JP4942085B2 - Brass-plated steel wire manufacturing method, steel cord and tire - Google Patents

Description

  The present invention relates to a method for producing a brass-plated steel wire (hereinafter, also simply referred to as “manufacturing method”), and more specifically, a method for producing a brass-plated steel wire for a steel cord suitably used as a reinforcing material for a tire, and The present invention relates to a steel cord and a tire using the steel cord.

  Conventionally, a steel wire having a surface plated with brass has been used as a steel wire for reinforcing a rubber article used for a wire of a steel cord for reinforcing a tire. A brass-plated steel wire is usually manufactured by drawing a steel wire material subjected to a heat treatment such as patenting and a brass plating process to a predetermined wire diameter using a multi-stage slip type wet wire drawing method.

  Regarding the adhesion between the brass-plated steel wire and the rubber, for example, in the vulcanization process at the time of manufacturing the tire, it is heated in contact with the rubber, so that sulfur, cobalt, etc. in the rubber and copper in the brass plating are It is known that an adhesive layer is formed by reaction. In particular, it is known that adhesion reactivity with rubber decreases under dry environment conditions in winter.

  The rubber-steel wire adhesive layer is formed quickly and reliably in the vulcanization process (initial adhesion performance), and the formed adhesive layer is exposed to moisture and heat during use of the rubber article. Since it is required not to deteriorate (adhesion durability performance), various studies have been made so far in order to obtain an adhesive layer having both of them. As a technique related to the improvement of the adhesion performance between the brass-plated steel wire and the rubber, for example, in Patent Document 1, in the continuous wet wire drawing step, the final stage drawing is performed by three or more dies stacked dies, A steel wire manufacturing method is disclosed in which a skin pass with a surface area reduction ratio of 1.2 to 3.9% is performed with two or more dies on the upstream side excluding one die at the head of the die.

  Further, in Patent Document 2, when a brass-plated steel wire is drawn by a wet drawing method, the final drawing die is dipped in a lubricant solution and drawn, and the final drawing die or the final drawing die is drawn. A steel wire manufacturing method using a diamond die in a die and several dies upstream of the die is disclosed.

  However, sintered diamond dies are expensive, and the cost of using these sintered diamond dies as several dies including the final die is high, so low-cost and highly stable brass plating It is desirable to establish a steel wire drawing method. On the other hand, a technique for defining the bearing length by using a plurality of tungsten carbide (WC) dies is also known, but WC dies are inferior to diamond dies in terms of wear resistance, making quality stability difficult. I know that there is.

Further, in Patent Document 3, for the purpose of improving wet heat durability adhesion performance, the average Cu content of the brass-plated steel wire is set to 60 to 66%, and the Cu content is increased in the depth direction from the surface to 0. Although a technology for making the Cu content 50% at 0.02 to 0.04 μm is disclosed, details of the means are not disclosed, and whether or not it can be stably manufactured industrially is greatly I have doubts. Furthermore, in Patent Document 4, the Cu content of the brass-plated steel wire is 50 to 60% by weight, and the X-ray diffraction intensity ratio of the brass-plated crystal structure (β phase / α phase) is 0.2 to 2.0. It is disclosed that the adhesion performance in a humid environment is improved, and when the Cu content is 50% or less, it is difficult to draw due to the influence of a hard and brittle β phase, and preferably 55% by weight or more. The initial and durable adhesion under humid conditions is said to be improved. However, there is no description of specific measures for ensuring adhesion performance and improving wire drawing, particularly in a dry environment in winter.
Japanese Patent Laid-Open No. 11-33617 (Claims etc.) JP 2004-66271 A (Claims etc.) JP 11-93086 A (claims, etc.) Japanese Patent Publication No. 60-30543 (Claims)

  As described above, various studies have been made so far regarding improvement of adhesion between rubber in a brass-plated steel wire, but none of them is sufficient, and the above-described various requirements are better. There was a need to realize satisfactory technology.

  Accordingly, an object of the present invention is to provide a brass-plated steel wire that has good initial adhesion performance and durable adhesion performance with rubber in dry and humid environments and can be manufactured stably industrially. It is an object of the present invention to provide a manufacturing method, a steel cord excellent in adhesion to rubber, and a tire using the same.

  As a result of intensive studies, the inventors have determined that the most downstream drawing pass in the final stage in the wet drawing process is a skin pass drawing using a sintered diamond die, and the Cu content of the brass plating is prescribed. As a result, the inventors have found that the above problems can be solved, and have completed the present invention.

