JP2008248321A - Recovery method of resistance to twist-induced breaking of high strength ultra-fine steel wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recovery method of resistance to twist-induced breaking of a high strength ultra-fine steel wire, the method being characterized in that the high strength ultra-fine steel wire having ≥3.0 wire-drawing stress after being patented or ≥3,000 MPa tensile strength and continuously advancing in the length direction is subjected to repeated operation in which the steel wire is twisted in one direction, then is restored to the original shape or twisted in the reverse direction in a similar way. <P>SOLUTION: The high strength ultra-fine steel wire is given the prescribed twist by using the prescribed number of apparatuses. Each of the apparatus has, as basic constitution, an original wire bobbin 1 for paying out the ultra-fine steel wire being the treating object, a twister 3 for applying a prescribed twist to the steel wire by rotating while incorporating a guide roller 2 for guiding the steel wire so that the steel wire is not come off, and an intermediate reel 4. After winding the steel wire at the suitable turns around the intermediate reel, the next twist in the reverse direction to the first twist, is applied to the steel wire by passing through the reversely rotated next twister. The steel wire is passed through the prescribed number of the apparatuses while adjusting the mutual positions of the apparatuses, the number of revolution per unit time and the speed of a winding apparatus, and thus prescribed twist are given to the high strength ultra-fine steel wires. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to high-strength ultrafine steel wires such as tires, belt cords, high-pressure hoses, etc., steel cords used for reinforcing rubber and organic materials.

  Generally, ultra-fine steel wire is hot-rolled, adjusted and cooled to a high carbon wire with a diameter of about 4.0 to 5.5 mm, after intermediate wire drawing and dry primary wire drawing according to ductility deterioration of the steel wire. Repeatedly, after final patenting with a wire diameter corresponding to the target tensile strength, brass plating treatment is performed and wet wire drawing is performed.

  In order to use the ultra-fine steel wire thus manufactured as a reinforcing material for tires, belt cords, high-pressure hoses, etc., stranded wire processing is usually performed. At the time of stranded wire processing, a plurality of ultra-fine steel wires are brought together at high speed, so that each individual ultra-fine steel wire is required to have high toughness to withstand disconnection.

  In response to such demands, ultrafine steel wires have been developed conventionally. For example, in Patent Document 1, for steel wires with a tensile strength of 2450 MPa or more and a diameter of 0.5 mm or less, the Mn content is regulated to suppress the occurrence of supercooled structure during patenting, and C, Si, Mn A technique for improving the strength and tough ductility of the wire by defining the content and reducing the number of broken strands is disclosed.

  However, in recent years, with the reduction in weight and performance of tires, high tension of steel cords has rapidly progressed, and those with a tensile strength of 3000 MPa or more have become mainstream. When the tensile strength of a steel wire increases, ductility generally decreases, vertical cracks called delamination occur, and there is a tendency that breakage tends to occur during stranded wire processing.

  Therefore, in recent years, various developments have been made in order to obtain an ultrafine steel wire that secures ductility even at a high strength exceeding 3000 MPa in tensile strength and is difficult to break.

  For example, in Patent Document 2, the upper limit of the heating temperature at the time of patenting is defined, and the time when the surface layer temperature of the wire becomes lower than the internal temperature after the start of the cooling stage and before the pearlite transformation is provided. We have proposed a technique for improving the twisting characteristics of steel wires by making the structure 0.3 μm or smaller in size than the inside.

  Moreover, in patent document 3, in the forced cooling stage from the austenitizing temperature at the time of patenting, after cooling once to 500-560 degreeC, it is made to perform pearlite transformation after reheating, in the cross section of a wire drawing material. A technique has been proposed in which the product (Da × Db) of the major axis length (Da) and minor axis length (Db) of the ferrite grains is controlled to a certain value or less to suppress longitudinal cracks in the high strength material.

  In Patent Document 4, the upper limit of the maximum void diameter contained in the steel wire is defined in relation to the shear yield stress of the steel wire, and the upper limit value of the tensile residual stress value of the surface layer and the variation in the circumferential direction thereof are defined. Therefore, we have proposed a technology for manufacturing steel wires with excellent delamination resistance.

