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Welding S235JR structural steel isn’t tricky, but a few habits can save you from weak joints or hidden cracks. This mild carbon steel (similar to European EN 10025 grade) is widely used for beams, frames, and supports.

Start with a clean surface – remove rust, oil, and mill scale. For most shop welding, MAG (gas metal arc) or SMAW (stick) works fine. Use filler metals like G 42 2 M or E7018; they match S235JR’s strength and keep hydrogen low. Preheating? Usually not needed under 20mm thickness, but if the steel is chilly or damp, warm it to 50–80°C.

Keep heat input moderate – too much can warp thin sections or coarsen the heat-affected zone. For multi-pass welds, let each cool slightly between passes. No post-weld heat treatment is required for most jobs, but peening can relieve stress.

Common mistake: using old, wet electrodes. Store them dry. Also, avoid excessive weaving – stringer beads give better fusion. After welding, inspect for undercut or porosity. With these steps, your S235JR weld will be as strong as the base metal.