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Welding handbook 5.0 Properties of the heat-affected zone

5.0 Properties of the heat-affected zone
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As mentioned earlier in chapter 3, the heat-affected 5.1 The different parts of the HAZ
zone (HAZ) in the joint has mechanical properties
and microstructures that are different from the The welding thermal cycle affects different parts
unaffected parent metal. The mechanical properties of the HAZ in different ways. Depending on the
that are affected are toughness, strength and distance from the weld metal, each part of the HAZ
hardness. is subjected to a unique heat treatment. This creates
different microstructures and mechanical properties
The requirements and characteristics of the within the HAZ. As a consequence, the HAZ can
mechanical properties in the joint are mostly be divided into four different principal zones, with
emphasized for the Strenx grades because they are each zone sharing similar properties. They are the
high strength construction steels. The properties in coarse grain zone, the normalized zone, the partially
the HAZ of these steels are designed to attain a high transformed zone and the annealed zone, which are
standard of well-defined mechanical properties. illustrated for a butt joint in fig. 5.1.
Occasionally, structures welded with the Strenx
grades are also required to meet extraordinarily Temp.
high demands regarding the mechanical properties
in the joint. On these occasions, the properties in The fusion line
the HAZ can be further improved by optimizing The coarsed grained zone
the welding performance beyond the normal
welding recommendations. The weld metal The fine grained zone
The partially transformed zone
The Hardox grades are also developed to achieve The annealed zone
favorable properties in the HAZ. However, these
properties are adapted to suit structures subjected
to wear where the exact levels of toughness and
strength in the joint are typically of less importance
than those in the Strenx grades. Fig. 5.1: The different parts of tvhe HAZ.

This chapter will discuss the issues related to the
properties of the HAZ in the Hardox and Strenx
grades and how to attain advantageous properties
in this area. More information regarding the
individual properties for each of the microstructures
mentioned are found in chapter 21.

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. 31
It is the responsibility of the user of this brochure to adapt the recommendations contained therein to the requirements of individual applications.