Process for controlling inclusions in tire cord steel

Abstract

The invention relates to the technical field of steel and iron smelting, and provides a process for controlling inclusions in tire cord steel, which comprises the following steps: S1, smelting: adding synthetic slag into molten iron in the tapping process to obtain molten steel; s2, refining: refining the molten steel, adjusting element components, adding calcium carbide, silicon carbide and lime, and softly blowing to obtain refined molten steel; s3, continuous casting: casting the refined molten steel to obtain a casting blank, and rolling, spinning and cooling to obtain tire cord steel; the synthetic slag is prepared from, by weight, 50%-60% of SiO2, 20%-25% of CaO, smaller than or equal to 5% of Al2O3, smaller than or equal to 5% of MgO and the balance MnO, and the mass ratio of SiO2 to CaO is (5-6): 2. According to the technical scheme, the problem that the size of inclusions in tire cord steel is large in the prior art is solved.

Description

Technical Field

[0001] The invention relates to the technical field of steel smelting, and in particular to a process for controlling inclusions in cord steel. Background Art

[0002] In the field of modern tire manufacturing, radial tires have taken a leading position due to their excellent performance. Among them, cord steel, as the key skeleton material of radial tires, plays a pivotal supporting and strengthening role. Cord steel has the characteristics of high strength and good toughness, which can effectively improve the overall performance of tires and ensure the safety and stability of automobile driving.

[0003] The production process of cord steel is extremely challenging. The initial ф5.5mm wire rod needs to be drawn into ф0.15mm-ф0.38mm filaments through complex processes. In this process, the wire has to withstand severe deformation in various forms such as stretching, torsion, and bending. Not only is the processing technology extremely delicate and complex, but the precision of the wire rod specifications is also extremely high. At the same time, the subsequent service environment of cord steel is quite harsh. In view of this, the comprehensive quality control of cord steel wire has reached a strict level, such as nitrogen content, inclusion content, etc., which must meet high standards.

[0004] After years of technological accumulation and industrial development, many domestic steel companies, such as Qinggang, Yonggang, Weigang, Zhongtian, Angang, etc., have the production capacity of cord steel, which has met the market demand to a certain extent. However, it cannot be ignored that the current production technology of cord steel still faces a series of technical difficulties and challenges that need to be overcome. The presence of inclusions is one of them. The presence of inclusions will not only destroy the integrity of the internal structure of the cord steel, causing its strength and toughness to be greatly reduced, and then seriously affect the quality and performance of the cord steel. In a chain reaction, it will also have a negative impact on the performance of radial tires and even the overall performance of the car. Therefore, it is necessary to propose a process for controlling inclusions in cord steel. Summary of the invention

[0005] The invention provides a process for controlling inclusions in cord steel, which solves the problem of large size of inclusions in cord steel in the related art.

[0006] The technical solution of the present invention is as follows: The present invention proposes a process for controlling inclusions in cord steel, comprising the following steps: S1. Smelting: adding synthetic slag to molten iron during the steelmaking process to obtain molten steel; S2, refining: after the molten steel is sent to refining, the element composition is adjusted, calcium carbide, silicon carbide and lime are added, and refined molten steel is obtained after soft blowing; S3, continuous casting: casting the refined molten steel to obtain a cast billet, rolling, spinning and cooling to obtain cord steel; The synthetic slag is composed of the following components in weight percentage: SiO 2 50%~60%, CaO 20%~25%, Al 2 O 3 ≤5%, MgO≤5%, the balance is MnO, the SiO 2 The mass ratio of Al to CaO is 5~6:2.

[0007] As a further technical solution, the synthetic slag described in S1 is added twice, the first time when 1 / 3 of the steel is tapped, and the second time when 2 / 3 of the steel is tapped, and the amount of synthetic slag added in the first time is less than the amount of synthetic slag added in the second time.

[0008] As a further technical solution, the mass ratio of the amount of the first synthetic slag added to the amount of the second synthetic slag added is 2:3.

