JP2009095859A - Steel wire excellent in twisting properties, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a steel wire that hardly causes a vertical crack and to provide a steel cord stable in its quality. <P>SOLUTION: A steel wire 3 produced by dry-drawing process is subjected to a patenting process, a plating process, and further, a wet-drawing process using a lubricating oil 2 at temperature of 25 to 50°C. By this way, the steel wire is formed which is excellent in the twisting properties satisfying the expression (1): TN≥-0.025×A+52, herein, 400≤A≤2,080 and the expression (2): A=(TS-TS<SB>0</SB>)/exp(ε/4) wherein TN is a twisting value (times), A is a work hardening coefficient, ε is a true distortion by wet-drawing process, TS is a tensile strength [MPa] after wet-drawing process, TS<SB>0</SB>is a tensile strength [MPa] before wet-drawing process. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a steel wire excellent in twisting characteristics and a method for manufacturing the same, and more particularly to a steel wire used for a steel cord.

  A steel cord formed by twisting a plurality of steel wires is used as a reinforcing material for rubber products, and is widely used in various industrial fields such as automobile tires and conveyor belts. A steel wire used as an element wire of a steel cord is manufactured as follows. First, a high carbon steel wire manufactured by hot rolling is dry-drawn to a wire diameter of 0.95 mm to 3.00 mm, and then lead patenting is performed in order to remove distortion generated by dry drawing. As a result, a pearlite structure is deposited on the steel wire. Next, in order to improve the drawability, the steel wire is subjected to a plating treatment. Finally, an ultrafine steel wire having a desired wire diameter (0.150 mm to 0.410 mm) is obtained by wet drawing.

As described in Patent Document 1, the ultrafine steel wire manufactured as described above is obtained by twisting the ultrafine steel wires with a buncher or a tubular-type strand wire machine and vulcanizing the tire. A code is manufactured.
JP 2006-249635 A

  However, when twisting the steel wire, stress in the twisting direction is applied to the steel wire, so that there is a problem that delamination (longitudinal cracking) is likely to occur in the steel wire.

  As a method for solving such a problem, Japanese Patent Application Laid-Open No. 2002-28716 discloses that when a steel wire is continuously drawn, a wet lubricant is used at a temperature of 5 ° C. or lower (or 0 ° C. or lower). A method of wire processing (Claim 1 of JP-A-2002-28716, etc.) is described, and it is described that vertical cracking of a wire used for a steel cord can be prevented by lowering the temperature of the lubricating liquid. (FIG. 1 of Unexamined-Japanese-Patent No. 2002-28716).

  As described in this patent publication, based on the fact that the longitudinal cracking of the wire used in the steel cord can be prevented by lowering the lubricating liquid, the present inventor has the problem of preventing the longitudinal cracking of the steel wire rod. Numerous tests and research have been accumulated. As a result, it was found that when the temperature of the lubricant is lowered, the twisting characteristic is rather deteriorated, and when the temperature of the lubricating liquid is increased, the twisting characteristic is enhanced. Furthermore, the present inventors have found that the twisting characteristic has a specific relationship with a work hardening coefficient (described later) by wet drawing, and completed the present invention.

  A method of manufacturing a steel wire rod that has solved the above-mentioned problems is a method of performing a patenting treatment on a steel wire that has been dry-drawn, performing a plating treatment, and further drawing by wet drawing using a lubricating liquid at a temperature of 25 to 50 ° C. It is.

Moreover, the steel wire which has solved the above-mentioned problems is obtained by the above production method, and satisfies the following formulas (1) and (2).
TN ≧ −0.025 × A + 52 (1)
However, 400 ≦ A ≦ 2080
A = (TS−TS ₀ ) / exp (ε / 4) (2)
However, TN [times]: twist value, A: work hardening coefficient, ε: true strain by wet wire drawing, TS [MPa]: tensile strength after wet wire drawing, TS ₀ [MPa]: before wet wire drawing The tensile strength of

  Moreover, the said steel wire can be made into the aspect in which the lubricating liquid used in the case of the said wet wire drawing contains the water of the range of 60 mass% or more and 90 mass% or less.

