CA1084263A

CA1084263A - Apparatus for heat treatment of material

Info

Publication number: CA1084263A
Application number: CA274,383A
Authority: CA
Inventors: Bernhard Hilge; Friedrich W. Elhaus
Original assignee: Prolizenz AG
Current assignee: Prolizenz AG
Priority date: 1976-03-22
Filing date: 1977-03-21
Publication date: 1980-08-26
Also published as: DE2712279C2; NL7703092A; DD128911A5; BE852691R; JPS5743615B2; GB1578520A; NO147692C; NO770995L; RO72392A; ATA198977A; AT355324B; JPS52138004A; CH610010A5; FR2436189A2; NO147692B; FR2436189B2; YU76277A; FR2345521B2; FR2345521A2; HU175024B

Abstract

ABSTRACT OF THE DISCLOSURE

An apparatus for heat treatment of metal pieces comprising a first means for conveying a pre-heated furnace and a second conveying means adapted to convey the metal pieces through a holding furnace while rotating them along their longitudinal axes and a cooling station adapted to water-cool the rotating metal pieces. The second conveying means comprises stationary beams and lifting beams adapted to lifting the metal pieces from the stationary beams, convey them a predetermined distance and deposit them onto said stationary beams, after which the metal pieces are allowed to rotate through for a predetermined circumferential distance along said stationary beams.

Description

This invention relates to an apparatus for heclt -treatmont o~
material to be worked on, SllCh as cast s~r.ips and billets, as well as ingots, rods, tubes and tlle like, especially of aluminum or magnesium alloys The heat treatment is of the general type in which the material is first pre-heated and thereafter is held at a desired heat treatment temperature.
Cast strips, billets and extrusion and rolling products~ are ; customarily subjected to a heat treatment in order to homogenize, heterogenize, or otherwise heat treat the material, For example, continuously cast billets of aluminum alloys are first pre-heated after the casting, annealed at temperatures between 500 and 620C, and thereafter cooled, During this ~.
treatment, the billets receive the structure desi.red for fur~her working, such ~ ~.
as for example by extrusion or rolling, The material is customarily pre-heated with circulated hot gas, flue .
gas or with circulated hot air. As a result of the comparatively low temperature of such a source of heat or "heater", the pre-heating step takes .
a very long time, If the material is to be passed through the apparatus in a continuous manner or in a flow operation, one normally tries to transport the material ~ at an equal and constant speed through the pre-heating zone and subsequently :i through the holding heat treatment zone in the furnace. If the pre-heating is of long duration, the pre-heating zone ~ust be disproportionately long with respect to the holding zone or the material, upon entry into the holding zone, , does not attain the proper annealing temperature, :
In using prior art apparatus, in order to achieve different annealing ~
' temperatures, the temperature of the hot gas in the pre-heating area or zone :
and in the holding phase area or zone must be finely controllable. This is normally very difficult and a change in the temperature of the hot gas is ~-usually only possible within narrow limits. Additionally, as was noted above, in a flow-through operation, the material must normally be transported with equal speed through the pre-heating zone and the holding zone '~

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' ~ s a result, ~he prior art apparatus has the disadvantage of restricted flexibility in treatment of materials and, especially, a restricted adaptability to the changing of conditions under which the material is treated.
An additional serious drawback in known devices is that during heat treatment, ~hich eventually also comprises subsequent cooling, the material suffers uneven deformations which may result in distortion or bending of the ' material.
One of the principal objects of the invention is to provide an apparatuS of the kind referred to above but in which the noted drawbacks are avoided and ~ith which apparatus a material of consistent quality can be ~ produced.
- Uniform quality may be ensured and deormation or distortion such as bending, warping or curling of the billets may be controlled by the individual treatment of the billetsO For this purpose it is particularly advantageous if the billets are rotated about their longitudinal axes during the holding. Such a rotation appears to be appropriate for avoidance of warping or curving also during the cooling following the heat treatment.
The individual treatment of the pieces, i.e. the treatment of not packed-type charges, but of long single billets, or of groups of shorter series-arranged ingots, ensures a substantially uniform quality9 because the individual billets, or ingots, are exposed to uniform pre-heating and heat-maintaining conditions. The brief pre-heating period permits a better balancing of the pre-heating and heat maintaining phase, The pre-heating period for one billet made from an aluminum alloy to a final temperature of from 500 to 600C requires from 10 to 30 minutes, dependent upon the cross-section of the billet9 provided the pre-heating is carried out by means of direct exposure to flames and/or hot gas radiation. The pre-heating of a ;~ billet in a separate pre-heating furnace permits an accurate individual ' temperature-control during the pre-heating process. This temperature controlJ
as well as the individual adjustability of the cycle sequences required by ;

