Low-manganese stainless steel material and preparation method thereof

Abstract

The invention discloses a low-manganese stainless steel material and a preparation method thereof, and belongs to the field of stainless steel materials. Comprising the following steps: melting raw materials in a melting furnace to obtain stainless steel liquid and preserving heat; sampling the stainless steel liquid and analyzing the existing manganese content in the stainless steel liquid; calculating the content of a required manganese reducing agent and adding the manganese reducing agent into the stainless steel liquid; fully stirring to uniformly disperse the manganese reducing agent in the stainless steel liquid and fully react with manganese in the stainless steel liquid to generate manganese-containing inclusions; manganese-containing inclusions in the stainless steel liquid are repeatedly removed, and the stainless steel liquid is subjected to pre-purification treatment; and the stainless steel liquid subjected to pre-purification treatment is subjected to temperature control cooling casting forming, and the low-manganese stainless steel material is obtained. The manganese content in the stainless steel material preparation process can be efficiently and controllably reduced, the method has the advantages of being simple in process, short in flow, low in cost, high in efficiency and the like, and the prepared low-manganese stainless steel material is high in quality and excellent in comprehensive performance. The method is particularly suitable for preparing the low-manganese-content stainless steel material from the high-manganese-content stainless steel waste.

Description

Technical Field

[0001] The invention belongs to the field of stainless steel materials, and specifically relates to a low-manganese stainless steel material and a preparation method thereof, which is particularly suitable for preparing a low-manganese stainless steel material by using stainless steel waste with a high manganese content. Background Art

[0002] The manganese element in stainless steel materials mainly comes from pig iron, scrap steel, alloy raw materials, deoxidizers and desulfurizers in the smelting process. Manganese will be dissolved in the matrix or exist in the form of MnO and MnS inclusions in stainless steel materials. Manganese has a strong effect of promoting the precipitation of brittle phases such as σ phase, which will reduce the plastic toughness of stainless steel materials; MnO inclusions will break the continuity of the matrix, reduce the mechanical properties of stainless steel materials, and cause stress concentration during plastic deformation of stainless steel materials, becoming the starting point for crack initiation; MnS inclusions are easy to precipitate along the grain boundaries during the solidification of stainless steel liquid, and will dissolve in the corrosive medium, becoming a source of pitting and crevice corrosion, reducing the pitting and crevice corrosion resistance of stainless steel materials. With the rapid development of science and technology, all walks of life have higher and higher requirements for the quality of stainless steel materials. In particular, with the continuous development of circular economy and low-carbon economy, it is increasingly hoped that stainless steel materials can be directly prepared by short process using stainless steel waste, and the higher manganese content in high-manganese stainless steel waste has become a bottleneck problem in the preparation of low-manganese stainless steel materials. Therefore, reducing the manganese content in stainless steel materials is an urgent need for the short-process and low-cost preparation of low-manganese stainless steel materials.

[0003] In short, developing a technology for reducing the manganese content in stainless steel materials with good stability, low cost and high efficiency, and preparing stainless steel materials with low manganese content are of great significance for promoting the utilization of stainless steel waste, regulating the manganese content in stainless steel materials, and improving the quality of stainless steel materials. Summary of the invention

[0004] The present invention aims at the urgent requirement of reducing the manganese content in the process of preparing stainless steel materials using stainless steel waste as raw materials, and provides a low-manganese stainless steel material and a preparation method thereof, which is particularly suitable for preparing a low-manganese stainless steel material using stainless steel waste with a high manganese content.

[0005] According to a first aspect of the technical solution of the present invention, a method for preparing a low manganese stainless steel material is provided, comprising the following steps:

[0006] Step 1: Place the raw materials into a melting furnace for melting to obtain stainless steel liquid, and keep it warm;

[0007] Step 2: sampling and analyzing the existing manganese content in the stainless steel liquid, and calculating the content of the manganese reducing agent to be added according to the target manganese content and the existing manganese content;

[0008] Step 3: adding the manganese reducing agent to the stainless steel liquid and stirring the mixture sufficiently, so that the manganese reducing agent is evenly dispersed in the stainless steel liquid and fully reacts with the manganese in the stainless steel liquid to form manganese-containing inclusions;

[0009] Step 4: repeatedly removing the manganese-containing inclusions generated in the stainless steel liquid to achieve pre-purification of the stainless steel liquid;

[0010] Step 5: The stainless steel liquid after the pre-cleaning treatment is subjected to temperature-controlled cooling and casting to obtain a low-manganese stainless steel material.

