| The safety of pipe steel and weldment for transporting oil and gas has been focused. There are weld defect and high residual stress in the weld joints. Meanwhile, the content of H2S is high in the transportation pipe. Hence, the Hydrogen Induced Crack (HIC) and Stress Corrosion Crack (SCC) can easily occur. This thesis mainly covers the following aspects:1. According to the ASTM E92 standard, the microhardness and microstructure of pipeline steel weldment were conducted. It was observed that no crack was found in the weldments. The microstructure was uniform; the highest values of hardness were observed in the fusion line. The hardness in weld metal was higher than that in base metal. The hardness decreased from the HAZ to base metal. The hardness values in the weld joints are all less than the limit value of HV 250 in acidic solution. Hence, the welding procedure adopted in the present study was successful.2. HIC test results showed that no obvious HIC and hydrogen blistering was observed in all weld joint. The sensitivity indexes of HIC (CLR,CTR,CSR) in almost all samples were 0. Only slight HIC occurred in few samples whose sensitivity indexes were far less than the technical index stated by the pipeline factory. Hence, the corrosion resistance against HIC in the weld joint was excellent. The welding procedure adopted in the present study was successful.3. SSCC test results showed that small crack propagation was seen in all samples. It means that the initial load was slightly higher than the KISCC of materials. As the crack propagating, K values decreased. When a certain propagation extent occurred, K reached a crucial value. The crack no longer propagated.
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