Suggest me how to avoid 14C28N warping

[PEU]

Hi guys, I'm a huge fan of Sandvik 14C28N, you can say its an improved version of AEB-L.
I use it for all my culinary knives in 2mm (0.08") thickness with great success.

BUT

It seems at one point Sandvik rolls the sheets and this tension is never relieved before shipping to the customers (its my theory), so after laser cutting a seemingly flat sheet all the knives end up with a noticeable warp.

To solve this, I thermal cycle them first to 850C and then heat to 600C and leave them overnight so they are soft again.

Then I do what I need to do, holes etc, and do the hardening/tempering using my watercooled hardening press, even with this pressure, I estimate around 50kg/100 pounds, some of them, around 10% still warp.

On the other hand, steels from Bohler, say K110 (D2) or K720 (O2) end up dead flat 99% of the time at the same thickness.

Is there something you guys suggest to improve my good shield using 14C28N?

Thanks

Pablo

 

[Larrin]

Maybe you should try a full anneal instead.

 

[PEU]

Thanks Larrin, 735C for a sub-critical anneal is right? How long would you leave it heating and then cooling?

 

[JTknives]

I get this same issue with aebl, granted we can work through 99.9% of this but still frustrating. I’m wondering if thy employ a straightening technique that the aluminum guys use by stretching it. I thought I remember seeing something like that on my last invoice.

 

[Larrin]

Thanks Larrin, 735C for a sub-critical anneal is right? How long would you leave it heating and then cooling?

Try a full anneal. 900C for 2 hours and then cool at 15C/hr.

 

[PEU]

Will do, 15C/hr until what temp is reached? (hopefully you don't say room temp! that's six days! ) Thanks!

 

[Larrin]

Will do, 15C/hr until what temp is reached? (hopefully you don't say room temp! that's six days! ) Thanks!

600C. Make sure you wrap it in foil.

 

[P.Brewster]

watercooled hardening press

I'm just here for pics of your water-cooled hardening press. I had the same idea.

Below is a copy/paste of another maker's method for AEB-L, if anything seems useful. I think the first plate quench is done only for straightening.

-Straighten any warps -Wrap with stainless foil -Fast ramp to 1350, when oven hits 1350, place blades in, and soak at 1350 for 4 hours. -Remove and air cool -At this point they are now annealed and stress relieved. -Ramp oven to 1725 -Once oven hits 1725 place wrapped blades in oven, allow to come up to temp and soak 10 minutes. -Plate quench after 10 minute soak. -Ramp oven to 1970. -Once oven hits 1970, place wrapped blades in, allow to come to temp and soak 15 minutes. -Plate quench -Remove from foil pack -Subzero treatment in 99% alcohol and dry ice, or liquid nitrogen, but the dry ice works just fine. 1 hour is enough but sometimes I leave mine overnight depending what time of night it is. Sometimes I end up heat treating at midnight or later.

 

[PEU]

I'm just here for pics of your water-cooled hardening press. I had the same idea.

Here are some photos, the plates were CNC machined and then sealed with regular silicone, the pump is the one used for aquariums that goes inside the water

You can check more photos here: https://peu.net/cuchillos/index.php?/category/10

 

[Robert Erickson]

Personally, I have found that I get the least amount of warpage if I leave the blade tightly clamped in between my quench plates until it's completely cooled off. It's usually 4-5 minutes. Then right in the liquid nitrogen.

 

[DevinT]

I would grind the HAZ, do a pre-quench from 1750f, full quench from 1950-1975, all between the plates.

If there is a problem after the pre-quench with warping, do a sub-critical anneal, straighten, then quench from 1950-1975.

Hoss

 

[PEU]

Its around 10% of the batches that bug me the most, today was holiday here in Argentina, will try this week the suggestions. Thanks!!

Pablo

 

[PEU]

Try a full anneal. 900C for 2 hours and then cool at 15C/hr.

Came back to this thread to say Thanks Larrin!.
After doing this procedure, a new batch of laser cut blades came out of the full TT unwarped, only a couple of knives out of 50+ had to be straightened.

Pablo

 

[Larrin]

That’s great I didn’t even remember this thread.

 

[Willie71]

Thanks for this. I struggle with AEB-l, and find z-finit has the same issues. I have dome a subcritical anneal, and fixed ober 90% of the problems. I will do a full anneal next time and see how that works. M4 in thin stock has been an issue too.

 

[PEU]

I keep coming to this thread when I have problems with warping, so again, thanks Larrin

There is also another older thread with a comment from the late Mete (RIP friend), where he suggested doing a subcritical at 650C, what would be better?

Pablo
PS: Mete's comment https://www.bladeforums.com/threads...ment-etc-need-some-help.1293631/post-14829931

 

[scott kozub]

I had issues with AEBL. I use aluminum plates in a vice like most people but in a vertical orientation. The plate are loose in the vice.

What i did was to drill and tap holes in each corner of my plates. I clamp in the vice then use an impact driver to drive in the bolts. Then the plates (now bolted together) get dunked into water. I agitate the plates for a bit till they're cold. I then unbolt the plates and remove the blade, cut off the foil in go into the liquid nitrogen. I have had no warps since doing this.

I use bolts that are long enough so that they are started but I can still separate the plates enough to insert the blade.