Presoaking stainless steel heatreatment? How to HT 420HC?

[FredyCro]

I am about to recieve my first HT oven and am getting up to speed on ABCs of HTing stainless.

A lot of SS HT procedures call for a presoak at a lower temperature. If I understand it correctly you would need more than one oven to do it right.

I think I read it is ok to put the knife at a lower temp and then ramp up to a higher temp. Is this correct? What if the oven needs a long time to get to the final temp?

Finally, what is the drawback of not doing a presoak? Lower hardness, different structure?

I have a pile of 420HC which is considered a low budget steel. There is a number of threads that this steel can be HT up to 60 Hrc and is actually not that bad if HT correctly? How would you HT if you had one oven and access to dry ice.

And yes, I plan to buy larrins book in the future!

 

[Daniel Carraher]

Presoak isn’t necessary for most stainless steels in knifemaking. That’s generally for pieces much thicker than we use.

 

[FredyCro]

Presoak isn’t necessary for most stainless steels in knifemaking. That’s generally for pieces much thicker than we use.

Thats one of the opinions I stumbled upon.

So, the recipes calling for presoak are not knife specific?

One piece of info from Sandvik homepage:

"Batch hardening
When larger batches are hardened, there is a risk of temperature difference within the batch. The material should therefore be given a chance to achieve uniform temperature by soaking it at 850°C (1562°F) during the heating process. The material should also be given a longer soaking time and slightly lower temperature in relation to piece hardening."

Does this mean that the presoak is mostly meant for the industry hardening procedure?

 

[FredyCro]

Found Larrings article on the topic, will make sure to read this first and come back with questions

 

[FredyCro]

So from what I gather (simplified!) no presoak and no prequench necessary?

I have following steels to play with:

Plate quench
D2
14C28N
440B
BECUT
1.4034 (420HC)

Oil quench
80crv2
75cr1

Now I just need to figure out where to test for hardness. Maybe I could ask someone at the technical university..

 

[FredyCro]

I am going to bump this for further advice. Any recipes for 420hc (1.4034)? Any further opinions on presoaking? Thanks.

 

[Larrin]

Presoaking is not necessary. 1925F austenitize would be a good starting point. Doing coupons in 25F increments around that would tell you peak hardness. Go as cold as you can directly after the quench.

 

[FredyCro]

Presoaking is not necessary. 1925F austenitize would be a good starting point. Doing coupons in 25F increments around that would tell you peak hardness. Go as cold as you can directly after the quench.

Thanks, I am happy that now I have a reason (oven) and time (exam leave) to go through your homepage completely. Ordered the book yesterday

 

[Scaniaman]

Then there is the pre quench that some people are doing on steel like AEB-L, for grain refinement.

And then there is annealing prior to austenizing, to reduce warpiness.

I haven't done either yet, but have the ambition to try at some point.

14c28n is dirt cheap, a breeze to machine and performs great. I recomend it. I austenize at 1070 C and freeze to -40 celcius and get 61-62 Hrc after 155 C temper.

 

[FredyCro]

Then there is the pre quench that some people are doing on steel like AEB-L, for grain refinement.

And then there is annealing prior to austenizing, to reduce warpiness.

I haven't done either yet, but have the ambition to try at some point.

14c28n is dirt cheap, a breeze to machine and performs great. I recomend it. I austenize at 1070 C and freeze to -40 celcius and get 61-62 Hrc after 155 C temper.

Yes, prequench is definetly interesting. All this calls for at least hardness and toughness testing, which I am not equipped for. Hopefully I will be able to reach someone at uni to do some coupon testing.

I am looking forward to using 14c28n.

1.4034 is the only stainless I was able to find in 1mm, 1.2mm and 1.5mm thickness. I think it will make good kitchen blades for home users if I could reach 59-60 hrc. Definetly will use dry ice, I have a box already and I can get it cheaply nearby.

 

[Scaniaman]

Definetly will use dry ice, I have a box already and I can get it cheaply nearby

I envy you. Getting it here is slightly complicated and price. I am looking into a 15 kg CO2 tank instead, seems handy.

Another great and available stainless is RWL-34. With the same HT as above I get 63.5 Hrc and it holds a great edge and easily strops back to hair popping when needed.