TWI448562B - Resin-coated galvanized steel sheet - Google Patents

Description

Resin-coated galvanized steel sheet

The present invention relates to a resin-coated galvanized steel sheet excellent in thermal conductivity and heat dissipation, and particularly to a resin-coated material suitable for use as a raw material of an electronic device component which is required to be a heat source and partially contact the steel sheet and which requires high thermal conductivity and heat dissipation. Galvanized steel. Examples of such electronic equipment parts (including electrical equipment parts and optical equipment parts) include a heat sink, a back casing of a plasma TV, and a metal casing (housing) in which electronic equipment components containing a heat source are housed. Wait.

In the progress of thinning LCD TVs and plasma TVs, the problem of heat generation has become increasingly serious. Under such circumstances, various electrical equipment manufacturing companies have made great efforts to reduce the temperature during the work of the product by 1 ° C, and the current situation is to use expensive parts to cope with heat. In particular, the back casing of the plasma television (PDP-TV) is a component that is partially connected to the plasma element of the heat source via the glass panel, so that the heat dissipation performance of the heat-dissipating component in the heat-resistant component that is in contact with the heat source accounts for Maximum weight. As a component that responds to heat, it is currently the case that aluminum having excellent thermal conductivity is widely used as a raw material.

On the other hand, in the thin TV market such as PDP-TV, cost competition is also intensifying, and it is expected that a high-priced aluminum component can be replaced with a cheap steel component, and the product can be significantly reduced in cost.

However, aluminum parts have higher thermal conductivity than steel parts, so it is of course not a simple steel plate. In other words, in order to replace the steel parts, it is sought to reduce the heat source temperature even if it is smaller than the conventional steel materials.

To date, various proposals have been made for steel parts for electronic equipment parts. For example, in Japanese Laid-Open Patent Publication No. 2006-307260, a technique for an inexpensive plasma display panel having excellent corrosion resistance or heat dissipation is proposed. This technique is a hot-rolled steel sheet in which a steel sheet composed of continuous cast steel is hot-rolled at a high-pressure rate and then quenched to form a structure in which martensite is dispersed in ferrite, and then the hot-rolled steel sheet is once cooled. After the rolling, the steel sheet is subjected to Zn plating, and a chemical conversion treatment layer for improving corrosion resistance or heat dissipation is formed thereon. However, in this technique, there is no consideration for improving the thermal conductivity of the original plate (base steel plate), and sufficient effects cannot be obtained in terms of improving heat dissipation.

On the other hand, a casing assembly for a plasma display device having a casing having a thermal conductivity of 10 W/mK to 100 W/mK is proposed in Japanese Laid-Open Patent Publication No. 2005-222042. In addition, it is also disclosed in the art that those having a high thermal conductivity are advantageous in terms of heat release ability. However, this technique is considered from the viewpoint of being able to reduce the discharge delay phenomenon caused by the temperature drop, and in such a technique, it is not always possible to exhibit sufficient effects in terms of improving heat dissipation.

The present invention is directed to a developer in such a situation, and an object of the invention is to provide a galvanized steel sheet coated with a resin, which exhibits high thermal conductivity and heat dissipation, and can be used as a raw material for electronic equipment parts that are partially connected to a heat source.

In the resin-coated galvanized steel sheet according to the present invention for achieving the above object, the base steel sheet contains C: 0.0010 to 0.040% (meaning "% by mass", the same applies hereinafter), Si: 0.2% or less, and Mn: 0.1%. 0.80% and Al: 0.01% to 0.1%, the balance is composed of iron and unavoidable impurities, and galvanization of 70 g/m ² or more per surface is applied to both surfaces of the base steel sheet, and infrared rays are heated to 100 ° C. A resin film having an integrated emissivity of 0.60 or more (wavelength: 4.5 to 15.4 μm) is coated on at least one surface of the galvanization.

