hollow drill steel

基本解释

Common round steel or steel tube may be rolled into solid or hollow twist drill rods by using the said rolling mill.
普通元鋼或普通鋼琯經此軋機後，可直接變成實心或空心麻花鑽杆鋼。
ip.com
In order to enhance the service hfe of hollow steel for rock drill stem, the odd number side section shape hollow steel has been designed.
爲了提高鑿巖釺杆用中空鋼的使用壽命，設計了奇數邊截麪形狀的中空鋼。
For improving the quality of hot drawn hollow steel drill, the total quality control must be adopted though the whole process (from steelmaking to finished product).
文章指出，爲了提高熱拔中空鋼的質量，必須從冶鍊開始對全部工序進行質量控制。