Long-life bearing steel, preparation method thereof and electroslag remelting casting powder

Abstract

The invention discloses long-life bearing steel, a preparation method thereof and electroslag remelting casting powder, the long-life bearing steel is prepared by electric furnace or converter smelting, LF refining, vacuum degassing, continuous casting or die casting pouring, electroslag remelting and rolling, and rare earth alloy lanthanum and cerium are added into molten steel before continuous casting or die casting. And new electroslag remelting protection slag is designed, so that the problem that the contact fatigue life of the bearing steel is influenced by precipitation of inclusions and carbides is solved, and the 4.5 GPa contact fatigue life L10 value of the bearing steel can be stably increased to 5 * 10 < 7 > or above, so that the requirements of bearing steel in high-end fields such as high-speed rail bearings, aviation bearings and wind power bearings are met.

Description

Technical Field

[0001] The present invention relates to the technical field of steelmaking, and more specifically to a long-life bearing steel and a preparation method thereof, and an electroslag remelting protective slag. Background Art

[0002] As the core components of advanced manufacturing, bearings are large in quantity and wide in scope, and play an important supporting role in the manufacturing industry. Their development trend is higher reliability, longer life and better environmental adaptability. The most widely used bearing steel is high-carbon chromium GCr15 bearing steel. The L10 value of the contact fatigue life of ordinary bearing steel under 4.5GPa conditions is lower than 107. It can meet the relevant fatigue life requirements when used in ordinary automobiles or mechanical parts. However, for EMU high-speed rail or aerospace fields, ordinary bearing steel cannot meet its reliability and long life requirements, so it is necessary to develop long-life bearing steel to meet the relevant requirements. The L10 value of contact fatigue life must be higher than 2*107. There are mainly two factors that affect the contact fatigue life of bearing steel: inclusions and carbide precipitation. The development of long-life bearing steel requires solving key problems such as complete harmlessness of inclusions and extremely fine carbides. Among them, smelting and casting processes are key processes to control the precipitation of inclusions and carbides.

[0003] In recent years, relevant studies have shown that rare earth treatment can improve the fatigue life of bearing steel. However, even if a large number of fine rare earth inclusions with a size less than 15μm are formed by rare earth treatment, large rare earth inclusions with a size greater than 50μm that cannot be eliminated are still inevitably generated, which greatly damage the stability of bearing steel. In order to solve the problem of large rare earth inclusions, relevant technologies propose the idea of ​​electroslag remelting after rare earth treatment. For example, Chinese patent application No. 201210105658.X discloses a rare earth-doped bearing steel and a preparation method thereof, comprising the following steps: a) weighing each component by weight percentage; b) vacuum induction melting; c) pouring and remelting electrode rods; d) electroslag remelting to obtain steel ingots; e) homogenization heat treatment; f) forging bearing processing rods; g) spheroidizing heat treatment. However, this preparation method does not realize how the rare earth content affects the contact fatigue life of bearing steel, nor does it propose how to stably control the rare earth content to ensure that the contact fatigue life meets the long life requirement. Chinese patent application No. 202210290982 proposes a new material and preparation method for rare earth railway carburized bearing steel. The method proposes a control range of rare earth element Ce and proposes electroslag treatment. However, the slag system used in the electroslag is an ordinary electroslag slag system, and the composition of the electroslag remelting protective slag is: CaF2: 30%, Al2O3: 45%, CaO: 30%, MgO: 5%. After using such a slag system electroslag, the electrode rod rare earth inclusions in the electroslag will inevitably return to the traditional alumina inclusions or calcium aluminate Ds inclusions. At the same time, the rare earth element content in the steel is also difficult to control within the ideal range.

[0004] In view of the above situation, it is urgent to study a process method for smelting long-life bearing steel. On the basis of a thorough study of the effect of rare earth content on contact fatigue life, the influence of rare earth treatment on the precipitation of inclusions and carbides should be comprehensively considered to improve the fatigue life of bearing steel. Summary of the invention

[0005] In view of the problem that inclusions and carbide precipitation in the prior art affect the contact fatigue life of bearing steel, the purpose of the present invention is to provide a long-life bearing steel and a preparation method thereof and an electroslag remelting protective slag, which can extend the 4.5 GPa contact fatigue life of the bearing steel to L 10 The value is steadily increased to 5×10 7 The above are to meet the requirements of bearing steel in high-end fields such as high-speed rail bearings, aviation bearings, and wind power bearings.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] A first aspect of the present invention provides a method for preparing a long-life bearing steel, comprising the following steps:

[0008] S1, preparing ingots by electric furnace / converter smelting - LF refining - vacuum degassing - continuous casting / mold casting, adding rare earth alloys lanthanum and cerium into the molten steel before continuous casting / mold casting;

[0009] S2, cleaning the surface of the ingot and making it into an electrode rod for electroslag remelting;

[0010] S3, using the electrode rod as a raw material, and performing electroslag remelting in an electroslag furnace to obtain an electroslag ingot; the electroslag remelting protective slag used in the electroslag remelting process includes the following components in weight percentage: CaF2: 40-65%, Al2O3: 5-10%, ZrO2: 10-15%, CaO: 5-10%, MgO: 2-5%, SiO2: 3-5%, Ce2O3+La2O3: 10-15%;

[0011] S4, the electroslag ingot is rolled into a long-life bearing steel after being diffused at high temperature in a soaking furnace.

[0012] Preferably, in step S1, the method of adding the rare earth alloys lanthanum and cerium adopts an injection method. Before injecting the rare earth alloy, argon gas is blown from the bottom of the ladle containing molten steel to blow open the slag surface to expose the molten steel, and then the rare earth alloy is injected into the molten steel; the composition of the rare earth alloy in the molten steel is controlled to be Ce: 0.006~0.011%, La: 0.003~0.006%.

