Method for producing an iron-chromium alloy

Abstract

The invention relates to a method for producing a component, made of an iron-chromium alloy that precipitates Laves phases and/or particles containing Fe and/or particles containing Cr and/or particles containing Si and/or carbides, by subjecting a semi-finished product made of the alloy to a thermomechanical treatment, wherein in a first step, the alloy is solution heat treated at temperatures≧the solution heat treatment temperature and is subsequently quenched in stationary protective gas or air, moving (blown) protective gas or air, or water. In a second step, a mechanical forming of the semi-finished product in a range from 0.05 to 99% is performed, and in a subsequent step, Laves phases Fe 2 (M, Si) or Fe 7 (M, Si) 6 and/or particles containing Fe and/or particles containing Cr and/or particles containing Si and/or carbides are precipitated in a specific and finely distributed manner in that the component produced from the formed semi-finished product is brought to an application temperature between 550° C. and 1000° C. by means of heating at 0.1° C./min to 1000° C./min.

1 . Method for production of a component, from an iron-chromium alloy precipitating Laves phases and/or Fe-containing particles and/or Cr-containing particles and/or Si-containing particles and/or carbides, in that a semifinished product produced from the alloy is subjected to a thermomechanical treatment, wherein in a first step the alloy is solution annealed at temperatures≧the solution-annealing temperature, followed by quenching in stationary protective gas or air, moving (blown) protective gas or air or in water, in a second step mechanical working of the semifinished product in the range from 0.05 to 99% is performed and in a subsequent step Fe 2 (M, Si) or Fe 7 (M, Si) 6  Laves phases and/or Fe-containing particles and/or Cr-containing particles and/or Si-containing particles and/or carbides are precipitated purposefully and in finely dispersed form, by the fact that the component made from the worked semifinished product is brought to an application temperature between 550° C. and 1000° C. by heating at 0.1° C./min to 1000° C./min. 
     
     
         2 . Method for production of a component from an iron-chromium alloy precipitating Laves phases and/or Fe-containing particles and/or Cr-containing particles and/or Si-containing particles and/or carbides, in that a semifinished product produced from the alloy is subjected to a thermomechanical treatment, wherein in a first step the alloy is solution annealed at temperatures≧the solution-annealing temperature, followed by quenching in stationary protective gas or air, moving (blown) protective gas or air or in water, in a second step mechanical working of the semifinished product in the range from 0.05 to 99% is performed and in a subsequent step Fe 2 (M, Si) or Fe 7 (M, Si) 6  Laves phases and/or Fe-containing particles and/or Cr-containing particles and/or Si-containing particles and/or carbides are precipitated purposefully and in finely dispersed form by the fact that the worked semifinished product is subjected for a time between t min  and t max  to a heat treatment in the temperature range between 550° C. and 1060° C. under protective gas or air, followed by quenching in stationary protective gas or air, moving (blown) protective gas or air or in water or for heat treatments up to 800° C. is quenched in the oven, wherein and t min  and t max  are calculated according to the following formulas:
     t   min   =T   a ·10 (6740/Ta−9.216)  and  t   max   =T   a ·10 (17960/Ta−15.72)  where  T   a   =T+ 273.15,
 
 and wherein the desired component is made before or after this heat treatment. 
 
     
     
         3 . Method according to  claim 1 , wherein, in the first step, the alloy is solution annealed at a temperature ≧1050° C. for longer than 6 minutes. 
     
     
         4 . Method according to  claim 1 , wherein, in the first step, the alloy is solution annealed at a temperature ≧1060° C. for longer than 1 minute. 
     
     
         5 . Method according to  claim 1 , wherein semifinished product of the following chemical composition (in % by weight) is thermomechanically treated:
 Cr 12-30%   Mn 0.001-2.5%   Nb 0.1-2%   W 0.1-5%   Si 0.05-1%   C 0.002-0.1%   N 0.002-0.1%   S max. 0.01%   Fe remainder   as well as the usual melting-related impurities, wherein a mechanical deformability at room temperature of >13% is obtained, measured as plastic elongation in the tension test.   
     
