Wire rod for short-process high-strength tire bead wire and production method of wire rod

Abstract

The invention provides a wire rod for a short-process high-strength tire bead steel wire and a production method of the wire rod. The wire rod comprises the following components in percentage by weight: 0.05%-0.12% of [C], 0.08%-0.15% of [Si], 0.40%-0.55% of [Mn], 0.0050%-0.015% of [P], 0.0040%-0.015% of [S], 0.0020%-0.0040% of [N], 0.0010%-0.0025% of total oxygen, 0.0005%-0.0020% of [Als], 0.01%-0.05% of [Cr], 0.0003%-0.0010% of [V] and 0.00005%-0.0004% of [Se]. And the balance of Fe and inevitable impurities. The production method comprises the steps of smelting, continuous casting, heating, wire rod rolling and wire rod cooling. According to the wire rod produced through the method, the tensile strength of the wire rod ranges from 410 MPa to 450 MPa, the area reduction rate ranges from 65% to 70%, the surface crack depth is not larger than 0.1 mm, and the requirement of a user in the drawing process is met; the continuous rolling procedure with high cost is removed, the production cost of the wire rod is reduced, the wire rod has high market competitiveness, and the high-quality and low-cost wire rod is provided for a user.

Description

Technical Field

[0001] The present invention belongs to the field of metal materials, and in particular relates to a short-process high-strength wire rod for tire bead wire and a production method thereof. Background Art

[0002] To improve the service performance of high-strength bead wire, high-carbon steel wire is combined with a small amount of low-carbon steel wire to produce high-strength bead wire, thereby increasing its overall toughness. To further reduce the manufacturing cost of bead wire, short-process production processes are gradually being applied in production practice.

[0003] The patent document "High Carbon Steel Wire Rod for the Production of Fine Steel Wire" (Publication No.: CN102268596B) discloses a wire rod having the following chemical composition by weight: [C]: 0.6% to 0.88%, [Si]: 0.1% to 1.0%, [Mn]: 0.3% to 1.0%, [P] ≤ 0.015%, [S] ≤ 0.010%, [N] ≤ 0.004%, [O] ≤ 0.002%, [Al] ≤ 0.002%, [Ti] ≤ 0.002%, [Mg] ≤ 0.001%, and other unavoidable impurities not exceeding 0.1%, with the remainder being iron. The high carbon steel wire rod has a rational composition design and excellent processing performance. The inclusions in the wire rod have a low melting point, and during hot rolling, they elongate along the rolling direction, resulting in an aspect ratio greater than 3. This can reduce the wire breakage rate during steel wire processing by 16% to 28%. This patent focuses on a high-carbon steel wire rod process for producing fine wires. Its shortcoming is that it does not propose a technical solution for reducing the manufacturing cost of wire rods for tire bead wires.

[0004] The present invention carries out a systematic design from the aspects of chemical composition, smelting process and rolling process, reduces the manufacturing cost of the wire rod for the bead wire, and lays a foundation for improving the market competitiveness of the bead wire. Summary of the Invention

[0005] The object of the present invention is to overcome the above problems and shortcomings and provide a short-process high-strength bead wire wire and a production method thereof that reduce the manufacturing cost of the wire rod.

[0006] The object of the invention is achieved like this:

[0007] A short-process high-strength wire rod for bead wire, the composition of the wire rod is as follows in percentage by weight: [C] 0.05%~0.12%, [Si] 0.08%~0.15%, [Mn] 0.40%~0.55%, [P] 0.0050%~0.015%, [S] 0.0040%~0.015%, [N] 0.0020%~0.0040%, total oxygen 0.0010%~0.0025%, [Als] 0.0005%~0.0020%, [Cr] 0.01%~0.05%, [V] 0.0003%~0.0010%, [Se] 0.00005%~0.0004%; the rest is Fe and inevitable impurities.

[0008] The tensile strength of the wire rod is 410-450 MPa, the elongation is 65%-70%, and the surface crack depth is not greater than 0.1 mm.

[0009] The wire rod specification diameter is 5.0~8 mm.

[0010] The component design reasons of the application are as follows:

[0011] [C]: the excessive carbon content in the wire rod will lead to the purpose of improving the service performance of the bead wire processed from the wire rod; the low carbon content in the wire rod cannot meet the strength requirement of the bead wire by the user; therefore, the carbon content is controlled in 0.05%~0.12% in the application.

[0012] [Si]: the silicon element makes the eutectoid transformation temperature of the steel increase, makes the pearlite structure of the wire rod coarse, and is not conducive to the complex deformation of the short-process wire rod in the bead wire processing process; the silicon is the main deoxidizing element in the high-carbon steel; the excessive silicon content in the steel will cause the coarse silicate and impurities after the deoxidization of the molten steel, and the low silicon content will cause the insufficient deoxidization of the molten steel, thereby reducing the deformation capacity of the wire rod in the wire processing process; therefore, the silicon content is controlled in 0.08%~0.15% in the application.

