JP2733739B2 - High adhesion and high strength deformed steel bars - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to civil engineering. For steel bars for building concrete or steel bars for prestressed concrete, reinforcing bars, and other earth anchors, etc., which are used by rolling screw processing or cross-wire welding and that require adhesive strength to concrete. It is related to a deformed steel bar.

[0002]

2. Description of the Related Art A conventional deformed steel bar for concrete is shown in FIG.
As in the case of the hot-pressed deformed steel bar 1 described above, a bar-shaped steel bar whose surface is provided with protruding nodes 11 at regular intervals by hot rolling to increase the adhesion strength to concrete is used.

However, these hot-rolled deformed steel bars have a large height of projections and a large adhesive force of concrete, but have poor roundness due to hot rolling and have a gap between the upper and lower rolling rolls. Two ribs 12 in the rolling direction
It is difficult to roll the end of the screw when rolling, and poor weldability due to poor electrode contact during cross-wire welding. In addition, straightening with straightening rolls when using a coil material as a straight material Also, there are drawbacks such as difficulty in handling continuous feed by a feed roller. Especially in the case of high-strength deformed steel bars such as pre-stressed concrete steel that has been heat-treated, if the roundness is poor due to the high hardness of the steel, thread rolling cannot be performed directly. Had to be thread rolled.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a hot-rolled deformed steel bar which has been deformed by knotting by hot rolling, and further light-drawing to reduce the roundness of the concrete steel bar cross section. It is an object of the present invention to provide a high-adhesion and high-strength deformed steel bar in which secondary processing such as thread rolling is facilitated and welding workability at the time of execution is improved.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for producing a deformed bar or wire rod for concrete having a spiral projection having an outer diameter by hot rolling. Provided is a high-adhesion, high-strength deformed steel bar characterized by being subjected to a heat treatment of quenching and tempering after being processed into a perfect circle with a reduced surface area in which the height of the rolling node remains as the original node.

Also, C: 0.1-0.6% by weight, S
i: 0.15 to 2.00%, Mn: 0.6 to 2.00
%, Cr: facilities remainder comprising 0.6% or less in a steel bar or wire rod 5~50mm diameter consisting of iron and inevitable impurities, tensile strength 930N / mm ² or more, the heat treatment the yield point 785N / mm ² or more Characterized in that the high adhesion
Provide high strength deformed steel bars.

[0007]

In the structure of the present invention, the use of a deformed bar or wire rod for concrete having a spiral projection with an outer diameter formed by hot rolling is used because the roundness is poor when hot rolling is performed. The reason is that since the material already has nodes, the subsequent steps can be reduced, and a deformed steel bar having high concrete adhesion can be easily obtained. In addition, how much the height of the nodes of the hot rolling is left is determined by the reference diameter of the deformed steel bar, the height of the nodes and the inner diameter of the die. It is desirable to limit the processing to the minimum reduction in area and leave as much as possible the nodal height of hot rolling. The present invention is based on the results of experiments.
It is desirable to perform a perfect circle processing with a reduction in area remaining at least 40% of the height of the original node. The heat treatment of quenching and tempering is for obtaining the required mechanical strength.

The reasons for limiting the composition of the material of the deformed steel bar are as follows. 0.1 to 0.6 by weight of C
The reason for setting the percentage is that if it is 0.1% or less, the required strength cannot be obtained by quenching, and if it is 0.6% or more, the toughness decreases. Further, Si is an effective component for reducing high-temperature relaxation, and the amount of Si is 0.15 to 2.00.
The reason is that if it is 0.15% or less, the effect of reducing high-temperature relaxation cannot be obtained, and if it is 2.00% or more, the toughness decreases. The reason for setting the Mn content to 0.6 to 2.00% is to improve the hardenability, and if the Mn content is 0.6% or less, the effect is insufficient, and if it is 2.00% or more, the retained austenite after quenching increases. Because. Cr increases the hardenability and increases the tempering resistance, but the Cr content of 0.6% or more is economically disadvantageous, and the required properties can be obtained without adding Cr in small-diameter steel bars. .

The size is limited to a diameter of 5 to 50 mm because it is a range usually used as a high-strength deformed steel bar for concrete. The strength tensile strength 930N / mm ² or more, is to obtain a strength required for the prestressing steel bars to heat treatment yield point 785N / mm ² or more.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be specifically described below. FIG. 2 is a view showing a manufacturing process of a high-adhesion / high-strength deformed steel bar of the present invention (hereinafter, simply referred to as a high-strength deformed steel bar). In FIG. 2, a hot rolled deformed steel bar or wire (hereinafter simply referred to as a hot-pressed deformed steel bar) having the shape of FIG. 8 wound in a coil shape is used as a raw material. Surface scale is removed.
Next, in a drawing step, drawing is performed cold with a predetermined round die. Next, in the quenching step, the steel sheet is continuously heated to a quenching temperature by a high-frequency induction heating means or a direct current applying means and quenched by rapid cooling with water cooling. Thereafter, in the tempering step, the material is similarly continuously heated to the tempering temperature by the high-frequency induction heating means or the direct current applying means, tempered and rapidly cooled. Then, in the processing step, the wire is coiled, and the bar is cut straight, threaded, or the like while keeping a straight line, and is shipped as a product after an inspection step.

