5200MPa grade steel wire, hot-rolled wire rod and production method of wire rod

Abstract

The present application discloses a 5200MPa grade steel wire, hot-rolled wire rod and a production method of the wire rod. The chemical composition of the wire rod includes, by mass percentage, C 0.95-0.98%, Si 0.45-0.65%, Mn 0.20-0.40%, Cr 0.20-0.40%, Ni 0.05-0.30%, and the rest is Fe and unavoidable impurities, and the content of the impurity elements is controlled to be: Al≤0.002%, Ti≤0.0008%, S≤0.005%, P≤0.008%, O≤0.0010%, N≤0.0020%. The wire rod can be used as a parent material for the production of steel wire with a diameter of 0.03-0.045mm and a tensile strength of ≥5200MPa, and in the process of further drawing the wire rod to prepare the steel wire, the mileage of the wire rod without breaking can be achieved ≥300km.

Description

Technical Field

[0001] The present application belongs to the technical field of steel smelting, and relates to a hot-rolled wire rod for 5200MPa grade steel wire, and also relates to a 5200MPa grade steel wire further processed from the hot-rolled wire rod for 5200MPa grade steel wire, and a production method of the hot-rolled wire rod for 5200MPa grade steel wire. Background Art

[0002] Diamond wire is an important consumable in the manufacturing of photovoltaic silicon wafers and is mainly used in the cutting of photovoltaic silicon wafers. As a linear cutting tool, the raw materials for the manufacture of diamond wire mainly include busbars, diamond powder particles, nickel, etc. According to the different materials of the busbars, the diamond wires used for photovoltaic silicon wafers are currently mainly divided into high-carbon steel wire diamond wires (also known as carbon steel diamond wires or carbon steel wires) and tungsten wire diamond wires (also known as tungsten wires). High-carbon steel wire diamond wires are currently the most widely used in the cutting of photovoltaic silicon wafers.

[0003] The cutting quality and cutting loss of silicon wafers are closely related to the mother wire diameter of diamond wire and the particle size of diamond powder. In order to reduce the loss of photovoltaic silicon wafers during cutting, high carbon steel wire diamond wire is constantly developing in the direction of finer diameter and higher strength to meet the increasing market demand. Summary of the invention

[0004] In order to solve at least one of the above technical problems, the purpose of the present application is to provide a hot-rolled wire rod for 5200MPa grade steel wire, and also relates to a 5200MPa grade steel wire further processed from the hot-rolled wire rod for 5200MPa grade steel wire, and a production method for a hot-rolled wire rod for 5200MPa grade steel wire.

[0005] To achieve one of the above purposes, an embodiment of the present application provides a 5200MPa grade hot-rolled wire rod for steel wire, the chemical composition of the wire rod comprising, by mass percentage: C 0.95-0.98%, Si 0.45-0.65%, Mn 0.20-0.40%, Cr 0.20-0.40%, Ni 0.05-0.30%, and the rest are Fe and unavoidable impurities, and the content of impurity elements is controlled to be: Al≤0.002%, Ti≤0.0008%, S≤0.005%, P≤0.008%, O≤0.0010%, and N≤0.0020%.

[0006] The wire rod can be used as a mother material for producing steel wires with a diameter of 0.03-0.045 mm and a tensile strength of ≥5200 MPa, and in the process of further drawing the wire rod to prepare the steel wire, a mileage of ≥300 km without wire breakage can be achieved.

[0007] Among them, C is an important component element in steel, which can significantly improve the strength of steel, and the C content can also affect the organizational structure of steel; among common steel organizations, the eutectoid organization has the characteristics of high strength and high work hardening rate, so the eutectoid steel is particularly suitable for high-strength steel wire products; however, too high a C content will lead to the formation of a pro-eutectoid network cementite organization in the steel, which will destroy the continuity of the eutectoid organization, leading to the formation of microcracks during the wire drawing process, and even causing wire breakage. In this application, the upper limit of the C content to avoid the appearance of local network cementite is increased, and the C content is limited to 0.95~0.98%.

[0008] Si can increase the strength of ferrite in pearlite, play a role in solid solution strengthening, thereby increasing the strength of the final prepared steel wire, and can also reduce the oxygen content in the steel; however, too high Si content will reduce the plasticity of the steel, aggravate the decarburization tendency of the steel billet, and is not conducive to the surface quality control of the wire rod; in this application, the Si content is limited to 0.45~0.65%.

[0009] Mn is a carbide-forming element, which can play a role in solid solution strengthening, improve the strength of wire rod, and can also combine with harmful element S to reduce hot brittleness; however, too high Mn content will lead to enhanced hardenability of steel, and bainite or martensite will easily appear after hot rolling, reducing the plasticity and wire drawing performance of wire rod; in this application, the Mn content is limited to 0.20~0.40%.

[0010] Cr can refine the pearlite structure, reduce the interlamellar spacing, and improve the strength of the wire rod; however, too high a Cr content will increase the hardenability, and bainite or martensite is likely to appear after hot rolling. In this application, the Cr content is limited to 0.20~0.40%.

[0011] Ni can significantly improve the strength of pearlite, but when the Ni content is too high, it is easy to form martensite structure during cooling and heat treatment, affecting the drawing performance of the wire rod. In this application, the Ni content is limited to 0.05~0.30%.

[0012] Al is a harmful element in this application. Al is easy to combine with O in steel to form Al2O3 inclusions. Al2O3 is large in size, easy to agglomerate, has a high melting point and poor plasticity, which is one of the main reasons for the breakage of fine steel wires. In this application, the Al content is limited to ≤0.002%.

[0013] Ti is a harmful element in this application. Ti is very likely to form large-sized inclusions with C and N. These inclusions are sharp and angular, which can easily cause stress concentration and form microcracks. The Ti content is limited to ≤0.0008% in this application.

[0014] S, P, O, and N are harmful impurity elements, and the lower their content, the better. In this application, S is limited to 0.005%, P ≤ 0.008%, O ≤ 0.0010%, and N ≤ 0.0020%.

[0015] In summary, the present application controls the size, strength and purity of the wire rod by controlling each chemical component and its mass percentage, so that the wire rod has a small component segregation and a uniform structure, thereby improving its drawing performance; wherein, the upper limit of the C content to avoid the occurrence of local network cementite is increased, so that the wire rod structure is mainly a eutectoid structure, which is conducive to the preparation of high-strength steel wire, and the wire rod has the advantages of small component segregation and uniform structure; the strength of the wire rod is improved by the solid solution strengthening effect of Si and Mn and the refinement of the pearlite structure by Cr and Ni, and the upper limit of the content of Si, Mn, Cr, and Ni is controlled to avoid the decarburization tendency of the steel billet during the wire rod production process, and to avoid the appearance of bainite or martensite after hot rolling, thereby improving the plasticity and wire drawing performance of the wire rod; by limiting the upper limit of the content of impurity elements Al and Ti, Al2O3 inclusions and large-sized inclusions formed by Ti, C, and N can be reduced, and the formation of microcracks can be avoided, resulting in wire breakage during drawing; and the harmful impurity elements S, P, O, and N are controlled to reduce the performance damage of the wire rod.

