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Static vs. dynamic loading welding rods

Yesterday's Tractor Forums
S

Stan in Oly, WA

Well-known Member
The issue of welding rods being designed either for static loading of for dynamic loading comes up regularly in discussions of the merits of different rods. It's often brought up as a comeback to someone who states that 6013 is just as good a rod as 6010 or 6011, if applied correctly, because they're all 60,000 psi tensile strength rods.

It occurred to me recently that the information about which rods are for static loading and which are for dynamic loading can’t just be some secret information passed along by word of mouth between 32nd Degree Master Weldors. Who would benefit by that? It must be in the nature of the steel as applied, and therefore should be definable from the description of mechanical properties. The information about the mechanical properties of stick electrodes provided by manufacturers generally includes Yield Strength, Tensile Strength, Elongation, and Charpy V-Notch specs. Are any of those the specific mechanical property which distinguishes an electrode meant for static loading from one designed for dynamic loading? If not, what properties are?

Stan
 
From a structural engineering standpoint, fatigue cracks require a propagation site. The heat affected zone of the weld at a weld toe is provides plenty of opportunity for a crack to grow under cyclical or dynamic loading. The rate of growth is related to the "toughness" of the material which is controlled by the chemistry. Welding can alter the chemistry of the steel in the heat affected zone and introduce stresses that make the crack propagate faster. Also introduction of hydrogen into the steel matrix cause the steel to be more brittle (hence low H rods). Finally the chemistry of the steel and the weld rod can determine the transition temperature for steel (where steel goes from being ductile to brittle). All these factors will affect the service life of a weld under cyclical or dynamic loading.

Under a static scenario, yes 60ksi is 60ksi.
 
I agree with you.However in the case of welding anything there are a lot of things that you have to look at.A very obvious reason that 6011 is better than 6013 is that it penetrates a whole lot more.Also if you see a weld fail,which you wont see a lot of if something is welded right,a 6013 is likely to crack right in the weld.Now somebody can come up with some fancy way of describing it,but the plain simple term for it is that 6013 just is not very strong of a weld.Lets just put it this way,weld a nice purty weld on one side with 6013,and then break it with a hammer.Before you even get it bent all the way down it will probably break.Do the same with 6011.You might not get it broke beating it back and maybe have to do it a couple of times to get it to break.That should show you most of what the difference is.The 6013 just sets on top of the metal and has very little strength.Now say you hooked your weld to a chain some way,say maybe you could make a chain link of 6013 and one of 6011,then they will probably break at about the same time.That would be your 60,000 strength.However the quality of your weld is always going to be better with the 6011 if its done right.If you do 6011 wrong it can break too.If you do 7018 wrong it can break.
I know this probably wont satisfy everybody,but thats how it is.
Now just in case you are a 6013 fan,do some of those hammer tests and see how little penetration there is.Weldo something with 6011 and see the difference.then weld something with 7018 and see the difference and also 7014.By far,the poorest weld,will be the 6013.It deposites the metal real fast and doesnt burn in deep enough.If you turn it up it melts before you get the rod used up.It just is not that good of a rod.YOu can maybe get by with it but think about this,what if you were building something and you had to weld steps up the side of your project and you were way off of the ground.you"weld"it on with 6013 and step on it and then go crashing to the earth.Plus the worst thing is,what if you tell a bunch of these guys to use 6013 and they build a trailer to pull their tractor down the 2 lane highway.They get up to about 60,in heavy traffic and the hitch falls off?Plus the welds look really purty except where the slag inclusions are.You can get slag inclusions in about every rod,but if the weld is already weak,its a bad deal.
 
Excellent explanation! It's so nice having an engineer on the forum. My backhoe, that I'm in the process of repairing, broke because the things you mentioned more than because of tougher digging conditions or operator abuse like some have suggested.

1. There wasn't much reinforcement around the bushing to begin with
2. The bushing was welded to the plate with flux-core wire with probably no preheat and had porosity in the weld that wasn't repaired
3. There was no bevel to get better penetration or a larger weld
3. There was a grease fitting installed in the area where there already wasn't much reinforcement around the welded in bushing and took 1/3rd of the material thickness away

All these things together contributed to the failure. It is obvious the grease fitting location was the propagation site. The crack started at the hole for the grease fitting because it was right down the center like it was cut with an exacto knife. Then the crack just followed the weld around the bushing. As good as engineers are, sometimes they can miss things too, just like everyone else. Great to have someone in the know explain the real reason why things can fail and also understands the difference between static and dynamic loading. Thanks to both you and Stan for posting.
 
