Vacuum gas quenching process of T15 steel and T15 steel

Abstract

This application relates to the field of vacuum heat treatment technology, specifically disclosing a vacuum air quenching strengthening process for T15 steel, including the following steps: vacuum annealing, vacuum air quenching, and vacuum tempering. The vacuum air quenching steps are as follows: the T15 steel workpiece is placed in a furnace and a vacuum is drawn; then the temperature is increased to 650±10℃ at a rate of ≤10℃ / min and held for 60±5min; then the temperature is increased to 850±10℃ at a rate of ≤10℃ / min and held for 30±5min; the temperature is further increased to 1050±10℃ at a rate of ≤10℃ / min and held for 20±5min; finally, the temperature is increased to 1220±10℃ at a rate of ≤5℃ / min and held for 20±5min; after completion, nitrogen is used for cooling to below 60℃, and the charging pressure is set to 5500-6000mbar. The vacuum air quenching strengthening process for T15 steel of this application can obtain T15 steel with a Rockwell hardness >66HRC.

Description

Technical Field

[0001] This application relates to the field of vacuum heat treatment technology, specifically to a vacuum quenching strengthening process for T15 steel and T15 steel. Background Technology

[0002] T15 steel is a high-performance powder metallurgy tungsten-based high-speed steel. Due to its excellent performance at high temperatures and extremely high hardness, it is widely used in the manufacture of various precision cutting tools, such as taps, bimetallic saw blades, roughing end mills, drills, and inserts. This material can be quenched at temperatures close to its melting point, and rapid cooling at high temperatures allows the alloy carbides to fully dissolve in the austenitic matrix, thereby significantly improving the material's hardness and strength.

[0003] To ensure T15 steel achieves optimal performance in practical applications, traditional heat treatment methods typically include vacuum annealing, oil quenching, and tempering. Vacuum annealing primarily relieves stress and improves microstructure uniformity, while oil quenching achieves high hardness and wear resistance through rapid cooling. However, in actual production, oil quenching suffers from severe environmental pollution and workpiece distortion. Therefore, more and more companies are turning to the more environmentally friendly and efficient vacuum quenching process. While existing vacuum quenching technologies can address environmental pollution and workpiece deformation, the hardness of the final product often falls short of expectations, especially in applications requiring extremely high hardness and wear resistance.

[0004] Therefore, it is particularly important to develop a vacuum quenching strengthening process that can effectively improve the hardness and strength of T15 steel. Summary of the Invention

[0005] To further improve the hardness of T15 steel, this application provides a vacuum quenching strengthening process for T15 steel and T15 steel itself.

[0006] Firstly, this application provides a vacuum quenching strengthening process for T15 steel, employing the following technical solution: A vacuum air quenching strengthening process for T15 steel includes the following steps: vacuum annealing, vacuum air quenching, and vacuum tempering; The vacuum air quenching process is as follows: The T15 steel workpiece after vacuum annealing is placed in the furnace and a vacuum is drawn; then, the temperature is increased to 650±10℃ at a rate of ≤10℃ / min and held for 60±5min; then, the temperature is increased to 850±10℃ at a rate of ≤10℃ / min and held for 30±5min. After the holding period begins, nitrogen gas is used to protect the workpiece, with a nitrogen pressure of 95-105Pa; the temperature is continued to increase to 1050±10℃ at a rate of ≤10℃ / min and held for 20±5min; finally, the temperature is increased to 1220±10℃ at a rate of ≤5℃ / min and held for 20±5min; after the process, nitrogen gas is used to cool the workpiece to below 60℃, with the charging pressure set to 5500-6000mbar and the charging time 10±3s.

[0007] This application provides a vacuum air quenching strengthening process for T15 steel. This process features high quenching pressure, high quenching rate, and good quenching effect, significantly improving the hardness of T15 steel and thus enhancing its wear resistance during use. Specifically, this application ensures that the alloy carbides (M6C) are fully dissolved into the austenite matrix by gradually controlling the heating rate and holding time at each stage during vacuum quenching under vacuum conditions, thereby increasing the hardening degree of the material. Simultaneously, nitrogen purging at high temperatures effectively prevents oxidation of the workpiece surface, ensuring the purity and performance stability of the material. Finally, by controlling the purging pressure and cooling, a fine and uniform microstructure is formed inside the material, further enhancing the comprehensive mechanical properties of T15 steel.

