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Up Topic American Welding Society Services / Technical Standards & Publications / base metal crack
- - By hittman375 (*) Date 03-04-2012 18:29
I was giving a welder qualification test on Friday and ran into a situation that I haven't seen before. The welder put down good looking welds but when I cut and bent the test coupons from his vertical plate, there was a crack in the base metal that was 3/16 in length and was well outside of the weld metal area. He did have a small crack with no slag inclusion in the base metal but it was small enough to still pass. I looked in D1.1 but didn't find anything about cracks in the base metal. I checked his welds in between passes and checked the plates with a temperature gun before he made passes. Can someone give some advice on how I should handle the base metal crack?
Parent - - By waccobird (****) Date 03-04-2012 18:39
hittman375

How small is small enough to still pass in D1.1?

Marshall
Parent - - By Lawrence (*****) Date 03-04-2012 19:09 Edited 03-04-2012 19:15
1/8" or less after bending   :)

Keeping exception of corner crack rules in mind as a side note.

My code book isn't in front of me at the moment.  But the examination rules are right there...  Something along the lines of inspecting the bent coupon on the convex face...   We can only look for defects where we are "told" to look.

So for example if we are doing a face bend and a root bend...  Let's say the convex face of the root bend is fine but the concave side of the root bend shows a flaw..  Can we reject on the basis of flaws on the concave side of a bend?   Nope.

If your "Base metal" you found to have a discontinuity is outside of the zone that the code tells us to inspect in the guided bend coupon examination, there is no justification to reject on that basis in my opinion.

But you might want to look at direction of rolling as a reason for what you are seeing...  In fact if you use the forum search function you will find an article linked from Omar Blodgett that speaks specifically to direction of rolling on test plates.
Parent - By 803056 (*****) Date 03-05-2012 01:03
The direction of roll influences the mechanical properties of the base metal. The mechanical properties are most favorable parallel to the direction of roll.

I purchase my base metal as bar stock with a width equal to the length of the weld. My grooved test plates are typically 3/8 x 4 x 8 or 1 x 4 x 8 inches, so the bar stock is ordered as 3/8 x 8 or 1 x 8 so I know the direction of roll.

Best regards - Al
Parent - By aevald (*****) Date 03-05-2012 02:26
Hello hittman375, I am with the others, cracks outside of the deposited weld metal and beyond the weld metal/parent metal interface should not be considered as a part of the inspection process, IMHO. It is certainly likely that you are seeing the result of a grain direction issue in the parent metal. Best regards, Allan
- - By hittman375 (*) Date 03-05-2012 13:46
Thank all of you for your input. My first thought was to disregard the crack outside of the weld metal area but thought it better to ask others here since there are more experienced people here. I don't do testing/inspection full time at my work so there are probably a fair amount of situations that I have not seen. Once again, thank you for your help. This forum is truly an asset.
Parent - - By 803056 (*****) Date 03-06-2012 06:50
Unfortunately we are required to abide by the code that applies to the work being done.

If you are working to API the decision to accept or reject a crack beyond the weld is a company decision. That isn't the case with other welding standards such as AWS or ASME. The inspector must check the convex surface for open discontinuities which does include the base metal to either side of the weld.

In the case of AWS D1.1, there is a note that the direction of roll is optional, but my experience is that when an option is noted, there is usually a reason for it, take heed. Anyone that has attended a CWI seminar has probably heard the instructor mention the direction of roll is important.

Just as likely, the instructor mentioned that the direction of grinding was important when removing weld reinforcement or backing.

Both points are easily overlooked, but the ramification is the test specimen may crack when the warnings are not heeded.

Best regards - Al
Parent - - By aevald (*****) Date 03-06-2012 08:03
Hello Al, your reference to API regarding crack/discontinuity location, is this a consideration that is specific to a particular grade or grades of material? and as such, does this vary for particular grades? Are there generally preheat, interpass, and post weld treatments that might apply to this scenario during this type of testing and lead to negative results? As I am not familiar with API that is the reason for my questions.
     I can also appreciate your mention of direction of roll/material orientation and attention to grind preparation, on many occasions our students have found out "the hard way" that there are a number of issues that can negatively affect test specimens when these factors are ignored or unknown. Thank you for the additional information. Best regards, Allan
Parent - - By 803056 (*****) Date 03-06-2012 17:40 Edited 03-07-2012 15:05
Hello Allen;

API 1104 is the API standard for qualifying welders and procedures. They provide little in the way of direction for the contractor or the welder. Everything is pretty much left up to the contractor and the company. Preheat, interpass temperature, post weld heat treatment, etc. is left to the contractor to figure out. The process of qualifying the WPS establishes the parameters. From there on out, API simply suggests what range of thicknesses are qualified, what diameters are qualified, etc. It is like a watered down version of ASME Section IX. ASME Section IX serves as the basis of how a WPS or welder is qualified, but Section IX is tied into a construction code that further modifies the requirements of Section IX. From what I can see API 1104 is pretty much a standalone document.

Back to evaluating qualification specimens, API uses the nick break test as the primary means of testing for soundness. They also permit alternatives, but in the end, even when the sample "fails" to meet the published acceptance criteria, the contractor can pretty much disregard the criteria and say "good enough.

I've made the motion to discontinue offering API 1104 as an open book alternative for the CWI examination. Very little is written in "concrete" in API 1104. As welding standards go, it is the most useless welding standard I've worked with. Woops! Back the train up, nothing beats the welding standard used by the open web joist manufacturers. Reconsidering my comment on API 1104, I have to say the welding standard used for OWJ is the most useless. I believe it was modeled after the Farm Code.

That's just my opinion on the subject. I'm sure others will have different opinions, but what other welding standard have you used would allow a pipe test coupon to have "burn through" and still be acceptable? Only in API 1104 is a complete joint penetration groove weld considered to be a fillet weld (specifically: branch connections).

Loosey goosey is the best description I can come up with.

If I were to run a welding school with the sole purpose of turning out "qualified welders", I would test the students to API 1104. It would be hard to fail anyone. I could claim a 95% passing rate! Maybe I am exagerating a little, but not by much. :wink:

Best regards - Al
Parent - By aevald (*****) Date 03-06-2012 19:21
Hello Al, thank you for the commentary on my questions. I appreciate any input that individuals have whether they are necessarily agreeable to that of mine or others. Just from the general jist of much that I have read regarding the various codes there does appear to be as many differences as there are similarities. I believe you have further enforced some of my views regarding the strictness of various codes and how they are applied. Certainly application can be a large factor in order to govern intended use and expectations. Thank you for the input/information and best regards, Allan
Up Topic American Welding Society Services / Technical Standards & Publications / base metal crack

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