Degradation of Pipeline Steel’s Strength under High Temperature and Load due to Cavity Formation

The study aims to determine the load contributes to changes in the tensile strength of steel P22 at high temperatures. The steel sample was loaded under 95 and 125 N at a temperature of 700 °C for 72 hours. The results showed that the strength of P22 decreased with increasing load. At the temperature of 700 °C, the yield strength (YS) value decreased from 200 to 182 MPa and the ultimate tensile strength (UTS) reduced from 353 to 321 MPa as the load increased from 95 to 125 N. The precipitation of carbide in the matrix of P22 was observed in the steel sample loaded under 125 N at 700 °C for 72 hours. Furthermore, the cavity formation located on the boundary and near the carbide was confirmed when the temperature was 700 °C and the load increased from 95 to 125 N. The cavity was proof of a stress increase near the grain boundary, causing a decrease in the steel’s strength after a certain period of working time at high temperatures.