A heat treatment process for AISI420 stainless steel metal powder injection molding parts

Abstract

The present invention discloses a heat treatment process for AISI420 stainless steel metal powder injection molded parts, comprising the following steps: step 1, hanging the AISI420 stainless steel metal powder injection molded parts in a quenching device; step 2, raising the temperature in the quenching device to 850°C±3°C and maintaining the temperature under a vacuum environment; step 3, raising the temperature to 1100°C±3°C and maintaining the temperature; step 4, oil quenching the workpiece; step 5, placing the workpiece in a tempering device; step 6, evacuating the interior of the tempering device; step 7, raising the temperature in the tempering device to 450°C±3°C and maintaining the temperature under a vacuum environment; then performing forced cooling; step 8, completely cooling the tempering device; step 9, evacuating the interior of the tempering device; step 10, raising the temperature to 450°C±3°C and maintaining the temperature under a vacuum environment; step 11, performing forced cooling; and step 12, completely cooling the tempering device to obtain the product.

Description

Technical Field

[0001] The invention relates to the field of heat treatment technology for AISI 420 stainless steel metal parts, in particular to a heat treatment technology for AISI 420 stainless steel metal powder injection molded parts. Background Art

[0002] Metal powder injection molding (MPIM) is an advanced metal forming technology that combines the advantages of powder metallurgy and plastic injection molding. It overcomes the limitations of traditional metal powder forming processes in product shape and has become a near-net-shape technology for modern manufacturing of high-quality precision parts. AISI 420 stainless steel is a martensitic stainless steel with high hardness, strength, and wear resistance, making it widely used in measuring tools, cutting tools, and surgical instruments.

[0003] The conventional size range of AISI420 stainless steel metal powder injection molded parts is 3-150mm. Metal parts with a size exceeding 200mm and a wall thickness less than 5mm are considered large-sized thin-walled parts in the industry. During the forming process of large-sized thin-walled parts made by AISI420 stainless steel metal powder injection molding, due to the residual stress generated during the forming process, warping and deformation are very likely to occur, resulting in the flatness of the workpiece exceeding the tolerance range. Heat treatment is a key step in the forming process of AISI420 stainless steel metal powder injection molded parts. Workpieces produced using existing heat treatment processes have relatively large residual stresses, which causes the workpieces to exhibit relatively large warping and deformation after being placed for a period of time. Summary of the Invention

[0004] The present invention provides a heat treatment process for AISI420 stainless steel metal powder injection molded parts, so as to solve the problem of large residual stress in the forming process of large-size thin-walled parts made of AISI420 stainless steel metal powder injection molded parts in the prior art.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] The heat treatment process of AISI420 stainless steel metal powder injection molding parts includes the following steps:

[0007] Step 1: Hang AISI420 stainless steel metal powder injection molded parts in a quenching device;

[0008] Step 2: Evacuate the quenching equipment, then raise the temperature in the quenching equipment to 850°C ± 3°C at a heating rate of 7°C ± 0.1°C / min under the vacuum environment, and then maintain the temperature at 850°C ± 3°C for 60 min ± 3 min;

[0009] Step 3: Under vacuum, raise the temperature in the quenching equipment to 1100°C ± 3°C at a heating rate of 2.5°C ± 0.1°C / min, and then maintain the temperature at 1100°C ± 3°C for 120 min ± 3 min;

[0010] Step 4: After removing the AISI420 stainless steel metal powder injection molded part from the quenching equipment, oil quenching is performed for 5 min ± 1 min to achieve rapid cooling of the AISI420 stainless steel metal powder injection molded part to room temperature;

[0011] Step 5: placing the quenched AISI420 stainless steel metal powder injection molded part in a tempering device;

[0012] Step 6: Vacuum the interior of the tempering equipment;

[0013] Step 7. Under a vacuum environment, the temperature in the tempering equipment is raised from room temperature to 450°C ± 3°C at a rate of 5°C ± 0.1°C / min; then, the temperature is maintained at 450°C ± 3°C for 270 min ± 3 min; then, cooling gas is introduced into the tempering equipment for forced cooling for 30 min ± 3 min, and the pressure of the introduced cooling gas is 85 kPa ± 5 kPa;

[0014] Step 8: Leave the tempering equipment for a while to ensure that it is completely cooled;

[0015] Step 9: Re-evacuate the tempering equipment;

[0016] Step 10: Under vacuum, raise the temperature in the tempering equipment from room temperature to 450°C ± 3°C at a rate of 5°C ± 0.1°C / min, and maintain the temperature at 450°C ± 3°C for 270 min ± 3 min;

[0017] Step 11: Cooling gas is introduced into the tempering equipment for forced cooling. The forced cooling time is 30 min ± 3 min, and the pressure of the introduced cooling gas is 85 kPa ± 5 kPa.

