JPH11172373A - Extremely thick rolled wide flange shape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an extremely thick rolled wide flange shape combining a low yield ratio, high toughness and excellent weldability and having >=590 MPa tensile strength and >=35 mm flange thickness. SOLUTION: The chemical components of the stock are composed of the ones contg., by weight, 0.010 to 0.040% C, 0.05 to 0.50% Si, 0.60 to 1.60% Mn, 0.005 to 0.100% Nb, 0.003 to 0.030% Ti and 0.0003 to 0.0040% B, also satisfying C>=Nb/7+0.005, moreover contg. one or >= two kinds among 0.05 to 0.60% Mo, 0.05 to 0.70% Cu and 0.05 to l.20% Ni, and the balance iron with inevitable impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a column material having a low yield ratio, a narrow YP range, a high toughness, and a tensile strength of 590 MPa or more, which is required as a steel material for building, and a flange thickness of 35 mm or more. The present invention relates to an extremely thick rolled H-section steel excellent in weldability.

[0002]

2. Description of the Related Art Steel columns having a low yield ratio are used for columns of high-rise buildings having a steel structure from the viewpoint of seismic design. Column materials used for high-rise buildings using such a design method include box columns, steel columns, or columns that have been worked warm or cold with little change in the section modulus in each section direction. Pillars are used. However, in the case of box columns, technology is required for the construction of square welding, in the case of cylinders, the processing of the connection part to connect to the beam material becomes complicated, in the case of thick column columns, the corner part is required However, there are drawbacks such as high molding cost for performing molding that satisfies the low yield ratio. Therefore, there is a demand for a pillar material capable of reducing the total cost including the material cost and the construction cost.

[0003] In the case of H-section steels, the section modulus differs between the H direction and the I direction. However, there are many advantages that a pillar can be manufactured without performing complicated bending and welding work, and that a connection part for attaching a beam material can be simply and simply constructed by carbon dioxide welding. It is well known that differences in section modulus can be considered at the design stage. From the above points, there is a demand for an ultra-thick rolled high-strength H-section steel that satisfies a low yield ratio (80% or less) and high toughness (vE0 ≧ 47J) and has excellent weldability. Such a steel material having a low yield ratio used for a high-rise building is disclosed in JP-A-9-137218 in the field of a thin H-section steel having a flange thickness of less than 35 mm.

[0004]

The above publication discloses that the temperature is 900 ° C.
The present invention relates to an H-section steel having a relatively small flange thickness capable of ensuring the following cumulative reduction ratio of 50% or more. However, in the field of extremely thick rolled H-section steel suitable for a column material having a flange thickness of 35 mm or more, the rolling conditions are determined mainly to adjust the shape and satisfy the dimensional accuracy. On the basis of this, it is difficult to perform rolling such that a cumulative draft of 900% or less and 50% or more is applied. Regarding the application of the TMCP (working heat treatment) technique to such an extremely thick rolled H-section steel for a column material, see JP-A-53-141119 and JP-A-9-141.
Japanese Patent Application Laid-Open No. 111397 proposes an accelerated cooling condition as disclosed in Japanese Patent Application Laid-Open No. 111397. However, it is not possible to sufficiently perform low-temperature rolling at 900 ° C. or less. Nothing is known about production by cooling.

The inventor of the present invention has developed a high strength (TS ≧ 590 MPa) flange having a thickness of 35 mm or more that combines low yield ratio, high toughness, and weldability even under such production conditions in which sufficient low-temperature rolling cannot be performed. A method for producing a thick H-section steel by rolling has been studied. It is obvious that the strength can be increased as it is rolled by adding a large amount of various alloying elements.
If sufficient rolling cannot be performed in a low temperature range, it is difficult to secure high toughness. It is not desirable from the viewpoint of weldability. In view of the above, the present inventor has considered that even under the condition that the cumulative rolling reduction at 900 ° C. or less can be less than 50%, the tensile strength having low yield ratio, high toughness, and excellent weldability is 590 MPa. Above, and the flange thickness is 35
As a result of studying an ultra-thick H-section steel having a thickness of not less than 1 mm, a high-toughness extra-thickness rolled H-section steel having the above characteristics has been found by optimizing alloy elements.

The present invention is based on this finding and has a low yield ratio, high toughness, excellent weldability, a tensile strength of 590 MPa or more, and a flange thickness of 35 mm.
It is an object of the present invention to provide an extremely thick rolled H-section steel of not less than mm.

[0007]

The flange thickness is 35 mm.
From the viewpoints of shape stability, dimensional accuracy, and reduction of the load applied to a rolling mill, the above-mentioned extremely thick rolled H-section steel has a heating temperature and
It is difficult to secure high toughness because the rolling finishing temperature is high. In addition, it is difficult to perform a heat treatment using a heat treatment furnace or the like after rolling because of a large unit weight and a complicated cross-sectional shape. Therefore, the present inventors have attempted to optimize the chemical components on the assumption that they are allowed to cool after rolling, and as a result, have a low yield ratio at room temperature, have high toughness, and have excellent tensile strength with excellent weldability. A component capable of producing a high toughness extremely thick H-section steel (flange thickness of 35 mm or more) for buildings of 590 MPa or more was found.

