... on. Our API drill pipes are of high physical property, for their strictly controlled processing of sulphur and phosphorus.To ensure ... thread gauges. To improve the galling-resistance during initial break-in and drilling operation, all threads are also phosphated or coppered ... -1, NS-1. RUSSIA RTN, RUSSIA GOST-R, ISO 9001,ISO 14001, OHSAS 18001, Arnco Hardbanding Certificates and so on. 2 3/8--5 1/2 ...