Abstract: In this paper the technology of cold form tapping in superhigh strength steels is investigated when threading in high strength materials, severe wear and breakage of the cold forming tap are often encountered. Nevertheless, cold form tapping in superhigh strength steels is theoretically proved to be feasible. And then, investigation on the influence of different conditions such as pre-tapped hole size, lubricant, etc., on cold form tapping in superhigh strength steels are carried out. In addition, the microhardness is measured on the cross section of formed threads, and the feature of the microhardness and strengthening of formed threads are analysed in details.

Key words: superhigh strength steel, cold forming tap, formed thread, microhardness