Bend test surface crack causes

By jackx429 Date 02-10-2017 20:56

Hi, I've been welding for about 1 and a half years. I have the entry level certs and have passed 2g and 3g bend tests with stick welding.
I recently applied for a job mainly using MIG, and was required to pass a 2g bend test.

Now, I've taken a couple bend tests before, so I had a good idea of what I was doing, but this one came with some curve balls.

1) The wire was thick. They told me it was .052
2) Upon doing my research before the test I was unable to find a decent reference as to what setting should be used when welding 1/4" metal with .052 wire
3) The machines did not have weld setting charts specific to themselves for reference either.
4) The CWI made the coupon for me, and the scaling of the steel was on everything except the 22.5 degree cuts. (I think that's not regulation since I know you're supposed to grind off scaling on the backing strip and 1" on either side of the bevel)
5) note: gas used was a 75/25 mix. just FYI.
6) I was only given a half hour to figure out what settings to use

With this situation I was left in a booth with a machine that was zeroed out and I was left to find my own settings.
I thought " well that's fine. I'll just kind of feel it out."

I had ended up with the settings at 23 V and 335 WS with the root pass. I wanted to take my time with that so I could make sure it was nice and flat and fused to the edges of the coupon.

Then to fill in the rest, I turned it up the voltage to 25, and left the wire speed where it was. I felt pretty good about the test, but didn't hear anything for 3 days. (Ridiculous because they told me they'd check it the morning after the test and it takes like an hour tops to cut and bend a coupon)

Anyways, they call me and say that 2/3 of my strips had cracks. I have no more info. I don't know where the cracks were, or if they were on the face or root side.

But I was wondering if anyone might have any input as to what might have caused this cracking and what I might be able to do to avoid it in the future.

By jwright650 (*****)

Date 02-10-2017 21:48 Edited 02-10-2017 21:54

Did they give you a welding procedure to weld this coupon out with? If not, they should have...next time when a WPS is not provided ask for one so that you can show them that you know how to use it...and it will give you a range of parameters to set the welding machine. That is a bummer that they left you without much in the way of instructions of what they were looking for out of you.

Just breezing through Lincoln's website and looking at the typical welding parameters for ER70S-3, it looks like for that size wire that you would have to travel pretty quickly or risk burning through 1/4" materials. I hope it had a backing strip and wasn't an open root test...yikes!
Lincoln didn't show the .052 wire with 75/25 shielding, they had the .052 listed with a 90/10 mix which gets you into a spray mode of transfer around 30v and 300-320 WFS using a CTWD of 1/2"-3/4".

Hard to say what happened as far as the cracking...did they say if it cracked while bending? I'm just wondering what bend radius they may have used and if it was correct for the strength of the material that you welded.

By jackx429 Date 02-11-2017 04:16 Edited 02-11-2017 04:20

Yes, as I said, they zeroed out the machine and gave me nothing to go off of. I did have burn through issues while welding some scraps and thats why I had the voltage down.

No idea what radius they bent to, but as far as I can tell, it did "crack" while bending. Although this info was given to me over the phone, and I wasn't actually able to see the bent strips myself.

By welderbrent (*****)

Date 02-10-2017 22:29

Some things we don't know:
1) The classification nor specification of the wire/electrode
2) The grade of steel
3) The applicable code
4) A proper test should have included a WPS which would have answered most of your questions on settings
5) Why a 1/4" thick material?
6) If the direction of grain was properly established and set up by the inspector.

Some things we do know:
1) With that gas on thinner material you were probably working with Short Circuiting, which is not normally acceptable for Structural but that is IF D1.1 is the applicable code
2) Your WFS was possibly a little high for the volts you were set at.
3) IF the material was A36 and the steel was not rusty the mill scale is up for grabs though I personally like it removed. I can generally pass tests with it on.

This is pure speculation with the lack of information and I have not looked up any parameters for that size electrode since I don't know what class electrode we are looking at.

More information would be great.