[0009] In the present invention, synthetic slag is added in two steps, and the amount of synthetic slag added for the first time is less than that added for the second time. The addition of the synthetic slag for the first time plays a mild and precise pretreatment role, creating preliminary conditions for the subsequent floating of inclusions. The addition of the synthetic slag for the second time is to strengthen and consolidate the initial reaction. The synthetic slag is added in two steps, closely coordinated and progressively, to further reduce the size of inclusions in the cord steel.

[0010] As a further technical solution, the amount of synthetic slag added in S1 is 1% to 1.5% of the mass of the molten iron.

[0011] As a further technical solution, the mass ratio of molten steel, calcium carbide, silicon carbide and lime in S2 is 100:5:10~12:10.

[0012] As a further technical solution, the silicon carbide described in S2 is added in three times. The first addition of silicon carbide begins at the beginning of refining, and it is added every 10 minutes. The amount of silicon carbide added for the first time: the amount of silicon carbide added for the second time: the amount of silicon carbide added for the third time is 3:5:2~4.

[0013] In the present invention, silicon carbide is added three times to control the inclusions in the molten steel in an all-round and multi-level manner, thereby further reducing the size of the inclusions in the cord steel.

[0014] As a further technical solution, the raw materials of the molten iron include one or two of Q195 and welding wire scrap steel.

[0015] As a further technical solution, the casting in S3 specifically includes the following steps: injecting the refined molten steel into a tundish, forming a billet shell after entering a crystallizer, and obtaining the cast billet after billet drawing and cooling in a secondary cooling zone.

[0016] As a further technical solution, the temperature of the tundish is 1483-1593°C, the target drawing speed of the billet is 1.8 m / min, and the continuous casting water volume of the secondary cooling zone is 0.8 L / kg.

[0017] As a further technical solution, the rolling temperature is 900-930°C, and the spinning temperature is 910-930°C.

[0018] The present invention also proposes a cord steel obtained by the process of controlling inclusions in cord steel, which 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≤0.020%, S≤0.015%, Cu≤0.10%, Cr≤0.10%, Ni≤0.10%, Als≤0.003%, Ti≤0.0015%, and the balance is Fe and unavoidable impurities.

[0019] The working principle and beneficial effects of the present invention are: In the present invention, molten iron is successively smelted, refined, and continuously cast to prepare cord steel. During the smelting process, SiO 2 The mass ratio of CaO to MgO can be improved, the metallurgical properties of the slag system can be optimized, the appropriate viscosity of the slag system can be maintained, the formation of inclusions can be effectively removed and inhibited, and the size of inclusions in the cord steel can be reduced. DETAILED DESCRIPTION

[0020] 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 described embodiments 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 creative work are within the scope of protection of the present invention.

[0021] Example 1 A process for controlling inclusions in cord steel comprises the following steps: S1. Smelting: Q195 is selected as raw material, which is melted to form molten iron. Synthetic slag is added to the molten iron during the steelmaking process. The amount of synthetic slag added is 1% of the mass of the molten steel. The synthetic slag is composed of the following components in weight percentage: SiO 2 50%, CaO20%, Al 2 O 3 5%, MgO 5%, the balance is MnO; S2, refining: sending the molten steel to a refining furnace for refining, adjusting the element composition, heating the refining furnace and starting to add calcium carbide, silicon carbide and lime, heating to 1512°C, and soft blowing for 20 minutes to obtain refined molten steel, wherein the mass ratio of molten steel, calcium carbide, silicon carbide and lime is 100:5:10:10; S3. Continuous casting: the refined molten steel is injected into a tundish with a temperature of 1483°C. After the molten steel enters the crystallizer from the tundish through the submerged water nozzle, the molten steel rapidly solidifies to form a billet shell under the cooling effect of the crystallizer wall. The billet is drawn at a target drawing speed of 1.8m / min. After leaving the crystallizer, it enters the secondary cooling zone and is mist-cooled according to the parameter of continuous casting specific water volume of 0.8L / kg to obtain a cast billet. After the cast billet is rolled at 900°C, wire-spinning at 910°C, and cooled, a cord steel is obtained. The obtained cord steel consists of the following components in weight percentage: C 0.80%, Si 0.15%, Mn 0.45%, P 0.08%, S 0.005%, Cu 0.05%, Cr 0.05%, Ni 0.05%, Als 0.001%, Ti 0.0010%, and the balance is Fe and unavoidable impurities.

