GB2101025A - Rolling steel rods and wires with grooveless rolls - Google Patents

Abstract

A method of rolling steel rods or wires by grooveless rolls involves limiting to less than 1.5 the ratio of a long side to a short side of a rectangular cross-section blank material which has passed through each pair of grooveless rolls, or limiting the ratio of a diameter of each pair of grooveless rolls to a gap therebetween. A guide for rolling steel rods for supporting sides thereof comprises front and rear rolling guide frames consisting of partitions abuttingly connected to each other in a gap between a pair of rolls having cylindrical surface barrels to form defined rolling zones which are side by side along the roll barrels and divided by the partitions and capable of retaining steel rods being rolled, thereby effectively carrying out rolling of steel rods with grooveless rolls without twisting and deforming the steel rods into incorrect cross-sections. <IMAGE>

Description

SPECIFICATION Method of rolling steel rods and wires with grooveless rolls and grooveless rolling guides This invention relates to a method of rolling steel rods and wires with grooveless rolls, and more particularly to rolling guides for use in rolling steel rods with grooveless rolls for supporting sides of the rods and guiding the rods into roll gaps to improve the grooveless rolling.

The term "steel rod" used herein is intended to designate elongated metal rods such as square, rectangular or circular cross-sectional rods and wires of steel and non-ferrous materials.

The term "grooveless roll" or "caliberless roll" used herein means a roll which is not formed with a caliber or calibers in its barrel.

In rolling blank materials having square cross-sections to produce steel rods, wires or the like having rectangular or circular cross-sections, caliber rolls have been exclusively used for rolling them. Referring to Fig. 1 illustrating a typical pass schedule, a blank material w having a square cross-section is rolled through square and parallelogram calibers s and d one or more times and thereafter rolled through calibers having substantially the same sectional shapes as the above to obtain square cross-sectional steel products p or alternately through oval and round calibers o and r to obtain circular cross-sectional steel products p'. In this case, the material is generally subjected to a continuous rolling wherein the material passes through one pass of each one rolling mill of a continuous series of rolling mills M1, M2, M3, . .M, as shown in Fig. 2.

With the rolling operation with the continuous series of rolling mills including the caliber rolls, the number of roll stands for reductions of the material is determined by dimensions of ultimate products and cross-sections of the blank materials. In case that circular cross-sectional rods having an outer diameter of 20 mm are produced from blank materials of a square section having sides of 145 mm, for example, it requires six roughing, intermediate and finishing roll stands, respectively, which include rolls having calibers as shown in Fig. 1. Such rolling operations with the caliber rolls with encounter the following problems.

(1) When a pair of calibers are shifted from their alignment positions or centers of the calibers and centers of guide means for introducing materials to be rolled into the calibers are shifted to each other, protrusions in the form of fins would occur on the materials in their longitudinal directions delivered from the calibers, which collapse during next rolling operations to cause defects such as overlaps on the surfaces of the rods.

(2) In order to avoid the above defects, it is necessary to set the rolls and guide means with high accuracy requiring long down time.

(3) The accuracy of dimension and shape of the calibers directly relates to the quality of products to a great extent, so that high technique and high expensive roll lathes are required for machining the caliber rolls.

(4) Differences in circumferential speed between respective in the calibers give rise to frictional irregular wear, so that the rolls must be many times machined to correct the calibers with resulting increased cost.

(5) If a size of rods to be rolled is changed (for example, from a 1 6 mm outer diameter of circular cross-sectional rods to a 40 mm outer diameter), many caliber rolls must be changed to increase the down time of the rolling mills. It is impossible to use a pair of caliber rolls over a wide range of sizes of rods to be rolled.

(6) If a gap between a pair of caliber rolls is unintentionally made smaller than a predetermined value, protrusions occur on the surfaces of the rolled materials, which collapse during next rolling operations to form defects such as overlaps on the surfaces.

(7) There is a risk of breaking off due to reduced diameters at calibers, so that the rolls are required to have large initial diameters to avoid the breaking off at the calibers.

In order to avoid the above disadvantages of the caliber rolling, a rolling method using caliberless rolls has recently been proposed wherein the blank materials are rolled by the caliberless rolls for the mainly purpose of reducing the cross-sectional areas of the rods and are further rolled by caliber rolls for obtaining ultimate shapes of the products. Fig. 3 illustrates a basic pass schedule for the method, in which the caliberless rolls are used in upstream passes u and intermediate passes m immediately before forming passes and caliber rolls are used in the forming passes f.

In case of caliberless rolls in substitution for caliber rolls, the machining of calibers is not naturally required and the damage and wear on the surfaces of the caliberless rolls are less than those in caliber rolls to elongate the life of the rolls resulting in lower cost and shorter down time because the change of rolls is not required even if shapes and sizes of products to be rolled are changed. However, the caliberless rolls have the following disadvantages.