[0016] As a further improvement of an embodiment of the present application, the diameter of the wire rod is 5.0-5.5 mm, the tensile strength is 1200-1300 MPa, the cross-sectional shrinkage is ≥28%, and the elongation is ≥8%;

[0017] The wire rod has a mileage of ≥300 km without breaking during the process of drawing the steel wire with a diameter of 0.03-0.045 mm.

[0018] In this way, the wire rod can be further drawn to prepare steel wire with a diameter of 0.03~0.045mm and a tensile strength of ≥5200MPa, and the internal damage of the wire rod during drawing can be reduced, the mold loss during drawing can be reduced, and the wire mileage during the drawing process is not less than 300km, thereby improving the drawing yield.

[0019] As a further improvement of an embodiment of the present application, in the wire rod, the number density of inclusions is ≤5 / mm 2 , inclusions with a size of ≤4μm account for ≥90%, and the maximum inclusion size is ≤6μm; among the inclusions, Al2O3 inclusions account for ≤3%, MnS inclusions account for ≥85%, and the rest are SiO2 and other inclusions;

[0020] The wire rod is etched with sodium picrate, and there is no network carbide in the metallographic structure;

[0021] By adopting nitric acid alcohol corrosion, there is no martensite and bainite structure in the wire rod.

[0022] It can be seen that the overall inclusion content in the wire rod is small, especially large-sized inclusions are less, small-sized inclusions account for a larger proportion, the Al2O3 inclusion content is less, the wire rod has excellent internal quality and structure, and excellent drawing performance.

[0023] To achieve one of the above objectives, an embodiment of the present application provides a 5200 MPa grade steel wire, which is prepared using the above-mentioned hot-rolled wire rod as a base material.

[0024] As a further improvement of an embodiment of the present application, the steel wire is prepared by the following steps:

[0025] Rough drawing: After the wire rod is roughly drawn to a diameter of 2.3 mm, it is heated to 970-990° C. and then sent to a salt bath tank for salt bath treatment at a salt bath temperature of 560-600° C.;

[0026] Middle drawing: after the wire rod is middle drawn to a diameter of 1.3 mm, it is heated to 940-950° C. and then sent to a salt bath tank for salt bath treatment at a salt bath temperature of 580-610° C.;

[0027] Fine drawing: after the wire rod is fine drawn into a diameter of 0.38 mm, it is heated to 920-940° C., and then sent to a salt bath tank for salt bath treatment, and the salt bath temperature is 550-590° C.;

[0028] Copper plating and water tank drawing are used to obtain steel wire with a diameter of 0.03~0.045mm.

[0029] By rough drawing, medium drawing and fine drawing of the wire rod and performing heat treatment after each drawing, in combination with the heating temperature in the heat treatment and the salt bath treatment temperature, copper plating and water tank drawing are further performed after fine drawing, the final prepared steel wire with a diameter of 0.03~0.045mm can have extremely high strength, and the uninterrupted wire mileage in the process of preparing the steel wire by drawing the wire rod can be greatly improved.

[0030] As a further improvement of an embodiment of the present application, the diameter of the steel wire is 0.03-0.045 mm, and the tensile strength is ≥5200 MPa. The steel wire is not only small in diameter, but also has extremely high strength, with a tensile strength level of 5200 MPa, and can be used as a raw material for diamond wire busbars, and when used for photovoltaic silicon wafer cutting, it can improve the silicon wafer cutting quality and reduce cutting loss.

[0031] To achieve one of the above purposes, an embodiment of the present application provides a method for producing a hot-rolled wire rod for 5200MPa grade steel wire, wherein the chemical composition of the wire rod comprises, by mass percentage: C 0.95-0.98%, Si 0.45-0.65%, Mn 0.20-0.40%, Cr 0.20-0.40%, Ni 0.05-0.30%, and the rest is Fe and unavoidable impurities, and the content of impurity elements is controlled to be: Al≤0.002%, Ti≤0.0008%, S≤0.005%, P≤0.008%, O≤0.0010%, N≤0.0020%;

[0032] The production method of the wire rod comprises the following steps:

[0033] Vacuum smelting: melting the charge in a vacuum induction melting furnace, refining and regulating the chemical composition and inclusions in the molten steel, and then pouring the steel into ingots;

[0034] Remelting: using the steel ingot as a consumable electrode rod for vacuum consumable crystallization and remelting to obtain a remelted ingot, wherein the segregation ratio of the obtained remelted ingot is 0.98-1.02;

[0035] Opening: Open the obtained remelted ingot into small square billets, and cool the small square billets when the temperature drops to 950-1000°C, control the surface cooling rate of the small square billets to be ≤6°C / s, and the corner cooling rate to be ≤9°C / s, and put them into the holding pit for slow cooling when they are cooled to 600-650°C, and the cooling rate of the small square billets in the holding pit is ≤3°C / s;

[0036] Grinding;

[0037] High-speed wire rolling, after heating the billet, it is subjected to rough rolling, intermediate rolling, pre-finishing rolling, finishing rolling, and sizing rolling in sequence to obtain wire rods. During heating, the temperature difference between the surface and the core of the billet is controlled to be ≤10°C, and during rolling, the torsion angle of the rolled piece is controlled to be ≤20°. The rolls of the four rolling mills before rough rolling are water-cooled to control the corner temperature of the billet to be 1050~1100°C, the start rolling temperature of finishing rolling is 920~950°C, and the rolling temperature during sizing rolling is 860~880°C;

[0038] Stelmor controlled cooling, turned on the 1st to 4th fans and the 7th to 8th fans, and turned off the other fans. The insulation covers corresponding to the 5th to 6th fans were turned off, and the other insulation covers were turned on. The Jialing device was used to adjust the wind speed at the overlapping points of the wire rods on the rollers corresponding to the 1st to 4th fans to 1.5 to 2.0 times the wind speed at the non-overlapping points, and the wind speed at the overlapping points of the wire rods on the rollers corresponding to the 5th to 8th fans was adjusted to 1.2 to 1.6 times the wind speed at the non-overlapping points.

[0039] In the present application, on the basis of the aforementioned chemical composition design scheme, through the improvement of the production method, the C content in the chemical composition can be increased as much as possible under the premise of avoiding the occurrence of local network cementite, thereby increasing the upper limit of the C content that avoids the occurrence of local network cementite; combined with the strengthening effects of Si, Mn, Cr, and Ni as well as the remelting, billet opening, and high-wire rolling processes, the decarburization tendency of the steel billet during the wire rod production process is avoided, and the occurrence of bainite or martensite after hot rolling is avoided, thereby improving the plasticity and wire drawing performance of the wire rod; by limiting the upper limit of the content of impurity elements Al and Ti, combined with vacuum melting and remelting processes, precise control of the chemical composition of the wire rod can be achieved, reducing Al2O3 inclusions and large-sized inclusions formed by Ti, C, and N, and achieving the formation of inclusions. The control of the composition and crystallization direction can improve its purity, avoid the formation of microcracks, and further control the center segregation of the wire rod; combined with the control of the fan, insulation cover and wind speed in the Stelmor controlled cooling process, the cooling uniformity of the wire rod in the early and middle stages of the phase transformation can be improved, the cooling rate in the middle and late stages of the phase transformation can be reduced, the organizational uniformity of the wire rod can be improved, the drawing performance can be improved, and the generation of abnormal tissues such as network carbides and martensite can be reduced; in short, the finally prepared wire rod has the advantages of small component segregation, uniform organization and excellent drawing performance, ensuring that it has high strength, excellent drawing performance and high purity, thereby ensuring that the steel wire prepared by drawing has ultra-small diameter, ultra-high tensile strength, ultra-long unbroken wire mileage and ultra-high purity, laying the foundation for the preparation of 5200MPa grade steel wire.

