Abstract: In the production of low-carbon steel, particularly low-carbon steel sheet containing less than 0.25% of Mn, improvements in the method and apparatus, which comprises hot rolling a steel having a controlled range content of Mn, O and S contents, then coiling thus hot rolled steel at temperatures between 600.degree.-800.degree. C., further cold rolling the hot rolled plate down to a prescribed thickness, annealing and overaging the steel in a continuous furnace, rapidly cooling the steel near room temperatures and skin pass rolling, leveling, and recoiling the sheet. Thus produced steel sheet is very useful for applications such as pressed automobile body parts which require good workability particularly good drawability.

Abstract: An apparatus for continuous treatment of cold rolled steel sheet. The apparatus has a continuous annealing furnace through which the sheet is continuously passed and which is composed of, in succession, a heating chamber for heating the cold rolled steel sheet to a temperature range of 700.degree. to 900.degree. C. within 2 minutes, a soaking chamber for keeping the sheet in the above temperature range for two minutes or less, a primary cooling chamber for rapidly cooling the sheet from the above temperature range to an overageing at a rate of 5.degree. to 30.degree. C./sec., an overageing chamber for keeping the sheet between 300.degree. to 400.degree. C. for up to eight minutes, and a secondary cooling chamber for cooling the sheet from the above overageing temperature to below 50.degree. C. within 2 minutes. Adjacent the output end of said furnace is apparatus for successively skin pass rolling, levelling and recoiling the sheet from the annealing furnace.