[0022] Example 2 A process for controlling inclusions in cord steel comprises the following steps: S1. Smelting: Q195 is selected as raw material, which is melted to form molten iron. Synthetic slag is added to the molten iron during the steelmaking process to obtain molten steel, wherein the amount of synthetic slag added is 1.2% of the mass of the molten steel. The synthetic slag is composed of the following components in weight percentage: SiO 2 50%, CaO 22%, Al 2 O 3 5%, MgO 5%, the balance is MnO; S2, refining: sending the molten steel to a refining furnace for refining, adjusting the element composition, heating the refining furnace and starting to add calcium carbide, silicon carbide and lime, heating to 1532°C, and soft blowing for 20 minutes to obtain refined molten steel, wherein the mass ratio of molten steel, calcium carbide, silicon carbide and lime is 100:5:10:10; S3. Continuous casting: the refined molten steel is injected into a tundish with a temperature of 1543°C. After the molten steel enters the crystallizer from the tundish through the submerged water nozzle, the molten steel rapidly solidifies to form a billet shell under the cooling effect of the crystallizer wall. The billet is drawn at a target drawing speed of 1.8m / min. After leaving the crystallizer, it enters the secondary cooling zone and is mist-cooled according to the parameter of continuous casting specific water volume of 0.8L / kg to obtain a cast billet. After the cast billet is rolled at 915°C, wire-spinning at 920°C, and cooled, a cord steel is obtained. The obtained cord steel consists of the following components in weight percentage: C 0.82%, Si 0.20%, Mn 0.55%, P 0.007%, S 0.004%, Cu 0.04%, Cr 0.04%, Ni 0.04%, Als 0.002%, Ti 0.0012%, and the balance is Fe and unavoidable impurities.

[0023] Example 3 A process for controlling inclusions in cord steel comprises the following steps: S1. Smelting: Welding wire scrap steel is selected as raw material, which is melted to form molten iron. Synthetic slag is added to the molten iron during the steel-making process to obtain molten steel, wherein the amount of synthetic slag added is 1.5% of the mass of the molten steel. The synthetic slag is composed of the following components in weight percentage: SiO 2 50%, CaO 25%, Al 2 O 3 5%, MgO 5%, the balance is MnO; S2, refining: sending the molten steel to a refining furnace for refining, adjusting the element composition, heating the refining furnace and starting to add calcium carbide, silicon carbide and lime, heating to 1552°C, and soft blowing for 20 minutes to obtain refined molten steel, wherein the mass ratio of molten steel, calcium carbide, silicon carbide and lime is 100:5:10:10; S3. Continuous casting: the refined molten steel is injected into a tundish with a temperature of 1593°C. After the molten steel enters the crystallizer from the tundish through the submerged water nozzle, the molten steel solidifies rapidly to form a billet shell under the cooling effect of the crystallizer wall. The billet is drawn at a target drawing speed of 1.8m / min. After leaving the crystallizer, the billet enters the secondary cooling zone and is mist-cooled according to the parameter of continuous casting specific water volume of 0.8L / kg to obtain a cast billet. The cast billet is rolled at 930°C, wire-spinning at 930°C, and cooled to obtain cord steel. The obtained cord steel consists of the following components in weight percentage: C 0.85%, Si 0.30%, Mn 0.60%, P 0.005%, S 0.003%, Cu 0.05%, Cr 0.03%, Ni 0.03%, Als 0.002%, Ti 0.0011%, and the balance is Fe and unavoidable impurities.

[0024] Example 4 Compared with Example 1, the difference of Example 4 is that the SiO2 The total amount of SiO 2 The mass ratio of CaO is 6:2.

[0025] Example 5 Compared with Example 4, Example 5 is different in that S1 comprises the following steps: selecting Q195 steel as a raw material, melting it to form molten iron, adding synthetic slag for the first time when 1 / 3 of the steel is tapped, and adding synthetic slag for the second time when 2 / 3 of the steel is tapped, the mass ratio of the first synthetic slag added to the second synthetic slag added is 2:3, and molten steel is obtained, wherein the total amount of synthetic slag added is 1% of the mass of the molten steel, and the synthetic slag is composed of the following components in weight percentage: SiO 2 50%, CaO 20%, Al 2 O 3 5%, MgO5%, and the balance is MnO.

