JPH10131340A - Fire-resisting laminate for covering steel frame and execution method of fore-resisting steel frame - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fire-resisting laminate having excellent workability and fire resistance and being used for covering a steel frame and the execution method of the fire-resisting steel frame. SOLUTION: In the fire-resisting laminate for covering a steel frame, a fire- resisting expansion sheet a,2 in thickness of 0.5-40mm and a sheet b,4 capable of holding the shape of the fire-resisting expansion sheet a,2 without distributing the expansion of the fire-resisting expansion sheet a,2 and capable of interrupting a flame are laminated. D'D/=1.1-20 is established in the relationship of thickness D before heating and thickness D' after heating at the time of heating at 300 deg.C in the fire-resisting expansion sheet a,2 at that time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fire-resistant laminate for covering steel frames having excellent fire resistance and workability.

[0002]

2. Description of the Related Art With the rise of buildings and the like, lightweight steel frames have been used as beams, columns, etc., which are structural materials of buildings. Steel frames used as structural materials for buildings include Ministry of Construction Notification No. 2999 and JIS A130
4 stipulates fire performance standards, and in order to satisfy the standards, it is common practice to coat the surface of a steel frame with a material having excellent fire resistance.

[0003] As a coating material for imparting fire resistance to steel frames, Japanese Patent Application Laid-Open No. Hei 6-32664 discloses a material in which inorganic components such as vermiculite and rock wool are mixed with water glass or hydraulic cement. . However, this method had to be applied or sprayed on the steel frame at the time of construction, and the workability was poor. Further, the thickness of the formed refractory coating layer tends to be uneven, and when the thickness is uneven, sufficient fire resistance cannot be exhibited. In addition, cracks may occur in the formed fire-resistant coating layer, and the fire resistance may decrease. Furthermore, when spraying by a wet or semi-dry method, it takes a long time to cure and the working efficiency is poor.

[0004] Refractory paints are commercially available from Mitsui Kinzoku Paint Co., Ltd., and such refractory paints are used at construction sites.
Since it is necessary to mix different types of paints, coating unevenness is likely to occur, and it has been difficult to impart uniform fire resistance to steel frames. There is also a method of installing a light cull plate so as to surround a steel frame. However, since it is necessary to fix it with a large number of nails, screws, etc., the workability is very poor.

[0005] JP-A-7-133640 discloses a coating material in which a water-absorbing gel is packed with aluminum-evaporated polyethylene and further wrapped with a ceramic mat. However, in this case, the gel portion may be cut off at the time of construction, or if the nail is hit, the internal water-absorbing gel may leak out and become unusable.

[0006]

DISCLOSURE OF THE INVENTION In view of the above, the present invention provides a fire-resistant laminate for steel frame coating having excellent workability and fire resistance.
It is another object of the present invention to provide a method for constructing a fire-resistant steel frame.

[0007]

According to the present invention, a thickness of 0.5 to 0.5 mm is provided.
A 40 mm refractory expansion sheet (a) and a sheet capable of retaining the shape of the refractory expansion sheet (a) without hindering the expansion of the refractory expansion sheet (a) and blocking a flame ( b), wherein the fire-resistant expansion sheet (a) is at 300 ° C.
In this case, the relationship between the thickness (D) before heating and the thickness (D ') after heating is D' / D = 1.1 to 20. Hereinafter, the present invention will be described in detail.

[0008] The refractory laminate for steel frame coating of the present invention is obtained by laminating a refractory expansion sheet (a) and a sheet (b). The fire resistant expansion sheet (a) forms a fire resistant heat insulating layer by expanding due to heat at the time of fire.

When the refractory expansion sheet (a) is heated to 300 ° C., the relationship between the thickness before heating (D) and the thickness after heating (D ′) is as follows: D ′ / D = 1.1 to 20. If it is less than 1.1, the heat insulating property is deteriorated, and sufficient fire resistance cannot be imparted to the steel frame. If it exceeds 20, the expanded shape cannot be maintained and the steel frame falls off from the steel frame. Limited to range. Preferably, D '/
D = 1.5-15. When heated to 300 ° C., those having a thickness (D ′) after heating that is twice or more the thickness (D) before heating are more preferably used.

