A high-wear-resistant high-speed steel and its strengthening method

Abstract

The present invention relates to the field of high-speed steel heat treatment, and provides a high-wear-resistant high-speed steel and a strengthening method thereof. The preparation method of the high-wear-resistant high-speed steel comprises the following steps: first subjecting commercial high-speed steel to a pulse current austenitizing treatment and then quenching, and then subjecting it to a pulse current multi-gradient tempering treatment. The present invention shortens the long-term, high-temperature heat treatment process, reduces costs and energy consumption, simplifies the process, and through the coordinated regulation of process and parameters, refines the grains and carbides at the same time. The obtained high-speed steel has better hardness and wear resistance than the high-speed steel obtained by the prior art (high-temperature and long-term treatment: austenitizing + quenching + tempering), and is suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to the field of high-speed steel heat treatment, and in particular to a high-wear-resistant high-speed steel and a strengthening method thereof. Background Art

[0002] High-speed steel (HSS) plays a crucial role in the cutting tool industry. With the development of the manufacturing industry, the demand for cutting tool performance is increasingly stringent. Therefore, there is an urgent need to find methods to improve the wear resistance of cutting tool materials. Traditional austenitizing followed by quenching and tempering is a common method for improving the wear resistance of HSS. Post-austenitizing quenching incorporates elements into the matrix, creating a supersaturated solid solution. This quenching produces high-strength martensite. Tempering, which is then held at a specific temperature for a specified period of time, produces a large amount of secondary carbides, thereby improving the wear resistance of HSS. However, traditional heat treatment processes require heat treatment equipment such as heat treatment furnaces and involve a series of steps, including austenitizing, quenching, and multiple tempering cycles. This consumes significant time and energy, significantly reducing production efficiency and increasing costs. Furthermore, prolonged heat treatment can lead to carbide and grain growth within the HSS microstructure, limiting improvements in the steel's ductility, toughness, and wear resistance. Furthermore, high levels of retained austenite in HSS after traditional heat treatment quenching significantly impact the hardness and dimensional stability of the HSS workpiece. Therefore, how to reduce production costs, achieve short-process processing, and obtain high-speed steel with high strength and high wear resistance is a technical problem that needs to be solved urgently. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention provides a high-wear-resistant high-speed steel, the preparation method of which comprises the following steps:

[0004] (1) Commercial high-speed steel is subjected to wire cutting, sandpaper polishing, and then pulse current austenitization treatment and quenching to obtain quenched high-speed steel. The pulse current austenitization treatment is: 1-4 pulse current treatments, and the process of each pulse current treatment is: voltage 30-65V, current density 3×10 4 -8.8×10 4 A / m 2 , processing time 0.5-5s;

[0005] The quenched high-speed steel obtained in step (1) is subjected to a multi-gradient electric pulse tempering treatment to obtain a high-wear-resistant high-speed steel, wherein the multi-gradient electric pulse tempering treatment comprises 1-6 gradient electric pulse tempering treatments, each gradient electric pulse tempering treatment being performed at a voltage of 35-60 V and a current density of 3.1×10 4 -7.5×10 4 A / m 2, processing time 0.6-4s. Further, the high speed steel in step (1) is one of W6Mo5Cr4V2Co5 high speed steel, ASP30 high speed steel, W18Cr4V high speed steel or Cr12MoV high speed steel.

[0006] Furthermore, the voltage in step (1) is 40-55V.

[0007] Furthermore, the current density in step (1) is 5×10 4 -8×10 4 A / m 2 .

[0008] Furthermore, the processing time of step (1) is 0.8-2s.

[0009] Furthermore, the voltage in step (2) is 35-50V.

[0010] Furthermore, the current density in step (2) is 3.3×10 4 -7×10 4 A / m 2 .

[0011] Furthermore, the processing time of step (2) is 1-3s.