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the pieces in the pre-heating Eurnace ancl the speed o passa~e o~ the billet through the pre-11eating furnace~ p~r~it gr~at Elexibility of cycle frequcnce, desirable to satisfy the requirements of post~treatment, of alloys requiring different treatment, of interrupted operation, or of operation on partial load.
In view of the high efficiency of the pre-heating furnace and of its increased throughput, the ratio of investment costs and production capacity of this prior system is relatively small, It permits a continuous flow of pieces, In comparison with the conventional processes and systems~

these factors combined represent a substantial rationali~ing effect.
n A5 ~
It is ~ ~ of the present invention to modify the prior system with regard to a further improvement in uniformity of quality of the properties of the pieces and of the geometric form of the pieces as well as of the economy of the process, ~', ,4sp~6-~
This~Jbr36~ has been achieved by using a system of the aforestated kind, in that the transporting means inside the holding or heat-maintaining furnace is provided with memberspermitting the rotation of the individual ~i work piece about its longitudinal axis during its transportation, and the cooling station is provided with means for a preferably continuous rotation of the individual work piece during its cooling process, According to the apparatus of the present invention, the required manipulation of the work pieces has become reduced to a minimum.
The present invention comprises an apparatus for heat treatment `
of unfinished metal pieces comprising a pre-heating furnace, a first conveying ~1 means adapted to convey said metal pieces individually through said pre-i heating furnace; a holding furnace; a second conveying means adapted to convey said metal pieces individuallythrough said holding furnace and -simultaneously to rotate said metal pieces along their longitudinal axes;
and a cooling station adapted to expose said metal pieces individually to a cooling strec~m while said metal pieces are rotating along their longitudinal _3_ .

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Ihe holding or heat-maintaining furnace is preferably adapted to be heated either electrically, or by means of a fuel and offers a forced circulation of the air in the furnace. The pre-heating furnace may be heated in the same fashion, as long as it is ensured that the pre-heating temperature of the heat carrier is higher than the heat-treatment temperature of the material inside ~he heat-maintaining furnace.
~ccording to one advantageous embodimen~ of the pr~sent invention, the transporting device is provided with stationary beams having Elat suraces slightly declining in the direction of transportation of the pieces as well as in the direction of lift with saw-tooth shaped projections on said flat surfaces and, independent therefrom, lifting beams adapted to be driven in ; the direction of advance of the work pieces, said lifting beams being disposed between and - in rest position - below the stationary beams and forming a surface for receiving the work pieces. The lifting beams are provided with successive prismatic abutments exceeding the diameter of the work pieces.
The work pieces are lifted from a depression formed by two neighbouring saw-teeth by means of the lifting beams and lowered in controlled fashion onto the declining surface of the subsequent depression, from where the pieces by the force of their own weight roll into the bottom of the depression while maintaining contact with the lifting beam which is being lowered in controlled fashion opposite to the lifting direction, For a fuller understanding of the nature and objects of the invention, re~erence should be had to the following detailed description, taken in connection with the accompanying drawings in which:
Figure 1 is a schematic view of an apparatus according to the invention with two pre-heating furnaces and a successively arranged holding ;
or heat-treatment furnace;
Figure 2 is a cross-section through a pre-heating furnace which is preferably employed in an apparatus according to the present invention;

