US3284191A - Nickel-aluminum alloy steel for production of gears, steel plate and the like - Google Patents
Nickel-aluminum alloy steel for production of gears, steel plate and the like Download PDFInfo
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- steel plate is a significant tonnage item in industry as a constructional material (including forms derived from plate), it would be thus most advantageous to also provide an alloy steel capable of manifesting prop erties which would enable it to be used in the form of steel plate and the like and thus lend versatility and diverse use to its role of application.
- an optimum combination of properties can be achieved with tempaging steels having compositions (based on weight percentage) within the following most advantageous ranges: 0.04% to about 0.16% carbon, about 5%, and preferably about 6%, to 10% nickel, at least 0.7%, and preferably at least 0.8%, and up to about 1.1% aluminum, about 0.75% to about 1.5% molybdenum, up to 1% chromium, manganese in an amount up to not more than about 0.3%, silicon in an amount up to not more than about 0.3% and the balance essentially iron.
- a tempaging period of up to 30 hours or more can be used, but it is advantageous to avoid prolonged tempaging periods and 2 to 10 hours is quite satisfactory.
- a tempering action which induces a softening response and a precipitation action which induces an opposed hardening reaction.
- a slight tempering effect occurs but there is an insuflicient aging response.
- temperatures of about 1050" F. and above, e.g., 1100 F. a greater degree of tempering coupled with overaging occurs and this provides a softening effect.
- the steels can be air-cooled from the austenitizing temperature as opposed to liquid quenched. This is particularly applicable with regard to the alloy steels having higher nickel contents,
- Table II illustrates that yield strengths of up to about 200,000 p.s.i. together with impact strengths of up to 50 ft.-lbs. (and even much higher) can be attained in accordance with the invention.
- yield strengths of up to about 200,000 p.s.i. together with impact strengths of up to 50 ft.-lbs. (and even much higher) can be attained in accordance with the invention.
- air-cooling techniques can be utilized as noted hereinbefore, particularly with respect to steels containing at least 7% nickel, e.g., 7.5% to 10% nickel, and yield strengths of the order of 150,000 p.s.i. and higher can still be attained. This is illustrated by the data in Table VII which pertains to steels which were air-cooled from an austenitizing temperature of 1600 F. and then aged at 1000 F. for 2 hours.
- Rockwell hardnesses of at least Re 37 and up to at least Rc 43 which comprises heating a low alloy tempaging steel containing 0.04% and up to not more than 0.25 carbon, at least 4.5 and up to 10% nickel, at least 0.6% and up to about 1.2% aluminum, the ratio of nickel to aluminum being at least 5 to 1, about 0.5% to 2% molybdenum, up to 1.5% chromium, manganese in an amount up to 0.5%, silicon in an amount up to 0.5%, up to 5% cobalt, up to 2% copper and the balance essentially iron to a temperature of about 1550 F. to about 1700 F., cooling said alloy steel, reheating said alloy steel to a temperature of about 950 F. to 1125 F. and thereafter cooling said steel.
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Description
United States Patent M 3,284,191 NlCKEL-ALUMINUM ALLEY STEEL FUR PRODUC- TIUN 0F GEARS, STEEL PLATE AND THE LIKE Peter Paul Hydrean, Mahwah, Damian Vincent Gullotti, Jersey City, and John Trirnhle Eash, Allendale, N.J., and Ralph Bertram Grenville Yeo, Pittsburgh, Pa., assignors to The International Nickel Company, lino, New
York, N.Y., a corporation of Delaware No Drawing. Filed Feb. 9, 1966, Ser. No. 526,034 13 Claims. (Cl. 75l124) This is a continuation-in-part of application Serial No. 306,340, filed September 3, 1963, now abandoned.
The present invention relates to low alloy, precipitation-hardenable steels, and more particularly to low alloy, nickel-aluminum tempaging steels (i.e., steels which undergo a tempering reaction and, simultaneously therewith, a precipitation-hardening reaction upon heat treatment) of special composition which manifest an improved combination of properties, including strength, hardness and toughness, of such magnitude that the steels are eminently suitable for diversified use, such as plates, gears, dies, etc.
Within the past decade, substantial improvements have been made with regard to the low alloy, precipitationhardenable steels. In particular, the nickel-aluminum class of such steels, to wit, those referred to as the Ni-2% Al steels, have been advanced as particularly attractive for the production of gears and dies as a result of their capability of being produced within close dimensional tolerance upon hardening. That is to say, such steels, in contrast to many of the low alloy quenched and tempered steels, harden with minimum distortion or warping and this attribute is notably beneficial in processing the steels to gears and the like. Some of the salient virtues of such steels are succinctly set forth by J. B. Seabrook in an article entitled Properties of Ni-AlAge- Hardening Steel, Metal Progress, vol. 79 (1961), pages 80 through 84. The author summarizes the 5% Ni-2% Al steel as providing moderate material cost, low processing cost, good forgeability and machinability, low distortion, strengths similar to conventional steels and age hardnesses up to Rockwell C53 and confirms that such steels possess good machinability at relatively high intermediate hardness levels, i.e., such steels can be readily finish-machined prior to final hardening which, of course, eliminates or minimizes the considerable difficulties encountered in machining steels in the fully hardened condition.
