US2537477A - Valve and turbine steels - Google Patents

Description

Jan. 9, 1951 G. MOHLING ET AL VALVE AND TURBINE STEELS Filed Jan. 15, 1947 INVENTOP 5 m Patented Jan. 9, 19 51 UNITED STATES; enrszur oFFICE.

VALVE AND S'EEELS Wilson, Albany; N. Y., assi'gnors to Allegheny- Ludl m Steel. Corporation, a corporation of Pennsylvania,

Application J anuary, l5, 194;7', Serial No. 722,118"

8' Claims. I

The present inventionv pertains to high temperature steels of moderate strength, generally, lower alloy content and, incidentally, lower cost. The strength at heat oi these alloys is, however, considerably higher than that of commercial a1- loys in use at the beginning of Word War II.

- 'IF-woprevious pa ents of Gunther; Moh n Numbers 2137mm and. agel ss. deal; wi h. alloys of maximum strength at high temperatures, the utilizations of which were mainly confined to; gas tur ines for military aircraft.

There is a wide field for-use of; alloys; oi; our invention, for instance, improved valves for internal combustion engines, improved steam turbine buckets and gas turbine buckets for the low temperature stages of multi-stage turbines.

There has been a continuous. demand. for im-.. proved alloys that may be used in this general field and an increased demand for less expensive. alloys. It will be appreciated thatsteels or alloys. used in connection; with internal combustion en-. 'gines. are subjected to. considerable temperature variations and to relatively high temperatures, at least; periqdically. Steels used for turbines are; also subjected toconsiderable temperature varia tionsand to. relatively high temperatures during; their utilization. Such steels mutt, thus, have: spe ial. phy ical, tr ctural, nd o her. q li es, such that th y wilt withsta d the temperature; conditions. encountered, will. hav a reason ble: period of life, and will also. have. resistance. to. corrosion under service conditions. For example, in combustion engines, lead ethyl; bromides are extremely corrosive, and although in turbine utilization the steam ongases are not as-highly corrosive, they are, strongly corrosive. due. to. the, te liperature at which the parts are utilized.

Steels torturbines, such-as herein contemplated, should be. capable of withstanding temperatures from about 900 to 1350 F., while valve steels should be capable of withstanding temperatures from about 1000 to 1400" F.

It will be apparent that steels or alloys such as herein considered, should have a high resist! ance to, the normal corrosive action of combustion fluids, and exhaust; gases of internal combus; tion engines and to the high temperature gases employed in turbine utilizations. They should have high resistance to deformation at thetemperatures involved and while being subjected to stress and wear conditions. Adequate hardness must be maintained at; a temperature as high as. about l4; 0O F. and afterprolonged exposure to continuous or intermittent application thereoi,,

In connection with turbine utilizations, the steels should have good dampingcapacity; They- 2 I should have enoughor sufiicient ductility that the parts will give-some warning before they-gimewair entirely, nearthe end of their normal periodofi life.

All steels herein considered, when made in. ac: cordance with ourinvention, have improved com-.. mon characteristics, such as better corrosion re-i sistance at high temperature without an excessive loss of strength; that is, they have better oxidize. ing resistance torany temperature. of the operate ing'rangen They are also. less. expensive than steels of comparable. strengths since they make. possible the utilizationof: smaller percentages; 05 thestrategically critical elements, such as. molybdenum, tungsten and columbium.

It has thus beenv an object of ourinvention to provide new and improved steels for high teme. perature utilizations.

Another object has been to'providehigh tem-.

peraturesteels that may successfully utilize lower percentages of ments.

Another object has been to providev high. .tem:v perature alloy steels that may be used as cash, forged or machinedengine valves and turbine vanes or buckets.

These andmany other objects of our invention:

the more expensive alloying vele:

will appear to those skilled in the-art: from the:

description thereof, the claims: and; the exemplars:- i-llustrations;

Ln: the drawings:

Figure 1 is a perspective View in elevation of a typical metal valve it utilizing steel of our invention;

Figure 2 is a perspective sectional view of a typical turbine wheel l5 having metal buckets or vanes l6 utilizing steel of our invention.

