JP7499063B2 - Fireproofing material installation method - Google Patents

Description

The present invention relates to a method for constructing a fire-resistant component and a fire-resistant component, and in particular to a method for constructing a fire-resistant component by stud welding to a component to which a fire-resistant paint has previously been applied, and to the fire-resistant component.

Conventionally, when a structure made of steel, such as a steel building, is exposed to a fire, the strength and rigidity of the steel material decreases due to the rise in temperature, and there is a risk that the structure will collapse. For this reason, fire-resistant coating is applied to the beams and columns of steel-framed structures to suppress the rise in temperature caused by fire heating (see, for example, Patent Document 1).

One fire-resistant coating material is a fire-resistant paint whose main component is ammonium polyphosphate. When this fire-resistant paint is exposed to heat during a fire, it begins to foam at around 250°C, expanding 20 to 30 times in size to form an insulating layer and suppress the temperature rise of the steel material.

When a steel beam is pre-painted with fire-resistant paint at a factory or other location (hereinafter referred to as a pre-coated beam) except for the top surface of the top flange where the floor, etc. will be installed, and then transported to the construction site for erection, it is common to weld headed studs (hereinafter referred to as stud welding) to the top surface of the top flange of the beam in order to integrate it with a reinforced concrete floor that uses a deck plate or a reinforced concrete floor that does not use a deck plate.

Japanese Patent Application Laid-Open No. 2-308046

However, when stud welding is performed on the upper surface of the upper flange, which is not coated with fire-resistant paint, of a precoated member such as a precoated beam that has been pre-painted with fire-resistant paint at the factory, there is a concern that the coating of the fire-resistant paint that was pre-painted at the factory (particularly the coating on the underside of the upper flange and the coating on the web surface close to the upper flange) may be adversely affected by the heat generated during welding. In particular, if the temperature of the steel material reaches about 250°C, the foaming temperature of the fire-resistant paint mentioned above, when stud welding is performed on the steel material, the fire-resistant paint may foam even though it is not exposed to fire, and it may not be able to perform as required in the event of a fire. For this reason, there has been a demand for a technology that allows the fire-resistant paint to perform as required in the event of a fire without the welding heat adversely affecting the coating of the fire-resistant paint when stud welding is performed on a precoated member.

In order to solve these problems, the present inventors have conducted extensive research into stud welding of precoated members, and have found that the following phenomena are believed to be factors that affect the heat generated during stud welding:
- The greater the electrical energy applied during welding, the higher the steel temperature of the welded plate element.
・The larger the diameter of the headed stud, the greater the energy required for welding.
- The thicker the welded plate element, the greater the heat capacity, so the amount of rise in steel temperature of the welded plate element is suppressed.
- Because the fire-resistant paint film acts like an insulating material, the thicker the fire-resistant paint film, the more likely it is that the temperature of the steel in the welded plate element will rise.

Based on the above findings, the inventors have come up with the invention in which the energy required to weld a headed stud to a precoated member is limited by the diameter of the headed stud, the thickness of the welded plate element of the welded member, and the coating thickness of the main material of the fire-resistant paint in order to keep the steel temperature of the welded plate element of the welded member below 250°C, preferably below 200°C, which is the foaming temperature of the fire-resistant paint.

The present invention has been made in consideration of the above, and aims to provide a method for installing fire-resistant components and fire-resistant components in which the heat of stud welding does not adversely affect the fire-resistant paint.

In order to solve the above problems and achieve the objectives, the method of construction of fire-resistant components according to the present invention is characterized in that, for a fire-resistant component having a foaming fire-resistant paint applied to the non-welding surface of a steel plate element to be welded, which foams at a predetermined foaming temperature when heated, the temperature of the steel is controlled to be below the foaming temperature of the fire-resistant paint when a stud is welded from the welding surface of the welded plate element, which is the non-fire-resistant paint-coated surface.

Another method of installing fire-resistant components according to the present invention is characterized in that, in the above-mentioned invention, the welding energy is set based on the diameter of the stud, the thickness of the steel, and the thickness of the fire-resistant paint coating to control the temperature of the steel to below the foaming temperature of the fire-resistant paint, and the stud is welded based on the set welding energy.

