Wire rod capable of improving service performance of high-strength tire bead wire and manufacturing method of wire rod

Abstract

The invention provides a wire rod capable of improving the service performance of a high-strength tire bead wire and a manufacturing method of the wire rod, and the wire rod comprises the following components in percentage by weight: 0.02%-0.12% of C, 0.10%-0.20% of Si, 0.40%-0.50% of Mn, less than or equal to 0.015% of P, 0.0040%-0.015% of S, less than or equal to 0.0050% of N, 0.0020%-0.0060% of Als, 0.0005%-0.0012% of Nb, 0.0003%-0.0012% of Mo, 0.00005%-0.0004% of Se and the balance of Fe and inevitable impurities. The invention provides a manufacturing method of a wire rod capable of improving the service performance of a high-strength tire bead wire. The manufacturing method comprises the steps of smelting, continuous casting, continuous casting billet heating and rolling, wire rod rolling and wire rod cooling. The tensile strength of the steel wire rod ranges from 400 MPa to 470 MPa, the area reduction rate ranges from 60% to 75%, and the specification of the steel wire rod ranges from 5.0 mm to 8.0 mm.

Description

TECHNICAL FIELD

[0001] The present application relates to a high-strength bead wire rod and its production process, and belongs to the field of wire rod production methods. BACKGROUND

[0002] High-strength bead wire is the main supporting material of tires, ensuring the safety performance of tires during operation, and is an important safety component of automobiles. In the production process of bead wire, the strength of the wire made of wire rod is generally improved by increasing the carbon content of the raw material wire rod. However, this process also leads to a decrease in the plasticity of the bead wire, which poses a safety hazard to tire operation.

[0003] Chinese patent application CN202310976619.5 provides a kind of super high strength hot-dip galvanized steel wire rope and its production method, and its chemical composition mass percentage is as follows: C: 0.85-0.88%, Si: 0.18-0.25%, Mn: 0.50-0.55%, Cr: ≤0.05%, P≤0.012%, S≤0.008%, Ni≤0.05%, Cu≤0.05%, Mo≤0.03%, Al≤0.0020%, Ti≤0.0012%, O≤0.0030%, N≤0.0050%, the balance is Fe and inevitable impurities. In production, sequentially through molten steel smelting, LF refining, continuous casting and rolling, super high strength hot-dip galvanized steel wire rope wire rod can be produced, solving the problem of improving the strength of the wire rod while solving the problem of wire rod core segregation, net-shaped cementite and insufficient sorbite content.

[0004] This patent focuses on super high strength hot-dip galvanized steel wire rope, and does not provide a technical solution to improve the service performance of high-strength bead wire and reduce the safety hazard during operation. The present application is designed from the aspects of chemical composition, smelting process and rolling process to improve the service performance of high-strength bead wire. SUMMARY

[0005] In view of the shortcomings of the prior art, the present application aims to provide a high-strength bead wire rod and its production process to improve the service performance of high-strength bead wire and meet the service performance requirements of high-strength bead wire.

[0006] The present application is achieved as follows:

[0007] The chemical composition of the wire rod suitable for the present invention (in percentage by mass) is as follows: C: 0.02% ~ 0.12%, Si: 0.10% ~ 0.20%, Mn: 0.40% ~ 0.50%, P ≤ 0.015%, S: 0.0040% ~ 0.015%, N: ≤ 0.0050%, Als: 0.0020% ~ 0.0060%, Nb: 0.0005% ~ 0.0012%, Mo: 0.0003% ~ 0.0012%, Se: 0.00005% ~ 0.0004%, and the balance is Fe and unavoidable impurities.

[0008] The reasons for setting the ranges of these components are as follows.

[0009] The present invention uses a steel wire with a lower carbon content together with a steel wire with a high carbon steel content to improve the service performance of the entire tire bead wire.

