Page 64 - SSAB Welding Handbook Edition 2

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11.0 Cutting of Weldox and Hardox Welding handbook

When using torches, fig 11.7 and fig. 11.8, it is of
importance to not overheat. The temperature of
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the cut edge must not exceed 700 °C, preferentially
300 to 500 °C. Normally post heat treatment using
torches is done manually and in this case it is of im-
portance to know how to control the temperature.
This is done by looking at the color of the cut edge
at the torch, it should just start to glow (very dark
red). If the color is bright sherry or dark orange the
temperature is too high and the postheating will not
Fig. 11.6: Preheating lances. be successful.

Electrical mats is a slow preheating method, so to
preheat to 150-200 °C, a good practice is to preheat
overnight and begin the cutting operation the next
morning.

Postheating

Postheating is another method to avoid cut edge
cracking. This can either be done in a furnace or Fig. 11.7: Color of the cut edge behind the postheating torch.
with torches. It is important that the postheating
process takes place as soon as possible after the part
has been cut out. The time between start of
cutting procedure and start of postheating
procedure should be as short as possible and never
exceed 60 minutes.

Using furnaces, the temperature should not exceed
the maximum allowable temperature listed in tables
11.4–11.5 and the plate has to stay in the furnace
until it reaches this temperature. Depending on the
thickness of the plate the time will vary, but as a
general rule of thumb the time of postheating should
be at least 5 minutes for every mm of plate thickness
(i.e. 50 minutes for a 10 mm thick plate). Postheat-
ing in a furnace will allow more hydrogen migration Fig. 11.8: Manually postheating.
from the HAZ as well as a small reduction of tensile
stresses in the HAZ. It is also possible to control the temperature with
an infrared thermometer, pointed directly to the cut
edge at the flame see fig. 11.9.

64 This handbook contains general suggestions and information without any expressed or implied warranty of any kind. SSAB hereby expressly disclaims
all liability of any kind, including any damages, in connection with the use of the information and for their suitability for individual applications.
It is the responsibility of the user of this brochure to adapt the recommendations contained therein to the requirements of individual applications.