Material purchase principle of the mould
(1) Meet the requirement of condition of work
1.Wearability
The blank is when plasticity changes the sex in mould type, one of surfaces is flow as well as slipped along the type, produce violent friction among making type one of surfaces and blank, thus lead to the fact the mould loses efficiency because of wearing and tearing.
So the wearability of the material is one of the most basic, most important performance of the mould.
The hardness is a main factor of influencing the wearability. Generally speaking, the higher the hardness of the part of the mould is, the smaller the wearing and tearing amount is, the better the wearability is. In addition, the wearability, still with the kind, quantity, shape, size and distributing to have something to do with of the carbide in the material.
2.Strong toughness
Conditions of work of the mould are mostly very abominable, some often bear greater impact load, thus cause the fracture of fragility. In order to prevent the mould part from being broken while working fragily suddenly, the mould should have higher intensity and toughness.
Mainly depend on the carbon content of the material, crystalline grain degree and organize the state in toughness of the mould.
3.Tired fracture performance
Of the the working course of the mould, under acting on for a long time in cycle stress, lead to the fact and rupture tiredly often. Its form has numerous impacts of light energy to rupture, draw and rupture tiredly tiredly to contact rupturing tiredly and rupturing crookedly and tiredly.
The tired fracture performance of the mould mainly depends on the content of the inclusion in its intensity, toughness, hardness, and material.
4.High-temperature performance
It is getting higher at the working temperature of the mould, will make the hardness and intensity drop, lead to the fact the mould wears and tears or produces plasticity out of shape and loses efficiency in early days. So, the mould material should have higher resisting flash back stability, so as to ensure the mould is at working temperature, have higher hardness and intensity.
5.Able to bear cold and hot tired performance
State that some moulds are in heating and cooling repeatedly in job, the making type function that one of surfaces is drawn, the pressure turns into the stress, it is full of cracks and peeling off to cause the surface, increase frictional force, hinder plasticity out of shape, has reduced the size precision, thus lead to the fact the mould loses efficiency. It is hot to make mould invalid main form one of to be cold and hot and tired, help the mould should have able to bear cold and hot tired performancing higher.
6.Corrosion resistance
Some moulds are while working like the plastic mould, because there are elements such as chlorine, Fluorine,etc. in the plastics, heat, decompose and precipitate to get strong aggressive gas such as HCI, HF, corrode mould type one of surfaces, strengthen its roughness of surface, aggravate and wear and tear to lose efficiency.
(2) Meet the performance requirement of the craft
The manufacture of the moulds generally all should be through forging, cutting several processes such as processing, heat treatment. In order to guarantee the manufacture quality of the mould, reduce the production cost, its material should have good malleability, cutting processability, quenches the sex rigidly, quenches completely and can be rubed the paring; Should also have small inclination of oxidizing, taking off the carbon sensitiveness and quenching deformation to fracture.
1.Malleability
Lower heat forges deformation and resists strength, plasticity is good, it is wide to forge the temperature range, forge and split coldly and split and precipitate to get the netted carbide and is inclined to low.
2.Annealing craft
Ball anneal temperature range to be wide, anneal hardness to be low fluctuating range little, ball rate high.
3.Cut processability
Cut consumption big, the cutter losses low, the surface roughness of processing is low.
4.Oxidize, take off the carbon sensitiveness
It can be good to cherish anti-oxidantly while heating at high temperature, it is slow to take off carbons, to heating the insensitivity of medium, produce a bit more roughly and is inclined to small.
5.It is rigid to quench
Have even and high surface hardness after quenching.
6.Quench the sex completely
Can get deeper quenching hard layer after quenching, adopting the quenching medium relaxed can be quenched hard.
7.Quench deformation fracture inclination
The routine quenches the volume to change small, form warping, distortion are slight, unusual deformation is inclined to low. The routine quenches the sensitiveness of fracturing low, to quenching temperature and work piece form insensitivity.
8.Can rub the paring
Emery wheel relative to loss light, have, burn terminal to rub, sharpen consumption to be loud, insensitive to emery wheel quality and cooling condition, non- incident to rub and hurt and rub and pare the crackle.
(3) Meet the economic requirement
Selecting suitable materials for the mould, must consider this principle of economy, reduce the manufacturing cost as much as possible. So, on the premise of meeting serviceability, it is lower in price to select for use at first, can not use the alloy steel with the steel of carbon, needn’t import materials with the domestic material.
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