Preparation method of elliptic steel wire applied to steel cord

Abstract

The invention discloses a preparation method of an elliptical steel wire applied to a steel cord, and belongs to the technical field of metal processing. The method specifically comprises the following steps that after surface treatment is conducted on a raw material high-carbon wire rod, first-time drawing is conducted, a heavy drawn steel wire is obtained, after aging treatment is conducted after take-up, second-time drawing is conducted, and a medium drawn steel wire is obtained; carrying out heat treatment on the medium-drawn steel wire, then electroplating copper and zinc, and carrying out medium-frequency diffusion to form a brass steel wire; the brass steel wire is subjected to wet drawing, and after multi-pass wet drawing is conducted, the round steel wire with the corresponding strength is obtained according to the change of the compression amount; carrying out low-speed primary rolling on the wet-drawn finished steel wire through a rolling mill to obtain a flat round steel wire; and the flat round steel wire is subjected to secondary wet drawing and finished product mold re-drawing once, and the oval steel wire is obtained. Compared with the prior art, the technology for preparing the oval steel wire through rolling and re-drawing combines the advantages of the two machining methods, and the oval steel wire can be obtained on the premise that the mechanical property of a steel wire body is not sacrificed or even improved.

Description

Technical Field

[0001] This invention relates to the field of metal processing technology, and in particular to a method for preparing elliptical steel wires for use in steel cords. Background Technology

[0002] As the core skeleton material of radial tires, the adhesion performance of steel cord to rubber directly determines the tire's durability, safety, and service life. Currently, the steel cord monofilaments used in the market are mainly circular, resulting in a limited contact area with the rubber and a "linear" bonding interface. During tire use, when subjected to impact or excessive friction and heat, the rubber at the interface is prone to peeling, leading to damage and significantly shortening the tire's lifespan.

[0003] Steel cord is made by twisting wet-drawn monofilaments of different specifications together using a twisting machine with precise twist pitch and tension. Its adhesive performance can be reflected by the rubber penetration ability: the more fully the rubber penetrates, the higher the adhesive strength. Currently, most mainstream steel cords use round steel wires, with a few using flat wires. The round steel wire structure is not conducive to rubber penetration, easily leading to insufficient coverage of the core strand by the outer steel wires, which in turn causes core strand movement, resulting in tire punctures, decreased cord stability, and even interlayer torsion. While flat steel wires can improve rubber penetration and torsional resistance to some extent and increase the contact area with rubber, they are extremely difficult to process, suffer severe deformation and damage during production, experience rapid wear of drawing dies, and have a high wire breakage rate, leading to decreased fatigue performance and a sharp increase in production costs. Existing elliptical steel wires are produced through direct drawing or rolling, a single-stage, drastic forming process that severely damages the internal lattice structure of the steel wire, resulting in decreased breaking strength and significantly worsened torsional performance, failing to meet the high-performance requirements of steel cords.

[0004] Therefore, there is an urgent need for an elliptical steel wire with stable performance after processing, which can be used to twist steel cords with better overall performance. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing elliptical steel wires for steel cords. Its core innovation lies in a composite finishing process of "rolling + re-drawing." First, a circular steel wire substrate with the required diameter is obtained through a standard 23-pass wet drawing process. This circular steel wire is then rolled using a set of precisely designed rolls. Finally, the pre-elliptical steel wire is re-drawn through a wet drawing die to sizing and calibrate the wire. This re-drawing process eliminates minor surface defects that may occur during rolling, further refines the grains, and makes the internal structure of the steel wire more uniform and dense, thereby comprehensively improving its mechanical properties and solving the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing elliptical steel wires for use in steel cords includes the following steps: Step 1: After surface treatment of the raw material high carbon wire rod, it is drawn for the first time (referred to as large drawing) to obtain large drawn steel wire. After winding and aging treatment, it is drawn for the second time (referred to as medium drawing) to obtain medium drawn steel wire.

[0007] Step 2: The medium-stretched steel wire from Step 1 is first heat-treated, then electroplated with copper and zinc, and then subjected to medium-frequency diffusion to form brass steel wire.

[0008] Step 3: Perform wet drawing on the brass steel wire from Step 2. After multiple wet drawing passes, obtain round steel wires of corresponding strength based on the changes in compression.

[0009] Step 4: The wet-drawn finished steel wire from Step 3 is rolled at low speed once through a rolling mill to obtain a flat round steel wire.

[0010] Step 5: Perform a second wet drawing of the flat circular steel wire from Step 4 using a finished product mold to obtain an elliptical steel wire.

