Processing instructions-
DI-MC
Welding
DI-MC – THE WELDER´S FIRST CHOICE
Excellent weldability
DI-MC´s decisive advantage over conventional structural steels is its excellent weldability.
This is the result of these material´s low levels of carbon and other alloying and impurity
elements, which allow extremely low values for carbon equivalent. Various formulae for the
calculation of this equivalent have been evolved, depending on the particular application, and
can be used for the assessment of the weldability of a steel.
See
Plate thickness t DI-MC 355 B/T DI-MC 355 B/T DI-MC 355 B/T
EN 10025-4
[mm] typical CET [%] typical CEV [%] max. CEV [%]
max. CEV [%]
8 ≤ t ≤ 16 0.24 0.34 0.36 0.39
16 < t ≤ 40 0.24 0.35 0.37 0.39
40 < t ≤ 63 0.21 0.33 0.34 0.40
63 < t < 80 0.21 0.33 0.35 0.45
80 ≤ t ≤ 120 0.22 0.33 0.35 0.45
120 < t ≤ 150 0.23 0.38 0.40 0.45
Plate thickness t DI-MC 460 B/T DI-MC 460 B/T DI-MC 460 B/T See EN 10025-4
[mm] typical CET [%] typical CEV [%] max. CEV [%] max. CEV [%]
t ≤ 16 0.27 0.38 0.40 0.45
16 < t ≤ 40 0.27 0.38 0.40 0.46
40 < t ≤ 63 0.25 0.37 0.39 0.47
63 < t ≤ 80 0.25 0.37 0.39 0.48
80 < t ≤ 100 0.25 0.38 0.41 0.48
100 < t ≤ 120 0.25 0.40 0.42 0.48
120 < t ≤ 150 0.26 0.41 0.43 0.48
Typical and max. carbon equivalents of DI-MC steels
DI-MC steels express their excellent weldability in three important features:
1. Preheating can be significantly reduced or even omitted completely, permitting significant
savings on fabrication time and costs.
2. After welding, DI-MC steels exhibit extremely good toughness and low hardness values in
the heat affected zone (HAZ), enhancing process reliability and product strength and stability.
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3. Thanks to these special properties, DI-MC can tolerate much greater variations in welding
conditions than conventional structural steels, with a concomitant significant reduction in the
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Processing instructions-
DI-MC
Welding
Reduced preheating temperature
Due to the risk of cold cracking, steel plates in grade S355N/NL are usually preheated for
welding, depending on the particular standards applied and the technological status of the in-
dividual fabrication shop, whenever plate thickness is greater than 20 to 30 mm. This time and
cost intensive operation can generally be simplified or even omitted completely for welding
of DI-MC steels, however. Below figures illustrate well the reduction of preheat temperature
made possible by the use of DI-MC steels. The limit for the necessity of preheating can be
extended up to the maximum suppliable plate thickness when, in particular, welding filler
materials with low hydrogen contents are used. The preconditions in every case for this are
quality assurance provisions such as the correct selection, storage and handling of the welding
filler materials.
Extensive recommendations concerning welding, including selection of the minimum neces-
sary preheating temperature, can be found, for example, in Method B in the EN 1011-2, stan-
dard, and in the SEW 088 guideline. These recommendations state that Carbon Equivalent
CET, as an indicator of susceptibility to hydrogen cracking, can be used for calculation of
minimum preheating temperature. It is presupposed for this purpose that the Carbon Equi-
valent CET of the filler metal is lower than that of the base material by not less than 0.03%.
Otherwise, the preheating temperature for cold cracking resistant welding is based on the CET
of the filler metal plus a safety addition of 0.03%.
Preheating temperature [°C]
Preheating temperature [°C]
Plate thickness [mm] Plate thickness [mm]
Comparison of preheating temperatures calculated in accordance with EN 1011-2, Method B, for typical analyses of
S355N/S460N and DI-MC 355/DI-MC 460 as a function of plate thickness and hydrogen content HD of the welding filler
material
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Processing instructions-
DI-MC
Welding
At its E-Service area, Dillinger provides for its customers a welding assistance program which permits
simple and clear calculation of characteristics and parameters relevant for welding. As a first step,
the various carbon equivalents can be calculated via input of chemical composition. Using this data,
the suggested minimum preheating temperature can be determined as a function of plate thickness by
stating further welding parameters.