     
         6 . Method according to  claim 1 , wherein only little or even no Fe 2 (M, Si) or Fe 7 (M, Si) 6  Laves phases and/or Fe-containing particles and/or Cr-containing particles and/or Si-containing particles and/or carbides are still present in the semifinished product after solution annealing at temperatures the solution-annealing temperature, preferably ≧1050° C. for longer than 6 minutes or ≧1060° C. for longer than 1 minute, followed by quenching in stationary protective gas or air, moving (blown) protective gas or air or in water, in the initial state before deformation. 
     
     
         7 . Method according to  claim 1 , wherein the working of the semifinished product takes place by hot working. 
     
     
         8 . Method according to  claim 1 , wherein the hot working of the semifinished product begins with a starting temperature >1070° C., wherein the last 0.05 to 90% of mechanical deformation is applied between 1000° C. and 500° C. 
     
     
         9 . Method according to  claim 1 , wherein the hot working of the semifinished product begins with a starting temperature >1070° C., wherein the last 0.05 to 95% of mechanical deformation is applied between 1000° C. and 500° C. 
     
     
         10 . Method according to  claim 1 , wherein the hot working of the semifinished product begins with a starting temperature >1070° C., wherein the last 0.05 to 99% of mechanical deformation is applied between 1000° C. and 500° C. 
     
     
         11 . Method according to  claim 1 , wherein the hot working of the semifinished product is followed by cold working. 
     
     
         12 . Method according to  claim 1 , wherein the working of the semifinished product is carried out by cold working. 
     
     
         13 . Method according to  claim 12 , wherein the degree of cold working of the semifinished product is 0.05 to 99%. 
     
     
         14 . Method according to  claim 12 , wherein the cold working of the semifinished product is 0.05 to 95%. 
     
     
         15 . Method according to  claim 12 , wherein the cold working of the semifinished product is 0.05 to 90% 
     
     
         16 . Method according to  claim 1 , wherein the mechanical working of the semifinished product is 20 to 99% and then the worked semifinished product is subjected for a time between t min  and t max  to a heat treatment in the temperature range between 950° C. and 1060° C. under protective gas or air, followed by quenching in stationary protective gas or air, moving (blown) protective gas or air or in water and after this the desired component is made with
     t   min   =T   a ·10 (6740/Ta−9.216)  and
 
     t   max   =T   a ·10 (17960/Ta−15.72)  where  T   a =T+273.15
 
 
       and indication of t min  and t max  in minutes and of heat-treatment temperature T in ° C. 
     
     
         17 . Method according to  claim 1 , wherein the alloy additionally contains (in % by weight) 0.02 to 0.3% La. 
     
     
         18 . Method according to  claim 1 , wherein the alloy additionally contains (in % by weight) 0.01 to 0.5% Ti. 
     
     
         19 . Method according to  claim 1 , wherein the alloy additionally contains 0.02 to 0.3% of one or more of the elements Ce, Pr, Ne, Sc, Y, Zr or Hf. 
     
     
         20 . Method according to  claim 1 , wherein the alloy additionally contains (in % by weight) 0.001 to 0.5% Al. 
     
     
         21 . Method according to  claim 1 , wherein the alloy additionally contains (in % by weight) 2.0 to 6.0% Al. 
     
     
         22 . Method according to  claim 21 , wherein the alloy additionally contains (in % by weight) 2.5 to 5.0% Al. 
     
     
         23 . Method according to  claim 1 , wherein the alloy additionally contains one or more of the elements 0.0001 to 0.07% Mg, 0.0001 to 0.07% Ca, 0.002-0.03% P. 
     
     
         24 . Method according to  claim 1 , wherein the alloy further contains 0.01 to 3.0% of one or more of the elements Ni, Co or Cu. 
     
     
         25 . Method according to  claim 1 , wherein the alloy further contains up to 0.005% B. 
     
     
         26 . Method according to  claim 1 , wherein the iron-chromium alloy, which is thermomechanically treated and which precipitates Laves phases in finely dispersed form, has the following composition containing (in % by weight)
 Cr 12-30%   Mn 0.001-2.5%   Nb 0.1-2%   W 0.1-5%   Si 0.05-1%   C 0.002-0.03%   N 0.002-0.03%   S max. 0.005%   Fe remainder   as well as the usual melting-related impurities.   
     