The above-mentioned fire-resistant expansion sheet (a) can be obtained by molding a resin composition obtained by blending an expanding agent and an inorganic filler with a thermoplastic resin into a sheet. The thermoplastic resin is not particularly limited, and examples thereof include a polyolefin resin such as a polypropylene resin and a polyethylene resin, a poly (1-) butene resin, a polypentene resin, a polystyrene resin, and an acrylonitrile-butadiene-styrene resin. Polycarbonate resin, polyphenylene ether resin, acrylic resin, polyamide resin, polyvinyl chloride resin, phenol resin, polyurethane resin, polybutene, polychloroprene, polybutadiene, polyisobutylene, nitrile rubber and the like.

[0011] The expandable material prevents the transfer of heat by forming an expanded heat insulating layer at the time of heating. The expanding material is not particularly limited, and examples thereof include unfired vermiculite, borates, silicates, and thermally expandable graphite. Of these, unfired vermiculite and thermally expandable graphite are preferably used in view of kneadability and moldability with the thermoplastic resin. The unsintered vermiculite and the heat-expandable graphite start expanding at about 200 ° C., whereas borates and the like start expanding at about 100 to 150 ° C., so that the kneading with the thermoplastic resin starts. May swell.

The inorganic filler is compounded to increase the heat capacity of the refractory expansion sheet (a). The inorganic filler is not particularly limited as long as it is generally used as an inorganic filler, for example,
Silica, diatomaceous earth, alumina, titanium oxide, calcium oxide, magnesium oxide, iron oxide, tin oxide, antimony oxide, ferrites, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, basic magnesium carbonate,
Calcium carbonate, magnesium carbonate, zinc carbonate, barium carbonate, dawsonite, hydrotalcite, calcium sulfate, barium sulfate, gypsum fiber, calcium silicate,
Talc, clay, mica, montmorillonite, bentonite, activated clay, sepiolite, imogolite, cerisalite, glass fiber, glass beads, silica balun,
Aluminum nitride, boron nitride, silicon nitride, carbon black, graphite, carbon fiber, carbon balun, charcoal powder, various metal powders, potassium titanate, MOS (trade name), lead zirconate titanate, aluminum borate,
Examples include molybdenum sulfide, silicon carbide, stainless steel fiber, zinc borate, various magnetic powders, slag fiber, fly ash, dehydrated sludge, and the like. Of these, dehydrated when heated,
A hydrous inorganic substance having an endothermic effect is preferably used.

In the present invention, the fire-resistant expansion sheet (a) comprises a resin composition containing a phosphorus compound, neutralized heat-expandable graphite, and an inorganic filler in a thermoplastic resin. For 100 parts by weight of resin,
The total amount of the phosphorus compound and the neutralized heat-expandable graphite is 20 to 200 parts by weight, and the inorganic filler is 50 to 200 parts by weight.
It is preferable to use 500 parts by weight of the phosphorus compound and the neutralized thermally expandable graphite in a weight ratio of 1: 9 to 9: 1. Such a fire-resistant expansion sheet (a) is more excellent in shape retention and fire resistance.

The phosphorus compound is not particularly limited.
For example, red phosphorus; various phosphates such as triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, xylendiphenyl phosphate; phosphorus such as sodium phosphate, potassium phosphate, and magnesium phosphate Acid metal salts; ammonium polyphosphates; and compounds represented by the following general formula (1). Among these, from the viewpoint of fire resistance, red phosphorus, ammonium polyphosphates, and compounds represented by the following general formula (1) are preferably used.

[0015]

Embedded image

In the formula, R ¹ and R ³ are hydrogen, C ¹ -C 1
6 represents a linear or branched alkyl group or an aryl group having 6 to 16 carbon atoms. R ² is a hydroxyl group, a linear or branched alkyl group having 1 to 16 carbon atoms, a linear or branched alkoxyl group having 1 to 16 carbon atoms, an aryl group having 6 to 16 carbon atoms, Represents an aryloxy group represented by Formulas 6 to 16.

