Steel bar for rotor of automobile compressor and production and manufacturing method therefor

Abstract

Disclosed in the present invention are a steel bar for a rotor of an automobile compressor and a production and manufacturing method therefor. The steel bar comprises, in percentage by mass: C: 0.31%-0.36%, Si: 0.20%-0.35%, Mn: 0.42%-0.60%, P: ≤0.015%, S: ≤0.010%, Cr: 1.02%-1.20%, Ni: ≤0.25%, Mo: 0.21%-0.28%, V: 0.11%-0.18%, Cu: ≤0.15%, the balance being iron and inevitable impurities. A process route comprises: smelting in an electric furnace, refining in an LF furnace, VD refining, continuous casting billet, heating in a heating furnace, rolling, and heat preservation. The present invention employs an electric furnace, LF, RH, and continuous casting smelting process combined with a rolling process to produce the steel bar for a rotor of an automobile compressor, which has a production specification of Φ120 mm, meeting the requirements of mechanical properties, and ensuring the steel cleanliness. Reasonable composition design and production processes ensure the mechanical and impact properties; and the macrostructure, non-metallic inclusions, and mechanical properties of a finished steel product meet the requirements of high-end products.

Description

Steel bar for automobile compressor rotor and production method thereof TECHNICAL FIELD

[0001] The present application relates to a steel bar for automobile compressor rotor and a production method thereof, and belongs to the field of steelmaking. BACKGROUND

[0002] The automobile compressor is the core of the automobile refrigeration system, which adopts a closed structure and does not need to add lubricant, and can be adjusted and controlled according to the real-time changes of the vehicle speed, room temperature and refrigeration load. The automobile compressor rotor, as the main part of the automobile compressor, is required to have good wear resistance, tensile strength and temperature resistance. In addition, it should also have good fatigue resistance, impact resistance and vibration resistance to ensure the normal operation of the automobile compressor. The automobile compressor rotor is an important component of the refrigeration device, and the quality requirement is strict.

[0003] The quality of the steel bar for automobile compressor rotor directly affects the service life and wear resistance of the refrigeration device, and even relates to the safety of the entire refrigeration device working process.

[0004] The steel bar for automobile compressor rotor is produced by adopting the electric furnace + LF + VD + continuous casting smelting process and rolling process, meets the high-end use requirement, and realizes the breakthrough of batch production of the steel bar for automobile compressor rotor by the electric furnace continuous casting process.

[0005] SUMMARY

[0006] The purpose of the present application is to provide a production process preparation method of a steel bar for automobile compressor rotor, which smelts by adopting the electric furnace + LF + VD + continuous casting smelting process, produces and manufactures the steel bar for automobile compressor rotor, and guarantees the mechanical properties, impact properties and high steel purity of the finished steel bar for automobile compressor rotor, and guarantees the surface quality level of the steel bar for automobile compressor rotor.

[0007] In order to achieve the above-mentioned purpose of the application, the present application provides a component design and process design of a steel bar for automobile compressor rotor, and the specific steps are: electric furnace smelting + LF furnace refining + VD refining + continuous casting blank→heating furnace heating→rolling→heat preservation. The quality requirement of the steel bar for automobile compressor rotor is met, and the mechanical properties, impact properties and high steel purity can also meet the standard requirements.

[0008] The present application provides a steel bar for automobile compressor rotor, which contains the following components in percentage by mass:

[0009] C: 0.31% to 0.36%, Si: 0.20% to 0.35%, Mn: 0.42% to 0.60%, P: ≤0.015%, S: ≤0.010%, Cr: 1.02% to 1.20%, Ni: ≤0.25%, Mo: 0.21% to 0.28%, V: 0.11% to 0.18%, Cu: ≤0.15%, the balance being iron and inevitable impurities.

[0010] The application provides a preparation method of the automobile compressor rotor steel bar.

[0011] The electric furnace smelting is as follows: 60% to 65% molten iron and 35% to 40% scrap steel are smelted; oxygen is oxidized, and fierce boiling, automatic slag flow and full melting temperature of 1590 to 1600 DEG C are realized; the tapping temperature is 1675 to 1685 DEG C; the C content is 0.03% to 0.08% when tapping; the P content is ≤0.010%; slag material, pre-deoxidizer and ferroalloy are added when 1 / 4 to 1 / 3 of the molten steel is tapped; the adding amount of alloy per ton of steel is as follows: 1.2 to 1.3 Kg / t of aluminum iron, 4 to 4.1 Kg / t of high-carbon ferromanganese and 14 to 15 Kg / t of high-carbon ferrochrome; the adding amount of auxiliary material per ton of steel is as follows: 4 to 4.1 Kg / t of aluminum oxide ball, 0.6 to 0.7 Kg / t of coke powder carbonizer, 2.6 to 2.7 Kg / t of electric furnace foaming agent, 1.0 to 1.1 Kg / t of tapping hole filler and 32 to 33 Kg / t of active lime.

[0012] The LF furnace refining is: using 20000-25000A large current to heat up the slag, refining time 70-75min, to LF site temperature 1518-1625℃, when the slag surface fluctuates, the molten steel and the arc are not exposed, supplementing active lime, 4-6min after the first sampling analysis chemical composition, supplementing alloy according to the chemical composition target value, and increasing carbon, the alloy and carbon powder should be added to the argon stream to promote the alloy and carbon powder to melt and homogenize quickly. When the molten steel temperature reaches 1550-1560℃, add diffusion deoxidizer for diffusion deoxidation, when the molten steel temperature reaches 1600-1610℃, second sampling analysis chemical composition to confirm the deviation of each chemical element composition from the target value, after the second sampling, supplementing diffusion deoxidizer continues to adjust the slag, the ladle temperature is 1675-1685℃. Supplementing alloy: high-carbon ferromanganese 1.8-1.9kg / t, high-carbon ferrochrome 1.4-1.5kg / t, ferromolybdenum 3.5-3.6kg / t, ferrovanadium 2.2-2.3kg / t, aluminum wire 2.4-2.5m / t, ferrosilicon powder 3.6-3.7kg / t. Auxiliary materials: active lime 9-9.5kg / t, carbide slag 1.2-1.3kg / t, alumina ball 1.0-1.1kg / t, fluorite briquette 1.0-1.1kg / t, coke powder carbon additive 0.3-0.35kg / t. At the same time, continue white slag smelting for 20-30min. LF slag sample basicity requirement: binary basicity R1≥10, ternary basicity R2≥12, quaternary basicity R3≥1.5.