  In Patent Document 5, the strength of the final patenting material, the area ratio of pro-eutectoid ferrite / cementite, and the wire drawing method after patenting are specified, so that the tensile residual stress on the surface of the steel wire depends on the wire diameter. We are proposing a technology that suppresses delamination by keeping the value below this value.

  However, according to the study by the present inventors, in the case of a high-strength material exceeding 3000 MPa, even with the above-described conventional technology, effects such as improvement of twisting characteristics, suppression of vertical cracking and delamination are not sufficient. It was. In addition, all of the prior arts are technologies that include patenting and wire drawing methods from the component design of steel materials, and intended to recover the ductility of ultrafine steel wires that have deteriorated stranded wire breakage resistance due to strain aging, etc. after wire drawing. It is not a thing.

JP 60-204865 A Japanese Patent Application Laid-Open No. 11-241280 Japanese Patent Laid-Open No. 11-199978 JP 2001-279380 A JP 2001-279281 A

  The present invention has been made in view of the circumstances as described above, and has a tensile strength of 3.0 or more and 3000 MPa or more in the wire drawing strain after patenting, and the ductility is caused by strain aging or the like after wire drawing. An object of the present invention is to provide a method for recovering the wire breakage resistance of a deteriorated ultrafine steel wire.

  The inventors of the present invention have provided a high-strength ultrafine steel wire having a tensile strength of 3.0 or more and 3000 MPa or more in the wire drawing strain after patenting, and having deteriorated ductility due to strain aging or the like after wire drawing. As a result of earnest research on the method of restoring the twisted wire breakage, as a result, after twisting in the positive direction 2 to 20 times per 1000 times the wire diameter of the high-strength ultrafine steel wire, Twisting in the reverse direction 2 to 20 times per 1000 times the length, and repeatedly performing the twisting in the forward direction and the twisting in the reverse direction, thereby twisting resistance of the high-strength ultrafine steel wire The present invention has been completed by finding that the disconnection can be recovered.

  The gist of the present invention is as follows.

  (1) By mass%, C: 0.75 to 1.1%, Si: 0.5 to 2.0%, Mn: 0.2 to 2.0% Al: 0.005% or less, The balance is austenitized at 750 ° C. to 1100 ° C., followed by patenting for a steel wire consisting of Fe and inevitable impurities, and approach angle of die: 6-20 ° Bearing length of die: 0.1-0. To a high-strength ultrafine steel wire having a tensile strength of 3000 MPa or more, obtained by performing cold wire drawing with a drawing strain of 3.0 or more using a die that satisfies the condition of 7D (D: die diameter) , After twisting in the forward direction 2 to 20 times per 1000 times the length of the wire diameter, performing twisting in the reverse direction 2 to 20 times per 1000 times the length of the wire diameter, Repeat the twisting in the forward direction and the twisting in the reverse direction to twist in the forward direction. And the cumulative amount of twisting in the reverse direction is set to two or more and less than 200 times, and the cumulative amount of twisting in the forward direction and the cumulative amount of twisting in the reverse direction A method for recovering breakage of twisted wire of a high-strength ultrafine steel wire, characterized in that the difference is less than 50 times.

  (2) Twisted wire breakage resistance of high-strength ultrafine steel wire according to (1) above, wherein the number of twists in the forward direction and the number of subsequent twists in the reverse direction are the same. Recovery method.

  (3) The number of twists in the reverse direction following the twist in the forward direction exceeds the number of twists in the forward direction, and further, the twist in the forward direction following the reverse direction. The number of times of twisting exceeds the difference between the number of times of twisting in the reverse direction and the number of times of twisting in the forward direction, The high-strength ultrafine steel wire according to (1) above Method for recovering twisted wire breakage.

  (4) The number of twists in the reverse direction following the twist in the forward direction is twice the number of twists in the forward direction. The number of twists in the direction is twice the difference between the number of twists in the reverse direction and the number of twists in the forward direction. A method for recovering the breakage of stranded wires from high-strength ultrafine steel wires.

  (5) The high-strength ultrafine steel according to any one of (1) to (4) above, wherein the twisting in the forward direction and the twisting in the reverse direction are performed 1 to 10 times, respectively. Method for recovering wire breakage resistance.