In the resin-coated galvanized steel sheet according to the above aspect of the invention, the base steel sheet to be used may further contain Ti: 0.001% to 0.20%. Thereby, the characteristics of the galvanized steel sheet coated with the resin can be further improved.

In the resin-coated galvanized steel sheet according to the above aspect of the invention, the thickness of the resin film is preferably 50 μm or less, which is preferable in terms of improving heat dissipation.

The resin-coated galvanized steel sheet of the present invention can be effectively used as a component for electronic equipment. In particular, in the back casing of the PDP-TV, it is particularly useful because of the wide area used.

In the present invention, the chemical composition of the base steel sheet is appropriately defined, and the amount of galvanized adhesion formed on the surface (both sides) of the base steel sheet and the emissivity of the surface of the resin film coated on at least one side of the galvanized steel are appropriately controlled. In this way, it is possible to realize a resin-coated galvanized steel sheet which exhibits high thermal conductivity and heat dissipation, and can be used as a material of an electronic equipment component that is partially connected to a heat source.

The present inventors have studied from various angles in order to realize a resin-coated galvanized steel sheet (hereinafter referred to as "surface-treated steel sheet") that exhibits high heat conductivity and heat dissipation. Further, first, as a result of examining the relationship between the type of the base steel sheet component and the thermal conductivity, it was found that components such as C, Mn, and Al have an influence on the thermal conductivity of the steel sheet. Further, by increasing the adhesion amount of the galvanization formed on the surface (both sides) of the base steel sheet, the heat dissipation performance can be further improved, and the emissivity can be coated on at least one side of the galvanized steel sheet (at least on the side opposite to the heat source). The high resin film can impart greater heat dissipation performance, and it has been found that such a surface-treated steel sheet can be a surface-treated steel sheet suitable for the above purpose, and thus the present invention has been completed. Hereinafter, each requirement specified in the present invention will be described.

(chemical composition of the base steel plate)

The base steel sheet used in the present invention is required to appropriately define its chemical composition, but the reason for limiting the respective components is as follows.

[C: 0.0010 to 0.040%]

C is the element that has the greatest influence on the thermal conductivity of the base steel sheet. The lower the C content, the higher the thermal conductivity. Therefore, it is necessary to set C to 0.040% or less. It is preferably 0.03% or less, more preferably 0.02% or less. On the other hand, C is an element useful in securing the strength when forming a steel sheet. In the case of a steel sheet having insufficient strength, when it is used as a large electronic equipment component such as a back casing, it is difficult to support the structure, or it is difficult to ensure the flatness of the steel sheet. Thus, by combining with other elements, the necessary strength as the back casing is ensured. The lower limit of the C content in the range which can be used as the back casing without lowering the strength is set to 0.0010%. It is preferably 0.0015% or more, more preferably 0.0020% or more.

[Si: 0.2% or less]

Si is an element that affects the wettability of the plating. In order to maintain the plating wettability well, it is necessary to set the Si content to 0.2% or less. It is preferably 0.18% or less, more preferably 0.16% or less. In the present invention, it is preferred that the Si content be as small as possible.

[Mn: 0.10 to 0.80%]

Mn is an element that affects the thermal conductivity of the base steel sheet. The smaller the Mn content is, the higher the thermal conductivity is. Therefore, it is necessary to set Mn to 0.80% or less. However, Mn is also an element that contributes to the improvement of hardenability. Therefore, in order to secure the strength of the steel sheet, it is necessary to contain 0.10% or more of Mn. It is preferably 0.12% or more, more preferably 0.14% or more.

[Al: 0.01 to 0.1%]

Al is an element that affects the thermal conductivity of the base steel sheet. In order to maintain the thermal conductivity well, it is necessary to set the Al content to 0.1% or less. It is preferably 0.08% or less, more preferably 0.05% or less. However, Al acts as a deoxidizing element, and in order to effectively exhibit such an effect, it is necessary to set the content to 0.01% or more. It is preferably 0.02% or more, more preferably 0.03% or more.

