KR19990037851A - Method for preparing steel cords - Google Patents

Abstract

The present invention provides a method for manufacturing a steel cord for reinforcing rubber products such as tires, high pressure hoses, conveyor belts, in particular, copper plating and zinc plating on steel wires sequentially, followed by thermal diffusion of the plating layer using a fluidized bed heating furnace to produce a uniform brass plating layer. The present invention relates to a method for manufacturing a steel cord, the method of the present invention provides a uniform diffusion quality and to provide a new workability by providing a brass plated steel wire of a uniform α-phase crystal structure in the post-drawing process Provide a significant improvement.

Description

Manufacturing method of steel cords {Method for preparing steel cords}

The present invention relates to a method of manufacturing a steel cord for reinforcing rubber products, and more particularly, after copper plating and zinc plating are sequentially performed on a steel wire, the plated layer is thermally diffused by using a fluidized bed furnace. It relates to a method for producing a steel cord, characterized in that to obtain a brass layer.

Steel cords are used to reinforce rubber products such as tires, high pressure hoses, conveyor belts, etc. because they have superior strength, modulus, heat resistance, and fatigue resistance compared to other types of inorganic and organic fibers. The steel cord is subjected to copper plating having a thickness of 0.5 to 1.5 μm on the surface of the steel wire having a carbon content of 0.6 to 0.95% by weight and proceeding with a wire diameter of 0.8 to 1.8 mm at a speed of 20 to 80 m / min. , Zinc plating of 0.3 to 1.0μm sequentially on it and thermal diffusion to obtain a brass plating layer by various methods, and then wire drawing produced by 0.1 to 0.6 mm in diameter to a variety of structures (1 × 3, 1 × 4, 2 + 2, 2 + 7, 3 + 6, 3 + 9 + 15, etc.).

In the manufacture of steel cords, it is desirable to obtain a uniform brass alloy plating layer by mutual thermal diffusion of copper and zinc atoms plated on the surface of the steel wire. In the conventional heat diffusion method, a distance of 3 to 15 m from the surface of the plated steel wire is used. The electric circuit is composed of three coin rollers and the electricity is flowed directly to the steel wire, which is heated by the electric resistance heat generated by the electric resistance of the steel wire itself, and the induction current is formed by using a high frequency induction oscillator. Therefore, a non-contact induction heating method that generates heat by the electric resistance heat of the steel wire itself is generally used.

In general electric resistance heat heating method, the steel wire proceeding at a speed of 20 to 80 m / min is directly contacted using three rollers, and the steel wire is heated by supplying electric power of 2000 to 5000 watts (W). It is a way to. In this Joule Effect heating method, the heat generation amount H of the steel wire is expressed as Equation 1 as a function of current I, resistance R, and time t provided through the current.

H = I ² Rt [Joule]

However, the electrical resistance (R) of the steel wire is increased with the temperature increase of the steel wire in the temperature increase step, the increasing value is increased very rapidly, such as 4 to 6 times of 0 ℃ at 600 ℃. In addition, the electrical resistance (R) of the steel wire increases as the carbon content in the steel wire increases, and also changes due to the diameter deviation of the steel wire.

In addition, the heat generation amount (H) of the steel wire is changed by various factors that change the diffusion degree between copper and zinc on the surface of the wire, such as the thermal efficiency varies depending on the external temperature (ambient temperature during actual operation). The method has a problem that the quality deviation of diffusion is very large at the same current and the same voltage. In addition, when the contact area between the steel wire and the roller changes due to the tension change during the electric current, an electric spark occurs between the roller and the steel wire. In the steel wire part where sparks occurred, martensite structure is produced due to the change of metal structure, and this martensite structure is a hard and brittle structure, which causes breakage of the wire in the drawing process. It lowers fresh workability.

