Steel wire rod for 2300MPa-grade steel-cored aluminum stranded wire and production method of steel wire rod

Abstract

The invention provides a steel wire rod for a 2300MPa-grade steel-cored aluminum strand and a production method of the steel wire rod. The method sequentially comprises the following steps of molten iron pre-desulfurization, converter smelting, external refining, continuous casting, casting blank heating, high-speed wire rolling and online isothermal quenching and tempering, and the steel wire rod is obtained. On the basis of adjustment of chemical components of the wire rod and control over production processes such as continuous casting, rolling and online quenching-tempering treatment, the homogeneity of steel is improved, the metallographic structure of the wire rod prepared through the production method is mainly sorbite, the sorbite rate is larger than or equal to 97%, and the sorbite lamellar spacing is 45-65 nm; the tensile strength is 1620 to 1700 MPa, and the percentage reduction of area is 35 to 44 percent; the steel wire rod is drawn, galvanized and twisted into a galvanized steel strand which can be used for a steel core of a steel-cored aluminum strand.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of steel metallurgy, and particularly relates to a 2300MPa-grade steel core aluminum strand wire rod and a production method thereof. BACKGROUND

[0002] Ultra-high voltage, long-distance, large-capacity power transmission and large-scale grid utilization of clean energy put forward higher requirements on the transmission capacity and safety and reliability of overhead conductors. For steel core aluminum strand wires, the steel core plays a load-bearing role, and the outer aluminum wire mainly plays a conductive function.

[0003] At present, the strength of ordinary steel core aluminum strand wire is 1300-1400MPa, and a small number of them reach 1820MPa. In application, the following problems exist: the sag increases during long-term use, which brings safety hazards to overhead transmission lines; the steel / aluminum weight of the conductor is large, and there is a large dead weight; in order to ensure safety, the steel core diameter can only be further increased, which causes a vicious cycle and makes it impossible to use in scenarios such as old line capacity expansion and reconstruction. If the strength of the steel core can be increased to 2300MPa, the advantages of ultra-high strength steel in mechanical properties can be fully utilized, the steel core weight ratio can be reduced, the sag height can be reduced, the tower load can be reduced, and the tower design span can be increased.

[0004] The steel core of the aluminum strand wire is generally made of high-carbon steel wire rod, which is processed into galvanized steel wire through drawing and galvanizing, and the steel wire is twisted to obtain a steel strand. The document "Preparation and performance characterization of ultra-strong prestressed steel core for overhead conductor" uses YL82B wire rod to prepare an overhead conductor steel core with a tensile strength of 2100MPa by increasing the drawing deformation and increasing the cold deformation processing strengthening. The strength is greatly improved through cold deformation, but the strength loss is large during the subsequent use process due to the increase in temperature, which causes the disadvantage of large sag of the steel core aluminum strand wire, and the initial strength is only 2100MPa. The invention with the publication number CN116895403A discloses a low-sag capacity expansion type low-wind-pressure overhead conductor and a preparation method thereof. It uses carbon fiber rods as the support material of the conductor core, and the tensile strength of the carbon fiber rods reaches 2400MPa. However, the carbon fiber rods are brittle, and the conductor is prone to breaking due to external forces such as strong winds, which causes safety problems. In order to reduce the sag of the conductor, invar alloy can also be used to improve the high-temperature resistance of the conductor by using its unconventional thermal expansion law as the support material of the conductor core. However, invar alloy is expensive and has low mechanical properties, which makes it difficult to be widely used. SUMMARY

[0005] The present application aims to solve the technical problems of the long-term use of ordinary steel core aluminum strand wire and the large steel / aluminum weight of the conductor. A production method for preparing a 2300MPa-grade steel core aluminum strand wire rod based on the adjustment of the chemical composition of the wire rod, combined with continuous casting, rolling, and on-line quenching-tempering treatment, is proposed.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A type of 2300MPa grade steel-cored aluminum stranded wire rod has the following chemical composition and weight percentage: C 0.94-0.98%, Si 1.20-1.60%, Mn 0.60-1.00%, Cr 0.20-0.50%, V 0.02-0.04%, Mo≤0.20%, Ni≤0.30%, S≤0.020%, P≤0.010%, N≤0.0040%, O≤0.0020%, with the remainder being Fe and other unavoidable impurities.