[0040] As a further improvement of an embodiment of the present application, in the vacuum smelting process, ultrapure Fe blocks, metal Cr, metal Ni, and carbon particles are fed into a vacuum smelting furnace for electric smelting, the smelting temperature is 1620-1625° C., the vacuum pressure in the furnace is <0.3 mbar, metal Mn and ferrosilicon are added during smelting to adjust the composition, and after the target composition is reached, synthetic slag is added to slag and stirred, and after the slag is made, the slag is fished out and the steel is tapped;

[0041] The purity of the ultrapure iron block is ≥99.96%. In this way, the content of impurity elements in the ultrapure iron block can be controlled to be ≤0.04%, thereby reducing the introduction of impurity elements during vacuum smelting and reducing the content of impurity elements in the finally prepared wire rod.

[0042] As a further improvement of an embodiment of the present application, in the vacuum melting process, argon gas is introduced into the bottom of the vacuum melting furnace during melting to stir the molten steel. Argon gas stirring can promote internal circulation of the molten steel, accelerate the floating of inclusions and the aggregation, growth and floating of small-sized inclusions, thereby reducing the inclusions in the molten steel and improving the purity of the molten steel.

[0043] As a further improvement of an embodiment of the present application, in the vacuum smelting process, the basicity of the synthetic slag is 0.95-0.98. That is, the synthetic slag is controlled to be acidic slag, and the inclusions are adjusted to the plastic inclusion range suitable for deformation by adjusting the ratio of SiO2 and CaO.

[0044] As a further improvement of an embodiment of the present application, in the vacuum melting process, after slag making is completed, the slag is removed by a slag removal rod, and the tapping temperature is 1552-1558° C. This temperature range can not only ensure that the molten steel has good castability, but also ensure the stable floating of inclusions, further improving the purity of the molten steel.

[0045] As a further improvement of an embodiment of the present application, in the remelting process, the melting rate of the remelting is 2.5-2.8 kg / min. The melting rate within this range can not only ensure that the remelted ingot has good crystal quality and surface quality, but also that there are no solidification defects such as shrinkage, looseness, segregation, etc. in the remelted ingot, and the surface of the remelted ingot is smooth, thereby ensuring that the finally prepared wire rod has high strength, excellent toughness and drawing performance.

[0046] As a further improvement of an embodiment of the present application, in the blanking process, the obtained remelted ingot is subjected to 6 reciprocating blanking to obtain a small square billet, the rolling temperature is 1180-1230°C, the elongation coefficient of the first three passes is 1.82-1.90, and the elongation coefficient of the last three passes is 1.58-1.72. By adopting large reduction rolling in the blanking process and controlling the rolling temperature according to the characteristics of the steel grade, the uniformity of the organizational composition of the small square billet can be improved.

[0047] As a further improvement of an embodiment of the present application, the grinding process uses a 24-mesh grinding wheel, a single grinding depth of ≤0.4mm, a total grinding depth of ≥1.2mm, and a grinding wheel linear speed of 72~76m / s during grinding. The grinding wheel pressure is controlled to be 65~78MPa when grinding the surface, and the grinding wheel pressure is controlled to be 48~60MPa when grinding the corner. The grinding quality of the blank surface is closely related to the grinding wheel particle size. The use of a 24-mesh grinding wheel can ensure that the roughness of the blank surface after grinding is more appropriate; by controlling the grinding wheel pressure during the grinding process, the generation of grinding burrs can be reduced, and the quality of the blank surface after grinding can be further improved.

[0048] As a further improvement of an embodiment of the present application, in the grinding process, the number of flaw detection defects of the small square billet after grinding is controlled to be ≤0.2 pieces / m, so as to reduce the surface defects of the finally prepared wire rod and reduce the wire breakage rate during drawing.

[0049] As a further improvement of an embodiment of the present application, in the high-speed wire rolling process, blast furnace gas and air are introduced into the heating furnace during heating, the pressure in the furnace is controlled to be 6.5-8KPa, the temperature of the preheating section and the heating section is controlled to be ≥960°C, the temperature of the furnace top in the heating furnace is controlled to be higher than the temperature of the furnace bottom, and the temperature difference between the furnace top and the furnace bottom is ≤100°C. In this way, the upper and lower surfaces of the billet can be heated evenly.

[0050] As a further improvement of an embodiment of the present application, the high-speed wire rolling process adopts a 28-stand rolling mill for rolling, and the 28-stand rolling mill includes 6 roughing mills + 6 medium rolling mills + 4 pre-finishing mills + 10 finishing mills + 2 sizing mills.

[0051] As a further improvement of an embodiment of the present application, in the high-speed wire rolling process, when the rollers of the four rolling mills before rough rolling are water-cooled, the temperature of the cooling water is controlled to be ≤30°C and the water pressure is 0.1~0.8MPa. By controlling the temperature and water pressure of the cooling water, the surface and corner temperatures of the rolled piece during the rolling process can be controlled to appropriate temperatures, reducing the generation of surface cracks, especially corner cracks.

[0052] As a further improvement of an implementation mode of the present application, in the Stelmor controlled cooling process, the angle of the Jialing device corresponding to the 1st to 4th fans is 10-13°, and the angle of the Jialing device corresponding to the 5th to 8th fans is 8-11°. By adjusting the angle of the Jialing device, the uniformity of the lateral distribution of the cold air on the Stelmor cooling line can be improved, and the air volume of the fan can be adjusted according to the phase change characteristics of the wire rods in different areas on the Stelmor cooling line, so as to control the cooling speed and improve the uniformity of the organizational performance of the wire rods.

[0053] As a further improvement of an embodiment of the present application, in the Stelmor controlled cooling process, the maximum air volume of the fan is 280,000 m 3 / h, control the air volume of the 1st to 4th fans to 30-100%, and the air volume of the 7th to 8th fans to 20-30%. In this way, the cooling rate of the wire rod before, during and after the phase transformation can be reasonably controlled, thereby improving the uniformity of the wire rod structure, improving the drawing performance, and reducing the generation of abnormal structures such as network carbides and martensite. DETAILED DESCRIPTION

[0054] The technical solution of the present application is further introduced below in conjunction with specific implementation methods, but the scope of protection required is not limited to the description.

[0055] One embodiment of the present application provides a hot-rolled wire rod for 5200 MPa grade steel wire, and a production method of a hot-rolled wire rod for 5200 MPa grade steel wire.

[0056] The 5200MPa grade hot-rolled wire rod for steel wire of the present application has a chemical composition, by mass percentage, of C 0.95-0.98%, Si 0.45-0.65%, Mn 0.20-0.40%, Cr 0.20-0.40%, Ni 0.05-0.30%, and the rest is Fe and unavoidable impurities, and the content of impurity elements is controlled to be: Al≤0.002%, Ti≤0.0008%, S≤0.005%, P≤0.008%, O≤0.0010%, and N≤0.0020%.