(1) The caliberless rolls do not restrain the materials in width directions thereof because they do not have calibers, so that elongations of the materials in rolling directions are less than those in caliber rolls. In order to obtain the elongations of the materials in the rolling directions substantially equivalent to those in caliber rolls, reductions must be increased. The increased reduction however, makes a fiat ratio larger, which is defined as B0/H0 shown in Fig. 4.

Because of the excess flat ratio, the cross-section of the material is incorrectly deformed in the next caliberless roll pass as shown in Fig. 4, so that an overturn a/H increases depending upon the flat ratio B,/H,, which makes it impossible to continue the rolling operation.

(2) When the reduction is comparatively large, free surfaces of the materials which are not in contact with the rolls bulge as shown in Fig. 5. If a bulge ratio which is defined as b/Ho is too large, an overturn a/H becomes large which makes it impossible to effect the next rolling.

(3) When an existing rolling installation is changed from caliber rolling to caliberless rolling passes, the number of the passes must be increased because of less elongations of materials in rolling directions, to decrease the productivity of the installation and in turn to increase the number of roll stands in continuous rolling mills.

It is an object of the invention to provide an improved method of rolling steel rods and wires by grooveless rolls in rolling processes for reducing sectional areas of the rods and wires other than forming processes for obtaining final profiles of the rods and wires to achieve stable rolling by the grooveless rolls.

In order to achieve this object, the rolling method of steel rods or wires by passing rectangular cross-sectionai blank material through plural pairs of grooveless rolls of a series of continuous rolling mills according to the invention comprises a step of setting a gap of each pair of grooveless rolls so as to keep less than 1.5 a ratio of a long side to a short side of a crosssection of the blank material which has passed through the gap.

It is another object of the invention to provide a method of rolling steel rods and wires by grooveless rolls to achieve high elongation efficiency to make stable the rolling operation.

For this purpose, according to the invention, a diameter of each pair of grooveless rolls is comparatively small such that a ratio of the diameter D to the gap H fulfils a relation 100 D/H;;;;-- + 5, H thereby exclusively deforming the blank material in a rolling direction as much as possible.

It is an object of the invention to provide a guide for supporting sides of steel rods subjected to rolling, which comprises defined rolling zones having predetermined widths in gaps between the rolls to realize the rolling with the grooveless rolls without twisting and overturning of the steel rods.

in order to achieve this obiect, the guide for rolling steel rods according to the invention comprises front and rear rolling guide frames abuttingly combined with each other in a gap between a pair of rolling rolls having cylindrical surface barrels to embrace said pair of rolls on front and rear sides thereof so as to form defined rolling zones which are side by side along said roll barrels and divided by said rolling guide frames.

It is another object of the invention to provide a guide for supporting sides of steel rods subjected to rolling, which is adjustable in an axial direction of a pair of rolls to enable all the barrel surfaces of the pair of grooveless rolls to be effectively used as operative rolling surfaces thereby elongating the life of the rolls and simplifying the repairing of the rolls.

It is a further object of the invention to provide a guide for supporting sides of steel rods subjected to rolling, which may be easily applied to existing rolling mills, for example, to rest bars for mounting guides for conventional caliber roll mills.

It is an object of the invention to provide a guide secureiy holding a blank material from an entry to an exit in a roll gap to eliminate the troubles occurring at ends of the blank material which are inherent in rolling by grooveless rolls.

For this object, the guide as a grooveless roll entry guide for rolling steel rods and wires according to the invention comprises guide plates mating with each other and having respective inner taper surfaces for supporting side surfaces of blank material to be rolled to introduce it into a gap of grooveless rolls, a pair of holders embracing said guide plates and having guide rollers supporting said side surfaces of the blank material downstream of taper ends of said inner taper surfaces of said guide plates and a box-shaped guide having therein an assembly of said guide plates and said pair of holders and fixing said guide rollers whose gap therebetween is adjustable, and each said holder extending in said gap to at least a delivery end of said gap and having a bill-like holder integrally formed therewith preventing an end of the blank material not supported by said guide rollers from twisting.

The invention will be more fully understood by referring to the following detailed specification and claims taken in connection with the appended drawings.

