Case hardened: a case hardened fastener is a fastener of ferrousmaterial having a surface which has been made harder than the core.
表面硬化：表面硬化的紧固件是黑色金属，其表面经过处理后比内心硬度要高。
2
The principle materials used for tools can be divided into three major categories: ferrousmaterial, nonferrous material, and nonmetallic material.
用来做工具的主要材料可以被分为三大类：黑色金属材料，有色金属材料，非金属材料。
3
The Current research status, potential advantages and outlook of ferrous, nonferrous rare metals and precious metals material of Yunnan in 2005 are summarized and reviewed.