Page 35 - SSAB Welding Handbook Edition 2

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Welding handbook 5.0 Properties of the heat-affected zone

Effects of the chemical composition in Due to the less stringent requirements for joints in the
the steel Hardox grades, the recommended values for the heat
©SSAB
input are approximate.
The level of alloy elements in the Strenx and
Hardox grades influences the character of the soft
zone. Each individual alloy element contributes to a During multi-pass welding, the interpass
different extent. Generally, the soft zone narrows as temperatures in the joint occasionally can be higher
the carbon equivalent of the steel increases. than the minimum preheat temperature. When this
situation occurs, one can either let the joint cool to
Welding with a single-pass sequence the minimum preheat temperature before welding
compared to a multi-pass sequence the next pass or perform the subsequent pass at
temperatures higher than the minimum preheat
Welding a joint with more than one pass subjects temperature. Welding with preheat temperatures
the HAZ to different types of heat treatments since that are above the minimum requirements means
the weld passes are superimposed on to one another. that the maximum heat input is reduced. Fig. 5.8
As a result, the microstructures in the HAZ can illustrates the recommended heat inputs for the
change after each weld pass and combinations of Strenx grades at two different preheat temperatures.
microstructures from the different weld sequences
can occur. A location in the HAZ, for example, Recommended heat inputs for other preheat
can be characterized as a tempered coarse grained temperatures can be determined conveniently by
zone. However, the Hardox and Strenx grades are using the WeldCalc software developed and
designed to attain the beneficial properties in joints, supplied by SSAB.
accounted for in this welding handbook, for both
single-pass and multi-pass techniques. In the recommendations presented in fig. 5.7-fig. 5.8,
the heat inputs correspond to t values according to
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5.3 Recommended levels of heat table 5.1 for the Strenx grades.
input and t values
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Steel grade Recommended t intervals*
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The heat input will affect the mechanical properties Strenx 700 5-25 s
in the joint. SSAB has stated suitable levels of heat Strenx 900 5-20 s
inputs for welding of the Hardox and Strenx grades.
The basis for the stated recommendations regarding Strenx 960 - Strenx 1300 5-15 s
heat input, stated in fig. 5.7, for the Strenx and * Valid for a typical min. impact toughness of 27 J at -40°C in the HAZ.
Hardox grades are that: Table 5.1: Recommended t intervals.
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4 The typical minimum impact toughness in the
HAZ should be at least 27 J measured at -40ºC There are fewer restrictions regarding toughness
for each Strenx grade. and strength in the HAZ for the Hardox grades

4 The strength in the joints of Strenx grades shall be verses the Strenx grades. as a consequence there are
on a very high level. Further information about less stringent requirements for suitable t values
8/5
typical strength in joints is found in TechSupport for Hardox. However approximate values exist
no. 60. and they are related to the specific steel grade and
its plate thickness. They are further defined in our
4 The recommendations for the heat input are software WeldCalc.
based on welding with the minimum preheat
temperatures stated in chapter 4.
4 The recommendations regarding heat input are
valid for the conventional welding processes MAG,
MMA, SAW and TIG. If other welding methods are
to be used, contact SSAB for assistance regarding
suitable heat inputs.
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. 35
It is the responsibility of the user of this brochure to adapt the recommendations contained therein to the requirements of individual applications.