As the above-mentioned red phosphorus, commercially available red phosphorus can be used, but those obtained by coating the surface of red phosphorus particles with a resin are preferred from the viewpoint of moisture resistance and safety such as not spontaneously igniting during kneading. Used for

The above ammonium polyphosphates are not particularly limited, and include, for example, ammonium polyphosphate and melamine-modified ammonium polyphosphate. Of these, ammonium polyphosphate is preferably used from the viewpoint of handleability and the like. As a commercially available product, for example, "AP4" manufactured by Hoechst
62 "and" Sumisafe P "manufactured by Sumitomo Chemical Co., Ltd.

The compound represented by the above general formula (1) is not particularly restricted but includes, for example, methylphosphonic acid, dimethyl methylphosphonate, diethyl methylphosphonate, ethylphosphonic acid, propylphosphonic acid, butylphosphonic acid, 2-methylpropyl Phosphonic acid, t-butylphosphonic acid, 2,3-dimethyl-butylphosphonic acid, octylphosphonic acid, phenylphosphonic acid, dioctylphenylphosphonate, dimethylphosphinic acid, methylethylphosphinic acid, methylpropylphosphinic acid, diethylphosphinic acid, dioctyl Examples include phosphinic acid, phenylphosphinic acid, diethylphenylphosphinic acid, diphenylphosphinic acid, and bis (4-methoxyphenyl) phosphinic acid. The above phosphorus compounds may be used alone or in combination of two or more.

The neutralized heat-expandable graphite is obtained by neutralizing heat-expandable graphite which is a conventionally known substance. The heat-expandable graphite, natural scaly graphite, pyrolytic graphite, powder such as quiche graphite, concentrated sulfuric acid, nitric acid,
Inorganic acids such as selenic acid and concentrated nitric acid, perchloric acid, perchlorate,
It is a graphite insertion compound obtained by treating with a strong oxidizing agent such as permanganate, dichromate, hydrogen peroxide and the like. When the thermally expanded graphite is heated, the inserted sulfuric acid or the like gasifies, and the gas pressure causes the interlayer to expand tens to hundreds times perpendicularly to the layer surface, thereby forming a heat insulating layer.

The heat-expandable graphite obtained by the acid treatment as described above is further neutralized by ammonia, an aliphatic lower amine, an alkali metal compound, an alkaline earth metal compound, etc. Heat-expandable graphite. Because the heat-expandable graphite obtained by the acid treatment has a high acidity,
If the neutralization treatment is not performed, there is a possibility that the additive reacts with other additives.

The aliphatic lower amine is not particularly restricted but includes, for example, monomethylamine, dimethylamine, trimethylamine, ethylamine, propylamine, butylamine and the like. The alkali metal compound and alkaline earth metal compound are not particularly limited, and include, for example, hydroxides, oxides, carbonates, sulfates, and organic acid salts of potassium, sodium, calcium, barium, magnesium, and the like. . Specific examples of the neutralized heat-expandable graphite are not particularly limited. For example, CA-6
OS (manufactured by Nippon Kasei Co., Ltd.) and the like.

The compounding amount of the phosphorus compound and the neutralized thermally expandable graphite is preferably 20 to 200 parts by weight in total with respect to 100 parts by weight of the thermoplastic resin. 2
If the amount is less than 0 parts by weight, sufficient fire resistance cannot be obtained, and
If it exceeds 0 parts by weight, the mechanical properties are greatly reduced, and it cannot be used. More preferably, it is 40 to 180 parts by weight.

The weight ratio between the phosphorus compound and the neutralized thermally expandable graphite is such that the neutralized thermally expandable graphite is excessively expanded by polyphosphoric acid generated when the phosphorus compound is burned. From the viewpoint of suppressing the inability to maintain the shape of the fire-resistant expansion sheet (a), the ratio is preferably 1: 9 to 9: 1. If the amount of the heat-expandable graphite subjected to the neutralization treatment is too large, it is difficult to maintain the shape of the fire-resistant expansion sheet (a), and sufficient fire resistance cannot be obtained. If too little,
The heat insulating layer is not sufficiently formed, and the fire resistance is reduced. More preferably, it is 1: 5 to 5: 1, and still more preferably,
1: 3 to 3: 1.

