My first heat treating, what do the experts say

[Dan512]

So i just made my first batch of 4 small kitchên knifes.

steel,is 80CrV2 (or 1.2235 as we call it in Europe). Thickness at the spine is just under 3mm.

Hardened at 830°C / 1526°F in my electric oven and quenched in canola oil (45°C / 113° F)

2 blades came out all bent and I broke them trying to straighten them out before the tempering, gotta learn the hard way.

But at least this way I could put them under the kids cheapo USB microscope.

So here are the pucs

The 1st one is of a knife that I had to put through the oven 3 times before the file would slide over it, the final time I left it 10 minutes in the oven. So in all it will have spend approx 20 mi utes at 830°C.

The 2nd and 3rd are from the second knife, it spent 6 minutes in the oven.

What do the experts think about the grain?

[jimmontg]

When you quench in oil did you shove them in edge first and only move them up and down, no sideways motion? Prevents some of the warping.
How far did you grind them before heat treat? Grind no more than 90%, leave a mm of edge on the blade.
Did you use a flash when you took the pictures, too many reflections? They all look like the grain is too big, but the 1st one definitely is. Proper grain should look like grey velvet.
Proper heat for this steel is 1545 to 1615. Heat to 1200 let soak for ten to 15 minutes then ramp up to 1570 for 5 minutes then quench in your hot oil. Be quick from oven to oil.
Temper at 400 to 430 F for two hours two times.
When doing the initial grind did you keep the metal from getting too hot? I always keep quenching it because if you grind a hot spot (turn it colors) it tends to warp there.

[Dan512]

Originally Posted by jimmontg

When you quench in oil did you shove them in edge first and only move them up and down, no sideways motion? Prevents some of the warping.
How far did you grind them before heat treat? Grind no more than 90%, leave a mm of edge on the blade.
Did you use a flash when you took the pictures, too many reflections? They all look like the grain is too big, but the 1st one definitely is. Proper grain should look like grey velvet.
Proper heat for this steel is 1545 to 1615. Heat to 1200 let soak for ten to 15 minutes then ramp up to 1570 for 5 minutes then quench in your hot oil. Be quick from oven to oil.
Temper at 400 to 430 F for two hours two times.
When doing the initial grind did you keep the metal from getting too hot? I always keep quenching it because if you grind a hot spot (turn it colors) it tends to warp there.

I think I might have move the blades sideways. Will cut the oil next time.

The reflections are from the Led-light that is integrated into the microscope. It turned it down as far as possible. Any more and the picture was to dark (it’s a $25 thingie from Ebay)

I quench every grind, so no hot spots but good to know they can cause warping.

My oven will need quite some time to get from 1200 to 1570, is it ok to leave the blade in there for 1 hour or so, as long as I stay below the 1545°?

[jimmontg]

Then go from room temp to 1570 as fast as your oven works, but you cannot spend 30 minutes above 1450 as that will cause grain growth even with the vanadium. Vanadium at 0.20% restricts grain growth, but not for much longer than 30 minutes above trans formative heat. Aim for whatever takes 30 minutes from 1420 to 1570 then quench. Note the temperature at 30 minutes.

You might be better off with O1 tool steel at 15 mins at 1475, then quench in oil from 120 to 130. What kind of oven do you have?

[Dan512]

Originally Posted by jimmontg

Then go from room temp to 1570 as fast as your oven works, but you cannot spend 30 minutes above 1450 as that will cause grain growth even with the vanadium. Vanadium at 0.20% restricts grain growth, but not for much longer than 30 minutes above trans formative heat. Aim for whatever takes 30 minutes from 1420 to 1570 then quench. Note the temperature at 30 minutes.

You might be better off with O1 tool steel at 15 mins at 1475, then quench in oil from 120 to 130. What kind of oven do you have?

I have an electric lab oven, but it’s older and the heating coils are worn out so it needs around 2,5 hours to get it up 1520°F. I will have to time it to see how long it takes to get it from 1200 to 1520

[jimmontg]

Try putting your blades in your home oven and heat up to 450-600 for 20 minutes and then transfer to your heat treat oven at 13500 and crank it up to 1520. 1420 is where steel becomes nonmagnetic and minor austenizing begins before that. Hopefully your oven can go up to 1520 in 15 minutes, then I'd quench as soon as it gets there. 30 minutes above 1400 will cause some unwanted grain growth even with the vanadium I would think.

Because of your oven you're going to have to experiment some to get a decent knife without much grain growth. Make some pieces to test and break, like I said proper grain should look like grey velvet, no crystals, not even tiny ones if you can see crystals with your naked eye then the knife will tend to brittleness.
You wouldn't have a forge would you?

[Dan512]

Originally Posted by jimmontg

Try putting your blades in your home oven and heat up to 450-600 for 20 minutes and then transfer to your heat treat oven at 13500 and crank it up to 1520. 1420 is where steel becomes nonmagnetic and minor austenizing begins before that. Hopefully your oven can go up to 1520 in 15 minutes, then I'd quench as soon as it gets there. 30 minutes above 1400 will cause some unwanted grain growth even with the vanadium I would think.

Because of your oven you're going to have to experiment some to get a decent knife without much grain growth. Make some pieces to test and break, like I said proper grain should look like grey velvet, no crystals, not even tiny ones if you can see crystals with your naked eye then the knife will tend to brittleness.
You wouldn't have a forge would you?

I have a 2 burner gas forge, haven‘t gotten around to using it so far.

[jimmontg]

Since your oven is too slow then to the forge. First buy some tinted safety glasses or at least sunglasses, the forge heat/light is harmful to your eyes, plus a piece could pop sparks.
But anyway get a magnet and start heating up your blade, when it starts to get red start touching it with the magnet, when the magnet stops sticking to it, heat for 5 minutes more making sure you don't over heat any one part of it. Or in other words move it around then quench. It should pass the file test. Then temper and break it to make sure your grain is good.