The amount of nitrogen added as an alloying component to SAF 2507 has been elevated to restore the austenite/ferrite stability more quickly during cooling, so this grade of duplex is somewhat extra forgiving with respect to ferrite. However, the upper share of chromium and molybdenum on this alloy increases the propensity for sigma formation thus making welding warmth input management essential. Filler materials overalloyed in nickel is typically added during welding to overcome the tendency in direction of greater ferrite numbers.

These welds met requirements for all applicable codes and requirements together with bend and tensile exams for qualification to ASME Sect. IX of the Boiler and Pressure Vessel Code9, important pitting temperature in accordance with ASTM G-48A10, Vickers Hardness Testing, and have been certified to the Norwegian requirements, NORSOK. In production all welds are examined by radiography immediately after welding. Sandvik stated that the long coil application wouldn't have been possible with out orbital welding know-how. During welding, the liquid puddle solidifies as ferrite and during cooling there's partial transformation of the ferrite to austenite.

For SAF 2507 the popular wire is 25.10.4L which incorporates 25% chrome, 10% nickel, compared to 7% nickel within the base metallic, four% molybdenum and less than zero.02% carbon. In addition to the marking prescribed in Specification A1016/A1016M, the marking shall point out whether the tubing is seamless or welded and the wall designation . NOTE 2—For pressure and hardness check requirements, the term lot applies to all tubes prior to slicing, of the same nominal diameter and wall thickness which might be produced from the same heat of metal. When ultimate warmth remedy is in a batch-kind furnace, lots shall embody solely these tubes of the same size and the same warmth which are warmth handled in the identical furnace cost.

The proportion of austenite to ferrite in the finished weld is dependent upon the base metallic chemistry and on the welding thermal cycle. Most specs for offshore/subsea purposes permit a variety of 35 to 65% ferrite within the weld and HAZ, however for the more important purposes requiring superior corrosion resistance, ferrite numbers under 50 are preferred6. Control of base metal chemistry was step one in achieving predictable ferrite counts after welding7, nonetheless, precise management of heat enter during welding can also be important to keep up the optimum phase stability. Too rapid cooling can make the part steadiness shift to a too-high ferrite content material with a lack of corrosion resistance, ductility, and elevated susceptibility to hydrogen cracking. The variable warmth enter from weld-to-weld and at completely different locations inside manual welds of duplex can result in unacceptably excessive ferrite numbers.

For thin-wall tubing of 1 inch diameter and fewer, the weld look utilizing an insert is superior to both orbital fusion butt welds or orbital welds with filler wire. with a T-shaped ring or flat on both surfaces with a washer-shaped ring of the same diameter as the tubing. Orbital welding of duplex tubing with filler wire It is troublesome on skinny-wall material (0.065 inches and fewer) to add wire uniformly by hand so the looks of handbook welds with wire could also be somewhat irregular. Model open-body kind orbital weld head with wire feed capabilities to provide easy even welds in the course of the manufacturing of coiled 2507 tremendous duplex tubing for subsea applications4. The AMI Model 227 energy supply was programmed to regulate the wire feed price in synchronization with the first and background current pulses.