Remedial methods and applications for defects in the hot isostatic pressing process of tungsten-based powder high-speed steel.

Abstract

This invention belongs to the field of powder metallurgy technology and relates to a remedial method and its application for defects in the hot isostatic pressing (HIP) process of tungsten-based powder high-speed steel. The remedial method includes: Step 1, removing the original cladding nozzle from the scrap tungsten-based powder high-speed steel part after traditional HIP, welding a new cladding nozzle and filling it with an appropriate amount of powder, while simultaneously welding a degassing pipe to the new cladding nozzle for degassing and sealing; Step 2, performing a second HIP on the entire cladding of the degassed and sealed tungsten-based powder high-speed steel. This invention involves prolonged degassing at high temperatures to fully remove inert gases from the cladding, and densification of the original part through a second HIP process, ultimately producing tungsten-based powder high-speed steel identical to the normal part. This invention utilizes existing scrap parts, offering the significant advantage of "turning waste into treasure," and has a simple process flow and operation. It can be used for batch remediation of uncompacted tungsten-based powder high-speed steel on the production line, fully realizing cost minimization and efficiency maximization.

Description

Technical Field

[0001] This invention belongs to the field of powder metallurgy technology, and relates to tungsten-based powder high-speed steel, and particularly to a method for remedying defects in the hot isostatic pressing process of tungsten-based powder high-speed steel and its application. Background Art

[0002] Currently, high-performance powder high-speed steel parts are mainly prepared using processes such as hot isostatic pressing (HIP). Before implementing HIP, powder loading, degassing, and sealing are performed sequentially using a pre-designed casing. Throughout the entire preparation process, each step must adhere to standardized operating procedures and undergo rigorous quality checks to ensure the smooth progress of the subsequent HIP densification process (see Chinese Invention Patent, Publication No.: CN118028685A, Publication Date: May 14, 2024; e.g., Steel Res. Int. 2024; 2400745: 1-9). Therefore, each step in the product preparation process must be strictly implemented and supervised; if the casing has welding defects or the sealing is not tight after degassing, problems such as powder leakage or ineffective pressurization can easily occur during HIP. When a leak in the casing is detected, preventing hot isostatic pressing (HIP) from achieving material densification, a scrapping strategy is typically adopted. This requires re-executing the entire process, including casing procurement, surface shot peening, welding assembly, airtightness testing, vacuum heat treatment, pre-cleaning, powder loading, compaction, degassing via welding degassing pipes, sealing by welding, and HIP forming. This approach not only results in raw material loss and energy waste but also significantly increases the production cost of the parts.

[0003] In the field of hot isostatic pressing (HIP) preparation of powder high-speed steel, there is currently no publicly available effective remedy when leaks in the cladding cause the material to fail to compact. Such failed parts are essentially high-temperature, pressureless sintering products that have not undergone effective pressure. During HIP, due to cladding sealing defects, loosely packed, vibrated, and unpressurized high-speed steel powder only undergoes interparticle bridging at high temperatures. This prevents the cladding from shrinking and deforming as expected, resulting in numerous gaps and pores within the powder. Its microstructure retains significant original powder particle characteristics and fails to exhibit the dense metallic properties expected of powder metallurgy high-speed steel parts.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a remedial method for defects in the hot isostatic pressing process of tungsten-based powder high-speed steel and its application. By reusing the original waste parts, the process flow is reduced, and a simple remedial measure is used to "turn waste into treasure" and produce tungsten-based powder high-speed steel that is the same as other normal parts.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] On the one hand, the present invention provides a method for remedying defects in the hot isostatic pressing process of tungsten-based powder high-speed steel, specifically including the following steps:

[0008] Step 1: Remove the original cladding nozzle from the waste tungsten-based powder high-speed steel part after traditional hot isostatic pressing, weld a new cladding nozzle and fill it with an appropriate amount of powder, and weld a degassing tube to the new cladding nozzle for degassing and sealing.

[0009] Step 2: Perform a second hot isostatic pressing on the entire cladding of the degassed and sealed tungsten-based powder high-speed steel to remedy the defects of the first hot isostatic pressing process.

