Wire rod aging method for large-size high-strength steel strand

Abstract

The present application relates to the technical field of steel rolling, and discloses a wire rod aging method for large-size high-strength steel strand, which comprises the following process steps: intermediate ladle hydrogen determination, casting blank stacking and slow cooling, casting blank heating, high-speed wire rolling, wire spitting, Stelmor line phase change post-heat preservation, coil collecting, PF conveying chain heat preservation, finishing, packaging, weighing, and entering slow cooling pit for heat preservation to obtain the wire rod; in the Stelmor line phase change post-heat preservation process, the initial speed of the roller bed is 0.56 m / s, and the speed is increased by 0.01 m / s in stages; the heat preservation process is carried out in stages, including: the first stage: the temperature is 890±10℃-650±10℃, the second stage: the temperature is 650±10℃-590±10℃, the third stage: the temperature is 590±10℃-500±10℃, the fourth stage: the temperature is 450±10℃-300±10℃, and the fifth stage: the temperature is 200℃±10℃-room temperature; the method solves the technical problem that the natural aging period of the wire rod for large-size high-strength steel strand is long, brittle fracture easily occurs during use, and continuous production cannot be met.

Description

Technical Field

[0001] The present invention relates to the technical field of steel rolling, and in particular to an online aging method for wire rods for large-size high-strength steel strands. Background Art

[0002] Wire rod for high-strength steel strand is often produced without vacuum treatment, thereby reducing costs and increasing efficiency for steelmakers. However, hydrogen content in molten steel, as measured by intermediate hydrogenation equipment, often shows [H] levels of 3-5 ppm. This can easily lead to hydrogen-induced cracking in the steel. Combined with the high crack sensitivity of high-carbon steel wire rod, users often experience a sudden increase in wire breakage during use, severely impacting the quality and production efficiency of the steel strand. Furthermore, unaged wire rod has a very low cross-sectional shrinkage, allowing gases in the steel to accumulate near non-metallic inclusions or within cracks, embrittle the wire rod, making it more susceptible to surface defects during handling and introducing further defects before use. Conventional practice requires the wire rod to be left in a natural environment for a period of time (longer at lower temperatures) to allow gases and residual stresses to be released continuously, ultimately stabilizing the wire rod's plasticity at ≥30%. This duration varies with fluctuating gas content from heat to heat, leading to difficulties in shipping, product backlogs, and capital flow.

[0003] Therefore, there is a need in the prior art for an online aging method for wire rods for large-size high-strength steel strands. Summary of the Invention

[0004] In view of this, the purpose of an embodiment of the present invention is to propose an online aging method for wire rods for large-size high-strength steel strands. Through slow cooling of wire rod ingots for steel strands, Stelmor air-cooling line controlled cooling process after rolling, waste heat insulation on PF transport chain and slow cooling in slow cooling pit, a wire rod for high-strength steel strands with plasticity stabilized without natural aging treatment is obtained, which solves the technical problem that the natural aging period of wire rods for large-size high-strength steel strands is long, brittle fracture is prone to occur during use and cannot meet the requirements of continuous production.

[0005] Based on the above purpose, the embodiment of the present invention provides an online aging method for wire rods for large-size high-strength steel strands, and the process flow includes: hydrogen determination in the tundish → slow cooling of the billet stacking → heating of the billet → high-speed wire rolling → spinning → insulation after the Stelmor line phase change → coiling → insulation of the PF transport chain → finishing, packaging, and weighing → insulation in the slow cooling pit to obtain the wire rod. During the insulation process after the Stelmor line phase change, the initial speed of the roller is 0.56 m / s, and increases by 0.01 m / s step by step. The insulation process is carried out in stages, including:

[0006] Stage 1: The temperature is 890±10℃~650±10℃, the fan is turned on, the cooling speed is controlled at 8~10℃ / s, and the heat preservation cover is opened;

[0007] The second stage: the temperature is 650±10℃~590±10℃, the cooling rate is controlled at 3~5℃ / s, and the heat preservation cover is opened;

[0008] The third stage: the temperature is 590±10℃~500±10℃, the fan is turned off, the insulation cover is closed, the cooling speed is controlled to 0.5~1.5℃ / s, and the residence time in the insulation cover is ≥90s.

