US2429776A - Heat-treatment of metal articles - Google Patents

Description

'ct. 28, l A A E, SHORTER 2,429,775

HEAT TREATMENT 0F METAL ARTICLES A INVENTOA A ALBERT E., SHORTER A. E. sHoRTER HEAT TREATMENT oF METAL ARTcLEs oct. 28,' -1947.

Fiied April" 9. 1945 s sheets-sheet 2 IN VEN TOR. ALBERT E.- sHoRTER BY f ATTORNEY Oct. 28, 1947. A; E. SHOW-nana l HEAT TREATMENT OF METAL ARTICLES Filed April 9; 1945 3 Sheets-Sheet 3 ATTORNEY v Patented Oct. 1947 STATES PMENTDFFICB l l. l l v l I r l* y y Albert- Edward Shorter, Shefiield,Eng`land, assignor to The Linde Ali-@Products Company, a

corporation of Ohio Application Api-i1 9, `1943, serial' No. 482,367 In Great Britain June 3, 1942 s claims.

and firing pins;.,also annular surfaces such as l.

ball races and small crown wheels. `'For Asurface hardening articles having-a .lim ited superficial-area there has been adopted la method known as spot hardening. This method comprisesA applying high temperature heat yto the surface to be treated so that the whole surface is raised to the required temperature, without effecting, during the heating period, any relative movement betweenthe surface and the heating means. When the surface has attained the required temperature, the supply of heat is cut off,'and the heated part is thereupon cooled or quenched.- A, l In practice it has been found that a surface treated in this manner tends to crack on quenching. Such cracking is believed to be due, at least in part, to non-uniformity either in heating or in quenching or both, with consequent lack of uniformity in hardness as between different parts of lthe surface. Where ariV irregular surface is to be hardened, lack ofV uniform heating may be due to the difcultyof locating a suitable heating unit capable of raising all parts of the surface to a uniform temperature.

. Again,` whenl automatically hardening articles on a mass production basis where each of a series Vof similar articlesis introduced in turn -into a burner flame and then withdrawn therefrom, a `localised portion of the leading edge of the surface anda similarv localised portion of the trailing edge orv even a narrowband extending across the surface may besubjected for a slightly longer period tothe influence of the heating flamethan -the other parts of the surface, giving rise to nonuniformity inheating. rFor example, it has been proposed to insert boltsand like small articles in heat conductingblocks.provided-with pockets .for the reception of. kthe a rticles and, while-in these blocks, to feed-,the ,articles` at selected intervals firstr to a heating. .deviceand then to a quenching device. It hasgbeen lproposed to carry suchqa method intoeffect` bycmeans-'of apparatus com- .prisinga rotatabledrumpver. the 1periphery of ywhich are distriinited fmej'.,al blocksr having pockets, for.- theI reception of A the, articlesk to be hardducting blocks., it is possible in such cases to `hold the articles for a suilicient time for the heat therefore la ymethod .of -heat treating a surface or a localised'y surface portion of a lmetal article comprises directing high temperature heat therei upon simultaneously rotating the article about an axis normal or substantially normal to the surface or surfaceportion whereby the surface or surface portion is heated uniformly and cooling said heated surface.

According to another feature of this invention a method of heat treating a surface or surface portion of eachof a series of-articles comprises mounting the articles in` spaced relationship, effecting a relative translatory movement between the articles and a source of high temperature heat in order to present each article in turn to the influence of the high temperature heat for a predetermined period and imparting to each article While under the influence of the high temperature heat a vrotary motion about an axis normal or substantially normal to the surface or surface portion to be heated.