[0011] Furthermore, the method further comprises: placing the cast low-manganese stainless steel material into the melting furnace again to melt it into a stainless steel melt, controlling its melting temperature to be between the liquidus temperature of the low-manganese stainless steel material and the melting point of residual manganese-containing inclusions solidified and precipitated in the low-manganese stainless steel material, so that the residual manganese-containing inclusions are suspended in the stainless steel melt or float to the surface of the stainless steel melt, repeatedly removing the residual manganese-containing inclusions to achieve purification of the stainless steel melt, and then solidifying and forming the stainless steel melt to obtain a stainless steel material with a lower manganese content.

[0012] Furthermore, the raw materials contain at least stainless steel waste and alloy materials with high manganese content.

[0013] Furthermore, the melting furnace is at least one of an electric arc furnace, an induction furnace or a resistance furnace.

[0014] Furthermore, the manganese reducing agent is at least one of metal sulfide or metal oxide, the metal sulfide is at least one of ferrous sulfide, chromium sulfide or nickel sulfide, and the metal oxide is at least one of iron oxide or ferrous oxide.

[0015] Furthermore, the stirring method after the manganese reducing agent is added to the stainless steel liquid is at least one of mechanical stirring, electromagnetic stirring, gas stirring or ultrasonic stirring.

[0016] Furthermore, the manganese-containing inclusions or the residual manganese-containing inclusions are at least one of manganese sulfide, manganese oxide, manganese sulfide or manganese oxide in which other elements are solid-dissolved, and complex inclusions consisting of manganese sulfide or manganese oxide and other oxides.

[0017] Furthermore, the method for removing the manganese-containing inclusions or the residual manganese-containing inclusions is at least one of a slag removal method, a static clarification method, an electromagnetic purification method, a filtration method, a slag washing method, a bubble flotation method, a negative pressure drainage method or a solidification sawing method.

[0018] Furthermore, the treated stainless steel liquid or the stainless steel melt is subjected to subsequent refining treatments such as decarburization, desulfurization, deoxidation or alloying to obtain the desired stainless steel material.

[0019] Furthermore, the equipment used for the refining process is at least one of AOD, VOD, VD or LF refining furnaces.

[0020] According to a second aspect of the technical solution of the present invention, a low manganese stainless steel material is provided. The low manganese stainless steel material is prepared by the preparation method according to any one of the above aspects.

[0021] The advantages of the present invention are:

[0022] 1. The method of the present invention adds low-melting-point metal sulfide or metal oxide to stainless steel liquid with high manganese content, so that it reacts with manganese element in the stainless steel liquid or in the subsequent temperature-controlled cooling casting process to generate high-melting-point manganese-containing inclusions, which can significantly reduce the manganese content in the stainless steel material after removal, and obtain low-manganese stainless steel material. The present invention avoids the traditional direct injection of oxygen-containing gas into the cast iron melt, which makes the oxygen content in the cast iron melt difficult to control, and the direct injection of oxygen-containing gas into the stainless steel melt, which causes serious oxidation loss of other elements such as chromium in the stainless steel melt and high oxygen content. It also avoids the traditional direct addition of mixed sodium sulfate or sulfur-based demanganese treatment agents to the cast iron melt or steel melt, which leads to excessive increase in sulfur content in the cast iron melt or steel melt and produces a large amount of sulfur slag, and brings desulfurization problems to subsequent production.

[0023] 2. The method of the present invention melts the cast low-manganese stainless steel material again, and controls its melting temperature between its liquidus temperature and the melting point of residual manganese-containing inclusions precipitated from its solidification, so that the residual manganese-containing inclusions are suspended in the stainless steel melt or float to the surface of the stainless steel melt and are removed by physical methods, thereby obtaining a stainless steel material with a lower manganese content, which has the advantage of a higher manganese reduction rate.

[0024] 3. The method of the present invention utilizes the characteristic that the metal sulfide or metal oxide added to the stainless steel liquid easily reacts with manganese to generate high-melting-point manganese-containing inclusions. The manganese content in the high-manganese-content stainless steel material can be quickly and effectively reduced only by pre-purifying the molten steel with metal sulfides or metal oxides, temperature-controlled cooling casting, re-melting and physically removing the manganese-containing inclusions. The low-manganese stainless steel material can be prepared conveniently and quickly. The method has the advantages of simple process, short flow, low cost, high efficiency, etc., and is particularly suitable for preparing low-manganese-content stainless steel materials using high-manganese-content stainless steel waste.