Table I gives the analysis of 'a number of melts which are in the preferred composition range of our present invention. Common to all these melts is the simultaneous presence of molybdenum, tungsten and columbium in the range of about 2 to substantially less than 6 percent total and of a minimum total of about 1.20 percent. The carbon content of all melts is below about 1 percent. Chromium is present from about 12 to percent and nickel between about 3 to 20 percent. It is common knowledge that the alloys of chromium and nickel are mostly ierritic or magnetic if the nickel content is somewhat below 7 percent. These alloys will be useful in the lower end of the temperature range, that is up to about l F. If the nickel content is substantially above '7 percent the alloy becomes a stable austenite and may be used in the higher end of the temperature range. Three exemplary melts con- 3 tain up to 20% of cobalt. These may be used if a somewhat higher strength and hot hardness is required and the application warrants the extra cost.

Manganese and silicon may be present up to about 2.50 percent; while they are not essential elements in an alloy of our invention, they may be present in usual commercial amounts. A certain amount of silicon is usually present due to its appearance in other ferroalloys used in making the alloying additions. Nitrogen, although not essential, may be present up to about .25 percent; additions to the melt may be accomplished for this purpose,

In addition to other beneficial effects, proper amounts of nickel insure a stable steel under conditions of service and proper amounts of chromium insure corrosion resistance. Cobalt (not essential) may be used to produce beneficial effects such as hot hardness and strength. The carbon content is maintained below about 1% and is preferably kept about or below 50%.

The alloys of our invention may contain normal amounts of other alloying elements in such quantities as to not alter desired properties of the alloy. That is, some additional alloying element or elements may be added without changing the essential characteristics of the alloy. Remainder substantially iron as herein employed means that the alloy may contain percentages of additional non-ferrous alloying elements of such nature and quantity as to not destroy the basic improved properties of the alloy.

1 Table II shows a number of time to rupture tests on these melts, in which a heat treated or 4 sten is replaced with 1 /2 percent of molybdenum, 1 percent of tungsten and .50 percent of columbium according to our invention.

It is evident from comparison of Tables II and III that the properties of all alloys in Table II (see also 17-34 of Table III) are very far superior to the commercial alloys in Table III. For example, the life of 13-34 at 1500" F. is about three times that of steel #2, see Table III. Steel #1 of Table III may be compared, for example, with steels 8-921 and 8-931 of Table II.

What we claim as new according to our invention are alloys for intermediate high temperature service, which fall in substantially the fol lowing ranges of composition:

Carbon .051.00 Silicon 2.50% maximum Manganese -.20-2.50 Chromium 12-30 Nickel 3-20% Molybdenum -50-2.00 Tungsten -50-2.00 Columbium .50-2.00 (may be as low as about 20 The total of the last three elements being less than 6 and preferably, within a maximum of about 4.5%, see Table I.

With or without cobalt.

Remainder iron, or substantially iron with or without some nitrogen.

TABLE I Analyses of experimental-melts cast test piece was subjected to a constant load Heat No. 0 Mn S1 Or Ni 00 \I0 W Cb at temperatures of 1000, 1100, 1200, 1350 and 1500 F. The life in hOlllS llIltll failure 1s g1ven, 1,194 1369 L18 L20 L92 together wlth the elongation and reduction in .50 .50 20.74 19.66 1.10 1.03 1.96 area is in percent of original. The double heat treatment given to each test piece is described 1. 59 .42 20.10 4.10 1.14 .90 1.12 in the Mohling Patent #2,40l,580 of June-4, 1946. 1: fggg i: i:

Table III showsrupture properties of two com- 1.50 .45 18.41 4. 0s .89 .95 1.00 mercial steels, #1 a prominent automotive valve 12% 3; 533 i: :5 steel and #2 an aircraft exhaust valve steel. #1 .02 ;43 23.57 13. s1 1.52 .58 .54 is'a chromium-nickel alloy containing about 3 i 52, 5 3 i i: percent of molybdenum; #2 a chromium-nickel 10.42 alloy containing about 3 percent of tungsten. 18:35 :11: U-34 is the same alloy as #2 in which the tung- TABLE II Time-to-rupture tests Elonga- Rcduc Hot Heat No. Heat Treatment fi i ifi] 3. BIS? Cent Cent 1400I1.

