High-wear-resistance high-speed steel and strengthening method thereof

Abstract

The invention relates to the field of high-speed steel heat treatment, and provides high-wear-resistance high-speed steel and a strengthening method thereof. The preparation method of the high-wear-resistance high-speed steel comprises the following steps: firstly carrying out pulse current austenitizing treatment on commercial high-speed steel, then quenching, and then carrying out pulse current multi-gradient tempering treatment. According to the method, the long-time and high-temperature heat treatment process is shortened, the cost and the energy consumption are reduced, the process is simplified, grains and carbides are refined at the same time through the cooperative regulation effect of the process and parameters, and the obtained high-speed steel is superior to the high-speed steel obtained through high-temperature and long-time treatment: austenitizing, quenching and tempering in the prior art in hardness and wear resistance, and has the good application prospect. The method is suitable for industrial production.

Description

Technical Field

[0001] The 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 occupies an important position in the cutting tool industry. With the development of the manufacturing industry, the cutting performance requirements of the tool are getting higher and higher. Therefore, it is urgent to find a way to improve the wear resistance of the tool material. Traditional austenitization and quenching and tempering treatment are common methods to improve the wear resistance of high-speed steel. After austenitization, quenching treatment can dissolve the elements into the matrix to obtain a supersaturated solid solution; after quenching, a high-strength martensite is obtained; after tempering treatment, a large amount of secondary carbides can be obtained by keeping the temperature at a specific temperature for a certain period of time, thereby improving the wear resistance of high-speed steel. However, the traditional heat treatment process needs to be carried out in heat treatment equipment such as heat treatment furnaces, and undergoes austenitization-quenching-multiple tempering and other processes, which consumes a lot of time and energy, which greatly reduces production efficiency and increases costs. Moreover, long-term heat treatment will cause carbides and grains in the high-speed steel organization to grow, limiting the improvement of the plasticity, toughness and wear resistance of high-speed steel. In addition, the content of residual austenite in high-speed steel after traditional heat treatment quenching is high, which seriously affects the hardness and dimensional stability of high-speed steel workpieces. 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, and its preparation method comprises the following steps:

[0004] (1) The commercial high-speed steel is subjected to wire cutting processing, 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 multi-gradient electric pulse tempering treatment to obtain 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 comprises: a voltage of 35 to 60 V, a current density of 3.1×10 4 -7.5×10 4 A / m 2, the processing time is 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] The present invention shortens the long-term, high-temperature heat treatment process, reduces costs and energy consumption, simplifies the process, and refines the grains and carbides at the same time through the coordinated regulation of the process and parameters. 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: austenitization + quenching + tempering), and is suitable for industrial production. The present invention achieves the following excellent results through the coordinated regulation of components and process parameters:

[0015] 1. The present invention adopts a combination of pulse current austenitization treatment and multi-gradient pulse current tempering treatment to strengthen high-speed steel within 10 seconds, and quickly improves the hardness and wear resistance of high-speed steel. In the prior art, if the hardness and wear resistance of high-speed steel are to be improved, high-temperature long-term austenitization, quenching and high-temperature long-term tempering treatment are required, which takes more than several hours. The present invention reduces the austenitization, quenching and tempering processes of traditional heat treatment, greatly reduces time and energy consumption costs, and avoids the defects of traditional heat treatment;

[0016] 2. The pulse current voltage used in the present invention is low, the current density is small, and a short process can be realized. The present invention is characterized by high energy efficiency, environmental protection, high safety, low maintenance cost, controllable relevant process parameters, and wide application range;

[0017] 3. The present invention uses 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 heating rate of the present invention is extremely fast, so that the dislocations generated by phase change and thermal compressive stress do not have enough time to annihilate, and are therefore 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, makes the carbides evenly distributed in the matrix, forms a coupling effect of fine grain strengthening and precipitation strengthening, and ultimately simultaneously improves 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 respectively 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;

[0021] Figure 2 (a1), 2(b1), 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), 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 is further described in detail below with reference to the accompanying drawings and in combination with specific embodiments. It should be noted that these embodiments are used to illustrate the present invention, rather than to limit the present invention, and the protection scope of the present invention is not limited to the following embodiments. The parameters of all the following embodiments are within the protection scope of the claims.

