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Welding Dissimilar Metals: Carbon Steel to Stainless Steel

Blog | February 28th, 2018

This next topic happens when cost factors influence engineering procedures. Straight to the point, we’re talking about a structural fabrication project that entails the welding of dissimilar metals. The alloys in question are both steel, but they exhibit certain material differences. Included with the stainless steel parts, there’s a substantial quantity of carbon steel in that project. The question is, what’s the established method for welding carbon steel to stainless steel?

When Stainless Steel Won’t Work 

Ideally, we’d like to use stainless steel throughout the project. The alloy is extremely corrosion-resistant. Used in marine applications, an added layer of chromium oxide makes the metal a natural choice, even when the environment is loaded with salty air. However, massive stainless steel components are exorbitantly expensive, which is why a cost-conscious client might opt for a less costly candidate, one that we find in the form of carbon steel. Remember, the two alloys are both structurally hard. They’re also both corrosion-resistant, although stainless steel has the edge regarding this particular feature.

Welding Dissimilar Ferrous Alloys: Carbon and Stainless Steel 

The selection of a superior filler is importance. Address this issue by selecting stainless steel electrodes. An E309 filler metal works well here, so call in an FCAW rig (Flux Cored Arc Welding) rig, fit the filler rods, and tick the equipment setup box. Alternatively, GTAW (Gas Tungsten Arc Welding) gear can be considered, but do remember that this option is a lot slower than FCAW and that it uses a consumable tungsten electrode, not the required stainless steel rod. Now, before the carbon steel to stainless steel welding operation commences, the fuse zone edges need some prep work. Bevel those edges. This machining stage maximizes the weld surfaces. A quick glance at the checklist tells us that the welding equipment is ready and the weld surfaces are prepped. Turn on the equipment, bring the temperature level up, and closely monitor the applied heat. If too much heat is applied, the required corrosion-resistance feature, a desirable property in a marine-grade fabrication alloy, could be curbed.

No precise temperature levels have been supplied today. That’s because of the carbon content in these alloys. More carbon means more thermal energy, a shift in applied welding energy that can only be addressed during the welding process. If at all possible, select a stainless steel material that closely matches its carbon steel companion piece. In this way, the regulated weld temperature accounts for each alloy piece’s associated heat sensitization range. When those ranges are closely matched, it’s easier for the welder to maintain the required corrosion-resistance level in both structural segments.

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