1. A production process for producing steel for an automobile door hinge by using a converter is characterized by comprising the working procedures of converter smelting, LF refining, RH refining, continuous casting, heating and rolling;

in the converter smelting process, the composition percentage of the discharged molten steel is controlled as follows: c: 0.10-0.15%, Si: 0.20-0.40%, Mn: 1.25-1.55%, P is less than or equal to 0.015%, S is less than or equal to 0.025, V: 0.015-0.045%, more than or equal to 0.020% of Al, less than or equal to 0.30% of Cr, less than or equal to 0.30% of Ni and less than or equal to 0.20% of Cu;

the RH vacuum degassing step: vacuum degree is less than 67Pa, circulating gas flow: 0.8Nm³G circulation gas flow rate not less than 1.8 Nm/min³Min, circulation gas flow rate is specifically 0.8Nm³/min-1.2Nm³/min-1.5Nm³/min-1.2Nm³/min-0.8Nm³The pure degassing time is 10-15min, the soft blowing time is 10-15min, the standing time of the molten steel is more than or equal to 15min, and the components are ensured to be within a target value range before the continuous casting and pouring of the molten steel;

the heating procedure comprises the heating temperature of 950-.

2. The production process of the steel for the automobile door hinge by the converter according to claim 1, wherein the converter smelting process comprises the following steps: controlling the charging temperature of molten iron to be more than or equal to 1270 ℃, the phosphorus content to be less than or equal to 0.140 percent, the sulfur content to be less than or equal to 0.040 percent, and controlling the mass proportion of the added molten iron to be more than or equal to 80 percent; smelting by adopting a 120-ton top-bottom combined blown converter, controlling the end point carbon component to be 0.06-0.14 percent and the end point phosphorus component to be less than or equal to 0.015 percent, carrying out deoxidation alloying on the steel tapping, and sequentially adding aluminum ingots, ferrosilicon, silicoferromanganese, medium carbon ferromanganese, ferrovanadium, synthetic slag and lime when the steel tapping is 1/4.

3. The production process of the steel for the automobile door hinge by the converter according to claim 1, wherein the LF refining process comprises the following steps: adding lime, fluorite submerged arc slagging and feeding into an aluminum wire to deoxidize and make white slag, finely adjusting white ash and fluorite in the heating process, making high-alkalinity reduction white slag, controlling the white slag making time to be 15-30 minutes, controlling the alkalinity of refining slag to be 4.0-5.5, and ensuring that smelting components C, Si, Mn and Al are controlled according to the upper limit of the following ranges: c: 0.16-0.18%, Si: 0.30-0.35%, Mn: 1.45-1.50%, Al: 0.030 to 0.045 percent.

4. The process for producing the steel for the automobile door hinge by the converter according to claim 1, wherein the continuous casting step comprises the following steps: the section of the casting blank is 200 mm/200 mm, the continuous casting of the square blank adopts full-process protection pouring, the long water opening of the steel ladle adopts argon seal protection, and the argon flow is 3.0-4.5m³H; the mold flux of the crystallizer keeps black slag operation, the water gap insertion depth is 75-120mm, the slag changing line operation is carried out, the special mold flux of peritectic steel is used, the consumption is 0.45-0.55Kg/T, the manual temperature measurement is carried out when the first tundish furnace is started for casting, the continuous and automatic temperature measurement is carried out on the tundish, the casting delta T at the low superheat degree is =15-35 ℃, and the casting speed is controlled at 1.1 +/-0.1 m/min; secondary cooling water distribution selection is carried out in an intermediate cooling mode, and the specific water amount is L/Kg.min: 0.65-0.75; the vibration waveform of the crystallizer adopts a non-sinusoidal mode, and the vibration frequency is 160-; and (3) controlling the height of the liquid level in the crystallizer: the distance from the upper opening of the crystallizer copper plate is 100 +/-5 mm; when automatic accuse flows: the allowable fluctuation range of the liquid level of the steel in the crystallizer is less than or equal to +/-3 mm; when manual flow control is performed: the allowable fluctuation range of the liquid level of the steel in the crystallizer is less than or equal to +/-5 mm; the liquid level fluctuation requirement of the crystallizer is less than or equal to +/-5 mm, the continuous fluctuation of the crystallizer exceeding +/-5 mm exceeds the casting blank identifier of 30min, and the electromagnetic stirring I =350 +/-20A, f =2.5 +/-0.5 Hz of the crystallizer; and (5) casting blank off-line stacking and slow cooling for not less than 48 hours.

5. The production process of steel for an automobile door hinge produced by a converter according to claim 1, wherein in the rolling step, the suitable specification diameter of the rolled round steel is 30-90mm, and the rolling is performed by using a continuous rolling mill set, and the rolling temperature is 950-1050 ℃.

