Update...it was all a misunderstanding. What the CWI was explaining as a rule of thumb (weave width as it relates to electrode diameter) was misunderstood by the instructor to be in the D1.1 code. That's what happens when you ask a question on voicemail and get the response by voicemail. And before you all get the wrong idea and go bashing the instructor (Ron) or our resident expert (Mr. Smith), read his reply to my query....
Mr. Yates, I didn't say the info was in the code. I don't quote the code often, but I do know where to look. I told Ron that it is recommended practice. (Rule of thumb) I would never allow my welders (I have supervised several) to exceed the recommendations that I gave to Ron.
If you are giving a guided bend test, you are lowering the passing possibilities by wider weaves or even wider welds for that matter. Take into consideration the yield and tensile strength of the electrode and you will realize that the poor old A-36 plate is already losing the "tug of war" battle. The average yield for an E-7018 electrode is around 58 to 65 KSI. The yield for the A 36 is around 36 to 38 KSI. The yield is reached for the electrode as soon as it solidfies. You may very often see the stretch marks in the HAZ before you begin to prepare the coupon for testing. If it were not for the ductility belonging to the A-36, the weld would fail as soon as it is made.
The codes will tell you what the maximum depth of weld made in one pass can be. For instance, the ASME Code allows a single pass weld with Sub Arc to be 1/2" thick. An .035" GMAW wire is allowed to produce a 1/4" weld in one pass.
The D1.1 Code does however, offer a suggestion and a mandate about the ratio of width to depth of a groove weld. The maximum (and minimum) size fillet weld that you refer to is based on the material thickness Not the amount of weave or electrode size!
As for your question about how to achieve a weld bead equal to the electrode diameter, the speed of travel will determine bead width. Also that is dependent upon the type of electrode. The E-7018 low hydrogen will produce a bead wider than its core diameter. If an E-6010 is deposited as it should be (with a whip and pause technique) one can nearly double the width of the electrode. I am aware of a company in Sistersville that welds small piping components and they make 3/32" welds with a 1/8" electrode all day long. Of course the pipe is turning on a positioner. Regulation of the travel angle also controls the bead width. The greater the travel angle in the drag direction, the smaller the bead may be produced. If a "push" angle is used, the bead will be wider.
In the case of GMAW, amps to volts ratio becomes a factor. The higher the voltage to amperage ratio, the wider and more shallow the bead becomes. If the amperage is on the high end of the ratio the bead will become tall and narrow.
My answer to the questions are to use good judgement in the production of a weld. The wider the bead, the more residual stress is built into the weld-so even before external stress is applied, the weld has aching muscles. A good inspector can differentiate the "hog weld" from a suitable weld. A good welding technician will not tolerate a bead that is unnecessarily wide. It will be sent back to the drawing board. If it extends about a sixteenth of an inch beyond the bevel, it will look and act OK.
These things have been argued and discussed for ages and I don't have a feeling that everyone will EVER agree. My advice is to go to an ASME code pipe shop to see what they do and go to an AISC approved structural shop to see what they do and follow suit. (The AISC uses AWS codes, D1.1, D 1.5, D 14.3, etc.)
Professor xxxxxxxxxxxxxxxxxxxxxx
AWS CWI, CWE, NDE Level III
AWS Education and Certification Chair
Sounds good to me...
There are a few things I can take issue with, including but not limited to a few references to code requirements.
The reference to the 1/2 inch layer thickness is not limited exclusively to SAW.
The width of a weave bead using low hydrogen SMAW electrode is not restricted by AWS D1.1, however, if the limiting size of a vertical single pass fillet weld is 1/2 inch, then the width of the weave is on the order of 5 times the maximum electrode diameter and more if smaller electrode diameters are used. The width of an individual weave bead deposited by SMAW is not limited, however the thickness of the layer is. We do differentiate between a weld bead and a weld layer. The width of a layer for FCAW and GMAW is limited by the requirement that a split layer be employed with the width of the previous weld layer exceeds some value.
I have welded many 1 inch thick test plates where the width of the cover layer was on the order of 1 1/4 inches. The cover and most intermediate layers were deposited as weave beads. I had no difficulty passing the requisite guided bend tests that are required to achieve 20% elongation.
Regarding angular distortion; when qualifying on a grooved plate, regardless of the electrode classification, welders that deposit numerous stringer beads to fill the groove invariably have more angular distortion then the welder that uses wide weaves.
It has been my experience that as demonstrated by fillet break tests, a single pass fillet weld, up to and including the largest single pass fillets permitted by AWS D1.1, invariably exhibit better ductility than multipass fillets of the same size.
Having expressed my opinion on the matters noted I see no reason not to use good judgment when teaching students how to weld. Any practice carried to extremes can produce less than desirable results. However, I cringe when someone uses the code to substantiate their position when the restriction is not in the code cited.
Best regards - Al
When it comes to teaching there is a time for both opinion and fact.
The fact is that in the real world, our students may be called upon to do both weaves and stringers...
Why? Because some projects have heat input restrictions and weaves take longer to get from point "A" to point "B"... Some contractors prefer weaves over stringers or visa versa... It doesn't really matter why... Both "may" be compliant in some cases.
So it just makes sense to teach both stringers and weaves with FCAW, SMAW and GMAW (short circuiting).
I expect my students to master both and inform them that there may be times when either may be required out there in the real world and sometimes it's dealers choice if the WPS is silent...... But if there is a limitation that it's an engineering level decision that will be reflected in the WPS and shall be obeyed.
I agree that both techniques should be taught and mastered. My objection is citing the restrictions as being code requirements when in fact the requirement or restriction is nonexistent. A restriction may be imposed to ensure heat input criteria are met. That is usually addressed by the code(s) as a supplemental variable that apply only when notch toughness is a requirement, i.e., a special case. Even then, the code restriction is imposed on the heat input or interpass temperature, not the width of the weld bead.
As you noted, the employer uses the WPS as the vehicle that provides specific information to the welder such as travel speed, arc voltage, amperage, wire feed speed, etc. Bead width is sometimes used to limit travel speed, but I often wonder if the bead width limitation is based on data or if it is simply a case of "that's how we always do it." I believe the latter is the case in most organizations.
Best regards - Al
Heat input issues aside, I have seen vastly more vertical stick plates fail bend tests when run with stringers due to lack of fusion than I have seen fail from lack of fusion or slag inclusion when running weaves. It seems many welders run a very low level of current in order to control the bead shape with stringers.
So true; when restricting the discussion to carbon and low alloy steels.
Al
I cut up a pretty 3G SMAW coupon several days ago and the backing bar actually fell off and I had to look around in the saw chip tray to find it. I sent it back to the welder so he could see what happened to his test sample and can adjust his technique for the lack of penetration into the backing strip.
So, did he use a weave or stringer technique?
Just asking.
Al
that one was a weave.
I had a similar situation with a 3/8 inch test plate that passed RT. When I picked up the plate I could see daylight between the backing bar and the test plate. I cut off the tacks at the very ends and the backing fell off. I guess there is no substitute for skill.
I still have that test plate in my collection. I use it for VT, PT, and MT demonstrations. I should use it for UT as well. The incomplete fusion is barely perceptible with VT and PT, but it shows up very nicely with MT.
Best regards - Al
Don't sound so good to me...........