SAND CASTING EQUIPMENT.

Sand casting surface firmly adhered to the sticky sand defects can be divided into two kinds of mechanical and chemical sticky sand. Mechanical sticky sand is caused by the metal liquid drilling into the pores between sand grains of the sand type. Chemically sticky sand is the sand SiO2 and metal oxides such as FeO and other chemical reaction to generate ferrous silicate (iron olivine) and castings stuck together. The chemical composition of ductile iron castings with high carbon content does not produce ferrous silicate, and the resulting sticky sand is only mechanical sticky sand.

1、ductile iron large pieces of sticky sand production of large pieces of clay dry type, resin sand type, water glass sand type. Casting larger castings usually use zirconia powder, chromite powder, brown corundum powder, magnesium sand powder, graphite powder and other refractory aggregates of high quality coatings. But the coating manufacturers may save production costs, too much powder mixed with certain inexpensive materials such as quartz powder, bauxite powder, coke powder, etc., it will reduce its anti-sticky sand effect.

2、wet type medium and small ductile iron parts sticky sand cast iron parts sand contains mostly coal dust, casting produces a large amount of reducing gas, will not cause chemical sticky sand. xinyuanzhuGroup discusses the impact of various factors on mechanical sticky sand in conjunction with the casting process of ductile iron.
2.1 The degree of sand compactness of manual modeling and shock molding is generally low, the sand surface of the sand is loose, the possibility of metal liquid drilling into the pores between the sand particles is greater, the sand cavity pits and corners of the local may also appear loose. Workers can take the finger plug tight, with the tip of the punch hammer local punch tight. Whether the high productivity of high-density molding has local looseness depends on the sand flow, so many factories try to reduce the sand compacting rate to improve the sand flow. The use of micro-vibration in the sand addition and compaction process is very effective. It also depends on the setting of the compacting pressure of the moulding machine.
2.2 Pouring temperature High metal fluid temperature and good fluidity make it easy to penetrate into the pores between the sand grains and produce mechanical sand sticking and surface roughness. But from the castings to avoid porosity, cold compartment and other defects, pouring temperature can not be arbitrarily reduced. The production of complex thin-walled castings especially need high pouring temperature.
2.3 sand particle size and air permeability of wet sand grain thickness on the one hand to ensure that the exhaust after pouring, on the other hand, the air permeability of wet sand is not too high, so as not to easily penetrate the metal liquid into the sand pores. Manual modeling production of small pieces of sand type tied with more exhaust holes, and often use surface sand, sand grain can be fine, sand permeability 30 ~ 60 has been appropriate. Machine molding wet sand sand size is roughly 70/140 mesh, air permeability mostly in the range of 60 to 90. High-density sand is more dense, the sand is required to have a high air permeability. Most of the sand size is 50/140 or 140/50 mesh, and the air permeability is mostly concentrated in the range of 100~140. Usually the original sand size for the core of internal combustion engine casting is 50/100 mesh, which is coarser than the sand size. Long-term production will have a large number of core sand mixed into the sand and make the sand particle size coarse, resulting in some factories air permeability up to 160 or more, unless the sand surface spray coating, the casting surface will appear rough or even have a local mechanical sand sticky. If there is coarse sand size, add 100, 140 mesh two sieve fine grain new sand to correct the sand mixing.
2.4 sand coating, machine modeling more than 100 kg of larger wet ductile iron castings, you can spray alcohol-based coating on the lower sand type, ignition can be under the core and close the type. Generally the upper type can not spray paint, because the hydraulic head of the metal subjected to smaller than the lower type. Another advantage of spraying paint is to improve the sand surface scouring resistance. When producing general ductile iron cast iron with resin core or oil sand core, in order to prevent the metal liquid from drilling into the core, you can apply the coating paste made of machine oil or other binder plus graphite powder, quartz powder or other refractory powder on the surface of the core after hardening, and then cool and dry it to the core. When producing cast iron parts with high requirements of inner cavity cleanliness and finish (such as cylinder head, body of internal combustion engine, valve parts of hydraulic system, etc.), the sand core must be coated as a whole and then dried on the surface. When producing small ductile iron parts by hand, soft brush is often used to paint graphite powder carefully on the surface of wet sand type and sand core. Some of them are sprayed with graphite and water mixture, and then poured after natural drying. Graphite powder can fill the pores, not wetted by iron, and it is difficult for iron to drill into the sand between the grains.

Xinyuanzhu Group specializes in the production of Ductile iron castings, Pig iron gray iron casting, Steel casting, Brass Casting, Malleable Iron Casting, and undertakes batch casting processing of castings. Welcome guests to cooperate with pictures or samples.