JP2565695B2 - Manufacturing method of nominal 13 mm type D deformed PC steel bar - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is directed to a mesh rod having a maximum diameter of 13 mm among the deformed rods of PC steel rods of class D (SBPD130 / 145) limited to JIS Z3109. Specifically, the present invention relates to a treatment method after a raw steel rod is subjected to a step such as deforming and continuously feeding, and subjected to a process such as heat treatment to obtain a high-strength wire having mechanical properties satisfying the D-class standard.

(Prior Art) Not only deformed bars but also PC steel bars are required to maintain linearity during use.

Therefore, when manufacturing a PC steel rod, after subjecting the material wire rod to the high strength imparting step, if the diameter of the wire rod obtained is relatively small, the linearity should be restored when it is rewound during use. A coiled product that is wound within the elastic limit and can be loaded on the truck bed to be transported and has a winding inner diameter of 2200 mm or less, and has a relatively large wire diameter (round bar is 32 mm in name).
Products with a large diameter) are cut into a predetermined length without winding and made into straight rod products.

The deformed bar has a nominal diameter of up to 13 mm and is naturally suitable as a coiled product. In fact, Class B and C are nominally 7.4 mm to 13 mm, and Class D is nominally 7.4 mm to 11 mm as a coiled product. Shipping. However, as the only exception, the 13 mm D type deformed bar, which is called by name, has a large elastic diameter because the relationship between the strength and the bending stress at the time of winding does not exceed the elastic limit unless the winding inner diameter is at least 2600 mm unsuitable for truck transportation. It was customary to cut the product to a specified length before shipping it, similar to a PC rod with a diameter, that is, after imparting the specified mechanical properties.

(Problems existing in the prior art) For PC steel rods, especially those with a relatively small diameter used for pile poles, it is necessary to rewind the coiled one to the required length before use, and the material yield is User is welcomed as good. Despite being used for pile poles, the 13 mm D type deformed bar is called as a standard length material from the factory due to the correlation between strength and transportation. The user who obtains it as a scale will not use it easily because the specified length will be the specified length if the yield is to be improved. Conversely, if the user wants to improve the yield, it will be more than the required length. However, there is a problem that the yield is deteriorated because the dimension of (1) is set to the specified scale, and an improvement measure is desired.

(Object of the invention) The present invention has been made to solve the above-mentioned problems existing in a nominally 13 mm D type deformed bar in a PC steel rod, and after imparting predetermined mechanical properties as a PC steel rod, it has a small diameter. By winding around the inner diameter of the winding to enable truck transportation, recovering the linearity during use, and possessing various mechanical properties that satisfy JIS standards, by searching and setting the winding and unwinding conditions. An object of the present invention is to provide a method for manufacturing a nominally 13 mm deformed PC steel bar, which enables the user to obtain a product with a good yield and usability.

(Structure of the Invention) The structure of the present invention is as follows: (1) The material steel wire rod having a predetermined diameter wound in a coil shape is deformed to have a nominal diameter of 13 mm, and heat-treated or otherwise treated during continuous feeding to yield. Points: 130 Kgf / mm ² or more, tensile strength; 145 Kgf / mm ² or more, and various properties required as a PC steel rod are given. (2) Arc height value of 15 mm / M for continuously running wire rod.
Bending in the winding direction within the range not exceeding, (3) winding into a predetermined winding inner diameter to form a coiled material, (4) rewinding the coiled material as much as possible It is a manufacturing method for a nominal 13 mm type D deformed PC steel bar, which is characterized by lightly straightening the steel to restore its linearity.

(Effect of the Invention) The present invention refers to a material steel wire rod by subjecting it to a predetermined process
After imparting mechanical properties for a mmD type deformed PC steel bar, the wire rod obtained is subjected to pre-bending in a range that does not exceed the arc height value of 15 mm / M, which bends toward the winding side. Even if the inner diameter is wound, it is possible to use it as a straight rod with mechanical properties that satisfy the specified value just by lightly straightening it, the winding torque required to wind to a predetermined winding inner diameter that exceeds the elastic limit Has the effect of reducing the size and the effect of alleviating the difficulty of loosening during rewinding.

