JP4736205B2 - Manufacturing method of high strength H-section steel of TS590MPa or more excellent in earthquake resistance and small heat input weldability - Google Patents

Description

【００３７】
【実施例】
表１に示す成分組成の鋼を用い、種々の条件で圧延Ｈ形鋼を製造した。表２に製造条件および得られた機械的特性を示す。
【００３８】
尚、表１、２の鋼Ｎｏ．１〜１０は共通とし、表２中、末尾の英記号は製造条件が変化していることを示す。また、表１中、最高硬さはＨＡＺ最高硬さを示し、ＪＩＳ Ｚ３１０１により求めた。
【００３９】
鋼番１の鋼を用いた実施例において、鋼１Ａは、冷却速度が２℃／ｓ未満で、５９０ＭＰａ級の強度が得られず、０℃でのシャルピー衝撃試験の吸収エネルギーも低く比較例となっている。
【００４０】
一方、鋼１Ｂ、１Ｃ、１Ｄは、冷却速度が２℃／ｓ以上で、５９０ＭＰａ級の建築用大型圧延Ｈ形鋼として十分な機械的性質が得られている。
【００４１】
尚、鋼番１の鋼の最高硬さは２７０と低く優れた硬度が得られている。
【００４２】
鋼番２の鋼を用いた実施例において、鋼２Ａは、冷却速度が２℃／ｓ未満で、５９０ＭＰａ級の強度が得られず、０℃でのシャルピー衝撃試験の吸収エネルギーも低く比較例となっている。
【００４４】
尚、鋼番２の鋼の最高硬さは３１０と低く優れた硬度が得られている。
【００４５】
鋼番３の鋼を用いた実施例において、鋼３Ａは、５９０ＭＰａ級の建築用大型圧延Ｈ形鋼として十分な機械的性質が得られている。
【００４６】
鋼３Ｂは、３Ａの圧延仕上温度を更に低下させたもので、５９０ＭＰａ級の建築用大型圧延Ｈ形鋼として更に優れた機械的性質が得られている。
【００４７】
鋼番４〜７の鋼の最高硬さは低Ｃ系のため２６３〜２８０と低くＨＡＺ硬化性が低い。
【００４８】
鋼４Ａ〜鋼７Ａは、５９０ＭＰａ級の建築用大型圧延Ｈ形鋼として十分な機械的性質が得られている。
【００４９】
鋼番８は、Ｍｏ添加量が本発明範囲外で、最高硬さは２５８と低いが、強度が５９０ＭＰａ級としては劣る。
【００５０】
鋼番９は、Ｂが添加され、鋼番１０はＣ添加量が０．１３％と高く、本発明範囲外であり、５９０ＭＰａ級の建築用大型圧延Ｈ形鋼として十分な機械的性質が得られているものの、最高硬さが３５０を超え、小入熱溶接性に劣っている。
【００５１】
【表２】

