US2087336A - Ferrous alloy - Google Patents

Description

July 20, 1937. K. s. sl-:LJl-:sAE'rl-:R

FERROUS ALLOY Filed March 20, 1930 awa aan aan Patented July 20, 1937 UNITED STATESPATENT OFFICE FERROUS ALLOY Kaare S. Seljesaeter, Chicago, Ill., assigner to.

Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application March 20, 1930, Serial No. 437,317

11 Claims. (Cl. 14S-21.5)

'I'his invention relates tov ferrous alloys and methods of producing the same, and more particularly to alloys of iron with titanium, and to methods of treating such alloys so as to produce certain desirable mechanical and magnetic characteristics.

An object of the invention is to provide an alloy in which certain desirable physical and magnetic properties are4 produced by special treatment.

In accordance with the general featuresof the invention as embodied in one specific form thereof, a quantity of iron, preferably substantially free of carbon, is alloyed with titanium and the mass is then cast in the form of ingots, which are then formed by forging or other means into any desired shape, or such shapes may if desired be formed directly from the molten metal. The forgings are then heated to a temperature just below the eutectic point of-the alloy, andthis temperature is maintained for a suftlciently long period of time to cause substantially all of the resulting solute constituentl to enter solution in the iron, and the alloy is then quenched at a sufficiently rapid rate to cause the solute constituent to remain in the iron in the form of a supersaturated solid solution, after which the alloy is caused to assume a more stable state by aging. The hardness of the alloy as quenched may be increased by more than 200 percent by such aging, and the secondary hardness is retained even at elevated temperatures. In the manufacture of articles such as dies or permanent magnets from an alloy of the type just described, an article may be forged or otherwise formed from the alloy and the formed article then subjected to the above outlined heating, cooling, and aging operations.

The above described and other objects and features of the invention will be apparent from the following detailed description, taken in connection with the accompanying drawing, in-

f with its physical hardness.

Although it is not known with certainty what the solute constituent of the alloy is, it is believed that the titanium combines chemically with a part of the iron to form iron'titanid FesTi, which enters into solid solution in the remainder of the 5 iron and may under certain conditions be precipitated in the form of microscopic or submicroscopic particles dispersed throughout the alloy. The various steps constituting the processes described below are the same regardless of whether the titanium is dissolved in the iron as titanium or as a compound, and it is to be understood, therefore, that in the following description and appended claims the term "solute constitucnt may include titanium either combined or uncombined as the case may actually be.

In practicing one method of producing alloys in accordance with the invention,'a quantity 'of titanium greater than that which will enter solid solution in iron at room temperature, but not substantially more than is soluble at the eutectic temperature, (3% -to 9% of titanium) is alloyed with iron and the resulting alloy'ls caused .to solidify. The alloy is then heated at a temperatur of about 1200 to 1300 C. until a substantially homogeneous solid solution is formed, and is then quenched at a rate sufficiently rapid to cause most or all of the titanium to be retained in the iron in the form of a supersaturated solid solution, and the alloy is subsequently aged at a temperature of about 600 C. or upwards.

The proper length of time and temperature of the solution forming step, quenching or supersaturating step, and the aging step, wherein the alloy is allowed to assume a more stable state, 5 together with the proper proportions of iron and alloy ingredient, will vary with the properties desired in the alloy and the uses to which the alloy is to be put. However, the following example has been found to produce a satisfactory alloy for 40 permanent magnets. To 93 parts of substantially carbon-free iron is added 7 parts of titanium, preferably in the form of an iron-titanium alloy rich in titanium, and the two ingredients are agitated in any known manner while in the molten state to produce ahomogeneous alloy. The alloy is then cast into ingotsv and fabricated into desired shapes, which are then brought to a temperature just below the eutectic temperature, and maintained at such temperature for a sufficient 5 time to produce a solid solution of the titanium in the iron. The parts are then quickly cooled by quenching, thus producing a solid solution of the solute constituent in the iron. The parts are then heated to about '100 C., and maintained at 55 5 treatment, will be found to have a magneticv remanence and coercive force higher than that of iron-titanium alloys heretofore produced, and Ais suitable for use in permanent magnets.

