Study And Development Of QT800-6 Crankshaft Material

Automobile is one of the important communication tools of the current time. With the development and the advancing of the civilization of the society, the requirement to the automobile is higher and higher. The automobile in the means of tradition is losing the characteristics and is replaced by the modern automobile that includes various new technologies. The level of the design and the manufacture of engine as the heart of the vehicle determine the various performance of the vehicle directly. The distribution of the works of the engine is more and more in the whole work. By the research and the application of the new techniques and new materials, the technique level of the modern diesel engine has achieved a lot of advanced. The advanced modern diesel engines of automobile have adapted many new technologies such as the turbo charge and the inter cooler, multi-valve, the electronic control technology, the high-pressure injection, the post processing (EGR) etc. With the increasing of the power of the diesel engine, the crankshaft will bear the higher alternating loads. The requirement to the strength, the ductility and the reliability of the material of the crankshaft is higher and higher. The original crankshaft and the medium strength crankshaft cannot satisfy the demand. Currently, the material of the crankshaft of the engine using in the large power engine is dominating by the forging steel. The crankshaft of the forging steel has many problems such as the poor capability of producing, the complex technics and the more expensive. Since the cast iron crankshaft has the advantages, which the forging steel crankshaft is not of, the research work to the cast iron crankshaft, get deep gradually. But affecting of the traditional idea "the iron is not better then steel", the development of the work is not satisfied. In the country, the research to the nodular cast iron crankshaft is limited in the QT700-3,QT800-2,QT900-2 which is lower ductility and plasticity material. The performance of the QT800-5 crankshaft produced by Shandong Tianrun is close to the performance of the forging steel crankshaft, but cannot reach the level of QT800-5 material steadily. In the paper, based on keeping high strength of the crankshaft. The research and the development to the QT800-6 crankshaft raises the ductility of nodular cast iron greatly, has make the specific elongation rising 6 percent average, the measurement adapted as follow: 1. Analysis to the metallographic structure and chemical component of the QT900-2 crankshaft, which the specific elongation is higher than 4.0 percent.2. Analysis to the demand to the metallographic structure that raise the specific elongation under the condition of keeping the high strength. 3.Analysis to the demand to the technics of the cast and heat treatment which include: raising the quality of the molten iron, suitable control of the alloy element, improving the quality of the spheroidization, improving the quality of the inoculation. The contents of technics test include: normalizing treatment, tempering treatment, cooling treatment. 4. Harmony test of both cast and heat treatment working procedure. 5. The fatigue contrast test to the QT800-6 nodular cast crankshaft and other material crankshafts had carried out. It was performed to the statistic analysis of the test data. 6.Improving and testing until obtaining the satisfaction result. By implementing the measurements described as above, the QT800-6 crankshaft by normalizing treatment appeared advantages as follow: 1. Reliability. The fatigue fracture is the main reason of the failures of the crankshaft. It was discovered that the QT800-6 crankshaft with normalizing treatment have the same resisting fatigue performance as the non-quenching and tempering treatment steel by contrasting the test results of the fatigueunder flexing limit of it and other material crankshaft. 2. Technics stability. The production of the QT800-6 crankshaft with normalizing treatment does not need the complex equipment and vast invests. Further, the raw and processed materials and equipments and relate technics are very maturity. So the its production has many advantages such as lower invest, easy control, larger production, high benefit, cheaper cost, no limit to the size of the element etc. the technics stability is very well. 3. In the aspect of cost. The cost of materials of crankshafts reduced according to the order of the quenching and tempering steel, the non-quenching and tempering steel, isothermal quenching treatment nodular cast iron, the normalizing treatment cast iron and the nodular cast iron as cast condition . The cost of the normalizing treatment cast iron is 40 to 50 percent of the cost of the forging steel and 70 to 80 percent of the cost of the isothermal quenching treatment nodular cast and higher 10 percent than the cost of the nodular cast iron as cast condition. Contrasting with the forging steel crankshaft, the nodular cast iron crankshaft is cheaper. The development trend of crankshaft is using the nodular cast iron instead of the steel, and using the nodular cast iron as cast condition crankshaft instead of the heat treatment crankshaft. By through the research and development of QT800-6 normalizingtreatment crankshaft, it is discovered that there are some potential of the material, which have not utilized, the material will have a good application in the future.