Wire rod for enhancing service performance of high-strength tire bead wire and structure control method

Abstract

The invention provides a wire rod for enhancing the service performance of a high-strength tire bead wire and a structure control method. The wire rod comprises the following components in percentage by weight: 0.06%-0.12% of [C], 0.15%-0.25% of [Si], 0.50%-0.60% of [Mn], less than or equal to 0.015% of [P], 0.0030%-0.010% of [S], 0.0010%-0.0030% of total oxygen, 0.0005%-0.0015% of [Als], 0.0001%-0.0009% of [V] and 0.0002%-0.0011% of [Mg]. And the balance of Fe and inevitable impurities. The steel wire rod structure control method comprises the steps of smelting, continuous casting, heating, rolling, steel wire rod rolling and steel wire rod cooling. According to the wire rod produced through the method, the grain size is not larger than 25 microns, and the grain size difference is not larger than 2 levels. The wire rod structure is composed of ferrite and pearlite, and the ferrite content is larger than 90%. The tensile strength of the wire rod is 410-450 MPa, and the ductility is 30%-40%.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of metal, and particularly relates to a wire rod for enhancing service performance of high-strength bead wire and a structure control process. BACKGROUND

[0002] High-strength bead wire needs to have good service performance, so low-strength bead wire is applied to the production process of high-strength bead wire to prevent the phenomenon of fracture of the bead wire from occurring in the service process. The raw material wire rod for producing such steel wire needs to have the characteristics of small grain size.

[0003] The patent document "Hot-rolled wire rod for 80-grade bead wire and preparation method thereof, and automobile tire" (publication number: CN114959484B) discloses an invention that provides a hot-rolled wire rod for 80-grade bead wire and a preparation method thereof, and an automobile tire, belonging to the technical field of steel preparation. The chemical composition of the hot-rolled wire rod for 80-grade bead wire includes C, Si, Mn, P, S, Cr, V, Fe, and impurities from the preparation of the hot-rolled wire rod for 80-grade bead wire. Among them, the value of (Mn+V) / Si is 2.3-3.3 in mass fraction, and the value of (Cr+V) is 0.12%-0.15%. This application limits the value of (Mn+V) / Si to 2.3-3.3 to ensure excellent strength and ductility and drawing performance of the wire rod; and limits the value of (Cr+V) to 0.12%-0.15% to ensure that the hot-rolled wire rod for 80-grade bead wire has excellent hardenability to increase the content of sorbite, thereby preventing wire breakage during drawing, meeting the manufacturing requirements of high-strength bead wire and the deep drawing requirements of steel cord enterprises.

[0004] The deficiency is that the patent does not design the composition and production process of the wire rod for enhancing high-strength bead wire from the perspective of grain size difference. With the increasing requirements of the automobile tire industry on the service performance of bead wire, it is necessary to specially design the grain size difference control of the wire rod for enhancing the service performance of bead wire. SUMMARY

[0005] The present application aims to overcome the above problems and deficiencies and provide a wire rod for enhancing the service performance of high-strength bead wire, which ensures that the grain size level difference of the wire rod is not greater than 2 levels.

[0006] The purpose of the present application is achieved as follows:

[0007] A wire rod for enhancing service performance of high strength bead wire, the wire rod has the following components in percentage by weight: [C] 0.06%~0.12%, [Si] 0.15%~0.25%, [Mn] 0.50%~0.60%, [P] ≤0.015%, [S] 0.0030%~0.010%, total oxygen 0.0010%~0.0030%, [Als] 0.0005~0.0015%, [V] 0.0001%~0.0009%, [Mg] 0.0002%~0.0011%; the rest is Fe and inevitable impurities.

[0008] Further, [V]+[Mg] in the steel is 0.0005~0.0020%.

[0009] Further, the tensile strength of the wire rod is 410~450MPa, and the elongation of the wire rod is 30%~40%.

