US2247876A - Alloy steel for the manufacture of wheels and tires - Google Patents

Description

and similar articles of manufacture which have not heat-treated may be less than, the cost of thermore, heat treating adds to the cost and its composition is so controlled as to be merely comlationship between strength and ductility, the cost understood by the comparisons made hereinafter.

than that of heat treated plain carbon steel. but not maximum, degree of both specified qual- The object of my invention is to increase the ities is desirable, my improved steel is characterservice life of such wheels and tires by providing ized by these qualities to a deg ee h he to unan alloy steel which, in respect to the qualities kn wn inp in bon eel. adapted to resist the types of failures above speci- My improved steel contains carbon within a 'fied, more particularly hardness, tensile strength, range known in plain carbon steels of this type,

Patented July I, 1 941 UNITED STATES PATENT OFFICE ALLOY STEEL FOR THE MANUFACTURE OF WHEELS AND TIRES Harry L. Frevert, Philadelphia, Pa., assignor to The Midvale Company, Philadelphia, Pa., a corporation of Delaware No Drawing. Application February 16, 1940,

. Serial No. 319,237

4 Claims. (Cl. 295-30) My invention relates to alloy steel for the manquires no heat treatment. The cost of my imufacture of locomotive tires, forged steel wheels proved steel does not, therefore, exceed, and if to withstand the effects of heat, deformation and heat treated plain carbon steel. In some cases, wear and which at the same time have to possess however, heat treatment of my improved steel sufiicient toughness or ductility to resist breakage will, as in the case of most steels, measurably due to sudden overloading or to stress concen improve it in respect of the qualities above named. trations. However, in the absence of any treatment,- other Locomotive tires and forged wheels have been than those normally incident to the hot working made for manyyears from plain carbon-steel of the article from the raw ingot form to the containing .5 to .8% of carbon, about the same finished product, compositions embodying my inpercentage of manganese, silicon in amounts up vention possess properties sufficiently superior to to .30% and the usual very small percentage of those at present available in tires and wheels to impurities, particularly sulphur and phosphorus, make heat treatm t unn y excepting in common to steels of this type, Such tires and special cases. It will therefore be understood that wheels have been subject, particularly under pres-' my improved steel is capable of being produced entday conditions, to certain types of failure on a compet t ve basis with plain Carbon Steel. which have rendered them unfit for service or W c is One f the Objects f y inventionhave necessitated frequent turning of the tread I will be understo d that in the manufacture to produce the necessary service and life. The of carbon steel a fairly high degree (but often principal modes of failure have been by e, shatterin degree less than is desirable) of hardness and ing,'spawling or shelling of the tread, by exstrength is obtainable with sacrifice of toughness cessive wear or flow of the tread metal, or by and ductility and that a fairly h gh degree of "heat checking that may result in breakage, toughness and ductility is obtainable with sacri- It has been found possible to retard failures of 5 fice 'of hardness and streng these qualities tires and wheels to some extent by heat treating g Controlled mainly y varying the Percentage them to increase strength and ductility prior to of carbon. For different uses primary consideraplacing them in service. However, heat treattion must be given to one or the other of these ments, particularly those involving liquid quenchq a t sn y v t also, both of these t ing, unless carefully controlled, may produce dequalities are not obtainable in maximum degree fects diflicult to detect by ordinary inspection and in a y Single eempesitien- My p v S e which eventually lead to complete failure. Furhowever, s Characterized y the feet that if its effects are sometimes nullified to more or less p a e w h Plain bo Steel ha g, for S c extent by the heating incid nt t shrinking of steel, a high degree of hardness and strength, it tires or other types of rings on the wheel centers. greatly excels it in toughness and ductility, while Efiorts have been made to improve tires and if its composition is so controlled as to be merely wheels by the use of alloy steels but the alloy comparable in toughness and ductility with plain contents have been so high or of such a characcarbon steel having, for such steel, 2. high degree ter as to require that the finished article be also 40 f toughness and ductility, it a y exceeds it heat'treated in order to attain the proper rein hardness and strength; as will be morefully of the finished product then being much higher On the other hand, for most uses, where a high,

ductility and toughness, is definitely superior to but to attain a given tensile strength, the pe plain carbon steel. I accomplish this object by centage of carbon is,distinct1y lower. It contains controlling the percentages of manganese and manganese, within a range whose minimum is silicon and by adding, in such small percentages little, if any, below the maximum of the range as not to add greatly to the cost, elements not usual in carbon steel. It contains, also, small present in carbon steel. My improved steel-repercentages of chromium and molybdenum. The

Mn Si Cr Mo Percent Percent Percent Percent Percent It is of no substantial other element to the composition. Of course the usual amounts of sulfur and phosphorus, unavoidably present in steel, are contained, as impurities, in my composition, but if any other element is added it must be added in very small proportion and no element can be added that would impair the qualities characterizing my composition. As an example, an exceptional element that, when added in very small proportion, has no appreciable injurious effect and may have a slightly beneficial influence, is nickel, which, however, if present, should be held below .25%, since in greater amounts it tends to increase the air-hardening characteristics of the metal to too great an extent.

Tires, rings, wheels and forgings of this analysis forge and roll with the same facility as do plain carbon steels. The finished product is allowed to cool normally and uniformly in air.

The superiority of the above compositions to plain carbon steel will be appreciated by comparing them with the average properties found to characterize a large number of plain carbon steel locomotive tires such as are in everyday A comparison of composition (a) with composition (0) shows a pronounced improvement in strength and hardness, without impairment of, but on the contrary an improvement in, ductility and toughness. A comparison of composition (b) with composition (d) is equally favorable. On the other hand, a comparison of composition (a) with composition ((1), which compositions are fairly comparable in hardness and strength, shows composition (a) to be greatly superior to composition (d) in ductility and toughness.