Trucker, no disrespect, but I think bjb being a structural engineer and very well schooled on the subject has it covered.
 
Stan, I think charpy V notch values apply to dynamic loading. I don't think rods for static loading require charpy V notch ratings because they aren't designed to take stress in the first place. I know 7018 has to meet 20 ft. lbs at -20F and other XX18 rods can meet 20ft. lbs. as low as -60F. I just looked and the Esab site has a list that shows what rods require charpy V notch ratings. 6010, 6011 and 6027 all require minimum 20 ft. lbs. at -20F the same as 7018. No other rods require Charpy V notch ratings. So that confirms what I originally thought. Great question Stan! I was always told about static and dynamic loading but don't remember being told what distinguishes how to tell what rods are for dynamic loading. I just remember being taught that 6010 and 7018 were for dynamic loading applications. It's also possible I was told but forgot. It was a long time ago. LoL
 

I think it's easier on the job, because you always work off of engineered drawings. And when you don't understand you can send in a RFI.
It's this back yard engineering that gets out of hand! I know myself the only way I know how to design / engineer things, is most likely I've done something like it in the past, or very close.
 
Charpy V-notch is more important for cold weather operation. For dynamically loaded structures, it is more important that welds be 'full-penetration' welds that do not leave a built-in crack for stress risers to occur. Regular fillet welds are not full-penetration welds, for example.
 
There's lots of dynamically loaded structures that don't have full penetration welds and use fillet welds though. Charpy V notch does indicate toughness in lower temperatures but I noticed that only rods designed for dynamic loading require charpy impact values. Interstingly, I also noticed that 7028 only requires 20 ft. lbs. at OF instead of at -20F like 7018. The additional iron powder must take some of the toughness away?
 
It was an excellent question.bjb did a good job with it in technical terms,I just tried to put it words everybody could understand.
You seem to fail to realize you arent talking to people who eat,sleep and live welding,which was Stans point to begin with.You kind of remind me of Jethro Bodine with his double naught spy routine,and then you admit you dont even know the difference yourself,you just know the words static and dynamic.
I think its because like the expert said there is a difference in the weld metal,like its more brittle,and the different heat affects the metal differently and one is easier to break.
No disrespect to you either.Just when you want to explain something,explain it.Its not like its the secret of the ages.If you can explain better why this is happening with this rod go for it.I have wondered myself why it was so weak.I just know that it is,not really why.Penetration has to be some of it.
 
(quoted from post at 19:33:26 06/20/11)You kind of remind me of Jethro Bodine with his double naught spy routine
Click to expand...

trucker 40 I' am so glad I wasn't drinking anything when I read this part of your post, otherwise I would have spit it all over my monitor! :lol: :lol:
 
It was a very good question for sure. I never said I don't know the difference. I also think Stan knows quite a bit about welding and was looking for a more detailed explanation. I certainly don't have the knowledge or schooling a structural engineer does and could never explain it as well as bjb did. There are so many variables in welding and welding rods. That's why there are volumes and volumes on it. ASME codes could take a lifetime to learn and they're constantly changing. Stan mentioned several years ago that he had never heard the terms static and dynamic loading when referring to welding but after checking in to it, ackowledged it is legitimate. I was the one who first mentioned the terms when someone was asking about what welding rods to use. As I mentioned, with preperation, you could have the same penetration with both rods. That doesn't mean they will both be the same strength. There are many factors involved.
 
Thats interesting, because thats exactly how a 6010 weld will break, right down the middle.

That was something we did in school when we were learning to run 6010s, we welded a horizontal T joint, and ran over and dunked it in water before it cooled, and then beat on it until it broke. I forgot how far mine made it before breaking, but pretty dang far. And then it broke, right down the middle, with some weld on the top, and some on the bottom...

Idk, Id kind of expect a weld will little/no penetration to simply pull out of the base metal...
 
Well I remember way back there being a description of sideways and twisting force associated with static and dynamic.Like for something that just sets there is one way,static and if it has a lot of different stress twisting is the other way dynamic.I understand that,but where Im loosing it and where I think Stan is also loosing it is how is it that its 60,000 tensile strength then?I guess in the case of 6013 its 60,000 tensile strength as long as you dont try to twist it?It looks to me like they need a different way to rate it if they are going to say its the same as 6011 then they have to have some way to make it as strong as 6011,either by how you use it,or whatever.If it doesnt penetrate and create a strong weld they maybe ought to say its not 60,000 tensile strength.Or is it that it wont take twisting,but it will resist stretching as well as 6011? I mean why is it supposedly as strong as 6011 according to its tensile rating?
 
