Steel cord for tire skeleton reinforcement material and preparation method thereof

Abstract

The method for preparing a steel cord for a tire skeleton reinforcement material adopts a raw material with a low carbon content and adds chromium and vanadium alloy elements. Due to the reduced carbon content, mold loss can be reduced and product surface quality can be improved during the early drawing process. The added chromium and vanadium alloy elements refine the grains of the steel wire, strengthen the grain boundaries, improve the thermal strength and hardenability, and provide certain corrosion resistance. On this basis, combined with the control of the steel wire structure morphology during the process, it is ensured that the strength and breaking force of the steel wire are the same as those of the original process when the carbon content is reduced. Due to the improved early drawing performance, the wire breakage rate in the entire production process is reduced, the product quality is improved, and the production cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of steel cords, in particular to a steel cord for tire skeleton reinforcement material and a preparation method thereof. Background Art

[0002] Steel cord, the backbone of radial tires, faces significant challenges in its production, primarily drawing 5.5mm wire rods into 0.15-0.35mm steel wires and minimizing wire breakage during the stranding process. If a wire break occurs during production, it must be welded in a subsequent process. The welded wire is only about 40% of its original strength, and the welded wire cannot be used in other areas, such as the tire carcass, significantly reducing the value of the steel cord.

[0003] Therefore, how to reduce wire breakage during the steel cord production process is a major issue in the steel cord industry. Summary of the Invention

[0004] The purpose of the present invention is to address the problem that existing steel cords are prone to breakage during the drawing and twisting process, and to provide a steel cord for tire skeleton reinforcement material and a preparation method thereof. By controlling the components and proportions of the raw materials and combining specific processes to control the organization of the materials, while ensuring the mechanical properties of the steel wire, the drawing performance is improved, the breakage rate in the entire production process is reduced, the product quality is improved, and the production cost is reduced.

[0005] According to a first aspect of the present invention, there is provided a method for preparing a steel cord for a tire skeleton reinforcement material, comprising the following steps:

[0006] S1. After grinding and removing oxide scale from a wire rod as a raw material, the wire rod is washed with water and coated with boron, and a borax coating is applied to the surface of the wire rod; wherein the composition of the wire rod, in terms of mass percentage, comprises: C 0.74-0.78%, Mn 0.45-0.55%, Si 0.15-0.25%, Cr 0.15-0.25%, V 0.02-0.04%, and the remainder is Fe and other impurities;

[0007] S2, rough drawing and intermediate drawing of the wire rod obtained in step S1 to obtain intermediate drawn steel wire with a diameter of 1.55 to 1.95 mm;

[0008] S3, subjecting the intermediate drawn steel wire obtained in step S2 to complete austenitization through heat treatment, and then quenching it in AQ liquid water to form a microstructure with a sorbite content of 80-95%;

[0009] S4, performing pickling and flavonoid coating processes on the intermediate drawn steel wire after completing step S3 to obtain a brass-plated steel wire with a diameter of 1.55 to 1.95 mm;

[0010] S5, drawing the brass-plated steel wire obtained in step S4 into a single wire of 0.20-0.38 mm through a water tank;

[0011] S6. Select five monofilaments obtained in step S5 and twist them by double twisting to obtain a steel cord with a (1×5) structure.

[0012] In an optional embodiment, in step S1, the composition of the wire rod, in mass percentage, includes: C 0.75%, Mn 0.50%, Si 0.20%, Cr 0.20%, V 0.03%, and the remainder is Fe and other impurities.

[0013] In an optional embodiment, in step S1, the boron coating process includes: immersing the washed wire rod in a borax solution at 90±5°C and 330±40g / L for 1±0.2s to form a borax coating of 1.5 to 5g / ㎡ on the surface.

[0014] In an optional embodiment, in step S2, the wire rod obtained in step S1 is drawn through a die for 9 to 13 times to obtain a medium-drawn steel wire with a thickness of 1.55 to 1.95 mm.

[0015] In an optional embodiment, in step S3, the heat treatment temperature is 920-950°C, and the strength of the steel wire after quenching reaches 1250±50 MPa.

