Submerged Arc Welding Optimization

by Naddir M Patel
(Calgary, Alberta)

Submerged arc welding is considered one of the most economical and efficient methods of welding.

Yet, in the search for fine tuning this process, obvious solutions have been ignored at the expense of exotic and expensive welding heads and power sources.

I came across such an item a few years back.

I ran a Submerged Arc Welding flux manufacturing facility in Mumbai, India (Silico Products). Optimizing clients SAW operations was therefore part and parcel of the sales efforts.

One thing I noticed that, in-spite of the SAW process being the most efficient weld metal depositor, there was a tremendous time loss between processes. There were also defects of "burn-through" because welders were not proactively measuring the inter-pass temperatures.

The ideal Poke-Yoke (fool proofing) solution was therefore to somehow control the heat input to the parent metal.

India, having a very cost conscious business style, opting for twin wire, tandem wire or Power wave were not viable options simply from the capital cost point of view.

Re-training welders and/or re-qualifying weld procedures would also pump up the capital costs of the project. This high capital investment would still have limited versatility in a typical multi-tasking weld shop with circumferential welds changing from 6" to 42" diameters in various plate thicknesses.

A literature survey, however, indicated that increasing electrode extension would seem to be the ideal remedy for increasing production rates and decrease the heat input.

1. WRC Jan 1956, "The effect of I²R heating on electrode melting rate" by Wilson and al.
   
2. Welding Journal April 1960, "Pre-heated welding wires" by Delong and al.

Whereas earlier attempts to increase electrode stick out (extension) were not very successful or consistent, we located a company by the name of Tipmate that made ceramic nozzles that guided the hot wire without jamming it.

It is a simple ceramic nozzle that is screwed onto the contact tip of the SA (submerged arc welding) head. The device allows electrode extensions of 3" or more without wire straying.

Importantly arc wandering was eliminated, weld penetration was adequate and weld beads were perfect. As welding parameters were not changed (except for a very small voltage increase) there was no need re-qualify weld procedures.

We found the ceramic nozzle directly screws onto the contact tip and can be easily and quickly changed based on our wire/electrode diameter. Guided by the vendor we increased the electrode extension in increments to yield deposition rate increases of 45% without any RT (radiographic testing) defects showing up.

As the heat affected zone was narrower, we designed narrower grooves for greater efficiencies and less distortion.

For normal welds we found a 2.4mm (3/32") electrode with a 56mm (2 1/4") extension could be used over a range of thicknesses. Heavy walled welds were completed with 4mm (5/32") electrode.

All these tests were conducted at various (welding flux) customer locations and a wide range of groove welding applications for both MS and SS (mild steel and stainless steel) materials, in a 350-650A range.

Although I am based in Canada now, I cannot disclose the companies' names for proprietary reasons.

In summary, with weld deposition rates increasing by 50% and minimal change in existing welding parameters, it became obvious that this was a force multiplier not only in terms of production throughput, but also in a drastic decrease in burn-throughs and subsequent repair....all with no capital expense.

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