SMAW Voltage?

Date 07-31-2003 23:10

I don't have an answer , rather a question. Why do you need to get precise information for a manual process?
I mean no disrespect here, just curious because the SMAW machines I'm used to are not that precise. Most don't even have meters, just scales with marks the welders made when they found a good setting.

Even the D1.5 Bridge code doesn't list voltage as an essential variable for SMAW, nor is a PQR required for the listed SMAW electrodes. So I was just wondering what kind of interesting project you're have?

Chet Guilford

By William T (*)

Date 08-01-2003 13:41

When the governing construction Code requires impact testing, ASME IX specifies that an increase in heat input becomes an essential variable.

I'm from the great white north, Alberta, Canada. We do alot of low temp work with mandatory impact testing.

Per ASME IX, Heat input is measured as, Joules/in, can be calculated with the following formula, Amps X Volts X 60 / IPM;

Or,

An increase in heat input is defined as "an increase in size or a decrease in length of weld bead per unit length of electrode."

Typically during qualification of low temp procedures the amperage, voltage and travel speed are documented and used to calculate the maximum heat input qualified.

The method of selecting the specific voltage to be used in the calculation is not well defined. Most procedure writers that I have talked with use calibrated voltmeters. They take the average reading per pass. Then select the pass with the combination of amperage, voltage, and travel speed that results in the highest number of Joules/in to limit the upper end of their heat input range.

The table I want to provide is a reference tool to provide a reasonably accurate indication of compliance for our Welders and Inspectors.

Note: We have 39 welding machines (23-pheonix 456, 4-dimension 652, 4-XMT 304's, 4-dimension 400's, 4-aerowaves) in our shop that have continous voltage readout gauges.

Any good way to select a reasonably accurate representative average for voltage per specific AWS electrode class, diameter and amperage?

By jwright650 (*****)

Date 08-01-2003 14:01

William,
Would "Tempilstik" sticks work to show that your max temp has not been reached during interpasses? Make a mark outside of the joint with a temp stick that is just under your max temp and when the joint gets hot enough to melt the mark stop and let it cool before continuing. The temp sticks are fairly accurate within 1%. You can get them in 103 systematically spaced temp ratings from 100F(38C)-2500F(1371C).
John Wright

By William T (*)

Date 08-01-2003 14:20

We do monitor interpass with tempilsticks. The heat input requirement is in addition to interpass.

Thanks for the thought though.

I don't know that anyone will be able to give me a good published voltage per amperage average for SMAW. Voltage does vary. However that is what I'm looking for if it does exist.

By JTMcC

Date 08-01-2003 22:38

Those of us that regularly take SMAW pipe welding tests know that the inspector will record amp and volt readings on every pass. And I have had them tell me to turn it down, as I was out of the allowable range.

JTMcC.

By Niekie3 (***)

Date 08-02-2003 07:56

Hi William T

You will never be able to get a direct correlation between Volts and Amps, because the voltage is a function of the arc length. (For a CC power source like used for SMAW.)

The voltage is therefore more of a "welder technique" variable that anything else. Having said this, there are relatively narrow ranges of voltage used while welding with SMAW, because the arc legnths do not vary THAT much between welders. This is obviously a generalisation.

I do believe that your project is a very worthwhile exercise though, and think that maybe you need to just take typical V ranges for particular electrode sizes and possibly list the highest and lowest values and allow the welders to interpolate the values between these.

You also mentioned the machines with the V meters on the machine. Depending on the length of your cables, these values can be rather far off the real values close to the arc. You will have to take this into account also!

When you get to the point where you have worked out some usefull tables, please let us know. I personally would like to have a copy, if at all possible.

Regards
Niekie Jooste
Fabristruct Solutions

By sayeeprasad (*)

Date 08-17-2003 10:26

In addition to what Niekie has already said, I would like to add that it is very difficult to make a table for heat inputs because two of the three variables are related to the welder skill, voltage and travel speed. As metioned, voltage varies with the arc length for a CC power source and there is a considerable variation in the arc voltage for different welders. However If I were in yopur place, I would take the second option for maeasuring/monitoring heat input."An increase in heat input is defined as "an increase in size or a decrease in length of weld bead per unit length of electrode." " This parameter is also called the ROL(Run Out Length) and is the length of weld metal bead deposited per unit length of electrode consumed. This is easy to understand as well as measure for both welders and inspectors alike. If you still need the typical voltages for electrodes(They are also a function of the classification), send me your email and I'll send the details by email. Please specify the AWS classification and sizes you are using in that case.