JPH08253004A - Highly endurable pneumatic steel radial tire - Google Patents

Abstract

PURPOSE: To enhance the separation resisting performance of a steel wire by specifying both mean thickness and standard deviation of thickness distribution of the steel wire and applying brass plating, in which copper and zinc whose weight % is specified are used, to a wire rod consisting of a pearlite. CONSTITUTION: Uneveness 2 is formed in many places of the surface of a steel material 1 for forming a steel cord, and plating 3 is applied in correspondence to the uneveness 2. In this case, the mean thickness of the plating 3 is specified as 50nm<=X<=150nm, while the standard deviation (σ) of the thickness distribution is specified as 10nm<=σ<=30nm. In preparing the wire steel 1, carbon steel, in which carbon content is 0.60 to 0.95% in weight %, undergoes heat treatment to become hypo-eutectoid or eutectoid steel consisting of two phases made up of (pearlite + cementite) or (ferrite + cementite). After this, the wire material 1 is drawn under the 'WET' condition to become a wire rod having the diameter of 0.15 to 0.45mm. In addition, the surface of the wire rod is plated by means of a brass plating method, in which 60 to 70% (in weight) of copper and 40 to 30% of zinc are contained and sometimes cobalt or nickel, whose content in total is less than 10%, is added.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly durable pneumatic steel radial tire in which the adhesion between rubber and steel cord is improved by improving the plating of steel wire used in the pneumatic steel radial tire.

[0002]

2. Description of the Related Art Generally, a pneumatic steel radial tire uses a steel ply in which a steel wire or a steel cord formed by twisting a plurality of steel wires is embedded in a rubber sheet in order to increase the reinforcing force of a carcass layer. However, in order to exert the reinforcing effect of the steel ply, the steel wire is required to have excellent adhesiveness with rubber. For this reason, steel wires have conventionally been brass-plated.For brass-plated steel wires and brass-plated steel cords in which a plurality of these are twisted together, the ratio of brass-plated copper and zinc or the brass-plated thickness is set. A method of improving the adhesiveness with rubber by making it appropriate is widely known. Regarding the adhesiveness with rubber, and above all, the dependence of heat aging adhesiveness and wet heat aging adhesiveness on the plating thickness, certain knowledge has been established. In particular, regarding the plating thickness, we examined the composite adhesion of the DRY-plated steel wire that is brass-plated to this steel wire and the rubber adjacent to it by drawing a metal wire into a small-diameter steel wire. A thickness of about 20 to 50 nm is necessary and sufficient, and the smaller the variation in the adhesion thickness of the plating is, the thinner the adhesive layer formed at the interface between the plating and the rubber adjacent to it is dense. It is known that the adhesion stability against heat and moist heat becomes excellent. From this, it is clear that the direction of thinning is more preferable as the plating applied to the surface of the steel wire.

On the other hand, in the so-called WET drawing process in which a metal wire plated by a brass plating method, which is usually used for steel wire, is drawn in a lubricating oil to make a steel wire, it is thinly drawn. With respect to such plating, it is desirable that the plating thickness be thin and uniform as described above. However, conventionally, the plating thickness adhering to the surface of the steel wire has a large variation, such as a portion having a thickness of 1/10 of the average thickness and a portion having a thickness of about 10 times the average thickness. It has become clear that it is uniform by using the latest surface analysis equipment. However, until now, the factors controlling the plating thickness distribution have not been sufficiently clarified,
Thinning could not be realized.

Therefore, in order to secure the initial adhesiveness with rubber and the heat aging adhesiveness, JP-A-53-106853.
As disclosed in Japanese Unexamined Patent Publication No. Hei 11 (1999) -135, the amount of plating adhered to the surface of the steel wire is practically about 4.
It is commonly used in a region of 0 g / kg, about 0.20 μm (when the wire diameter is 0.23 mm) or more in terms of thickness. For example, as shown in Comparative Example 1 of Table 1, the wire diameter is actually 0. ．
The thickness of the plating adhered to the 175 mm steel wire was 200 nm on average, and the standard deviation σ showing the degree of the variation was 70 nm.

