Aluminum alloy die-casting mold vacuum heat treatment

The failure modes of die casting molds include thermal fatigue cracking, thermal wear and thermal erosion. The performance requirements for die-casting molds are: high heat resistance and good high temperature mechanical properties; excellent cold and heat fatigue resistance and high thermal conductivity; good oxidation resistance and corrosion resistance; High hardenability. The hardness of the concave mold is 5660HRC, but it requires high toughness. Die-casting mold materials. my country’s aluminum alloy die-casting molds have been made of 3Cr2W8V steel for many years. Although this steel has good high temperature strength and hot hardness, it has toughness and thermal fatigue resistance. Inferiority is a major weakness, causing molds made from this steel to suffer from premature thermal fatigue cracks and faster propagation, which affects product quality. 4CrSMOSiN (H13 for short) is a new type of hot die steel, an air-cooled hardening hot work die steel widely used in the world. H13 steel has high thermal strength and thermal hardness, high toughness and thermal fatigue resistance, and is not prone to thermal fatigue cracks. Even if thermal fatigue cracks occur, they are thin and short and not easy to expand. The service life of the die has been greatly improved. At present, the die-casting die block material is mostly H13H13 annealed die blank, and the hardness is 192229HBSH13 steel chemical composition C 0.320.45 Mn 0.200.50 Si0.801.20 Gr 4.755-5 Mo1.101.75V0.8O1,20 (The vacuum heat treatment process for hot work molds is commonly used, and the vacuum heat treatment of mold materials is completed in a steel mill to ensure that the steel material, such as basic mechanical properties, and the metallographic structure must comply with national standards or industry standards. The characteristic is mass production in large industrial furnaces. .Vacuum heat treatment of mold parts: Completed in mold manufacturing plant, or professional vacuum heat treatment plant. It is characterized by small batch or single-piece production, complex and diverse processes, and sophisticated equipment.

The vacuum heat treatment process method is divided into preliminary vacuum heat treatment and final vacuum heat treatment. Common methods are: vacuum normalizing, vacuum annealing, vacuum quenching, quenching and tempering, vacuum carburizing and vacuum nitriding, etc. The vacuum heat treatment of molds includes vacuum heat treatment of mold materials and vacuum heat treatment of mold parts. The carbide band segregation of H13 steel after forging is sometimes serious, and the conventional annealing process (flake pearlite + few star block carbide) cannot be satisfied. Using the isothermal spheroidizing annealing process in the high temperature solid solution period (the organization is spherical pearlite + a small amount of dispersed granular carbides), the carbides can reach the ultra-fine level, and the ribbon segregation of carbides can be homogenized, so secondary carbonization Things appear less often. The uneven distribution of carbides has been significantly improved, or even eliminated, vacuum annealing process, vacuum quenching process. According to the service characteristics of the hot work die, the vacuum quenching temperature is selected at 1020°C. The vacuum quenching temperature is selected to obtain the most critical properties. The high temperature strength increases with the increase of quenching temperature, but the increase of strength is obtained under the condition of sacrificing toughness. The higher the quenching temperature, the more sensitive the steel is to grain growth. Coarse-grained steel is less tough than fine-grained steel, and is prone to cracks and damage. The low cooling rate leads to poor impact toughness and is prone to cracks and damage. Low cooling rate leads to low impact toughness. In order to obtain the best impact toughness of H13 steel, high quenching temperature and high cooling rate should be properly combined. The heating rate of aluminum alloy die-casting mold is about 200 per hour. Ideal. Preheating can also be performed quickly. The purpose of preheating is to prevent the deformation caused by thermal stress or phase transformation stress during the heating process, and the shrinkage deformation caused by phase transformation at about 800°C, so secondary preheating is used. The first preheating temperature is 550, the second preheating temperature is 800, and the final heating is 1020. Using air cooling and first-level quenching, the aluminum alloy die-casting mold is prone to cracking and has a low service life. It is ideal to use two-stage classification quenching. Now comparing the graded quenching process, the neutral salt bath temperature for graded quenching of the first-stage salt bath is 500 and 200, and the tempering stability of the vacuum tempering process is one of the main properties of the hot work die steel, which reflects the die steel. The ability to resist softening at high working temperature is related to the high temperature hardness, high temperature strength, and thermal fatigue resistance of steel. Improved tempering stability can help extend tool life. In order to prevent cracking, the mold should be tempered immediately after cooling to about 100 degrees after vacuum quenching (especially the mold with complex shape should be tempered immediately after quenching). According to the working conditions of the mold, secondary hardening is obtained near 500, the highest tempering hardness is about 55HRC, the impact toughness of the steel is significantly reduced, and tempering brittleness occurs, which should be avoided.

Equipment selection: The RVA series vacuum heat treatment furnace produced by SIMUWU is a high-quality product for the vacuum heat treatment of tooling and molds. Good temperature control accuracy and temperature control uniformity ensure the effective progress of the vacuum heat treatment process. SIMUWU specializes in the manufacture of vacuum furnaces, has more than ten years of relevant experience, and has a good reputation in the field of vacuum furnace manufacturing. The product line includes vacuum air quenching furnace, vacuum oil quenching furnace, vacuum brazing furnace, etc., which are widely sold in developed and developing countries.