High-speed steel post-processing method and application thereof

Abstract

The invention relates to the technical field of machining, in particular to a high-speed steel post-processing method and application thereof. The high-speed steel post-treatment method comprises the steps that after high-speed steel is cut and polished, at least two times of pulse current austenitizing treatment and at least two times of pulse current tempering treatment are sequentially conducted; wherein the voltage of each time of pulse current austenitizing treatment is 10-15 V, and the current is 15.5 * 10 < 6 >-18.8 * 10 < 6 > A / m < 2 >; the voltage of each time of pulse current tempering treatment is 12-17V, and the current is 16.1 * 10 < 6 >-20.1 * 10 < 6 > A / m < 2 >. By respectively controlling the voltage and the current of the pulse current austenitizing treatment and the pulse current tempering treatment, the hardness and the wear resistance of the high-speed steel are improved, the probability of occurrence of phenomena such as tipping and failure in the machining process is reduced, the machining efficiency and the machining precision are improved, and meanwhile, the machining cost is reduced. And the processing cost and the use cost are reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mechanical processing, in particular to a high-speed steel post-processing method and application thereof. BACKGROUND

[0002] With the rapid development of electric vehicles, the precision requirements of the battery pack lower box in mechanical processing are becoming more and more strict. Therefore, it is particularly important to improve the processing efficiency and the processing precision.

[0003] High-speed cutting is widely used in the field of mechanical processing of electric drive and battery pack box, and the working environment of the tool becomes complex. When processing aluminum alloy, the tool wears faster, and it is urgent to find a method to improve the mechanical properties of tool materials to reduce tool grinding and replacement, improve processing efficiency and reduce processing cost.

[0004] Therefore, the present application is proposed. SUMMARY

[0005] The first object of the present application is to provide a high-speed steel post-processing method, which can improve the hardness and wear resistance of high-speed steel by controlling the voltage and current of pulse current austenitizing treatment and pulse current tempering treatment respectively, reduce the probability of occurrence of phenomena such as edge collapse and failure in the mechanical processing process, and is suitable for the mechanical processing process of electric drive and battery pack box, thereby improving the processing efficiency and the processing precision, and reducing the processing cost and the use cost.

[0006] The second object of the present application is to provide the application of the high-speed steel post-processing method in the field of mechanical processing.

[0007] In order to achieve the above object of the present application, the following technical scheme is adopted: The present application first provides a high-speed steel post-processing method, comprising the following steps: after high-speed steel is cut and polished, at least two pulse current austenitizing treatments are performed to obtain an intermediate steel material; wherein the voltage of each pulse current austenitizing treatment is 10-15V, and the current is 15.5x10 6 ~18.8x10 6 A / m 2 ; further, the intermediate steel material is subjected to at least two pulse current tempering treatments to obtain a processed high-speed steel; wherein the voltage of each pulse current tempering treatment is 12-17V, and the current is 16.1x10 6 ~20.1x10 6 A / m 2 .

[0008] Further, the voltage of each pulse current austenitizing treatment is 13.5-14.5V.

[0009] Further, the voltage of each pulse current austenitizing treatment is 10~15V. 6 Further, the voltage of each pulse current austenitizing treatment is 10~15V. 6 A / m 2 .

[0010] Further, the processing time of each pulse current austenitizing treatment is 2~5s.

[0011] Further, the number of pulse current austenitizing treatments is 3~5 times.

[0012] Further, the processing time of each pulse current austenitizing treatment is 2.8~4.2s.

[0013] Further, the number of pulse current austenitizing treatments is 3~4 times.

[0014] Further, the voltage of each pulse current tempering treatment is 13~15V.

[0015] Further, the current of each pulse current tempering treatment is 16×10 6 ~18×10 6 A / m 2 .

[0016] Further, the processing time of each pulse current tempering treatment is 3~6s.

[0017] Further, the number of pulse current tempering treatments is 5~10 times.

[0018] Further, the processing time of each pulse current tempering treatment is 3~5s.

[0019] Further, the number of pulse current tempering treatments is 5~8 times.

