CA1091958A - Iron-chromium-nickel heat resistant castings - Google Patents
Iron-chromium-nickel heat resistant castingsInfo
- Publication number
- CA1091958A CA1091958A CA295,035A CA295035A CA1091958A CA 1091958 A CA1091958 A CA 1091958A CA 295035 A CA295035 A CA 295035A CA 1091958 A CA1091958 A CA 1091958A
- Authority
- CA
- Canada
- Prior art keywords
- tungsten
- titanium
- chromium
- heat resistant
- nickel
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C19/00—Alloys based on nickel or cobalt
- C22C19/03—Alloys based on nickel or cobalt based on nickel
- C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
- C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
- C22C19/055—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 20% but less than 30%
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
- Turbine Rotor Nozzle Sealing (AREA)
- Treatment Of Steel In Its Molten State (AREA)
- Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
- Compositions Of Oxide Ceramics (AREA)
Abstract
Abstract of the Disclosure Castings of carbon 0.2/0.8, nickel 8/62, chromium 12/32, tungsten 0.05/2, titanium 0.05/1, balance iron (sub-stantially) of austenitic microstructure, essentially free of cobalt and molybdenum, and not requiring heat treatment to develop service properties considerably improved compared to standard ACI alloy grades.
Description
This invention relates to a class of alloys which feature in castings employed in hydrogen reformer service as well as related types of castings widely used for high temperature industrial applica-tions.
These alloys are standardized by the ~lloy Casting Institute (ACI) Division of the Steel Founders' Society of America.
The generally available specifications are ASTM A297, A447, A567 ~nd A608.
The ACI designation uses the prefixes of H and C
to indicate sui-tability for heat-resistant and corrosion service, respectively. The second let-te~ is arbi-trarily assigned to show alloy type, with a rough alphabeticcll sequence as nickel content rises ~see Table A). There is provision for showing carbon content of the ~I grades, the numbers following -the two let-ters being the mid-point of the carbon specification.
The function of the various alloying elements differ; for instance, chromium increases oxidation resistance and corrosion by hot gases. Manganese and silicon are added for steel-making purposes, but silicon also influences oxidation and carburizing resistance. Nickel confers the austeni-tic structure associated with hot strength, but it also confers resistance to carburization and to some extent oxidation resistance.
High nickel alloys, however, are vulnerable to sulphur attack, especially under reducing conditions. Carbon is a potent element for controlling hot strength; nitrogen may also be impor-tant for strength.
The ACI standard grades which feature predominantly in the invention are those set forth in Table A below:
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While high temperature strength, measured as creep rupture strength, is usually the predominant property of interest in this alloy class, ductility may be of equal importance in a casting subjected to repeated tensile stresses in a service environment where large temperature differentials result in repeated expansion and contraction of the casting, which is inherent in certain discontinuous high temperature ~rocesses as distinguished from a continuous process conducte~
at a substantially constant temperature. Even soy good ductility (the ability to stretch predictably without suddenly and unexpectedly fracturing under certain loads) is invariably deemed a valuable characteristic to the design engineer because it represents a reserve against failure, which is ~o say that if two steels are oE equal strength, at the same cost, the one having superior ductility will be chosen because of its capacity to signal approaching failure priar to catastrophic failure.
Welding these castings as an incidçnt to cosmetic repair and/or assembly into larger units t a~ter bein~ cast, is desirable and necessary for the most part~ Hot ductility contribukes in a very large way to being able to weld without cracking: hot ductility allows the metal to stretch sudaenly while the weld is being made, and to contract after~-ardsr without cracking.
The objects of the present invention are to enhance hot tensile strength and to substantially improve hot ductility and creep rupture strength over virtually the entire range of austenitic standard ACI alloys/ and to accomplish this by means of very small additions to the standard alloy bases not heretofore recognized as promoting so ~reat an e~Efect ~09~158 over so wide a rancJe of alloy composi.tion, whicll additions are inexpensive, do not involve strategi.c (domestically scarce) elements and which indeed enable the invention to be applied to the standard ACI grades with scarcely any increase in cost.
( IN THE DRA~YING:
Figs. 1, 2, 3 and 4 are plots, on logarithmic scalel of data presen~ed in Tables I, II, III and IV~
respectively; the b~ld reference lines are for the standard alloy in each instance and the lighter lines perpendicular thereto denote the advantageous displacements achieved un~er the present invention;
~ ig. 5 is a photomicrograph (500X) exhibiting typical microstructure (HP grade alloy) .characterizing alloys of the present invention;
Fig. 6 .is a perspective view of heat resistant alloy cas~ings assembled into a unit ready for inskallatinn, !
s~ .
TABLE I
Effect of Alloyinq (23OCr, 35%Ni) Heat Resistant All~y with Ti-tanium and Tungsten .
.. .. . . .. . . . . . . ... .. . .. .. ....
- Chemical Composition - We;ght Percent~ -~eat Mo. C% Mn% Si% Cr% Ni% W% Ti% N% Heat No.
~A) 46-681 .49.87 1.36 26~60~4.90 - - .060 (A~
~B) 76-407 .48.62 .94 23 2535.21 - - .100 (B) (C) 76-139 .51;62 1.01 22.8034.90 - .12 .120 (C) (D) 76-144 .46.59 1.03 22.~034.56 - .30 .102 (D) (E) AS1394 .51.89 1.71 23.5033.64 5.35 - .103 (E) (F) AX69 .48.38 1.16 21.4037~00 5.07 - ~ (P) (G) 76-148-.52.61 1.00 22.6035.15 .51 ,16 .107 (G) (~) 76-103 .38.59 1.10 22.3435.91 1.04 .16 .109 (H) (I) 76-121 .46.56 1.03 22.0035.9Q 1.04 .22 .110 (I) (J) 76-162 .~3.63 .38 22.9035.50 .52 .32 .072 ~ (3) (K) 76-440 .43.64 .6? 23.1636.60 .56 .43 .101 (K) (L) 76-370 .~8.56 .~9 23.2335.48 .56 .48 .124 (L) ~M) 76-342 .~5.63 .91 23.3034.72 .54 .~9 .073 (M) ~N) 76-375 .47.56 .52 22.~035.22 1.06 .76 .098 (N) (O) 76-379 .~7.57 .50 22.35 3~.93 .~8 1.16 .Og2 ~O) Rupture Li~e at Conditions Speci~ied Hours 1800F-6.0 Ksi 1800F-5.0 Ksl 1800F-4.0 Ksi 2000F-2.5 Ksi .. . _ _ _ _ . . ... .. .
(~) 23 - - 196 t~) ~B) 35 149 ~ 214 ~B) ~C) 57 - 1252 1~2 ` (C) (D) 73 _ 1342 264 (D) (E) g4 - _ 214 (E) (F) - 380 1232 - 193 (F) (G) 80 _ 16~9 2~5 (G) tH3 78 _ 2005 296 ~H) ~I) 122 _ 2249 435 (I~
(~) 306 1015 - 813 tJ) ~K) 279 - - 1056 (L) - ~ ~ 701 ~) tM) - 1206 _ _ ~M~
(N) 91 - _ 622 (N) (O) 79 ~ ~ ~53 ~O) .
