阅读说明：本技术 一种易切削电渣重熔不锈钢的制备方法及该方法制得的不锈钢 (Preparation method of free-cutting electroslag remelting stainless steel and stainless steel prepared by method ) 是由 施晓芳 常立忠 于 2021-08-27 设计创作，主要内容包括：本发明公开了一种易切削电渣重熔不锈钢的制备方法及该方法制得的不锈钢,属于特殊钢冶金技术领域。它将X吨目标钢材熔融后依次进行AOD脱碳处理、LF精炼处理和铸模,再将铸模得到的金属电极作为自耗电极进行电渣重熔,从而得到易切削的不锈钢；所述AOD脱碳处理过程中添加硫化锰进行增硫,所述硫化锰中硫的质量为Y千克,Y/X＝1.4～3.0；所述LF精炼处理过程中添加矿渣,所述矿渣中包括1.5wt％～2.5wt％的S。本发明能使得电渣重熔得到的电渣锭硫含量也得到精准的提升,从而提升切削钢的切削性能,同时能够降低生产成本并保证冶炼过程硫的收得率稳定性。(The invention discloses a preparation method of free-cutting electroslag remelting stainless steel and stainless steel prepared by the method, and belongs to the technical field of special steel metallurgy. Melting X tons of target steel, sequentially carrying out AOD decarburization treatment, LF refining treatment and casting mould, and carrying out electroslag remelting by taking a metal electrode obtained by the casting mould as a consumable electrode so as to obtain free-cutting stainless steel; adding manganese sulfide for increasing sulfur in the AOD decarburization treatment process, wherein the mass of sulfur in the manganese sulfide is Y kg, and the mass ratio of Y/X is 1.4-3.0; and adding slag in the LF refining process, wherein the slag comprises 1.5-2.5 wt% of S. The method can accurately improve the sulfur content of the electroslag ingot obtained by electroslag remelting, thereby improving the cutting performance of cutting steel, reducing the production cost and ensuring the stability of the yield of sulfur in the smelting process.)

1. A preparation method of free-cutting electroslag remelting stainless steel is characterized in that X tons of target steel are melted and then subjected to AOD decarburization treatment, LF refining treatment and casting mold in sequence, and then a metal electrode obtained by the casting mold is used as a consumable electrode to be subjected to electroslag remelting, so that the free-cutting stainless steel is obtained; adding manganese sulfide for increasing sulfur in the AOD decarburization treatment process, wherein the mass of sulfur in the manganese sulfide is Y kg, and the mass ratio of Y/X is 1.4-3.0; and adding slag in the LF refining process, wherein the slag comprises 1.5-2.5 wt% of S.

2. The method for preparing free-cutting electroslag remelting stainless steel according to claim 1, which is characterized by comprising the following specific preparation steps:

(1) smelting the target steel at high temperature in an electric arc furnace;

(2) injecting the smelted molten steel into an AOD furnace through a steel ladle for smelting, blowing mixed gas of oxygen and argon during smelting to decarbonize the molten steel, simultaneously adding a reducing agent for reduction, removing slag completely, adding sulfur-manganese ore into the AOD furnace for increasing sulfur, and tapping;

(3) adding slag along with steel flow in the tapping process of the AOD furnace, then refining at an LF station, and casting into a consumable electrode after the refining is finished;

(4) and carrying out electroslag remelting on the consumable electrode obtained by LF refining to obtain the free-cutting stainless steel.

3. The method for preparing free-cutting electroslag remelting stainless steel according to claim 2, wherein in the step (2), when the heterolite contains 20-25 wt% of S, 7-10 kg of heterolite is added per ton of target steel; when the manganosite contains 25-30 wt% of S, 6-8 kg of the manganosite is added to each ton of target steel; and when the sulfur-manganese ore contains more than 30 wt% of S, 5 kg-7 kg of sulfur-manganese ore is added to each ton of target steel.

4. The method for preparing free-cutting electroslag remelting stainless steel according to claim 3, wherein in the step (2), the ratio of the mixed gas of oxygen and argon is (0.2-4): 1; the reducing agent added for reduction comprises ferrosilicon; and blowing argon gas and stirring for 2-3 min after the sulfur manganese ore is added, and then tapping.