[0005]

In recent years, it has become an urgent task to further extend the life of tires due to the demand for longer life and severe environmental conditions in which steel radial tires are used, but as mentioned above. Since the plating thickness is still thick and the plating thickness is not uniform in the conventional plating, the adhesion between rubber and steel wire cannot be said to be sufficient, and the steel ply from the shoulder part to the bead part of the tire cannot be said. It has been strongly desired to improve the separation resistance of the. Therefore, an object of the present invention is to achieve excellent separation resistance by using a thin and even brass-plated brass-plated steel wire and a brass-plated steel cord formed by twisting a plurality of the brass-plated steel wires. To obtain high durability pneumatic steel radial tires.

[0006]

Therefore, such an object is toroidal carcass layer consisting of left and right bead cores and steel plies in which a large number of steel cords extending in the radial direction across the bead cores are embedded. A pneumatic steel radial tire comprising: a belt layer arranged on the outer side in the radial direction of the carcass layer and configured by laminating two or more belts; and a tread arranged on the outer side in the radial direction of the belt layer. The average thickness X of the plating applied to the surface of the steel wire constituting the steel cord is 50 nm ≦ X ≦ 150 nm, and the standard deviation σ of the plating thickness distribution is in the range of 10 nm ≦ σ ≦ 30 nm. The steel wire is formed by heat-treating carbon steel having a carbon content of 0.60 to 0.95% by weight to form a perlite or ferrite. / Cementite consisting of two phases of hypo-eutectoid-eutectoid pearlite steel, and then drawn under WET conditions with a diameter of 0.15 to 0.45 mm. This can be achieved by using a highly durable pneumatic steel radial tire that is brass-plated by a brass plating method containing cobalt, nickel and the like in an amount of 70% by weight, 40 to 30% by weight of zinc, or 10% thereof.

[0007]

First of all, the present inventors first apply copper and zinc plating to the surface of a metal wire, which is usually used for steel wire, and then alloy it by a heat diffusion treatment to form W.
A method of controlling the thickness distribution of the plating applied to the surface of the steel wire by being thinly drawn in the ET wire drawing process was studied. Specifically, the unevenness of the amount of plating applied to the surface of the metal element wire before drawing, the oxidation of the plating due to the thermal diffusion process for the subsequent plating alloying, and the subsequent descaling (scale down). Non-uniformity due to plating loss due to), external damage due to wire drawing, plating loss, especially in the case of brass plating Cu / Zn
The distribution of the plating thickness, such as the relationship between the β brass ratio that varies depending on the ratio and the wire drawability, and the non-uniformity due to external scratches and plating loss that occur during the wire twisting process after drawing and straightener processing Various factors that may have an influence were investigated and studied by repeating experiments.
However, it has not been possible to sufficiently control the distribution of plating thickness.

Further, as a result of intensive studies by the inventors, as shown in FIG. 3, which is an enlarged schematic diagram of a part of the radial surface layer cross section of the conventional brass-plated steel wire, as shown in FIG.
On the surface of the steel wire steel material 1 after ET drawing, a large number of streaks 2 having various stripes along the longitudinal direction of the steel wire are formed.
It was found that the depth, shape, and distribution of the unevenness 2 greatly affect the thickness of the plating 3.
That is, the deep groove 4 is formed with the thick plating 3 having the thickness D1, and the shallow groove 5 is formed with the thin plating 3 having the thickness D2. Further, since the steel wire steel material 1 is a polycrystalline body made of pearlite and the crystal grains grow while curling due to rotation / translation in the wire drawing process, there is also a difference in the elongation of the plating, and the thickness of the deposited plating increases. It was found that the steel wire steel material 1 became non-uniform, and the pearlite crystal grain size of the steel wire steel material 1 was further refined to reduce the unevenness of the surface of the steel wire steel material 1 during and after the wire drawing, thereby reducing the plating thickness. It was clarified that the distribution width can be made smaller and more uniform.

