JP2588336B2 - Manufacturing method of exterior stainless steel sheet having anti-glare property and corrosion resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stainless steel sheet having anti-glare properties and corrosion resistance used for exterior materials such as roofs.

[0002]

2. Description of the Related Art When a stainless steel plate is used for an exterior material such as a roof, in addition to corrosion resistance, antiglare properties and a color tone unique to stainless steel are required. It is effective for the anti-glare property to make large irregularities on the steel sheet surface to reduce the light reflectance. Irregularities on the surface of the steel sheet are formed by transferring the roll surface to the steel sheet by rolling using a dull roll whose surface has been processed.

As a stainless steel provided with anti-glare properties, there is a dull-finished stainless steel disclosed in JP-A-61-227193 and JP-A-1-162779, all of which are colored by chemical coloring. It is a stainless steel plate, which is fundamentally different from the present invention relating to achromatic to white stainless steel.

[0004] An example of the use of stainless steel plates for roofs is the special roof for shopping centers in Paris.
Nickel, Volume 6, Number 3, 1991, P.8 describes an example of using a satin-finished austenitic stainless steel sheet.

[0005] color tone of the surface of the stainless steel plate (whiteness) is how to process annealing, pickling (AP) the annealing step, it is known that depends on how to bright annealing (BA) process. In the AP process, the finish is white, and the whiteness tends to increase. On the other hand, in the BA process, unlike the AP process, since there is no pickling (P) process, the whiteness is lower than that in the AP process, and the metal process has a color tone unique to metal. Although this BA steel sheet is finished as an exterior material for roofs and the like, it has a drawback that its corrosion resistance is inferior to that of the AP process material. At the present time, it is extremely difficult to obtain a steel sheet having a color tone similar to that of the BA process in the AP process.

[0006]

The steel sheet that has undergone the BA process after dull rolling has a reduced whiteness, and thus has the characteristic of having excellent antiglare properties while maintaining metallic luster. However, there is a problem that the corrosion resistance of the steel sheet that has passed through this step is inferior to that of the steel sheet that has passed through the AP step after dull rolling. An object of the present invention is to provide a method for producing a low-whiteness stainless steel sheet having both anti-glare properties and corrosion resistance, which solves the above problems.

[0007]

Means for Solving the Problems Although the antiglare property can be imparted by dulling, the corrosion resistance is lowered. The steel sheet which has been annealed after dull rolling and pickled with a mixed acid of (nitric acid + hydrofluoric acid) is assured of corrosion resistance. However, at present, stainless steel sheets having antiglare properties, corrosion resistance, and low whiteness could not be obtained, for example, the whiteness was too high.

The anti-glare property cannot be imparted by the surface roughness of a crystal grain unit, and it is necessary that the surface has irregularities in a unit of several to several tens of crystal grains. It was found that the roughness also affected the corrosion resistance and color tone under long-term atmospheric exposure. For this purpose, it is necessary to perform one or more passes of rolling with a dull roll before annealing to adjust the surface roughness to an appropriate value.

[0009] In order to clarify the relationship between dulling and corrosion resistance, the surface of the steel sheet after dull rolling was examined in detail. As a result, the steel sheet surface was in contact with the convex portion of the dull roll surface and was rolled under high surface pressure. It was found that there were strong processed parts and collapses, and the processed structures on these surfaces affected the corrosion resistance.

On the other hand, although the steel sheet which has been annealed after the dull rolling and then annealed and pickled with a mixed acid of (nitric acid + hydrofluoric acid) has a small amount of collapse, the dissolution of the crystal grain boundaries is remarkable, and this causes white color. The degree is getting higher. In particular, the oxide scale of the steel sheet annealed at a temperature higher than 900 ° C. cannot be removed unless it is immersed in an alkali molten salt. Immersion in an alkali molten salt increases the whiteness after pickling.

[0011] Stainless steel used for exterior materials such as roofs comes in contact with rainwater containing various pollutants and salts, and is exposed to an environment in which wet-drying is repeated. Therefore, in order to maintain the initial state of construction for a long period of time, corrosion resistance superior to general-purpose stainless steel is required.

[0012] In an atmospheric environment in which wet and dry conditions are repeated, stainless steel plates having high antiglare properties and low whiteness were examined in terms of corrosion resistance, antiglare properties and color tone. : 0.020% or less, Cr: 17.0
３５35.0%, Mo: 0.5 to 4.0%, Cr + 3M
o: 26 to 40%, Si: 0.05 to 1.0%, Mn:
Cold rolled steel sheet composed of 0.05 to 0.5%, Al: 0.005 to 0.2%, balance Fe and other unavoidable impurities, and having a surface roughness (Ra) of 0.5 to 10.0 μm. 6
After heating to 00 to 900 ° C, it is cooled at a cooling rate of 2 ° C / sec or more, electrolyzed in a neutral salt solution under the conditions of 1 to 20 A / dm ² , and then immersed in a mixed acid of nitric acid and hydrofluoric acid or nitric acid By doing so, an exterior stainless steel sheet having both antiglare properties and corrosion resistance can be manufactured.

