A hot-rolled H-shaped steel for assembled building and preparation method thereof

Abstract

The present invention belongs to the field of metallurgy technology, and relates to a hot-rolled H-shaped steel for prefabricated buildings and a preparation method thereof. The weight percentage of the chemical composition of the hot-rolled H-shaped steel for prefabricated buildings is: C: 0.16% to 0.20%, Si: 0.15% to 0.65%, Mn: 1.00% to 1.70%, P≤0.015%, S≤0.012%, V, Ni, Mo, and the rest is iron and inevitable trace impurities; wherein, V+Ni+Mo=0.06 to 0.12%, V:Ni:Mo=3 to 2:4:3 to 4. The present invention mainly improves strength, fire resistance and weather resistance through microalloying. Microalloying mainly adopts vanadium nitrogen alloy, nickel plate and molybdenum iron. The yield strength is 355 to 390 MPa on average, and the tensile strength is 620 to 680 MPa on average, which meets the requirements for fire resistance and weather resistance testing, and can fully meet the high quality requirements of hot-rolled H-shaped steel for prefabricated buildings.

Description

Technical Field

[0001] The present invention belongs to the field of metallurgy technology, and in particular, the present invention relates to a high-strength fire-resistant and weather-resistant hot-rolled H-shaped steel, and more particularly, to a hot-rolled H-shaped steel for assembled buildings and a preparation method thereof. Background Art

[0002] The strength level of hot-rolled H-shaped steel used in buildings is usually 235MPa and 355MPa, which only guarantees the conventional strength, elongation and bending performance. In the design and construction of steel structures, anti-corrosion materials and fire-resistant materials are often used to protect the steel. Compared with concrete structures, the building area increases by 5% to 8%, the construction period is shortened by 30% to 60%, the material recycling rate is increased by 20% to 30%, and the carbon emissions are reduced by 50%. The economic, social and environmental benefits are significant. Therefore, steel structure buildings have ushered in rapid development. Prefabricated buildings have developed from single-story and multi-story to high-rise. Considering the difference between steel structure buildings and reinforced concrete buildings, the service life of prefabricated buildings is required to be less than 50 years. The commonly used anti-corrosion and fire-resistant forms can no longer meet the actual needs. Therefore, high-performance requirements for high strength, fire resistance and weather resistance are put forward for hot-rolled steel for prefabricated buildings to ensure the safety and reliability of prefabricated buildings.

[0003] For high-rise prefabricated buildings, the yield strength is usually required to be greater than 355MPa and meet the requirements of high-temperature tensile test and corrosion resistance test. However, the current production process has not yet achieved high-quality steel with multiple composite properties. High-strength weathering steel coated with fire-resistant coating or high-strength fire-resistant steel coated with weathering coating is often used to ensure the building's strength, fire resistance and weather resistance requirements. Summary of the invention

[0004] The object of the present invention is to overcome the above problems and provide a high-strength, fire-resistant, weather-resistant, high-performance composite hot-rolled H-shaped steel for assembled buildings and a preparation method thereof.

[0005] In order to achieve the above-mentioned purpose, another aspect of the present invention provides a hot-rolled H-shaped steel for prefabricated buildings, wherein the weight percentage of the chemical composition of the hot-rolled H-shaped steel for prefabricated buildings is C: 0.16%~0.20%, Si: 0.15%~0.65%, Mn: 1.00%~1.70%, P≤0.015%, S≤0.012%, V+Ni+Mo=0.06~0.12%, V:Ni:Mo=3~2:4:3~4, and the rest is iron and inevitable trace impurities.

[0006] According to another aspect of the present invention, the weight percentage of the chemical composition of the hot-rolled H-shaped steel for prefabricated buildings is preferably: C: 0.16% to 0.18%, Si: 0.35% to 0.60%, Mn: 1.20% to 1.40%, P≤0.015%, S≤0.012%, V+Ni+Mo=0.08 to 0.10%, V: 0.025 to 0.030%, Ni: 0.035 to 0.040%, Mo: 0.025 to 0.030%, and the rest is iron and inevitable trace impurities.

