Slag for preparing low-oxygen low-aluminum high-nitrogen stainless steel through pressurized electroslag remelting and using method

Abstract

The invention relates to the technical field of high-nitrogen stainless steel smelting, and provides slag charge for preparing low-oxygen low-aluminum high-nitrogen stainless steel through pressurized electroslag remelting and a using method. And the slag charge comprises the following components in percentage by mass: 64-72% of CaF2, 14-18% of CaO, 2-6% of MgO, 4-10% of SiO2, 2.5-7% of Ce2O3 and the balance of impurities which are lower than 0.5%. The using method comprises the steps that pressurized electroslag remelting is used for preparing slag of the low-oxygen low-aluminum high-nitrogen stainless steel, the high-nitrogen stainless steel to be remelted serves as a consumable electrode, a deoxidizing agent is continuously added in a composite electrode mode, electroslag remelting is conducted under the pressurized nitrogen atmosphere, and the high-nitrogen stainless steel electroslag ingot is obtained. Low-oxygen control is realized by combining the advantages of the slag charge and the deoxidizer; the aluminum content is controlled by controlling the slag-gold reaction, and the melting speed is increased by replacing Al2O3 in the existing slag with Ce2O3. And the smelted high-nitrogen stainless steel electroslag ingot is high in cleanliness, good in surface quality and compact in solidification structure.

Description

Technical Field

[0001] The present application relates to the technical field of high-nitrogen stainless steel smelting, and in particular to a slag material for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel by pressurized electroslag remelting and a method for using the slag material. Background Art

[0002] High-nitrogen stainless steel, a new type of engineering material, boasts a key advantage: the addition of the inexpensive and environmentally friendly alloying element nitrogen to stainless steel significantly improves its mechanical properties, corrosion resistance, and other properties. Pressurized electroslag remelting (ESR) combines the advantages of ESR with pressurized enhanced cooling, significantly improving the cleanliness and microstructure of high-nitrogen steel ESR ingots while also refining the solidified structure. Therefore, pressurized ESR is currently the primary process for producing high-nitrogen stainless steel.

[0003] It is well known that oxygen is an important indicator reflecting the cleanliness of stainless steel. Especially for bearing steel, oxygen is usually required to be less than 10ppm. The type, size and number of inclusions in bearing steel are closely related to the content of impurity elements such as oxygen. The presence of inclusions will not only deteriorate the mechanical and corrosion resistance of bearing steel, but may also become a source of cracks that lead to fatigue failure. However, there are many ways to increase oxygen in the electroslag remelting process, including the original oxygen in the consumable electrode, the oxide scale remaining on the consumable electrode, the oxidation products generated on the side during the remelting process, and unstable oxides in the slag. In addition, the trend of changes in oxygen content in the electroslag remelting process varies depending on the smelting conditions. Therefore, electroslag remelting is usually an oxygen enrichment process.

[0004] On the other hand, due to its high nitrogen content, high-nitrogen stainless steel is extremely sensitive to aluminum in the steel and is prone to forming AlN inclusions during melting, solidification, or heat treatment. Taking high-nitrogen stainless bearing steel as an example, the presence of angular, hard AlN inclusions can significantly reduce its fatigue life. However, for the most widely used CaF2-CaO-Al2O3 electroslag remelting slag system, the decomposition of Al2O3 in the slag at high temperatures increases the aluminum content in the molten steel, leading to the formation of AlN inclusions. Furthermore, the decomposition of Al2O3 in the slag also increases the oxygen potential of the slag, resulting in increased oxygenation in the electroslag ingot.

[0005] Taking reasonable measures to achieve dealumination while preventing oxygen addition from low-oxygen electrodes during the electroslag remelting process is a pressing challenge in the production of high-nitrogen stainless steel using pressurized electroslag remelting. Therefore, a slag material for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel using pressurized electroslag remelting, as well as a method for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel using pressurized electroslag remelting, are urgently needed to effectively improve the quality of electroslag ingots for high-nitrogen stainless steel varieties. Summary of the Invention

[0006] To solve the above problems, the present application provides a slag material and a method for using it to prepare low-oxygen, low-aluminum, high-nitrogen stainless steel by pressurized electroslag remelting. On the premise of ensuring the smooth progress of the pressurized electroslag remelting process, it can effectively inhibit the oxygen increase of the electroslag ingot and reduce the aluminum content, thereby obtaining high-quality high-nitrogen stainless steel electroslag ingots with high cleanliness, good surface quality and dense solidification structure.

