Effect of manganese on the recrystallization texture of P-containing low-carbon steel sheet
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I.
INTRODUCTION
IT has
been reported that a high manganese content in low-carbon steel sheets was inferior for the development of {111} recrystallization textures which are favorable for plastic anisotropy, i.e., r-value. 1,2 Some clusters and/or precipitates such as AIN in deep drawing quality or extra deep drawing quality Al-killed steel can play an important role in desirable texture formation. 3'4 In a steel with a high manganese content, however, it is thought that the activity of interstitial atoms such as carbon and nitrogen will be decreased due to possible effects of Mn-C 5 and Mn-N 6"7interactions resulting from the manganese addition. In such a high manganese steel, some precipitates favorable to the formation of {111} textures might be barely formed during heating even if a slow heating cycle such as the conventional box annealing method is applied after cold rolling. Hu and Goodman2 and Hughes and Page s suggested that the interaction between manganese and carbon would affect the recovery and/or recrystallization kinetics and therefore recrystallization textures. Also, Matsudo et al. 9 suggested the detrimental effect of the Mn-C interaction on the r-value. On the other hand, it is widely known that steels containing phosphorus are likely to show a banded structure with segregated P-bearing ferrite, suggesting phosphorus and carbon in steel can act as repulsive elements to each other. Furthermore, Hu 1~reported that the r-value of low-carbon steel containing 0.067 pct P decreased more gradually than that of P-free steel with increasing manganese content up to 0.3 pct. In the present work, low-carbon Al-killed steels having three levels of phosphorus and various levels of manganese were used to investigate the effect of manganese on annealing textures. In this case, phosphorus might act as a softening element for the Mn-C interaction. On the basis of this consideration, it was investigated whether phosphorus could alter the precipitation behavior of the carbide which might exert a significant influence in developing {111} recrystallization textures.
II.
Most of the materials used in this investigation were melted in a laboratory vacuum induction furnace and cast into iron molds. The chemical compositions of the cast steels are given in Table I. The low-carbon Al-killed steels containing 0.08, 0.1, and 0.2 pct P were used to investigate the effect of manganese on the texture formation. The P-free steels were also used as a comparison. For the 2 pct Mn steels with four levels of phosphorus, the influence of phosphorus on precipitation was investigated. All steels were soaked at 1523 K (1250 ~ hot rolled to a thickness of 3.2 mm at 1223 K (950 ~ and air cooled. For the 0.1 pct P steels and P-free steels, normalizing at 1203 K (930 ~ for 30 minutes was applied in order not only to refine the grain structures but also to precipitate nitrogen as A1N. The hot rolled or normalized sheets were preaged at 823 K (550 ~ 843 K (570 ~ 893 K (620 ~ 923 K (650 ~ and 993 K (720 ~ for 24 or 120 hours to simulate the
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