Steels_ Metallurgy and Applications, Third Edition

Low.carbon structural steels 153

However, BS 4360 has now been superseded by various European standards, of

which the following are the more important:

BS EN 10025:1993

BS EN 10133:1993

Hot rolled products of non-alloy structural steels.

Hot rolled products in weldable fine grain

structural steels.

The designation and property requirements of these European specifications are

shown in Tables 2.3 (a) and 2.3 (b) which also provide a useful comparison with

the grades specified in the former BS 4360 standard. Thus the former BS 4360

grades, 40, 43 and 50 A, B, C and D, are now covered by BS EN 10025:1993

and the higher toughness grades DD, E and EE, together with the high-strength

grades (55C and 55EE), are superseded by grades in BS EN 10113: 1993. To

complete the puzzle, the former BS 4360 grades, 50F and 55F, have now been

incorporated in the following, recently published European standard:

BS EN 10137:1996 High yield strength structural steels in the quenched

and tempered or precipitation hardened condition.

A European standard has also been introduced for weathering steels (BS EN
10155: 1993) and this will be discussed later in this chapter.
A possible source for confusion is that the current UK specifications dealing
with the design of steel bridges and buildings have not yet been updated to
deal with the changes from BS to European standards and they still refer to
steels specified in BS 4360. However, this aspect will also be discussed in the
appropriate parts of this chapter.

Steel prices

The basis prices of some of the plates, specified in BS EN 10025:1993 and
BS EN 10113: 1993, are shown in Figure 2.11. It should be stressed that the
prices shown in this figure were those in force in March 1997 and it must be
borne in mind that steel prices are adjusted from time to time. As indicated
in Figure 2.11, the prices increase progressively at a given strength level as
the specified impact properties are improved and also as the minimum yield
strength values are increased. However, as illustrated in Figure 2.12, the ratio of
cost: yield strength (at a given level of toughness) falls very significantly as the
strength of these steels is increased. Therefore there is a major cost incentive to
utilize higher-strength grades in structures where design is based primarily on
yield strength.

Weathering steels

The term weathering steels is given to structural grades in which the resistance
to atmospheric corrosion has been improved by the addition of small amounts of
elements such as copper, phosphorus, silicon and chromium. These steels rust at a