SK278942B6 - Steel wire for reinforcing the embedding material, especially concrete, and process for making it - Google Patents

Abstract

The contour line (4) closed a steel wire is of a shape related to tri-arm epitrochoid and along the created bands, there as two ribs (5) being created and wanished, with the constant thread lead, the maximal depth of which corresponds to the difference between the cross-section circumcircle radius (rk) and cross-section in radius (rb). The outgoing steel wire (1) is being pulled with the use of the stationary plate, while this wire is of an annular cross-section or the pre-formed steel wire (6) and a semi-product closed to the steel wire (8) of a shape related to tri-arm trochoidal contour line (4) and with a lowered cross-section, at about 16 up to 30 percent, is created as a result of that, while the semi-product closed to steel wire (8) is being pulled with the use of a coaster rotary plate (3) with a tensile hexagonal hole having rounded peaks, with the curved, helix surfaces, while they have a constant lead.

Description

Technical field

The invention relates to steel wire for reinforcing cast materials, in particular concrete, and to a method for producing the same.

BACKGROUND OF THE INVENTION

The steel wire according to the invention serves not only for reinforcing the concrete or its prestressing, but is also used in other fields of technology. For example, the use of steel wire has also become widespread in the rubber industry, with some products being reinforced with steel wire, such as conveyor belts or rubber tires for vehicles. Since the largest number of steel wires are used in reinforced concrete structures, the solution according to the invention will be described in relation to concrete, with the main aspects of use also valid in other areas.

Conventional steel wires, which are used to reinforce concrete structures, are produced either directly by rolling or by further processing of wires obtained by rolling. Steel wires used for prestressing of concrete with high crack resistance (R. 1600 - 2000 MPa) are cold drawn products.

The steel wire pre-stressed in the concrete has the task of causing the cast reinforced concrete structure to be loaded with a force equal to that which results in the tensile stress. The effectiveness between the steel wire and the concrete is guaranteed by anchoring which is greatly supported by the rib made on the steel wire. Rebro has the task of transmitting the force between the concrete and the steel wire.

In known steel wires intended for prestressing and reinforcing concrete, the rib is either discontinuous or periodic in shape or is spiral-shaped. The cross-section of the steel wire with the periodic rib is not constant, since on the outer part of the steel wire the rib is formed by various repetitive indentations, which implies that the cross-section at the indentations is clearly smaller.

The steel wire with a spiral rib tends to twist in the concrete under load. The removal or prevention of the twisting of the steel wire is achieved, for example, by distorting the circular cross-section of the wire, for example by punching on both sides, or the ribs are intermittent, or the ribbed strips are formed with opposite thread pitch. Both in the periodic rib and in the spiral ribs, there are sharp transitions, corners, and it is well known that these spots concentrate stresses within themselves and are therefore prone to cracking due to the formation of stress peaks.

The described drawbacks arise during the use of these wires, whereby the periodic ribs of known steel wires or the deformation of the circular cross-section have to be considered as disadvantages in terms of production. Indeed, during the production of the steel wire, by drawing the wire in separate working operations, a periodic rib is formed or the cross-section deforms, thereby in the steel wire material the primary fibrous structure - formed during drawing - breaks down the secondary fibrous structure during further working operations, thereby greatly affecting the mechanical properties of the steel wire (number of bends, elongation).

An example of a known solution is, for example, the Hungarian patent HU-PS 159 837, which describes a steel wire and a process for its production. The proposed solution serves here for the production of low-strength steel wires (R _m - 1200 MPa). According to this solution, the wire is cold drawn, gradually forming and disappearing the inclined rib by a plurality of rollers for flattening and re-forming the rib.

One of the drawbacks of the said process is that processing with profiled rollers from the group of rollers that shape the rib is very expensive.

Another disadvantage is that the service life of the rollers is low due to the high stress. In the production of high strength steel wires (R _m - 1600 - 2000 MPa), the service life of the rollers is so short that the use of the rollers seems unreasonable due to increased stress.

The Hungarian patent HU-PS 158 074 proposes a solution for the production of high-strength steel wires. According to this solution, two opposed rollers flatten together as a pair of rollers - a wire with a circular cross-section, immediately afterwards a spiral rib with a constant thread pitch is formed on the profile wire thus formed, namely by means of a freewheel die with a drawing hole with a curved spiral surface. Since the spiral rib itself has a more satisfactory torsional adhesion to the concrete than a smooth cylindrical surface, a flattening is necessary in this solution.

