A method for refining as-cast structure of high speed steel

Abstract

The application provides a method for refining as-cast structure of high-speed steel, and relates to the technical field of high-speed steel ingot preparation.The method for refining as-cast structure of high-speed steel comprises raw material proportioning, raw material weighing, raw material smelting, suction casting forming, annealing treatment and tempering treatment.The high-speed steel material is as follows in terms of element mass percentage: C 0.8-1.3%, W 2-10.0%, Mo 2.0-9.0%, Cr 4.0-5.0%, V 1-3.0%, Co 1.5-8.0%, Si 0-1.5%, Mn 0.2-0.4%, Al 0-1.8%, and the balance is iron and inevitable impurity elements.The application selects a preparation method and selects to add oxide instead of part of carbide forming elements, so that the utilization rate of silicon and molybdenum oxide raw materials of the high-speed steel is higher, the traditional preparation cost is reduced, the thermal energy consumption is small, the primary carbide of the prepared high-speed steel is refined multiple times, the toughness, hardness and red hardness of the material are improved, the subsequent machinability is strong, the smelting refining process is simple, the operation difficulty is low, the process is short, the efficiency is high, and the application is beneficial to industrial large-scale production and promotion.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-speed steel ingot preparation, and particularly relates to a method for refining the as-cast structure of high-speed steel. BACKGROUND

[0002] High-speed steel is a high-alloy steel containing multiple strong carbide-forming elements such as tungsten, molybdenum, chromium and vanadium. In addition to these elements, high-performance high-speed steel usually contains a certain amount of cobalt, such as M42 high-speed steel. After proper heat treatment, excellent red hardness, tempering hardness and wear resistance can be obtained, and it is widely used in the fields of cutters and molds.

[0003] The wear resistance of high-speed steel mainly comes from the high hardness of martensite and a large amount of carbides, and the more uniform and finer the distribution of carbides, the better the wear resistance. Experiments have shown that the combination of high molybdenum and low tungsten can achieve a good combination of toughness and hardness, low vanadium content is beneficial to grinding performance, and the addition of cobalt is important for heat treatment hardness and heat resistance. However, due to the high content of alloying elements in the steel, after melting or pouring, even after forging and rolling, coarse primary carbides still exist in the interior, and serious composition segregation causes deterioration of material toughness, and cracks are easily formed along the carbide boundaries.

[0004] Tungsten and molybdenum are commonly used carbide-forming elements in high-speed steel. Because molybdenum and tungsten have similar properties, and the weight of molybdenum is about half of that of tungsten, many high-speed steels use high molybdenum and low tungsten. For high-molybdenum high-speed steel, the primary carbide contains a large amount of M2C eutectic carbide. This carbide is metastable at high temperatures and decomposes to form M6C and MC.

[0005] China is rich in tungsten resources (tungsten oxide), accounting for 65.5% of the world's total reserves, ranking first in the world, and molybdenum resource output (molybdenum oxide) ranks second in the world. Reducing metal oxides to elemental metals and then to molybdenum iron / tungsten iron alloys requires a large amount of energy.

[0006] For example, Chinese patent CN116652128A discloses a method for refining the as-cast structure of M2 high-speed steel. Obviously, the composition selection of this high-speed steel contains high-cost trace rare earth elements, the melting process is relatively complex, and high-temperature diffusion treatment is needed after continuous casting billet forming to refine the as-cast structure. The continuous casting crystallizer needs to use strong cooling + weak cooling, and the two cooling is accompanied by forward and reverse roller type electromagnetic stirring, which is complex and difficult to operate.

[0007] Chinese patent CN 113355587A discloses a method for improving the as-cast structure of high-speed steel by magnesium and rare earth micro-alloying and increasing solidification pressure. Obviously, the raw material selection is a metal elemental raw material. First, part of the metal raw material and part of the graphite are used to prepare a pre-deoxidized molten steel. Then, other metal raw materials and the remaining graphite are added to the pre-deoxidized molten steel for alloying. After that, magnesium alloy and rare earth are added under pressure for micro-alloying. The improved ingot structure is obtained by pressurized electroslag remelting of the obtained cast ingot. Obviously, this method has high requirements for the composition and pressure of the molten steel, and the operation is difficult. After multiple different melting, the process is long, the operation is difficult, the cost is high, and the efficiency is low.

[0008] Chinese patent CN 1904107A discloses a process for improving the comprehensive performance of M42 high-speed steel. The content of silicon and chromium needs to be adjusted to 0.5-0.55% and 7.9-8.1% respectively, and the nitrogen content in the steel needs to be 250-880ppm. A certain amount of composite deoxidizer and rare earth elements are added before and during tapping. The composite deoxidizer is SiAlBaCa or a mixture of any two or more of the four substances containing Si, Al, Ba and Ca as main components. Therefore, the batching requirements are very strict, and the addition of composite deoxidizer and rare earth elements increases the cost, which is not conducive to industrial production and promotion. SUMMARY

[0009] In order to solve the technical problems of low utilization rate of raw materials, high cost, high heat consumption, coarse primary carbides of prepared high-speed steel, reduced toughness of materials, easy to produce cracks, need to add high-cost rare earth elements for refinement, complex smelting and refining process, difficult operation, strict component proportioning requirements, and special control of cooling in the crystallizer before casting in the prior art, an embodiment of the present application provides a low-cost, short-process, and full-raw-material-utilization method for refining the as-cast structure of high-speed steel. The technical solution is as follows:

[0010] A method for refining the as-cast structure of high-speed steel, the method comprising the following steps:

[0011] S1, raw material proportioning: selecting raw materials according to each element in high-speed steel to obtain selected raw materials; wherein, part of the required molybdenum elemental raw material is replaced by molybdenum oxide; in order to eliminate the influence of impurity elements, except for the oxides used, the rest are elemental raw materials with a purity higher than 99.9wt.%;

[0012] S2, raw material weighing: using an electronic balance to weigh and proportion the selected raw materials of S1 according to the weight ratio of each element in high-speed steel to obtain weighed raw materials;

[0013] S3, raw material smelting: using non-consumable vacuum arc furnace smelting, 50g of S2 weighed raw materials are placed in the crucible for raw material smelting, and alloy melt is obtained;

[0014] S4, suction casting: using vacuum suction to directly suck the alloy melt of S3 into a water-cooled copper mold to form a high-speed steel button ingot;

[0015] S5, high temperature diffusion treatment: high temperature diffusion treatment is performed on the high-speed steel button ingot of S4 to obtain a high temperature diffusion treated high-speed steel button ingot;

[0016] S6, tempering treatment: the high temperature diffusion treated high-speed steel button ingot of S5 is subjected to multiple tempering treatment to obtain a high-speed steel with refined as-cast structure.