The preferred basic composition of the base steel sheet is as described above, and the balance is iron and unavoidable impurities. As the above-mentioned unavoidable impurities, P, S, N, and the like are exemplified as the representative elements, but it is preferred that these unavoidable impurities are adjusted as follows.

[S: 0.030% or less]

The S-based unavoidable impurities combine with Mn to deteriorate the ductility of the steel sheet. Therefore, the smaller the better, from this viewpoint, it is preferably set to 0.030% or less. More preferably, it is 0.025% or less, and particularly preferably 0.020% or less. Further, as long as it is within this range, it does not affect the thermal conductivity of the base steel sheet.

[P: 0.20% or less]

P is an unavoidable impurity, and since the grain boundary segregation contributes to the grain boundary destruction, the content thereof is preferably as small as possible. From this viewpoint, the P content is preferably set to 0.20% or less. More preferably, it is 0.15% or less, and particularly preferably 0.10% or less.

[N: 0.020% or less]

N series unavoidable impurities. N is an element which forms coarse inclusions (TiN or the like) and deteriorates the toughness of the base steel sheet. Therefore, it is desirable to reduce the content as much as possible. From this viewpoint, the N content is preferably set to 0.020% or less. More preferably, it is 0.015% or less, and particularly preferably 0.010% or less. In addition, as long as it is within this range, it does not affect the thermal conductivity.

Examples of unavoidable impurities other than the above include Cr, Ni, Mo, Cu, and the like. When the content of each of these elements is 0.1% or less, impurities are contained in the usual production steps, and if it is within this range, the thermal conductivity is not affected. However, all of the elements which improve the hardenability are in the range which does not affect the thermal conductivity, and it is good if the content is in the range of 1.0% or less.

In the base steel sheet used in the present invention, in addition to the above-described basic elements, it is also useful as a further element, if necessary, Ti: 0.001 to 0.20%, whereby the properties of the base steel sheet of the present invention can be further improved. The preferred range when Ti is contained and the reason for the limitation are as follows.

[Ti: 0.001 to 0.20%]

In order to exhibit such an effect, the Ti-based system forms a carbide with C and forms a carbide to lower the solid solution C, and preferably contains 0.001% or more. More preferably, it is 0.002% or more, and particularly preferably 0.003% or more. However, when the Ti content is excessive, the strength of the base steel sheet is deteriorated. Therefore, the upper limit is made 0.20%. The upper limit of the Ti content is preferably 0.15%, and the upper limit is more preferably 0.10%. Further, as long as it is within this range, it does not affect the thermal conductivity of the base steel sheet.

(galvanized)

The surface-treated steel sheet of the present invention is galvanized on both surfaces of the base steel sheet, and the amount of the galvanized coating needs to be as large as possible from the viewpoint of improving the thermal conductivity and exhibiting heat dissipation properties satisfactorily. From this point of view, it is necessary to set the adhesion amount of galvanizing to 70 g/m ² or more on each side. It is preferably 80 g/m ² or more, more preferably 90 g/m ² or more. However, when the amount of adhesion of galvanizing is excessive, the surface appearance is extremely poor, so the upper limit of the amount of galvanizing adhesion is preferably set to 150 g/m ² . It is more preferably set to 140 g/m ² or less, and particularly preferably set to 130 g/m ² or less. Further, the composition of the galvanizing is preferably pure Zn or a trace amount of Al (0.08 to 0.30%) in Zn. In the galvanized layer, the lower the impurity, the higher the thermal conductivity. Therefore, in order to improve the heat dissipation performance, it is preferable that the impurities are extremely small. Further, the composition of the galvanizing may be an auxiliary component containing Si, Pb, Fe, Ti, Cr, Ni, or a rare earth element.

