CN110527917B - 30MnSiBCa hot-rolled wire rod for PC steel bar and preparation method thereof - Google Patents

30MnSiBCa hot-rolled wire rod for PC steel bar and preparation method thereof Download PDF

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CN110527917B
CN110527917B CN201910941058.9A CN201910941058A CN110527917B CN 110527917 B CN110527917 B CN 110527917B CN 201910941058 A CN201910941058 A CN 201910941058A CN 110527917 B CN110527917 B CN 110527917B
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steel
equal
percent
temperature
less
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CN110527917A (en
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傅余东
左都伟
樊尧桂
周和敏
郝飞翔
聂志斌
刘富贵
张俊
徐洪军
沈朋飞
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阳春新钢铁有限责任公司
钢研晟华科技股份有限公司
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    • 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 BY DECARBURISATION, TEMPERING OR OTHER TREATMENTS
    • 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
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • 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
    • C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
    • 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
    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • 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 BY DECARBURISATION, TEMPERING OR OTHER TREATMENTS
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • 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 BY DECARBURISATION, TEMPERING OR OTHER TREATMENTS
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Abstract

The invention relates to a 30MnSiBCa hot-rolled wire rod for a PC steel bar and a preparation method thereof, wherein B and Ca elements are added into the 30MnSiBCa hot-rolled wire rod, and the proportion of B to Cr, Mn to Si and the content of Ca and B are controlled to improve the hardenability and the delayed fracture resistance of the wire rod; meanwhile, the existing preparation process of the hot-rolled wire rod is optimized, and the 30MnSiBCa hot-rolled wire rod is prepared by adopting a converter/electric furnace molten steel smelting process, an LF furnace refining process, a continuous casting billet process and a hot-rolling cooling control process route, so that the head and tail of the hot-rolled wire rod in the same batch and the performance of the hot-rolled wire rod in different batches are stable, the component fluctuation is small, the purity of steel is greatly improved, and the technical effects of avoiding frequent adjustment of the subsequent PC steel rod production process and high cost are achieved.

Description

30MnSiBCa hot-rolled wire rod for PC steel bar and preparation method thereof

Technical Field

The invention relates to the technical field of steel preparation, in particular to a 30MnSiBCa hot-rolled wire rod for a PC steel bar and a preparation method thereof.

Background

The tubular pile has the characteristics of high construction efficiency, low cost and good safety, replaces the traditional construction method of the building foundation from the last 90 years, and is widely applied to the field of building engineering in China, particularly to the projects of roads, high-speed railway bridges, high-rise buildings and the like in bead triangle and long triangle areas. High-strength prestressed reinforcement (also called PC steel bar) used as a tubular pile frame is required to have excellent properties such as high strength, low relaxation, and good plasticity, and is generally produced by using a hot-rolled wire rod as a raw material through the steps of female thread drawing, induction heating, quenching, tempering, and the like.

At present, the domestic PC steel bar is mainly provided with 30MnSi and 45Si2Cr, wherein GB/T24587-2009 Hot rolled wire rod for prestressed concrete steel bar stipulates that the chemical components of 30MnSi comprise 0.28-0.33% of C, 0.7-1.1% of Si, 0.9-1.3% of Mn and the content ranges of Cr, P, S, Ni, Cu and other components; the main quality problems of the method are as follows: 1) the PC steel bar has weak delayed fracture resistance; 2) the mechanical property is unstable, and the fluctuation range of the mechanical property of the same batch of even the same PC steel bar is large; 3) poor flatness; 4) the hot heading performance is poor, which is characterized in that the heading is cracked and the mechanical property of the heading is greatly reduced compared with that of the parent metal; 5) poor weldability, which means that the mechanical properties at the welding point are greatly reduced compared with those of the base material.

The components and the heat treatment process of the hot-rolled wire rod have important influence on the performance of the PC steel rod, and the PC steel rods prepared from different raw materials need different heat treatment processes. Even under the same quenching condition, the raw material with good hardenability can obtain higher strength; the deviation of the tensile strength of the same batch of raw materials exceeds +/-50 MPa, and the technological parameters need to be adjusted in the production process of the PC steel bar, so that great inconvenience is brought to production operation.

Therefore, how to prepare the PC steel bar with excellent performance through reasonable element proportion and screening of a heat treatment process is still the focus of current research, and the excellent performance mainly means that the poker has uniform performance, good surface quality, high mechanical strength, no delayed fracture phenomenon, good upsetting performance, good weldability and the like.

Disclosure of Invention

In order to overcome the defects of the prior art, one of the purposes of the invention is to provide a 30MnSiBCa hot-rolled wire rod for a PC steel rod and a preparation method thereof, which are used for solving the problems of frequent adjustment and high cost of the subsequent production process of the PC steel rod caused by large performance fluctuation of the raw materials for the PC steel rod, and simultaneously preparing the PC steel rod with excellent performance by reasonably optimizing the components in the PC steel rod and screening a proper heat treatment process, wherein the excellent performance mainly means that the wire rod has uniform performance, good surface quality, high mechanical strength, no delayed fracture phenomenon, good upsetting performance, good weldability and the like.

The above object of the present invention is mainly achieved by the following technical solutions: a30 MnSiBCa hot-rolled wire rod for a PC steel rod comprises the following components in percentage by weight: 0.25 to 0.35 percent of C, 0.50 to 1.30 percent of Si, 0.70 to 1.50 percent of Mn, 0.002 to 0.004 percent of B, 0.001 to 0.003 percent of Ca, 0.1 to 0.2 percent of Cr, less than or equal to 0.015 percent of P, less than or equal to 0.015 percent of S, less than or equal to 0.25 percent of Ni, less than or equal to 0.20 percent of Cu, less than or equal to 0.004 percent of O, less than or equal to 0.006 percent of N, and the balance of Fe and inevitable impurities,

preferably, in order to improve hardenability and resistance to delayed fracture and elastic straightening properties, etc., the weight ratio of B to Cr is selected to be 1:40-80, the weight ratio of Mn to Si is 1.0-2.0: 1, and 0.05 to 0.1 part by weight of Ca and 0.06 to 0.25 part by weight of B based on 100 parts by weight of C, Si and Mn.

