Cold cutting instead of flame cutting: pipe cutting without a heat-affected zone
Flame and plasma cutting are fast and available everywhere – but on pipelines made of creep-resistant, stainless or high-strength steels they create follow-up work: preheating before the cut, hardening and oxide at the cut edge, regrinding before welding and flying sparks in the plant. Machine cold cutting cuts and bevels in almost a single operation, without heat input. This page shows when that pays off.
What thermal cutting leaves at the cut edge
- ▸Heat-affected zone: Next to the kerf, the material briefly becomes very hot and cools quickly. In hardenable steels, this produces a hardened, brittle edge.
- ▸Oxide and slag: The cut face is scaled and must be ground to bright metal before welding.
- ▸Dimensional deviation: Hand-guided cuts are rarely exactly square; bevel and root face must be reworked before the joint fits.
- ▸Sparks and fumes: In operating plants and hazardous areas, every flame requires a permit, gas testing and a fire watch.
Creep-resistant steels: preheating even before the cut
With creep-resistant CrMo steels, the preheating requirement does not only apply to welding. High-alloy grades such as X11CrMo5 (P5) or X10CrMoVNb9-1 (P91) are also brought up to temperature before flame cutting, otherwise there is a risk of hardening cracks at the cut edge. With 16Mo3 and 13CrMo4-5, flame cutting is followed, depending on the specification, by prompt welding or stress relieving.
With cold cutting, this step is eliminated: there is no heat-affected zone, the cut edge retains the microstructure of the parent metal, and the bevel can be welded directly – preheating is then only required according to the welding procedure specification.
Stainless steels and duplex
With stainless steel and duplex, the heat of thermal cutting affects the corrosion resistance at the cut edge: temper discolouration and an altered surface zone form, which must be removed mechanically. Cold-cut and bevelled edges do not need this rework – all that matters is clean tools reserved for stainless steel, so that no foreign iron is introduced.
Comparison: thermal or cold
| Criterion | Flame cutting / plasma | Machine cold cutting |
|---|---|---|
| Heat-affected zone | yes, with possible hardening | no |
| Preheating before the cut (creep-resistant steels) | required depending on material | not required |
| Rework before welding | grinding, adjusting bevel and root face | bevel produced in the same operation |
| Dimensional accuracy | depends on hand and guidance | square, repeatable |
| Sparks in the plant | yes – permit and fire watch | spark-free possible |
| Speed of the cut itself | high | lower, but without follow-up work |
Simplified comparison. Which process is permitted is determined by the welding procedure specification, pipe class and operator.
When cold cutting pays off in particular
- ▸Creep-resistant steels: 16Mo3, 13CrMo4-5, 10CrMo9-10, P5, P91 – no preheating and no rework.
- ▸Stainless steel, duplex, nickel alloys: no temper discolouration, no damaged surface zone.
- ▸Work in operating plants: spark-free, without a hot work permit for the cut.
- ▸Thick-walled pipes and large nominal sizes: cutting and bevelling in a single operation, including complex joint shapes.
- ▸Replacing pipe sections: exact length and bevel, so that the closure piece fits without rework.
We cut and bevel pipes by machine directly on the line – cold, dimensionally accurate and with the joint shape from your welding procedure specification, including on unequal wall thicknesses and on branches.
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Frequently asked questions
Is cold cutting slower than flame cutting?
The cut itself takes longer. Because the bevel is produced in the same operation and preheating, grinding and rework are eliminated, the joint is often ready for welding sooner overall – especially with creep-resistant and stainless steels.
Can cold cutting also be done during operation or in hazardous areas?
Spark-free cold cutting is also possible in hazardous areas or close to operating equipment. The prerequisites are the operator’s permits and a line that is depressurised, drained and isolated – for work on lines under pressure, there is hot tapping.
Which joint shapes are possible?
All common shapes to EN ISO 9692-1 and ASME B16.25, i.e. V, Y, U and compound bevels, plus matching of unequal wall thicknesses by internal counterboring. You will find the overview of joint shapes on our pipe bevelling page.
General description based on practical experience, without guarantee. The welding procedure specification, pipe class and operator requirements are authoritative.
Cold cutting and bevelling pipes – directly on the line
Send us the material, diameter, wall thickness and joint shape – we will tell you how quickly the bevels will be ready for welding.