[0013] Preferably, the rare earth alloy is added at a yield of 50-60%.

[0014] Preferably, in step S1, when continuous casting is adopted, the superheat of the molten steel is controlled at 30-40° C., and a stopper rod is used to control the flow in the casting crystallizer, and argon is blown into the stopper rod.

[0015] Preferably, in step S1, the mass of the ingot is 1.5-3 tons, and when the ingot is a square billet, the side length of the ingot is 0.33-0.38 m, and the length is 2-4 m; when the ingot is a round ingot, its diameter is 0.35-0.4 m, and the length is 2-3 m.

[0016] Preferably, in step S3, the electroslag remelting process is carried out under a protective atmosphere, using constant melting rate smelting, and the melting rate in the electroslag remelting process is 5 to 8 kg / min.

[0017] Preferably, in step S3, the amount of electroslag remelting protective slag added is 40-60 kg / t 钢 .

[0018] Preferably, the long-life bearing steel comprises the following chemical components in weight percentage: C: 0.9-1.1%, Cr: 1.4-1.6%, Mn: 0.3-0.6%, Si: 0.2-0.3%, Al: 0.008-0.03%, Ce: 0.004-0.01%, La: 0.002-0.006%, Ti<0.0015%, N<0.005%, S<0.01%, P<0.015%, and the remainder is iron and other inevitable impurities.

[0019] Preferably, more than 95% of the inclusions in the long-life bearing steel are fine inclusions with a rare earth oxide content exceeding 60% and a size less than 10 μm, and the remaining less than 5% are composite inclusions of rare earth oxide-aluminum oxide-calcium oxide-silicon oxide, and the size of the composite inclusions is less than 15 μm.

[0020] Preferably, the contact fatigue life of the long-life bearing steel under 4.5 GPa is L 10 Greater than 5×10 7 .

[0021] The second aspect of the present invention provides a long-life bearing steel prepared by the preparation method of long-life bearing steel as described in the first aspect of the present invention, wherein the long-life bearing steel comprises the following chemical components in weight percentage: C: 0.9~1.1%, Cr: 1.4~1.6%, Mn: 0.3~0.6%, Si: 0.2~0.3%, Al: 0.008~0.03%, Ce: 0.004~0.01%, La: 0.002~0.006%, Ti<0.0015%, N<0.005%, S<0.01%, P<0.015%, and the remainder is iron and other inevitable impurities.

[0022] The third aspect of the present invention provides an electroslag remelting protective slag used in the preparation method of long-life bearing steel as described in the first aspect of the present invention, and the electroslag remelting protective slag includes the following components in weight percentage: CaF2: 40~65%, Al2O3: 5~10%, ZrO2: 10~15%, CaO: 5~10%, MgO: 2~5%, SiO2: 3~5%, Ce2O3+La2O3: 10~15%.

[0023] The present invention has the following beneficial effects:

[0024] The long-life bearing steel and its preparation method and electroslag remelting protective slag of the present invention produce a long-life bearing steel whose contact fatigue life L10 value (contact fatigue life that satisfies the failure probability of less than 10%) under 4.5GPa is stable and greater than 5×107, far exceeding the ordinary high-carbon chromium bearing steel GCr15, and can be widely used in high-end fields such as high-speed rail bearings, aviation bearings, and wind power bearings. At the same time, the long-life bearing steel produced by the present invention can replace carburized bearing steel with higher manufacturing costs in the field of industrial applications. DETAILED DESCRIPTION

[0025] In order to better understand the above technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with embodiments.

[0026] The present invention provides a method for preparing long-life bearing steel, the process of which is electric furnace (or converter) smelting - LF refining - VD (or RH) vacuum degassing - continuous casting (or mold casting) pouring - electroslag remelting - rolling. The key to the process design is to stably control the rare earth content and rare earth inclusions, and finally completely eliminate the hazards of inclusions. Under the premise of not affecting the performance of the bearing steel, the rare earth elements are used to inhibit the precipitation of carbide grain boundaries, thereby achieving the effect of significantly improving the life of the bearing steel. The prepared high-carbon chromium bearing steel has a contact fatigue life that exceeds that of carburized bearing steel, and can replace carburized bearing steel with higher costs in industrial applications.

[0027] The method for preparing the long-life bearing steel of the present invention specifically comprises the following steps:

[0028] S1, adopting electric furnace / converter smelting - LF refining - vacuum degassing - continuous casting / mold casting to prepare ingots, adding rare earth alloys lanthanum and cerium before continuous casting / mold casting;

[0029] Specifically, a large production process of electric furnace / converter smelting - LF refining - VD (or RH) vacuum degassing - large square billet continuous casting (or round billet continuous casting or mold casting) is used to prepare square or round ingots, and rare earth alloys lanthanum and cerium are added to the molten steel before continuous casting / mold casting. The mass of the prepared ingot is 1.5 to 3 tons. If the final ingot is a square billet, the side length of the ingot is 0.33 to 0.38 m, and the length is 2 to 4 m; if the ingot is a round ingot, its diameter is 0.35 to 0.4 m, and the length is 2 to 3 m; the above ingot design is selected to meet the reasonable size requirements of the subsequent electroslag electric shock rod.

[0030] In the above large-scale production process, the flux of the electric furnace or converter is 60-150t. If the ingot size of the square billet or round billet is larger than the size described above, the round billet can be prepared by initial rolling as the electrode rod for electroslag remelting, with a diameter of 0.35-0.4m and a length of 2-3m. Among them, the capacity of the electric furnace or converter is 60-150t, which can ensure a certain scale of production of subsequent electroslag electrode rods. If the capacity of the primary refining furnace is too low, the production cost of bearing steel will be too high. If the capacity of the primary refining furnace is too large, it will make it difficult to cast stably during the continuous casting process. At the same time, considering that the ingot shape of the continuous casting billet or the mold casting ingot shape may not meet the electrode rod size requirements, the electrode rod size requirements can be achieved after initial rolling.

