I have a pry bar like this
Anywho, it's basically a piece of flat section steel strip bent to shape, then heat treated [?] in some way so it stays that shape.
I want to make up something similar to assist with installing awnings.
I can get the steel strip, I can bend it to the shape I want - how do I heat treat it?
Heat is excessively hot, drop into water to quench it. Heat it up again to exactly the right temperature, which is determined by colour changes on the metal, then drop it back in the water.
NT
It will be something somewhat stronger than mild steel, so wen you say you can get the steel, are you sure? It needs probably to be an alloy steel (ie chromium and molybdenum as well as carbon)
AWEM
If you've got a piece of mild steel to begin with, at the end of the treatment all you have is a piece of heat-treated mild steel. If you have a piece of steel with a higher carbon content then you'll likely break it before you bend it to shape. There are two possible ways out of this.
One is to take your higher carbon steel and anneal it before you bend it. Heat it up to cherry-red then let it cool slowly and it should be more maleable; follow NTs heat treatment plan to get the hardness back again.
The other is to use mild steel and case-harden it. An amateur way of doing this without having to buy difficult-to-explain chemicals is to shape it and bend it and hone it then heat it up to cherry red and cover it up with flour (or some say sawdust) so the carbon produced from the heat has a chance to bond into the surface of the steel as it slowly cools. You might want to do this several times. Then follow the NT heat treatment plan to temper it. This will never be as strong as using high carbon steel but it will be slightly stronger overall than untreated mild steel and the edges will be more resistant against wear and tear.
We were taught to do this in O Level metalwork classes about 45 years ago so my apologies if I may have misremembered details.
Nick
You need a medium carbon hardening steel - O1 ought to work and is readily available from most steel stockists.
If you don't already know, I recommend finding a company that does heat treatment and getting them to do it for you. Tell them what you want to use it for and they will sort out exactly what treatment it needs.
Colin Bignell
this
It depends upon the steel. Some are oil hardening, rather than water hardening.
Colin Bignell
Do you not also need to maintain the temperature for a period of time before quenching?
The important thing is to get all the steel to above the upper critical temperature before quenching. If you heat to cherry red, which is only just hot enough, then you do need to hold it there for a while, to allow the heat to soak through. If you heat to yellow, then many pieces will be hot enough right through to quench immediately.
Colin Bignell
While none of the other posts are incorrect, you basically need steel with a sufficiently high carbon content: mild steel will not do. (Case hardening is fine for something like a cold chisel, but not for something to resist bending like a pry bar, for which you need hardness all the way through).
Amateur blacksmiths often start with material from scrap-yards, for example drive shafts for round stock or leaf springs for flat stock (in the good old days when everything had leaf springs).
If the Wickes pry bar is almost right but needs adjustment, you might consider starting with one of these. Heat to red heat with a big propane torch, using something like bricks or firebricks or vermiculite insulation blocks (readily available on the net) to prevent heat loss. When it's red hot you can forge it by hitting it with a hammer on an anvil or something sufficiently solid, or even bend it in a vice. If you let it cool slowly, it will end up "soft" like mild steel. Re-heat to red heat and drop in water or oil and this will harden it. Very high carbon stuff like chisels will end up brittle, you need to temper them. Loads of info on the web about tempering. My guess is that you wouldn't need to temper a pry bar but YMMV.
For something like a pry bar you can probably forge and then harden one end while holding the other in your hand or at most a welding glove. Only the really hot bit gets softened.
Know any friendly blacksmiths or metallurgy lecturers?
Pretty much answered already but some things have not been mentioned. Heat treatment achieves two things.
1) It increases the tensile strength of steels that are designed to take it by a factor of two or more. 2) It increases the hardness and durability of the steel by potentially an order of magnitude.However, you only need to do this if the component is too weak or too soft in the untreated state which is obviously a function of the section thickness and the loadings it will encounter and the type of steel you make it from.
Ordinary mild steel only has a tensile strength of 30 tons/square inch or so - no more than high tensile aluminium alloy and it can't be "through" heat treated, only case hardened.
However even mild steel may suffice for your purpose if the loadings are low and the steel doesn't need to be hardened because it's being used against soft materials (you indicate plastic awnings).
Heat treatable steels contain higher levels of carbon and/or other alloying elements to increase both strength and heat treatability. EN8 or EN16 are common examples and ideal for general purpose low duty tool making. More specialised alloy steels are stronger still.
uk.rec.models.engineering is where the people who can help you best tend to lurk and someone will almost certainly have a strip of something lying about that will do you nicely for a couple of beer tokens.
It's all search engine optimisatiob bollox, the address could say anything you like, and still work, e.g.
Best thing is to get a 1950s textbook for either school metalwork lessons, or else a better handbook for engineering apprentices. In the
1950s, pretty much everything possible was still at the level where it could be understood by the DIY worker, and most of it could still be done over the kitchen sink. It's a useful generation for practical textbooks (unless they have numbers in, in which case you want a metric / SI one).Then fins the right piece of steel. You just can't heat treat most steel, it needs to have an adequate carbon content before it will respond. So forget random bits of steel, forget new mild steel, forget case hardening. What you need is old leafspring, so find a van or truck scrappie. Don't use coilsprings, those alloys are really awkward to handle.
The usual process is to harden (make it too hard, pretty much as hard as you can), then temper it (soften it in a more controlled manner, to reduce brittleness).
You harden by heating and rapid cooling. Heating is a big gas blowtorch, or a coal fire (charcoal won't have the heat, unless blown) and then a quench by a rapid dunk into oil (old engine oil) or maybe water (not IMHO, unless I'm making edged tools). Leave it in the quench tank until cold enough to handle. BTW - oil may well ignite on quenching, so use a big fireproof tank and have a lid ready to shut over it and just leave it to its own devices. My tank is a big ammo box. Heat until it reaches its Curie point - when a magnet on a bit of coathanger wire stops being attracted to it - or just a bright red is close enough for jazz. It needs to be hot throughout (at least on the hard bits), but doesn't need to soak very long at this temperature.
Quenching involves polishing the surface up afterwards, then gently heating from the middle (softer) part of your tool and watching the temper colours travel towards the brittle edges. When the right colour gets there, then quench again (probably in water). The colour you want is up to you and your uses - but blue or purple is about right for a crowbar.
Afterwards, test before use. Also don't trust the thing (until you're good at making them) and expect bits to chip and fly off. You really do want eye protection here!
It's cheap to buy leafsprings, once you've found them. So get several and make a number of tools. You'll break some to start with.
Otherwise (both better and simpler) is to have a blacksmith make it for you, to order. Best of all is to apprentice to a smith for an afternoon and make it yourself, under their supervision.
There are also a number of US cutlery books like "$50 knife shop" that are cheap and useful.
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