CA1066925A - Cast maraging steel - Google Patents
Cast maraging steelInfo
- Publication number
- CA1066925A CA1066925A CA217,649A CA217649A CA1066925A CA 1066925 A CA1066925 A CA 1066925A CA 217649 A CA217649 A CA 217649A CA 1066925 A CA1066925 A CA 1066925A
- Authority
- CA
- Canada
- Prior art keywords
- cast
- silicon
- cobalt
- steels
- maraging steel
- 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
Landscapes
- Treatment Of Steel In Its Molten State (AREA)
Abstract
Abstract of the Disclosure A cast maraging steel containing correlated percentages of nickel, cobalt, molybdenum, silicon, aluminum, titanium, carbon and titanium as well as iron. The alloy, by reason of its strength, tough-ness and corrosion resistance, is deemed useful in aircraft and the applications as well.
Description
. ~)66925 The subject invention is addressed to cast maraging steels.
As those skilled in the art are aware, more than a decade has passed since the advent of the maraging steels. During that period, these steels, at least those in the wrought condition, achieved a position of prominence in various areas of application. But, all their attributes not-withstanding, the cast versions have apparently disappeared from the com-mercial scene. Perhaps the reason forthis was largely occasioned by the necessity to vacuum melt and vacuum pour in an effort to achieve a satis-factory combination of properties. Of course, this would increase cost markedly. It would appear, therefore, that cast maraging steels which could be produced in accordance with air melting technology but capable of delivering a satisfactory combination of metallurgical characteristics, notably strength and toughness, would become a more formidable competitor in the marketplace.
It has now been found that vacuum processing can be dispensed with and that a high level of strength and toughness can be attained using air melting processing provided the cast steels contain special amounts of nickel, cobalt, molybdenum, silicon, aluminum, titanium and carbon.
Generally speaking, and in accordance with the present invention, cast maraging steels are contemplated which contain from about 15 to 19%
nickel, from about 8 or 9% to about 12.5% cobalt, about 1.5 to 2.5%
molybdenum, 0.01 to 0.2% of each of aluminum and titanium, from 0.3 to 0.6% silicon, 0.001 to 0.1%, e.g., 0.005 to 0.05%, carbon, the balance being essentially iron. Such steels consistenLly afford a minimum yield strength of at least 175,000 or 180,000 psi together with the capability of absorbing high levels of impact energy. (All percentages given herein are in weight percent.) With regard to the chemistry above given, it is noteworthy to men-tion that the steels contain, comparatively speaking, a rather substantial amount of silicon. Heretofore, it has been deemed that silicon was detrimental . .
- ~0~69Z5 particularly in respect of toughness. Indeed, in speaking of maraging steels in general, it has been said that the silicon content thereof should be held to a maximum of 0.1%. However, as will be shown herein, provided that cast maraging steels contain the proper constituents, the percentages of which are particularly correlated, not only can high strength levels be achieved, but -, .
more than satisfactory toughness as well. Of considerable importance, since the instant steels accept high silicon levels, less pure materials can be used in . : -:
production, thus offering a further economic advantage commercially. The silicon can be extended down to 0.1% with a cobalt level from about 11.5 to 12.5%. ;~
The following illustrative data are given.
A series of steels were prepared in accordance with the invention using conventional air melting techniques. In this regard, 30-lb. air induction melts were made using electrolytic type charge materials. The melts were cast into one-inch thick keel block sand molds. Tensile, Charpy V-notch impact and, in some instances, fracture toughness tests were conducted, these tests being performed at room temperature, The compositions of various steels are given in Table I, Alloys 1-8 being within the invention whereas Alloys A-F
are beyond the scope thereof.
TABLE I
~ = ___ . .. _ .....
Ni Co Mo Si Al Ti C Fe Alloy__ % % 96 % ~, % % %
18.012.2 1.7 .44 .04 .04 .022Bal.