[0009] In some embodiments, the chemical composition of the wire rod includes, by mass fraction: C: 0.84% ​​to 0.87%, Si: 0.50% to 0.60%, Mn: 0.60% to 0.80%, P≤0.015%, S≤0.010%, Cr: 0.25% to 0.35%, Cu≤0.20%, Ni≤0.10%, N≤40ppm, O≤12ppm, H≤1.0ppm, and the rest is Fe and unavoidable impurities.

[0010] In some embodiments, during the slow cooling process of the ingot stacking, the temperature is controlled at 350-450° C., and the stacking time is controlled at 32-48 hours.

[0011] In some embodiments, during the tundish hydrogen determination process, the hydrogen content in the molten steel is monitored in real time, and the hydrogen content does not exceed 5.0 ppm.

[0012] In some embodiments, in the slab heating process, the slab is heated at an soaking temperature of 1080-1150° C., and the heating time t=(0.7-1.2)H, where H is the slab thickness in mm and the heating time t is in min.

[0013] In some embodiments, the cast strand is heated using a walking beam furnace.

[0014] In some embodiments, after the high-speed wire rolling process, water cooling control is performed in a post-rolling water tank to control the wire rod spinning temperature to 890±10°C.

[0015] In some embodiments, the maximum flow rate of the fan in the first stage is 200,000 m 3 / h, the maximum flow of the fan in the second stage is 155,000m 3 / h.

[0016] In some embodiments, the temperature of the wire rod entering the PF chain insulation corridor after double-core rod coiling is controlled at 450℃±10℃, the residence time in the PF chain insulation corridor is ≥600s, and the temperature of the wire rod in the finishing process is controlled at 300℃±10℃.

[0017] In some embodiments, the temperature of the wire rod entering the slow cooling pit is 200° C.±10° C., and the slow cooling time is 22 to 24 hours.

[0018] The present invention has at least the following beneficial technical effects:

[0019] The present invention aims to solve the common technical problem of long aging period of wire rod for large-size high-strength steel strand and provides an online aging method for wire rod for large-size high-strength steel strand. Through slow cooling of wire rod ingots stacked for steel strand, Stelmor air-cooling line controlled cooling process after rolling, waste heat insulation on PF transport chain and slow cooling in wire rod slow cooling pit, a wire rod for high-strength steel strand with plasticity stabilized without natural aging treatment is obtained, which solves the technical problem that wire rod for large-size high-strength steel strand has long natural aging period and is prone to brittle fracture during use and cannot meet the requirements of continuous production. The wire rod is cooled to below 50°C and then subjected to mechanical property testing. The tensile strength of the wire rod is in the range of 1280~1320MPa, and the cross-sectional area reduction is 30%~40%, which does not change with time, reaching the level of artificial aging test and realizing online aging plastic recovery of the wire rod. The network cementite and martensite grades in the organization are both ≤1.0. After being sent to the user, it can be directly dephosphorized and drawn. The wire breakage rate per 100 tons is ≤1.0 times, and the strength of the finished steel strand is in the range of 1990~2050MPa. DETAILED DESCRIPTION

[0020] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in conjunction with specific embodiments.

[0021] The terms "including," "having," and any variations thereof, in the specification and claims of the present invention are intended to cover non-exclusive inclusions. The terms "first," "second," and the like in the specification and claims of the present invention are used to distinguish between different items, not to describe a particular order. "Multiple" means two or more, unless otherwise expressly specified.

[0022] Furthermore, references herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute a separate or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0023] The present invention provides an online aging method for wire rods for large-size high-strength steel strands. The process includes: hydrogenation in a tundish → slow cooling of billet stacking → heating of billets → high-speed wire rolling → spinning → heat preservation after phase change on a Stelmor line → coiling → heat preservation on a PF transport chain → finishing, packaging, and weighing → heat preservation in a slow cooling pit to obtain wire rods. During the heat preservation process after phase change on a Stelmor line, the initial roller speed is 0.56 m / s and increases by 0.01 m / s step by step. The heat preservation process is carried out in stages, including:

[0024] Stage 1: The temperature is 890±10℃~650±10℃, the fan is turned on, the cooling speed is controlled at 8~10℃ / s, and the heat preservation cover is opened;

[0025] The second stage: the temperature is 650±10℃~590±10℃, the cooling rate is controlled at 3~5℃ / s, and the heat preservation cover is opened;

[0026] The third stage: the temperature is 590±10℃~500±10℃, the fan is turned off, the insulation cover is closed, the cooling speed is controlled to 0.5~1.5℃ / s, and the residence time in the insulation cover is ≥90s.

