Heat treatment process for AISI420 stainless steel metal powder injection molding part

Abstract

The invention discloses a heat treatment process for an AISI420 stainless steel metal powder injection molding part. The heat treatment process comprises the following steps: step 1, hanging the AISI420 stainless steel metal powder injection molding part in quenching equipment; 2, the temperature in the quenching equipment is increased to 850 + / -3 DEG C in the vacuum environment, and heat preservation is conducted; step 3, raising the temperature to 1100 + / -3 DEG C and keeping the temperature; 4, the workpiece is subjected to oil quenching; 5, the workpiece is placed in tempering equipment; and 6, the interior of the tempering equipment is vacuumized. 7, in the vacuum environment, the temperature in the tempering equipment is increased to 450 + / -3 DEG C, and heat preservation is conducted; then carrying out forced cooling; 8, tempering equipment is completely cooled; step 9, vacuumizing the inside of the tempering equipment; step 10, in a vacuum environment, raising the temperature to 450 + / -3 DEG C and keeping the temperature; 11, forced cooling is conducted in the tempering equipment; and 12, the tempering equipment is completely cooled, and the product can be obtained.

Description

Technical Field

[0001] The invention relates to the field of heat treatment technology of AISI420 stainless steel metal parts, in particular to a heat treatment technology of AISI420 stainless steel metal powder injection molding parts. Background Art

[0002] Metal powder injection molding is an advanced metal forming technology that combines the advantages of powder metallurgy and plastic injection molding, breaks through the limitations of traditional metal powder forming processes in product shape, and becomes a near-net forming technology for modern manufacturing of high-quality precision parts. AISI420 stainless steel is a martensitic stainless steel with high hardness, strength and wear resistance, so it is widely used in the fields of measuring tools, knives and surgical medical devices.

[0003] The conventional size range of AISI420 stainless steel metal powder injection molded parts is 3-150mm. Metal parts with a size of more than 200mm and a wall thickness of less than 5mm are large-sized thin-walled parts in the industry. During the forming process of AISI420 stainless steel metal powder injection molded large-sized thin-walled parts, 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 link in the forming process of AISI420 stainless steel metal powder injection molded parts. The workpieces produced using the existing heat treatment process have relatively large residual stress, which causes the workpieces to have relatively large warping and deformation after being placed for a period of time. Summary of the invention

[0004] The 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 AISI420 stainless steel metal powder injection molded large-size thin-walled parts in the prior art.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: AISI420 stainless steel metal powder injection molding heat treatment process includes the following steps: 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 vacuum, and then keep the temperature at 850°C±3°C for 60min±3min; Step 3, under vacuum environment, 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 keep the temperature at 1100°C±3°C for 120min±3min; Step 4, taking the AISI420 stainless steel metal powder injection molded part out of the quenching equipment and performing oil quenching, the oil quenching time is 5min±1min, so as 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, evacuate the interior of the tempering equipment; Step 7, under 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 kept at 450°C±3°C for 270min±3min; then cooling gas is introduced into the tempering equipment for forced cooling, the forced cooling time is 30min±3min, and the pressure of the introduced cooling gas is 85KPa±5KPa; 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 environment, at a heating rate of 5°C±0.1°C / min, the temperature in the tempering equipment is raised from room temperature to 450°C±3°C, and kept at 450°C±3°C for 270min±3min; Step 11, introducing cooling gas into the tempering equipment for forced cooling, the forced cooling time is 30min±3min, and the pressure of the introduced cooling gas is 85KPa±5KPa; Step 12: Leave the tempering equipment for a period of time to ensure that the tempering equipment is completely cooled, and then the heat-treated product can be obtained.

[0006] Furthermore, the quenching equipment described in step 1 to step 4 is a double-chamber oil-quenching pressurized air-cooled vacuum furnace.

[0007] Furthermore, the tempering equipment described in step 5 to step 12 is a vacuum degreasing sintering furnace.

[0008] Furthermore, the cooling gas in step 7 and step 11 is argon.

