Impact Testing Welds in Duplex and Super Duplex 1

[stanier]

Is there any benefit in impact testing welder qulafiction procedures in these materials? The process duty doesnt go below 10C or above 45C. The requirement was found in a specification and I dont want to propogate a myth.

Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng

http://www.waterhammer.bigblog.com.au

 

[stanier]

From a different perspective. If a pin hole leak occurred because of corrosion and injured someone what would the judge say. It is no longer just a matter of complying with Codes and Standards.

We are dealing with 75 bar pressures. A jet of water at this pressure would cut you in half.

I tend to agree corrosion is as equally important as strength. The Codes & Standards are quiet on many things that the committee doesnt understand or cant agree on.

Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng

http://www.waterhammer.bigblog.com.au

 

[GRoberts]

I only see a benefit of welder qualification testing in duplex or superaustenitic stainless steels by impact or corrosion resistance for the open root welds done with GTAW. The welder can comply with the WPS, but if they do not add an apropriate amount of filler metal on the root pass, the pass can be to base metal diluted with base metal and throw off the composition or phase balance. Or if the root pass is too thin, the 2nd pass can overheat it. It can mostly happen with GTAW because the filler metal is added independant of the heat input. For SMAW or GMAW welds, the heat input of the WPS essentialy governs the dilution ratio and bead thickness.

 

[JamesCKelly]

The Charpy impact test is to ensure that each individual welder can make a joint that won't shatter when one strikes it with a heavy hammer. That incident is exactly what initiated Avesta Code Plus Two, followed by A 923. Ask Mr. Tony Scribner, West Virginia. Brittle welds can happen, thought they are no longer a common problem with modern S32205 material. Superduplex grades, e.g., 2507, Ferralium 255 or Zeron 100, have less tolerance for incorrect heat input, interpass temperature, etc. Personally I think the impact test is more important for superduplex. The only horrible weld test I ran into was from a fellow who used about a dozen passes to weld 1/2" 2205 plate using flux cored wire. After the metal had spent maybe 1/2 hour at the most embrittling temperature, it would not even pass a bend test, let alone impact. Uncommon but Mr. Murphy is still quite active, I understand.