[0007] In the chemical composition of this invention: C is the most important strengthening element in steel. To ensure the ultra-high tensile strength of galvanized steel strand, the present invention limits the C content to 0.94-0.98%.

[0008] Si is a strengthening and deoxidizing element in steel, which reduces the strength loss of steel wire during galvanizing and subsequent engineering applications. In addition, it helps to improve the steel's resistance to relaxation and is an important element to ensure that the conductor sag is reduced. In this invention, the Si content is limited to 1.20-1.60%.

[0009] Mn is a strengthening element in steel, which can improve the strength and hardenability of steel and ensure a good work hardening rate of wire rod. In this invention, the Mn content is limited to 0.60-1.00%.

[0010] Cr can refine pearlite lamellars and improve the stability of carbides, thereby reducing conductor sag; however, excessive Cr content increases the difficulty of controlling segregation. This invention limits the Cr content to 0.20-0.50%.

[0011] The carbonitrides formed by V play a role in precipitation enhancement and have good thermal stability. This invention limits the V content to 0.02-0.04%.

[0012] Mo carbides help improve the high-temperature strength of materials, but due to their high cost, the present invention limits the amount added to less than 0.30%.

[0013] Ni is a strengthening element in steel and can improve the toughness of steel and enhance the high-temperature performance of materials. To control costs, the amount added is limited to less than 0.30%.

[0014] S tends to segregate at grain boundaries, which can embrittle the grain boundaries and reduce the strength and plasticity of steel. In addition, S can react with Mn to form MnS, thereby reducing the solid solution strengthening effect of Mn. In this invention, the S content is limited to ≤0.010%.

[0015] P is an impurity element in steel, which is easy to segregate at grain boundaries and make the grain boundaries brittle, and further reduce the strength and plasticity of the steel, and the P content is limited to ≤0.020% in the application.

[0016] N can cause the plasticity of the steel to deteriorate, increase the risk of delay fracture of the wire rod, and high N content can cause AlN and TiN to coarsen, which is not conducive to fine-grain strengthening, in addition, free nitrogen atoms in the steel wire occur dynamic aging and reduce the plasticity of the steel wire, and the nitrogen content is limited to ≤0.0040% in the application.

[0017] O combines with alloying elements in steel to form non-metallic inclusions, affecting the strength and plasticity of the wire rod and the fatigue and corrosion resistance of the steel wire, and the O content needs to be limited to ≤0.0020%.

[0018] As preferred, the chemical composition and weight percentage are: C 0.94-0.98%, Si 1.25-1.55%, Mn 0.62-0.90%, Cr 0.25-0.35%, V 0.02-0.04%, Mo ≤0.15, Ni 0.10-0.25%, S ≤0.008%, P ≤0.010%, N ≤0.0040%, O ≤0.0020%, and the rest is Fe and other unavoidable impurities.

[0019] As preferred, the diameter of the wire rod is 5.5-8mm.

[0020] The application also provides a production method of the wire rod for the 2300MPa-grade steel-cored aluminum strand, which comprises the following steps performed in sequence: hot metal pre-desulfurization, converter smelting, secondary refining, continuous casting, billet heating, high-speed wire rolling, online isothermal quenching and tempering, to obtain the wire rod. In the high-speed wire rolling step, the rolling temperature is adjusted to 1050-1100℃ by adjusting the heating temperature and time, the water tank flow is adjusted to make the temperature entering the pre-precision rolling mill 900-940℃, the temperature entering the precision rolling mill 890-930℃, and the temperature entering the reducing and sizing mill set 880-920℃. The temperature during rolling can be rolled in the full austenite state according to the characteristics of the production line, so as to ensure that the austenite grain size is small and uniform.