(resin film)

A resin film is coated on at least one surface of the galvanized steel sheet (that is, "the surface corresponding to the side opposite to the heat source"). The integral emissivity (hereinafter referred to as "infrared integral emissivity") of infrared rays (wavelength: 4.5 to 15‧4 μm) when the surface of the resin film is heated to 100 ° C is required to be set to 0.60 or more. The infrared integrated emissivity indicates a higher value, and the heat dissipation performance of the surface-treated steel sheet is higher. Therefore, the infrared integrated emissivity is required to be set to 0.60 or more. It is preferably 0.65, more preferably 0.70. The resin film can function as the surface-treated steel sheet of the present invention as long as it is coated on at least one surface, and the resin film may be coated on both surfaces of the galvanized steel from the viewpoint of corrosion resistance. The thickness of the resin film may be any thickness that satisfies the above-described conditions of the infrared integral emissivity. However, in the general resin film, since the thermal conductivity is lower than that of the base steel sheet, the thermal conductivity is lowered when the film is too thick. Therefore, the thickness of the resin film is preferably set to 50 μm or less, more preferably 45 μm or less, and particularly preferably 40 μm or less.

Here, the above-mentioned "infrared integral emissivity", in other words, the ease of release of infrared rays (thermal energy) (difficulty of absorption). Therefore, the higher the infrared ray emissivity is, the larger the thermal energy released (absorbed) becomes. For example, when 100% of the heat is applied to the object (the resin film in the present invention), the infrared integrated emissivity is 1.

In the present invention, the infrared ray emissivity at the time of heating to 100 ° C is set, and it is considered that the surface-treated steel sheet of the present invention is suitable for use in electronic equipment parts (which varies depending on parts, etc., but the usual ambient temperature is about 50 to 70). °C, up to about 100 ° C), in order to match the practical temperature, the heating temperature is set to 100 ° C.

The method for measuring the infrared integrated emissivity in the present invention is as follows.

Device: JIR-5500 Fourier Transform Infrared Spectrophotometer and Radiation Measurement Unit "IRR-200" manufactured by JEOL Ltd.

Measuring wavelength range: 4.5 to 15.4 μm

Measuring temperature: set the heating temperature of the sample to 100 ° C

The total number of calculations: 200 times

Decomposition energy: 16cm ^-1

The spectroscopic radiation intensity (measured value) of the sample in the infrared wavelength region (4.5 to 15.4 μm) was measured using the above apparatus. In addition, the measured value of the sample, the radiation intensity of the background, and the device function are measured as the added/added values. In order to correct the values, the emissivity measurement program [Emission Rate Measurement Program by JEOL Ltd.] is used to calculate the value. Integrated emissivity. The calculation method is as follows.

The symbols in the formula mean the following:

ε(λ): Spectral emissivity (%) of the sample of wavelength λ

E(T): integral emissivity (%) of sample at temperature T (°C)

M(λ, T): Spectral radiation intensity (measured value) of sample with wavelength λ and temperature T (°C)

A(λ): device function

K _FB (λ): Spectral radiation intensity of a fixed background of wavelength λ (background that does not vary with the sample)

K _TB (λ, T _TB ): the spectral intensity of the well black body with wavelength λ and temperature T _TB (°C)

K _B (λ, T): the spectral emission intensity of the black body of the wavelength λ and the temperature T (°C) (calculated from the theoretical formula of the blank)

λ ₁ , λ ₂ : the wavelength range of the integration.

Here, the above A (λ: device function) and the above K _FB (λ: spectroscopic radiation intensity of a fixed background) are measured values of spectroscopic radiation intensity of two black body furnaces (80 ° C, 160 ° C), and the temperature region The spectral intensity of the black body (calculated from the theoretical formula of the blank) is calculated by the following formula.