Preferably. the rotary motion is imparted' to the article before the leading edge thereof comes under the influence of the high temperature heat whereby localised overheating of the leading edge is prevented. Likewise, it is preferred For the `,heat treatment of a circularsurface of rsmall diameter, such as afbolthead or valve tappet, a burner nozzle emitting a single or multiple jet may be used as the heat emitting source,

but where more extended surfaces are ,to be heated a pluralityof such' burnerf nozzleslmay -be required, being preferably so arranged that heat lis distributedk .uniformly over thev surface without overheating the edge portions which are then heated solelyby" conduction. .Y

For heat treating 'an annular `surface such*v as 3 a bail racea multi-jet burner may be employed, the je'tsY being spaced at intervals aroimd the circumference of a circle having a diameter subwstantialiyequaltothemeandiameteroftheball racesothatthejetsimpingecentrallyonthey bottomoftheballgroove. Aseriesof quenching oriiices may be disposed between the burner jets orincloseproximitytheretosothattheheating operation may, if desired. be followed by quenching. Where, as in the case of a crown wheel, theannularsurfaeetobetreatedisof substantial width, a burner having a plurality of concentric rings of nozales may be usedand the spacingbetween the jets in one ring may diiier from that in another ring to eil'ect uniform heatingofannularzoneswherethemass of metalin one sone differs from that in another zone. By spinning the annular surface, in accordance with the invention, whilst the surface is presented to the burner jets and quenching orifices, not only canuniformsurfacehardnessbeimparted tothe surface but distortion is avoided.

To enable a series of similar articles to be heat treated on a mass production basis, the method aforesaid may be carried into effect by means of apparatus comprising a conveyor carrying a pluralityof rotatable work supporting means each adapted to receive an article to be heat treated, the conveyor being movable intermittently so as to bring each work supporting means in succession to a feeding device adapted to feed an article to be heat treated to the supporting means and then to a heat treating device adapted to direct high temperature heat upon the surface to be heated, means being provided for rotating the supporting means whilst the article is under the influence of the applied heat. If it is desired to quench the heated surface, the heat treating device may comprise a heating unit and a quenching unit adapted to emit a stream of quenching fluid mounted in spaced relationship to the heating unit so that, as the conveyor advances from the feeding device, the article iirst comes under the'inuence of the heating unit and then upon further movement ofthe conveyor the heated surface is presented to the quenching iiuid. Alternatively, a heat treating device comprising a heating and quenching unit combined to form a -unitary structure may be employed, the conveyor in such case remaining stationary for a period of suilicient duration to enable both the heating and the quenching operations to be carried out at the same station. Depending upon the sharpness of the quench required, the quenching fluid may be a liquid such as cold water, oil or a mixture of soluble oil and water, or a gas, usually air.

By way of example an apparatus suitable for the repetition heat treatment of small parts'on.

a mass production basis is shown in the accompanying drawings, in which- Fig. 1 is a view of the apparatus in side eleva.- tion, some parts being shown merely diagrammatically and other parts, well known per se, being omitted for the sake of clarity;

Fig.` 2 is a view of the same apparatus infront elevation;

Fig. 3 is a longitudinal section of a burner suit.. able for heat treating the tipsof articles, such as rins pins; e

Fig. 4 is a transverse section on the line IV-IV of Fig. 3; and

Fig. 5 is a longitudinal section of a burner suitable for heat treating annuli.

Referring to Figs. 1 and 2, the apparatus may able work supporting means J, each adapted to hold an article A to be treated. a heat treating device comprising a heating unit H, a quenching` unit Q, anda magazine M with automatic feedingmeans forloadingthearticlesinturnonto the drum D. In operation, the articles to be heat treatedareplacedinthemagazineMwhichfeedseachinturnintothejigs-T. DrumDisrotated intermittently in the direction of the arrow X so as to move the jigs carrying the articles from the loading station Vto the heating station. As the article is approaching the heating station. thereisimparted toitinamannerdescribedbelow, a rotary motion about an axis extending radially withrespecttothedrumDandnormal to the surface to be heated, and this rotary movement continues until the article is moved out of the heating station; When the article is at the heating station, heating unit H heats the upper end surface thereof to the requisite temperature, the duration of the heating being determined empirically. From the heating station the article A is moved to the quenching station where the quenching unit Q cools the heated surface. When, upon further rotation of the drum D, the article A is conveyed to a station below the hori-I zontal, it drops out of its jig and the latter, upon fstill further rotation of the-drum D, returns to the loading position where it is loaded with another article from the magazine M.

The apparatus referred to in general -terms above will now be described in further detail.