[0013] The VD refining is: the temperature before entering VD is 1670-1675℃, the argon pressure is controlled at 0.1-0.3MPa before the vacuum pump starts, the free space is 850-860mm, the slag surface is slightly moving and the molten steel is not exposed, when the vacuum degree reaches 95-100Pa, the timing starts, the holding time is 15-20min, the vacuum breaking temperature is 1600-1610℃, the alloy is supplemented according to the molten steel composition, at the same time, the argon pressure is adjusted to 0.3-0.5MPa, the static argon blowing time is 25-30min, after the static argon blowing is finished, Φ10-Φ12mm silicon-calcium cored wire 2.0-2.1m / t is added, the ladle temperature is 1570-1578℃. Auxiliary materials: carbonized rice husk 0.7-0.8kg / t.

[0014] Further, in the above technical solution, the continuous casting is: the ladle to station temperature continuous casting 1560-1570℃, the tundish H control≤2ppm, the tundish temperature 1524-1527℃, the casting speed 0.83-0.85m / min, the whole process is protected casting, the mold powder used is medium carbon steel powder.

[0015] Further, in the technical scheme, the heating process is: the temperature of entering the heating furnace is 350-500 DEG C, the temperature requirement of the preheating section is 650-700 DEG C, the time is 1.0-1.2 h; the temperature requirement of heating 2 section is 840-860 DEG C, the time is 1.0-1.2 h; the temperature requirement of heating 1 section is 1190-1220 DEG C, the time is 1.2-1.5 h; the temperature requirement of the soaking section is 1180-1210 DEG C, the time is 1.0-1.2 h; the temperature of discharging is 1170-1190 DEG C.

[0016] Further, in the technical scheme, the rolling includes the billet BD blooming process and the continuous rolling process.

[0017] The billet BD blooming process: rolling 3 passes, the rolling reduction: turning over the steel → the first pass high 263-263.1 mm, wide 239-239.1 mm, roll gap 103-103.1 mm, reduction 7-7.1 mm; → the second pass high 263-263.1 mm, wide 239-239.1 mm, roll gap 103-103.1 mm, reduction 0 mm; → turning over the steel → the third pass high 233-233.1 mm, wide 265-265.1 mm, roll gap 73-73.1 mm, reduction 6-6.1 mm, passing through 3 850 mm rolling mills, 1 735 mm rolling mill, then entering 8 continuous rolling mill groups to roll.

[0018] Continuous rolling process: 9 passes, 1st pass high 229-229.1mm, width 245-245.1mm, roll gap 53-53.1mm, rolling speed 0.27-0.28m / s; 2nd pass high 192-192.1mm, width 235-235.1mm, roll gap 16-16.1mm, rolling speed 0.31-0.32m / s; 3rd pass high 200-200.1mm, width 195-195.1mm, roll gap 24-24.1mm, rolling speed 0.35-0.351m / s; 4th pass high 160-160.1mm, width 214.7-214.8mm, roll gap 10-10.1mm, rolling speed 0.474-0.475m / s; 5th pass high 168-168.1mm, width 174.6-174.7mm, roll gap 12-12.1mm, rolling speed 0.598-0.599m / s; 6th pass high 120-120.1mm, width 187.6-187.7mm, roll gap 14-14.1mm, rolling speed 0.743-0.744m / s; 7th pass high 142-142.1mm, width 138.5-138.6mm, roll gap 22-22.1mm, rolling speed 0.934-0.935m / s; 8th pass high 111-111.1mm, width 151.5-151.6mm, roll gap 17-17.1mm, rolling speed 1.102-1.103m / s; 9th pass high 122.04-122.05mm, width 122.04-122.05mm, roll gap 7.4-7.5mm, rolling speed 1.217-1.218m / s; after 9 passes, the finished product is discharged.

[0019] Further, in the above technical solution, the heat preservation process is that: the steel material is heat preserved, the temperature of the lower heat preservation pit is ≥600℃, the heat preservation time is 48-55h, and the pit discharge temperature is ≤150℃.

[0020] Further, in the above technical solution, the heat treated steel material is heat treated, and the heat treatment comprises the following steps:

[0021] 1) first quenching: 880-920℃, heat preservation time 0.8-1.0h, oil cooling;

[0022] 2) tempering: 620-640℃, heat preservation time 1.8-2.2h, air cooling.

[0023] Advantages of the application

[0024] (1) The steel bar for automobile compressor rotor is produced by adopting the electric furnace+LF+RH+continuous casting smelting process and rolling process, the production specification is Φ120mm, the mechanical property requirements are met, and the steel purity is ensured.

[0025] (2) Reasonable component design and production process ensure mechanical properties and impact properties.

[0026] (3) The macrostructure, non-metallic inclusions and mechanical properties of the finished steel meet the requirements of high-end products. DETAILED DESCRIPTION

[0027] Example 1

[0028] 1. Chemical composition of the steel bar for automobile compressor rotor

[0029] The internal control chemical composition is determined as follows in terms of mass percentage: C: 0.33%, Si: 0.25%, Mn: 0.49%, P: 0.010%, S: 0.005%, Cr: 1.09%, Ni: 0.02%, Mo: 0.25%, V: 0.15%, Cu: 0.02%, and the balance being iron and inevitable impurities.

[0030] 2. Steel bar production process for automobile compressor rotor by electric furnace continuous casting, comprising the following steps:

[0031] Process route: electric furnace + LF + VD + continuous casting billet → heating furnace heating → rolling → heat preservation → finishing → inspection → packaging and delivery to warehouse → delivery.

[0032] (1) Electric furnace smelting

[0033] 64% molten iron and 36% scrap steel are used for smelting; oxygen oxidation, vigorous boiling, automatic slag flow, full melting temperature 1595℃, tapping temperature 1680℃, C 0.04% and P 0.008% at tapping time, auxiliary materials and alloys are added at 1 / 4 tapping time. Alloy addition per ton of steel: aluminum iron 1.2Kg / t, high-carbon ferromanganese 4Kg / t, high-carbon ferrochrome 14.5Kg / t. Auxiliary material addition per ton of steel: aluminum oxide ball 4Kg / t (as a pre-deoxidizer), coke powder carbonizer 0.6Kg / t (as a pre-deoxidizer), electric furnace foaming agent 2.67Kg / t (as a slag material), tapping hole filler 1.0Kg / t (as a slag material), and active lime 32.4Kg / t (as a slag material).

[0034] (2) LF furnace refining

[0035] The refining time is 72 min, the temperature at LF position is 1520 °C, when the slag surface fluctuates, the molten steel and the arc are not exposed, the active lime, carbide slag and fluorite briquette are added, the chemical composition is analyzed after 5 min, the alloy is added according to the target value of the chemical composition, and the coke powder carbonizer is added to increase carbon, and the alloy and the coke powder should be added to the argon stream to promote the alloy and the carbon powder to melt and homogenize quickly. When the temperature of the molten steel reaches 1555 °C, the diffusion deoxidizer alumina ball is added to carry out diffusion deoxidation, and when the temperature of the molten steel reaches 1605 °C, the chemical composition is analyzed for the second time to confirm the deviation of the content of each chemical element composition from the target value, after the second sample is taken away, the diffusion deoxidizer alumina ball is continuously added to adjust the slag, and the ladle temperature is 1679 °C. At the same time, the white slag smelting is continuously maintained for 25 min. The slag sample after LF requires that the binary basicity R1 is 10.5, the ternary basicity R2 is 12.4, and the quaternary basicity R3 is 1.6.

