Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S148/00—Metal treatment
  • Y10S148/902—Metal treatment having portions of differing metallurgical properties or characteristics
  • Y10S148/905—Cutting tool

Definitions

• the hardness of the steel plus its temper-resistance makes it especially useful for making cutting edges, e.g. knives and especially razor blades having improved temper-resistance.
• the steel is made by (a) heating a steel comprising from about 7 to about 30% manganese and about 0.6 to about 1.4% carbon to at least the austenizing temperature to make it fully austenitic and to dissolve suflicient carbides so as to depress the Ms temperature sufliciently below room temperature that the steel will remain mainly in the austenitic form, e.g.
• the cutting edge is formed between the cold-working step and the ageing step.
• the fluorocarbon coatings still provide a substantial improvement in shaving comfort and ease.
• the benefits of such coatings would be even more fully realized if they could be applied to blades which intially had at least the hardness of carbon steels and which had substantially better temper-resistance.
• One object of the present invention is to provide processes for making novel steel, which in its finished form, is mainly austenitic, e.g. at least 80% (with the accompanying good temper-resistance) but which has hardnesse and strength which are at least comparable of those of high carbon martensitic steel.
• Another object is to provide new and improved cutting edges such as knives and scalpels and especially razor blades comprising said steel.
• the above objects are achieved by (a) heating a steel comprising carbon and manganese in the ranges specified below to at least the austenizing temperature for a suflicient time to make it fully austenitic and to dissolve sufiicient carbides so as to depress the Ms temperature Patented Sept. 4, 1973 sufiiciently below room temperature that the steel will remain mainly in the austenitic form when it is both cooled to room temperature, preferably by quenching, and subsequently cold-Worked; (b) cold-working the steel and (c) thereafter age-hardening the steel.
• the cutting edge is formed, e.g. by grinding between the cold-working step and the age hardening step.
• the blades of the present invention are made from steels which comprise by weight about 0.6 to about 1.4% carbon, about 7 to 30% manganese and the balance iron or iron and other alloying elements which will enhance the properties of the steel but not interfere with the processes.
• the steels may contain one or more alloying elements which are known to decrease the stacking fault energy of the steel. As examples of such elements (and the range in which they may usually be present), mention may be made of the following:
• the steel will contain sufficient chromium so as to render it stainless. Usually this can be accomplished by incorporating at least 10% chromium into the composition. In the embodiments which will be the most commercially feasible, usually the steel will contain between about 10 to 20% chromium. When appreciable amounts of chromium are added such as set forth above to enhance the corrosion-resistance of the steel, larger amounts of manganese should be present in order to offset the carbide-forming propensity of the chromium.
• manganese will preferably be present in amounts ranging between about 7 to 14%.
• Another steel which was found useful in the processes of the invention contained 1.01% carbon, 12.3% manganese and the balance iron with the small amounts of impurities normally found therein.
• the steel is heated to at least the austenizing temperature, for a sufiicient time, to make it fully austenitic and to dissolve sufficient carbides so as to depress the Ms temperature sufficiently below room temperature that the steel will remain mainly austenitic, e.g. at least when it is both cooled, preferably by quenching, and subsequently cold-worked.
• the steel is so heat treated that the Ms" temperature will be at least below C. and preferably below 200 C.
• the Ms temperature can'be sufficiently depressed by heating the steel to a temperature between about 1000 C. and 1250 C.
• the steel is heated to a temperature between 1050 C. and 1250 C. Particularly useful results were obtained by heating the steel to a temperature of 1050 C. and holding it there for about one half hour.
• the cold-working step which imparts a substantial increase in hardness to the steel, may be carried out by any of the well-known methods, e.g. rolling, stamping, pressing, drawing, etc. Further when the processes disclosed herein are used in making cutting edges such as razor blades at least a portion of the cold-working may be accomplished in the grinding operation which is used in forming the cutting edge. In preferred embodiments, the coldworking is carried out by cold-rolling. Generally the extent to which the steel can be cold-worked without being converted to martensite will depend upon the Ms temperature. Usually the lower the Ms temperature, the more the steel can be cold-worked without being appreciably converted to the martensitic form.
• the steel subsequent to cold-working contain less than 20% martensite and preferably less than
• the steel is substantially fully austenitic subsequent to the cold-working step.
• a steel whose Ms temperature has been sufficiently depressed e.g. to at least below 200 C.
• Substantial increases in the hardness can be achieved by coldworking the steel until there has been a reduction in thickness of at least 50%.
• the maximum hardness which can be obtained in the cold-working step will generally be achieved by cold-working the steel until there has been a reduction in thickness of at least between about 70% and 96%. It is to be understood that reductions beyond this extent may be made, but generally they will not result in additional hardening.
• the cold-Working which is necessary to provide the maximum hardness which is obtainable in this step may be provided at least in part by the grinding step which is normally employed in forming the cutting edge.
• the grinding step which is normally employed in forming the cutting edge.
• one may, for example, partially harden the strip by, for example, coldrolling; carry out any desired stamping or perforation steps and then complete the cold-working step at least in the edge area by the grinding operation.