You know Lanse,not seeing what your weld looked like or knowing what you did,its hard for me to say why your weld would crack right down the middle of the weld.I know that a weld made right wont crack.If it does fail it will be right beside it.I had a FFA course in school so long ago I dont even remember much of it.However when they were teaching me at work,what they wanted,there was definitely reasons why your weld better never break.I have made some welds that broke,and maybe it was stress,or maybe I didnt have the machine set right,or maybe it was the kind of metal,I dont remember now.I do remember that a weld should not break if its done right.If you have any more welds that break,look closely and see if its right beside the weld or not.If its in the center of the weld you need to figure that out because you cant be welding stuff and then having the weld crack,it will give you a bad reputation!
I have welded stuff with 6011 that cracked for some reason that I remember.I think it was because it had so much stress that it caused it to crack.Mostly when I weld something I just weld it with 7018.I have welded stuff with a root pass of 6011,and then used 7018 on top of it.
So if your weld is cracking down the middle,you have some kind of problem,maybe even dirt in the weld,or slag in the weld.You know you can get small slag inclusions in a weld and not be able to see them real good.They show up in an Xray.Its hard to say.
Now try and break a 6013 weld and then a 6010/6011 weld and see which one is stronger.
One time this guy was welding and telling about how good he could weld,using 6013,and I have to admit,it looked good,but I hit it with my fist with a glove on,real hard and broke it right off! It even surprised me that it broke that easy.Ever since then I havent liked 6013.If they will break that easy then its kind of a waste of time using them.Its not that you cant use them,and some people probably are great at welding with them,and make strong welds with them,its just that its possible to make a good looking with with the stuff that is worthless.
 
Lanse, if you get a chance, weld up some full penetration V groove welds with 6010 and let them cool till they get to 650deg.F and then bend them with a hyd press or a big cheater bar. They will break and you'll be able to see the grain structure of the weld. If I remember Lincoln would break down the middle of the weld and Hobart would break along the edge, so it was a better experiment using Lincoln rods. Both rods met the required specs. though. It was a neat experiment but the temperature had to be pretty close or it wouldn't work right.
 

This is what I love about this site, and some of you. Gets me to thinking of things I haven't thought of in years! And I really had to think about this one, so I hope I'm right.
I was under the impression that a weld was suppose to break right down the center. Not pull out of the base material. I know when ever we would do a quick and dirty fillet weld test with a hammer, if the weld broke down the center we'd say, well she gave her all. But if it pulled out of the base material we would pick on that guy for a week or so! :lol:

I might have to do some research on this!

 
Exactly. If you do your job and get it bonded to the base metal... it should not pull out. The weld will break which will be it's yeild...

Rod
 
The weld is not supposed to break,it is supposed to tear the metal out on one side or the other.Now I didnt go to welding school,but Ive taken welding tests and your weld better not break in a test or you wont get the job,at least not where I was at.
There also is a whole bunch about flexible and non flexible,which for some reason is why 7018 is better.I didnt know until recently that 7018,unless its brand new from a sealed container,or a rod oven, lacks any low hydrogen qualitys.So I take it that means 7018 kept in a box is no better than 7024,or any other rod with 70,000 tensile strength.
The whole low hydrogen deal is so that the weld has some flex to it and is not as brittle as other rods.Now if your weld is thinner than the metal you are welding,its alright to break the weld.But if its welded with low hydrogen,you better have to bend it back and forth several times.I know the difference between MIG welds and Low Hydrogen is that the MIG weld is more brittle.
I had more than one place give me a welding test and all of them looked for the weld to stay and pull the metal out instead of the weld breaking.
I know Im not quite the expert some are on this kind of stuff,I just know what I learned from welding in the past.Maybe welding different things they want a different kind of weld that will break.I do know that all of it is about how you have the welder set.If its peeling the slag its about as good as it gets.If the weld breaks they pass over you.
 
Unless the strength of the weld is greater than the strength of the material is is bonded too. Most mild steel is a minimum 36 ksi (A36), structural steel is usually around 50ksi. A 70XX rod is 70 ksi. You don't get any more strength from 70 ksi rod than 60 ksi rod if you are welding the two steels I just mentioned. Structurally speaking the welds (fillet) are idealized as a triangle and analyzed as the throat thickness (distance from the corner to the hypotenuse). However if you make a nice round weld with more area in this spot, the weld very well could pull out regardless of the bonding. It will yield first wherever the stress ratio (stress to yield stress) is the highest.
 