[0010] Further, the grain size of the wire rod is not more than 25um, and the grain size difference is not more than 2 levels; the structure of the wire rod is composed of ferrite+pearlite, and the content of ferrite is more than 90%.

[0011] Further, the specification of the wire rod is Φ5~8mm.

[0012] The wire rod is designed as follows:

[0013] [C]: If the carbon content in the wire rod is too high, the bead wire processed from the wire rod will exceed the strength requirement; meanwhile, the higher strength will result in an increase in the wire breaking rate during the preparation of the bead wire, and the waste rate of the user will increase. If the carbon content in the wire rod is too low, the strength requirement of the bead wire for the user cannot be met. Therefore, the carbon content in the present application is controlled to be 0.06%~0.12%.

[0014] [Si]: Silicon is a main deoxidizing element in high carbon steel. If the silicon content in the steel is too high, coarse silicates and impurities will appear after the deoxidization of the molten steel, and if the silicon content is low, the deoxidization of the molten steel will be insufficient, thereby reducing the deformation capacity of the wire rod during the processing of the bead wire. Silicon element increases the eutectoid transformation temperature of the steel, and makes the ferrite+pearlite structure of the wire rod coarse, which is not conducive to the uniformity control of the structure of the bead wire. Therefore, the silicon content in the present application is controlled to be 0.15%~0.25%.

[0015] [Mn]: Manganese is an element for improving the strength of the wire rod, which is conducive to ensuring that the bead wire processed from the wire rod meets the tensile strength requirement of the user; manganese element refines the pearlite structure of the wire rod, reduces the grain size difference of the final wire rod structure, and improves the deformation capacity of the wire rod during the processing of the bead wire. Therefore, the manganese content in the present application is controlled to be 0.50%~0.60%.

[0016] [P]: phosphorus reduces the deformation ability of the wire rod in the processing of the bead wire, causing the wire to crack and break, so the phosphorus content in the invention is controlled at ≤0.015%.

[0017] [S]: a higher sulfur content in the steel reduces the cold working performance of the wire rod. Since the MnS inclusions have good deformation ability, an appropriate amount of sulfur in the steel can reduce the harm of the crystalline inclusions, so the sulfur content in the invention is controlled at 0.0030% to 0.010%.

[0018] Total oxygen: when the oxygen content is low, the inclusions in the wire rod have poor deformation ability, which is not conducive to the processing of the bead wire; when the oxygen content in the wire rod is high, the inclusions in the steel are large in size and numerous, which easily causes the wire to crack and break during processing. Therefore, the total oxygen content in the wire rod is controlled at 0.0010% to 0.0030% in the invention.

[0019] [Als]: 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 wire rod is too low, the inclusions in the steel have a high melting point, and cracking easily occurs between the inclusions and the matrix during processing, causing the wire to crack and break during processing. Therefore, the acid-soluble aluminum content is controlled at 0.0005% to 0.0015% in the invention.

[0020] [V]: vanadium is dissolved into the steel to improve the strength of the steel. However, the vanadium content in the steel should not be too high to prevent the high strength of the wire rod from reducing the drawing performance of the wire rod. Vanadium can inhibit the growth of the billet grains when the billet is heated, thereby refining the ferrite + pearlite structure of the wire rod and being conducive to improving the uniform deformation ability of the wire rod during the processing of the bead wire. Therefore, the vanadium content is controlled at 0.0001% to 0.0009% in the invention.

[0021] [Mg]: an appropriate amount of magnesium content in the steel improves the deformation ability of the inclusions and expands the area with high deformation of the inclusions, which is conducive to improving the deformation ability of the wire rod. However, too high a magnesium content reduces the deformation ability of the wire rod during the processing of the bead wire. Therefore, the magnesium content is controlled at 0.0002% to 0.0011% in the invention.

[0022] [V] + [Mg]: in order to play the beneficial role of V and Mg elements and avoid the harmful role of V and Mg elements, the invention controls [V] + [Mg] at 0.0005% to 0.0020%.

