Page 67 - SSAB Welding Handbook Edition 2

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Welding handbook 11.0 Cutting of Weldox and Hardox

Cutting of small parts avoided by submerged cutting at low cutting speeds
or with a post heat treatment of the cut parts. The
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When small parts are cut, the heat supplied by the postheating can be done either with a torch or in a
cutting torch and by preheating will be accumulated furnace.
in the workpiece. The smaller the size of the cut part
the greater the risk of softening. When oxy-fuel is
used for cutting 30 mm or thicker plate, the rule of
thumb is that there is a risk of loss of hardness of
the entire component if the distance between two
cuts is less than 200 mm. For thicknesses below 30
mm it is possible to cut smaller parts without loss of
hardness. A convenient way to determine if the piece
is too small is to measure the temperature of the part
directly after it has been cut out. Maximum allowable
temperatures can be found in table 11.4-11.5.

The best way of eliminating the risk of softening is Fig. 11.12: Submerged cutting.
to use cold cutting methods, such as abrasive water
jet cutting. If thermal cutting must be performed,
laser or plasma cutting is preferable to oxy-fuel 11.7 Plate handling
cutting. This is because oxy-fuel cutting introduces
more heat to the work piece compared to plasma or While storing Hardox 550, Hardox 600 and Hardox
laser cutting. Extreme, make sure the plates are not subjected to 3
point bending. Three point bending can occur if the
plates are stapled with wood between the layers and
11.6 Submerged cutting the wood is not properly placed. Always make sure

An effective way of limiting and reducing the extent that the wood in each layer is placed on top of the
of the soft zone is to water-cool the plate and the wood in the layer below, see fig 11.13.
cut surface during the cutting operation. This can
be done either by submerging the plate in water (fig.
11.12) or by spraying water on the piece during and
after cutting. Submerged cutting can be done both in
plasma cutting and in oxy-fuel cutting.

Some advantages offered by submerged cutting are:

4 Prevents loss of hardness of the whole component Fig. 11.13: Properly stapled plates.
4 Reduced distortion of the cut part
As stated before never return a plate to the stock
4 Parts are cooled directly after cutting
with any sharp corners left. Always make a clean
4 No fumes or dust
cut to remove such sharp corners before the plate
4 Reduced noise level is returned to stock. This is true for all cutting
methods, both thermal and cold cutting methods
Since preheating is not applicable for submerged like AWJ cutting. Hardox 550, Hardox 600 and
cutting, the only available measures to counteract Hardox Extreme are especially sensitive to this
the risk for hydrogen cracking are postheating and phenomenon.
reduced cutting speed. When small parts are cut by
oxy-fuel from thick Hardox plate, there is risk of
softening as well as cut edge cracking. This is best
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. 67
It is the responsibility of the user of this brochure to adapt the recommendations contained therein to the requirements of individual applications.