JP3412564B2 - Stainless steel sheet excellent in surface smoothness and method for producing the same - 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 high gloss and image clarity and excellent surface smoothness, and a method for producing the same. More specifically, the present invention relates to a stainless steel sheet having high gloss and image clarity and excellent surface smoothness as it is temper-rolled without depending on a polishing process, and a method for producing the same.

[0002]

2. Description of the Related Art As stainless steel sheet products, there are BA products, 2B products and polished products defined in JIS. These stainless steel sheet products are required to have high surface gloss and high image clarity. BA products and 2
The product B has its surface gloss ensured by cold rolling. The abrasive product is manufactured by using a BA product or a 2B product as a raw material and performing a polishing process with an abrasive cloth or a feather cloth to obtain particularly excellent gloss and image clarity.

[0003] The work of polishing the quilt is carried out by using a quilt having a fine grain of 1000 or 2000. Therefore, the polishing amount in the thickness direction of the steel sheet is extremely small,
It is up to about 0.5 μm. On the other hand, the surface of the stainless steel plate after cold rolling such as temper rolling has an average roughness Ra of 0.05 to 0.2 μm and a maximum roughness Rmax of 0.5 to 0.2 μm.
It is 2.0 μm. Such roughness is due to residual surface irregularities during pickling of hot-rolled steel strip before cold rolling, oil pits (fine oil pools) during cold rolling, and roll transfer flaws (transfer flaws of roll polishing eyes, Indentation), scratches, annealing after cold rolling
This is due to recess defects such as etch pits due to pickling. Therefore, in order to remove these defective portions by polishing, it is necessary to polish all the convex portions (trapezoidal plane portions) that occupy most of the surface, and it takes a huge amount of time such as increasing the number of polishing.

Therefore, various measures have been taken to reduce irregularities on the surface of the steel sheet in the cold rolling process.

For example, JP-A-5-96309 and JP-A-5-104110 disclose a cold rolling roll having a specific surface roughness, and JP-A-6-170432 discloses a pre-cold rolling roll. The descaling method for reducing surface irregularities during pickling of hot-rolled steel strip is disclosed in Japanese Patent Laid-Open No. 7-1001 and a manufacturing method for defining roll surface roughness and cold rolling conditions is disclosed in Japanese Patent Laid-Open No. 9-155404. Each of the publications proposes a method of increasing the polishing efficiency by changing the surface roughness form.

[0006]

However, Japanese Patent Laid-Open No. 6-1 is used.
The method described in Japanese Patent No. 70432 requires significant facility remodeling, and the surface finish state may change depending on the rolling conditions in the subsequent cold rolling, so that sufficient glossiness may not be obtained. On the other hand, the method described in Japanese Patent Laid-Open No. 7-1001 does not have sufficient gloss because of the presence of minute recesses having a shallow depth. Further, the methods described in JP-A-5-96309, JP-A-5-104110, and the like are to roll by a roll having the direction of the polishing grain as the roll axis direction on average, and the gloss is originally obtained. This is a rolling method for obtaining the same gloss as rolling using a small diameter roll in rolling when the roll diameter is large, but the glossiness and image clarity values are not necessarily higher than when using a small diameter roll. .

Even if the surface roughness of the cold-rolled sheet is reduced to improve the smoothness, the smoothness is lowered in the subsequent finish annealing step or finish annealing / pickling step. Therefore, tempering after finish annealing is important for ensuring smoothness. However, in temper rolling, the rolling reduction was less than about 2%, and there was a limit to the improvement of smoothness.

As described above, various improvements have been made in the past, but although it has the effect of reducing the surface roughness of the cold-rolled sheet and improving the efficiency of the polishing process, it does not have the effect of temper rolling finish. Until now, it was not possible to obtain the high gloss and high image clarity comparable to those of polished products, and further improvement was necessary.

The object of the present invention is to solve the above-mentioned problems of the prior art, and to achieve a high glossiness comparable to that of a polished product without a polishing step.
It is an object of the present invention to provide a surface condition of a stainless steel plate capable of obtaining high image clarity and a manufacturing method thereof.

[0010]

Means for Solving the Problems In the temper rolling after finish annealing, the present inventor investigated and studied the relationship between rolling conditions, glossiness and image quality in detail, and obtained the following findings. Hereinafter, the value measured by a gloss meter is referred to as gloss, and the evaluation by visual observation is referred to as visual gloss or simply gloss.

A. In temper rolling without lubrication, 1
The higher the pass reduction rate, the higher the glossiness. However, if the pass reduction rate is too high, the flatness tends to be impaired, and sufficient glossiness cannot always be obtained.

