JP2004027332A - Method for heating slab and heating furnace therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for heating a slab by which the slab can be heated uniformly in its width direction, and to provide a heating furnace therefor. <P>SOLUTION: In this method for heating the slab S while being conveyed into the heating furnace, the temperature near the furnace walls 1b of the heating furnace is raised up to the temperature range in the center part. The heating furnace for the slab is provided with a main burner and auxiliary burners 5 for heating the furnace wall side end parts of the slab S on the furnace walls 1b. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a slab heating method and a heating furnace capable of heating so that the temperature in the furnace width direction of the slab becomes uniform.
[0002]
[Prior art]
Conventionally, when a slab (steel slab) is hot-rolled, the slab is usually heated while being conveyed in a heating furnace for the purpose of raising the temperature of the slab to a specific temperature range prior to hot rolling. Yes. The heating furnace is generally provided with a main burner as a main heating source, and the slab temperature is raised by adjusting the heating power of the main burner.
[0003]
On the other hand, the slab size has become diversified due to diversification of needs. Conventionally, heat treatment is usually applied to slabs with a certain margin to the furnace width. However, in recent years, in addition to the slab full of the furnace width, those that are more susceptible to temperature deviation in terms of material are often heat-treated.
However, when the full width slab is heat-treated, there is a problem that the temperature at the end of the slab on the furnace wall side is not lowered to a uniform temperature. Further, the thermal power of the main burner was adjusted to make the temperature uniform, but it was difficult to make the slab temperature uniform only by adjusting the thermal power.
[0004]
[Problems to be solved by the invention]
The present invention solves the conventional problems as described above, and provides a slab heating method and a heating furnace capable of uniformly heating the temperature in the furnace width direction for any size slab. It was completed as a purpose.
[0005]
[Means for Solving the Problems]
The present invention made in order to solve the above-mentioned problem is a method for heating a slab in which the slab is heated while being conveyed in a heating furnace, wherein the temperature in the vicinity of the furnace wall of the heating furnace is a temperature region in the center of the furnace. A slab heating method characterized in that the temperature is raised to a slab, and a slab heating furnace provided with a main burner, wherein an auxiliary burner for heating the furnace wall side end of the slab is provided on the furnace wall This is a slab heating furnace.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a walking beam type heating furnace in which a pre-tropical zone, a heating zone, and a soaking zone are formed in the longitudinal direction, and is a system in which the slab S is heated while being conveyed in the heating furnace. In the figure, 1 is a furnace body, 1a is a ceiling, 1b is a furnace wall, 2a is a movable beam, and 2b is a fixed beam. Further, as the main burner, a roof burner 3 is provided on the ceiling 1a, and a side burner 4 for heating from the lower side of the slab S is provided on the furnace wall 1b. It is almost the same as a furnace.
The main burner may be a roof burner 3 and a side burner 4 as shown in the figure, a roof burner 3 only, or a side burner 4 only.
[0007]
And in this invention, the auxiliary | assistant burner 5 which heats the furnace wall side edge part of the slab S further in the said furnace wall 1b is provided. The auxiliary burner 5 is provided separately from the side burner 4, and as shown in FIG. 2, the auxiliary burner 5 is provided above and below the slab S so as to heat only the furnace wall side end of the slab S by the burner flame. A pair is provided. In this case, if the burner flame is in direct contact with the slab S, the temperature rises greatly. Therefore, it is preferable that the burner flame is slightly opened on both sides and indirectly heated by radiant heat.
[0008]
Conventionally, in a slab heating furnace, heat treatment is performed on a slab having a certain margin with respect to the furnace width. In this case, the slab is heated by three-surface heating of the top and bottom and the end face. It is common knowledge that the temperature is higher than the temperature at the center, and various techniques for cooling the end of the slab have been developed and proposed in order to obtain a uniform temperature of the slab.
However, according to the study of the present inventor, when the width of the slab S approaches the limit of the furnace width, the phenomenon completely opposite to the conventional phenomenon, that is, the temperature at the end of the slab is higher than the temperature at the center of the slab. Clarified that the phenomenon of lowering occurs. Therefore, when the width of the slab S is large, the conventional method cannot control the slab to a uniform temperature. As a result, the temperature at the end of the slab S on the furnace wall side is lowered, and the slab having a uniform temperature is obtained. The problem that cannot be obtained has arisen. In particular, the diversification of needs has led to a wide variety of slab dimensions, and it has become impossible to uniformly control the slab temperature simply by cooling the vicinity of the furnace wall uniformly as in the past.
[0009]
Based on the above findings, in the present invention, the temperature in the vicinity of the furnace wall of the heating furnace is raised to an arbitrary temperature range, thereby uniformly controlling the slab temperature during extraction of the heating furnace. Such temperature control is preferably performed in all zones of the pre-tropical zone, the heating zone, and the soaking zone, but the object can be achieved even if it is performed at least in the soaking zone that is the final step.
[0010]
In addition, it can be completely clarified quantitatively whether the phenomenon that the temperature in the vicinity of the furnace wall becomes lower than the temperature in the center of the furnace when the width of the slab S approaches the furnace width. However, according to the research of the present inventors, this phenomenon occurs when the width of the slab S is 85% or more with respect to the width in the furnace, and it has been confirmed that the heating method of the present invention is extremely effective. .
[0011]
The slab S with a width of 9300 mm was put into a heating furnace with a width of 9800 mm in the furnace and heat treatment was performed. The heating furnace is as shown in FIG. 1, and two auxiliary burners 5 are provided on the upper and lower sides so as to heat the end of the slab S on the furnace wall side. The in-furnace time is 220 minutes, the auxiliary burner 5 has a combustion load of 50% (120 Nm ³ / Hr), the fuel is COG, and the air ratio is 1: 1.
The result is as shown by the solid line in the graph of FIG. 3, and the temperature of only the furnace wall side end portion of the slab S increased, and a substantially uniform temperature distribution could be obtained. In addition, the broken line in a graph shows the case where the auxiliary burner 5 is not ignited, and it turns out that the temperature of the furnace wall side edge part of the slab S is 25 degreeC lower than this invention, and has an uneven temperature distribution.
[0012]
【The invention's effect】
As is clear from the above description, the present invention can increase the temperature in the furnace wall side evenly even when the width of the slab S is large, and can uniformly heat the temperature in the furnace width direction. A temperature slab can be obtained.
Therefore, the present invention greatly contributes to the development of the industry as a slab heating method and a heating furnace that eliminates the conventional problems.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional front view showing an installation portion of an auxiliary burner.
FIG. 3 is a graph showing changes in slab temperature when heated with an auxiliary burner and when not heated.
[Explanation of symbols]
1 Furnace body 1a Ceiling 1b Furnace wall 3 Roof burner 4 Side burner 5 Auxiliary burner S Slab

Claims (4)

A method for heating a slab in which the temperature in the vicinity of the furnace wall of the heating furnace is raised to a temperature range in the center of the furnace in the heating method for a slab in which the slab is heated while being conveyed in a heating furnace. A slab heating furnace provided with a main burner, wherein an auxiliary burner for heating a furnace wall side end of the slab is provided on the furnace wall. The slab heating furnace according to claim 2, wherein the main burner is a side burner. The slab heating furnace according to claim 2 or 3, wherein the main burner is a side burner and a roof burner.

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