CN114000048B - SWRH82B hot-rolled wire rod for prestressed steel strand with nominal diameter of 12.5mm and preparation method thereof - Google Patents

SWRH82B hot-rolled wire rod for prestressed steel strand with nominal diameter of 12.5mm and preparation method thereof Download PDF

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CN114000048B
CN114000048B CN202111154032.3A CN202111154032A CN114000048B CN 114000048 B CN114000048 B CN 114000048B CN 202111154032 A CN202111154032 A CN 202111154032A CN 114000048 B CN114000048 B CN 114000048B
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steel
molten steel
slag
weight percent
equal
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CN114000048A (en
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陈伟
张卫强
张红斌
刘林刚
尹波
王卫东
李艳萍
邹应春
王文锋
杨春雷
马松
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Wugang Group Kunming Iron and Steel Co Ltd
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Wugang Group Kunming Iron and Steel Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C1/00—Refining of pig-iron; Cast iron
    • C21C1/02—Dephosphorising or desulfurising
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28—Manufacture of steel in the converter
    • C21C5/36—Processes yielding slags of special composition
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0025—Adding carbon material
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/06—Deoxidising, e.g. killing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/064—Dephosphorising; Desulfurising
    • C21C7/0645—Agents used for dephosphorising or desulfurising
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/10—Handling in a vacuum
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C22C33/06—Making ferrous alloys by melting using master alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium

Abstract

The invention discloses a SWRH82B hot-rolled wire rod with nominal diameter of 12.5mm for a high-cleanliness high-strength prestressed steel strand and a preparation method thereof. The hot-rolled wire rod comprises the following chemical components: 0.79 to 0.83 weight percent of C, 0.18 to 0.27 weight percent of Si, 0.78 to 0.87 weight percent of Mn, 0.25 to 0.30 weight percent of Cr, less than or equal to 0.007 weight percent of S, less than or equal to 0.012 weight percent of P, less than or equal to 0.0025 weight percent of N, less than or equal to 0.0015 weight percent of O, less than or equal to 0.0002 weight percent of H, and the balance of Fe and inevitable impurities. The preparation method is realized by the following steps in sequence: molten iron pretreatment desulfurization, molten steel smelting, deoxidation alloying, molten steel LF furnace refining, molten steel VD furnace vacuum refining, molten steel casting, billet heating, rolling and cooling control. The process has the characteristics of strong process applicability and controllability and the like, the produced wire rod has high steel cleanliness, few inclusions, low gas content, good microstructure proportion, sorbite content of more than or equal to 92 percent and reticular cementite grade of less than or equal to 0.5 grade, has excellent plastic toughness and drawing deformation capability and good fatigue resistance, and can effectively avoid wire breakage in the drawing process when manufacturing prestressed wires and steel stranded wires.

Description

SWRH82B hot-rolled wire rod for prestressed steel strand with nominal diameter of 12.5mm and preparation method thereof
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to a SWRH82B hot-rolled wire rod with a nominal diameter of 12.5mm and for a high-cleanliness high-strength prestressed steel strand and a preparation method thereof.
Background
The hot-rolled wire rod SWRH82B for the high-strength prestressed steel strand is mainly used for manufacturing prestressed steel wires, steel strand wires and the like, is widely used for a plurality of major projects such as bridges, airports, overpasses, power stations, dams, high-rise buildings and the like, bears the comprehensive action of various loads in the use process, and is required to have higher yield strength, tensile strength and toughness so as to prevent fracture and deformation under impact or overload; meanwhile, the steel is required to have good processing technological properties in the processing process, and has higher requirements on the deep processing properties of the parent metal. The SWRH82B hot-rolled wire rod serving as the steel strand raw material not only needs to ensure good drawing performance, but also has higher requirements on the strength performance of the original wire rod according to different grade requirements, and simultaneously requires that the wire rod has good surface quality, smaller same-winding strength and same-circle strength fluctuation, and the molten steel has higher cleanliness.
At present, the domestic production of the SWRH82B high-speed wire rod for the steel strand mainly adopts a molten iron pretreatment → smelting in a top-bottom combined blown converter → refining in an LF furnace → vacuum refining in an RH furnace → whole-process protection casting of a small square billet → a rolling control and cooling control process route of a high-wind-rate high-speed rolling mill with a reducing sizing mill set. Because a small amount of precious micro-alloy is added into the steel, the production cost is high by adopting the process; in addition, the process has high requirement on the precision of equipment, and the produced SWRH82B hot rolled wire rod has the following defects: the high sorbite rate is unstable, a small amount of martensite and 1.5-3.0-grade net cementite structure exist, the reduction of area is low, the microstructure proportion of steel is not optimal, a small amount of wire breakage phenomenon still exists in the drawing process of the wire rod, and the use of the product is restricted.
Aiming at the problems, the invention aims to provide a high-cleanliness high-strength hot-rolled wire rod with the nominal diameter of 12.5mmSWRH82B for prestressed steel strands and a preparation method thereof, so as to better meet the use requirements of users.
Disclosure of Invention
The first purpose of the invention is to provide a SWRH82B hot-rolled wire rod for a high-cleanliness high-strength prestressed steel strand with a nominal diameter of 12.5mm, and the second purpose of the invention is to provide a preparation method of the SWRH82B hot-rolled wire rod for the high-cleanliness high-strength prestressed steel strand with the nominal diameter of 12.5 mm.
The first purpose of the invention is realized by that a high-cleanliness high-strength prestressed steel strand hot-rolled wire rod with a nominal diameter of 12.5mm is formed by SWRH82B, and the wire rod comprises the following chemical components in parts by weight: 0.79 to 0.83 weight percent of C, 0.18 to 0.27 weight percent of Si, 0.78 to 0.87 weight percent of Mn, 0.25 to 0.30 weight percent of Cr, less than or equal to 0.007 weight percent of S, less than or equal to 0.012 weight percent of P, less than or equal to 0.0025 weight percent of N, less than or equal to 0.0015 weight percent of O, less than or equal to 0.0002 weight percent of H, and the balance of Fe and inevitable impurities.
The second purpose of the invention is realized by a preparation method of a high-cleanliness high-strength prestressed steel strand hot-rolled wire rod with a nominal diameter of 12.5mm by using SWRH82B, which comprises the following steps in sequence:
A. molten iron pretreatment and desulfurization: conveying blast furnace molten iron to a KR method molten iron pretreatment device for desulfurization treatment, wherein the temperature of the molten iron is more than or equal to 1320 ℃, the insertion depth of a stirring head is controlled to be 2100mm, and the amount of the stirring head is 12.0-15.0 kg/tSteelAdding a conventional CaO desulfurizer for desulfurization treatment, and controlling the stirring time to be 8 minutes; after stirring, carrying out slag skimming operation to ensure that the iron water surface in the steel ladle is exposed to be more than or equal to 4/5, and skimming the desulfurized slag; the pretreated molten iron comprises the following components: 4.2 to 4.5 weight percent of C, 0.25 to 0.40 weight percent of Si, 0.30 to 0.50 weight percent of Mn, 0.080 to 0.100 weight percent of P, less than or equal to 0.008 weight percent of S and the balance of Fe and inevitable impurities; the blast furnace molten iron comprises the following chemical components: c4.2-4.5 wt%, Si 0.25-0.40wt%, Mn 0.30-0.50wt%, and P0.080-0 wt%.100wt%, S less than or equal to 0.025wt%, and the balance of Fe and inevitable impurities;
B. smelting molten steel: respectively processing the pretreated molten iron and the scrap steel in the step A according to 940kg/tSteel、135kg/tSteelThe mixed slag is added into an LD converter according to the mixture ratio to carry out conventional top-bottom combined blowing, the converter smelting adopts a double-slag method, and the first slag charge in the earlier stage of smelting is respectively 16-20 kg/tSteel、12～15kg/tSteel、1～2kg/tSteelAdding lime, light-burned dolomite and magnesite balls for slagging, adding a second batch of slag after the first batch of slag is subjected to slagging and the slag is poured into a furnace, wherein the second batch of slag is respectively 8-10 kg/tSteel、10kg/tSteelAdding lime and light-burned dolomite for slagging again, and controlling the end point molten steel C content to be more than or equal to 0.45wt%, the O content to be less than or equal to 0.030wt% and the tapping temperature to be less than or equal to 1600 ℃; 2.0kg/t of steel ladle bottom before tappingSteelAdding the following slag washing desulfurizing agent in the following mass ratio for slag washing: CaF28.5wt%，SiO2 5.2wt%，CaO 57.5wt%，Na28.3wt% of O, 2.5wt% of Al, 0.056wt% of P, 0.082wt% of S and the balance of inevitable impurities, wherein a whole-process bottom argon blowing process is adopted in the tapping process, and the flow rate of argon is controlled to be 15-20 NL/min; the chemical components of the scrap steel comprise 0.20-0.25wt% of C, 0.35-0.60wt% of Si, 1.15-1.50wt% of Mn, 0.015-0.025wt% of P, 0.018-0.030wt% of S, and the balance of Fe and inevitable impurities;
