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I have some laser-cut filing templates, about the size of a business card, made from 3mm-thick 1095 carbon steel. These parts will be used to guide a round metal file when filing odd shaped holes in aluminum. They will be clamped onto 13mm-thick aluminum and used as a filing "stencil". Thus the parts are not structural, but they need to withstand light pressure from a file without themselves being substantially filed. Aluminum is very soft, and I believe that with only light filing pressure, if the steel stencil pieces are hardened properly, the file will "skate" over them so they last essentially forever.

This is the process I was given by the laser cutter for hardening the 1095 steel:

  1. Coat pieces with boric acid to prevent scale and decarburation. Heat the pieces up until they don't attract a magnet
  2. Immediately quench the pieces into light oil, brine, or water (how do I choose?)
  3. Immediately temper at 200C for 1 hour and allow to natuarally cool

From what I can tell, the last step is designed to prevent the parts from being excessively brittle, but may slightly reduce surface hardness. Since the parts aren't structural anyway, and I am trying to achieve maximum hardness, is there any benefit to performing the tempering step?

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You are asking how to quench and temper 1095, aka; carbon steel, to make it "file hard" ( the hardness described in the question).

File hard depends a little on the file and the person but Rockwell C 60 is a good level and can be made with your relatively thin 1095.

A concentrated solution of boric acid may reduce decarburization , dip parts and let them dry.

However do not hold the 1095 at austenitizing temperature more than a few minutes. I see Curie temperature is 1390 F ( non-magnetic - cherry red ); that is NOT hot enough. An austenitizing temperature of 1650 F ( bright yellowish orange) is best. Quench choice if easy , cold brine.

The hardenability is not high so you need to cool as fast as possible ; You need to cool to black -1000F- within 5 seconds., and continue cooling to the water temperature.

I used a 1080 TTT curve for the cooling time as I do not have a 1095 TTT curve handy ( they will be very similar). I would temper at 325 F as you don't want to lose any hardness.

A Rockwell hardness tester and a couple trials would be best. you may find tempering could be done up to 450 F. Cooling after tempering is not a factor.

YES, you must temper ,it sounds like you have some internal corners so you must have some toughness .

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