6. The production process for producing the steel for the automobile door hinge by the converter according to any one of claims 1 to 5, wherein S is less than or equal to 0.008 percent, Mn/Si is less than or equal to 5.2 and less than or equal to 6.5 percent, and V/Al is less than or equal to 0.65 and less than or equal to 1.2 percent in the finished product of the steel for the automobile door hinge.

7. The production process of steel for automobile door hinges by using a converter as claimed in claim 6, wherein the steel for automobile door hinges has yield strength of 370-400MPa, tensile strength of 560-590MPa, low-temperature impact performance of-20 ℃ of 124-227J, and elongation after fracture of 24-30%.

8. The production process of steel for an automobile door hinge by using a converter as claimed in claim 7, wherein the steel for an automobile door hinge has a band structure of grade less than or equal to 2.5, CEV: 0.42 percent < CEV < 0.47 percent, has uniform fine-grain ferrite and pearlite structure and the grain size range of 7.5 to 10.0.

Background

At present, rare earth elements or multiple elements are commonly added to low-alloy high-strength structural steel (Q355B) to improve and enhance the mechanical properties of the steel, but with the development of economy and society, the requirement of the automobile industry on the toughness of the steel for automobile door hinges is greatly enhanced, and simultaneously, higher requirements on energy conservation and environmental protection are provided. The invention mainly adds trace alloy elements vanadium and aluminum elements, and greatly reduces the banded structure of the finished hot-rolled round steel product while ensuring the strength requirement of the product by controlling the heating process. The optimal proportion of trace alloy vanadium element and aluminum element is adjusted to reduce the production cost and improve the product stability.

Disclosure of Invention

The invention discloses a production process for producing steel for an automobile door hinge by a converter, which mainly plays roles of precipitation strengthening and grain refining by adding trace alloy vanadium element and the optimal proportion of aluminum element, keeps the content of sulfur element in the steel at 0.010-0.025 percent and controls the cutting processing performance of the material. The heating temperature and the heat preservation time of austenitizing are controlled, the rolling temperature is reduced, and conditions are provided for low-temperature austenite zone rolling. The uniform diffusion of alloy elements of the casting blank is ensured by controlling the heating process, and the segregation of the rolled material is effectively improved. Finally, the hot-rolled round steel which has higher fatigue property, high impact property, uniform structure, good weldability and better processability and is prepared by utilizing widely available alloy elements has cost advantage and benefit.

In order to achieve the purpose, the invention adopts the following technical scheme: a production process for producing steel for an automobile door hinge by using a converter comprises the working procedures of converter smelting, LF refining, RH refining, continuous casting, heating and rolling;

the components of the common steel are obtained in the converter steelmaking production, the aluminum deoxidation is carried out on the steel, a deoxidizer is added to the bottom of a steel ladle, and the percentage content of the converter crude steelmaking water is controlled as follows: c: 0.10-0.15%, Si: 0.20-0.40%, Mn: 1.25-1.55%, P is less than or equal to 0.015%, S is less than or equal to 0.025%, V: 0.015-0.045%, more than or equal to 0.020% of Al, less than or equal to 0.30% of Cr, less than or equal to 0.30% of Ni and less than or equal to 0.20% of Cu;

the RH vacuum degassing step: degassing by adopting a 120-ton RH refining furnace, adopting the processing mode for RH vacuum refining, wherein the vacuum degree is less than 67Pa, and the flow of circulating gas is as follows: 0.8Nm³G circulation gas flow rate not less than 1.8 Nm/min³The pure degassing time is 10-15min, the soft blowing time is 10-15min, the molten steel standing time is more than or equal to 15min, and before continuous casting and pouring of the molten steel, the components are ensured to be at target valuesWithin the range.

The rolling process heating procedure is used for rolling at the temperature, so that the outer surface layer and the core part of the casting blank are promoted to be uniformly deformed while the compression ratio is met. The heating procedure is to use a stepping heating furnace to heat the temperature of 1050 ℃ in the 1 section, 950 to 1160 ℃ in the heating 2 section, 1100 to 1160 ℃ in the soaking section and 120 to 240min in the heating time. The step aims to control the heating temperature and the heat preservation time of austenitizing, reduce the rolling temperature and provide conditions for low-temperature austenite zone rolling. The process ensures the uniform diffusion of alloy elements of the casting blank by controlling the heating process, and effectively improves the segregation of rolled materials.

