How do u determine range on wps?

[CD]

Hi,

When you see the amps, voltage , speed and heat energy input RANGE on a weld procedure. How was it determined? Ex: Amps 70-110, volts 12-14, speed 35-55 . Then I know the formula to find heat input, but don't know how to determine the range in the first place.

And also, say it's GTAW and there are 3 passes, then when working out preheat temp we need the heat input, but which heat input do we use? Ex (pass 1- 0.74 to 2.65), (pass 2- 1.29 to 4.10), (pass 3- 1.44 to 5.0) Do we use minimum, average ore add together or what?

Any input and help on these 2 questions would be appreciated. Thanks!

[Flash]

Hi CD
good questions

Firstly lets look at where the variable ranges come from all welding codes have essential variables
we will use AS1554.1 as an example, see table 4.11 A essential variables
this lists the variables that effect the qualification of the WPS
depending on the process As1554.1 lists the following ranges +- 10% amps, 7% volts, 15% travel speed
so off of your PQR (original test record) you apply these ranges and you end up with the ranges for your WPS

Now comes an variation to this AS3992 uses heat input as the variable not amps, volts and TS
AS3992 allows -50% and +80% heat input on non impact tested materials
This can be difficult to work out and apply back to amps, volts and TS the things the welders use
I generally apply the AS1554.1 variables to AS3992 WPSs to make sure the WPS is still useable in the workshop and the variables are not too far from the test weld that I know worked

Now for the second part of the Question
I do not think this is stated in any code that I know of and it is a good question
I use the following logic generally (maybe with the exception of really thick sections)
I use the lowest heat input from the first run to calculate the preheat, because after the first run typically the joint has effectively been preheated by the first run
But always use the worse case scenario when in doubt
Keep in mind you can reduce preheat if you can prove via a hardness test that it is not required, but apply caution when doing this

I hope this helps
R
Flash

[CD]

Thanks for your help on my questions, much appreciated.

I have another one though, How do we work out the maximum interpass temperature for a wps? Iv’e been looking in as1554.1 and I can’t find out how. An example off an old pqr from work says interpass temp for passes 1.-ambient, 2.-105, 3.-135, 4.-115, 5.-90, then on the wps the max interpass is 250’c

Thanks!

[Flash]

Another Valid question
maximum interpass temperature for materials covered under AS1554.1 is not a huge concern, but it is for part 4 for Q&T materials

but it is generally excepted that that maximum interpass for AS3678 grade 250/350 should not exceed 300
remember WPS must cover the standard requirements as a minimum and can have additional restrictions outside of the standard

AS1554.1 does list interpass temperature as an essential variable table 4.11 A (m) decrease of interpass temp of 20C is an essential variable

This is tighter than that allowed by AS3992 which allows -50 +100C for other than group F and G materials

Lets clarify what Interpass temperature is, it is the temperature measured directly before each run with 75mm of the each of the preparation or weld

With that being said you measure the interpass temperature of before every run during the test weld and replicate this on your WPS applying the -20 C range, as far as I am aware there is no maximum but I generally apply a maximum of 250 or 300C for non impact tested materials, outside of 250-300 interpass temp it can effect the welding characteristics eg the material just gets too hot to cap

I hope this goes some way to answer your questions
R
Flash 

[verdi]

hi

there is a clause regarding consumables in 1554.1 – 4.6.1.3 which mentions a minimum of 300 c for inter run temperatures but this is for designated seismic service.

i cant see that using this as a guide would be detrimental.

cheers

[mkseogirl]

Hi

I undertsand the first ans bt i unable to understand 2nd ans..

[Larry]

Hi All,

Using AS1554.1 with AS3992 for your WPS essential variables should be avoided at all times. Its a structural code not a pressure code, even if the energy input range in AS3992 is a bit far fetched. Stick with AS3992, don’t deviate. All the information in AS3992 works, that why its an Australian Standard, recognised by the Australian Government . Put together by professional. If it didn’t work it wouldn’t be in there.Standards are there for a reason. Please be careful.

Thank you  🙂

[Author]

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