PDF brochure (You need ACROBAT READER - download program)

Abrasion-resistant HARDOX steels and high-strength WELDOX structural steels produced by SSAB Oxelösund contain few quenching elements. Hence their carbon equivalent is low.
Therefore these plates are easy to weld to all common construction sheet metal, using standard arc welding technology.

When welding HARDOX steel, the aim is:

to retain the hardness of the Heat Affected Zone (HAZ)
to achieve acceptable toughness of this area

When welding WELDOX and DOMEX (QSTE..., S...MC) steel, the aim is:

to guarantee the required strength of the weld
to achieve acceptable toughness of the weld

For their strength, HARDOX and WELDOX grades of steel products have low carbon equivalents:

Steel with low carbon equivalent (CE) is easier to weld than steel with high carbon equivalent. Usual CE values for particular steel plate thickness are shown in our specifications.

Carbon equivalent (by IIW) is determined using the following equation:

Steel type	Thickness range (mm)	Carbon equivalent CE (IIW)*
S355	5 - 100 mm	0,39 - 0,43
WELDOX 355	8 - 25 mm	0,34 - 0,37
WELDOX 420	6 - 80 mm	0,37 - 0,39
WELDOX 460	6 - 80 mm	0,37 - 0,42
WELDOX 500	8 - 80 mm	0,37 - 0,42
WELDOX 700	4 - 130 mm	0,39 - 0,64
WELDOX 900	4 - 80 mm	0,56
WELDOX 960	4 - 50 mm	0,56 - 0,64
WELDOX 1100	5 - 40 mm	0,68 - 0,72
HARDOX 400	4 - 130 mm	0,36 - 0,70
HARDOX 450	4 - 80 mm	0,41 - 0,62
HARDOX 500	5 - 80 mm	0.58 - 0,68

*) Standard values

Product temperature during welding

When welding abrasion-resistant structural steel, it is important to minimise the risk of cracks developing in cold state (sometimes called hydrogen cracks and delayed cracks). The main cause of these cracks developing is the presence of hydrogen and a development of tension in the weld. The risk of cracks developing can be minimised by the following procedure:

preheating the material before welding
thorough cleaning and drying of all gaps
minimising shrinkage tension. This can be achieved by accurate positioning of the product and suitably planned welding procedure
selecting filler material with low hydrogen content

Preheating

Preheating is extremely important when tack welding and root-welding.
The higher the temperature is during and after the welding, the easier it is for hydrogen to escape.
The need to apply preheating increases with the material thickness (see the table below), in order to compensate the thicker material's quicker cooling and also because thicker material has higher CE value than a thinner one.
When the ambient temperature is high or when the temperature is below +5°C, the values shown in the table should be increased by 25°C. And the temperature should be similarly increased when the material being welded is rigidly fixed.

When welding different types of steel, or when using electrodes with higher carbon equivalent CE than the carbon equivalent of the material being welded, the required preheating is determined according to the steel (or electrode) with higher carbon equivalent.

Recommended preheating temperatures for different combined (cumulative) material thickness [mm]														Recommended temperature interpass
t₁+ t₂+ t₃=	30		40	50	60	70		80	90	100	110	120	130	[°C]
S355 (SS2132)											75 °C			225-250
WELDOX 355														225-250
WELDOX 420/460											75 °C			225-250
WELDOX 500											75 °C			200-225
WELDOX 700				75 °C						100 °C		150 °C		200-225
WELDOX 900*	75		100 °C									150 °C		150-175
WELDOX 960*		100 °C										150 °C		150-175
WELDOX 1100*						150 °C					175 °C			150-175
HARDOX 400				75 °C			100 °C				175 °C			150-175
HARDOX 500	100		125	150 °C		175 °C								150-175

*) The preheating temperature is determined according to the filler material, provided the carbon equivalent of this material is higher that the carbon equivalent of the steel.

The recommended product temperatures are based on the assumption that:

the hydrogen content is lower than 5 ml per 100 g of the metal being welded
the heat input is roughly 1.7 kJ/mm

Measure temperatures here

Combined (cumulative) material thickness [mm]
T1 = median thickness at a 75 mm distance from the welded joint

Post-heating

When the weld is heated immediately after being made, it will be easier for hydrogen to escape from the steel.
The post-heating temperature should be the same as the preheating temperature.
The heating time should not be less than 5 minutes per millimetre of material thickness, but not less than one hour.

Post-treatment

Annealing to reduce tension

Annealing to reduce tension is done in order to reduce residual tension after welding.
WELDOX may be annealed to reduce tension only if such procedure is required by the construction regulations.

HARDOX and WELDOX 1100 may not be annealed to reduce tension!

Measures to increase the fatigue strength

Fatigue strength of welds can be increased by various post-treatments. This will lead to smoother transition between the weld and the steel and reduce the concentration of tension.
For further details refer to the Handbook on welding of Oxelösund steels.
When welding HARDOX and WELDOX materials, we recommend to abide by the heat input limits shown below. The heat input lower than values shown will guarantee achieving a satisfactory combination of toughness and strength, and a sufficient hardness of the heat effect zone (HEZ).

	Filler metal	*Filler material (Grade AWS)*
		MMA Manual arc welding	SAW Submerged arc welding with wire	MIG/MAG Shielded arc welding with wire	FCAW Welding with tubular wire
Recommended strength of the welded metal for flash welds when a high load capacity transversally to the welded joint is required
Strength of the welded metal for other welded joints
	N.B.: "X" denotes one or more characters

Selecting filler material

When welding HARDOX and WELDOX steels, any common arc welding method can be used, which are suitable for welding standard plate and high-strength plate.
Select filler material according to the requirements on mechanical properties of the particular weld.
When welding the HARDOX and WELDOX steels, use basic electrodes. Select filler material with hydrogen content <= 5 ml per 100 g of the welded metal.

When selecting the filler material yield strength, available are the following options:

filler metal with lower yield strength* than the yield strength of the material to be welded
filler metal with identical yield strength*
filler metal with higher yield strength* than the yield strength of the material to be welded

*) Relates to the nominal minimum value of tensile yield strength.

When welding WELDOX 700 to WELDOX 1100 steels, we recommend to combine electrodes of different strength, e.g. soft electrodes for root welds and higher strength electrodes for the remaining part of the weld.

These are the main benefits when we select low-strength filler material (yield strength below 500 MPa) rather than high-strength filler material:

higher toughness of the welded metal
better ductility of the weld
reduced tendency to develop cracks

When making corner welds, we recommend using a material of lower yield strength.

Recommended strength when welding HARDOX and WELDOX steel
WELDOX 355/420	Greater strength than the base material
WELDOX 460/500	Greater or equal strength than the base material
WELDOX 700	Equal or lower strength than the base material
WELDOX 900/960	Lower strength than the base material
WELDOX 1100	Lower strength than the base material
HARDOX 400/500	Lower strength than the base material

Using soft electrodes for welding HARDOX steel

HARDOX should be welded with soft electrodes. A soft electrode is a filler material with yield strength less than 500 MPa. These electrodes reduce the level of residual tension in the weld and hence the tendency of the material to develop cracks in cold state.
Provided the weld is situated in a place where it is subjected to considerable wear and tear, it is possible to use hard electrodes.
HARDOX can be successfully welded using austenitic stainless steel filler materials when:

the welded components are rigidly clamped
the product cannot be preheated
the material is thicker than 60 mm

Welding