[0008] In some embodiments, the nitrogen charging pressure during the vacuum air quenching step can be 5500-5600mba, 5500-5700mba, 5500-5800mba, 5500-5900mba, 5500-6000mba, 5600-5700mba, 5600-5800mba, 5600-5900mba, 5600-6000mba, 5700-5800mba, 5700-5900mba, 5700-6000mba, 5800-5900mba, 5800-6000mba, or 5900-6000mba.

[0009] In one specific implementation, the nitrogen charging pressure during the vacuum quenching step can also be 5500mba, 5600mba, 5700mba, 5800mba, 5900mba, or 6000mba.

[0010] Optionally, the vacuum annealing step is as follows: the pretreated T15 steel workpiece is placed in the furnace, and a vacuum is drawn to (4-6)×10. -3Pa; then raise the temperature to 850±10℃ at a rate of ≤10℃ / min and hold for 110±5min; after the end, slowly lower the temperature to 720±10℃ at a rate of ≤1℃ / min, and finally cool it down to 50-70℃ with the furnace.

[0011] Optionally, the vacuum tempering step is as follows: after the gas-quenched T15 steel workpiece is placed in the furnace, a vacuum is drawn to (4-6)×10. - 3 Pa, with a heating rate of ≤15℃ / min to 540±10℃, and held at that temperature for 180±5min; after the end, purge with nitrogen and cool to below 60℃, with the purge pressure set to 300-500mbar.

[0012] In this application, the nitrogen charging pressure during the vacuum tempering process also affects the hardness of T15 steel. When the stamping pressure is too low, the tempering gas quenching cooling rate is low, leading to coarsening of the microstructure and a decrease in material hardness. Conversely, when the stamping pressure is too high, the cooling rate is too fast, generating residual stress and making cracking more likely. Therefore, the inventors of this application discovered through experiments that setting the charging pressure within the aforementioned range allows for the production of T15 steel with a Rockwell hardness > 66 HRC.

[0013] In some embodiments, the nitrogen charging pressure during the nitrogen cooling process in the vacuum tempering step can be 300-350mba, 300-400mba, 300-450mba, 300-500mba, 350-400mba, 350-450mba, 350-500mba, 400-450mba, 400-500mba, or 450-500mba.

[0014] In one specific implementation, the nitrogen charging pressure during the nitrogen cooling process in the vacuum tempering step can also be 300mba, 350mba, 400mba, 450mba, or 500mba.

[0015] Optionally, the vacuum tempering is performed 3-5 times.

[0016] In some implementations, the vacuum tempering is performed 3-4 times or 4-5 times.

[0017] In one specific implementation, the vacuum tempering is performed 3, 4, or 5 times.

[0018] Optionally, in the vacuum annealing, vacuum air quenching, and vacuum tempering steps, the pressure after vacuuming is (4-6)×10⁻⁶. -3 Pa.

[0019] Optionally, the vacuum quenching strengthening process further includes pretreatment, specifically: first, cleaning the T15 steel workpiece with anhydrous ethanol and deionized water, and then drying it with a blower.

[0020] Optionally, the chemical composition of the T15 steel is W12Cr4V5Co5.

[0021] Secondly, this application provides a vacuum quenching strengthening process for obtaining T15 steel.

[0022] Optionally, the Rockwell hardness of the T15 steel is >66HRC.

[0023] In summary, this application has the following beneficial effects: 1. This application provides a vacuum quenching strengthening process for T15 steel. The vacuum quenching strengthening process for T15 steel obtains T15 steel with a Rockwell hardness > 66HRC by controlling the heating rate, temperature, holding time and the charging pressure during the nitrogen cooling process in the vacuum quenching step.

[0024] 2. This application further controls the charging pressure during the nitrogen cooling process in the vacuum air quenching step within the range of 5700-5900 mbar, resulting in T15 steel with higher hardness, and its Rockwell hardness ≥66.5HRC.

