EP0504219B1 - Steel wire for reinforcing the embedding material, especially concrete, and process for making it - Google Patents

Abstract

Steel wire for reinforcing embedding materials, especially concrete, in which the outline (4) of the cross-section is a three-branched epitrochoid which also has gradually widening and disappearing ribbing (5) along three generatrices with a constant increase in thread pitch, the maximum depth of which corresponds to the difference between the radius (rk) of the circle which can be described around the cross-section and the radius (rb) of that which can be inscribed in it.

Description

The invention relates to a steel wire for reinforcing an embedding material, in particular for reinforcing concrete, and to the method for producing the steel wire.

The steel wire according to the invention is not only used for reinforcing the concrete or for prestressing, but it is also possible to use the steel wire in other areas. So z. B. the use of steel wire is also widespread in the rubber industry, with some products being reinforced with steel wire, e.g. B. in conveyor belts and rubber tires of vehicles. In view of the fact that the largest amount of steel wire is used in reinforced concrete structures, we will describe the application of the solution according to the invention in connection with concrete, the principle of the invention - analogously - can also be used in other areas.

The steel wires commonly used to reinforce concrete structures are obtained directly by rolling or by further processing rolled wires. The steel wires used for prestressing the concrete with a high tensile strength (R _m = 1600-2000 MPa) are cold drawn products.

The steel wire prestressing the concrete has the task that the concrete structure embedding the steel wire can also be loaded with a force which causes a corresponding tensile stress in the steel wire. The interaction between steel wire and concrete is guaranteed by the anchoring, which is largely promoted by ribs on the steel wire. Accordingly, this rib structure has the task of transferring the force between the concrete and steel wire.

The rib structure of the known steel wires used in the prestressing or reinforcement of the concrete either has a discontinuous or periodic shape, or it has a spiral shape. The cross section of the steel wire with a periodic rib structure is by no means constant, since the ribs are formed - repetitively - between different impressions formed on the outer circumference of the steel wire, from which it follows that the wire cross section is obviously smaller in the impressions. The steel wire with a spiral rib structure tends to twist under load in the concrete. This twist is such. B. prevented by distortion of the circular cross section of the steel wire, z. B. by flattening on both sides, or the ribs are torn, or rib strips are used with opposite thread pitch. Both the periodic rib structure and the spiral rib structure have abrupt transitions or corners. It is known that these are stress-collecting points where cracks can arise as a result of stress peaks. The disadvantages described here occur in the course of use, the periodic rib structure occurring in known steel wires or the distortion of the circular cross section also being considered disadvantageous from the point of view of production. In the course of the production of the steel wire, the periodic rib structure is created or the cross section deformed in separate operations after the wire has been drawn. During these later operations, the fiber texture or the secondary fibrousness previously formed during the drawing process is destroyed in the steel wire material, as a result of which the mechanical parameters of the steel wire (bending number, elongation) are impaired. As an example of the known solutions we would like to mention the Hungarian patent specification HU-PS 159 837, in which steel wire and the process for its production are described. The solution proposed there is used to manufacture steel wires with low strength (R _m = 1200 MPa). In the sense of this solution, the wire rod is drawn cold, whereupon the gradually occurring and disappearing oblique ribs are generated with a cylinder group for flattening and rib design. One of the disadvantages of the method mentioned is that the machining of the profiled cylinders of the cylinder group producing the rib structure is extremely expensive.

Another disadvantage is that the life of the cylinders is short due to the high load. In the manufacture of prestressing steel wires with high strength (R _m = 1600-2000 MPa), the lifespan of the cylinders is so short due to the increased use that the application seems senseless. The Hungarian patent HU-PS 158 074 proposes a solution for the production of high-strength steel wires. In the sense of the patent, two cylinders lying opposite one another - as a pair of cylinders - flatten the wire with the circular cross-section, after which the spiral-shaped rib structure with a constant thread pitch is produced on the profiled wire thus produced, with a free-running drawing tool that has a drawing hole with distorted has a spiral surface. The flattening of this solution is necessary because the spiral ribs - due to the twisting, the "twisting" - do not guarantee a more satisfactory adhesion in the concrete than a smooth cylinder surface.

