Metal treatment – Process of modifying or maintaining internal physical... – Carburizing or nitriding using externally supplied carbon or...
Reexamination Certificate
1998-10-16
2001-07-31
Sheehan, John (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
Carburizing or nitriding using externally supplied carbon or...
C148S237000, C148S316000, C148S317000, C148S669000, C428S610000
Reexamination Certificate
active
06267825
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to a process for treating metal workpieces, and deals more particularly with a process by which a non-ferrous metal workpiece is heat treated in combination with an interstitial element, the resultant non-ferrous metal workpiece thereby exhibiting a high degree of stress resistance.
BACKGROUND OF THE INVENTION
There has long been a great demand for strong yet lightweight metal products covering a wide range of diverse arts. The manufacture of guns, and in particular handguns, having such a resilient lightweight metal structure has been especially troublesome given the localized stresses involved when the handgun is fired. There presently exists a need to produce a lightweight handgun for those individuals, such as law enforcement personnel, who are forced out of necessity to carry handguns continuously for long periods of time. Metals and associated alloys such as Aluminum and stainless steel are known materials for the manufacture of handguns, such as those manufactured by Smith and Wesson, assignee of the present invention. A process for heat treating these metals and associated alloys for use in handguns is also known in the art.
In a known process for heat treating metal handgun parts, the parts are placed in a furnace and subjected to high temperatures. Handguns made in this way still have, due to the particular metals currently used, a weight which is detrimental to a user, especially in the larger caliber handguns currently on the market and desired by law enforcement personnel.
Other non-ferrous metals, such as Titanium, are commonly utilized in bio-medical and aircraft structures for its inherent strength and lightweightness. While Aluminum typically has a strength of 78-80 KSi, that is Aluminum can withstand up to 78-80 thousands of pounds of pressure per square inch before failing, Titanium has a KSi of around 135. Given Titanium's advantage over Aluminum in this respect, and the fact that it is even lighter than Aluminum, Titanium is an ideal prospect for use in, among other fields, handgun manufacture.
The problem with the construction of handguns using Titanium as a material is that, when formed as a barrel and cylinder combination, Titanium exhibits an undesirable amount of erosion and spauling on its cylinder surface after exposure to repeated firings of ammunition rounds. This is due in large part to Titanium being a relatively porous material compared to other metals, and thereby being especially sensitive to these stresses.
Another problem with the use of Titanium in handgun design is that, in the heating process, there is sometimes formed what is known in the art as an Alpha layer upon the surface of the Titanium. An Alpha layer is a normally detrimental thin oxide layer formed on Titanium through the interaction of various interstitial elements, typically N
2
, O
2
or H
2
, with the porous surface of the Titanium.
With the forgoing problems and concerns in mind, it is the general object of the present invention to provide a process for the treatment of metal workpieces, such as those made from Titanium, which overcomes the above-described drawbacks, as well as to affirmatively use Titanium workpieces in the manufacture of large caliber handguns.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a process for treating a metal workpiece. The process includes heating the metal workpiece to a predetermined temperature for a predetermined amount of time, and introducing a predetermined concentration of an interstitial element in the area adjacent to the surface of the metal workpiece as the metal workpiece is heated, so as to produce a region of diffused interstitial element extending into the body of the metal workpiece.
A preferred embodiment of the present invention also includes the use of non-ferrous metal workpieces, such as a Titanium workpiece. The non-ferrous workpiece is prepared, with particular attention to cleaning the surfaces thereof. This cleaning can be accomplished using an ultra-sonic or electro-chemical cleaning method. The cleaned non-ferrous metal workpieces are then placed within a furnace while Carbon is added in a defined quantity to act as an interstitial element. The non-ferrous metal workpieces are heat soaked for a predetermined amount of time at a predetermined temperature. Finally, the treated non-ferrous metal workpieces are then air cooled and the resultant workpieces exhibit a far superior resistance to tensile stresses than has heretofore been perceived.
Preferably, the heat treatment of the non-ferrous metal workpieces enables a diffusion process to affect the body of the non-ferrous metal workpieces whereby interstitial Carbon atoms are diffused into the body of the non-ferrous metal workpieces. This diffusion of Carbon atoms does not create a defined outer layer, such as an Alpha layer, but rather extends some distance below the surface area of the non-ferrous metal workpieces, infusing the body of the non-ferrous metal workpieces with interstitial Carbon atoms.
In a preferred operation, the treatment process is particularly useful in the manufacture of lightweight guns which experience repeated, localized exposure to high tensile stresses, and where failure of the operable part would be extremely dangerous and undesirable. Use of this process is not, however, limited in this regard, as many other uses of non-ferrous metal workpieces so produced can be envisioned in many diverse arts.
These and other objectives of the present invention, and their preferred embodiments, shall become clear by consideration of the specification, claims and drawings taken as a whole.
REFERENCES:
patent: 2892743 (1959-06-01), Griest et al.
patent: 5466305 (1995-11-01), Sato et al.
Curry Brett
Fleury Kevin R.
Mariani Craig A.
Poulin Michael J.
Stall Thomas C.
McCormick Paulding & Huber LLP
Oltmans Andrew L.
Sheehan John
Smith & Wesson Corp.
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