Conversion Units (and see Tables-following):
Rsi ~a kg/mm2 __ _ 1~0~ 760 1.5 10.3~ 1.05~
1600 871 2.0 13.79 ~.~061 1800 982 2.5 17.2~ 1.7577 2000 1093 4.0 27.~8 2.8123 5.03~.47 3,5153 6.0~1.37 ~.218~
S~
The fol 10~7 i n~ commen t s app ly to Table I:
(1) Heat A is representative of HP, the nearest stanaara ACI alloy to heat (B).
These alloys are standardized by the ~lloy Casting Institute (ACI) Division of the Steel Founders' Society of America.
The generally available specifications are ASTM A297, A447, A567 ~nd A608.
The ACI designation uses the prefixes of H and C
to indicate sui-tability for heat-resistant and corrosion service, respectively. The second let-te~ is arbi-trarily assigned to show alloy type, with a rough alphabeticcll sequence as nickel content rises ~see Table A). There is provision for showing carbon content of the ~I grades, the numbers following -the two let-ters being the mid-point of the carbon specification.
The function of the various alloying elements differ; for instance, chromium increases oxidation resistance and corrosion by hot gases. Manganese and silicon are added for steel-making purposes, but silicon also influences oxidation and carburizing resistance. Nickel confers the austeni-tic structure associated with hot strength, but it also confers resistance to carburization and to some extent oxidation resistance.
High nickel alloys, however, are vulnerable to sulphur attack, especially under reducing conditions. Carbon is a potent element for controlling hot strength; nitrogen may also be impor-tant for strength.
The ACI standard grades which feature predominantly in the invention are those set forth in Table A below:
U~
~ :3 .
* ~
XXXX XXXXXX
. ~
3~ .... ......
oooo oooooo ,.
-rl ~ ~ ~ ~O ~ ~ O 0~ ~
~ . .
,C) ~ r~ 1 rl t~ ~ ~ ~ 1~) ~D
i~ ~~ ~rl I
aJ ~ r~l C~l ~ ~ ~10 ~1 h . r¦ .~
'~ ~1 ~0 o ot ~J '~, ~J C~ ~I N ~) ~I c~ 1 ~r-l ' ~n ~ ~1 ',~ . ~ ~.) a~ P CO ~ ~ tO t--O
td r I ~ ~ ;1 r l N ~I r-lr l i-J .~
'S~ 1~ .
o '~;: Xoooo oooooo 4~ :~ ~n do ....... .......
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rl l.
r I ~ x o o o o o o o o oo ,c O~I
. ~Pl E~ oooo oooooo ~ ~ ~ .
~ ~0 oooo oooooo ,1 m ~rl x o o o oo o o u~ u~Lo ; I 8 Ul ~ C~l N N ~ N N N C~ NN
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:~ . . ' U
'L~
td o o o o o o ~ u~
O O O O O O O O 00 ~3 ol Q
o o o o o o ~ ut ~U ~
- . . . . . . . . . . .
O O O O ' O O O 0 00 ' 10 o . X
'~ . ~ .
~) O rl t.q ~ u~
~d ~I Q) S~
While high temperature strength, measured as creep rupture strength, is usually the predominant property of interest in this alloy class, ductility may be of equal importance in a casting subjected to repeated tensile stresses in a service environment where large temperature differentials result in repeated expansion and contraction of the casting, which is inherent in certain discontinuous high temperature ~rocesses as distinguished from a continuous process conducte~
at a substantially constant temperature. Even soy good ductility (the ability to stretch predictably without suddenly and unexpectedly fracturing under certain loads) is invariably deemed a valuable characteristic to the design engineer because it represents a reserve against failure, which is ~o say that if two steels are oE equal strength, at the same cost, the one having superior ductility will be chosen because of its capacity to signal approaching failure priar to catastrophic failure.
Welding these castings as an incidçnt to cosmetic repair and/or assembly into larger units t a~ter bein~ cast, is desirable and necessary for the most part~ Hot ductility contribukes in a very large way to being able to weld without cracking: hot ductility allows the metal to stretch sudaenly while the weld is being made, and to contract after~-ardsr without cracking.
The objects of the present invention are to enhance hot tensile strength and to substantially improve hot ductility and creep rupture strength over virtually the entire range of austenitic standard ACI alloys/ and to accomplish this by means of very small additions to the standard alloy bases not heretofore recognized as promoting so ~reat an e~Efect ~09~158 over so wide a rancJe of alloy composi.tion, whicll additions are inexpensive, do not involve strategi.c (domestically scarce) elements and which indeed enable the invention to be applied to the standard ACI grades with scarcely any increase in cost.
( IN THE DRA~YING:
Figs. 1, 2, 3 and 4 are plots, on logarithmic scalel of data presen~ed in Tables I, II, III and IV~
respectively; the b~ld reference lines are for the standard alloy in each instance and the lighter lines perpendicular thereto denote the advantageous displacements achieved un~er the present invention;
~ ig. 5 is a photomicrograph (500X) exhibiting typical microstructure (HP grade alloy) .characterizing alloys of the present invention;
Fig. 6 .is a perspective view of heat resistant alloy cas~ings assembled into a unit ready for inskallatinn, !
s~ .
TABLE I
Effect of Alloyinq (23OCr, 35%Ni) Heat Resistant All~y with Ti-tanium and Tungsten .
.. .. . . .. . . . . . . ... .. . .. .. ....
- Chemical Composition - We;ght Percent~ -~eat Mo. C% Mn% Si% Cr% Ni% W% Ti% N% Heat No.
~A) 46-681 .49.87 1.36 26~60~4.90 - - .060 (A~
~B) 76-407 .48.62 .94 23 2535.21 - - .100 (B) (C) 76-139 .51;62 1.01 22.8034.90 - .12 .120 (C) (D) 76-144 .46.59 1.03 22.~034.56 - .30 .102 (D) (E) AS1394 .51.89 1.71 23.5033.64 5.35 - .103 (E) (F) AX69 .48.38 1.16 21.4037~00 5.07 - ~ (P) (G) 76-148-.52.61 1.00 22.6035.15 .51 ,16 .107 (G) (~) 76-103 .38.59 1.10 22.3435.91 1.04 .16 .109 (H) (I) 76-121 .46.56 1.03 22.0035.9Q 1.04 .22 .110 (I) (J) 76-162 .~3.63 .38 22.9035.50 .52 .32 .072 ~ (3) (K) 76-440 .43.64 .6? 23.1636.60 .56 .43 .101 (K) (L) 76-370 .~8.56 .~9 23.2335.48 .56 .48 .124 (L) ~M) 76-342 .~5.63 .91 23.3034.72 .54 .~9 .073 (M) ~N) 76-375 .47.56 .52 22.~035.22 1.06 .76 .098 (N) (O) 76-379 .~7.57 .50 22.35 3~.93 .~8 1.16 .Og2 ~O) Rupture Li~e at Conditions Speci~ied Hours 1800F-6.0 Ksi 1800F-5.0 Ksl 1800F-4.0 Ksi 2000F-2.5 Ksi .. . _ _ _ _ . . ... .. .