The function of the various components in the PC steel bar is further explained below:

c: carbon is one of main strengthening elements, the content of C is determined according to the specification of the produced PC steel bar, the content of C in the steel for the small-specification PC steel bar is slightly lower, and the content of C in the steel for the large-specification PC steel bar is slightly higher. In order to ensure the hot heading performance and the welding performance of the PC steel bar and reduce the content of C as much as possible, the performance of the PC steel bar is met by adding trace elements, and the deviation of the content of C is controlled within +/-0.02%;

si: silicon can improve the strength of steel and is beneficial to improving hardenability, but simultaneously causes the tendency of coarsening of the structure in the heating process, and widmannstatten structure is easy to appear, so the content of the silicon is controlled to be 0.50-1.30%;

mn: manganese is a main solid-solution strengthening element and can improve the hardenability of steel, but is easy to segregate to form MnS, so that the toughness and the plasticity of the steel are influenced;

cr: the chromium can enhance the strength and hardness of the steel and remarkably improve the hardenability and oxidation resistance;

b: boron can improve hardenability, the effect of adding 0.0010-0.0040% of B is equivalent to 0.6% of Mn, and a large amount of alloy elements can be saved; the hardenability improving effect of the alloy elements generally increases with the content of the alloy elements in steel, but the B has an optimal content, and the improvement of the hardenability is not favorable when the B is too much or too little;

ca: calcium improves delayed fracture resistance, primarily because it controls the morphology of inclusions, helps to deoxidize and inhibit austenite formation, but too much calcium coarsens the oxides.

The invention also aims to provide a preparation method of the 30MnSiBCa hot-rolled wire rod for the PC steel bar, which has the following approximate process route: molten iron (low phosphorus and low sulfur) → converter → argon blowing station → LF furnace → continuous casting machine (M-EMS) → heating furnace → high wire rolling → controlled cooling → coiling → finishing → bundling → weighing → unloading → warehousing → external delivery;

the method specifically comprises the following steps:

step 1, smelting molten steel: adding molten iron or scrap steel serving as a raw material into a converter or an electric furnace, adopting a top-bottom combined blowing process, adding lime, and adopting a high-tension blowing-in method to draw carbon, wherein the end-point carbon content is controlled to be 0.08-0.15%, and the tapping temperature is controlled to be 1580-;

argon is blown in the whole tapping process, the argon flow is 15-25NL/min, high-aluminum manganese-iron alloy is added when tapping is started, silicon-manganese alloy and silicon-iron alloy are added when tapping is 1/4, and the addition amounts of the high-aluminum manganese-iron alloy, the silicon-manganese alloy and the silicon-iron alloy are respectively 0.6-0.7kg/t steel, 12-16kg/t steel and 6-8kg/t steel; the high aluminum manganese iron alloy, the silicon manganese alloy and the silicon iron alloy are added when 3/4 steel is tapped, 0.8-1.0kg/t steel of silicon aluminum barium alloy slag is added after the addition, a slag blocking rod is arranged for blocking slag, the slag discharging of a steel ladle is ensured to be less than or equal to 50mm, and the smelting molten steel is obtained;

step 2, argon blowing station temperature measurement sampling: controlling the temperature of the smelting molten steel obtained in the step 1 to be more than or equal to 1560 ℃, measuring the temperature of the molten steel within 2min after the molten steel enters a station, and sampling, determining oxygen and taking a slag sample after 2 min;

and 3, refining in an LF furnace: adding the qualified smelted molten steel after temperature measurement and sampling in the step 2 into an LF furnace, introducing argon gas for 3min after 20-35NL/min argon blowing, and transmitting electricity for 15-25min by adopting 7-9 gears; adding calcium carbide 0.4-0.7kg/t steel for deoxidation to produce white slag for 15-25 min; adjusting argon flow to 15-25NL/min, adding 0.3-0.5kg/t steel of low-carbon ferroboron, wherein the components are 0.05-0.1% of C, 9-25% of B, and the balance of Fe and inevitable impurities; heating the molten steel to 1580-1595 ℃, adding a silicon-calcium-iron alloy for wire feeding treatment, wherein the components comprise 50-56% of Si, 25-35% of Ca and the balance of Fe and inevitable impurities; the wire feeding amount is 200-300m, the wire feeding speed is 2-4m/s, 15-20 NL/min argon is introduced after the wire feeding is finished, and the time is 12-16 min;

and 4, molten steel continuous casting: adjusting the temperature of the upper platform of the continuous casting furnace to 1550-; controlling the liquidus temperature to be 1495 ℃, the steel drawing temperature to be 1515-;

step 5, steel rolling: adding the steel billet in the step 4 into a walking beam type side-in side-out three-section heating furnace, controlling the soaking temperature to be 1100 +/-20 ℃, controlling the temperature difference of the steel billet along the length direction to be not more than 30 ℃, and heating for 80-120 min; the steel tapping temperature of the steel billet is 980-1020 ℃, the initial rolling temperature is 1000-1050 ℃, the finish rolling temperature is 950-990 ℃, the finish rolling temperature is 920-980 ℃, and the spinning temperature is 900-960 ℃;

and after spinning is finished, the wire enters an air cooling line for controlling cooling, the cooling roller way is controlled to be covered completely, finally, the wire rod coil is naturally cooled to room temperature in air, and the 30MnSiBCa hot rolled wire rod for the PC steel rod is prepared after coiling, finishing, bundling, weighing and coil unloading.

Furthermore, in the step 1, S in the molten iron is less than or equal to 0.025 percent, P is less than or equal to 0.120 percent, and the waste steel is mainly self-produced waste steel without adding slag steel, pig iron and bean steel; the weight ratio of the molten iron to the scrap steel is 100-104: 20-24; CaO of the lime is more than or equal to 88 percent, and the activity degree is more than or equal to 280 ml;

the composition requirements of the end point of molten steel smelting in the step 1 are as follows: 0.22 to 0.28 percent of C, 0.7 to 0.8 percent of Si, 0.95 to 1.05 percent of Mn, less than or equal to 0.013 percent of P, less than or equal to 0.025 percent of S, less than or equal to 0.004 percent of O, less than or equal to 0.006 percent of N, low gas content and low inclusion content;

when the carbon is pulled by adopting a high-tension blowing-in method in the step 1, coordinated tapping of carbon temperature is ensured, and the post-blowing frequency is strictly controlled to be less than or equal to 1 time;

further, in the step 2, argon is blown in the whole tapping process, explosion blowing is strictly prohibited, and the steel is discharged and then needs to enter an argon blowing station for temperature measurement and sampling so as to be discharged and enter the LF furnace;

further, in the step 3, when the soft blowing time is less than 12 minutes but not less than 9 minutes, the furnace casting blank is not allowed to roll a wire rod with the diameter of more than 16 mm; the soft blowing time is less than 9 minutes, and the whole casting blank furnace judges waste; when the LF furnace is out of the station, taking a pinhole sample as an oxygen, nitrogen, hydrogen and slag sample, and controlling the activity oxygen of the outlet station to be less than or equal to 10 PPm;

