US2369730A - Method of rolling metal bars - Google Patents

Description

Feb. 20, 1945. G. L. FISK METHOD OF ROLLING METAL BARS Filed June 12, 1942 4 Sheets-Sheet 1 Qw 6% H P NN mum Wm hm Feb. 20, 1945. G. L. FISK METHOD OF ROLLING METAL BARS 4 Sheets-Sheet 2 Filed June 12 1942 4% 0 J I, l S E Y \I Y Z W 1 ii w- V 517/ M my R m mm mm Nb w fr n r Q W ET w MM l. w m Q Q QM ww mm MW NM QM 9w Mm mmu Aw NN NQN QQN a v mm *m m M t i mw x 3 QQNHIAMQE Us A Q}, T E m N NW L 1 J W NQAN' QwN QMNI QM. WW.

' Patented Felo. 20, 1945 UNITED STATES PATENT OFFICE METHOD or ROLLING METAL BARS Gustaf L. Fisk, New Fair-field, Conn. Application June 12, 1942, Serial No. 446,716

8 .Claims.

This invention relates to the rolling of bars of a great variety of sections, commonly known as merchant bars and shapes, including bars of circular cross section, known as rounds, and particularly to a method whereby they may be finished to precise dimensions within close tolerances.

The round isperhaps the most common but also one of the more difilcult sections to produce to accurate dimensions. The need and demand for accuracy in rounds are so pronounced and the problems involved in producing an accurate round have received so much attention in the trade, that I have chosen to explain my improved method of rolling with particular reference to this section.

Merchant bars have usually been made heretofore by hot-rolling to finished size. According to one method of rolling rounds, a billet is reduced by hot-rolling to an approximate round slightly larger than the desired finished size. It

i then entered repeatedly by hand while still hot, into a finishing pass between a pair of rolls having grooves of circular section therein relieved at the parting, thus permitting slight side spread of the bar as it is rolled. For this reason, after the first finishing pass, the bar must be gripped to hold it in such position that the major axis of its section is perpendicular to the axes of the rolls. To this end, the operator grips the rear end of the bar with tongs when entering the lead end into the pass and follows the bar up to the mill as it is rolled, maintaining his tong grip thereon until the rear end of the bar enters the pass. This method limits the peripheral speed of the rolls to the speed at which the operator can walk and control the bar. Only short lengths of bar, furthermore, can conveniently be held against turning in the pass. Thus, while the method produces accurate products, the cost is prohibitive because of the low output.

According to another method of producing rounds, a billet is reduced to an approximate ellipse and entered into the finishing pass between side guides placed close to the pass. These guides enter the bar properly with the major axis of its section perpendicular to the axes of the rolls. This requires that the bar have a section with the major axis much greater than its minor axis and this in turn necessitates a considerable side spread in converting the elliptical section to a round in the finishing pass and the amount of such spread is subject to little control. Any slight change in size. shape or temperature along the length of the entering bar or between successive bars will produce a considerable diflerence in the amount of side spread. As a result, the horizontal diameter of the bar as it leaves the finishing pass is characterized by excessive variations from the desired dimension. For these reasons, relatively large tolerances are permitted, via, for a 1" round $1709", and a maximum .013" out-of-round at any given point. The tolerances vary, of course, with the size of the bar.

The various factors which cause inaccuracy in the finished dimensions of rolled metal bars including that just explained, may be summarized asfo-llows:

A. Misalignment of rolls and changes in pass area, principally due to bearing wear during the rolling operation. In the case of the more modern mills, however, these difliculties have been eliminated with the use of anti-friction radial and thrust bearings for the rolls and with rigs for micrometer roll adjustments.

B. Change in temperature from end to end of the bar, due to the longer exposure of its rear end prior to the finishing pass; temperature varitions between difierent bars, due to mill delays; and temperature differentials due to improper heating. Naturally, the colder the metal in passage between the rolls, the greater the pressure on the rolls and the larger the section emerging from the pass. With improved furnace and mill design and practice, inaccuracies due to temperature fluctuations of the metal in process have been materially reduced but by no means eliminated.

C. Improper entry of bars into the roll passes, particularly at the finishing end of the mill, or, to obtain, proper entry, the delivery of a section to the finishing rolls, which cannot be duly controlled as to side-spread" for accuracy of product.

