US 3136054 A
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June 9, 1964 o. PALMER ETAL ROD ROLLING METHOD Filed April 16, 1958 United States Patent Ofiice 3,136,054 Patented June 9, 1964 3,136,054 ROD ROLLING METHOD Oskar Palmer and Karl Gies, Dusseldorf, Germany, assignors to Baustahlgewebe G.m.b.H., Dusseldorf-fiberkassel, Germany Filed Apr. 16, 1958, Ser. No. 729,005 Claims priority, application Germany Apr. 20, 1957 6 Claims. (Cl. 29-547) This invention relates 'to methods of producing reinforceinent steel with transverse indentations on the peripheral surface thereof.
Whereas smooth rolled wire was once used for reinforcing concrete, this has now for many years been superseded by rolled wire with a surface partly or wholly transverselyribbed, indented, twisted, or otherwise deformed to establish a better bond with the concrete. Moreover, for improving the peripheral properties of bars for reinforcing concrete, recourse has been had to hardening them, especially by means of cold deformation, such as stretching or twisting. However, it has been found that owing to the notch sensitivity of the steel the bending fatigue strength of ribbed or indented reinforcing bars is adversely affected by this cold deformation frequently to such an extent as to make them unfit for use. The production of reinforcements of this kind, which first seemed so promising, has therefore been widely discontinued.
In the special case of pre-stressed concrete and in many other applications, drawn wire is used to provide the reinforcement. Whereas in actual practice a smooth round section wire is nearly exclusively used, it has nevertheless already been proposed to provide the wire surface with special profiles for improving the bond with the concrete in much the same Way as does the ribbing on bars in ordinary reinforced concrete. The wires for pre-stressed concrete are thus formed for instance with ribs by cold rolling the wire to forge the required deformations during or after the straightening process and after the wire has been drawn. However, such wires have not been successful. The cold rolling deforms the circular section and gives rise to subsequent difliculties when straightening or welding the wires and when welding the wires into a mesh inasmuch as additional strains are set up and warping occurs. Moreover, the notch sensitivity of the wires, as already mentioned, so reduces their cold deformability, especially their bending fatigue strength, that the rolled indentations must necessarily beso shallow that the bond in the concrete is scarcely improved or that the wire cannot be drawn down sufiiciently to secure the desired improvement in strength.
The present invention provides a simple and inexpensive method of producing a concrete reinforcing wire of a kind that will give an optimum bond in concrete and at the same time retain excellent cold deformation characteristics, especially in regard to its bending fatigue strength, in that the wire is subjected to compression stress in the peripheral zone and to tension stress in the core.
According to the invention, the wire is first provided, by rolling indentations into the same, with transverse rib-like surfaces for bonding with the concrete and is then drawn down through a wire-drawing die or drag plate to a section which is less than that prior to ribbing. Preferably the process is performed on a round section wire which is first rolled in a shaping mill which forms grooves in opposite sides of the wire, said grooves leaving lands constituting the ribbing between them. The rolling imparts an oval section to the wire. Alternatively, an oval-sectioned wire could be used ab initio. In any event, it is expedient to form the ribs on the flatter sides of the oval cross section. The advantage of the oval cross section is that, in drawing the wire through a die with a circular opening, the discontinuities in the section will not interfere with the smooth passage of the wire through the die. Despite the presence of the ribs, no special difficulties will therefore arise in the drawing. Further, to reduce the generation of undue stress in the die, it is advisable to stagger the indentations on either side of the wire in such manner that a land will always be situated diametrically opposite a groove in any one section. For the same reason, the ribs may also be pitched obliquely in relation to the axis of the wire, so that the wire cross section will be the same or substantially the same along the entire length of the wire. Indentations may also be formed in the wire when hot rolling the same.
By carefully choosing the depth of the indentations in accordance with the reduction in section when drawing, it is possible to achieve an increase in tensile strength in the surface regions which are cold deformed substantially the same as the increase in strength achieved in the regions which are subject to cold deformation merely or chiefly by stretching. The rolling produces slight compression stresses on the surface or in the peripheral zone of the wire while the die-drawing produces substantial compression stresses in said zone and tension stresses in the core or central zone.
It may be stated in this connection that, in the production of smooth tubes or bars, it is already known first to roll the material and then to draw it through a die in one operation. However, the object in this known procedure differs from that contemplated by the present proposal in that the known process is merely intended to remove the burrs and to calibrate the material to an accurately determined dimension.
The invention will now be described with reference to the accompanying drawings in which:
FIG. 1 is a perspective view of a rolled wire as used for performing the method according to the invention;
FIG. 2 is a similar perspective view of a ribbed wire produced by cold rolling the rolled wire shown in FIG. 1;
FIG. 3 is a perspective view illustrating a reinforcing wire produced according to the invention by drawing a wire of the. kind shown in FIG. 2 through a circular die;
. FIG. 4 is a ribbed wire similar to that shown in FIG. 2 but provided with obliquely pitched ribs, and
FIG. 5 diagrammatically illustrates the general layout of apparatus for producing a reinforcing wire according to FIG. 3 from a rolled wire of the kind shown in FIG. 1.