【００５２】
【発明の効果】
本発明によれば、柱材として使用が可能で、且つ付属物を取り付ける際の小入熱溶接性に優れたフランジ厚さ３２ｍｍ以上の５９０ＭＰａ級高強度圧延Ｈ形鋼が生産性良く得られ、産業上極めて優れた効果を有する。
【図面の簡単な説明】
【図１】最高硬さ（ＪＩＳＺ３１０１）に及ぼす炭素当量の影響を示す図
【図２】圧延Ｈ形鋼の機械的性質に及ぼす加速冷却条件（冷却速度）の影響を示す図
【図３】圧延Ｈ形鋼の機械的性質に及ぼす加速冷却条件（冷却停止温度）の影響を示す図[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a manufacturing method of rolled H-section steel excellent in earthquake resistance (low yield ratio), narrow YP range and high toughness for use in construction. Particularly, it is a large 590 MPa class flange with a thickness of 32 mm or more, assembly welding and repair. The present invention relates to a material having small HAZ curability at the time of small heat input welding such as welding and suitable for a column material.
[0002]
[Prior art]
Column materials for high-rise buildings include box columns, cylinders using steel pipes, and column columns that are processed warmly or coldly. Construction is difficult, and thick column columns used for high-rise buildings have the disadvantage that the molding cost to satisfy the low yield ratio at the corners is expensive.
[0003]
Further, in the case of a cylinder, there is a drawback that the processing of the joint for connecting to the beam material becomes complicated, and the column pillar has a dimensional restriction that it is difficult to increase the size.
[0004]
In contrast, when rolled H-section steel is used for the column material, the section modulus differs between the H direction and the I direction, but the difference can be dealt with at the design stage and has a basic shape as a column material as it is rolled. As a result, there is no need for assembly work such as bending and welding, and there are many advantages, such as that the joint part to which the beam material is attached can be easily constructed by carbon dioxide welding, and costs including material costs and construction costs are low. Reduced.
[0005]
And establishment of the manufacturing technology of the large-sized rolling H-section steel provided with the small heat input weldability and the earthquake resistance at the time of attaching the attachment required as a pillar material was desired.
[0006]
Japanese Patent Application Laid-Open No. 8-197105 discloses a method for producing an H-section steel excellent in weldability with a carbon equivalent reduced to 0.40% or less. However, HAZ hardness is not considered, and the strength is as low as 490 MPa.
[0007]
Japanese Patent Application Laid-Open No. 11-193440 discloses a large H-section steel of 590 MPa class with little HAZ hardening. However, the amount of C addition is extremely reduced, and expensive alloy elements such as Cu and Ni are added. It was inferior in economic efficiency.
[0008]
[Problems to be solved by the invention]
The present invention has been made in view of the above points, and has a flange thickness of 32 mm or more, which has earthquake resistance (YR ≦ 80%), high strength (TS ≧ 590 MPa), and excellent small heat input weldability. It aims at providing the manufacturing method of H-section steel.
[0009]
[Means for Solving the Problems]
Rolled H-shaped steel with a flange thickness of 32 mm or larger, the stability of the shape, dimensional accuracy, and the load on the rolling mill must be taken into consideration, and the heating temperature and the finishing temperature of the rolling mill have to be high. Austenite grain refinement and subsequent austenite grain refinement by recrystallization austenite region rolling cannot be fully utilized.
[0010]
Therefore, the present inventors have studied the chemical composition, controlled rolling and accelerated cooling conditions on the premise that the carbon equivalent is 0.47% or less, and the 590 MPa class large-sized rolled H-form excellent in earthquake resistance and weldability. The production conditions of steel were found.
[0011]
The present invention has been made on the basis of the above study, that is, the present invention
1. In mass%, C: 0.05 to 0.12%, Si: 0.05 to 0.5%, Mn: 0.6 to 1.6%, Mo: 0.2 to 0.5%, V: 0.02 to 0.06%, B: 0.0003% or less and steel composed of Ceq ≦ 0.47%, remaining Fe and inevitable impurities, heated to 1100 to 1350 ° C., and then 1100 ° C. or less And hot rolling at a rolling reduction temperature of 800 to 1000 ° C. at a rolling reduction temperature of 800 to 1000 ° C., and then immediately performing accelerated cooling with a cooling rate of 11 ° C./s or more and a water cooling stop temperature of 600 to 300 ° C. A method for producing a high-strength H-section steel of TS590 MPa or more that is excellent in earthquake resistance and small heat input weldability.
[0012]
2. Further, Cu: 0.05 to 0.5%, Ni: 0.05 to 0.5%, Cr: 0.05 to 0.1%, Nb: 0.005 to 0.05%, one or two kinds 2. The method for producing a high strength H-section steel of TS590 MPa or more which is excellent in earthquake resistance and small heat input weldability according to 1, which contains the above .
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The reasons for limiting the component composition and production conditions of the present invention will be described.
[0014]
1. Ingredient composition C
C is an element effective for ensuring the strength of the steel stably, and 0.05% or more is added to obtain the effect. On the other hand, if it exceeds 0.12%, the weldability deteriorates and the HAZ hardness during small heat input welding is remarkably increased, so 0.05 to 0.12% (0.05% or more, 0.12% The following.
[0015]
Si
Si is an element effective for increasing the strength of the deoxidizer and is added in an amount of 0.05% or more in order to obtain the effect. On the other hand, if it exceeds 0.5%, the increase in strength is saturated and the weldability is impaired, so the content is made 0.05 to 0.5%.
[0016]
Mn
Mn is added in an amount of 0.6% or more to ensure strength. On the other hand, if added over 1.6%, the weldability is impaired, and the segregated portion is markedly cured, so the content is made 0.6 to 1.6%.
[0017]
Mo
Mo improves the hardenability and is effective for increasing the strength of the steel by precipitation strengthening and is added in an amount of 0.2% or more. On the other hand, if it exceeds 0.5%, the cost increases and the toughness of the welded portion is deteriorated.
[0018]
V
V is effective for increasing the strength when added in a small amount, and is added in an amount of 0.02% or more in order to increase the YP of the large rolled H-section steel. On the other hand, if it exceeds 0.06%, coarse V carbonitrides are produced and the toughness is deteriorated, so the content is made 0.02 to 0.06%.
[0019]
B
In order to remarkably increase the hardness of the HAZ part, B is restricted to 3 ppm or less as an impurity in the present invention.
[0020]
From the viewpoint of securing toughness, N is preferably 0.0050% or less.
[0021]
FIG. 1 shows the maximum hardness (JIS Z3101) of the weld heat affected zone (HAZ) in a steel having a carbon equivalent (Ceq) of 0.47% or less (chemical components are shown in Table 1). As the carbon equivalent increases, the maximum hardness increases. However, when C and B outside the scope of the present invention are contained, they are markedly cured.
[0022]
Ceq
Ceq is set to 0.47% or less in order to reduce the HAZ hardness during small heat input welding.
[0023]
In the present invention, one or more of Cu, Ni, Cr, and Nb can be added as necessary in addition to the above basic components.
[0024]
Cu
Cu is an element effective for increasing the strength. To obtain the effect, 0.05% or more is added. On the other hand, if it exceeds 0.5%, the production cost increases, and the nonuniformity of strength in the thickness direction and surface scratches occur.
[0025]
Ni
Ni is effective in improving strength and toughness, and 0.05% or more is added to obtain the effect. On the other hand, if it exceeds 0.5%, the weldability is impaired and the production cost increases, so the content is made 0.05 to 0.5%.
[0026]
Cr
Cr is effective in increasing the strength, and 0.05% or more is added to obtain the effect. On the other hand, if it exceeds 0.1%, the weldability is deteriorated, so 0.05 to 0.1%.
[0027]
Nb
Nb is effective in increasing the strength, and when the effect is obtained, 0.005% or more is added. On the other hand, if it exceeds 0.05%, the toughness deteriorates, so the content is made 0.005 to 0.05%.
[0028]
2. Manufacturing conditions Slab heating temperature: 1100-1350 ° C
As the dimension of the rolled H-section steel increases, it is desirable to finish the rolling in a high temperature range in consideration of deformation resistance and dimensional accuracy during rolling. When the heating temperature is less than 1100 ° C., the temperature drop during rolling is remarkable, and the toughness is excellent, but the dimensional accuracy is lowered.
[0029]
On the other hand, when the temperature exceeds 1350 ° C., the austenite grain size at the time of heating becomes remarkably large, and the toughness is insufficient as building steel, and the furnace body of the heating furnace is damaged.
[0030]
When the cumulative rolling reduction at 1100 ° C. or less is 20% or more and 1100 ° C. or less and the cumulative rolling reduction in the austenite recrystallization region is less than 20%, the coarse austenite grains make it difficult to refine the ferrite grains and deteriorate toughness. Therefore, 20% or more.
[0031]
Accelerated cooling rate: 2 ° C./s or higher In order to achieve TS ≧ 590 MPa class, the accelerated cooling rate is 2 ° C./s or higher at the center of the plate thickness. The accelerated cooling is performed immediately after rolling.
[0032]
In FIG. 2, a steel having a carbon equivalent of 0.47% or less (shown in Table 1 with chemical components) is heated to 1230 ° C., and after rolling at 1100 ° C. or less and a cumulative reduction ratio of 20% or more and a finishing temperature of 900 ° C., It shows the mechanical properties when cooled to about 500 ° C. at various cooling rates and then allowed to cool. When the cooling rate is 2 ° C./s or higher, TS ≧ 590 MPa class.
[0033]
Further, in the present invention, it is desirable that the cooling stop temperature is 600 to 300 ° C. for earthquake resistance (YR ≦ 80%) and high toughness.
[0034]
FIG. 3 shows a steel sheet having a carbon equivalent of 0.47% or less (shown in Table 1 with chemical components) heated to 1230 ° C., rolled at 1100 ° C. or less and a cumulative reduction of 20% or more, and finished at a temperature of 900 ° C. Then, immediately after accelerated cooling at 2 ° C./s or more, the mechanical properties are shown when water cooling is stopped at various temperatures.
[0035]
As the stop temperature decreases, the yield ratio decreases, and a rolled H-section steel with excellent earthquake resistance with a cooling stop temperature of 600 ° C. or less and YR ≦ 80% is obtained. When the cooling stop temperature is 600 to 300 ° C., high toughness is obtained together with earthquake resistance.
[0036]
[Table 1]