Figure 1 is a schematic illustration for explaining various calibers for use in steel rod rolling as mentioned above; Figure 2 schematically illustrates a series of rolling mills for explaining the caliber rolling of the prior art as mentioned above; Figure 3 shows pass schedules for rolling steel rods or wires with caliber rolls and caliberless rolls as mentioned above; Figure 4 is a graph showing a main cause for overturns in rolling caliberless rolls; Figure 5 is a graph showing a main cause for bulges on free surfaces of blank materials; Figure 6 is a schematic elevation showing an outline of rolling with caliberless rolls; Figure 7 is a schematic view explaining various dimensions for calculating aspect ratios of blank materials immediately after rolled; Figure 8 is a view for explaining an occurrence of twisting of a blank material;; Figure 9 is a view for explaining an occurrence of overturn of a blank material; Figure 10 is a graph illustrating relations between aspect ratios and overturns of the blank materials; Figure 11 is a schematic view explaining a formation of a double barrel; Figure 12 is a schematic view explaining a formation of a single barrel; .Figure 13 is an explanatory view illustrating an actual example of a series of continuous rolling mills; Figure 14 is a graph showing relations between roll diameters and elongations; Figure 15 is a graph illustrating conditions for obtaining elongation efficiency with grooveless rolls equivalent to those with caliber rolls; Figure 16 is a perspective view of a preferred embodiment of a side guide according to the invention;; Figures 1 7a and 1 7b are explanatory elevations illustrating an entry guide for guiding a blank material in conventional rolling with caliber and caliberless rolls; Figure 18 is a perspective view showing a defect at a tail end of the material to be rolled; Figure 19 is a perspective view showing fins due to the defect shown in Fig. 18; Figure 20 is a sectional view showing the adverse effect of the defect on caliber rolling; Figure 21 is a sectional view perpendicular to axes of rolls illustrating the basic constitution of the entry guide according to the invention; Figure 22 is a sectional view in parallel with the axes of the rolls illustrating the same constitution of the guide as that shown in Fig. 21; Figure 23 is a view for explaining a twist at a leading end of a rolled blank material;; Figures 24a and 24b are a plan and a side view of an embodiment of the entry guide according to the invention; Figure 25 is a perspective view of the entry guide shown in Figs. 24a and 24b; Figure 26 is an exploded perspective view of the entry guide shown in Fig. 25; Figure 27a is a sectional view illustrating a small overturn angle according to the invention; Figure 27b is a sectional view illustrating a great overturn angle in conventional rolling; Figure 28 is a graph in comparison of fin lengths at tail end of rods with the entry guide according to the invention with the conventional guide; Figure 29 is a plan view of one example of a series of rolling mills for carrying out the rolling method according to the invention; Figure 30 illustrates a pass schedule for the rolling method according to the invention;; Figure 31 shows a pass schedule for the conventional caliber rolling; and Figure 32 illustrates a pass schedule for the caliberless rolling of the prior art.

According to the invention, a blank material W having, for example, a square cross-section is continuously rolled through pairs of rolls 101, 101', 102, 102',. ., n and n' to reduce the cross-sectional area so as to obtain a rolled product having a required cross-sectional shape as shown in Fig. 6. It has been found that a roll gap between a pair of rolls r and r' is so adjusted that the reduction of the material is too large or an aspect ratio B/H is more than 1.5 where B and H are a long axis and a short axis perpendicular thereto of a cross-section of the material W delivered from a pair of rolls r and r' as shown in Fig. 7, a twisting and an overturn of the material occur in the next reduction pass as shown in Figs. 8 and 9. These tendencies increase multiplicatively as the number of passes increase until the rolling operation becomes impossible.

According to the invention, each roll gap between a pair of rolls r and r' in continuous pass rolling with grooveless rolls is so adjusted that the aspect ratio B/H of the material delivered from the gap of the rolls r and r' is less than 1.5 to realize a stable rolling without twisting and overturn of the material.

Fig. 10 illustrates relations between the aspect ratio B/H and overturn x X 100% H when gaps of pairs of rolls are changed. As shown in this graph, when B/H~1.5, the overturn increases greatly and twisting often occurs before the next roll stand, so that the material tends to collide against guides on an entry side of the next roll pair resulting in a miss roll. When the overturn is more excessive, the cross-sectional shape will be more incorrectly deformed in the next rolling to make it impossible to effect the continuous rolling.

In contrast herewith, when B/H < 1.5- the overturn is less than 0.5% and the continuous pass rolling is stably effected without any noticeable twisting. In view of this, the aspect ratio of rolled material immediately after passing through a pair of rolls is limited to less than 1.5 according to the invention.

Moreover, when the aspect ratio B/H I is much larger than 1.5, the cross-sectional shape of rolled material through each rolling pass is apt to be in the form of double barrels 107 and 107' which cause wrinkles 109 on a surface 108 in the next rolling as shown in Fig. 11. On the contrary, when the aspect ratio B/H is less than 1 .5, the cross-section is in the form of a single barrel 1 10 which does not cause wrinkles on the face in the next rolling as shown in Fig. 1 2.

It is of course understood that in order to obtain ultimate products of square and circular cross-sectional rods, the materials subjected to the above reduction with the grooveless rolls to have predetermined sections are then rolled through box, oval or round-shaped calibers of caliber rolls in a conventional manner.