On the other hand, the thermal diffusion method using the induction heating method generates an induction current in the steel wire proceeding inside the inductor by flowing a high frequency current through the inductor (induction coil) in the form of a circular tube, and the Joule effect of the steel wire by the same Joule effect It is a method of generating heat by electric resistance heat. Since this method is a method of flowing an induction current in a non-contact manner to the steel wire that proceeds into the inductor, unlike the electrical resistance heating method of heating the wire by direct contact with the steel wire, there is no electrical spark generation due to a poor electrical contact, Due to the change in the electrical resistance of the steel wire itself, the heat generation amount of the steel wire has a problem that the quality deviation of diffusion at the same current and the same voltage is very large.

The present invention overcomes the problems of the prior art described above, and provides a method for producing a steel cord with improved fresh workability by maintaining the diffusion temperature uniformly based on the fact that mutual diffusion between solids is most affected by the diffusion temperature. It is.

That is, the present invention is to provide a method for producing a steel cord, characterized in that to obtain a uniform brass plated layer by thermal diffusion of the plated layer using a fluidized bed heating furnace immediately after galvanizing after copper plating on the steel wire.

1 is a schematic view of the manufacturing process of the steel cord according to the present invention,

Figure 2a is a schematic diagram of the thermal diffusion steel plated layer,

Figure 2b is a schematic diagram of the thermal diffusion steel wire plating layer,

Figure 3 is a temperature rising graph of the steel wire according to the fluidized bed heating time of the present invention.

Hereinafter, with reference to the accompanying drawings of the present invention will be described in more detail.

In the method of manufacturing the steel cord of the present invention, a fluidized bed filled with zircon sand or alumina sand is maintained at a constant temperature to mutually thermally diffuse copper and zinc atoms plated on the steel wire surface to obtain a uniform brass alloy plated layer. The steel wire is passed through a heated bed (Fluidized Bed Furnace). At this time, zircon sand or alumina sand used as the internal filling material is preferable because the heating rate is faster than the electric diffusion or induction diffusion.

1 is a schematic diagram of a steel cord manufacturing process according to the present invention. In the case of manufacturing the steel cord according to the manufacturing method of the steel cord of the present invention, as shown in Fig. 1, the wire rod in the state as shown in Fig. 2a by performing copper plating and zinc plating sequentially on the steel wire To obtain. Immediately after galvanizing, the wire is thermally diffused using a fluidized bed furnace to form a uniform brass alloy plated layer and wound up with a winder. The plating layer obtained by this thermal diffusion process is as shown in Fig. 2b.

In the present invention, the heating temperature of the fluidized bed heating furnace during thermal diffusion is preferably 500 to 650 ° C. If the heating temperature is less than 500 ° C, the diffusion rate of copper and zinc is very slow, so a long diffusion time of 20 seconds or more is required, and in order to do so, the length of the fluidized bed heating furnace must be designed to increase the equipment cost. On the contrary, when the heating temperature exceeds 650 ° C., cementite is decomposed in the pearlite structure of the steel wire itself, so that the structure changes to spheroidal cementite, resulting in a 2-5% reduction in the tensile strength of the steel wire. In this invention, it is essential that the heating temperature of the fluidized bed heating furnace is in the above range.

In the present invention, the treatment time in the fluidized bed furnace is preferably about 4 seconds to about 10 seconds. Since the surface temperature of the steel wire is about 3 seconds until the temperature of the fluidized bed is raised to the temperature of the fluidized bed, it is not possible to maintain a uniform temperature when the treatment time is less than 4 seconds, and thus the intended effect of the present invention cannot be obtained. On the contrary, if the treatment time exceeds 10 seconds, the length of the fluidized bed heating furnace becomes longer and the cost of equipment becomes expensive, which causes a cost increase. For example, in the case where the heating temperature is 580 ° C. and the diffusion is performed for 6 seconds, the temperature rising graph of the steel wire according to the fluidized bed heating time is shown in FIG. 3.

