tailieunhanh - Ductile Iron Episode 2

Tham khảo tài liệu 'ductile iron episode 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Dynamic Tear Testing The dynamic tear test an accepted ASTM fracture test method overcomes many of the shortcomings of the Charpy test and is cheaper and more suitable than plane strain fracture toughness testing for production testing of ferrous castings. This test has become widely accepted in the automotive industry and has been made mandatory for the characterization of the fracture properties of castings used in critical applications. To ensure validity of test results the dynamic tear specimens are cast to size in the foundry and tested full size to replicate performance of an actual casting. Figures illustrate dynamic tear behaviour for as-cast ferritic and pearlitic and annealed ferritic Ductile Irons respectively. When compared to similar charpy data in Figure the dynamic tear data in Figure reveals a slightly higher transition temperature for the ferritic sample but significantly lower transition temperatures for the pearlitic grades. Figure is noteworthy for two features the low transition temperature of the low phosphorus annealed ferritic iron and the significant increase in ừansition temperature and reduction in upper shelf energy produced by an increase in phosphorus content to per cent. Figure compares the dynamic tear data for four ferritic cast irons. A full ferritizing anneal reduces the fracture transition temperature and increases the upper shelf energy of Ductile Iron compared to an as-cast ferritic structure. The use of a subcritical annealing instead of a normal full ferritizing treatment resulted in a similar transition temperature but a higher upper shelf energy. In addition to slightly better impact properties a subcritical anneal also produces improved fatigue strength. Temper Embrittlement SECTION III Temper embrittlement as found in certain quenched and tempered steels may also occur in similarly treated Ductile Irons with susceptible compositions. This form of embrittlement which does not affect .