Ductile iron casting sand casting process
Ductile iron castings are widely used in the mechanical […]
Ductile iron castings are widely used in the mechanical manufacturing industry because of their excellent properties and can sometimes replace expensive cast steel and forged steel in use. The metallurgical industry used to think that ductile iron was invented by the British in 1947. Some Western scholars even claim that it is unthinkable to invent spheroidal graphite cast iron without modern technology. In 1981, China's ductile iron experts used modern scientific methods to study the 513 pieces of ancient Han and Wei irons unearthed. Through a large amount of data, it was determined that spheroidal graphite cast iron appeared in China in the Han Dynasty. The papers were read at the 18th World Congress of Science and Technology History, which sensationalized the foundry industry and the history of science and technology. After verifying this in 1987, experts in metallurgy believed that ancient China had already explored the law of making ductile iron with cast iron softening, which is of great significance for re-staging the world metallurgical history. Cast iron parts are often quenched and tempered at low temperatures. The process is: various castings are heated to a temperature of 860-900 ° C, the original substrate is all austenitized and then cooled in oil or molten salt to achieve quenching, and then heated and tempered at 250-350 ° C, the original matrix conversion For tempered martensite and retained austenite structure, the original spheroidal graphite has the same shape. The treated casting has high hardness and certain toughness, retains the lubricating properties of the graphite, and improves the wear resistance.
Coated sand is a new type of coated sand produced by special process formula technology with excellent high temperature performance (high strength at high temperature, long heat resistance, small thermal expansion, low gas generation) and comprehensive casting performance. Coated sand is especially suitable for the production of complex thin-walled precision cast iron parts (such as automobile engine blocks, cylinder heads, etc.) and high-demand steel castings (such as container angles and train brakes; middle casings, etc.). Effectively eliminate casting defects such as sand, deformation, hot cracks and pores. It can make the surface of castings smooth, accurate in size, reduce or eliminate the need for machining, shorten the production cycle, save metal materials and reduce cost; and the mold can be made by automatic machine (carrying core machine must be used), no skilled workers are needed; It is especially suitable for batch and mass production of small and medium-sized castings of various metals.
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