KR101205144B1 - H-steel for building structure and method for producing the same - Google Patents

Abstract

The present invention relates to an H-beam and a method of manufacturing the same. 0.01 to 0.2 wt% of carbon (C), 0.01 to 0.4 wt% of silicon (Si), 0.5 to 1.5 wt% of manganese (Mn), 0.035 wt% or less of phosphorus (P), and 0.03 wt% or less of sulfur (S) , Copper (Cu) 0.6% by weight or less, titanium (Ti) 0.005-0.04% by weight, niobium (Nb) 0.001-0.05% by weight, vanadium (V) 0.01-0.11% by weight, aluminum (Al) 0.01-0.03% by weight, Nitrogen (N) 60 ~ 150 ppm by weight, the balance iron (Fe) and other unavoidable impurities. The present invention improves the plastic deformation performance due to the high tensile strength characteristics and the low yield ratio and improves the seismic performance, provides an improved low temperature impact value that can prevent sudden brittleness at low temperature, and by limiting the carbon equivalent As it improves welding performance, it can be usefully used for high performance and high quality steel.

Description

H-beam for building structure and manufacturing method thereof {H-steel for building structure and method for producing the same}

The present invention relates to an H-shaped steel for building structures and a method of manufacturing the same, and more particularly, to an H-shaped steel for building structures and a method of manufacturing the improved tensile strength, yield ratio, low-temperature impact value and welding performance.

The higher and larger the structure, the more diversified and complex the structural forms are. Therefore, not only steel materials with high design reference strength are required, but also high-performance steels with improved safety and seismic performance are required. Performance required for structural structural steels include high strength, resistance ratio, yield point, welding performance, and impact toughness. Higher strength has the advantage of reducing the weight of steel structure, reducing the quantity of steel, and reducing the size of members, and the resistance ratio increases the plastic deformation capacity of the steel to secure seismic performance. In addition, the narrow yield point reduces the displacement of the yield point and requires high-performance steels to regulate the carbon equivalent value below a certain level so that the work can be performed without the occurrence of welding defects, and the impact toughness prevents sudden brittleness at low temperatures.

The purpose of the present invention is to add titanium (Ti), niobium (Nb) and vanadium (V) to distribute titanium, niobium and vanadium precipitates on flanges and webs of H-shaped steel by controlled rolling and accelerated cooling without additional heat treatment. It is to provide a H-shaped steel for building structures and a method of manufacturing the improved structural strength by adjusting the precipitate distribution, yield strength, low-temperature impact value and welding performance.

According to a feature of the present invention for achieving the above object, the present invention is 0.01 to 0.2% by weight of carbon (C), 0.01 to 0.4% by weight of silicon (Si), 0.5 to 1.5% by weight of manganese (Mn), phosphorus (P) ) 0.035 wt% or less, sulfur (S) 0.03 wt% or less, copper (Cu) 0.6 wt% or less, titanium (Ti) 0.005-0.04 wt%, niobium (Nb) 0.001-0.05 wt%, vanadium (V) 0.01- 0.11% by weight, aluminum (Al) 0.01-0.03% by weight, nitrogen (N) 60-150% by weight, balance iron (Fe) and other unavoidable impurities.

The manganese (Mn) / sulfur (S) is 20 or more, the total of niobium (Nb) and vanadium (V) is 0.15 or less, carbon equivalent (Ceq) is 0.40 ~ 0.45% by weight (where Ceq = C + Mn / 6 + (Cr + Mo + V) / 5 + (Ni + Cu) / 15).

The H-shaped steel has a tensile strength of 570 MPa or more, a yield ratio of 85% or less, and a low temperature impact value of 47 Joules or more at -5 ° C.

The surface of the H-beam is a bainite (bainite) structure, the central portion is a pearlite (pearlite) and ferrite (ferrite) structure.

