A process technology for smelting high-purity, high-sulfur, and high-aluminum automotive rack steel.

Abstract

This invention discloses a smelting process for high-purity, high-sulfur, and high-alumina automotive rack steel. Belonging to the field of steel smelting technology, it employs a strong oxidation reduction process, low-alkalinity slag system process control technology, pre-adjustment of easily decaying elements such as Al, S, and Ti, and precise micro-calcium treatment technology based on thermodynamic equilibrium calculations after vacuum. Through these technologies, high-purity, high-sulfur, and high-alumina automotive rack steel is produced. The specific steps include: determining the tapping carbon (C), controlling the aluminum content, and determining the vacuum degree. This invention produces high-purity, high-sulfur, and high-alumina automotive rack steel with microscopic inclusion control: A. fine sulfide series ≤ 3 levels, A. coarse sulfide series ≤ 2 levels, B. fine alumina series ≤ 1.5 levels, B. coarse alumina series ≤ 1.0 levels, D. fine spherical oxide series ≤ 1.0 levels, and D. coarse spherical oxide series ≤ 1.0 levels. The number of consecutive casting furnaces can reach 7 or more.

Description

Technical Field

[0001] This invention belongs to the field of steel smelting technology and relates to a smelting process and method for high-purity, high-sulfur, and high-aluminum automotive rack steel. Background Technology

[0002] High-sulfur, high-alumina gear steel is widely used in automotive steering gear transmission racks, showing promising market prospects. With increasing orders, end-users are placing higher demands on the purity of the steel, making the issue of steel purity crucial. During the smelting process, aluminum-deoxidized steel generates a large amount of Al2O3 inclusions, which are high-melting-point and difficult-to-deform inclusions. These inclusions easily accumulate on the inner wall of the nozzle during casting, worsening the steel's castability. Currently, the commonly used technique is calcium treatment, which can transform the high-melting-point, non-deformable Al2O3 inclusions into low-melting-point, deformable calcium aluminates. However, if the steel contains high levels of sulfur, calcium treatment also generates a significant amount of high-melting-point CaS inclusions, similarly causing severe nozzle blockage, which can even lead to complete nozzle clogging and production shutdowns. Summary of the Invention

[0003] To address the aforementioned problems, the present invention aims to overcome the deficiencies in the existing technology by proposing a smelting process technology for high-purity, high-sulfur, and high-aluminum automotive rack steel. Through the above technology, high-purity, high-sulfur, and high-aluminum automotive rack steel can be produced with better control of microscopic inclusions, and the number of consecutive casting furnaces can be increased to more than 7.

[0004] The technical solution of the present invention is: a high-purity, high-sulfur, and high-aluminum automotive rack steel smelting process technology and method described in the present invention; adopting electric furnace low oxygen level control technology, refining micro-desulfurization slag control technology, pre-adjustment of easily decaying elements such as Al, S, and Ti, and precise micro-calcium treatment technology based on thermodynamic equilibrium state calculation of VD.

[0005] The specific steps are as follows:

[0006] (1) The carbon content of the tapped steel is ≥0.10%, and the oxidizing property of the primary steel is controlled to be ≤300ppm. The tapping volume is 100±2 tons / furnace. Aluminum shot (kg) 90±10kg; silicon-manganese alloy 750-800kg / furnace; high-carbon ferromanganese 550-600kg / furnace; active lime 400±20kg; modified refining slag 250±20kg;

[0007] (2) Use aluminum wire and silicon carbide diffusion deoxidation, and keep the white slag for ≥30 min; control the aluminum content: control the aluminum content at the LF endpoint between 0.045-0.055%; add (300-400) kg / furnace of iron sulfide 5 min before entering the vacuum, and control the other elements according to the target value. Calcium treatment is strictly prohibited.

[0008] (3) Maintain vacuum degree ≤ 1 mbar for ≥ 10 min; after breaking the vacuum, take samples to analyze the full composition and carbon / sulfur, immediately feed in 30-40 m of calcium wire, feed in aluminum wire according to the target value based on the sample composition, feed in sulfur wire according to the target value based on the S composition of the carbon and sulfur meter 15 min after adding calcium wire; after fine-tuning according to the sample composition, stir statically for ≥ 15 min.

[0009] The beneficial effects of this invention are as follows: The invention produces high-purity, high-sulfur, and high-alumina steel for automotive racks, with microscopic inclusion control as follows: A. fine sulfide series ≤ grade 3, A. coarse sulfide series ≤ grade 2, B. fine alumina series ≤ grade 1.5, B. coarse alumina series ≤ grade 1.0, D. fine spheroidal oxide series ≤ grade 1.0, and D. coarse spheroidal oxide series ≤ grade 1.0. The number of consecutive casting furnaces can reach 7 or more. Detailed Implementation

[0010] The specific technical solution of the present invention will be further described in detail below with reference to specific examples.

