Page 63 - SSAB Welding Handbook Edition 2

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Welding handbook 11.0 Cutting of Weldox and Hardox

Preheating Material Max
preheating
©SSAB
One method to avoid hydrogen cracking when temp. (˚C)
cutting is to preheat the material. The heat will Strenx 700 300
allow more hydrogen to diffuse away from the cut Strenx 900 300
edge and it will reduce the cooling speed of the cut Strenx 960 300
edge which reduces the introduced tensile stresses. Strenx 1100 150
Preheating can preferably be used prior to oxy-fuel Strenx 1300 150
cutting and plasma cutting with oxygen as plasma gas.
Requirements are stated in table 11.4. Table 11.5: Recommended maximum preheat levels for Strenx.

Grade Plate Minimum preheating Maximum preheat Regarding all type of laser cutting and plasma
thickness temp. (ºC) temperature (ºC)
cutting with nitrogen, preheating is not
Hardox HiTemp 5 - 51 mm No preheating 500
recommended due to its negative effect of the cut
Hardox HiTuf < 90 mm No preheating 300
≥ 90 mm 100 edge quality.
Hardox 400 < 44,9 mm No preheating 225
45 - 59,9 mm 100 Depending on the situation, either part of the plate
60 - 80 mm 150 or the entire plate can be heated. The most common
> 80 mm 175
way to preheat the plate is:
Hardox 450 < 39,9 mm No preheating 225
40 - 49,9 mm 100
50 - 69,9 mm 150 4Heating furnace
70 - 80 mm 175
4Preheating lances
Hardox 500Tuf 4 - 25,4 mm No preheating
4Electrical mats
Hardox 500 < 25 mm No preheating 225
25 - 49,9 mm 100
50 - 59,9 mm 150 Heating in furnaces is the best way to preheat
60 - 80 mm 175
the plate since it gives an even temperature of the
Hardox 550 10 - 19,9 mm No preheating 225 entire plate. Preheating lances can also be applied
20 - 50 mm 150
for preheating of Hardox and Strenx plates see
Hardox 600 12 - 50 mm 175 225
fig. 11.6. It is of importance that the lances are in
Hardox 8 - 25 mm 100 + reduced 100 motion so that the temperature of the plates does
Extreme* cutting speed
not exceed maximum allowable temperature, see
Table11.4: Preheat temperatures for oxy-fuel cutting and plasma table 11.4–11.5.
cutting with oxygen of the Hardox grades. *SSAB recommends AWJ
cutting.
To avoid softening of the material the temperature
Most Strenx grades in moderate thicknesses have a should be controlled on both sides of the plate.
high enough resistance to hydrogen cracks that it is On the side where the preheating is applied the
unnecessary to take additional steps, such as temperature must not exceed the maximum
preheating, to avoid cut edge cracking. However allowable temperature while the temperature on
when cutting Strenx 700-960 in thicknesses above the opposite side must reach the minimum required
80 mm and Strenx 1100 in thicknesses above 30 preheating temperature.
mm the risk for cut edge cracking increases. The
risk for cut edge cracking can be reduced by either
preheating the plate, use postheating or apply slow
cutting.
Suitable preheating temperature for Strenx 700-960
is 150 ˚C and just below 150˚C for Strenx 1100.

If preheating is applied the preheat temperatures
should not exceed the ones mentioned in table 11.5.
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. 63
It is the responsibility of the user of this brochure to adapt the recommendations contained therein to the requirements of individual applications.