With this steel wire, too, there is an edge when the flattened part and the cylindrical jacket part meet; at this point the product tends to crack. Another disadvantage is that the smooth cylinders can only be fitted into the drawing process with difficulty because of the high wire strength. Another disadvantage is that the storage can not be realized with full certainty in small dimensions. For the sake of good order, it should be noted become that with smooth wires or with wires that have only a spiral rib structure, a satisfactory anchoring can only be achieved if these are twisted in strands. The strand can neither twist nor be twisted apart. If several steel wires are used in the strands, however, additional costs arise, which are also increased by the twisting, since it represents a separate working step.

The object of the invention is to eliminate the errors, deficiencies and other disadvantages of the known solutions which serve the same purposes. More precisely, a cold-drawn steel wire is to be created which has an equivalent rib structure in all cross-sections, the ribs not having sharp corners at their base, and which has a characteristic fibrous texture and secondary fibrousness.

The aim of the process according to the invention was that it should not essentially deviate from the usual cold drawing method. The method is to be implemented using simple and inexpensive means, and no ancillary operations and means are to be claimed. In summary, the production should be made possible in a single operation, and the usual fibrous texture and secondary fibrousness of the cold drawn wires should in no way be destroyed. In the steel wire according to the invention, the set goal is achieved in that the wire cross-section is delimited by a three-armed epitrochoid contour line and in that the wire has a spiral-like rib structure with ribs which gradually emerge along the three arms of the epitrochoid and merge into the contour line.

The method according to the invention essentially ensures that the set goal is achieved in that the wire, which originally has a circular cross section, is designed with the cross section with the epitrochoid contour line by means of a pulling tool in the course of a cold drawing process, which is followed by a cold pulling operation using a rotating tool, in the course of which a special drawing hole determines and designs the spiral-like ribs of the wire and the final cross-section of the wire.

Based on our investigations, it emerges that there should be a ratio of at most 1.15 between the radii of the circumscribing circle of the epitrochoid contour line determining the cross section of the steel wire and the inscribed circle of the contour line. Likewise, the design is considered to be advantageous in which the thread pitch of the ribs is 10 to 15 times the diameter of the center circle between the aforementioned circles and in which there are six ribs within the thread pitch. This rib structure is otherwise spiral and periodic.

The method according to the invention expediently represents a plurality of work steps forming a process. It may happen that the wire serving as the starting piece has to be subjected to a preforming so that a steel wire with a corresponding surface quality and favorable dimensions can be obtained for the work steps according to the invention. A material in such a state is called a preformed steel wire. At least within the course of the method according to the invention in the narrower sense, this designation also applies if the preforming is unnecessary in the course of implementing the method according to the invention.

In the cold state, the preformed steel wire, which is cylindrical or has a circular cross section, is pulled through a stationary drawing tool, the drawing hole of which determines a cross section with a three-armed epitrochoid contour line. The circle circumscribing the cross section has the diameter d _k (the radius r _k ). The cross section of the semi-finished steel wire resulting from the aforementioned shaping is 16 to 30% smaller than that of the preformed steel wire. This means that the cross section is reduced by 16 to 30% in the course of pulling through the stationary drawing tool.

Then the semi-finished steel wire with the cross section with the epitrochoid contour line is drawn through a rotating drawing tool - also in the cold state. The drawing hole of the rotating drawing tool has a hexagonal cross section with rounded corners and has a distorted spiral surface with constant thread pitch that brings about the rib structure. This rotating, known pulling tool is free-running and supported in the usual way. The product that leaves the rotating drawing tool is considered in the sense of the invention as a finished steel wire. At the end of the manufacturing process, the finished steel wire can be wound onto a drum.

wobei $$\text{d =}\frac{{\text{d}}_{\text{k}}{\text{+ d}}_{\text{b}}}{\text{2}}\text{.}$$