However, a serious drawback characteristic of the foregoing 5% Ni-2% Al steels has been their lack of high toughness at desired strength and hardness levels. What is presently needed is a low alloy steel of the nickelaluminum type capable of providing characteristics comparable to those aforementioned including hardnesses of about Re 40 or higher, yield strengths of up to 200,000 pounds per square inch (p.s.i.), e.g., 150,000 to 200,000 p.s.i., etc., but with impact energy levels of at least 20 foot-pounds (ft-lbs), e.g., 25 ft.-lbs. and higher, at room temperature as determined by standard Charpy V-Notch procedures. This desideratum has presented a formidable barrier to commercial development and application.
The 5% Ni-2% Al steels disclosed in US. Patent No. 2,708,159 indeed represent a significant improvement over what had been accomplished theretofore. In accordance therewith, it was considered that the amount of carbon had to be correlated to the nickel and aluminum contents expressed by the stoichiometric relation NiAl. However, the steels disclosed therein had an average Charpy Keyhole Notch impact value only on the order of about 9 or 10 ft.-lbs. on bar specimens. As indicated in that patent, it is necessary for such steels to possess 3,284,191 Patented Nov. 8, 1966 a hardness of about 40 or above as measured on the Rockwell C (Re) scale to qualify as good gear steels. Indeed, such hardnesses were attained, but not with a high level of toughness. The nickel-aluminum steels advanced in US. Patent No. 2,715,576 (the illustrative steels therein having nickel and aluminum contents of about 3.6% and about 1.2%, respectively, i.e., a ratio of nickel to aluminum of about 3 to 1) are also afflicted with the same disadvantage, i.e., low toughness. In this latter patent it was considered that a special heat treatment prior to aging together with the utilization of a strong carbide former, to wit, vanadium and/or colurnbium and/ or titanium, was necessary, the amount of the carbide former being related to the carbon content. We have found that the approaches to the problem as set forth in the aforementioned patents markedly diifer from the concepts of the present invention. Perhaps it can be said that the nickel-aluminum steels proposed heretofore have been preordained with a lack of good toughness at high strength levels, a fact seemingly confirmed by the data presented in the above-mentioned article by J. B. Seabrook.
A further notable disadvantage of the aforementioned prior art 5% Ni-2% Al steels is their lack of versatility for diverse application. That is to say, such steels have been somewhat restricted to considerations involving nitrided parts, e.g., gears. Seemingly, this aspect evolves from the insufficient toughness which is characteristic of such steels, a lack of toughness which would, as a practical matter, commercially minimize (it not preclude) their use as a structural alloy steel in the form of, say, plate. Since steel plate is a significant tonnage item in industry as a constructional material (including forms derived from plate), it would be thus most advantageous to also provide an alloy steel capable of manifesting prop erties which would enable it to be used in the form of steel plate and the like and thus lend versatility and diverse use to its role of application.
The problem of providing high toughness together with other desired properties in steels of the type under consideration is one of particular severity for a variety of rather complicated and interrelated factors. For example, in the type of alloys in question, there is a basic hardening reaction occurring in the formation of a precipitating phase at the age-hardening temperature. Concurrently and in competition therewith, there is a tempering (softening) reaction. In other words, this overall combined reaction, referred to herein as tempaging, involves two competing forces which, to a degree, tend to oppose the effect of each other. In addition, the picture is further complicated by the nature of the initial transformation product formed during cooling from the austenitizing temperature and the effects of the hardening reactions on the properties of the transformed matrix. Together with these factors is the problem attendant the formation of complex carbides and the combined influences of the elements in solid solution.
In approaching this complex problem, it was thought that by varying heat treatment conditions (particularly the rate of cooling) with regard to nickel-aluminum steels heretofore proposed, a practical solution might be achieved. It was found that by furnace cooling at a rate of about 300 F. per hour from a solution treating temperature of about 1275 F., Charpy V-Notch impact energies of only about 10 ft.-lbs. could be obtained together with Rockwell hardnesses of Re 43. Furnace cooling at a rate of F. per hour from the same solution treatment temperature resulted in an increase in impact energy to about 16 or 17 ft.-lbs.; however, yield and tensile strengths were adversely affected. Since one of the virtues of the type of steel under consideration is its insensitivity to distortion or warping upon age hardening, this approach (utilization of a slow furnace cool) was considered inappropriate from a commercial and economic viewpoint particularly since it did not appear that sufliciently high levels of impact inergy could be attained. In addition, slow cooling rates merely served to prolong the period of heat treatment and this is also unattractive from the commercial viewpoint.