[0020] Further, the high-speed steel comprises W6Mo5Cr4V2Co5 high-speed steel or ASP30 high-speed steel.

[0021] The application further provides application of the high-speed steel post-processing method in the field of mechanical processing.

[0022] Compared with the prior art, the application has the following beneficial effects: (1) The application can improve the hardness and wear resistance of the high-speed steel, reduce the probability of occurrence of phenomena such as edge collapse and failure in the mechanical processing process, improve the processing efficiency and processing precision, and reduce the processing cost and use cost.

[0023] (2) The pulse voltage used in the application is low, the current density is small, and the experiment is convenient, and the application can realize the refinement of high-speed steel grains, effectively improve the number of small-size carbides, and finally simultaneously improve the hardness and wear resistance of the high-speed steel through the synergistic regulation of process and parameters.

[0024] (3) In the application, the combination of pulse current austenitizing treatment and pulse current tempering treatment can realize the rapid strengthening of high-speed steel. If the prior art wants to realize the strengthening of high-speed steel, austenitizing, quenching and high-temperature tempering treatment are needed, and the austenitizing and tempering treatment cycle is long, which needs nearly ten hours. The pulse current treatment of the application discards the austenitizing, quenching and tempering process of the traditional heat treatment, greatly reduces the time cost, and avoids the defects easily produced by the traditional heat treatment.

[0025] (4) Compared with the traditional quenching and tempering process, the pulse current treatment process of the application obtains high-hardness and high-wear-resistance high-speed steel in a short time, the post-treatment method of the high-speed steel of the application has high efficiency, is environmentally friendly, has high safety, has low maintenance cost, and the related process parameters are controllable and have wide application range.

[0026] (5) The strengthening method provided by the application is low-voltage alternating current strengthening, and compared with the prior art, the treatment time is shorter and the treatment times are fewer. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the specific embodiments of the application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0028] Figure 1 The carbide morphology distribution graph of the treated W6Mo5Cr4V2Co5 high-speed steel obtained in Example 1 provided by the application is shown in the figure; Figure 2 The grain size distribution graph of the treated W6Mo5Cr4V2Co5 high-speed steel obtained in Example 1 provided by the application is shown in the figure; Figure 3 The carbide morphology distribution graph of the treated ASP30 high-speed steel obtained in Example 2 provided by the application is shown in the figure; Figure 4 The carbide morphology distribution graph of the treated W6Mo5Cr4V2Co5 high-speed steel obtained in Example 3 provided by the application is shown in the figure. DETAILED DESCRIPTION

[0029] The technical solutions of the present application will be described clearly and completely below in combination with the drawings and specific embodiments, but those skilled in the art will understand that the following described embodiments are part of the embodiments of the present application, not all the embodiments, and are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. If the specific conditions are not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are used. If the manufacturers of the reagents or instruments used are not specified, they are all conventional products that can be purchased on the market.

[0030] If not specifically stated, in the present application, "first aspect", "second aspect", "third aspect", "fourth aspect" and the like are only used for description purposes, and cannot be understood as indicating or implying relative importance or quantity, nor can it be understood as implying the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth" and the like only serve the purpose of non-exhaustive enumeration and description, and should be understood as not constituting a closed limitation on the quantity.

[0031] If not specifically stated, "including" and "containing" mentioned in the present application mean open-ended, and can also be closed-ended. For example, "including" and "containing" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0032] If not specifically stated, in the present application, "one or more" or "at least one" means any one, any two or any two or more of the listed items. Among them, "several" means any two or more.

[0033] In a first aspect, the present application provides a high-speed steel post-processing method, comprising the following steps: After cutting and polishing the high-speed steel in an annealed state, at least two pulse current austenitizing treatments are carried out to obtain an intermediate steel material.

[0034] Among them, the voltage of each pulse current austenitizing treatment is 10-15V, including but not limited to any one of 10V, 11V, 12V, 13V, 14V, 15V or a range value between any two of them.

