Can anybody tell me what this term means?
Ah, finally a question I can answer. My father was a welder for
25 years and I, well, I was a welder’s helper for about 15.
Alexander G. Weygers writes the following in “The Making of
Tools” (reprinted as “The Complete Blacksmith”, 10 Speed Press,
Mild Steel: such steel is of a low-carbon content (<0.25%)
and is not temperable, although its surface can be hardened
through a process called 'case-herdening' (heating in a
high carbon environment). Some tools can be made of mild
steel, such as those that do not require hard-cutting or
long-wearing parts (eg. garden tools).
In practical terms most medium-carbon (<0.50% carbon) are often
grouped into the Mild Steel category because they hold temper
poorly. Above 0.5% you’re getting into serviceable cutting edges
and are dealing with so-called high-carbon steels. All of the
steel tools used to cut other metals are high-carbon, alloyed
steels and fall above 0.75% carbon, often as high as 0.90% or
Needless to say, the addition of alloying elements other than
carbon (chromium, tungsten, molybdenum, vanadium, cobalt, nickel,
silicon, etc, etc) vastly complicates the issue and bends most of
the general “rules”.
Examples, and sources, of mild steel include basic nails,
bailing/binding wire, wrought iron fences, etc. Screws,
machinery parts, gears and axles are generally medium-carbon
Hope that helps.