A low-manganese stainless steel material and its preparation method

Abstract

This invention discloses a low-manganese stainless steel material and its preparation method, belonging to the field of stainless steel materials. The method includes melting raw materials in a melting furnace to obtain stainless steel liquid and maintaining the temperature; sampling and analyzing the existing manganese content of the stainless steel liquid; calculating the required manganese-reducing agent content and adding it to the stainless steel liquid; thoroughly stirring to ensure the manganese-reducing agent is uniformly dispersed in the stainless steel liquid and fully reacts with the manganese in the stainless steel liquid to generate manganese-containing inclusions; repeatedly removing manganese-containing inclusions from the stainless steel liquid to pre-purify it; and then temperature-controlled cooling and casting the pre-purified stainless steel liquid to obtain the low-manganese stainless steel material. This invention can achieve efficient and controllable reduction of manganese content during the preparation of stainless steel materials, and has advantages such as simple process, short flow, low cost, and high efficiency. The prepared low-manganese stainless steel material has high quality and excellent comprehensive performance. It is particularly suitable for preparing low-manganese stainless steel materials from high-manganese stainless steel scrap.

Description

Technical Field

[0001] This invention belongs to the field of stainless steel materials, specifically relating to a low-manganese stainless steel material and its preparation method. It is particularly suitable for preparing low-manganese stainless steel materials from high-manganese stainless steel scrap. Background Technology

[0002] Manganese in stainless steel mainly originates from pig iron, scrap steel, alloy raw materials, deoxidizers, and desulfurizers used in the smelting process. Manganese exists in stainless steel either dissolved in the matrix or as MnO and MnS inclusions. Manganese strongly promotes the precipitation of brittle phases such as the σ phase, reducing the plasticity and toughness of stainless steel. MnO inclusions disrupt the continuity of the matrix, reducing the mechanical properties of stainless steel and causing stress concentration during plastic deformation, thus becoming the starting point for crack initiation. MnS inclusions easily precipitate along grain boundaries during the solidification of molten stainless steel, dissolving in corrosive media and becoming sources of pitting and crevice corrosion, reducing the stainless steel's resistance to pitting and crevice corrosion. With rapid technological advancements, various industries have increasingly higher requirements for the quality of stainless steel materials. Especially with the continuous development of the circular economy and low-carbon economy, there is a growing desire to directly produce stainless steel materials from stainless steel scrap using short-process methods. However, the high manganese content in high-manganese stainless steel scrap has become a bottleneck in the preparation of low-manganese stainless steel materials. Therefore, reducing the manganese content in stainless steel is an urgent need for the short-process, low-cost preparation of low-manganese stainless steel.

[0003] In summary, developing a stable, low-cost, and efficient technology for reducing the manganese content of stainless steel materials, and preparing stainless steel materials with low manganese content, is of great significance for promoting the utilization of stainless steel waste, controlling the manganese content in stainless steel materials, and improving the quality of stainless steel materials. Summary of the Invention

[0004] This invention addresses the urgent need to reduce manganese content in the preparation of stainless steel materials using stainless steel scrap as raw material, providing a low-manganese stainless steel material and its preparation method. It is particularly suitable for preparing low-manganese stainless steel materials from high-manganese stainless steel scrap.

[0005] According to a first aspect 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 to melt them, obtain molten stainless steel, and keep it at a constant temperature;

[0007] Step 2: Sample and analyze the existing manganese content in the stainless steel liquid. Based on the target manganese content and the existing manganese content, calculate the required amount of manganese-reducing agent to be added.

[0008] Step 3: Add the manganese reducing agent to the stainless steel liquid and stir thoroughly to make the manganese reducing agent evenly dispersed in the stainless steel liquid and react fully with the manganese in the stainless steel liquid to generate manganese-containing inclusions;

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

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

[0011] Furthermore, the process also includes: placing the cast low-manganese stainless steel material back into the melting furnace to melt it into a stainless steel melt, controlling its melting temperature between the liquidus temperature of the low-manganese stainless steel material and the melting point of the residual manganese inclusions that solidify and precipitate in the low-manganese stainless steel material, so that the residual manganese inclusions are suspended in the stainless steel melt or float to the surface of the stainless steel melt, repeatedly removing the residual manganese inclusions to achieve purification treatment of the stainless steel melt, and then allowing the stainless steel melt to solidify and form a stainless steel material with even lower manganese content.