The fire-resistant component according to the present invention is characterized by comprising a steel material, a foaming fire-resistant paint that is applied to the surface of the steel material and foams at a predetermined foaming temperature when heated, and a stud that is welded to the non-fire-resistant paint-coated surface of the steel material by stud welding in which the temperature of the steel material is controlled to be equal to or lower than the foaming temperature of the fire-resistant paint.

Another fire-resistant member according to the present invention is characterized in that, in the above-mentioned invention, the studs are welded with a welding energy set based on the diameter of the stud, the thickness of the steel, and the thickness of the fire-resistant paint coating in order to control the temperature of the steel below the foaming temperature of the fire-resistant paint.

According to the method for applying fire-resistant components of the present invention, when a stud is welded to a fire-resistant component having a foaming fire-resistant paint applied to the non-welded surface of a steel plate element to be welded, which foams at a predetermined foaming temperature when heated, from the welded surface of the plate element to be welded, which is the non-fire-resistant paint-coated surface, the temperature of the steel is controlled to be below the foaming temperature of the fire-resistant paint, so that the heat of the stud welding does not adversely affect the fire-resistant paint. This has the effect of allowing the fire-resistant paint to perform as required in the event of a fire.

In addition, according to another method of installing fire-resistant components according to the present invention, the welding energy for controlling the temperature of the steel to below the foaming temperature of the fire-resistant paint is set based on the diameter of the stud, the thickness of the steel, and the thickness of the fire-resistant paint coating, and the stud is welded based on the set welding energy, which has the effect of controlling the temperature of the steel to below the foaming temperature of the fire-resistant paint during stud welding.

The fire-resistant member according to the present invention comprises a steel material, a foaming fire-resistant paint that is applied to the surface of the steel material and foams at a predetermined foaming temperature when heated, and a stud that is welded to the non-fire-resistant paint-coated surface of the steel material by stud welding that controls the temperature of the steel material to below the foaming temperature of the fire-resistant paint, so that the heat of the stud welding does not adversely affect the fire-resistant paint. This has the effect of allowing the fire-resistant paint to perform as required in the event of a fire.

In addition, according to another fire-resistant component of the present invention, the stud is welded with a welding energy set based on the diameter of the stud, the thickness of the steel, and the thickness of the fire-resistant paint coating in order to control the temperature of the steel below the foaming temperature of the fire-resistant paint, which has the effect of controlling the temperature of the steel below the foaming temperature of the fire-resistant paint during stud welding.

FIG. 1 is a cross-sectional view showing an embodiment of a fireproof member and a method for installing the fireproof member according to the present invention. FIG. 2 is a diagram showing an example of stud welding conditions. FIG. 3 is a diagram showing an example of conditions for realizing the welding energy. FIG. 4 is a diagram showing materials used in the test specimen. FIG. 5 is a diagram showing the maximum temperature of the steel plate and the time required to reach the maximum temperature for each type of test specimen. FIG. 6 is a diagram showing the change in steel plate temperature over time during stud welding. FIG. 7 is a diagram showing the relationship between the maximum steel sheet temperature and the steel sheet thickness.

Below, an embodiment of the fire-resistant member and the installation method of the fire-resistant member according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to this embodiment.

As shown in FIG. 1, a fire-resistant component 10 according to an embodiment of the present invention comprises a steel plate 12 (steel material) and a fire-resistant paint 14 applied to the non-welded surface of the steel plate 12. When the fire-resistant paint 14 is exposed to heat during a fire, it starts to foam at around 250°C (foaming temperature) and foams 20 to 30 times to form a heat insulating layer and suppress the temperature rise of the steel plate 12. This fire-resistant paint 14 can be composed of a fire-resistant paint whose main component is ammonium polyphosphate, for example.

In the fire-resistant member 10, a headed stud 16 is welded to the non-fire-resistant paint surface of the steel plate 12. The non-fire-resistant paint surface is the surface that is not coated with fire-resistant paint 14. It is desirable to weld the stud 16 by controlling the temperature of the steel plate 12 to 250°C or less, which is the foaming temperature of the fire-resistant paint 14, and more preferably to 200°C or less. By welding in this manner, the heat of the stud welding does not adversely affect the fire-resistant paint. Therefore, the fire-resistant paint 14 applied to the non-welded surface of the fire-resistant member 10 to which the stud 16 is welded can perform as required in the event of a fire.