[0057] In addition, the diameter of the hot-rolled wire rod for the 5200MPa grade steel wire is 5.0~5.5mm. A large number of experimental studies have shown that the tensile strength of the wire rod is 1200~1300MPa, the cross-sectional shrinkage rate is ≥28%, and the elongation rate is ≥8%; the mileage of the wire rod without wire breakage during the process of drawing and preparing steel wire with a diameter of 0.03~0.045mm is ≥300km.

[0058] In the wire rod, the number density of inclusions is ≤5 / mm 2 Among the inclusions, inclusions with a size of ≤4μm account for ≥90%, and the maximum inclusion size is ≤6μm; among the inclusions, the proportion of Al2O3 inclusions is ≤3%, the proportion of MnS inclusions is ≥85%, and the rest are SiO2 and other inclusions.

[0059] By adopting sodium picrate corrosion, there is no network carbide in the metallographic structure of the wire rod.

[0060] By adopting nitric acid alcohol corrosion, there is no martensite and bainite structure in the wire rod.

[0061] Furthermore, the 5200MPa grade hot-rolled wire rod can be used as a base material for the production of steel wire with a diameter of 0.03-0.045mm and a tensile strength ≥5200MPa, and in the process of further drawing the wire rod to prepare a steel wire with a diameter of 0.03-0.045mm, a mileage of ≥300km without wire breakage can be achieved.

[0062] From another perspective, an embodiment of the present application further provides a 5200 MPa grade steel wire, which is prepared using the 5200 MPa grade steel wire hot-rolled wire rod as a base material.

[0063] Accordingly, the chemical composition of the steel wire includes, by mass percentage, C 0.95-0.98%, Si 0.45-0.65%, Mn 0.20-0.40%, Cr 0.20-0.40%, Ni 0.05-0.30%, and the rest is Fe and unavoidable impurities, and the content of impurity elements is controlled to be: Al≤0.002%, Ti≤0.0008%, S≤0.005%, P≤0.008%, O≤0.0010%, and N≤0.0020%.

[0064] For example, the 5200MPa grade steel wire can be prepared by further drawing the hot-rolled wire rod, the diameter of the 5200MPa grade steel wire is 0.03-0.045mm, the tensile strength is ≥5200MPa, and the mileage of the wire without breakage during the drawing preparation process is ≥300km.

[0065] Specifically, the 5200MPa grade steel wire is prepared by the following steps:

[0066] Rough drawing: After the wire rod is roughly drawn to a diameter of 2.3 mm, it is heated to 970-990° C. and then sent to a salt bath tank for salt bath treatment at a salt bath temperature of 560-600° C.;

[0067] Middle drawing: after the wire rod is middle drawn to a diameter of 1.3 mm, it is heated to 940-950° C. and then sent to a salt bath tank for salt bath treatment at a salt bath temperature of 580-610° C.;

[0068] Fine drawing: after the wire rod is finely drawn into a steel wire with a diameter of 0.38 mm, it is heated to 920-940° C. and then sent to a salt bath tank for salt bath treatment at a temperature of 550-590° C.;

[0069] Copper plating and water tank drawing are used to obtain steel wire with a diameter of 0.03~0.045mm.

[0070] One embodiment of the present application also provides a production method for preparing the hot-rolled wire rod for the 5200MPa grade steel wire. As mentioned above, the production method of the present application is obtained based on a large number of experimental studies. The following is a further description of each process in the production method in conjunction with specific examples.

[0071] The production method of the 5200MPa grade hot-rolled wire rod comprises the following steps:

[0072] (1) Vacuum melting process

[0073] The charge is melted in a vacuum induction melting furnace, refined and the chemical composition and inclusions in the molten steel are regulated, and the steel is cast to obtain a steel ingot.

[0074] It is understood that the chemical composition of the steel ingot is consistent with the chemical composition of the final wire rod. That is, the chemical composition of the steel ingot includes, by mass percentage: C 0.95-0.98%, Si 0.45-0.65%, Mn 0.20-0.40%, Cr 0.20-0.40%, Ni 0.05-0.30%, and the rest is Fe and unavoidable impurities, and the content of impurity elements is controlled to be: Al≤0.002%, Ti≤0.0008%, S≤0.005%, P≤0.008%, O≤0.0010%, N≤0.0020%.

[0075] Specifically, ultrapure Fe blocks, metal Cr, metal Ni and carbon particles are fed into a vacuum melting furnace for electric melting. The melting temperature is 1620-1625°C and the vacuum pressure in the furnace is <0.3 mbar. Metal Mn and ferrosilicon are added during melting to adjust the composition. After the target composition is reached, synthetic slag is added to make slag and stirred. After the slag making is completed, the slag is fished out and the steel is tapped. The purity of the ultrapure iron block is ≥99.96%.

[0076] Preferably, during smelting, argon gas is introduced into the bottom of the vacuum melting furnace to stir the molten steel.

[0077] Preferably, the basicity of the synthetic slag is 0.95-0.98.

[0078] Preferably, after slag making is completed, the slag is scooped out by a slag scooping rod, and the tapping temperature is 1552~1558℃.

[0079] (2) Remelting process

[0080] The smelted steel ingot is used as a consumable electrode rod for vacuum consumable crystallization and then remelted to obtain a remelted ingot, and the segregation ratio of the obtained remelted ingot is 0.98~1.02.

[0081] The segregation ratio of the remelted ingot refers to the ratio of the carbon content in the core of the remelted ingot to the average carbon content at the 1 / 4 position thereof.

[0082] Preferably, the remelting rate is 2.5-2.8 kg / min.

[0083] Preferably, after remelting, the remelted ingot is subjected to heat preservation treatment for 60 to 72 hours, and then subjected to wind-proof pile cooling to reduce cracks on the surface and core of the remelted ingot due to stress.

[0084] (3) Blanking process

[0085] The obtained remelted ingot is cut into small square billets, and when the temperature of the small square billet drops to 950-1000°C, it is cooled, and the surface cooling rate of the small square billet is controlled to be ≤6°C / s, and the corner cooling rate is ≤9°C / s. When it is cooled to 600-650°C, it is put into a holding pit for slow cooling, and the cooling rate of the small square billet in the holding pit is ≤3°C / s.

[0086] Specifically, the cooling of the billet is carried out on a cooling bed.

[0087] Preferably, the obtained remelted ingot is subjected to 6 reciprocating billeting passes to obtain a small square billet, the rolling temperature is 1180-1230° C., the elongation coefficient of the first three passes is 1.82-1.90, and the elongation coefficient of the last three passes is 1.58-1.72.

[0088] (4) Grinding process

[0089] The surface of the billet is fully ground to eliminate the influence of the surface defects of the billet on subsequent high-speed wire rolling and drawing.

[0090] Preferably, a 24-mesh grinding wheel is used for grinding, the single grinding depth is ≤0.4 mm, the total grinding depth is ≥1.2 mm, the linear speed of the grinding wheel is controlled to be 72-76 m / s during grinding, the grinding wheel pressure is controlled to be 65-78 MPa when grinding the surface, and the grinding wheel pressure is controlled to be 48-60 MPa when grinding the corner.

