Ultra-high strength steel wire for tire carcass and preparation method thereof

Abstract

The present invention provides an ultra-high-strength steel wire for tire carcasses. The steel wire comprises a core wire and outer layer wires evenly distributed around the core wire. The core wire is composed of three core wires with a diameter of D1, and the outer layer wires are composed of nine outer layer monofilaments with a diameter of D2. The core wires and outer layer monofilaments are twisted together in the same twist direction. The ratio of D1 to D2 is between 1 and 1.2. The core wires and outer layer monofilaments are made of steel wire with the same composition, which, by mass percentage, includes: C 0.89-0.99%, Si 0.12-0.22%, Mn 0.32-0.42%, Cr 0.18-0.28%, with the remainder being Fe and other impurities. The present invention also provides a method for preparing the ultra-high-strength steel wire for tire carcasses. The steel wire of the present invention has a small diameter, high cord breaking strength, and a thin cord thickness, thereby reducing the amount of steel cord used, saving manufacturing costs, and achieving lightweight tires and reduced tire rolling resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of steel cords, and in particular to an ultra-high strength steel wire for a tire carcass and a preparation method thereof. Background Art

[0002] Steel cord, with its high strength, toughness, and fatigue resistance, is the primary tire skeleton material. With the rapid development of the automotive and transportation industries, radial tires are developing toward lightweight, low rolling resistance, high safety, and retreadability. Therefore, the carcass cord, a key component of all-steel radial truck tires, plays a crucial role in the finished tire's weight, load capacity, safety, wear resistance, and retreadability.

[0003] At present, the steel cord used as the tire carcass mainly adopts the structure of 3+9×0.22+0.15HT. The breaking force of the cord cannot meet the requirements. Moreover, due to the large thickness of the cord, the amount of steel cord used increases, which cannot meet the requirements of lightweight and low rolling resistance and increases the cost. Summary of the Invention

[0004] The present invention aims to address the deficiencies in the prior art and provide an ultra-high-strength steel wire for a tire carcass and a preparation method thereof. The invention adopts steel cords with a single-filament strength of 3800 to 4000 MPa to twist into a 3×D1 / 9×D2 CCUT steel wire rope with a small diameter, high cord breaking force, and small cord thickness, thereby reducing the amount of steel cord used, saving manufacturing costs, and achieving lightweight tires and reducing tire rolling resistance.

[0005] According to a first aspect of the present invention, there is provided an ultra-high-strength steel wire for a tire carcass, the steel wire comprising a core wire and outer layer wires uniformly distributed around the core wire, the core wire being composed of three core wires having a diameter D1, the outer layer wires being composed of nine outer layer monofilaments having a diameter D2, the core wires and the outer layer monofilaments being twisted together in the same twist direction;

[0006] Among them, the ratio of D1 to D2 is between 1 and 1.2;

[0007] The core wire and the outer layer monofilament are made of steel wire with the same composition, which includes, by mass percentage, C 0.89-0.99%, Si 0.12-0.22%, Mn 0.32-0.42%, Cr 0.18-0.28%, and the rest is Fe and other impurities.

[0008] In an optional embodiment, the diameter D1 of the core wire ranges from 0.17 to 0.27 mm.

[0009] In an optional embodiment, the diameter D2 of the outer monofilament ranges from 0.15 to 0.25 mm.

[0010] In an optional embodiment, the composition of the steel wire includes, by mass percentage, C 0.94%, Si 0.17%, Mn 0.37%, S 0.003%, Ni 0.003%, Cu 0.005%, Al 0.001%, P+S 0.015%, Cr 0.23%, and the remainder is Fe.

