JPS58100660A - Austenitic stainless steel plate for coloring - Google Patents

Abstract

PURPOSE:To obtain an austenitic stainless steel causing no color shading in a chemical coloring method by adding specified amounts of C, Si, Mn, P, Ni and Cr to a steel. CONSTITUTION:The composition of an austenitic stainless steel plate for coloring is composed of, by weight, <0.08% C, 1-2% Si, <2% Mn, <0.04% P, <0.03% S, 8-10.5% Ni, 18-20% Cr and the balance Fe with inevitable impurities. Since the steel contains 1-2% Si, Si is distributed uniformly and densely in the surface layer of the plate. Accordingly, even if the dew point is slightly changed during annealing, the whole surface potential and a coloring oxidation reaction related to the surface potential are made uniform to prevent color shading.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stainless steel sheet that eliminates the occurrence of color unevenness when colored by a chemical coloring method.

BACKGROUND ART Conventionally, a method of coloring stainless steel by oxidizing the stainless steel with an oxidizing treatment liquid has been used. According to this method, the color tone can be adjusted to various colors by adjusting the coloring potential during the oxidation treatment, and thus colored stainless steel sheets of various colors have been manufactured using this method. However, in order to make the color tone of the stainless steel sheet uniform and the same every time using this method, it is necessary to keep the coloring potential constant, to clean the steel sheet surface tmv, and to make the concentration and temperature distribution of the treatment liquid uniform. There is. For this reason, conventionally, when coloring, pretreatments such as degreasing and electrolytic polishing were performed before coloring, and stirring was performed during the coloring process.

However, the coloring potential in the above method employs a method in which the surface potential of the entire steel plate is controlled by a mixed potential, and it is not possible to control the surface potential of individual parts. Therefore, even if the coloring potential is kept constant, if there are parts of the steel plate with different surface potentials, the oxidation reaction in those parts will be different from other parts, causing the problem of color unevenness. Ta.

Regarding this color unevenness problem, various studies have been done in the past from the aspect of coloring technology, but the reality is that there is still no fundamental solution, and for this reason, the development of a stainless steel plate with a uniform overall surface potential has been developed. was desired.

Among such stainless steel plates, the present invention particularly aims to provide an austenitic electrostatic detection stainless steel plate.

Regarding conventional austenitic cold-rolled stainless steel sheets,
SUS 304 with BA finish is used to manufacture colored stainless steel sheets. However, in the case of 5US304 as well, if the color tone was controlled by the coloring potential, color unevenness occurred, which significantly reduced the commercial value.

The inventors conducted various investigations into the causes of this color unevenness, and found that the color unevenness occurs due to non-uniform concentration of Si in the steel to the surface layer of the steel sheet during annealing, resulting in non-uniform surface potential. It has been found.

That is, when a 5US304 cold-rolled steel sheet is brightly annealed, the components in the steel are concentrated in the surface layer of the steel sheet. This concentration generally changes depending on the annealing conditions, so when annealing, conventional temperature, time,
The composition and dew point of the atmospheric gas were kept constant.

However, it is difficult to keep the dew point constant in a large furnace such as a bright annealing furnace, and fluctuations in the dew point during annealing cannot be avoided.

On the other hand, according to the research conducted by the present inventors, the concentration of St in steel in the surface layer of the steel sheet is significantly influenced by the dew point of the atmospheric gas, and easily changes due to fluctuations in the dew point. For example, 9 content is 0.51
Weight% of 5US304 cold rolled steel plate N2: N2=3
: Bright annealing was carried out in the atmospheric gas of 1 at different dew points, and when the SL concentration state of the surface layer was investigated using an ion microanalyzer, it changed markedly depending on the dew point, as shown in FIG. Therefore, if the dew point changes during annealing as described in 5 above, the steel plate 1
1! The Si distribution on the surface becomes non-uniform, causing a difference in surface potential, and as a result, a difference occurs in the oxidation reaction during coloring, resulting in uneven color.

