JP3297798B2 - Manufacturing method of austenitic stainless steel sheet for roll forming - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an austenitic stainless steel sheet for roll forming having excellent pocket wave resistance.

[0002]

2. Description of the Related Art Usually, in order to manufacture a cut sheet-shaped steel sheet or a steel strip of austenitic stainless steel for roll forming (hereinafter simply referred to as a steel sheet), a slab is subjected to hot rolling. Annealing and pickling were performed, cold rolling was performed once, or cold rolling was performed twice with intermediate annealing, followed by final annealing and, if necessary, skin pass rolling.

When performing roll forming on an austenitic stainless steel sheet manufactured by this method, it has been a problem that pocket waves are generated and the appearance of the processed product is impaired. A pocket wave is, as shown in FIG.
When a steel sheet is rolled, a part of the surface of the steel sheet becomes uneven.

As a method of manufacturing an austenitic stainless steel sheet which does not generate pocket waves, Japanese Patent Application Laid-Open No. 4-168227 discloses a method in which cold rolling, final annealing, and skin pass rolling are performed, and then a temperature of 300 to 700 ° C. is applied. There is disclosed a method of performing an aging heat treatment for at least seconds and not more than 50 hours. However, this method has a drawback in that it requires an aging heat treatment, and requires one additional step, which requires extra labor and cost. Further, in this method, since the aging heat treatment is performed after the skin pass rolling step, the gloss of the steel sheet obtained by the skin pass rolling is lost. Further, this method has a disadvantage that the number of pickling steps for removing oxide scale generated on the surface of the steel sheet by the aging heat treatment is increased.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method capable of producing an austenitic stainless steel sheet for roll forming excellent in pocket wave resistance without aging heat treatment.

[0006]

The gist of the present invention resides in the following method for producing an austenitic stainless steel sheet for roll forming.

"In weight%, C: 0.08% or less, N:
0.04 to 0.2%, Mn: 0 to 2%, Si: 0.1 to
2%, P: 0.04% or less, Ni: 7.5 to 10%, C
u: 0.1 to 3%, Nb: 0.1 to 0.8%, Mo:
The first cold rolling at a rolling reduction of 30 to 50% is performed on a hot-rolled austenitic stainless steel sheet having a chemical composition of 0.1 to 5%, Cr: 16 to 25%, and the balance being Fe and unavoidable impurities. After the application, 1000 ~ 1150 ℃ 1.5 ~
Intermediate annealing is performed for 10 minutes, and the temperature of the cold-rolled annealed sheet is reduced to 100 ° C. or less, and then the rolling reduction of 65 to 80% is performed.
The first cold rolling is performed, and then 1000 to 1150 ° C.
A method of producing an austenitic stainless steel sheet for roll forming, wherein the final annealing is performed for 1.5 to 10 minutes.

However, the total rolling ratio of the first and second cold rollings satisfies 78 to 88%, and the rolling ratios of the first and second cold rollings are (rolling ratio of the second cold rolling). ) / (Rolling rate of first cold rolling)> 1.4. As an example of the method of the present invention, after the final annealing, skin pass rolling at a rolling reduction of 0.3 to 0.7% can be performed. Thus, an austenitic stainless steel sheet for roll forming having a smooth surface and good gloss can be manufactured.

The “hot-rolled austenitic stainless steel sheet” before cold rolling has a composition specified above and is formed into a sheet by ordinary hot rolling. The thickness is about 2 to 4 mm. It may be one that has been subjected to annealing and pickling after hot rolling.

This steel sheet is subjected to a first cold rolling at a rolling rate of 30 to 50%. The “rolling ratio” here is defined as (thickness reduction by n-th cold rolling / thickness before n-th cold rolling) × 100 (in the present invention, n is 1 or 2). The cold rolling may be performed under ordinary conditions except for the rolling reduction, and for example, a hot rolled sheet at 100 ° C. or lower is rolled using a roll rolling mill.

[0011] After the first cold rolling, the cold rolled sheet is heated by an annealing line or the like, and is heated at 1000 to 1150 ° C for 1.5 to 1
Intermediate annealing is performed for 0 minutes. After the temperature of the cold-rolled annealed sheet after the intermediate annealing is lowered to 100 ° C. or less by air cooling or the like, the second cold rolling is performed under the condition of a rolling reduction of 65 to 80%.
At that time, the total rolling reduction of the first and second cold rolling was 78 to 88%, and (the rolling reduction of the first cold rolling).
/ (Rolling rate of second cold rolling)> 1.4. "Total rolling ratio" here means
(Thickness reduction by first and second cold rolling / thickness of hot rolled sheet before cold rolling) × 100.