[0016] In an optional embodiment, in step S4, the intermediate drawn steel wire of step S3 is pickled with hydrochloric acid at a concentration of 150 g / L and a temperature of 65±5° C. to remove the oxide scale.

[0017] In an optional embodiment, in step S4, the flavonoid plating process includes: electroplating the pickled medium-drawn steel wire in a copper pyrophosphate solution with a copper content of 30±5 g / L and a zinc sulfate solution with a concentration of 250±40 g / L, and obtaining a brass-plated steel wire with a diameter of 1.55 to 1.95 mm through induction diffusion, and forming a brass plating layer of 3.5 to 4.5 g / kg on the surface of the steel wire, with a copper content of 61.5 to 64.5% and a strength of 1250±50 MPa.

[0018] In an optional embodiment, in step S5, the brass-plated steel wire is drawn through a water tank through 22 to 24 passes of a die to a single wire of 0.20 to 0.38 mm.

[0019] In an optional embodiment, in step S6, two monofilaments obtained in step S5 are selected and twisted by double twisting, and the diameter of the monofilament is 0.35 mm.

[0020] According to a second aspect of the present invention, there is provided a steel cord for tire skeleton reinforcement material prepared by the above method.

[0021] Compared with the prior art, the present invention has the following significant beneficial effects:

[0022] The method for preparing a steel cord for a tire skeleton reinforcement material adopts a raw material with a low carbon content and adds chromium and vanadium alloy elements. Due to the reduced carbon content, mold loss can be reduced and product surface quality can be improved during the early drawing process. The added chromium and vanadium alloy elements refine the grains of the steel wire, strengthen the grain boundaries, improve the thermal strength and hardenability, and provide certain corrosion resistance. On this basis, combined with the control of the steel wire structure morphology during the process, it is ensured that the strength and breaking force of the steel wire are the same as those of the original process when the carbon content is reduced. Due to the improved early drawing performance, the wire breakage rate in the entire production process is reduced, the product quality is improved, and the production cost is reduced. DETAILED DESCRIPTION

[0023] The embodiments of the present disclosure are not necessarily intended to include all aspects of the invention.It should be understood that the various concepts and embodiments introduced above, as well as those described in more detail below, can be implemented in any of many ways.

[0024] In an exemplary embodiment of the present invention, a method for preparing a steel cord for a tire frame reinforcement material is provided, comprising the following steps:

[0025] S1. After grinding and removing oxide scale from a wire rod as a raw material, the wire rod is washed with water and coated with boron, and a borax coating is applied to the surface of the wire rod; wherein the composition of the wire rod, in terms of mass percentage, comprises: C 0.74-0.78%, Mn 0.45-0.55%, Si 0.15-0.25%, Cr 0.15-0.25%, V 0.02-0.04%, and the remainder is Fe and other impurities;

[0026] S2, rough drawing and intermediate drawing of the wire rod obtained in step S1 to obtain intermediate drawn steel wire with a diameter of 1.55 to 1.95 mm;

[0027] S3, subjecting the intermediate drawn steel wire obtained in step S2 to complete austenitization through heat treatment, and then quenching it in AQ liquid water to form a microstructure with a sorbite content of 80-95%;

[0028] S4, performing pickling and flavonoid coating processes on the intermediate drawn steel wire after completing step S3 to obtain a brass-plated steel wire with a diameter of 1.55 to 1.95 mm;

[0029] S5, drawing the brass-plated steel wire obtained in step S4 into a single wire of 0.20-0.38 mm through a water tank;

[0030] S6. Select five monofilaments obtained in step S5 and twist them by double twisting to obtain a steel cord with a (1×5) structure.

[0031] In an optional embodiment, in step S1, the composition of the wire rod, in mass percentage, includes: C 0.75%, Mn 0.50%, Si 0.20%, Cr 0.20%, V 0.03%, and the remainder is Fe and other impurities.

[0032] In an optional embodiment, in step S1, the boron coating process includes: immersing the washed wire rod in a borax solution at 90±5°C and 330±40g / L for 1±0.2s to form a borax coating of 1.5 to 5g / ㎡ on the surface.