[0027] Furthermore, the chemical composition (mass fraction) of the wire rod for large-size steel strand is: C 0.84%-0.87%, Si 0.50%-0.60%, Mn 0.60%-0.80%, P≤0.015%, S≤0.010%, Cr 0.25%-0.35%, Cu≤0.20%, Ni≤0.10%, N≤40ppm, O≤12ppm, H≤1.0ppm; the rest is Fe and unavoidable impurities;

[0028] The specification of high-strength wire rod is Φ14.0mm, which is used to prepare 1960MPa grade and above steel strands.

[0029] The control of N and O in the chemical composition is achieved through the quality control of raw and auxiliary materials in the converter smelting + refining process and the control of the deoxidation process, ensuring a high degree of cleanliness of the molten steel.

[0030] The H content in the chemical composition cannot exceed 5.0ppm, otherwise hydrogen-induced cracks are easily formed in the ingot, and it is impossible to reduce the gas content in the steel through online aging methods to improve the plasticity of the wire rod.

[0031] Furthermore, hydrogen is determined in the tundish: during the continuous casting process, the hydrogen content in the molten steel is monitored to control the hydrogen release in the subsequent slow cooling process of the cast billet.

[0032] Furthermore, the billet is stacked and slowly cooled: the continuous casting billet is cut to a fixed length, and then stacked and slowly cooled. The stacking slow cooling temperature is controlled at 350~450℃, and the stacking time is controlled at 32~48h.

[0033] Furthermore, the wire rod before the phase transformation of the Stelmor air-cooled line is obtained by heating the ingot in a walking beam heating furnace, high-speed wire rolling and spinning on a spinning machine. The uniform heating temperature of the ingot during heating is 1080-1150°C, and the heating time t=(0.7-1.2)H, where H is the thickness of the ingot in mm and the heating time t is in min. The spinning temperature of the wire rod is controlled at 890±10°C by water cooling in a post-rolling water tank.

[0034] Further, the temperature of the wire rod in the PF chain heat preservation corridor is controlled at 450℃±10℃, the residence time of the wire rod in the PF chain heat preservation corridor is ≥600s, and the temperature of the wire rod in the finishing process is controlled at 300℃±10℃.

[0035] Further, the finishing, packing and weighing processes of the wire rod are carried out in a closed environment, and wind blowing of the wire rod is strictly prohibited to further prolong the release time of residual stress, nitrogen and hydrogen during high temperature period, so as to improve the section shrinkage and realize the wire rod online aging.

[0036] Further, the wire rod is cooled to room temperature, and then the mechanical property test is carried out, the tensile strength of the wire rod is in the range of 1280-1320MPa, the section shrinkage is 30%-40%, and does not change with time, reaches the artificial aging test level, realizes the wire rod online aging plastic recovery, the organization of the wire rod is in the range of 1.0 level, and the wire rod can be directly dephosphorized and drawn after being sent to the user, the wire rod is in the range of 1.0 time, and the strength of the finished steel strand is in the range of 1990-2050MPa.

[0037] The wire rod is cooled to room temperature, and then the mechanical property test is carried out, the tensile strength of the wire rod is in the range of 1280-1320MPa, the section shrinkage is 30%-40%, and does not change with time, reaches the artificial aging test level, realizes the wire rod online aging plastic recovery, the organization of the wire rod is in the range of 1.0 level, and the wire rod can be directly dephosphorized and drawn after being sent to the user, the wire rod is in the range of 1.0 time, and the strength of the finished steel strand is in the range of 1990-2050MPa.

[0038] The wire rod is cooled to room temperature, and then the mechanical property test is carried out, the tensile strength of the wire rod is in the range of 1280-1320MPa, the section shrinkage is 30%-40%, and does not change with time, reaches the artificial aging test level, realizes the wire rod online aging plastic recovery, the organization of the wire rod is in the range of 1.0 level, and the wire rod can be directly dephosphorized and drawn after being sent to the user, the wire rod is in the range of 1.0 time, and the strength of the finished steel strand is in the range of 1990-2050MPa.

[0039] Example 1

[0040] A metal product company adopts the present application technology to prepare a wire rod for 1960MPa grade steel strand with a specification of Φ14.0mm, and the production process is as follows: intermediate ladle hydrogen setting, casting blank stacking slow cooling, casting blank step type heating furnace heating, high-speed wire rod mill rolling, wire rod discharging machine discharging, Stelmor wire phase change post-heat preservation, coiling, PF conveying chain long time heat preservation, finishing, packing, weighing, and wire rod slow cooling pit heat preservation.