[0007] This application adopts the following technical solutions:

[0008] In a first aspect, the present application provides a slag material for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel by pressurized electroslag remelting, the slag material comprising, in percentage by mass:

[0009] CaF2: 64-72%, CaO: 14-18%, MgO: 2-6%, SiO2: 4-10%, Ce2O3: 2.5-7%, and the rest are impurities less than 0.5%.

[0010] Optionally, the impurities include oxides, and the oxides include:

[0011] FeO, MnO and Al2O3, etc.

[0012] In a second aspect, the present application provides a method for using slag for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel by pressurized electroslag remelting, the method comprising:

[0013] The pressurized electroslag remelting is used to prepare a slag material of low-oxygen, low-aluminum, high-nitrogen stainless steel, the high-nitrogen stainless steel to be remelted is used as a consumable electrode, a deoxidizer is continuously added in the form of a composite electrode, and electroslag remelting is carried out in a pressurized nitrogen atmosphere to obtain a high-nitrogen stainless steel electroslag ingot.

[0014] Optionally, the slag is pre-treated before use;

[0015] Preprocessing, including:

[0016] Pre-melting the slag;

[0017] The pre-melted slag is baked at a temperature of 600 to 800° C. for 6 to 8 hours.

[0018] Optional consumable electrodes are expressed in mass percentage and include:

[0019] C: 0.25~0.35%, Mn≤1.0%, Cr: 14.0~16.0%, Si: 0.3~0.7%, Mo: 0.85~1.10%, Ni≤0.50%, N: 0.35~0.45%, S≤0.01%, P≤0.03%, Al≤0.03%, O≤0.003%, balance Fe.

[0020] Optionally, the deoxidizer is a magnesium-cerium alloy, and the magnesium-cerium alloy comprises, by mass percentage, Ce ≥ 30%, Mg ≥ 10%, Si ≤ 45%, Fe ≤ 15%, and C ≤ 0.1%.

[0021] Optionally, the mass of the slag is 4-12% of the mass of the consumable electrode, and the mass of the deoxidizer is 0.2-0.4% of the mass of the consumable electrode.

[0022] Optional, composite electrode form:

[0023] The deoxidizer is placed in a stainless steel tube at the same height as the consumable electrode and fixed on the surface of the consumable electrode.

[0024] Optionally, electroslag remelting is performed under a pressurized nitrogen atmosphere, including: slagging and remelting;

[0025] During the slag forming process, the secondary voltage of the slag forming process is 27 to 32 V, and the secondary current of the slag forming process is 1.5 to 1.8 kA;

[0026] During the remelting, the secondary voltage of the remelting is 33-36V, the secondary current of the remelting is 2.2-2.8kA, and the melting rate fluctuation of the consumable electrode is ≤1.0kg / h;

[0027] Wherein, the pressure of the nitrogen is 1.0-1.5 MPa.

[0028] At least one of the above technical solutions adopted in this application can achieve the following beneficial effects:

[0029] The present application provides a method for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel by pressurized electroslag remelting. The method uses a slag material containing no Al2O3 to prepare low-oxygen, low-aluminum, high-nitrogen stainless steel by pressurized electroslag remelting. The high-nitrogen stainless steel to be remelted is used as a consumable electrode. A magnesium-cerium alloy deoxidizer is continuously added in the form of a composite electrode. The electroslag remelting is performed under a pressurized nitrogen atmosphere to obtain a high-nitrogen stainless steel electroslag ingot. Combining the advantages of the slag material and the deoxidizer, the activity of oxygen in the molten steel can be balanced, thereby achieving low-oxygen control in the pressurized electroslag remelting process. The aluminum content is effectively controlled by controlling the reaction between the slag and the metal, and the melting rate is increased by replacing Al2O3 with Ce2O3. The high-nitrogen stainless steel smelted according to the application has high cleanliness, good surface quality, and a dense solidification structure. DETAILED DESCRIPTION

[0030] The exemplary embodiments of the present application will be described in more detail below. However, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0031] The disclosure of the present invention provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described in the present invention. Of course, they are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numbers and / or reference letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0032] Generally, terms can be understood at least in part based on the usage of the above disclosure. For example, the term "one or more" used in the present disclosure depends at least in part on the above disclosure and can be used to describe any component, structure or feature in the singular, or can be used to describe a combination of components, structures or features in the plural. Similarly, terms such as "one", "an" or "the" can also be understood at least in part based on the above disclosure as conveying singular usage or conveying plural usage. In addition, the term "based on..." can be understood as not necessarily intended to convey a set of exclusive factors, but can alternatively, at least in part depending on the context, allow for the presence of additional factors that do not necessarily have to be explicitly described.

