WO1999035303A1

WO1999035303A1 - Razor steel alloy

Info

Publication number: WO1999035303A1
Application number: PCT/US1998/023920
Authority: WO
Inventors: Randy Nicolosi
Original assignee: Warner-Lambert Company
Priority date: 1998-01-12
Filing date: 1998-11-10
Publication date: 1999-07-15
Also published as: AU1393199A

Abstract

A steel alloy for use in razor blades containing approximately 0.45 - 0.7 % carbon, 12 - 14 % chromium, 0.5 - 2 % molybdenum, several trace elements and the remainder iron. The advantage of the alloy is that it allows for carbon coatings to be adhered directly to the steel without the need for any intermediate layer.

Description

RAZOR STEEL ALLOY

Background of the Invention

1. Field of the Invention

This invention relates to a steel alloy for use in razor blades which provides a suitable substrate for carbon film deposition.

2. Description of Related Art

In the past, high carbon steel containing 1.2% by weight of carbon was utilized to make razor blades. This material provided a high degree of hardness and a high level of cutting quality when heat treated, however the resulting razor blade was easily corroded and rusted upon exposure to the wet and humid conditions encountered during shaving.

In order to avoid the corrosion and rust issues associated with high carbon steel, a lower carbon steel similar to 440A grade steel (GIN 5) steel replaced the high carbon steel for use by razor blade manufacturers. The lower carbon steel contains approximately .6 - .7% by weight carbon and 12 - 14% by weight of chromium. In addition, trace amounts of various elements including manganese, sulfur, silicon, nickel and phosphorus are present and the remainder is iron. To increase user satisfaction, razor blade manufacturers have continued to attempt to improve the quality of razor blades. One means for improving the quality of the blades is to improve the steel in razor blades by providing a carbon coating on the steel. Carbon coatings have been disclosed in various forms, including diamond, amorphous diamond and diamond-like carbon coatings. A major difficulty in providing a carbon coating on steel is the lack of adhesion between steel and carbon. Consequently, intermediate coatings have traditionally been provided between the steel and the carbon to provide adhesion for the coating. Among the materials which have been used as intermediate coatings are molybdenum, hafnium and niobium. While providing better adhesion, the use of such coatings has several drawbacks. First, the application of the intermediate coating adds to the complexity and cost of producing the razor blade. Second, the coating changes the shape of the razor blade by thickening the blade and thus dulls the cutting edge.

Consequently, it would be advantageous to provide a steel alloy for use in razor blades which would not require an intermediate coating before the application of a carbon coating. The desired steel alloy would provide a substrate to which carbon coatings would firmly adhere.

Summary of the Invention

The present invention is directed to steel alloy for use in razor blades. The alloy contains approximately .6 - .7% carbon, 12 - 14 % chromium, .5 - 2% molybdenum, several trace elements and the remainder iron. The advantage of the alloy of the present invention is that it allows for carbon coatings to be adhered directly to the steel without the need for any intermediate layer.

Description of Preferred Embodiments

Reference will now be made in detail to the presently preferred embodiments of the present invention.

Razor blade manufacturers have continually refined the quality of the steel used to manufacture the razor blades. Among the properties that the manufacturers are seeking are hardness, durability, corrosion-resistance, and, most importantly, comfort for the users. To achieve these properties, a preferred steel alloy has been determined. This preferred steel alloy comprises about 0.45- 0.7% by weight carbon, 12 - 14% by weight chromium, trace amounts of manganese, silicon, sulphur, nickle and phosphorus, with the 85 - 87% by weight consisting of iron and traces of inevitable impurities. Preferably the carbon is in the range of about 0.6 - 0.7% by weight of the alloy. The method of manufacture of steel having these properties is disclosed in U.S. Patent No. 5,433,801 which is hereby incorporated by reference herein.

One means by which the properties of the razor blade steel are improved is via coating of the blade. Preferred coatings include carbon coatings such as diamond, amorphous diamond and diamond-like carbon (DLC) coatings. The coatings may be applied to the steel via any of a number of known methods, including sputtering and electric arc deposition. A particularly preferred method of coating the razor blades with a hard carbon coating is cathodic arc deposition and a method of performing such coating is described in U.S. Patent No. 5,458,754, which is incorporated herein by reference.

Most steel alloys require an intermediate coating layer between the steel and the hard carbon coating. This intermediate layer, commonly molybdenum, hafnium or niobium, provides a site for adhesion of the hard carbon coating. However, it is particularly advantageous to coat the molybdenum-containing alloy set forth above with a hard carbon coating because the molybdenum within the alloy provides a suitable substrate for adhesion of a hard carbon film coating. The molybdenum-containing alloy does not require the additional step of adding an interlayer for adhesion of a hard carbon film coating. Further, the coating of the alloy eliminates the thickness added to the razor blade caused by the addition of the intermediate layer. The elimination of this thickness is useful because the thicker cutting edges tend to reduce the sharpness of the blade. The hard carbon film coating may be applied to the molybdenum-containing alloy in a variety of known manners, including sputtering and cathodic arc deposition. The thickness of the coating may vary, but preferably the thickness is in the range of about 200 to 2000 angstroms.

While there have been described what are presently believed to be the preferred embodiments of the present invention, those skilled in the art will realize that various changes and modifications may be made to the invention without departing from the spirit of the invention, and it is intended to claim all such changes and modifications as fall within the scope of the invention.

Claims

We claim:

1. A razor blade comprising, by weight: a) 0.45 - 0.7% carbon; b) 12 - 14 % chromium; c) 0.5 - 2% molybdenum; d) iron; and e) a carbon film coating.

2. A razor blade according to claim 1 , wherein the carbon component is in the range of about 0.6 - 0.7% by weight.

3. A razor blade according to claim 2, wherein the carbon film is selected from the group consisting of diamond, amorphous diamond and diamond-like carbon.

4. A method of manufacturing a razor blade comprising the steps of: a) providing a razor blade having a steel alloy comprising about 0.45 - 0.7% carbon, about 12 - 14 % chromium, about 0.5 - 2% molybdenum and iron; and b) coating the razor blade with a hard carbon film coating.

5. A method according to claim 4, wherein the hard carbon film coating is selected from the group consisting of diamond, amorphous diamond and diamond-like carbon.