In this embodiment, JIS 3 having a knot of a spiral projection with a right twist of about 30 degrees and a shape shown in FIG.
Name D10 with a nominal diameter of 9.53 mm specified in 112
Was used. Table 1 shows the chemical composition of the hot-press deformed steel bar.

[0012]

[Table 1]

FIG. 3 shows the cross-sectional shape. That is, in FIG. 3, the body diameter of the steel bar is 8.85 to 8.90 φm.
m, the height of the rib was 0.36 to 0.38 mm, and the height of the node was 0.58 to 0.63 mm.

[0014] This hot-pressed deformed steel bar has an inner diameter of 9.10 mmφ.
Was drawn cold using a round die. FIG. 4 shows a cross section of the steel bar after the drawing process. As shown in the figure, the body diameter is the same as the material, but the height of the rib 12 is 0.24 to 0.2.
8 mm, 63 to 78% of the original height, the height of the node 11 becomes 0.25 to 0.30 mm, 4 to the original height
0-52%. The appearance is shown in FIG. As shown in the drawing, in the drawn deformed steel bar 2, the vertices of the nodes 11 and the ribs 12 are slightly flattened. As a result, the height of the joints was reduced as compared with the hot-press deformed steel bar, and the adhesive force of concrete was slightly reduced,
Roundness was improved and thread rolling properties were improved.

An adhesion strength test of the drawn deformed steel bars to concrete was performed based on "Method (draft) of Japan Concrete Institute". The specimen is shown in FIG. In the figure, a specimen 4 has a deformed steel bar 7 as a test material placed at the center of a concrete cube 5 of 10 cm cubic, around which a winding diameter of 8 cm and a helical pitch a = 4 cm, 6 mm.
Reinforcing bars 6 of φ diameter (ends were horizontally 1.5 rolls and 0.5 rolls were omitted) were arranged. In addition, the concrete was laterally cast (bars were arranged horizontally), and the quality of the concrete was as follows. Material age 28 days Curing conditions 14-24 ° C Cured in water Concrete strength σc 300 ± 30 kgf / cm ² Slump 8 ± 2 cm. The test was performed by a method shown in FIG. 6 using a 30-t tensile tester. In the drawing, a specimen 4 was placed on a receiving table 41 of a fixing portion of a tensile tester via a spherical seat 42 and a washer 43, and a pulling force was applied to the test deformed steel bar 7 in the direction of arrow P by a clamp 44. Then, the slip amount of the test deformed steel bar 7 is measured by the dial gauge 45, and the XY recorder 4
7, the relationship between the slip amount and the pulling force was recorded.

FIG. 7 and Table 2 show the test results. FIG.
, The vertical axis represents the pull-out force (KN), and the horizontal axis represents the amount of slip (m).
m). Curve A is a hot-pressed deformed steel bar as rolled, curve B is a drawn deformed steel bar of the present invention, and curve C is a comparative material of 9.2 mm urbon (a drawn material with a 10φ groove, urbon is a registered trademark of Induction Heating Co., Ltd.) ) Shows a drawing force-sliding diagram. Table 2 shows the slip amount, 0.05 m, based on the results of FIG.
m, 0.1 mm, 0.25 mm, average value and maximum adhesive force. From the results of Table 2 and FIG. 7, when the hot-pressed deformed steel bar is drawn, the maximum adhesive force is reduced from 36.8 KN to 26.5 KN due to the decrease in the height of the nodes, but it is still higher than that of the comparative material Urbon. The strength is large,
Sufficient adhesive strength was obtained for use.

[0017]

[Table 2]

Next, the drawn deformed steel bars were subjected to a heat treatment using a continuous quenching and tempering apparatus 30 shown in FIG. In FIG. 10, the material W of the deformed steel bar that has been drawn is continuously fed through a pinch roll 31, a vertical straightening roll 32, a horizontal straightening roll 33, and a pinch roll 34, and a quenching high-frequency induction heating coil 35. At 920
Heated to a quenching temperature of
And quenched. Next, after being heated to a tempering temperature of 370 to 380 ° C. by the high-frequency induction heating coil 37 for tempering, it is rapidly cooled by a water cooling jacket 38 and sent out by a pinch roll 39.

Table 3 shows the mechanical properties of the deformed steel bars after the heat treatment. The mechanical strength is improved by the heat treatment. Both the non-grooved deformed steel bar and the grooved deformed steel bar have the JIS as shown in the table.
G3109 standard yield point load, tensile load, elongation at break,
We are satisfied with aperture.