The converter smelting process comprises the following steps: controlling the charging temperature of molten iron to be more than or equal to 1270 ℃, the phosphorus content to be less than or equal to 0.140 percent, the sulfur content to be less than or equal to 0.040 percent, and controlling the mass proportion of the added molten iron to be more than or equal to 80 percent; smelting by adopting a 120-ton top-bottom combined blown converter, controlling the end point carbon content to be 0.06% -0.14% and the end point phosphorus content to be less than or equal to 0.015%, automatically making steel by using a sublance, stopping slag and tapping by using a sliding plate, automatically detecting slag, deoxidizing and alloying the tapped steel, and sequentially adding aluminum ingots, ferrosilicon, silicoferromanganese, medium carbon ferromanganese, ferrovanadium and synthetic slag and lime when tapping 1/4.

The LF refining process comprises the following steps: adopting a 120-ton double-station LF refining furnace, feeding molten steel into the furnace, adding lime, fluorite submerged arc slagging and feeding an aluminum wire for deoxidation to produce white slag, finely adjusting white ash and fluorite in the heating process, producing high-alkalinity reduction white slag, controlling the white slag producing time to be 15-30 minutes, controlling the alkalinity of the refining slag to be 4.0-5.5, and controlling the smelting components C, Si, Mn and Al according to the upper limit of the following ranges: c: 0.16-0.18%, Si: 0.30-0.35%, Mn: 1.40-1.50%, Al: 0.030 to 0.045 percent. The purpose of LF refining is to ensure that not only does not finely adjust the components in the RH refining process, but also the target component requirements are met after RH vacuum degassing treatment.

The continuous casting process of the invention comprises the following steps: the section of the casting blank is 200 mm/200 mm, the continuous casting of the square blank adopts full-process protection pouring, the long water opening of the steel ladle adopts argon seal protection, and the argon flow is 3.0-4.5m³H is used as the reference value. The crystallizer covering slag keeps black slag operation, the water gap insertion depth is 75-120mm, the slag changing line operation is carried out, the covering slag special for peritectic steel is used, the consumption is 0.45-0.55Kg/t, manual temperature measurement is carried out when the first tundish furnace is started for pouring, and the middle temperature is measuredThe ladle continuously and automatically measures the temperature, the casting delta T of the low superheat degree is =15-35 ℃, and the drawing speed is controlled to be 1.1 +/-0.1 m/min; secondary cooling water distribution selection is carried out in an intermediate cooling mode, and the specific water amount is L/Kg.min: 0.65-0.75; the vibration waveform of the crystallizer adopts a non-sinusoidal mode, and the vibration frequency is 160-; and (3) controlling the height of the liquid level in the crystallizer: the distance from the upper opening of the crystallizer copper plate is 100 +/-5 mm; when automatic accuse flows: the allowable fluctuation range of the liquid level of the steel in the crystallizer is less than or equal to +/-3 mm; when manual flow control is performed: the allowable fluctuation range of the liquid level of the steel in the crystallizer is less than or equal to +/-5 mm; the liquid level fluctuation requirement of the crystallizer is less than or equal to +/-5 mm, the continuous fluctuation of the crystallizer exceeding +/-5 mm exceeds the casting blank identifier of 30min, and the electromagnetic stirring I =350 +/-20A, f =2.5 +/-0.5 Hz of the crystallizer; and (5) casting blank off-line stacking and slow cooling for not less than 48 hours.

According to the rolling process, the suitable specification diameter of rolled round steel is 30-90mm, a continuous rolling mill set is used for rolling, and the initial rolling temperature is 950-1050 ℃. The rolling in the temperature range aims at meeting the requirement of the thermoplastic deformation of the steel, and the steel is rolled in a low-temperature austenite region to obtain a rolled structure with fine and uniform grain size.

The proper amount of silicon and manganese in the present invention can increase the required fatigue limit of the alloy steel. The best Mn/Si is more than or equal to 5.2 and less than or equal to 6.5, and the tensile strength of the obtained steel for the automobile door hinge is more than or equal to 510 MPa. Vanadium and nitrogen, so that the carbon-nitrogen hardening is ensured, the tensile strength of the obtained round steel is more than or equal to 510MPa, and the yield strength of the obtained round steel is more than or equal to 355 MPa. Narrow component control of carbon and manganese and low-phosphorus and low-nitrogen control, and the low-temperature impact property is more than or equal to 34J (-20 ℃). Narrow component control of carbon and manganese, low phosphorus and low superheat degree pouring and rolling, and prolonged heating time, and the obtained banded structure is less than or equal to 2.5 grade. The good weldability of the material ensures that CEV is less than 0.47%, CEV = C + Mn/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15, carbon and manganese can not simultaneously take the upper limit or the lower limit of internal control, the component control is carried out, and when the diameter of the produced round steel is 30-90mm, 0.42% < CEV < 0.47% is ensured. Meanwhile, the lower limit of the sulfur content is increased, and the processing performance of the material is improved according to the target value control.

