E6010 & E7018 combination

Date 01-10-2002 11:31

Weber, one of the reasons E6010 is used for a root pass is that E7018 is not to be used on an open root. All low hydrogen SMAW electrodes have this restriction. Instead of E6010 you may use a backing strip, GTAW or GMAW for the root pass. The Hydrogen from the root pass diffusing into the cover pass is an interesting point. It apparently is not a problem since this is a common practice in pipe welding. Perhaps one of the engineers on this site will give the specifics on this.

Respectfully,
Mike Sherman

By dasimonds (**)

Date 01-10-2002 13:19

Mike,
Even though it is not a common practice anymore, E7018 was, and sometimes still is, used in an open root capacity.
My personal experience is that E6010 is much easier, or more forgiving, to use in an open root situation than E7018. Joint tolerences are not as critical with E6010.
Also, E6010 is much more of a "digging" arc, giving better penetration.
The hydrogen question is interesting. I'd guess that hydrogen is not that big an issue in this case. If it is an issue with a particular base material, then the relevent code prohibits the use of E6010.
What is "st37"?
Hope this helps.
Dale Simonds

By Michael Sherman (***)

Date 01-10-2002 21:38

Dale, this is a topic that I would like to pursue, at least moderately. From experience, literature and the small amount of education I have in the field, I know that when an open root is welded with a low hydrogen electrode it is very, very difficult to achieve both full penetration and a quality weld. The point here is that if you achieve full penetration, you will probably pull a long arc, possibly introduce hydrogen, raise your amperage by increasing your resistance and have a hole in your pipe. I have had this discussion before with Lincoln Electric engineers and we are both surprised that this is not common knowledge. Please correct me where I am wrong. I will not be offended, but please back up your argument with references I can research. I own a welding company and I am always interested in others techniques.

Respectfully,
Mike Sherman

By dasimonds (**)

Date 01-11-2002 01:17

Mike,
I am in complete agreement with you on the difficulty of doing an E7018 open root. If I have a choice, I would always choose E6010 over E7018.
I personally have found that the long arc you mentioned is just what you want to avoid, for the reasons you mentioned.
I attempted the test a few months ago. What a frustrating experience. The CWI sent to administer the test had no experience with E7018 open root, didn't know what the joint geometry should be, and neither did I. After 4 coupons,which is all he brought with him, I had the top half of the joint looking pretty good, no undercut and a good root profile. but the bottom half was still sucked back and had a lot of undercut. Without some good pointers, and parameters, I figured I was just wasting coupons. I later talked with our welding instructor, whom also had never done the test until recently, said he ran 47 coupons before he got a good one. But when things are slow in the test shop, he has the time to figure out what the fit up, land, root opening, rod size, etc... need to be. He found that using 3/32" E7018, 3/32" land, 3/32" root opening, and in his words, "keep it tight, and pray it doesn't keyhole on you, because if it does, your all done!"
Perhaps someone else can give you some references to research. I don't have any books that specifically cite the use of E7018 in an open root capacity. Contacting your local D.O.T. might be a start. I'm not sure if it is still in effect, but when I passed my D.O.T. structural test in 1980, the pipe test was E7018 open root.
Does the API 1104 cover E7018 open root?
I prefer to stay away from it(E7018).
Hope this helps
Dale Simonds

By pipewelder_1999 (****)

Date 01-11-2002 04:23

E-7018 has been used for the root pass in composite (Sa210 with 304 clad) boiler tube repairs on black liquor recovery boilers (Window welds).

With proper fitup and welding parameters it works quite well. More difficult than E-6010 but with the right welder GTAW roots are more difficult than E-6010. Or was that the other way around?

As with all processes, they are alot easier if you have the skill, training and desire to make them work.

Electrodes for SMAW have no "Restriction". The welding procedure is qualified based on the ability of the procedure to perform within a "range". The code of fabrication/construction may have restrictions or the project specifications may. The electrode may perform better in certain situations. But is not restricted.

As far as hydrogen goes. I think in some cases we get a little "hydrogen crazy". In many applications using plain carbon steel I think we spend a little too much time "over inspecting" or "over engineering" a simple product. Just my opinion.

Good day

Gerald Austin
http://www.weldinginspectionsvcs.com/

By - Date 01-10-2002 21:09

Just to add to what the other respondents have said. E6010 has a deeper penetrating arc than E7018, making it more suitable for root penetration. In addition, E6010 has a fast freezing slag that permits down-hill welding. (Also called stove pipe welding.) This technique is preferred by many welders because of the higher welding speeds that it allows. Speed is one of the major issues when welding long distance pipe lines.