Although attempts were made to overcome the foregoing difficulties and other difiiculties, none, as far as We are aware, was entirely successful when carried into practice commercially on an industrial scale.
It has now been discovered that low alloy, nickel-aluminun, tempaging steels containing special and correlated amounts of carbon, nickel, aluminum, molybdenum, chromium, silicon and manganese can be provided whereby toughness levels are achieved of a magnitude substantially greater than that heretofore attained with nickelaluminum steels heretofore proposed, i.e., those set forth in the patents referred to above. This marked improvement can be obtained without a concomitant detrimental loss of strength and hardness. Perhaps it is worthy to mention at this point that the presence of the element tin should be avoided or kept to very low levels as will be further detailed since it has been discovered that tin is a potent performer in adversely affecting toughness. Further, we have found that by overaging steels within the invention, a highly satisfactory and most expedient method is provided for achieving desired combinations of properties, particularly in steel plate of substantial section size. In addition, alloy steels contemplated herein can be air cooled (as distinct from liquid quenching) prior to aging and a satisfactory combination of properties can be achieved.
It is an object of the present invention to provide new and improved low alloy, nickel-aluminum tempaging steels.
Another object of the invention is to provide low alloy, nickel-aluminum steels which undergo a tempaging reaction during heat treatment and which are characterized by a combination of impact energy, hardness and strength manifestly superior to that heretofore characteristic of what might be considered as comparable steels.
The invention also contemplates providing low alloy, nickel-aluminum, tempaging steels capable of exhibiting Charpy V-Notch impact energies of up to at least 50 ft.- lbs. at hardnesses of up to about Re 43 together with yield strengths (0.2% offset) of up to approximately 200,000 p.s.i., e.g., 150,000 p.s.i. to 195,000 p.s.i.
It is also an object of the invention to provide a special heat treating process for accomplishing the foregoing.
It is a further object of the invention to provide low alloy, nickel-aluminum tempaging steels characterized by properties which render them eminently suitable in the form of steel plate as well as nitrided parts such as gears and the like.
Other objects and advantages will become apparent from the following description of the invention.
In accordance with the invention, an optimum combination of properties can be achieved with tempaging steels having compositions (based on weight percentage) within the following most advantageous ranges: 0.04% to about 0.16% carbon, about 5%, and preferably about 6%, to 10% nickel, at least 0.7%, and preferably at least 0.8%, and up to about 1.1% aluminum, about 0.75% to about 1.5% molybdenum, up to 1% chromium, manganese in an amount up to not more than about 0.3%, silicon in an amount up to not more than about 0.3% and the balance essentially iron. Within these ranges high levels of resistance to impact (toughness) of at least ft.-lbs., e.g., ft.-lbs., and up to 50 ft.-lbs. or higher at room temperature as measured in accordance with standard Charpy V-Notch procedures can be achieved together with yield strengths of 150,000 p.s.i. (0.2% offset) and upwards of 200,000 p.s.i. in combination with hardness levels of about Re 37 to Re 43 and higher. In addition, the steels manifest elongation values (measured at a gage length of one inch on 0.252-inch diameter bars) of well over 10%, e.g., 15% to 20%, and reduction of areas of at least 40%. A particular virtue of the steels is that they can be satisfactorily provided in the form of plate as well as for manufacture into gears and dies. In this connection, it is rather unusual to find a steel which is capable of providing the degree of hardness necessary for a gear steel and still manifest a toughness satisfactory for a plate steel. Eminently satisfactory properties can be obtained in steel plate up to thicknesses of 2 inches or more.
A further benefit of the steels in accordance with the invention is that special control of sulfur and phosphorus contents is not necessary in achieving a satisfactory level of properties. However, while up to 0.03% of each of these constituents can be present, it has been found that where optimum toughness is desired (as determined by the capability of the steels to absorb impact energy) the respective amounts of phosphorus and sulfur should not exceed about 0.01%. This applies to'the steels in the form of plate as Well as bar, rod, etc. Although the probability is rather remote, tin which might possibly be picked up if scrap material is used should not exceed 0.005% and most advantageously should be less than 0.003% since this element is a potent subversive to the attainment of desired properties in the steels of the invention, particularly in regard to toughness.
