Hi, I'm a fantasy and science fiction writer, and was recommended to
this group for a technical question.
Well, maybe 'technical' is stretching things.
I've written a bit where snaps and shackles were made of a steel. They
tested well in normal temperatures, but shattered under load at about
-40. I used manganese as a placeholder, but would like to use a correct
alloying material to have my 'expert' character tell the journeyman to
"try using a little less (or a little more) X" where X is my manganese
Can anybody help me? Have I provided enough information?
Try using more nickel in an alloy steel. See discussion in
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Nickel would increase toughness but might not be required, if you only
want -40°C not -80°C.
Phosphorous would be bad but would be an impurity not a deliberate addition.
Vanadium or manganese might be good. Carbon might be bad.
Finishing rolling or forging at too high a temperature might be bad.
The materials on page 24 (mainly plates?) are all pretty tough at -40°C.
I do need it to be able to withstand lower than -40, That's just the
temp when the metal started shattering. Assumably what I'd want would
survive down to at least -60C. It has to be able to handle extreme
weather in an arctic environment...
Sorry for the boring reply but:-
EN10025 and EN10028 include several steels charpy tested to as low as
at -50°C with no minimum Ni and maximum Ni levels of between 0.35 and 0.85%.
The Low temperature Ni alloy steel parts of these standards include
materials tested from -60°C to -196°C with as you say increasing levels of
Ni being tougher at low temp.
Also thin material, particularly if not welded, can be used at lower
temperatures than it has been charpy tested.
For instance PD5500 Fig D.2.:- 4mm material tested at room temperature can
be used down to -55°C,
or EN1993-1-10 table 2.1:- S355JR tested at 20°C can be used at -50°C up to
I have seen very few real fractures caused by temperature, (excluding
overloads that just happened to be at cold times), probably due to the
relatively mild winters we have. Those I have seen were very brittle
materials often strain ageing, and very high nitrogen levels (poor casting
technique/bad segregation/bad heat treatment/bad welding technique/poor
material specification (low manganese & aluminium)).
I found an article in key-to-steel that showed a good steel for
cryogenic uses. It contained 16 percent Mn and 5.8% nickel.
comparing that to a basic steel gave me enough information to work with,
so I consider my problem solved.
Thanks everybody who contributed.
"A little more manganese" would actually be correct as it stands.
Or Nickel, nickel and manganese are the two main alloying components used
for increasing cold toughness.
"A little less nitrogen" is another possibility.
Agreed that Nitrogen is Bad. Also that Mn and Al are good, especially
together - but are they needed? Afaik the 9% nickel steel traditionally used
for cryo purposes has little of either.
Low temperature (-40 to -100 C) and cryogenic (-200 C or so) steels are not
quite the same - I know very little about low temperature steels, but from
what I have learned here they do seem to be similar.
For cryogenic steels Nickel is more commonly used, but some newer (and some
very old) cryo steels use manganese as well as or instead of nickel (and Al
instead of chromium, Cr can reduce cold toughness).
9% nickel steel is "the standard" cryo steel, and the best-known, with afaik
little Mn in it. Some other cryo steels have ~ 16% Mn with 6% Ni, some have
~22% Mn and virtually no Ni.
Manganese cryo steels are cheaper even than 9% nickel, which is "Approved"
for more purposes - however unless they are using large quantities people
often use 300 series stainless for cryo work, avoiding anything with an N at
the end, as it is easily available.
Manganese cryo steels have been overshadowed by those for many years, though
Manganese steels are being used more often recently, especially in LNG plant