[0018] Step 12: Place the tempering equipment for a period of time to ensure that the tempering equipment is completely cooled, and the heat-treated product can be obtained.

[0019] Furthermore, the quenching equipment described in steps 1 to 4 is a double-chamber oil-quenching pressurized air-cooled vacuum furnace.

[0020] Furthermore, the tempering equipment described in steps 5 to 12 is a vacuum degreasing sintering furnace.

[0021] Furthermore, the cooling gas in step 7 and step 11 is argon.

[0022] The heat treatment process of the present invention has the effect of significantly reducing residual stress while ensuring that the hardness of the product can meet the requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a process diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further described below with reference to the accompanying drawings and examples.

[0025] like Figure 1 As shown, this embodiment discloses a heat treatment process for AISI420 stainless steel metal powder injection molded parts, comprising the following steps:

[0026] Step 1: Use a double-chamber oil quenching pressurized air-cooled vacuum furnace as the quenching equipment, hang the AISI420 stainless steel metal powder injection molded parts in an iron cage with steel wire, and then push the iron cage into the double-chamber oil quenching pressurized air-cooled vacuum furnace, so that the AISI420 stainless steel metal powder injection molded parts are hung in the double-chamber oil quenching pressurized air-cooled vacuum furnace.

[0027] Step 2: Evacuate the double-chamber oil-quenching pressurized air-cooled vacuum furnace, then raise the temperature to 850°C±3°C at a heating rate of 7°C±0.1°C / min under a vacuum environment, and then keep it at 850°C±3°C for 60min±3min.

[0028] Step 3: Under vacuum, heat the double-chamber oil-quenched pressurized air-cooled vacuum furnace to 1100°C ± 3°C at a heating rate of 2.5°C ± 0.1°C / min, and then maintain the temperature at 1100°C ± 3°C for 120 min ± 3 min.

[0029] Step 4: Remove the cage containing the AISI 420 stainless steel powder injection molded parts from the dual-chamber oil-quenching, pressurized, air-cooled vacuum furnace and immerse them in the quenching oil in the oil pool for 5 min ± 1 min to quickly cool the AISI 420 stainless steel powder injection molded parts to room temperature. The cage is then lifted, the AISI 420 stainless steel powder injection molded parts removed, and cleaned.

[0030] Step 5: Use a metal injection molding vacuum degreasing and sintering furnace as a tempering device, place the ceramic plate on the graphite plate in the vacuum degreasing and sintering furnace, and then place the AISI420 stainless steel metal powder injection molded parts to be tempered after quenching on the ceramic plate. The AISI420 stainless steel metal powder injection molded parts are staggered and must not overlap, so that the AISI420 stainless steel metal powder injection molded parts are placed in the vacuum degreasing and sintering furnace.

[0031] Step 6: Vacuum the interior of the vacuum degreasing sintering furnace.

[0032] Step 7: Under vacuum, raise the temperature in the vacuum debinding and sintering furnace from room temperature to 450°C ± 3°C at a rate of 5°C ± 0.1°C / min. Maintain the temperature at 450°C ± 3°C under vacuum for 270 min ± 3 min. Then, introduce argon gas as a cooling gas into the vacuum debinding and sintering furnace for forced cooling for 30 min ± 3 min at a pressure of 85 kPa ± 5 kPa.

[0033] Step 8: Leave the vacuum degreasing and sintering furnace for a while to ensure that the vacuum degreasing and sintering furnace is completely cooled.

[0034] Step 9: Re-evacuate the vacuum degreasing sintering furnace.

[0035] Step 10: Under vacuum conditions, raise the temperature in the vacuum debinding sintering furnace from room temperature to 450°C±3°C at a heating rate of 5°C±0.1 / min, and maintain the temperature at 450°C±3°C for 270 min±3 min.

[0036] Step 11: introduce argon as cooling gas into the vacuum degreasing sintering furnace for forced cooling. The forced cooling time is 30 min ± 3 min, and the pressure of the introduced argon is 85 KPa ± 5 KPa.

