JPS62133083A - Baking method for painted steel sheet - Google Patents

Abstract

PURPOSE:To permit efficient baking treatment by treating a painted steel sheet by a combination of heating with an induction heater intended only for the evaporation of a solvent and gas heating intended for the inherent baking, i.e., melting and softening of the paint. CONSTITUTION:The steel sheet S is painted on the front side by a painting roll 1 in the position where the steel sheet is wound on a hold back roll 5. The steel sheet is then painted on the rear side by a painting roll 2 between support rolls 6 and 7. The steel sheet is immediately introduced into the induction heater 3 where the greater part of the solvent is evaporated. The steel sheet is introduced into a heating furnace 4 where the steel sheet is subjected to the inherent baking including the melting and softening of the paint. The gas contg. the evaporated solvent in the induction heater 3 is conducted by a suction blower 8 to a combustion furnace 9 where the gas is thoroughly burned by a burner 10. Part of the exhaust gas generated by the combustion is supplied as a dilute gas through a piping 12 to the induction heater 3.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for baking painted steel sheets.

[Conventional technology and its problems]

The gas heating method and the induction heating method are well known as typical baking methods for installed steel sheets.

Among these, the gas heating method heats the painted surface by spraying heat lice onto it, but it has the following problems.

■Since the heat transfer mechanism is from the outside of the paint to the steel plate, the solvent in the paint cannot evaporate properly unless it is heated slowly during the solvent evaporation process. For this reason, recent floaters
Even in oven 1, the solvent evaporation zone is 172 in the furnace length.
Due to the above reasons, the overall length of the furnace has to be increased.

■During the solvent evaporation process, if the speed of hot air blowing is too high, there is a problem that wind ripples will form on the painted surface, and if the heating speed is increased, the painted surface will become stiff and the surface appearance will deteriorate significantly. Therefore, in gas heating, it is necessary to suppress the spraying speed and the heating rate, which inevitably lengthens the solvent evaporation zone.

■There is a danger of explosion if the solvent that evaporates during heating fills the furnace, so the concentration should be kept below the explosive limit of 174 liters.
It is necessary to supply a large amount of dilution gas (fresh air) to dilute this, but this dilution gas must be heated before being supplied to prevent heat loss in the furnace, and this heating requires a large amount of energy. Therefore, the energy consumption rate is poor.

On the other hand, with the induction heating method, the paint is
Since it is heated from the steel plate side), the solvent evaporates smoothly and has the advantage of increasing the evaporation rate. However, this method also has the following problems.

■The edge of the l-II tube is overheated and +u in the width direction.
Unevenness of K appears.

■When heating painted steel plates, it is necessary to select an appropriate heating pattern depending on the material, plate thickness, plate width% paint type, and operation becomes more complicated than gas heating.

■Like the gas heating method, it is necessary to supply a large amount of diluent gas to prevent the risk of explosion. As the temperature decreases, the solvent solidifies and forms a resin-like coating that adheres to the side walls of the furnace and the surface of the visiting coil. (about 2000)
It is necessary to introduce it into the furnace, and a sl addition device and fuel are required for this purpose.

In view of these conventional problems, the present invention has been developed to achieve a high baking processing speed, to keep the energy consumption low, and to bake coated steel sheets appropriately without complicating operations. The aim is to provide a method that can be used.

[Means to solve the problem]

For this reason, the present invention heats a painted steel plate with an induction heater to evaporate most of the solvent, and then introduces it into a gas heating furnace to bake the paint. Burn the evaporated solvent and
Its basic feature is that a part of the combustion exhaust gas is supplied to the induction heater as a diluent gas.

In the present invention, a painted steel plate is heated by an induction heater in the first stage and an eight-burner gas furnace in the second stage. A gas heating furnace is used to heat the paint for baking (melting and softening).
Used for j11.

By doing this, the coating film is heated from the inside (steel plate 11111) by the induction heater heating plate, so the solvent evaporates smoothly. Therefore, the solvent evaporates in a short period of time, and in the subsequent gas heating, the coating film is heated from inside (steel plate 11111). Rapid heating is possible because there is no need for an arrangement for chemical evaporation, and as a result of the above, the length of the furnace can be easily shortened compared to the conventional gas heating system.

In addition, since heating with an induction heater is performed only for the purpose of evaporating the bath agent, it is difficult to apply the coating using only an induction heater. Moreover, uneven temperature distribution in the width direction is not a problem.

In addition, since most of the solvent in the gas heating stage 1 bamboo has already evaporated, there is no need to introduce diluent gas into the gas heating furnace, which saves energy for heating gas at the station. As the dilution gas supplied to the induction heater is the waste gas after burning the evaporated solvent discharged from the induction heater, there is no need to heat the dilution gas to prevent the solvent from coagulating. y
It is possible to reduce iM cost and energy consumption rate.

