Page 34 - SSAB Welding Handbook Edition 2

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5.0 Properties of the heat-affected zone Welding handbook

The area in the HAZ with the lowest hardness is As for Strenx 700-960, and Hardox Steels tem-
called the soft zone. SSAB defines the soft zone as the pered at 550-700°C the welding process notably
©SSAB
width of the HAZ where the hardness values are up influences the hardness values in the areas of the
to 90% of the unaffected parent metal. HAZ that are exposed to peak temperatures above
the tempering temperature. The width of the soft
The hardness properties in the HAZ follow two zone becomes comparatively wide for these steels,
general patterns. One relates to Strenx 1100-1300 according to fig. 5.5. The quenched steels have a
and the Hardox grades except Hardox HiTemp and similar appearance in the HAZ.
Hardox HiTuf. The other is valid for Strenx 700-960
and Hardox HiTemp and Hardox HiTuf.
Hardness profile across the weld
Hardness properties in the HAZ for Strenx 600
700-960, Hardox HiTuf and Hardox HiTemp 500
The parent metals of Strenx 700-960, Hardox HiTemp 400
and Hardox HiTuf are quenched and tempered steels HV 300
that are subjected to tempering at temperatures in the 200 Weld metal
range of 550°C-700°C during manufacturing. 100
0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0
The hardness levels in the HAZ are only significantly Distance [mm]
changed for the sections where the peak temperature
during welding has exceeded the maximum tempering Fig. 5.5: Hardness profile for a MAG welded single-V butt joint
temperature. Consequently, the soft zone in the HAZ in Strenx 1300. Plate thickness throughout the joint: 12 mm,
is narrow for these steel grades, which is illustrated in Heat input: 0.7 kJ/mm, t value: 6 s.
8/5
fig. 5.4.
The effect of heat input with regard to the
Hardness profile across the joint hardness values in the HAZ
600 The width of the soft zone will, to some extent,
500 Weld metal decrease with reduced heat inputs. This is true of all
400 Hardox and Strenx grades. The fig. 5.6 illustrates this
HV
300 effect for a butt joint in Hardox 400.
200
100
0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 Brinell, Vickers,
[HB] [HV(5)]
Distance [mm]
Hardness profile Heat input
Fig. 5.4: Hardness profile for single-V butt joint of Strenx 700 welded Hardox 400 Q <Q <Q
with MAG. The plate thickness is 25 mm throughout the joint. The 1 2 3
heat input (Q) is 0.9 kJ/mm and the t value is 5 s in this case. 400
8/5
Hardness properties in the HAZ for Strenx 1100- 300
1300 and all Hardox grades except Hardox HiTuf
and Hardox HiTemp. 200 The hardness of the weld metal
depends on the electrode used

Strenx 1100-1300 and all Hardox grades except
Hardox HiTemp and Hardox HiTuf are produced Fig. 5.6: Schematic hardness profile values transverse to a joint of
Hardox 400 welded with different heat inputs.
as either quenched or quenched and tempered steels.
When tempering is carried out, the peak temperature
reaches approximately 250°C.
34 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.