[0025] 4. The low manganese stainless steel material of the present invention has low manganese content, high purity and excellent comprehensive performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 The figure is a flow chart of the preparation method of the low manganese stainless steel material according to the present invention. DETAILED DESCRIPTION

[0028] The present invention is described in detail below in conjunction with embodiments. It is necessary to point out that the embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. A person skilled in the art can make some non-essential improvements and adjustments based on the contents of the present invention.

[0029] The technical solution of the present invention first provides a method for preparing a low manganese stainless steel material, such as Figure 1 As shown, the following steps are included:

[0030] Step 101: Put the raw materials into a melting furnace for melting to obtain stainless steel liquid, and keep the temperature.

[0031] In a preferred embodiment, the raw materials contain at least stainless steel scrap and alloy material with high manganese content.

[0032] In a preferred embodiment, the melting furnace is at least one of an electric arc furnace, an induction furnace or a resistance furnace.

[0033] Step 102: sampling and analyzing the existing manganese content in the stainless steel liquid; and calculating the content of the manganese reducing agent to be added according to the target manganese content and the existing manganese content.

[0034] In a preferred embodiment, the manganese reducing agent is at least one of metal sulfide or metal oxide, the metal sulfide is at least one of ferrous sulfide, chromium sulfide or nickel sulfide, and the metal oxide is at least one of iron oxide or ferrous oxide.

[0035] Step 103: adding the manganese reducing agent to the stainless steel liquid and stirring the mixture sufficiently, so that the manganese reducing agent is evenly dispersed in the stainless steel liquid and fully reacts with the manganese in the stainless steel liquid to generate manganese-containing inclusions.

[0036] In a preferred embodiment, the stirring method after the manganese reducing agent is added to the stainless steel liquid is at least one of mechanical stirring, electromagnetic stirring, gas stirring or ultrasonic stirring.

[0037] Step 104: repeatedly removing the manganese-containing inclusions generated in the stainless steel liquid to achieve pre-purification of the stainless steel liquid.

[0038] Step 105: The stainless steel liquid after the pre-cleaning treatment is subjected to temperature-controlled cooling and casting to obtain a low-manganese stainless steel material.

[0039] In a preferred embodiment, the cast low-manganese stainless steel material is further put into the melting furnace again to be melted into a stainless steel melt, and its melting temperature is controlled between the liquidus temperature of the low-manganese stainless steel material and the melting point of residual manganese-containing inclusions solidified and precipitated in the low-manganese stainless steel material, so that the residual manganese-containing inclusions are suspended in the stainless steel melt or float to the surface of the stainless steel melt, and the residual manganese-containing inclusions are repeatedly removed to achieve purification of the stainless steel melt, and then the stainless steel melt is solidified and formed to obtain a stainless steel material with a lower manganese content.

[0040] In a preferred embodiment, the manganese-containing inclusions or the residual manganese-containing inclusions are at least one of manganese sulfide, manganese oxide, manganese sulfide or manganese oxide in which other elements are solid-dissolved, and complex inclusions consisting of manganese sulfide or manganese oxide and other oxides.

[0041] In a preferred embodiment, the method for removing the manganese-containing inclusions or the residual manganese-containing inclusions is at least one of a slag removal method, a static clarification method, an electromagnetic purification method, a filtration method, a slag washing method, a bubble flotation method, a negative pressure drainage method or a solidification sawing method.

[0042] In a preferred embodiment, the treated stainless steel liquid or the stainless steel melt is subjected to subsequent refining treatments such as decarburization, desulfurization, deoxidation or alloying to obtain the desired stainless steel material.

[0043] In a preferred embodiment, the equipment used for the refining process is at least one of AOD, VOD, VD or LF refining furnaces.

[0044] The technical solution of the present invention also provides a low manganese stainless steel material, which is prepared by the preparation method described above.

[0045] Example 1: Preparation of low manganese 304 stainless steel material with a manganese content of 0.3 wt.%

[0046] An electric arc furnace is used to melt 5 tons of 304 stainless steel waste, alloy materials with high manganese content and other raw materials to obtain stainless steel liquid, and the stainless steel liquid is kept warm at 1600°C; the stainless steel liquid is sampled and analyzed for components, and the existing manganese content in the stainless steel liquid is 1.2wt.%; according to the target manganese content and the existing manganese content, 59 kg of ferrous oxide is added to the stainless steel liquid after calculation, and the stainless steel liquid with the ferrous oxide is fully stirred by electromagnetic stirring technology, so that the ferrous oxide is evenly dispersed in the stainless steel liquid and fully reacts with the manganese in the stainless steel liquid to generate manganese-containing inclusions such as manganese dioxide, and the manganese-containing inclusions generated in the stainless steel liquid are repeatedly removed by slag removal to achieve pre-purification of the stainless steel liquid; the stainless steel liquid after the pre-purification is temperature-controlled cooled and cast, and the cooling rate is less than 40°C / min, so as to obtain a low-manganese 304 stainless steel material with a manganese content of 0.3wt.%.