C. and (3) deoxidation alloying: tapping the molten steel, and when the amount of the molten steel in the ladle is more than 1/4, carrying out the following deoxidation alloying sequence: low Al-Si-Ca-Ba → high-carbon ferrochrome → high-carbon ferromanganese → low-nitrogen carburant, and the following substances are sequentially added into a steel ladle: according to 3.5-4.2 kg/tSteelAdding the following low aluminum, silicon, calcium and barium in mass ratio: 52.5wt% of Si, 12.5wt% of Ba, 10.3wt% of Ca, 1.2wt% of Al, and the balance of Fe and inevitable impurities; according to 2.9-3.5 kg/tSteelAdding the following high-carbon ferrochrome in mass ratio: 56.7wt% of Cr, 7.2wt% of C, and the balance of Fe and inevitable impurities; according to the weight of 9.6-10.9 kg/tSteelAdding the following high-carbon ferromanganese in mass ratio: 75.6wt% of Mn, 6.7wt% of C and the balance of Fe and inevitable impurities; according to 1.2-2.4 kg/tSteelAdding the following low-nitrogen carburant in mass ratio:98.1wt% of C, 0.025wt% of N, 0.035wt% of P, 0.065wt% of S and the balance of inevitable impurities; when the amount of the molten steel in the steel ladle reaches 4/5, the alloy is added; after tapping, hoisting the molten steel to an LF furnace for refining;
D. refining in a molten steel LF furnace: and C, hoisting the molten steel after the steel tapping in the step C to an LF refining station to connect an argon gas zone, starting argon gas, blowing argon for 2 minutes by adopting a small argon amount of 20-30 NL/min, slagging by adopting a gear of 7-9 for a lower electrode, and adding 0.4-0.8 kg/t of ferrosilicon powderSteelSlag mixing; after the furnace is electrified for 8 minutes, lifting an electrode to observe the slagging condition in the furnace, and then measuring and sampling the temperature; if the slag condition is relatively dilute, adding 4.0-6.0 kg/t limeSteelThen adding 0.6kg/t ferrosilicon powderSteel0.5kg/t calcium carbideSteelRegulating slag, otherwise, adding premelted refining slag for regulating slag, and controlling the slag alkalinity to be 5.0-6.0; according to the analysis result of the steel sample, adding ferrosilicon powder, a low-nitrogen carburant and alloy to adjust the components of the molten steel, ensuring that all chemical components are in a target range, and controlling the oxygen activity of the molten steel to be less than or equal to 10 ppm; controlling the number of times of the lower electrode in the refining process to be less than or equal to 3 times; then heating the molten steel to 1640-1655 ℃, carrying out soft argon blowing on the molten steel by adopting a small argon flow of 20-25 NL/min under a white slag state, wherein the soft argon blowing time is 20 minutes, and then adding a molten steel covering agent, wherein the adding amount is controlled to be 1.0kg/tSteelThen hoisting the molten steel to a vacuum refining station of a VD furnace;
E. vacuum refining in a molten steel VD furnace: after the molten steel is hoisted to a VD vacuum refining furnace, an argon blowing pipe is connected, argon is started to be blown for 2 minutes by adopting a small argon flow of 20-30 NL/min, then oxygen and hydrogen are determined for the molten steel, and meanwhile, temperature measurement and sampling are carried out; after sampling, turning on a vacuum tank cover vehicle to a working position, closing the vacuum tank cover, vacuumizing, starting vacuum-maintaining degassing treatment when vacuum is pumped to 67Pa, simultaneously performing bottom blowing argon treatment, controlling the flow of argon to be 30-40 NL/min, and degassing the molten steel for 15 minutes under the condition of vacuum degree of 67 Pa; closing the vacuum main valve after the vacuum degassing treatment is finished, lifting the tank cover, sampling the molten steel, and determining oxygen and hydrogen; then, carrying out soft argon blowing treatment on the molten steel with small argon flow of 20-30 NL/min for 2 minutes; after the soft argon blowing of the molten steel is finished, adding the molten steel covering agent, wherein the adding amount is controlled to be 1.0kg/tSteelThen, hoisting the molten steel to a casting station;
F. casting molten steel: under the conditions that the temperature of a tundish is 1480-1490 ℃, the pulling speed is 1.8m/min, the secondary cooling specific water amount is 0.8-1.0L/kg, the electromagnetic stirring current intensity of a crystallizer is 270A, and the operating frequency is 4HZ, the molten steel in the step E is continuously cast into a billet with the cross section of 150mm multiplied by 150mm in a whole-process protection manner by adopting an R9m straight arc continuous straightening 5-flow small square billet casting machine;
G. heating a steel billet: feeding the steel billets obtained in the step F into a heating furnace with the furnace temperature of a soaking section of 1070-1100 ℃, heating for 50-70 minutes, discharging steel from the steel billets, discharging scales from the steel billets through high-pressure water, and pushing the steel billets to a high-speed wire rod mill for rolling;
H. rolling and cooling control: the billet steel in the step G is sent into a high-speed wire rod rolling mill with 28 racks for rolling, and is subjected to rough rolling for 6 passes under the rolling condition that the speed is 0.15 m/s; then, under the rolling condition that the speed is 10.0m/s, carrying out medium rolling for 12 passes; then pre-water cooling and controlled cooling are carried out before finish rolling, and the cooling water quantity is 120m3Controlling the cooling for 3 seconds under the condition of/h; then, finish rolling for 5 passes under the rolling conditions that the finish rolling temperature is 880-910 ℃ and the speed is 20 m/s; then, spinning at the temperature of 820-840 ℃ and the speed of 20-30 m/s; after spinning, the wire rod enters a stelmor air cooling line for controlled cooling; the stelmor air-cooled line control cold-time fan and the heat-preservation cover cap are all opened, the air quantity of the fan is 11.5m3The speed of the roller way is controlled to be 0.85-1.05 m/s; and controlling the temperature of the coil collection to be 530-550 ℃ after stelmor air cooling is finished, and naturally air cooling the coil to room temperature to obtain a high-cleanliness high-strength prestressed steel strand hot-rolled wire rod with a nominal diameter of 12.5mm, wherein the wire rod is hot-rolled by SWRH 82B.
The invention provides a preparation method of a SWRH82B hot-rolled wire rod for a high-cleanliness high-strength prestressed steel strand with a nominal diameter of 12.5mm, wherein a top-bottom combined blowing full-process argon blowing mode is adopted for converter smelting, molten steel at a smelting end point is subjected to high carbon-drawing tapping, the end point C is controlled to be more than or equal to 0.45wt%, a low-nitrogen carburant with the content of N0.025 wt% is simultaneously adopted for recarburization, a slag washing desulfurizer is adopted for full-process slag washing in the tapping process, and the content of molten steel [ O ] is reduced]、[N]The gas content greatly improves the cleanliness of the molten steel; the converter smelting adopts a double slag method for dephosphorization, and the dephosphorization rate>93%, is significantThe P content of the molten steel at the end point is reduced, and the content of harmful elements in the molten steel is greatly reduced; the LF furnace adopts ferrosilicon powder and a low-nitrogen increasing agent to adjust slag and deoxidize, thereby avoiding Al2O3Brittle inclusions are formed, and the drawing performance is improved; the refining period of the white slag of the LF furnace is controlled for 20 minutes, so that impurities in molten steel are promoted to fully float and be removed, and the cleanliness of the molten steel is improved; the LF furnace refining molten steel is subjected to vacuum refining treatment by a VD furnace, so that the gas content and inclusions in the steel are obviously reduced, P is less than or equal to 0.012wt%, S is less than or equal to 0.007wt%, O is less than or equal to 0.0015wt%, N is less than or equal to 0.0025wt%, H is less than or equal to 0.0002wt%, and nonmetallic inclusions are less than or equal to 1.5 grade, so that the ductility and the drawing performance of the wire rod are obviously improved; the steel rolling process controls lower initial rolling temperature, finish rolling temperature and spinning temperature, and promotes the refinement of ferrite grains; the cooling of the wire rod after spinning is controlled by adopting a stelmor cooling mode, and the air quantity is 11.6 ten thousand m3The 10 medium air volume fans are used for air cooling, so that the formation of a martensite structure is avoided; the stelmor controlled cooling is carried out at a high roller way speed (0.90-1.05m/s), the strength fluctuation of the same coil and the same ring is reduced, a fine sorbite and pearlite microstructure is obtained, the sorbite content is more than or equal to 92%, the mesh cementite level is less than or equal to 0.5, the plastic toughness and the drawing deformation capacity of the steel are obviously improved, and the wire breakage phenomenon in the drawing process of the wire rod is effectively avoided.