In addition, the present invention is 0.01 to 0.2% by weight of carbon (C), 0.01 to 0.4% by weight of silicon (Si), 0.5 to 1.5% by weight of manganese (Mn), 0.035% by weight or less of phosphorus (P), 0.03% by weight of sulfur (S) % Or less, Copper (Cu) 0.6% or less, Titanium (Ti) 0.005 to 0.04 weight%, Niobium (Nb) 0.001 to 0.05 weight%, Vanadium (V) 0.01 to 0.11 weight%, Aluminum (Al) 0.01 to 0.03 weight Preparing a beam blank in a continuous casting process of molten steel having an alloy composition of%, 60 to 150 ppm by weight of nitrogen (N), balance iron (Fe) and other unavoidable impurities; And heat-treating the beam blank, followed by hot rolling at an Ar3 temperature or higher, accelerated cooling, and air cooling.

The solution heat treatment is performed for 2 to 3 hours at 1200 ~ 1300 ℃.

The hot rolling includes rough rolling, intermediate rolling and filament rolling.

The accelerated cooling is cooled at a temperature below Ar3 and terminated at a temperature above 500 ° C.

The cooling rate during the accelerated cooling is 5 ~ 10 ℃ / s to pass the H-shaped steel 2 to 4 m / s.

The flange and the web of the H-shaped steel have a precipitate frequency of 1.5 to 4: 1.

The present invention distributes titanium, niobium and vanadium precipitates on the flanges and webs of H-beams in a controlled rolling and accelerated cooling process by adding titanium (Ti), niobium (Nb) and vanadium (V), and controls the distribution of precipitates. To prepare the surface of the H-shaped steel is bainite structure, the center is a pearlite and ferrite structure.

The H-shaped steel has a tensile strength of 570 MPa or more, a yield ratio of 85% or less, and a low temperature impact value of 47 Joules or more at -5 ° C. Therefore, it is effective in ships, offshore structures, upper structures of double deck bridges and the like that require improved low temperature impact toughness.

In addition, the present invention is limited to the carbon equivalent of 0.40 to 0.45% by weight has the effect of improving the welding performance of steel for building structures.

Therefore, due to high tensile strength characteristics and low yield ratio, the plastic deformation performance is improved due to the low yield ratio, and the seismic performance is improved, and the low temperature impact value is provided to prevent sudden brittleness at low temperature, and the welding is limited by the carbon equivalent. As it improves performance, it can be usefully used for high performance and high quality steel.

1 is a process schematic diagram of the present invention.
Figure 2 is an optical micrograph showing the microstructure change according to the passage speed of the H-beam in the accelerated cooling process of the present invention.
3 is a graph showing the distribution and the interval between the precipitate according to the precipitate size of the flange and the web of the H-shaped steel according to the present invention.
Figure 4 is an optical micrograph showing the precipitate of the H-shaped steel according to the present invention.
5 is an optical micrograph showing the microstructure of the flange and the web of the H-shaped steel according to the manufacturing method of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, the H-shaped steel for building structures and its manufacturing method of this invention are demonstrated in detail.

H-shaped steel of this invention is 0.01-0.2 weight% of carbon (C), 0.01-0.4 weight% of silicon (Si), 0.5-1.5 weight% of manganese (Mn), 0.035 weight% or less of phosphorus (P), sulfur (S) 0.03 wt% or less, Copper (Cu) 0.6 wt% or less, Titanium (Ti) 0.005-0.04 wt%, Niobium (Nb) 0.001-0.05 wt%, Vanadium (V) 0.01-0.11 wt%, Aluminum (Al) 0.01- 0.03% by weight, nitrogen (N) 60-150% by weight, balance iron (Fe) and other unavoidable impurities.

Specifically, the present invention adjusts the distribution of titanium (Ti), niobium (Nb) and vanadium (V) precipitates to improve high tensile strength, resistance ratio, low temperature impact value and welding performance.

Titanium forms TiN precipitates to inhibit the growth of austenite grains and to inhibit the growth of austenite recrystallized grains in the hot rolling process to refine the grains. Aluminum combines with nitrogen to contribute to solid solution strengthening and grain refinement. Nitrogen combines with aluminum, titanium, niobium, vanadium and the like to refine grains.