(~) 23 - - 196 t~) ~B) 35 149 ~ 214 ~B) ~C) 57 - 1252 1~2 ` (C) (D) 73 _ 1342 264 (D) (E) g4 - _ 214 (E) (F) - 380 1232 - 193 (F) (G) 80 _ 16~9 2~5 (G) tH3 78 _ 2005 296 ~H) ~I) 122 _ 2249 435 (I~
(~) 306 1015 - 813 tJ) ~K) 279 - - 1056 (L) - ~ ~ 701 ~) tM) - 1206 _ _ ~M~
(N) 91 - _ 622 (N) (O) 79 ~ ~ ~53 ~O) .
Conversion Units (and see Tables-following):
Rsi ~a kg/mm2 __ _ 1~0~ 760 1.5 10.3~ 1.05~
1600 871 2.0 13.79 ~.~061 1800 982 2.5 17.2~ 1.7577 2000 1093 4.0 27.~8 2.8123 5.03~.47 3,5153 6.0~1.37 ~.218~
S~
The fol 10~7 i n~ commen t s app ly to Table I:
(1) Heat A is representative of HP, the nearest stanaara ACI alloy to heat (B).
(2) Heats C and D show the effeot of increas-ing amounts o~ titanium in the absence of tungsten~
(3) Heats G and H show that increasing quantities of tungsten ~rom .51 ~o 1.04 at a constant .16% titanium level o~fex no appreciable advanta~e to creep rupture - strength.
~4) Heats E and ~ containing 5%W, 0% titanium show an advantage over the standard alloy base, but each is inferior in creep rupture strengkh to heats alloyed with tungsten plus a minimum .l6% t;tanium.
t5) Heats J, K, L and M fall in the alloy range ~or optimum creep ru~ture strength.
(6) Hot tensile data were not collected f~r heat (B) and accordinglg bot tensile data ~re not comparable.
.
.
~ABLE II
Effect oE Alloying (25%Cr, 20%Ni) Heat Resistan~ Alloy with Titanium and Tungsten Heat No. C% Mn% S% P% S% Cr~ Ni% W% Ti% N%
(A) Published .45 O50 1.O .02 .02 25.0 20.0 ~ A) Data Typical Analysis (B) ~461 .41 .44 1.12 - - 24.8 21.0 .10 .02 .126 ~B) ~C) 74-096 .39 .60 .99 .012 .014 2~.1 19.3 - ~16 .15~ (C) (D) 73-411 .39 .51 .94 .011 .010 25.5 19.6 - .24 .140 (D) ~E) 73-406 .39 .53 .96 .013 .006 24.3 19.5 - .18 .160 (E) (F) 73-25~ .41 .60 1.10 .014 .014 24.S 20.1 .10 .25 .160 (~) (G) 74-250 .45 .55 1.09 .012 .014 25.7 20.1 .11 .18 .140 ~G) .
, _ pture Life at Conditions Specified Hours 1800~F-6.0 Xsi 1800F-4.0 Rsi 2000F-2.0 Ksi .
(A) 35 . 220 150 tA) (B) 40 263 - (B) : (C) - 360 - ~C) (D) . .51 536 _ tD) .
~E~ _ . 634 _ (E) (~) 140 . 1371 557 (F) (G) 197 1094 937 . ~G) ~lot Tensile Property Co~parison ~25% Cr, 20% Ni) Yiela Tensile Strength Reduction Temp. Strength . -.2%- Elongation of Area Heat (F) (Ksi) (Ksi~ (~) t%) ACI (A)1400 37.5 24.4 . 12.0 _- -~F) 1400 45.3 28.7 28.0 .31.9 -(F) 1400 46.3 29.1 36.0 32.4 ACI (A)1600 23.3 14.7 16.0 (P) 1600 25.9 20.6 4~.0 57.8 (F) 1&00 26.6 20.6 46.5 60.8 ACI (A)1800 12.4 8.7 42.0 ~F) 18Q0 15.7 12.6 51.0 71~0 (F) 1800 16.4 13.1 50,0 72.0 ACX (A)2Q00 5.6 5.0 55.0 ~F) 2000 8.4 7~5 75-5 77 7 (F) 2000 8.5 7.7 60.0 77.8 s~
The following comments apply to Table I~:
~ 1) Heat A is a typical HK al:Loy, the properties of which represent the central tendency of published data .
(2) Heat B shows no beneficial effect on creep rupture strength with a .10~ tungsten and ~02~ titanium addition.
~ 3) Heats C, D and E show some improvement in creep rupture strength with small titanium a~ditions in the absence of tungsten.
54) Heats F and G show the effect ~f alloying with the same tungsten level as in Heat B, with a modest increase in titanium content.
(5) Note considerable enhancement of hot tensile steength and ductility comparing heats ~ and r.
' .. :
~09~ 513 TABI.E III
Effec-t of Alloying (25%Cr, 12%Ni) Hea~ Resistant Allo~ith Titanium and Tungsten Chemical Composition-Weight Percent , Heat No. C% Mn% Si% Cr% Ni% W% Ti% N%
. (A) Published ~35 '.50 1.O 25.0 12.0 - .08 ~A) .
: Data Typical Analysis -(B) 76-492 .36 .57 .93 24.6 13.2 .36 .43 .13 (~) , .
' Rupture Life at Conditions S~eci~lea Hours , . lÇ00F-6~0 Ksi 1600F-5.,0 Ksi 1800.~-6.0 ~rsi 1800F-5.0 Ksi (A? 165 340 12 21 (A) (B) ' 88~ ' 1971 83 . 298 . (3) .
. .
. . .... .
Hot Te'n's'il'e''Pxope'r'ty'Comparis'on ' '' - (2;5%,Cr,,12% Nir ' ' Yiel'd ' Tensile. Strength' Reduction ' Temp. Strength' -~2%- ~longation . o~ Area ; Heat '('~F~, ''' ~Rsi'1 (Ks'i'~ ' ' '(%) ; ' ~%)' '.,.
' ......... ACI (A) 140037.4 19.8 16.0 . _ -~B) 1400. 40.1 22.6 42.5 '43.1 ' ' (B) 1400 40,5 ~2.8 40Ø 43u4 .
- ACI'(A) 1600 21~5 16Ø 18Ø _ , .
' (B) 1600......... 24.0 17.9 53.5 52.1 (B) 1600 23.7 17.7 68.5 55.2 ACI (A~ 1800 10.9 7.3 31~0 , (B~ 1800 12.3 9.8 73.0 64.7 ,(B) 1800 13.8 10.8 73.0 53,4 ACI (A) 2000 5,5 - - _ (B) 2000 7.6 6.8 73.5 62.9 (B) 2000 7.7 6.9 69.0 60.3 9~L~s~
The following comments apply to Table III:
(1) Heat A is a typical HH alloy, the properties of which represent the central tendency oE publishe~ data.