[0041] The chemical composition (mass fraction) of the wire rod is as follows: C: 0.86%, Si: 0.52%, Mn: 0.75%, P: 0.011%, S: 0.009%, Cr 0.30%, Cu: 0.04%, Ni: 0.03%, N: 36ppm, O 10ppm, H 0.8ppm, and the rest is Fe and inevitable impurities.

[0042] The intermediate ladle molten steel is set to 4.5ppm.

[0043] Casting blank stacking slow cooling: the continuous casting square billet is cut to a specified size, and then is subjected to stacking slow cooling, the stacking slow cooling temperature is controlled at 350-450℃, and the stacking time is controlled at 40h.

[0044] The wire rod before phase transformation of the Stelmor air-cooled line is obtained by heating the billet in a walking beam heating furnace, high-speed wire rolling and spinning on a spinning machine. The billet specification is 200mm×200mm, the uniform heating temperature during billet heating is 1080~1150℃, the heating time is 210min, and the spinning temperature of the wire rod is controlled at 890±10℃ through water cooling control in a water tank after rolling.

[0045] The air cooling control parameters of the phase change process are: the initial roller speed is 0.56m / s, and increases by 0.01m / s step by step. (1) 890±10℃ to 650±10℃, using a maximum flow rate of 200,000m 3 / h fan, control the cooling rate to 8℃ / s to avoid the precipitation of pro-eutectoid cementite, and open the heat preservation cover at this time; (2) 650±10℃ to 590±10℃, use the maximum flow rate of 155,000m 3 / h fan, control the cooling rate to 4℃ / s, so that the high-temperature wire rod is supercooled to the sorbitization temperature range, fully sorbitized, and the transformation time is extended. At this time, the insulation cover is opened; (3) 590±10℃ to 500±10℃, turn off the fan, close the insulation cover, control the cooling rate to 1.0℃ / s, and the residence time in the insulation cover is 96s.

[0046] After coiling, the temperature of the wire rod entering the PF chain insulation corridor is controlled at 450℃±10℃, the residence time in the PF chain insulation corridor is 600s, and the temperature of the wire rod in the finishing process is controlled at 300℃±10℃.

[0047] The finishing, packaging and weighing processes of wire rods are carried out in a closed environment. It is strictly forbidden to cool the wire rods by wind, which further prolongs the release time of residual stress, nitrogen, hydrogen, etc. during high temperature, so as to increase the cross-sectional shrinkage rate and realize online aging of residual heat of wire rods.

[0048] Insulation in the slow cooling pit: The temperature of the wire rod entering the slow cooling pit is 200℃±10℃, and the slow cooling time is 24h.

[0049] After the wire rod is cooled to room temperature, the mechanical properties are tested. The tensile strength of the wire rod is in the range of 1280MPa, the cross-sectional area reduction is 36%, and it does not change with time, reaching the level of artificial aging test, and realizing the online aging plastic recovery of the wire rod. The network cementite and martensite grades in the organization are both 1.0. After being sent to the user, it can be directly dephosphorized and drawn. The wire breakage rate is 1.0 times per 100 tons, and the strength of the finished steel strand is 2030MPa.

[0050] Example 2

[0051] The chemical composition (mass fraction) of the wire rod is: C: 0.85%, Si: 0.55%, Mn: 0.80%, P: 0.008%, S: 0.008%, Cr: 0.35%, Cu: 0.05%, Ni: 0.03%, N: 40ppm, O: 12ppm, H: 1.0ppm, and the rest are Fe and unavoidable impurities.

[0052] The H content of molten steel in the tundish is set to 3.0ppm.

[0053] Billet stacking and slow cooling: The continuous casting billets are cut to a fixed length and then stacked and slowly cooled. The stacking slow cooling temperature is controlled at 350~450℃ and the stacking time is controlled at 32h.

[0054] The wire rod before phase transformation of the Stelmor air-cooled line is obtained by heating the billet in a walking beam heating furnace, high-speed wire rolling and spinning on a spinning machine. The billet specification is 200mm×200mm, the uniform heating temperature during billet heating is 1080~1150℃, the heating time is 140min, and the spinning temperature of the wire rod is controlled at 890±10℃ through water cooling control in the water tank after rolling.

