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Steel Designers' Manual - 6th Edition (2003)
Ensuring weld quality and properties by the use of standards 689
BS EN 10137: 1996, 9 Plates and wide flats made of high strength structural steels in
the quenched and tempered or precipitation hardened conditions
BS EN 10155: 1993, 1 Structural steels with improved atmospheric corrosion resistance
BS EN 10210: 1994, 10 Hot finished structural hollow sections of non-alloy and fine
grain structural steels
BS EN 10219: 1997, 11 Cold formed structural hollow sections of non-alloy and fine
grain structural steels
BS 7668: 1994, 12 Specification for weldable structural steels – Hot finished structural
steels in weather resistant steels.
The designations of strength, toughness, type of steel, and supply condition, e.g.
BS EN 10025: l993, 7 S355K2G4, are more informative than previous systems (such
as BS 4360: 1990, Grade 50D), and they provide better guidance to the steelwork
contractor in the choice of welding consumables.
Steels have their Charpy V-notch impact toughness (at least 27J) tested at either
room temperature, 0°C, or -20°C, and are adequate for most structural work in
the UK. For applications at lower temperatures, some grades covered by BS EN
10113-2 8 have 40J impact toughness at -20°C and 27J toughness at -50°C. (For
further details refer to Chapter 7.)
In order to prevent cold cracking and lamellar tearing see the recommendations
of BS EN 1011–2: 2001. 4
The use of the various product forms, standard sizes, and grades available in structural
steels can result in considerable savings in cutting and welding costs, but not
all shapes can be produced in all grades. Designers should check availability and
cost before specifying.
24.2.3 Substitutions – thickness, yield strength, impact toughness,
weldability, quality
Fabricators may request, for reasons of availability and cost, the substitution of
the specified grade and thickness by another grade and thickness. Steelwork contractors
and engineers should be familiar with the importance of several factors:
thickness, yield strength, ratio of yield to ultimate strengths, impact toughness, weldability,
and quality. Although it may appear that a substitute steel with higher yield
strength and/or thicker sections may be beneficial because it will provide more
strength, its impact energy may not comply with the code requirements and weldability
might be adversely affected.
Thicker steel imposes several penalties. Both BS 5950 2 (clause 2.4.4) and BS 5400 3
(clause 6.5) show that moving to a thicker substitute and/or higher yield strength
may require higher impact toughness and higher weld preheat temperatures to
prevent cracking.
Steels with inferior impact toughness should not be accepted. For instance, a steel
with a designation for 27J at 0°C should not be used to replace a steel designated