JP3359471B2 - Ferritic stainless steel sheet with excellent roping 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 ferritic stainless steel sheet having a high surface quality by suppressing the occurrence of roping, which is a problem of a ferritic stainless steel sheet.

[0002]

2. Description of the Related Art A ferritic stainless steel sheet sometimes has a specific unevenness in the rolling direction called roping at the time of cold rolling, and the surface quality of a product may be significantly deteriorated. In general, it is considered that the cause of the roping is the same as the cause of the ridging, and the deformation is locally different due to the presence of a region having a similar crystal orientation in the steel plate in a colony manner, thereby causing irregularities. In the case of ridging, since the target is a steel sheet recrystallized after cold rolling, improvement can be made if there is a means for crushing the colony orientation group during annealing. One example, as seen in SUS430,
The generation of ridging is suppressed by leaving the α 'phase on the hot-rolled sheet and using it as a nucleation site for recrystallization to promote recrystallization. However, a problem with roping is that there is a colony-like orientation group in a hot-rolled steel sheet.

Although it has been confirmed that recrystallization after rough rolling is effective as a measure for improving roping (see JP-A-4-160117), the effect cannot be said to be sufficient. The reason is that it is certain that dispersion of orientation will occur due to recrystallization, but even if recrystallization,
This is because it is not obvious whether the azimuth dispersion is sufficient to suppress the occurrence of roping.

Many techniques have been disclosed in which Ti and B are added in combination to improve the formability and partial ridging resistance (JP-B-47-4786, JP-A-58-713).
No. 56, Japanese Patent Publication No. 59-10990, Japanese Patent Publication No. 5
7-55787, JP-A-57-70230, etc.). However, these techniques make little mention of roping. In Japanese Patent Publication No. 47-4786, the term "roping" is used, which means wrinkles similar to ridging appearing during press working.
It differs from roping in the sense of the present invention. Roping means, in the present invention, stripes appearing parallel to the rolling direction that appear during cold rolling.

[0005]

An object of the present invention is to provide a ferritic stainless steel cold-rolled steel sheet which suppresses the occurrence of roping and has excellent surface quality.

[0006]

As a measure for improving roping, it has been confirmed that recrystallization after rough rolling is effective (Japanese Patent Application Laid-Open No. 4-160117). Even if it is crystallized, it is not obvious whether it achieves sufficient azimuthal dispersion to suppress the occurrence of roping, and its effect cannot be said to be sufficient. Analysis of the texture of the hot-rolled sheet revealed that the {100} oriented grains existed in colonies in the steel sheet where roping was observed. In a hot-rolled sheet of ferritic stainless steel, {100], which is the texture of the cast structure, remains strongly. This is because when the cast grains having the {100} orientation are hot-worked and recrystallized, recrystallization usually occurs from the crystal grain boundaries, and the orientation of the recrystallized grains at that time is also likely to be {100}.

However, the present inventors have conducted detailed studies on the texture of the hot-rolled sheet, particularly the effect of added elements on the formation of colonies. I found what happened. Conventionally,
It was thought that deformation bands were not easily formed inside the {100} grains, and recrystallization from the grains did not occur.
By adding compound (Sb and Bi have the same effect), recrystallization tends to occur from the inside of {100} grains, and the orientation of the recrystallized grains is often other than {100}. It is not clear why the combined addition of B and Sn causes such hot recrystallization behavior that leads to the crushing of colonies, but it has been recognized that the addition of Sn increases the number of deformation zones in the grains. And that B segregates at the grain boundary and delays the nucleation of recrystallization from the grain boundary. It is presumed that a large number of recrystallized grains other than {100} were generated from the deformed band formed in FIG. The present invention has been constructed based on these experimental results.

That is, the gist of the present invention is as follows: C: 0.02% or more, 0.08% or less, Si: 1% or less, Mn: 1% or less, Cr: 13% or more, 30% by weight. %, N: 0.03% or less, Ti: 0.03% or less, Al: 0.005% or more, 0.08% or less, One or more of Sn, Sb, Bi: 0.005% Above, 0.2% or less , and B: satisfy the relationship of 0.4 <11 (N-14Ti / 48) / (14B) <2, and further contain Mo: 3% or less as necessary, with the balance Fe and A ferritic stainless steel sheet having excellent roping resistance characterized by being composed of unavoidable impurities .