(2) Heat B shows the e~fect of alloying with small tungsten and titanium additions.
(3) Note considerable enha~cement o~ hot tensile strength and ductility.
, ~ .
_ ~9~58 T~BLE IV
Ef~ect of Alloying (22%CrJ 25~Ni) Heat Resistant Allo~ with Titanium and Tungsten Chemical Composition-Weight Percent .
Eeat No. C~ Mn% Si% Cr% Ni'~ W~ Ti% N%
(A) Published O40 .50 1.0 21.0 ~S,.0 ~ A) Data Typical Analysis (B) 76-soo .40 .64 1.35 22.0 24.6 ~41 .39 .132 (B) '' , '.
~upture Life At Conditions Specified Hours , 1800F-6.0Ksi 1800F-.4.0 Ksl 2000F-2.5 Ksi 2000.F-1.5 Ksi (A) 70 470 lS0 630 (A) . ~B) 268 2070 411 1884 (~
.
Hot Tehsile Proper~y Co~parison ~ (22% Cr, 25% Ni) Yield .
TensileStrength ~eduction Temp . Strength - . 2~ n~ation of Area ~Iea~ ~F) ~Ksi) (Ksi) ` ~%) ACI ~A) 1600 20.2 14.5 37.0 tB) 1600 23.5 18.4 51.0 59O7 -~B) 1600 2~1 17.8 54.0 69.4 -ACI (A) 1300 11.9 9.6 51.0 (B) 1800 13.5 10.1 66.Q 73.4 tB) 1800 14.6 11.2 . 67.5 63.4 .
ACI (A) 2000 6.16 4.92 55.0 (B) 2000 7.67 6.97 57.5 70.6 (~) 2000 ?.63 7.05 51.0 75.~
'~he following comments apply to Table IV:
(1) Heat A is a typlcal HN alloy, the properties of which represent the central tendency of published data.
(2) Heat B shows the effect of alloying with 5small tungsten and -titanium additions.
(3) Shows same trend for hot tensile strength ~nd ductility.
` ~0~51~
TABLE V
Ef~ec~ of Alloying (23%Cr, 35%Ni) Heat Resistant Allo~With T~taniUm, Tungsten! and Niobium Chemical Composition ~eat ~o. C% Mn% Si~ Cr% Ni% W~ Ti% Nb% N~ ~Ieat No (A) 407 .48 .62 ~94 23.25 35.21 - - - ,101 tAj 407 (B) 681 .49.87 1.36 26.60 34.90 - - - .060 ~B) 6~
(C) 40~ .51.63 1.05 23.07 35.36 - - .35 .160 (C~ 4U8 (~) 411 .51.56 .g2 22.68 35.56 .54 - .36 .11~ ~D) 411 ~E) 162 .43.63 .38 22.90 35.50 .52 ~32 - .072 (E) 162 tF) 373 .43.57 ~74 22.52 35.15 .56 .42 .38 .153 (F) 373 Rupture Life_At Condition~ Specified 1800F 1800~F 2000~F
6.0 Xsi-Hrs. 5.0 Ksi-Hrs~ 2.5 Ksi-Hrs.
'' `~ (A) 35 149 _ (A) ~B) 23 _ 196 (B) (C) 81 371 - (C) (D) ~49 708 278 ~D) (E) 306 1015 B13 ~) tF) 174 936 131 (F) . -. , ' ' '.
" ., , .' ~4 Niobi~m contributes to creep r~pture strength as can be seen by comparing heat C to heats A and B of TABLE Vo There is an improvement with tungsten theat D) but not nearly so pronounced as the strengthening possible with tungsten and titanium evident when comparing heats D and E. That Nb is deficient in this regard is evident when comparing heat F, TABLE V to heat K, TABLE I. Niobium, possibly up to 2%, may be included in an alloy which contains both tungsten and titaniumr and doubtless other small additions as well, but at the risk of reducing the high temperature creep rupture strength, particularly at 2000F.
Experience with these castings establishes that with titanium levels greater than 1% it is difficult to produce castings which do not con~ain massive, titahium-rich non-metallic inclusions, in the form of TiO2 or even more complex oxi~es of titanium,. which detract from tensile properties. This is established b~ the data in TABLE ~I
(below) comparing heats K and O of:TABLE I; these data, to the metallurgist, mean more than about 1~ titanium is to be avoided throughout the range o~ the standard ACI grades. In view of these values and bearing in mind that titanium has a great af~inity for oxygen, requiring a careful deoxidation practice before adding titaniumr we therefore set a limit of less than 1% titanium and preferably no more than about 0.g6~.
TABLE VI
Effect Of Inclusions Due to High ~ 1.0%) Titanium Content On ~Room Temperature) Tensile Properties _ _ _ _ _ _ _ _ Tensile Yield Red.
Strength Strength Elong Area Heat No. Ti~ (Ksi) _ (Ksi) (%) (%) 76-440(K) 0.43 72.6 31.9 18.5 19.5 76-379(0) 1.16 37.8 27.5 2.5 7.,~
10~1~5B
In the drawings (Figs. 1-4~ shading has been applied to the straight line relationships which them-selves represent the central tendency of applied stress vs time of the standard ACI alloy grades for heat resistant castings. These central tendency lines have been published and are well known in this field of technology. The shading represents the expected scatter~ plus or minus 20% of the applied stress.
It will be observed that all our data points, applicable to the combination of tungsten and titanium under the present invention, exceed the upper limit of the accepted plus-or-minus 20% scatter for the standard ACI cast alloy grades, varying from a minimum upward dis-placement of about 5% (HP type grade) to a maximum dis-placement of about 100% for the HH type grade.
The foundry superintendent nQeds 1atitude to account for unexpected oxidation or melting losses; varia-tions in the furnace charge material and so on. In accor-dance with the present invention, and based on our previous foundry experience with commercial grades of iron-chromium-nickel heat resistant alloy castings, the following four alloys represent preferred foundry tolerance specifica-tions for the more popular ACI grades, both centr;~ugal and static castings:
3L~9~L95~
. ~ABLE VII.
.
Comparable . .
ACI
Alloy C% Mn% Si% P% S% Cr% Ni% 1~7% Ti~ Fe%
HH .2 2 3 5 .04 .04 24 :Ll .l ~l Bal .5 ~ax. Max. Max. Max~ 28 .i4 l.2 .6 ~K .~ 2 3 5 .04 .04 24 18 .l .l Bal.
Max. Max. Max. Max. 28 22 1.~ .6 ~N . .2 2 3.5 ~04 ~04 l9 23 .l .l Bal .5 Max~ ~ax. Max.Max. 23 27l.2 .6 - HP .2 2 3.5 .04 04 20 34 l 1 Bal.
.6 Max. ~ax. Max.Max. 24 .38l.2 .6 .
Within these ranges the preferred amount of tungsten, for best strength, is O.l/0.6 and indeed this preferred amount applies to.the ACI grades within the representative range ~IH through ~.