[0033] In an optional embodiment, in step S2, the wire rod obtained in step S1 is drawn through a die for 9 to 13 times to obtain a medium-drawn steel wire with a thickness of 1.55 to 1.95 mm.

[0034] In an optional embodiment, in step S3, the heat treatment temperature is 920-950°C, and the strength of the steel wire after quenching reaches 1250±50 MPa.

[0035] In an optional embodiment, in step S4, the intermediate drawn steel wire of step S3 is pickled with hydrochloric acid at a concentration of 150 g / L and a temperature of 65±5° C. to remove the oxide scale.

[0036] In an optional embodiment, in step S4, the flavonoid plating process includes: electroplating the pickled medium-drawn steel wire in a copper pyrophosphate solution with a copper content of 30±5 g / L and a zinc sulfate solution with a concentration of 250±40 g / L, and obtaining a brass-plated steel wire with a diameter of 1.55 to 1.95 mm through induction diffusion, and forming a brass plating layer of 3.5 to 4.5 g / kg on the surface of the steel wire, with a copper content of 61.5 to 64.5% and a strength of 1250±50 MPa.

[0037] In an optional embodiment, in step S5, the brass-plated steel wire is drawn through a water tank through 22 to 24 passes of a die to a single wire of 0.20 to 0.38 mm.

[0038] In an optional embodiment, in step S6, two monofilaments obtained in step S5 are selected and twisted by double twisting, and the diameter of the monofilament is 0.35 mm.

[0039] It can be understood that twisting into ropes is a common technical means in this field. Existing technology can be used for twisting, and parameters can be adjusted according to actual conditions. No further limitations are made here.

[0040] In another exemplary embodiment of the present invention, a steel cord for tire skeleton reinforcement material prepared by the aforementioned method is provided, wherein the breaking force of the steel cord is greater than 1350 MPa, the wire breakage rate during the drawing process is about 0.2 times / t, and the wire breakage rate during the plying process is about 0.4 times / t.

[0041] For better understanding, the present invention is further described below with reference to specific examples, but the process is not limited thereto, and the content of the present invention is not limited thereto.

[0042] Example 1

[0043] The composition of the raw material wire rod selected is in percentage by mass: C 0.75%, Mn 0.50%, Si 0.20%, Cr 0.20%, V 0.03%, S 0.010%, P 0.015%, Cu 0.02%, Ni 0.01%, and the remainder is Fe.

[0044] The wire rod is used to be deformed and bent 30-90 degrees by 7 wire wheels to remove the oxide scale, and then polished with two sets of 180-mesh sandpaper to further remove the oxide scale.

[0045] After washing with flowing water and passing through a 330±40g / L borax solution at 90±5℃ for 1±0.2s, a 1.5-5g / ㎡ borax coating is formed on the surface.

[0046] After 11 passes of die drawing, a 1.75mm medium-drawn steel wire is obtained. The above steel wire is heated to 940°C through heat treatment to achieve complete austenitization, and is quenched in AQ liquid water to form a sorbite content of 80-95%. By adjusting the water quenching time in liquid, the strength is adjusted to 1250±50Mpa.

[0047] The oxide scale is removed by pickling with 150g / L hydrochloric acid at 65±5℃; the wire is electroplated with a copper pyrophosphate solution with a copper content of 30±5g / L and a zinc sulfate solution with a concentration of 250±40g / L, and then subjected to induction diffusion to obtain a brass-plated steel wire with a diameter of 1.70mm. The brass coating on the surface of the steel wire is about 4.0g / kg, the copper content is about 63%, and the strength is 1250±50Mpa.

[0048] The brass-plated steel wire is drawn through a water tank through 23 passes of a die to a single filament of 0.30 mm, and then to the plying process, and double-twisted (the twisting tension is 6N, the twist length is 17.9 mm, and the twist direction is S) to produce the required finished product 1×5*0.30HT steel cord.

[0049] The 1×5*0.35HT steel cord produced in this embodiment had a wire breakage rate of approximately 0.2 times / ton during the drawing process, a 50% decrease compared to the conventional process. The wire breakage rate during the plying process was approximately 0.4 times / ton, also a 50% decrease compared to the conventional process. The average breaking strength of the finished cord produced in this embodiment was 970N.