[0010] C: 0.02%~0.12%

[0011] Too high a carbon content in the wire rod will result in reduced service performance of the bead wire made from the wire rod; too low a carbon content in the wire rod cannot meet the user's strength requirements for the bead wire. Therefore, the carbon content in the present invention is controlled to be 0.02% to 0.12%.

[0012] Si: 0.10% to 0.20%

[0013] Silicon increases the eutectoid transformation temperature of steel, coarsening the ferrite and pearlite structure of the wire rod. This hinders the complex deformation during the processing of low-carbon bead wire and impairs the service performance of the wire produced from the wire rod. Silicon is the primary deoxidizing element in high-carbon steel. Excessive silicon content in steel leads to the formation of coarse silicates and impurities after deoxidation of the molten steel. Low silicon content results in insufficient deoxidation of the molten steel, reducing the deformability of the wire rod during the processing of low-carbon steel wire. Therefore, the silicon content in the present invention is controlled to 0.10% to 0.20%.

[0014] Mn: 0.40% to 0.50%

[0015] Manganese is an element that increases wire strength, helping ensure that bead wire processed from wire rod meets the user's tensile strength requirements. Manganese lowers the eutectoid transformation temperature of steel, refines the ferrite and pearlite structure of the wire rod, improves the deformation capacity during the processing of low-carbon bead wire wire, and enhances the service performance of the wire made from the wire rod. Therefore, the manganese content in the present invention is controlled to 0.40% to 0.50%.

[0016] P≤0.015%

[0017] Phosphorus reduces the deformation ability of the wire rod during bead wire processing, causing the wire to crack and break, so the phosphorus content in the present invention is controlled to be ≤0.015%.

[0018] S: 0.0040% to 0.015%

[0019] The higher sulfur content in the steel reduces the cold working performance of the rod. Since the MnS inclusions have good deformation capacity, the appropriate amount of sulfur in the steel can reduce the damage of non-deformation brittle inclusions, improve the drawing performance of the rod, and improve the service performance of the rod made into steel wire. Therefore, the sulfur content in the present application is controlled at 0.0040% to 0.015%.

[0020] N: ≤0.0050%

[0021] The nitrogen content needs to be controlled to a lower range to reduce the hardening effect during the processing of the bead wire and improve the deformation capacity of the steel wire. Therefore, the nitrogen content in the present application is controlled at ≤0.0050%.

[0022] Als: 0.0020% to 0.0060%

[0023] When the acid-soluble aluminum content is high, large-sized Al2O3 inclusions will appear in the steel; when the acid-soluble aluminum content in the rod is too low, the inclusions in the steel deviate from the region with good deformation, and cracking between the inclusions and the matrix is prone to occur during processing, which reduces the service performance of the rod made into bead steel wire. Therefore, the acid-soluble aluminum content in the present application is controlled at 0.0020% to 0.0060%.

[0024] Nb: 0.0005% to 0.0012%

[0025] The niobium element can refine the pearlite structure of the rod by inhibiting the grain growth of the billet during heating, thereby improving the service performance of the rod made into steel wire. However, a higher niobium content leads to a higher content of niobium carbonitride in the steel, and the rod is severely work-hardened during the processing of the steel wire, which is not conducive to the improvement of the service performance of the steel wire. Therefore, the niobium content in the present application is controlled at 0.0005% to 0.0012%.

[0026] Mo: 0.0003% to 0.0012%

[0027] Molybdenum is a carbide-forming element that reduces the austenite grain size of the rod, improves the deformation capacity of the rod during the processing of the bead steel wire, and improves the service performance of the rod made into steel wire. However, too high a molybdenum content increases the strength of the rod and reduces the processing performance of the rod and the steel wire. Therefore, the molybdenum content in the present application is controlled at 0.0003% to 0.0012%.

[0028] Se: 0.00005% to 0.0004%

[0029] Selenium in steel with manganese, niobium and other elements form selenide, selenide than sulfide more fine, more significant inhibition of micro-crack propagation, improve the service performance of steel wire. But the high selenium content of steel reduces the drawing performance of the rod. Therefore, the selenium content of the present application is controlled at 0.00005% to 0.0004%.