Also with this steel wire there is an edge at the point of contact of the flattened and cylindrical parts, which tends to develop cracks.

A further disadvantage is that, due to the high strength, the smooth rollers of the drawing process are difficult to adapt to. A further disadvantage is that, with small dimensions, it is not possible to mount them in full confidence.

For the sake of convenience, it should be noted that for wires with smooth or exclusively spiral ribs, satisfactory anchoring can only be achieved if they are twisted into strands. The strand may further twist even further. On the other hand, when more steel wires are to be used in strands, additional costs are incurred, which are further increased by twisting, since this is a separate operation.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION It is an object of the invention to eliminate the defects, drawbacks and other disadvantages of known solutions and to provide a steel wire produced by cold drawing having a uniform rib in all cross-sections, with no sharp passage corners at the ribs. secondary fibrity.

The object of the method according to the invention is to produce a wire in a manner not substantially different from the conventional cold drawing process, the method according to the invention being simpler and cheaper, without any particular operation and means, in summary, production should be carried out in a single operation. the normal structure of the fibers and the secondary fibrity of the cold-drawn wires shall in no case be impaired.

The object of the invention is fulfilled by a steel wire for reinforcing cast materials, in particular concrete, according to the invention, characterized in that the contour line of its cross-section is a three-armed epitrochoid and spirally formed on its surface along three formed strips. the maximum depth corresponds to the difference between the cross-sectional radius of the described circle and the radius of the inscribed circle.

The principle of the steel wire manufacturing process according to the invention is that the wire is formed from a round wire during a cold drawing process with an epitrochoidal contour cross-sectional shape, and then subjected to cold drawing in a rotary die during which it is drawn through the drawn hole. and shape the spiral ribs and the final cross-sectional shape of the steel wire.

Tests have shown that there may be a ratio of not more than 1.15 between the radius of the described epitrochoid contour line determining the steel wire cross-section and the radius of the inscribed circle. At the same time, it is preferred that the pitch of the ribs is 10 to 15 times the diameter of the central circle between the two circles and there are six ribs inside. Moreover, these ribs are spiral and periodic.

Advantageously, the method according to the invention is a process comprising a plurality of operations. It may be the case that a wire serving as a starting piece must be subjected to a preforming operation in order to obtain a steel wire with adequate surface quality and proper dimensions. The material in this state is referred to as preforming steel wire. This name remains even after the preforming has been maintained during the implementation of the method according to the invention.

The preformed steel wire having a cylindrical or circular cross-section is cold drawn through a stationary die, the drawing opening of which determines the cross-section with a three-armed epitrochoid contour line. The circle described by the cross-section has a diameter d _k (radius r _k ). The cross-section of the semi-finished steel wire (semi-finished product) produced during the said shaping is 16 to 30% smaller than the cross-section of the pre-formed wire. This means that stretching the stationary die will reduce the cross-section by 16 to 30%.

Therefore, the epitrochoid contour cross-section of the steel wire blank is further drawn through the rotating die - also in the cold state. The draw hole of the swivel die has a hexagonal cross-section with rounded peaks and has ribs corresponding to spiral curved surfaces with a steady gradient. This rotary die known per se is free-running and fixed in the usual manner. The product which leaves the rotating die is, in the sense of the invention, referred to as a finished steel wire. At the end of the finishing process, the finished steel wire can be wound onto a drum.

The distance I _{of the} vertices of a hexagon chamfered peaks in the cross section of the rotating die is equal to the diameter d _of the circumscribed circle trailing flank contour line (I _k - d _k), and at the same distance _Ib surfaces of a hexagon corresponding to the diameter D _b of the inscribed circle epitroehoidnej closure line (I _b = d _b ). In this way, the steel wire creates themselves to drag rotating a pulley rib to the longitudinal axis of the steel wire runs obliquely, with six sections, and along three of the resulting bands were gradually formed and extinguished the height of the ribs is the difference between the radius r _the circumscribed circle and the radius r _{b of the} inscribed circle, that is r _k - r _b .

Inside the ribs, the spacing of the ribs is 1.6 to 2.5 times the mean diameter, indicated in the contour line of the steel wire cross-section,

1.6 d - 2.5 d, with _{d =} 1 '

The maximum rib height is 4 to 7% of the indicated mean diameter d only. The ribs formed in this way are shaped without any other technological operations by pulling in dies.

