A method for controlling cord steel segregation

Abstract

The present invention relates to the technical field of cord steel and proposes a method for controlling cord steel segregation. The method comprises sequentially performing molten iron pretreatment, converter smelting, LF furnace refining, continuous casting, rolling, spinning, and heat treatment. The cord steel comprises the following components by weight: C 0.80%-0.85%, Si 0.15%-0.30%, Mn 0.10%-0.55%, V 0.13%-0.25%, Sn 0.12%-0.22%, P ≤ 0.008%, S ≤ 0.005%, Cu 0.01%-0.05%, Ni 0.001%-0.05%, Cr 0.02%-0.05%, Al 0.001%-0.005%, N ≤ 0.005%, with the remainder being iron and its inevitable impurities. The above technical solution solves the problem of poor cord steel segregation control 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 segregation of cord steel. Background Art

[0002] Cord steel, primarily used for radial reinforcement in tires, features high strength and toughness, making it one of the most demanding and challenging wire products to produce. Segregation is a common problem during the production process. Segregation in cord steel refers to the uneven distribution of chemical composition and microstructure within the steel, primarily including carbon segregation and segregation of other alloying elements. Segregation in cord steel has a significant impact on the performance and quality of the steel. Excessive segregation in the cord steel billet can negatively impact microstructure control during the rolling process, leading to uneven inclusion distribution and increased risk of wire breakage during processing. Furthermore, centerline segregation reduces the wire drawing limit and ductility of the cord steel, particularly significantly reducing toughness and impacting its drawing properties. Therefore, controlling segregation in cord steel is crucial during production, but it is difficult. Traditional methods for controlling segregation include low-superheat casting, mist cooling, electromagnetic stirring in the mold, end-stage electric stirring, and soft reduction techniques, but these approaches have proven ineffective. Therefore, proposing a control method for cord steel segregation can reasonably and effectively reduce the cord steel segregation problem, which is a technical problem that needs to be solved urgently. Summary of the Invention

[0003] The present invention provides a method for controlling cord steel segregation, which solves the problem of poor control effect of cord steel segregation in the related art.

[0004] The technical solutions of the present invention are as follows:

[0005] The present invention provides a method for controlling segregation of cord steel, comprising sequentially performing molten iron pretreatment, converter smelting, LF furnace refining, continuous casting, rolling, spinning and heat treatment, wherein the cord steel is composed of the following components in percentage by weight:

[0006] C 0.80%~0.85%, Si 0.15%~0.30%, Mn 0.10%~0.55%, V 0.13%~0.25%, Sn 0.12%~0.22%, P≤0.008%, S≤0.005%, Cu 0.01%~0.05%, Ni 0.001%~0.05%, Cr 0.02%~0.05%, Al0.001%~0.005%, N≤0.005%, and the rest are iron and its inevitable impurities.

[0007] As a further technical solution, the weight ratio of the sum of the weights of V and Sn to that of Mn is 1:0.5~1.

[0008] In the present invention, when the weight ratio of the sum of V and Sn to Mn is 1:0.5-1, the control effect of cord steel segregation can be further improved.

[0009] As a further technical solution, the weight ratio of V to Sn is 1:1.

[0010] As a further technical solution, the heat treatment includes a first stage heat treatment, a second stage heat treatment and a third stage heat treatment.

[0011] In the present invention, the heat treatment process is a segmented heat treatment process. By optimizing the heat treatment process and rationally regulating and optimizing the heat treatment temperature, the diffusion of component elements and the transformation of the organizational structure of the cord steel can be further promoted, thereby obtaining a cord steel with more uniform composition.

[0012] As a further technical solution, during the first heat treatment, the temperature is 350~450℃, the holding time is 60~100min, and the material is cooled to room temperature after holding; during the second heat treatment, the temperature is 650~750℃, the holding time is 40~60min, and the material is cooled to room temperature after holding; during the third heat treatment, the temperature is 400~500℃, the holding time is 50~80min, and the material is cooled to room temperature after holding.

[0013] As a further technical solution, during the first heat treatment and the third heat treatment, the cooling rate is independently 8-12°C / min; during the second heat treatment, the cooling rate is 20-25°C / min.

[0014] During heat treatment, the cooling rate has a significant impact on the composition uniformity and structural stability of the cord steel. Strict and reasonable control of the cooling rate can further improve the control effect of cord steel segregation. In the present invention, when the cooling rates of the first and third heat treatments are independently 8-12°C / min, and the cooling rate of the second heat treatment is 20-25°C / min, the control effect of cord steel segregation can be further improved by reasonably regulating the cooling rates of the three heat treatments.

[0015] As a further technical solution, pure water cooling is adopted during the continuous casting, and the water flow rate of the pure water cooling is 120~130cm 3 / h.

