Remediation method for tungsten powder high-speed steel hot isostatic pressing process defects and application thereof

Abstract

The invention belongs to the technical field of powder metallurgy, and relates to a remedying method for tungsten powder high-speed steel hot isostatic pressing process defects and application of the remedying method. The remedying method comprises the following steps: step 1, cutting off an original sheath nozzle from a tungsten powder high-speed steel waste part subjected to traditional hot isostatic pressing, performing repair welding on a new sheath nozzle, filling a proper amount of powder, and performing degassing and seal welding on a degassing pipe welded on the new sheath nozzle; and step 2, carrying out secondary hot isostatic pressing on the whole sheath of the tungsten powder high-speed steel subjected to degassing and seal welding. According to the method, degassing is conducted for a long time at the high temperature so that inert gas in the sheath can be fully discharged, densification of an original workpiece is achieved through the secondary hot isostatic pressing technology, and finally the tungsten-series powder high-speed steel identical to a normal workpiece is prepared. According to the method, original waste parts are utilized, the remarkable advantage of turning waste into wealth is achieved, the technological process is simple, operation is easy, batch remediation can be conducted on the uncompacted tungsten-series powder high-speed steel on a production line, and cost minimization and benefit maximization are fully achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of powder metallurgy, relates to tungsten-based powder high-speed steel, and particularly relates 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] At present, high-performance powder high-speed steel parts are mainly prepared by processes such as hot isostatic pressing. Before implementing the hot isostatic pressing process, operations such as powder filling, degassing, and sealing welding need to be completed in sequence through a pre-designed envelope. In the entire preparation process, each operation needs to follow standardized operating specifications and strict quality inspections to ensure the smooth progress of the subsequent hot isostatic pressing densification process (see Chinese invention patent, publication number: CN118028685A, publication date: May 14, 2024; such as Document 1, Steel Res. Int. 2024; 2400745: 1-9). Therefore, in the product preparation process, each operation needs to be strictly implemented and supervised; if there are welding defects in the envelope or the sealing after degassing is not tight, problems such as powder leakage or ineffective pressurization are likely to occur during hot isostatic pressing. When it is detected that the leakage point of the envelope causes the material to not be densified during hot isostatic pressing, a scrapping treatment strategy is usually adopted, that is, it is necessary to re-perform the entire process including envelope procurement, surface shot peening treatment, welding assembly, airtightness detection, vacuum heat treatment, cleaning pretreatment, and powder filling, vibration compaction, degassing by welding an exhaust pipe, sealing welding, and hot isostatic pressing forming. The above treatment method not only causes waste of raw materials and energy, but also significantly increases the production cost of the parts.

[0003] In the field of preparing tungsten-based powder high-speed steel by hot isostatic pressing, when there is a leakage point in the envelope resulting in the material not being compacted and formed, there is currently no publicly available effective remedial measure. Such defective parts essentially belong to high-temperature non-pressure sintered products without effective pressure action. During hot isostatic pressing, due to the sealing defect of the envelope, the loose-packed and vibrated high-speed steel powder only undergoes intergranular bridging at high temperature, resulting in the envelope being unable to shrink and deform as expected, and a large number of interstitial holes are formed inside the powder. Its microstructure still retains the significant characteristics of the original powder particles and cannot exhibit the dense metal characteristics that powder metallurgy high-speed steel parts should have.

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

[0005] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art, and provide a method for remedying 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 through simple remedial measures, "turning waste into treasure" is achieved, and tungsten-based powder high-speed steel identical to other normal parts is prepared.

[0006] To achieve the above object, the present invention provides the following technical solutions: On the one hand, the present invention provides a method for remedying the defects of the hot isostatic pressing process of tungsten-based powder high-speed steel, which specifically includes the following steps: Step 1: Cut off the original sleeve nozzle of the waste tungsten-based powder high-speed steel after traditional hot isostatic pressing, weld a new sleeve nozzle and load an appropriate amount of powder, degas and seal-weld the welding degassing pipe of the new sleeve nozzle; Step 2: Perform secondary hot isostatic pressing on the entire sleeve of the tungsten-based powder high-speed steel after degassing and seal-welding to achieve the remedy of the defects of the first hot isostatic pressing process.

