JPS6034767A - Drying device of automobile body after chemical conversion treatment - Google Patents

Abstract

PURPOSE:To provide a drying device after chemical conversion treatment of an automobile body capable of preventing unevenness of electrodeposition by elevating the temp. of car-body member by preheating by heating at least the last dipping tank for washing with water, and drying quickly by heating with gas at high-temp. CONSTITUTION:After subjecting a member of automobile cody to chemical conversion treatment, it is washed with water in a dipping tank. A heating means 21 is provided to at least the last dipping tank 20 and the car body member is preheated by elevating the temp. of the tank. Simultaneously, high-temp. gas is blown to the member in a direct heating furnace 10 to perform quick drying with hot gas. If the temp. of water in the dipping tank is not elevated sufficiently by some seasonal resaons, etc. and preheating of the member is insufficient, blowing out of hot gas at the inlet side of the direct heating furnace 10 is stopped and the temp. of the member is elevated to a desired temp. When the car-body member obtd. by the above described treatment is coated by electrodeposition, no uneveness of coating is resulted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a drying apparatus for automobile body parts after chemical conversion treatment as pre-painting treatment.

(Prior Art) As a pre-painting treatment for automobile body parts, a chemical conversion treatment is generally performed in which a chemical conversion film such as zinc phosphate is formed on the surface after hot water washing and degreasing treatment. This film is effective in preventing corrosion of the base material and improving the adhesion of paint, but if the subsequent washing and drying processes are insufficient, water may leak into joints, grooves, etc. of car body parts. This may result in poor formation of the electrodeposited film, or uneven coating, ie, scratch marks, may occur when the product is placed in the electrodeposition tank.

However, even if the above-mentioned drying process is sufficiently performed, the electrodeposition coating for the undercoat still has a locally thick coating film.
Occasionally, the unevenness in the coating may appear as unevenness in the topcoat. Conventionally, there was no means to prevent this uneven coating, and the thick coating was removed by polishing after the fact.

The present inventors have discovered that the above-mentioned coating unevenness is caused by the drying method after chemical conversion treatment, and have completed the present invention.

(Objective of the Present Invention) Therefore, an object of the present invention is to provide a drying device after chemical conversion treatment that can prevent the occurrence of the above-mentioned uneven coating in electrodeposition coating.

(Configuration and Effects of the Present Invention) The above objects of the present invention can be achieved by the following configuration. That is, the present invention provides an apparatus for drying an automobile body part whose surface is subjected to a chemical conversion treatment, washed with water, dried, and then subjected to electrodeposition coating, the apparatus comprising: At least the final heating tank is equipped with a heating means, and a direct heating furnace is equipped with a means for blowing out high-temperature gas and directly performs hot air drying by blowing the high-temperature gas onto the vehicle body parts, and the direct heating furnace is equipped with at least an inlet. It is characterized by being able to stop blowing out some high temperature gas on the side.

A common phenomenon that occurs during the drying process after washing with water is that the water film breaks locally at a relatively early stage of the drying process, resulting in a partially dried state. This partially dry state is maintained for a certain period of time, and then when the remaining parts begin to dry, it takes a relatively short time to reach complete dryness.

This phenomenon is thought to be based on the fact that when the surface temperature of vehicle body parts exceeds a certain temperature, drying progresses rapidly.

The present inventors discovered that in the partially dry state, the thickness of the electric M coating near the boundary between the dry part and the unmounted one box part, that is, the swirl part, is thicker than other parts, and this is the cause of coating unevenness. I found out that it was.

Therefore, in order to prevent the occurrence of paint blemishes, it is best to prevent the occurrence of this partially dry state, or to shorten the time period during which this state is maintained as much as possible.

According to the present invention, at least the final dipping tank of the dipping tank is provided with a heating means to raise the water temperature in the tank to preheat and heat up the car body parts, and after that, high-temperature gas is directly blown outside in a heating furnace. , to quickly dry with hot air. In this case, if it is not possible to sufficiently raise the water temperature in the Aitubu tank due to seasonal factors, and therefore the car body parts cannot be sufficiently preheated in the Aitubu tank, the high temperature gas may be blown directly from the inlet of the heating furnace. Stop and heat the vehicle body parts to the desired temperature. The part on the inlet side of the direct heating furnace where gas blowing is stopped receives heat from the hot gas blowing out from the outlet side, creating a high-temperature chamber with almost no wind, and this part suppresses evaporation from the surface of car body parts. It is possible to raise the temperature while That is, it is possible to compensate for insufficient preheating in the dip tank and raise the temperature to a desired temperature while maintaining the surface of the vehicle body part in a pliable state.

Therefore, it is possible to reduce the duration of the partial drying state, which is the cause of the above-mentioned uneven coating, as much as possible.

As a means of heating the water temperature in the dip tank, it is recommended to install a heating coil that circulates steam in the dip tank, and the water temperature can be controlled by the steam temperature and the water temperature. This can be done by adjusting the In amount. in this case,
It is desirable that the surface temperature of the vehicle body parts be raised to about 30C or higher, and for this reason, it is appropriate that the water temperature of the water tank is 700C or higher.

A direct heating furnace that performs direct hot air drying has a temperature of
10C-/! It is desirable to operate at OC, vehicle body parts retention time S~ no θ minutes, and convection flow rate 6~/Om/see.

