Flame Hardening Carbon Steel Runners

[rpotcova]

I have a very old set of Sarns runners that I reshaped, thinned and profiled for snow plates. Seems that any heat treating that was performed is now non existent. Aluminun stiffener is now removed also.

Has anyone here ever flame hardened a runner edge?   I watch videos of knife makers and they heat and quench the entire blade and stock. Then they anneal as required.  I know that I could send them out to a heat treater but thats no fun.  Oxy/Acetylene torch is hot enough but heat is concentrated and unable to get the entire edge to its critical temperature all at once. I'm about ready to resort to old world methods of hot coals and blower.

I assume the steel that Bill used had enough carbon to heat treat.  I also assume that Bill treated them in his shop using his own equipment and methods.

Anyone ever take a stab at this? 

Rich

[Bob Rast DN1313]

The steel Sarns used was a machine tool steel  maybe D2 which has high carbon contenet

I have been doing some reading on the same topic. Not sure how to proceed read somewhere that quencing in old motor oil was a option would probably start on fire when you drop in the steel.
I ve thought that may be a propane torch or two  wired together might do a better job than one burner or perhaps soldering tips on multiple MEP Gas cyclinders
I guess once you harden you also have to do it again to anneal them.
If you have a acetylene torch  might be able to heat up several inches and quench with a hose and continue down the blade

Let me know how it works out

Thanks
Bob Rast

[Bob Rast DN1313]

If you still have original edges and just heated up when working on them you may have not  have affected the hardness unless you got them up to 1800 degrees or so which would have been cherry red.You might just need to re temper which you can do in a oven at 350 degrees

Have you checked the hardness, ? Are the easy to file or hard   file doesnt scratch them?

Might be easier to build a small charcoal forge  charcoal and air 

[Paul Goodwin - US 46]

I'm afraid you guys have gone down the wrong path. Bill used SAE 1060 steel, which is not easy to harden. The runner edge was induction hardened to around 3/4" from the edge to about Rockwell C52.  I think you will have a hard time flame hardening this steel.  But I would be surprised if you had ground through 3/4" of steel, so I'm with Bob - check the edge with a file to see if it is still hard.

[Rolley]

Good stuff guys.  If Sarns were paying retail for D2 steel, they'd be hard pressed to show a profit even at $800 a set.   I'm assuming SAE 1060 is a lot cheaper.

[rpotcova]

Thanks for all the input on this.  I initially thought Sarns used an SAE 10xx series steel but wasn't sure.  SAE 1060 has .55% to .65% carbon by weight which should be sufficient for heat treating.

These runners were very old, maybe 1955 when the origional US 216 was built?  They had about 2" of .008 and were radically shaped at the ends.  I easily took off 0.5" of edge at the center of the blade.  Regardless, they never held an edge and seem soft when scratched. 

So with nothing to loose and extremly dangerous with my BSE degree and You Tube videos, I set out last night to harden runners.

Fired up 16 pounds of charcoal in a standard grill.  (26" runners just fit diag.) Do not attempt in garage.
Used compressed air nozzle in hole of grill to stoke the coals. Not full on but about 50% full open.
Placed blades in coals sharp down when coals were about 30% involved.  This brought up the temp slowly.
Once coals were fully involved, about 2" of edge of runner was red hot in about 15-20 minutes.
Its important that the edge is not magnetized when red hot.  If it is then continue heating.
Remove from heat and oil quench with used motor oil. Do not use water.  Do this outside so neighbors can laugh.
I used about a gallon of oil but it quickly heats, boils and catched on fire.  Chemical fire extinguisher required here. NO WATER ON HOT OIL!  Cooling oil somehow between quenches or using a larger amount is prefered.

Results:

Blades slightly warped and lots of crud to clean off the steel.  Edge very hard compared to the upper portion of runner.
I will get a Rockwell C number and report back.
My edges were sharp.  That is a mistake.  Only bevel slightly leaving runner dull (flat on bottom) I had chipping from the process.
Yard is a mess with charcoal ash and burnt oil on my fire pit.  No fire truck visits to report.
Tempering is possibly required to reduce brittleness.  Maybe not due to the fact that the upper portion of the runner is still soft. As long as I can sharpen and the edge doesn't nick easily then I should be ok.

So there you have it.  Individual results may vary.  Doug Harvey would probably cringe if he read this. 

Next Lesson:  Teflon Nickle Coating

RP

[Bob Rast DN1313]

Cool I have 2 sets un hardened Ill have to get some charcoal and a grill nobody wants.
I read that to temper you only need 350 degrees which you could do in oven if you dont mind the oil smell in your kitchen
or reheat with the charcoal but only need to get blades blue and quench
You tube is awesome you should video the next operation

so the edges melted or chipped ?

[rpotcova]

Working with some smart guys in regards to the tempering. Its a lost art for sure.   Yes they can be done in a standard oven but not sure of the time and temp yet.  I will temper then straighten...hopefully without damage.

My edges did chip or melt...hard to tell.  Not real bad.  Can be sanded out.

More info after the weekend.

[rpotcova]

Made the decision to temper the plate runners.  They seemed to be very stiff and difficult to shape back to straight.  I was concerned with cracking them when I beat them on the anvil.

After some research, I placed the 3 runners in my oven at 500 degrees for 1.5 hours then quenched with water.  This formula should have made the runners workable but maintained hardness.  In theory, I should have lost about 10% hardness but gained about 30% toughness or workability.  That is a good trade off in my opinion.

After this process the runners were somewhat easier to straighten and seemed to maintain most of the hardness. Sorry, no Rockwell data.  Now its time for clean up and off to the plater.

As you can tell, these are becoming pretty expensive runners with no guarentees of the final product working as planned. 

If you see these at a swap meet next fall the answer should be apparent.