Process engineering measures in a continuous casting machine at the start of casting, at the end of casting and when producing a transitional piece

A method for operating a continuous casting machine at the end of casting, wherein

• the continuous casting machine comprises:
• a mold, a strand guide comprising at least one pair of adjustable strand guiding rollers and at least one cooling nozzle;
• the method comprising the steps in sequence:
• continuously casting a strand by casting liquid steel in the mold to form an at least partially solidified strand;
• stopping the feeding of liquid steel into the mold and forming an end of the strand in the mold, so that the strand has an end, forming a following end region of the strand with a length B, 0.5<B<5 m, and thereafter forming a main part of the strand;
• withdrawing the strand from the mold in a casting direction;
• recording a position of the end of the strand in the strand guide;
• before the end of the strand, passing a lower end of the end region of the strand, past the pair of adjustable strand guiding rollers;
• then retracting the pair of adjustable strand guiding rollers, so that the pair of guiding rollers is not touching the strand;
• cooling the main part of the strand with Q≈Qnom, with the cooling nozzle delivering an amount of coolant Q that is substantially equal to a nominal amount of coolant Qnom to the main part of the strand;
• cooling the end region of the strand with Q<Qnom, by delivering an amount of coolant Q <Qnom to the end region of the strand by the cooling nozzle;
• and
• cooling the end of the strand with Q≧Qnom, by delivering an amount of coolant Q≧Qnom to the end of the strand by the cooling nozzle.

A method for operating a continuous casting machine when there is a temporary slowing down of the casting operation, wherein

• the continuous casting machine comprises:
• a mold, a strand guide comprising at least one pair of adjustable strand guiding rollers and at least one cooling nozzle;
• the method comprising in sequence:
• continuously casting a strand, by casting liquid steel in the mold to form an at least partially solidified strand;
• withdrawing the strand from the mold at a rate v, in a casting direction with v substantially equal to a nominal rate vnom;
• reducing a feeding rate of liquid steel into the mold for forming a transitional piece;
• withdrawing the strand at v<vnom;
• increasing the feeding rate of liquid steel into the mold ending the formation of the transitional piece for providing the strand with a lower main part of the strand, the transitional piece and an upper main part of the strand;
• withdrawing the strand at v≈vnom;
• recording the positions of a lower end and an upper end of the transitional piece in the strand guide;
• before the lower end of the transitional piece has passed the pair of adjustable strand guiding rollers, retracting the pair of adjustable strand guiding rollers from the strand, so that the roller pair is not touching the transitional piece;
• once the upper end of the transitional piece has passed the pair of adjustable strand guiding rollers, adjusting the pair of adjustable strand guiding rollers against the strand, so that the roller pair is touching the strand;
• cooling a main part of the strand with Q≈Qnom, by the cooling nozzle delivering an amount of coolant Q that is substantially equal to a nominal amount of coolant Qnom to the main part of the strand;
• and
• cooling the transitional piece with Q<Qnom, by the cooling nozzle delivering an amount of coolant Q<Qnom to the transitional piece.