JPH10102199A - Transverse constraint reinforcing bar for concrete pipe, with high bending toughness, reinforcing bar basket using the transverse constraint reinforcing bar, and their production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the desired state of welding of a reinforcing bar basket by providing a hot rolling steel material with a composition into which specific weight percentages of C, Si, Mn, Al, and N are incorporated. SOLUTION: A steel, having a composition consisting of, by weight, 0.05-0.22% C, 0.5-2.0% Si, 0.5-2.0% Mn, <=0.04% (including 0%) each of P and S, <=0.080% (not including 0%) Al, <=100ppm (including 0ppm) N, and the balance Fe with inevitable impurities, is used. This steel can further contain at least one kind selected from the group consisting of <=1.5% Cr, <=1.0% Mo, <=0.5% Ti, <=0.5% V, <=0.010% B, and <=0.10% Nb (each does not include 0%). A hot rolled steel stock is wiredrawn into a steel wire having >=650N/mm<2> yield point strength and 40-95% yield ratio. By this method, the rate of reduction in yield point strength, due to the welding of transverse constraint reinforcing bars, can be always maintained at a fixed value or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lateral restraining bar for a high bending toughness concrete pile in which a tensile strength does not decrease even by welding and a high bending toughness concrete pile can be manufactured by a reinforcing steel cage by welding. The present invention relates to a used reinforcing cage for a high bending toughness concrete pile and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, in a concrete pile, a PC steel material is inserted in an axial direction and then tensioned to introduce a prestress in an axial direction into a concrete member, or a steel bar for reinforced concrete as an axial reinforcement. Used RC pile,
There is also a PRC pile using both a PC steel material and a steel bar for reinforced concrete as an axial bar, and this type of concrete pile usually has a yield point strength of 300 to 500 N / mm.
² , 50 ~ 100 ordinary iron wire with diameter of about 3 ~ 6mm
In general, a reinforcing rod cage used at intervals of about mm and spot-welded to a vertical streak is disposed in a member.

Further, in order to increase the bending toughness of this type of pile and to increase the shear strength by increasing the shear strength, as shown in Japanese Patent Publication No. Sho 62-280418, axial reinforcement is required. In addition to using a steel material with high uniform elongation performance, sufficient arrangement of transverse restraining bars such as band reinforcing bars and spiral bars in the direction perpendicular to the axial direction near the outer periphery of the concrete pile, and yield strength of the transverse restraining bars Is 60
Wires using PC steel wires or hard steel wires of 0 N / mm ² or more have been developed.

[0004]

However, the above-mentioned PC
In the case of high bending toughness piles that use steel wires or hard steel wires as lateral restraint bars, the knitting machines that are conventionally used for the production of reinforced cages use PC steel wires or hard steel wires that are deteriorated during welding. As a result, the strength was extremely reduced, so that it was not usable. For this reason, there has been a problem that a reinforcing bar cage has to be manufactured by hand knitting using a bundling, a clip or the like, work efficiency is remarkably poor, a lot of labor is required, and it has to be expensive.

The present invention has been made in view of such a conventional problem,
Provided is a lateral restraining bar for a high bending toughness concrete pile, a reinforcing cage using the lateral restraining bar, and a method of manufacturing the same, in which a high-strength reinforcing cage can be knitted by welding and a high bending toughness concrete pile can be manufactured at low cost. It was made for the purpose.

[0006]

The features of the present invention which solve the conventional problems as described above and achieve the intended object are as follows. First, C: 0.05 to 0.22% (hereinafter not particularly specified) As much as% by weight), Si: 0.5 to 2.0%, Mn:
0.5 to 2.0%, P: 0.04% or less (including 0%), S: 0.04% or less (including 0%), Al: 0.
080% or less (excluding 0%), N: 100 ppm
(Including 0 ppm), with the balance being Fe and laterally restrained bars for high bending toughness concrete piles manufactured using hot rolled steel which is an unavoidable impurity. Second, hot rolled steel is used as another component. , Cr: 1.5% or less (excluding 0%),
Mo: 1.0% or less (excluding 0%), Ti: 0.5
% Or less (not including 0%), V: 0.5% or less (not including 0%), B: 0.010% or less (not including 0%), Nb: 0.10% or less (0% And (c) excluding at least one element selected from the group consisting of (a) and (b). The horizontal restraint bars for high bending toughness concrete piles made of steel wire with a yield point strength of 650 N / mm ² or more and a yield ratio of 40 to 95%
And yield strength 650 N / mm ²
As described above, the lateral restraining bars made of a steel wire having a yield ratio of 40 to 95% are wound around the outside of a number of vertical bars, and all or a part of the contact portions between the respective vertical bars and the horizontal restraining bars are welded to each other. Fifthly, the above-described wire drawing is performed on a reinforced cage for high-bending tough concrete piles having a yield point strength of 600 N / mm ² or more in the portion of the lateral restraint bars, and a yield point strength of 650 N / mm ² or more,
A lateral restraint made of a steel wire having a yield ratio of 40 to 95% is wound around a large number of vertical streaks, and all or a part of a contact portion between each longitudinal streak and the horizontal restraint is applied with a voltage of 5 to 30 V and a conduction time. 0.0
Reinforced basket for high bending toughness concrete piles characterized in that welding is performed under the condition that the product (A · S) of the current value (A) and the energization time (S) is 140 to 1300 for 2 to 0.20 seconds. Manufacturing method.