[0011] According to a second aspect of the present invention, there is provided a method for preparing the aforementioned ultra-high strength steel wire for tire carcasses, comprising the following steps:

[0012] S1. Pre-treating the wire rod for later use, wherein the composition of the wire rod, in percentage by mass, comprises: C 0.89-0.99%, Si 0.12-0.22%, Mn 0.32-0.42%, Cr 0.18-0.28%, and the remainder being Fe and other impurities;

[0013] S2, subjecting the wire rod pretreated in step S1 to rough drawing and intermediate drawing processes to obtain a first intermediate drawing wire and a second intermediate drawing wire, respectively, wherein the diameter of the first intermediate drawing wire is larger than the diameter of the second intermediate drawing wire;

[0014] S3, subjecting the first and second drawn wires obtained in step S2 to heat treatment to achieve complete austenitization, and then quenching them in AQ liquid water to form a sorbite structure;

[0015] S4, performing pickling and flavonoid coating processes on the first and second middle drawn wires after step S3 to obtain the brass-plated first and second middle drawn wires;

[0016] S5, drawing the brass-plated first intermediate drawn wire obtained in step S4 through a water tank into a first monofilament with a diameter of D1, and drawing the brass-plated second intermediate drawn wire through a water tank into a second monofilament with a diameter of D2, wherein the ratio of D1 to D2 is between 1 and 1.2;

[0017] S6. Select three first monofilaments as core filaments and nine second monofilaments as outer monofilaments, twist the core filaments and outer filaments at one time through a double twisting machine to form a 3×D1 / 9×D2 CCUT steel wire rope, and inspect it to obtain an ultra-high strength steel wire with a compact structure.

[0018] In an optional embodiment, in step S1, the pretreatment process of the wire rod includes: the wire rod is subjected to water washing, acid washing, water washing, and boron coating processes, and a borax coating is applied on the surface of the wire rod.

[0019] In an optional embodiment, in step S2, the diameter of the wire rod after rough drawing is 3.15-3.25 mm.

[0020] In an optional embodiment, the diameter of the first middle drawn wire is 1.55 mm, and the diameter of the second middle drawn wire is 1.50 mm.

[0021] In an optional embodiment, in step S3, the heat treatment temperature is 960-1060° C.; and the concentration of the AQ solution is 7-13%.

[0022] In an optional embodiment, in step S5, the diameter of the first monofilament is in the range of 0.17 to 0.27 mm, and the diameter D2 of the second monofilament is in the range of 0.15 to 0.25 mm.

[0023] Compared with the prior art, the present invention has the following significant beneficial effects:

[0024] The ultra-high-strength steel wire for tire carcasses of the present invention is a steel wire rope with a 3×D1 / 9×D2 CCUT structure twisted from steel cords with a single-filament strength of 3800 to 4000 MPa. The steel wire rope has a small diameter, a high cord breaking force, and a small cord thickness, thereby reducing the amount of steel cord used, saving manufacturing costs, achieving lightweight tires, and reducing tire rolling resistance. In addition, the steel wire structure is changed from point contact between layers to line contact between steel cord layers, thereby avoiding local stress concentration when the steel cord is used in the tire, greatly improving the tire fatigue performance and service life.

[0025] The ultra-high strength steel wire for tire carcasses of the present invention has a breaking force of not less than 1500N, reduces cord thickness and mass, improves cord fatigue, and reduces cord stiffness; the outer edge size and strength performance of the finished tire meet standard requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic structural diagram of the ultra-high strength steel wire used for tire carcass of the present invention.

[0027] Figure 2 This is the crystal phase structure diagram of the first wire drawing after heat treatment in Example 1 of the present invention.

[0028] Figure 3 This is the crystal phase organization diagram of the second wire drawing after heat treatment in Example 1 of the present invention.

[0029] Figure 4 This is a compression rate trend chart for each pass from 1.55UT to 0.22UT in the water tank drawing in Example 1 of the present invention.

[0030] Figure 5 This is a compression rate trend diagram of each pass from 1.50UT to 0.20UT in the water tank drawing in Example 1 of the present invention.

[0031] Figure 6This is a physical picture of the calendering process when the steel wire of Example 1 of the present invention is used to prepare the finished product.

[0032] Figure 7 This is a physical picture of the cutting process when the steel wire of Example 1 of the present invention is used to prepare the finished product. DETAILED DESCRIPTION

[0033] In order to better understand the technical content of the present invention, specific embodiments are given and described below with reference to the accompanying drawings.

