JP2704834B2 - High-adhesion, high-strength deformed steel bar and method for producing the same - 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. The present invention relates to a deformed steel bar and a method for producing the same.

[0002]

2. Description of the Related Art A conventional deformed steel bar for concrete is shown in FIG.
As in the case of a hot-press deformed steel bar 1 of 0, a bar-shaped steel bar having a projecting node 11 provided at regular intervals by hot rolling on the surface thereof 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. on the other hand,
To solve this drawback, it is possible to improve the roundness by skin pass processing, but in this case, there is a drawback that the nodes are crushed, the height of the nodes is reduced, and the bonding strength with concrete is reduced.

[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. Higher adhesion that facilitates secondary processing such as thread rolling, improves welding workability at the time of construction, and forms multiple new spiral grooves to reinforce the bonding force with concrete -To provide a high-strength deformed steel bar and a method for producing the same.

[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. The height of the rolling node is a perfect circle processing with a reduction in area so that the original node remains, and a plurality of spiral grooves with a twist direction opposite to the twist direction of the spiral of the node are applied to the outer diameter. A high-strength, high-strength deformed steel bar which has been subjected to quenching and tempering heat treatment.

Also, C: 0.1-0.6% by weight, S
i: 0.15 to 2.00%, Mn: 0.6 to 2.00
%, Cr: 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, has been heat treated to yield 785N / mm ² or more A highly adhered and high-strength deformed steel bar as described above is provided.

[0007] Further, a deformed steel bar or wire rod for concrete having a spiral projection with an outer diameter formed by hot rolling is provided with a plurality of spirals having an inner diameter with a twist in a direction opposite to the twisting direction of the spiral of the knot. Using a round die having a shape projection, drawing at a reduced area ratio such that the nodes of the hot rolling remain, and continuously feeding the steel bar or wire rod to the quenching temperature while using a high-frequency induction heating means or a direct energizing means to cut the entire cross section After rapid heating, rapidly cooling and quenching, then rapidly heating to the tempering temperature by high frequency induction heating means or direct current means, then quenching and tempering, the high adhesion and high strength variant as described above. Provided is a method for manufacturing a steel bar.

[0008]

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. Further, the reason why a plurality of spiral grooves are newly formed on the outer diameter is to compensate for a decrease in the height of the nodes due to the roundness processing and a decrease in concrete adhesion. The heat treatment of quenching and tempering is for obtaining the required mechanical strength.

[0009] Further, the plurality of spiral grooves having a twist in a direction opposite to the twist direction of the spiral of the node of the hot rolling is provided.
This is because the spiral groove is hidden at the bottom of the node in the same direction as that of the node of the hot rolling and the effect of increasing the concrete adhesive force is reduced. This is for obtaining a synergistic effect of the concrete adhesive force of the newly provided spiral groove.

[0010] The components of the raw material of the deformed bar are limited for the following reasons. 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 reason why the size is limited to a diameter of 5 to 50 mm is that the range is 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.

In the manufacturing method of the present invention, the drawing using a round die having a plurality of spiral projections on the inner diameter is advantageous as a method of simultaneously performing the round processing and the processing of the plurality of spiral grooves. That's why. In addition, mass production of uniform quality is facilitated by performing continuous quenching and tempering heat treatment by high-frequency induction heating means or direct current supply means.

[0013]

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, the raw material uses a hot-rolled deformed steel bar or wire (hereinafter simply referred to as a hot-press deformed steel bar) having a shape shown in FIG. 10 wound in a coil shape.
Surface scale is removed through a multi-roll straightener. 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, a JIS having a node of a spiral projection with a right-handed twist of about 30 degrees and a shape shown in FIG.
Name D1 with a nominal diameter of 9.53 mm specified in 3112
A hot-press deformed steel bar of 0 was used. Table 1 shows the chemical composition of the hot-press deformed steel bar.

[0015]

[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.

One of the hot-press deformed steel bars has an inner diameter of 9.10.
Round dies with no protrusion on the inside diameter of mmφ.
Cold drawing was performed using a round die 21 having an inner diameter of 9.20 mmφ and six spiral projections 22 with a left helix angle of 18 degrees on the inner diameter shown in FIG. FIG. 4 shows the cross section of the steel bar after the drawing process in the case of die drawing without protrusions, and FIG. 5 shows the case of the die drawing with protrusions. Twist angle 1 of the spiral projection
It is desirable that 8 degrees is large from the viewpoint of concrete adhesion. However, if the twist angle is large, it becomes difficult to perform the drawing process.
8 degrees.

FIG. 4 is a cross-sectional view of a steel bar when the bar is pulled out with a projection-less die. As shown in the figure, the body diameter is the same as that of the material, but the height of the rib 12 is 0.24 to 0.28 mm, which is 63 to 78% of the original height, and the height of the node 11 is 0.
25-0.30mm, 40-52% of original height
Became. As a result, the roundness was improved and the thread rolling properties were improved, but the adhesive strength of the concrete was slightly reduced due to the reduced height of the nodes. The test results will be described later.

FIG. 5 is a cross-sectional view of a steel bar obtained by cold drawing using a round die having a spiral projection on the inner diameter. As shown in FIG.
On the other hand, the size of the ribs 12 and the nodes 11 is slightly larger than that of the dies without projections because the dies with projections are 9.20 mm, but as shown in FIG. 1.3mm width, 0.4 depth
Six spiral grooves 13 of 0 mm are formed. FIG. 1 shows an external view thereof. That is, as shown in FIG. 1, a spiral groove having a right-hand twist of 30 degrees and a converse left-hand twist of 18 degrees are formed on the outer diameter of the grooved drawn deformed steel bar 2 in FIG.
The helical groove compensates for the reduction in the height of the nodes of the hot-pressed deformed steel bar due to the drawing, thereby reducing the concrete adhesion.

