Inconel to Stainless.

[skidmark1973]

Maybe someone can help with a second opinion on this. The company I currently work for has taken on a job fabricating some heat exchangers. The can of the exchanger is constructed of Inconel and 304 stainless the job was originally botched from bad engineering a welding miss information. I did'nt weld the job, but I'm the lucky guy who gets to fix it. My boss claims 309 stainless rod will work on all welded seems of the job. This is what they originally used, and ended up with cracks and leaks everywhere. From what I understand will Inconel 625 work for Inconel to 304 stainless, (another note I don't know what grade the Inconel is, and Engineering staff doesnt know as well.)

Thank You.

[HeliArc84]

Courtesy of Burns Stainless Website.....

Inconel 625 can be welded using conventional stainless steel TIG welding techniques. Inconel Filler Metal 625 rod is used to weld Inconel to Inconel as well as to dissimilar metals including stainless steel. Inconel weldments are high strength and are highly resistant to corrosion and oxidation. Many welders describe that welding Inconel as "dirty". In other words, the weld pool appears to be under a "skin" and is not well defined. In addition, the weld pool is somewhat "sluggish" as compared with steel or stainless steel. These characteristics tend to result in a "coarse" appearing weldment as compared to stainless steel. Welding Inconel is not necessarily more difficult to weld than stainless, just different. By following the welding procedures outlined in the header construction tips article, successful welds with Inconel 625 are possible.

[atc250r]

^^^^ Exactly as said above.

[Showdog75]

We use 625 at my work welding carbon to stainless boiler tube. They stopped using 309 years ago and haven't had any crack related issues since going to 625. Back when they still used 309 in this application they had alot of issues and came up with the EPRI prep. EPRI stands for electric power research institute . It is a collaboration of electric power co-ops and manufacturers of this type of equipment to come up with better and more cost effective solutions to power plant issues.

Development of a New Nickel Filler for Dissimilar Metal Welds and Repair
Category: Technical Results Published: 7/9/2009 Product ID: 1018991
Type/Size: Adobe PDF (.pdf), 19.20 MB Program: Fossil Materials and Repair

Abstract: In the late 1980s, the domestic utility industry suffered from dissimilar metal weld (DMW) failures between low-alloy ferritic tubing and austenitic tubing in superheaters and reheaters. The Electric Power Research Institute (EPRI) performed extensive research into the problem and found that nickel-based filler metals showed significant service life improvements over 309 SS filler metals. Furthermore, improved joint geometries and additional weld-metal reinforcements have provided added service life. To ...


Current Version of: 1004916

[Daniel]

Type 309—better temperature resistance than 304, also sometimes used as filler metal when welding dissimilar steels, along with inconel.

Any filler metals of the ERNICr group will work as well. But if your metal is not the cleanest, it doesn't matter with what type of filler you're welding with, as inconel and any nickel base alloys are very prone to hot cracking cause by sulphur and any inpurities.

[Hillbilly69]

Inconel to stainless

Inconel needs to be preheated, very clean, and returned to preheat temps before the next pass is welded.

UTP 625 is good filler and UTP have a good website for filler selection.

Dilution of the base metal into the weld puddle is a definite NO. It will crack for sure if you dilute the weld puddle with the 304. Buttering of the 304 base metal with Nickel rod may also help. Grind all of your stop/starts.

This job probably needs a metalurgist, an approved WPS, and PMI (Positive Material Identification) of the base metals. A little more involved than what the average TIG welder should know. Don't lose sleep over it. The base metal is probably diluted by the previous welding being done incorrectly and be thrown in the scrap

Good Luck

[atc250r]

Inconel needs to be preheated, very clean, and returned to preheat temps before the next pass is welded.

UTP 625 is good filler and UTP have a good website for filler selection.

Dilution of the base metal into the weld puddle is a definite NO. It will crack for sure if you dilute the weld puddle with the 304. Buttering of the 304 base metal with Nickel rod may also help. Grind all of your stop/starts.

This job probably needs a metalurgist, an approved WPS, and PMI (Positive Material Identification) of the base metals. A little more involved than what the average TIG welder should know. Don't lose sleep over it. The base metal is probably diluted by the previous welding being done incorrectly and be thrown in the scrap

Good Luck

Never have I seen more than a 70F preheat required for Inconel.

[Wheelchair]

Never have I seen more than a 70F preheat required for Inconel.

I have welded more inconel in my career at a shipyard than I care to remember and never once preheated. Ambient temps is all that was required. Interpass temperature is the only thing to be maintained. You are absolutely correct.

Wheelchair