[0036] In this step, the above-mentioned substances are added in the following amounts: the added alloy is 1.8 kg / t of high-carbon ferromanganese, 1.4 kg / t of high-carbon ferrochrome, 3.5 kg / t of ferromolybdenum, 2.2 kg / t of ferrovanadium, 2.4 m / t of aluminum wire, and 3.6 kg / t of ferrosilicon powder. The auxiliary materials are 9.2 kg / t of active lime, 1.2 kg / t of carbide slag, 1.0 kg / t of alumina ball, 1.0 kg / t of fluorite briquette, and 0.33 kg / t of coke powder carbonizer.

[0037] (3) VD refining

[0038] The temperature before entering the VD is 1672 °C, the argon pressure is controlled at 0.2 MPa before the vacuum pump is started, the free space is 854 mm, the molten steel is not exposed with the slag surface slightly moving, the timing is started when the vacuum degree reaches 100 Pa, the holding time is 17 min, the vacuum breaking temperature is 1603 °C, the chemical composition is analyzed by taking a sample of the molten steel, the alloy (high-carbon ferromanganese, high-carbon ferrochrome, ferromolybdenum, and ferrovanadium) and the auxiliary materials are added according to the target value of the chemical composition, the argon pressure is adjusted to 0.4 MPa at the same time, the static argon blowing time is 26 min, after the static argon blowing is completed, 2.0 m / t of Φ10 mm silicon-calcium cored wire is added, and the ladle temperature is 1575 °C. The auxiliary materials are 0.7 kg / t of carbonized rice husk.

[0039] (4) Continuous casting

[0040] The temperature of the ladle at the station is 1564 °C for continuous casting, the H control in the tundish is 1.3 ppm, the temperature of the tundish is 1525 °C, the casting speed is 0.84 m / min, the whole process is protected casting, and the mold protection slag is a medium-carbon steel protection slag.

[0041] (5) Heating process

[0042] The heating process in chronological order is: entering the heating furnace at 450°C, preheating at 660°C for 1.1 h, heating at 850°C for 1.0 h, heating at 1200°C for 1.3 h, soaking at 1200°C for 1.0 h, and tapping at 1180°C.

[0043] (6) Rolling process

[0044] The blooming process of the continuous casting billet BD is as follows: using a 1150 mm BD blooming mill, 3 passes, rolling reduction: turning over → the first pass high 263 mm, wide 239 mm, roll gap 103 mm, reduction 7 mm; → the second pass high 263 mm, wide 239 mm, roll gap 103 mm, reduction 0 mm; → turning over → the third pass high 233 mm, wide 265 mm, roll gap 73 mm, reduction 6 mm, passing through 3 850 mm rolling mills and 1 735 mm rolling mill, and then entering an 8-stand continuous rolling mill group.

[0045] The continuous rolling process of 9 passes is as follows: the first pass high 229 mm, wide 245 mm, roll gap 53 mm, rolling speed 0.27 m / s; the second pass high 192 mm, wide 235 mm, roll gap 16 mm, rolling speed 0.31 m / s; the third pass high 200 mm, wide 195 mm, roll gap 24 mm, rolling speed 0.35 m / s; the fourth pass high 160 mm, wide 214.7 mm, roll gap 10 mm, rolling speed 0.474 m / s; the fifth pass high 168 mm, wide 174.6 mm, roll gap 12 mm, rolling speed 0.598 m / s; the sixth pass high 120 mm, wide 187.6 mm, roll gap 14 mm, rolling speed 0.743 m / s; the seventh pass high 142 mm, wide 138.5 mm, roll gap 22 mm, rolling speed 0.934 m / s; the eighth pass high 111 mm, wide 151.5 mm, roll gap 17 mm, rolling speed 1.102 m / s; the ninth pass high 122.04 mm, wide 122.04 mm, roll gap 7.4 mm, rolling speed 1.217 m / s; and the finished product is discharged after 9 passes.

[0046] (7) Soaking process

[0047] The soaking process is as follows: the steel is soaked at a temperature of 620°C for 52 h in a soaking pit, and the temperature of the steel discharged from the pit is 120°C.

[0048] (8) Heat treatment

[0049] The steel after soaking is subjected to heat treatment, and the heat treatment comprises the following steps:

[0050] 1) first quenching: 900°C, soaking for 0.9 h, oil cooling;

[0051] 2) tempering: 630 °C, holding for 2 h, air cooling.

[0052] Example 2:

[0053] 1. Chemical composition of steel bar for automobile compressor rotor

[0054] C: 0.34%, Si: 0.24%, Mn: 0.48%, P: 0.009%, S: 0.004%, Cr: 1.06%, Ni: 0.03%, Mo: 0.25%, V: 0.14%, Cu: 0.02%, the balance being iron and inevitable impurities, by mass percent.

[0055] 2. EAF continuous casting process of steel bar for automobile compressor rotor, comprising the following steps:

[0056] Process route: EAF + LF + VD + continuous casting billet → heating furnace heating → rolling → holding → finishing → inspection → packaging and delivery to warehouse → shipment.

[0057] (1) EAF smelting

[0058] 62% hot metal and 38% scrap steel were used for smelting; oxygen oxidation, vigorous boiling, automatic slag flow, full melting temperature 1594 °C, tapping temperature 1680 °C, C 0.04% and P 0.007% at tapping time, auxiliary materials and alloys were added at 1 / 4 tapping time. Alloy addition per ton of steel: aluminum iron 1.2 Kg / t, high-carbon ferromanganese 4 Kg / t, high-carbon ferrochrome 14.4 Kg / t. Auxiliary material addition per ton of steel: aluminum oxide ball 4 Kg / t (as pre-deoxidizer), coke powder carbonizer 0.6 Kg / t (as pre-deoxidizer), EAF foaming agent 2.6 Kg / t (as slag material), tapping hole filler 1.0 Kg / t (as slag material), active lime 32.6 Kg / t (as slag material).

