From Newsgroup: rec.crafts.metalworking
Bob La Londe <
none@none.com99> writes:
Machines like 12L14, but without the lead exposure. Maybe better.
I was making some rotating assemblies for my prototype wire fender
yesterday and I was stunned (reminded) with how fast I could turn
it. Unfortunately it only appears to be available in round and hex. I looked. I found some Chinese companies years ago when I looked that
claimed to have it in other forms, but ordering a container of steel
from China is beyond my means, even if if it was legit.
The biggest issue with 1144 is it tends to hot short when welded. At
100KSI most shops use it as produced, but it can be heat treated.
After struggling with every other steel (except 1018 which is far
easier than some would have you believe) using some 1144 yesterday was
a dream. I also made the handles for the rotating assembly from 1/4
inch 1144 round. It manages simple forging, (smashing the ends to
retain them in the assembly) just fine as well, but I did all my
squishing from a dull to medium red, but not cherry red.
Makes me wish Iggy was still selling those large round drops on eBay
cheap.
Just about all grades were resulphurised in my first job at a Sheffield
(UK) alloy steelmaker over 4 decades ago.
The market niche made that so.
I then worked in a steelworks which made more expensive steels for very high-end purposes and sometimes we double-slagged to very low sulphur -
first the "basic" (chemically) slag under oxidising conditions, then
clear the liquid steel bath in the furnace, raking it out when you
couldn't pour-off more slag without metal loss, then make a new basic
slag but with carbon in it and keep the conditions "reducing"
(chemically). Which shifts the sulphur.
Necessary for the likes of ball-bearing / rolling-bearing steels - but
you'll be seeing the expense implications.
When you are on an aeroplane on take-off - I think the principles of
physics mean all the thrust pushing you back in your seat must be
transmitted through the bearings at that high engine revs (?). We
sweated buckets to get that effect. These days of very high performance refractories you can have a ladle furnace with a tightly fitting cap,
have a small arc just to counter conductive heat loss, and cheaply
refine to very low sulphur levels that is what is called for.
Back to resulphurised...
For machinability...
I think it was "got away with" because the parts were forged - which
curved the "grain" of the steel around the shapes.
[transverse strength is much lower than longitudinal strength - half or
less - so in forging must avoid "breaking the grain"]
Customers - well biggest was Ford Motor Co.
"our" billets ("crude" round-cornered squares) went to drop-forgers,
most in the Midlands are Birmingham.
All these parts for car engines, etc., needed machining and that's where
the resulphurised came in - I think it made machining vastly cheaper.
I've never see machinability tests, I admit...
As I knew it 4 decades ago.
For welded steels, weld contraction makes for high through-thickness
stresses, so those steels need very low sulphur and other impurities to
achieve that - transverse and in particular through-thickness tensiles
close to the longitudinal tensile strength.
So that was a different world.
Back again to resulphurised steels - a very common grade in my first job
was C-Cr-Mo, typically the UK equivalent to 4140 steel.
Good enough for a lot of small engine parts (it doesn't
through-thickness harden as well as when you start adding nickel -
getting to typically 4340 steel) - but for smaller parts which in
cross-section you could wrap your fingers around in the palm of your
hand it does the job, cheaper).
Most of the time things like screw-threads - which "cut the grain" - the
number of threads (the length and number of turns of the thread) give
you plenty of strength through large area taking the load across the cut
grain where strength will be half or less the longitudinal strength.
Hope that's helpful.
Best wishes,
Rich Smith
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