[0025] 3. This application further controls the nitrogen charging pressure during the nitrogen cooling process in the vacuum tempering step within the range of 350-450 mbar, resulting in higher hardness of the obtained T15 steel, with its Rockwell hardness reaching above 67.0 HRC. Detailed Implementation

[0026] This application provides a vacuum quenching strengthening process for T15 steel, comprising the following steps: (1) Pretreatment: First, clean the T15 steel workpiece with anhydrous ethanol and deionized water, and then dry it with a blower; (2) Vacuum annealing: The pretreated T15 steel workpiece is placed in the furnace and vacuumed to (4-6)×10 -3 Pa; then raise the temperature to 850±10℃ at a rate of ≤10℃ / min and hold for 110±5min; after the end, slowly lower the temperature to 720±10℃ at a rate of ≤1℃ / min, and finally cool it down to 50-70℃ with the furnace. (3) Vacuum quenching: The annealed T15 steel workpiece is placed in the furnace and vacuumed to (4-6)×10⁻⁶. -3Pa; then raise the temperature to 650±10℃ at a rate of ≤10℃ / min and hold for 60±5min; then raise the temperature to 850±10℃ at a rate of ≤10℃ / min and hold for 30±5min. After the holding period begins, purge the workpiece with nitrogen at a pressure of 95-105Pa; continue raising the temperature to 1050±10℃ at a rate of ≤10℃ / min and hold for 20±5min; finally, raise the temperature to 1220±10℃ at a rate of ≤5℃ / min and hold for 20±5min; after the end of the process, purge with nitrogen and cool to below 60℃. The purging pressure is set to 5500-6000mbar and the purging time is 10±3s. (4) Vacuum tempering: After the gas-quenched T15 steel workpiece is placed in the furnace, a vacuum is drawn to (4-6)×10. -3 Heat the temperature to 540±10℃ at a rate of ≤15℃ / min and hold for 180±5min. After that, cool the temperature to below 60℃ with nitrogen gas and set the charging pressure to 300-500mbar r. Perform vacuum tempering 3-5 times according to the above steps.

[0027] In this application, the chemical composition of T15 steel is W12Cr4V5Co5. All raw materials, reagents, and solvents used in this application are commercially available.

[0028] The present application will be further described in detail below with reference to embodiments and performance testing.

[0029] Example 1 Example 1 provides a vacuum quenching strengthening process for T15 steel, including the following steps: (1) Pretreatment: First, clean the T15 steel workpiece with anhydrous ethanol and deionized water, and then dry it with a blower; (2) Vacuum annealing: The pretreated T15 steel workpiece is placed in the furnace and vacuumed to 5×10⁻⁶. -3 Pa; then raise the temperature to 850℃ at a rate of 5℃ / min and hold for 110min; after the end, slowly lower the temperature to 720℃ at a rate of 0.5℃ / min, and finally cool it to 60℃ with the furnace; (3) Vacuum quenching: the annealed T15 steel workpiece is put into the furnace and vacuumed to 5×10 -3 Pa; then raise the temperature to 650℃ at a rate of 8℃ / min and hold for 60min; then raise the temperature to 850℃ at a rate of 8℃ / min and hold for 30min. After the holding period begins, purge the workpiece with nitrogen at a pressure of 100Pa; continue raising the temperature to 1050℃ at a rate of 8℃ / min and hold for 20min; finally, raise the temperature to 1220℃ at a rate of 3℃ / min and hold for 20min; after the end, purge with nitrogen and cool to 50℃. The purging pressure is set to 5500mbar and the purging time is 10s. (4) Vacuum tempering: After the gas-quenched T15 steel workpiece is placed in the furnace, a vacuum of 5×10⁻⁶ is drawn. -3 Pa, heated to 540℃ at a rate of 12℃ / min, and held for 180min; after the end, purged with nitrogen and cooled to 50℃, with the purging pressure set to 300mbar; and then vacuum tempered three times according to the above steps.

[0030] Examples 2-6 Examples 2-6 provide a vacuum quenching strengthening process for T15 steel.

[0031] The difference between the above embodiment and Embodiment 1 is the charging pressure during the nitrogen cooling process in step (3). See Table 1 below for details.

