Factors affecting the service life of die casting die and treatment methods
- Date：2022-07-05
- Read：1384
Due to the long production cycle, high investment, high manufacturing accuracy, and high cost, die-casting molds are expected to have a long service life. However, due to a series of internal and external factors such as materials and mechanical processing, molds fail and are scrapped prematurely, resulting in huge waste. Today, we will introduce the factors that affect the service life of die-casting molds and their treatment methods.
The main forms of die casting mold failure are: sharp corners Crack at the corner crackle. Hot cracks (fissures) Wear and tear Erosion, etc. The main reasons for the failure of die-casting molds are: defects in the material itself, as well as the processing, use, maintenance, and heat treatment of die-casting molds.
1、 Defects in the material itself
As is well known, the usage conditions of die-casting molds are extremely harsh. Taking aluminum die-casting molds as an example, the melting point of aluminum is 580-740 ℃, and the temperature of the aluminum liquid is controlled at 650-720 ℃ during use. Die casting does not preheat the mold, and the surface temperature of the cavity rises from room temperature to liquid temperature, resulting in significant tensile stress on the cavity surface. When opening the top of the mold, the surface of the cavity is subjected to significant compressive stress. After thousands of die-casting processes, defects such as cracks appeared on the surface of the mold.
It can be seen that the usage conditions for die-casting are rapid heating and rapid cooling. The mold material should be selected from hot mold steel with high thermal fatigue resistance, fracture toughness, and thermal stability. H13 (4Cr5Mov1Si) is currently a widely used material. According to reports, H13 is used in 80% of the cavities abroad. At present, 3Cr2W8VV is still widely used in China, but it has poor artistic performance, poor thermal conductivity, high coefficient of linear expansion, and high thermal stress during operation, which leads to mold cracking or even rupture. It is easy to decarburize during heating, reducing the wear resistance of the mold. Therefore, it belongs to the category of eliminating steel grades. Martensitic aging steel is suitable for molds with low requirements for heat crack resistance, wear resistance, and corrosion resistance. Tungsten molybdenum and other heat-resistant alloys are limited to small inserts with hot cracks and severe corrosion. Although these alloys are brittle and sensitive to notches, their advantage is good thermal conductivity, and they still have good adaptability and production management for thick die-casting molds that require cooling but cannot be set with water channels. Therefore, H13 still has good heat treatment performance.
The materials used to manufacture die-casting molds should meet the design requirements in all aspects to ensure that the die-casting molds reach their designed service life under normal usage conditions. Therefore, before putting into production, a series of inspections should be carried out on the materials to prevent defective materials from wasting early scrap and processing costs of molds. The commonly used inspection method is macroscopic corrosion inspection. Metallographic examination. Ultrasonic examination.
(1) Macroscopic corrosion inspection. Mainly inspect the porosity of the material Segregation crackle. crackle. Non metallic inclusions and surface hammer cracking Seam.
(2) Metallographic examination. Mainly inspect the segregation of carbides on the grain boundaries of materials Distribution status Crystallinity and mixture between grains.
(3) Ultrasonic examination. Mainly inspect the defects and size inside the material.
2、 Processing, use, and maintenance of die-casting molds
The mold design manual provides a detailed introduction to the issues that should be noted in the design of die-casting molds, but when determining the injection speed, the speed should not exceed 100m/s. Excessive speed will increase mold corrosion and deposits on the cavity and core; However, being too low can easily lead to casting defects. Therefore, the low-pressure injection velocity of magnesium, aluminum, and zinc is 27.18
The main forms of die casting mold failure are: sharp corners Crack at the corner crackle. Hot cracks (fissures) Wear and tear Erosion, etc. The main reasons for the failure of die-casting molds are: defects in the material itself, as well as the processing, use, maintenance, and heat treatment of die-casting molds.
1、 Defects in the material itself
As is well known, the usage conditions of die-casting molds are extremely harsh. Taking aluminum die-casting molds as an example, the melting point of aluminum is 580-740 ℃, and the temperature of the aluminum liquid is controlled at 650-720 ℃ during use. Die casting does not preheat the mold, and the surface temperature of the cavity rises from room temperature to liquid temperature, resulting in significant tensile stress on the cavity surface. When opening the top of the mold, the surface of the cavity is subjected to significant compressive stress. After thousands of die-casting processes, defects such as cracks appeared on the surface of the mold.
It can be seen that the usage conditions for die-casting are rapid heating and rapid cooling. The mold material should be selected from hot mold steel with high thermal fatigue resistance, fracture toughness, and thermal stability. H13 (4Cr5Mov1Si) is currently a widely used material. According to reports, H13 is used in 80% of the cavities abroad. At present, 3Cr2W8VV is still widely used in China, but it has poor artistic performance, poor thermal conductivity, high coefficient of linear expansion, and high thermal stress during operation, which leads to mold cracking or even rupture. It is easy to decarburize during heating, reducing the wear resistance of the mold. Therefore, it belongs to the category of eliminating steel grades. Martensitic aging steel is suitable for molds with low requirements for heat crack resistance, wear resistance, and corrosion resistance. Tungsten molybdenum and other heat-resistant alloys are limited to small inserts with hot cracks and severe corrosion. Although these alloys are brittle and sensitive to notches, their advantage is good thermal conductivity, and they still have good adaptability and production management for thick die-casting molds that require cooling but cannot be set with water channels. Therefore, H13 still has good heat treatment performance.
The materials used to manufacture die-casting molds should meet the design requirements in all aspects to ensure that the die-casting molds reach their designed service life under normal usage conditions. Therefore, before putting into production, a series of inspections should be carried out on the materials to prevent defective materials from wasting early scrap and processing costs of molds. The commonly used inspection method is macroscopic corrosion inspection. Metallographic examination. Ultrasonic examination.
(1) Macroscopic corrosion inspection. Mainly inspect the porosity of the material Segregation crackle. crackle. Non metallic inclusions and surface hammer cracking Seam.
(2) Metallographic examination. Mainly inspect the segregation of carbides on the grain boundaries of materials Distribution status Crystallinity and mixture between grains.
(3) Ultrasonic examination. Mainly inspect the defects and size inside the material.
2、 Processing, use, and maintenance of die-casting molds
The mold design manual provides a detailed introduction to the issues that should be noted in the design of die-casting molds, but when determining the injection speed, the speed should not exceed 100m/s. Excessive speed will increase mold corrosion and deposits on the cavity and core; However, being too low can easily lead to casting defects. Therefore, the low-pressure injection velocity of magnesium, aluminum, and zinc is 27.18
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