Composite-performance shaped steel and manufacturing method thereof

Abstract

A composite-performance shaped steel according to an embodiment of the present invention comprises 0.08-0.17 wt% of carbon (C), 0.10-0.50 wt% of silicon (Si), 0.50-1.60 wt%, of manganese (Mn), 0.020 wt% or less (excluding 0) of phosphorus (P), 0.010 wt% or less (excluding 0) of sulfur (S), 0.10-0.70 wt% of chromium (Cr), 0.30-0.73 wt% of molybdenum (Mo), 0.50 wt% or less (excluding 0) of copper (Cu), 0.05 wt% or less (excluding 0) of niobium (Nb), 0.003 wt% or less (excluding 0) of boron (B), 0.012 wt% or less (excluding 0) of nitrogen (N), and the remainder of iron (Fe) and inevitable impurities, and the composite-performance shaped steel has a high-temperature yield strength (YS, 600℃) of 300 MPa or more.

Description

Composite performance steel and manufacturing method thereof

[0001] The present invention relates to a composite performance steel and a method for manufacturing the same.

[0002] Section steel generally refers to steel with a diverse range of cross-sectional shapes. Section steel is used as structural steel, such as columns in large buildings, and also as temporary structures for civil engineering projects such as subways and bridges, as well as as foundation piles. Section steel can be manufactured by hot rolling cast steel, such as blooms, billets, and beam blanks, produced through continuous casting.

[0003] Due to the recent frequent occurrence of earthquakes on the Korean Peninsula and fires in high-rise buildings, public interest in safety steel is increasing. In particular, the increasing size of buildings is linked to the number of fires caused by electric leakage following earthquakes, and thus, a realistic solution is urgently needed.

[0004] In this environment, various movements are taking place to strengthen domestic earthquake-resistant design standards, and composite performance of steel beams is required to enhance disaster response capabilities at the level of advanced countries.

[0005] Therefore, there is a need to develop composite performance steel and its manufacturing method that can have excellent strength and earthquake-resistant fire-resistant performance.

[0006] According to one embodiment of the present invention, the purpose is to provide a composite performance steel and a method for manufacturing the same, which can secure not only yield strength in a high temperature environment but also tensile strength and yield strength in a room temperature environment.

[0007] The tasks of the present invention are not limited to the tasks mentioned above, and other tasks not mentioned will be clearly understood by those skilled in the art from the description below.

[0008] According to one embodiment of the present invention, a composite performance steel includes carbon (C) 0.08 to 0.17 wt%, silicon (Si) 0.10 to 0.50 wt%, manganese (Mn) 0.50 to 1.60 wt%, phosphorus (P) 0.020 wt% or less (excluding 0), sulfur (S) 0.010 wt% or less (excluding 0), chromium (Cr) 0.10 to 0.70 wt%, molybdenum (Mo) 0.30 to 0.73 wt%, copper (Cu) 0.50 wt% or less (excluding 0), niobium (Nb) 0.05 wt% or less (excluding 0), boron (B) 0.003 wt% or less (excluding 0), nitrogen (N) 0.012 wt% or less (excluding 0), and the remainder iron (Fe) and inevitable impurities, and has a high temperature yield strength (YS, 600℃) can be 300MPa or more.

[0009] At this time, the room temperature tensile strength (TS) may be 570 MPa or more.

[0010] Alternatively, the room temperature yield strength (YS) may be 460 MPa or greater.

[0011] Alternatively, the room temperature yield ratio (YR) may be less than 85%.

[0012] Alternatively, the room temperature elongation (EL) may be greater than 15%.

[0013] Alternatively, the low temperature impact toughness (CVN, -5℃) may be 45J or greater.

[0014] Alternatively, the remaining Fe may be replaced by titanium (Ti) of 0.001 wt% or less (excluding 0).

[0015] Alternatively, the composite performance steel may be an H-shaped steel including a web portion and flange portions arranged on both sides of the web portion.

