A control method for homogenizing cord steel structure

Abstract

The present invention relates to the technical field of cord steel and proposes a method for controlling the uniformity of cord steel structure, comprising the following steps: pretreatment, smelting, refining, continuous casting, rolling, and spinning. The cord steel is composed of the following components by weight: C 0.80% to 0.85%, Si 0.15% to 0.30%, Mn 0.45% to 0.60%, P ≤ 0.02%, S ≤ 0.015%, Cu 0.012% to 0.048%, Cr 0.012% to 0.054%, Ni 0.028% to 0.048%, Al ≤ 0.003%, Ti ≤ 0.0015%, with the remainder being Fe and other unavoidable impurities. This technical solution solves the problems of uneven cord steel structure and low strength in related technologies.

Description

Technical Field

[0001] The present invention relates to the technical field of cord steel, and in particular to a method for controlling cord steel structure homogenization. Background Art

[0002] In the automotive industry, tires are the only part of a vehicle that comes into contact with the road. Their performance directly impacts a vehicle's driving safety and energy efficiency. Radial tires are highly favored in the market due to their improved stability, lower rolling resistance, and longer service life.

[0003] Cord steel, the structural material of radial tires, is crucial for improving overall tire performance. The production process involves drawing wire rods into filaments. This process involves undergoing a series of deformations, including stretching, torsion, and bending, placing stringent demands on the uniformity of the cord steel's structure. Inhomogeneous structure in cord steel manifests itself in a low sorbite content. This nonuniform structure directly impacts the strength of the cord steel, making it susceptible to fracture. Therefore, developing a method to control the uniformity of cord steel structure is crucial. Summary of the Invention

[0004] The present invention provides a control method for homogenizing the structure of a cord steel, which solves the problems of uneven structure and low strength of the cord steel in the related art.

[0005] The technical solutions of the present invention are as follows:

[0006] The present invention provides a control method for homogenizing the structure of a cord steel, comprising the following steps:

[0007] S1. Pretreatment: After the molten iron is desulfurized, pretreated molten iron is obtained;

[0008] S2, smelting: adding scrap steel to the pretreated molten iron, smelting, tapping, and obtaining smelted molten steel;

[0009] S3, refining: adjusting the chemical composition of the smelted molten steel, refining, and soft argon blowing to obtain refined molten steel;

[0010] S4, continuous casting: the refined molten steel is cast to obtain a continuous casting billet;

[0011] S5, blanking: the continuous casting blank is heated and blanked to obtain an intermediate blank;

[0012] S6, rolling: rolling the intermediate billet to obtain a wire rod;

[0013] S7, spinning: the wire rod is spun, cooled, and then rolled to obtain cord steel;

[0014] The cord steel is composed of the following components in weight percentage: C 0.80%-0.85%, Si 0.15%-0.30%, Mn 0.45%-0.60%, P≤0.02%, S≤0.015%, Cu 0.012%-0.048%, Cr 0.012%-0.054%, Ni 0.028%-0.048%, Als≤0.003%, Ti≤0.0015%, and the rest is Fe and other inevitable impurities.

[0015] As a further technical solution, the microstructure of the cord steel is sorbite and pearlite.

[0016] In the present invention, the microstructure of the cord steel is sorbite and pearlite, and does not contain harmful structures such as network ferrite, which avoids the network ferrite from undergoing a large amount of plastic deformation during the drawing process, resulting in a large amount of dislocation accumulation, inducing crack formation and thus causing wire breakage.

[0017] As a further technical solution, the sorbite rate of the microstructure is ≥90%.

[0018] In the present invention, the sorbite ratio in the microstructure of the cord steel is ≥90%, breaking through the limitation of sorbite ratio ≥85% of similar products at home and abroad.

[0019] As a further technical solution, in terms of weight percentage, the relationship among Cu, Cr and Ni satisfies 1≤(Cu+Cr) / Ni≤2.

[0020] In the present invention, when the relationship among Cu, Cr and Ni satisfies 1≤(Cu+Cr) / Ni≤2, it helps to further increase the sorbite ratio of the cord steel and further improve the structural uniformity and strength of the cord steel.

[0021] As a further technical solution, the weight percentage of Cu is equal to the weight percentage of Cr.

[0022] In the present invention, when the relationship among Cu, Cr and Ni satisfies 1≤(Cu+Cr) / Ni≤2 and the weight percentage of Cu is equal to the weight percentage of Cr, it helps to further increase the sorbite ratio of the cord steel and further improve the structural uniformity and strength of the cord steel.

