# US 10,501,818 B2 · Method for improving an iron-nickel-chromium-manganese alloy for timepiece applications

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- Number: US 10,501,818 B2
- Document ID: US10501818B2
- Status: Granted
- Kind: B2
- Application number: 15/244,594
- Filed: 2016-08-23
- Published: 2017-06-08
- Granted: 2019-12-10
- Earliest claimed: 2015-12-02
- Assignees: Nivarox-FAR S.A.
- Applicants: Nivarox-FAR S.A.
- Inventors: Christian Charbon
- Web page: https://patentgrep.com/patent/US10501818B2

## CPC

- C21D 9/02: for springs
- B22D 7/00: Casting ingots, {e.g. from ferrous metals}(equipment for conveying molten metal B22D35/00)
- C21D 1/18: Hardening (C21D1/02 takes precedence); Quenching with or without subsequent tempering (quenching devices C21D1/62)
- C21D 9/0081: {for slabs; for billets}
- C22C 22/00: Alloys based on manganese
- C22C 27/06: Alloys based on chromium
- C22C 33/04: by melting
- C22C 33/06: using master alloys
- C22C 38/001: {containing N}
- C22C 38/04: containing manganese
- C22C 38/38: with more than 1.5% by weight of manganese
- C22C 38/42: with copper
- C22C 38/44: with molybdenum or tungsten
- C22C 38/58: with more than 1.5% by weight of manganese
- F16F 1/021: {characterised by their composition, e.g. comprising materials providing for particular spring properties (composition and manufacture of clock or watch springs G04B1/145)}
- G04B 17/063: {Balance construction (balances with frequency adjustment screw G04B18/006; balances with temperature compensation G04B17/222; balancing devices G04B17/28)}
- G04B 17/066: {Manufacture of the spiral spring (locking of the spiral spring by the regulating lever G04B18/026; spiral spring with temperature compensation G04B17/227; fixation of the spiral spring on the collet G04B17/32; mainspring G04B1/14)}
- G04B 17/22: for the effect of variations of temperature {(alloys with small expansion coefficient C21C, C22C; adjustment of the regulator dependant on adjustment of the hands G04B18/028; depending on the difference in time with a comparison clockwork G04C11/007)}
- 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 (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)
- B22D: CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES (shaping of plastics or substances in a plastic state B29C; metallurgical processing, selection of substances to be added to metal C21, C22)
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- F16F: SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
- G04B: MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS (spring- or weight-driven mechanisms in general F03G; electromechanical clocks or watches G04C; electromechanical clocks with attached or built-in means operating any device at pre-selected times or after predetermined time intervals G04C23/00; clocks or watches with stop devices G04F7/08)

## Abstract

A method for improving an iron-nickel-chromium-manganese alloy for timepiece applications, particularly for producing a balance spring, is described. The base alloy contains, by mass, from 9.0% to 13.0% of nickel, from 4.0% to 12.0% of chromium, from 21.0% to 25.0% of manganese, from 0 to 5.0% of molybdenum, and/or from 0 to 5.0% of copper in addition to iron. The alloy is hardened while its anti-ferromagnetic properties are maintained by introducing 0.10% to 1.20% of carbon and 0.10% to 1.20% of nitrogen interstitially, based on the mass of the base alloy.

## Claims

### Claim 1

A method for hardening an iron-nickel-chromium-manganese base alloy, the method comprising:
introducing, based on the base alloy, 0.10% to 1.20% by mass of carbon and 0.10% to 1.20% by mass of nitrogen interstitially into the base alloy with a mass ratio of carbon to nitrogen ranging from 1.0 to 2.0 so as to harden the base alloy and maintain anti-ferromagnetic properties of the base alloy,
wherein the base alloy comprises, by mass:
from 4.0% to 13.0% of nickel,
from 4.0% to 12.0% of chromium,
from 21.0% to 25.0% of manganese,
from 0 to 5.0% of molybdenum and/or from 0 to 5.0% of copper, and
iron.

### Claim 2 (depends on 1)

The method according to claim 1, wherein a sum of the introduced carbon and nitrogen ranges between 0.60% and 0.95%.

### Claim 3 (depends on 2)

The method according to claim 2, wherein the sum of the introduced carbon and nitrogen ranges between 0.75% and 0.95%.

### Claim 4 (depends on 3)

The method according to claim 3, wherein the sum of the introduced carbon and nitrogen ranges between 0.80% and 0.85%.

### Claim 5 (depends on 1)

The method according to claim 1, wherein said base alloy comprises at least 8.0% of chromium.

### Claim 6 (depends on 1)

The method according to claim 1, wherein said base alloy comprises, by mass: from 0.5% to 5.0% of molybdenum and/or copper.

### Claim 7 (depends on 1)

The method according to claim 1, wherein ferrochromium is added to nitrogen.

### Claim 8 (depends on 1)

The method according to claim 1, wherein ferromanganese is added to carbon.

### Claim 9 (depends on 1)

The method according to claim 1, wherein ferrochromium is added to nitrogen, and ferromanganese is added to carbon.

### Claim 10 (depends on 1)

A timepiece balance spring, comprising:
an alloy produced by the method according to claim 1.