[0010] Specifically, in step 1, the repair welding of the new sleeve nozzle is as follows:

[0011] DC TIG welding is used, with a welding wire diameter of 1.5mm~2.5mm, a starting current of 10A~50A, a welding current of 110A~160A, an arc termination current of 10A~40A, a rise time of 1s~5s, a fall time of 1s~10s, a gas stop delay of 5s~20s, and the welded position is silvery white or light yellow.

[0012] The powder filling requirements for the new nozzle are as follows: the powder filling height should be 3 / 4 to 7 / 8 of the total height of the new nozzle, and the powder tap density should be 5.81 g / cm³. 3 ~5.89g / cm 3 ;

[0013] The welding parameters for the degassing pipe are as follows:

[0014] DC TIG welding is used, with a welding wire diameter of 1.5mm~2.1mm, a starting current of 10A~50A, a welding current of 90A~150A, an arc termination current of 10A~40A, a rise time of 1s~5s, a fall time of 1s~10s, a gas stop delay of 5s~20s, and the welded position is silvery white or light yellow.

[0015] Furthermore, in step 1, the powder loading process for filling the new packaging nozzle is as follows:

[0016] First, a double cone rotary vacuum dryer of model SZG-500 is used to process the powder to be loaded into the new packaging nozzle. The rotation speed is controlled at 5rpm~11rpm, the temperature at 50℃~150℃, and the time at 1h~3h. While drying the powder, it can also eliminate the gas attached to the surface of the powder particles, so as to avoid the formation of impurities such as oxides during the subsequent hot isostatic pressing process, which would affect the density of the final part.

[0017] Then, during the powder loading process, the longitudinal frequency is controlled at 20Hz~40Hz, the transverse force at 20N~200N, and the vibration frequency is 1 time / s~5 times / s, so as to meet the set powder compaction density requirements.

[0018] Furthermore, in step 1,

[0019] The process parameters used for degassing are as follows: degassing temperature is 400℃~500℃, and vacuum degree is 1×10⁻⁶. -5 Pa ~ 9×10 -5 Pa, degassing time is 24h~96h;

[0020] The specific process of the sealing welding is as follows: DC TIG welding is used, the welding wire diameter is 1.2mm~1.8mm, the starting current is 10A~50A, the welding current is 60A~120A, the arc termination current is 10A~40A, the rise time is 1s~5s, the fall time is 1s~10s, the gas stop delay is 5s~20s, and the welding position is silvery white or light yellow.

[0021] After the sealing weld is completed, leak testing is performed. Specifically, the new sleeve nozzle is connected sequentially to the vacuum pump and leak detector, ensuring that all components are tightly connected and leak-free. First, the mechanical pump is turned on to pump the system pressure to 3Pa~5Pa. After the pressure stabilizes, the molecular pump is turned on to continue pumping air, so that the system pressure reaches 1×10⁻⁶. -5 Pa ~ 9×10 -5 Pa; Turn off the mechanical pump, keeping only the molecular pump and leak detector running normally, and continue evacuating until the system vacuum reaches 1×10⁻⁶. -10 mbar·l / s ~9×10 -10 Leak detection is performed along the weld joint using mbar·l / s. If the waveform is a straight horizontal line without fluctuations, it indicates that the integrity and sealing of the entire enclosure meet the requirements.

[0022] Specifically, in step 2, the process parameters for the secondary hot isostatic pressing are as follows:

[0023] The secondary hot isostatic pressing temperature is 0℃~80℃ higher than the traditional hot isostatic pressing temperature, the secondary hot isostatic pressing pressure is 0MPa~30MPa higher than the traditional hot isostatic pressing pressure, and the secondary hot isostatic pressing holding time is 0h~1h longer than the traditional hot isostatic pressing holding time; the traditional hot isostatic pressing temperature is 1110℃~1170℃, the pressure is 70MPa~120MPa, and the holding time is 1h~4h.

[0024] Specifically, the remedial method further includes the following steps:

[0025] Step 31: Cut off the nozzle of the tungsten-based powder high-speed steel after secondary hot isostatic pressing and obtain the corresponding optical micrograph. Determine whether the tungsten-based powder high-speed steel part has been successfully salvaged based on the density of the tungsten-based powder high-speed steel part reflected in the optical micrograph: if the tungsten-based powder high-speed steel microstructure shown in the optical micrograph has no pores or cracks, the salvage is successful; otherwise, the salvage fails.