60,000 441 5.0 s-921- As Cast. 50,000 1,181 3.4 40, 000 3, 097 '5; 0 11-241.... 2150 30 min. w+

' 1100 10 hrs. 11.. 20, 0 egg I 0, 0 ,1 50,000 1, 598 5. 2

' 50,000 73 2.9 11.3 As 1 0,330 1,05 3g 0 0 11-247---" 2150 -30 n 11n.W+ 501000 416 i 5 5 7 14 16 1000 1, 75s 3. 1 5. 2

TABLE; rates-minced A a yses of, esp t mentcl mfilts Con-b nued Hot R No. Hewearmw .92s. 1 an 2? e Cent Gent 1400 E S-9.31'- .-;2l5 1' TI11i11 .,W+' 300 5. 3; .10 12001 6,hrs.A 25,000, 5,078 6.9 4.0 S-764-" '2l50- 1 hr. W+ 1 v 3 1400216 h1 S.,A 25,000 7; 431-2r 9.0 5.6 S. 920, 215 0 1 h I. W-l 30,000, 152,. .8.0 22.0

1400 16 hrs. A. 000 3, 254 1 4.0 2. .4

= 20s, 13.5 13.10 7.3. 111 I! 2,095 5 3.0 E 372* 6 4.0 232 7 3.5 315 6.0 837' 1 0. 6.2

52150 1, hr... W-i: .5

14009- 16111'5. A..- 20,000 2.21. 12.5 12.8 d0 279' 10.0" 7.0 000 41; 255.0;i 24:0 243 11.5 16.0 665 17.0 16.0 297 19.0 17.0 420 7.0 6.0

S673 2150 1 hr. W-i- 1 ?100,=l6*hr,$. A 12,500: 91,. 1 9.0 S764 12, 500 106 3 U-so- 10,000 24 5.0 128 U-89 000 166 0 I56 III-88- 10, 000 i 299 120: I56 0 280 1.

uilhis meanslhour temperature treatment at-2150 F. r llowedby a Water, quench.

The second part ofthe heat treatment is at 14002F. for 1 6 hoursjollowed by air cooling. The .sameinterpretatiomapplies. to. the

TABLE III Time-to-rupture tests on dommercial valve steels I Elonga- 5 Reduc- .Load Time tum, non,

D. s. 1. Hours Pengent EROLQBM 25,000 148 20 34 steel #1 "120,00 37g 34 g3 25,00 4 5 Steel #2 {20, 000 10s 38 37 Steel #1 20,000 0 46 47 Steel #2 0 95 5 5 Steel #1 7,000 13 70 57 0 Steel #2 10,000 139 3 2 U-34 (Same steel as steel #2, modified according to our invention) 10,000 334 3 4 other heat treatments set forth.

strength, said, alloy containing below about 1% carbon, about 12-26% chromium, about 3-2,0% nickel; molybdenum, tungsten, and columbium in a minimum total. amount. of about 1-2%, and up to a. total amount of substantially lessv than 6%, and v the remainder: iron; all, of. the named elements, as, its. essential. elements, with usual. commercial. amounts. oi the; elements man'- ganese and silicon.

2. An improved, inexpensive, heat resistant alloy that will withstand temperature variations and that has a better corrosion resistance at high temperatures without an excessive loss of strength, said alloy containing below about 1% carbon, about 12-30% chromium, about 3 to 7% nickel, the elements molybdenum, tungsten, and columbium in a total minimum amount of about 1.2% and up to a total amount of substantially less than 6%, up to about 2.5% of each of the elements manganese and silicon, up to about 25% nitrogen, up to about 20% cobalt, and the remainder substantially iron; the essential elements being carbon, chromium, nickel, molybdenum, tungsten, columbium and iron; the carbon, chromium, nickel, molybdenum, tungsten, and columbium being essential in the proportions stated.

