JPS5861297A - Plating method for steel wire for tire cord - Google Patents

Abstract

PURPOSE:To obtain a titled steel wire having good adhesiveness to rubber by plating copper and zinc alternately >=2 times on the steel wire and further plating copper on the outermost layer then drawing the wire with plural pieces of dies and diffusing the copper and zinc during this time. CONSTITUTION:After a blank steel wire 1 is heat-treated through a heating furnace 2 and a lead hardening tank 3, the wire is pretreated by passing through an electrolytic pickling tank 4, a rinsing tank 5, an alkali washing tank 6 and a rinsing tank 5. The pretreated wire 1 is applied with copper plating for the 1st layer in a plating cell 17, is then applied with zinc plating for the 2nd layer in a zinc plating cell 18 via a rinsing tank 5 and is rinsed in a rinsing tank 5. Thereafter, the wire is subjected to alternate repetitions of required times of the copper plating by the cells 17 and the zinc plating by the cell 18. Finally, the wire is applied with copper plating for the outermost layer in the cell 17 and is rinsed 5 then dried and is taken up with a coiler 10. The wire 1 applied with the multilayered plating is drawn through plural pieces of dies of multistage drawing machines so that the copper and zinc in the plating layers are diffused mutually by the working heat and pressure thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a positive plating method for steel wire for tire cords.

Tire cords are used by being embedded in rubber, but in order to provide adhesion to the rubber, the tire cords are manufactured by applying positive plating to the surface and going through a wire drawing and stranding process.

The positive plating method is 1. Conventionally, a so-called alloy plating method has been used in which steel and zinc are deposited simultaneously using a cyanide bath containing zinc.

However, cyanide baths are highly toxic and harm the working environment, and pollution control measures such as waste liquid treatment are also a major problem in production.In addition, they have the drawback of requiring strict management to control the composition.

Therefore, in recent years, as shown in FIG. 1, a method has generally been used in which alloying is performed by applying copper plating and zinc plating thereon, and then heating the steel to interdiffuse the steel and zinc.

In the figure, a steel cable 1 is heat-treated through a heating furnace 2 and a lead quenching tank 3, and then pretreated through an electrolytic pickling tank 4, a water washing tank 5, an alkali washing tank 6, and a water washing tank 5, and then a hot pot. Copper plated in plating tank 7, passed through washing tank 5t, galvanized in galvanizing tank 8, rinsed with water in washing tank 5, heated to around 500'C by electric heating device 9 and subjected to diffusion treatment, then rolled up. It is wound up on the machine IO.

For the steel plating tank 7 and the galvanizing tank 8, a pyrophosphate steel bath and a zinc sulfate bath, which cause less pollution problems, are used, respectively.

In this method, the plating layer before diffusion treatment consists of two layers, a copper plating layer and a zinc plating layer, and a heating device for diffusion is required, and this heating temperature control ensures a high degree of stability. Furthermore, since the heating temperature is generally around 500°C, the zinc on the outermost surface is oxidized, and the oxide tends to fall off during the subsequent wire drawing process, and zinc, which has a high vapor pressure during heating, tends to evaporate. The yield of the predetermined plating layer is poor, and when comparing the amount of plating deposited immediately after plating and after wire drawing, a loss of about 1096 occurs.

The present invention was made to solve the above-mentioned problems, and consists of repeating copper plating and zinc plating alternately two or more times,
Furthermore, by applying copper plating to the outermost layer to create a multi-layer plating, which is then wire-drawn, and the steel and zinc are completely diffused between them, there is no special heat-diffusion treatment for gold, and instead of the conventional heat-diffusion treatment. It is an object of the present invention to provide a method for plating steel wire for tire cords, which can completely prevent oxidation, shedding, and evaporation of zinc, improve the plating yield, and easily control the plating composition.

