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What is the material selection and technological performance of the mold?
Die material selection. Mold material selection is a very important link in the whole mold manufacturing process. The material selection of the mold needs to meet three principles, the mold meets the requirements of wear resistance, strength and toughness, the mold meets the process requirements, and the mold should meet the economic applicability.
Die material selection.
Mold material selection is a very important link in the whole mold manufacturing process.
The material selection of the mold needs to meet three principles, the mold meets the requirements of wear resistance, strength and toughness, the mold meets the process requirements, and the mold should meet the economic applicability.
Conditional requirement.
1. Wear resistance.
When the billet is plastically denatured in the mold cavity, it flows and slides along the cavity surface, resulting in severe friction between the cavity surface and the billet, resulting in die failure due to wear.
Therefore, the wear resistance of the material is one of the most basic and important properties of the mold.
Hardness is the main factor affecting wear resistance.
In general, the higher the hardness of the mold parts, the smaller the amount of wear, 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 material.
2. Strength and toughness.
Most of the working conditions of the die are very bad, and some of them often bear a large impact load, which leads to brittle fracture.
In order to prevent the die parts from sudden brittle fracture at work, the mold should have high strength and toughness.
The toughness of the die mainly depends on the carbon content, grain size and microstructure of the material.
3. Fatigue fracture performance.
In the process of die work, fatigue fracture is often caused by the long-term action of cyclic stress.
Its forms are small energy multiple impact fatigue fracture, tensile fatigue fracture contact fatigue fracture and bending fatigue fracture.
The fatigue fracture performance of the die mainly depends on its strength, toughness, hardness and the content of inclusions in the material.
4. High temperature performance.
When the working temperature of the die is higher, the hardness and strength will decrease, resulting in early wear or plastic deformation and failure.
Therefore, the mold material should have high anti-tempering stability to ensure that the mold has high hardness and strength at the working temperature.
5. Resistance to cold and hot fatigue.
Some molds are in the state of repeated heating and cooling in the working process, which causes the surface of the cavity to be subjected to tension and pressure, which causes surface cracking and peeling, increases friction, hinders plastic deformation, and reduces dimensional accuracy. resulting in mold failure.
Hot and cold fatigue is one of the main forms of failure of hot work molds, and this kind of molds should have high resistance to cold and hot fatigue.
6. Corrosion resistance.
When some molds such as plastic molds are working, due to the existence of chlorine, fluorine and other elements in plastics, strong corrosive gases such as HCI and HF are decomposed and precipitated after heating, which erodes the surface of mold cavity, increases its surface roughness and aggravates wear failure.
Technological performance.
The manufacture of molds generally goes through several processes, such as forging, cutting, heat treatment and so on.
In order to ensure the manufacturing quality of the die and reduce the production cost, the material should have good malleability, machinability, hardenability, hardenability and grindability, as well as small oxidation, decarburization sensitivity and quenching deformation cracking tendency.
1. Malleability.
It has low hot forging deformation resistance, good plasticity, wide forging temperature range, low tendency of forging crack and precipitation of reticulated carbide.
2. Annealing process.
The spheroidizing annealing temperature range is wide, the annealing hardness is low, the fluctuation range is small and the spheroidizing rate is high.
3. Machinability.
The utility model has the advantages of large cutting parameters, low tool loss and low machined surface roughness.
4. Sensitivity to oxidation and decarbonization.
When heated at high temperature, the antioxidant capacity is good, the decarburization rate is slow, it is not sensitive to the heating medium, and the tendency to produce pockmarks is small.
5. Hardenability.
It has uniform and high surface hardness after quenching.
6. Hardenability.
A deeper hardening layer can be obtained after quenching, and it can be hardened by using mild quenchant.
7. Quenching deformation cracking tendency.
The volume change of conventional quenching is small, the shape warping and distortion are slight, and the abnormal deformation tendency is low.
The cracking sensitivity of conventional quenching is low, and it is not sensitive to quenching temperature and workpiece shape.
