Nitre Blueing question.

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SkytopBrewster

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I have done a lot of hot caustic and recently set up a tank for nitre blueing with good results on small parts. I have a Sig 1911 that I want to redo. Want to straw all the small parts (mag release, safety, trigger etc), Hot caustic the frame (Bead blasted) and nitre the slide to a blue purple (mirror polish). My question is, and probably a dumb one is will 540+ f ruin the temper of that slide, I am not sure what exact steel it is. I think it would look awesome. What would they normally draw that slide back to as far color, forgive me, I have not memorized the colors/temps to Rockwell hardness, yet.
 
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No it won't be red hot, it will be purple, I was under the understanding that the higher the temp before critical temp (red) softens the metal. ie yellow and quench after critical = file hard, red hot and quench = very hard. Am I wrong here, need an experienced gunsmith or metal worker's advice here.
 
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I make a moderate number of springs from drill rod which I suspect is around 1095 steel. To correct one of your beliefs on hardening steel, steel is heated red hot (or to non magnetic) at around 1400 F. It is then quenched in various solutions (depending on alloy and shape) which leaves it brittle hard. It is then reheated to a temperature lower than red hot to bring it to a working hardness. In the case of leaf springs, I draw the brittle hard drill rod to around 720 - 740 F and hold it there for about 3 minutes. Others may use special heat treating furnaces and longer soaks to draw the temper but the principle is the same; make it brittle hard then reheat and make the metal progressively softer the hotter you reheat to. When I am making a reamer from drill rod, I don't use a thermometer but reheat to about golden brown and I am guessing that the temperature is somewhere around 450 - 500 F.

I would suspect that the slide on your gun, if heat treated would be no harder than a spring at around 720 - 740, so as long as you have a good control of your temperature, I doubt that 540 F is going to soften it

cheers mooncoon
 
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