The invention has the beneficial effects that:
the process has the characteristics of strong process applicability, strong controllability and the like, and through the integrated innovation of multiple processes such as converter smelting, deoxidation alloying process, steel tapping slag washing, LF furnace refining, VD furnace vacuum refining, continuous casting, steel rolling heating system, rolling control, stelmor controlled cooling and the like, the produced SWRH82B wire rod has high steel cleanliness, few inclusions, low gas content (O is less than or equal to 0.0015wt%, N is less than or equal to 0.0025wt%, H is less than or equal to 0.0002wt%), good microstructure proportion (fine sorbite and pearlite), sorbite content is more than or equal to 92%, and reticular cementite level is less than or equal to 0.5 level, so that the wire rod has excellent plastic toughness, drawing deformation capability and good fatigue resistance, and the wire breaking phenomenon in the drawing process can be effectively avoided when the wire rod is used for manufacturing prestressed wires and steel stranded wires, and the market competitiveness is remarkably improved.
Detailed Description
The present invention is further illustrated by the following examples, which are not intended to be limiting in any way, and any modifications or alterations based on the teachings of the present invention are intended to fall within the scope of the present invention.
The invention relates to a high-cleanliness high-strength prestressed steel strand SWRH82B hot-rolled wire rod with a nominal diameter of 12.5mm, which comprises the following chemical components in parts by weight: 0.79 to 0.83 weight percent of C, 0.18 to 0.27 weight percent of Si, 0.78 to 0.87 weight percent of Mn, 0.25 to 0.30 weight percent of Cr, less than or equal to 0.007 weight percent of S, less than or equal to 0.012 weight percent of P, less than or equal to 0.0025 weight percent of N, less than or equal to 0.0015 weight percent of O, less than or equal to 0.0002 weight percent of H, and the balance of Fe and inevitable impurities.
The high-cleanliness high-strength prestressed steel strand with the nominal diameter of 12.5mm is prepared by using an SWRH82B hot rolling wire rod through the following process steps:
A. molten iron pretreatment and desulfurization: conveying blast furnace molten iron to a KR method molten iron pretreatment device for desulfurization treatment, wherein the temperature of the molten iron is more than or equal to 1320 ℃, the insertion depth of a stirring head is controlled to be 2100mm, and the amount of the stirring head is 12.0-15.0 kg/tSteelAdding a conventional CaO desulfurizer for desulfurization treatment, and controlling the stirring time to be 8 minutes; after stirring, carrying out slag skimming operation to ensure that the exposure of the molten iron surface in the steel ladle is more than or equal to 4/5, and skimming the desulfurized slag; the pretreated molten iron comprises the following components: 4.2 to 4.5 weight percent of C, 0.25 to 0.40 weight percent of Si, 0.30 to 0.50 weight percent of Mn, 0.080 to 0.100 weight percent of P, less than or equal to 0.008 weight percent of S and the balance of Fe and inevitable impurities; the blast furnace molten iron comprises the following chemical components: c4.2-4.5 wt%, Si 0.25-0.40wt%, Mn 0.30-0.50wt%, P0.080-0.100 wt%, S less than or equal to 0.025wt%, and Fe and inevitable impurities in balance;
B. smelting molten steel: respectively processing the pretreated molten iron and the scrap steel in the step A according to 940kg/tSteel、135kg/tSteelThe mixed slag is added into an LD converter according to the mixture ratio to carry out conventional top-bottom combined blowing, the converter smelting adopts a double-slag method, and the first slag charge in the earlier stage of smelting is respectively 16-20 kg/tSteel、12～15kg/tSteel、1～2kg/tSteelAdding lime, light-burned dolomite and magnesite balls for slagging, adding a second batch of slag after the first batch of slag is subjected to slagging and the slag is poured into a furnace, wherein the second batch of slag is respectively 8-10 kg/tSteel、10kg/tSteelAdding lime,Slagging is carried out on the lightly calcined dolomite again, the C content of molten steel at the end point is controlled to be more than or equal to 0.45wt%, the O content is controlled to be less than or equal to 0.030wt%, and the tapping temperature is controlled to be less than or equal to 1600 ℃; 2.0kg/t of steel ladle bottom before tappingSteelAdding the following slag washing desulfurizing agent in the following mass ratio for slag washing: CaF28.5wt%，SiO2 5.2wt%，CaO 57.5wt%，Na28.3wt% of O, 2.5wt% of Al, 0.056wt% of P, 0.082wt% of S and the balance of inevitable impurities, wherein a whole-process bottom argon blowing process is adopted in the tapping process, and the flow rate of argon is controlled to be 15-20 NL/min; the chemical components of the scrap steel comprise 0.20-0.25wt% of C, 0.35-0.60wt% of Si, 1.15-1.50wt% of Mn, 0.015-0.025wt% of P, 0.018-0.030wt% of S, and the balance of Fe and inevitable impurities;
C. and (3) deoxidation alloying: tapping the molten steel, and when the amount of the molten steel in the ladle is more than 1/4, carrying out the following deoxidation alloying sequence: low Al-Si-Ca-Ba → high-carbon ferrochrome → high-carbon ferromanganese → low-nitrogen carburant, and the following substances are sequentially added into a steel ladle: according to 3.5-4.2 kg/tSteelAdding the following low aluminum, silicon, calcium and barium in mass ratio: 52.5wt% of Si, 12.5wt% of Ba, 10.3wt% of Ca, 1.2wt% of Al, and the balance of Fe and inevitable impurities; according to 2.9-3.5 kg/tSteelAdding the following high-carbon ferrochrome in mass ratio: 56.7wt% of Cr, 7.2wt% of C, and the balance of Fe and inevitable impurities; according to the weight of 9.6-10.9 kg/tSteelAdding the following high-carbon ferromanganese in mass ratio: 75.6wt% of Mn, 6.7wt% of C and the balance of Fe and inevitable impurities; according to 1.2-2.4 kg/tSteelAdding the following low-nitrogen carburant in mass ratio: 98.1wt% of C, 0.025wt% of N, 0.035wt% of P, 0.065wt% of S and the balance of inevitable impurities; when the amount of the molten steel in the steel ladle reaches 4/5, the alloy is added; after tapping, hoisting the molten steel to an LF furnace for refining;
D. refining in a molten steel LF furnace: and C, hoisting the molten steel after the steel tapping in the step C to an LF refining station to connect an argon gas zone, starting argon gas, blowing argon for 2 minutes by adopting a small argon amount of 20-30 NL/min, slagging by adopting a gear of 7-9 for a lower electrode, and adding 0.4-0.8 kg/t of ferrosilicon powderSteelSlag mixing; after the furnace is electrified for 8 minutes, lifting an electrode to observe the slagging condition in the furnace, and then measuring and sampling the temperature; if the slag condition is relatively dilute, adding 4.0-6.0 kg/t limeSteelThen adding ferrosilicon0.6kg/t of powderSteel0.5kg/t calcium carbideSteelRegulating slag, otherwise, adding premelted refining slag for regulating slag, and controlling the slag alkalinity to be 5.0-6.0; according to the analysis result of the steel sample, adding ferrosilicon powder, a low-nitrogen carburant and alloy to adjust the components of the molten steel, ensuring that all chemical components are in a target range, and controlling the oxygen activity of the molten steel to be less than or equal to 10 ppm; controlling the number of times of the lower electrode in the refining process to be less than or equal to 3 times; then heating the molten steel to 1640-1655 ℃, carrying out soft argon blowing on the molten steel by adopting a small argon flow of 20-25 NL/min under a white slag state, wherein the soft argon blowing time is 20 minutes, and then adding a molten steel covering agent, wherein the adding amount is controlled to be 1.0kg/tSteelThen hoisting the molten steel to a vacuum refining station of a VD furnace;
E. vacuum refining in a molten steel VD furnace: after the molten steel is hoisted to a VD vacuum refining furnace, an argon blowing pipe is connected, argon is started to be blown for 2 minutes by adopting a small argon flow of 20-30 NL/min, then oxygen and hydrogen are determined for the molten steel, and meanwhile, temperature measurement and sampling are carried out; after sampling, turning on a vacuum tank cover vehicle to a working position, closing the vacuum tank cover, vacuumizing, starting vacuum-maintaining degassing treatment when vacuum is pumped to 67Pa, simultaneously performing bottom blowing argon treatment, controlling the flow of argon to be 30-40 NL/min, and degassing the molten steel for 15 minutes under the condition of vacuum degree of 67 Pa; closing the vacuum main valve after the vacuum degassing treatment is finished, lifting the tank cover, sampling the molten steel, and determining oxygen and hydrogen; then, carrying out soft argon blowing treatment on the molten steel with small argon flow of 20-30 NL/min for 2 minutes; after the soft argon blowing of the molten steel is finished, adding the molten steel covering agent, wherein the adding amount is controlled to be 1.0kg/tSteelThen, hoisting the molten steel to a casting station;
F. casting molten steel: under the conditions that the temperature of a tundish is 1480-1490 ℃, the pulling speed is 1.8m/min, the secondary cooling specific water amount is 0.8-1.0L/kg, the electromagnetic stirring current intensity of a crystallizer is 270A, and the operating frequency is 4HZ, the molten steel in the step E is continuously cast into a billet with the cross section of 150mm multiplied by 150mm in a whole-process protection manner by adopting an R9m straight arc continuous straightening 5-flow small square billet casting machine;
G. heating a steel billet: feeding the steel billets obtained in the step F into a heating furnace with the furnace temperature of a soaking section of 1070-1100 ℃, heating for 50-70 minutes, discharging steel from the steel billets, discharging scales from the steel billets through high-pressure water, and pushing the steel billets to a high-speed wire rod mill for rolling;
H. rolling and cooling control: the billet steel in the step G is sent into a high-speed wire rod rolling mill with 28 racks for rolling, and is subjected to rough rolling for 6 passes under the rolling condition that the speed is 0.15 m/s; then, under the rolling condition that the speed is 10.0m/s, carrying out medium rolling for 12 passes; then pre-water cooling and controlled cooling are carried out before finish rolling, and the cooling water quantity is 120m3Controlling the cooling for 3 seconds under the condition of/h; then, finish rolling for 5 passes under the rolling conditions that the finish rolling temperature is 880-910 ℃ and the speed is 20 m/s; then, spinning at the temperature of 820-840 ℃ and the speed of 20-30 m/s; after spinning, the wire rod enters a stelmor air cooling line for controlled cooling; the stelmor air-cooled line control cold-time fan and the heat-preservation cover cap are all opened, the air quantity of the fan is 11.5m3The speed of the roller way is controlled to be 0.85-1.05 m/s; and controlling the temperature of the coil collection to be 530-550 ℃ after stelmor air cooling is finished, and naturally air cooling the coil to room temperature to obtain a high-cleanliness high-strength prestressed steel strand hot-rolled wire rod with a nominal diameter of 12.5mm, wherein the wire rod is hot-rolled by SWRH 82B.