[0017] Optionally, in S1, the high-speed steel material is 0.8-1.3% C, 2-10.0% W, 2.0-9.0% Mo, 4.0-5.0% Cr, 1-3.0% V, 1.5-8.0% Co, 0-1.5% Si, 0.2-0.4% Mn, 0-1.8% Al, and the balance is iron and unavoidable impurity elements, wherein the total amount of W and Mo is not higher than 15%, and Si and Al are added according to 0.3-0.4 times the mass of the added oxide.

[0018] Optionally, in S2, the electronic balance is a high-precision 0.001g electronic balance with an error of ±0.03g.

[0019] Optionally, in S2, the raw materials need to be ultrasonically oscillated in anhydrous ethanol before weighing, with a frequency of 20-40KHz and a power of 100-450W, and then dried and weighed.

[0020] Optionally, in S3, before raw material smelting, vacuum is first extracted to 5×10 -3 Pa, high-purity argon is filled, and the above steps are repeated, and the vacuum is extracted to below 5×10 -4 Pa; the S2 weighed raw materials are placed in the crucible, and silicon and molybdenum oxide are placed together; the raw material smelting needs to be repeated for more than 8 times, 2 minutes each time.

[0021] Optionally, in S4, the diameter of the water-cooled copper mold is 30mm; the as-cast structure of the high-speed steel button ingot is isolated and discontinuous austenite matrix and 10.2-21μm eutectic ledeburite network, and the as-cast hardness is 53-59HRC.

[0022] Optionally, in S5, the high temperature diffusion treatment temperature is 1050-1250℃, the heating rate is 8-10℃ / min, and the time is 3-5h.

[0023] Optionally, the as-cast structure of the high-speed steel button ingot after high-temperature diffusion in S5 is a quenched austenite matrix and eutectic ledeburite nets of 12-23 microns, and the hardness is 63-68 HRC.

[0024] Optionally, the number of times of the multiple tempering treatment in S6 is 2-4 times, the temperature is 450-580 DEG C, the heating rate is 8-10 DEG C / min, and the time is 2-4 h.

[0025] Optionally, the as-cast structure of the high-speed steel button ingot after high-temperature diffusion in S5 is a quenched austenite matrix and eutectic ledeburite nets of 12-23 microns, and the hardness is 63-68 HRC.

[0026] The technical scheme has at least the following beneficial effects compared with the prior art:

[0027] The technical scheme has at least the following beneficial effects compared with the prior art:

[0028] The technical scheme has at least the following beneficial effects compared with the prior art:

[0029] The technical scheme has at least the following beneficial effects compared with the prior art:

[0030] The technical scheme has at least the following beneficial effects compared with the prior art:

[0031] The technical scheme has at least the following beneficial effects compared with the prior art:

[0032] The high-speed steel with refined as-cast structure has a higher secondary hardening peak, better red hardness below 600 DEG C, and higher wear resistance than the high-speed steel prepared by the same preparation method; after being kept at 600 DEG C for 60 min and then air-cooled, the surface oxide layer is removed after the process is repeated for 4 times continuously, and then the hardness is 62-67.1 HRC.

[0033] In summary, compared with other conventional methods, the method of the present application has higher utilization of silicon and molybdenum oxide raw materials, lower traditional preparation cost, and less heat energy consumption, by the selection of preparation method and the selection of adding part of carbide forming elements with oxides instead of carbides. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0035] Figure 1 is the SEM microstructure of the as-cast structure of the high-speed steel with refined as-cast structure prepared by the method for refining the as-cast structure of high-speed steel in Example 1 of the present application;

[0036] Figure 2 is the SEM microstructure of the as-cast structure of the high-speed steel with refined as-cast structure prepared by the method for refining the as-cast structure of high-speed steel in Comparative Example 1 of the present application;

[0037] Figure 3 is the SEM microstructure of the as-cast structure of the high-speed steel with refined as-cast structure prepared by the method for refining the as-cast structure of high-speed steel in Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0038] The technical solutions in the present application will be described below with reference to the drawings.

[0039] In the embodiments of the present application, the words such as "example", "for example" are used to represent as an example, illustration or description. Any embodiment or design scheme described as "example" in the present application should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. In fact, the word "example" is intended to present the concept in a specific way. In addition, in the embodiments of the present application, the meaning expressed by "and / or" can be both, or can be one of the two.

[0040] In the embodiments of the present application, the terms "image" and "picture" can be used interchangeably, and the meanings expressed thereby are consistent when no distinction is emphasized.

[0041] In the embodiments of the present application, the subscript such as W1 can be written in the form of non-subscript such as W1, and the meanings expressed thereby are consistent when no distinction is emphasized.

[0042] To make the technical problems, technical solutions and advantages of the present application clearer, specific embodiments will be described in detail below with reference to the drawings.

[0043] A method for refining as-cast structure of high-speed steel, comprising the following steps:

[0044] S1, raw material proportioning: selecting raw materials according to elements in high-speed steel to obtain selected raw materials; wherein, part of the required molybdenum elemental raw material is replaced by molybdenum oxide; in order to eliminate the influence of impurity elements, except for the oxides used, the rest are elemental raw materials with a purity higher than 99.9wt.%;

[0045] S2, raw material weighing: using an electronic balance to weigh and proportion the selected raw materials of S1 according to the weight ratio of each element in high-speed steel to obtain weighed raw materials;

[0046] S3, raw material smelting: using a non-consumable vacuum arc furnace to smelt, placing 50g of the weighed raw materials of S2 in a crucible to smelt the raw materials, and obtaining an alloy melt;

[0047] S4, suction casting forming: using vacuum suction casting to directly suck the alloy melt of S3 into a water-cooled copper mold to form, and obtaining a high-speed steel button ingot;

[0048] S5, high-temperature diffusion treatment: performing high-temperature diffusion treatment on the high-speed steel button ingot of S4 to obtain a quenched high-speed steel button ingot;

[0049] S6, tempering treatment: performing multiple tempering treatments on the high-speed steel button ingot after high-temperature diffusion of S5 to obtain high-speed steel with refined as-cast structure.

