Study of Embrittlement of the 2.25Cr-1Mo-V Steel Weld Metal by Hydrogen Charge and High Pressure Hydrogen Gas Environment

Abstract

It is well-known that hydrogen would accumulate at internal defects of pressure vessels during shutdown and hydrogen embrittlement occurred. However it has not been clear that the effect of hydrogen gas environment for 2.25Cr-1Mo-V steel (22V) weld metal. For this reason, the purpose of this work is to identify and understand the potential for embrittlement of the 22V steel by hydrogen charge and high pressure hydrogen gas environment.Therefore, rising load test was carried out in this study to examine the effect of dissolved hydrogen by high temperature, high pressure hydrogen exposure and high pressure hydrogen gas environment on hydrogen embrittlement at room temperature (R.T.) and 150 ̊C. 22V forged steel base metal was used and welding was conducted by submerged arc welding (SAW) process. High and low toughness weld metals were prepared by changing PWHT condition and notch location in order to consider variation of product's weld metal.From rising load test results, hydrogen gas environment had effect on the embrittlement of the 2.25Cr-1Mo-V steel weld metal. In contrast, dissolved hydrogen had little effect on the embrittlement. Moreover, KIH value of high toughness weld metal (KIH value is about 90 MPa√m) was higher than that of low toughness (KIH value is about 70 MPa√m) at RT. However, KIH value of low toughness weld metal was the similar level (KIH value is about 110 MPa√m) of high toughness weld metal at 150 ̊C.