Therefore, the carbon content before wire drawing is 0.60 to 0.9.
The austenite grain size is refined by heat-treating 5% by weight of carbon steel wire to form a hypoeutectoid-eutectoid pearlite steel consisting of two phases of pearlite or ferrite / cementite, whereby fine pearlite grains are formed. After obtaining, 60 to 70% by weight of copper on the surface of the carbon steel material wire,
Zinc 40 to 30% by weight, or 10% of zinc in the range is plated by a brass plating method containing cobalt, nickel, etc. to form a metal busbar, and this metal busbar is WET drawn to 0.15 to 0.45 mm. The diameter of the steel wire can reduce the depth of the unevenness of the steel wire steel surface after the WET drawing, and the average adhesion thickness of brass plating on the steel wire surface, which was virtually impossible up to now, can be achieved. It is in the range of 50 nm to 150 nm, and the standard deviation of the brass plating thickness distribution is 10 nm to 30 nm.
It is now possible to obtain a brass-plated steel wire with a uniform and thin plating in the range of. And the steel ply using this brass-plated steel wire and brass-plated steel cord has very good adhesion, and the separation resistance of the steel ply from the shoulder part to the bead part of the tire will be greatly improved. A highly durable pneumatic steel radial tire with a longer running life can be obtained.

[0010]

EXAMPLES Examples will be described below with reference to FIG. FIG. 1 shows a highly durable pneumatic steel radial tire (tire size 11/70 R22.
5) shows a half cross-section in the width direction, in which a high durability pneumatic steel radial tire 15 has a carcass layer composed of a toroidal steel ply 11 straddled between the left and right bead cores 10, 10. Both ends 14 of the steel ply 11 have left and right bead cores 10, 10
It is held by being folded back from bottom to top. A belt layer 12 including a plurality of belts is arranged on the outer side in the radial direction of the steel ply 11, and a tread 13 is arranged on the outer side in the radial direction of the belt layer 12. The steel ply 11 is formed by embedding a steel cord formed by twisting a plurality of steel wires in a rubber sheet in the radial direction. In the highly durable pneumatic steel radial tire 15, while the surface of the tread 13 is in contact with the road surface and travels, the shoulder portion 16 moves to the bead core 1
Since severe bending is repeated in the side portion 17 up to 0, the separation resistance of the steel ply 11 forming the skeleton of the side portion 17 is particularly required. Then, in order to improve the separation resistance of the steel ply 11, it is necessary to improve various adhesive properties between the steel cord and the rubber.

Therefore, hereinafter, a brass-plated steel cord obtained by twisting the brass-plated steel wire obtained by the example according to the present invention and a brass obtained by twisting the conventional brass-plated steel wire obtained by the comparative example are shown. Initial adhesion test and corrosion fatigue resistance test and their evaluation using plated steel cord,
Further, after the tires produced by using the above-mentioned cords were run on the market for a predetermined distance, the post-run adhesion test and evaluation were performed. In addition, the same carbon steel material having a carbon content of 0.60 to 0.95% by weight is used for the metal wires of the following examples and comparative examples. Further, in the following examples and comparative examples, the rubber coating the brass-plated steel cords are all the same, and the composition of the rubber is
When the component weight of natural rubber is 100, carbon black: 50% by weight, zinc white: 5% by weight, antioxidant: 1% by weight, organometallic acid cobalt salt: 2% by weight,
Vulcanization accelerator: 1.5% by weight, sulfur: 5% by weight.