[0034] Various aspects of the present invention are described in this disclosure with reference to the accompanying drawings, in which a number of illustrative embodiments are shown. The embodiments of the present disclosure are not necessarily intended to be comprehensive. It should be understood that the various concepts and embodiments described above, as well as those described in more detail below, can be implemented in any of a number of ways.

[0035] Combine Figure 1 As shown, in a preferred embodiment of the present invention, an ultra-high strength steel wire for a tire carcass is provided, the steel wire comprising a core wire 1 and outer layer wires 2 evenly distributed around the core wire, the core wire 1 being composed of three core wires 11 with a diameter of D1, the outer layer wires 2 being composed of nine outer layer monofilaments 21 with a diameter of D2, the core wires and the outer layer monofilaments being twisted into shape in one go in the same twist direction;

[0036] Among them, the ratio of D1 to D2 is between 1 and 1.2;

[0037] The core wire and the outer layer monofilament are made of steel wire with the same composition, which includes, by mass percentage, C 0.89-0.99%, Si 0.12-0.22%, Mn 0.32-0.42%, Cr 0.18-0.28%, and the rest is Fe and other impurities.

[0038] In an optional embodiment, the diameter D1 of the core wire ranges from 0.17 to 0.27.

[0039] In an optional embodiment, the diameter D2 of the outer monofilament is in the range of 0.15 to 0.25.

[0040] In an optional embodiment, the composition of the steel wire includes, by mass percentage, C 0.94%, Si 0.17%, Mn 0.37%, S 0.003%, Ni 0.003%, Cu 0.005%, Al 0.001%, P+S 0.015%, Cr 0.23%, and the remainder is Fe.

[0041] In another preferred embodiment of the present invention, a method for preparing the aforementioned ultra-high strength steel wire for tire carcass is provided, comprising the following steps:

[0042] S1. Pre-treating the wire rod for later use, wherein the composition of the wire rod, in percentage by mass, comprises: C 0.89-0.99%, Si 0.12-0.22%, Mn 0.32-0.42%, Cr 0.18-0.28%, and the remainder being Fe and other impurities;

[0043] S2, subjecting the wire rod pretreated in step S1 to rough drawing and intermediate drawing processes to obtain a first intermediate drawing wire and a second intermediate drawing wire, respectively, wherein the diameter of the first intermediate drawing wire is larger than the diameter of the second intermediate drawing wire;

[0044] S3, subjecting the first and second drawn wires obtained in step S2 to complete austenitization by heat treatment, and then quenching them in AQ liquid water to form a sorbite structure;

[0045] S4, performing pickling and flavonoid coating processes on the first and second middle drawn wires after step S3 to obtain the brass-plated first and second middle drawn wires;

[0046] S5, drawing the brass-plated first intermediate drawn wire obtained in step S4 through a water tank into a first monofilament with a diameter of D1, and drawing the brass-plated second intermediate drawn wire through a water tank into a second monofilament with a diameter of D2, wherein the ratio of D1 to D2 is between 1 and 1.2;

[0047] S6. Select three first monofilaments as core filaments and nine second monofilaments as outer monofilaments, twist the core filaments and outer filaments at one time through a double twisting machine to form a 3×D1 / 9×D2 CCUT steel wire rope, and inspect it to obtain an ultra-high strength steel wire with a compact structure.

[0048] In an optional embodiment, in step S1, the pretreatment process of the wire rod includes: the wire rod is subjected to water washing, acid washing, water washing, and boron coating processes, and a borax coating is applied on the surface of the wire rod.

[0049] In an optional embodiment, in step S2, the diameter of the wire rod after rough drawing is 3.15-3.25 mm.

[0050] In an optional embodiment, the diameter of the first middle drawn wire is 1.55 mm, and the diameter of the second middle drawn wire is 1.50 mm.

[0051] In an optional embodiment, in step S3, the heat treatment temperature is 960-1060° C.; and the concentration of the AQ solution is 7-13%.

[0052] In an optional embodiment, in step S5, the diameter of the first monofilament is in the range of 0.17 to 0.27, and the diameter D2 of the second monofilament is in the range of 0.15 to 0.25.

[0053] 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.

