Hello,

I came across four freebies I couldn't pass up from an injection molding process.  I was looking for some ideas on heat treatment. 

Two slabs are. 3x11x29 weight is about 275lbs each and two slabs that are 4.25x22x29 and weight is about 800lbs.  The material is 420 stainless steel.

Im looking to use the 800lbs slabs.  Any thoughts on how I can heat treat the top few inches?  

I have kaowool (4ft wide roll) and a few 55 gallon drums.

My initial thoughts were to  hang it from an engine lift 2 feet off the ground with the face of the anvil pointed down. Then build a makeshift forge around the bottom 10 inches of the slab using some 1/8th 316 plate that I have an abundance of.  Calc the total volume and add 3/4 or 1" burners  based on cubic inches of space inside of the makeshift forge, positioned to swirl.

My thought is that I can simply raise the slab higher up out of the makeshift forge, move the engine lift slightly to the 55 gallon oil drum to quench.  

Temper-  I'm not 100% sure.  Probably will lay a 29x29 x1.5in slab down, put a layer of kaowool over it and set the newly quenched anvil slab on it with the hard face up.  Cover the inside of a 55 gallon drum with kaowool and place the drum upside down over the slab.  Mount two burners in the drum and dial in the temperature to 400.

The things I mentioned are things that I have sitting around. I don't mind investing if it makes life easier.

I'm looking for any ideas or ways of doing this that may make life easier.

Image is the 11x3x29 slabs, not the 4.25x22x29s

420 SS has issue with tempering embrittlement, and it’s not real impact resistant to start with. If it were me I would use it soft and let it work harden or have it professionally heat treated.

Just my 2cents,

David

 

Good Morning,

You will be beyond 'Old and Grey' before you need to do anything about it. Enjoy the journey!!

Neil

Totally agree with Goods. Mount it, dress the edges, and get to forging!

I think i can agree based on what i would have to do to pull it off.  But I think i may have improved my odds.  It will fit in my kiln, mostly.  I haven't used it in a long time.  Would probably have to cut a hole in a ceramic lid the same dimension as the steel and hang it.  That would work for heating and temper with much higher odds of success.    

Any thoughts?

My big question is how to quench such a large block. Normal 420SS is air hardened, but with so much mass, you may have to oil quench it. That would be one massive tank to prevent the oil from over heating and flashing in a massive fire ball. You might get lucky with a several good consistent air blows on it. I understand where you’re coming from, but it could be a very difficult task outside of an industrial setting. With section this large there is serious cracking concerns with both austenitizing and quenching…

Also, I take back my comment about the block work hardening. Apparently 420SS doesn’t take kindly to work hardening. If you happen to have an induction forge you may be able to surface harden it that way… a bit risk though.

Sorry, not trying to be a downer 

 

Keep it fun,

David

 

I agree with almost everything in David’s last comment, with one exception: I am trying to be a downer. I really think that unless you can get a professional heat-treatment shop to handle the hardening and tempering, you will be MUCH better served by just putting it to use. 

According to the ASTM Heat Treatment app, you’ll need to get the piece up to 1950°F and then hold it there for two and a half hours. That’s not a small expense in fuel. 

Then you’ll need to quench it in oil, which creates its own issues. First of all, the general rule of thumb for quenching volume is one gallon per pound of steel, and that’s 800 gallons. Even if you go with half that volume, you’ll need to acquire 400 gallons of quenching oil and dispose of it when you’re done. 

In short, you’re undertaking major expense and hassle for a doubtful outcome of uncertain benefit. I would strongly advise you to consider what other tools and materials you could invest in and to what better use you could put that time. 

Have you checked it's current hardness? If it's an air hardening steel there's a very good chance it is already at a decent range.

If you did temper it back, the "blue" range is about as high as you would want to go, and even then, you can't trust oxidation colors on something that big. Too complicated to harden at home and really much safer just using it. If you have issues down the road, there's plenty of mass to dress it up again.

Those would make lovely Brian Brazeal style anvils, i.e. mounted sideways so the long end points sideways and the narrow side is up, with dies ground into it, although I shudder to think of the costs of the abrasives needed on something that hard and that large. I believe his are generally mild steel and dressed as needed.

 

I am no expert on materials such as stainless, but seem to be an increasing expert on the limitations of the human being’s ability to ruin or not ruin objects.

Are you going to be pounding hot steel on it with a 2lb hammer? That’s what I do - it’s not nearly enough to mushroom out an 800 lb block very quickly. My advice if you want to use it as an anvil is realizing that we are people, not machines, and that your arm is not a power hammer. Use it as is and IF you need to dress it cross that bridge down the line.

I want this new anvil to be a clear upgrade over my existing ones that already perform well.  Since this is a large block, selective hardening may be perfect.   Oil quenching is ideal here because it provides a slower, more controlled cooling rate than water or brine, reducing the risk of cracking on a massive piece like this. I don’t mind the time, effort, or expense — what matters most is successfully completing the project once I start it. With four blocks available, I have room to experiment and refine the process.

My understanding is that oil quenching will be the best method for this situation. I’ll only be heating the face and top of the anvil. The heated zone can be as shallow as ~3 inches deep or as deep as 2 feet, depending on the final quench oil volume.  The rest of the block will stay significantly cooler, acting as a heat sink.

• If I heat only the top 3 inches of the face, that equates to roughly 85 lbs of steel being fully austenitized.
• Heat transfer rates on stainless (if using stainless are about half that of plain steels which helps control the process.
• I plan to use a high-flow oil drum setup with controlled dipping depth to manage the quench effectively.

Thermal calculations:

The math shows that preheating the oil to 125°Fish, the total temperature rise from quenching a piece sized approximately 4.5" × 3" × 22" (heated portion) at 1950°F would be about 100°F in 55 gallons — bringing the final oil temperature to ~225°F. Scaling up to 75 or 100 gallons of oil gives me a much safer margin in real-world conditions and helps keep the quench more consistent.

I’m fully prepared for the work and any associated costs. This anvil will see some modifications before hardening, and having four chances means I can iterate if needed. The priority is ending up with a superior, reliable tool rather than rushing the process.

You all have been very helpful in helping me hash out the details and risks. The process is already very different from where it started.   

Godspeed and DOCUMENT IT! We would love to be regularly updated with either successes or failures, despite our warnings to the contrary. 

Keep us updated, but more importantly be safe! You may even plan on quenching outside at a good distance from other combustibles…

Like I said, I understand where you’re coming from!

I just had another thought. Have you considered contacting an other mold shop to see if they would be interested in trading materials or buying the 420SS from you? You might be able to get some big 4140 or even H13 (twice the toughness with the about the same hardness) and any of cuts or extra pieces would make wonderful stock for tools.

Keep it Fun,

David