Six Principles Of Mold Selection

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1. Wear resistance

When the blank is plastically deformed in the mold cavity, it flows and slides along the surface of the cavity, causing violent friction between
the surface of the cavity and the blank, which causes the mold to fail due to wear. Therefore, the wear resistance of the material is one of
the most basic and important properties of the mold. Hardness is the main factor affecting wear resistance. In general, the higher the
hardness of the mold parts, the smaller the amount of wear and the better the wear resistance. In addition, wear resistance is also
related to the type, quantity, shape, size and distribution of carbides in the material.

2. Strength 

The working conditions of the molds are mostly very bad, and some of them are often subjected to large impact loads, which leads to
brittle fracture. In order to prevent sudden brittle fracture of mold parts during work, the mold must have high strength and toughness.
The toughness of the mold mainly depends on the carbon content, grain size and organization state of the material.

3. Fatigue fracture performance

During the working process of the mold, fatigue fracture is often caused under the period of cyclic stress. Its forms include low-energy
multiple impact fatigue fracture, tensile fatigue fracture, contact fatigue fracture, and bending fatigue fracture. The fatigue fracture
performance of the mold mainly depends on its strength, toughness, hardness, and the content of inclusions in the material.

4. High temperature performance 

When the working temperature of the mold is higher, the hardness and strength will decrease, leading to early wear of the mold
or plastic deformation and failure. Therefore, the mold material should have high anti-tempering stability to ensure that the mold
has high hardness and strength at the working temperature.

5. Resistance to cold and heat fatigue

Some molds are in a state of repeated heating and cooling during the working process, which causes the surface of the cavity to
be pulled and pressure to change the stress, causing surface cracks and peeling, increasing friction, hindering plastic deformation,
and reducing dimensional accuracy. Mold failure. Heat and cold fatigue is one of the main forms of failure of hot work molds,
and this type of mold should have high resistance to cold and heat fatigue.

6. Corrosion resistance

When some molds such as plastic molds are in operation, due to the presence of chlorine and fluorine in the plastics, strong
corrosive gases such as HCI and HF will be resolved after being heated, which will erode the surface of the mold cavity, increase
its surface roughness, and aggravate wear failure.


Post time: Jul-26-2021