JPH08332454A - Coating method - Google Patents

Abstract

PURPOSE: To provide a reasonable coating method capable of saving a coating material, unnecessitating a troublesome and expensive full surface electrodeposition coating and realizing the effective utilization of the coating material, the simplification of coating work and the demand of cost down or the like. CONSTITUTION: This coating method comprides a process for applying shape machining or welding 7, or shape machining and welding to form a work on a precoated steel sheet 1 having the surface coated with a coating film of a non-conductive material, a process for applying rust preventive treatment on a part 8 where the coating film of the precoated steel sheet is stripped by shape machining or welding and a process for applying a top coating 11, if necessary after applying a intermediate coating 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a steel plate material having a shape
And a work formed by welding, for example, an improvement of a coating method of a vehicle body, a fuel tank of a motorcycle, a frame and the like.

[0002]

2. Description of the Related Art A car body is manufactured, for example, as shown in FIG. 14, in which a steel plate material 100 is processed into a predetermined shape in a pressing step 101, and then the processed material is welded in a welding step 102 to obtain a work. Next, painting is performed in a painting step 103, and finally, an assembly step 104 is performed to assemble the vehicle body.

In detail, as shown in FIG. 15, processed steel plates 105 and 106 are overlapped with each other to form upper and lower electrodes 107, 1
As shown in FIG. 15 (a), spot welding is performed on the predetermined portion through 08, and coating is performed in the subsequent coating step 103. Generally, as shown in FIG.
The undercoat coatings 109 and 119 by electrodeposition coating are applied to the front surface of 5, 106 and the back surface of the welded joint, and then the intermediate coating 110 is applied as shown in (c) of FIG. 15, and finally (d) of FIG. As shown in FIG. A vehicle body or the like is obtained by following the steps described above.

As a conventional technique, Japanese Patent Laid-Open No. 56-10
The techniques disclosed in Japanese Patent Laid-Open No. 397 and Japanese Patent Laid-Open No. 3-66036 are disclosed. This technique relates to a method for coating a vehicle body of an automobile, in which powder coating is applied to an outer panel of the automobile, and then electrodeposition coating such as electrophoretic coating is performed.

[0005]

Among the conventional techniques, the former, that is, a general coating method requires welding a press-formed product of a steel plate material, and then performing each coating process of undercoating, intermediate coating, and topcoating. However, this is disadvantageous in terms of cost and other factors, because of the large number of coating processes, the large number of coating equipment, and the large number of man-hours. Further, it is necessary to apply expensive electrodeposition coating on the entire surface of the vehicle body, which causes a cost increase.

On the other hand, in the disclosed technique, the powder coating is performed from the beginning. By the way, powder coating has a poor coating efficiency of the powder coating, for example, 50 to 60% in the shape portion and 60 to 70% in the flat portion. Poor, wasteful paint, and cost disadvantage.

The present invention has been made to solve the above-mentioned problems, and the above-mentioned inconvenience in coating a press-welded work of a steel plate material from the beginning, therefore,
If a steel sheet coated at the stage of steel sheet material is used, it is sufficient to perform rust prevention treatment such as painting only on the part where the coating film has peeled off by welding or pressing, and therefore, repair is easy,
The present invention has been made by paying attention to the above.

Therefore, the object of the present invention is to eliminate the waste of the paint, the troublesome and expensive work of the whole surface electrodeposition coating, and the efficient use of the paint, the simplification of the painting work, the cost reduction, etc. To provide a rational coating method that can fulfill the above requirements.

[0009]

Therefore, the means according to the present invention for solving the above-mentioned problems is, in claim 1, formed into a precoated steel sheet whose surface is coated with a film of a non-conductive material, or is welded. Or a step of forming a work by performing shape processing and welding, a step of performing a rust preventive treatment on the peeled portion of the coating film of the precoated steel sheet by the shape processing or welding, and then, if necessary. This is a coating method comprising the steps of applying an intermediate coat and then applying a top coat.

In the second aspect of the present invention, the anticorrosive treatment of the peeled portion of the coating film of the precoated steel sheet is electrodeposition coating, and the thickness of the coating film of the precoated steel sheet is selected to be a thickness at which the electrodeposition coating does not adhere. It is a painting method.

[0011]

According to the above-mentioned claim 1, a precoated steel plate is used for press working and welding to form a work, and coating such as rust prevention is applied only to the peeled portion of the coating by pressing and the peeled portion of the coating by welding. Only with this, the undercoat film of the work can be formed.

In the above-mentioned claim 2, since the film thickness of the pre-coated steel sheet is set to a thickness at which the electrodeposition coating does not adhere, the electrodeposition coating is insulated by the film during the electrodeposition coating, and the electrodeposition coating is applied only to the peeled portion of the film. Done.