[0021] In the online quenching and tempering step, the wire rod drawing temperature is 850-900℃, which ensures that the wire rod has full austenite structure and small grain size, so as to promote phase transformation nucleation, refine the pearlite size and improve the final plasticity. After drawing, the wire rod is directly immersed in a salt bath for isothermal quenching, the salt bath temperature is 520-540℃, and the time is 120-200s, to obtain fine pearlite structure and ensure that the transformation amount is more than 95%; the wire rod after isothermal quenching is hot coiled, the temperature drop during coiling is ≤50℃, and then enters the online tempering in the heat preservation corridor, the tempering temperature is 400-450℃, and the time is ≥60min, which plays a role in complete phase transformation in the segregation area and eliminates internal stress.

[0022] As preferred, in the continuous casting step, the superheat of the molten steel is controlled to be 20-25℃, the stirring current of the crystallizer is 270±25A, the stirring frequency of the crystallizer is 3±0.5Hz, the casting speed is 1.2±0.05m / min, the water amount per unit length of the continuous casting is 0.22±0.01L / kg, the end stirring current is 450±25A, the end stirring frequency is 8±0.5Hz, and the total amount of the light reduction is 15.0±0.2mm. The low superheat, the casting speed control, the electromagnetic stirring and the light reduction can ensure that the continuous casting billet has good segregation.

[0023] As preferred, the rectangular billet with a cross-sectional size of not less than 240mm×180mm is obtained through the continuous casting step.

[0024] Compared with the prior art, the application has the advantages and positive effects that: (1) The application improves the homogeneity of the steel based on the adjustment of the chemical composition of the wire rod, the control of the production processes such as continuous casting, rolling and on-line quenching-tempering treatment, the metallographic structure of the wire rod prepared by the production method of the application is mainly sorbite, the sorbitizing rate is ≥97%, the sorbite lamella spacing is 45-65nm, the tensile strength is 1620-1700MPa, and the reduction of area is 35-44%; the wire rod is twisted into galvanized steel strand after drawing, galvanizing and twisting, and can be used for the steel core of the steel-cored aluminum stranded wire.

[0025] (2) The high-temperature strength of the material is improved by adding alloy elements such as Mo, Ni and V to form stable carbides, and the sag under the application environment of the overhead conductor is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The scanning electron microscope picture of the microstructure of the wire rod prepared in Example 1; Figure 2 The scanning electron microscope picture of the microstructure of the wire rod prepared in Example 2; Figure 3 The scanning electron microscope picture of the microstructure of the wire rod prepared in Example 3; Figure 4 The scanning electron microscope picture of the microstructure of the wire rod prepared in Comparative Example 1; Figure 5 The scanning electron microscope picture of the microstructure of the wire rod prepared in Comparative Example 2; Figure 6 The scanning electron microscope picture of the microstructure of the wire rod prepared in Comparative Example 3. DETAILED DESCRIPTION

[0027] In order to better understand the application, the following will be specifically described in combination with the drawings and examples. Example 1

[0028] A production method of wire rod for 2300MPa steel core aluminum strand, comprising the following steps: (1) Steel smelting The steel is smelted by the steps of converter smelting and LF refining, and the chemical composition and mass percentage of the steel at the end of smelting are shown in Table 1. In addition, the chemical composition of the continuous casting billet obtained in the continuous casting step and the chemical composition of the high-carbon steel wire rod for ultra-high strength prestressed steel strand finally prepared are consistent with the chemical composition of the steel at the end of the steel smelting step, and are shown in Table 1.

[0029] In the converter smelting step, the molten iron is mixed with scrap steel into molten steel in the converter, and desiliconization, dephosphorization, oxygen blowing decarburization are carried out, and alloy is added into the ladle at the time of tapping for deoxidization and alloying; in the refining step, the molten steel after converter smelting is sent into the LF refining furnace for chemical composition adjustment and temperature control, and the inclusions in the molten steel are controlled by soft stirring, and the molten steel is tapped after the temperature and chemical composition reach the standard.

[0030] (2) Continuous casting In the continuous casting step, the superheat degree of the molten steel is controlled to be 20-25℃, the stirring current of the crystallizer is 270±25A, the stirring frequency of the crystallizer is 3±0.5Hz, the casting speed is 1.2±0.05m / min, the specific water consumption is 0.22±0.01L / kg, the end stirring current is 450±25A, the end stirring frequency is 8±0.5Hz, and the total amount of light reduction is 15.0±0.2mm. The rectangular billet with a cross-sectional size not less than 240mm×180mm is obtained in the continuous casting step to ensure that the wire rod has sufficient compression ratio after being rolled to ensure the homogeneity of the wire rod.

