JPH05311248A - Manufacture of plated high tensile strength steel wire - Google Patents

Abstract

PURPOSE:To easily obtain a high tensile strength plated steel wire by subjecting a plain carbon steel wire to plating treatment after rapid cooling at the time of patenting, executing reheating at the time of plating diffusion and thereafter gradually cooling it. CONSTITUTION:A plain carbon steel wire contg. 0.65 to 0.95% C is charged to a patenting furnace and is hardened to generate pearlitic transformation. After the completion of the transformation, this steel wire is rapidly cooled to a room temp. Then, plating of Cu, Zn or the like is applied, and successively, the plain carbon steel wire is reheated to 500 to 600 deg.C in a thermal diffusing furnace to form the state of carbon as solid solution in ferrite in the structure into a one in which it is diffusible. After the reheating, the steel wire is gradually cooled to <=400 deg.C at 25 to 50 deg.C/sec cooling rate and is thereafter rapidly cooled to a room temp. Next, an oxidized film is removed by a posttreating apparatus, and it is coiled round a bobbin 2. Then, cold drawing is executed, and about 3.45 to 3.90 true strains are given thereto. In this way, the objective high strength plated steel wire having >=3500MPs tensile strength and provided with toughness can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a plated high tensile strength steel wire used as a rubber reinforcing material.

[0002]

2. Description of the Related Art Steel wires having a small cross-sectional area are manufactured by cold drawing a raw material wire. However, in order to improve the mechanical properties of the steel wire, especially the tensile strength, a patenting treatment is performed. It is customary to do so to adjust the steel composition and then cold draw. In the manufacturing process of such a steel wire, in JP-A-62-192532, by adjusting the cooling rate after patenting transformation, the subsequent drawing workability is improved and a true strain of 3.5 or more is given. It has been proposed to produce high strength steel wires.
In this prior art, when patenting a carbon steel wire having a C content of 0.70 to 0.85 wt%, the wire is gradually cooled at 25 to 45 ° C./sec after completion of pearlite transformation, and is then subjected to cold drawing. It is stated that by giving a true strain of 3.8 to 4.2, a steel wire having a tensile strength of 3500 MPa or more can be obtained without impairing the toughness. And, one of the reasons that the gradual cooling after completion of pearlite transformation improves the workability of the wire is that carbon in ferrite gradually precipitates on the cementite thin layer during the gradual cooling, that is, in the ferrite layer. It is because the supersaturated carbon is reduced.

However, wires for reinforcing rubber products such as tires, hoses and conveyor belts are brass-plated in order to improve adhesion with rubber. In the production of such plated steel wire, after the patenting treatment, the wire is plated with two layers of copper and zinc, and heat diffusion is performed to achieve brass plating. Therefore, a reheating process is performed after the patenting process. Therefore, when the slow cooling is performed after the patenting as in the prior art, there is a problem that the effect is lost and it cannot be utilized for the later cold workability.

The present invention was devised in order to solve the above-mentioned problems, and an object thereof is to manufacture a high tensile strength steel wire with plating using a plain carbon steel wire rod. To provide a method.

[0005]

In order to achieve the above object, the present inventor has used a plain carbon material for 3500M.
In order to obtain a high tensile strength steel wire of Pa or higher, the idea that gradual cooling after patenting transformation was considered indispensable was changed, and at the time of patenting, the wire after transformation was rapidly cooled to prevent the subsequent diffusion of plating. Therefore, high tensile strength equal to or higher than that of the prior art is realized by performing the controlled cooling by utilizing the reheating time. That is, the feature of the present invention is that the carbon content is 3500 by cold drawing using a plain carbon steel wire having a carbon content of 0.65 to 0.95%.
In obtaining a brass-plated steel wire for steel cord having a pressure of MPa or more, the plain carbon steel wire is rapidly cooled to room temperature after completion of pearlite transformation during patenting, and then plated to diffuse the plated plain carbon steel wire at 500 to 600 ° C. Reheating, and after the reheating, the cooling rate up to 400 ° C. or less is gradually cooled at 25 to 50 ° C./sec.

The present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an outline of a method for producing a plated high tensile strength steel wire according to the present invention. Reference numeral 1 is a raw material wire bobbin, 2 is a winding bobbin, and a heating furnace 3, a patenting furnace 4, a water cooling mechanism 5, a plating pretreatment device 6, and C are provided between the raw material wire bobbin 1 and the winding bobbin 2.
A u plating tank 7, a Zn plating tank 8 and a thermal diffusion furnace 9 are arranged. The patenting furnace 4 is preferably a fluidized bed type, but may be a molten lead type or a molten salt type.
Further, according to the present invention, the adjustment cooling device 10 is provided continuously or separately on the outlet side of the heat diffusion furnace 9, and the water cooling mechanism 11 is arranged downstream thereof. Reference numeral 12 denotes a post-treatment device, which comprises an oxide film removing tank and the like.

W is a plain carbon steel wire, the C content is 0.65 to 0.95% by weight, and the diameter is 0.6 to 2.2.
The mm one is used. Here, the plain carbon steel wire has a chemical composition of Si: 0.15 to 0.15 by weight.
0.35%, Mn: 0.3 to 0.9% The balance is iron and inevitable impurities. The lower limit of C amount is 0.65%
The reason for this is that if the carbon amount is less than this, sufficient strength cannot be obtained, and the upper limit is set to 0.95%,
This is because the required toughness cannot be obtained with an amount of carbon exceeding this amount. The plain carbon steel wire W is paid out from the raw material wire bobbin 1 and heated to 910 to 960 ° C. in a heating furnace 3 of, for example, a gas direct fire type. This forms a uniform austenite phase. Then, the plain carbon steel wire W is fed into the patenting furnace 4,
Here, it is quenched to 500 to 600 ° C. and transformed into pearlite. When this pearlite transformation is completed, the water cooling mechanism 5
To rapidly cool to room temperature.

