Smelting method of sulfur-containing gear steel

Abstract

The invention discloses a smelting method of molten sulfur-containing gear steel, which is characterized in that S removal is not carried out in the converting process of a converter or an electric furnace, ferro-aluminum, a slagging agent and lime are added within 1 / 3 time before the tapping process to carry out pre-deoxidation and slag washing, and the top slag components of a converter steel ladle are controlled: the content of CaO is 45-55 wt%, the content of Al2O3 is 15-25 wt%, the content of SiO2 is 5-15 wt%, and the content of MgO is 5-10 wt%, so that the content of S in the molten steel is less than or equal to 0.045%; in the LF refining step, after molten steel enters a station, white slag is rapidly made, and after the white slag is kept for more than or equal to 10 minutes, quartz sand is added for slag adjustment, the refining final slag components are controlled, and the S content of the molten steel is 0.015-0.030%; according to the method, the sulfur content of the molten steel can be stably controlled and the cleanliness of the molten steel can be improved under the condition that tooling equipment is not added, and the sulfur content requirement of the sulfur-containing gear steel can be met without feeding a sulfur line or adding a sulfur-iron alloy in the later stage of refining.

Description

Technical Field

[0001] The invention belongs to the technical field of sulfur-containing gear steel, and in particular relates to a smelting method of sulfur-containing gear steel. Background Art

[0002] Gear steel is widely used in transmission systems such as automobiles and machinery. In order to improve the cutting performance of gear steel, a certain amount of sulfur is usually added to the steel. There are a large number of plastic inclusions, mainly MnS, in sulfur-containing steel, which can act as a stress concentration source, making the product easy to break chips during the cutting process, which can improve the cutting performance of the product, thereby improving processing efficiency and reducing processing costs.

[0003] However, the production of sulfur-containing steel is more difficult. Compared with the production lines of traditional steel grades, additional equipment is required, and the production cost is higher. In addition, in order to ensure the sulfur content, it is often necessary to feed sulfur wire or add sulfur-iron alloy in the later stage of refining, which will also lead to increased production costs.

[0004] Chinese patent CN115341071A discloses a smelting method for reducing sulfide inclusions in sulfur-containing structural steel. The alloy is baked after the furnace until the alloy temperature is 500-550℃ and is ready for use. After the EBT furnace is smelted, the steel is tapped. When the steel is tapped to 1 / 3, alloys are added according to the difficulty of alloy oxidation. Acidic refractory materials are added in the refining process to reduce the basicity of the reducing slag, so that the refining slag changes from white or yellow to gray or black. Fluorite is added to reduce the viscosity of the reducing slag, so that the thickness of the sticky slag layer is less than 0.5 mm. According to the sulfur composition, an appropriate amount of sulfur wire is fed into the refining furnace ladle and soft blown for 5-10 minutes. This process requires an alloy baking box after the furnace, which has certain limitations. The refining process produces gray or black refining slag, which may lead to poor deoxidation of molten steel and affect the cleanliness of molten steel.

[0005] Chinese patent CN104789734A discloses a method for smelting sulfur-containing steel, which includes feeding molten steel into an LF refining furnace for slag making, adding slag regulator to control the fluidity of the slag, diffusing and deoxidizing the slag to make it white slag, feeding the sulfur line into the LF refining for sulfur alloying, and performing calcification treatment during LF refining steel tapping; and performing slag removal after the LF refining furnace is smelted. This method requires the LF refining furnace to be equipped with slag removal equipment, which has certain limitations; and performing sulfur alloying after making white slag in the refining process will reduce the sulfur recovery rate and increase production costs. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a method for smelting sulfur-containing gear steel molten steel. Without adding tooling equipment, slag is made through a converter and a refining process, so that the sulfur content of the molten steel can be stably controlled while improving the cleanliness of the molten steel.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A method for smelting sulfur-containing gear steel molten steel, wherein the percentage of sulfur in the molten steel is 0.015-0.030%; the smelting method comprises the following steps: converter or electric furnace smelting-LF refining;

[0009] In the converter or electric furnace smelting steps, no desulfurization is carried out during the blowing process. Aluminum blocks, slag-removing agents and lime are added during the steel-making process for pre-deoxidation and slag washing, and the process is completed within the first 1 / 3 of the steel-making process. The CaO content in the converter ladle top slag is 45wt%-55wt%, the Al2O3 content is 15wt%-25wt%, the SiO2 content is 5wt%-15wt%, and the MgO content is 5wt%-10wt%, so that the S content in the molten steel is ≤0.045%.

[0010] In the LF refining step, white slag is quickly produced after the molten steel enters the station. After the white slag is kept for ≥10 minutes, quartz sand is added for slag adjustment to control the CaO content of the final refined slag to 30wt%-40wt%, the Al2O3 content to 15wt%-25wt%, the SiO2 content to 15wt%-25wt%, and the MgO content to 5wt%-10wt%, so that the S content of the molten steel is 0.015-0.030%.