At this time, manganese (Mn) / sulfur (S) is 20 or more, the total of niobium (Nb) and vanadium (V) is 0.15% by weight or less. If the manganese (Mn) / sulfur (S) ratio is 20 or more Mn amount is increased, so that the substitution type solid solution is formed to increase the solid-solution strengthening effect, MnS inclusions are stretched during hot rolling, the final product without cracking by inclusions Can produce. On the other hand, when the manganese (Mn) / sulfur (S) ratio is less than 20, the grain boundary segregation of the MnS inclusions deepen the anisotropy and heterogeneity of the microstructure and cracks in the final product. In addition, if the total amount of vanadium (V) and niobium (Nb) is 0.15% or less, ferrite is refined by the action of vanadium or niobium precipitates. On the other hand, when the total amount of vanadium and niobium exceeds 0.15%, coarse carbonitrides are precipitated by vanadium or niobium precipitates, which acts like non-metallic inclusions, causing fatigue characteristics and causing cracks in production. .

Hereinafter, the reason for limitation of the function and content of the alloying elements of the present invention will be described.

Carbon (C): 0.01-0.2 wt%

Carbon is added to improve material strength. When carbon is added in less than 0.01% by weight, the strength is lowered and austenite is transformed into ferrite, making it difficult to obtain a pearlite fraction. In addition, when added in excess of 0.2% by weight, the weldability is lowered and the ductility and stretch-flange properties with increasing strength are lowered.

Silicon (Si): 0.01-0.4 wt%

Silicon enhances the strength of the steel sheet by the solid solution strengthening effect, promotes the cleanliness of the steel and promotes carbon enrichment in the austenite, and increases the stability of the austenite, thereby retaining austenite at room temperature.

In addition, silicon improves the fluidity of molten metal during welding in the steel to which the appropriate manganese is added, thereby minimizing the inclusion residues in the weld, improving the strength without compromising the yield ratio, strength and elongation balance, and improving the carbon in the ferrite. It slows down the diffusion rate, suppresses carbide growth, stabilizes ferrite and improves elongation.

When the content of silicon is added below 0.01% by weight, the strength of the ferrite is reduced and the effect of inhibiting oxidation and carbon inclusions is reduced. In addition, the addition of more than 0.4% by weight surface defects due to red scale occurs.

Manganese (Mn): 0.5-1.5 wt%

Manganese improves strength and toughness and stabilizes austenite to increase quenchability. In addition, by lowering the Ar3 temperature to enlarge the rolling process temperature range, the austenite grains are refined.

If the content of manganese is added less than 0.5% by weight does not contribute to the strength improvement, when the content of more than 1.5% by weight is added, the hardenability is increased, poor workability and carbon equivalents are high, weldability is lowered.

Phosphorus (P): greater than 0 and less than 0.035% by weight

Phosphorus has the effect of increasing the inevitable addition element and strength. When phosphorus is added in a large amount, not only the workability is lowered but also the weldability is reduced, so it is preferable to limit the amount to 0.035% by weight or less.

Sulfur (S): more than 0 and less than 0.03% by weight

Sulfur is an inevitable addition element in the manufacture of steel, and sulfur inhibits toughness and weldability, forms emulsion-based inclusions (MnS, etc.), causes cracks, and increases coarse inclusions to deteriorate fatigue properties. desirable.

Copper (Cu): greater than 0 and less than 0.6 wt%

Copper is an element that can increase strength while minimizing deterioration of toughness. However, if a large amount of copper is added, it is preferable to limit the product surface quality to 0.6 wt% or less.

Titanium (Ti): 0.005 to 0.04 wt%

Titanium is an important alloying element for grain refinement that forms TiN precipitates during steel solidification to inhibit the growth of austenite grains during beam blank heating and to suppress the growth of austenite recrystallized grains during hot rolling. The amount of titanium added varies depending on the content of nitrogen. However, when the amount of titanium is relatively small compared to the amount of nitrogen, the amount of TiN formed is small, which is disadvantageous to refine the grains. TiN is coarsened by crystallization in the liquid phase during casting, and the grain growth inhibition effect is reduced by coarsening TiN during heating. Therefore, it is preferable that Ti addition amount is 0.005-0.04 weight%.