[0023] As a further technical solution, in step S1, in the pretreated molten iron, S≤0.01% and P≤0.01% by weight.

[0024] In the present invention, by controlling the contents of S and P in the molten iron after pretreatment, the contents of S and P in the final components of the cord steel are effectively ensured to be within an ideal range, thereby avoiding the phenomenon that the cord steel breaks when deep drawing, torsion, and subjected to alternating loads due to the cold brittleness and hot brittleness easily caused by S and P.

[0025] As a further technical solution, in step S3, the soft argon blowing treatment is performed for a time of ≥20 min.

[0026] As a further technical solution, in step S5, the heating includes a heating section and a soaking section;

[0027] During the heating stage, the temperature is 1070-1090°C and the time is 50-70 minutes;

[0028] During the soaking stage, the temperature is 1090-1110° C. and the time is 50-70 minutes.

[0029] As a further technical solution, in step S6, during the rolling, the starting rolling temperature is 900-930°C, and the finishing rolling temperature is 1000-1050°C.

[0030] In the present invention, by optimizing the temperature during rolling, it is helpful to refine the original austenite grain size, thereby refining the sorbite grain size.

[0031] As a further technical solution, in step S7, the temperature during spinning is 910-930°C.

[0032] As a further technical solution, in step S7, the cooling includes first-stage cooling, second-stage cooling and third-stage cooling;

[0033] During the first stage of cooling, the steel is cooled to 800°C at a cooling rate of 22-24°C / s;

[0034] During the second stage of cooling, the material is cooled to 650°C at a cooling rate of 18-20°C / s;

[0035] During the third stage of cooling, the temperature is cooled to 500° C. at a cooling rate of 5-10° C. / s.

[0036] In the present invention, by optimizing the controlled cooling process, especially the controlled cooling process and cooling rate before phase transformation, the sorbite rate of the cord steel is further increased, and the structural uniformity and strength of the cord steel are further improved.

[0037] As a further technical solution, in step S7, the temperature during coiling is 400-450°C.

[0038] The working principle and beneficial effects of the present invention are:

[0039] In the present invention, by optimizing the component composition of the cord steel, especially optimizing the contents of Cu, Cr and Ni elements, the microstructure of the cord steel is composed of sorbite and pearlite, and the sorbite rate can reach more than 90%, thereby avoiding the generation of harmful structures such as martensite, network cementite and network ferrite, and significantly improving the structural uniformity and strength of the cord steel. DETAILED DESCRIPTION

[0040] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0041] Example 1

[0042] A method for controlling the homogenization of cord steel structure comprises the following steps:

[0043] S1. Pretreatment: After the molten iron is desulfurized, pretreated molten iron is obtained;

[0044] Among them, in terms of weight percentage, S 0.01% and P 0.01% in the pretreated molten iron;

[0045] S2, smelting: adding Q195 scrap steel to the pretreated molten iron according to the target composition, smelting, tapping, and obtaining smelted molten steel;

[0046] S3, refining: adjusting the chemical composition of the smelted molten steel according to the target composition, refining, and soft argon blowing treatment for 20 minutes to obtain refined molten steel;

[0047] S4, continuous casting: the refined molten steel is cast to obtain a continuous casting billet;

[0048] S5. Coiling: After the continuous casting billet is heated and cobbled, an intermediate billet is obtained;

[0049] The heating process includes a heating section and a soaking section. In the heating section, the temperature is 1070°C and the time is 70 minutes; in the soaking section, the temperature is 1090°C and the time is 70 minutes.

[0050] S6, rolling: After the intermediate billet is rolled, wire rod is obtained;

[0051] During rolling, the starting rolling temperature is 900℃ and the finishing rolling temperature is 1000℃;

[0052] S7, spinning: the wire rod is spun at 910°C, cooled, and then coiled at 400°C to obtain a cord steel with a diameter of 5.5 mm;

[0053] The cooling process includes a first stage cooling and a second stage cooling. In the first stage cooling, the material is cooled to 650°C at a cooling rate of 18°C / s; in the second stage cooling, the material is cooled to 500°C at a cooling rate of 5°C / s.

[0054] The cord steel is composed of the following components in weight percentage: C 0.80%, Si 0.15%, Mn 0.45%, P 0.02%, S 0.015%, Cu 0.012%, Cr 0.012%, Ni 0.028%, Als 0.003%, Ti 0.0015%, and the remainder is Fe and other inevitable impurities;

[0055] The microstructure of cord steel is sorbite and pearlite.

