JP2011007469A - Near infrared ray heating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a means for heating a metal plate-like object with near infrared rays while suppressing reduction in absorption rate even when the output ratio is reduced as the whole near infrared ray heating device.SOLUTION: A near infrared lamp to be lighted is selected according to heating temperature, and the selected near infrared lamp is lighted by the output ratio not less than 40% according to the heating temperature. For selecting the near infrared lamps to be lighted, a distance in the plate-width direction between the near infrared lamps to be lighted should not exceed 50 mm.

Description

  The present invention relates to a method for heating near infrared rays of a metal plate such as a steel plate, and more particularly to an efficient lighting method for a near infrared lamp used for heating.

In recent years, a surface-treated steel sheet in which the surface of a hot-dip plated steel sheet is directly coated with a polyolefin resin, a polyurethane resin, or the like has been used as a steel sheet used for a housing of home appliances.
In this surface-treated steel sheet, after applying the resin, it is necessary to perform a baking process at a temperature of 100 ° C. or higher in order to cure the resin.

  One means for performing such heating is heating by near infrared rays as disclosed in Patent Documents 1 and 2. This near-infrared heating uses a heat source having a wavelength of 0.72 to 2.0 μm, and is easy to control the output, and is known as a heating method that has better thermal energy permeability than mid-infrared rays and far-infrared rays. It has been.

  In near-infrared heating, a rod-like or spherical one is used as a near-infrared lamp serving as a heater. Therefore, when the heated object needs to heat a large area such as a steel plate, it is necessary to arrange a large number of lamps. is there. An example of such a steel sheet heating apparatus is shown in FIG.

  As shown in FIG. 1, a near-infrared lamp 2 that serves as a heater is disposed through a quartz glass 3 between the steel plate 1 to be heated. The entrance side and the exit side of the near-infrared lamp 2 are surrounded by a reflecting plate 4 in a tunnel shape, and the side portion of the quartz glass 3 is also surrounded by the reflecting plate 4 to prevent heat dissipation.

The near-infrared lamps 2 are arranged in the width direction of the steel plate 1, for example, about several tens to 100 at intervals of about 15 to 25 mm, and further arranged in a plurality of rows in the running direction of the steel plate. FIG. 1 shows an example in which the near infrared lamps 2 are arranged in two rows.
The near-infrared lamp 2 has a length in the direction parallel to the sheet passing direction of the steel plate 1 of about 250 mm, for example, and has an output of about 3 to 5 kW per lamp.

  When heating, the steel plate 1 is moved at an appropriate speed, and when passing under the lit near-infrared lamp 2, the steel plate 1 is heated by radiant heat transfer. Near-infrared lamps turn on and heat all lamps that cover the entire width of the steel sheet with uniform output. When the conditions of the steel plate thickness and the sheet passing speed change, the output of the near-infrared lamp is adjusted according to the heating temperature so that the temperature after heating becomes constant. At that time, when the output of the near-infrared lamp is lowered, there are the following problems.

FIG. 5 shows a galvanized steel sheet in which all the near infrared lamps of the near infrared heating apparatus shown in FIG. 1 are uniformly lit and the outputs of all the near infrared lamps are continuously changed to 10 to 100%. The relationship between the absorptance with respect to the lamp output ratio and the temperature of the near-infrared lamp when the lamp is heated is shown.
The absorption rate represents the ratio of the amount of heat received by the steel plate to the power input to the lamp. The input power is obtained by measuring the voltage and current of electricity supplied to the lamp, and the amount of heat received by the steel plate. Is obtained by multiplying the steel plate temperature difference before and after heating by the treatment amount and specific heat.

As shown in FIG. 5, the output ratio of the lamp decreases and the temperature of the near infrared lamp is 3000.
When it falls below K, the absorption rate decreases rapidly.

The reason why the absorption rate decreases in this way is considered as follows.
In general, the wavelength distribution of the radiant energy emitted by the near-infrared lamp depends on the temperature of the near-infrared lamp as shown in FIG. 2, and the higher the lamp temperature, the higher the proportion of energy with shorter wavelengths.

Further, according to the inventor's investigation, the relationship between the wavelength of the radiant energy and the absorptance in the hot dip plated steel sheet is, for example, as shown in FIGS. The shorter the wavelength, the more efficiently the steel sheet can be heated.
In the example of the Sn—Zn hot-dip steel sheet shown in FIG. 3, the shorter the wavelength of the radiation energy, the higher the absorptance of the steel sheet. In the example of the Zn hot-dip steel sheet shown in FIG. In this case as well, the shorter the wavelength, the higher the absorptance.

  From this, it is considered that when the output ratio of the near-infrared lamp decreases, the lamp temperature decreases, the ratio of radiation energy having a long wavelength increases, and as a result, the absorption rate of the steel sheet decreases.

