Introduction of Products


Is cemented carbide hard?

What do you imagine when someone asks what cemented carbides is?
You may say, "What is it? I don't know exactly. It sounds very hard. Is it harder han diamond?" What kinds of hard material do you know in our environment? You may think of glass, sapphire, stone, iron and diamond. What is the order of hardness among them? In your elementary or junior high school days, you might try to rub two stones each other and study that one got hurt is the softer. The hardness determined by that method is Moh's hardness. Table 1 shows an example of the hardness. The table also shows other indexes for hardness.

In the table, cemented carbide is classified as degree 9, showing that it is harder than almost all minerals such as sapphire. Among natural minerals, diamond is only harder than cemented carbide, and those in artificial minerals harder than cemented carbide are very few like silicon carbide and boron carbide. Therefore, cemented carbide is not the hardest material. Why is it called "ultra hard" alloy ? That is because it is the hardest in metals.

Then why is it the hardest in metals?

All the metals we can see have shapes. They are a body and parts of a car, parts of a pencil case, and a screw. They all have the shapes according to applications.

In giving a shape to a metal, the metal must be cut or shaved. The saw or knife used in such a work is the cemented carbide. Therefore, cemented carbide must be the hardest in metals. In addition, the secret of the hardness is that cemented carbide contains hard substance and tough metals that bond the substance. The hard subsistence is tungsten carbide (WC), carbide of tungsten. Diamond made of carbon is as hard as diamond is, and the composite of tungsten and carbon is the second hardest. Tough metals are cobalt (Co) and nickel (Ni) which are the families of iron. These two metals make a hard and strong alloy in combination with each other. The structure of cemented carbide is shown in Fig. 1 below.

Main properties of cemented carbide

The main properties are hard, (HrA 80 to 94), strong (transverse resistance is about 2 GPa, 200kg/mm²) and large Young's modulus (about three time that of iron).

Nippon Tungsten produces original cemented carbide, making use of the above properties and adding further improvement.

We realized that cemented carbide had high-strength and high-hardness by making the matrix WC particle ultra fine. The product shows high performance when used as NT die cutters and metal mold parts.


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