High-silicon low-manganese hot-rolled h-beam and method for manufacturing the same

Abstract

The application discloses a hot-rolled H-shaped steel containing high silicon and low manganese and a preparation method thereof, and relates to the technical field of material metallurgy. The H-shaped steel comprises the following chemical components in percentage by mass: C: 0.20-0.23%, Si: 0.45-0.58%, Mn: 1.10-1.35%, P: 0.030% or less, S: 0.025% or less, Ceq: 0.38-0.46%, and the balance of Fe and inevitable metallurgical impurities; and the mass ratio of Si / Mn is 0.38-0.45. The application constructs a component system of high silicon and low manganese without precious metals, and combines a double grain refinement mechanism composed of a four-stage trapezoidal heating process, coarse rolling dynamic recrystallization and a special static recrystallization period, and a hierarchical gradient cooling system composed of wing plate fan-shaped directional water cooling and a three-stage gradient cooling system, so that the H-shaped steel with a grain size of 9 levels and excellent upper yield strength, tensile strength and elongation performance is finally obtained.

Description

Technical Field

[0001] This invention relates to the field of materials metallurgy, specifically to a hot-rolled H-beam with high silicon and low manganese content and its preparation method. Background Technology

[0002] Hot-rolled H-beams possess several advantages, including good cross-sectional mechanical properties; no welding required, high quality precision, efficient production, and low consumption; low residual stress and high load-bearing capacity; convenient connection structure, easy installation, and short construction period; ease of standardization and low overall cost. The hot-rolled H-beam grade Q355B consists of three parts: yield strength designation, strength value, and quality grade. The prefix Q is the first letter of the Chinese pinyin for "yield," representing the steel's yield strength; the number 355 indicates the minimum upper yield strength of 355 MPa; and the final letter B represents the steel's quality grade B. Unless otherwise specified, the steel is delivered in hot-rolled condition by default, and the hot-rolled delivery condition designation is not reflected in the grade designation.

[0003] Hot-rolled H-beams Q355B require an upper yield strength of over 355 MPa. Therefore, currently, the upper yield strength of H-beams is typically increased by adding high levels of manganese, high levels of silicon, and large amounts of expensive alloying elements such as V, Nb, and Ti. However, this method has high production costs, reduces efficiency, and consumes a significant amount of alloy resources.

[0004] Therefore, how to optimize the alloy composition of H-beams to save resources, while ensuring product performance meets standards through improved production processes, and how to achieve low-cost production while obtaining the required mechanical properties, is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a hot-rolled H-beam with high silicon and low manganese content and its preparation method.

[0006] The objective of this invention can be achieved through the following technical solutions: A hot-rolled H-beam containing high silicon and low manganese, comprising the following chemical composition by mass percentage: C: 0.20-0.23%, Si: 0.45-0.58%, Mn: 1.10-1.35%, P≤0.030%, S≤0.025%, Ceq: 0.38-0.46%, with the balance being Fe and unavoidable metallurgical impurities; Furthermore, the Si / Mn mass ratio is 0.38-0.45.

[0007] A method for preparing hot-rolled H-beams with high silicon and low manganese content includes the following steps: Step (1): Preparing the steel billet: Pretreatment: The molten iron entering the furnace is desulfurized using a desulfurizing agent to obtain pretreated molten iron; Primary refining: The pretreated molten iron is sent to a top and bottom blowing converter for primary refining. During the tapping process, silicon-manganese alloy is added to obtain primary molten steel. Refining: The primary molten steel is fed into the LF refining furnace for high-basicity white slag refining, with argon gas blown from the bottom throughout the process, to obtain refined molten steel; Cast steel: Refined molten steel is continuously cast. The tundish is preheated. The refined molten steel flows from the ladle into the tundish through a long nozzle in a closed manner. A covering agent is added. Argon gas is continuously purged throughout the process. The steel billet is then continuously cast into the crystallizer through a submerged entry nozzle in the tundish. Furthermore, during the pretreatment process, the desulfurization temperature is 1320-1360℃; during the primary refining process, the converter top-blown oxygen pressure is 0.80-0.90MPa, the bottom-blown nitrogen pressure is 0.90-1.20MPa, and the tapping temperature is 1630-1650℃; during the refining process, the basicity R is 3.6-4.2, and the argon flow rate is 10-13L / min; during the casting process, the tundish is preheated to 1120-1160℃, the argon flow rate at the long nozzle is 48-52L / min, the argon sealing pressure is 0.025-0.035MPa, the superheat during continuous casting is controlled at 25-32℃, the casting machine speed is 0.82-0.92m / min, the crystallizer cooling water pressure is 0.45-0.55MPa, and the billet straightening temperature is 920-1020℃.

[0008] Step (2): The steel billet is fed into a walking beam furnace for segmented gradient heating. After being heated in each section of the heating furnace, a heated steel billet is obtained; the surface of the heated steel billet is then subjected to high-pressure water descaling treatment to obtain a descaled steel billet. Furthermore, the heating furnace is divided into a preheating section, heating section 1, heating section 2, and a soaking section. The temperatures of each section are as follows: preheating section 1120-1180℃, heating section 1220-1280℃, heating section 2 1260-1310℃, and soaking section 1260-1290℃. The total furnace time is 2.5-3 hours, and the furnace time ratio of the preheating section, heating section 1, heating section 2, and soaking section is 3:4:4:3. Furthermore, the descaling water pressure is 20-22 MPa, the cooling water temperature is 20-25℃, and the descaling time is 1.0-1.2 s.

