CN-121976112-A - Method for producing sulfur-containing free-cutting steel by taking molten iron desulfurization slag-off iron as raw material

CN121976112ACN 121976112 ACN121976112 ACN 121976112ACN-121976112-A

Abstract

The invention relates to the technical field of ferrous metallurgy, in particular to a method for producing sulfur-containing free-cutting steel by taking molten iron desulfurization slag-off iron as a raw material. The method comprises the following steps of S1, preprocessing slag-removed iron, S2, raw material preparation, S3, electric furnace smelting, S4, deoxidization alloying and sulfur content regulation, and S5, continuous casting and forming. The invention takes molten iron desulfurization slag-removing iron as a main raw material to replace part of common pig iron and scrap steel, realizes high-value recycling of slag-removing iron resources, reduces the raw material cost by 15% -20%, avoids the influence of slag charge on molten steel components by controlling the slag content in the slag-removing iron and the slag alkalinity in the converter slag-forming process, improves the sulfur content stability of the molten steel, and improves the product qualification rate from below 85% to above 98% of the traditional method.

Inventors

LI DEJUN
ZHAO LIANG
JIA JIXIANG
HUANG YUPING
YANG JI
LI BOYANG
WANG HAIWEI
SUN SHEN

Assignees

鞍钢股份有限公司

Dates

Publication Date: 20260505
Application Date: 20260205

Claims (10)

1. The method for producing the sulfur-containing free-cutting steel by taking the molten iron desulfurization slag-off iron as the raw material is characterized by comprising the following steps of: S1, slag iron removing pretreatment: Preprocessing slag-removed iron generated in molten iron desulfurization; S2, preparing raw materials: the method comprises the steps of selecting slag-raking iron and scrap steel as metal furnace charges and taking sulfur-containing alloy, a slag former and a deoxidizer as auxiliary raw materials, wherein the iron content in the slag-raking iron is more than or equal to 90wt%, the slag content is less than or equal to 6wt%, the sulfur content is 0.02-0.06 wt%, the phosphorus content in the scrap steel is less than or equal to 0.015wt%, and the sulfur content in the sulfur-containing alloy is more than or equal to 35wt% based on the total content of CaO, mgO, siO 2 ; s3, electric furnace smelting treatment: According to the mass ratio of the slag iron to the scrap steel of 7-9:1, sequentially adding the slag iron and the scrap steel into an electric furnace, then carrying out electrode arc heating, introducing oxygen into the furnace for converting after a metal molten pool is formed, and controlling the oxygen blowing strength to be 0.5-1.5 Nm 3 /(t) Min), adding a slag former in the smelting process to carry out slag forming treatment, and controlling the alkalinity of slag to be 1-2; s4, deoxidization alloying and sulfur content regulation: Regulating the carbon content of molten steel to 0.10-0.20 wt% within 15min before tapping, stopping oxygen blowing, adding a deoxidizer into the molten steel for deoxidizing treatment, stirring for 3-6 min after the addition is finished to ensure that the oxygen content of the molten steel is less than or equal to 0.005wt%, adding a sulfur-containing alloy for regulating the sulfur content according to the sulfur content requirement of a target steel grade, and continuously stirring for 5-8 min; S5, continuous casting molding: And (5) carrying out continuous casting on the molten steel after the alloying treatment.
2. The method for producing sulfur-containing free-cutting steel from molten iron desulfurization and slag-off iron as set forth in claim 1, wherein in step S1, the pretreatment method of slag-off iron is as follows: (1) Crushing the slag-removed iron into blocks with the block size of 5-150 mm; (2) Placing the crushed slag-removed iron into a baking furnace for baking, wherein the baking temperature is 600-900 ℃, and the temperature is kept for 120-160 min; (3) And (3) cooling the temperature to room temperature by blowing nitrogen, and then screening, wherein the diameter of the sieve holes is 5-10 mm.
3. The method for producing sulfur-containing free-cutting steel from molten iron desulfurization and slag-off iron as set forth in claim 1, wherein in step S2, the sulfur-containing alloy is ferrous sulfide or a sulfur-iron alloy.
4. The method for producing the sulfur-containing free-cutting steel by taking the molten iron desulfurization slag-off iron as a raw material, which is characterized in that in the step S2, the slag former adopts a composite proportion of lime and fluorite, wherein the CaO content in the lime is more than or equal to 90wt%, the CaF 2 content in the fluorite is more than or equal to 85wt%, and the mass ratio of the lime to the fluorite is 5-8:1.
5. The method for producing sulfur-containing free-cutting steel by taking molten iron desulfurization slag-off iron as a raw material according to claim 1, wherein in the step S2, the deoxidizer is ferrosilicon and ferromanganese, wherein the silicon content in the ferrosilicon is more than or equal to 75wt% and the Mn content in the ferromanganese is more than or equal to 80wt%.
6. The method for producing the sulfur-containing free-cutting steel by taking the molten iron desulfurization slag-off iron as a raw material, which is characterized in that in the step S3, the slag former is added in batches, the total addition amount of the slag former is 3% -5% of the mass of the metal furnace burden, the concrete adding time sequence is that the slag former accounting for 25% -35% of the total addition amount is firstly added within 10 minutes after the metal furnace burden is completely melted, and the residual slag former is added when the temperature of molten steel is raised to 1400-1550 ℃.
7. The method for producing the sulfur-containing free-cutting steel by taking the molten iron desulfurization slag-off iron as a raw material, which is characterized in that in the step S4, the addition amount of the deoxidizer is 0.8-1.2 kg/t of ferrosilicon, and the addition amount of ferromanganese is 1.5-2.0 kg/t of steel.
8. The method for producing sulfur-containing free-cutting steel by taking molten iron desulfurization slag-off iron as a raw material according to claim 1, wherein in the step S4, the addition amount of the sulfur-containing alloy is 1.0-2.5 kg/t steel.
9. The method for producing the sulfur-containing free-cutting steel by taking the molten iron desulfurization slag-off iron as a raw material, which is characterized in that in the step S5, an arc continuous casting process is adopted, wherein control parameters in the continuous casting process are that the water temperature of a crystallizer is 25-30 ℃, the billet drawing speed is regulated and controlled to be 1.5-3 m/min, and the cooling intensity of a secondary cooling area is 0.9-1.5L/kg of steel.
10. The method for producing the sulfur-containing free-cutting steel by taking the molten iron desulfurization slag-off iron as a raw material according to claim 1, wherein the sulfur content of the finished product of the sulfur-containing free-cutting steel is 0.08-0.15 wt%.

