US1482563A - Superhardened steel and process for producing the same - Google Patents

Description

Patent Feb. 5, 1924.

" uurreo STATES ice.

AXEL GUSTAIF EMANUEL HULTGREN, OF GOTTEHBORG, SWEDEN.

SUPERHARDENED STEEL AND PROCESS FOR PRODUCING THE SAME.

No Drawing.

To all whom it may concern:

Be it known that I, AXEL GUs'rAr EMAN- UEL HULTGREN, a subject of the King of Sweden, residing at Gottenborg, Sweden, have invented certain new and useful Improvements in Superhardened Steel and Processes for Producing the Same, of which the following is a specification.

This invention relates to a new product '10 and the method ofproducing the same, and to superhardening heat treated hardened metal articles. It is peculiarly adapted for mechanically superhardening the metal at and adjacent the surface of articles which have been hardened by heat treatment and preferably ground and polished or otherwise;

previously reduced to approximately their finished form.

There are many practicable applications 3:) to which this invention may be applied, one of which being the interengaging parts of anti-friction bearings, as for instance, the surfaces of the race grooves of ball and I roller bearings, and also the .sur-

faces of the rolling elements, namely the balls and the rollers. 7

Broadly stated, this inventionhas to do with cold working an article of hardened steel to make its surface still harder.

It has been well known since the earliest ages that many metals when they are in a soft condition and cold can be mechanically hardened by the application of pressure, or a series of blows, to the surface. This primitive method was employed on metals not capable of being hardened by heat treatment as now practiced upon steel. I have discovered that metal which has been brought to a high state of hardness by quenching from proper hardening temperature, which in some instances is followed by tempering, may be still further hardened, or more properly superhardened by cold working to an extent which produces a permanent deforma-- tion.

By the term heat treatment, as used in this specification and the appended claims, is meant that effect produced upon the steel by more or less suddenly cooling from a temperature above the transformation temerature. This statement is made not to imit the scope of the material worked upon,

but to simplify the description and to prevent equivocation arising from a meaning 1 sometimes placed upon t e term heat treat- Applieation filed June 15, 1920. Serial 1W0. 389,182.

ment to include not only the hardening but also the softening or annealing.

In many industries, such as the manufacture of the rings and the rolling elements for ball and roller bearings, the parts are not heated a second time to a temperature sufiiciently high to come under the more technical definition of tempering. In the heat treatment to which theyare subjected they are heated to a fairly high degree of temperature, submerged in a cold quenching bath and then soaked for quite an extended period in a warm bath of only sufficient temperature to remove or modify the internal stresses created by the quenching.

One illustration of an article so made, and the method of treating the same is a deep groove single row ball bearing. The rings of this are formed in some well known or other suitable manner, they are then heated to approximately 1500 degrees Fahrenheit, .and' quenched in a bath of approximately at-' mospheric temperature, and removed from this bath and immersed for approximately an hour in a bath of oil heated to about 300 degrees Fahrenheit. It is to be understood that this is merely an illustration and cited to assist in the general understanding of this invention. In those articlesin which it is not. necessary to remove the internal' hardening stresses, the step of soaking in. the tempering bath may be eliminated, and also that in those articles where it is desired to have greater toughness thanthat produced by the recited method, the modifying heat may be of such magnitude that the resultant may be technically described as tempering.

In the case of a ball bearing, after the parts are heat treated the major surfaces are ground and polished, and the inner and guilzier rings assembled with a complement of Each individual ball bearing is designed by its maker to carry a certain amount of load, and a radial bearing is designed to carry a certain amount of pure radlal load or a certain amount' of pure axial or thrust load or certain combinations of these, such loads to be carried-for extended intervals over a long period of time. The bearing, however, and its different parts is generally capable of sustaining an enormous amount 7 of overload for a brief interval. When it is, therefore, desired to mechanically superharden the bearing surfaces of the elements occupied normally by the balls wearing away by the balls 1 which resultant formation superhardened, or with whatever of a ball bearing it is purposed by this invention to overload the bearing while rotating. As an illustration, the bearing is rotated for a short time while loaded to about ten times its rated capacity and exerts a pressure upon the surfaces being treated beyond their elastic limit. The effect of thus working the surface of the rings at the race grooves by the contact of the balls while rolling under heavy overload is to effect permanent deformation and harden the metal at and adjacent the surfaces. While engaged in'this rolling of the race rings the balls themselves are re-acted upon' and their metal at and adjacent the surface is similarly permanently deformed and hardened. The result is that the ball bearing when subsequently subjected to the loads which it is normally designed to carry presents engaging surfaces between the rolling elements or the relatively moving elements which are of high durability thereby adding greatly to the length of life of the entire structure. In ball bearings there is no such thing as the grooves and balls gradually and uniformly rolling over the race ways of these grooves. Under ideal conditions there is no sliding friction between the parts and absolutely no wear or other destructive action. -Ideal conditions, however, rarely exist or persist for long periods of time. Overload and shock loads bring about destructive tendencies which generally result in fatiguing the surfaces are in rolling engagement with the of mlnute fatigue cracks which cause flaking of the surfaces. Superhardened surfaces such as are herein described present a structure which has great power of resistance and which can endure all the abusive conditions usually encountered without fatiguing the metal.

