Spring making

Thanks All.
I suck at trying to see colors in "glowing" metal. I cheated and modified an Aim glass/pottery kiln with a digital controller for heat treating & tempering. Furnace is rated for cone 10 (1305°C / 2381°F). The controller ia a PID w/ K type thermocouple. Controller cost $35.
Used kilns are available. A broken one can easily be repaired.

I also have a pi based controller that I built on another kiln for investment casting (burning out wax from molds) that allow different ramp temps for different times.
These are charts were provided by AI & google. They talk about pre & post heat... what is that??





It is also wise to pack the metal in a charcoal mixture or stainless foil to mitigate decarburization & scale.
If anyone else heat treats using a furnace please share your tips!
Bone vs willow charcoal?
Mix of ?

Thanks in advance!
William

Usually only air hardening steels require foil protection or advanced atmosphere protection. Coatings such as ATP-641 are good at preventing/reducing decarb. Pre heating then post heating is a waste of time unless you think the piece needs to be stress relieved. Even then you need to know what temps and times you need. No need of packing in carbon unless you are case hardening your piece. The goal is to turn the steel from ferrite to Austenite which is the condition heat has caused the crystal structure to change to and absorb the carbon making a solid solution. As best I recall this begins at around 1334°F. At 1414°F the steel becomes nonmagnetic but needs to reach 1475° and soak a few minutes to make a good solution if it is a eutectoid steel, which has .8% or more carbon content. Non eutectoid steels need a higher heat to make a good solution. 1525/50°F. Most eutectoid steels should not be taken beyond 1475/80°F or they may begin losing carbon in the solution to become free carbides which really have little purpose. Know that common 1095 is low in magnesium and requires a quench speed of about .6/.8 of one second to go from 1475° to under 900° to get the desired hardness. Only a brine quench, or something better, will do that. Parks #50 oil, and clones will do well enough to make a good decent piece. Warmed canola oil will do fairly well for knife blades and springs. In quenching in other oils, 150°F oil is ridiculous! You will not get the needed result. You will slow your quench. Your oil should be around 120/130°f. No more is required. Parks #50 is normally used at no more than 100°F. Temper heats vary according to how hard or soft you want your piece. Just FYI, when you quench your steel, it will not harden until the temp nears 400°. Between 900° and 450°, if you had the means and need, you could hold whatever temp the steel has reached and take a break, come back in a while and proceed to take it under 400°. At that time, it will reach a point when suddenly, at the speed of sound, it will harden. 1075 does not require the treatment given to 1095. 1075 is very forgiving in heat treating and is not a eutectic steel. Most any thin oil will do for quenching it. It is great for springs as well as pretty good for knives.

2 shots said:

for how long??

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In an oven, maybe an hour. In lead 15/20 minutes seem enough because the steel has full contact with the heat. The thickness off the steel also should be a factor.

Thank you, PhD Brewer has given the pertinent information to spring making with 1095 and according to his data I’m on track. Funning how decades of working with metal of various types I managed to get this one right. Even my charcoal case coloring turns out good enough.


IMG_0424 by Oliver Sudden, on Flickr

Thanks @Phil Coffins. Being an Enginerd... I like accurate, repeatable processes. Replace guesswork with science to make things better.
Case coloring looks great!
What type of charcoal and temps are you using?

William

PhDBrewer said:

Thanks @Phil Coffins. Being an Enginerd... I like accurate, repeatable processes. Replace guesswork with science to make things better.
Case coloring looks great!
What type of charcoal and temps are you using?

William

Click to expand...

That one was 4-1 wood to bone at 1375 quenched in cool water then drawn at 375. Different mixes and quench will give more or less colors depending on what is desired. For these projects the furnace is used and some experience is required. Warm water quench is more muted color.
AA0149F3-4E50-45BB-8CAC-B4D4D9909E96 by Oliver Sudden, on Flickr

That's one GORGEOUS lock!