[0011] Example 1

[0012] The present invention discloses a high-purity, high-sulfur, and high-alumina rack steel smelting process technology, which combines a strong oxidation reduction process in steel tapping, a low-alkalinity slag system process control technology, pre-adjustment of easily decaying elements such as Al, S, and Ti, and a precise micro-calcium treatment technology based on thermodynamic equilibrium calculation after vacuum. Through the above technologies, high-purity, high-sulfur, and high-alumina automotive rack steel is produced with better control of micro-inclusions, and the number of consecutive casting furnaces is increased to more than 7.

[0013] The specific operating steps are as follows:

[0014] (1) Steel tapping C: 0.15%, steel tapping amount 100 tons / furnace; aluminum shot (kg) 90kg; silicon manganese alloy 780kg / furnace, high carbon ferromanganese 580kg / furnace; active lime 400kg; modified refining slag 250kg;

[0015] (2) Use aluminum wire and silicon carbide diffusion deoxidation, and keep the white slag for ≥30 min; aluminum content control: control the aluminum content at the LF endpoint to be between 0.048%; 5 min before entering the vacuum, add 350 kg / furnace of iron sulfide, and control the other elements according to the target value. Calcium treatment is strictly prohibited.

[0016] (3) Maintain vacuum degree ≤ 1 mbar for 10 min; after breaking the vacuum, take samples to analyze the full composition and carbon / sulfur, immediately feed in 30 m of calcium wire, feed in aluminum wire according to the target value based on the sample composition, feed in sulfur wire according to the target value based on the S composition of the carbon and sulfur meter 15 min after adding calcium wire; after fine-tuning according to the sample composition, stir for 20 min.

[0017] Rolled material samples were tested for microscopic inclusions according to GB-10561 standard. The microscopic inclusion control levels were as follows: A. Fine sulfide series 2.5 grade, A. Coarse sulfide series 1.5 grade, B. Fine alumina series 1.0 grade, B. Fine alumina series 0.5 grade, D. Fine spherical oxide series 1.0 grade, D. Coarse spherical oxide series 0.5 grade.

[0018] Example 2

[0019] The present invention discloses a high-purity, high-sulfur, and high-alumina rack steel smelting process technology, which combines a strong oxidation reduction process in steel tapping, a low-basicity slag system process control technology, pre-adjustment of easily decaying elements such as Al, S, and Ti, and a precise micro-calcium treatment technology based on thermodynamic equilibrium calculation after vacuum. Through the above technologies, high-purity, high-sulfur, and high-alumina automotive rack steel is produced with better control of micro-inclusions, and the number of consecutive casting furnaces can be increased to more than 7.

[0020] The specific operating steps are as follows:

[0021] (1) Steel tapping C: 0.14%, control the oxidizing property of primary steel molten steel ≤ 500ppm, steel tapping amount 101 tons / furnace; aluminum shot (kg) 100kg; silicon manganese alloy 800kg / furnace, high carbon ferromanganese 600kg / furnace; active lime 420kg; modified refining slag 260kg;

[0022] (2) Use aluminum wire and silicon carbide diffusion deoxidation, and keep the white slag for ≥30 min; control the aluminum content: control the aluminum content at the LF endpoint between 0.045-0.055%; add 380 kg / furnace of iron sulfide 5 min before entering the vacuum, and control the other elements according to the target value. Calcium treatment is strictly prohibited.

[0023] (3) Maintain a vacuum of ≤1 mbar for 10 min. After breaking the vacuum, take a sample to analyze the full composition and carbon / sulfur. Immediately feed in 30 m of calcium wire. Feed in aluminum wire according to the target value based on the sample composition. 15 min after adding the calcium wire, feed in sulfur wire according to the target value based on the S composition of the carbon and sulfur analyzer. After fine-tuning according to the sample composition, stir for 18 min.

[0024] Rolled material samples were tested for microscopic inclusions according to GB-10561 standard. The microscopic inclusion control levels were as follows: A. Fine sulfide series 2.0 grade, A. Coarse sulfide series 1.5 grade, B. Fine alumina series 1.0 grade, B. Fine alumina series 0.5 grade, D. Fine spherical oxide series 1.0 grade, D. Coarse spherical oxide series 0.5 grade.

[0025] Example 3

[0026] The present invention describes a high-purity, high-sulfur, and high-alumina rack steel smelting process technology, which combines a strong oxidation reduction process during steel tapping, a low-basicity slag system process control technology, pre-adjustment of easily decaying elements such as Al, S, and Ti, and a precise micro-calcium treatment technology based on thermodynamic equilibrium calculations after vacuum. Through the above technologies, high-purity, high-sulfur, and high-alumina automotive rack steel is produced with better control of micro-inclusions, and the number of consecutive casting furnaces can be increased to more than 7.