Further, Nb: 0.1-0.5%, Ti:
When a stainless steel sheet containing one or more elements of 0.1 to 0.5% and V: 0.05 to 0.5% is used, corrosion resistance,
It was found to be advantageous for producing a stainless steel sheet for exterior use such as a roof having excellent anti-glare properties and color tone.

[0014]

The present invention will be described below in more detail. First,
The reasons for limiting the components and surface properties of the stainless steel used in the present invention will be described.

C: If it is more than 0.02%, Cr carbides are formed by heat treatment during the production, so that the corrosion resistance is reduced.
Therefore, the amount of C was limited to 0.02% or less.

Cr: An essential component for imparting corrosion resistance, but if less than 17%, it rusts due to long-term exposure to the atmosphere. On the other hand, if it exceeds 35%, ductility and toughness are significantly reduced, and the productivity of a thin plate is significantly impaired. Therefore, the content of Cr is limited to 17 to 35%.

Mo: effective in improving pitting corrosion resistance,
If it is less than 5%, the tendency of pitting corrosion to occur in air exposure increases. On the other hand, when the content exceeds 4.0%, the hot workability is significantly reduced. Therefore, the content of Mo is set to 0.5 to 4.0.
%.

The contents of Cr and Mo are expressed by weight% (Cr +
The index represented by 3Mo) is preferably 26 to 40.

In order to ensure the effect of improving the corrosion resistance of Cr,
The addition of Nb, Ti and V is effective. In the present invention, the addition amounts of Nb, Ti and V are limited as follows.

Nb: It is an element that combines with C to form carbides, suppresses precipitation of Cr carbides at grain boundaries, and is effective for improving corrosion resistance. If it is less than 0.1%, the effect of suppressing the formation of Cr carbide is small, and if it is more than 0.5%, the toughness is reduced. Therefore, the content of Nb is limited to 0.1 to 0.5%.

Ti: It is an element that combines with C to form carbides, suppresses precipitation of Cr carbides at grain boundaries, and is effective for improving corrosion resistance. If it is less than 0.1%, the effect of suppressing the formation of Cr carbide is small, and if it is more than 0.5%, the toughness is reduced. Therefore, the content of Ti is limited to 0.1 to 0.5%.

V: V is an element that combines with C to form carbides, suppresses precipitation of Cr carbides at grain boundaries, and is effective in improving corrosion resistance. If it is less than 0.05 %, the effect of suppressing the formation of Cr carbide is small, and if it is more than 0.5%, the toughness is reduced. Therefore, the content of V is limited to 0.05 to 0.5%.

Si: added as a deoxidizer, 0.05
%, The effect is small, and if it exceeds 1.0%, the mechanical properties are adversely affected. Therefore, the additive amount of Si is 0.1.
It was limited to 05 to 1.0%.

Mn: If it exceeds 0.5%, the corrosion resistance decreases. On the other hand, if it is less than 0.05%, economic efficiency is impaired. Therefore, the addition amount of Mn is limited to 0.05 to 0.5%.

Al: added as a deoxidizing agent, but 0.00
If it is less than 5%, the effect is small, and if it exceeds 0.2%, the mechanical properties are adversely affected. Therefore, the addition amount of Al is limited to 0.005 to 0.2%.

It is necessary to dull a stainless steel plate having the above chemical composition in order to impart corrosion resistance and anti-glare properties. When the surface roughness (Ra) due to the dulling process is smaller than 0.5 μm, if the incident angle of sunlight is smaller than 60 °, glare is felt. On the other hand, the surface roughness is 10.
If it exceeds 0 μm, contaminants floating in the atmosphere during exposure to the atmosphere accumulate, and the corrosion resistance is extremely reduced. Therefore, the surface roughness was limited to 0.5 to 10.0 μm.

In the present invention, the stainless steel having the above-described components and surface properties is subjected to the following treatment to produce an exterior stainless steel having both antiglare property and corrosion resistance.

First, the stainless steel is subjected to a heating and cooling treatment. If the heating temperature exceeds 900 ° C, the whiteness of the steel sheet is high, it becomes a whitish plate, and the generation of oxide scale tends to be uneven, and in addition, it reacts remarkably with the high-temperature alkali molten salt. Prone. When the heating temperature is lower than 600 ° C., the softening of the dulled portion is insufficient, and surface defects such as collapse generated by the dulling process cannot be removed by pickling, resulting in a hard material having low corrosion resistance. Therefore, the heating temperature was limited to 600 to 900 ° C.

