US3425877A

US3425877A - Safety razor blades

Info

Publication number: US3425877A
Application number: US502460A
Authority: US
Inventors: Roger Frederick Deacon
Original assignee: Wilkinson Sword Ltd; Uddeholms AB
Current assignee: Wilkinson Sword Ltd; Uddeholms AB
Priority date: 1965-10-22
Filing date: 1965-10-22
Publication date: 1969-02-04
Anticipated expiration: 1986-02-04

Description

United States Patent O 3,425,877 SAFETY RAZOR BLADES Roger Frederick Deacon, Richmond, Surrey, England,

assignor to Wilkinson Sword Limited, London, England,

a British company, and Uddehohns Aktiebolag, Uddeholm, Sweden, a Swedish joint-stock company No Drawing. Filed Oct. 22, 1965, Ser. No. 502,460

US. Cl. 148-12.4 6 Claims Int. Cl. C2111 7/14, 9/18 ABSTRACT OF THE DISCLOSURE Razor blade strip is manufactured from a corrosionresistant stainless steel having a chromium content of from 10.0 to 20.0%, the composition being such that it can be annealed to form austenite and thereafter cooled to an elevated temperature at which the austenite is metasta- 'ble. At this elevated temperature each edge region of the strip where a cutting edge is required is subjected to a substantial cross-sectional reduction to deform the austenite, strip being cooled thereafter to transform the deformed austenite to martensite.

This invention relates to methods of manufacturing razor blade strip and to razor blades produced from such strip.

According to the present invention there is provided a method of manufacturing razor blade strip from a steel containing metastable austenite at an elevated temperature, wherein at least one edge of the strip is submitted to cross-sectional reduction at said temperature to deform the austenite and the strip is subsequently cooled to transform the deformed austenite to martensite.

The present invention also provides a method of manufacturing razor blade strip from steel whose composition is such that it can be annealed to form austenite and thereafter cooled to an elevated temperature at which the austenite is metastable, wherein deformation is effected at this temperature, at least in the region where a cutting edge is to be formed, and the strip then cooled to convert at least partially the deformed austenite in said region to martensite.

The present invention further provides a method of manufacturing razor blade strip from a steel whose composition and treatment is such that at a predetermined elevated temperature the steel contains metastable austen ite, comprising effecting a cross-sectional reduction of one or both edges of the strip at said elevated temperature to deform the austenite in the region of the edge or edges, cooling to effect hardening of the strip, by transformation of the deformed austenite to martensite the subsequent formation of the cutting edge or edges being at least partly effected by an electrolytic process.

One method of manufacturing razor blade strip in accordance with the present invention will now be described, by way of example.

The steel used must be one whose composition is such that it can be annealed to form austenite, generally at temperatures within the range 800 to 1200 C., the austenite being metastable after cooling to a temperature which will generally be within the range 300 to 800 C. The detailed composition of such steels will be considered in greater detail below.

Strip of such a steel is formed to the required final blade shape, that is to say without the cutting edge or cutting edges formed thereon but with what will eventually be the individual blades joined end-to-end. Such formation may, for example, be effected by punching and may include formation of a central slot where doubleedged blades are to be produced. Such strip is fed into 3,425,877 Patented Feb. 4, 1969 an austenitising furnace in which it is heated to the austenitising temperature. From the furnace the strip is passed through a cooling muffie to cool it to a temperature at which the austenite is metastable, the cooling rate being controlled to avoid any undesired transformation of the austenite. From the cooling muffle the strip is passed to a press maintained at an elevated temperature at which the austenite is still metastable, for example within the range 300 to 800 C. The atmosphere may be controlled throughout the passage of the strip through the austenitising furnace, the cooling mufile and the press and may be an inert or reducing atmosphere, for example of cracked ammonia. In the press the edges of the blade are deformed by the use of suitable dies or other means to form at least partly the required cross section for the cutting edges. On cooling the deformed austenite is transformed to martensite with consequent increase in the eventual hardness of the cutting edges.

