JP3174098B2 - Low-yield-ratio web thin-walled H-section steel and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention has a tensile strength of 490 to 610MP.
a ( 50-62 kgf / mm ² ) and a yield ratio of 75
% Low-yield ratio web thin-walled H-section steel for architectural use, and a method for producing the same.

[0002]

2. Description of the Related Art In general, the cross-sectional dimension of an H-section steel is such that the flange plate thickness is larger than the web plate thickness, so that the cooling rate of the web is higher than that of the flange in the rolling process. Temperature difference between the web and the web.
If a compressive stress exceeding the buckling limit is generated on the web due to this temperature difference, a web wave is generated.

[0003] By the way, H-shaped steels having a small web thickness have been mainly produced by a welding method using a rolled plate. However, from the viewpoint of cost reduction, H-shaped steels by rolling have been demanded. became. In the manufacture of a web thin-walled H-section steel by the rolling method, the temperature difference between the web and the flange is larger than that of the conventional H-section steel, so that a web wave is easily generated during cooling. In order to reduce such a temperature difference between the flange and the web and to prevent a web wave, forcible cooling of a flange having a high temperature is one of effective means. However, there was a problem that a low-temperature transformation product was formed by forced cooling, mechanical properties fluctuated, and a yield ratio was increased.

In recent years, ultimate limit state design in consideration of prevention of collapse of a building due to a large earthquake has begun to be adopted.
Steel frame materials for such applications are required to have a low yield ratio from the viewpoint of securing plastic deformation capacity. It is necessary to provide a low yield ratio in order to utilize the economical rolled web thin-walled H-section steel for buildings based on the seismic design method.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a thin web H having a low yield ratio, which is applicable to a building steel material having a seismic design.
It is an object of the present invention to obtain a shaped steel by adding a specific chemical component, and to manufacture such an H-shaped steel by a hot rolling method in which rolling and cooling are optimized.

[0006]

According to the present invention, C: 0.01 to 0.10 wt% Si: 0.01 to 1.50 wt% Mn: 0.05 to 0.80 wt% Ti: 0.04 to 0 wt% .40 wt% (however, Ti / C: 6.
5 Super 8 below) Al: comprises 0.005～0.050Wt%, and the balance Fe and unavoidable impurities, the tensile strength of 490~610MPa (50~62kgf / m
m ² ), a low-yield-ratio web thin-walled H-section steel having a yield ratio of 75% or less. Further, in addition to the above components, Cu: 0.05 to 0.50 wt% Ni: 0.05 to 0.50 wt% Cr: 0.05 to 0.50 wt%, and Nb: 0.005 to 0.050 wt% When one or more kinds are included, preferable characteristics can be obtained.

According to the method of the present invention for obtaining a thin H-section steel having a low yield ratio, C: 0.01 to 0.10 wt% Si: 0.01 to 1.50 wt% Mn: 0.05 to 0.80 wt% % Ti: 0.04 to 0.40 wt% (however, Ti / C: 6.
5 Super 8 below) Al: comprises 0.005～0.050Wt%, the steel and the balance Fe and unavoidable impurities, 1
It is heated to a temperature of 200 ° C. or more, hot-worked at a temperature of ₃ points or more of Ar, and then cooled at a cooling rate of 80 ° C./sec or less.
This is a method for producing a low-yield-ratio web thin-walled H-section steel having a yield ratio of 610 MPa (50 to 62 kgf / mm ² ) and a yield ratio of 75% or less. In the method of the present invention, in addition to the above components, Cu: 0.05 to 0.50 wt% Ni: 0.05 to 0.50 wt% Cr: 0.05 to 0.50 wt% Nb: 0.005 to 0.5 wt% It is more preferable to use steel containing one or more of 050 wt% and the balance being Fe and unavoidable impurities.

[0008]

The present inventors have conducted various studies to achieve the above object, and as a result, have found that a low yield ratio web thin-walled H-section steel can be obtained by a rolling method by limiting specific chemical components. Was. The reason for limiting the numerical values of the additional elements of the present invention will be described below. C is an element effective for improving the strength, but its effect is small when it is less than 0.01% by weight.
1 wt% was made the lower limit. On the other hand, if it exceeds 0.10 wt%, both the yield strength and the tensile strength become too high, so that
The upper limit was wt%.

Si is an element effective for accelerating the precipitation reaction of TiC in the cooling process after hot rolling. In the present invention, if the content is less than 0.01 wt%, the effect is small. 01 wt% was made the lower limit. 1.5wt%
If it exceeds 300, the deposited TiC becomes coarse and the effect of increasing the strength cannot be obtained, and the deterioration of toughness also increases. Therefore, the upper limit is set to 1.50 wt%.

Mn slows down the Ar ₃ transformation and also reduces TiC
Is an element that suppresses the precipitation reaction of Ti and is effective for refining TiC particles. Less than 0.05 wt% has no effect
5 wt% was made the lower limit. If the content exceeds 0.80 wt%, the tensile strength becomes too high, so the upper limit is set to 0.80 wt%.
%. Ti is combined with C to form TiC, and is an element that is effective in improving the strength and reducing solid solution C required for lowering the yield ratio, and is positively added in the present invention. Since it is small, the lower limit was set to 0.04 wt%.
If it exceeds 0.40 wt%, the strength becomes too high, so 0.40 wt% was made the upper limit. Further, in order to reduce solid solution C which is harmful to the low yield ratio, Ti / C needs to be more than 6.5 and 8 or less in order to fix with C by Ti. Ti
When / C is too high, the toughness tends to deteriorate, so that 8 or less is preferable. Therefore, Ti / C: 6.5
Limited to super 8 or less.