Attempts have been made in the past, with more or less success, to reduce the inaccuracies due to uncertain side spread in rolling guide rounds, i. e., rounds rolled by introducing an elliptical bar into a finishing pass by side guides as above described. One such attempt calls for a separate finishing stand equipped with a pair of vertical rolls and, in immediate juxtaposition thereto, with a pair of horizontal rolls grooved to furnish the finishing pass. This stand is add- 1 ed beyond the last pair of rolls of the guide aces,

signed to produce an approximate round in the ing stand are relatively slight, and the uncertain side spread correspondingly small. The approximate round and the ellipse cannot be held against axial turning in the passes of the finishing stand, but the very limited distance between the passes of the two sets of rolls is intended to preclude improper entry into the. finishing pass. With perior accuracy, but cold working also improves the surface and (cold drawing in particular) the physical properties of rolled products.

It is one of the purposes of my invention to obtain the advantages of cold drawing by a new and economical method of cold rolling long lengths at high speed in conjunction with a hot any slight variation in size, shape or temperature, however, the hot bar in motion between the two passes of the finishing stand would be subject to serious variations of tension or compression or both, due to the close proximity of the two sets of rolls, resulting in serious fluctuations in sectional area of the finished bar. were separated, on the other hand, to allow for a loop or slack between the we roll passes, then proper entry of the ellipse into the finishing pass,

could not be accomplished.

A better method for reducing the inaccuracies due to uncertain side spread calls for a stand of vertical rolls to furnish the final pass, beyond but in fairly close proximity to the last stand of the horizontal rolls of the guide mill. In this method, the bar is rolled to final size in the pass of the last stand of the guide mill, except that excess metal is forced into the roll cavities to concentrate all variations in sectional area, due to uncertain side spread into definite over-fills. The bar is then passed immediately between a pair of grooved vertical rolls. The object of the final pass in the vertical rolls is to eradicate the over-fills, as far as possible, to complete the round. The rolls are placed in line for straight delivery of the bar from the corresponding pass in the rolls of the last stand of the guide mill, and the guides immediately aheadof these guidemill rolls, serve to hold the bar against axial turning. By aid of modern mill machinery, a skillful operator may thus roll within narrow tolerance limits. By way of example, 1" rounds may be rolled in this manner within a total variation of .005" in diameter and .003" out of round, but such accuracy cannot be maintained without sacrifice of output.

Cross-rolling of hot guide rounds, in special rolls, has been proposed to reduce their inaccuracies. Although this scheme is entirely feasible, it has little practical value due to the strictly limited speed of the cross-rolling process.

The inaccuracies of hot-rolled bars may also be reduced by cold working. Cross rolls serve to improve the roundness and surface of cold bars and, under certain conditions as to angular position and shape of rolls, may also serve to reduce their sectional area. Cold drawing, through dies in draw-benches, is a common and dependable way to produce bars of superior accuracy. By way of example, 1" rounds may be drawn in this manner within a total variation of as little as .001" in diameter.

Except for the field of wire drawing, by aid methods are limited to short lengths and are slow and expensive as compared to hot rolling. On the other hand, they furnish not only su- If the sets mill, but without restricting the hot mill as to output or accuracy beyond those of the ordinary tonnage mill.

It'is a further object of' my invention to remove the inaccuracies characterizing hot rolled bars by eliminating variations in the temperature of the bar as it progresses through the final passes and by insuring proper entry and control of side spread in these passes.

In a preferred practice of my invention, I roll a rough round on-a guide mill having its last pass shaped to give the bare. slightly oval shape, 1. e., round with overfills on opposite sides, and a size greater than that desired in the final prodnot. After the hot-roller bar hascooled to a temperature below .the recrystallization temperature, preferably on a pack-annealing cooling bed,

tion and the advantages thereof may be gained from th following detailed description and explanation which refer to the accompanying drawings illustrating diagrammatically the preferred practice of th invention. In the drawings,

Figure 1 is a partial section through the rolls of the last stand of a hot mill for producing a rough round adapted tobe finished according to my invention;

Figure 2 is a diagrammatic plan view illustrating one mode of applying the invention;

Figures 3 and 4 are partial sections through the rolls of the stands of the mill of Figure 2 showing the shape of the passes therebetween;

Figure 5 is a view similar to Figure l illustrating a modified practice;

Figure 6 is a diagrammatic plan view of the mill utilized in the modified practice;

Figures 7 through 10 are views similar to Figures 3 and 4 showing the shape of the passes between the rolls of the several stands of the mill of Figure 6;

Figure 11 is a diagrammatic layout of a mill adapted to carry out the invention;

of dies and blocks, the present cold working Figures l2--A and 12-3 together constitute a modified mill layout;

Figure 13 is a diagrammatic plan view illustrating a modification of my invention adapted for efiecting a heavy cold reduction of a hot rolled bar to produce a cold-rolled bar of much smaller size for further processing:

Figure 14 is a partial sectional view taken on the plane of line XIV-XIV of Figure 13, and

Figures 15 through 18 are views similar to Figures 3 and 4 showing'the shapes and relative sizes of the passes between the rolls of the several stands of the mill of Figure 13.