[0011] In the converter or electric furnace smelting steps, aluminum blocks, slag-removing agents and lime are added during the steel-making process for pre-deoxidation and slag washing, and this is completed within the first 1 / 3 of the steel-making process.

[0012] In the converter or electric furnace smelting step, the added amounts of aluminum block, slag reducing agent and lime are 1.5-2.0kg / t, 1-2kg / t and 5-6kg / t respectively.

[0013] In the LF refining step, the added amounts of refining slag and lime are 1-2kg / t and 2-3kg / t respectively.

[0014] In the LF refining step, the amount of quartz sand added is 1 to 2 kg / t.

[0015] In the LF refining step, the final slag binary basicity is 1.5-2.5.

[0016] In the LF refining step, no sulfur wire is fed or sulfur-iron alloy is added in the later stage of refining.

[0017] After LF refining is completed, the molten steel is not subjected to calcium treatment and the soft argon blowing time is ≥15min.

[0018] The chemical composition and weight percentage of the sulfur-containing gear steel liquid are: C 0.17-0.23%, Mn 1.25-1.35%, Cr 1.15-1.25%, Si≤0.15%, S 0.020-0.025%, Al 0.010-0.030%, and the balance is Fe and unavoidable impurities.

[0019] In the smelting method of sulfur-containing gear steel molten steel provided by the present invention, the flowable slag is quickly made by mixing steel and slag in the first 1 / 3 of the converter tapping process. In the LF refining process, white slag deoxidation is carried out in the early stage of refining to improve the cleanliness of molten steel; slag changing operation is carried out in the later stage of refining, and the sulfur content requirement of the sulfur-containing gear steel can be met without feeding sulfur wire or adding sulfur iron alloy.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention controls the slag composition in stages, ensures diffusion deoxidation, improves the cleanliness of molten steel, and does not need to feed sulfur wire or add sulfur iron alloy in the later stage of refining, so as to meet the sulfur content requirement of sulfur-containing gear steel. Compared with the existing sulfur-containing steel production technology, the smelting method of sulfur-containing gear steel molten steel provided by the present invention does not need to add equipment, has low production cost, and is convenient and easy to operate. DETAILED DESCRIPTION

[0022] The present invention is described in detail below with reference to the embodiments.

[0023] Example 1

[0024] A method for smelting molten steel containing sulfur gear steel, comprising the following steps: 120t converter smelting - 120t LF refining, specifically:

[0025] Converter smelting: low-basicity slag is produced during the converter blowing process. Ferrosilicon, low manganese, high chromium and low chromium alloy are added for alloying during the steelmaking process. 200kg of aluminum blocks, 150kg of slagging agent and 600kg of lime are added at the beginning of steelmaking for pre-deoxidation and slag washing, which are completed within the first 1 / 3 of the steelmaking process; the composition of the ladle top slag: CaO content is 52wt%, Al2O3 content is 22wt%, SiO2 content is 13%, MgO content is 8%, and the sulfur content of the molten steel is 0.035%.

[0026] LF refining: After the molten steel enters the station, 150kg of refining slag and 280kg of lime are added to carry out rapid white slag making operation. After the white slag is kept for 15 minutes, 160kg of quartz sand is added for slag adjustment. The components of the final refined slag are controlled to have a CaO content of 35wt%, an Al2O3 content of 15wt%, a SiO2 content of 20wt%, a MgO content of 9%, a final slag binary basicity of 1.75, and a S content of 0.022% in the molten steel.

[0027] After LF refining, the molten steel is not subjected to calcium treatment and the soft argon blowing time is 20 minutes.

[0028] The sulfur-containing gear steel smelted in this embodiment has the following components and weight percentages: C 0.18%, Mn 1.28%, Cr 1.19%, Si 0.13%, S 0.022%, Al 0.024%, and the remainder is Fe and unavoidable impurities.

[0029] Example 2

[0030] A method for smelting molten steel containing sulfur gear steel, comprising the following steps: 120t converter smelting - 120t LF refining, specifically:

[0031] Converter smelting: low basicity slag is produced during the converter blowing process, ferrosilicon, low manganese, high chromium and low chromium alloy are added for alloying during the steelmaking process, and 220kg of aluminum blocks, 200kg of slagging agent and 700kg of lime are added at the beginning of converter steelmaking for pre-deoxidation and slag washing; the composition of the ladle top slag: CaO content is 50wt%, Al2O3 content is 22wt%, SiO2 content is 14%, MgO content is 6%, and the sulfur content of the molten steel is 0.044%.