[0059] (2) LF refining

[0060] The refining time is 72 min, the temperature at LF position is 1521 ℃, when the slag surface fluctuates, the molten steel and the arc are not exposed, the active lime, carbide slag and fluorite briquette are added, the chemical composition is analyzed after 5 min, the alloy is added according to the target value of the chemical composition, and the coke powder carbonizer is added to increase carbon, and the alloy and the coke powder should be added to the argon stream to promote the alloy and the carbon powder to melt and homogenize quickly. When the temperature of the molten steel reaches 1556 ℃, the diffusion deoxidizer alumina ball is added to carry out diffusion deoxidation, and when the temperature of the molten steel reaches 1604 ℃, the chemical composition is analyzed for the second time to confirm the deviation of the content of each chemical element composition from the target value, after the second sample is taken away, the diffusion deoxidizer alumina ball is continuously added to adjust the slag, and the ladle temperature is 1679 ℃. At the same time, the white slag smelting is continuously maintained for 26 min. The slag sample after LF requires that the binary basicity R1 is 10.5, the ternary basicity R2 is 12.6, and the quaternary basicity R3 is 1.7.

[0061] In this step, the above-mentioned substances are added in the following amounts: the added alloy is 1.8 kg / t of high-carbon ferromanganese, 1.4 kg / t of high-carbon ferrochrome, 3.5 kg / t of ferromolybdenum, 2.2 kg / t of ferrovanadium, 2.4 m / t of aluminum wire, and 3.6 kg / t of ferrosilicon powder. The auxiliary materials are 9.3 kg / t of active lime, 1.2 kg / t of carbide slag, 1.0 kg / t of alumina ball, 1.0 kg / t of fluorite briquette, and 0.34 kg / t of coke powder carbonizer.

[0062] (3) VD refining

[0063] The temperature before entering the VD is 1672 ℃, the argon pressure is controlled at 0.2 MPa before the vacuum pump is started, the free space is 854 mm, the molten steel is not exposed with the slag surface slightly moving, the timing is started when the vacuum degree reaches 100 Pa, the holding time is 17 min, the vacuum breaking temperature is 1605 ℃, the chemical composition of the molten steel is analyzed, the alloy (high-carbon ferromanganese, high-carbon ferrochrome, ferromolybdenum, and ferrovanadium) and the auxiliary materials are added according to the target value of the chemical composition, the argon pressure is adjusted to 0.4 MPa, the time of static argon blowing is 28 min, after the static argon blowing is completed, 2.0 m / t of Φ10 mm silicon-calcium cored wire is added, and the ladle temperature is 1575 ℃. The auxiliary materials are 0.7 kg / t of carbonized rice husk.

[0064] (4) Continuous casting

[0065] The temperature of the ladle at the station is 1564 ℃ for continuous casting, the H value in the tundish is controlled at 1.4 ppm, the temperature of the tundish is 1525 ℃, the casting speed is 0.83 m / min, the whole process is protected casting, and the mold protection slag is a medium-carbon steel protection slag.

[0066] (5) Heating process

[0067] The heating process in time sequence is: entering the heating furnace at 420℃, preheating at 660℃ for 1.1 h, heating at 850℃ for 1.1 h, heating at 1210℃ for 1.2 h, soaking at 1205℃ for 1.1 h, and discharging at 1180℃.

[0068] (6) Rolling process

[0069] The blooming process of the continuous casting billet BD is as follows: using a 1150mm BD blooming mill, 3 passes, rolling reduction: turning over→1st pass high 263mm, wide 239mm, roll gap 103mm, reduction 7mm;→2nd pass high 263mm, wide 239mm, roll gap 103mm, reduction 0mm;→turning over→3rd pass high 233mm, wide 265mm, roll gap 73mm, reduction 6mm, passing through 3 850mm rolling mills and 1 735mm rolling mill, and then entering an 8-stand continuous rolling mill group.

[0070] The continuous rolling process of 9 passes is as follows: 1st pass high 229mm, wide 245mm, roll gap 53mm, rolling speed 0.27m / s; 2nd pass high 192mm, wide 235mm, roll gap 16mm, rolling speed 0.31m / s; 3rd pass high 200mm, wide 195mm, roll gap 24mm, rolling speed 0.35m / s; 4th pass high 160mm, wide 214.7mm, roll gap 10mm, rolling speed 0.474m / s; 5th pass high 168mm, wide 174.6mm, roll gap 12mm, rolling speed 0.598m / s; 6th pass high 120mm, wide 187.6mm, roll gap 14mm, rolling speed 0.743m / s; 7th pass high 142mm, wide 138.5mm, roll gap 22mm, rolling speed 0.934m / s; 8th pass high 111mm, wide 151.5mm, roll gap 17mm, rolling speed 1.102m / s; 9th pass high 122.04mm, wide 122.04mm, roll gap 7.45mm, rolling speed 1.217m / s; and the finished product is discharged after 9 passes.

[0071] (7) Soaking process

[0072] The soaking process is as follows: the steel is soaked at 610℃ for 53h in a soaking pit, and the temperature of the steel discharged from the pit is 110℃.

[0073] (8) Heat treatment

[0074] The steel after soaking is subjected to heat treatment, and the heat treatment comprises the following steps:

[0075] 1) first quenching: 900℃, soaking for 0.9h, oil cooling;

[0076] 2) tempering: 630 °C, holding for 2 h, air cooling.

[0077] Example 3:

[0078] 1. Chemical composition of steel bar for automobile compressor rotor

[0079] C: 0.34%, Si: 0.25%, Mn: 0.48%, P: 0.010%, S: 0.004%, Cr: 1.08%, Ni: 0.03%, Mo: 0.24%, V: 0.15%, Cu: 0.03%, the balance being iron and inevitable impurities, by mass percent.

[0080] 2. Steel bar production process for automobile compressor rotor by electric furnace continuous casting, comprising the following steps:

[0081] Process route: electric furnace + LF + VD + continuous casting billet → heating furnace heating → rolling → holding → finishing → inspection → packaging and delivery to warehouse → shipment.

[0082] (1) Electric furnace smelting

[0083] 64% molten iron and 36% scrap steel were used for smelting; oxygen oxidation, vigorous boiling, automatic slag flow, full melting temperature 1595 °C, tapping temperature 1681 °C, C 0.06% and P 0.008% at tapping time, auxiliary materials and alloys were added at 1 / 4 tapping time. Alloy addition per ton of steel: aluminum iron 1.2 Kg / t, high-carbon ferromanganese 4 Kg / t, high-carbon ferrochrome 14.5 g / t. Auxiliary material addition per ton of steel: aluminum oxide ball 4 Kg / t (as pre-deoxidizer), coke powder carbonizer 0.64 Kg / t (as pre-deoxidizer), electric furnace foaming agent 2.6 Kg / t (as slag material), tapping hole filler 1.0 Kg / t (as slag material), active lime 32.5 Kg / t (as slag material).

