Industrial production method of high-carbon high-temperature chromium stainless bearing steel

Abstract

The application provides an industrial manufacturing method of high-carbon chromium high-temperature stainless bearing steel and relates to the technical field of manufacturing methods of metal materials, and comprises the following steps: placing steelmaking raw materials in a vacuum induction furnace to perform smelting, so as to obtain an electrode used as an electrode of a vacuum consumable furnace; performing vacuum consumable remelting crystallization on the electrode, and further performing soaking treatment; performing upsetting and elongating treatment on the steel ingot after the soaking treatment, then performing radial forging, and finally performing annealing treatment to obtain the high-carbon chromium high-temperature stainless bearing steel, wherein the high-carbon chromium high-temperature stainless bearing steel is free of defects on the surface and inside, and is uniform in chemical composition and structure. The vacuum consumable smelting process is stable, the surface and internal quality is good, the chemical composition and structure are uniform, the ultrasonic flaw detection reaches the level of GB / T4162A, the chemical composition meets the target requirement, the eutectic carbide meets the requirement of GB / 14979 fifth evaluation diagram 4 level, and the macrostructure is uniform and free of black spots, white spots, radial segregation and ring pattern.

Description

Technical Field

[0001] This invention relates to the field of manufacturing methods for metallic materials, and in particular to an industrial manufacturing method for high-carbon chromium high-temperature stainless bearing steel. Background Technology

[0002] Currently, conventional high-temperature bearing steels include 8Cr4Mo4V, G13Cr4Ni4Mo4V, and 9Cr18Mo. Among them, 8Cr4Mo4V and G13Cr4Ni4Mo4V have high strength and high hardness, but their oxidation resistance and corrosion resistance are inferior to 9Cr18Mo. 9Cr18Mo steel has oxidation resistance and corrosion resistance, but its strength and hardness are inferior to 8Cr4Mo4V and G13Cr4Ni4Mo4V. Therefore, there is a need for a high-temperature stainless bearing steel that has both high strength and high hardness as well as oxidation resistance and corrosion resistance. Cr15Mo5V steel is a new type of high-temperature stainless bearing steel developed based on the above conditions.

[0003] Currently, only small-batch trials of Cr15Mo5V steel have been conducted in laboratories in China. The industrial production technology using vacuum induction furnace smelting + vacuum arc remelting + forging is still immature domestically. The standard for Cr15Mo5V steel specifies C: 1.0-1.5%, Si: 0.2-0.5%, Mn: 0.1-0.4%, P: ≤0.015%, S: ≤0.010%, Cr: 14.5-16.0%, Mo: 3.5-4.5%, and V: 1.0-1.5%. Due to the high content of carbon, chromium, molybdenum, and vanadium in the steel, these elements easily combine with carbon to form various primary and secondary carbides. Simultaneously, different microstructures are formed within the steel. The presence of these carbides and microstructures can cause various problems during the smelting process, such as uneven chemical composition of the ingot, instability in the ingot smelting process, and cracking of forged bars. Therefore, a stable industrial manufacturing technology is needed to produce this steel. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned problems in the prior art and provide an industrial manufacturing method for high-carbon chromium high-temperature stainless bearing steel that has a stable steel ingot smelting process, good surface and internal quality, and uniform chemical composition.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides an industrial manufacturing method for high-carbon chromium high-temperature stainless bearing steel, comprising the following steps:

[0007] S1: The steelmaking raw materials are placed in a vacuum induction furnace for melting. The melting includes melting treatment, refining treatment, sample conditioning treatment and casting in sequence. The cast steel ingot is subjected to first mold cooling, demolding and first annealing to obtain an electrode for use as a vacuum arc furnace.

[0008] S2: The electrode is subjected to vacuum self-consumption remelting and crystallization, and the remelted and crystallized steel ingot is subjected to a second mold cooling, demolding and a second annealing, and further subjected to homogenization heat treatment;

[0009] S3: After heat treatment, the steel ingot is upsetting and drawing, then radial forging, and finally annealed to obtain high carbon chromium high temperature stainless bearing steel.

[0010] The high-carbon chromium high-temperature stainless bearing steel comprises, by mass percentage, C: 1.0-1.5%, Si: 0.2-0.5%, Mn: 0.1-0.4%, P: ≤0.015%, S: ≤0.010%, Cr: 14.5-16.0%, Mo: 3.5-4.5%, V: 1.0-1.5%, and N: 0.02-0.03%, with the balance being Fe and unavoidable impurities.

[0011] Furthermore, based on the above technical solution of the present invention, the first mold cooling time is more than 3 hours, so as to ensure that the temperature of the cast steel ingot is less than 800°C when it is demolded.

[0012] And / or, the second molding cooling time is more than 3 hours, in order to ensure that the temperature of the steel ingot after the second molding cooling is less than 800°C;

[0013] And / or, the first annealing and the second annealing are both held at temperatures between 850-890°C in the two-phase region for 10-20 hours, and then cooled to room temperature at a rate not exceeding 30-50°C / h.

[0014] Furthermore, based on the above-described technical solution of the present invention, in step S1:

[0015] The steelmaking raw materials include metallic chromium, ferrovanadium, ferromolybdenum, photoelectric carbon, metallic manganese, ferrosilicon, ferrochrome nitride, and raw steel.

[0016] And / or, ferrovanadium, ferromolybdenum, photoelectric carbon, ferrosilicon and raw steel are first added to a vacuum induction furnace for melting and refining treatment, while metallic chromium, ferrochrome nitride and metallic manganese are added during sample conditioning.

[0017] Furthermore, based on the above technical solution of the present invention, the conditions for the melting process include: a vacuum degree less than or equal to 5 Pa, an electric power of 800-1000 KW, and a time of 6-8 h; preferably, when the vacuum degree begins to decrease and is greater than 5 Pa, the electric power is 300-400 KW.

[0018] And / or, the temperature of the molten steel after melting treatment is controlled in the range of 1500-1600℃, preferably 1530-1560℃.