[0054] Example 1

[0055] 1. Pre-treat the wire rod for later use. The wire rod composition, by mass percentage, includes: C 0.94%, Si 0.17%, Mn 0.37%, S 0.003%, Ni 0.003%, Cu 0.005%, Al 0.001%, P+S 0.015%, Cr 0.23%, and the remainder is Fe. The pre-treatment control requirements are shown in Table 1.

[0056] Table 1

[0057]

[0058]

[0059] 2. The pre-treated wire rod is subjected to rough drawing and medium drawing processes to obtain a first medium drawing wire and a second medium drawing wire respectively, wherein the diameter of the first medium drawing wire is larger than the diameter of the second medium drawing wire.

[0060] The control requirements and die sequence process of rough drawing are shown in Table 2 and Table 3 respectively.

[0061] Table 2

[0062]

[0063] Table 3

[0064]

[0065] The control requirements for intermediate drawing are shown in Table 4, the die sequence process for the first intermediate drawing is shown in Table 5, and the die sequence process for the second intermediate drawing is shown in Table 6.

[0066] Table 4

[0067]

[0068] Table 5

[0069]

[0070] Table 6

[0071]

[0072] 3. The first and second middle drawn wires are subjected to heat treatment to achieve complete austenitization, and then quenched in AQ liquid water to form a sorbite structure. Thereafter, pickling and flavonoid coating processes are performed to obtain the brass-plated first and second middle drawn wires; the process is shown in Table 7.

[0073] Table 7

[0074]

[0075]

[0076]

[0077] The first medium drawing wire (1.55UT) and the second medium drawing wire (1.50UT) obtain a sorbite structure after heat treatment and have good drawing properties. The specifications and properties of the first medium drawing wire (1.55UT) and the second medium drawing wire (1.50UT) are shown in Table 8.

[0078] Table 8

[0079] project 1.50UT 1.55UT Tensile strength / Mpa 1430 1420 Shrinkage rate / % 39 38.5 Diameter / mm 1.502 1.548

[0080] 4. The brass-plated first middle wire is drawn by water tank drawing in 23 passes to a first single wire with a diameter of 0.22, and the brass-plated second middle wire is drawn in 22 passes to a second single wire with a diameter of 0.20.

[0081] For high-strength steel wires that rely on cold drawing with high compression rates, their torsional properties determine the breakage of strands and production efficiency. Single wires with poor torsional properties are prone to breakage, and the fracture ends are basically torsionally brittle and flat ends, which is the biggest obstacle to high-compression high-carbon steel wires.

[0082] According to the high carbon steel drawing process, the specifications and properties of the first and second monofilaments are shown in Table 9. The strength can reach 3800-4000 MPa, and the torsion test shows that they have good toughness (such as Figure 4 and Figure 5 shown).

[0083] Table 9

[0084] project 0.22UT 0.20UT Diameter / mm 0.223 0.203 Breaking force / N 156 131 Tensile strength / (Mpa) 3990 4050 Twist / turn 65 60

[0085] 5. Select three first monofilaments as core wires and nine second monofilaments as outer monofilaments. The core wires are arranged in a triangle, and three outer monofilaments are arranged on each side of the circumference. The core wires and outer wires are twisted into a 3×0.22 / 9×0.20 CCUT steel wire rope at one time through a double twisting machine. Its performance parameters are: twist direction: S, diameter: 0.87mm, linear density: 3.38g / m, lay length: 12.5mm, breaking strength: ≥1500N.

[0086] The plying process parameters are shown in Tables 10 and 11.

[0087] Table 10

[0088] 1 Synchronous pulley / twist gear 44 / 56 2 die 0.88mm 3 Door mold 0.90mm 4 Line hub 5 ATC flat spring 1.2*0.33mm 6 Reel 7 straightener Fixed TAS-29-6+P2913 flat plate straightener 8 Straightener wheels 6mm*90°, 13mm*90°diameter*angle 9 Straightener pressure Population: 6±1mm, outlet: 5±2mm (reference value), TAS handle must be fastened 10 Filter 3 slots 2 wheels 10° 11 Rope rack 12 Distribution board 3+9 holes see attached Figure 1 13 Pre-deformation / pressing amount Three-piece deformer 14 Reverse wheel / angle UU 15 Tension belt (core wire) 16 (Noodles) 17 Tension spring (core wire) 18 (Noodles) 19 (Center traction) 20 Broken wire protection type Zhongrun detector