(Example) The present invention will be described in detail below with reference to an example shown in Figs. 1 (a) to 1 (c) in which the high strength imparting step is, for example, heat treatment.

In FIG. 1 (a), L1 is a manufacturing line installed on the manufacturer side, in which a raw steel wire after being deformed is wound around a pay-off stand 1, straightening machines 2a, 2b,
From a quenching device 3 comprising a predetermined heating means and a quenching means, a tempering device 4 comprising a predetermined heating means and a cooling means, a pre-bending device 5, a winding stand 6, and a drive roller 7 arranged at a plurality of locations. It is configured. L2 is a rewinding line installed by the deformed bar user who is a manufacturer of piles, poles, etc., and includes a rewinding stand 8, straightening machines 9a and 9b,
And a driving roller 7. Production line L1
The arrow drawn from the take-up stand 6 to the rewind stand 8 of the rewind line L2 indicates the truck transportation.

The pre-bending device 5 in the production line L1 is
For example, three rolls R1 to R3 as shown in FIG. 1 (b)
Each of the peripheral surfaces of the rolls R1 and R3 has a concave arc, and the upper peripheral surfaces of the rolls R1 and R3 are linear.
Is a common tangent line and is arranged at a predetermined interval, and the roll R2 is arranged in the middle of the above interval from a roll center O'of a virtual position drawn by a broken line with the wire rod feeding passage 1 as a tangent line on the lower peripheral surface in the drawing. The roll center O is placed at a position vertically offset by H from the wire feed passage 1 toward the rolls R1 and R3. Accordingly, the roll R2 is a pushing roll, and the pushing load is applied from above to the wire rod which is driven by the driving roll 7 and travels in the wire feed passage 1 in accordance with the pushing amount H of the pushing roll R2. Thus, the winding stand 6 on the front side in the feeding direction is set so as to wind up the wire material which is bent upward and is bent in the winding direction corresponding to the bending deformation.

The straightening machines 9a and 9b in the rewinding line L2 are a1 to a6 and b1 to b6, respectively, as shown in FIG. 1 (c).
The straightening machine 9a is set as a vertical type in the vertical direction, and the straightening machine 9b is set as a horizontal type in the horizontal direction so that a predetermined pushing load can be applied to the wire rod.

In the above configuration, the material steel wire W is the rewinding stand 1
It is rewound from, passed through the straighteners 2a and 2b to be in a straight line state, and continuously fed to the quenching device 3 and the tempering device 4. While the raw steel wire W passes through the quenching device 3 and the quenching device 4 under a predetermined tension applied by the drive roller 7,
Yield point: 130Kgf / mm ² or more, tensile strength: 145Kgf / mm ² or more, and a high-strength steel wire for a deformed PC steel bar with a nominal name of 13mm, which has various properties specified as a PC steel bar, and then a pre-bending device After traveling to 5, the pre-bending device 5 applies a predetermined amount of bending, and then the winding is performed on the winding stand 6 with a winding inner diameter of, for example, 2200 mm.

The coiled high-strength steel wire wound up is transported from the manufacturer to the user by truck transportation as shown by the arrow, mounted on the rewinding stand 8 of the rewinding line L2 on the side of the user and required according to the reception. It is rewound by the indexing force of the drive roller 7 by length, but at the time of the rewinding, by passing through the straightening machines 9a and 9b, the winding distortion generated at the time of winding is lightly corrected to restore the linearity, A variant that is a straight bar with a nominal name of 13 mm
Used as a PC steel rod for manufacturing piles, poles, etc.

Thus, in the present invention, the bending amount of the wire obtained in accordance with the pushing amount H by the pushing roll R2 of the pre-bending device 5, that is, the arc height value shown as h in FIG. 2 (the bending amount after the spring back for pushing; mm / M) affects the mechanical properties of the steel bar during use, how difficult is the winding after bending, is the workability and the appearance of the winding, and is the difficulty of rewinding when used. Since the important point is how it affects the straightening before use, etc., the following experiment was carried out to determine the appropriate value.

[Experiment]

 ☆ Material Steel wire: S35CSi material However, the chemical composition was as shown in Table 1.