     
         27 . Method according to  claim 1 , wherein the alloy additionally contains (in % by weight) 0.02 to 0.2% of the element La. 
     
     
         28 . Method according to  claim 1 , wherein the alloy additionally contains (in % by weight) 0.02 to 0.2% Ti. 
     
     
         29 . Method according to  claim 1 , wherein the alloy additionally contains (in % by weight) 0.02 to 0.2% of one or more of the elements Ce, Pr, Ne, Sc, Y, Zr or Hf. 
     
     
         30 . Method according to  claim 1 , wherein the alloy additionally contains (in % by weight) one or more of the elements 0.0001-0.05% Mg, 0.0001-0.03% Ca, 0.002-0.03% P. 
     
     
         31 . Method according to  claim 1 , wherein the alloy further contains (in % by weight) up to 0.003% B. 
     
     
         32 . Method according to  claim 1 , wherein (in % by weight) the Nb content is 0.3 to 1.0% and the Si content is 0.15-0.5%. 
     
     
         33 . Method according to  claim 1 , wherein the W content is replaced entirely or partly by at least one of the elements Mo and/or Ta. 
     
     
         34 . Method according to  claim 1 , wherein the alloy contains (in % by weight) max. 0.2% V and/or max. 0.005% S. 
     
     
         35 . Method according to  claim 1 , wherein the alloy contains (in % by weight) max. 0.01% O. 
     
     
         36 . Method according to  claim 1 , wherein the alloy contains (in % by weight) max. 0.01% of each of the elements Zn, Sn, Pb, Se, Te, Bi and Sb respectively. 
     
     
         37 . Method according to  claim 1 , wherein the semifinished product is formed by sheet, strip, bar, forging, pipe or wire. 
     
     
         38 . Method according to  claim 1 , wherein the heat treatment is carried out only after finishing of the component. 
     
     
         39 . Method according to  claim 1 , wherein, by the thermomechanical treatment of the semifinished product, a particularly high creep strength is produced in the semifinished product and/or in the component with simultaneous elongation >13% in the tension test at room temperature. 
     
     
         40 . Metallic component or semifinished product, consisting of the following chemical composition (in % by weight)
 Cr 12-30%   Mn 0.001-2.5%   Nb 0.1-2%   W 0.1-5%   Si 0.05-1%   C 0.002-0.1%   N 0.002-0.1%   S max. 0.01%   Fe remainder   as well as the usual melting-related impurities,   which at the end of a thermomechanical treatment has a deformed microstructure, to the effect that Laves phase(s) is or are embedded in finely dispersed form in the microstructural dislocations of the microstructure, wherein, in a creep test with, in particular, 35 MPa at 750° C. and an elongation of at least 18%, a time to break that exceeds the time to break of a coarse-grained, completely recrystallized microstructure by a factor of at least 1.5 is established in the microstructure.   
     
     
         41 . Metallic component or semifinished product, consisting of the following chemical composition (in % by weight)
 Cr 12-30%   Mn 0.001-2.5%   Nb 0.1-2%   W 0.1-5%   Si 0.05-1%   C 0.002-0.1%   N 0.002-0.1%   S max. 0.01%   Fe remainder   as well as the usual melting-related impurities,   which at the end of a thermomechanical treatment has a deformed microstructure, to the effect that Laves phase(s) is or are embedded in finely dispersed form in the microstructural dislocations of the microstructure, wherein, in a creep test with, in particular, 35 MPa at 750° C. and an elongation of at least 18%, a time to break hours that exceeds the time to break of a coarse-grained, completely recrystallized microstructure by a factor of at least 3 is established in the microstructure.   
     
     
         42 . Use of a component produced according to  claim 1  as interconnector in a fuel cell. 
     
     
         43 . Use of a component produced according to  claim 1  as material in a component, such as a reformer or a heat exchanger or in an ancillary aggregate of a fuel cell. 
     
     
         44 . Use of a component produced according to  claim 1  in the exhaust-gas line of a combustion engine. 
     
     
         45 . Use of a component produced according to  claim 1  for steam boilers, superheaters, turbines and other parts of a power plant or in the chemical process industry.