Magnacut Preheat/Ramp Time?

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ak650

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Feb 22, 2024
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I tried several searches, but came up short, so forgive me if this has been beat to death already.

Doing my first stainless steel heat treat, which will be Magnacut, that's about .102" thick and in foil pouch. The Crucible data sheet says preheat to 1550-1600°F and Equalize. OK, equalize for how long? Then on to the Austenitize temp ( which will be 2000°F for 25 minutes, as that's the max temp for my oven ). What should the ramp time be from Equalize to Austenitize?

Will then plate quench/blast with air, and then into dry ice/alchohol before a 350°F/ 2 hour temper X 2.

For this first go, it will just be a small pairing knife I made with the scrap cut, along with a couple of small test coupons. So if I screw it up, it won't be the end of the world. Then will do the kitchen knife I'm making for my wife.

Thanks for the advice!
 
Get oven to a stable austenitizing target temp. (15-30 minutes to soak the refractory)
Insert blade.
Start timer when the temperature rebounds to the target temp. It takes from one minute to five minutes to rebound, depending on your oven type.
Remove blade and place in quench plates. (I see no need in an air blast for a knife blade thickness.)
Immediate sub-zero quench for 10 minutes.
Immediate tempering cycles.
 
Stacy E. Apelt - Bladesmith said:
Get oven to a stable austenitizing target temp. (15-30 minutes to soak the refractory)
Insert blade.
Start timer when the temperature rebounds to the target temp. It takes from one minute to five minutes to rebound, depending on your oven type.
Remove blade and place in quench plates. (I see no need in an air blast for a knife blade thickness.)
Immediate sub-zero quench for 10 minutes.
Immediate tempering cycles.
Click to expand...
I stopped blasting my blades with air in the plates because of how fast the plates are I don’t see a benefit to the air.
 
Thanks guys.
I'll try skipping the air blast. My plates are 1-1/2" X 6" X 12", and the blade steel is only .102" thick. Should quench pretty quickly clamped in the plates. Looking forward to giving it a try!
 
I was curuios a few days ago and so checked on a 3/32 blank in plates 20 seconds after I placed it in plates and it was cold to the touch.
 
Scaniaman said:
Yes it is 100% pointless
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I don’t think I agree here. I do use air when plate quenching. I think it has a lot to do with the mass of hot metal going in to cooler metal contact that determines how quickly the cooling takes place. If you have a large set of plates and a single thin blade this is ideal and perhaps there is minimal benefit. Four blades that are 12” long and 0.25” thick changes that significantly on the same plates….know what I mean? 😊
 
Thanks to all who commented here. I believe the first Magnacut heat treat attempt was a success. Pre-heated the kiln to 2000°F and then let it soak for 30 minutes. Put the small blade and test coupons in, and when the kiln recovered back at 2000 started the 25 minute austenitize cycle. Plate quenched, and you guys were correct, no air blast needed. After 20 seconds between clamped plates, the pieces were already at ambient temp. The only hangup, was the foil pouches( Maudlin brand 309 hi temp stainless ). They essentially turned into vacuum bags, and were fused to the Magnacut. So, I just cut them as close to the parts as I could with snips, and into the dry ice/alchohol they went. Then into 350°F oven for 2 hours, cooled, and back in for another 2 hours. The foil was a bit of a PITA to remove, but a little cussing, pliers, and a razor blade removed it. Very happy to uncover super clean, silver steel! Will do a proper hardness test tomorrow with the Ames 1. Did a quick check with files, and the 65 HRC bites a little, and the 60 HRC skids off with a light scratch. Theoretically, they should be around 61 HRC. Appreciate the advice guys!

FQT1uWb.jpeg
 
ak650 said:
Thanks to all who commented here. I believe the first Magnacut heat treat attempt was a success. Pre-heated the kiln to 2000°F and then let it soak for 30 minutes. Put the small blade and test coupons in, and when the kiln recovered back at 2000 started the 25 minute austenitize cycle. Plate quenched, and you guys were correct, no air blast needed. After 20 seconds between clamped plates, the pieces were already at ambient temp. The only hangup, was the foil pouches( Maudlin brand 309 hi temp stainless ). They essentially turned into vacuum bags, and were fused to the Magnacut. So, I just cut them as close to the parts as I could with snips, and into the dry ice/alchohol they went. Then into 350°F oven for 2 hours, cooled, and back in for another 2 hours. The foil was a bit of a PITA to remove, but a little cussing, pliers, and a razor blade removed it. Very happy to uncover super clean, silver steel! Will do a proper hardness test tomorrow with the Ames 1. Did a quick check with files, and the 65 HRC bites a little, and the 60 HRC skids off with a light scratch. Theoretically, they should be around 61 HRC. Appreciate the advice guys!

FQT1uWb.jpeg
Click to expand...
A light dusting of baby powder on the blade before putting it in foil will completely eliminate the issue of the foil sticking.
 
Glad it worked out.

If you have to scrape the foil off, PLEASE use a window scraper handle to hold the razorblade. The foil is hardened and very sharp. Gloves are wise, too.
 
Stacy E. Apelt - Bladesmith said:
Glad it worked out.

If you have to scrape the foil off, PLEASE use a window scraper handle to hold the razorblade. The foil is hardened and very sharp. Gloves are wise, too.
Click to expand...
Good point Stacy, the foil is super sharp! I just used the razor to lift the edges of the foil enough for the pliers to grab. No scraping.
 
Thescrawnylumberjack said:
oh it certainly does. I did a batch of knives using 309 foil it’s the only foil I use and had the foil stick something fierce this time around.
Click to expand...
I have never had a problem with 309 sticking on 600 blanks heat treated. Before I switched and was using 321 I experienced many sticking foil issues.
 
On blanks I too never had any problem. But with already grinded and hand sanded to 1000grit blades I had foil welding to knife. Pressure from plates, surface sanded, temperature - no wonder why. Started to use talc powder. Hope not to get any welding. 10v knife with welded foil is really no fun to grind and sand.
 
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