JPS63134629A - Production of designation 13mmd class deformed pc steel bar - Google Patents

Abstract

PURPOSE:To produce a titled deformed PC steel bar having a good yield and ease of use by subjecting a stock steel wire rod to prescribed stages to impart mechanical properties thereto and subjecting the take-up side thereof to prebending so that the wire rod can be used with light leveling. CONSTITUTION:The stock steel wire rod W is un-coiled and is worked to a deformed shape of 13mm nominal diameter by levelers 2a, 2b, by which the wire rod is straightened. The wire rod is then continuously fed via driving rollers 7 to a hardening device 3 and a tempering device 4. The wire rod W is imparted with >=130kgf/mm<2> yielding point, >=145kgf/mm<2> tensile strength and various properties required as the PC steel bar in the above-mentioned stage. The wire rod W is then given bending in the coiling direction within the range of not exceeding 15mm/M arc height value by a prebending device 5. Such coiled high-strength wire rod is carried by a truck to a user side and is mounted on an un-coiling stand 8. The wire rod is then lightly straightened of the winding set by straighteners 9a, 9b by which the linearity is restored. Such wire rod is used as the deformed PC steel bar which is a straight bar of designation 13mm.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention applies to a 13 mm 0 steel bar having the largest diameter among the irregularly shaped PC steel bars (SBPD 130/145') specified in JIS G3109. The target manufacturing method is specifically a processing method after a raw steel bar is subjected to processes such as heat treatment while being deformed and continuously fed to produce a high-strength wire rod having mechanical properties satisfying the D-class standard.

(Prior Art) It is essential for PC steel bars, including irregularly shaped bars, to maintain linearity during use.

Therefore, when manufacturing PCil rods, after subjecting the raw material wire to a high-strength imparting process, if the resulting wire has a relatively small diameter, it is necessary to unwind it before use so that its straightness is restored. It is wound into a coiled product within its elastic limit and within the inner diameter of 2200 mm that can be loaded on the truck bed for transportation, and the wire rod has a relatively large diameter (round bars have a large diameter of up to 32 mm). The one without winding up twice.

It is cut into a predetermined length to produce a straight bar product.

Irregular-shaped rods have small diameters up to 13 mm, and are naturally appropriate as coiled products.In fact, Class B and C types each have a nominal diameter of 7.4 mm to 13 mm, and Type D has a nominal diameter of 7.4 mm to 11 mm. is shipped as a coiled product. However, the only exception is the nickname 13m.
For mD type irregular shaped rods, the inner diameter of 2 turns is at least 260 mm, which is unsuitable for truck transportation due to the relationship between strength and bending stress during winding.
If the diameter is not greater than 0 mm, the elastic limit will be exceeded, so
The conventional method was to cut it into a predetermined length and ship it after giving it a certain mechanical property.

(Problems with the prior art) When using PC steel, especially those with a relatively small diameter used for piles and poles, it is necessary to unwind the coiled material to the required length before use, which reduces the material yield. It is welcomed by users as being good. The name of the 13mm type odd-shaped rod is pile.
Although it is used for poles, due to the relationship between strength and transportation, as mentioned above, it is not shipped to a fixed length from the factory (
If a user who obtains standard length materials is trying to improve the yield, he or she will end up using the specified length at the very edge of the required length, making it inconvenient to use. If an attempt was made to improve the quality, the specified length would have to be longer than the required length, resulting in a poor yield, and there was a need for an improvement measure.

(Objective of the Invention) The present invention was made to solve the above-mentioned problems of the 13mm D type variant in the pcJli rod.
After imparting predetermined mechanical properties as a prestressed steel bar, it can be wound around a small inner winding diameter to enable truck transport, restore linearity during use, and provide various mechanical properties that satisfy JIS standards. By searching and setting the winding and unwinding conditions such as having the following properties, users can obtain products with good yield and usability
The purpose of the present invention is to provide a method for manufacturing a deformed PC steel bar.

(Structure of the invention) The configuration of the present invention is as follows: (1) A raw steel wire rod of a predetermined diameter is rolled into a coil.

