Hot-rolled austenite wire rod for high-elongation steel strand and preparation method of hot-rolled austenite wire rod

Abstract

The invention relates to a hot-rolled austenite wire rod for a high-elongation steel strand and a preparation method of the hot-rolled austenite wire rod. The wire rod comprises the following chemical components in percentage by mass: 0.25-0.38% of C, 0.20-0.40% of Si, 10-13% of Mn, 0.03-0.10% of Nb, 0.5-1.0% of Cr, 0.02-0.08% of V, less than or equal to 0.015% of P, less than or equal to 0.015% of S and the balance of Fe and inevitable impurity elements. The whole technological process comprises the steps of molten iron desulphurization, converter smelting, argon blowing, LF furnace treatment, RH vacuum treatment, square billet continuous casting, square billet heating, high-speed wire rolling, stelmor air cooling and coil collection. The comprehensive use performance of the steel strand is improved, the requirement for large-scale engineering construction is met, and the production method is simple, high in operability and easy to apply and popularize.

Description

Technical Field

[0001] The invention relates to the field of industrial wire rod production, and more specifically to a hot-rolled austenite wire rod for high-elongation steel strands and a preparation method thereof. Background Art

[0002] As the scale of engineering construction in my country continues to expand, the depth and difficulty of major engineering fields such as mining, tunnel excavation, large-scale slope protection pit support, bridge engineering, etc. are also increasing. Extremely high engineering stress and large structural deformation and other destructive effects are becoming more frequent, which puts higher requirements on the performance of prestressed steel strand products. The elongation of traditional prestressed steel strand products is low. For example, the elongation of SWRH82B hot-rolled wire rod is about 10-15%, and the elongation after processing into steel strand is only about 3%. In addition, uneven deformation and necking are prone to occur during the stretching and shearing process, which makes it difficult to meet the requirements of deep underground engineering and large-scale slope protection pit support for steel strand materials with high strength and high ductility. Hot-rolled wire rods for high-ductility prestressed steel strands have better performance than traditional steel strand materials in terms of impact resistance and energy absorption, and have broad application prospects in energy mines, transportation tunnels, earthquake-resistant buildings and bridge engineering.

[0003] Patent CN1778486A discloses a post-rolling forced cooling process for 82B wire rod for steel strands. By accelerating the cooling rate during phase change and improving the lateral distribution of air volume, the uniform sorbite interweaving of the wire rod is achieved, thereby reducing the highest temperature point during the transformation from austenite to pearlite, reducing the wire breakage rate during wire rod drawing, and improving the quality and production efficiency of steel strands. Patent CN1778981A discloses a microalloying method for producing 82B wire rod for steel strands using continuous casting small square billets, which solves the problem of how to produce 82B wire rods that meet the performance requirements through microalloying methods under ordinary production equipment conditions to meet the needs of wire products with the highest strength level and the highest technical content in building materials.

[0004] Patent CN101831522A discloses a composite strengthening production method for wire rods for high-strength steel strands. By adding composite strengthening elements Cr and V, the wire rod steel forms a composite strengthening mode in which multiple strengthening means such as organizational strengthening, fine grain strengthening, and precipitation strengthening coexist. The produced high-strength steel strand wire rod SWRS82B product has stable performance, the wire rod product strength reaches 1250-1300MPa, and the average troostite sheet spacing is 0.16-0.18μm, which can be used to make 2000MPa high-strength steel strands. Patent CN101831591 discloses a wire rod for high-strength steel strands and a production method thereof. It solves the problem of how to improve the strength and cold drawing performance of SWRS82B wire rods without increasing costs to meet the needs of large-size high-strength prestressed steel wires and steel strands. Patent CN1395012A discloses a ductile prestressed concrete structural member and a manufacturing method thereof, including concrete and prestressed tendons, wherein the compressive strength of the concrete is greater than 60MPa, and the prestressed tendons are prestressed steel strands, whose strength is ≥1860MPa, relaxation rate is ≤2.5%, and elongation is ≥5%. The bending deflection ductility ratio of the prestressed concrete structure that meets the above process parameters is greater than 3.0. This technology mainly utilizes the combination of high-performance concrete and high-elongation steel strands to obtain a prestressed concrete structural member with a bending deflection coefficient of more than 3.0, so that the ductility of the prestressed concrete structure is better than that of an ordinary concrete structure.