Stopping the gas blowout on the inlet side of the direct heating furnace and making up for the lack of preheating by creating a high-temperature chamber 8. This phenomenon occurs during seasons other than summer, and in this case, favorable results can be obtained by fulfilling the following external conditions. Let's talk about it. Atmosphere temperature! ;0-10θC1 car body parts f: 11 storage time/minute (spring/autumn), 15 minutes (winter).

(Description of Examples) (Comparative Example) Automotive body parts were pre-treated as shown in FIG. First, the car body parts were washed with hot water and degreased, then washed with water, and then subjected to chemical conversion treatment fX: which forms a chemical film of zinc phosphate or the like on the surface.

After the chemical conversion treatment, a dipping operation in which the car body parts were immersed in a dip tank, that is, a water tank and washed with water, was performed as follows.

(Final dip operation) Water temperature 3C-koθC Total immersion time: 2 minutes Tank capacity 70m3 Next, the car body parts were spray cleaned using the following thread.

Water temperature: 3C-20C Spray time: 10 to 20 seconds Spray time: 20θt/mln Next, the car body parts were dried in a direct drying oven shown in FIGS. 2 and 3. Referring to FIGS. 2 and 3, the direct drying oven 1
A header 16.1B having a plurality of ejection ports 14 biased thereon is attached along both side wall surfaces in the transport direction of the vehicle body part 12 of No. 0. The hot gas from these headers 16.18 burners 22 is sent by a blower fan 24 to the duct 2B.
, 28. Duct 2
6.2B are provided with regulating valves 32 and 34, respectively, for adjusting the gas amount and controlling the furnace temperature.

The vehicle body part 12 enters the furnace from the left in FIG. 3 and is dried by being blown with hot gas while moving to the right.

When a part of the regulating valves 32, 34 is fully opened, the atmosphere in that part changes to a high temperature with almost no wind. Therefore, it is possible to raise the surface temperature while suppressing evaporation from the vehicle body parts as much as possible. The operating conditions of the direct drying oven are as follows.

Atmosphere temperature: 1 ioc ~ 1 soc Time: 5 io min Wind speed: 4 ~ 70 m/degree Specific component in atmosphere CO...S~/Oppm Nox ---3~4L ppm (Max 15p
pm) α ......Several ppm or more The car body parts obtained by the treatment had a problem in that after the electrodeposition coating, streak-like steps were formed on the surface of the electrodeposition coating. This striped step had a height of 7 μm to 3 μm and a length of 2 ran or more. This example condition is commonly encountered, especially during the winter months, and is most likely to occur in areas such as nets, roofs, and trunk parts. As for the occurrence rate, taking bonnets as an example, the above phenomenon was observed in bonnets with an angle of approximately 6θ.

(Example) As shown in the figure, operations up to chemical conversion treatment were performed under the same conditions as in the above-mentioned comparative example. In this example, as shown in FIG.
1 was installed to maintain the water temperature relatively high. The operating conditions of the final dip tank are as follows.

Water temperature: Hiro OC or higher Total immersion time: 70 m3 Tank capacity: 70 m3 Next, the car body parts were spray-cleaned with a spray time of 30 m3 under the following conditions.

Water temperature ti-sc Spray time /゛θ~200~20 seconds θOt/mln Next, in the drying oven 10 shown in Figs. 2 and 3, a part of the inlet side of the regulating valve 32, 340 is fully opened, and Parts were preheated and heated. The heating conditions are as follows.

Atmosphere temperature: gOC Residence time of vehicle body parts: 15 minutes Convection flow rate: 7 m/m/lower Next, hot air drying was performed by blowing high-temperature gas from the outlet 14 at the outlet side of the drying oven 10. The processing conditions in this case are as follows.

Atmospheric temperature: /3θC Residence time for vehicle body parts: 3 minutes Convection flow rate: gm1% No defects were observed on the surfaces of vehicle body components obtained after electrodeposition coating, even in winter. This is because by inserting the heating coil 21 into the dip tank and raising the water temperature, the surface temperature of the car body parts can be raised, and depending on seasonal factors, the heating temperature in the dip tank may be sufficient to 1/'1. In this case, the temperature is raised to the desired temperature in a stagnant state by creating a non-evaporative atmosphere at the inlet side of the thermal furnace. That is,
It is possible to prevent uneven coating from occurring regardless of fluctuations in the water temperature state of the dip tank.

[Brief explanation of the drawing]

Figure 1 is a schematic flowchart of conventional painting pretreatment, and Figure 2 is:
FIG. 3 is a schematic diagram showing a cross section of the drying oven; FIG. 3 is a schematic diagram showing a plan cross section of the drying oven; FIG. FIG. Explanation of symbols 10...Drying oven 12...Car body parts 2
0...Heating coil 22...Nononer 24...Blower fan Patent applicant Toyo Kogyo Co., Ltd. Figure 1 Figure 2

Claims (1)

[Claims] A device for drying an automobile body part whose surface is subjected to a chemical conversion treatment, washed with water, dried, and then subjected to electrodeposition coating, wherein at least the final dip shelter is used for the washing treatment. is equipped with a heating means and a direct drying oven which has a means for blowing out high temperature gas and directly performs hot air drying by blowing the high temperature gas onto the vehicle body parts; A drying device for car body parts after chemical conversion treatment, characterized in that the blowing of gas is stopped and the drying device is dry.