Prequalified WPS Travel Speed

Date 02-11-2008 20:24

There have been some past threads on this topic, try search "travel speed prequalified".

The important sections of the code dealing with this issue are: Section 3.6, Table 3.7, Table 4.5, and Commentary C-3.6.

The one sentence that really catches my eye when reviewing these sections is in the C-3.6. It says, "The code requires that four critical variables be specified on the written prequalified WPS within limits that will insure that it provides meaningful guidance to those who implement its provisions."

The phrase "meaningful guidance" jumps out at me. When I see prequalified procedures that have huge ranges for volts, amps, and travel speed, it is hard to convince me that the procedure is providing meaningful guidance. I also believe the ranges in Table 4.5 are meant to be applied to a single value; some will argue that the >10% amps, >7% volts, or >10% travels speed can be applied to a random range or the manufacturer's recommended range. That seems more like rationale to avoid writing the necessary number of WPS since again this practice starts to drift away from "meaningful guidance".

Table 3.7 does not have any direct limitations on travel speed, but the restrictions on electrode diameter, current, root pass thickness, fill pass thickness, fillet weld size, and single pass layer will all indirectly restrict your possible travel speed values since they all have some relation to each other.

By MBSims

Date 02-18-2008 04:50

"I also believe the ranges in Table 4.5 are meant to be applied to a single value; some will argue that the >10% amps, >7% volts, or >10% travels speed can be applied to a random range or the manufacturer's recommended range. That seems more like rationale to avoid writing the necessary number of WPS since again this practice starts to drift away from "meaningful guidance"."

Actually, the D1 Committee published an interpretation stating that for prequalified WPS's the tolerance does not have to be applied to a single value but can be applied to a "range", except that the range must still be within the electrode manufacturer's recommended ranges. To have multiple WPS's just to cover a workable range of settings would be overkill and unnecessary. However, I agree the range must provide meaningful guidance. Too many WPS's are written as CYA documents rather than to provide guidance to the welder.

By ctacker (****)

Date 02-11-2008 20:24

should be able to get it from your filler metal supplier. most have websites where you can get the info by googling the filler metal brand!

By CHGuilford (****)

Date 02-11-2008 21:57

The best way to get your travel speed is to time and measure your welds (that is not meant to be a smart aleck comment). I would have a welder run some beads at the high and low ends of your WPS volts and amps. Make sure the pass sizes are what you want them to be, then time the welder.
If you determine the fastest and the slowest travel that will achieve the pass size you need, you will have your travel limits. The beauty of that is your WPS will be based on what you can actually do.

By James Corbin (**)

Date 02-11-2008 23:20

I typically use the manufactures Volts, Amps, and Wire feed speed (melt rate) as a start figure in the fillet weld size range I am looking for i.e. 3/16" to 5/16". Then figure give or take leg times leg times 500 to get kJin then take volts time amps times .06 divided by the kJin and that will give travel speed.

example: A 1/4 inch fillet (.25 times .25 times 500 = 31.25 kJin) Lincoln outershield 71 w/CO2 shielding .045 diameter WFS 300 Volts 26 amps 190 with 31.25 kJin heat input would give you a travel speed of 9.48 (round off as you see fit)
Then on Table 4.5 #18 FCAW TS is 25% + or- to finish off your data. Try it in the shop as see if it needs tweaked a bit. This will give you a very good starting point. Use the same math for the range you need min/max V & A & TS to equal the weld size range you need.
Hope this helps

By whosgotthefyah Date 02-12-2008 13:59

Holy cow. I came into this AWS forum a little sketchy, like maybe no one would answer / ever checks it... Boy was I wrong! Thank you so much for the input. That was very fast, i didn't expect an answer for quite a while. Thanks everyone who posted. This forum is actually very helpful and I will try to skim it as much as possible. Once again Thanks everyone!!

-Clint Cox

By Goose-em (**)

Date 02-14-2008 00:30

.25 x .25 x 500 = 31.25, true true. Lets try another leg size like 1/2 inch or .5, .5 x .5 x 500 = 125, true. How about a 3/8 inch leg, .375 x .375 x 500 = 70.31, true. But do these heat inputs look or even sound correct? don't think so. Heat input is calculated using the following formula:

Amps X volts X 60 / 1000 X travel speed(inches per minute)

Given this for the stated 26 volts and 190 amps you get 190 x 26 x 60 / 1000TS = kJ/in Inserting the advertised travel speed the actual heat input would be...31.26 wow! pretty close.

Lets try another, .375 x .375 x 500 = 70.31 so 190 x 26 X .06 / 70.31 = 4.22 inches per minute, wow! pretty slow. Now the right way; 190 x 26 x 60 / 1000 x 4.22 = 70.24, wow! pretty close again, but whoever heard of welding with the mig process as 4.22 inches per minute. I would fire that guy for being to slow.