[0016] A method for manufacturing a composite performance steel according to one embodiment of the present invention comprises the steps of (S1) preparing a steel material, (S2) reheating the steel material, (S3) hot rolling the steel material to form a hot-rolled product, and (S4) cooling the hot-rolled product to form a final product, wherein the final product comprises carbon (C) 0.08 to 0.17 wt%, silicon (Si) 0.10 to 0.50 wt%, manganese (Mn) 0.50 to 1.60 wt%, phosphorus (P) 0.020 wt% or less (excluding 0), sulfur (S) 0.010 wt% or less (excluding 0), chromium (Cr) 0.10 to 0.70 wt%, molybdenum (Mo) 0.30 to 0.73 wt%, copper (Cu) 0.50 wt% or less (excluding 0), niobium (Nb) 0.05 It contains less than 0 wt% (excluding 0), 0.003 wt% or less of boron (B), 0.012 wt% or less of nitrogen (N), and the remainder of iron (Fe) and unavoidable impurities, and the high temperature yield strength (YS, 600℃) may be 300 MPa or more.

[0017] At this time, the reheating temperature of the above (S2) step may be 1200 to 1250°C.

[0018] Alternatively, the rolling start temperature of the above (S3) step may be 1050 to 1100°C.

[0019] Alternatively, the rolling end temperature of the above (S3) step may be 740°C or higher.

[0020] Alternatively, the cooling end temperature of the above (S4) step may be 640 to 680°C.

[0021] At this time, the cooling of the above step (S4) may be characterized as being performed by water cooling.

[0022] And the final product may further include 0.001 wt% or less (excluding 0) of titanium (Ti) to replace the remaining Fe.

[0023] It is possible to provide a composite performance steel and a manufacturing method thereof that can secure not only yield strength and tensile strength in a room temperature environment but also yield strength in a high temperature environment.

[0024] Additionally, by reducing the amount of fire-resistant paint used in architectural design, construction periods can be shortened and costs can be reduced.

[0025] The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

[0026] Figure 1 is a flowchart showing a method for manufacturing a composite performance steel according to one embodiment of the present invention.

[0027] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the present invention is not limited or restricted by the following embodiments.

[0028] Additionally, when a component (or region, layer, portion, etc.) is referred to as being "on," "connected to," or "coupled to" another component, it means that it can be directly placed / connected / coupled to the other component, or that a third component may be placed between them.

[0029] Terms such as "include" or "have" should be understood to specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but not to exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0030] In order to clearly explain the present invention, a detailed description of a part that is irrelevant to the description or a related known technology that may unnecessarily obscure the gist of the present invention has been omitted, and when adding reference signs to components of each drawing in this specification, the same or similar reference signs are attached to the same or similar components throughout the specification.

[0031] In addition, terms and words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0032] Unless otherwise specified, the notation 'A to B' for numerical values ​​A and B means 'A or more and B or less'. In such notation, if a unit is attached only to numerical value B, the unit shall be applied to numerical value A as well.

[0033] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0034]

[0035] composite performance steel

[0036] The composite performance steel according to one embodiment of the present invention may be a steel for use in buildings or structures. For example, the composite performance steel may be an H-shaped steel including a web portion and flange portions arranged on both sides of the web portion.

[0037] According to one embodiment of the present invention, a composite performance steel may contain carbon (C) 0.08 to 0.17 wt%, silicon (Si) 0.10 to 0.50 wt%, manganese (Mn) 0.50 to 1.60 wt%, phosphorus (P) 0.020 wt% or less (excluding 0), sulfur (S) 0.010 wt% or less (excluding 0), chromium (Cr) 0.10 to 0.35 wt%, molybdenum (Mo) 0.30 to 0.73 wt%, copper (Cu) 0.50 wt% or less (excluding 0), niobium (Nb) 0.04 to 0.06 wt%, nitrogen (N) 0.012 wt% or less (excluding 0), and the remainder iron (Fe) and unavoidable impurities.

[0038] Hereinafter, the role and content of each alloy element included in the composite performance steel according to one embodiment of the present invention will be described in detail.

[0039]

[0040] Carbon (C)

[0041] Carbon (C) is the most effective and important element for increasing the strength of steel.

[0042] Carbon is incorporated into austenite, which can form martensite during quenching. Furthermore, increasing carbon content can improve hardness.

[0043] In addition, carbon effectively contributes to improving strength through precipitation strengthening by reacting with niobium (Nb), titanium (Ti), etc. to promote the formation of fine carbides, and at the same time, it is effective in securing fire resistance by improving high-temperature strength by hindering dislocation movement at high temperatures.

[0044] In this case, if the carbon content is insufficient, the aforementioned effects may be insufficient, making it difficult to secure sufficient strength. Conversely, if the carbon content is excessive, it may cause deformation during quenching or a decrease in the steel's elongation and low-temperature toughness.