[0016] As a further technical solution, the rolling includes heating treatment, soaking treatment and start rolling;

[0017] During the heating treatment, the temperature is 990-1010° C. and the time is 2-2.5 hours;

[0018] During the soaking treatment, the temperature is 1090-1110°C and the time is 3.5-4 hours;

[0019] During the rolling, the temperature is 990-1010°C.

[0020] As a further technical solution, after the converter smelting, the weight percentage of P is ≤0.006%, and the weight percentage of S is ≤0.003%.

[0021] As a further technical solution, during the LF furnace refining, the refining slag adopts a CaO-SiO2 binary slag system, and the final slag basicity is 0.95-1.10.

[0022] The working principle and beneficial effects of the present invention are:

[0023] Among them, the cord steel contains V, Sn and Mn elements. By reasonably controlling the content ratio of the three, the uniformity of the cord steel composition and the stability of the internal structure are ensured, thereby achieving the best control effect of cord steel segregation, reducing the problem of cord steel breakage caused by segregation, and ultimately improving the qualified rate of cord steel products. DETAILED DESCRIPTION

[0024] 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.

[0025] Example 1

[0026] A method for controlling segregation of cord steel comprises sequentially performing molten iron pretreatment, converter smelting, LF furnace refining, continuous casting, rolling, wire laying, and heat treatment, wherein the cord steel comprises the following components in percentage by weight:

[0027] C 0.80%, Si 0.15%, Mn 0.10%, V 0.13%, Sn 0.12%, P 0.008%, S 0.005%, Cu 0.01%, Ni 0.001%, Cr 0.02%, Al 0.001%, N 0.005%, and the rest is iron and its inevitable impurities.

[0028] After converter smelting, the weight percentage of P is 0.003%, and the weight percentage of S is 0.002%;

[0029] During LF furnace refining, the refining slag adopts CaO-SiO2 binary slag system, and the final slag basicity is 0.95;

[0030] During continuous casting, 120cm 3 / h of water flow rate to obtain pure water cooling cord steel ingot;

[0031] The cord steel ingot was heated in a heating section at 990° C. for 2.5 hours, soaked in a soaking section at 1090° C. for 4 hours, and then rolled at 990° C. to obtain a rolled cord steel ingot;

[0032] The rolled cord steel ingot was subjected to the first heat treatment at 350°C, kept warm for 100 minutes, and then cooled to room temperature at a cooling rate of 6°C / min; the second heat treatment was carried out at 650°C, kept warm for 60 minutes, and then cooled to room temperature at a cooling rate of 6°C / min; the third heat treatment was carried out at 400°C, kept warm for 80 minutes, and then cooled to room temperature at a cooling rate of 6°C / min, completing the heat treatment process to obtain cord steel.

[0033] Example 2

[0034] A method for controlling segregation of cord steel comprises sequentially performing molten iron pretreatment, converter smelting, LF furnace refining, continuous casting, rolling, wire laying, and heat treatment, wherein the cord steel comprises the following components in percentage by weight:

[0035] C 0.83%, Si 0.20%, Mn 0.34%, V 0.13%, Sn 0.13%, P 0.008%, S 0.005%, Cu 0.03%, Ni 0.01%, Cr 0.03%, Al 0.003%, N 0.003%, and the rest is iron and its inevitable impurities.

[0036] After converter smelting, the weight percentage of P is 0.006%, and the weight percentage of S is 0.003%;

[0037] During LF furnace refining, the refining slag adopts CaO-SiO2 binary slag system, and the final slag basicity is 1.00;

[0038] During continuous casting, 125cm 3 / h of water flow rate to obtain pure water cooling cord steel ingot;

[0039] The cord steel ingot is heated in a heating section at 1000° C. for 2.5 hours, soaked in a soaking section at 1100° C. for 3.5 hours, and then rolled at 1000° C. to obtain a rolled cord steel ingot;

[0040] The rolled cord steel ingot is subjected to the first heat treatment at 400°C, kept at this temperature for 80 minutes, and then cooled to room temperature at a cooling rate of 6°C / min; the second heat treatment is carried out at 700°C, kept at this temperature for 50 minutes, and then cooled to room temperature at a cooling rate of 6°C / min; the third heat treatment is carried out at 450°C, kept at this temperature for 65 minutes, and then cooled to room temperature at a cooling rate of 6°C / min, completing the heat treatment process to obtain cord steel.

[0041] Example 3

[0042] A method for controlling segregation of cord steel comprises sequentially performing molten iron pretreatment, converter smelting, LF furnace refining, continuous casting, rolling, wire laying, and heat treatment, wherein the cord steel comprises the following components in percentage by weight:

[0043] C 0.85%, Si 0.30%, Mn 0.55%, V 0.25%, Sn 0.22%, P 0.008%, S 0.005%, Cu 0.05%, Ni 0.05%, Cr 0.05%, Al 0.005%, N 0.005%, and the rest is iron and its inevitable impurities.