[0013] [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; the manganese element has the effect of reducing the eutectoid transformation temperature of the steel, refining the ferrite+pearlite structure of the wire rod, and improving the deformation capacity of the wire rod in the process of processing the bead wire by using the short-process technology; therefore, the manganese content is controlled in 0.40%~0.55% in the application.

[0014] [P]: the phosphorus element can reduce the melting point of the eutectic product of Fe2SiO4 and FeO between the wire rod matrix and the oxide scale, improve the removal performance of the oxide scale on the billet surface in the high-pressure water descaling process, and further improve the removal performance of the oxide scale on the wire rod surface in the mechanical dephosphorization process of the user; therefore, the phosphorus content is controlled in 0.0050%~0.015% in the application.

[0015] [S]: Higher sulfur content in steel reduces the cold working performance of the rod. Appropriate amount of sulfur in the steel can reduce the harm of crystalline inclusions. At the same time, S element can also reduce the melting point of Fe2SiO4 and FeO eutectic product between the rod matrix and the iron scale, and improve the removal performance of the iron scale on the billet surface in the high-pressure water descaling process. Therefore, the sulfur content in the present application is controlled at 0.0040% to 0.015%.

[0016] [N]: The nitrogen content needs to be controlled in an appropriate range, so that the nitrogen element forms fine precipitated phase with Nb and V elements in the steel, thereby improving the fracture resistance of the rod produced by the short process during the wire processing. Therefore, the nitrogen content in the present application is controlled at 0.0020% to 0.0040%.

[0017] Total oxygen: When the oxygen content is low, the deformation ability of the inclusions in the rod is poor, which is not conducive to the processing of the bead wire; when the oxygen content in the rod is high, the size and quantity of the inclusions in the steel are large, which easily leads to cracking and fracture of the bead wire during processing. Therefore, the total oxygen content in the rod in the present application is controlled at 0.0010% to 0.0025%.

[0018] [Als]: When the acid-soluble aluminum content is high, large-size Al2O3 inclusions will appear in the steel; when the acid-soluble aluminum content in the rod is too low, the melting point of the inclusions in the steel is high, which easily causes cracking between the inclusions and the matrix during processing, leading to cracking and fracture of the bead wire during processing. Therefore, the acid-soluble aluminum content in the present application is controlled at 0.0005% to 0.0020%.

[0019] [Cr]: Chromium element can improve the strength of the rod and the wire, and the chromium element improves the stability of austenite, and promotes the decrease of the austenite transformation temperature to pearlite. During the heat treatment of low-carbon wire, the fluctuation of the chromium content in the wire leads to the difference of the phase transition point of the wire, thereby causing the fluctuation of the strength of the wire. In order to improve the stability of the strength of the low-carbon wire, the niobium content in the present application is controlled at 0.01% to 0.05%.

[0020] [V]: Vanadium element solid solution in the steel improves the strength of the steel. However, the vanadium content in the steel should not be too high, in order to prevent the high strength of the rod from reducing the drawing performance of the rod. Vanadium element can inhibit the grain growth of the billet during heating, thereby refining the ferrite + pearlite structure of the rod, which is beneficial to improve the uniform deformation ability of the rod produced by the short process during the processing of the bead wire. Therefore, the vanadium content in the present application is controlled at 0.0003% to 0.0010%.

[0021] [Se]: Selenium element in the steel with manganese, niobium and other elements form selenide, selenide than sulfide small, help to reduce the crack sensitivity of wire rod and steel wire in the process of processing, help to improve the wire rod processing performance, thus improve the short process wire rod and steel wire in the process of surface quality, reduce the short process wire rod in the drawing process of wire breakage rate. But the steel of selenium content is too high to reduce the drawing performance of wire rod. Therefore, the selenium content of the present application is controlled at 0.00005% to 0.0004%.

[0022] The second technical scheme of the present application is to provide a production method of short process high strength tire bead wire rod, including smelting, continuous casting, heating, wire rod rolling, wire rod cooling;

[0023] Smelting, continuous casting:

[0024] The sulfur content of the molten iron after pretreatment is not more than 0.0050%, the desulfurized slag removal rate is not less than 90% after desulfurization and slagging treatment, and a 200kg-400kg small particle lime cover tank is used after slagging.