[0032] Table 1 shows the nitrogen charging pressure during step (3) of Examples 2-6. Example Inflation pressure (mbar) 2 5600 3 5700 4 5800 5 5900 6 6000 Examples 7-10 Examples 7-10 provide a vacuum quenching strengthening process for T15 steel.

[0033] The difference between the above embodiment and embodiment 4 is the charging pressure during the nitrogen cooling process in step (4). See Table 2 below for details.

[0034] Table 2 shows the nitrogen charging pressure during step (4) of Examples 7-10. Example Inflation pressure (mbar) 4 300 7 350 8 400 9 450 10 500 Example 11 Example 11 provides a vacuum quenching strengthening process for T15 steel.

[0035] The difference between the above embodiment and embodiment 4 is that the vacuum tempering in step (3) is performed 4 times.

[0036] Example 12 Example 12 provides a vacuum quenching strengthening process for T15 steel.

[0037] The difference between the above embodiment and embodiment 4 is that the vacuum tempering in step (3) is performed 5 times.

[0038] Comparative Example 1 Comparative Example 1 provides a vacuum quenching strengthening process for T15 steel.

[0039] The difference between the above comparative example and Example 1 is that the charging pressure in step (3) during the nitrogen cooling process is 3000 mbar.

[0040] Comparative Example 2 Comparative Example 2 provides a vacuum quenching strengthening process for T15 steel.

[0041] The difference between the above comparative example and Example 1 is that the nitrogen charging pressure in step (3) during the nitrogen cooling process is 5000 mbar.

[0042] Comparative Example 3 Comparative Example 3 provides a vacuum quenching strengthening process for T15 steel.

[0043] The difference between the above comparative example and Example 1 is that the specific steps of step (3) are as follows: (3) Vacuum air quenching: The annealed T15 steel workpiece is placed in the furnace and vacuumed to 5×10⁻⁶. -3 Pa; then raise the temperature to 830℃ at a rate of 8℃ / min and hold for 60min. After the holding period begins, purge the workpiece with nitrogen at a pressure of 100Pa; continue raising the temperature to 1020℃ at a rate of 8℃ / min and hold for 60min; finally, raise the temperature to 1210℃ at a rate of 3℃ / min and hold for 60min; after the end, purge with nitrogen and cool to 40℃, with the purge pressure set at 5500mbar and the purge time at 10s.

[0044] Comparative Example 4 Comparative Example 4 provides a vacuum quenching strengthening process for T15 steel.

[0045] The difference between the above comparative example and Example 4 is that the vacuum tempering in step (3) is performed twice.

[0046] Performance testing The Rockwell hardness of the T15 steels obtained in Examples 1-10 and Comparative Examples 1-4 was tested, and the results are shown in Table 3 below.

[0047] Table 3. Rockwell hardness test results of T15 steel obtained in Examples 1-10 and Comparative Examples 1-4. The test results of Examples 1-12 and Comparative Examples 1-3 show that, in Examples 1-12, by gradually controlling the heating rate and holding time of each stage in the vacuum air quenching process, and controlling the nitrogen charging pressure during the nitrogen cooling process in the vacuum air quenching step to 5500-6000 mbar, the Rockwell hardness of the obtained T15 steel is 66.2-67.3 HRC. However, in Comparative Examples 1-2, when the nitrogen charging pressure during the nitrogen cooling process in the vacuum air quenching step is controlled to 3000 mbar or 5000 mbar, the Rockwell hardness of the obtained T15 steel is only 65.2-65.6 HRC. Under the heating rate and holding time of each stage in the vacuum air quenching provided in Comparative Example 3, the Rockwell hardness of the obtained T15 steel is only 64.8 HRC. Therefore, it is demonstrated that the vacuum air quenching strengthening process for T15 steel provided in this application can significantly improve the hardness of T15 steel. Further comparison revealed that the Rockwell hardness of the T15 steel obtained in Examples 3-4 was 66.6-66.8 HRC (≥66.5 HRC), indicating that by further controlling the charging pressure during the nitrogen cooling process in the vacuum air quenching step within the range of 5700-5900 mbar, the T15 steel obtained in this application has a higher hardness.