[0035] The current of each pulse current austenitizing treatment is 15.5×10 6 -18.8×10 6 A / m 2 , including but not limited to 15.5×10 6 A / m 2 , 16×10 6 A / m2 , 16.5 x 10 6 A / m 2 , 17 x 10 6 A / m 2 , 17.5 x 10 6 A / m 2 , 18 x 10 6 A / m 2 , 18.5 x 10 6 A / m 2 , 18.8 x 10 6 A / m 2 , 19 x 10 6 A / m 6 , 19.5 x 10 2 A / m 6 , 20 x 10 2 A / m 6 , 20.1 x 10 2 A / m 6 , including but not limited to any one of the point values or a range value between any two of 12 V, 13 V, 14 V, 15 V, 16 V, 17 V.

[0036] The cutting method includes but is not limited to wire cutting.

[0037] The polishing method includes but is not limited to sandpaper polishing, and the polishing is to bright.

[0038] Subsequently, the intermediate steel material is subjected to at least two pulse current tempering treatments to obtain a treated high-speed steel with good wear resistance.

[0039] The voltage of each pulse current tempering treatment is 12-17 V, including but not limited to any one of the point values or a range value between any two of 12 V, 13 V, 14 V, 15 V, 16 V, 17 V.

[0040] The current of each pulse current tempering treatment is 16.1 x 10 6 -20.1 x 10 6 A / m 2 , including but not limited to any one of the point values or a range value between any two of 16.5 x 10 6 A / m 2 , 17 x 10 6 A / m 2 , 17.5 x 10 6 A / m 2 , 18 x 10 6 A / m 2 , 18.5 x 10 6 A / m 2 , 19 x 10 6 A / m 2 , 19.5 x 10 6 A / m 2 , 20 x 10 6 A / m 2 , 20.1 x 10 6 A / m 2 .

[0041] The application can improve the hardness and wear resistance of high-speed steel, reduce the probability of phenomena such as edge collapse and failure occurring in the machining process, improve machining efficiency and machining precision, and reduce machining cost and use cost by respectively controlling the voltage and current of pulse current austenitizing treatment and pulse current tempering treatment.

[0042] The pulse voltage used in the application is low, the current density is small, and the experiment is convenient. The application can refine high-speed steel grains, effectively increase the number of small-size carbides, and ultimately simultaneously improve the hardness and wear resistance of high-speed steel by synergistic regulation of process and parameters. That is, the application can make high-speed steel obtain mechanical properties superior to traditional quenching and tempering treatment samples, especially high hardness and high wear resistance, by optimizing the process parameters of pulse current austenitizing treatment and pulse current tempering treatment.

[0043] Moreover, the application discards the long post-processing process, omits the traditional heat treatment processes such as austenitizing, quenching, and tempering which take a long time, shortens the process flow, and reduces production cost, which is conducive to strengthening the industrial production of high-speed steel.

[0044] In some specific embodiments, in order to further improve the hardness and wear resistance of high-speed steel, the voltage of the pulse current austenitizing treatment each time is 13.5-14.5V, including but not limited to any one of the point values of 13.5V, 13.8V, 14V, 14.2V, and 14.5V or a range value between any two of them.

[0045] In some specific embodiments, in order to further improve the hardness and wear resistance of high-speed steel, the current of the pulse current austenitizing treatment each time is 17x10 6 -18x10 6 A / m 2 , including but not limited to any one of the point values of 17x10 6 A / m 2 , 17.2x10 6 A / m 2 , 17.5x10 6 A / m 2 , 17.8x10 6 A / m 2 , and 18x10 6 A / m 2 or a range value between any two of them.

[0046] In some specific embodiments, in order to further improve the hardness and wear resistance of high-speed steel, the treatment time of the pulse current austenitizing treatment each time is 2-5s, including but not limited to any one of the point values of 2s, 3s, 4s, and 5s or a range value between any two of them.

[0047] In some specific embodiments, in order to further improve the hardness and wear resistance of the high speed steel, the number of the pulse current austenitizing treatment is 3-5, including but not limited to any one of the point values of 3, 4, 5 or the range value between any two of them.

[0048] In some specific embodiments, the treatment time of each pulse current austenitizing treatment is 2.8-4.2 s, including but not limited to any one of the point values of 2.8 s, 3 s, 3.5 s, 4 s, 4.2 s or the range value between any two of them.

