Thu, 07 Jun 2018 02:05:27 +0000
The development of powder metallurgy technology and its advantages and disadvantages
A. There are three important marks for the development of modern powder metallurgy technology:
1. Overcome the difficulties in the process of refractory metal casting. The manufacture of electric lamp tungsten wire in 1909 promoted the development of powder metallurgy. The appearance of powder metallurgy cemented carbide in 1923 is regarded as the revolution in mechanical processing.
2. Successful production of porous oil bearing in the 1930s; Then the development of iron – based mechanical parts in powder metallurgy gives full play to the advantages of less cutting and even no cutting in powder metallurgy.
3. Develop to more advanced new materials and technologies. In the forties, metal ceramics, dispersion strengthening and other materials appeared. From the late 1960s to the early 1970s, powder high speed steel and powder high temperature alloy appeared successively. High strength parts can be made by using powder metallurgy forging and thermal static pressure.
Ii. Advantages of powder metallurgy process:
1. Most refractory metals and their compounds, fake alloys and porous materials can only be manufactured by powder metallurgy.
2. As the powder metallurgy method can be used to press the final size of the blank without requiring or rarely requiring subsequent mechanical processing, it can greatly save metal and reduce product cost. In the manufacture of products by powder metallurgy, the loss of metal is only 1-5%, while in the production by general smelting, the loss of metal may reach 80%.
3. Because the powder metallurgy process does not melt the material during the production of the material, it is not afraid to mix into the impurities brought by the crucible and the deoxidizer, while sintering is usually carried out in a vacuum and reducing atmosphere, without fear of oxidation and any contamination of the material, so it is possible to prepare the material with high purity.
4. Powder metallurgy can guarantee the accuracy and uniformity of material composition proportion.
5. Powder metallurgy is suitable for the production of many products with the same shape, especially those with high processing costs such as gears. The manufacturing of powder metallurgy can greatly reduce the production cost.
Iii. Disadvantages of powder metallurgy:
General disadvantages: 1) there are always pores in the product; 2) the strength of ordinary powder metallurgy products is lower than that of corresponding forgings or castings (about 20%~30% lower); 3) as the powder is far less liquid than liquid metal in the forming process, there are certain restrictions on the product structure and shape; 4) high pressure is required for pressing and forming, so products are limited by the capacity of pressing equipment. 5) high die cost, generally only applicable to batch or mass production. Metal powder: the final product quality is difficult to control freely; Metal powder is expensive; The powder does not conform to the laws of hydraulics, which limits the shape of the product structure. Manufacturing equipment and method: 1) the pressure machine, often need to use expensive powerful press 2) die, consumables, the high cost of 3) easy oxidation of sintering furnace 4) powder, mixed need long time restrictions on the size and shape of 5) products.