[0031] (3) High-speed wire rolling In the rolling step, the rolling temperature is controlled to be 1060-1100℃ by adjusting the heating temperature and time. The water tank flow is adjusted to make the temperature entering the pre-precision rolling mill be 920±10℃, the temperature entering the precision rolling mill be 910±10℃, and the temperature entering the reducing and sizing mill be 900±10℃, and the wire rod with a diameter of 8mm is rolled.

[0032] (4) On-line quenching and tempering In the on-line quenching and tempering step, the wire drawing temperature is 880±10℃. The wire rod after wire drawing is directly immersed in a salt bath for isothermal quenching, and the salt bath temperature is 535±2℃ and the time is 120s. The wire rod after isothermal quenching is hot coiled, and then enters the heat preservation corridor for on-line tempering, the tempering temperature is 410±10℃ and the time is 60min, and the finished wire rod is obtained. Example 2

[0033] A production method of wire rod for 2300MPa steel core aluminum strand, comprising the following steps: (1) Molten steel smelting The molten steel is smelted by sequentially performing a converter smelting step and an LF furnace refining step. The chemical composition of the molten steel at the end of the smelting is shown in Table 1 in terms of mass percentage. In addition, the chemical composition of the continuous casting billet obtained in the continuous casting step, and the chemical composition of the high-carbon steel wire rod for ultra-high-strength prestressed steel strand finally prepared are consistent with the chemical composition of the molten steel at the end of the molten steel smelting step, and are shown in Table 1.

[0034] In the converter smelting step, the molten iron is mixed with scrap steel into molten steel in the converter, and desiliconization, dephosphorization, oxygen blowing decarburization are performed, and alloying is performed by adding alloy to the ladle at the time of tapping; in the refining step, the molten steel after the converter smelting is sent to the LF refining furnace to adjust the chemical composition and temperature, and the inclusions in the molten steel are controlled by soft stirring, and the molten steel is tapped after the temperature and chemical composition reach the standard.

[0035] (2) Continuous casting In the continuous casting step, the superheat of the molten steel is controlled to be 20-25℃, the stirring current of the crystallizer is 270±25A, the stirring frequency of the crystallizer is 3±0.5Hz, the casting speed is 1.2±0.05m / min, the specific water consumption is 0.22±0.01L / kg, the end stirring current is 450±25A, the end stirring frequency is 8±0.5Hz, and the total amount of light reduction is 15.0±0.2mm. The rectangular billet with a cross-sectional size of not less than 240mm×180mm is obtained in the continuous casting step to ensure that the wire rod has sufficient compression ratio after being rolled into a wire rod to ensure the homogeneity of the wire rod.

[0036] (3) High-speed wire rolling In the rolling step, the rolling temperature is adjusted to be 1050-1090℃ by adjusting the heating temperature and time, the water tank flow is adjusted to make the temperature entering the pre-precision rolling be 910±10℃, the temperature entering the precision rolling mill be 900±10℃, and the temperature entering the reducing and sizing mill be 900±10℃, and the wire rod with a diameter of 8mm is rolled. (4) On-line quenching and tempering In the on-line quenching and tempering step, the wire drawing temperature is 880±10℃. The wire rod after wire drawing is directly immersed in a salt bath for isothermal quenching, the salt bath temperature is 525±2℃, and the time is 150s; the wire rod after isothermal quenching is hot coiled, and then enters the heat preservation corridor for on-line tempering, the tempering temperature is 425±10℃, and the time is 70min, to obtain the finished wire rod. Example 3

[0037] A production method of a wire rod for a 2300MPa grade steel core aluminum strand, comprising the following steps: (1) Molten steel smelting The molten steel is smelted by sequentially performing a converter smelting step and an LF furnace refining step. The chemical composition of the molten steel at the end of the smelting step is shown in Table 1. In addition, the chemical composition of the continuous casting billet obtained in the continuous casting step and the chemical composition of the high-carbon steel wire rod for ultra-high-strength prestressed steel strand finally prepared are consistent with the chemical composition of the molten steel at the end of the molten steel smelting step, and are shown in Table 1.

