What is powder metallurgy high speed steel, and what are the differences from ordinary high speed steel?
Views : 3177
Author : Xiangrong Yuan
Update time : 2017-08-11 09:51:00
Figure 1 are the difference of the microstructure of powder metallurgy high-speed steel and traditional high-speed steel under the microscope. Obviously, traditional high-speed steel has a lot of coarse blocks, and its impact toughness must be poor.
Compared with tungsten carbide, its normal service life in a perfect working environment is not better. But its impact toughness is far better than tungsten carbide, so the actual life in use may be better than that of tungsten carbide. The tungsten carbide is very brittle, and it will not work once it cracks. In addition, powder metallurgy high-speed steel has very good machinability. It can be processed like ordinary steel, such as heat treatment and machining including turning, planing, milling, and grinding, but tungsten carbide cannot do this, which greatly saves the cost of the mold.
In order to improve this shortcoming of traditional high-speed steel, powder metallurgy has been adopted in the world. The high-speed steel in the molten state is blown into small particles with compressed air like milk powder, and then placed in a specific shape. In the mold, high-speed steel particles are pressed into a cylinder or sheet with high pressure, and then various spare parts are manufactured. This kind of high speed steel is called powder metallurgy high speed steel.
After smelting, high-speed steel is poured into the ingot mold. Although the ingot mold has been preheated, the maximum temperature is about 300 °C. When high-speed steel molten steel at a high temperature of 1500 °C is poured into the ingot mold, the molten steel in contact with the inner wall of the ingot mold will quickly cool and harden, while the molten steel in the middle of the ingot mold still has a certain temperature due to the surrounding layer of high-speed steel. So it can only be cooled slowly. Its hardness and metallographic structure will be different from the surrounding high-speed steel. Although forging and heat treatment will improve the situation in the future, the problem still exists. And it is difficult to make the structure uniform. This is the problem of traditional high-speed steel.
Hot high-speed steel hardens quickly in the air which shows that its quenching progress is extremely fast. So higher requirements are put forward for the smelting and heat treatment of high-speed steel. If it is slow, it will affect its good performance.
High-speed steel contains high tungsten content, and it is known for its good high-speed cutting performance in the machining industry. Due to its different tungsten content, high-speed steel is roughly divided into two types in the market: one is 18/4/2, similar to T1, and its chemical composition is W18Cr4Mo2. The other is 6/5/4/2, equivalent to M2, and its chemical composition is W6Cr5Mo4V2. At present, the latter is gradually replacing the former.
Compared with tungsten carbide, its normal service life in a perfect working environment is not better. But its impact toughness is far better than tungsten carbide, so the actual life in use may be better than that of tungsten carbide. The tungsten carbide is very brittle, and it will not work once it cracks. In addition, powder metallurgy high-speed steel has very good machinability. It can be processed like ordinary steel, such as heat treatment and machining including turning, planing, milling, and grinding, but tungsten carbide cannot do this, which greatly saves the cost of the mold.
In order to improve this shortcoming of traditional high-speed steel, powder metallurgy has been adopted in the world. The high-speed steel in the molten state is blown into small particles with compressed air like milk powder, and then placed in a specific shape. In the mold, high-speed steel particles are pressed into a cylinder or sheet with high pressure, and then various spare parts are manufactured. This kind of high speed steel is called powder metallurgy high speed steel.
After smelting, high-speed steel is poured into the ingot mold. Although the ingot mold has been preheated, the maximum temperature is about 300 °C. When high-speed steel molten steel at a high temperature of 1500 °C is poured into the ingot mold, the molten steel in contact with the inner wall of the ingot mold will quickly cool and harden, while the molten steel in the middle of the ingot mold still has a certain temperature due to the surrounding layer of high-speed steel. So it can only be cooled slowly. Its hardness and metallographic structure will be different from the surrounding high-speed steel. Although forging and heat treatment will improve the situation in the future, the problem still exists. And it is difficult to make the structure uniform. This is the problem of traditional high-speed steel.
Hot high-speed steel hardens quickly in the air which shows that its quenching progress is extremely fast. So higher requirements are put forward for the smelting and heat treatment of high-speed steel. If it is slow, it will affect its good performance.
High-speed steel contains high tungsten content, and it is known for its good high-speed cutting performance in the machining industry. Due to its different tungsten content, high-speed steel is roughly divided into two types in the market: one is 18/4/2, similar to T1, and its chemical composition is W18Cr4Mo2. The other is 6/5/4/2, equivalent to M2, and its chemical composition is W6Cr5Mo4V2. At present, the latter is gradually replacing the former.
Fig. 1 Microstructure of Powder Metallurgy High-speed Steel And Traditional High-speed Steel
