Very thin steel sheet and production method thereof

A very thin steel sheet characterized in containing, in mass %,

• C:
• 0.0004 to 0.0108%,
• N:
• 0.0032 to 0.0749%,
• Si:
• 0.0001 to 1.99%,
• Mn:
• 0.006 to 1.99%,
• S:
• 0.0001 to 0.089%,
• P:
• 0.001 to 0.069%, and
• Al:
• 0.070 to 1.99%;
• further containing one or both of Ti and Nb at
• Ti:
• 0.0005 to 0.0804%, and
• Nb:
• 0.0051 to 0.0894%,
• within the range of
• Ti+Nb:
• 0.0101 to 0.1394%;
• further satisfying the relationships of N−C≧0.0020%, C+N≧0.0054%, Al/N>10, (Ti+Nb)/Al≦0.8, (Ti/48+Nb/93)×12/C≧0.5, and 0.31<(Ti/48+Nb/93)/(C/12+N/14)≦2.0;
• having a balance of iron and unavoidable impurities;
• and
• having a thickness of 0.4 mm or less.