The Damasteel Got Here !!!!

Yes Mete, even I noticed that. I think this one is the worse of all three. This one I busted right too. Lined it up straight in the jaws with the score line just visable and wacked it one good one. Snaped great, right off - first wack. I thought I had something.

I hate to go through that same #3 HT again because it takes so much time and I am sure the soak is short but I really do want to eliminate my current quenching method until we get this HT tuned in. I still have about 24 inches of RWL-34 to work with. No use making a blade now until the HT is optimized and now that I'm into it I ain't quiting until I can put up good results here with a good HT procedure for this steel. So long as I oil quench without atmosphere control I will not grind decarb and therefore will not Rockwell. I'm going after good grain structure only until it is acheived. I have to depend you fellows to tell if it is good or not and I will try to make better pictures.

RL
 
Out of focus. Photo lesson -if your camera has point focus use that instead of averaging focus. Always take photos with full resolution, you can always reduce it later. Take a few shots and pick the best. Your shallow lighting angle seems ok, that's necessary to show the texture. Sometimes things show up better with same angle but different direction...... Comparing #3 and #4 - That material ,full hardened should have a fine texture like the finer side of #3 but it seems to have a texture of the coarser side.
 
Now that I know better what to want I will carry on until I hit it. I suppose what I need is a smooth break with little or no highs and lows and fine looking in texture throughout the surfaces.

The last one you looked at WAS air quenched and double tempered @ 460 F. / 2hr. per., but without cryo. Other data: 1950 / 20 min., after double temper: 57 HRc

The one I am tempering now was quenched using aluminum plates. Tempers: 475 F.. This one will be cryo'ed after 1st temper and then tempered again @ 475. Other data: 1950 / 20 min. Results posted tomorrow evening.

EDIT: I looked at my camera manual again and it seems I may be trying to get to close to the target to be photograped. It explains I need to be a minimum of 8 inches and I am sure I have been crowding that.
 
http://www.bucorp.com/pdfs/UddeholmHeatTreatmentofToolSteel.pdf

Roger,

The link above is for Uddeholm's discussion of heat treating including ramping rates and soak times. They only talk about tool steels here, but I think it applies to High Carbon SS also. They also manufacture the RWL 34 I think.

They call for cryo treatments at dry ice temperatures. Crucible also cites this temperature. I don't know of any steel manufacturers that call for lN2 temperatures.
 
Thanks for that but I had previously checked with the RWL-34 vendor concerning deep cryo vs. dry ice. His only real concern was an increase in micr-fracture, which is a concern with most of the steels we makers deep cryo. As far as transformation, I got nothing negative from him.

RL
 
shgeo, their "untransformed austenite is very brittle" is incorrect. It's actually fairly ductile . It is untempered martensite that is very brittle. Read my tutorial.
 
I realize that it is the new martensite that is brittle. The reason I brought the whole business up is that cryo at dry ice temps gets a bad rap on the forums. I haven't found non-involved technical sources that stress the necessity for deep cryo.

The Uddeholm PDF on heat treatment calls for slow ramping and thorough soaking at Austenitizing temperature to dissolve the carbides into solid solution. I have been using their specs for D2 for a couple of years now: soak 30 minutes at 1870°,then oil quench and immediate cryo upon cooling to room temperature. I do leave the bleades on the dry ice overnight and temper three times at 400°F for 2 hours each. I get some of them tested at a machine shop and give the rest a scratch test on a Nickleson file which I assume is 60 HRC. All I have ever had tested were between 60 and 61.

Edited to add: I am hardening D2 tonight, thus the divergence from Damasteel.
 
I have not used dry ice just the N2
but I've only know the Dry ice to get down to -90 deg
and I don't believe that is
cold enough to work fully on some of the SS's :confused:
it's recommended at least -120 to work
just two cents added.....
 
Dry ice is -78.5°C/-109.3°F. The only stainless steel I use is S30V and its manufacturer recommends -112°F, but has verbally said dry ice temps.