In the step B, the baked and dried waste vanadium slag added into the steel ladle comprises the following components: 98.1wt% of C, 0.025wt% of N, 0.035wt% of P, 0.065wt% of S and the balance of inevitable impurities.
In the step D, the low-nitrogen carburant comprises the following components in percentage by mass: the mass ratio of C is 98.1wt%, N is 0.025wt%, P is 0.035wt%, S is 0.065wt%, and the rest is inevitable impurities.
And in the step F, a billet caster adopted for casting the molten steel into the section steel billet is an R9m straight-arc continuous straightening 5-machine 5-flow billet caster.
In the step F, the secondary cooling specific water amount refers to: the ratio of the total water consumption in unit time of the secondary cooling area of the continuous casting machine to the mass of the casting blank passing through the secondary cooling area in unit time is an index of the secondary cooling water spray intensity of continuous casting by taking L/kg as a unit.
And G, controlling the steel tapping temperature of the steel billet to be 980-1010 ℃.
In the step H, the cooling water quantity of the pre-water cooling device is 120m3And/h, the controlled cooling time is 3 seconds.
In the step H, the stelmor air cooling line cooling mode is as follows:the fan and the heat preservation cover cap are all opened, and the air quantity of the fan is 11.5 ten thousand meters3The speed of the roller way is controlled to be 0.85-1.05 m/s.
The mechanical properties and the microstructure of the high-cleanliness high-strength prestressed steel strand hot-rolled wire rod for the SWRH82B with the nominal diameter of 12.5mm are respectively shown in the table 1 and the table 2.
TABLE 1 mechanical Properties of the nominal 12.5mm SWRH82B wire rod produced according to the invention
Figure 378124DEST_PATH_IMAGE001
TABLE 2 metallographic structure of wire rod of nominal diameter 12.5mmSWRH82B produced by the invention
Figure 498527DEST_PATH_IMAGE002
Example 1
A. Molten iron pretreatment and desulfurization: blast furnace molten iron (chemical components C4.2 wt%, Si 0.25wt%, Mn 0.30wt%, P0.080 wt%, S0.015 wt%, and the balance Fe and inevitable impurities) is transported to KR molten iron pretreatment device for desulfurization treatment, molten iron temperature is 1320 deg.C, stirring head insertion depth is controlled to 2100mm, and stirring head insertion depth is 12.0kg/tSteelAdding a conventional CaO desulfurizer for desulfurization treatment, and controlling the stirring time to be 8 minutes; after stirring, carrying out slag skimming operation to ensure that the iron water surface in the steel ladle is exposed to be more than or equal to 4/5, and skimming the desulfurized slag; the components of the pretreated molten iron are controlled as follows: 4.2wt% of C, 0.25wt% of Si, 0.30wt% of Mn, 0.080wt% of P, 0.005wt% of S, and the balance Fe and inevitable impurities.
B. Smelting molten steel: respectively 940kg/t of pretreated deep desulfurization molten iron (C4.2 wt%, Si 0.25wt%, Mn 0.30wt%, P0.080 wt%, S0.005 wt%, and the balance of Fe and inevitable impurities) and high-quality scrap (chemical components C0.20 wt%, Si 0.35wt%, Mn 1.15wt%, P0.015 wt%, S0.018 wt%, and the balance of Fe and inevitable impurities) in the step ASteel、135kg/tSteelCharging molten iron and scrap steel into an LD converter in proportion, and performing conventional top-bottom recombinationBlowing, smelting in a converter by adopting a double-slag method, and smelting the first slag charge in the earlier stage according to 16kg/tSteel、12kg/tSteel、1kg/tSteelAdding lime, light-burned dolomite and magnesite balls for slagging, adding a second batch of slag after the first batch of slag is slagging and the slag is poured into a furnace, wherein the second batch of slag is respectively 8kg/tSteel、10kg/tSteelAdding lime and light burned dolomite for slagging again, and controlling the end point molten steel C content to be 0.45wt%, the O content to be 0.030wt% and the tapping temperature to be 1600 ℃; 2.0kg/t of steel ladle bottom before tappingSteelAdding the following slag washing desulfurizing agent in the following mass ratio for slag washing: CaF2 8.5wt%，SiO2 5.2wt%，CaO 57.5wt%，Na28.3wt% of O, 2.5wt% of Al, 0.056wt% of P, 0.082wt% of S and the balance of inevitable impurities, wherein the whole process of bottom blowing argon is adopted in the tapping process, and the flow rate of argon is controlled to be 15 NL/min.
C. And (3) deoxidation alloying: tapping the molten steel smelted in the step B, and when the amount of the molten steel in the ladle is more than 1/4, carrying out the following deoxidation alloying sequence: low Al-Si-Ca-Ba → high-carbon ferrochrome → high-carbon ferromanganese → low-nitrogen carburant, and the following substances are sequentially added into a steel ladle: at 3.5kg/tSteelAdding the following low aluminum, silicon, calcium and barium in mass ratio: 52.5wt% of Si, 12.5wt% of Ba, 10.3wt% of Ca, 1.2wt% of Al, and the balance of Fe and inevitable impurities; at a rate of 2.9kg/tSteelAdding the following high-carbon ferrochrome in mass ratio: 56.7wt% of Cr, 7.2wt% of C, and the balance of Fe and inevitable impurities; according to the weight of 9.6-10.9 kg/tSteelAdding the following high-carbon ferromanganese in mass ratio: 75.6wt% of Mn, 6.7wt% of C, and the balance of Fe and inevitable impurities; at a rate of 1.2kg/tSteelAdding the following low-nitrogen carburant in mass ratio: 98.1wt% of C, 0.025wt% of N, 0.035wt% of P, 0.065wt% of S and the balance of inevitable impurities; when the amount of the molten steel in the steel ladle reaches 4/5, the alloy is added; and after tapping, hoisting the molten steel to an LF furnace for refining.
D. Refining in a molten steel LF furnace: c, hoisting the molten steel after the steel tapping in the step C to a refining station of an LF furnace, connecting an argon zone, starting argon, blowing argon for 2 minutes by adopting small argon amount (20NL/min), melting slag by adopting a gear 7 on a lower electrode, and adding 0.4 kg/t of ferrosilicon powder for slag regulation; current supply 8After minutes, lifting the electrode to observe the slagging condition in the furnace, and then measuring and sampling the temperature; if the slag condition is relatively dilute, adding 4.0kg/t of limeSteelThen adding 0.6kg/t ferrosilicon powderSteel0.5kg/t calcium carbideSteelRegulating slag, otherwise, adding premelted refining slag for regulating slag, and controlling the slag alkalinity to be 5.0; according to the analysis result of the steel sample, adding ferrosilicon powder, a low-nitrogen carburant (the mass ratio of C98.1 wt%, N0.025 wt%, P0.035 wt%, S0.065 wt%, and the balance unavoidable impurities) and an alloy to adjust the components of the molten steel, ensuring that all chemical components are in a target range, and controlling the oxygen activity of the molten steel to be 10 ppm; controlling the number of times of lower electrodes in the refining process for 3 times; then heating the molten steel to 1655 ℃, carrying out soft argon blowing on the molten steel by adopting a small argon flow with the flow of 20NL/min under the white slag state, wherein the soft argon blowing time is 20 minutes, and then adding a molten steel covering agent, wherein the adding amount is controlled to be 1.0kg/tSteelAnd then hoisting the molten steel to a vacuum refining station of the VD furnace.