[0019] Furthermore, based on the above technical solution of the present invention, the refining conditions include: an electric power of 400-500KW, a vacuum degree of ≤2Pa, a temperature of 1500-1600℃, and a stirring time of 20-40min at industrial frequency.

[0020] Furthermore, based on the above-described technical solution of the present invention, the sample adjustment process includes:

[0021] First, the refined molten steel is subjected to compositional analysis. The composition of the molten steel is adjusted so that the contents of C, Si, Mo, and V in the molten steel meet the target contents. Then, metallic chromium is added to adjust the chromium composition so that the Cr content in the molten steel meets the target chromium content in the high-carbon chromium high-temperature stainless bearing steel. Argon gas is then introduced for stirring. Metallic manganese and ferrochrome nitride are added to the molten steel so that the manganese and nitrogen contents in the molten steel meet the target manganese and nitrogen contents in the high-carbon chromium high-temperature stainless bearing steel.

[0022] Furthermore, based on the above-described technical solution of the present invention, the casting process includes:

[0023] The molten steel after sample treatment is poured into the steel ingot mold, and 1-10% by weight of molten steel is reserved for compensating for shrinkage cavities in the cast electrode. Then, the first mold cooling, demolding and first annealing are carried out.

[0024] And / or, the casting conditions preferably include: a tapping temperature of 1500-1600℃ and a tapping speed of 400-800 kg / min;

[0025] Preferably, 1-8% by weight of molten steel is selected to compensate for shrinkage cavities in the cast electrode.

[0026] Furthermore, based on the above-described technical solution of the present invention, in step S2:

[0027] The vacuum self-consumable crystallization includes: using the electrode as the base material of the vacuum self-consumable furnace for secondary remelting and crystallization;

[0028] And / or, the conditions for the vacuum self-consumption crystallization are:

[0029] Current setting: 6500-7000A, voltage setting: 23.5-24.0V, melting rate setting: 3.0-4.0kg / min, droplet short-circuit time setting: 0.2-0.3s, droplet level setting: 8-9, helium pressure setting: 0Pa for steel ingots weighing less than 200kg, 200-300Pa for steel ingots weighing 200-700kg, and 400-500Pa for steel ingots weighing 700-1500kg.

[0030] Furthermore, based on the above-described technical solution of the present invention, in step S2:

[0031] The homogenization process involves loading the steel ingot obtained after the second annealing into a heating furnace, heating the furnace to 1130-1150°C at a heating rate of 1-10°C / min, and holding it at that temperature for 3-5 hours.

[0032] Furthermore, based on the above-described technical solution of this invention, in step S3:

[0033] The upsetting conditions include: initial forging temperature ≥1000℃, final forging temperature ≥900℃, upsetting time of 5-20min per upsetting, and ingot height reduction of 200-500mm.

[0034] And / or, the preferred upsetting conditions are: initial forging temperature of 1050-1100℃, final forging temperature of 900-950℃, upsetting time of 5-15 min per upsetting, and ingot height reduction of 300-400 mm.

[0035] And / or, the upsetting pressing is done once, the steel after upsetting is returned to the furnace and reheated at 1130-1150℃ for 2-3 hours, the steel ingot after reheating is drawn after exiting the furnace, and the single-sided pressing amount of each pass of the press should be controlled to be less than 40mm, preferably 20-30mm.

[0036] And / or, the conditions for radial forging include: initial forging temperature of 1000-1120℃, final forging temperature of 900-950℃, and time of 5-20min;

[0037] Preferably, the conditions for radial forging include: an initial forging temperature of 1000-1050℃, a final forging temperature of 900-940℃, and a time of 10-20 min.

[0038] The present invention provides an industrial manufacturing method for high-carbon chromium high-temperature stainless bearing steel, which has the following beneficial effects:

[0039] By controlling the steel ingot within a specific composition range, the electrode is mold-cooled and annealed in a specific manner to eliminate structural stress. The electrode is then used as the base material for a vacuum arc remelting furnace for remelting and crystallization. During the crystallization process, a specific method is used to eliminate the instability of the smelting process. Then, mold-cooling and annealing are performed in a specific manner to eliminate structural stress. Finally, through specific heating and forging techniques, a high-carbon chromium high-temperature stainless bearing steel with no defects on the surface and inside, and uniform chemical composition and structure is obtained. Not only is the vacuum arc remelting process stable, with good surface and internal quality, and uniform chemical composition and structure, but ultrasonic testing also reaches the GB / T4162 Class A level. The chemical composition meets the target requirements, and the eutectic carbides meet the requirements of GB / 14979 Fifth Rating Figure 4. The low-magnification structure is uniform and free of black spots, white spots, radial segregation, and annular patterns. Attached Figure Description

[0040] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0041] Figure 1 This is a low-magnification microstructure image of the 100mm diameter steel bar prepared in Example 1 of the present invention;

[0042] Figure 2 The image shows the microstructure of a 100 mm diameter steel bar prepared in Comparative Example 1.

[0043] Figure 3 This is a low-magnification microstructure of the 100 mm diameter steel bar prepared in Comparative Example 3. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be considered as specific limitations thereof. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Process parameters not specifically specified in the following embodiments are generally performed under conventional conditions.

[0045] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0046] According to a first aspect of the present invention, an industrial manufacturing method for high-carbon chromium high-temperature stainless bearing steel is provided, comprising the following steps:

[0047] S1: The steelmaking raw materials are placed in a vacuum induction furnace for melting. The melting includes melting treatment, refining treatment, sample conditioning treatment and casting in sequence. The cast steel ingot is subjected to first mold cooling, demolding and first annealing to obtain an electrode for use as a vacuum arc furnace.

[0048] S2: The electrode is subjected to vacuum self-consumption remelting and crystallization, and the remelted and crystallized steel ingot is subjected to a second mold cooling, demolding and a second annealing, and further subjected to homogenization heat treatment;

[0049] S3: After heat treatment, the steel ingot is upsetting and drawing, then radial forging, and finally annealed to obtain high carbon chromium high temperature stainless bearing steel.

