US1732244A - Method of hardening steel - Google Patents

Description

S. I. SALZMAN METHOD OF HARDENING STEEL Filed March 29. 1928 m mml Q 000 OOOXOWW kk gmemloz Samue/ I. Sa/zman Patented Oct. 22, 1929- UNITED. STATES PATENT, ornca BAIUELI. BALM, OI BALTIMORE, MARYLAND KE'IHOD HARDMG STEEL Application fled men 20, 1928. Serial no. 2 5,530.

- sired degree of elasticity, toughness, and capacity for resisting shock. p

A further object is to devise a method as above described, and particularly one that is adapted for the hardening of thin steel, which.

is characterized by a high production rate, with a minimum of handling on the part of the o erator.

A urther object is to devise a method of hardening thin steel sheets in the form of razor blades which is designed to effect a substantially individual treatment of the blades without preventing the attainment of a favorable rate of manufacture.

A further object is to devise an apparatus for performing the hardening or tempering steps of the method which is designed to-efiect the chilling of the heated steel with marked rapidity, while at the same time absolutely preventing the creation of a warped cond1 tion through inadequately relieving the internal strains.-

My improved method and the apparatus for efiectuatin I the same are more particularly intended oruse in the heat treatment of thin razor blades of a well known ty As now practicedin the art, the blade lanks after perforation and forming, are assembled in stacked and interleaved relation on a frame with sheets having a high heat conductivity,

Y usually co' r. This assembly is then 4 blanks;

clamped, su ected to heat, and finally chilled to harden the blade blanks, the copper sheets serving both to conduct heat inwardly to and outwardly from the uncovered areas' of the Thepractice of the foregoing method prevents penetration of the blanks by oxidat1on,

' except over limited areas luring the heatin tain disadvantages which detract from its desirability for use. The stacking of the blades not only requires undue time and labor, but the manifest difliculty of uniformly clamping, heating, and cooling the blanks quickly at a uniform rate results in the production of blades having varying quahtiesl and capacities for maintaining a cutting edge. The method and apparatus embodied in the present application are intended to conserve the advantage of the older type of heat treatment in respect of preventing oxidation, while at the same time substantially effecting an individual treatment of the blanks, thus satisfying the ideal requirements. Notwithstanding this advantage, the production rate is not lessened, owing to the improved mode of handling, and may in reality be increased over existing methods. The product is characterized'by amarkeduniformity of structure, with a resulting capacity for withstandin shock and maintaininga cutting edge over a onger period of time than now obtains in the art.

For purposes of disclosure, the methodand apparatus are described with reference to the manufacture above noted, but it will be obvious that application of the central idea in-- volved may be made with equal facility to other products such as wire, springs of various types, and other articles reqmri treatment.

These and further objects of my inventionwill be set forth in the following specification, reference being had to the accompanyng .heat

lized in carrying out my im roved method,

arranged in the order of then operation. Figs. 2, 3 and 4 aresections taken along lines of the same respective numerical desig- 85 ing drawing, and the novel means by which nation in Fig. 1,.look-ing in the direction of 1 A steel strip 10 of any desired length and having a width and thicknessappropriate for thin razor blades is first perforated to form the usual openings 11 and 12, and is scored as at 13 to indicate the end edges of the blades. These operations are performed prior to the hardening and the stripmay then be fed di' rectly to the apparatus hereinafter described, or it may be wound on a spindle 14 in the manner-indicated by the numeral 15. From the spindle 14:, the strip 10 is unwound and drawn through the various apparatus hereinafter described by a pair pf coacting rollers 16, appropriately mounted and suitably driven, between which said strip passes.

The first step in my improved method is the heating of the strip 10 to a predetermined temperature which is effected by passage through a tube 17 of approved cross section which is arranged in a furnace 18 provided with a burner 19. The strip 10 is propelled by the rollers 16 at a predetermined, constant speed and the furnace 18 is of a length adequate to insure the heating of the strip 10 to the desired temperautre before it issues therefrom.

Immediately adjacent the delivery opening of the tube 17 is arranged the apparatus for effecting the chilling of the heated strip for hardening the same. This apparatus comprises a pair of coacting chambers 20 and 21, preferably arranged in vertical relation, with the strip 10 passing therebetween and subjected to the weight of the upper casing 20.

' A chilling fluid 22 passes continually through said casings, ducts 23 and 24-comn1unicatiug with the upper casing 20 for this purpose and ducts 25 and 26 with the lower casing 21. Said casings are preferably formed of a ma-- terial having a high heat conductivity, so that the heated strip 10 in passing therebetween will be quickly chilled, the abstracted heat being conducted to the chilling medium 22.

In order to relieve any internal strains that may be present in the strip 10 after being subjected to the action of the chilling medium and to properly temper the same for insuring the obtention of a fine cutting edge, said strip next passes between a pair of coacting channel frames 27 and 28, also arranged in vertical relation, the bases of said frames serving to clamp said strip under the weight of the upper frame 27 and the. upstanding sides thereof to properly confine the heat received from burners 29 and 30. During passage between said frames, the strip will be again heated, but to a temperature less than the initial temperature receivedin the furnace 18'.

After leaving this second heated zone, the strip 10 is again chilled by moving between coacting casings 31 and 32 which are similarly arranged and constructed to the casings 20 and 2 1. The heat treatment of the strip 10 is then completed, after which it may be severed along the scored lines 13 to form the blade blanks which may then be ground'and" polished in any approved manner.

It will be observed that, according to my improved method, the heat treatment is' a continuous operation, thus insuring a high production rate even though the, successive blade blank portions of the strip 10 are treat ed individually. Two desirable, but heretofore conflicting characteristics, are therefore successfully combined. Heating and chilling of the strip 10 are effected without oxidation thereof or contact with the flame or chilling medium and moreover, adequate pressure is maintained during the chilling and second heating operation to prevent warping of the strip. However, the latter pressure will not be sufficiently great to prevent movement of the strip 10 by the rolls 16 and this pressure may be exerted either in the manner shown, under the action of gravity, or it may be effected mechanically, which would permit the positioning of the chilling casings and heating frames in other position relations than vertical.

The product resulting from this mode of treatment possesses a high degree of elasticity without affecting its capacity for receiving and maintaining a cutting edge over a considerable period of time, characteristics which are highly desirable in razor blades. As before stated, it is contemplated that the strip 10 will be propelled through the various steps of the tprocess by the rollers 16 at a constant rate 0 dling has been found suitable for the heat treatment of razor blades, but it will be obvious that other types of products might requlre a varying or intermittent rate of speed.

While I have shown one set of elements and combinations thereof for effecting my improved method and apparatus for the heat treatment of steel, it will be understood that the same are intended for the purpose of i1 lustration bnly and in nowise to restrict the same to the exact steps and combinations shown, for many changes may be made therein without departing from the spirit of my invention.

I claim:

1. The herein described method of hardening lengths of steel which consists in drawspeed, which mode of hanheated zone, a chilled zone, a. second heated zone including the application of heat to the opposite sides of said steel, and a second chilled zone to harden and temper the original length progressively, a redetermined pressure being maintained on t e portions of said steel passing through said chilled zones and said second heated zone, and said steel being maintained free from contact with the chilling medium employed.

In testimony whereof, I aflix my signature,

. AMUEL I. SALZMAN.

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