[0025] The molten steel is smelted by molten iron + scrap steel, the scrap steel ratio is 3%-11%, the aluminum content in the silicon-calcium composite deoxidizer is not more than 1%, the phosphorus content is not more than 0.04%, and the sulfur content is not more than 0.03%; by controlling the residual element content of the deoxidizer, the cleanliness of the steel is improved, and the drawing performance of the wire rod is improved;

[0026] The oxygen activity of the molten steel after converter smelting is controlled at 60-115ppm; by controlling the oxygen activity of the molten steel after converter smelting, the inclusions in the steel are promoted to transform into low melting point inclusions.

[0027] The molten steel is refined by LF, the LF refining time of the molten steel is controlled at 35-55min, and the refining temperature is controlled at 1470℃-1540℃.

[0028] The cross-section size of the continuous casting billet is (140-180)mm*(140-180)mm, and the continuous casting speed is 1.5m / min-1.80m / min.

[0029] Heating: The wire rod is produced by continuous casting billet, which saves the large billet continuous rolling process and reduces the production cost of the wire rod; the total billet time in the furnace is 180min-200min, the preheating temperature is not higher than 700℃, the soaking temperature is 1120℃-1150℃, and the soaking time of the billet is 50-60min. By high temperature diffusion of the billet, the segregation of the billet is reduced, the surface defects of the billet are removed by oxidation loss, and the surface and drawing performance of the wire rod directly rolled by continuous casting billet is improved.

[0030] Rod rolling: after the billet is heated, it is subjected to rough rolling, medium rolling, pre-precision rolling and precision rolling, and then rod drawing operation is performed. The temperature of the rod out of the pre-precision rolling is 980-995 DEG C, the temperature of the rod into the precision rolling is 890-930 DEG C, the temperature of the rod into the double module is 910-940 DEG C, and the temperature of the rod drawing is controlled at 900-930 DEG C. Through the high temperature of the rod drawing, the cooling speed of the rod on the air cooling roller is improved, and the foundation for controlling the final organization of the rod produced by the short process is laid. The rod rolling specification is 5-8 mm;

[0031] Rod cooling: after the rod is drawn, the rod is cooled on the air cooling roller, the phase change temperature of the rod is controlled at 620-650 DEG C, and the phase change time of the rod on the air cooling line is 15-30 s. Through the cooling of the rod on the air cooling line, the organization of the short process rod meets the drawing processing requirements of the user.

[0032] Beneficial effects:

[0033] The rod produced by the application removes the continuous rolling process with high cost, reduces the production cost of the rod, makes the rod have strong market competitiveness, and also provides the user with high-quality and low-cost rods. The tensile strength of the rod is 410-450 MPa, the area reduction is 65%-70%, and the surface crack depth is not greater than 0.1 mm, which meets the requirements of the user in the drawing process. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 It is a microstructure metallographic diagram of the rod surface. DETAILED DESCRIPTION

[0035] The application will be further described below through examples.

[0036] According to the component ratio of the technical scheme, the example of the application is smelted, continuously cast, heated, rod rolled and cooled.

[0037] Heating: the rod is produced by square billet; the total time of the billet in the furnace is 180-200 min, the temperature in the preheating section is not higher than 700 DEG C, the temperature in the soaking section is 1120-1150 DEG C, and the soaking time in the soaking section is 50-60 min;

[0038] Rod rolling: after the billet is heated, it is subjected to rough rolling, medium rolling, pre-precision rolling and precision rolling, and then rod drawing operation is performed. The temperature of the rod out of the pre-precision rolling is 980-995 DEG C, the temperature of the rod into the precision rolling is 890-930 DEG C, the temperature of the rod into the double module is 910-940 DEG C, and the temperature of the rod drawing is controlled at 900-930 DEG C.

[0039] Rod cooling: after the rod is drawn, the rod is cooled on the air cooling roller, the phase change temperature of the rod is controlled at 620-650 DEG C, and the phase change time of the rod on the air cooling line is 15-30 s. Through the cooling of the rod on the air cooling line, the organization of the short process rod meets the drawing processing requirements of the user.

[0040] Further, smelting, continuous casting:

[0041] The sulfur content after the hot metal pretreatment is not more than 0.0050%, the hot metal is treated by deslagging after desulfurization, the deslagging rate of the desulfurization slag is not less than 90%, and a 200-400kg small-grained lime cover tank is used after deslagging;

[0042] The molten steel is smelted by hot metal+scrap steel, the scrap steel ratio is 3%-11%, the aluminum content in the silicon-calcium composite deoxidizer is not more than 1%, the phosphorus content is not more than 0.04%, and the sulfur content is not more than 0.03%;

[0043] The oxygen activity of the molten steel after the converter smelting is controlled to be 60-115ppm;

[0044] The molten steel is refined by LF, the LF refining time of the molten steel is controlled to be 35-55min, and the refining temperature is controlled to be 1470℃-1540℃;

[0045] The cross-section size of the continuous casting square billet is (140-180)mm*(140-180)mm, and the continuous casting speed is 1.5m / min-1.80m / min.

