JP3219927B2 - Heating control method for baking painted metal sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating control method for baking a coated metal sheet.

[0002]

2. Description of the Related Art Conventional heating methods for baking painted metal sheets include:
A hot air heating method of heating a metal plate from the outside has been widely used. On the other hand, since heating control is easy, an induction heating device is introduced for heating a magnetic body such as a steel plate, and a baking furnace for a coated metal plate is disclosed in JP-A-3-284372 and JP-A-3-28.
As disclosed in Japanese Patent No. 4374 and Japanese Patent Application Laid-Open No. 3-284375, as a method of baking a coated metal plate, temperature control suitable for the material and thickness of the metal plate to be baked and the paint is performed to reduce the baking speed. It has been adopted as a method for obtaining a coated metal plate having good surface performance in a short time in a short time.

However, in the heating of the induction heating apparatus, conventionally, only the heat quantity required for the base metal plate, the convective heat transfer and the radiant heat transfer by the equipment in the furnace are calculated, and the heat quantity required for the baking of the paint and the amount of the paint already applied have been calculated. The amount of heat required to raise the temperature of a given coating film was only considered in terms of fixed constants and actual corrections. As a result, the temperature of the holding plate and the temperature of the exit side of the furnace vary greatly due to the type of paint and the difference in the thickness of the coating film, and stable quality cannot be ensured for products with severe coating film performance. In addition, many actual painting tests have to be carried out in order to ascertain the operating conditions such as the type of new paints, which has necessitated extremely inefficient work.

[0004] Examples of an arithmetic expression used in conventional heating _{control, P = {(P S +} P E) × (w × 10 -3) × (v / 60) + P CON + P RAD} / η P: Electric power input to the induction heating device (kw) P _S : required heating amount of steel sheet per unit area (kwH / m
²⁾ P _E: necessary heating amount per unit area coating (kWh / m
² ) w: metal plate width (mm) v: passing speed (m / min) P _CON : heat input / output by convective heat transfer (kw) P _RAD : heat input / output by radiant heat transfer (kw) η: induction heating device efficiency

[0005]

Result of repeated intensive study INVENTION Problems to be Solved problems, necessary heating amount per unit area coating in the control calculation formula for P _E, the various constants obtained from the basic characteristics of the paint by quantifying the P _E,
The purpose is to suppress the variation of the holding plate temperature in the furnace and the plate temperature on the exit side of the furnace due to the type of paint and the difference in the thickness of the coating, etc., and to ensure stable quality even for products with severe coating performance. Accordingly, it is an object of the present invention to avoid many actual painting tests in order to ascertain operating conditions such as new paint types.

[0006]

In order to achieve the above object, in the present invention, the content of the required amount of heating of the coating film is defined as the sum of the following amounts of heat. Q ₁ : Heat required for raising the solid content per unit area of metal sheet of paint applied just before baking furnace Q ₂ : Heating of volatile content per unit area of metal sheet of paint applied just before baking furnace And the heat required for volatilization Q ₃ : The heat required to raise the temperature per unit area of the metal plate of the coating already applied before the coating equipment immediately before the baking furnace

That is, P _E = K (Q ₁ + Q ₂ + Q ₃ ). Specifically, Q ₁ = t ₁ ρ ₁ C ₁₁ (θ ₂ −θ ₁ ) Q ₂ = (t ₁ ρ ₁ / N ₁ ) (1-N ₁ ) × ｛C ₁₂ (θ _1b −θ ₁ ) + Q _1b ｝ × α ₁ Q ₃ = t ₂ ρ ₂ C ₂₁ (θ ₂ −θ ₁ )

The definitions of the numerical values are as follows. t ₁ : Dry film thickness of paint applied immediately before the baking furnace ρ ₁ : Dry film specific gravity of paint applied immediately before the baking furnace C ₁₁ : Dry film specific heat of paint applied immediately before the baking furnace θ ₁ : Inlet plate temperature in this region of the baking furnace θ ₂ : Outlet plate temperature in each region of the baking furnace N ₁ : Solid content ratio of paint applied immediately before the baking furnace C ₁₂ : Volatilization of paint applied immediately before the baking furnace Specific heat θ _1b : Volatile boiling point of paint painted just before baking furnace

Q _1b : latent heat of vaporization of volatiles of paint coated immediately before the baking furnace α ₁ : heat input load ratio of volatiles of paint coated immediately before the baking furnace in this region of the baking furnace t ₂ : baking furnace Dry coating thickness of paint already applied before the previous coating equipment ρ ₂ : Specific gravity of dry coating of paint already applied before the coating equipment immediately before the baking furnace C ₂₁ : Prior to the coating equipment immediately before the baking furnace in already dry coating specific heat above formula in the painting process of painting paint there is only one step may be omitted the section Q _3.