JP 2007-275828 A JP 2006-500747 A

  Accordingly, an object of the present invention is to provide means for heating so that the decrease in the absorption rate is small even when the output ratio of the entire near-infrared heating apparatus is decreased.

When reducing the output ratio of the near-infrared heating device as a whole, the present inventor does not decrease the output ratio of all the near-infrared lamps in the same way, but makes the temperature of the near-infrared lamp as high as possible. By switching the lighting pattern, the above problem was solved by keeping the absorption rate (= heating efficiency) of the steel sheet at a high level.
The gist of the present invention is as follows.

(1) In a near-infrared heating method for heating a plate-like object to be heated that is disposed facing a plurality of near-infrared lamps,
A near-infrared heating method, wherein a near-infrared lamp to be lit is selected according to a heating temperature, and the selected near-infrared lamp is lit at an output ratio of 40% or more according to the heating temperature.
(2) The near-infrared heating method according to (1), wherein the near-infrared lamp to be lit is selected so that the interval in the plate width direction of the near-infrared lamp to be lit does not exceed 50 mm.
(3) The near-infrared heating method according to (1) or (2), wherein the plate-shaped object to be heated is a surface-treated steel sheet in which the surface of a hot-dip plated steel sheet is directly coated with a polyolefin resin or a polyurethane resin.

  Even when reducing the output ratio of the near infrared heating device as a whole, means for heating the near infrared lamp to turn on so that the amount of decrease in the output ratio of each near infrared lamp is reduced, and to reduce the decrease in heating efficiency. Can be provided.

It is a figure which shows roughly the structure of a near-infrared heating apparatus. It is a figure which shows the relationship between the wavelength of the light to irradiate, and radiation energy. It is a figure which shows the relationship between the wavelength of the light irradiated to the to-be-heated material in a Sn-Zn hot dip plated steel plate, and an absorptance. It is a figure which shows the relationship similar to FIG. 3 in a Zn hot-dip plated steel plate. It is a figure which shows an example of the relationship between the absorption factor with respect to a lamp output ratio, and the temperature of a lamp | ramp when the lighting pattern of a near-infrared lamp is changed by this invention. It is a figure which shows the relationship between the absorption factor with respect to a lamp output ratio, and the temperature of a lamp | ramp in the lighting pattern of the conventional near-infrared lamp.

  In order to increase the absorptance, the present inventor needs to heat at a short wavelength, and the higher the lamp temperature, the greater the proportion of radiation energy with a short wavelength, and thus a large heat output is required. Even in the case of non-heating, the means for lighting the near-infrared lamp with as high an output as possible was studied.

  As a result, in the heating apparatus having a plurality of near-infrared lamps as shown in FIG. 1, instead of lighting all the near-infrared lamps, the number of lamps to be lit may be increased or decreased according to the required heat output. At that time, it was conceived that instead of simply increasing or decreasing the number of lamps, it is necessary to light up the output of the near infrared lamp as high as possible.

Therefore, the following experiment was performed using the apparatus shown in FIG.
The number of lamps lit and the output ratio of the lit lamps were changed as shown in (a) to (d).
In (a), one-fourth of the lamps are turned on with an output of 40 to 100%.
In (b), one-half of the number of lamps are turned on with an output of 50 to 100%.
In (c), three-quarters of the lamps are turned on with an output of 67 to 100%.
In (d), all the lamps are turned on at an output of 75 to 100%.

FIG. 4 shows the relationship between the absorption rate with respect to the lamp output ratio and the temperature of the near-infrared lamp.
As shown in FIG. 4, in the region where the output ratio of all lamps is 50% or less, when the lamps are lit as shown in (a) and (b), compared to the case where the lamps are lit uniformly as in the conventional case. The decrease in the absorption rate is greatly reduced, and the lamps are selectively turned on, and the output ratio of each lamp is set to at least 40%, so that the absorption rate can be efficiently reduced. It was confirmed that the object to be heated could be heated.

  Therefore, the conditions for selecting a near-infrared lamp according to the heating temperature were examined.

  First, in order to obtain the arrangement of lighting lamps necessary for uniformly heating the plate-shaped object to be heated, the steel sheet as the object to be heated is heated little by little with the near-infrared lamps all turned on. The temperature distribution of the steel sheet was measured while turning off the light.

When every other lamp was extinguished, there was no temperature difference between the lighting part of the lamp and the steel sheet located in the extinguishing part. Next, when the light was turned on every third line (two-thirds turned off), the temperature of the steel sheet located in the turned-off portion was low.
The above experiment was performed for the case where the lamps were arranged at an interval of 15 to 25 mm. All of the results were the same, and the interval between the lamps to be turned on did not exceed the interval of two lamps (30 to 50 mm). In addition, it has been found that it is possible to heat uniformly by alternately arranging the lighting lamp and the extinguishing lamp.

