Ultra-pure intermediate alloy for high-temperature bearing steel and preparation method

Abstract

The invention relates to the technical field of iron-chromium-vanadium alloy purification, in particular to an ultra-pure intermediate alloy for high-temperature bearing steel and a preparation method of the ultra-pure intermediate alloy. The alloy comprises, by mass, 5%-25% of Cr, 1.3%-7% of V, smaller than or equal to 0.3% of C, smaller than or equal to 0.05% of Si, smaller than or equal to 0.01% of P, smaller than or equal to 0.001% of S, smaller than or equal to 0.0015% of O, smaller than or equal to 0.05% of Al, smaller than or equal to 0.05% of Mn, smaller than or equal to 0.0020% of Ti and the balance Fe and inevitable impurities, and the ratio of Cr to V is (3-4.5): 1. According to the intermediate alloy, the content of impurity elements is reduced with lower cost, so that the high-temperature bearing steel prepared from the intermediate alloy can obtain higher purity and cleanliness, and the fatigue life in a complex high-temperature environment is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of iron-chromium-vanadium alloy purification, and in particular to an ultra-pure master alloy for high-temperature bearing steel and a preparation method thereof. Background Art

[0002] In the preparation process of ultra-pure high-temperature bearing steel, not only a low S content is required, but also strict control of the P, Si, Mn, Al, and Ti contents. There is a significant relationship between the Ti content and the fatigue life of the bearing steel. Ti is a strong nitride-forming element that easily combines with nitrogen in steel to form titanium nitride (TiN). The distribution and size of these titanium nitride particles in steel have an important influence on the fatigue performance of bearing steel. Control of the titanium content is crucial to improving the fatigue life of bearing steel.

[0003] More than 90% of vanadium is used in the steel industry. It is mainly used in the production of special steel to refine the grains and increase the strength and toughness of the steel. The main reason for adding vanadium to steel is that the melting point of vanadium is 1890℃. It is not easy to dissolve and cause segregation of vanadium in steel when directly added to steel. The previous methods for producing ferrovanadium are: carbon thermal method, electric thermal method, electric silicon thermal method, metal thermal method (mainly aluminothermic method). The aluminothermic method is to use the activity of aluminum to reduce the vanadium in vanadium pentoxide. The basic method is to ignite metal aluminum and reduce vanadium at a certain temperature. All of the above methods will pollute the environment, and the impurity content of the produced ferrovanadium is high and the purity is not high, especially the silicon and sulfur content is high.

[0004] At present, the impurity element content of ferrovanadium produced by the aluminothermic method is high, and the physical quality purity is low, especially the content of sulfur and oxygen is high. It can only be used for adding vanadium microalloying in ordinary steel, and is not suitable for manufacturing high-end products, such as raw materials for producing ultra-high purity high-temperature bearing steel M50 (8Cr4Mo4V) and M50NiL (13Cr4Mo4Ni4V), and it cannot be used for cutting-edge stainless steel alloys and high-quality parts. Because the preparation of ultra-high purity M50 (8Cr4Mo4V) and M50NiL (13Cr4Mo4Ni4V) steel requires the use of vacuum induction furnace (VIM) + vacuum arc consumable furnace (VAR) process smelting, and alloying smelting of C, Cr, Mo, V, and Ni is carried out in the vacuum induction furnace. At the same time, only the vacuum function of VIM + VAR can be used for carbon deoxidation and denitrification, but other residual elements such as S, P, Si, Mn, Al, and Ti are almost difficult to remove or reduce.

[0005] Currently, ferrochrome and metallic chromium are important alloying additives for steelmaking. Generally, the product standards for ferrochrome are not very strict on sulfur content. For example, high carbon ferrochrome requires S content ≤ 0.04%, and medium carbon ferrochrome, low carbon ferrochrome and micro carbon ferrochrome require S content ≤ 0.025%. This cannot meet the requirements for ultra-low S and O content of alloying raw materials when preparing special alloys.

