Method for producing an alloy for a reforming tube

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.