Niobium (Nb): 0.001 to 0.05 wt%

Niobium forms Nb (C, N) precipitates or improves the strength of steel through solid solution strengthening in Fe. In some cases, when the basic additive element is reduced, Nb can be added to increase the strength without impairing the formability.

When niobium is added in an amount less than 0.001% by weight, the effect is insignificant, and when it is added in excess of 0.05% by weight, the precipitation strengthening effect is excessive and the strength is greatly increased.

Vanadium (V): 0.01-0.11 wt%

In the present invention, vanadium inhibits the movement of austenite grain boundaries during reheating and hot rolling, thereby miniaturizing austenite grains, inhibiting nucleation at the austenite grain boundary during phase transformation, increasing the hardenability of reinforcing bars, and phase transformation from austenite. Form precipitates to increase the strength of the rebar. For reference, vanadium precipitates VN at high temperatures and VC at low temperatures. If the content is less than 0.01% by weight, the effect is insignificant, and if the content is more than 0.11% by weight, the workability is reduced to cause cracks in the material during rolling.

Aluminum (Al): 0.01-0.03 wt%

Aluminum is added as a deoxidizer during steelmaking, and aluminum combines with nitrogen to precipitate nitride (AlN) finely to enhance the solid solution and refine the grain, but when it exceeds 0.03% by weight, it forms a large amount of inclusions such as alumina and thus impact toughness. Since it falls, it is preferable that the content is 0.01 to 0.03 weight%.

Nitrogen (N): 60 to 150 ppm by weight

Nitrogen combines with other alloying elements such as aluminum, titanium, vanadium, and niobium to form nitrides to make fine grains. However, when a large amount is added, there is a problem that the amount of nitrogen increases and the elongation and formability of the steel are lowered. When nitrogen is added below 60 wtppm, there is a problem that the crystal grains cannot be refined, and when it exceeds 150 wtppm, elongation and moldability are deteriorated, so the content thereof is preferably 60 to 150 wtppm. Do.

The H-shaped steel of the present invention includes the above components, the remainder is remaining iron (Fe) and other unavoidable elements, and the fine incorporation of unavoidable impurities may be allowed as elements contained according to the situation of raw materials, materials, manufacturing facilities, and the like. .

And, in order to secure the welding performance of the steel sheet, the carbon equivalent (Ceq) is 0.40 to 0.45% by weight (where Ceq = C + Mn / 6 + (Cr + Mo + V) / 5 + (Ni + Cu) / 15 .) Make sure that the range is met. When the total amount of the alloying elements is too large, the hardenability of the steel as a whole increases more than necessary, so that the possibility of defects in the heat affected zone during welding increases.

The manufacturing process of the present invention is as follows.

[Solution Heat Treatment]

A molten steel having the composition as described above is manufactured by a steelmaking process in an electric furnace. The molten steel produced by the electric steelmaking process is manufactured in the form of a beam blank by a continuous casting process through a refining process. The beam blank produced by the continuous casting process is subjected to a solution heat treatment (Solid solution) for 2 to 3 hours at 1200 ~ 1300 ℃. The solution heat treatment prevents segregation of pores, inclusions, solutes, and the like in the high temperature austenite temperature range, and inhibits growth of austenite particles by precipitation of titanium during solution heat treatment. Maintains large austenite grain boundaries per area.

[Control Rolling (Hot Rolling) Process]

After the solution heat treatment, hot rolling is performed at an Ar3 or higher temperature. The hot rolling process is carried out in the stages of rough rolling, intermediate rolling and finishing rolling, and the titanium (Ti), niobium (Nb) and vanadium (V) alloying elements do not recrystallize the austenite particles during the hot rolling, but the austenite Defects and shear bands are densely formed inside the nit particles to provide ferrite nucleation sites where the ferrite particles can grow finely. In addition, the hot rolling process above the Ar3 temperature is because the austenitic particles of the FCC structure, which is soft at high temperatures, are relatively low in processing power than the ferrite of the hard BCC structure. In addition, niobium (Nb) in the hot rolling process is present at the austenite interface in solid solution or generates strained organic precipitates of several nanometers (nm) in size. The precipitate suppresses recrystallization of the austenite particles after the rolling until the next rolling to maintain the deformed austenite particles in the elongated form. In addition, in order to manufacture in the 'H' form rolls in a constant rolling ratio with a ball roll in the four directions up, down, left, right.