A preferred practice of my new method for removing the inaccuracies of hot-rolled rough rounds will be explained with particular reference for the present to Figures 1 through 4. As

- shown in Figure 2. I subject the hot-rolled bars,

after they have cooled to a temperature below the recrystallization temperature, to cold-rollin8 in a z-stand, tandem cold mill I. This cold mill comprises a stand of horizontal rolls 2 and a stand of vertical rolls 8. The rolls of both stands are driven, in the customary manner by an individual' motor, and are grooved for a series of roll passes. For the sake of clarity, only one pass is shown in each pair of rolls; that is, pass 4 in the horizontal rolls and the corresponding pass 5 in the vertical rolls. These passes are shown in detail in Figures 3 and 4. A bar in passing through the cold mill, follows a fixed and straight pass line and the horizontal and the vertical rolls are made adjustable in the longitudinal direction to bring any desired pass into alignment with the pass line. The two sets of rolls are placed in close proximity to one another, say on 2' centers, and with this purpose in view, the horizontal and the vertical rolls are preferably mounted in a common housing.

The cold mill rolls are joumaled in anti-friction bearings for radial and thrust loads and micrometer roll adjustments may be provided, to eliminate inaccuracies inmill products due to bearing wear or misalignment of rolls. Since the products are rolled cold, inaccuracies due to tem-- perature variations of the metal in process are also eliminated. Proper entry into the roll passes 30 and control or elimination of side spread, are accomplished in the manner now to be set forth. To produce a cold rolled round such as shown in finishing pass 5, a rough round B of somewhat larger diameter is first produced in a stand 6 of the hot mill, having a pass 6a shown in Figure 1. By way of example, if it be desired to cold roll a 1" round and the hot mill can readily roll within a total tolerance of .020", then the rough round may be produced varying in diameter within 1.010" to 1.030", except when measured horizontally as it emerges from the pass. In that direction the dimensions will preferably be made greater by forcing metal into the roll cavities 1 to produce over-fills 8 and give the rough round a definite major axis. I

The hot-rolle'd bars are delivered to any convenient form of cooling bed by a suitable runoutconveyor, and preferably to a pack-annealing cooling bed for slow cooling below the recrystallization temperature prior to finishing by cold rolling. Suitable arrangements of conveyors, cooling beds and associated apparatus are shown in Figures 11, 12A and l2-B and will be described in detail later.

Referring now to the cold mill I, the rough round after cooling is entered into the pass 4of the horizontal rolls with its major axis horizontal, thus preventing the bar from turning in the pass by allowing it to take the path of least resistance. Since the finishing pass 5 in the vertical rolls is in strict alignment with pass 4 in the horizontal rolls, since the two sets of rolls are in close proximity to one another, and since the cold bar has the necessary stiffness in passing from the rolls 2 to the rolls 3, proper entry into the finishing pass 5 is assured. The proper entry of the rough round into the pass 4 of the hori-- zontal rolls 2 of the cold mill is facilitated by the tendency of the bar to lie with its major axis in horizontal position. Furthermore, the over-fills a will be plainly visible to the operator in that the metal there will be less smooth than where it contacted the rolls in the final pass of the hot mill. The rough round, preparatory to entry into the cold mill. rests freely on a cold mill approach table and can be turned by the operator, by aid of a pair of tongs, as required for exact entry in feedinll the bar to the mill.