[0050] The composition of the high-carbon chromium high-temperature stainless bearing steel, by mass percentage, includes: C: 1.0-1.5%, Si: 0.2-0.5%, Mn: 0.1-0.4%, P: ≤0.015%, S: ≤0.010%, Cr: 14.5-16.0%, Mo: 3.5-4.5%, V: 1.0-1.5%, and N: 0.02-0.03%, with the balance being Fe and unavoidable impurities.

[0051] To address the issue of uneven eutectic carbides in Cr15Mo5V steel, the inventors added 0.02-0.03% nitrogen (N) to the high-carbon chromium high-temperature stainless bearing steel. This is because nitrogen is a solid solution strengthening element; adding nitrogen to steel can improve its high-temperature hardness, ensuring it maintains a high hardness value even at 400-600℃. Furthermore, nitrogen is also an austenite-forming element; its addition can expand the austenite phase region, allowing more carbides to integrate into the matrix, thus resulting in more uniform carbide precipitation.

[0052] As an optional embodiment of the present invention, the first mold cooling time is more than 3 hours, so as to ensure that the temperature of the cast steel ingot is less than 800°C when it is demolded.

[0053] And / or, the second molding cooling time is more than 3 hours, in order to ensure that the temperature of the steel ingot after the second molding cooling is less than 800°C;

[0054] And / or, the first annealing and the second annealing are both held at temperatures between 850-890°C in the two-phase region for 10-20 hours, and then cooled to room temperature at a rate not exceeding 30-50°C / h.

[0055] The AC3 point of high-carbon chromium high-temperature stainless bearing steel is around 890℃. Cooling the steel ingot to below 800℃ can ensure that the microstructure of the steel ingot is all below the AC3 point. This makes the microstructure of the steel ingot more uniform, which is beneficial for subsequent transfer and annealing treatment. If the temperature is too high, the microstructure of the steel will still be above the AC3 point in some areas. This will result in an uneven microstructure of the steel ingot, which will make it prone to cracking during subsequent transfer or annealing.

[0056] Furthermore, the annealing temperature should be lower than AC3, within the range of 850-890℃, to make the steel structure more uniform.

[0057] The cooling rate needs to be strictly controlled between 30-50℃ / h. A cooling rate greater than 50℃ / h will cause the steel's microstructure to transform too drastically, eventually leading to cracking due to excessive microstructure stress. A cooling rate less than 30℃ / h will affect production efficiency.

[0058] As an optional embodiment of the present invention, in step S1:

[0059] The steelmaking raw materials include metallic chromium, ferrovanadium, ferromolybdenum, photoelectric carbon, metallic manganese, ferrosilicon, ferrochrome nitride, and raw steel.

[0060] And / or, ferrovanadium, ferromolybdenum, photoelectric carbon, ferrosilicon and raw steel are first added to a vacuum induction furnace for melting and refining treatment, while metallic chromium, ferrochrome nitride and metallic manganese are added during sample conditioning.

[0061] Specifically, metallic chromium, ferrovanadium, ferromolybdenum, photoelectric carbon, metallic manganese, ferrosilicon, ferrochrome nitride, and raw steel can be various metals conventionally used in the field for refining stainless steel series; furthermore, the raw steel is molten iron, pure iron, etc., and it is particularly preferred to use steel that has been purified by EAF+LF+VOD smelting to remove impurity elements such as S, P, H, and O as raw steel to ensure that the impurity content in the steel product is low.

[0062] Furthermore, although the steelmaking raw materials can be formulated according to the above composition, in order to obtain high-quality steel ingots, it is preferable to reserve some of the metallic chromium and metallic manganese in the steelmaking raw materials for use as additives in the sample preparation process. Firstly, because the purity of metallic chromium and metallic manganese is above 99% and the content of impurities and gases is lower, their later addition is beneficial to the quality of the steel. In addition, metallic chromium is easily burned off and metallic manganese is easily volatilized, making them suitable for subsequent addition.

[0063] As an optional embodiment of the present invention, the melting treatment conditions include: vacuum degree less than or equal to 5 Pa, electric power of 800-1000 KW, and time of 6-8 h; preferably, when the vacuum degree begins to decrease and the vacuum degree is greater than 5 Pa, the electric power is 300-400 KW.

[0064] And / or, the temperature of the molten steel after melting treatment is controlled in the range of 1500-1600℃, preferably 1530-1560℃.

[0065] According to the present invention, the melting process in a vacuum induction furnace refers to the process of adding the steelmaking raw materials into the vacuum induction furnace and then melting and mixing the steelmaking raw materials by adjusting a certain vacuum degree and electrical power.

[0066] In the initial stage of melting, since the vacuum degree cannot immediately meet the requirement of ≤5Pa, preferably, when the vacuum degree is greater than 5Pa, the electric power is 300-400KW.

[0067] After melting treatment, the smelting raw materials reach a fully molten state, and the temperature of the fully molten steel is controlled in the range of 1500-1600℃, preferably 1530-1560℃.

[0068] As an optional embodiment of the present invention, the refining conditions include: an electric power of 400-500KW, a vacuum degree of ≤2Pa, a temperature of 1500-1600℃, and a stirring time of 20-40min at industrial frequency.

[0069] Specifically, after the melting process is completed, the fully molten steel undergoes refining. Since vacuum induction furnace smelting produces no slag compared to electric arc furnaces or non-vacuum induction furnaces, deoxidation, degassing, and inclusion removal must all be completed during the refining process. Furthermore, under these conditions, the steel after this refining process has a more uniform composition and also achieves deoxidation and degassing.