Accelerated Cooling Process

After the hot rolling process, an accelerated cooling process is performed. The accelerated cooling process is carried out below the Ar3 temperature and austenite is phase-transformed into ferrite to start to produce fine ferrite particles. The accelerated cooling process is preferably terminated at 500 ℃ or more to improve the mechanical properties such as yield strength, tensile strength, low-temperature impact value, martensite transformation starts in the microstructure when the cooling is finished below 500 ℃. Due to the volume expansion caused by the operation potential occurs, there is a problem that the strength is lowered, elongation and impact value is lowered. In addition, it is preferable that the accelerated cooling rate is 5 to 10 ° C./s so that the H-shaped steel can be transferred, for example, a predetermined roll device allows the shaped steel to pass at 2 to 4 m / s. If it is less than 2 m / s, there is a problem that the production cost increases due to the large productivity is reduced, and if it exceeds 4 m / s there is a problem that the cooling effect is not enough enough to increase the size of the ferrite particles to increase the tensile strength have.

[Air cooling process]

Air cooling after the accelerated cooling process is the bainite is produced on the surface and the pearlite and ferrite is generated in the center.

In the hot rolling and accelerated cooling process, more precipitates are distributed on the flange than the web of the H-shaped steel. It is preferable that the precipitate frequency of the flange and the web of the H-beam is 1.5 to 4: 1. The high distribution of precipitates on the flanges indicates that the flanges have a higher strength than the web due to the precipitation strengthening effect. In addition, the spacing between the precipitates can also be manufactured to maintain a tight spacing compared to the web to improve the tensile strength and low temperature impact value. If the precipitate frequency of the flange is less than 1.5, the tensile strength and the low temperature impact value of the H-shaped steel are lowered, and the frequency exceeding 4 is not easy in the process and the strength difference from the web due to the high strength due to the precipitation strengthening effect of the flange. Therefore, there is a problem that the tensile strength and low temperature impact value of the H-shaped steel is lowered.

Hereinafter, the above-described H-shaped steel for building structures and a method of manufacturing the same will be described in detail with reference to examples.

Table 1 shows the component ratios of the examples of the present invention.

(Far Fe, Unit: wt%) division C Si Mn P S Cu Ti Nb V Al N
(ppm) Ceq size
(Weight (ton)) Example 1 0.15 0.26 1.32 0.025 0.016 0.3 0.04 0.04 0.078 0.011 80 0.42 H305 × 305
(30.5) Example 2 0.15 0.26 1.32 0.025 0.016 0.3 0.04 0.04 0.078 0.011 80 0.42 H400 × 400
(21) Example 3 0.16 0.30 1.33 0.023 0.012 0.17 0.035 0.04 0.099 0.015 130 0.45 H428 × 407
(35) Example 4 0.16 0.30 1.33 0.023 0.012 0.17 0.035 0.04 0.099 0.015 130 0.45 H400 × 400
(21)

division The tensile strength
(MPa) Yield strength
(MPa) Elongation
(%) Yield ratio
(%) Impact test
(Joule) -5 ℃ Example 1 594 465 27.2 78 145 Example 2 603 480 29.8 80 159 Example 3 631 462 27.3 73 109 658 466 24.6 71 61 Example 4 651 472 23.9 73 104 656 473 24.7 72 79

The beam blank was prepared by continuous casting process of molten steel as shown in Table 1, and then hot-rolled, accelerated cooling, and air-cooled at an Ar3 temperature or higher to manufacture H-beam.

