US1859623A - Cast steel body and method of hardening same - Google Patents

Description

A. W. GREGG May 24, 1932.

- CA ST STEEL BODY AND METHOD OF HARDENING SAME Filed June 25, 1930 v gwomtu Alfred W. (i rcgg Aw g Patented May 24, 1932 UNITED STATES PATENT OFFICE ALFRED W. GREGG, OF COLUMBUS, OHIO, ASSIGIiOIR/TO THE BONNEY-FLOYD COMPANY, OF COLUMBUS, OHIO, A CORPORATION OF OHIO CAST STEEL BODY AND METHOD OF HARDENING SAME Application filed June 25,

' This invention relates to a method and means for treating steel bodies or articles, such as car wheels, sheaves, sprockets, gears and pinions in order to provide an easily practiced and efficient technic for producing in such integral bodies and articles regions or areas possessing a hardness" capable of withstanding wear and abrasion to a high degree and other areas or regions in the same bodies and of the same materials which possess a lower degree of hardness and are readily capable of responding to ordinary machine methods and practices to produce tooled 0r machined surfaces.

In steel articles, especially those of the character above described, as well as many others not set forth, it is highly desirable that the wear-receiving surfaces, such as the wheel treads, cable guides and gear or sprock et teeth shall possess a high degree of hardness to resist wear, abrasions and other destroying influences to the greatest possible extent. Likewise, it is also necessary that the hub portions of such members, for ex ample, shall possess a lower degree of hardness so that such hub surfaces may be machined or tooled toexact measurements, and it is therefore a primary object of the present invention to obtain these ends in a single, integral steel body. D

In order to properly harden steel bodies of the character specified, it is customary to heat the same to a temperature in the neighborhood of 1650 F. in a suitable furnace and after such heating the bodies are quenched or intimately contacted with quenching media such as liquid or air. The

surfaces of the bodies directly exposed to the uenching media are rapidly cooled to prouce the desired condition of hardness, and the bodies or articles are then reheated to a temperature below the critical hardening range, in order to relieve stresses set up in such articles by virtue of the quenching step,

thereby producing the required hardness on the part of the metal which can be varied according to the temperature of this draw heat.

Heretofore the usual quenching operation has been carried out in such manner that the 1930. Serial No. 463,777.

entire body possesses a Brinell hardness within the limits of practical machine shop practice, in order that. the hubs, cores or other machinable areas or surfaces of such bodies or articles may be finished or dressed with the aid of tools to desired degrees of accuracy. It will be evident, however, that this usual practice results in producing or leaving relatively soft wear-receiving surfaces, since, for instance, the teeth of'a gear wheel or sprocket, when so treated, possess no sub stanti ally reater degree of hardness than the hub or b0 y portions thereof. Following the machining of such anarticle and the placing of the same into active use,the teeth receive practically all of the wear and due-to thereiatively soft character thereof rapid"';Wear takes place with correspondingly short use of the article in the capacities and services for which it is designed.

Steel may be machined with facility when it possesses a Brinell hardness not in excess of 210, although with special tools and equipment steel having a Brinell hardnessv of 250 may be machined in a commercially practicable manner. Generally stated, however, it

is desirable that the Brinell hardness of steel should not exceed 210 when high production or when ordinary methods of manufacture are to be employed. With reference to the wear-receiving surfaces of such an article such, for example, as the teeth of a cast gear or sprocket, the flange or tread of a car wheel, or the cable groove of a sheave wheel, the Brinell hardness should be preferably of the order of from 27 5 to 500. As explained, previous methods of hardening cast steel through ordinary quenching and subsequent heat treatment do not produce this differential hardening but, as stated, produce a substantially uniform degree of hardening throughout the entire body which must be low to provide for the machining of certain surfaces. The present invention, therefore, is directed to a novel method and means whereby through the use of the quenching operation an integral steel body may be provided or formed, as desired, with wear-receiving surfaces of high Brinell hardness and with machinable surfaces of low Briuell hardness. Experience has disclosed that in quenching steel bodies that portion of such a body which comes into direct contact with quenching media and which possesses small cross-sectional area may be hardened to a very high degree, but that part of the article which possesses greater cross-sectional area and which retains its heat longest when subjected to the quenchin step, does not respond so readily to the bar ening treatment and as a result possesses a lower degree of hardness or a softer condition.

