US2129346A - Alloy - Google Patents

Description

Patented se ta, 193a UNITED STATES PATENT, OFFICE I "Armor Anthony G. ;de Golyen; New York, N. Y.-

No. Drawing.

Application October 20, 19st, Serial No. 106,515 I I 1 Claim. (CL 75 -123)- Thisinvention relates to a new alloy steel, and relates particularlyto analloy steel containing manganese,-boron and molybdenum.

' The object of this inventipii is to supply a manganese alloy steel which doesnot require thermal treatment to render it commercially useful; which has materially greater resistance to abrasion and impact than the heretoforev known manganese steelsyand, which may be readily repaired-or rebuilt by welding with no adversev effects' on the physical properties 0! the parent'- metal.

Cast manganese steel, containing from 10% to 14 manganese and more than 1% carbon, commonly termed Hadfield steel, has been extensively used for parts of equipment subjected to wear by abrasion and impact. This type a of steel is extremely brittle in the as cast condition owing to the presence of a relatively high percentage of free carbides of iron and manganese. A thermal treatment is necessary to change the structure of the steel, and develop the required tensile,

strength and toughness, Briefly, this treatment comprises slowly heating the cast steel'to a temperature of approximately 1850 degrees F., and 1 maintaining it at such temperature for a protracted period of time to form a solid solution of v the manganese and iron carbides in the iron matrix. When the steel is converted to a substantially austenitic condition it is quenched in water to preventprecipitation of manganese and iron carbides, which occurs when the steel cools at a normal rate.

Properly heat treated steel of this type is characterized by fairly high tensile strength, e. g.,

' 90,000 to 120,000 lbs. p. s. 1., a 10W elastic limit,

but considerable ductility and toughness, and low hardness, i. e., 180 to 200 Brinell.

, Repeated cold work on-the surface of the heat treated-steel effects a material change or structure, apparently causing segregation of the hard I and brittle manganese and iron carbides, with the result that the hardness of such outer layer i's'i'ncreased to from .400 to 480 Brinell. At the point where the hardness approaches the above maximum, the outer layer becomes so brittle that it flakes or chips olI, exposing ciably lower hardness. v The grade of ordinary manganese steel best adapted for use on wearing parts of equipment contains from 12% to '13.5%j manganese and at least one-tenth as much carbon; this ratio of carbon being required. to give to the steel the work hardening characteristic. Some forged manganese steels'contain slightly lessthan 1% metal of apprecarbon, and. while a relatively high tensile strength and toughness can be developed in such steels theywill not'resist abrasive wear to the same degree as the steels containing a higher ratio of carbon. 5 It has been determined that more than 2% manganese in steel acts to appreciably lower the carbon ratioot. the. eutectoid. Consequently, in

- all commercial manganese steel the carbon is above the eutectoid ratio.: When such steel is 10 heated to a temperature of some 700 degrees F., or higher and permitted to-cool at a normal rate in air the autenitic structure is destroyed, and the steel is embrittled. When ordinary manganese steel is welded a portion of steel adjacent 15 to the weld is heated to a temperature sufilciently high to result in reversion of the polyhedral structure to one approximating that of the original casting. For this reason the Hadfield type of steel is not suitable for use as a weld rod, except when the deposited metal and the embrittled parent metal can be properly heated and quenched in water; The disadvantages of this in industrial operations are obvious. l

A steel containing from 2% to 10% nickel, in

addition to the usual amounts of manganese and carbon, has been proposed in an attempt toovercome some of the difficulties of welding manganese steel. In this case nickel functions to form a more stable solid solution of iron and 30 manganese carbides in the iron matrix, and thus inhibit the'precipitation of free carbides when the steel is allowed to cool at a normal rate from elevated temperatures. It has been found, however, that the presenceof an eflective amount of 85 nickel also acts to greatly retard surface hardening of the steel under cold work. Consequently, manganese steel containing nickel does'not resist abrasion as well as ordinary manganese steel, and, for this reason industrial use of the 40 nickel containing, steel is restricted to weld rods.

I have discovered that an alloy containing manganese from approximately 6.25% to 16%, boron 0.25% to'1.75%, molybdenum 0.25% to 5%, carbon from approximately 0.10% to not more than 0.85%, and the balance principally iron, has maternally higher hardness than previously known manganese steels, and that many of the other physical properties and characteristics are also superior.

One distinct advantage of the alloy of the present invention is that it may be used for a wide variety of industrial purposes including wearing parts of equipment, in the as cast conditlon. The cast metal has a minimum hardness for the majority of industrial applications.

of about 525 Brinell. and this is increased from degree of weldability, that is, castings or other 150 to 200 hardness numbers by cold work. The forms of the alloy may be surface or rebuilt to tensile strength, ductility and toughness ofthe original dimensions with weld rods having subalioy are, in general, superior to similar properstantially the same composition, or materially ties of heat treated manganese steel of the previdifferent compositions. Bars, plates or other ously known types. shapes of the alloy may be joined by welding to The boron containing alloy is amenable to fabricate parts of equipments, etc. 'By reason of thermal treatment for the modification or imthe fact that the rate of cooling does not adprovement of various physical properties, such versely affect the physical properties of the alloy,

as, tensile strength and hardness. I have found, any suitable method of welding may be employed.

however, that thermal treatmentisnot necessary Examples of alloys within the scope'of the not desirable when the cast alloy is to be used present invention which I have found to be particularly valuable for wearing parts of equipment The outstanding advantages of the present are: Manganese 9.50%, boron 0.65%, molybdealloy are due, chiefly, to the fact that hardness num 0.60%, carbon 0.25%, and the balance suband other physical properties are developed by stantially iron; manganese 12.50%, boron 0.85%,

- the combination of boron with one or more of molybdenum 1%, carbon 0.50%, and the balance the other essential components. Carbon is not substantially iron; manganese 15%, boron 1.10%,

essential in my alloy, but by reason of the fact molybdenum 2.50%, carbon 0.45%, and the balthat varying amounts of carbon are present in ance substantially iron.

commercial grades of materials used in producr The alloy of the present invention comprises:

ing the alloy I find that it is desirable to allow for manganese 6.25% to 16%, boron 0.20% to 1.75%,

the inclusion of a small percentage of carbon. molybdenum 0.25% to carbon-from approxi- In order to obtain the maximum value of physmately 0.10% to not more than 0.85%, and the ical properties and characteristics it is important balance substantially iron.

It will-be understood that the alloy will conthat the carbon content in the present alloy does not exceed the theoretical ratio of 'the iron-, carbon eutectoid. By thus restricting the maximum amount of carbon the precipitation of free phur .and phosphorus. Commercial grades 'of carbides during slow cooling of the alloy from ferro-alloys and steel invariably contain silicon, elevated temperatures is entirely avoided. I and consequently, varying amounts of silicon are usually prefer to limit the carbon content to ]introduced into the present alloy as impurities from 0.10% to 0.35%. I have found, however, incidental to manufacture. The amount of silithat when the alloy contains as much as 0.85% vcon in the alloy should not exceed 1%. carbon no free carbides are found in the as Iclaim: cast or welded material, regardless of-the rate of An alloy characterized by relatively high recooling. sistance to deformation and abrasion containing It will be apparent, therefore, that the stru manganese 6.25% to 16%, boron 0.20% to 1.75%, ture of the manganese-boron steel is markedly molybdenum 0.25% to 5%, carbon not exceeding different from the structures of heretofore known a maximum of 0.85% and the balance iron. manganese steels. I I

The alloy of the present, invention has a high tain fractional percentages of impurities inci- ANTHONY a. n: GOLYER.

dental to manufacture, such for example, as sul-