Al is an element having a strong deoxidizing effect, but less than 0.005 wt% has little effect.
005 wt% was made the lower limit. Further, even if added in an amount exceeding 0.050 wt%, the effect is saturated, so that 0.050 wt%
Was set as the upper limit. In addition to the above elements, the following elements can be added as necessary. A for Cu, Ni and Cr
It is useful to increase the amount of precipitation effect when used in an appropriate amount range for achieving finer TiC through the effect of delaying the r ₃ transformation. However, these elements are 0.05wt%
If it is less than 0.05%, the effect is small, so the lower limit is 0.05 wt%. Further, if it exceeds 0.50 wt%, the economical advantage is lost, so 0.50 wt% was made the upper limit.

Nb is a carbide and a nitride and is an element effective for toughening. However, if the content is less than 0.005% by weight, the effect is small. Therefore, the lower limit is set to 0.005% by weight. Further, even if added in excess of 0.050 wt%, the effect is saturated, so 0.050 wt% was made the upper limit. Next, the manufacturing conditions will be described. The steel having the chemical composition as described above is melted in a converter or an electric furnace and formed into an ingot with a mold. The soaking and rolling in the lumps may be performed by ordinary methods. Also, the bloom or beam blank may be manufactured directly from molten steel by a continuous casting method. The heating temperature of the H-section rolling is 1200 ° C. to dissolve TiC.
The above is preferred. If the temperature is lower than 1200 ° C., the solution becomes insufficient, and a sufficient precipitation effect cannot be obtained after cooling. However, if the temperature exceeds 1350 ° C., the austenite grains become too coarse, which has an adverse effect on the material after rolling, and is economically disadvantageous.

The finish rolling temperature is preferably not lower than the Ar ₃ point temperature in order to obtain a stable yield strength. Finish rolling temperature is Ar
_The reason why the number of points is set to _three or more is that if the temperature is lower than this, a processed structure may be mixed and the variation in the material may be increased. The cooling after the finish rolling may be allowed to cool naturally, but in order to obtain a stable precipitation effect, the cooling is performed at 2 ° C / sec or more and 80 ° C / sec.
Intense cooling is performed at the following cooling rate. Cooling rate 80 ° C / s
If it exceeds ec, the amount of TiC deposited is small, and a sufficient precipitation effect cannot be obtained.

[0014]

EXAMPLE A beam blank was prepared from a molten steel having the chemical composition shown in Table 1 by a continuous casting method. This is heated to 1250 ° C., and 500 × 200 × 6 × 16 m by hot rolling.
It was rolled into an m-size web thin H-section steel. After finish rolling,
JI from the flange of H-section steel cooled at 40 ° C / sec
Table 2 shows the results obtained by cutting out the S1 tensile test piece and measuring the mechanical properties. As shown in Table 2, according to the method of the present invention, the tensile strength is 490 to 610 MPa ( 50 to 62 kgf / mm).
^In the range of ² ) , a yield ratio of 75% or less can be obtained. However, in Comparative Example No. 1, No. 7 to 9 are cases where the chemical composition or the manufacturing conditions are out of the claims, and one or both of the tensile strength and the yield ratio of the mechanical properties are outside the claims.

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

[0018]

As described above, according to the present invention, the tensile strength is
Since thin web H-section steel with a yield ratio of 490 to 610 MPa ( 50 to 62 kgf / mm ² ) and a yield ratio of 75% or less can be manufactured by an economical hot rolling method, it can be widely applied to buildings with seismic design. Has a great economic effect.

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI C22C 38/48 C22C 38/48 (72) Inventor Shosaburo Naka 1 Kawasaki-cho, Chiba-shi Kawasaki Steel Corp. Technical Research Division (56) References Special JP-A-3-130345 (JP, A) JP-A-2-282419 (JP, A) JP-A-56-44723 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 38 / 00-38/60

Claims (4)

(57) [Claims] C: 0.01 to 0.10 wt% Si: 0.01 to 1.50 wt% Mn: 0.05 to 0.80 wt% Ti: 0.04 to 0.40 wt% (however, Ti / C : 6.
5 Super 8 below) Al: containing 0.005～0.050Wt%, and the balance Fe and unavoidable impurities, the tensile strength of 490~610MPa (50~62kgf / mm
² ), low yield ratio web thin-walled H having a yield ratio of 75% or less
Shaped steel. Further, Cu: 0.05 to 0.50 wt% Ni: 0.05 to 0.50 wt% Cr: 0.05 to 0.50 wt%, and Nb: 0.005 to 0.050 wt% The low-yield-ratio web thin-walled H-section steel according to claim 1, comprising one or more of the above. 3. The method according to claim 1, wherein the steel comprises 120
After heating to a temperature of 0 ° C. or more, hot working at a temperature of Ar ₃ points or more, and cooling at a cooling rate of 80 ° C./sec or less, the tensile strength is 490 to 610 MPa (50
６２62 kgf / mm ² ), a method for producing a low-yield-ratio web thin-walled H-section steel having a yield ratio of 75% or less. 4. The method for producing a low-yield-ratio web thin-walled H-section steel according to claim 3, wherein the steel component is the component according to claim 2.