(1) Strict requirements on the chemical composition, The carbon and silicon content of raw iron liquid is higher than that of gray cast iron, Reduce manganese in ductile iron, Phosphorus, sulfur content (2) iron oven temperature is higher than gray cast than iron, Than compensation sphere change, Loss of iron liquid temperature during gestation treatment (3) Bulping treatment, That is, add ball agent to iron liquid (4) for gestation treatment (5) ductile casting fluidity, With a large contraction, Therefore, a higher pouring temperature and a larger pouring system size are required, Multi-application mouth, chiller, Using the sequential solidification principle (VI) Heat treatment of ductile iron as a bearing requires higher hardness, The cast iron part is often quenched and tempered at low temperature.The process is: various castings are heated to a temperature of 860-900℃, and the original matrix is all oltenitic and then cooled in oil or molten salt to achieve quenching. After 250-350℃ heating and tempering, the original matrix is converted into tempering martensite and residual austenitic tissue, and the original spherical graphite shape remains unchanged.

With the development of high strength and lightweight direction, the market of ductile iron parts is relatively getting bigger and bigger.The production of spherical iron thin small pieces should control its can not occur white mouth, hard edge, the solution: (1) control the chemical composition (2) increase the pouring gate, (3) the baked iron liquid temperature> 1450℃, improve the pouring temperature.Ball iron thick large fill and shrinkage outlet, casting cooling is slow, easy to produce spherical decline, shrinkage loosening and graphite floating, often single casting test rod qualified, casting body has shrinkage loosening or gold unqualified.Solution: Remove or shrink the shrinkage opening.Place the local or most of the cold iron.The production of spherical iron from the casting process, chemical composition and spherical control of the experience.First, casting process: one, the casting principle classification surface as far as possible the main cavity in the bottom box, conducive to the process design, sand box rigid strong sand to eat less, balanced solidification, thick with direct cold iron or sand separation cold iron, accelerate cooling to get qualified organization.The design principle of pouring system is fast pouring, slag retaining, filling and shrinkage, economy and easy to clean up.The shape of the inner pouring is better (rectangle or approximate square), easy to shrink and the temperature difference is small.semicircle or triangular inner pouring port should not open poor shrinkage effect, semicircle or triangular pouring center insulation is strong, pouring center and casting joint easy to form a shrinkage hole.After filling solidification quickly improve the smoothness and internal density of the casting, no mouth to simplify the process saves the cost, the mouth as far as possible with dark pressure mouth easy to operate, if large parts can not be poured full must be manual fire (iron filling) effect is lar

⑴, almost various shapes and quite complex precision iron platform casting; ⑵, independent of the size of the shape, weight, can make hundreds of grams of small parts, hundreds of tons of large parts; ⑶, using a wide range of metal and alloy surface, can make all alloy parts; ⑷, can single production, and mass production.Casting and forging, stamping, powder metallurgy, welding and other metal processing technology compared, weight size, part shape, alloy type, especially the number of production and other aspects of the range is very wide, is a very broad road process technology.The characteristic of various metals that can reach the required shape and parts is the biggest characteristic of casting technology, which is not reached by other metal processing methods.The characteristic metal cast has a very high deformation resistance, with the cold processing method, it is not easy to make the required shape.But casting can melt the solid metal with large deformation resistance, making it a liquid metal with small deformation resistance, and pour into the casting to produce the shape of the parts.This characteristic of casting is that other processing methods can not follow, as a processing method, it is really a clever method.

What factors affect the quality of cast iron parts?This site believes that the first iron geometry, size, size effect and solidification, shrinkage, stress.Second, structure, weight and size.The third is the quality of the raw materials used for casting.The quality of metal furnace material, refractory materials, fuel, flux, metamorphic agent and cast sand, type sand binder, coating and other materials is not in standard, which will make the cast iron parts produce pores, pinhole, slag, sticky sand and other defects, affecting the appearance quality and internal quality of the cast iron parts, and the cast iron will be scrapped.The fourth is the process operation, to develop a reasonable process operation procedures, improve the technical level of workers, so that the process procedures are correctly implemented.

Ductile cast iron parts have low cost, good process performance, remelting and regeneration, resources and energy saving, so the application and development of this material is always lasting.Such as research and development of electric furnace double smelting technology and equipment; widely adopt advanced iron liquid desulfurization, filtration technology; thin-wall high strength casting manufacturing technology; cast iron composite manufacturing technology; cast iron surface or partial reinforcement technology; isothermal quenching ductile iron complete technology; color metal casting and metal type sand casting, continuous casting and other special processes and equipment.High strengthening and thin wall are the development direction of grey cast iron in China. Casting iron with thin wall, lightweight and strong toughness are designed to meet the requirements of engineering circles for energy saving and reuse of engineering materials, and to meet the needs of "human sustainable development strategy".For the production of cast iron parts, the particularity of the solidification mode and many influencing factors become more difficult.Alloy composition, graphitic expansion, casting stiffness and crystalline core all affect the final quality of the casting, but it is difficult to give a more accurate quantitative description.For example, alloy composition, due to the implementation of gestation, spherical chemical and other processes, it is difficult to determine the composition of iron when the final pouring.Casting iron surface layer laser reinforcement treatment and surface alloying technology of casting can form a metallurgical combined alloy layer on the surface of ordinary casting, making the casting has composite properties.The above technology has been gradually applied to the production of wear-resistant parts, and has achieved obvious results.Like the casting stiffness coefficient, the graphitization expansion coefficient is a