5. The method for preparing free-cutting electroslag remelting stainless steel according to claim 2, wherein in the step (3), fluorite and slag are simultaneously added along with steel flow during AOD furnace tapping, and refining time is 50min to 100 min; the mass ratio of fluorite to slag is 1: (5-10), adding 20-25 kg of fluorite slag mixture per ton of target steel.

6. The method for preparing free-cutting electroslag remelting stainless steel according to claim 5, wherein in the step (3), the slag further comprises 40-45 wt% of CaO, 44-48 wt% of SiO₂5 to 10 weight percent of MgO and 0 to 10 weight percent of Al₂O₃。

7. The method for preparing free-cutting electroslag remelting stainless steel according to claim 1, wherein in the step (4), a metal consumable electrode with a diameter smaller than that of the remelting crystallizer is cast after LF refining is completed, the metal consumable electrode is subjected to electroslag remelting, slag used for remelting comprises fluorite, slag and quartz sand, and the mass ratio of the fluorite to the slag to the quartz sand is (3-6): (1-5): 1, adding 30 kg-40 kg of slag charge into each ton of target steel.

8. The method for preparing free-cutting electroslag remelted stainless steel according to claim 7, wherein in the step (4), the slag used for electroslag remelting comprises 35-40 wt% CaO and 35-40 wt% SiO₂5 to 10 weight percent of MgO and 15 to 20 weight percent of Al₂O₃And 0.2 wt% to 0.5 wt% S;

and/or the current of the electroslag remelting is 8000A-15000A, and the voltage is 55V-85V.

9. The method for preparing free-cutting electroslag remelting stainless steel according to any one of claims 1 to 8, wherein the sulfur content of the molten steel after AOD decarburization is A; sampling the molten steel in the LF refining process to detect that the sulfur content in the molten steel is B; stopping LF refining when the B ═ A + (0.01 wt% to 0.03 wt%).

10. A stainless steel produced by the method for producing a free-cutting electroslag remelting stainless steel according to any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of special steel metallurgy, and particularly relates to a preparation method of free-cutting electroslag remelting stainless steel and the stainless steel prepared by the method.

Background

Accurate control of the sulfur content in free-cutting stainless steels is critical. In the current steelmaking technology, sulfur feeding wires or ferro-sulphur are often adopted for alloying, so that the cost is higher; meanwhile, the unreasonable control of the refining slag system leads to unstable sulfur yield and influences the easy-cutting property of stainless steel, and the refining slag adopts refined synthetic slag and has high production cost. In the electroslag remelting stage, expensive low-sulfur slag systems are often adopted for remelting, but the burning loss of sulfur is caused, and how to adopt slag systems with lower cost and reasonable composition for remelting is very important.

Through search, the Chinese invention patent CN101307416A discloses a homogeneous free-cutting steel and a production method thereof, wherein the homogeneous free-cutting steel comprises the following components (by weight percentage); the steel is characterized in that C is less than or equal to 0.12 percent, Si is less than or equal to 0.07 percent, Mn0.803-1.31 percent, P is less than or equal to 0.07 percent, S is 0.23-0.37 percent, Al is less than or equal to 0.001 percent, and the balance is Fe and residual elements. However, the method can only ensure that the content of S in the cutting steel is unchanged as much as possible, and in the subsequent electroslag remelting process, the burning loss of sulfur cannot be avoided even if sulfur is added as a slag material, so that the cutting performance of the cutting steel cannot be effectively improved; in addition, as the sulfur content of the cutting steel produced by this method increases, Al inclusions, MnS inclusions, FeS inclusions, etc. are also produced, and the presence of these inclusions also reduces the cutting performance of the cutting steel, so that the improvement of the cutting performance of the cutting steel by increasing the sulfur feeding amount is not achieved by this method.