There is, however, a further bonus possible under the present invention, not necessarily requiring adherence to the optimum amount of tungsten. Referring to TABLE I it will be noted that when tungsten is in excess of the amount inducing maximum strength, when combined with titanium., the creep rupture life still exceeds that of the standard grade. Thus, while heat N, containing l.06% tungsten, showed a decline of about forty percent in rupture life (2000F, 2.5 Ksi load~ it outlasted .the standard alloy casting by nearl~ three times (622 hours vs. 196 hours~.
It can be seen then that tungsten in excess of the optimum for strength may be permissible, either for no more reason than a broad allowance in the kind of scrap used in melting, or for some clearly defined additional benefit of which resis-tance to carburization ( ~9~L958 is perhaps the be~t example, noting that tungsten is quite potent for that function. It is for reasons such as these that we conclude the amount of tungsten may be limited to about 2%, principally for economy because with tungsten in excess of about 0.6~ it seems the strengthening e~fect has attained a plateau (a little below optimum as already noted) where the inclusion of tungsten for some other reason becomes a ma~ter of balancing economy against results, particularly if tungsten exceeds two percent.
We have discovered an unusual con~luence of beneficial properties effected.by very small adaitions of tungsten and titanium opera~ive in four representative comm~rcial alloys representin~ a wide range of compo5itions. Our experience with those represen~ati~e alloys permi~s us to an~icipa~e a practical effect on hot tensile stre~g~h and ductility together with creep rupture strength over the fo~lowing range t% by weigh-t) of compositions, with the balance iron exclusive o~ the.usual unavoidable foundry impurities (such as aluminum deoxidizer and molybdehum which ma~ be presen~ in impure melt stock~ and tramp elemen~s such as phosphoru~ and sulfur~
Carbon 0~25/ 0.8 Chromium . 12.0 /32 . Nickel 8 0 ~62.0 Manganese . - 0 / 3 0 Silicon .O / 3 5 Tungsten 0.~5/ 2 Titanium 0.05/~1 . .
1~
5E~
The effect is achieved in the presence of what ~70uld normally be considered lligh levels of nitrogen, as well as at the lower nitrogen levels representative of conventional induction melting practices, that is, nitrogen does not have an adverse effect. Possibly further enhancement of stren~-th can be achieved by lower, or even higher levels of nitrogen;
however, nitrogen up to 0.3% is doubtless permissable.
Any standard or preferred melting practice applicable to the known alloy bases may be used. Tun~sten may be added as ferro-tungsten (which is not a strategic material) and titanium in sheet form may be added when -the furnace is tapped; but to obtain maximum titanium recovery deo~idation should be made in the furnace or in any other manner 5Ui table ~o the reduction of oxygen con~ent to very low levels prior to the addition of titanium.
We recognize that this range of composi-tions encompasses certain combinations of extremes -that might produce an alloy containing major to minor amounts of detrimental ferrite in its microstructure. These combinations are to be àvoided, in that our alloys are intended to have a mircostructure that is essentially austenite plus carbide (substantially free of ferrite) as seen in Fig. 5. The presence of ferri-te in the microstructure promotes the eventual formation of the embrittling sigma phase at temperatures below 1700F. The lower temperature limit or the formation of sigma is determined by specific alloy composition and by time of exposure, but embrittlement at temperatures as low as 1200F has been observed. The presence of sigma would be generally detrimental to the life of these alloys under cyclic thermal loading and to ductility in general.
-- 19 -- , .
19~8 For this reason, our invention should be practiced in alloys so balanced as to produce a microstructure essential.ly free of the sigma-forming ferrite.
In practice the alloy is cast essentially to the service configuration only requiring removal of the risers and gating, some machining perhaps where cosmetic appearance is important or where close tolerances are involved, and welding to complete an assembly from component as-cast parts in certain instances such as the assembly shown in Fig. 6. Even in the instance of welding the cast components to complete an assembly (of bends and straight sections, Fiy. 6) those components individually have the configuration for service. Thus, heat treatment is not required to develop service properties.
Conceivably some cobalt or molybdenum migh-t be present in trace amounts in a heat due to impure melt stock but in any event our alloy is essentially free of each and requires neither of those elemen-ts to produce the beneficial confluence of hot tensile strength, ho-t ductility and creep rupture strength bestowed uniformly, without exception, on standard ACI grades by so small a change. By the same token, the alloy is distinguishable from -the so-called super alloys - where large amounts of addition elements are employed for various purposes, of which cobalt and tungsten are examples, sometimes requiring vacuum melting techniques as compared to the present castings which may be cast atmospherically a-t ambient conditions.
- ~o _ .
L95~il Nonetheless the chief advantage of the a].loy is the surprisingly large displacement in mechanical prope.rties, achieved by little change and low cost, in th~ as-cast condition essentially ready for service without heat treatmen-t: a casting with considerably greater reserves of hot tensile strength and ductility for increasing thermal fatigue resistance, wi-th the added benefit of a significant increase in the value of creep rupture strength.
- 21 -.
~4) Heats E and ~ containing 5%W, 0% titanium show an advantage over the standard alloy base, but each is inferior in creep rupture strengkh to heats alloyed with tungsten plus a minimum .l6% t;tanium.
t5) Heats J, K, L and M fall in the alloy range ~or optimum creep ru~ture strength.
(6) Hot tensile data were not collected f~r heat (B) and accordinglg bot tensile data ~re not comparable.
.
.
~ABLE II
Effect oE Alloying (25%Cr, 20%Ni) Heat Resistan~ Alloy with Titanium and Tungsten Heat No. C% Mn% S% P% S% Cr~ Ni% W% Ti% N%
(A) Published .45 O50 1.O .02 .02 25.0 20.0 ~ A) Data Typical Analysis (B) ~461 .41 .44 1.12 - - 24.8 21.0 .10 .02 .126 ~B) ~C) 74-096 .39 .60 .99 .012 .014 2~.1 19.3 - ~16 .15~ (C) (D) 73-411 .39 .51 .94 .011 .010 25.5 19.6 - .24 .140 (D) ~E) 73-406 .39 .53 .96 .013 .006 24.3 19.5 - .18 .160 (E) (F) 73-25~ .41 .60 1.10 .014 .014 24.S 20.1 .10 .25 .160 (~) (G) 74-250 .45 .55 1.09 .012 .014 25.7 20.1 .11 .18 .140 ~G) .
, _ pture Life at Conditions Specified Hours 1800~F-6.0 Xsi 1800F-4.0 Rsi 2000F-2.0 Ksi .
(A) 35 . 220 150 tA) (B) 40 263 - (B) : (C) - 360 - ~C) (D) . .51 536 _ tD) .