Puddles, you are 1000% correct! A weld that breaks down the middle is a sign that the weld was sound. Consider that the opposite side in your example wasn't welded. That makes it act like a big crack opposite the weld, so if the weld rips out of the base metal means there had to be poor fusion at the edges of the weld. A weld ripping out of the base metal is considered a weld fault. It could be from undercut or lack of fusion or not washing the puddle into the edge, etc. To make it easier to understand, consider MIG welding a fillet weld. If you don't have the right heat and/or don't weave the puddle into the edges, you could have all your welds pull out of the base metal. That's why Lincoln was never a big fan of MIG when it came out and also why Lincoln was so late to get into MIG.
 
The choice of full pen verse fillet in an dynamically loaded structure is dependent on the direction of the stress. To propagate a crack, the stresses need to be perpendicular to the weld. Therefore in a plate girder, it usually is possible to use a fillet weld to attach the flanges to the webs (stresses parallel to the weld), but you need to use a full pen weld when splicing the plates (stresses perpendicular).

Crack growth is related to the size of the initial crack. With a full pen usually the crack is limited to inclusions in the weld toe. The maximum size of these cracks are controlled and that is why you do some form of non destructive testing (ie ultrasonic). With a Fillet weld on both sides of a plate, the initial crack size will be the plate's thickness.
 
You can still get a stress rise with a full pen weld, depending on the orientation of the two pieces being joined and the profile of the full pen weld. Two identical cross sections that are butt welded together with a full pen weld and then ground smooth will THEORETICALLY have no stress rise.
 
Trucker, you gave a perfect example of why it's a really good idea to go through an apprenticeship if you want to be a welder. You learn all about weld flaws and what makes a good weld and all kinds of other important information. Sounds like some of your employers should have had some better quality control personel or went to school themselfs. 7018 is still low hydrogen as long as it's kept dry. Code and x-ray work requires rod ovens and many shops use ovens just so they don't have any problems and the rods burn nicer. Many factors contribute to a sound weld.
 

Found this on ESAB's website.

Visit http://www.esabna.com/ for more information about our products.
Destructive Testing of Welds
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Destructive weld testing, as the name suggests, involves the physical destruction of the completed weld in order to evaluate its characteristics. This method of testing is used frequently for a number of applications. Some of these applications include welding procedure qualification and welder performance qualification testing, sampling inspection of production welds, research inspection, and failure analysis work. A number of destructive weld testing methods are used to determine weld integrity or performance. Typically they involve sectioning and/or breaking the welded component and evaluating various mechanical and/or physical characteristics. We shall briefly examine some of the more common methods of this type of welding inspection. We shall consider the macro etch test, the fillet weld break test, the transverse tension test, and the guided bend test. We shall consider how they are used, and what types of weld characteristics they are designed to determine. We shall examine their advantages over other inspection methods and their limitations.

[b:b9bd3a639d]Macro Etch Testing[/b:b9bd3a639d] – This method of testing typically involves the removal of small samples of the welded joint. These samples are polished across their cross-section and then etched using some type of mild acid mixture, dependent on the base material used. The acid etch provides a clear visual appearance of the internal structure of the weld. Particular interest is often shown at the fusion line, this being the transition between the weld and the base material. Such items as depth of penetration, lack of fusion, inadequate root penetration, internal porosity, cracking and inclusions can be detected during inspection of the etched sample. This type of inspection is obviously a snapshot of the overall weld length quality when used for sampling inspection of production welds. This type of testing is often used extremely successfully to pinpoint welding problems such as crack initiation, when used for failure analyses.

[b:b9bd3a639d]Fillet Weld Break Test [/b:b9bd3a639d]– This type of testing involves breaking a sample fillet weld that is welded on one side only. The sample has load applied to its unwelded side, transverse to the weld and directed to its unwelded side (typically in a press). The load is increased until the weld has failed. The failed sample is then inspected to establish the presence and extent of any welding discontinuities. This test will provide a good indication as to the extent of discontinuities within the entire length of weld tested (normally 6 to 12 inches) rather that a cross-sectional snapspot like the macro etch test. This type of weld inspection can detect such items as lack of fusion, internal porosity and slag inclusions. This testing method is often used in conjunction with the macro etch test. These two testing methods complement each other by providing information on similar characteristics in different detail and in different ways.

