Welding stainless steel: heat input, preheating and interpass temperature

By Robert Lahnsteiner, International Welding Engineer (IWE) · Updated: November 2026

Why stainless steel tolerates little heat

Austenitic steels conduct heat poorly and expand a great deal. The heat stays at the weld, and the component distorts more than carbon steel. The rule is therefore: limit the heat input, keep to the interpass temperature, and as a rule do not preheat.

According to DVS 0931, too much heat can lead to the following damage, depending on the material:

more distortion and residual stresses,
undesirable precipitates such as carbides or sigma phase,
coarse grain and loss of toughness in the heat-affected zone,
hot cracks, especially in fully austenitic steels,
higher susceptibility to intergranular corrosion,
more oxidation and temper colours.

The material properties compared are given in What makes stainless steel stainless, the causes of hot cracks in Microstructure, delta ferrite and hot cracking.

Calculating arc energy and heat input

The arc energy is the electrical power of the arc per centimetre of weld. The heat input is the part of it that actually goes into the component. To obtain it, the arc energy is multiplied by the thermal efficiency of the process.

Arc energy E [kJ/cm] = U [V] · I [A] · 60 / (v [cm/min] · 1000)

Heat input Q [kJ/cm] = k · E

For gas metal arc welding, DVS 0931 assumes an efficiency of k = 0.8. In TIG welding it is considerably lower, about 0.6 according to EN 1011-1. For manual metal arc welding it is also 0.8, for submerged arc 1.0.

MAG example: 24 V, 180 A, 30 cm/min gives E = 24 · 180 · 60 / (30 · 1000) = 8.6 kJ/cm and Q = 0.8 · 8.6 ≈ 6.9 kJ/cm.

This can be calculated with the Heat input calculator.

How to keep the heat input low

weld faster,
reduce current and voltage,
use thinner wire, for example for vertical-up welds,
stringer beads instead of wide weave passes, more passes with a smaller cross-section.

Preheating and interpass temperature

Austenitic steels are generally not preheated. The interpass temperature is more important: the next pass may only be welded once the weld has cooled below the limit.

Material group	Preheating	Interpass temperature	Source
Austenitic (1.4301, 1.4404, 1.4571 …)	no; only in special cases up to 150 °C	150 to a maximum of 180 °C	DVS 0931
Fully austenitic (1.4539 …), nickel base	no	100 to 120 °C	DVS 0931
Duplex (1.4462, 1.4362 …)	usually no; from about 10 to 20 mm wall thickness 80 to 120 °C	maximum 150 °C (DVS 0931) or 250 °C (DVS 0946)	DVS 0931, DVS 0946
Super duplex (1.4410, 1.4501 …)	usually no	maximum 150 °C	DVS 0946
Soft martensitic (1.4313)	from about 30 mm at least 100 °C	100 to 150 °C	DVS 0931
Ferritic (1.4016, 1.4512 …)	multi-pass, depending on thickness 200 to 300 °C	–	DVS 0931

Guide values. The recommendations of the steel and filler metal manufacturers and the welding procedure specification take precedence. For duplex, the two DVS technical bulletins give different limits. To stay on the safe side, work with 150 °C.

Measure, don’t guess: the temperature is checked next to the weld with a contact thermometer or temperature-indicating crayon.
Do not cool artificially: according to DVS 0946, compressed air or water between passes is expressly not permitted for duplex. Draughts and cold also affect cooling.
Do not preheat fully austenitic steels: with steels such as 1.4539, the risk of hot cracking otherwise increases, especially when welding thin sheet without filler metal.
Ferritic steels tend towards coarse grain and chromium carbides in the heat-affected zone. They are welded with the smallest possible weld pool, i.e. with thin electrodes and low arc energy.

Preheat temperatures for unalloyed and low-alloy steels are provided by the Preheat temperature calculator. It is not intended for stainless steels.

Duplex: neither too much nor too little

Duplex steels have a heat window. If the heat is too low, the weld cools too quickly, too little austenite forms, and toughness and corrosion resistance drop. If it is too high, sigma phase and other intermetallic precipitates are a risk.

Arc energy according to DVS 0946: duplex 5 to 25 kJ/cm, super duplex 2 to 15 kJ/cm.
Austenite content in the weld metal: 30 to 70 % if no solution annealing is carried out.
Nitrogen in the steel and in the shielding gas promotes the formation of austenite. Modern duplex steels usually contain over 0.15 % N and therefore hardly need preheating. According to the ISER information sheet, there is hardly any risk of too little austenite with the usual arc processes.
Plan the welding sequence so that the parts can cool between passes.

The cooling time can be estimated with the t8/5 cooling time calculator. More on the gases and the microstructure in Duplex and super duplex.

Limiting distortion

Above all, little heat and short tack spacings help against distortion.

weld with low arc energy,
dissipate heat via copper bars, which also support the root,
weld in fixtures,
tack more closely than with carbon steel,
weld symmetrically and with backstep welding so that the stresses balance out.

Tack spacings by sheet thickness: Joint preparation and tack welding.

Heat treatment after welding

Austenitic welded joints are generally not heat-treated, because undesirable precipitates can form during annealing.

For duplex steels, only solution annealing comes into question, if at all. According to DVS 0946, this is done at 1020 to 1050 °C with a holding time of 5 minutes after through-heating, followed by quenching in water. For ferritic and martensitic steels, the heat treatment depends on the material and filler metal.

Frequently asked questions

Do I have to preheat stainless steel?

Austenitic steels generally not. Exceptions are thick ferritic chromium steels, soft martensitic steels from about 30 mm and occasionally thick duplex components.

How hot may the weld be before the next pass?

For standard austenitic grades 150 to 180 °C, for fully austenitic and nickel-base grades 100 to 120 °C, for super duplex 150 °C.

May I cool the weld with water?

Not with duplex; DVS 0946 rules it out. With austenitic grades it is metallurgically less critical, but the water must not leave residues such as chlorides or dirt in the weld.

Why does heat input matter more than current?

Because the speed is also decisive. The same current brings far more heat into the workpiece in a slow weave pass than in a fast stringer bead.