The finished steel product for the automobile door hinge has the advantages that S is less than or equal to 0.008 percent, Mn/Si is less than or equal to 6.5 percent and is less than or equal to 5.2 percent, and V/Al is less than or equal to 1.2 and is less than or equal to 0.65.

The steel for the automobile door hinge has the yield strength of 370-400MPa, the tensile strength of 560-590MPa, and the low-temperature impact performance of-20 ℃ of 124-227J.

The steel for the automobile door hinge has a banded structure less than or equal to 2.5 grades, a CEV: 0.42 percent < CEV < 0.47 percent, has uniform fine-grain ferrite and pearlite structure and the grain size range of 7.5 to 10.0.

The key processing steps of the invention are characterized in that: through RH degassing treatment, the circulation gas flow rate was in a small-medium-small mode (0.8 Nm)³/min-1.2Nm³/min-1.5Nm³/min-1.2Nm³/min-0.8Nm³/min) are sequentially processed. The continuous casting adopts non-sinusoidal vibration and a vibration mode with high vibration frequency and small amplitude to improve the lubricating effect of the casting powder, the vibration frequency is 180 times/min, and the amplitude is +/-3 mm.

Adopt the produced beneficial effect of above-mentioned technical scheme to lie in: according to the invention, through RH degassing treatment, control of narrow components of carbon and manganese, a high-vibration-frequency small-amplitude vibration mode, crystallizer electric stirring application, low-superheat pouring and rolling process optimized heating temperature and time optimized process are adopted for continuous casting, and ferrite and pearlite structures with uniform tissues and fine grain sizes are obtained.

Drawings

FIG. 1 is a metallographic structure diagram of steel for an automobile door hinge according to the present invention.

Detailed Description

The production process of the steel for the automobile door hinge by the converter comprises the working procedures of converter smelting, LF refining, RH refining, continuous casting, heating and rolling.

The technical solution of the present patent will be further described in detail with reference to the following embodiments.

Example 1

(1) Smelting in a converter: the charging temperature of molten iron is 1275 ℃, the phosphorus content is 0.140 percent, the sulfur content is 0.040 percent, and the mass proportion of the added molten iron is 85 percent; smelting by adopting a 120-ton top-bottom combined blown converter, automatically making steel by using a sublance, stopping slag and tapping by using a sliding plate, automatically detecting slag, carrying out deoxidation alloying on the tapped steel, and sequentially adding aluminum ingots, ferrosilicon, ferro-silico-manganese, medium carbon ferromanganese, ferrovanadium, synthetic slag and lime when tapping 1/4;

the converter crude steelmaking water comprises the following components in percentage by weight: c: 0.13%, Si: 0.20%, Mn: 1.25%, P: 0.012%, S: 0.030%, V: 0.028%, Al: 0.022%, Cr: 0.03%, Ni: 0.010%, Cu: 0.013%, wherein Mn/Si: 6.2.

(2) LF refining: adopt 120 tons of duplex position LF fineries, molten steel is gone into the station and is added lime, fluorite submerged arc slagging and feeding aluminum wire and deoxidize and make white sediment and handle, and the intensification process fine setting lime, fluorite make high basicity reduction white sediment, and control makes white sediment time 15 minutes, control refining slag basicity 4.2, smelt composition C: 0.15%, Si: 0.30%, Mn: 1.40%, Al: 0.045%.

(3) RH vacuum degassing process: degassing by adopting a 120-ton RH refining furnace, wherein RH vacuum refining adopts the treatment mode, the vacuum degree is 60Pa, and the flow of circulating gas is as follows: 1.0Nm³The method comprises the following steps of/min, pure degassing time of 12min, soft blowing time of 12min, molten steel standing time of 18 min, and ensuring that components are within a target value range before continuous casting and pouring of the molten steel.

(4) And (3) continuous casting process: the continuous casting of square billets (casting billet cross section 200mm x 200 mm) adopts full-process protection pouring, the long ladle nozzle adopts argon seal protection, and the argon flow is 3.0m³H is used as the reference value. The mold flux of the crystallizer keeps black slag operation, the water gap insertion depth is 80mm, the slag changing line operation is carried out, the special mold flux of peritectic steel is used, the consumption is 0.45Kg/T, manual temperature measurement is carried out when the first tundish furnace is started for casting, continuous and automatic temperature measurement is carried out on the tundish, the casting delta T with low superheat degree is =20 ℃, and the casting speed is 1.2 m/min; secondary cooling water distribution is selected by an intermediate cooling mode, and the specific water amount is 0.65L/Kg.min; the vibration waveform of the crystallizer adopts a non-sinusoidal mode, and the liquid level in the crystallizer is controlled according to the standard: the distance from the upper opening of the crystallizer copper plate is 100 +/-5 mm; when automatic accuse flows: the allowable fluctuation range of the liquid level of the steel in the crystallizer is less than or equal to +/-3 mm; when manual flow control is performed: the allowable fluctuation range of the liquid level of the steel in the crystallizer is less than or equal to +/-5 mm; the liquid level fluctuation requirement of the crystallizer is less than or equal to +/-5 mm, the continuous fluctuation of the crystallizer exceeding +/-5 mm exceeds the casting blank identifier of 30min, and the electromagnetic stirring I =350 +/-20A, f =2.5 +/-0.5 Hz of the crystallizer; and (5) stacking and slowly cooling the casting blank off the line for 48 hours.