  In the steel wire, an embodiment in which the wet wire drawing is performed by a submerged type (immersion type) is preferably used.

  The steel wire material is preferably such that the wet drawing is performed by a plurality of dies, and the area reduction rate by the first passing die is smaller than the area reduction rate by the second passing die.

  In the steel wire material, it is preferable that the wet wire drawing is performed by a plurality of dies, the last die to be passed is a double die, and correction is performed by a roller or a blade after passing through the final die.

  A steel cord can be manufactured by twisting one of the above steel wires.

  According to the present invention, by drawing a steel wire by wet drawing using a lubricating liquid at a temperature of 25 to 50 ° C., it is possible to produce a steel wire that is less prone to vertical cracking due to stranded wire, and stable quality. Steel cord can be provided.

  Hereinafter, the manufacturing method of the steel wire material concerning embodiment of this invention is demonstrated. FIG. 1 is a flowchart of a wire drawing process in the embodiment of the present invention.

(Outline of steel cord manufacturing process example)
In FIG. 1, a steel wire having a wire diameter of 0.95 to 2.10 mm is obtained by drawing a steel wire having a wire diameter of 5.5 mm subjected to the pre-drawing process by a dry drawing method. Next, the steel wire is subjected to patenting treatment and brass plating treatment. Subsequently, a steel wire rod having a wire diameter of 0.150 mm to 0.410 mm is obtained by wet wire drawing in which the steel wire rod is immersed in a lubricating liquid. Finally, the steel wires are twisted together with a buncher or a tubular type twisted wire machine, and the tire is vulcanized to produce a steel cord.

(Details of each process)
In the process up to the pre-drawing treatment, the steel piece is heated to about 1150 ° C. and hot-rolled to produce a steel wire having a diameter of 5.5 mm. Thereafter, the steel wire material is controlled (adjusted) and cooled on the stealmore conveyor, so that the steel wire material has a ferrite / pearlite structure. Furthermore, after the scale adhering to the surface of the steel wire is removed, the steel wire is coated.

  Conventionally, the wire drawing pretreatment was usually performed after the steel wire was pickled, and then the zinc phosphate (bonde) coating was applied. However, due to environmental problems, the scale was removed by a mechanical descaler without using acid, and the wire drawing was performed. During the wire process (in-line), it is becoming common to perform a borax film treatment described below.

  In the dry wire drawing step, for example, a steel wire having a wire diameter of 0.95 to 2.10 mm is obtained by drawing a steel wire having a wire diameter of 5.5 mm supplied from a lot by a dry wire drawing method. In the dry wire drawing device, a plurality of dies (not shown) are arranged in series, and the steel wire material is gradually thinned each time it passes through one die. Depending on the target wire diameter and the wire speed at that time, the number of passes through the dry wire drawing device may be one or may be divided into a plurality of times.

The dry wire drawing apparatus is provided with a borax apparatus which is a coating liquid adhesion apparatus. In the borax apparatus, a borax solution (a compound of 10 hydrate represented by Na ₂ B ₄ O ₇ .10H ₂ O) is stored. The borax liquid is heated to 40 to 95 ° C, preferably 80 to 90 ° C. As the steel wire travels in the borax liquid, borax adheres to the surface of the steel wire. After the borax apparatus, a drying path for supplying hot air of 200 ° C. is provided, and the borax is dried. Generally, when it is dried to about 2-3 hydrates, it becomes easy to adhere a solid lubricant for dry drawing to a steel wire.

As a coating solution used in such a coating solution deposition apparatus, besides borax, for example, sodium sulfate (Na ₂ SO ₄ ), sodium sulfite (Na ₂ SO ₃ ), sodium metasilicate (Na ₂ SiO ₃ ), An aqueous solution mainly composed of sodium salt such as sodium orthosilicate (Na ₂ SiO ₄ ), potassium sulfate (K ₂ SO ₄ ), potassium tetraborate (K ₂ B ₄ O ₇ ), potassium pentaborate (KB ₅ O ₈₎ ), Potassium metaborate (KB ₅ O ₂ ), potassium metasilicate (K ₂ SiO ₃ ), potassium tetrasilicate (K ₂ Si ₄ O ₉ ), potassium hydrogen silicate (KHSi ₂ O ₅ ), etc. An aqueous solution as a component, a mixed aqueous solution of sodium salt and potassium salt, lime solution, or the like can also be selected. These coating solutions are preferably heated to 40 to 95 ° C. in advance.

