Hardening a Rail-Road Spike

[Hayden H]

Well the top line about sums it up, I forged out 2 hawks, out of 2 rail road spikes. I quenched both of them, but it seems to me that neither of them got very hard. I read somewhere that spikes where 1095 carbon or along those lines. I used one old spike and a fairly new one. I quenched in water, not oil. I did a fair bit of grinding to knock of the scale to temper it, it didn't get over 175 degrees in grinding. I put an edge on one just to see the hardness, and it wasn't very hard at all. What'd I do wrong?

[Nakedanvil - Grant Sarver]

I think even "high-carbon" spikes are barely .35 carbon and most are pretty much mild steel.

[Hayden H]

Well crap, I think I might cut a slot, and forge weld in an old Nicholson file peice

[CurlyGeorge]

I make a lot of RR spike knives and always tell the folks that buy them that they are more of a novelty knife than anything, because they don't hold a very good edge. I do my final quench in oil. But it's still not very tough. :)

[MattBower]

Mix up some 10% brine, or Superquench if you're feeling ambitious, and re-HT using that as your quenchant. The theoretical maximum should be over RC 50, but you'l need a very severe quench to get anywhere near that.

[jimmy seale]

also there is no need to temper, unless you add the h/c bit to it

[Nakedanvil - Grant Sarver]

Mix up some 10% brine, or Superquench if you're feeling ambitious, and re-HT using that as your quenchant. The theoretical maximum should be over RC 50, but you'l need a very severe quench to get anywhere near that.

Hey Matt! What carbon level is that based on? 25 or 35?

[Nakedanvil - Grant Sarver]

Actually, I usually make throwing 'hawks from A-36 as forged and carry a file to dress them.

[Nathan Hall]

Im not sure of what they RC at, but the "Superquench" does make them harder than water or oil, if my testing method is accurate.............. one quenched in Super quench can scratch one from either water or oil, not very scientific, but was more of a curiosity thing anyway as they are just novelty items, if I remember it I will take one to a shop I order steel from and have them rockwell for me

[MattBower]

Grant, I've seen a couple charts in different engineering/metallurgy texts that say 0.3% C can reach 54-55 RC. To me that seems a little hard to believe in the real world (outside of something like H13, with really high alloy content), which is why I hedged my bets a bit.

[Hayden H]

Even if I forge welded a peice into it, I shouldn't necessarily have to temper it. Due to the fact that I'd want the inside hard as possible, and the outside (spike) would be relatively soft. Right?

[MattBower]

Only if you want it to be virtually unsharpenable with hand tools, and prone to chipping along the edge. If you've never had the pleasure of working on something well over RC 60 with a stone, it's a treat!

[Hayden H]

I didn't think of the extreme hardness factor

[Nakedanvil - Grant Sarver]

Even if I forge welded a peice into it, I shouldn't necessarily have to temper it. Due to the fact that I'd want the inside hard as possible, and the outside (spike) would be relatively soft. Right?

Don't know any practical way to make it hard on the inside and soft on the outside.

[MattBower]

He means san mai construction. Forge welded envelope of low-carbon steel around a high carbon core.

[Steve Sells]

he will still have the Martinsite brittleness factor to deal with, unless he tempers it at least at 325F or so, Also as for carbon levels, Migrations happens a lot faster than most people think *(for proof look for the thread about it) so it will still be less than the hard inside and soft outside you may imagine :)

[MattBower]

I agree, Steve. That's why I told him to temper unless he wants an unsharpenable blade with a chippy edge.

Migration does happen fairly fast, but it's not as big a deal in san mai where you have relatively thick layers and you're not folding and welding repeatedly. WIth an acid etch, you can often see the carbon "transition zone" along the weld seam.

[thingmaker3]

Im not sure of what they RC at, but the "Superquench" does make them harder than water or oil, if my testing method is accurate.............. one quenched in Super quench can scratch one from either water or oil, not very scientific, but was more of a curiosity thing anyway as they are just novelty items, if I remember it I will take one to a shop I order steel from and have them rockwell for me

That actually IS scientific, Nathan. It's just a matter of qualitative versus quantitative.

Grant, I've seen a couple charts in different engineering/metallurgy texts that say 0.3% C can reach 54-55 RC. To me that seems a little hard to believe in the real world (outside of something like H13, with really high alloy content), which is why I hedged my bets a bit.

