How to Weld: Metal Identification Basics

Before you learn welding techniques, you need a basic understanding of the materials you’ll be working with.

| November 16, 2012

Almost anyone can learn the craft of welding, Andrew Pearce argues in his straightforward and handy guide to do-it-yourself metal work, Farm and Workshop Welding (Fox Chapel Publishing, 2012). In this excerpt from the book’s introduction, Pearce gets things started by explaining the compositions of different alloys and the properties of different metals. 

Buy this book from the MOTHER EARTH NEWS store: Farm and Workshop Welding.

What Is Welding?

It’s the process of joining materials using heat. In fusion welding, joint components are heated until they melt together or are positively fused by pressure. Blacksmiths use heat and hammer blows, but here we’re more concerned with getting heat alone to do the work.

This heat will come from either an electric arc, a gas flame, or in the case of plastics, from a hot air gun. Filler is usually added to the joint from an electrode or separate rod. Non-fusion welding techniques like braze (or bronze) welding and soldering use heat too, but not enough to melt the metals that form the joint.

Metal Identification

Although accurate identification of steel is a complex business, the main classes can be sorted out with a file, a grinder and some basic ground rules. Wrought iron is no longer very common, but in the past has been used extensively for chains and hooks. It’s very low in carbon, and malleable. Mild steel is the common user-friendly stuff. It doesn’t usually harden when heated and cooled, and is easy to bend and weld. Black mild steel is what you’d normally buy: as strip it comes with rounded edges and retains its coating of mill scale from hot-rolling. Bright mild steel in its flat form has square edges, is shiny and is more accurately sized than mild steel. It’s made by cleaning and cold-rolling black mild steel, leaving the metal stronger but less ductile.

Silver steel looks like bright steel but is much harder. It contains chromium but, oddly, no silver and is usually sold in short lengths. Black and bright mild steels are easily filed and give off long, light yellow sparks under an angle grinder. Both are readily weldable. Silver steel is not.

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