The section of rough round B is shown by dotand-dash arcs in Figure 3 in relation to pass 4 to indicate the draft 5 in the horizontal rolls 2 of the cold mill. The draft Ill in the finishing pass 5 of the vertical rolls 3 is also illustrated in Figure 4 where the dot-and-dash arcs indicate the section of the bar after traversing pass 4. It will be noted that the bar is rolled to finished height in the horizontal rolls 2 and that no side spread is permitted by the final pass 5 in the vertical rolls. a

I eliminate or control side spread in the passes of the cold mill by maintaining the metal under controlled tension during cold rolling. If the bar be subjected to sufllcient pull in longitudinal direction, then the reductions in the roll passes will cause the metal to elongate in the direction of pull rather than spread in directions at right angles thereto. Furthermore, if the reduction be made proportionate throughout the section, then all the metal will tend to flow in the direction of pull, to take the shape of the pass, without side spread. Thus my new process is, in eiiect, a combination of rolling and drawing between rolling dies.

The desired tension in the bar is maintained in the distance between the horizontal and the vertical rolls of the cold mill, by the use of motors of suitable characteristics to drive the respective sets of rolls. The tension is controlled by controlling the relative speeds of the motors.

40 operation.

When the rough round B is fed to the cold mill, the horizontal rolls 2 are run at relatively slow speed. The vertical rolls 3 are operated at a somewhat higher speed, to compensate for the reduction in the pass 5 and to produce desired ull on the bar when its front end enters the pass 5. At that instant, the increased load on the motor driving the vertical rolls 3 causes a load relay to function so as to automatically increase the speed of rolls 2 and 3, while maintaining the tension in the bar unchanged. The excess speed of rolls 3 results in a pull on the bar, by forcing their motor to also take part of the load on rolls 2, to cause their corresponding increase a in speed. In other words, the rolls 2 and their motor furnish a drag on the bar. adjustable by motor speed control. As the rear end of the bar is nearing the pass 4, a flag switch or other suitable device functions to automatically and progressively reduce the speed of the rolls 2 and 3. The purpose is to cause the bar, now in motion at high speed, to exert a limited pull on the rolls 3 and thus continue the metal under tension in pass 5. while the rear end of the bar travels the distance, in whole or part, from pass 4 to pass 5. The momentum of the bar is thus utilized to maintain a limited tension asits rear end leaves and travels beyond the horizontal rolls 2. The speed of the rolls is reduced in this way to the suitable speed of entry, the next rough round is fed to the cold mill and the'proce'ss is repeated. As to the rate of rolling, two cold mills I will usiillflly keep pace with the production of the hot in The front end of the bar is not subject to tenltt i e made small'as compared to draft l0, and the rolls 2 are-shapedto'fonn cavities llkto allow' for, thecorresponding'ly small side spreadatthe'front;

end of the bar inlpass 4." Furthermore, -thissliglit input is idtpundui high, the lackf of tension, not

quireddorthe' paSs reductions.- It also eliminates .chaneesjifor jcompressioriofjthe metal in the bar between adjacent stands, whichwculd cause varv iations infsize'of finished bar.

Due togthe absence of temperature fluctuations ofthje metal in' process, 'thevariations'in-the pres-' :sureon the rolls will be due to the limited variain sizeofthe rough rounds, andwill cause 1 but slight deviations in the deflection of the rolls -'rough round above referred to, .if made of soft steel and-iinished by 'cold rolling in the manner specified above, and using rolls of a size ordinarily used in the finishing end of the hot mill,

' assumed sion while it covers the distance from pass 6 to I pass ,5. I To compensate, the draft 9 is purposely pose, I use a cold mill l2 shown in plan view in Fig, 6. Each stand of'rollsfis-drive'n-by an indil noted a asst-hem that the tension serves tic-materially reduce the power revidual motor and ii timeiarer h wihn ii bar, in'passingthroug hecold'mill, follows f ax and jstraightpass line and the'horizontal ticali'rolls are made adjustable in lonlled roundf such as. shown 'a blank "of, larger ,diameter,

- to allow for req'ulred cold working, is first produced inthje hot'mill. The final pass i! in the hot mill,'is.illustratedfin-Figure 5 and provides 'forroll cavities ll 8. '-The blank I9 is preferably rolled with pronounced over-fills 20,"?to. give it a definite major axisLr Proper entryinto'the several passes of the cold mill is then accomplished in the manner alreadyde'scribed-with reference to cold mill I. in-the .cold mill. By way of exampleythe 1" v v e passes 13 throug ii are designed to eliminatejside spread by maintaining the metal in would vary in diameter, due to roll deflection,

much less than .001".