[0005] The above-mentioned patents related to prestressed steel strands mainly focus on improving the strength of wire rods through micro-alloying, steel rolling technology, controlled cooling technology and other methods, and do not involve improving the elongation of steel strand wire rods. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a hot-rolled austenitic wire rod for high-elongation steel strand and a preparation method thereof, which obtains high-elongation prestressed steel strand hot-rolled wire rod by reasonably setting the chemical composition and the smelting and rolling processes, thereby improving the comprehensive performance of the steel strand and meeting the needs of large-scale engineering construction.

[0007] The technical solution adopted by the present invention to solve the technical problem is: constructing a hot-rolled austenitic wire rod for high-elongation steel strand, the chemical composition of the wire rod is C: 0.25-0.38%, Si: 0.20-0.40%, Mn: 10-13%, Nb: 0.03-0.10%, Cr: 0.5-1.0%, V: 0.02-0.08%, P: ≤0.015%, S: ≤0.015%, and the rest is Fe and unavoidable impurity elements.

[0008] According to the above scheme, the tensile strength of the wire rod is ≥1000MPa, the elongation is ≥30%, the area reduction is ≥50%, the tensile strength difference is ≤60MPa, and the room temperature metallographic structure is austenite.

[0009] The present invention also provides a method for preparing hot-rolled austenitic wire rod for high-elongation steel strand, and the whole process flow is: molten iron desulfurization → converter smelting → argon blowing → LF furnace treatment → RH vacuum treatment → billet continuous casting → billet heating → high-speed wire rolling → Stelmor air cooling → coiling.

[0010] According to the above scheme, the method is specifically as follows: the molten iron desulfurization adopts the magnesium powder spraying desulfurization process, and the sulfur content of the molten iron out of the station is ≤0.005%; the converter smelting adopts the top and bottom blowing process, the steel tapping temperature is 1600-1650℃, the final slag basicity is ≥2.5, alloy materials and carburizers are added to about 1 / 3 of the steel tapping, and the addition is completed before 2 / 3 of the steel tapping, and active lime ≥400kg is added with the steel flow after the converter tapping; the bottom argon blowing time is ≥5min; the argon pressure is 0.2-0.3MPa.

[0011] According to the above scheme, the slag basicity of LF off-furnace refining is controlled at 1.8-2.4, the refining time is 25-28min, and argon is blown throughout the refining process; the RH bottom blowing argon pressure is 0.40-0.55MPa, the soft blowing time is 5-7min, the vacuum degree is ≤100pa, and the continuous casting process adopts a large tank long nozzle and a crystallizer immersed nozzle to protect the pouring to prevent molten steel oxidation.

[0012] According to the above scheme, the ingot is heated at a heating temperature of 1180-1240°C and a holding time of 100-160min; the starting temperature of high-speed wire rolling is 1020-1060°C, the temperature entering the finishing mill is 930-980°C, the temperature entering the sizing mill is 910-950°C, the wire laying temperature is 890-920°C, and the wire rod diameter is 8-12mm.

[0013] According to the above plan, the rolled wire rod is Stelmor air-cooled. The Stelmor air-cooling line is 130 meters long and has 16 sets of fans. The rated air volume of 1-5# fans is 300,000m3 / h, the rated air volume of 6-16# fans is 180,000m3 / h, the power of 1#-5# fans is 30-50%, the power of 6#-10# fans is 40-55%, 10# and subsequent fans are closed, and the insulation cover is fully opened; the starting speed of the roller is 0.6m / s, and the speed difference of the next group of rollers is 1.01-1.03 compared with the previous group of rollers, and then the finished products are rolled and bundled for storage.

[0014] The hot-rolled austenite wire rod for high elongation steel strand and the production method thereof of the present invention have the following characteristics:

[0015] Beneficial effects:

[0016] The present invention provides a hot-rolled austenite wire rod for prestressed steel strands with an elongation greater than 30% and a production method thereof. The manganese element in the component system can make the base metallographic structure at room temperature austenite and reduce the stacking fault energy, thereby generating a higher dislocation density and a large number of deformation twins during the tensile deformation process, resisting strain concentration and necking during deformation, and obtaining a hot-rolled wire rod for prestressed steel strands with high elongation, thereby improving the comprehensive performance of the steel strands and meeting the needs of large-scale engineering construction in my country. The production method is simple, highly operable, and easy to promote and apply. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0018] Figure 1 It is a typical metallographic structure schematic diagram of the present invention. DETAILED DESCRIPTION

[0019] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific embodiments of the present invention are now described in detail.