[0027] The specific steps are as follows:

[0028] (1) Steel tapping C: 0.16%, control the oxidation of primary steel molten steel ≤ 500ppm, steel tapping amount 99 tons / furnace; aluminum shot (kg) 80kg; silicon manganese alloy 760kg / furnace, high carbon ferromanganese 560kg / furnace; active lime 390kg; modified refining slag 240kg;

[0029] (2) Use aluminum wire and silicon carbide diffusion deoxidation, and keep the white slag for ≥30 min; aluminum content control: control the aluminum content at the LF endpoint to be between 0.052%; 5 min before entering the vacuum, add 320 kg / furnace of iron sulfide, and control the other elements according to the target value. Calcium treatment is strictly prohibited.

[0030] (3) Maintain vacuum degree ≤ 1 mbar for 10 min; after breaking the vacuum, take samples to analyze the full composition and carbon / sulfur, immediately feed in 30-40 m of calcium wire, feed in aluminum wire according to the target value based on the sample composition, feed in sulfur wire according to the target value based on the S composition of the carbon and sulfur meter 15 min after adding calcium wire; after fine-tuning according to the sample composition, stir for 25 min.

[0031] Rolled material samples were tested for microscopic inclusions according to GB-10561 standard. The microscopic inclusion control levels were as follows: A. Fine sulfide series: Level 3; A. Coarse sulfide series: Level 2; B. Fine alumina series: Level 1.0; D. Fine spherical oxide series: Level 1.0; D. Coarse spherical oxide series: Level 0.5.

[0032] Based on the chemical composition of high-sulfur and high-alumina rack steel, this invention designs a smelting method for high-purity high-sulfur and high-alumina rack steel (Al≥0.020%, S≥0.040%). Specifically, it involves electric furnace low-oxygen level control technology, refining micro-desulfurization slag control technology, pre-refining adjustment of Al, S and other elements, and precise micro-calcium treatment technology after VD. The above technologies realize a smelting process technology for high-purity high-sulfur and high-alumina rack steel.

[0033] Compared to ordinary sulfur-containing and aluminum-containing steel (Al: 0.005-0.020%, S: 0.010%-0.020%), this invention produces steel with extremely high sulfur and aluminum content (Al: 0.020-0.040%, S: 0.040%-0.060%). This invention achieves high-purity smelting of high-sulfur and high-alumina rack steel through electric furnace low-oxygen level control technology, refining micro-desulfurization slag control technology, pre-refining adjustment of Al and S elements, and precise micro-calcium treatment after VD. Microscopic inclusion control is achieved as follows: A. Fine sulfide series ≤ 3 levels, A. Coarse sulfide series ≤ 2 levels, B. Fine alumina series ≤ 1.5 levels, B. Coarse alumina series ≤ 1.0 levels, D. Fine spherical oxide series ≤ 1.0 levels, D. Coarse spherical oxide series ≤ 1.0 levels. The number of consecutive casting furnaces can reach 7 or more.

Claims

1. A high-purity high-sulfur high-aluminum steel smelting process technology method for automobile rack, characterized in that: By employing a strong oxidation reduction process, a low-alkalinity slag system process control technology, pre-adjustment of easily decaying elements, and a precise micro-calcium treatment technology after vacuum calculation based on thermodynamic equilibrium, high-purity, high-sulfur, and high-aluminum automotive rack steel can be produced. ​ The operating steps are as follows: (1): Determine the steel output C; In step (1), the steel output C is ≥0.10%, the oxidizing power of the primary steel is controlled to be ≤300ppm, and the steel output is 100±2 tons / furnace; Aluminum shot: 90±10kg; silicon-manganese alloy: 750-800kg / furnace; high-carbon ferromanganese: 550-600kg / furnace; active lime: 400±20kg; modified refining slag: 250±20kg; (2): Aluminum content control; In step (2), before controlling the aluminum content: aluminum wire and silicon carbide diffusion deoxidation must be used, and the white slag retention time must be ≥30min; The aluminum content control is as follows: the aluminum content at the LF endpoint is controlled between 0.045% and 0.055%. Five minutes before vacuuming, add (300-400) kg / furnace of iron sulfide, and control the other elements according to the target values. (3): Determine the vacuum level; In step (3), the vacuum level is ≤1 mbar and the holding time is ≥10 min; After breaking the vacuum, take samples to analyze the full composition and carbon / sulfur ratio. Feed in 30-40m of calcium wire. Feed in aluminum wire according to the target value based on the sample composition. 15min after adding the calcium wire, feed in sulfur wire according to the target value based on the S composition of the carbon and sulfur analyzer. After fine-tuning according to the sample composition, stir for ≥15min.

2. The smelting process for high-purity, high-sulfur, and high-aluminum automotive rack steel according to claim 1, characterized in that: The high-purity, high-sulfur, and high-alumina automotive rack steel prepared has the following micro-inclusion control: A. fine sulfide series ≤ grade 3, A. coarse sulfide series ≤ grade 2, B. fine alumina series ≤ grade 1.5, B. coarse alumina series ≤ grade 1.0, D. fine spheroidal oxide series ≤ grade 1.0, D. coarse spheroidal oxide series ≤ grade 1.0, and the number of consecutive casting furnaces reaches 7 or more.