.001" in diameter, except possibly for the extreme ends of the rolled lengths,

, By. removing the causes of inaccuracy in rolling metal bars, as explained in preceding paragraphs, my new process permits the rolling of merchant bars and shapes within cold drawn tolerances. The cold rolling operation, preferably done in conjunction with the hot mill, in no way limits or interferes with the operation of the hot mill. The cold mills roll annealed bars, using the cooling bed lengths produced on the hot mill, and have sufficient finishing capacity to keep pace with the hot mill. 2-high rolls furnish the necessary stiffness for the cold rolling required in finishing .bars of ordinary size and hardnesaand the cost'of the extra equipment needed to practice the new process is relatively small when compared to the total cost of the complete hot mill. The cold rolling is accomplished with a minimum of handling and'the extra labor involved is a minor itemwhen com I pared toithe total labor force on' the complete mill. All' of these factors, combining high production and low' cost with superior accuracy, make for quality and economy not attainable'by any hitherto known process.

In case of products requiring a bright finish, it is necessary to free the bars from scale, by pickling, prior to cold rolling. In this connection, th desired surface hardness and physical prop- It is thus entirely feasible, in case of 1" rounds used as an example, to roll within a total tolerance variation of as little as process under controlled tension; 'The desired tension loads on the bar are established in the distances separating the several sets of rolls,

by aid of motor and electric control equipment,

such as already referred to in connection with (cold mill I. I

When the blank l9 is fed to the cold mill, the first set of horizontal rolls l3 are run at relatively slow speed. The succeeding sets of rolls ll, 1'5 and I6 are operated at progressively higher speeds to compensate for the drafts in passes l4, l5 and I6 and to produce the various desired pulls on the bar'. When the front end of the bar enters the pass 14, the speed of all the rolls is automatically increased, to speed the rolling operation,'while maintaining the established tension loads on the bar unchanged. As

the rear end of the bar is nearing the pass l5, the

speed 0'! all the rolls is automatically and progressively reduced, at a rate to utilize the mo- 7 mentum of the bar to maintain a limited tension on the metal in the finishing pass l6, as its rear end leaves and travels beyond the pass l5. Practically the entire lengthof bar can thus be rolled with reference to cold mill As to the rate of erties may-be imparted to the bars by controlling the amount of cold working. Withoutresortlng to 4-high rolls, which would be expensive ,nd complicated, considerable reductions can be 1' .de in the passes of the Z-high cold mill withczr ioss rolling, two cold mills I! are preferably used to keep pace with the hot mill.

By way of example, rounds of desirable physical properties and of superior accuracy and surface, may thus, be rolled-from blanks of soft steel, in, 2-high'rol1s journaled in anti-friction bearings. l 1 'Becausei'of the tension maintained in the metal during the cold rolling process, the motor horse-power requirements and the power consumption are relatively small.

A mill layout for'practicing my invention is shown in Figure 11. In it, 2| represents the last set of rolls in a guide. mill, of any suitable conof accuracy, particularly on the smaller bar sizes. i

Naturally, the narrower the'section, the smaller the pressure on the rolls and the larger thedraft struction and arrangement, for hot rolling of merchant bars and shapes, including rounds. Thehot' rolled productsare delivered by run-in tables 22 to position for handling by the mechanisms of a'double cooling bed 23. This bed, ordinarily 250 ft. or more, in length, to accommodate the rolled lengths, is of the pack-annealing type. In other words, it is equipped for slow cooling of the hot bars in contact with one another. Such cooling beds have been on the market for a number of years, available for an-' nealing of rounds, squares, flats and other sections, but they have been used principally for the annealing of spring flats. One of the objects of my invention is to utilize the advantages of such beds, not only for annealing of spring steels and the like, but also for the production of soft metal bars of superior accuracy, surface and physical properties.

The run-out tables 24, from the cooling bed, lead to crop shears 25, and run-out extension tables 26 lead to the bar shears 21, back-shear tables 28 and cradles 29. The cooled bars, annealed or not as required, are collected in batches at the delivery sides of the cooling bed 23 and these batches are transferred to the run-out tables 24; all in accordance with usual practice. In case of bars, the rolling of which is completed on the hot mill, the batches thus transferred are conveyed by run-out tables 24 and extension tables 26 for shearing to length on bar shears 21, and the sheared'bars are conveyed by back-shear tables 28 to cradles 29 for removal by overhead crane; all in keeping with prevalent practice. By way of example, high carbon spring flats may advantageously b handled in this manner, so also structural and other sections, in case of which accuracy, surface and properties required, are obtainable on the hot mill and the cooling bed. a

