Cracking when welding carbon steel to stainless

[KSor]

Hi, I need some help! We are having issues with welding carbon steel parts to stainless steel parts. We are getting cracking of the weld, usually on the root pass.

The carbon is generally A105 and and the stainless 304 or 316. It is a highly restrained full penetration bevel joint, and we are having cracking using both 309 filler and ERNiCrMo-3 filler.

I am not sure what else to try to eliminate this cracking, any advice would be helpful, thanks!

 

[btrueblood]

Try Hastelloy-W or similar high-nickel rod.

 

[connectegr]

Depending on the carbon steel thickness, are you providing adequate pre-heat?

http://www.FerrellEngineering.com

 

[metengr]

Are you preheating the weld joint? Preheat is necessary for this type of weld joint - the filler metal selection is not the issue.

 

[MikeMet]

It would be helpful to know where the cracking is occurring? If it is in the middle of the weld, it may be due to restraint and a preheat may help. If the cracking is at the toe of the weld, it may be other factors.

 

[Guest102023]

You won't solve this by throwing more alloy at it. You need not only more preheat, but preheat to a greater distance from the joint.

 

[KSor]

The crack is occuring in the middle of the weld. We are definitely not preheating the joint very much, our current weld procedure doesn't call for it beyond the basic 70deg.

Thanks for the advice, I'm going try a sample with a hefty dose of preheating to see how it reacts.

 

[drawoh]

KSor,

Have you looked up coefficients of thermal expansion? These vary with the grade of stainless steel, and it appears, with grades of carbon steel too.

JHG

 

[11041977]

hi

which is the tichness?

in the past i got the same problem, i solved it in this way:

1) clean very well the parts to be joined, there no should be grease on them, the best way to do that is using acetone that is a secret

2)whic gas do you use? C02 2% Argon 98?

3) metal filler AISI 307,

the most importants thing is to use a low current 170- 180 Ampere, go pretty fast, to obtain a small bead.


aisi 307 is not expensive filler metal, than hastelloy
and this procedure do not require preheating
if you have need to know more you can contact me personally my email is matteomunari@yahoo.it
greetings

 

[Duwe6]

I prefer the 309 you are using. Centerline cracking is from too-fast cooling on a too-small bead. The weld rips itself apart due to the weld shrinkage due to cooling faster than the weld will allow itself to stretch and compensate for the shrinkage. Preheating to 200-275 deg-F will help a lot. Controlling the cooling by heating the weld area with a propane torch [fat, soft, neutral flame] IMMEDIATLY after welding will help a lot. By immediatly, I mean that the welder will be too slow to do it himself. Needs a helper with the torch, following the weld puddle, about 6-inches back.

The first pass needs to be big, with a lot of heat input into the base metals. For a big, meaty bead try Gas shielded Flux-core FCAW-G with an amperage of 200 or higher. Alternatively, stick weld SMAW using 1/8" rods E309-16 or -17.

The welder cannot stop welding for a coffee break until the joint is at welded at least 1/3 of the way out. This will have enough strength to resist tearing due to shrinkage, and each new bead will stress-relieve the bead under it, compensating for shrinkage.