[0010]

FIG. 1 shows the state of baking of a coated steel sheet on a general coating film in a baking furnace. The control method of the present invention improves the accuracy of the outlet steel sheet temperature in each region. The change in the state during the baking process of the coating film will be described with reference to FIG. The paint on the steel plate which has been wet at the entrance of the heating furnace in FIG. 1 mainly has a solvent contained in the coating which volatilizes in the former stage of the heating furnace, and the coating film becomes solid or close to it. In a later stage of the heating furnace, the temperature rise causes a crosslinking reaction to proceed in the coating film resin, and a curing state that satisfies various properties as a coating film is obtained. Explanation of symbols in the figure θ ₁ : Steel sheet temperature at the entrance of the baking furnace θ ₂ : Steel sheet temperature at the exit of the previous stage of the baking furnace θ ₃ : Steel sheet temperature at the exit of the baking furnace

FIG. 2 shows an embodiment of a coated steel sheet manufacturing facility using the present invention. First coater: Undercoating is carried out with 1; first coat baking furnace: 2 undercoat is dried and baked; first coat bake-cooler: 3 to cool to room temperature. Further, the top coat is applied by the second coater: 4, the top coat is dried and baked in the second coat baking furnace: 5, and the second coat baking-cooling unit: 6 is cooled to room temperature. In addition, coil unwinding device, coil joining device, degreasing cleaning device, pretreatment device, etc. are arranged in the steel strip entrance direction in FIG. 2, and coil inspection equipment, coating surface A protective film sticking device, a coil winding device, and the like are arranged. (Neither is shown)

FIG. 3 shows a case where the top coat is baked in the second coat baking furnace 5 shown in FIG. 2 using the apparatus shown in FIG. 1 according to the arithmetic expression used in the conventional heating control. It is an example. The temperature of the steel plate at the outlet of the heating furnace is a measured value at the target temperature of 230 ° C., and an error of about 10 ° C. occurs at the maximum. The steel sheet temperature calculation timing indicates a timing at which a new heating condition is changed when the size, the conveying speed, and the like of the steel sheet are changed.

The system and operating conditions of the paint used in the examples are as follows: t ₁ : Dry coating thickness of paint (top coat) applied immediately before the baking furnace = 17 (μ) ρ ₁ : Painted immediately before the baking furnace Specific gravity of the dried coating of the paint (top coating) = 1.80 C ₁₁ : Specific heat of the dried coating of the coating (top coating) applied immediately before the baking furnace = 0.40 θ ₁ : Temperature of the entrance side of the former stage of the baking furnace = 20 (° C) θ ₂ : Outgoing sheet temperature in front of baking furnace = 150 (° C) θ ₃ : Outgoing sheet temperature in downstream of baking furnace = 230 (° C) N ₁ : Paint applied just before baking furnace (overcoat) Solid content ratio of paint) = 0.51 C ₁₂ : Volatile content of paint (top coat) applied just before baking furnace Specific heat = 0.42 θ _1b : Volatility of paint (top coat) applied just before baking furnace Boiling point = 130 (℃)

Q _1b : latent heat of vaporization of the volatile matter of the paint (top coat) applied immediately before the baking furnace = 46.0 (cal / g) α ₁ : paint applied just before the baking furnace in the preceding stage of the baking furnace ( top coating) of volatiles heat input load ratio = 0.9 alpha _2: heat input load of the volatile content of the paint painted with該焼with furnace just before the subsequent baking furnace (top coating) ratio = 0.1 t ₂ ： Dry film thickness of paint (undercoat) already applied before the coating equipment immediately before the baking furnace = 17 (μ) ρ ₂ : Paint already applied before the coating equipment immediately before the baking furnace (undercoat) Specific gravity of dried coating film of 1.80 C ₂₁ : Specific heat of dried coating film of paint (undercoat) already applied before the coating equipment immediately before the baking furnace = 0.41 w: Metal plate width = 600 to 1200 (mm) ) V: Passing speed = 30 to 70 (mpm)

