以下哪种铸铁的断口呈灰黑色?() ["马口铁","白口铸铁","麻口铸铁","灰铸铁"]
经回火后,能使工件()。 ["A、获得适当的硬度","B、提高内应力","C、增大脆性","D、获得较差的综合力学性能"]
焊缝质量等级中,焊缝质量最好的是() ["Ⅰ","Ⅱ","Ⅲ","Ⅳ"]
铅笔、炭笔、木炭条都属于()中笔的种类。 ["A、素描","B、色彩","C、水粉","D、水彩"]
电动势是衡量电源将()本领的物理量 ["非电能转换成电能","电能转换成非电能","热能转换成电能","电能转换成热能"]
设计水头