~E~ _ . 634 _ (E) (~) 140 . 1371 557 (F) (G) 197 1094 937 . ~G) ~lot Tensile Property Co~parison ~25% Cr, 20% Ni) Yiela Tensile Strength Reduction Temp. Strength . -.2%- Elongation of Area Heat (F) (Ksi) (Ksi~ (~) t%) ACI (A)1400 37.5 24.4 . 12.0 _- -~F) 1400 45.3 28.7 28.0 .31.9 -(F) 1400 46.3 29.1 36.0 32.4 ACI (A)1600 23.3 14.7 16.0 (P) 1600 25.9 20.6 4~.0 57.8 (F) 1&00 26.6 20.6 46.5 60.8 ACI (A)1800 12.4 8.7 42.0 ~F) 18Q0 15.7 12.6 51.0 71~0 (F) 1800 16.4 13.1 50,0 72.0 ACX (A)2Q00 5.6 5.0 55.0 ~F) 2000 8.4 7~5 75-5 77 7 (F) 2000 8.5 7.7 60.0 77.8 s~
The following comments apply to Table I~:
~ 1) Heat A is a typical HK al:Loy, the properties of which represent the central tendency of published data .
(2) Heat B shows no beneficial effect on creep rupture strength with a .10~ tungsten and ~02~ titanium addition.
~ 3) Heats C, D and E show some improvement in creep rupture strength with small titanium a~ditions in the absence of tungsten.
54) Heats F and G show the effect ~f alloying with the same tungsten level as in Heat B, with a modest increase in titanium content.
(5) Note considerable enhancement of hot tensile steength and ductility comparing heats ~ and r.
' .. :
~09~ 513 TABI.E III
Effec-t of Alloying (25%Cr, 12%Ni) Hea~ Resistant Allo~ith Titanium and Tungsten Chemical Composition-Weight Percent , Heat No. C% Mn% Si% Cr% Ni% W% Ti% N%
. (A) Published ~35 '.50 1.O 25.0 12.0 - .08 ~A) .
: Data Typical Analysis -(B) 76-492 .36 .57 .93 24.6 13.2 .36 .43 .13 (~) , .
' Rupture Life at Conditions S~eci~lea Hours , . lÇ00F-6~0 Ksi 1600F-5.,0 Ksi 1800.~-6.0 ~rsi 1800F-5.0 Ksi (A? 165 340 12 21 (A) (B) ' 88~ ' 1971 83 . 298 . (3) .
. .
. . .... .
Hot Te'n's'il'e''Pxope'r'ty'Comparis'on ' '' - (2;5%,Cr,,12% Nir ' ' Yiel'd ' Tensile. Strength' Reduction ' Temp. Strength' -~2%- ~longation . o~ Area ; Heat '('~F~, ''' ~Rsi'1 (Ks'i'~ ' ' '(%) ; ' ~%)' '.,.
' ......... ACI (A) 140037.4 19.8 16.0 . _ -~B) 1400. 40.1 22.6 42.5 '43.1 ' ' (B) 1400 40,5 ~2.8 40Ø 43u4 .
- ACI'(A) 1600 21~5 16Ø 18Ø _ , .
' (B) 1600......... 24.0 17.9 53.5 52.1 (B) 1600 23.7 17.7 68.5 55.2 ACI (A~ 1800 10.9 7.3 31~0 , (B~ 1800 12.3 9.8 73.0 64.7 ,(B) 1800 13.8 10.8 73.0 53,4 ACI (A) 2000 5,5 - - _ (B) 2000 7.6 6.8 73.5 62.9 (B) 2000 7.7 6.9 69.0 60.3 9~L~s~
The following comments apply to Table III:
(1) Heat A is a typical HH alloy, the properties of which represent the central tendency oE publishe~ data.
(2) Heat B shows the e~fect of alloying with small tungsten and titanium additions.
(3) Note considerable enha~cement o~ hot tensile strength and ductility.
, ~ .
_ ~9~58 T~BLE IV
Ef~ect of Alloying (22%CrJ 25~Ni) Heat Resistant Allo~ with Titanium and Tungsten Chemical Composition-Weight Percent .
Eeat No. C~ Mn% Si% Cr% Ni'~ W~ Ti% N%
(A) Published O40 .50 1.0 21.0 ~S,.0 ~ A) Data Typical Analysis (B) 76-soo .40 .64 1.35 22.0 24.6 ~41 .39 .132 (B) '' , '.
~upture Life At Conditions Specified Hours , 1800F-6.0Ksi 1800F-.4.0 Ksl 2000F-2.5 Ksi 2000.F-1.5 Ksi (A) 70 470 lS0 630 (A) . ~B) 268 2070 411 1884 (~
.
Hot Tehsile Proper~y Co~parison ~ (22% Cr, 25% Ni) Yield .
TensileStrength ~eduction Temp . Strength - . 2~ n~ation of Area ~Iea~ ~F) ~Ksi) (Ksi) ` ~%) ACI ~A) 1600 20.2 14.5 37.0 tB) 1600 23.5 18.4 51.0 59O7 -~B) 1600 2~1 17.8 54.0 69.4 -ACI (A) 1300 11.9 9.6 51.0 (B) 1800 13.5 10.1 66.Q 73.4 tB) 1800 14.6 11.2 . 67.5 63.4 .
ACI (A) 2000 6.16 4.92 55.0 (B) 2000 7.67 6.97 57.5 70.6 (~) 2000 ?.63 7.05 51.0 75.~
'~he following comments apply to Table IV:
(1) Heat A is a typlcal HN alloy, the properties of which represent the central tendency of published data.
(2) Heat B shows the effect of alloying with 5small tungsten and -titanium additions.
(3) Shows same trend for hot tensile strength ~nd ductility.
` ~0~51~
TABLE V
Ef~ec~ of Alloying (23%Cr, 35%Ni) Heat Resistant Allo~With T~taniUm, Tungsten! and Niobium Chemical Composition ~eat ~o. C% Mn% Si~ Cr% Ni% W~ Ti% Nb% N~ ~Ieat No (A) 407 .48 .62 ~94 23.25 35.21 - - - ,101 tAj 407 (B) 681 .49.87 1.36 26.60 34.90 - - - .060 ~B) 6~
(C) 40~ .51.63 1.05 23.07 35.36 - - .35 .160 (C~ 4U8 (~) 411 .51.56 .g2 22.68 35.56 .54 - .36 .11~ ~D) 411 ~E) 162 .43.63 .38 22.90 35.50 .52 ~32 - .072 (E) 162 tF) 373 .43.57 ~74 22.52 35.15 .56 .42 .38 .153 (F) 373 Rupture Life_At Condition~ Specified 1800F 1800~F 2000~F
6.0 Xsi-Hrs. 5.0 Ksi-Hrs~ 2.5 Ksi-Hrs.
'' `~ (A) 35 149 _ (A) ~B) 23 _ 196 (B) (C) 81 371 - (C) (D) ~49 708 278 ~D) (E) 306 1015 B13 ~) tF) 174 936 131 (F) . -. , ' ' '.
" ., , .' ~4 Niobi~m contributes to creep r~pture strength as can be seen by comparing heat C to heats A and B of TABLE Vo There is an improvement with tungsten theat D) but not nearly so pronounced as the strengthening possible with tungsten and titanium evident when comparing heats D and E. That Nb is deficient in this regard is evident when comparing heat F, TABLE V to heat K, TABLE I. Niobium, possibly up to 2%, may be included in an alloy which contains both tungsten and titaniumr and doubtless other small additions as well, but at the risk of reducing the high temperature creep rupture strength, particularly at 2000F.
