The Complete Guide to Custom Stainless Steel Fabrication

Start with Material

Every fabrication project begins before the first cut, with material selection and traceability. The right grade depends on the service environment — austenitic like 304 or 316 for most work, duplex for high-strength corrosion resistance, specialty alloys for extreme service. Mill certifications travel with the material through the shop, and heat numbers get transferred to every sub-component so the finished assembly carries a complete lineage back to the mill.

Cutting and Forming

Plate and sheet come in via CNC laser, plasma, or waterjet depending on thickness and edge requirements. Tube and pipe cut on a tube laser or orbital saw with prepped weld ends. Forming is where dimensional control starts: press brake work for bends and flanges, plate rolling for cylinders and cones, heavy cylinder rollers for pressure-vessel diameters. Accurate forming here saves rework at fit-up and alignment later.

Welding Is the Hinge

Welding is where fabricated stainless either earns or loses its value. Northern runs GTAW for sanitary and code work, GMAW for high-deposition structural welds, and robotic cells for repeatable long seams. Every procedure is qualified to ASME Section IX, and every welder is current on the material, thickness, and position they’re assigned. The welding plan is written into the job traveler before the first arc strikes.

Finishing and Passivation

Raw stainless welds are not finished product. Surface discoloration, free iron contamination, and residual oxides from welding will corrode in service if left on the part. Finishing — grinding, polishing, and chemical passivation per ASTM A380 — restores the passive chromium oxide layer that makes stainless stainless. Skip it and the same alloy that was chosen for corrosion resistance will rust at the first weld.

Inspection and Documentation

Final quality is not an inspection step at the end — it’s the documentation package assembled from every stage: material certs, weld maps, NDT reports (radiographic, PT, UT as specified), dimensional inspection records, and passivation confirmation. On ASME code work, the package is reviewed and signed by an authorized inspector before the code stamp goes on. That package is what the customer pays for, and it’s what separates fabrication from just welding parts together.