CN-122013029-A - Grain refinement smelting process of 20 CrMnTiSH1-H5 steel

CN122013029ACN 122013029 ACN122013029 ACN 122013029ACN-122013029-A

Abstract

The invention relates to the technical field of steel smelting, and discloses a grain refining smelting process of 20 CrMnTiSH1-H5 steel, which comprises an S1 raw material pretreatment stage, an S2 converter smelting stage, an S3 refining purification stage, an S4 continuous casting process optimization stage, an S5 heating and refining auxiliary stage and an S6 quality inspection and control stage, wherein the process realizes raw material purification and slag formation optimization, lays a grain refining foundation, and effectively reduces the contents of harmful elements of phosphorus, sulfur and boron and nonmetallic inclusion by strictly screening high-purity raw materials (waste steel purity is more than or equal to 99.5%), magnetic separation impurity removal and low-boron pre-slag precise proportioning (alkalinity is 3.5-5.0), fully adsorbs impurities for subsequent grain refining, eliminates 'pollution sources', and double purification of raw materials and pre-slag, ensures that the size of the inclusion in the steel is less than or equal to 8 mu m, and provides a clean matrix for uniform growth of grains.

Inventors

LUO JINGXIAN
DU JIANG
YUAN LIN
Pan Xiquan
WU MIN
HUANG ZHENHUA
LUO XIAO
YUAN YUAN

Assignees

湖南华菱湘潭钢铁有限公司

Dates

Publication Date: 20260512
Application Date: 20260226

Claims (10)