[0084] (2) LF furnace refining

[0085] The 21000A large current temperature slag is used, the refining time is 72 min, the temperature is 1622℃ in the LF position, when the slag surface fluctuates, the molten steel and the arc are not exposed, the active lime, the carbide slag and the fluorite briquette are supplemented, the first sampling analysis chemical composition is taken after 5 min, the alloy and the coke powder carbonizer are added according to the chemical composition target value, and the alloy and the coke powder are added on the argon stream to promote the alloy and the carbon powder to melt and homogenize quickly. When the temperature of the molten steel reaches 1556℃, the diffusion deoxidizer alumina ball is added to carry out diffusion deoxidation, and when the temperature of the molten steel reaches 1605℃, the second sampling analysis chemical composition is taken to confirm the deviation of the chemical element composition content from the target value required, after the second sampling is taken away, the diffusion deoxidizer alumina ball is supplemented to continue to adjust the slag, and the ladle temperature is 1681℃. At the same time, the white slag smelting is continued for 26 min. The LF slag sample basicity requirement is that the binary basicity R1 is 10.6, the ternary basicity R2 is 12.6, and the quaternary basicity R3 is 1.7.

[0086] In this step, the above-mentioned material adding amount is that the alloy is supplemented: high-carbon ferromanganese 1.8 kg / t, high-carbon ferrochrome 1.4 kg / t, ferromolybdenum 3.5 kg / t, ferrovanadium 2.2 kg / t, aluminum wire 2.4 m / t, and ferrosilicon powder 3.6 kg / t. The auxiliary material is: active lime 9.3 kg / t, carbide slag 1.2 kg / t, alumina ball 1.0 kg / t, fluorite briquette 1.0 kg / t, and coke powder carbonizer 0.32 kg / t.

[0087] (3) VD refining

[0088] The temperature before entering the VD is 1672℃, the argon pressure is controlled to be 0.1 MPa before the vacuum pump is started, the free space is 855 mm, the molten steel is not exposed with the slag surface slightly moving, the timing is started when the vacuum degree reaches 100 Pa, the holding time is 18 min, the vacuum breaking temperature is 1606℃, the chemical composition is analyzed by taking the molten steel sample, the alloy (high-carbon ferromanganese, high-carbon ferrochrome, ferromolybdenum, and ferrovanadium) and the auxiliary material are supplemented according to the chemical composition target value, the argon pressure is adjusted to be 0.4 MPa at the same time, the static argon blowing time is 27 min, after the static argon blowing is finished, the Φ10 mm silicon-calcium cored wire is added at 2.0 m / t, and the ladle temperature is 1575℃. The auxiliary material is: carbonized rice husk 0.7 kg / t.

[0089] (4) continuous casting

[0090] The ladle arrival temperature is continuously cast at 1565℃, the tundish H control is 1.3 ppm, the tundish temperature is 1525℃, the casting speed is 0.83 m / min, the whole process is protected casting, and the crystallizer protection slag is a medium-carbon steel protection slag.

[0091] (5) heating process

[0092] The heating process in time sequence is: entering the heating furnace at 440°C, preheating at 680°C for 1.0 h, heating at 850°C for 1.0 h, heating at 1205°C for 1.3 h, soaking at 1206°C for 1.1 h, and discharging at 1180°C.

[0093] (6) Rolling process

[0094] The blooming process of the continuous casting billet BD is as follows: using a 1150 mm BD blooming mill, 3 passes, rolling reduction: turning over the steel → the first pass high 263 mm, wide 239 mm, roll gap 103 mm, reduction 7 mm; → the second pass high 263 mm, wide 239 mm, roll gap 103 mm, reduction 0 mm; → turning over the steel → the third pass high 233 mm, wide 265 mm, roll gap 73 mm, reduction 6 mm, passing through 3 850 mm rolling mills and 1 735 mm rolling mill, and then entering an 8-stand continuous rolling mill group.

[0095] The continuous rolling process of 9 passes is as follows: the first pass high 229 mm, wide 245 mm, roll gap 53 mm, rolling speed 0.27 m / s; the second pass high 192 mm, wide 235 mm, roll gap 16 mm, rolling speed 0.31 m / s; the third pass high 200 mm, wide 195 mm, roll gap 24 mm, rolling speed 0.35 m / s; the fourth pass high 160 mm, wide 214.7 mm, roll gap 10 mm, rolling speed 0.474 m / s; the fifth pass high 168 mm, wide 174.6 mm, roll gap 12 mm, rolling speed 0.598 m / s; the sixth pass high 120 mm, wide 187.6 mm, roll gap 14 mm, rolling speed 0.743 m / s; the seventh pass high 142 mm, wide 138.5 mm, roll gap 22 mm, rolling speed 0.934 m / s; the eighth pass high 111 mm, wide 151.5 mm, roll gap 17 mm, rolling speed 1.102 m / s; the ninth pass high 122.045 mm, wide 122.04 mm, roll gap 7.4 mm, rolling speed 1.217 m / s; and the finished product is discharged after 9 passes.

[0096] (7) Soaking process

[0097] The soaking process is as follows: the steel is soaked at 610°C for 52 h in a soaking pit, and the pit temperature is 110°C.

[0098] (8) Heat treatment

[0099] The steel after soaking is subjected to heat treatment, and the heat treatment comprises the following steps:

[0100] 1) first quenching: 900°C, soaking for 0.9 h, oil cooling;

[0101] 2) tempering: 630 °C, holding for 2 h, air cooling.

[0102] Example 4:

[0103] 1. Chemical composition of steel bar for automobile compressor rotor

[0104] C: 0.34%, Si: 0.25%, Mn: 0.48%, P: 0.010%, S: 0.004%, Cr: 1.08%, Ni: 0.03%, Mo: 0.25%, V: 0.14%, Cu: 0.03% by mass.

[0105] 2. Steel bar production process for automobile compressor rotor by electric furnace continuous casting, comprising the following steps:

[0106] Process route: electric furnace + LF + VD + continuous casting billet → heating furnace heating → rolling → holding → finishing → inspection → packaging and delivery to warehouse → shipment.

[0107] (1) Electric furnace smelting

[0108] 63% molten iron and 37% scrap steel were used for smelting; oxygen oxidation, vigorous boiling, automatic slag flow, full melting temperature 1596 °C, tapping temperature 1681 °C, C 0.05% and P 0.008% at tapping time, auxiliary materials and alloys were added at 1 / 4 tapping time. Alloy addition per ton of steel: aluminum iron 1.2 Kg / t, high-carbon ferromanganese 4 Kg / t, high-carbon ferrochrome 14.6 Kg / t. Auxiliary material addition per ton of steel: aluminum oxide ball 4 Kg / t (as pre-deoxidizer), coke powder carbonizer 0.6 Kg / t (as pre-deoxidizer), electric furnace foaming agent 2.6 Kg / t (as slag material), tapping hole filler 1.0 Kg / t (as slag material), active lime 32.4 Kg / t (as slag material).

