KR20150075580A - Complex steel structure and method of manufacturing the same - Google Patents

Complex steel structure and method of manufacturing the same Download PDF

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Publication number
KR20150075580A
KR20150075580A KR1020130163670A KR20130163670A KR20150075580A KR 20150075580 A KR20150075580 A KR 20150075580A KR 1020130163670 A KR1020130163670 A KR 1020130163670A KR 20130163670 A KR20130163670 A KR 20130163670A KR 20150075580 A KR20150075580 A KR 20150075580A
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South Korea
Prior art keywords
steel
steel structure
structural member
heating
cooling
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KR1020130163670A
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Korean (ko)
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박성필
백승철
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현대하이스코 주식회사
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Priority to KR1020130163670A priority Critical patent/KR20150075580A/en
Publication of KR20150075580A publication Critical patent/KR20150075580A/en

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Articles (AREA)

Abstract

The present invention relates to a composite steel structure capable of differently controlling the mechanical properties of an outer surface of a steel structure, and a method for manufacturing the composite steel structure, comprising the steps of: preparing a steel structural member having a hollow; heat treating the steel structural member; Forming a martensite structure by performing a cooling process on the outer side of the heat treated steel structure, and performing a heating process on the inner side of the heat treated steel structure to form a structure more ductile than the martensite structure, Wherein the heating step is performed simultaneously, and a method of manufacturing the same.

Description

TECHNICAL FIELD The present invention relates to a composite steel structure and a manufacturing method thereof,

TECHNICAL FIELD The present invention relates to a steel structural member, and more particularly, to a composite steel structural member and a manufacturing method thereof.

Generally, the collision members such as door beams, seat frames, bumper bins in the automobile field, high-strength heat treatment products in the field of API oil pipeline, high-strength structural materials and high-pressure pressure tubes in the construction field, steel structures applied to earthquake- It is usual that high pressure acts on the steel structure material buried in the ground because the high pressure crude oil or gas flows mainly in the steel structure material. In order to use steel structural materials in such polar regions and cold regions, such steel materials must have high strength and low temperature toughness, and also require high deformability due to earthquake and other crustal changes have.

1. Korean Patent Publication No. 2012-0000766 2. Korean Patent No. 10-1169654

However, such a conventional composite steel structure material and a manufacturing method thereof have a problem of high strength and brittleness due to insufficient ductility of the steel structure material.

It is an object of the present invention to provide a composite steel structural member capable of differently controlling the mechanical properties of an outer surface of a steel structural member and a method of manufacturing the same. However, these problems are exemplary and do not limit the scope of the present invention.

According to one aspect of the present invention, there is provided a method of manufacturing a steel structure comprising the steps of preparing a steel structural material having a hollow, heat treating the steel structural material, cooling the outer side of the heat treated steel structural material to form a martensitic structure, Wherein the cooling step and the heating step are simultaneously performed by performing a heating process on the inner side of the steel structure material to form a ductile structure than the martensite structure.

In the method for manufacturing the composite steel structure material, the cooling step and the heating step may be performed simultaneously.

In the method for manufacturing the composite steel structure, the heating process is performed using a heating member, and the heating process can be inserted into the hollow of the heat treated steel structure to heat the inside portion.

In the method for manufacturing the composite steel structure, the heating member may be inserted into the hollow of the heat treated steel structure member during the cooling process.

In the method for manufacturing the composite steel structure, the cooling process may include a water quenching hardening process.

In the method for manufacturing the composite steel structural member, the steel structural member may include a steel pipe.

In the method of manufacturing the composite steel structure material, the structure that is more ductile than the martensitic structure may include bainite or pearlite.

In the method for manufacturing the composite steel structure, the heat treatment may include a high frequency heat treatment.

A method of manufacturing a composite steel structure according to another aspect of the present invention includes the steps of preparing a steel structural member having a hollow structure, heat treating the steel structural member to form an austenitic structure, Forming a martensite structure by performing a first cooling process at a speed lower than the first cooling rate and a second cooling process at a second cooling rate lower than the first cooling rate with respect to the inner side of the heat treated steel structure to form a bainite or perlite structure And the first cooling step and the second cooling step may be performed simultaneously.

According to still another aspect of the present invention, there is provided a composite steel structural member implemented by the above-described method of manufacturing a composite steel structural member.