Remember that heat input is a function of the heat put into the metal, and where does this heat come from? That's right amps, volts, and dwell time or as we call it travel speed. You cannot just take the leg size and square it then multiply it by 500. What happens when you turn up the amps? Let me show you.

lets say we are using .045 dual shield running 100% CO2 with say 250 amps and 26 volts. 250 x 26 x 60 / 1000 x 9.48 (I am taking liberty with the travel speed) we get a heat input of 41.13

So how do we calculate actual travel speed? Easy, we use our experience gained through years of welding practice to estimate the travel speed, what! you say? Thats right we use our judgement because this is a pre-qualified procedure. If it were a procedure you were testing you would still use your judgement but adjust it accordingly as your test results dictated.

Ok, so what would I guess the travel speed to be for the above stated parameters, probably around 12 ipm. But just to be sure I would go out in the shop and have a welder weld at said parameters and time how long it takes him to weld a piece of material 12 inches long. Really simple.

In the end even so called pre-qualified procedures sometimes should be tested, without actually doing all the bend tests, tensile tests etc., in order to ensure a sound weld. Not all welds are equal!

By James Corbin (**)

Date 02-14-2008 02:12

Thank you for making my point. When you increased the amps to 250 and increased the travel speed to 12 you hit 32.5 kJin again close enough to the 31.25 kJin ¼ inch fillet target. Remember it is just a target that must be checked later in the shop with reality. When the material has less mass I reduce the kJin if it has a lot of mass I can increase the kJin. In this way I can help control the cooling rate. I have been using this method for 11 years it has never let me down.

Also if you check the Lincoln recommended parameters you should use 29 volts (+or-) with the 250 amps, that lets you increase the travel speed to 14 and still get 31.1 kJin. I never start making a procedure in the shop. I "Do the Math" first to predict the outcome, then do the +or - 10% Amps 7% Volts to see if those min max parameters will also work, if not adjust the optimum so the entire WPS spread is usable. When making a PQR I set the machine not the weldor.

By James Corbin (**)

Date 02-15-2008 15:46 Edited 02-15-2008 17:14

Sense I have been asked off board and for the rest of you who read this when using the LxLx500 calc, let's review; this calculation will predict the total heat input needed for a given fillet (perfect triangle). It does not mean you go as slow as you need to (see D1.1-table 4.5 #18) get the 1/2" fillet with the procedure you have, something else must change.

If your WPS (Supported by the filler manufacturer's recommendations) will not support your weld size in one pass you do it 2 or 3 or 6 what ever it takes to equal the fillet heat input calc. Let's say your weld size is 1/2 inch or .5 x .5 x 500 = 125 and your WPS heat input is 29V x 250A x .06 divided by 14 that would equal 31.1 -- 125 divided by 31.1 would give you 4.01 that means it will take 4 passes to fill this 1/2 inch fillet with the above WPS "all things being equal".
If you do not like the 4 passes change your WPS to 30V x 275A x .06 divided by 12 ipm with equals 41.3. The 125 divided 41.3 would give you 3.02 or 3 passes, again "all things being equal."

The math works and is a great predictor. Once you "Do the Math" check the prediction in your shop. It does not replace good welding practice. If your weldor slows down or speeds up beyond the WPS ipm, the predicted size will change. Even gun angle and ESO will affect the outcome. No WPS will work if the weldor does what ever he/she wants to, it must be followed. The whole idea is doing what we know works (a PQR) and not changing it much (D1.1 - Table 4.5) to predict a good outcome. It does not mean you can put a 1/2" fillet weld on a 1/4" plate without paying a penalty, see D1.1 - 5.21 and good design practice.
Weldor's running-a-muck WILL give consistent outcomes, its called "crap."

By 803056

Date 02-18-2008 00:15

I don't know if its "old school" or not, but I usually do as Chet suggested, i.e., the WPS and parameters used for welder qualification are somewhat broad. Based on the actual parameters used by those welders that "pass" the test, the WPS used for production is "tweaked" or tightened up to provide more consistency on the production floor. This is intended to imply that I do monitor the welder qualifications and I do record the actual welding parameters. That data is not listed on the performance qualification report.

I also concur with those that use the manufacturer's data published on their websites as a starting point. Most of the data they post is on the mark and backed up by testing.

Best regards - Al

By ziggy

Date 02-19-2008 01:13

Goose-em's comment regarding "even so called pre-qualified procedures sometimes should be tested, without actually doing all the bend tests, tensile tests etc., in order to ensure a sound weld" is well said.

Sometimes a pre-qualified WPS is created, issued to production and forgotten about. The limitations of the WPS variables (Section 3.6 - Amp, Volt, Travel Speed, and Shielding Gas Flow Rate) may never be periodically checked for conformance against Table 4.5 Essential Variables.

In the D1.1:2006 section 6.3.3 requires the contractor's inspector to "make certain that all welding operations are performed in conformance with WPSs that meet the requirements of this code."

This might be fun to try -
1. randomly check at least 25% of the machines in production against the written pre-qualified WPS for the welding being performed on the shop floor.
2. Without making ANY adjustments to machine, gas flow or personnel, record your results.
3. What percentage of each of the four variables make it past the verification the first time?

Has anyone tried this? If so, what were your results?