In cooling after heating, the cooling rate is 2 ° C. /
If the time is longer than sec, the cooling rate is limited to 2 ° C./sec or more because the toughness decreases. The lower the cooling stop temperature, the better, preferably 450 ° C. or less.

Next, an electrolytic treatment is performed in a neutral salt. During ~
As the salt, sodium sulfate or the like can be preferably used.
Wear. Regarding the electrolysis conditions, electrolysis in neutral salt solution
Current value is 1 A / dm^Two If less, take time to descaling
In short, 20A / dm^Two Above which the economy is low
Down. Therefore, the electrolytic current value is set to 1 to 20 A / dm. ^Two 
Limited to. The electrolysis time should be 10 to 120 sec.
Is good.

The electrolytic treatment alone in the above neutral salt is insufficient in corrosion resistance. Therefore, the surface of the stainless steel plate is immersed in an acid to passivate the surface. The acid used is preferably a mixed acid of nitric acid and hydrofluoric acid or nitric acid. Mixed acid temperature 40-80
° C, concentration 5-25%, nitric acid temperature 30-70 ° C, concentration 8
It is good to be ~ 20%. Note that the immersion time may be appropriately selected.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments.

Example A steel having the chemical composition shown in Table 1 was melted and hot-rolled to obtain a steel plate having a thickness of 4 mm. 1
After performing a quenching heat treatment at 000 ° C. × 10 min, the oxide scale was removed by pickling. These steel sheets were cold rolled to 0.8 mm, and the final pass was rolled with dull rolls having a surface roughness of 4 to 20 μm. The dulled steel sheet was treated in the steps shown in Table 2. The annealing conditions are 400 to 100.
0 ° C, furnace in 120s, 40 minutes in alkali molten salt immersion
Using a molten salt of (NaOH + NaNO ₃ ) at 0 ° C.,
20% Na ₂ SO at 70 ° C for neutral salt electrolysis
Electrolysis was performed for 20 seconds using the _four solutions. Table 3 shows the results of measuring the whiteness, glossiness, pitting potential and impact value of the final product.

As is apparent from Table 3, the steel sheet according to the present invention has excellent corrosion resistance and anti-glare properties, and the color tone is almost the same as that of the steel sheet which has been dulled and bright annealed.

The gloss was measured using a gloss meter under the condition of an incident angle of 20 °.

The whiteness can be measured using L, a, b using a colorimeter.
Was calculated by the Hunter formula W (Lab) = 100 − [(100−L) ² + a ² + b ² ] ^1/2 .

The impact value was evaluated by a value tested at room temperature using a subsize 2 mm V notch Charpy test piece.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

[Table 3]

[0041]

According to the present invention, the chemical composition of stainless steel is limited to a specific range to secure long-term corrosion resistance during exposure to the atmosphere, and to reduce the decrease in corrosion resistance due to dull processing for imparting antiglare properties. This was avoided by devising the conditions of cooling and subsequent electrolysis in a neutral salt solution and the acid method, and a low whiteness stainless steel sheet excellent in corrosion resistance and anti-glare properties was obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location C25F 1/06 C25F 1/06 B (72) Inventor Masaaki Ishikawa Wakihama Kaigandori, Chuo-ku, Kobe-shi No. 88 Kawasaki Steel Corporation Hanshin Factory (72) Inventor Masayuki Hino No. 2-88 Wakihama Kaigandori, Chuo-ku, Kobe Kawasaki Steel Corporation Hanshin Factory

Claims (3)

(57) [Claims] (1) In terms of% by weight, C: 0.020% or less, Cr:
17.0 to 35.0%, Mo: 0.5 to 4.0%, Cr
+ 3Mo: 26 to 40%, Si: 0.05 to 1.0%,
Mn: 0.05-0.5%, Al: 0.005-0.2
%, The balance being Fe and other unavoidable impurities, a steel sheet having a surface roughness (Ra) of 0.5 to 10.0 μm is heated to 600 to 900 ° C. and then cooled at a cooling rate of 2 ° C./sec or more. Cool, 1-20 A / dm in neutral salt solution
^A method for producing an exterior stainless steel sheet having both anti-glare properties and corrosion resistance, characterized by performing electrolysis under the conditions of ² , and thereafter immersing the same in a mixed acid of nitric acid and hydrofluoric acid or nitric acid. 2. Nb: 0.1-0.5%, Ti: 0.1-
The method for producing an exterior stainless steel sheet having both antiglare properties and corrosion resistance according to claim 1, which contains one or more elements of 0.5% and V: 0.05 to 0.5%. 3. The cooling stop temperature in the cooling step is 450 ° C.
The method for producing a stainless steel sheet for exterior use having anti-glare properties and corrosion resistance according to claim 1 or 2, which is as follows.