It is shaped to a nominal diameter of 13 mm and subjected to heat treatment and other treatments during continuous feeding to reach a yield point of 130 Kgf.
/ m g or more, tensile strength; 145 Kgf/mm'
The above and the various properties required for a PCil rod are imparted, (2) the arc height value is 15 m to the subsequently running wire.
After imparting a bend in the winding direction within a range not exceeding m / M, (3) winding it to a predetermined inner diameter to form a coiled material, (4
) The coiled material is unwound and straightened as lightly as possible to recover its linearity when used.It is called 13mmD type variant P (in the JR rod manufacturing method).

(Function of the invention) The present invention provides a method for applying the material steel wire rod to a predetermined process.
After imparting mechanical properties for use with mmD type PC steel bars, the resulting wire has an arc height value of 1 when bent toward the winding side.
By applying pre-bending within a range not exceeding 5mm/M, even if the rod is wound to a predetermined winding inner diameter that exceeds the elastic limit, it can be used as a straight bar with mechanical properties that meet the standard values with only slight straightening. It has the effect of reducing the winding torque required when winding to a predetermined inner diameter exceeding the elastic limit, and the effect of alleviating the difficulty of unraveling during unwinding.

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

In FIG. 1(a), Ll is a production line installed on the manufacturer's side, and payoff stand 1. Straightening machine 2a・
2b, a quenching device 3 consisting of predetermined heating means and rapid cooling means;
．． 4. A tempering device comprising predetermined heating means and cooling means. Pre-bending equipment 51 winding stand 6. and drive rollers 7 arranged at a plurality of locations. Further, L2 is a rewinding line installed by the user of the irregular shape pile, which is a manufacturer of piles, poles, etc., and the rewinding stand 8. It is composed of straightening machines 9a and 9b and a drive roller 7. An arrow drawn from the winding stand 6 of the production line L1 to the unwinding stand 8 of the unwinding line L2 indicates truck transportation.

The prebending device 5 in the production line L1 is
For example, three rolls R1~ as shown in FIG. 1(b)
R3, each peripheral surface exhibits a concave arc, and the roll R
The upper circumferential surfaces of rolls R1 and R3 in the drawing are arranged at a predetermined interval with the straight wire feeding path l as a common tangent, and the roll R2, which is disposed in the middle of the above-mentioned interval, has the lower circumferential surface in the drawing. The roll center 0 is placed at a position vertically H toward the rolls R1 and R3 from the imaginary roll center O'' drawn by a broken line with the wire rod feed path β as a tangent to the wire rod feed path l. The roll R2 is a push roll, and the wire that is driven by the drive roll 7 and travels through the wire rod feeding path 1 is subjected to a push load from above according to the push (jlH) of the push roll R2. The winding stand 6 at the front in the feeding direction is set to wind up a wire rod which has been given an upwardly curved bending deformation in a winding direction corresponding to the bending deformation.

As shown in FIG. 1(c), the straightening machines 9a and 9b in the unwinding line L2 are
．． The straightening machine 9 has pushing rolls shown as bl to b6.
A is a vertical type so that a predetermined indentation load can be applied to the wire from the vertical direction, and straight i9b is a horizontal type so that a predetermined pushing load can be applied to the wire from the lateral direction.

In the above configuration, the raw steel wire W is unwound from the unwinding stand, passed through the straightening machines 2a and 2b, made into a straight line, and continuously fed to the hardening device 3 and the tempering device 4. . While the raw steel wire W passes through the quenching device 3 and the tempering device 4 under a predetermined tension applied state by the drive roller 7,
Yield point: 130Kgf/mtd or more, tensile strength: 14
5 Kgf/mrr? In addition to the above, the deformed PC &
li! The wire becomes a high-strength steel wire for rods, then travels to the pre-bending device 5, where it is given a predetermined amount of bending, and then wound onto a winding stand 6 with an inner diameter of 2, for example, 2200 mm.

The coiled high-strength steel wire is transported from the manufacturer to the user by truck as shown by the arrow, and is attached to the unwinding stand 8 of the unwinding line L2 on the user's side, where it is processed according to demand. It is rewound by the traction force of the drive roller rough by the required length.
By passing the wire through the wire, the winding distortion caused during winding is slightly corrected and linearity is restored, and the wire is used as a deformed PC steel bar, which is a straight bar with a diameter of 13 mm, for example, in the manufacture of piles, poles, etc.