The corner width l _k of the hexagon with rounded corners determined by the cross section of the rotating drawing tool corresponds to the diameter of the circumscribing circle d _{k of} the epitrochoid contour line (l _k = d _k ), at the same time the area width l _{b of} the hexagon corresponds to the diameter d _{b of} the inscribed circle of the epitrochoid contour line (l _b = d _b ). In this way, ribs are brought about on the steel wire by pulling through the rotating drawing tool, said ribs being inclined with respect to the longitudinal axis of the steel wire with six cuts of the three arms of the epitrochoid gradually come into being and merge into the contour line, the height of the ribs corresponding to the difference r _k - r _b between the radius r _{k of} the circumscribing circle and the radius r _{b of} the inscribed circle. The mutual distance l between the ribs along the longitudinal axis of the steel wire is 1.6 to 2.5 times the mean diameter d of the contour line of the cross section of a continuously smooth envelope surface of the steel wire that circumscribes the wire and, for a straight wire, forms the peripheral surface of a generalized cylinder, ie $$\text{l = 1.6 d to 2.5 d,}$$

in which $$\text{d =}\frac{{\text{d}}_{\text{k}}{\text{+ d}}_{\text{b}}}{\text{2nd}}\text{.}$$

The maximum height of the ribs is 4 to 7% of the mean diameter d thus defined. The resulting rib structure is produced without any further technological step only by pulling it through the drawing tools.

In the system for realizing the method according to the invention, the tools required for a possible preforming, the rollers deflecting and moving the steel wire and the stationary drawing tool and the rotating drawing tool are expediently arranged in such a way that the steel wire can be designed in a single production process. Of course, the system must be provided with other necessary, known means, for. B. for lubrication and cooling, furthermore you have to take care of the storage of the rotating tool and the elements that absorb the axial and radial loads.

$${\text{y = 4 r}}_{\text{e}}{\text{sin (φ) - λ r}}_{\text{e}}\text{sin (4 φ)}$$

wobei

r_e

der Radius des die Trochoide ableitenden abrollen den Kreises und

φ

der Parameter ist.

The design of the special drawing holes of the drawing tools can expediently be carried out using the spark erosion process. The electrode required for the spark erosion process can be produced with the system according to the Hungarian patent specification 156 607. In connection with the solution according to the invention, the epitrochoid determination in question is possible according to the following equations: $${\text{x = 4 r}}_{\text{e}}{\text{cos (φ) - λ r}}_{\text{e}}\text{cos (4 φ)}$$

$${\text{y = 4 r}}_{\text{e}}{\text{sin (φ) - λ r}}_{\text{e}}\text{sin (4 φ)}$$

in which

r _e

the radius of the trochoid deriving the circle and

φ

the parameter is.

und der Radius r_b des eingeschriebenen Kreises der Trochoide beträgt $${\text{r}}_{\text{b}}{\text{= (4 - λ) r}}_{\text{e}}\text{.}$$

The radius r _k of the circle circumscribing the trochoids is $${\text{r}}_{\text{k}}{\text{= (4 + λ) r}}_{\text{e}}$$

and the radius r _{b of} the inscribed circle of the trochoids is $${\text{r}}_{\text{b}}{\text{= (4 - λ) r}}_{\text{e}}\text{.}$$

The mean radius r is r = 4 r _e .

The area of the cross section of the enveloping surface of the steel wire according to the invention which is delimited by epitrochiodic curves can be replaced in practice by the area of a circle with the central radius r.

The value of the parameter λ is λ ≦ 0.28, but it seems advisable to choose the value 0.18 to 0.19.

The essential characteristic of the steel wire according to the invention shows that the contour line of the cross section of the envelope surface is a three-armed epitrochoid, the maximum depth of the ribs Difference of the radius of the circumscribing circle of the cross section and the radius of the inscribed circle corresponds and the ribs thus gradually come about along the three arms of the epitrochoid and merge into the contour line and are designed with a constant thread pitch. In an advantageous embodiment of the proposed steel wire, the quotient of the radius of the circumscribing circle of the cross section and the radius of the inscribed circle is at most 1.15, the thread pitch of the ribs being 10 to 15 times the mean diameter of the cross section.