[0031] The large-scale production process is used to prepare the electrode rods required for subsequent electroslag smelting, which is closer to the conventional process for producing bearing steel. The purpose of this choice is to reduce the preparation cost. The difference from the bearing steel produced by the conventional process is that the rare earth alloy is added before pouring to provide the original rare earth for the stable control of the rare earth composition of the final long-life bearing steel. Among them, the method of adding the rare earth alloys lanthanum and cerium adopts the method of input. Before the rare earth alloy is added, argon is blown from the bottom of the ladle containing molten steel to blow open the slag surface to expose the molten steel, and then the rare earth alloy is put into the molten steel. The rare earth alloy is added at a yield of 50-60%; after the rare earth alloy is added to the molten steel, the composition in the molten steel is controlled at Ce: 0.006-0.011%, La: 0.003-0.006%. The rare earth recovery rate of adding rare earth alloy by the input method is high, the operation is convenient, and the rare earth final composition is controllable; after the rare earth alloy is added to the molten steel, the rare earth composition in the molten steel is required to be controlled at Ce: 0.006~0.011%, La: 0.003~0.006%. This content is slightly higher than the rare earth content requirement in the steel after the final electroslag remelting, mainly considering that the rare earth elements are slightly attenuated in the electroslag process.

[0032] When the above-mentioned ingot is cast by continuous casting, the superheat of the molten steel is controlled at 30-40°C, and a stopper rod is used to control the flow in the casting crystallizer, and argon is blown into the stopper rod to prevent the nozzle from clogging during the casting process. Among them, the casting superheat of 30-40°C is selected mainly because the castability of the molten steel will be slightly reduced after the addition of rare earths, so a slightly higher superheat of the molten steel is set, and argon is blown into the casting nozzle of the crystallizer to avoid clogging of the nozzle. Because only the electrode rod for subsequent electroslag is prepared in this step, the segregation problem caused by high superheat and the bubble problem caused by argon blowing considered in the production of conventional bearing steel billets do not exist in the present invention because the subsequent electroslag remelting is required.

[0033] S2, cleaning the surface of the ingot and making it into an electrode rod for electroslag remelting;

[0034] S3, using electrode rods as raw materials, and performing electroslag remelting smelting in an electroslag furnace to obtain electroslag ingots; the electroslag remelting protective slag used in the electroslag remelting process includes the following components in weight percentage: CaF2: 40-65%, Al2O3: 5-10%, ZrO2: 10-15%, CaO: 5-10%, MgO: 2-5%, SiO2: 3-5%, Ce2O3+La2O3: 10-15%, and the addition amount of the electroslag remelting protective slag is 40-60kg / t 钢 The electroslag ingot obtained by electroslag remelting is a cylindrical electroslag ingot, and the diameter of the electroslag ingot is required to be 0.4 to 0.6m.

[0035] Electroslag remelting is a key link in the production of long-life bearing steel. The main reason is that the bearing steel produced by the large production process inevitably has inclusions with a particle size greater than 15μm. In particular, after the rare earth treatment in step S1, the rare earth inclusions generated have high density, and the large-particle rare earth inclusions generated will inevitably reduce its contact fatigue life. Therefore, for the rare earth-treated bearing steel, it is necessary to undergo electroslag remelting to stably improve its contact fatigue life. Electroslag remelting is to connect the electrode rod-slag-crystallizer molten steel into an energized circuit. Under low-voltage and high-current conditions, the local heating of the slag is used to gradually dissolve the top of the electrode rod in contact with the slag into droplets. A large number of separated droplets pass through the slag layer and fall into the molten steel pool of the crystallizer. The molten steel pool contacts the crystallizer and solidifies again. Electroslag remelting filters the molten steel through the slag to completely remove large inclusions.

[0036] The present invention newly designs an electroslag remelting protective slag system, which can not only remove large inclusions, but also play a role in stabilizing and controlling the rare earth content. Since too high or too low rare earth content in bearing steel cannot play a role in improving the contact fatigue life and bending fatigue life of bearing steel, when the rare earth content is in the range of Ce: 0.004-0.01%, La: 0.002-0.006%, it can ensure that the contact fatigue life is greatly improved. The reason is that in addition to reducing the harm of inclusions and improving the contact fatigue life, rare earth elements can also limit the diffusion of carbon and inhibit the precipitation of carbon at grain boundaries. However, if the rare earth content is too high, because the rare earths are all large atoms, it will affect the overall plasticity of the bearing steel and thus affect its contact fatigue life. If the rare earth content is too low, the steel cannot produce rare earth oxide inclusions, but traditional aluminum-calcium oxide inclusions, which are harmful and will affect the contact fatigue life of the bearing steel. Therefore, the rare earth content should be controlled within the above range during the electroslag remelting process. Since rare earth is an active element, it is particularly easy to react with electroslag protective slag in the electroslag process, resulting in attenuation of rare earth elements. Through multiple experiments, the present invention finally determined the electroslag remelting protective slag system: CaF2: 40-65%, Al2O3: 5-10%, ZrO2: 10-15%, CaO: 5-10%, MgO: 2-5%, SiO2: 3-5%, Ce2O3+La2O3: 10-15%, which can ensure that the rare earth content in the electroslag process is stably controlled within the target range. At the same time, the inclusions after electroslag remelting are basically controlled to be fine inclusions of rare earth oxides, which are not only harmless, but also improve the solidification structure of bearing steel because they serve as nucleation particles.