Fig. 13 illustrates a preferred example of a series of rolling mills to which is applied the invention. The series of the rolling mills 111 consist of a roughing mill lila, an intermediate mill 111 b and a finishing mill 111 c. The roughing mill 1 1 1 a comprises horizontal rolls 11 2, 114 and 116 and vertical rolls 11 3, 1 5 and 11 7. The intermediate mill 111 b comprises horizontal rolls 118, 120, and 122 and vertical rolls 119, 121 and 123.The finishing mill 111 c comprises horizontal rolls 124, 1 26 and 1 28 and vertical rolls 125, 127 and 1 29. The rolls 112-125 are ail grooveless rolls, while the four pairs of rolls 126-129 on the downstream sides are caliber rolls for obtaining round steel rods from square cross-sectional rods. In case of ultimate products of square cross-sections, caliber rolls are not needed.

Shaded sections 1 30 are cross-sections of the material immediately after passed through the respective pairs of rolls, all the aspect ratios of which are less than 1.5 by suitably setting roll gaps. Although the horizontal and vertical roll pairs are alternately arranged in the series of rolling mills shown in Fig. 1 3, these roll pairs may be arranged in a different manner and twister devices may be arranged between the horizontal rolling mills for rotating the materials to be rolled through 90 about their axes.

In order to eliminate the disadvantages in rolling with grooveless rolls mentioned in the preamble of this specification, the inventors investigated the behavior of steel rods in grooveless roll passes with many experiments to find that elongations of the steel rods subjected to rolling by grooveless rolls greatly depend upon diameters of the rolls. Fig. 14 illustrates one example of the results of the experiments, wherein the relations between the various diameters D of grooveless rolls and elongations A of 20 x 20 mm square blank materials which were subjected to reduction of 8 mm. As can be seen from Fig. 14, the smaller the diameters of the grooveless rolls, the larger are the elongations.

The elongation A is a ratio of a length of the material after rolled to a length before rolled. An elongation efficiency 71 is then defined as a ratio of such an actual elongation A to an ideal elongation A' obtained by assuming that the material was elongated only in the rolling direction without being widened perpendicularly to the rolling direction. The inventors continued experiments of rolling with grooveless rollings to research rolling conditions for obtaining the elongation efficiency equivalent to or more than that in caliber rolling. As the result, it has been found that the high elongation efficiency is obtained with grooveless rolls under a rollig condition zone ss shaded in Fig. 15 illustrating relations between grooveless roll diameters D and ratios D/H of the diameters D to roll gaps H. This zone ss is expressed by the following formula.

100 D/H--- + 5 H Values D/H are easily calculated approximately along respective diagonal lines as follows: when H60 mm, D/H ;;;;5, H when 60 mm > H#20 mm, D/H#12.5# 8 H when 20 mm > Hi0 mm, D/H=20 , and 2 when H < 10 mm, D/H'35-2H.

As can be seen from the values of the ratios D/H, the diameters D must be much smaller than those such as 360 mmf of hitherto used caliberless or grooveless rolls, so that it is preferable to use back up rolls supporting rolling reaction forces in order to compensate for the rigidity of the small diameter grooveless rolls. However, the back up rolls are easily applied to the mills with the aid of the experience of the multiple roll mills.

The use of grooveless rolls within the zone ss according to the invention achieves the high elongation efficiency which means that a ratio of effective energy consumed with the elongation or reduction of cross-section of the material to the total energy for rolling is high, while a ratio of superfluous energy consumed with the widening of the material is small, so that the present invention is also advantageous from a viewpoint of energy conservation. In this manner, the stable rolling with groove less rolls is carried into effect by effectively restraining the widening of materials according to the invention.

It has been found in experiments on an actual operation scale that the results of rolling are greatly affected by the fact that there are no holding means for rolled materials in gaps between caliberless rolls. In contrast herewith, caliber flanges of the caliber rolls serve to prevent the steel rods from twisting and overturning or deforming into incorrect (parallelogram) cross-sections, although guides arranged on the entry and exit sides only serve to guide the steel rods into the calibers at locations remote from the calibers. In view of the discovery, the inventors conceived side guides for rolling steel rods capable of retaining steel rods to be rolled through gaps between the caliberless rolls.

Fig. 1 6 illustrates one embodiment of the side guide for supporting sides of rods according to the invention applied to a first stage mill for rolling steel rods, such as square rods of the order of 80 mm, 115 mm and 145 mm in width and round rods of the order of 75-85 mm, 90-100 mm and 110 mm in outer diameter rolled from square blooms of 250 mm width. At this first stage mill, the rods are fed alternately in normal and reverse directions by rotating rolls in normal and reverse directions to be subjected to roughing and intermediate rollings and are also continuously fed in the normal direction to be subjected to finishing rolling.