  (6) The twisting in the forward direction and the twisting in the reverse direction are performed as 50 to 95% of the twist yield point strain, as described in any one of (1) to (5) above A method for recovering the breakage of stranded wires from high-strength ultrafine steel wires.

  According to the present invention, the wire drawing strain after patenting has a tensile strength of 3.0 or more and 3000 MPa or more, and the wire breakage resistance is deteriorated due to strain aging or the like after wire drawing. This makes it possible to recover the ductility of the ultrafine steel wire that has become impossible, and in particular, this makes it possible to process a stranded wire of an ultrafine steel wire having a tensile strength of 3000 MPa or more, and thus contributes greatly to the industry.

  Hereinafter, a method for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a basic operation explanatory view of a repeated twisting device according to the present invention. As shown in FIG. 1, the present invention rotates while incorporating a main wire bobbin 1 for feeding out an ultrafine steel wire to be processed and a guide roller 2 for guiding the steel wire so as not to be derailed. This is realized by passing through a device having a twister (twister) 3a for applying twist and an intermediate reel 4 as basic components. In FIG. 1, twisting in the forward direction and the reverse direction is given by two twisters 3 a and 3 b installed via intermediate reels, respectively. When a single twister is used, the main bobbin and the intermediate reel are structured so that they can be fed and wound, and the twisting in the forward direction and the twisting in the reverse direction are alternately performed by one twister. It is also possible.

  After passing through the positively rotating twister and being twisted in the positive direction, it is wound around the intermediate reel 4 an appropriate number of times. Since the movement of the ultrafine steel wire wound around the intermediate reel in the circumferential direction of the ultrafine wire is fixed by the friction force, twisting is imparted to the ultrafine steel wire. By passing through the next reversely rotating twister 3b after the intermediate reel 4, the steel wire is twisted in the direction opposite to the initial direction. By passing a predetermined number of basic units of this configuration, it is possible to give a predetermined twist to the steel wire. The ultrafine steel wire to which a predetermined twist is applied is finally wound around the winder 5.

  The method of the present invention is realized by adjusting the position, the number of rotations per hour, and the speed of the winding device so that a predetermined twist is applied to the device having the configuration shown in FIG. .

  Next, the reasons for limiting the components, tensile strength, and wire drawing distortion of the ultrafine steel wire that is the material to be treated according to the present invention will be described.

  The reason for limiting the components of the steel that is the subject of the present invention will be described. Hereinafter, “%” means “% by mass”.

C: 0.75 to 1.1%
C has the effect of increasing the tensile strength after the patenting treatment and increasing the wire drawing work hardening rate, and can increase the tensile strength of the steel wire with less wire drawing strain. If it is less than 0.75%, even if an alloy element is added, the tensile strength after the patenting treatment is low, and the wire drawing work hardening rate is also small, so that a high strength steel wire cannot be obtained. On the other hand, if it exceeds 1.1%, pro-eutectoid cementite precipitates at the austenite grain boundaries during the patenting process, and the wire drawing workability deteriorates, and breakage is likely to occur in the wire drawing process. % Range.

Si: 0.5 to 2.0%,
Si is an element that is necessary for strengthening ferrite in pearlite and for deoxidation of steel, and is extremely effective for suppressing a decrease in strength due to heat. If it is less than 0.5%, the above effect cannot be expected. On the other hand, if it exceeds 2.0%, surface decarburization is likely to occur in the hot rolling process, so the content is limited to 0.5 to 2.0%.

Mn: 0.2 to 2.0%,
Mn is not only necessary for deoxidation and desulfurization, but also an element effective for improving the hardenability of steel and increasing the tensile strength after patenting treatment. The effect of can not be obtained. On the other hand, if it exceeds 2.0%, the above effect is saturated, and further, the processing time for completing the pearlite transformation during the patenting process becomes too long and the productivity is lowered. % Range.

Al: 0.005% or less,
If Al exceeds 0.005%, the hardest Al2O3 inclusions among the inclusions in the steel are likely to be generated, which may be the starting point and cause disconnection during wire drawing or stranded wire processing. Therefore, it was limited to 0.005% or less.