3. An improved, inexpensive, essentially ferritic-magnetic, heat resistant alloy that will withstand temperature variations and that has a better corrosion resistance at high temperatures without an excessive loss of strength, said alloy containing below about 1% carbon, about 1226% chromium, about 3-7% nickel, the elements molybdenum, tungsten and columbium in 1*- a total amount of not less than about 1.2% and up to a total amount of substantially less than 6%, up to about 2.5% of each of the elements manganese and silicon, up to about 25% nitrogen, up to about cobalt, and the remainder substantially iron; the essential elements being carbon, chromium, nickel, molybdenum, tungsten, columbium, and iron.

4. An improved, inexpensive, heat resistant, austenitic alloy that will withstand temperature variations and that has a better corrosion resistance at high temperatures without an excessive loss of strength, said alloy containing" below about 1% carbon, about 12-26% chromium, about 7-20% nickel, the elements molybdenum, tungsten, and columbium in a total minimum amount of not less than about 1.2% and up to a total amount of substantially less than 6%, up to about 2.5% of each of the elements manganese and silicon, up to about nitrogen, and the remainder iron; the essential elements being carbon, chromium, nickel, molybdenum, tungsten, columbium and iron.

5. An improved, inexpensive, heat resistant alloy that will withstand temperature variations and that has a better corrosion resistance at high temperatures without an excessive loss of strength, said alloy containing carbon within the range of about .05-1%, about 12-30 %"'chromium, about 3-20% nickel, about .50-2% of each of the elements molybdenum and tungsten, about .202% columbium; the molybdenum, tungsten,

and columbium being in a maximum total amount of substantially less than 6%, about 20-25% manganese, up to about 2.5% maximum silicon, up to about 25% nitrogen, and the remainder iron; the elements carbon, chromium, nickel, molybdenum, tungsten and columbium"- 81 20% nickel, the elements molybdenum, tungsten and columbium in a total minimum amount of 5 about 1.2% and up to a total amount of substantially less than 6% and in substantially equal proportions, up to about 2.5% of each of the elements manganese and silicon, up to about .25% of nitrogen, and the remainder iron; the essential elements being carbon,

containing below about 1% carbon, about 12 to chromium, about 3 to 7% nickel; molyb f denum, tungsten and columbium in a minimum. total amount of about 1.2% and'up' to'a'total 20 amount of substantially less than 6%, and the remainder substantially iron; the essential ele- -'ments being carbomchromium, nickel, molybdenum, tungsten, columbium and iron;' and, with" usual commercial amounts of the elements man.-

25 ganese and silicon.

GUNTI-IER MOELINGJ THOMAS Y. WILSON.

REFERENCES CITED The following references are of record in the file of this patent: UNITED STATES PATENTS Number Name Date 2,229,065 Franks 'Jan. 21, 1941' 2,397,034 Mohling Mar. 19, 1946 2,398,702 Fleischmann Apr. 16, 1946' 2,416,515 Evans Feb.,25, 1947" 2,429,800 Briggs Oct. 28, 1947 40 2,432,615 Franks Dec. 6, 1947 OTHER REFERENCES Progress Report on Heat Resisting Metals for Gas Turbine Parts (N-102), P. B. 39579; by the 5 War Metallurgy Division, National Research Defense Committee. Published September 21, 1943; declassified February 18, 1946, Y

chromium, nickel, molybdenum, tungsten and columbium in lo the proportions stated. 8. An improved, inexpensive, essentiallyier ritic-magnetic, heat resistant alloy that will withstand temperature variations and that has a, better corrosion resistance at high temperatures 15 without an excessive loss of strength, said alloy

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