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.-Figure 3 is a section along the lines III-III of Figure 2;
Figure 4 is a longitudillal section through a holding furnace which can be emp.Loyed in the appara~us according to the .invention, with a transport device constructed in accordance with the invention, ;
Figure 5 is a partial section according to lines V-V of Figure ~;
Figure 6a to 6e are transport phases succeeding one another in time, in transporting the material through the heat retaining furnace; and ~ Figures 7 and 8 are, respectively, a partial longitudinal section, - and a cross section according to line VIII-VIII of Figure 7, of a cooling station at the outlet side of the heat retaining furnace.
.~ In the schematic plan view according to Figure 1, work pieces comprising bars or billets are indicated by the reference numeral 1. From :
. a supply device or a magazine 2, the billets or bars 1 are automatically ;
transferred individually to a transport device 8, which can supply step-by-step, in the direction of the horizontal arrows, into the pre-heating pre- ;: .
treatment furnaces 3 arranged to left and right of it, as seen in ~igure 1.
;` The billets or bars I are brought rapidly to full annealing temperature individually in the pre-h ating pretreatment furnaces 3 in stationary . condition by direct flame impingement by means of burners.
The individually heated ingots or billets are then discharged from the pre-heating furnace 3 and are successively passed one by one from the transporting device 8 to a heat-maintaining furnace ~, This furnace ~ is a continuous flow furnace operated with circulated hot gas, for example hot ~.
air. The high annealing, cr maintaining tffmperature is kept constant within . a narrow margin of tolerance across the length of the heat-maintaining furnace so that in case the billet failed to reached the required temperature during pre-heatingl it will attain its high annealing temperature in the heat-maintaining furnace after a brief path of travel through the heat-. maintaining furnace.
The pre-heating temperature can be adjusted finely and over a wide :;
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:i range, by alteration o the pre-heating time, that is of t~le period of time in which -the billets 1 are held in thc preheating furnaces 3, an~ by control of the burners, making it possible to obtain a uni~orm pre-h~ating of the billets The holding time in the holding or tr~a~men~ furnace ~ can be varied according to the alloy composition of the billets and the desired structure by alteration of the speed of through travel. The temperature in the holding -~ furnzce 4 can be altered, for example by control of the temperature of the hot air gas.
In the holding furnace 4 devices are provided for rotation of the billets 1 about their longi~udinal axes, so that these are completely uniformly heated and warping or curving cannot occur, and curved bars are straightened.Th~bars,plas~icised by the annealing,automatically straighten themselves by reason of their own weight. If the heat treatment does not require a cooling step, and the holding or full annealing temperature is suitable for further working, for instance for extrusion or rolling, the billets emerging from the holding furnace ~ can be conveyed directly to a further working device 5, for example, to an extrusion press or to a rolling ` mill.
In the case of where an adjustment of the temperature of the billets is required prior to further working, the billets 1 are transferred from the ` exit of the heat retaining furnaces ~ to a cooling station 6I where they are cooled individually with water and/or air At the cooling station 6 there is arranged, as shown in detail in Figs. 5 and 6, a device for turning the billets during cooling, to achieve a uniform cooling effect from all sides and to prevent bending or distortion of the billets.
From the cooling station 6 the billets 1 reach a magazine 7, from where they are conveyed to another station for further working.
The separation of the pre-heating and heat maintaining steps opens the possibility of individually con~rolling the temperature, or transport ,, -6- `
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spccd and seq~l~nce in the pre~heating and heat main~aining phase. This leads to a very hi~h flexibility of the whole installation, brought about by the optimal adaptability in each case to tlle different requirements during operation, such as realization o~ dif~erent peak annealing tempera~ures, desirable in practice for different alloys, interrupted operations, or operation under part load and in adapting to successive devices or to stoppages in the billet supply. A pre-heating or pre-treatment furnace operating by direct flame impingement is smaller than other systems, resul~ing in reduced space requirements of the installation. The material flow is greatly improved ~ -and the quantity of the material flow is increased due to the continuous or quasi-continuous performance. ~ -Figs. 2 and 3 show a preferred preheating furnace in detail.
The pre-heating furnace has such a leng*h that a billet of the largest size available in practice ~7-8m) fits into it lengthwise. In the preheating furnace 3 there is a provided double strand or strip conveyor chain 13 with carrier devices 12 mounted thereon to support the billets l.
The carrier devices 12 reach through a longitudinal slot into a cylindrical furnace chamber 15 formed by two furnace shells 14. The furnace shells are each journalled to swing by their lower ends on a carrier rail 16 and are ~;
held together above by spacing members 17, ~aterally, the furnace shells are supported on the ~urnace wall by radial supporting bars 18, By removal of the spacing members 17 and slight swinging inwards aro~md the supporting points on the carrier rail 16, the furnace shells 14 can be dismantled - without difficulty, The furnace shells 14 have four radially directed rows of openings 22, into which discharge the nozzles 21, likewise radially directed, of pre-mixed burners l9, 20, The radially directed rows of burners extend over the entire length of the furnace shells 14, In doing so, the lower rows of -: ~ :
burners 20 are arranged close to the supporting devices 12 and directed obliquely upwards, while the two upper rows of burners are offset by about 90 ~7~
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;3 ~o thc corr~spon~:lng low~r rows of burners and directe~ obliquely downwards.
The upper rows o burllers 19 can bc acljusted with respect to the lower rows of burners 20.
sy virtuc of the arrangement of the rows of burners 19, 20 during heating of billets 1 or 1' (of smaller ~iameter), the surfac~s for heat transfer are employed in an optimum manner, so that a circularly symmetrical temperature distribution over the cross-section of the billets is achieved.
The output of burner nozzles 21 is individually adjustable so that the desired temperature distribution is attained in each case at the end of ~he pre-heating period.
The billets lie freely on the supporting means 12 throughout thepre-heating period so that ~he heat-produced lengthwise expansion of the billets does not exert any undue horizontal orce on ~he conveyor chains 13.
The carrier devices 12 for the billets 1 or 1' have, at the place where they penetrate into the slot formed between the two furnace shells 14, a shaft which is rectangular in cross-section and which fills up the slot, except for a safety spacing necessary for thermal expansion The flue gases leave the furnace cavi~y 15 upwards through the slot formed by the furnace shells 14 and the spacer members 17, and are, together with fresh air, drawn away through a suction fan along the exhaust duct 26. The outer casing 27 serves in this connection at the same time as an air duct for the fresh air drawn in.
The pipes 28 necessary for the mixing and measuring of the combustion gas, as well as a device 29 ~or measurement of the temperature of bars 1 or 1', are arranged at the right-hand side of the furnace as seen in Fig. 2.
For pre-heating, the billets are pushed into the furnace from the transport device 8 and are taken over by the carrier devices 12 which are moved by the double-run conveyor chain 13. The drive for the double-run conveyor chain is controlled by a limit switch, not shown, which turns off : ., .. ,. . ; . ~ , r~~~