〔Example〕

Fig. 1 shows a state of implementation of the present invention, in which (1) is a coating roll for coating the surface of a steel plate, (5) is a holdback roll, (2) is a coating roll for coating the back side of a steel plate, and (3) is a paint roll for coating the back side of a steel plate. (4) is an induction heater that constitutes a paint baking device;
is also a gas heating furnace, and (61 (7) is a support roll.

The steel plate (S) is wrapped around the holdback roll (5) and then applied to the coating roll (1).Surface 1
1. Painting tongue 71, then supporting roll (61) forming the catenary face center (X) (71 between painting rolls (2)
The back side is painted off. Immediately after such coating, it is introduced into an induction heater (3) and heated to evaporate most of the solvent. With this induction heater (3), the paint is heated at 150~160'
Most of the solvent evaporates by heating to about O.

The heating by the induction heater (3) is intended only for the purpose of evaporating the solvent, and heating that would significantly melt and soften the paint is not performed. The steel plate (S) is immediately introduced from the induction heater (3) into the gas heating furnace (4), where it is melted and softened to prevent the original paint baking.

Furthermore, in the present invention, the evaporated solvent discharged from the induction heater (3) is combusted, and a part of the exhaust gas is supplied to the induction heater (3) as a diluent gas.
In the figure, (8) is a suction blower for evaporated solvent, (9) is a dream agent combustion furnace, uO is an auxiliary combustion burner in the furnace, αυ is a diluent gas supply blower, and evaporated solvent in induction heater (3). The gas (approximately 200 ()) containing
750~8 from the auxiliary burner aat 5.
The fuel is pumped up to 00'O and burns almost completely.

A part of the exhaust gas generated during kneading is supplied as dilution gas to the induction heater (3) through pipe α2.
This diluent gas is introduced into the induction heater (3) at a temperature of about 200゛0, and therefore the thermometer C13 in the middle of the pipe (6)! The gas temperature is measured from this, and based on this measured temperature, the valve α of the air injection pipe CI4 is
to inject air and control the temperature of the diluent gas.

In addition, the flow meter in the middle of piping α2 (diluted gas flow according to IQ;
The damper q7J is also controlled based on the measurements.

Furthermore, in this embodiment, the energy consumption rate is reduced by 2 tl by utilizing the sensible heat of the evaporation bath and the combustion exhaust gas as a heat source for the gas heating furnace (4). That is, the remaining gas from the solvent combustion furnace (91) that is not supplied to the induction heater side is introduced into the heat exchanger Q barrel, where it is heat exchanged with the air supplied to the gas heating furnace (4). , Due to this heat exchange, the air becomes 300 to 350
The temperature rises to about 0t, and hot air is supplied from the piping αν and the blower ring (4) into the gas heating furnace (4).
S) is heated. The heat-exchanged exhaust gas is transferred to an exhaust blower (
11, the gas is discharged from the gas heating furnace (4) into the atmosphere together with the filtrate gas.

Fig. 2 shows another embodiment. In this embodiment, the exhaust gas discharged from the solvent combustion furnace (9) is not directly supplied to the induction heater (3), but is instead supplied with gas heating furnace air and heat. After replacing it, a part of it is introduced into the induction heater (3) as a diluent gas through piping 4. The exhaust gas that has been heat exchanged in the heat exchanger 06 still has a temperature of about 350 to 450 °C, and in this case, the temperature IW meter 4 in the middle of the distribution, the air pressure injection pipe Q, υ, and Valve u9 (Koyoru Gas Temperature Control I・1) 1,
Furthermore, a flower by flow spear meter αG and damper Qη? ffl
Control is exercised.

〔Effect of the invention〕

According to the present invention as described above, a coated steel sheet is treated by a combination of induction heater heating for the sole purpose of solvent evaporation and gas heating for the original baking purpose of melting and softening the ζ material. As a result, it is possible to perform an efficient baking process by increasing the heating speed IW, thereby making it possible to significantly shorten the length of the furnace compared to the conventional gas heating method.

In addition, since there is no evaporation of hAll in a gas heating furnace, there is no need to introduce diluent gas, which saves energy for heating the diluent gas. Since the exhaust gas is used after being discharged and evaporated, there is no need to heat the diluted residue to prevent solvent coagulation, reducing equipment costs and energy consumption. I can do it.

≠fi of the drawing? Simple Explanation FIG. 1 is an explanatory diagram showing one embodiment of the present invention. FIG. 2 is an explanatory diagram showing another embodiment of the present invention.

In the figure, (3) indicates an induction heater, (4) a gas heating furnace, and (9) a solvent combustion furnace.

Claims (1)

[Claims] Heating a painted steel plate with an induction heater to evaporate most of the solvent, then evaporate the gas. Introduced into a heating furnace, painted and baked, and then Evaporated solvent discharged from duction heater A part of the combustion exhaust gas from this combustion to the induction heater as diluent gas. Baking of painted steel plate characterized by supplying Method.