The amount of the inorganic filler is preferably 50 to 500 parts by weight based on 100 parts by weight of the thermoplastic resin. If it is less than 50 parts by weight, sufficient fire resistance cannot be obtained, and if it exceeds 500 parts by weight, the mechanical properties are greatly reduced, and it cannot be used. More preferably, it is 60 to 300 parts by weight.

In the present invention, an antioxidant may be added to the resin composition as long as the physical properties of the resin composition are not impaired.
Flame retardants, antioxidants, metal harm inhibitors, antistatic agents, stabilizers, crosslinking agents, lubricants, softeners, pigments, tackifiers and the like may be added.

The above resin composition can be obtained by melt-kneading the above components using a known kneading apparatus such as a single-screw extruder, a twin-screw extruder, a Banbury mixer, a kneader mixer, or a two-roller. The resin composition can be formed into the fire-resistant expansion sheet (a) by a conventionally known method such as press molding.

The thickness of the refractory expansion sheet (a) is set to 0.1.
5 to 40 mm. If it is less than 0.5 mm, it will not exhibit sufficient heat insulating properties even if expanded, and if it exceeds 40 mm, the weight will be heavy and workability will be problematic, so it is limited to the above range. Preferably, it is 2 to 25 mm.

In the present invention, the fire-resistant expansion sheet (a) preferably has tackiness.
By having the adhesive property, the workability in coating the steel frame with the refractory laminate for steel frame coating of the present invention is further improved. The tackiness can be imparted to the fire resistant expansion sheet (a) by, for example, adding a tackifier to the thermoplastic resin.

The tackifier is not particularly limited.
For example, tackifier resins, plasticizers, oils and fats, low-molecular high polymers, and the like can be used. The tackifying resin is not particularly limited, and includes, for example, rosin, rosin derivative, dammar, copal, coumarone, indene resin, polyterpene, non-reactive phenol resin, alkyd resin, petroleum hydrocarbon resin, xylene resin, epoxy resin, etc. Is mentioned.

Although it is difficult for the plasticizer alone to impart tackiness to the fire resistant expansion sheet (a), it is possible to further improve the tackiness when used in combination with the tackifier resin. The plasticizer is not particularly limited and includes, for example, phthalic acid plasticizer, phosphate ester plasticizer, adipate ester plasticizer, sabatate ester plasticizer, ricinoleate ester plasticizer, polyester plasticizer , An epoxy plasticizer, and paraffin chloride.

The above fats and oils have the same action as the above plasticizer, and can be used for the purpose of imparting plasticity and controlling the adhesion. The fats and oils are not particularly limited, and include, for example, animal fats and oils, vegetable fats and oils, mineral oils, silicone oils and the like.

The above-mentioned low molecular weight polymer can be used for the purpose of improving cold resistance and adjusting the flow in addition to imparting tackiness. The polymer low-polymer is not particularly limited. For example, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), 1,2-polybutadiene rubber (1,2-
BR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), nitrile rubber (NBR), butyl rubber (IIR), ethylene-propylene rubber (EPM,
EPDM), chlorosulfonated polyethylene (CS
M), low polymers such as acrylic rubber (ACM, ANM), epichlorohydrin rubber (CO, ECO), polyvulcanized rubber (T), silicone rubber (Q), fluoro rubber (FKM, FZ), urethane rubber (U) And the like.

The refractory laminate for steel frame covering of the present invention is obtained by laminating the sheet (b) on the above-mentioned refractory expansion sheet (a). The sheet (b) is for blocking the flame without hindering the expansion of the fire resistant expansion sheet (a). As the sheet (b), the flame does not penetrate, and the flame directly contacts the fire-resistant expansion sheet (a) and the fire-resistant expansion sheet (a)
The material is not particularly limited as long as it can prevent combustion of, for example, a ceramic sheet; a metal plate such as iron, stainless steel, and aluminum. The phrase “does not hinder the expansion of the refractory expansion sheet (a)” means that the refractory expansion sheet for a steel frame formed by laminating the sheet (b) on the refractory expansion sheet (a) is heated to 300 ° C. It means that the thickness (D) of the sheet (a) before heating and the thickness (D ') after heating satisfy the relationship of D' / D = 1.1 to 20.

