SMAW WPS

Date 10-05-2005 13:39

When I set a welding machine to perform SMAW I always set it by the amps never volts.Everytime I see typical operating procedures for stick electrodes all it shows is amps never volts.

So in my opinion when I write a WPS for Shielded Metal Arc Welding,the section where it asks for amps I have to use the manufacture's recomended amps.When it asks for volts I should be able to type in NA(not applicable) because the manufacture does not list volts in the typical operating procedures.

Every WPS I have ever seen for SMAW always has a number for the amps and then a number for volts.I want to know where the volts number comes from? I guess I could pull a couple of numbers out of the air,but why should I.

This is my opinion(not saying I am right). I would just like to hear y'all's opinion on the subject.

By Lawrence (*****)

Date 10-05-2005 15:07

It's a good question and I think could be asked about manual GTAW also.

I've never written an SMAW WPS but I do have an AWS authored SWPS right here (ANSI/AWS B2.1.001-90) which is totally silent on voltage.

We all know that in Constant Current processes (SMAW GTAW) the voltage varies with arc length, but in manual operations a real time measurement for arc length would be more accurate than prescribing a voltage that will keep an arc length near a certain stated length.

Having said that, I have been involved in Semi-automatic GTAW procedure qualification that required very strictly detailed Arc Voltage parameters n because the Sciaky welding unit used an adaptive feedback control which linked Arc Voltage to the servo that controlled the arc length via the torch head on the Z axis. For this procedure the Electrode type and prep angles were also essencial because a slight change could affect the arc voltage and send the tungsten up into the air or down into the work :)

For manual work though, It seems right to discuss if/why arc voltages are/should be required.

What say others?

By Lawrence (*****)

Date 10-05-2005 18:15

After having a closer look at D1.1 2005 I think you are perfect!

Table 4.5 14) PQR Essential Variable Changes Requiring WPS Requalificaton for SMAW says the following:
A change in the voltage for each diameter used by: To a value not recommended by the electrode manufacturer.

Even the most detailed manufacturers recommendations http://www.hobartbrothers.com/pdf/Pipemaster60.pdf do not include a voltage value to stay within.

If they do not recommend you can't list.

Does that make sense?

By jwright650 (*****)

Date 10-05-2005 18:29

I have N/A in that blank.
John Wright

By QCCWI

Date 10-05-2005 18:41

Here is another question. What do you have for travel speed? I put as req.(as required) as in you will move faster to run an 1/8" welds and slower if you wanted a 1/4 inch weld.

By jwright650 (*****)

Date 10-05-2005 19:20

Table 4.5(16) doesn't address travel speed for SMAW...I have N/A in that blank also. But do take notice of Note 3 at the end of Table 4.5.
Hope that helps,
John Wright

edit: I should say that travel speed isn't an essential variable unless you have heat input restrictions. Note 4 explains more about heat input.

By CHGuilford (****)

Date 10-05-2005 21:50

My understanding for D1.1 is that voltage and travel speed are N/A as non-essential variables. That is how I write my SMAW WPSs for D1.1.
D1.5 is a bit more clouded on the matter.
Basically, voltage and travel speed are N/A with the bridge code. However, many times I can't get my WPS approved if I leave those out. Customers want to know the heat input to expect from the WPS; mostly to assure there is enough rather than too much. We all understand that if you turn up the amps with SMAW the heat input goes up too, but sometimes welders might run fast travel speeds which puts the heat input too low as well as the weld size. Check out D1.5 Table 2.1 for minimum size of welds and note that those must be single pass (the notes provide some exceptions). Some customers have higher restrictions. For that reason, the volts and travel speed parameters are normally listed on the SMAW WPS even though they are not essential variables.

D1.1 has some limits in Table 5.8 but those are not quite as restrictive. The general thought (I believe) is that you must be getting enough heat input if your amps are set per manufacturer's recommendations and you weld profiles are acceptable with thorough fusion. That is based on ---what? 100+ years? of SMAW welding.

Chet