I haven't heard of copper as an alloying element in steel. Has
> it ever been tried? Any useful properties? In particular, what color
> was/would be the resulting alloy?
> ----------------------------
> Mr. P.V.'d
> formerly Droll Troll
>
>
I was surfing and came upon this thread from March. The discussion> it ever been tried? Any useful properties? In particular, what color
> was/would be the resulting alloy?
> ----------------------------
> Mr. P.V.'d
> formerly Droll Troll
>
>
was interesting, but while there was some dicussion of weathering
steels such as the COR-TEN types, there really wasn't any mention of
copper strengthened medium strength (up to 100ksi) structural steels.
This link:
formatting link
takes you to a brochure for ISG steel company's medium strength copper
strengthened steels. There are 5 grades listed (3 actually with a
couple of variations for different thickness ranges). The HPS grade
(spartan V) is a 100ksi yield strength bridge weathering steel, the
others are 80 and 100 ksi yield strength ship hull steels. None of
these steels are "stainless steels".
All of these steels have copper precipitation hardening as their
primary strengthening mechanism. The amount of copper far exceeds
that needed for weathering. The ship steels aren't considered
weathering since that mechanism doesn't work in chloride containing
water.
The copper was added specifically to replace carbon for the purpose of
significantly improving weldability. While copper is an expensive
alloy replacement for carbon strengthening, the improved weldability
more than makes up for the increased alloy cost.
The corresponding steels that were replaced had approximately 0.12% to
0.18% (or slightly more) carbon and were quench and temper martensitic
strengthened steels. The copper versions have up to 1.75% copper and
more complex strengthening mechanisms, but are solution treated,
quenched, and aged with most of the strength from copper
precipitation. The temperatures and cooling rates for each step are
about the same for the old and new alloys, but the metallurgical
reactions are differerent, hence the different names. Also the
effects of each step are different. The carbon containing steels are
very hard and brittle after quenching and then moderate their strength
and greatly increase their impact and fracture toughness during
tempering. The copper steels are not very hard after quenching, and
the strength increases during aging. This is one of the features that
makes them more weldable - the weld HAZ hardness doesn't spike like it
does in the carbon martensite steels.
The brochure gives some good tables and charts showing how these
steels respond to heat treatment.
By the way, the color of the steel looks like steel at this level of
copper.
Tom
(not associated with ISG)