[0026] Alternatively, the remedy may further include the following steps:

[0027] Step 32: By comparing the dimensional changes of the entire cladding of the tungsten-based powder high-speed steel before and after the secondary hot isostatic pressing, calculate the shrinkage rate, and determine whether the salvage of the scrap tungsten-based powder high-speed steel parts is successful based on the shrinkage rate: if the shrinkage rate is 6%~8%, the salvage is successful; otherwise, the salvage fails.

[0028] Furthermore, in the tungsten-based powder high-speed steel, the powder with a particle size <53μm accounts for 46%~80% by mass, and the powder with a particle size between 53μm and 150μm accounts for 20%~54% by mass. In the original powder state, (Fe,W)₂C and (Fe,V)C powders account for 10%~40% by mass, with the remaining component being the steel matrix. After remedial treatment, (Fe,W)₆C and (Fe,V)C powders account for 25%~45% by mass, with the steel matrix still constituting the remaining component. Moreover, the tungsten-based powder high-speed steel obtained by the remedial method provided by this invention has a density of 99.7%~99.9%.

[0029] On the other hand, the present invention also provides a method for remedying defects in the hot isostatic pressing process of tungsten-based powder high-speed steel as described in part or all of the above descriptions, in the formation of scrap parts in the conventional hot isostatic pressing process of tungsten-based powder high-speed steel.

[0030] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0031] 1) Since the traditional hot isostatic pressing of tungsten-based powder high-speed steel is not compacted, it is actually equivalent to pressureless sintering of the tungsten-based powder high-speed steel powder at high temperature. Due to the lack of pressure between powder particles, the sintering is insufficient and not dense, and most of the characteristics of the powder are still retained. Based on a comprehensive consideration of the above factors, this invention adopts a specific remedial method combined with a secondary hot isostatic pressing process to complete the preparation of tungsten-based powder high-speed steel with the same characteristics as normal parts.

[0032] 2) This invention addresses the issue of inert gases contained in the original tungsten-based powder high-speed steel from the hot isostatic pressing (HIP) equipment. By performing prolonged degassing at high temperatures, the inert gases within the cladding are fully expelled, laying a solid foundation for subsequent secondary HIP. Furthermore, the secondary HIP process employed in this invention, using the same or higher temperatures and pressures, and the same or longer holding times as traditional HIP processes, effectively densifies the original waste parts. This fundamentally solves the problem encountered in actual production where leaks in the tungsten-based powder high-speed steel go undetected, resulting in insufficient compaction. This process demonstrates the significant advantage of "turning waste into treasure."

[0033] 3) This invention employs a specific remedial method combined with a secondary hot isostatic pressing process. By reusing existing scrap parts, the process flow is reduced, and tungsten-based powder high-speed steel identical to other normally manufactured parts can be produced through simple remedial measures. This invention features a simple process and easy operation, filling a technological gap. It allows for batch remediation of uncompacted tungsten-based powder high-speed steel (i.e., scrap parts) on the production line, offering significant advantages in saving time, materials, energy, and reducing costs, thus fully realizing cost minimization and efficiency maximization. Attached Figure Description

[0034] The accompanying drawings are incorporated in and form part of this specification, and together with the description serve to explain the principles of the invention.

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 A flowchart of a method for remedying defects in the hot isostatic pressing process of tungsten-based powder high-speed steel provided by the present invention;

[0037] Figure 2 An optical photograph of the tungsten-based powder high-speed steel obtained in Example 1 of this invention;

[0038] Figure 3 The image shown is an optical microscope image of the tungsten-based powder high-speed steel obtained in Example 2 of this invention.

[0039] Figure 4 The image shown is an optical microscope image of the tungsten-based powder high-speed steel obtained in Example 3 of this invention.

[0040] Figure 5 Optical microscope images of tungsten-based powder high-speed steel produced by conventional hot isostatic pressing (HIP) for comparison. Detailed Implementation

[0041] Exemplary embodiments will now be described in detail. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples consistent with some aspects of the invention as detailed in the appended claims.