Through search, the Chinese invention patent CN105950880A discloses an electroslag remelting process for sulfur-containing steel, wherein CaF is selected during electroslag remelting₂-SiO₂A CaO ternary slag system, wherein slag materials are fully dried by a baking furnace before remelting to reduce water in the slag, and the slag materials are subjected to electroslag production under the protection of dry argon atmosphere; the graphite electrode is adopted for cold arc striking, fluorite powder is added during slag melting, and after the fluorite powder is added, silica powder and lime blocks are alternately and slowly added to prevent slag materials from completely covering a hearth; adding a certain amount of iron sulfide in the slag melting process and the remelting process to deoxidize the slag; the filling ratio of electroslag remelting is designed to be 0.65-0.75, and the melting rate (Kg/h) of electroslag remelting is (0.8-0.95) multiplied by the diameter (mm) of the crystallizer. In the patent, an automatic feeder is adopted to continuously add iron sulfide for deoxidation and sulfur retention in the remelting process, so that the uniformity of chemical components of an electroslag ingot is ensured, but the chemical components are detected from the chemical componentsThe measurement result shows that the burning loss of sulfur in the electroslag ingot can still be caused, and the cutting performance is reduced; in addition, the patent directly adds pyrite in the electroslag remelting stage, and a reasonable preparation method is not provided for target steel with different sulfur contents, so that the method cannot effectively ensure the sulfur content in an electroslag ingot.

In summary, for the preparation process of the free-cutting stainless steel formed by remelting the scrap steel, the process should be comprehensively considered from the target steel stage to the electroslag remelting stage, and should be reasonably designed in combination with the slag system with lower cost and reasonable composition. Therefore, how to accurately control the sulfur content in the free-cutting stainless steel at low cost is an important means for ensuring the performance and improving the competitiveness of the free-cutting stainless steel, and a preparation method of the free-cutting stainless steel is urgently needed to be designed at present.

Disclosure of Invention

1. Problems to be solved

Aiming at the problems that in the prior art, the sulfur content in the electroslag remelting stainless steel cannot be effectively controlled, the cutting performance is poor, and the cost of the conventional free-cutting stainless steel is high, the invention provides a preparation method of the free-cutting electroslag remelting stainless steel and the stainless steel prepared by the method; by adding cheap manganese sulfide at the end of AOD and reasonably designing a slag system in LF refining process, burning loss of sulfur can be effectively avoided at the electroslag remelting stage, so that the problems that the sulfur content in electroslag remelting stainless steel cannot be effectively controlled and the cutting performance is poor are effectively solved.

2. Technical scheme

In order to solve the problems, the technical scheme adopted by the invention is as follows:

the invention relates to a preparation method of free-cutting electroslag remelting stainless steel, which comprises the steps of melting X tons of target steel, sequentially carrying out AOD decarburization treatment, LF refining treatment and casting mould, and carrying out electroslag remelting by taking a metal electrode obtained by the casting mould as a consumable electrode so as to obtain the free-cutting stainless steel; adding manganese sulfide for increasing sulfur in the AOD decarburization treatment process, wherein the mass of sulfur in the manganese sulfide is Y kg, and the mass ratio of Y/X is 1.4-3.0; and adding slag in the LF refining process, wherein the slag comprises 1.5-2.5 wt% of S. The preparation method is suitable for target steel with different sulfur contents, particularly target steel with the sulfur content of 0.1-0.3 wt%, and can effectively control the sulfur content of an electroslag ingot subjected to electroslag remelting and improve the cutting performance of cutting steel for the target steel.

It should be noted that the AOD described in the present invention is the conventional term "argon oxygen decarburization" in the art, and the treatment is mainly to inject molten steel or alloy obtained by melting into an AOD furnace through a ladle and blow O into the furnace during smelting₂Decarbonizing the molten steel by using the Ar mixed gas, and simultaneously adding a reducing agent or ferroalloy and the like into a feeding system to adjust the components and the temperature of the molten steel so as to smelt qualified stainless steel; the AOD decarburization treatment in the present invention is limited to the addition of a specific amount of manganese sulfide for increasing sulfur during the decarburization treatment.

Similarly, the LF described in the present invention is also the conventional term "ladle refining furnace" in the art, and the process mainly includes refining the molten steel obtained by the AOD decarburization by adding slag, and casting after the refining; the LF refining treatment in the invention is limited to adding slag with specific sulfur content and a slag system comprising the slag in the refining process, and the specific slag system components are further explained in the following; the difference lies in that the conventional LF refining has a desulfurization effect, and the specific slag system designed in the invention is used for ensuring the sulfur content in the molten steel, thereby laying a foundation for the subsequent electroslag remelting.