[0044] After converter smelting, the weight percentage of P is 0.006%, and the weight percentage of S is 0.003%;

[0045] During LF furnace refining, the refining slag adopts CaO-SiO2 binary slag system, and the final slag basicity is 1.10;

[0046] During continuous casting, 130cm 3 / h of water flow rate to obtain pure water cooling cord steel ingot;

[0047] The cord steel ingot was heated in a heating section at 1010° C. for 2 hours, soaked in a soaking section at 1110° C. for 3.5 hours, and then rolled at 1010° C. to obtain a rolled cord steel ingot;

[0048] The rolled cord steel ingot is subjected to the first heat treatment at 450°C, kept warm for 60 minutes, and then cooled to room temperature at a cooling rate of 6°C / min; the second heat treatment is carried out at 750°C, kept warm for 40 minutes, and then cooled to room temperature at a cooling rate of 6°C / min; the third heat treatment is carried out at 500°C, kept warm for 50 minutes, and then cooled to room temperature at a cooling rate of 6°C / min. The heat treatment process is completed to obtain cord steel.

[0049] Example 4

[0050] The only difference between this embodiment and embodiment 2 is that, in this embodiment, the weight percentage of Mn is 0.16%, the weight percentage of V is 0.22%, and the weight percentage of Sn is 0.22%.

[0051] Example 5

[0052] The only difference between this embodiment and embodiment 2 is that, in this embodiment, the weight percentage of Mn is 0.20%, the weight percentage of V is 0.20%, and the weight percentage of Sn is 0.20%.

[0053] Example 6

[0054] The only difference between this embodiment and embodiment 2 is that, in this embodiment, the weight percentage of Mn is 0.30%, the weight percentage of V is 0.15%, and the weight percentage of Sn is 0.15%.

[0055] Example 7

[0056] The only difference between this embodiment and embodiment 6 is that, in this embodiment, when performing the heat treatment process, the cooling rate of the first stage heat treatment is 12°C / min, the cooling rate of the second stage heat treatment is 16°C / min, and the cooling rate of the third stage heat treatment is 12°C / min.

[0057] Example 8

[0058] The only difference between this embodiment and embodiment 7 is that, in this embodiment, when performing the heat treatment process, the cooling rate of the first stage heat treatment is 12°C / min, the cooling rate of the second stage heat treatment is 30°C / min, and the cooling rate of the third stage heat treatment is 12°C / min.

[0059] Example 9

[0060] The only difference between this embodiment and embodiment 7 is that, in this embodiment, when performing the heat treatment process, the cooling rate of the first stage heat treatment is 6°C / min, the cooling rate of the second stage heat treatment is 25°C / min, and the cooling rate of the third stage heat treatment is 6°C / min.

[0061] Example 10

[0062] The only difference between this embodiment and embodiment 7 is that, in this embodiment, when performing the heat treatment process, the cooling rate of the first stage heat treatment is 16°C / min, the cooling rate of the second stage heat treatment is 25°C / min, and the cooling rate of the third stage heat treatment is 16°C / min.

[0063] Example 11

[0064] The only difference between this embodiment and embodiment 7 is that, in this embodiment, when performing the heat treatment process, the cooling rate of the first stage heat treatment is 6°C / min, the cooling rate of the second stage heat treatment is 16°C / min, and the cooling rate of the third stage heat treatment is 6°C / min.

[0065] Example 12

[0066] The only difference between this embodiment and embodiment 7 is that, in this embodiment, when performing the heat treatment process, the cooling rate of the first stage heat treatment is 16°C / min, the cooling rate of the second stage heat treatment is 30°C / min, and the cooling rate of the third stage heat treatment is 16°C / min.

[0067] Example 13

[0068] The only difference between this embodiment and embodiment 7 is that, in this embodiment, when performing the heat treatment process, the cooling rate of the first stage heat treatment is 8°C / min, the cooling rate of the second stage heat treatment is 20°C / min, and the cooling rate of the third stage heat treatment is 8°C / min.

[0069] Example 14

[0070] The only difference between this embodiment and embodiment 6 is that, in this embodiment, when performing the heat treatment process, the cooling rate of the first stage heat treatment is 12°C / min, the cooling rate of the second stage heat treatment is 25°C / min, and the cooling rate of the third stage heat treatment is 12°C / min.

[0071] Comparative Example 1

[0072] The only difference between this comparative example and Example 1 is that in this comparative example, no Mn is added, and the weight percentages of V and Sn added are 0.18% and 0.17%, respectively.