The essential characteristic of the method according to the invention shows that the steel wire serving as the starting product with a circular cross section or a possibly preformed steel wire is pulled through a stationary drawing tool, whereby the cross section is reduced by 16 to 30% and a semi-finished steel wire with a cross section with three arms Epitrochoidal contour line arises, whereupon the semi-finished steel wire is pulled through a free-running, but supported drawing tool, which has a distorted spiral surface with constant thread pitch and a drawing hole with a sexagonal cross section with rounded corners, in which the area of the hexagon corresponds to the diameter of the inscribed one Circle of the contour line of the cross section corresponds to the enveloping surface of the finished steel wire, while the corner width of the hexagon corresponds to the diameter of the circumscribing circle - which tangi the contour of the finished steel wire ert - corresponds and in which the diameter of the latter circumscribing circle corresponds to the diameter of the concentric circle rounding off the corners of the hexagon.

Fig. 1

den Querschnitt einer Ausführung des erfindungsgemäßen Stahldrahts,

Fig. 2

die wichtigeren Bestandteile der Anlage zur Durchführung des erfindungsgemäßen Verfahrens,

Fig. 3

aufeinander gezeichnet den Querschnitt des Stahldrahts nach der Vorformung und den Querschnitt des halbfertigen Stahldrahts,

Fig. 4

aufeinander gezeichnet den Querschnitt des Ziehlochs des rotierenden Ziehwerkzeugs und den Querschnitt des halbfertigen Stahldrahts.

The steel wire according to the invention and the manufacturing process are explained in more detail on the basis of the accompanying drawings. Show it:

Fig. 1

the cross section of an embodiment of the steel wire according to the invention,

Fig. 2

the more important components of the plant for carrying out the method according to the invention,

Fig. 3

drawn on top of each other, the cross section of the steel wire after preforming and the cross section of the semi-finished steel wire,

Fig. 4

drawn on top of each other the cross section of the drawing hole of the rotating drawing tool and the cross section of the semi-finished steel wire.

wobei der Mittelradius r dem Wert r = d/2 entspricht.In the steel wire 9 according to the invention shown in FIG. 1 with the illustrated cross section of the enveloping surface, the rib structure 5 and the epitrochoid contour line 4 can be clearly seen. The circle circumscribing the contour line 4 is shown with a thin line. The diameter d _{k of} the circumscribing circle and the diameter d _{b of} the inscribed circle are shown. Using these designations, the mean diameter d is given by: $$\text{d =}\frac{{\text{d}}_{\text{k}}{\text{+ d}}_{\text{b}}}{\text{2nd}}\text{,}$$

where the center radius r corresponds to the value r = d / 2.

FIG. 1 clearly shows that the height h of the ribs 5 corresponds to the difference between the radius r _{k of} the circumscribing circle and the radius r _{b of} the inscribed circle, ie h = r _k - r _b , where $${\text{r}}_{\text{k}}{\text{= d}}_{\text{k}}{\text{/ 2 and r}}_{\text{b}}{\text{= d}}_{\text{b}}\text{/ 2nd}$$

The geometrical relationships are expediently chosen such that the maximum height h of the rib structure 5 is approximately 4 to 7% of the mean diameter.

The sketch in FIG. 2 shows a possible embodiment of the plant used to produce the steel wire according to the invention. The method according to the invention is described in detail in connection with FIG. 2. The starting steel wire 1 represents the material entered in the method used as an example. According to the respective requirement, the material must be subjected to heat treatment or surface preparation is required. It is possible to change the cross section with the preparatory tools 11. In the course of the operations, the rollers 10 secure the movement, guidance and deflection of the steel wire 1. The operations previously mentioned are known per se; they do not belong to the scope of the invention. In the course of this forming, the cross section of the material gradually decreases and the strength increases. After any preforming, the steel wire is formed, the shaping of which takes place using the method according to the invention in the narrower sense. This means that the individual preforming operations can take place in separate processes.