Referring to the drawing, curve B of Fig. 1 and curve E of Fig. 2 indicate the magnetic remanence obtained by treating the alloy at various temperatures and subjecting the parts to a magnetizing force of 1000 gilberts per centimeter, while the coercive force is indicated in curves C and F respectively. Both these characteristics reach a maximum when the alloy is aged at about 700 C. In order to obtain the maximum mechanical hardness, the alloy may be aged at a temperature of about 600 C'. as will be seen from an examination of curves A and D. An alloy aged at the latter temperature is suitable for use in dies for die casting machines and for analogous uses since it is capable of withstanding high temperatures without losing its hardness.

Alloys produced in accordance with the process lherein disclosed may be used for a variety of other purposes, and it is Within the scope of this invention to add to the alloy such other ingredients as may be found desirable to adapt the alloy to the special purpose to which it is to be put. Thus,cobalt, tungsten, molybdenum, manganese, nickel. and vanadium may be incorporated in the alloy in addition to the titanium to produce ternary and quaternary alloys having such special properties as are necessary to meet special requirements.

It is to be understood that the invention is not limited to the embodiments above described, but that it may be embodied in other forms, and is not to be limited except by the terms of the appended claims.

What is claimed is:

1. A magnet formed of an age-hardened sub- 45 stantially carbon-free iron-titanium alloy containing substantially 5% of titanium.

2. The process of producing a magnet which comprises heating a binary alloy containing substantially 5% of titanium and the balance iron 50 to an elevated temperature below its melting point, but suiciently high to cause the titanium to go into vsolution with the iron, quenching the alloy, reheating the alloy to a temperature below that of the initial heating, but sufficiently high and for a period of time sufcient to obtain a substantial increase in the magnetic hardness of the alloy, and magnetizing the alloy to render it permanently magnetic.

3. A magnet formed of a precipitation-hard- 60 ened substantially carbon-free binary alloy of iron and titanium containing from about 3% to about 9% of titanium.

. 4. The process of making a magnet of a. binary alloy consisting of from about 3% to about 9% 65 of titanium and the balance iron, which comprises heating the alloy to an elevated temperature below its melting point but sufficiently high to cause the titanium to go into solid solution with the iron, quenching the alloy, reheating the alloy at substantially the temperature below that of the initial heating at which the maximum magnetic hardness of the alloy is obtained for a period of time suicient to produce a substantial improvement in the magnetic hardness thereof, and magnetizing the alloy to render it permanently magnetic.

5. A magnet formed of a precipitation-hardened substantially carbon-free iron-titanium a1- loy containing from vabout 3% to about 9% of titanium.

6. A magnet formed of a precipitation-hardened iron-titanium alloy which may contain minor amounts of other usual iron alloying ingredients, and from about 3% to about 9% titanium.

7. A magnet formed of a precipiation-hardened iron-titanium alloy containing from about 3% to about 9% titanium and having a coercive force of over 30 gilberts per centimeter.

8. A magnet formed of a precipitation-hardened iron-titanium alloy which may contain minor amounts of other usual iron alloying ingredients and from about 3% to about 9% titanium, and having a coercive force of over 30 gilberts per centimeter.

9. A method of making a magnet which comprises heating an iron-titanium alloy containing from about 3% to about 9% of titanium to an elevated temperature below its melting pdint but suiiiciently high to cause the age-hardening element to go into solution with the iron, quenching the alloy, reheating the alloy to a temperature below that of the initial heating, but suiiiciently high and for a period of time suilicient to obtain a substantial increase in the magnetic hardness of the alloy, and magnetizing the alloy to render it permanently magnetic.

10. A method of making a magnet which comprises heating an iron-titanium alloy, containing from about 3% to about 9% of titanium and which may contain minor amounts of other usual iron alloying ingredients, to an elevated temperature below its melting point, but sufriciently high to cause the age-hardening element to go into solution with the iron, quenching the alloy, reheating the allo-y to a temperature below that lof the initial heating but suiiciently high and for a period of time sufficient to obtain a substantial increase in the magnetic hardness of the alloy, and magnetizing the alloy to render it permanently magnetic.

11. A method of making a magnet which comprises heating an iron-titanium alloy containing from about 3% to about 9% of titanium to an elevated temperature below its melting point but sufficiently high to cause a hardening constitue'nt to go into solid solution with the iron, quenching the alloy, reheating the alloy at substantially the temperature below that of the initial heating at which the optimum magnetic properties are obtained for a period of time sufficient to produce a substantial improvement in the magnetic properties of the alloys, and magnetizing the alloy to render it permanently magnetic.

KAARE S. SELJESAETER.

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