[0006] At present, 99-99.96% ultra-pure metal vanadium V1-V3 and 99.96% ultra-pure electrolytic metal chromium JCr99.95-A with high purity are used as alloying raw materials for high-temperature alloys and special alloy steels. Although they can meet the requirements for ultra-low S, P, O, N, Si, Mn, Al, and Ti content, their selling price is more than ten times that of ferrovanadium and ferrochrome, and the cost is too high. Summary of the invention

[0007] The purpose of the present invention is to provide an ultra-pure master alloy for high-temperature bearing steel and a preparation method thereof, wherein the iron-chromium-vanadium alloy is further purified by electroslag remelting, so that the S content is further reduced, and the contents of O, N, Si, Mn, and Al are further reduced, and the ultra-pure metal vanadium and electrolytic pure chromium can be replaced as raw materials for simultaneous alloying of special alloys. The application of iron-chromium-vanadium alloys is expanded in new fields. The present invention reduces the content of impurity elements at a lower cost, so that the high-temperature bearing steel prepared using the master alloy can obtain higher purity and cleanliness, thereby improving the fatigue life in complex high-temperature environments.

[0008] In order to achieve the above object, the technical solution of the present invention is as follows:

[0009] On the one hand, the present invention provides an ultra-pure master alloy for high-temperature bearing steel. The alloy has the following components, measured by mass percentage: Cr: 5%-25%, V: 1.3%-7%, C≤0.3%, Si≤0.05%, P≤0.01%, S≤0.001%, O≤0.0015%, Al≤0.05%, Mn≤0.05%, Ti≤0.0020wt%, the remainder being Fe and unavoidable impurities, and Cr / V=3~4.5:1.

[0010] Another aspect of the present invention provides a method for preparing the ultrapure master alloy for high-temperature bearing steel, the method comprising the following steps:

[0011] 1) Select FeV80 alloy as ferrovanadium raw material, and require that the raw material contains: P≤0.01wt%, S≤0.03wt%, Si≤0.6wt%, Mn≤0.15wt%, Al≤1.0wt%, Ti≤0.005wt%, C≤0.2wt%; select JCr99.2 as metal chromium raw material, and require that the raw material contains: P≤0.002wt%, S≤0.005wt%; select pure iron raw material, and require that the raw material contains: P≤0.002wt%, S≤0.003wt%, Ti≤0.002wt%;

[0012] 2) Vacuum induction furnace smelting, according to the composition of the master alloy, ferrovanadium, 1 / 3 metallic chromium, 2 / 3 pure iron raw materials and high-purity graphite carbon blocks are loaded into the furnace, the carbon content is ≤0.3%, the vacuum degree is required to be ≤1Pa when melting begins, medium power melting, the remaining 1 / 3 pure iron is added before melting, the refining temperature is 1590-1610°C, the time is greater than 30 minutes, and two refinings are performed, wherein after the first refining is completed, the remaining 2 / 3 metallic chromium is added, and then the second refining is performed;

[0013] 3) The refined molten steel is subjected to low temperature mold casting, with the tapping temperature of 1580-1590°C to obtain an ingot;

[0014] 4) The ingot obtained in step (3) is subjected to deep desulfurization and removal of large rare earth inclusions through an electroslag remelting process, thereby enhancing the deep desulfurization capability of the slag system while taking into account the melting point. The slag is composed of CaF2, Al2O3, and CaO, and the mass ratio thereof is CaF2:Al2O3:CaO=3:1:1.

[0015] In the above technical solution, further, in step 1), P in the ferrovanadium raw material is ≤ 0.008 wt%.

[0016] In the above technical solution, further, in step 2), after the charge is melted, the vacuum degree of the induction furnace is not higher than 1 Pa during vacuum deep deoxidation in the refining stage, and the holding time is not less than 50 minutes.

[0017] In the above technical solution, further, in step 2), sampling and analysis of [N] are performed at the end of the second refining. If [N] ≤ 0.01%, stirring is performed for 5 minutes before proceeding to the next step. If [N] > 0.01%, graphite carbon blocks are continuously added to continue deoxidation and denitrification. The key points of controlling the refining time and strengthening the stirring are to ensure that [N] ≤ 0.01% at the end of refining.