[0009] Step (3): Rough rolling of the descaled steel billet: First, the descaled steel billet is subjected to reciprocating billet rolling to obtain intermediate billet. The intermediate billet is then fed into the heat-insulating roller table for static setting to obtain static intermediate billet. Furthermore, the number of passes in the reciprocating billet rolling is 7-9, the temperature of the initial rolling flange is 1150-1220℃, the rolling speed of the last pass in the billet rolling is 2.8-3.5m / s, and the overall elongation ratio is controlled at 1:2.4-2.9. Furthermore, the temperature of the heat-insulating roller conveyor is 1100-1120℃ and the holding time is 35-40s.

[0010] Step (four): Finish rolling the intermediate billet after it has been left to stand. The intermediate billet after standing is fed into a universal rolling mill and subjected to continuous unidirectional precision rolling to obtain shaped steel. Furthermore, the universal rolling mill unit consists of 11-13 universal rolling mill stands connected in series, with the finishing mill opening flange temperature being 1080-1140℃, the finishing mill final flange temperature being 920-950℃, the overall elongation ratio being 1:4.2-5.5, and the rolling speed of the last finishing mill stand being 2.0-2.5m / s.

[0011] Step (5): Cooling the formed steel: Flange-shaped pre-cooling: The formed steel is pre-cooled in a flange-shaped manner, and the temperature, pressure and cooling time of the cooling water are controlled to obtain the pre-cooled formed steel. Three-stage gradient cooling: The pre-water-cooled forming steel is fed into a cooling bed. First, the front section is air-cooled: the flange of the pre-water-cooled forming steel is naturally cooled; then, the middle section is water mist-cooled: water mist cooling is used to cool the flange temperature; then, the rear section is naturally slow-cooled: the mist cooling is turned off and natural air cooling is performed to obtain the cooled forming steel. Furthermore, during the directional fan-shaped pre-water cooling process of the wingplate, the cooling water temperature is 20-25℃, the pressure is 0.22-0.28MPa, and the cooling time is 2.5-3.2s; Furthermore, in the three-stage gradient cooling process, the first stage of air cooling involves naturally cooling the pre-water-cooled formed steel flange to 400-450℃; the second stage of water vapor atomization cooling involves controlling the compressed air pressure to 0.50-0.55MPa, the cooling water temperature to 20-25℃, and the water pressure to 0.30-0.35MPa to cool the flange temperature to 250-300℃; and the third stage of natural slow cooling involves naturally air cooling the flange temperature to 180-220℃.

[0012] Step (six): Straighten the cooled shaped steel: The cooled shaped steel is sent to a ten-roll straightener for straightening to obtain hot-rolled H-beams with high silicon and low manganese content.

[0013] Furthermore, the straightening temperature is 220-240℃, and the overall straightening time for a single steel section is 5-7 seconds.

[0014] The beneficial effects of this invention are: This invention discloses a hot-rolled H-beam containing high silicon and low manganese and its preparation method. The H-beam comprises the following chemical composition by mass percentage: C: 0.20-0.23%, Si: 0.45-0.58%, Mn: 1.10-1.35%, P≤0.030%, S≤0.025%, Ceq: 0.38-0.46%, with the balance being Fe and unavoidable metallurgical impurities; the Si / Mn mass ratio is 0.38-0.45. The invention first pre-treats the molten iron with desulfurization, then performs initial refining in a top-and-bottom blowing converter with the addition of silicon-manganese alloy to control the Si / Mn ratio, followed by refining in an LF furnace, and then continuously casting to obtain a billet. The billet is then subjected to four-stage gradient temperature-controlled heating in a walking beam furnace, high-pressure water descaling, and rough rolling to obtain an intermediate billet. After temperature homogenization, the intermediate billet is precision rolled into shape. The formed steel is first pre-water cooled in a fan-shaped flange, then cooled in three-stage gradient temperature-controlled cooling, and finally straightened to obtain the H-beam.

[0015] This invention abandons expensive microalloying elements such as V and Nb, and through a precise Si / Mn ratio coupled with a toughening mechanism, utilizes the high-silicon solid solution strengthening properties to precisely match and compensate for the strength loss of the low-manganese system, solving the problem that traditional steels must rely on microalloying precipitation strengthening to meet standards. The exclusive high-silicon, low-manganese ratio effectively suppresses the precipitation of grain boundary network carbides and refines the pearlite lamellar structure, breaking the industry bottleneck of the mutual exclusion of strength, plasticity, and toughness in traditional low-alloy steels. Through a specific 3:4:4:3 four-segment trapezoidal heating sequence, it can be specifically adapted to the high-temperature oxidation characteristics of high-silicon, low-manganese steel. Compared with traditional uniform high-temperature heating, it can reduce energy consumption, significantly shorten the high-temperature residence time, and ensure highly uniform internal and external temperatures of the billet, avoiding problems such as uneven deformation and microstructure dispersion caused by rolling temperature differences. Without microalloying grain boundary pinning, it can effectively suppress the coarsening of the original austenite grains, achieving primary grain refinement of the cast billet, laying a solid microstructure foundation for subsequent ultra-fine rolling treatment. The dual grain refinement mechanism, consisting of dynamic recrystallization during rough rolling and static recrystallization during a specific time period, is adapted to high-silicon and low-manganese steel. Unlike conventional steel rolling processes, it utilizes a dedicated static window with grain boundary dragging characteristics of high-silicon steel to improve the problems of mixed grains and coarse grains that are prone to occur in zero-microalloy systems, thereby enhancing grain uniformity and obtaining a high-grain size microstructure of grade 9.