That is, the method of manufacturing the brass-plated steel wire of the present invention is a method of manufacturing a steel wire subjected to brass plating through a step of wet drawing with a multi-stage slip type wire drawing machine,
The Cu content of the steel wire brass plating is 55 to 62%, and drawing is performed using one or more dies in the final stage of the multi-stage slip type wire drawing machine, and at least of the one or more dies A sintered diamond die is used as the most downstream die, and the area reduction of the most downstream die is less than 2%, and the β phase in the crystal structure of the steel wire brass plating before the wet wire drawing step The X-ray diffraction intensity ratio (β phase / α phase) with the α phase is 1.5 or less.

  In this invention, it is preferable that the average plating thickness of the said steel wire after a wet wire drawing process shall be 0.1-0.4 micrometer. Further, among the one or more dies, it is preferable to use a sintered diamond die for a plurality including the most downstream side, and among the one or more dies, a plurality of area reduction ratios including the most downstream side are set. It is also preferable to make it less than 2%. Further, as the sintered diamond die, one made of a sintered body of diamond particles having a particle diameter of 1 μm or less is preferably used.

  The steel cord of the present invention is characterized by comprising a single wire or a plurality of twisted steel wires manufactured by the method for manufacturing a brass-plated steel wire of the present invention.

  Furthermore, the tire of the present invention is characterized by using the steel cord of the present invention as a reinforcing material.

  According to the present invention, the above-described configuration enables the initial plating performance and the durable bonding performance with rubber in dry and humid environments to be favorable and can be manufactured stably industrially. A method of manufacturing a steel wire could be realized, and thereby a steel cord excellent in adhesion performance at the initial stage and durability and a tire using the steel cord could be realized.

Hereinafter, preferred embodiments of the present invention will be described in detail.
The present invention is a technique relating to an improvement of a method for manufacturing a steel wire subjected to brass plating through a step of wet drawing with a multi-stage slip type wire drawing machine.

  FIG. 1 shows a schematic diagram of a multi-stage slip type wire drawing machine. The wire drawing machine 10 shown in the figure includes a lubricant tank 11 filled with a lubricant, multistage drive capstans 12a to 12d and a plurality of dies 13 installed in the lubricant tank, and dies 14a to 14c. In the wire drawing machine 10, in the process of alternately passing the brass-plated steel wire 1 to each stage between a pair of drive capstans 12 a, 12 b and 12 c, 12 d arranged to face each other, each stage Then, the wire is drawn by a die 13 and subjected to a wire drawing process up to a predetermined diameter via the final-stage dies 14a to 14c.

  In the present invention, at the final stage of such a multi-stage slip type wire drawing machine, wire drawing is performed using one or more dies (three dies 14a to 14c in the illustrated example), and the one or more dies are drawn. Of these, a sintered diamond die is used as at least the most downstream die (die 14c in the illustrated example), and it is important that the area reduction of the most downstream die is less than 2%. In the wet wire drawing process, as the most downstream die in at least the final stage, a sintered diamond die having a hole diameter that is almost the same as the wire diameter of the incoming steel wire is used, and the downstreammost die of this final stage is drawn. By making the wire pass a skin pass drawing with a surface area reduction of less than 2%, the surface layer of the brass-plated steel wire can be processed intensively and stably, and the sintered diamond die has excellent self-lubricity. (Low frictional resistance) and wear-resistant materials make it possible to suppress heat generation during wire drawing, and as a result, the initial adhesion of brass-plated steel wire can be greatly improved. .

  In the present invention, the area reduction ratio of the most downstream die is required to be less than 2%, and considering the die finishing tolerance, the effect can be sufficiently obtained even when the area reduction ratio is close to 2%. However, it is preferably 1% or less. If the hole diameter of the die is equal to or greater than the diameter of the steel wire to be inserted, the area reduction rate due to the die will be substantially 0%. However, in the actual process (operation), subtle misalignment or steel wire Since vibration is accompanied, the surface of the steel wire and the wall surface of the die are brought into contact with each other and the surface of the brass plating is subjected to processing by the die by setting the diameter of the hole of the die to the diameter of the steel wire to be inserted. If the area reduction rate is substantially 0%, the influence on the underlying steel material is small, and may be preferable.

  By the skin pass drawing using one sintered diamond die (bearing length 20-30%), the initial adhesion performance of the brass-plated steel wire can be secured well, and the sustainability of the effect is also confirmed. However, as described above, regarding durable adhesiveness, although it shows good performance at the very initial stage of quantitative wire drawing, durable adhesive performance becomes unstable as the drawing dose (production amount) increases, The effect is insufficient. Therefore, in the present invention, in order to achieve both the bonding performance at the initial stage and at the end of durability, and to ensure these performances stably over a long period of time, the skin pass wire drawing process using the sintered diamond die is used, and the steel wire is used. The Cu content of brass plating is regulated to 55 to 62%. By making the Cu content of brass plating within the above range lower than the conventional general ratio, the thickness of the adhesive layer generated by the vulcanization reaction can be made thin, uniform and strong, and the durable adhesive performance Can be improved.

