RAZOR BLADE AND COMPOSITION FOR A RAZOR BLADE

Abstract

A razor blade has a first and a second portion. The first portion has a cutting edge at an exterior end and is angled relative to the second portion by a bending process. A bent region that can be arcuate is intermediate the first and second portions. The razor blade is manufactured from martensitic stainless steel being mostly iron and having (by weight): 0.40 to 0.60% C; 0.30 to 0.55% Si; 0.70 to 0.90% Mn; 13.0 to 14.0% Cr; 0.50 to 1.0% Mo; and 0.03 to 0.2%, more preferably 0.03-0.1% N.

Claims

1. A razor blade (50), comprising: a first portion (66) and a second portion (68), the first portion (66) having a cutting edge (20) at an exterior end thereof and being angled relative to the second portion (68) by a bending process; and a bent region (52) intermediate the first portion (66) and the second portion (68); wherein the razor blade (50) comprises a martensitic stainless steel comprising mainly iron and having (by weight): 0.40 to 0.60% Carbon 0.30 to 0.55% Silicon 0.70 to 0.90% Manganese 13.0 to 14.0% Chromium 0.50 to 1.0% Molybdenum, and 0.03 to 0.2% Nitrogen.

2. The razor blade (50) of claim 1, wherein the first portion (66) is angled relative to the second portion (68) by an angle (60) in a range 105 to 130 degrees.

3. The razor blade (50) of claim 1, wherein the bent region (52) includes an external radius (54) in a range 0.2 to 1.5 mm.

4. The razor blade (50) of claim 1, wherein the second portion (68) has a thickness (14) in a range 0.05 to 0.125 mm.

5. The razor blade (50) of claim 1, wherein the bending process is not preceded by a reheating process to modify the structure at a bending region (70).

6. The razor blade (50) of claim 1, wherein the martensitic stainless steel further comprises (by weight): Sulphur in a range up to 0.02% and Phosphorous in a range up to 0.0025%.

7. The razor blade (50) of claim 1, wherein the razor blade (50), in a region of the cutting edge (20), has a hardness in a range 550 to 640 HV.

8. The razor blade (50) of claim 1, wherein the cutting edge (20) extends along a length (40) of the razor blade (50).

9. A method of making a razor blade (50), comprising the steps of: a) providing a martensitic stainless steel strip (10) having a width (12) and a thickness (14) and including a front edge portion (16) and a back edge portion (18), the strip (10) comprising mainly iron and having (by weight): 0.40 to 0.60% Carbon 0.30 to 0.55% Silicon 0.70 to 0.90% Manganese 13.0 to 14.0% Chromium 0.50 to 1.0% Molybdenum, and 0.03 to 0.2% nitrogen; b) hardening the strip (10); c) forming a cutting edge (20) along at least one of the front edge portion (16) and rear edge portion (18); d) applying a coating (30) comprising at least a fluoropolymer material to the cutting edge (20) and curing the fluoropolymer material to thereby anneal at least a portion containing the cutting edge (20) to a hardness at least 550 HV; preferably 620-640 HV e) separating the strip (10) to provide a discrete length (40); and f) forming the discrete length (40) in a bending process to provide a bent region (52) intermediate a first portion (66) having the cutting edge (20) at an exterior end thereof, the first portion (66) being angled relative to a second portion (68).

10. The method of claim 9, wherein step d) is performed after step e).

11. The method of claim 9, wherein the bent region (52) includes an external radius (54) in a range 0.2 to 1.5 mm.

12. The method of claim 9, wherein the strip (10) has a thickness (14) in a range 0.05 to 0.125 mm.

13. The method of claim 9, wherein the first portion (66) is angled relative to the second portion (68) by an angle (60) in a range 105 to 130 degrees.

14. The method of claim 9, wherein the strip (10) further comprises (by weight): Sulphur in a range up to 0.02% and Phosphorous in a range up to 0.0025%.