An example of stud welding conditions for controlling the temperature of the steel plate 12 to 250°C or less, which is the foaming temperature of the fire-resistant paint 14, and preferably 200°C or less, is shown in Figure 2. As shown in this figure, the welding energy of stud welding is limited to the welding energy according to the shaft diameter of the stud, the thickness of the steel plate, and the coating thickness of the main material of the fire-resistant paint. For example, when the shaft diameter of the stud is 16 mm, the thickness of the steel plate is 12 mm or more, the coating thickness of the main material of the fire-resistant paint is 4.8 mm or less, and the welding energy is limited to 25,200 J. Also, when the shaft diameter of the stud is 19 mm, the thickness of the steel plate is 16 mm or more, the coating thickness of the main material of the fire-resistant paint is 4.8 mm or less, and the welding energy is limited to 38,400 J. Figure 3 shows an example of the voltage, current, and welding time for achieving the welding energy of Figure 2.

According to this embodiment, when stud welding is performed on a steel plate 12 coated with fire-resistant paint 14, the coating of fire-resistant paint 14 after stud welding can exhibit a predetermined fire resistance. This can ease the restrictions on the thermal effects caused by stud welding, and can expand the versatility of fire-resistant paint precoats.

In the above embodiment, the foaming temperature of the fire-resistant paint is around 250°C, but the present invention is not limited to this and can be applied to fire-resistant paints with foaming temperatures other than this. In any case, the welding energy is set according to the shaft diameter of the stud, the thickness of the steel plate, and the coating thickness of the main material of the fire-resistant paint, and the stud welding is performed based on this welding energy. In this way, the same effects as those described above can be achieved.

(Verification of the Effects of the Present Invention)
Next, an experiment conducted to verify the effects of the present invention and the results thereof will be described. In this experiment, a headed stud was welded to a steel plate coated with fire-resistant paint from the non-fire-resistant paint side, the temperature of the steel plate during welding was measured, and then the fire-resistant painted side of the steel plate was heated as if a fire were occurring, and the heat insulating performance due to foaming of the fire-resistant paint was examined.

First, to simulate stud welding after fire-resistant coating, the following test specimens were produced by coating steel plates with thicknesses of 12 mm, 16 mm, and 22 mm with fire-resistant coatings of main material thicknesses of 1.75 mm and 4.8 mm, and then performing stud welding from the unpainted side.
・A test specimen with a fireproof paint main material thickness of 1.75 mm and one φ16 mm headed stud welded ・A test specimen with a fireproof paint main material thickness of 1.75 mm and two φ19 mm headed studs welded ・A test specimen with a fireproof paint main material thickness of 4.8 mm and one φ16 mm headed stud welded ・A test specimen with a fireproof paint main material thickness of 4.8 mm and one φ19 mm headed stud welded

Figure 4 shows the materials used for the test specimens. An epoxy resin paint was used as the undercoat of the fireproof paint, and a combination of Firetecto E (epoxy resin paint) and Firetecto F (fluororesin paint) was selected for the top coat (Firetecto is a registered trademark). Headed studs were used with φ16mm and φ19mm, which are the main sizes used in construction. Studs are used for two purposes: to secure deck plates and to prevent slippage, and the only difference between the two is the number of studs in the design. There are generally restrictions on the welding position and shaft diameter of headed studs, with downward welding being φ25mm or less, horizontal welding being φ16mm or less, and upward welding being φ16mm or less. The ferrules are made of ceramics whose main components are silica anhydride and aluminum oxide, and are auxiliary parts designed to ensure stable welding quality.

Thermocouples were attached to the test specimens to measure the steel temperature during welding. The stud welding conditions shown in Figure 3 above were used. Figure 5 shows the type of test specimen, maximum steel temperature, and time to reach maximum temperature. Figure 6 shows the results of measuring the steel temperature during stud welding. Figure 7 shows the relationship between maximum steel temperature and steel plate thickness based on the results of each test specimen.