An adhesion strength test of the drawn deformed steel bars to concrete was carried out based on "Method (draft) of Japan Concrete Institute". The test 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. 7 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. 8 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-rolled deformed steel bar as rolled, curve B is a drawn non-grooved deformed steel bar, curve C is a grooved drawn deformed steel bar, and curve D is a 9.2 mm urbon (10 mm) comparative material.
A drawing material with a φ groove, Urbon, is a drawing diagram of a drawing force-sliding line diagram of a high-frequency hot-melting Co., Ltd.). Table 2 shows the slip amounts, 0.05 mm, 0.1 mm, and 0.25 from the results of FIG.
It shows the mm, the average value and the maximum adhesive force. Summarizing these results, the following can be said. That is, when the hot-press deformed steel bar is drawn without grooves, the height of the nodes is reduced, so that the adhesive force is still larger than that of the comparative material Urbon, but the maximum adhesive force is reduced from 36.8 KN to 26.5 KN. On the other hand, the grooved and drawn deformed steel bars have a maximum adhesive force of 34.7 KN, which is almost the same as that of the hot-press deformed steel bars. It is observed that the new spiral groove by grooved drawing compensates for the reduction in the height of the nodes of the hot pressed deformed steel bars due to the drawing and thus the decrease in concrete adhesion.

[0022]

[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. 12, the drawn W of the deformed steel bar is continuously sent out via 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.

[0025]

[Table 3]

A thread rolling test was performed on the deformed steel bar product using a RL23 type rolling machine manufactured by Induction Hot Rolling Co., Ltd. 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.

[0027]

[Table 4]

Next, the deformed steel bar was head-forged into a shape as shown in FIG. 11 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.

[0029]

[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.

[0031]

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.

[0032] Further, it is preferable to leave a node of 40% or more of the height of the spiral projection of the original node of the hot-rolled material,
In addition, by providing a plurality of spiral grooves having a twist in a direction opposite to the twist direction of the spiral of the knot in the outer diameter, the adhesive force of concrete is improved.

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. .

According to the manufacturing method of the present invention, the hot-rolled material is pulled out using a round die having a plurality of spiral-shaped projections having a twist in a direction opposite to the twist direction of the spiral of the node of the hot-rolled material. The remaining amount of the knot height of the inter-rolled material can be set arbitrarily, and a spiral groove of an arbitrary width, depth, and number of steps in the direction opposite to the spiral of the original knot can be formed, and concrete adhesion And a high-strength deformed steel bar having a good shape can be obtained. Also,
By continuously heat-treating with high-frequency induction heating means or direct current supply means, high-strength deformed steel bars with high strength and uniform quality can be economically mass-produced.

[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 cross-sectional view of a non-grooved deformed steel bar drawn with a die without protrusions according to an embodiment of the present invention.

FIG. 5 is a cross-sectional view of a grooved deformed steel bar pulled out by a die having protrusions according to an embodiment of the present invention.

FIG. 6 is a cross-sectional view of a specimen for a concrete adhesion strength test according to an example of the present invention.

FIG. 7 is a conceptual diagram of a test device for a concrete adhesion strength test according to an example of the present invention.

FIG. 8 is a graph showing test results of a concrete adhesion strength test according to an example of the present invention.

FIG. 9 is a perspective view of a drawing die having a spiral projection on the inner diameter according to the embodiment of the present invention.

FIG. 10 is an external view of a hot-rolled deformed steel bar as a raw material.

FIG. 11 is a view showing the shape of the head forging process of a high-adhesion and high-strength deformed steel bar according to an example of the present invention.

FIG. 12 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 material 2 Drawing deformed steel bar 4 Specimen for adhesion strength test 5 Concrete cube 6 Reinforcement 7 Test steel bar 11 Section 12 Rib 13 Spiral groove 21 Round die 22 Spiral projection 30 Continuous quenching / tempering device 31 Feed roller 32 Horizontal roll straightener 33 Vertical roll straightener 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 front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication location C21D 9/00 9542-4K C21D 9/00 H 9/28 9/28 A 9/52 103 9 / 52 103B C22C 38/00 301 C22C 38/00 301Y 38/18 38/18 E04C 5/03

Claims (3)

(57) [Claims] 1. A deformed steel bar or wire rod for concrete having a spiral projection with an outer diameter formed by hot rolling is subjected to perfect circle processing at a reduced area ratio such that the nodes of the hot rolling remain. A high-adhesion, high-strength deformed steel bar subjected to quenching and tempering heat treatment, wherein a plurality of spiral grooves having a twist direction opposite to the twist direction of the spiral of the node are provided on the outer diameter. 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
0N / mm ² or more, a high adhesion and high strength deformed steel bar according to claim 1 which is heat treated to yield 785N / mm ² or more. 3. A plurality of spirals having a twist in a direction opposite to the twisting direction of the spiral of the knot in the inner diameter of a deformed steel bar or a shaped rod for concrete, which has been subjected to knot rolling and having spiral projections on the outer diameter by hot rolling. After drawing using a round die with shape projections at a reduction in area such that the nodes of the hot rolling remain,
While continuously feeding the bar or wire rod, the entire cross section is rapidly heated to a quenching temperature by a high-frequency induction heating means or a direct energizing means, then rapidly cooled and quenched, and then rapidly heated to a tempering temperature by a high-frequency induction heating means or a direct energizing means. The method for producing a high-adhesion and high-strength deformed steel bar according to claim 1 or 2, wherein the material is rapidly cooled and then tempered.