[0007] The present invention gives full play to the role of each element. V mainly plays a role in fine grain strengthening and precipitation strengthening, improves the strength of steel materials, and improves the toughness and plasticity of materials. The role of Ni is mainly to ensure the corrosion resistance of materials, and the role of Mo is to improve the fire resistance of materials. However, the combined addition of V+Ni+Mo should fully consider the mutual influence of each element and low cost. That is, below this range, the comprehensive performance of high strength, fire resistance and weather resistance of the material cannot be guaranteed; exceeding this range, the production cost is too high, and it may also bring some other production problems, such as cracks in the casting caused by high alloy.

[0008] In order to achieve the above object, one aspect of the present invention provides a method for preparing hot-rolled H-shaped steel for assembled buildings, the method comprising the following steps:

[0009] 1) Pre-desulfurization of molten iron to control the sulfur content in the molten iron after desulfurization to not exceed 0.018wt%;

[0010] 2) Converter smelting, using top and bottom combined blowing converter smelting, and in the converter smelting process, using high purity aluminum blocks for deoxidation, controlling the oxygen content in the molten steel to be less than 20ppm; adding vanadium nitrogen alloy, nickel plate, and ferromolybdenum during the converter steelmaking process, and the amount added is calculated according to the content limit;

[0011] 3) LF refining: during the refining process, the slag is first fully stirred to produce white slag or yellow-white slag;

[0012] 4) Continuous casting: during the continuous casting process, a common tundish is used and the profiled blank is cast with full protection;

[0013] 5) Rolling: positive deviation rolling is adopted, and the height and width deviations of the H-shaped steel shall not exceed 0-4mm and 0-3mm respectively; the weight percentage of the chemical composition of the hot-rolled H-shaped steel obtained by rolling is: C: 0.16%-0.18%, Si: 0.15%-0.65%, Mn: 1.00%-1.70%, P≤0.015%, S≤0.012%, V+Ni+Mo=0.06-0.12%, V:Ni:Mo=3-2:4:3-4, and the rest is iron and inevitable trace impurities.

[0014] According to one aspect of the present invention, in step 1), a KR station spray gun desulfurizer method is used, wherein the calcium oxide content in the desulfurizer is not less than 80%, the spray gun is inserted to a depth of 0.5 to 1.5 m, and the spraying carrier is nitrogen.

[0015] According to one aspect of the present invention, the amount of high-purity aluminum block added in step 2) is 1kg / t steel to 2kg / t steel, and the aluminum content of the high-purity aluminum ingot should not be less than 99.5%.

[0016] According to one aspect of the present invention, in the step 2), in the converter smelting process, the ladle uses a red clean ladle, and the baking temperature is ≥800°C; the endpoint carbon content is controlled to be not less than 0.10wt%; a double slag-blocking steel-making process is adopted, the steel-releasing time is not less than 1.5min, and the slag amount under the converter is controlled to be <70mm; vanadium nitrogen, nickel plate, and molybdenum-iron alloy are used for alloying, the alloy is added to the impact zone of the quasi-steel flow, and the alloy composition is controlled according to the middle limit; calcined coal is used as a carburizer, and the quasi-steel flow is evenly added, and it is added before 3 / 4 of the steel is tapped; slag-blocking balls are added when 3 / 5 to 4 / 5 of the steel is tapped to ensure a good slag-blocking effect, and the slag thickness of the ladle is ensured to be ≤70mm.

[0017] According to one aspect of the present invention, in step 3), in the LF refining process, argon is blown at the bottom for stirring throughout the whole process, and the slag is adjusted to white slag or yellow-white slag by silicon carbide or re-desulfurization; and vanadium nitrogen, nickel plate and molybdenum iron alloy are added before leaving the station according to the refining composition. Aluminum wire is fed once, and after the temperature and composition of the molten steel meet the casting requirements, 50-80m / furnace of calcium wire is fed before leaving the station.

