1.1 This specification covers grades of hot-formed welded and
seamless high-strength low-alloy square, rectangular, round, or
special shape structural tubing for welded, riveted, or bolted
construction of bridges and buildings and for general structural
purposes. When the steel is used in welded construction, the
welding procedure shall be suitable for the steel and the
intended service. 1.2 Grade II has atmospheric corrosion
resistance equivalent to that of carbon steel with copper (0.20
minimum Cu) Grades Ia and Ib have atmospheric corrosion
resistance substantially better than that of Grade II (Note 1).
When properly exposed to the atmosphere, Grades Ia and Ib can be
used bare (unpainted) for many applications. When enhanced
corrosion resistance is desired, Grade III, copper limits may be
specified. Note 1--For methods of estimating the atmospheric
corrosion resistance of low alloy steels see Guide G101 or
actual data. 1.3 The values stated in inch-pound units are to be
regarded as the standard. high-stren