Nodular cast iron crankshaft castings

As one of the important parts of the engine, the force of the crankshaft is complex in work. The constant changes of gas pressure, inertia force and torque acting on the crankshaft lead to alternating stresses such as bending, torsion, tension and compression, shear and so on. As the crankshaft is one of the most important working parts of the engine, engine products put forward high performance requirements for the crankshaft: high tensile strength, fatigue strength and surface strength, strong core toughness and certain wear resistance. Moreover, with the requirements of environmental protection and energy conservation and emission reduction in the new era, choosing a safe, environmental friendly and efficient crankshaft preparation process has become an urgent task in the field of crankshaft preparation.

Since the advent of nodular cast iron in 1947, after a short time of efforts, its tensile strength has increased to 600-800mpa, which is close to or higher than the level of carbon steel. Therefore, nodular cast iron has the ability to replace forged steel to make crankshaft. In the mid-1950s, nodular cast iron was used to produce diesel and gasoline engine crankshafts. In the 1970s and 1980s, due to the advantages of nodular cast iron in manufacturing and economy, a number of professional production plants of nodular cast iron crankshaft appeared. In recent years, with the development of automobile industry, the application of nodular cast iron crankshaft has been further expanded and developed.

At present, domestic crankshaft products are generally made of forged steel and nodular cast iron. Among them, the forged steel materials are generally medium carbon steel and medium carbon low alloy steel, such as 45 steel, 53 steel, 35CrMo, 40Cr, etc; The grades of nodular cast iron suitable for crankshaft include QT600-3, QT700-2, QT800-2, QT900-2, QT900-5, etc. In addition, according to the analysis, the casting forging ratio of crankshafts of light vehicles and cars in China is that with the replacement of Forged Crankshafts by nodular iron castings in a wider range, the casting forging ratio will be improved. At present, the general development trend of crankshaft materials at home and abroad is that nodular cast iron crankshaft is used to replace forged steel crankshaft. High strength and Toughness Nodular Cast Iron Crankshaft with high tensile strength and high elongation will become the recent development direction. The statistical data show that the proportion of nodular cast iron used in vehicle engine crankshaft is 90% in the United States, 85% in the United Kingdom and 60% in Japan, In addition, Germany, Belgium and other countries have also adopted a large number of ductile iron materials.

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