JPS6034768A - Drying device of automobile body after chemical conversion treatment - Google Patents

Abstract

PURPOSE:To prevent unevenness of electrodeposition coating on a automobile body member by heating at least the last dipping tank used for water washing and elevating the temp. of the member by preheating, and then drying quickly with gas at high temp. CONSTITUTION:After subjecting a member of automobile body to chemical conversion treatment, the member is washed with water in a dipping tank. A heating means 42 is provided to at least the last dipping tank 40, and the temp. of the member is elevated by preheating and elevating the water temp. of the tank. The member is then dried quickly by blowing hot gas thereto in a direct heating furnace 10. If the preheating in the dipping tank is insufficient by some seasonal reason, etc., the heating means at a part of the inlet side of the direct heating hot gas drying furnace 10 is changed to an indirect heating means using nonvaporizable atmosphere, and the temp. is elevated by preheating. Then, the member is quickly dried by the direct heating drying means using hot gas 10. If the preheating is sufficient, the drying is performed by the direct heating hot gas drying means 10.

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. This film is effective in preventing corrosion of the substrate and improving the density of the paint, but
If the subsequent rinsing, draining, and drying processes are insufficiently dried, water may remain in the joints and joints of car body parts, resulting in poor formation of the electrocoated film or failure to enter the electrocoat bath. Occasionally, paint unevenness, or hash marks, may occur.

However, even if the above-mentioned drying is carried out sufficiently, m
During the coating process, coating unevenness with a locally thick coating may occur, and the coating unevenness may appear as unevenness in the top coat. Conventionally, there was no means to prevent this uneven coating, and the thick coating film was removed by polishing after Φ.

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

(Object 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 one-coat coating.

(479 Structures 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 automobile body parts whose surfaces are subjected to chemical conversion treatment, washed with water, dried, and then subjected to electrodeposition coating, and which includes a dip tank for carrying out the washing treatment. At least the final dipping tank is equipped with a heating means, and a means for rapid direct hot air drying of the car body parts after water washing, and 7 parts on the inlet side of the rapid direct hot air drying means are indirect heating means in a non-evaporative atmosphere. It is characterized in that it can be switched to.

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 after that, when drying begins to proceed to the crosspiece p, it takes a relatively short time to reach complete dryness.

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

The inventors Q, the thickness of the electrodeposited coating near the boundary between the above-mentioned partially dry state (separated dry part and non-dried part, i.e., the L part) is thicker than other parts, and this causes coating unevenness. I found out that it depends on the cause.

Therefore, in order to prevent the occurrence of this partially dry state or to shorten the time during which this state is maintained as much as possible, the present invention provides a heating means in at least the final dip tank of the dip tank. The water temperature is raised to preheat the car body parts, and then they are quickly dried using direct hot air drying means. The surface temperature of the body parts at the outlet of the tank changes.

According to the present invention, when preheating of the dip tank is insufficient, a part of the inlet side of the direct hot air drying means is switched to indirect heating means in a non-evaporative atmosphere, and the temperature is further preheated to a desired temperature. and then rapidly dried by direct hot air drying means. If the preheating is sufficient, the material is immediately dried by hot air drying means. When the car body parts are dried using the above operations, Ding f4'! It is possible to compensate for the lack of preheating due to seasonal factors, etc., and reach the desired temperature in a wet state, thereby shortening the time it takes to remain partially dry and reliably preventing the occurrence of uneven coating. can do.

As a means for heating the water temperature in the dip tank, a heating coil for circulating steam can be disposed in the dip tank, and the water temperature can be controlled by adjusting the steam temperature and flow rate. In this case, it is desirable that the surface temperature of the vehicle body parts be raised to about 30° C. or higher, and for this purpose, the water temperature in the dip tank is appropriately set to tlO° C. or higher. Examples of the direct hot air drying means include a direct drying oven that blows high-temperature gas onto vehicle body parts from an outlet to dry them. This direct drying furnace is equipped with an indirect heating means such as a heat panel in which a high-temperature fluid flows inside the F section on the inlet side.
When the blowing of the high-temperature gas is stopped, the indirect heating means functions as an indirect heating furnace that can raise the temperature of the vehicle body parts while keeping them in a wet state due to heat radiation from the indirect heating means. That is, it can be used as an indirect heating means for a non-evaporative atmosphere according to the present invention. Therefore, if the surface temperature at the outlet of the dip tank does not reach the desired temperature, the inlet side portion of the direct heating furnace is switched to an indirect heating furnace to further raise the temperature. The need for preheating with an indirect heating furnace occurs mainly during seasons other than summer;
Desirable operating conditions for an indirect heating furnace are as follows.

Furnace ambient temperature Sθ~lθ0℃ Vehicle body parts residence time/min (
Spring/Autumn), /, 5 minutes (Winter). Further, it is preferable that a direct drying oven for direct hot air drying be operated at an oven atmospheric temperature of /10°C to /SO°C, a vehicle body parts retention time of /θ minutes, and a convection flow rate of 6 to /θ1−.

