# US 10,501,820 B2 · Method for producing a strand from stainless steel and strand made of stainless steel

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- Number: US 10,501,820 B2
- Document ID: US10501820B2
- Status: Granted
- Kind: B2
- Application number: 15/551,545
- Filed: 2016-02-15
- Published: 2018-08-09
- Granted: 2019-12-10
- Earliest claimed: 2015-02-17
- Assignees: Sandvik Materials Technology Deutschland GmbH
- Applicants: Sandvik Materials Technology Deutschland GmbH
- Inventors: Thomas Frobose; Christofer Hedvall; Udo Rauffmann
- Web page: https://patentgrep.com/patent/US10501820B2

## CPC

- C21D 9/525: {for wire, for rods (C21D9/54 takes precedence)}
- B21C 23/085: {Making tubes (B21C23/10 take precedence)}
- C21D 6/004: {containing Cr and Ni}
- C21D 6/005: {containing Mn}
- C21D 6/008: {containing Si}
- C21D 8/10: during manufacturing of tubular bodies
- C21D 9/14: wear-resistant or pressure-resistant pipes
- C21D 9/52: for wires; for strips {; for rods of unlimited length}
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/22: with molybdenum or tungsten
- C22C 38/44: with molybdenum or tungsten
- C21D 6/002: {containing Cr (C21D6/004 takes precedence)}
- C21D 2211/001: Austenite
- 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)
- B21C: MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES, PROFILES OR LIKE SEMI-MANUFACTURED PRODUCTS OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- C22C: ALLOYS (treatment of alloys C21D, C22F)

## Abstract

A method for manufacturing a strand from a stainless steel by cold forming a billet into the cold-hardened strand and subsequently annealing the strand is provided. The method allows stainless steel strands to be produced, which have both a high tensile strength, as well as a high degree of elongation. The strand is heated to a temperature ranging from 400° C. to 460° C. while the strand is being annealed, and the cold-hardened strand is surrounded by a protective gas atmosphere during the heating process.

## Claims

### Claim 1

A method for manufacturing a strand of stainless steel comprising:
cold forming a billet into a strain-hardened strand; and
subsequently annealing the strand,
wherein during annealing of the strand the strand is heated to a temperature in a range from 400° C. to 460° C., and
wherein the strain-hardened strand is surrounded by a protective gas atmosphere during heating, and
wherein the material of the billet is an austenitic stainless steel having a composition consisting of not more than 0.06 weight % carbon, not more than 2 weight % manganese, not more than 0.7 weight % silicon, 16 to 20 weight % chromium, 2.0 to 2.6 weight % molybdenum, with a balance of iron and unavoidable impurities.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the strand is heated to a temperature in the range from 410° C. to 450° C.

### Claim 3 (depends on 1)

The method according to claim 1, further comprising the step of cooling the strand after heating, wherein the strand during cooling is surrounded by the protective gas atmosphere.

### Claim 4 (depends on 1)

The method according to claim 1, wherein the protective gas atmosphere includes argon, having a fraction of argon of more than 95% by volume.

### Claim 5 (depends on 1)

The method according to claim 1, wherein the protective gas atmosphere has an oxygen content of less than 50 ppm.

### Claim 6 (depends on 1)

The method according to claim 1, wherein a dew point of the protective gas atmosphere at atmospheric pressure is at a temperature of −40° C. or less.

### Claim 7 (depends on 1)

The method according to claim 1, wherein the strand is a tube.

### Claim 8 (depends on 1)

The method according to claim 1, wherein the billet and the strand are in the form of a tube with an inner diameter and an outer diameter, and wherein by the cold forming a tube is formed, the inner diameter of which is half of the outer diameter or less.

### Claim 9 (depends on 1)

The method according to claim 1, wherein the cold forming is carried out by cold pilger milling.

### Claim 10 (depends on 1)

A strand of stainless steel made according to the method of claim 1.

### Claim 11 (depends on 10)

The strand of stainless steel according to claim 10, wherein the strand is a tube with an inner diameter and an outer diameter, the inner diameter being one half of the outer diameter or less.

### Claim 12 (depends on 1)

The method according to claim 1, wherein the strand is heated to a temperature in the range from 435° C. to 445° C.

### Claim 13 (depends on 1)

The method according to claim 1, wherein the strand is heated to a temperature of 440° C.