Experience with these castings establishes that with titanium levels greater than 1% it is difficult to produce castings which do not con~ain massive, titahium-rich non-metallic inclusions, in the form of TiO2 or even more complex oxi~es of titanium,. which detract from tensile properties. This is established b~ the data in TABLE ~I
(below) comparing heats K and O of:TABLE I; these data, to the metallurgist, mean more than about 1~ titanium is to be avoided throughout the range o~ the standard ACI grades. In view of these values and bearing in mind that titanium has a great af~inity for oxygen, requiring a careful deoxidation practice before adding titaniumr we therefore set a limit of less than 1% titanium and preferably no more than about 0.g6~.
TABLE VI
Effect Of Inclusions Due to High ~ 1.0%) Titanium Content On ~Room Temperature) Tensile Properties _ _ _ _ _ _ _ _ Tensile Yield Red.
Strength Strength Elong Area Heat No. Ti~ (Ksi) _ (Ksi) (%) (%) 76-440(K) 0.43 72.6 31.9 18.5 19.5 76-379(0) 1.16 37.8 27.5 2.5 7.,~
10~1~5B
In the drawings (Figs. 1-4~ shading has been applied to the straight line relationships which them-selves represent the central tendency of applied stress vs time of the standard ACI alloy grades for heat resistant castings. These central tendency lines have been published and are well known in this field of technology. The shading represents the expected scatter~ plus or minus 20% of the applied stress.
It will be observed that all our data points, applicable to the combination of tungsten and titanium under the present invention, exceed the upper limit of the accepted plus-or-minus 20% scatter for the standard ACI cast alloy grades, varying from a minimum upward dis-placement of about 5% (HP type grade) to a maximum dis-placement of about 100% for the HH type grade.
The foundry superintendent nQeds 1atitude to account for unexpected oxidation or melting losses; varia-tions in the furnace charge material and so on. In accor-dance with the present invention, and based on our previous foundry experience with commercial grades of iron-chromium-nickel heat resistant alloy castings, the following four alloys represent preferred foundry tolerance specifica-tions for the more popular ACI grades, both centr;~ugal and static castings:
3L~9~L95~
. ~ABLE VII.
.
Comparable . .
ACI
Alloy C% Mn% Si% P% S% Cr% Ni% 1~7% Ti~ Fe%
HH .2 2 3 5 .04 .04 24 :Ll .l ~l Bal .5 ~ax. Max. Max. Max~ 28 .i4 l.2 .6 ~K .~ 2 3 5 .04 .04 24 18 .l .l Bal.
Max. Max. Max. Max. 28 22 1.~ .6 ~N . .2 2 3.5 ~04 ~04 l9 23 .l .l Bal .5 Max~ ~ax. Max.Max. 23 27l.2 .6 - HP .2 2 3.5 .04 04 20 34 l 1 Bal.
.6 Max. ~ax. Max.Max. 24 .38l.2 .6 .
Within these ranges the preferred amount of tungsten, for best strength, is O.l/0.6 and indeed this preferred amount applies to.the ACI grades within the representative range ~IH through ~.
There is, however, a further bonus possible under the present invention, not necessarily requiring adherence to the optimum amount of tungsten. Referring to TABLE I it will be noted that when tungsten is in excess of the amount inducing maximum strength, when combined with titanium., the creep rupture life still exceeds that of the standard grade. Thus, while heat N, containing l.06% tungsten, showed a decline of about forty percent in rupture life (2000F, 2.5 Ksi load~ it outlasted .the standard alloy casting by nearl~ three times (622 hours vs. 196 hours~.
It can be seen then that tungsten in excess of the optimum for strength may be permissible, either for no more reason than a broad allowance in the kind of scrap used in melting, or for some clearly defined additional benefit of which resis-tance to carburization ( ~9~L958 is perhaps the be~t example, noting that tungsten is quite potent for that function. It is for reasons such as these that we conclude the amount of tungsten may be limited to about 2%, principally for economy because with tungsten in excess of about 0.6~ it seems the strengthening e~fect has attained a plateau (a little below optimum as already noted) where the inclusion of tungsten for some other reason becomes a ma~ter of balancing economy against results, particularly if tungsten exceeds two percent.
We have discovered an unusual con~luence of beneficial properties effected.by very small adaitions of tungsten and titanium opera~ive in four representative comm~rcial alloys representin~ a wide range of compo5itions. Our experience with those represen~ati~e alloys permi~s us to an~icipa~e a practical effect on hot tensile stre~g~h and ductility together with creep rupture strength over the fo~lowing range t% by weigh-t) of compositions, with the balance iron exclusive o~ the.usual unavoidable foundry impurities (such as aluminum deoxidizer and molybdehum which ma~ be presen~ in impure melt stock~ and tramp elemen~s such as phosphoru~ and sulfur~
Carbon 0~25/ 0.8 Chromium . 12.0 /32 . Nickel 8 0 ~62.0 Manganese . - 0 / 3 0 Silicon .O / 3 5 Tungsten 0.~5/ 2 Titanium 0.05/~1 . .
1~
5E~
The effect is achieved in the presence of what ~70uld normally be considered lligh levels of nitrogen, as well as at the lower nitrogen levels representative of conventional induction melting practices, that is, nitrogen does not have an adverse effect. Possibly further enhancement of stren~-th can be achieved by lower, or even higher levels of nitrogen;
however, nitrogen up to 0.3% is doubtless permissable.
Any standard or preferred melting practice applicable to the known alloy bases may be used. Tun~sten may be added as ferro-tungsten (which is not a strategic material) and titanium in sheet form may be added when -the furnace is tapped; but to obtain maximum titanium recovery deo~idation should be made in the furnace or in any other manner 5Ui table ~o the reduction of oxygen con~ent to very low levels prior to the addition of titanium.
We recognize that this range of composi-tions encompasses certain combinations of extremes -that might produce an alloy containing major to minor amounts of detrimental ferrite in its microstructure. These combinations are to be àvoided, in that our alloys are intended to have a mircostructure that is essentially austenite plus carbide (substantially free of ferrite) as seen in Fig. 5. The presence of ferri-te in the microstructure promotes the eventual formation of the embrittling sigma phase at temperatures below 1700F. The lower temperature limit or the formation of sigma is determined by specific alloy composition and by time of exposure, but embrittlement at temperatures as low as 1200F has been observed. The presence of sigma would be generally detrimental to the life of these alloys under cyclic thermal loading and to ductility in general.
-- 19 -- , .
19~8 For this reason, our invention should be practiced in alloys so balanced as to produce a microstructure essential.ly free of the sigma-forming ferrite.
In practice the alloy is cast essentially to the service configuration only requiring removal of the risers and gating, some machining perhaps where cosmetic appearance is important or where close tolerances are involved, and welding to complete an assembly from component as-cast parts in certain instances such as the assembly shown in Fig. 6. Even in the instance of welding the cast components to complete an assembly (of bends and straight sections, Fiy. 6) those components individually have the configuration for service. Thus, heat treatment is not required to develop service properties.
