Your Opinion: The best PM stainless steel you have used.

Just to re open this thread. I think one of the most important aspects of this conversation has been that the steel can take you so far, but the heat treatment is what will really make or break the steel.

In using R2/SG2 core san mai over the last couple of weeks, I did as any good maker does and I sacrificed a few smaller pieces to determine what the steel does at certain heats. I first used the manufacturer specifications which were... very very open to interpretation. The heat treat range was from 1080 - 1120C and "no longer than 10 minutes". I also know the particular alloy in question can perform drastically different at certain temps and goes from very tough to very brittle over a certain range for only 1 - 1.5HRC difference.

As you can see below, I had a few samples, at three designated temps. These temps were within and one outside the recommended HT process, keeping below the "10 minute" mark. FYI, 5 minutes compared to 10minutes at certain temps is the difference between a horrid HT and an amazing HT. Think of AEB-L, it requires very precise timings at temps or it is destroyed.

In these photos I have three mid-finished blades at two different HT temps based on the preference of my findings. You will also see three little blades bent over, which obviously broke a different points. Herein lies the difference of 15 degrees Celsius at the exact same hold time at temp, which is obvious to anyone. Hotter the temp, more brittle, lower temp, less so.

I also have attached the picture of a blade which represents a few of the larger ones I had. (I heat treated 7 blades, and two fractured whilst two other had minor cracks, three blades survived unhurt.) As you can see the sheer force of the core hardening and the jacket shrinking during the heat treatment cycle was enough the tear the core steel straight down the center. It was interesting to see, as it happened at both temperatures. I have a strong suspicion as to why it happened, and I will know on the next heat treat batch. The surviving blades have been tested by myself, and a a couple of them by mert tansu the other night.

Rockwell testing will give me more information during the week. So far, just in test steel and HT fun I have lost about $750 worth, that I cannot recoup from busted blades. Lets just say, I cannot possibly do more than I am to pull as much performance out of these blades as is possible whilst keeping the steel in a serviceable state.

Sometimes when you fly too close to the sun your wings melt. That just means you have to make better wings.

 

Slow chiming in here but to me it shows what a true craftsman you are to take the time and spend the money to find the "sweet spot" like you are instead of just "going by the book". You are to be commended for your efforts to offer the best product you can! Big thumbs up Chadd!

 

The steel in the Gessh in Kagero is truly fantastic in edge holding and ability to have a fine edge, although I do not know the exact steel

 

just checking . you have 2 kilns so you can preheat and then jump to aus heat for quench? or are you soakig to temp (these things matter as per data sheets )

 

I will update you in the next year on the newest heat treating furnaces I have been sponsored/ambassador for, to test (flagship model kiln and 2 x salt pots designs I have been collaborating with the company on). I'll reveal more info on this as the video series comes out.

In short, yes I have a thermostat controlled forge for lower temps and a kiln for high temps. I make and sell forges as a side, mert has one of them as do other australian makers.

I will be releasing videos and data sheets, backed with scientific metallurgical analysis of the steel micro structure for different blade steels. It should help you with any heat treating problems you have.

Cheers,
Chadd.

 

For certain steels there is no pre soak time, such as RWL34. A lot of others do too, so just make sure you know which steel you are using and what heat treat you are comfortable with.

Also make sure you are aware of the heat transfer rate per thickness of steel as some cross sections of a particular thickness do not require a low temp aus prior to critical temp aus time. Depends what microstructure you are after too.

Get some of your blades metallurgically tested and then adjust from there. ThE SG2 post on here was from July. You would be suprised what happens in 6 months of testing

 

no worries had an issue and got a full work up from car-tec to see what the issues was. will share micrographs if need be
been workig up xhp for a few years and even take intoo account my kiln ageing. i buy 250lb of sheet at a time so i can make sure its all from the same melt and has been treated the same before i get my hands on it. can even get the ISO files to track back if need be

 

Sounds great! What furnace were you running and what issues did you have? It would be good to see how you rectified them. Im quite interested in these things.

Posting a micrograms would be awesome! Don't hold back

Buying single sheets is a very good idea, couple of testers to dial it in and then rinse and repeat. Good job!

 

issue was not the HT found a few odd pits in the steeel as i was finishing. im still not sure what it was but it was only on an early batch of steel. HT came out to 63RC with no problems. got to see how to save PDF files as Jpeg so i can post them
since the issue i have bought 14 sheets all from the latest batch and no issues for anyone that is wondering if i still trusted the steel supply (5K$ in steel at one time is a big chunk of cash for me)

 

Butch, would you mind posting you heat treat recipe for XHP at 63rc?

 

sure
in my kiln (others will have to tweek for the temps )
start room temp kiln full ramp to 1500f hold 5 min full ramp 2000f 20 min soak
quench between AL plates (i use a 12 ton shop press to clamp) let the blades get to room temp then soak them over night in LN
in the morning i set the kiln to 400f and preheat it at the same time i pull the blades from the cryo. at nearly the same time the kiln stablizes and the blades have come back to room temp
blades in kiln for 2 hours ... pull blades let them go to room temp and then back into the kiln for another 2 hours
CAR-TEC lab RC tested 63.3 std devaition 0.13 over 10 spots tested did not get a grain size rating but was said to be inspec with alloy and HT
looks liek i will have to screen shot the PDF as im unsure how to convert

 

Between screenshots and MS Paint, mant a profressional presentation had beeb made.

 

got to retake the others are they didnt come out clear HRC3 was at the tang of the blade that i didnt grind clean so thats why the numbers are off. the thing to note from this for any make is to make sure you grind the edge clean on not just the bevels but also the face (it does not take much but that light decarb can be what makes you getting a great edge quickly so hard to do )