15. The method of claim 9, wherein step f) is a swivel bending process.

16. The razor blade of claim 1, wherein the martensitic stainless steel contains (by weight) 0.03 to 0.1% Nitrogen.

17. The method of claim 9, wherein the martensitic stainless steel contains (by weight) 0.03 to 0.1% Nitrogen.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a schematic representation of the process steps of the present disclosure, and.

[0014] FIG. 2 is a schematic sectional view of a razor blade of the present disclosure.

DETAILED DESCRIPTION

[0015] Martensitic stainless steels having a carbon content 0.6-0.7% or more, about 13% (e.g. 12.5% to 13.5%) chromium and substantially free of molybdenum have been used for making razor blades. These materials are widely available, have adequate corrosion resistance for their intended use and can be sharpened to provide a high-quality cutting edge. Exemplary commercially available materials are those such as GINS made by HITACHI METALS and 13C26 made by SANDVIK. These materials appear as Alloy 1 in Table 1, below. Another commercially available martensitic stainless steel suitable for manufacturing razor blades is the grade designated GIN7 manufactured by HITACHI METALS that appears as Alloy 2 in Table 1. Alloy 3 and Alloy 4 are experimental compositions according to the present disclosure.

TABLE-US-00001 TABLE 1 (All % by weight) C % Cr % Si % Mn % Mo % N % Fe Alloy 1 0.62-0.75 12.7-13.7 0.2-0.5 0.45-0.75 ≤trace 0 Balance Alloy 2 0.48-0.52 13.0-14.0  0.3-0.55 0.7-0.9 1.2-1.4 0 Balance Alloy 3 0.45-0.6  13.0-14.0  0.3-0.55 0.7-0.9 0.5-1.0 0 Balance Alloy 4 0.45-0.6  13.0-14.0  0.3-0.55 0.7-0.9 0.5-1.0 0.03-0.1  Balance (All alloys can contain ≤0.02 Sulphur and ≤0.0025 Phosphorous, Alloy 4 can contain 0.03-0.2% N).

[0016] Referring now to the drawings and in particular FIG. 1, exemplary process steps for the manufacture of a so-called single edge razor blade having a bent portion of the alloys under evaluation are schematically depicted. Elongated stainless steel strip 10, as provided, is depicted at step (a). The strip has a width 12 and a thickness 14 and includes a front edge portion 16 and a back edge portion 18. The width of the strip is preferably about 3 mm wide but can be any width to suit the application at hand from about 2 mm or less to about 22 mm or more. The thickness 14 of the strip as-provided can be 0.1 mm or less but is preferably about 0.076 mm. In other cases strip having a thickness 14 of about 0.025-0.05 mm or greater than 0.1 mm, e.g. 0.125 mm can be employed. At step (b) the strip 10 is hardened and tempered to a hardness about 660-850 HV by well-known process(es). At step (c) the front edge is sharpened by any well-known sharpening process such as grinding and honing to provide an elongated cutting edge 20. As an alternative to the aforementioned, a double-edge razor blade can be employed. Strip material having a suitable width (e.g. about 22 mm) is perforated in continuous strip form to provide apertures that can include an elongated center slot that can be used to support or locate the blade strip during subsequent processes such as edge forming and edge coating and location holes that can be used to index the strip or to locate a discrete razor blade during certain processes. Process steps (b) and (c) are performed as described above, with an exception that both the front edge and back edge portions 16, 18 are sharpened to provide cutting edges. The elongated strip is then separated into discrete double edge razor blades. Process step (d) (below) is performed to both cutting edges as described above. The double edge razor blade is then split preferably adjacent the ends of the center slot to provide two single edge razor blades. Thereafter process step (f) (below) is performed. Returning to the single edge razor blade, at step (d) suitable coating(s) 30 applied to the cutting edge by well-known processes. One or more under-coatings can include, but are not limited to, one or more of chromium, platinum, niobium, titanium, alloys of the aforementioned materials and compounds of the aforementioned materials compounded with e.g. carbon or nitrogen. A suitable titanium coating is disclosed in commonly assigned U.S. patent application publication 2007/0186424 the disclosure of which is hereby incorporated for reference in its entirety. Also various types of hard carbon coatings such as amorphous diamond, diamond-like-carbon (DLC) and combinations with the above can be applied. An outer coating of a fluoropolymer material, preferably PTFE is applied. A suitable PTFE coating is disclosed in commonly assigned U.S. patent application publication 2007/0124944 the disclosure of which is hereby incorporated for reference in its entirety, but the present application is not limited in this regard and any suitable PTFE coating can be employed. The PTFE coating can be cured and the curing process has a secondary effect of annealing at least the portion of the strip containing the cutting edge to a hardness at least 550 HV and preferably about 620-640 HV. At step (e) a lengthwise extending portion 40 is cut from the strip to provide a discrete razor blade 50. The discrete razor blade has properties of the strip from which it was cut. At step (1) the razor blade 50 is bent to provide a bent portion 52 intermediate a first portion 66 containing the cutting edge 20 and a second portion 68 containing the back edge portion 18.

