India is a large and rapidly growing economy. The energy requirements of the country in terms of oil products and natural gas is also huge. Given its vast geographical size, there is ever-growing need to transport these oil & gas products over large distances but economically. For this purpose, several new projects for laying of new pipeline networks are at different stages of planning. In order to keep the cost of such large pipeline projects lower, countries around the world have shifted to higher strength API grades of steel. This was facilitated by advances in steel-making and processing technology and modern facilities that came up in advanced countries. India is no different and we have seen a gradual shift towards higher strength API grades being used for pipelines. Essar Steel has been a major producer of API grades of steel in India over the last 15 years initially through its hot-strip mill and more recently adding a state-of-the-art 5M wide plate mill as well as pipe mills, both LSAW & HSAW.
Different alloy designs have been used around the world to produce high strength and high toughness API grades. These have produced essentially two types of microstructures which are either ferrite + pearlite or ferrite + acicular ferrite. But these microstructures show varying response to the pipe-making process. Choice of alloy design also has a major bearing on the cost of steel, but is partly influenced by mill capability. At Essar, while cost was a major determining criterion for selection of suitable alloy design, mill capability was not a constraint. Essar Steel has successfully produced X-80 plates and pipes with a modified HTP alloy design and using the new facilities of plate mill & pipe mill. The paper gives some of the key highlights of this development activity.
This was a collaborative effort between the metallurgists & engineers at Essar Steel India Limited and experts from CBMM.