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Sand molding for sand casting process

Accordingly to production requirements, Chemical hardening sand and clay mortar sands are all widely used for sand casting. But there're lots of differences between them.

1)Chemical hardening sand

*Strength of Chemical hardening sand castings is higher than the clay mortar sand castings. After the chemical hardening, strength of the sand shell will be higher, which will help demoulding process, and no need more work to reshape the castings. Thus, it's easier to control the size accuracy of the castings.

*Viscosity of used binder and hardener for chemical hardening sands are low. So, they can be mixed uniformly. Structure of mixing equipment is simple and light, but the production rate is high. This will also simple the sand heat treatment process.

*The fluidity of the mixed sands is good before hardening. So, it's easy to shape and not require for complex shaping machines.

*Patterns for chemical hardening sand casting can be made in material of wood, plastic, or metal.

*Binder used for chemical hardening sand casting is lower than clay mortar sand casting, and there's no powder accessory used. Thus, the gaps between the 

chemical hardening sand is higher than clay mortar sands. To avoid the metal water permeating to the gaps of the sands,surface of the sand shells or sand cores will be protected by high qualified coating.

*Using sodium silicate as binder, the production costs of the chemical hardening sand castings are low, and there's no bad smell in working environment. But it's difficult to clear the sand shell after casting process. The used sands can not be recycled directly. 

*Some foundry uses resin sand as bonder for chemical hardening sand casting. The cost is high. But castings can be easily  separately from sand shell. It saves working time, and the sands can be recyled directly after casting.

2)Clay mortar sand

Using clay and water as the main binder to mix the sand and make the sand shells. Then, start mould covering and casting process directly. 

Advantages of clay mortar sand casting are as below,

*Resourcing of clay is abundant and cost is low.
*After casting, the sand can be recycled directly.
*Production time is short and work efficiency is higher.
*Mixed sand can be used for a long time.

Disadvantages of clay mortar sand casting are,

*To mix the sand uniformly, a good mixing equipment is required.
*The strength of the mixed sand is higher and fluidity is low. It takes time to make the shell manually. The costs is high to equip factory with complex equipment.

*Strength and size accuracy of the clay mortar sand casting are low.

*Castings made by clay mortar sand casting process are with defects of sand inserts, pores, and sand cuts, etc.