The present invention involves plating a steel wire by repeating copper plating and zinc plating two or more times alternately, further plating the outermost layer with copper, and then drawing the plated steel wire using a plurality of dies. , a method for plating steel wire for tire cords, characterized in that the plating layer is made gold-positive by diffusing copper and zinc during the wire drawing process.

Hereinafter, the present invention will be explained by examples using the drawings. FIG. 2 is a block diagram for explaining the entire embodiment of the method of the present invention. In the figure, the same reference numerals as in FIG. 1 indicate the same parts.

In the figure, the steel cable 1 has been heat treated in the same way as in FIG.
After that, it is pretreated, washed in a pot plating tank 17, and washed in a washing tank 5. Thereafter, copper plating in the copper plating tank 17 and zinc plating in the zinc plating tank 18 are repeated as many times as necessary. Finally, after the outermost copper plating is applied in the copper plating tank 17, it is washed with water in the washing tank 5.
After drying, it is wound up on a winding machine 1o.

Note that the above-described copper plating and zinc plating may be repeated any number of times as long as it is two or more times. In the figure, copper plating is performed three times and zinc plating is performed twice.

The copper plating bath used in the present invention is preferably a copper pyrophosphate bath, a copper sulfate bath, etc., which cause less pollution problems, but is not limited to these baths. Further, the zinc plating bath is preferably a zinc sulfate bath or the like, which causes less pollution problems, but is not limited thereto.

The cross section of the wire after being plated in this way is shown schematically in FIG.
1. There are a zinc plating layer 12, a copper plating layer 18, a zinc plating layer 14, and an outermost copper plating layer 15.

Next, the multi-layer plated steel material is wire-drawn using a multi-stage wire drawing machine through a plurality of dies.

Due to the processing heat and pressure during this wire drawing process, the copper and zinc in the plating layer diffuse into each other and become positive.

Now, the biggest reason for plus plating on tire cords is to impart adhesion to rubber, and the composition of the outermost surface of the plating is most important for this purpose. In other words, the optimal plating surface varies depending on the composition of the rubber, but generally the ratio of copper to zinc is 7:3 to 6.
It is said that :, 4.

Further, the total thickness of the plating layer is, for example, 4 to 5 μm in the case of 1.25111/steel cable wire.

If such plating is applied to one layer each of copper and zinc as in the past, each plating thickness will be approximately 3 μm and two layers will be once thick. It is nearly impossible to sufficiently diffuse copper and zinc using only processing heat and pressure during wire drawing. The reason for this is that wire drawing normally uses a wet lubricant, which generates heat of up to 200° C. within the die, but the wire is cooled down before entering the next die.

The inventor studied these conditions and found that in order to diffusion alloy steel and zinc, the plating layer only needs to be a stack of thin plating layers, and two copper and two zinc plating layers each are required. It was found that the above was necessary. Therefore, in the plating layer according to the present invention that satisfies this condition, copper and zinc can be sufficiently diffused by processing heat and pressure during wire drawing.

Furthermore, one of the features of the present invention is that the outermost plating layer is a copper layer. As mentioned above, the composition of the outermost plated surface is most important for adhesion to rubber, and the ratio of copper and zinc on the outermost surface after wire drawing is important for this. In the conventional heating diffusion method, sufficient heat is applied so that the plating layer has a substantially uniform alloy composition, but in the diffusion method using wire drawing as in the present invention, a uniform alloy composition is not necessarily obtained. In particular, if the outermost layer is a galvanized layer, the outermost surface after wire drawing will be rich in zinc and good adhesion to rubber cannot be obtained. Therefore, when the outermost gold-copper plating layer is used as in the present invention, it becomes copper-rich and the desired copper-to-zinc ratio of 7:3 to 6:4 is easily obtained. As a result, good adhesion to rubber can be obtained.

Another reason for using the outermost all-copper layer is to facilitate wire drawing. Zinc has poor deformability and does not have a good lubricating effect with the die.

