Choosing mold materials is a very important part of the entire mold making process. The selection of mold materials needs to meet three principles. The mold meets the work requirements of wear resistance, toughness, etc. The mold meets the process requirements, and the mold should meet the economic applicability. It can be divided into the following six requirements.
● When the blank is plastically denatured in the mold cavity, it moves and slides along the outer surface of the cavity, causing a sharp conflict between the outer surface of the cavity and the blank, and then the mold fails due to wear. Therefore, the wear resistance of the data is one of the most basic and important functions of the mold.
● Hardness is the primary factor affecting wear resistance. In general, the higher the hardness of the mold part, the smaller the wear amount, and the better the wear resistance. In addition, the wear resistance is also related to the type, quantity, shape, size and distribution of carbides in the guess.
● Most of the working conditions of the mold are very bad, and some often withstand large impact loads, and then cause brittle cracking. In order to avoid the mold parts being suddenly brittle during operation, the mold must have high strength and durability.
● The tolerance of the mold depends mainly on the carbon content, grain size and microstructure of the data.
Fatigue cracking function
● During the operation of the mold, under the long-term action of the cyclic stress, it often leads to fatigue cracking. In this way, small energy repeatedly impacts fatigue cracking, stretching fatigue, cracking, fatigue, cracking, and tortuous cracking.
● The fatigue cracking function of the mold depends mainly on its strength, durability, hardness, and the amount of inclusions in the guess.
High temperature function
When the working temperature of the mold is higher, the hardness and strength are lowered, resulting in failure of the mold in the early stage of wear or plastic deformation. Because the mold data should have high anti-tempering stability to ensure that the mold has high hardness and strength at the working temperature.
Resistance to hot and cold fatigue
Some molds are in a state of repeated heating and cooling during the operation, which causes the external appearance of the cavity to be pulled and pressure-stressed, causing surface cracking and shedding, increasing the conflicting force, preventing plastic deformation, reducing the scale accuracy, and then causing mold failed. Hot and cold fatigue is one of the primary ways to prevent hot mold failure. This type of mold should have high resistance to cold and heat.
Because there are elements such as chlorine and fluorine in the material, some strong corrosive gases may be decomposed after being heated. Some molds, such as plastic molds, corrode the outer surface of the mold cavity during operation, increasing the roughness of the outer surface and aggravating wear and tear.