further, in the step 4, a long nozzle is used for protecting pouring, and the long nozzle is unloaded when the left 5 tons of the ladle is weighed; the molten steel of the tundish is not exposed: adding a molten steel composite heat-preserving agent (10-15 packages) into the tundish when the liquid level of molten steel in the tundish of the casting tank is more than or equal to 300mm or the amount of the molten steel is more than or equal to 10 tons, and adding the molten steel composite heat-preserving agent (3-6 packages) into a tundish accepting steel port after the liquid level is stable; adding molten steel compound heat preservation agent (2-5 bags) into the continuous casting tank according to the situation;

the pouring liquid level of the tundish is more than or equal to 300mm or the molten steel amount is more than or equal to 10 tons, the normal liquid level is more than or equal to 650mm or the molten steel amount is more than or equal to 20 tons, the liquid level of the tundish is kept relatively stable, and the pouring liquid level of the tundish is less than or equal to 300 mm. The liquid level of the ladle in the pouring and ladle changing processes is lower than 300mm, and the ladle must be discarded.

The tundish adopts continuous and automatic temperature measurement, and the manual temperature measurement and the continuous temperature measurement cannot exceed 5 ℃; under normal conditions, manually measuring the temperature once in 5 minutes before pouring the bale and 5 minutes before transferring the bale; and (5) casting the ladle for 15-20 minutes (the weight of the ladle molten steel is less than or equal to 75 tons) and taking two tundish finished samples by using a static sampler.

The upper opening of the crystallizer cannot have water seepage phenomenon (the upper opening is checked by compressed air); the nozzle of the secondary cooling chamber is not allowed to be blocked, and the angle of the nozzle which can not leak water is correct; the mold flux of the crystallizer is ordinary steel mold flux and is kept dry.

The lower nozzle is immersed into the crystallizer, the depth of the molten steel is 80-120mm, and when the nozzle is changed, the reconnection blank must be discarded; the water flow of the crystallizer is controlled to be more than or equal to 130m3And h, molten steel in the crystallizer is not exposed, slag is added frequently and slag picking rings are arranged. When the fluctuation of the liquid level of the crystallizer exceeds +/-20 mm, the waste is required to be picked up.

The relationship between the degree of superheat and the drawing speed in the drawing process is shown in table 1:

table 1:

degree of superheat deg.C ＜15 15-25 25-35 35-45 ＞45 Pulling speed m/min ＞2.6 2.50-2.6 2.50-2.40 2.40-2.20 ≤2.20

And the casting blank is subjected to YB/T2011-2004 continuous casting steel square billet and rectangular billet standard in aspects of stripping, bending, bulging and scratching, and is subjected to waste throwing or casting stopping if the casting blank does not meet the requirement.

Further, the heating time in the step 5 is 80-90min for hot charging and 90-120min for cold charging.

The invention has the following beneficial effects:

1. by optimizing the components of the hot-rolled wire rod for the PC steel rod, the method has the advantages that the C content is reduced, the Mn content is reduced, the Si content is improved, the extremely trace amount of B and Ca is added, the hardenability and the elastic straightening performance of the PC steel rod are improved, and the production cost of the wire rod can be greatly reduced;

wherein, the important components of 30MnSi in the PC steel bar are C, Mn and Si, and the design of C, Mn is mainly to ensure the strength of the PC steel bar; si contributes to the improvement of hardenability of PC steel bars, however, in order to balance the overall properties of the steel bars, the above composition should be in a reasonable range; specifically, in order to improve the hardenability, the delayed fracture resistance, the elastic straightening performance and the like of the PC steel bar, the weight ratio of B to Cr is 1:40-80, the weight ratio of Mn to Si is 1.0-2.0: 1, and 0.05 to 0.1 part by weight of Ca and 0.06 to 0.25 part by weight of B based on 100 parts by weight of C, Si and Mn.

2. The invention also controls the continuous casting billet steel produced by fine control of the steel smelting, refining and continuous casting processes not to have brittle inclusions larger than 15 mu m, D-type inclusions (spherical oxides) are less than or equal to 1.5 grade, Ds-type inclusions (single spherical oxides) are less than or equal to 1.5 grade; the porosity and crack grade is less than or equal to 1 grade, the equiaxial crystal grain is more than or equal to 30 percent, the center C segregation index of the continuous casting billet is less than or equal to 1.12, and the low power defect meets the requirement of the qualified continuous casting billet, thereby avoiding the subsequent PC steel bar heading cracking phenomenon.

3. According to the invention, through the control of raw material components and a production process, the mechanical properties of the produced wire rod for the PC steel rod are 450-500 MPa in yield strength, 680-730 MPa in tensile strength, more than or equal to 28% in elongation after fracture and more than or equal to 45% in reduction of area; the wire rod structure is ferrite F + pearlite P, and the grain size is as follows: 8.0-10.0 grade.

Meanwhile, after the PC steel rod is manufactured by using the wire rod prepared by the method, the tensile strength is 1490-1530 Mpa, the fluctuation range of the same batch of steel rods is within 30Mpa, the quality is relatively stable, the head and tail performance deviation is small, the performance difference of the same batch is within 20Mpa when the PC steel rod is processed, and the process parameter adjustment is not needed in the operation process of the PC steel rod.

4. According to the invention, through the control of smelting components and smelting process and the strict control of a steel rolling heating system, a rolling system and a controlled cooling degree, the qualified wire rods with the same furnace batch, different furnace batch numbers and small fluctuation of the performance of the whole wire rod are obtained, the adjustment of process parameters in the subsequent production process of the PC steel rod is greatly reduced, the quality and the qualification rate are improved, the PC cost is reduced, and the method has strong market competitiveness;

drawings

FIG. 1 is a schematic process flow diagram of the present invention.

Detailed Description

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate preferred embodiments of the invention and together with the description, serve to explain the principles of the invention and not to limit the scope of the invention.