In carrying the invention into practice, it is preferred in achieving an optimum combination of properties that the steels be austenitized within a temperature range of about 1550 F. to 1700 F. and then liquid quenched. If austenitized much above 1700 F., excessive austentite grain growth occurs with attendant loss in toughness. On the other hand, austenitizing temperatures of, say, 1525 F. can result in incomplete transformation to austenite. It is most advantageous to employ an austenitizing temperature range of 1575 F. to 1650 F. Subsequent to quenching, the steels are tempaged at a temperature of 950 F. to about 1050 F. A tempaging period of up to 30 hours or more can be used, but it is advantageous to avoid prolonged tempaging periods and 2 to 10 hours is quite satisfactory. As indicated above herein, there simultaneously occurs a tempering action which induces a softening response and a precipitation action which induces an opposed hardening reaction. Thus, at tempaging temperatures of about 900 F. or below, e.g., 800 F., a slight tempering effect occurs but there is an insuflicient aging response. At temperatures of about 1050" F. and above, e.g., 1100 F., a greater degree of tempering coupled with overaging occurs and this provides a softening effect. However, tempaging temperatures at about 1050 F. and over can be employed to advantage particularly with regard to alloy steels wherein the nickel content is at the high side of the nickel range, e.g., 6.5% or 7% to 9.5% or 10% nickel. Nickel has been found to be a potent hardener and confers a high degree of hardenability to the steels of the present invention. This high degree of hardenability is particularly beneficial for produccing steel plate of substantial thickness (section size). By overaging, to wit, employing a tempaging temperature of 1050 F. or higher, e.g., about 1080 F. or 1100 F. and up to about 1125 F., the hardness (and strength) of the steels will be reduced (at 1050 F. the loss of strength is very slight), but the toughness (impact energy levels) thereof will be appreciably increased. Significantly lowering the nickel content below 6.5% or 7% and thus reducing the hardness in an effort to obtain higher toughness is inappropriate because of the attendant loss in hardenability. Further, by lowering the nickel content it does not at all necessarily follow that the toughness will be enhanced. Accordingly, where intended applications may not require the absolute maximum in hardness and strength but would require the optimum hardenability and toughness, overaging provides a simple and expedient method for accomplishing such an objective. However, the overaging temperature should not exceed 1125 F. because of the danger of incurring retention of 5 excessive austenite. Thus, it is advantageous that the overaging temperature not exceed about 1100 F. Following the tempaging treatment the steels are cooled.
With further regard to the foregoing description of heat treatment, if necessary for a particular application,
e.g., where the configuration of the product to be produced is not conductive to quenching, the steels can be air-cooled from the austenitizing temperature as opposed to liquid quenched. This is particularly applicable with regard to the alloy steels having higher nickel contents,
Le, 7% to 10% and preferably 7.5% or 8% to 10% nickel, and is especially advantageous with regard to steels to be produced in the form of plate. As is known, many of the conventional constructional steels have a yield strength ranging from 30,000 psi. upwards to the order cooling has an additional advantage in that distortion and 30 warping are further minimized.
For the purpose of giving those skilled in the art a better understanding of the invention and/ or a better ap- In accordance In general, the steels were prepared in an induction furnace and processed into ingot form. The ingots were soaked for a minimum of about 2 hours at 2300 F. which was subsequently lowered to 2150" F. Thereafter they were forged to l-inch by 3 /2-inch plate. After forging, the plates were reheated for about /1 hour at 2150 F. and then hot rolled in one pass to a thickness of about inch. The plates were cooled in air to 1800 F. and given a final hot-rolling pass. The resulting plates had a thickness of /2 inch and a width of about 4 inches and were cut into 7-inch lengths. Some ingots were reduced to %-.inch round bar by forging at 2150 F. to 2- inch square bar and hot rolled to 4-inch round bar after heating to 2150 F. subsequent to forging. The round bars (Alloys Nos. 1 to 7 of Table I) 'and. plates (Alloys Nos. 8 to 16 of Table I) were machined to 0.252-inch diameter specimens and subsequently subjected to test. The heat treatment consisted of austenitizing at about 1600 F. for about 1 hour, water quenching, tempaging at about 1000 F. for about 2 hours and air cooling. The properties obtained are set forth in Table 11 wherein the 0.2% offset yield strength (Y.S.) and ultimate tensile strength (U.T.S.) are given in thousands of pounds per square inch (K.S.I.), the average Charpy V-Notch (C.V.N.) values obtained using standard procedures (longitudinal direction) are given in foot-pounds (ft-lbs). the elongation values are given in percent (Elong. percent) and represent the measurements taken using a gage length of 1 inch, the reduction of area is given in percent reduction in area (RA. percent) and the Rockwell hardness as measured on the C-scale (Re) is given for the values obtained both prior to and after tempaging (Re 501., Rc aged, respectively).