[0045] Therefore, the composite performance steel according to one embodiment of the present invention may contain carbon (C) in an amount of 0.08 to 0.17 wt%, preferably 0.08 to 0.10 wt%.

[0046]

[0047] Silicon (Si)

[0048] Silicon (Si) is added as a deoxidizer to remove oxygen in steel during the steelmaking process together with aluminum, and as a ferrite stabilizing element with a solid solution strengthening effect, it can induce ferrite formation and improve the hardenability and softening resistance of steel.

[0049] If the silicon content is insufficient, the aforementioned effects may be minimal. Conversely, if the silicon content is excessive, toughness may be reduced and plastic workability may be impaired.

[0050] Therefore, the composite performance steel according to one embodiment of the present invention may contain 0.1 to 0.5 wt% of silicon (Si), preferably 0.1 to 0.28 wt%.

[0051]

[0052] manganese (Mn)

[0053] Manganese (Mn) is a solid-solution strengthening element that not only contributes to strength enhancement, but also enhances the hardenability of steel, effectively promoting the formation of bainite. Furthermore, increasing the manganese content can lead to finer pearlite and enhanced solid-solution strengthening of ferrite, thereby improving yield strength.

[0054] If manganese content is insufficient, the aforementioned effects may be minimal. Conversely, if manganese content is excessive, it may combine with sulfur (S) to form MnS inclusions or cause central segregation in the ingot. Furthermore, austenite may remain, reducing strength and toughness.

[0055] Therefore, the composite performance steel according to one embodiment of the present invention may contain manganese (Mn) in an amount of 0.5 to 1.60 wt%, preferably 0.5 to 1.52 wt%.

[0056]

[0057] Person (P)

[0058] Phosphorus (P) is an element that contributes to strength enhancement. However, excessive phosphorus content can deteriorate the ductility of steel and cause final material deviations due to billet center segregation. When phosphorus content exceeds 0.02 wt%, it can form center segregation and microsegregation, reducing the ductility of the steel. Furthermore, precipitation behavior can reduce impact strength.

[0059] Therefore, the composite performance steel according to one embodiment of the present invention may contain phosphorus (P) in an amount of 0.02 wt% or less (excluding 0).

[0060]

[0061] Yellow (S)

[0062] Sulfur (S) combines with manganese, zinc, titanium, molybdenum, and other elements to improve the machinability of steel. It can also combine with manganese to form fine precipitates (e.g., MnS), enhancing workability. However, if the amount of manganese in the steel is insufficient, it can combine with iron to form sulfides (e.g., FeS), which can cause cracks during hot and cold working. Sulfur content exceeding 0.01 wt% can reduce the ductility of the steel and deteriorate its toughness and weldability.

[0063] Therefore, the composite performance steel according to one embodiment of the present invention may contain sulfur (S) in an amount of 0.01 wt% or less (excluding 0).

[0064]

[0065] chromium (Cr)

[0066] Chromium (Cr) is a ferrite-stabilizing element. When added to C-Mn steel, it impedes carbon diffusion due to its solute-interfering effect, thereby contributing to grain refinement. Furthermore, chromium enhances the hardenability of steel, contributing to the formation of a bainite microstructure and improving hardenability. However, excessive chromium content can lead to the formation of coarse carbides at grain boundaries, which can reduce the steel's room- and low-temperature ductility and increase its manufacturing cost.

[0067] Therefore, the composite performance steel according to one embodiment of the present invention may contain chromium (Cr) in an amount of 0.10 to 0.70 wt%, preferably 0.10 to 0.35 wt%, and more preferably 0.10 to 0.32 wt%.

[0068]

[0069] molybdenum (Mo)

[0070] Molybdenum (Mo) can enhance the hardenability of steel, contributing to the formation of a bainite microstructure and being highly effective in securing high-temperature strength. Specifically, even small additions of molybdenum (Mo) can enhance hardenability by up to 10 times that of nickel (Ni), and it also prevents temper embrittlement, imparting resistance to tempering.

[0071] Molybdenum (Mo) also forms carbides, making it an effective alloying element for advanced cutting tools and increasing the grain coarsening temperature. Its effectiveness is enhanced when combined with chromium rather than used alone to enhance hardenability.