[0018] In the above technical solution, further, in step 2), at the end of refining vacuum deep deoxidation, 0.15-0.2 kg / t cerium, lanthanum or a mixture of lanthanum, cerium, praseodymium and neodymium is added through a vacuum silo to carry out deep desulfurization, deep deoxidation and denaturation of inclusions in ferrochrome alloy.

[0019] In the above technical scheme, further, in step 3), after mold casting, the ingot is allowed to be broken after furnace cooling for 15 minutes, and a long spoon is used to add a heating agent and a covering agent to the surface of the ingot. The ingot is demolded and air-cooled. The ingot specification limit is preferably such that it can be directly used as an electroslag remelting consumable electrode after peeling.

[0020] In the above technical solution, further, in step 4), the ingot shape is Ф250mm and the slag amount is 17±2kg / t.

[0021] In the above technical solution, further, in step 4), no deoxidizer such as aluminum silicon is added during the smelting process, and only carbon powder is added to deoxidize the slag system to ensure the stability of the slag system, thereby ensuring the consistency of the purity of the components at the arc starting end and the feeding end of the electroslag ingot.

[0022] The present invention also provides a use of the ultra-pure master alloy in the preparation of high-temperature bearing steel.

[0023] The beneficial effects of the present invention are:

[0024] The present invention selects low-P, low-Ti ferrovanadium, metallic chromium and pure iron raw materials, and then removes O and N at the same time by using carbon blocks in a vacuum induction furnace, avoiding the addition of additional deoxidizers such as aluminum, silicon and manganese for deoxidation, so as to avoid increasing the content of aluminum, silicon and manganese in the iron-chrome-vanadium alloy; adding a trace amount of mixed rare earth at the end of deoxidation can effectively further remove O, S and modify inclusions in the iron-chrome-vanadium alloy. In the process of electroslag remelting, the S content in the iron-chrome-vanadium alloy is further reduced, and the content of O, Si, Mn, Al and Ti is further reduced, and large particle inclusions are removed. The field of iron-chrome-vanadium alloy composition design and its application in new fields are expanded, so that the iron-chrome-vanadium alloy can replace electrolytic pure chromium and ultra-pure metallic vanadium as the raw material for simultaneous chromium and vanadium alloying when preparing special alloy steel.

[0025] By using selected ferrovanadium, metallic chromium and pure iron raw materials, iron-chrome-vanadium alloy with a certain proportion of components is mixed, and the iron-chrome-vanadium alloy is further purified by induction furnace + electroslag remelting process. Compared with electrolytic pure chromium and ultra-pure metallic vanadium, the cost is greatly reduced, so that the ultra-pure iron-chrome-vanadium alloy can replace electrolytic pure chromium and ultra-pure metallic vanadium as the raw material for the preparation of ultra-high purity and high-temperature bearing steel M50 (8Cr4Mo4V) and M50NiL (13Cr4Mo4Ni4V) that requires simultaneous alloying of chromium and vanadium. DETAILED DESCRIPTION

[0026] The present invention is described in detail below in conjunction with specific implementation modes, but the present invention is not limited thereto.

[0027] The invention discloses an ultra-pure master alloy for high-temperature bearing steel. The alloy has the following components, calculated by mass percentage: Cr: 5%-25%, V: 1.3%-7%, C≤0.3%, Si≤0.05%, P≤0.01%, S≤0.001%, O≤0.0015%, Al≤0.05%, Mn≤0.05%, Ti≤0.0020wt%, and the remainder is Fe and unavoidable impurities, and Cr / V=3-4.5:1.

[0028] For the specific ultra-pure high-temperature bearing steel M50 (8Cr4Mo4V), the alloy ratio of Cr and V in the ultra-pure iron-chromium-vanadium alloy is set to 4.1:1, and for the specific ultra-pure high-temperature bearing steel M50NiL (13Cr4Mo4Ni4V), the alloy ratio of Cr and V in the ultra-pure iron-chromium-vanadium alloy is set to 4:1.2.

