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Powder metallurgy parts processing difficulties

Date:09 30,2017 Hits: Source:STR-Precision

While one of the development goals of the powder metallurgy industry is to require only a small amount of processing to machine and process the main attraction, many parts still require machining accuracy and better surface finish. Unfortunately, the processing of these parts is very difficult. Most of the trouble encountered is porous.

Pore leads to leaf micro fatigue. Cut the cutting edge of the cut, which passes between the particles and the holes. The impact caused by repeated small cracks at the cutting edge. Fatigue cracks increase until the cutting edge is cut. This is usually very small micro-cutting, wear wear is usually normal.

Also reduces the thermal conductivity of PM porous components. The result is at the cutting edge of the high temperature and may cause the crater to wear and deform. The path connected to the internal porous structure provides the cutting fluid discharged from the cutting area. This will lead to hot cracking or deformation, especially important for drilling.

The surface area of the porous structure caused by the internal increase also allows oxidation and / or carbonation to occur during the heat treatment. As mentioned earlier, oxides and carbides are hardened.

It is very important that the porous structure also gives the hardness components of the faulty parts. When planning to measure the macro hardness of the PM part, it includes the hole hardness factor. The porous structure leads to the collapse of the structure, the relatively soft part of the wrong impression. Lots of hard particles to the individual. As mentioned above, the difference is significant.

The inclusions in the powder metallurgy section are negative. In this process, when the particles are rubbed from the cutting tool, the particles are pulled out from the surface and may form scratches or scratches on the surface of the part. These inclusions are usually large and leave visible holes on the surface of the part.

The mixed carbon content results in inconsistent processing. For example, the carbon content of the FC0208 alloy is between 0.6% and 0.9%. A group of 0.9% of the carbon content of the material is relatively hard, resulting in poor tool life, while the other batch of carbon content of 0.6% of the material has excellent tool life. Both alloys are within the allowable range.

The final machining problem is related to the type of cutting that occurs on the PM part. As the parts close to the final shape, the cutting depth is very shallow. This requires free cutting. The edge of the cutting edge often leads to a slight collapse.

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