[0056] Example 2

[0057] A method for controlling the homogenization of cord steel structure comprises the following steps:

[0058] S1. Pretreatment: After the molten iron is desulfurized, pretreated molten iron is obtained;

[0059] Among them, in terms of weight percentage, the pretreated molten iron contains 0.008% S and 0.008% P;

[0060] S2, smelting: adding Q195 scrap steel to the pretreated molten iron according to the target composition, smelting, tapping, and obtaining smelted molten steel;

[0061] S3, refining: adjusting the chemical composition of the smelted molten steel according to the target composition, refining, and soft argon blowing treatment for 25 minutes to obtain refined molten steel;

[0062] S4, continuous casting: the refined molten steel is cast to obtain a continuous casting billet;

[0063] S5. Coiling: After the continuous casting billet is heated and cobbled, an intermediate billet is obtained;

[0064] The heating process includes a heating section and a soaking section. In the heating section, the temperature is 1090°C and the time is 50 minutes. In the soaking section, the temperature is 1100°C and the time is 50 minutes.

[0065] S6, rolling: After the intermediate billet is rolled, wire rod is obtained;

[0066] During rolling, the starting rolling temperature is 930℃ and the finishing rolling temperature is 1050℃;

[0067] S7, spinning: the wire rod is spun at 930°C, cooled, and then coiled at 450°C to obtain a cord steel with a diameter of 5.5 mm;

[0068] The cooling process includes a first stage cooling and a second stage cooling. In the first stage cooling, the temperature is cooled to 650°C at a cooling rate of 24°C / s; in the second stage cooling, the temperature is cooled to 500°C at a cooling rate of 10°C / s.

[0069] The cord steel is composed of the following components in weight percentage: C 0.85%, Si 0.30%, Mn 0.60%, P 0.015%, S0.01%, Cu 0.048%, Cr 0.054%, Ni 0.048%, Als 0.002%, Ti 0.001%, and the remainder is Fe and other inevitable impurities;

[0070] The microstructure of cord steel is sorbite and pearlite.

[0071] Example 3

[0072] A method for controlling the homogenization of cord steel structure comprises the following steps:

[0073] S1. Pretreatment: After the molten iron is desulfurized, pretreated molten iron is obtained;

[0074] Among them, in terms of weight percentage, the pretreated molten iron contains 0.008% S and 0.008% P;

[0075] S2, smelting: adding Q195 scrap steel to the pretreated molten iron according to the target composition, smelting, tapping, and obtaining smelted molten steel;

[0076] S3, refining: adjusting the chemical composition of the smelted molten steel according to the target composition, refining, and soft argon blowing treatment for 25 minutes to obtain refined molten steel;

[0077] S4, continuous casting: the refined molten steel is cast to obtain a continuous casting billet;

[0078] S5. Coiling: After the continuous casting billet is heated and cobbled, an intermediate billet is obtained;

[0079] The heating process includes a heating section and a soaking section. In the heating section, the temperature is 1090°C and the time is 50 minutes. In the soaking section, the temperature is 1100°C and the time is 50 minutes.

[0080] S6, rolling: After the intermediate billet is rolled, wire rod is obtained;

[0081] During rolling, the starting rolling temperature is 930℃ and the finishing rolling temperature is 1050℃;

[0082] S7, spinning: the wire rod is spun at 930°C, cooled, and then coiled at 450°C to obtain a cord steel with a diameter of 5.5 mm;

[0083] The cooling process includes a first stage cooling and a second stage cooling. In the first stage cooling, the material is cooled to 650°C at a cooling rate of 21°C / s; in the second stage cooling, the material is cooled to 500°C at a cooling rate of 8°C / s.

[0084] The cord steel is composed of the following components in weight percentage: C 0.83%, Si 0.22%, Mn 0.5%, P 0.015%, S0.01%, Cu 0.018%, Cr 0.024%, Ni 0.048%, Als 0.002%, Ti 0.001%, and the remainder is Fe and other inevitable impurities;

[0085] The microstructure of cord steel is sorbite and pearlite.

[0086] Example 4

[0087] The only difference between this embodiment and embodiment 3 is that, in this embodiment, the cord steel is composed of the following components in weight percentage: C 0.83%, Si 0.22%, Mn 0.5%, P 0.015%, S 0.01%, Cu 0.027%, Cr 0.035%, Ni 0.028%, Als 0.002%, Ti 0.001%, and the rest is Fe and other inevitable impurities.

[0088] Example 5

[0089] The only difference between this embodiment and embodiment 3 is that, in this embodiment, the cord steel is composed of the following components in weight percentage: C 0.83%, Si 0.22%, Mn 0.5%, P 0.015%, S 0.01%, Cu 0.02%, Cr 0.025%, Ni 0.045%, Als 0.002%, Ti 0.001%, and the remainder is Fe and other inevitable impurities.