The thickness of the sheet (b) may be any as long as it satisfies the function of blocking the flame, and varies depending on the material. Preferably, the thickness (D) of the refractory expansion sheet (a) before heating is obtained.
0.1 to 10 times. If it is less than 0.1 times, it may be broken at the time of fire and the flame may penetrate, and if it exceeds 10 times, the expansion of the fire resistant expansion sheet (a) is hindered and the fire resistance is reduced.

The refractory laminate for covering a steel frame of the present invention is provided such that the refractory expansion sheet (a) is coated on the steel frame such that the steel frame is on the steel frame side and the sheet (b) is on the outside, and welding screws,
It is fixed with nails, screws, bolts, etc. In the event of a fire, the fire resistant expansion sheet (a) expands to form a fire resistant heat insulating layer, and the sheet (b) prevents the flame from reaching the fire resistant expansion sheet (a), so that heat is transmitted to the steel frame. To prevent

Further, the refractory laminate for steel frame coating of the present invention comprises:
Because it is sheet-shaped, it can be easily processed into an appropriate shape according to the shape of the steel frame to be coated.
If the fire-resistant expansion sheet (a) having adhesiveness is used, the steel-frame-coated fire-resistant laminate of the present invention can be temporarily held on the steel frame surface until it is fixed with welding screws or the like. Excellent workability. A fire-resistant steel frame obtained by coating a steel frame with the fire-resistant laminate for steel frame coating of the present invention,
For example, it can be suitably used as a beam, a column, etc. of a steel building.

According to the second aspect of the present invention, the surface of the steel frame is coated with the fire-resistant expansion sheet (a), and the shape of the fire-resistant expansion sheet (a) is further prevented without hindering the expansion of the fire-resistant expansion sheet (a). This is a method for constructing a refractory steel frame that covers the sheet (b) that can hold the sheet and can block the flame.

The steel structure is not particularly limited, and examples thereof include steel structures made of H-type, I-type and C-type (box type) steel materials. The method for coating the refractory expansion sheet (a) and the sheet (b) on the surface of the steel frame is not particularly limited, and for example, a method of fixing with welding screws, nails, screws, bolts, or the like may be employed. Can be. Preferably, a method is used in which the refractory expansion sheet (a) and the sheet (b) are fixed at once with a common welding screw or the like. In this case, by using an adhesive material as the fire-resistant expansion sheet (a),
After coating the refractory expansion sheet (a), the refractory expansion sheet (a) may be held on the steel frame surface until the sheet (b) is further covered and fixed with welding screws or the like. It becomes possible and the workability is improved.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. FIG. 1 schematically shows a refractory steel frame in which the surface of an I-shaped steel frame 1 attached to a building 5 is coated with a fire-resistant expansion sheet (a) 2 and a sheet (b) 4. Also, the fire-resistant expansion sheet (a) 2 and the sheet (b) 4
FIG. 2 schematically shows a refractory steel frame coated with. The refractory expansion sheet (a) 2 and the sheet (b) 4 are fixed to the steel frame 1 by common welding screws 3. In addition, since the fire-resistant expansion sheet (a) 2 can be temporarily fixed to the steel frame 1 by using an adhesive material as the fire-resistant expansion sheet (a) 2, the sheet (b) to be performed thereafter is used.
4 and easy to fix by welding screw 3,
Workability is improved. Further, a sheet in which the above-mentioned sheet (b) is laminated on the fire-resistant expansion sheet (a) in advance can be constructed so that the fire-resistant expansion sheet (a) is in contact with the steel frame 1.

[0041]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Examples 1 to 4 According to the various composition shown in Table 1, melt kneading was carried out using two rolls to obtain a resin composition. The obtained resin composition was pressed at a molding temperature shown in Table 1 and molded into a sheet to obtain a fire-resistant expanded sheet. This refractory expansion sheet was laminated on an iron plate having a thickness of 1.5 mm. Further, a ceramic sheet (fineflex blanket, manufactured by Nichias) having a thickness of 6.0 mm was laminated on the fire-resistant expansion sheet, and was fixed to an iron plate with welding screws to obtain an evaluation sample.
About the obtained evaluation sample, fire resistance and shape retention were evaluated by the following methods. The results are shown in Table 1.