It will be apparent from the foregoing that by the aid of my invention, products subject to strict tolerances, or of the kind in which superior accuracy is advantageous, such as rounds, by way of example, are produced from rough bars, rolled on a hot mill. After pack-annealing and cooling on the bed 23, the rough rounds are conveyed in batches by run-out tables 24 to the crop shears for removal of any bad ends, at the forward ends of the bars, by cold shearing. The batches are then conveyed by tables 24 and 26 to position alongside transfers 30. By aid of shuffle bars, Or other suitable mechanisms, the batches are then moved onto transfers 30 and the rough rounds are fed from there as required, one by one, onto the cold mill approach tables 3|. After passing through the cold mills l and being converted into rounds of desired accuracy, the individual bars are conveyed by the cold mill run-out tables 33 to position alongside transfers 34. By aid of shufile-bars or other suitable mechanisms. the finished rounds are moved from the tables 33, collected in batches on transfers 34 and the batches delivered onto tables 26. After shearing on bar shears 21, the finished lengths are conveyed by back shear tables 28 to cradles 29 for further handling in customary manner.

35. By aid of shuille bars or other suitable mechanisms, thebatches are then moved onto'transfers 35. Overhead pickling machines of suitable design remove the batches from the transfers for pickling in troughs 36, washing in troughs 31 and delivery to transfers 38. The time required by the hot mill to roll the rough rounds or blanks which make up the batches provides sufficient time for the picking operations. By aid of shuille bars or other suitable mechanisms, the pickled and washed rough rounds or blanks are then fed as required, one by one, onto the cold mill approach tables 39. After passing through the cold mills l2 to be converted into rounds of desired finish, physical properties and accuracy, the individual bars are conveyed by the cold mill run-out tables 4| to position alongside transfers 42. By aid of Shllflle bars or other suitable mechanisms, the finished rounds are moved from the tables 4|, collected in batches on transfers 42 and the batches delivered onto tables 26. After shearing on bar shears 21, the finished lengths are handled same as other finished prodpassage for the bars in process.

ucts already referred to.

It will be recognized that not less than two sets of cold rolls are needed to practice my invention. The number of additional sets of rolls required, is determined by the amount of cold work demanded from the mill to achieve desired objectives. If a cold mill be built with suilicient sets of rolls to meet maximum demands, it need only use the number of sets required for any particular purpose. In that case, the rolls of the unused sets are merely opened up to allow free With this idea in view, the theoretical plan shown in Figure 11, has been simplified into the practical and more economical rolling mill layout shown in Figures l2A and 12-3.

Referring now to Figures l2A and 12B, a heating furnace 68 is indicated as part of a hot mill designated generally at 69, The hot rolling is completed, either in rolls ID or in rolls ll,

4 the latter intended principally for coiled prod- In case of products requiring bright finish.

ucts. When the rolls l0 constitute the final pass in the hot mill, then the subsequent sets of hot mill rolls are opened up or removed to allow free passage of products. The hot rolled bars are conveyed by run-in table I2 to a single cooling bed '13 equipped for continuous pack-annealing. Not only does the single cooling bed meet the requirements of the hot mill for capacity, but it affords a much better opportunity for pack-annealing than the double bed, in that all the hot bars go into one continuous pack. They can thus be better annealed and the cost ofthe cooling bed equipment, an expensive item, is cut in half. The cooled bars, collected at the delivery side of the cooling bed are transferred in batches to the run-out table I4, which can deliver in either of two directions. In case of products the rolling of which may be completed on the hot mill, the batches may be conveyed by run-out table 14 and extension run-out table 15 for shearing on bar shear 16, and the sheared lengths are conveyed by back-shear tablell for delivery to cradle 18. Every second batch, however, is conveyed by tables l4 and 15 to position alongside transferl9. by which it is moved onto run-out table 80, leading to bar shear 8|. An opening is provided in the frame of the bar shear 16 to allow the batches to pass through on their way to shear 8|. The sheared lengths are conveyed by back shear table 82 and delivered to cradle 83. Double shearing is thus provided for, notwithstand. ing the use of a single cooling bed.