[0012] Furthermore, the raw materials contain at least stainless steel scrap 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 a metal sulfide or a metal oxide, wherein the metal sulfide is at least one of ferrous sulfide, chromium sulfide, or nickel sulfide, and the metal oxide is at least one of ferric 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 with other elements dissolved in solid solution, or complex inclusions composed of manganese sulfide or manganese oxide and other oxides.

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

[0018] Furthermore, the treated stainless steel liquid or 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 refining process is carried out using at least one of AOD, VOD, VD, or LF refining furnaces.

[0020] According to a second aspect of the present invention, a low-manganese stainless steel material is provided, wherein the low-manganese stainless steel material is prepared by the preparation method described in any of the above aspects.

[0021] The advantages of this invention are:

[0022] 1. The method of this invention involves adding low-melting-point metal sulfides or oxides to stainless steel molten steel with high manganese content. These react with manganese in the molten steel or during subsequent temperature-controlled cooling casting to generate high-melting-point manganese inclusions. Removal of these inclusions significantly reduces the manganese content in the stainless steel material, resulting in low-manganese stainless steel. This invention avoids the problems of traditional methods, such as directly introducing oxygen-containing gas into molten cast iron, which makes it difficult to control the oxygen content, and directly introducing oxygen-containing gas into molten stainless steel, which leads to severe oxidation and loss of chromium and other elements, resulting in high oxygen content. It also avoids the problems of traditional methods, such as directly adding mixed sodium sulfate or sulfur-based demanganese treatment agents to molten cast iron or steel, which leads to excessive sulfur content and the generation of large amounts of sulfur slag, and creates desulfurization difficulties in subsequent production.

[0023] 2. The method of the present invention remelts the cast low-manganese stainless steel material and controls its melting temperature between its liquidus temperature and the melting point of the residual manganese inclusions that precipitate during solidification. This allows the residual manganese inclusions to be suspended in the stainless steel melt or float to the surface of the stainless steel melt and removed by physical methods. This method can obtain stainless steel material with even lower manganese content and has the advantage of a higher manganese reduction rate.

[0024] 3. The method of this invention utilizes the characteristic that metal sulfides or metal oxides added to molten stainless steel readily react with manganese to form high-melting-point manganese inclusions. By pre-purifying the molten steel with metal sulfides or metal oxides, controlling the temperature for casting, remelting, and removing manganese inclusions through physical methods, the manganese content in high-manganese stainless steel materials can be rapidly and effectively reduced. This method facilitates the quick and easy preparation of low-manganese stainless steel materials and has advantages such as simple process, short process, low cost, and high efficiency. It is particularly suitable for preparing low-manganese stainless steel materials from high-manganese stainless steel scrap.

[0025] 4. The low-manganese stainless steel material of the present invention has low manganese content, high purity, and excellent comprehensive performance. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments or prior art, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a flowchart illustrating the preparation method of low-manganese stainless steel material according to the present invention. Detailed Implementation

[0028] The present invention will be described in detail below with reference to the embodiments. It should be noted that the embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments based on the above content of the present invention.

[0029] The technical solution of this invention first provides a method for preparing low-manganese stainless steel material, such as... Figure 1 As shown, it includes the following steps:

[0030] Step 101: Place the raw materials into a melting furnace to melt them, obtain molten stainless steel, and keep it at a constant temperature.

[0031] In a preferred embodiment, the raw materials contain at least stainless steel scrap and alloy materials 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: Sample and analyze the existing manganese content in the stainless steel liquid; calculate the required amount of manganese-reducing agent to be added based on the target manganese content and the existing manganese content.

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

[0035] Step 103: Add the manganese-reducing agent to the stainless steel liquid and stir thoroughly to make the manganese-reducing agent evenly dispersed in the stainless steel liquid and react fully 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 remove the manganese-containing inclusions generated in the stainless steel liquid to achieve pre-purification treatment of the stainless steel liquid.