TABLE 11 Alloy No. Y.S U.T.S., C.V.N Elong., R.A., Re Re k.s.1 ksi. ft.-lbs Percent Percent Sol. Aged 195 203 50 1G 65 39 43 185 191 54 17 no 41 166 172 98 21 71 38 38 178 185 32 18 69 39 41 192 199 27 17 G7 42 4 1 187 194 25 16 70 36 44 159 168 69 18 67 38 152 160 71 19 68 37 173 186 47 17 64 41 1% 205 30 14 59 34 193 202 27 15 62 33 45 200 212 28 16 45 178 184 35 15 63 42 203 33. 5 16 65 39 43 185 191 35 17 (16 39 41 166 172 62 21 71 38 38 preciation of the advantages of the invention, the following illustrative data are given:
A series of steels were prepared having compositions as 55 given in Table I.
i TABLE I Table II illustrates that yield strengths of up to about 200,000 p.s.i. together with impact strengths of up to 50 ft.-lbs. (and even much higher) can be attained in accordance with the invention. The results obtained from Al, Mo, Cr, Mn, Pcr- Per- Percent cent cent Ni, Percent Alloy N 0.
cent
1 Balance essentially iron with sulfur not exceeding about 0.004% and phosphorus not exceeding about 0.003%.
both the round bar and plate material were very satisfactory. A comparison of round bar and plate results is afforded by Alloys Nos. 1 and 14, 2 and 15 and 3 and 16, which pairs of alloy steels are of the same composition.
TABLE III Alloy No. 0, Ni, A1, Mo, Cr, Mn, Si, Y.S., C.V.N.,
percent percent percent percent percent percent percent K.S.I. 1t.-ll s.
As indicated hereinbefore, it is rather diflicult and perhaps hazardous to assess the attributes of each of the individual elements; however, nickel exerts a pronounced hardenability and strengthening efiect without a concomitant deleterious loss in toughness. Lowering the nickel content adversely affects strength without an appreciable increase in toughness. The nickel content should not be less than 4.5% and the amounts of nickel and aluminum must be correlated such that the amount of nickel is at least five times the aluminum content if a 15 Since steels within the invention and which contain about 7.5 nickel or more are relatively immune to fluctuation in carbon content as above-noted, it is thus most advantageous to employ low carbon contents, e.g., 0.04% to 0.1%, to obtain the optimal regarding weldability characteristics. As is known, an attendant characteristic of high carbon contents is the increased difficulty in achieving good weldability. Accordingly, low carbon contents are quite beneficial. However, carbon does contribute to hardenability and strength and this is most pronounced good combination of properties is to be achieved. The t ni k l l v ls below Thus, the Carbon Content data in Table 11 further illustrate that if a hardness level hould not be lower than 0.04% If a SatlSfaCtOIY of Re or higher is necessary, a nickel content of over Pmatlon of P p 15 to be Obtfllned- Broadly p 5%, e.g., 6% or higher, is most advantageous, parti mg, the carbon content should not exceed 0.25%; otherlarly if amounts of the other elements, notably aluminum 3O W156 can E? f f y affected- FOr Optimum and molybdenum, at the lower end of their ranges ar machinabilrty and fa rlcabllity, the carbon content should not exceed about 0.2%, and, most advantageously, should employed d h h not exceed 016% a e wit t e invenion The role carbon i gg 61a Siml behavior as The respective amounts of aluminum, molybdenum, fioes not at a necessan i S b t 1 n manganese and silicon have also been found to be im- 1 Xample, the queue e an tempere car on s ee ortant in accordance with the invention. Thus, the alu- That is to say, 1t does not necessarily follow that by uti minum content Should not exceed 12% and While 12mg low carbon to, say, (108%, amounts of aluminum as low as about 0.6% can be an increase 1n toughness Wlll. be achieved. In fact, and employed, it is most advantageous that a range of 0.7% in accordance with the invention, at nickel contents above 40 o 0.8% t 1 1% l i b d, Si the steels about 7%, e.g., 7.5% to 10%, the steels of the invention of the present invention are tempaging steels, if the when liquid quenched from austenitizing temperatures, amount of aluminum is appreciably lower than 0.6%, are virtually insensitive, as a practical matter, to carbon e.g., 0.3% or 0.4%, the tempering effect can greatly over TABLE IV Alloy No. 0, Ni, A1, Mo, Cr, Mn, Y. s., C.V.N.,
percent percent percent percent percent percent percent K.S.I. it.-lbs.
Aluminum Effect Chromium Efiect Manganese Efiect Silicon Eflect 1 While manganese lowers toughness as the amount is increased, the general level of toughness for Alloys Nos. 31, 32 and 33 was generally low because those Alloys contained 0.012%, 0.012%, and 0.011% of tin, respectively.
shadow the hardening effect and this brings about a rather severe loss in strength. On the other hand, significant 10 (longitudinal direction) were determined at room temperature.