  When the tensile strength of the ultra fine steel wire is less than 3000 MPa and the wire drawing strain is less than 3.0, the stranded wire breakage resistance of the steel wire is not deteriorated, so that it is not necessary to apply the present invention. Accordingly, the tensile strength is set to 3000 MPa or more, or the wire drawing distortion is set to 3.0 or more. The wire drawing distortion is a value defined by ln (S0 / S), where S is the cross-sectional area of the steel wire after drawing and S0 is the cross-sectional area of the steel wire before drawing.

  Next, the reasons for limiting the patenting conditions and the die shape used for drawing the steel wire will be described.

  When the heating temperature at the time of patenting is less than 750 ° C., the time required for austenite becomes longer and the productivity is lowered, so the heating temperature is limited to 750 ° C. or higher. Further, when the heating temperature is set to exceed 1100 ° C., the austenite crystal grains become extremely coarse and the ductility of the steel wire is remarkably lowered. Therefore, the heating temperature is limited to 1100 ° C. or less.

  When the approach angle of the die used for wire drawing is less than 6 ° or more than 20 ° and when the bearing length of the die is less than 0.1D or more than 0.7D, the characteristics in the cross section after drawing In order to reduce the ductility of the wire material remarkably, the above limitation was applied.

Next, the reason for limiting the operation of the device of the present invention will be described. When the amount of twist per 1000 times the wire diameter is less than 2 times, there is no effect of improving the twist resistance of the steel wire, and the effect of reducing the number of breaks is not manifested. Was defined as 2 times or more per 1000 times the wire diameter.
Also, when the amount of one twist per 1000 times the wire diameter exceeds 20 times, or when the cumulative amount of twist in one final direction exceeds 200 times, or in the forward and reverse directions When the difference in the amount of twisted wire exceeds 50 times, the wire breakage resistance of the steel wire is improved, but the tensile strength is lowered, so it was excluded from the scope of the invention.

  Next, the reason why the number of twists in the forward direction and the number of subsequent twists in the reverse direction are the same will be described. If the rotation from the natural shape is the same in the forward direction and the reverse direction, after adding rotation in either direction, it can be returned to the natural shape simply by releasing the constraint, so the number of twisters required is small, The apparatus configuration can be simplified. For this reason, the forward / reverse rotation from the natural shape is defined to be the same.

Next, the number of twists in the reverse direction following the twist in the forward direction exceeds the number of twists in the forward direction, and further, the twist in the forward direction following the reverse direction. The reason why the number of twists exceeds the difference between the number of twists in the reverse direction and the number of twists in the forward direction will be described.
Since the deformation can be given in both directions from the natural shape and the wire wrinkles are easily improved as compared with the case where the twist from the natural shape is only in one direction, it is defined in this way.

Next, the number of twists in the reverse direction following the twist in the forward direction is twice the number of twists in the forward direction, and the subsequent forward twist in the reverse direction. The reason why the number of twists in the direction is twice the difference between the number of twists in the reverse direction and the number of twists in the forward direction is described.
Since the deformation can be equally applied in both directions from the natural shape, and the wire wrinkles are more easily improved than in the case of the previous item, it is defined in this way.

  Next, the reason why the twisting in the forward direction and the twisting in the reverse direction are defined as 1 to 10 times will be described. When the forward / reverse repetition was performed 11 times or more, although the stranded wire breakage resistance of the steel wire was improved, the tensile strength was lowered, so it was excluded from the scope of the invention.

  Next, the reason why the twist in the forward direction and the twist in the reverse direction are limited to 50 to 95% of the twist yield point strain will be described. Even if twisting of less than 50% of the twist yield point strain was performed, the effect of improving the resistance to twisting wire breakage was not exhibited, so it was excluded from the range. Further, when twisting exceeding 95% of the twist yield point strain is performed, the tensile strength is reduced although the twist resistance of the steel wire is improved, so it was excluded from the scope of the invention.

  Here, the torsion yield point is θ / 1000D = 0.0 when the twist angle of the plastic deformation from the natural shape remaining when the chuck is opened after twisting is θ and the wire diameter is D. It is defined by a twist amount of 002.