[0048] The test results of Examples 4 and 7-10 show that as the charging pressure during the nitrogen cooling process in the vacuum tempering step increases, the Rockwell hardness of the obtained T15 steel exhibits a trend of first increasing and then decreasing. Further comparison reveals that the Rockwell hardness of the T15 steel obtained in Examples 7-9 is 67.1-67.3 HRC (≥67.0 HRC). Therefore, this application demonstrates that by further controlling the charging pressure during the nitrogen cooling process in the vacuum tempering step within the range of 350-450 mbar, the hardness of the obtained T15 steel is even higher.

[0049] The test results of Examples 4, 11-12, and Comparative Example 4 show that in Examples 4 and 11-12, when the number of vacuum tempering cycles was controlled to 3-5, the Rockwell hardness of the resulting T15 steel was 66.3-66.8 HRC; while in Comparative Example 4, when the number of vacuum tempering cycles was controlled to 2, the Rockwell hardness of the resulting T15 steel was 65.4 HRC. Therefore, this application demonstrates that by adjusting the number of vacuum tempering cycles, the Rockwell hardness of T15 steel can be further improved, thus enhancing its wear resistance.

[0050] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A vacuum air quenching strengthening process for T15 steel, characterized in that, Includes the following steps: Vacuum annealing, vacuum air quenching, vacuum tempering; The vacuum air quenching process is as follows: The T15 steel workpiece after vacuum annealing is placed in the furnace and a vacuum is drawn; then, the temperature is increased to 650±10℃ at a rate of ≤10℃ / min and held for 60±5min; then, the temperature is increased to 850±10℃ at a rate of ≤10℃ / min and held for 30±5min. After the holding period begins, nitrogen gas is used to protect the workpiece, with a nitrogen pressure of 95-105Pa; the temperature is continued to increase to 1050±10℃ at a rate of ≤10℃ / min and held for 20±5min; finally, the temperature is increased to 1220±10℃ at a rate of ≤5℃ / min and held for 20±5min; after the process, nitrogen gas is used to cool the workpiece to below 60℃, with the charging pressure set to 5500-6000mbar and the charging time 10±3s.

2. The vacuum air quenching strengthening process for T15 steel according to claim 1, characterized in that, The vacuum annealing step is as follows: the pretreated T15 steel workpiece is placed in the furnace, and a vacuum is drawn to (4-6)×10. -3 Pa; then raise the temperature to 850±10℃ at a rate of ≤10℃ / min and hold for 110±5min; after the end, slowly lower the temperature to 720±10℃ at a rate of ≤1℃ / min, and finally cool it down to 50-70℃ with the furnace.

3. The vacuum air quenching strengthening process for T15 steel according to claim 1, characterized in that, The vacuum tempering step is as follows: After the gas-quenched T15 steel workpiece is placed in the furnace, a vacuum is drawn to (4-6)×10. -3 Pa, with a heating rate of ≤15℃ / min to 540±10℃, and held at that temperature for 180±5min; after the end, purge with nitrogen and cool to below 60℃, with the purge pressure set to 300-500mbar.

4. The vacuum air quenching strengthening process for T15 steel according to claim 3, characterized in that, The vacuum tempering is performed 3-5 times.

5. The vacuum air quenching strengthening process for T15 steel according to any one of claims 1-4, characterized in that, In the vacuum annealing, vacuum air quenching, and vacuum tempering steps, the pressure after vacuuming is (4-6)×10. -3 Pa.

6. The vacuum air quenching strengthening process for T15 steel according to claim 5, characterized in that, The vacuum air quenching strengthening process also includes pretreatment, the specific steps of which are: first, clean the T15 steel workpiece with anhydrous ethanol and deionized water, and then dry it with a blower.

7. The vacuum air quenching strengthening process for T15 steel according to claim 1, characterized in that, The chemical composition of the T15 steel is W12Cr4V5Co5.

8. T15 steel obtained by vacuum quenching strengthening process of T15 steel as described in any one of claims 1-7.

9. The T15 steel according to claim 8, characterized in that, The Rockwell hardness of the T15 steel is >66HRC.

Images