1075 heat treatment

[Andrew Gillespie]

What temperature do I use for 1075 for normalising, hardening and tempering?

[Alan Longmire]

What is your heating setup?  Just a forge, or do you have a kiln?  And if a forge, gas or solid fuel?  How are you judging temperature, in other words?

 

1075 is one of the easiest steels to heat treat, since it's right at the eutectoid point with reference to the iron/carbon phase diagrams and it has no other carbide-forming elements.  This means no soaking needed, as there are no big carbides to break up or distribute.  Your only variable is manganese, which ranges from 0.4% on the low side (the maximum recommended for good hamon) to around 0.8% on the high side (deeper hardening).  

 

If you're using a forge with no thermocouple, watch for decalescence as always.  If you have a way to accurately measure temperature, normalize by heating to 885 C/ 1625 F and cool to black in still air. You can do descending heats down to 815C/1500F.  Harden by heating to 815C/1500F and do not soak, quench immediately in warm oil for thicknesses below 6.5mm or so.  Thicker sections may need water or brine.

 

Temper immediately for at least two one-hour cycles. Depending on intended use, temper at anywhere between 163C/325F to 232C/450F.  I'd go with 163C for a fine slicer, 175-200C for a general chopper/EDC.

[Andrew Gillespie]

Thanks! I use an electric kiln with thermocouple. I only do stock removal. This particular knife is 3mm thick and meant to be a fine slicer.

 

I will try: normalize 885 C, heat to 815 C and quench in 40 C oil and then 2 one hour cycles at 163 C.

[Alan Longmire]

Since you're doing stock removal only, you may want to normalize two or three times to refine the grain.  The raw barstock is probably spheroidized annealed, and the grain will be on the large side.

[Andrew Gillespie]

Thanks, I will do so.

[Andrew Gillespie]

I messed up, the piece curved. I am not totally sure why, but I was cooling it outside the furnace between heating. I think that it might have cooled faster on one side. Is there any good way to straighten it?

[Alan Longmire]

Since it's not hardened yet, just bend it back straight. Hot or cold. If you do it hot it reduces the chance of it warping again.

 

Did you put it down while it was cooling? 

[Andrew Gillespie]

I didn't put it down, I hung it with a wire hook through a hole drilled into the handle section. I will try the straightening hot, hopefully I will get it right.

[Gerhard Gerber]

On 7/30/2021 at 1:36 PM, Alan Longmire said:

Since you're doing stock removal only, you may want to normalize two or three times to refine the grain.  The raw barstock is probably spheroidized annealed, and the grain will be on the large side.

This.......I did not know.  Not unhappy with my 1070 results, but if it could be better.....

[Alan Longmire]

Hmm...  So, uneven cooling somehow.  Is it a thick chisel grind?  Those can make interesting warps...

 

3 hours ago, Gerhard Gerber said:

This.......I did not know.  Not unhappy with my 1070 results, but if it could be better.....

 

For any low-alloy steel a normalizing cycle or two before hardening can't hurt.  If you're using your kiln, be sure to protect against decarburization.  

[billyO]

I was just looking this info up for a friend, so I thought I'd add what Dr Larrin Thomas says in his book Knife Engineering:

Recommended normalizing temp for 1075 - 1525F. 

But he does say "It is better to use a relatively high temperature to normalize, followed by 1-2 grain refinement steps at a single lower temperature optimized for grain size."

Earlier in the chapter he says that the normalizing temperatures he recommends are generally the "minimum" temps, and "As much as 100F higher than the recommended temperature in the table is probably reasonable."

He also writes:  - "the 'descending' temperature cycling method does not really help with the goal of grain refinement."  and "1450F is a safe grain refining temperature for most low alloy knife steels."

 

For hardening, his recommendation for 1075 is 1475F for 10 minutes, fast oil quench, temper at 350F-400F.

Edited August 3, 2021 by billyO

[Gerhard Gerber]

On 8/3/2021 at 8:09 PM, Alan Longmire said:

Hmm...  So, uneven cooling somehow.  Is it a thick chisel grind?  Those can make interesting warps...

 

 

For any low-alloy steel a normalizing cycle or two before hardening can't hurt.  If you're using your kiln, be sure to protect against decarburization.  

I was wondering about that.....
I have a roll of stainless foil, but its expensive and difficult to get more, so I use it only for stainless

[Charles dP]

Still not enough caffeine to employ all my neurons but I seem to remember an old thread where people were experimenting with making home-made anti-scaling compound which I believe stops decarb (did anyone ever manage to make a good one?). @Joshua States, will the titanium oxide white paint stop decarb too?

[Andrew Gillespie]

I wish I could buy the commercial anti-scale, but I can't find anyone who sells it. My attempt at using boric acid was not 100% but it helped a little. I'm wondering if I applied it unevenly causing one side to cool at a slower rate.

[Alan Longmire]

Time to get creative, then.  Start with finely powdered charcoal and clay, and try to find a binder like molasses or cider dregs. That's not too far from Theophilus' recipe from 1100 AD or so. Adjust quantities to get a stiff dry paste.  Use as thin a coat as you can.  Maybe add some borax or boric acid. 

[Joshua States]

17 hours ago, Charles dP said:

will the titanium oxide white paint stop decarb too?

Yes it does.

This is what I use. Works great.

[Eric Morgan]

I wonder if a wash of titanium dioxide would have the same effect… I can get loads of the stuff from work for nothing.

[Joshua States]

1 hour ago, Eric Morgan said:

I wonder if a wash of titanium dioxide would have the same effect… I can get loads of the stuff from work for nothing.

Just figure out a way to put it into a solution that will stick to the metal

 

[Eric Morgan]

51 minutes ago, Joshua States said:

Just figure out a way to put it into a solution that will stick to the metal

 

I’ll get some this weekend and give it a go when I get a chance

[Andrew Gillespie]

I read that carbon will damage the heating elements in an electric kiln. Is that true?

[Jerrod Miller]

7 hours ago, Andrew Gillespie said:

I read that carbon will damage the heating elements in an electric kiln. Is that true?

It can, depending on the material of the elements.  

[Andrew Gillespie]

I managed to get hold of an anti-scale Consursal Z1100 which is a german product. Works well, but is very expensive.

[Andrew Gillespie]

I continued experiments with boric acid out of curiosity. I am now convinced that it cannot work for steel as it becomes too corrosive at the temperatures needed for steel. Rather leave it for the jewellers working with precious metals and lower temperatures.

[Gerhard Gerber]

On 8/5/2021 at 11:20 AM, Gerhard Gerber said:

I was wondering about that.....
I have a roll of stainless foil, but its expensive and difficult to get more, so I use it only for stainless

This has been bothering me, especially since I just got some more 1070 and one piece of 1084.
Foil situation is unchanged, difficult to get and expensive, reserved for stainless, more so because I hope to get a piece of Elmax in the near future.

 

So I was thinking, I have the gas forge, even if I'm guessing temperature, as long as I don't completely cook the blades they could benefit from a few normalizing cycles before HT in the electric kiln?

[Alan Longmire]

I'm going to say yes. They certainly could.  Is there anything you can mix up as anti-scale compound? Something as simple as half refractory clay and half charcoal powder will work, as long as it stays on the blade until it hits the quench.  A paper thin layer is enough. Mix with just enough water so you can smear it on.