In carrying out this method according to the illustrative example above set forth of superhardening the arts of an individual ball bearing it has been assumed that the ball bearing will be assembled prior to being subjected to this treatment, and will remain as originally assembled. It is, however, quite desirable in many instances to superharden the surfaces upon which the balls roll by other rolling elements than theballs which enter into the structure when put into use. This may be accomplished by specially formed rollers applied to the rings individ ually or to rollers in the form of balls be? tween such rings 'and occupying the position therein. Those superhardened rings are then assembled either with" balls otherwise especiallya requirements of the bearing in use demand. There are many'uses to which superhardened balls are put other than as the rolling elements between innerand outer race rings balls the one of these is the hardness testing method of Brinnells machine. A tough hard ball is a thing which is desired in this testing method especially in testing hardened steel,

in which case the generally used Brinnells ball, having the same hardness as the steel to be tested, is to som extent flattened out by the pressure, thus giving an incorrect test result. In; manufacturing superhardened balls according to my invention a ball made of the .proper steel and brought to the highest practicable hardness by heat treatment is then subjected to cold working to harden it to such an extent that when in the hardness test it is subjected to the pressure its spherical form will be practically unalterable. The ball must also be of such characteristics that repeated applications of testing pressure will not permanently deform it or break it.

In the manufacture of articles for certain purposes it has been found desirable to subject the worked article to a tempering heat preferably a low tempering heat for relieving the stresses of workin In the manufacture of suchv articles as razor blades and analogous articles it may be found expedient to grind and polish por- .tions which have been superhardened and this work will be done in proper sequence with the second tempering where this is practiced. It might be in the case of razor blades that the grinding would precede the second tempering, and the polishing succeed it.

It is to be understood that the invention is applicable to a wide range of manufactured articles, and that the examples selected for specific'description are illustrative of a wide range of subject matter. It is quite obvious that not only is it desirable to superharden surfaces which are intended to support loads and bodies which are to be held against deformation when loaded, but also edged tools of various descriptions which are required to retain a very fine edge.

I claim as my invention,

1. The method which consists of forming a steel article, then hardening the same, and then subjecting such article to a rolling pressure for superhardening the steel thereof at and adjacent the surface.

2. The method which consists of forming an article of steel, then hardening the article by quenching from a proper hardening surface thereof. 7

3. The method which, consists of forming an article of steel, then hardening the article .by quenching from a proper hardening temperature, then grinding'and polishing 'certainfaces thereof, then subjecting such faces msaaaa temperature, and then subjecting such ar-- ticle to a rolling pressure for superhardening the metal at and adjacent the said surface thereof.

5. The method which consists of forming an article of metal, then hardening the article by quenching from a proper hardening temperature, then subjecting such article to a rolling pressure for superhardening the metal at and adjacent the said surface thereplf, and then drawing at a low tempering eat.

6. That improvement in the art of treating metal which consists in hardening a formed metal article by heat treating the same, and then superhardening the surface thereof by the application of a series of blows or the equivalent thereof.

7. That improvement inthe art of treating metals which consists in forming a metal article, heat treating the article for hardening, cleaning certain surfaces thereof, then subjecting said surfaces to a relative rolling action thereby superhardening the said surface.

I 8. The method which consists in forming bearings which consists in forming the race rings and balls and hardening the same by heat treatment, then assembling the bearing and then subjecting the bearing to an excessive overload while rotatingthe bearing for the purpose of superhardening the metal at the track grooves and for superhardening the metal of the balls at-the surface.

11. The method of manufacturing steel balls which consists in forming the balls and hardening the same by heat treatment, then assembling the balls in bearing rings, and then subjecting the bearing to an excessive overload while rotating the bearing for the purpose of superhardening the metal of the balls at the surface.

12. The method of forming superhardened balls which consists in forming balls of suitable metal, then heat treating the balls for hardening the sax'ne, then subjecting the heat treated hardened balls to a rolling, motion between two hardened surfaces for superhardening the balls.

13. As an article of manufacture a steel ball formed of heat treated hardened metal, and having the metal at and adjacent its surface superhardened by rolling and pressure.

14. As an article of manufacture a roller bearing comprising a pair of race rings and a series of rollers therebetween, the race rings and rollers being formed of heat treated hardened steel, and the engaging surfaces thereof being superhardened by rolling pressure.

15. A ball formed of tempered steel having the metal at and adjacent its surface permanently deformed and superhardened.

16. The method which consists in forming an article of steel, then hardening and tempering the said steel, and then subjecting the surface thereof to a force to permanently deform and superharden the same.

\ 17. The method of manufacturing roller bearings which consists in forming race rings and hardening the same by heat treatment, then assembling the rings with rollers therebetween, and then subjecting the assembled bearing to an excessive overload while rotating same for the purpose of hardening the metal at the roller track.

In testimony whereof, I have afiixed my signature hereto.

AXEL GUSTAF EMANUEL HULTGREN.