1. A grain refining smelting process of 20 CrMnTiSH1-H5 steel comprises an S1 raw material pretreatment stage, an S2 converter smelting stage, an S3 refining purification stage, an S4 continuous casting process optimization stage, an S5 heating and refining auxiliary stage and an S6 quality inspection and control stage, and is characterized in that the S1 raw material pretreatment stage comprises an S1.1 raw material screening and purifying stage and an S1.2 premelting slag preparation stage; wherein the S2 converter smelting stage comprises S2.1 smelting and temperature control and S2.2 primary deoxidation process; wherein, the S3 refining and purifying stage comprises S3.1 LF furnace refining, S3.2 vacuum degassing treatment and precise regulation and control of S3.3 components; the optimization stage of the S4 continuous casting process comprises S4.1 continuous casting blank specification and charging, S4.2 continuous casting process parameter control and S4.3 casting blank slow cooling treatment; Wherein the S5 heating and refining auxiliary stage comprises S5.1 homogenizing heating and S5.2 microalloying strengthening refining; The S6 quality inspection and control stage comprises S6.1 grain size detection, S6.2 organization and inclusion inspection and S6.3 mechanical property verification.
2. The grain refining smelting process of 20 CrMnTiSH1-H5 steel, as set forth in claim 1, is characterized in that the S1.1 raw material is selected and purified: Selecting low-phosphorus, low-sulfur and low-boron high-quality scrap steel and alloy materials, wherein key parameters are that the purity of the scrap steel is more than or equal to 99.5%, the phosphorus content is less than or equal to 0.010%, the sulfur content is less than or equal to 0.008%, the boron content of the alloy materials (ferrochrome, ferromanganese and ferrotitanium) is less than or equal to 0.0003%, and the purity of titanium in ferrotitanium is more than or equal to 99.0%, taking care that the raw materials are subjected to magnetic separation and impurity removal before entering the field to remove metal oxide and nonmetallic inclusion impurities; S1.2, preparation of premelting slag: The low-boron premelting slag is adopted for slag making, the key parameters are premelting slag alkalinity (CaO/SiO 2 ）3.5-5.0,Al 2 O 3 content is 15-25%, mgO content is 8-12%, water content is less than or equal to 0.5%, premelting slag granularity is 5-20mm, baking is carried out in advance until 150-250 ℃ and heat preservation is carried out for 2-4 hours, and moisture and adsorbed gas are removed, and the attention is paid to that premelting slag is added in batches, so that the sudden drop of the temperature of a molten pool caused by one-time addition is avoided.
3. The grain refining smelting process of 20 CrMnTiSH1-H5 steel, as set forth in claim 1, is characterized in that the S2.1 smelting and temperature control: The method adopts a top-bottom combined blown converter for smelting, and has the key parameters of matching the charging amount according to the furnace volume, the molten iron proportion being 85-90%, the oxygen blowing strength being 3.0-4.0m 3 /(t-min), the end point carbon content being 0.04-0.08%, the end point temperature being 1620-1680 ℃, the heating rate being controlled at 40-60 ℃ per min, avoiding local overheating, taking care that the temperature and the carbon content of a molten pool are monitored in real time in the blowing process, and the end point parameters are accurately controlled by adjusting the height of an oxygen lance and the oxygen blowing flow; S2.2, primary deoxidation process: The key parameters of precipitation deoxidization are that 0.8-1.5kg/t of aluminum iron is added when the tapping amount reaches 1/3, the aluminum iron purity is more than or equal to 98% in the late tapping stage, the tapping time is 8-12min, the argon protection is carried out in the tapping process, the argon flow is 0.3-0.8m 3 /h, the taking care is that slag is avoided from being discharged, the slag amount is less than or equal to 0.5%, and slag back phosphorus and sulfur are prevented.
4. The grain refining smelting process of 20 CrMnTiSH1-H5 steel, which is characterized in that the S3.1 LF furnace is used for refining: Transferring molten steel into an LF furnace for refining, wherein key parameters are refining time is 60-90min, argon stirring flow is 0.6-1.5m 3 /h (early strong stirring and later weak stirring), slag forming agent adding amount is 3-5kg/t, slag thickness is kept to be 8-15mm, white slag keeping time is 30-50min, diffusion deoxidization adopts silicon carbide and aluminum particle composite deoxidization, silicon carbide adding amount is 1.0-2.0kg/t, aluminum particle adding amount is 0.3-0.6kg/t, and precautions are that detecting components are sampled every 15min in refining process, and alloy adding amount is timely adjusted.
5. The grain refining smelting process of 20 CrMnTiSH1-H5 steel, as set forth in claim 1, is characterized in that the S3.2 vacuum degassing treatment: the vacuum degassing process includes vacuum degree less than or equal to 67Pa, vacuum time of 15-25min, molten steel temperature 1580-1620 deg.c before vacuum treatment, vacuum treatment temperature drop of 30-50 deg.c, soft blowing argon for 25-40min after breaking, argon flow rate of 0.5-1.0m 3 /h, and the maintaining matters include avoiding molten steel exposure during vacuum treatment, preventing secondary oxidation, ensuring molten steel level to be stable during soft blowing and no obvious rolling.
6. The grain refinement smelting process of 20 CrMnTiSH1-H5 steel, which is disclosed in claim 1, is characterized in that the S3.3 component is accurately regulated: The alloy components are optimized to promote grain refinement, the key parameters are C0.16-0.24%, mn 0.85-1.20%, cr 1.00-1.40%, ti 0.03-0.08%, si less than or equal to 0.25%, residual element Cu less than or equal to 0.18%, ni less than or equal to 0.22%, B less than or equal to 0.0003%, gas content control is that O less than or equal to 10ppm, N less than or equal to 65ppm, H less than or equal to 1.8ppm, notes are that Ti alloy is added after vacuum treatment, oxidation burning loss caused by early addition is avoided, and quenching and grain refinement effects are balanced by adjusting Mn/Cr proportion.