According to one embodiment of the present invention as described above, a composite steel structural member capable of differently controlling the mechanical properties of the outer surface in the steel structural member and the manufacturing method thereof can be implemented. Of course, the scope of the present invention is not limited by these effects.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart schematically showing a method of manufacturing a composite steel structural member according to an embodiment of the present invention; FIG.
2 is a view schematically showing a method of manufacturing a composite steel structural member according to an embodiment of the present invention.
3A is a cross-sectional view schematically showing a heating member of a composite steel structural member according to an embodiment of the present invention.
3B is a cross-sectional view schematically showing a heating member of a composite steel structural member according to another embodiment of the present invention.
3C is a cross-sectional view schematically showing a heating member of a composite steel structural member according to another embodiment of the present invention.
FIG. 3D is a cross-sectional view schematically showing a heating member of a composite steel structural member according to another embodiment of the present invention. FIG.
4 is a cross-sectional view schematically showing a composite steel structure formed by a method of manufacturing a composite steel structural member according to embodiments of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, Is provided to fully inform the user. Also, for convenience of explanation, the components may be exaggerated or reduced in size.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart schematically showing a method of manufacturing a composite steel structural member according to an embodiment of the present invention; FIG.

Referring to FIG. 1, a composite steel structural member according to an embodiment of the present invention and a method of manufacturing the same include a step S10 of preparing a steel structural member having a hollow (100 in FIG. 3), a steel structural member (100 in FIG. (S30) of performing a cooling process on the outer side portion (10 of FIG. 3) of the heat treated steel material (100 of FIG. 3) and the inner side portion of the heat treated steel material (S40 in FIG. 3). For example, a steel structure member (100 in Fig. 3) is prepared, heat treatment is applied to the prepared steel structure member (100 in Fig. 3), and then the outer side portion including the outer surface of the heat treated steel structure member (10 in Fig. 3) is subjected to a cooling process to form a martensitic structure (40 in Fig. 4), and the inner portion (20 in Fig. 3) including the inner surface of the heat treated steel structural member A heating process can be performed to form a structure superior in ductility to the martensitic structure (40 in Fig. 4). The inner portion (20 in Fig. 3) of the steel structural member (100 in Fig. 3) is a surface defining a hollow (30 in Fig. 3) formed inside the steel structural member (100 in Fig. 3), for example.

The structure having superior ductility than the martensitic structure (40 in Fig. 4) may include, for example, bainite or pearlite structure (50 in Fig. 4).

The heat treatment may include, for example, a high frequency heat treatment, and the cooling step may include, for example, water quenching and the like.

In addition, the steel structure 100 may include all kinds of steel materials capable of being heat-treated, such as general carbon steel and boron steel, and may include, for example, steel pipes classified into a square pipe and a circular pipe, The steel pipe may include an electric welded steel pipe, a spiral steel pipe, a roll bending steel pipe, a corrugated steel pipe, and a non-steel pipe formed by perforating the steel pipe.

FIG. 2 is a schematic view showing a method of manufacturing a composite steel structural member according to an embodiment of the present invention, and FIGS. 3A, 3B, 3C and 3D are views showing a method of heating a composite steel structural member according to an embodiment of the present invention Sectional view schematically showing the member.

2 and 3, the heating process is performed using the heating member 110 and is inserted into the hollow 30 of the heat treated steel structure 100 to form the inner side portion 20 of the steel structure 100 It can be heated to a constant temperature. The heating member 110 is a heat transfer tool that can transfer heat to the hollow of the steel structure 100 and can be heated to a temperature desired by the inventor. In addition, The heating member may be formed of a heating rod which is inserted into the hollow 30 of the heating member 100 and can control the temperature of the inner member 20 uniformly. It may be formed in two parallel long bar shapes so that the effect is better, or may be formed in an S-shaped serpentine shape, for example, as shown in FIG. 3C. The heating member 110 may be formed in a long straight nozzle shape, for example, as shown in FIG. 3D, and may be formed to supply hot steam or hot water to the inner side portion 20 of the steel structural member 100. However, the heating member 110 of the composite steel structural member according to the embodiments of the present invention and the method of manufacturing the same is not limited thereto. For example, the heating member 110 may be a coil- A heating member 110, and the like.

