Water content of the mixed materials will have a great influence on the performance of the powder. Besides, it will also have a great influence on the subsequent performance of the blanks. The reason is that the water content has the influence on the body temperature to a certain extent, which decreasing or improving the glass transition temperature of the molding agent and affecting the strength of the green body.

 

It is clear from the above picture that the strength of the blank also increases with the increase of water content. When the water content is less, the strength of the body is small and fragile. When the water content is increased, the strength of the blank is improved obviously. At this time, the billet has enough strength to be carried and is not easy to remove the edge angle.

 

 

With the increase of water content, the strength of the billet will continue to increase. In the experiment, it is found that the green compact strength will rise further when the water content continues to increase, but the release of the blank is more and more difficult, and the viscosity of the die is more serious.

 

The effect of the water content of the mixture on the strength of the billet can be explained from the angle of the glass transition temperature of the paraffin binder, the θg. The paraffin wax is plastic when the ambient temperature is higher than θg. With the increase of paraffin plasticity, the granulation particles are easily deformed when the body is formed, forming a uniform structure of the body.

 

When the ambient temperature is lower than θg, paraffin is brittle, and granulation particles have strong ability to resist deformation when molding, so that they remain almost in the original form in the green body. The water content affects the glass transition temperature g of the paraffin wax, which affects the formability and the strength of the billet. Water can reduce the θg temperature of the paraffin, and the paraffin is equivalent to the plasticizer.

 

As the water content closes to zero, the θg of the paraffin is higher than that of the ambient temperature (such as 25 ℃), and the bond strength between the particles in the body is low. The paraffin wax is reduced to a constant amount of G with the increase of the water content, which makes the particles more easily deformed under the same molding pressure and decreases the pores in the particles. 

 

However, when the water content is too high, it will cause the powder to be easy to stick to the mold because of the increase of the viscosity of the paraffin, and it is difficult to press the blank. Therefore, it is necessary to take comprehensive consideration when controlling the water content of the mixture.