[0109] (2) LF furnace refining

[0110] The refining time is 72 min, the temperature at LF position is 1622℃, when the slag surface fluctuates, the molten steel and the arc are not exposed, the active lime, carbide slag and fluorite briquette are added, the chemical composition is analyzed after 5 min, the alloy is added according to the target value of the chemical composition, and the coke powder carbonizer is added to increase carbon, and the alloy and the coke powder should be added to the argon stream to promote the alloy and the carbon powder to melt and homogenize quickly. When the temperature of the molten steel reaches 1554℃, the diffusion deoxidizer alumina ball is added to carry out diffusion deoxidation, and when the temperature of the molten steel reaches 1605℃, the chemical composition is analyzed for the second time to confirm the deviation of the content of each chemical element composition from the target value, after the second sample is taken away, the diffusion deoxidizer alumina ball is added to continue to adjust the slag, and the ladle temperature is 1680℃. At the same time, the white slag smelting is continued for 25 min. The slag sample after LF requires that the binary basicity R1 is 10.3, the ternary basicity R2 is 12.6, and the quaternary basicity R3 is 1.7.

[0111] In this step, the above-mentioned substances are added in the following amounts: the alloy: high-carbon ferromanganese 1.8 kg / t, high-carbon ferrochrome 1.4 kg / t, ferromolybdenum 3.5 kg / t, ferrovanadium 2.2 kg / t, aluminum wire 2.4 m / t, and ferrosilicon powder 3.6 kg / t. The auxiliary materials: active lime 9.2 kg / t, carbide slag 1.2 kg / t, alumina ball 1.0 kg / t, fluorite briquette 1.0 kg / t, and coke powder carbonizer 0.3 kg / t.

[0112] (3) VD refining

[0113] The temperature before entering the VD is 1672℃, the argon pressure is controlled at 0.1 MPa before the vacuum pump is started, the free space is 854 mm, the molten steel is not exposed with the slag surface slightly moving, the timing is started when the vacuum degree reaches 100 Pa, the holding time is 17 min, the vacuum breaking temperature is 1604℃, the chemical composition is analyzed by taking a sample of the molten steel, the alloy (high-carbon ferromanganese, high-carbon ferrochrome, ferromolybdenum, and ferrovanadium) and the auxiliary materials are added according to the target value of the chemical composition, the argon pressure is adjusted to 0.3 MPa at the same time, the static argon blowing time is 27 min, after the static argon blowing is completed, the Φ10 mm silicon-calcium cored wire is added at 2.0 m / t, and the ladle temperature is 1573℃. The auxiliary materials: carbonized rice husk 0.7 kg / t.

[0114] (4) Continuous casting

[0115] The temperature of the ladle at the station is 1564℃ for continuous casting, the H control in the tundish is 1.2 ppm, the tundish temperature is 1525℃, the casting speed is 0.83 m / min, the whole process is protected casting, and the mold protection slag is a medium-carbon steel protection slag.

[0116] (5) Heating process

[0117] The heating process in chronological order is: entering the heating furnace at 460°C, preheating at 680°C for 1.0 h, heating at 850°C for 1.1 h, heating at 1210°C for 1.3 h, soaking at 1200°C for 1.1 h, and exiting at 1183°C.

[0118] (6) Rolling process

[0119] The blooming process of the continuous casting billet BD is as follows: using a 1150 mm BD blooming mill, 3 passes, rolling reduction: turning over the steel → the first pass high 263 mm, wide 239 mm, roll gap 103 mm, reduction 7 mm; → the second pass high 263 mm, wide 239 mm, roll gap 103 mm, reduction 0 mm; → turning over the steel → the third pass high 233 mm, wide 265 mm, roll gap 73 mm, reduction 6 mm, passing through 3 850 mm rolling mills and 1 735 mm rolling mill, and then entering an 8-stand continuous rolling mill group.

[0120] The continuous rolling process of 9 passes is as follows: the first pass high 229 mm, wide 245 mm, roll gap 53 mm, rolling speed 0.27 m / s; the second pass high 192 mm, wide 235 mm, roll gap 16 mm, rolling speed 0.31 m / s; the third pass high 200 mm, wide 195 mm, roll gap 24 mm, rolling speed 0.35 m / s; the fourth pass high 160 mm, wide 214.7 mm, roll gap 10 mm, rolling speed 0.474 m / s; the fifth pass high 168 mm, wide 174.6 mm, roll gap 12 mm, rolling speed 0.598 m / s; the sixth pass high 120 mm, wide 187.6 mm, roll gap 14 mm, rolling speed 0.743 m / s; the seventh pass high 142 mm, wide 138.5 mm, roll gap 22 mm, rolling speed 0.934 m / s; the eighth pass high 111 mm, wide 151.5 mm, roll gap 17 mm, rolling speed 1.102 m / s; the ninth pass high 122.04 mm, wide 122.04 mm, roll gap 7.4 mm, rolling speed 1.217 m / s; exiting the finished product after 9 passes.

[0121] (7) Soaking process

[0122] The soaking process is as follows: the steel is soaked at a temperature of 620°C for 51 h in a soaking pit, and the temperature of the steel exiting the pit is 120°C.

[0123] (8) Heat treatment

[0124] The steel after soaking is subjected to heat treatment, and the heat treatment comprises the following steps:

[0125] 1) first quenching: 900°C, soaking for 0.9 h, oil cooling;

[0126] 2) tempering: 630 °C, holding for 2 h, air cooling.

[0127] Example 5:

[0128] 1. Chemical composition of steel bar for automobile compressor rotor

[0129] C: 0.33%, Si: 0.26%, Mn: 0.48%, P: 0.010%, S: 0.005%, Cr: 1.08%, Ni: 0.03%, Mo: 0.25%, V: 0.15%, Cu: 0.04%, the balance being iron and inevitable impurities, by mass percent.

[0130] 2. Steel bar production process for automobile compressor rotor by electric furnace continuous casting, comprising the following steps:

[0131] Process route: electric furnace + LF + VD + continuous casting billet → heating furnace heating → rolling → holding → finishing → inspection → packaging and delivery to warehouse → shipment.

[0132] (1) Electric furnace smelting

[0133] 62% molten iron and 38% scrap steel were used for smelting; oxygen oxidation, vigorous boiling, automatic slag flow, full melting temperature 1595 °C, tapping temperature 1680 °C, C 0.05% and P 0.009% at tapping time, auxiliary materials and alloys were added at 1 / 4 tapping time. Alloy addition per ton of steel: aluminum iron 1.2 Kg / t, high-carbon ferromanganese 4 Kg / t, high-carbon ferrochrome 14.6 Kg / t. Auxiliary material addition per ton of steel: aluminum oxide ball 4 Kg / t (as pre-deoxidizer), coke powder carbonizer 0.6 Kg / t (as pre-deoxidizer), electric furnace foaming agent 2.6 Kg / t (as slag material), tapping hole filler 1.0 Kg / t (as slag material), active lime 32.5 Kg / t (as slag material).

