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Changing Over to Metal-Cored Wire in SAW
Q: One of my vendors recently approached me about replacing the solid wire in my submerged arc welding (SAW) application with a metal-cored wire. Should I consider making the change?
A: Depending on your application, you should certainly consider making the change. Metal-cored wires can provide substantial benefits in SAW, including welding structural steels, pipes, boil and pressure vessels, ship plates, cast steels, and fine-grained steels on carbon and certain low-alloy steels.
Several classifications of metal-cored wires have been developed that can be substituted anywhere a corresponding solid wire is used (for example, EM12KS metal-cored wire for EM12K solid wire).
With a solid wire, the welding current is carried by the entire cross section of the wire, and the resulting molten droplets are large. Metal-cored wire produces finer droplets and a less turbulent weld pool because the current is concentrated on the outside sheath of the tubular wire. Because of the spray transfer pattern, metal-cored wire can bridge gaps and help eliminate cold lap. It is ideal when fit-up is less than optimal. In addition, because of its broader penetration profile, metal-cored wire can weld thin materials with less chance of burn-through.
Perhaps the best reason to use metal-cored wire with the SAW process is the high deposition rate. With the same flux, welding current, and electrical stick-out, metal-cored wire can allow you to either reduce the number of passes or increase your travel speed. Depending on thickness, speed increases of 10 percent to 15 percent are not uncommon.>/p>
Finally, there is a cost difference between using metal-cored and solid wires. It is important to distinguish between product price and total cost. The product price is what you pay upfront, typically in dollars per pound of wire. The total cost is the overall expense of using the product, typically in dollars per pound of deposited weld metal. Total cost takes into account the price of the wire and all other welding costs, such as flux and labor.
Labor accounts for up to 85 percent of the cost of a weld. Because of its higher deposition rates, metal-cored wire can provide labor cost savings that more than offset the higher price of the wire. So while the price of metal-cored wires is typically higher than solid wire, your total cost may actually be lower. As a rule of thumb, you will have the greatest chance of seeing a total cost reduction with metal-cored SAW wires if you are welding on thin steel at high speeds.
This article originally appeared in The WELDER magazine.
It is reprinted here with permission of the Fabricators & Manufacturers Association, Intl.