The preformed steel wire, which is in the cold state, is pulled through the stationary drawing tool 2. The drawing hole has a cross section with a three-armed epitrochoid contour line. The steel wire 6 entering the stationary drawing tool has a circular cross-section, while the emerging semi-finished steel wire 8, as can be seen in FIG. 3, is profiled. In the course of pulling through the stationary drawing tool 2, the cross section of the steel wire, depending on the material quality, decreases by approximately 16 to 30%. From Fig. 3 it can be seen that the preformed steel wire 6 still has a circular cross section through the diameter D 'can be characterized after preforming. (The diameter D 'after the possible preforming operations is smaller than the initial diameter D.) The semi-finished steel wire 8, which is present after the stationary drawing tool 2, has a cross section with three-armed epitrochoid contour line 4. The method is explained further with the aid of FIG. 4. The semi-finished steel wire 8 is transformed into the finished steel wire 9 with the aid of the rotating drawing tool 3. The rotating drawing tool 3 has a drawing hole, the cross section of which forms a hexagon with rounded corners with a contour line 7. The drawing hole has a distorted spiral surface with a uniform thread pitch in the axial direction. The rotating drawing tool is supported in a manner known per se; it is free running. With respect to the hexagon with rounded corners with the contour line 7, the corner width l _k corresponds to the diameter d _{k of} the circumscribing circle of the contour line 4 of the cross section of the semi-finished steel wire 8, at the same time the area width l _b corresponds to the diameter d _{b of} the inscribed circle. The rotating drawing tool 3 is also designed using the spark erosion method.

Finally, the finished steel wire 9 can be wound on the drum 12 (Fig. 2). The force required to pull can be partially exerted by the drum 12.

The steel wire according to the invention, which is produced in the course of the method according to the invention, can have a high strength. For example, with a steel wire with a diameter of 5 mm, the strength R _m = 1600-2000 MPa. An advantage of the invention is shown in that the rib structure is designed simply by pulling through the drawing tools without any separate technological phases. Another advantageous characteristic consists in that the steel wire retains the fiber texture and the secondary fiber structure that is created during cold drawing. This has the consequence that the mechanical properties such. B. the number of bends and the elongation will be favorable.

Another advantage of the steel wire according to the invention is that slipping out of the embedding material, such as. As concrete, and torsion can be prevented by the rib structure and the epitrochoid shape. With such a geometric design, there are no sharp corners, as a result of which stress-collecting parts in the finished steel wire are avoided.

The steel wire according to the invention can be used as an independent strand or twisted in strands.

Claims (5)

1. Steelwire for the reinforcement of embedding materials in particular concrete, characterized in that the contour (4) of the cross section of a cylindrical enveloping surface of the wire (9) is essentially a three-armed epitrochoid, furtheron the steelwire (9) is provided with ribs (5) with a constant threadpitch, said ribs reaching up to the enveloping surface and the bottom of said ribs starting from a circular cylindrical surface defined by the inscribed circle of the contour (4).
2. Steelwire as claimed in Claim 1, characterized in that it is formed with six threads.
3. Steelwire as claimed in Claim 1 or 2, characterized in that the quotient (r_k/r_b) of the radius (r_k) of circumscribing circle of the contour (4) of the cross-section and the radius (r_b) of the inscribed circle of the contour (4) amounts to 1.15 at the most, while the threadpitch of the ribs (5) amounts to the 10 - 15 fold of the average diameter (d) of the contour (4).
4. Process for producing steelwire as claimed in Claim 2 or 3, characterized in that the basic steelwire (1) with a circular cross-section or a prefabricated steelwire (8) is drawn through a stationary draw-tool (2), whereby a semi-finished steelwire (8) with a three-armed epitorchoidal contour (4) of the cross-section and with a cross-section being reduced by 16-30 % is obtained, thereafter the semi-finished steelwire (8) is drawn through a supported, however free-running draw-tool (3), the draw-tool being provided with a draw-hole, which has a sexagonal cross-section being rounded-off at the corners by running along a rounding-off circle and is provided with a constant threadpitch and distorted helical surface, whereas the surface width (l_b) of the hexagone corresponds to the diameter of the inscribed circle of the contour (4) of the cross-section of the enveloping surface of the finished steelwire (9) and the corner-width (l_k) correponds to the diameter of the circumscribing circle of the contour (4), while the diameter (d_k) of this circumscribing circle corresponds to the diameter of the rounding-off circle being concentric with it.
5. Process as claimed in Claim 4, charcterized in that the production of the semi-finsihed steelwire (8) and the production of the finished steelwire (9) is effected along with an eventual pre-formation in one single processing step.

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