Conceivably some cobalt or molybdenum migh-t be present in trace amounts in a heat due to impure melt stock but in any event our alloy is essentially free of each and requires neither of those elemen-ts to produce the beneficial confluence of hot tensile strength, ho-t ductility and creep rupture strength bestowed uniformly, without exception, on standard ACI grades by so small a change. By the same token, the alloy is distinguishable from -the so-called super alloys - where large amounts of addition elements are employed for various purposes, of which cobalt and tungsten are examples, sometimes requiring vacuum melting techniques as compared to the present castings which may be cast atmospherically a-t ambient conditions.
- ~o _ .
L95~il Nonetheless the chief advantage of the a].loy is the surprisingly large displacement in mechanical prope.rties, achieved by little change and low cost, in th~ as-cast condition essentially ready for service without heat treatmen-t: a casting with considerably greater reserves of hot tensile strength and ductility for increasing thermal fatigue resistance, wi-th the added benefit of a significant increase in the value of creep rupture strength.
- 21 -.
Claims (6)
1. A heat resistant alloy in as-cast form essentially in the configuration required for service, neither worked nor heat treated, said casting consisting substantially of the following elements in weight percent:
wherein (a) the elements carbon, nickel and chromium are so balanced that the microstructure is austenite substan-tially devoid of ferrite whilst (b) the amount of tungsten combined with titanium is present in amounts which produce a value of creep rupture strength exceeding the creep rupture strength of the alloy not containing tungsten and titanium.
wherein (a) the elements carbon, nickel and chromium are so balanced that the microstructure is austenite substan-tially devoid of ferrite whilst (b) the amount of tungsten combined with titanium is present in amounts which produce a value of creep rupture strength exceeding the creep rupture strength of the alloy not containing tungsten and titanium.
2. A heat resistant alloy casting according to claim 1 in which the amount of tungsten is in the range of about 0.1 to about 0.6 percent.
3. A heat resistant allow casting according to claim 1 in which the amount of chromium is 24/28 and that of nickel is 11/14, in which tungsten is 0.1/1.2 and in which titanium is 0.1/0.6.
4. A heat resistant alloy casting according to claim 1 in which the amount of chromium is 24/28 and that of nickel is 18/22, in which tungsten is 0.1/1.2 and in which titanium is 0.1/0.6.
5. A heat resistant alloy casting according to claim 1 in which the amount of chromium is 19/23 and that of nickel is 23/27, in which -tungsten is 0.1/1.2 and in which titanium is 0.1/0.6.
6. A heat resistant alloy casting according to claim 1 in which the amount of chromium is 20/24 and in which the amount of nickel is 34/38, in which tungsten is 0.1/1.2 and in which titanium is 0.1/0.6.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US79384877A | 1977-05-04 | 1977-05-04 | |
| US793,848 | 1977-05-04 | ||
| US05/824,637 US4077801A (en) | 1977-05-04 | 1977-08-15 | Iron-chromium-nickel heat resistant castings |
| US824,637 | 1977-08-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1091958A true CA1091958A (en) | 1980-12-23 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA295,035A Expired CA1091958A (en) | 1977-05-04 | 1978-01-16 | Iron-chromium-nickel heat resistant castings |
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| Country | Link |
|---|---|
| JP (1) | JPS53137817A (en) |
| BR (1) | BR7802753A (en) |
| CA (1) | CA1091958A (en) |
| DE (1) | DE2819529C2 (en) |
| FR (1) | FR2389681B1 (en) |
| GB (1) | GB1544614A (en) |
| IN (1) | IN149220B (en) |
| IT (1) | IT1105256B (en) |
| MX (1) | MX5781E (en) |
| SE (1) | SE445469B (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4236921A (en) * | 1979-03-02 | 1980-12-02 | Abex Corporation | Heat resistant alloy castings |
| JPS5857506B2 (en) * | 1980-06-03 | 1983-12-20 | 太平金属工業株式会社 | heat resistant alloy |
| US4410362A (en) * | 1981-01-12 | 1983-10-18 | Kubota Ltd. | Heat resistant cast iron-nickel-chromium alloy |
| JPS596910B2 (en) * | 1981-01-12 | 1984-02-15 | 株式会社クボタ | heat resistant cast steel |
| JPS6331535A (en) * | 1986-07-23 | 1988-02-10 | Jgc Corp | Apparatus for treating carbon-containing compound having carbon precipitation suppressing property |
| KR101326375B1 (en) * | 2005-10-31 | 2013-11-11 | 구보다코포레이션 | HEAT-RESISTANT ALLOY CAPABLE OF DEPOSITING FINE Ti-Nb-Cr CARBIDE OR Ti-Nb-Zr-Cr CARBIDE |
| CA2953240C (en) * | 2014-07-10 | 2023-08-01 | Paralloy Limited | Low ductility alloy |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR908191A (en) * | 1944-06-16 | 1946-04-02 | Commentry Fourchambault & Deca | Process for improving the creep resistance of austenitic alloys and alloys thus obtained |
| FR1397644A (en) * | 1964-05-21 | 1965-04-30 | Chrysler Corp | Iron-based alloys having in particular a high resistance to temperatures above 650 u deg. vs |
| JPS5040099B1 (en) * | 1971-03-09 | 1975-12-22 | ||
| SE355825B (en) * | 1971-12-21 | 1973-05-07 | Sandvik Ab |
-
1978
- 1978-01-05 GB GB399/78A patent/GB1544614A/en not_active Expired
- 1978-01-05 IN IN19/CAL/78A patent/IN149220B/en unknown
- 1978-01-16 CA CA295,035A patent/CA1091958A/en not_active Expired
- 1978-02-21 FR FR7804913A patent/FR2389681B1/fr not_active Expired
- 1978-03-23 IT IT7848577A patent/IT1105256B/en active
- 1978-04-28 SE SE7804951A patent/SE445469B/en not_active IP Right Cessation
- 1978-05-03 DE DE2819529A patent/DE2819529C2/en not_active Expired
- 1978-05-03 BR BR7802753A patent/BR7802753A/en unknown
- 1978-05-04 MX MX787059U patent/MX5781E/en unknown
- 1978-05-04 JP JP5363578A patent/JPS53137817A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| SE445469B (en) | 1986-06-23 |
| GB1544614A (en) | 1979-04-25 |
| BR7802753A (en) | 1978-10-10 |
| MX5781E (en) | 1984-07-11 |
| IT7848577A0 (en) | 1978-03-23 |
| FR2389681A1 (en) | 1978-12-01 |
| IN149220B (en) | 1981-10-10 |
| FR2389681B1 (en) | 1981-07-17 |
| DE2819529C2 (en) | 1984-06-28 |
| JPS53137817A (en) | 1978-12-01 |
| SE7804951L (en) | 1978-11-05 |
| DE2819529A1 (en) | 1978-11-16 |
| IT1105256B (en) | 1985-10-28 |
| JPS5740900B2 (en) | 1982-08-31 |
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