Description

Method for producing sulfur-containing free-cutting steel by taking molten iron desulfurization slag-off iron as raw material Technical Field The invention relates to the technical field of ferrous metallurgy, in particular to a method for producing sulfur-containing free-cutting steel by taking molten iron desulfurization slag-off iron as a raw material. Background The sulfur-containing free-cutting steel forms sulfide with metal due to sulfur element in the steel, can obviously improve the cutting processing performance of the steel, and has wide application in the fields of machine manufacturing, automobile parts and the like. At present, the sulfur-containing free-cutting steel is produced by taking common pig iron or molten iron which is not subjected to desulfurization and slag skimming treatment as a raw material and adding a sulfur-containing iron alloy, and the problems that the common pig iron raw material has higher cost, the desulfurization treatment is required to be additionally carried out, the production process and the energy consumption are increased, and if the molten iron which is not subjected to desulfurization and slag skimming treatment is directly used for producing the sulfur-containing free-cutting steel, the sulfur content is low, so that the mechanical property and the cutting property of the free-cutting steel are affected. Patent application number CN202310879501.0 discloses a recycling method of solid waste of molten iron pretreatment. After sequentially performing hot disintegrating, crushing, magnetic separation and drying treatment on KR desulfurization slag, recycling the residual tailings and using the residual tailings in a smelting process of sulfur-containing free-cutting steel, and finally realizing sulfur increase of molten steel. However, this patent only realizes the recovery of sulfur element in the molten iron desulfurization slag, does not effectively utilize sulfur contained in the slag iron, and fails to apply the sulfur element to the production link of sulfur-containing free-cutting steel. Patent application number CN202110543363.X discloses a method for smelting sulfur-containing steel by using desulfurization slag. The method has the core principle that sulfur replacement is realized by means of the oxidizing property of sulfur element in the desulfurization slag, and the sulfur element is stably blended into molten steel by optimizing a smelting process, so that the desulfurization slag is recycled. However, the method has obvious disadvantages that firstly, desulfurization slag needs to be added into a ladle in advance before tapping of the converter, which requires that deoxidation and alloying processes of converter smelting are delayed to be carried out, and certain interference is caused to the normal smelting process flow of the converter, and secondly, special types of deoxidizers such as silicon carbide and the like are required to be used for ensuring the recovery efficiency of sulfur, so that the process specificity and limiting conditions are increased. Patent application number CN202110201652.1 discloses a process method for producing high-sulfur steel by recycling slag. When the tapping link of converter smelting is started, KR desulfurization slag is added into the system, so that the recycling of slag and the production target of high-sulfur steel are realized. From the analysis of the practical application level, the process method has obvious operation limitation, and the core problem is interference on the normal smelting flow of the converter. Specifically, as KR desulfurization slag is added at the beginning of tapping, in order to adapt to the material adding step, the critical deoxidization process and alloying process in converter smelting have to be delayed, thus potentially affecting the stability of key parameters such as temperature control, component adjustment and the like in the smelting process and increasing the control difficulty in the production process. In addition, the process method has special requirements on raw materials and auxiliary materials, and further limits the application range of industrialized popularization. On the one hand, the method definitely requires the cooperation of a special deoxidizer for ensuring the technological effect, the deoxidizer has special limit on preparation cost or use condition compared with the common deoxidizer used in conventional smelting, on the other hand, the technology also designates that a specific steelmaking product of 'cord steel refined recovery slag' is matched with not a general steelmaking auxiliary material, the production of the refining procedure depending on the specific steel type of cord steel is generated, the production and the acquisition channel are limited by the production scale of the cord steel, and the process is difficult to obtain widely in different types of steel enterprises. In a comprehensive view, the process method provides a certain though