(5) A heating procedure of a rolling process: a stepping heating furnace is used for heating the 1-section temperature to 1050 ℃, the 2-section temperature to 1050 ℃, the soaking section temperature to 1100 ℃ and the heating time to 240 min. The suitable specification diameter of rolled round steel is 30mm, the rolling is carried out by using a continuous rolling mill set, and the initial rolling temperature is 1050 ℃.

Steel for automobile door hinges, wherein S: 0.004%, Mn/Si: 6.2, V/Al: 0.88, yield strength 399MPa, tensile strength 576MPa, low-temperature impact property at-20 ℃ 124.6J, elongation after fracture 29.5%, ribbon structure 2.0 grade, CEV: 0.44 percent, has a uniform fine-grained ferrite plus pearlite structure, and has the grain size range of 8.0.

Example 2

(1) Smelting in a converter: the charging temperature of molten iron is 1295 ℃, the phosphorus content is 0.110 percent, the sulfur content is 0.030 percent, and the mass proportion of the added molten iron is 85 percent; smelting by adopting a 120-ton top-bottom combined blown converter, automatically making steel by using a sublance, stopping slag and tapping by using a sliding plate, automatically detecting slag, carrying out deoxidation alloying on the tapped steel, and sequentially adding aluminum ingots, ferrosilicon, ferro-silico-manganese, medium carbon ferromanganese, ferrovanadium, synthetic slag and lime when tapping 1/4;

the converter crude steelmaking water comprises the following components in percentage by weight: c: 0.11%, Si: 0.20%, Mn: 1.35%, P: 0.009%, S: 0.020%, V: 0.027%, Al: 0.026%, Cr: 0.026%, Ni: 0.009%, Cu: 0.014%, wherein Mn/Si: 6.5.

(2) LF refining: adopt 120 tons of duplex position LF fineries, molten steel is gone into the station and is added lime, fluorite submerged arc slagging and feeding aluminum wire and deoxidize and make white sediment and handle, and the white ash, fluorite are finely tuned in the intensification process, make high basicity reduction white sediment, and the white sediment time of controlling to make is 20 minutes, and control refining slag basicity 4.4, smelt composition C: 0.16%, Si: 0.32%, Mn: 1.42%, Al: 0.040%.

(3) RH vacuum degassing process: degassing by adopting a 120-ton RH refining furnace, wherein RH vacuum refining adopts the treatment mode, the vacuum degree is 65Pa, and the flow of circulating gas is as follows: 1.5Nm³The method comprises the following steps of/min, pure degassing time 10min, soft blowing time 12min, molten steel standing time 15min, and ensuring that components are within a target value range before continuous casting and pouring of the molten steel.

(4) And (3) continuous casting process: the continuous casting of square billets (casting billet cross section 200mm x 200 mm) adopts full-process protection pouring, the long ladle nozzle adopts argon seal protection, and the argon flow is 4.5m³H is used as the reference value. The mold flux of the crystallizer keeps black slag operation, the water gap insertion depth is 100mm, the slag changing line operation is carried out, the special mold flux of peritectic steel is used, the consumption is 0.47Kg/t, manual temperature measurement is carried out when the first tundish furnace is started for casting, continuous and automatic temperature measurement is carried out on the tundish, and low overheating is achievedCasting delta T =20 ℃, and the casting speed is 1.2 m/min; secondary cooling water distribution is carried out in an intermediate cooling mode, and the specific water amount is 0.70L/Kg.min; the vibration waveform of the crystallizer adopts a non-sinusoidal mode, and the liquid level in the crystallizer is controlled according to the standard: the distance from the upper opening of the crystallizer copper plate is 100 +/-5 mm; when automatic accuse flows: the allowable fluctuation range of the liquid level of the steel in the crystallizer is less than or equal to +/-3 mm; when manual flow control is performed: the allowable fluctuation range of the liquid level of the steel in the crystallizer is less than or equal to +/-5 mm; the liquid level fluctuation requirement of the crystallizer is less than or equal to +/-5 mm, the continuous fluctuation of the crystallizer exceeding +/-5 mm exceeds the casting blank identifier of 30min, and the electromagnetic stirring I =350 +/-20A, f =2.5 +/-0.5 Hz of the crystallizer; and (5) casting blank off-line stacking and slow cooling for 50 hours.