[0050] In particular, the high-speed steel material in S1 is 0.8-1.3% of C, 2-10.0% of W, 2.0-9.0% of Mo, 4.0-5.0% of Cr, 1-3.0% of V, 1.5-8.0% of Co, 0-1.5% of Si, 0.2-0.4% of Mn, 0-1.8% of Al, and the balance is iron and unavoidable impurity elements, wherein the total amount of W and Mo is not higher than 15%, and Si and Al are added according to 0.3-0.4 times the mass of the added oxides.

[0051] In particular, the electronic balance in S2 is a high-precision 0.001 g electronic balance with an error of ±0.03 g.

[0052] In particular, the raw materials in S2 need to be ultrasonically oscillated in anhydrous ethanol before weighing, with a frequency of 20-40 KHz and a power of 100-450 W, and then weighed after drying.

[0053] In particular, in S3, the raw materials need to be vacuumed to 5×10 -3 Pa, and high-purity argon is filled, and the above steps are repeated to vacuum to 5×10 -4 Pa; the weighed raw materials in S2 are placed in the crucible, and silicon and molybdenum oxide are placed together; the raw materials need to be repeatedly melted for more than 8 times, each time for 2 minutes.

[0054] In particular, in S4, the diameter of the water-cooled copper mold is 30 mm; the as-cast structure of the high-speed steel button ingot is an isolated and discontinuous austenite matrix and a eutectic ledeburite network of 10.2-21 μm, and the as-cast hardness is 53-59 HRC.

[0055] In particular, in S5, the high-temperature diffusion treatment temperature is 1050-1250°C, the heating rate is 8-10°C / min, and the time is 3-5 h.

[0056] In particular, in S5, the as-cast structure of the high-speed steel button ingot after high-temperature diffusion is a quenched austenite matrix and a eutectic ledeburite network of 12-23 μm, and the hardness is 63-68 HRC.

[0057] In particular, in S6, the number of multiple tempering treatments is 2-4 times, the temperature is 450-580°C, the heating rate is 8-10°C / min, and the time is 2-4 h.

[0058] In particular, in S6, the as-cast structure of the high-speed steel refined as-cast structure is a martensite matrix and a eutectic carbide, and a secondary precipitate phase of 0.5-2 μm, and the tempering hardness is 66-69 HRC, and after holding at 600°C for 60 min and air cooling, the surface oxide layer is continuously repeated for 4 times, and then the hardness obtained is 62-67.1 HRC.

[0059] Example 1

[0060] A method for refining the as-cast structure of a high-speed steel, the method for refining the as-cast structure of a high-speed steel comprising the following steps:

[0061] S1, raw material ratio: select raw materials according to the elements in the high-speed steel, and obtain the selected raw materials; wherein, part of the required molybdenum elemental raw material is replaced by molybdenum oxide; in order to eliminate the influence of impurity elements, in addition to the oxides used, the rest are elemental raw materials, with a purity of more than 99.9wt.%; the high-speed steel material of the present embodiment is as follows in terms of element mass percentage: C 1.1%, W 2.0%, Mo 9.0%, Cr 4.0%, V 1.0%, Co 8.0%, Si 1.0%, Mn 0.2%, Al 0.7%, and the balance is iron and unavoidable impurity elements;

[0062] S2, raw material weighing: using an electronic balance, the selected raw materials of S1 are weighed and matched according to the weight ratio of each element in the high-speed steel, 5% molybdenum oxide is used to replace 4% molybdenum, and the weighed raw materials are obtained; wherein, the electronic balance is a high-precision electronic balance of 0.001g, with an error of ±0.03g; before weighing the raw materials, ultrasonic oscillation in anhydrous ethanol is required, with a frequency of 40KHz and a power of 100W; after drying, the raw materials are weighed;

[0063] S3, raw material smelting: using a non-consumable vacuum arc furnace for smelting, before smelting the raw materials, vacuum is first extracted to 5×10 -3 Pa, high-purity argon is filled, and the previous steps are repeated to extract the vacuum to 5×10 -4 Pa below; the weighed raw materials of S2 are placed in the crucible, and silicon and molybdenum oxide are placed together; the raw material smelting needs to be repeated for more than 8 times, 2 minutes each time; then 50g of the weighed raw materials of S2 are placed in the crucible for raw material smelting, and an alloy melt is obtained;

[0064] S4, suction casting: using vacuum suction casting, the alloy melt of S3 is directly sucked into a water-cooled copper mold with a diameter of 30mm for forming, and a high-speed steel button ingot is obtained; the as-cast structure of the high-speed steel button ingot is isolated and discontinuous austenite matrix and eutectic ledeburite network (average size 10.2μm), and the as-cast hardness is 59.0HRC;

[0065] S5, high-temperature diffusion treatment: the high-speed steel button ingot of S4 is subjected to high-temperature diffusion treatment, the temperature is 1150℃, the heating rate is 8℃ / min, and the time is 3h, and an annealed high-speed steel button ingot is obtained; the as-cast structure of the high-speed steel button ingot after high-temperature diffusion treatment is quenched austenite matrix and eutectic ledeburite network (average size 12.3μm), and the hardness is 68.0HRC;

[0066] S6, tempering treatment: the high-speed steel button ingot after high-temperature diffusion of S5 is subjected to multiple tempering treatment, the number of multiple tempering treatment is 3 times, the temperature is 560℃, the heating rate is 10℃ / min, and the time is 3h, and a high-speed steel with refined as-cast structure is obtained.

[0067] For example, Figure 1As shown, the as-cast structure of the fine-grained as-cast high-speed steel prepared in the embodiment is a martensite matrix and eutectic carbide, and a secondary precipitated phase (0.5-2 μm). The tempering hardness is 69.5 HRC, and after being kept at 600 ℃ for 60 min and then air-cooled, the hardness is 64.7 HRC after the surface oxidation layer is removed after being continuously repeated for 4 times.