[0070] As an optional embodiment of the present invention, the sample adjustment process includes:

[0071] First, the refined molten steel is subjected to compositional analysis. The composition of the molten steel is adjusted so that the contents of C, Si, Mo, and V in the molten steel meet the target contents. Then, metallic chromium is added to adjust the chromium composition so that the Cr content in the molten steel meets the target chromium content in the high-carbon chromium high-temperature stainless bearing steel. Argon gas is then introduced for stirring. Metallic manganese and ferrochrome nitride are added to the molten steel so that the manganese and nitrogen contents in the molten steel meet the target manganese and nitrogen contents in the high-carbon chromium high-temperature stainless bearing steel.

[0072] Specifically, in the sample conditioning process, the elements such as C, Si, Mo, and V are first brought to the target composition, then chromium is brought to the target composition, and finally manganese and nitrogen are brought to the target composition.

[0073] After argon gas is introduced, the remaining metallic manganese and ferrochrome nitride are added according to the composition of the molten steel because the steel is smelted under high vacuum conditions, during which metallic manganese volatilizes and metallic chromium is burned off. Therefore, it is necessary to add the remaining metallic manganese and metallic chromium to the molten steel to ensure that the components in the molten steel reach the target content.

[0074] As an optional embodiment of the present invention, the casting process includes:

[0075] The molten steel after the sample treatment is poured into the steel ingot mold, and 1-10% by weight of the molten steel is reserved for compensating for shrinkage cavities in the cast steel ingot. Then, the first mold cooling, demolding and first annealing are carried out.

[0076] And / or, the casting conditions preferably include: a tapping temperature of 1500-1600℃ and a tapping speed of 400-800 kg / min;

[0077] Preferably, 1-8% by weight of molten steel is selected to compensate for shrinkage cavities in the cast steel ingot.

[0078] Specifically, cooling before the first mold cooling is required, including:

[0079] After the steel ingot is shrunken, it is first cooled to 1000-1300℃ at a cooling rate of 10-50℃ / min and then hollowed out. After hollowing out, it is immediately subjected to the first mold cooling for 2-4 hours to 700-900℃ before demolding.

[0080] Preferably, the mold is first cooled to 800°C and then demolded. After demolding, a first annealing is performed at a temperature of 850-890°C. The annealing is held at this temperature for more than 15 hours and then slowly cooled to room temperature at a rate of no more than 50°C / hour.

[0081] As an optional embodiment of the present invention, in step S2:

[0082] The vacuum self-consumable crystallization includes: using the electrode as the base material of the vacuum self-consumable furnace for secondary remelting and crystallization;

[0083] And / or, the conditions for the vacuum self-consumption crystallization are:

[0084] Current setting: 6500-7000A, voltage setting: 23.5-24.0V, melting rate setting: 3.0-4.0kg / min, droplet short-circuit time setting: 0.2-0.3s, droplet level setting: 8-9, helium pressure setting: 0Pa for steel ingots weighing less than 200kg, 200-300Pa for steel ingots weighing 200-700kg, and 400-500Pa for steel ingots weighing 700-1500kg.

[0085] Because the heat of the steel ingot is constantly increasing during the smelting process, and the main purpose of adding helium is to cool it, the helium pressure also increases as the weight of the steel ingot increases.

[0086] Specifically, the electrodes obtained after the first molding and the first annealing are used as the base material for a vacuum arc remelting furnace. When energized, the electrodes melt, and the molten steel is dripped into a crystallizer to crystallize, resulting in steel ingots of the following size: If the remelting conditions for vacuum arc remelting are not properly selected, defects such as unevenly sized eutectic carbides may occur, leading to instability in the vacuum arc remelting process and substandard chemical composition. Specifically, excessive current will increase the melting rate, which in turn will shorten the droplet time, resulting in smaller droplet sizes and consequently lower voltage. Conversely, insufficient current will have the opposite effect, ultimately causing an unstable number of droplets and an unstable molten pool. Therefore, it is necessary to strictly control the conditions for vacuum arc remelting.

[0087] Specifically, cooling before the second mold cooling is required to break the air gap, including:

[0088] The steel ingot obtained by vacuum self-consumable remelting crystallization is first cooled to 1000-1300℃ at a cooling rate of 10-50℃ / min and then broken open. After breaking open, it is immediately subjected to a second mold cooling for 2-4 hours to 700-900℃ before demolding.

[0089] Preferably, the mold is first cooled to 800°C for the second time before demolding. After demolding, a second annealing is performed at a temperature of 850-890°C. The annealing is held at this temperature for more than 15 hours and then slowly cooled to room temperature at a rate not exceeding 50°C / h.

[0090] As an optional embodiment of the present invention, in step S2:

[0091] The homogenization process involves loading the steel ingot obtained after the second annealing into a heating furnace, heating the furnace to 1130-1150°C at a heating rate of 1-10°C / min, and holding it at that temperature for 3-5 hours.

[0092] As an optional embodiment of the present invention, in step S3:

[0093] The upsetting conditions include: initial forging temperature ≥1000℃, final forging temperature ≥900℃, upsetting time of 5-20min per upsetting, and ingot height reduction of 200-500mm.

[0094] Preferably, the upsetting conditions are: initial forging temperature of 1050-1100℃, final forging temperature of 900-950℃, upsetting time of 5-15 minutes per upsetting, and ingot height reduction of 300-400 mm.

[0095] And / or, the upsetting pressing is done once, the steel after upsetting is returned to the furnace and reheated at 1130-1150℃ for 2-3 hours, the steel ingot after reheating is drawn after exiting the furnace, and the single-sided pressing amount of each pass of the press should be controlled to be less than 40mm, preferably 20-30mm.

[0096] And / or, the conditions for radial forging include: initial forging temperature of 1000-1120℃, final forging temperature of 900-950℃, and time of 5-20min;

[0097] Preferably, the conditions for radial forging include: an initial forging temperature of 1000-1050℃, a final forging temperature of 900-940℃, and a time of 10-20 min.

[0098] Specifically, the above-mentioned upsetting refers to a single-pass upsetting, and the drawing refers to a multi-pass drawing. After each pass, the bar is reheated in the furnace to reach the required forging temperature. Preferably, the reheating conditions after each pressing pass include: a temperature of 1130-1150℃, a time of 2-4 hours, and a reduction in bar diameter of less than 100mm per drawing pass. Furthermore, the reheating conditions after the final pressing pass can adopt the above-mentioned reheating conditions.