[0091] After grinding, magnetic particle inspection is used. The moving speed of the billet is controlled to be 0.12-0.15 m / s during inspection, and the magnetic particle concentration is controlled to be 0.62-0.68 g / L to ensure comprehensive inspection. Preferably, the number of inspection defects of the small square billet after grinding is controlled to be ≤0.2 / m.

[0092] (5) High-speed wire rolling process

[0093] After heating the billet, rough rolling, intermediate rolling, pre-finishing rolling, finishing rolling and sizing rolling are carried out in sequence to obtain a wire rod with a diameter of 5.0-5.5 mm.

[0094] Among them, during heating, the temperature difference between the surface and the core of the small square billet is controlled to be ≤10℃, during rolling, the torsion angle of the rolled piece is controlled to be ≤20°, the rolls of the four rolling mills before rough rolling are water-cooled to control the corner temperature of the billet to 1050~1100℃, the starting temperature of finishing rolling is 920~950℃, and the rolling temperature during sizing rolling is 860~880℃.

[0095] Preferably, blast furnace gas and air are introduced into the heating furnace during heating, the pressure in the furnace is controlled to be 6.5~8KPa, the temperature of the preheating section and the heating section is controlled to be ≥960℃, the temperature of the top of the heating furnace is controlled to be higher than the temperature of the bottom of the furnace, and the temperature difference between the top and the bottom of the furnace is ≤100℃.

[0096] The high-speed wire rolling process adopts a 28-stand rolling mill for rolling, and the 28-stand rolling mill includes 6 rough rolling mills + 6 intermediate rolling mills + 4 pre-finishing rolling mills + 10 finishing rolling mills + 2 sizing mills. Thus, correspondingly, after heating, the small square billet is subjected to 6 rough rolling passes, 6 intermediate rolling passes, 4 pre-finishing rolling passes, 10 finishing rolling passes, and 2 sizing rolling passes in sequence to obtain the wire rod.

[0097] Preferably, when water cooling is performed on the rolls of the first four rolling mills of the rough rolling, the temperature of the cooling water is controlled to be ≤30°C and the water pressure is controlled to be 0.1-0.8MPa.

[0098] (6) Stelmor controlled cooling process

[0099] Use the Stelmor cooling line for temperature-controlled cooling, turn on the 1st to 4th fans and the 7th to 8th fans, and turn off the other fans. Turn off the insulation covers corresponding to the 5th to 6th fans, and turn on the other insulation covers. Use the Jialing device to adjust the wind speed at the overlapping points of the wire rods on the rollers corresponding to the 1st to 4th fans to 1.5 to 2.0 times the wind speed at the non-overlapping points, and adjust the wind speed at the overlapping points of the wire rods on the rollers corresponding to the 5th to 8th fans to 1.2 to 1.6 times the wind speed at the non-overlapping points.

[0100] Preferably, the angle of the Jialing device corresponding to the 1st to 4th fans is 10-13°, and the angle of the Jialing device corresponding to the 5th to 8th fans is 8-11°.

[0101] Among them, the maximum air volume of the fan is 280,000 m 3 / h, control the air volume of the 1st to 4th fans to 30~100% of the maximum air volume, and the air volume of the 7th to 8th fans to 20~30% of the maximum air volume.

[0102] After testing, the tensile strength of the obtained wire rod is 1200~1300MPa, the cross-sectional shrinkage is ≥28%, and the elongation is ≥8%;

[0103] The number density of inclusions in the obtained wire rod is ≤5 / mm 2 , inclusions with a size of ≤4μm account for ≥90%, and the maximum inclusion size is ≤6μm; among the inclusions, Al2O3 inclusions account for ≤3%, MnS inclusions account for ≥85%, and the rest are SiO2 and other inclusions;

[0104] The wire rod is etched with sodium picrate, and there is no network carbide in the metallographic structure;

[0105] By adopting nitric acid alcohol corrosion, there is no martensite and bainite structure in the wire rod.

[0106] In summary, on the basis of the chemical composition design of the present application, combined with the control of the aforementioned production process flow, not only the cleanliness and surface quality of the wire rod are improved, the structure of the wire rod is refined, and the finally prepared wire rod has high strength, excellent drawing performance and high purity, the tensile strength of the obtained wire rod is 1200~1300MPa, the cross-sectional shrinkage rate is ≥28%, and the elongation is ≥8%. It can not only effectively reduce the wire breakage rate during further drawing to prepare steel wire, but also lays the foundation for further drawing and preparing steel wire with a diameter of 0.03~0.045mm and a tensile strength of ≥5200MPa.

[0107] Furthermore, the obtained wire rod can be prepared into steel wire through further drawing.

[0108] (7) Drawing process

[0109] The obtained wire rod is subjected to rough drawing, medium drawing, fine drawing and water tank drawing in sequence to obtain a steel wire with a diameter of 0.03-0.045 mm.

[0110] Specifically, during rough drawing, the wire rod is roughly drawn to a diameter of 2.3 mm, heated to 970-990° C., and then sent to a salt bath tank for salt bath treatment, and the salt bath temperature is 560-600° C.;

[0111] During the intermediate drawing, the wire rod is intermediately drawn to a diameter of 1.3 mm, heated to 940-950° C., and then sent to a salt bath tank for salt bath treatment at a salt bath temperature of 580-610° C.;

[0112] During fine drawing, the wire rod is fine drawn into a diameter of 0.38 mm, heated to 920-940° C., and then sent to a salt bath tank for salt bath treatment at a temperature of 550-590° C.;

[0113] Copper plating and water tank drawing are used to obtain steel wire with a diameter of 0.03~0.045mm.

[0114] On the basis of the aforementioned wire rod, by rough drawing, medium drawing and fine drawing of the wire rod, and heat treatment after each drawing, combined with the heating temperature in the heat treatment and the salt bath treatment temperature, copper plating and water tank drawing are further performed after fine drawing, so that the final prepared steel wire with a diameter of 0.03~0.045mm has extremely high strength, and the wire rod has an unbroken wire mileage of ≥300km in the process of drawing the steel wire.

[0115] After testing, the tensile strength of the obtained steel wire is ≥5200MPa, that is, the tensile strength level of the obtained steel wire reaches 5200MPa, and the diameter of the steel wire is only 0.03~0.045mm, which can be used as raw material for diamond wire busbar, and when used for photovoltaic silicon wafer cutting, it can improve the silicon wafer cutting quality and greatly reduce cutting loss.

[0116] The specific implementation methods of the present application are further described below through specific examples. Of course, these examples are only a part of the many variations of the present implementation methods, not all of them. Other examples based on the above-mentioned implementation methods do not deviate from the technical purpose of the present application.

[0117] Specifically, Examples 1 and 2 provide a 5200 MPa grade hot rolled wire rod for steel wire and a 5200 MPa grade steel wire, respectively, whose chemical compositions are shown in Table 1 in terms of mass percentage. In addition to the chemical compositions in Table 1, the rest are Fe and unavoidable impurities.

[0118] Table 1

[0119]

[0120] The individual steps in the production method are as follows.

[0121] (1) Vacuum melting process

[0122] The charge is melted in a vacuum induction melting furnace, refined and the chemical composition and inclusions in the molten steel are regulated, and the steel is cast to obtain a steel ingot. The chemical composition of the steel ingot is also shown in Table 1.