B. The glossiness is improved by increasing the difference between the exit speed of the rolled material and the roll peripheral speed.

C. The higher the glossiness is, the more the glossiness is improved. However, even if the glossiness is the same, the glossiness is lowered if the average inclination angle (θa) of roughness represented by the following formula (1) is large. Less than,
The average inclination angle of this roughness is also simply referred to as the average inclination angle.

[0014]

[Equation 2]

FIG. 1 is a schematic diagram showing a steel plate surface condition for explaining the average inclination angle. Reference numeral ΔYi is a vertical distance between the steel plate surfaces at two adjacent points, ΔX is a measurement pitch, and L is a measurement pitch.
Indicates the reference measurement length. As shown in FIG. 1, the average inclination angle is calculated from the equation (1) by dividing the reference measurement length L into N by ΔX: 2 μm, measuring ΔY of each divided section.

E. The smaller the center line average roughness (Ra), the higher the glossiness, but the larger the average inclination angle, the lower the glossiness.

F. Under temper rolling conditions in which the tensile stress on the inlet side (hereinafter referred to as the inlet tension) and the tensile stress on the outlet side (hereinafter referred to as the outlet tension) are approximately equal, the steel plate has a wrinkle-like wrinkle or a wavelength of 1 Waviness of about several mm is likely to occur, the centerline average roughness and the average inclination angle increase, and the glossiness decreases.

G. A steel sheet having an average inclination angle of less than 0.3 ° and a center line average roughness of 0.04 μm or less has glossiness comparable to that of a polished product.

H. The glossiness is improved by increasing the difference between the entrance tension and the exit tension.

I. Reduction ratio r, inlet tension σ _F and outlet tension σ
_Keeping the ratio with _B (σ _F / σ _B , hereinafter referred to as tension ratio) and the ratio of the advance rate f and the reduction rate r (f / r, hereinafter referred to as advance rate ratio) within appropriate ranges. Then, temper rolling is performed to obtain a steel sheet having gloss equivalent to that of a polished product. The reduction ratio r and the advance ratio f are expressed by the following equations.

R = (t ₀ −t ₁ ) / t ₀ × 100 (%) f = (V _O / V _R −1) × 100 (%) where t ₀ : entrance side plate thickness, t ₁ : exit side plate thickness, V _O: exit side speed of the rolled material, V _R: roll peripheral speed.

The present invention has been completed based on the above findings, and its gist is as follows. (1) On the surface of a temper-rolled steel sheet, the average inclination angle (θa) of roughness is less than 0.30 °, and the centerline average roughness (Ra) is 0.040 μm or less. A stainless steel plate with excellent surface smoothness.

(2) In the temper rolling process after finish annealing, the ratio (σ) between the inlet side tension σ _F and the outlet side tension σ _B when the reduction ratio of one pass is 0.5% or more and 1.0% or less. _F / σ _B ) is 0.
Temper rolling with a ratio (f / r) of the advance rate f and the reduction rate r of 0.7 or more and 1.0 or less or 0.0 or more and 0.3 or less with 1 or more and 0.5 or less or 2 or more and 10 or less. A method for producing a stainless steel sheet having excellent surface smoothness, which comprises:

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION The stainless steel sheet of the present invention is a hot-rolled steel sheet that is cold-rolled into a thin steel sheet, and after annealing, a scale is formed on the surface of the steel sheet. Washing is performed, and if necessary, cold rolling, annealing and pickling are performed again, and then temper rolling is performed in a single pass or a plurality of passes at a predetermined reduction ratio to impart mechanical properties. The temper rolling is performed in a non-lubricated state or a lubricated state, but it is desirable to perform the temper rolling in a non-lubricated state.

The stainless steel sheet of the present invention defines the surface condition of a steel sheet that has been temper-rolled and finished. Further, the manufacturing method defines the temper rolling conditions, and after the cold rolling under normal conditions, annealing, and optionally a step of pickling, which has been carried out once or more times, the tempering conditions are changed. By applying, the surface condition of the steel sheet specified in the present invention can be obtained.

The reasons for limiting the stainless steel sheet and the method for producing the same according to the present invention will be described below. In order to obtain a stainless steel sheet having excellent surface smoothness, the center line average roughness (Ra) in each of the width direction and the rolling direction is 0.04 μm or less on the surface of the temper-rolled finish steel sheet, and the width direction It is important that the respective average inclination angles (θa) in the rolling direction and the rolling direction are less than 0.3 °.

