace smelting + LF refining + RH refining + continuous casting billet → heating furnace heating process → rolling process → heat preservation process → heat treatment process. Among them:

[0100] (1) Ecological electric furnace smelting

[0101] Adopt 100% scrap steel smelting process, tapping temperature 1617°C, C is 0.009% and P is 0.008% at tapping. Add auxiliary materials and alloys when 1 / 4 of the steel is tapped. The smelting cycle is 42 min, and the oxygen consumption of the furnace is 26 m 3 / t of steel. Alloy addition per ton of steel: silicomanganese alloy 5.5 Kg / t, high-carbon ferrochrome 14.2 Kg / t, aluminum wire segment (Φ13 mm) 0.9 Kg / t. Auxiliary material addition per ton of steel: coke particles 31 Kg / t, ladle ash 5.9 Kg / t, active lime (Φ30 mm) 41 Kg / t, magnesite (Φ40 mm) 15 Kg / t.

[0102] (2) LF furnace refining

[0103] The LF tapping temperature is 1513°C. With a large current of 35600 A for heating and slag melting, when the slag surface fluctuates and the molten steel and arc are not exposed, add reactive lime. Take the first chemical composition analysis sample after 6 minutes. Add alloys and silicon carbide according to the target values of chemical composition, and add coke particles for carbon enrichment. The alloys, silicon carbide, and coke particles should be added onto the argon flow to promote their rapid melting and homogenization. When the molten steel temperature reaches 1615°C, add 1.6 kg / t of diffusion deoxidizer (aluminum oxide pellets) for diffusion deoxidation, close the furnace door for 12 minutes. When the molten steel temperature reaches 1645°C, take the second chemical composition analysis sample to confirm the deviation of the content of each chemical element from the target value. After taking the second sample, when the molten steel temperature reaches 1665°C, leave the station. The LF smelting cycle is 67 minutes, and the freeboard is 450 mm. The addition amount of alloys per ton of steel: ferrosilicon 0.32 kg / t, high-carbon ferromanganese 0.7 kg / t, high-carbon ferrochrome 0.9 kg / t, ferromolybdenum 2.9 kg / t, aluminum wire segment (Φ13 mm) 0.33 Kg / t. The addition amount of auxiliary materials per ton of steel: coke particles 0.22 Kg / t, silicon carbide 2.2 kg / t, reactive lime (Φ30 mm) 4.1 Kg / t.

[0104] (3) RH refining

[0105] The tapping temperature is 1658°C, and the operation time is 46 minutes. Before starting the vacuum pump, control the argon pressure at 0.1 MPa to keep the slag surface slightly moving and the molten steel not exposed. Start timing when the vacuum degree reaches 106 Pa, maintain for 12 minutes, and at the same time adjust the argon pressure to 0.3 MPa. Add 0.85 kg / t of calcium-silicon alloy cored wire (Φ14 mm). After the static argon blowing ends, add 0.6 kg / t of covering agent. The freeboard is 455 mm. The temperature for refining recompression is 1625°C, and the leaving station temperature is 1605°C. (4) Continuous casting

[0106] The ladle arrival temperature is 1595°C, the medium package H is controlled at 1.5 ppm, the casting time is 59 minutes, the superheat is 23°C, the casting speed is 0.43 m / min, and the whole process is protected by casting. The mold powder used is medium-carbon steel mold powder at 3.6 kg / t.

[0107] (5) Heating process

[0108] Heating process: The temperature entering the heating furnace is 530°C, the temperature requirement for the preheating section is 630°C, and the time is 1.5 h; the temperature requirement for the second heating section is 860°C, and the time is 1.5 h; the temperature requirement for the first heating section is 1220°C, and the time is 1.5 h; the temperature requirement for the soaking section is 1215°C, and the time is 1.4 h; the tapping temperature is 1205°C.