(5) A heating procedure of a rolling process: a step-type heating furnace is used for heating the 1-section temperature to 1050 ℃, the 2-section temperature to 1050 ℃, the soaking section temperature to 1140 ℃ and the heating time to 180 min. The suitable specification diameter of the rolled round steel is 60mm, the rolling is carried out by using a continuous rolling mill set, and the initial rolling temperature is 1000 ℃.

Steel for automobile door hinges, wherein S: 0.003%, Mn/Si: 6.5, V/Al: 1.0, yield strength 374MPa, tensile strength 560MPa, low-temperature impact property at-20 ℃ of 125.3J, elongation after fracture of 26%, band-shaped structure 2.5 grade, CEV: 0.44 percent, has a uniform fine-grained ferrite plus pearlite structure, and has the grain size range of 8.5.

Example 3

(1) Smelting in a converter: the charging temperature of the molten iron is 1300 ℃, the phosphorus content is 0.100 percent, the sulfur content is 0.026 percent, and the mass proportion of the molten iron is 80 percent; smelting by adopting a 120-ton top-bottom combined blown converter, automatically making steel by using a sublance, stopping slag and tapping by using a sliding plate, automatically detecting slag, carrying out deoxidation alloying on the tapped steel, and sequentially adding aluminum ingots, ferrosilicon, ferro-silico-manganese, medium carbon ferromanganese, ferrovanadium, synthetic slag and lime when tapping 1/4;

the converter crude steelmaking water comprises the following components in percentage by weight: c: 0.12%, Si: 0.23%, Mn: 1.25%, P: 0.011%, S: 0.018%, V: 0.035%, Al: 0.035%, Cr: 0.009%, Ni: 0.012%, Cu: 0.017% in which Mn/Si: 5.4.

(2) LF refining: adopt 120 tons of duplex position LF fineries, molten steel is gone into the station and is added lime, fluorite submerged arc slagging and feeding aluminum wire and deoxidize and make white sediment and handle, and the white ash, fluorite are finely tuned in the intensification process, make high basicity reduction white sediment, and the white sediment time of controlling making is 22 minutes, and control refining slag basicity 5.0, smelt composition C: 0.16%, Si: 0.32%, Mn: 1.47%, Al: 0.042 percent.

(3) RH vacuum degassing process: degassing by adopting a 120-ton RH refining furnace, wherein RH vacuum refining adopts the treatment mode, the vacuum degree is 65Pa, and the flow of circulating gas is as follows: 0.8Nm³The method comprises the following steps of/min, pure degassing time 15min, soft blowing time 12min, molten steel standing time 18 min, and ensuring that the components are within a target value range before the molten steel is continuously cast and poured.

(4) And (3) continuous casting process: the continuous casting of square billets (casting billet cross section 200mm x 200 mm) adopts full-process protection pouring, the long ladle nozzle adopts argon seal protection, and the argon flow is 3.8m³H is used as the reference value. The mold flux of the crystallizer keeps black slag operation, the water gap insertion depth is 120mm, the slag changing line operation is carried out, the special mold flux of peritectic steel is used, the consumption is 0.45Kg/T, manual temperature measurement is carried out when the first tundish furnace is started for casting, continuous and automatic temperature measurement is carried out on the tundish, the casting delta T with low superheat degree is =25 ℃, and the casting speed is 1.2 m/min; secondary cooling water distribution is carried out in an intermediate cooling mode, and the specific water amount is 0.70L/Kg.min; the vibration waveform of the crystallizer adopts a non-sinusoidal mode, and the liquid level in the crystallizer is controlled according to the standard: the distance from the upper opening of the crystallizer copper plate is 100 +/-5 mm; when automatic accuse flows: the allowable fluctuation range of the liquid level of the steel in the crystallizer is less than or equal to +/-3 mm; when manual flow control is performed: the allowable fluctuation range of the liquid level of the steel in the crystallizer is less than or equal to +/-5 mm; the liquid level fluctuation requirement of the crystallizer is less than or equal to +/-5 mm, the continuous fluctuation of the crystallizer exceeding +/-5 mm exceeds the casting blank identifier of 30min, and the electromagnetic stirring I =350 +/-20A, f =2.5 +/-0.5 Hz of the crystallizer; and (5) stacking and slowly cooling the casting blank off the line for 52 hours.