[0089] Table 11

[0090] 1 Synchronous pulley / twist gear 44 / 56 2 die 0.88mm 3 Door mold 0.90mm 4 Line hub 5 ATC flat spring 1.2*0.33mm 6 Reel 7 straightener Fixed TAS-29-6+P2913 flat plate straightener 8 Straightener wheels 6mm*90°, 13mm*90°diameter*angle 9 Straightener pressure Inlet: 6±1mm, outlet: 5±2mm (reference value), TAS handle must be fastened 10 Twister 3 slots 2 wheels 10° 11 Rope rack 12 Distribution board 3+9 holes see attached Figure 1 13 Pre-deformation / pressing amount Three-piece deformer 14 Reverse wheel / angle UU 15 Tension belt (core wire) 16 (Noodles) 17 Tension spring (core wire) 18 (Noodles) 19 (Center traction) 20 Broken wire protection type Zhongrun detector

[0091] Performance Testing

[0092] Test objects: 3×0.22 / 9×0.20 CCUT obtained in Example 1 and the company's existing 3+9×0.22+0.15HT steel cord;

[0093] The performance of steel cord is tested according to GB / T16586-1996 and GB / T33159 standards;

[0094] The outer rim dimensions and strength performance of finished tires are tested according to GB / T521-2003 and GB / T4501-2008 standards respectively.

[0095] (1) Basic performance, as shown in Table 12

[0096] Table 12

[0097] project 3×0.22 / 9×0.20 CCUT 3+9×0.22+0.15HT Monofilament diameter / mm 0.22 / 0.20 0.22 / 0.15 Cord diameter / mm 0.87±0.04 1.18±0.06 <![CDATA[Linear density / g.m -1 > 3.38±0.17 3.85±0.19 Breaking force / N ≥1500 ≥1410 <![CDATA[Breaking force / diameter (N.mm -1 )]]> 1724 1194 <![CDATA[Breaking force / linear density (N.(g.m -1 ) -1 )]]> 444 366 Twist length / mm 12.5 12.5 / 3.5 twist direction S SZ

[0098] The performance of 3×0.22 / 9×0.20 CCUT steel cord is better than that of 3+9×0.22+0.15HT.

[0099] (2) Comparison of fatigue performance of the two steel wires in a three-roll fatigue machine. The results are shown in Table 13

[0100] Table 13

[0101]

[0102] The fatigue performance data of 3×0.22 / 9×0.20CCUT is better than that of 3+9×0.22+0.15HT.

[0103] (3) Aging performance, the results are shown in Table 14

[0104] Table 14

[0105]

[0106] The aging data of 3×0.22 / 9×0.20CCUT is better than that of 3+9×0.22+0.15HT.

[0107] The steel wire of Example 1 is used to make a finished tire, which is obtained by calendering, cutting and molding.

[0108] (1) 3×0.22 / 9×0.20CCUT steel cord was used for calendering. The calendering parameters are shown in Table 15.

[0109] Table 15

[0110] project 0.3×0.22 / 9×0.20CCUT 3+9×0.22+0.15HT Calendering density 63 67 Cord thickness 2.1 2.2 Wire quality 2129 2579 Rubber quality 2101 2150

[0111] The calendering process is very smooth. There is no skipping, thinning or paralleling of cords. The cord surface is smooth and flat, the glue is evenly coated and the thickness is controlled normally. Figure 6 shown.

[0112] (2) The cross section of 3×0.22 / 9×0.20CCUT steel cord is smooth during cutting, without core popping; there is no warping at the four corners and no arching at the upper and lower edges; the data analysis within 1m of the joint is normal, and the splicing joint is very good, such as Figure 7 shown.

[0113] (3) Due to the small diameter and stiffness of the 3×0.22 / 9×0.20CCUT steel cord, no abnormality was found in the steel cord joints during the molding process, and the carcass wrapping was normal.