Wire diameter …… 14mm ☆ Preparation of specimen: After pickling the above steel wire rod, it is deformed to a nominal diameter of 13 mm by drawing, and the straightening machines 2a and 2b and quenching device 3 in the production line L1 shown in Fig. 1 (a) are used. Then, the wire rod was continuously fed to the tempering device 4 and was made into a wire rod which maintained the linearity imparted with various mechanical properties as a type D deformed PC steel rod, and this was used as a test wire rod.

 The heat treatment conditions were as shown below.

Quenching: Heating temperature: 1030 ° C Quenching: Cooling: Water cooling Tempering: Heating temperature: 550 ° C However, the target return temperature of σB150Kgf / mm ² Cooling: Water cooling ☆ Experimental method: Set indentation amount for the above test wire H
To the pre-bending device 5 with various arc height values h to obtain wire rods having different arc height values h, wound on the winding tan 6 with an inner diameter of 2200 mm, and further sent the wound sample wire rod to the rewinding line L2. Straightening was performed by straightening machines 9a and 9b to obtain straight rods, and various tests were performed on the obtained straight rods during the process.

In addition, at the time of straightening for straightening, we initially tried to set the condition aiming at the minimum correction amount, and in the experimental process,
When the pushing amount is 3.8 mm or less, the linearity becomes unstable,
Since the mechanical properties were significantly deteriorated when the thickness was 4.5 mm or more, the indentation amount for all the test wire rods was unified according to the conditions in Table 2.

☆ Test ○ Pre-bending condition search / setting test; rolls R1 to R3 of the pre-bending device 5 and their arrangement are as follows,
The indentation amount H was changed by the device to obtain wire rods having different arc height values h. The test results are shown in Table 3.

Roll size used: R1 to R3 are all the same. Valley diameter …… 90mm Peak diameter …… 100mm Distance between R1 and R3; 115mm ○ Winding required torque measurement test: The test wire was wound around the winding stand 6 at a winding inner diameter of 2200 mm, and the torque that could be easily wound was measured. The measurement results are shown in the prescribed column of the attached Table 4 together with the required torque when winding with a winding inner diameter of 2600 mm (a winding diameter that does not cause plastic deformation, hereinafter referred to as conventional product).

○ Straightening test: As shown in Table 2 above, each of the specimen steel wires having different arc height values h obtained by varying the indentation amount H was straightened, and the bending amount (mm / M) immediately after the straightening was measured. The measurement results are shown in a predetermined column of Attached Table 4.

○ Various tests on mechanical properties; pre-bending with different arc height value h after heat treatment, winding inner diameter 2200mm
The specimens that had been wound up in the above manner and straightened into straight rods were subjected to various tests regarding mechanical properties according to the test methods specified in JIS. The number of test specimens was 4-5. The test results are shown in Table 4 of the attached sheet together with those of the conventional product.

FIG. 3 is a diagram showing the results of the relaxation test, which is a part of the test.

○ Residual stress measurement test; using an X-ray stress measuring device, a specimen wire rod that has been subjected to heat treatment, a specimen wire rod after pre-bending with a different arc height value h, pre-bending and winding with an inner diameter of 2200 mm. The residual stress on the inside and outside in the axial direction related to bending was measured for each of the test wire rods that were straightened. Inside (a) of FIG. 4,
In (b), the outer measurement result is shown as a line graph for each different arc height value h. In addition, in the same figure, the measurement results of the specimen wire rod having the arc height value h; 45 (level) are also shown.

From the above test results and work knowledge, the following considerations were obtained.

(1) After straightening without heat treatment (pre-bending) (arc height value h; 0) with a winding inner diameter of 2200 mm and straightening.

* Winding: Requires nearly twice as much winding torque as conventional products.

* Winding: Slightly defective due to spring back.

* Rewinding: High elasticity is maintained, high risk and poor workability.

* Deflection amount immediately after modification: Although the amount of deflection is small, it is uneven and not constant.

* Mechanical properties: Tensile strength, yield point, elongation and drawing are almost the same as conventional products. The relaxation value is slightly lowered, but it satisfies the JIS standard.

(2) Pre-bending is applied after heat treatment to reduce the winding inner diameter to 22
About a straight rod that was rolled up and straightened to 00 mm.

1. Ark height value of 5 (target value).

* Winding: Winding can be done easily with a winding torque smaller than that of conventional products.

