JP4437863B2 - Manufacturing method of steel sheet for steel house with excellent fire resistance - Google Patents

Description

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【表２】

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【表３】

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【発明の効果】
以上述べたごとく本発明によれば、スチールハウスにおいて火災時の構造体の強度低下を抑制し、火災による被害を最小限にとどめることを可能にするスチールハウス部材用の鋼板を得ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steel house in which a structural member is formed of a thin steel plate, and relates to a method of manufacturing a thin steel plate used for improving fire resistance.
[0002]
[Prior art]
In recent years, the number of steel house starts has increased significantly, mainly in North America, as a housing that meets market demands for environmental protection, shortening construction periods, and reducing construction costs. This steel house is a construction method in which the lumbar of 2 × 4 construction method is replaced with a structural member mainly made of steel plate with a thickness of about 0.6 to 3 mm, and the dimensional accuracy is high, and the frame material and panel are fastened with screws and screws. It is characterized by simple construction. In addition, since the strength of the structure can be increased because a steel plate having a strength higher than that of wood is used as a member, the number of construction starts is expected to increase in Japan where there are concerns about the collapse of a house due to an earthquake or the like.
[0003]
Since the strength of the structure is greatly influenced by the joining method of the members, improvement is achieved by the techniques disclosed in Japanese Patent Laid-Open Nos. 9-273250 and 10-131288. Since the material is mainly processed lightly by bending by roll processing, strength is given priority over workability as a material, and annealing after cold rolling is performed with component steel to which no special elements are added from the viewpoint of material cost reduction. In many cases, a work-hardened steel plate is used.
[0004]
One of the dangers of damaging a house is due to the earthquakes mentioned above, but the more likely one is fire burning. For earthquakes, measures can be taken by considering the structure and strength of the material under normal conditions, but in the case of a fire, alterations due to exposure of the components to high temperatures, that is, high-temperature strength, or part of existing houses due to semi-firing. When rebuilding a house, it is necessary to consider the strength of the member in consideration of alteration due to exposure to high temperatures.
[0005]
If these are not taken into account, not only will there be an increased possibility of damage due to the deformation of the housing structure during a fire, but in the case of rebuilding while leaving a part of the half-baked house for structural safety Since it becomes necessary to remove more members, a great waste is generated in terms of resources.
[0006]
Steel materials having a plate thickness exceeding 10 mm used in buildings such as larger buildings are represented by JP-A-5-59433, JP-A-5-112822, and JP-A-7-207338. As described above, many studies have been made to ensure high temperature strength by forming fine precipitates such as carbides such as Mo, V, Nb, Ti, and W, but from the viewpoint of weldability and toughness. The components are limited, and cold-worked steel materials are rarely used, and simply applying these findings to steel plates for steel houses will have problems with steel materials for steel houses. It is not enough to solve the problem.
[0007]
[Problems to be solved by the invention]
In the present invention, assuming that the fire is considered to be most likely to damage the house, the member formed by the material as cold-rolled mainly used in the steel house is subjected to a high temperature change, By securing so-called high-temperature strength, not only can the deformation of buildings during fires be suppressed to minimize damage, but also the deterioration of structural members due to exposure to high temperatures can be reduced, resulting in a half-fired When rebuilding a house leaving a part, a method of manufacturing a steel sheet for steel houses with excellent fire resistance that enables the reconstruction of a house with a sufficient structure by replacing the parts with a minimum The purpose is to provide.
[0008]
[Means for Solving the Problems]
While examining the material change at high temperature of the material as cold-rolled, the present inventors improve the strength at high temperature above a specific temperature and the strength after high-temperature heat treatment above a specific temperature by specifying the components. The present invention has been achieved by knowing what to do.
The gist of the present invention is a steel plate characterized by maintaining a high value during the heat treatment at a specific temperature or higher and the strength after the heat treatment, mainly in a steel plate for a steel house member, particularly a steel house member. By applying it to the cold-rolled steel sheet used, the damage in the fire is minimized.
[0009]
That is, the gist of the present invention has the following configuration.
(1) By mass% C: 0.02 to 0.20%, Si: 0.02 to 0.27%,
Mn: 0.50 to 1.14%, P: 0.006 to 0.011%,
S: 0.004 to 0.012%, Al: 0.005 to 0.064%,
N: 0.002 to 0.005%, W <1.0%,
At least one of the following Mo, Nb, V and Ti contains Mo <1.0%, Nb <0.6%,
V <0.8%,
Ti <0.6%,
And Mo + Nb + V + W + Ti: contained to be 0.04 to 1.5%,
After the steel slab consisting of Fe and unavoidable impurities is hot-rolled, the steel sheet is cold-rolled at a cold rolling rate of 20 to 90%, and then plated at 1100 ° C. or lower without undergoing an annealing process. A method for producing a thin steel plate for a steel house, which is excellent in fire resistance, characterized by not causing it to occur.
(2) The method for producing a thin steel sheet for steel house having excellent fire resistance as described in (1) above, wherein the steel slab heating temperature during hot rolling is> 1100 ° C. and the coiling temperature is <700 ° C.
(3) The thin steel plate has a 0.2% proof stress: 400 MPa or more, a total elongation: 20% or less, and a plate thickness of 0.6 mm to 5.0 mm, as described in (1) or (2) above A method of manufacturing thin steel sheets for steel houses with excellent fire resistance.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the reason for limiting the components and the like in the present invention will be described in detail together with the action and the mechanism of expression of the invention. The content of the component is mass%.