[0026] Example 6 Compared with Example 5, the difference of Example 6 is that the mass ratio of the added amount of the first synthetic slag to the added amount of the second synthetic slag is 1:1.

[0027] Example 7 Compared with Example 5, the difference of Example 7 is that the mass ratio of the added amount of the first synthetic slag to the added amount of the second synthetic slag is 3:2.

[0028] Example 8 Compared with Example 5, the difference of Example 8 is that the mass ratio of molten steel, calcium carbide, silicon carbide and lime is 100:5:12:10.

[0029] Example 9 Compared with Example 8, the difference of Example 9 is that S2 includes the following steps: sending molten steel to a refining furnace for refining, adjusting the elemental composition, setting the temperature of the refining furnace to 1552°C, starting to add calcium carbide, the first silicon carbide and lime when the refining furnace is heated up, adding the second silicon carbide after 10 minutes, adding the third silicon carbide 10 minutes after the second silicon carbide is added, and obtaining refined molten steel after soft blowing for 20 minutes, wherein the mass ratio of molten steel, calcium carbide, silicon carbide and lime is 100:5:10:10, and the mass ratio of the added amount of the first silicon carbide, the second silicon carbide and the third silicon carbide is 3:5:2.

[0030] Example 10 Compared with Example 9, the difference of Example 10 is that the mass ratio of the first addition of silicon carbide, the second addition of silicon carbide, and the third addition of silicon carbide is 3:5:4.

[0031] Embodiment 11 Compared with Example 9, the difference of Example 11 is that the mass ratio of the first addition of silicon carbide, the second addition of silicon carbide, and the third addition of silicon carbide is 5:2.5:2.5.

[0032] Example 12 Compared with Example 9, the difference of Example 12 is that the mass ratio of the first addition of silicon carbide, the second addition of silicon carbide, and the third addition of silicon carbide is 3:4:5.

[0033] Comparative Example 1 Compared with Example 1, the difference of Comparative Example 1 is that the SiO 2 The total amount of SiO 2 The mass ratio of CaO is 4:2.

[0034] Comparative Example 2 Compared with Example 1, the difference of Comparative Example 2 is that the SiO 2 The total amount of SiO 2 The mass ratio of CaO is 7:2.

[0035] Comparative Example 3 Compared with Example 1, the difference of Comparative Example 3 is that the SiO 2 The total amount of SiO 2 The mass ratio of CaO is 2:2.

[0036] Comparative Example 4 Compared with Example 1, the difference of Comparative Example 4 is that a process for controlling inclusions in cord steel, S1 and S2 include the following steps: S1. Smelting: Select Q195 as raw material, melt it to form molten iron, and then tap it to get molten steel; S2. Refining: The molten steel is sent to a refining furnace for refining, and the element composition is adjusted. When the refining furnace is heated, synthetic slag, calcium carbide, silicon carbide and lime are added, and the temperature is raised to 1532°C. After soft blowing for 20 minutes, refined molten steel is obtained, wherein the mass ratio of molten steel, calcium carbide, silicon carbide and lime is 100:5:10:10, and the amount of synthetic slag added is 1.2% of the total mass of the molten iron. The synthetic slag is composed of the following components in weight percentage: SiO 2 50%, CaO 22%, Al 2 O 3 5%, MgO 5%, and the balance is MnO and inevitable impurities.

[0037] The cord steels obtained in Examples 1 to 12 and Comparative Examples 1 to 4 were tested according to the following method: Non-metallic inclusion control level: According to the test method A specified in GB / T 10561-2023 "Standard rating chart microscopic examination method for the determination of non-metallic inclusion content in steel", the non-metallic inclusion level of the test sample is tested.

[0038] The test results are shown in the following table: Table 1 Performance test results of the cord steels obtained in Examples 1 to 12 and Comparative Examples 1 to 4

[0039] Compared with Comparative Examples 1, 2, and 3, Examples 1 and 4 add different mass ratios of SiO 2 and CaO. As a result, the proportion of non-metallic inclusions in Examples 1 and 4 in the level range is higher than that in Comparative Examples 1, 2, and 3, indicating that when SiO 2 When the mass ratio of CaO to Si is 5~6:2, the size of inclusions in the cord steel can be reduced.