[0018] According to one aspect of the present invention, in the step 4), in the continuous casting process, the secondary cooling adopts weak cooling, the crystallizer adopts non-sinusoidal vibration, the superheat of the tundish is controlled at 15°C ~ 25°C, the tundish adopts a low-carbon alkaline covering agent, the amount of the covering agent added is 1 ~ 1.5 kg / t steel, and the pulling speed is 1.2 ~ 1.6 m / min.

[0019] According to one aspect of the present invention, in the step 5), in the rolling process, the soaking temperature of the heating furnace is 1220℃~1250℃, the start rolling temperature is not less than 1150℃, the final rolling temperature is not higher than 950℃, the rolling adopts positive deviation rolling, and the height and width deviations of the H-shaped steel shall not exceed 0~4mm and 0~3mm respectively; the rolled material adopts natural cooling + water spray cooling on the cooling bed, and the straightening temperature is less than 100℃. According to an embodiment of the present invention, the specification of the rolled material is preferably H300×200×8×15.

[0020] The invention has an alloy ratio, which ensures comprehensive performance and realizes low cost; adopts a KR station spray gun desulfurizer method, wherein the calcium oxide content in the desulfurizer is not less than 80%, the spray gun is inserted into a depth of 0.5 to 1.5 m, and the spray carrier is nitrogen, which has a better desulfurization effect than the existing desulfurization process and ensures the purity of the steel; and the rolling adopts positive deviation rolling to meet the use requirements of prefabricated buildings, such as welding into box-type columns requires high precision.

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] The present invention mainly improves the strength, fire resistance and weather resistance through micro-alloying. The micro-alloying mainly adopts vanadium-nitrogen alloy, nickel plate and molybdenum iron. The average yield strength is 355-390MPa and the average tensile strength is 620-680MPa, which meets the requirements of fire resistance and weather resistance testing and can fully meet the high quality requirements of hot-rolled H-shaped steel for prefabricated buildings. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with specific embodiments.

[0024] The present invention mainly aims at the problems in the composition, smelting and rolling process of fire-resistant and weather-resistant high-strength hot-rolled H-shaped steel for prefabricated buildings, and provides a fire-resistant and weather-resistant high-strength hot-rolled H-shaped steel for prefabricated buildings and a preparation method thereof. The fire-resistant and weather-resistant high-strength hot-rolled H-shaped steel for prefabricated buildings produced according to the method of the present invention has good composite properties such as high strength, fire resistance and weather resistance.

[0025] The fire-resistant and weather-resistant high-strength hot-rolled H-shaped steel for prefabricated buildings and the manufacturing method thereof according to the present invention will be described in detail below.

[0026] The weight percentage of the chemical composition of the fire-resistant and weather-resistant high-strength hot-rolled H-shaped steel for prefabricated buildings according to the present invention is: C 0.16% to 0.20%, Si 0.15% to 0.65%, Mn 1.00% to 1.70%, P≤0.015%, S≤0.012%, V+Ni+Mo=0.06~0.12%, V:Ni:Mo=3~2:4:3~4, and the rest is iron and inevitable trace impurities. Preferably: V:Ni:Mo=3:4:3, V:Ni:Mo=2:4:4.

[0027] The fire-resistant and weather-resistant high-strength hot-rolled H-shaped steel for prefabricated buildings according to the present invention has the following composition design characteristics: low P and S content, and the use of V+Ni+Mo composite micro-alloying. In order to ensure the requirements of high strength, fire resistance and weather resistance, it is clarified that V:Ni:Mo should be controlled within 3-2:4:3-4, thereby ensuring that the product has good fire resistance and weather resistance while having high strength.

[0028] In order to ensure that the fire-resistant and weather-resistant high-strength hot-rolled H-shaped steel for prefabricated buildings in the present invention has good fire resistance and weather resistance, the sulfide and oxide content in the steel must be reduced. The present invention improves the purity of molten steel by reducing the S content and the O content, wherein the molten iron pre-desulfurization adopts the method of KR station spray gun desulfurizer, wherein the calcium oxide content in the desulfurizer is not less than 80%, the spray gun is inserted at a depth of 0.5 to 1.5m, and the spray carrier is nitrogen, and the sulfur content in the molten iron after desulfurization is controlled not to exceed 0.018wt%; high-purity aluminum blocks are used for converter deoxidation, and the addition amount is 1kg / t steel to 2kg / t steel. The aluminum content of the high-purity aluminum ingot should not be less than 99.5%, and the oxygen content in the molten steel is controlled to be less than 20ppm;

