Nippon Steel Corporation

Keisuke Fujisaki

Hiroshi Harada

Takehiko Toh

Eiichi Takeuchi

Hajime Hasegawa

Katsuhiro Sasai

Kiyoshi Wajima

Masahiro Tani

Ryu Hirayama

Kenji Umetsu

Hideki Matsuda

Tomohiro Konno

Kenzo Sawada

Kensuke Okazawa

Kazuomi Tomita

Yasushi Okumura

Takatsugu Ueyama

Yasuji Tomizawa

Sumio Matsumori

Akinori Wakagi

The present invention provides a previously unattainable compact and high thrust electromagnetic stirrer coil, that is, an electromagnetic stirrer coil for stirring molten steel in a mold by electromagnetic force, in which electromagnetic stirrer coil a space factor of the yoke sectional area (&#x2212;) with respect to an inside area in a vertical cross-section of said electromagnetic stirrer coil is 0.5 to 0.9 and a yoke width B is 100 mm to 300 mm. Preferably, a magnetomotive force F of said electromagnetic stirrer coil divided by the yoke width B, that is, a value of F/B, is 800 kAT/m or more.

Electromagnetic stirrer coil

A flaw detection device for a steel bar enabling inspection of a high temperature steel bar at a high temperature. A pre-treatment unit, detection unit, and post-treatment unitare arranged along a running direction of a steel bar. The pre-treatment unit and post-treatment unit have the same structure. Direct current coilsandare wound around the outside of the sleevesand. The steel bar is magnetically saturated by the direct current magnetic field. An eddy current is generated at the surface of the steel bar by an alternating current coilof a detection unit. The change in the magnetic field caused by the eddy current is detected by the detection windingsand. The sleeves are made of nonmagnetic materials, so the strength of the direct current magnetic field becomes flat along the running axis of the steel bar. Even when moving the steel bar at a high speed, the occurrence of noise due to changes in strength of the direct current magnetic field is suppressed.

Flaw detection device for steel bar

A cast slab has a negative segregation zone composed of a multilayer structure of negative segregation layers disposed between dendrite or crystalline layers. The dendrite or crystalline layers are a deflection structure caused by vibration during formation of the cast slab. The negative segregation layers have a distance between them of not more than 2 mm and the number of negative segregation layers is not less than 3. The cast slab has an equi-axed crystal ratio of not less than 50% inside the multilayer negative segregation zone.

Method for casting molten metal, apparatus for the same, and cast slab

The present invention provides a continuous casting method in which vibration is given to molten metal by a shifting magnetic field so that the equi-axed crystal ratio can be enhanced and the equi-axed crystals can be made fine without generating surface defects caused by powder trapping. Further, the present invention provides an apparatus to which the continuous casting method is applied. Furthermore the present invention provides a cast slab produced by the above method and apparatus. The method of casting molten metal comprises the following steps: pouring molten metal into a mold and solidifying it in the mold while applying an electromagnetic force, which is generated by an electromagnetic coil arranged in the proximity of a molten metal pool in the mold, upon the molten metal; and vibrating the molten metal, which has been solidified in the mold while being cooled and solidified, by a shifting magnetic field generated by the electromagnetic coil so that the molten metal is accelerated by a high intensity and a low intensity of acceleration in a range not exceeding a predetermined flow velocity when the directional vectors of high acceleration and low acceleration in the same direction or in the opposite direction are combined with each other.

Method for casting molten metal

The present invention relates to a continuous casting apparatus for continuously casting molten metal. More particularly, the present invention provides a method and an apparatus for controlling a surface level of molten metal in a mold when molten metal is continuously cast. The continuous casting apparatus of the invention comprises: a mold in which molten metal is poured and solidified; and an eddy current type molten metal surface level sensor for detecting a molten metal surface level in the mold. In the continuous casting apparatus having an electromagnetic coil arranged in such a manner that the electromagnetic coil surrounds the mold and also having an electric power supply for generating a pulse magnetic field from the electromagnetic coil, there are provided a mechanism for taking out a pulse trigger signal corresponding to the magnetic field from the electric power supply, and a mechanism for controlling a time of detecting a surface of molten metal by the molten metal level sensor.

Continuous casting apparatus using a molten metal level gauge

Continuous casting method and apparatus

Growing community of inventors

Futtsu, Japan

Keisuke Fujisaki