[0012] Furthermore, the multi-gradient electric pulse tempering treatment is: 2-5 times gradient electric pulse tempering treatment.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] This invention shortens the long, high-temperature heat treatment process, reduces costs and energy consumption, and simplifies the process. Through the coordinated regulation of process and parameters, it simultaneously refines grains and carbides. The resulting high-speed steel has superior hardness and wear resistance to high-speed steel obtained using the existing technology (high-temperature, long-term treatment: austenitization + quenching + tempering), making it suitable for industrial production. Through the coordinated regulation of components and process parameters, this invention achieves the following excellent results:

[0015] 1. The present invention combines pulsed current austenitization with multi-gradient pulsed current tempering to strengthen high-speed steel in less than 10 seconds, rapidly improving its hardness and wear resistance. Existing methods for improving the hardness and wear resistance of high-speed steel require long-term high-temperature austenitization, quenching, and tempering, which takes several hours or more. This invention eliminates the austenitization, quenching, and tempering steps of traditional heat treatment, significantly reducing time and energy costs while avoiding the drawbacks of traditional heat treatment.

[0016] 2. The pulse current voltage and current density used in the present invention are low, which can realize a short process. The characteristics of the present invention are high energy efficiency, environmental protection, high safety, low maintenance cost, controllable relevant process parameters, and wide application range;

[0017] 3. The present invention applies pulse current treatment to effectively reduce the nucleation barrier of austenite, so that the austenite is significantly refined, and finally fine martensite is formed after quenching.

[0018] 4. The present invention has an extremely fast heating rate, which does not allow the dislocations generated by phase transformation and thermal compressive stress to have sufficient time to annihilate, and thus they are retained. A large number of dislocations can serve as nucleation sites for secondary carbides, precipitating small and evenly distributed carbides in the matrix;

[0019] 5. Compared with the traditional quenching and tempering process, the present invention refines the high-speed steel grains, effectively increases the number of small-sized carbides, and makes the carbides evenly distributed in the matrix, forming a coupling effect of fine grain strengthening and precipitation strengthening, and ultimately simultaneously improving the hardness and wear resistance of the high-speed steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 (a), 1(b), and 1(c) are comparative diagrams of the carbide morphology distribution of the conventional quenched and tempered high-speed steel (CQT) obtained in step (3) of Comparative Example 1, the W6Mo5Cr4V2Co5 high-speed steel (EQT1) obtained in Example 1, and the ASP30 high-speed steel (EQT2) obtained in Example 2, respectively;

[0021] Figure 2 (a1), 2(b1), and 2(c1) are grain morphology comparison diagrams of the conventional quenched and tempered high-speed steel (CQT) obtained in step (3) of Comparative Example 1, the W6Mo5Cr4V2Co5 high-speed steel (EQT1) obtained in Example 1, and the ASP30 high-speed steel (EQT2) obtained in Example 2, respectively;

[0022] Figure 3 (a1), 3(b1), and 3(c1) are grain size distribution diagrams of the conventional quenched and tempered high-speed steel (CQT) obtained in step (3) of Comparative Example 1, the W6Mo5Cr4V2Co5 high-speed steel (EQT1) obtained in Example 1, and the ASP30 high-speed steel (EQT2) obtained in Example 2, respectively;

[0023] Figure 4 This is a Rockwell hardness comparison chart of the conventional quenched and tempered high-speed steel (CQT) obtained in step (3) of Comparative Example 1, the W6Mo5Cr4V2Co5 high-speed steel (EQT1) obtained in Example 1, and the ASP30 high-speed steel (EQT2) obtained in Example 2;

[0024] Figure 5(a), 5(b), and 5(c) are comparison diagrams of the average wear depth of the conventional quenched and tempered high-speed steel (CQT) obtained in step (3) of Comparative Example 1, the W6Mo5Cr4V2Co5 high-speed steel (EQT1) obtained in Example 1, and the ASP30 high-speed steel (EQT2) obtained in Example 2, respectively;

[0025] Figure 6 (d) is a comparison chart of the wear rates of the conventional quenched and tempered high-speed steel (CQT) obtained in step (3) of Comparative Example 1, the W6Mo5Cr4V2Co5 high-speed steel (EQT1) obtained in Example 1, and the ASP30 high-speed steel (EQT2) obtained in Example 2. DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and in conjunction with specific embodiments. It should be noted that these embodiments are intended to illustrate the present invention rather than to limit it, and the scope of protection of the present invention is not limited to the following embodiments. Parameters in all the following embodiments are within the scope of protection of the claims.

