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Up Topic Welding Industry / Technical Discussions / Crack in weld metal in multi pass welding by Low Alloy Steel
- - By Mayur (*) Date 11-29-2018 07:10
What may be root cause of occurrence of long crack ( longitudinal direction along the seam ) in the weld metal of weld joint having multipass weld beads deposition by low alloy steel electrodes? Does bead shape induced centerline crack occur in multi pass weld bead deposited weld metal? Does bead shape induced centerline crack only happen in single pass weld deposite joint?
Parent - - By 803056 (*****) Date 11-29-2018 17:08
Are you using an active flux or a neutral flux.

The depth to width ratio must be controlled. The depth of the bead should not exceed the width of the weld face.

The shape of the weld face should be slightly convex. A weld face that is concave will tend to crack more often than welds that are convex.

Al
Parent - - By Mayur (*) Date 11-30-2018 03:17
I am welding with SMAW process low alloyed electrodes.

Is bead shape induced centerline crack possible in multipass per layer welding also? or is bead shape induced crack only possible in case of single pass per layer welding if width to depth ratio is not proper?
Parent - By 803056 (*****) Date 11-30-2018 04:07
Somehow I thought you were welding with SAW.

Al
Parent - - By waqasmalik (**) Date 11-30-2018 05:04
What is the material which you are welding?
Parent - - By Mayur (*) Date 11-30-2018 05:27
It is High Strength Low Alloy steel base material. Crack in weld metal. low alloy steel wire.
Parent - By Tyrone (***) Date 11-30-2018 12:20
You may have a hydrogen issue. The only way to know for sure is to do a metallurgical analysis. 

Baring that, I would switch to a low hydrogen filler metal.  Maintain interpass temp during multi-pass.  How thick is your base material?

Tyrone
Parent - By 803056 (*****) Date 11-30-2018 15:05
I believe we need a lot more detail about what you are welding; what is the chemistry of the base metal you are joining, what is the exact type of filler metal (classification), what is the preheat your using, what is the degree of restraint, etc.

With the level of detail we now have, the question is akin to, "Why is the house on fire Daddy?"

Best regards - Al
Parent - By pipewelder_1999 (****) Date 12-02-2018 13:40
You are very vague about your actual application and it is hard to really answer your questions.

Please give us some background on what is happening.

The root pass is the pass most subject to concave profiles. Should a root pass crack, then the subsequent passes regardless of shape may allow the crack to propagate through.

Putting more "passes"over a cracked root pass will not stop the crack.

Read these

https://app.aws.org/wj/supplement/WJ_1978_08_s217.pdf

https://www.thefabricator.com/article/arcwelding/cracking-down-on-weld-cracks

https://m.lincolnelectric.com/en-us/support/process-and-theory/Documents/weldcracking.pdf

http://www.kobelco.co.jp/english/welding/events/files/2015_KOBELCO_Defect.pdf
- By Mayur (*) Date 12-07-2018 04:09
When I cut a macro section to understand the crack, I found that at the start location of crack there was a void like lack of fusion defect in weld metal and crack started from that void lack of fusion. Is it like that lack of fusion defect in the weld metal turned into crack initiator due to stress concentration at the lack of fusion void and propagated due to welding stresses as crack?  Does lack of fusion defect in the weld metal turn into crack due to welding stress? Are there any example, case studies, literature, articles available with anyone. If available, please share on mayur211092@gmail.com
Up Topic Welding Industry / Technical Discussions / Crack in weld metal in multi pass welding by Low Alloy Steel

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