[0020] Example 1

[0021] The production method of wire rod includes hot metal desulfurization, converter smelting, argon blowing, LF furnace treatment, RH vacuum treatment, billet continuous casting, billet heating, high-speed wire rolling, Stelmor controlled cooling, coiling and other processes. Among them, the hot metal desulfurization adopts the magnesium powder spraying desulfurization process, and the sulfur content of the hot metal out of the station is ≤0.005%. The converter smelting adopts the top and bottom combined blowing process, the steel tapping temperature is 1620℃, the final slag basicity is 2.7, alloy materials and carburizers are added to about 1 / 3 of the steel tapping, and they are added before 2 / 3 of the steel tapping. After the converter tapping, 420kg of active lime is added with the steel flow. The bottom argon blowing time is 6min; the argon pressure is 0.22MPa. The slag basicity of LF furnace refining is 1.9, the refining time is 26min, and argon is blown throughout the refining process. The RH bottom blowing argon pressure is 0.45MPa, the soft blowing time is 5.5min, the vacuum degree is 70pa, and the continuous casting process adopts a large tank long nozzle and a crystallizer immersed nozzle to protect the pouring to prevent the oxidation of molten steel. The ingot is heated to 1190℃ and the holding time is 130min; the high-speed rolling start temperature is 1030℃, the temperature of entering the finishing mill is 970℃, the temperature of entering the sizing mill is 940℃, and the wire laying temperature is 910℃. The wire rod is Stelmor air-cooled after rolling. The 1-5# fans are three fans in a herringbone shape, the fan power is 35%, the 6#-10# fans have a power of 45%, the 10# and subsequent fans are closed, and the insulation cover is fully opened. The starting speed of the roller is 0.6m / s, and the speed difference of the next group of rollers is 1.01 compared with the previous group of rollers, and then the finished products are bundled and put into storage.

[0022] The typical metallographic structure of the wire rod obtained in this embodiment is as follows: Figure 1 shown.

[0023] Example 2

[0024] The desulfurization of hot metal adopts the magnesium powder spraying desulfurization process, and the sulfur content of the hot metal out of the station is ≤0.005%. The converter smelting adopts the top and bottom combined blowing process, the steel tapping temperature is 1610℃, the final slag basicity is 2.6, and alloy materials and carburizers are added to about 1 / 3 of the steel tapping, and the addition is completed before 2 / 3 of the steel tapping. After the converter taps, 410kg of active lime is added with the steel flow. The bottom argon blowing time is 8min; the argon pressure is 0.26MPa. The slag basicity of LF refining outside the furnace is controlled at 2.2, the refining time is 26min, and argon is blown throughout the refining process. The RH bottom blowing argon pressure is 0.48MPa, the soft blowing time is 6.5min, and the vacuum degree is 80pa. The continuous casting process adopts a large tank long nozzle and a crystallizer immersed nozzle to protect the pouring to prevent the oxidation of molten steel. The ingot is heated to 1220℃ and the holding time is 150min. The starting temperature of high-speed wire rolling is 1030℃, the temperature of entering the finishing mill is 950℃, the temperature of entering the sizing mill is 930℃, and the wire laying temperature is 890℃. The wire rod is Stelmor air-cooled after rolling. The 1-5# fans are three fans in a herringbone shape with a fan power of 40%, the 6#-10# fans have a power of 52%, and the 10# and subsequent fans are closed, and the insulation cover is fully opened. The starting speed of the roller is 0.6m / s, and the speed difference of the next group of rollers is 1.02 compared with the previous group of rollers. Then the finished products are rolled and bundled for storage.