The drum' D is mounted upon a horizontal shaft il supported in bearings carried by the framework F, the shaft being coupled to electricallyenergized driving mechanism ilr adapted to impart to the shaft an intermittent rotatory motion of variable frequency. The driving mechanism' may, for example, comprise an electrohydraulic reciprocating device or a variable. delivery oil pump driven by a constant speed motor or ak constant delivery pump havingA a by-pass valve and driven by a constant speed motor. 'I'he .construction and arrangement of such driving mechanism are well known to those skilled in the art and onlyy a diagrammatic representation thereof is accordingly given in the drawings. The drum D is octagonal and carries eight jigs J, J2, J3, JI, J5, J6, J1, J8.. Jig J is mounted on a. spindle i2 which extends radially from the drum D and is furnished with an annular boss or friction wheel I3 adapted, when at the heating station, to engage frictionallyv with a friction disc I4 mounted upon an horizontal shaft I5 which. like shaft I0, is journalled' in bearings supported by the framework F, and is driven by a continuously rotatable electric motor i6. The other jigs are all identical with jig J.

The heating unit H comprises ar burner held in a clamp il mounted on vertical and horizontal slides i8, I9,.respective1y, which permit of the burner nozzle being. accurately located with respect to the surface to be treated. The burner is supplied with an Oxy-fuel gas mixture through valves 20 having gas inlets 2|, and a pilotiight 22 may be provided to ignite the issuing gas jet.

The quenching unit Q is supplied with cold water from a reservoir 23, a pump 2| driven by an electric motor 25 serving to feed water from the reservoior 23 to the quenching unit Q. Water discharged by the quenching unit` is led back to the reservoir by means of a shute 2i which also serves to collect the treated articles as they drop out of the jigs.

The magazine M comprises a vertical housing 21 down which the articles are fed by gravity to a plunger 28 operable by means-of a solenoid 29. When, in the course of rotation of the drum' D, a jig comes `into alignment'with the plunger 28.

the solenoid is energised causing the plunger 28 to thrust an article from the magazine into the jig.

the electric supply mains through conveniently located terminals and a master switch (not shown), and the supply of current to the driving mechanism I I, the friction disc motor I6, the pump motor 25 and the magazine solenoid 29 may be controlled by means of relays 30 housed in the carrying out the automatic heat treatment of a.

series of articles in the manner now to be described.

1t will be assumed that the drumDis in the position shown in Fig.v 2 where an article A in jig J is at the heating station and thatthe jigs J2 and J3 are each loaded with a similar article. Switches 3l, 32, 33, 34 are placed in the "on position and the gas valve v2l) is turned on simultaneously with the closing of switch 35 to set the train of operations in motion. The periodic thrust imparted 4to the shaft I9 by the driving mechanism I I will have previously been adjusted in frequency so thatthe drum D' remains stationary for the requisite heating period, but immediately switch 35 has been closed friction disc I4 is set in motion to rotate the work as the heating flame impinges thereupon. At the conclusion-of the heating period, an impulse is imparted by the driving mechanism -II to shaft I so as to rotate drum D through one-eighth of a complete revolution. This brings'jig yJ intothe quenching position where water or other cold liquid from the quenching unit Q is directedupon the heated surface of'article A whilst jig J2 is advanced to the heating station and as it does so, is caused to rotate by the friction disc I4 to spin the work in accordance with the invention. At the instant when drum D comes to rest with jig J2 at the heating station, the magazine solenoid 29 is momentarily energised through the intermediary of one of the relays 30 to feed an article from the magazine to the empty jig J4 which has advanced into alignment with plunger 28. After a period determined by the setting of the driving mechanism II, drum D is again advanced through a The apparatus is adapted to` be connected to ing to the quenching lstations in the manner described above. In such .cases both operations may be carried out at one and the same station using a heat-treating device comprisin vboth heating and quenching means. Suitablefieat treating devices for carrying such a method nto effect are shown for instance in Figs. 3, 4 and to which reference will now be made.

Figs. 3 and 4 show a device comprising twin burner nozzles 40 and triple quenching'nozzles 4I. Such a device may be used on plane surfaces but is especially useful for heat treating objects such as a firing pin.42, where the surface tapers to a point which is likely to become overheated if the flame from a single burner were to be directed thereon. By arranging the burner nozzles as shown in vFig, so that the flames impingenot on the point but at zones removed a short distance therefrom, overheating of the point may be predistance of one-eighth of an arc of revolution to bring jig J 2 into the quenching station. When. upon further advancement of the drum D, Jig J reaches the position occupied by jig J 6 in Fig. 2, the article A falls out of its jig and drops into the shute l26. This series of operations continu'ts automatically until switch 35 is opened.