If the center line average roughness (Ra) or the average inclination angle is large, the glossiness decreases. The center line average roughness (Ra) is 0.04 μm or less, and the average inclination angle (θa) is 0.3.
By setting it to be less than 0 °, a highly glossy steel sheet having high image clarity comparable to that of a polished product can be obtained. Preferably, the center line average roughness (Ra) is 0.025 μm or less, and the average inclination angle (θa) is less than 0.15 °.

To obtain the stainless steel sheet of the present invention,
In temper rolling, the rolling reduction in one pass is 0.5% or more,
In one or more passes of 1.0% or less, the tension ratio is 0.
Rolling is performed at 1 or more and 0.5 or less or 2 or more and 10 or less and an advanced ratio of 0.7 or more and 1.0 or less or 0.0 or more and 0.3 or less. The diameter and surface roughness of the roll used for temper rolling are not particularly limited, but may be about the commonly used roll, for example, the diameter is 500 to 900.
The center line roughness in the roll width direction is 0.01 to 0.
A roll of about 04 μm can be used.

When the rolling reduction is less than 0.5%, the transfer of the roll roughness is insufficient and excellent gloss cannot be obtained. If the rolling reduction is more than 1.0%, the flatness and shape of the rolled material are likely to collapse, and oxides of the rolled material are likely to adhere to the roll surface, so that sufficient glossiness cannot be obtained. Therefore, the rolling reduction is 0.5% or more and 1.0% or less.

When the tension ratio is less than 0.1, rolling troubles such as meandering and plate breakage are likely to occur, and when it is more than 0.5 and less than 2, gloss improvement is insufficient, and when it is more than 10, meandering and plate breakage occurs. Rolling troubles such as are likely to occur.
Therefore, the tension ratio is 0.1 or more and 0.5 or less, or 2 or more and 10 or less. Preferably, the tension ratio is 0.15 or more and 0.4 or less, or 2.5 or more and 4 or less.

Next, the reason why the advanced ratio is set to 0.7 or more and 1.0 or less or 0.0 to 0.3 or less will be described. FIG. 2 is a rolling direction cross-sectional view schematically showing the relative sliding direction between the roll and the steel plate surface during temper rolling, and FIG. 2 (a) shows the case where the advance ratio ratio is about 0.5. FIG. 7B shows the case where the advanced ratio is 1.0, and FIG. 7C shows the case where the advanced ratio is 0. In FIGS. 1A, 1B, and 1C, reference numerals 1 and 2 denote steel plates, N denotes a neutral point, l denotes a contact arc length, O denotes a roll axis center, and θ denotes a contact angle. A is the roll rotation direction,
Arrow B represents the rolling direction, and arrow C represents the relative sliding direction between the roll and the steel plate surface.

As shown in FIG. 2 (a), the advanced ratio is 0.
In the case of around 5, the neutral point N at which the roll peripheral velocity and the velocity of the steel sheet surface match is located at the substantially central position in the contact arc, and the relative slip direction is reversed at the neutral point, so that the slip length in the same direction is It gets shorter. On the other hand, in FIGS. 2B and 2C,
In each case, the neutral point moves to the outgoing side and the incoming side in the contact arc, the sliding length in the same direction becomes longer than in Fig. 2 (a), and the smoothing of the steel plate surface by the transfer of roll roughness is efficiently performed. Done.

The advanced ratio is 0.7 to 1.0 or 0 to 0.
By setting 3, the relative slip length between the roll and the rolled material becomes long, the function of smoothing the surface of the rolled material with the smooth surface of the roll works, and the effect of transferring the roughness of the roll by compressing the rolled material with the roll Smoothing can be enhanced. By this transfer action, even minute waviness such as crease wrinkles and ridging having a wavelength of 1 to several mm can be smoothed.

If the ratio of the advanced ratio is more than 0.3 and less than 0.7, the smooth surface of the roll is not sufficiently smoothed by the relative slip between the roll and the rolled material, and a target smooth flat surface is obtained. I can't. Further, when the advance ratio is less than 0.0, that is, when the advance ratio is negative and when the advance ratio is larger than 1.0, the neutral point is not in the contact arc between the rolled material and the roll, and the slip state is complete. For this reason, it is difficult to control the speed of the rolled material and the roll, and the rolling becomes unstable, causing an excessive speed difference and causing slip defects.

The tension on the inlet side and the outlet side is 25 kgf / m.
Beyond m ^2, unwinding of the coil, or slippage occurs in the coil layer at the time of winding, the surface flaws such as tightening flaw occurs, the tension of the entry side and the delivery side 25 kgf / m
It is desirable to be less than m ² .

