Nippon Steel Corporation

Hiroshi Ikegami

Norichika Nagira

Katsuhiko Yui

Kozaburo Ichida

Katsuyoshi Kobayashi

Ichiro Shimbashi

Tadashige Namba

Takeo Dazai

Yoshio Saitoh

Hideharu Bando

Yasuo Misawa

Hiroji Baba

Kanji Yahano

In an apparatus for continuously annealing a steel strip after cold rolling, stable operation of the annealing apparatus can be obtained by preventing slippage of bridle rolls and hearth rolls. The diameter D of a bridle roll is set so that a surface pressure p defined by an equation p=h(.sigma..sub.1 +.sigma..sub.2)/D can be 10 kPa (kilopascal) or more, wherein the unit tension of a steel strip at the inlet side of the bridle roll and hearth rolls of the apparatus is .sigma..sub.1, the unit tension at the outlet side is .sigma..sub.2, the thickness of the steel strip is h and the diameter of the bridle roll is D.

Method for continuously annealing steel strip

The present invention relates to a method for cooling a steel strip in a continuous-annealing furnace. Conventionally, the steel strip is cooled by a water medium and, thus, oxidation is inevitable. Recently developed roll cooling methods can prevent oxidation but are disadvantageous in that the steel strip (1) is nonuniformly cooled as seen in its short width direction. The present invention attains uniform cooling by means of feedback-feedforward control, in which the blowing width of the gas-jet cooler (21, 53) is controlled by detecting the sheet temperature distribution with thermometers (24, 55, 60).

Method for cooling a steel strip in a continuous annealing furnace

Steel strip is continuously annealed while successively travelling through a heating, soaking, primary cooling, overaging and secondary cooling zone in an annealing furnace. In the overaging zone, an endless steel strip is allowed to run through a passageway that extends spirally from the entry end of the overaging zone to the point where overaging is completed, at a given distance in the direction of radius. The guide strip travels at the same speed as the steel strip being processed that is delivered from the primary cooling zone. On the entry side of the overaging zone, the strip being processed is laid over the guide strip so that the two strips spirally travel through the overaging zone side by side. The processed and guide strips running together are shifted out of the spiral passageway at the point where overaging is completed. Then, the processed strip is separated from the guide strip by shifting at least one of the two strips. While the separated processed strip is delivered to the subsequent secondary cooling zone, the guide strip is returned to the entry end of the overaging zone for the next trip through the spiral passageway. Helical devices are used for changing the position and running direction of the strip being processed and the guide strip. The overaging furnace is annular in shape, provided with a number of radially disposed guide rolls on the inside. Each guide roll has a plurality of guide grooves in which both edges of the guide strip are fitted.

Method and apparatus for continuously annealing steel sheet

In controlledly cooling steel strip in a continuous annealing line, the heat transfer rate needed for attaining the desired cooling rate is calculated from an equation including strip thickness, the cooling starting and finishing temperatures, and the desired cooling rate, and the obtained heat transfer rate is corrected according to the effect of natural cooling in idle-pass zones preceding and following the coolant spray zone. The flow rate of coolant is determined and set by using an equation expressing the predetermined relationship between the heat transfer rate and coolant flow rate. The length of the coolant spraying region extending in the direction of strip travel is calculated from the running speed of the strip, the cooling starting and finishing temperatures, and the desired cooling rate. The nozzles are set to turn on and off so that the coolant is sprayed from such a number of nozzles as correspond to the length of the spraying region thus calculated. Based on these settings, the coolant flow rate is corrected by re-calculating the heat transfer rate when strip thickness varies in the course of controlled cooling. Also, the on-off pattern of the nozzles is corrected by re-calculating the length of the coolant spraying region when the running speed of the strip varies.

Method of controlled cooling for steel strip

A surface treatment apparatus for producing a steel strip having an enhanced phosphatizing property, has a plurality of guide rolls for guiding the strip along a predetermined path, a pickling vessel having nozzles for spraying a pickling liquid onto the surface of the strip, a first rinsing vessel having nozzles for spraying water onto the strip surface, an electrolytic treating vessel having an anode and a temperature control for the electrolytic treating liquid, a second rinsing vessel having nozzles for spraying water onto the strip surface, and a voltage supply for applying a voltage between an anode and a cathode consisting of a guide roll located beside and close to the electrolytic treating liquid contained in the electrolytic treating vessel.

Apparatus for surface treatment of a steel strip

A continuous cold rolling and annealing apparatus for a steel strip so that interruption of a cold rolling mill part does not directly cause a continuous annealing furnace part to be interrupted, in which apparatus at least one cold rolling mill is located upstream of the entrance of a continuous annealing furnace and an intermediate reel for supplying a spare steel strip coil to said continuous annealing furnace, is arranged between the cold rolling mill and the continuous annealing furnace.

Growing community of inventors

Kitakyushu, Japan

Hiroshi Ikegami