[0029] In addition, according to the present invention, the hot rolling process of the fire-resistant and weather-resistant high-strength hot-rolled H-shaped steel for prefabricated buildings adopts positive deviation rolling, mainly to ensure good matching during the processing and construction of prefabricated buildings, especially for the height and width deviations of the H-shaped steel shall not exceed 0-4mm and 0-3mm respectively.

[0030] Example 1

[0031] The present invention provides a method for preparing hot-rolled H-shaped steel for assembled buildings, the method comprising the following steps:

[0032] 1) Pre-desulfurization of molten iron, controlling the sulfur content in the molten iron after desulfurization to not exceed 0.018wt%; adopting the method of KR station spray gun desulfurizer, wherein the calcium oxide content in the desulfurizer is not less than 80%, the spray gun is inserted to a depth of 1m, and the spray carrier is nitrogen.

[0033] 2) Converter smelting, top and bottom double blowing converter smelting is adopted, and in the converter smelting process, high purity aluminum blocks are used for deoxidation, and the addition amount of high purity aluminum blocks is 1.8kg / t steel, and the oxygen content in the molten steel is controlled to be less than 20ppm; vanadium nitrogen alloy, nickel plate and ferromolybdenum are added during the converter tapping process, and the addition amount is calculated according to the content limit; in the converter smelting process, the ladle adopts red clean ladle, and the baking temperature is ≥800℃; the end point carbon content is controlled to be not less than 0.10wt%; double slag blocking steel tapping process is adopted, the steel release time is not less than 1.5min, and the slag amount under the converter is controlled to be <70mm; vanadium nitrogen, nickel plate and ferromolybdenum alloy are used for alloying, and the alloy is added to the impact zone of the quasi-steel flow, and the alloy composition is controlled according to the medium limit; calcined coal is used as the carburizer, and the quasi-steel flow is evenly added, and it is added before 3 / 4 of the steel is tapped; slag blocking balls are added when 3 / 5 to 4 / 5 of the steel is tapped to ensure a good slag blocking effect, and the slag thickness of the ladle is ensured to be ≤70mm.

[0034] 3) LF refining: during the refining process, the slag is first fully stirred, argon is blown at the bottom for stirring, and the slag is adjusted to white slag or yellow-white slag with silicon carbide or re-desulfurization; and vanadium nitrogen, nickel plate and molybdenum iron alloy are added before leaving the station according to the refining composition. Aluminum wire is fed once, and after the temperature and composition of the molten steel meet the pouring requirements, calcium wire is fed 60m / furnace before leaving the station.

[0035] 4) Continuous casting: During the continuous casting process, an ordinary tundish is used, and full-protection casting of special-shaped billets is adopted; in the continuous casting process, weak cooling is adopted for the secondary cooling, and the crystallizer adopts non-sinusoidal vibration. The superheat of the tundish is controlled at 15℃~25℃, and a low-carbon alkaline covering agent is used for the tundish. The amount of the covering agent added is 1~1.5kg / t steel, and the pulling speed is 1.2~1.6m / min.

[0036] 5) Rolling: positive deviation rolling is adopted, and the height and width deviations of H-shaped steel shall not exceed 0-4mm and 0-3mm respectively; in the rolling process, the uniform heating temperature of the heating furnace is 1220℃~1250℃, the start rolling temperature is not lower than 1150℃, and the final rolling temperature is not higher than 950℃. Positive deviation rolling is adopted for rolling, and the height and width deviations of H-shaped steel shall not exceed 0-4mm and 0-3mm respectively; the rolled material adopts natural cooling + water spray cooling on the cooling bed, and the straightening temperature is less than 100℃.