[0009] 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

[0010] Figure 1 It is a process diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0011] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0012] like Figure 1As shown, this embodiment discloses a heat treatment process for AISI420 stainless steel metal powder injection molding parts, comprising the following steps: Step 1: Use a double-chamber oil quenching pressurized air-cooled vacuum furnace as a 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.

[0013] 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.

[0014] Step 3: In a vacuum environment, heat the double-chamber oil-quenching pressurized air-cooled vacuum furnace to 1100°C±3°C at a heating rate of 2.5°C±0.1°C / min, and then keep it at 1100°C±3°C for 120min±3min.

[0015] Step 4: Take the cage containing AISI420 stainless steel metal powder injection molded parts out of the double-chamber oil quenching pressurized air-cooled vacuum furnace, and immerse it in the quenching oil medium in the oil pool for oil quenching. The oil quenching time is 5min±1min, so as to achieve rapid cooling of the AISI420 stainless steel metal powder injection molded parts to room temperature. Then lift the cage, take out the AISI420 stainless steel metal powder injection molded parts, and clean them.

[0016] 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.

[0017] Step 6: Evacuate the interior of the vacuum degreasing sintering furnace.

[0018] Step 7: In a vacuum environment, the temperature in the vacuum debinding sintering furnace is raised from room temperature to 450°C±3°C at a rate of 5°C±0.1°C / min. Then, the temperature is kept at 450°C±3°C for 270min±3min in a vacuum environment. Then, argon gas is introduced into the vacuum debinding sintering furnace as a cooling gas for forced cooling, and the forced cooling time is 30min±3min, and the pressure of the introduced argon gas is 85KPa±5KPa.

[0019] Step 8: Leave the vacuum degreasing sintering furnace for a while to ensure that the vacuum degreasing sintering furnace is completely cooled.

[0020] Step 9: Re-evacuate the vacuum degreasing sintering furnace.

[0021] Step 10: In a vacuum environment, 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 keep it at 450°C±3°C for 270min±3min.

[0022] 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.

[0023] 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.

[0024] The product indicators obtained in this embodiment are shown in Table 1: Table 1 Comparison of the heat treatment process of this embodiment and the original heat treatment process data

[0025] It can be seen from Table 1 that the residual stress of the AISI420 stainless steel metal powder injection molded large-size thin-walled parts after the heat treatment process of this embodiment is 1.4MPa, which is 99.7% lower than the residual stress of the original process; the hardness of the product obtained by the process of this embodiment reaches 49.6HRC, which is 13.4% lower than the hardness of the original process. Therefore, the hardness of the process of this embodiment can still meet the requirements without a large drop in hardness, and the residual stress is significantly reduced.

[0026] The preferred embodiments of the present invention are described in detail above in conjunction with 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 without contradiction, and such combinations should also be regarded as the contents disclosed in the present 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.

[0027] The present invention is not limited to the specific details of the above-mentioned embodiments. Within 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 technical personnel in this field should fall within the protection scope 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 vacuum, and then keep the temperature at 850°C±3°C for 60min±3min; Step 3, under vacuum environment, 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 keep the temperature at 1100°C±3°C for 120min±3min; Step 4, taking the AISI420 stainless steel metal powder injection molded part out of the quenching equipment and performing oil quenching, the oil quenching time is 5min±1min, so as 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, evacuate the interior of the tempering equipment; Step 7, under 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 kept at 450°C±3°C for 270min±3min; then cooling gas is introduced into the tempering equipment for forced cooling, the forced cooling time is 30min±3min, and the pressure of the introduced cooling gas is 85KPa±5KPa; 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 environment, at a heating rate of 5°C±0.1°C / min, the temperature in the tempering equipment is raised from room temperature to 450°C±3°C, and kept at 450°C±3°C for 270min±3min; Step 11, introducing cooling gas into the tempering equipment for forced cooling, the forced cooling time is 30min±3min, and the pressure of the introduced cooling gas is 85KPa±5KPa; Step 12: Leave the tempering equipment for a period of time to ensure that the tempering equipment is completely cooled, and then 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 step 1 to step 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 step 7 and step 11 is argon gas.

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