TABLE V Alloy No. 0, Ni, Al. M0, Cr, Mn, S1, Y. S., C.V.N.,
percent percent percent percent percent percent percent K.S.I. ft.lls.
Mn and Si were below 0.2% and 0.25% respectively. Balance iron and impurities.
amounts of aluminum above 1.2%, e.g., 1.5% and higher,
In addition to the data in Table V, it might be menare afflicted with quite a consequential eifect on toughness. troned that With a plate thickness of the order of, say, Molybdenum is essential in obtaining necessary strength /2 inch, the influence exerted by phosphorus and sulfur levels and to resist temper embrittlement but toughness is is generally more pronounced with regard to toughness. impaired if the amount of molybdenum is excessive. This is deemed attributable to the faster cooling rate This is particularly significant when the molybdenum obtained in respect of a K2 inch plate as opposed to that content exceeds about 1.5%. An increase in molybmanifested in respect of a plate 4 inches thick. A subdenum above 1.5 other factors being equal, does not stantially complete martensitic structure results with the result in an appreciable increase in strength, but toughfaster cooling rate whereas with a section size of 4 inches ness is rather strongly atfected. While the molybdenum an appreciable amount of bainite is also present. As becontent can be present in an amount up to 2%, an optitween the two structures, the former is thought to exhibit mum combination of properties is achieved if it is maina greater susceptibility to loss of toughness. tained at a level of not more than about 1.5 In addi- It has been previously pointed out above herein that tion, the amount of molybdenum should not be lower where desirable, overaging can be employed to achieve than 0.5%; otherwise, the strength of the steels is sigenhanced toughness particularly with regard to steels of nificantly impaired. A molybdenum range of 0.75% or the invention having nickel contents of 7% to 10.0%. 0.8% to 1.5% has been found to be the most effective. This is illustrated by the data in Table VI. In this con- The amounts of manganese and silicon should not exnection, the steels (plate stock) were austenitized for 1 ceed 0.5% and preferably should not exceed about 0.3%. hour, liquid quenched and Fagfid at 1000 f 2 ur High amounts of these elements have been found to have (H at Tr atm HTfA) or aged at 1050 F. for 2 an adverse effect on toughness. hours (Heat Treatment, H.T.B) or aged at 1100 F.
Where high hardenability is desired, it is advantageous for 2 hours (Hea Treatment,
TABLE VI Alloy 0. Per- Ni. Per- Al, Per- M0, Per- Cr, Pen Mn. Per- Si, Per- FLT. Y.S., C.V.N N0. cent cent cent cent cent cent cent K.S.I. ft.-lbs.
0.00 7.05 0.81 0. 93 0.10 0.19 0.17 A 173 47 B 105 52 41 0. 04 7. a 0. 97 1. 0 0. 2 0.1 A 102 27 C 158 00 42 0.10 7.52 1.10 1.10 0.12 0. 21 0 a A 200 28 B 190 29 43 0. 04 9.8 0. 91 0.75 0. 2 0.1 A 188 31 o 148 75 1 Water quenched from austenitiniug temperature. 2 Oil quenched from austenitizing temperature.
The general eifects of aluminum, molybdenum, manganese, silicon and chromium on yield strength and toughness are reflected in Table IV for alloys Nos. 21 through 34 which were treated in the manner described in connection with Tables I and II.
As indicated above herein, in providing steels characterized by maximum toughness it is most advantageous that the levels of phosphorus and sulfur not exceed about 0.01%. This is illustrated by the data of Table V. In this connection, 8 plate specimens each /2 inch thick were stacked in a suitable fixture and water quenched. This was done to simulate the expected cooling rate of a steel plate 4 inches in thickness. pared by vacuum induction melting (30 lb. melts) followed by forging and hot rolling to plate, the finishing temperature being about 1800 F. The steels were austenitized at 1600 F. (held 1 hour), water quenched and individually tempaged at 1050 F. for about 2 hours and then cooled. The Charpy V-Notch impact values The steels were pre- The results set forth in Table VI reflect that a high level of toughness can be achieved by overaging. Of course, as will be understood by those skilled in the art, the overaging temperature cannot be selected indiscriminately if the attributes of overaging are to be obtained. This is purposely manifested by a comparison of Alloys Nos. 42 and 41 which have similar compositions. Alloy No. 42 aged at 1050 F. did not exhibit much by way of increased toughness and the strength level remained about the same. This indicates that at 1050" F. Alloy No. 42 was at about its peak aging temperature, i.e., at 1050 F. little overaging occurred. Alloy No. 41 afforded a tremendously higher level of toughness when aged at 1100 F. and the yield strength was still over 150,000 p.s.i. However, if a better balance of strength and toughness would be necessary for such steels, it can be obtained with an intermediate overaging temperature of 1075 F. Thus, as referred to herein, overaging affords a simple expedient for achieving desired combination of properties without sacrifice of hardenability and is particularly beneficial in providing steel .plate of substantial thickness without loss of through hardening.