Example 1

The embodiment provides a 30MnSiBCa hot-rolled wire rod for a PC steel bar, which comprises the following components in percentage by weight:

0.29 percent of C, 0.78 percent of Si, 1.05 percent of Mn, 0.011 percent of P, 0.004 percent of S, 0.0023 percent of B, 0.0018 percent of Ca0.0018 percent of Cr, 0.12 percent of Ni, 0.038 percent of Cu, 0.052 percent of O, 0.0008 percent of N, and the balance of Fe and inevitable impurities,

the embodiment also provides a preparation method of the 30MnSiBCa hot-rolled wire rod for the PC steel rod, which specifically comprises the following steps:

step 1, smelting molten steel: 100t of molten iron with S less than or equal to 0.025 percent and P less than or equal to 0.120 percent and 24t of scrap steel are taken as raw materials and added into a converter, a top-bottom combined blowing process is adopted, the CaO content is 90 percent, lime with the activity of 300ml is added, a high-tension compensation blowing method is adopted for carbon pulling, the end point carbon content is controlled to be 0.12 percent, and the tapping temperature is 1600 ℃;

argon is blown in the whole tapping process, the argon flow is 25NL/min, high-aluminum manganese iron alloy is added when tapping is started, silicon-manganese alloy and silicon-iron alloy are added when tapping is 1/4, and the addition amount of the high-aluminum manganese iron alloy, the silicon-manganese alloy and the silicon-iron alloy is 0.7kg/t steel, 13kg/t steel and 6kg/t steel respectively; the high aluminum manganese iron alloy, the silicon manganese alloy and the silicon iron alloy are added when 3/4 steel is tapped, 0.8kg/t steel of silicon aluminum barium alloy slag is added after the addition, a slag blocking rod is arranged for blocking slag, the slag dropping of a steel ladle is ensured to be less than or equal to 50mm, and the smelting molten steel is obtained;

step 2, argon blowing station temperature measurement sampling: controlling the temperature of the smelting molten steel obtained in the step 1 to be more than or equal to 1560 ℃, measuring the temperature of the molten steel within 2min after the molten steel enters a station, and sampling, determining oxygen and taking a slag sample after 2 min;

and 3, refining in an LF furnace: adding the qualified smelted molten steel after temperature measurement and sampling in the step 2 into an LF furnace, introducing argon gas for 3min at 35NL/min, and transmitting electricity for 18min at 7 grades; adding calcium carbide 0.5kg/t steel for deoxidation to produce white slag, wherein the time is 20 min; then adjusting the argon flow rate to 25NL/min, adding 0.3kg/t steel of low-carbon ferroboron, the components of which are 0.05-0.1% of C, 9-25% of B, and the balance of Fe and inevitable impurities; heating the molten steel to 1590 ℃, adding a silicon-calcium-iron alloy for wire feeding treatment, wherein the components comprise 50-56% of Si, 25-35% of Ca and the balance of Fe and inevitable impurities; the wire feeding amount is 250m, the wire feeding speed is 3m/s, 15NL/min argon is introduced after the wire feeding is finished, and the time is 16 min;

and 4, molten steel continuous casting: adjusting the temperature of the upper table of the continuous casting furnace to 1555 ℃, and adding a compound heat preservation agent into the tundish molten steel, wherein the addition amount is 2kg/t steel; controlling the liquidus temperature to be 1495 ℃, the drawing temperature to be 1520 ℃, the drawing speed to be 2.6m/min, the secondary cooling specific water amount to be 1.5L/kg, starting crystallization electromagnetic stirring in the whole process, carrying out current 320A and frequency 5HZ, and continuously casting the molten steel in the step 3 into a steel billet by adopting a square billet casting machine;

step 5, steel rolling: adding the steel billet obtained in the step 4 into a walking beam type side-in side-out three-section heating furnace, controlling the soaking temperature at 1100 ℃, controlling the temperature difference of the steel billet along the length direction to be not more than 30 ℃, and heating for 100 min; the steel tapping temperature of the billet is 1000 ℃, the initial rolling temperature is 1050 ℃, the finish rolling temperature is 980 ℃, the finish rolling temperature is 940 ℃, and the spinning temperature is 950 ℃; and after spinning is finished, the wire enters an air cooling line for controlling cooling, the cooling roller way is controlled to be covered completely, finally, the wire rod coil is naturally cooled to room temperature in air, and the 30MnSiBCa hot rolled wire rod for the PC steel rod is prepared after coiling, finishing, bundling, weighing and coil unloading.

Example 2

The embodiment provides a 30MnSiBCa hot-rolled wire rod for a PC steel bar, which comprises the following components in percentage by weight:

0.29 percent of C, 0.81 percent of Si, 1.06 percent of Mn, 0.014 percent of P, 0.006 percent of S, 0.0028 percent of B, 0.0018 percent of Ca0.0018 percent of Cr, 0.14 percent of Ni, 0.028 percent of Cu, 0.036 percent of O, 0.0006 percent of N <0.0009 percent, and the balance of Fe and inevitable impurities,

the method specifically comprises the following steps:

step 1, smelting molten steel: 100t of molten iron with S less than or equal to 0.025 percent and P less than or equal to 0.120 percent and 24t of scrap steel are taken as raw materials and added into an electric furnace, a top-bottom combined blowing process is adopted, 90 percent of CaO content and 300ml of lime with activity are added, a high-tension complementary blowing method is adopted to pull carbon, the end point carbon content is controlled to be 0.12 percent, and the tapping temperature is 1600 ℃;

argon is blown in the whole tapping process, the argon flow is 24NL/min, high-aluminum manganese iron alloy is added when tapping is started, silicon-manganese alloy and silicon-iron alloy are added when tapping is 1/4, and the addition amount of the high-aluminum manganese iron alloy, the silicon-manganese alloy and the silicon-iron alloy is 0.68kg/t steel, 13.4kg/t steel and 6.5kg/t steel respectively; the high aluminum manganese iron alloy, the silicon manganese alloy and the silicon iron alloy are added when 3/4 steel is tapped, 0.9kg/t steel of silicon aluminum barium alloy slag is added after the addition, a slag blocking rod is arranged for blocking slag, the slag dropping of a steel ladle is ensured to be less than or equal to 50mm, and the smelting molten steel is obtained;

step 2, argon blowing station temperature measurement sampling: controlling the temperature of the smelting molten steel obtained in the step 1 to be more than or equal to 1560 ℃, measuring the temperature of the molten steel within 2min after the molten steel enters a station, and sampling, determining oxygen and taking a slag sample after 2 min;

and 3, refining in an LF furnace: adding the qualified smelted molten steel after temperature measurement and sampling in the step 2 into an LF furnace, introducing argon gas 34NL/min, blowing the argon gas for 3min, and transmitting the power for 20min by adopting a 7-gear power transmission mode; adding calcium carbide 0.56kg/t steel for deoxidation to produce white slag, wherein the time is 22 min; adjusting argon flow to 24NL/min, adding 0.36kg/t steel of low-carbon ferroboron, wherein the components are 0.05-0.1% of C, 9-25% of B, and the balance of Fe and inevitable impurities; heating the molten steel to 1590 ℃, adding a silicon-calcium-iron alloy for wire feeding treatment, wherein the components comprise 50-56% of Si, 25-35% of Ca and the balance of Fe and inevitable impurities; the wire feeding amount is 250m, the wire feeding speed is 3m/s, 18NL/min argon is introduced after the wire feeding is finished, and the time is 14 min;