[0025] Example 3

[0026] The desulfurization of hot metal adopts the magnesium powder spraying desulfurization process, and the sulfur content of the hot metal out of the station is ≤0.005%. The converter smelting adopts the top and bottom combined blowing process, the steel tapping temperature is 1650℃, the final slag basicity is 2.6, and alloy materials and carburizers are added to about 1 / 3 of the steel tapping, and the addition is completed before 2 / 3 of the steel tapping. After the converter taps, 400kg of active lime is added with the steel flow. The bottom argon blowing time is 5min; the argon pressure is 0.24MPa. The slag basicity of LF refining outside the furnace is controlled at 1.9, the refining time is 26min, and argon is blown throughout the refining process. The RH bottom blowing argon pressure is 0.52MPa, the soft blowing time is 5min, and the vacuum degree is 90pa. The continuous casting process adopts a large tank long nozzle and a crystallizer immersed nozzle to protect the pouring to prevent the oxidation of molten steel. The ingot is heated to 1210℃ and the holding time is 120min. The starting temperature of high-speed wire rolling is 1050℃, the temperature of entering the finishing mill is 950℃, the temperature of entering the sizing mill is 920℃, and the wire laying temperature is 910℃. The wire rod is Stelmor air-cooled after rolling. The 1-5# fans are three fans in a herringbone shape with a fan power of 48%, the 6#-10# fans have a power of 50%, the 10# and subsequent fans are closed, and the insulation cover is fully opened. The starting speed of the roller is 0.6m / s, and the speed difference of the next group of rollers is 1.03 compared with the previous group of rollers. Then the finished products are rolled and bundled for storage.

[0027] Example 4

[0028] The desulfurization of hot metal adopts the magnesium powder spraying desulfurization process, and the sulfur content of the hot metal out of the station is ≤0.005%. The converter smelting adopts the top and bottom combined blowing process, the steel tapping temperature is 1610℃, the final slag basicity is 2.7, and alloy materials and carburizers are added to about 1 / 3 of the steel tapping, and the addition is completed before 2 / 3 of the steel tapping. After the converter taps, 430kg of active lime is added with the steel flow. The bottom argon blowing time is 6min; the argon pressure is 0.28MPa. The slag basicity of LF refining outside the furnace is controlled at 2.3, the refining time is 27min, and argon is blown throughout the refining process. The RH bottom blowing argon pressure is 0.52MPa, the soft blowing time is 7min, and the vacuum degree is 80pa. The continuous casting process adopts a large tank long nozzle and a crystallizer immersed nozzle to protect the pouring to prevent the oxidation of molten steel. The ingot is heated to 1220℃ and the holding time is 150min. The starting temperature of high-speed wire rolling is 1030℃, the temperature of entering the finishing mill is 960℃, the temperature of entering the sizing mill is 940℃, and the wire laying temperature is 910℃. The wire rod is Stelmor air-cooled after rolling. The 1-5# fans are three fans in a herringbone shape with a fan power of 40%, the 6#-10# fans have a power of 50%, and the 10# and subsequent fans are closed, and the insulation cover is fully opened. The starting speed of the roller is 0.6m / s, and the speed difference of the next group of rollers is 1.02 compared with the previous group of rollers. Then the finished products are rolled and bundled for storage.

[0029] Example 5

[0030] The desulfurization of hot metal adopts the magnesium powder spraying desulfurization process, and the sulfur content of the hot metal out of the station is ≤0.005%. The converter smelting adopts the top and bottom combined blowing process, the steel tapping temperature is 1630℃, the final slag basicity is 2.6, and alloy materials and carburizers are added to about 1 / 3 of the steel tapping, and the addition is completed before 2 / 3 of the steel tapping. After the converter taps, 420kg of active lime is added with the steel flow. The bottom argon blowing time is 6min; the argon pressure is 0.23MPa. The slag basicity of LF refining outside the furnace is controlled at 2.0, the refining time is 26min, and argon is blown throughout the refining process. The RH bottom blowing argon pressure is 0.48MPa, the soft blowing time is 6min, and the vacuum degree is 80pa. The continuous casting process adopts a large tank long nozzle and a crystallizer immersed nozzle to protect the pouring to prevent the oxidation of molten steel. The ingot is heated to 1200℃ and the holding time is 140min. The starting temperature of high-speed wire rolling is 1050℃, the temperature of entering the finishing mill is 940℃, the temperature of entering the sizing mill is 920℃, and the wire-spinning temperature is 900℃. The wire rod is Stelmor air-cooled after rolling. The 1-5# fans are three fans in a herringbone shape with a fan power of 35%, the 6#-10# fans have a power of 50%, the 10# and subsequent fans are closed, and the insulation cover is fully opened. The starting speed of the roller is 0.6m / s, and the speed difference of the next group of rollers is 1.03 compared with the previous group of rollers. Then the finished products are rolled and bundled for storage.