Regarding the strength issue, we have to see the bigger picture. A single pass of E6010 will have only very minor effects in reducing the strength when compared to possibly five or six passes of E7018.

Regarding the H content, we again have to look at it in terms of one pass versus five or six. If all the passes were made with E6010, then you could possibly have problems with H cracking. If only one is made with the high H electrode, then in total, the amount of H is still low enough.

As mentioned, with some materials, even a single pass with E6010 will result in H cracking. I assume st37 is not one of those steels. (I know this is a German spec, but I can not remember exactly the composition of the steel.)

Hope this helps

Regards
Niekie Jooste

By DGXL

Date 01-10-2002 21:50

There are several companies on this side that require open root welder qualification tests using E7018 electrodes. I have trained welders using this electrode, the coupons bend just as well as any other. The degree of difficulty and the probability of discontinuities is increased as noted above. Some never get the "knack" of this type of weld.

I do not know what application this test is applied to. Not sure why these companies require this test either, but they do. Maybe we'll here from someone with specific knowledge on this subject.

Also, the subsequent passes (beyond the 6010 root pass) will benefit from the low-hydrogen electrode deposit through admixture.

By Michael Sherman (***)

Date 01-11-2002 11:22

Thank you everyone for your replies. I didn't realize it was so common to use E7018 for the open root. I shouldn't have said it was restricted. I know it is only restricted as to whether or not you can qualify it, and the literature I have says only that it is not suggested. In my company ( I have eight employees ) I restrict it because of it's high degree of difficulty and the high rate of failure associated with that difficulty. I find it is better use either backing rings, E6010, GTAW or GMAW for the root and have near 100% pass rate. Again thank you.

Mike Sherman

By welder_guy2001 (***)

Date 01-12-2002 02:02

To answer the hydrogen question: when using E6010 for a root pass, after welding the excess bead is ground down and some of the wagon tracks are smoothed out...but too much grinding will cause burn-through. the weld is ground down for a couple of reasons....1) to increase the ability to burn out wagon tracks and 2) to re-melt the root bead during the second pass (the "hot pass") to allow hydrogen, slag, and other impurities to escape the bead. so, essentially, it's safe to use an E6010 electrode, as long as sufficient heat is applied to it soon after it's welded

By dasimonds (**)

Date 01-12-2002 04:25

Welder_guy2001,
How does that account for a joint that is completely welded with only E6010? No E7018. Can you explain what the "other impurities" are?
I think the hydrogen issue is as pipewelder_1999 put it. For plain carbon steel, probably not an issue most of the time. Try running some E6010 on some high strength steels, and that's another case all together, as Niekie 2 stated.
It is my understanding that hydrogen cracking mainly raises it's ugly head when there is a susceptible microstructure involved, such as martensite.
Dale Simonds

By - Date 01-12-2002 07:53

You are right, you must have a susceptible microstructure to get H cracking. As such H cracking is not an issue in plain carbon steels up to approximately 15mm in thickness. Above about 20mm however the heat sink becomes great enough to cause this susceptible microstructure. It is here that you then need to start using H controlled consumables and / or pre-heats.

Obviously it is not quite as simple as stated above, because it also depends on the actual composition of the plate, and one heat of "plain C steel" can be quite different from another heat. The statement above is however a reasonable rule of thumb.

Regards
Niekie

By weber

Date 01-12-2002 19:51

Thank you very much for the immediate replies and excuse me for answering late. I must confess that it shocked me when I saw “(11 new)” on the board after 2 days. Thanks for your attention.

St37 is DIN (German standard) identification. It’s as same as ASTM A36, a plain carbon structural steel.
As some gentlemen mentioned above it’s possible to weld root pass by E7018.
Of course, it’s easier to weld root pass by E6010.
Now I understood plain carbon steels are not susceptible to hydrogen cracking.
But:
1) There are E7010-X and E8010-X electrodes, E7010-A1 for example.
It means cellulosic electrodes are used for low alloy steels; and these kinds of steels are susceptible to hydrogen cracking.
2) E6013 is enough for A36.
I think usage of E7018 for A36 is over designing and wasting money.
But it’s common to use E7018 for A36!!!