Table 2 shows the results of measuring the mechanical properties of the examples of Table 1.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a process schematic diagram of the present invention.

Referring to FIG. 1, after manufacturing molten steel having the alloying element composition in a steelmaking process in an electric furnace, the molten steel is manufactured in the form of a beam blank using a continuous casting process and subjected to solution heat treatment for 1200 to 1300 ° C. and a heating time of 2 to 3 hours in a heating furnace. After solid solution), hot rolling over Ar3 temperature, accelerated cooling, and air cooling.

The solution heat treatment prevents segregation of pores, inclusions, solutes, etc. in the high temperature austenite temperature range, and inhibits the growth of austenite particles by precipitation of titanium during solution heat treatment, thereby per unit area. A large number of austenite grain boundaries are maintained.

In addition, the hot rolling process is carried out in the steps of rough rolling, intermediate rolling and finishing rolling, and the recrystallization of austenite particles does not occur due to titanium (Ti), niobium (Nb) and vanadium (V) alloying elements during hot rolling. Instead, densities and shear bands are densely formed in the austenite particles, thereby providing a ferrite nucleation site where the ferrite particles can grow finely. In addition, the hot rolling process at an Ar3 temperature or higher is because relatively low processing power is required to roll the austenitic particles of the FCC structure, which is soft at high temperature, to the ferrite of the BCC structure, which is hard. In addition, niobium (Nb) during the hot rolling process is present at the austenite interface in the solid solution state or produces a modified organic precipitate having a size of several nanometers (nm). The precipitate suppresses recrystallization of the austenite particles after rolling to maintain the deformed austenite particles in an elongated form.

After the hot rolling process, an accelerated cooling process is performed. The accelerated cooling process is carried out below the Ar3 temperature and the austenite phase-transforms into ferrite, producing fine ferrite particles. The accelerated cooling process is terminated at 500 ℃ or more to improve the mechanical properties such as yield strength, tensile strength, low temperature impact value, the acceleration cooling rate is 5 ~ 10 ℃ / s, H-shaped steel is 2 ~ 4 m / s Let it pass

After the accelerated cooling process, the H-beam is subjected to an air cooling process at less than 500 ° C. to produce bainite on the surface, and pearlite and ferrite in the center.

Figure 2 is an optical micrograph showing the microstructure change according to the passage speed of the H-beam in the accelerated cooling process of the present invention.

Referring to FIG. 2, the ferrite grain size was 8.3 μm when the H-beam passed through 2 m / s in the accelerated cooling process, the ferrite grains were 11.6 μm at 3 m / s, and the ferrite particles at 4 m / s. Was 13.3 μm. Therefore, the passage speed of the beam blank was suitably in the range of 2 to 4 m / s.

3 is a graph showing the distribution and the interval between the precipitate according to the precipitate size of the flange and the web of the H-shaped steel according to the present invention.

Referring to FIG. 3, in the case of flanges, precipitates having a size of about 10 nm appeared most frequently (see FIG. 3 (a)) and were distributed at intervals of about 20 to 30 nm (see FIG. 3 (b)). In the case of the web, precipitates of about 5 nm size appeared most frequently (see FIG. 3 (a)) and were distributed at intervals of about 20-30 nm (see FIG. 3 (b)).

Figure 4 is an optical micrograph showing the precipitate of the H-shaped steel according to the present invention.

Referring to Figure 4, it can be seen that the vanadium, titanium and niobium precipitates were formed on the web (Fig. 4 (a)) and the flange (Fig. 4 (b)) of the H-shaped steel produced by the manufacturing method of the present invention. .

5 is an optical micrograph showing the microstructure of the flange and the web of the H-shaped steel according to the manufacturing method of the present invention.

Referring to FIG. 5, the H-shaped steel that has completed the accelerated cooling process is cut to length and then transferred to the cooling zone. At this time, there is a difference in the H-steel surface and the microstructure of the central portion due to the temperature rise (latent heat) inside the H-steel.