In the apparatus for carrying out the method according to the invention, the tools necessary for preforming, the rollers for deflecting and moving the steel wire and the stationary die and rotary die are expediently arranged such that the steel wire can be formed in only a single production process. The device must, of course, be equipped with the necessary known means, for example for lubrication and cooling, and appropriate devices for accommodating the axial and radial loads are required for receiving the rotary tools.

The shaping of the particular drawing holes in the dies is preferably carried out by means of an electro-spark machining. The electrode required for the electro-spark machining can be produced by a device according to Hungarian patent 156,607.

For the solution according to the invention, the epitrochoid can be determined by the following formulas: x = 4. r ". cos α - λ. r _c . cos 4 and y = 4. r _e . sin and - λ. r _e . sin 4a, where r _e = circle radius for derivation and rolling of trochoids λ = parameter.

Radius of the trochoid circle described: r _k = (4 + λ). r _e

Radius of trochoid circle inscribed:

r _b = (4-I). r _e The mean radius r = 4. r _e

In practice, the cross-sectional area bounded by the epitrochoid curves of the steel wire according to the invention can be replaced by a flat circle with a medium radius.

The value of λ is λ <0.28, and it seems appropriate to use a value of 0.18 to 0.19.

Thus, an essential feature of the steel wire according to the invention is that the cross-sectional contour line is a three-armed epitrochoid, the maximum rib depth corresponding to the difference in the radius of the cross-section described along the three formed bands.

In a preferred embodiment of the proposed steel wire, the ratio of the radius of the cross-sectional circle described and the radius of the circle inscribed is at most 1.15, the rib pitch being 10 to 15 times the mean diameter of the cross-section.

An essential feature of the method according to the invention is that the steel wire with a circular cross-section serving as a starting material or possibly another preformed steel wire is overlaid by a stationary die, thereby reducing the cross-section by 16 to 30% and producing a steel wire blank with three-armed epitrochoid , immediately thereafter, the blank is drawn by a free but firmly supported rotary die having a curved spiral surface with a constant pitch and a hexagonal cross-sectional opening with rounded peaks at which the distance of the areas of the six shells corresponds to the tangent of the circle the contour line of the finished steel wire, while the vertex distance of the hexagon corresponds to the diameter of the described circle - which is the tangent of the finished steel wire - and at which the diameter of the described circle corresponds to the diameter of the concentric kr chinchilla described by the top of the hexagon.

BRIEF DESCRIPTION OF THE DRAWINGS

The steel wire according to the invention and the method for its production will be explained in more detail with reference to the accompanying drawings, in which FIG. 1 shows a cross-section of one embodiment of a steel wire according to the invention, FIG. 2 shows more important parts of an apparatus for carrying out the method according to the invention, FIG. 3 is a cross-sectional view of a steel wire prior to preforming and a cross-section of the steel wire blank shown in succession; FIG. 4 shows the cross-section of the draw-through hole of the swivel die and the cross-section of the steel wire blank.

DETAILED DESCRIPTION OF THE INVENTION

With the steel wire 9 according to the invention shown in FIG. 1 in cross section, the epitrochoid contour line 4 and the rib 5 are well visible. The circle described by the contour line 4 is represented by a thin line. The diameter d _{k of the} described circle and the diameter d _{b of the} inscribed circle are indicated. When this designation is used, the mean diameter may be expressed by the following formula:

And the mean radius r is d r = -.

FIG. 1 clearly shows that the height of the rib 5 corresponds to the difference between the radius r _{k of the} described circle and the radius r _{b of the} inscribed circle, i. r _k - r _b , where

Preferably, the geometric ratios are chosen such that the maximum rib height 5 corresponds to 4 to 7% of the mean diameter.

Fig. 2 illustrates a possible embodiment of a steel wire manufacturing apparatus according to the invention and a manufacturing method according to the invention will be described according to this apparatus.

The starting steel wire 1 represents the material used in the exemplary embodiment of the method according to the invention. This material must be subjected to a heat treatment, if necessary, a preforming of the surfaces is necessary, eventually it can be changed with the preparation tools 11 of the cross-section. During the process, the wire is transported, guided and deflected by the roller 10. The above-mentioned working operations are known per se and do not fall within the scope of the invention. During this shaping, the diameter of the material gradually decreases, the strength increases.