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

[0039] In a preferred embodiment, the cast low-manganese stainless steel material is further placed back into the melting furnace to melt into a stainless steel melt. The melting temperature is controlled between the liquidus temperature of the low-manganese stainless steel material and the melting point of the residual manganese inclusions that solidify and precipitate in the low-manganese stainless steel material. This allows the residual manganese inclusions to suspend in the stainless steel melt or float to the surface of the stainless steel melt. The residual manganese inclusions are repeatedly removed to purify the stainless steel melt. Then, the stainless steel melt is solidified to obtain a stainless steel material with an even lower manganese content.

[0040] In a preferred embodiment, the manganese-containing inclusion or the residual manganese-containing inclusion is at least one of manganese sulfide, manganese oxide, manganese sulfide or manganese oxide with other elements dissolved in solid solution, or a complex inclusion composed of manganese sulfide or manganese oxide and other oxides.

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

[0042] In a preferred embodiment, the treated stainless steel liquid or 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 refining process is performed using at least one of AOD, VOD, VD, or LF refining furnaces.

[0044] 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] Five tons of 304 stainless steel scrap and high-manganese alloy materials were melted in an electric arc furnace to obtain molten stainless steel, which was then held at 1600℃. The molten stainless steel was sampled and analyzed, revealing a manganese content of 1.2 wt.%. Based on the target manganese content and the existing manganese content, 59 kg of ferrous oxide was added to the molten stainless steel. Electromagnetic stirring was used to thoroughly stir the molten stainless steel with added ferrous oxide, ensuring uniform dispersion and reaction with the manganese in the molten stainless steel to generate manganese dioxide and other manganese inclusions. Repeated slag removal was performed to remove these manganese inclusions, achieving pre-purification of the molten stainless steel. The pre-purified molten stainless steel was then subjected to controlled-temperature cooling and casting, with a cooling rate of less than 40℃ / min, yielding low-manganese 304 stainless steel material with a manganese content of 0.3 wt.%.

[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 was used to melt 10 tons of 304L stainless steel scrap and high-manganese alloy materials to obtain molten stainless steel, which was then held at 1600℃. Sampling and analysis of the molten stainless steel revealed a manganese content of 1.5 wt.%. Based on the target manganese content and the existing manganese content, 118 kg of ferrous oxide and 67 kg of ferrous sulfide were added to the molten stainless steel. Electromagnetic stirring was used to thoroughly stir the molten stainless steel with the added ferrous oxide and ferrous sulfide, ensuring uniform dispersion and reaction with the manganese in the molten stainless steel to generate manganese dioxide and manganese sulfide, among other manganese inclusions. This process was repeated to remove the manganese inclusions from the molten stainless steel. The process involves pre-purification of molten stainless steel; followed by temperature-controlled cooling and casting of the pre-purified molten stainless steel at a rate of less than 30°C / min to obtain low-manganese stainless steel material with a manganese content of 0.6 wt.%; the cast low-manganese stainless steel material is then melted again in a medium-frequency induction furnace at a controlled melting temperature of 1500°C. After settling, residual manganese inclusions are allowed to float to the surface of the molten stainless steel, and repeated slag removal is performed to remove these inclusions, thus purifying the molten stainless steel; the treated molten stainless steel is then subjected to further refining processes such as decarburization, desulfurization, deoxidation, or alloying in an AOD furnace to obtain low-manganese 304L stainless steel material with a manganese content of 0.18 wt.%.

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

[0050] Five tons of 316LN stainless steel scrap and high-manganese alloy materials were melted in a medium-frequency induction furnace to obtain molten stainless steel, which was then held at 1600℃. Sampling and analysis of the molten stainless steel revealed a manganese content of 2.5 wt.%. Based on the target manganese content and the existing manganese content, 100 kg of ferrous oxide and 54 kg of ferrous sulfide were added to the molten stainless steel. Gas stirring technology was used to thoroughly stir the molten stainless steel with the added ferrous oxide and ferrous sulfide, ensuring uniform dispersion and reaction with the manganese in the molten stainless steel to generate manganese dioxide and manganese sulfide, among other manganese inclusions. This process was repeated to remove the manganese inclusions from the molten stainless steel. The process involves pre-purification of molten stainless steel; followed by temperature-controlled cooling and casting of the pre-purified molten stainless steel at a rate of less than 20°C / min to obtain low-manganese stainless steel material with a manganese content of 0.97 wt.%; the cast low-manganese stainless steel material is then melted again in a medium-frequency induction furnace at a controlled melting temperature of 1500°C, suspending residual manganese inclusions in the molten stainless steel; these inclusions are repeatedly removed by filtration to purify the molten stainless steel; the treated molten stainless steel is then further refined in an AOD furnace through decarburization, desulfurization, deoxidation, or alloying to obtain low-manganese 316LN stainless steel material with a manganese content of 0.3 wt.%.

