Tungsten carbide die tooling sintering process

       

The sintering process of tungsten carbide die toolings can be divided into four fundamental stages:

1: Removal of forming agent and pre-sintering stage, at this stage the sintered body undergoes the following changes:

 

Removal of the forming agent, following the increase in temperature at the beginning of sintering, the forming agent gradually decomposes or vaporizes to remove the sintered body. At the same time, the forming agent more or less carbonizes the sintered body. Variety, quantity and sintering process are different.

The surface oxide of the powder is restored. At the sintering temperature, hydrogen can restore the oxides of cobalt and tungsten. If the forming agent is removed in vacuum and sintering, the carbon and oxygen reaction is not strong. The contact stress between the powder particles is gradually eliminated, the bonding metal powder begins to recover and recrystallize, the surface dispersion begins to occur, and the briquette strength is improved.

 

2: solid phase sintering stage (800℃--eutectic temperature)

At the temperature before the liquid phase, in addition to continuing the process that occurred in the previous stage, the solid phase noise and dispersion increase, the plastic activity increases, and the sintered body shows a significant shortening.

 

3: Liquid phase sintering stage (eutectic temperature-sintering temperature)

When the sintered body presents a liquid phase, the shortening is quickly completed, and then crystalline transformation occurs to form the basic structure and structure of the alloy.

 

4: Cooling stage (sintering temperature-room temperature)

At this stage, the structure and phase composition of tungsten carbide undergo some changes with different cooling conditions. This feature can be used to heat treat tungsten carbide to improve its physical and mechanical functions.

 

Most of the cold heading of the product is processed and formed at one time through a large amount of deformation, so the production power of the product is higher and the benefit is greatly improved. However, the die tooling accepts a large load and causes many problems, such as wear, out-of-tolerance, fine cracks, material sticking, etc. Therefore, tungsten carbide with different characteristics should be used sensitively in the die tooling design stage to get used to the corresponding working conditions.

For example, in order to avoid the occurrence of fine cracks, it is necessary to consider the persistence of tungsten carbide inlay, inlay method, cavity shape, cavity finish requirements, selection of high toughness tungsten carbide materials, etc.; in order to avoid data sticking to the die tooling, detailed study of tungsten carbide die toolings Structure shape, select corresponding die tooling precision, tungsten carbide raw material and corresponding coating, etc.