the drive when a billet 1 runs against an abutment 30 at one end of the furnace shells 1~
Measuring devices, not ShOWTI, arranged at uniform spacings over the length of the urnace shells 14 measure the length of the billet inserted at each moment. These measuring devices control the noz~les 21 in groups, so ; that at each moment only a number of nozzles corresponding to the length of a billet is actuated for pre-heating. The burners are switched on when a corresponding billet 1 has reached the position shown in Fig, 3 against the abutment 30 With shorter billet lengths, it is also possible that the pre-heating furnace 3 is supplied with a plurality of bars.
` The pre-heating furnace described above is also capable of continuous operation, in which case billets are preheated in moving condition.
The drive is, however, preferably intermittent, so t~at the necessary matching with the following period of annealing in the holding furnace 4 is achieved.
The holding furnace 4 shown in Figure 4 in longitudinal section is constructed for continuous flow operation and is heated by hot gas. The hot ~ gas, for instancej hot air~ is blown by a radial-axial blower 40 against the ;` billets 1 or 1' which are to be kept hot, and is circulated in the furnace.
The billets lie in saw-tooth-shape depressions 42 with oblique surfaces 42a formed on stationary beams 44 extending longitudinally through the furnace space 43. The beams 44 are arranged with spaces inbetween, at least two of which have a width x (Figure 5). Lifting beams 45 extend intermediate and parallel to the beams 44. The lifting beams have flat - surface portions 45' capable of receiving the billets 1 or 1'.
These flat surface portions 45' are defined and restricted by prismatic abutments in the form of angle profiles 46 welded onto the flat surfaces of the lifting beams. Adjacent angle profiles are spaced at distances at least approximately equal to those of adjacent depressions 42 cl;s~ p c æ l

