RWL34 warping during HT ??

[Rob J Evs]

Hi Guy's

I'm starting to 'loose it' with this steel - I love the way it works / grinds, I love the super fine edge I can get but this warping during HT is driving me nuts....

I bought a length of 3.5mm thick RWL34 and so far 4 out of the 5 blades have warped during HT.

I only cut the blades out with a hacksaw (no angel grinders overheating the steel)
I've used fresh ceramic belts with regular cooling to avoid overheating the steel while grinding
All cutting edges have been left at 0.5mm - 0.75mm (apart from one that was over ground ... my fault totally)
I've had different makers HT the blades for me with the same result....

I also had a damasteel blade HT'd at the same time with no warping at all ...

Now RWL34 is not a cheap steel, is this something I have to get used to or do you think I maybe had a 'faulty' batch .... or am I missing something / doing something wrong? ... Nothing more frustrating than sending a perfect blade for HT to get it back warped

If anyone has any ideas or comments I would be very grateful

Cheers
Rob

[shing]

Steel warps all the time during heat treating. What you need to do is after taking it out of the kiln and wait until it cools down, as soon as its cool enough to handle check for warps. If it is warped then straighten it before it cools completely. The steel is slightly plastic at this stage. I put mine down between two pieces of wood with a gap in between and use a G clamp to bend it straight. Do this very carefully though since it might snap the steel if you bend it too far. It seems to work for all types of steel.

Don't wait until after tempering it to straighten it, it doesn't work.

If you send your blades out for HT, you need to find a heat treater that will straighten blades if they warp or else, grind your knives thick so you will have plenty of steel to grind out the warps.

[Chris Grant]

The plate quench is popular with these steel types, but I almost always oil harden RWL, vertcal quench with consistant straighness.

The only RWL warp I have to date was taper grind 2mm but that was down to the blade leaning at an angle, on the blade rack posts.
I plate quenched the edge in a vice and that sorted that...


Taper grinds and tapered tangs can go banana, some steels are more prone to it than others, but if it's your usual scandi grind Rob, I'd not say RWL was particulary prone to warping.

It might be the rack setup in the HT furnace being off centre, could be many things...

I guess you could specify a plate quench to be done...

Have you tried vacuum heat treatment yet?


CG

[Rob J Evs]

Thanks both for your input, I will take your point on-board

Have you tried vacuum heat treatment yet ?

Chris, I've tried it - same result (from the same length of steel too) - maybe it was just that piece of steel ?

but if it's your usual scandi grind Rob, I'd not say RWL was particulary prone to warping

Wrong Rob Evans Chris 1 blade had a 3/4 full flat all others had a full flat grind I dont find RWL that great for scandi grinds

Do you think I would be better getting the blades HT'd and then grinding ??

Cheers Rob

[Guycep]

I used to have a few warpage problems with RWL-34, until I switched to a plate quench. I quench in oil for 5-6 seconds and then they go straight into the vice between two heavy, flat steel plates. Doing it this way stops the foil wrap welding to the blade and I get great results without a single warpage problem.

Guy

[FGYT]

Do you think I would be better getting the blades HT'd and then grinding ??

Cheers Rob

Thats what I do tho Ive not had any warp from either Vacuum HT or Oil quench I grind all blades after HT


However Chris says that the Stainless property is only available in the top surface after HT which you would grind off but again Ive not had any problem or complaint so far about rusting

From the thickness ( or thinness ) of the rust proof layer Chris is talking about any finishing at all except polishing would remove it any way so you would need to fully finish and Vacuum HT only to enable that

ATB

Duncan

[Chris Grant]

I'm sorry Rob, apologies.

I think it sucks for scandis too BTW.

I guess you can try grinding after HT, however, see Duncan's point and the link I have provided to Joel Bolden's information on lower stain resistance after grinding.

Wrong Rob Evans Chris 1 blade had a 3/4 full flat all others had a full flat grind I dont find RWL that great for scandi grinds

Do you think I would be better getting the blades HT'd and then grinding ??

Cheers Rob

I didn't say that actually, Joel Bolden did HERE
And I was more asking a question about the level of (reduced) stain resistance
(specifically on RWL-34 as it is very close to 154cm...other SS may be different and I think it'd be useful to know.)

You can achive no scaling without vacuum HT easily with correctly sealed foil and brown paper (or injected argon), you get a slight grey discolouration which merely requires a slight buff.

Thats what I do tho Ive not had any warp from either Vacuum HT or Oil quench I grind all blades after HT


However Chris says that the Stainless property is only available in the top surface after HT which you would grind off but again Ive not had any problem or complaint so far about rusting

From the thickness ( or thinness ) of the rust proof layer Chris is talking about any finishing at all except polishing would remove it any way so you would need to fully finish and Vacuum HT only to enable that

ATB

Duncan

[FGYT]

I'm sorry Rob, apologies.

I think it sucks for scandis too BTW.

I guess you can try grinding after HT, however, see Duncan's point and the link I have provided to Joel Bolden's information on lower stain resistance after grinding.





I didn't say that actually, Joel Bolden did HERE
And I was more asking a question about the level of (reduced) stain resistance
(specifically on RWL-34 as it is very close to 154cm...other SS may be different and I think it'd be useful to know.)

You can achive no scaling without vacuum HT easily with correctly sealed foil and brown paper (or injected argon), you get a slight grey discolouration which merely requires a slight buff.

Sorry Chris yes it was some thing you mentioned to me after seeing it brought up

and yes it would be good to know what difference the Stainless nessssss is as you grind back

Maybe we need to Harden a bit of 7mm RWL and chisel grind a big flat on it and leave it out in the garden for a bit and see


ATB

Duncan

[Rob J Evs]

Thanks all for taking the time to reply and thanks for the link Chris / Duncan

Makes some interesting reading ...

I have a few blades almost ready so I may well grind post HT I also have some s30v and cpm154 will give those a whirl too

Thanks again
Rob

[Noddy]

Looking forward to seeing them Rob we will get pics, right?

[Rob J Evs]

Looking forward to seeing them Rob we will get pics, right?

Of course