新澳门六合彩投注

With a recent increase in deep well drilling, there is a growing need for high collapse casing in a minimum yield strength of 95 ksi (655 MPa) grade. Collapse resistance is affected by yield strength, deviation of wall thick-ness, roundness, residual stress and D/t (D for outside diameter and t for wall thickness).Reducing the deviation of wall thickness at hot rolling, controlling yield strength by closely reg- ulating heat treatment conditions,and minimizing the deterioration of roundness and straightness during cooling are performed. This process is governed by our special techniques and knowhow.