[0049] In some specific embodiments, the number of the pulse current austenitizing treatment is 3-4.

[0050] In some specific embodiments, in order to further improve the hardness and wear resistance of the high speed steel, the voltage of each pulse current tempering treatment is 13-15 V, including but not limited to any one of the point values of 13 V, 13.5 V, 14 V, 14.5 V, 15 V or the range value between any two of them.

[0051] In some specific embodiments, in order to further improve the hardness and wear resistance of the high speed steel, the current of each pulse current tempering treatment is 16×10 6 -18×10 6 A / m 2 , including but not limited to any one of the point values of 16×10 6 A / m 2 , 16.3×10 6 A / m 2 , 16.5×10 6 A / m 2 , 16.8×10 6 A / m 2 , 17×10 6 A / m 2 , 17.2×10 6 A / m 2 , 17.5×10 6 A / m 2 , 17.8×10 6 A / m 2 , 18×10 6 A / m 2 or the range value between any two of them.

[0052] In some specific embodiments, in order to further improve the hardness and wear resistance of the high-speed steel, the processing time of each pulse current tempering treatment is 3-6s, including but not limited to any one of 3s, 3.5s, 4s, 4.5s, 5s, 5.5s, 6s or a range value between any two of them.

[0053] In some specific embodiments, in order to further improve the hardness and wear resistance of the high-speed steel, the number of pulse current tempering treatments is 5-10 times, including but not limited to any one of 5 times, 6 times, 7 times, 8 times, 9 times, 10 times or a range value between any two of them.

[0054] In some specific embodiments, the processing time of each pulse current tempering treatment is 3-5s, including but not limited to any one of 3s, 3.2s, 3.5s, 3.8s, 4s, 4.3s, 4.5s, 4.8s, 5s or a range value between any two of them.

[0055] In some specific embodiments, the number of pulse current tempering treatments is 5-8 times, including but not limited to any one of 5 times, 6 times, 7 times, 8 times or a range value between any two of them.

[0056] The high-speed steel post-treatment method (strengthening method) provided by the application is low-voltage alternating current strengthening, and has shorter processing time and fewer processing times.

[0057] In some specific embodiments, the high-speed steel includes W6Mo5Cr4V2Co5 high-speed steel or ASP30 high-speed steel.

[0058] The application can improve the strength and hardness of high-speed steel, and the effect of improving the strength, hardness and wear resistance of high-speed steel by electrical treatment is better.

[0059] In a second aspect, the application provides the application of the above high-speed steel post-treatment method in the field of mechanical processing.

[0060] The high-speed steel post-treatment method provided by the application is suitable for the field of mechanical processing such as electric drive and battery pack box, and can improve the mechanical properties of high-speed steel.

[0061] The embodiments of the application will be described in detail below with reference to the examples, but those skilled in the art will understand that the following examples are only for illustration of the application and should not be regarded as limiting the scope of the application. If the specific conditions are not specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be obtained by purchase.

[0062] Example 1 The high-speed steel post-processing method provided in this embodiment includes the following steps: The annealed W6Mo5Cr4V2Co5 high-speed steel was wire-cut and polished with sandpaper. Then, it underwent four pulse current austenitization treatments and seven pulse current tempering treatments to obtain the treated high-speed steel.

[0063] In each pulsed current austenitizing treatment, the voltage was 12V and the current was 17.2×10⁻⁶. 6 A / m 2 The processing time for all cases is 4 seconds.

[0064] The voltage for each pulse current tempering process is 14V, and the current is 18.5 × 10⁻⁶. 6 A / m 2 Each processing session takes 5 seconds.

[0065] Figure 1 This is a carbide morphology distribution diagram of the processed W6Mo5Cr4V2Co5 high-speed steel obtained in Example 1 of this invention. Figure 1 It can be seen that the average size of the carbides is 2.78 μm and they are evenly distributed in the matrix.