[0033] It should be noted that, in the description of this application, the meanings of the terms "on," "over," "above," "over," etc. should be interpreted in the broadest sense, meaning that the description containing these terms is interpreted as "the component can be set on another component in direct contact, or there can be an intermediate component or layer between the components."

[0034] In a first aspect, embodiments of the present application provide a slag material for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel by pressurized electroslag remelting.

[0035] The slag material for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel by pressurized electroslag remelting proposed in this application includes, by mass percentage, the following: CaF2: 64-72%, CaO: 14-18%, MgO: 2-6%, SiO2: 4-10%, Ce2O3: 2.5-7%, and the rest are impurities all below 0.5%.

[0036] In the present application, CaF2 is used as the main component of the slag material, and its content is controlled. CaF2, within the above-mentioned range, can lower the melting point of the slag material and promote slag flow, so that the slag and the refined metal melt can be better separated, and slag inclusion in the metal melt can be avoided. In actual circumstances, the low melting point of CaF2 can be utilized to slag, that is, a portion of CaF2 is first added around the arc starter, and then the rest of the slag material is added successively.

[0037] In the present application, adding CaO and controlling its content within the above range can make the slag have a stronger desulfurization ability. CaO has extremely high stability. Compared with other types of oxides, CaO basically does not decompose and cause oxygen increase.

[0038] In this application, MgO is added and its content is controlled within the above range. During the remelting process, MgO can form a slag film on the surface of the slag pool, reducing the penetration of O2 and H2O and improving the refining effect of the slag. MgO also has a desulfurization effect.

[0039] In this application, adding SiO2 and controlling its content within the above range can reduce the aluminum content in the electroslag ingot to below 60ppm, thereby avoiding the formation of AlN inclusions. However, since SiO2 is unstable, excessive SiO2 content will lead to decomposition and subsequent oxygenation, so its content needs to be strictly controlled.

[0040] In the present application, adding Ce2O3 and controlling its content within the above range can increase the melting point and resistivity of the slag, thereby increasing the melting rate of the pressurized electroslag remelting process and improving production efficiency.

[0041] In the present application, the slag includes inevitable impurities, and the mass percentage of each impurity is less than 0.5%.

[0042] In some optional embodiments, the slag for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel by pressurized electroslag remelting proposed in the present application includes, in mass percentage, the following: CaF2: 66-72%, CaO: 15-17%, MgO: 2-4%, SiO2: 5-10%, Ce2O3: 4-6%, and the rest are impurities all below 0.2%.

[0043] In addition, impurities include oxides such as FeO, MnO and Al2O3.

[0044] In a second aspect, the embodiments of the present application provide a method for using slag material for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel by pressurized electroslag remelting. That is, a method for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel by pressurized electroslag remelting is provided.

[0045] The method for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel by pressurized electroslag remelting proposed in the present application comprises: using the slag material for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel by the above-mentioned pressurized electroslag remelting, using the high-nitrogen stainless steel to be remelted as a consumable electrode, continuously adding a deoxidizer in the form of a composite electrode, and performing electroslag remelting in a pressurized nitrogen atmosphere to obtain a high-nitrogen stainless steel electroslag ingot.

[0046] The present application uses the above-mentioned pressurized electroslag remelting method to prepare slag of low-oxygen, low-aluminum, high-nitrogen stainless steel. The slag needs to be pretreated before use.

[0047] In some optional embodiments, the slag is pretreated before use; the pretreatment includes: pre-melting the slag; baking the pre-melted slag at a temperature of 600-800° C. and a baking time of 6-8 hours.

[0048] In this application, the slag is pre-melted before use. There are no specific requirements for the pre-melting method; pre-melted slag preparation methods well known in the art can be used. Using pre-melted slag facilitates arcing and slag formation, shortens slag formation time, and improves the bottom quality of the electroslag ingot. Furthermore, the pre-melted slag is granular, which prevents dust from being generated at the production site during use.

[0049] In this application, the slag material needs to be baked before use. By baking the slag material, free water and bound water in the slag material can be removed, slag collapse during the refining process can be avoided, and operational safety can be ensured.

