JPH08246099A - High strength steel linear body and its production - Google Patents

Abstract

PURPOSE: To produce a high strength steel linear body having required straightness by subjecting a steel having a specified compsn. to heat treatment to straightening and further subjecting the straightened steel to a straightening before its cutting to a prescribed length. CONSTITUTION: A steel contg., by weight, 0.20 to 0.40% C, 0.05 to 2.00% Si, 0.60 to 2.00% Mn and 0.10 to 2.00% Cr, and the balance Fe with inevitable impurities is subjected to hot rolling and is immediately subjected to rapid cooling in warm water to form into a linear body in which the diameter of a martensitic structure is regulated to about 10mm. This linear body is tempered, is thereafter subjected to straightening of <=1.0% bending strain and is cut to a prescribed length to regulate the straightness in 1.5m of the cut linear body to <=1.0mm. Thus, the steel linear body having required straightness without executing severe production control and inventory control can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prestressed concrete (PC), particularly a high strength steel filament used for a tension material such as high strength pile and pole, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as this type of steel filament, a steel wire is hardened and tempered to obtain a predetermined high strength, and a wire rod is patented and then drawn to a predetermined high strength. Some have gained strength. The present invention relates to the former, and the former will be described below.

The PC steel wire obtained by quenching and tempering is usually wound into a coil, and when it is used for manufacturing a high strength pile or pole, it is cut into a predetermined length, Heading processing and thread rolling processing for fixing after tension are applied to both ends thereof. A basket knitting is performed by spot welding a reinforcing steel wire around a plurality of PC steel wires that have been subjected to this processing. After mounting this basket in the mold, high-strength piles and poles are manufactured by tension load, concrete pouring, centrifugal molding, concrete hardening by steam curing, and the like.

Regarding the production of PC steel wire by the heat treatment of quenching and tempering, the following three methods are known.
One of them is using wire rods that have been hot-rolled, which have been subjected to wire drawing or profile processing to increase adhesion with concrete in order to obtain a predetermined wire diameter, then heat and quench to the austenite state. After that, it is a method of performing tempering heating for obtaining a predetermined strength and toughness, cooling and winding in a coil shape.

The other is a method proposed by Japanese Examined Patent Publication No. 3-79410 for imparting bending strain in a tempered heating state in order to improve the relaxation characteristics of PC steel wire.

[0006] Another one is that the hot-rolled wire proposed by Japanese Patent Publication No. 61-15926 is immediately tempered by forced cooling or wind, and then self-tempering (self-tempering).
Is a method of obtaining a steel wire having a predetermined strength and toughness, and further performing warm straightening to provide a PC steel wire having excellent straightness and relaxation characteristics.

[0007]

When manufacturing high-strength piles and poles, PC steel wires are cut into required lengths of about several tens of cm to about 20 m, and the rear end is processed and used. It is required to have excellent straightness in terms of both the work and the basket knitting work during use.

Therefore, in the production of PC steel wire, measures such as selection of heat treatment conditions and straightening before winding into a coil are added.

However, the PC steel wire wound in the form of a coil is gradually curled during storage and its straightness is lowered. As measures against this, it is considered to increase the winding diameter and shorten the storage period, but the former is difficult to transport about 2 m or more, and the latter makes production and inventory management complicated. There is. Also, such as the above proposal,
The selection and addition in terms of manufacturing conditions still have problems such as an increase in the number of steps and an increase in cost.

[0010]

The present invention has been made to solve the above problems, and the first feature of the present invention is to specify the steel composition and heat treatment conditions so as to obtain a linear body. While improving the mechanical strength and straightness of
The straightening process was performed immediately before cutting to a predetermined length to ensure the straightness of the linear body having a predetermined length to be used.

A second feature is that a head having a specific shape and a specific tensile strength is provided at the end of the linear body having the predetermined length.

Another feature of the present invention is that the steel composition and various conditions in each step of heat treatment, straightening, and cutting are determined in order to produce the above-mentioned steel filament having high strength and excellent straightness. Is. The contents will be described in detail below with reference to Examples and Actions.

