JPS645961B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a painted rolled plate made of aluminum and aluminum alloy. [Prior art] Conventionally, rolled plates used for painting include those with a mirror-like surface, that is, a bright finished surface (BC), and those with a dull finished surface (DC), which is slightly rougher than the bright finished surface but sufficiently flat. ) are generally used. For example, vehicles such as cars and trains, electrical equipment, building materials such as blinds, container caps,
The above-mentioned rolled plates, which are used as food cans and the like after processing and painting, are used for long periods of time in a severely corrosive environment, so the material deteriorates due to moisture entering through coating defects such as scratches and paint pinholes during use. Thread-like corrosion occurs in Al or Al alloy, causing problems in appearance and requiring repair of the corroded parts.
In the past, attempts have been made to prevent corrosion by improving coating techniques and paints, or by improving the Al material itself (chemical composition, structure, manufacturing process), etc., but at present, corrosion has not been completely resolved. [Purpose of the Invention] The present invention was made in view of the above problems, and an object of the present invention is to improve the thread rust resistance of a rolled plate without changing the material of the rolled plate or its structure. do. [Background of the Invention] As a result of conducting tests, the present inventor found that by roughening the surface of a rolled plate to some extent, the thread rust resistance can be significantly improved. The reason for this is not clear, but it is assumed that the progression of thread rust is hindered by the unevenness of the board surface.
The maximum roughness Rmax and PPI (peak point per inch) were used as the evaluation criteria for the surface roughness of the rolled plate. That is, as shown in the drawing, the maximum roughness Rmal
is the highest peak within 1 inch length of the rolled plate
Defined as the difference in height between Mo and the lowest valley Vo,
On the other hand, PPI is a mountain M, M, which has a height of 25μ inches or more with respect to the reference plane B within the above 1 inch length,
..., M and the number of valleys V, V, ..., V having a depth of 25 microinches or more. Currently, the standards for evaluating yarn rust resistance are as follows:
It has not yet been regulated by JIS, etc., and the evaluation standards vary among manufacturers (e.g. automobile manufacturers) who use this type of aluminum plate (alloy plate), but basically, It is thought that the length of the thread rust should be used as a standard, and the current situation is that the length of the thread rust is approximately 2 to 4 mm, and anything over 4 mm is definitely rejected. Therefore, if thread rust can be reduced to 1 mm or less, thread rust resistance can be evaluated as good, and according to the test conducted by the present inventors, which will be described later, Rmax can be reduced to a range of 2 μm or more. , and good yarn rust resistance was obtained when PPI was set to 30 or more. That is, Rmax
is less than 2μm, or PPI (h≧25μinch) is 30
If the number is less than 1, the yarn rust resistance of the rolled plate will not improve much. Note that the upper limit of Rmax is considered to be approximately 30 μm due to restrictions such as rolling equipment, and if the PPI exceeds 400 pieces, extremely good yarn rust resistance can be obtained, but in reality to
It is difficult to set the PPI to 400 or more with the current production equipment, and even if it were possible to set it to 400 or more, it would be difficult to achieve sufficient mass production, so the PPI should be in the range of 30 to 400. It is preferable to set it to . Also, Rmax and PPI must be within the above setting range within 1 inch length in all directions of the rolled plate, that is, each peak (or valley) has an independent conical shape. However, from the viewpoint of ease of measurement of Rmax and PPI and mass production of rolled sheets, it is desirable that the above setting range be within the above setting range in at least two directions, that is, in parallel and at right angles to the rolling direction. It was considered good as long as it stayed on. Note that methods for roughening a rolled plate include (i) rolling it with a rolling roll whose surface has been roughened, and transferring the rough surface shape of the roll surface to the rolled material;
(ii) It is possible to perform chemical treatment (etching, etc.) or electrochemical treatment after rolling, but method (ii) is disadvantageous in practice because it increases the number of steps and costs. [Structure of the Invention] Based on the above-mentioned findings, the present invention is based on the above-mentioned findings, and the present invention is based on the above-mentioned findings. The surface roughness is reduced by the above-mentioned rolling rolls so that the number of peaks or valleys having a height or depth of 25 μinch or more within a length of 1 inch is 30 or more. It is an object of the present invention to provide a rolled plate for coating, which is characterized by being adjusted. The materials for the above-mentioned rolled sheets are mainly pure aluminum and aluminum alloys standardized by JIS, namely silicon, copper, manganese, magnesium, chromium, zinc, lead, iron, titanium, nickel, etc., and various metals such as aluminum and aluminum. Alloys can be used. Further, as the above-mentioned rolling roll, for example, a steel roll can be used, and the surface of the steel roll is roughened by means such as shot blasting and electrical discharge machining. In addition, when rolling a rolled plate, for example, in the case of a rolled plate made of aluminum alloy, 1
Pass rolling is preferred, and rolling may be performed multiple times if necessary. [Example] As a representative example of the present invention, the results of investigating the relationship between Rmax, PPI, and thread rust resistance of a JIS5182 Al-Mg aluminum alloy rolled plate (thickness: 1.0 mm) were used for rolling. Table 1 on page 8 shows the surface roughness of the steel rolls. Invention material No. in the same table.
Nos. 1 to 9 were rolled using rolling rolls having various surface roughnesses as shown in Table 1 so that Rmax and PPI fell within the setting range of the present invention (Rmax: 2 μm or more, PPI: 30 or more). It is something. In addition, the same table shows comparative materials Nos. 1 to 4 of rolled plates in which either or both of Rmax and PPI are out of the setting range of the present invention.
It was shown as Among these, comparative material No. 1 was rolled with a BC rolling roll, comparative material No. 2 was rolled with a DC rolling roll, and Nos. 3 and 4 had a rough surface shape that was rougher than that of the DC rolling roll. It is rolled with a roll having In addition, in Table 1, when comparing Inventive Material 3 and Comparative Material 3, the surface roughness of the rolls used for rolling
Although the Rmax is almost the same, the Rmax of the rolled materials is different. It is thought that rolling conditions such as rolling reduction and rolling speed are involved in this, and the surface roughness of the rolled material varies depending on the rolling conditions. Incidentally, the rolling reduction rate and rolling speed for Inventive Material 3 are 2% and 100 m/min; for Comparative Material 3,
They were 1% and 130 m/min, respectively. In this way, a desired surface roughness can be achieved by appropriately selecting the surface roughness of the roll and adjusting the rolling reduction and rolling speed.

