A) working conditions to meet the requirements of the mold
1, abrasion resistance
Blank in the mold cavity in the plastic degeneration, both the flow and along the cavity surface of the slide, so that the cavity surface and generates intense friction between the blank, leading to mold due to wear and failure. Therefore, wear resistance is the most basic mold, one of the most important performance.
Hardness of the main factors affecting the wear resistance. In general, the higher the hardness of the mold parts, the smaller the amount of wear, wear resistance is also better. In addition, the wear resistance of carbide materials with the type, quantity, shape, size and distribution of the.
2, strength and toughness
Most of the mold is very bad working conditions, often bear some of the larger impact load, leading to brittle fracture. To prevent mold parts sudden brittle fracture at work, die to have high strength and toughness.
Toughness of the mold depends on the carbon content of the material, grain size and organization of the state.
3, fatigue fracture properties
To mold the work process, in the long-term effect of cyclic stress, often leading to fatigue fracture. The form of a small number of energy impact fatigue fracture, fatigue fracture of contacts stretching and bending fatigue fracture fatigue fracture.
Fatigue fracture properties of the mold depends on their strength, toughness, hardness, and material content of inclusions.
4, high temperature performance
When the mold into the higher operating temperature, hardness and strength will decrease, leading to early wear or mold the plastic deformation and failure. Due to mold material should have high resistance to tempering stability, to ensure that the mold in the temperature, the higher the hardness and strength.
5, anti-fatigue properties of hot and cold
Some die in the course of repeated heating and cooling in the state of the cavity surface tension, the pressure change the role of stress, causing surface cracking and spalling, increased friction and hinder plastic deformation, reducing the dimensional accuracy, resulting in die failure. Hot and cold is hot die fatigue failure of the main forms of help such mold should have a high resistance to thermal fatigue.
6, corrosion resistance
Some molds, such as plastic mold at work, because there are plastic chlorine, fluorine and other elements, heat decomposition of precipitation hci, hf and other strong corrosive gases, eroding the surface of the mold cavity, increasing its surface roughness, increased wear failure.
(B) the mold meet the technical performance requirements
Mold manufacturing generally go through forging, machining, heat treatment, several processes. To ensure the quality of the mold manufacturing, lower production costs, the material should have good malleability, machinability, hardenability, hardenability and can be grinding of; should also have a small oxidation, decarbonization sensitivity and hardening deformation cracking tendency.
Deformation resistance of hot forging with a lower, plastic, forging temperature range, cold forging crack crack mesh carbide precipitation and a low propensity.
2, the annealing process of
Ball annealing temperature range, low hardness and the fluctuations in annealed small range, the ball high.
3, the cutting of
Large cutting tool, low loss, low surface roughness.
4, oxidation, decarbonization sensitivity
Pregnant when heated to high temperatures can be a good antioxidant, decarburization slow, not sensitive to the heating medium, resulting in pitting tendency of small.
After quenching with a uniform and high surface hardness.
After quenching the hardened layer can be deeper, with ease of quenching medium can be hardened.
7, the quenching deformation cracking tendency
Conventional quenching small volume change, shape warping, slight distortion, a low propensity abnormal deformation. Low sensitivity of conventional quench cracking on quenching temperature and the shape of the workpiece is not sensitive.
8, may be grinding of
Grinding wheel is relatively small loss, no amount of grinding burn limit large, the quality of the wheel and the cooling conditions are not sensitive, less prone to injuries mill grinding cracks.
(C) to meet the economic requirements of the mold
In the selection is to die, we must consider the principle of economy as much as possible to reduce manufacturing costs. Therefore, to meet the performance under the premise of first use cheaper, can not steel on steel, can use domestic materials do not need to import materials. In addition, the market should also be considered in the selection of the production and supply of selected steel should be minimal and concentrated, easy to buy.