[0016] This invention employs a fan-shaped pre-water cooling system with wing plates and a three-stage gradient cooling system, precisely adapting to the phase transformation kinetics of high-silicon, low-manganese steel and the geometric characteristics of thin-gauge H-beams. Differential control of the cross-sectional cooling rate effectively eliminates the core problems of warping, twisting, and stress concentration in thin-gauge steel, improving product dimensional accuracy. Furthermore, the graded gradient cooling achieves uniform nucleation of high-silicon ferrite and refined precipitation of pearlite, solving problems such as microstructure segregation and property dispersion that easily occur with conventional cooling of high-silicon materials, ensuring uniform and refined multiphase microstructure. Using high-silicon, low-manganese steel adapted to a medium-temperature straightening process avoids the problems of austenite grain coarsening and microstructure deterioration caused by traditional high-temperature hot straightening, while significantly reducing the risk of strain-aging embrittlement caused by conventional low-temperature straightening. This approach maintains a refined microstructure while stabilizing the overall mechanical properties of the steel. Detailed Implementation

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example

[0018] A hot-rolled H-beam with high silicon and low manganese content comprises the following chemical composition by mass percentage: C: 0.20%, Si: 0.45%, Mn: 1.10%, P: 0.030%, S: 0.025%, Ceq: 0.38%, with the balance being Fe and unavoidable metallurgical impurities; the Si / Mn mass ratio is 0.41.

[0019] A method for preparing hot-rolled H-beams with high silicon and low manganese content includes the following steps: Step (1): Preparing the steel billet: Pretreatment: The molten iron entering the furnace was desulfurized at 1320℃ for 15 minutes using a desulfurizing agent for iron and steel smelting (supplier: Henan Juye Biotechnology Co., Ltd., external dimensions: 2000mm), with S controlled at 0.025% and P at 0.030%, to obtain pretreated molten iron; Primary smelting: The pretreated molten iron is fed into a top-and-bottom blowing converter for primary smelting. The inlet temperature is 1320℃, and the top-blown oxygen pressure is controlled at 0.80MPa and the bottom-blown nitrogen pressure is controlled at 0.90MPa. The endpoint adopts a constant temperature and constant carbon dual control mode, and the tapping temperature is 1630℃. During the tapping process, silicon-manganese alloy (supplier: Anyang Fenglan Metallurgical Refractory Co., Ltd.) is added three times. The mass of silicon-manganese alloy added each time is equal, and the interval between each addition is 30s. At the tapping endpoint, the C: 0.18%, Si: 0.45%, and Mn: 1.10% are controlled, and the Si / Mn mass ratio is controlled at 0.41 to obtain the primary smelted steel. Refining: The primary molten steel is fed into the LF refining furnace for high-basicity white slag refining. Lime (supplier: Shijiazhuang Hualang Mineral Products Trading Co., Ltd., packaging specification: 25kg) and bauxite (supplier: Lingshou County Beiqiu Building Materials Sales Co., Ltd., packaging specification: 25kg / bag) are added to control the basicity R (R=w(CaO) / w(SiO2)) at 3.6. Argon is blown from the bottom throughout the process, and the argon flow rate is controlled at 10L / min. During the refining process, a carbon raiser (supplier: Hebei Jiyan Mineral Products Co., Ltd., specification: 1-3mm) is used to control C: 0.20%, while ensuring P: 0.030%, S: 0.025%, Ceq: 0.38%, and Si / Mn mass ratio of 0.41 to obtain refined molten steel. Casting steel: Refined molten steel is continuously cast. First, the tundish is preheated to 1120℃. The refined molten steel is then flowed from the ladle into the tundish through a long nozzle in a closed manner. A covering agent for steelmaking (supplier: Lingshou County Pengxia Furnace Lining Material Processing Plant, specification 30mm) is then added. Argon gas is continuously purged throughout the process. The argon flow rate at the long nozzle is controlled at 48L / min and the argon sealing pressure is 0.025MPa. The molten steel is then injected into the crystallizer through a tundish immersion nozzle in a closed manner. During the continuous casting process, the superheat is controlled at 25℃, the casting machine speed is controlled at 0.82m / min, the crystallizer uses non-sinusoidal vibration, the crystallizer cooling water pressure is 0.45MPa, and the straightening temperature is controlled at 920℃ during the billet conveying process. Finally, a steel billet is obtained. Step (2): The steel billet is fed into a walking beam furnace for segmented gradient heating. The heating furnace is divided into a preheating section, heating section 1, heating section 2, and soaking section. The temperature control of each section is as follows: preheating section 1120℃, heating section 1220℃, heating section 2 1260℃, and soaking section 1260℃. Finally, the steel billet is heated to 1260℃, with a total furnace time of 2.5 hours. The furnace time ratio of the preheating section, heating section 1, heating section 2, and soaking section is 3:4:4:3, resulting in a heated steel billet. The surface of the heated steel billet is then subjected to high-pressure water descaling treatment, with the descaling water pressure controlled at 20MPa, the cooling water temperature at 20℃, and the descaling time at 1.0s, resulting in a descaled steel billet.