Therefore, the present invention resides lar ely in maintaining that portion of a steel bofy at a higher temperature during the quenching step than that portion of the body or article which in later use is adapted to receive the greater part of the wear, abrasion, and other destructive forces which are in practice applied thereto. In the quenching of cast steel bodies, either gear, sprocket, car wheels or sheaves, I have found that by placing in the axle or shaft-receiving bores thereof, a removable pin or plug, which may or may not be headed, that when such articles are quenched, the pins or plugs carried by the hubs, prevent the quenching media from directly contacting with the surfaces of said bores which subsequently require machining. Moreover, since the pins or plugs are placed in said bores during the heating of such articles immediately prior to the quenching step, the said plugs are likewise heated to the same degree of temperature as the balance of the article, and due to the increased mass of heated metal thus present and the relatively great cross-sectional area thereof, the temperature of the hub portions of such articles during and immediately after the quenching o eration remains higher than that which 0 tains in the toothed or flanged portions of such articles which are of relatively reduced cross-sectional area and are directly exposed to the quenching media. This retention of heat by the hub and the spacing of the machinable surfaces thereof from the quenching media produces the desired additional hardening of the steel article or body and solves in a simple and practicable manner a problem which heretofore has caused considerable difiiculty in producing articles of this nature.

A consideration of the accompanying drawings will facilitate a further understanding of the specific details of the invention.

In said drawings: 1

Figure 1 is a view in vertical cross-section taken through a gear wheel provided with a removable quenching plug formed in accordance with the present invention,

Figure 2 is a side elevation of the wheel,

Figure 3 is a perspective view of the plug,

Figure 4 is a vertical sectional view showing a car wheel provided with a set of the quenching plugs, and

reason the wheel 1 has been selected for the purposes of illustration and description, although it will be understood, as it is above pointed out, that the present invention finds application in connection with the hardening treatment of integral steel bodies adapted for many different uses and purposes, and such bodies may be either cast, forged, fabricated, welded or otherwise produced.

The gear 1 embodies the usual hub 2 and a toothed perimeter 3. This gear is produced by customary foundry practice in the form of a single integral body with the teeth 3 cast or otherwise formed thereon. After the initial casting or formation of the body it is then subjected to a hardening treatment. In accordance with the present invention this hardening treatment is carried out by placing in the axle or shaft receiving bore 4 of the wheel a removable lug or pin 5 also formed from cast steel. ThlS plug may be provided at one or both ends with a head 6 arranged to closely engage with one or more of the vertical sides 7 of the hub 2. As

shown in Figure 4, a car wheel 8 has the bore 9 of itshub 10 formed with annular axle engaging ribs 11, and for this reason the present invention employs a plurality of headed plugs 12 which are inserted into the bore 9 from each end thereof. The headed surfaces 13 of the plugs 12 engage with the vertical surfaces of the hub 10 to protect both ends of the hub 10 against contact with a quenching media.

Following the positioning of the plugs 5 and 12 in the wheels, as shown, the said wheels are placed in a heating furnace (not shown) and in such furnace are subjected for a desired period of time to temperatures of the order of approximately 1650 F. so that the plugs become heated with the bodies of said wheels to substantially the temperature specified. Following this heating of the plugged wheels the latter are removed from the furnace and are immersed in a quenching media, such as water or by being subjected to an air blast for a given time which is determined by the cross-sectional thickness of the metal section, so that the temperature of such bodies drops rapidly to effect the desired chilling and hardening of the wear receiving portions thereof. It should be noted, at this juncture, that by the provision of the plugs 5 and 12 the wheels contain a large mass of heated material at the hubs thereof and it will be observed that the surfaces 4,

the cooling or quenching media.

fit fairly snugly in the axle bores and any water which would tend to enter the joints between the plugs and the axle bores will be instantly transformed into steam and de- 5 livered back into the quenching media. By the provision of the plugs 5 and 12 in the quenching operation described, the hubs or other machinable parts of such bodies are maintained at a higher temperature or above critical hardening temperature than the outer thinner portions of such bodies which are brought into direct contact with the quenching media. Therefore the rate of cooling of the hub portions is relatively slow with respect to the rate of cooling of the outer and thinner portions of said bodies which do not possess the mass of metal which obtains 1n the hubs when the plugs 5 and 12 are utilized. Subsequent to the quenching step, the wheels or other articles, with the plugs withdrawn, are again reheated to atemperature below critical hardening temperatures to relieve said articles of strains or stresses set up therein by the quenching operation. The subsequent heating step is carried out in such manner that it does not affect the previous hardening treatment to any material degree.