He Is In Control, Have a Great Day, Brent

By jackx429 Date 02-11-2017 04:19

Right, they didn't give me much info. No info on the electrode, and certainly no info on grain direction or steel grade. I have no clue why they chose 1/4" but that's what the CWI brought me for the coupon he had made.

Could you give me some more information about short circuiting, and grain direction?

Much appreciated

By jwright650 (*****)

Date 02-13-2017 19:45 Edited 02-13-2017 19:49

Short circuit is a mode of metal transfer. The electrode actually touches the base material and shorts out the welding circuit until the wire gets hot enough to finally melt off. With Spray mode, the wire vaporizes into tiny droplets and is carried across the arc to the base materials through the ionized plasma created by the higher welding current and the larger amount of argon present. Typically it takes more than 80 % argon to get the spray characteristics.
Grain direction depends on the direction of rolling at the mill when the plate was made. If you bend the coupon against the grain, it can cause it to crack.

By Lawrence (*****)

Date 02-14-2017 14:49 Edited 02-14-2017 16:16

I thought about posting and have held back because I don't want to confuse a fairly new learner... But there is something I think is being overlooked. (but not by our new young poster)   I'll try to explain in detail so everybody understands.

75/25 Ar/Co2 GMAW shield gas is not limited to Short circuit transfer at all. Not with .052 electrode wire.

It is bad that the man being tested was not provided with a written WPS... Shame on the CWI.

Back to business... The 75/25 and .052 solid wire can indeed produce globular transfer mode, which is in fact a prequalified D1.1 process and quite capable of producing a weldment required in the original post.

For example: With .052 wire and 75/25
330 - 360 IPM WFS will produce between 260-300 amps with a CTWD (stick-out) of 5/8" This will be the case with any typical transformer or inverter power supply.

27-30 volts will provide a globular transfer mode that would be defined by an open arc and droplets being transferred that are larger than the electrode diameter.   33+ volts might even get it to reduce the droplets to spray transfer, but this would be very uncomfortable and make a wide flat bead that is difficult to control.

While that is not an optimal combination for 1/4" base metal grooves (it's a little hot) it is doable if stringers are placed. And this combination will do quite well for 1/4" or larger fillets, with no burn-thru on base metals 10ga and greater.

I would suspect at the 23-25 volts and the 335 WFS that the operator probably saw a lot of spatter and perhaps even felt the electrode wire "pushing back" slightly against the gun, accompanied by a very harsh arc crackle sound. So as Al mentioned, our original poster was probably experiencing short circuiting transfer.

I would start at 27.5-28 volts and 330 WFS.... If I saw excessive spatter and felt push-back, I would increase in half volt increments until the spatter was somewhat reduced. I would not think you would need to exceed 30 volts.   If I saw undercut, I would reduce volts in 1/2 volt increments until it was gone. Operate the gun at a slight 10-15 degree push angle and a steady, straight push. No weaving and no whipping

The suggested parameters will produce about 12.5 lbs. per hour deposition and a 1/4" slightly convex fillet at about 17 inches per minute

Edit:
The relatively high deposition is "probably" what the employer is after. .052 is not a typical filler choice, but can be a very smart one. A 90/10 Ar/Co2 gas would provide a more desirable spray transfer at similar WFS and voltages... Even a 98/2 Ar/Oxygen combination would be preferable to the 75/25 gas.

I think the .052 is a bad choice if the end game is an electrode wire that can do both thin and thick base metals with the gas choice they have and a typical transformer... Especially without the benefit of GMAWP, Which can produce some pretty nice profiles with .052 on a surprising variety of base metal thicknesses when a slick wave form and appropriate shield gas combination is used.

By welderbrent (*****)

Date 02-11-2017 22:36

No arguments here. It is amazing how some places totally ignore all proper qualification procedures and claim that is how they can know you know what you are doing. If they really wanted to prove a person's skills and more than just being able to 'GUESS' how to adjust that particular welder they would test to see if you know what WPS's are and how to follow them, test plan/welding symbol reading ability, math skills, tape measure reading, safety knowledge, etc.

