A refining method for micro-desulfurization

Abstract

The invention discloses a refining method for micro-desulfurization. By optimizing the slag system design and formulation in the alloying process of electric furnace steel tapping, the addition of refining deoxidizers, and the refining sulfur control process, the sulfur recovery rate can be stabilized, and the re-replenishment of S after vacuum can be avoided, the occurrence rate of S component accidents can be reduced, the vacuum operation rate and the effect of weak stirring of molten steel after vacuum can be improved, and at the same time, the use of iron sulfide can be reduced, the production efficiency and purity of sulfur-containing gear steel, cold heading steel, and non-quenched and tempered steel can be improved, the high-quality development of special steel can be driven, and the method has broad application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of steel smelting, and in particular to a micro-desulfurization refining method. Background Art

[0002] The general smelting process of sulfur-controlled steels such as gear steel, cold heading steel, and non-quenched and tempered steel is to use high-basicity slag system to first refine and desulfurize to 0.10%, and then add iron sulfide in a vacuum. The iron sulfide consumption is large, the yield is unstable, there are many composition accidents, the process nodes are long after vacuum, and the production efficiency is low. More importantly, the traditional high-basicity slag system and smelting process can no longer meet the purity requirements of high-end steel grades.

[0003] With the increasing demand for new energy vehicles and the requirement for lightweight vehicles, the performance requirements for high-end non-adjustable crankshafts and gear steels are becoming increasingly higher. While meeting high strength and high fatigue performance, they should also have good cutting performance and high purity. Summary of the invention

[0004] In order to meet the requirements of steel grade upgrading and fully consider the route of advancing metallurgical purity, the present invention takes the Mannesmann index of refined slag as a theoretical basis, meets the needs of producing sulfur-containing steel using the electric furnace + LF + VD + CCM process flow, and provides a micro-desulfurization refining method.

[0005] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0006] A micro-desulfurization refining method, characterized by comprising:

[0007] 1) In the electric furnace smelting process, the carbon, P and temperature process requirements of the steel grade must be met before steel is tapped, and the Mannesmann index of the steel-tapping refined slag must be controlled at 0.20-0.22;

[0008] 2) During the LF refining and deoxidation process, the amount of deoxidizer is 1.50-1.80kg / t to meet the alloying effect of bottom stirring and the floating effect of impurities;

[0009] 3) Control the Mannesmann index of the LF end slag ≤ 0.15, and control the sulfur at the LF end point within the S lower limit of the steel grade + S lower limit * (30% ~ 40%). After the temperature and composition are qualified, proceed to the VD vacuum degassing process.

[0010] The micro-desulfurization refining method of the present invention breaks through the traditional sulfur-containing steel production process. By optimizing the slag system design and formulation in the electric furnace steel alloying process, the addition of refining deoxidizers, and the refining sulfur control process, the vacuum process desulfurization rate is reduced and stabilized, the sulfur recovery rate is stabilized, and the re-replenishment of S after vacuum is avoided, the occurrence rate of S component accidents is reduced, the vacuum operation rate and the effect of weak stirring of molten steel after vacuum are improved, while the use of iron sulfide is reduced, and the alloy cost of steel grades is further reduced, opening up a new way for the production of high-efficiency and high-quality automotive steel, improving the production efficiency and purity of sulfur-containing gear steel, cold heading steel, and non-quenched and tempered steel, driving the high-quality development of special steel, and having broad application prospects. DETAILED DESCRIPTION

[0011] The present invention will be further described below in conjunction with specific embodiments. Example 1

[0012] A refining method for micro-desulfurization comprises the following steps:

[0013] 1) In the electric furnace smelting process, the carbon, P and temperature process requirements of the steel grade must be met before steel is tapped, and the Mannesmann index of the tapped refined slag must be controlled at 0.20.

[0014] 2) During the LF refining and deoxidation process, the deoxidizer dosage is 1.50kg / t to meet the alloying effect of bottom stirring and the floating effect of impurities.

[0015] 3) Control the Mannesmann index of the LF end slag ≤ 0.15, and the sulfur at the LF end is controlled at the lower limit of S of the steel grade + the lower limit of S * 32%. After the temperature and composition are qualified, proceed to the VD vacuum degassing process. Example 2

[0016] A micro-desulfurization refining process comprises the following steps:

[0017] 1) In the electric furnace smelting process, the carbon, P and temperature process requirements of the steel grade must be met before steel is tapped, and the Mannesmann index of the steel-tapping refined slag must be controlled at 0.22.

[0018] 2) During the LF refining and deoxidation process, the deoxidizer dosage is 1.80kg / t to meet the alloying effect of bottom stirring and the floating effect of impurities.

[0019] 3) Control the Mannesmann index of the LF end slag ≤ 0.15, and the sulfur at the LF end is controlled at the lower limit of S of the steel grade + the lower limit of S * 40%. After the temperature and composition are qualified, proceed to the VD vacuum degassing process. Example 3

[0020] A micro-desulfurization refining process comprises the following steps:

[0021] 1) In the electric furnace smelting process, the carbon, P and temperature process requirements of the steel grade must be met before steel is tapped, and the Mannesmann index of the tapped refined slag must be controlled at 0.21.

[0022] 2) During the LF refining and deoxidation process, the deoxidizer dosage is 1.60kg / t to meet the alloying effect of bottom stirring and the floating effect of impurities.

[0023] 3) Control the Mannesmann index of the LF end slag ≤ 0.15, and the sulfur at the LF end is controlled at the lower limit of S of the steel grade + the lower limit of S * 30%. After the temperature and composition are qualified, proceed to the VD vacuum degassing process.

[0024] The completion status of the above examples and the change of S content are shown in Table 1:

[0025] Table 1 Various embodiments

[0026]

[0027] It can be seen that the method of the present invention can effectively reduce and stabilize the desulfurization rate in the vacuum process (from 40-60% in the prior art to 15-25%), stabilize the sulfur recovery rate, and ensure that the S element after vacuum meets the requirements for steel grade determination.

Claims

1. A refining method for micro-desulfurization, characterized in that: include: 1) In the electric furnace smelting process, the carbon, P and temperature process requirements of the steel grade must be met before steel is tapped, and the Mannesmann index of the steel-tapping refined slag must be controlled at 0.20-0.22; 2) During the LF refining and deoxidation process, the amount of deoxidizer is 1.50-1.80kg / t to meet the alloying effect of the furnace bottom stirring and the floating effect of inclusions; 3) Control the Mannesmann index of the LF end slag ≤ 0.15, and the sulfur at the LF end is controlled at: 1.3 to 1.4 times the lower limit of the steel grade S. After the temperature and composition are qualified, proceed to the VD vacuum degassing process; the desulfurization rate of the VD vacuum process is 15 to 25%.

2. The micro-desulfurization refining method according to claim 1, characterized in that: The steel grade is 30MnVS, the LF end point slag Mannesmann index is 0.13, the LF end point sulfur content is 0.085%, and the VD vacuum process desulfurization rate is 17.67%.

3. The micro-desulfurization refining method according to claim 1, characterized in that: The steel grade is 38MnSiV5, the LF end point slag Mannesmann index is 0.14, the LF end point sulfur content is 0.062%, and the VD vacuum process desulfurization rate is 22.51%.

4. The micro-desulfurization refining method according to claim 1, characterized in that: The steel grade is SCr420H, the LF end point slag Mannesmann index is 0.12, the LF end point sulfur content is 0.024%, and the VD vacuum process desulfurization rate is 20.00%.

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