[0068] Comparative Example 1

[0069] A method for refining the as-cast structure of a high-speed steel, the method comprising the following steps:

[0070] S1, raw material proportioning: selecting raw materials according to the elements in the high-speed steel to obtain the selected raw materials; wherein, part of the required molybdenum elemental raw material is replaced by molybdenum oxide; in order to eliminate the influence of impurity elements, except for the oxides used, the rest are elemental raw materials with a purity of more than 99.9wt.%; the high-speed steel material of the present comparative example is as follows in terms of element mass percentage: C 1.1%, W 2.0%, Mo 9.0%, Cr 4.0%, V 1.0%, Co 8.0%, Si 0.6%, Mn 0.2%, and the balance is iron and unavoidable impurity elements;

[0071] S2, raw material weighing: using an electronic balance to weigh and proportion the selected raw materials of S1 according to the weight ratio of each element in the high-speed steel, replacing 4% of molybdenum with 5% of molybdenum oxide to obtain the weighed raw materials; wherein, the electronic balance is a high-precision electronic balance with an accuracy of 0.001 g and an error of ±0.03 g; before weighing the raw materials, ultrasonic oscillation in anhydrous ethanol is required, with a frequency of 40 KHz and a power of 100 W, and the weighed raw materials are dried;

[0072] S3, raw material melting: using a non-consumable vacuum arc furnace for melting, before melting the raw materials, vacuum is first extracted to 5×10 -3 Pa, high-purity argon is filled, and the foregoing steps are repeated, and the vacuum is extracted to below 5×10 -4 Pa; the weighed raw materials of S2 are placed in the crucible, and silicon and molybdenum oxide are placed together; the raw material melting needs to be repeated for more than 8 times, 2 minutes each time; then 50 g of the weighed raw materials of S2 are placed in the crucible for raw material melting to obtain an alloy melt;

[0073] S4, suction casting: using vacuum suction casting to directly suck the alloy melt of S3 into a water-cooled copper mold with a diameter of 30 mm to form a high-speed steel button ingot; the as-cast structure of the high-speed steel button ingot is isolated and discontinuous austenite matrix and eutectic ledeburite network (average size 17.8 μm), and the as-cast hardness is 56.2 HRC;

[0074] S5, high temperature diffusion treatment: the high speed steel button ingot of S4 is subjected to high temperature diffusion treatment, the temperature is 1150℃, the heating rate is 8℃ / min, the time is 3h, and the high temperature diffusion high speed steel button ingot is obtained; the as-cast structure of the high temperature diffusion high speed steel button ingot is quenched austenite matrix and eutectic ledeburite network (20.2μm), and the hardness is 66HRC;

[0075] S6, tempering treatment: the high temperature diffusion high speed steel button ingot of S5 is subjected to multiple tempering treatment, the number of multiple tempering treatment is 3 times, the temperature is 560℃, the heating rate is 10℃ / min, the time is 3h, and the high speed steel with refined as-cast structure is obtained.

[0076] As shown in Figure 2 , the as-cast structure of the high speed steel with refined as-cast structure prepared in the present comparative example is martensite matrix and eutectic carbide, and secondary precipitated phase (0.5-2μm). The tempering hardness is 67.5HRC, after holding at 600℃ for 60min and air cooling, continuously repeating for 4 times, and then removing the surface oxidation layer, the hardness obtained is 62.7HRC.

[0077] Comparative Example 2

[0078] A method for refining the as-cast structure of high speed steel, the method for refining the as-cast structure of high speed steel comprises the following steps:

[0079] S1, raw material proportioning: selecting raw materials according to the elements in high speed steel to obtain selected raw materials; wherein, using molybdenum oxide to replace part of the required molybdenum elemental raw material; in order to eliminate the influence of impurity elements, in addition to the oxides used, the rest are elemental raw materials with a purity of more than 99.9wt.%; the high speed steel material of the present comparative example is as follows in terms of element mass percentage: C 1.1%, W 2.0%, Mo 9.0%, Cr 4.0%, V 1.0%, Co 8.0%, Si 1.5%, Mn 0.2%, and the balance is iron and unavoidable impurity elements;

[0080] S2, raw material weighing: using an electronic balance to weigh and proportion the selected raw materials of S1 according to the weight ratio of each element in high speed steel, using 5% molybdenum oxide to replace 4% molybdenum, to obtain weighed raw materials; wherein, the electronic balance is a high-precision 0.001g electronic balance with an error of ±0.03g; before weighing the raw materials, ultrasonic oscillation in anhydrous ethanol is required, the frequency is 40KHz, and the power is 100W; after drying, weighing is performed;

[0081] S3, raw material melting: using a non-consumable vacuum arc furnace for melting, before raw material melting, vacuum needs to be first extracted to 5×10 -3 Pa, high-purity argon is filled, the foregoing steps are repeated, and the vacuum is extracted to 5×10 -4Below Pa; place the weighed raw material of S2 in a crucible, and put silicon and molybdenum oxide together; the raw material melting needs to be repeated more than 8 times, each time for 2 minutes; then put 50g of the weighed raw material of S2 in a crucible for raw material melting to obtain alloy melt;

[0082] S4. Vacuum casting: The alloy melt of S3 is directly drawn into a water-cooled copper mold with a diameter of 30mm using vacuum casting to form a high-speed steel button ingot. The as-cast microstructure of the high-speed steel button ingot consists of an isolated discontinuous austenite matrix and a eutectic ledeburite network (average size 13.8μm), and the as-cast hardness is 58.3HRC.

[0083] S5. High-temperature diffusion treatment: S4 high-speed steel button ingots were subjected to high-temperature diffusion treatment at a temperature of 1150℃, a heating rate of 8℃ / min, and a time of 3h to obtain high-speed steel button ingots after high-temperature diffusion treatment. The as-cast microstructure of the high-speed steel button ingots after high-temperature diffusion treatment is quenched austenite matrix and eutectic ledeburite network (18.5μm), and the hardness is 67.1HRC.

[0084] S6. Tempering treatment: The high-speed steel button ingot after S5 high-temperature diffusion was subjected to multiple tempering treatments. The number of tempering treatments was 3 times, the temperature was 560℃, the heating rate was 10℃ / min, and the time was 3h, to obtain high-speed steel with a refined as-cast structure.