[0007]

Next, an embodiment of the present invention will be described.

First, a description will be given of an embodiment of a lateral restraint bar for a high bending toughness concrete pile according to the present invention. The chemical composition and the ratio of the hot rolled steel used for the lateral restraint bar of the present invention are as follows. It is on the street.

C (carbon): 0.05 to 0.22% (the same applies to weight% or less) Si (silicon): 0.5 to 2.0% Mn (manganese): 0.5 to 2.0% P ( Phosphorus: 0.04% or less (including 0%) S (sulfur): 0.04% or less (including 0%) Al (aluminum): 0.080% or less (excluding 0%) N (nitrogen) ): 100 ppm (including 0 ppm) Fe (iron) and unavoidable impurities: balance In these chemical components, C is a strengthening element and a quenching improving element. Therefore, it is an element indispensable to obtain high strength in a state of being subjected to heat treatment and then drawing, and if it is less than 0.05%, the amount as a strengthening element is insufficient and hardenability is also increased. Insufficient strength cannot be obtained. On the other hand, if the amount of C exceeds 0.22%, not only is the toughness and ductility of the wire reduced and wire breakage or the like is liable to occur during processing, but also the weldability is significantly reduced, and a supercooled structure is formed during quenching after welding. And the reduction in toughness due to embrittlement becomes a major problem. The preferred amount of C for satisfying the strength, workability, and weldability is 0.10 to 0.1%.
It is in the range of 17%.

[0010] Si acts as a deacidifying element at the time of welding and is also an important element in increasing the welding strength. That is, the present invention has one important purpose for improving the weldability. Since the steel material is partially melted in the welding process, oxygen in the atmosphere is taken into the weld metal and bubbles and oxides are generated. Etc., and deteriorate the properties of the weld metal. Therefore, in order to avoid such a problem caused by oxygen mixed during welding, it is necessary to include Si as a deoxidizing element in the steel material.

[0011] Further, Si has a function of improving the sag resistance and relaxation properties of a steel wire or a spring when subjected to wire drawing, and further strengthens ferrite as a solid solution strengthening element. At the same time, it also has the effect of enhancing hardenability and increasing strength.

In order to exert such an effect effectively, S
i must be contained at 0.5% or more.
If the amount is too large, not only does the ductility deteriorate, adversely affecting workability and drawability, but also adversely affecting bending performance, etc., so that the content should be suppressed to 2.0% or less. Si
Is more preferably from 0.7 to 1.7%.

Mn is an element effective for strengthening the base material in addition to the deoxidizing effect at the time of welding, similarly to Si, and it is easy to develop high strength. The preferred content of Mn varies depending on the amounts of C and other elements, but must be at least 0.5% or more to ensure sufficient hardenability.

However, even if the amount of Mn is too large, an improvement effect of a certain level or more cannot be obtained, which is economically disadvantageous, and excessive addition of Mn tends to inhibit toughness due to positive segregation of Mn. , Grain boundary strength decreases. For these reasons, the upper limit of the Mn content is preferably 2.0%. In addition,
A more preferable range of the amount of Mn is 0.7 to 1.7%.
P and S are harmful elements that not only deteriorate the toughness and ductility of the steel material but also cause segregation to cause variation in hardenability. In order not to cause these defects, both P and S must be P and S. It is necessary to suppress the content to 0.04% or less, more preferably 0.02% or less.