  Based on the above examination results, how to determine the number and distribution of the lighting lamps and the output of the lighting lamps with respect to the target heating temperature will be described.

First, the number of lamps to be used and the output of the lighting lamp are determined in advance as follows with respect to the output ratio of the entire near infrared heating device.
(A) When the output ratio of the entire heating device is 0% or more and less than 25%, a quarter number of lamps are turned on as shown in FIG. 4 (a), and each lamp is set to 40 to 100%. Lights at output.
(B) Similarly, when 25% or more and less than 50%, a half number of lamps are turned on as shown in FIG. 4B, and individual lamps are turned on with an output of 50 to 100%.
(C) Similarly, in the case of 50% or more and less than 75%, three-quarters of the lamps are turned on as shown in FIG. 4C, and individual lamps are turned on with an output of 67 to 100%.
(D) Similarly, in the case of 75% or more, all the lamps are turned on at an output of 75 to 100%.
And steel plate temperature is measured with the thermometer installed in the exit of the near-infrared heating apparatus, and the output ratio of the near-infrared lamp which lights up so that it may become target heating temperature is adjusted by feedback control.

As described above, the near infrared heating method of the present invention cures the coated resin by heating it at a temperature around 100 ° C. in the production of a surface-treated steel sheet in which the surface of a hot-dip steel sheet is directly coated with a polyolefin resin or a polyurethane resin. It is particularly suitable for performing a baking treatment, and can be efficiently heated at a low cost.
Hereinafter, the polyolefin resin or polyurethane resin used in that case will be described.

  The polyolefin resin and the polyurethane resin may contain a crosslinking agent for forming a coating, a rust preventive agent for obtaining a corrosion resistance effect, and a lubricant for imparting lubricity during processing. In addition to conductive fillers for improving weldability, coloring pigments for improving design properties, anti-settling agents, leveling agents, thickeners for adjusting viscosity, and the like may be added.

  Examples of the crosslinking agent include amino resins, polyisocyanate compounds and blocks thereof, epoxy compounds, carbodiimide compounds, silane compounds, crosslinkable zirconium compounds, titanium compounds, and the like.

  As said amino resin, generally well-known amino resins, such as methylated melamine resin, butylated melamine resin, imino group type melamine resin, benzoguanamine resin, glycoluril resin, urea resin, can be used. These resins include those commercially available, for example, “CymelTM” and “My Coat” manufactured by Mitsui Cytec (both are registered trademarks of Mitsui Cytech), “BeccaminTM” manufactured by Dainippon Ink and Chemicals, Inc. , “Super Becamine ™” (both are registered trademarks of Dainippon Ink & Chemicals, Inc.) and the like can be used. A plurality of types of amino resins may be mixed and used. Among these, in particular, when hexamethoxymethylated melamine is used, the balance between the corrosion resistance and the adhesion is good and more preferable.

  Examples of the polyisocyanate compound include hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, and tolylene diisocyanate. The blocked product is a blocked product of the polyisocyanate compound.

  Examples of the epoxy compound include adipic acid diglycidyl ester, phthalic acid diglycidyl ester, terephthalic acid diglycidyl ester, sorbitan polyglycidyl ether, pentaerythritol polyglycidyl ether, glycerin polyglycidyl ether, trimethylpropane polyglycidyl ether, neopentyl. Glycol polyglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol glycol diglycidyl ether, polypropylene glycol glycol diglycidyl ether, 2,2-bis- (4′-glycidyloxyphenyl) propane, tris (2 , 3-epoxypropyl) isocyanurate, bisphenol A diglycidyl ether, hydrogenated It can be exemplified bisphenol A diglycidyl ether and the like.

  As the carbodiimide compound, for example, an isocyanate-terminated polycarbodiimide is synthesized by a condensation reaction involving decarbonization of a diisocyanate compound such as an aromatic diisocyanate, an aliphatic diisocyanate, and an alicyclic diisocyanate, and then further reacted with an isocyanate group. Examples thereof include compounds to which a hydrophilic segment having a functional group is added.

  Examples of the silane compound include vinyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ- Examples thereof include isocyanate propyl triethoxysilane and γ-ureidopropyltriethoxysilane.