[0023] The second technical scheme of the invention is to provide a structure control method for a wire rod for enhancing the service performance of high-strength bead wire, which comprises smelting, continuous casting, heating, rolling, wire rod rolling, and wire rod cooling.

[0024] Smelting, continuous casting: converter smelting using the carbon content of 4.0% ~ 4.5% molten iron, silicon content of 0.21% ~ 0.25%, manganese content of 0.51% ~ 0.55%, phosphorus content of 0.04% ~ 0.07%, molten iron sulfur content of 0.031% ~ 0.045%. Molten iron temperature 1260 ℃ ~ 1350 ℃. Adopt high quality molten iron, to lay the foundation for improving the cleanliness of steel. Steel liquid using molten iron + scrap smelting, scrap ratio 3% ~ 10%; silicon content of 70% ~ 80% ferrosilicon, phosphorus content is not more than 0.05%, sulfur content is not more than 0.04%, particle size 20 ~ 70 mm, chromium content is not more than 0.4%; through the control of residual element content and particle size of ferrosilicon, improve the yield of alloy, improve the composition uniformity of alloying process of liquid steel.

[0025] The oxygen activity of liquid steel after converter smelting is controlled at 90 ppm ~ 250 ppm;

[0026] The liquid steel is refined by LF, and the LF refining time of liquid steel is controlled at 35 ~ 60 min, and the refining temperature is controlled at 1470 ℃ ~ 1520 ℃; the argon blowing flow rate of liquid steel during refining is 200 ~ 400 NL / min;

[0027] After the liquid steel is refined, continuous casting is carried out, the cross-sectional size of continuous casting billet is (300 ~ 340) mm * (400 ~ 440) mm, the continuous casting speed is 0.45 m / min ~ 0.60 m / min, the liquid steel superheat during continuous casting is not more than 30 ℃, so that the composition uniformity of the billet is ensured, and the foundation for controlling the grain size uniformity of the rod is laid;

[0028] Heating: the continuous casting billet is hot charged, and the total furnace time is 3.5 ~ 4.3 hours; the preheating temperature is not more than 600 ℃, the soaking temperature is controlled at 1110 ~ 1160 ℃, and the holding time is 30 ~ 45 min; through high temperature diffusion of continuous casting billet, the composition uniformity of continuous casting billet is improved, and the foundation for controlling the uniformity of rod structure is laid.

[0029] Rolling: after the continuous casting billet is heated, continuous rolling is carried out, and the final rolling temperature is controlled at 920 ℃ ~ 990 ℃; the cross-sectional size of continuous rolling billet is (140 ~ 180) * (140 ~ 180);

[0030] Rod rolling: the rod is produced by square billet, the total billet furnace time is 150 min ~ 165 min, the soaking temperature is 1040 ℃ ~ 1090 ℃, and the billet soaking time is 40 ~ 50 min; after the billet is heated, it is subjected to rough rolling, intermediate rolling, pre-precision rolling and precision rolling, and then rod wire drawing operation is carried out; the rod temperature after pre-precision rolling is 980 ℃ ~ 1000 ℃; the temperature entering the precision rolling is 890 ℃ ~ 930 ℃; the temperature entering the double module is 880 ℃ ~ 910 ℃; the rod wire drawing temperature is controlled at 860 ℃ ~ 900 ℃, so that the rod grain size is uniformly distributed.

[0031] Rod cooling: after wire drawing, the rod is cooled on the air cooling roller way, the phase transition temperature of the rod is controlled at 610-660 DEG C, the phase transition time of the rod on the air cooling line is 10-20 s, so that the rod has sufficient time to complete the pearlite transformation, and the uniformity of the rod structure is ensured. The rod coiling temperature is 280-450 DEG C, the rod is packed after cooling, and the packing pressure is 29-33 tons. The high packing temperature of the rod is prevented from causing the rod to be bruised. The thickness of the iron oxide skin of the rod is controlled at 10-22 um, and the iron oxide skin on the surface of the rod is prevented from falling off during storage and transportation, so as to cause the surface of the rod to be rusted.