If, upon austenitizing, liquid quenching cannot be em ployed, air-cooling techniques can be utilized as noted hereinbefore, particularly with respect to steels containing at least 7% nickel, e.g., 7.5% to 10% nickel, and yield strengths of the order of 150,000 p.s.i. and higher can still be attained. This is illustrated by the data in Table VII which pertains to steels which were air-cooled from an austenitizing temperature of 1600 F. and then aged at 1000 F. for 2 hours.
ganese in an amount up to 0.5%, silicon in an amount up to 0.5%, up to 5% cobalt, up to 2% copper and the balance essentially iron.
2. As a new article of manufacture, a steel plate made from the alloy steel set forth in claim 1.
3. The alloy steel as set forth in claim 1 wherein the carbon is present in an amount not exceeding 0.2%.
1 Bar, 0.75 inch diameter. 2 Plate, 0.5 inch thick.
It is perhaps worthy of mention, that when the nickel content is between about 7% and up to about 7.5% and air cooling is employed, it is advantageous that the carbon content be at least 0.08%, e.g., 0.1% to 0.15% carbon. Carbon does contribute to hardenability and strength in a more pronounced manner for the air-cooled steels as compared with quench steels. It should also be noted that air cooling a 0.5-inch thick plate is approximately equivalent to water quenching a plate 6 inches in thickness. This aspect coupled with the data in Table VII serves to emphasize that plates of substantial thickness can be provided with a high degree of hardenability.
In view of the excellent combination of mechanical properties characteristic of the low alloy tempaging steels Within the invention, the steels are suitable for wide commerical application including structural members, e.g., girders and beams, pressure vessels, high strength forgings including aircraft undercarriage forgings, fluid storage containers, armor plate, etc., as well as for dies and nitrided parts, e.g. gears, etc.
As will be readily understood by those skilled in the art, the term balance or balance essentially when used to refer to the iron content of the steels does not exclude the presence of other elements commonly present as incidental elements, e.g., deoxidizing and cleansing elements, and impurities ordinarily associated therewith in amounts which do not adversely affect the basic characteristics of the steels. Up to 5% cobalt and up to 1.5% or 2% copper can be present in the steels of the invention. Tungsten can be used to replace the molybdenum in whole or in part; however, molybdenum is significantly more elfective than tungsten and it is thus preferred to use the former. Carbide formers such as vanadium, columbium, and titanium are quite unnecessary and, more importantly, the use of these elements has been found to be causative of detrimental embrittling effects.
Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. lSuch modifications and variations are considered to be Within the purview and scope of the invention and appended claims.
We claim:
1. A novel, low alloy tempaging steel characterized in the aged condition by a yield strength of up to about 200,000 p.s.i., a Rockwell hardness of at least about Rc 37 and up to at least Re 43 and a Charpy V-Notch impact energy level of about at least 20 ft.-lbs. and having a composition within the following ranges: 0.04% and up to not more than 0.25% carbon, at least 4.5% and up to 10% nickel, at least 0.6% and up to about 1.2% aluminum, the ratio of nickel to aluminum being at least 5 to 1, about 0.5% to 2% molybdenum, up to 1.5 chromium, man- 4. The alloy steel as set forth in claim 3 wherein the nickel is present in an amount of at least 5% and the aluminum is present in an amount of at least 0.7%.
5. The alloy steel as set forth in claim 1 in which the carbon is from 0.04% to about 0.16%, the nickel is from about 5% to 10%, the aluminum is from about 0.7% and up to not more than about 1.2%, the ratio of nickel to aluminum being at least 5 to 1, the molybdenum is from about 0.75% to about 1.5%, the chromium is up to 1%, the manganese is up to 0.3%, and the silicon is up to 0.3%.
6. As a new article of manufacture, a steel plate made from the alloy steel set forth in claim 5.
7. The alloy steel as set forth in claim 5 wherein the nickel is present in an amount of at least and the aluminum content does not exceed about 1.1%.
8. The alloy steel as set forth in claim 7 wherein the carbon is present in an amount not exceeding about 0.1%.
9. The alloy steel as set forth in claim 5 in which the nickel is from about 7% to 10%, the aluminum is from about 0.8% to about 1.1% and the molybdenum is from about 0.8% to about 1.5%.