[0037] The electroslag remelting protective slag system uses ZrO2, mainly considering that ZrO2 has too strong neutral characteristics and is not easy to react with rare earths. It is also not easy to absorb water relative to MgO and CaO, and can well adjust the electroslag performance. The MgO and CaO contents are both controlled to be low, the purpose is to prevent the protective slag from absorbing water and causing hydrogen-induced cracks in the bearing steel. Compared with the electroslag slag system of ordinary bearing steel, the slag system Al2O3 designed in the present invention is greatly reduced, mainly considering that the electroslag process can no longer produce Al2O3 brittle inclusions in large quantities. Al2O3 brittle inclusions are better than high hardness and have a greater impact on the contact fatigue life of steel.

[0038] In the above-mentioned electroslag remelting process, argon is blown into the crystallizer for more than 20 minutes before power is turned on to drive away the remaining air in the crystallizer; the electroslag remelting process needs to be carried out in a protective atmosphere, and constant melting rate electroslag remelting is adopted. The melting rate during the electroslag remelting process is controlled at 5-8kg / min; after the electroslag remelting is powered on, argon blowing protection needs to be maintained for more than 15 minutes to prevent secondary oxidation. Among them, electroslag remelting under a protective atmosphere is mainly to prevent secondary oxidation. If a protective atmosphere is not used, it is easy to cause serious oxidation attenuation of silicon, carbon and rare earth in the molten steel. The electroslag Rongsu control ensures the stable control of the final electroslag ingot structure.

[0039] The diameter of the electroslag ingot obtained by electroslag remelting is required to be 0.4 to 0.6 m, mainly to meet the ingot size requirements for subsequent initial rolling and high-temperature diffusion in the soaking furnace.

[0040] S4, the electroslag ingot is rolled into long-life bearing steel after high-temperature diffusion in a soaking furnace.

[0041] The purpose of selecting the electroslag ingot for high temperature diffusion in the soaking furnace is to further reduce the carbide size, thereby playing a role in improving the contact fatigue life. The high temperature diffusion temperature in the soaking furnace is 1200-1250°C.

[0042] The above-mentioned long-life bearing steel includes the following chemical components in weight percentage: C: 0.9-1.1%, Cr: 1.4-1.6%, Mn: 0.3-0.6%, Si: 0.2-0.3%, Al: 0.008-0.03%, Ce: 0.004-0.01%, La: 0.002-0.006%, Ti<0.0015%, N<0.005%, S<0.01%, P<0.015%, and the remainder is iron and other inevitable impurities. Among them, the key is the content range of rare earth content in the steel composition requirements. As mentioned above, the rare earth content is controlled at Ce: 0.004 ~ 0.01%, La: 0.002 ~ 0.006% can greatly improve the contact fatigue life of steel. In the preparation of electrode rods and the electroslag remelting process, setting a reasonable electroslag remelting protective slag can achieve a stable control of the rare earth content within the above range; too high or too low rare earth alloy content cannot play a role in improving the contact fatigue life and bending fatigue life of bearing steel. The content of other elements in bearing steel is set close to that of conventional bearing steel.

[0043] More than 95% of the inclusions in the long-life bearing steel mentioned above are fine inclusions with a rare earth oxide content of more than 60% and a size of less than 10μm, and the remaining less than 5% are composite inclusions of rare earth oxide-aluminum oxide-calcium oxide-silicon oxide, and the size of the composite inclusions is less than 15μm. In the above preparation method, for the control of inclusions in long-life bearing steel, in addition to controlling the size, it is also necessary to control the composition of the inclusions. Through the above process control, it can be achieved that most of the final inclusions are harmless fine-grained rare earth oxide inclusions. The deformation of the rare earth oxide inclusions during the rolling process is basically the same as that of the steel matrix, and can basically be regarded as harmless. The above inclusion control requirements also limit the amount of conventional alumina-calcium oxide-silicon oxide inclusions, which can meet the long life requirements of bearing steel.

[0044] The contact fatigue life of the above-mentioned long-life bearing steel under 4.5GPa is L 10 (Contact fatigue life with failure probability less than 10%) Stable greater than 5×10 7, far exceeding ordinary high carbon chromium bearing steel, and can be widely used in high-end fields such as high-speed rail bearings, aviation bearings, and wind power bearings.

[0045] The long-life bearing steel and its preparation method and the electroslag remelting protective slag of the present invention are further introduced below with reference to specific examples.

[0046] Example 1

[0047] This embodiment uses 150t electric furnace-LF-VD-bloom continuous casting-electroslag remelting-rolling, and its main process steps are as follows:

[0048] 1) 150t electric furnace - LF refining - VD vacuum degassing, smelting and refining bearing steel according to the bearing steel production method. After VD treatment, the composition of molten steel is [C]: 0.98%, [Cr]: 1.48%, [Mn]: 0.41%, [Si]: 0.25%, [Al]: 0.015%, [Ti]: 0.0011%, [N]: 0.0045%, [S]: 0.0045%, [P]: 0.013%, and the composition reaches the conventional standard of bearing steel GCr15. After the composition test is qualified, the bottom blowing argon flow of the ladle is increased to blow open the slag surface, and 15kg of rare earth alloy containing La and Ce is manually added (according to the recovery rate of 55%), and then the bottom blowing flow is slightly reduced to ensure that the slag surface is closed. After slightly blowing and stirring for 2 minutes, the bottom blowing argon flow is adjusted to the bottom blowing flow required for normal weak stirring. Subsequently, the rare earth content of the molten steel was measured to be [Ce]: 0.0065%, [La]: 0.0034%. After soft blowing and stirring in the ladle, the molten steel was transferred to the continuous casting process and cast into a square billet with a side length of 0.35m, and then cut into a square ingot with a length of 3.8m. The superheat of the molten steel during the continuous casting process was controlled at 35°C, and a stopper rod was used to control the flow. Argon was blown into the stopper rod to prevent the water nozzle from clogging during the casting process. Since the continuous casting process can continuously cast many furnaces of steel, the ingots of one furnace of steel can be selected and cut into ingots for subsequent electroslag. One furnace of steel can produce multiple ingots.