Al binds to N in steel and turns into Al ₂ O ₃ during scouring and deoxidation to remove oxygen. In addition, Al binds to O in steel to form AlN and contributes to refinement of the structure.
If the amount exceeds 0.08%, on the contrary, the crystal grains become coarse and inclusions such as Al ₂ O ₃ in the steel increase, thereby impairing the toughness.

N is a factor of deteriorating the ductility of a steel wire due to time hardening when wire drawing is performed after hot rolling, and the obstacle appears remarkably when it exceeds 100 ppm. Note that N
Is usually an unavoidable element to be mixed in, and a smaller amount is preferable, but a content of 20 to 100 ppm is acceptable.

The balance of the steel used in the present invention is Fe and inevitable impurities. In addition, it is also effective to include the following elements for the purpose of increasing the strength by improving the hardenability. That is, Cr (chromium): 1.5% or less (excluding 0%) Mo (molybdenum): 1.0% or less (excluding 0%) Ti (titanium): 0.5% or less (0% V (vanadium): 0.5% or less (excluding 0%) B (boron): 0.010% or less (excluding 0%) Nb (niobium): 0.10% or less (0%) At least one element selected from these groups.

These elements have the same effect in that they are all components that enhance hardenability and contribute to high strength. Among these elements, especially Cr and Mo contribute to the enhancement of the hardenability and the enhancement of the strength. Further, the steel used in the present invention is an effective element from the viewpoint of suppressing a decrease in strength due to welding heat during use and further increasing welding strength as described above. In addition, V, Ti, and Nb contribute to improvement of hardenability and also have an effect of preventing austenite crystal grains from being coarsened and increasing toughness. In addition, B improves the hardenability of steel by scattering at the grain boundaries, and also reduces the Mn of the grain boundaries.
And P have the effect of suppressing segregation and precipitation.

These effects are exhibited by containing one or more of these elements, but from the viewpoint of more surely exerting the effect of adding each element, the preferred lower limits are Cr: 0.05%, Mo: 0.05%, Ti: 0.01
%, V: 0.05%, B: 0.0005, Nb: 0.0
1%. In addition, even if the content is excessively exceeded beyond the above-mentioned upper limit, the effect of a certain degree or more is not exhibited, and it is economically disadvantageous.

Next, an embodiment of a method for manufacturing a lateral restraint bar for a high bending toughness concrete pile according to the present invention will be described.

This manufacturing method uses a mechanical or chemical descaling method to remove the oxide scale on the surface of a hot-rolled steel material used for the above-mentioned lateral restraint bar for high bending toughness concrete piles, and then removes the physical coating. Treatment, then wire drawing, yield point strength 650N / mm ² or more, yield ratio 40 ~
95% steel wire.

Although the required yield point strength can be obtained from hot-rolled steel even if the cooling rate after rolling is adjusted, if wire drawing is not performed, the deviation in wire diameter and the surface roughness are large. As a result, current variations occur during spot welding, and the strength of the lateral restraint bars is reduced, or a detachment phenomenon occurs at the welded portion.

In this case, the wire drawing is preferably performed by cold drawing, but any other method may be used as long as a predetermined strength can be obtained.

The yield ratio of the lateral restraint muscle is a ratio obtained by the following equation.

Yield ratio = (yield point strength / tensile strength) × 100 (%) When the yield ratio is 40% or less, when the lateral restraining bars are wound around the outside of the vertical bars and welded, the welding with the vertical bars is performed. The lateral restraint bends at the contact. On the other hand, if it is 95% or more, the repulsive force of the lateral restraint bars is too strong, the detachment phenomenon at spot welding and the variation in the upsetting amount of the welded portion occur, and the desired properties of the concrete pile manufactured cannot be obtained.

Table 1 shows test examples for verifying the relationship between the drawing ratio, the yield strength, and the yield ratio.

[0027]

Next, an embodiment of a method of manufacturing a reinforcing rod cage for a high bending toughness concrete pile according to the present invention, which is manufactured using the above-described lateral restraint bars, will be described.

In this embodiment, a conventionally used rebar basket knitting machine by spot welding is used.
As shown in FIG. 1, a large number of longitudinal streaks 1, 1... Are sequentially extruded in the axial direction on the same cylinder, and a lateral restraint streak 2 is wound around the outside thereof at a fixed position. , 1
The lateral restraining muscles 2 are sequentially spirally wound around the outer periphery of.
At the same time as this winding, the intersection of each longitudinal muscle 1 and lateral restraining muscle 2 is sandwiched by the fixed electrode 3 inside the vertical muscle group and the moving electrode 4 outside the horizontal restraining muscle 2, and electricity is applied to both muscles. The contact portions are spot-welded to sequentially knit a steel cage.
Note that this welding may be performed on all of the above-mentioned intersections, or may be performed on a part of the intersections, for example, every other intersection in one direction of the vertical stripe.