Sequential copper plating and zinc plating in the present invention is carried out by copper pyrophosphate plating and zinc sulfate plating or pyrophosphate copper plating, copper sulfate plating and zinc sulfate plating. 5 to 15% by weight of trihydric pyrophosphate (Cu ₂ P ₂ O _7. 3H ₂ O) and 20 to 60% by weight of pyrophosphate (K ₄ P) when plating by copper pyrophosphate plating and zinc sulfate plating method ₂ O ₇ ) was electroplated for 5 to 20 seconds in a current density range of 5 to 20 A / dm ² while maintaining the temperature at 30 to 60 ° C., followed by copper plating with a thickness of 0.5 to 1.5. 5 to 50% by weight of zinc sulfate can (ZnS0 ₄ .5H ₂ O) to an aqueous solution containing 30 to a temperature in a maintained state to the 60 ℃ 10 to 40 a / dm 1 to 10 seconds electroplating at a current density range of ² After performing zinc plating with a thickness of 0.3 to 1.0 μm in sequence, the temperature is elevated for 4 to 10 seconds in a temperature range of 500 to 650 ° C. by a fluidized bed heating furnace. Obtain a plating layer.

Copper pyrophosphate plating and copper sulfate plating are sequentially performed to increase the copper plating rate. In this method, 5 to 15% by weight of copper pyrophosphate (Cu ₂ P ₂ O _7. 3H ₂ O) and 20 Electroplating for 5 to 20 seconds in a current density range of 5 to 20 A / dm ² while maintaining an aqueous solution containing from about 60% by weight to a pyrophosphate carbohydrate (K ₄ P ₂ O ₇ ) at a temperature of 30 to 60 ℃. 0.4 to 1.0 μm thick pyrophosphate copper plating, and then an aqueous solution containing 10 to 40 wt% copper pentasulphate (CuSO _4. 5H ₂ O) and 2 to 8 wt% sulfuric acid (H ₂ SO ₄ ). 10 to 50% by weight of pentasulfuric acid after electroplating for 0.2 to 1.0 μm thickness by electroplating for 1 to 10 seconds in the current density range of 10 to 40 A / dm ² while maintaining the temperature at 30 to 60 ℃ zinc (ZnS0 ₄ .5H ₂ O) in the maintaining the aqueous solution at a temperature of 30 to 60 ℃ state of 10 to 40 a / dm ² Electroplating for 1 to 10 seconds in the flow density range, followed by zinc plating with a thickness of 0.2 to 1.0 μm in sequence, and then heated to a temperature of 500 to 650 ° C. for 4 to 10 seconds by a fluidized bed heating furnace, and copper plated on the steel wire surface. Thermal diffusion of atoms of and zinc together yields a brass alloy plated layer.

According to the method of the present invention, α exhibiting excellent freshness in the range of 62.0% to 68.0% of the ratio (copper amount / [copper amount + zinc amount] × 100%) of copper in the alloy component of copper and zinc in the plating layer applied to the steel cord. It is possible to obtain 95% or more of brass (face-centered cubic lattice) having a phase crystal structure, and to minimize the generation of brass (body-centered cubic lattice) having a beta-phase crystal structure that reduces freshness.

Hereinafter, the present invention will be described in more detail with reference to examples, but the following examples are only to explain the present invention and should not be construed as limiting the protection scope of the present invention as defined by the appended claims. .

Examples 1-5

Steel cords were subjected to diffusion for 6 seconds in a fluidized bed heating furnace maintained at 580 ° C after plating while varying the alloy ratio of copper and zinc on a high carbon steel wire containing 0.82% carbon having a diameter of 1.4 mm as shown in Table 1 below. To prepare and measure the overall physical properties are shown in Table 1 below.

Comparative Examples 1 to 5

By using the electric resistance heating method and the induction heating method, the alloys of copper and zinc were plated on the high carbon steel wire containing 0.82% carbon with a diameter of 1.4 mm while varying as shown in Table 1, and then the voltages shown in Table 1, The steel cord was manufactured by diffusing for 6 seconds in a current or frequency state, and various physical properties were measured. The results are shown in Table 1 together.

Examples 6-10

6 seconds while changing the heating temperature in the fluidized bed furnace within the range of 550 ℃ to 600 ℃ while maintaining a constant copper and zinc alloy ratio of 64:36 in a high carbon steel wire containing 0.82% carbon with a diameter of 1.4mm. Steel cord was prepared by diffusion, and various physical properties were measured. The results are shown in Table 2 below.