[0038] In the converter smelting step, the molten iron is mixed with scrap steel into molten steel in the converter, and desiliconization, dephosphorization, oxygen blowing decarburization are performed, and alloying is performed by adding alloy to the ladle at the time of tapping; in the refining step, the molten steel after the converter smelting is sent to the LF refining furnace to adjust the chemical composition and temperature, and the inclusions in the molten steel are controlled by soft stirring, and the molten steel is tapped after the temperature and chemical composition reach the standard.

[0039] (2) Continuous casting In the continuous casting step, the superheat of the molten steel is controlled to be 20-25℃, the stirring current of the crystallizer is 270±25A, the stirring frequency of the crystallizer is 3±0.5Hz, the casting speed is 1.2±0.05m / min, the water amount during continuous casting is 0.22±0.01L / kg, the end stirring current is 450±25A, the end stirring frequency is 8±0.5Hz, and the total amount of light reduction is 15.0±0.2mm. The rectangular billet with a cross-sectional size of not less than 240mm×180mm is obtained in the continuous casting step to ensure that the wire rod has sufficient compression ratio after being rolled into a wire rod to ensure the homogeneity of the wire rod.

[0040] (3) High-speed wire rolling In the rolling step, the rolling temperature is adjusted to be 1050-1080℃ by adjusting the heating temperature and time, the water tank flow is adjusted to make the temperature entering the pre-precision rolling mill be 930±10℃, the temperature entering the precision rolling mill be 920±10℃, and the temperature entering the reducing and sizing mill be 900±10℃, and the wire rod with a diameter of 8mm is rolled. (4) On-line quenching and tempering In the on-line quenching and tempering step, the wire drawing temperature is 860±10℃. The wire rod after wire drawing is directly immersed in a salt bath for isothermal quenching, the salt bath temperature is 530±2℃, and the time is 200s; the wire rod after isothermal quenching is hot coiled, and then enters the heat preservation corridor for on-line tempering, the tempering temperature is 430±10℃, and the time is 90min, to obtain the finished product.

[0041] Comparative Example 1 A production method of a wire rod for steel-cored aluminum strand, comprising the following steps: (1) Molten steel smelting process The molten steel is smelted by sequentially performing a converter smelting step and an LF furnace refining step. The chemical composition of the molten steel at the end of the smelting is shown in Table 1. The chemical composition of the continuous casting billet obtained in the continuous casting process and the chemical composition of the high-carbon steel wire rod for ultra-high-strength pre-stressed steel strand finally prepared are consistent with the chemical composition of the molten steel at the end of the molten steel smelting process, and are shown in Table 1.

[0042] In the converter smelting step, the molten iron is mixed with scrap steel into molten steel in the converter, and desiliconization, dephosphorization, oxygen blowing decarburization are performed, and alloying is performed by adding alloy to the ladle at the time of tapping; in the refining step, the molten steel after the converter smelting is sent to the LF refining furnace to adjust the chemical composition and temperature, and the inclusions in the molten steel are controlled by soft stirring, and the molten steel is tapped after the temperature and chemical composition reach the standard.

[0043] (2) Continuous casting process In the continuous casting process, the superheat of the molten steel is controlled to be 20-25℃, the stirring current of the crystallizer is 270±25A, the stirring frequency of the crystallizer is 3±0.5Hz, the casting speed is 1.2±0.05m / min, the water volume during continuous casting is 0.22±0.01L / kg, the end stirring current is 450±25A, the end stirring frequency is 8±0.5Hz, and the total amount of light reduction is 15.0±0.2mm. The continuous casting process obtains a rectangular billet with a cross-sectional size of not less than 240mm×180mm to ensure that the wire rod has sufficient compression ratio after being rolled into a wire rod to ensure the homogeneity of the wire rod.

