Method and apparatus to determine and control the carbon content of steel in a BOF vessel

Abstract

Apparatus for determining in-blow % carbon content and / or the First Turn Down Carbon of a BOF heat includes a light sensor housed within a temperature regulated case having a sighting window including air wipe means to shield the light sensor from steelmaking dust and fume. The apparatus also includes a means to generate a signal that corresponds to the amount of oxygen blown into the BOF during a heat, and a programmable logic controller. The logic controller is programmed to continuously process oxygen blown signals from the signal generating means, and light intensity signals received from the light sensor. The program calculates continuous in-blow % carbon content of the heat based upon the difference in light intensity from a point of maximum light intensity emitted from the BOF vessel in relation to the amount of oxygen blown into the BOF vessel during the same period of time.

Description

BACKGROUND OF THE INVENTIONThis invention is directed to a method and apparatus for controlling or determining the carbon content of a heat in a BOF vessel, and more particularly, to a method for determining the in-blow carbon content and the First Turn Down Carbon (FTDC), in low carbon steel BOF heats containing 0.06% or less carbon.Users of flat rolled steel product demand low carbon grade steel because of its good formability properties. For example, in the automotive industry, such low carbon steel permits auto manufacturers to stamp and form complex automobile shapes without encountering steel spring-back after the foraging operations. This makes it necessary for steelmakers to accurately manage and control the carbon content of their BOF heats to produce a product having the proper metallurgical requirements.In the BOF .[.steehnaking.]. .Iadd.steelmaking .Iaddend.process carbon saturated liquid iron is poured into the vessel along with various amounts of steel scrap. .[.tligh....

AI Technical Summary

Benefits of technology

It is still a further object of this invention to accurately control or determine the carbon content of a BOF heat by measuring a difference in visible light intensity emitted from the BOF vessel in relation to the amount of oxygen blown into the vessel.

And finally, it is still a further object of this invention to provide apparatus, for controlling and / or determining the carbon content of a BOF heat, that includes a self cleaning means to prevent an accumulation of fume or dust on its sensor devices.

Problems solved by technology

Therefore, although Denis has provided some improvement in providing an instantaneous reading of carbon content during a heat, his patent shows a wide margin of error in his predicted carbon levels based upon his flame drop readings.

However, the authors also teach that carbon predictions, based upon flame intensity measurements, are not satisfactory for the more stringent present day needs.

It is well known that such mass / temperature calculations contain a margin of error, and they often lead to either overblowing or underblowing the BOF heats.

In instances where a heat is overblown various undesirable chemical reactions take place within the vessel.

For example, in an overblown heat, the oxygen consumes an excessive amount of carbon and a steel product having an undesirable low carbon level is produced.

This reduces the iron yield of a heat.

Overblowing a heat will also overheat the steelmaking vessel, cause premature wear on its protective refractory lining, and reduce the service life of the vessel.

This increases production time and cost, and causes excess refractory wear.

The excess refractory wear is due to the iron oxides that are formed in the slag during the reblow.

Another problem encountered with BOF control systems is dealing with the hostile environment adjacent the hot BOF vessel.

The radiant heat emitted from a BOF vessel during the steelmaking process overheats sensitive electronic equipment located near the vessel and causes system failures.

The dust and fume causes control equipment sensors to become fouled and dirty, and results in poor readings and inaccurate metallurgical analysis.

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