[0042] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Example 1

[0043] See Figure 1 As shown, this embodiment provides a method for remedying defects in the hot isostatic pressing process of tungsten-based powder high-speed steel, specifically including the following steps:

[0044] Step 1: Remove the original cladding nozzle from the uncompacted tungsten-based powder high-speed steel scrap after traditional hot isostatic pressing, weld a new cladding nozzle, and fill it with an appropriate amount of powder; weld a degassing tube to the new cladding nozzle for degassing and sealing; wherein,

[0045] The specific welding procedures for the new nozzle are as follows: DC TIG welding is used, with 316L welding wire diameter of 1.5mm, starting current of 10A, welding current of 110A, arc termination current of 10A, rise time of 1s, fall time of 1s, gas stop delay of 5s, and the welded position is silver-white or light yellow.

[0046] The powder filling requirements for the new nozzle are as follows: the powder filling height should be 7 / 8 of the total height of the new nozzle, and the powder tap density should be 5.81 g / cm³. 3 ;

[0047] The specific welding parameters for the degassing pipe are as follows: DC TIG welding is used, with a 316L welding wire diameter of 1.5mm, a starting current of 10A, a welding current of 90A, an arc termination current of 10A, a rise time of 1s, a fall time of 1s, a lag gas stop of 5s, and the welded position is silver-white or light yellow.

[0048] The process parameters used for degassing are as follows: degassing temperature is 450℃, and vacuum degree is 1×10⁻⁶. -5 Pa, degassing time is 96h;

[0049] The specific process of the sealing welding is as follows: DC TIG welding is used, the welding wire diameter is 1.2mm, the starting current is 10A, the welding current is 60A, the arc termination current is 10A, the rise time is 1s, the fall time is 1s, the gas stop delay is 5s, and the welding position is silvery white or light yellow.

[0050] After the sealing weld is completed, a leak test is performed. Specifically, the new sleeve nozzle is connected sequentially to the vacuum pump and the leak detector, ensuring that all components are tightly connected and leak-free. First, the mechanical pump is turned on to pump the system pressure to 3 Pa. After the pressure stabilizes, the molecular pump is turned on to continue pumping air, so that the system pressure reaches 1 × 10⁻⁶ Pa. -5 At Pa, shut down the mechanical pump, keeping only the molecular pump and leak detector running normally, and continue evacuating until the system vacuum reaches 1×10⁻⁶. -10 Leak detection is performed along the weld joint using mbar·l / s. If the waveform is a straight horizontal line without fluctuations, it indicates that the integrity and sealing of the entire enclosure meet the requirements.

[0051] Furthermore, in step 1, the powder loading process for filling the new packaging nozzle is as follows:

[0052] First, a double cone rotary vacuum dryer of model SZG-500 is used to process the powder to be loaded into the new packaging nozzle. The rotation speed is controlled at 5 rpm, the temperature at 150℃, and the time is 1 hour. While drying the powder, it can also eliminate the gas attached to the surface of the powder particles, so as to avoid the formation of oxides and other impurities during the subsequent hot isostatic pressing process, which would affect the density of the final part.

[0053] Then, during the powder loading process, the longitudinal frequency is controlled at 20Hz, the transverse force at 20N, and the vibration frequency is 5 times / s, thereby meeting the set powder compaction density requirements.

[0054] Step 2: Perform secondary hot isostatic pressing on the entire cladding of the degassed and sealed tungsten-based powder high-speed steel. The secondary hot isostatic pressing process parameters are as follows: the secondary hot isostatic pressing temperature, pressure, and holding time are the same as those of the traditional hot isostatic pressing.

[0055] To further verify the performance of the tungsten-based powder high-speed steel after the remedial treatment in this embodiment, the following steps were performed after the secondary hot isostatic pressing:

[0056] Step 31: Cut off the cladding nozzle of the tungsten-based powder high-speed steel after the secondary hot isostatic pressing in Step 2 for observation and verification of its microstructure, thus obtaining the salvaged tungsten-based powder high-speed steel (I). See the optical micrograph for details. Figure 2 ,Depend on Figure 2 It can be seen that the microstructure of tungsten-based powder high-speed steel is free of pores and cracks and has a dense structure. This indicates that the remedial method provided in this embodiment can fully remove the residual inert gas in the original hot isostatic pressing part, and the secondary hot isostatic pressing process can effectively avoid thermal stress cracking and achieve densification.

