US1213902A - Carbon-steel car-wheel. - Google Patents

Description

'WINFIELD S. PO'LETER, 0F NEVI YORK, N. Y., ASSIGNOR 0F ONE-HALF TO LOUIS M. SLACK, OF HEX/V YORK, N. Y.

CARBON -STEEL CAR-WHEEL.

No Drawing. Uriginal application filed December 16,1911, Serial No. 66G,23?.

filed February 20, 1912.

To all whom it may concern:

Be it known that I, VINFIELD S. POTTER, a citizen of the United States, and residing in the borough of Manhattan, in the city, county, and State of New York, have invented certain new and useful improve ments in Carbon-Steel Car-Wheels; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

In. Letters Patent of the United States No. 1,018,365, granted February 20, 1912, upon an application filed by me under date of December 16, 1911, Serial No. 666,237, I have described certain new and useful improvements in the method of producing a carbon steel car wheel in a thoroughly wrought condition throughout, and of a uniform very fine-grained and suitably hard and dense structure, particularly in the flange and tread portions of the wheel, the manufacture being so conducted as to avoid in the preliminary and in the final forming operations, various laininations and other irregularities of structure in the steel which tend to cause breakage and irregular or rapid wear of the wheel in service.

The present application is a division of my application and patent above referred to and relates to the product, that is to say, a carbon steel car wheel having the characteristics of structure indicated, and wherein the tread portion is dense, fine-grained and free from lamination and which is tempered, the hardness and temper of the tread portion varying from a machinable state in the hub portion to a harder state in the tread portion.

In the usual procedure adopted for the manufacture of wrought carbon steel car wheels, the ingot or primary cast shape from which the manufacture is initlated is cast in the ordinary manner, so that usually blow holes, slag inclusions and other defects are present to a greater or less extent in the ingot after freezing.

In so far as I am aware, the manufacture of wrought steel car wheels has been heretofore so conducted that the steel is very coarsely re-grained by the use of very high temperatures prior to each portion of the forming operation, and, in the forming op- Specification of Letters Patent.

Divided and. this application Serial No. 678,850.

eration itself, the steel is laminated by elongation, flattening, etc, of the coarse grains, and the elongation of any blow holes and other casting defects that are present, so that the resulting structure presents throughout its mass corresponding surfaces of greater or less extent which have relatively weak co-- hesion, one with the other. In the practice of my invention, I avoid these difficulties, my improved wheel when brought to its final form and dimensions being substantially devoid of laminations and weak cleavsurfaces, and in a condition of great strength, the tread and flange portions particularly being in a state of maximum l1ard ness consistent with the necessary toughness and shock-resistance. My improved wheel is, therefore, capable of enduring service longer than other steel wheels and with a more uniform wearing ofits tread and flange portions.

In carrying out my invention, the carbon steel, while still molten, is suitably cleansed by reducing agents and by means of fluxes, and is held in the ladle prior to casting until the impurities have floated out of the metal. The ingot is then cast of a size to produce several wheel blanks and may be of the usual tapered form. The casting is so conducted as to avoid porosity in the main body portion of the ingot, that is to say, in that portion which is to be cut up into wheel blanks. To this end, the metal is preferably poured into molds having tops which retain the steel longer molten in the upper than in the lower portion of the mold, so that the impurities of the steel accumulate in that portion or part of the upper portion of the ingot which is to be rejected by crop ping after the first stage of the forming operation. To this end, a mold having a suitable refractory top portion may be e1nployed. Or the ingot may be cast in accordance with my United States Patent No. 967830, dated August 16, 1910.

When the ingot has been cast, as above or in any other suitable manner to avoid porosity, it is permitted to freeze, and is then stripped of the mold, while still hot, and is placed in the heating furnace or soaking pit. At the time of stripping the ingot, and when it is introduced into the soaking pit, it has frozen and cooled to a temperature in the average of about 1100 C. In the soaking pit, the ingot is equalized at a temperature between about 850 C. and 1250 (1., but preferably between 1050 C. and 1150 C. to eliminate irregularities of composition occurring during freezing and cooling. Great care is to be exercised at this juncture to avoid any coarse regrain1ng of the steel, and, to this end, after the ingot has been soaked within the "temperature range referred to and has been equalized throughout, it is withdrawn from the soaking pit, for the reason that to retain it therein after the irregularities of composition have been removed tends to bring about the coarse re-graining referred to. So also, the retaining of the ingot within the soaking pit after the irregularities of composition have been removed has the further tendency to bring about, to a greater or less extent, an evolution of gases within the mass which cor espondingly forces apart the crystals of the steel and thereby decreases their cohesion.

lVhen the ingot has been brought, in the soaking pit, to the desired condition and has been removed therefrom, it is reduced to parallel shape, 71. 0., to a bloom of substantially uniform cross-section throughout its length, and is then cut into wheel blanks of the required weight, preferably without heating it above 1150 C. For example, the bloom,may be cut by one or more retating cutting disks into suitable wheel blanks. Instead of cutting these blanks of a length and diameter approximating the ultimate diameter of the finished wheel, I prefer, in the first instance, to roll or otherwise worr the ingot, when bringing it to parallel form, down to a considerably lesser cross-section, so that in cutting off a blank of the requisite weight therefrom, the blank will be correspondingly longer than the ultimate average thickness of the wheel. By this expedient, I am enabled to more accurately cut the ingot into blanks of the de sired weight. The blank is then worked in its outer portions, for example, it is placed in a suitable die, closely fitting its margin and is then subjected to heavy pressure and is thoroughly worked in its outer portions particularly, the die being of such a character as to prevent any substantial amount of stretching in this tread portion. The purpose of this preliminary working of this outer or tread portion of the blank, while at the same time preventing elongation or stretching of said tread portion, is to avoid any such lamination in the finished product as would be due to internal flaws in the blank. That is to say, the thorough working of the outer or tread portion oftheblank at this stage of the operation has the effect of consolidating the metal in the tread portion and eliminating any possible internal flaws or cleavage surfaces therein. The blank is then removed from the die and reheated for further forming. By a suitable rolling or pressing operation the central part of the innermost portions of the blank are suitably worked to bring them into the desired wrought condition in so far as this can be accomplished in one heating, or during one or more re-heatings, and the blank as a whole is finally brought to the desired form throughout, either in a single operation or a plurality of pressing or rolling operations.

