(A) mold to meet the working conditions
1, wear resistance
When the blank is deformed in the mold cavity, it flows and slides along the cavity surface, causing severe friction between the cavity surface and the blank, which causes the mold to fail due to wear. So the material wear resistance mold one of the most basic and most important performance.
Hardness is the main factor affecting wear resistance. Under normal circumstances, the higher the hardness of mold parts, the smaller the wear, wear resistance is also better. In addition, the wear resistance is also related to the type, quantity, shape, size and distribution of carbides in the material.
2, toughness
Mold working conditions are mostly very bad, and some often bear a greater impact load, resulting in brittle fracture. In order to prevent the mold parts in the work suddenly brittle fracture, the mold to have a high strength and toughness.
The toughness of the mold depends mainly on the carbon content of the material, grain size and tissue state.
3, fatigue fracture performance
Mold work in the process, the role of the cycle of stress, often lead to fatigue fracture. Its form has a small energy multiple impact fatigue fracture, tensile fatigue fracture contact fatigue fracture and bending fatigue fracture.
The fatigue fracture properties of the mold mainly depend on its strength, toughness, hardness, and the content of inclusions in the material.
4, high temperature performance
When the mold working temperature higher, will make the hardness and strength decreased, leading to early wear or plastic deformation of the mold and failure. Therefore, the mold material should have a high resistance to tempering stability, to ensure that the mold at the operating temperature, with a high hardness and strength.
5, resistance to hot and cold fatigue performance
Some molds are in the process of repeated heating and cooling, so that the surface of the cavity by the tension, the role of stress stress, causing the surface cracking and peeling, increased friction, blocking plastic deformation, reducing the size of the accuracy, resulting in Mold failure. Hot and cold fatigue is one of the main forms of hot die failure, gang mold should have a high resistance to hot and cold fatigue performance.
6, corrosion resistance
Some molds such as plastic mold at work, due to the presence of chlorine in the plastic, fluorine and other elements, heat decomposition after the decomposition of HCI, HF and other strong corrosive gases, erosion mold cavity surface, increase its surface roughness, exacerbate wear failure.
(B) mold to meet the performance requirements
Mold manufacturing generally have to go through forging, cutting, heat treatment and other processes. In order to ensure the quality of mold manufacturing and reduce the production cost, the material should have good malleability, machinability, hardenability, hardenability and grindingability. It should also have small oxidation, decarburization sensitivity and quenching Deformation Cracking tendency.
1, malleable
Has a low hot forging deformation resistance, good plasticity, wide forging temperature range, forging cold cracking and precipitation of creep carbide tendency.
2, annealing process
Spherical annealing temperature range is wide, the annealing hardness is low and the fluctuation range is small, the spheroidization rate is high.
3, cutting workability
Cutting the amount of large, low tool loss, low surface roughness.
4, oxidation, decarburization sensitivity
High temperature heating, good resistance to oxidation, decarburization slow, not sensitive to the heating medium, resulting in pits tend to small.
5, hardened
After quenching with uniform and high surface hardness.
6, hardenability
After quenching can get a deeper hardened layer, the use of moderate quenching medium can be hardened.
7, quenching deformation cracking tendency
Conventional quenching volume change is small, shape warpage, distortion is slight, abnormal deformation tendency is low. Conventional quenching cracking sensitivity is low, the quenching temperature and the shape of the workpiece is not sensitive.
8, grindable
Grinding wheel relative loss is small, no burn limit grinding large amount of grinding wheel quality and cooling conditions are not sensitive, less prone to wear and grinding cracks.
(C) mold to meet the economic requirements
In the selection of molds, we must consider the principle of economy, as much as possible to reduce manufacturing costs. Therefore, to meet the use of performance under the premise of the first choice of lower prices, can use carbon steel without alloy steel, can use the material without the import of materials. In addition, the selection of the market should also consider the production and supply situation, the selected steel should be as small as possible and easy to buy.
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winnie
winnie
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