In this respect, copper is rich in these elements, and has the great advantage of good wire drawability when the outermost layer is copper.

Example: A steel cable wire with a strength of 1.25 mm was used, and the total amount of plating deposited on the steel wire was 1.25 mm. The following three types of plated steel cables were prepared by plating at 4f per Kf so that the ratio of copper to zinc was 7=3.

Example of the present invention: Using the equipment shown in Figure 2, copper plating and zinc plating are applied alternately, with three copper plating layers and two zinc plating layers, with the outermost layer being the copper plating layer, and special heat diffusion treatment. Those who do not.

Comparative Example A1: After plating one copper plating layer and one zinc plating layer using the apparatus shown in FIG. 1, a diffusion treatment was performed at 50° C. for 2 seconds using an electric heating device 9.

Comparative Example/I62: Plated in the same manner as Comparative Example &l, but without heat diffusion treatment.

These plated steel cables are processed into 16 pieces using a wet continuous wire drawing machine.
The wire was drawn to 0.2511 ff using two dies, and then a 5-twist I (1 x 5 x 0.25 wire) wire cord was created using a wire twisting machine.

The plating composition of the nine tire cords obtained was as shown in Table 1.

In addition, a sample was ground from each tire cord, sandwiched between two unvulcanized rubber sheets, and after being pressure-vulcanized, it was peeled off at the cord section and the adhesion to the rubber was evaluated. As shown in Table 1.

Regarding the evaluation of adhesion to rubber, if 100% of the rubber adheres to the cord surface after peeling off, the score will be 10, if the entire cord surface is exposed, the score will be 0. Scores will be made proportionately.

Table 1 (Note) The * mark and 9744 indicate the adhesion amount (2) per Ikg of steel wire.

From Table 1, it can be seen that the plating yield of the present invention is very good, similar to Comparative Example 2, and the adhesion to rubber, which is one of the important properties for a tire cord, is very good.

On the other hand, in Comparative Example 1, the plating yield was poor due to the heating and diffusion treatment, and in particular, zinc was oxidized, dropped, and evaporated frequently due to heating. However, since it was sufficiently diffused, the adhesion was 7 points. However, if plating is performed with full consideration of yield,
It is possible to adapt it to your requirements.

In Comparative Example 42, the plating yield was good, but the adhesion to rubber was very poor because the diffusion was insufficient and the surface was rich in zinc.

As described above, the method of the present invention involves plating a steel wire by repeating copper plating and zinc plating two or more times, and then plating the outermost layer with copper. Since wire drawing is performed using dies, each plating layer can be made thinner by forming multiple plating layers, and the processing heat and pressure caused by wire drawing causes diffusion of copper and zinc, so special heating is not required as in conventional methods. It has the advantage of not requiring diffusion treatment.

Furthermore, since the method of the present invention does not involve heating and diffusion treatment, it has the advantage that it is easy to control the dependent composition.

Since it is easy to obtain a copper-rich alloy with good adhesion, tire cords with good adhesion to rubber can be easily obtained, and wire drawability is also good.

[Brief explanation of drawings]

FIG. 1 is a block diagram for explaining an example of a conventional tire cord steel wire manufacturing method. FIG. 2 is a block diagram for explaining an embodiment of the method of the present invention, and FIG. 3 is a plating depickling tank, 5
...Water washing tank, 6...Alkaline washing tank, 7.17-6
・Copper plating tank, 8.18... Zinc plating tank ・9...
Electrification heating device, 10... winding machine, 11. I3,15・
...Copper plating layer, 12.14...Zinc plating layer. Agent Patent Attorney Hidetomi Aoki

Claims (1)

[Claims] (1) Copper plating and zinc plating are alternately repeated two or more times on the steel wire, and the outermost layer is further plated with copper, and then the plated steel wire is drawn using multiple dies, A method for plating steel wire for tire cords, characterized in that the plating layer is made positive by diffusing copper and zinc during the wire drawing process.