In the present invention, the amount of bending of the wire rod obtained according to the push (IH) by the push roll R2 of the pre-bending device 5, that is, the arc height value shown as h in FIG. 2 (the amount of bend after springback against push; mm7M )
■ How does this affect the mechanical properties of the steel bar during use? ■ Difficulty of winding after bending 1 What is the workability and appearance of the winding? ■ Difficulty of unwinding before use Since the important points are how γ affects the straightening before use, etc., the following experiment was conducted to find the appropriate value.

〔experiment〕

☆Material steel wire rod: 535C3i material However, the chemical composition is shown in Table 1. It was exactly as expected.

Wire diameter: 14 mm Table 1: Preparation of specimen 2. Materials listed above! After pickling the wire rod, it was drawn into a special shape with a nominal diameter of 13 mm, and this was shown in Figure 1 (
Straightening machines 2a and 2b in the production line L1 shown in a),
Quenching equipment 3. The wire rod was continuously fed to a tempering device 4 to obtain a wire rod that maintained linearity and had various mechanical properties as a type D deformed PC steel rod, and this was used as a specimen wire rod.

The heat treatment conditions were as shown below.

Quenching: Heating temperature - 1030℃ Quenching cooling - Water cooling Tempering: Heating temperature - 550℃ However, σB 150Kgf / mn? Return temperature cooling with a target of -・・−・・−・−−−11 Water cooling ☆ Experimental method 2 The above specimen wire was sent to the prebending device 5 with various set indentation amounts H to determine the arc height value. In addition to using wire rods with different diameters, the winding inner diameter is 2200 mm on the winding retandro.
mm, and the further wound specimen wire is sent to the unwinding line L2, and straightened by straightening machines 9a and 9b to make a straight bar.During this process, and the obtained straight bar, various It was subjected to the test.

In addition, when straightening to make a straight bar, we initially attempted to set conditions that aimed at minimizing the amount of correction, but during the experimental process, we found that the linearity became unstable when the amount of indentation was less than 3.3 mm. Since it was found that the mechanical properties were significantly deteriorated when the indentation depth exceeded .5 mm, the indentation amount for all the specimen wires was unified under the conditions shown in Table 2.

Table 2 ☆ Test ○ Pre-bending condition search/setting test; The rolls R1 to R3 of the pre-bending device 5 and their arrangement were as shown below, and wire rods with different arc height values were obtained by changing the pushing amount H using the device. The test results are shown in Table 3.

Roll dimensions used: R1-R3 all have the same valley diameter---
--・-90mm Mountain diameter ---100mm Distance between R1 and R3: 115rnm Table 3 (n=5) 0 winding required torque measurement test; easily winding the specimen wire on the winding stand 6 with an inner diameter of 2200 mm The winding torque was measured. The measurement results are shown in the specified column of Appendix Table 4, along with the required torque when winding with a winding inner diameter of 2600 mm (winding diameter that does not cause plastic deformation, hereinafter referred to as conventional product).

O-straightening test: As shown in Table 2 above, specimen steel wires with different arc height values obtained by varying the indentation amount H were straightened, and the amount of bending (mm/M) immediately after straightening was measured. . The measurement results are shown in the designated columns of Appendix Table 4.

○Various tests regarding mechanical properties: After heat treatment, pre-bending with different arc height values was performed, and the winding inner diameter was 220.
The specimen was wound to a thickness of 0 mm and then straightened into a straight bar.
Each was subjected to various tests regarding mechanical properties according to the test methods specified in JIS. Note that the number of subjects was 4 to 5. The test results are shown in Appendix Table 4 along with those of the conventional product.

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

○Residual stress measurement test: Using an X-ray stress measurement device, test wires were tested using an X-ray stress measuring device to measure the heat-treated wire specimen, the pre-bend wire specimen with a different arc height value, the pre-bend wire specimen that had been pre-bended and wound to an internal winding diameter of 2200 mm, and then straightened. For each of the test wire rods that were straightened into straight rods, the residual stress on the inside and outside in the axial direction related to bending was measured. The measurement results for the inside (a) and the outside (b) of FIG. 4 are shown as a line graph for each different arc height value.

In addition, the measurement results of the specimen wire with an arc height value of hi4s (level) are also shown in the same figure.

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

(1) Regarding a straight bar that was not prebended after heat treatment (arc height value h: 0) and was wound and straightened with a winding inner diameter of 2200 mm.