[0072] Molybdenum (Mo) possesses exceptionally high heat resistance at high temperatures, maintains metallic strength and hardness at high temperatures, and possesses a high melting point, allowing it to exist in a stable form even at high temperatures. Furthermore, molybdenum has excellent oxidation resistance at high temperatures, which can enhance corrosion resistance in high-temperature oxidizing environments, playing a key role in high-temperature physical properties.

[0073] If the molybdenum content is insufficient, the aforementioned effects may be minimal. Conversely, excessive molybdenum content increases the manufacturing cost of the steel, reduces weldability, and, in particular, reduces the steel's shock absorption energy, making it unsuitable for achieving seismic resistance.

[0074] Accordingly, the composite performance steel according to one embodiment of the present invention may contain molybdenum (Mo) in an amount of 0.30 to 0.73 wt%, preferably 0.30 to 0.70 wt%, and more preferably 0.35 to 0.40 wt%.

[0075]

[0076] copper (Cu)

[0077] Copper (Cu) is usually contained in steel at about 0.1 to 0.3 wt%, which can increase corrosion resistance in the air or seawater.

[0078] Copper is dissolved in ferrite at room temperature in concentrations of up to 0.35 wt%, exhibiting a solid-solution strengthening effect that can improve strength and hardness. Adding more than 0.35 wt% copper can further improve hardness, as fine copper precipitation results in a precipitation hardening effect.

[0079] However, if the copper content is excessive, the elongation may be reduced and it may cause red-hot embrittlement.

[0080] Therefore, the composite performance steel according to one embodiment of the present invention may contain copper (Cu) in an amount of 0.50 wt% or less (excluding 0), preferably 0.14 to 0.16 wt%.

[0081]

[0082] niobium (Nb)

[0083] Niobium (Nb) can increase hardness by combining with carbon to form precipitates such as NbC within the grains.

[0084] In addition, it is an element that is advantageous in improving strength by refining crystal grains. If the niobium content is too low, the aforementioned effect will not be observed, and if the niobium content exceeds 0.06 wt%, the precipitation strengthening effect will be excessive, increasing strength but reducing ductility.

[0085] Therefore, the composite performance steel according to one embodiment of the present invention may contain niobium in an amount of 0.05 wt% or less (excluding 0), preferably 0.040 to 0.043 wt%.

[0086]

[0087] Nitrogen (N)

[0088] Even trace amounts of nitrogen (N) significantly affect the mechanical properties of steel. As nitrogen content increases, tensile strength and yield strength increase, while elongation decreases. In particular, the decrease in impact strength and the increase in transition temperature are notable.

[0089] When nitrogen is added, nitrides are formed and grains are refined, but if the nitrogen content is excessive, high-temperature toughness may decrease and grain boundary embrittlement may occur due to nitride precipitation at the austenite grain boundaries.

[0090] Therefore, the composite performance steel according to one embodiment of the present invention may contain nitrogen (N) in an amount of 0.012 wt% or less (excluding 0), preferably 0.0094 to 0.0100 wt%.

[0091]

[0092] The composite performance steel according to one embodiment of the present invention may optionally further include additional alloy elements, such as titanium (Ti) and boron (B), in addition to the aforementioned alloy elements.

[0093]

[0094] titanium (Ti)

[0095] Titanium can form TiN together with nitrogen. In the present invention, the formation of proeutectoid ferrite in austenite grains is suppressed by adding boron as a method for improving the hardenability of steel. At this time, if boron and nitrogen combine to form BN during the steelmaking process, the hardenability improvement mechanism cannot be implemented. Therefore, a process is required in the steelmaking process to limit the nitrogen content to 100 ppm or less by applying a VD (Vacuum Degassing) process, and in addition, titanium can be added to suppress the combination of residual nitrogen and boron to preferentially form TiN, which can ultimately play a role in improving the hardenability of steel.

[0096] To this end, the composite performance steel according to one embodiment of the present invention may contain titanium (Ti) in an amount of 0.001 wt% or less (excluding 0).

[0097]

[0098] Boron (B)

[0099] Boron preferentially segregates at austenite grain boundaries, inhibiting the formation of soft ferrite during cooling and enhancing hardenability. However, excessive addition can lead to grain boundary embrittlement.

[0100] To this end, the composite performance steel according to one embodiment of the present invention may contain boron (B) in an amount of 0.003 wt% or less (excluding), preferably 0.0003 wt% or less (excluding 0).

[0101]

[0102] In addition to the aforementioned steel components, the remainder may contain iron and unavoidable impurities. Unavoidable impurities are impurities introduced during the steelmaking process and the steelmaking process. Since these impurities are widely known in the field, a detailed description will be omitted.