[0029] The preparation method of the ultra-pure master alloy for high-temperature bearing steel has a process route of: selecting low-phosphorus and low-titanium ferrovanadium, low-phosphorus metallic chromium and low-phosphorus and low-titanium pure iron → vacuum induction furnace smelting (removing N, O and S) → electroslag remelting (removing S, O, Si, Mn and Al), which specifically includes the following steps:

[0030] 1) Select FeV80 alloy, a ferrovanadium raw material, wherein P≤0.01wt%, preferably P≤0.008wt%, S≤0.03wt%, Si≤0.6wt%, Mn≤0.15wt%, Al≤1.0wt%, Ti≤0.005wt%, and C≤0.2wt%; select JCr99.2, a metallic chromium raw material, wherein P≤0.002wt%, S≤0.005wt%; select pure iron raw material, wherein P≤0.002wt%, S≤0.003wt%, and Ti≤0.002wt%;

[0031] 2) Vacuum induction furnace smelting, according to the composition of the master alloy, ferrovanadium, 1 / 3 metallic chromium, 2 / 3 pure iron raw materials and high-purity graphite carbon blocks are loaded into the furnace, the carbon content is ≤0.3%, the vacuum degree is required to be ≤1Pa when melting begins, medium power melting, the remaining 1 / 3 pure iron is added before melting, the refining temperature is 1590-1610°C, the time is greater than 30 minutes, and two refinings are performed, wherein after the first refining is completed, the remaining 2 / 3 metallic chromium is added, and then the second refining is performed;

[0032] After the charge is melted, the vacuum degree of the induction furnace shall not be higher than 1Pa during vacuum deep deoxidation in the refining period, and the holding time shall not be less than 50 minutes;

[0033] Take samples and analyze [N] at the end of the second refining. If [N] ≤ 0.01%, stir for 5 minutes and proceed to the next step. If [N] > 0.01%, continue to add graphite carbon blocks to continue deoxidation and denitrification. The key to controlling the refining time and strengthening the stirring is to ensure that N ≤ 0.01% at the end of refining.

[0034] At the end of refining vacuum deep deoxidation, 0.15-0.2kg / t cerium, lanthanum or a mixture of lanthanum, cerium, praseodymium and neodymium is added through the vacuum silo for deep desulfurization, deep deoxidation and denaturation of inclusions in the iron-chrome-vanadium alloy;

[0035] 3) The refined molten steel is subjected to low temperature die casting, with the tapping temperature of 1580°C-1590°C to obtain an ingot;

[0036] After mold casting, the ingot is allowed to be broken into air after cooling in the furnace for 15 minutes. A long spoon is used to add heating agent and covering agent to the surface of the ingot. The ingot is demolded and air-cooled. The ingot specification limit is preferably such that it can be directly used as an electroslag remelting consumable electrode after peeling.

[0037] 4) The ingot obtained in step (3) is subjected to deep desulfurization and removal of large rare earth inclusions through an electroslag remelting process, thereby enhancing the deep desulfurization capability of the slag system while taking into account the melting point, wherein the slag is composed of CaF2, Al2O3, and CaO, and the mass ratio thereof is CaF2:Al2O3:CaO=60:20:20 (wt%);

[0038] In step 4), the ingot shape is Φ250 mm and the slag amount is 17±2 kg / t.

[0039] During the electroslag remelting process, no deoxidizers such as aluminum and silicon are added. Only carbon powder is added to deoxidize the slag system to ensure the stability of the slag system, thereby ensuring the consistency of the purity of the components at the arc starting end and the feeding end of the electroslag ingot.

[0040] Examples 1-5

[0041] The composition contents of the ultrapure master alloys of Examples 1-5 are shown in Table 1.

[0042] Table 1: Content of components in ultrapure master alloys in Examples 1-5 (wt%)

[0043] No. C Cr V Si Mn S P Al Ti O Fe 1 0.17 6.15 1.48 0.005 0.005 0.0005 0.0019 0.005 0.0010 0.0015 Bal. 2 0.18 6.16 1.49 0.009 0.005 0.0005 0.0019 0.005 0.0009 0.0015 Bal. 3 0.17 6.15 1.49 0.008 0.005 0.0007 0.0019 0.005 0.0012 0.0014 Bal. 4 0.16 6.01 1.80 0.009 0.005 0.0006 0.0018 0.005 0.0011 0.0013 Bal. 5 0.16 6.01 1.81 0.006 0.005 0.0006 0.0019 0.005 0.0009 0.0015 Bal.

