Hot dip coating apparatus and method

A hot dip coating method for coating a steel strip, in which the steel strip is introduced into a coating tank through a bottom slit of said coating tank and pulled upward so as to run through said coating tank, and in which a molten metal is supplied to a lower portion of said coating tank through a molten metal supply passage and drained from an upper portion of said coating tank to circulate the molten metal through said coating tank, said molten metal being held in said coating tank a magnetic field applied thereto by means of a plurality of magnetic field applying means arranged at both sides of the steel strip at a predetermined spacing from each other, so that the steel strip is coated with said molten metal while it runs upward through said coating tank, said method comprising the steps of:

• allowing said molten metal to overflow the upper end of said coating tank so as to be drained from said coating tank;
• supplying said molten metal into said coating tank through a buffer provided in communication with said molten metal supply passage, such that said molten metal is supplied through said buffer towards the steel strip,
• wherein the coating operation is started through the steps of:
• causing the steel strip to run at a predetermined velocity without starting the supply of said molten metal into said coating tank, while moving a pair of sealing members into contact with or to positions in the close proximity of the steel strip at a location immediately below said bottom slit of said coating tank and/or blowing a gas onto the steel strip at said location;
• applying the magnetic field to said coating tank;
• and
• commencing the supply of said molten metal into said coating tank, thereby starting up the coating operation.

A hot dip coating method for coating a steel strip, in which the steel strip is introduced into a coating tank through a bottom slit of said coating tank and pulled upward so as to run through said coating tank, and in which a molten metal is supplied to a lower portion of said coating tank through a molten metal supply passage and drained from an upper portion of said coating tank to circulate the molten metal through said coating tank, said molten metal being held in said coating tank a magnetic field applied thereto by means of a plurality of magnetic field applying means arranged at both sides of the steel strip at a predetermined spacing from each other, so that the steel strip is coated with said molten metal while it runs upward through said coating tank, said method comprising the steps of:

• allowing said molten metal to overflow the upper end of said coating tank so as to be drained from said coating tank;
• supplying said molten metal into said coating tank through a buffer provided in communication with said molten metal supply passage, such that said molten metal is supplied through said buffer towards the steel strip,
• wherein the coating operation is terminated through the steps of:
• stopping the supply of said molten metal into said coating tank, while moving a pair of sealing members into contact with or to positions in the close proximity of the steel strip at a location immediately below said bottom slit of said coating tank and/or blowing a gas onto the steel strip at said location;
• evacuating said coating tank by causing the molten metal remaining in said coating tank to attach to and be conveyed by the running steel strip or by shifting the molten metal into an auxiliary tank;
• and
• ceasing the application of the magnetic field, thereby terminating the coating operation.

A hot dip coating method for coating a steel strip, in which the steel strip is introduced into a coating tank through a bottom slit of said coating tank and pulled upward so as to run through said coating tank, and in which a molten metal is supplied to a lower portion of said coating tank through a molten metal supply passage and drained from an upper portion of said coating tank to circulate the molten metal through said coating tank, said molten metal being held in said coating tank a magnetic field applied thereto by means of a plurality of magnetic field applying means arranged at both sides of the steel strip at a predetermined spacing from each other, so that the steel strip is coated with said molten metal while it runs upward through said coating tank, said method comprising the steps of:

• allowing said molten metal to overflow the upper end of said coating tank so as to be drained from said coating tank;
• supplying said molten metal into said coating tank through a buffer provided in communication with said molten metal supply passage, such that said molten metal is supplied through said buffer towards the steel strip,
• wherein the coating operation is started through the steps of:
• disposing, at a location within or immediately above said bottom slit of said coating tank, sealing members made of a material meltable at a temperature not higher than the melting temperature of the coating metal, so as to block said bottom slit of said coating tank, while the supply of the molten metal into said coating tank has not yet been commenced;
• causing the steel strip to run through said bottom slit, past said sealing members;
• commencing the supply of the molten metal into said coating tank;
• and
• commencing application of the magnetic field to said coating tank, thereby starting up the coating operation.