[0057] It should be further noted that in the tungsten-based powder high-speed steel, the powder with a particle size <53μm accounts for 46% by mass, and the powder with a particle size between 53μm and 150μm accounts for 54% by mass. In the original powder state, (Fe,W)₂C and (Fe,V)C powders account for 10% by mass, with the remainder being the steel matrix. After remedial treatment, (Fe,W)₆C and (Fe,V)C powders account for 25% by mass, with the steel matrix still constituting the remaining components. Furthermore, the tungsten-based powder high-speed steel obtained by the remedial method provided by this invention has a density of 99.7%. Example 2

[0058] This embodiment provides a method for remedying defects in the hot isostatic pressing process of tungsten-based powder high-speed steel, specifically including the following steps:

[0059] Step 1: Remove the original cladding nozzle from the uncompacted tungsten-based powder high-speed steel scrap after traditional hot isostatic pressing, weld a new cladding nozzle, and fill it with an appropriate amount of powder; simultaneously, degas and seal the new cladding nozzle by welding a degassing tube; wherein,

[0060] The specific welding procedures for the new nozzle are as follows: DC TIG welding is used, with a 316L welding wire diameter of 2.5mm, a starting current of 50A, a welding current of 160A, an arc termination current of 40A, a rise time of 5s, a fall time of 10s, a lag gas stop of 20s, and the welded position is silver-white or light yellow.

[0061] The powder filling requirements for the new nozzle are as follows: the powder filling height should be 3 / 4 of the total height of the new nozzle, and the powder tap density should be 5.89 g / cm³. 3 ;

[0062] The specific welding parameters for the degassing pipe are as follows: DC TIG welding is used, with a 316L welding wire diameter of 2.1mm, a starting current of 50A, a welding current of 150A, an arc termination current of 40A, a rise time of 5s, a fall time of 10s, a lag gas stop of 20s, and the welded position is silver-white or light yellow.

[0063] The process parameters used for degassing are as follows: degassing temperature is 400℃, and vacuum degree is 9×10⁻⁶. -5 Pa, degassing time 24h;

[0064] The specific process of the sealing welding is as follows: DC TIG welding is used, the welding wire diameter is 1.8mm, the starting current is 50A, the welding current is 120A, the arc termination current is 40A, the rise time is 5s, the fall time is 10s, the gas stop delay is 20s, and the welding position is silvery white or light yellow.

[0065] After the sealing weld is completed, a leak test is performed. Specifically, the new sleeve nozzle is connected sequentially to the vacuum pump and the leak detector, ensuring that all components are tightly connected and leak-free. First, the mechanical pump is turned on to pump the system pressure to 5 Pa. After the pressure stabilizes, the molecular pump is turned on to continue pumping air, so that the system pressure reaches 9 × 10⁻⁶ Pa. -5 Pa; Turn off the mechanical pump, keeping only the molecular pump and leak detector running normally, and continue evacuating until the system vacuum reaches 9 × 10⁻⁶. -10 Leak detection is performed along the weld joint using mbar·l / s. If the waveform is a straight horizontal line without fluctuations, it indicates that the integrity and sealing of the entire enclosure meet the requirements.

[0066] Furthermore, in step 1, the powder loading process for filling the new packaging nozzle is as follows:

[0067] First, a double cone rotary vacuum dryer of model SZG-500 is used to process the powder to be loaded into the new packaging nozzle. The rotation speed is controlled at 8 rpm, the temperature at 100℃, and the time is 2 hours. While drying the powder, it can also eliminate the gas attached to the surface of the powder particles, so as to avoid the formation of oxides and other impurities during the subsequent hot isostatic pressing process, which would affect the density of the final part.

[0068] Then, during the powder loading process, the longitudinal frequency is controlled at 30Hz, the transverse force at 100N, and the vibration frequency is applied at 3 times / s, thereby meeting the set powder tap density requirements.