[0109] (6) Rolling process

[0110] Ingot rolling process: 11 rolling passes, steel turning → Pass 1: width 405.2 mm, height 435 mm, reduction 51.01 mm, rolling speed 2.31 m / s → Pass 2: width 416.45 mm, height 390 mm, reduction 45.01 mm, rolling speed 2.51 m / s → steel turning → Pass 3: width 400.95 mm, height 380 mm, reduction 36.46 mm, rolling speed 2.51 m / s → Pass 4: width 408.44 mm, height 355 mm, reduction 25 mm, rolling speed 2.51 m / s → steel turning → Pass 5: width 372.54 mm, height 350 mm, reduction 58.45 mm, rolling speed 2.51 m / s → Pass 6: width 387.54 mm, height 300 mm, reduction 50.01 mm, rolling speed 2.51 m / s → steel turning → Pass 7: width 317.27 mm, height 330 mm, reduction 57.54 mm, rolling speed 2.5 m / s → Pass 8: width 332.87 mm, height 278.01 mm, reduction 52 mm, rolling speed 2.51 m / s → steel turning → Pass 9: width 290.87 mm, height 290.01 mm, reduction 42.87 mm, rolling speed 2.51 m / s → Pass 10: width 304.06 mm, height 246.01 mm, reduction 44 mm, rolling speed 2.51 m / s → steel turning → Pass 11: width 267.62 mm, height 232.01 mm, reduction 72.06 mm, rolling speed 2.5 m / s; Passing through 3 sets of 850 mm rolling mills and 1 set of 735 mm rolling mill, then entering the continuous rolling mill for rolling.

[0111] Continuous rolling process for finished products: 5 rolling passes, Pass 1: height 229 mm, width 245.01 mm, rolling speed 0.271 m / s; Pass 2: height 192.01 mm, width 235 mm, rolling speed 0.311 m / s; Pass 3: height 200.01 mm, width 195 mm, rolling speed 0.351 m / s; Pass 4: height 159 mm, width 198.01 mm, rolling speed 0.462 m / s; Pass 5: height 172.29 mm, width 172.30 mm, rolling speed 0.573 m / s; Finished products are obtained after 5 passes.

[0112] (7) Heat preservation process

[0113] Heat preservation process: Heat preservation of steel, the temperature in the lower heat preservation pit is 580 °C, heat preservation for 52 h, and the temperature out of the pit is 130 °C.

[0114] (8) Heat treatment process

[0115] Samples are taken from the heat-preserved steel for heat treatment, and the heat treatment includes the following steps:

[0116] 1) Quenching: 850 °C, heat preservation for 1.0 h, oil cooling;

[0117] 2) Tempering: 550 °C, holding for 2.0 h, oil cooling.

[0118] Example 5

[0119] 1 Chemical composition of steel bars for heavy-duty truck axles

[0120] By mass percentage: C: 0.35%, Si: 0.25%, Mn: 0.49%, P: 0.012%, S: 0.005%, Cr: 0.90%, Ni: 0.06%, Mo: 0.19%, Cu: 0.05%, and the balance is iron and unavoidable impurities.

[0121] 2 Production processes of electric furnace continuous casting of steel bars for heavy-duty truck axles

[0122] Process route: Ecological electric furnace smelting + LF refining + RH refining + continuous casting billet → heating furnace heating process → rolling process → heat preservation process → heat treatment process. Among them:

[0123] (1) Ecological electric furnace smelting

[0124] Adopt 100% scrap steel smelting process, tapping temperature 1618 °C, C is 0.07% and P is 0.009% at tapping. Add auxiliary materials and alloys when 1 / 4 of the steel is tapped. The smelting cycle is 42 min, and the furnace oxygen consumption is 26 m 3 / t of steel. Alloy addition per ton of steel: silicomanganese alloy 5.5 Kg / t, high-carbon ferrochrome 14.0 Kg / t, aluminum wire segment (Φ13 mm) 0.8 Kg / t. Auxiliary material addition per ton of steel: coke particles 30 Kg / t, ladle ash 5.9 Kg / t, active lime (Φ30 mm) 40 Kg / t, magnesite (Φ40 mm) 15 Kg / t.