[0013]

An embodiment of the present invention will be described below in detail with reference to the accompanying drawings. 1 is a partially enlarged vertical side view of a precoated steel sheet, FIG. 2 is an enlarged partially explanatory longitudinal side view of spot welding between a precoated steel sheet and a general steel sheet, and FIG. 3 is a longitudinal side view showing a state of localized film peeling by spot welding. FIG. 4 is a partially enlarged explanatory vertical side view showing a partially coated undercoat (partial electrodeposition coating), FIG. 5 is a partially enlarged explanatory vertical side view showing an intermediate coating state, and FIG. 6 is a partially enlarged top coating state. FIG. 7 is an explanatory vertical side view, FIG. 7 is a view similar to FIG. 2 of an embodiment in which both are precoated steel plates in lap spot welding of steel plates, FIG. 8 is a view corresponding to FIG. 3, and FIG. 4 corresponds to FIG. 10, FIG. 10 corresponds to FIG. 5, and FIG. 11 corresponds to FIG.
12 corresponds to FIG. 12, FIG. 12 is an explanatory enlarged vertical sectional side view of a main part showing local peeling or shrinkage of a bending portion generated by press forming of a precoated steel sheet, and FIG. 13 is an undercoat of the local peeling or shrinkage of FIG. FIG. 14 is a diagram showing a repaired state, FIG. 14 is a block diagram showing a manufacturing process including a conventional general coating process of an automobile body, and FIGS. 15 (a) to 15 (d) are specific welding and painting processes. It is a principal part enlarged vertical side view which shows the method.

FIG. 1 is a partially enlarged vertical side view of the precoated steel plate 1. Reference numeral 2 denotes a steel plate material, and a precoat film 3 is preliminarily applied and formed on the surface 2a of the steel plate 2. Coating 2 on surface 2
The pre-coated steel sheet 1 formed in a may be a pre-coated steel sheet obtained by purchasing a ready-made commercially available product, or a steel sheet 2 may be purchased, and the user may apply the coating 3 on the surface of the steel sheet 2 to obtain the pre-coated steel sheet. The steel plate 1 may be obtained.

The precoated steel sheet 1 is obtained by coating the surface 2a of the steel sheet 2 with a non-conductive coating as a coating for rust prevention treatment or the like to form a non-conductive coating 3, which corresponds to a so-called undercoat coating film. As described above, it functions as an anticorrosion treatment film. As the paint, for example, acrylic resin paint, polyester resin paint, epoxy resin paint or the like is used.

The plate thickness of the steel plate 2 is, for example, 0.5 mm in the case of a steel plate constituting a car body of an automobile, and the thickness of the coating film 3 on the surface is 15 μm. In the figure, for convenience of explanation, the thickness of the coating film 3 is shown thicker than it actually is. Coating 3 on steel plate 2 surface 2a
Can be formed by electrophoretic coating, dip electrodeposition coating, brush coating, powder coating, etc.In any case, the plate is rust-proof coated, so it is easier to coat compared to shaped products. There is little waste of paint.

The above pre-coated steel plate 1 is pressed to obtain a pressed member forming a part of an automobile body having a predetermined steel sheet property, and welded to another pressed steel plate. 2 to 6 show a series of steps from the welding process to the painting process, showing the welding and coating of the peeling portion of the precoat layer (coating 3) by the welding, the welding portion, and the partial enlargement of the peeling portion of the coating due to this It is a figure. An example of spot welding an unpainted ordinary steel plate 4 to the above-mentioned precoated steel plate 1 will be described. Uncoated back surface 2b of the precoated steel sheet 1
Then, the surface 4a of the unpainted ordinary steel plate 4 is struck.

The upper and lower electrodes 5 and 6 are coaxially applied to the surface of the coating film 3 of the precoated steel plate 1 and the lower surface 4b of the steel plate 4 corresponding thereto, and spot welding is performed. As a result, a nugget 7 (melted portion) is formed on the joining boundary surface of the steel plates 1 and 4 facing the electrodes 5 and 6, and the steel plates 1 and 4 are spot-welded. As a result, a work forming a part of the automobile body is formed.

As a result of the above spot welding, the portion of the coating 3 on the surface of the steel sheet 2 of the precoated steel sheet 1 where the electrodes are located is destroyed, the coating peels off, and the peeling portion 8 is generated as a welding mark as shown in FIG. , The peeling portion 8 has the coating peeled off, and the steel plate 2
The bare skin of will be exposed. Since the peeled portion 8 is formed at the spot welded portion, and therefore there are usually many spot welded portions, a large number of peeled portions 8 are formed.

