Study and Analysis on the Tensile Test Elongation Variation Law for High-Strength Pipeline Steel

In view of the tensile test elongation conversion problems for high-strength pipeline steel, several kinds of high-strength pipeline steel were selected to study the corresponding tensile test elongation variation laws. Then, a statistical analysis was carried out on a large collection of test data. The test results showed that the Oliver formula, which was established based on old carbon steel and low-alloy steel, is still applicable to high-strength pipeline steel but with different material coefficients than those used for carbon steel and low-alloy steel. This study established tensile test elongation variation formulas for new-made X65 to X90 pipeline steels and a formula for high-strength pipeline steel with a fixed 50 mm gauge length. The test data and the requirements were analyzed and compared according to the new material coefficients and formulas, through which a revision was proposed for the standards.