[0044] (3) High-speed wire rolling process In the rolling process, the opening rolling temperature is adjusted to be 1050-1100℃ by adjusting the heating temperature and time, the water tank flow is adjusted to make the pre-precision rolling temperature be 910±10℃, the precision rolling temperature be 900±10℃, and the temperature entering the reducing and sizing unit be 900±10℃, and the wire rod with a diameter of 8mm is rolled. (4) On-line quenching and tempering process In the on-line quenching and tempering process, the wire drawing temperature is 890±10℃. After wire drawing, the wire rod is directly immersed in a salt bath for isothermal quenching, the salt bath temperature is 500±2℃, and the time is 120s; the wire rod after isothermal quenching is hot coiled, and then enters the heat preservation corridor for on-line tempering, the tempering temperature is 410±10℃, and the time is 60min.

[0045] Comparative Example 2 A production method of a 2300MPa grade steel core aluminum strand wire rod, comprising the following steps: (1) Molten steel smelting process The molten steel was smelted by sequentially performing a converter smelting step and an LF furnace refining step. The chemical composition of the molten steel at the end of the smelting was as shown in Table 1 for Comparative Example 1. In addition, the chemical composition of the continuous casting billet obtained in the continuous casting process and the chemical composition of the high-carbon steel wire rod for ultra-high-strength prestressed steel strand finally prepared were consistent with the chemical composition of the molten steel at the end of the molten steel smelting process, and were as shown in Table 1.

[0046] In the converter smelting step, the molten iron is mixed with scrap steel into molten steel in the converter, and desiliconization, dephosphorization, oxygen blowing decarburization are performed, and at the time of tapping, alloy is added to the ladle for deoxidization and alloying. In the refining step, the molten steel after the converter smelting is sent to the LF refining furnace for chemical composition adjustment and temperature control, and the inclusions in the molten steel are controlled by soft stirring, and after the temperature and chemical composition reach the standard, the molten steel is tapped.

[0047] (2) Continuous casting process In the continuous casting process, the superheat of the molten steel is controlled to be 20-25℃, the stirring current of the crystallizer is 270±25A, the stirring frequency of the crystallizer is 3±0.5Hz, the casting speed is 1.2±0.05m / min, the water volume during continuous casting is 0.22±0.01L / kg, the end stirring current is 450±25A, the end stirring frequency is 8±0.5Hz, and the total amount of light reduction is 15.0±0.2mm. The continuous casting process obtains a rectangular billet with a cross-sectional size of not less than 240mm×180mm to ensure that the wire rod has sufficient compression ratio after being rolled into a wire rod to ensure the homogeneity of the wire rod.

[0048] (3) High-speed wire rolling process In the rolling process, the opening rolling temperature is adjusted to be 1050-1100℃ by adjusting the heating temperature and time, the water tank flow is adjusted to make the pre-precision rolling temperature be 910±10℃, the precision rolling temperature be 900±10℃, and the temperature entering the reducing and sizing machine group be 900±10℃, and the wire rod with a diameter of 8mm is rolled. (4) On-line quenching and tempering process In the on-line quenching and tempering process, the wire drawing temperature is 890±10℃. After wire drawing, the wire rod is directly immersed in a salt bath for isothermal quenching, the salt bath temperature is 525±2℃, and the time is 120s; the wire rod after isothermal quenching is hot coiled, and then enters the holding corridor for on-line tempering, the tempering temperature is 500±10℃, and the time is 60min.

[0049] Comparative Example 3 The composition of YL82B is as shown in Table 1. A wire rod with a diameter of 7mm was prepared by using a conventional smelting-rolling-Stelmor cooling process route in the industry, and the specific steps are as follows: (1) Molten steel smelting process The molten steel was smelted by sequentially performing a converter smelting step and an LF furnace refining step. The chemical composition of the molten steel at the end of smelting was as shown in Table 1 for Comparative Example 1. In addition, the chemical composition of the continuous casting billet obtained in the continuous casting process and the chemical composition of the high-carbon steel wire rod for ultra-high-strength prestressed steel strand finally prepared were consistent with the chemical composition of the molten steel at the end of the molten steel smelting process, and were as shown in Table 1.