[Example 1] Austenite crystals were obtained by heat-treating a metal element wire having a wire diameter of 1.20 mm under the following conditions to obtain a hypoeutectoid-eutectoid pearlite steel composed of two phases of ferrite / cementite. The wire having a fine grain size and fine pearlite crystal grains thereby obtained is brass-plated by a diffusion method (brass plating method) with a composition containing Cu: 65% by weight and Zn: 35% by weight. A metal bus bar was used, and WET drawing was repeated on this metal bus bar to reduce the diameter to 0.175 mm to obtain a brass-plated steel wire. Then, a corrosion-plated steel cord having a twist structure of 3 + 9 + 15 + 1 formed by twisting a plurality of the brass-plated steel wires was used to perform a corrosion fatigue resistance test. Next, a steel ply was made using the brass-plated steel cord, and a tire (tire size 11/70 R2
After 2.5) was vulcanized and molded at 145 ° C. for 30 minutes, a predetermined size of steel ply was cut out from this vulcanized tire and an initial adhesion test was conducted. In addition, a tire made using the brass plated steel cord (tire size 1
After 1/70 R22.5) was vulcanized and molded at 145 ° C. for 30 minutes, the vulcanized tire was allowed to run on the market for 100,000 km, and then the post-run adhesion I and post-run adhesion II tests were conducted.
In the above wording, the contents from the metal element wire having a wire diameter of 1.20 mm to the post-running adhesiveness I and post-running adhesiveness II tests are all the same in Examples 1 to 3 and are duplicated. Therefore, it will not be described in the description of Embodiments 2 and 3 below. Heat treatment conditions: austenitizing temperature 1050 ° C, pearlite transformation temperature 550 ° C, coating weight: 3.0 g / kg (plating weight g per 1 kg of wire, the same applies below)

[Example 2] Heat treatment conditions: austenitizing temperature 950 ° C, pearlite transformation temperature 550 ° C, coating weight: 2.0 g / kg

[Example 3] Heat treatment conditions: austenitizing temperature 830 ° C, pearlite transformation temperature 550 ° C, coating weight: 1.0 g / kg

[Comparative Example 1] A metal wire having a wire diameter of 1.20 mm was heat-treated under the following conditions. The wire material was subjected to a diffusion method (brass plating method) with Cu: 65 wt% and Zn. The metal bus bar was subjected to brass plating with a composition containing 35% by weight, and the metal bus bar was repeatedly WET drawn to reduce the diameter to 0.175 mm to obtain a brass-plated steel wire. First, a twisted structure made by twisting a plurality of brass-plated steel wires 3 + 9 + 15 + 1
Corrosion fatigue resistance test was conducted using the brass-plated steel cord. Next, a steel ply was made using the brass-plated steel cord, and a tire using the steel ply (tire size 11/70
After R22.5) was vulcanized and molded at 145 ° C. for 30 minutes, a steel ply was cut out from the vulcanized tire in a predetermined size and an initial adhesion test was conducted. Further, a tire (tire size 11/70 R22.5) made by using the brass-plated steel cord was vulcanized and molded at 145 ° C. for 30 minutes, and then this vulcanized tire was run on the market for 100,000 km. After that, the adhesion after running I and the adhesion after running II tests were conducted. In the above-mentioned wording, the contents from the metal element wire having a wire diameter of 1.20 mm to the post-running adhesiveness I and post-running adhesiveness II tests are all the same in Comparative Examples 1 and 2 and overlap. Therefore, it will not be described in the following description of the second embodiment. Heat treatment conditions: austenitizing temperature 1200 ° C, pearlite transformation temperature 600 ° C, coating weight: 4.0 g / kg

[Comparative Example 2] Heat treatment conditions: austenitizing temperature 1200 ° C, pearlite transformation temperature 600 ° C, coating weight: 2.0 g / kg