[0013]

EXAMPLES The compositions of steels in Examples and Comparative Examples shown in FIGS. 1 and 2 and Tables 1 and 2 are C: 0.30 in% by weight.
%, Si: 0.80%, Mn: 1.20%, Cr: 0.90%, and the balance Fe and unavoidable impurities. The diameter of the hot-rolled wire rod is 10 mm.

The manufacturing process of the steel filaments in Examples and Comparative Examples is as follows: (1) hot rolling, (2) quenching, (3) winding,
(4) Pot furnace tempering, (5) Rotary straightening, (6) Standard length cutting, and (7) Hot heading are specified during each of the following steps.

(2) Quenching Steel wire rolled to a diameter of 10 mm by the hot rolling of (1) is
While being sequentially wound into a ring, the steel wire is martensitic in its entirety by immersing and deploying it on a conveyor that moves in 90 ° C warm water and cooling at a cooling rate of 17 ° C / sec. (3) Winding The steel wire sent on the conveyor is wound and converged into a coil having an inner diameter of 1 m. (4) Pot furnace tempering The wound steel wire is charged into a pot furnace and tempered at 340 ° C.

(5) Rotational straightening processing One of the features of the present invention is when this processing is performed. Immediately before performing the next step of the fixed length cutting processing or as close as possible to the time when the cutting processing is performed. Is what you do. In this example, it was performed immediately before. The processing conditions were that the bending strain between the upper and lower straightening rolls was 0.3%, 0.6% and 1.0% in Examples 1, 2 and 3, respectively, and 1.2% and 1.5% in Comparative Examples 4 and 5, respectively. I set it so that it would pass through.

Table 1 shows the tensile strength, elongation and straightness of the straightened steel wire. As shown in FIG. 1, the straightness is represented by the value of the bending height H in mm when the value of the sample length L of the steel wire is 1.50 m.

[0018]

[Table 1]

(6) Standard length cutting process Depending on the specifications of the destination, it cuts from about 30 cm to about 20 m. In this embodiment, the length is 1.5 m.

(7) Hot Heading Process Hot heading process was applied to both ends of the cut steel wire. The processing conditions are those of Examples 2 and 2 as shown in Table 2 for Examples 2 and Comparative Example 4, respectively.
Heading processing was performed under different conditions so that the head shapes and dimensions of 2, 2-3 and Comparative Examples 4-1 and 4-2 were formed. The mechanical properties of each of these are also shown in Table 2.

[0021]

[Table 2]

The heading processed product is shipped and used for each purpose. Since it is not wound after the straightening process, there is no concern about deterioration of straightness due to curling. However, without applying this straightening process,
The tempered coil-wound steel wire of (4) may be shipped for free, and the straightening process of (5), the cutting process of (6), and the heading process of (7) may be performed at the place of use.

In the embodiment, the diameter of the steel wire is 10 m.
Although m, the temperature of hot water is 90 ° C and the tempering temperature is 340 ° C, the diameter may be 7 to 13 mm and the temperature may be 80 to 100 ° C. Also, a non-circular filament may be used.

[0024]

In the steel filament having the component system according to the present invention, if the diameter of the filament is about 7 to 13 mm, it is necessary to cool it at a cooling rate of 10 ° C / sec or more in order to uniformly quench the entire filament. . C as a component is added to enhance the hardenability and to obtain a predetermined strength. If it is less than 0.2%, its effect is weak, and if it exceeds 0.4%, the mechanical properties after spot welding are significantly deteriorated, which is not preferable. .

Si is effective for enhancing hardenability and strength and toughness, but if it is less than 0.05%, it is ineffective and 2.0
%, The toughness decreases, which is not preferable. Mn and Cr
Has an effect on hardenability, but 0.60-2.00% and 0.10-2.00 respectively
If it is less than%, the effect is not obtained, and if it exceeds this range, toughness is lowered and raw material cost is increased, which is not preferable.

The tempered steel wire is tempered at 300 to 500 ° C. This temperature was set to obtain strength as a reinforcing material for high strength piles and poles. The tempered coiled steel wire is subjected to repeated bending by a rotary straightening machine at a bending strain of 1.0% or less before cutting and straightening is straightened, but if the bending strain exceeds this, ductility decreases. So
In order to secure sufficient ductility, it was set to 1.0% or less. Of course, if it is too small, sufficient straightness cannot be obtained, so about 0.6% is preferable.