[0030] The second technical scheme of the present application is to provide a manufacturing method of a rod with improved service performance of high-strength bead wire, including smelting, continuous casting, continuous casting billet heating and rolling, rod rolling and rod cooling.

[0031] 1) Smelting: The molten steel is smelted by molten iron + scrap steel, and the scrap steel ratio is 5%-12%. The alloy drying time before converter smelting should not be less than 4 hours, the manganese content in manganese iron is 60%-70%, the phosphorus content is not more than 0.5%, and the sulfur content is not more than 0.03%. Through the decrease of the residual element content of the alloy, the cleanliness of the rod is improved, and the service performance of the steel wire made of the rod is improved. The oxygen activity of the molten steel after converter smelting is controlled at 100-240ppm. The molten steel is refined by LF, and the LF refining time of the molten steel is controlled at 35-50min, and the refining temperature is controlled at 1490℃-1560℃.

[0032] 2) Continuous casting: After refining, the molten steel is continuously cast, and the cross-sectional size of the continuous casting billet is (300-340)mm*(400-440)mm, and the continuous casting speed is 0.45m / min-0.60m / min.

[0033] 3) Continuous casting billet heating and rolling: The continuous casting billet is hot charged, and the total furnace time is 3.2-4.0 hours. The preheating temperature is not more than 500℃. The soaking temperature is controlled at 1120-1140℃, and the holding time is 30-50min. After the continuous casting billet is heated, high-pressure water descaling treatment is carried out, and the descaling pressure is not less than 18MPa. After the billet is treated by high-pressure water descaling, it is continuously rolled. The final rolling temperature is controlled at 920℃-990℃. The cross-sectional size of the continuously rolled billet is (140-180)mm*(140-180)mm. Through the high-temperature diffusion of the continuous casting billet in the continuous rolling heating process and the high-pressure water descaling of the continuous rolling, the surface quality of the continuously rolled billet is improved, which lays the foundation for finally improving the surface quality of the rod and the service performance of the steel wire made of the rod.

[0034] 4) Wire rod rolling: the wire rod is produced by using bloom, the total heating time of the bloom is 145 min to 165 min, the temperature of the heating section is 1050 DEG C to 1080 DEG C, and the holding time of the bloom in the heating section is 35 min to 55 min. After the bloom is heated, the wire rod is formed by wire drawing after rough rolling, intermediate rolling, pre-precision rolling and precision rolling. The temperature of the wire rod after pre-precision rolling is 980 DEG C to 1010 DEG C, the temperature of the wire rod before precision rolling is 900 DEG C to 930 DEG C, the temperature of the wire rod before entering the double module is 900 DEG C to 920 DEG C, and the rolling speed of the wire rod entering the double module is 90 m / s to 100 m / s. The temperature of the wire rod after wire drawing is controlled at 870 DEG C to 910 DEG C. The wire rod rolling specification is 5.0 mm to 8.0 mm.

[0035] 5) Wire rod cooling: the wire rod is cooled on the air cooling roller after wire drawing, the phase change temperature of the wire rod is controlled at 620 DEG C to 670 DEG C, and the phase change time of the wire rod on the air cooling line is 10 s to 25 s. The thickness of the iron scale of the wire rod is 10 um to 20 um, and the content of FeO in the iron scale is not less than 50%, so that the removal performance of the wire rod surface iron scale is improved, and the service performance of the wire rod is improved.

[0036] The present application has the following advantages:

[0037] The wire rod for the bead wire produced by the technical scheme of the present application has a tensile strength of 400 MPa to 470 MPa, a surface reduction of 60% to 75%, and a wire rod specification of 5.0 mm to 8.0 mm. The wire rod has good service performance, and the wire rod processing diameter is 0.4 mm to 1.2 mm, so that the wire breaking phenomenon in the service process of the high-strength bead wire is avoided. DETAILED DESCRIPTION

[0038] The present application will be further described below by examples.

