The present invention provides a method for casting a slab having a good cast surface. The method includes heating the surface of molten metal on a metal inlet side of a mold by a first heat source so that the following formulas: q≧0.87 and c≦11.762q+0.3095 are satisfied where c is a cycle time [sec] of turning movement of the first heat source, and q is an average amount of heat input [MW/m.sup.2] determined by accumulating an amount of heat input applied by at least the first heat source to the contact region between the upper surface of the slab on the metal inlet side and the mold, along the path of turning movement of the first heat source, and dividing the resultant accumulated value by the cycle time c.

The present invention provides a method for casting a slab having a good cast surface. The method includes heating the surface of molten metal on a metal inlet side of a mold by a first heat source so that the following formulas: q≧0.87 and c≦11.762q+0.3095 are satisfied where c is a cycle time [sec] of turning movement of the first heat source, and q is an average amount of heat input [MW/m.sup.2] determined by accumulating an amount of heat input applied by at least the first heat source to the contact region between the upper surface of the slab on the metal inlet side and the mold, along the path of turning movement of the first heat source, and dividing the resultant accumulated value by the cycle time c.

In production of a reactive metal using a melting furnace for producing metal having a hearth, ingots can be efficiently produced by efficiently cooling the ingots extracted from the mold provided in the melting furnace. In addition, an apparatus structure in which multiple ingots can be produced with high efficiency and high quality from one hearth, is provided. A melting furnace for producing metal is provided, the furnace has a hearth for having molten metal formed by melting raw material, a mold in which the molten metal is poured, an extracting jig which is provided below the mold for extracting ingot cooled and solidified downwardly, a cooling member for cooling the ingot extracted downwardly of the mold, and an outer case for keeping the hearth, the mold, the extracting jig, and the cooling member separated from the air, wherein at least one mold and extracting jig are provided in the outer case, and the cooling member is provided between the outer case and the ingot, or between the multiple ingots.

A heat flux derivation unit (202) derives a value q.sub.y of a y-axis direction component of a heat flux vector. A molten metal surface level derivation unit (203) derives, as a molten metal surface level, a position where the absolute value of the value q.sub.y of the y-axis direction component of the heat flux vector whose y-axis component vector is in a direction opposite to a casting direction is maximum.

A method for semi-continuous casting of a strand (1) of steel in a strand casting machine and a strand casting machine for such casting. The strand has little segregation of the center and porosity. Yet it is castable rapidly. The method steps are: at a casting start of the strand casting machine, pouring liquid steel into an open-ended mold (2). The mold is closed by a cold strand (6). The liquid steel forms, together with the cold strand, a completely solidified strand start (1a) and subsequently forms a semi-solidified strand (1b). Then extracting the semi-solidified strand (1b) from the open-ended mold (2). Supporting and guiding the semi-solidified strand (1b) in a strand guide (3). Cooling the semi-solidified strand (1b) by secondary cooling (4) at the casting end of the strand casting machine, ending the pouring of liquid steel into the open-ended mold (2) and forming a strand end (1c). Extracting the strand end (1c) from the open-ended mold (2). Ending the extraction such that the strand end (1c) lies outside the open-ended mold (2). Ending the secondary cooling (4). Controlling or regulating cooling of the semi-solidified strand (1b) until complete solidification of the strand (1) in a tertiary cooling zone (5) of the strand casting machine. The cooling effect is stronger at the strand start (1a) and decreases towards the strand end (1c). Discharging the strand (1) from the strand casting machine.

A method for semi-continuous casting of a strand (1) of steel in a strand casting machine and a strand casting machine for such casting. The strand has little segregation of the center and porosity. Yet it is castable rapidly. The method steps are: at a casting start of the strand casting machine, pouring liquid steel into an open-ended mold (2). The mold is closed by a cold strand (6). The liquid steel forms, together with the cold strand, a completely solidified strand start (1a) and subsequently forms a semi-solidified strand (1b). Then extracting the semi-solidified strand (1b) from the open-ended mold (2). Supporting and guiding the semi-solidified strand (1b) in a strand guide (3). Cooling the semi-solidified strand (1b) by secondary cooling (4) at the casting end of the strand casting machine, ending the pouring of liquid steel into the open-ended mold (2) and forming a strand end (1c). Extracting the strand end (1c) from the open-ended mold (2). Ending the extraction such that the strand end (1c) lies outside the open-ended mold (2). Ending the secondary cooling (4). Controlling or regulating cooling of the semi-solidified strand (1b) until complete solidification of the strand (1) in a tertiary cooling zone (5) of the strand casting machine. The cooling effect is stronger at the strand start (1a) and decreases towards the strand end (1c). Discharging the strand (1) from the strand casting machine.

The present invention provides a titanium slab for hot rolling which can be fed into a general purpose hot-rolling mill for producing strip coil, without passage through a breakdown process such as blooming or a straightening process, and can further suppress surface defect occurrence of the hot-rolled strip coil, and a method of producing and a method of rolling the same, characterized in that in the cast titanium slab an angle θ formed by the crystal growth direction (solidification direction) from the surface layer toward the interior and a direction parallel to the slab casting direction (longitudinal direction) is 45 to 90°, and moreover, there is a surface layer structure of 10 mm or greater whose θ is 70 to 90°, and further characterized in that a crystal grain layer of 10 mm or greater is formed whose C-axis direction inclination of a titanium α phase is, as viewed from the side of the slab to be hot rolled, in the range of 35 to 90° from the normal direction of the surface to be hot rolled. The titanium slab concerned is produced using an electron beam melting furnace by casting at an extraction rate of 1.0 cm/min or greater.

The present invention provides a titanium slab for hot rolling which can be fed into a general purpose hot-rolling mill for producing strip coil, without passage through a breakdown process such as blooming or a straightening process, and can further suppress surface defect occurrence of the hot-rolled strip coil, and a method of producing and a method of rolling the same, characterized in that in the cast titanium slab an angle θ formed by the crystal growth direction (solidification direction) from the surface layer toward the interior and a direction parallel to the slab casting direction (longitudinal direction) is 45 to 90°, and moreover, there is a surface layer structure of 10 mm or greater whose θ is 70 to 90°, and further characterized in that a crystal grain layer of 10 mm or greater is formed whose C-axis direction inclination of a titanium α phase is, as viewed from the side of the slab to be hot rolled, in the range of 35 to 90° from the normal direction of the surface to be hot rolled. The titanium slab concerned is produced using an electron beam melting furnace by casting at an extraction rate of 1.0 cm/min or greater.

An arrangement for controlling flow speed in a mold for continuous casting of metal includes: at least two first front cores with associated first magnetic coils arranged on one side of the mold; at least two second front cores with associated second magnetic coils arranged on an opposite side of the mold in substantial alignment with the first front cores; an external magnetic loop connecting the second front cores to the first front cores, to allow a one-directional magnetic flux to pass through the mold from the first front cores to the second front cores or vice versa; and a control interface enabling independent control of two subsets of the first magnetic coils.

An arrangement for controlling flow speed in a mold for continuous casting of metal includes: at least two first front cores with associated first magnetic coils arranged on one side of the mold; at least two second front cores with associated second magnetic coils arranged on an opposite side of the mold in substantial alignment with the first front cores; an external magnetic loop connecting the second front cores to the first front cores, to allow a one-directional magnetic flux to pass through the mold from the first front cores to the second front cores or vice versa; and a control interface enabling independent control of two subsets of the first magnetic coils.