[0099] When the steel ingot size reaches Then, radial forging is performed. The initial forging temperature of the radial forging (1600t) is the same as the temperature of the steel after reheating in the furnace. The radial forging is carried out on a 1600t radial forging machine and is formed by one heat treatment. The steel after radial forging is then annealed.

[0100] The present invention will now be described in further detail with reference to specific embodiments and comparative examples.

[0101] Example 1

[0102] Metallic chromium, metallic molybdenum, ferrovanadium, ferrosilicon, metallic manganese, ferrochrome nitride, and raw steel (purified through EAF+LF+VOD smelting) were batched according to the following composition of the resulting steel ingot: C: 1.4%, Si: 0.4%, Mn: 0.3%, P: ≤0.015%, S: ≤0.010%, Cr: 15.5%, Mo: 4.2%, V: 1.4%, N: 0.03%. Except for ferrochrome nitride, metallic chromium, and metallic manganese, all other raw materials were added to a vacuum induction furnace and melted for 7 hours under a vacuum of 5 Pa and an electric power of 800 kW. During the first 10 minutes, due to the vacuum being higher than 5 Pa, the electric power was maintained at 300 kW, and the temperature of the fully melted steel was 1550℃. Then, under industrial frequency stirring, the vacuum was controlled at 2 Pa and the electric power... The steel was refined for 30 minutes at a rate of 400KW. Then, samples were taken for analysis and adjusted with reserved metallic chromium until the composition of the molten steel met the requirements. Next, under argon gas stirring, metallic manganese and ferrochromium nitride were added to make the manganese and nitrogen content in the molten steel meet the target content. Then, the molten steel was poured into a 410mm diameter steel ingot mold at a tapping temperature of 1560℃ and a tapping speed of 400kg / min. The remaining 3% by weight of molten steel was used to feed the ingot in the ingot mold. The fed ingot was cooled to 1200℃ at a rate of 25℃ / min and then punctured. After cooling for another 3 hours until the ingot temperature was less than 800℃, it was demolded and then annealed in a furnace at a temperature of 870℃. After holding at that temperature for 20 hours, it was slowly cooled to room temperature at a rate of no more than 50℃ / h to obtain the electrode used as a vacuum arc furnace.

[0103] The poorly sized portion of the obtained electrode was removed and its surface was machined. It was then used as the base material for a vacuum arc remelting furnace. The remelting conditions were: current setting: 6700A, voltage setting: 23.7V, melting rate setting: 3.5kg / min, droplet short-circuit time setting: 0.25s, droplet level setting: 8, and helium pressure setting: 0Pa for ingots weighing less than 200kg, 250Pa for ingots weighing 200-700kg, and 450Pa for ingots weighing 700-1500kg, until the ingot size reached [specific value missing]. When filling stops, the steel ingot is cooled for 3 hours until the temperature of the steel ingot is less than 800℃, then demolded and put into the furnace for annealing. The annealing temperature is 850℃, and the ingot is held for more than 15 hours. Then it is slowly cooled to room temperature at a rate of no more than 50℃ / h.

[0104] The air-cooled and machined steel ingot was homogenized under the following conditions: It was first heated to 1150℃ at a heating rate of 1.3℃ / min and held at that temperature for 4 hours. Then, it was fed into a 4500t press for upsetting, reducing the ingot height by 400mm. The initial upsetting temperature was 1080℃, and the upsetting time was 10 minutes. After reheating in the furnace at 1140℃ for 2.5 hours, it was fed back into the 4500t press for a single drawing process of 10 minutes, with a single-sided reduction of 20mm. The initial drawing temperature was 1070℃, and the final forging temperature was 930℃, resulting in a diameter of 380mm. It was then reheated in the furnace at 1140℃ for 2.5 hours, and then fed back into the 4500t press for a single drawing process of 10 minutes, with a single-sided reduction of 30mm. The initial drawing temperature was 1070℃, and the final forging temperature was 930℃, resulting in a diameter of 380mm. The diameter is 320mm after being drawn from 930℃ to 1130℃ for 2.5 hours in the furnace. Then, it is drawn for 10 minutes in a 4500t press with a single-sided reduction of 35mm. The initial drawing temperature is 1060℃, and the final forging temperature is 920℃, resulting in a diameter of 270mm. After being drawn from 1130℃ to 1130℃ for 2.0 hours in the furnace, it is drawn for 10 minutes in a 4500t press with a single-sided reduction of 40mm. The initial drawing temperature is 1060℃, and the final forging temperature is 910℃, resulting in a diameter of 190mm. After being drawn from 1130℃ to 1130℃ for 2.0 hours in the furnace, it is drawn for 15 minutes in a 1600t press (radial forging mill) with an initial drawing temperature of 1060℃ and a final forging temperature of 910℃, resulting in a diameter of 100mm. Then, it is placed in a furnace at 400-600℃ and held for 3-5 hours. After that, the temperature is raised to 850℃ and held for more than 15 hours. Then, it is slowly cooled to room temperature at a rate of no more than 50℃ / h to obtain a high-temperature stainless bearing steel Cr15Mo5V steel bar with a diameter of 100mm.

[0105] like Figure 1 As shown, the prepared 100mm diameter steel bar has good surface and internal quality, uniform chemical composition and structure, and ultrasonic flaw detection reaches the GB / T4162A level. The chemical composition meets the target requirements, and the eutectic carbides meet the requirements of GB / 14979 fifth rating figure 4. The low magnification structure is uniform without obvious stripes, black spots, white spots, radial segregation and annular patterns.