Preferably, the specific preparation steps are as follows:

(1) smelting the target steel at high temperature in an electric arc furnace;

(2) injecting the smelted molten steel into an AOD furnace through a steel ladle for smelting, blowing mixed gas of oxygen and argon during smelting to decarbonize the molten steel, simultaneously adding a reducing agent for reduction, removing slag completely, adding sulfur-manganese ore into the AOD furnace for increasing sulfur, and tapping;

(3) adding slag along with steel flow in the tapping process of the AOD furnace, then refining at an LF station, and casting into a consumable electrode after the refining is finished;

(4) and carrying out electroslag remelting on the consumable electrode obtained by LF refining to obtain the free-cutting stainless steel.

Preferably, in the step (2), when the manganosite contains 20 to 25 wt% of S, 7 to 10kg of the manganosite is added per ton of target steel; when the manganosite contains 25-30 wt% of S, 6-8 kg of the manganosite is added to each ton of target steel; and when the sulfur-manganese ore contains more than 30 wt% of S, 5 kg-7 kg of sulfur-manganese ore is added to each ton of target steel.

Preferably, in the step (2), the ratio of oxygen to argon in the mixed gas is (0.2-4): 1; the reducing agent added for reduction comprises ferrosilicon; and blowing argon gas and stirring for 2-3 min after the sulfur manganese ore is added, and then tapping.

Preferably, in the step (3), fluorite and slag are added simultaneously with steel flow during AOD furnace tapping, and the refining time is not less than 50 min-100 min; the mass ratio of fluorite to slag is 1: (5-10), adding 20-25 kg of fluorite slag mixture per ton of target steel.

Preferably, in the step (3), the slag further includes 40 to 45 wt% of CaO, 44 to 48 wt% of SiO₂5 to 10 weight percent of MgO and 0 to 10 weight percent of Al₂O₃。

Preferably, in the step (4), after the LF refining is completed, a metal consumable electrode with a diameter smaller than that of the remelting crystallizer is cast, wherein the diameter of the metal consumable electrode is 300-640 mm, and the diameter of the remelting crystallizer is 500-800 mm; carrying out electroslag remelting on the metal consumable electrode, wherein slag used for remelting comprises fluorite, slag and quartz sand, and the mass ratio of the fluorite to the slag to the quartz sand is (3-6): (1-5): 1, adding 30 kg-40 kg of slag charge into each ton of target steel.

Preferably, in the step (4), the slag used for electroslag remelting includes 35 wt% to 40 wt% of CaO and 35 wt% to 40 wt% of SiO₂5 to 10 weight percent of MgO and 15 to 20 weight percent of Al₂O₃And 0.2 wt% to 0.5 wt% S; by adding sulfur with specific content in the electroslag remelting process and designing the remelting slag system, the burning loss of the sulfur can be effectively avoided, and under the combined action of the sulfur and the consumable electrode obtained by LF refining, the sulfur content before and after the electroslag remelting is a fewThe sulfur content is controlled accurately.

Preferably, in the step (4), the current of the electroslag remelting is 8000A-15000A, and the voltage is 55V-85V.

Preferably, sampling the molten steel after the AOD decarburization treatment to detect that the sulfur content in the molten steel is A; sampling the molten steel in the LF refining process to detect that the sulfur content in the molten steel is B; stopping LF refining when the B ═ A + (0.01 wt% to 0.03 wt%). Through the arrangement, under the LF refining effect of the specific slag system, the refining progress is accurately controlled, the sulfur content in the electroslag ingot obtained by electroslag remelting can be accurately controlled, and the cutting performance of the cutting steel is effectively improved.

The stainless steel is prepared by the preparation method of the free-cutting electroslag remelting stainless steel.