[0027] Example 1

[0028] The commercial W6Mo5Cr4V2Co5 high-speed steel was first subjected to a pulse current austenitizing treatment and then to three pulse current gradient tempering treatments to obtain high-speed steel 1 (hereinafter referred to as EQT1). The process includes: 1 pulse current austenitizing treatment: voltage 40V, current 7.5×10 4 A / m 2 , the processing time is 1s; 3 pulse current gradient tempering treatments: the first treatment: voltage is 35V, current is 6.5×10 4 A / m 2 , processing time is 1.1s; second processing: voltage is 37V, current is 5.5×10 4 A / m 2 , processing time 1.2s; the third processing: voltage 39V, current 4.0×10 4 A / m 2 , processing time 1.7s. The test performance of EQT1 is as follows: Figure 1 It can be seen that the average size of carbides in EQT1 is small (~1.32 μm) and is evenly distributed in the matrix; Figure 2 and 3 It can be seen that the grain size of EQT1 is ~4.84 μm; Figure 4 It can be seen that the hardness of EQT1 is ~66.7HRC; Figure 5 It can be seen that the average wear depth of high-speed steel EQT1 is ~16.98μm. Figure 6It can be seen that the wear rate is ~1.88×10 -6 mm 3 N -1 m -1 .

[0029] Example 2

[0030] The commercial ASP30 high-speed steel was subjected to two pulse current austenitization treatments and then four pulse current gradient tempering treatments to obtain high-speed steel 2 (hereinafter referred to as EQT2). The process includes: the pulse current austenitization treatment is as follows: the first treatment: voltage 45V, current 7.8×10 4 A / m 2 , the processing time is 1.7s. The second processing: voltage is 52V, current is 6.4×10 4 A / m 2 The processing time is 1.3s; 4 pulse gradient current tempering treatments: the first treatment: voltage 38V, current 6.0×10 4 A / m 2 , processing time is 1.2s; second processing: voltage is 36V, current is 4.5×10 4 A / m 2 , processing time 1.8s, the third processing: voltage 41V, current 4.2×10 4 A / m 2 , the processing time is 2s. The fourth processing: voltage is 42V, current is 3.7×10 4 A / m 2 The processing time is 1.9s. The test performance of EQT2 is as follows: Figure 1 It can be seen from the figure that the carbides in EQT2 are small in size (1.48 μm) and evenly distributed in the matrix; Figure 2 and 3 It can be seen that the grain size of EQT2 is 5.83 μm. Figure 4 It can be seen that the hardness of EQT2 is ~66.3HRC; Figure 5 It can be seen that the average wear depth of high-speed steel EQT2 is ~19.23μm. Figure 6 It can be seen that the wear rate is ~2.84×10 -6 mm 3 N -1 m -1 .

[0031] Example 3

[0032] The commercial W6Mo5Cr4V2Co5 high-speed steel was first subjected to a pulse current austenitizing treatment and then to a pulse current gradient tempering treatment twice to obtain high-speed steel 3. The process includes: a pulse current austenitizing treatment: voltage 55V, current 7.6×10 4 A / m 2 , the processing time is 0.8s; 2 pulse current gradient tempering treatments: the first treatment: voltage is 44V, current is 4.7×10 4 A / m 2 , processing time is 1.6s; second processing: voltage is 46V, current is 3.8×10 4 A / m 2 The test properties of high-speed steel 3 are as follows: the average carbide size in high-speed steel 3 is ~1.6μm and is evenly distributed in the matrix; the grain size is ~5.92μm; the hardness is ~65.5HRC; the average wear depth is ~19.91μm, and the wear rate is ~2.96×10 -6 mm 3 N -1 m -1 .