When heat treating certain types of work it may be n ecessary for the quenching operation to be carried out immediately upon cessation of heating, that is to say, without introducing the delay which occurs-in moving the article from the heatvented.

The burner nozzles 40 and quenching nozzles 4I project from a block 43 provided with gas passages 44 and with passages 45 for the quenching medium. Gas passages 44 lead to a distributing chamber 46 adapted to be connected to the gas supply lines through the valves 20 (Figs. 1 and 2) Passages connect to a header 41 supplied with quenching medium through pipe 48, the quenching medium also serving as coolant for the burner.

In the arrangement shown in Figs. 1 and 2, the burner may be perpetually alight and the quenching 'medium issuing continuously from the quenching unit but, Where aheat treating device as shown in Figs. 3 and 4 is used, it is necessary to make provision for turning the gas supply on and oil automatically at the commencement and conclusion respectively of each heating period. and for turning the supply of quenching medium on and oil? automatically at the commencement and conclusion respectively of each quenching period. For effecting the automatic control of the gas supply, valves 20 may be of the solenoidoperated type, the periods of operation being determined by means of gas timing mechanism 38 mounted on the panel 31. For controlling the quenching period, ,thequenching medium supplied by pump 24.may be arranged to pass 'through a solenoid operated valve 49 associated with quench timing mechanism 50 also mounted on panel 31.v These valve-operated devices are arranged, through the intermediary of suitable relays, to be introduced into the cycle upon closure of a further push button switch 36 on panel 31.

Since'both heating and vquenching are to be effected at one and the same station, the fre-` quency of the thrust imparted by the driving mechanism Il to the shaft I0 must be adjusted to provide the requisite extended dwell at the heat treating station. This adjustment in frequency having been elected and the gas and quench-timing mechanism set at the appropriate values, the cycle of operations will be as follows.

With an article in the jig at the heat treating station and with switchesl, 32, 33, 34, 36 closed,

the automatic push button switch 35 is closed. This causes, through certain of the relays 30, the energisation of the solenoids controlling the gas valves 20 to turn these valves on, and the gas is ignited by the pilot light 22. After a period determined by the setting of the gas timing mechanism 31, the gas supply is cut off and lthe supply of quenching medium is turned on by the automatic energisation of the solenoid-operated valve 49. Upon completion of the quenching period,

as determined by the setting of the quench timing mechanism 50, the supply of quenching medium' is automatically cut oif and the driving mechanism il rotates the drum D through oneeighth of a revolution to advance the next jig into the heat treating station. When this jig has attained this position, the gas supply is again automatically turned on whilst at the same time the magazine solenoid 29 is energised to cause plunger 28 to feed another article to the .iig which has advanced into alignment therewith. This series of operations continues automatically until switch 35 is again opened.

For` heat'treating annuli such as ball races, a heat treating device comprising heating and quenching means as shown in Fig. may be used. Like the device shown in Fig. 4, that shown in Fig. 5 comprises a plurality of burner nozzles 40 arranged uniformly around the circumference of a circle having a diameter substantially equal to the mean diameter of the annulus to be treated, quenching nozzles 4|, burner block 43 with gas passages 44 and quench passages 45, gas distributing chamber 46 and header 41 for quenching medium supplied through pipe B8.

The device is mounted in position on the apparatus shown in Figs. 1 and 2 with the burner nozzles 4l) located so as to direct the gas jets upon each annulus as the annulus is advanced in itsjig to the heating station. To facilitate the location of the burner centrally with respect to the annulus, a central screw-threaded recess 5| accommodating a locating pin 52 may be provided in the burner block. The burner having been accurately located, the pin 52 is removed and the cycle of operations for eiiectingthe desired heat treatment may then be carried out automatically as aforesaid.