[0123] Specifically, ultrapure Fe blocks, metal Cr, metal Ni and carbon particles are fed into a vacuum melting furnace for electric melting at a melting temperature of 1620-1625°C. The vacuum pressure in the furnace in Examples 1 and 2 is controlled to be 0.25 mbar and 0.28 mbar, respectively. Metal Mn and ferrosilicon are added during smelting to adjust the composition. After the target composition is reached, synthetic slag is added to make slag and stirred. The basicity of the synthetic slag is 0.95-0.98. During the smelting process, argon gas is introduced into the bottom of the vacuum melting furnace to stir the molten steel. After slag making is completed, the slag is fished out by a slag rod and the steel is tapped. The tapping temperature is 1552-1558°C. The purity of the ultrapure iron block is ≥99.96%.

[0124] (2) Remelting process

[0125] The smelted steel ingot is used as a consumable electrode rod for vacuum consumable crystallization and remelting to obtain a remelted ingot, and then the remelted ingot is subjected to heat preservation treatment and then to wind-proof pile cooling. The melting rates of the remelting in Examples 1 and 2 are 2.5-2.7 kg / min and 2.6-2.8 kg / min, respectively; and the heat preservation time in Examples 1 and 2 is 60 h and 72 h, respectively.

[0126] The carbon contents in the core and the 1 / 4 position area along the diagonal line of the remelted ingot were measured respectively, and the segregation ratio of the remelted ingot was calculated. Segregation ratio = core carbon content / (carbon content in the 1 / 4 position area). The segregation ratios of the remelted ingots of Examples 1 and 2 were measured to be 1.01 and 0.99 respectively.

[0127] (3) Blanking process

[0128] The obtained remelted ingot was subjected to six reciprocating billeting operations using a reciprocating billeting machine to obtain a small square billet.

[0129] Among them, in Example 1, the cross-sectional size of the small square billet is 140mm×140mm, the rolling temperature is 1180~1200℃, the elongation coefficient of the first three passes is 1.82~1.90, and the elongation coefficient of the last three passes is 1.58~1.72; when the temperature of the small square billet drops to 960~980℃, the small square billet is sent to the cooling bed for cooling, and the surface cooling rate of the small square billet is controlled to be 3~5℃ / s, and the corner cooling rate is 6~9℃ / s. When cooled to 630℃, it is put into the insulation pit for slow cooling, and the cooling rate of the small square billet in the insulation pit is 2~3℃ / s; when the foot temperature of the small square billet is ≤100℃, it is taken out of the insulation pit and cooled to room temperature.

[0130] In Example 2, the cross-sectional size of the small square billet is 150mm×150mm, the rolling temperature is 1200~1230℃, the elongation coefficient of the first three passes is 1.82~1.90, and the elongation coefficient of the last three passes is 1.58~1.68; when the temperature of the small square billet drops to 980~1000℃, the small square billet is sent to the cooling bed for cooling, and the surface cooling rate of the small square billet is controlled to be 5~6℃ / s, and the corner cooling rate is 6~8℃ / s. When cooled to 630℃, it is put into the holding pit for slow cooling, and the cooling rate of the small square billet in the holding pit is 2~3℃ / s; when the foot temperature of the small square billet is ≤100℃, it is taken out of the holding pit and cooled to room temperature.

[0131] (4) Grinding process

[0132] The surface of the small square billet is fully ground using a 24-grit grinding wheel, and multiple grinding is performed.

[0133] In Example 1, the single grinding depth is controlled to be 0.35 mm, the total grinding depth is controlled to be 1.4 mm, the linear speed of the grinding wheel is controlled to be 76 m / s during grinding, the grinding wheel pressure is controlled to be 65 MPa when grinding the surface, and the grinding wheel pressure is controlled to be 50 MPa when grinding the corner.

[0134] In Example 2, the single grinding depth is controlled to be 0.30 mm, the total grinding depth is controlled to be 1.6 mm, the linear speed of the grinding wheel is controlled to be 73 m / s during grinding, the grinding wheel pressure is controlled to be 75 MPa when grinding the surface, and the grinding wheel pressure is controlled to be 48 MPa when grinding the corner.

[0135] After grinding, magnetic particle inspection was used. The moving speed of the blank, i.e., the small square billet, was controlled to be 0.12-0.15 m / s during inspection, and the magnetic powder concentration was controlled to be 0.62-0.68 g / L. In Examples 1 and 2, the number of defects in the small square billet after grinding was ≤0.2 pieces / m.

[0136] (5) High-speed wire rolling process

[0137] The small square billet is heated and then rolled by a 28-stand rolling mill, which includes 6 rough rolling mills + 6 intermediate rolling mills + 4 pre-finishing rolling mills + 10 finishing rolling mills + 2 sizing mills. That is, after the small square billet is heated, 6 rough rolling passes, 6 intermediate rolling passes, 4 pre-finishing rolling passes, 10 finishing rolling passes, and 2 sizing rolling passes are sequentially performed to obtain a wire rod with a diameter of 5.0 mm.

[0138] During heating, blast furnace gas and air are introduced into the heating furnace.

[0139] In Example 1, the pressure in the furnace is controlled to be 6.6~7.0KPa, the temperature of the preheating section is controlled to be 960~980℃, the temperature of the heating section is controlled to be 990~1020℃, and the amount of gas and air entering the heating furnace is adjusted to control the temperature of the furnace top in the heating furnace to be higher than the temperature of the furnace bottom, and the temperature difference between the furnace top and the furnace bottom is ≤80℃, so as to control the temperature difference between the upper and lower surfaces and the core of the small square billet to be ≤10℃; during rolling, the torsion angle of the rolled piece is controlled to be ≤20°, the rollers of the first four rolling mills of rough rolling are water-cooled, the temperature of the cooling water is controlled to be ≤30℃, and the water pressure is 0.6~0.8MPa, so as to control the corner temperature of the billet to be 1050~1070℃, the starting rolling temperature of the finishing rolling is 920~940℃, and the rolling temperature during sizing rolling is 860~880℃.

[0140] In Example 2, the pressure in the furnace is controlled to be 7.2~8.0KPa, the temperature of the preheating section is controlled to be 970~990℃, the temperature of the heating section is controlled to be 1000~1030℃, and the amount of gas and air entering the heating furnace is adjusted to control the temperature of the furnace top in the heating furnace to be higher than the temperature of the furnace bottom, and the temperature difference between the furnace top and the furnace bottom is ≤90℃, so as to control the temperature difference between the upper and lower surfaces and the core of the small square billet to be ≤10℃; during rolling, the torsion angle of the rolled piece is controlled to be ≤20°, the rollers of the first four rolling mills of rough rolling are water-cooled, the temperature of the cooling water is controlled to be ≤30℃, and the water pressure is 0.6~0.8MPa, so as to control the corner temperature of the billet to be 1080~1100℃, the starting rolling temperature of the finishing rolling is 930~950℃, and the rolling temperature during sizing rolling is 860~880℃.