[0012] After the second cold rolling, 1000 ° C to 1 ° C
A final anneal is held at 150 ° C. for 1.5-10 minutes.

As a step after the final annealing, skin pass rolling at a rolling ratio of 0.3 to 0.7% may be performed as necessary to smooth the surface of the steel sheet and to impart gloss. Skin pass rolling is not a special method except for the rolling rate. The temperature of the steel sheet at the time of skin pass rolling is preferably set to 100 ° C. or less.

The austenitic stainless steel sheet manufactured in the present invention is a material used for roll forming. For example, it is formed into a square wave shape or a spandrel shape using a roll forming device, and is used for applications such as stainless steel wall materials and roof materials.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described specifically.

In the present invention, "%" of the chemical composition is used.
Means "% by weight".

(1) Chemical composition C: C is an impurity element unavoidably mixed from a raw material to be dissolved or the like. The upper limit of the content is 0.
08%. If the amount exceeds this, the intergranular corrosion resistance is significantly reduced.

N: N has the effect of improving pocket wave resistance. In order to obtain the effect, it is necessary to contain 0.04% or more. However, if it exceeds 0.2%, the effect is not only saturated, but also the corrosion resistance and the cold formability deteriorate. Therefore, the content is 0.04 to 0.2
%.

Mn: Mn need not be added, but if added, the austenite phase can be stabilized and the amount of expensive Ni added can be reduced. In order to exhibit this stabilizing effect more, it is preferable to contain 0.5% or more. Also,
If the content exceeds 2%, roll formability and corrosion resistance deteriorate. Therefore, when Mn is added, the content is desirably 0.5 to 2%.

Si: Si is an element required as a deoxidizing agent for molten steel, and must be contained at least 0.1% or more. However, if the content exceeds 2%, the material becomes brittle and becomes hard during hot working, and the roll formability deteriorates. Therefore, the content is set to 0.1 to 2%.

P: P is an impurity element which is inevitably mixed from the raw material to be dissolved or the like. The upper limit of the content is 0.04%. If the amount exceeds this, hot workability and corrosion resistance deteriorate.

Ni: Ni is an element necessary for stabilizing the austenite structure. In order to obtain the effect, it is necessary to contain at least 7.5% or more. But N
When the content of i exceeds 10%, the pocket wave resistance tends to decrease. In addition, if expensive Ni is contained in an amount of 10% or more, the production cost increases. Therefore, the content was set to 7.5 to 10%.

Cu: Cu is an element for improving corrosion resistance. Austenitic stainless steel sheet produced by the method of the present invention may be used as a wall material or a roof material,
It is required to have excellent corrosion resistance. Therefore, Cu is contained. However, if the content is less than 0.1%, there is almost no effect of suppressing the progress of pitting corrosion,
It is necessary to contain 0.1% or more. If the content exceeds 3%, the roll formability deteriorates. Therefore,
The content was set to 0.1 to 3%.

Nb: Nb is an element added to improve corrosion resistance. When the content is less than 0.1%, the effect of suppressing the grain boundary precipitation of carbide is not recognized, and the corrosion resistance cannot be improved. If the content exceeds 0.8%, the amount of carbonitrides increases, and the roll formability deteriorates. Therefore, the content was set to 0.1 to 0.8%.

Mo: Mo is an element added for improving the corrosion resistance. In order to suppress the progress of pitting corrosion, use 0.
It is necessary to contain 1% or more. On the other hand, if the content exceeds 5%, the effect is saturated, and the steel sheet becomes hard and the roll formability deteriorates. Including more expensive Mo than 5% increases the production cost. Therefore,
The content was set to 0.1 to 5%.

Cr: Cr is an element added to improve corrosion resistance. In order to obtain the effect, it is necessary to contain 16% or more. However, when the content of Cr is 25
%, Not only the roll formability decreases, but also the production cost increases. Therefore, the content is 16 to 2
5%.

(2) Conditions for Twice Cold Rolling, Intermediate Annealing, and Final Annealing The present invention is characterized in that pocket cold resistance is improved by performing two cold rollings. The reason why the number of times of cold rolling is set to two is that the in-plane anisotropy | Δr | of the r value which is a value for evaluating the deep drawability of the cold-rolled annealed sheet can be reduced. When | Δr | is low, the pocket wave resistance of the steel sheet is improved. The steel plate that has been cold-rolled twice can reduce | Δr | as compared with the steel plate that has been cold-rolled once, and the pocket wave resistance can be further improved.

The first cold rolling reduction is 30 to 50%.
The reason is that if it is less than 30%, the effect of suppressing | Δr | is low, and a large pocket wave is generated during roll forming. Further, it is confirmed by experiments that the pocket wave becomes large when the ratio exceeds 50%.