As those skilled in the art are aware, more than a decade has passed since the advent of the maraging steels. During that period, these steels, at least those in the wrought condition, achieved a position of prominence in various areas of application. But, all their attributes not-withstanding, the cast versions have apparently disappeared from the com-mercial scene. Perhaps the reason forthis was largely occasioned by the necessity to vacuum melt and vacuum pour in an effort to achieve a satis-factory combination of properties. Of course, this would increase cost markedly. It would appear, therefore, that cast maraging steels which could be produced in accordance with air melting technology but capable of delivering a satisfactory combination of metallurgical characteristics, notably strength and toughness, would become a more formidable competitor in the marketplace.
It has now been found that vacuum processing can be dispensed with and that a high level of strength and toughness can be attained using air melting processing provided the cast steels contain special amounts of nickel, cobalt, molybdenum, silicon, aluminum, titanium and carbon.
Generally speaking, and in accordance with the present invention, cast maraging steels are contemplated which contain from about 15 to 19%
nickel, from about 8 or 9% to about 12.5% cobalt, about 1.5 to 2.5%
molybdenum, 0.01 to 0.2% of each of aluminum and titanium, from 0.3 to 0.6% silicon, 0.001 to 0.1%, e.g., 0.005 to 0.05%, carbon, the balance being essentially iron. Such steels consistenLly afford a minimum yield strength of at least 175,000 or 180,000 psi together with the capability of absorbing high levels of impact energy. (All percentages given herein are in weight percent.) With regard to the chemistry above given, it is noteworthy to men-tion that the steels contain, comparatively speaking, a rather substantial amount of silicon. Heretofore, it has been deemed that silicon was detrimental . .
- ~0~69Z5 particularly in respect of toughness. Indeed, in speaking of maraging steels in general, it has been said that the silicon content thereof should be held to a maximum of 0.1%. However, as will be shown herein, provided that cast maraging steels contain the proper constituents, the percentages of which are particularly correlated, not only can high strength levels be achieved, but -, .
more than satisfactory toughness as well. Of considerable importance, since the instant steels accept high silicon levels, less pure materials can be used in . : -:
production, thus offering a further economic advantage commercially. The silicon can be extended down to 0.1% with a cobalt level from about 11.5 to 12.5%. ;~
The following illustrative data are given.
A series of steels were prepared in accordance with the invention using conventional air melting techniques. In this regard, 30-lb. air induction melts were made using electrolytic type charge materials. The melts were cast into one-inch thick keel block sand molds. Tensile, Charpy V-notch impact and, in some instances, fracture toughness tests were conducted, these tests being performed at room temperature, The compositions of various steels are given in Table I, Alloys 1-8 being within the invention whereas Alloys A-F
are beyond the scope thereof.
TABLE I
~ = ___ . .. _ .....
Ni Co Mo Si Al Ti C Fe Alloy__ % % 96 % ~, % % %
18.012.2 1.7 .44 .04 .04 .022Bal.
2 17.512.4 1.9 .37 .04 .04 .010Bal.
3 17.812.6 2.0 .38 .03 .05 .011Bal.
4 18.110.2 2.0 .30 .04 .04 .019Bal.
17.910.5 1.6 .36 .03 .06 . 021 Bal .
6 18.08.1 2.1 .35 .02 .06 .031Bal.
7 17.98.4 1.7 .42 .02 .07 .047Bal.
8 17.712.5 1.9 .11 .09 .02 .006Bal.
A 17.615.3 2.6 .45 .03 .02 .015Bal .
B 17.915.4 2.5 .33 .04 .04 .039Bal.
C 12.012.4 2.1 . 03 .01 .04 .009Bal .
D 18.24.2 2.55 .23 .02 .04 .011Bal.
E 17.96.3 1.52 .36 .02 .05 .010Bal .
F 18.16.2 2. 30 .36 .02 .07 .009Bal .
.
' ` - 10669ZS
The alloys were subjected to a heat treatment consisting of (i) solution annealing at 2100F. for 1 hour, air cooling, (ii) heating at 1100F. for 1 hour, air cooling, (iii) followed by heating at 1500F. for 1 hour and air cooling, the alloys thereafter being (iv) aged at 900F. for 3 hours. The results of these tests are reported in Table II below.