[0047] Example 2: Preparation of low manganese 304L stainless steel material with a manganese content of 0.18 wt.%

[0048] A medium frequency induction furnace is used to melt 10 tons of 304L stainless steel waste, alloy materials with high manganese content and other raw materials to obtain stainless steel liquid, and the stainless steel liquid is kept warm at 1600°C; the stainless steel liquid is sampled and analyzed for composition, and the existing manganese content in the stainless steel liquid is 1.5wt.%; according to the target manganese content and the existing manganese content, 118 kg of ferrous oxide and 67 kg of ferrous sulfide are added to the stainless steel liquid after calculation, and the stainless steel liquid with ferrous oxide and ferrous sulfide added is fully stirred using electromagnetic stirring technology, so that the ferrous oxide and ferrous sulfide are uniformly dispersed in the stainless steel liquid and fully react with the manganese in the stainless steel liquid to generate manganese-containing inclusions such as manganese dioxide and manganese sulfide, and the manganese-containing inclusions generated in the stainless steel liquid are repeatedly removed. The stainless steel liquid is pre-purified; the stainless steel liquid after the pre-purification treatment is subjected to temperature-controlled cooling and casting, and the cooling rate is less than 30°C / min, so as to obtain a stainless steel material with a low manganese content of 0.6wt.%; the cast stainless steel material with a low manganese content is again placed in a medium frequency induction furnace to be melted into a stainless steel liquid, and its melting temperature is controlled to be 1500°C. After standing, residual manganese-containing inclusions are floated to the surface of the stainless steel liquid, and the residual manganese-containing inclusions are repeatedly removed by slag removal to achieve purification of the stainless steel liquid; and the treated stainless steel liquid is subjected to subsequent refining treatments such as decarburization, desulfurization, deoxidation or alloying in an AOD furnace to obtain a low manganese 304L stainless steel material with a manganese content of 0.18wt.%.

[0049] Example 3: Preparation of low manganese 316LN stainless steel material with a manganese content of 0.3 wt.%

[0050] A medium frequency induction furnace is used to melt 5 tons of 316LN stainless steel scrap, alloy material with high manganese content and other raw materials to obtain stainless steel liquid, and the stainless steel liquid is kept warm at 1600°C; the stainless steel liquid is sampled and analyzed for composition, and the existing manganese content in the stainless steel liquid is 2.5wt.%; according to the target manganese content and the existing manganese content, 100 kg of ferrous oxide and 54 kg of ferrous sulfide are added to the stainless steel liquid after calculation, and the stainless steel liquid with ferrous oxide and ferrous sulfide added is fully stirred using gas stirring technology, so that the ferrous oxide and ferrous sulfide are uniformly dispersed in the stainless steel liquid and fully react with the manganese in the stainless steel liquid to generate manganese-containing inclusions such as manganese dioxide and manganese sulfide, and the manganese-containing inclusions generated in the stainless steel liquid are repeatedly removed. The stainless steel liquid is pre-purified; the stainless steel liquid after the pre-purification treatment is subjected to temperature-controlled cooling and casting, with a cooling rate of less than 20°C / min, to obtain a stainless steel material with a low manganese content of 0.97wt.%; the cast stainless steel material with a low manganese content is again placed in a medium frequency induction furnace to be melted into a stainless steel liquid, and its melting temperature is controlled to be 1500°C, so that residual manganese-containing inclusions are suspended in the stainless steel liquid, and the residual manganese-containing inclusions are repeatedly removed by filtering to achieve purification of the stainless steel liquid; and the treated stainless steel liquid is subjected to subsequent refining treatments such as decarburization, desulfurization, deoxidation or alloying in an AOD furnace to obtain a low manganese 316LN stainless steel material with a manganese content of 0.3wt.%.