[0069] Step 2: Perform secondary hot isostatic pressing on the entire cladding of the degassed and sealed tungsten-based powder high-speed steel. The secondary hot isostatic pressing process parameters are as follows: the secondary hot isostatic pressing temperature is 80°C higher than the traditional hot isostatic pressing temperature, the secondary hot isostatic pressing pressure is 30MPa higher than the traditional hot isostatic pressing pressure, and the secondary hot isostatic pressing holding time is 1 hour longer than the traditional hot isostatic pressing holding time.

[0070] To further verify the performance of the tungsten-based powder high-speed steel after the remedial treatment in this embodiment, the following steps were performed after the secondary hot isostatic pressing:

[0071] Step 31: Cut off the cladding nozzle of the tungsten-based powder high-speed steel after the second hot isostatic pressing in Step 2 for observation and verification of the microstructure, thus obtaining the salvaged tungsten-based powder high-speed steel (II). See the optical micrograph for details. Figure 3 ,Depend on Figure 3 It can be seen that the microstructure of tungsten-based powder high-speed steel is free of pores and cracks and has a dense structure. This indicates that the remedial method provided in this embodiment can fully remove the residual inert gas in the original hot isostatic pressing part, and the secondary hot isostatic pressing process can effectively avoid thermal stress cracking and achieve densification.

[0072] To further clarify, in the aforementioned tungsten-based powder high-speed steel, the mass percentage of powder with a particle size <53μm is 50%, and the mass percentage of powder with a particle size between 53μm and 150μm is 50%. In the original powder state, the mass percentage of (Fe,W)₂C and (Fe,V)C powders is 20%, with the remainder being the steel matrix. After remedial treatment, the mass percentage of (Fe,W)₆C and (Fe,V)C powders is 35%, with the steel matrix still constituting the remaining components. Furthermore, the tungsten-based powder high-speed steel obtained by the remedial method provided by this invention has a density of 99.8%. Example 3

[0073] This embodiment provides a method for remedying defects in the hot isostatic pressing process of tungsten-based powder high-speed steel, specifically including the following steps:

[0074] Step 1: Remove the original cladding nozzle from the uncompacted tungsten-based powder high-speed steel scrap after traditional hot isostatic pressing, weld a new cladding nozzle, and fill it with an appropriate amount of powder; simultaneously, degas and seal the new cladding nozzle by welding a degassing tube; wherein,

[0075] The specific welding procedures for the new nozzle are as follows: DC TIG welding is used, with 316L welding wire diameter of 2mm, starting current of 30A, welding current of 135A, arc termination current of 25A, rise time of 3s, fall time of 5.5s, gas stop delay of 12.5s, and the welded position is silver-white or light yellow.

[0076] The powder filling requirements for the new nozzle are as follows: the powder filling height should be 13 / 16 of the total height of the new nozzle, and the powder tap density should be 5.85 g / cm³. 3 ;

[0077] The specific welding parameters for the degassing pipe are as follows: DC TIG welding is used, with a 316L welding wire diameter of 1.8mm, a starting current of 30A, a welding current of 120A, an arc termination current of 25A, a rise time of 3s, a fall time of 5.5s, a lag gas stop of 12.5s, and the welded position is silver-white or light yellow.

[0078] The process parameters used for degassing are as follows: degassing temperature is 500℃, and vacuum degree is 5×10⁻⁶. -5 Pa, degassing time 60h;

[0079] The specific process of the sealing welding is as follows: DC TIG welding is used, the welding wire diameter is 1.5mm, the starting current is 30A, the welding current is 90A, the arc termination current is 25A, the rise time is 3s, the fall time is 5.5s, the gas stop delay is 12.5s, and the welding position is silvery white or light yellow.

[0080] After the sealing weld is completed, a leak test is performed. Specifically, the new sleeve nozzle is connected sequentially to the vacuum pump and the leak detector, ensuring that all components are tightly connected and leak-free. First, the mechanical pump is turned on to pump the system pressure to 4 Pa. After the pressure stabilizes, the molecular pump is turned on to continue pumping air, so that the system pressure reaches 5 × 10⁻⁶ Pa. -5 At Pa, shut down the mechanical pump, keeping only the molecular pump and leak detector running normally, and continue evacuating until the system vacuum reaches 5 × 10⁻⁶. -10 Leak detection is performed along the weld joint using mbar·l / s. If the waveform is a straight horizontal line without fluctuations, it indicates that the integrity and sealing of the entire enclosure meet the requirements.