TABLE II
Yield Strength UTSElong. R.A.CVN
Alloy0.2% offset, ksi ksi % %ft.-lbs.
196 20610 4327.0 2 203 20810 5225.0 3 211 21511 5024.7 4 197 20410 4725.7 190 19414 5727.5 6 193 19811 3824.2 -7 190 19412 5222.2 8 198 20211 5124.0 A 241 251 8 335.2 B* 260 271 2 44.0 C 141 15410 3214.7 D 169 17614 4920.5 E 149 15818 6447.0 F 163 17715 5534.5 *Aged at 800F. for 24 hours The data reported in Tables I and II reflect the disadvantages in appreciably departing from the cast steel compositions in accordance herewith.
For example, Alloys A and B had high cobalt levels (the molybdenum also being at the high end of its alloying range). And while strength was high, tensile ductility and toughness were relatively low. On the other hand, whereas ductility and toughness were acceptable in respect of, say, Alloys E
30 and F, strength was unsatisfactory. Alloy 8 has been included in Tables I
and II to illustrate that lower percentages of silicon can be used when high levels of cobalt are present. Such an alloy, while within the invention, is more costly and does not provide any real benefit. Alloy 8 can be compared with Alloy 3 in terms of silicon effect. These steels were rather similar in composition, the latter containing 0.38% silicon versus 0.11% for the ~ormer .
-- 10669~5 Notwithstanding the higher silicon level, Alloy 3 exhibited comparable toughness, its yield strength being 13,000 psi higher . With cobalt per-centages below about 9.5 or 10%, the molybdenum should be upwards of 1.7%.
The foregoing data indicate that provided a properly correlated chemical balance is employed, "cast maraging" steels can be produced with a quite acceptable combination of strength and toughness, this obtaining with air melting processing.
It might also be added that it is of significance that steels in accordance herewith combine the capability of offering high strength, e.g., 180,000 psi and above in thick sections. As indicated in a recent National Advisory Board Report, such a cast steel would be desirable. It was indicated that, subject to further development work, even HY-180 probably would have to be vacuum melted. In this regard, a 300 lb. air induction melt of the following composition was sand cast into not only one and three inch castings, but also a six inch thick casting with good results (193 KSI Y.S. plus 34 CVN at room temperature):
17.7% nickel, 10.1% cobalt, 1.61% molybdenum, 0.28% silicon, 0.01% aluminum, 0.04% titanium, 0. 009% carbon, balance iron and impurities .
A particularly satisfactory cast alloy contains 16. 5 to 18% nickel, 9.75 to 11% cobalt, 1 . 6 or 1. 7 to 2 . 1% molybdenum, 0 . 01 to 0 . 1% each of aluminum and titanium, about 0.01 to 0.0596 carbon and the balance essentially iron.
Although the invention has been described in connection with ;
preferred embodiments, modifications may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such are considered within the purview and scope of the invention and appended claims.
17.910.5 1.6 .36 .03 .06 . 021 Bal .
6 18.08.1 2.1 .35 .02 .06 .031Bal.
7 17.98.4 1.7 .42 .02 .07 .047Bal.
8 17.712.5 1.9 .11 .09 .02 .006Bal.
A 17.615.3 2.6 .45 .03 .02 .015Bal .
B 17.915.4 2.5 .33 .04 .04 .039Bal.
C 12.012.4 2.1 . 03 .01 .04 .009Bal .
D 18.24.2 2.55 .23 .02 .04 .011Bal.
E 17.96.3 1.52 .36 .02 .05 .010Bal .
F 18.16.2 2. 30 .36 .02 .07 .009Bal .
.
' ` - 10669ZS
The alloys were subjected to a heat treatment consisting of (i) solution annealing at 2100F. for 1 hour, air cooling, (ii) heating at 1100F. for 1 hour, air cooling, (iii) followed by heating at 1500F. for 1 hour and air cooling, the alloys thereafter being (iv) aged at 900F. for 3 hours. The results of these tests are reported in Table II below.
TABLE II
Yield Strength UTSElong. R.A.CVN
Alloy0.2% offset, ksi ksi % %ft.-lbs.