The welding conditions are such that the voltage is set in the range of 5 to 30 V, and the product (A · S) of the current value (A ampere) and the conduction time (S second) is in the range of 140 to 1300.

When the voltage is 30 V or more, there is an effect on the human body due to electric shock, and the safety of work is impaired. When the voltage is 5 V or less, a stable welding state cannot be obtained when the voltage fluctuates. Generally, it is preferable to set the voltage to about 15V.

When (A · S) is 140 or less, the yield strength reduction rate is small, but the shear strength of the spot welded portion is low, and the shape of the rebar cage during knitting movement is reduced. Difficult to maintain.

Generally, when manufacturing a concrete pile, the shear strength required at a spot weld of a reinforced cage is 50.
It is about kg or more.

When (A · S) is 1300 or more, the influence of the spot welding on the base metal becomes too large, the rate of reduction in the strength of the welded portion increases, and a higher strength material is required to maintain the desired strength. Is necessary and the efficiency is low.

With regard to the range of the energization time, if the energization time is extremely short, the variation in the strength of the welded portion becomes large and hinders the work. Therefore, in practice, the energization time is preferably set in the range of 0.02 to 0.20 seconds.

[0036]

[Example] As a vertical bar, steel bar SD3 for reinforced concrete
45 steel wires having a diameter of 775 N / mm ^{2 with} a yield point strength of 775 N / mm ² and spirally wound at a pitch of 50 mm at a pitch of 50 mm were used as the lateral restraining bars. The tensile test result of the lateral restraint bar of the reinforced cage manufactured by using the reinforced cage knitting machine according to
It was as shown in the table. The knitting was performed with the voltage set to 15 V and the pressing force of the electrode during spot welding set to 70 kg.

[0037]

[0038]

As described above, the lateral restraint bar for high bending toughness concrete piles of the present invention has a small decrease in tensile strength even by welding, and is safe and secure when being knitted by a rebar cage automatic knitting machine by welding. Thus, it is possible to reliably obtain a desired reinforcing rod cage welding state.

According to the method for manufacturing a reinforcing rod cage of the present invention,
By performing welding under specific welding conditions, the reduction rate of the yield point strength due to welding of the lateral restraint bars can always be kept at a certain level or less, and the lateral restraint bar yield point strength of 600 N / mm ² or more is always maintained. Reinforcement cages can be mass-produced by an automatic knitting machine by spot welding, and mass-production of high-shear-strength, high-bending tough concrete piles with excellent seismic resistance can be mass-produced.

[Brief description of the drawings]

FIG. 1 is a side view of an apparatus used for a method of manufacturing a reinforcing rod cage according to the present invention.

FIG. 2 is a front view of the same.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Longitudinal muscle 2 Lateral restraint muscle 3 Fixed electrode 4 Moving electrode

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] October 30, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006]

The features of the present invention which solve the conventional problems as described above and achieve the intended object are as follows. First, C: 0.05 to 0.22% (hereinafter not particularly specified) As much as% by weight), Si: 0.5 to 2.0%, Mn:
0.5 to 2.0%, P: 0.04% or less (including 0%), S: 0.04% or less (including 0%), Al: 0.
080% or less (not including 0%), N: 100ppm or less
Include lower (including 0 ppm), there the remainder to a high bending toughness concrete pile for Confined muscle produced using the hot-rolled steel is Fe and unavoidable impurities, to a second, hot-rolled steel material of the other ingredients Cr: 1.5% or less (excluding 0%), Mo: 1.0% or less (excluding 0%), Ti:
0.5% or less (excluding 0%), V: 0.5% or less (excluding 0%), B: 0.010% or less (excluding 0%), Nb: 0.10% or less The lateral restraining bar for a high bending toughness concrete pile according to claim 1, which comprises at least one element selected from the group consisting of (not including 0%), thirdly, the hot-rolled steel material is drawn. yield strength 650 N / mm ² or more is subjected to machining, yield ratio 40% to 95%
For lateral restraint bars for high bending toughness concrete piles made of steel wire,
Fourth, the above wire drawing is performed, and the yield point strength is 650 N / m.
m ² or more, a lateral restraint muscle and yield ratio 40% to 95% of the steel wire, wound around the outside of a number of vertical stripes, welded the whole or part of the contact portion between the vertical line and horizontal restraint muscle each other, The yield point strength of the lateral restraint bar at the welded portion is 600 N / mm ²
The above-mentioned reinforced cage for high bending toughness concrete piles
And yield strength 650 N / mm ²
As described above, the lateral restraining bars made of a steel wire having a yield ratio of 40 to 95% are wound around the outside of a large number of vertical bars, and all or a part of the contact portion between each vertical bar and the horizontal restraining bars is applied with a voltage of 5 to 30 V, High-bending toughness concrete characterized in that welding is performed under the condition that the energizing time is 0.02 to 0.20 second and the product (A · S) of the current value (A) and the energizing time (S) is 140 to 1300. In the method of manufacturing a steel cage for piles.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