[0125] (2) LF furnace refining

[0126] The LF tapping temperature is 1513°C. With a large current of 35500A, the temperature is increased to melt the slag. When the slag surface fluctuates and the molten steel and arc are not exposed, reactive lime is added. After 6 minutes, the first sample is taken for chemical composition analysis. According to the target values of the chemical composition, alloys and silicon carbide are added, and coke particles are added for carbon enrichment. The alloys, silicon carbide, and coke particles should be added onto the argon flow to promote the rapid melting and homogenization of the alloys, silicon carbide, and coke particles. When the molten steel temperature reaches 1615°C, 1.5 kg / t of diffusion deoxidizer (aluminum oxide pellet balls) is added for diffusion deoxidation. The furnace door is closed for 11 minutes. When the molten steel temperature reaches 1646°C, the second sample is taken for chemical composition analysis to confirm the deviation of the content of each chemical element from the requirements of the composition target values. After the second sample is taken away, when the molten steel temperature reaches 1665°C, it leaves the station. The LF smelting cycle is 65 minutes, and the free space is 450 mm. The addition amount of alloys per ton of steel: ferrosilicon 0.33 kg / t, high-carbon ferromanganese 0.7 kg / t, high-carbon ferrochrome 0.9 kg / t, ferromolybdenum 2.9 kg / t, aluminum wire segment (Φ13 mm) 0.34 Kg / t. The addition amount of auxiliary materials per ton of steel: coke particles 0.235 Kg / t, silicon carbide 2.2 kg / t, reactive lime (Φ30 mm) 4.1 Kg / t.

[0127] (3) RH refining

[0128] The tapping temperature is 1660°C, and the operation time is 46 minutes. Before starting the vacuum pump, the argon pressure is controlled at 0.1 MPa, with the slag surface slightly moving and the molten steel not exposed. When the vacuum degree reaches 104 Pa, the timing starts, and the holding time is 12 minutes. At the same time, the argon pressure is adjusted to 0.3 MPa, and 0.85 kg / t of calcium-silicon alloy cored wire (Φ14 mm) is added. After the static argon blowing ends, 0.6 kg / t of covering agent is added. The free space is 455 mm. The refining recompression temperature is 1625°C, and the leaving station temperature is 1606°C. (4) Continuous casting

[0129] The ladle arrival temperature is 1595°C, the middle package H is controlled at 1.4 ppm, the casting time is 62 minutes, the superheat is 22°C, the drawing speed is 0.43 m / min, and the whole process is protected by casting. The mold powder used is medium-carbon steel mold powder at 3.6 kg / t.

[0130] (5) Heating process

[0131] Heating process: The temperature entering the heating furnace is 520°C, the temperature requirement for the preheating section is 620°C, and the time is 1.5 h; the temperature requirement for the heating section 2 is 860°C, and the time is 1.4 h; the temperature requirement for the heating section 1 is 1225°C, and the time is 1.5 h; the temperature requirement for the soaking section is 1214°C, and the time is 1.5 h; the tapping temperature is 1202°C.

[0132] (6) Rolling process

[0133] Primary rolling process: 11 rolling passes, steel turning → In the 1st pass, width is 405.2 mm, height is 435 mm, reduction is 51 mm, rolling speed is 2.31 m / s → In the 2nd pass, width is 416.46 mm, height is 390 mm, reduction is 45.01 mm, rolling speed is 2.51 m / s → steel turning → In the 3rd pass, width is 400.95 mm, height is 380 mm, reduction is 36.46 mm, rolling speed is 2.51 m / s → In the 4th pass, width is 408.44 mm, height is 355 mm, reduction is 25.01 mm, rolling speed is 2.5 m / s → steel turning → In the 5th pass, width is 372.53 mm, height is 350.01 mm, reduction is 58.45 mm, rolling speed is 2.5 m / s → In the 6th pass, width is 387.54 mm, height is 300 mm, reduction is 50 mm, rolling speed is 2.51 m / s → steel turning → In the 7th pass, width is 317.27 mm, height is 330.01 mm, reduction is 57.53 mm, rolling speed is 2.51 m / s → In the 8th pass, width is 332.87 mm, height is 278 mm, reduction is 52.01 mm, rolling speed is 2.5 m / s → steel turning → In the 9th pass, width is 290.87 mm, height is 290 mm, reduction is 42.87 mm, rolling speed is 2.5 m / s → In the 10th pass, width is 304.07 mm, height is 246.01 mm, reduction is 44.01 mm, rolling speed is 2.5 m / s → steel turning → In the 11th pass, width is 267.63 mm, height is 232 mm, reduction is 72.07 mm, rolling speed is 2.51 m / s; Pass through 3 850-mm rolling mills and 1 735-mm rolling mill, and then enter the continuous rolling mill for rolling.