[0037] The weight percentages of the chemical composition of the hot-rolled H-beam obtained by rolling are: C: 0.16%, Si: 0.35%, Mn: 1.35%, P≤0.015%, S≤0.012%, V+Ni+Mo=0.10%, V:Ni:Mo=3:4:3, and the rest are iron and inevitable trace impurities.

[0038] Example 2

[0039] The present invention provides a method for preparing hot-rolled H-shaped steel for assembled buildings, the method comprising the following steps:

[0040] 1) Pre-desulfurization of molten iron, controlling the sulfur content in the molten iron after desulfurization to not exceed 0.018wt%; adopting the method of KR station spray gun desulfurizer, wherein the calcium oxide content in the desulfurizer is not less than 80%, the spray gun is inserted to a depth of 1.2m, and the spray carrier is nitrogen.

[0041] 2) Converter smelting, top and bottom double blowing converter smelting is adopted, and in the converter smelting process, high purity aluminum blocks are used for deoxidation, and the addition amount of high purity aluminum blocks is 1kg / t steel, and the oxygen content in the molten steel is controlled to be less than 20ppm; vanadium nitrogen alloy, nickel plate and ferromolybdenum are added during the converter tapping process, and the addition amount is calculated according to the content limit; in the converter smelting process, the ladle adopts red clean ladle, and the baking temperature is ≥800℃; the end point carbon content is controlled to be not less than 0.10wt%; double slag blocking steel tapping process is adopted, the steel release time is not less than 1.5min, and the slag amount under the converter is controlled to be <70mm; vanadium nitrogen, nickel plate and ferromolybdenum alloy are used for alloying, and the alloy is added to the impact zone of the quasi-steel flow, and the alloy composition is controlled according to the medium limit; calcined coal is used as the carburizer, and the quasi-steel flow is evenly added, and it is added before 3 / 4 of the steel is tapped; slag blocking balls are added when 3 / 5 to 4 / 5 of the steel is tapped to ensure a good slag blocking effect, and the slag thickness of the ladle is ensured to be ≤70mm.

[0042] 3) LF refining: during the refining process, the slag is first fully stirred, argon is blown at the bottom for stirring, and the slag is adjusted to white slag or yellow-white slag with silicon carbide or re-desulfurization; and vanadium nitrogen, nickel plate and molybdenum iron alloy are added before leaving the station according to the refining composition. Aluminum wire is fed once, and after the temperature and composition of the molten steel meet the pouring requirements, calcium wire is fed 70m / furnace before leaving the station.

[0043] 4) Continuous casting: During the continuous casting process, an ordinary tundish is used, and full-protection casting of special-shaped billets is adopted; in the continuous casting process, weak cooling is adopted for the secondary cooling, and the crystallizer adopts non-sinusoidal vibration. The superheat of the tundish is controlled at 15℃~25℃, and a low-carbon alkaline covering agent is used for the tundish. The amount of the covering agent added is 1~1.5kg / t steel, and the pulling speed is 1.2~1.6m / min.

[0044] 5) Rolling: positive deviation rolling is adopted, and the height and width deviations of H-shaped steel shall not exceed 0-4mm and 0-3mm respectively; in the rolling process, the uniform heating temperature of the heating furnace is 1220℃~1250℃, the start rolling temperature is not lower than 1150℃, and the final rolling temperature is not higher than 950℃. Positive deviation rolling is adopted for rolling, and the height and width deviations of H-shaped steel shall not exceed 0-4mm and 0-3mm respectively; the rolled material adopts natural cooling + water spray cooling on the cooling bed, and the straightening temperature is less than 100℃.

[0045] The weight percentages of the chemical composition of the hot-rolled H-beam obtained by rolling are: C: 0.17%, Si: 0.35%, Mn: 1.30%, P≤0.015%, S≤0.012%, V+Ni+Mo=0.08%, V:Ni:Mo=2:4:4, and the rest are iron and inevitable trace impurities.

[0046] Example 3

[0047] The present invention provides a method for preparing hot-rolled H-shaped steel for assembled buildings, the method comprising the following steps:

[0048] 1) Pre-desulfurization of molten iron, controlling the sulfur content in the molten iron after desulfurization to not exceed 0.018wt%; adopting the method of KR station spray gun desulfurizer, wherein the calcium oxide content in the desulfurizer is not less than 80%, the spray gun is inserted to a depth of 0.8m, and the spray carrier is nitrogen.