196 20610 4327.0 2 203 20810 5225.0 3 211 21511 5024.7 4 197 20410 4725.7 190 19414 5727.5 6 193 19811 3824.2 -7 190 19412 5222.2 8 198 20211 5124.0 A 241 251 8 335.2 B* 260 271 2 44.0 C 141 15410 3214.7 D 169 17614 4920.5 E 149 15818 6447.0 F 163 17715 5534.5 *Aged at 800F. for 24 hours The data reported in Tables I and II reflect the disadvantages in appreciably departing from the cast steel compositions in accordance herewith.
For example, Alloys A and B had high cobalt levels (the molybdenum also being at the high end of its alloying range). And while strength was high, tensile ductility and toughness were relatively low. On the other hand, whereas ductility and toughness were acceptable in respect of, say, Alloys E
30 and F, strength was unsatisfactory. Alloy 8 has been included in Tables I
and II to illustrate that lower percentages of silicon can be used when high levels of cobalt are present. Such an alloy, while within the invention, is more costly and does not provide any real benefit. Alloy 8 can be compared with Alloy 3 in terms of silicon effect. These steels were rather similar in composition, the latter containing 0.38% silicon versus 0.11% for the ~ormer .
-- 10669~5 Notwithstanding the higher silicon level, Alloy 3 exhibited comparable toughness, its yield strength being 13,000 psi higher . With cobalt per-centages below about 9.5 or 10%, the molybdenum should be upwards of 1.7%.
The foregoing data indicate that provided a properly correlated chemical balance is employed, "cast maraging" steels can be produced with a quite acceptable combination of strength and toughness, this obtaining with air melting processing.
It might also be added that it is of significance that steels in accordance herewith combine the capability of offering high strength, e.g., 180,000 psi and above in thick sections. As indicated in a recent National Advisory Board Report, such a cast steel would be desirable. It was indicated that, subject to further development work, even HY-180 probably would have to be vacuum melted. In this regard, a 300 lb. air induction melt of the following composition was sand cast into not only one and three inch castings, but also a six inch thick casting with good results (193 KSI Y.S. plus 34 CVN at room temperature):
17.7% nickel, 10.1% cobalt, 1.61% molybdenum, 0.28% silicon, 0.01% aluminum, 0.04% titanium, 0. 009% carbon, balance iron and impurities .
A particularly satisfactory cast alloy contains 16. 5 to 18% nickel, 9.75 to 11% cobalt, 1 . 6 or 1. 7 to 2 . 1% molybdenum, 0 . 01 to 0 . 1% each of aluminum and titanium, about 0.01 to 0.0596 carbon and the balance essentially iron.
Although the invention has been described in connection with ;
preferred embodiments, modifications may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such are considered within the purview and scope of the invention and appended claims.
Claims
1. A maraging steel in cast form consisting essentially of from 15% to 19% nickel, 8 to about 12.5% cobalt, about 1.5 to 2.5% molybdenum, 0.01 to about 0.2% each of aluminum and titanium, from 0.1 to about 0.6%
silicon, the silicon being about 0.3% or more when the cobalt is less than about 11.5%, 0.001% to about 0.1% carbon, and the balance essentially iron.
silicon, the silicon being about 0.3% or more when the cobalt is less than about 11.5%, 0.001% to about 0.1% carbon, and the balance essentially iron.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US47981274A | 1974-06-17 | 1974-06-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1066925A true CA1066925A (en) | 1979-11-27 |
Family
ID=23905551
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA217,649A Expired CA1066925A (en) | 1974-06-17 | 1975-01-09 | Cast maraging steel |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS50159814A (en) |
| AU (1) | AU8187475A (en) |
| CA (1) | CA1066925A (en) |
-
1975
- 1975-01-09 CA CA217,649A patent/CA1066925A/en not_active Expired
- 1975-03-19 JP JP3251375A patent/JPS50159814A/ja active Pending
- 1975-06-05 AU AU81874/75A patent/AU8187475A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS50159814A (en) | 1975-12-24 |
| AU8187475A (en) | 1976-12-09 |
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