[0114] Cost accounting

[0115] The costing of 3×0.22 / 9×0.20CCUT and 3+9×0.22+0.15HT steel cords is shown in Table 16.

[0116] Table 16

[0117] Cord structure 3+9×0.22+0.15HT 3×0.22 / 9×0.20CCUT Average diameter (mm) 1.18 0.87 Breaking force (N)Min 1410 1500 Linear density (g / m2) 3.85 3.38 Cord density (pieces / dm) 67 63 Cord thickness (mm) 2.2 2.1 Cord strength (N / dm) 94470 94500 Cord strength ratio (%) 100％ 100％ <![CDATA[Cord consumption (g / m 2 )]]> 2579.5 2129.4 <![CDATA[Amount of rubber compound used (g / m 2 )]]> 2150 2101 Cord usage ratio (%) 100％ 83％ Rubber content ratio (%) 100％ 98％ Reduced cord usage -450 Reduced amount of rubber -49

[0118] The density is 63 dm –1 The 3×0.22 / 9×0.20CCUT silk cord replaces the 3+9×0.22+0.15HT steel cord, reducing the tire cord usage by 450g·m -2 The amount of rubber used is reduced by 49g·m-2, and the total weight of the cord is reduced by 499g·m -2 .

[0119] From the above, it can be seen that when the steel cord of the present invention is used in the carcass of an all-steel radial tire, the thickness and weight of the steel cord are reduced, the cord fatigue is improved, and the cord stiffness is reduced; the outer edge size and strength performance of the finished tire meet the standard requirements.

[0120] 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 ultra-high strength steel wire for tire carcass, characterized in that: The following steps are involved: S1. Pre-treating the wire rod for later use, wherein the composition of the wire rod, in percentage by mass, comprises: C 0.89-0.99%, Si 0.12-0.22%, Mn 0.32-0.42%, Cr 0.18-0.28%, and the remainder is Fe and other impurities; S2, subjecting the wire rod pretreated in step S1 to rough drawing and intermediate drawing processes to obtain a first intermediate drawing wire and a second intermediate drawing wire, respectively, wherein the diameter of the first intermediate drawing wire is larger than the diameter of the second intermediate drawing wire; S3, subjecting the first and second drawn wires obtained in step S2 to heat treatment to achieve complete austenitization, and then quenching them in AQ liquid water to form a sorbite structure; S4, performing pickling and flavonoid coating processes on the first and second middle drawn wires after step S3 to obtain the brass-plated first and second middle drawn wires; S5, drawing the brass-plated first intermediate drawn wire obtained in step S4 through a water tank into a first monofilament with a diameter of D1, and drawing the brass-plated second intermediate drawn wire through a water tank into a second monofilament with a diameter of D2, wherein the ratio of D1 to D2 is between 1 and 1.2; S6. Select three first monofilaments as core filaments and nine second monofilaments as outer monofilaments, twist the core filaments and outer filaments at one time through a double twisting machine to form a 3×D1 / 9×D2 CCUT steel wire rope, and inspect it to obtain an ultra-high strength steel wire with a compact structure.

2. The method for preparing an ultra-high strength steel wire for a tire carcass according to claim 1, wherein: In step S1, the pretreatment process of the wire rod includes: the wire rod is subjected to water washing, pickling, water washing, and boron coating processes, and a borax coating is applied on the surface of the wire rod.

3. The method for preparing an ultra-high strength steel wire for a tire carcass according to claim 1, wherein: In step S2, the diameter of the wire rod after rough drawing is 3.15-3.25 mm.

4. The method for preparing an ultra-high strength steel wire for a tire carcass according to claim 1, wherein: The diameter of the first drawn wire is 1.55 mm, and the diameter of the second drawn wire is 1.50 mm.

5. The method for preparing an ultra-high strength steel wire for a tire carcass according to claim 1, wherein: In step S3, the heat treatment temperature is 960-1060° C.; the concentration of the AQ solution is 7-13%.

6. The method for preparing an ultra-high strength steel wire for a tire carcass according to claim 1, wherein: In step S5, the diameter of the first monofilament is in the range of 0.17-0.27 mm, and the diameter of the second monofilament is in the range of 0.15-0.25 mm.

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