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Corten is a trade name for weathering steel. In other words, it's steel that still goes rusty, but it rusts a nice color, and it resists the spalling black lumps that fall off ordinary mild steel. Corten contains small amounts of chromium, nickel, and copper, which impart the weather resistance. It is used mostly in structural applications. Many buildings appear to have been painted orange but, in reality, are untreated Corten steel.
Critical Laser Parameters for Corten Steel
Cutting Corten requires a different approach compared to standard mild steel due to its alloy content.
- Cutting Speed: We typically run Corten with slightly lower cutting speeds than mild steel of the same thickness. The alloy content increases melt viscosity, so if we move too fast, we end up with dross and rough edges.
- Laser Power: Power needs to be stable and sufficient to maintain a consistent kerf. Too much power causes excessive oxidation and edge rounding, while too little leads to incomplete cuts.
- Focus Position: This is critical. We usually set the focal point slightly below the surface to improve melt ejection and edge straightness, especially on plates above 5 mm.
Gas Selection: Oxygen vs. Nitrogen
This is where most edge-quality differences come from. In our experience, oxygen and nitrogen serve very different purposes when cutting Corten steel.
- Oxygen (O₂): When we need higher productivity and don't mind a darker, oxidized edge, we use oxygen.
- Pros: Oxygen reacts exothermically with the steel, adding heat to the process and allowing faster cutting speeds at lower laser power.
- Cons: This reaction forms a thicker oxide layer on the cut edge, which can be an issue if the part will be welded or coated later.
2. Nitrogen (N₂): For applications where edge cleanliness really matters, we switch to nitrogen.
- Pros: Nitrogen is inert, so it doesn't react with the molten steel. The result is a brighter, cleaner edge with minimal oxidation and better dimensional accuracy.
- Cons: The trade-off is higher gas pressure and increased operating cost, but for architectural or visible components, it's usually worth it.
Pro Tip: We pay close attention to gas pressure and nozzle condition. High-pressure nitrogen with a clean, centered nozzle makes a huge difference in dross-free cutting. Even small misalignments can ruin an otherwise perfect parameter set.
Welding Considerations After Cutting
When welding Corten, the precautions are similar to mild steel, except that you may need a special filler material to produce the weathering steel weld.
- For Thickness ≤ 10 mm (Single Pass): You can use an E7018 or SG2 MIG wire. This is because you will get enough dilution from the plate to render the weld weathering.
- For Thickness > 10 mm (or Multi-Pass): You need to use a filler containing approximately 1% Nickel and 0.5% Copper, or one containing 2.5% nickel.
In short, clean edges on Corten steel come from balancing speed, power, focus, and most importantly, choosing the right assist gas for the job.
Need Laser-Ready Corten Steel?
Don't let warped plates ruin your cutting parameters. Promisteel supplies tension-leveled, stress-relieved Corten Steel Sheets designed specifically for high-precision laser cutting.