and 4, molten steel continuous casting: adjusting the temperature of the upper table of the continuous casting furnace to 1555 ℃, and adding a compound heat preservation agent into the tundish molten steel, wherein the addition amount is 2kg/t steel; controlling the liquidus temperature to be 1495 ℃, the drawing temperature to be 1520 ℃, the drawing speed to be 3m/min, the secondary cooling specific water amount to be 1.6L/kg, starting crystallization electromagnetic stirring in the whole process, controlling the current to be 320A and the frequency to be 4HZ, and continuously casting the molten steel in the step 3 into a steel billet by adopting a square billet casting machine;

step 5, steel rolling: adding the steel billet obtained in the step 4 into a walking beam type side-in side-out three-section heating furnace, controlling the soaking temperature at 1100 ℃, controlling the temperature difference of the steel billet along the length direction to be not more than 30 ℃, and heating for 100 min; the steel tapping temperature of the billet is 1000 ℃, the initial rolling temperature is 1030 ℃, the finish rolling temperature is 970 ℃, the finish rolling temperature is 950 ℃, and the spinning temperature is 940 ℃; and after spinning is finished, the wire enters an air cooling line for controlling cooling, the cooling roller way is controlled to be covered completely, finally, the wire rod coil is naturally cooled to room temperature in air, and the 30MnSiBCa hot rolled wire rod for the PC steel rod is prepared after coiling, finishing, bundling, weighing and coil unloading.

Example 3

The embodiment provides a 30MnSiBCa hot-rolled wire rod for a PC steel bar, which comprises the following components in percentage by weight:

0.31 percent of C, 0.79 percent of Si, 1.16 percent of Mn, 0.011 percent of P, 0.008 percent of S, 0.0035 percent of B, 0.0022 percent of Ca0.12 percent of Cr, 0.048 percent of Ni, 0.066 percent of Cu, 0.0007 percent of O, less than 0.0007 percent of N, and the balance of Fe and inevitable impurities,

the method specifically comprises the following steps:

step 1, smelting molten steel: adding 110t of molten iron with S being less than or equal to 0.025 percent and P being less than or equal to 0.120 percent and 14t of scrap steel serving as raw materials into an electric furnace, adopting a top-bottom combined blowing process, adding 90 percent of CaO content, 300ml of lime with activity, adopting a high-tension supplementing blowing method to pull carbon, controlling the end point carbon content to be 0.13 percent and the tapping temperature to be 1620 ℃;

argon is blown in the whole tapping process, the argon flow is 20NL/min, high-aluminum manganese iron alloy is added when tapping is started, silicon-manganese alloy and silicon-iron alloy are added when tapping is carried out at 1/4, and the adding amount of the high-aluminum manganese iron alloy, the silicon-manganese alloy and the silicon-iron alloy is 0.7kg/t steel, 14kg/t steel and 8kg/t steel respectively; the high aluminum manganese iron alloy, the silicon manganese alloy and the silicon iron alloy are added when 3/4 steel is tapped, 1.0kg/t steel of silicon aluminum barium alloy slag is added after the addition, a slag blocking rod is arranged for blocking slag, the slag dropping of a steel ladle is ensured to be less than or equal to 50mm, and the smelting molten steel is obtained;

step 2, argon blowing station temperature measurement sampling: controlling the temperature of the smelting molten steel obtained in the step 1 to be more than or equal to 1560 ℃, measuring the temperature of the molten steel within 2min after the molten steel enters a station, and sampling, determining oxygen and taking a slag sample after 2 min;

and 3, refining in an LF furnace: adding the qualified smelted molten steel after temperature measurement and sampling in the step 2 into an LF furnace, introducing argon gas for 3min at 35NL/min, and transmitting power for 25min at 9 grades; adding calcium carbide 0.6kg/t steel for deoxidation to produce white slag, wherein the time is 20 min; adjusting the argon flow rate to 20NL/min, adding 0.5kg/t steel of low-carbon ferroboron, wherein the components are 0.05-0.1% of C, 9-25% of B, and the balance of Fe and inevitable impurities; heating the molten steel to 1585 ℃, adding silicon-calcium-iron alloy for wire feeding treatment, wherein the components comprise 50-56% of Si, 25-35% of Ca and the balance of Fe and inevitable impurities; the wire feeding amount is 300m, the wire feeding speed is 4m/s, 15NL/min argon is introduced after the wire feeding is finished, and the time is 12 min;

and 4, molten steel continuous casting: adjusting the temperature of the upper table of the continuous casting furnace to 1560 ℃, and adding 3kg/t of steel into the tundish molten steel; controlling the liquidus temperature to be 1495 ℃, the steel drawing temperature to be 1525 ℃, the drawing speed to be 3.0m/min, the secondary cooling specific water amount to be 1.7L/kg, starting crystallization electromagnetic stirring in the whole process, carrying out current 320A and frequency 5HZ, and continuously casting the molten steel in the step 3 into a steel billet by adopting a square billet casting machine;

step 5, steel rolling: adding the steel billet obtained in the step 4 into a walking beam type side-in side-out three-section heating furnace, controlling the soaking temperature to be 1120 ℃, controlling the temperature difference of the steel billet along the length direction to be not more than 30 ℃, and heating for 120 min; the steel tapping temperature of the steel billet is 1020 ℃, the initial rolling temperature is 1040 ℃, the finish rolling temperature is 980 ℃, the finish rolling temperature is 940 ℃, and the spinning temperature is 920 ℃; and after spinning is finished, the wire enters an air cooling line for controlling cooling, the cooling roller way is controlled to be covered completely, finally, the wire rod coil is naturally cooled to room temperature in air, and the 30MnSiBCa hot rolled wire rod for the PC steel rod is prepared after coiling, finishing, bundling, weighing and coil unloading.