[0007] Specifically, in Step 1, the welding of the new sleeve nozzle is as follows: Use DC TIG welding, the wire diameter is 1.5 mm to 2.5 mm, the starting current is 10 A to 50 A, the welding current is 110 A to 160 A, the arc extinguishing current is 10 A to 40 A, the rise time is 1 s to 5 s, the fall time is 1 s to 10 s, the post-gas stop is 5 s to 20 s, and the welding position is silver-white or light yellow; The powder loading requirements in the new sleeve nozzle are as follows: the powder filling height accounts for 3 / 4 to 7 / 8 of the total height of the new sleeve nozzle, and the tapped density of the powder is 5.81 g / cm 3 ~5.89 g / cm 3 ; The welding parameters of the degassing pipe are as follows: Use DC TIG welding, the wire diameter is 1.5 mm to 2.1 mm, the starting current is 10 A to 50 A, the welding current is 90 A to 150 A, the arc extinguishing current is 10 A to 40 A, the rise time is 1 s to 5 s, the fall time is 1 s to 10 s, the post-gas stop is 5 s to 20 s, and the welding position is silver-white or light yellow.

[0008] Further, in Step 1, the powder loading process of the powder loaded into the new sleeve nozzle is as follows: First, use a double-cone rotary vacuum dryer of model SZG-500 to process the powder to be loaded into the new sleeve nozzle, control the rotation speed to be 5 rpm to 11 rpm, the temperature to be 50 °C to 150 °C, and the time to be 1 h to 3 h. While drying the powder, it can also eliminate the gas attached to the surface of the powder particles to avoid affecting the density of the final product due to the formation of oxides and other impurities during the subsequent hot isostatic pressing process; Then, during the powder loading process, control the longitudinal frequency to be 20 Hz to 40 Hz, the lateral force to be 20 N to 200 N, and the vibration application frequency to be 1 time / s to 5 times / s, so as to meet the set tapped density requirements of the powder.

[0009] Further, in Step 1, The process parameters for degassing are as follows: the degassing temperature is 400°C to 500°C, the vacuum degree is 1×10 -5 Pa to 9×10 -5 Pa, and the degassing time is 24h to 96h; The specific process of the seal welding is as follows: DC TIG welding is used, the wire diameter is 1.2mm to 1.8mm, the starting current is 10A to 50A, the welding current is 60A to 120A, the arc extinguishing current is 10A to 40A, the rise time is 1s to 5s, the fall time is 1s to 10s, the post-gas shutdown is 5s to 20s, and the welding position is silver-white or light yellow; After the seal welding is completed, leak detection is carried out. Specifically: the new shroud nozzle is successively connected to the vacuum pump and the leak detector to ensure that all components are tightly connected without leakage; first, turn on the mechanical pump to pump the system pressure to 3Pa to 5Pa. After the pressure is stable, turn on the molecular pump to continue pumping to make the system pressure reach 1×10 -5 Pa to 9×10 -5 Pa; turn off the mechanical pump, only keep the molecular pump and the leak detector running normally, and continue pumping until the system vacuum degree reaches 1×10 -10 mbar·l / s to 9×10 -10 mbar·l / s, and leak detection is carried out along the welding joint. If the waveform is a horizontal straight line without fluctuations, it indicates that the integrity and sealing performance of the entire shroud meet the requirements.

[0010] Specifically, in step 2, the process parameters of the secondary hot isostatic pressing are as follows: The temperature of the secondary hot isostatic pressing is 0°C to 80°C higher than that of the traditional hot isostatic pressing, the pressure of the secondary hot isostatic pressing is 0MPa to 30MPa higher than that of the traditional hot isostatic pressing, and the holding time of the secondary hot isostatic pressing is 0h to 1h longer than that of the traditional hot isostatic pressing; the temperature of the traditional hot isostatic pressing is 1110°C to 1170°C, the pressure is 70MPa to 120MPa, and the holding time is 1h to 4h.

