Method for improving an iron-nickel-chromium-manganese alloy for timepiece applications

Patent metadata

Field	Value
Publication number	US-10501818-B2
Application number	US-201615244594-A
Country	US
Kind code	B2
Filing date	Aug 23, 2016
Priority date	Dec 2, 2015
Publication date	Dec 10, 2019
Grant date	Dec 10, 2019

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.

First claim

What is claimed is:

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.

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

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

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

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

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

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

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

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

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

Assignees

• Nivarox Sa

Inventors

• Charbon Christian

Classifications

• C22C38/58

  with more than 1.5% by weight of manganese · CPC title

• C22C38/001

  containing N · CPC title

• B22D7/00

  Casting ingots, {e.g. from ferrous metals}(equipment for conveying molten metal B22D35/00) · CPC title

• C22C38/42

  with copper · CPC title

• C21D1/18

  Hardening (C21D1/02 takes precedence); Quenching with or without subsequent tempering (quenching devices C21D1/62) · CPC title