A rolled wire 1 (FIG. 1) of circular section is drawn by a dog 2 in succession through a shaping mill with a pair of rolls 3, 4 and a die or drag plate 5 (FIG. 5). The rolls are provided with equidistantly spaced ribs 30 and 4a and are coupled by intermeshing gear wheels 6 and 7 in such a way that the ribs 3a and 4a will be alternately pressed into opposite sides of the wire. The action of the rolls 3 and 4 is to deform the rolled wire 1 into the shape illustrated in FIG. 2, that is to say the cross section of the wire is deformed into an oval cross section (FIG. 2), indentations 8 being pressed into the flattened sides of the oval cross section leaving lands between neighbouring indentations, which form ribs 9, the ribs 9 on one side of the wire being staggered in relation to the ribs 9 on the opposite side of the Wire by half the pitch of the ribs (FIG. 5). As the wire is immediately drawn through the die 5 the cross section is reduced by about 15 to 50% and its length increased accordingly by about 15 to 50% (FIG. 3). The diameter of the round section wire thus produced (FIG. 3) is approximately equal to or less than that of the circle (dotted line, FIG. 2) which can be inscribed between the indentations 8 in the wire section formed when the wire has been cold-formed by the rolls 3 and 4. The drawn wire is finally straightened into bars on revolving straightening machines and then cut to length in conventional manner.
The initial rolled wire (FIG. 1) may be a round steel wire having a diameter of 8.5 mm, a tensile strength of 40-45 kg./mm. a yield point stress of 24-32 kg./mm. and an ultimate elongation of 25 to 30%. After having been cold rolled, the width b of the wire (FIG. 2) may be about 9 mm. and its height it say 8 mm., its tensile strength being 48 to 50 kg./mm. its yield point stress 30 to 38 kg./mm. and its ultimate elongation at fracture 5 to 7%, the indentations 8 having a maximum depth of 0.5 mm. The pitch of the ribs 9 being about 10 mm., the indentations 8 may be 4 mm. and the ribs 6 mm. wide. After drawing, the wire (FIG. 3) may have a diameter d of 7 mm., a tensile strength of 60 to 65 kg./mm. a yield point stress of 52 to 55 kg./mm. and an ultimate elongation of 8%. The drawing speed may be, for example, 2.5 meters/see, and the reduction about 40%. In other Words, if the pitch of the ribs before drawing was 10 mm. (FIG. 2), it will be 14 mm. (FIG. 3) after the drawing. On the other hand, the depth of the indentations will have been reduced from 0.5 mm. to 0.3 mm. The indentations or ribs on the drawn wire are quite sufficient for creating the required bond with the concrete. By this procedure the strength and yield point stress of the wire has been considerably raised without reducing its cold deformability, whereas the depth of the indentations is sufficient to give an excellent bond in the concrete.
In the wire shown in FIG. 4, the indentations 8a rolled into the wire are obliquely placed in relation to the wire axis so that the cross section of the wire will be substantially the same throughout its length.
The ribs or indentations may also be of some other shape. For example, the surface of the rolled wire may be formed with round or polygonal indentations by hot or cold rolling, so that the resultant ribs will be of reticular pattern. If the drag plate has a circular opening and the ribs are already produced in hot rolling the wire, it is advisable to impart an oval cross section to the Wire as shown in FIG. 2.
The method proposed by the invention can naturally be applied to wires of other cross sectional profile and other than circular drawing dies could be used.
What is claimed is:
1. A method of producing a reinforcing element comprising rolling spaced transverse notches into a wire of substantially circular cross-section, and die-drawing the wire to a circular cross-section which is at most approximately equal to the cross-section of the largest concentric circle which can be inscribed in the first said cross-section adjacent a notch.
2. A method as claimed in claim 1 comprising rolling said notches into an oval wire.
3. A method as claimed in claim 1 comprising rolling said notches into a circular wire whereby flattening of said wire into oval shape occurs.
4. A method of producing a reinforcing element comprising rolling spaced transverse notches in a wire of substantially circular cross-section, the depth of the notches and the deformation of the wire resulting from said rolling being of a size to limit the stresses set up substantially to the surface of the wire, and then die-drawing the wire to a circular cross-section which is at most approximately equal to the cross-section of the largest concentric circle which can be inscribed in the first said cross-section adjacent a notch.
5. A method of producing a reinforcing element comprising the step of rolling spaced transverse notches into a wire of rounded circumference, the wire at the end of said rolling step remaining rounded on its entire circumference and the depth of the notches and the deformation of the wire resulting from said step being of a size to limit the stresses set up substantially to the surface of the wire, and then die-drawing the wire to a circular cross-section which is at most approximately equal to the cross-section of the largest concentric circle which can be inscribed in the first said cross-section adjacent a notch.
6. A method of producing a reinforcing element comprising the step of rolling a wire of substantially circular cross-section into an oval cross-section, while applying spaced transverse notches thereto, the depth of the notches and the deformation of the wire resulting from said step being of a size to limit the stresses set up substantially to the surface of the wire, and then die-drawing the wire to a circular cross-section which is at most approximately equal to the cross-section of the largest concentric circle which can be inscribed in the first said cross-section adjacent a notch.
References Cited in the file of this patent UNITED STATES PATENTS 1,929,695 Julien Oct. 10, 1933 1,930,446 Weybrecht Oct. 10, 1933 1,982,352 Richardson Nov. 27, 1934 2,036,034 Fulmer Mar. 31, 1936 2,078,434 Wise Apr. 27, 1937 2,260,779 Hoffman Oct. 28, 1941 2,333,238 Finnie Nov. 2, 1943 2,335,418 Johnson Nov. 30, 1943 FOREIGN PATENTS 728,636 Great Britain Apr. 20, 1955 OTHER REFERENCES WireDrawing and the Cold Working of Steel; A. T. Adam, 1926, pages 97-144, H. F. and G. Witherby, London.
Design of Machine Elements: M. F. Spotts, 2nd edition 1953, pages 68, 69, and 472 relied upon, Prentice Hall, New York, NY.
Metals Handbook, (1948), Published by ASM, Cleveland, Ohio, pages 536 and 537 relied upon.