[0049] 2) Converter smelting, top and bottom double blowing converter smelting is adopted, and in the converter smelting process, high purity aluminum blocks are used for deoxidation, and the addition amount of high purity aluminum blocks is 2kg / t steel, and the oxygen content in the molten steel is controlled to be less than 20ppm; vanadium nitrogen alloy, nickel plate and ferromolybdenum are added during the converter tapping process, and the addition amount is calculated according to the content limit; in the converter smelting process, the ladle adopts red clean ladle, and the baking temperature is ≥800℃; the end point carbon content is controlled to be not less than 0.10wt%; double slag blocking steel tapping process is adopted, the steel release time is not less than 1.5min, and the slag amount under the converter is controlled to be <70mm; vanadium nitrogen, nickel plate and ferromolybdenum alloy are used for alloying, and the alloy is added to the impact zone of the quasi-steel flow, and the alloy composition is controlled according to the medium limit; calcined coal is used as the carburizer, and the quasi-steel flow is evenly added, and it is added before 3 / 4 of the steel is tapped; slag blocking balls are added when 3 / 5 to 4 / 5 of the steel is tapped to ensure a good slag blocking effect, and the slag thickness of the ladle is ensured to be ≤70mm.

[0050] 3) LF refining: during the refining process, the slag is first fully stirred, argon is blown at the bottom for stirring, and the slag is adjusted to white slag or yellow-white slag with silicon carbide or re-desulfurization; and vanadium nitrogen, nickel plate and molybdenum iron alloy are added before leaving the station according to the refining composition. Aluminum wire is fed once, and after the temperature and composition of the molten steel meet the pouring requirements, calcium wire is fed 70m / furnace before leaving the station.

[0051] 4) Continuous casting: During the continuous casting process, an ordinary tundish is used, and full-protection casting of special-shaped billets is adopted; in the continuous casting process, weak cooling is adopted for the secondary cooling, and the crystallizer adopts non-sinusoidal vibration. The superheat of the tundish is controlled at 15℃~25℃, and a low-carbon alkaline covering agent is used for the tundish. The amount of the covering agent added is 1~1.5kg / t steel, and the pulling speed is 1.2~1.6m / min.

[0052] 5) Rolling: positive deviation rolling is adopted, and the height and width deviations of H-shaped steel shall not exceed 0-4mm and 0-3mm respectively; in the rolling process, the uniform heating temperature of the heating furnace is 1220℃~1250℃, the start rolling temperature is not lower than 1150℃, and the final rolling temperature is not higher than 950℃. Positive deviation rolling is adopted for rolling, and the height and width deviations of H-shaped steel shall not exceed 0-4mm and 0-3mm respectively; the rolled material adopts natural cooling + water spray cooling on the cooling bed, and the straightening temperature is less than 100℃.

[0053] The weight percentages of the chemical composition of the hot-rolled H-beam obtained by rolling are: C: 0.18%, Si: 0.30%, Mn: 1.30%, P≤0.015%, S≤0.012%, V+Ni+Mo=0.06%, V:Ni:Mo=2.5:5:2.5, and the rest are iron and inevitable trace impurities.

[0054] In addition, in order to avoid blurring the subject of the present invention, a detailed description of the known technologies / processes included herein will be omitted. Therefore, in the method for preparing the fire-resistant and weather-resistant high-strength hot-rolled H-shaped steel for prefabricated buildings of the present invention, the processes not mentioned herein can all adopt the existing technologies.

[0055] Any contents not described in detail in the present invention can be based on the conventional technical knowledge in the art.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the embodiments, it should be understood by those skilled in the art that any modification or equivalent replacement of the technical solutions of the present invention does not depart from the spirit and scope of the technical solutions of the present invention and should be included in the scope of the claims of the present invention.