[0051] In summary, the technical solution of this invention utilizes low-melting-point metal sulfides or metal oxides as manganese-reducing agents to form high-melting-point manganese-containing inclusions in molten stainless steel or during subsequent temperature-controlled cooling casting. The molten stainless steel is pre-purified using physical methods and then subjected to temperature-controlled cooling casting. Alternatively, the cast low-manganese-content stainless steel material is melted at a controlled temperature to remove residual manganese-containing inclusions, or subsequent refining treatments such as decarburization, desulfurization, deoxidation, or alloying are performed to obtain the desired low-manganese stainless steel material. The advantages of this invention are that it enables efficient and controllable reduction of manganese content during the preparation of stainless steel materials, featuring simple processes, short flow, low cost, and high efficiency. The prepared low-manganese stainless steel material exhibits high quality and excellent comprehensive performance. It is particularly suitable for preparing low-manganese-content stainless steel materials from high-manganese-content stainless steel scrap.

[0052] The embodiments of the present invention have been described above, but the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these are within the protection scope of the present invention.

Claims

1. A method for preparing low-manganese stainless steel material, characterized in that, The preparation method can avoid severe oxidation and loss of chromium in the stainless steel liquid; the specific steps of the preparation method are as follows: Step 1: Place the raw materials into a melting furnace for melting to obtain stainless steel liquid, and keep it at a constant temperature; wherein the raw materials contain at least stainless steel scrap and alloy materials with high manganese content; Step 2: Sample and analyze the existing manganese content in the stainless steel liquid. Based on the target manganese content and the existing manganese content, calculate the required amount of manganese-reducing agent to be added. Step 3: Add the manganese reducing agent to the stainless steel liquid and stir thoroughly to make the manganese reducing agent evenly dispersed in the stainless steel liquid and react fully with the manganese in the stainless steel liquid to generate manganese-containing inclusions; Step 4: Repeatedly remove the manganese-containing inclusions generated in the stainless steel liquid to achieve pre-purification treatment of the stainless steel liquid; Step 5: The pre-purified stainless steel liquid is subjected to temperature-controlled cooling and casting to obtain low-manganese stainless steel material. The method further includes: The cast low-manganese stainless steel material is placed back into the melting furnace to melt into stainless steel melt. The melting temperature is controlled between the liquidus temperature of the low-manganese stainless steel material and the melting point of the residual manganese inclusions that solidify and precipitate in the low-manganese stainless steel material. This allows the residual manganese inclusions to suspend in the stainless steel melt or float to the surface of the stainless steel melt. The residual manganese inclusions are repeatedly removed to purify the stainless steel melt. Then, the stainless steel melt is solidified to obtain stainless steel material with even lower manganese content.

2. 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.

3. 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 a metal sulfide or a metal oxide, wherein the metal sulfide is at least one of ferrous sulfide, chromium sulfide, or nickel sulfide, and the metal oxide is at least one of ferric oxide or ferrous oxide.

4. 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.

5. The method for preparing a low-manganese stainless steel material according to claim 1, characterized in that, The manganese inclusions or the residual manganese inclusions are at least one of manganese sulfide and manganese oxide.

6. The method for preparing a low-manganese stainless steel material according to claim 1, characterized in that, The method for removing the manganese inclusions or the residual manganese inclusions is at least one of the following: slag removal, static clarification, electromagnetic purification, filtration, slag washing, bubble flotation, negative pressure diversion, or solidification sawing.

7. The method for preparing a low-manganese stainless steel material according to claim 1, characterized in that, The treated stainless steel liquid or stainless steel melt is subjected to subsequent decarburization, desulfurization, deoxidation or alloying refining treatment 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 furnace.

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