[0020] Step (3): Rough rolling of the descaled steel billet: First, the descaled steel billet is subjected to 7 passes of reciprocating slab rolling, with the temperature of the slab rolling flange controlled at 1150℃, the rolling speed of the last slab rolling pass being 2.8m / s, and the overall elongation ratio controlled at 1:2.4. The intermediate billet is obtained by rolling, and then the intermediate billet is fed into the heat-insulating roller table and placed at 1100℃ for 35s to obtain the intermediate billet after standing. Step (four): Finish rolling the intermediate billet after it has been left to stand. After standing, the intermediate billet is fed into a universal rolling mill consisting of 11 universal rolling mill stands connected in series for continuous finishing rolling in one direction. The temperature of the first finishing rolling flange is controlled at 1080℃, the temperature of the final finishing rolling flange is controlled at 920℃, the overall elongation ratio is 1:4.2, and the rolling speed of the last finishing mill stand is 2.0m / s to obtain the shaped steel. Step (5): Cooling the formed steel: Flange-shaped pre-water cooling: The formed steel is pre-water cooled in a flange-shaped manner, with the cooling water temperature controlled at 20℃, the pressure at 0.22MPa, and the cooling time at 2.5s, to obtain the pre-water-cooled formed steel; Three-stage gradient cooling: The pre-water-cooled forming steel is fed into a cooling bed. First, it undergoes front-stage air cooling: the pre-water-cooled forming steel flanges are naturally cooled to 400℃. Then, it undergoes middle-stage water mist cooling: water mist cooling is used, with compressed air pressure controlled at 0.50MPa, cooling water temperature at 20℃, and water pressure at 0.30MPa, cooling the flange temperature to 250℃. Finally, it undergoes rear-stage natural slow cooling: the mist cooling is turned off, and the flange temperature is naturally air-cooled to 180℃, resulting in the cooled forming steel. Step (six): Straighten the cooled shaped steel: The cooled shaped steel is sent to a ten-roll straightener and straightened at 220°C. The overall straightening time of a single steel section is controlled to be 5 seconds, resulting in hot-rolled H-beams with high silicon and low manganese content. Example

[0021] A hot-rolled H-beam with high silicon and low manganese content comprises the following chemical composition by mass percentage: C: 0.21%, Si: 0.51%, Mn: 1.22%, P: 0.030%, S: 0.025%, Ceq: 0.41%, with the balance being Fe and unavoidable metallurgical impurities; the Si / Mn mass ratio is 0.42.

[0022] A method for preparing hot-rolled H-beams with high silicon and low manganese content includes the following steps: Step (1): Preparing the steel billet: Pretreatment: The molten iron entering the furnace was desulfurized at 1340℃ for 15 minutes using a desulfurizing agent for iron and steel smelting (supplier: Henan Juye Biotechnology Co., Ltd., external dimensions: 2000mm), with S controlled at 0.025% and P at 0.030% to obtain pretreated molten iron; Primary smelting: The pretreated molten iron is fed into a top-and-bottom blowing converter for primary smelting. The inlet temperature is 1320℃, the top-blown oxygen pressure is controlled at 0.85MPa, and the bottom-blown nitrogen pressure is controlled at 1.05MPa. The endpoint adopts a constant temperature and constant carbon dual control mode, and the tapping temperature is 1640℃. During the tapping process, silicon-manganese alloy (supplier: Anyang Fenglan Metallurgical Refractory Co., Ltd.) is added three times. The mass of silicon-manganese alloy added each time is equal, and the interval between each addition is 33s. At the tapping endpoint, the C: 0.19%, Si: 0.51%, and Mn: 1.22% are controlled, and the Si / Mn mass ratio is controlled at 0.42 to obtain the primary smelted steel. Refining: The primary molten steel is fed into the LF refining furnace for high-basicity white slag refining. The high-basicity white slag refining process is adopted. Lime (supplier: Shijiazhuang Hualang Mineral Products Trading Co., Ltd., packaging specification: 25kg) and bauxite (supplier: Lingshou County Beiqiu Building Materials Sales Co., Ltd., packaging specification: 25kg / bag) are added to control the basicity R (R=w(CaO) / w(SiO2)) at 3.9. Argon is blown from the bottom throughout the process, and the argon flow rate is controlled at 11L / min. During the refining process, a carbon raiser (supplier: Hebei Jiyan Mineral Products Co., Ltd., specification: 1-3mm) is used to control C: 0.21%, while ensuring P: 0.030%, S: 0.025%, Ceq: 0.41%, and Si / Mn mass ratio of 0.42 to obtain refined molten steel. Casting steel: Refined molten steel is continuously cast. First, the tundish is preheated to 1140℃. The refined molten steel is then flowed from the ladle into the tundish through a long nozzle in a closed manner. A covering agent for steelmaking (supplier: Lingshou County Pengxia Furnace Lining Material Processing Plant, specification 30mm) is then added. Argon gas is continuously purged throughout the process. The argon flow rate at the long nozzle is controlled at 50L / min and the argon sealing pressure is 0.030MPa. The steel is then injected into the crystallizer through a tundish immersion nozzle in a closed manner. During the continuous casting process, the superheat is controlled at 28℃, the casting machine speed is controlled at 0.87m / min, the crystallizer uses non-sinusoidal vibration, the crystallizer cooling water pressure is 0.50MPa, and the straightening temperature is controlled at 970℃ during the billet conveying process. Finally, a steel billet is obtained. Step (2): The steel billet is fed into a walking beam furnace for segmented gradient heating. The heating furnace is divided into a preheating section, heating section 1, heating section 2, and soaking section. The temperature control of each section is as follows: preheating section 1150℃, heating section 1250℃, heating section 2 1285℃, and soaking section 1275℃. Finally, the steel billet is heated to 1275℃, with a total furnace time of 2.8 hours. The furnace time ratio of the preheating section, heating section 1, heating section 2, and soaking section is 3:4:4:3, resulting in a heated steel billet. The surface of the heated steel billet is then subjected to high-pressure water descaling treatment, with the descaling water pressure controlled at 21MPa, the cooling water temperature at 22℃, and the descaling time at 1.1s, resulting in a descaled steel billet.