[0106] Example 2

[0107] Metallic chromium, metallic molybdenum, ferrovanadium, ferrosilicon, metallic manganese, ferrochrome nitride, and raw steel (purified through EAF+LF+VOD smelting) were batched according to the following composition of the resulting steel ingot: C: 1.3%, Si: 0.4%, Mn: 0.3%, P: ≤0.015%, S: ≤0.010%, Cr: 15.5%, Mo: 4.2%, V: 1.4%, N: 0.03%. Except for ferrochrome nitride, metallic chromium, and metallic manganese, all other raw materials were added to a vacuum induction furnace. Melting was carried out for 7 hours under a vacuum of 5 Pa and an electric power of 800 KW. During the first 10 minutes, due to the vacuum being higher than 5 Pa, the electric power was maintained at 300 KW, and the temperature of the fully melted steel was 1550℃. Then, under industrial frequency stirring, the vacuum was controlled at 2 Pa... The steel was refined for 30 minutes with an electric power of 400KW. Then, samples were taken for analysis and adjusted with reserved metallic chromium until the composition of the molten steel met the requirements. Next, under argon gas stirring, metallic manganese and ferrochromium nitride were added to make the manganese and nitrogen content in the molten steel meet the target content. Then, the molten steel was poured into a 410mm diameter ingot mold at a tapping temperature of 1560℃ and a tapping speed of 400kg / min. The remaining 3% by weight of molten steel was used to feed the ingot in the ingot mold. The fed ingot was cooled to 1200℃ at a rate of 25℃ / min and then punctured. After cooling for another 3 hours until the ingot temperature was less than 800℃, it was demolded and then annealed in a furnace at a temperature of 880℃. After holding at that temperature for 15 hours, it was slowly cooled to room temperature at a rate of no more than 50℃ / h to obtain the electrode used as a vacuum arc furnace.

[0108] The poorly sized portion of the obtained electrode was removed and its surface was machined. It was then used as the base material for a vacuum arc remelting furnace. The remelting conditions were: current setting: 6500A, voltage setting: 23.9V, melting rate setting: 3.7kg / min, droplet short-circuit time setting: 0.27s, droplet level setting: 8, and helium pressure setting: 0Pa for ingots weighing less than 200kg, 200Pa for ingots weighing 200-700kg, and 400Pa for ingots weighing 700-1500kg, until the ingot size reached [specific value missing]. When filling stops, the steel ingot is cooled for 3 hours until the temperature of the steel ingot is less than 850°C, then demolded and put into the furnace for annealing. The annealing temperature is 870°C, and the ingot is held for more than 15 hours. Then it is slowly cooled to room temperature at a rate of no more than 50°C / h.

[0109] The air-cooled and machined steel ingot was homogenized under the following conditions: It was first heated to 1150℃ at a heating rate of 1.3℃ / min and held at that temperature for 4 hours. Then, it was fed into a 4500t press for upsetting, reducing the ingot height by 400mm. The initial upsetting temperature was 1080℃, and the upsetting time was 10 minutes. After reheating in the furnace at 1150℃ for 2.5 hours, it was fed back into the 4500t press for a single drawing process of 10 minutes, with a single-sided reduction of 30mm. The initial drawing temperature was 1070℃, and the final forging temperature was 930℃, resulting in a diameter of 380mm. It was then reheated in the furnace at 1150℃ for 2.5 hours, and then fed back into the 4500t press for a single drawing process of 10 minutes, with a single-sided reduction of 30mm. The initial drawing temperature was 1070℃, and the final forging temperature was 930℃, resulting in a diameter of 380mm. The diameter is 320mm after being drawn from 930℃ to 1150℃ for 2.5 hours in the furnace. Then, it is drawn once for 10 minutes in a 4500t press with a single-sided reduction of 30mm. The initial drawing temperature is 1060℃, and the final forging temperature is 920℃, resulting in a diameter of 270mm. After being drawn from 1150℃ to 1150℃ for 2.0 hours in the furnace, it is drawn once for 10 minutes in a 4500t press with a single-sided reduction of 30mm. The initial drawing temperature is 1060℃, and the final forging temperature is 910℃, resulting in a diameter of 190mm. After being drawn from 1140℃ to 1140℃ for 2.0 hours in the furnace, it is drawn once for 15 minutes in a 1600t press (radial forging mill) with an initial drawing temperature of 1060℃ and a final forging temperature of 910℃, resulting in a diameter of 100mm. Then, it is placed in a furnace at 400-600℃ and held for 3-5 hours. After that, the temperature is raised to 880℃ and held for more than 15 hours. Then, it is slowly cooled to room temperature at a rate of no more than 50℃ / h to obtain a high-temperature stainless bearing steel Cr15Mo5V steel bar with a diameter of 100mm.

[0110] The prepared 100mm diameter steel bar was inspected and found to have good surface and internal quality, uniform chemical composition and structure. The ultrasonic flaw detection reached the GB / T4162A level, the chemical composition met the target requirements, the eutectic carbides met the requirements of GB / 14979 fifth rating figure 4, and the low magnification structure was uniform without black spots, white spots, radial segregation and annular patterns.

[0111] Comparative Example 1

[0112] The difference between this comparative example and Example 1 is that no nitrogen element is added during the smelting of the steel ingot. The steel ingot is prepared according to the following composition: C: 1.4%, Si: 0.4%, Mn: 0.3%, P: ≤0.015%, S: ≤0.010%, Cr: 15.5%, Mo: 4.2%, V: 1.4%. The remaining operating steps are the same as in Example 1.

[0113] like Figure 2As shown, in this comparative example, no nitrogen element was added during the smelting of the steel ingot. The 100mm diameter steel bar prepared was inspected and found to have good surface and internal quality, but the chemical composition and microstructure were not uniform. The ultrasonic flaw detection reached the GB / T4162 Grade A level. Except for the nitrogen element, the other chemical compositions met the target requirements. See Table 1 for details. The low magnification microstructure was uniform without black spots, white spots, radial segregation and annular patterns. However, the eutectic carbides were rated at Grade 5.5 according to the fifth rating chart of GB / 14979, with relatively obvious carbide bands, which did not meet the Grade 4 requirement.

