H13 and skd618407 are the most widely used materials for die casting. However, due to the large-scale of die casting, the required molds are also developed to large-scale ones. In order to prevent quenching deformation and cracks of the molds, it is necessary to develop low deformation rapid cooling skills with improved resistance and improve the tolerance level of the mold materials. High cycle operation is required to improve the production power and reduce the cost of die casting. Compared with previous molds, high cycle operation increases the heat load due to lack of cooling, which increases the surface temperature of the mold and then causes the hot crack to occur in advance. Read on and learn the key of die casting mold design process.
Die Casting Mold
Due to the addition of internal cooling holes and closer to the cavity, the temperature difference between the internal cooling holes and the cavity surface increases the tensile thermal stress load and reduces the rigidity, and stress corrosion cracking is easy to occur, so that water leakage is connected to the cavity and then the life of the mold is reduced. Therefore, it is necessary to develop new materials that can improve longevity more than skd6l. DAC is similar to SKD61 and is widely used, but its brevity is better than SKD61. The dac-s developed in order to improve its endurance is 60% better than the DAC. In order to comment on the tolerance level of die casting mold data, the North American Die Casting Association (NADCA) set the Charpy impact value of AISI H13 (equivalent to SKD61), and set the Charpy impact value of premium H13 and superion H13 of higher grades in order to ensure more stable die life. Dac-p is equivalent to the former and dac-s is equivalent to the latter. The hot cracking countermeasure of the die-casting mold needs to have high temperature strength. Generally speaking, the resistance and strength are opposite. Due to their high-definition purification and fine arrangement, dac-p and dac-s have equal strength with DAC at room temperature and 600 ° C, and have 0.2% higher endurance than DAC at room temperature and 600 ° C. As mentioned above, there should be mould materials with higher grade than SKD61, which can greatly improve the longevity, high temperature strength and resistance. As high-performance die-casting die materials, dacio, dac55, dac45 and the latest developed zhd435. Daci0: it has superior strength in the temperature range of 600 degrees and is equivalent to DAC’s resistance. It is suitable for fine die casting of high precision parts for electrical appliances and communication machines. Dac45: it has higher strength than other materials at 700 ° C. It has the characteristics of resisting softening together, but it has poor resistance compared with DAC. Special attention should be paid to the cooling of broken fire. Suitable for medium and small-scale die casting molds. DAC55； It is characterized by high resistance, and hardness can be improved at the initial stage. It is a material with balanced resistance and strength. Its service life is 1.4 times higher than that of skd6l. It can be applied to the cylinder block, cylinder head and parts of the drive system of the car. ZHD435。 It has the same bremsstrahlung property as dac55 and can be used for large parts. It has higher high temperature strength than dac55 and is more advantageous than dac55 in terms of thermal cracking and life.
Machining of Die Casting Mold
The processing of die-casting die is an important aspect to ensure the quality and reduce the cost. The production system of CAD / CAM / CAE, five axis machining machine and the latest cutting tools are selected to process the die, so that the quality and production power of the die are constantly improved. Its intention has three aspects: the machining method based on three-dimensional model, the replacement of EDM with machining center cutting, and the automation of hole machining. In terms of three-dimensional model, the first thing is to fully select three-dimensional model for mold design, simplify NC digital programming, and build a quality assurance system after processing. EDM is replaced by machining center. The main reason is that electrode machining requires more work than cutting. Therefore, EDM is mainly used because the mold has a rib like deep groove shape. Now, the deep groove shape may also be processed by cutting, and then the production power of the mold will be improved. Automation of hole processing: there are many kinds of holes in the mold, which can generally be divided into shallow holes with a depth of less than 100mm but accuracy requirements of h7-h8 and deep holes with a depth of 100-600nun for cooling and air release, but the accuracy is not as required as shallow holes. The hole processing occupies a large part of the time in the mold processing. In addition, the hardness of the mold raw materials (hrc48 degree) makes the hole processing more difficult. The selection of the quality engineering evaluation technology on the machining center is to find the best policy based on the discussion of the hole processing conditions. The best data selected on the machining center has improved the surface roughness by 1 / 3, the error of the hole diameter by 1 / 5, and the service life of the cutting tool by more than 5 times. The machining of holes on curved surfaces and inclined surfaces has also been automated.
Surface Treatment of Die Casting Mold
There are several methods such as dispersion treatment, coating, nitriding + coating. Although there are various trade names for the dispersion treatment method, the main ones are the nitriding, soft nitriding, sulfur impregnation nitriding, oxidation, nitriding + oxidation treatment of N, C, s and 0 alone or in combination. When the representative nitriding treatment is performed, the compound layer (white layer) has good melting loss resistance, over burning resistance and adhesion resistance, but poor crack resistance. On the other hand, if the compound free layer only constitutes the dispersion layer, the heat cracking resistance is good, but the melting loss resistance, over burning resistance, and adhesion resistance are poor. The recent dispersion treatment trend is that oxidation treatment or nitriding + oxidation composite treatment is the main stream, which is suitable for various surface treatment methods of die casting molds.