[0023] Step (3): Rough rolling of the descaled steel billet: First, the descaled steel billet is subjected to 8 passes of reciprocating slab rolling, with the temperature of the slab rolling flange controlled at 1185℃, the rolling speed of the last slab rolling pass being 3.2m / s, and the overall elongation ratio controlled at 1:2.7. The intermediate billet is obtained by rolling, and then the intermediate billet is fed into the heat-insulating roller table and placed at 1110℃ for 37s to obtain the intermediate billet after standing. Step (four): Finish rolling the intermediate billet after it has been left to stand. After standing, the intermediate billet is fed into a universal rolling mill consisting of 12 universal rolling mills connected in series for continuous finishing rolling in one direction. The temperature of the first finishing rolling flange is controlled at 1110℃, the temperature of the final finishing rolling flange is controlled at 935℃, the overall elongation ratio is 1:4.8, and the rolling speed of the last finishing mill is 2.2m / s to obtain the shaped steel. Step (5): Cooling the formed steel: Flange-shaped pre-water cooling: The formed steel is pre-water cooled in a flange-shaped manner, with the cooling water temperature controlled at 22℃, the pressure at 0.25MPa, and the cooling time at 2.8s, to obtain the pre-water-cooled formed steel; Three-stage gradient cooling: The pre-water-cooled forming steel is fed into a cooling bed. First, it undergoes front-stage air cooling: the pre-water-cooled forming steel flanges are naturally cooled to 430°C. Then, it undergoes middle-stage water mist cooling: water mist cooling is used, with compressed air pressure controlled at 0.52 MPa, cooling water temperature at 22°C, and water pressure at 0.32 MPa, cooling the flange temperature to 275°C. Finally, it undergoes rear-stage natural slow cooling: the mist cooling is turned off, and the flange temperature is naturally air-cooled to 200°C, resulting in the cooled forming steel. Step (six): Straighten the cooled shaped steel: The cooled shaped steel is sent to a ten-roll straightener and straightened at 230°C. The overall straightening time of a single steel section is controlled to be 6 seconds, resulting in hot-rolled H-beams with high silicon and low manganese content. Example

[0024] A hot-rolled H-beam with high silicon and low manganese content comprises the following chemical composition by mass percentage: C: 0.23%, Si: 0.58%, Mn: 1.35%, P: 0.030%, S: 0.025%, Ceq: 0.46%, with the balance being Fe and unavoidable metallurgical impurities; the Si / Mn mass ratio is 0.43.

[0025] A method for preparing hot-rolled H-beams with high silicon and low manganese content includes the following steps: Step (1): Preparing the steel billet: Pretreatment: The molten iron entering the furnace was desulfurized at 1360℃ for 15 minutes using a desulfurizing agent for iron and steel smelting (supplier: Henan Juye Biotechnology Co., Ltd., external dimensions: 2000mm), with S controlled at 0.025% and P at 0.030%, to obtain pretreated molten iron; Primary smelting: The pretreated molten iron is fed into a top-and-bottom blowing converter for primary smelting. The inlet temperature is 1320℃, the top-blown oxygen pressure is controlled at 0.90MPa, and the bottom-blown nitrogen pressure is controlled at 1.20MPa. The endpoint adopts a constant temperature and constant carbon dual control mode, and the tapping temperature is 1650℃. During the tapping process, silicon-manganese alloy (supplier: Anyang Fenglan Metallurgical Refractory Co., Ltd.) is added three times. The mass of silicon-manganese alloy added each time is equal, and the interval between each addition is 35s. At the tapping endpoint, the C: 0.20%, Si: 0.58%, and Mn: 1.35% are controlled, and the Si / Mn mass ratio is controlled at 0.43 to obtain the primary smelted steel. Refining: The primary molten steel is fed into the LF refining furnace for high-basicity white slag refining. Lime (supplier: Shijiazhuang Hualang Mineral Products Trading Co., Ltd., packaging specification: 25kg) and bauxite (supplier: Lingshou County Beiqiu Building Materials Sales Co., Ltd., packaging specification: 25kg / bag) are added to control the basicity R (R=w(CaO) / w(SiO2)) at 4.2. Argon is blown from the bottom throughout the process, and the argon flow rate is controlled at 13L / min. During the refining process, a carbon raiser (supplier: Hebei Jiyan Mineral Products Co., Ltd., specification: 1-3mm) is used to control C: 0.23%, while ensuring P: 0.030%, S: 0.025%, Ceq: 0.46%, and Si / Mn mass ratio of 0.43 to obtain refined molten steel. Casting steel: Refined molten steel is continuously cast. First, the tundish is preheated to 1160℃. The refined molten steel flows from the ladle into the tundish through a long nozzle in a closed manner. A covering agent (supplier: Lingshou County Pengxia Furnace Lining Material Processing Plant, specification 30mm) is then added. Argon gas is continuously purged throughout the process. The argon flow rate at the long nozzle is controlled at 52L / min and the argon sealing pressure is 0.035MPa. The molten steel is then injected into the crystallizer through a tundish immersion nozzle in a closed manner. During the continuous casting process, the superheat is controlled at 32℃, the casting machine speed is controlled at 0.92m / min, the crystallizer uses non-sinusoidal vibration, the crystallizer cooling water pressure is 0.55MPa, and the straightening temperature is controlled at 1020℃ during the billet conveying process. Finally, a steel billet is obtained. Step (2): The steel billet is fed into a walking beam furnace for segmented gradient heating. The heating furnace is divided into a preheating section, heating section 1, heating section 2, and soaking section. The temperature control of each section is as follows: preheating section 1180℃, heating section 1280℃, heating section 2 1310℃, and soaking section 1290℃. Finally, the steel billet is heated to 1290℃, with a total furnace time of 3 hours. The furnace time ratio of the preheating section, heating section 1, heating section 2, and soaking section is 3:4:4:3, resulting in a heated steel billet. The surface of the heated steel billet is then subjected to high-pressure water descaling treatment, with the descaling water pressure controlled at 22MPa, the cooling water temperature at 25℃, and the descaling time at 1.2s, resulting in a descaled steel billet.