3. Advantageous effects

Compared with the prior art, the invention has the beneficial effects that:

(1) the invention relates to a preparation method of free-cutting electroslag remelting stainless steel, which comprises the steps of melting X tons of target steel, sequentially carrying out AOD decarburization treatment, LF refining treatment and casting mould, and carrying out electroslag remelting by taking a metal electrode obtained by the casting mould as a consumable electrode so as to obtain the free-cutting stainless steel; adding manganese sulfide for increasing sulfur in the AOD decarburization treatment process, wherein the mass of sulfur in the manganese sulfide is Y kg, and the mass ratio of Y/X is 1.4-3.0; adding slag in the LF refining process, wherein the slag comprises 1.5-2.5 wt% of S; by the method, manganese sulfide with specific content is added at the last stage of AOD for direct alloying, favorable conditions of AOD decarburization treatment are utilized to fully increase sulfur in molten steel, high-sulfur and low-cost ironmaking slag is adopted as refining slag in LF stage, so that cost can be reduced, burning loss of sulfur can be avoided, sulfur content in molten steel is increased to a certain extent, and sulfur content of electroslag ingots obtained by electroslag remelting is accurately increased, so that cutting performance of cutting steel is improved; in addition, by selecting the manganese sulfide and the slag with low price as main raw materials, the production cost can be reduced to the maximum extent, and the stability of sulfur in the smelting process can be ensured, so that the free-cutting stainless steel with strong competitiveness and stable quality can be produced.

(2) The stainless steel is prepared by the preparation method of the free-cutting electroslag remelting stainless steel; the free-cutting stainless steel has stable yield of sulfur and excellent cutting performance.

Detailed Description

The following more detailed description of the embodiments of the invention is not intended to limit the scope of the invention, as claimed, but is presented for purposes of illustration only and not limitation to describe the features and characteristics of the invention, to set forth the best mode of carrying out the invention, and to sufficiently enable one skilled in the art to practice the invention. It will, however, be understood that various modifications and changes may be made without departing from the scope of the invention as defined in the appended claims. The detailed description is to be construed as illustrative only and not restrictive, and any such modifications and variations are intended to be included within the scope of the invention as described herein. Furthermore, the background is intended to be illustrative of the state of the art as developed and the meaning of the present technology and is not intended to limit the scope of the invention or the application and field of application of the invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs; the terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention; as used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The invention is further described with reference to specific examples.

Example 1

The embodiment provides a preparation method of free-cutting electroslag remelting stainless steel and the stainless steel prepared by the method, the target steel is austenitic stainless steel 316F, the sulfur content is more than or equal to 0.1 wt%, and the specific preparation steps are as follows:

(1) melting the scrap steel in an electric arc furnace, wherein the proportion of the austenitic stainless steel 316F return material is 70 wt%, the rest is carbon scrap steel, and the addition amount of lime per ton of steel is 18 kg; when the temperature is 1600-1650 ℃, stopping smelting, completely removing slag, and preparing for tapping;

(2) injecting smelted molten steel into an AOD furnace through a steel ladle for smelting, blowing mixed gas of oxygen and argon for decarburization during smelting, wherein the ratio of oxygen to argon in the mixed gas is 3:1, then gradually reducing the ratio to 1:3, adding ferrosilicon for reduction after decarburization is finished, removing slag, adding manganite into the AOD furnace for increasing sulfur, wherein the content of S in the manganite is 20 wt%, 7kg of the manganite is added to each ton of target steel, blowing argon on the side for stirring for 2.5min after the completion of the addition of the manganite, effectively increasing the sulfur content in the molten steel under the stirring action, sampling to detect that the sulfur content is 0.14 wt%, and tapping;

(3) after the adding of the manganese sulfide of the AOD furnace is finished and the stirring is finished, tapping is poured into a steel ladle, fluorite and slag are added along with steel flow in the tapping process, and the mass ratio of the fluorite to the slag is 1:5, wherein the slag comprises 43 wt% of CaO and 45 wt% of SiO₂5 wt% of MgO, 5.5 wt% of Al₂O₃And 1.5 wt% of S, 20kg of fluorite and slag mixture per ton of the target steel; then hoisting the ladle to an LF station for refining, adding no deoxidizing agent in the refining process, stopping refining when the sulfur content is detected to be 0.15 wt% by sampling, and casting the refined ladle into a metal consumable electrode with the diameter of 300 mm;

(4) carrying out electroslag remelting on the metal consumable electrode obtained by LF refining, wherein the diameter of a crystallizer used for electroslag remelting is 500mm, the current is 7000A-9000A, and the voltage is 55V-65V; the slag used for electroslag remelting comprises fluorite, slag and quartz sand, wherein the mass ratio of the fluorite to the slag to the quartz sand is 4: 5: 1, adding 37kg of slag charge to each ton of target steel; the slag comprises 38 wt% of CaO and 37 wt% of SiO₂8.8 wt% of MgO, 16 wt% of Al₂O₃And 0.2 wt% S; after remelting, the free-cutting stainless steel was obtained, and the content of S in the steel was measured and shown in table 1.