[0050] This application uses remelted high-nitrogen stainless steel as the consumable electrode. There are no specific requirements for the preparation method of the remelted high-nitrogen stainless steel used as the consumable electrode; common preparation methods in the art can be used. In practical applications, the remelted high-nitrogen stainless steel can be prepared by pressurized induction melting followed by casting.

[0051] In this application, the high-nitrogen stainless steel to be remelted as the consumable electrode can be a forged high-nitrogen stainless steel ingot. Parameters such as the cross-sectional dimensions and length of the high-nitrogen stainless steel to be remelted as the consumable electrode can be determined based on the size of the electroslag furnace mold, and the forging process can be determined based on the composition of the high-nitrogen stainless steel ingot.

[0052] In the present application, after the high nitrogen stainless steel ingot is forged, it can be turned and mechanically polished to remove the iron oxide scale on the surface as much as possible, thereby obtaining the high nitrogen stainless steel to be remelted as a consumable electrode.

[0053] In some optional embodiments, the consumable electrode includes, by mass percentage, C: 0.25-0.35%, Mn≤1.0%, Cr: 14.0-16.0%, Si: 0.3-0.7%, Mo: 0.85-1.10%, Ni≤0.50%, N: 0.35-0.45%, S≤0.01%, P≤0.03%, Al≤0.03%, O≤0.003%, and the balance Fe.

[0054] In some optional embodiments, the deoxidizer is a magnesium-cerium alloy.

[0055] In this application, there are no specific requirements for the raw material source of the magnesium-cerium alloy used as a deoxidizer; commercially available products known in the art can be used. In practice, the magnesium-cerium alloy used as a deoxidizer comprises, by mass percentage, ≥30% Ce, ≥10% Mg, ≤45% Si, ≤15% Fe, and ≤0.1% C. The particle size of the magnesium-cerium alloy used as a deoxidizer is 1-2 mm. The Mg and Ce in the magnesium-cerium alloy used as a deoxidizer can effectively reduce the oxygen potential of the slag.

[0056] In some optional embodiments, the mass of the slag is 4-12% of the mass of the consumable electrode, and the mass of the added deoxidizer is 0.2-0.4% of the mass of the consumable electrode.

[0057] In some optional embodiments, the composite electrode is in the form of: the deoxidizer is placed in a stainless steel tube at the same height as the consumable electrode and fixed on the surface of the consumable electrode.

[0058] In this application, the deoxidation system is as follows: the deoxidizer is placed in a stainless steel tube at the same height as the consumable electrode and fixed on the surface of the consumable electrode.

[0059] In some optional embodiments, electroslag remelting is performed under a pressurized nitrogen atmosphere, including: slagging and remelting.

[0060] In the present invention, pressurized electroslag remelting includes slagging, remelting, etc. performed sequentially.

[0061] In the present application, a starter plate and an arc starter are placed in an electroslag furnace, and a consumable electrode with a fixed deoxidizer is installed.

[0062] There are no special requirements for the material of the starter plate; ordinary steel can be used. In practical applications, a material with the same or similar composition as the consumable electrode can be selected. The starter plate can be polished to ensure good contact with the bottom mold. In practical applications, the contact surface between the starter plate and the bottom mold should be greater than 70% of the starter plate area to avoid gaps between the bottom mold and the starter plate, which could cause arcing. The starter plate diameter can be determined based on the mold inner diameter, and the starter plate thickness can range from 10 to 30 mm.

[0063] There are no special requirements for the amount of arc starter charged, as long as it can achieve stable arc ignition and slag removal. In actual circumstances, the arc starter can use arc starting steel scraps with the same or similar composition as the consumable electrode, and avoid using titanium arc starting slag to prevent the increase of nitride inclusions at the bottom of the high-nitrogen stainless steel electroslag ingot.

[0064] There are no special requirements for the installation of the consumable electrode with the deoxidizer fixed thereon. The installation of the consumable electrode well known in the art can be performed to achieve the stability requirement.

[0065] In this application, after loading the pre-treated slag, argon gas is introduced to expel air. After the electroslag furnace is sealed, nitrogen is added to pressurize it, and solid-state slag arcing is performed. The secondary voltage of the slag melting process is 27-32V, and the secondary current of the slag melting process is 1.5-1.8kA.