[0032] The rod rolling specification is 5-8 mm.

[0033] The beneficial effects of the present application are that:

[0034] The grain size of the rod produced by the present application is not greater than 25 um, and the grain size difference is not greater than 2 levels. The rod structure is composed of ferrite + pearlite, and the ferrite content is greater than 90%. The tensile strength of the rod is 410-450 MPa, and the elongation is 30-40%. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The present application is a microstructure metallographic chart of the rod of example 1. DETAILED DESCRIPTION

[0036] The present application is further described below through examples.

[0037] According to the component proportion of the technical scheme, the present application is smelted, continuously cast, heated, rolled, rod rolled, and rod cooled.

[0038] Heating: the continuously cast blank is hot charged, and the total furnace time is 3.5-4.3 hours; the preheating section temperature is not greater than 600 DEG C, the soaking section temperature is controlled at 1110-1160 DEG C, and the holding time is 30-45 min;

[0039] Rolling: the continuously cast blank is continuously rolled after heating, and the continuous rolling final rolling temperature is controlled at 920-990 DEG C; the continuous rolling blank section size is (140-180)*(140-180);

[0040] Rod rolling: the rod is produced by square blank, the total furnace time of the steel blank is 150-165 min, the soaking section temperature is 1040-1090 DEG C, and the soaking section holding time of the steel blank is 40-50 min; after the steel blank is heated, the rod is wire drawn after rough rolling, intermediate rolling, pre-precision rolling and precision rolling; the rod pre-precision rolling temperature is 980-1000 DEG C; the precision rolling temperature is 890-930 DEG C; the double module temperature is 880-910 DEG C; and the rod wire drawing temperature is controlled at 860-900 DEG C;

[0041] Rod cooling: after wire drawing, the rod is cooled on the air cooling roller way, the phase transition temperature of the rod is controlled at 610-660℃, and the phase transition time of the rod on the air cooling line is 10-20s.

[0042] Further, smelting and continuous casting: the molten steel is smelted by molten iron + scrap steel, the scrap steel ratio is 3%-10%; the silicon content of ferrosilicon is 70%-80%, the phosphorus content is not more than 0.05%, the sulfur content is not more than 0.04%, the particle size is 20-70mm, and the chromium content is not more than 0.4%;

[0043] The oxygen activity of the molten steel after converter smelting is controlled at 90ppm-250ppm;

[0044] The molten steel is refined by LF, the LF refining time of the molten steel is controlled at 35-60min, and the refining temperature is controlled at 1470-1520℃; the argon blowing flow of the molten steel in the refining process is 200-400NL / min;

[0045] The molten steel is continuously cast after refining, the cross-sectional size of the continuously cast blank is (300-340)mm*(400-440)mm, the continuous casting speed is 0.45-0.60m / min, and the superheat degree of the molten steel in the continuous casting process is not more than 30℃.

[0046] Further, the carbon content of the molten iron used in the converter smelting is 4.0%-4.5%, the silicon content is 0.21%-0.25%, the manganese content is 0.51%-0.55%, the phosphorus content is 0.04%-0.07%, and the sulfur content of the molten iron is 0.031%-0.045%. The temperature of the molten iron is 1260-1350℃.

[0047] Further, the rod collecting temperature is 280-450℃, the rod is packed after cooling, the packing pressure is 29-33 tons, and the thickness of the iron oxide skin of the rod is controlled at 10-22um.