[0031] The chemical compositions of Examples 1-5 are shown in Table 1.

[0032] Table 1 Chemical composition of the examples

[0033]

[0034] The tensile strength, elongation and other performance indicators of the wire rods of Examples 1-5 were tested, and the results are shown in Table 2.

[0035] Table 2 Comparison of mechanical properties of examples

[0036]

[0037] It can be seen that the hot-rolled austenitic wire rod for prestressed steel strand obtained in the embodiment has good mechanical properties, including tensile strength ≥1000MPa, elongation ≥30%, area reduction ≥50%, and tensile strength difference ≤60MPa.

[0038] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A hot-rolled austenitic wire rod for high elongation steel strand, characterized in that: The chemical composition of the wire rod is, by mass percentage, C: 0.25-0.38%, Si: 0.20-0.40%, Mn: 10-13%, Nb: 0.03-0.10%, Cr: 0.5-1.0%, V: 0.02-0.08%, P: ≤0.015%, S: ≤0.015%, and the rest is Fe and unavoidable impurity elements.

2. The hot-rolled austenitic wire rod for high elongation steel strand according to claim 1, characterized in that: The wire rod has a tensile strength of ≥1000MPa, an elongation of ≥30%, a surface reduction of ≥50%, a tensile strength difference of ≤60MPa, and a room temperature metallographic structure of austenite.

3. A method for preparing the hot-rolled austenitic wire rod for high elongation steel strand according to claim 1, characterized in that: The entire process flow is: molten iron desulfurization → converter smelting → argon blowing → LF furnace treatment → RH vacuum treatment → billet continuous casting → billet heating → high-speed wire rolling → Stelmor air cooling → coiling.

4. The method for preparing the hot-rolled austenitic wire rod for high elongation steel strand according to claim 3, characterized in that: The molten iron desulfurization adopts the magnesium powder spraying desulfurization process, and the sulfur content of the molten iron outgoing is ≤0.005%; the converter smelting adopts the top and bottom blowing process, the steelmaking temperature is 1600-1650℃, the final slag basicity is ≥2.5, alloy materials and carburizers are added to about 1 / 3 of the steel, and the addition is completed before 2 / 3 of the steel is tapped, and active lime ≥400kg is added with the steel flow after the converter taps; the bottom argon blowing time is ≥5min; the argon pressure is 0.2-0.3MPa.

5. The method for preparing the hot-rolled austenitic wire rod for high elongation steel strand according to claim 3, characterized in that: The slag basicity of LF off-furnace refining is controlled at 1.8-2.4, the refining time is 25-28min, and argon is blown throughout the refining process; the RH bottom blowing argon pressure is 0.40-0.55MPa, the soft blowing time is 5-7min, the vacuum degree is ≤100pa, and the continuous casting process adopts a large tank long nozzle and a crystallizer immersed nozzle to protect the casting.

6. The method for preparing the hot-rolled austenitic wire rod for high elongation steel strand according to claim 3, characterized in that: The ingot is heated to a temperature of 1180-1240°C and a holding time of 100-160 min; the starting temperature of high-speed wire rolling is 1020-1060°C, the temperature entering the finishing mill is 930-980°C, the temperature entering the sizing mill is 910-950°C, the wire laying temperature is 890-920°C, and the wire rod diameter is 8-12 mm.

7. The method for preparing the hot-rolled austenitic wire rod for high elongation steel strand according to claim 3, characterized in that: The rolled wire rods are Stelmor air-cooled. The Stelmor air-cooling line is 130 meters long and has 16 sets of fans. The rated air volume of 1-5# fans is 300,000m3 / h, and the rated air volume of 6-16# fans is 180,000m3 / h. The power of 1#-5# fans is 30-50%, and the power of 6#-10# fans is 40-55%. 10# and subsequent fans are closed, and the insulation cover is fully open. The starting speed of the roller is 0.6m / s, and the speed difference between the next group of rollers and the previous group of rollers is 1.01-1.

03. The finished products are then rolled and bundled for storage.

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