[0051] In summary, the technical solution of the present invention utilizes low-melting-point metal sulfides or metal oxides as manganese-reducing agents to form high-melting-point manganese-containing inclusions in the stainless steel liquid or in the subsequent temperature-controlled cooling casting process, and pre-purifies the stainless steel liquid by physical methods and performs temperature-controlled cooling casting, or melts the cast stainless steel material with a low manganese content and removes residual manganese-containing inclusions, or performs subsequent refining treatments such as decarburization, desulfurization, deoxidation or alloying to obtain the desired low-manganese stainless steel material. The advantage of the present invention is that it can achieve efficient and controllable reduction of manganese content in the preparation process of stainless steel materials, and has the advantages of simple process, short process, low cost, high efficiency, etc. The prepared low-manganese stainless steel material has high quality and excellent comprehensive performance. It is particularly suitable for preparing stainless steel materials with low manganese content using stainless steel waste with high manganese content.

[0052] The embodiments of the present invention are described above, but the present invention is not limited to the above-mentioned specific implementation modes. The above-mentioned specific implementation modes are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which are all within the protection of the present invention.

Claims

1. A method for preparing a low manganese stainless steel material, characterized in that: The specific steps are as follows: Step 1: Place the raw materials into a melting furnace for melting to obtain stainless steel liquid, and keep it warm; Step 2: sampling and analyzing the existing manganese content in the stainless steel liquid, and calculating the content of the manganese reducing agent to be added according to the target manganese content and the existing manganese content; Step 3: adding the manganese reducing agent to the stainless steel liquid and stirring the mixture sufficiently, so that the manganese reducing agent is evenly dispersed in the stainless steel liquid and fully reacts with the manganese in the stainless steel liquid to form manganese-containing inclusions; Step 4: repeatedly removing the manganese-containing inclusions generated in the stainless steel liquid to achieve pre-purification of the stainless steel liquid; Step 5: The stainless steel liquid after the pre-cleaning treatment is subjected to temperature-controlled cooling and casting to obtain a low-manganese stainless steel material.

2. The method for preparing a low manganese stainless steel material according to claim 1, characterized in that: Also includes: The cast low-manganese stainless steel material is put into the melting furnace again to be melted into a stainless steel melt, and its melting temperature is controlled between the liquidus temperature of the low-manganese stainless steel material and the melting point of residual manganese-containing inclusions solidified and precipitated in the low-manganese stainless steel material, so that the residual manganese-containing inclusions are suspended in the stainless steel melt or float to the surface of the stainless steel melt, and the residual manganese-containing inclusions are repeatedly removed to achieve purification of the stainless steel melt, and then the stainless steel melt is solidified and formed to obtain a stainless steel material with a lower manganese content.

3. The method for preparing a low manganese stainless steel material according to claim 1, characterized in that: The raw materials contain at least stainless steel waste and alloy material with high manganese content.

4. The method for preparing a low manganese stainless steel material according to claim 1, characterized in that: The melting furnace is at least one of an electric arc furnace, an induction furnace or a resistance furnace.

5. The method for preparing a low manganese stainless steel material according to claim 1, characterized in that: The manganese reducing agent is at least one of metal sulfide or metal oxide, the metal sulfide is at least one of ferrous sulfide, chromium sulfide or nickel sulfide, and the metal oxide is at least one of iron oxide or ferrous oxide.

6. The method for preparing a low manganese stainless steel material according to claim 1, characterized in that: The stirring method after the manganese reducing agent is added to the stainless steel liquid is at least one of mechanical stirring, electromagnetic stirring, gas stirring or ultrasonic stirring.

7. The method for preparing a low manganese stainless steel material according to claim 2, characterized in that: The manganese-containing inclusions or the residual manganese-containing inclusions are at least one of manganese sulfide, manganese oxide, manganese sulfide or manganese oxide in which other elements are solid-dissolved, and complex inclusions consisting of manganese sulfide or manganese oxide and other oxides.

8. The method for preparing a low manganese stainless steel material according to claim 2, characterized in that: The method for removing the manganese-containing inclusions or the residual manganese-containing inclusions is at least one of a slag removal method, a static clarification method, an electromagnetic purification method, a filtration method, a slag washing method, a bubble flotation method, a negative pressure drainage method or a solidification sawing method.

9. The method for preparing a low manganese stainless steel material according to claim 1, characterized in that: The treated stainless steel liquid or the stainless steel melt is subjected to subsequent refining treatments such as decarburization, desulfurization, deoxidation or alloying to obtain the desired stainless steel material; the equipment used for the refining treatment is at least one of AOD, VOD, VD or LF refining furnaces.

10. A low manganese stainless steel material, characterized in that: The low manganese stainless steel material is prepared by the preparation method according to any one of claims 1 to 9.

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