The rolling rate of the second cold rolling is 65 to 65.
The reason for setting it to 80% is that if it is less than 65%, the effect of suppressing | Δr | is weakened, and a large pocket wave is generated during roll forming. It is also confirmed by experiments that the pocket wave becomes large when the ratio exceeds 80%.

Further, the total rolling ratio of the first and second cold rolling is 78 to 88% and (the rolling ratio of the second cold rolling).
It is necessary to satisfy the condition of / (rolling rate of the first cold rolling)> 1.4 because there is a possibility that a large pocket wave may be generated during roll forming if cold rolling that does not satisfy this condition is performed. Because there is.

FIG. 2 shows the rolling ratio of the first cold rolling, the rolling ratio of the second cold rolling, and the occurrence of pocket waves when intermediate annealing and final annealing are performed at 1080 ° C. to 1100 ° C. It is a thing. In the figure, ○ indicates that almost no pocket wave is generated and the pocket wave resistance is very good, Δ indicates that only a small pocket wave is generated, and the pocket wave resistance is good, and X indicates that a large pocket wave is generated. This indicates that the pocket wave resistance is poor. From FIG. 2, the rolling rate of the first cold rolling is 30 to 50%, the rolling rate of the second cold rolling is 65 to 80%, and the total rolling rate of the cold rolling is 78.
８８88% (the area between the curves in FIG. 2), (rolling rate of the second cold rolling) / (rolling rate of the first cold rolling)> 1.4 (in FIG. 2 It can be seen that the pocket wave resistance is good in the region below the straight line).

The temperatures of the intermediate annealing after the first cold rolling and the final annealing after the second cold rolling are both 1000 to 1000.
The range is 1150 ° C. If the temperature is lower than 1000 ° C., recrystallization may be insufficient and the effect of annealing may not be obtained.
If the temperature exceeds 0 ° C., the crystal grains may be too coarse and the roll formability may deteriorate. The annealing time was 1.5 to 10 minutes. If the time is less than 1.5 minutes, recrystallization is insufficient, and the austenitic stainless steel sheet may not be sufficiently softened. Also, annealing such as exceeding 10 minutes is unnecessary,
Not economic. Therefore, the annealing time was set to 1.5 to 10 minutes.

(3) Skin Pass Rolling The method of the present invention may include a step of subjecting the resulting steel sheet to skin pass rolling after final annealing, if necessary, in order to smooth the surface and improve gloss.

When skin pass rolling is performed, the rolling ratio of skin pass rolling is specified to be 0.3 to 0.7% in order to obtain a smoother and more glossy surface of the steel sheet without deteriorating pocket wave resistance. . If the rolling ratio is less than 0.3%, the smoothness and gloss of the surface of the steel sheet are almost the same as those in the case where skin pass rolling is not performed, and there is no point in performing skin pass rolling. When the rolling ratio exceeds 0.7%, the proportional limit and the proof stress of the steel sheet with respect to the tensile stress decrease, and the pocket wave resistance becomes poor.

[0035]

EXAMPLE A slab of austenitic stainless steel having the chemical compositions of A to Q shown in Table 1 was heated to 1200 ° C., and then hot-rolled to obtain a hot-rolled sheet having a thickness of 1.8 to 4.0 mm. Processed to.

[0036]

[Table 1]

Thereafter, the hot-rolled sheets A to N were subjected to the first cold rolling shown in Table 2 to be processed into cold-rolled sheets having a thickness of 1.0 to 3.0 mm. Intermediate annealing was performed at 1100 ° C. for 6 minutes. Thereafter, a second cold rolling shown in Table 2 was performed to form a cold-rolled annealed sheet having a thickness of 0.41 to 0.42 mm, and finally a final annealing was performed at 1800 to 1100 ° C. for 5 minutes to perform austenite. Finished into stainless steel sheet.

On the other hand, the O-Q hot-rolled sheets were not subjected to the first cold rolling and the intermediate annealing, but were subjected to the second cold rolling shown in Table 2 and the final annealing described above to obtain an austenitic stainless steel sheet. Finished.

The aging heat treatment after the final annealing was not performed on all the austenitic stainless steel sheets A to Q.

[0040]

[Table 2]

The austenitic stainless steel sheets A to Q manufactured by the above method are subjected to roll forming in the rolling direction 2 as shown in FIG. 1 to finish into a spandrel shape, and pockets formed in the formed product The relationship between the size of the wave 3 and the rolling reduction was investigated.