  An example of an embodiment of the present invention is shown below. The present invention is not limited to the following examples.

  The ultra-fine steel wire is a hot rolled material with a diameter of 5.5φ, and an iron wire that has been dry drawn to 3.5 to 1.6 mm is austenitized at 750 ° C to 1100 ° C, preferably 850 ° C to 1000 ° C. Die treatment, die approach angle: 6-20 ° bearing length: 0.1-0.7 D (D: die diameter) using a die that satisfies the conditions of wet drawing to 0.35 mm, or dry A similar patenting treatment was performed on an iron wire that had been subjected to a dry drawing process to 2.0 to 0.9 mm, and was manufactured using a wet drawing method to 0.2 mm. The component composition is shown in Table 1.

  In Table 1, each of C, Si, Mn, and Al is appropriate for steel types A, B, and C, so the steelmaking process is not hindered, there are few disconnection troubles during wire drawing, and productivity during heat treatment. It is an example that can be manufactured up to ultrafine wires without hindering.

  Steel type D is an example in which the C content cannot be reached because the steel content D is insufficient. On the contrary, steel type E is an example in which the C content is excessive, so that the pro-eutectoid cementite precipitates at the austenite grain boundaries during the patenting process, and the wire drawing workability deteriorates and wire breakage is likely to occur in the wire drawing process. .

  Steel type F is an unsuitable example because the Si content is excessive and surface decarburization is likely to occur in the hot rolling process, and the fatigue life characteristics of the steel cord are significantly reduced.

  Steel type G is an unsuitable example because the Mn content is excessive, so that the processing time for completing the pearlite transformation during the patenting process becomes too long and the productivity is lowered.

Steel type H has an excessive Al content, so it is easy to produce the hardest Al ₂ O ₃ inclusions in the inclusions in the steel, and this is the starting point for wire drawing or stranded wire processing. This is an example that is not suitable because it causes disconnection.

  For ultra-fine wires with various tensile strengths (TS) and wire drawing strains, the device of the present invention can be used for two reels each weighing 100 kg at various levels of the number of twists per 1000 d and the number of repeated twists. A total of 200 kg was collected and evaluated for resistance to stranded wire breakage. 1000d means a length 1000 times the wire diameter.

  The definition and evaluation apparatus of the twist resistance against breakage will be described.

  FIG. 2 is an explanatory diagram relating to a stranded wire breakage evaluation apparatus and an evaluation method. As shown in FIG. 2, the steel wire stranded wire breakability evaluation device performs an actual stranded wire processing step by continuously twisting two ultrafine steel wires at a constant angle while maintaining a certain tension. Mock up.

  The high-strength ultrafine steel wire is fed out at a constant speed of 100 m / min from two payoff reels 8a and 8b having speedometers 6a and 6b and tension meters 7a and 7b. Moreover, the line tension is controlled in the range of 9.5 to 10.5% of the high-strength ultrafine steel wire single wire by the tension meters 7a and 7b.

  The two steel wires are brought close together by a twister 9 that rotates at a constant speed of 1000 revolutions / minute. The winding speed of the stranded wire by the bobbin in the twister is controlled so that the knot of the stranded wire is photographed at a high speed by the control camera 11 from the side and the position is constant within a certain range. The apparatus is installed so that the main wire and the stranded wire form an angle of 120 ° with each other.

  Using two reels of ultra fine steel wire having a weight of 100 kg per reel, the stranded wire is carried out with the above-mentioned apparatus, and the number of twist-resistant wire breaks per 200 kg is counted. This is performed with and without applying the method of the present invention in which the twist in the forward direction and the twist in the reverse direction are applied. It is examined how many times the number of stranded wire breaks is greater than the number of stranded wire breaks when the method of the present invention is not applied. If the ratio of the number of times of stranded wire breakage is less than 1.0, the stranded wire breakage resistance of the ultra fine steel wire to which the present invention is applied is improved.

  The results are shown in Table 2. Since Examples 1 to 10 of the present invention are all suitable for wire drawing strain, tensile strength, number of twists per 1000 times the length of the wire diameter, and the number of repeated sets of twists, This is an example in which the resistance to breakage of the twisted wire is clearly improved as compared with the case where the material according to the invention was not passed.