[0049] 2) Clean the surface of the square ingot, grind off the oxidized iron scale on the surface of the ingot, and make electrode rods that can be used for slag smelting.

[0050] 3) The electrode rod is used as a raw material and loaded into an electroslag furnace for electroslag remelting. The electroslag furnace is used for electroslag remelting under an Ar gas protective atmosphere. Argon is blown into the crystallizer for more than 20 minutes before the electroslag is powered on to drive away the remaining air in the crystallizer. The crystallizer is selected to have a diameter of 0.6m. The electroslag remelting protective slag composition is CaF2: 45%, Al2O3: 8%, ZrO2: 15%, CaO: 8%, MgO: 5%, SiO2: 4%, Ce2O3 + La2O3: 15%, and the total amount of remelting protective slag added is 160kg. Then, the electroslag remelting treatment is started by powering on to prepare an electroslag ingot with a diameter of 0.6m and a length of 1.6m. The electroslag remelting process needs to be carried out under a protective atmosphere, and a constant melting rate electroslag remelting smelting is adopted. The melting rate of the electroslag remelting process is controlled at 6kg / min. After the electroslag is powered on, argon blowing protection needs to be maintained for 15 minutes to prevent secondary oxidation.

[0051] 4) The electroslag ingot is transported to a soaking furnace at 1220℃ for 16 hours of high-temperature diffusion, followed by initial rolling into 140mm square billets, and then finish rolling into long-life bearing steel with a diameter of less than 60mm according to user needs. Its composition is: [C]: 0.97%, [Cr]: 1.45%, [Mn]: 0.40%, [Si]: 0.24%, [Al]: 0.014%, [Ce]: 0.005%, [La]: 0.0032%, [Ti]: 0.0012%, [N]: 0.0048%, [S]: 0.003%, [P]: 0.012%. The inclusions in the steel are automatically scanned and detected, and more than 98% are fine inclusions with a rare earth oxide content of more than 60%, and their sizes are all less than 10μm, and 2% are rare earth oxide-aluminum oxide-calcium oxide-silicon oxide composite inclusions, with a size of less than 15μm. At the same time, the contact fatigue life of bearing steel under 4.5GPa conditions was tested. A total of 12 samples were tested and the results showed that L 10 The value is 5.7×10 7 .

[0052] The prepared long-life bearing steel has stable performance and long fatigue life, and is used in high-end fields such as high-speed rail bearings, aviation bearings, and wind power bearings.

[0053] Example 2

[0054] This embodiment uses 150t electric furnace-LF-RH-round billet continuous casting-electroslag remelting-rolling, and its main process steps are as follows:

[0055] 1) 150t converter - LF refining - RH vacuum degassing, smelting and refining bearing steel according to the bearing steel production method. After RH treatment, the composition of molten steel is [C]: 1.05%, [Cr]: 1.58%, [Mn]: 0.59%, [Si]: 0.28%, [Al]: 0.029%, [Ti]: 0.0014%, [N]: 0.0035%, [S]: 0.0065%, [P]: 0.014%, and the composition reaches the conventional standard of bearing steel GCr15. After the composition test is qualified, the bottom blowing argon flow of the ladle is increased to blow open the slag surface, and 20kg of rare earth alloy containing La and Ce is manually added (based on the recovery rate of 50%), and then the bottom blowing flow is slightly reduced to ensure that the slag surface is closed. After slightly blowing and stirring for 2 minutes, the bottom blowing argon flow is adjusted to the bottom blowing flow required for normal weak stirring. Subsequently, the rare earth composition of the molten steel was determined to be [Ce]: 0.009%, [La]: 0.0045%. After soft blowing and stirring in the ladle, the molten steel was transferred to the continuous casting process and cast into round billets with a side length of 0.38m, and then cut into round ingots with a length of 2.9m. The superheat of the molten steel during the continuous casting process was controlled at 39°C, and a stopper rod was used to control the flow. Argon was blown into the stopper rod to prevent the water nozzle from clogging during the casting process. Since the continuous casting process can continuously cast many furnaces of steel, the ingots of one furnace of steel can be selected and cut into ingots for subsequent electroslag. One furnace of steel can produce multiple ingots.

[0056] 2) Clean the surface of the round ingot, grind off the oxidized iron scale on the surface of the ingot, and make electrode rods that can be used for slag smelting.

[0057] 3) The electrode rod is used as a raw material and loaded into an electroslag furnace for electroslag remelting. The electroslag furnace is used for electroslag remelting under an Ar gas protective atmosphere. Argon is blown into the crystallizer for more than 25 minutes before the electroslag is powered on to drive away the remaining air in the crystallizer. The crystallizer is selected to have a diameter of 0.48m. The electroslag remelting protective slag composition is CaF2: 64%, Al2O3: 5%, ZrO2: 10%, CaO: 5%, MgO: 3%, SiO2: 3%, Ce2O3 + La2O3: 10%, and the total amount of remelting protective slag added is 100kg. Then, the electroslag treatment is started by powering on to prepare an electroslag ingot with a diameter of 0.48m and a length of 1.9m. The electroslag process needs to be carried out under a protective atmosphere, and a constant melting rate electroslag remelting smelting is adopted. The melting rate of the electroslag remelting process is controlled at 5kg / min. After the electroslag is powered on, argon blowing protection is required to be maintained for 20 minutes to prevent secondary oxidation.