Repeated practical operations using the method above employed discloses that the protected hub surfaces possess a Brinell hardness of substantially 180 and this may vary depending upon conditions between 175 and 250 Brinell, depending upon the composition of the steel and other factors, whereas the unprotected wear-receiving surfaces such, for example, as the gear teeth 3, possess a Brinell hardness of approximately 340, although this figure is susceptible, according to operation conditions, between 275 and 500.

In Figure 5 the plugs 14 are formed with annular channels 15 which completely surround the thin hub portion 16 of a wheel or other steel body 17. In cases where the hub 16 is of thin cross-section or if the bore 18 is of small diameter, this form of plug provides for the desired mass of heated metal which, during the quenching step, maintains the hub area at a sufiiciently elevated temperature to prevent the metal comprising the ing temperatures. Likewise, in Figure 6 where a solid hub 19 is used the caps 20 are placed around said hub as indicated.

From the foregoing it will be seen that the ody having areas possessing relatively differring states of hardness and wherein this condition is obtained without subjecting the bodies to any additional steps of operation than those which are used in the ordinary hardening of steel bodies. In fact, the present invention requires no variation in standard practice with the exception of the employment of the removable plugs, indicated at 5 and 12, and the accompanying controlsaid hub area from passing critical harden-- present invention provides an integral steel ling of the heating and quenchin operations to produce a higher degree of bar ness on the part of the wear-receiving surfaces than is usually employed. The PlIlS 5 and 12 may be used repeatedly on different groups of castings, their initial cost being low and their period of usage prolonged indefinitely.

In the following claims, the word steel is used in defining such objects as steel wheels, steel bodies and the like and it will be understood that while steel is a definite name for a certain alloy, yet this word is used in a general sense as describin any wheel or body composed of plain car on or alloy steel requirlng heat-treating, such as steel wheels, sprockets, gears and the like. It will also be understood that the process is applicable to the heat treatment of metallic bodies other than cast steel and refers to rolled and drawn steel, such as shafting, bars, rods and the like. By the expression removable plugs, 1 contemplate the use of such objects as pins, cylinders, shafting, bars, rods and other similar heat retaining'devices which may be removably connected with the steel bodies during the heat treating operation specified.

What is claimed is:

1. The method of hardening steel wheels which consists in placing in the axle bore of such a wheel a removable and relatively close fitting metallic plug, heating the wheel'with the plug retained therein to at least a critical hardening temperature, and in then immersing the wheel with the plug retained therein in a quenching media.

2. The method of regulating the hardening of steel wheels provided with hubs having surfaces which require subsequent machining, which consists in positioning within the bore of the hub of such. a wheel a re movable metallic plug which closely engages with such surfaces, then heating the wheel to a critical hardening temperature, and finally immersing the wheel with the plug retained thereby in quenching media in such manner that the plugged surfaces prevent such media from contacting with the surfaces of the wheel requiring machining.

3. The method of regulating the hardening of steel wheels provided with hubs hav-.

4. The method of controlling the hardness of a steel article to provide localized hardening thereof, which comprises closing the surface of that portion of the article desired to be unhardened by a metallic heat retaining member adapted to be removed from the article said member being of substantial mass suflicient to retain heat without passing thru the critical hardening temperature upon quenching of the entire article, heatin the article with the heat retaining member therein to at least a critical hardening temperature, and then quenching the combined mass.

5. The method of regulating the hardening of a steel body to secure regions in said body possessing relatively different degrees of hardness comprising: the application to such a steel body of an insertable and removable body of metal in close contact to the region wherein a lower state of hardness is desired, heating said bodies to at least a critical hardening temperature, and then subjecting said bodies to a quenching operation wherein the re ions which are to possess a high degree 0% critical hardening temperatures and the regions which possess the larger mass of material and which are to be maintained at a lower state of hardness are cooled at a slower rate and without passing through the critical hardening temperatures.

6. The method of effecting a differential hardening of an integral steel body, which consists in applying close contact to the areas of said body which are to possess a lower degree of hardness, an insertable and removable mass of heat retaining metal, the areas of said body which are to possess a high degree of hardness being independent of the influence of said mass of metal, heating the body together with said mass of metal to a temperature of approximately 1650 F., and then immersing said body together with said mass of metal in a fluid quenching medium and retaining the body in said quenching medium for a suflicient period of time to permit the areas of said body to be treated to a high state of hardness to pass rapidly through critical hardening temperatures but without permitting corresponding rapid reduction in temperature in the removable mass of metal and adjacent areas of said body through said critical hardening temperatures.

In testimony whereof I aflix my signature.

ALFRED W. GREGG.

hardness are rapidly cooled through

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