Integral forming process of square shaft rocker arm

Abstract

The invention discloses an integral forming process of a square shaft rocker arm, which comprises the following steps: mixing metal powder and an organic binder according to an accurate proportion, and heating and stirring to form uniform feed; preparing the uniformly mixed feed into granules; a corresponding mold is designed according to the shape and size of the square shaft rocker arm; feeding the granular feed into an injection molding machine, injecting the granular feed into a preset mold under high-temperature and high-pressure conditions, and gradually removing the binder in the green body through a thermal degreasing method; putting into a high-temperature sintering furnace, and heating to a high temperature below a metal melting point in vacuum, so that metal particles are fused to form a compact structure; quenching, tempering and other processes are conducted on the sintered square shaft rocker arm, and electroplating treatment is conducted on the surface of the square shaft rocker arm; the method has the beneficial effects that the compactness and the mechanical property of the product are remarkably improved by utilizing a metal injection molding technology, and the service life of the product is far beyond that of a conventional part.

Description

Technical Field

[0001] The present invention belongs to the technical field of door and window lock accessories, and particularly relates to an integral forming process for a square shaft rocker arm. Background Art

[0002] The square shaft rocker arm belongs to one of the door and window lock accessories and is an important part of the door and window hardware system. Its main function is to realize the locking and opening operations of doors and windows.

[0003] The conventional forming of the square shaft rocker arm adopts the zinc alloy die-casting and pouring process. The structure of the formed part is not dense enough, and defects and holes are likely to appear, which affects the use effect and strength of the square shaft rocker arm. Summary of the Invention

[0004] To solve the above problems, the present invention provides an integral forming process for a square shaft rocker arm, which includes the following steps: S1. Mix the metal powder and the binder: Mix the metal powder and the organic binder in an accurate proportion, and form a uniform feed by heating and stirring. S2. Granulation: Make the uniformly mixed feed into granular form to facilitate the feeding and conveying of the subsequent injection molding machine. S3. Preset the mold size: Design a corresponding mold according to the shape and size of the square shaft rocker arm. The size of the mold should be 15% - 20% larger than the preset size. S4. Injection of green body: Feed the granular feed into the injection molding machine and inject it into the preset mold under high temperature and high pressure conditions to form a green body. S5. Debinding treatment: Gradually remove the binder in the green body by the thermal debinding method. S6. Sintering treatment: Put the debound green body into a high-temperature sintering furnace, heat it to a high temperature below the melting point of the metal in a vacuum to make the metal particles fuse to form a dense structure. S7. Post-treatment: Perform processes such as quenching and tempering on the sintered square shaft rocker arm to adjust the hardness, strength, and toughness of the part, and perform electroplating treatment on the surface.

[0005] Preferably, the heating temperature in step S1 is 150°C - 200°C.

[0006] Preferably, the high temperature in step S4 is 180°C - 200°C, and the high pressure is 80 MPa - 150 MPa.

[0007] Preferably, the thermal debinding method in step S5 is to slowly heat up to 400°C - 600°C in a protective gas to decompose and volatilize the binder, while avoiding cracking of the green body.

[0008] Preferably, the protective gas is one of hydrogen, nitrogen, argon, or carbon monoxide.

[0009] The advantages of the present invention are as follows: Through the metal injection molding technology, that is, a process that integrates two completely different processing technologies (powder metallurgy and plastic injection molding), the density and mechanical properties of the square shaft rocker arm have been significantly improved, and the quality and production efficiency of the square shaft rocker arm have been greatly increased. Specific embodiments

[0010] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described.

[0011] An integral molding process for a square shaft rocker arm includes the following steps: S1. Mix the metal powder with the binder: Select 316L stainless steel powder with a particle size of 35 μm and an organic binder of 60% POM polyoxymethylene + 40% paraffin wax in a mass ratio of 85:15 and add it to a high-speed mixer. Form a uniform feed by heating and stirring. The heating temperature is selected as 190°C, and stir at a speed of 300 rpm for 60 minutes to ensure that the powder uniformly coats the binder; after cooling to room temperature, extrude it into a strip-shaped feed through an extruder for subsequent granulation.

