The progressive die is the representative of the precision stamping die. Its high speed, high efficiency and high precision make it very widely used in the production and manufacture of precision micro electronic parts. And an increasing number of large and medium-sized parts are also made of carbide progressive die. 

 

However, such high-speed, high-precision, micro and large-scale work requirements also challenge the strength and wear resistance of dies. Die wear will reduce the precision of the product and die life. The cutting edge grinding or die breaking will delay the working hours, reduce the production efficiency and increase the production cost. Therefore, improving the strength and wear resistance of the die means reducing the cost and improving the production efficiency.

 

Mold material is the main factor that determines the strength and wear resistance of dies. There are many reasons for mold failure, including die structure, mold processing technology, working conditions of dies, etc. But in the final analysis, the direct factor that leads to the wear and fracture failure of the die is the strength and toughness of the material itself. 

 

 

Tungsten carbide is widely used in precision progressive die because of its high strength, high toughness and high wear resistance. With the improvement of stamping speed, stamping accuracy and die life requirement of precision progressive die, the demand for tungsten carbide materials is increasing. Researchers are studying the wear failure mechanism, causes and wear resistance measures of tungsten carbide progressive die from various angles. Most of them study the failure of tungsten carbide progressive die from the perspective of external macro factors.

 

From the study of the properties of WC-Co tungsten carbide, it can be known that the strength and toughness of tungsten carbide largely depend on the content and bonding state of Co. In the fractured convex specimens, the wear and tear of Co elements are lost, and the content of Co components is also significantly reduced. Loss of Co destroys the continuity of WC hard phase skeleton, and the bonding state of WC block also changes.

 

When the loss of Co phase around WC block reaches a certain extent, the effect of Co on the bonding and recombination enhancement of WC particles is greatly weakened or even disappeared. It causes WC particles to fall off the material matrix, forming pits on the die surface. At the same time, the WC block which is not grind is also exposed. The original hard phase skeleton structure was destroyed, and the exposed WC blocks with sharp edges and corners reduced the wear resistance of the tungsten carbide and accelerated the wear of the cemented carbide at the same time, further accelerating the loss of the Co element.

 

The effect of Co and WC particles on the shedding cycle is aggravating. Finally, the toughness and strength of the material decrease until the limit is reached, so the die is broken at that place. Scholars have obtained the following conclusions through the study:

 

1, The content and distribution uniformity of Co phase elements have an important influence on the performance of WC-Co cemented carbide, and the loss of Co elements will directly lead to the degradation of the properties of the cemented carbide materials.

 

2, In the process of high speed blanking, after the wear of the tungsten carbide die, the surface of the die surface is uneven, and the skeleton structure is destroyed by the falling off of the Co and WC particles.

 

3, Under the condition of high speed blanking, the die wear shows a significant reduction in the content of Co elements. The Co relative to the hard phase of the hard phase of the WC is weakened, which reduces the strength and toughness of the material, accelerates the wear of the material, and causes the die to break.