Claims

1. A hot-rolled H-shaped steel for assembled buildings, characterized in that: The weight percentage of the chemical composition of the hot-rolled H-shaped steel for prefabricated buildings is: C: 0.16% to 0.18%, Si: 0.35% to 0.60%, Mn: 1.20% to 1.40%, P≤0.015%, S≤0.012%, V: 0.025 to 0.030%, Ni: 0.035 to 0.040%, Mo: 0.025 to 0.030%, and the rest is iron and unavoidable trace impurities; Among them, V +Ni+Mo=0.08~0.10%, V:Ni:Mo=3~2:4:3~4; The method for preparing the hot-rolled H-shaped steel for prefabricated buildings comprises the following steps: 1) Pre-desulfurization of hot metal: The sulfur content in the hot metal after desulfurization is controlled to be no more than 0.018wt%, and the desulfurizer is sprayed with a KR station gun, wherein the calcium oxide content in the desulfurizer is not less than 80%, and the spray gun is inserted at a depth of 0.5~1.5m; the spray carrier is nitrogen; 2) Converter smelting: top and bottom combined blowing converter smelting is adopted to control the oxygen content in molten steel to be less than 20ppm; Vanadium-nitrogen alloy, nickel plate and ferromolybdenum are added during the converter tapping process; The steel ladle adopts red clean steel ladle, and the baking temperature is ≥800℃; the final carbon content is controlled to be not less than 0.10wt%; the double slag-blocking steel-making process is adopted, the steel-release time is not less than 1.5min, and the slag volume under the converter is controlled to be less than 70mm; vanadium-nitrogen alloy, nickel plate, and molybdenum iron are used for alloying, and the alloy is added to the impact zone of the quasi-steel flow, and the alloy composition is controlled according to the medium limit; the carburizer adopts calcined coal, and the quasi-steel flow is added evenly, and the addition is completed before 3 / 4 of the steel is tapped; the slag-blocking ball is added when the steel is tapped 3 / 5 to 4 / 5, to ensure that the slag thickness of the ladle is ≤70mm; high-purity aluminum blocks are used for converter deoxidation, and the addition amount is 1kg / t steel to 2kg / t steel, and the aluminum content of high-purity aluminum ingots should be not less than 99.5%; 3) Continuous casting: The full protection casting of profiled blanks is adopted in the continuous casting process; 4) Rolling: positive deviation rolling is adopted; Micro-alloying mainly uses vanadium-nitrogen alloy, nickel plate, and molybdenum iron. The yield strength of the hot-rolled H-shaped steel for prefabricated buildings is 355~390MPa on average, and the tensile strength of the hot-rolled H-shaped steel for prefabricated buildings is 620~680MPa on average.

2. The hot-rolled H-shaped steel for prefabricated buildings according to claim 1, characterized in that: The preparation method also includes a LF refining process: in the LF refining process, argon is blown bottom for stirring throughout the whole process, and the slag is adjusted to white slag or yellow-white slag by using silicon carbide or re-desulfurization; aluminum wire is fed once, and after the temperature and composition of the molten steel meet the casting requirements, 50 to 80 m of calcium wire is fed into the furnace before leaving the station.

3. The hot-rolled H-shaped steel for prefabricated buildings according to claim 1, characterized in that: In the step 3), in the continuous casting process, weak cooling is used for the secondary cooling, non-sinusoidal vibration is used for the crystallizer, the superheat of the tundish is controlled at 15°C to 25°C, a low-carbon alkaline covering agent is used for the tundish, the amount of the covering agent added is 1 to 1.5 kg / t steel, and the casting speed is 1.2 m / min to 1.6 m / min.

4. The hot-rolled H-shaped steel for prefabricated buildings according to claim 1, characterized in that: In the step 4), in the rolling process, the soaking temperature of the heating furnace is 1220°C to 1250°C, the start rolling temperature is not lower than 1150°C, the final rolling temperature is not higher than 950°C, the rolling adopts positive deviation rolling, and the height and width deviations of the H-shaped steel shall not exceed 0~4mm and 0~3mm respectively; the rolled material adopts a cooling method of natural cooling + water spray cooling on the cooling bed, and the straightening temperature is less than 100°C.