FIG. 4 shows the second paint baking furnace of FIG. 2 using the apparatus of FIG. 1 according to the calculation conditions of claim 4 of the present invention.
This is an example when baking of the top coat is performed. The temperature of the steel plate at the outlet of the heating furnace is the actual value at the target temperature of 230 ° C, and converges to an error of about 2 ° C at the maximum, indicating that stable quality can be ensured even for products with severe coating film performance. I have. The steel sheet temperature calculation timing indicates a timing at which a new heating condition is changed when the size, the transport speed, or the like of the steel sheet is changed.

The coating system and working conditions used in the examples are as follows: t ₁ : Dry coating film thickness of paint (top coat) applied immediately before the baking furnace = 17 (μ) ρ ₁ : Painted immediately before the baking furnace Specific gravity of the dried coating of the paint (top coating) = 1.80 C ₁₁ : Specific heat of the dried coating of the coating (top coating) applied immediately before the baking furnace = 0.40 θ ₁ : Temperature of the entrance side of the former stage of the baking furnace = 20 (° C) θ ₂ : Outgoing sheet temperature in front of baking furnace = 150 (° C) θ ₃ : Outgoing sheet temperature in downstream of baking furnace = 230 (° C) N ₁ : Paint applied just before baking furnace (overcoating) solid content = 0.51 C ₁₂ of the paint): volatiles specific heat = 0.42 theta _1b paint painted with baking oven immediately before (top coating): volatile paint painted with baking oven immediately before (top coating) min boiling = 130 (℃) q _1b: volatiles latent heat of vaporization of the baking furnace just before painting paint (top coat) 46.0 (cal / g)

Α ₁ : Heat input load ratio of volatile matter of the paint (overcoat) applied immediately before the baking furnace before the baking furnace = 0.9 α ₂ : Painting immediately before the baking furnace after the baking furnace Heat input load ratio of volatiles of the applied paint (overcoat) = 0.1 t ₂ : Dry coating thickness of paint (undercoat) already applied before the coating equipment immediately before the baking furnace = 17 (μ) ρ ₂ : Specific gravity of the dried paint film of the paint (undercoat paint) already applied before the coating equipment immediately before the baking furnace = 1.80 C ₂₁ : Paint already applied before the paint equipment immediately before the baking furnace (undercoat paint) ) Specific heat of dried coating film = 0.41 w: metal plate width = 600-1200 (mm) v: threading speed = 30-70 (mpm)

[0018]

As described above, according to the present invention, an excellent effect can be obtained in which a variation in the temperature of the retaining plate and the temperature of the exit side plate in the coated metal sheet baking furnace can be suppressed and stable quality can be ensured. Things.

[Brief description of the drawings]

FIG. 1 is a diagram showing a general state of coating film baking in a baking furnace for coated steel sheets;

FIG. 2 is a diagram showing a coated steel sheet manufacturing facility using the present invention;

FIG. 3 is a diagram showing a relationship between a steel sheet temperature calculation timing and a steel sheet temperature at a heating furnace outlet performed under calculation conditions used conventionally,

FIG. 4 is a diagram showing the relationship between the timing of steel sheet temperature calculation performed under the calculation conditions according to the present invention and the steel sheet temperature at the heating furnace outlet.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 1st coating apparatus 1 '1st coating apparatus which has the same function as 1 2 1st coating baking furnace (high frequency induction heating furnace) 3 1st coating baking-cooling apparatus 4 2nd coating apparatus 4' 4 Similar functions as 4 5 Second coating baking furnace (high-frequency induction heating furnace) 6 Second coating baking-cooling device 7 Coated steel strip θ ₁ Temperature of steel sheet at entrance of baking furnace θ ₂ Temperature of steel sheet at exit of preceding baking furnace θ ₍₃₎ Steel plate temperature at the exit of the baking furnace