[b:b9bd3a639d]Transverse Tension Test[/b:b9bd3a639d] – Since a large proportion of design is based on tensile properties of the welded joint, it is important that the tensile properties of the base metal, the weld metal, the bond between the base and the weld, and the heat-affected zone conform to the design requirements. Tensile strength of the welded joint is obtained by pulling specimens to failure. Tensile strength is determined by dividing the maximum load required during testing by the cross-sectional area. The result will be in units of tension per cross-sectional area. This test is nearly always required as part of the mechanical testing when qualifying welding procedure specifications for groove welds.

[b:b9bd3a639d]Guided Bend Test[/b:b9bd3a639d] – This is a test method in which a specimen is bent to a specified bend radius. Various types of bend tests are used to evaluate the ductility and soundness of welded joints. Guided bend tests are usually taken transverse to the weld axis and may be bent in plunger type test machines or in wrap-around bend test jigs. Face bend tests are made with the weld face in tension, and root bend tests are made with the weld root in tension. When bend testing thick plates, side bend test specimens are usually cut from the welded joint and bent with the weld cross section in tension. The guided bend test is most commonly used in welding procedure and welder performance qualification tests. This type of testing is particularly good at finding liner fusion defects, which will often open up in the plate surface during the testing procedure.


http://www.esabna.com/us/en/education/knowledge/weldinginspection/Destructive-Testing-of-Welds.cfm
 
I may not be saying what all there is to a welding test.I Remember that you weld it and grind it down and they bend it both ways and look at that,but also they would have us just put it in a vise and break it.The metal is supposed to break before the weld does,or you are doing something wrong.Now you might have to bend 7018 back and forth to break it.I didnt say that.But I remember very well they frowned on anybodys weld that broke.It had to have steel torn out instead of weld breaking.Plus Here is a discussion on Hobart welders where somebody says the same thing.Look at what Mark Whiddon says.
http://www.hobartwelders.com/weldtalk/archive/index.php/t-4811.html
 
Trucker, are you questioniong the most experienced welder on this forum? Sorry but Puddles knows what he's talking about. I think you're confusing different weld tests.
 
I went over to Hobart and did a search for Mark Whiddon, found the post you're talking about. Dated 1-16-2004. This guy has a total of 100 posts, his last post was 7-20-2004, so I started reading them. This guy is a rookie, and some of the questions he ask are comical at best. If this guy told me it was raining, I'd look up. :lol:
 

Went back and read some more, I love this one.


Mark Whiddon
Senior Member
 
Join Date: Sep 2002
Posts: 100
? on keeping things square

Hey guys,
I have a question concerning keeping shelves squared up with the rest of a bookshelf. I think I probably have it figured out, but maybe I could get a different opinion on how to fix it. My problem is that I can make shelves (either angle or square tubing) and keep the shelf itself square. My problem comes in when I attach more than one shelf to the rack. Here is how I have been going about making it. I would make one shelf, lay the verticle supports down on a flat surface. The shelf is verticle at this point and the verticle supports are laying horizontal on the table. I tack the two V supports, flip it over and add two more V supports. I try to keep the shelf square as I tack it by checking it with a carpenter's sqaure. It seems that the more shelves the more off sqaure it gets. I am sure the heating of the welds is causing some if not most of the movement by warping. I am wondering if my cutting might also be somewhat at fault. I try to cut pretty precise with my bandsaw but I may have a difference of 1/16" sometimes. I know it is plenty small enough to fill in any discrepancies with weld metal, but is that what would be causing the twisting as I assemble the bookshelf? Or is it just the heat warping that is causing it to come out not square? Would it work better if I assemble the V supports to the shelf in a X type manner such as assemble the 2 oclock piece and then the 8 oclock piece, the 10 oclock piece then the 4 oclock piece? I have been doing it by just rotating the bookshelf as if I was going 2,4,8,10. If there is a homemade jig idea I would appreciate any help and I am sorry for the long post.
thanks Mark
 
We had a rod oven.I guess what stuff I was working on didnt need it mostly.Its been so long ago that I cant say any more what they did say about it.Ive forgotten a lot of stuff over the years,especially since I spent 10 years as a mechanic and 15 years as a truck driver since those days.
I remember the welding test they gave for the government jobs good though.I passed it,and not many young guys did.
I do remember having to put rods in the oven and use rods out of the oven.Thats about it.There was at least 20 welders on a shift,and for quite a while there was 40 welders on a shift.So they would tell you what they wanted and that was about it.Other welders would tell you stuff,and I know we watched some films from time to time,but it wasnt welding school.I dont remember all that well what they did say about it.I know I had a letter punch to mark my welds.
 