Table 1 comparison of S content in target steels, AOD tapping, LF tapping, and finally-produced stainless steels in examples and comparative examples

Example 2

The embodiment provides a preparation method of free-cutting electroslag remelting stainless steel and the stainless steel prepared by the method, the target steel is martensitic stainless steel 416, the sulfur content is more than or equal to 0.15 wt%, and the specific preparation steps are as follows:

(1) melting scrap steel in an electric arc furnace, wherein the return material proportion of the martensitic stainless steel 416 is 80 wt%, the rest is carbon scrap steel, and the addition amount of lime per ton of steel is 20 kg; when the temperature is 1600-1650 ℃, stopping smelting, completely removing slag, and preparing for tapping;

(2) injecting smelted molten steel into an AOD furnace through a steel ladle for smelting, blowing mixed gas of oxygen and argon for decarburization during smelting, wherein the ratio of oxygen to argon in the mixed gas is 3:1, then gradually reducing the ratio to 1:4, simultaneously adding ferrosilicon for reduction, removing slag, adding manganosite into the AOD furnace for increasing sulfur, wherein the manganosite contains 26 wt% of S, 8kg of the manganosite is added into each ton of target steel, blowing argon on the side for stirring for 3min after the completion of the addition of the manganosite, effectively increasing the sulfur content in the molten steel under the stirring action, sampling and detecting that the sulfur content is 0.20 wt%, and tapping;

(3) after the adding of the manganese sulfide of the AOD furnace is finished and the stirring is finished, tapping is poured into a steel ladle, fluorite and slag are added along with steel flow in the tapping process, and the mass ratio of the fluorite to the slag is 1:5, wherein the slag comprises 44 wt% of CaO, 46 wt% of SiO₂4 wt% of MgO, 4.3 wt% of Al₂O₃And 1.7 wt% of S, 22kg of fluorite and slag mixture per ton of the target steel; then hoisting the ladle to an LF stationRefining, wherein no deoxidizing agent is added in the refining process, the refining time is 50min, the refining is stopped when the sulfur content is detected to be 0.22 wt% by sampling, and a metal consumable electrode with the diameter of 520mm is cast after the refining is finished;

(4) carrying out electroslag remelting on the metal consumable electrode obtained by LF refining, wherein the diameter of a crystallizer used for the electroslag remelting is 680mm, the current is 10000-11000A, and the voltage is 65-75V; the slag used for electroslag remelting comprises fluorite, slag and quartz sand, wherein the mass ratio of the fluorite to the slag to the quartz sand is 5: 4:1, adding 35kg of slag charge to each ton of target steel; the slag comprises 36 wt% of CaO and 39 wt% of SiO₂6.7 wt% of MgO, 18 wt% of Al₂O₃And 0.3 wt% S; after remelting, the free-cutting stainless steel was obtained, and the content of S in the steel was measured and shown in table 1.

Example 3

The embodiment provides a preparation method of free-cutting electroslag remelting stainless steel and the stainless steel prepared by the method, the target steel is ferritic stainless steel 430F, the sulfur content is more than or equal to 0.15 wt%, and the specific preparation steps are as follows:

(1) melting the scrap steel in an electric arc furnace, wherein the proportion of the 430F return material of the ferritic stainless steel is 60 wt%, the rest is carbon scrap steel, and the addition amount of lime per ton of steel is 23 kg; when the temperature is 1600-1650 ℃, stopping smelting, completely removing slag, and preparing for tapping;