Fig. 1 6 illustrates a front and rear rolling guide frames 1 and 1' and rest bars 2 (only one shown in the drawing) for supporting the rolling guide frames. As the rolling guide frames 1 and 1' are substantially the same as in constitution, the front rolling guide frame 1 will be mainly explained hereinafter.

The rolling guide frame 1 comprises a plurality of partition plates 4 chamfered at 3 on the sides thereof facing steel rods to be rolled (not shown, at the lower left hand corner in the drawing) for facilitating the introduction of the steel rods between the partition plates 4 and arranged on a base member 5 side by side in parallel with one another with different intervals (for example, progressively narrowed from the left to the right as viewed in the drawing), whose upper ends are held by parallel rail members 6, 7 and 8 welded thereto. In this embodiment, as the partition plates 4 are different in height as shown by suffixed "4a" and "4b", spacers 9 are arranged welded between the partition plates 4b and the rail member 6.

At an abutting end of the front and rear rolling guide frames 1 and 1' in a gap between the pair of rolls, the partitions 4 are formed with arc-shaped notches 10 substantially concentric to the respective rolls to avoid any interference with surfaces of the rolls. The notches 10 preferably have a radius somewhat larger than a diameter of rolls at an initial rolling stage and a parallel portion 11 having a length in the rolling direction in the proximity of its abutting end.

The partitions 4 are preferably formed along the notches with chamfers 1 2 concentric thereto except the three partitions particularly at the front guide frame 1 at the right hand in the drawing in order to facilitate introducing rolled materials leaving between the rolls.

It is required that the three distances B'1, B'2 and B'3 are larger than the three distances B,, B2 and B3 between the partitions in order to allow the rolled materials to be widened in a one direction continuous rolling.

As shown in the drawing, the partitions 4a and 4b arranged on the left side of the third partitions from the rightmost partitions as viewed in the drawing define rolling zones therebetween for the roughing and intermediate rollings and the partitions 4a and 4b on the sides of the front and rear guide frames are connected at their abutting ends by fitting of vertical grooves 1 3 and vertical ridges 14 formed therein to enable the partitions to resist traverse pressures transmitted from the rolled materials.

The outermost partitions 4a' and 4b' are provided with protrusions 1 5 extending in axial directions of the rolls for connecting the front and rear partitions 4a' and 4b' at their abutting positions by means of connecting members 16 bolted to the protrusions 1 5 with bolts 1 7.

This connection of the front and rear partitions is effected in a condition that the respective guide frames 1 and 1' abut against to each other so as to embrace the pair of rolls and their base members 5 are supported on the rest bars 2. The base member 5 is clamped in any position in the axial direction of the rolls by a restraining plate 1 8 bolted to the rest bar 2 with bolts 1 9 to fix the side frames in any adjusted positions. Base guides are arranged between the partitions 4b as shown in the drawing.

In one example of rolling, blooms of 250 mm width were rolled through six passes in the defined roughing rolling zones a and three passes in the defined roughing rolling zones b alternately in normal and reverse directions and further rolled through two passes in alternate normal and reverse directions in the defined intermediate rolling zone c and one pass in the reverse direction in the defined intermediate rolling zone d to obtain billets of 1 70 mm width.

Thereafter the billets were rolled progressively in the finishing rolling zones e, f and g in normal directions to obtain billets of 1 50 mm width which were then passed in succession through tandem finishing rolling mills to obtain required billets.

The rolls had a barrel length of substantially 1,000 mm and an initial outer diameter 650 which was reduced to 410 mm of the minimum diameter by repeatedly machining the barrel for correcting the barrel surface during the use. When caliber rolls having the same initial outer diameter had been used, they were discarded at a barrel diameter of 570 mm. The side guides according to the invention bring uniform wear of a roll and reduce the number of rolls to be maintained, which in conjunction of the effective use of the rolls to the above minimum diameter consequently reduce the initial unit price of rolls to one tenth of that of the prior art.

The side guides according to the invention further improve the rate of rolling mill operation by 3-4% because of the reduction of labor for changing and adjusting the rolls and increase the yield rate by approximately 0.5% for the improvement of crop configurations of products.

The defined rolling zones for roughing and intermediate rolling preferably have widths on entry and exit sides at least 10 mm larger than the widths of the material and the defined rolling zones for finishing rolling preferably have widths on entry sides about 10 mm larger and on exit sides about 20 mm than the widths of the material. In this case, the widths of the material are widened by about 30% of the reduction. while in case of caliber rolls those values were about 20%.

With the caliberless roll passes, moreover, entry guides have been used for correctly introducing materials to be rolled into roll gaps in the same manner as in the caliber roll passes.

As its one example shown in Figs. 1 7a and 1 7b. the material w to be rolled is fed into a gap of caliberless rolls 204 and 204' for rolling, while the material is guided by guide plates 202 and 202 of an entrance guide 201 and maintained in position by guide rollers 203 and 203'. In this case, so long as the material w is kept by the guide rollers 203 and 203' as shown in Fig.

