JP3790283B2 - Method for producing ferritic stainless steel sheet with excellent roping resistance, ridging resistance and deep drawability - Google Patents

Description

【００１５】
表１から明らかなように、本発明の範囲を満足した実験番号１〜５、１２〜１６の材料は、ローピングはほとんど見えず、リジング評点も１と優れ、高い表面品質を示し、ｒ値も高い。
【００１６】
一方、一回目の巻取後の保持時間が本発明の範囲より長い、実験番号６では粒界にＰの偏析が起こったためか、きらきら光る疵が検証された。また、保持時間が短かった実験番号７では熱延板組織の再結晶が十分起こらなかったためか、ｒ値が低く、ローピング、リジング共に良好ではなかった。同様の結果が一回目の巻取温度が低い実験番号１０の材料でも観察された。
実験番号８は通常の製造方法で、低温巻取をするとｒ値が低く、ローピングが不良になり、高温巻取を施行した実験番号９では耐リジング性が悪く、きらきら疵も発生した。２回目の巻取温度が高い実験番号１１の場合も耐リジング性が悪く、きらきら疵が観察された。
【００１７】
【発明の効果】
本発明によれば、熱延板焼鈍をすることなしに耐ローピング性、耐リジング性、表面品質ならびに深絞り性に優れたフェライト系ステンレス鋼板を製造することができる。[0001]
[Industrial application fields]
The present invention relates to a method for producing a deep drawing ferritic stainless steel sheet having high surface quality by suppressing the occurrence of roping and ridging, which are problems of ferritic stainless steel sheets.
[0002]
[Prior art]
In some cases, ferritic stainless steel sheets may have specific irregularities along the rolling direction called roping during cold rolling, which may significantly deteriorate the surface quality of the product.
[0003]
As a roping prevention measure, it is known that it is effective to perform hot-rolled sheet annealing after hot rolling. However, performing hot-rolled sheet annealing leads to an increase in manufacturing costs, and in recent years, techniques for omitting hot-rolled sheet annealing and suppressing the occurrence of roping have been studied, but satisfactory results have always been obtained. Not.
[0004]
In general, the cause of the occurrence of roping is considered to be unevenness because the deformation is locally different due to the colony of regions having similar crystal orientations in the steel sheet, as in the cause of ridging. In the case of ridging, since steel sheets recrystallized after cold rolling are targeted, improvement is possible if there is a means for crushing colony orientation groups during annealing. As an example, as seen in SUS430, the generation of ridging is suppressed by allowing the α ′ phase to remain in the hot-rolled sheet and using it as a nucleation site for recrystallization to promote recrystallization. However, there is a problem with roping that there is a colony-oriented group of hot-rolled steel sheets.
[0005]
Although it has been confirmed that recrystallization after rough rolling is effective as an improvement measure for roping (see JP-A-4-160117), it cannot be said that the effect is sufficient. The reason is that although the recrystallization causes the orientation dispersion to occur, it is not obvious that even if the recrystallization is performed, the orientation dispersion is sufficient to suppress the occurrence of roping.
[0006]
On the other hand, if recrystallization is performed after finish rolling, the same effect as that obtained by performing hot-rolled sheet annealing can be obtained, which is extremely effective in suppressing the occurrence of roping. However, in normal continuous hot rolling, since cold winding is performed for the following reasons, it is necessary to rapidly cool after finish rolling, and it is difficult to sufficiently recrystallize the hot rolled sheet structure. The reason for performing low temperature winding is 1) to form the hard second phase described above to improve ridging resistance, and 2) when high temperature winding is performed, grain boundary segregation of P occurs remarkably and during pickling. This is because the grain boundaries are significantly corroded and uneven deformation occurs in the vicinity of the grain boundaries during cold rolling, so that the surface glitters unevenly and the surface quality deteriorates.
[0007]
[Problems to be solved by the invention]
The present invention provides a method for producing a ferritic stainless steel sheet for deep drawing that suppresses the occurrence of roping and ridging and has high surface quality without performing hot-rolled sheet annealing.
[0008]
[Means for Solving the Problems]
The gist of the present invention is that after finish rolling of ferritic stainless steel, it is wound at a temperature of 750 ° C. or more and 1000 ° C. or less, held for 10 seconds or more and 10 minutes or less, then unwound, and again 650 ° C. It is a method for producing a ferritic stainless steel sheet excellent in roping resistance, ridging resistance, surface quality and deep drawability, characterized by winding at the following temperature, followed by cold rolling and annealing.
[0009]
The present invention is described in detail below.
After finishing rolling, the reason why the winding is performed at a temperature of 750 ° C. or higher and 1000 ° C. or lower and held for 10 seconds or longer and 10 minutes or shorter will be described. This is because if rewinding at a temperature of 750 ° C. or lower, recrystallization does not occur sufficiently in a short time. Further, if the coiling temperature is to be increased, the slab heating temperature must be increased, and the generation of wrinkles due to high-temperature heating becomes remarkable, so the upper limit of the coiling temperature was set to 1000 ° C. The holding time in winding is the time from the end of winding to the start of unwinding, and the lower limit is set to 10 seconds. This is because the occurrence cannot be suppressed. On the other hand, the reason why the upper limit is set to 10 minutes is that when the temperature is kept for a longer time, the grain boundary segregation of P becomes remarkable, and the product plate is likely to shine brightly.
[0010]
Next, the upper limit of the coiling temperature when unwinding after unwinding is limited to 650 ° C. The steel plate that effectively uses the α ′ phase as in SUS430 to suppress the generation of ridging, This is because the α ′ phase needs to be wound at a temperature below this temperature. Further, even in the case of a ferritic single phase steel such as SUS430LX, it is necessary to perform low temperature winding in order to avoid P grain boundary segregation. The lower limit of the coiling temperature is not particularly limited. However, in steel in which a transformation structure from γ is generated, deformation resistance at the time of cold rolling increases as the coiling temperature decreases, and therefore, the temperature is preferably 300 ° C. or higher. On the other hand, when the hot-rolled sheet is a ferrite single phase, even if the coiling temperature is 100 ° C. or lower, no significant influence is exerted on the deformation resistance of cold rolling.
Manufacturing conditions such as descaling after hot rolling, cold rolling, and annealing may be in accordance with ordinary methods.
[0011]
【Example】
Examples of the present invention will be described below.
In the examples, SUS430 (steel type A), SUS430LX (steel type B), and SUS436L (steel type C), which are representative steel types of ferritic stainless steel, were used. Table 1 shows the winding conditions after finish rolling and the characteristic values after cold rolling and annealing. The standard conditions were slab thickness: 250 mm, hot rolled sheet thickness: 3 mm, heating temperature HT: 1200 ° C., cold rolling rate: 80%, annealing temperature: 820 ° C.
[0012]
As an index representing the anti-roping property, the swell height in the direction perpendicular to the rolling direction of the product plate was determined using a stylus type roughness meter. When the undulation height is 0.2 μm or less, roping is hardly observed with the naked eye, which is an excellent state.
The r value was obtained from the dimensional change after 15% pulling of the JIS No. 5 test piece.
[0013]
The ridging resistance was evaluated from the height of the swell of the steel sheet by pulling 15% of a JIS No. 5 tensile test piece cut from the rolling direction and then measuring the surface with a roughness meter. Rank 1 had a swell height of 20 μm or less, rank 2: 20-30 μm, rank 3: 30-40 μm, rank 4: 40-70 μm, rank 5: 70 μm or more. Up to rank 2, there is no problem in practical use.
Regarding the deterioration of the surface quality that appears due to the intergranular corrosion that occurs during pickling, it was visually determined whether or not a sparkling glazing would appear when the cellophane was applied to the product plate and peeled off.
[0014]
[Table 1]