[0036]

[Example] 2H equipped with a roll having a diameter of 800 mm and a surface roughness Ra of 0.01 μm or less as a temper rolling mill
Using i rolling mill, material is SUS430 and plate thickness is 0.6m
m after cold rolling for finish annealing / pickling material and material is SU
In S304, the bright annealed material having a plate thickness of 0.6 mm after cold rolling was used as a test material, and one pass non-lubricated temper rolling was performed at a rolling speed of 100 m / min. Table 1 shows the main specifications of the test material,
Table 2 shows the temper rolling conditions.

[0037]

[Table 1]

[0038]

[Table 2]

As shown in Table 2, the rolling reduction is in the range of 0.4 to 1.2% by changing the outlet plate thickness, and the tension ratio is 0.16 to 0.1 in which the inlet tension and the outlet tension are changed. The range was set to 3.3.

The outgoing steel plate speed during rolling was measured, the advanced ratio was determined, and the advanced ratio was calculated. On the surface of the steel sheet after temper rolling, the surface roughness, the average inclination angle and the image clarity were measured, and the glossiness was evaluated by visual observation. As the surface roughness, the center line average roughness in the rolling direction and the width direction was measured based on JISB0601. The average inclination angle is, as shown in FIG.
Assuming that L is 12.5 mm and ΔX is 2 μm, the uneven heights ΔY at 6250 points were measured in the rolling direction and the width direction, respectively, and calculated from the formula (1). The degree of image resolution is JIS 868
Based on No. 6, the value in the plate width direction was measured. The glossiness by visual observation was evaluated according to the following three ranks, and ◯ and ⊚ passed. The results are shown in Table 3.

<Glossiness Criteria> Δ: Level equivalent to that of the surface after conventional temper rolling, ◯: Gloss improved compared to the surface after conventional temper rolling, and equivalent to a low-grade polished product Level, ⊚: The glossiness is significantly improved compared to the surface after conventional temper rolling, and is a level equivalent to a high-grade polished product.

[0042]

[Table 3]

As shown in Table 3, the test No. In Examples 1 to 12 of the present invention, the image clarity was 85 or more, and the high gloss of a low grade or more of the abrasive product was obtained. In particular, the test No. 2, 4 ~
In Examples 10 and 12 of the present invention, the image clarity was 90 or more and the gloss equivalent to the high grade of the abrasive product was obtained. No. The comparative examples of 13 to 19 had the same level of gloss as the surface after the conventional temper rolling.

[0044]

EFFECTS OF THE INVENTION According to the present invention, a stainless steel plate having a high gloss and a high image clarity comparable to a polished product and excellent in smoothness can be obtained without passing through a polishing process. Therefore, it is possible to remarkably improve the production efficiency of the stainless steel plate having high gloss and high image clarity.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a steel plate surface condition for explaining an average inclination angle.

FIG. 2 is a rolling direction sectional view schematically showing a relative sliding direction between a roll and a steel sheet surface during temper rolling, and FIG. 2 (a) shows the case where the advance ratio is about 0.5. (B) shows the case where the advanced ratio is 1.0, and (c) of the figure shows the case where the advanced ratio is 0.

[Explanation of symbols]

1: Roll, 2: Steel plate, N: Neutral point, O: Roll axis center, θ: Contact angle, 1: Contact arc length, L: Standard measurement length.

Claims (2)

(57) [Claims] 1. On the surface of a steel plate that has been temper-rolled and finished,
The average inclination angle (θa) of roughness expressed by the following equation (1) is 0.30
Less than ° and centerline average roughness (Ra) of 0.040 μ
A stainless steel sheet having excellent surface smoothness characterized by being m or less. [Equation 1] However, ΔY _i : reference measurement length L in the width direction and the rolling direction
Is the distance in the vertical direction of the steel plate surface at two adjacent points when N is divided by the pitch ΔX, ΔX: 2 μm, N: the number of divisions (= L / ΔX). 2. In the temper rolling step after finish annealing, 1
The pass reduction ratio is 0.5% or more and 1.0% or less, and the ratio of the inlet side tension σ _F to the outlet side tension σ _B (σ _F / σ _B ) is 0.1 or more and 0.5 or less, or 2 or more. When the ratio is 10 or less, the ratio (f / r) between the advanced rate f and the reduction rate r is 0.7 or more and 1.0 or less, or 0.
A method for producing a stainless steel sheet having excellent surface smoothness, which comprises performing temper rolling at 0 or more and 0.3 or less.