[0081] Furthermore, in step 1, the powder loading process for filling the new packaging nozzle is as follows:

[0082] First, a double cone rotary vacuum dryer of model SZG-500 is used to process the powder to be loaded into the new packaging nozzle. The speed is controlled at 11 rpm, the temperature at 150℃, and the time is 3 hours. While drying the powder, it can also eliminate the gas attached to the surface of the powder particles, so as to avoid the formation of oxides and other impurities during the subsequent hot isostatic pressing process, which would affect the density of the final part.

[0083] Then, during the powder loading process, the longitudinal frequency is controlled at 40Hz, the transverse force at 200N, and the vibration frequency is 5 times / s, thereby meeting the set powder compaction density requirements.

[0084] Step 2: Perform secondary hot isostatic pressing on the entire cladding of the degassed and sealed tungsten-based powder high-speed steel. The secondary hot isostatic pressing process parameters are as follows: the secondary hot isostatic pressing temperature is 40°C higher than the traditional hot isostatic pressing temperature, the secondary hot isostatic pressing pressure is 15MPa higher than the traditional hot isostatic pressing pressure, and the secondary hot isostatic pressing holding time is 0.5h longer than the traditional hot isostatic pressing holding time.

[0085] To further verify the performance of the tungsten-based powder high-speed steel after the remedial treatment in this embodiment, the following steps were performed after the secondary hot isostatic pressing:

[0086] Step 31: Cut off the cladding nozzle of the tungsten-based powder high-speed steel after the secondary hot isostatic pressing in Step 2 for observation and verification of its microstructure, thus obtaining the salvaged tungsten-based powder high-speed steel (III). See the optical micrograph for details. Figure 4 ,Depend on Figure 4 It can be seen that the microstructure of tungsten-based powder high-speed steel is free of pores and cracks and has a dense structure. This indicates that the remedial method provided in this embodiment can fully remove the residual inert gas in the original hot isostatic pressing part, and the secondary hot isostatic pressing process can effectively avoid thermal stress cracking and achieve densification.

[0087] To further clarify, in the aforementioned tungsten-based powder high-speed steel, powder with a particle size <53μm accounts for 80% by mass, and powder with a particle size between 53μm and 150μm accounts for 20% by mass. In the original powder state, (Fe,W)₂C and (Fe,V)C powders account for 40% by mass, with the remainder being the steel matrix. After remedial treatment, (Fe,W)₆C and (Fe,V)C powders account for 45% by mass, with the steel matrix still constituting the remaining components. Furthermore, the tungsten-based powder high-speed steel obtained by the remedial method provided by this invention has a density of 99.9%. Example 4

[0088] The difference between this embodiment and Embodiment 3 is that, in order to further verify the performance of the tungsten-based powder high-speed steel after the remedial treatment in this embodiment, the following steps are performed after the secondary hot isostatic pressing:

[0089] Step 32: By comparing the dimensional changes of the entire cladding of the tungsten-based powder high-speed steel before and after the secondary hot isostatic pressing, the shrinkage rate is calculated to be 6%, indicating that the remediation was successful, that is, the preparation of the remediated tungsten-based powder high-speed steel is completed. Comparative Example

[0090] This comparative example provides a hot isostatic pressing (HIP) process for tungsten-based powder high-speed steel. The traditional HIP process is used to treat the tungsten-based powder high-speed steel. The relevant process parameters are as follows: the traditional HIP temperature is 1110℃~1170℃, the HIP pressure is 70MPa~120MPa, and the HIP holding time is 1h~4h.

[0091] Optical micrographs of tungsten-based powder high-speed steel produced by the above-mentioned conventional hot isostatic pressing process can be found here. Figure 5 ,Depend on Figure 5 It can be seen that the microstructure of tungsten-based powder high-speed steel has pores, cracks and poor density, indicating that the hot isostatic pressing process remedial method provided in this comparative example cannot fully remove the residual inert gas in the original hot isostatic pressed part, and the secondary hot isostatic pressing process cannot effectively avoid thermal stress cracking and achieve densification.