* Volume: Good.

* Rewinding: Good workability.

* The amount of bending right after the modification: Good.

* Mechanical properties: Tensile strength, yield point, elongation, and drawing are almost the same as the conventional products, but the relaxation value is almost the same as the one that is immediately wound around the inner diameter of 2200mm without pre-bending and straightening. Although it shows a decrease, JIS
Satisfies the standard sufficiently.

2. With an arc height value of 10 (target value).

* Winding: It is easy to wind like the arc height value 5 above.

* Volume: Good.

* Rewind: Good workability.

* Amount of bending right after grading: There is some bending, but there is no problem in use.

* Mechanical properties: Tensile strength, yield point, elongation and drawing are almost the same as conventional products. The relaxation value is slightly lower, but it satisfies the JIS standard.

* Residual stress: By applying straightening, both inside and outside have recovered to almost zero.

3. An arc height value of 15 (target value).

* Winding: Easy to wind.

* Winding: The winding is somewhat irregular.

* Rewind: Good workability. The amount of bending after rewinding is constant.

* Amount of bending right after grading: Some bending is noticeable, which may cause trouble.

* Mechanical properties: Tensile strength, yield point, elongation and drawing are almost the same as conventional products, but relaxation values may deviate from JIS standards.

4. Those with an arc height value of 20 (target value).

* Winding: Both are easy to wind.

* Winding: The winding is extremely irregular.

* Rewinding: Workability is extremely poor due to entanglement.

* Bending amount immediately after grading: The linearity is not restored and it causes trouble in use.

* Mechanical properties: Tensile strength, elongation and drawing are the same as those of conventional products, but the yield point is noticeably reduced and the relaxation value does not meet JIS standards.

* Residual stress: Even if straightening is applied, it does not recover to 0 on both the inside and outside.

From the above consideration, a method of winding immediately beyond the elastic limit and straightening at the time of use after giving the predetermined mechanical properties can obtain a straight rod having sufficient mechanical properties, but the winding torque and workability are not improved. It was confirmed that there was a difficulty, and the treatment method of pre-bending with an arc height value of 15 or more, winding, and straightening at the time of use was unsuitable for the required mechanical properties and residual stress.

On the other hand, the treatment method of applying a light pre-bending with an arc height value of less than 15 and then winding it and lightly straightening it is mechanical properties, residual stress, winding torque, winding appearance, workability, etc. Since it has been proved that all the points are satisfied, the present invention calls this treatment method the name 13 mm type D variant P.
This is a part of the method for manufacturing C steel rod.

(Effect of the invention) By carrying out the present invention, the nominal 13 mm type D deformed PC steel rod can be transported by truck as a coiled material, and the user can rewind the coiled material at the time of use and lightly straighten it. Since it can be used as a straight rod for the length, it greatly contributes to improvement in yield and usability.

[Brief description of drawings]

1 (a) is a block diagram showing an outline of an embodiment of the present invention, FIG. 1 (b) is a front view showing an example of a pre-bending device used in the present invention, and FIG. 1 (c) is a book. A front view showing an example of a straightening machine used in the present invention, FIG. 2 is a front view of a wire for explaining an arc height value, FIG. 3 is a diagram showing a relaxation test result, and FIG. 4 (a). And (b) are diagrams showing residual stress measurement test results, respectively.

Claims (2)

(57) [Claims] 1. A steel wire rod having a predetermined diameter wound in a coil shape is deformed to have a nominal diameter of 13 mm, and heat treated or other treatment is applied during continuous feeding to yield point; 130 Kgf / mm ² or more, tensile Strength: 145 Kgf / mm ² or more, and various properties required as a PC steel rod are given, and the wire running subsequently is bent in the winding direction within an arc height value of not more than 15 mm / M. In addition, the coiled material is wound into a predetermined winding inner diameter to form a coiled material, and the coiled material is rewound when used to be straightened as lightly as possible to restore linearity. Manufacturing method of 13mm D type deformed PC steel bar. 2. A coiled material having a winding inner diameter of 2000 mm or more and 2600 m
A method for producing a 13 mm type D deformed PC steel bar with the nominal name according to claim 1, which is less than m.