[0026] Step (3): Rough rolling of the descaled steel billet: First, the descaled steel billet is subjected to 9 passes of reciprocating slab rolling, with the temperature of the slab rolling flange controlled at 1220℃, the rolling speed of the last slab rolling pass being 3.5m / s, and the overall elongation ratio controlled at 1:2.9. The intermediate billet is rolled and then fed into the heat-insulating roller table and placed at 1120℃ for 40s to obtain the intermediate billet after standing. Step (four): Finish rolling the intermediate billet after it has been left to stand. After standing, the intermediate billet is fed into a universal rolling mill consisting of 13 universal rolling mills connected in series for continuous finishing rolling in one direction. The temperature of the first finishing rolling flange is controlled at 1140℃, the temperature of the last finishing rolling flange is controlled at 950℃, the overall elongation ratio is 1:5.5, and the rolling speed of the last finishing mill is 2.5m / s to obtain the shaped steel. Step (5): Cooling the formed steel: Flange-shaped pre-water cooling: The formed steel is pre-water cooled in a flange-shaped manner, with the cooling water temperature controlled at 25℃, the pressure at 0.28MPa, and the cooling time at 3.2s, to obtain the pre-water-cooled formed steel; Three-stage gradient cooling: The pre-water-cooled forming steel is fed into a cooling bed. First, it undergoes front-stage air cooling: the pre-water-cooled forming steel flanges are naturally cooled to 450°C. Then, it undergoes middle-stage water mist cooling: water mist cooling is used, with compressed air pressure controlled at 0.55MPa, cooling water temperature at 25°C, and water pressure at 0.35MPa, cooling the flange temperature to 300°C. Finally, it undergoes rear-stage natural slow cooling: the mist cooling is turned off, and the flange temperature is naturally air-cooled to 220°C, resulting in the cooled forming steel. Step (six): Straighten the cooled shaped steel: The cooled shaped steel is sent to a ten-roll straightener and straightened at 240°C. The overall straightening time of a single steel section is controlled to be 7 seconds, resulting in hot-rolled H-beams with high silicon and low manganese content.

[0027] Comparative Example 1 Compared with Example 3, the mass percentage of Mn was adjusted to Mn: 1.10%, and the mass ratio of Si / Mn was 0.58 / 1.10 = 0.53. The rest was exactly the same as in Example 3, and hot-rolled H-beams with high silicon and low manganese were obtained.

[0028] Comparative Example 2 Compared with Example 3, the Si mass percentage was adjusted to Si: 0.45%, and the Si / Mn mass ratio was 0.45 / 1.35 = 0.33. The rest was exactly the same as in Example 3, and hot-rolled H-beams with high silicon and low manganese were obtained.

[0029] Comparative Example 3 Compared with Example 3, the furnace time ratio of the preheating section, heating section 1, heating section 2 and soaking section in step (II) is adjusted to 5:4:4:1, and the rest is exactly the same as in Example 3, to obtain hot-rolled H-beams with high silicon and low manganese.

[0030] Comparative Example 4 Compared with Example 3, the time ratio of the preheating section, heating section 1, heating section 2, and soaking section in step (II) was adjusted to 1:4:4:5, while the rest was exactly the same as in Example 3, to obtain hot-rolled H-beams with high silicon and low manganese content.

[0031] Comparative Example 5 Compared with Example 3, the intermediate billet in step (iii) is not sent to the heat-insulating roller table for static storage, but is directly used in step (iv). The rest is exactly the same as in Example 3, and hot-rolled H-beams with high silicon and low manganese are obtained. Specifically: Step (3): Rough rolling of the descaled steel billet: First, the descaled steel billet is subjected to 9 passes of reciprocating slab rolling, with the temperature of the slab flange controlled at 1220℃, the rolling speed of the last slab being 3.5m / s, and the overall elongation ratio controlled at 1:2.9, to obtain the intermediate billet. Step (4): The intermediate billet is fed into a universal rolling mill consisting of 13 universal rolling mill stands connected in series for continuous finishing rolling in one direction. The temperature of the initial finishing rolling flange is controlled at 1080℃, the temperature of the final finishing rolling flange is controlled at 950℃, the overall elongation ratio is controlled at 1:5.5, and the rolling speed of the last finishing mill stand is 2.5m / s to obtain the formed steel-1.

[0032] Comparative Example 6 Compared with Example 3, the directional fan-shaped pre-water cooling of the wing plate in step (5) is cancelled, and three-stage gradient cooling is directly carried out. The rest is exactly the same as Example 3, and hot-rolled H-beams with high silicon and low manganese are obtained. Specifically: Step (5): Cooling the formed steel: The formed steel is fed into a cooling bed and first undergoes front-stage air cooling: the flange of the formed steel is naturally cooled to 450℃; then, it undergoes middle-stage water mist cooling: water mist cooling is used, with compressed air pressure controlled at 0.55MPa, cooling water temperature controlled at 25℃, and water pressure controlled at 0.35MPa, cooling the flange temperature to 300℃; then, it undergoes rear-stage natural slow cooling: the mist cooling is turned off, and it is naturally air cooled to 220℃, resulting in cooled formed steel-1.