The specific component ranges of the high toughness extremely thick H-section steel of the present invention are shown below. (1) The chemical component of the material is C: 0.010 by weight%
0.040%, Si: 0.05 to 0.50%, Mn:
0.60 to 1.60%, Nb: 0.005 to 0.100
%, Ti: 0.003 to 0.030%, B: 0.000
3 to 0.0040%, and C ≧ Nb / 7 +
0.005, and Mo: 0.05 to 0.6
0%, Cu: 0.05-0.70%, Ni: 0.05-
One or two or more kinds are contained, and the balance consists of iron and inevitable impurities. (2) In addition to the above materials, V: 0.005 to 0.20
0%, Cr: 0.05-0.80%, Zr: 0.005
-0.05%, REM: 0.0005-0.0500
%, Ca: 0.0005 to 0.0100%.

Hereinafter, the present invention will be described in detail. FIG. 1 shows that 0.025C-1.5Mn-0.60Cu-0.
In 65Ni-Nb-0.015Ti-0.0015B steel, the steel with the Nb content changed is heated to 1300C,
The characteristic of the center part of the flange thickness when the extremely thick rolled H-section steel with a flange thickness of 65 mm is rolled at 900 ° C. finish is shown. N
If the amount of b is not contained, target TS ≧ 590MP
It does not reach a. On the other hand, when 0.005% or more of Nb is contained, the target YS ≧ 440MPa
a, TS ≧ 590 MPa, and sufficiently high toughness. In the figure, the results for the steel without B (curve marked with △ or △) and the steel without added Ti (curve with 併) are also shown, but none of them reached the target strength level.
From these results, it was found that 0.005% or more of N
It turns out that the complex addition of b and Ti and B is indispensable.

FIG. 2 shows that C-
1.45Mn-0.40Cu-1Ni-Nb-0.02
0Ti-0.0035B steel is heated to 1250 ° C.
A rolled H-section steel with a flange thickness of 50 mm is rolled at a finish of 850 ° C. by applying a cumulative rolling reduction of 30% or less at 0 ° C.
J / cm) shows the toughness of the heat affected zone by welding.
In the region where the C content is less than Nb / 7 + 0.005, grain boundary fracture occurred and the toughness was significantly reduced. In addition, C content is 0.04%
Good toughness could not be obtained even in the region exceeding.
On the other hand, in the region of Nb / 7 + 0.005 ≦ C ≦ 0.04 (shaded region), the weld and the heat-affected zone have excellent toughness.

The reasons for limiting the chemical components in the present invention are described below.

C: 0.010-0.040% C is an effective element for stably securing the strength of steel. However, if it is less than 0.010%, it is difficult to obtain the required strength, and if it exceeds 0.040%, the toughness of the base metal and the welded part deteriorates. Therefore, 0.010
The range was 0.040%.

Si: 0.05 to 0.50% Si is an element effective for deoxidation and increasing the strength. For that purpose, it is necessary to add 0.05% or more of Si. Addition impairs weldability. Therefore, 0.05-
0.50%.

Mn: 0.60 to 1.60% Mn is an effective element for securing the strength. In particular, to increase the strength, it is necessary to add 0.60% or more. on the other hand,
Addition exceeding 1.60% impairs weldability. Therefore, the range is 0.60 to 1.60%.

Nb: 0.005 to 0.100% Nb, as shown in FIG. 1, significantly increases the strength by adding a small amount thereof, and is indispensable for increasing the strength of the extremely thick rolled H-section steel as in the present invention. It is. 0.005% to achieve this effect
The above addition is effective. However, if it exceeds 0.100%, the weldability is impaired. Therefore, 0.005
The range was 0.100%.

Ti: 0.003 to 0.030% Ti is indispensable for fixing N and exerting high strength by B. To exhibit this effect, 0.003% or more of addition is required.
It forms iC and impairs weldability. Therefore, 0.003 ~
The range was 0.0030%.

B: 0.0003% to 0.0040% B is an indispensable element for exhibiting high strength as shown in FIG. 0.0003% to achieve this effect
Although the above addition is necessary, addition exceeding 0.0040% impairs toughness. Therefore, 0.0003 to 0.004
The range was 0%.

In the present invention, in addition to the above basic components, M
It is necessary to add one or more of o, Cu, and Ni. If necessary, one or more of Cr, V, REM, and Ca can be added.

Mo: 0.05 to 0.60% Mo is effective in improving the hardenability, strengthening the precipitation, etc., and increasing the strength of the steel. In order to exhibit this effect, it is necessary to add 0.05% or more. However, if it exceeds 0.60%, the cost increases and the weldability deteriorates. Therefore,
It was limited to the range of 0.05 to 0.60%.