10. The alloy steel as set forth in claim 9 wherein the nickel is present in an amount of at least 7.5%.
11. The all-0y steel as set forth in claim 9 wherein the carbon is present in an amount not exceeding about 0.1%.
12. Anew and improved process for heat treating nickel-aluminum tempaging steels to obtain yield strengths of about 150,000 p.s.i. to 200,000 p.s.i. together with Charpy V-Notch impact energy levels of at least 20 ft.-lbs. and up to at least 50 ft.-lbs. and Rockwell hardnesses of at least Re 37 and up to at least Rc 43 which comprises heating a low alloy tempaging steel containing 0.04% and up to not more than 0.25 carbon, at least 4.5 and up to 10% nickel, at least 0.6% and up to about 1.2% aluminum, the ratio of nickel to aluminum being at least 5 to 1, about 0.5% to 2% molybdenum, up to 1.5% chromium, manganese in an amount up to 0.5%, silicon in an amount up to 0.5%, up to 5% cobalt, up to 2% copper and the balance essentially iron to a temperature of about 1550 F. to about 1700 F., cooling said alloy steel, reheating said alloy steel to a temperature of about 950 F. to 1125 F. and thereafter cooling said steel.
13. A novel, low alloy tempaging steel having a composition within the following ranges: 0.04% and up to about 0.2% carbon, at least 4.5 and up to 10% nickel, at least 0.6% and up to about 1.1% aluminum, the ratio of nickel to aluminum being at least 5 to 1, about 0.5 to 2% molybdenum, up to 1.5% chromium, manganese in an amount up to 0.5%, silicon in an amount up to 0.5%, and the balance essentially iron.
No references cited.
DAVID L. RECK, Primary Examiner. C. N. LOVELL, Examiner.
UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,284,191 November 8, 1966 Peter Paul Hydrean et a1.
It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.
Column 3, line 6, for "inergy" read energy lines 14 and 15, for "aluminun" read aluminum column 4, line 35, for "austentite" read austenite lines 61 and 62, for "produccing" read producing column 5, line 12, for "conductive" read conducive columns 7 and 8, strike out "TABLE IV", in its entirety, and insert the same table after "Tables 1 and II." in line 61, column 9; column 11, line 26, for "quench" read quenched lines 34 and 35, for "commerical" read commercial line 69, for "about" read above Signed and sealed this 19th day of September 1967.
(SEAL) Attest:
ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents
Claims (1)
1. A NOVEL, LOW ALLOY TEMPAGING STEEL CHARACTERIZED IN THE AGED CONDITION BY A YIELD STRENGTH OF UP TO ABOUT 200,000 P.S.I., A ROCKWELL HARDNESS OF AT LEAST ABOUT RC 37 AND UP TO AT LEAST RC 43 AND A CHARPY V-NOTCH IMPACT ENERGY LEVEL OF ABOUT AT LEAST 20 FT.-LBS. AND HAVING A COMPOSITION WITHIN THE FOLLOWING RANGES: 0.04% AND UP TO NOT MORE THAN 0.25% CARBON, AT LEAST 4.5% AND UP TO 10% NICKEL, AT LEAST 0.6% AND UP ABOUT 1.2% ALUMINUM, THE RATIO OF NICKEL TO ALUMINUM BEING AT LEAST 5 TO 1, ABOUT 0.5%TO 2% MOLYBDENUM, UP TO 1.5% CHROMINUM, MANGANSES IN AN AMOUNT UP TO 1.5% CHROMIUN, MANTO 0.5%, UP TO 5% COBALT, UP TO 2% COPPER AND THE BALANCE ESSENTIALLY IRON.
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US526034A US3284191A (en) | 1966-02-09 | 1966-02-09 | Nickel-aluminum alloy steel for production of gears, steel plate and the like |
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US526034A US3284191A (en) | 1966-02-09 | 1966-02-09 | Nickel-aluminum alloy steel for production of gears, steel plate and the like |
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Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3475164A (en) * | 1966-10-20 | 1969-10-28 | Int Nickel Co | Steels for hydrocracker vessels containing aluminum,columbium,molybdenum and nickel |
US4146409A (en) * | 1977-06-06 | 1979-03-27 | The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration | Process for making a high toughness-high strength iron alloy |
US4214902A (en) * | 1979-01-25 | 1980-07-29 | The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration | High toughness-high strength iron alloy |
-
1966
- 1966-02-09 US US526034A patent/US3284191A/en not_active Expired - Lifetime
Non-Patent Citations (1)
Title |
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None * |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3475164A (en) * | 1966-10-20 | 1969-10-28 | Int Nickel Co | Steels for hydrocracker vessels containing aluminum,columbium,molybdenum and nickel |
US4146409A (en) * | 1977-06-06 | 1979-03-27 | The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration | Process for making a high toughness-high strength iron alloy |
US4214902A (en) * | 1979-01-25 | 1980-07-29 | The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration | High toughness-high strength iron alloy |
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