[0085] like Figure 3 As shown, the high-speed steel with refined as-cast microstructure prepared in this comparative example has a martensitic matrix, eutectic carbides, and secondary precipitates (0.5-2 μm). The tempering hardness is 68.4 HRC. After holding at 600℃ for 60 min and then air cooling, this process was repeated 4 times to remove the surface oxide layer, and the resulting hardness was 63.0 HRC.

[0086] Comparing Example 1 with Comparative Examples 1 and 2, which are standard M42 high-speed steel compositions and both used a single silicon reducing agent for reduction, Comparative Example 1 had a lower silicon content than Comparative Example 2. The average size of the network eutectic carbides in the as-cast microstructure was 22.5% smaller in Comparative Example 2 than in Comparative Example 1. Example 1 used an aluminum-silicon composite as the reducing agent, with a total content of 1.7%, and the average size of the network eutectic carbides was even smaller than in Comparative Examples 1 and 2. The as-cast hardness and tempered hardness of Comparative Example 2 and Example 1 were slightly higher than those of Comparative Example 1, while the as-cast hardness and tempered hardness of Example 1 were slightly higher than those of Comparative Example 2. This is due to fine-grain strengthening.

[0087] Example 2

[0088] A method for refining the microstructure of as-cast high-speed steel, the method comprising the following steps:

[0089] S1, raw material ratio: select raw materials according to the elements in the high-speed steel, and obtain the selected raw materials; wherein, part of the required molybdenum elemental raw material is replaced by molybdenum oxide; in order to eliminate the influence of impurity elements, in addition to the oxides used, the rest are elemental raw materials with a purity of more than 99.9wt.%; the high-speed steel material of the present embodiment is as follows in terms of element mass percentage: C 1.2%, W 6.0%, Mo 5.0%, Cr 4.0%, V 2.0%, Co 1.5%, Mn 0.2%, Al 1.8%, and the balance is iron and unavoidable impurity elements;

[0090] S2, raw material weighing: use an electronic balance to weigh and proportion the selected raw materials of S1 according to the weight ratio of each element in the high-speed steel, replace 4% of molybdenum with 5% of molybdenum oxide, and obtain the weighed raw materials; wherein, the electronic balance is a high-precision electronic balance with an accuracy of 0.001g, and the error is ±0.03g; before weighing the raw materials, ultrasonic oscillation is required in anhydrous ethanol, the frequency is 20KHz, and the power is 200W; after drying, weigh;

[0091] S3, raw material smelting: adopt non-consumable vacuum arc furnace smelting, and before smelting the raw materials, vacuum needs to be extracted to 5×10 -3 Pa, fill in high-purity argon, repeat the previous steps, and extract the vacuum to below 5×10 -4 Pa; the weighed raw materials of S2 are placed in the crucible, and silicon and molybdenum oxide are placed together; the raw material smelting needs to be repeated for more than 8 times, 2 minutes each time; then 50g of the weighed raw materials of S2 are placed in the crucible for raw material smelting, and an alloy melt is obtained;

[0092] S4, suction casting: adopt vacuum suction casting to directly suck the alloy melt of S3 into a water-cooled copper mold with a diameter of 30mm for forming, and obtain a high-speed steel button ingot; the as-cast structure of the high-speed steel button ingot is isolated and discontinuous austenite matrix and eutectic ledeburite network (average size 19.8μm), and the as-cast hardness is 54.3HRC;

[0093] S5, high-temperature diffusion treatment: the high-speed steel button ingot of S4 is subjected to high-temperature diffusion treatment, the temperature is 1220℃, the heating rate is 8℃ / min, and the time is 3h, and the high-temperature diffusion high-speed steel button ingot is obtained; the as-cast structure of the high-temperature diffusion high-speed steel button ingot is quenched austenite matrix and eutectic ledeburite network (21.9μm), and the hardness is 64HRC;

[0094] S6, tempering treatment: the high-temperature diffusion high-speed steel button ingot of S5 is subjected to multiple tempering treatments, the number of multiple tempering treatments is 4 times, the temperature is 555℃, the heating rate is 10℃ / min, and the time is 4h, and a high-speed steel with refined as-cast structure is obtained.

[0095] The as-cast structure of the fine-grained as-cast high-speed steel prepared in the embodiment is martensite matrix and eutectic carbide, and secondary precipitated phase (0.5-2 μm). The tempering hardness is 68 HRC, and after being kept at 600 ℃ for 60 min and then air-cooled, the hardness is 62 HRC after the surface oxidation layer is removed after being continuously repeated for 4 times.

[0096] Example 3

[0097] A method for refining the as-cast structure of high-speed steel, the method comprising the following steps:

[0098] S1, raw material proportioning: selecting raw materials according to the elements in the high-speed steel to obtain the selected raw materials; wherein, part of the required molybdenum elemental raw material is replaced by molybdenum oxide; in order to eliminate the influence of impurity elements, except for the oxides used, the rest are elemental raw materials with a purity of more than 99.9wt.%; the high-speed steel material in the embodiment is as follows in terms of element mass percentage: C 0.8%, W 6.0%, Mo 5.0%, Cr 4.0%, V 2.0%, Co 5.0%, Si 0.5%, Mn 0.2%, Al 0.8%, and the balance is iron and unavoidable impurity elements;

[0099] S2, raw material weighing: using an electronic balance to weigh and proportion the selected raw materials in S1 according to the weight ratio of each element in the high-speed steel, replacing 4% of molybdenum with 5% of molybdenum oxide, to obtain the weighed raw materials; wherein, the electronic balance is a high-precision electronic balance with an accuracy of 0.001 g and an error of ±0.03 g; before weighing the raw materials, ultrasonic oscillation is required in anhydrous ethanol with a frequency of 40 KHz and a power of 450 W, and the raw materials are weighed after drying;

[0100] S3, raw material melting: using a non-consumable vacuum arc furnace to melt, before melting the raw materials, vacuum is first extracted to 5×10 -3 Pa, high-purity argon is filled, and the foregoing steps are repeated, and the vacuum is extracted to below 5×10 -4 Pa; the weighed raw materials in S2 are placed in the crucible, and silicon and molybdenum oxide are placed together; the raw material melting needs to be repeated for more than 8 times, 2 minutes each time; then 50 g of the weighed raw materials in S2 are placed in the crucible for raw material melting, to obtain an alloy melt;