[0044] The method for preparing the above-mentioned ultrapure master alloy comprises the following steps:

[0045] 1) Selecting vanadium iron raw material FeV80 alloy, selecting metal chromium raw material JCr99.2, and selecting pure iron raw material. The components and proportions of FeV80 alloy, JCr99.2, and pure iron in Examples 1-5 are shown in Table 2;

[0046] Table 2 Composition of ferrovanadium, metallic chromium and pure iron in Examples 1-5 (wt%)

[0047]

[0048] 2) Vacuum induction furnace smelting: according to the composition of the intermediate alloy, ferrovanadium, 1 / 3 metallic chromium, 2 / 3 pure iron raw materials and high-purity graphite carbon blocks are charged into the furnace, with a carbon content of 0.23%. The furnace is smelted in a 150kg vacuum induction furnace. The vacuum degree is required to be ≤1Pa when the melting starts, the melting period is 3h, and the melting is carried out at medium power. The remaining 1 / 3 pure iron is added before the melting is completed, and two refinings are carried out. After the first refining is completed, the remaining 2 / 3 metallic chromium is added, and the second refining is carried out. During the vacuum deep deoxidation in the refining period, the vacuum degree of the induction furnace is ≤1Pa, the refining temperature is 1600°C, and the time is not less than 50min. At the end of the refining vacuum deep deoxidation, 0.15kg / t rare earth lanthanum is added through the vacuum silo for deep desulfurization, deep deoxidation and denaturation of inclusions in the iron-chromium-vanadium alloy.

[0049] 3) The refined molten steel is subjected to low-temperature mold casting, and the tapping temperature is 1580°C. After the mold casting is completed and furnace cooling is completed for 15 minutes, the mold is allowed to be broken into air, and a heating agent and a covering agent are added to the surface of the ingot using a long spoon. The mold casting ingot can be demolded and then air-cooled to form an ingot of 200 mm in diameter;

[0050] 4) The ingot obtained in step (3) is subjected to a 150kg electroslag remelting process for deep desulfurization and removal of large rare earth inclusions, thereby enhancing the deep desulfurization capability of the slag system while taking into account the melting point. The slag is composed of CaF2, Al2O3, and CaO, wherein CaF2:Al2O3:CaO=60:20:20 (wt%), the ingot shape is Ф250mm, and the slag amount is 17±2kg / t.

[0051] During the electroslag remelting process, no deoxidizers such as aluminum and silicon are added. Only carbon powder is added to deoxidize the slag system to ensure the stability of the slag system, thereby ensuring the consistency of the purity of the components at the arc starting end and the feeding end of the electroslag ingot.

[0052] As can be seen from Tables 1 and 2, after the electroslag remelting process, the contents of S, Si, Mn, Al, P, and O are all reduced, and the Fe-Cr-V alloy is further purified. As can be seen from Table 1, the contents of each residual element in the ultrapure Fe-Cr-V alloy in Examples 1-5 meet the technical requirements, especially the sulfur content can be controlled at or below 0.0007%, and the titanium content can be controlled at or below 0.0015%.

[0053] The ultrapure iron-chromium-vanadium alloy prepared by the technical solution of the present invention is particularly suitable for being used as a raw material for alloying chromium and vanadium simultaneously when producing ultrapure high-temperature bearing steel M50 (8Cr4Mo4V) and M50NiL (13Cr4Mo4Ni4V). In specific embodiments 1-3, the alloy ratio of Cr to V is 4.1:1, which is particularly suitable for preparing M50 (8Cr4Mo4V), and in embodiments 4-5, the alloy ratio of Cr to V is 4:1.2, which is particularly suitable for preparing M50NiL (13Cr4Mo4Ni4V). At the same time, the composition ratio range of Cr and V in the ultrapure iron-chromium-vanadium alloy can also be expanded, and it can be applied to the production of ultrapure high-quality stainless steel, special alloy steel, etc.