Cu: 0.05-0.70% Cu is an element effective for increasing the strength.
Addition of not less than 0.05% is necessary, but addition of more than 0.70% increases the cost.
Limited to the range.

Ni: 0.05-1.20% Ni is effective not only for increasing the strength but also for improving the toughness, but for this purpose, 0.05% or more must be added. On the other hand, addition of 1.20% or more impairs weldability,
This also leads to higher costs. Therefore, 0.05 to 1.2
The range was limited to 0%.

Cr: 0.05 to 0.80% Cr is effective in increasing the strength, and for that purpose, 0.05 to 0.80%
% Or more is required. However, addition exceeding 0.80% causes deterioration of weldability. Therefore, 0.05-
The range was 0.80%.

V: 0.005 to 0.200% V is effective for increasing the strength by adding a small amount of V.
Addition of 5% or more is required. On the other hand, the addition exceeding 0.200% deteriorates the weldability. Therefore, 0.005
The range was limited to 0.200%.

Zr: 0.005 to 0.050% Zr fixes N similarly to Ti and exerts high strength by B. To exert this effect, 0.005% or more must be added, but if it exceeds 0.050%, the weldability is impaired. Therefore, the range is 0.005 to 0.050%.

REM: 0.0005-0.0500% REM controls the form of inclusions and is effective in improving ductility. To exert this effect, 0.0005% or more must be added, but if it exceeds 0.0500%, the toughness is impaired. Therefore, the range is 0.0005 to 0.0500%.

Ca: 0.0005% to 0.0100% Ca controls the form of inclusions similarly to REM, and is effective in improving ductility. 0.0005% to achieve this effect
Although the above addition is necessary, addition exceeding 0.0100% impairs toughness. Therefore, 0.0005 to 0.010
The range was 0%.

In the present invention, although the production conditions are not particularly limited, sufficient strength, toughness, and weldability can be ensured even under the condition that the cumulative draft at 900 ° C. or less is less than 50%.

[0028]

Embodiments of the present invention will be described below. (Example 1) Steel No. 1 having the chemical components shown in Table 1 was used. 1 to
After heating at 1270 ° C and applying a cumulative rolling reduction of 10% or less at 900 ° C or less, a flange thickness of 80 mm
Was rolled, and the characteristics of the base metal and the welded portion (carbon dioxide welding: heat input 20 kJ / cm) were examined.

[0029]

[Table 1]

The steel No. satisfying the conditions of the present invention. 1-3, 8,
9, 11, and 12 are all YS ≧ 440 MPa, TS ≧
It has high strength enough to satisfy 590 MPa, a low yield ratio of 80% or less, and high toughness of the base metal and the welded part sufficiently satisfying vE0 ≧ 47J. On the other hand, steel No. 4 is Ti
But steel No. B is steel No. 5 and 10; 6 and 13 are Nb
Does not satisfy the conditions of the present invention, the target YS ≧
It does not satisfy 440 MPa and TS ≧ 590 MPa.
Furthermore, steel No. 7, 14 are the conditions of the present invention C ≧ Nb
/7+0.005, the toughness of the weld is extremely low.

(Example 2) Steel No. 2 having the chemical components shown in Table 2 was used. Using 15-26, 900 ℃ after heating at 1150 ℃
A rolled H-section steel having a flange thickness of 50 mm was rolled at a finish of 750 ° C. by applying a cumulative rolling reduction of 30% below, and the characteristics of the base metal and the welded portion (carbon dioxide welding: heat input 20 kJ / cm) were examined. . Since both satisfy the conditions of the present invention, YS
It has high strength enough to satisfy ≧ 440 MPa and TS ≧ 590 MPa, low yield ratio of 80% or less, and high toughness of the base material and the weld part sufficiently satisfying vE0 ≧ 47J.

[0032]

[Table 2]

[0033]

As described above, according to the present invention, by limiting the chemical components, the low yield ratio, high toughness, 59 tensile strength with excellent weldability
It has become possible to manufacture an extremely thick H-section steel having a flange thickness of 0 MPa or more and a thickness of 35 mm or more.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the amount of Nb added and the mechanical properties of a base material.

FIG. 2 is a diagram showing the relationship between the amounts of C and Nb and the toughness of a weld.

Claims (2)

[Claims] 1. The chemical composition of a raw material is as follows: C: 0.010 to 0.040% Si: 0.05 to 0.50% Mn: 0.60 to 1.60% Nb: 0.005% by weight 0.100% Ti: 0.003 to 0.030% B: 0.0003 to 0.0040%, and satisfies C ≧ Nb / 7 + 0.005,
In addition, an electrode containing one or more of Mo: 0.05 to 0.60% Cu: 0.05 to 0.70% Ni: 0.05 to 1.20%, with the balance being iron and unavoidable impurities Thick rolled H-section steel. 2. The above-mentioned material, V: 0.005 to 0.200% Cr: 0.05 to 0.80% Zr: 0.005 to 0.050% REM: 0.0005 to 0.0500% Ca : One or two or more of 0.0005 to 0.0100% are contained.