17a, an overturn of the material w does not occur. As soon as a tail end of the material leaves the guide rollers 203 and 203' as shown in Fig. 17b, the material ioses its holding means, so that the material is apt to cause the overturn so as to change the cross-section of the tail and c to parallelogram sectional as shown in Fig. 1 8. The larger the flat ratio B0/H0 and bulge ratio b/Ho of the material, the acuter is the overturn to make it impossible to effect the predetermined rolling processes.

As shown in Fig. 1 9 illustrating one example of a tail end of a product subjected to a forming pass, fins e occur on the tail end which must be removed in an extra process. When such fins e become excessive, the fins will be subjected to rolling operation in a small gap other than calibers, causing extraordinarily large rolling load resulting in stoppage and damage of rolling mills. If the overturn becomes excessive, the sectional size becomes larger than a predetermined value, so that the material cannot pass through entrance and exit guides at rolls, causing stoppage of the mill and breakage of the guides.

In order to avoid such disadvantages inherent in the caiiberless rolls, an entry guide for caliberless rolling is proposed according to the invention, which supports the material to be rolled until it leaves a grooveless roll gap to mitigate an overturn which would otherwise apt to occur on a tail end of the material, and prevent the above improved productivity owing to the high elongation efficiency from being lowered due to the decreased yield rate resulting from removal of crops on tail ends of rolled materials.

Figs. 21 and 22 are explanatory views illustrating of a fundamental construction of the above entry guide. As shown in the drawings, there are provided guide plates 202 and 202' and guide rollers 203 and 203' as the prior art in Figs. 1 7a and 1 7b and bill-like holders 205 and 205' arranged between the guide rollers 203 and 203' and grooveless rolls 204 and 204' and extending through a gap of the grooveless rolls 204 and 204' at least to an exit 8 where the deformation of the material is completed so as to embrace and support the material in axial directions of the rolls. Although a pair of guide rollers 203 and 203' have been shown in the drawings, with a roughing stand operating at relatively low rolling speeds two pairs of guide rollers are preferably provided to enhance the holding of the material and in addition thereto, a guide roller or guide rollers are more preferably provided on the exit side.

The material w to be rolled is naturally deformed to extend in axial directions of the rolls by rolling with the grooveless rolls. In other words, the deformation of the material w advances in streamlines in the axial directions of the rolls to widen its width from the beginning to the termination of rolling. The shape of the deformation can be roughly anticipated. Accordingly, the bill-like holders 205 and 205' have inner relief surfaces 206 and 206' substantially corresponding to the transition of deformation of the material in the axial directions of the grooveless rolls.

The relief surfaces 206 and 206' are set so as to obtain the optimum clearances k between the surfaces and the material to be rolled. When the clearance k is less than 1 mm, the side surfaces of the material to be rolled are apt to contact the relief surfaces 206 and 206' to cause scratches in the surfaces of the material. On the other hand, when the clearance k is as much as more than 5 mm, the holders 205 and 205' do not serve to restrain the material and therefore to not prevent the overturn of the material. Accordingly, the clearance k is preferably 1-5 mm for preventing the overturn over the length of the material to stably effect the rolling operation with grooveless rolls.

The bill-like holders 205 and 205' also serve to guide the leading end of the material w into the roll gap. When the material is guided only by the guide rolls 203 and 203' without the billlike holders, the leading end of the rolled material w delivered from the roll gap twists about its axis, which makes it impossible to introduce the material into the next roll stand. Such a rolling trouble can be eliminated by the bill-like holders.

Figs. 24a and 24b illustrate in a plan and a side view a concrete construction of the entry guide 201 according to the invention applied to horizontal grooveless rolls 204 and 204' showing the important part in section. Fig. 25 illustrates the outline of the entry guide 201 in a perspective view and Fig. 26 is an exploded perspective view. The entry guide 201 comprises guide plates 202 and 202' mating with each other and having respective inner taper surfaces, a pair of holders 207 and 207' embracing the guide plates 202 and 202' and including guide rollers 203 and 203' supporting the sides of the material w next to front ends of the taper surfaces of the guide plates 202 and 202', and a box-shaped guide 208 housing therein the assembly of the guide plates 202 and 202' and holders 207 and 207' and adjustably fixing the guide rollers 203 and 203'.The holders 207 and 207' are retained by retaining bolts 209 passing through sidewalls of the box-shaped guide 208 and screwed into threaded holes 209' formed in the holders. Adjusting set screws 210 are screwed into sidewalls of the box-shaped guide 208 to adjustably set a distance between the holders 207 and 207'. Adjusting set screws 211 are screwed into the holders 207 and 207' to abut against reaction plates 212 and the aid of which the set screws 211 set the clearances of the guide rollers 203 and 203'. Set screws 21 3 and 214 are screwed into an upper wall of the box-shaped guide 208 to fix the guide plates 202 and 202' and holders 207 and 207'. The guide rollers are rotatably supported on pins 215 through bearings 216.In this embodiment, although the bill-like holders 205 and 205' extending in the gap of the grooveless rolls 204 and 204' to the exit have been shown integrally with the holders 207 and 207' at their ends, the bill-like holders may be formed separately from and fixed to the holders 207 and 207' by welding or set screws.