[0011] A further improvement of the present invention is that, in step 1, the surface treatment of the steel wire includes mechanical descaling, pickling and washing, and borax coating. The concentration of hydrochloric acid used for pickling is WL: 18-220 g / L, and the iron ion concentration is Fe. 2+ : 40~60g / L.

[0012] A further improvement of the present invention is that, in step 2, the heat treatment is quenching of the steel wire in AQ liquid, and the copper plating process uses copper pyrophosphate, with the electroplating current density being: copper plating ≤16, zinc plating ≤35.

[0013] A further improvement of the present invention is that the number of wet drawing passes in step 3 is 23.

[0014] A further improvement of the present invention is that the rolling speed in step 4 should be less than 1 m / min to prevent overheating and the occurrence of an annealing-like phenomenon that would lead to a decrease in strength.

[0015] A further improvement of the present invention is that, in step 5, a wet-drawing finished product die is selected. Through mechanical drawing, the overstretched portion of the flat circular steel wire is filled into the flat area to form an ellipse. After rolling, the grains are further refined and strengthened, the stress state is changed, defects are reduced, anisotropy is improved, torsional performance is enhanced, and deformation heat effect is generated during the rolling deformation process (deformation heat). This heat can produce a certain "dynamic recovery" effect on the steel wire, partially eliminating work hardening and slightly restoring plasticity. This is beneficial for subsequent re-drawing processing and reduces the risk of direct wire breakage.

[0016] The beneficial effects of this invention are: The present invention provides a method for preparing elliptical steel wires for steel cords. This method combines the advantages of two processing methods by using a "rolling + re-drawing" process to prepare elliptical steel wires. It can obtain elliptical steel wires without sacrificing or even improving the mechanical properties of the steel wire itself.

[0017] The present invention provides a method for preparing elliptical steel wires for steel cords, which solves the problems of rubber penetration rate and center protrusion of existing round steel wires, increases rubber adhesion, and improves tire durability. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the process for preparing elliptical steel wires for steel cords according to the present invention.

[0019] Figure 2 A schematic diagram of the elliptical steel wire prepared for this invention.

[0020] Figure 3 This is a schematic diagram of the secondary drawing process of the elliptical steel wire of the present invention.

[0021] Figure 4 This is a schematic diagram of the elliptical steel wire in Example 1.

[0022] Figure 5 This is a comparison chart of the performance of the 0.205mm UT steel wire round wire in Example 1 and the elliptical steel wire of the present invention.

[0023] Figure 6 This is a schematic diagram of the elliptical steel wire in Example 2.

[0024] Figure 7 This is a comparison chart of the performance of the 0.225mm ST steel wire round wire in Example 2 and the elliptical steel wire of the present invention. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0026] like Figures 1-3 As shown, a method for preparing elliptical steel wires for use in steel cords: Step 1: After surface treatment of the raw material high carbon wire rod, it is drawn for the first time to obtain large-drawn steel wire. After winding and aging treatment, it is drawn for the second time to obtain medium-drawn steel wire.

[0027] Step 2: The medium-stretched steel wire from Step 1 is first heat-treated, then electroplated with copper and zinc, and then subjected to medium-frequency diffusion to form brass steel wire.

[0028] Step 3: Perform wet drawing on the brass steel wire from Step 2. After multiple wet drawing passes, obtain round steel wires of corresponding strength based on the changes in compression.

[0029] Step 4: The wet-drawn finished steel wire from Step 3 is rolled at low speed once through a rolling mill to obtain a flat round steel wire.

[0030] Step 5: Perform a second wet drawing of the flat circular steel wire from Step 4 using a finished product mold to obtain an elliptical steel wire.

[0031] The present invention will be further described below through specific embodiments. Example 1

[0032] Using 86c wire rod with a diameter of 5.5mm as raw material, large and medium drawing were performed to obtain medium-drawn steel wire with a diameter of 1.53mm.

[0033] After heat treatment, the steel wire structure is restored, which facilitates subsequent drawing. After pickling and washing, the heat-treated steel wire is electroplated with copper-zinc alloy. Through medium-frequency diffusion, the copper and zinc atoms on the surface are fully diffused to form brass steel wire.

[0034] A brass wire with a diameter of 1.58±0.05mm was threaded into a wet drawing machine and subjected to 23 wet drawing passes at a drawing speed of 6m / s to obtain a wire with a diameter of 0.205mm.

[0035] After starting the mill, adjust the gap to 0.195mm and set the rolling speed to 0.5m / min. Feed the 0.205mm steel wire to the mill along the guide wheel and obtain a flat steel wire after rolling.