[0033] Comparative Example 7 Compared with Example 3, the three-stage gradient cooling in step (v) is replaced with two-stage gradient cooling, and the rest is exactly the same as in Example 3, to obtain hot-rolled H-beams with high silicon and low manganese content; Specifically: Step (5): Cooling the formed steel: Flange-shaped pre-water cooling: The formed steel is pre-water cooled in a flange-shaped manner. The cooling water temperature is controlled at 25℃, the pressure is controlled at 0.28MPa, and the cooling time is controlled at 3.2s to obtain the pre-water-cooled formed steel. Two-stage gradient cooling: The pre-water-cooled forming steel is fed into a cooling bed and first undergoes front-stage air cooling: the pre-water-cooled forming steel flanges are naturally cooled to 450℃; then, the middle-stage water mist cooling is performed: water mist cooling is adopted, the compressed air pressure is controlled at 0.55MPa, the cooling water temperature is controlled at 25℃, and the water pressure is controlled at 0.35MPa, the flange temperature is cooled to 220℃, and the cooled forming steel-2 is obtained.

[0034] The following is a further effect test on the hot-rolled H-beams containing high silicon and low manganese prepared in Examples 1-3 and Comparative Examples 1-7 of the present invention. The test results are shown below.

[0035] Refer to GB / T 11263-2024 for test section specifications, which are expressed as H (height) × flange width × web thickness × flange thickness, with the units for height, flange width, web thickness, and flange thickness all in mm; refer to GB / T 6394-2017 for metallographic testing of grain size; refer to GB / T 228.1-2021 for room temperature tensile testing, testing upper yield strength, tensile strength, and elongation; refer to GB / T 229-2020 for room temperature V-notch Charpy impact testing, testing impact energy.

[0036] The specific test results are recorded in Table 1.

[0037] Table 1: Performance Test Results of Hot-Rolled H-Beams Containing High Silicon and Low Manganese

[0038] According to the data in Table 1, the hot-rolled H-beams with high silicon and low manganese prepared in Examples 1-3 of the present invention have a grain size of up to grade 9, and at the same time have good tensile strength, upper yield strength, elongation and room temperature V-shaped Charpy impact energy.

[0039] Comparing Example 3 with Comparative Example 1, it can be seen that when the mass percentage of Mn is adjusted to Mn: 1.10%, the mass ratio of Si / Mn is 0.58 / 1.10 = 0.53, which does not meet the requirement of a mass ratio of Si / Mn of 0.38-0.45. This indicates that the present invention uses the precise Si / Mn ratio coupling strengthening mechanism to precisely match and compensate for the strength loss of the low manganese system by utilizing the high silicon solid solution strengthening characteristics. This is more conducive to improving the tensile strength, upper yield strength, elongation and room temperature V-shaped Charpy impact energy of H-beams.

[0040] Comparing Example 3 with Comparative Example 2, it can be seen that when the Si mass percentage is adjusted to Si: 0.45%, the Si / Mn mass ratio is 0.45 / 1.35 = 0.33, which does not meet the requirement of Si / Mn mass ratio of 0.38-0.45. This indicates that the present invention uses the precise Si / Mn ratio coupling strengthening mechanism to precisely match and compensate for the strength loss of the low manganese system by utilizing the high silicon solid solution strengthening characteristics. This is more conducive to improving the tensile strength, upper yield strength, elongation and room temperature V-shaped Charpy impact energy of H-beams.

[0041] Comparing Example 3 with Comparative Example 3, it can be seen that adjusting the furnace time ratio of the preheating section, heating section 1, heating section 2, and soaking section in step (II) to 5:4:4:1 indicates that the four-segment trapezoidal heating sequence of 3:4:4:3 adopted in this invention is suitable for the high silicon and low manganese steel of this invention, which can ensure uniform internal and external temperature of the billet and is more conducive to improving the tensile strength, upper yield strength, elongation, and room temperature V-shaped Charpy impact energy of H-beam steel.

[0042] Comparing Example 3 with Comparative Example 4, it can be seen that adjusting the furnace time ratio of the preheating section, heating section 1, heating section 2, and soaking section in step (II) to 1:4:4:5 indicates that the four-segment trapezoidal heating sequence of 3:4:4:3 adopted in this invention is suitable for the high silicon and low manganese steel of this invention, which can ensure uniform internal and external temperature of the billet and is more conducive to improving the tensile strength, upper yield strength, elongation, and room temperature V-shaped Charpy impact energy of H-beam steel.

[0043] Comparing Example 3 with Comparative Example 5, it can be seen that by not feeding the intermediate billet in step (III) into the heat-insulating roller table for static placement, but directly using it in step (IV), the present invention can reduce the temperature gradient, uniformize the temperature, reduce the difference in deformation resistance of various parts in the finishing rolling process, and make the rolling elongation synchronous, which is beneficial to improving the tensile strength, upper yield strength, elongation and room temperature V-shaped Charpy impact energy of H-beams.

[0044] Comparing Example 3 with Comparative Example 6, it can be seen that by canceling the directional fan-shaped pre-water cooling of the flange in step (v) and directly performing three-stage gradient cooling, it can be shown that the use of directional fan-shaped pre-water cooling of the flange combined with the three-stage gradient cooling process can quickly balance the temperature difference between the web and the flange, suppress the warping caused by the temperature difference of the cross section, and help improve the tensile strength, upper yield strength, elongation and room temperature V-shaped Charpy impact energy of H-beams.

[0045] Comparing Example 3 with Comparative Example 7, it can be seen that replacing the three-stage gradient cooling in step (v) with two-stage gradient cooling shows that the present invention uses three-stage gradient cooling combined with the directional fan-shaped pre-water cooling process of the wing plate, which can avoid the imbalance of the overall thermal shrinkage gradient of the cross section and is beneficial to the improvement of the tensile strength, upper yield strength, elongation and room temperature V-shaped Charpy impact energy of H-beam steel.