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The reason for setting the lower limit of the C amount to 0.02% is that the C amount is not yet satisfied.
Is because the intergranular corrosion resistance of the full the weld is deteriorated, the upper limit was set to 0.08% is to become the C amount exceeds this workability is deteriorated. Since it is preferable that both Si and Mn have low corrosion resistance and workability, the upper limits of the addition amounts thereof are each set to 1%.

[0010] Cr is indispensable in ferritic stainless steels, and when it is added in an amount of 13% or more, the corrosion resistance is greatly improved with an increase in the content. However, Cr is deteriorates the formability of 30 percent. N is effective for controlling the γ potential, but excessive addition deteriorates the workability, so the upper limit was made 0.03%.

The addition of Ti is advantageous not only for effective use of B, but also for suppressing roping since TiN generated at a high temperature has the effect of suppressing grain growth during heating. However, the addition of excessive Ti tends to cause premature cracking, so the upper limit was made 0.03%. Al is to perform the deoxidation enough is required at least 0.005% or more, since the addition 0.08 percent degrades the weldability, the upper limit was made 0.08%.

[0012] Sn, Sb, reasons for limiting one or more of the added amount of Bi is in the addition of less than 0.005% is because the not improved roping, becomes 0.2 percent heat This is because the inter-workability is significantly deteriorated. B addition amount is 0.4 <11 (N-14Ti / 48) / (14B)
The reason for limiting to satisfy the relationship of <2 is that B is 11 (N
By adding -14Ti / 48) / 28 or more,
B> 27.5 (N
When -14Ti / 48) / 14, the effect of improving roping is saturated, so the upper limit is limited in view of alloy cost.

When particularly excellent corrosion resistance is required, Mo
Is effective and 3% or less is selectively added. Upper limit 3
% Is provided from the viewpoint of workability. The above-described steel sheet of the present invention can be manufactured through a process of manufacturing a normal ferritic stainless steel sheet.

[0014]

Next, embodiments of the present invention will be described. Using ferritic stainless steel having the chemical components shown in Table 1,
The most important property after cold rolling and annealing, ie, the roping property which influences the surface quality most, was investigated. Table 2 shows the production conditions and the results of roping. The basic manufacturing conditions A are as follows: slab thickness 250 mm, heating temperature 1200 ° C., coarse bar thickness 30 mm, finish thickness 3 mm, finish temperature 900 ° C., winding temperature 6
The temperature was set at 00 ° C., the cold rolling rate was 80%, and the annealing temperature was 820 ° C. Manufacturing condition B is when the finishing temperature is 800 ° C. in the basic manufacturing condition A, manufacturing condition C is when the winding temperature is 750 ° C. in the basic manufacturing condition A, and manufacturing condition D is 800 ° C. 3
This is the case where the hot-rolled sheet annealing for a long time is added.

[0015] As an index indicating the roping resistance, the undulation height in the direction perpendicular to the rolling direction of the product sheet was determined using a stylus type roughness meter. When the undulation height is 0.2 μm or less, roping can hardly be observed with the naked eye, and it can be recognized as an extremely excellent state. Roping measurements were made without skin pass after final annealing.

Experiment Nos. 1 to 10 satisfying the scope of the present invention
The material has very little roping and shows high surface quality. The production condition D to which the hot-rolled sheet annealing is added has a lower roping undulation height than the basic production condition A. Remarkable roping was observed in the materials of steels E to H outside the scope of the present invention.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

According to the present invention, a ferritic stainless steel sheet having excellent roping resistance can be manufactured without performing hot-rolled sheet annealing.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-1-201445 (JP, A) JP-A-6-73458 (JP, A) JP-A-7-11333 (JP, A) JP-A-7-733 41916 (JP, A) JP-A-60-174828 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 38/00-38/60

Claims (2)

(57) [Claims] C .: 0.02% or more and 0.08% or less, Si: 1% or less, Mn: 1% or less, Cr: 13% or more, 30% or less, and N: 0.03 % by weight. % Or less, Ti: 0.03% or less, Al: 0.005% or more, 0.08% or less, one or more of Sn, Sb, Bi: 0.005%
Or 0.2% or less, and B: 0.4 <11 (N- 14Ti / 48) / (14B) < meets two of the relationships, the balance being Fe and unavoidable impurities <br />, wherein the Ferritic stainless steel sheet with excellent roping resistance. To 2. A other components according to claim 1, in further weight%, Mo: Excellent ferritic stainless steel sheet resistance roping of claim 1, wherein the containing 3% or less.