Takahiro Kushida

Role of microstructures on stress corrosion cracking of pipeline steels in carbonate-bicarbonate solution

Abstract Stress corrosion cracking (SCC) on the external surface of pipelines contributes to the major failure of pipelines. The great majority of SCC is intergranular and occurs in a carbonate-bic...

Development of High Strength Line Pipe for Sour Service and Full Ring Evaluation in Sour Environment

To establish mass production technology of high strength line pipe up to API-X70 grade for sour service, the HIC (Hydrogen Induced Cracking) phenomena in line pipe has been carefully examined. The micro-segregation zone originated at final solidification front, which has MnS inclusion and hard phase, was identified as the location of the initiation site of HIC. The proper procedures of Ca treatment to eliminate elongated MnS and TMCP application to reduce maximum hardness have proved to increase the HIC resistance in such segregation zone. In addition to the standard HIC test, full ring test under applied stress was conducted to assure the performance of high strength line pipe in sour service. The clean steel in mass production, which has enough HIC resistance, was attained for high strength line pipe up to API-X70.© 2004 ASME

Threshold Hydrogen Content for Hydrogen Embrittlement of Low Alloy Steels and 13Cr Steels

ABSTRACT Hydrogen embrittlement (HE) of low alloy steels and 13Cr steels was investigated by the constant load test under cathodic hydrogen charging, and the electrochemical hydrogen permeation test was conducted to measure the threshold hydrogen permeation rate for HE (Jth), the diffusion coefficient of hydrogen (D) and the threshold hydrogen content (Cth). The results were as follows. The Jth was decreased with the increase in the strength and the applied stress, and the Jth and the D of 13Cr steels were about 1/10 of those of low alloy steels. On the other hand, the Cth was almost constant regardless of the strength, and the Cth of 13Cr steels was almost the same as that of low alloy steels. The Cth was decreased with the increase in the applied stress.

PRESSURE VESSEL STEEL PLATES WITH IMPROVED WELDABILITY

ABSTRACT Normalized and tempered heavy thick plates have high content of carbon (C) and other alloying elements to meet the specified strength. These steels require high preheating temperature to avoid cracking during the welding process. Another problem with the steels for pressure vessels is the temper embrittlement in chromium (Cr) - molybdenum (Mo) steels (Bruscato, 1970; Swift, 1973). The decrease of manganese (Mn) as well as silicon (Si) content is very effective for suppressing temper embrittlement, but it reduces tensile and yield strength because of poor hardenability. As boron (B) is effective in increasing the strength of steels without the penalty of increasing the weld cracking susceptibility, it has usually been added to quenched and tempered steels (Melloy, 1973; Watanabe, 1983). A preliminary survey revealed that B was also effective for normalized steels. Moreover, fundamental research exhibited that a lower quantity of B was effective to obtain the maximum effect in normalizing than that in quenching (Ohtani, 1979; Watanabe, 1983).