  After the dry wire drawing is completed, a patenting process (after austenitizing, rapid cooling with a salt bath, a lead bath, etc.) is performed in order to remove processing distortion and obtain fine pearlite. As described above, when dry drawing is performed in a plurality of times, an intermediate patenting process may be performed every time one dry drawing is completed.

  Next, for the purpose of improving drawability in wet drawing and improving adhesion to tire rubber, brass made of Cu and Zn is plated on the surface of the steel wire. Plating is preferably performed uniformly, and the plating thickness is desirably 1 to 6 μm (preferably 2 to 5 μm).

  Subsequently, a steel wire having a wire diameter of, for example, 0.150 mm to 0.410 mm is obtained by wet drawing in which the steel wire is dipped in a lubricating liquid. FIG. 2 is a diagram showing a wet wire drawing machine in the embodiment of the present invention. As shown in FIG. 2, a lubricating liquid 2 is stored in the wet wire drawing machine 1. In this lubricating liquid 2, a group of dies for reducing the surface of the steel wire 3 (first die 4S, last double die 4E, die 4M located between them (to avoid drawing complexity) And a pair of capstans 5 and 6 for guiding the steel wire 3 to pass through these dies. The capstans 5 and 6 are driven by the rotation of the wire drawing machine motor, and the steel wire 3 is successively reduced by the dies 4S to 4E.

  As the lubricating liquid 2, a solution containing 60 to 90% by mass (preferably 70 to 80% by mass) of water and mixed with a fatty acid, an amine salt, and a surfactant (for example, sodium stearate) was used.

  Moreover, the heater 7 is provided in the lubricating liquid 2, and the temperature of the lubricating liquid 2 is set to the range of 25-50 degreeC. By controlling the temperature of the lubricating liquid 2 within this range, the twisting characteristic of the steel wire 3 is improved as will be shown in the later-described experiment. When the temperature of the lubricating liquid 2 is less than 20 ° C., it is difficult to emulsify (emulsify) the lubricating liquid, and the fatty acid is difficult to be adsorbed to the steel wire 3. Since the gist of the present invention is to improve the twisting characteristics of the steel wire 3 by setting the temperature of the lubricating liquid 2 to 25 ° C. or higher, the upper limit of the temperature is not particularly limited. When the temperature exceeds 50 ° C., the fatty acid deteriorates due to the long-term use of the lubricating liquid 2, the frequency of seizure and disconnection increases, and the twist value also decreases. It was street. A more preferable range of the temperature of the lubricating liquid 2 is 30 to 45 ° C.

The steel wire manufactured as described above has excellent twist characteristics. That is, the twist value of the drawn steel wire is TN [times], the work hardening coefficient is A, the true strain due to wet wire drawing is ε, the tensile strength after wet wire drawing is TS [MPa], and wet wire drawing. If the previous tensile strength is defined as TS ₀ [MPa], the following equation (1) is easily satisfied.
TN ≧ −0.025 × A + 52 (1)
However, 400 ≦ A ≦ 2080
A = (TS−TS ₀ ) / exp (ε / 4) (2)

  In the above formula (1), 400 ≦ A is because if the work hardening coefficient is less than 400, the problem of vertical cracks usually does not occur, and A ≦ 2080 is set because A exceeds 2080. The twist value TN is less than 0, which is physically impossible.

  The wet wire drawing in the embodiment of the present invention does not necessarily have to be performed by the all-immersion method (immersion method), but may be performed by the injection method, but if performed by the all-immersion method, the heater immersed in the lubricating liquid is used. By using it, the temperature of the lubricating liquid can be uniformly controlled, and the effect of the present invention of improving the twisting characteristics can be obtained more reliably.