Table 2 shows the cold rolling reduction, the total rolling reduction, the wave height (hw), and the sheet thickness after the cold rolling. The position where the pocket wave was measured was the center of the flat portion where the pocket wave was most undulating. As a method of evaluating the size of the pocket wave, a wave height hw representing the sum of (the height of the pocket wave / the width of the pocket wave) per 1 m of the flat central portion of the molded article was used.

A steel plate having a wave height hw of less than 12 × 10 ⁻³ mm has good pocket wave resistance and a wave height hw of 12 × 1.
A steel sheet of 0 ^-3 mm or more was evaluated as having poor pocket wave resistance.

An austenitic stainless steel sheet having a wave height hw of less than 12 × 10 ⁻³ mm has excellent pocket wave resistance and can be sufficiently used as a material for roll forming.

Table 2 shows that the austenitic stainless steel sheet produced by the method of the present invention has excellent pocket wave resistance.

D prepared by the method of the invention described above,
Austenitic stainless steel sheets having chemical compositions of G, H, K and L were subjected to skin pass rolling at various rolling rates.

The pocket waves generated in these steel sheets, the gloss of the steel sheets, and the smoothness of the surface of the steel sheets were measured. The evaluation method of the pocket wave is the same as described above.
The evaluation of the gloss of the steel sheet was visually carried out. In Table 3, a sample determined to have normal gloss was indicated by ○, and a sample determined to have good gloss was indicated by ◎. Surface smoothness is JIS B0
The maximum height (Ry) of the surface roughness was measured according to 601 and those having a maximum height (Ry) of 1.3 μm or less were judged to have extremely smooth surfaces.

[0048]

[Table 3]

The surface of the steel sheet produced by the method of the present invention was very smooth and had good gloss. The surface of the steel sheet manufactured by the method of the invention and not subjected to skin pass rolling had normal smoothness and normal gloss. On the other hand, the steel sheet manufactured by rolling at a rolling reduction of 0.7% or more in the skin pass rolling specified by the method of the present invention had a very smooth surface and good gloss, but all had a hw of 12 ×. 1
At 0 ^-3 mm or more, a large pocket wave occurred, so the product was defective.

[0050]

According to the method of the present invention, an austenitic stainless steel sheet for roll forming excellent in pocket wave resistance can be manufactured without performing aging heat treatment after annealing. Cost can be reduced. The austenitic stainless steel sheet manufactured by the method of the present invention hardly generates pocket waves during roll forming, so that the product yield can be improved. Furthermore, by performing skin pass rolling as needed, an austenitic stainless steel sheet for roll forming having a smooth and glossy surface can be manufactured.

[Brief description of the drawings]

FIG. 1 is a view showing a molded product of an austenitic stainless steel sheet finished in a spandrel shape.

FIG. 2 is a diagram showing the relationship between the rolling ratio of the first cold rolling, the rolling ratio of the second cold rolling, and the degree of pocket waves in the present invention.

[Explanation of symbols]

 1 ... Spandle molded product 2 ... Rolling direction of cold rolling 3 ... Pocket wave

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-8-165524 (JP, A) JP 2-44891 (JP, B2) JP-B 61-48569 (JP, B2) (58) Field (Int.Cl. ⁷ , DB name) C21D 9/46-9/48 C21D 8/00-8/04

Claims (2)

(57) [Claims] (1) In terms of% by weight, C: 0.08% or less;
04-0.2%, Mn: 0-2%, Si: 0.1-2
%, P: 0.04% or less, Ni: 7.5 to 10%, C
u: 0.1 to 3%, Nb: 0.1 to 0.8%, Mo:
The first cold rolling at a rolling reduction of 30 to 50% is performed on a hot-rolled austenitic stainless steel sheet having a chemical composition of 0.1 to 5%, Cr: 16 to 25%, and the balance being Fe and unavoidable impurities. After the application, 1000 ~ 1150 ℃ 1.5 ~
Intermediate annealing is performed for 10 minutes, and the temperature of the cold-rolled annealed sheet is reduced to 100 ° C. or less, and then the rolling reduction of 65 to 80% is performed.
The first cold rolling is performed, and then 1000 to 1150 ° C.
A method of producing an austenitic stainless steel sheet for roll forming, wherein the final annealing is performed for 1.5 to 10 minutes. However, the total rolling ratio of the first and second cold rolling satisfies 78 to 88%, and the rolling ratio of the first and second cold rolling is (rolling ratio of the second cold rolling) / ( The rolling ratio of the first cold rolling)> 1.4. 2. After the final annealing, the rolling rate is further reduced to 0.3 to 0.7.
The method for producing an austenitic stainless steel sheet for roll forming according to claim 1, wherein skin pass rolling is performed on the stainless steel sheet.