Low-carbon strip steels 123molybdenum sulphide as a slip agent during forming. It is reported that Ford are
applying duplex coatings to the bonnets of all Granadas/Scorpios and Fiestas,
achieving a 20% reduction in stone-chip damage and the complete elimination
of red-rust corrosion.
Dasarathy and Goodwin 45 comment on the need for preprimed steel for auto-
motive construction which would replace the electropfiming and surfacer primer
stages of finishing at the manufacturers. Such a product would be hot dip or
electro-deposited zinc-coated steel with a 25 t~m organic coating. However, the
authors state that this type of material is still very much at the development stage
and one of the major problems that must be overcome is that current organic
coatings are not weldable.
Before leaving automotive applications, reference should also be made to the
use of terne-coated steel products, i.e. with tin-lead coatings. Ternex 19~ has a
hot dip coating of 92% Pb 8% Sn, applied over a nickel flash, electrolytically
deposited over the steel surface. Such materials are resistant to attack by auto-
motive fuels and are used extensively for the manufacture of petrol tanks.
Strip steels in buildings
The construction industry is a major consumer of strip steel but still represents
a major growth sector for this product.
Steel.framed houses
Following earlier problems, interest has now been revived in steel-framed housing
since it offers many advantages over traditional construction. In particular, the
frame can be erected very quickly and made weatherproof so as to allow internal
work to proceed at an early date. Labour costs and construction times are also
reduced which leads to lower interest costs and faster financial returns. Benefits
also accrue to the householder since the steel frame does not absorb moisture
and is not subject to shrinkage or warping. The risk of cracking in wall linings
is therefore reduced and the steel frame is also fire resistant.
Earlier attempts to introduce steel-framed houses were unsuccessful because
the designs were geared to rapid construction rather than aesthetic appeal. The
initial steel frames were also manufactured in painted mild steels which were
prone to corrosion problems. 191 In current construction, these problems have
been overcome by:
- Preserving a traditional exterior of bricks and mortar around a load-bearing
steel frame. - Employing hot dip galvanized steel in place of painted steel for corrosion
resistance.
An illustration of the construction of a steel-framed house with the preservation
of a traditional exterior is shown in Figures 1.121(a) and (b).
The structural members that make up the steel frame are roll-formed U chan-
nels in Z28 (280 N/ram 2 rain. YS) grade steel with a zinc coating of 275 g/m 2