In case of products requiring superior accuracy, rough sections of somewhat larger dimensions and of suitable shape are rolled on the hot mill. After pack-annealing and cooling on the bed I3, the, rough sections are conveyed in batches by run-out table I4 to the crop shear 88 for removal of any bad ends at the forward ends of the bars. The batches are then conveyed by tables I4 and I5 to position alongside transfers I8 and 85. Batches are moved onto transfer 85, where the bars of the batch are separated to deliver the rough sections, one by one, onto the cold mill approach table 86. The cold mill 81. has several sets of rolls, but preferably only the first two sets are used in cold rolling the rough sections to finished size. The remaining sets of rolls are opened up to allow free passage of the cold rolled bars onto cold mill run-out table 88. Individual bars are thus conveyed to position alongside transfer 88, on which they are collected in batches for transfer to run-out table I5. After shearing, the finished lengths are collected in cradle I8. Every second batch of rough sections arriving alongside transfer I8, however, is moved by this transfer onto run-out table 88, where it remains at rest until it is moved onto transfer 88. There the bars of the batch are separated to deliver the rough sections, one by one, onto the cold mill approach table 8|. After passing through the cold mill 82, in the manner described for cold mill 81, the individual cold rolled bars are conveyed on cold mill run-out table 83 to position alongside transfer 84. On it, they are collected in batches for transfer to runout table 88. After shearing, the finished lengths are collected in cradle 88. Two complete sets of cold-rolling and shearing facilities can thus be operated without interference with one another, to roll and shear products of superior accuracy from rough sections, annealed on a single cooling bed.

surface or physical properties, are produced from blanks of proper size and shape, to allow for necessary cold reductions. These rough sections or blanks, rolled on the hot mill 88 and packannealed on the cooling bed I3, are delivered in batches on the run-out table I4. Each batch is conveyed to the crop shear 84 for removal of any bad ends at the forward ends of the bars. The direction of travel of the run-out table I4 is then reversed, to convey the batch to the dividing shear 85. If large reductions are called for in the cold mills, it may be necessary to divide the blanks into two or more lengths for cold rolling, in order to limit the finished product to lengths which would be produced were the rolling to be completed on the hot mill. The entire batch of divided cooling bed lengths is conveyed by runout tables I4 and 88 to position alongside transfer 81. It is moved onto this transfer, successively pickled in troughs 88 and 88 and delivered to transfer table I88. It is conveyed by this transfer table to position alongside the washing tough I8Ii After washing in this trough, it is delivered to transfer I82 which moves it onto table I88. It is conveyed by this table and the run-out table 88 to position alongside transfers I8 and 88. An opening is provided in the frame of the crop shear 84 to allow the batches to pass throul A batch of rough sections, or a batch of blanks divided in suitable lengths forcold rolling, may now be moved by transfers I8 and II for cold rolling on mill 81. Every second batch, however,

is moved by transfer 88 for cold rolling on mill" 8!. The number of sets of rolls used in the cold rolling operation varies with the amount of cold working to be done and the parts of each divided bar follow one another through the cold mills. The procedure is otherwise the same as already described in cold rolling for accuracy only, until the finished lengths arriv in cradles I8 and 88. Rough sections or blanks, annealed on a single cooling bed, can thus be pickled and fed to two complete sets of cold rolling and shearing facilities; all in a continuous process and without interference between th several operations.

The entire mill layout shown in Figures 12-A and 12-3 is preferably housed in suitable buildlugs, and the pickling equipment is preferably segregated and located in a separate building. Furthermore, the hot rolling, annealing, pickling, cold-rolling and shearing equipment has been duly balanced for capacity of output.

My invention may also be employed for reducing hot-rolled bars to cold-rolled blanks, of great accuracy and very much smaller sectional area, for subsequent annealing or heat treatment and further cold working. By way of example, number five wire rod may thus be produced from, say, hot-rolled blanks in the manner illustrated in Figures 13 through 18. Such blanks are preferably finished in the vertical rolls II of the hot mill (see Figure 12--A), in the form of pronounced ovals with the major axis vertical, for coiling on reels I88 w th vertical spindles, in order to facilitate the coiling of the blank with its major axis throughout the coil maintained in parallel with the spindle of the reel, i. e., the axis of the coil. A limited quant ty of such coils may be rolled on the cold mills 81 and 82, particularly by utilizing the time when the hot m ll may be rolling finished products, but to handle large tonnages additional cold millsare necessary. In

either event, the hot-rolled coils are annealed, handled and transported according to well-known practice. The particular cold mill illustrated-in plan view in Figure 13 and the pass reductions. as they are shown in Figures 15 through 18, are predicated on coils such as above referred to, feeding the mill with their axes horizontal.