[0114] Comparative Example 2

[0115] The difference between this comparative example and Example 1 is that the steel ingot cast in step S1 is cooled for 1 hour, and when the ingot temperature is above 900°C, it is demolded and then annealed in a furnace at a temperature of 900-950°C. After holding at that temperature for more than 15 hours, it is slowly cooled to room temperature at a rate not exceeding 50°C / hour. The remaining operating steps are the same as in Example 1.

[0116] The die-cast electrodes cracked and became unusable after being slowly cooled to room temperature, making subsequent vacuum consumable production impossible. ， Therefore, only samples of the scrapped electrodes are taken for eutectic carbide testing; other testing items cannot be performed.

[0117] Comparative Example 3

[0118] The difference between this comparative example and Example 1 lies in the vacuum consumable metallurgy process. Specifically, the droplet short-circuit time setting is 0.15s, the droplet level setting is 4, and the helium pressure setting is 0Pa for ingots weighing less than 200kg and 450Pa for ingots weighing 200-1500kg, until the ingot size is [value missing]. When filling stops, the remaining operation steps are the same as in Implementation 1.

[0119] like Figure 3 As shown, the vacuum self-consuming process parameters were not designed properly, resulting in the 100mm diameter steel bar having internal cracks, unqualified manganese content, and a eutectic carbide grade of 5.5 according to GB / 14979 fifth rating chart, which does not meet the requirements of grade 4. The low magnification structure has radial segregation defects, and the carbide bands are relatively obvious and also contain black void defects.

[0120] Comparative Example 4

[0121] The difference between the comparative example and Example 1 lies in the forging process, specifically:

[0122] The air-cooled and machined steel ingot was homogenized under the following conditions: It was first heated to 1150℃ at a heating rate of 1.3℃ / min and held at that temperature for 4 hours. Then, it was fed into a 4500t press for upsetting, reducing the ingot height by 400mm. After reheating in the furnace at 1120℃ for 2.5 hours, it was again fed into the 4500t press for a single drawing process of 10 minutes, with a single-sided reduction of 20mm. The final forging temperature was 930℃, resulting in a diameter of 380mm. It was then reheated in the furnace at 1120℃ for 2.5 hours, and again fed into the 4500t press for a single drawing process of 10 minutes, with a single-sided reduction of 30mm. The final forging temperature was 930℃, resulting in a diameter of 320mm. Finally, it was reheated in the furnace at 1100℃ for 2.5 hours, and again fed into the 4500t press for a single drawing process of 10 minutes. The forging process involves a single-sided reduction of 35mm, a final forging temperature of 920℃, and a diameter of 270mm. The steel is then reheated at 1100℃ for 2.0h in a furnace. Next, it is fed into a 4500t press for a single-sided drawing process of 10min, with a single-sided reduction of 40mm, a final forging temperature of 910℃, and a diameter of 190mm. This process is repeated twice, with the steel reheated at 1100℃ for 2.0h in a furnace. Finally, it is fed into a 1600t press (radial forging mill) for a single drawing process of 15min, a final forging temperature of 910℃, and a diameter of 100mm. The steel is then placed in a 400-600℃ preheating furnace and held for 3-5 hours. Afterward, the temperature is raised to 850-890℃ and held for more than 15 hours. Finally, it is slowly cooled to room temperature at a rate not exceeding 50℃ / h to obtain a high-temperature stainless bearing steel Cr15Mo5V bar with a diameter of 100mm.

[0123] The prepared 100mm diameter steel bars were found to have surface and internal cracks upon inspection, and the steel was scrapped. Table 1 shows the main components (wt%) of the steel ingots obtained by the vacuum arc remelting step in Examples 1-2 and Comparative Examples 1, 3, and 4, and the steel ingot obtained by the ingot casting step in Comparative Example 2.

[0124]

[0125] Table 2 shows the test results of the steel bars obtained in Examples 1-2 and Comparative Examples 1, 3, and 4, and the steel ingot obtained in Comparative Example 2.

[0126]

[0127] Based on the data in the table above, a comparison between Example 1 and Comparative Example 1 shows that the absence of nitrogen in the steel is not conducive to the control of carbide uniformity, resulting in unqualified carbides.

[0128] Based on the data in the table above, a comparison between Example 1 and Comparative Example 2 shows that if the steel ingot is cooled to below 900°C or the annealing temperature is above 900°C, the steel at room temperature will have a large amount of quenched martensite structure and uneven structure, which will eventually lead to cracking of the steel ingot.

[0129] Based on the data in the table above, a comparison between Example 1 and Comparative Example 3 shows that an unreasonable vacuum self-consumption process for steel ingots can lead to uneven microstructure and chemical composition of the steel, resulting in all inspection indicators of the steel failing to meet standards.

[0130] Based on the data in the table above, a comparison between Example 1 and Comparative Example 4 shows that the lower the temperature, the lower the adhesion between the carbides in the steel and the matrix. A lower forging temperature of the steel ingot will lead to a decrease in the processing plasticity of the steel ingot, which will eventually lead to cracking and scrapping of the steel.

