When the wire drawing die is produced, there is a chemical reaction that generates gas:
After the sintered body appears in the liquid phase, there is a chemical reaction that generates gas, such as the reduction reaction of oxides. If the pressure of the gas generated under this condition is not enough to overcome the resistance of the liquid phase and escape from the sintered body, a hole is formed in the alloy. Because some oxides, such as titanium oxides, can only be reduced by carbon at high temperatures. Other oxides, such as the oxidized agglomeration of the mixture of tungsten carbide and cobalt, can be reduced by hydrogen at lower temperatures, but because they are quite dense, they are not completely reduced when the liquid phase appears.