[0134] (2) LF furnace refining

[0135] The refining time is 72 min, the temperature at LF position is 1622℃, when the slag surface fluctuates, the molten steel and the arc are not exposed, the active lime, carbide slag and fluorite briquette are added, the chemical composition is analyzed after 5 min, the alloy is added according to the target value of the chemical composition, and the coke powder carbonizer is added to increase carbon, and the alloy and the coke powder should be added to the argon stream to promote the alloy and the carbon powder to melt and homogenize quickly. When the temperature of the molten steel reaches 1556℃, the diffusion deoxidizer alumina ball is added to carry out diffusion deoxidation, and when the temperature of the molten steel reaches 1604℃, the chemical composition is analyzed for the second time to confirm the deviation of the content of each chemical element composition from the target value, after the second sample is taken away, the diffusion deoxidizer alumina ball is added to continue slagging, and the ladle temperature is 1682℃. At the same time, the white slag smelting is continued for 25 min. The slag sample after LF requires that the binary basicity R1 is 10.5, the ternary basicity R2 is 12.4, and the quaternary basicity R3 is 1.6.

[0136] In this step, the above-mentioned substances are added in the following amounts: the added alloy is 1.8 kg / t of high-carbon ferromanganese, 1.4 kg / t of high-carbon ferrochrome, 3.5 kg / t of ferromolybdenum, 2.2 kg / t of ferrovanadium, 2.4 m / t of aluminum wire, and 3.6 kg / t of ferrosilicon powder. The auxiliary materials are 9.1 kg / t of active lime, 1.2 kg / t of carbide slag, 1.0 kg / t of alumina ball, 1.0 kg / t of fluorite briquette, and 0.32 kg / t of coke powder carbonizer.

[0137] (3) VD refining

[0138] The temperature before entering the VD is 1672℃, the argon pressure is controlled at 0.1 MPa before the vacuum pump is started, the free space is 854 mm, the molten steel is not exposed with the slag surface slightly moving, the timing is started when the vacuum degree reaches 100 Pa, the holding time is 17 min, the vacuum breaking temperature is 1605℃, the chemical composition is analyzed by taking a sample of the molten steel, the alloy (high-carbon ferromanganese, high-carbon ferrochrome, ferromolybdenum, and ferrovanadium) and the auxiliary materials are added according to the target value of the chemical composition, the argon pressure is adjusted to 0.3 MPa, the time of static argon blowing is 27 min, after the static argon blowing is completed, 2.0 m / t of Φ10 mm silicon-calcium cored wire is added, and the ladle temperature is 1574℃. The auxiliary materials are 0.7 kg / t of carbonized rice husk.

[0139] (4) Continuous casting

[0140] The temperature of the ladle at the station is 1565℃ for continuous casting, the H control in the tundish is 1.2 ppm, the tundish temperature is 1525℃, the casting speed is 0.84 m / min, the whole process is protected casting, and the mold protection slag is a medium-carbon steel protection slag.

[0141] (5) Heating process

[0142] The heating process in time sequence is: entering the heating furnace at 450℃, preheating at 670℃ for 1.1h, heating at 850℃ for 1.1h, heating at 1210℃ for 1.3h, soaking at 1195℃ for 1.1h, and discharging at 1180℃.

[0143] (6) Rolling process

[0144] The blooming process of the continuous casting billet BD is as follows: using a 1150mm BD blooming mill, 3 passes, rolling reduction: turning over→1st pass high 263mm, wide 239mm, roll gap 103mm, reduction 7mm;→2nd pass high 263mm, wide 239mm, roll gap 103mm, reduction 0mm;→turning over→3rd pass high 233mm, wide 265mm, roll gap 73mm, reduction 6mm, passing through 3 850mm rolling mills and 1 735mm rolling mill, and then entering an 8-stand continuous rolling mill group.

[0145] The continuous rolling process of 9 passes is as follows: 1st pass high 229mm, wide 245mm, roll gap 53mm, rolling speed 0.27m / s; 2nd pass high 192mm, wide 235mm, roll gap 16mm, rolling speed 0.31m / s; 3rd pass high 200mm, wide 195mm, roll gap 24mm, rolling speed 0.35m / s; 4th pass high 160mm, wide 214.7mm, roll gap 10mm, rolling speed 0.474m / s; 5th pass high 168mm, wide 174.6mm, roll gap 12mm, rolling speed 0.598m / s; 6th pass high 120mm, wide 187.6mm, roll gap 14mm, rolling speed 0.743m / s; 7th pass high 142mm, wide 138.5mm, roll gap 22mm, rolling speed 0.934m / s; 8th pass high 111mm, wide 151.5mm, roll gap 17mm, rolling speed 1.102m / s; 9th pass high 122.04mm, wide 122.04mm, roll gap 7.44mm, rolling speed 1.217m / s; and the finished product is discharged after 9 passes.

[0146] (7) Soaking process

[0147] The soaking process is as follows: the steel is soaked at 610℃ for 52h in a soaking pit, and the pit temperature is 120℃.

[0148] (8) Heat treatment

[0149] The steel after soaking is subjected to heat treatment, and the heat treatment comprises the following steps:

[0150] 1) first quenching at 900℃ for 0.9h and oil cooling;

[0151] 2) tempering: 630°C, 2h, air cooling.

[0152] Results of finished product inspection of examples 1-5, 2 samples per heat of steel were inspected

[0153] (1) Macrostructure of Φ120mm size (finished steel obtained by holding process)

[0154] (2) Non-metallic inclusions of Φ120mm size (finished steel obtained by holding process)

[0155] (3) Mechanical properties of Φ120mm size (finished steel obtained after heat treatment)

Claims

1. A steel bar for a rotor of an automotive compressor, characterized by, By mass percent: C: 0.31% to 0.36%, Si: 0.20% to 0.35%, Mn: 0.42% to 0.60%, P: ≤0.015%, S: ≤0.010%, Cr: 1.02% to 1.20%, Ni: ≤0.25%, Mo: 0.21% to 0.28%, V: 0.11% to 0.18%, Cu: ≤0.15%, balance of iron and inevitable impurities.

