Aluminum die casting shrinkage, shrinkage causes and solutions
Currently casting Shrinkage question is a very common phenomenon, aluminum die casting manufacturer --HONESTMEN CASTING for everyone to produce a list of some of the aluminum die casting shrinkage, shrinkage of reason, to help you better address these problem.
1, aluminum die casting structural reasons
Since aluminum die casting section too thick, resulting in poor feeding craters formed. Casting uneven thickness, resulting shrinkage in the thickness of the portion of the thermal section or shrinkage.
Since the hole diameter is too small aluminum die casting sand core holes formed at high temperature liquid metal is heated, a long period of high temperature, reducing the aluminum die-cast hole surface of the metal solidification rate, while the sand core is a gas or atmospheric provides channel, resulting in hole wall produce shrinkage and embroidered loose.
2, aluminum die casting process design reasons
(1) principles of gating system design is unreasonable solidified gating system design and aluminum die casting contradiction, it may lead to shrinkage or shrinkage produce castings. Mainly for casting position does not fit, is not conducive to solidification, the gate location and size is not correct. For gray cast iron and ductile iron, if the gate open in the casting thick-walled office, while the thicker inner gate size, after pouring, the gate is a long time in a liquid state. The expansion of the role of the graphite occurs solidification of molten iron, iron will backflow through the gate sprue, thus casting produce shrinkage and shrinkage.
(2) Riser riser design is unreasonable position, quantity, size and riser neck size could not promote the casting solidification, may lead to shrinkage and shrinkage to produce castings. If the top of the riser is not placed in a dark strain relief, or improper use of cold iron, can lead to aluminum die casting produce shrinkage and shrinkage.
(3) sand, core sand aspect sand reasons (core sand) refractoriness and low temperature strength, thermal deformation amount is too large. When under the influence of static pressure or graphitization expansion force of the liquid metal, type of wall or core wall will have to move. The casting shrinkage complement the actual need for increased or new hot spot in the expansion area, resulting in shrinkage and produces aluminum die casting shrinkage. This phenomenon of large and medium casting is very sensitive. Further, if the moisture content is too high the molding sand, the dry layer thickness will type wall surface area to reduce moisture condensation and moisture increases, expanded, so that the shaped wall mobility increases, resulting in the generation of shrinkage and shrinkage.
Workaround die casting
From the casting process principles that solve casting Shrinkage defects, only in accordance with the process by feeding thoughts. Phase change process of solidification shrinkage is a natural physical phenomenon, we can not reverse this law natural phenomenon, but it can only follow the law, to solve this problem.
Feeding of two ways: on the casting of feeding, there are two ways, one natural feeding, one forced feeding. To achieve a natural feeding, our casting process system, there should be able to achieve the "solidification" process measures. Many people intuitively think that can be solved using the low pressure casting method of casting Shrinkage defects, but the fact is not such a thing. using low pressure casting process, does not mean that we can solve Shrinkage defects casting, low pressure casting process if the system is not provided with the feeding process measures, then this means low-pressure casting produced by the rough is one hundred percent may exist Shrinkage defects.