Thank you, again

By bspeirs (*)

Date 01-12-2002 21:07

Multiple pass welds with EXX10 electrodes may not have that much hydrogen left - lots of plant piping has been completed with E6010.
Time at temperature allows the hydrogen to migrate out. A low hydrogen deposit overtop the 6010 will provide sufficient heat to substantially remove the hydrogen

Many companies weld medium strength Q&T pipe ( 80 ksi tensile) vertical down with E8010-G electrodes - about 300F preheat required, but interpass does not typically need additional heat since the welding keeps the temp up. Blanket wrap the weld to slow the cooling down which aso helpd hydrogen escape.

By George-kh (**)

Date 01-12-2002 22:36

Dear bspeirs
I’ve never heard before to weld Q & T steels by cellulosic electrodes.
Preheat temperature gives chance to escape H2 but not completely because if it does hydrogen cracking never appears (low alloy steels always has been preheated).

By bspeirs (*)

Date 01-13-2002 04:59

We (my employer) probably have over 100 km of CSA Grade 448 (65 ksi yield, 80 ksi tensile) installed. This has been going on for at least 15 years; probably closer to 20.

Design and construction to ASME B31.3, ASME IX weld procedures (20 % strain side bends, not the 12.5% bend generally used in pipelines).

10, 12 14 and 16 " pipe; used in steam service; DP 2500 psi at 650 F.
Wall thickness of the 16" pipe is 20 - 24 mm (say 3/4 to 1")

Typically do root plus 3 passes; a second crew comes along a day or so later for the fill and cap.

I do recall one crack on a tie in weld - probably due to not enough preheat and too much stress on the weld - the picker let off the load too soon.

There is some joy in Exx10 electrodes - do not have to be concerned about keeping the rods dry/hot - which can be a bit pain if the crews are not used to 7018.

We switched to gas shielded FCAW about 3 years ago becasue of the productivity improvement; side benefit is controlled hydrogen, so we we able to reduce the preheat on the fill and cap to about 200 F.

More details on Ed Craig's website www.weldreality.com under the recent applications section.

Recently made aware of an X80 pipeline (80 ksi yield, 90-something tensile) On this one they went to a downhand 9018 after the root, but fill and cap the FCAW.

By welder_guy2001 (***)

Date 01-14-2002 14:58

yes, that's true, it doesn't matter with mild C steel...you could probably really mess up a weld with mild C steel and still have a weld that is of sufficient strength. as for a joint completely welded with E6010, if you don't go too fast and keep the puddle hot, a lot of the H will be dissipated. think about all the pipelines that are welded with EXX10 rods in the downhill position...i'd think in that case H cracking would be a problem. but if the puddle is hot and preheat/postheat is used where necessary, there shouldn't be a problem. i know...the original question was for mild C steel....i guess i'm just answering for ppl for future references.

By - Date 01-14-2002 18:15

Just an issue with your statement that a hot puddle will dissipate the hydrogen. The reason that H cracking is a problem at all, is that the amount of H that can be dissolved in liquid iron and Austenite (high temperature phase of plain C/Steel) is much higher than can be in solution in Ferrite. (low temperature phase)

The hotter puddle will not substantially reduce the amount of H. It may reduce it very slightly if the puddle is slightly more fluid, but I believe this effect will be almost negligible. (My opinion)

A higher heat input will however tend to "bake" out some of the H contained in the weldment that sees temperatures in the range of around 300 - 750°C.

Regards
Niekie Jooste

By welder_guy2001 (***)

Date 01-15-2002 02:54

ok...so it seems that welding is more of a "guesswork" profession. there are just as many opinions out there as there are ideas of how to do something. there doesn't seem to be any clear consensus on what IS correct, and what is totally wrong. too many gray areas here...thank you all for helping me to see that i need to just read my books and stick to that information rather than rely on word of mouth info.

By 357max

Date 01-15-2002 16:28

Working with SkillsUSA-VICA contestants, preparing for the International Skills Contest, All position open root, multiple pass E7018 is used. They prefer the E7016 which has no iron powder and is therefore less fluid. In the international arena this is a typical job skill. And they use Alternating Current preferring the square wave for the root pass and may or may not switch to Direct Current electrode positive for the hot, fill and cover passes.
Vertical Downhill travel (fyi "down hand" is the flat position) low hydrogen SMAW may utilize the E7048 instead of the cellulose EXX11 or 10's electrodes for pipe. The cellulose electrodes utilize compounds in the flux coating which include hydrogen which can get trapped in the weld.
What is the "right way" of welding? As long as the welding procedure is qualified it is the "right way".
This topic has provided a good discussion.