[0131] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An industrial manufacturing method for high-carbon chromium high-temperature stainless bearing steel, characterized in that, The steps include the following: S1: The steelmaking raw materials are placed in a vacuum induction furnace for melting. The melting includes melting treatment, refining treatment, sample conditioning treatment and casting in sequence. The cast steel ingot is subjected to first mold cooling, demolding and first annealing to obtain an electrode for use as a vacuum arc furnace. The first cooling time is more than 3 hours to ensure that the temperature of the cast steel ingot is less than 800°C when it is demolded. S2: The electrode is subjected to vacuum self-consumption remelting and crystallization, and the remelted and crystallized steel ingot is subjected to a second mold cooling, demolding and a second annealing, and further subjected to homogenization heat treatment; The vacuum self-consuming remelting and crystallization includes: using the electrode as the base material of the vacuum self-consuming furnace for secondary remelting and crystallization; The conditions for the vacuum self-consumable remelting crystallization are as follows: Current setting: 6500-7000A, voltage setting: 23.5-24.0V, melting rate setting: 3.0-4.0 kg / min, droplet short-circuit time setting: 0.2-0.3s, droplet level setting: 8-9, helium pressure setting: 0Pa for steel ingots weighing less than 200kg, 200-300Pa for steel ingots weighing 200-700kg, and 400-500Pa for steel ingots weighing 700-1500kg. The homogenization process involves loading the steel ingot obtained after the second annealing into a heating furnace, heating the furnace to 1130-1150°C at a heating rate of 1-10°C / min, and holding it at that temperature for 3-5 hours. The second mold cooling time is more than 3 hours to ensure that the temperature of the steel ingot after the second mold cooling is less than 800℃. The first annealing and the second annealing are both held at 850-890℃ in the two-phase region for 10-20 hours, and then cooled to room temperature at a rate of no more than 30-50℃ / h. S3: After heat treatment, the steel ingot is upsetting and drawing, then radial forging, and finally annealed to obtain high carbon chromium high temperature stainless bearing steel. The upsetting conditions include: initial forging temperature ≥1000℃, final forging temperature ≥900℃, upsetting time of 5-20min per upsetting, and ingot height reduction of 200-500mm. The upsetting process is carried out once. The steel after upsetting is returned to the furnace and reheated at 1130-1150℃ for 2-3 hours. After reheating, the steel ingot is drawn out of the furnace and the single-sided pressing amount of each pass is controlled to be less than 40mm. The conditions for radial forging include: initial forging temperature of 1000-1120℃, final forging temperature of 900-950℃, and time of 5-20 min; The composition of the high-carbon chromium high-temperature stainless bearing steel, by mass percentage, includes: C: 1.0-1.5%, Si: 0.2-0.5%, Mn: 0.1-0.4%, P: ≤0.015%, S: ≤0.010%, Cr: 14.5-16.0%, Mo: 3.5-4.5%, V: 1.0-1.5%, and N: 0.02-0.03%, with the balance being Fe and unavoidable impurities.

2. The industrial manufacturing method of high-carbon chromium high-temperature stainless bearing steel according to claim 1, characterized in that, In step S1: The steelmaking raw materials include metallic chromium, ferrovanadium, ferromolybdenum, photoelectric carbon, metallic manganese, ferrosilicon, ferrochrome nitride, and raw steel. And / or, ferrovanadium, ferromolybdenum, photoelectric carbon, ferrosilicon and raw steel are first added to a vacuum induction furnace for melting and refining treatment, while metallic chromium, ferrochrome nitride and metallic manganese are added during sample conditioning.

3. The industrial manufacturing method of high-carbon chromium high-temperature stainless bearing steel according to claim 1, characterized in that, The conditions for the melting process include: a vacuum degree less than or equal to 5 Pa, an electric power of 800-1000 kW, and a time of 6-8 h; And / or, the temperature of the molten steel after melting treatment is controlled within the range of 1500-1600℃.

4. The industrial manufacturing method of high-carbon chromium high-temperature stainless bearing steel according to claim 3, characterized in that, The conditions for the melting process include: when the vacuum level begins to decrease and is greater than 5 Pa, the electrical power is 300-400 kW.

5. The industrial manufacturing method of high-carbon chromium high-temperature stainless bearing steel according to claim 3, characterized in that, The temperature of the molten steel after melting is controlled within the range of 1530-1560℃.

6. The industrial manufacturing method of high-carbon chromium high-temperature stainless bearing steel according to claim 1, characterized in that, The refining conditions include: an electric power of 400-500kW, a vacuum degree of ≤2Pa, a temperature of 1500-1600℃, and a stirring time of 20-40min at industrial frequency.

7. The industrial manufacturing method of high-carbon chromium high-temperature stainless bearing steel according to claim 1, characterized in that, The sample processing includes: First, the refined molten steel is subjected to compositional analysis. The composition of the molten steel is adjusted so that the contents of C, Si, Mo, and V in the molten steel meet the target contents. Then, metallic chromium is added to adjust the chromium composition so that the Cr content in the molten steel meets the target chromium content in the high-carbon chromium high-temperature stainless bearing steel. Argon gas is then introduced for stirring. Metallic manganese and ferrochrome nitride are added to the molten steel so that the manganese and nitrogen contents in the molten steel meet the target manganese and nitrogen contents in the high-carbon chromium high-temperature stainless bearing steel.

8. The industrial manufacturing method of high-carbon chromium high-temperature stainless bearing steel according to claim 1, characterized in that, The casting process includes: The molten steel after the sample treatment is poured into the steel ingot mold, and 1-10% by weight of the molten steel is reserved to compensate for the shrinkage cavities of the cast steel ingot. Then, the first mold cooling, demolding and first annealing are carried out.

9. The industrial manufacturing method of high-carbon chromium high-temperature stainless bearing steel according to claim 8, characterized in that, The casting conditions include: tapping temperature of 1500-1600℃ and tapping speed of 400-800 kg / min.

10. The industrial manufacturing method of high-carbon chromium high-temperature stainless bearing steel according to claim 8, characterized in that, Select 1-8% by weight of molten steel to compensate for shrinkage cavities in cast steel ingots.

11. The industrial manufacturing method of high-carbon chromium high-temperature stainless bearing steel according to claim 1, characterized in that, In step S3: The upsetting conditions are as follows: the initial forging temperature is 1050-1100℃, the final forging temperature is 900-950℃, the upsetting time for each upsetting is 5-15 minutes, and the ingot height is reduced by 300-400 mm.

12. The industrial manufacturing method of high-carbon chromium high-temperature stainless bearing steel according to claim 1, characterized in that, The single-sided pressing amount of each pass of the press should be controlled at 20-30mm.

13. The industrial manufacturing method of high-carbon chromium high-temperature stainless bearing steel according to claim 1, characterized in that, The conditions for radial forging include: initial forging temperature of 1000-1050℃, final forging temperature of 900-940℃, and time of 10-20 min.

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