[0011] Specifically, the remedial method further includes the following steps: Step 31: Cut off the shroud nozzle of the tungsten-based powder high-speed steel after the secondary hot isostatic pressing, obtain the corresponding optical micrograph, and judge whether the remediation of the tungsten-based powder high-speed steel waste part is successful according to the density of the tungsten-based powder high-speed steel parts reflected by the optical micrograph: if the tungsten-based powder high-speed steel microstructure presented by the optical micrograph has no pores and no cracks, it indicates that the remediation is successful; otherwise, the remediation fails.

[0012] Or, the remedial method further includes the following steps: Step 32: By comparing the dimensional changes of the entire sheath of tungsten-based powder high-speed steel before and after secondary hot isostatic pressing, calculate the shrinkage rate, and determine whether the remediation of the tungsten-based powder high-speed steel waste part is successful based on the shrinkage rate: If the shrinkage rate is 6% - 8%, it indicates that the remediation is successful; otherwise, the remediation fails.

[0013] Furthermore, in the tungsten-based powder high-speed steel, the mass ratio of powders with a particle size < 53μm is 46% - 80%, and the mass ratio of powders with a particle size between 53μm and 150μm is 20% - 54%; in the original powder state, the mass ratio of (Fe,W)2C and (Fe,V)C powders is 10% - 40%, and the remaining components are the steel matrix; after remediation treatment, the mass ratio of (Fe,W)6C and (Fe,V)C powders is 25% - 45%, and the steel matrix remains the remaining components. Moreover, the tungsten-based powder high-speed steel prepared by the remediation method provided by the present invention has a relative density of 99.7% - 99.9%.

[0014] On the other hand, the present invention also provides an application of the remediation method for the hot isostatic pressing process defects of the tungsten-based powder high-speed steel as described above, in part or in whole, in the waste parts formed by the traditional hot isostatic pressing process of tungsten-based powder high-speed steel.

[0015] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects: 1) Since the traditional hot isostatic pressing of tungsten-based powder high-speed steel is not compacted, it is actually equivalent to performing pressureless sintering on the powder of tungsten-based powder high-speed steel 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, the present invention adopts a specific remediation method combined with the secondary hot isostatic pressing process to complete the preparation of tungsten-based powder high-speed steel identical to normal parts.

[0016] 2) Since the original tungsten-based powder high-speed steel contains inert gas in the hot isostatic pressing equipment, degassing is carried out at a relatively high temperature for a long time to fully discharge the inert gas in the sheath, laying a solid foundation for the subsequent secondary hot isostatic pressing. Moreover, the secondary hot isostatic pressing process adopted by the present invention can effectively densify the original waste parts through the same or higher temperature and pressure, and the same or longer holding time as the traditional hot isostatic pressing process, substantially solving the problem that leakage points in tungsten-based powder high-speed steel are not detected and thus not compacted in actual production, and having the remarkable advantage of "turning waste into treasure".

[0017] 3) The present invention adopts a specific remedial method in combination with a secondary hot isostatic pressing process. By reusing the original waste parts, the process flow is reduced. Through simple remedial measures, tungsten-based powder high-speed steel identical to other normal parts can be prepared. The process of the present invention is simple and easy to operate, filling a technological gap. It can batch-remedy the uncompacted tungsten-based powder high-speed steel (i.e., waste parts) on the production line, with obvious advantages such as time, material, and energy savings and cost reduction, fully realizing the minimization of cost and the maximization of benefits. Brief Description of the Drawings

[0018] The accompanying drawings here are incorporated into the specification and form a part of this specification, and are used together with the specification to explain the principles of the present invention.

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the accompanying drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0020] Figure 1 It is a flowchart of a remedial method for defects in the hot isostatic pressing process of tungsten-based powder high-speed steel provided by the present invention; Figure 2 It is an optical photograph of the tungsten-based powder high-speed steel obtained in Example 1 of the present invention; Figure 3 It is an optical microscope picture of the tungsten-based powder high-speed steel obtained in Example 2 of the present invention; Figure 4 It is an optical microscope picture of the tungsten-based powder high-speed steel obtained in Example 3 of the present invention; Figure 5 It is an optical microscope picture of the tungsten-based powder high-speed steel obtained by the comparative example using the traditional hot isostatic pressing process. Detailed Embodiments

[0021] Here, the exemplary embodiments will be described in detail. The implementation manners described in the following exemplary embodiments do not represent all implementation manners consistent with the present invention. On the contrary, they are only examples consistent with some aspects of the present invention detailed in the appended claims.