Pressing may be limited to the cross-sectional area reduction necessary to give the requisite hardness increment or may be continued to give a relatively fine cutting edge requiring little subsequent finishing. The resultant included angle of the finished edge may for example be as little as 10 to 14.

On leaving the press the strip is hardened by quenching to room temperature, for example by passage between Water cooled chill blocks, by natural cooling in still air or by quenching in water, oil or other suitable liquids. Optionally, to increase the hardness and convert at least some of any retained austenite to martensite, further cooling substantially below room temperature may be effected, for example to minus 78 C.

It will be understood that the deformation of austenite at the elevated temperature may be effected by subjecting the whole strip to reduction of cross-sectional area, for example by rolling or forging, in which case the reduction will replace some of the normal cold rolling reduction. The degree of deformation should preferably exceed 30% and may rise to as high at The precise temperature at which deformation is effected is governed by the amount of improvement required and the type of equipment available to effect the deformation. In this connection it will be appreciated that a greater force will be required for a given reduction at lower temperatures but that a greater increase in hardness will result from effecting the deformation at lower temperatures. By way of example it may be stated that typical values of temperature for the austenitising furnace (T1) and the press (T2) for the steels specified are as follows:

After hardening, the formation or finishing (the latter case being when the edge has been partly formed during deformation at elevated temperatures) of the cutting edge or edges may be effected by conventional methods or by electrolytic processing such as described in our co-pending patent application No. 30,658 of 1963 and cognate No. 20,032 of 1964.

Considering now in greater detail the steels which may be used for the present invention it will be appreciated that their composition must be such that the steel :can be cooled to the deformation temperature without transforming to ferrite. Suitability of any given steel can usually be assessed by a metallurgist, particularly with the aid of an isothermal transformation diagram, but of course in cases of doubt the suitability can readily be determined experimentally.

Examples of steels which have improved properties after such hot deformation, by comparison with their properties after conventional heat treatment, are those known as hot work die steels as for instance AlSl, type No. H11. Other examples are those steels usually known as 43XX types, as for instance AlSl type No. 4340, and ultra-high strength steels such as for instance Ladish D6A, Labelle H.T. and Supertricent. Further examples are British Standards Specification 970 types Nos. EN. 24, EN. 30A and EN. 30B. Examples of corrosion resistant steels to which improved properties can be imparted are alloys based on iron and containing 10-20%- by weight of chromium. They may, in addition, contain -2% carbon, 03% nickel, 04% molybdenum, 04% manganese, 04% copper, 010% cobalt, 03% tungsten, 0-2% vanadium, 03% silicon, together with the usual adventitious amounts of phosphorous and sulphur. Examples of materials of this type are those conforming to British Standards Specification 970 types EN. 56 and EN. 57 and those known as AlSl types Nos. 410, 403, 41 4, 416,

4 annealing the strip at a first temperature within the range 800 to 1200 C., cooling the annealed strip to a second temperature within the range 300 to 800 C. at which the austenite in the strip is metastable, effecting a cross-sectional reduction of one edge of the strip whilst the strip is maintained at said second temperature to give said edge a profile substantially that of the desired final cutting edge, cooling the strip to room temperature, finishing said edge of the strip to a cutting edge, and severing the strip transversely to form razor blades. 4. The manufacture of razor blades from austenitic steel strip, said strip containing at least 13% by weight of chromium, comprising the steps of annealing the strip at a first temperature within the range 1000 to 115 0 C.,

cooling the annealed strip to a second temperature within the range 550 to 650 C. at which the austenite 418, 420, 431, 440A and 440C. Other examples are those f SHIP metatable: steels made by Uddeholm g and id tifi d by them effecting a cross-sectional reduction of between as numbers ss1, S5716, ss731, AEB, SS6, SSB6 and and 95% of one edge of the strip whilst the strip i Orvar II, maintained at said second temperature,

