| Abstract Scope |
Line pipe steels are mostly used for oil and natural gas transmission pipelines. Due to high pressure and remote operating conditions, the requirements for mechanical properties of these steels are stringent. High operating pressure is necessary for high transmission efficiency. This calls for steel with high strength. Meanwhile, high toughness is also required for high-performance line pipe steels. Over the last 25 years, advanced high-strength line pipe steels with strength level as high as 120 ksi (827 MPa) have been developed to meet the demand. Similar to any other steel, microstructure is the key to producing the required mechanical properties. For different strength levels, microstructural constituents could be different. However, a fine grain structure is always desirable because grain refinement is the only microstructural parameter that contributes positively to both strength and toughness. Achieving a fine grain structure and appropriate microstructure for a given steel grade requires careful consideration in designing steel chemistry and thermomechanical processing. This presentation will discuss the concept of alloy design and the strategies for thermomechanical processing to achieve desirable mechanical properties for line pipe steels. |