(5) A heating procedure of a rolling process: a stepping heating furnace is used for heating the 1-section temperature to 1050 ℃, the 2-section temperature to 1150 ℃, the soaking section temperature to 1150 ℃ and the heating time to 120 min. The suitable specification diameter of rolled round steel is 70mm, the rolled round steel is rolled by a continuous rolling mill set, and the initial rolling temperature is 1050 ℃.

Steel for automobile door hinges, wherein S: 0.005%, Mn/Si: 6.2, V/Al: 1.2, yield strength 396MPa, tensile strength 590MPa, low-temperature impact property 226.7J at-20 ℃, elongation after fracture 28%, band-shaped structure 2.5 grade, CEV: 0.45 percent, has a uniform fine-grained ferrite and pearlite structure, and has the grain size range of 9.0.

Example 4

(1) Smelting in a converter: the charging temperature of molten iron is 1310 ℃, the phosphorus content is 0.130%, the sulfur content is 0.035%, and the molten iron is added according to the mass proportion of 85%; smelting by adopting a 120-ton top-bottom combined blown converter, automatically making steel by using a sublance, stopping slag and tapping by using a sliding plate, automatically detecting slag, carrying out deoxidation alloying on the tapped steel, and sequentially adding aluminum ingots, ferrosilicon, ferro-silico-manganese, medium carbon ferromanganese, ferrovanadium, synthetic slag and lime when tapping 1/4;

the converter crude steelmaking water comprises the following components in percentage by weight: c: 0.12%, Si: 0.25%, Mn: 1.28%, P: 0.013%, S: 0.024%, V: 0.032%, Al: 0.030%, Cr: 0.02%, Ni: 0.015%, Cu: 0.003%, wherein Mn/Si: 5.2.

(2) LF refining: adopt 120 tons of duplex position LF fineries, molten steel is gone into the station and is added lime, fluorite submerged arc slagging and feeding aluminum wire and deoxidize and make white sediment and handle, and the white ash, fluorite are finely tuned in the intensification process, make high basicity reduction white sediment, and control makes white sediment time 25 minutes, control refining slag basicity 4.4, smelt composition C: 0.15%, Si: 0.30%, Mn: 1.42%, Al: 0.044 percent.

(3) RH vacuum degassing process: degassing by adopting a 120-ton RH refining furnace, wherein RH vacuum refining adopts the treatment mode, the vacuum degree is 65Pa, and the flow of circulating gas is as follows: 1.2Nm³The method comprises the following steps of/min, pure degassing time 13min, soft blowing time 12min, molten steel standing time 15min, and ensuring that components are within a target value range before continuous casting and pouring of the molten steel.

(4) And (3) continuous casting process: the continuous casting of square billets (casting billet cross section 200mm x 200 mm) adopts full-process protection pouring, the long ladle nozzle adopts argon seal protection, and the argon flow is 3.8m³H is used as the reference value. The mold flux of the crystallizer keeps black slag operation, the water gap insertion depth is 120mm, the slag changing line operation is carried out, the special mold flux of peritectic steel is used, the consumption is 0.47Kg/T, manual temperature measurement is carried out when the first tundish furnace is started for casting, continuous and automatic temperature measurement is carried out on the tundish, the casting delta T with low superheat degree is =28 ℃, and the casting speed is 1.2 m/min; secondary cooling water distribution is carried out in an intermediate cooling mode, and the specific water amount is 0.70L/Kg.min; the vibration waveform of the crystallizer adopts a non-sinusoidal mode, and the liquid level in the crystallizer is controlled according to the standard: the distance from the upper opening of the crystallizer copper plate is 100 +/-5 mm; when automatic accuse flows: the allowable fluctuation range of the liquid level of the steel in the crystallizer is less than or equal to +/-3 mm; when manual flow control is performed: allowable fluctuation range of steel liquid level in crystallizerLess than or equal to +/-5 mm; the liquid level fluctuation requirement of the crystallizer is less than or equal to +/-5 mm, the continuous fluctuation of the crystallizer exceeding +/-5 mm exceeds the casting blank identifier of 30min, and the electromagnetic stirring I =350 +/-20A, f =2.5 +/-0.5 Hz of the crystallizer; and (5) stacking and slowly cooling the casting blank off the line for 48 hours.

(5) A heating procedure of a rolling process: a stepping heating furnace is used for heating the 1-section temperature to 1050 ℃, the 2-section temperature to 1150 ℃, the soaking section temperature to 1160 ℃ and the heating time to 120 min. The suitable specification diameter of rolled round steel is 80mm, the rolled round steel is rolled by a continuous rolling mill set, and the initial rolling temperature is 1050 ℃.

