I have seen a lot of gear manufacturing, including hobbing, milling, shaping and other processes. Today, I will talk about the process of pressing metal powder, which is powder metallurgy:
Powder metallurgy gears are commonly used in various automobile engines. Although they are very economical and practical in large quantities, they also need to be improved in other aspects. Let's take a look at the advantages and disadvantages of powder metallurgy gears.
Advantages:
1. Generally, there are fewer manufacturing processes for powder metallurgy gears.
2. When manufacturing gears by 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 by dies, under normal use conditions, a pair of dies can press tens to hundreds of thousands of gear blanks.
4. Powder metallurgy can manufacture several parts in one piece
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.
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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 has a pressure of several tons to several hundred tons, and the diameter can be made into powder metallurgy within 110MM;
3. Powder metallurgy gears are limited by structure. Due to pressing and mold reasons, it is generally not suitable to produce worm gears, herringbone gears and helical gears with a helical angle greater than 35°. It is generally recommended to design the helical teeth within 15 degrees for helical gears;
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 gear's height longitudinal density, the thickness of the powder metallurgy gear is also very important;
What is powder metallurgy
It is a process technology for making metal or using metal powder (or a mixture of metal powder and non-metallic powder) as raw materials, forming and sintering, to manufacture metal materials, composite materials and various types of products. The broad sense of powder metallurgy products industry includes iron and stone tools, cemented carbide, magnetic materials and powder metallurgy products. The narrow sense of powder metallurgy products industry refers only to powder metallurgy products, including powder metallurgy parts (accounting for the vast majority), oil-containing bearings and metal injection molding products.
Process characteristics
1. The density of the product is controllable, such as porous materials, high-density materials, etc.;
2. Small grains, uniform microstructure, 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;
6. Preparation of refractory metals, ceramic materials and nuclear materials.
Basic process flow
1. Powder making
Powder making is the process of making raw materials into powder. Commonly used powder making methods are oxide reduction method and mechanical method.
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2. Mixing
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.
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3. Forming
Forming is the process of putting 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 forming.
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4. Sintering
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.
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5. Post-processing
The 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.
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Now that we know about powder metallurgy, we have to talk about machine tool cutting tools. Every time I see a processing video, my friends ask how this cutting tool is made. In fact, this has been posted before, so if you have seen it, just ignore it.
Content source: Internet