E. Vacuum refining in a molten steel VD furnace: d, hoisting the molten steel in the step D to a VD vacuum refining furnace, connecting an argon blowing pipe, starting argon, blowing argon for 2 minutes by adopting small argon amount (20NL/min), then, fixing oxygen and hydrogen for the molten steel, and measuring temperature and sampling; after sampling, turning on a vacuum tank cover to a working position, closing the vacuum tank cover, vacuumizing, starting vacuum-maintaining degassing treatment when vacuum is pumped to 67Pa, simultaneously carrying out bottom blowing argon treatment, controlling the flow of argon to be 30NL/min, and degassing the molten steel for 15 minutes under the condition of vacuum degree of 67 Pa; closing the vacuum main valve after the vacuum degassing treatment is finished, lifting the tank cover, sampling molten steel, and determining oxygen and hydrogen; then, carrying out soft argon blowing treatment on the molten steel with small argon flow of 20NL/min for 2 minutes; after the soft argon blowing of the molten steel is finished, adding the molten steel covering agent, wherein the adding amount is controlled to be 1.0kg/tSteelThen, hoisting the molten steel to a casting station;
F. casting molten steel: under the conditions that the temperature of a tundish is 1490 ℃, the pulling speed is 1.8m/min, the secondary cooling specific water amount is 1.0L/kg, the electromagnetic stirring current intensity of a crystallizer is 270A, and the operating frequency is 4HZ, the molten steel in the step E is continuously cast into a billet with the cross section of 150mm multiplied by 150mm in a whole-process protection manner by adopting an R9m straight-arc continuous straightening 5-flow small square billet casting machine;
G. heating a steel billet: and F, feeding the steel billet in the step F into a heating furnace with the furnace temperature of the soaking section of 1100 ℃, heating for 70 minutes, discharging steel at the temperature of 1010 ℃, discharging scale through high-pressure water, and pushing the steel billet to a high-speed wire rod mill for rolling.
H. Rolling and cooling control: the billet steel in the step G is sent into a high-speed wire rod rolling mill with 28 racks for rolling, and is subjected to rough rolling for 6 passes under the rolling condition that the speed is 0.15 m/s; then, under the rolling condition that the speed is 10.0m/s, carrying out medium rolling for 12 passes; then pre-water cooling and controlled cooling are carried out before finish rolling, and the cooling water quantity is 120m3Controlling the cooling for 3 seconds under the condition of/h; then, finish rolling is carried out for 5 passes under the rolling conditions that the finish rolling temperature is 910 ℃ and the speed is 20 m/s; then, spinning at the temperature of 840 ℃ and the speed of 20 m/s; after spinning, the wire rod enters a stelmor air cooling line for controlled cooling; the stelmor air-cooled line control cold-time fan and the heat-preservation cover cap are all opened, the air quantity of the fan is 11.5m3The speed of the roller way is controlled to be 1.05 m/s; controlling the coiling temperature to be 550 ℃ after Stelmor air cooling is finished, naturally air cooling the coil to room temperature to obtain a high-cleanliness high-strength prestressed steel strand hot-rolled wire rod with a nominal diameter of 12.5mm, and hot-rolling the wire rod by using SWRH82B, wherein the wire rod comprises the following chemical components in percentage by weight: 0.79wt% of C, 0.18wt% of Si, 0.78wt% of Mn, 0.25wt% of Cr, 0.004wt% of S, 0.008wt% of P, 0.0018wt% of N, 0.0009wt% of O, 0.0001wt% of H, and the balance of Fe and inevitable impurities.
The mechanical properties and the microstructure of the high-cleanliness high-strength prestressed steel strand hot-rolled wire rod with the SWRH82B provided by the embodiment 1 and with the nominal diameter of 12.5mm are respectively shown in tables 3 and 4.
Table 3 mechanical properties of wire rod of nominal diameter 12.5mm swrh82B produced in example 1
Figure 747106DEST_PATH_IMAGE003
Table 4 metallographic structure of wire rod of nominal diameter 12.5mmSWRH82B produced in example 1
Figure 860424DEST_PATH_IMAGE004
Example 2
A. Molten iron pretreatment and desulfurization: blast furnace molten iron (chemical components C4.3 wt%, Si 0.32wt%, Mn 0.40wt%, P0.090 wt%, S0.020 wt%, and the balance Fe and inevitable impurities) is transported to KR molten iron pretreatment device for desulfurization treatment, molten iron temperature is 1340 deg.C, stirring head insertion depth is controlled to be 2100mm, and stirring head insertion depth is controlled to be 13.5kg/tSteelAdding a conventional CaO desulfurizer for desulfurization treatment, and controlling the stirring time to be 8 minutes; after stirring, carrying out slag skimming operation to ensure that the iron water surface in the steel ladle is exposed to be more than or equal to 4/5, and skimming the desulfurized slag; the pretreated molten iron comprises the following components: 4.4wt% of C, 0.32wt% of Si, 0.40wt% of Mn, 0.090wt% of P, 0.007wt% of S and the balance of Fe and inevitable impurities.
B. Smelting molten steel: respectively 940kg/t of the pretreated deep desulfurization molten iron (C4.4 wt%, Si 0.32wt%, Mn 0.40wt%, P0.090 wt%, S0.007 wt%, and the balance of Fe and unavoidable impurities) and high-quality scrap (chemical components C0.22 wt%, Si 0.48wt%, Mn 1.32wt%, P0.020 wt%, S0.024 wt%, and the balance of Fe and unavoidable impurities) in the step ASteel、135kg/tSteelThe molten iron and the scrap steel are added into an LD converter according to a mixture ratio to carry out conventional top-bottom combined blowing, the converter smelting adopts a double-slag method, and the first slag charge in the earlier stage of smelting is respectively 18kg/tSteel、14kg/tSteel、2kg/tSteelAdding lime, light-burned dolomite and magnesite balls for slagging, adding a second batch of slag after the first batch of slag is slagging and the slag is poured into a furnace, wherein the second batch of slag is 9kg/tSteel、10kg/tSteelAdding lime and light burned dolomite for slagging again, and controlling the end-point molten steel C content to be 0.52wt%, the O content to be 0.026wt% and the tapping temperature to be 1590 ℃; adding the following slag washing desulfurizing agent into the bottom of a steel ladle according to the mass ratio of 2.0kg/t steel before tapping for slag washing: CaF2 8.5wt%，SiO2 5.2wt%，CaO 57.5wt%，Na28.3wt% of O, 2.5wt% of Al, 0.056wt% of P, 0.082wt% of S and the balance of inevitable impurities, wherein the whole process of bottom blowing argon is adopted in the tapping process, and the flow rate of argon is controlled to be 20 NL/min.
C. And (3) deoxidation alloying: finishing the smelting in the step BWhen the amount of the molten steel in the ladle is more than 1/4, tapping the molten steel according to the following deoxidation alloying sequence: low Al-Si-Ca-Ba → high-carbon ferrochrome → high-carbon ferromanganese → low-nitrogen carburant, and the following substances are sequentially added into a steel ladle: at 3.9kg/tSteelAdding the following low aluminum, silicon, calcium and barium in mass ratio: 52.5wt% of Si, 12.5wt% of Ba, 10.3wt% of Ca, 1.2wt% of Al, and the balance of Fe and inevitable impurities; at 3.2kg/tSteelAdding the following high-carbon ferrochrome in mass ratio: 56.7wt% of Cr, 7.2wt% of C, and the balance of Fe and inevitable impurities; at a rate of 10.2kg/tSteelAdding the following high-carbon ferromanganese in mass ratio: 75.6wt% of Mn, 6.7wt% of C and the balance of Fe and inevitable impurities; at a rate of 1.8kg/tSteelAdding the following low-nitrogen carburant in mass ratio: 98.1wt% of C, 0.025wt% of N, 0.035wt% of P, 0.065wt% of S and the balance of inevitable impurities; when the amount of the molten steel in the steel ladle reaches 4/5, the alloy is added; and after tapping, hoisting the molten steel to an LF furnace for refining.