The symbols in the formula mean the following:

M _{160 ° C} (λ, 160 ° C): Spectral radiation intensity (measured value) of a black body furnace at a wavelength of λ of 160 ° C

M _{80 ° C} (λ, 80 ° C): Spectral radiation intensity (measured value) of a black body furnace at a wavelength of λ of 80 ° C

K _{160 ° C} (λ, 160 ° C): Spectral radiation intensity of a black body furnace at a wavelength of λ of 160 ° C (calculated from the theoretical formula of the blank)

K _{80 ° C} (λ, 80 ° C): Spectral radiation intensity of a black body furnace at a wavelength of λ of 80 ° C (calculated from the theoretical formula of the blank).

The reason why K _TB (λ, T _TB ) is considered in the calculation of the infrared integrated emissivity E (T = 100 ° C) is because a water-cooled trap black body is disposed around the sample during the measurement. By providing the above-described trap black body, it is possible to change the background radiation (meaning the background radiation which varies depending on the sample. The radiation from the sample is reflected by the surface of the sample, and therefore, the measured value of the spectroscopic radiation intensity of the sample is added to the background emission. The numerical value of the spectroscopic radiation intensity is controlled to be low. The well black body described above used a suspected black body having an emissivity of 0.96, and the spectral radiance of the well black body of the above K _TB [(λ, T _TB ): wavelength λ, temperature T _TB (°C) was calculated as follows.

K _TB (λ, T _TB ) = 0.96 × K _B (λ, T _TB )

In the formula, K _TB (λ, T _TB ) means the spectral emission intensity of the black body of the wavelength λ and the temperature T _TB (° C.).

In the surface-treated steel sheet of the present invention, the type of the coating resin film on the galvanized surface is not particularly limited, and the propylene resin, the urethane resin, and the polyolefin resin can be suitably used. A polyester resin, a fluorine resin, an anthrone resin, or a mixed or modified resin thereof. Further, a crosslinking agent may be added to the resin film. Examples of such a crosslinking agent include a melamine-based compound and an isocyanate-based compound, and these may be added in an amount of 0.5 to 20% by weight in one or two or more kinds.

In the resin film, the infrared ray emissivity may be set to 0.60 or more, and the resin film may contain a carbon-based high emissivity material such as carbon black or acetylene black, if necessary, and / or a powder of a high emissivity material such as cordierite, spodumene, tantalum nitride, tantalum carbide, aluminum oxide or cerium oxide. By including these, the above-described integral emissivity of the surface of the resin film can be further improved, which is preferable.

According to the surface-treated steel sheet of the present invention, high thermal conductivity and heat dissipation can be exhibited by using the above-described configuration, and in particular, in an electronic device component such as a back casing of a PDP-TV, the heat dissipating surface has a large area, and therefore, In the surface-treated steel sheet of the invention, the heat dissipation performance when applied to such applications can be sufficiently exhibited.

[Examples]

In the following, the present invention will be specifically described by way of examples. However, the present invention is not limited by the following examples, and may be appropriately modified and implemented within the scope of the above-described embodiments, which are included in the present invention. Within the technical scope.

[Example 1]

The slabs having the chemical composition (steel type A to I) shown in the following Table 1 were hot rolled at 1200 ° C, and subjected to finish rolling at 900 ° C, and coiled at 500 to 700 ° C, and then the obtained hot rolled steel sheets were subjected to acid removal. The washing was carried out by cold rolling at a reduction ratio of 30 to 60% to obtain a steel sheet having a thickness of 0.8 mm. Further, for the analysis of each component, a combustion-infrared absorption method was employed for C, an inert gas fusion-thermal conductivity method for N, and a luminescence spectroscopic analysis method for other components.

The thermal conductivity of each of the obtained steel sheets was measured by a laser flash method. The method is summarized as follows. Further, in the above Table 1, the measurement results of the thermal conductivity were simultaneously recorded.

[Laser flash method]

Measuring device: Laser flashing thermal constant measuring device "TC-7000 ARUPACK Technology Co., Ltd."