[0033] Comparative Example 1

[0034] The steps of heat treating commercial W6Mo5Cr4V2Co5 high-speed steel in this comparative example are as follows:

[0035] (1) Austenitizing treatment

[0036] Commercial W6Mo5Cr4V2Co5 high-speed steel was heated to 1200°C at a heating rate of 10°C / min and held at this temperature for 5 minutes to obtain solid solution high-speed steel.

[0037] (2) Quenching treatment

[0038] Quenching the solid solution high speed steel obtained in step (1) in boiling water to obtain quenched W6Mo5Cr4V2Co5 high speed steel;

[0039] (3) Tempering

[0040] The quenched W6Mo5Cr4V2Co5 high-speed steel obtained in step (2) was kept at 550℃ for 2h and then air-cooled. This process was repeated three times to obtain the tempered W6Mo5Cr4V2Co5 high-speed steel (hereinafter referred to as CQT). Figure 1 It can be seen that the average size of carbides in CQT is 1.7 μm, and the carbides are distributed on the grain boundaries and are not uniformly distributed. Figure 2 and 3 It can be seen that the average grain size of CQT is 8.54 μm. Figure 4The CQT hardness is ~64.8HRC; Figure 5 The average wear depth is ~34.59 μm. Figure 6 It can be seen that the wear rate is ∼3.81×10 -6 mm 3 N -1 m -1 .

[0041] Comparative Example 2

[0042] This comparative example is based on the paper "Effect of deep cryogenic treatment on wear and galling properties of high-speed steels" by Patricia Joviˇcevi′c-Klug of the Institute of Metals and Technology, Slovenia, published in Materials in September 2021, cited on pages 3-7. The specific steps are as follows:

[0043] (1) Quenching treatment after austenitization

[0044] W6Mo5Cr4V2Co5 high-speed steel was kept at 1160 / 1230℃ for 2 minutes and then quenched with nitrogen at a pressure of 5 bar, with an average quenching rate of 7-8℃ / s.

[0045] (2) Then, the mixture was cryogenically treated by keeping it at -196°C for 24 hours.

[0046] (3) The post-treated W6Mo5Cr4V2Co5 high-speed steel sample was obtained by tempering once at 620 / 550℃ for 2h.

[0047] The difference between Comparative Example 2 and the present invention is that Comparative Example 2 adopts high-temperature austenitization followed by nitrogen quenching, followed by cryogenic treatment, and finally high-temperature tempering. After treatment, the W6Mo5Cr4V2Co5 high-speed steel obtains a hardness of 57HRC and a wear rate of 4.2×10 -6 mm 3 N -1 m -1 The minimum performance of the W6Mo5Cr4V2Co5 high-speed steel obtained by the present invention is: hardness ~65.5HRC; wear rate ~2.96×10 -6 mm 3 N -1 m -1, and has a finer grain size. Compared with Comparative Example 2, the minimum hardness and wear resistance of the high-speed steel obtained by the present invention are both higher than the optimal effect obtained in Comparative Example 2. Compared with Comparative Example 2, the grains obtained by the present invention are finer and a large number of fine-sized carbides are precipitated. Compared with the existing technology (strengthening time is generally more than several hours), the present invention can quickly strengthen the high-speed steel within 10 seconds, and the hardness and wear resistance are both higher than the high-speed steel obtained by the existing technology.

[0048] Comparative Example 3

[0049] In this comparative example, commercial ASP30 high-speed steel was subjected to pulse current treatment. The preparation steps included: first performing a pulse current austenitization treatment, and then performing a pulse current tempering treatment three times to obtain ASP30 high-speed steel 2. The process included: 1 pulse current austenitization: voltage 25V, current 2.1×10 4 A / m 2 , the processing time is 7s. 3 pulse current tempering treatments: each treatment voltage is 20V, the current is 2.5×10 4 A / m 2 The treatment time is 10s. The average carbide size of ASP30 high-speed steel 2 is ~2.3μm and is evenly distributed in the matrix; the grain size is ~7.92μm; the hardness is ~64HRC; the average wear depth is ~37.76μm, and the wear rate is ~3.92×10 -6 mm 3 N -1 m -1 .