[0055] The air cooling control parameters of the phase change process are: the initial roller speed is 0.56m / s, and increases by 0.01m / s step by step. (1) 890±10℃ to 650±10℃, using a maximum flow rate of 200,000m 3 / h, control the cooling rate to 9℃ / s to avoid the precipitation of pro-eutectoid cementite, and open the heat preservation cover at this time; (2) 650±10℃ to 590±10℃, use the maximum flow rate of 155,000m 3 / h fan, control the cooling rate to 3℃ / s, so that the high-temperature wire rod is supercooled to the sorbitization temperature range, fully sorbitized, and the transformation time is extended. At this time, the insulation cover is opened; (3) 590±10℃ to 500±10℃, turn off the fan, close the insulation cover, control the cooling rate to 1.5℃ / s, and the residence time in the insulation cover is 96s.

[0056] After coiling, the temperature of the wire rod entering the PF chain insulation corridor is controlled at 450℃±10℃, the residence time in the PF chain insulation corridor is 610s, and the temperature of the wire rod in the finishing process is controlled at 300℃±10℃.

[0057] The finishing, packaging and weighing processes of wire rods are carried out in a closed environment. It is strictly forbidden to cool the wire rods by wind, which further prolongs the release time of residual stress, nitrogen, hydrogen, etc. during high temperature, so as to increase the cross-sectional shrinkage rate and realize online aging of residual heat of wire rods.

[0058] Insulation in the slow cooling pit: The temperature of the wire rod entering the slow cooling pit is 200℃±10℃, and the slow cooling time is 24h.

[0059] After the wire rod is cooled to room temperature, the mechanical properties are tested. The tensile strength of the wire rod is in the range of 1300MPa, the cross-sectional area reduction is 40%, and it does not change with time, reaching the level of artificial aging test, and realizing the online aging plastic recovery of the wire rod. The network cementite and martensite grades in the organization are both level 0. After being sent to the user, it can be directly dephosphorized and drawn. The wire breakage rate is 0.7 times per 100 tons, and the strength of the finished steel strand is 2050MPa.

[0060] Example 3

[0061] The chemical composition (mass fraction) of the wire rod is: C: 0.87%, Si: 0.50%, Mn: 0.60%, P: 0.015%, S: 0.010%, Cr: 0.25%, Cu: 0.04%, Ni: 0.03%, N: 31ppm, O: 8ppm, H: 0.5ppm, and the rest are Fe and unavoidable impurities.

[0062] The H content of the tundish molten steel is set to 5.0ppm.

[0063] Billet stacking and slow cooling: The continuous casting billets are cut to a fixed length and then stacked and slowly cooled. The stacking slow cooling temperature is controlled at 350~450℃ and the stacking time is controlled at 48h.

[0064] The wire rod before phase transformation of the Stelmor air-cooled line is obtained by heating the billet in a walking beam heating furnace, high-speed wire rolling and spinning on a spinning machine. The billet specification is 200mm×200mm, the uniform heating temperature during billet heating is 1080~1150℃, the heating time is 240min, and the spinning temperature of the wire rod is controlled at 890±10℃ through water cooling control in a water tank after rolling.

[0065] The air cooling control parameters of the phase change process are: the initial roller speed is 0.56m / s, and increases by 0.01m / s step by step. (1) 890±10℃ to 650±10℃, using a maximum flow rate of 200,000m 3 / h fan, control the cooling rate to 10℃ / s to avoid the precipitation of pro-eutectoid cementite, and open the heat preservation cover at this time; (2) 650±10℃ to 590±10℃, use the maximum flow rate of 155,000m 3 / h fan, control the cooling rate to 4℃ / s, so that the high-temperature wire rod is supercooled to the sorbitization temperature range, fully sorbitized, and the transformation time is extended. At this time, the insulation cover is opened; (3) 590±10℃ to 500±10℃, turn off the fan, close the insulation cover, control the cooling rate to 0.5℃ / s, and the residence time in the insulation cover is 96s.

[0066] After coiling, the temperature of the wire rod entering the PF chain insulation corridor is controlled at 450℃±10℃, the residence time in the PF chain insulation corridor is 605s, and the temperature of the wire rod in the finishing process is controlled at 300℃±10℃.

