Base Metal Groupings

Date 01-09-2014 19:26

Tyrone,

You’ve asked why it’s okay to use the A36 PQR to qualify A106 when more discretion is required. I may be missing your question, but A36 and A106B are prequalified base metal/filler metal combinations in Group 1 of Table 3.1, so I’m unsure of your PQR reference, since the two are a prequalified combination.

I’m a bit curious as to why you're referencing and possibly using an out of date D1.1. Anyway, C3.3 in the 2002 edition, page 427, explains that groups of steel specifications are matched with filler metals having similar tensile strengths, and then, for those joints of base metals having different tensile strengths, electrodes applicable to the lower tensile strength material can be used as long as the electrode is of the low hydrogen type, and, if the higher tensile strength base metal allows such use of that particular electrode. Table 3.1 doesn't address carbon equivalency, so I wouldn't think that it would be an issue as long as the carbon content of a prequalified base metal is within the ranges allowed by the ASTM. Table 3.1 only addresses the minimum yield strength and tensile ranges of a prequalified base metal, so my personal thought is that the rationale is based on that criteria.

My only experience with addressing the carbon equivalency is when we’ve welded rebar. If I remember correctly, with rebar, typically the C.E. has to be calculated prior to welding. The lower the carbon equivalent, the more weldable the steel. Steels with carbon contents less than 0.35% are considered to be readily weldable. D1.4 requires the C.E. for #7 bars and larger should be less than 0.45% and for #6 and smaller bars, C.E. should be less than 0.55% in order to weld them. If the C.E. is not less than the value indicated, then the bars must be preheated. The higher the strength and the carbon equivalent of the steel, the more susceptible it is to cold cracking when it’s welded. I only mention this is because I tend to think that carbon equivalency is a bigger concern with rebar than it is with the prequalified base metal combinations in D1.1, which only reference minimum yield points and tensile ranges in Table 3.1

By Tyrone

Date 01-10-2014 12:00

Hi Scott,
I guess my real question is, "Why are these base metals combinations prequalified since one may need preheat?"
I used A106 B as an example, but the C.E. is all over the map for Group I steels.

I understand that Table 3.1 uses yield strengths to determine filler metal only. I just don't see any correlation justifying swapping out base metals by grouping (at least not by C.E.).

Tyrone

By welderbrent (*****)

Date 01-10-2014 12:51

They ALL require pre-heat at some time. Ambient Temperature combined with base metal temperature is more the factor than carbon content.

The CE may be many different levels but they are still weldable with the basic procedures. 8018 is still a low hydrogen electrode, and is to be used on steels with a higher CE than those weldable with 7018.

I don't really understand your dilemma here. CE, pre-heat, and so many other factors will vary from situation to situation all depending upon base metal classification, temperature, CE, thickness, applicable code (D1.8 instead of D1.1 for example), job requirements, and more.

The Pre-approved/qualified classification is more from the repeated, recorded, successful welding for many thousands of welds and structures on those particular materials over many years. Sure, some have differing welding requirements. But, it has been proven that it can be successfully accomplished without MAJOR special handling. There are materials there that require PWHT. Why are they there?

Bottom line, welders who are qualified to the standard D1.1 welding performance tests can also weld any of these other materials without re-testing. It is within the proven limits of their current skills set.

Have a Great Day, Brent

By SCOTTN

Date 01-10-2014 16:28

Tyrone,

Look at and compare Table 3.1 and 3.2 with regard to steel specs. All the steel specifications in Table 3.1, Group 1, for prequalified base metal/filler metal combinations for matching strength are the exact same as the steel specifications in Table 3.2, Category A, for prequalified minimum preheat and interpass temperatures. It's my understanding that the correlation and the reasoning behind grouping and categorizing these base metals together for filler metal compatability and preheat requirements is because they have similar tensile and yield strengths, and similar chemical composition. Also, for those same reasons, the prerequisite for filler metal and preheat of auxiliary attachments that are subject to EOR approval is based on similar material strengths and chemical compositions.

By jarsanb (***)

Date 01-10-2014 17:45

Little confused with Brent's second sentance. First off, Carbon Equivalent (CE) and Carbon Content are not interchangeable.... Two similar materials with two similar CE's and one with a higher actual carbon content can expect higher hardness values (more martensite) in he "as welded" condition. Without digging through D1.1, I would think CE and welding process would drive material temp (preheat) requirements long before ambient temps would be considerered. No?

By welderbrent (*****)

Date 01-14-2014 14:23

Okay, not sure I totally disagree with what you said but let's see if we can clarify some communication.

You are correct, CE and carbon content are not 'inter-changeable'. But, they are relational. Carbon is the major element determining a material's CE. No matter which carbon equivalency formula one is using. There is more than one depending upon the purpose for finding CE. Hydrogen control, hardness, re-bar weldability, etc.

Now, my reference to ambient temps is in regard to original 'pre-heating'. Many do not understand that ambient temperature IS preheat. If the ambient temps are high enough, and thus, the temp of the material is high enough, then 'further' pre-heat is not required. And, within the welding process the inter-pass temps are also regulated by not only the welding heat input but by ambient temps as well. All this was in support of my first statement that all materials require preheat at some time. I don't care what their CE, carbon content, or any other properties are, at some point the ambient temperature will require that even 1/4 X 2" A-36 flat bar be pre-heated. As is the case with ALL other materials in group I, II, or III.