[0050] Compared with the present invention, the process used in Comparative Example 3 is similar to that of the present invention, but the relevant parameters are not within the scope of protection of the claims of the present invention. As a result, the grain size, hardness and wear resistance of ASP30 high-speed steel 2 obtained in Comparative Example 3 are lower than those of EQT2 obtained in Example 2 of the present invention.

[0051] Compared with the prior art, the present invention achieves the following beneficial effects through the coordinated regulation of components, processes, and related process parameters: It simultaneously refines grains and carbides, creating a coupled effect of grain refinement and precipitation strengthening. The pulsed current promotes austenite nucleation, refining the original austenite grains in a very short time. During the cooling process, the fine original austenite grain boundaries result in a fine martensitic structure after quenching. Simultaneously, the martensitic transformation and thermal compressive stresses generate a large number of dislocations, which, as regions of high defect energy, provide nucleation sites for secondary carbides. This results in the precipitation of smaller secondary carbides with a higher volume fraction, which are evenly distributed throughout the matrix. The large number of precipitated secondary carbides achieves secondary strengthening, enhancing the metal's wear resistance. This invention eliminates the complex and time-consuming processing required by the prior art, simplifies the process, expands the process window for high-speed steel heat treatment, and addresses the problems of carbides distributed at grain boundaries, a small and uneven carbide count, and coarse grains in the high-speed steel obtained by the prior art. Ultimately, it simultaneously improves the material's hardness and wear resistance. In addition, it can be seen from the embodiments of the present invention that the process parameters of each embodiment are different, and the carbide, grain size, hardness, wear depth and wear rate of the material obtained in each embodiment are different, and the present invention has better mechanical properties than the prior art. In summary, the material with the best performance obtained by the present invention is achieved by the coordinated regulation of components, processes and parameters, and the best comprehensive performance can only be achieved within the scope of the claims of the present invention.

Claims

1. A high-wear-resistant high-speed steel, the preparation method of which comprises the following steps: (1) Commercial high-speed steel is subjected to wire cutting, sandpaper polishing, and then pulse current austenitization treatment and quenching to obtain quenched high-speed steel. The pulse current austenitization treatment is: 1-4 pulse current treatments, and the process of each pulse current treatment is: voltage 30-65V, current density 3×10 4 -8.8×10 4 A / m 2 , processing time 0.5-5s; (2) The quenched high-speed steel obtained in step (1) is subjected to a multi-gradient electric pulse tempering treatment to obtain a high-wear-resistant high-speed steel, wherein the multi-gradient electric pulse tempering treatment comprises 1 to 6 gradient electric pulse tempering treatments, each gradient electric pulse tempering treatment being performed at a voltage of 35 to 60 V and a current density of 3.1×10 4 -7.5×10 4 A / m 2 , processing time 0.6-4s.

2. The high wear-resistant high-speed steel according to claim 1, characterized in that: Its preparation method comprises the following steps: the high-speed steel described in step (1) is one of W6Mo5Cr4V2Co5 high-speed steel, ASP30 high-speed steel, W18Cr4V high-speed steel or Cr12MoV high-speed steel.

3. The high wear-resistant high-speed steel according to claim 1, characterized in that: The voltage in step (1) is 40-55V.

4. The high wear-resistant high-speed steel according to claim 1, characterized in that: The current density in step (1) is 5×10 4 -8×10 4 A / m 2 .

5. The high wear-resistant high-speed steel according to claim 1, characterized in that: The processing time of step (1) is 0.8-2s.

6. The high wear-resistant high-speed steel according to claim 1, characterized in that: The voltage in step (2) is 35-50V.

7. The high wear-resistant high-speed steel according to claim 1, characterized in that: The current density in step (2) is 3.3×10 4 -7×10 4 A / m 2 .

8. The high wear-resistant high-speed steel according to claim 1, characterized in that: The processing time of step (2) is 1-3s.

9. The high wear-resistant high-speed steel according to claim 1, characterized in that: The multi-gradient electric pulse tempering treatment described in step (2) is: 2-5 times gradient electric pulse tempering treatment.

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