During any of the reheating operations, the re-heating is to be so conducted as to avoid any coarse re-graining of the steel after its initial working; moreover the reheating operations should be of but moderate duration, so that neither the temperature of the re-heating nor its duration shall have the effeetof bringing about a feeble cohesion between the grains of the steel, particularly in the tread and flange portions of the blank. The standard practice, therefore, as just indicated, should preferably exelude a re-heating of the tread portions of the blank at any time above 1150 C. or thereabout. It, however, the exigencies of the case require that, in order to suitably form the hub and web of the wheel, the entire blank should be reheated for a short time above 1150 C. (say 1900 C.) it will then be desirable to cool the tread portion of the blank, before submitting it to any further forming operation, to a temperature below 650 C. and then to reheat it for the next succeeding forming operation to the forming temperature (say 050 (7. to 1150" C.) in order to suitably re-grain the steel in the tread portion before the tread portion is further worked.

The final working of the tread portion for the production of the greatest densitv and strength of metal should begin at an initial temperature throughout below 050 and is preferably finished at the temperature below 850 C. Thereafter, the trend and flange portions should not again be re-heated to temperatures above 850 C. or thereabout. However, for the final working, the tread portion may be heated to a temperature above 950 C. providing it is thoroughly worked at temperatures below 950 C. as the metal cools.

At the termination of the final working, the finished wheel may be immediately cooled, as hereinafter described, or it may be placed in a furnace having av temperature range, for example from 7 50 to 850 (1., but preferably about 800 C., for a. short time sufficiently to substantially equalize the temperature throughout the wheel, and the wheel is then taken from the furnace and subjected to a cooling and hardening operation.

The cooling and hardening operation may llT;

be carried out by first rapidly cooling from about 800 C. to below 550 C. (as for eX- ample, to 500 C.) equalizing the temperatures in the wheel at about 400 C. to 650 (3. according to the hardness or temper desired and to remove strains, and then evenly and gradually cooling the wheel to atmospheric temperature. The rapid cooling may be carried out by immersing the entire Wheel in oil or in molten lead; or in any other suitable manner appropriate to rap idly extracting a greater part of the heat of the wheel. The reheating of the wheel for equalizing the temperatures thereof at about 500 C. or 550 C. if the wheel has been cooled much below 500 C. is conducted in so gradual a manner and with such care as to avoid strains or cracks. Or, the rapid cooling of the wheel after it has been equalized at a temperature of about 800 C. may be executed by supporting the wheel from its central opening on a shaft by which it is rotated, and during this rotation, subjecting it continuously or intermittently to a shower of water until its temperature is reduced to from 400 C. to 650 C in its various parts; whereupon its temperatures are equalized and for a short time held at t00 C. to 650 0. according to the composition of the steel and the hardness desired. The wheel is then gradually or slowly cooled to atmospheric temperature.

The tread and flange portions of the wheel may be given a harder and stiffer temper than the central portions, if desired, by cooling said tread and flange portions rapidly to a lower temperature than that to which the central portions are cooled (as, for example) by cooling the tread and flange portions to a temperature of about 400 C. and the central or hub and web portions to about 650 (1), and then partially equalizing the temperatures within the wheel by permitting a gradual flow of the heat from the hotter central portions to the periphery of the wheel, until the tread and flange portions have received the desired temper heat. Thereupon the outward flow of heat from the central portions may be checked by the use of the water-spray or by rotating the wheel with its tread and flange in a bath of molten lead, or by any other suitable means of determining the extent of the re-heating, and for finally cooling the tread and flange portions, which should be gradually cooled to atmospheric temperatures from the temper heat.

By the designation carbon steel as used in this specification, I intend the steels known to the trade by that name, including such steels as contain-moderate quantities or other ingredients but not to such a de gree as to change the laws concerning the crystallography and critical points of the steel greatly from the corresponding prop erties of pearlitic or carbon steels.

Having thus described my invention, what I claim is:

1. A carbon-steel car wheel having a dense tread portion, devoid of irregularities of composition occurring during freezing and cooling of the original ingot casting from which the Wheel blank was produced, said tread portion being unstretched or unelongated radially while being wrought, free from laminations, and having its structure, due to the mechanical forming, changed to a fine grain; substantially as described.

2. A carbon steel wrought car wheel having a dense, fine-grained tread portion free from lamination and tempered; substantially as described.

8. A carbon steel wrought car wheel having a dense, fine-grained .tread portion free from lamination and of a graduated hardness and temper varying from a machine able state in the hub portion to a harder state in the tread portion; substantially as described.

In testimony whereof I alfix my signature, in presence of two witnesses.

WTNFTELD S. POTTER.

Witnesses:

JOHN C. PENNIE, MINERVA LOBEL.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D 0.