Example 4

The embodiment provides a 30MnSiBCa hot-rolled wire rod for a PC steel bar, which comprises the following components in percentage by weight:

0.26% of C, 1.21% of Si, 1.02% of Mn, 0.009% of P, 0.005% of S, 0.0031% of B, 0.0025% of Ca0.15% of Cr, 0.015% of Ni, 0.036% of Cu, 0.0008% of O, less than 0.0009% of N, and the balance of Fe and inevitable impurities,

the method specifically comprises the following steps:

step 1, smelting molten steel: adding 110t of molten iron with S being less than or equal to 0.025 percent and P being less than or equal to 0.120 percent and 14t of scrap steel into an electric furnace, adopting a top-bottom composite blowing process, adding 90 percent of CaO content, 300ml of lime with activity and adopting a high-tension supplementing blowing method to pull carbon, controlling the end point carbon content to be 0.15 percent and the tapping temperature to be 1590 ℃;

argon is blown in the whole tapping process, the argon flow is 20NL/min, high-aluminum manganese iron alloy is added when tapping is started, silicon-manganese alloy and silicon-iron alloy are added when tapping is carried out at 1/4, and the adding amount of the high-aluminum manganese iron alloy, the silicon-manganese alloy and the silicon-iron alloy is 0.6kg/t steel, 13kg/t steel and 8kg/t steel respectively; the high aluminum manganese iron alloy, the silicon manganese alloy and the silicon iron alloy are added when 3/4 steel is tapped, 0.8kg/t steel of silicon aluminum barium alloy slag is added after the addition, a slag blocking rod is arranged for blocking slag, the slag dropping of a steel ladle is ensured to be less than or equal to 50mm, and the smelting molten steel is obtained;

step 2, argon blowing station temperature measurement sampling: controlling the temperature of the smelting molten steel obtained in the step 1 to be more than or equal to 1560 ℃, measuring the temperature of the molten steel within 2min after the molten steel enters a station, and sampling, determining oxygen and taking a slag sample after 2 min;

and 3, refining in an LF furnace: adding the qualified smelted molten steel after temperature measurement and sampling in the step 2 into an LF furnace, introducing argon gas 25NL/min, blowing the argon gas for 3min, and transmitting electricity for 15min by adopting 8 grades; adding calcium carbide 0.5kg/t steel for deoxidation to produce white slag for 18 min; then adjusting the argon flow to be 18NL/min, adding 0.45kg/t of steel low-carbon ferroboron, wherein the components are 0.05-0.1% of C, 9-25% of B, and the balance of Fe and inevitable impurities; heating the molten steel to 1590 ℃, adding a silicon-calcium-iron alloy for wire feeding treatment, wherein the components comprise 50-56% of Si, 25-35% of Ca and the balance of Fe and inevitable impurities; the wire feeding amount is 200m, the wire feeding speed is 2m/s, 15NL/min argon is introduced after the wire feeding is finished, and the time is 16 min;

and 4, molten steel continuous casting: adjusting the temperature of the upper table of the continuous casting furnace to 1555 ℃, and adding the composite heat preservation agent into the tundish molten steel, wherein the addition amount is 3kg/t steel; controlling the liquidus temperature to be 1495 ℃, the drawing temperature to be 1520 ℃, the drawing speed to be 2.9m/min, the secondary cooling specific water amount to be 1.8L/kg, starting crystallization electromagnetic stirring in the whole process, carrying out current 320A and frequency 5HZ, and continuously casting the molten steel in the step 3 into a steel billet by adopting a square billet casting machine;

step 5, steel rolling: adding the steel billet obtained in the step 4 into a walking beam type side-in side-out three-section heating furnace, controlling the soaking temperature at 1090 ℃, controlling the temperature difference of the steel billet along the length direction to be not more than 30 ℃, and heating for 100 min; the steel tapping temperature of the billet is 990 ℃, the initial rolling temperature is 1000 ℃, the finish rolling temperature is 960 ℃, the finish rolling temperature is 930 ℃ and the spinning temperature is 950 ℃; and after spinning is finished, the wire enters an air cooling line for controlling cooling, the cooling roller way is controlled to be covered completely, finally, the wire rod coil is naturally cooled to room temperature in air, and the 30MnSiBCa hot rolled wire rod for the PC steel rod is prepared after coiling, finishing, bundling, weighing and coil unloading.

Example 5

The embodiment provides a 30MnSiBCa hot-rolled wire rod for a PC steel bar, which comprises the following components in percentage by weight:

0.26 percent of C, 0.77 percent of Si, 0.98 percent of Mn, 0.01 percent of P, 0.007 percent of S, 0.0029 percent of B, 0.0026 percent of Ca0.0026 percent, 0.13 percent of Cr, 0.015 percent of Ni, 0.036 percent of Cu, 0.0008 percent of O, less than 0.0009 percent of N, and the balance of Fe and inevitable impurities,

the method specifically comprises the following steps:

step 1, smelting molten steel: adding 104t of molten iron with S less than or equal to 0.025 percent and P less than or equal to 0.120 percent and 20t of scrap steel serving as raw materials into an electric furnace, adopting a top-bottom composite blowing process, adding 90 percent of CaO content, adding 300ml of lime with activity, adopting a high-tension back-blowing method to pull carbon, controlling the end point carbon content to be 0.13 percent and the tapping temperature to be 1630 ℃;

argon is blown in the whole tapping process, the argon flow is 25NL/min, high-aluminum manganese iron alloy is added when tapping is started, silicon-manganese alloy and silicon-iron alloy are added when tapping is 1/4, and the addition amount of the high-aluminum manganese iron alloy, the silicon-manganese alloy and the silicon-iron alloy is 0.6kg/t steel, 12kg/t steel and 8kg/t steel respectively; the high aluminum manganese iron alloy, the silicon manganese alloy and the silicon iron alloy are added when 3/4 steel is tapped, 1.0kg/t steel of silicon aluminum barium alloy slag is added after the addition, a slag blocking rod is arranged for blocking slag, the slag dropping of a steel ladle is ensured to be less than or equal to 50mm, and the smelting molten steel is obtained;

step 2, argon blowing station temperature measurement sampling: controlling the temperature of the smelting molten steel obtained in the step 1 to be more than or equal to 1560 ℃, measuring the temperature of the molten steel within 2min after the molten steel enters a station, and sampling, determining oxygen and taking a slag sample after 2 min;

and 3, refining in an LF furnace: adding the qualified smelted molten steel after temperature measurement and sampling in the step 2 into an LF furnace, introducing argon gas 33NL/min, blowing the argon gas for 3min, and transmitting the power for 25min by adopting a 9-gear power transmission mode; adding calcium carbide 0.7kg/t steel for deoxidation to produce white slag, wherein the time is 25 min; then adjusting the argon flow to 19NL/min, adding 0.39kg/t steel of low-carbon ferroboron, the components of which are 0.05-0.1% of C, 9-25% of B, and the balance of Fe and inevitable impurities; heating the molten steel to 1588 ℃, adding silicon-calcium-iron alloy for wire feeding treatment, wherein the components comprise 50-56% of Si, 25-35% of Ca and the balance of Fe and inevitable impurities; the wire feeding amount is 280m, the wire feeding speed is 4m/s, 15NL/min argon is introduced after the wire feeding is finished, and the time is 16 min;