[0066] Figure 2 This is a grain size distribution diagram of the processed W6Mo5Cr4V2Co5 high-speed steel obtained in Example 1 of this invention. (The diagram is presented in the original text.) Figure 2 It can be seen that the average grain size is 7.83 μm.

[0067] Example 2 The post-processing method for high-speed steel provided in this embodiment is basically the same as that in Embodiment 1, except that the annealed W6Mo5Cr4V2Co5 high-speed steel is replaced with annealed ASP30 high-speed steel.

[0068] Figure 3 This is a carbide morphology distribution diagram of the processed ASP30 high-speed steel obtained in Example 2 of this invention. (The diagram is presented in the original text.) Figure 3 It can be seen that the average size of the carbides is 2.56 μm and they are evenly distributed in the matrix.

[0069] Example 3 The high-speed steel post-processing method provided in this embodiment includes the following steps: The annealed W6Mo5Cr4V2Co5 high-speed steel was wire-cut and polished with sandpaper. Then, it underwent three pulse current austenitization treatments and eight pulse current tempering treatments to obtain the treated high-speed steel.

[0070] In each pulsed current austenitizing treatment, the voltage was 13V and the current was 17.6×10⁻⁶.6 A / m 2 , the processing time is 4.5 s.

[0071] The voltage of each pulse current tempering treatment is 13 V, and the current is 16.7 x 10 6 A / m 2 , and the processing time is 5 s.

[0072] Figure 4 Figure 2 is a carbide morphology distribution diagram of the treated W6Mo5Cr4V2Co5 high-speed steel obtained in Example 3. By means of Figure 4 It can be seen that the average size of the carbide is 2.8 μm, and the carbide is uniformly distributed in the matrix.

[0073] Example 4 The high-speed steel post-treatment method provided in the example is basically the same as that in Example 1, except that the voltage of each pulse current austenitizing treatment is 14 V, and the current is 18 x 10 6 A / m 2 , and the processing time is 3 s.

[0074] Example 5 The high-speed steel post-treatment method provided in the example is basically the same as that in Example 1, except that the voltage of each pulse current austenitizing treatment is 10 V, and the current is 16 x 10 6 A / m 2 , and the processing time is 2 s.

[0075] Example 6 The high-speed steel post-treatment method provided in the example is basically the same as that in Example 1, except that the number of pulse current austenitizing treatments is 5 times, and the voltage of each pulse current austenitizing treatment is 15 V, and the current is 18.5 x 10 6 A / m 2 , and the processing time is 5 s.

[0076] Example 7 The high-speed steel post-treatment method provided in the example is basically the same as that in Example 1, except that the voltage of each pulse current tempering treatment is 15 V, and the current is 18 x 10 6 A / m 2 , and the processing time is 4 s.

[0077] Example 8 The high-speed steel post-treatment method provided in the example is basically the same as that in Example 1, except that the voltage of each pulse current tempering treatment is 12 V, and the current is 16.1 x 10 6 A / m 2 , and the processing time is 6 s.

[0078] Example 9 The high speed steel post-treatment method provided in this example is basically the same as that in Example 1, except that the number of pulse current tempering treatments is 5, and the voltage and current of each pulse current tempering treatment are 17 V and 20 x 10 6 A / m 2 respectively, and the treatment time of each treatment is 3 s.

[0079] Comparative Example 1 The high speed steel post-treatment method provided in this comparative example is basically the same as that in Example 1, except that the voltage and current of each pulse current austenitizing treatment are 25 V and 10 x 10 4 A / m 2 respectively.

[0080] Comparative Example 2 The high speed steel post-treatment method provided in this comparative example is basically the same as that in Example 1, except that the voltage and current of each pulse current austenitizing treatment are 12 V and 25 x 10 6 A / m 2 respectively.

[0081] Comparative Example 3 The high speed steel post-treatment method provided in this comparative example is basically the same as that in Example 1, except that the voltage and current of each pulse current tempering treatment are 20 V and 10 x 10 4 A / m 2 respectively.

[0082] Comparative Example 4 The high speed steel post-treatment method provided in this comparative example is basically the same as that in Example 1, except that the voltage and current of each pulse current tempering treatment are 14 V and 25 x 10 6 A / m 2 respectively.