As shown in FIG. 3, the coating 3 of the precoated steel plate 1
Although the peeled portion 8 is formed on the surface of the steel sheet by spot welding, it is not preferable to apply the coating on the coating film 3 as it is because the ground surface of the steel sheet 2 is exposed at the peeled portion 8. Therefore, the surface of the steel plate 1 that has been spot-welded is subjected to electrodeposition coating as a rust preventive treatment. As a result, the coating material enters the peeling portion 8 and is electrodeposited to form the hole-filling coating film 9 as shown in FIG.

At this time, the thickness of the coating film 3 is
It is selected so that the paint does not adhere to the surface of the coating 3 by electrodeposition. As a result, the electrodeposition coating is purely filled in the peeling portion 8 to block only this portion and does not adhere to other portions of the coating film 3. Therefore, while the electrodeposition coating is being performed, the coating material does not double adhere to other portions of the surface of the coating film 3 other than the peeling portion 8, there is no waste of the coating material, and it is economical. Since only the hole filling coating of the portion 8 is performed, the base repair coating such as the rust prevention treatment is quickly performed.

By the way, when the above-mentioned electrodeposition coating is performed, the back surface 4b corresponding to the unwelded portion of the unpainted steel plate 4 is subjected to the same electrodeposition coating as the peeling portion 8 described above. At the same time, the electrodeposition coating film 19 is simultaneously formed,
A coating film is also formed on the unpainted steel sheet.

After that, as shown in FIG. 5, the surface of the coating film 3 containing the hole-filling coating film 9 is subjected to intermediate coating, whereby the intermediate coating film 10 is formed on the surfaces of the coating film 3 and the hole-filling coating film 9. Further, as shown in FIG. 6, the surface of the intermediate coating film 10 is top-coated, and the upper coating film 11 is formed on the surface of the intermediate coating film 10.

As described above, the non-conductive coating 3 for anticorrosion treatment is preliminarily formed on the surface of the precoated steel sheet 1. However, the coating is destroyed during spot welding, and the bare surface of the steel sheet 2 becomes the peeling portion 8. Since the exposed and conductive background is exposed, the electrodeposition of the paint is surely performed during the electrodeposition coating. Instead of the electrodeposition coating, a touch-up paint process of manually applying the paint to the peeling portion 8 may be performed.

By the way, although the peeled portion of the precoated steel sheet 1 is generated, it is generated in addition to the spot welding described above. FIG. 12 shows a case where a peeling portion similar to the above occurs in the press working process. For example, when the pre-coated steel plate 51 in which the rust preventive coating film 53 is preliminarily formed on the surface of the steel plate 52 is formed by drawing or the like, the corner portion A in the direction in which the film 53 of the pressed member 54 shrinks becomes wrinkled due to wrinkles, Recesses 55 ... Are formed.

On the other hand, the coating 53 of the pressed member 54.
When the steel sheet is bent, the coating film 53 extends at the corner portion B in the direction in which the cracks 56, ... May occur. In FIG. 12, the concave portion 55 ..., The crack portion 56
, Are schematically shown for convenience of explanation.

By such press working, fold-shaped concave portions 55 ... And cracked portions 56 ... Are generated also in the bent corner portion, which damages the rust preventive coating 53 on the surface of the press working member 54. Becomes Therefore, in the same manner as described above, the surface of the concave portion 55 ... and the crack portion 56 ... is corrected and coated by electrodeposition coating or touch-up paint, and the surface of the coating film 53 is scratched to cope with the coating after the intermediate coating. Repair.

FIG. 13 shows the state of the recesses 55 ... and the cracks 56 ... After coating with the repair coating. As shown in the figure, the repair coatings 57 and 58 are formed on the coating defect portions of the recesses 55. . After that, similarly to the above, the surface of the coating 53 of the precoated steel sheet including the repair coatings 57 and 58 is subjected to intermediate coating and top coating. The coating process is omitted because it is the same as that shown in FIGS.

7 to 11 show an embodiment of spot welding between precoated steel sheets. Pre-coated steel sheet 21, 31
Conductive surface (back surface) 2 that does not have non-conductive coatings 23 and 33 of
3b and 33b are superposed so as to face each other, and the electrodes 25,
At 35, a predetermined portion of the precoated steel plates 21, 31 having the coating films 23, 33 is spot welded. This state is shown in Figure 7.
, And 27 is a molten nugget portion by spot welding.

After the welding, as shown in FIG. 8, the coatings 23, 33 are formed at the welded portions of the non-conductive coatings 23, 33 on the surfaces of the precoated steel sheets 21, 31 joined by spot welding.
Is destroyed and peeling portions 28 and 38 are generated. The peeled portions 23 and 33 expose the ground surfaces 22a and 32a of the steel plates 22 and 32 as described above.

Then, in the same manner as described above, the welded and bonded body 40 is subjected to, for example, electrodeposition coating for rust prevention, and the peeled portion 2
Hole-filling coatings 29 and 39 are formed on 8 and 38. The repair coating for filling the holes may be formed by touch-up paint by hand, as described above. FIG. 9 shows a state in which the hole filling films 29 and 39 for repair are formed.