3 ~ and have, relative to the~id~h ~f the flat surface portions 45/j (d~ e _9_ .

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5~ k-rn~g~ , a small longitudinal expansion ~ when vi~wed in the direction A
J~ . ~-of travel of the billets 1 so that the bille~s 1, 1~ of conYentional cross-section can roll off the flat surface portions 45' The angle profiles 46 merely form safety abutments, providing restraint in case the billets 1, 1' should, for any reason, for example in lifted-up position, rotate, possibly due to a torque acquired during the lifting.
Three lifting pipes 50, having a square cross-sec*ion, engage each lifting beam 45 from below They are vertically moveable but non-rotatingly held in rectangular longitudinal slots 51 in the floor 52 of the heat maintaining furnace. One of these longitudinal slots 51 is shown for better understanding in dot-and-dash lines in Figure 5, with floor 52 omitted.
One possible construction is shown at the right in Figure 4 Into the lower end of each lifting pipe 50 there is welded a nut 53, through which is passed a spindle 54, in screw-threaded engagement therewith, Each spindle 54 carries at its lower end a bevel pinion 55 which meshes with a bevel pinion shifted by 90. All bevel pinions 56 are arranged on a common horizontal shaft 57 which is actuatable by a drive mo~or 58 in order to simultaneously raise the lifting pipes 50 and therewith the lifting beams 45.
The shaft 57 is journalled in housings 47, each associated with a -~ 20 corresponding spindle 54, lifting pipe 50, and bevel pinion pair 55, 56.
The motor 58 and the housing 47 are mounted on a carriage 59 which operates on rollers 60. This carriage is operated by a double-acting fluid cylinder 61 and is movable by a horizontal stroke y (shown in Fig. 6~c)~ which corresponds approximately to the horizontal component of the length of the oblique surfaces 42a~, The vertical travel z ~shown in Fig. 6(d~) of the lifting beam 45 is produceable by the above described lifting arrangement which is geared in such a manner that the lifting beams 45 with the angle profiles 46 are adapted to be freely adjustable underneath the billets 1~
in their lowered positions and, in lifted-up position, the bill0ts 1, 1', placed on the lif~ing beams 45, during horizontal transportationdo not run up ;~