[0036] After rolling, the flat steel wire is threaded into a wet-drawing die with a diameter of 0.205mm, and then wet-drawn again to obtain an elliptical steel wire, which facilitates a visual demonstration of how it will be after inlay. Figure 4 As shown, the measured diameter of the major axis is 0.214 mm and the diameter of the minor axis is 0.196 mm.

[0037] The performance of the finished elliptical steel wire compared with that of the same round steel wire is as follows: Figure 5 As shown. The elliptical steel wire prepared by the method of the present invention has better overall performance (such as a breaking tensile strength increase of about 1.6%, a breaking elongation of 3.65%, and a torsion count of about 0.19%). Example 2

[0038] Using 82c wire rod with a diameter of 5.5mm as raw material, large and medium drawing were performed to obtain medium-drawn steel wire with a diameter of 1.48mm.

[0039] After heat treatment, the steel wire structure is restored, which facilitates subsequent drawing. After pickling and washing, the heat-treated steel wire is electroplated with copper-zinc alloy. Through medium-frequency diffusion, the copper and zinc atoms on the surface are fully diffused to form brass steel wire.

[0040] A brass wire with a diameter of 1.48±0.0.5mm was threaded into a wet drawing machine and subjected to 23 wet drawing passes at a drawing speed of 13m / s to obtain a wire with a diameter of 0.225mm.

[0041] After starting the mill, adjust the gap to 0.210mm and set the rolling speed to 1m / min. Feed the 0.225mm steel wire to the mill along the guide wheel and roll it to obtain a flat steel wire.

[0042] After rolling, the flat steel wire is passed through a wet-drawing die with a diameter of 0.225mm, and wet-drawn again to obtain an elliptical steel wire. Figure 6 As shown, the short axis of the steel wire is approximately 0.203 mm, and the long axis is approximately 0.236 mm.

[0043] The performance of the finished elliptical steel wire compared with that of the same round steel wire is as follows: Figure 7 As shown. The elliptical steel wire prepared by the method of the present invention has better overall performance (such as an increase in breaking tensile strength of about 2.27%, an increase in elongation at break of about 5.61%, and an increase in the number of torsion cycles of about 0.29%).

[0044] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing elliptical steel wires for use in steel cord, characterized in that, Includes the following steps: Step 1: After surface treatment of the raw material high carbon wire rod, it is drawn for the first time to obtain large-drawn steel wire. After winding and aging treatment, it is drawn for the second time to obtain medium-drawn steel wire. Step 2: The medium-stretched steel wire from Step 1 is first heat-treated, then electroplated with copper and zinc, and then subjected to medium-frequency diffusion to form brass steel wire; Step 3: Perform wet drawing on the brass steel wire from Step 2. After multiple wet drawing passes, obtain round steel wires of corresponding strength based on the changes in compression. Step 4: The wet-drawn finished steel wire from Step 3 is rolled at low speed once through a rolling mill to obtain a flat round steel wire; Step 5: Perform a second wet drawing of the flat circular steel wire from Step 4 using a finished product mold to obtain an elliptical steel wire.

2. The method for preparing elliptical steel wires for use in steel cord as described in claim 1, characterized in that: In step 1, the surface treatment of the steel wire includes mechanical descaling, pickling and washing, and borax coating. The hydrochloric acid concentration for pickling is WL: 18~220g / L, and the iron ion concentration is Fe. 2+ : 40~60g / L.

3. The method for preparing elliptical steel wires for use in steel cord as described in claim 1, characterized in that: In step 2, the heat treatment involves quenching the steel wire in AQ liquid, and the copper plating process uses copper pyrophosphate. The electroplating current density is: copper plating ≤16, zinc plating ≤35.

4. The method for preparing elliptical steel wires for use in steel cord as described in claim 1, characterized in that: In step 3, the number of wet drawing passes is 23.

5. The method for preparing elliptical steel wires for use in steel cord as described in claim 1, characterized in that: In step 4, the rolling speed should be less than 1 m / min to prevent overheating and the resulting annealing-like phenomenon, which would lead to a decrease in strength.

6. The method for preparing elliptical steel wires for use in steel cord as described in claim 1, characterized in that: In step 5, a wet-drawing die is used. Through mechanical drawing, the overstretched portion of the flat circular steel wire is filled into the flat area to form an ellipse. After rolling, the grains are further refined and strengthened, the stress state is changed, defects are reduced, anisotropy is improved, torsional performance is enhanced, and deformation heat effect occurs. Heat is generated during the rolling deformation process. This heat can produce a certain "dynamic recovery" effect on the steel wire, partially eliminating work hardening and slightly restoring plasticity. This is beneficial for subsequent redrawing processing and reduces the risk of direct wire breakage.

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