A method of manufacturing a composite steel structure according to embodiments of the present invention includes the steps of performing a cooling process S30 on the outer side portion 10 of the heat treated steel structure 100 and a step of cooling the inner side portion 20 of the heat treated steel structure 100, (S40) may be performed simultaneously with the heating process. For example, the cooling process is performed on the outer side 10 of the steel structural member 100, and the heating member 110 is inserted into the inner side 30 of the steel structural member 100, 20 may be subjected to a heating process. For example, a cooling process such as water quenching is performed on the outer side portion 10 of the heat treated steel structure 100, and a heating member 110, for example, The inner side portion 20 of the steel structural member 100 can be heated by inserting a heating rod capable of controlling the temperature of the long flat bar.

The cooling step S30 of the outer side 10 of the heat treated steel member 100 and the heating step S40 of the inner side 20 of the heat treated steel structure 100 are simultaneously performed The inner side portion 20 of the heat treated steel material 100 may be subjected to a heating process (e.g., a heat treatment process) to heat the steel material 100 after the cooling process is performed on the outer side portion 10 of the heat treated steel material 100 (Step S40) may be performed sequentially. The step of performing a cooling process on the outer side portion 10 of the heat treated steel structure 100 after the step S40 of performing the heating process on the inner side portion 20 of the heat treated steel structure 100, for example, (S30) may be performed sequentially.

For example, after the cooling process is performed on the outer side 10 of the steel structural member 100, the heating member 110 is inserted into the inner side 30 of the steel structural member 100, A heating process may be performed on the inner side 20 such that a heating element 110 is inserted into the inner side 30 of the steel structure 100 so that the inner side 20 of the steel structure 100 After the heating process has been performed, the cooling process may be performed on the outer side 10 of the steel structure 100.

4 is a cross-sectional view schematically showing a composite steel structure formed by a method of manufacturing a composite steel structural member according to embodiments of the present invention.

2 to 4, a composite steel structural member according to embodiments of the present invention and a steel structural member 100 manufactured by the manufacturing method according to embodiments of the present invention are manufactured by performing high frequency heat treatment on the steel structural member 100, for example, A cooling process such as water quenching and the like is performed on the outer side portion 10 of the steel structural member 100 and a heating member such as a heating rod is attached to the inner side portion 20 of the steel structural member 100, The quenching rate of the steel structural member 100 is rapidly increased to such an extent that the carbon diffusion is prevented by the cooling process in the outer side portion 10 to form the martensitic structure 40, The inner portion 20 may be formed with a bainite or pearlite structure 50 depending on the temperature at which the heating process is performed. For example, since the transformation temperature of bainite occurs below the transformation temperature of the pearlite, the temperature of the heating member 110 may include a higher temperature than when the pearlite structure forms a bainite structure.

For example, when the steel structural member 100 is subjected to an ultrasonic heat treatment, for example, a high-frequency heat treatment, the structure of the steel structural member 100 may be transformed into an austenitic structure and may be changed depending on the carbon content of the steel structural member 100 . For example, when carbon steel of 0.8% C or less is heated, all of the ferrite may contain a temperature A 3 uniformly transforming into austenite. For example, when heating carbon steel of 0.8% C or higher, Lt; RTI ID = 0.0 > A CM < / RTI > at which the titanium is uniformly transformed into austenite.

For example, in the case of vacancy steel (0.8% C steel), at constant temperature transformation curves (S curves) showing the time at which transformation begins and ends, pearlite is formed by constant temperature transformation over the nose temperature At constant temperature below the nose, bainite is formed. When the vacant steel is cooled from 850 ° C to 750 ° C and kept at this temperature, no transformation occurs. However, if the pellet is cooled to 650 ° C and maintained at a constant temperature, pearlite transformation starts after 1 second and transformation is completed within 10 seconds. As the pearlite formation temperature is lowered, the layered pearlite becomes finer and the structure hardens further.

On the other hand, if the vacant steel is subjected to constant temperature transformation at a temperature of about 550 DEG C or lower, bainite starts to be formed. It is assumed that the formation of bainite starts from the formation of ferrite nuclei in the austenite grain boundaries.

Both pearlite and bainite are composed of ferrite and cementite, but pearlite shows a layered structure in which the two phases are alternately repeated, and bainite shows a shape close to the bed. The pearlite formed at a relatively high temperature in the pearlite forming temperature range is coarse, and the pearlite formed at a relatively low temperature is fine. The upper bainite (upper bainite) formed at a temperature in the range of 350 to 550 ° C precipitates the cementite around the ferrite, while the lower part of the bainite formed at the temperature range of 250 to 350 ° C In bainite (lower bay knit), cementite is precipitated in the ferrite.