Comparative Examples 6 to 10

By using the electric resistance heating method and the induction heating method, the heating temperature in the fluidized bed heating furnace was maintained at 550 with a constant alloy ratio of 64:36 on a high carbon steel wire containing 0.82% carbon with a diameter of 1.4 mm. The steel cord was prepared by diffusion for 6 seconds while changing within the range of ℃ to 600 ℃ to measure the overall physical properties and the results are shown in Table 2 together.

In this example, physical properties were evaluated by the following method.

¹⁾ Brass plated layer crystal structure: X-ray diffractometer (XRD, X-Ray Diffractometer) was measured using.

²⁾ Copper ratio in the brass plating layer was measured by using an inductively coupled plasma spectrometer (ICP).

³⁾ Thickness of brass plating layer: It was immersed at room temperature for 10 minutes in a solution mixed with ammonia and hydrogen peroxide at 10: 1 to dissolve the brass plating layer, and the weight was measured before and after dissolution.

division Example Comparative example One 2 3 4 5 One 2 3 4 5 Thermal diffusion method Fluidized bed furnace Electric resistance heat Induction heating Diffusion conditions Temperature 580 ℃ 580 ℃ 580 ℃ 580 ℃ 580 ℃ electric current 60A 60A 60A 70 A 70 A Voltage 40 V 40 V 40 V 850 V 850 V frequency 20KHz 20KHz Brass Plating Layer Crystal Structure α-brass 99% 100% 100% 100% 100% 65% 76% 85% 75% 88% β-brass One% 0% 0% 0% 0% 35% 24% 15% 25% 12% Brass plating layer thickness 1.48 μm 1.48 μm 1.48 μm 1.48 μm 1.48 μm 1.48 μm 1.48 μm 1.48 μm 1.48 μm 1.48 μm Copper ratio of the brass plated layer ^* 62 63 64 65 66 62 63 64 65 66

* Copper ratio in brass plating layer = (copper amount / [copper amount + zinc amount] × 100%)

division Example Comparative example 6 7 8 9 10 6 7 8 9 10 Thermal diffusion method Fluidized bed furnace Electric resistance heat Induction heating Diffusion conditions Temperature 550 ℃ 560 ℃ 580 ℃ 590 ℃ 600 ℃ electric current 50 A 60A 70 A 60A 80A Voltage 30 V 40 V 45 V 800 V 950 V frequency 20KHz 20KHz Brass Plating Layer Crystal Structure α-brass 99% 100% 100% 100% 100% 60% 76% 83% 71% 85% β-brass One% 0% 0% 0% 0% 40% 24% 17% 29% 15% Brass plating layer thickness 1.48 μm 1.48 μm 1.48 μm 1.48 μm 1.48 μm 1.48 μm 1.48 μm 1.48 μm 1.48 μm 1.48 μm Copper ratio of the brass plated layer ^* 64% 64% 64% 64% 64% 64% 64% 64% 64% 64%

* Copper ratio in brass plating layer = (copper amount / [copper amount + zinc amount] × 100%)

The method of the present invention provides a uniform diffusion quality in the manufacture of steel cords for reinforcing rubber products such as tires, high pressure hoses, conveyor belts, and provides a brass plated steel wire having a uniform α-phase crystal structure in the post-drawing process. Significantly improve workability.

Claims (4)

A method of producing a steel cord, characterized in that a copper plating and zinc plating are sequentially performed on a steel wire, and then a uniform brass plating layer is obtained by thermally diffusing the plating layer using a fluidized bed heating furnace. The method of manufacturing a steel cord according to claim 1, wherein a heating temperature of the fluidized bed heating furnace is 500 to 650 ° C. The method of manufacturing a steel cord according to claim 1, wherein the processing time in the fluidized bed heating furnace is 4 seconds to 10 seconds. The method of manufacturing a steel cord according to claim 1, wherein the copper plating and zinc plating are pyrophosphate copper plating and zinc sulfate plating or pyrophosphate copper plating, copper sulfate plating and zinc sulfate plating.