| 摘要 |
An earth working tool, such as a mining and construction cutter bit, has an elongated body, and a working element, such as a hard tip attached on a forward end of the body. The working element or hard tip is fabricated of a composition of essentially tungsten carbide of large grain size. The composition has one of a plurality of different percents, X, by weight of cobalt as a binder and one of a plurality of different Rockwell A scale hardnesses, Y. The cobalt percents X and hardnesses Y are paired in sets and have nominal values which satisfy the relationship: Y = 91 - 0.62X, where X is selected from within a range of from about 4.5 to 11.5 percent. Also, the values of Y in the sets of X and Y have upper and lower limits which satisfy the respective relationships: Y = 91.1 - 0.57X and Y = 90.9 - 0.67X, where X is selected from the aforementioned range of from about 4.5 to 11.5 percent. More particularly, each composition has one set of cobalt percent X and hardness Y values selected from a plurality of different sets of (X, Y) as follows: (4.5 +/- 0.3, 88.2 +/- 0.3), (5.0 +/- 0.3, 87.9 +/- 0.3), (8.5 +/- 0.5, 85.8 +/- 0.5) and (10.5 +/- 0.5, 84.5 +/- 0.6). |