Table 1 includes the evaluations of various tests carried out under the respective specifications as described above, and various adhesiveness tests and evaluation methods in Table 1 will be described below. (1) Crystal grain size The grain size was measured using the austenite grain size measuring method according to JIS standard G0551. The numbers in parentheses to the right of the numbers indicating the granularity are the numbers indicating the granularity according to the JIS standard. (2) Plating Thickness A standard sample produced by DRY plating and having a uniform plating thickness and a known plating thickness is AES (Auger E
The relationship between the plating thickness and the sputtering time was obtained from the sputtering time when analyzed in the depth direction under the following conditions using a Fluoron Microscope).
The same analysis in the depth direction was performed on the brass-plated steel wires manufactured in the above-mentioned Examples and Comparative Examples, and the sputtering time was converted into the plating thickness. In each of the examples and the comparative examples, the number of measured plating thickness was 100 points, and the average value X and standard deviation σ of the 100 points were obtained. The plating thickness frequency distribution chart thus obtained is shown in FIG. 2, in which the horizontal axis represents the plating thickness and the vertical axis represents the frequency. In the figure, it can be seen that Examples 1 to 3 are superior to Comparative Example 1 in both average plating thickness and plating thickness frequency distribution. The average plating thickness of Comparative Example 2 is 100 nm, which is the same as that of Example 2. However, in Comparative Example 2, the frequency distribution of the plating thickness greatly spreads to the left and right, and it can be seen that the variation in the plating thickness is greater than in any of the Examples.

(3) Initial Adhesion Test First, one end of the steel cord of a steel ply of a predetermined size cut out from the above-mentioned unrunning vulcanized tire is grasped and the steel cord is peeled off. Then, the state of the rubber remaining attached to the surface of the steel wire of the outermost layer of the peeled steel cord was observed and evaluated by the evaluation method described later. (4) Adhesion I test after running First, a steel ply is cut out to a predetermined size from the above-mentioned running tire, one end of the steel cord of this steel ply is grasped, and the steel cord is peeled off. Then, the state of the rubber remaining attached to the surface of the steel wire of the outermost layer of the peeled steel cord was observed and evaluated by the evaluation method described later. (5) Adhesion II test after running First, a steel ply is cut out to a predetermined size from the above-mentioned run tire, one end of the steel cord of this steel ply is grasped, and the steel cord is peeled off. Then, the state of the rubber remaining adhering to the surface of the wrapping wire spirally wrapped with one steel wire so as to bundle the stripped steel cords was observed and evaluated by the evaluation method described later. .

(6) Evaluation Method for Rubber Adhesion Test The results of the initial adhesion and post-travel adhesion I tests were evaluated by the following methods. The state of the rubber remaining adhered to the surface of the steel wire of the outermost layer of the peeled steel cord was evaluated by a five-level evaluation from A to E. In A, rubber remains on the entire surface of the outermost steel wire, and the plated surface of the steel cord is
It means the best adhesiveness when it is not visible all around. E means the worst adhesion in a state where no rubber remains on the entire surface of the outermost steel wire and the plated surface of the steel cord is visible over the entire length and circumference. Divide between A and E into three equal parts, C shows a state in which about 50% of the rubber remains in the intermediate area, and B is in the middle of A and C, and D is between E and C. The middle is shown. In each of the above-mentioned initial adhesion test and post-running adhesion I test, five steel cords were peeled off and evaluated, and the number shown on the right side of the alphabet indicates the number of evaluations. .
The results of the adhesion II test after running were evaluated by the following methods. The number of exposed areas where the rubber is not attached to the surface of the stripped steel cord wrapping wire is counted, and the adhesiveness is evaluated by the number of exposed pieces. Therefore, the smaller the number, the better the adhesiveness. In the above-mentioned post-running adhesion II test, all five steel cords were tested, and the average value of the five steel cords was calculated and displayed.

(7) Corrosion Fatigue Resistance Test The corrosion fatigue resistance test is a test for evaluating the repeated bending fatigue failure resistance performance of the steel ply from the shoulder portion to the side portion of the tire. With the steel cord bent freely at a bending radius of 40 mm and approximately 90 degrees while being freely rotatably supported and held at the other end by a rotary chuck, the steel cord is immersed in a corrosive liquid containing sodium chloride to form the rotary chuck. Rotation speed 30
The steel cord was rotated at 00 rpm to repeatedly perform a repeated bending fatigue test, and the number of revolutions until the steel cord was broken was measured. Therefore, in this test, the steel cord was not coated with rubber. In addition, this test was carried out for 10 steel wires in each of the examples and the comparative examples, and an average value of 10 wires was obtained.
It is indicated by an index of 00. Therefore, a number greater than 100 indicates that the corrosion fatigue resistance is superior to Comparative Example 1.