[0101] S4, suction casting forming: using vacuum suction casting to directly suck the alloy melt in S3 into a water-cooled copper mold with a diameter of 30 mm to form a high-speed steel button ingot; the as-cast structure of the high-speed steel button ingot is isolated and discontinuous austenite matrix and eutectic ledeburite network (average size 18.0 μm), and the as-cast hardness is 55.1 HRC;

[0102] S5, high temperature diffusion treatment: the high speed steel button ingot of S4 is subjected to high temperature diffusion treatment, the temperature is 1180℃, the heating rate is 8℃ / min, the time is 5h, and the high temperature diffusion high speed steel button ingot is obtained; the as-cast structure of the high temperature diffusion high speed steel button ingot is quenched austenite matrix and eutectic ledeburite network (20.8μm), and the hardness is 63.8HRC;

[0103] S6, tempering treatment: the high temperature diffusion high speed steel button ingot of S5 is subjected to multiple tempering treatment, the number of multiple tempering treatment is 4 times, the temperature is 555℃, the heating rate is 10℃ / min, the time is 4h, and the high speed steel with refined as-cast structure is obtained.

[0104] The as-cast structure of the high speed steel with refined as-cast structure prepared in the embodiment is martensite matrix and eutectic carbide, and secondary precipitated phase (0.5-2μm). The tempering hardness is 68.3HRC, after being kept at 600℃ for 60min and then air-cooled, after being repeatedly performed for 4 times in succession and then the surface oxidation layer is removed, the hardness obtained is 63.5HRC.

[0105] Example 4

[0106] A method for refining the as-cast structure of high speed steel, the method comprising the following steps:

[0107] S1, raw material proportioning: selecting raw materials according to the elements in the high speed steel to obtain the selected raw materials; wherein, part of the required molybdenum elemental raw material is replaced by molybdenum oxide; in order to eliminate the influence of impurity elements, except for the oxides used, the rest are elemental raw materials with a purity of more than 99.9wt.%; the high speed steel material in this embodiment is as follows in terms of element mass percentage: C 1.0%, W 6.0%, Mo 5.0%, Cr 4.0%, V 2.0%, Si 1.2%, Mn 0.2%, and the balance is iron and unavoidable impurity elements;

[0108] S2, raw material weighing: using an electronic balance to weigh and proportion the selected raw materials of S1 according to the weight ratio of each element in the high speed steel, replacing 3.8% of molybdenum with 4% of molybdenum oxide, to obtain the weighed raw materials; wherein, the electronic balance is a high-precision electronic balance of 0.001g, with an error of ±0.03g; before weighing the raw materials, ultrasonic oscillation in anhydrous ethanol is required, with a frequency of 20KHz and a power of 100W, and the weighed raw materials are dried;

[0109] S3, raw material melting: using a non-consumable vacuum arc furnace for melting, before melting the raw materials, vacuum is first extracted to 5×10 -3 Pa, high-purity argon is filled, the previous steps are repeated, and the vacuum is extracted to 5×10 -4Pa or below; S2: the weighed raw materials are placed in the crucible, and the silicon and molybdenum oxide are placed together; the raw material smelting needs to be repeated for more than 8 times, 2 minutes each time; then 50g of the weighed raw materials of S2 are placed in the crucible for raw material smelting to obtain an alloy melt;

[0110] S4, suction casting: the alloy melt of S3 is directly sucked into a water-cooled copper mold with a diameter of 30mm by vacuum suction casting to form a high-speed steel button ingot; the as-cast structure of the high-speed steel button ingot is isolated and discontinuous austenite matrix and eutectic ledeburite network (average size 21.0μm), and the as-cast hardness is 53.5HRC;

[0111] S5, high-temperature diffusion treatment: the high-speed steel button ingot of S4 is subjected to high-temperature diffusion treatment, the temperature is 1240℃, the heating rate is 8℃ / min, and the time is 4h to obtain a high-temperature diffusion treated high-speed steel button ingot; the as-cast structure of the high-temperature diffusion treated high-speed steel button ingot is quenched austenite matrix and eutectic ledeburite network (23.0μm), and the hardness is 61.0HRC;

[0112] S6, tempering treatment: the high-temperature diffusion treated high-speed steel button ingot of S5 is subjected to multiple tempering treatments, the number of multiple tempering treatments is 3 times, the temperature is 560℃, the heating rate is 10℃ / min, and the time is 4.5h to obtain a high-speed steel with refined as-cast structure.

[0113] The as-cast structure of the high-speed steel with refined as-cast structure prepared in this embodiment is martensite matrix and eutectic carbide, and secondary precipitated phase (0.5-2μm). The tempering hardness is 68.8HRC, after keeping at 600℃ for 60 minutes and air cooling, continuously repeating for 4 times, and then removing the surface oxidation layer, the obtained hardness is 66.8HRC.

[0114] Example 5

[0115] A method for refining the as-cast structure of a high-speed steel, the method comprising the following steps:

[0116] S1, raw material proportioning: selecting raw materials according to the elements in the high-speed steel to obtain selected raw materials; wherein, molybdenum oxide is used to replace part of the required molybdenum elemental raw material; in order to eliminate the influence of impurity elements, except for the oxides used, the rest are elemental raw materials with a purity of more than 99.9wt.%; the high-speed steel material in this embodiment is as follows in terms of element mass percentage: C 1.3%, W 10.0%, Mo 4.0%, Cr 4.0%, V 3.0%, Mn 0.4%, Al 1.5%, and the balance is iron and unavoidable impurity elements;

[0117] S2, raw material weighing: using an electronic balance to weigh and match the raw materials selected in S1 according to the weight ratio of each element in high-speed steel, using 4% molybdenum oxide to replace 3.8% molybdenum, to obtain the weighed raw materials; wherein the electronic balance is a high-precision 0.001 g electronic balance with an error of ±0.03 g; before weighing the raw materials, ultrasonic oscillation in anhydrous ethanol is required, with a frequency of 20 KHz and a power of 100 W, and the weighed raw materials are dried;

