Welding Tips and Tricks

When welding something that requires multiple passes what should you let the original pass naturally cool to before running the next pass?

bigworm40 wrote:When welding something that requires multiple passes what should you let the original pass naturally cool to before running the next pass?

For steel, around 350 deg F.

Is the're different temps for different processes? Guess I should have stated I'm using fcaw-g.

bigworm40 wrote:Is the're different temps for different processes? Guess I should have stated I'm using fcaw-g.

It's called the interpass temperature and it changes for different metal types and different thicknesses.

If you google search it you will find more information than a person would think even exists

bigworm40 wrote:Is the're different temps for different processes? Guess I should have stated I'm using fcaw-g.

Keep it under 350 deg, between passes, and your good.

However, on special (low alloys) steels, the interpass temp should not drop below any preheat temp. (I tack welded 3and a 1-2" thock chro-moly cylinders once and they were preheated to 350°c before welding. Took a while)

Inter pass temps vary based on a number of factors, what standard your working to, material, thickness, intended use, joint design etc. It will be called out in your wps.

So I've been researching this a little and found a few posts that claim they have seen up to 150 degree f inconsistentakes When using an infrared gun. Has any one else seen this and what's is the preferred method for checking temps?

bigworm40 wrote:So I've been researching this a little and found a few posts that claim they have seen up to 150 degree f inconsistentakes When using an infrared gun. Has any one else seen this and what's is the preferred method for checking temps?

Tempilsticks are cheap, no batteries required, and work good.

You may find that infra red thermometers are rubbish unless you buy a very high end one. The literature included should explain. I believe they vary according to how far away you are and all sorts of things. Tempilsticks are good, but you have to put a substance on the job, may not be allowed, and they don't change back once lower temps are reached (do they?) we use contact pyrometers. Calibration required so there is no errors.

OK so this all started because i ran a pass today on some A570 1" thick with a miller 252 settings 24.3/380 fcaw-g 75/25 and took the temp in various locations from on the weld to 1" intervals up to 3" away from the weld and seemed like the highest temp I got was 225F. I took these temps using a blue point infrared gun. I thought that seemed really low and thats how this topic started!

I found one of the references that would seem appropriate.

Im not following any code and have not been given any weld specs by the engineer, there for no preheat. What should it have been?

If i'm reading AWS D1.1 correctly with the type of steel i'm using the minimum preheat for anything .750 to 1.50 only requires a 50 degree preheat.

bigworm40 wrote:Im not following any code and have not been given any weld specs by the engineer, there for no preheat. What should it have been?

If i'm reading AWS D1.1 correctly with the type of steel i'm using the minimum preheat for anything .750 to 1.50 only requires a 50 degree preheat.

That's how I read it

MinnesotaDave wrote:I found one of the references that would seem appropriate.

image.jpg

Dave,
can you link where you found this please, looks like there's conflicting info.

bigworm40 wrote:

MinnesotaDave wrote:I found one of the references that would seem appropriate.

image.jpg

Dave,
can you link where you found this please, looks like there's conflicting info.

Are you referring to two different pre-heats for the same material?
It's due to the process used, low hydrogen vs. non low hydrogen.

For a non low hydrogen process, a higher pre heat is used.

Sorry Dave for the time delay in my response, I know see what you mean and yes that what i meant but I understand now that i had a chance too sit and look at it.

AKweldshop wrote:

bigworm40 wrote:Is the're different temps for different processes? Guess I should have stated I'm using fcaw-g.

Keep it under 350 deg, between passes, and your good.

A blanket rule of 350 deg is not accurate nor recommended. There are so many variables to consider, material type and types welded together, filler material used and process, material size, ambiant temperature, etc. If one were to follow this rule it could lead to problems if used for materials where this interpass temp would either be to low or high. Also, keep in mind that if you use a 350 deg interpass temp and I use a 200 degree interpass temp, your material will see more heat input than mine which could lead to all sorts of problems, again depending on variables.