7. The grain refining smelting process of 20 CrMnTiSH1-H5 steel, as set forth in claim 1, is characterized in that the S4.1 continuous casting billet specification and charging: The method adopts square billet continuous casting, and has the key parameters that the section of the continuous casting billet is 260 multiplied by 260 to 300 multiplied by 300mm, the length is 6 to 9m, the surface of the casting billet is cleaned and then is charged, the cleaning depth is less than or equal to 0.5mm, the cleaning width is more than or equal to 5 times of depth, and the attention is paid that the temperature of the casting billet is more than or equal to 300 ℃ before charging, so that the thermal stress generated by charging at low temperature is avoided; S4.2, continuous casting process parameter control: The key parameters are that the pulling speed is 0.65-0.85m/min, the medium package superheat degree is 12-28 ℃, the electromagnetic stirring current of the crystallizer is 120-180A, the frequency is 2.0-3.0Hz, the electromagnetic stirring current of the tail end is 200-280A, the frequency is 7.0-9.0Hz, the secondary cooling area adopts sectional water distribution, the specific water quantity is 0.30-0.45L/kg, the front section is strongly cooled, the rear section is slowly cooled, the attention is paid to the water quantity of the crystallizer is 2600-3000L/min, the fluctuation of the liquid level is kept to be less than or equal to +/-3 mm, the abrasion condition of a copper plate of the crystallizer is checked regularly, and the surface defect of a casting blank is avoided; s4.3, slow cooling treatment of casting blanks: And (3) carrying out stack cooling or pit cooling after the continuous casting blank is taken off line, wherein key parameters are that the slow cooling temperature is 800-850 ℃, the heat preservation time is 12-24h, the cooling rate is 20-40 ℃ per hour, and the cooling rate is cooled to below 300 ℃ and then air-cooled to room temperature, and the attention is paid to the fact that the casting blank is prevented from being stacked too densely, ventilation uniformity is ensured, the surface oxidation of the casting blank is prevented, and a heat preservation material is covered during stack cooling.
8. The grain refining smelting process of 20 CrMnTiSH1-H5 steel, as set forth in claim 1, is characterized in that the S5.1 is homogenized and heated: The casting blank is heated by sections, the key parameters are that the preheating section temperature is 600-700 ℃, the heat preservation is carried out for 60-120min, the heating section temperature is 1100-1150 ℃, the heat preservation is carried out for 120-180min, the soaking section temperature is 1180-1230 ℃, the heat preservation is carried out for 300-400min, the heating rate is 80-120 ℃ per hour, the attention is paid to the fact that nitrogen is introduced in the heating process for protection, the flow is 0.8-1.5m 3 per hour, the soaking temperature is strictly controlled, and the excessive growth of austenite grains is avoided; s5.2 microalloying strengthening refinement: The Ti element and N, C form carbonitride and pinning grain boundary, the key parameters are that the Ti/N ratio is 2.5-4.0, so that enough TiN particles are ensured to be formed, the Ti content in steel is precisely matched with the C, N content, coarse TiC inclusion is avoided, and the attention is paid to that ferrotitanium is added by adopting a wire feeding method, the wire feeding speed is 3-5m/min, and the Ti element is ensured to be uniformly distributed.
9. The grain refinement smelting process of 20 CrMnTiSH1-H5 steel, as set forth in claim 1, is characterized in that the S6.1 grain size detection: Adopting a metallographic microscope to detect austenite grain size, wherein key parameters are that the grain size is more than or equal to 7 grades, the grain uniformity deviation is less than or equal to 1.0 grade, no grains with the grain size being coarser than 6 grades are adopted, the detection position is 1/2R of a casting blank, 6 points are uniformly taken from the circumference, and precautions are taken that the grain size is assessed by adopting GB/T6394 standard, and each batch of samples is subjected to spot inspection of 3-5 pieces; s6.2, tissue and inclusion inspection: The key parameters are that the porosity at the center of the low-power structure is less than or equal to 1.5 level, the general porosity is less than or equal to 1.5 level, shrinkage cavities and cracks are avoided, nonmetallic inclusion A is less than or equal to 2.0 level, B is less than or equal to 1.5 level, C is less than or equal to 1.0 level, D is less than or equal to 1.0 level, the size of titanium nitride inclusion is less than or equal to 8 mu m, the metallographic structure is free of Wittin structure, the banded structure is less than or equal to 1.5 level, and attention is paid to that inclusion detection adopts GB/T10561 standard A method, and 2 samples are taken for each furnace for detection.
10. The grain refinement smelting process of 20 CrMnTiSH1-H5 steel, which is characterized by comprising the following steps of: The key parameters are that the tensile strength is more than or equal to 1300MPa (high-grade), the yield strength is more than or equal to 1080MPa, the impact absorption work Aku2 is more than or equal to 75J, the hardness uniformity deviation is less than or equal to 5HB, and the attention is paid to the fact that the mechanical property samples are prepared according to GB/T228.1, and 3 joint samples are extracted for each batch for testing.

