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.
普通元钢或普通钢管经此轧机后，可直接变成实心或空心麻花钻杆钢。
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.
为了提高凿岩钎杆用中空钢的使用寿命，设计了奇数边截面形状的中空钢。
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，为了提高热拔中空钢的质量，必须从冶炼开始对全部工序进行质量控制。