Specific compositions of some of the above mentioned 25 Cooling the strip to at least room tfimperatufc, steels (in percent by weight) are as follows: sharpening said edge of the strip to a cutting edge, and

0 Mn si Cr Mo Ni v Ladish DGA 0. 75 0. 22 1. 0 Labelle HT... 0. 43 1. 2. 25 1. 35 Supertricent. 0. 55 0. 8 2. 0. 9 Uddeholm ss1. 0.10 0. 45 0. 13. 7 Uddeholm $8716-. 0.35 0.45 0.45 13.6 Uddeholm ss731.. 0. 22 0. 0.30 13. 2 Uddeholm AEB.. 0. 95 1. 05 0.18 13. 5 Uddeholm 856.-.. 0. 32 0. 45 0. 40 0. 40 Uddeholm SSB6 0.40 0. 37 0. 37 14.0 Uddeholm Orvar I 0. 37 0. 45 1.00 5. 3

By means of the present invention it is possible to produce razor blades having a cutting edge which is harder than when the same or a similar steel is conventionally treated. This is particularly advantageous when a subsequent coating process, such as a polymer coating, involves heating which is liable to reduce the hardness of the cutting edges. Furthermore there is normally an increase in properties such as toughness, fatigue strength and proof stress which permit the production of an improved edge.

It will be appreciated that the strip may be severed transversely to form the individual razor blades either before or after the final stage of formation of the cutting edge or edges.

I claim:

1. In the manufacture of razor blade strip from a stainless steel having a chromium content of from approximately 10.0% and which contains metastable austenite at an elevated temperature, the steps of submitting an edge region only of the strip to crosssectional reduction at said elevated temperature to deform the austenite, and, thereafter,

cooling the strip to transform the deformed austenite to martensite.

2. In the manufacture of razor blade strip from corrosion-resistant stainless steel alloy having a chromium content of from 10.0 to 20.0% and whose composition is such that it can be annealed to form austenite and thereafter cooled to an elevated temperature at which the austenite is metastable the steps of effecting deformation of the strip at this elevated temperature, in each region where a cutting edge is to be formed and, subsequently,

cooling said strip to convert at least partially to martensite the austenite in the deformed region.

3. The manufacture of razor blades from a strip of corrosion-resistant austenitic stainless steel alloy having a chromium content of at least 10.0% comprising the steps of severing the strip transversely into individual razor blades. 5. The manufacture of razor blades as claimed in claim 4, wherein said strip is cooled to a temperature substantially below room temperature.

6. The manufacture of razor blades from corrosion resistant austenitic steel strip, said strip being of a steel alloy containing by weight percentages of 1020% chromium, up to 2% carbon, up to 3% nickel, up to 4% molybdenum, up to 4% manganese, up to 4% copper, up to 10% cobalt, up to 3% tungsten, up to 2% vanadium and up to 3% silicon, comprising the steps of annealing the strip at a first temperature within the range 800 to 1200" C.,

cooling the annealed strip to a second temperature within the range 300 to 800 C. at which the austenite in the strip is metastable,

deforming each edge of the strip whilst the strip is maintained at said second temperature, said deformation giving each edge a cross-sectional profile approximating to the desired final edge shape,

cooling the strip to room temperature,

electrolytically finishing said edge of the strip to a cutting edge, and

severing the strip transversely to form razor blades.

References Cited UNITED STATES PATENTS 2,934,463 4/1960 Schmatz et al. 148-124 3,210,221 10/1965 Nachtman et al 14812.4 3,215,565 11/1965 Harvey 14812.4 3,240,634 3/1966 Nachtman l48--l2.4 3,340,102 9/1967 Kulin et al. 14812.4

HYLAND BIZOT, Primary Examiner.

WAYLAND W. STALLARD, Assistant Examiner.