Huizhou Shuangcheng Aluminum Alloy Die Casting Factory

Operation method

In the process of die casting, due to the high volatilization point and large gas emission of some coatings, it has a direct impact on the porosity of castings. The release agent is mainly sprayed manually, and the amount is mainly determined by experience. If the spraying amount is too much and the spraying time is too long, it is easy to cause large gas volatilization. In addition, the mold temperature is low, and the volatilization is not timely, and other factors lead to large porosity. Therefore, the paint with low volatile point and small amount of gas shall be selected in the production process. At the same time, the blowing time can be appropriately extended to ensure that the dynamic and fixed molds are dried. For the mold with complex shell structure, it is necessary to dry the excess demoulding water or oil on the mating surface of the injection chamber and the punch, the cavity surface of the mold, the core pulling position and the runner

Examples of improving casting air tightness

An example of improving the airtightness of CLQ81 base is as follows. The airtightness requirements of CLQ81 base (see Figure 5) for automobiles

When strict, 100% leakage detection must be achieved, otherwise, oil leakage will be caused in use, affecting the normal use of vehicles. Ensuring air tightness in the production process is the focus of quality inspection

In the early mold design, because the air tightness was not considered as a major problem, the air leakage rate of CLQ81 base castings during production was very high, especially after a period of production, the mold surface would appear serious cracks, local strains were also very serious, which increased the air leakage rate of castings. The poor airtightness of product parts has become the main bottleneck restricting production (although it can be remedied by later infiltration, the production cost has been greatly increased). To solve this problem, we have analyzed the causes of air leakage of castings

Due to the large amount of waste parts and runner materials used for remelting in production, the impurity content of castings in later production increases, which is extremely unfavorable to the assurance of casting quality. At the same time, in the machining process, due to the large machining allowance, the air holes and sand holes inside the casting are exposed more, which aggravates the air leakage of the casting. In response to the above analysis, we have taken the following measures

(1) The use of recycled materials shall be strictly controlled, nitrogen shall be blown into the aluminum liquid, and powder refining agent shall be added at the same time, so that the aluminum liquid in the furnace can fully contact with the gas and refining agent, and the gas and impurities in the aluminum liquid can be removed as much as possible

(2) In order to ensure the air tightness of aluminum alloy die castings after machining, we will improve the design of the machining fixture in the later machining process, improve the positioning accuracy of the machining, and reduce the machining allowance as much as possible on the premise of ensuring the size required by the drawings

(3) In order to reduce the surface defects such as cracks and strains in the later use of the mold, the corresponding parts of the mold shall be strengthened, and the surface shall be coated with titanium when making new core pulling cores. After the above measures have been implemented for a period of time, the air leakage rate of the casting has been greatly reduced, and there is basically no need for infiltration treatment

Due to the characteristics of the die casting process itself, it is necessary to establish a natural” Sequential solidification” It is difficult and complicated to take the technological measures of The most fundamental reason may also be,” Sequential solidification” The process measures of the die casting process always require a relatively long solidification time, which is somewhat contradictory to the die casting process itself.; The biggest feature of forced solidification feeding is that the solidification time is short. Generally, it only reaches” Sequential solidification” Therefore, on the basis of the die-casting process system, the addition of forced feeding process measures is suitable for the characteristics of die-casting process, which can well solve the problem of shrinkage cavity and porosity of die-casting

4. There are two levels of forced feeding: extrusion feeding and forging feeding. There are two levels of forced feeding for castings. One is basically to eliminate the shrinkage cavity and porosity of the casting, and the other is to make the inside of the blank reach the level of broken grain or forged structure. If we want to use different words to express the two different degrees, we can use” for the former; Extrusion feeding” To express the latter, we can use” Forging feeding” To express. We should pay full attention to the understanding that replenishment is a direct means and cannot be completed indirectly. In terms of process, we can have a process parameter to express it, which is” Feed pressure”. In physical principle, the concept of pressure can occur in two ways: one is in the liquid situation, namely” Pascal's Law” For clarity, we define it as” Liquid pressure”, The other one appears in the solid state. We define it as” Solid pressure”. It should be noted that the applicable conditions of the pressure concept in these two different states will cause major problems if we mix them up