[0054] Embodiment 6-8

[0055] The ultrapure master alloys of Examples 1-3 are respectively alloyed with 99.96% ultrapure metal vanadium V1 and ultrapure electrolytic metal chromium JCr99.95-A for chromium and vanadium, and the M50 (8Cr4Mo4V) steel is prepared by melting using the VIM+VAR process flow. Using 1 part of the ultrapure iron-chromium-vanadium of Examples 1-3 for alloying is equivalent to simultaneously alloying 1.5 parts of vanadium and chromium to prepare M50.

[0056] Comparative Examples 1-3

[0057] M50 (8Cr4Mo4V) steel is prepared by smelting using VIM+VAR process flow, using 99.96% ultra-pure metal vanadium V1 for vanadium alloying and 99.96% ultra-pure electrolytic metal chromium JCr99.95-A for chromium alloying.

[0058] Table 3 is a comparison of the cleanliness of M50 (8Cr4Mo4V) steel prepared in Examples 6-8 and Comparative Examples 1-3.

[0059] Table 3 Comparison of cleanliness of M50 (8Cr4Mo4V) steel prepared in Examples 6-8 and Comparative Examples 1-3 (wt%)

[0060] Group C Cr Mo V Si Mn S P Al Ti O N Fe Example 6 0.80 4.11 4.20 1.01 0.21 0.21 0.0005 0.0017 0.005 0.0010 0.0005 0.0004 Bal. Example 7 0.80 4.12 4.21 1.00 0.20 0.21 0.0005 0.0017 0.005 0.0009 0.0005 0.0003 Bal. Example 8 0.80 4.10 4.21 1.01 0.20 0.20 0.0006 0.0017 0.005 0.0010 0.0005 0.0004 Bal. Comparative Example 1 0.81 4.11 4.19 1.01 0.20 0.20 0.0007 0.0020 0.006 0.0012 0.0005 0.0004 Bal. Comparative Example 2 0.80 4.10 4.20 1.00 0.20 0.19 0.0008 0.0018 0.006 0.0011 0.0006 0.0005 Bal. Comparative Example 3 0.80 4.11 4.21 1.00 0.19 0.20 0.0008 0.0019 0.007 0.0012 0.0005 0.0004 Bal.

[0061] As can be seen from Table 3, when comparing the cleanliness control levels of Examples 6-8 and Comparative Examples 1-3, the O and N contents of the two are at the same level, but the residual element contents of S, P, Al, and Ti of Examples 6-8 are slightly lower.

[0062] Examples 9-10

[0063] The ultrapure master alloys of Examples 4-5 are respectively alloyed with 99.96% ultrapure metal vanadium V1 and ultrapure electrolytic metal chromium JCr99.95-A for chromium and vanadium, and the M50NiL (13Cr4Mo4Ni4V) steel is prepared by melting using the VIM+VAR process flow. Using 1 part of the ultrapure iron-chromium-vanadium of Examples 4-5 for alloying is equivalent to simultaneously alloying 1.5 parts of vanadium and chromium to prepare M50NiL.

[0064] Comparative Examples 4-5

[0065] M50NiL (13Cr4Mo4Ni4V) steel is prepared by smelting with VIM+VAR process flow using 99.96% ultra-pure metal vanadium V1 for vanadium alloying and 99.96% ultra-pure electrolytic metal chromium JCr99.95-A for chromium alloying.

[0066] Table 4 is a comparison of the cleanliness of M50 (8Cr4Mo4V) steel prepared in Examples 6-8 and Comparative Examples 1-3.

[0067] Table 4 Comparison of cleanliness of M50 (8Cr4Mo4V) steel prepared in Examples 6-8 and Comparative Examples 1-3 (wt%)

[0068]

[0069]

[0070] As can be seen from Table 4, when comparing the cleanliness control levels of Examples 9-10 and Comparative Examples 4-5, the O and N contents of the two are at the same level, but the residual element contents of S, P, Al, and Ti of Examples 9-10 are slightly lower.