[0083] Experimental Example The hardness and wear resistance of the treated high speed steels obtained in each example and each comparative example were tested, and the results are shown in Table 1.

[0084] Table 1 Hardness and wear resistance test results of each treated high speed steel

[0085] As can be seen from Table 1, compared with each comparative example, the treated high speed steel obtained in each example has higher hardness and wear resistance.

[0086] In each pulse current austenitizing treatment and pulse current tempering treatment of each comparative example, the voltage or current is not appropriate, resulting in no obvious electron wind effect, the temperature of the sample cannot be increased to the austenitizing temperature range in the pulse current austenitizing process, and the residual austenite content increases after incomplete cooling; in the pulse tempering process, the content of residual austenite converted into martensite is less, resulting in low hardness and poor wear resistance of the sample.

[0087] It can be seen that, by controlling the voltage and current of the pulse current austenitizing treatment and the pulse current tempering treatment respectively, the hardness and wear resistance of the high-speed steel can be effectively improved.

[0088] At the same time, by Figures 1-4 As can be seen from the above and Table 1, the hardness and wear resistance of the high-speed steel obtained by each embodiment of the present application are higher, which is due to the synergistic effect of the fine grains and a large amount of carbide precipitated to pin dislocations, so that the high-speed steel obtained by the present application has excellent hardness and wear resistance. Therefore, the present application can realize the rapid strengthening of high-speed steel (short treatment time and less treatment times), and the hardness and wear resistance are higher than those of the high-speed steel obtained by the prior art.

[0089] Although the present application has been illustrated and described with reference to specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced equivalently without departing from the spirit and scope of the present application; these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application; therefore, this means that all these replacements and modifications within the scope of the present application are included in the appended claims.

Claims

1. A method of post-treating a high speed steel, characterized in that, The method comprises the following steps: The high-speed steel is cut and polished, and then subjected to at least two pulse current austenitizing treatments to obtain an intermediate steel material; wherein the voltage of each pulse current austenitizing treatment is 10-15 V, the current is 15.5×10 6 ~18.8×10 6 A / m 2 ; The intermediate steel material is subjected to at least two pulse current tempering treatments to obtain a treated high-speed steel; wherein the voltage of each pulse current tempering treatment is 12-17 V, the current is 16.1×10 6 ~20.1×10 6 A / m 2 .

2. The method of claim 1, wherein the high speed steel post treatment process is characterized by, The voltage of each pulse current austenitizing treatment is 13.5-14.5V; And / or, the current for each pulsed current austenitizing treatment is 17 × 10⁻⁶. 6 ~18×10 6 A / m 2 .

3. The method of claim 1, wherein the high speed steel post treatment process is characterized by, The treatment time of each pulse current austenitizing treatment is 2-5s; And / or, the number of pulse current austenitizing treatments is 3-5 times.

4. The method of claim 3, wherein the high speed steel post treatment process is characterized by, The treatment time of each pulse current austenitizing treatment is 2.8-4.2s; And / or, the number of pulse current austenitizing treatments is 3-4 times.

5. The method of claim 1, wherein the high speed steel post treatment process is characterized by, The voltage of each pulse current tempering treatment is 13-15V; and / or, the current of each of the pulse current tempering treatments is 16 x 10 6 A / m 6 A / m 2 .

6. The method of claim 1, wherein the high speed steel post treatment process is characterized by, The treatment time of each pulse current tempering treatment is 3-6s; And / or, the number of pulse current tempering treatments is 5-10 times.

7. The high speed steel post-processing method according to claim 6, wherein The treatment time of each pulse current tempering treatment is 3-5s.

8. The method of claim 6, wherein the high speed steel post treatment process is characterized by, The number of pulse current tempering treatments is 5-8 times.

9. The method of claim 1-8, wherein the high speed steel is post treated by, The high-speed steel comprises W6Mo5Cr4V2Co5 high-speed steel or ASP30 high-speed steel.

10. Application of the high-speed steel post-treatment method according to any one of claims 1-9 in the field of machining.

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