(2) injecting smelted molten steel into an AOD furnace through a steel ladle for smelting, blowing mixed gas of oxygen and argon for decarburization during smelting, wherein the ratio of oxygen to argon in the mixed gas is firstly 4:1, then gradually reducing to 1:4, simultaneously adding ferrosilicon for reduction, removing slag, then adding manganite into the AOD furnace for increasing sulfur, wherein the manganite contains 32 wt% of S, 6kg of the manganite is added into each ton of target steel, blowing argon on the side for stirring for 2min after the completion of the addition of the manganite, effectively increasing the sulfur content in the molten steel under the stirring action, sampling and detecting that the sulfur content is 0.18 wt%, and tapping;

(3) after the AOD furnace is completely filled with manganese sulfide and stirred, pouring the steel into a ladle, and adding fluorite and ore along with steel flow in the process of steel tappingAnd slag, wherein the mass ratio of fluorite to slag is 1:5, wherein the slag comprises 43 wt% of CaO and 47 wt% of SiO₂3 wt% of MgO, 5 wt% of Al₂O₃And 2 wt% of S, 24kg of fluorite and slag mixture per ton of the target steel; then hoisting the ladle to an LF station for refining, adding no deoxidizing agent in the refining process, stopping refining when the sulfur content is detected to be 0.20 wt% by sampling, and casting into a metal consumable electrode with the diameter of 640mm after refining is finished;

(4) carrying out electroslag remelting on the metal consumable electrode obtained by LF refining, wherein the diameter of a crystallizer used for electroslag remelting is 800mm, the current is 14000-15000A, and the voltage is 75-85V; the slag used for electroslag remelting comprises fluorite, slag and quartz sand, wherein the mass ratio of the fluorite to the slag to the quartz sand is 6: 3:1, adding 33kg of slag charge to each ton of target steel; the slag comprises 35 wt% of CaO and 36 wt% of SiO₂8.7 wt% of MgO and 20 wt% of Al₂O₃And 0.3 wt% S; after remelting, the free-cutting stainless steel was obtained, and the content of S in the steel was measured and shown in table 1.

Example 4

The embodiment provides a preparation method of free-cutting electroslag remelting stainless steel and the stainless steel prepared by the method, the target steel is ferritic stainless steel 303, the sulfur content is more than or equal to 0.25 wt%, and the specific preparation steps are as follows:

(1) melting the scrap steel in an electric arc furnace, wherein the proportion of return materials of the ferritic stainless steel 303 is 90 wt%, the rest are carbon scrap steel, and the addition amount of lime per ton of steel is 25 kg; when the temperature is 1600-1650 ℃, stopping smelting, completely removing slag, and preparing for tapping;

(2) injecting smelted molten steel into an AOD furnace through a steel ladle for smelting, blowing mixed gas of oxygen and argon for decarburization during smelting, wherein the ratio of oxygen to argon in the mixed gas is firstly 4:1, then gradually reducing to 1:5, simultaneously adding ferrosilicon for reduction, removing slag, then adding manganite into the AOD furnace for increasing sulfur, wherein the manganite contains 35 wt% of S, 8kg of the manganite is added into each ton of target steel, blowing argon on the side for stirring for 2min after the completion of the addition of the manganite, effectively increasing the sulfur content in the molten steel under the stirring action, sampling and detecting that the sulfur content is 0.27 wt%, and tapping;

(3) after the adding of the manganese sulfide of the AOD furnace is finished and the stirring is finished, tapping is poured into a steel ladle, fluorite and slag are added along with steel flow in the tapping process, and the mass ratio of the fluorite to the slag is 1:5, wherein the slag comprises 42 wt% of CaO, 48 wt% of SiO₂4 wt% of MgO, 3.5 wt% of Al₂O₃And 2.5 wt% of S, 25kg of fluorite and slag mixture per ton of the target steel; then hoisting the ladle to an LF station for refining, adding no deoxidizing agent in the refining process, stopping refining when the sulfur content is detected to be 0.28 wt% by sampling, and casting into a metal consumable electrode with the diameter of 400mm after refining is finished;

(4) carrying out electroslag remelting on the metal consumable electrode obtained by LF refining, wherein the diameter of a crystallizer used for electroslag remelting is 580mm, the current is 8000A-10000A, and the voltage is 58V-68V; the slag used for electroslag remelting comprises fluorite, slag and quartz sand, wherein the mass ratio of the fluorite to the slag to the quartz sand is 6: 2: 2, adding 40kg of slag charge into each ton of target steel; the slag comprises 37 wt% of CaO and 38 wt% of SiO₂8.6 wt% of MgO, 16 wt% of Al₂O₃And 0.4 wt% S; after remelting, the free-cutting stainless steel was obtained, and the content of S in the steel was measured and shown in table 1.