There doesn't seem to be a whole lot out there about fillet weld testing, and passable results. I did find some idle chit chat on one of the forums where someone stated generally the metal will fail on the outside edge of the HAZ.
I did find this also.

 
I clearly remember from high school asking the very question about fillet weld strength. The weld should break down the middle on a test piece. A HAZ crack is a flaw. Other reasons for the weld breaking at the edge are undercut, too much build up resulting in a notch effect or an unequal leg fillet. Puddles, you were 100% right the first time. A properly done fillet weld should break down the middle of the weld and not break in the base metal.
 
There just doesn't seem to be a lot of information out there about fillet weld testing. Maybe because it's such a rudimentary test. After reading a few article about it, I'm coming to the conclusion the weld is suppose to break right down the middle so the inside of the weld can be visually inspected. Kind of a poor mans x-ray, or UT. :lol:

 
Puddles, as you know there's more to a proper weld than just soundness in the weld metal. A fillet weld should have the same leg dimension on both sides as the thickness being welded and the right weld profile, slightly convex. When the plates start to bend you notice the definite "crack" right opposite the root of the weld formed by the edge of the one plate sitting on the other plate. The root of the weld is like the middle of a hinge. If it breaks somewhere other than the middle of the weld would indicate a faulty weld. It already had a "crack" started to propagate a deeper crack right through the middle of the weld. To break on either of the plates would indicate there wasn't proper fusion on one side. I know I could have worded that better but I hope it makes sense.
 

No it makes perfect sense to me, I think the word hinge sums it up perfectly too!
If you think about it, this is a bad joint design. What I mean is, if the force was applied in the opposite direction the weld would be so much stronger, thicker the plate the more force it would take to break the weld.
Having the weld pull out of the base metal is the last thing you want, lack of fusion!
Once the inside of the weld is exposed then you can look for lack of penetration, porosity, slag inclusions, etc,etc. Pretty good test, and the average guy can do it with minimal tools.
 
One thing about it,you sure are trying.I can see the weld breaking if you weld a 3/8 weld on a 3/4 plate and then hit that.If you weld a 3/8 weld on a 3/8 plate Im sure its not supposed to break in the middle of the weld,it is supposed to tear the metal out.You can break a weld in a press,but you are supposed to not have the weld break.Now think about it a while.If the weld breaks then its not as strong as the base metal.If the weld holds then its stronger than the base metal.I wont say that if you were welding some kind of metal the weld wouldnt break.But for structural steel,the weld shouldnt break,at least not without putting it in a press or without a lot of difficulty.
There is a lot more to it Im sure.LIke the affected area from welding,and how different heat settings would work on different types of steel and a whole bunch of stuff I dont know about.However with structural steel it should tear the metal instead of break the weld.
Thats my story and Im stickin to it!
 
"However with structural steel it should tear the metal instead of break the weld.
Thats my story and Im stickin to it!"

That's why you'd be completely wrong! How do you think they came up with the simple formula that the leg of a fillet weld should equal the thickness of the material being welded? We're not talking about a 3/8" weld on 3/4" plate, although it should break down the middle of the weld as well. It's the same principle but we're talking about an equal leg 3/8" weld on 3/8" plate or a 1/4" weld on 1/4" plate. In order for the weld to rip out of the plate, the crack would have to travel sideways from the natural crack already inherent at the root of the weld instead of just continuing right through the center of the weld. That would definately indicate lack of fusion or other defect in the weld. The very middle of the weld root is like the middle of a hinge and the unwelded back side acts like a natural crack. The exact same way as if you hacksawed something partly through and then broke it. It would break where you sawed it, not somehwere beside where you cracked it. Any fillet weld that rips out along the edge of the weld is for sure a faulty weld. There is nothing more to it. It's no different for a MIG fillet weld either. Why do think MIG has such a bad reputation for lack of fusion if it isn't done right? You'd know instantly with a fillet weld test if you were doing it right.

I've welded lots of temporary lifting hooks and plates for wedges and pry bars from one side. When you go to knock them off, you don't worry that the plate is going to rip out. 99% of the time, the weld breaks right down the middle. The only time it might rip from your temporary piece is if it's been welded over an old weld that was never cleaned up. Sorry to disappoint you trucker, but you could really benefit from some formal schooling. Like I said before, I think you're confusing different weld tests.
 

