This report may be updated and revised periodically in response to the needs of the technical community; up-to-date versions can be requested from the editors at the address given below or downloaded at http://www.ca.sandia.gov/matlsTechRef/ . The content of this report will also be incorporated into a Sandia National Laboratory report (SAND2008-1163); the most recent version can be obtained from the link above. The success of this reference depends upon feedback from the technical community; please forward your comments, suggestions, criticisms and relevant public-domain data to the authors C. San Marchi (cwsanma@sandia.gov) and/or B.P. Somerday (bpsomer@sandia.gov) at: Sandia National Laboratories Technical Reference on Hydrogen Compatibility of Materials MS-9404 7011 East Ave Livermore CA 94550.

/pdf/technical-reference-on-hydrogen-compatibility-of-materials-1t81po2upz.pdf

Technical Reference on Hydrogen Compatibility of Materials

Hot crack prevention in materials production and processing is an essential prerequisite for welded component safety. The causes of hot cracking can ultimately be attributed to the occurrence of metallurgical effects and to structural loads. More than 140 hot cracking test procedures have hitherto been developed for determining the hot cracking resistance. In principle, they are divided in self-restraint and externally loaded hot cracking tests with diverse process variants. Only some of the hot cracking tests are international standardized. Although various factors are known that encourage or prevent hot cracking, it is often not possible even with defined welding conditions to draw immediate conclusions about the hot cracking resistance of a welded component alone from a metallurgical composition of the base and filler materials. Based on an evaluation of the existing theories relating to hot cracking susceptibility assessment, this study summarizes the major hot cracking test procedures and highlights the application limits of the test procedures by presenting overviews along with explanations. It shows that weld hot cracking tests can generally be used to rank materials, welding consumables, and welding conditions. The evaluation of hot cracking test results and of their transferability among one another and to real components always requires consideration of the close relationships between metallurgy, welding process, and parameters, respectively, and prevailing restraint conditions.

Cold cracking tests—an overview of present technologies and applications

Duplex Stainless Steels (DSS) and Super Duplex Stainless Steel (SDSS) have excellent integration of mechanical and corrosion properties. However, the formation of intermetallic phases is a major problem in their usage. The mechanical and corrosion properties are deteriorated due to the presence of intermetallic phases. These phases are induced during welding, prolonged exposure to high temperatures, and improper heat treatments. The main emphasis of this review article is on intermetallic phases and their effects on corrosion and mechanical properties. First the effect of various alloying elements on DSS and SDSS has been discussed followed by formation of various intermetallic phases. The intermetallic phases affect impact toughness and corrosion resistance significantly. Their deleterious effect on weldments has also been reviewed.

/pdf/effect-of-intermetallic-phases-on-corrosion-behavior-and-18p7di1stc.pdf

Effect of intermetallic phases on corrosion behavior and mechanical properties of duplex stainless steel and super-duplex stainless steel

Abstract The present work was conducted to assess the weldability of duplex stainless steel in underwater conditions. Metal manual arc welding (MMA) with the use of coated electrodes was used in the investigations. Tekken weldability tests were performed underwater at 0.5 m depth and in the air. Nondestructive tests, metallographic examinations of welds, ferrite content assessment in microstructure and hardness test were performed. The good weldability at underwater conditions of duplex stainless with the use of MMA method was confirmed, however difficulties in stable arc burning were revealed.

/pdf/the-effect-of-wet-underwater-welding-on-cold-cracking-3d5u4o33km.pdf

The Effect of Wet Underwater Welding on Cold Cracking Susceptibility of Duplex Stainless Steel

Approaches to determining ferrite fraction (%) and ferrite number (FN) were examined for super duplex stainless steel (SDSS) welds. A reference sample was produced by bead-on-plate gas–tungsten arc welding of a type-2507 SDSS plate. By comparing different etchants and measurement practices, it was realized that etching with modified Beraha followed by computerized image analysis (IA) was the most accurate and quickest technique to measure ferrite fraction, which determined the same ferrite fraction (68.0 ± 2.6%) as that measured by electron diffraction backscattered analysis (67.6 ± 2.3%). A Round Robin test was performed on a reference sample at University West, Swerea KIMAB, Outokumpu Stainless, and Sandvik Materials Technology to investigate the repeatability of the technique. The ferrite fraction measurements performed at different laboratories showed very small variations, which were in the range of those seen when changing microscope in the same laboratory. After verification of the technique, the relationship between ferrite fraction and ferrite number (measured with FERITSCOPE®) was determined using 14 single (root) pass welds, including butt, corner, and T-, V-, and double V-joint geometries. The best-fit equation found in this study was ferrite number (FN) = 1.1 × ferrite fraction (%). To conclude, the ferrite fraction technique suggested in the present paper was accurate and repeatable, which made it possible to determine a ferrite fraction–ferrite number formula for SDSS single-pass welds.

/pdf/ferrite-content-measurement-in-super-duplex-stainless-steel-206elxjaxt.pdf

Ferrite content measurement in super duplex stainless steel welds

Hydrogen cracking in duplex stainless steel weld metal was examined using two laboratory cracking tests (LB-TRC and WM-SERT testing). The cracking susceptibility markedly increased when the ferrite content exceeded 50% in weld metal deposited during GTA welding with Ar-10 vol-% H 2 shielding gas. Fractographic examination indicated that crack growth was inhibited by austenite plates at austenite grain boundaries. Increasing nitrogen content increased the cracking sensitivity of the ferrite phase. This detrimental effect of nitrogen was associated with increased Cr 2 N precipitation in ferrite

T. H. North

Papers

Hydrogen cracking in duplex stainless steel weld metal : cracking sensitivity appears related to an excess of 50% delta ferrite in the weld