Furthermore, in order to fix the PC steel wire after tensioning, hot heading is applied to both ends or one end (the other end is to be threaded) of the cut steel wire. In order to sufficiently endure, the tensile strength of the head must be at least 90% or more of the predetermined strength of the steel wire matrix. In addition to this strength, a hardness of about 300 to 400 HmV is required to prevent the head from falling out during tensioning work and to prevent breakage due to delayed fracture during concrete steam curing.

In order to secure these, the shape of the head 1 is such that the diameter d of the enlarged portion is 1.8 to 2.2 times the diameter D of the steel wire,
The thickness T must be 0.7 to 2.0 times. In addition, in the examples, although the production method is specified, when viewed as a striatum, the characteristics are those obtained by the production method as described in the claims. Of course, other manufacturing methods may be used as long as they are equivalent or higher.

[0029]

Industrial Applicability According to the present invention, a steel filament having excellent straightness obtained by a specific steel composition and heat treatment is straightened before being cut into a predetermined length. Therefore, it is possible to obtain a steel wire strip having a required straightness without the need for special strict production control and inventory control as in the past.

In addition, the heading of the steel wire ends is also
Since it has an appropriate shape and strength, it is suitable as a tension material for high-strength piles and poles. Further, in the production, each specified process itself is not peculiar to each other, so that there is no special burden on facilities and operations, it is suitable for industrial production, and the production cost can be suppressed.

[Brief description of drawings]

FIG. 1 is a schematic side view of a steel filament for explaining the method for measuring the straightness of the steel filament in the present invention.

FIG. 2 is a schematic view from the side surface of the head for explaining the shape of the head provided at both ends or one end of the steel linear member of the present invention.

[Explanation of symbols]

 1 Head provided at the end of the steel filament D Diameter of the steel filament d Diameter of the enlarged portion of the head 1 T Thickness of the head 1 L Length of sample for measuring the straightness of the steel filament Sag H bending height at sample length L

Continuation of front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location E04C 5/08 E04C 5/08 (72) Inventor Taiji Mikami 1-1 1-1 Kunyokita, Itami City, Hyogo Prefecture Sumitomo Electric Industries, Ltd. Itami Works

Claims (4)

[Claims] 1. C: 0.20 to 0.40% by weight%, Si: 0.05
-2.00%, Mn: 0.60-2.00%, Cr: 0.10-2.00%, the balance consisting of Fe and unavoidable impurities is rapidly cooled in hot water immediately after hot rolling to form a martensitic striation. , After bending the filament, bending strain 1.0%
A high-strength steel filament, characterized in that a straightened piece is cut to a predetermined length and the straightness of the cut filament at 1.5 m is 1.0 mm or less. 2. The diameter of the enlarged portion is 1.8 to 2.2 times and the thickness is 0.7 to 2 times the diameter of the filament at one end or both ends of the filament.
The high-strength steel filament according to claim 1, wherein the head has a tensile strength of 0 times and the tensile strength of the head is 90% or more of the strength of the filament matrix. 3. C: 0.20 to 0.40% by weight, Si: 0.05
~ 2.00%, Mn: 0.60 ~ 2.00%, Cr: 0.10 ~ 2.00%, the balance of the steel consisting of Fe and unavoidable impurities, immediately after hot rolling, a continuous ring on the conveyor in hot water at 80 ~ 100 ℃ To form a martensite structure on the entire linear body by cooling it at a cooling rate of 10 ° C / sec or more, and converging the linear body into a coil and tempering it in a pot furnace at 300 to 500 ° C. And the step of paying out the coiled filamentous body and performing straightening correction within 1.0% of bending strain by a rotary straightening machine,
A method of manufacturing a high-strength steel filament, comprising the step of cutting the straightened filament into a predetermined length. 4. The diameter of the enlarged portion is 1.8 to 2.2 times the diameter of the linear body and the thickness is 0.7 to 2.0 by hot heading at one or both ends of the linear body cut into a predetermined length. 4. The manufacturing method according to claim 3, wherein a double head portion is formed, and the tensile strength of the head portion is 90% or more of the striatal matrix strength.