[0090] Example 6

[0091] The only difference between this embodiment and embodiment 3 is that, in this embodiment, the cord steel is composed of the following components in weight percentage: C 0.83%, Si 0.22%, Mn 0.5%, P 0.015%, S 0.01%, Cu 0.04%, Cr 0.02%, Ni 0.03%, Als 0.002%, Ti 0.001%, and the rest is Fe and other inevitable impurities.

[0092] Example 7

[0093] The only difference between this embodiment and embodiment 3 is that, in this embodiment, the cord steel is composed of the following components in weight percentage: C 0.83%, Si 0.22%, Mn 0.5%, P 0.015%, S 0.01%, Cu 0.02%, Cr 0.04%, Ni 0.03%, Als 0.002%, Ti 0.001%, and the rest is Fe and other inevitable impurities.

[0094] Example 8

[0095] The only difference between this embodiment and embodiment 3 is that, in this embodiment, the cord steel is composed of the following components in weight percentage: C 0.83%, Si 0.22%, Mn 0.5%, P 0.015%, S 0.01%, Cu 0.03%, Cr 0.03%, Ni 0.03%, Als 0.002%, Ti 0.001%, and the rest is Fe and other inevitable impurities.

[0096] Example 9

[0097] The only difference between this embodiment and embodiment 8 is that in this embodiment, in step S7, the cooling includes a first stage cooling, a second stage cooling and a third stage cooling;

[0098] In the first stage of cooling, the steel was cooled to 800°C at a cooling rate of 18°C / s;

[0099] In the second stage of cooling, the temperature was cooled to 650°C at a cooling rate of 24°C / s;

[0100] In the third stage of cooling, the steel is cooled to 500°C at a cooling rate of 8°C / s.

[0101] Example 10

[0102] The only difference between this embodiment and embodiment 8 is that in this embodiment, in step S7, the cooling includes a first stage cooling, a second stage cooling and a third stage cooling;

[0103] In the first stage of cooling, the steel was cooled to 800°C at a cooling rate of 24°C / s;

[0104] In the second stage of cooling, the temperature was cooled to 650°C at a cooling rate of 18°C / s;

[0105] In the third stage of cooling, the steel is cooled to 500°C at a cooling rate of 8°C / s.

[0106] Example 11

[0107] The only difference between this embodiment and embodiment 8 is that in this embodiment, in step S7, the cooling includes a first stage cooling, a second stage cooling and a third stage cooling;

[0108] In the first stage of cooling, the steel was cooled to 800°C at a cooling rate of 22°C / s;

[0109] In the second stage of cooling, the temperature was cooled to 650°C at a cooling rate of 20°C / s;

[0110] In the third stage of cooling, the steel is cooled to 500°C at a cooling rate of 8°C / s.

[0111] Comparative Example 1

[0112] The only difference between this comparative example and Example 1 is that, in this comparative example, the cord steel consists of the following components in weight percentage: C 0.80%, Si 0.15%, Mn 0.45%, P 0.02%, S 0.015%, Cu 0.024%, Ni 0.028%, Als 0.003%, Ti 0.0015%, and the remainder is Fe and other inevitable impurities.

[0113] Comparative Example 2

[0114] The only difference between this comparative example and Example 1 is that, in this comparative example, the cord steel is composed of the following components in weight percentage: C 0.80%, Si 0.15%, Mn 0.45%, P 0.02%, S 0.015%, Cr 0.024%, Ni 0.028%, Als 0.003%, Ti 0.0015%, and the remainder is Fe and other inevitable impurities.

[0115] Comparative Example 3

[0116] The only difference between this comparative example and Example 1 is that, in this comparative example, the cord steel consists of the following components in weight percentage: C 0.80%, Si 0.15%, Mn 0.45%, P 0.02%, S 0.015%, Cu 0.026%, Cr 0.026%, Als 0.003%, Ti 0.0015%, and the remainder is Fe and other inevitable impurities.

[0117] Comparative Example 4

[0118] The only difference between this comparative example and Example 1 is that, in this comparative example, the cord steel consists of the following components in weight percentage: C 0.80%, Si 0.15%, Mn 0.45%, P 0.02%, S 0.015%, Ni 0.052%, Als 0.003%, Ti 0.0015%, and the remainder is Fe and other inevitable impurities.