A blank material of 1 50 mm square was rolled by grooveless rolls through 1 2 passes with above entry guides 201 and further rolled by caliber rolls through six passes to obtain round steel rods of a 1 6 mm diameter. On the other hand, the same material was rolled in the same manner by the use of conventional entrance guides having guide rollers 203 and 203' but having no bili-like holders 205 and 205'.In comparison of the overturn of tail ends of the rolled materials, when the clearances k between the material and the relief surfaces 206 and 206' of the bill-like holders 205 and 205' are 3-5 mm, overturn angles at the tail ends of the material were within 5" as shown in Fig. 27a which angles did not impede the following caliber rolling, while with the conventional entrance guides considerable overturns at the tail ends of the material occurred so that one third of the rest rods did not pass through entrance guides of next mills and remaining two thirds were not impossible to be rolled to 1 6 mm diameter, but lengths of fins formed on the tail ends were more than five times of those according to the invention to considerably lower the yield rate as shown in Fig. 28.

The entry guides according to the invention were applied to rolling with grooveless rolls for small diameter steel rods and wires, in which the entry guides are important for improving the yield rate. Use was made of a continuous finishing tandem rolling mill apparatus consisting of six horizontal and vertical mills alternately arranged, that is, four sets of four high mills 217, 218, 219 and 220 including back up rolls for four upstream passes and two sets of two high mills 221 and 222 for two downstream passes. A blank material of 1 8 mm square was progressively rolled according to a pass schedule shown in Fig. 29 to produce 11 mm diameter round steel rods.

In contrast herewith, with the conventional all caliber rolling, although it was possible to roll the 1 8 mm square blank material to 11 mm round rods through six passes of alternate oval and round calibers, it encountered the above mentioned disadvantages. On the other hand, when the 18 mm square blank rods were rolled to 11 mm round rods through four upstream passes using two high mills including grooveless rolls according to the conventional method and remaining two upstream passes by caliber rolls, the rolled rods through the grooveless rolls were excessively flatened to make unstable the rolling. This resulted from the fact that roll diameters of the two high mills are comparatively large such as 360 mm, so that the ratio D/H are also large to considerably lower the elongation efficiency, in other words, to produce superfluous widening of material in width. Table shows the considerable difference in elongation efficiency between the pass schedule of the prior art in Fig. 32 and that according to the invention in Fig.

30.

Table

Fig. 32 (Prior art) Fig. 30 (According to the invention) Pass Roll Roll Reduc- Roll Roll Reduc No. Elonga- Elongation Elonga- Elongation diameter gap tion diameter gap tion tion efficiency tion efficiency (mm) (mm) (%) (mm) (mm) (%) 0 18# 18# 1 360 11 39 1.23 0.75 100 13.5 25 1.26 0.95 2 do 10 58 1.20 0.50 do 12.5 34 1.28 0.84 3 do 8.5 61 1.23 0.48 do 11 31 1.21 0.83 4 do 8 62 1.24 0.47 do 11 27 1.15 0.85 5 do 8 56 1.31 0.52 360 8 38 1.30 0.68 6 do 11# 35 1.13 0.87 do 11# 35 1.13 0.87 According to the invention, as above mentioned the diameters of grooveless rolls can be reduced to an extent of 100 mm with the aid of back up rolls, so that the ratios D/H are much smaller than in the conventional grooveless roll rolling method to improve the elongation efficiency or prevent the widening in width of rolled material as shown in Fig. 30, thereby achieving a stable rolling.

Although the above example has been explained an application of the method according to the invention to the continuous finishing mill in the manufacturing process of the 11 mm diameter round steel rods, the invention can be advantageously applied to upstream passes having the purpose of reducing sectional areas of rods other than the forming passes for giving final cross-sectional shapes to products. Moreover, the invention may be applied not only to continuous mills but also single mills such as reverse mills. Although the four high mills have been exemplarily illustrated, the back up means are not essential for the invention.