Now, in Tyrone's second post he asked, "Why are these base metals combinations prequalified since one may need preheat?"

That is what I was responding to. It is not that "one" may require pre-heat. All require pre-heat. Some will require it at higher ambient temps than others. None of this is what the classification is about.

As to his original question, it is beyond my paygrade. Bottom line, they are grouped according to filler metal and base metal compatibility, usage, and many other factors that really are not dependent upon pre-heat temps being even remotely the same from one material to the next. Thus, the CE being different from one to the other is not a contributing factor when determining their placement on the table.

Oh, BTW, Scott, there are no out of date editions of D1.1. Some may still be in use from several years back if the project is old enough and specified that particular edition as being designed, fabricated, and inspected to.

Have a Great Day, Brent

By Tyrone

Date 01-14-2014 11:31

Thanks for the input guys.
I guess what others may be considered MINOR is in my mind MAJOR.
Tyrone

By SCOTTN

Date 01-14-2014 16:25

Brent,

I've actually experienced at least a couple lengthy projects where the specs referenced the current code at the start of the project, and a later edition of D1.1 was released during fabrication, but we still adhered to the D1.1 that was referenced in the specs. My curiosity with Tyrone's post was why the 2002 edition was referenced because compared to the 2010 D1.1, it's an out of date edition, particularly if the current edition is referenced in the job specs. That's why I wondered about him referencing and possibly using an out of date code. A certified fabricator is required to have the latest edition in their library. I would have thought that other fabricators do the same, but I've occasionally found that's not the case, as I've seen out of date D1.1's being used when the job specs clearly referenced a later edition. I've even seen job specs reference an out of date D1.1. When I see this, I submit an RFI asking whether we need to use the referenced edition of D1.1 or whether we need to use the current edition. The EOR has always replied to use the current edition. Over the years, I've reviewed a lot of what I call "canned" specs, where they're used over and over, regardless of the project, and without modifications applicable to each project, other than changing the name of the project. The EOR takes this shortcut and pretty much leaves it up to the estimating, project management, detailing, fabrication, and inspection teams to figure out what's applicable to the project. Some are obvious, but some warrant RFI's that wouldn't be necessary if the specs were 100% related to the project.

I remember a 3rd party inspector reject some work in D1.4. I asked him the basis for his rejection because it didn't sound correct to me. I looked in my current D1.4 and realized that he was incorrect. I also had the previous D1.4, so I looked in it and found his cause for rejection. I asked him which edition of D1.4 he was using. I told him that he was using an out of date code, as the job spec referenced the current D1.4. Then he asked me how long had it been since the latest edition was released.

By Mwccwi

Date 01-14-2014 18:07

3rd parties like that scare me.

By 46.00

Date 01-14-2014 22:27

The year of issue of standard being adhered to is totally dependant on the client. Most times in my experience, some paragraph in the contract specifications will stipulate the 'most current issue' of AWS/ASME XXX eg.
However, I have recently completed contracts that insisted that all structural steel fabrication was carried out to 2006 issue of D1.1. I have also seen B31.3 2008 issue stipulated and was an audit point when a later version was found in the contractors possession where this work was being performed. the reasons for using non current versions are many, for instance a specific year of issue may have a specific clause that the designer needs to incorporate into his structure.

By welderbrent (*****)

Date 01-15-2014 00:21

Agreed all the way through and with Martin and Glyn as well.

We did not get away from scary issues when we became inspectors instead of welders.

For the record, thanks for clarification Scott. I was just making sure as your post didn't necessarily sound that way.

Have a Great Day, Brent

By Tyrone

Date 01-15-2014 12:10

I wanted to generalize my situation, but I think I need to expand it...

I am the Customer. My drawing does not specify the revision level of D1.1 (Pulled out an old hardcopy of 2002 to do some thinking). The part consists of various Group I materials. The Contractor supplying the weldments asked if they can use one PQR to qualify other similar joints based on Group number. The joint type, angles, thicknesses, etc are identical, just the material type is different.

So......looking at the C.E. I thought it's not a good idea, but D1.1 seems to allow it.

Tyrone

By jarsanb (***)

Date 01-15-2014 20:16

To paraphrase a saying from the legendary Mr. Blodgett...."you have the code in one hand and the truth in the other". I see your where you are coming from. I can think of two fairly recent issues I've been involved with regarding issues with CE.

The first was on carbon steel pipe and sleeve (5L-X52 with .52 CE as determined by lab). Root pass with E6010, fill/cap with 7018.
Hydrogen cracks developed impediately upon solidifaction of the E6010 pass even though as-welded hardness values were significantly below established limits. Tempering of the HAZ with 7018 passes had occured, just too late.

Valve installation: CE of valves below maximum criteria but all root passes were cracking before first fill pass (hot-pass) was applied. Root deposited with lo-hy process. Lab analysis showed high carbon content in relation to specified CE. Even though dozens of previous valves had no issues, this order was not usable even though it technically met mfg. criteria.

Full circle to my paraphrase......

By Tyrone

Date 01-16-2014 12:49

That Mr. Blodgett is one smart cookie!

Using sound Engineering judgement (imho), I think I'll ask for separate PQRs. That will just drive up the price of the parts, but at least I can sleep soundly at night.

Tyrone