[0039] According to the component proportion of the technical scheme, the present application is smelted, continuously cast, heated and rolled, wire rod is rolled, and the wire rod is cooled.

[0040] Continuous casting:

[0041] After the molten steel is refined, the continuous casting is performed, the cross-sectional size of the continuously cast blank is (300-340) mm * (400-440) mm, and the continuous casting speed is 0.45 m / min to 0.60 m / min.

[0042] Heating and rolling of the continuously cast blank:

[0043] The continuously cast blank is hot-charged, the total heating time is 3.2 hours to 4.0 hours, the temperature of the preheating section is not more than 500 DEG C, the temperature of the heating section is controlled at 1120 DEG C to 1140 DEG C, and the holding time is 30 min to 50 min. The final rolling temperature of the continuous rolling is controlled at 920 DEG C to 990 DEG C, and the cross-sectional size of the continuously rolled blank is (140-180) mm * (140-180) mm.

[0044] Wire rod rolling:

[0045] The wire rod is produced from square billets. The total billet in-furnace time is 145-165 minutes, the soaking section temperature is 1050-1080°C, and the soaking section holding time is 35-55 minutes. After heating, the billet undergoes rough rolling, intermediate rolling, pre-finishing rolling, and finishing rolling before the wire rod extrusion operation. The wire rod exiting pre-finishing rolling is 980-1010°C; the wire rod entering finishing rolling is 900-930°C; and the wire rod entering the dual module is 900-920°C. The wire rod entering the dual module has a rolling speed of 90-100 m / s, and the wire rod extrusion temperature is controlled at 870-910°C.

[0046] Wire rod cooling:

[0047] After spinning, the wire rod is cooled on an air-cooled roller, and the phase change temperature of the wire rod is controlled at 620°C to 670°C. The phase change time of the wire rod on the air-cooled line is 10 to 25 seconds.

[0048] Furthermore, in the smelting process, the molten steel is smelted using molten iron + scrap steel, the scrap steel ratio is 5%-12%, the alloy drying time before converter smelting shall not be less than 4 hours, the manganese content in the ferromanganese is 60%-70%, the phosphorus content is not more than 0.5%, and the sulfur content is not more than 0.03%; the oxygen activity of the molten steel after converter smelting is controlled at 100-240ppm; the molten steel is refined using LF, the LF furnace refining time of the molten steel is controlled at 35-50min, and the refining temperature is controlled at 1490°C-1560°C.

[0049] Furthermore, in the continuous casting process, the continuous casting billet is subjected to high-pressure water descaling treatment after heating, and the descaling pressure is not less than 18 MPa.

[0050] The chemical composition of the inventive wire rod embodiment is shown in Table 1, and the process parameters are shown in Table 2.

[0051] Table 1 Chemical composition of the embodiments of the present invention (wt, %)

[0052] Example C，％ Si, % Mn, % P，％ S，％ 1 0.11 0.14 0.49 0.014 0.012 2 0.10 0.17 0.42 0.011 0.0076 3 0.05 0.18 0.45 0.009 0.011 4 0.09 0.12 0.42 0.008 0.0052 5 0.06 0.18 0.48 0.015 0.0045 6 0.07 0.17 0.44 0.012 0.0081 Example N，％ Acid soluble aluminium, % Nb, % Mo, % Se, % 1 0.0023 0.0038 0.0008 0.0006 0.0003 2 0.0025 0.0032 0.0007 0.0004 0.0002 3 0.0031 0.0043 0.0007 0.0009 0.00009 4 0.0032 0.0029 0.0007 0.0006 0.0001 5 0.0037 0.0021 0.0005 0.0005 0.0003 6 0.0041 0.0027 0.0006 0.0005 0.0002

[0053] Table 2 Process and performance of the embodiments of the present invention

[0054]

[0055]

[0056] For the purpose of illustrating the present application, the best mode for the same will be described in the above embodiments with reference to the accompanying drawings. The embodiments are presented herein for purposes of illustration and description and are not intended to limit the scope of the present application. The skilled person in the art, without departing from the spirit and scope of the present application, can make various changes and modifications, and any modification, equivalent replacement, improvement, etc. made should be included in the protection scope of the present application. The patent protection scope of the present application should be defined by the claims.

