Recommendation? Rwl 34 best HT and grind before or after?

B

Brijac

Joined
Mar 2, 2019
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Hi. I have a question for you seasoned rwl 34 smiths out there. I have a project in mind in creating sakimaru takohiki 330mm out of rwl 34. As it is a single bevel grind, do you recommend grinding it before or after HT?
As for the heat treat. There are a couple of HT recipes for rwl i have found and read (all of them don't recommend factory one), and are quite old. Can you give me some advice on it or share your recipe. Blade is 4mm thick trough it while except for the tip that will be of course ground.
I am creating electric kiln for this purpose, 3kw, 12x12.5x55cm, as no one in my country has the length that the blade requires.
Thank you.
 
Put blade in a foil packet
Ramp to 1450F - insert packet - hold 10 minutes
Ramp to 1950F - hold 20-30 minutes
Remove from oven and plate quench packet
Sub-zero for 10 minutes or cyro for 6 hours
Temper at 425F to 450F one hour - twice.

This should give you around Rc60

Grind the single bevel partway before HT if you want, but it will be just as easy to do it all post-HT.
 
Since it's a delicate slicer, i'm aiming for 64hrc. So i guess 1100c and one 2h temper?
If it's that easy to grind then i'll go safe and post HT.
I have a question about heating. So i heat up the furnace first to 1450f then insert and hold? Do i leave it in while it ramps up to austenizing? Since it begins at 1050 and i need 1100, will 3kw furnace be enough to ramp it up fast enough?
 
I think you are looking at the high edge hardness regime:
1100C/2020F for 20 minutes sub zero/cryo
temper three times for 1 hour at 520C/950 F with sub-zero/cryo between tempers ( one temper won't be sufficient)

Using one or two 200C/400F tempers will get about the same final hardness. IIRC, the lower temp austenitization (1050C/1920F) yields a harder blade by a point or two.​

I think people greatly overestimate the value of hardness vs better geometry. I use S35VN at 60-61, and the edge last a LONG time.
I used to use ATS-34/154-cm/CPM-154/RWL34 at Rc 60 and never had an issue.
 
I was thinking a flat 12.5 degree grind 18mm in, with microbevel, but might give it an extra effort and go traditional. Thank for the info m8, cheers. Will post results.
 
Brijac said:
Since it's a delicate slicer, i'm aiming for 64hrc. So i guess 1100c and one 2h temper?
If it's that easy to grind then i'll go safe and post HT.
I have a question about heating. So i heat up the furnace first to 1450f then insert and hold? Do i leave it in while it ramps up to austenizing? Since it begins at 1050 and i need 1100, will 3kw furnace be enough to ramp it up fast enough?
Click to expand...

If you build it reasonably well and use appropriate materials, you'll have no problem with 3 kW giving a reasonably fast ramp-up, though you can't expect instant heating.

My last homebuilt oven was 7" W x 6" H x 28" long internally (175mm x 150mm x 700mm) with 3 kW of heating and from room temperature 800 degC (1472 degF) was reached in 22 ½ minutes, 1100 degC (2012 degF) took 54 ½ minutes, the temperature at an hour was 1125 degC (2057 degF) and 1177 degC (2150 degF) took 71 minutes.

I wondered if it would reach 1288 degC (2350 degF), which is the quoted "suitable for use up to" temperature for the Evenheat KO-series HT ovens, and set the controller to suit. It seemed fine at that temperature and I then reset the controller to 1300 degC (2372 degF). At 1300 degC, it was at the maximum temperature for the TypeN thermocouple and the PID controller would not let it go any higher. It had taken slightly under 2 hours to get there, including the (fairly brief) pauses at 1177 degC and 1288 degC.
 
Preheat the furnace at 1958F

Put the blade in and when the furnace back to temp, soak for 15-18 min

Plate quench to about 150F (uncomfortable to touch) and immediately go straight to subzero. Soak for 2 hours.

temper at 380F for 2 hours

Subzero again

Another tempering.

I got 64.5-65.1 HRC tested by commercial HT company with this recipe.
 
T timgunn1962 , thermo insulating firebrick and cement rated for 1300C, 1.5mm kanthal A1 heating element, PID and k type 1250c rated thermocouple. 12x12.5x55cm internal. Most of the elements arrive today. Will add another outer layer of ceramic wool and pack it all inside inox casing. If that doesn't hold heat i dont know what will :D
S shqxk Thanks! Cryo soak time in between tempers?
 
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