Microstructure and properties of HT350 high strength gray cast iron

Due to its good casting performance, low manufacturing cost, easy control of casting quality and some specific excellent properties, such as wear resistance, shock absorption and machining performance, grey cast iron has become the preferred material for many castings in casting production, such as engine cylinder head and cylinder liner, ingot mold, machine bed and guide rail, rotary compressor cylinder, piston ring Water pipelines are made of gray cast iron.

Despite the continuous development of material science, gray cast iron still occupies an important position in the field of casting application, especially in the automotive industry. In 2010, the output of heavy trucks in China exceeded 1 million. It is expected that the number of vehicles will reach more than 5 million during the 12th Five Year Plan period. Most of the diesel engine cylinders and cylinder heads of ultra heavy trucks are made of high-strength gray cast iron. At present, among the internationally famous enterprises, only Ford wutaishang, man and Mercedes Benz use vermicular cast iron to produce high-power diesel engine cylinders, while other enterprises and domestic high-power diesel engine enterprises still use high-strength gray cast iron to produce high-power diesel engine cylinders. Diesel engine has high working pressure and high requirements for mechanical properties of materials, so how to improve the strength has become one of the key bottlenecks. At present, the strength and hardness of the cylinder block are mainly improved by adding an appropriate amount of Cr, Cu, Sn, Ni and other alloy elements to the gray cast iron. Generally, the tensile strength is required to be ≥ 250Mpa and the body hardness is 220-275 Hb. However, the addition of alloy elements will also deteriorate the machining performance and increase the tool wear. For a long time, the diesel engine cylinder block of super heavy truck depends on import, which not only has high price, but also is controlled by others, which seriously restricts the development of high-power diesel engine cylinder block in China. In order to further meet the needs of the development of super heavy trucks and improve market competitiveness, and considering the sustainable development of human living environment, save energy and protect the environment, a “high strength and high carbon equivalent grey cast iron with low cost and good processability” is proposed. Therefore, it is urgent to solve the key bottleneck problem of “whether there is and development controlled by others” in China’s high-power diesel engine cylinder block.

Jilin University cooperates with FAW Group foundry company. After several years of research, it adopts the research results with independent intellectual property rights, The cylinder block blank of HT300 high strength and high horsepower diesel engine was successfully produced (the tensile strength of the body reaches 240mpa) and has good cutting performance. It has been widely used to manufacture CA6DL, ca6dm and ca6dn series engines generated by FAW Wuxi Diesel Engine Co., Ltd. and 52d high-power diesel engine of Deutz FAW Group Dalian Diesel Engine Co., Ltd. the new fuel-saving high-power diesel engine of FAW Wuxi Diesel engine plant has been developed After the success, the market occupation rate will be greatly improved, which provides priority opportunities for the future development of FAW casting company and FAW Jiefang company. From 2008 to 2010, the first foundry of FAW Foundry Co., Ltd. industrialized and produced 152107 high-power diesel engine cylinders of different models such as 52d, 29d, 36d, a81d and 53d.

In order to further improve the market competitiveness, Wuxi Diesel Engine Plant of FAW Group proposes to develop a new fuel-saving high horsepower diesel engine, which must improve the explosion pressure of the engine. The improvement of explosion force puts forward more strict requirements for the performance of the cylinder block, FAW Foundry is required to provide ht350 diesel engine cylinder block (the tensile strength of the body is more than 280mpa) and there is no precedent in China. Therefore, the research and development of ht350 high-power diesel engine cylinder block blank not only has significant social benefits for energy conservation, emission reduction and green environmental protection, but also has significant economic significance for increasing the market share of FAW heavy truck at home and abroad and promoting the development of automobile industry in Jilin Province Benefits. To carry out the research on the production of high horsepower diesel engine cylinder block blank by ht350, we should not only study the optimization design of alloy composition, microalloying, inoculation and modification treatment, but also study the influence of various treatments on alloy casting properties, but also study the influence of the improvement of gray cast iron strength on its machinability, etc. the above research belongs to the forefront of cast iron research.