[0103] In one embodiment of the present invention, the addition of elements other than the aforementioned alloy components is not excluded, and various elements may be included within a range that does not impair the technical spirit of the present invention. When additional elements are included, they may be included to replace the remaining iron (Fe).

[0104] The composite performance steel according to one embodiment of the present invention may have a high temperature yield strength (YS) of 300 MPa or more. Here, high temperature means 600°C.

[0105] The composite performance steel according to one embodiment of the present invention may have a room temperature tensile strength (TS) of 570 MPa or more, preferably 570 to 720 MPa. Here, room temperature means 20°C.

[0106] In addition, the composite performance steel according to one embodiment of the present invention may have a room temperature yield strength (YS) of 460 MPa or more.

[0107] In addition, the composite performance steel according to one embodiment of the present invention may have a room temperature yield ratio (YR) of 85% or less, preferably 70% or less.

[0108] In addition, the composite performance steel according to one embodiment of the present invention may have a room temperature elongation (EL) of 17% or more, preferably 19% or more.

[0109] In addition, the composite performance steel according to one embodiment of the present invention may have a low-temperature impact toughness (CVN) of 47 J or more, preferably 75 J or more. Here, low temperature means -5°C.

[0110] And, according to one embodiment of the present invention, the composite performance steel may have a flange thickness of less than 25 mm, preferably less than 24 mm.

[0111] Hereinafter, a method for manufacturing a composite performance steel according to one embodiment of the present invention will be described in detail.

[0112]

[0113] Method for manufacturing composite performance steel

[0114] Hereinafter, a method for manufacturing a composite performance steel according to one embodiment of the present invention will be described with reference to FIG. 1.

[0115] Figure 1 is a flowchart showing a method for manufacturing a composite performance steel according to one embodiment of the present invention.

[0116] A method for manufacturing a composite performance steel according to one embodiment of the present invention includes a step (S1) of preparing a semi-finished steel material, a step (S2) of reheating the steel material, a step (S3) of hot-rolling the steel material to form a hot-rolled steel material, and a step (S4) of cooling the formed hot-rolled steel material.

[0117] Hereinafter, each step of a method for manufacturing a composite performance steel according to one embodiment of the present invention will be described in detail.

[0118] According to one embodiment of the present invention, the step (S1) of preparing a semi-finished steel product is a step of preparing a steel product having the above-described alloy composition range in order to manufacture a composite performance steel product as a final product.

[0119] Specifically, the steel preparation step (S1) may be a step of designing alloy components within the aforementioned alloy composition range to manufacture a semi-finished product. The semi-finished product may be a billet or bloom, but is not limited thereto. Furthermore, the manufacture of the semi-finished product may be performed using processes known in the relevant technical field, such as a steelmaking process or a casting process.

[0120] According to one embodiment of the present invention, a step (S2) of reheating the steel may be performed after the step (S1) of preparing the steel.

[0121] The step (S2) of reheating the steel is a pretreatment step of the rolling step, and may be a step of uniformly heating the steel by charging the steel into a heating furnace so that plastic deformation can be easily performed, thereby re-dissolving the components segregated during casting of the steel.

[0122] In the reheating step (S2), the steel may be reheated to 1200 to 1250°C. If the reheating temperature is below 1200°C, the rolling load may increase. Conversely, if the reheating temperature exceeds 1250°C, austenite grains may coarsen or decarburization may occur, reducing strength. Furthermore, increased heating costs and time may lead to increased manufacturing costs and reduced productivity.

[0123] Therefore, in the present invention, the steel can be reheated at a temperature of 1200 to 1250°C.

[0124] According to one embodiment of the present invention, a step (S3) of hot rolling the steel to form a hot-rolled steel may be performed after a step (S2) of reheating the steel.

[0125] In the step of forming hot-rolled steel (S3), the temperature of the reheated steel is lowered due to transport or other reasons, so that hot rolling can begin at a temperature range of 1050 to 1100°C.

[0126] The above hot rolling may include rough rolling and finish rolling processes. Here, the rough rolling process may be to make the steel into a rolled material having an appropriate shape, thickness, and width, and the finish rolling process may be to adjust the steel to a specified size and roll it at a finishing temperature suitable for the intended use to obtain a good surface and shape.