[0022] In order 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

[0023] See Figure 1 As shown, this embodiment provides a remedial method for defects in the hot isostatic pressing process of tungsten-based powder high-speed steel, specifically including the following steps: Step 1: Cut off the original sheath nozzle of the uncompacted tungsten-based powder high-speed steel waste piece after traditional hot isostatic pressing, repair weld a new sheath nozzle and load an appropriate amount of powder; weld an exhaust pipe to the new sheath nozzle for degassing and then seal weld it; among them, The repair welding of the new sheath nozzle is specifically as follows: Use DC TIG welding, the diameter of the 316L welding wire is 1.5 mm, the starting current is 10 A, the welding current is 110 A, the arc extinguishing current is 10 A, the rise time is 1 s, the fall time is 1 s, the post-gas shut-off time is 5 s, and the welding position is silver-white or light yellow; The powder loading requirements in the new sheath nozzle are as follows: The height of the powder filling accounts for 7 / 8 of the total height of the new sheath nozzle, and the tapped density of the powder is 5.81 g / cm 3 ; The welding parameters of the exhaust pipe are specifically as follows: Use DC TIG welding, the diameter of the 316L welding wire is 1.5 mm, the starting current is 10 A, the welding current is 90 A, the arc extinguishing current is 10 A, the rise time is 1 s, the fall time is 1 s, the post-gas shut-off time is 5 s, and the welding position is silver-white or light yellow; The process parameters for degassing are as follows: The degassing temperature is 450 °C, the vacuum degree is 1×10 -5 Pa, and the degassing time is 96 h; The specific process of the seal welding is as follows: Use DC TIG welding, the diameter of the welding wire is 1.2 mm, the starting current is 10 A, the welding current is 60 A, the arc extinguishing current is 10 A, the rise time is 1 s, the fall time is 1 s, the post-gas shut-off time is 5 s, and the welding position is silver-white or light yellow; After the seal welding is completed, leak detection is carried out. Specifically: Connect the new sheath nozzle to the vacuum pump and the leak detector in sequence to ensure that all components are tightly connected without leakage; First, turn on the mechanical pump to pump the system pressure down to 3 Pa. After the pressure is stable, turn on the molecular pump to continue pumping air until the system pressure reaches 1×10 -5 Pa, turn off the mechanical pump, and only keep the molecular pump and the leak detector running normally. Continue pumping air until the system vacuum degree reaches 1×10 -10 mbar·l / s, and conduct leak detection along the welding area. If the waveform is a horizontal straight line without fluctuations, it indicates that the integrity and tightness of the entire sheath meet the requirements.

[0024] Further, in Step 1, the powder loading process of the powder loaded into the new sheath nozzle is as follows: First, use a double-cone rotary vacuum dryer of model SZG-500 to process the powder to be loaded into the new sheath nozzle, control the rotation speed at 5 rpm, the temperature at 150 °C, and the time at 1 h. While drying the powder, it can also eliminate the gas attached to the surface of the powder particles to avoid affecting the density of the final workpiece due to the formation of oxides and other impurities during the subsequent hot isostatic pressing process; Then, during the powder filling process, the longitudinal frequency is controlled at 20 Hz, the transverse force is 20 N, and the vibration application frequency is 5 times / s, so as to meet the set requirements for the tapped density of the powder.

[0025] Step 2: Perform secondary hot isostatic pressing on the entire jacket of the tungsten-based powder high-speed steel after degassing and sealing welding; the process parameters of the secondary hot isostatic pressing are as follows: the secondary hot isostatic pressing temperature, pressure, and holding time are the same as those of the traditional hot isostatic pressing.