C (carbon): 0.05 to 0.22% (the same applies to weight% or less) Si (silicon): 0.5 to 2.0% Mn (manganese): 0.5 to 2.0% P ( Phosphorus: 0.04% or less (including 0%) S (sulfur): 0.04% or less (including 0%) Al (aluminum): 0.080% or less (excluding 0%) N (nitrogen) ): 100 ppm or less (including 0 ppm) Fe (iron) and unavoidable impurities: balance In these chemical components, C is a strengthening element and a quenching improving element. If necessary, it is an element that is indispensable for obtaining high strength when subjected to heat treatment and then wire drawing. If it is less than 0.05%, the amount as a strengthening element is insufficient and hardenability Is also insufficient and satisfactory strength cannot be obtained . On the other hand, if the amount of C exceeds 0.22%, not only is the toughness and ductility of the wire reduced and wire breakage or the like is liable to occur during processing, but also the weldability is significantly reduced, and a supercooled structure is formed during quenching after welding. And the reduction in toughness due to embrittlement becomes a major problem. The preferred amount of C for satisfying the strength, workability, and weldability is 0.10 to 0.1%.
It is in the range of 17%.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // E04C 5/06 E04C 5/06 (72) Inventor Nobuhiko Ibaraki 2 Nadahama-Higashi-cho, Nada-ku, Kobe Kobe Steel Co., Ltd. (72) Inventor Kenji Ochiai 2 Nadahama-Higashi-cho, Nada-ku, Kobe, Japan Kobe Steel, Ltd. Sanchome No. 1 Nishida Steelworks Co., Ltd.

Claims (5)

[Claims] 1. C: 0.05 to 0.22% (hereinafter referred to as% by weight unless otherwise specified) Si: 0.5 to 2.0% Mn: 0.5 to 2.0% P: 0. 04% or less (including 0%) S: 0.04% or less (including 0%) Al: 0.080% or less (not including 0%) N: 100 ppm (including 0 ppm) Balance: Fe and inevitable Lateral restraint bars for high bending toughness concrete piles manufactured using hot rolled steel that meets the requirements for impurities. 2. The hot-rolled steel material contains, as other components, Cr: 1.5% or less (excluding 0%) Mo: 1.0% or less (excluding 0%) Ti: 0.5% or less ( V: 0.5% or less (excluding 0%) B: 0.010% or less (excluding 0%) Nb: 0.10% or less (excluding 0%) The lateral restraint bar for a high bending toughness concrete pile according to claim 1, wherein the lateral restraint bar contains at least one element selected from the group. 3. The cross-section for a high bending toughness concrete pile according to claim 1, wherein the hot-rolled steel material is subjected to wire drawing to form a steel wire having a yield point strength of 650 N / mm ² or more and a yield ratio of 40 to 95%. Restraint muscle. 4. The lateral restraining bar according to claim 3 is wound around a plurality of vertical bars, and all or a part of contact portions between each vertical bar and the horizontal restraining bar is welded to each other. Reinforced basket for high bending toughness concrete piles with a yield strength of lateral restraint bars of 600 N / mm ² or more. 5. The lateral restraining muscle according to claim 3 is wound around a plurality of vertical muscles, and all or a part of a contact portion between each longitudinal muscle and the horizontal restraining muscle is applied with a voltage of 5 to 30 V and a conduction time. 0.0
Reinforced basket for high bending toughness concrete piles characterized in that welding is performed under the condition that the product (A · S) of the current value (A) and the energization time (S) is 140 to 1300 for 2 to 0.20 seconds. Manufacturing method.