Common problems and cause analysis of cemented carbide pressing

Cemented carbide is an alloy material made of hard compounds of refractory metals and bonding metals by powder metallurgy process. It has the properties of high hardness, wear resistance, strength and toughness. Because of its unique performance, it is often used to make rock drilling tools, mining tools, drilling tools, measuring tools and so on. It is widely used in oil and gas, chemical industry, engineering machinery, fluid control and other fields. Cemented carbide is a material pressed by powder metallurgy process. Today, we will introduce several major problems we often encounter in the pressing process, and briefly analyze the reasons.

1. In the process of cemented carbide pressing, the common pressing waste is delamination

It appears along the edge of the compression block at a certain angle with the compression surface to form a neat interface, which is called delamination. Most of the delamination starts from the edges and extends into the blank. The reason for the delamination of the briquette is the elastic internal stress or elastic tension in the briquette. For example, the cobalt content of the mixture is relatively low, the hardness of carbides is high, the finer the powder or particle, the less or uneven distribution of molding agent, the mixture is too wet or too dry, the pressing pressure is too large, the unit weight is too large, the shape of the pressing block is complex, the mold finish is too poor, and the table surface is uneven, which may cause delamination.

Therefore, it is an effective method to improve the strength of the compactor and reduce the internal stress and elastic back whistle of the compactor.

2. In the process of cemented carbide pressing, the phenomenon of incomplete pressing (obvious particles) will also occur

Because the hole size of the compact is too large, it can not disappear completely in the sintering process, resulting in more special holes in the sintering body. The material grain is too hard, the material grain is too coarse, and the loose loading of the material is too large; The loose charge particles are unevenly distributed in the mold cavity and the unit weight is low. May cause not pressed well.

3. Another common phenomenon of carbide pressing waste is crack

The phenomenon of irregular local fracture in the pressing block is called crack. Because the tensile stress inside the compression block is greater than the tensile strength of the compression block. The tensile stress in the compression block comes from the elastic internal stress. The factors affecting delamination also affect the crack. The following measures can be taken to reduce the occurrence of cracks: prolong the pressure holding time or pressurize for many times, reduce the pressure, single weight, improve the mold design and appropriately increase the mold thickness, speed up the demoulding speed, increase the molding agent, improve the loose density of materials, etc.