【table】

[Table] Next, the test procedure for yarn rust resistance will be explained. (i) First, test pieces taken from each invention material and each comparison material are pretreated, ie, painted, under the following conditions. (Pre-treatment conditions) Degreasing → washing with water → zinc phosphate treatment → washing with water → washing with pure water and drying → cationic electrodeposition (20 μm thick, heated at 160°C for 20 minutes) → intermediate coating (coating film = 30 μm, heated at 140°C for 25 minutes)
→ Top coat (coating film = 35 μm, heating at 145°C for 25 minutes) (ii) Next, each test piece is tested for thread rust resistance under the following conditions. (Thread rust resistance test conditions) Put a notch in the paint film → Salt water spray (JIS 24 hour exposure) → Warm water (temperature = 45℃, humidity = 95%, 20 days exposure) → Visual evaluation The evaluation criteria for thread rust resistance are It is as shown in Table 2.
As is clear from the column of yarn rust resistance evaluation in Table 1, the yarn rust resistance of the invention material is considerably improved compared to the comparative material. [Effect of the invention] As explained above, in the present invention, the surface of the rolled plate is roughened to some extent (specifically, Rmax
(2 μm or more, PPI 30 or more), it is possible to improve the thread rust resistance of the rolled plate. In addition, in an application filed on the same day as the present application by the same applicant as the present applicant, Rmax is 3 to 13 μm and PPI is
It is disclosed that if the number is 30 or more, the formability of the rolled plate, that is, the stretchability, bending workability, etc., can be improved. It is disclosed that fingerprint resistance can be improved by making the ridge shape sharp when forming, and in addition to improving thread rust resistance, it is possible to improve moldability and fingerprint resistance. You can also do it.

[Brief explanation of drawings]

The drawing is an enlarged schematic view showing the surface shape of the rolled plate. M...Mountain, V...Valley.

Claims (1)

[Claims] 1 Rolled with a rolling roll with a roughened surface,
At least one direction parallel to and perpendicular to the rolling direction
The maximum roughness (Rmax) within the inch length is 2μm or more, and the number of peaks or valleys (PPI) having a height or depth of 25μinch or more within the 1 inch length is 30. As described above, there are provided aluminum and aluminum alloy plates for painting which have excellent thread rust resistance and whose surface roughness is controlled by the above-mentioned rolling rolls.