[0032] LF refining: After the molten steel enters the station, 200kg of refining slag and 350kg of lime are added to carry out rapid white slag making operation. After the white slag is kept for 13 minutes, 190kg of quartz sand is added for slag adjustment. The components of the final refined slag are controlled to have a CaO content of 38wt%, an Al2O3 content of 20wt%, a SiO2 content of 18wt%, and a MgO content of 7%. The binary basicity of the final slag is 2.11, and the S content of the molten steel is 0.025%.

[0033] After LF refining, the molten steel was not subjected to calcium treatment and the soft argon blowing time was 18 minutes.

[0034] The sulfur-containing gear steel smelted in this embodiment has the following components and weight percentages: C 0.22%, Mn 1.31%, Cr 1.22%, Si 0.12%, S 0.017%, Al 0.022%, and the remainder is Fe and unavoidable impurities.

[0035] Comparative Example 1

[0036] The rest is the same as Example 1, except that in the converter smelting step, 150kg of slagging agent and 600kg of lime are added at the beginning of steel tapping, no aluminum block is added, and the process is completed within the first 1 / 2 time of the steel tapping process; the composition of the ladle top slag: CaO content is 58wt%, Al2O3 content is 12wt%, SiO2 content is 16%, MgO content is 9%, and the sulfur content of the molten steel is 0.050%.

[0037] In the LF refining step, the S content of the molten steel is 0.038%.

[0038] Comparative Example 2

[0039] The rest is the same as Example 1, except that in the LF refining step, quartz sand is not added for slag adjustment, and the final slag components are controlled to have a CaO content of 55wt%, an Al2O3 content of 23wt%, a SiO2 content of 12wt%, a MgO content of 6%, a final slag binary basicity of 4.58, and a S content in the molten steel of 0.005%.

[0040] The cleanliness data of the molten steel and the sulfur content of the molten steel in the above-mentioned embodiments and comparative examples are shown in Table 1.

[0041] Table 1 Statistics of S content and non-metallic inclusion levels in different embodiments and comparative examples

[0042]

[0043] The detailed description of a smelting method for sulfur-containing gear steel with reference to the above embodiment is illustrative rather than restrictive, and several embodiments can be listed according to the limited scope. Therefore, changes and modifications without departing from the overall concept of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for smelting sulfur-containing gear steel, characterized in that: The percentage of sulfur in the molten steel is 0.015-0.030%; the smelting method comprises the following steps: converter or electric furnace smelting-LF refining; In the converter or electric furnace smelting step, no desulfurization is performed during the blowing process, and aluminum blocks, slag-removing agents and lime are added during the steel-making process for pre-deoxidation and slag washing, which are completed within the first 1 / 3 of the steel-making process; the CaO content in the converter ladle top slag is 45wt%-55wt%, the Al2O3 content is 15wt%-25wt%, the SiO2 content is 5wt%-15wt%, and the MgO content is 5wt%-10wt%, so that the S content of the molten steel is ≤0.045%; In the LF refining step, white slag is quickly produced after the molten steel enters the station. After the white slag is kept for ≥10 minutes, quartz sand is added for slag adjustment to control the CaO content of the final refined slag to 30wt%-40wt%, the Al2O3 content to 15wt%-25wt%, the SiO2 content to 15wt%-25wt%, and the MgO content to 5wt%-10wt%, so that the S content of the molten steel is 0.015-0.030%.

2. The smelting method according to claim 1, characterized in that: In the converter or electric furnace smelting step, the amount of aluminum blocks added is 1.5-2.0 kg / t.

3. The smelting method according to claim 1 or 2, characterized in that: In the converter or electric furnace smelting step, the added amounts of slagging agent and lime are 1-2kg / t and 5-6kg / t respectively.

4. The smelting method according to claim 1, characterized in that: In the LF refining step, the added amounts of refining slag and lime are 1-2kg / t and 2-3kg / t respectively.

5. The smelting method according to claim 1, characterized in that: In the LF refining step, the amount of quartz sand added is 1 to 2 kg / t.

6. The smelting method according to claim 1, characterized in that: In the LF refining step, the final slag binary basicity is 1.5-2.

5.

7. The smelting method according to claim 1, characterized in that: In the LF refining step, no sulfur wire is fed or sulfur-iron alloy is added in the later stage of refining.

8. The smelting method according to claim 1, characterized in that: After LF refining is completed, the molten steel is not subjected to calcium treatment and the soft argon blowing time is ≥15min.

9. The smelting method according to claim 1, characterized in that: The chemical composition and weight percentage of the sulfur-containing gear steel are: C 0.17-0.23%, Mn 1.25-1.35%, Cr 1.15-1.25%, Si≤0.15%, S 0.020-0.025%, Al 0.010-0.030%, and the balance is Fe and unavoidable impurities.

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