The crosslinkable zirconium compound is not particularly limited as long as it is a zirconium-containing compound having a plurality of functional groups capable of reacting with a carboxyl group or a hydroxyl group, but is preferably a compound that is soluble in water or an organic solvent. More preferably, it is a zirconium compound. An example of such a compound is zirconyl ammonium carbonate.
Examples of the titanium compound include dipropoxy bis (triethanolaminato) titanium, dipropoxy bis (diethanolaminato) titanium, propoxy tris (diethanolaminato) titanium, dibutoxy bis (triethanolaminato) titanium, dibutoxy bis (diethanolaminato). Nato) titanium, dipropoxy bis (acetylacetonato) titanium, dibutoxy bis (acetylacetonato) titanium, dihydroxy bis (lactato) titanium monoammonium salt, dihydroxy bis (lactato) titanium diammonium salt, propanedioxytitanium bis (Ethyl acetoacetate), oxotitanium bis (monoammonium oxalate), isopropyltri (N-amidoethyl / aminoethyl) titanate, and the like.

  Examples of the rust inhibitor include silica particles, phosphoric acid compounds, niobium compounds, and zirconium compounds.

  By including the silica particles in the resin, the corrosion resistance can be further improved. Although it does not specifically limit as said silica particle, Since a membrane | film | coat is a thin film, it is preferable that they are silica fine particles, such as colloidal silica with a primary particle diameter of 5-50 nm, and fumed silica. Examples of commercially available products include Snowtex C, Snowtex O, Snowtex N, Snowtex S, Snowtex UP, Snowtex PS-M, Snowtex PS-L, Snowtex 20, Snowtex 30, Snowtex 40. (All manufactured by Nissan Chemical Industries, Ltd.), Adelite AT-20N, Adelite AT-20A, Adelite AT-20Q (all manufactured by Asahi Denka Kogyo), Aerosil 2 0 0 (Nippon Aerosil), and the like.

  Examples of the phosphoric acid compound include phosphoric acids such as orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, triphosphoric acid, and tetraphosphoric acid, and salts thereof, and aminotri (methylenephosphonic acid), 1-hydroxyethylidene-1, Examples thereof include phosphonic acids such as 1-diphosphonic acid, ethylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid) and salts thereof, and phytate.

Examples of the niobium compound include niobium oxide, niobic acid and salts thereof, fluoroniobate, and fluorooxoniobate.
Examples of the zirconium compound include zirconium oxide, hexafluorozirconic acid and salts thereof.

  Examples of the lubricant include polyolefin wax and derivatives thereof, and silicone and derivatives thereof.

  Examples of the polyolefin wax and derivatives thereof include hydrocarbon waxes such as paraffin, microcrystalline, and polyethylene, and derivatives thereof. Examples of the derivative include carboxylated polyolefin and chlorinated polyolefin. Examples of the leveling agent include hydrophilic solvents such as butyl cellosolve. As said thickener, polyacrylic acid etc. can be mentioned, for example.

  As described above, according to the present invention, even when the output ratio of the near-infrared heating apparatus as a whole is decreased, heating can be performed so that the decrease in heating efficiency is small. The feasibility and effect of the will be described.

  70 near-infrared lamps having a length in a direction parallel to the sheet passing direction of the steel plate of 250 mm and an output of about 1 to 5 kW are arranged at intervals of 20 mm in the width direction of the steel plate, and further the traveling direction of the steel plate The Sn—Zn hot-dip plated steel sheet was heated to 100 ° C. under various lighting conditions using a near-infrared heating apparatus similar to the apparatus shown in FIG.

Table 1 shows lighting conditions and absorption rates.
In the example of the invention, the output of each lighting lamp was set to 80%, the lighting lamp pattern was changed to three kinds, and the traveling speed of the steel sheet was adjusted to 100 ° C. In the comparative example, the outputs of all the lamps were uniformly changed in three stages and similarly heated to 100 ° C. (the output of each lamp and the output of the entire lamp are the same).

  According to the example of the present invention, the steel sheet could be heated with a higher absorption rate than the comparative example. In addition, even when the entire lamp was lit at a low output ratio, the invention example could be heated at the same absorption rate as in the case of the high output ratio.

1 Steel plate to be heated 2 Near-infrared lamp 3 Quartz glass 4 Reflector

Claims (3)

In a near-infrared heating method of heating a plate-like object to be heated that is disposed opposite to the lamp using a plurality of near-infrared lamps,
A near-infrared heating method, wherein a near-infrared lamp to be lit is selected according to a heating temperature, and the selected near-infrared lamp is lit at an output ratio of 40% or more according to the heating temperature.   The near-infrared heating method according to claim 1, wherein the near-infrared lamp to be lit is selected so that the interval in the plate width direction of the near-infrared lamp to be lit does not exceed 50 mm.   The near-infrared heating method according to claim 1 or 2, wherein the plate-like object to be heated is a surface-treated steel sheet in which the surface of the hot-dip plated steel sheet is directly coated with a polyolefin resin or a polyurethane resin.

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