C is an element that increases the strength and is added to ensure a predetermined strength. In the present invention, C is a useful element for forming fine carbides such as Nb and Mo. If it is less than 0.02%, the effect of addition is small. On the other hand, if it exceeds 0.20%, workability and toughness deteriorate significantly, so the content is limited to 0.02 to 0.20%. Preferably it is 0.03 to 0.12%.
[0011]
Mo, Nb, V, W, and Ti are effective elements for forming fine carbides and forming a preferable dislocation structure in cold rolling in the steel sheet manufacturing process, and preferably control dislocation structure change during high-temperature heat treatment. By doing so, in order to realize securing of strength during and after heat treatment , W is an essential element and at least one of Mo, Nb, V, and Ti is added.
In consideration of effect expression and addition cost, Mo <1.0%, Nb <0.6%, V <0.8%, W <1.0%, Ti <0.6%, and Mo + Nb + V + W + Ti : Limited to 0.04 to 1.5%. Preferably, Mo + Nb + V + W + Ti: 0.10 to 0.80%.
[0012]
The hot rolling conditions are not particularly limited, but when manufactured by a normal continuous casting-re-ripening-hot rolling one winding process, for example, slab heating temperature> 1100 ° C., winding temperature <700 ° C. As a result, the intended strength is improved. Although the cause of this is not clear, it is considered to be because the precipitation of Mo, Nb, V, W, and Ti mainly composed of carbides is suppressed or refined.
[0013]
Cold rolling conditions are important in the present invention. This is because the dislocation structure introduced in the cold rolling process needs to be desirably controlled to the intended characteristics. The dislocation structure is affected by the cold-rolled roll diameter, lubrication, rolling temperature, etc., but it is not practical to control these for this purpose in the normal iron making process, and the effect is relatively small. In the invention, it is controlled by the cold rolling rate. As described above, the steel plate with the controlled component (precipitate) exhibits the effect of the present invention in a specific cold rolling rate range.
When the cold rolling rate is low, the effect of the present invention is not remarkable, and the amount is limited to 20 to 90% in consideration of the equipment capability of the cold rolling machine. Considering the plate thickness, operability, and production cost of the final product usually used, 40 to 85% is preferable.
[0014]
Since the steel of the present invention basically becomes a product with cold rolling except for the heat history due to plating, it has higher proof stress and lower ductility than those subjected to the normal annealing process, which is also a feature of the steel of the present invention. is there. That is, steel having a special dislocation structure required in the present invention has relatively high yield strength and low ductility. A high yield strength of the material is necessary to provide the structural strength of the building and is advantageous in this respect.
[0015]
For this reason, the object of the present invention is limited to a steel sheet having a 0.2% proof stress in a tensile test at room temperature using a JlS5 tensile test piece of 400 MPa or more and a total elongation of 20% or less. If the 0.2% proof stress is less than this, it is less attractive as a material for imparting the strength of the building structure as compared with the conventional materials, and the components and cold components whose 0.2% proof stress or ductility is out of this range are insufficient. The effect of the present invention no longer appears in steel sheets that have been subjected to a rolling condition or a thermal history that is outside this range. The effect of the present invention can be more prominently obtained with a steel sheet having a 0.2% proof stress in a tensile test at room temperature using a JlS5 tensile test piece of 450 MPa or more and a total elongation of 15% or less.
[0016]
The steel of the present invention becomes a product without undergoing an annealing process after cold rolling. However, from the viewpoint of corrosion resistance, steel plate for steel house is usually subjected to galvanization, aluminum plating, etc., and is therefore affected by the high temperature retention associated with this. If the temperature in this process is too high, for example, if it exceeds 1100 ° C., the effect of the present invention is lost, but if it is a normal plating method, it is difficult to think of such a high temperature, There is no particular restriction. The effect of the present invention is not lost as long as the heat history is as high as that obtained by a normal plating method.
[0017]
The mechanism by which the effect of the present invention is obtained is not clear, but is considered as follows. In general, the strength of steel sheets depends on the type and amount of solid solution elements, the type and amount of precipitates, the structure and size of the crystal structure, the structure and amount of dislocations, and the strength at high temperatures also basically depends on these factors. It has been decided. In the present invention, precipitates mainly composed of solid solution elements and fine carbides change the dislocation structure and amount formed by processing, and dislocations having this special structure strongly interact with solid solution elements and precipitates. It is believed that the effect persists even in a high temperature range, so that the high temperature strength is improved, and the strength after heat treatment is maintained because it remains after cooling.
[0018]
The effect of the present invention is particularly dependent on the cold rolling conditions in the steel sheet manufacturing process, suggesting that the special dislocation structure formed in the cold rolling process due to precipitates has an important meaning. ing.
[0019]
【Example】
Table 3 summarizes the properties of the steel sheets obtained by hot rolling and cold rolling the steel having the chemical composition shown in Table 1 under the conditions shown in Table 2. Effect of components by comparing the steel 3,5,6, can see the effect of the present invention about the influence of hot rolling conditions by comparing the steel 10 13, the present invention steels improves strength at high temperatures You can see that
[0020]
[Table 1]

