HIC CRACKING BEHAVIOR DUE TO PLASTIC STRAIN IN HSLA STEELAPI 5L X52 AND X60

• Main Author: TAUFIQ (NIM : 22110025), TANIA
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/20567
• Institution: Institut Teknologi Bandung

Hydrogen Induced Cracking (HIC) is a problem that often occurs in oil and gas pipeline on the environment exposed to aqeous hydrogen sulfide (H2S) (sour service).[1] To date, many researches have been conducted to study the phenomenon on different HIC types in some alloys. However, references that discuss the influence of plastic deformation on the crack pattern HIC are still inconsederable. Research on the effect of plastic strain in the steel to HIC resistance is important because in the pipeline manufacturing process, steel plate experiences many plastic deformations. The study was conducted to analyze the correlations between plastic deformation in API 5L X52 and X60 to the changes <br /> <br /> <br /> in mechanical properties, microstructures, and cracking behavior by the HIC. Tests were carried out with reference to NACE TM0284-2003 standard. Variable in this study is the percentage of strain. Tests were conducted on two types of alloy steels X52 and X60. Specimens were taken from the HRC plate which had been given specific strains. Mechanical properties changes then tested <br /> <br /> <br /> after specimens had been stretched before prepared for HIC test. Dimensions of test specimens, test solutions, and testing steps are fully refered to the NACE TM0284-2003 standard. Duration of specimens exposure to the test solution was extended to 168 hours to provide more crack formed due to observation importance. After HIC test, incontinuous laminations were examined using UT. <br /> <br /> <br /> Metallography of specimens were then examined to quantify cracks so that CSR, CLR, and CTR can be determined. Tests using SEM was also conducted to <br /> <br /> <br /> analyze the mode of fracture by hydrogen. From the results,it can be concluded that increasing the plastic strain in alloy steels X52 and X60 couldgive the impact on strengthening of both. However, strengthening and increasing the value of hardness had an unfavorable influence on the resistance of material to the HIC. This was indicated by the increasing value of CLR alloy reached 30.73% X52 and 43.3% for X60 at 12% strain. From <br /> <br /> <br /> the results of metallography examinations, we found more cracks of SWC (stepwise cracking) on X60 alloy steels compared toX52,due to X60 had more nonmetallic <br /> <br /> <br /> inclusions. Non-metallic inclusions, in this case the MnS, has been stated posseses a high affinity for hydrogen thus increasing the vulnerability of steel. As <br /> <br /> <br /> seen from the SEM results it can be concluded that cracks due to hydrogen was a transgranular brittle fracture.