Comparative example 1

The comparative example provides a stainless steel and a preparation method thereof, the target steel is austenitic stainless steel 316F, the sulfur content is more than or equal to 0.1 wt%, the specific preparation steps are basically the same as those of the example 1, and the main differences are as follows: in the LF refining treatment, sulfur-containing slag is not added, but the traditional refining slag is adopted, and the alkalinity is more than or equal to 2.0.

The S content in the stainless steel finally obtained by electroslag remelting is shown in table 1.

Comparative example 2

This comparative example provides a stainless steel and a method for its preparation, the target steel grade being martensitic stainless steel 416, having a sulphur content of not less than 0.15 wt%, the specific manufacturing procedure being essentially the same as in example 2, with the main difference that: in the electroslag remelting process, sulfur-containing slag is not added, and the traditional 30 wt% Al is adopted₂O₃And 70 wt% of CaF₂Remelting slag system.

The S content in the stainless steel finally obtained by electroslag remelting is shown in table 1.

Comparative example 3

The comparative example provides a stainless steel and a preparation method thereof, the target steel is ferritic stainless steel 303, the sulfur content is more than or equal to 0.25 wt%, the specific preparation steps are basically the same as those of example 4, and the main differences are as follows: and after AOD decarburization treatment, sampling and detecting the sulfur content A of the molten steel to be 0.25%, and stopping LF refining when sampling and detecting the sulfur content B of the molten steel to be 0.23% in the LF refining treatment process.

The S content in the stainless steel finally obtained by electroslag remelting is shown in table 1.

By comparing example 1 with comparative example 1, it can be seen that when the fluorite and slag mixture designed by the invention is not added in the LF refining treatment process, the S content of LF tapping is greatly reduced, which indicates that obvious burning loss occurs in sulfur, and even if a sulfur-containing slag system is designed in the electroslag remelting stage, the burning loss cannot be compensated; a similar result can be seen by comparing the example 2 with the comparative example 2, and the burning loss of sulfur can be effectively avoided only by reasonably designing slag systems in an LF stage and an electroslag remelting stage, so that the cutting performance of the stainless steel is ensured. Comparing examples 1-4 with comparative example 3, it can be seen that under the effect of the slag system designed by the invention, the sulfur content in the finally prepared stainless steel can be accurately controlled by controlling the refining progress of LF refining treatment, and further, when B is within the optimal range designed by the invention, the cutting performance of the stainless steel can be effectively ensured.

More specifically, although exemplary embodiments of the invention have been described herein, the invention is not limited to these embodiments, but includes any and all embodiments modified, omitted, combined, e.g., between various embodiments, adapted and/or substituted, as would be recognized by those skilled in the art from the foregoing detailed description. The limitations in the claims are to be interpreted broadly based the language employed in the claims and not limited to examples described in the foregoing detailed description or during the prosecution of the application, which examples are to be construed as non-exclusive. Any steps recited in any method or process claims may be executed in any order and are not limited to the order presented in the claims. The scope of the invention should, therefore, be determined only by the appended claims and their legal equivalents, rather than by the descriptions and examples given above.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control. When "mass, mass ratio, composition, diameter, time, current, voltage, or other value or parameter is expressed as a range, preferred range, or a range defined by a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, a range of 1 to 50 should be understood to include any number, combination of numbers, or subrange selected from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, and all fractional values between the above integers, e.g., 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. With respect to sub-ranges, specifically consider "nested sub-ranges" that extend from any endpoint within the range. For example, nested sub-ranges of exemplary ranges 1-50 may include 1-10, 1-20, 1-30, and 1-40 in one direction, or 50-40, 50-30, 50-20, and 50-10 in another direction.