[0026] To further verify the performance of the tungsten-based powder high-speed steel after remediation in this embodiment, after the secondary hot isostatic pressing is completed, the following steps are also performed: Step 31: Cut off the nozzle of the jacket of the tungsten-based powder high-speed steel after secondary hot isostatic pressing in Step 2 for observation to verify the microstructure, and obtain the tungsten-based powder high-speed steel (I) prepared by remediation. The optical micrograph is shown in Figure 2 , from Figure 2 it can be seen that the microstructure of the tungsten-based powder high-speed steel has no pores, no cracks, and is dense, indicating that the remediation method provided in this embodiment can fully remove the residual inert gas in the original hot isostatic pressing parts, and the secondary hot isostatic pressing process can effectively avoid thermal stress cracking and achieve densification.

[0027] It should be supplemented that in the tungsten-based powder high-speed steel, the mass ratio of the powder with a particle size < 53 μm is 46%, and the mass ratio of the powder with a particle size between 53 μm and 150 μm is 54%; in the original powder state, the mass ratio of (Fe,W)2C and (Fe,V)C powders is 10%, and the remaining components are the steel matrix; after the remediation treatment, the mass ratio of (Fe,W)6C and (Fe,V)C powders is 25%, and the steel matrix remains the rest of the components. Moreover, the tungsten-based powder high-speed steel prepared by the remediation method provided by the present invention has a density of 99.7%. Example 2

[0028] This embodiment provides a remediation method for the defects of the hot isostatic pressing process of tungsten-based powder high-speed steel, which specifically includes the following steps: Step 1: Cut off the original nozzle of the jacket of the uncompacted tungsten-based powder high-speed steel waste piece after traditional hot isostatic pressing, weld a new nozzle and fill it with an appropriate amount of powder; at the same time, degas and seal the welding degassing pipe of the new nozzle; among them, The welding of the new nozzle is specifically as follows: DC TIG welding is used, the diameter of the 316L welding wire is 2.5 mm, the starting current is 50 A, the welding current is 160 A, the arc extinguishing current is 40 A, the rise time is 5 s, the fall time is 10 s, the post-gas shut-off time is 20 s, and the welding position is silver-white or light yellow; The powder filling requirements in the new nozzle are as follows: the powder filling height accounts for 3 / 4 of the total height of the new nozzle, and the tapped density of the powder is 5.89 g / cm 3 ; The specific welding parameters of the degassing pipe are as follows: DC TIG welding, 316L welding wire diameter is 2.1mm, starting current is 50A, welding current is 150A, arc ending current is 40A, rising time is 5s, falling time is 10s, delayed gas stop is 20s, and the welding position is silvery white or light yellow; The process parameters used for degassing are as follows: degassing temperature is 400°C, vacuum degree is 9×10 -5 Pa, degassing time is 24h; The specific process of the sealing welding is as follows: DC TIG welding is used, the wire diameter is 1.8 mm, the starting current is 50A, the welding current is 120A, the arc closing current is 40A, the rising time is 5s, the falling time is 10s, the gas is stopped after 20s, and the welding position is silvery white or light yellow; After the sealing and welding is completed, leak detection is performed. Specifically, the new bag nozzle is connected to the vacuum pump and the leak detector in turn to ensure that all components are tightly connected and leak-free; first, the mechanical pump is turned on to pump the system pressure to 5Pa. After the pressure stabilizes, the molecular pump is turned on to continue pumping until the system pressure reaches 9×10 -5 Pa; turn off the mechanical pump, and only keep the molecular pump and leak detector running normally, and continue to pump air until the system vacuum reaches 9×10 -10 mbar·l / s, leak detection is carried out along the welding point. If the waveform is a horizontal straight line without fluctuation, it means that the integrity and sealing of the whole package meet the requirements.

[0029] Furthermore, in step 1, the powder filling process of the new bag nozzle is as follows: First, a double-cone rotary vacuum dryer of model SZG-500 is used to treat the powder to be loaded into the new bag nozzle. The speed is controlled to be 8rpm, the temperature is 100℃, and the time is 2h. While drying the powder, it can also eliminate the gas attached to the surface of the powder particles to avoid the formation of impurities such as oxides in the subsequent hot isostatic pressing process, which affects the density of the final product. Then, during the powder filling process, the longitudinal frequency was controlled to be 30 Hz, the lateral force to be 100 N, and the vibration application frequency to be 3 times / s, so as to meet the set powder tap density requirements.

