Materials of automobile crankshaft

There are two main types of crankshaft materials:
The crankshaft is made of cast iron, a new kind of composite material.
Steel crankshafts are mainly made of steel materials, which determine the main quality of crankshafts. In addition, the processing technology and processing accuracy. Steel Crankshafts generally use fillet rolling technology. The accuracy of crankshaft industry is invisible to the naked eye.
Nodular cast iron crankshaft not only uses fillet rolling process, but also needs nitriding treatment. The color of nitriding treated crankshaft is black. It is recommended for ordinary personnel to buy crankshafts that are original from the engine manufacturer, which can basically ensure the quality. When selecting, just pay attention not to have trachoma, pull mark, etc. in the curved path. Generally, there will be no problem.
Since the 1990s, high-strength aluminum alloy has been widely used abroad to replace traditional materials in order to realize lightweight. It is reported that Honda, Nissan, BMW and Audi have all produced aluminum engines, and their crankshafts are made of pressure cast fiber and particle reinforced aluminum alloy composites. The application of fiber reinforced and particle reinforced composite technology in industrial production has not been reported, mainly due to the complex production process of composite materials. At present, it only stays in the single piece and small batch production in the laboratory
The forms of crankshaft deformation include bending and twisting deformation of the main axis of the crankshaft. The detection method is to measure the journal circular runout of the intermediate journal to the journals at both ends. Support the journals at both ends of the crankshaft on the platform with V-shaped iron blocks, and lower the contact pin of the dial indicator on the middle journal. Rotate the crankshaft, record the small reading of the dial indicator, and then rotate the crankshaft by degrees to record the reading of the dial indicator. The difference between the large reading and the small reading of the dial indicator is the radial circular runout. The radial circular runout of the crankshaft shall not be greater than 0.15mm. When the runout error of the radial circle on the side is less than 0.15mm, it can be corrected in combination with smooth grinding. If it is greater than 0.15mm, it shall be corrected before crankshaft grinding.
The principle of material selection is to meet the service performance first, and then consider a series of requirements such as cost, lightweight and environmental protection. Among the materials listed above, the mechanical properties of steel are excellent, followed by ductile iron and aluminum alloy composites. However, steel with excellent performance is not selected in all cases, but should be considered comprehensively from all aspects. The performance price ratio we usually talk about is put forward in this sense. For the crankshaft with high power requirements, the general ductile iron can not meet the requirements, and the forged steel with excellent performance is mostly selected. The appearance of Austenite Isothermal Quenching Process has greatly improved the mechanical properties of nodular iron and made it close to forged steel. In addition, with its low cost and excellent process characteristics, on the premise of meeting the mechanical properties, some forged steel crankshafts have been gradually replaced by ADI. However, ADI needs to strictly control the process parameters of isothermal quenching heat treatment, and puts forward higher technical and management requirements for manufacturers, resulting in its production not being popularized. In addition, in forging steel, microalloyed non quenched and tempered steel is used to replace quenched and tempered carbon steel and quenched and tempered alloy steel to reduce the cost. For low and medium power crankshafts, ductile iron has almost completely replaced forged steel due to its excellent performance, low cost and improving process. In ductile iron, as cast ductile iron tends to replace heat-treated ductile iron. At the same time, the emergence of high-strength aluminum alloy composites can partially replace nodular iron crankshafts. However, at present, the process is not mature and can not meet the requirements of large-scale industrial production.
In the material selection of crankshaft, the above materials have their own application scope and development prospect according to their characteristics. Forged steel has excellent mechanical properties, ductile iron has wide application range and low cost; Aluminum alloy is the future direction and has development potential. Among them, as cast qt740-3 has a wide range of application, excellent performance price ratio and competitiveness in the crankshaft Market of light vehicles and cars.