1, For the working environment, the aluminum alloy die casting molds needs to meet the following conditions:
1. Good wear resistance
When the aluminum alloy is plastically deformed in the die-casting die cavity, it flows and slides along the cavity surface, resulting in severe friction between the cavity surface and the blank, which leads to the failure of the aluminum alloy die-casting molds due to wear. Therefore, the wear resistance of materials is one of the most basic and important properties of the aluminum alloy die-casting molds.
Hardness is the main factor affecting wear resistance. In general, the higher the hardness of aluminum alloy die-casting mold parts, the less the wear, and the better the wear resistance. In addition, the wear resistance is also related to the type, quantity, morphology, size and distribution of carbides in the material.
2. Strength and toughness
The working conditions of die-casting molds are mostly very bad, and some of them often bear large impact loads, resulting in brittle fracture. In order to prevent the sudden brittle fracture of aluminum alloy die-casting die parts, the die 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 working process of aluminum alloy die-casting die, fatigue fracture often occurs under the long-term action of cyclic stress. Its forms include low energy multiple impact fatigue fracture, tensile fatigue fracture, contact fatigue fracture and bending fatigue fracture. The fatigue fracture performance of aluminum alloy die casting 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 aluminum alloy die-casting molds is high, the hardness and strength will decrease, resulting in early wear or plastic deformation of the aluminum alloy die-casting molds and failure. The aluminum alloy die-casting die material should have high tempering resistance stability to ensure that the aluminum alloy die-casting die has high hardness and strength at the working temperature.
5. Cold and hot fatigue resistance
Some aluminum alloy die-casting moulds are in a state of repeated heating and cooling during the working process, which makes the surface of the cavity subject to tensile and pressure stress, causing surface cracking and peeling, increasing friction, hindering plastic deformation, reducing dimensional accuracy, and leading to die failure. Cold and thermal fatigue is one of the main failure forms of hot working aluminum alloy die-casting dies. This kind of aluminum alloy die-casting dies should have high cold and thermal fatigue resistance.
6. Corrosion resistance
When some aluminum alloy die-casting molds, such as plastic molds, are working, due to the presence of chlorine, fluorine and other elements in the plastic, strong corrosive gases will be separated out after heating, which will erode the surface of the mold cavity, increase its surface roughness, and intensify wear failure.
Problems to be considered in making aluminum alloy die casting molds
2, The mold meets the process performance requirements
The manufacturing of aluminum alloy die-casting molds generally goes through several processes, such as forging, cutting and heat treatment. In order to ensure the manufacturing quality of the mold and reduce the production cost, the material should have good malleability, machinability, hardenability, hardenability and grindability; It should also have small oxidation, decarburization sensitivity and quenching deformation cracking tendency.
It has low hot forging deformation resistance, good plasticity, wide forging temperature range, low forging crack, cold crack and precipitation of network carbide.
2. Annealing process
The spheroidizing annealing temperature range is wide, the annealing hardness is low and the fluctuation range is small, and the spheroidizing rate is high.
Large cutting amount, low tool loss and low machined surface roughness.
4. Oxidation and decarbonization sensitivity
When heated at high temperature, it has good oxidation resistance, slow decarbonization speed, insensitive to heating medium, and little tendency to produce pitting.
It has uniform and high surface hardness after quenching.
After quenching, a deeper hardening layer can be obtained, and it can be hardened by using a moderate quenching medium.
7. Quenching deformation cracking tendency
Conventional quenching has small volume change, slight shape warpage and distortion, and low abnormal deformation tendency. Conventional quenching has low sensitivity to cracking and is insensitive to quenching temperature and workpiece shape.
The relative loss of the grinding wheel is small, there is no burn, the limit grinding consumption is large, and it is insensitive to the quality of the grinding wheel and the cooling conditions, so it is not easy to cause abrasion damage and grinding cracks.
3, Aluminum alloy die should be cost-effective
When selecting materials for aluminum alloy die, cost performance must be considered to reduce manufacturing cost as much as possible. Therefore, on the premise of meeting the service performance, the first choice is to use the low-cost carbon steel without alloy steel, and the domestic materials without imported materials. In addition, when selecting materials, the production and supply of the market should also be considered. The selected steel grades should be as few and concentrated as possible and easy to purchase.
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