From: Robert Bastow <"teenut"@ hotmail.com> Newsgroups: rec.crafts.metalworking Subject: Re: Case hardening Date: Fri, 16 Jun 2000 00:10:13 GMT Case hardening is nothing but a simple process during which soft, low carbon iron or steel is heated in the intimate presence of a carbon donating (carburising) material. this can be charcoal, cyanide, acetylene gas or any of many other materials. The carbon, is infused into the surface layer of the soft iron, and turns it into a HIGH CARBON STEEL. This when quenched from a suitable temperature, results in a thin, surface CASING of glass hard, wear resistant material. Case hardening is NOT a cheap man's rout to a harder material..Rather it is a expensive and complex process done to provide the OPTIMUM of material conditions..a soft, tough core for shock resistance, coupled to a glass hard exterior for wear resistance. It is the process of choice for such things as automotive transmission gears, gun parts, etc Your local heat treatment company will case harden parts for a reasonable fee. They will either Gas Carburise or Cyanide (salt bath) carburise before quenching to leave a pale grey, glass hard surface on the part. There is some risk of distortion with intricate or thin parts..you may want to ask about Nitriding which is done at a lower temperature. You can specify the depth of case required to quite narrow limits. "Kasenit" and similar products such as "Hard N' Tuff" are used by, first, heating the part to a dull red heat, rolling or dunking the part in the sand like compound, until a glassy, melted coating covers it. The component is then brought up to a bright red heat and quenched in clear cool water. This process can be repeated to give a thicker coating. Traditional Case Hardening is done by packing the soft iron or steel parts in a cast iron box, together with a mixture of charred bone meal, leather scraps or parings from hooves etc. The top is wired in place and sealed with fireclay. The entire box is then heated in forge or furnace, to a medium red heat for several hours, after which it is removed, the wires clipped and the entire contents dumped into clear cold water. COLOR case hardening is a similar process to the above. In this case however the parts are first polished to about a 400 grit finish and CAREFULLY DEGREASED. They are then packed in the bone meal/leather charcoal mix and sealed absolutely air tight. After heating, the contents of the box are dumped into a barrel of clean, cool water to which a small amount of nitrate may be added to enhance the color ranges. This tub of water will have a grill half way down to separate the box contents and will be arranged with a vigorously bubbling supply of air from a perforated pipe at the bottom of the tub. Beautiful ranges and variations of colors can be obtained..though getting CONSISTANT, REPEATABLE, PREDICTABLE results make this the realm of a few VERY practised masters. teenut Stephen Young wrote: > > There is a product called Casenite for case hardening metals. You heat > up your part and then drop it in this sandy-powder material. That's it. > Don't know where to get it - maybe McMaster Carr? > > gfulton wrote: > > > Was wondering if anyone knew of a home shop method for case hardening.
From: Robert Bastow <"teenut"@ hotmail.com> Newsgroups: rec.crafts.metalworking Subject: Re: Case hardening Date: Fri, 16 Jun 2000 02:31:47 GMT Yes, Particularly on highly stressed parts. The "dead quenched" high carbon steel outer layer can be treated like any other High carbon steel and tempered according to requirement. Often the component is allowed to cool slowly after carburising so as to give a soft outer layer. This can then be further machined before final heat treatment. Areas that one doesn't require to be carburised can be "masked" by a variety of means..whitewash being one, copperplating another.. teenut email@example.com wrote: > > In article <Ffe25.firstname.lastname@example.org>, > Robert Bastow <"teenut"@ hotmail.com> wrote: > > > .. when quenched from a suitable > > temperature, results in a thin, surface CASING of glass hard, wear > resistant material. > > Interesting post. Thank you. > > Are there ever situations where the hardness of the case is > drawn after the initial quenching, to provide a surface hardness > below that of glass-hard?