  The Cu content of the brass plating is preferably 58 to 62%, more preferably about 60%. If the Cu content is less than 58%, the hard and brittle β phase increases in the crystal phase of the brass plating, resulting in a problem of wire drawing. On the other hand, if it exceeds 62%, the adhesive layer becomes thick and brittle. As it is accompanied, it may not be preferable. If the Cu content is reduced, the β phase increases, which is not good for wire drawing. However, since the Zn content is large, a zinc phosphate coating that is an extreme pressure coating of a lubricant is generated thickly. However, in some cases, it may be preferable, and in order to minimize the proportion of the β phase, it can be adjusted by optimizing the thermal diffusion strength in the plating process.

  In the production method of the present invention, when the combination condition of the skin pass wire drawing using the sintered diamond die and the Cu content of the brass plating is applied, the rubber side is in any of dry or humid environmental conditions. As a result, it has become possible to stably and industrially manufacture brass-plated steel wires having excellent initial bonding performance and excellent durability bonding performance.

  In the present invention, the skin pass wire drawing needs to be performed at least on the most downstream die among one or more dies used in the final stage. However, in the final stage, a plurality of dies including the most downstream side are used. It is also effective to use a sintered diamond die and perform skin pass drawing with a plurality of dies at the final stage, with the area reduction rate of the plurality of dies including the most downstream side being less than 2%. That is, in the present invention, the surface layer portion is activated by processing the surface layer of the plating on the surface of the brass-plated steel wire by skin pass drawing, and the initial adhesion performance can be improved by improving the adhesion reactivity with rubber. However, the effect can be maintained and maintained by performing skin pass drawing with a plurality of dies. In addition, the Cu content of the bulk plating under the plating electrode surface layer part has an influence on the durable adhesion, and the plating part (increased Zn rich part) remaining after Cu is consumed in the vulcanization reaction is It is considered that a good adhesion state is maintained by acting as a barrier against deterioration factors such as water and oxygen, and the effect is greatly reflected as the Cu content is lowered.

  As the sintered diamond die used in the present invention, a sintered diamond die having a particle size of 1 μm or less, particularly about 0.1 to 0.5 μm is suitable. Thereby, the heat_generation | fever suppression effect at the time of wire drawing can be maintained over a long period of time, and the ductility value can be improved, and also high adhesiveness can be maintained stably. In other words, the life of the die can be extended, contributing to quality stabilization.

  Moreover, in this invention, it is preferable to set plating conditions so that the average plating thickness of the brass plating steel wire after wet drawing may be 0.1-0.4 micrometer. When the average plating thickness after wire drawing is less than 0.1 μm, the portion where the base is exposed increases and the initial adhesiveness is inhibited. On the other hand, when it exceeds 0.4 μm, it is excessive due to heat during use of the rubber article. Adhesion reaction proceeds and only brittle adhesion can be obtained. Further, the X-ray diffraction intensity ratio (β phase / α phase) between the β phase and the α phase in the crystal structure of the steel wire brass plating immediately after the wet drawing, that is, immediately after the brass plating, is preferably 1.5. Hereinafter, it is more preferably 1.0 or less. By lowering the strength ratio, that is, by suppressing the hard and brittle β phase as much as possible, adverse effects on the subsequent wire drawing process can be prevented.

  In the production method of the present invention, wire drawing conditions other than the conditions relating to the above-mentioned skin pass wire drawing and brass plating, and processes other than multi-stage wet wire drawing, such as initial dry wire drawing, patenting treatment, brass plating treatment, etc. Can be appropriately carried out according to a conventional method, and is not particularly limited. The production method of the present invention is suitably applied when producing a brass-plated steel wire having a diameter of about 0.08 to 0.4 mm.

  Further, the steel cord of the present invention is a single wire of a brass-plated steel wire produced by the above-described method for producing a brass-plated steel wire or a plurality of twisted wires (twisted cord formed by twisting with a twisting machine) ) And has excellent adhesion performance to rubber, and can be suitably used as a reinforcing material for rubber articles such as tires and industrial belts. In addition, about the twist structure in the case of using the steel cord of this invention as a twisted cord, it can determine suitably according to a use, and it does not restrict | limit in particular.

  Furthermore, the tire of the present invention uses the steel cord as a reinforcing material for a belt or a carcass ply, and the other tire structures and materials are not particularly limited. According to the present invention, a tire having excellent durability can be obtained by using the steel cord as a reinforcing material.

