Nickel-chromium-iron-aluminum alloy having good processability, creep resistance and corrosion resistance, and use thereof

Abstract

A nickel-chromium-iron-aluminum alloy contains (in wt. %)>17 to 33% chromium, 1.8 to <4.0% aluminum, 0.10 to 15.0% iron, 0.001 to 0.50% silicon, 0.001 to 2.0% manganese, 0.00 to 0.60% titanium, 0.0002 to 0.05% each of magnesium and/or calcium, 0.005 to 0.12% carbon, 0.001 to 0.050% nitrogen, 0.0001 to 0.020% oxygen, 0.001 to 0.030% phosphorus, not more than 0.010% sulfur, not more than 2.0% molybdenum, not more than 2.0% tungsten, the remainder nickel with nickel ≥50% and the usual process-related impurities, for use in solar power tower plants using nitrate salt melts as the heat transfer medium, wherein the following relations must be satisfied: Fp≤39.9 (2a) with Fp=Cr+0.272*Fe+2.36*Al+2.22*Si+2.48*Ti+0.374*Mo+0.538*W−11.8*C (3a), wherein Cr, Fe, Al, Si, Ti, Mo, W and C is the concentration of the respective elements in % by weight.

1 : A nickel-chromium-aluminum-iron alloy containing (in mass-%) >17 to 33% chromium, 1.8 to <4.0% aluminum, 0.10 to 15.0% iron, 0.001 to 0.50% silicon, 0.001 to 2.0% manganese, 0.00 to 0.60% titanium, respectively 0.0002 to 0.05% magnesium and/or calcium, 0.005 to 0.12% carbon, 0.001 to 0.050% nitrogen, 0.0001 to 0.020% oxygen, 0.001 to 0.030% phosphorus, max. 0.010% sulfur, max. 2.0% molybdenum, max. 2.0% tungsten, the rest nickel with nickel ≥50% and the common process-related impurities for the use in solar tower power plants using nitrate salt melts as the heat-transfer medium, wherein the following relationship must be satisfied:
   Fp≤39.9 with  (2a)
 
   Fp=Cr+0.272*Fe+2.36*Al+2.22*Si+2.48*Ti+0.374*Mo+0.538*W−11.8*C   (3a)
 
 wherein Cr, Fe, Al, Si, Ti, Mo, W and C are the concentrations of the elements in question in mass-%. 
 
     
     
         2 : The alloy according to  claim 1 , especially for all components that are used are in contact with the molten salt. 
     
     
         3 : The alloy according to  claim 1 , wherein the alloy is usable up to a maximum temperature of 800° C. 
     
     
         4 : The alloy according to  claim 1 , with a chromium content of >18 to 33%. 
     
     
         5 : The alloy according to  claim 1 , with an aluminum content of 1.8 to 3.8%. 
     
     
         6 : The alloy according to  claim 1 , with an iron content of 0.1 to 12.0%. 
     
     
         7 : The alloy according to  claim 1 , with a silicon content of 0.001-<0.40%. 
     
     
         8 : The alloy according to  claim 1 , with a manganese content of 0.001 to 0.50%. 
     
     
         9 : The alloy according to  claim 1 , with a titanium content of 0.001 to 0.50%. 
     
     
         10 : The alloy according to  claim 1 , with a carbon content of 0.01 to 0.10%. 
     
     
         11 : The alloy according to  claim 1 , optionally with
 an yttrium content of 0.001 to 0.20%;   a lanthanum content of 0.001 to 0.20%;   a cerium content of 0.001 to 0.20%;   a cerium mixed metal content of 0.001 to 0.20%;   a zirconium content of 0.001 to 0.20%; and   a hafnium content of 0.001 to 0.20%.   
     
     
         12 . (canceled) 
     
     
         13 . (canceled) 
     
     
         14 . (canceled) 
     
     
         15 : The alloy according to  claim 1 , optionally with a content of niobium of 0.0 to 1.1%, wherein the formula (3a) is supplemented by a term for Nb:
   Fp=Cr+0.272*Fe+2.36*Al+2.22*Si+2.48*Ti+1.26*Nb+0.374*Mo+0.538*W−11.8*C  (3b)
   and Cr, Fe, Al, Si, Ti, Nb, Mo, W and C are the concentrations of the elements in question in mass-%.   
     
     
         16 . (canceled) 
     
     
         17 . (canceled) 
     
     
         18 : The alloy according to  claim 1 , optionally with a content of boron of 0.0001 to 0.008%. 
     
     
         19 : The alloy according to  claim 1 , optionally further containing 0.0 to 5.0% cobalt. 
     
     
         20 : The alloy according to  claim 1 , further containing at most 0.5% copper, wherein the formula (3a) is supplemented by a term for Cu:
   Fp=Cr+0.272*Fe+2.36*Al+2.22*Si+2.48*Ti+0.477*Cu+0.374*Mo+0.538*W−11.8*C  (3c).
   and Cr, Fe, Al, Si, Ti Cu, Mo, W and C are the concentrations of the elements in question in mass-%.   
     
     
         21 : The alloy according to  claim 1 , further containing at most 0.5% vanadium 
     
     
         22 : The alloy according to  claim 1 , wherein the impurities are adjusted in contents of max. 0.002% lead, max. 0.002% zinc, max. 0.002% tin. 
     
     
         23 : The alloy according to  claim 1 , in which the following formula is satisfied and thus a particularly good processability is achieved: Fa□60 (4a) with Fa=Cr+20.4*Ti+201*C (5a) for an alloy without Nb, wherein Cr, Ti and C are the concentrations of the elements in question in mass-%, or with Fa=Cr+6.15*Nb+20.4*Ti+201*C (5b) for an alloy containing Nb, wherein Cr, Nb, Ti and C are the concentrations of the elements in question in mass-%. 
     
     
         24 : The alloy according to  claim 1 , in which the following formula is satisfied and thus a particularly hot strength/creep strength is achieved: Fk≥47 (6a) with Fk=Cr+19*Ti+10.2*Al+12.5*Si+98*C (7a) for an alloy without B and Nb, wherein Cr, Ti, Al, Si and C are the concentrations of the elements in question in mass-%, or with Fk=Cr+19*Ti+34.3*Nb+10.2*Al+12.5*Si+98*C+2245*B (7b) for an alloy containing B and/or Nb, wherein Cr, Ti, Nb, Al, Si, C and B are the concentrations of the elements in question in mass-%. 
     
     
         25 : A use of the alloy according to  claim 1  as strip, sheet, wire, rod, longitudinally welded tube and seamless tube. 
     
     
         26 : A use of the alloy according to  claim 1  for the manufacture of strip, sheet, wire, rod, longitudinally welded tube and seamless tubes.