Description

Grain refinement smelting process of 20 CrMnTiSH1-H5 steel Technical Field The invention relates to the technical field of steel smelting, in particular to a grain refining smelting process of 20 CrMnTiSH1-H5 steel. Background The high-strength gear steel is used as a core material of heavy-duty equipment such as an automobile transmission system, engineering machinery and the like, and needs to have high hardness, high toughness and excellent wear resistance, and grain refinement is a key way for improving the comprehensive performance of the high-strength gear steel. The prior smelting process has a plurality of short plates with the technical problems of incomplete raw material screening and purification, higher content of harmful elements such as phosphorus, sulfur, boron and the like and nonmetallic inclusion in scrap steel and alloy materials, hidden danger for subsequent grain refinement, unreasonable regulation and control of premelt alkalinity, insufficient baking, poor slagging effect, incapability of effectively adsorbing impurities in steel, overlarge temperature fluctuation in the converter smelting process, insufficient control precision of end point components, easy initiation of local overheating, coarse austenite grains, insufficient degassing in the refining stage, improper stirring strength matching, excessive gas content (O, N, H) in steel, uneven alloy element distribution, aggravated component segregation, unreasonable design of continuous casting pulling speed, superheat degree and electromagnetic stirring parameters, serious component segregation in the casting blank solidification process, formation of coarse columnar crystals, incapability of forming uniformly dispersed carbonitride particles due to incapability of effectively pinning grain boundaries, incapacitation of grains due to the lack of accurate regulation and control of full-flow grain size and tissue performance, uneven grain size of products, large fluctuation of mechanical performance, easy occurrence of fatigue resistance of the product under the conditions of high-quality peeling off of high-quality gear, and the like, and the difficulty of meeting the high-quality requirements of fatigue-end gear peeling-off under heavy load and the severe loading conditions. Disclosure of Invention (One) solving the technical problems Aiming at the defects of the prior art, the invention provides a grain refining smelting process of 20 CrMnTiSH1-H5 steel, which has the advantages of raw material purification and slag formation optimization, laying a grain refining foundation and the like, and solves the problems of incomplete raw material screening and purification. (II) technical scheme The invention provides a grain refining smelting process of 20 CrMnTiSH1-H5 steel, which comprises an S1 raw material pretreatment stage, an S2 converter smelting stage, an S3 refining purification stage, an S4 continuous casting process optimization stage, an S5 heating and refining auxiliary stage and an S6 quality inspection and control stage, wherein the S1 raw material pretreatment stage comprises an S1.1 raw material screening and purifying stage and an S1.2 premelting slag preparation stage; wherein the S2 converter smelting stage comprises S2.1 smelting and temperature control and S2.2 primary deoxidation process; wherein, the S3 refining and purifying stage comprises S3.1 LF furnace refining, S3.2 vacuum degassing treatment and precise regulation and control of S3.3 components; the optimization stage of the S4 continuous casting process comprises S4.1 continuous casting blank specification and charging, S4.2 continuous casting process parameter control and S4.3 casting blank slow cooling treatment; Wherein the S5 heating and refining auxiliary stage comprises S5.1 homogenizing heating and S5.2 microalloying strengthening refining; The S6 quality inspection and control stage comprises S6.1 grain size detection, S6.2 organization and inclusion inspection and S6.3 mechanical property verification. Preferably, the S1.1 raw material screening and purifying: Selecting low-phosphorus, low-sulfur and low-boron high-quality scrap steel and alloy materials, wherein key parameters are that the purity of the scrap steel is more than or equal to 99.5%, the phosphorus content is less than or equal to 0.010%, the sulfur content is less than or equal to 0.008%, the boron content of the alloy materials (ferrochrome, ferromanganese and ferrotitanium) is less than or equal to 0.0003%, and the purity of titanium in ferrotitanium is more than or equal to 99.0%, taking care that the raw materials are subjected to magnetic separation and impurity removal before entering the field to remove metal oxide and nonmetallic inclusion impurities; S1.2, preparation of premelting slag: The low-boron premelting slag is adopted for slag making, the key parameters are premelting slag alkalinity (CaO/SiO 2）3.5-5.0,Al2O3 content is 15-25%, mgO content is 8-12%, water content i