[0118] S3, raw material smelting: using a non-consumable vacuum arc furnace for smelting, and before smelting the raw materials, vacuum is first extracted to 5×10 -3 Pa, high-purity argon is filled, and the foregoing steps are repeated to extract the vacuum to 5×10 -4 Pa; the raw materials weighed in S2 are placed in the crucible, and silicon and molybdenum oxide are placed together; the raw material smelting needs to be repeated for more than 8 times, 2 minutes each time; then 50 g of the raw materials weighed in S2 are placed in the crucible for raw material smelting, to obtain an alloy melt;

[0119] S4, suction casting: using vacuum suction to directly suck the alloy melt in S3 into a water-cooled copper mold with a diameter of 30 mm for forming, to obtain a high-speed steel button ingot; the as-cast structure of the high-speed steel button ingot is isolated and discontinuous austenite matrix and eutectic ledeburite network (average size 19.6 μm), and the as-cast hardness is 56.6 HRC;

[0120] S5, high-temperature diffusion treatment: the high-speed steel button ingot in S4 is subjected to high-temperature diffusion treatment, the temperature is 1240℃, the heating rate is 8℃ / min, and the time is 3.5h, to obtain a high-temperature diffusion treated high-speed steel button ingot; the as-cast structure of the high-temperature diffusion treated high-speed steel button ingot is quenched austenite matrix and eutectic ledeburite network (20.8 μm), and the hardness is 66.0 HRC;

[0121] S6, tempering treatment: the high-temperature diffusion treated high-speed steel button ingot in S5 is subjected to multiple tempering treatments, the number of multiple tempering treatments is 4 times, the temperature is 540℃, the heating rate is 10℃ / min, and the time is 4h, to obtain a high-speed steel with refined as-cast structure.

[0122] The as-cast structure of the high-speed steel with refined as-cast structure prepared in this embodiment is martensite matrix and eutectic carbide, and secondary precipitated phase (0.5-2 μm). The tempering hardness is 68.3 HRC, after being kept at 600℃ for 60 min and air-cooled, the surface oxide layer is removed after continuously repeating 4 times, and then the hardness obtained is 67.1 HRC.

[0123] Example 6

[0124] A method for refining the as-cast structure of high-speed steel, the method comprising the following steps:

[0125] S1, raw material ratio: select raw materials according to the elements in the high-speed steel, and obtain the selected raw materials; wherein, part of the required molybdenum elemental raw material is replaced by molybdenum oxide; in order to eliminate the influence of impurity elements, in addition to the oxides used, the rest are elemental raw materials with a purity of more than 99.9wt.%; the high-speed steel material of this embodiment is as follows in terms of element mass percentage: C 1.3%, W 10.0%, Mo 4.0%, Cr 4.0%, V 3.0%, Mn 0.4%, Si 1.2%, and the balance is iron and unavoidable impurity elements;

[0126] S2, raw material weighing: using an electronic balance, the selected raw materials of S1 are weighed and matched according to the weight ratio of each element in the high-speed steel, 5% molybdenum oxide is used to replace 4% molybdenum, and the weighed raw materials are obtained; wherein, the electronic balance is a high-precision electronic balance of 0.001g, with an error of ±0.03g; before weighing the raw materials, ultrasonic oscillation in anhydrous ethanol is required, with a frequency of 20KHz and a power of 100W; after drying, the weighing is carried out;

[0127] S3, raw material smelting: using a non-consumable vacuum arc furnace for smelting, before smelting the raw materials, vacuum is first extracted to 5×10 -3 Pa, high-purity argon is filled, and the previous steps are repeated to extract the vacuum to 5×10 -4 Pa below; the weighed raw materials of S2 are placed in the crucible, and silicon and molybdenum oxide are placed together; the raw material smelting needs to be repeated for more than 8 times, 2 minutes each time; then 50g of the weighed raw materials of S2 are placed in the crucible for raw material smelting, and the alloy melt is obtained;

[0128] S4, suction casting: the alloy melt of S3 is directly sucked into a water-cooled copper mold with a diameter of 30mm by vacuum suction casting to form a high-speed steel button ingot; the as-cast structure of the high-speed steel button ingot is isolated and discontinuous austenite matrix and eutectic ledeburite network (average size 20.6μm), and the as-cast hardness is 55.6HRC;

[0129] S5, high-temperature diffusion treatment: the high-speed steel button ingot of S4 is subjected to high-temperature diffusion treatment at a temperature of 1240℃, a heating rate of 8℃ / min and a time of 3.5h, to obtain a high-temperature diffusion treated high-speed steel button ingot; the as-cast structure of the high-temperature diffusion treated high-speed steel button ingot is quenched austenite matrix and eutectic ledeburite network (21.3μm), and the hardness is 64.9HRC;

[0130] S6, tempering treatment: the high-temperature diffusion treated high-speed steel button ingot of S5 is subjected to multiple tempering treatments, the number of multiple tempering treatments is 4 times, the temperature is 540℃, the heating rate is 10℃ / min, and the time is 4h, to obtain a high-speed steel with refined as-cast structure.

[0131] The as-cast structure of the high speed steel with refined as-cast structure prepared in the embodiment is martensite matrix and eutectic carbide, and secondary precipitated phase (0.5-2 µm). The tempering hardness is 67.8 HRC, after being kept at 600 ℃ for 60 min and then air-cooled, after the surface oxidation layer is removed after being continuously repeated for 4 times, the hardness is 65.8 HRC.

[0132] The above scheme, the application provides a method for refining the as-cast structure of high speed steel, which can solve the technical problems in the prior art, such as low utilization rate of raw materials, high cost, large heat energy consumption, coarse primary carbide of prepared high speed steel, reduced toughness of material, easy to produce cracks, need to add high-cost rare earth elements for refining, complex smelting and refining process, high operation difficulty, strict component ratio requirement, and special control of cooling in the crystallizer before casting.

[0133] In the application, the oxide is used to replace part of the carbide forming elements, and the aluminum and silicon are used as reducing agents for reduction, and the reaction product is the carbide forming element and aluminum oxide and silicon oxide, wherein the aluminum oxide and silicon oxide are removed as slag system, the production cost is reduced, the technical defects caused by excessive aluminum element are avoided, the reticular eutectic carbide is significantly refined,

[0134] The addition of silicon can refine the austenite grain size, thereby refining the reticular eutectic carbide, and the silicon remains a content of 0.2-1.0% in addition to being used for reducing the oxide, the presence of residual silicon promotes the decomposition of M2C, and the carbide size can be effectively refined.

