1. Powder metallurgy high speed steel smelting characteristics Compared with common high speed steel smelting, powder metallurgy of high speed steel smelting has its particularity and more advanced. Common high speed steel by electric arc furnace and induction furnace melting, pouring molten steel directly into ingot, then through forging, rolling processing ChengGangCai, but because of the liquid steel ingot casting condensed, solidification speed is slow, the separation of metal from liquid steel carbide, forms the herringbone ledeburite and crumb bulky eutectic carbide, and produce carbide segregation, directly affect the various mechanical properties of steel, especially the toughness of the steel.
And powder metallurgy high speed steel smelting is different, after the electric arc furnace and induction furnace melting liquid steel is not cast ingot directly, but will melt liquid steel through the nozzle, spray into the high pressure nitrogen gas flow, liquid steel was quickly atomization cooling into fine grain steel, it is less than 1 mm in diameter. Then this powder in steel barrels, made of steel to steel drum, vacuum between the steel powder barrels pumped air into vacuum state, then welded steel drum, then under the high temperature and high pressure in the steel drum steel powder compacting, the formation of hot isostatic pressing sintering preparation technology. Which could produce density is almost 100% of the powder metallurgy high speed Steel billet, and then the next forging, rolling ChengGangCai because of powder metallurgy in the process of spray powder, steel liquid cooling speed is very fast, to avoid the common high speed steel ingot casting, many defects in the process of atomization of liquid steel in the carbide form crumb grew up too late to gather, carbide particles small, uniform, therefore, the general is 1 ~ 3 microns (largest size less than 6 microns), this greatly improves the strength and toughness of steel. 2. The performance and characteristics of powder metallurgy HSS Powder metallurgy special smelting method, compared with common high speed steel has more excellent performance and characteristics (see table 1).
As you can see in table 1, powder metallurgy HSS is very superior performance, it has high strength, high hardness, high toughness, high abrasion resistance, and good machinability characteristics, is a kind of new material between cemented carbide and high speed steel. Because made in powder metallurgy HSS tool cutting performance in all machining field full beyond the original high speed steel, its toughness is better than that of solid carbide cutting tools and more and more get the favour of tool industry. 3. Powder metallurgy high speed steel grades, components and conventional heat treatment process
Powder metallurgy HSS because smelting process is very complex, the manufacturing cost is higher, so far the world's only Sweden, the United States, Austria, France, Japan and Russia a few developed countries such as the production. Due to the dosage of powder metallurgy is not much, there is no production of powder metallurgy HSS in our country, but with the development of mechanical manufacturing and international machinery manufacturing industry to the transfer of domestic, believe our powder metallurgy production will come quickly. Table 2 for powder metallurgy high speed steel grades in several countries, composition and heat treatment process.