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on the oblique surfaces 42a of the saw-t~othe~ depressions 42 of the stationary beams 44. ;~
In a second preferred embodiment ~lllustrated in Figure 4 at th~
left hand spindle gear)> the nut 53 of each spindle gear 54 is movably held in the housing 47 and tightly connected with the lower end of the lifting pipe 50 and not turnable, but vertically movable in the housing 47 in the axial direction. All component parts of the spindle gear are in this CQS0 lodged and mounted in the housing 47 and the lifting pipe 50 no longer contains any movable parts of the drive gear This is advantageous for mounting and maintenance ` The transport of the billets 1 by means of the transport device shown in Figures 4 and 5 will now be described with reference to Figures 6a to 6e.
The lifting beam 45, according to a preferred construction, is ; provided with prismatic abutments in the form of angle profiles 46 welded , ,:
onto the flat surface 45' of the lifting beam 45, which serve merely to ensure a minimal spacing of the bars 1 lying one next to the other, In the rest position of the lifting beam 45 (Figures 4 and 6~, the flat surface portions 45' between the angle profiles 46 are slightly shifted ahead of the depressions , ~ 20 420 In principle, the transport device would also function without the angle . .
` profiles 46, that means with a lifting beam 45 having a horizontal flat surface.
Figure 6a shows in the depression 42 a billet 1 of larger cross-section with its CentTe offset against the direction o transportation A.
This is due to the incline of the oblique surface 42a which is smaller than its denoted opposite surface.
In the rest position, according to Figure 6a the billets lie in the depressions 42 of the stationary beams 44. The lifting beams 45 lie below `
the stationary beams. By actuation of the spindle gears~ the lifting beams are moved upwards in lifting direction B. engaging the billets 1 and lifting ,; -11- ~,:

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~hese upwards ~roln tlle ~epressions ~2 through the distance z (L~igures 6~ .
After eompl~tion of this lifting movement, each lif~ing beam 45 is movecl to the right as shown in Pigure Gc, by means of ~he drive cyl:inder 61, through the distance y in transport direction ~. During this movement the billets 1 move to above the oblique sur~ace ~2a of the next follow;ng depressions ~2 in transport direction A. This ~nsures that also those billets which were curved before exposure to heat treatment pass the holding furnace wi-thout trouble, After completed advance of the beam in the transport direction A, the spindle gear is again actuated, bu~ now in direction s' which is opposite to the lifting direction B, The speed of this movement is controlled in such a way that the billets are gently lowered onto the oblique surfaces 42a of the stationary beams (Figure 6d). The billets 1, due to their own weigh~J
now roll from the oblique surfaces 42a into the depressions ~2. During this, they turn about an angle (Figure 6e~. However, this rolling movement is controlled by the lowering movement of the lifting beam in the direction B', that is to say it is braked to such an extent that no impact blow is created on arrival in the depression 42 that would damage the shape and surface of the billets which are annealed~ to plasticity, The length and incline of the oblique surfaces 42a are such that a sector of the billets turned through the angle reaches the depressions 42 and at each next following depression the billets arrive turned to another sector, so that in each case another sector or portion of the billets comes in contact with the circulated hot gas or the circulated hot air. Thus the entire body of each billet may be maintained at a very uniform temperature. ~-The rolling of the billets on the oblique surfaces 42a, controlled by the downward movement of the lifting beam 45, leads to the automatic straightening ~ ;
of the billets due to their own weight, thus eliminating curvatures that might have occurred for any reason.
In the manner described, the billets are transported through the !~ ~

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heat treatment furnace, avoidin~ any gripping between the lifting beams ~5 an~ the stationary b~ams ~4, so tha~ the dange~ of injuring the ~illets is practically eliminated, Simultaneously with th~ lifting movement of the lifting bcam 45, the furnace doors 48, 49, are opened for admitting or discharging the bars 1 or 1'. The furnace doors ~8, 49 are shown in Figure ~ in broken lines in opened position.
In practice, the billets can attain weights of the order of 1 ton T. Hence, according to the number of billets received at once in the furnace, between 25 and 40 tons must be lifted, lowered and transported, in a ~, controlled manner. This is not possible with a usual ~ombined drive, such as an eccentric drive, and has been attainable for the first time by the separation of lifting and transporting motion according to the invention, The cooling station shown in Figures 7 and 8 has a spray chamber 70, on the upper wall 71 of which there is mounted an internal closed water channel, comprising several segments 72 aligned in succession in the longitudinal , : . , direction. Each segment 72 of the water channel has a separate water supply ; pipe 73 and in its lower wall is provided with spray holes 74 which are arranged close to one another in a row in ~he longitudinal direction of the water channel. Below the water channel a shaft 75 a plurality of axles 76, as well as a shaft 77 extend through the spray chamber, parallel to one another. Shafts 75, 77 and axles 76 are all supported by bearing blocks 78; shafts 75, 77 and axles 76 being movable in journals 79, 80.
Shaft 75 is driven by a drive motor 81 arranged outside the spray chamber 70 and carries a plurality of rolls 82 secured to it in a co-axial relationship at regular intervals, Axles 76 are mounted to rock about shaft 77 by means of at least two rockers 8~. In the~normal position shown in Figure 7, axles 76 lie in the same horizontal plane as shaft 75 and at a distance from it adjusted to the size of the billets l and 1' to be handled, which distance is smaller than the diameter of the billets.