[0066] The argon filling rate can be 10-15 L / min, and the argon filling time can be 9-12 minutes. Filling argon before arcing can quickly remove residual air in the furnace chamber, reduce the oxygen partial pressure in the atmosphere, and reduce the risk of oxygen in the atmosphere oxidizing the consumable electrode at high temperatures and seeping into the slag pool.

[0067] The nitrogen pressure can be determined based on the nitrogen content of the consumable electrode. For high-nitrogen stainless steel to be remelted with a nitrogen content of 0.35-0.45%, the nitrogen pressure can be determined to be 1.0-1.5 MPa. In practical situations, the nitrogen pressure can be further determined to be 1.1-1.3 MPa. By applying nitrogen pressure before slagging, a nitrogen atmosphere is formed, thereby forming a protective gas for pressurized electroslag remelting. This suppresses nitrogen outflow from the molten steel and the vaporization of the deoxidizer, thereby improving the solidification structure of the high-nitrogen stainless steel electroslag ingot.

[0068] In addition, when nitrogen is filled, the water-gas balance device is opened to achieve pressure synchronization to balance the pressure inside and outside the crystallizer.

[0069] In addition, the cooling water system, power system, mechanical system and gas system are inspected before slagging to ensure safe production.

[0070] In the present application, the secondary voltage of the remelting is 33-36 V, the secondary current of the remelting is 2.2-2.8 kA, and the melting rate fluctuation of the consumable electrode is ≤1.0 kg / h.

[0071] By controlling the fluctuation range of the melting speed during the remelting of the consumable electrode, the consumable electrode can be melted uniformly and the uneven composition of the electroslag ingot can be avoided.

[0072] In this application, after remelting is completed, the consumable electrode is lifted to be away from the slag surface, the remelting secondary voltage is reduced by 10% to 15%, the remelting secondary current is reduced by 20% to 30%, and the consumable electrode is inserted into the slag for remelting for 3 to 6 minutes to perform shrinkage feeding.

[0073] In the present application, the pressure in the electroslag furnace is released to normal pressure 10 to 20 minutes after feeding and the electroslag furnace is simultaneously water-cooled until the final temperature of the high nitrogen stainless steel electroslag ingot is lower than 300° C., and then the high nitrogen stainless steel electroslag ingot is removed.

[0074] The method for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel by pressurized electroslag remelting provided in the present application uses a deoxidized, dealuminated slag material that does not contain Al2O3, takes the high-nitrogen stainless steel to be remelted as a consumable electrode, continuously adds a magnesium-cerium alloy deoxidizer in the form of a composite electrode, and performs electroslag remelting under a pressurized nitrogen atmosphere. Combining the advantages of the slag and the deoxidizer, it is possible to balance the activity of oxygen in the molten steel, thereby achieving low-oxygen control in the pressurized electroslag remelting process. At the same time, the aluminum content is effectively controlled by controlling the reaction between the slag and the metal, and the melting rate is increased by replacing Al2O3 in the existing slag with Ce2O3. The high-nitrogen stainless steel electroslag ingot smelted according to the present application has high cleanliness, good surface quality, and dense solidification structure.

[0075] Specific examples are given below.

[0076] Example 1

[0077] The slag composition is CaF2: 72%, CaO: 16.8%, MgO: 3%, SiO2: 5%, Ce2O3: 3%, and the oxide impurities such as FeO, MnO, and Al2O3 are all less than 0.2% by mass. After pre-melting, the slag is baked in a drying oven at 700°C for 8 hours.

[0078] The consumable electrode is made of 30Cr15Mo1N aviation high nitrogen stainless bearing steel (50kg), and its composition is shown in Table 1 below.

[0079] Table 1:

[0080]

[0081] The deoxidizer is a magnesium-cerium alloy comprising, by mass percentage, 35.94% Ce, 14.82% Mg, 37.12% Si, 12.02% Fe, and 0.10% C. The added mass of the deoxidizer is 0.2% of the mass of the consumable electrode. The deoxidizer is placed in a stainless steel tube at the same height as the consumable electrode and fixed to the surface of the consumable electrode.

[0082] The pretreated slag was used as the consumable electrode, and a magnesium-cerium alloy deoxidizer was continuously added in the form of a composite electrode. The high-nitrogen stainless steel electroslag ingot S1 was obtained by electroslag remelting under a pressurized nitrogen atmosphere. The composition of the 30Cr15Mo1N high-nitrogen stainless steel electroslag ingot S1 was analyzed.