[0058] 4) The electroslag ingot is transported to a 1200℃ soaking furnace for 14 hours of high-temperature diffusion, followed by initial rolling into 140mm square billets, and then fine rolling into bearing steel with a diameter of less than 60mm according to user requirements. The final steel composition: [C]: 1.01%, [Cr]: 1.53%, [Mn]: 0.56%, [Si]: 0.25%, [Al]: 0.023%, [Ce]: 0.006%, [La]: 0.004%, [Ti]: 0.0009%, [N]: 0.0038%, [S]: 0.007%, [P]: 0.012%. The inclusions in the steel are automatically scanned and detected, and more than 99% are fine inclusions with a rare earth oxide content of more than 60%, and the size is less than 10μm, and 1% are rare earth oxide-aluminum oxide-calcium oxide-silicon oxide composite inclusions, with a size less than 15μm. At the same time, the contact fatigue life of bearing steel under 4.5GPa conditions was tested. A total of 12 samples were tested and the results showed that L 10 The value is 5.2×10 7 .

[0059] The prepared long-life bearing steel has stable performance and long fatigue life, and is used in high-end fields such as high-speed rail bearings, aviation bearings, and wind power bearings.

[0060] Example 3

[0061] This embodiment uses 150t electric furnace-LF-RH-die casting-initial rolling-electroslag remelting-rolling, and its main process steps are as follows:

[0062] 1) 150t converter - LF refining - RH vacuum degassing, bearing steel is smelted and refined according to the bearing steel production method. After RH treatment, the composition of molten steel is [C]: 0.98%, [Cr]: 1.42%, [Mn]: 0.38%, [Si]: 0.25%, [Al]: 0.01%, [Ti]: 0.001%, [N]: 0.0045%, [S]: 0.0055%, [P]: 0.013%, and the composition reaches the conventional standard of bearing steel GCr15. After the composition test is qualified, the bottom blowing argon flow of the ladle is increased to blow open the slag surface, and 22kg of rare earth alloy containing La and Ce (based on the recovery rate of 58%) is manually added. Then the bottom blowing flow is slightly reduced to ensure that the slag surface is closed. After slightly blowing and stirring for 2 minutes, the bottom blowing argon flow is adjusted to the bottom blowing flow required for normal weak stirring. Subsequently, the rare earth content of the molten steel was determined to be [Ce]: 0.01%, [La]: 0.005%. After soft blowing and stirring in the ladle, the molten steel was transferred to the mold casting and cast into a 6-ton round ingot with a diameter of 0.6m.

[0063] 2) The 6-ton round ingot is initially rolled, rolled and cut into round ingots with a diameter of 0.34m and a length of 3.5m.

[0064] 3) Clean the surface of the round ingot, grind off the oxidized iron scale on the surface of the ingot, and make electrode rods that can be used for slag smelting.

[0065] 4) The electrode rod is used as a raw material and loaded into an electroslag furnace for electroslag remelting. The electroslag furnace is used for electroslag remelting under an Ar gas protective atmosphere. Argon is blown into the crystallizer for more than 15 minutes before the electroslag is powered on to drive away the remaining air in the crystallizer. The crystallizer is selected to have a diameter of 0.42m. The electroslag remelting protective slag composition is CaF2: 45%, Al2O3: 9%, ZrO2: 14%, CaO: 9%, MgO: 5%, SiO2: 5%, Ce2O3 + La2O3: 13%, and the total amount of remelting protective slag added is 94kg. Then, the electroslag treatment is started by powering on to prepare an electroslag ingot with a diameter of 0.42m and a length of 2.2m. The electroslag process needs to be carried out under a protective atmosphere, and a constant melting rate electroslag remelting smelting is adopted. The melting rate of the electroslag remelting process is controlled at 4.5kg / min. After the electroslag is powered on, argon blowing protection is required to be maintained for 20 minutes to prevent secondary oxidation.

[0066] 5) The electroslag ingot is transported to a 1200℃ soaking furnace for 14 hours of high-temperature diffusion, followed by initial rolling into 140mm square billets, and then finish rolling into bearing steel with a diameter of less than 60mm according to user needs. The final steel composition is: [C]: 1.01%, [Cr]: 1.53%, [Mn]: 0.56%, [Si]: 0.25%, [Al]: 0.023%,

[0067] [Ce]: 0.006%, [La]: 0.004%, [Ti]: 0.0009%, [N]: 0.0038%, [S]: 0.007%, [P]: 0.012%. The inclusions in the steel were automatically scanned and detected. More than 99% of the inclusions were fine inclusions with rare earth oxide content exceeding 60%, and the size was less than 10μm. 1% was rare earth oxide-aluminum oxide-calcium oxide-silicon oxide composite inclusions, and the size was less than 15μm. At the same time, the contact fatigue life of the bearing steel under 4.5GPa conditions was tested. A total of 12 samples were tested, and the L 10 The value is 5.8×10 7 .

[0068] The prepared long-life bearing steel has stable performance and long fatigue life, and is used in high-end fields such as high-speed rail bearings, aviation bearings, and wind power bearings.

[0069] Example 4

[0070] This embodiment uses 150t electric furnace-LF-RH-round billet continuous casting-electroslag remelting-rolling, and its main process steps are as follows:

[0071] 1) 150t converter - LF refining - RH vacuum degassing, smelting and refining bearing steel according to the bearing steel production method. After RH treatment, the composition of molten steel is [C]: 1.05%, [Cr]: 1.58%, [Mn]: 0.59%, [Si]: 0.28%, [Al]: 0.029%, [Ti]: 0.0014%, [N]: 0.0035%, [S]: 0.0065%, [P]: 0.014%, and the composition reaches the conventional standard of bearing steel GCr15. After the composition test is qualified, the bottom blowing argon flow of the ladle is increased to blow open the slag surface, and 20kg of rare earth alloy containing La and Ce is manually added (based on the recovery rate of 50%), and then the bottom blowing flow is slightly reduced to ensure that the slag surface is closed. After slightly blowing and stirring for 2 minutes, the bottom blowing argon flow is adjusted to the bottom blowing flow required for normal weak stirring. Subsequently, the rare earth composition of the molten steel was determined to be [Ce]: 0.009%, [La]: 0.0045%. After soft blowing and stirring in the ladle, the molten steel was transferred to the continuous casting process and cast into round billets with a side length of 0.38m, and then cut into round ingots with a length of 2.9m. The superheat of the molten steel during the continuous casting process was controlled at 39°C, and a stopper rod was used to control the flow. Argon was blown into the stopper rod to prevent the water nozzle from clogging during the casting process. Since the continuous casting process can continuously cast many furnaces of steel, the ingots of one furnace of steel can be selected and cut into ingots for subsequent electroslag. One furnace of steel can produce multiple ingots.