[0027] Example 1

[0028] The commercial W6Mo5Cr4V2Co5 high-speed steel was first subjected to a pulse current austenitizing treatment and then subjected to three pulse current gradient tempering treatments to obtain high-speed steel 1 (hereinafter referred to as EQT1). The process includes: a 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 austenitizing 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 austenitizing treatment is as follows: the first treatment: the voltage is 45V, the current is 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 is 38V, current is 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 ~19.23 μm. 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 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: the voltage is 44V, the current is 4.7×10 4 A / m 2 , the processing time is 1.6s; the second processing: voltage is 46V, current is 3.8×10 4 A / m 2 , the processing time is 1.4s. The test properties of high-speed steel 3 are as follows: the average size of carbides 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 treatment of commercial W6Mo5Cr4V2Co5 high speed steel in this comparative example are as follows:

[0035] (1) Austenitizing treatment

[0036] The commercial W6Mo5Cr4V2Co5 high-speed steel was heated to 1200℃, with a heating rate of 10℃ / min and a holding time of 5min to obtain a solid solution high-speed steel.

[0037] (2) Quenching treatment

[0038] The solid solution high speed steel obtained in step (1) is quenched 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°C 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 1.7μm, and the carbides are distributed on the grain boundaries without achieving uniform distribution. Figure 2 and 3 It can be seen that the average grain size of CQT is 8.54 μm. Figure 4The hardness of CQT 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 cited from the paper "Effect of deep cryogenic treatment on wear and galling properties of high-speed steels" by Patricia Joviˇcevi′c-Klug of the Slovenian Institute of Metals and Technology, published in Materials in September 2021, and the reference range is pages 3-7. The specific steps are as follows:

[0043] (1) Quenching after austenitizing

[0044] W6Mo5Cr4V2Co5 high speed steel was kept at 1160 / 1230℃ for 2min and then quenched with nitrogen at a pressure of 5bar, 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) After tempering once at 620 / 550℃ for 2h, the post-treated W6Mo5Cr4V2Co5 high-speed steel sample was obtained.

[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 has 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 is ~65.5HRC; wear rate is ~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 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 carbides are precipitated. Compared with the prior art (the 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 higher than the high-speed steel obtained by the prior art.

[0048] Comparative Example 3

[0049] In this comparative example, commercial ASP30 high-speed steel is subjected to pulse current treatment. The preparation steps include: firstly, a pulse current austenitizing treatment is performed once, and then a pulse current tempering treatment is performed three times to obtain ASP30 high-speed steel 2. The process includes: 1 pulse current austenitizing: voltage is 25V, current is 2.1×10 4 A / m 2 , the processing time is 7s. 3 times pulse current tempering treatment: 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 protection scope 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, related process parameters, etc.: the present invention simultaneously refines the grains and carbides, forming a coupling effect of fine grain strengthening and precipitation strengthening. The pulse current promotes the nucleation of austenite, and refines the original austenite grains in a very short time; during the cooling process, the fine original austenite grain boundaries enable the sample to obtain a fine martensite structure after quenching. At the same time, the martensitic phase transformation and the hot compressive stress produce a large number of dislocations, and the dislocations, as regions with higher defect energy, provide nucleation sites for secondary carbides. As a result, secondary carbides with smaller size and higher volume fraction are precipitated, and the carbides are evenly distributed in the matrix; a large number of precipitated secondary carbides achieve secondary strengthening and improve the wear resistance of the metal. The present invention breaks the complex and long-term processing of the prior art, simplifies the process, expands the process window of high-speed steel heat treatment, solves the problems of carbides distributed at grain boundaries, small and unevenly distributed carbides, and coarse grains in the high-speed steel obtained by the prior art, and finally improves the hardness and wear resistance of the material simultaneously. In addition, it can be seen from the embodiments of the present invention that the process parameters of each embodiment are different, the carbide, grain size, hardness, wear depth and wear rate of the material obtained in each embodiment are different, and the present invention has obtained 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 only within the scope of the claims of the present invention can the best comprehensive performance be achieved.

Claims

1. A high wear-resistant high-speed steel, the preparation method of which comprises the following steps: (1) The commercial high-speed steel is subjected to wire cutting processing, 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 multi-gradient electric pulse tempering treatment to obtain 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 comprises: a voltage of 35 to 60 V, 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 annealing treatment described in step (2) is: 2-5 times of gradient electric pulse annealing treatment.

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