and 4, molten steel continuous casting: adjusting the temperature of the upper table of the continuous casting furnace to 1558 ℃, and adding 1.5kg/t of steel into the tundish molten steel by using a composite heat preservation agent; controlling the liquidus temperature to be 1495 ℃, the steel drawing temperature to be 1520 ℃, the drawing speed to be 3.1m/min, the secondary cooling specific water amount to be 1.6L/kg, starting crystallization electromagnetic stirring in the whole process, carrying out current 300A and frequency 5HZ, and continuously casting the molten steel in the step 3 into a steel billet by adopting a square billet casting machine;

step 5, steel rolling: adding the steel billet obtained in the step 4 into a walking beam type side-in side-out three-section heating furnace, controlling the soaking temperature at 1100 ℃, controlling the temperature difference of the steel billet along the length direction to be not more than 30 ℃, and heating for 110 min; the steel tapping temperature of the steel billet is 1010 ℃, the initial rolling temperature is 1040 ℃, the finish rolling temperature is 970 ℃, the finish rolling temperature is 930 ℃ and the spinning temperature is 960 ℃; and after spinning is finished, the wire enters an air cooling line for controlling cooling, the cooling roller way is controlled to be covered completely, finally, the wire rod coil is naturally cooled to room temperature in air, and the 30MnSiBCa hot rolled wire rod for the PC steel rod is prepared after coiling, finishing, bundling, weighing and coil unloading.

Example 6

The embodiment provides a 30MnSiBCa hot-rolled wire rod for a PC steel bar, which comprises the following components in percentage by weight:

0.33 percent of C, 1.02 percent of Si, 1.16 percent of Mn1, 0.007 percent of P, 0.009 percent of S, 0.0024 percent of B, 0.0016 percent of Ca0.0016 percent of Cr, 0.025 percent of Ni, 0.035 percent of Cu, 0.0009 percent of O, less than 0.0006 percent of N, and the balance of Fe and inevitable impurities,

the method specifically comprises the following steps:

step 1, smelting molten steel: adding 104t of molten iron with S less than or equal to 0.025 percent and P less than or equal to 0.120 percent and 20t of scrap steel serving as raw materials into a converter, adopting a top-bottom combined blowing process, adding 90 percent of CaO content, 300ml of lime with activity and adopting a high-tension compensation blowing method to pull carbon, controlling the end point carbon content to be 0.11 percent and the tapping temperature to be 1590 ℃;

argon is blown in the whole tapping process, the argon flow is 22NL/min, high-aluminum manganese iron alloy is added when tapping is started, silicon-manganese alloy and silicon-iron alloy are added when tapping is 1/4, and the addition amount of the high-aluminum manganese iron alloy, the silicon-manganese alloy and the silicon-iron alloy is 0.63kg/t steel, 15kg/t steel and 7.4kg/t steel respectively; the high aluminum manganese iron alloy, the silicon manganese alloy and the silicon iron alloy are added when 3/4 steel is tapped, 0.9kg/t steel of silicon aluminum barium alloy slag is added after the addition, a slag blocking rod is arranged for blocking slag, the slag dropping of a steel ladle is ensured to be less than or equal to 50mm, and the smelting molten steel is obtained;

step 2, argon blowing station temperature measurement sampling: controlling the temperature of the smelting molten steel obtained in the step 1 to be more than or equal to 1560 ℃, measuring the temperature of the molten steel within 2min after the molten steel enters a station, and sampling, determining oxygen and taking a slag sample after 2 min;

and 3, refining in an LF furnace: adding the qualified smelted molten steel after temperature measurement and sampling in the step 2 into an LF furnace, introducing argon gas for 3min at the speed of 24NL/min, and then transmitting electricity for 17min at the speed of 7; adding calcium carbide 0.6kg/t steel for deoxidation to produce white slag for 18 min; adjusting the flow rate of argon gas to 20NL/min, adding 0.33kg/t steel of low-carbon ferroboron, wherein the components are 0.05-0.1% of C, 9-25% of B, and the balance of Fe and inevitable impurities; heating the molten steel to 1586 ℃, adding silicon-calcium-iron alloy for wire feeding treatment, wherein the components comprise 50-56% of Si, 25-35% of Ca and the balance of Fe and inevitable impurities; the wire feeding amount is 239m, the wire feeding speed is 3m/s, 18NL/min argon is introduced after the wire feeding is finished, and the time is 14 min;

and 4, molten steel continuous casting: adjusting the temperature of the upper platform of the continuous casting furnace to 1557 ℃, and adding a composite heat preservation agent into the tundish molten steel, wherein the addition amount is 2kg/t steel; controlling the liquidus temperature to be 1495 ℃, the steel drawing temperature to be 1522 ℃, the drawing speed to be 2.8m/min, the secondary cooling specific water amount to be 1.6L/kg, starting crystallization electromagnetic stirring in the whole process, carrying out current 320A and frequency 4HZ, and continuously casting the molten steel in the step 3 into a steel billet by adopting a square billet casting machine;

step 5, steel rolling: adding the steel billet obtained in the step 4 into a walking beam type side-in side-out three-section heating furnace, controlling the soaking temperature at 1090 ℃, controlling the temperature difference of the steel billet along the length direction to be not more than 30 ℃, and heating for 90 min; the steel tapping temperature of the steel billet is 990 ℃, the initial rolling temperature is 1030 ℃, the finish rolling temperature is 970 ℃, the finish rolling temperature is 960 ℃, and the spinning temperature is 940 ℃; and after spinning is finished, the wire enters an air cooling line for controlling cooling, the cooling roller way is controlled to be covered completely, finally, the wire rod coil is naturally cooled to room temperature in air, and the 30MnSiBCa hot rolled wire rod for the PC steel rod is prepared after coiling, finishing, bundling, weighing and coil unloading.

The PC steel rods prepared in examples 1-6 were subjected to mechanical property tests using 30MnSiBCa hot rolled wire rods, and the results are shown in Table 2:

TABLE 2

As can be seen from Table 2, the 30MnSiBCa hot-rolled wire rod for the PC steel rod prepared by the invention has excellent mechanical properties, steel rods with different specifications can be prepared, the properties are stable, and particularly the yield strength and the tensile strength are excellent; meanwhile, it can be found that the performance of examples 1-2 and 6 is more stable and superior than that of examples 3-5.

The same lot of head and tail wire rods were manufactured by the manufacturing processes of examples 1 and 2 and were subjected to performance tests, the results of which are shown in table 3:

TABLE 3

As can be seen from Table 3, the preparation method of the 30MnSiBCa hot-rolled wire rod for the PC steel rod has the advantage of good stability, and the wire rod produced in the same batch has small performance deviation.