[0030] Step 2, performing secondary hot isostatic pressing on the entire sheath of the tungsten powder high-speed steel after degassing and sealing welding; 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 1h longer than the traditional hot isostatic pressing holding time.

[0031] In order to further verify the performance of the remedied tungsten powder high speed steel of this embodiment, the following steps are further performed after the secondary hot isostatic pressing is completed: Step 31: Cut off the sleeve nozzle of the tungsten-based powder high-speed steel after secondary hot isostatic pressing in Step 2 for observation to verify the microstructure, and obtain the remedially prepared tungsten-based powder high-speed steel (II). See the optical micrograph in Figure 3 , from Figure 3 it can be seen that the microstructure of the tungsten-based powder high-speed steel has no pores, no cracks, and is dense, indicating that the remedial method provided in this embodiment can fully remove the residual inert gas in the original hot isostatic pressing parts, and the secondary hot isostatic pressing process can effectively avoid thermal stress cracking and achieve densification.

[0032] It should be supplemented that in the tungsten-based powder high-speed steel, the mass ratio of powders with a particle size < 53μm is 50%, and the mass ratio of powders with a particle size between 53μm and 150μm is 50%; in the original powder state, the mass ratio of (Fe,W)2C and (Fe,V)C powders is 20%, and the remaining components are the steel matrix; after remedial treatment, the mass ratio of (Fe,W)6C and (Fe,V)C powders is 35%, and the steel matrix is still the remaining components. Moreover, the tungsten-based powder high-speed steel prepared by the remedial method provided by the present invention has a density of 99.8%. Example 3

[0033] This embodiment provides a remedial method for the defects of the hot isostatic pressing process of tungsten-based powder high-speed steel, which specifically includes the following steps: Step 1: Cut off the original sleeve nozzle of the uncompacted tungsten-based powder high-speed steel waste piece after traditional hot isostatic pressing, weld a new sleeve nozzle and load an appropriate amount of powder; at the same time, degas and seal-weld the degassing pipe welded to the new sleeve nozzle; among them, The specific welding of the new sleeve nozzle is as follows: Use DC TIG welding, the diameter of the 316L welding wire is 2mm, the starting current is 30A, the welding current is 135A, the arc extinguishing current is 25A, the rise time is 3s, the fall time is 5.5s, the post-gas shut-off time is 12.5s, and the welding position is silver-white or light yellow; The powder loading requirements in the new sleeve nozzle are as follows: The powder filling height accounts for 13 / 16 of the total height of the new sleeve nozzle, and the tapped density of the powder is 5.85g / cm 3 ; The welding parameters of the degassing pipe are specifically as follows: Use DC TIG welding, the diameter of the 316L welding wire is 1.8mm, the starting current is 30A, the welding current is 120A, the arc extinguishing current is 25A, the rise time is 3s, the fall time is 5.5s, the post-gas shut-off time is 12.5s, and the welding position is silver-white or light yellow; The process parameters for degassing are as follows: The degassing temperature is 500°C, the vacuum degree is 5×10 -5 Pa, and the degassing time is 60h; The specific process of the seal welding is as follows: DC TIG welding is adopted, the wire diameter is 1.5 mm, the starting current is 30 A, the welding current is 90 A, the arc extinguishing current is 25 A, the rise time is 3 s, the fall time is 5.5 s, the post-gas shut-off time is 12.5 s, and the welding position shows a silver-white or light yellow color; After the seal welding is completed, leak detection is carried out. Specifically: Connect the new shroud nozzle to the vacuum pump and the leak detector in sequence to ensure that all components are tightly connected without leakage; First, turn on the mechanical pump to pump the system pressure down to 4 Pa. After the pressure is stable, turn on the molecular pump to continue pumping air until the system pressure reaches 5×10 -5 Pa, turn off the mechanical pump, and only keep the molecular pump and the leak detector running normally. Continue pumping air until the system vacuum degree reaches 5×10 -10 mbar·l / s. Conduct leak detection along the welding area. If the waveform shows a horizontal straight line without fluctuations, it indicates that the integrity and sealing performance of the entire shroud meet the requirements.

