Tham khảo tài liệu 'friction, lubrication, and wear technology (1997) part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | The results by Thomas Ref 43 also showed a strong correlation between wear resistance and alloy content Fig. 17 . The low-alloy steel No. 5 die steel which is equivalent to steel number 1 in Fig. 15 and 8 a and Table 8 b had relatively poor wear resistance when compared to the 5 Cr hot-work die steel H12 and the 12 Cr steel. This was true irrespective of the hardness level to which the steels were tempered and even to a certain degree of the type of workpiece material. Fig. 17 Influence of initial die hardness on wear of die steels. The wear index is defined as average crosssectional area of wear depressions in dies. No. 5 die steel C Si Mn Ni Cr Mo 5 Cr steel C Si Mn Cr Mo W V 12 Cr steel C Si Mn Ni Cr Mo V. Source Ref 43 These findings have been verified and further expanded by other researchers. For example in their carefully controlled forging experiments Doege Melching and Kowallick Ref 48 and Hecht and Hiller Ref 50 found low-alloy steels to have far inferior wear resistance as compared to hot-work die steels Fig. 18 because alloying led to higher hardness and the ability to retain strength at high die temperatures. The work of Netthofel Ref 49 is also in agreement with these observations. Number of forgings Fig. 18 Amount of wear of hot-work tool steels as a function of the number of forgings. Equivalent steels are in parentheses. Source Ref 48 Up to now most of the discussion of alloying has centered on die steels. Several workers have also investigated the wear characteristics of nonferrous die materials. In Netthofel s Ref 49 experiments on forging die wear it was found that the nickel-base alloy Nimonic 90 had a wear resistance between that of an H12 and H19 steel at a die temperature of 255 C 490 F . This is an important finding in view of the fact that the nickel-based alloys are generally many times the cost of the die steel alloys and are also harder to machine. .
