The Damasteel Got Here !!!!

Dan, its probably because I wrote the HTML code. I'll email the pic to you right away. Please respond here about your observation.

Sorry. Hope it works for others.

Expect an email soon.

Oh, wait a minute: the top set in the picture is the #1 test piece, bottom set is the last HT test piece (#2).

RL
 
I can see the photos just fine. They do not show grain, but do show brittle shear structure. The top one appears to have impact features evidenced by conchoidal fractures in two places. The lower one has what are called Riedel shear features that appear to show rotational strain in the plain of the fracture. CCW in the case of the right hand piece.

The only way I know of to observe grain structure in metals if to polish the piece and acid etch to bring up the texture. Then using a polarizing microscope with reflected light you can see the way it has crystallized.
 
Steve, very good. I am glad you could see enough of them. Not knowing the correct terms and not having experience in analysing grain structure from looking at broken steel I wasn't sure enough what to think but did see things in both examples that made me think there was brittleness.

I already have my ideas what about each HT might have helped cause this. Could you please look at the HT procedures used and give me your thoughts here ?

Thanks Steve.

Roger
 
I think that what I am calling shear features are probably what is commonly called grain on metal fractures. I think that there is not enough control of the fracturing in your process to see differences in the steel. You would need to set up identical conditions of breakage and run multiple trials to determine differences in the steel samples.

My scientific background is in deformation of materials (rocks). There are essentially two types of failure in solids, brittle and ductile (or plastic). Ductile strain usually happens at higher temperatures or over longer time periods and involves stretching and folding. We see ductile deformation in steel when we look at some damascus textures.

When material fails rapidly, it is usually by brittle failure. There is an array of failure features (structures) that indicate how the material failed, where the failure originated and the direction of propagation of crack tips. It really is not within my capabilities to tell much from the photos.

I have treated some Damasteel, but just used the procedure listed above. I had good results but have not had hardness tested. It would be difficult to test the damascus. I think the Damasteel is some pretty impressive stuff. I don't use it too often because of the cost and because I really like S30V and D2 which I use all the time
 
Another thread that I should have followed. Can't get that ssdamascus website. In any case ALWAYS temper after cryo since cryo will transform austenite to UNtempered martensite. There is a definite difference in the fracture surface of the two samples. Of course there is twice the soak time . But I would like to see the recommended HT. Does anyone have a copy?...... shgeo, what we call shear surface is something very different and in fact it's usually a term we only use when we are blanking material which is a shearing operation.The shear plane is about 45 degrees to the applied stress. The photos of Rogers are brittle fractures but there is a difference in the two. I'll be following this thread now.
 
Mete, as I stated above, my experience is in earth sciences and the materials are minerals, but are analogous. The 45 degree shear planes are the ideal that is modelled in the equations (pure shear). In real systems, fractures are generated as a series of primary and secondary shears that originate at an angle controlled by the internal physical properties of the material (simple shear). This angle to the overall shear direction for primary shears in natural materials is almost always 20 to 30 degrees. Secondary shears form allowing rotation of the stresses at 90 degrees minus the primary shear angle to the overall shear direction. These two initiate a "plane" of fracture through the material that may actually involve up to 5 or 6 different conjugate shears. This is the Riedel shear array.

You can see step features in the surface of the lower photo that show the shear features developed as the piece broke in simple shear. The upper photo looks more like an impact due to the conchoidally fractured areas-higher strain rate anyway. That is the reason I said above that the experimental conditions need to be more controlled.
 
Mete, I'll email you a copy of the Damasteel web site tech. data.

I'll try to post better pics today.

EDIT: Now I can't bring up their site. Their site seems to be down for the moment.

Mete, I learned from you some good while back that we need to temper after cryo. The purpose of the second HT example was to follow their HT example and specs for it as closely as I could and as best I understood what they wrote about it. I am not sure I understand exactly and is why I was hoping others would look at their specs and let me know what they thought they ment. I hope their site comes back up soon.

In the mean time I have another piece in the oven and trying another, different, HT.

Roger
 
OK, now I've seen the website. Yes it is confusing . I do not consider it good practice to freeze without subsequent temper .Do they do that for improved corrosion resistance ? I wish they would explain things beyond just hardness. I wonder , looking at the fracture samples ,if the 12 minutes should be increased when wrapping in foil.
 
Mete, where you say "subsequent temper" do you mean temper after freeze or also temper before freeze ? I have been advised by another HT expert to cryo SS before temper. I'm just an ol'ex-WV coal miner and I think you mean temper after - not before but have to ask to be sure. I do know to temper after though, regardless.

I have one in cryo now and intend to temper twice at 450 F.

Another question: before breaking should I score both sides or only one surface ? Unless advised otherwise I will clamp the piece in the vise with the score line against the outside of jaws. I did not do that the last time :confused:. I had the score line hanging out there in in free space :o .

RL
 
I had hoped that all of you had memorized my tutorial ( on Dan Gray's site) by now. When you freeze you are transforming austenite to UNtempered , BRITTLE martensite, that must be tempered. I don't understand Damasteels suggestions to do otherwise. Tempering BEFORE cryo is different .It reduces the chance of cracking when immersing in things like liquid nitrogen. So there, as suggested by Crucible, you temper first , then cryo, then double temper. That gives you minimum retained austenite and a very stable martensite.....The fracture samples I made were scored to give a predictable fracture location ( easier to photograph) and easier to break. I scored about 1/32" deep on three sides with a Dremel cut off wheel.I put the sample in the vise with the score just beyond the jaws and struck the sample on the scored side. And eye protection and a box to catch it.
 
Thank you ol'master of the heat waves.:)

Tutorial on Dan's site. I had forgotten about that being there.

Anyhow, I have one in cryo now but it is too late to temper before cryo. It will get a double 2 hour temper this evening.

RL
 
One last ignorant question about breaking the steel: should I give it one hard deliberate wack or should I start out light and build up until it breaks ?

RL
 
Roger, don't be a whimp, use a big hammer and give it one good whack !! Just have something to catch it in.
 
Dan, outstanding and thanks. I was going to look it up on your site anyhow. REALLY, I was - honest.

Mete, Mountaineers aren't whimps. Of course ----- there are exceptions I guess :) . I'll wack it a good one.

Its in 1st temper now. Maybe by early morning EST I'll have a pic.

Might as well go ahead and spec the HT now.
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Test Piece #3 RWL-34 (0.75 X 1.5 X ~ 0.138 inch)

Pre-heat oven to 1410 F. , place foil packet in oven and hold 10 min.

Ramp to 1950 F. and soak 10 min. (the oven ramped from 1900 F. to 1950 F. in 6 min.. From 1900 F. to end of soak = 16 min.)

Rapid air quench

Deep Cryo: only 6 hr.

Double Temper: 450 F. / 2 hr. per
----------------------------

Rockwell after midnight EST
 
RWL-34 test piece #3: 61 HRc - that's different.

Here is the picture of the HT #3 break: http://riflestocks.tripod.com/steelgrain2.html

Maybe the soak time should be increased. On this one I went down on soak time. What ya think ? Maybe I'm not getting a quick enough quench ? Same quench I've been getting 62 Rc with on the previous two.

I think before tweaking soak times again I should eliminate the quenching question I now have. Tomorrow I will repeat test #3 except that I will not foil wrap and will warm oil quench. We'll see what difference that makes. In fact, it may be best to oil quench until the soak time is tweaked in and then foil wrap/air quench and test again using the final optimum HT. Just throw the Rockwell out and don't worry about grinding decarb until the breaks look good. Does that make sense or not ?
 
Something wrong with #3, the texture should be the same on each side of the piece.
 
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