' The oval blank III is reduced to rod III in rolls H2, H8, Illand III, to change the blank coil H8 into rod coil III. Guides II8, provided immediately ahead of rolls II2, assure proper entry. Controlled tension is maintained in the bar H8 between the several sets of rolls in the manner already explained with reference to cold mill I2. During the rolling operation, the blank coil -III is retained in position with respect to the mill rolls, on a spindle of suitable construction, and the rod coil III is formed on the motor-driven drum of a eoiler, at the delivery end ofthe mill. By controlling the speed of the motor, the bar I I8 is subjected to required pull also between the set of rolls III and the rod coil III, to complete the rolling'of the rear end under tension. The front end or the bar may pass from rolls I I! to rolls II3 without benefit of tens on. but the extreme front end of the rod in finished coil II'I would then be more or less inaccurate.

If superior accuracy be demanded throughout the finished coiled length, then the spindle supporting the blank coil 8 must also be controlled as to speed.

aseavso 7 my new method of cold rolling such rods from hot rolled products of much larger sectional area has other advantages. The ordinary merchant bar mill could thus roll a product of large enough sectional area to be economical and which, by

. aid of a relatively simple cold mill, could be converted into superior wire rod. An extra annealing operation is required to condition the cold rolled material, but the use of a separate rod mill is obviated. My new method would be particularly advantageous when the required rod tonme is small.

7 Although I have described certain preferred applications of my invention, its advantages may be realized in other ways, within the scope of the appended claims.

I claim: r

. 1. In a method of producing metal bars to precise finished dimensions, the steps including hotrolling bars in cooling-bed lengths which are many times the desired length of the bars, slowly cooling said bars, then subjecting them to coldrolling' in a plurality of passes at least one of which is at an angle to its predecessor, and dividing the bars into desired lengths only after the completion of the cold-rolling.

2. A method as defined by claim 1 characterizedby tensioning the lengths during cold rolling sufliciently to limit lateral spread of the metal.

3. A method as defined by claim 1 characterized by decelerating the rolls of one of said passes as the trailing end of a length leaves the preceding pass thereby maintaining tension during the rolling of said endafter it has left said lastmentioned pass. p

4. In amethod of rolling round metal bars of precise finished dimensions, the steps including hot-rolling a blank sufllciently out-of-round to have definite major and minor axes, cooling the blank to cold-rolling temperature, entering the blank in the position of least resistanc into a pass formed by parallel rolls, permitting the blank to adjust itseli progressively to the position of least resistance, cold-rolling the blank in said pass to reduce the minor axis thereof, entering the blank while it is still in said pass into a pass formed by a second set of rolls, and cold-rolling the blank therein to reduce said major axis.

5. In a method 01' rolling round metal bars of precise finished dimensions, the steps including hot-rolling a blank sufliciently out-of-round to have definite major and minor axes, cooling the blank to cold-rolling temperature, entering the blank in the position of least resistance into an oval pass formed by a set of parallel rolls, cold- .rolling the blank in-said'pass to reduce the minor axis thereof. entering the blank while it is still in saidpass and guided-thereby, into a pass formed by a second set of rolls, cold-rolling the blank therein to reduce said major axis, and subjecting the portion oi. the blank between said sets of rolls to controlled tension.

6. In a method of rolling roun'd metal bars of precise finished dimensions, the steps including hot-rolling a blank sufliclently out-of-round to have definite major and minor axis, cooling the blank to cold-rolling temperature, progressively gripping the sides of the blank which lie adjacent the ends of the minor axis, entering th blank while it is guided by said gripping action, into a pass formed by parallel rolls, and cold-rolling the blank therein to reduce said major axis.

'7. In a method of producing round metal bars to precise dimensions, the steps including hotrolling an oval bar with a section" having distinctly diilerent major and minor axes and a larger area than that of the desired finished bar, coiling the bar while hot from rolling and slowly cooling it in coiled form, then reducing the section of the bar to circular form by cold-rolling the bar in a plurality of passes under'tens'ion sufllcient to limit lateral spread of metal under the pressure of the rolls.

8. In a method of producing round metal bars to precise dimensions, the steps including hotrolling an oval bar with a section having distinctly diflerent major and minor axes and a larger area than that of the desired finished bars, annealing the bars by slowly cooling them in contact with one another from the hot-rolling temperature,

' then reducing the section of the bars to circular form by cold-rolling the bars in a plurality of passes under tension sufficient to limit lateral spread of metal under the pressure of the rolls.

GUSTAF L. FISK.

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