First, the thermal diffusivity of each steel sheet was measured by the following method.

(Measurement of thermal diffusivity)

(1) Diameter: The surface of the sample (steel plate) cut into 10 mmφ was blackened by carbon coating.

(2) The laser beam is irradiated to the blackened surface of the sample instantaneously, and the temperature change on the back surface is measured by a thermocouple or an infrared detector.

(3) The thermal diffusivity is obtained from the obtained time-temperature rise curve.

(4) The distance between the laser irradiation point and the temperature detection point (that is, the thickness of each steel plate) is set to L (mm), and the time at which the back surface of the sample reaches a temperature of 1/2 of the highest reaching temperature is set to t _{1 . In the case of /2} (sec), the thermal diffusivity α (m ² /sec) is represented by the following formula (this measurement method is referred to as a half-life method).

Thermal diffusivity α = 1.37 (L / π) ² ‧ 1 / t _1/2 (m ² / sec) Next, the specific heat of each steel sheet was measured by the following method.

(measurement of specific heat)

(1) When the sample is irradiated with laser light instantaneously, the heat absorbed by the sample is set to Q (J/cm ² ), the mass of the sample is set to M (g), and the temperature rise amount is set to ΔT (K). The specific heat Cp (J/(g‧K)) is represented by the following formula.

Specific heat Cp=Q/(M‧ΔT)(J/(g‧K))

Based on the thermal diffusivity α (m ² /sec) and the specific heat Cp (J/(g‧K)) calculated as described above, the thermal conductivity of each steel sheet was measured according to the following method.

(Measurement of thermal conductivity)

(1) When the thermal conductivity is set to α (m ² /sec), the specific heat is set to Cp (J/(g‧K)), and the density is set to ρ (g/cm ³ ), the thermal conductivity η (W/ (m‧K)) is expressed by the following formula. The density ρ is a value measured by the Archimedes method.

Thermal conductivity η=Cp‧α‧ρ[W/(m‧K)]

According to the results of the above Table 1, it was found that the thermal conductivity changes depending on the components such as C, Mn, and Al, and the above-described appropriate range can be set as a result of further investigation of each element.

[Embodiment 2]

Using the steel grades C, D, and G shown in the above Table 1 as a base steel sheet, a galvanized steel sheet which was subjected to galvanization (electrogalvanization or hot-dip galvanizing) on both surfaces of each steel sheet was produced by the following method. The produced galvanized steel sheet was cut by a cutter. At this time, the size of each steel plate was 150 mm × 250 mm (thickness: 0.8 mm).

[Production of electrogalvanized steel sheet]

(1) Alkaline solution immersion degreasing: 3 wt% aqueous caustic soda, 60 ° C, 2 sec

(2) Alkaline solution immersion degreasing: 3 wt% aqueous caustic soda, 60 ° C, 2 sec, 10 -30 A/dm ²

(3) Washing

(4) Pickling: 3 to 7 wt% aqueous sulfuric acid solution, 40 ° C, 2 seconds

(5) Washing

(6) Electroplated zinc (such as the following conditions)

(7) Washing

(8) Drying

(conditions for electroplating)

Plating bath: horizontal plating bath

Composition of electroplating solution: ZnSO ₄ ‧7H ₂ O 300～400g/L

Na ₂ SO ₄ 50～100g/L

H ₂ SO ₄ 25～35g/L

Current density: 50 ~ 200A / dm ²

Electroplating bath temperature: 60 ° C

Electroplating bath flow rate: 1 ~ 2m / sec

Electrode (anode): IrO ₂ alloy electrode

Plating adhesion: 20g/m ² (each side)

[Production of hot-dip galvanized steel sheet]

The cold-rolled steel sheet was subjected to hot-dip galvanizing without undergoing an acid washing step. The hot-dip galvanizing is reduced by heating in a reducing gas atmosphere, immersed in a galvanizing bath, and hot-dip galvanizing is performed using a gas broom. The composition of the plating bath was set to Zn-0.2% Al.

