L390MB pipeline steel properties

The main mechanical properties of L390MB pipeline steel are strength, toughness and mechanical properties under environmental media.
　　
The tensile strength and yield strength of L390MB steel are determined by the chemical composition of the steel and the rolling process. When selecting materials for gas pipelines, steel grades with higher yield strength should be selected to reduce steel consumption. But it is not that the higher the yield strength, the better. Too high a yield strength will reduce the toughness of the steel. When selecting steel grades, the proportional relationship between the yield strength and tensile strength of the steel—yield strength ratio—is used to ensure the pipe forming quality and welding performance.
 
API SPEC 5L standard: API 5L X56 (L390) grade
Mechanical properties non-proportional extension strength RP0.2 (MPa): 485-605
Tensile strength MPa: ≥570
Elongation A (%): ≥18
　　
Chemical analysis
C: ≤0.16, Si: ≤0.45, Mn: ≤1.70, P: ≤0.020, S: ≤0.010, V: ≤0.06, Nb: ≤0.05, Ti: ≤0.06
 
In the oil and gas environment of L390MB pipeline steel containing hydrogen sulfide, hydrogen generated due to corrosion penetrates into the steel and causes hydrogen-induced cracking. Therefore, pipeline steel for transporting sour oil and gas should have low sulfur content, carry out effective non-metallic inclusion morphology control and reduce micro-component segregation. In order to prevent hydrogen-induced cracking in steel, it is generally believed that the hardness should be controlled below HV265.
 

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