TAILIEUCHUNG - Castings 2 Episode 8

Tham khảo tài liệu 'castings 2 episode 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | difference may be the result of a higher Si content in this region. Finally in this region there is a high incidence of small inclusions that appear to be mainly magnesium silicates. All these features are consistent with the defect being an oxide bifilm probably a magnesium silicate explaining the high Si content and the higher inclusion content and possibly malformed spheroids as a result of local loss of Mg. The planar form arises from the bifilm being pushed by the raft of austenite dendrites and organized into an interdendritic sheet similar to that commonly seen in other alloy systems Figures . The vertical orientation is explained by the greater rate of heat transfer from the base of the casting where gravity retains the contact with the mould so that these grains grow fastest and furthest. In addition the buoyancy of the magnesium silicate bifilm will encourage its vertical orientation and so assist the advancing dendrite to straighten the film. Spheroids in interdendritic regions would then be revealed at the regular spacing dictated by the dendrite arm size normally a section at a random angle to the dendrite growth directions would obscure this natural regularity that is almost certainly present in all ductile iron structures. Thus it should not be looked upon as a defective structure in itself as has occasionally been assumed. The bifilm probably disintegrates to some extent because of its surface energy tending to spherodize it the high temperature also assisting this effect. What remains are the changes in chemistry and numerous silicate fragments as inclusions to encourage the direction of growth of the crack that finally causes failure. Other features of plate fracture are its occurrence in slowly cooled regions such as in a feeder neck. This may be the result of the lower rate of growth allowing the dendrites to straighten films more successfully at high growth velocity the drag resistance of films would resist dendrite growth and resist

Đã phát hiện trình chặn quảng cáo AdBlock
Trang web này phụ thuộc vào doanh thu từ số lần hiển thị quảng cáo để tồn tại. Vui lòng tắt trình chặn quảng cáo của bạn hoặc tạm dừng tính năng chặn quảng cáo cho trang web này.