I haven't seen specs calling for -120°F., some non-US companies call for -50°to -70°C.
 
I won't knock dry ice usage. I wonder if the dry ice bath gets to the temp. of dry ice. I also wonder if a bath is not used will all the steel be consistant in temperature. I used dry ice before scrapping and scrounging for a dewar. I just became tired of driving 20 - 25 miles round trip and paying 7 - 10 bucks each time for dry ice. Now I drive the same round trip, pay more each time but only have to do it twice a year.

I am guessing the slow ramp rate you mentioned would be to ensure all the steel cross section reaches target temp. at close the same time.

RL
 
I don't use a dry ice bath, I sandwich the steel between two blocks. The conductivity inherent in metals keeps small peices like blades at the same temperature as soon as they equilibrate. Safeway is only 2 miles and they get $.59/lb for it.

You can even lay the blades on the dry ice and they will sink in until they are even with the surface and then stay even with the surface as it sublimates. If there was a temperature differential between the steel and the dry ice, the blades would continue to sink in instead of staying even with the surface. Just to be safe, I use two pieces.

I would consider the lN2 if I could afford the dewar, as it is easy to get here.

has anyone ever tried liquid Helium? It is expensive, but is only a few degrees above absolute zero.
 
I no of no where local to me I can get blocks. I had to settle for pellets. Fifty nine cents a pound sounds real good to me. Seems like I had to pay alot mote than that for just pellets. When I used dry ice I would put the cooler in the freezer. I could squeese out not quite two days (40 some hours I think).

I wonder what the structure would be like after visiting a couple or so degrees above 0 K. ?

RL
 
There are practical limits to what you can achieve with cryo ,don't get paranoid about it.
 
Well taken but you just know before too long I'll have to do a side-by-side HT that compares LN vs. dry ice.:)
 
Here is a good one for us. Just finished #5. This HT is like #1 with these exceptions (RWL-34 , both foil wrapped during quench):
-----------------
#1: 1950 F. / 22 min. #5: 1950 / 20 min.

#1: air quench #5: aluminum plate quench

#1: cryo 19 1/2 hr., double temper (475F.) #5: single temper, cryo 18 1/2 hr., single temper (475F.)
-----------------

#1 Rockwell: 62 #5 Rockwell: 58
-----------------

The plate quench was super fast. I am guessing that has nothing to do with the vast difference in hardness since the air quench sample tested so much harder. My guess is temper before cryo is the main reason. If not the only real thing I see left is soak time is short and that don't make a whole lot of sense either.

I have not yet broken the test piece but will shortly. If this break does not look good I think that might say something about soak time. If it does look good it might say alot good about the plate quench.

What think ?

RL
 
Originally posted by rlinger
Here is a good one for us. Just finished #5. This HT is like #1 with these exceptions (RWL-34 , both foil wrapped during quench):
-----------------
#1: 1950 F. / 22 min. #5: 1950 / 20 min.

#1: air quench #5: aluminum plate quench

#1: cryo 19 1/2 hr., double temper (475F.) #5: single temper, cryo 18 1/2 hr., single temper (475F.)
-----------------

#1 Rockwell: 62 #5 Rockwell: 58
-----------------

The plate quench was super fast. I am guessing that has nothing to do with the vast difference in hardness since the air quench sample tested so much harder. My guess is temper before cryo is the main reason. If not the only real thing I see left is soak time is short and that don't make a whole lot of sense either.

I have not yet broken the test piece but will shortly. If this break does not look good I think that might say something about soak time. If it does look good it might say alot good about the plate quench.

What think ?

RL
Click to expand...

2 min is not much, but I'm sure it's adding some to it.
I still maintain,
a longer soak will result in a higher rock thus having
to temper at a higher temperture to get a targeted Rockwell.
.. there are too many variables to nail it too one definitive ansser..
soak time
the plates
temper sequence.. just two cent:( :)
 
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