5 and 6, the measurement results of the steel temperature show the following trends.
- The maximum steel temperature is higher for studs with a diameter of φ19 mm than for studs with a diameter of φ16 mm.
- The maximum temperature of steel is higher as the thickness of the steel plate is thinner (22 mm < 16 mm < 12 mm).
- The maximum temperature of the steel is slightly higher when the thickness of the main material of the fire-resistant paint is thicker.

The above-mentioned tendency of maximum steel temperature can also be confirmed from Figure 7, which shows that the thicker the stud diameter, the thinner the steel plate, and the thicker the main material of the fire-resistant paint, the higher the maximum steel temperature tends to be. Fire-resistant paint (main material) foams at approximately 250°C (see Architectural Institute of Japan: Fire Resistance Guidebook for Structural Materials, 2017), so it can be said that fire-resistant paint does not foam in the temperature range measured in the stud welding in this experiment.

Heating experiments were also conducted on the above stud-welded test specimens. As a result, the amount and rate of steel temperature rise of the stud-welded test specimens were both lower than those without stud welding. The reason for this was thought to be an increase in heat capacity due to the welding of headed studs. From these results, it can be said that the required fire resistance performance (1-hour fire resistance, 2-hour fire resistance) can be ensured even when headed studs with diameters of φ16 mm and φ19 mm are welded to the unpainted surface of a steel plate with a thickness of 12 mm or more that has been applied with fire-resistant paint.

As explained above, according to the method for applying fire-resistant components of the present invention, when a stud is welded to a fire-resistant component having a foaming fire-resistant paint applied to the non-welded surface of a steel plate element to be welded, which foams at a predetermined foaming temperature when heated, from the welded surface of the plate element to be welded, which is the non-fire-resistant paint-coated surface, the temperature of the steel is controlled to be below the foaming temperature of the fire-resistant paint, so that the heat of the stud welding does not adversely affect the fire-resistant paint. This allows the fire-resistant paint to perform as required in the event of a fire.

In addition, according to another method of installing fire-resistant components according to the present invention, the welding energy for controlling the temperature of the steel to below the foaming temperature of the fire-resistant paint is set based on the diameter of the stud, the thickness of the steel, and the thickness of the fire-resistant paint coating, and the stud is welded based on the set welding energy, so that the temperature of the steel can be controlled to below the foaming temperature of the fire-resistant paint during stud welding.

The fire-resistant component according to the present invention comprises a steel material, a foaming fire-resistant paint that is applied to the surface of the steel material and foams at a predetermined foaming temperature when heated, and a stud that is welded to the non-fire-resistant paint-coated surface of the steel material by stud welding that controls the temperature of the steel material to below the foaming temperature of the fire-resistant paint, so that the heat of the stud welding does not adversely affect the fire-resistant paint. As a result, the fire-resistant paint can perform as required in the event of a fire.

In addition, according to another fire-resistant component of the present invention, the stud is welded with a welding energy set based on the diameter of the stud, the thickness of the steel, and the thickness of the fire-resistant paint coating in order to control the temperature of the steel below the foaming temperature of the fire-resistant paint, so that the temperature of the steel can be controlled below the foaming temperature of the fire-resistant paint during stud welding.

As described above, the fire-resistant component installation method and fire-resistant component of the present invention are useful when welding studs to precoated components that have been pre-painted with fire-resistant paint at a factory, and are particularly suitable for eliminating the risk of the heat of stud welding adversely affecting the fire-resistant paint.

10 Fireproof member 12 Steel plate (steel material)
14 Fireproof paint 16 Stud

Claims (2)

A method of construction of fire-resistant components in which a foaming fire-resistant paint that foams at a predetermined foaming temperature when heated is applied to the non-welded surface of a steel plate element to be welded, the temperature of the steel is controlled to be below the foaming temperature of the fire-resistant paint when a stud is welded from the welding surface of the welded plate element, which is the non-fire-resistant paint coated surface. The method for constructing fire-resistant components described in claim 1, characterized in that the welding energy is set based on the diameter of the stud, the thickness of the steel, and the thickness of the fire-resistant paint coating to control the temperature of the steel to below the foaming temperature of the fire-resistant paint, and the stud is welded based on the set welding energy.

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