(Description of Examples) (Comparative Example) Pre-painting treatment of automobile body parts was carried out as shown in FIG. First, the car body parts were washed with hot water and degreased, and then the washed sickles were subjected to chemical conversion treatment to form a chemical film such as zinc phosphate on the surface.

After the chemical conversion treatment, a dizzo operation in which the car body parts were immersed in a dip bath, that is, a water tank and washed with water, was performed under the following conditions.

(Final Buzzo operation) Water temperature: 5°C to dθ°C Total immersion time: Tank capacity: 7θ Next, the car body parts were spray washed under the following conditions.

water temperature ri℃〜koθ℃ spray cleaning 70-2θ seconds Spray amount 2001/Familiar Next, the car body parts were dried in a direct drying oven shown in FIG.

Referring to FIG. 2, a header 16.1B having a plurality of spout ports 14 is installed along both side wall surfaces of the direct drying oven 100 in the conveyance direction of the vehicle body parts 12. Further, a hollow plate-shaped heating duct 20 is disposed at the bottom. These headers 16, 18 and ducts 20 are supplied with hot gas from the burner 22 by means of a blower fan 24 and via ducts 26, 28 and 30. Duct 26.28.30VCtfi Regulating valve 32.3 for adjusting the gas amount and controlling the furnace temperature
4.36 are provided respectively. In the drying oven of this example, by injecting and supplying high-temperature gas from the jet nozzle 14,
Not only can forced convection be carried out inside the furnace, but also the adjustment valve 3
By closing 2.34, indirect heating can be performed by the heat released from the heating duct.

In addition, the high temperature gas from the heating duct passes through the duct 38, and the high temperature gas injected into the furnace is recovered and recirculated by a duct (not shown)1.The operating conditions of the direct drying furnace are as follows. It is common knowledge.

Atmosphere temperature 7106~730℃ Time 5~70 minutes Wind speed 6~/θrB/vxr Specific component in atmosphere CO...S~/Oppm N0X-3~+ ppm (MaX/!; ppm) α...Several ppm After the car body parts obtained by the above treatment were electrodeposited, a problem occurred in that streak-like steps were formed on the surface of the deposited coating film. This striped step has a height of /μ~aμ,
It was over 2cm long. This example condition is commonly encountered, especially during the winter months, and is likely to occur primarily in the hood, roof, and trunk parts. As for the occurrence rate... Taking Bonnet as an example, the above phenomenon was observed in about 60% of 11-sonnets.

(Example) As shown in FIG. 3, 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. 7, a zero heat coil 42 through which steam circulates was disposed in the final dipping tank 40 to maintain the water temperature relatively high. The operating conditions of the final diruff 6 tank 40 are as follows.

Water, X hiro θ℃ or higher Total immersion time: minutes Tank capacity 7θ- Next, the car body parts were spray cleaned under the following conditions.

Water @ 4t5℃ spray time 10-20 seconds Spray amount 200t/- Next, the temperature was preheated using an indirect heating furnace.

The indirect heating furnace is a drying furnace 1o in FIG.
2.34 fully closed was used. The operations outside the indirect heating furnace operation system are as follows.

Atmospheric temperature: 30° C. Residence time of car body parts: /, 5 minutes Convection flow rate: /mm or less Next, the parts were dried by heat using the drying oven shown in FIG. 7. The operating conditions for the drying oven are as follows.

Atmospheric temperature: 730°C Residence time of car body parts: g minutes Convective flow rate: g m/sec No defects were observed on the surfaces of the car body parts obtained by the above treatment after electrodeposition coating, even in winter. By inserting a heating coil into the heating tank and raising the water temperature, it is possible to raise the surface temperature of the car body parts. This is based on the fact that a portion of the drying process is switched to an indirect heating furnace to raise the surface temperature sufficiently before hot air drying is performed.

[Brief explanation of drawings]

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 a drying oven, FIG. 3 is a schematic flowchart of a process according to the present invention, and FIG. 9 is a schematic diagram of a processing apparatus according to the present invention. Description of symbols 10...Drying oven 12...Car body parts 22...Burner 24...Blower fan 42...Heating coil Patent applicant Toyo Kogyo Co., Ltd. Figure 1 Figure 2

Claims (1)

[Claims] A device for drying automobile body parts whose surfaces are subjected to chemical conversion treatment, washed with water, dried, and then subjected to electrodeposition coating, wherein at least the final delag tank of the derag tank ρ for performing the water washing treatment is provided. In addition to being equipped with heating means,
An automobile body comprising means for rapid direct hot air drying of vehicle body parts after washing with water, wherein seven parts on the inlet side of the rapid direct hot air drying means are switchable to indirect heating means in a non-evaporative atmosphere. Drying equipment after chemical conversion treatment of parts.