However, according to embodiments of the present invention, the composite steel structural members and the manufacturing method thereof are not limited thereto. For example, the composite steel structural members and the manufacturing method thereof may include boron steel (0.25% C steel) have.

According to another aspect of the present invention, there is provided a method of manufacturing a composite steel structural member, comprising the steps of: preparing a steel structural body 100 having a hollow 30; Forming a martensitic structure (40) by performing a first cooling process at a first cooling rate on the outer side (10) of the heat treated steel structure material (100) to form an austenite structure; And performing a second cooling process on the inner side portion (20) of the steel structure material (100) at a second cooling rate that is slower than the first cooling rate to form a bainite or pearlite structure (50) The one cooling step and the second cooling step may be performed simultaneously. For example, performing the first cooling process at the first cooling rate may include water quenching, for example, performing a second cooling process at a second cooling rate that is slower than the first cooling rate May include, for example, the heating process using the heating member 110. [0050] That is, due to the differentiated performance of the first cooling step performed on the outer side portion 10 of the steel structural member 100 and the second cooling step performed on the inner side portion 20, the outer side portion 10 is provided with the martensite structure 40 And a bainite or pearlite structure 50 can be formed on the inner side portion 20.

According to the composite steel structural member and the manufacturing method thereof according to the embodiments of the present invention described above, for example, a martensitic structure 40 having excellent strength is formed on the outer side portion 10 of the steel structural member 100, A bainite or pearlite structure 50 superior in ductility to the martensitic structure 40 is formed in the steel plate 20 so that the super high strength composite steel structure 100 having improved ductility can be manufactured. For example, in the case of 0.25C boron steel, the inner part of the boron steel can be manufactured at 1000 MPa (elongation 10%) and the outer part 1500 MPa (elongation 6%).

The mechanical strength of the inner side portion 20 and the outer side portion 10 of the steel structural member 100 can be adjusted differently by the above-described composite steel structural member and the manufacturing method thereof, And therefore, the existing high-strength brittle problem can be solved. In other words, it reinforces the ductility of the inner surface to compensate the brittleness of the ultra high strength quenched product.

In addition, the mechanical properties of the inner and outer portions of the metal can be adjusted to produce a product of hybrid structure. The manufactured composite steel structure 100 can be used as a door beam, a seat frame, a collision member such as a bumper, It can be applied to high-strength heat treatment products in pipelines, high-strength structural materials in construction fields, high-pressure pipelines, and earthquake-resistant structures.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

10:
20: medial side
30: hollow
40: Martensite structure
50: Bainite or pearlite structure
100: Steel structural member
110: heating member

Claims (10)

Preparing a steel structural member having a hollow;
Heat treating the steel structure material;
Performing a cooling process on the outer side of the heat treated steel structure to form a martensite structure; And
Performing a heating process on the inner side of the heat treated steel structure to form a structure more ductile than the martensite structure;
Lt; / RTI >
Wherein the cooling step and the heating step are performed simultaneously. The method according to claim 1,
Wherein the cooling step and the heating step are performed simultaneously. The method according to claim 1,
Wherein the heating process is performed using a heating member and is inserted into the hollow of the heat treated steel structure to heat the inside portion. The method of claim 3,
Wherein the heating member is inserted into the hollow of the heat treated steel structure member during the cooling process. The method according to claim 1,
Wherein the cooling process comprises water quenching. The method according to claim 1,
Wherein the steel structure material comprises a steel pipe. The method according to claim 1,
Wherein the ductile structure is made of bainite or pearlite. The method according to claim 1,
Wherein the heat treatment comprises a high frequency heat treatment. Preparing a steel structural member having a hollow;
Heat treating the steel structure material to form an austenite structure;
Forming a martensite structure by performing a first cooling process on the outer side of the heat treated steel structure material at a first cooling rate; And
And performing a second cooling process with respect to the inner side of the heat treated steel structure material at a second cooling rate lower than the first cooling rate to form a bainite or pearlite structure,
Wherein the first cooling step and the second cooling step are performed simultaneously. A composite steel structural material as claimed in any one of claims 1 to 9.

KR1020130163670A 2013-12-26 2013-12-26 Complex steel structure and method of manufacturing the same KR20150075580A (en)

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