Understanding of precision steel casting

Sand cast has a long history in the field of casting, and the output of castings is also considerable. However, there are many difficulties in the production of precision steel casting with coated sand casting: sticky sand (scarring), cold air insulation. It is up to us to further solve these problems.

1. Understanding and understanding of coated sand for precision steel castings (coated sand is an organic binder type. Core sand)

(1) Film sand characteristics: has appropriate strength performance; Good fluidity, clear shape of sand core, dense organization, can make complex sand core; The surface quality of sand mold (core) is excellent. The results show that the surface roughness is between 6.3~12.5 microns, the dimensional accuracy reaches CT7~CT9, the collapsibility is good, and the casting is easy to clean.

(2) Scope of application: the coated sand can be made into mold or sand core, and the core or core of the coated sand can be used with each other, and can be used with other sand (core); Not only can be used for metal type gravity casting or low pressure casting, can be used for iron type sand casting, can also be used for thermal centrifugal casting, can be used for cast iron. Production of non-ferrous alloy castings, can also be used for casting steel.

Preparation of covering sand.

1. Cover the sand composition.

Commonly used refractory materials. Adhesive. Curing agent. Lubricants and special additives.

(1) Refractory material is the main body of coated sand. High temperature resistance requirements: high temperature resistance, small volatility, more round particles. Strong and durable. Natural silica sand is usually chosen for scrubbing. Silica sand filter material requirements: high SiO2 content (cast iron and non-ferrous alloy casting parts require more than 90%, cast steel requires more than 97%); The mud content is not more than 0.3%(for scrubbing sand),[the specified value of the mud content of washed sand is less than; the particle size ① is distributed on the adjacent 3 to 5 sieve numbers; the Angle coefficient cannot exceed 1.3, and the acid consumption value is not less than 5ml.

(2) Adhesives usually use phenolic resin.

(3) The curing agent is usually used with ulotropine, and the lubricant of calcium stearate is generally used with it, its role is to prevent the covering sand from caking and improve the fluidity. The main function of the additives is to improve the performance of the coated sand.

(4) The ratio of coated sand base (mass fraction, %) : raw sand 100 scrub sand, phenolic resin 1.0~3.0 raw sand weight, Ulotropine (aqueous solution 2)10~15 resin weight, additives 0.1~0.5 raw sand. The resin weight of 2.10~15 is 1~15, the calcium stearate is 5~7, and the additive 0.1~0.5 is the original sand weight.