Ferrite particles composed of similar particle size and equiaxed crystals were formed on the flange and web center layer of H-shaped steel according to the present invention, and ferrite and cementite (Fe ₃ C) were formed from fine ferrite particles and austenite particles remaining in the accelerated cooling process. A perlite structure with an incomplete layered structure that could not be degraded was formed. Ferrite particles of about 8.7 μm particle size were formed in the center of the flange, and ferrite particles of about 9.5 μm particle size were formed in the center of the web.

The surface layers of the flanges and the web have densely formed bainite structures due to rapid cooling during accelerated cooling.

The boundary layer between the flange and the web was formed by mixing bainite, pearlite, and ferrite structures, and there was no significant difference between the flange and the web in the size and shape of the individual particles. The ferrite grain size measured at the boundary layer of the flange was 5.3 ~ 6.8 ㎛, and the ferrite grain size measured at the boundary layer of the web was 2.5 ~ 2.8 ㎛. Due to the shape of the section steel, the cooling water can stay in the web for a long time compared to the flange, and it is believed that the ferrite grain size is smaller than that of the flange.

Within the scope of the basic technical idea of the present invention, many other modifications are possible to those skilled in the art, and the scope of the present invention should be interpreted based on the appended claims. will be.

Claims (9)

0.01-0.2 wt% of carbon (C), 0.01-0.4 wt% of silicon (Si), 0.5-1.5 wt% of manganese (Mn), 0.035 wt% or less of phosphorus (P), 0.03 wt% or less of sulfur (S), copper ( Cu) 0.6% by weight or less, titanium (Ti) 0.005-0.04% by weight, niobium (Nb) 0.001-0.05% by weight, vanadium (V) 0.01-0.11% by weight, aluminum (Al) 0.01-0.03% by weight, nitrogen (N ) H-shaped steel for building structures containing 60 to 150 ppm by weight, balance iron (Fe) and other unavoidable impurities. The method according to claim 1,
The manganese (Mn) / sulfur (S) is 20 or more, the total amount of niobium (Nb) and vanadium (V) is 0.15% by weight or less, carbon equivalent (Ceq) is 0.40 to 0.45% by weight (where Ceq = C + Mn / 6 + (Cr + Mo + V) / 5 + (Ni + Cu) / 15). The method according to claim 1,
The H-shaped steel has a tensile strength of 570 MPa or more, a resistive ratio of 85% or less, and a low temperature impact value of 47 joules or more at -5 ° C. The method according to claim 1,
The surface of the H-beam is a bainite (bainite) structure, the central portion of the structural structural H-shaped steel, characterized in that the pearlite (pearlite) and ferrite (ferrite) structure. 0.01-0.2 wt% of carbon (C), 0.01-0.4 wt% of silicon (Si), 0.5-1.5 wt% of manganese (Mn), 0.035 wt% or less of phosphorus (P), 0.03 wt% or less of sulfur (S), copper ( Cu) 0.6% by weight or less, titanium (Ti) 0.005-0.04% by weight, niobium (Nb) 0.001-0.05% by weight, vanadium (V) 0.01-0.11% by weight, aluminum (Al) 0.01-0.03% by weight, nitrogen (N ) Preparing a molten steel having an alloy composition of 60 to 150 ppm by weight, balance iron (Fe) and other unavoidable impurities;
Manufacturing a beam blank of the molten steel by a continuous casting process; And
Performing a solution heat treatment on the beam blank, followed by hot rolling at an Ar3 temperature or higher, accelerated cooling, and air cooling,
The accelerated cooling is cooled at a temperature below Ar3 and terminated at a temperature above 500 ° C,
Cooling rate during the accelerated cooling is 5 ~ 10 ℃ / s H-shaped steel manufacturing method characterized in that passing through at a rate of 2 ~ 4 m / s. The method according to claim 5,
The solution heat treatment is a manufacturing method of H-shaped steel for building structure, characterized in that performed for 2 to 3 hours at 1200 ~ 1300 ℃. delete delete The method according to claim 5,
The flange and the web of the H-shaped steel is a manufacturing method of H-shaped steel for building structure, characterized in that the ratio of 1.5 to 4: 1 ratio.

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