[0072] 2) Clean the surface of the round ingot, grind off the oxidized iron scale on the surface of the ingot, and make electrode rods that can be used for slag smelting.

[0073] 3) The electrode rod is used as a raw material and loaded into an electroslag furnace for electroslag remelting. The electroslag furnace is used for electroslag remelting under an Ar gas protective atmosphere. Argon is blown into the crystallizer for more than 25 minutes before the electroslag is powered on to drive away the remaining air in the crystallizer. The crystallizer is selected to have a diameter of 0.48m. The electroslag remelting protective slag composition is CaF2: 40%, Al2O3: 10%, ZrO2: 15%, CaO: 10%, MgO: 5%, SiO2: 5%, Ce2O3 + La2O3: 15%, and the total amount of remelting protective slag added is 105kg. Then, the electroslag treatment is started by powering on to prepare an electroslag ingot with a diameter of 0.48m and a length of 1.9m. The electroslag process needs to be carried out under a protective atmosphere, and a constant melting rate electroslag remelting smelting is adopted. The melting rate of the electroslag remelting process is controlled at 5kg / min. After the electroslag is powered on, argon blowing protection is required to be maintained for 20 minutes to prevent secondary oxidation.

[0074] 4) The electroslag ingot is transported to a 1230℃ soaking furnace for 14 hours of high-temperature diffusion, followed by initial rolling into 140mm square billets, and then fine rolling into bearing steel with a diameter of less than 60mm according to user requirements. The final steel composition: [C]: 1.01%, [Cr]: 1.53%, [Mn]: 0.56%, [Si]: 0.25%, [Al]: 0.023%, [Ce]: 0.006%, [La]: 0.004%, [Ti]: 0.0009%, [N]: 0.0038%, [S]: 0.007%, [P]: 0.012%. The inclusions in the steel are automatically scanned and detected, and more than 99% are fine inclusions with a rare earth oxide content of more than 60%, and the size is less than 10μm, and 1% are rare earth oxide-aluminum oxide-calcium oxide-silicon oxide composite inclusions, with a size less than 15μm. At the same time, the contact fatigue life of bearing steel under 4.5GPa conditions was tested. A total of 12 samples were tested and the results showed that L 10 The value is 5.2×10 7 .

[0075] The prepared long-life bearing steel has stable performance and long fatigue life, and is used in high-end fields such as high-speed rail bearings, aviation bearings, and wind power bearings.

[0076] Example 5

[0077] This embodiment uses 150t electric furnace-LF-RH-round billet continuous casting-electroslag remelting-rolling, and its main process steps are as follows:

[0078] 1) 150t converter - LF refining - RH vacuum degassing, bearing steel is smelted and refined according to the bearing steel production method. After RH treatment, the composition of molten steel is [C]: 1.05%, [Cr]: 1.58%, [Mn]: 0.59%, [Si]: 0.28%, [Al]: 0.029%, [Ti]: 0.0014%, [N]: 0.0035%, [S]: 0.0065%, [P]: 0.014%, and the composition reaches the conventional standard of bearing steel GCr15. After the composition test is qualified, the bottom blowing argon flow of the ladle is increased to blow open the slag surface, and 20kg of rare earth alloy containing La and Ce is manually added (based on the recovery rate of 60%), and then the bottom blowing flow is slightly reduced to ensure that the slag surface is closed. After slightly blowing and stirring for 2 minutes, the bottom blowing argon flow is adjusted to the bottom blowing flow required for normal weak stirring. Subsequently, the rare earth composition of the molten steel was determined to be [Ce]: 0.009%, [La]: 0.0045%. After soft blowing and stirring in the ladle, the molten steel was transferred to the continuous casting process and cast into round billets with a side length of 0.38m, and then cut into round ingots with a length of 2.9m. The superheat of the molten steel during the continuous casting process was controlled at 39°C, and a stopper rod was used to control the flow. Argon was blown into the stopper rod to prevent the water nozzle from clogging during the casting process. Since the continuous casting process can continuously cast many furnaces of steel, the ingots of one furnace of steel can be selected and cut into ingots for subsequent electroslag. One furnace of steel can produce multiple ingots.

[0079] 2) Clean the surface of the round ingot, grind off the oxidized iron scale on the surface of the ingot, and make electrode rods that can be used for slag smelting.

[0080] 3) The electrode rod is used as a raw material and loaded into an electroslag furnace for electroslag remelting. The electroslag furnace is used for electroslag remelting under an Ar gas protective atmosphere. Argon is blown into the crystallizer for more than 25 minutes before the electroslag is powered on to drive away the remaining air in the crystallizer. The crystallizer is selected to have a diameter of 0.48m. The electroslag remelting protective slag composition is CaF2: 65%, Al2O3: 5%, ZrO2: 10%, CaO: 5%, MgO: 2%, SiO2: 3%, Ce2O3 + La2O3: 10%, and the total amount of remelting protective slag added is 105kg. Then, the electroslag treatment is started by powering on to prepare an electroslag ingot with a diameter of 0.48m and a length of 1.9m. The electroslag process needs to be carried out under a protective atmosphere, and a constant melting rate electroslag remelting smelting is adopted. The melting rate of the electroslag remelting process is controlled at 5kg / min. After the electroslag is powered on, argon blowing protection is required to be maintained for 20 minutes to prevent secondary oxidation.