In the present invention, since color unevenness occurs due to such causes,
The object of the present invention is to provide an austenitic stainless steel sheet in which Si in the steel is uniformly concentrated on the surface layer of the steel sheet even if there is a slight change in dew point during annealing.

The present inventors developed a steel composition of 5US304, with the Q components other than Si kept unchanged, and when the Si content was increased (over 1%), the dew point of the atmospheric gas slightly changed during bright annealing. At f! degrees, there is almost no difference in the degree of Si concentration fK on the steel plate surface layer, and it was found that color unevenness does not occur even when chemically colored.However, when it exceeds 2%, color unevenness occurs. However, it has been found that the upper limit should be 2% or less because it causes various difficulties during manufacturing and also deteriorates the material properties.

Therefore, the stainless steel plate for chemical coloring provided by the present invention has C: 0.08% or less and S: 1 by weight.
% more than 2%, Ma: 2.00% or less, P: 0.0
40% or less, S: 0.030% or less, Ni: 8.0-1
0.50%, Cr: 18.00 to 20.00 or less, the balance being iron and unavoidable impurities in an austenitic stainless steel sheet.

As mentioned above, increase the K content to more than 1% but not more than 2%.The reason why the Si concentration becomes more uniform than K is because as the Si content increases, the difference in Si concentration at each dew point becomes smaller, and the dew point fluctuates slightly. This is thought to be because the degree of Si concentration does not change depending on the degree of concentration. For example, when a stainless steel plate with a Si content of around 5US304 is brightly annealed by changing only the dew point of the atmospheric gas and keeping other conditions constant, and the degree of Si concentration on the surface of the steel plate is investigated using an ion microanalyzer, the results are shown in Figure 2. I'll show you 5
ic Si content is not affected by large dew point fluctuations. Therefore, in the case of 5US304 with a Si content of tO% or less, the Si distribution on the steel plate surface becomes partially uneven due to brightness dullness, but as in the present invention (if the Si content exceeds tO%, the Si distribution becomes almost uniform). it is conceivable that.

Next, the present invention will be explained with reference to examples.

An austenitic cold-rolled stainless steel sheet with the composition shown in Table 1 was brightly annealed under the conditions shown in the fsz table, and then Cr0s
The sample was immersed in a 80C mixed acid containing 250%, HzSO4,500flA, and colored until the desired color tone was obtained while monitoring the coloring potential. Thereafter, this colored stainless steel plate was immersed in a mixed acid of phosphorus and chromic acid, and the colored film was cured by applying electricity to obtain a colored stainless steel plate. Next, the color tone and color unevenness of the obtained colored stainless steel sheet were investigated. The color unevenness was visually divided into normal areas and uneven color areas, and the color difference between the areas was measured using a color analyzer. Table 3 shows the results of this survey.

Table 2 wc Table 3] (Note) Color unevenness judgment criteria ○ Color difference by color analyzer LO or less However, when it exceeds LO%, color unevenness does not occur.

As described above, even though there is a slight dew point variation during annealing of the steel plate of the present invention, 81 is uniformly concentrated on the surface layer of the steel plate, so the overall surface potential and the accompanying coloring oxidation reaction are also uniform. Color unevenness will no longer occur.

[Brief explanation of the drawing]

Figure 1 shows a 5US304 cold-hardened steel sheet with a Si content of 0.51 weight, brightly annealed in an atmospheric gas of y Hz:Nz-3:1, and the state of the separate fabrication of the steel sheet surface layer was investigated using an ion microanalyzer. It is. FIG. 2 shows the influence of the atmospheric gas dew point when bright annealing a stainless steel plate with a Si content of about 5US304. Figure 1 @ @ Itl yo so reason (A) ZI! I Sj order/11t (%)

Claims (1)

[Claims] C: 0.08% or less, Si: more than 1% and 2% by weight
Below, Pigeon: 5&OO% or less, P: 0.040% or less, S
: 0.030% or less, Ni: 8. O~10.50%, C
An austenitic stainless steel plate for coloring consisting of r: 1&OO to 20.00% or less, the balance being iron and unavoidable impurities.