The reduction temperature is set to 560 to 900 ° C (preferably 650 to 800 ° C), and the heating and reduction of the scale layer of the hot-rolled steel sheet can be performed by the pickling step in the continuous molten electroplating line without the pickling step. In the reducing gas environment, the plate is continuously passed. There is no particular limitation on the reduction time, but the time which can be achieved by using a usual continuous melt-plating line is about 10 to 80 seconds. After the reduction, hot-dip galvanizing was carried out, but the steel sheet was previously lowered to the vicinity of the plating bath temperature.

(melt plating conditions)

Reduction temperature: 780 ° C ~ 860 ° C

Plating composition: Zn-0.2% Al

Electroplating bath temperature: 455 ~ 465 ° C

Zinc adhesion: 80 ~ 133g / m ²

Using each of the galvanized steel sheets obtained by the above method, the resin film was coated in accordance with the following method. Further, the resin film is coated on a surface corresponding to the heat source (referred to as "back surface").

[Cladding of resin film]

(substrate treatment)

First, a non-chromate film ("CTE-203" manufactured by Japan PARKERIZING Co., Ltd.) was used as a base treatment for each galvanized steel sheet, and the amount of adhesion was 100 mg/m ² . Further, since the film is a film of the polar book, the influence on the heat dissipation property of the resin-coated steel sheet is negligible.

(resin film)

The resin is an organic solvent-soluble polyester resin ("BYRON (registered trademark) 650" manufactured by Toyobo Co., Ltd.). The directory value had a Tg (glass transition temperature) of 10 ° C and a number average molecular weight of 23 × 10 ⁴ .

(crosslinking agent)

A melamine resin ("SUMI MARLE (registered trademark) M-40ST": manufactured by Sumitomo Chemical Co., Ltd.: solid content 80%) was used.

(carbon black)

"Mitsubishi carbon black (average particle diameter: 25 nm)" (manufactured by Mitsubishi Chemical Corporation) was used as carbon black.

The above polyester resin and the above-mentioned crosslinking agent (solid content: 80%) were mixed in a mass ratio (dry) of 100:20 to prepare a matrix resin, and the above carbon black was added so as to have a content of 10%. Dilute with a xylene/cyclohexanone mixed solvent (xylene/cyclohexanone = 1:1) in such a manner that the viscosity of the raw material composition is about 30 to 100 seconds (Ford Cup N0.4), and manually stir. The mixture was stirred at a number of revolutions of 10,000 rpm for 10 minutes to prepare a raw material composition (a raw material composition for a resin film).

The raw material composition for the resin film was applied to the back side of each galvanized steel sheet by a coater so as to have a film thickness of 10 μm, and was sintered in a hot air drying furnace at a plate temperature of 230 ° C for about 60 seconds. The resin is coated with a galvanized steel sheet. The film thickness at this time is a value obtained by measuring the mass of the film and converting it by specific gravity. The sample was prepared by sintering and drying. With respect to each of the samples, the emissivity of the surface of the resin film was measured according to the above method, and the heat dissipation property of the surface-treated steel sheet was evaluated according to the following method.

[Method for evaluating heat dissipation of steel sheet]

The size of the sample plate (surface treated steel sheet) used at this time was 150 mm × 250 mm, and the size of the heater was 56 mm × 96 mm.

As shown in Fig. 1, [Fig. 1 (a) is a plan view, Fig. 1 (b) is a front view, Fig. 1 (c) is a cross-sectional view of Fig. 1 (b) AA, and the sample plate 1 is fixed to the ground in a vertical direction. The heater 2 is fixed to the center of the back surface of the sample plate 1, and is covered by the heat insulating material 3. Further, the thermocouple 4 was placed on the back surface of the sample plate (on the right side of Fig. 1). The maximum temperature was evaluated using a thermocouple placed in the sample center.