Steel for automobile door hinges, wherein S: 0.003%, Mn/Si: 5.2, V/Al: 0.92, yield strength 396MPa, tensile strength 590MPa, low-temperature impact property at-20 ℃ of 163.3J, elongation after fracture of 24%, band structure 2.5 grade, CEV: 0.45 percent, has a uniform fine-grained ferrite and pearlite structure, and has the grain size range of 9.0.

Example 5

(1) Smelting in a converter: molten iron charging temperature is 1330 ℃, phosphorus content is 0.090%, sulfur content is 0.029%, and molten iron adding mass ratio is 80%; smelting by adopting a 120-ton top-bottom combined blown converter, automatically making steel by using a sublance, stopping slag and tapping by using a sliding plate, automatically detecting slag, carrying out deoxidation alloying on the tapped steel, and sequentially adding aluminum ingots, ferrosilicon, ferro-silico-manganese, medium carbon ferromanganese, ferrovanadium, synthetic slag and lime when tapping 1/4;

the converter crude steelmaking water comprises the following components in percentage by weight: c: 0.12%, Si: 0.25%, Mn: 1.35%, P: 0.010%, S: 0.020%, V: 0.033%, Al: 0.038%, Cr: 0.009%, Ni: 0.018%, Cu: 0.013%, wherein Mn/Si: 5.4.

(2) LF refining: adopt 120 tons of duplex position LF fineries, molten steel is gone into the station and is added lime, fluorite submerged arc slagging and feeding aluminum wire and deoxidize and make white sediment and handle, and the white ash, fluorite are finely tuned in the intensification process, make high basicity reduction white sediment, and the white sediment time of controlling making is 22 minutes, and control refining slag basicity 4.8, smelt composition C: 0.16%, Si: 0.32%, Mn: 1.45%, Al: 0.041 percent.

(3) RH vacuum degassing process: degassing by adopting a 120-ton RH refining furnace, wherein RH vacuum refining adopts the treatment mode, the vacuum degree is 65Pa, and the flow of circulating gas is as follows: 1.2Nm³Min, pure degassing time of 12min, soft blowing time of 13min,the standing time of the molten steel is 20 minutes, and the components are ensured to be within a target value range before the molten steel is continuously cast and poured.

(4) And (3) continuous casting process: the continuous casting of square billets (casting billet cross section 200mm x 200 mm) adopts full-process protection pouring, the long ladle nozzle adopts argon seal protection, and the argon flow is 3.8m³H is used as the reference value. The mold flux of the crystallizer keeps black slag operation, the water gap insertion depth is 120mm, the slag changing line operation is carried out, the special mold flux of peritectic steel is used, the consumption is 0.47Kg/T, manual temperature measurement is carried out when the first tundish furnace is started for casting, continuous and automatic temperature measurement is carried out on the tundish, the casting delta T with low superheat degree is =32 ℃, and the casting speed is 1.1 m/min; secondary cooling water distribution is carried out in an intermediate cooling mode, and the specific water amount is 0.70L/Kg.min; the vibration waveform of the crystallizer adopts a non-sinusoidal mode, and the liquid level in the crystallizer is controlled according to the standard: the distance from the upper opening of the crystallizer copper plate is 100 +/-5 mm; when automatic accuse flows: the allowable fluctuation range of the liquid level of the steel in the crystallizer is less than or equal to +/-3 mm; when manual flow control is performed: the allowable fluctuation range of the liquid level of the steel in the crystallizer is less than or equal to +/-5 mm; the liquid level fluctuation requirement of the crystallizer is less than or equal to +/-5 mm, the continuous fluctuation of the crystallizer exceeding +/-5 mm exceeds the casting blank identifier of 30min, and the electromagnetic stirring I =350 +/-20A, f =2.5 +/-0.5 Hz of the crystallizer; and (5) casting blank off-line stacking and slow cooling for 50 hours.

(5) A heating procedure of a rolling process: a stepping heating furnace is used for heating the 1-section temperature to 1050 ℃, the 2-section temperature to 1160 ℃, the soaking section temperature to 1160 ℃ and the heating time to 120 min. The suitable specification diameter of rolled round steel is 90mm, the rolled round steel is rolled by a continuous rolling mill set, and the initial rolling temperature is 1050 ℃.

Steel for automobile door hinges, wherein S: 0.004%, Mn/Si: 5.6, V/Al: 0.65, yield strength 391MPa, tensile strength 577MPa, low-temperature impact property at-20 ℃ of 160J, elongation after fracture of 27%, band-shaped structure 2.5 grade, CEV: 0.45 percent of the steel, has a uniform fine-grain ferrite and pearlite structure, and has the grain size range of 8.5.

Although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that: modifications and equivalents may be made thereto without departing from the spirit and scope of the invention and it is intended to cover in the claims the invention as defined in the appended claims.