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:, . ,~ . ,. : . , l~olls 83, w!l:ich are of the same diameter as the rolls 82 of the shaft 75 are loosely nlounted on the axlc 76. Rolls 82, 83 are associated in pairs, and form a prismatic reccss :for billets 1 or 1' Rockers 84 supporting axles 76 are rigidly connected to shaft 77 This shaft 77 is shiftable by a pivoted cylindcr 85 and a crank arm 86 fixed to the shaft 77 and pivotally connected to a pist~n rod 87 of ~he cylinder 85. The rocker 84 is shown in rotated position in dot-and-dash lines Thexe is furtllermore provided at least one transfer arm 88 to feed the billets 1 into the spray device, This arm 88 is shiftable by a cylinder 89 with a piston rod 94, between the two positions shown in full and in dot-and-dash lines, about the a~is of the shaft 75.
In the lower portion of the spray chamber 70 there is a collecting tub or reservoir 90, from the deepest loca~ion of which there .issues a discharge pipe 91 directed vertically downwards.
The spray device described operates as follows:
A hot billet 1 or 1' coming from the heat maintaining furnace is set in motion along a roller conveyor 92 arranged alongside the spray device.
: The cyli.nder 89 has been actuated so that the transfer arm 88 lies below the : track of the billet 1. When ~he conveyor 92 stops, the cylinder 89 is ..
extended, and hence the transfer arm 88 is lifted, raising the billet 1 -; from the position shown in dot-dash lines, so that the billet may roll along the flat surface 93 of the transfer arm 88, which is now slightly sloping towards the rolls 82, 83 and the billet may thereby reach the prismatic recess between the rolls 82, 83.
In order to prevent a hard drop of the billet into the prism formed by rolls 82, 83 and possible damage to the billet, cylinder 85 is extended simultaneously with cylinder 89, or remains extended from the preceding operational phase. The rocker 84 is in lifted-up position, as denoted by the dot-dash line in Fig. 8. In this position, roll 83 intercepts the billet 1, rolling down the transfer arm, without damaging the surface of the billet ' 2~3 Cylinder 85 is -then retracted so that roeker 8~, placed in a controlled fashion in the lowered position - sho~n in drawn-out line - permits the billet to be softly placed into the roll prism. Drlve motor 81 then begins to rotate shaft 75 an~ thus rolls 82 (Figure 8) in clock-wise directionJ causing the billet on the prism ~ormed by rolls 82, 83 to continuously rotate about its longitudinal axis in counter-clock-wise direction. Rockers 8~, with their axles 76 and rolls 83, are in their lower posi~ions, resiliently supported by the column of air remaining in cylinder 85 even in its lowered position. This ensures that any blowsJ possibly occurring during the rotation of the billet, are yieldingly taken up and there is no danger of - any surface damage, or distortion to a billet by any such blow. Water is then sprayed through the spray holes 74 onto the billet 1 or 1', Since ~he spray holes 74 are arranged over the whole length of the billet and at small distances from one another, a very uniform cooling of the billet is achieved.
To discharge the cooled billet, piston rod 87 of cylinder 85 is extended, .:
after previous retraction of piston rod 94 of cylinder 89 and consequent shifting of transfer arm 88 into the lower positon shown in ull lines, so that rockers 84 and axle 76 move from the full-line position into the dot-dash-line position, This moves the billet out of the prismatic recess between rolls 82J 83 onto the now outwardly sloping surface 93 of the ; transfer arm, from which it rolls down onto roller conveyor 92 for further handling. Piston rod 94 of cylinder 89 is fully withdrawn and surface 93 of the transfer arm is placed in its lowered position as shown in Fig. 8 in full lines.
Rotary brushes (not shown in the figures), adapted to engage the surface of the work pieces, may be installed at suitable positions of the apparatus of the present invention for surface treatment (by mechanical scrubbing) of the work pieces.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Apparatus for heat treatment of unfinished metal pieces comprising a pre-heating furnace; a first conveying means adapted to convey said metal pieces individually through said pre-heating furnace; a holding furnace;
a second conveying means adapted to convey said metal pieces individually through said holding furnace and simultaneously to rotate said metal pieces along their longitudinal axes; and a cooling station adapted to expose said metal pieces individually to a plurality of cooling streams of water while said metal pieces are rotating along their longitudinal axes.