A plurality of (eight in FIG. 2) members 5 (components) shown in FIG. 1 were stacked, and the experimental apparatus shown in FIG. 2 was constructed, and the heat dissipation property of each sample was evaluated. The heat source is set to an electric heater, and the voltage from the power source (indicated by "100V power supply" in Fig. 2) is adjusted by the power supply stabilizing device and the output adjusting device to adjust the heat output of the heater.

With such an experimental apparatus, after about 5 hours from the start of heating until the measurement value of the thermocouple is stabilized, the temperature measurement data is acquired by the temperature measurement data recorder to be displayed by the display device 6. The experimental conditions at this time were room temperature, and the heater output was 20 W.

The results of the temperature measured by the above experiment (hereinafter referred to as "the highest temperature") are shown together with the sample (galvanizing method, galvanized adhesion amount on each surface, thermal conductivity of the base steel sheet, and emissivity on the back surface). Table 2. Further, in Experimental Nos. 1 to 3, no resin film was formed.

From this result, we can refine the following. First, in the experiment No. 1, the chemical composition of the base steel sheet was outside the range specified by the present invention, and the adhesion amount of the galvanization was also small, and the high conductivity of the base steel sheet could not be achieved. Further, since the emissivity of the back surface (uncoated resin film) is lowered, the maximum temperature is increased, and the heat dissipation property of the steel sheet is not good.

In Experiment Nos. 2 and 3, the chemical composition of the base steel sheet is the steel specified in the present invention, and the thermal conductivity of the base steel sheet can be increased, and the adhesion amount of the galvanized steel can be increased. In this case, although the maximum temperature is lowered by the high heat conduction of the base steel sheet, the emissivity of the back surface (uncovered resin film) is lowered, and therefore the maximum temperature is still high.

In the experiment No. 4, the back surface of the base steel sheet of Experiment No. 1 was covered with a resin film having an emissivity of 0.81. The maximum temperature is lowered due to the coating effect of the resin film having a high emissivity. However, the high thermal conductivity of the steel sheet cannot be said to be completely achievable.

In Experimental Nos. 5 and 6, steel sheets coated with a resin film having an emissivity of 0.81 and 0.82 on the steel sheets of Experiment Nos. 2 and 3 were used. Since the base steel sheet has higher heat conductivity than the experimental No. 4, the maximum temperature is lowered, and it is understood that the heat dissipation property can be exhibited.

Comparison of Test Nos. 7 to 11 and Test Nos. 12 to 16 revealed the influence of the back emissivity on the maximum temperature in various conditions.

1. . . Sample board

2. . . Heater

3. . . Insulation materials

4. . . Thermocouple

5. . . member

6. . . Display device

1 is a view for explaining constituent elements of an experimental apparatus for evaluating heat dissipation;

Fig. 2 is a schematic explanatory view showing the configuration of an experimental apparatus for evaluating heat dissipation.

Claims (3)

A galvanized steel sheet coated with a resin, which is used as a raw material of an electronic device component in which a heat source is partially connected to the steel sheet, and is characterized in that the base steel sheet contains C: 0.0010 to 0.040% by mass%, and Si: 0.2% or less. Mn: 0.1 to 0.80% and Al: 0.01 to 0.1%, the balance being iron and unavoidable impurities, and galvanization of 90 g/m ² or more per surface is applied to both surfaces of the base steel sheet, and heated to 100 A resin film having an integrated emissivity of 0.60 or more of infrared rays having a wavelength of 4.5 to 15.4 μm at a temperature of ° C is coated on at least one side of the galvanized. The resin-coated galvanized steel sheet according to the first aspect of the invention, wherein the base steel sheet further contains Ti: 0.001 to 0.20% by mass%. A resin-coated galvanized steel sheet according to the first aspect of the invention, wherein the resin film has a thickness of 50 μm or less.