Alloying elements other than carbon and boron have no effect on how hard the steel can get. They do change the amount of time you have to get there. Also, just because one can get 55Rc at 0.30% carbon (or 60Rc at 0.40%) does not mean one will get it.

Regarding diffusion rates, (whales migrate, carbon diffuses) "Fast" and "slow" don't have any numbers attached to them. Nobody has defined "medium" yet in this thread.

Look up "Fick's Second Law of Diffusion" using your favorite search engine. The diffusion coefficient of carbon in iron is dependent on concentration. Complicated stuff! Not the kind of thing about which we should be tossing absolute statements.

One thing we can indeed state empirically about diffusion rates: plenty of smiths throughout history have welded steel to iron to make serviceable tools.

[cracker72]

I'm in the uk so I don't know if the C content of our spikes is different to yours. I've managed to get a pretty hard edge quenching at orange in veg oil.
A helpful test would be to draw out a bit of spike and try quenching at different colors. Try and snap each piece you quench to test hardness and examine the grain quality. You need at least 40 points of C to heat treat successfully.

[ThomasPowers]

Page 5-2-3: Specifications for high carbon steel track spikes 1968. Carbon not greater than 0.30%, nor greater than 0.20% copper. Page 5-2-4. Section 6a. Bending properties: The body of a full size finished spike shall stand being bent cold through 120 degrees around a pin, the diameter of which is not greater than the thickness of the spike without cracking on the outside portion of the bent portion.

Page 5-2-5 Section 11. Marking: A letter or brand indicating manufacturer and also the letters "HC" indicating high carbon, shall be pressed on the head of each spike while it is being formed. When copper is specified, the letters "CU" shall be added."

Additionally included in a fax to Mike Blue by the gentleman at Wellington industries, a division of Sheffield Steel:
"Because of the bending tests required, the carbon content will not be greater than 0.30%. After all, brittle spikes would not be desirable as a track spike. A bent spike still holds the rail while a fractured spike would not. The consequences for the industry would be too great to consider. However, we refer to them as high carbon, they are not within the range of steels known as high carbon or hypereutectoid according to the steel industry standards, and have not been since at least 1926, when most track spikes were previously manufactured from wrought iron."

[thingmaker3]

Here's the old spec most of the knife sites misquote: http://www.worldclas...ikes/spikes.pdf Note it stated minimum rather than maximum carbon content, and that content depended on smelting process.

The current ASTM spec lists 3 "grades" of spike. The beefiest of the three is identical to A36.

How old are your spikes?

[Jim L.]

What if the spike head is stamped "1" over a symbol that looks like the letter "B" laying on it's back,, and under that , "MC"?

There were a few of those mixed in with a metric butt-load of the "CU"'s I found abandoned in a shallow grave near some tracks.

[Steve Sells]

Grant, I've seen a couple charts in different engineering/metallurgy texts that say 0.3% C can reach 54-55 RC. To me that seems a little hard to believe in the real world (outside of something like H13, with really high alloy content), which is why I hedged my bets a bit.

I know and have proof that human beings can have an IQ above 180. But there have been very few that test that high in the real world. Same as getting a RR spike to hold a good edge.

The cost for scrap at 40 cents a pound is not that far from the $4 per pound of buying real knife steels when one looks at how much metal it really takes to make a knife, or steel an edge.

Remember it was a large Nail, it never wanted to be a knife. It was made to hold RR track to the ties, and they have done a wonderful job of that for many years. If we want to make it into a knife, fine they are cool Only I feel its pushing it to expect magic for edge holding.

I think its very strange that when we use scrap steel to make a knife, grabbing what ever metal we have salvaged, we seem to expect that scrap piece we found to have exact standards as to what it is made from because of the shape, or our perceived ideas of its prior use? Why do so many think everyone else must have tight metallurgical demands for a piece, when we do not have much of any themselves for the blades we are making?

[MattBower]

I have never made a spike knife. I buy known steel from Aldo and Admiral. But industry does have standards for some things, and for those who for whatever reason enjoy playing with scrap steel, it is possible to make some educated guesses as to what kind of steel certain scrap is made of, and thus how to heat treat it properly. I have no beef with those who want to try, as long as they have no illusions about it. I do think it's much easier to learn on known steel, though, and I recommend that.