[0050] Example 2

[0051] The composition of the raw material wire rod selected is in percentage by mass: C 0.75%, Mn 0.50%, Si 0.20%, Cr 0.20%, V 0.03%, S 0.010%, P 0.015%, Cu 0.02%, Ni 0.01%, and the remainder is Fe.

[0052] The wire rod is used to be deformed and bent 30-90 degrees by 7 wire wheels to remove the oxide scale, and then polished with two sets of 180-mesh sandpaper to further remove the oxide scale.

[0053] After washing with flowing water and passing through a 330±40g / L borax solution at 90±5℃ for 1±0.2s, a 1.5-5g / ㎡ borax coating is formed on the surface.

[0054] After 9 passes of die drawing, a 1.95mm medium-drawn steel wire is obtained. The above steel wire is heated to 940°C through heat treatment to achieve complete austenitization, and is quenched in AQ liquid water to form a sorbite content of 80-95%. By adjusting the water quenching time in liquid, the strength is adjusted to 1250±50Mpa.

[0055] The oxide scale is removed by pickling with 150g / L hydrochloric acid at 65±5℃; the wire is electroplated with a copper pyrophosphate solution with a copper content of 30±5g / L and a zinc sulfate solution with a concentration of 250±40g / L, and then subjected to induction diffusion to obtain a brass-plated steel wire with a diameter of 1.95mm. The brass coating on the surface of the steel wire is about 4.0g / kg, the copper content is about 62%, and the strength is 1250±50Mpa.

[0056] The brass-plated steel wire is drawn through a water tank through 22 passes of a die to a single filament of 0.35 mm, and then to the plying process, and double-twisted (the twisting tension is 6N, the twist length is 17.9 mm, and the twist direction is S) to produce the required finished product 1×5*0.35HT steel cord.

[0057] The 1×5*0.35HT steel cord produced in this example had a wire breakage rate of approximately 0.2 times / ton during the drawing process, a 50% reduction compared to the conventional process. The wire breakage rate during the plying process was approximately 0.4 times / ton, also a 50% reduction compared to the conventional process. The average breaking strength of the finished cord was 1360N, exceeding the national standard requirement of 1310N.

[0058] Example 3

[0059] The composition of the raw material wire rod selected is in percentage by mass: C 0.75%, Mn 0.50%, Si 0.20%, Cr 0.20%, V 0.03%, S 0.010%, P 0.015%, Cu 0.02%, Ni 0.01%, and the remainder is Fe.

[0060] The wire rod is used to be deformed and bent 30-90 degrees by 7 wire wheels to remove the oxide scale, and then polished with two sets of 180-mesh sandpaper to further remove the oxide scale.

[0061] After washing with flowing water and passing through a 330±40g / L borax solution at 90±5℃ for 1±0.2s, a 1.5-5g / ㎡ borax coating is formed on the surface.

[0062] After 13 passes of die drawing, a 1.55mm medium-drawn steel wire is obtained. The above steel wire is heated to 940°C through heat treatment to achieve complete austenitization, and is quenched in AQ liquid water to form a sorbite content of 80-95%. By adjusting the water quenching time in liquid, the strength is adjusted to 1250±50Mpa.

[0063] The oxide scale is removed by pickling with 150g / L hydrochloric acid at 65±5℃; the wire is electroplated with a copper pyrophosphate solution with a copper content of 30±5g / L and a zinc sulfate solution with a concentration of 250±40g / L, and then subjected to induction diffusion to obtain a brass-plated steel wire with a diameter of 1.95mm. The brass coating on the surface of the steel wire is about 4.0g / kg, the copper content is about 62%, and the strength is 1250±50Mpa.

[0064] The brass-plated steel wire is drawn through a water tank through 23 passes of a die to a single filament of 0.20 mm, and then to the plying process, and double-twisted (the twisting tension is 6N, the twist length is 17.9 mm, and the twist direction is S) to produce the required finished product 1×5*0.20HT steel cord.

[0065] The 1×5*0.35HT steel cord obtained in this embodiment had a wire breakage rate of approximately 0.2 times / ton during the drawing process, a 50% decrease compared to the conventional process. The wire breakage rate during the plying process was approximately 0.4 times / ton, also a 50% decrease compared to the conventional process. The finished cords in this embodiment all had a breaking force of 430N.

