Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Patent
1983-12-16
1986-09-09
Thibodeau, Paul J.
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
428397, 428400, B32B 302, D02G 300
Patent
active
046109269
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
Proposed are concrete reinforcing steel fibers, especially steel fibers of particular shape produced from war materials of fine wires, and a producing process thereof.
BACKGROUND OF THE INVENTION
Steel fibers of 0.1 to 0.4 mm.sup.2 in cross sectional area and 20 to 40 mm in length have been employed for improving characteristics of concrete structures or concrete products such as cracks, tension and others. Known reinforcing steel fibers are those of cut wire type produced from steel wires, sheared fiber type from thin sheet, machined fiber type from thick plate, and ME fiber type directly extracted from molten steel. Among them, in the cut wire type, cold drawn materials could be used as they are and tensile strength thereof is more excellent than others.
However, since the cut wire type has in general smooth circular cross section, it has demerits that ratio of the surface area is small and adhesive strength with concrete or mortar is low (only drawing resistance by friction). For countermeasure to those demerits, the prior art has made concaves and convexes equidistantly over the full length of the fiber. However although such considerations are made on the fibers but if their cross sections were uniform in width or thickness, adhesion would not increase satisfactorily. If the adhesion were increased by elaborating said considerations and the fibers had uniform tensile strength over the full length, and if the concrete were subjected to external actions such as bendings or tension, combination of the fibers and the concrete matrix would be broken at once. Thus, the high tensile strength would turn out rather harmful causes and invite abrupt changing in load of the concrete structure.
Further, there has been a technique which bends the fibers in trapezoid in cross section, but this technique is inferior in workability at mixture and easily makes fiber balls. In addition, such fibers are easily broken at bending portion.
With respect to the steel fibers depending upon the conventional wire cut type, an ingot is passed through a rough roll to reduce the diameter to 5 or 6 mm, and through a drawing die of multi-steps, i.e. a die formed with tapering hole or roll die.
This process positions a tension step by means of a coiling roll such as capstans or drums, per each of the drawings, and therefore since a stretching process is discontinuous, the processing efficiency is lowered and reduction of cross section could not be made much as well. Besides, the rolling depends upon the tension system so that drive force is made large and an intermediate coiling is necessary, so that the apparatus is large scaled and complicated as a whole. Therefore, the fiber production is lower in efficiency, but high in producing cost.
SUMMARY OF THE INVENTION
The present invention has been devised to remove defects involved about the conventional steel fibers.
An object of the invention is to provide concrete reinforcing steel fibers of wire cut type, in which adhesion strength of the concrete is large than tensile strength of the fiber, and with which reinforced concrete of high toughness may be obtained without generating of abrupt changing in load, and breaking of combination of the fibers and the concrete matrix when the concrete is destructed.
A second object of the invention is to provide a process of producing steel fibers of wire cut type, with which the steel fibers having the above mentioned characteristics may be easily produced at high efficiency, and the production cost is largely lowered.
For accomplishing the objects, the invention keeps a shaft portion for changing elongation, which has strength equivalent to that of a mother material, remaining on a central part of a fine fiber of determined length, and forms a plurality of hard knots in such a manner that those knots alternately protrude in thickness (vertical) and width (lateral), and the protruding amount becomes gradually larger as going towards the ends of the fiber.
According to the steel fibers of such structure, the knots protruding
REFERENCES:
patent: 4054993 (1977-10-01), Kamp et al.
patent: 4229501 (1980-10-01), Kern
patent: 4233364 (1980-11-01), van Thiel
Striker Michael J.
Thibodeau Paul J.
Tokyo Rope Manufacturing Co. Ltd.
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