If the blade was made out of a leaf spring he should have stress relieved
the steel before forging it into a blade i.e. forging the curve in the
opposite direction and or normalizing (heating above the critical temp for a
long time and cooling slowly) in a heat treat furnace if available Maybe he
was just showing off! (what I dont know?)
Well there's leaf spring and there's spring steel.
I buy lengths of spring steel and get about 5 standard sword blades and
an odd one out of it.
I've never used a leaf springs, as I don't know what it's been through,
and there is a lot of bad press about using old leaf springs.
If he was just showing off he deserves a kick in the nut sack >:-(
re:old leaf springs
Old leaf springs have microfractures in them from all those years of being flexed
over billions of potholes, and no amount of heat precesses or forging will remove
them. Steel is cheap, why risk a catastrophic failure if you don't have to? OLS
good for machetes, get new stock for blades that matter.
1070... geez and he's still getting warping, he must be grinding the
sh*t out of the blades.
Some stats about this metal:
1070 is a plain carbon (non-alloy) steel
Carbon: 0.65 to 0.75
Manganese: 0.60 to 0.90
Wear resistance: medium
Toughness: high to medium, depending upon carbon content
Red hardness: very low
Distortion in heat treating: very low
Forging: Start at 1,750 to 1,850 F
Austenite forging: yes
Hardening: 1.450 to 1,550 F
Tempering: 300 to 500 F
Rc hardness: 62 to 55, depending upon carbon content.
I suspect he's using a higher carbon content steel and he definitely
shouldn't be quenching in brine.
If he had quenched in oil and pulled it out as soon as it quit
glowing... he could have straightened it out before it "hardened
all the way up".
The more Cr and/or Mn in it, the more time you got.
The whole thing doesn't switch to martensite at once, some of the
blade is still austenite at some point. Right? ;)
BTDT :) ...with butcher knife blanks and they are tricky as anything
to straighten while the sucker is fresh out of the quench tank. :)
Using pliers and the oil on it is smoking to beat heck so it's not
the easiest thing for me to see either. Especially since I heat
treat at night? :)
What's tricky is while you're fiddling with it, the stiffness and
elasticity of the blade is changing constantly. The dangged thing
is turning into mostly untempered-martensite from all-austenite.
If you got the-warp-out half-way... then about triple that same
strain is going to be needed the very next try. It's constantly
changing and it's changing fast. :) If you warped it backwards
double what it was... ;)
But for a true sword-maker I figure a guy could get good at taking
major warps out of the sword fresh from the quench tank and take
care of the little warps later after it's tempered? <shrug>
I finish grind my blades extra thin so I have to do the grinding in
a two step process, having figured out that a hollow ground blade,
the edge needs to be at least 1/32" thick, and I later grind it to
half to one third that.
So yeah, a thick-club;) of a knife could be heat treated and
polished without later grinding... just not any of my knvies. ;)
I quench in real quenching oil and never use brine but my extra
thin 1095, 1.22%C (old files) and 50100-B blades don't need water
anyway, let alone the O1 or 8670-M blades.
See? All you've got to do is get it below about 750F quickly and
"you've got it done-quenched ;)" and the time from there, don't
really matter if it's cooling in air it'll turn to martensite
What do you think? :)
Alvin in AZ
ps- The swords to beat are Howard Clark's made from L6 (like 4370)
bainite using salt tanks. He forges the blades from L6 rounds.
pps- don't know why, but swords have never done a thing for me :/
On Jan 27, 8:46 pm, snipped-for-privacy@XX.com wrote:
Hi Alvin. Good to hear from you. Thanks for the information. This
is useful to remember. So, you use the TTT diagram to tell you when
to stop tweaking? The danger zone should be some combination of
temperature and fraction martensite. I guess if the blade is balanced
(finish ground), there should not be too much tweaking to do. I have
never heat treated a knife or sword, but may have to do it one of
(ASMs "Tool Steels")
The line they call the "M point" is usually called the "Ms-line" for
Some older graphs you'll see an "Mf line" for "martensite finish"
and those are now considered bogus... there is no "real" Mf-point.
The colder you get it (without letting it stop cooling) the more
martensite will be formed from the retained austenite.
That's why I cold treat my knife blades.
"higher hardness with no loss of toughness" -Roberts and Cary (ASM)
See the point at 1000F and at 10 seconds?
Quench the steel from ~1500F down to and hold it at 1000F for 10s.
That's 100% pearlite.
Like railroad rail... or the top half of a cold chisel.
Actually that part of it is all in the "feel". :)
The TTT or ITT graph only shows you what's going-on in-theory.
The TTT graph is a road map to show you where you are and what you
can get-away-with ...in this case. ;)
Yes, you can see in the graph the temperature constraints you'll
need to stay within for certain things to happen... also the time
constraints are shown too.
Time Temperature Transformation graph
The graph itself doesn't tell it all... left-out are things like
you've got time to plastically deform the part before it gets "too
hard" and-so too resistance to plastic deformation etc...
That part's, in the wordy part. ;)
Dangged wordy part anyway. ;)
Metallurgy books are my-kinda-books, they are full of graphs and
tables and only enough words in between to make sure you "got"
everything out of the graphs and tables. Cool huh? :)
I'm not into books without indexes.
Finding-out what you can get away with is in your own hands and
There are a lot of chapters dedicated to warp prevention and
suggested steps to take to limit warping. Warp prevention is big
business. Take A2 tool steel for an example, tough to find tool
steels for sale where A2 isn't listed and it's a "go between"
warping vs expense.
"Metallurgy Theory and Practice" by Dell K. Allen ;)
Alvin in AZ
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