[0037] Step 12: Leave the vacuum degreasing and sintering furnace for a period of time to ensure that the vacuum degreasing and sintering furnace is completely cooled, and then the heat-treated product can be obtained.

[0038] The product indicators obtained in this embodiment are shown in Table 1:

[0039] Table 1 Comparison of the heat treatment process of this embodiment and the original heat treatment process data

[0040]

[0041] Table 1 shows that after the heat treatment process of this embodiment, the residual stress of a large-scale, thin-walled AISI420 stainless steel metal powder injection molded part was 1.4 MPa, a 99.7% reduction compared to the residual stress of the original process. The hardness of the product obtained by this embodiment reached 49.6 HRC, a 13.4% reduction compared to the original process. Therefore, the process of this embodiment can still meet the hardness requirements without significantly reducing the hardness, and significantly reduces residual stress.

[0042] The preferred embodiments of the present invention are described in detail above with reference to the accompanying drawings. The embodiments described in the present invention are merely descriptions of the preferred embodiments of the present invention and do not limit the concept and scope of the present invention. The various specific technical features described in the above specific embodiments can be combined in any suitable manner unless there is any contradiction. Such combinations should also be regarded as the contents disclosed in this disclosure as long as they do not violate the concept of the present invention. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0043] The present invention is not limited to the specific details of the above-mentioned embodiments. Within the scope of the technical concept of the present invention and without departing from the design concept of the present invention, various modifications and improvements made to the technical solution of the present invention by those skilled in the art should fall within the scope of protection of the present invention. The technical contents for which protection is sought in the present invention have been fully recorded in the claims.

Claims

1. A heat treatment process for AISI420 stainless steel metal powder injection molding parts, characterized in that: The following steps are involved: Step 1: Hang AISI420 stainless steel metal powder injection molded parts in a quenching device; Step 2: Evacuate the quenching equipment, then raise the temperature in the quenching equipment to 850°C ± 3°C at a heating rate of 7°C ± 0.1°C / min under the vacuum environment, and then maintain the temperature at 850°C ± 3°C for 60 min ± 3 min; Step 3: Under vacuum, raise the temperature in the quenching equipment to 1100°C ± 3°C at a heating rate of 2.5°C ± 0.1°C / min, and then maintain the temperature at 1100°C ± 3°C for 120 min ± 3 min; Step 4: After removing the AISI420 stainless steel metal powder injection molded part from the quenching equipment, oil quenching is performed for 5 min ± 1 min to achieve rapid cooling of the AISI420 stainless steel metal powder injection molded part to room temperature; Step 5: placing the quenched AISI420 stainless steel metal powder injection molded part in a tempering device; Step 6: Vacuum the interior of the tempering equipment; Step 7. Under a vacuum environment, the temperature in the tempering equipment is raised from room temperature to 450°C ± 3°C at a rate of 5°C ± 0.1°C / min; then, the temperature is maintained at 450°C ± 3°C for 270 min ± 3 min; then, cooling gas is introduced into the tempering equipment for forced cooling for 30 min ± 3 min, and the pressure of the introduced cooling gas is 85 kPa ± 5 kPa; Step 8: Leave the tempering equipment for a while to ensure that it is completely cooled; Step 9: Re-evacuate the tempering equipment; Step 10: Under vacuum, raise the temperature in the tempering equipment from room temperature to 450°C ± 3°C at a rate of 5°C ± 0.1°C / min, and maintain the temperature at 450°C ± 3°C for 270 min ± 3 min; Step 11: Cooling gas is introduced into the tempering equipment for forced cooling. The forced cooling time is 30 min ± 3 min, and the pressure of the introduced cooling gas is 85 kPa ± 5 kPa. Step 12: Place the tempering equipment for a period of time to ensure that the tempering equipment is completely cooled, and the heat-treated product can be obtained.

2. The heat treatment process for AISI420 stainless steel metal powder injection molded parts according to claim 1, characterized in that: The quenching equipment described in steps 1 to 4 is a double-chamber oil-quenching pressurized air-cooled vacuum furnace.

3. The heat treatment process for AISI420 stainless steel metal powder injection molded parts according to claim 1, characterized in that: The tempering equipment described in step 5 to step 12 is a vacuum degreasing sintering furnace.

4. The heat treatment process for AISI420 stainless steel metal powder injection molded parts according to claim 1, characterized in that: The cooling gas in steps 7 and 11 is argon.

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