Case-hardening my own gauntlet fingers?

[Halfdan]

I think I have the ability, witht he help of a crafty shire-mate, to make my own set of carbon stell gauntlet fingers. First, what do I need to know about working with the material? And where do I get some steel suitable for hardening?

Also, this is a local place I found that does hardening:
http://midsouthmetallurgica.rtrk.com/?s ... rgical.com

Does this look like a good place to take the steel to have it hardened.

Of course, I plan on doing a few practive runs before I make some indestructable parts ofr assembly.

Any and all input is appreciated!

Halfdan

[Sean Powell]

The first question is " Do you really mean case hardening or just heat treating?"

If you DO mean case hardening then you want to start with mild steel and preferably of a know alloy and not just 'some random mild steel from Home Depot'.

If you mean heat treating then you want to start with say 1040 to 1050 carbon steel. and you should know what sort of parameters you want to achieve in the heat treating process or at least the process you want them to use.

The company you linked to seems rather high-tech, not a mom and pop type place. They are likely to be expensive. You certain you want to work through them?

Sean

[Baron Alcyoneus]

A local company here has a $200 or so minimum. Other places are different.

[Halfdan]

Thanks for the responses. I'm still in the process of learning what all I don't know.

Yes, I want to heat treat the steel, not case harden it.

I have a few friends who are accomplished blacksmiths, but I don't know how them tempering (?) the steel would turn out. I'm under the impression that improperly treated spring steel has the capacity to fail catastrophically.

Thanks!

[Konstantin the Red]

Well, Halfdan, from what you're saying I'd recommend you read up on heat treatment of steels.

It's a two-step process: first, fully harden; next, bake it to varied temperatures to draw out some of the hardness by cooking away some of the martensitic structures within the steel.

Full hardening is that part where the smith heats it to red and dunks it in a quenching tub. Depending on the alloy, the quenchant can be anything from just waving it in the air (the air hardening steels) to, in order of severity, oil or transmission fluid, warm water, cold water, or salty brine. Beyond this is SuperQuench, which can bring some hardening to mild steel. Impressive if you need that sort of hardening on that material.

Quenchants should match your steel type: air hardening, oil hardening, or water hardening. Using a quenchant that is too severe (fast) will warp or crack your piece from severe internal stresses. Some designators for steels indicate which of these media they use for quenching.

Full-hard steel is brittle. You can make machine tools of it to cut other steels with lathes and mills. You can shatter such tools with a hammerblow.

But next comes tempering: cooking the steel at temps ranging from 300 to 575 degrees F, which decrystallizes the martensitic form of the microcrystals and softens the steel back down, greatly increasing its toughness -- the kind of thing you want in plate armor. The higher the temp the piece reaches, the softer and tougher it becomes. Bake a piece hot enough and the hardening would completely disappear, leaving the piece annealed once again. (And still rehardenable.)

In springsteel plate, a springy temper and an Rc hardness of 30-40ish is about what you want, if I understand correctly.

[Sean Powell]

Full hardening is that part where the smith heats it to red and dunks it in a quenching tub. Depending on the alloy, the quenchant can be anything from just waving it in the air (the air hardening steels) to, in order of severity, oil or transmission fluid, warm water, cold water, or salty brine.

In springsteel plate, a springy temper and an Rc hardness of 30-40ish is about what you want, if I understand correctly.

For all of the waters you have to be careful. The hot steel will evaporate the water into steam. By causing a phase change the water sucks a lot of heat out quickly at point of contact BUT the rising sheet of steam can insulate other parts of the metal and cause them to not quench properly. The addition of salt affects thermal conductivity but it also affects the boiling point of water to try to cause it to boil and sheet less.

Floating a layer of oil on top of the water is supposed to be a best of both worlds since the oil sheets to the steel conducting the heat to the water and keeping the air bubble layer away from the steel but still allowing the phase change to suck out heat.

Adding liquid soap as a wetting agent has a similar effect to floating oil on top.

Super-quench really isn't much more then dish-soap, salt and water. Maybe you can and maybe you can't get noticible changes quenching some grades of mild steel in super-quench... but I don't think it will ever perform as well as 1050 treated properly and since 1050 is shapeable I don't think I would ever bother with super-quench and mild steel... (super-quench and 1050 or 4130 is a strong possibility)

1040 quenched from 1500F and tempered 600F runs 260 Brinell hardness and 4140 quenched from 1500F and tempered 600F runs 426 Brinell hardness. There is a translation between Brinell and Rockwell but I can't find it at the moment... but as you can see there is a wide range of hardnesses achieveable in sheet spring steel.

Now that I'm looking at the chart. I con't have data on 4130 but 4140 has almost twice the tensile strength and fully twice the yield strength as 1040 with only a slight reduction in reduction in area and elongation. I think 4140 tempered to around 625-650 would probably outperform 1040 on just about every level.

I have not found a good single source for this information. I just pulled data from 3 books. It's not an easy topic to learn but it is a fun one to experiment with. Go play and see what you get.

Sean

[James Arlen Gillaspie]

See the post, 'Spring Steel VS. Mild Proofing Test'. Absolutely a MUST for anyone trying to figure out what to do with spring steel.