"Green Manufacturing" Technology - Powder Metallurgy

1. Definition and Principle

Powder metallurgy is a process technology for preparing metal powder or using metal powder as raw material, forming and sintering, to manufacture metal materials, composite materials and various types of products. Its basic process includes powder preparation, powder forming, sintering and subsequent treatment. This technology originated from ancient metallurgical technology, but the development of modern powder metallurgy technology began in the early 20th century and gradually became an important branch of materials science and engineering technology.

1. Process

1. Powdering is the process of making raw materials into powder. Commonly used powdering methods include oxide reduction method and mechanical method.

2. Mixing is the process of mixing various required powders in a certain proportion and homogenizing them into blank powder. There are three types: dry, semi-dry and wet, which are used for different requirements.

3. Forming is the process of loading the uniformly mixed mixture into a die and pressing it into a blank with a certain shape, size and density. The forming methods are basically divided into pressure forming and pressureless forming. The most commonly used in pressure forming is compression molding.

4. Sintering is a key process in powder metallurgy. The formed blank is sintered to obtain the required final physical and mechanical properties. Sintering is divided into unit system sintering and multi-component system sintering. In addition to ordinary sintering, there are also special sintering processes such as loose sintering, melt infiltration, hot pressing, etc.

5. Post-sintering treatment can be carried out in a variety of ways according to different product requirements. Such as finishing, oil immersion, machining, heat treatment and electroplating. In addition, in recent years, some new processes such as rolling and forging have also been applied to the processing of powder metallurgy materials after sintering, achieving relatively ideal results.

3. Clamping system in common gear processing methods

From ordinary turning → gear hobbing → gear shaping → gear shaving → hard turning → gear grinding → honing → drilling → inner hole grinding → welding → measurement, it is particularly important to configure a suitable clamping system for this process.

4. Process characteristics

1. The density of the product can be controlled, such as porous materials, high-density materials, etc.

2. Fine grains, uniform microstructure, and no component segregation.

3. Near-molding, raw material utilization rate > 95%.

4. Less or no cutting, cutting processing is only 40%~50%.

5. The material components are controllable, which is conducive to the preparation of composite materials.

1. Advantages, Disadvantages & Applications

Advantages:

1. Generally, powder metallurgy gears have fewer manufacturing processes.
2. When manufacturing gears using powder metallurgy, the material utilization rate can reach more than 95%.
3. The repeatability of powder metallurgy gears is very good. Because powder metallurgy gears are pressed into shape using molds, under normal conditions of use, a pair of molds can press tens to hundreds of thousands of gear blanks.
4. Powder metallurgy can manufacture several parts in one.
5. The material density of powder metallurgy gears is controllable.

6. In powder metallurgy production, in order to facilitate the removal of the blank from the die after forming, the roughness of the die working surface is very good.

Disadvantages:

1. Batch production is required. Generally speaking, batches of more than 5,000 pieces are more suitable for powder metallurgy production.
2. The size is limited by the pressing capacity of the press. The press generally withstands pressures ranging from a few tons to hundreds of tons, and the diameter can basically be produced within 110mm.
3. Powder metallurgy gears are limited by the structure. Due to pressing and mold reasons, it is generally not suitable to produce worm gears, herringbone gears and helical gears with a helix angle greater than 35°. It is generally recommended to design the helical teeth of helical gears within 15°.
4. The thickness of powder metallurgy gears is limited. The cavity depth and press stroke must be 2 to 2.5 times the thickness of the gear. At the same time, considering the uniformity of the longitudinal density of the gear height, the thickness of the powder metallurgy gear is also very important.

Applications:

1. Automobile industry: Many automotive parts are manufactured using powder metallurgy technology, such as gears, synchronizer rings, engine parts, bearings, brake system components, etc.
2. Mechanical engineering: In the field of mechanical engineering, powder metallurgy is used to manufacture various parts with complex structures, such as pumps, valves, connecting rods, etc.
3. Electrical and electronic industries: Powder metallurgy technology can be used to produce iron core components in electromagnetic equipment, such as ferrite cores of transformers and inductors.
4. Aerospace: Due to the characteristics of low density, high strength and good thermal stability of powder metallurgy parts, they are widely used in the aerospace field, such as manufacturing engine parts, satellite components, etc.

In summary, powder metallurgy is an important material preparation technology with broad application prospects and significant advantages. With the continuous progress and development of science and technology, powder metallurgy technology will continue to improve and innovate, making greater contributions to the development of materials science and engineering technology.