[0134] Continuous rolling product rolling process: 5 rolling passes, in the 1st pass, height is 229 mm, width is 245.01 mm, rolling speed is 0.271 m / s; in the 2nd pass, height is 192 mm, width is 235.01 mm, rolling speed is 0.311 m / s; in the 3rd pass, height is 200.01 mm, width is 195 mm, rolling speed is 0.351 m / s; in the 4th pass, height is 159.01 mm, width is 198 mm, rolling speed is 0.462 m / s; in the 5th pass, height is 172.29 mm, width is 172.30 mm, rolling speed is 0.573 m / s; After 5 passes, the finished product comes out.

[0135] (7) Heat preservation process

[0136] Heat preservation process: The steel is heat-preserved, the temperature in the lower heat-preservation pit is 580 °C, heat preservation lasts for 54 h, and the temperature when coming out of the pit is 130 °C.

[0137] (8) Heat treatment process

[0138] The heat-preserved steel takes samples for heat treatment, and the heat treatment includes the following steps:

[0139] 1) Quenching: 850 °C, heat preservation for 1.0 h, oil cooling;

[0140] 2) Tempering: 550 °C, holding for 2.0 h, oil cooling.

[0141] Final inspection results of Examples 1 - 5

[0142] (1) Macrostructure of steel bars with a diameter of Φ170 mm (finished steel bars obtained by the holding process)

[0143]

[0144]

[0145] (2) Non-metallic inclusions in steel bars with a diameter of Φ170 mm (finished steel bars obtained by the holding process)

[0146]

[0147] (3) Mechanical properties of steel bars with a diameter of Φ170 mm (finished steel bars obtained after heat treatment)

[0148] Serial number Quenching / °C Holding time Tempering / °C Holding time Rm / MPa Rel / MPa A / ％ z / ％ KU2 / J Standard 850, oil cooling 0.8～1.2h 550, oil cooling 1.8～2.2h ≥980 ≥835 ≥12 ≥45 ≥63 Example 1 850, oil cooling 1h 550, oil cooling 2h 1155 925 14 67 78 Example 1 850, oil cooling 1h 550, oil cooling 2h 1162 932 16 65 80 Example 2 850, oil cooling 1h 550, oil cooling 2h 1146 922 17 69 82 Example 2 850, oil cooling 1h 550, oil cooling 2h 1140 915 15 62 81 Example 3 850, oil cooling 1h 550, oil cooling 2h 1155 926 17 60 80 Example 3 850, oil cooling 1h 550, oil cooling 2h 1148 918 15 62 79 Example 4 850, oil cooling 1h 550, oil cooling 2h 1154 920 16 65 75 Example 4 850, oil cooling 1h 550, oil cooling 2h 1140 918 15 64 69 Example 5 850, oil cooling 1h 550, oil cooling 2h 1142 920 18 64 73 Example 5 850, oil cooling 1h 550, oil cooling 2h 1150 9930 14 63 72

Claims

1. A steel bar for heavy-duty automobile axles, characterized in that: In terms of mass percentage, C: 0.33% ~ 0.38%, Si: 0.20% ~ 0.35%, Mn: 0.42% ~ 0.60%, P: ≤ 0.015%, S: ≤ 0.006%, Cr: 0.80% ~ 1.00%, Ni: ≤ 0.25%, Mo: 0.16% ~ 0.23%, Cu: ≤ 0.15%, and the balance is iron and unavoidable impurities.