[0127] In the step (S3) of forming a hot-rolled product, if the finishing rolling temperature falls below the preset range, the rolling load may increase, reducing productivity and reducing the heat treatment effect. Conversely, if the finishing rolling temperature exceeds the preset range, coarse pearlite structures may form, leading to a rapid decrease in strength.

[0128] In other words, the finish rolling temperature plays a crucial role in the hot-rolled steel forming process, significantly influencing the metal's microstructure and properties. Specifically, at higher finish rolling temperatures, the grains within the metal can grow larger, which tends to decrease the metal's hardness but increase its toughness. This means that the material is more ductile and resistant to fracture at high temperatures. These characteristics can be particularly ideal for parts used in high-temperature environments. Conversely, at lower finish rolling temperatures, the grains within the metal remain smaller, which increases the metal's hardness but may decrease its toughness. This means that the material has higher strength but may be less resistant to fracture at high temperatures. Therefore, the finish rolling temperature significantly influences the high-temperature properties of hot-rolled steel, which can significantly influence its ultimate applications and performance.

[0129] In one embodiment of the present invention, the finishing rolling temperature may be 730°C or higher, and preferably 740°C or higher.

[0130] According to one embodiment of the present invention, after performing the step (S3) of forming a hot-rolled material, a step (S4) of cooling the formed hot-rolled material may be performed.

[0131] The step (S4) of cooling the hot-rolled material can be performed by water cooling using a cooling facility. That is, the cooling facility may be a temp-core facility. In other words, the hot-rolled material can be rapidly cooled using cooling water and then reheated using residual heat.

[0132] Specifically, when hot-rolled steel is cooled rapidly, smaller grains form within the metal, increasing the material's strength and hardness while reducing its toughness and ductility. Rapid cooling rates often induce hardening, which increases the metal's strength but can also increase its brittleness. When hot-rolled steel is cooled slowly, larger grains grow, increasing the metal's toughness while decreasing its hardness. This, in turn, increases the material's ductility and, thus, its resistance to fracture. Thus, the cooling rate of hot-rolled steel significantly influences the material's properties.

[0133] Therefore, according to one embodiment of the present invention, in the step (S4) of cooling the hot-rolled material, the cooling end temperature can be achieved in a temperature range of 640 to 680°C.

[0134] After the step of cooling the hot rolled material (S4) is performed, the final product, a composite performance steel, can be formed.

[0135] The composite performance steel manufactured by the composite performance steel manufacturing method according to one embodiment of the present invention can satisfy all of the above-mentioned room temperature yield strength (YS), room temperature tensile strength (TS), room temperature yield ratio (%), room temperature elongation (EL), low temperature impact toughness (CVN, -5℃), and high temperature yield strength (YS, 600℃) values.

[0136]

[0137] Comparative examples and examples

[0138] Below, preferred comparative examples and examples are presented to aid in understanding the present invention. However, the following comparative examples and examples are provided solely to aid in understanding the present invention, and the present invention is not limited to the examples below.

[0139] Table 1 shows the alloy element compositions of comparative examples and examples, Table 2 shows the process conditions of comparative examples and examples, and Table 3 shows the physical property values ​​of comparative examples and examples.

[0140] Other than the conditions described above, the manufacturing process of the comparative examples and examples of the present invention was controlled under the same conditions within the range described in the method for manufacturing composite performance steel according to one embodiment of the present invention described above, as a control variable.

[0141] In addition, the room temperature properties of the comparative examples and examples were measured in an environment of 20°C.

[0142] In Table 1 below, the unit of composition of alloy elements is weight%, and in Table 2 below, the unit of room temperature yield strength (YS), room temperature tensile strength (TS), and high temperature yield strength (YS) is MPa, the unit of room temperature yield ratio (YR) and room temperature elongation (EL) is %, and the unit of low temperature impact toughness (CVN) is J.