Brent

By jackx429 Date 02-14-2017 21:32

I'd like to thank everyone for the input. It's been a very helpful learning experience.
After reading what everyone said, I felt that it seems to fairly unanimous that the testing process was flawed or at least poorly executed.
I've reached out to the welding supervisor to express some of these concerns to perhaps allow for a retest with the proper brief, if not just for the purpose of expressing the information I've gotten from everyone.

I also was told that the CWI was there as a welder to start and gained his position based on seniority. As far as anyone can tell me, he has never actually gotten any formal training.

By jackx429 Date 02-14-2017 21:40

Also, I want to bring this sort of information the the attention of the supervisor, because this company produces the suspension and axles for large construction trucks and sells them to plants like Peterbilt.

If there is an underlying problem with all of this, I would be concerned as to the stability of these frames.
When this occurred to me, I was actually worried about driving next to large trucks because if they were assembled poorly they could fail at any moment.

By jwright650 (*****)

Date 02-15-2017 13:56

Sounds like you are getting some sage advice here, I agree with the others be cautious and approach them with an attitude of gratefulness if they agree to a retest. Then knock it out of the park and pass that test.

By welderbrent (*****)

Date 02-15-2017 13:01

As someone who just failed their test, be careful and make sure that if you go to anyone you approach them with a proper attitude and well prepared appeal to authority.

Know this, they are not truly under D1.1 with the type of work that they do. But, they can default to that code for welder qualifications and QC of components if they chose. They are probably mostly under their state DOT as well as Federal Highway Regulations for most QC and procedures.

Next, they can do any kind of a test they have established. Our first comments were offered with little background and purely opinions based upon speculation. It is still true that taking the test as you described would not qualify a welder to any AWS Code but they are apparently not interested in that. They have their own program and are still able to say that their welders are qualified to THEIR standards even though that is not a code directed test.

Even after testing to a code such as D1.1, employers can still add other testing to assure themselves the welding personnel can perform exactly as the work will require; things like special joint configurations, specialty materials, special electrodes, etc.

While the Short Circuiting process is not pre-approved for Structural Steel under D1.1, it may be totally acceptable for what they do. Having said that, it is still questionable. There are many aspects of Short Arc that are suspect when doing work on material of any thickness and need for high quality. And, since they didn't supply you with any information, they may be using it at elevated operating parameters which would be more of a Globular mode and more accepted as well as more successful for the work.

You have some learning to do from the sounds of it since you are uncertain about some of our terminology and things said. Thus, be careful in approaching them and telling them their system is flawed.

He Is In Control, Have a Great Day, Brent

By Lawrence (*****)

Date 02-15-2017 13:16

I'm in TOTAL agreement with Brent about a cautious approach if you talk to these guys again.

IF... Your story is accurate about how they test... I guarantee that they have a very high failure rate related to prospective employees.... This will give them the *feeling* that they are doing high level work and that the skill level required is just more than the market has to offer.... (a delusion)

But from their perspective you will be one of the many many guys that failed the test... And now you are going to tell them that their process is out of control? They will not hear it.

So, why not think of a more winsome approach to just simply ask for a retest... If they grant it... Take the advice you have been given here and pass their test... (That will impress them more than words) ..... Work for a while in silence, and when you receive your first raise or promotion, *begin* to talk to them about code and process control...

By SWN1158 (***)

Date 02-15-2017 16:02

A lot of responses. In case it hasn't already been mentioned, the edges of the coupons should have a 1/8" radius, which helps prevent cracking at the edges.

By jackx429 Date 02-15-2017 16:43

The long edges or short edges?

By jackx429 Date 02-15-2017 17:04

Hi Everyone,

I'd like it to be clear that I'm not walking up to the office building and calling them out. In fact, I was only going to ask for a retest and then express my concerns to the person who tested me.

The company only hires specifically through a staffing agency because they have their hiring contracted out.
In order to have this done at all, I had to call the agency, who emailed HR, for a call to be made back to the agency.
Somewhere along that line, the staffing agent told them that I had concerns and the company actually reached out to me for this input.

By Lawrence (*****)

Date 02-15-2017 17:39

Well there you go!

Tell them you will answer their questions after your retest :)

That way your opinions are responses that are asked for.