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Welding handbook 23.0 The influence of the alloys and contaminants on the Weldox and Hardox grades

23.0 The influence of the alloys and
©SSAB
contaminants on the Hardox and Strenx

grades

The chemical analyses for each Hardox and Strenx Carbon contributes to the:
grade is of essential importance for the properties in 4 Formation of different microstructures that
the HAZ as well as those in the unaffected parent appear in the parent metal. For instance, the
metal. The main part of these steels consists of iron ability to form martensite is strengthened by the
(Fe) where the alloy content is in the range of 2-4 addition of carbon.
weight %. A characteristic of the Hardox and Strenx 4 Mechanisms of interstitial solution hardening,
grades is that they are refined from contaminates to a precipitation hardening, and grain refinement in
very large extent.
the parent metal.

Each alloy element contributes to specific properties Since parts of these mechanisms support a reduction
in the parent metal. There are benefits as well as of the toughness of the steel, it is important that the
drawbacks for each given alloy. The positive effect carbon content in the parent metal is well balanced.
from an alloy can be furthered by increasing its In relation to other alloy elements, carbon has a
level in the steel - up to a certain point. If the alloy’s larger influence on the steel’s resistance to hydrogen
content is increased too much, disadvantages might cracks in the joint. As the carbon level increases, so
occur instead.
does the sensitivity towards hydrogen cracks. As a
consequence, an enhanced level of carbon content
The total chemical composition of the steel is in a steel means that more precautions, such as
carefully selected and evaluated in order to achieve increased preheating levels, are needed in order to
the desired properties of each Hardox and Strenx prevent hydrogen cracks during welding and cutting
grade. In the following text, different aspects of each operations.
alloy element and contaminant are described. The
effects from the alloy elements and contaminants
are frequently the same in both the HAZ and the 23.2 Manganese (Mn)
unaffected parent metal. Common characteristics
that are valid for both of these sections are referred The addition of manganese promotes increased yield
to as the parent metal in the following text. strength, tensile strength, hardness and toughness
in the parent metal. Manganese improves the ability
to form martensite in the parent metal and it can
23.1 Carbon (C) achieve grain refinement and substitutional solution
hardening.
Carbon plays a significant role in the mechanical
properties of the parent metal, especially for the Manganese also counteracts the negative influence
non-tempered and low temperature tempered of the contaminant sulfur by reacting with it to form
martensitic steels. It is added to the steel in order to manganese sulfide (MnS). If manganese were not
increase the yield strength, the tensile strength and added, the sulfur content would form other sulfides,
the hardness values.
which could increase the sensitivity to solidification
cracks during welding.

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