Effect of oxygen on Impact toughness of Duplex Stainless-steel welds

The toughness of weld deposits varies by the welding process due to the differences in the amount of oxygen in the weld typical for each process. Figure 1 shows that higher toughness is generally achieved with GTAW, PAW and GMAW than with SMAW, SAW and FCAW.


As the oxygen content increases, the content of non- metallic inclusions. This increase means that non- metallic inclusions in the welded part are mainly composed of oxides. When compared by welding process, GTAW has the lowest oxygen content, while FCAW has the highest oxygen content. the oxide inclusions were mainly Mn- Si TYPE and Mn- Si- Ti TYPE and the oxygen in the clumping portion exists in the form of inclusions by reacting with the deoxidizer (Mn. Si. Ti…) that has a high affinity for oxygen.

When oxidized inclusions exist in the welded area, the bonding force between metals adjacent to the oxidized inclusions is weakened, so it is thought that the generation of micro- voids is facilitated, and the impact value is lowered. This is supported by the discontinuous appearance of dimples near the oxidized inclusions in the SEM fracture image of the welded part in Figure 2.



  1. API 938-C, Use of Duplex Stainless Steels in the Oil Refining Industry.
  2. Effect of Oxygen Content on Impact toughness of Austenitic and Duplex Stainless steel weld metal, Journal of the Korean Welding society-1987, Y.H. Moon, H.T. Kim, S.D. Hur

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Nikhil (Team Weldknowledge)

PTC (production test coupon) requirement for Titanium & Zirconium Weld as per ASME Section VIII, Div. 1

As per Clause UNF-95 of ASME Section VIII, Div. 1, there is a mandatory requirement of PTC for all the category A and B joints of titanium and zirconium welds.

A production test plate of same specification, grade and thickness shall be made of sufficient size to provide one face bend and one root bend or two side bends dependent upon the plate thickness.

Here, thickness of the plate is essential variable. for each plate thickness, each PTC is required.

Also, type of welding process i.e. manual or Automatic shall also be covered by each PTC.

Reference: ASME BPVC Section VIII, Div. 1.

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