Cutting stainless steel: laser, plasma, abrasive waterjet
Laser cutting of stainless steel gives a narrow kerf and a neat edge on thin and medium metal, plasma is faster on thick metal, and an abrasive waterjet does not heat the metal at all.
The choice of method is determined by the thickness, the requirements for the edge and what happens next: if the edge goes for welding or into an aggressive environment, the condition of the cut is more important than speed.
Below — a comparison of the methods, the specifics of laser, plasma and abrasive waterjet, and how to calculate the cost for a task without illusions.
What stainless steel is cut with
Stainless steel is cut by thermal methods — laser and plasma — by abrasive waterjet and mechanically: with a band saw, a cutting disc, a guillotine. Thermal methods are faster but leave a heat-affected zone and scale. Mechanical methods do not heat the metal but produce a burr and are inferior in speed on a complex contour.
| Method | Metal | Edge | Heating | Where it is better |
|---|---|---|---|---|
| Laser | sheet of small and medium thickness | narrow, even | local | complex contour, precise parts |
| Plasma | medium and large thickness | wider, with scale | noticeable | structures, thick sheet |
| Abrasive waterjet | any thickness | matt, without scale | none | parts where heating is unacceptable |
| Band saw, disc | pipe, round bar, profile | with a burr | local | cut-to-length cutting of long products |
| Guillotine | sheet | even, but with a kink | none | straight cuts, blanks |
The first thing looked at when choosing is what will happen to the edge next. For welding, the edge is prepared in the same way regardless of the method: scale and the depleted layer are removed. If the edge remains visible and is not ground, a method is chosen that gives a surface for the required class.
Laser
Laser is the main method for sheet of small and medium thickness. Fibre machines cut stainless steel in a shielding gas, and the result depends on the gas. With nitrogen, a light edge is obtained without oxidation, suitable for welding and finishing. With oxygen, cutting is faster, but the edge becomes covered with scale and darkens. With air, work is done where economy matters and a darker edge with a film is acceptable.
| Gas | Edge | Speed | When it is chosen |
|---|---|---|---|
| Nitrogen | light, without scale | lower | welding, finishing, food parts |
| Oxygen | dark, with scale | higher | rough cutting, structures |
| Air | with a film | medium | non-critical parts, gas savings |
Laser gives a narrow kerf and a small heat-affected zone, so the part distorts less. But on thick metal productivity drops, and the edge requires more power and better focusing. A common mistake is to cut thick sheet with oxygen and then weld along the oxidised edge without cleaning. It is exactly such an edge that causes corrosion along the seam.
Plasma
Plasma takes on the thickness at which laser is already slow. The equipment is simpler and cheaper to maintain, the cut is fast, but the edge is wider and the heated zone is larger. On stainless steel, plasma leaves scale and a nitride layer, which must be removed before welding.
Plasma is convenient for structures that do not need jeweller's precision: base plates, gussets, blanks for further machining. For visible parts and thin sheet it is not suitable: the edge will have to be ground, and thin metal is easy to overheat and distort. When working with plasma it is important to monitor the consumption of the plasma gas and the condition of the nozzle: a worn nozzle produces a slanted cut and dross.
Abrasive waterjet
An abrasive waterjet cuts with a jet of water with abrasive. The metal does not heat up, there is no heat-affected zone, so the method is used where heating is unacceptable: thick sheet, parts with dense geometry, materials that cannot be distorted thermally. The surface of the edge is matt, without scale, but with a slight taper.
The limitations are speed and consumables. The cut is slower than laser, the abrasive is consumed constantly, and the edge remains wet and requires drying and cleaning. On the other hand, an abrasive waterjet works equally well with any metal and does not change the properties of the edge. If the part is welded afterwards, the edge is still cleaned of abrasive: its residues interfere with the formation of the seam.
What is cheaper for the task
The cost of cutting is determined not only by the method but also by what happens afterwards. The full chain must be compared: cutting plus cleaning of the edge plus possible rejects. A laser with nitrogen is more expensive to run, but often removes the need for cleaning and pickling. Plasma is cheaper on thick metal, but adds a cleaning operation. An abrasive waterjet is more expensive in consumables, but it does not heat the part and does not produce scale.
| What influences | How to take it into account |
|---|---|
| Thickness | laser is advantageous on thin, plasma and abrasive waterjet — on thick |
| Cut length and contour | complex geometry increases the role of the precision of the method |
| Requirement for the edge | a clean edge saves cleaning and pickling |
| Serial production | nesting with minimal waste reduces metal consumption |
| Post-processing | cleaning, straightening, removal of scale go into the same estimate |
| Gas | nitrogen is more expensive than oxygen but gives an edge for welding |
You can find references for the cost of cutting in the section prices and quotations: there you can also see that the total depends on the batch and urgency. If bending is planned after cutting, the order of operations is better thought through in advance — about this in the article bending stainless steel.
Frequently asked questions
What is better for cutting stainless steel
It depends on the thickness and the edge. Thin and medium sheet, a complex contour — laser. Thick metal and structures — plasma. Parts where heating is not allowed — abrasive waterjet. Long products are more convenient to cut mechanically.
What is stainless steel cut with on a laser: oxygen or air
Oxygen is faster, but the edge oxidises and darkens. Air is more economical, and the edge acquires a film. For welding and finishing, nitrogen is used: it gives a light edge without scale.
Why is the edge dark after laser cutting
Because the cut was made in oxygen or air. The active gas oxidises the metal, and scale remains on the edge. It is removed mechanically or by pickling before welding, otherwise corrosion will start from the edge.
Is it necessary to clean the edge after plasma
It is essential before welding and before contact with an aggressive environment. Plasma leaves scale and a nitride layer that destroys the passive film. Cleaning restores the normal composition of the surface.
Abrasive waterjet or laser for thick sheet
For large thickness, an abrasive waterjet is often more advantageous: it does not heat the metal and does not change the edge. A laser loses speed on thick metal, and the edge requires more attention.
How cutting affects corrosion resistance
Thermal methods change the composition of the surface layer and leave scale, where chromium is bound and does not work. That is why, after laser and plasma, the edge is cleaned and pickled if necessary.
Can stainless steel be cut on a guillotine
Yes, for straight cuts of sheet. The edge comes out even, but on thick austenite a kink is possible, which is then removed. The blades and the table must be separate from those used for carbon steel.
What to do next
Before cutting, decide on the thickness, the contour and the requirements for the edge — the cutting method and the amount of cleaning depend on this. On the GCX exchange you can obtain sheet, pipe, round bar and angle of AISI 201, 304, 316L and 430. An order specifies the grade, the size, the surface and the shipment week.