D. Refining in a molten steel LF furnace: c, hoisting the molten steel after the steel tapping in the step C to an LF refining station to connect an argon zone, starting argon, blowing argon for 2 minutes by adopting small argon amount (25NL/min), melting slag by adopting a gear 8 gear on a lower electrode, and adding 0.6kg/t of ferrosilicon powderSteelSlag mixing; after the furnace is electrified for 8 minutes, lifting an electrode to observe the slagging condition in the furnace, and then measuring and sampling the temperature; if the slag condition is thinner, 5.0kg/t lime is addedSteelThen adding 0.6kg/t ferrosilicon powderSteel0.5kg/t calcium carbideSteelRegulating slag, otherwise, adding premelted refining slag for regulating slag, and controlling the slag alkalinity to be 5.5; according to the analysis result of the steel sample, adding ferrosilicon powder, a low-nitrogen carburant (the mass ratio of C98.1 wt%, N0.025 wt%, P0.035 wt%, S0.065 wt%, and the balance unavoidable impurities) and an alloy to adjust the components of the molten steel, ensuring that all chemical components are in a target range, and controlling the oxygen activity of the molten steel to be 8 ppm; controlling the number of times of electrode lowering in the refining process for 2 times; then heating the molten steel to 1649 ℃, carrying out soft argon blowing on the molten steel by adopting a small argon flow with the flow of 25NL/min under the white slag state, wherein the soft blowing time is 20 minutes, and then adding a molten steel covering agent, wherein the adding amount is controlled to be 1.0kg/tSteelAnd then hoisting the molten steel to a vacuum refining station of the VD furnace.
E. Vacuum refining in a molten steel VD furnace: d, after the molten steel in the step D is hoisted to a VD vacuum refining furnace, connecting an argon blowing pipe, starting argon, blowing argon for 2 minutes by adopting small argon amount (25NL/min), then fixing oxygen and hydrogen for the molten steel, and measuring and sampling the temperature; after sampling, turning on a vacuum tank cover to a working position, closing the vacuum tank cover, vacuumizing, starting vacuum-maintaining degassing treatment when vacuum is pumped to 67Pa, simultaneously performing bottom blowing argon treatment, controlling the flow of argon to be 35NL/min, and degassing the molten steel for 15 minutes under the condition of vacuum degree of 67 Pa; closing the vacuum main valve after the vacuum degassing treatment is finished, lifting the tank cover, sampling the molten steel, and determining oxygen and hydrogen; then, carrying out soft argon blowing treatment on the molten steel with small argon flow of 25NL/min for 2 minutes; after the soft argon blowing of the molten steel is finished, adding the molten steel covering agent, wherein the adding amount is controlled to be 1.0kg/tSteelThen, hoisting the molten steel to a casting station;
F. casting molten steel: under the conditions that the temperature of a tundish is 1485 ℃, the pulling speed is 1.8m/min, the secondary cooling specific water amount is 0.9L/kg, the electromagnetic stirring current intensity of a crystallizer is 270A, and the operating frequency is 4HZ, the molten steel in the step E is continuously cast into a billet with the cross section of 150mm multiplied by 150mm in a whole-process protection manner by using an R9m straight-arc continuous straightening 5-flow small square billet casting machine;
G. heating a steel billet: and F, feeding the steel billet in the step F into a heating furnace with the soaking section furnace temperature of 1085 ℃, heating for 60 minutes, discharging steel from the steel billet at 990 ℃, discharging scale through high-pressure water, and pushing the steel billet to a high-speed wire rod mill for rolling.
H. Rolling and cooling control: the billet steel in the step G is sent into a high-speed wire rod rolling mill with 28 racks for rolling, and is subjected to rough rolling for 6 passes under the rolling condition that the speed is 0.15 m/s; then, under the rolling condition that the speed is 10.0m/s, carrying out medium rolling for 12 passes; then pre-water cooling and controlled cooling are carried out before finish rolling, and the cooling water quantity is 120m3Controlling the cooling for 3 seconds under the condition of/h; then, finish rolling is carried out for 5 passes under the rolling conditions that the finish rolling temperature is 890 ℃ and the speed is 20 m/s; then, spinning at the temperature of 830 ℃ and the speed of 25 m/s; after spinning, the wire rod enters a stelmor air cooling line for controlled cooling; the stelmor air-cooled line control cold-time fan and the heat-insulating cover cap are all opened, and the air quantity of the fan is 11.5m3/h，The roller speed is controlled to be 0.90 m/s; controlling the coiling temperature to be 540 ℃ after the stelmor air cooling is finished, naturally air cooling the coil to room temperature to obtain a high-cleanliness high-strength prestressed steel strand hot-rolled wire rod with a nominal diameter of 12.5mm, and hot-rolling the wire rod by using SWRH82B, wherein the wire rod comprises the following chemical components in percentage by weight: 0.81wt% of C, 0.22wt% of Si, 0.83wt% of Mn, 0.27wt% of Cr, 0.005wt% of S, 0.010wt% of P, 0.0020wt% of N, 0.0012wt% of O, 0.0002wt% of H, and the balance of Fe and inevitable impurities.
The mechanical properties and the microstructure of the high-cleanliness high-strength prestressed steel strand hot-rolled wire rod with the SWRH82B provided by the embodiment 2 and with the nominal diameter of 12.5mm are respectively shown in tables 5 and 6.
TABLE 5 mechanical Properties of wire rod with nominal diameter of 12.5mmSWRH82B produced in example 2
Figure 143638DEST_PATH_IMAGE005
Table 6 nominal diameter 12.5mmSWRH82B wire rod metallographic structure produced in example 2
Figure 434942DEST_PATH_IMAGE006
Example 3
A. Pretreating and desulfurizing molten iron: blast furnace molten iron (chemical components C4.5 wt%, Si 0.40wt%, Mn 0.50wt%, P0.100 wt%, S0.025 wt%, and the balance Fe and inevitable impurities) is transported to KR molten iron pretreatment device for desulfurization treatment, wherein molten iron temperature is 1340 deg.C, stirring head insertion depth is controlled to 2100mm, and stirring head insertion depth is controlled to 15.0kg/tSteelAdding a conventional CaO desulfurizer for desulfurization treatment, and controlling the stirring time to be 8 minutes; after stirring, carrying out slag skimming operation to ensure that the iron water surface in the steel ladle is exposed to be more than or equal to 4/5, and skimming the desulfurized slag; the pretreated molten iron comprises the following components: 4.5wt% of C, 0.40wt% of Si, 0.50wt% of Mn, 0.100wt% of P, 0.008wt% of S, and the balance of Fe and inevitable impurities.
B. Smelting molten steel: the pre-treated deep desulfurization molten iron (C4.5 wt%, Si 0.40wt%, Mn 0.50wt%, P) of the step A0.100wt%, S0.008 wt%, and the balance Fe and unavoidable impurities), high quality scrap (chemical composition C0.25 wt%, Si 0.60wt%, Mn 1.50wt%, P0.025 wt%, S0.030 wt%, and the balance Fe and unavoidable impurities) 940kg/tSteel、135kg/tSteelThe molten iron and the scrap steel are added into an LD converter according to a mixture ratio to carry out conventional top-bottom combined blowing, the converter smelting adopts a double-slag method, and the first slag charge in the earlier stage of smelting is respectively 20kg/tSteel、15kg/tSteel、2kg/tSteelAdding lime, light-burned dolomite and magnesite balls for slagging, adding a second batch of slag after the first batch of slag is slagging and the slag is poured into a furnace, wherein the second batch of slag is 10kg/tSteel、10kg/tSteelAdding lime and light-burned dolomite for slagging again, and controlling the C content of the end-point molten steel to be 0.58wt%, the O content to be 0.022wt% and the tapping temperature to be 1580 ℃; 2.0kg/t of steel ladle bottom before tappingSteelAdding the following slag washing desulfurizing agent in the following mass ratio for slag washing: CaF2 8.5wt%，SiO2 5.2wt%，CaO 57.5wt%，Na28.3wt% of O, 2.5wt% of Al, 0.056wt% of P, 0.082wt% of S and the balance of inevitable impurities, wherein the whole bottom argon blowing process is adopted in the tapping process, and the flow rate of argon is controlled to be 20 NL/min.
C. And (3) deoxidation alloying: tapping the molten steel smelted in the step B, and when the molten steel amount in a ladle is more than 1/4, carrying out the following deoxidation alloying order: low Al-Si-Ca-Ba → high-carbon ferrochrome → high-carbon ferromanganese → low-nitrogen carburant, and the following substances are sequentially added into a steel ladle: at 4.2kg/tSteelAdding the following low aluminum silicon calcium barium in mass ratio: 52.5wt% of Si, 12.5wt% of Ba, 10.3wt% of Ca, 1.2wt% of Al and the balance of Fe and inevitable impurities; at 3.5kg/tSteelAdding the following high-carbon ferrochrome in mass ratio: 56.7wt% of Cr, 7.2wt% of C, and the balance of Fe and inevitable impurities; at a rate of 10.9kg/tSteelAdding the following high-carbon ferromanganese in mass ratio: 75.6wt% of Mn, 6.7wt% of C and the balance of Fe and inevitable impurities; at a rate of 2.4kg/tSteelAdding the following low-nitrogen carburant in mass ratio: 98.1wt% of C, 0.025wt% of N, 0.035wt% of P, 0.065wt% of S and the balance of inevitable impurities; when the amount of the molten steel in the steel ladle reaches 4/5, the alloy is added; tappingAnd after finishing, hoisting the molten steel to an LF furnace for refining.