I think it's just a matter of leverage. The way the weld is taking the impact the center of the weld is the weak point. Now if you beveled the top plate, and did a 100% penetration weld that would be a different story. This really gets back to proper joint prep, and joint design. This simple fillet weld test, is the worst thing you can do to a weld. Weld on both sides of the top plate, and it'd be harder to break it. Put a double bevel on the top plate, and do a full penetration weld on both side, and it better bend right over on top of the bottom plate without breaking!

When I first got my Dynasty, there was too many bells and whistles for me, so some guys on another site were helping me dial it in. I was having trouble getting good penetration down in the heel of fillet welds on aluminum. Once I got the settings correct here is the results. Don't remember if I ever finished breaking this 1/4 inch aluminum plate or not. Do remember it took quite a wallop to bend it this far. And I was quite happy with these results, remember it's aluminum, only 16,000-PSI.
 

Wait a minute, I found some pictures of broken fillet welds. I got to organize this computer one of these days! :lol: Note the undercut on the top leg, left side? And it still didn't pull out of the base metal!







 
Your talking about 2 different failure mechanisms. The cracks at the toe will fail under cyclical loading conditions that slowly grow the crack larger (days, months, years).

The strength of the fillet weld is determined by the throat area. In a strength test, depending on how it is done, the highest stress should be in the throat area IF it is uniform. If you are going to bend a fillet weld then the stress are not uniform and it will fail where the stresses are the highest. Unless the weld is extremely brittle, cracks don't affect the strength.
 