[0092] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0093] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for remedying defects in the hot isostatic pressing process of tungsten-based powder high-speed steel, characterized in that, Specifically, the following steps are included: Step 1: Remove the original cladding nozzle from the waste tungsten-based powder high-speed steel part after traditional hot isostatic pressing, weld a new cladding nozzle and fill it with an appropriate amount of powder, and weld a degassing tube to the new cladding nozzle for degassing and sealing. Step 2: Perform a second hot isostatic pressing on the entire cladding of the degassed and sealed tungsten-based powder high-speed steel to remedy the defects of the first hot isostatic pressing process; the tungsten-based powder high-speed steel obtained by the above-mentioned remedial method has a density of 99.7%~99.9%; In step 1, the powder filling requirements for the new nozzle are as follows: the powder filling height should be 3 / 4 to 7 / 8 of the total height of the new nozzle, and the powder tap density should be 5.81 g / cm³. 3 ~5.89g / cm 3 The powder loading process for the new nozzle is as follows: First, a double-cone rotary vacuum dryer (model SZG-500) is used to process the powder to be loaded into the new nozzle. The rotation speed is controlled at 5 rpm to 11 rpm, the temperature at 50℃ to 150℃, and the time at 1 h to 3 h. This process dries the powder and eliminates gases adhering to the surface of the powder particles, thus preventing the formation of oxides and other impurities during the subsequent hot isostatic pressing process, which could affect the density of the final part. Then, during the powder loading process, the longitudinal frequency is controlled at 20 Hz to 40 Hz, the transverse force at 20 N to 200 N, and the vibration frequency at 1 to 5 times per second to meet the set powder tap density requirements. In step 1, the process parameters used for degassing are as follows: degassing temperature is 400℃~500℃, and vacuum degree is 1×10⁻⁶. -5 Pa ~ 9×10 -5 Pa, degassing time is 24h~96h; In step 2, the secondary hot isostatic pressing process parameters are as follows: the secondary hot isostatic pressing temperature is 0℃~80℃ higher than the traditional hot isostatic pressing temperature; the secondary hot isostatic pressing pressure is 0MPa~30MPa higher than the traditional hot isostatic pressing pressure; and the secondary hot isostatic pressing holding time is 0h~1h longer than the traditional hot isostatic pressing holding time.

2. The method for remedying defects in the hot isostatic pressing process of tungsten-based powder high-speed steel according to claim 1, characterized in that, In step 1, the repair welding of the new sleeve nozzle is as follows: DC TIG welding is used, with a welding wire diameter of 1.5mm~2.5mm, a starting current of 10A~50A, a welding current of 110A~160A, an arc termination current of 10A~40A, a rise time of 1s~5s, a fall time of 1s~10s, and a gas stop delay of 5s~20s.

3. The method for remedying defects in the hot isostatic pressing process of tungsten-based powder high-speed steel according to claim 1, characterized in that, In step 1, the welding parameters for the degassing pipe are as follows: DC TIG welding is used, with a welding wire diameter of 1.5mm~2.1mm, a starting current of 10A~50A, a welding current of 90A~150A, an arc termination current of 10A~40A, a rise time of 1s~5s, a fall time of 1s~10s, and a gas stop delay of 5s~20s.

4. The method for remedying defects in the hot isostatic pressing process of tungsten-based powder high-speed steel according to claim 1, characterized in that, It also includes the following steps: Step 31: Cut off the nozzle of the tungsten-based powder high-speed steel after secondary hot isostatic pressing, and obtain the corresponding optical micrograph. Determine whether the salvage of the tungsten-based powder high-speed steel part is successful based on the density of the tungsten-based powder high-speed steel part reflected in the optical micrograph.

5. The method for remedying defects in the hot isostatic pressing process of tungsten-based powder high-speed steel according to claim 1, characterized in that, It also includes the following steps: Step 32: By comparing the dimensional changes of the entire cladding of the tungsten-based powder high-speed steel before and after the secondary hot isostatic pressing, calculate the shrinkage rate, and determine whether the salvage of the scrap tungsten-based powder high-speed steel parts is successful based on the shrinkage rate.

6. The application of a method for remedying defects in the hot isostatic pressing process of tungsten-based powder high-speed steel as described in any one of claims 1 to 5 in the formation of scrap parts in the conventional hot isostatic pressing process of tungsten-based powder high-speed steel.

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