2. The apparatus of claim 1 wherein said second conveying means comprises at least three stationary beams with upper surfaces formed of a series of successive saw-tooth like transverse elevations and depressions, having oblique surfaces slightly inclined in the direction of transport and capable of supportively receiving said metal pieces; at least two lifting beams located intermediate and parallel to said stationary beams below said upper surfaces of said stationary beams but capable of being repeatedly and reversibly raised above said upper surfaces, said lifting beams having flat upper surfaces with a plurality of prismatic abutments, said lifting beams being repeatedly and movable in the transport direction in their raised position and in the direction opposite said transport direction in their lowered positions.

3. Apparatus of claim 2 wherein said prismatic abutments are arranged on said flat upper surfaces of said lifting beams at intervals greater than the diameter of said metal pieces.

4, Apparatus of one of claims 2 or 3 wherein said prismatic abutments comprise angled sections, the dimension of which in the transport direction is small in relation to the intermediate flat surface portions, whereby said metal pieces are allowed to roll through a controlled circumferential distance on said flat surface portions.

5. Apparatus of claim 2, wherein said lifting beams are supported by lifting devices simultaneously and repeatedly operable in the lifting direction; and wherein said lifting devices are supported on a common carriage, shiftable repeatedly horizontally in the transport direction.

6. Apparatus of one of claims 2 or 5, wherein said lifting beams are movable in the lifting direction, and in the opposite direction, by means of a double-acting cylinder.

7. Apparatus of one of claims 2 or 5, in which said lifting beams are movable in the lifting direction, and in the opposite direction, by means of screw drives.

8. Apparatus of claim 5, wherein said carriage is movable in said transport direction, and in the opposite direction, by means of double-acting fluid cylinder.

9. Apparatus of claim 1 wherein said metal pieces are rotated in said cooling station by a rotating means, said rotating means comprising at least one pair of rollers, wherein the two rollers of each of said pairs constitute a prismatic recess for supporting said metal pieces.

10. Apparatus of claim 9, wherein at least one of the tow rollers of each of said pairs can be driven.

11. Apparatus of one of claims 9 or 10 wherein one of the two said rollers of each of said pairs is journalled on a lifting and lowering device movable relatively to the other of the two rollers, for inserting and discharging of said metal pieces.

12. Apparatus of one of claims 9 or 10, wherein said cooling station has a water conduit situated above said means for rotation and along said metal pieces, said conduit having in its lower wall a plurality of water outlet openings adapted to delver of plurality of streams of water onto said metal pieces.

13. Apparatus according to one of claims 1, 5 or 9, including rotary brushes for cleaning said metal pieces.

14. An apparatus according to claim 1, 2 or 3 wherein said preheating furnace is heated electrically or by means of fuel either through direct flame impingement or by forced air circulation.