While I see what you are saying about the other side being a crack and by breaking the weld you think thats right,but you think pulling out the metal is wrong?No I dont buy that.The weld is supposed to be stronger than the base metal of structural steel.Now I dont care what school you went to,or what they told you,Im right sure they didnt tell you the base metal was stronger than the weld.Did they?They did tell you that a weld that will bend is stronger than one that will break.Thats the difference between MIG and 7018.7018 will bend more than MIG.Yeah us guys who weld may not go to school,but we arent stupid either.You seem to think they dont teach you anything.Well they had a real good impression on me then because the last I welded for some place on Structural steel was in about 1977 and I still remember some of it like it was yesterday.
I am not impressed all that much with what they taught you,if you are trying to say that you know it all,clearly you dont.What I think it means if the weld breaks is that the weld is too brittle.The weld should be stronger than the base metal.I can see a MIG weld breaking down the middle and we did just that, to look at the weld.7018 is a different story.It ought to bend the plate as in the picture that Puddles put up of I think aluminum.7018 should go way further than MIG before breaking or something is wrong with it.Now since Its been so long,I really dont remember how much farther it is supposed to bend before breaking,but its quite a bit.See we did those tests at work to see whether we were doing the welds right or not.Im sure the engineers wanted to know how the tests came out.They also used tests to determine which welders worked on which projects.
So dont be so full of it all the time.School is one thing,actual doing is something else.Dont assume because you went to school means you know all there is to know about a subject,because that will come back and bite you a lot of times.Nothing wrong with school either.However I think you assume far more than you actually know or were taught in school.You know I didnt go to school,but that doesnt mean I dont know ,or have not worked with people that did.Also where I worked the engineers were right across the street and I have seen more than one argument going on between them and the bosses over what they were trying to do.They had to decide what kinds of welds to put on skyscraper parts,and in some cases it was easy,in other cases it wasnt.Im sure the higher they went,the harder this stuff is to decide.I think we easily put way more than was necessary weld on stuff because it was designed that way by the engineers.Thats why some stuff can be welded with Jet Rod and some has to be welded with low hydrogen.
So back to the discussion of the break or no break,on a 3/8 plate,with a certain size rod,it is supposed to penetrate so much on the top plate,the center and the bottom plate.You are supposed to hold your rod or push the weld up on the top plate so as to have good penetration in the seam.That means that some of what you are saying about this is kind of wrong as you weld should have penetrated at least part of the way through the crack and if you have more weld on the bottom,as in just running your rod and letting most of the weld go to the bottom,then the top of the weld is going to be weaker.Im sure you remember welding gauges and what they show.Well the first thing before they would break a weld is put a gauge on it to see if it passed that test.Maybe if you have more on the bottom the weld will break instead of pull out.
I actually can see Jet Rod breaking in the middle like you are trying to say for 7018.Are you sure you arent trying to say that 7018 by breaking is really what Jet Rod does?You cant get the jet rod to lay in as good as 7018 and it would have to be built up to get a good hold on the top piece.So that would mean that Jet Rod weld like that would probably break.
Now from school maybe you know how much say a 1/8 low hydrogen rod will penetrate a 3/8 inch plate.I dont.I think 1/8 was about the smallest rod we had.Some of the rods we used were almost 1/4,so maybe thats part of it too.Seems like I remember the weld area to be like a circle and it should have nearly as much penetration on the top as the bottom.The crack could be a start of a weld to break but you also weld across the ends before you start.
I dont think there is anything wrong with school,in fact I think it is a good thing for people to go to school.Im sure I dont know as much as somebody who went to school.However Im no dummy either.In a lot of these arguments you and I have had over the years I fail to see where you ever were able to prove that you knew a lot because you went to school.I do however know people who went to welding school that do know a lot about it.I dont doubt there are quite a few things you do know about it,but sometimes I also notice that you are just trying to be beligerent instead of discuss anything.Puddles however searches for his answers and offers proof.
I think everybody has it in their nature to kind of be beligerent about stuff sometimes,so dont take that wrong,but next time think whether you really know,or are being beligerent about stuff.
Im sure some people like these discussions,and I do myself,it makes me think.
So to end this novel here Im going to say that I dont buy your story on the weld breaking down the middle if its done right,even though I see what you are saying about the leverage part of it,I think the weld is supposed to be stronger than the base metal.Ive tried to explain why to the best of my ability.If you think the weld should break,I think you need to prove why the weld should break.Of course the weld has to be within the welding gauge for the size weld it is supposed to be,which means to me it has to be pushed up on the side,or weaved or circles or whatever it takes to make a strong weld for that welder.Get somebody at a welding school to tell you if you know somebody there.Id like to hear what they say.But dont try and insult my intelligence,or anybody elses for that matter,Im afraid you are going to be the one who comes up lacking if you do that.
Ive been told by people who went to welding school that a 7018 weld is not supposed to break if you did it right.It should break beside of the weld,or tear out the metal with it.Ive noticed on the broken stuff that Ive seen,even a pretty bad looking weld done with 7018 will probably break beside of the weld,not the weld itsself.You may have to look at it real close to see it,but that area right next to the weld is where it breaks 99% of the time.Ask them at welding school if thats true or not.Most of the time it will break somewhere else and break in a bad way.I think that would be because of stress.Like say a truck crossmember.It has a lot of stress and the welded area will still be good,but it will break somewhere else and break completely off.Just like your backhoe job,the weld didnt break,it was the grease zerk hole was the weak link and caused a whole bunch of other damage.
So the weld should hold,the base metal should break.Im not convinced with anything you said.However the stuff Puddles is putting up is real interesting.
 
In a fillet weld test where only one side is welded, like in Puddles first diagram, I am 100% positive that the break should be right down the center of the weld. If you've ever had to knock off temporary braces, you'd know that the hardest ones to break off, broke down the center and left part of the weld on either side. It doesn't matter what rod or welding process was used. A stronger rod will just take more force to break. Puddles aluminum example is a little different because it's aluminum which will bend a lot easier than steel. Puddles is a darn good welder. I bet that if he did a practice fillet weld test with 7018 it would break right down the middle and if he did 100 tests, they'd all break right down the middle. Not one of them would rip out of the plate. I learned welding by some highly experienced welders with decades of combined experience on some of the most critical jobs. Are you telling me that they are wrong too? You can think all you want. I am absolutely positive that a fillet weld test should break down the middle of the weld. If a weld breaks along the edge is a weld flaw or procedure flaw.
I think leverage right at the root of the fillet, like Puddles said, is the reason the weld should break down the center.
 
Puddles, I don't think trucker would get it if 100 welders, even more experienced than you, explained it to him. If it was a full penetration fillet, even from only one side, then I think the plate should bend over and not even crack. Maybe you could do a sample with 7018 to show him how a proper fillet should break down the middle. I don't think you'd have to try more than one attempt. On the other hand, to get a sample to rip out of the plate, I think you'd need to prepare a lot of test plates and do some less than stellar welds to make that happen.:wink:
 
I think trucker has the tests confused. A single sided fillet weld bent back against itself puts the most stress on the throat of the weld and that's why a proper weld should break down the middle and not rip out of the base metal.
 
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