1. Match the Cutting Parameters to the Thickness
The first rule of corten cutting is that one setting does not fit all thicknesses. Cutting speed, gas pressure and nozzle size must be adjusted according to the plate thickness: thin plate needs higher speed and lower gas pressure with a smaller nozzle, while thick plate requires reduced speed, higher gas pressure and a larger nozzle to maintain a clean kerf and full penetration. Cutting parameters should be taken from the equipment manufacturer's tables for the specific process, whether oxy-fuel, plasma or laser, and then verified on a sample of the actual plate. The alloying elements of corten steel can slow the cut compared with mild steel, so the speed should be tuned by observing the drag lines on the cut edge.
2. Keep the Cut Face Perpendicular
Poor edge squareness is one of the most common complaints. To correct it, minimise the number of horizontal and vertical cuts that change the torch attitude, and use a square to check and adjust the verticality of the cutting torch before starting. With the torch perpendicular to the plate surface, the cut face is square, which is important for welded joints and for edge quality in visible architectural parts. Where a slight bevel is unavoidable with the selected process, it should be consistent and within the tolerance of the project specification, and the torch offset should be set to put the acceptable side of the tolerance on the finished part.
3. Piercing and Hole Cutting Rules
Hole cutting requires separate control. When cutting holes, reduce the size of the inner hole and the perimeter as needed to hold the dimensional accuracy of the hole and the surrounding material. For piercing (starting the cut in the middle of the plate), choose a sensible blasthole and adjust the cutting speed and the oxygen regulating valve carefully during the piercing sequence. Two practical limits apply: if the hole diameter is smaller than the plate thickness, or if the plate thickness exceeds about 120 mm, piercing and cutting the hole directly is not suitable; the hole should be drilled, or a pilot hole and a different starting method should be used.
4. Controlling Distortion and Arched Cuts
Traditional cutting sequences can produce arches and distortions, especially when the heat input is uneven or the part is slender. The heat of the cut expands the steel locally, and when the part cools it can bow or warp. The solution is to balance the heat input: cut in an order that keeps the heat spread across the plate, use water-cooled cutting tables where possible, and for slender pieces use bridge cutting, in which small connecting bridges are left between adjacent parts during cutting. The bridges hold the parts in position and prevent distortion; they are removed after cutting and the stubs are ground flush. This technique effectively controls the quality of long, thin components.
5. Edge Quality and Finishing
After cutting, the edge quality determines the next operation. Dross on the underside should be removed while it is still warm, and the oxide layer on the cut face should be ground off where the edge will be welded, painted or left visible. For architectural corten panels, the cut edges are often ground and polished to blend with the patina. If the cut edge shows drag lines or a pronounced taper, the speed or the gas mixture should be adjusted for the next part. All finished parts should be checked against the drawing for dimensions, squareness and edge condition before release to the next process.
Frequently Asked Questions
Why is my corten steel cut edge not square? The torch may not be perpendicular to the plate. Check and adjust the torch verticality with a square, and verify that the plate is level. Speed and gas pressure that are too high or low can also increase taper.
When is piercing not possible on corten plate? Piercing is not suitable when the hole diameter is smaller than the plate thickness, or when the plate is thicker than about 120 mm. Drill the hole or use a pilot hole and a different starting method instead.
What is bridge cutting? It is a technique where small connecting bridges are left between adjacent slender parts during cutting, so the parts stay in position and do not distort. The bridges are removed after cutting and ground flush.
How do I prevent distortion when cutting corten steel? Balance the heat input with a proper cutting sequence, keep the heat spread across the plate, use water-cooled tables where possible and apply bridge cutting for slender parts.
Does corten steel need different cutting settings than mild steel? Yes. The alloying elements slow the cut, so the speed, gas pressure and nozzle are adjusted per thickness, and the settings should be verified on a sample of the actual plate before production.
What should be done with the cut edge before welding? Remove dross and the oxide layer from the cut face by grinding, so that the weld joint is clean and the edge is prepared for sound fusion.