By George-kh (**)

Date 01-18-2002 21:52

Dear 357max
In ASME IX, foreword part, it’s written:
“The code is not a handbook and cannot replace education, experience, and the use of engineering judgment.”
Just having a passed PQR doesn’t guarantee the work.

By RonG

Date 01-15-2002 19:02

To many cooks spoil the broth huh?

But like 357 MAX says if the procedure is qualified what else can you say.

By - Date 01-17-2002 18:55

Different books will also give different info. If this was not so, there would only be one book on any particular topic printed.

So what am I saying?

Life is not simple, and todays right is tomorrows wrong. It is for this reason that experience is such a good teacher. It helps you to decide what works in your reality and what does not. That is why a forum such as this one is great. It helps to open your mind through the experience of others.

Regards
Niekie

By dasimonds (**)

Date 01-18-2002 10:25

welder_guy2001,
I'd have to disagree on your opinion that welding is a "guesswork" profession. I think it can become a "guesswork" profession when one fails to follow procedures. The Welding Procedure Specifications, WPS, were developed to take the "guesswork" out of the equation. Problems arise when one tries to shortcut around some of the established essential variables, such as filler metal selection, preweld cleaning, joint fitup, preheat, heat input, shielding gas, PWHT, etc... .

A procedure is basically a set of instructions, which when followed, ensure that anyone can produce a satisfactory weld, provided they followed the procedure.

Even a box of muffin mix has a procedure written on the side of it, giving all the information needed to be successful at making muffins.

I'd be willing to bet that most all welding failures can be attributed to working outside procedures and parameters. I'll also bet the phrase "close enough", and even worse "I didn't have time" was used somewhere in the process. There's always time to do a repair though.

Complications arise with the large number of possible base metal compositions used around the world today. What works for plain carbon steel won't work for high carbon steel, as an example, or what works for something 1/4" in thickness won't work for something 2" thick, even though it's of the same composition.
Dale Simonds

By weber

Date 01-18-2002 21:54

Thank you everybody.
Your experiences trained me a lot.
However, nobody answered this:
“E6013 is enough for A36.
I think usage of E7018 for A36 is over designing and wasting money.
But it’s common to use E7018 for A36!!!”

By - Date 01-19-2002 14:39

Theoretically if the strength of the filler is equal to or exceeds the strength of the base metal, you are OK in terms of strength. There are however other considerations such as H when the section becomes too thick. Then you need to control the H. The "weakest" H controlled rod that I know of that is typically used is the E7018 electrode.

Then there are also other considerations that have little to do with the technical, but are rather "policy" decisions. Typically on our plant, NO E6013 electrodes are allowed irrespective of the job that is to be performed. Why? Because it complicates electrode control on other jobs. If you have non H controlled electrodes lying around, it will only be a matter of time before it is used on aplications that need H controlled electrodes.

Regards
Niekie

By welder_guy2001 (***)

Date 01-19-2002 01:01

ok, so when i tested for certification w/ a 6010 root and a 7018 fill, the WPS was wrong? is that what you're saying? should i not do a hot pass? should i not grind out the root pass and run over that pass w/ a quick hot pass and then fill in the rest of the groove w/ 7018? hhhmmmm....maybe the testing institute i went to hasn't been qualifying their welders for the Alaska Pipeline with the proper WPS's. i'm speaking from what i've read and from what i've been taught FROM experienced and certified welders and inspectors. what i don't understand is, how can somebody say something contrary to scientific proof? wait a second...don't answer anything...i'm just gonna go

By dasimonds (**)

Date 01-19-2002 06:33

welder_guy2001,
What's your point?
Dale Simonds

By - Date 01-19-2002 15:02

While procedures are there to be followed, I have on a number of occasions seen difficulties where welders were following the procedures to the T and still experienced problems. Why is this?

The basic answer is VARIABILITY. All materials have variations between batches, and even within batches. This may include variations in chemical composition, microstructure and even segregation of constituents. All shielding gasses have different impurities, even if they fall within the specification tolerance. Every welder has a slightly different technique. The weather is constantly changeing, so the temperature and humidity is constantly different. The constituents of electrode coatings are never exactly the same... The list just goes on. We live not in a precise world, but in a world of statistical variation.