[0048] The composition of the rod in the embodiment of the application is shown in Table 1. The performance and the metallographic structure of the rod in the embodiment of the application are shown in Table 2. The main parameters of the molten iron for smelting the rod in the embodiment of the application are shown in Table 3. The main process parameters of the smelting of the rod in the embodiment of the application are shown in Table 4. The main process parameters of the continuous casting and heating of the rod in the embodiment of the application are shown in Table 5. The main process parameters of the rolling and cooling of the rod in the embodiment of the application are shown in Table 6. The main process parameters of the rolling and cooling of the rod in the embodiment of the application are shown in Table 7.

[0049] Table 1 Composition of the rod in the embodiment of the application (wt%)

[0050] Examples C Si Mn P S Total oxygen Acid-soluble aluminium V Mg V + Mg 1 0.07 0.15 0.50 0.012 0.0092 0.0026 0.0008 0.0005 0.0008 0.0008 2 0.10 0.24 0.52 0.011 0.0076 0.0016 0.0012 0.0006 0.0004 0.0007 3 0.09 0.22 0.51 0.007 0.0082 0.0025 0.0013 0.0007 0.0003 0.0012 4 0.12 0.16 0.55 0.008 0.0042 0.0012 0.0011 0.0008 0.0006 0.0013 5 0.11 0.21 0.53 0.011 0.0037 0.0021 0.0014 0.0008 0.0005 0.0015 6 0.11 0.17 0.55 0.012 0.0085 0.0018 0.0013 0.0005 0.0004 0.0014

[0051] Table 2 Performance and metallographic structure of the rod in the embodiment of the application

[0052] Examples Tensile strength, MPa Elongation, % Difference in grain size, class Maximum grain size, um Ferrite content, % 1 432 32 1 22 98 2 428 35 0 24 96 3 422 33 1 23 97 4 431 34 0 22 95 5 417 35 1 24 98 6 431 33 1 25 95

[0053] Table 3 Main parameters of the molten iron for wire rod smelting in the embodiment of the present application

[0054]

[0055] Table 4 Main process parameters of wire rod smelting in the embodiment of the present application

[0056]

[0057] Table 5 Main process parameters of wire rod continuous casting and heating in the embodiment of the present application

[0058]

[0059] Table 6 Main process parameters of wire rod rolling and cooling in the embodiment of the present application

[0060]

[0061] Table 7 Main process parameters of wire rod rolling and cooling in the embodiment of the present application

[0062] Examples Coiling temperature, °C Packaging pressure, tons Oxide scale thickness, um 1 326 31 16 2 317 32 15 3 295 30 18 4 332 31 17 5 401 32 12 6 376 31 15

[0063] As can be seen from the above, the wire rod produced by using the present application has a grain size of not more than 25 um and a grain size difference of not more than 2 levels. The wire rod has a structure composed of ferrite + pearlite, and the ferrite content is greater than 90%. The tensile strength of the wire rod is 410-450 MPa, and the elongation is 30%-40%.

[0064] In order to describe the present application, the above embodiment has been described appropriately and sufficiently in the above description, and the above embodiment is only used for illustrating the present application, but is not used for limiting the present application. Any modification, equivalent replacement, improvement, etc. made by those skilled in the art without departing from the spirit and scope of the present application should be included in the protection scope of the present application, and the patent protection scope of the present application should be defined by the claims.

Claims

1. A wire rod for enhancing the service performance of high-strength bead wire, characterized in that: The components of the wire rod are as follows by weight percentage: [C] 0.06% to 0.12%, [Si] 0.15% to 0.25%, [Mn] 0.50% to 0.60%, [P] ≤ 0.015%, [S] 0.0030% to 0.010%, total oxygen 0.0010% to 0.0030%, [Als] 0.0005 to 0.0015%, [V] 0.0001% to 0.0009%, [Mg] 0.0002% to 0.0011%; the rest is Fe and unavoidable impurities.

2. The wire rod for enhancing the service performance of high-strength bead wire according to claim 1, characterized in that: [V]+[Mg] in the steel: 0.0005-0.0020%.