I was talking to a good friend the other day about his welding and he was sharing with me how their WPS' call out specific interpass temps that are supposed to be followed. He follows them but others around him do not and always have problems with warpage and some of the material they weld cannot be fixed after welding. Interpass temp is very important.
-Jonathan

Exactly my sentimonies

Superiorwelding wrote:

AKweldshop wrote:

bigworm40 wrote:Is the're different temps for different processes? Guess I should have stated I'm using fcaw-g.

Keep it under 350 deg, between passes, and your good.

A blanket rule of 350 deg is not accurate nor recommended. There are so many variables to consider, material type and types welded together, filler material used and process, material size, ambient temperature, etc. If one were to follow this rule it could lead to problems if used for materials where this interpass temp would either be to low or high. Also, keep in mind that if you use a 350 deg interpass temp and I use a 200 degree interpass temp, your material will see more heat input than mine which could lead to all sorts of problems, again depending on variables.

I was talking to a good friend the other day about his welding and he was sharing with me how their WPS' call out specific interpass temps that are supposed to be followed. He follows them but others around him do not and always have problems with warpage and some of the material they weld cannot be fixed after welding. Interpass temp is very important.
-Jonathan

I already had to send something out to be line bored because of warp issues due to heat issues without a doubt. I've done some welding in the past but nothing to the level i'm working at now. For the most part i'm learning as I go like so many others have. From what Dave has just posted it sounds like i need to focus my look at hydrogen levels and process. Reading that it still seems like because im using FCAW and my shop is over 50 f and im using material less then 1.500" theres no need for preheat?

Interpass temp has to do with heat input, post weld heat treatment and correct treatment of consumables is where hydrogen is the issue. If you have problems with hydrogen, you will have weld metal cracking. Nor distortion.

The chart above shows minimums for preheat and interpass. Back to my original question, What temp should I let the material cool to before i make my second pass??

Interesting reading on the subject:

http://www.jflf.org/pdfs/papers/keyconcepts3.pdf

https://www.mwsco.com/kb/kb_frameset.asp?ArticleID=73

Superiorwelding wrote:

AKweldshop wrote:

bigworm40 wrote:Is the're different temps for different processes? Guess I should have stated I'm using fcaw-g.

Keep it under 350 deg, between passes, and your good.

A blanket rule of 350 deg is not accurate nor recommended. There are so many variables to consider, material type and types welded together, filler material used and process, material size, ambiant temperature, etc. If one were to follow this rule it could lead to problems if used for materials where this interpass temp would either be to low or high. Also, keep in mind that if you use a 350 deg interpass temp and I use a 200 degree interpass temp, your material will see more heat input than mine which could lead to all sorts of problems, again depending on variables.

I was talking to a good friend the other day about his welding and he was sharing with me how their WPS' call out specific interpass temps that are supposed to be followed. He follows them but others around him do not and always have problems with warpage and some of the material they weld cannot be fixed after welding. Interpass temp is very important.
-Jonathan

Sorry for the "blanket" statement.
I know bigworm is running duel-shield on heavy plate.
I was talking to my CWI earlier this week about preheat and interpass temperature for structural welding tests.....

He said 350 interpass temperature for Stick and Duelshield.

That's all I got.

~John

Superiorwelding wrote:

AKweldshop wrote:

bigworm40 wrote:Is the're different temps for different processes? Guess I should have stated I'm using fcaw-g.

Keep it under 350 deg, between passes, and your good.

A blanket rule of 350 deg is not accurate nor recommended. There are so many variables to consider, material type and types welded together, filler material used and process, material size, ambiant temperature, etc. If one were to follow this rule it could lead to problems if used for materials where this interpass temp would either be to low or high. Also, keep in mind that if you use a 350 deg interpass temp and I use a 200 degree interpass temp, your material will see more heat input than mine which could lead to all sorts of problems, again depending on variables.

I was talking to a good friend the other day about his welding and he was sharing with me how their WPS' call out specific interpass temps that are supposed to be followed. He follows them but others around him do not and always have problems with warpage and some of the material they weld cannot be fixed after welding. Interpass temp is very important.
-Jonathan

^this, there are simply too many variables to make a blanket statement. I work with/write wps's and if interpass temps are violated, parts are scrapped, there's no reworking.

You really need to follow your wps, it's there for a reason.