  In the wet wire drawing in the embodiment of the present invention, it is desirable to use a slip-type wire drawing machine and make the area reduction rate of the first die 4S to be smaller than the area reduction rate by the second die 4M. In other words, it is desirable that the first pass be lightly reduced. For example, when the area reduction rate by the second passing die 4M is 15% or more and 16% or less, the area reduction rate by the first passing die 4S is preferably 10% or more and less than 15%. This is because if it is less than 10% or 15% or more, the slip ratio cannot be accommodated, and disconnection may occur.

  The slip-type wire drawing machine is a wet wire drawing machine in which the peripheral speed of the capstan is slightly faster than the line speed in anticipation of the hole diameter and wear of the die. The slip ratio represents the delay of the steel wire passing over the capstan circumference with respect to the capstan circumferential speed, and is desirably as small as possible and constant.

  In the above manufacturing method, it is preferable that wet wire drawing is performed with a plurality of dies, and the last die to be passed is a double die 4E, and after passing through the double die 4E, correction with a roller or a blade is performed. Thereby, the improvement of the twist characteristic of a steel wire becomes more reliable.

  As shown in FIG. 2 or FIG. 3 which is an enlarged view of the double die, the double die is a continuous arrangement of two dies, and the second die is lighter. The surface is reduced (for example, the reduction rate is 2 to 7%). Moreover, the state of correction by a roller is shown in FIG. FIG. 4 shows a process of sandwiching the steel wire with a plurality of bending rollers and correcting the peculiarity of the steel wire.

  Although the chemical composition and structure of the wire used in the present embodiment are not particularly limited, in order to further improve the longitudinal crack resistance of the wire, the chemical composition of steel is C: 0.6 to 1.2% by mass ( Preferably 0.8 to 1.1 mass%), Si: 0.05 to 1.2 mass% (preferably 0.1 to 0.8 mass%), Mn: 0.2 to 1.0 mass% ( Preferably 0.3 to 0.8 mass%), P: 0.02 mass% or less (excluding 0 mass%), S: 0.03 mass% or less (not including 0 mass%), Cr: 0 Desirably, 0.01 to 1.0% by mass (preferably 0.02 to 0.5% by mass), balance: iron and inevitable impurities.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

  A billet having a chemical composition shown in Table 1 is produced by a continuous casting machine, heated for 3 hours, and then a billet having a cross-sectional shape of 155 mm × 155 mm can be produced by split rolling. After heating this to 1150 degreeC, hot rolling is performed and the wire diameter: 5.5 mm is obtained. The wound steel wire was applied to a stealmore cooling device, and the steel wire was controlled and cooled on a stealmore conveyor to obtain a ferrite / pearlite structure.

  After removing the scale of the surface of the obtained steel wire with a mechanical descaler, a borax film is applied, and a solid lubricant mainly composed of sodium stearate is adhered to dry wire diameters from 0.95 mm to 2.10 mm. Drawing was performed. In order to control the obtained steel wire to a fine pearlite structure, final patenting (heating temperature 960 ° C., constant temperature holding temperature 560 ° C.) was performed. The obtained steel wire was plated with brass made of Cu and Zn to obtain a test steel wire. The plating thickness was 3.7 μm.

The obtained test steel wire was subjected to a slip-type continuous wet wire drawing machine and drawn until the final wire diameter became 0.170 to 0.410 mm. The conditions for wet wire drawing are as follows.
Wet wire drawing machine: FM26 type continuous wire drawing machine manufactured by Saikawa Co., Ltd. Lubricant: 30% by mass of F. Colube manufactured by ADEKA Chemical Supply Co., Ltd.
What added 70 mass% of water was prepared.
Lubricating liquid temperature: 7 ° C, 20 ° C, 40 ° C
Die area reduction: 15%
Area reduction ratio of the first die (first pass): as described in Tables 2 to 4 Area reduction ratio of the final die (double die): front stage ... 12.3%, rear stage ... 3.0%

About the steel wire which passed the double die, the correction process shown in FIG. 4 was also performed.
The result of the twist test done about the obtained steel wire is described in Tables 2-4. In the twisting test, a test piece having a length of 200 mm is taken from a steel wire, and the test is performed under the conditions of a distance between gauge points: 50 mm and a twisting speed: 1 rpm, and the number of twists (times) and breaking torque ( N · m) was measured, and the number of twists (twist value in terms of 100D) when the distance between the gauge points was [diameter (D) × 100] was calculated based on the following formula (3).
Twist value (100D conversion) = twist number × (diameter / distance between gauge points) × 100 (3)

  In Tables 2 to 4, when the value of the expression (3) derived from the experimental value is larger than the right side of the expression (1) that is the calculated value, that is, when the inequality of the expression (1) is established, Longitudinal cracks have not occurred.