2. A method of producing a steel bar for a rotor of an automotive compressor as claimed in claim 1, characterized in that, Comprising the following steps: The process route is: electric furnace smelting + LF furnace refining + VD refining + continuous casting billet → heating furnace heating → rolling → heat preservation; The electric furnace smelting is: smelting with 60wt% to 65wt% molten iron and 35wt% to 40wt% scrap steel; oxygen oxidation, vigorous boiling, automatic slag flow, full melting temperature 1590 to 1600℃, tapping temperature 1675 to 1685℃, C 0.03 to 0.08wt% at tapping time, P ≤0.010wt%, auxiliary materials and alloys are added at 1 / 4 to 1 / 3 of tapping time; The LF furnace refining is: using 20000 to 25000A large current to heat and slag, refining time 70 to 75min, to LF position temperature 1518 to 1625℃, when the slag surface fluctuates, the molten steel and the electric arc are not exposed, active lime, carbide slag and fluorite briquettes are supplemented, after 4 to 6min, the first sampling analysis of chemical composition is carried out, according to the chemical composition target value, alloys are supplemented, coke powder carbonizer powder should be added to argon stream to promote rapid melting and homogenization of alloys and coke powder; when the molten steel temperature reaches 1550 to 1560℃, diffusion deoxidizer alumina balls are added for diffusion deoxidation, when the molten steel temperature reaches 1600 to 1610℃, the second sampling analysis of chemical composition is carried out to confirm the deviation of each chemical element composition from the target value requirement, after the second sampling is taken away, diffusion deoxidizer alumina balls are supplemented to continue slag adjustment, the ladle temperature is 1675 to 1685℃; at the same time, white slag smelting is continued for 20 to 30min; LF post slag sample basicity requirement: binary basicity R1 ≥10, ternary basicity R2 ≥12, quaternary basicity R3 ≥1.5; The VD refining is: temperature before entering VD 1670 to 1675℃, argon pressure is controlled at 0.1 to 0.3MPa before vacuum pump starts, free space 850 to 860mm, with slag surface micro-motion, the molten steel is not exposed, when the vacuum degree reaches 95 to 100Pa, the timing starts, the holding time is 15 to 20min, the breaking vacuum temperature is 1600 to 1610℃, the molten steel sample is analyzed for chemical composition, according to the chemical composition target value, alloys and auxiliary materials are supplemented, at the same time, the argon pressure is adjusted to 0.3 to 0.5MPa, the static argon blowing time is 25 to 30min, after static argon blowing is finished, Φ10 to Φ12mm silicon-calcium cored wire 2.0 to 2.1m / t is added, the ladle temperature is 1570 to 1578℃; auxiliary materials: carbonized rice husk 0.7 to 0.8kg / t. ​ 3. The preparation method according to claim 2, characterized in that, In the electric furnace smelting, the alloy ton steel addition amount: aluminum iron 1.2~1.3Kg / t, high carbon ferromanganese 4~4.1Kg / t, high carbon ferrochrome 14~15Kg / t; auxiliary material ton steel addition amount: alumina ball 4~4.1Kg / t, coke powder carbonizer 0.6~0.7Kg / t, electric furnace foaming agent 2.6~2.7Kg / t, tapping hole filler 1.0~1.1Kg / t, active lime 32~33Kg / t.

4. The production method according to claim 2, characterized by, In the LF furnace refining, the alloy addition amount is: high carbon ferromanganese 1.8~1.9kg / t, high carbon ferrochrome 1.4~1.5kg / t, ferromolybdenum 3.5~3.6kg / t, ferrovanadium 2.2~2.3kg / t, aluminum wire 2.4~2.5m / t, silicon iron powder 3.6~3.7kg / t; the auxiliary material addition amount is: active lime 9~9.5kg / t, carbide slag 1.2~1.3kg / t, alumina ball 1.0~1.1kg / t, fluorite briquette 1.0~1.1kg / t, coke powder carbonizer 0.3~0.35kg / t.

5. The preparation method according to claim 2, characterized in that, The continuous casting is: the ladle to station temperature continuous casting 1560~1570℃, the tundish H control ≤2ppm, the tundish temperature 1524℃~1527℃, the pulling speed 0.83~0.85m / min, the whole process protection casting, the crystallizer protection slag uses medium carbon steel protection slag.

6. The preparation method according to claim 2, characterized in that, The time sequence heating process is: the entering heating furnace temperature 350℃~500℃, the preheating section temperature requirement 650℃~700℃, the time 1.0~1.2h; the heating 2 section temperature requirement 840℃~860℃, the time 1.0~1.2h; the heating 1 section temperature requirement 1190℃~1220℃, the time 1.2~1.5h; the soaking section temperature requirement 1180℃~1210℃, the time 1.0~1.2h; the tapping temperature 1170℃~1190℃.

7. The preparation method according to claim 2, characterized in that, The rolling includes continuous casting billet BD blooming process and continuous rolling process; The continuous casting billet BD blooming process: adopting the blooming mill blooming, rolling 3 passes, the rolling reduction: turning over the steel → the 1st pass high 263~263.1mm, wide 239~239.1mm, roll gap 103~103.1mm, reduction 7~7.1mm; → the 2nd pass high 263~263.1mm, wide 239~239.1mm, roll gap 103~103.1mm, reduction 0mm; → turning over the steel → the 3rd pass high 233~233.1mm, wide 265~265.1mm, roll gap 73~73.1mm, reduction 6~6.1mm, passing through 3 sets of 850mm rolling mill, 1 set of 735mm rolling mill, and then entering 8 sets of continuous rolling mill group rolling; 8. The preparation method according to claim 5, characterized in that, The continuous rolling process is as follows: 9 passes, the first pass high 229-229.1 mm, width 245-245.1 mm, roll gap 53-53.1 mm, rolling speed 0.27-0.28 m / s; the second pass high 192-192.1 mm, width 235-235.1 mm, roll gap 16-16.1 mm, rolling speed 0.31-0.32 m / s; the third pass high 200-200.1 mm, width 195-195.1 mm, roll gap 24-24.1 mm, rolling speed 0.35-0.351 m / s; the fourth pass high 160-160.1 mm, width 214.7-214.8 mm, roll gap 10-10.1 mm, rolling speed 0.474-0.475 m / s; the fifth pass high 168-168.1 mm, width 174.6-174.7 mm, roll gap 12-12.1 mm, rolling speed 0.598-0.599 m / s; the sixth pass high 120-120.1 mm, width 187.6-187.7 mm, roll gap 14-14.1 mm, rolling speed 0.743-0.744 m / s; the seventh pass high 142-142.1 mm, width 138.5-138.6 mm, roll gap 22-22.1 mm, rolling speed 0.934-0.935 m / s; the eighth pass high 111-111.1 mm, width 151.5-151.6 mm, roll gap 17-17.1 mm, rolling speed 1.102-1.103 m / s; the ninth pass high 122.04-122.05 mm, width 122.04-122.05 mm, roll gap 7.4-7.5 mm, rolling speed 1.217-1.218 m / s; after 9 passes, the finished product is discharged.

9. The preparation method according to claim 2, characterized in that, The heat preservation process is as follows: the steel material is preserved, the temperature of the lower preservation pit is greater than or equal to 600 DEG C, the preservation time is 48-55 h, and the discharge pit temperature is less than or equal to 150 DEG C.

10. The method of claim 2, wherein, The steel material after heat preservation is subjected to heat treatment, and the heat treatment comprises the following steps: 1) first quenching: 880-920 DEG C, heat preservation for 0.8-1.0 h, oil cooling; 2) tempering: 620-640 DEG C, heat preservation for 1.8-2.2 h, air cooling.

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