[0067] The finishing, packaging and weighing processes of wire rods are carried out in a closed environment. It is strictly forbidden to cool the wire rods by wind, which further prolongs the release time of residual stress, nitrogen, hydrogen, etc. during high temperature, so as to increase the cross-sectional shrinkage rate and realize online aging of residual heat of wire rods.

[0068] Insulation in the slow cooling pit: The temperature of the wire rod entering the slow cooling pit is 200℃±10℃, and the slow cooling time is 24h.

[0069] After the wire rod is cooled to room temperature, the mechanical properties are tested. The tensile strength of the wire rod is in the range of 1320MPa, the cross-sectional area reduction is 30%, and it does not change with time, reaching the level of artificial aging test, and realizing the online aging plastic recovery of the wire rod. The network cementite and martensite grades in the organization are both 0.5. After being sent to the user, it can be directly dephosphorized and drawn. The wire breakage rate is 0.5 times per 100 tons, and the strength of the finished steel strand is 1990MPa.

[0070] Example 4

[0071] The chemical composition (mass fraction) of the wire rod is: C: 0.84%, Si: 0.60%, Mn: 0.71%, P: 0.012%, S: 0.008%, Cr: 0.28%, Cu: 0.04%, Ni: 0.03%, N: 39ppm, O: 11ppm, H: 0.6ppm, and the rest are Fe and unavoidable impurities.

[0072] The H content of molten steel in the tundish is set to 4.2ppm.

[0073] Billet stacking and slow cooling: The continuous casting billets are cut to a fixed length and then stacked and slowly cooled. The stacking slow cooling temperature is controlled at 350~450℃ and the stacking time is controlled at 40h.

[0074] The wire rod before phase transformation of the Stelmor air-cooled line is obtained by heating the billet in a walking beam heating furnace, high-speed wire rolling and spinning on a spinning machine. The billet specification is 200mm×200mm, the uniform heating temperature during billet heating is 1080~1150℃, the heating time is 220min, and the spinning temperature of the wire rod is controlled at 890±10℃ through water cooling control in a water tank after rolling.

[0075] The air cooling control parameters of the phase change process are: the initial roller speed is 0.56m / s, and increases by 0.01m / s step by step. (1) 890±10℃ to 650±10℃, using a maximum flow rate of 200,000m 3 / h fan, control the cooling rate to 9℃ / s to avoid the precipitation of pro-eutectoid cementite, and open the heat preservation cover at this time; (2) 650±10℃ to 590±10℃, use the maximum flow rate of 155,000m 3 / h fan, control the cooling rate to 5℃ / s, so that the high-temperature wire rod is supercooled to the sorbitization temperature range, fully sorbitized, and the transformation time is extended. At this time, the insulation cover is opened; (3) 590±10℃ to 500±10℃, turn off the fan, close the insulation cover, control the cooling rate to 0.8℃ / s, and the residence time in the insulation cover is 96s.

[0076] After coiling, the temperature of the wire rod entering the PF chain insulation corridor is controlled at 450℃±10℃, the residence time in the PF chain insulation corridor is 650s, and the temperature of the wire rod in the finishing process is controlled at 300℃±10℃.

[0077] The finishing, packaging and weighing processes of wire rods are carried out in a closed environment. It is strictly forbidden to cool the wire rods by wind, which further prolongs the release time of residual stress, nitrogen, hydrogen, etc. during high temperature, so as to increase the cross-sectional shrinkage rate and realize online aging of residual heat of wire rods.

[0078] Insulation in the slow cooling pit: The temperature of the wire rod entering the slow cooling pit is 200℃±10℃, and the slow cooling time is 24h.

[0079] After the wire rod is cooled to room temperature, the mechanical properties are tested. The tensile strength of the wire rod is in the range of 1310MPa, the cross-sectional area reduction is 35%, and it does not change with time, reaching the level of artificial aging test, and realizing the online aging plastic recovery of the wire rod. The network cementite in the structure is 1.0 level and the martensite is 0.5 level. After being sent to the user, it can be directly dephosphorized and drawn. The wire breakage rate is 0.8 times per 100 tons, and the strength of the finished steel strand is 2000MPa.

[0080] The above are exemplary embodiments disclosed in the present invention, but it should be noted that various changes and modifications may be made without departing from the scope of the embodiments disclosed in the claims. The functions, steps and / or actions of the method claims according to the disclosed embodiments described herein do not need to be performed in any particular order. In addition, although the elements disclosed in the embodiments of the present invention may be described or required in individual form, they may also be understood as multiple unless expressly limited to the singular.