Next, the plain carbon steel wire W is subjected to electrolytic pickling by removing the oxide film on the surface thereof in the plating pretreatment device 6. These conditions are the same as usual. Then, by passing through the Cu plating bath 7 and the Zn plating bath 8 next, Cu plating and Zn plating are applied in layers on the surface.
Cu plating and Zn plating are sufficient under normal conditions. Next, the plated plain carbon steel wire W is heated in the thermal diffusion furnace 9. The heat diffusion furnace 9 is preferably a fluidized bed type heat diffusion furnace. Here, the plain carbon steel wire W is 50
Reheat at 0-600 ° C for 5-15 seconds. By this reheating, the solid solution carbon in the ferrite of the structure of the plain carbon steel wire W becomes diffusible. The lower limit of the reheating temperature is 500 ° C., and the temperature lower than the lower limit cannot effectively diffuse heat in the two-layer plating. Upper limit of 600
It must be avoided at temperatures above ℃, as spheroidization of cementite begins.

In the above steps, the brass-plated steel wire then enters the controlled cooling device 10, where it is gradually cooled under predetermined conditions. As the adjustment cooling device 10, for example, a tunnel furnace with a heater or a hot air furnace is used, and the brass-plated steel wire is used here at a temperature of 400 ° C. or lower, preferably 300 ° C. or lower (but room temperature or higher), and a cooling rate of 25.
Cooled at ~ 50 ° C / sec. By the reheating and the gradual cooling, the carbon solid-dissolved in the ferrite matrix of the brass-plated steel wire structure advances on the cementite, thereby improving the lowering limit of the wire. If the cooling rate is 25 ° C./sec or less, the total line length becomes too long, and if the temperature exceeds 50 ° C./sec, solid solution carbon in the ferrite is insufficiently precipitated, so that neither is possible. Then, after gradually cooling to a temperature of 400 ° C. or lower, preferably 300 ° C. or lower, it is rapidly cooled to room temperature by the water cooling mechanism 11, the oxide film is removed by the post-treatment device 12, and then collected on the winding bobbin 2. It Up to this point, continuous processing is performed inline.

The brass-plated steel wire W wound as described above is then cold drawn by a wire drawing machine such as a slip type wet wire drawing machine to obtain a true strain of 3.45 to
3.90 is given to obtain a steel wire having a target wire diameter. This steel wire has a tensile strength of 3500 MPa or more and high strength with toughness.

[0011]

EXAMPLES Examples of the present invention will be described below. A brass-plated steel wire for tire cord was manufactured according to the present invention.
The raw material wire used was a plain carbon material having a diameter of 1.68 mm. Its composition is C: 0.82%, Si: 0.2
2%, Mn: 0.50% The balance is iron and inevitable impurities. The raw material wire rod was first heated to 950 ° C. in a gas direct-fired heating furnace, then quenched in a fluidized bed type patenting furnace at 550 ° C., and immediately water-cooled after completion of pearlite transformation. Then, after descaling and electrolytic pickling, Cu and Zn were plated in two layers by passing through a Cu bath and a Zn bath. Then, it was reheated in a fluidized bed type diffusion furnace and reheated to improve heat diffusion and drawing workability. The furnace temperature was about 550 ° C. and the temperature was maintained for 9 seconds. Then, in the adjacent hot-air stove type box, it is gradually cooled to 250 ° C over 8 seconds (cooling rate 3
(7.5 ° C./sec), then cooled to room temperature with water and wound up. The brass-plated wire obtained by the above in-line treatment was cold drawn by a slip type wet wire drawing machine to give a true strain of 3.73 to obtain a brass-plated steel wire having a diameter of 0.26 mm. The brass-plated steel wire had a tensile strength of 3520 MPa and exhibited excellent mechanical properties with a twist value of 32 times / 100 d. From the above results, it is clear that the wire may be rapidly cooled at the time of patenting, and high-tensile strength steel wire can be obtained by performing the controlled cooling by using reheating at the time of thermal diffusion of plating.

[0012]

According to the present invention described above, a brass plated high tensile strength steel wire can be easily manufactured using a plain carbon material, and
Since water cooling can be provided immediately after the patenting furnace, it is possible to save a considerable space for installing the slow cooling means and to shorten the total length of the line.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of the present invention.

[Explanation of symbols]

 3 Heating Furnace 4 Patenting Furnace 7 Cu Plating Tank 8 Zn Plating Tank 9 Thermal Diffusion Furnace 10 Adjusting Cooling Device

Claims (1)

[Claims] 1. A plain carbon steel wire having a C content of 0.65 to 0.95% is used and cold drawn to 3500M.
To obtain a brass-plated steel wire for steel cord of Pa or more, the plain carbon steel wire is rapidly cooled to room temperature after completion of pearlite transformation during patenting, and then plated to diffuse the plated plain carbon steel wire at 500 to 600 ° C. The method for producing a high tensile strength steel wire with plating, which comprises reheating to 100 ° C., followed by slow cooling to 400 ° C. or less at a cooling rate of 25 to 50 ° C./sec.