[0050] In the converter smelting step, the molten iron is mixed with scrap steel into molten steel in the converter, and desiliconization, dephosphorization, oxygen blowing decarburization are performed, and at the time of tapping, alloy is added to the ladle for deoxidization and alloying. In the refining step, the molten steel after the converter smelting is sent to the LF refining furnace for chemical composition adjustment and temperature control, and the inclusions in the molten steel are controlled by soft stirring, and the molten steel is tapped after the temperature and chemical composition meet the standards.

[0051] (2) Continuous casting process In the continuous casting process, the superheat of the molten steel is controlled to be 20-35℃, the stirring current of the crystallizer is 270±25A, the stirring frequency of the crystallizer is 3±0.5Hz, the casting speed during continuous casting is 1.2±0.05m / min, the continuous casting water amount is 0.22±0.01L / kg, the end stirring current is 450±25A, the end stirring frequency is 8±0.5Hz, and the total amount of light reduction is 12.0±0.2mm. The continuous casting process obtains a rectangular billet with a cross-sectional size of not less than 180mm×180mm.

[0052] (3) High-speed wire rolling process In the rolling process, the opening rolling temperature is adjusted to be 1050-1100℃ by adjusting the heating temperature and time, the water tank flow is adjusted to make the pre-precision rolling temperature be 920±10℃, the precision rolling temperature be 920±10℃, and the reducing diameter machine temperature be 920±10℃, and the wire rod with a diameter of 7mm is rolled.

[0053] Stelmor cooling process The wire drawing temperature is 920±10℃, the roller speed is 1.0m / s, and 1-12 fans are turned on for cooling, wherein the first 4 fans are turned on at 100%, the 5-8 fans are turned on at 60%, and the 9-12 fans are turned on at 40%.

[0054] Table 1 Wire rod composition table of Examples 1-3 and Comparative Examples 1-3

[0055] The wire rods prepared in Examples 1-3 and Comparative Examples 1-3 were sampled and subjected to metallographic structure detection and mechanical property detection according to the same test method. The specific test method and detection results are as follows: (1) Metallographic structure detection: Respectively from the head of the rod, the length of 10 cm of the rod was taken to make a metallographic sample, after mechanical grinding and polishing, nitric acid alcohol etching, placed under the metallographic microscope for observation, the metallographic structure pictures of the prepared rods of examples 1-3 and comparative examples 1-3 are shown in Figures 1 to 6 respectively. As can be seen from the figure, examples 1-3 all obtain ideal fine pearlite (sorbite) structure, see Figures 1-3 ; as shown in Figure 4 , comparative example 1 produces bainite structure due to the use of too low salt bath temperature; as shown in Figure 5 , comparative example 2 produces partial spheroidizing structure due to the use of too high tempering temperature; as shown in Figure 6 , comparative example 3, i.e. traditional process, also obtains sorbite structure, but the sorbitizing rate is low and abnormal structure such as network carbon is produced.

[0056] (2) Mechanical properties: According to the standard test method and definition of GB / T228, the tensile testing machine was used to test the mechanical properties of the rod, and the tensile strength and the reduction of area of the rods prepared in examples 1-3 and comparative examples 1-3 were measured as shown in table 2. As can be seen from table 2, examples 1-3 obtain high sorbitizing rate through component design combined with heat treatment process, and the strength and plasticity of the prepared rod are greatly improved; comparative example 1 produces bainite structure, its strength is high, but the reduction of area is too low; the strength of comparative example 2 is reduced after tempering at a higher temperature; the strength of the rod prepared by comparative example 3, i.e. traditional process, is much lower than that of examples 1-3.

[0057] Table 2 Metallographic structure detection and mechanical property detection table of the rods of examples 1-3 and comparative examples 1-3

[0058] The rods prepared in examples 1-3 and comparative examples 1-3 were directly drawn into steel wire after pickling and phosphating, and then the tensile strength and torsion index before and after galvanizing were detected, and the detection results are shown in table 3. As can be seen from table 3, under the combined action of alloying elements and microstructure, the cold-drawn steel wire prepared from the rods of examples 1-3 has good drawing performance and good high-temperature stability of the mechanical properties of the steel wire; comparative example 1 breaks due to abnormal structure; comparative example 2 has poor torsion performance due to abnormal structure, which does not meet the final use requirement; comparative example 3 can only reach the strength level of 2100 MPa.