[0034] Further, in step 1, the powder loading process for loading the powder into the new shroud nozzle is as follows: First, use a double-cone rotary vacuum dryer of model SZG-500 to process the powder to be loaded into the new shroud nozzle, control the rotation speed at 11 rpm, the temperature at 150 °C, and the time at 3 h. While drying the powder, it can also eliminate the gas attached to the surface of the powder particles to avoid affecting the density of the final workpiece due to the formation of oxides and other impurities during the subsequent hot isostatic pressing process; Then, during the powder loading process, control the longitudinal frequency at 40 Hz, the transverse force at 200 N, and the vibration application frequency at 5 times / s, so as to meet the set requirements for the tapped density of the powder.

[0035] Step 2: Perform secondary hot isostatic pressing on the entire shroud of the tungsten-based powder high-speed steel after degassing and seal welding; The process parameters of the secondary hot isostatic pressing are as follows: The temperature of the secondary hot isostatic pressing is 40 °C higher than the temperature of the traditional hot isostatic pressing, the pressure of the secondary hot isostatic pressing is 15 MPa higher than the pressure of the traditional hot isostatic pressing, and the holding time of the secondary hot isostatic pressing is 0.5 h longer than the holding time of the traditional hot isostatic pressing.

[0036] To further verify the performance of the tungsten-based powder high-speed steel after remediation in this embodiment, after the secondary hot isostatic pressing is completed, the following steps are also carried out: Step 31: Cut off the shroud nozzle of the tungsten-based powder high-speed steel after the secondary hot isostatic pressing in step 2 for observation to verify the microstructure, and obtain the tungsten-based powder high-speed steel (III) prepared by remediation. See the optical micrograph in Figure 4 , from Figure 4 it can be seen that the microstructure of the tungsten-based powder high-speed steel has no pores, no cracks, and the tissue is dense, indicating that the remediation method provided in this embodiment can fully remove the residual inert gas in the original hot isostatic pressed workpiece, and the secondary hot isostatic pressing process can effectively avoid thermal stress cracking and achieve densification.

[0037] It should be further noted that in the tungsten-based powder high-speed steel, the mass ratio of powders with a particle size < 53 μm is 80%, and the mass ratio of powders with a particle size between 53 μm and 150 μm is 20%; in the original powder state, the mass ratio of (Fe,W)2C and (Fe,V)C powders is 40%, and the remaining components are the steel matrix; after the remedial treatment, the mass ratio of (Fe,W)6C and (Fe,V)C powders is 45%, and the steel matrix remains the rest of the components. Moreover, the tungsten-based powder high-speed steel prepared by the remedial method provided by the present invention has a relative density of 99.9%. Example 4

[0038] The difference between this example and Example 3 is that: to further verify the performance of the tungsten-based powder high-speed steel after remediation in this example, after the secondary hot isostatic pressing is completed, the following steps are also carried out: Step 32: By comparing the dimensional changes of the entire sheath 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 is successful, that is, the preparation of the tungsten-based powder high-speed steel after remediation is completed. Comparative Example

[0039] This comparative example provides a hot isostatic pressing process for tungsten-based powder high-speed steel. The tungsten-based powder high-speed steel is subjected to hot isostatic pressing treatment by using a traditional hot isostatic pressing process. The relevant process parameters are as follows: the traditional hot isostatic pressing temperature is 1110°C to 1170°C, the hot isostatic pressing pressure is 70 MPa to 120 MPa, and the hot isostatic pressing holding time is 1 h to 4 h.

[0040] For the tungsten-based powder high-speed steel prepared by the above traditional hot isostatic pressing process, the optical micrograph is shown in Figure 5 , and it can be seen from Figure 5 that the microstructure of the tungsten-based powder high-speed steel has pores, cracks, and poor tissue compactness, indicating that the remedial method of the hot isostatic pressing process provided by this comparative example cannot fully remove the residual inert gas in the original hot isostatic pressed parts, and the secondary hot isostatic pressing process cannot effectively avoid thermal stress cracking and achieve densification.

[0041] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0042] 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 only limited by the appended claims.