[0119] The following performance tests were performed on the cord steels in Examples 1 to 11 and Comparative Examples 1 to 4:

[0120] ① Sorbite content: refer to YB / T 169-2014 "Metallographic determination method for sorbite content in high carbon steel wire rod" and use the metallographic manual detection method to determine the sorbite content, and retain one decimal place for the result;

[0121] ②Tensile strength: Refer to GB / T 228.1-2021 "Tensile tests on metallic materials - Part 1: Room temperature test methods" to test tensile strength, where the test rate is 0.006s -1 .

[0122] The test results are shown in Table 1 below.

[0123] Table 1 Cord steel performance test results

[0124]

[0125] From the comparison between Example 1 and Comparative Examples 1 to 4, it can be seen that by optimizing the types and contents of Cu, Cr, and Ni, the structural uniformity and strength of the cord steel can be significantly improved.

[0126] Comparison of Examples 3-4 with Examples 5-6 shows that when the relationship between Cu, Cr, and Ni satisfies 1≤(Cu+Cr) / Ni≤2, the microstructure uniformity and strength of the cord steel can be further improved. Comparison of Examples 6-7 with Example 8 shows that when the relationship between Cu, Cr, and Ni satisfies 1≤(Cu+Cr) / Ni≤2 and the weight percentage of Cu is equal to the weight percentage of Cr, the microstructure uniformity and strength of the cord steel can be further improved.

[0127] Comparison between Examples 8-9 and Examples 10-11 shows that by optimizing the controlled cooling process, especially the controlled cooling process and cooling rate before phase transformation, the microstructure uniformity and strength of the cord steel are further improved.

[0128] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for controlling the homogenization of cord steel structure, characterized in that: The following steps are involved: S1. Pretreatment: After the molten iron is desulfurized, pretreated molten iron is obtained; S2, smelting: adding scrap steel to the pretreated molten iron, smelting, tapping, and obtaining smelted molten steel; S3, refining: adjusting the chemical composition of the smelted molten steel, refining, and soft argon blowing to obtain refined molten steel; S4, continuous casting: the refined molten steel is cast to obtain a continuous casting billet; S5, blanking: the continuous casting blank is heated and blanked to obtain an intermediate blank; S6, rolling: rolling the intermediate billet to obtain a wire rod; S7, spinning: the wire rod is spun, cooled, and then rolled to obtain cord steel; The cord steel is composed of the following components in weight percentage: C 0.80%-0.85%, Si 0.15%-0.30%, Mn 0.45%-0.60%, P≤0.02%, S≤0.015%, Cu 0.012%-0.048%, Cr 0.012%-0.054%, Ni 0.028%-0.048%, Als≤0.003%, Ti≤0.0015%, and the rest is Fe and other inevitable impurities; the relationship among Cu, Cr and Ni satisfies 1≤(Cu+Cr) / Ni≤2.

2. The method for controlling the homogenization of the cord steel structure according to claim 1, characterized in that: The weight percentage of Cu is equal to the weight percentage of Cr.

3. The method for controlling the homogenization of the cord steel structure according to claim 1, characterized in that: In step S1, in the pretreated molten iron, S≤0.01% and P≤0.01% by weight.

4. The method for controlling the homogenization of the cord steel structure according to claim 1, characterized in that: In step S3, the soft argon blowing treatment is performed for a time of ≥20 min.

5. The method for controlling the homogenization of the cord steel structure according to claim 1, characterized in that: In step S5, the heating includes a heating section and a soaking section; During the heating stage, the temperature is 1070-1090°C and the time is 50-70 minutes; During the soaking stage, the temperature is 1090-1110° C. and the time is 50-70 minutes.

6. The method for controlling the homogenization of the cord steel structure according to claim 1, characterized in that: In step S6, during the rolling, the starting rolling temperature is 900-930°C, and the finishing rolling temperature is 1000-1050°C.

7. The method for controlling the homogenization of the cord steel structure according to claim 1, characterized in that: In step S7, the temperature during spinning is 910-930°C.

8. The method for controlling the homogenization of the cord steel structure according to claim 1, characterized in that: In step S7, the cooling includes first stage cooling, second stage cooling and third stage cooling; During the first stage of cooling, the steel is cooled to 800°C at a cooling rate of 22-24°C / s; During the second stage of cooling, the material is cooled to 650°C at a cooling rate of 18-20°C / s; During the third stage of cooling, the temperature is cooled to 500° C. at a cooling rate of 5-10° C. / s.

9. The method for controlling the homogenization of the cord steel structure according to claim 1, characterized in that: In step S7, the temperature during coiling is 400-450°C.

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