[0020]

[Table 3]

A screw rolling test was performed on the deformed steel bar product using an RL23 type rolling machine manufactured by K.K. Table 4 shows the results. Both the non-grooved deformed steel bar and the grooved deformed steel bar obtained results satisfying the standard values of JIS B 0221. It should be noted that although the hot-press deformed steel bar material was inferior in roundness and could not be thread-rolled, the product of this example could be thread-rolled without any problem.

[0022]

[Table 4]

Next, this deformed steel bar was head-forged into a shape as shown in FIG. 9 using an FP11 type forging machine manufactured by Induction Heating Co., Ltd., and a tensile test was performed. Table 5 shows the results.
All exhibited the specified tensile strength, and all fractured normally at the base material. Therefore, it was shown that the head molding could be performed under normal conditions.

[0024]

[Table 5]

In this embodiment, a deformed steel bar of D10 of JIS G 3112 is shown, but it is needless to say that the invention can be applied to D6 to D51 of the same standard.

[0026]

As described above, according to the present invention, the nodes and ribs of a hot-rolled deformed steel bar having poor roundness are crushed by drawing to improve the roundness. As it is, the roundness is poor and thread rolling cannot be carried out without cutting under the thread.This improves the disadvantages of thread rolling and facilitates thread rolling, and provides good electrode contact during cross-wire welding. , Welding becomes easy, handling on site is improved, and work efficiency is improved. Furthermore, when the hot-rolled material is used as it is, it is difficult to perform straightening with a straightening roll when the coil material is converted into a straight material, and handling becomes easier.

Further, desirably, by leaving a node of 40% or more of the height of the spiral projection of the original node of the hot-rolled material, the adhesive force of the concrete can be maintained at a value sufficient for use.

Further, the components of the raw materials are expressed in a weight ratio of C: 0.1 to
0.6%, Si: 0.15 to 2.00%, Mn: 0.6
If the content is limited to 2.00% and Cr: 0.6% or less and the balance is made up of iron and unavoidable impurities, the strength of the standard value can be easily obtained, and the safety of using the high-strength deformed steel bar increases. .

Since the hot-press deformed steel bar can be used as it is, there is an advantage that mass production is easy.

[Brief description of the drawings]

FIG. 1 is an external view of a high-adhesion and high-strength deformed steel bar according to an embodiment of the present invention.

FIG. 2 is a manufacturing process diagram of the embodiment of the present invention.

FIG. 3 is a cross-sectional view of a hot-press deformed steel bar material according to an embodiment of the present invention.

FIG. 4 is a sectional view of a deformed steel bar drawn by a die according to the embodiment of the present invention.

FIG. 5 is a cross-sectional view of a specimen for a concrete adhesion strength test according to an example of the present invention.

FIG. 6 is a conceptual diagram of a test device for a concrete adhesion strength test according to an example of the present invention.

FIG. 7 is a graph showing test results of a concrete adhesion strength test according to an example of the present invention.

FIG. 8 is an external view of a hot-rolled deformed steel bar as a raw material.

FIG. 9 is a view showing the shape of the head head forging of a highly adhered and high-strength deformed steel bar according to an example of the present invention.

FIG. 10 is a conceptual diagram of a continuous quenching and tempering apparatus used in an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hot-rolled deformed steel bar 2 Drawing deformed steel bar 4 Specimen for adhesion strength test 5 Concrete cube 6 Reinforcement 7 Test steel bar 11 Section 12 Rib 30 Continuous quenching / tempering device 31 Feed roller 32 Horizontal roll straightening machine 33 Vertical roll straightening Machine 34 Feed roller 35 High frequency heating coil 36 Water cooling jacket 37 High frequency heating coil 38 Water cooling jacket 39 Feed roller 41 Cradle 42 Spherical washer 44 Clamp 45 Dial gauge 46 Amplifier 47 XY recorder

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location C21D 9/28 C21D 9/28 A C22C 38/00 301 C22C 38/00 301Y 38/18 38/18 E04C 5/03

Claims (2)

(57) [Claims] After forming a deformed steel bar or wire rod for concrete having a helical projection on its outer diameter by hot rolling, the raw material of the deformed steel bar or wire rod is rounded at a reduced area ratio such that the nodes of the hot rolling remain. High-adhesion, high-strength deformed steel bars that have been subjected to quenching and tempering heat treatment. 2. C: 0.1 to 0.6% by weight, Si:
0.15 to 2.00%, Mn: 0.6 to 2.00%, C
r: a steel rod or wire rod having a diameter of 5 to 50 mm containing 0.6% or less and the balance being iron and unavoidable impurities, and having a tensile strength of 93
2. The high adhesion and high adhesion according to claim 1, wherein the heat treatment is performed at 0 N / mm ² or more and a yield point of 785 N / mm ² or more.
High-strength deformed steel bar.