[0083] The process of electroslag remelting under a pressurized nitrogen atmosphere includes:

[0084] Place the starter plate and arc starter into the electroslag furnace, and install the consumable electrode with the deoxidizer fixed on it;

[0085] After loading 4 kg of pre-treated slag, argon gas was introduced at 10 L / min to remove air;

[0086] After the electroslag furnace is sealed, nitrogen is filled and pressurized to 1.3 MPa to start the arc in solid slag;

[0087] During remelting, the melting rate of the consumable electrode is controlled to fluctuate within 1.0 kg / h, and the remelting melting rate is 26 kg / h;

[0088] When feeding, lift the consumable electrode away from the slag surface, reduce the remelting secondary voltage by 10%, reduce the remelting secondary current by 30%, insert the consumable electrode into the slag and remelt for 4 minutes to feed;

[0089] Ten minutes after the feeding, the pressure in the electroslag furnace was released to normal pressure and synchronously water-cooled to the final temperature of the high nitrogen stainless steel electroslag ingot of 300°C. The high nitrogen stainless steel electroslag ingot was then removed to obtain 30Cr15Mo1N high nitrogen stainless steel electroslag ingot S1.

[0090] Example 2

[0091] The slag composition is CaF2: 68.5%, CaO: 16.8%, MgO: 2.5%, SiO2: 7.5%, Ce2O3: 4.5%, and the oxide impurities such as FeO, MnO, and Al2O3 are all less than 0.2% by mass. After pre-melting, the slag is baked in a drying oven at 700°C for 8 hours.

[0092] The consumable electrode is made of 30Cr15Mo1N aviation high nitrogen stainless bearing steel (50kg), and its composition is shown in Table 1 above.

[0093] The deoxidizer is a magnesium-cerium alloy comprising, by mass percentage, 35.94% Ce, 14.82% Mg, 37.12% Si, 12.02% Fe, and 0.10% C. The added mass of the deoxidizer is 0.4% of the mass of the consumable electrode. The deoxidizer is placed in a stainless steel tube at the same height as the consumable electrode and fixed to the surface of the consumable electrode.

[0094] The pretreated slag was used as the consumable electrode, and a magnesium-cerium alloy deoxidizer was continuously added in the form of a composite electrode. The high-nitrogen stainless steel electroslag ingot S2 was obtained by electroslag remelting under a pressurized nitrogen atmosphere. The composition of the 30Cr15Mo1N high-nitrogen stainless steel electroslag ingot S2 was analyzed.

[0095] The electroslag remelting process is carried out in a pressurized nitrogen atmosphere, and except for the remelting rate being 29 kg / h, other aspects are the same as those of Example 1.

[0096] Example 3

[0097] The slag composition is CaF2: 66.3%, CaO: 15%, MgO: 2.5%, SiO2: 10%, Ce2O3: 6%, and the oxide impurities such as FeO, MnO, and Al2O3 are all less than 0.2% by mass. After pre-melting, the slag is baked in a drying oven at 700°C for 8 hours.

[0098] The consumable electrode is made of 30Cr15Mo1N aviation high nitrogen stainless bearing steel (50kg), and its composition is shown in Table 1 above.

[0099] The deoxidizer is a magnesium-cerium alloy comprising, by mass percentage, 35.94% Ce, 14.82% Mg, 37.12% Si, 12.02% Fe, and 0.10% C. The added mass of the deoxidizer is 0.4% of the mass of the consumable electrode. The deoxidizer is placed in a stainless steel tube at the same height as the consumable electrode and fixed to the surface of the consumable electrode.

[0100] The pretreated slag was used as the consumable electrode, and a magnesium-cerium alloy deoxidizer was continuously added in the form of a composite electrode. The high-nitrogen stainless steel electroslag ingot S3 was obtained by electroslag remelting under a pressurized nitrogen atmosphere. The composition of the 30Cr15Mo1N high-nitrogen stainless steel electroslag ingot S3 was analyzed.

[0101] The electroslag remelting process is carried out in a pressurized nitrogen atmosphere, and except for the remelting rate being 31 kg / h, other aspects are the same as those of Example 1.

[0102] Comparative Example 1

[0103] The slag material has a composition of CaF2: 61.8%, CaO: 19.8%, Al2O3: 15.2%, MgO: 3%, and oxide impurities such as FeO and MnO are all less than 0.2% by mass. After pre-melting, the slag material is baked in a drying oven at 700°C for 8 hours.