So even if you are actually within the ranges qualified, things can still go wrong. It may thus appear to some people as if we are dealing with guesswork, because there is not necessarily only one right answer to any given question. At the end of the day, there are many ways to kill a cat. (Appologies to cat lovers.)

My recommendation to anybody that does not "grasp" the concept of variation is to try to develop a standardized procedure for always throwing a six with a dice, or always getting a heads when flipping a coin.

Regards
Niekie Jooste

By dasimonds (**)

Date 01-19-2002 19:24

All the interesting and excellent points you made are true. Variability is inevitable. One of those things that come under the heading "things beyond our control ".

It's the "things in our control" that have needlessly been the source of numerous failures.

Low Hydrogen rod control would be an excellent example. It's the open box of E7018 sitting on the shelf in a gangbox, 10' from the wet end of a paper machine, the portable rod oven full of E9018-B2 that hasn't been plugged in for 2 weeks, the open box of E7018 A1-Mo sitting on a shelf right beside the empty 300 lb. electric rod oven. The list goes on and on. When we use these types of mishandled electrodes, what were really doing is introducing an element of uncertainty, that didn't need to be there.

Preheat would be another example of welding failures that resulted from an attempt to circumvent the established procedures.

How many stainless welds have failed in service, especially before the advent of the L grades, because of a failure to monitor, and stay within, the established interpass temperature range? Or the ignoring of the purge requirements?

How many welds have failed because of improper preweld cleaning?

I think if one were to do a statistical analysis of welding failures, I'd bet that the ones that fall under "things in our control" would far outweigh the failures that come under "things beyond our control".

Dale Simonds

By - Date 01-21-2002 18:59

Point taken. Too often welders and even supervisors feel that they do not need to follow the WPS, because they have done it differently so often without problems that they can just "do it my way" once again.

Regards
Niekie

By dasimonds (**)

Date 01-21-2002 21:19

Niekie 2,
Actually you touched on an excellent point about variations in consumable items, namely welding rods.

I know next to nothing about how welding rods are made or who makes them.

I'm currently working on a job where the company has purchased 12 cans of Murex welding rod. We used the same E7018-A1 SMAW electrodes on a job a couple of years ago, and had a lot of trouble with porosity filled starts and random porosity. On that job, we actually had a wire attendant, and he kept the ovens locked and under strict control, so I don't think it was a case of contaminated wire, such as they had been left out and picked up a bunch of moisture. Another plus to keeping the ovens locked was that nobody was heating up their lunch in the ovens!

Our engineer, and he's not a welding engineer, such as yourself, says ALL welding rods come from 1 of 2 places. When they come off the production line, one box gets a Lincoln tag, the next box gets a Murex tag, etc... , so switching rods won't make any difference. As I stated earlier, I know next to nothing about who and how the SMAW rods are made. I'd be most interested in hearing your feelings on the subject.

One thing I did learn about them today is the H4R designation and what it means. The H4 denotes the amount of diffusable H in ml/100g weldmetal deposited, meaning there should be 4ml of H per 100g of deposited weldmetal, if I read the whole thing correctly on Lincoln's website. The R in H4R means that their resistant to moisture pickup when exposed to an environment at 80 degrees F, containing 80% relative humidity, for a period not less than 9 hours.

Dale Simonds

By dasimonds (**)

Date 01-21-2002 23:15

I did receive an email from Mike "Seldom" Fales and I thought I'd post it.

>> Concerning your electrode question. As it was told to me years ago, there are only a couple of mills that draw the wire because it's really the same material. The wire is then purchased in bulk spools to other companies such as Murex and they straighten, cut to length, and apply the coating. It's the coating that causes the changes in metallurgy and arc characteristics. So maybe your engineers are only partly right! Must be each of the electrode companies have a little old lady with a secret flux recipe. Interestingly, Murex E7016 was what I had to test with on open roots when I started school. Well, apparently the little old lady must have died and took her recipe with her because in the mid 60"s their E7016 went off the market-period! Dow went to Airco and their E7016 was crap. It had a harsher arc and it was a porosity making phenomenon. It was banned from use in the whole plant. We then went to Lincoln E7018 as well as Alloy Rods Corp. and McKay (a little later)and the rest is history because they became the standby. We all shed a tear when the old Murex disappeared because it had the nicest, softest arc you ever saw and always burnt off square. It was one sweet rod to use!<<