Hereinafter, the present invention will be described in more detail with reference to examples.
Using the multi-stage slip type wire drawing machine shown in FIG. 1, wet drawing of a brass plated steel wire having a wire diameter of 0.30 mm and a tensile strength of about 3200 MPs was performed. The number of dies in the final stage of the wire drawing machine, the material of the dies, and the diameter of the wire entering the final stage are as shown in Table 1 below. Also, in Conventional Example 1, cemented carbide dies are used for all passes, and in Conventional Example 2, sintered diamond dies having a particle diameter of 1 μm are used for three passes including the final pass (therefore, the die cost is very high). high). Furthermore, all the passes other than the final pass in Examples 1 to 3 use sintered diamond dies having a particle diameter of 1 μm.

  Further, the Cu content of the brass plating of the steel wire used is as shown in Table 1 below, the average plating thickness of the brass plating is 0.25 μm, and the X-ray diffraction intensity of the β phase and the α phase in the crystal structure The ratio (β phase / α phase) was 0.57 for plating with a Cu content of 60% and 0.03 for plating with a Cu content of 63%.

(Initial adhesion)
The steel cord is peeled from the rubber-steel cord composite obtained by coating the wet-drawn brass-plated steel wire with rubber and vulcanizing it at 160 ° C for 7 to 15 minutes. Then, the subsequent rubber adhesion rate was visually determined, and the rubber level was evaluated at 0 to 100%. The result was displayed as an index value with the conventional example 1 as 100. It shows that it is excellent in initial stage adhesiveness, so that a numerical value is large. In the evaluation, the rubber used was dried (moisture content in rubber: 0.3%) and humid (water content in rubber: 1.2%), respectively, by humidity control, and the test was conducted under each environmental condition. .

(Durable adhesion)
The wet-drawn brass-plated steel wire is covered with rubber, and the resulting rubber-steel cord composite obtained by vulcanization under the conditions of 160 ° C. × 15 minutes is subjected to a 95% humidity and 75 ° C. atmospheric pressure. The steel cord was peeled off from the rubber after standing in the atmosphere for 7 to 14 days, and the rubber adhesion rate was visually judged, and the level with rubber was evaluated at 0 to 100%. The result was displayed as an index value with the conventional example 1 as 100. It shows that it is excellent in durable adhesiveness, so that a numerical value is large.

＊１）下流側から順に第１、第２、第３ダイス（１４ｃ，１４ｂ，１４ａ）とする。
＊２）ベアリング長さｘのダイス１４の穴径ｄに対する割合を百分率で示したものである（図２参照）。

* 1) First, second, and third dies (14c, 14b, 14a) in order from the downstream side.
* 2) The ratio of the bearing length x to the hole diameter d of the die 14 is expressed as a percentage (see FIG. 2).

  As can be seen from the results in Table 1 above, by applying the combined conditions of the skin pass drawing by the sintered diamond die according to the present invention and the limitation of the Cu content% of the brass plating, both dryness and high humidity on the rubber side are applied. It was confirmed that a brass-plated steel wire excellent in both initial bonding performance under environmental conditions and durable bonding performance can be obtained.

It is the schematic which shows the multistage slip type wire drawing machine which concerns on this invention. It is explanatory drawing which shows the bearing length of die | dye.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Brass plating steel wire 10 Multistage slip type wire drawing machine 11 Lubricant tank 12a-12d Multistage drive capstans 13, 14, 14a-14c Dice

Claims (7)

In a method of manufacturing a steel wire subjected to brass plating through a step of wet drawing with a multi-stage slip type wire drawing machine,
The Cu content of the steel wire brass plating is 55 to 62%, and drawing is performed using one or more dies in the final stage of the multi-stage slip type wire drawing machine, and at least of the one or more dies A sintered diamond die is used as the most downstream die, and the area reduction of the most downstream die is less than 2%, and the β phase in the brass plating crystal structure of the steel wire before the wet wire drawing step A method for producing a brass-plated steel wire, characterized in that the X-ray diffraction intensity ratio (β phase / α phase) between the α phase and the α phase is 1.5 or less .   The method for producing a brass-plated steel wire according to claim 1, wherein an average plating thickness of the steel wire after the wet wire drawing step is 0.1 to 0.4 µm. The method for producing a brass-plated steel wire according to claim 1 or 2 , wherein a sintered diamond die is used for a plurality of the one or more dies including the most downstream side. The method for producing a brass-plated steel wire according to any one of claims 1 to 3 , wherein among the one or more dies, a plurality of area reduction ratios including the most downstream side is less than 2%. The method for producing a brass-plated steel wire according to any one of claims 1 to 4 , wherein the sintered diamond die is made of a sintered body of diamond particles having a particle diameter of 1 µm or less. A steel cord comprising a single wire or a plurality of strands of a brass-plated steel wire manufactured by the method for manufacturing a brass-plated steel wire according to any one of claims 1 to 5 . A tire comprising the steel cord according to claim 6 as a reinforcing material.

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