[0081] It should be understood that, as used herein, the singular forms "a" and "an" are intended to include the plural forms as well, unless the context clearly supports an exception. It should also be understood that, as used herein, "and / or" is intended to include any and all possible combinations of one or more of the associated listed items.

[0082] The serial numbers of the embodiments disclosed in the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0083] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to limit the scope of the disclosure of the present invention (including the claims) to these examples. Within the spirit of the present invention, the technical features of the above embodiments or different embodiments may be combined, and many other variations exist in different aspects of the above embodiments, which are not provided in detail for the sake of clarity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An online aging method for large-size high-strength steel strand wire rod, characterized in that: The process includes: hydrogen addition in tundish → slow cooling of billet stacking → heating of billet → high-speed wire rolling → spinning → heat preservation after phase change on Stelmor line → coiling → heat preservation on PF transport chain → finishing, packaging, weighing → heat preservation in slow cooling pit to obtain wire rod. During the heat preservation process after phase change on Stelmor line, the initial roller speed is 0.56m / s and increases by 0.01m / s step by step. The heat preservation process is carried out in stages, including: Stage 1: The temperature is 890±10℃~650±10℃, the fan is turned on, the cooling speed is controlled at 8~10℃ / s, and the heat preservation cover is opened; The second stage: the temperature is 650±10℃~590±10℃, the cooling rate is controlled at 3~5℃ / s, and the heat preservation cover is opened; The third stage: the temperature is 590±10℃~500±10℃, the fan is turned off, the heat preservation cover is closed, the cooling rate is controlled to 0.5~1.5℃ / s, and the residence time in the heat preservation cover is ≥90s; The fourth stage: the temperature is 450±10℃~300±10℃, and insulation is completed in the insulation corridor; The fifth stage: The temperature is 200℃±10℃~room temperature, and insulation is completed in the aging pit.

2. The online aging method for wire rod for large-size high-strength steel strand according to claim 1, characterized in that: Calculated by mass fraction, the chemical composition of the wire rod includes: C: 0.84%~0.87%, Si: 0.50%~0.60%, Mn: 0.60%~0.80%, P≤0.015%, S≤0.010%, Cr: 0.25%~0.35%, Cu≤0.20%, Ni≤0.10%, N≤40ppm, O≤12ppm, H≤1.0ppm, and the rest is Fe and unavoidable impurities.

3. The online aging method for wire rod for large-size high-strength steel strand according to claim 1, characterized in that: After coiling, the temperature of the wire rod entering the PF chain insulation corridor is controlled at 450℃±10℃, the residence time in the PF chain insulation corridor is ≥600s, and the temperature of the wire rod in the finishing process is controlled at 300℃±10℃.

4. The online aging method for wire rod for large-size high-strength steel strand according to claim 1, characterized in that: In the ingot stacking slow cooling process, the temperature is controlled at 350-450° C., and the stacking time is controlled at 32-48 hours.

5. The online aging method for wire rod for large-size high-strength steel strand according to claim 1, characterized in that: In the tundish hydrogen determination process, the hydrogen content in the molten steel is monitored in real time, and the hydrogen content does not exceed 5.0 ppm.

6. The online aging method for wire rod for large-size high-strength steel strand according to claim 1, characterized in that: In the slab heating process, the slab is heated at an soaking temperature of 1080-1150° C., and the heating time t=(0.7-1.2)H, where H is the slab thickness in mm and the heating time t is in min.

7. The online aging method for wire rod for large-size high-strength steel strand according to claim 1, characterized in that: The casting blank is heated by a walking beam heating furnace.

8. The online aging method for wire rod for large-size high-strength steel strand according to claim 1, characterized in that: After the high-speed wire rolling process, water cooling control is performed in the post-rolling water tank so that the wire drawing temperature of the wire rod is controlled to be 890±10°C.

9. The online aging method for wire rod for large-size high-strength steel strand according to claim 1, characterized in that: The maximum flow rate of the fan in the first stage is 200,000 m 3 / h, the maximum flow of the fan in the second stage is 155,000m 3 / h.

10. The online aging method for wire rod for large-size high-strength steel strand according to claim 1, characterized in that: The temperature of the wire rod entering the slow cooling pit is 200°C ± 10°C, and the slow cooling time is 22 to 24 hours.