D. Refining in a molten steel LF furnace: c, hoisting the molten steel after the steel tapping in the step C to an LF refining station to connect an argon zone, starting argon, blowing argon for 2 minutes by adopting small argon amount (30NL/min), then melting slag by adopting a gear 9 on a lower electrode, and adding 0.8kg/t of ferrosilicon powderSteelSlag mixing; after the furnace is electrified for 8 minutes, lifting an electrode to observe the slagging condition in the furnace, and then measuring and sampling the temperature; if the slag condition is relatively dilute, 6.0kg/t of lime is supplementedSteelThen adding 0.6kg/t ferrosilicon powderSteel0.5kg/t calcium carbideSteelRegulating slag, otherwise, adding premelted refining slag for regulating slag, and controlling the slag alkalinity to be 6.0; according to the analysis result of the steel sample, adding ferrosilicon powder, a low-nitrogen carburant (the mass ratio of C98.1 wt%, N0.025 wt%, P0.035 wt%, S0.065 wt%, and the balance unavoidable impurities) and an alloy to adjust the components of the molten steel, ensuring that all chemical components are in a target range, and controlling the oxygen activity of the molten steel to be 7 ppm; controlling the number of times of lower electrodes in the refining process for 2 times; then heating the molten steel to 1640 ℃, carrying out soft argon blowing on the molten steel by adopting a small argon flow of 25NL/min under the white slag state, wherein the soft argon blowing time is 20 minutes, and then adding a molten steel covering agent, wherein the adding amount is controlled to be 1.0kg/tSteelAnd then hoisting the molten steel to a vacuum refining station of the VD furnace.
E. Vacuum refining in a molten steel VD furnace: d, hoisting the molten steel in the step D to a VD vacuum refining furnace, connecting an argon blowing pipe, starting argon, blowing argon for 2 minutes by adopting small argon amount (30NL/min), then, fixing oxygen and hydrogen for the molten steel, and simultaneously measuring temperature and sampling; after sampling, turning on a vacuum tank cover vehicle to a working position, closing the vacuum tank cover, vacuumizing, starting vacuum-maintaining and degassing treatment when vacuum is pumped to 67Pa, simultaneously performing bottom argon blowing treatment, controlling the flow of argon to be 40NL/min, and degassing the molten steel for 15 minutes under the condition of vacuum degree of 67 Pa; closing the vacuum main valve after the vacuum degassing treatment is finished, lifting the tank cover, sampling the molten steel, and determining oxygen and hydrogen; then, carrying out soft argon blowing treatment on the molten steel with small argon flow of 30NL/min for 2 minutes; after the soft argon blowing of the molten steel is finished, adding the molten steel covering agent, wherein the adding amount is controlled to be 1.0kg/tSteelThen, hoisting the molten steel to a casting station;
F. casting molten steel: under the conditions that the temperature of a tundish is 1480 ℃, the pulling speed is 1.8m/min, the secondary cooling specific water amount is 0.8L/kg, the electromagnetic stirring current intensity of a crystallizer is 270A, and the operating frequency is 4HZ, the molten steel in the step E is continuously cast into a billet with the cross section of 150mm multiplied by 150mm in a whole-process protection manner by using an R9m straight-arc continuous straightening 5-flow small square billet casting machine;
G. heating a steel billet: and F, feeding the steel billet in the step F into a heating furnace with the furnace temperature of a soaking section of 1070 ℃, heating for 50 minutes, discharging steel out of scales through high-pressure water after the steel billet tapping temperature is 980 ℃, and pushing the steel billet to a high-speed wire rod rolling mill for rolling.
H. Controlled rolling and controlled cooling: the billet steel in the step G is sent into a high-speed wire rod rolling mill with 28 racks for rolling, and is subjected to rough rolling for 6 passes under the rolling condition that the speed is 0.15 m/s; then, under the rolling condition that the speed is 10.0m/s, carrying out medium rolling for 12 passes; then pre-water cooling and controlled cooling are carried out before finish rolling, and the cooling water quantity is 120m3Controlling the cooling time for 3 seconds under the condition of/h; then, finish rolling is carried out for 5 passes under the rolling conditions that the finish rolling temperature is 880 ℃ and the speed is 20 m/s; then, spinning at the temperature of 820 ℃ and the speed of 30 m/s; after spinning, the wire rod enters a stelmor air cooling line for controlled cooling; the stelmor air-cooled line control cold-time fan and the heat-preservation cover cap are all opened, the air quantity of the fan is 11.5m3The speed of the roller way is controlled to be 0.85 m/s; after Stelmor air cooling is finished, the coil collecting temperature is controlled to 530 ℃, then the coil is naturally air-cooled to room temperature, and the high-cleanliness high-strength prestressed steel strand hot-rolled wire rod with the nominal diameter of 12.5mm is obtained, and the hot-rolled wire rod is hot-rolled by SWRH82B and comprises the following chemical components in percentage by weight: 0.83wt% of C, 0.27wt% of Si, 0.87wt% of Mn, 0.30wt% of Cr, 0.007wt% of S, 0.012wt% of P, 0.0025wt% of N, 0.0015wt% of O, 0.0002wt% of H, and the balance of Fe and inevitable impurities.
The mechanical properties and the microstructure of the high-cleanliness high-strength prestressed steel strand hot-rolled wire rod with the SWRH82B provided by the embodiment 3 and with the nominal diameter of 12.5mm are respectively shown in the tables 7 and 8.
TABLE 7 mechanical Properties of wire rod with nominal diameter of 12.5mmSWRH82B produced in example 3
Figure 170817DEST_PATH_IMAGE007
Table 8 metallographic structure of wire rod of nominal diameter 12.5mm swrh82B produced in example 3
Figure 87826DEST_PATH_IMAGE008

Claims (8)

1. A preparation method of a high-cleanliness high-strength prestressed steel strand hot-rolled wire rod with a nominal diameter of 12.5mm by using SWRH82B is realized by the following steps in sequence: the method comprises the following working procedures of molten iron pretreatment desulfurization, molten steel smelting, deoxidation alloying, molten steel LF furnace refining, molten steel VD furnace vacuum refining, molten steel casting, billet heating, controlled rolling and controlled cooling, and is characterized by comprising the following specific steps of:
A. molten iron pretreatment and desulfurization: conveying blast furnace molten iron to a KR method molten iron pretreatment device for desulfurization treatment, wherein the temperature of the molten iron is more than or equal to 1320 ℃, the insertion depth of a stirring head is controlled to be 2100mm, and the amount of the stirring head is 12.0-15.0 kg/tSteelAdding a conventional CaO desulfurizer for desulfurization treatment, and controlling the stirring time to be 8 minutes; after stirring, carrying out slag skimming operation to ensure that the iron water surface in the steel ladle is exposed to be more than or equal to 4/5, and skimming the desulfurized slag; the pretreated molten iron comprises the following components: 4.2 to 4.5 weight percent of C, 0.25 to 0.40 weight percent of Si, 0.30 to 0.50 weight percent of Mn, 0.080 to 0.100 weight percent of P, less than or equal to 0.008 weight percent of S and the balance of Fe and inevitable impurities; the blast furnace molten iron comprises the following chemical components: c4.2-4.5 wt%, Si 0.25-0.40wt%, Mn 0.30-0.50wt%, P0.080-0.100 wt%, S less than or equal to 0.025wt%, and Fe and inevitable impurities in balance;
B. smelting molten steel: respectively processing the pretreated molten iron and the scrap steel in the step A according to 940kg/tSteel、135kg/tSteelThe mixed slag is added into an LD converter according to the mixture ratio to carry out conventional top-bottom combined blowing, the converter smelting adopts a double-slag method, and the first slag charge in the earlier stage of smelting is respectively 16-20 kg/tSteel、12~15kg/tSteel、1~2kg/tSteelAdding lime, light-burned dolomite and magnesite balls for slagging, adding a second batch of slag after the first batch of slag is subjected to slagging and the slag is poured into a furnace, wherein the second batch of slag is respectively 8-10 kg/tSteel、10kg/tSteelAdding lime and light-burned dolomite for slagging again, and controlling the end point molten steel C content to be more than or equal to 0.45wt%, the O content to be less than or equal to 0.030wt% and the tapping temperature to be less than or equal to 1600 ℃; 2.0kg/t of steel ladle bottom before tappingSteelAdding the following slag washing desulfurizing agent in the following mass ratio for slag washing: CaF2 8.5wt%，SiO2 5.2wt%，CaO 57.5wt%，Na28.3wt% of O, 2.5wt% of Al, 0.056wt% of P, 0.082wt% of S and the balance of inevitable impurities, wherein a whole-process bottom argon blowing process is adopted in the tapping process, and the flow rate of argon is controlled to be 15-20 NL/min; the chemical components of the scrap steel comprise 0.20-0.25wt% of C, 0.35-0.60wt% of Si, 1.15-1.50wt% of Mn, 0.015-0.025wt% of P, 0.018-0.030wt% of S, and the balance of Fe and inevitable impurities;