[0021]
[Table 2]

[0022]
[Table 3]

[0023]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain a steel plate for a steel house member that can suppress a decrease in strength of the structure during a fire in the steel house and minimize damage caused by the fire.

Claims (3)

C: 0.02 to 0.20% in mass%,
Si: 0.02 to 0.27%,
Mn: 0.50 to 1.14%,
P: 0.006 to 0.011%,
S: 0.004 to 0.012%,
Al: 0.005 to 0.064%,
N: 0.002 to 0.005%,
W <1.0%,
At least one of the following Mo, Nb, V , and Ti contains Mo <1.0%,
Nb <0.6%,
V <0.8% ,
Ti <0.6%,
And Mo + Nb + V + W + Ti: contained to be 0.04 to 1.5%,
After the steel slab consisting of Fe and unavoidable impurities is hot-rolled, the steel sheet is cold-rolled at a cold rolling rate of 20 to 90%, and then plated at 1100 ° C. or lower without undergoing an annealing process. A method for producing a thin steel plate for a steel house, which is excellent in fire resistance, characterized by not causing it to occur.   The method for producing a steel sheet for steel house with excellent fire resistance according to claim 1, wherein the steel slab heating temperature during hot rolling is> 1100 ° C and the coiling temperature is <700 ° C.   The thin steel sheet has excellent fire resistance according to claim 1 or 2, characterized by 0.2% proof stress: 400 MPa or more, total elongation: 20% or less, and plate thickness of 0.6 mm to 5.0 mm. A manufacturing method of steel sheet for steel house.