Development of X70 and Heavy Wall X65 Plates For Sour Service Pipeline Application

Abstract

Abstract Brazil due to its extraordinary oil and gas fields is one of the upcoming future markets for heavy plates for sour service applications. Such heavy plates are steels with high-class quality demands. Depending on the quality of the sources the HIC (Hydrogen Induced Cracking) resistance is a special requirement of these steels. By minimizing the HIC crack initiation sites as well as the crack propagation the HIC resistance is accessible. To achieve this, a careful design of all micro-structural features of the steel is necessary. The utilization of the latest technology for steel and plate making is the central element of the production of such steels. Suitable metallurgical processes like clean steel treatment, casting in a technically sophisticated manner as well as special rolling techniques like the TMCP (Thermo-Mechanical Controlled Process) combined with suitable ACC (Accelerated Cooling) after final rolling provide the fundamentals of a homogeneous and resistance microstructure, especially with low level of imperfections, mainly non-metallic inclusions as well as reduced mid-thickness segregations. The paper will point out the integrated overall production concept which provides the basis for the production of steel plates with consistent and reliable HIC resistance. The essential parameters will be explained, including the utilization of an appropriate quality assurance system. The second part of the paper will focus on the gradual development to the strength level of grade API-5L X70 and higher wall thickness of grade API-5L X65. The feasibility of the production of such steels will be demonstrated by the presentation of recent deliveries, also interesting for the Brazilian market. Introduction The most line pipe projects with full sour service applications use the already established API-5L X65. But the still growing global demand on crude oil and natural gas and the involved shortage of the resources necessitate the exploitation of resources under more difficult conditions. Especially for the Brazilian oil and gas pipe market with its important resources in deep sea areas heavy wall API-5L X65 and/or API-5L X70 for full sour service are very meaningful for economically efficient as well as safe exploitation. From the point of costs it is also important to go to higher strength instead of enhancing wall thickness to manage high external pressure linked with deep sea areas. That is why all heavy plate producers in the world invest a lot of efforts in research and development of high strength line pipe grades for full sour applications [1–4].