[0143]

[0144] Classification Chemical Composition [wt.%] CSiMnPSCrMoCuNbTiBNExample 10.090.241.430.0120.0010.320.400.160.0430.0010.00030.0095 Actual Example 20.090.271.400.0120.0020.280.380.140.0400.0010.00030.0099 Comparative Example 10.110.321.530.0100.0010.310.140.150.0500.0010.0020.0096 Comparative Example 20.110.291. 550.0110.0010.300.740.150.0490.0010.0020.0093Comparative Example 30.080.261.390.0100.0010.300.400.200.0450.0010.00040.0103Comparative Example 40.090.241.430.0120.0010.320.400.160.0430.0010.00030.0097Comparative Example 50.090.241.430.0120.0010.320.400.160.0430.0010.00030.0097

[0145] ClassificationHeating (℃)Rolling start temperature (℃)Rolling end temperature (℃)Cooling / reheating temperature (℃ / sec)Thickness (mm)Example 11220110075267124Example 21220110077365924Comparative example 11220110076166524Comparative example 21220110075466924Comparative example 31220110072267024Comparative example 41220110077962124Comparative example 512301053783Air cooling / 1~524

[0146] ClassificationRoom temperature propertiesHigh temperature propertiesTSYSYield ratioELCVNYSExample 1713474672082313Example 2706464661980317Comparative example 15864547723124181Comparative example 2850584681812402Comparative example 3613389632373243Comparative example 4762518681827384Comparative example 5633426672079290

[0147] Referring to Tables 1 to 3 above, Comparative Example 1 is a comparative example in which the other alloy composition ranges all satisfy the ranges according to one embodiment of the present invention, but the molybdenum (Mo) content is 0.14 wt%. In the case of Comparative Example 1, it can be confirmed that the molybdenum (Mo) content does not satisfy the range of 0.30 to 0.73 wt% according to one embodiment of the present invention described above, and thus the high-temperature yield strength (YS) value is 181 MPa. In other words, it can be confirmed that the high-temperature yield strength (YS) value of Comparative Example 1 does not satisfy the range targeted by the present invention of 300 MPa or more.

[0148] Comparative Example 2 is a comparative example in which the other alloy composition range satisfies all the ranges according to one embodiment of the present invention, but the content of molybdenum (Mo) is 0.74 wt%.

[0149] In the case of Comparative Example 2, it can be confirmed that the content of molybdenum (Mo) did not satisfy the range of 0.30 to 0.73 wt% according to the above-described embodiment of the present invention, and thus the low-temperature impact toughness (CVN, -5°C) value was 12J.

[0150] In other words, in the case of Comparative Example 2, it can be confirmed that the low-temperature impact toughness (CVN, -5℃) value does not satisfy the range targeted by the present invention, which is 45J or more.

[0151] On the other hand, in the case of Examples 1 and 2 according to one embodiment of the present invention, it can be confirmed that the alloy composition range satisfies all of one embodiment of the present invention. Through this, it can be confirmed that the room temperature yield strength (YS), room temperature tensile strength (TS), room temperature yield ratio, room temperature elongation (EL), and low temperature impact toughness (CVN, -5℃) values ​​all satisfy the ranges targeted by the present invention.

[0152] Comparative Example 3 is a comparative example in which the alloy composition range satisfies all the ranges according to one embodiment of the present invention, but the rolling end temperature is 722°C.

[0153] In the case of Comparative Example 3, it can be confirmed that the rolling end temperature did not satisfy the range of 740°C or higher according to the above-described embodiment of the present invention, and thus the room temperature yield strength (YS) and high temperature yield strength (YS, 600°C) values ​​were 389 MPa and 243 MPa, respectively.

[0154] In other words, in the case of Comparative Example 3, it can be confirmed that the room temperature yield strength (YS) and high temperature yield strength (YS, 600℃) values ​​do not satisfy the ranges targeted by the present invention, which are 460 MPa or more and 300 MPa or more, respectively.

[0155] Comparative Example 4 is a comparative example in which the alloy composition range satisfies all the ranges according to one embodiment of the present invention, but the cooling end temperature is 621°C.

[0156] In the case of Comparative Example 4, it can be confirmed that the cooling end temperature did not satisfy the range of 640 to 680°C according to the above-described embodiment of the present invention, and thus the low-temperature impact toughness (CVN, -5°C) value was 27J.

[0157] In other words, in the case of Comparative Example 4, it can be confirmed that the low-temperature impact toughness (CVN, -5℃) value does not satisfy the range targeted by the present invention, which is 45J or more.

[0158] Comparative Example 5 is a comparative example in which the alloy composition range satisfies all the ranges according to one embodiment of the present invention, but the step (S4) of cooling the hot-rolled material described above is performed by air cooling.

[0159] In the case of Comparative Example 5, it can be confirmed that the yield strength (YS) was 426 MPa, which is different from the water-cooling cooling method according to the embodiment of the present invention described above.