Claims

1. A wire rod having improved service performance of high-strength bead wire, characterized in that: Calculated by weight, the invention comprises the following components: C: 0.02% to 0.12%, Si: 0.10% to 0.20%, Mn: 0.40% to 0.50%, P≤0.015%, S: 0.0040% to 0.015%, N: ≤0.0050%, Als: 0.0020% to 0.0060%, Nb: 0.0005% to 0.0012%, Mo: 0.0003% to 0.0012%, Se: 0.00005% to 0.0004%, and the balance is Fe and unavoidable impurities.

2. The wire rod having improved service performance of high-strength bead wire according to claim 1, characterized in that: The tensile strength of the wire rod is 400-470MPa, and the area reduction rate is 60%-75%.

3. The wire rod having improved service performance of high-strength bead wire according to claim 1, characterized in that: The wire rod specification is 5.0 to 8.0 mm.

4. A method for manufacturing a wire rod having improved service performance of high-strength bead wire according to claim 1, characterized in that: Including smelting, continuous casting, continuous casting billet heating and rolling, wire rod rolling, wire rod cooling; Continuous Casting: After the liquid steel is refined, it is continuously cast. The cross-sectional size of the continuous casting billet is (300-340) mm*(400-440) mm, and the continuous casting speed is 0.45 m / min-0.60 m / min. Continuous casting billet heating and rolling: The continuous casting slab is hot charged, with a total furnace time of 3.2 to 4.0 hours. The preheating section temperature is not higher than 500°C, the soaking section temperature is controlled at 1120 to 1140°C, and the holding time is 30 to 50 minutes. The finishing rolling temperature is controlled at 920 to 990°C, and the cross-sectional size of the continuous rolling slab is (140 to 180) mm*(140 to 180) mm. Wire rod rolling: The wire rod is produced from square billets. The total billet in-furnace time is 145-165 minutes, the soaking section temperature is 1050-1080°C, and the soaking section holding time is 35-55 minutes. After heating, the billet undergoes rough rolling, intermediate rolling, pre-finishing rolling, and finishing rolling before the wire rod extrusion operation. The wire rod exiting pre-finishing rolling is 980-1010°C; the wire rod entering finishing rolling is 900-930°C; and the wire rod entering the dual module is 900-920°C. The wire rod entering the dual module has a rolling speed of 90-100 m / s, and the wire rod extrusion temperature is controlled at 870-910°C. Wire rod cooling: After spinning, the wire rod is cooled on an air-cooled roller, and the phase change temperature of the wire rod is controlled at 620°C to 670°C. The phase change time of the wire rod on the air-cooled line is 10 to 25 seconds.

5. The method for manufacturing a wire rod having improved service performance of high-strength bead wire according to claim 4, characterized in that: In the smelting process, the molten steel is smelted by molten iron + scrap steel, the scrap steel ratio is 5%-12%, the alloy drying time before converter smelting shall not be less than 4 hours, the manganese content in the ferromanganese is 60%-70%, the phosphorus content is not more than 0.5%, and the sulfur content is not more than 0.03%; the oxygen activity of the molten steel after converter smelting is controlled at 100-240ppm; the molten steel is refined by LF, the LF furnace refining time of the molten steel is controlled at 35-50min, and the refining temperature is controlled at 1490°C-1560°C.

6. The method for manufacturing a wire rod having improved service performance of high-strength bead wire according to claim 4, characterized in that: In the continuous casting process, the continuous casting billet is subjected to high-pressure water descaling treatment after being heated, and the descaling pressure is not less than 18 MPa.

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