As can be seen from the above description, this invention is useful to stably effect the rolling steel rods and wires with the grooveless rolls with high elongation efficiency to considerably improve the productivity. The side guide according to the invention accomplishes the improved grooveless rolling without twisting and overturning steel rods to widen the field of the grooveless rolling with the following effects. As the rolls do not have any caliber, they are easily and inexpensively machined. As the surfaces of the rolls used for rolling are wider, the rolling operation per one roll increases. As the same rolls are able to be used for rolling products within wide ranges of sizes, the number of rolls to be maintained is less than that of the prior art.As the rolls are not formed with calibers, the initial outer diameters of the rolls are smaller than those of caliber rolls, with the result that the rolling mill bodies, housings, motors and accompanying installations are small-sized. There is no risk of breaking because of the grooveless rolls and the life of rolls is longer because they are able to be used to smaller diameters. It is not necessary to change rolls every time sizes of material to be rolled are changed. Accordingly, the down time is considerably decreased. It is possible to avoid down time for adjusting centers of upper and lower roll flanges during rolling, for repairing by grinding partially decayed or damaged calibers due to melting or burning, for adjusting centers of the guides and rolls and for others. The yield rate is improved resulting from the reduction of defects of products such as fishtails. Moreover the entry guide to be directly used in rolling with grooveless rolls ensures the holding the material to an exit of the roll gap to effectively prevent the inherent troubles in grooveless roll rolling, thereby obtaining the effective utilization of rolling energy and considerable improvement of product yield rates.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details can be made therein without departing from the spirit and scope of the invention.

Claims (14)

1. A rolling method of steel rods or wires by passing rectangular cross-sectional blank material through plural pairs of grooveless rolls of a series of continuous rolling mills, comprising a step of setting a gap of each pair of grooveless rolls so as to keep less than 1.5 a ratio of a long side to a short side of a cross-section of the blank material which has passed through said gap.

2. A rolling method as set forth in claim 1, wherein said blank material is a bloom.

3. A rolling method as set forth in claim 1, wherein said blank material is a billet.

4. A rolling method of steel rods or wires by passing rectangular cross-sectional blank material through plural pairs of grooveless rolls of a series of continuous rolling mills, wherein a diameter of said each pair of grooveless rolls is comparatively small such that a ratio of the diameter D to said gap H fulfills a reiation 100 D/H-- + 5 H thereby exclusively deforming the blank material in a rolling direction as much as possible.

5. A rolling method as set forth in claim 4, wherein the diameter of said each pair of grooveless roll fulfils the following relations: when H60 mm, D/H5, H when 60 mm > H20 mm, D/H;;;;12.5 8 H when 20 mm > HL10 mm, D/H2O-, and 2 when H < 10 mm, D/H35-2H.

6. A rolling method as set forth in claim 4 or 5, wherein at least part of said continuous rolling mills include back up rolls supporting rolling reactions.

7. A guide for supporting sides of steel rods subjected to grooveless rolling comprising front and rear rolling guide frames abuttingly combined with each other in a gap between a pair of rolling rolls having cylindrical surface barrels to embrace said pair of rolls on front and rear sides thereof so as to form defined rolling zones which are side by side in an axial direction of said rolls and divided by said rolling guide means.

8. A guide as set forth in claim 7, wherein the outermost rolling guide frames are provided on outsides of their abutting ends with connecting means of connecting members.

9. A guide as set forth in claim 7 or 8, wherein fitting connecting means are provided in the abutting ends of partitions of said rolling guide frames forming said defined rolling zones.

10. A guide as set forth in claim 7, 8 or 9, wherein said defined rolling zones have widths different from one another.

11. A guide as set forth in claim 7, 8, 9 or 10, wherein substantially half of said defined rolling zones on roughing rolling side and remaining half of said defined rolling zones are different in height.

1 2. A guide as set forth in claim 11, wherein said defined rolling zones higher in height are uniform in width on front and rear rolling sides and said defined rolling zones lower in height are wider on the rear rolling sides than on the front rolling sides.

1 3. A guide as set forth in claim 7, wherein said side guide is adjustable in the axial direction of said rolls.

14. A guide for holding rolling rods and wires subjected to grooveless rolling, comprising guide plates mating with each other and having respective inner taper surfaces for supporting side surfaces of blank material to be rolled to introduce it into a gap of grooveless rolls, a pair of holders embracing said guide plates and having guide rollers supporting said side surfaces of the blank material downstream of taper ends of said inner taper surfaces of said guide plates and a box-shaped guide having therein an assembly of said guide plates and said pair of holders and fixing said guide rollers whose gap therebetween is adjustable, and each said holder extending in said gap to at least a delivery end of said gap and having a bill-like holder integrally formed therewith preventing an end of the blank material not supported by said guide rollers from twisting.

1 5. A guide as set forth in claim 14, wherein each said bill-like holder includes an inner relief surface facing to the blank material and substantially corresponding to widening of the blank material owing to a reduction by the grooveless rolls.

1 6. A guide as set forth in claim 15, wherein said inner relief surface of the bill-like holder forms a clearance of 1-5 mm with the blank material.