[0015]
As is clear from Table 1, the materials of Experiment Nos. 1 to 5 and 12 to 16 satisfying the scope of the present invention showed almost no roping, excellent ridging score of 1, high surface quality, and r value. high.
[0016]
On the other hand, since the segregation of P occurred at the grain boundary in Experiment No. 6, where the holding time after the first winding was longer than the range of the present invention, a sparkle that was sparkling was verified. Also, in Experiment No. 7 where the holding time was short, the r value was low and the roping and ridging were not good because the recrystallization of the hot-rolled sheet structure did not occur sufficiently. Similar results were observed for the material of Experiment No. 10, where the first coiling temperature was low.
Experiment No. 8 is a normal production method. When low-temperature winding is performed, the r value is low, roping becomes poor, and in Experiment No. 9 in which high-temperature winding is performed, ridging resistance is poor and sparkle is generated. In the case of Experiment No. 11 where the coiling temperature at the second time was high, the ridging resistance was poor and sparkle was observed.
[0017]
【The invention's effect】
According to the present invention, a ferritic stainless steel sheet excellent in roping resistance, ridging resistance, surface quality, and deep drawability can be produced without performing hot-rolled sheet annealing.

Claims (1)

After finish rolling the ferritic stainless steel, it is wound at a temperature of 750 ° C. or more and 1000 ° C. or less, held for 10 seconds or more and 10 minutes or less, then unwound and wound again at a temperature of 650 ° C. or less, A method for producing a ferritic stainless steel sheet excellent in roping resistance, ridging resistance, surface quality and deep drawability, characterized by performing cold rolling and annealing.