From the above description, as is clear from Table 1, the crystal grain size of each of the examples according to the present invention is extremely smaller than that of the comparative example. As a result, it is shown that the example has a thinner plating thickness than the comparative example 1 and has less variation, that is, uniform plating. In addition, the initial adhesion, which indicates the adhesion between the rubber and the brass-plated steel cord, the adhesiveness after running I, the adhesiveness after running II, and the corrosion-fatigue resistance of the brass-plated steel cord itself, are all superior in the examples. You can see that

[0022]

INDUSTRIAL APPLICABILITY The present invention uses a steel cord formed by twisting a plurality of thin and evenly plated steel wires on a steel ply of a tire. This steel cord is superior to conventional steel cords. Various adhesion performances and corrosion resistance of steel cord itself are extremely excellent, and the separation resistance performance of steel ply from the shoulder portion to the bead portion of the tire is significantly improved.

[Brief description of drawings]

[Table 1] A table showing specifications, results, evaluations, etc. of various tests.

FIG. 1 is a view showing a width direction half cross section of a highly durable pneumatic steel radial tire obtained by the present invention.

FIG. 2 is a frequency distribution chart of plating thickness showing the relationship between the plating adhesion thickness and its frequency in Examples and Comparative Examples.

FIG. 3 is an enlarged schematic view of a part of a radial surface layer cross section of a conventional brass-plated steel wire.

[Explanation of symbols]

1: Steel material 2: Unevenness
3: Plating 4: Deep groove 5: Shallow groove 1
0: Bead core 11: Steel ply 15: Tire D
1, D2: Thickness X: Average thickness of plating (average plating thickness) σ: Standard deviation of plating thickness distribution

[Procedure amendment]

[Submission date] June 24, 1996

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a view showing a half cross section in a width direction of a highly durable pneumatic radial tire obtained by the present invention.

FIG. 2 is a frequency distribution chart of plating thickness showing the relationship between the plating adhesion thickness and its frequency in Examples and Comparative Examples.

FIG. 3 is an enlarged schematic view of a part of a radial surface layer cross section of a conventional brass-plated steel wire.

[Explanation of symbols] 1: Steel material 2: Unevenness
3: Plating 4: Deep groove 5: Shallow groove 1
0: Bead core 11: Steel ply 15: Tire D
1, D2: Thickness

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

From the above description, as is clear from Table 1, the crystal grain size of each of the examples according to the present invention is extremely smaller than that of the comparative example. As a result, it is shown that the example has a smaller plating thickness than the comparative example 1 and has less variation, that is, uniform plating. In addition, the initial adhesion, which indicates the adhesion between the rubber and the brass-plated steel cord, the adhesiveness after running I, the adhesiveness after running II, and the corrosion fatigue resistance of the brass-plated steel cord itself are all examples. It turns out that is excellent.

[Table 1]

Claims (1)

[Claims] 1. A toroidal carcass layer composed of left and right bead cores, a steel ply in which a large number of steel cords extending in the radial direction across the bead cores are buried, and a toroidal carcass layer arranged radially outside the carcass layer. In a pneumatic steel radial tire comprising a belt layer formed by superposing a plurality of belts, and a tread arranged radially outside the belt layer, the surface of the steel wire constituting the steel cord is applied. The average thickness X of the plated plating is 50 nm ≦ X ≦ 15
0 nm and standard deviation σ of plating thickness distribution is 10 nm
≦ σ ≦ 30 nm, and the steel wire has a carbon content of 0.
After heat treatment of 60 to 0.95% carbon steel into pearlite or hypoeutectoid to eutectoid pearlite steel consisting of two phases of ferrite / cementite, wire drawing is performed under WET conditions.
A wire rod having a diameter of 15 to 0.45 mm, the surface of which is 60 to 70% by weight of copper, 40 to 30% by weight of zinc, or a brass plating method containing cobalt or nickel in an amount of 10% by weight. A highly durable pneumatic steel radial tire characterized by being plated.