[0160] In other words, in the case of Comparative Example 5, it can be confirmed that the yield strength (YS) value does not satisfy the range targeted by the present invention, which is 460 MPa or more.

[0161] On the other hand, in the case of Examples 1 and 2 according to one embodiment of the present invention, it can be confirmed that the process range satisfies all of the embodiments of the present invention. Through this, it can be confirmed that the room temperature yield strength (YS), room temperature tensile strength (TS), room temperature yield ratio, room temperature elongation (EL), and low temperature impact toughness (CVN, -5℃) values ​​all satisfy the ranges targeted by the present invention.

[0162] As described above, preferred embodiments of the present invention have been described. It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms, in addition to the embodiments described above, without departing from the spirit or scope thereof. Therefore, the above-described embodiments should be considered illustrative rather than restrictive, and accordingly, the present invention is not limited to the above description, but may be modified within the scope of the appended claims and their equivalents.

Claims

1. Contains carbon (C) 0.08 to 0.17 wt%, silicon (Si) 0.10 to 0.50 wt%, manganese (Mn) 0.50 to 1.60 wt%, phosphorus (P) 0.020 wt% or less (excluding 0), sulfur (S) 0.010 wt% or less (excluding 0), chromium (Cr) 0.10 to 0.70 wt%, molybdenum (Mo) 0.30 to 0.73 wt%, copper (Cu) 0.50 wt% or less (excluding 0), niobium (Nb) 0.05 wt% or less (excluding 0), boron (B) 0.003 wt% or less (excluding 0), nitrogen (N) 0.012 wt% or less (excluding 0), and the remainder iron (Fe) and unavoidable impurities. High temperature yield strength (YS, 600℃) of 300MPa or more, Composite performance steel.

2. In paragraph 1, The room temperature tensile strength (TS) is 570 MPa or more, Composite performance steel.

3. In paragraph 1, The yield strength at room temperature (YS) is 460 MPa or more. Composite performance steel.

4. In paragraph 1, The room temperature yield ratio (YR) is 85% or less, Composite performance steel.

5. In paragraph 1, The room temperature elongation (EL) is 15% or more, Composite performance steel.

6. In paragraph 1, Low temperature impact toughness (CVN, -5℃) is 45J or higher, Composite performance steel.

7. In paragraph 1, By replacing the remaining Fe, Containing titanium (Ti) of 0.001 wt% or less (excluding 0), Composite performance steel.

8. In paragraph 1, The above composite performance steel is an H-shaped steel including a web portion and a flange portion arranged on both sides of the web portion. Composite performance steel. 9.(S1) Step of preparing steel; (S2) A step of reheating the above steel material; (S3) a step of hot rolling the above steel to form a hot-rolled steel; and (S4) A step of cooling the hot rolled material to form a final product; Including, but not limited to, The above final product contains carbon (C) 0.08 to 0.17 wt%, silicon (Si) 0.10 to 0.50 wt%, manganese (Mn) 0.50 to 1.60 wt%, phosphorus (P) 0.020 wt% or less (excluding 0), sulfur (S) 0.010 wt% or less (excluding 0), chromium (Cr) 0.10 to 0.70 wt%, molybdenum (Mo) 0.30 to 0.73 wt%, copper (Cu) 0.50 wt% or less (excluding 0), niobium (Nb) 0.05 wt% or less (excluding 0), boron (B) 0.003 wt% or less (excluding 0), nitrogen (N) 0.012 wt% or less (excluding 0), and the remainder iron (Fe) and unavoidable impurities. High temperature yield strength (YS, 600℃) of 300MPa or more, Method for manufacturing composite performance steel.

10. In paragraph 9, The reheating temperature of the above step (S2) is 1200 to 1250℃. Method for manufacturing composite performance steel.

11. In paragraph 9, The rolling start temperature of the above (S3) step is 1050 to 1100℃. Method for manufacturing composite performance steel.

12. In paragraph 9, The rolling end temperature of the above (S3) step is 740℃ or higher. Method for manufacturing composite performance steel.

13. In paragraph 9, The cooling end temperature of the above (S4) step is 640 to 680℃. Method for manufacturing composite performance steel.

14. In paragraph 13, The cooling of the above step (S4) is Characterized by being water-cooled, Method for manufacturing composite performance steel.

15. In paragraph 9, The above final product replaces the remaining Fe, Containing titanium (Ti) of 0.001 wt% or less (excluding 0), Method for manufacturing composite performance steel.

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