  FIG. 5 is a plot of the experimental results in Tables 2 to 4, with the work hardening coefficient A on the horizontal axis and the twist value TN on the vertical axis. In FIG. 5, (□) indicates that the temperature of the lubricating liquid is 40 ° C., (◇) indicates that the temperature of the lubricating liquid is 20 ° C., and (Δ) indicates that the temperature of the lubricating liquid is The case of 7 ° C. is shown, and the inside of each symbol (for example, (♦), (▲)) indicates a test example in which vertical cracking occurred.

  As is apparent from FIG. 5, in the case of a low temperature (7 ° C.) lubricating liquid which has been conventionally considered to improve the twisting characteristic, the twisting value (▲) is low in most cases. And (□) showing the case where the temperature of the lubricating liquid is 40 ° C. is located at a position where the twist value is generally higher than (□) showing the case where the temperature of the lubricating liquid is 20 ° C., and the twist characteristic is It can be seen that it has improved.

  Moreover, as shown in Table 3, although the vertical crack occurred in the steel wire rod 44 that did not pass through the double die and was not subjected to the straightening treatment, the steel wire rod 41 (stretched through the double die and subjected to the straightening treatment). In the wire condition, the vertical crack is not generated in the steel wire material 44). Similarly, although the vertical crack is generated in the steel wire material 45, the steel wire material 43 (the wire drawing condition is the same as the steel wire material 45). Then, no vertical crack has occurred. Although these are examples in which the temperature of the lubricating liquid is 20 ° C., it is understood that it is effective to prevent vertical cracks by subjecting the steel wire material to double die and straightening treatment.

FIG. 1 is a flowchart of a wire drawing process in the embodiment of the present invention. FIG. 2 is a diagram showing a wet wire drawing apparatus according to an embodiment of the present invention. FIG. 3 is a partially enlarged view of the wet wire drawing apparatus in the embodiment of the present invention. FIG. 4 is a diagram showing a correction device according to the embodiment of the present invention. FIG. 5 is a diagram showing twist characteristics in the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wet wire drawing machine 2 Lubricating liquid 3 Steel wire rod 4S Dies 4M Dies 4E Double dies 5 Capstan 6 Capstan 7 Heater

Claims (7)

  A steel wire rod excellent in twisting characteristics, characterized in that a dry-drawn steel wire rod is subjected to patenting treatment, plating treatment, and wire drawing by wet drawing using a lubricating liquid at a temperature of 25 to 50 ° C. Production method. A steel wire rod obtained by the production method according to claim 1 and having excellent twisting characteristics satisfying the following formulas (1) and (2).
TN ≧ −0.025 × A + 52 (1)
However, 400 ≦ A ≦ 2080
A = (TS−TS ₀ ) / exp (ε / 4) (2)
However, TN [times]: twist value, A: work hardening coefficient, ε: true strain by wet wire drawing, TS [MPa]: tensile strength after wet wire drawing, TS ₀ [MPa]: before wet wire drawing The tensile strength of   The steel wire according to claim 2, wherein the lubricating liquid used for the wet wire drawing contains water in a range of 60 mass% or more and 90 mass% or less.   The steel wire rod according to claim 2 or 3, wherein the wet wire drawing is performed by a submerged type.   The steel according to any one of claims 2 to 4, wherein the wet drawing is performed by a plurality of dies, and the area reduction rate by the first passing die is smaller than the area reduction rate by the second passing die. wire.   6. The wet drawing is performed by a plurality of dies, the last passing die is a double die, and after passing through the final die, correction is performed by a roller or a blade. Steel wire rod according to crab.   The steel cord obtained by twisting together the steel wire materials in any one of Claims 2-6.

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