[0037]
【Example】
Using the steel having the composition shown in Table 1, rolled H-section steel was produced under various conditions. Table 2 shows the manufacturing conditions and the mechanical properties obtained.
[0038]
In Tables 1 and 2, the steel No. 1 to 10 are common, and in Table 2, the alphabetical symbol at the end indicates that the manufacturing conditions have changed. In Table 1, the maximum hardness indicates the HAZ maximum hardness, and was determined according to JIS Z3101.
[0039]
In an example using steel No. 1, steel 1A has a cooling rate of less than 2 ° C./s, a strength of 590 MPa class is not obtained, and the absorbed energy of the Charpy impact test at 0 ° C. is also low. It has become.
[0040]
On the other hand, steels 1B, 1C, and 1D have a cooling rate of 2 ° C./s or more, and sufficient mechanical properties are obtained as a large-scale rolled H-section steel for 590 MPa class.
[0041]
Incidentally, the maximum hardness of steel No. 1 is as low as 270 and an excellent hardness is obtained.
[0042]
In an example using steel No. 2, steel 2A had a cooling rate of less than 2 ° C./s, a strength of 590 MPa was not obtained, and the absorbed energy of the Charpy impact test at 0 ° C. was also low. It has become.
[0044]
The maximum hardness of steel No. 2 is as low as 310, and excellent hardness is obtained.
[0045]
In an example using steel No. 3, steel 3A has sufficient mechanical properties as a large-sized rolled H-section steel for building of 590 MPa class.
[0046]
Steel 3B is obtained by further lowering the rolling finishing temperature of 3A, and has further excellent mechanical properties as a large-sized rolled H-section steel for 590 MPa class.
[0047]
The maximum hardness of steel Nos. 4 to 7 is low 263 to 280 because of the low C system, and the HAZ curability is low.
[0048]
Steel 4A to steel 7A have sufficient mechanical properties as a large-sized rolled H-section steel for building of 590 MPa class.
[0049]
Steel No. 8 has an Mo addition amount outside the scope of the present invention and a maximum hardness as low as 258, but the strength is inferior as a 590 MPa class.
[0050]
Steel No. 9 has B added, and Steel No. 10 has a high C addition of 0.13%, which is outside the scope of the present invention, and has sufficient mechanical properties as a large rolled H-section steel for 590 MPa class construction. However, the maximum hardness exceeds 350, and the low heat input weldability is poor.
[0051]
[Table 2]