[0059] Table 3 Performance detection table of the cold-drawn steel wire prepared from the rods of examples 1-3 and comparative examples 1-3 before and after galvanizing

[0060] The above merely describes preferred embodiments of the present application, but is not intended to limit the present application to other forms, any person skilled in the art can make changes or modifications to the above disclosed technical contents into equivalent embodiments with equivalent changes, and apply to other fields, but any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application without departing from the technical solution content of the present application still belongs to the protection scope of the present application technical solution.

Claims

1. A wire rod for 2300 MPa class steel-cored aluminum strand, characterized by, The chemical composition and weight percentage are: C 0.94-0.98%, Si 1.20-1.60%, Mn 0.60-1.00%, Cr 0.20-0.50%, V 0.02-0.04%, Mo≤0.20, Ni≤0.30, S≤0.020%, P≤0.010%, N≤0.0040%, O≤0.0020%, and the rest is Fe and other inevitable impurities.

2. The 2300 MPa grade steel wire for cored aluminium conductor strand according to claim 1, characterized in that, The chemical composition and weight percentage are: C 0.94-0.98%, Si 1.20-1.60%, Mn 0.60-1.00%, Cr 0.20-0.50%, V 0.02-0.04%, Mo≤0.20, Ni≤0.30, S≤0.020%, P≤0.010%, N≤0.0040%, O≤0.0020%, and the rest is Fe and other inevitable impurities.

3. The 2300 MPa grade steel wire for cored aluminium conductor strand in the form of a rod according to claim 1, characterized in that: The diameter of the wire rod is 5.5-8mm.

4. A method for producing wire rod for 2,300 MPa class steel-cored aluminum strand, characterized by, The wire rod is obtained by sequentially performing the following steps: hot metal pre-desulfurization, converter smelting, secondary refining, continuous casting, billet heating, high-speed wire rolling, on-line isothermal quenching and tempering. In the high-speed wire rolling step, the rolling temperature is adjusted to be 1050-1100℃ by adjusting the heating temperature and time, the pre-precision rolling temperature is adjusted to be 900-940℃ by adjusting the water tank flow, the precision rolling temperature is adjusted to be 890-930℃, and the reducing and sizing unit temperature is adjusted to be 880-920℃. In the on-line quenching and tempering step, the wire rod wire drawing temperature is 850-900℃, the wire rod is directly immersed in a salt bath for isothermal quenching after wire drawing, the salt bath temperature is 520-540℃, and the time is 120-200s, so that fine pearlite structure is obtained and the transformation amount is ensured to be more than 95%; the wire rod after isothermal quenching is hot coiled, and then enters the heat preservation corridor for on-line tempering, the tempering temperature is 400-450℃, and the time is ≥60min.

5. A process for production of 2300 MPa grade steel wire for aluminium clad steel wire as claimed in claim 1 wherein: In the continuous casting step, the superheat degree of the molten steel is controlled to be 20-25℃, the stirring current of the crystallizer is 270±25A, the stirring frequency of the crystallizer is 3±0.5Hz, the casting speed is 1.2±0.05m / min, the specific water consumption is 0.22±0.01L / kg, the end stirring current is 450±25A, the end stirring frequency is 8±0.5Hz, and the total amount of light reduction is 15.0±0.2mm.

6. A process for production of 2300 MPa grade steel wire for aluminium clad steel wire as claimed in claim 4 wherein: The rectangular billet with a cross-sectional size of not less than 240mm×180mm is obtained by the continuous casting step. The chemical composition and weight percentage are: C 0.94-0.98%, Si 1.20-1.60%, Mn 0.60-1.00%, Cr 0.20-0.50%, V 0.02-0.04%, Mo≤0.20, Ni≤0.30, S≤0.020%, P≤0.010%, N≤0.0040%, O≤0.0020%, and the rest is Fe and other inevitable impurities.

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