EP0392039B1 - Steel strip for concrete reinforcement - Google Patents

Abstract

The steel fibre has the form of a sheet-metal strip (1). It is provided as a reinforcing element for concrete. The sheet-metal strip (1) is provided on both longitudinal edges (2;3) with bead-like recesses (4), the bead-like recesses (4) on one longitudinal edge (2) being arranged offset in the longitudinal direction relative to those on the other longitudinal edge (3). <IMAGE>

Description

The invention relates to a steel fiber in the form of a sheet metal strip as a reinforcing element for concrete according to the preamble of claim 1 and to a method for its production according to the preamble of claim 4. A generic steel fiber and a method for its production is e.g. known from DE-C-2824777.

State of the art:

For concrete, which in the following also means screed and mortar, steel fibers are used as reinforcement elements. A concrete reinforced with steel fibers is improved in its properties, for example tensile strength, breaking strength, shear strength, stretchability, toughness, dynamic strength, fatigue strength. It is therefore used on a large scale. The steel fiber should have the following properties: It should be hard and strong. It should not break when mixed with concrete or aggregates. It should not be too short or too thick, otherwise it is insufficient in its strengthening. It should not be too long or too thin, otherwise it will tend to form spherical lumps of cement. In general, a steel fiber cross section of 0.1 to 1.0 mm², a steel fiber length of 20 to 50 mm and a weight fraction of the steel fibers of 15 to 150 kg / m³ of concrete are recommended. In addition to their properties, the cost-effective production of steel fibers is a top priority.

Basically, three groups of steel fibers are distinguished according to their external shape, the starting material and the process for their production. In the first group, the steel fiber is a round fiber which is cut off by a corrugated wire (EP 0 130 191 B1; GB 1 446 855 A1). In the second group, the steel fiber is a steel chip that is milled off from a steel block (DE 2 723 382 C3; DE 2 904 228 C2). In the third group, the steel fiber is in the form of a sheet metal strip which is sheared off from a sheet (DE 2 359 368 A1; DE 2 359 367 B2; DE 2 824 777 C3).

It is known that the steel fibers belonging to the third group have excellent properties. However, the process for their production has hitherto been associated with the lack of high production costs: the width of the steel sheet produced in the desired fiber thickness is split to the desired fiber length, after which the fibers are sheared off in the desired width.

Presentation of the invention:

The invention seeks to remedy this. The invention has for its object to provide steel fibers with further improved properties in a cost-effective manufacturing process from a sheet as a starting material.

This object is achieved according to the invention in a method of the type mentioned at the outset by the method steps and features of patent claim 4.

The dependent claims 5 to 7 relate to preferred embodiments of the method.

Steel fibers manufactured in accordance with the invention with their special configurations are specified in claims 1 to 3.

In the invention, the disadvantage inherent in the process for the production of steel fibers from sheet metal is eliminated that the sheet metal strips are first brought to a width which is equal to the length of the steel fiber. In the invention, the sheet width is theoretically arbitrary; in practice it depends on the width of the sheets on the market, and on the other hand on the dimensions of the punch press insert and the dimensions in which the tool can be produced economically. While the fiber length is also fixed in the known methods with the sheet metal strip width, this is variable in the invention: by exchanging the tool inserts, fibers of different dimensions, including lengths, can be produced for a given sheet metal strip width. The sheet is processed without scrap. The punching of the steel fibers and the introduction of the bead-like depressions takes place in the same operation. The beads can be designed variably.

The tool punches in a - for example in 4 - process or work steps. Then in the 1st step every 1st, 4th, 7th etc. row, in the 2nd step every 2nd, 5th, 8th etc. row, in the 3rd step every 3rd, 6th, 9th etc. Punched rows, in the 4th step the strips are punched between the rows. When adjusting the sheet width to the steel fiber length, the entire sheet is processed. All work steps are carried out simultaneously in the same follow-up tool; the tool engages in different places on the sheet metal to carry out one of a working steps. According to (a-1) - in the exemplary embodiment 3 - start-up strokes, all steel fibers are punched in the following tool in each working cycle.

The steel fiber itself has a high degree of inherent stability due to the beads / profiles on the edge. The edge formation also leads to better interlocking with the concrete. Due to the lack of waves, there can be no stretching of the steel fiber under load.

Brief description of the drawing:

Figur 1

in vergrößerter Darstellung die Aufsicht einer Stahlfaser;

Figur 2

eine Seitenansicht der Stahlfaser gegen die schmale Seite;

Figur 3

die Unteransicht der Stahlfaser;

Figur 4

ein Blech mit den Verfahrensschritten zum Stanzen der Stahlfasern.

An embodiment of the invention is shown in the drawing and will be described in detail below. Show it:

Figure 1

in an enlarged view the supervision of a steel fiber;

Figure 2

a side view of the steel fiber against the narrow side;

Figure 3

the bottom view of the steel fiber;

Figure 4

a sheet with the process steps for punching the steel fibers.

Best way to carry out the invention:

The steel fiber selected as an exemplary embodiment consists of a sheet metal strip 1. It has a selectable fiber length 1 and a selectable fiber width b. In the exemplary embodiment, the fiber length is approximately 36 mm, the fiber width is approximately 2 mm. Its thickness is approximately 0.4 mm. These dimensions can be changed within limits.

The metal strip 1 is provided on its longitudinal edges 2, 3 with bead-like depressions 4. The bead-like depressions 4 are on the one longitudinal edge 2 compared to those on the other longitudinal edge 3 in the longitudinal direction staggered: A bead-like depression on the other longitudinal edge 3 is provided symmetrically between two bead-like depressions 4 on one longitudinal edge 2.