[0046] The composition of the coil of the embodiment of the present application is shown in Table 1. The mechanical properties and surface crack depth of the coil of the embodiment of the present application are shown in Table 2. The main process parameters of the smelting of the coil of the embodiment of the present application are shown in Table 3. The continuous casting, heating, rolling and cooling process parameters of the coil of the embodiment of the present application are shown in Table 4.

[0047] Table 1 Composition of the coil of the embodiment of the present application (wt%)

[0048]

[0049] Table 2 Mechanical properties and microstructure of the coil of the embodiment of the present application

[0050] Example Tensile strength, MPa Shrinkage rate, % Surface crack depth, mm 1 424 67 0 2 436 68 0.05 3 450 67 0.04 4 443 65 0.03 5 423 66 0 6 431 67 0.02

[0051] Table 3 Main process parameters of the smelting of the coil of the embodiment of the present application

[0052]

[0053] Table 4 Continuous casting, heating, rolling and cooling process parameters of the coil of the embodiment of the present application

[0054]

[0055] The tensile strength of the coil produced by the present application is 410-450MPa, the area reduction is 65%-70%, and the surface crack depth is not more than 0.1mm, which meets the requirements of the user in the drawing process, and no surface defects with a depth greater than 0.1mm are seen.

[0056] For the purpose of describing the present application, the above-mentioned embodiments are appropriately and sufficiently described by way of examples, and the above embodiments are merely for illustrating the present application, and are not intended to limit 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 shall be included in the protection scope of the present application, and the patent protection scope of the present application shall be defined by the claims.

Claims

1. A short-process high-strength bead wire rod, characterized in that: The components of the wire rod are as follows by weight percentage: [C] 0.05% to 0.12%, [Si] 0.08% to 0.15%, [Mn] 0.40% to 0.55%, [P] 0.0050% to 0.015%, [S] 0.0040% to 0.015%, [N] 0.0020% to 0.0040%, total oxygen 0.0010% to 0.0025%, [Als] 0.0005% to 0.0020%, [Cr] 0.01% to 0.05%, [V] 0.0003% to 0.0010%, [Se] 0.00005% to 0.0004%; the rest is Fe and unavoidable impurities.

2. The short-process high-strength bead wire rod according to claim 1, characterized in that: The wire rod has a tensile strength of 410-450 MPa, an elongation of 65%-70%, and a surface crack depth of no more than 0.1 mm.

3. The short-process high-strength bead wire rod according to claim 1, characterized in that: The diameter of the wire rod is 5.0-8 mm.

4. A method for producing a short-process high-strength bead wire wire according to any one of claims 1 to 3, comprising smelting, continuous casting, heating, wire rod rolling, and wire rod cooling; characterized in that: Heating: Wire rod is produced from billets; the total billet in furnace time is 180-200 minutes, the preheating section temperature is not higher than 700°C, the soaking section temperature is 1120-1150°C, and the billet soaking section holding time is 50-60 minutes; Wire rod rolling: After the billet is heated, it goes through rough rolling, intermediate rolling, pre-finishing rolling and finishing rolling before the wire rod extrusion operation. The wire rod exit temperature from pre-finishing rolling is 980℃~995℃, and the wire rod entry temperature is 890℃~930℃; the wire rod entry temperature is 910℃~940℃; the wire rod extrusion temperature is controlled at 900℃~930℃; 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 620℃~650℃, and the phase change time of the wire rod on the air-cooled roller is 15~30s.

5. The method for producing a short-process high-strength bead wire according to claim 4, characterized in that: Smelting and continuous casting: The sulfur content of molten iron after pretreatment is not more than 0.0050%. After desulfurization, the molten iron is subjected to slag removal treatment, and the desulfurization slag removal rate is not less than 90%. After slag removal, 200-400kg of small-grain lime is used to cover the tank; The molten steel is smelted with molten iron and scrap steel, with the scrap steel ratio being 3% to 11%. The aluminum content of the silicon-calcium composite deoxidizer is not more than 1%, the phosphorus content is not more than 0.04%, and the sulfur content is not more than 0.03%. The oxygen activity of molten steel after converter smelting is controlled at 60-115ppm; The molten steel is refined by LF, the LF furnace refining time of the molten steel is controlled at 35-55 minutes, and the refining temperature is controlled at 1470℃~1540℃; The cross-sectional size of the continuous casting billet is (140-180) mm*(140-180) mm, and the continuous casting speed is 1.5 m / min-1.80 m / min.

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