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B05D 1/00-7/26 B05C 9/14

Claims (5)

(57) [Claims] 1. A coating having one or more zones in a furnace.
In the heating furnace for metal sheet baking, when calculating the required heating amount independently for each of the regions, the required heating amount of the coating film is regarded as the required heating amount accompanying a change in the state of the coating film, and the coating is performed immediately before the baking furnace. Calculating the sum of one or more heats of a group consisting of the heat required for raising the temperature of the solids of the paint and the heat required for raising and volatilizing the volatiles of the paint. Heating control method. 2. The thickness of the dried coating film of the paint is t, the specific gravity of the dried coating film is ρ, the specific heat of the dried coating film is C ₁ , the temperature of the entrance side plate of the baking furnace in the region is θ ₁ , Is the outlet plate temperature of each area
₂ , the solid content ratio of the paint is N, and the specific heat of volatiles of the paint is C ₂ ,
Assuming that the boiling point of the volatile matter of the paint is θ _b , the latent heat of evaporation of the volatile matter of the paint is q _b , and the heat input load ratio of the volatile matter of the paint in the baking furnace is α, the solid content per metal plate unit area of the paint the heating heat Q ₁ required, volatiles heating and volatilization amount of heat Q ₂ required respective metal plate per unit area of the _{paint, Q 1 = tρC 1 (θ} 2 -θ 1) Q 2 = ( tp / N) (1-N) ｛C ₂ (θ _b −θ ₁ ) +
The heating control method according to claim 1, wherein _qb ｝ × α. 3. A coating equipment provided with a baking furnace having the control method according to claim 1 provided with a plurality of coating steps, wherein a coating metal plate having at least one or more coating films is provided before entering the baking furnace. The amount of heat required to raise the solid content of the paint applied immediately before the baking furnace, and the temperature rise and volatilization of the volatile content of the paint applied immediately before the baking furnace as the required heating amount of each region of the baking furnace. One of the group consisting of the necessary heat quantity and the heat quantity required for raising the temperature of the coating film already applied before the coating equipment immediately before the baking furnace;
2. The heating control method according to claim 1, wherein a sum of a plurality of calories is calculated. 4. The coating thickness immediately before the baking furnace is t ₁ , the dry coating specific gravity of the coating material immediately before the baking furnace is ρ ₁ , and the coating weight just before the baking furnace is ρ ₁ . The specific heat of the dried coating film is C ₁₁ , the entrance plate temperature of the region of the baking furnace is θ ₁ , the exit plate temperature of each region of the baking furnace is θ ₂ , the solid content ratio of the paint applied immediately before the baking furnace. Is N ₁ , the specific heat of the volatile matter of the paint applied immediately before the baking furnace is C ₁₂ , the volatile matter boiling point of the paint applied immediately before the baking furnace is θ _1b , the volatile content of the paint applied immediately before the baking furnace is The latent heat of vaporization is q _1b , the heat input load ratio of the volatile matter of the paint applied immediately before the baking furnace in the area of the baking furnace is α ₁ , dry film thickness of t _{2, 2} a dry coating specific gravity of paint that have already been painted in an earlier than painting facilities of該焼with furnace just before ρ, painting equipment of該焼with furnace just before When the dry coating specific heat of the coating which has already been painted before the C _21, solid heat Q ₁ required for raising the temperature of the metal plate per unit area of coating painted with該焼with furnace immediately before, furnace immediately before with該焼heat Q ₂ necessary for raising the temperature and evaporation of volatiles metal plate per unit area of in painted coating,
The amount of heat Q ₃ necessary for raising the temperature of the already metal plate per unit area of the painted coating film than before painting facilities with furnace immediately before該焼 _{respectively, Q 1 = t 1 ρ 1} C 11 (θ 2 -θ 1) Q ₂ = (t ₁ ρ ₁ / N ₁ ) (1−N ₁ ) × {C ₁₂ (θ _1b −θ ₁ ) + q _1b } × α ₁ Q ₃ = t ₂ ρ ₂ C ₂₁ (θ ₂ −θ ₁ 4. The heating control method for baking a coated metal sheet according to claim 3, wherein 5. The heating control method according to claim 1, wherein the baking method is an induction heating method.