The bead-like depressions 4 create meandering lines in the view and in the rear view. Another configuration is possible by changing the arrangement and design of the bead-like depressions 4.

oder $\text{L1 = m · 1 < L}$

werden bei jedem von (a-1) Verfahrensschritten

Fasern aus dem Blech 10 gestanzt. Dabei sind a, m und n ganze Zahlen; a ist größer oder gleich 2.The output for the process for producing the steel fiber with the fiber length 1 and the fiber width b is a sheet with the sheet length L and the sheet width B. The sheet length L is arbitrary. The sheet width B is adapted to achieve a scrap-free punching process to the dimensions of the sheet metal strip 1 to be punched. It also depends on the dimensions of the insertion of the punch press and the tool. Over the sheet width B> m · 1 or B> n · b and over a length $\text{L1 = n · b <L}$

or $\text{L1 = m · 1 <L}$

are used in each of (a-1) process steps

Fibers punched out of sheet 10. Here a, m and n are integers; a is greater than or equal to 2.

Steel fibers of fiber length l are arranged in the axial direction over the sheet width B with the interposition of a strip of fiber width bm, n steel fibers of fiber width b are arranged next to one another in the transverse direction over the partial sheet length L1. In the exemplary embodiment, 3 steel fibers with the fiber length l = 36 mm are arranged over the sheet width B shown. N = 18 steel fibers of fiber width b = 2 mm are arranged next to one another in the transverse direction over the sheet metal part length L1, which in the exemplary embodiment is equal to the fiber length l.

It is possible to turn the position of the steel fibers by 90 ^o , i.e. to align the steel fibers in the longitudinal direction of the sheet.

werden beim 1. Verfahrensschritt alle (x·(a-1)+1)- ten Reihen, beim 2. Verfahrensschritt alle (x·(a-1)+2)- ten Reihen, beim (a - 1)- ten Verfahrensschritt die letzten Reihen und beim (a)- ten Verfahrensschritt die Streifen am Rand und zwischen den einzelnen Blechstreifen/Stahlfasern gestanzt, wobei x eine ganzzahlige Variable zwischen Null und

ist.In a process steps for the production of the steel fibers over the partial length of the sheet $\text{L1 = nb}$

in the 1st step all (x · (a-1) +1) - rows, in the 2nd step all (x · (a-1) +2) - rows, in the (a - 1) - th step the last rows and in the (a) th process step, the strips are stamped on the edge and between the individual sheet strips / steel fibers, where x is an integer variable between zero and

is.

In the exemplary embodiment, a = 3; there are therefore three procedural steps. The number of fiber rows distributed over the sheet width B is m = 3, the number of fibers distributed over the partial length L1 is n = 18. Sections I, II and III are of equal length; they are in the same follow-up tool at the same time. In the first process step, the first, third, fifth, thirteenth, fifteenth and seventeenth rows are punched from the full sheet metal - section I in FIG. 4, that is to say the first and each row after the next. After this first process step, the sheet has the shape shown in FIG. 4 in section II. In the second process step, the remaining rows, namely the 2nd, 4th, 6th, ... 14th, 16th and 18th rows are then punched. After this process step, the sheet has the shape shown in FIG. 1 in section III. In the third process step, the 4 strips - which are used for the exact manufacture of the steel fibers - are punched at the edge and between the individual steel fibers, which also have the dimensions of one steel fiber. Depending on the size of the follow-up tool, more than three fiber rows can be distributed over the sheet width B and integer multiples of 18 over the partial length L1.

During the punching process, the bead-like depressions 4 are simultaneously introduced into the sheet metal strip 1.

Commercial usability:

The steel fibers are used as reinforcement elements for concrete, screed and mortar. The process is used to manufacture these steel fibers.

Claims (7)

1. A steel fibre in the form of a sheet metal strip as a reinforcing element for concrete, characterised in that the sheet metal strip (1) is provided on at least one of its longitudinal edges (2; 3) with groove-like recesses (4).
2. A steel fibre according to claim 1, characterised in that the groove-like recesses (4) on one longitudinal edge (2) are arranged offset in the longitudinal direction relative to the recesses on the other longitudinal edge (3).
3. A steel fibre according to claim 1 or 2, characterised in that a groove-like recess (4) is arranged on the second longitudinal edge (3) symmetrically between two groove-like recesses (4) on the first longitudinal edge (2) in each case.
4. A method for manufacturing a steel fibre as a reinforcing element for concrete from sheet metal, characterised in that, with a selectable fibre length 1 and a selectable fibre width b, from the sheet having a sheet length L and a sheet width B over the sheet width B > m . 1 and over a partial length $\text{L1 = n . b < L}$

   

   or $\text{B > n . b}$

   

   

   and $\text{L1 = m . l < L}$

   

   ,

   

   fibres are stamped in each of (a - 1) method steps, a, m and n being integral numbers and a ≧ 2.
5. A method according to claim 4, characterised in that m steel fibres having the fibre length l are arranged adjacent one another in the axial direction over the sheet width B with the interposition of one strip having the fibre width b and n steel fibres having the fibre width b are arranged adjacent one another in the transverse direction over the sheet partial length L1, the product of the fibre width b and the number n of adjacent fibres being equal to an integral multiple of the fibre length 1.
6. A method according to claim 5, characterised in that in the a ^th method step, (m + 1) strips are stamped as steel fibres.
7. A method according to claim 5 or 6, characterised in that, with a method steps along the partial length of the sheet $\text{L1 = n . b}$

   

   , during the first method step the (x . (a - 1) + 1)^th rows, during the second method step the (x . (a - 1) + 2)^th rows, during the (a - 1)^th method step the last rows and during the (a)^th method step the strips [at the edge and between the individual sheet strips/steel fibres] are stamped, x being an integral variable between zero and

   

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