2. The method for preparing the steel bar for heavy-duty vehicle axles according to claim 1, characterized in that: The process includes the following steps: ecological electric furnace smelting → LF refining → RH refining → continuous casting → heating process → rolling process → insulation process; The ecological electric furnace smelting is as follows: using scrap steel for smelting, the tapping temperature is 1615-1620℃, C is 0.06-0.10% when tapping, P≤0.010%, auxiliary materials and alloys are added when 1 / 4-1 / 3 of the steel is tapped, the smelting cycle is 40-45min, and the furnace oxygen consumption is 26-27m 3 / t steel; alloy addition per ton of steel: 5.5-5.6kg / t silicon-manganese alloy, 14.0-14.2kg / t high carbon ferrochrome, 0.8-0.9kg / t aluminum wire segment; auxiliary material addition per ton of steel: 30-31kg / t coke particles, 5.8-6.2kg / t ladle ash, 40-41kg / t active lime, 15-16kg / t magnesite; The LF refining is as follows: the LF inlet temperature is 1510-1515°C, a high current of 35000-36000A is used to heat and melt the slag, when the slag surface fluctuates and the molten steel and the arc are not exposed, active lime is added, and the chemical composition is first sampled and analyzed after 5-6 minutes, and alloy and silicon carbide are added according to the target value of the chemical composition, and coke particles are added to increase carbon; when the temperature of the molten steel reaches 1610-1620°C, 1.5-1.6kg / t of diffusion deoxidizer is added for diffusion deoxidation, the furnace door is closed for 10-13 minutes, and when the temperature of the molten steel reaches 1640-1650°C, the chemical composition is sampled and analyzed for the second time to confirm the composition of each chemical element The deviation value of the content from the target value is required. After the secondary sample is taken, the station is left when the molten steel temperature reaches 1660-1670℃. The LF smelting cycle is 60min-70min, and the clearance is 440-460mm. The amount of additional alloy added per ton of steel: ferrosilicon 0.3-0.35kg / t, high carbon ferromanganese 0.6-0.7kg / t, high carbon ferrochrome 0.8-0.9kg / t, ferromolybdenum 2.8-2.9kg / t, aluminum wire segment 0.3-0.35kg / t; the amount of additional auxiliary materials added per ton of steel: coke particles 0.2-0.25kg / t, silicon carbide 2.1-2.2kg / t, active lime 4-4.2kg / t; The RH refining is as follows: the inlet temperature is 1655-1665°C, the operation time is 40-50 minutes, the argon pressure is controlled at 0.1-0.3MPa before the vacuum pump is started, the molten steel is not exposed when the slag surface is slightly moved, the timing starts when the vacuum degree reaches 100-110Pa, the holding time is 10-15 minutes, and the argon pressure is adjusted to 0.3-0.5MPa at the same time, 0.84-0.86kg / t of silicon-calcium alloy cored wire is added, and after the static argon blowing is completed, 0.6-0.7kg / t of covering agent is added, the clearance is 440-460mm, the refining re-pressing temperature is 1620-1630°C, and the leaving station temperature is 1600-1610°C; The continuous casting is as follows: the ladle arrival temperature is 1590-1600°C, the H of the tundish is controlled to be ≤2ppm, the casting time is 55min-65min, the superheat is 20-25°C, and the casting speed is 0.42-0.44m / min; The heating process is as follows: the temperature entering the heating furnace is 500°C~550°C, the temperature of the preheating section is required to be 600°C~650°C, and the time is 1.4~1.5h; the temperature of the heating section 2 is required to be 850°C~870°C, and the time is 1.3~1.5h; the temperature of the heating section 1 is required to be 1210°C~1230°C, and the time is 1.4~1.5h; the temperature of the soaking section is required to be 1200°C~1220°C, and the time is 1.4~1.5h; the steel tapping temperature is 1190°C~1210°C.

