来源：http://www.jnhjgs.cn 发布时间：2020-02-17 20:09:48 点击：
1. Zinc alloy die casting for layout
The zinc die casting is too thick, which leads to shrinkage and poor feeding. The wall thickness of the casting is not uniform, and there are some heat shrinkable holes in the thick wall.
Because the diameter of the die-casting zinc hole is too small in the sand core, forming a casting hole is heated by a hot metal liquid. Under the long-term high temperature condition, reducing the condensation rate and the appearance of the zinc die-casting metal hole together, the supply channel of the gas or atmospheric pressure sand core results in the attack of the shrinkage hole and the hole wall.
2. Technical planning of zinc die casting
(1) The design of the guideline and the casting system is not reasonable, and the casting system and planning of zinc alloy die casting are timely, which is easy to cause the defects of shrinkage cavity and porosity. The main properties of the casting do not conform to the solidification sequence, and the gate size and range are not correct. For gray cast iron and nodular cast iron, if the door is opened at the thicker part of the casting, plus the thickness of the internal brake pad, the gate after pouring will be in liquid state for a long time. In the process of graphitization and expansion of molten iron, solidification will occur, and the molten iron will be poured out from the inner gate, resulting in shrinkage cavity and porosity of the casting.
（2） The unreasonable planning of riser range, quantity, scale and riser neck scale can not promote the order solidification of castings and lead to the occurrence of shrinkage and porosity of castings. If the exhaust port of the exhaust port is not placed on the top of the dark riser, the improper use of the water chiller will cause the shrinkage cavity and porosity of the aluminum die casting.
(3) The reasons for the low fire resistance, high temperature strength and large thermal deformation of sand core and sand core (sand core). When the liquid metal static pressure or graphitized expanded wall, the core wall or attack will move. At present, it is a hot spot to increase or supplement the shrinkage expansion of new parts, which leads to the attack of shrinkage porosity in zinc die casting. This representation is very sensitive to large and medium-sized die castings. Otherwise, if the water content of molding sand is too high, the wall thickness will become thinner, the condensation area of water dry water will increase, the scale will expand, the mobile phone can be added to the wall, resulting in shrinkage and erosion.
Casting processing method
From the technical principle of die casting process, the shrinkage defects of castings can only be solved by the process. As cast condensation shortens the transformation process, which is a natural physical phenomenon. We can't change the natural expression of this law, we can only follow its law to deal with it.
There are two ways of feeding die casting, one is natural feeding, the other is forced feeding. In order to complete the natural feeding, our casting process system will have technical means to complete the "sequence" of condensation. Many people intuitively think that the choice of shrinkage rate of low-pressure castings can solve the shrinkage defects of castings, but it is not the case. Using low-pressure casting technology does not mean that the low-pressure casting system can reduce the treatment of casting defects. If the process and method are not compensated and contracted, the defect of the blank produced by low pressure casting can be reduced by 100%.
The above is a detailed introduction to the shrinkage conditions of aluminum die casting. For more information, please click http://www.jnhjgs.cn