[0104] The consumable electrode is made of 30Cr15Mo1N aviation high nitrogen stainless bearing steel (50kg), and its composition is shown in Table 1 above.

[0105] The pretreated slag was used as the consumable electrode for electroslag remelting (without adding a deoxidizer) in a pressurized nitrogen atmosphere using 30Cr15Mo1N aviation high nitrogen stainless bearing steel. A high nitrogen stainless steel electroslag ingot D1 was obtained, and the composition of the 30Cr15Mo1N high nitrogen stainless steel electroslag ingot D1 was analyzed.

[0106] The electroslag remelting process under a pressurized nitrogen atmosphere is the same as that of Example 1 except that the remelting rate is 30 kg / h.

[0107] Comparative Example 2

[0108] The slag material has a composition of CaF2: 66.8%, CaO: 19.8%, Al2O3: 10.2%, MgO: 3%, and oxide impurities such as FeO and MnO are all less than 0.2% by mass. After pre-melting, the slag material is baked in a drying oven at 700°C for 8 hours.

[0109] The consumable electrode is made of 30Cr15Mo1N aviation high nitrogen stainless bearing steel (50kg), and its composition is shown in Table 1 above.

[0110] The deoxidizer is a magnesium-cerium alloy comprising, by mass percentage, 35.94% Ce, 14.82% Mg, 37.12% Si, 12.02% Fe, and 0.10% C. The added mass of the deoxidizer is 0.4% of the mass of the consumable electrode. The deoxidizer is placed in a stainless steel tube at the same height as the consumable electrode and fixed to the surface of the consumable electrode.

[0111] The pretreated slag was used as the consumable electrode, and a magnesium-cerium alloy deoxidizer was continuously added in the form of a composite electrode. The high-nitrogen stainless steel electroslag ingot D2 was obtained by electroslag remelting under a pressurized nitrogen atmosphere. The composition of the 30Cr15Mo1N high-nitrogen stainless steel electroslag ingot D2 was analyzed.

[0112] The electroslag remelting process under a pressurized nitrogen atmosphere is the same as that of Example 1 except that the remelting rate is 29 kg / h.

[0113] The components of the 30Cr15Mo1N high nitrogen stainless steel electroslag ingots S1, S2, S3, D1 and D2 obtained in Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2 were analyzed. The analysis results are shown in Table 2 below, where each numerical value in Table 2 represents the content (wt.%).

[0114] Table 2:

[0115] project C Si Mn Cr Mo N Al O S Fe S1 0.30 0.41 0.50 15.20 0.98 0.39 0.0060 0.0012 0.0012 margin S2 0.30 0.41 0.50 15.20 0.98 0.39 0.0035 0.0009 0.0010 margin S3 0.30 0.41 0.50 15.20 0.98 0.39 0.0020 0.0011 0.0011 margin D1 0.30 0.37 0.50 15.20 0.98 0.39 0.0248 0.0032 0.0015 margin D2 0.30 0.38 0.50 15.20 0.98 0.39 0.0302 0.0029 0.0015 margin

[0116] The results shown in Table 2 indicate that the oxygen and aluminum contents in the 30Cr15Mo1N high-nitrogen stainless steel electroslag ingot S1 obtained in Example 1 are controlled to a certain extent. The oxygen content can be reduced from 20 ppm in the consumable electrode to 12 ppm, and the aluminum content can be reduced from 150 ppm in the consumable electrode to 60 ppm.

[0117] The results shown in Table 2 indicate that the oxygen and aluminum contents in the 30Cr15Mo1N high-nitrogen stainless steel electroslag ingot S2 obtained in Example 2 are controlled to a certain extent. The oxygen content can be reduced from 20 ppm in the consumable electrode to 9 ppm, and the aluminum content can be reduced from 150 ppm in the consumable electrode to 35 ppm.

[0118] The results shown in Table 2 indicate that the oxygen and aluminum contents in the 30Cr15Mo1N high-nitrogen stainless steel electroslag ingot S3 obtained in Example 3 are controlled to a certain extent. The oxygen content can be reduced from 20 ppm in the consumable electrode to 11 ppm, and the aluminum content can be reduced from 150 ppm in the consumable electrode to 20 ppm.

