Select hardware mold material, the expert suggests should focus on to see if can meet the requirements of the following three aspects:
(a) mold satisfies the requirement of working conditions
1. Wear resistance
Blank plastic changes in the mold cavity, the cavity surface flow and sliding, the cavity surface with a dramatic friction between billet, resulting in mould failure due to wear and tear. So the wear resistance of materials is one of the most basic, the most important performance of mould.
Hardness is the main factors influencing the abrasion resistance. Under normal circumstances, the mould parts of hardness is higher, the smaller the amount of wear and tear, abrasion resistance and the better. In addition, abrasion resistance and carbides in the material type, quantity, shape, size and distribution.
2. Strong toughness
Die working conditions are very bad, some often bear the impact load of larger, resulting in brittle fracture. Suddenly brittle fracture at work to prevent mold parts, mold with high strength and toughness.
Mould toughness mainly depends on the material state of carbon content, grain size and organization.
3. The fatigue fracture
Die working process, under the effect of cyclic stress of the long term, often leads to fatigue fracture. Its form has little energy repeated impact fatigue fracture and tensile fatigue fracture contact fatigue fracture and fatigue fracture.
Fatigue fracture properties of mold mainly depends on the strength, toughness, hardness, and the content of inclusions in the material.
4. The high temperature performance
When into the mold working temperature is higher, can make the hardness and strength, cause mould early wear or produce plastic deformation and failure. Therefore, die material should have high tempering stability, resistance to ensure that the mold in the working temperature, has high hardness and strength.
5. Cold and hot fatigue resistance
Some mold in the process of work is in a state of repeated heating and cooling, the cavity surface tension, pressure and stress effect, cause surface cracking and spalling, increase the friction, obstacles to plastic deformation, reduces the dimension precision, resulting in the mould failure. Cold and hot fatigue is one of the main form of hot-work die failure, help the mould should have high resistance to cold and hot fatigue performance.
6. The corrosion resistance
Some mould such as plastic die on the job, as a result of the elements such as chlorine, fluorine plastics, thermal decomposition after precipitation HCI, HF, such as strong erosion gas, erosion surface of mould cavity, increasing its surface roughness, aggravate the wear failure.
(2) the mold meet the requirements of process performance
Mould manufacturing is typically after forging, machining, heat treatment, and a few procedure. To ensure the manufacturing quality of mould, reduce production cost, the materials should have good malleability, cutting machining, hardenability, hardenability and grinding; Also should have little oxidation and decarburization sensitivity quenching distortion and cracking tendency.
1. The malleability
Have relatively low hot forging deformation resistance, good plasticity, forging temperature range wide, cold forging crack crack and precipitation carbide network tend to be low.
2. The annealing process
Wide temperature range and spheroidizing annealing annealing hardness is low and the fluctuation range is small, spheroidization rate is high.
3. The cutting processability
Low cutting parameter, cutting tool wear and tear, lower surface roughness.
4. The oxidation and decarburization sensitivity
When heated to high temperature oxidation resistance with good, decarbonization speed slow, is not sensitive to the heating medium, produce pitting tend to be small.
5. Hardenability
A uniform and high surface hardness after quenching.
6. Hardenability
After quenching can get deeper hardening layer, the ease of quenching medium can be hardened.
7. Quenching deformation and cracking tendency
Conventional quenching small volume change, shape warping, distortion mild, abnormal deformation tend to be low. Conventional quenching cracking sensitivity is low, is not sensitive to quenching temperature and shape of the workpiece.
8. Grinding can be
Limit dosage of grinding wheel relatively low loss, no burns, insensitive to the quality of grinding wheel and cooling conditions, are less grinding and grinding cracks.
(3) the mold satisfies the requirement of economy
Economy must be taken into account in to the mold material selection, the principle, the lower the manufacturing cost as much as possible. Therefore, on the premise of meet the performance, first choose low price, you won't have to alloy steel with carbon steel, can use domestic material don't have imported materials. In addition, still should consider when select material the production and supply of the market, the selected steel should be less as far as possible and concentrated, easy to buy.