[0141] (6) Stelmor controlled cooling process

[0142] The Stelmor cooling line is used for temperature control cooling. The 1st to 4th fans and the 7th to 8th fans are turned on, and the other fans are turned off. The maximum air volume of the fans is 280,000 m 3 / h, close the insulation covers corresponding to the 5th and 6th fans, and open the remaining insulation covers.

[0143] In Example 1, the angle of the Jialing device corresponding to the 1st to 4th fans is adjusted to 12°, so that the wind speed at the overlapping point of the wire rod on the roller corresponding to the 1st to 4th fans is 1.8 times the wind speed at the non-overlapping point; the angle of the Jialing device corresponding to the 5th to 8th fans is adjusted to 9°, so that the wind speed at the overlapping point of the wire rod on the roller corresponding to the 5th to 8th fans is 1.3 times the wind speed at the non-overlapping point; and the air volume of the 1st to 4th fans is controlled to be 100%, 90%, 30%, and 30% of the maximum air volume, respectively, and the air volume of the 7th to 8th fans is controlled to be 30% and 30% of the maximum air volume, respectively.

[0144] In Example 2, the angle of the Jialing device corresponding to the 1st to 4th fans is adjusted to 10°, so that the wind speed at the overlapping point of the wire rod on the roller corresponding to the 1st to 4th fans is 1.6 times the wind speed at the non-overlapping point; the angle of the Jialing device corresponding to the 5th to 8th fans is adjusted to 11°, so that the wind speed at the overlapping point of the wire rod on the roller corresponding to the 5th to 8th fans is 1.5 times the wind speed at the non-overlapping point; and the air volume of the 1st to 4th fans is controlled to 100%, 80%, 30%, and 30% of the maximum air volume, respectively, and the air volume of the 7th to 8th fans is controlled to 30% and 20% of the maximum air volume, respectively.

[0145] The wire rods of Examples 1 and 2 were sampled and subjected to mechanical property testing, inclusion testing, and structure testing according to the same testing method. The specific testing methods and test results are as follows:

[0146] 1) In terms of mechanical properties, referring to the standard test methods and definitions of ASTM A370 for mechanical properties of steel products, a tensile testing machine was used to sample the wire rods and conduct mechanical properties tests;

[0147] The tensile strength of the wire rod of Example 1 was measured to be 1230-1300 MPa, the cross-sectional shrinkage was 35-40%, and the elongation was 9-13%;

[0148] The tensile strength of the wire rod of Example 2 was measured to be 1250-1300 MPa, the cross-sectional shrinkage was 36-38%, and the elongation was 9-12%.

[0149] 2) In terms of inclusions, a scanning electron microscope was used to count the inclusions in the wire rod of the above embodiment;

[0150] The number density of inclusions in the wire rod of Example 1 was measured to be ≤5 / mm 2, no inclusions with a size > 4μm were detected, and the maximum inclusion size was ≤ 4μm; among the inclusions, Al2O3 inclusions accounted for only 1%, MnS inclusions accounted for ≥ 88%, and the rest were SiO2 and other inclusions;

[0151] The number density of inclusions in the wire rod of Example 2 was measured to be ≤5 / mm 2 No inclusions with a size > 4μm were detected, and the maximum inclusion size was ≤4μm; among the inclusions, Al2O3 inclusions accounted for only 0.8%, MnS inclusions accounted for ≥92%, and the rest were SiO2 and other inclusions.

[0152] 3) Organizational aspects,

[0153] According to the metallographic detection method of troostite content in high carbon steel wire rod in YB / T 169, the troostitization rate in the wire rod of Example 1 is 95-96%, and the troostitization rate in the wire rod of Example 2 is 92-96%;

[0154] When using sodium picrate corrosion, there is no network carbide in the metallographic structure of the wire rods in Examples 1 and 2;

[0155] Referring to YB / T 4411-2014 high carbon steel wire rod center martensite assessment method, nitric acid alcohol corrosion was used, and there was no martensite and bainite structure in the wire rods in Examples 1 and 2.

[0156] (7) Drawing process

[0157] After 12 days of natural aging, the obtained wire rod is subjected to rough drawing, medium drawing, fine drawing and water tank drawing in sequence to obtain steel wire with a diameter of 0.03~0.045mm.

[0158] During rough drawing, the wire rod is roughly drawn to a diameter of 2.3 mm, heated to 970-990° C., and then sent to a salt bath tank for salt bath treatment at a salt bath temperature of 560-600° C.;

[0159] During the intermediate drawing, the wire rod is intermediately drawn to a diameter of 1.3 mm, heated to 940-950° C., and then sent to a salt bath tank for salt bath treatment at a salt bath temperature of 580-610° C.;

[0160] During fine drawing, the wire rod is fine drawn into a diameter of 0.38 mm, heated to 920-940° C., and then sent to a salt bath tank for salt bath treatment at a temperature of 550-590° C.;

[0161] Copper plating and water tank drawing to obtain steel wire.

[0162] The diameters of the steel wires in Examples 1 and 2 are 0.038 mm and 0.042 mm, respectively. During the drawing process, the unbroken wire mileages of Examples 1 and 2 are both ≥300 km.

[0163] The steel wires of Examples 1 and 2 were sampled and tested for mechanical properties according to the same testing method.

[0164] Specifically, referring to the room temperature test method in Part 1 of GB / T228.1 Tensile Test for Metallic Materials, a tensile testing machine was used to test the mechanical properties of the steel wire, and the tensile strength of the steel wire of Example 1 was measured to be 5300 MPa, and the tensile strength of the steel wire of Example 2 was 5400 MPa.

[0165] In summary, the steel wire finally prepared in the present application has a diameter of 0.03~0.045mm and a tensile strength ≥5200MPa. It can be used as a raw material for diamond wire busbars, and when used for cutting photovoltaic silicon wafers, it can improve the cutting quality of silicon wafers and greatly reduce cutting losses.

[0166] It should be understood that although this specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation mode may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

[0167] The detailed descriptions listed above are merely specific descriptions of feasible implementation methods of the present application. They are not intended to limit the scope of protection of the present application. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present application should be included in the scope of protection of the present application.

Claims

1. A hot-rolled wire rod for 5200MPa grade steel wire, characterized in that: The chemical composition of the wire rod includes, by mass percentage, C 0.95-0.98%, Si 0.45-0.65%, Mn 0.20-0.40%, Cr 0.20-0.40%, Ni 0.05-0.30%, and the rest is Fe and unavoidable impurities, and the content of impurity elements is controlled to be: Al≤0.002%, Ti≤0.0008%, S≤0.005%, P≤0.008%, O≤0.0010%, N≤0.0020%; The wire rod has a diameter of 5.0-5.5 mm, a tensile strength of 1200-1300 MPa, a cross-sectional shrinkage of ≥28%, and an elongation of ≥8%; The wire rod has a mileage of ≥300 km without breaking during the process of drawing the steel wire with a diameter of 0.03-0.045 mm; In the wire rod, the number density of inclusions is ≤5 / mm 2 , inclusions with a size of ≤4μm account for ≥90%, and the maximum inclusion size is ≤6μm; among the inclusions, Al2O3 inclusions account for ≤3%, MnS inclusions account for ≥85%, and the rest are SiO2 and other inclusions; The wire rod is etched with sodium picrate, and there is no network carbide in the metallographic structure; By adopting nitric acid alcohol corrosion, there is no martensite and bainite structure in the wire rod.