[0052]
【The invention's effect】
According to the present invention, a 590 MPa class high-strength rolled H-section steel having a flange thickness of 32 mm or more, which can be used as a column material and has excellent small heat input weldability when attaching accessories, is obtained with high productivity. It has extremely excellent effects in industry.
[Brief description of the drawings]
FIG. 1 is a graph showing the effect of carbon equivalent on maximum hardness (JISZ3101). FIG. 2 is a graph showing the effect of accelerated cooling conditions (cooling rate) on the mechanical properties of rolled H-section steel. Diagram showing the effect of accelerated cooling conditions (cooling stop temperature) on the mechanical properties of H-section steel

Claims (2)

In mass%, C: 0.05 to 0.12%, Si: 0.05 to 0.5%, Mn: 0.6 to 1.6%, Mo: 0.2 to 0.5%, V: 0.02 to 0.06%, B: 0.0003% or less and steel composed of Ceq ≦ 0.47%, remaining Fe and inevitable impurities, heated to 1100 to 1350 ° C., and then 1100 ° C. or less And hot rolling at a rolling reduction temperature of 800 to 1000 ° C. at a rolling reduction temperature of 800 to 1000 ° C., and then immediately performing accelerated cooling with a cooling rate of 11 ° C./s or more and a water cooling stop temperature of 600 to 300 ° C. A method for producing a high-strength H-section steel of TS590 MPa or more that is excellent in earthquake resistance and small heat input weldability. Further, Cu: 0.05 to 0.5%, Ni: 0.05 to 0.5%, Cr: 0.05 to 0.1%, Nb: 0.005 to 0.05%, one or two kinds The method for producing a high-strength H-section steel of TS590 MPa or more excellent in earthquake resistance and small heat input weldability according to claim 1, comprising the above .

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