After a possible preforming, a steel wire is formed, which in the narrow sense is in fact formed by the method according to the invention. This means that the individual preforming operations can be performed in separate, separate processes.

The preformed wire - which is in the cold state - is drawn through the stationary die 2. The drawing hole has a cross-section of a three-armed epitrachoid. The preformed steel wire 6 entering the die 2 has a circular cross-section, the incoming steel wire blank 8 as seen in FIG. 3, is profiled. During drawing in the stationary die 2, the cross-section of the steel wire decreases - depending on the material quality by about 16 to 30%.

FIG. 3 shows that the preformed steel wire 6 still has a circular cross-section that can be characterized after preforming with diameter D '(Diameter D' after any preforming operations is smaller than the starting diameter D). The steel wire blank 8, which is produced by drawing in the stationary die 2, has a cross-section with a three-armed epitrochoid contour line 4.

The method according to the invention will be explained in more detail below with reference to FIG. 4. The steel wire blank 8 is transformed by means of a rotary die 3 into a finished steel wire 9. The rotary die 3 has a drawing hole whose hexagonal cross-section has a rounded apex. The cross-section is indicated by the contour line 7. The drawing opening has curved spiral surfaces with a uniform incline in the axial direction.

The swiveling die 3 is mounted in a known manner and is freewheeling. For the outline of a hexagon and the precipitated 7 peaks corresponding to the distance I, _{to the} top of the diameter d _of the circumscribed circle of the cross section of the blank of steel wire 8 with the contour line 4, while at the same distance corresponding to the average of the areas I _b d _b of the inscribed circle. The shaping of the opening of the rotary die 3 is carried out by electro-spark machining.

The finished steel wire 9 is wound onto a drum 12 (FIG. 2). The pulling force may be exerted in part by this drum 12.

The steel wire according to the invention, which is produced by the process according to the invention, has a high strength, for example for a steel wire of 5 mm diameter, this strength is R _m = 1600 - 2000 MPa.

The advantage of the solution according to the invention is that the ribbing takes place without any separate technological operations, only by stretching in the dies 2, 3.

A further advantage is that the steel wire according to the invention maintains the secondary fiber structure during the cold drawing, thus having advantageous mechanical properties such as bending number and elongation.

A further advantage of the steel wire according to the invention is that its slipping or slipping out of the cast material, for example concrete and its twisting, is prevented by the formation of an epitrochoid-shaped rib. With such geometric shaping, there are no sharp corners, so that there are no stress concentration points in the finished wire.

The steel wire according to the invention can be used either twisted into a single rope or in strands.

Claims (4)

PATENT CLAIMS Steel wire for reinforcing cast materials, in particular concrete, characterized in that the contour line (4) of its cross-section is a three-armed epitrochoid, ribs (5) are provided along the three formed strips, gradually protruding and disappearing, with constant thread pitch. the maximum depth corresponds to the difference between the radius (r _k ) of the circle described above and the radius (r _b ) of the inscribed circle. Steel wire according to claim 1, characterized in that the ratio of the radius (r _k ) of the cross-section described above and the radius (r _b ) of the inscribed circle, i.e. the ratio r _k / r _fc is at most 1.15, the thread pitch The rib (5) is 10 to 15 times the mean diameter (d) of the cross-section. Method for producing steel wire according to claim 1 or 2, characterized in that the stationary die (2) extends the starting steel wire (1) with a circular cross-section or the preformed steel wire (6) to form a steel wire blank (8) with a three-armed epitrochoid contour line (4), immediately thereafter the steel wire blank (8) is drawn through a fixed but idle rotary die (3), with a hexagonal cross-sectional aperture with rounded apexes, with curved, spiral faces with the distance (I _b ) of the hexagonal surfaces corresponds to the diameter (d _b ) of the circle inscribed as an internal tangent to the contour line (4) of the finished steel wire (9), while the vertex distance (I _k ) corresponds to the diameter (d _k ) of the circle described as outer tangent to the contour line (4) of the finished steel wire (9), the diameter (d _t ) of the circle described being equal to by the circle described by the precipitated vertex of the hexagon with it concentric. Method according to claim 3, characterized in that the shaping of the steel wire blank (8) and the finished steel wire (9), together with any preforming, is carried out in a single operation.