[0081] 4) The electroslag ingot is transported to a 1230℃ soaking furnace for 14 hours of high-temperature diffusion, followed by initial rolling into 140mm square billets, and then fine rolling into bearing steel with a diameter of less than 60mm according to user requirements. The final steel composition: [C]: 1.01%, [Cr]: 1.53%, [Mn]: 0.56%, [Si]: 0.25%, [Al]: 0.023%, [Ce]: 0.006%, [La]: 0.004%, [Ti]: 0.0009%, [N]: 0.0038%, [S]: 0.007%, [P]: 0.012%. The inclusions in the steel are automatically scanned and detected, and more than 99% are fine inclusions with a rare earth oxide content of more than 60%, and the size is less than 10μm, and 1% are rare earth oxide-aluminum oxide-calcium oxide-silicon oxide composite inclusions, with a size less than 15μm. At the same time, the contact fatigue life of bearing steel under 4.5GPa conditions was tested. A total of 12 samples were tested and the results showed that L 10 The value is 5.2×10 7 .

[0082] The prepared long-life bearing steel has stable performance and long fatigue life, and is used in high-end fields such as high-speed rail bearings, aviation bearings, and wind power bearings.

[0083] This embodiment. Those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A method for preparing long-life bearing steel, characterized in that: The following steps are involved: S1, preparing ingots by electric furnace / converter smelting - LF refining - vacuum degassing - continuous casting / mold casting, adding rare earth alloys lanthanum and cerium into the molten steel before continuous casting / mold casting; S2, cleaning the surface of the ingot and making it into an electrode rod for electroslag remelting; S3, using the electrode rod as a raw material, and performing electroslag remelting in an electroslag furnace to obtain an electroslag ingot; the electroslag remelting protective slag used in the electroslag remelting process includes the following components in weight percentage: CaF2: 40-65%, Al2O3: 5-10%, ZrO2: 10-15%, CaO: 5-10%, MgO: 2-5%, SiO2: 3-5%, Ce2O3+La2O3: 10-15%; S4, the electroslag ingot is rolled into a long-life bearing steel after being diffused at high temperature in a soaking furnace.

2. The method for preparing long-life bearing steel according to claim 1, characterized in that: In step S1, the method of adding the rare earth alloys lanthanum and cerium adopts the injection method. Before injecting the rare earth alloy, argon gas is blown into the bottom of the ladle containing molten steel to blow open the slag surface to expose the molten steel, and then the rare earth alloy is injected into the molten steel; the composition of the rare earth alloy in the molten steel is controlled to be Ce: 0.006~0.011%, La: 0.003~0.006%.

3. The method for preparing long-life bearing steel according to claim 1, characterized in that: The rare earth alloy is added according to a recovery rate of 50-60%.

4. The method for preparing long-life bearing steel according to claim 1, characterized in that: In the step S1, when continuous casting is adopted, the superheat of the molten steel is controlled at 30-40°C, and a stopper rod is used to control the flow in the casting crystallizer, and argon is blown into the stopper rod.

5. The method for preparing long-life bearing steel according to claim 1, characterized in that: In step S1, the mass of the ingot is 1.5-3 tons. When the ingot is a square billet, the side length of the ingot is 0.33-0.38 m and the length is 2-4 m. When the ingot is a round ingot, the diameter is 0.35-0.4 m and the length is 2-3 m.

6. The method for preparing long-life bearing steel according to claim 1, characterized in that: In the step S3, the electroslag remelting process is carried out under a protective atmosphere, using a constant melting rate smelting, and the melting rate in the electroslag remelting process is 5 to 8 kg / min.

7. The method for preparing long-life bearing steel according to claim 1, characterized in that: In step S3, the amount of electroslag remelting protective slag added is 40-60 kg / t 钢 .

8. The method for preparing long-life bearing steel according to claim 1, characterized in that: The long-life bearing steel includes the following chemical components in weight percentage: C: 0.9-1.1%, Cr: 1.4-1.6%, Mn: 0.3-0.6%, Si: 0.2-0.3%, Al: 0.008-0.03%, Ce: 0.004-0.01%, La: 0.002-0.006%, Ti<0.0015%, N<0.005%, S<0.01%, P<0.015%, and the remainder is iron and other inevitable impurities.

9. The method for preparing long-life bearing steel according to claim 1, characterized in that: More than 95% of the inclusions in the long-life bearing steel are fine inclusions with a rare earth oxide content exceeding 60% and a size less than 10 μm, and the remaining less than 5% are composite inclusions of rare earth oxide-aluminum oxide-calcium oxide-silicon oxide, and the size of the composite inclusions is less than 15 μm.

10. The method for preparing long-life bearing steel according to claim 1, characterized in that: The contact fatigue life of the long-life bearing steel is L 10 Greater than 5×10 7 .

11. A long-life bearing steel prepared by the preparation method of long-life bearing steel as described in any one of claims 1 to 10, wherein the long-life bearing steel comprises the following chemical components in weight percentage: C: 0.9-1.1%, Cr: 1.4-1.6%, Mn: 0.3-0.6%, Si: 0.2-0.3%, Al: 0.008-0.03%, Ce: 0.004-0.01%, La: 0.002-0.006%, Ti<0.0015%, N<0.005%, S<0.01%, P<0.015%, and the remainder is iron and other inevitable impurities.

12. An electroslag remelting protective slag used in the method for preparing long-life bearing steel as described in any one of claims 1-10, wherein the electroslag remelting protective slag comprises the following components in weight percentage: CaF2: 40-65%, Al2O3: 5-10%, ZrO2: 10-15%, CaO: 5-10%, MgO: 2-5%, SiO2: 3-5%, Ce2O3+La2O3: 10-15%.