[0012] S2. Granulation: Use a twin-screw extruder for granulation. The screw diameter is 30 mm, the length-diameter ratio is 20:1, the feed temperature is maintained at 190°C, the screw speed is 100 rpm, and underwater pelletizing is used. The particle size is controlled at 3 mm; S3. Preset the mold size: Design the corresponding mold according to the shape and size of the square shaft rocker arm. The size of the mold should be 18% larger than the preset size. Use high-hardness mold steel (such as H13 steel), and perform hard chromium plating treatment on the surface, with a roughness Ra = 0.4 μm; S4. Green body injection: Feed the granular feed into an injection molding machine and inject it into the preset mold under the conditions of a high temperature of 190°C and a high pressure of 120 MPa. Injection speed: 100 mm / s, and the holding pressure time is 5 seconds to form a green body; S5. Debinding treatment: Gradually remove the binder in the green body through the thermal debinding method. The thermal debinding method is to slowly heat up to 500°C in nitrogen to decompose and volatilize the binder, while avoiding cracking of the green body; the specific heating method is divided into two stages. The first stage: heat up from room temperature to 200°C at a heating rate of 1°C / min and hold for 2 hours to remove the paraffin; the second stage: heat up at a rate of 0.5°C / min and hold for 4 hours to decompose POM. When the green body deforms, a stepped support structure needs to be adopted in a timely manner to ensure that the green body does not crack and demold.

[0013] S6. Sintering treatment: Put the degreased green compact into a high-temperature sintering furnace, heat it to a high temperature below the melting point of the metal in a vacuum, with an ultimate vacuum degree ≤ 1×10⁻³ Pa and a temperature uniformity of ±5°C, so that the metal particles fuse to form a dense structure; S7. Post-treatment: Quench the sintered square shaft rocker arm by oil quenching at 1050°C, with a hardness of HRC 35 - 40, temper it at 600°C for 2 hours, and perform processes such as stress relief to adjust the hardness, strength and toughness of the parts, and perform electroplating treatment on the surface with a nickel plating layer thickness of 5 - 10 μm to improve corrosion resistance.

[0014] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An integrated forming process for a square shaft rocker arm, characterized in that It includes the following steps: S1. Mix the metal powder with the binder: Mix the metal powder and the organic binder in an exact proportion, and form a uniform feedstock through heating and stirring; S2. Granulation: Make the uniformly mixed feedstock into granular form to facilitate the feeding and conveying of the subsequent injection molding machine; S3. Preset the mold size: Design the corresponding mold according to the shape and size of the square shaft rocker arm, and the size of the mold should be 15% - 20% larger than the preset size; S4. Green body injection: Feed the granular feedstock into the injection molding machine, and inject it into the preset mold under high temperature and high pressure conditions to form a green body; S5. Debinding treatment: Gradually remove the binder in the green body through the thermal debinding method; S6. Sintering treatment: Put the debound green body into a high-temperature sintering furnace, heat it to a high temperature below the melting point of the metal in a vacuum, and fuse the metal particles to form a dense structure; S7. Post-treatment: Perform processes such as quenching and tempering on the sintered square shaft rocker arm to adjust the hardness, strength and toughness of the part, and perform electroplating treatment on the surface.

2. The one-piece forming process of the square shaft rocker arm according to claim 1, characterized in that: The heating temperature in step S1 is 150°C - 200°C.

3. The one-piece forming process of the square shaft rocker arm according to claim 1, characterized in that: The high temperature in step S4 is 180°C - 200°C, and the high pressure is 80 MPa - 150 MPa.

4. The one-piece forming process of the square shaft rocker arm according to claim 1, characterized in that: The thermal debinding method in step S5 is to slowly heat up to 400°C - 600°C in a protective gas to decompose and volatilize the binder while avoiding cracking of the green body.

5. The one-piece forming process of the square shaft rocker arm according to claim 4, characterized in that: The protective gas is one of hydrogen, nitrogen, argon or carbon monoxide.