Claims

1. A remedial method for the defects of the hot isostatic pressing process of tungsten-based powder high-speed steel, characterized in that, Specifically, it includes the following steps: Step 1: Cut off the original sheath nozzle of the tungsten-based powder high-speed steel waste piece after traditional hot isostatic pressing, weld a new sheath nozzle and load an appropriate amount of powder, degas and seal-weld the degassing pipe welded to the new sheath nozzle; Step 2: Perform secondary hot isostatic pressing on the entire sheath of the tungsten-based powder high-speed steel after degassing and seal-welding to remedy the defects of the first hot isostatic pressing process.

2. The remedial method for the hot isostatic pressing process defects of tungsten-based powder high-speed steel according to claim 1, characterized in that, In Step 1, the repair welding of the new sheath nozzle is specifically as follows: Use DC TIG welding, the wire diameter is 1.5 mm to 2.5 mm, the starting current is 10 A to 50 A, the welding current is 110 A to 160 A, the arc extinguishing current is 10 A to 40 A, the rise time is 1 s to 5 s, the fall time is 1 s to 10 s, and the post-gas shut-off time is 5 s to 20 s.

3. The remedy method for the HIP process defects of tungsten-based powder high-speed steel according to claim 1, characterized in that, In Step 1, the powder filling requirements in the new package nozzle are as follows: the height of the powder filling accounts for 3 / 4 to 7 / 8 of the total height of the new package nozzle, and the tapped density of the powder is 5.81 g / cm 3 ~5.89 g / cm 3 .

4. The remedy method for the HIP process defects of tungsten-based powder high-speed steel according to claim 1, characterized in that, In Step 1, the welding parameters of the degassing pipe are specifically as follows: Use DC TIG welding, the wire diameter is 1.5 mm to 2.1 mm, the starting current is 10 A to 50 A, the welding current is 90 A to 150 A, the arc extinguishing current is 10 A to 40 A, the rise time is 1 s to 5 s, the fall time is 1 s to 10 s, and the post-gas shut-off time is 5 s to 20 s.

5. The remedial method for the HIP process defects of tungsten-based powder high-speed steel according to claim 1, characterized in that, In Step 1, the process parameters used for degassing are as follows: The degassing temperature is 400°C to 500°C, the vacuum degree is 1×10 -5 Pa to 9×10 -5 Pa, and the degassing time is 24 h to 96 h.

6. The remedial method for the HIP process defects of tungsten-based powder high-speed steel according to claim 1, characterized in that, In Step 2, the process parameters of the secondary hot isostatic pressing are as follows: The temperature of the secondary hot isostatic pressing is 0 °C to 80 °C higher than that of the traditional hot isostatic pressing, the pressure of the secondary hot isostatic pressing is 0 MPa to 30 MPa higher than that of the traditional hot isostatic pressing, and the holding time of the secondary hot isostatic pressing is 0 h to 1 h longer than that of the traditional hot isostatic pressing.

7. The remedial method for the HIP process defects 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 sheath nozzle of the tungsten-based powder high-speed steel after secondary hot isostatic pressing, obtain the corresponding optical micrograph, and judge whether the remedy of the tungsten-based powder high-speed steel waste piece is successful according to the density of the tungsten-based powder high-speed steel part reflected in the optical micrograph.

8. The remedy method for the HIP process defects of tungsten-based powder high-speed steel according to claim 1, characterized in that, It also includes the following steps: Step 32: Calculate the shrinkage rate by comparing the dimensional changes of the entire sheath of the tungsten-based powder high-speed steel before and after secondary hot isostatic pressing, and judge whether the remedy of the tungsten-based powder high-speed steel waste piece is successful according to the shrinkage rate.

9. The remedial method for the HIP process defects of tungsten-based powder high-speed steel according to any one of claims 1 to 8, characterized in that, The tungsten-based powder high-speed steel prepared by the remedy method has a relative density of 99.7% to 99.9%.

10. An application of the method for remedying the hot isostatic pressing process defects of tungsten-based powder high-speed steel as described in any one of claims 1 to 8 in the waste pieces formed by the traditional hot isostatic pressing process of tungsten-based powder high-speed steel.

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