Method Large diameter oil tube and weighting rod are adopted to decrease lifting resistance of crude oil and to increase lowering-in energy of the string.
方法采用增大油管直径和下加重杆技术，来减少油流上升阻力和增大杆柱下行动力。
The invention relates to an improvement method of a core rod of a metal rolled tube, in particular to a hollow core rod used for a planetary rolling mill.
本发明涉及一种金属轧制管的芯棒改进方法，具体地说是一种行星轧机用空芯棒。
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