* Winding: Requires nearly twice the winding torque compared to conventional products.

*Slightly defective due to springback in the winding.

*Rewinding: Maintains high elasticity, is highly dangerous and has poor workability.

*Amount of bending immediately after straightening 2 Although the amount of bending is small, it is uneven and not constant.

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

(2) After heat treatment, perform pre-bending to reduce the inner diameter of the winding to 2
About the straight rod that was wound and straightened as 2QOmm.

1. Arkheight 5.

* Winding: Easy to wind with less winding torque than conventional products.

*Scroll appearance: Good condition.

*Good workability during rewinding.

*Amount of bending after straightening: Good.

*Mechanical properties: Tensile strength, yield point, elongation, and area of area are almost the same as conventional products, but the relaxation value is almost the same as that of a product that was immediately wound to an inner diameter of 2200 mm and straightened without pre-bending, and slightly Although it shows a decrease in the temperature, it fully satisfies the JIS standard.

2.7-') High '&10 (F!'*)hLfb
(D.

* Winding: Like the above arc height value 5, winding is easy.

* Roll appearance: Good *Rewinding: Good workability.

*Amount of bending immediately after straightening: There is some bending, but it does not affect use.

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

*By performing residual correction, both the inner and outer surfaces have been restored to almost O.

3. Arc height 15 (7, V).

* Winding: Easy to wind.

Mizumaki form: Wrapped somewhat irregularly.

*Rewinding: Good workability. The amount of bending after unwinding is constant.

*Amount of bending immediately after straightening: The surface is somewhat noticeable and may cause problems.

*Mechanical properties: Tensile strength 1 yield point, elongation, and area of area are almost the same as conventional products, but relaxation value is JIS
There is a risk of deviating from the rules.

4.7-kuhai 120F.

* Winding: Both are easy to wind.

Mizumaki form: Wound extremely irregularly.

*Rewinding: Workability is extremely poor due to intertwining.

*Amount of bending immediately after straightening: Straightness is not restored, causing problems in use.

*Mechanical properties: Compared to conventional products, the tensile strength, elongation, and area of area are unchanged, but the yield point is noticeably lower, and the relaxation value does not meet JIS standards.

* Even if the residual stress is straightened, neither the inside nor the outside will recover to O.

From the above considerations, it can be concluded that the processing method of immediately winding beyond the elastic limit after imparting the specified mechanical properties and straightening it during use will yield a straight bar with sufficient mechanical properties, but will reduce the per-winding torque and workability. It has been confirmed that the processing method of applying pre-bending to an arc height value of 15 or more, winding it up, and straightening it before use is unsuitable in terms of the required mechanical properties and residual stress.

On the other hand, a processing method in which a light pre-bending with an arc height value of less than 15 is performed, then the winding is performed, and then a light straightening is performed during use, is a processing method that takes into account various mechanical properties, residual stress, 2 winding torques, 1 winding shape, 2 workability, etc. Since it has been proven that all points are satisfactory, the present invention makes this treatment method a part of the method for manufacturing 13 mm D type deformed PC steel bars.

(Effects of the Invention) By carrying out the present invention, the 13 mm D variant PC steel rod can be transported by truck as a coiled material, and the user can unwind the coiled material and perform light straightening as required during use. It can be used as a straight bar due to its length, which greatly contributes to improving yield and ease of use.

[Brief explanation of the drawing]

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

Claims (1)

[Claims] 1) A raw steel wire rod of a predetermined diameter wound into a coil is deformed to a nominal diameter of 13 mm, and subjected to heat treatment and other treatments during continuous feeding to yield a yield point of 130 Kgf/md.
or more, tensile strength; 145Kgf/mm or more, and PC
After imparting the various properties required for a steel bar and subsequently imparting a bend in the winding direction within a range that does not exceed an arc height value of 15 mm/M to the running wire, the wire is wound to a predetermined inner diameter to form a coil. The coiled material is unwound and straightened as lightly as possible to restore linearity when used.
A method for producing different types of PC steel bars. 2) The inner diameter of the coiled material is 2000 mm or more, 260 mm.
Name 1 described in claim 1, which is less than 0 mm
A method for manufacturing a 3mmD type deformed PC steel bar.