As shown in FIG. 9, pre-coated steel sheets 21, 3 including repair coatings 29, 39 after repair rust prevention coating is applied.
Intermediate coatings were applied to the surfaces of the coatings 23 and 33 of No. 1 to form intermediate coating coatings 42 and 43, which are shown in FIG. Next, top coat coating is applied to the surfaces of the intermediate coat coatings 42 and 43 to form top coat coatings 44 and 45. This is shown in FIG.

Although the examples have been described above, spot welding marks on the precoated steel sheet, unevenness due to folds during press working, cracks and the like are generated in a complex manner. Since it is troublesome when many repair parts are required, in practice, electrodeposition coating is often performed.

In the above examples, the coating of the pre-coated steel sheet is a rust preventive coating, but the coating of the pre-coated steel sheet may be set thick or the coating may be colored to omit the intermediate coating step of coating. .

[0035]

As is apparent from the above, according to the present invention, according to claim 1, press working using a precoated steel sheet,
Since spot welding is performed and painting is performed, coating defects such as recesses and cracks that occur in the rust-preventive coating of the precoated steel sheet that occur due to bending during press working and coating peeling portions that occur during spot welding. This part requires only repair allowance by electro-deposition coating on this part, waste of paint is eliminated, there is no need to dispose of non-adhesive paint, and electro-deposition paint is used only for the peeling part etc. It is economical.

In particular, the present invention uses a precoated steel sheet,
Since the repair coating is formed by electrodeposition coating etc. only on the defective portion of the coating that occurs during press working or spot welding, etc. It can be formed and is advantageous in terms of time economy.

Further, in the present invention, it is possible to set the coating film of the pre-coated steel sheet to be thick or to color the coating film, and to omit the intermediate coating process of the coating, thus reducing and rationalizing the number of coating processes. It is also possible to improve economic efficiency.

According to the second aspect of the present invention, the anticorrosion treatment of the peeled portion of the coating film of the precoated steel sheet is performed by electrodeposition coating, and the thickness of the coating film of the precoated steel sheet is selected to be a thickness at which the electrodeposition coating does not adhere. It is economically extremely advantageous because there is no extra paint adhered at the time of coating and the economical use of the paint can be guaranteed, wasteful paint can be generated and the paint can be used efficiently.

[Brief description of drawings]

[Figure 1] Partial enlarged vertical side view of pre-coated steel sheet

FIG. 2 is a partially enlarged explanatory vertical side view of spot welding of a precoated steel plate and a general steel plate.

FIG. 3 is a vertical cross-sectional side view showing the state of localized peeling of the coating film by spot welding.

FIG. 4 is a partially enlarged explanatory vertical cross-sectional side view showing an undercoat (partial electrodeposition coating) of a locally peeled portion.

FIG. 5 is a partially enlarged explanatory vertical side view showing a partially coated state.

FIG. 6 is a partially enlarged explanatory vertical sectional side view showing a top coating state.

FIG. 7 is a view similar to FIG. 2 showing an example in which precoated steel sheets are used for both spot welding of superposed steel sheets.

FIG. 8 is a diagram corresponding to FIG. 3 above.

FIG. 9 is a view corresponding to FIG. 4 above.

FIG. 10 is a diagram corresponding to FIG. 5 above.

FIG. 11 is a view corresponding to FIG. 6 above.

FIG. 12 is an explanatory longitudinally enlarged side view of an essential part showing local peeling and contraction of a bent portion generated by press forming of a precoated steel sheet.

FIG. 13 is a view showing a state where the local peeling and shrinkage portion of FIG. 12 are underpainted and repaired.

FIG. 14 is a block diagram showing a manufacturing process including a conventional general car body painting process.

15 (a) to 15 (d) are enlarged longitudinal side views of main parts showing a specific method of conventional welding and coating processes.

[Explanation of symbols]

1 ... Precoated steel sheet, 7 ... Welded portion, 8 ... Peeled portion,
9 ... Anticorrosion treatment film, 10 Intermediate coating film, 11 ... Top coating film.

Claims (2)

[Claims] 1. A step of forming a work on a pre-coated steel sheet whose surface is coated with a coating of a non-conductive material, or a step of forming a work by performing a shape processing and a welding, and by the shape processing or welding, A coating method comprising the steps of: applying a rust preventive treatment to the peeled portion of the coating of the precoated steel sheet, and then applying an intermediate coating if necessary, and then applying a top coating. 2. The anticorrosion treatment of the peeled portion of the coating film of the precoated steel sheet is electrodeposition coating, and the thickness of the coating film of the precoated steel sheet is selected to a thickness at which the electrodeposition coating does not adhere. How to paint.