tailieunhanh - The Science and Technology of Materials in Automotive Engines Part 8

Tham khảo tài liệu 'the science and technology of materials in automotive engines part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | The valve spring 163 Table Chemical composition of cylinder head material JIS Si Fe Cu Mn Mg Zn Ni Ti Pb Sn Cr Al Hard- Heat ness treatment AC4B Balance 75 HB T6 to and an age-hardening effect is given by adding 3 Cu. The alloy has good castability as well as high strength at intermediate temperature range. The tensile strength is 111-176 MPa in the as-cast state and 218-299 MPa after T6 heat treatment. The cylinder head receives a great amount of heat from the cylinder block so dimensional stability is required over a long period of time. Thermal growth can result in microstructural change which decreases long-term dimensional stability. It occurs particularly in certain aluminum alloys at elevated temperatures. T7 heat treatment is generally carried out to restrict thermal distortion growth of the alloy during operation. T7 heat treatment overaged provides a more dimensionally stable microstructure than T4 naturally aged or T6 peak aged and can reduce microstructural The strength changes with the grain size of castings and generally the thinner the casting the higher the strength. The intermediate temperature strength of AC4B is sufficient while the corrosion resistance is a little low due to the included Cu. Conclusions Valve springs use the superior characteristics of steel. It is possible to use Ti alloys to reduce weight but steels will continue to be used for the majority of springs for the foreseeable future. The total balance of the system is crucial for the valve train. It is difficult to collect experimental data on the valve system during firing. Motoring testing is used to collect data instead by turning an engine with an electric motor through the drive shaft. Measurements are used to optimize design. Comprehensive quality control is very important for all aspects of valve spring manufacture. References and notes 1. Spring steels occur in two types. i The spring property results .