[0135] The high-temperature diffusion treatment and the tempering treatment of the application cause the metastable phase M2C to partially dissolve, the primary carbide is refined at the same time, the matrix solid solubility is increased, the secondary carbide is precipitated during tempering, thereby strengthening the material, and the room temperature hardness and red hardness are obviously improved.

[0136] The as-cast structure of the high speed steel button ingot is isolated and discontinuous austenite matrix and 10.2-21 µm eutectic ledeburite net, and the hardness under as-cast state is 53-59 HRC, and the smelting cost can be reduced by 10-20% due to the adoption of the oxide form of the carbide forming element.

[0137] The high speed steel with refined as-cast structure has a higher secondary hardening peak than the high speed steel prepared by the same method, has better red hardness below 600 ℃, and has higher wear resistance; after being kept at 600 ℃ for 60 min and then air-cooled, after the surface oxidation layer is removed after being continuously repeated for 4 times, the hardness is 62-67.1 HRC.

[0138] In summary, the method of the present application has higher utilization rate of silicon and molybdenum oxide raw materials in high-speed steel, reduces the traditional preparation cost, and has small heat energy consumption, by the selection of preparation method and the selection of adding part of carbide forming elements with oxides instead.

[0139] It should be understood that the term "and / or" in this document merely describes an associated relationship between associated objects, and means that there can be three relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone, where A and B can be singular or plural. In addition, the character " / " in this document generally represents an "or" relationship between the associated objects before and after it, but it can also represent an "and / or" relationship, which can be understood according to the context before and after it.

[0140] In the present application, "at least one" means one or more, and "multiple" means two or more. "At least one of the following" or the like means any combination of these items, including any combination of single item or multiple items. For example, at least one of a, b, or c can mean a, b, c, a-b, a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0141] It should be understood that in various embodiments of the present application, the size of the sequence number of the above-mentioned processes does not mean the order of execution, and the execution order of the processes should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0142] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method of refining the as-cast structure of a high speed steel, characterized in that, The method for refining the as-cast structure of the high-speed steel comprises the following steps: S1, raw material proportioning: selecting raw materials according to elements in the high-speed steel to obtain the selected raw materials; wherein, part of the required molybdenum elemental raw material is replaced by molybdenum oxide; in order to eliminate the influence of impurity elements, except for the oxides used, the rest of the elemental raw materials are used, and the purity is higher than 99.9wt.%; the high-speed steel material is calculated according to the mass percentage of elements as follows: C 0.8-1.3%, W 2-10.0%, Mo 2.0-9.0%, Cr 4.0-5.0%, V 1-3.0%, Co 1.5-8.0%, Si 0-1.5%, Mn 0.2-0.4%, Al 0-1.8%, and the balance is iron and inevitable impurity elements, wherein the total amount of W and Mo is not higher than 15%, and Si and Al are added according to 0.3-0.4 times the mass of the added oxides; S2, raw material weighing: using an electronic balance to weigh and proportion the selected raw materials in S1 according to the weight ratio of elements in the high-speed steel to obtain the weighed raw materials; S3, raw material smelting: using a non-consumable vacuum arc furnace to smelt, placing 50g of the weighed raw materials in S2 in a crucible to smelt the raw materials, and obtaining an alloy melt; S4, suction casting forming: directly sucking the alloy melt in S3 into a water-cooled copper mold to form a high-speed steel button ingot by using vacuum suction casting; S5, high-temperature diffusion treatment: performing high-temperature diffusion treatment on the high-speed steel button ingot in S4, the temperature of the high-temperature diffusion treatment is 1050-1250℃, the heating rate is 8-10℃ / min, and the time is 3-5h, to obtain a high-speed steel button ingot after high-temperature diffusion treatment; S6, tempering treatment: performing multiple tempering treatments on the high-speed steel button ingot after high-temperature diffusion treatment in S5, the number of times of the multiple tempering treatments is 2-4 times, the temperature is 450-580℃, the heating rate is 8-10℃ / min, and the time is 2-4h, to obtain a high-speed steel with refined as-cast structure.

2. The method of refining as-cast microstructure of high speed steel according to claim 1, characterized in that, The electronic balance in S2 is a high-precision electronic balance with an accuracy of 0.001g and an error of ±0.03g.

3. The method of refining as-cast microstructure of high speed steel according to claim 1, characterized in that, The raw materials need to be ultrasonically oscillated in anhydrous ethanol before weighing in S2, the frequency is 20-40KHz, and the power is 100-450W.

4. The method of refining as-cast microstructure of high speed steel according to claim 1, characterized in that, S3 needs to be vacuumed to 5x10 -3 Pa before smelting the raw materials, fill high-purity argon, repeat the previous steps, vacuum to 5x10 -4 Pa; S2 weigh the raw materials in the crucible, silicon and molybdenum oxide together; smelting raw materials need to repeat smelting more than 8 times, 2 minutes each time.

5. The method of refining as-cast microstructure of high speed steel according to claim 1, characterized in that, The diameter of the water-cooled copper mold in S4 is 30mm; the as-cast structure of the high-speed steel button ingot is isolated and discontinuous austenite matrix and eutectic ledeburite net with a size of 10.2-21μm, and the as-cast hardness is 53-59HRC.

6. The method of refining as-cast microstructure of high speed steel according to claim 1, characterized in that, The as-cast structure of the high-speed steel button ingot after high-temperature diffusion treatment in S5 is quenched austenite matrix and eutectic ledeburite net with a size of 12-23μm, and the hardness is 63-68HRC.

7. The method of refining as-cast microstructure of high speed steel according to claim 1, characterized in that, The as-cast structure of the high-speed steel with refined as-cast structure in S6 is martensite matrix and eutectic carbide, and secondary precipitated phase with a size of 0.5-2μm, the tempering hardness is 66-69HRC, the hardness is 62-67.1HRC after keeping at 600℃ for 60min and air cooling, and continuously repeating the process for 4 times and then removing the surface oxidation layer.

Images