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How to select mold material?
Jan 24, 2018

Mold selection is a very important part in the whole process of mold making.

The mold selection needs to meet the three principles, the mold meets the requirements of wear resistance, strong toughness and so on, the mold meets the technical requirements, and the mold should meet the economic applicability.

(1) the mold meets the working conditions.

1. Wear resistance.

When the blank is plastic in the mold cavity, it flows and slides along the surface of the cavity, causing severe friction between the surface of the cavity and the blank, thus causing the die to wear out.So the wearability of the material is one of the most basic and important properties of the mould.

Hardness is the main factor affecting wear resistance.Generally, the higher the hardness of the mold parts, the smaller the wear, and the better wear resistance.In addition, wear resistance is also related to the type, quantity, shape, size and distribution of carbide in the material.

2. Strong toughness

The working conditions of the mould are mostly very bad, some of which are often subjected to a large impact load, which leads to brittle fracture.In order to prevent the mold parts from breaking suddenly at work, the mold should have high strength and toughness.

The toughness of the mould depends mainly on the carbon content, grain size and organizational state of the material.

3. Fatigue fracture performance.

During the working process of the mould, the fatigue fracture is often caused by the long-term action of cyclic stress.Its form has small energy multiple impact fatigue fracture, tensile fatigue fracture contact fatigue fracture and bending fatigue fracture.

The fatigue fracture performance of the die depends on its strength, toughness, hardness and inclusions in the material.

4. High temperature performance

When the working temperature of the mold is high, the hardness and strength will be reduced, which will cause the die to wear out or to produce plastic deformation.Therefore, the mould material should have high tempering stability to ensure that the mould has higher hardness and strength at working temperature.

5. Resistance to cold and heat fatigue.

Some mold in the process of work is in a state of repeated heating and cooling, the cavity surface tension, pressure and stress effect, cause surface cracking and spalling, increase the friction, obstacles to plastic deformation, reduces the dimension precision, resulting in the mould failure.Cold and heat fatigue is one of the main forms of thermal die failure, which should have high resistance to cold and heat fatigue.

6. Corrosion resistance

Some mould such as plastic die on the job, as a result of the elements such as chlorine, fluorine plastics, thermal decomposition after precipitation HCI, HF, such as strong erosion gas, erosion surface of mould cavity, increasing its surface roughness, aggravate the wear failure.

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