C. and (3) deoxidation alloying: tapping the molten steel, and when the amount of the molten steel in the ladle is more than 1/4, carrying out the following deoxidation alloying sequence: low Al-Si-Ca-Ba → high-carbon ferrochrome → high-carbon ferromanganese → low-nitrogen carburant, and the following substances are sequentially added into a steel ladle: according to 3.5-4.2 kg/tSteelAdding the following low aluminum silicon calcium barium in mass ratio: 52.5wt% of Si, 12.5wt% of Ba, 10.3wt% of Ca, 1.2wt% of Al, and the balance of Fe and inevitable impurities; according to 2.9-3.5 kg/tSteelAdding the following high-carbon ferrochrome in mass ratio: 56.7wt% of Cr, 7.2wt% of C, and the balance of Fe and inevitable impurities; according to the weight of 9.6-10.9 kg/tSteelAdding the following high-carbon ferromanganese in mass ratio: 75.6wt% of Mn, 6.7wt% of C and the balance of Fe and inevitable impurities; according to 1.2-2.4 kg/tSteelAdding the following low-nitrogen carburant in mass ratio: 98.1wt% of C, 0.025wt% of N, 0.035wt% of P, 0.065wt% of S and the balance of inevitable impurities; when the amount of the molten steel in the steel ladle reaches 4/5, the alloy is added; after tapping, hoisting the molten steel to an LF furnace for refining;
D. refining in a molten steel LF furnace: and C, hoisting the molten steel after the steel tapping in the step C to an LF refining station to connect an argon gas zone, starting argon gas, blowing argon for 2 minutes by adopting a small argon amount of 20-30 NL/min, slagging by adopting a gear of 7-9 for a lower electrode, and adding 0.4-0.8 kg/t of ferrosilicon powderSteelSlag mixing; after the furnace is electrified for 8 minutes, lifting an electrode to observe the slagging condition in the furnace, and then measuring and sampling the temperature; if the slag condition is relatively dilute, adding 4.0-6.0 kg/t limeSteelAdding intoFerrosilicon powder 0.6kg/tSteel0.5kg/t calcium carbideSteelRegulating slag, otherwise, adding premelted refining slag for regulating slag, and controlling the slag alkalinity to be 5.0-6.0; according to the analysis result of the steel sample, adding ferrosilicon powder, a low-nitrogen carburant and alloy to adjust the components of the molten steel, ensuring that all chemical components are in a target range, and controlling the oxygen activity of the molten steel to be less than or equal to 10 ppm; controlling the number of times of the lower electrode in the refining process to be less than or equal to 3 times; then heating the molten steel to 1640-1655 ℃, carrying out soft argon blowing on the molten steel by adopting a small argon flow of 20-25 NL/min under a white slag state, wherein the soft argon blowing time is 20 minutes, and then adding a molten steel covering agent, wherein the adding amount is controlled to be 1.0kg/tSteelThen hoisting the molten steel to a vacuum refining station of a VD furnace;
E. vacuum refining in a molten steel VD furnace: after the molten steel is hoisted to a VD vacuum refining furnace, an argon blowing pipe is connected, argon is started to be blown for 2 minutes by adopting a small argon flow of 20-30 NL/min, then oxygen and hydrogen are determined for the molten steel, and meanwhile, temperature measurement and sampling are carried out; after sampling, turning on a vacuum tank cover vehicle to a working position, closing the vacuum tank cover, vacuumizing, starting vacuum-maintaining degassing treatment when vacuum is pumped to 67Pa, simultaneously performing bottom blowing argon treatment, controlling the flow of argon to be 30-40 NL/min, and degassing the molten steel for 15 minutes under the condition of vacuum degree of 67 Pa; closing the vacuum main valve after the vacuum degassing treatment is finished, lifting the tank cover, sampling the molten steel, and determining oxygen and hydrogen; then, carrying out soft argon blowing treatment on the molten steel with small argon flow of 20-30 NL/min for 2 minutes; after the soft argon blowing of the molten steel is finished, adding the molten steel covering agent, wherein the adding amount is controlled to be 1.0kg/tSteelThen, hoisting the molten steel to a casting station;
F. casting molten steel: under the conditions that the temperature of a tundish is 1480-1490 ℃, the pulling speed is 1.8m/min, the secondary cooling specific water amount is 0.8-1.0L/kg, the electromagnetic stirring current intensity of a crystallizer is 270A, and the operating frequency is 4Hz, the molten steel in the step E is continuously cast into a billet with the cross section of 150mm multiplied by 150mm in a whole-process protection manner by adopting an R9m straight arc continuous straightening 5-flow small square billet casting machine;
G. heating a steel billet: feeding the steel billets obtained in the step F into a heating furnace with the furnace temperature of a soaking section of 1070-1100 ℃, heating for 50-70 minutes, discharging steel from the steel billets, descaling by high-pressure water, and pushing the steel billets to a high-speed wire rod mill for rolling;
H. rolling and cooling control: the billet steel in the step G is sent into a high-speed wire rod mill with 28 racks for rolling, and is roughly rolled for 6 passes under the rolling condition that the speed is 0.15 m/s; then, under the rolling condition that the speed is 10.0m/s, carrying out medium rolling for 12 passes; then pre-water cooling and controlled cooling are carried out before finish rolling, and the cooling water quantity is 120m3Controlling the cooling for 3 seconds under the condition of/h; then, finish rolling for 5 passes under the rolling conditions that the finish rolling temperature is 880-910 ℃ and the speed is 20 m/s; then, spinning at the temperature of 820-840 ℃ and the speed of 20-30 m/s; after spinning, the wire rod enters a stelmor air cooling line for controlled cooling; the stelmor air-cooled line control cold-time fan and the heat-preservation cover cap are all opened, the air quantity of the fan is 11.5m3The speed of the roller way is controlled to be 0.85-1.05 m/s; controlling the coiling temperature to be 530-550 ℃ after stelmor air cooling is finished, naturally air cooling the coil to room temperature to obtain a high-cleanliness high-strength prestressed steel strand hot-rolled wire rod with a nominal diameter of 12.5mm, wherein the wire rod is hot-rolled by SWRH82B and comprises the following chemical components in parts by weight: 0.79 to 0.83 weight percent of C, 0.18 to 0.27 weight percent of Si, 0.78 to 0.87 weight percent of Mn, 0.25 to 0.30 weight percent of Cr, less than or equal to 0.007 weight percent of S, less than or equal to 0.012 weight percent of P, less than or equal to 0.0025 weight percent of N, less than or equal to 0.0015 weight percent of O, less than or equal to 0.0002 weight percent of H, and the balance of Fe and inevitable impurities.
2. The preparation method according to claim 1, wherein in the step B, the baked and dried waste vanadium slag added into the ladle comprises the following components: 98.1wt% of C, 0.025wt% of N, 0.035wt% of P, 0.065wt% of S and the balance of inevitable impurities.
3. The preparation method according to claim 1, wherein in the step D, the low-nitrogen carburant has the following components in mass ratio: the mass ratio of C is 98.1wt%, N is 0.025wt%, P is 0.035wt%, S is 0.065wt%, and the rest is inevitable impurities.
4. The method of claim 1, wherein in the step F, the billet caster used for casting the molten steel into the cross-section steel billet is an R9m straight arc continuous straightening 5-machine 5-flow billet caster.
5. The preparation method according to claim 1, wherein in the step G, the steel billet tapping temperature is 980-1010 ℃.
6. The preparation method according to claim 1, wherein in the step H, the amount of cooling water of the pre-water cooling device is 120m3And/h, the controlled cooling time is 3 seconds.
7. The method according to claim 1, wherein in step H, stelmor air cooling line cooling is as follows: the fan and the heat preservation cover cap are all opened, and the air quantity of the fan is 11.5 ten thousand meters3The speed of the roller way is controlled to be 0.85-1.05 m/s.
8. A high-cleanliness high-strength prestressed steel strand with a nominal diameter of 12.5mm obtained by the preparation method of any one of claims 1 to 7 is hot-rolled into a wire rod by using SWRH 82B.
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