[0017] A representative sectional view of the razor blade 50 having a bent portion 52 is shown in FIG. 2. The bending process can be a punch-and-die process. The bending process can also be a “swivel bending” process, e.g. as described in commonly assigned U.S. patent application publication 2010/0107425 the disclosure of which is hereby incorporated for reference for its disclosure of a bending process. The bending process can also be any suitable process to impart a bent portion to a razor blade. The bending process is preferably performed without any prior reheating process to modify the razor blade's structure or ductility in the region of the razor blade being bent, i.e. the region 70 (see FIG. 1) that subsequently becomes the bent portion 52 after the bending process.

[0018] Razor blades having bent portions of the four alloys (Alloy 1-Alloy 4) were produced according to varying thickness (t, 14), hardness (Hv), bend angle (α, 60) and outer bend radius (Ro, 54) as shown in Table 2, below and depicted in FIG. 2. The razor blades were examined for the presence of end cracks and evaluated for the relative durability of the cutting edge. Cutting edge durability can be evaluated by well-known methods of physically cutting the cutting edge into certain media multiple times and microscopically inspecting the razor blade for damage or permanent distortion of its extreme cutting edge.

TABLE-US-00002 TABLE 2 Test # Alloy t Hv α Ro Crack ED 1 Alloy 1 0.1 620 123 1.3 ≤100 1 2 Alloy 1  0.076 550 108-112  0.92 ≤10  4 3 Alloy 1  0.076 620 123  0.98 ≤100 1 4 Alloy 1  0.076 610 118  0.98 ≤100 1 5 Alloy 2  0.076 590 108-112  0.48 None 3 6 Alloy 3  0.076 610 110 0.7 None 2 7 Alloy 4  0.076 610 110  0.3-0.48 None 2 Where: t = strip thickness (mm); Hv = strip hardness (Vickers) at 200 g load on cross section, all hardness values ± 20 units; α = bend angle (degrees); Ro = outer radius of bent region (mm); Crack = presence of end cracks at dimension noted (microns); ED = cutting edge durability, ranked 1-4 where 1 = most durable, 4 = least durable, as evaluated.

[0019] The addition of Nitrogen to Alloy 4 advantageously provides a razor blade of desirable ductility wherein the bent portion can beneficially have a smaller outer bend radius with a low bend angle while the razor blade exhibits a relatively desirable cutting edge durability. Without being limited by theory, it is believed the nitrogen alloyed martensitic structure is finer and more uniform than carbon alloyed material, giving a very fine precipitate distribution and superior properties on tempering.

[0020] While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. For instance, modifications or changes as can be made within the scope of the attached claims and features disclosed in connection with any one embodiment can be used alone or in combination with each feature of the respective other embodiments. Thus, the breadth and scope of any embodiment should not be limited by any of the above described exemplary embodiments but should be defined only in accordance with the following claims and their equivalents.