Means of presintering and the wax infiltration can increase the green strength. Through years of technological innovation, a variety of production processes have been developed, such as warm compaction process, high-speed compaction, etc. 

 

The emergence of new technology has played a radical role in improving the mechanical properties of powder metallurgy compacts, promoting the rapid development of powder metallurgy industry.

 

1, Presintering

In actual production, the low temperature sintering stage can be taken as a single process, that is, presintering. The strength can be improved by presintering. At the same time, the forming agent is discharged to form an opening so as to meet the requirement of processing. The presintering temperature of tungsten carbide is usually below 1000℃.

 

2, Wax Infiltration

The purpose of wax penetration is to improve the plasticity of pre-sintered billets, so as to facilitate mechanical processing. Blank without presintering treatment is dried and soaked with boiling liquid paraffin at 400℃. Or it can be processed mechanically after cooled and removed. This method is usually called high temperature wax dipping method.

 

 

3, Warm Compaction Process

Warm compaction is a kind of forming technology which can produce high density PM parts at lower cost. It can effectively improve the density and strength of compacts whether the material is plastic powder or brittle powder.

 

In the compaction process, the densification mechanism mainly consists of particle rearrangement and plastic deformation. Temperature and pressure improved the rearrangement of the powder particles, the small powder is filled into the gap of large powder particles, but also enhances the plastic deformation of the powder particles, thereby improving the green density.

 

The addition of lubricant changes the surface properties of the powder, makes it in a viscous state at the temperature and pressure, enhances the lubrication effect between the powder particles in the pressing process, reduces the friction resistance, and has good filling property of the powder particles. Moreover, the compacting pressure can be better transferred, so as to improve the density of the pressed blank.

 

4, Development of New Molding Agent

As the intrinsic mechanical properties of polymer lubricants are higher than those of conventional lubricants, the green strength of tungsten increase. Some polymer lubricants can form a strong network of continuous, while it can increase the curing strength of parts in air at low temperature.

 

5, High Velocity Compaction Technology in Powder

High velocity compaction technology in powder can effectively improve the green density and strength.