8. Grindability.
The grinding wheel has the advantages of small relative loss, large non-burn limit grinding amount, insensitive to grinding wheel quality and cooling conditions, and not easy to occur grinding damage and grinding cracks.
Mold material selection is a very important link in the whole mold manufacturing process.
The material selection of the mold needs to meet three principles, the mold meets the requirements of wear resistance, strength and toughness, the mold meets the process requirements, and the mold should meet the economic applicability.
Conditional requirement.
1. Wear resistance.
When the billet is plastically denatured in the mold cavity, it flows and slides along the cavity surface, resulting in severe friction between the cavity surface and the billet, resulting in die failure due to wear.
Therefore, the wear resistance of the material is one of the most basic and important properties of the mold.
Hardness is the main factor affecting wear resistance.
In general, the higher the hardness of the mold parts, the smaller the amount of wear, 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 material.
2. Strength and toughness.
Most of the working conditions of the die are very bad, and some of them often bear a large impact load, which leads to brittle fracture.
In order to prevent the die parts from sudden brittle fracture at work, the mold should have high strength and toughness.
The toughness of the die mainly depends on the carbon content, grain size and microstructure of the material.
3. Fatigue fracture performance.
In the process of die work, fatigue fracture is often caused by the long-term action of cyclic stress.
Its forms are small energy multiple impact fatigue fracture, tensile fatigue fracture contact fatigue fracture and bending fatigue fracture.
The fatigue fracture performance of the die mainly depends on its strength, toughness, hardness and the content of inclusions in the material.
4. High temperature performance.
When the working temperature of the die is higher, the hardness and strength will decrease, resulting in early wear or plastic deformation and failure.
Therefore, the mold material should have high anti-tempering stability to ensure that the mold has high hardness and strength at the working temperature.
5. Resistance to cold and hot fatigue.
Some molds are in the state of repeated heating and cooling in the working process, which causes the surface of the cavity to be subjected to tension and pressure, which causes surface cracking and peeling, increases friction, hinders plastic deformation, and reduces dimensional accuracy. resulting in mold failure.
Hot and cold fatigue is one of the main forms of failure of hot work molds, and this kind of molds should have high resistance to cold and hot fatigue.
6. Corrosion resistance.
When some molds such as plastic molds are working, due to the existence of chlorine, fluorine and other elements in plastics, strong corrosive gases such as HCI and HF are decomposed and precipitated after heating, which erodes the surface of mold cavity, increases its surface roughness and aggravates wear failure.
Technological performance.
The manufacture of molds generally goes through several processes, such as forging, cutting, heat treatment and so on.
In order to ensure the manufacturing quality of the die and reduce the production cost, the material should have good malleability, machinability, hardenability, hardenability and grindability, as well as small oxidation, decarburization sensitivity and quenching deformation cracking tendency.
1. Malleability.
It has low hot forging deformation resistance, good plasticity, wide forging temperature range, low tendency of forging crack and precipitation of reticulated carbide.
2. Annealing process.
The spheroidizing annealing temperature range is wide, the annealing hardness is low, the fluctuation range is small and the spheroidizing rate is high.
3. Machinability.
The utility model has the advantages of large cutting parameters, low tool loss and low machined surface roughness.
4. Sensitivity to oxidation and decarbonization.
When heated at high temperature, the antioxidant capacity is good, the decarburization rate is slow, it is not sensitive to the heating medium, and the tendency to produce pockmarks is small.
5. Hardenability.
It has uniform and high surface hardness after quenching.
6. Hardenability.
A deeper hardening layer can be obtained after quenching, and it can be hardened by using mild quenchant.
7. Quenching deformation cracking tendency.
The volume change of conventional quenching is small, the shape warping and distortion are slight, and the abnormal deformation tendency is low.
The cracking sensitivity of conventional quenching is low, and it is not sensitive to quenching temperature and workpiece shape.
8. Grindability.
The grinding wheel has the advantages of small relative loss, large non-burn limit grinding amount, insensitive to grinding wheel quality and cooling conditions, and not easy to occur grinding damage and grinding cracks.
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