In producing plain carbon steel, where great hardness and strength for severe service are controlling, resort is had to high carbon, the upper limit of which, with the greatest practicable toleration of accompanying lower ductility, is about 375%. As our analyses show, the normal greatest tensile strength obtainable is about 133,000 pounds per square inch. In my improved steel advantage to add any 0 this degree of tensile strength is obtainable with carbon as low as .64%, without sacrifice of toughness and ductility in the smallest degree as compared with plain .64% carbon steel, which latter wholly fails to meetthe specified requirements of hardness and strength. On the other hand, with a carbon content even lower than my improved steel has a tensile strength nearly 20,000 pounds per square inch higher than .75% plain carbon steel and without sacrifice of toughness and ductility and indeed with a substantial improvement in this quality.

The determination of the resistance to flow of my improved composition under load at elevated temperatures shows it to have properties in this respect far superior to those of ordinary carbon steel. Since the surface of railroad tires and wheel treads is subjected to heating while under load during service the improved resistance of the composition forming the subject matter of this invention to flow and consequent failure \vhen'heated is of considerable advantage in prolonging life in service.

It is clear, from the typical examples given, that the composition must be varied, although within narrow limits, to meet special require ments. Generally speaking, as in plain carbon steel, where hardness and strength are the primary requisites. the percentage of carbon is increased, while if the highest degree of ductility and toughness is required, the carbon percentage is lowered. It is desirable, also, with increase in carbon, to slightly increase the percentage of most, if not all, of the alloying elements. In all compositions embodying my improvement the carbon should always substantially exceed 50% and should rarely be lower than .60%, while it is undesirable that the carbon should exceed 375%, although in exceptional cases it may ue increased to .80%. The percentage of manganese should never be lower than .70 or 375% and should not exceed 1.10%, although a percentage as high as 1.20 or 1.25% is exceptionally permissible.

Silicon should not exceed 40% and is preferably from .08 to .30 per cent. While chromium is indispensable, a very small percentage (not less, however, than .30 per cent.) will sufiice. In most of my improved compositions .35 to .55% chromium is adequate. A higher percentage, but not over about .90 or (at the most) 1.00 per cent., is of advantage in exceptional compositions eml odying my invention. Molybdenum, also, while indispensable, should not usually be in higher percentage than the chromium and should not usually exceed .30 per cent., although in exceptional cases it is advantageous to increase the percentage of molybdenum up to not over 37%. A percentage as low as .05% is sometimes adequate, although .10 to .15% is preferable.

In all compositions embodying my invention, the percentage of manganese substantially exceeds the combined percentage of any two of the other alloying ingredients (excluding carbon), while in compositions having in highest degree the characteristics hereinbefore described (illustrated by the specific compositions hereinbefore given) the percentage of manganese exceeds the combined percentage of all the other alloying elements (excluding carbon).

It will also be understood that the high carbon range herein specified is essential in the manufacture of tires, forged steel wheels and other articles, such as rings, roll sheets, sheave wheels and. crushing machinery that require a certain degree of hardness and strength and that are sube Sect to types of failures like'or similar to those to which wheels and tires are subjected.

It will also be understood that the manufacture alloy steel compositions, has superior resistance to the types of failure hereinbefore enumerated, which could be made only by making andtesting the same, constitutes a new and useful improvement and a pronounced advance in the art.

What I claim and desire to protect by Letters Patent is:

1. Wheel treads and other ring-shaped articles of substantial thickness which are subject to types of failure that unfit them for service or unduly shorten their service life, composed of an alloy steel containing manganese between .70 and 1.25%, silicon between .05 and .40 per cent, chromium between .30 and 1.00% and molybdenum between .05 and .70%, the percentage of manganese being substantially in excess of the total percentage of any two of the other above specified alloying elements, and carbon over .50 and not over .80%, the balance of the composition being substantially iron, said articles, whether or not heat-treated, being characterized by superior wear hardness and strength without sacrificeof ductility and toughness and possessing superior resistance to said types of failure.

,2. Wheel treads and other ring-shaped articles of substantial thickness which are subject to types of failure that unfit them for service or unduly shorten their service life, composed of an alloy steel containing manganese between .70 and 1.25%, silicon between .05 and .40%, chromium between .30 and 1.00% and molybdenum between .05 and 370%, the percentage of manganese be'- ing substantially in excess of the total percentage of all the other above specified alloying elements, and carbon over and not over .80%, the balance of the composition being substantially iron, said articles, whether or not heat-treated, being characterized by superior wear hardness and strength without sacrifice of ductility and toughness and possessing superior resistance to said types of failure.

3. Wheel treads and other ring-shaped articles of substantial thickness which are subject to types of failure that unfit them for service or unduly shorten their service life, composed of an alloy steel containing manganese between .80 and 1.10%, silicon between .08 and .30%, chromium r between .30 and .55% and molybdenum between .05 and .15%, the percentage of manganese being substantially inexcess of the total percentage of any two of the other above specified alloying elements, and carbon over .60 and not over .80%, the balance of the composition being substantially iron, said articles, whether or not heat-treated,

being characterized by superior wear hardness and strength without sacrifice of ductility and toughness and possessing superior resistanceto said types of failure.

4. Wheel treads and other ring-shaped articles of substantial thickness which are subject to types of failure that unfit them for service or unduly shorten their service life, composed of an alloy steel containing manganese between -.80 and 1.10%, silicon between .08 and .30%, chromium between .30 and .55% and molybdenum between .05 and .15%, the percentage of manganese being substantially in excess of the total percentage of all of the other above specified alloying elements,