3. The wire rod for enhancing the service performance of high-strength bead wire according to claim 1, characterized in that: The tensile strength of the wire rod is 410-450 MPa, and the elongation of the wire rod is 30%-40%.

4. The wire rod for enhancing the service performance of high-strength bead wire according to claim 1, characterized in that: The grain size of the wire rod is not greater than 25um, and the grain size grade difference is not greater than 2 levels; the wire rod structure is composed of ferrite + pearlite, and the ferrite content is greater than 90%.

5. The wire rod steel for enhancing the service performance of high-strength bead wire according to claim 1, characterized in that: The wire rod specifications are Ф5~8mm.

6. A method for controlling the microstructure of a wire rod for enhancing the service performance of a high-strength bead wire according to any one of claims 1 to 5, comprising smelting, continuous casting, heating, rolling, wire rod rolling, and wire rod cooling; characterized in that: Heating: The continuous casting billet is hot charged, with a total furnace time of 3.5 to 4.3 hours; the preheating section temperature is not higher than 600°C, the soaking section temperature is controlled at 1110 to 1160°C, and the holding time is 30 to 45 minutes; Rolling: The continuous casting billet is heated and then continuously rolled. The final rolling temperature is controlled at 920℃~990℃. The cross-sectional size of the continuous rolling billet is (140~180)*(140~180); Wire rod rolling: Wire rod is produced from square billets. The total billet in-furnace time is 150-165 minutes. The soaking section temperature is 1040-1090°C, and the soaking section holding time is 40-50 minutes. After the billet is heated, it undergoes rough rolling, intermediate rolling, pre-finishing rolling, and finishing rolling before the wire rod is rolled out. The wire rod exiting pre-finishing rolling is 980-1000°C; the wire rod entering finishing rolling is 890-930°C; the wire rod entering the double die is 880-910°C; and the wire rod rolling out temperature is controlled at 860-900°C. Wire rod cooling: After spinning, the wire rod is cooled on an air-cooled roller. The phase change temperature of the wire rod is controlled at 610℃~660℃, and the phase change time of the wire rod on the air-cooled roller is 10~20s.

7. The method for controlling the structure of a wire rod for enhancing the service performance of a high-strength bead wire according to claim 6, characterized in that: Smelting and continuous casting: The molten steel is smelted with molten iron + scrap steel, with the scrap steel ratio being 3% to 10%. The silicon content of the ferrosilicon is 70% to 80%, the phosphorus content is not more than 0.05%, the sulfur content is not more than 0.04%, the particle size is 20 to 70 mm, and the chromium content is not more than 0.4%. The oxygen activity of molten steel after converter smelting is controlled at 90ppm~250ppm; The molten steel is refined by LF, the refining time of the molten steel in the LF furnace is controlled at 35 to 60 minutes, and the refining temperature is controlled at 1470°C to 1520°C; the argon blowing flow rate of the molten steel during the refining process is 200 to 400NL / min; After the molten steel is refined, it is continuously cast. The cross-sectional size of the continuous casting billet is (300-340) mm*(400-440) mm. The continuous casting speed is 0.45 m / min-0.60 m / min. The superheat of the molten steel during the continuous casting process is not greater than 30°C.

8. The method for controlling the structure of a wire rod for enhancing the service performance of a high-strength bead wire according to claim 7, characterized in that: The molten iron used in converter smelting has a carbon content of 4.0% to 4.5%, a silicon content of 0.21% to 0.25%, a manganese content of 0.51% to 0.55%, a phosphorus content of 0.04% to 0.07%, and a sulfur content of 0.031% to 0.045%; the molten iron temperature is 1260°C to 1350°C.

9. The method for controlling the structure of a wire rod for enhancing the service performance of a high-strength bead wire according to claim 6, characterized in that: The coiling temperature of the wire rod is 280℃~450℃. The wire rod is packaged after cooling, and the packaging pressure is 29~33 tons. The thickness of the wire rod iron oxide scale is controlled at 10~22um.

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