• substantially all the cold-working may be carried out, for example, by coldrolling and the grinding step would contribute little additional hardening.
• electrosharpening methods could be employed in forming the cutting edge.
• the edge is formed prior to the age-hardening step when the steel is not as hard. It should be understood, however, that, when desired, the cutting edge may be formed subsequent to the age-hardening step but the steel will be appreciably harder.
• the methods which may be employed for forming the cutting edge are well-known to the art and the specifics thereof form no part of this invention.
• the age-hardening step which is carried out subsequent to the cold-working step is a time, temperature dependent reaction in which a further substantial increase in hardness is achieved.
• the optimum hardnesses will be achieved by heating the steel at a temperature between about 200 C. and 500 C. for periods, for example, of at least from about ten seconds to ten days.
• the shorter times will be applicable to the higher temperatures and the longer times to the lower temperatures.
• the age-hardening step should be preferably carried out at temperatures below 425 C. In carrying out the age-hardening step, excessively high temperatures for extended periods should be avoided in order to prevent over-ageing.
• EXAMPLE 1 A strip of steel containing 1.00% carbon, 21% manganese, 14% chromium and the balance iron and the usual trace impurities found therein, was made fully austenitic by heating it at 1200 C. for one-half hour and thereafter cooling it rapidly in water.
• the strip which had a hardness of 220 DPHN was cold-rolled to a thickness of four thousandths of an inch with a reduction of 96% in the thickness of the steel.
• the hardness was 740 DPHN and the strip was still substantially fully austenitic.
• the strip was then sharpened to produce an edge through conventional razor blade sharpening techniques. Subsequent to sharpening, the blade was heated to 350 C.
• Body Slntering temperature Body A steel strip containing 1.01% carbon, 12.3% manganese and the balance iron and the usual trace impurities found therein, was made fully austenitic by heating it at 1050 C. for one-half hour and thereafter quenching it to room temperature in water.
• the strip which had a hardness of 200 DPHN was cold-rolled to a thickness of four thousandths of an inch with a reduction of in the thickness of the steel.
• the hardness was 750 DPHN and the strip was still substantially fully austenitic.
• the strip was then sharpened to produce an edge through conventional razor blade sharpening techniques. Subsequent to sharpening, the blade was heated to 350 C.
• Example 1 A polytetrafiuoroethylene telomer coating was applied to the cutting edge and it was cured thereon at 343 C. for ten minutes. Subsequent to the cure, the blade had a body hardness of 850 DPHN which is substantially better than that of the typical carbon or stainless blades set forth in Example 1.
• EXAMPLE 3 Blades were prepared by a process similar to that of Example 2 except that the age-hardening step was carried out at 400 C. for fifteen minutes. The results were comparable to those of Example 2.
• agehardening and polymer sintering step can be carried out simultaneously.
• the steels of this invention due to their austenitic nature are generally non-magnetic and also have good low-temperature ductility. Accordingly, in addition to being useful for making cutting edges such as razor blades, they are also useful for other purposes in which one or more of their useful properties is desired, e.g. springs, cryogenic hardware, high-strength wire and cable, and any other end uses where their good temper-resistance may be useful.
• a process for making razor blades, the edges of which in their finished form are mainly austenitic, have hardnesses which are at least comparable to high carbon martensitic blade edges, and have improved temper-resistance comprising (a) heating a steel strip which comprises from about 7 to 30% manganese and 0.6 to about 1.4% carbon to at least the austenizing temperature for a sufficient time to make it fully austenitic and to dissolve sufi'icient carbides so as to depress the Ms temperature of said steel sufficiently below room temperature that the steel will remain mainly in the austenitic form when it is both cooled to room temperature and subsequently cold-worked; (b) cold-working the steel strip at least in the areas in which the cutting edge is to be formed; (c) age-hardening the steel and (d) at some time subsequent to the austenizing step forming the cutting edge.
• a steel razor blade having a cutting edge which is mainly austenitic and which comprises 0.6 to 1.4% carbon and 7 to 30% manganese.
• a steel razor blade as defined in claim 12 which has stainless properties and includes about 10 to 20% chromium.
• a razor blade the cutting edge of which in its finished form, is mainly austenitic, has a hardness which is at least comparable to high carbon martensitic blades and which has improved temper-resistance, said blade being made from steel which comprises about 0.6 to 1.4% carbon and about 7 to 30% manganese.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Heat Treatment Of Articles (AREA)
• Heat Treatment Of Steel (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=22716545

Family Applications (1)

Country Status (12)

Cited By (7)

Families Citing this family (3)

• 1971
  • 1971-11-01 US US00194166A patent/US3756865A/en not_active Expired - Lifetime
• 1972
  • 1972-10-26 CA CA154,908A patent/CA978394A/en not_active Expired
  • 1972-10-31 GB GB5011272A patent/GB1394262A/en not_active Expired
  • 1972-10-31 BR BR7651/72A patent/BR7207651D0/pt unknown
  • 1972-10-31 AR AR244916A patent/AR196497A1/es active
  • 1972-10-31 AU AU48350/72A patent/AU4835072A/en not_active Expired
  • 1972-10-31 IT IT53725/72A patent/IT966857B/it active
  • 1972-10-31 ES ES408152A patent/ES408152A1/es not_active Expired
  • 1972-11-01 NL NL7214758A patent/NL7214758A/xx unknown
  • 1972-11-01 DE DE2254165A patent/DE2254165A1/de active Pending
  • 1972-11-01 JP JP47109823A patent/JPS4856515A/ja active Pending
  • 1972-11-02 FR FR7238825A patent/FR2159982A5/fr not_active Expired

Also Published As

Similar Documents