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What are the casting methods and advantages and disadvantages of ordinary sand casting?
The basic raw materials for making sand mold are casting sand and molding sand binder. Sand casting is the most commonly used silica sand, the high temperature performance of silica sand cannot satisfy the requirements while using zircon sand, chromite sand, corundum sand special sand. The sand binder is the most widely used clay, also can be used in a variety of ganxingyou or half ganxingyou, water soluble silicate or phosphate and various kinds of synthetic resin sand binder.
The sand mould used in sand casting is divided into 3 types: Clay wet sand type, clay dry sand type and chemical hardening sand type according to the way of building sand binder and the way of building strength.
Sand casting is the most popular and simple type casting has been used for several years. The sand casting is used to make large parts, such as gray cast iron, nodular cast iron, stainless steel and other types of sand casting process. The main steps include painting, mould, core making, molding, melting and pouring, cleaning and so on.
Selection of process parameters:
Processing allowance:
The so-called allowance for machining is the surface that needs to be machined on the casting, and a certain allowance must be set aside in advance. The size depends on many factors, such as the type of casting alloy, the method of modeling, the size of the casting and the location of the machined surface in the mold.
Model slope:
In order to make it easy to remove from the mold, the slope added to the vertical wall perpendicular to the parting surface is called the slope of the model.
Casting round angle:
In order to prevent the casting stress and cracks in the wall and connected to the corner, to prevent mold damage and produce sharp sand in the design of casting, casting wall connection and the corner part should be designed as a fillet
In order to ensure the positioning, fixing and exhaust of the core in the mold, the mold and core should be designed for the core.
Due to the cooling contraction after casting, the shrinkage size of the casting should be added.
Advantage：
Clay is rich in resources and cheap in price. After proper sand treatment, most of the used clay wet sand can be reclaimed and reused.
The period of casting mould is short and the work efficiency is high
Long time used for mixed sand
It has a wide range of adaptability. Small, large, simple, complex parts, single and mass are used
Shortcomings and limitations:
Because each sand mold can only be poured once, after the casting is damaged, it must be remodeled, so the production efficiency of sand casting is low.
The rigidity of the mold is not high and the precision of the casting is poor.
The casting is easy to produce the defects such as sand, sand, air hole and so on