[0073] Comparative Example 2

[0074] The only difference between this comparative example and Example 1 is that in this comparative example, no V is added, the weight percentage of added Mn is 0.10%, and the weight percentage of added Sn is 0.25%.

[0075] Comparative Example 3

[0076] The only difference between this comparative example and Example 1 is that in this comparative example, Sn is not added, the weight percentage of Mn added is 0.10%, and the weight percentage of V added is 0.25%.

[0077] Comparative Example 4

[0078] The only difference between this comparative example and Example 1 is that in this comparative example, Mn, V and Sn are not added.

[0079] The cord steels obtained by the cord steel segregation control methods of Examples 1 to 14 and Comparative Examples 1 to 4 were tested for central segregation index according to the method in YB / T 4413-2014 "Metallurgical Evaluation Method for Central Segregation of High Carbon Steel Wire Rods". The results are shown in Table 1 below:

[0080] Table 1 Central segregation index of Examples 1 to 14 and Comparative Examples 1 to 4

[0081]

[0082] Compared with Comparative Examples 1 to 4, the central segregation index of Example 1 is significantly reduced, indicating that when the cord steel contains V, Sn and Mn elements, the three have a synergistic effect. By rationally regulating the content ratio of the three elements, the uniformity of the cord steel composition and the stability of the internal structure are ensured, which can significantly improve the control effect of cord steel segregation and improve the qualified rate of cord steel products.

[0083] Compared with Examples 2 and 4, the central segregation index of Examples 5-6 is reduced, indicating that when the weight ratio of V and Sn to Mn is 1:0.5-1, the control effect of cord steel segregation can be further improved.

[0084] Compared with Examples 6, 11, and 12, the central segregation index of Examples 7-10 and Examples 13-14 is lower, indicating that the cooling rate during heat treatment has a significant impact on the compositional uniformity and structural stability of the cord steel. Reasonable control of the cooling rate can further improve the control of cord steel segregation. Specifically, compared with Examples 7-10, the central segregation index of Examples 13-14 is lower, indicating that when the cooling rates of the first and third heat treatments are each independently 8-12°C / min, and the cooling rate of the second heat treatment is 20-25°C / min, the control of cord steel segregation can be further improved by reasonably controlling the cooling rates of the three heat treatments.

[0085] 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 cord steel segregation, characterized in that: The process comprises the following steps: molten iron pretreatment, converter smelting, LF furnace refining, continuous casting, rolling, spinning and heat treatment, wherein the cord steel is composed of the following components in weight percentage: C 0.80%~0.85%, Si 0.15%~0.30%, Mn 0.10%~0.55%, V 0.13%~0.25%, Sn 0.12%~0.22%, P≤0.008%, S≤0.005%, Cu 0.01%~0.05%, Ni 0.001%~0.05%, Cr 0.02%~0.05%, Al 0.001%~0.005%, N≤0.005%, the rest are iron and its inevitable impurities; The heat treatment includes a first stage heat treatment, a second stage heat treatment and a third stage heat treatment; During the first heat treatment, the temperature is 350-450°C, the holding time is 60-100 minutes, and the heat is cooled to room temperature after the heat treatment; during the second heat treatment, the temperature is 650-750°C, the holding time is 40-60 minutes, and the heat is cooled to room temperature after the heat treatment; during the third heat treatment, the temperature is 400-500°C, the holding time is 50-80 minutes, and the heat is cooled to room temperature after the heat treatment; During the first heat treatment and the third heat treatment, the cooling rate is independently 8-12°C / min; during the second heat treatment, the cooling rate is 20-25°C / min.

2. The method for controlling cord steel segregation according to claim 1, characterized in that: The weight ratio of the sum of the weights of the V and Sn to the weight of the Mn is 1:0.5-1.

3. The method for controlling cord steel segregation according to claim 1, characterized in that: During the continuous casting, pure water cooling is adopted, and the water flow rate of the pure water cooling is 120~130cm 3 / h.

4. The method for controlling cord steel segregation according to claim 1, characterized in that: The rolling process includes heating treatment, soaking treatment and start rolling; During the heating treatment, the temperature is 990-1010° C. and the time is 2-2.5 hours; During the soaking treatment, the temperature is 1090-1110°C and the time is 3.5-4 hours; During the rolling, the temperature is 990-1010°C.

5. The method for controlling cord steel segregation according to claim 1, characterized in that: After the converter smelting, the weight percentage of P is ≤0.006%, and the weight percentage of S is ≤0.003%.

6. The method for controlling cord steel segregation according to claim 1, characterized in that: During the LF furnace refining, the refining slag adopts a CaO-SiO2 binary slag system, and the final slag basicity is 0.95-1.

10.

7. The method for controlling cord steel segregation according to claim 1, characterized in that: During the continuous casting, the superheat degree is 17-23°C.

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