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normalising steel in a kithen oven

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  • normalising steel in a kithen oven

    so my oven will supposedly heat up to 500 °c for 90 minutes (never tried it). is that enought to normalise parts? (could i get a "shop oven" and maybe repeat the process several times, befor the kitchen gets on fire?) if i were to insulate it better, it might get hotter that that (well maybe not, as it is probably conrolled).
    Last edited by dian; 04-26-2013, 01:15 PM.

  • #2
    I've used the kitchen oven to draw back parts made from 0-1 and W-1 after hardening, with no problem. If you are trying to anneal hardened material to a softer state I don't think 500 C (932 F) is high enough, but I could be wrong.

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    • #3
      Not gonna happen, needs more temperature and for longer periods.
      Amount of experience is in direct proportion to the value of broken equipment.

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      • #4
        Nope. You have to heat the steel above the critical temperature, which depending on the particular alloy is probably around 1550F to 1650F, give or take.

        You can certainly use a kitchen oven to temper steel, and 500C it's going to end up fairly soft, but it won't be "normalized."
        ----------
        Try to make a living, not a killing. -- Utah Phillips
        Don't believe everything you know. -- Bumper sticker
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        • #5
          It depends entirely on what material you're normalizing. Get the specs for the material, then you'll know.

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          • #6
            well, i might have confused normalising and stress free annealing. according to my info the temperature for stress relieving is between 450 and 650°c, with a holding period of 1-2 hours for most steels. thats why i asked.

            (somehow i cannot grasp the diference between soft annealling, stress free annealing and normalising.)
            Last edited by dian; 04-27-2013, 01:01 PM.

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            • #7
              Wonder what the temp of the self cleaning ovens goes too ? I know its a lot hotter than 500 deg. would be interesting to figure it out. Probabaly no where near 1500, but Im not sure

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              • #8
                my instructions says 500°C for self cleaning.

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                • #9
                  A good kids science fair project would be for a kid with a thermocouple to figure out the actual temperature profile of a self cleaning oven, or better yet, multiple ovens.

                  To one sig fig, it probably does end up around "five hundred C" for some random amount of time, or maybe just an instant, or while grease drippings if any are burning off, or maybe its more like the manufacturer guarantees it'll never exceed 500C from a materials temp limit standpoint. I guarantee that every oven will probably perform differently.

                  I do know from the "lets turn a kitchen toaster oven into a SMD reflow oven" that consumer grade thermostats are usually not better than 10% accurate at best, so those guys use thermocouples and PID controllers to give a controlled heat and cooldown. Personally I hand solder SMD devices, after the second decade or so it starts getting pretty easy (SMD is old tech I started in the 80s)

                  To heat treat steel you need "sorta" precise temps and temp profiles. To burn off grease and what amounts to charcoal you merely have to heat it really hot. You can guess which side a budget conscious oven designer leans toward.

                  Also an interesting financial aspect is "value engineering" means the designer probably assumed you'd self clean once a season and they'd like to sell you a new oven every 5 years. So its probably carefully engineered to burn out the heating element after 20 or so self cleaning cycles. So you need to budget about 5% the cost of repair (or replacement if parts are intentionally no longer available?) per self clean cycle. Suddenly the price charged by a real heat treater who can do a much better job anyway, is starting to look cheap unless there are special circumstances (like you get "free" stoves from the town dump or something rather than using the "real" kitchen stove)

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                  • #10
                    A knife maker once told me to heat the steel until it would no longer attract a magnet. That was the critical point. Around the 1600F to 1700F numbers you mention. Probably applies here also and is sure easy to check! Now go pile up the SWARF.

                    Cool slowly in a bucket of sand or better yet, lime.
                    Last edited by rdhem2; 04-28-2013, 12:30 PM. Reason: Not complete
                    From the State of Lemmings, where three counties out of twenty-seven call the shots.

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