[0046] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A hot-rolled H-beam containing high silicon and low manganese, characterized in that: The chemical composition includes the following percentages by mass: C: 0.20-0.23%, Si: 0.45-0.58%, Mn: 1.10-1.35%, P≤0.030%, S≤0.025%, Ceq: 0.38-0.46%, with the balance being Fe and unavoidable metallurgical impurities; the Si / Mn mass ratio is 0.38-0.

45.

2. A method for preparing hot-rolled H-beams containing high silicon and low manganese as described in claim 1, characterized in that: Includes the following steps: Step (1): Preparing the steel billet: Pretreatment: The molten iron entering the furnace is desulfurized using a desulfurizing agent to obtain pretreated molten iron; Primary refining: The pretreated molten iron is sent to a top and bottom blowing converter for primary refining. During the tapping process, silicon-manganese alloy is added to obtain primary molten steel. Refining: The primary molten steel is fed into the LF refining furnace for high-basicity white slag refining, with argon gas blown from the bottom throughout the process, to obtain refined molten steel; Cast steel: Refined molten steel is continuously cast. The tundish is preheated. The refined molten steel flows from the ladle into the tundish through a long nozzle in a closed manner. A covering agent is added. Argon gas is continuously purged throughout the process. The steel billet is then continuously cast into the crystallizer through a submerged entry nozzle in the tundish. Step (2): The steel billet is fed into a walking beam furnace for segmented gradient heating. After being heated in each section of the heating furnace, a heated steel billet is obtained; the surface of the heated steel billet is then subjected to high-pressure water descaling treatment to obtain a descaled steel billet. Step (3): Rough rolling of the descaled steel billet: First, the descaled steel billet is subjected to reciprocating billet rolling to obtain intermediate billet. The intermediate billet is then fed into the heat-insulating roller table for static setting to obtain static intermediate billet. Step (four): Finish rolling the intermediate billet after it has been left to stand. The intermediate billet after standing is fed into a universal rolling mill and subjected to continuous unidirectional precision rolling to obtain shaped steel. Step (5): Cooling the formed steel: Flange-shaped pre-water cooling: The formed steel is pre-water cooled in a flange-shaped manner to obtain pre-water-cooled formed steel; Three-stage gradient cooling: The pre-water-cooled forming steel is fed into a cooling bed. First, the front section is air-cooled: the flange of the pre-water-cooled forming steel is naturally cooled; then, the middle section is water mist-cooled: water mist cooling is used to cool the flange temperature; then, the rear section is naturally slow-cooled: the mist cooling is turned off and natural air cooling is performed to obtain the cooled forming steel. Step (six): Straighten the cooled shaped steel: The cooled shaped steel is sent to a ten-roll straightener for straightening to obtain hot-rolled H-beams with high silicon and low manganese content.

3. The method for preparing a hot-rolled H-beam containing high silicon and low manganese according to claim 2, characterized in that: In step (i), during the refining process, the basicity R is 3.6-4.2 and the argon flow rate is 10-13 L / min; during the steel casting process, the tundish is preheated to 1120-1160℃, the argon flow rate at the long nozzle is 48-52 L / min, and the argon sealing pressure is 0.025-0.035 MPa.

4. The method for preparing a hot-rolled H-beam containing high silicon and low manganese according to claim 2, characterized in that: In step (ii), the temperatures of each section of the heating furnace are as follows: preheating section 1120-1180℃, heating section 1 1220-1280℃, heating section 2 1260-1310℃, and soaking section 1260-1290℃. The total furnace time is 2.5-3 hours, and the furnace time ratio of the preheating section, heating section 1, heating section 2, and soaking section is 3:4:4:

3.

5. The method for preparing a hot-rolled H-beam containing high silicon and low manganese according to claim 2, characterized in that: In step (ii), the descaling water pressure is 20-22 MPa, the cooling water temperature is 20-25℃, and the descaling time is 1.0-1.2 s.

6. The method for preparing a hot-rolled H-beam containing high silicon and low manganese according to claim 2, characterized in that: In step (iii), the number of passes in the reciprocating billet rolling is 7-9, the temperature of the rolling flange is 1150-1220℃, the rolling speed of the last pass is 2.8-3.5m / s, and the overall elongation ratio is controlled at 1:2.4-2.

9.

7. The method for preparing a hot-rolled H-beam containing high silicon and low manganese according to claim 2, characterized in that: In step (iii), the temperature of the heat preservation roller is 1100-1120℃ and the settling time is 35-40s.

8. The method for preparing a hot-rolled H-beam containing high silicon and low manganese according to claim 2, characterized in that: In step (iv), the temperature of the first slab of the finishing mill is 1080-1140℃, the temperature of the last slab of the finishing mill is 920-950℃, the overall elongation ratio is 1:4.2-5.5, and the rolling speed of the last mill stand of the finishing mill is 2.0-2.5m / s.

9. The method for preparing a hot-rolled H-beam containing high silicon and low manganese according to claim 2, characterized in that: In step (5), during the directional fan-shaped pre-water cooling process of the wing plate, the cooling water temperature is 20-25℃, the pressure is 0.22-0.28MPa, and the cooling time is 2.5-3.2s.

10. The method for preparing a hot-rolled H-beam containing high silicon and low manganese according to claim 2, characterized in that: In step (5), during the water vapor atomization cooling stage, the compressed air pressure is controlled at 0.50-0.55 MPa, the cooling water temperature is 20-25℃, and the water pressure is 0.30-0.35 MPa to cool the wing plate temperature to 250-300℃; the subsequent natural slow cooling stage involves naturally air cooling the wing plate temperature to 180-220℃.

Images