As shown in Table 1, EG8200 (manufactured by Dow), metallocene polyethylene, butyl 065 (manufactured by Exxon) as butyl rubber, 100R (manufactured by Idemitsu Petrochemical Company) as polybutene, and tackifier resin ESCOLETZ 5320 (manufactured by Exxon), C-60S (manufactured by Nippon Kasei) as thermally expandable graphite, AP422 (manufactured by Hoechst) as ammonium polyphosphate, H42M (manufactured by Showa Denko KK) as aluminum hydroxide, No-pared 120 (manufactured by Sakai Chemical Industry Co., Ltd.) was used as red phosphorus.

Evaluation method (1) Fire resistance Using a cone calorimeter (CONE2A, manufactured by Atlas), the irradiation heat quantity was 50 kWh / m ² (horizontal direction).
I went in. Evaluation sample (L: 200 mm × W: 100
mm × D: described in Table 1), the heat was given for 30 minutes, and the steel plate whose temperature did not exceed 350 ° C. was rated as ○, and the iron plate temperature was rated as x.

(2) Shape retention The evaluation sample after combustion did not collapse, and the sample which retained the shape was evaluated as ○, and the sample which was not maintained was evaluated as ×.

Comparative Example 1 As spraying agents, aluminum hydroxide 35% by weight, Portland cement 25% by weight, calcium carbonate 20% by weight, vermiculite 7% by weight, perlite 8% by weight, silicate powder 3% by weight, glass fiber 1 Spraying agent consisting of 20% by weight was applied to the iron plate used in Example 1 in an amount of 20 m.
The sample was sprayed so as to have a thickness of m. The obtained evaluation sample was evaluated in the same manner as in Example 1. The results are shown in Table 1. In addition, it was necessary to wear a mask during the spraying operation, and the workability was poor.

Comparative Examples 2 to 4 Evaluation samples were prepared and evaluated in the same manner as in Example 1 except that a fireproof expansion sheet was prepared with the composition shown in Table 1. The results are shown in Table 1. Comparative Examples 3 and 4 do not have shape retention properties and therefore cannot exhibit fire resistance.

[0048]

[Table 1]

[0049]

The fire-resistant laminate for steel frame coating of the present invention has excellent fire resistance and workability since it has the above-mentioned structure.
Further, since the method for constructing a refractory steel frame of the present invention has the above-described configuration, a refractory steel frame having excellent fire resistance can be obtained with excellent workability.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a first embodiment of a refractory laminate for steel frame coating of the present invention.

FIG. 2 is a schematic sectional view showing a second embodiment of the refractory laminate for steel frame coating of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steel frame 2 Fireproof expansion sheet (a) 3 Welding screw 4 Sheet (b) 5 Building

Claims (4)

[Claims] 1. A fire-resistant expansion sheet (a) having a thickness of 0.5 to 40 mm, which can maintain the shape of the fire-resistant expansion sheet (a) without hindering expansion of the fire-resistant expansion sheet (a), and And a sheet (b) capable of blocking a flame, wherein the fire-resistant expansion sheet (a) has a thickness before heating when heated to 300 ° C. D) and the thickness after heating (D ') are as follows: D' / D = 1.1 to 20. 2. The fire-resistant expansion sheet (a) comprises a resin composition containing a phosphorus compound, neutralized heat-expandable graphite and an inorganic filler in a thermoplastic resin, and 100 parts by weight of the thermoplastic resin. The total amount of the phosphorus compound and the neutralized thermally expandable graphite was 20 to 200 parts by weight, the inorganic filler was 50 to 500 parts by weight, and the phosphorus compound and the neutralized graphite were neutralized. The weight ratio with the heat-expandable graphite is
The refractory laminate for steel frame coating according to claim 1, wherein the ratio is 1: 9 to 9: 1. 3. The fire-resistant laminate for covering steel frames according to claim 1, wherein the fire-resistant expansion sheet (a) has adhesiveness. 4. A sheet (b) capable of covering a surface of a steel frame with a fire-resistant expansion sheet (a) and further blocking a flame without hindering expansion of the fire-resistant expansion sheet (a). A method for constructing a refractory steel frame characterized by coating.