Things Know about Tubular Goods

A group of seamless rolled products consisting of drill pipe, casing and tubing subjected to loading conditions according to a specific application is called tubular goods. A drill pipe is nothing but a heavy seamless tube that rotates the drill bit in order to circulate the drilling fluid. Segments of pipe that are almost 30 ft. long are coupled with tool joints to make it. Drill pipe is also simultaneously subjected to high torque by drilling, axial tension, and internal pressure by exclusion of drilling fluid. Casing pipe is subject to axial tension, internal pressure and it helps line the borehole. Casing is exposed to axial tension and internal pressure by pumped oil or gas emulsion. Tubing is pipe through which the oil or gas is transported. Sometimes, alternating bending loads are superimposed on these basic loading patterns. 

 Corrosion resistance is a very vital Tubular Goods characteristic, especially for casing and tubing under sour service conditions. A typical manufacturing process for above goods includes continuous mandrel-rolling process, push bench process, plug mill rolling, cross-roll piercing and pilger rolling. Most of these processes usually do not allow thermomechanical processing customary for the products used for welded pipe. Hence, high-strength seamless pipe has to be produced. This is usually done by increasing the alloy content and with a suitable heat treatment like quench or tempering. 

Chromium and Manganese are the major alloys used to produce good hard enable steel. Good harden ability is required to ensure large pipe wall thickness which is a fundamental requirement of any micro structure. Though the requirement of good sulphide stress cracking resistance limits the use of Manganese and Chromium, they are still used for their advantages. Manganese does tend to segregate during continuous casting and can reduce hydrogen induced cracking resistance. Higher levels of Chromium can lead to formation of chromium carbide precipitates with coarse plate-shaped morphology, which in turn collect hydrogen and initiate cracks. 

The limitations faced by use of Manganese and Chromium can be overcome by using Molybdenum which is much stronger and a better hardener. In the recent past, due to deep well drilling and reservoirs containing contaminants that cause corrosive attack, there is a demand for higher strength materials that can be resistant to hydrogen embrittlement and sulphide stress cracking.