# US 10,501,831 B2 · Method for producing an alloy for a reforming tube

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- Number: US 10,501,831 B2
- Document ID: US10501831B2
- Status: Granted
- Kind: B2
- Application number: 15/517,405
- Filed: 2015-09-16
- Published: 2017-10-19
- Granted: 2019-12-10
- Earliest claimed: 2014-10-08
- Assignees: L'Air Liquide, Societe Anonyme pour l'Etude et l'Exploitation des Procedes Georges Claude
- Applicants: L'Air Liquide, SociétéAnonyme pour l'Etude et l'Exploitation des Procédés Georges Claude
- Inventors: Anna Fraczkiewicz; Karolina Maminska; Pascal Del-Gallo; Jader Furtado; Daniel Gary
- Web page: https://patentgrep.com/patent/US10501831B2

## CPC

- C22C 38/40: with nickel
- C21D 6/004: {containing Cr and Ni}
- C21D 6/02: Hardening by precipitation
- C21D 9/08: for tubular bodies or pipes
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/44: with molybdenum or tungsten
- C22C 38/46: with vanadium
- C22C 38/48: with niobium or tantalum
- C22C 38/50: with titanium or zirconium
- C21D 2211/001: Austenite
- C21D 2211/004: Dispersions; Precipitations
- Y02E 60/50: Fuel cells
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- 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)
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

The invention relates to a microstructure of an alloy for a tube for reformers, having an austenitic matrix structure, characterised in that: i) primary micrometric precipitates in the form of M23C6-type carbides, where M=Fe, Ni or Cr, and/or M(C,N)-type carbides, where M==Nb or Ti, are formed during the solidification of the alloy; ii) secondary nanometric precipitates in the form of M23C6-type carbides, where M=Fe, Ni or Cr and/or M(C,N)-type carbides, where M==Nb or Ti, are formed during the activation of the tube; and iii) between 0.1 and 0.3% of Ni16Si7Nb6-type intermetallic precipitates is formed during the use of the tube.

## Claims

### Claim 1

A process for the manufacture of an alloy of iron, nickel and chromium, for a tube of reformers, comprising from 22 to 30% by weight of Cr, from 20 to 45% by weight of Ni and from 0.3 to 0.6% by weight of C and exhibiting a microstructure with an austenitic matrix such that:
i) micrometric primary precipitates in the form of carbides of M23C6 type with M=Fe, Ni or Cr and/or of M(C,N) type with M=Nb or Ti are formed during the solidification of the alloy;
ii) nanometric secondary precipitates in the form of carbides of M23C6 type with M=Fe, Ni or Cr and of M(C,N) type with M=Nb or Ti are formed during the bringing into service of the tube; and
iii) an amount of intermetallic precipitates of Ni16Si7Nb6 type of between 0.1 and 0.3% is formed during the use of the tube,
the process comprising a heat treatment of said alloy carried out in two stages:
a) a first stage of heat treatment at temperatures between 700° C. and 800° C. with a stationary phase of 10 h to 100 h, and
b) a second stage of heat treatment under operating conditions of the furnace of the reforming having as source a source of hydrocarbons and being subjected to a pressure varying between 1 and 4 MPa and a temperature between 900° C. and 1000° C.

### Claim 2 (depends on 1)

The process of claim 1, wherein the secondary precipitates form dislocation clusters.

### Claim 3 (depends on 1)

The process of claim 1, wherien the primary precipitates are micrometric.

### Claim 4 (depends on 1)

The process of claim 1, wherein the secondary precipitates are nanometric.

### Claim 5 (depends on 4)

The process of claim 4, wherein the secondary precipitates are between 5 nm and 50 nm.

### Claim 6 (depends on 1)

The process of claim 1, wherein the primary precipitates of M23C6 type represents from 3 to 8% of the chemical composition of the alloy and the M(C,N) precipitates represents from 0.5 to 2.5% of the chemical composition of the alloy.

### Claim 7 (depends on 1)

The process of claim 1, wherein the secondary precipitates of M23C6 type represents from 1 to 3% of the chemical composition of the alloy and the M(C,N) precipitates represents from 0.1 to 0.5% of the chemical composition of the alloy.