Application of Ductile Iron in Automotive Exhaust Manifold

In the 1940s, some scientific workers found that adding Ce, Mg and other elements into FERROCARBON alloys and nickel-carbon alloys can make graphite in the casting globular. Ductile iron has been on the stage of history since then.[32,33].Based on the special working conditions of automotive engine parts and in order to meet the requirements of energy saving and consumption reduction, the strength, hardness, creep strength, heat resistance and thermal expansion coefficient of materials are fully considered in the design to ensure the reliability of the entire engine operation. This is also the basic reliability for the application of ductile iron, which also enables ductile iron to be used.Basis for use.

Through the review and analysis of the papers on heat-resistant cast iron published in influential journals at home and abroad, it can be seen that the progress since 1980s has been obvious and remarkable. Some Chinese researchers have selected the subject with one branch of heat-resistant cast iron as their fixed research direction, gradually formed their academic characteristics, and promoted the development of heat-resistant cast iron from different perspectives.The heat-resistant cast iron brands produced in China tend to be diversified.In general, these heat-resistant cast iron can be divided into chromium, silicon, aluminium and nickel series according to the alloying elements and chemical composition added.Structurally, the mechanical properties of spherical graphite are mainly influenced by the matrix.To emphasize the importance of a matrix for controlling mechanical properties, ductile iron is often designed and classified by the name of the matrix. At present, there are mainly Ferritic Ductile iron, ferrite-pearlitic ductile iron, pearlitic ductile iron, martensitic ductile iron, bainitic ductile iron, Austenitic Ductile Iron and Austenitic Ductile iron.

Ductile iron is often added with some alloying elements in production, so it is also often called alloyed ductile iron nowadays. Alloy ductile iron can be roughly divided into Ferritic Ductile iron, bainite ductile iron and Austenitic Ductile Iron according to the structure formed after alloying.

Since the late 1970s, vehicle emission regulations have become more and more stringent. In order to improve catalytic efficiency, reduce emissions and continuously increase engine exhaust temperature, the operating temperature of exhaust manifold has been raised from 700-750 C to 800-850 C or higher.Exhaust manifolds and fasteners made of grey cast iron can crack due to thermal fatigue damage.Ductile iron has simple production process, better casting performance and lower cost than cast steel.Ductile iron was therefore considered by automakers to be a suitable exhaust manifold material.Nodular cast iron with high silicon and molybdenum and high nickel are commonly used in the market at present.