2. A 5200MPa grade steel wire, characterized in that: The steel wire is prepared using the hot-rolled wire rod described in claim 1 as a base material.

3. The steel wire according to claim 2, characterized in that The steel wire is prepared by the following steps: Rough drawing: After the wire rod is roughly drawn to a diameter of 2.3 mm, it is heated to 970-990° C. and then sent to a salt bath tank for salt bath treatment at a salt bath temperature of 560-600° C.; Middle drawing: after the wire rod is middle drawn to a diameter of 1.3 mm, it is heated to 940-950° C. and then sent to a salt bath tank for salt bath treatment at a salt bath temperature of 580-610° C.; Fine drawing: after the wire rod is fine drawn into a diameter of 0.38 mm, it is heated to 920-940° C., and then sent to a salt bath tank for salt bath treatment, and the salt bath temperature is 550-590° C.; Copper plating and water tank drawing are used to obtain steel wire with a diameter of 0.03~0.045mm.

4. The steel wire according to claim 2, characterized in that The diameter of the steel wire is 0.03-0.045 mm, and the tensile strength is ≥5200 MPa.

5. A method for producing a hot-rolled wire rod for 5200MPa grade steel wire, characterized in that: The chemical composition of the wire rod includes, by mass percentage, C 0.95-0.98%, Si 0.45-0.65%, Mn 0.20-0.40%, Cr 0.20-0.40%, Ni 0.05-0.30%, and the rest is Fe and unavoidable impurities, and the content of impurity elements is controlled to be: Al≤0.002%, Ti≤0.0008%, S≤0.005%, P≤0.008%, O≤0.0010%, N≤0.0020%; The production method of the wire rod comprises the following steps: Vacuum melting process: melting the charge in a vacuum induction melting furnace, refining and regulating the chemical composition and inclusions in the molten steel, and then pouring the steel to obtain an ingot; In the remelting process, the steel ingot is used as a consumable electrode rod for vacuum consumable crystallization and then remelted to obtain a remelted ingot, and the segregation ratio of the obtained remelted ingot is 0.98~1.02; In the billet opening process, the obtained remelted ingot is opened into a small square billet, and when the temperature of the small square billet drops to 950-1000°C, it is cooled, and the surface cooling rate of the small square billet is controlled to be ≤6°C / s, and the corner cooling rate is ≤9°C / s. When it is cooled to 600-650°C, it is put into a holding pit for slow cooling, and the cooling rate of the small square billet in the holding pit is ≤3°C / s; Grinding process; High-speed wire rolling process: After heating the billet, it is subjected to rough rolling, intermediate rolling, pre-finishing rolling, finishing rolling, and sizing rolling in sequence to obtain wire rods. During heating, the temperature difference between the surface and the core of the billet is controlled to be ≤10°C, and during rolling, the torsion angle of the rolled piece is controlled to be ≤20°. The rolls of the four rolling mills before rough rolling are water-cooled to control the corner temperature of the billet to be 1050~1100°C, the start rolling temperature of finishing rolling is 920~950°C, and the rolling temperature during sizing rolling is 860~880°C. In the Stelmor controlled cooling process, the 1st to 4th fans and the 7th to 8th fans are turned on, and the other fans are turned off. The insulation covers corresponding to the 5th to 6th fans are turned off, and the other insulation covers are turned on. The Jialing device is used to adjust the wind speed at the overlapping points of the wire rods on the rollers corresponding to the 1st to 4th fans to 1.5 to 2.0 times the wind speed at the non-overlapping points, and the wind speed at the overlapping points of the wire rods on the rollers corresponding to the 5th to 8th fans is adjusted to 1.2 to 1.6 times the wind speed at the non-overlapping points.

6. The production method according to claim 5, characterized in that In the vacuum smelting process, ultrapure Fe blocks, metal Cr, metal Ni, and carbon particles are fed into a vacuum smelting furnace for electric smelting. The smelting temperature is 1620-1625° C. The vacuum pressure in the furnace is less than 0.3 mbar. Metal Mn and ferrosilicon are added during smelting to adjust the composition. After the target composition is reached, synthetic slag is added to slag and stirred. After slag making is completed, the slag is fished out and the steel is tapped. Wherein, the purity of the ultrapure Fe block is ≥99.96%.

7. The production method according to claim 6, characterized in that: In the vacuum melting process, argon gas is introduced into the bottom of the vacuum melting furnace during melting to stir the molten steel.

8. The production method according to claim 6, characterized in that: In the vacuum smelting process, the basicity of the synthetic slag is 0.95-0.

98.

9. The production method according to claim 6, characterized in that: In the vacuum melting process, after slag making is completed, the slag is removed by a slag removal rod, and the tapping temperature is 1552~1558℃.

10. The production method according to claim 5, characterized in that: In the remelting process, the remelting rate is 2.5-2.8 kg / min.

11. The production method according to claim 5, characterized in that: In the billeting process, the obtained remelted ingot is subjected to six reciprocating billeting passes to obtain a small square billet, the rolling temperature is 1180-1230° C., the elongation coefficients of the first three passes are 1.82-1.90, and the elongation coefficients of the last three passes are 1.58-1.

72.

12. The production method according to claim 5, characterized in that: The grinding process uses a 24-mesh grinding wheel, a single grinding depth ≤0.4mm, a total grinding depth ≥1.2mm, a grinding wheel linear speed of 72-76m / s, a grinding wheel pressure of 65-78MPa when grinding the surface, and a grinding wheel pressure of 48-60MPa when grinding the corner.

13. The production method according to claim 5, characterized in that: In the grinding process, the number of flaw detection defects of the small square billet after grinding is controlled to be ≤0.2 pieces / m.

14. The production method according to claim 5, characterized in that: In the high-speed wire rolling process, blast furnace gas and air are introduced into the heating furnace during heating, the pressure in the furnace is controlled to be 6.5~8KPa, the temperature of the preheating section and the heating section is controlled to be ≥960℃, the temperature of the furnace top in the heating furnace is controlled to be higher than the temperature of the furnace bottom, and the temperature difference between the furnace top and the furnace bottom is ≤100℃.

15. The production method according to claim 5, characterized in that: The high-speed wire rolling process adopts a 28-stand rolling mill for rolling, and the 28-stand rolling mill includes 6 roughing mills + 6 medium rolling mills + 4 pre-finishing mills + 10 finishing mills + 2 sizing mills.

16. The production method according to claim 5, characterized in that: In the high-speed wire rolling process, when the rolls of the first four rolling mills of rough rolling are water-cooled, the temperature of the cooling water is controlled to be ≤30° C. and the water pressure is controlled to be 0.1-0.8 MPa.

17. The production method according to claim 5, characterized in that: In the Stelmor controlled cooling process, the angle of the Jialing device corresponding to the 1st to 4th fans is 10-13°, and the angle of the Jialing device corresponding to the 5th to 8th fans is 8-11°.

18. The production method according to claim 5, characterized in that: In the Stelmor controlled cooling process, the maximum air volume of the fan is 280,000 m 3 / h, control the air volume of the 1st to 4th fans to 30~100%, and the air volume of the 7th to 8th fans to 20~30%.

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