  Comparative Examples 11 to 13 are examples in which the effect of the present invention was not exhibited because the original ultrafine steel wire had a true strain of less than 3.0 and less than 3000 MPa. Since the twist resistance of the ultrafine steel wire was higher than the original, it did not change even when the product of the present invention was passed.

  In Comparative Examples 14 and 15, the number of twists with respect to a length of 1000 times the wire diameter was less than 2, and thus the effect of improving the twist resistance was not exhibited.

  In Comparative Examples 16 and 17, since the number of twists for one time with respect to the length of 1000 times the wire diameter exceeds 20, the recovery of the twist-resistant wire breakage can be seen, but the tensile strength decreases. It is an example.

  In Comparative Examples 18 and 19, the cumulative number of twists in one direction exceeds 200, and thus the tensile strength after the treatment is lowered even though the resistance to breakage of the twisted wire is improved.

  Comparative Example 20 is an example in which the tensile strength after the treatment was lowered even though the twist resistance against breakage was improved because the difference in the cumulative amount of twist in the forward and reverse directions exceeded 50 times. This is an example in which the tensile strength after treatment is reduced.

It is basic operation explanatory drawing of the repeated twisting apparatus which concerns on this invention. It is explanatory drawing regarding a twist-proof wire breakability evaluation apparatus and an evaluation method.

Explanation of symbols

1 Main line bobbin 2 Guide rollers 3a and 3b Twister 4 Intermediate reel 5 Winders 6a and 6b Speedometers 7a and 7b Tension meters 8a and 8b Payoff reel 9 Twister 10 Bobbin 11 Control camera

Claims (6)

  In mass%, C: 0.75 to 1.1%, Si: 0.5 to 2.0%, Mn: 0.2 to 2.0% Al: 0.005% or less, the balance being Fe And austenitizing a steel wire consisting of unavoidable impurities at 750 ° C. to 1100 ° C., followed by patenting treatment, die approach angle: 6-20 °, die bearing length: 0.1-0.7D ( D: a high-strength ultrafine steel wire having a tensile strength of 3000 MPa or more, obtained by performing cold wire drawing with a wire drawing strain of 3.0 or more using a die that satisfies the condition of D: Die diameter) Twist in the forward direction 2 to 20 times per 1000 times the diameter, then twist in the reverse direction 2 to 20 times per 1000 times the wire diameter, Repeatedly twisting in the reverse direction and twisting in the reverse direction, The cumulative amount of twisting in the reverse direction is set to 2 or more and less than 200 times, and the difference between the cumulative amount of twisting in the forward direction and the cumulative amount of twisting in the reverse direction The method of recovering the breakage resistance of the high-strength ultrafine steel wire, characterized by comprising   2. The method for recovering twist resistance of a high-strength ultrafine steel wire according to claim 1, wherein the number of twists in the forward direction and the number of subsequent twists in the reverse direction are made the same.   The number of twists in the reverse direction following the twist in the forward direction exceeds the number of twists in the forward direction, and further, the number of twists in the forward direction following the reverse direction. The number of times exceeds the difference between the number of times of twisting in the reverse direction and the number of times of twisting in the forward direction, and the twist-resistant wire breakage of the high-strength ultrafine steel wire according to claim 1 Sexual recovery method.   The number of twists in the reverse direction following the twist in the forward direction is twice the number of twists in the forward direction, and further, the number of twists in the forward direction following the reverse direction. The high-strength ultrafine steel according to claim 3, wherein the number of twists is twice the difference between the number of twists in the reverse direction and the number of twists in the forward direction. Method for recovering wire breakage resistance.   The twist-proof wire breakage of the high-strength ultrafine steel wire according to any one of claims 1 to 4, wherein twisting in the forward direction and twisting in the reverse direction are performed 1 to 10 times, respectively. Sexual recovery method.   The high-strength ultrafine steel wire according to any one of claims 1 to 5, wherein the twisting in the forward direction and the twisting in the reverse direction are performed as 50 to 95% of the twist yield point strain. Method for recovering twisted wire breakage.

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