The user interface of the welding assistance tool in Dillinger´s E-Service area
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Processing instructions-
DI-MC
Welding
Low hardening
DI-MC possesses only a low tendency towards hardening in the heat affected zone (HAZ). The
carbon equivalent CEV, in particular, which is also frequently specified in materials standards
and which is, as shown before, significantly reduced in the case of DI-MC steels, provides
information here. Thanks to their moderate alloying concept, the hardness values for DI-MC
steels for widely applied cooling times are generally below 270 HV 10. Slightly higher values
may occur in laser welding, as a result of the lower heat input and higher rate of cooling.
Comparison of hardness data in the heat affected zones of the top passes of welds in DI-MC 460 and conventional struc-
tural steel S460N. Due to the tempering effect of the subsequent welding beads, the hardness values in the filler passes
are generally lower.
Resistance to brittle fracture
DI-MC steel´s extremely high initial toughness has positive benefits for the brittle fracture
resistance of the heat affected zone. High standards for toughness in the HAZ are thus met
even after welding with high heat inputs. Below figure shows that Charpy V-notch impact
energy in the HAZ of a DI-MC 460 achieves extremely good values virtually irrespective of
the energy input per unit of weld length, with the result that extremely high component safety
can be assumed even with high heat inputs of up to 3.5 kJ/mm. The good toughness achieved
after welding also permits cost efficient and rapid fabrication without any need to anticipate
problems with the quality of the weld.
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Processing instructions-
DI-MC
Welding
Charpy V-notch impact energy at -40 ºC [J]
Effective heat input [kJ/mm]
Example of Charpy V-notch impact energy (average values, measured at - 40 °C) in the HAZ of a DI-MC 460, as a func-
tion of heat input during welding (FL = fusion line)
Hot cracking resistance
Hot cracking, i.e., cracks occurring at high temperatures due to low melting point phases
(e.g. sulphur compounds) are generally not a problem when using these grades, thanks to the
extremely high cleanness of these steels (extremely low levels of such impurity elements as
sulphur, phosphorus, boron, etc.).
Weld preparation
Weld preparation can be performed by means of machining or thermal (flame, laser or plasma)
cutting. The weld zone must be metallically bright, dry and free of thermal cutting slag, rust,
scale, paint and all other contamination before welding starts. Dillinger offers to its customers,
in the form of individual weld preparation by means of milling, an additional service which
assures high cost effectiveness for fabrication. Our staff will be pleased to advise you on this.
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Processing instructions-
DI-MC
Welding
Welding filler materials
Thanks to their outstanding weldability, all DI-MC steels can be welded using any of a large
range of suitable welding filler materials. Below table shows suitable welding filler materials.
Submerged arc
DI-MC Manual arc welding Shielded arc welding (MAG)
welding
355 EN 499 E42 6 B 42 H5 EN 756 S 42 EN 758 T42 BC3 H5 EN 440 G42
460 EN 499 E 46 6 1Ni B 42 H5 EN 756 S 46 EN 758 T 46 1Ni B C3 H5 EN 440 G46
Typical welding filler materials for use in welding of DI-MC steels
It is, of course, not possible to examine all the details of the welding behaviour of DI-MC steels
here. For this reason, Dillinger provides for special applications intensive technical consulting
services for its customers prior to the ordering of the steel.
Disclaimer:
The information and data provided concerning the quality and/or applicability of materials and/or products consti-
tute descriptions only. Any and all promises concerning the presence of specific properties and/or suitability for a
particular application shall in all cases be deemed to require separate written agreements.
Contact
AG der Dillinger Hüttenwerke Tel.: +49 6831 47 3456
Postfach 1580 Fax: +49 6831 47 992146
66748 Dillingen / Saar E-Mail: info@dillinger.biz
Germany
You can find your contact person on www.dillinger.de
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