Further, the PC steel rods prepared in examples 1 and 2 were produced using 30MnSiBCa hot rolled wire rod, and the mechanical properties of the steel rods are shown in Table 4:

TABLE 4

As can be seen from Table 4, when the PC steel rods of different batches are produced by using the 30MnSiBCa hot-rolled wire rod, the performance deviation of the raw materials of the same batch is within +/-20 Mpa, and workers do not need to adjust the performance deviation in the operation process.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.

Claims (3)

1. A preparation method of 30MnSiBCa hot-rolled wire rod for a PC steel bar is characterized by comprising the following steps: the method comprises the following steps:
step 1, smelting molten steel: adding molten iron or scrap steel serving as a raw material into a converter or an electric furnace, adopting a top-bottom combined blowing process, adding lime, and adopting a high-tension blowing-in method to draw carbon, wherein the end-point carbon content is controlled to be 0.08-0.15%, and the tapping temperature is controlled to be 1580-;
argon is blown in the whole tapping process, the argon flow is 15-25NL/min, high-aluminum manganese-iron alloy is added when tapping is started, silicon-manganese alloy and silicon-iron alloy are added when tapping is 1/4, and the addition amounts of the high-aluminum manganese-iron alloy, the silicon-manganese alloy and the silicon-iron alloy are respectively 0.6-0.7kg/t steel, 12-16kg/t steel and 6-8kg/t steel; the high aluminum manganese iron alloy, the silicon manganese alloy and the silicon iron alloy are added when 3/4 steel is tapped, 0.8-1.0kg/t steel of silicon aluminum barium alloy slag is added after the addition, a slag blocking rod is arranged for blocking slag, the slag discharging of a steel ladle is ensured to be less than or equal to 50mm, and the smelting molten steel is obtained;
step 2, argon blowing station temperature measurement sampling: controlling the temperature of the smelting molten steel obtained in the step 1 to be more than or equal to 1560 ℃, measuring the temperature of the molten steel within 2min after the molten steel enters a station, and sampling, determining oxygen and taking a slag sample after 2 min;
and 3, refining in an LF furnace: adding the qualified smelted molten steel after temperature measurement and sampling in the step 2 into an LF furnace, introducing argon gas for 3min after 20-35NL/min argon blowing, and transmitting electricity for 15-25min by adopting 7-9 gears; adding calcium carbide 0.4-0.7kg/t steel for deoxidation to produce white slag for 15-25 min; adjusting argon flow to 15-25NL/min, adding 0.3-0.5kg/t steel of low-carbon ferroboron, wherein the components are 0.05-0.1% of C, 9-25% of B, and the balance of Fe and inevitable impurities; heating the molten steel to 1580-1595 ℃, adding a silicon-calcium-iron alloy for wire feeding treatment, wherein the components comprise 50-56% of Si, 25-35% of Ca and the balance of Fe and inevitable impurities; the wire feeding amount is 200-300m, the wire feeding speed is 2-4m/s, 15-20 NL/min argon is introduced after the wire feeding is finished, and the time is 12-16 min;
and 4, molten steel continuous casting: adjusting the temperature of the upper platform of the continuous casting furnace to 1550-; controlling the liquidus temperature to be 1495 ℃, the steel drawing temperature to be 1515-;
step 5, steel rolling: adding the steel billet in the step 4 into a walking beam type side-in side-out three-section heating furnace, controlling the soaking temperature to be 1100 +/-20 ℃, controlling the temperature difference of the steel billet along the length direction to be not more than 30 ℃, and heating for 80-120 min; the steel tapping temperature of the steel billet is 980-1020 ℃, the initial rolling temperature is 1000-1050 ℃, the finish rolling temperature is 950-990 ℃, the finish rolling temperature is 920-980 ℃, and the spinning temperature is 900-960 ℃; after spinning is finished, the wire is cooled by an air cooling line control, the cooling roller way is controlled to be covered completely, finally, the wire rod coil is naturally cooled to room temperature by air, and the 30MnSiBCa hot-rolled wire rod for the PC steel rod is prepared after coiling, finishing, bundling, weighing and coil unloading;
the continuous casting billet in the step 4 cannot contain brittle inclusions larger than 15 mu m, D-type inclusions are less than or equal to 1.5 grade, and Ds-type inclusions are less than or equal to 1.5 grade; the porosity and crack grade is less than or equal to 1 grade, the equiaxial crystal grain is more than or equal to 30 percent, and the center C segregation index of the continuous casting slab is less than or equal to 1.12;
the 30MnSiBCa hot-rolled wire rod for the PC steel rod comprises the following components in percentage by weight: 0.25-0.35% of C, 0.50-1.30% of Si, 0.70-1.50% of Mn, 0.002-0.004% of B, 0.001-0.003% of Ca, 0.1-0.2% of Cr, less than or equal to 0.015% of P, less than or equal to 0.015% of S, less than or equal to 0.25% of Ni, less than or equal to 0.20% of Cu, less than or equal to 0.004% of O, less than or equal to 0.006% of N, and the balance of Fe and inevitable impurities;
wherein the weight ratio of B to Cr is 1:40-80, the weight ratio of Mn to Si is 1.0-2.0: 1, 0.05 to 0.1 part of Ca and 0.06 to 0.25 part of B based on 100 parts of C, Si and Mn;
the 30MnSiBCa hot-rolled wire rod for the PC steel rod has a structure of ferrite F + pearlite P, the grain size is 8.0-10.0 grade, the yield strength is 450-500 MPa, the tensile strength is 680-730 MPa, the elongation after fracture is more than or equal to 28%, and the reduction of area is more than or equal to 45%.
2. The method for preparing the 30MnSiBCa hot-rolled wire rod for the PC steel rod according to the claim 1, is characterized in that: in the step 1, S is less than or equal to 0.025 percent and P is less than or equal to 0.120 percent, and the weight ratio of the molten iron to the scrap steel is 100-; the composition requirements of the end point of smelting molten steel are as follows: 0.22 to 0.28 percent of C, 0.7 to 0.8 percent of Si, 0.95 to 1.05 percent of Mn, less than or equal to 0.013 percent of P, less than or equal to 0.025 percent of S, less than or equal to 0.004 percent of O and less than or equal to 0.006 percent of N.
3. The method for preparing the 30MnSiBCa hot-rolled wire rod for the PC steel rod according to the claim 2, is characterized in that: the heating time in the step 5 is 80-90min for hot charging and 90-120min for cold charging.
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JPH083639A (en) * 1994-06-21 1996-01-09 Nippon Steel Corp Production of high carbon steel wire rod or steel wire excellent in wire drawability
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