[0071] In addition to the above embodiments, the present invention may also have other implementations, such as designing iron-chromium-vanadium alloys with different Cr and V composition ratios and purifying them by induction furnace + electroslag remelting process for simultaneous alloying of chromium and vanadium to prepare other ultra-pure high-quality stainless steel, special alloy steel, etc. All technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope required by the present invention.

Claims

1. An ultra-pure master alloy for high-temperature bearing steel, characterized in that: The alloy has the following composition by mass percentage: Cr: 5%-25%, V: 1.3%-7%, C≤0.3%, Si≤0.05%, P≤0.01%, S≤0.001%, O≤0.0015%, Al≤0.05%, Mn≤0.05%, Ti≤0.0020wt%, and the remainder is Fe and unavoidable impurities, and Cr / V=3~4.5:

1.

2. A method for preparing the ultrapure master alloy for high temperature bearing steel according to claim 1, characterized in that: The method comprises the following steps: 1) Select FeV80 alloy as ferrovanadium raw material, and require that the raw material contains: P≤0.01wt%, S≤0.03wt%, Si≤0.6wt%, Mn≤0.15wt%, Al≤1.0wt%, Ti≤0.005wt%, C≤0.2wt%; select JCr99.2 as metal chromium raw material, and require that the raw material contains: P≤0.002wt%, S≤0.005wt%; select pure iron raw material, and require that the raw material contains: P≤0.002wt%, S≤0.003wt%, Ti≤0.002wt%; 2) Vacuum induction furnace smelting, according to the composition of the master alloy, ferrovanadium, 1 / 3 metallic chromium, 2 / 3 pure iron raw materials and high-purity graphite carbon blocks are loaded into the furnace, the carbon content is ≤0.3%, the vacuum degree is required to be ≤1Pa when melting begins, medium power melting, the remaining 1 / 3 pure iron is added before melting, the refining temperature is 1590-1610°C, the time is greater than 30 minutes, and two refinings are performed, wherein after the first refining is completed, the remaining 2 / 3 metallic chromium is added, and then the second refining is performed; 3) The refined molten steel is subjected to low temperature mold casting, with the tapping temperature of 1580-1590°C to obtain an ingot; 4) The ingot obtained in step (3) is subjected to electroslag remelting treatment, and the slag consists of CaF2, Al2O3, and CaO, and the mass ratio thereof is CaF2:Al2O3:CaO=3:1:

1.

3. The preparation method according to claim 2, characterized in that: In step 1), P in the ferrovanadium raw material is ≤ 0.008 wt%.

4. The preparation method according to claim 2, characterized in that: In step 2), after the charge is melted, the vacuum degree of the induction furnace is not higher than 1 Pa during vacuum deep deoxidation in the refining stage, and the holding time is not less than 50 minutes.

5. The preparation method according to claim 2, characterized in that: In step 2), after the second refining, take a sample and analyze [N]. If [N] ≤ 0.01%, stir for 5 minutes and proceed to the next step. If [N] > 0.01%, continue to add graphite carbon blocks to continue deoxidation and denitrification. The key points of controlling the refining time and strengthening the stirring are to ensure that [N] ≤ 0.01% at the end of refining.

6. The preparation method according to claim 2, characterized in that: In step 2), at the end of the refining vacuum deep deoxidation, 0.15-0.2 kg / t of cerium, lanthanum or a mixture of lanthanum, cerium, praseodymium and neodymium is added through a vacuum silo.

7. The preparation method according to claim 2, characterized in that: In step 3), after mold casting, the ingot is allowed to be broken into air after furnace cooling for 15 minutes, and a heating agent and a covering agent are added to the surface of the ingot. The ingot is demolded and air-cooled. The ingot specification limit is preferably such that it can be directly used as an electroslag remelting consumable electrode after peeling.

8. The preparation method according to claim 2, characterized in that: In step 4), the ingot shape is Φ250 mm and the slag amount is 17±2 kg / t.

9. Use of the ultrapure master alloy according to claim 1 or the ultrapure master alloy prepared by the preparation method according to any one of claims 2 to 8 in the preparation of high-temperature bearing steel.

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