[0119] The results shown in Table 2 indicate that the oxygen and aluminum contents in the 30Cr15Mo1N high-nitrogen stainless steel electroslag ingot D1 obtained in Comparative Example 1 were not controlled. The oxygen content increased from 20 ppm in the consumable electrode to 32 ppm, and the aluminum content increased from 150 ppm in the consumable electrode to 248 ppm.

[0120] The results shown in Table 2 indicate that the oxygen and aluminum contents in the 30Cr15Mo1N high-nitrogen stainless steel electroslag ingot D2 obtained in Comparative Example 2 were not controlled. The oxygen content increased from 20 ppm in the consumable electrode to 29 ppm, and the aluminum content increased from 150 ppm in the consumable electrode to 302 ppm.

[0121] The above description is only a specific embodiment of the present application. Based on the above teachings of the present application, those skilled in the art may make other improvements or modifications based on the above embodiments. Those skilled in the art should understand that the above description is only a better explanation of the purpose of the present application, and the scope of protection of the present application shall be based on the scope of protection of the claims.

[0122] Furthermore, those skilled in the art will appreciate that although some embodiments described herein include certain features that are included in other embodiments but not other features, combinations of features from different embodiments are intended to be within the scope of this application and to form different embodiments. For example, in the claims below, any of the claimed embodiments may be used in any combination.

Claims

1. A slag material for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel by pressurized electroslag remelting, characterized in that: The slag material comprises, by mass percentage: CaF2: 64-72%, CaO: 14-18%, MgO: 2-6%, SiO2: 4-10%, Ce2O3: 2.5-7%, and the rest are impurities less than 0.5%.

2. The slag material for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel by pressurized electroslag remelting according to claim 1, characterized in that: The impurities include oxides, and the oxides include: FeO, MnO and Al2O3, etc.

3. A method for using slag for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel by pressurized electroslag remelting, characterized in that: The method of use includes: The pressurized electroslag remelting method according to claim 1 or 2 is used to prepare the slag of low-oxygen, low-aluminum, high-nitrogen stainless steel, the high-nitrogen stainless steel to be remelted is used as a consumable electrode, a deoxidizer is continuously added in the form of a composite electrode, and the electroslag remelting is carried out in a pressurized nitrogen atmosphere to obtain a high-nitrogen stainless steel electroslag ingot.

4. The method for using slag for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel by pressurized electroslag remelting according to claim 3, characterized in that: The slag material is pretreated before use; The preprocessing comprises: Pre-melting the slag; The slag material after the pre-melting treatment is baked, the baking temperature is 600-800° C., and the baking time is 6-8 hours.

5. The method for using slag for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel by pressurized electroslag remelting according to claim 3, characterized in that: The consumable electrode comprises, by mass percentage: C: 0.25~0.35%, Mn≤1.0%, Cr: 14.0~16.0%, Si: 0.3~0.7%, Mo: 0.85~1.10%, Ni≤0.50%, N: 0.35~0.45%, S≤0.01%, P≤0.03%, Al≤0.03%, O≤0.003%, balance Fe.

6. The method for using slag for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel by pressurized electroslag remelting according to claim 3, characterized in that: The deoxidizer is a magnesium-cerium alloy, and the magnesium-cerium alloy, in terms of mass percentage, comprises Ce≥30%, Mg≥10%, Si≤45%, Fe≤15%, and C≤0.1%.

7. The method for using slag for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel by pressurized electroslag remelting according to claim 3, characterized in that: The mass of the slag material is 4-12% of the mass of the consumable electrode, and the mass of the deoxidizer is 0.2-0.4% of the mass of the consumable electrode.

8. The method for using slag for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel by pressurized electroslag remelting according to claim 3, characterized in that: The composite electrode is in the form of: The deoxidizer is placed in a stainless steel tube having the same height as the consumable electrode and fixed on the surface of the consumable electrode.

9. The method for using slag for preparing low-oxygen, low-aluminum, high-nitrogen stainless steel by pressurized electroslag remelting according to claim 3, characterized in that: The electroslag remelting under a pressurized nitrogen atmosphere comprises: slag melting and remelting; During the slag forming process, the secondary voltage of the slag forming process is 27 to 32 V, and the secondary current of the slag forming process is 1.5 to 1.8 kA; During the remelting, the secondary voltage of the remelting is 33-36V, the secondary current of the remelting is 2.2-2.8kA, and the melting rate fluctuation of the consumable electrode is ≤1.0kg / h; Wherein, the pressure of the nitrogen is 1.0-1.5 MPa.

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