[0066] From the above, it can be seen that the steel cord with a (1×5) structure obtained by the method of the present invention ensures the strength and breaking force of the steel wire while reducing the carbon content, reduces the wire breakage rate in the entire production process, improves product quality, and reduces production costs.

[0067] While the present invention has been disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Persons skilled in the art will readily appreciate that various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A method for preparing a steel cord for tire skeleton reinforcement material, characterized in that: The following steps are involved: S1. After grinding and removing oxide scale from a wire rod as a raw material, the wire rod is washed and coated with boron, and a borax coating is applied to the surface of the wire rod; wherein the composition of the wire rod, in terms of mass percentage, comprises: C 0.74-0.78%, Mn 0.45-0.55%, Si 0.15-0.25%, Cr 0.15-0.25%, V 0.02-0.04%, and the remainder is Fe and other impurities; S2, performing rough drawing and intermediate drawing on the wire rod obtained in step S1 to obtain intermediate drawn steel wire with a diameter of 1.55-1.95 mm; S3, subjecting the intermediate drawn steel wire obtained in step S2 to complete austenitization by heat treatment, and then quenching it in AQ liquid water to form a microstructure with a sorbite content of 80-95%; wherein the heat treatment temperature is 920-950° C.; S4, performing pickling and flavonoid coating processes on the intermediate drawn steel wire after completing step S3 to obtain a brass-plated steel wire with a diameter of 1.55-1.95 mm; S5, drawing the brass-plated steel wire obtained in step S4 through a die through 22 to 24 passes through a water tank to a single wire of 0.20 to 0.38 mm; S6. Select five monofilaments obtained in step S5 and twist them by double twisting to obtain a steel cord with a (1×5) structure.

2. The method for preparing a steel cord for a tire skeleton reinforcement material according to claim 1, characterized in that: In step S1, the composition of the wire rod, in terms of mass percentage, includes: C 0.75%, Mn 0.50%, Si 0.20%, Cr 0.20%, V 0.03%, and the remainder is Fe and other impurities.

3. The method for preparing a steel cord for a tire skeleton reinforcement material according to claim 1, characterized in that: In step S1, the boron coating process includes: immersing the washed wire rod in a borax solution at 90±5°C and 330±40g / L for 1±0.2s to form a borax coating of 1.5~5g / ㎡ on the surface.

4. The method for preparing a steel cord for tire skeleton reinforcement material according to claim 1, characterized in that: In the step S2, the wire rod obtained in the step S1 is drawn through a die for 9 to 13 passes to obtain a medium-drawn steel wire with a thickness of 1.55 to 1.95 mm.

5. The method for preparing a steel cord for tire skeleton reinforcement material according to claim 1, characterized in that: In step S3, the strength of the steel wire after quenching reaches 1250±50 MPa.

6. The method for preparing a steel cord for tire skeleton reinforcement material according to claim 1, characterized in that: In the step S4, the intermediate drawn steel wire of step S3 is pickled with hydrochloric acid at a concentration of 150 g / L and a temperature of 65±5° C. to remove the oxide scale.

7. The method for preparing a steel cord for tire skeleton reinforcement material according to claim 1, characterized in that: In step S4, the flavonoid layer plating process includes: electroplating the pickled medium-drawn steel wire in a copper pyrophosphate solution with a copper content of 30±5 g / L and a zinc sulfate solution with a concentration of 250±40 g / L in sequence, and obtaining a brass-plated steel wire with a diameter of 1.55~1.95 mm through induction diffusion. A brass plating layer of 3.5~4.5 g / kg is formed on the surface of the steel wire, with a copper content of 61.5~64.5% and a strength of 1250±50 MPa.

8. The method for preparing a steel cord for tire skeleton reinforcement material according to claim 1, characterized in that: In step S6, two monofilaments obtained in step S5 are selected and twisted by double twisting, and the diameter of the monofilaments is 0.35 mm.

9. A steel cord for tire skeleton reinforcement prepared by the method according to any one of claims 1 to 8.