Page 60 - SSAB Welding Handbook Edition 2

©2009-2019 by SSAB Group of companies (SSAB). All rights reserved. Only digital PDF file. No distribution. No printing allowed!
No part of this handbook may be reproduced in any form or by any means without permission in writing from SSAB.
11.0 Cutting of Weldox and Hardox Welding handbook

Fig. 11.1 shows cutting speed as a function of It is no difference to laser cut Hardox and Strenx
material thickness and available power for plasma compared to ordinary mild steel, i.e. use the same
©SSAB
cutting. process parameters.

12
6 5 Plasma gas: Oxygen 1500W
2000W
Cutting speed (m/min) 2 4 3 shielding gas: Air Cutting speed (m/min) 10 5700W
Secondary
3200W
8
6
80A
130A
4
200A
0 1 260A 2
400A
0
0 10 20 30 40 50 60 0 5 10 15 20 25
Material thickness (mm) Material thickness (mm)
Fig 11.1: General cutting speeds for different plasma Fig. 11.2: Laser cutting speeds of unprimed steel surfaces.
power sources.
Laser cutting of primed plates
As for oxy-fuel cutting, plasma cutting of primed
steel surfaces does not significantly affect the cutting To obtain acceptable cutting quality during laser
parameters. cutting of primed plates additional measures are
normally required.
11.3 Laser Cutting
There are 2 different measures that will improve the
Laser cutting of Hardox and Strenx can easily be quality.
done by using the normal processing parameters
for the given material thickness. The maximum 1. Removal of the primer at the intended cut.
thickness is approximately 30 mm depending on This can normally be done by the machine
the laser cutting equipment. Most commonly to cut with help of a “vaporization run”. The machine
is thicknesses below 25 mm. Generally features for runs the intended contour with an unfocused
laser cutting can be seen in table 11.3.
laser beam at maximum speed. The heat from the
Cutting Kerf HAZ Dim. tolerances laser beam vaporizes the paint. After the paint
method width has been removed the cutting operation can be
Laser cutting < 1 mm 0.2-2 mm ± 0.2 mm done at normal speed.
Table 11.3: General features for laser cutting.
2. Reduce the cutting speed with 50%.
One of the benefits with laser cutting is the high If the paint can’t be removed the cutting speed
cutting speed that can be used. Fig. 11.2 shows must be reduced with approximately 50% in
cutting speed as a function of material thickness order to get an acceptable cutting quality.
and laser power.
11.4 Hydrogen cracks
Due to the relatively thin thicknesses and small
thermal impact, preheating or postheating is not Cut edge cracking is a phenomenon that is closely
required during laser cutting of Hardox and Strenx related to hydrogen cracking in welds and most
steels. Preheating is instead detrimental to the cut commonly occurs when thermal cutting methods
edge quality. are used. If cut edge cracks should occur, they will
become visible between 24 hours and up to several
weeks after the cutting. The risk of cut edge
cracking increases with the steel hardness and plate
thickness. Even if cut edge cracking more often is
related to thermal cutting, it can arise from sawing
60 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.