3. The preparation method according to claim 2, characterized in that: In the LF refining step, alloy, silicon carbide and coke particles are added to an argon gas stream.

4. The preparation method according to claim 2, characterized in that: In the continuous casting step, the casting is protected throughout the whole process, and the mold protection slag uses medium carbon steel protection slag, and the amount of medium carbon steel protection slag is 3.6-3.7kg / t steel.

5. The preparation method according to claim 2, characterized in that: The diameter of the aluminum wire segment is 10-16 mm, the diameter of the active lime is 10-70 mm, and the diameter of the magnesite is 10-60 mm; the diffusion deoxidizer is aluminum particles; the covering agent is carbonized rice husk; and the diameter of the silicon-calcium alloy cored wire is 14-15 mm.

6. The preparation method according to claim 2, characterized in that: The rolling process is: (1) Primary rolling process: 11 passes, steel turning → 1st pass width 405.2~405.21mm, height 435~435.01mm, reduction 51~51.01mm, rolling speed 2.3~2.31m / s → 2nd pass width 416.45~416.46mm, height 390~390.01mm, reduction 45~45.01mm, rolling speed 2.5~2.51m / s → steel turning → 3rd pass width 400.94~400.95mm, height 380~380.01mm, reduction 36.45~36.46 mm, rolling speed 2.5~2.51m / s→4th pass width 408.44~408.45mm, height 355~355.01mm, reduction 25~25.01mm, rolling speed 2.5~2.51m / s→steel turning→5th pass width 372.53~372.54mm, height 350~350.01mm, reduction 58.44~58.45mm, rolling speed 2.5~2.51m / s→6th pass width 387.53~387.54mm, height 300~300.01mm, reduction 50~50. 01mm, rolling speed 2.5~2.51m / s→steel turning→7th pass width 317.26~317.27mm, height 330~330.01mm, reduction 57.53~57.54mm, rolling speed 2.5~2.51m / s→8th pass width 332.86~332.87mm, height 278~278.01mm, reduction 52~52.01mm, rolling speed 2.5~2.51m / s→steel turning→9th pass width 290.86~290.87mm, height 290~290.01mm, reduction 4 2.86~42.87mm, rolling speed 2.5~2.51m / s→10th pass width 304.06~304.07mm, height 246~246.01mm, reduction 44~44.01mm, rolling speed 2.5~2.51m / s→steel turning→11th pass width 267.62~267.63mm, height 232~232.01mm, reduction 72.06~72.07mm, rolling speed 2.5~2.51m / s; pass through 3 850mm rolling mills and 1 735mm rolling mill, and then enter the continuous rolling mill group for rolling; (2) Continuous rolling process: 5 passes, the first pass is 229-229.01 mm high, 245-245.01 mm wide, and the rolling speed is 0.27-0.271 m / s; the second pass is 192-192.01 mm high, 235-235.01 mm wide, and the rolling speed is 0.31-0.311 m / s; the third pass is 200-200.01 mm high, 195-1 95.01mm, rolling speed 0.35~0.351m / s; the 4th pass is 159~159.01mm high, 198~198.01mm wide, rolling speed 0.461~0.462m / s; the 5th pass is 172.29~172.30mm high, 172.29~172.30mm wide, rolling speed 0.572~0.573m / s; the finished product is produced after 5 passes.

7. The preparation method according to claim 2, characterized in that: The insulation process is as follows: steel insulation, lower insulation pit temperature ≥ 560°C, insulation 50-55h, pit exit temperature ≤ 150°C.

8. The preparation method according to claim 2, characterized in that: The steel after heat preservation is heat treated, and the heat treatment includes the following steps: 1) Quenching: 840-860°C, heat preservation for 0.8-1.2h, oil cooling; 2) Tempering: 540-560℃, keep warm for 1.8-2.2h, oil cooling.

Images