Powder metallurgy isostatic pressing process

PM pressing and MIM metal injection molding are common powder metallurgy technologies. There are also many forming methods, such as cold isostatic pressing, high-energy high-speed forming, triaxial pressing, extrusion of metal powder mixed with plasticizer and continuous pressing. These methods can overcome the shortcomings of conventional pressing, such as producing particularly complex or shaped powder metallurgy products.

Briefly introduce the advantages of several powder metallurgy forming processes

At present, the company mostly adopts the traditional method of pressing powder metallurgy products, which has the advantage of convenience and economy. Compared with the conventional traditional pressing, the advantage of cold pressing is that the density distribution of the compacts is relatively uniform. At present, Fuchi Intelligent Manufacturing Technology Co., Ltd., which is being expanded in Lianyungang, uses MIM metal injection molding technology. Injection molding is to mix metal powder with organic binder to form parts with complex shapes that cannot be pressed normally. MIM injection molding is also relatively popular at present. Lianyungang currently has PM and MIM technologies. In addition, the powder metallurgy forming process is high-energy high-speed forming and triaxial pressing at room temperature. The blanks produced by these two powder metallurgy processes are much higher than those produced by conventional PM pressing. The powder metallurgy extrusion process mixed with plasticizer is to produce powder metallurgy products with long direction.

In the company's industry news, we introduced the knowledge about isostatic pressing, which was explained by the technician Sun Liguang. The technician Sun Gong had worked in a powder metallurgy factory in Jiangsu before. This powder metallurgy factory used the cold pressing method. Isostatic pressing is to put the powder in a flexible mold, then immerse it in the fluid and apply pressure. The pressure acts on the powder uniformly through the outer surface of the flexible mold. Uniform force can effectively eliminate the friction between the powder and the female mold, which is superior to conventional pressing. The uneven force is the main reason affecting the quality of the blank. Isostatic pressing is to transfer the pressure to the metal powder through the mold when the pressure acts on the fluid, thus completing the compaction of powder metallurgy products.

1. Cold isostatic pressure of wet bag

The powder is sealed in a flexible bag and then placed in a pressurized liquid. The flexible package is made of polyurethane, silicone rubber, neoprene or natural rubber. The sheath is made by dipping or spraying, mechanical pressing, casting or injection molding. After the bag is filled with powder and sealed, it is completely immersed in the pressure medium. The pressure medium is usually water added with lubricant and preservative.

In addition to uniform production density, this method has other advantages over conventional pressing. For example, wet bag cold isostatic pressing can produce profiled P/M products with large height diameter ratio, concave corners, grooves and thin wall sections. Isostatic pressing does not need to mix the lubricant into the metal powder before pressing, so it is not necessary to burn the lubricant before sintering.

However, the disadvantage is that the wet bag cold isostatic pressing process is cumbersome and cannot be compared with the conventional production efficiency, so it cannot compete with the conventional pressed P/M products in the market, mainly to produce some large, complex shape and small batch P/M products.

2. Dry bag cold static pressure

Due to the slow efficiency of wet bag cold isostatic pressing, powder metallurgy manufacturers with isostatic pressing usually also have dry bag cold static pressing, and the dry bag cold static pressing package is * * * packed in the pressure vessel. Fill the bag cavity with powder and seal it with a cover plate. After applying pressure, relieve the pressure, open the cover plate, and take out the compact to complete a production cycle. The cool pressing sleeve of the dry bag needs to be reused, so it needs to be made with high quality and a little thicker. Although the production efficiency of cold pressing with dry bags is much faster than that of cold isostatic pressing with wet bags, cold pressing with dry bags is not as effective as cold isostatic pressing with wet bags when producing grooved P/M products.

The high-energy high-speed forming just introduced above: Although many methods of pressing metal powder at medium high energy and high speed have been developed, they have not been applied in industry. The process is to put metal powder into rigid molds, and the upper die punch receives the impact of projectiles driven by compressed gas at high speed. What's more, the powder metallurgy blanks produced have high density, high strength and uniform distribution. There is also three-axis pressing. The blank density of this method is higher than that of the conventional method. When pressing, the pressure acts radially around the cylindrical powder sample in the flexible jacket, and the other axial load is applied to the jacket through the piston. Another kind of explosive forming, as the name implies, uses the explosion to generate driving energy to make the piston impact the upper die punch in the rigid mold. In addition, it can also put the metal powder in the rubber sleeve to suspend in the water, and then explode to make the piston impact the water in the pressure vessel.

At present, MIM injection molding and conventional PM pressing have been popularized in industry and applied in many fields, such as automobile field, electrical appliance field, medical field, communication field, agriculture field, electric field, new energy field, etc.

Summary:

The powder metallurgy products produced by isostatic pressing have more uniform density than the conventional unidirectional pressing, and can also produce parts with higher diameter, groove and thin wall section than the conventional powder metallurgy, but the production speed is slow. The process of powder metallurgy products pressed by isostatic pressing is to pack the powder into a flexible package, and then immerse the package containing the powder into the fluid to apply pressure.

The dry bag isostatic pressing is more efficient than the wet bag isostatic pressing, but its shape is limited.

MIM metal injection molding and powder metallurgy PM conventional pressing * * * are popular, but they are not suitable for the production of larger powder metallurgy products.

MIM metal injection molding process is to mix MIM metal injection molding raw materials with thermoplastic resin, and then inject the mixture to form, solidify and demould it. The embryo density of MIM is 60% of the theoretical value.

The company has PM conventional powder metallurgy, and Lianyungang Fuchi Intelligent Manufacturing Technology Co., Ltd. has MIM metal injection molding powder metallurgy.