STEEL - Materials for Civil and Construction Engineers - page 105

T ABLE 3.5 Chemical Require-
ments of HPS 70W

Composition

Element (% by weight)

Carbon 0.11 max

Manganese 1.10-1.35

Phosphorus 0.020 max

…

Sulfur 0.006 max

Silicon 0.30-0.50

Copper 0.25-0.40

Nickel 0.25-0.40

Chromium 0.45-0.70

Molybdenum 0.02-0.08

Vanadium 0.04-0.08

Aluminum 0.01-0.04

Nitrogen 0.015 max

…

All HPS 70 must be calcium treated for
sulfide shape control

April 2002, more than 150 bridges with HPS have either been constructed or
were in the design and construction stage (FHWA, 2002).
The desire to improve the appearance and durability of steel structures
has produced an interest in designing structural members with stainless
steel. The durability of stainless steel has long been recognized, but the cost
of the material was prohibitive. The ability of stainless steel to resist corro-
sion rests in the high chromium content. Whereas common structural steels
have 0.3 to 0.4 percent chromium, stainless steel has in excess of 10 percent,
by definition. Five AISI grades of stainless steel are used for structural ap-
plications (SSINA, 1999):

304: the most readily available stainless steel, containing 18% chromi-
um and 8% nickel. Excellent corrosion resistance and formability,

■

316: similar to 304, but with the addition of 3-4 percent molybdenum
for greater corrosion resistance. Generally specified for highly corro-
sive environments such as industrial, chemical, and seacoast
atmospheres

■

409: a straight chrome alloy, 11 to 12 percent chromium. Primarily
used for interior applications.

■

410-3: a dual phase alloy with micro alloy element control that permits
welding in up to 1.25 inches.

■

2205: a duplex structure with about equal parts of austenite and ferrite.
Excellent corrosion resistance and about twice the yield strength of
conventional grades.

■

The chemical and tensile properties of these grades are summarized in
Table 3.6.