[0040] Compared with Comparative Example 4, Example 1 adds synthetic slag during the steel-making process. As a result, the proportion of the non-metallic inclusion level in Example 1 within the level range is higher than that in Comparative Example 4, indicating that when synthetic slag is added during the steel-making process, the size of inclusions in the cord steel can be reduced.

[0041] Compared with Example 4, Examples 5 to 7 added synthetic slag twice. As a result, the proportion of non-metallic inclusion levels in Examples 5 to 7 within the level range was higher than that in Example 4, indicating that when synthetic slag was added twice, the size of inclusions in the cord steel could be further reduced.

[0042] Compared with Example 8, Examples 9 to 12 added silicon carbide three times. As a result, the proportion of the non-metallic inclusion level in Examples 9 to 12 within the level range was higher than that in Example 8, indicating that when silicon carbide was added three times, the size of inclusions in the cord steel could be further reduced.

[0043] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A process for controlling inclusions in cord steel, characterized in that: The following steps are involved: S1. Smelting: adding synthetic slag to molten iron during the steelmaking process to obtain molten steel; S2, refining: after the molten steel is sent to refining, the element composition is adjusted, calcium carbide, silicon carbide and lime are added, and refined molten steel is obtained after soft blowing; S3, continuous casting: casting the refined molten steel to obtain a casting billet, rolling, spinning and cooling to obtain cord steel; The synthetic slag is composed of the following components in weight percentage: SiO2 50%~60%, CaO 20%~25%, Al2O3≤5%, MgO≤5%, and the balance is MnO. The mass ratio of SiO2 to CaO is 5~6:

2.

2. A process for controlling inclusions in cord steel according to claim 1, characterized in that: The synthetic slag in S1 is added twice, the first addition is when 1 / 3 of the steel is tapped, and the second addition is when 2 / 3 of the steel is tapped. The amount of synthetic slag added in the first addition is less than the amount of synthetic slag added in the second addition.

3. A process for controlling inclusions in cord steel according to claim 2, characterized in that: The mass ratio of the amount of the first synthetic slag added to the amount of the second synthetic slag added is 2:

3.

4. A process for controlling inclusions in cord steel according to claim 1, characterized in that: The amount of synthetic slag added in S1 is 1% to 1.5% of the mass of the molten iron.

5. A process for controlling inclusions in cord steel according to claim 1, characterized in that: The mass ratio of molten steel, calcium carbide, silicon carbide and lime in S2 is 100:5:10~12:

10.

6. A process for controlling inclusions in cord steel according to claim 1, characterized in that: The silicon carbide described in S2 is added in three times. The first addition of silicon carbide is at the beginning of refining, and it is added once every 10 minutes. The amount of silicon carbide added for the first time: the amount of silicon carbide added for the second time: the amount of silicon carbide added for the third time is 3:5:2~4.

7. A process for controlling inclusions in cord steel according to claim 1, characterized in that: The raw materials of the molten iron include one or two of Q195 and welding wire scrap steel.

8. A process for controlling inclusions in cord steel according to claim 1, characterized in that: The casting in S3 specifically includes the following steps: injecting the refined molten steel into a tundish, forming a billet shell after entering a crystallizer, and obtaining the cast billet after billet drawing and cooling in a secondary cooling zone.

9. A process for controlling inclusions in cord steel according to claim 8, characterized in that: The temperature of the tundish is 1483-1593° C., the target drawing speed of the billet is 1.8 m / min, and the continuous casting water volume of the secondary cooling zone is 0.8 L / kg.

10. The cord steel obtained by the process for controlling inclusions in cord steel according to any one of claims 1 to 9, characterized in that: It is composed of the following components in weight percentage: C 0.80%~0.85%, Si 0.15%~0.30%, Mn0.45%~0.60%, P≤0.020%, S≤0.015%, Cu≤0.10%, Cr≤0.10%, Ni≤0.10%, Als≤0.003%, Ti≤0.0015%, and the balance is Fe and unavoidable impurities.

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