Should it be desired to temper a surface hardened as aforesaid s0 as-,to impart greater toughness thereto, means may be provided for reheating the quenched surface to a temperature below the citical point. Where the heating and quenching are carried out at different stations, a reheating unit may be mounted in spaced relationship with respect to the quenching unit so that the quenched article comes under the influence of the reheating unit as the conveyor is advanced a further step. Alternatively, where the heating and quenching are carried out at one and the same station, the heating unit may be brought into operation to reheat the surface after it has been quenched, the duration of reheating being shorter ythan the initial period so as to ensure that the surface does not again attain the critical temperature. As inthe case of the initial high temperature heating, the duration of reheating may be determined by means of timing mechanism adapted by means of a suitable relay to be brought into operation automatically `upon cessation of the quenching operation.

In the foregoing particular description, the heat treatment has been described with reference to heating with gas burners, but it will be underhigh temperature heat upon the surface to be heated, a conveyor carrying a plurality of rotatable work supporting means, each adapted to recelve an article to be heat treated, the conveyor being movable intermittently so as to bring each work supporting means in succession to a feeding device'adapted to feed an article to be heat treated to the supporting means and then bring said supporting means with said article thereon to said heat treating device, in combination with means for rotating the supporting means whilst the article is under the influence of the applied heat.

2. Apparatus according to claim 1, wherein said heat treating device comprises a, heating unit and a quenching unit adapted to emit a stream of .quenching fluid mounted in spaced relationship to the heating unit so that as the conveyor ad.. vances from the feeding device, the article first comes under the influence of the heating unit and then, upon further movement of the conveyor, the heated surface is presented to the quenching fluid.

3. Apparatus according to claim 1 wherein said conveyor is coupled to driving mechanism adapted to impart an intermittent movement thereto, the frequency of the impulses imparted to the conveyor by said driving mechanism being variable in order that the duration o'f dwell may be adjusted to that required for carrying out the heat treatment.

4. Apparatus according to claim 1 wherein said heat treating device comprises a heating unit and quenching unit combined to form a unitary structure, the said conveyor being adapted to remain stationary for a period of suicient duration to enable both the heating and quenching operations to be carried out at the same station.

l5. Apparatus according to claim 1, wherein said heat treating device comprises a heating unit and quenching unit combined to form a unitary structure, the said conveyor being adapted to remain stationary for a period of suiiicient duration to enable both the heating and quenching operations to be carried out at the same station, and wherein the duration of the heating operation and that of the quenching operation are determined automatically by timing mechanisms.

6. Apparatus according to claim 1, wherein said heat treating unit and a quenching unit adapted to discharge a stream of quenching iiuid mounted in spaced relationship to the heating unit so that as the conveyor advances from the heating device, the article first comes under the influence of the heating unit and then, upon further movement of the conveyor, the heated surface ispresented to the quenching fluid, and wherein means are provided for reheating the quenched surface so as to impart greater toughness thereto.

'7. A heat treating apparatus for small articles comprising a drum rotatable about an axis and having a plurality of rotatable article-supporting means, each of said article-supporting means including a rotary element, a heat treating device and a rotating device respectively radially spaced from the drum axis, said rotating device being adapted to be successively engaged by the rotary elements of the respective article-supporting means prior to a leading edge of the article coming under the influence of the heating unit and continuing in engagement therewith until a trailing edge is out of the influence .of the heating unit.

8. Apparatus as claimed in claim 7, in which the radial spacing of the heat treating device is 9 greater, and that of the rotating device is less, than that of the article supporting means.

' ALBERT EDWARD SHORTER.

l REFERENCES CITED The following references are of record in the fue ofthis patent:

UNITED STATES PATENTS Hartley July 1, 1941 4 Number Number 15 Rolf, Selective Hardening with the Oiiyacetylene Flame, transactions of the A. S; March,

10. Name Date Wasson May 13, l1941 Klopp 'Nov. 8, 1932 Mitchell May 12,l 1942 Morgan May 12, 1874 Buttler Oct. 3, 1899 Shonnard Sept. 12, 1944 FOREXGN PATENTS Country Date Italy Nov. 9, 1927 Great Britain Mar. 10, 1939 OTHER REFERENCES 1939, pages 43-54 (particularly page 54). (Copy in Division 3.)

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