JPS62267051A - Method and apparatus for heating casting slab for direct rolling - Google Patents

Abstract

PURPOSE:To effectively restrain the temp. drop of a casting slab part comes into contact with the water cooling roll, by blowing a burner flame slantly to an edge part of the slab at the time of heating the edge part by the burner in the process of carrying for a direct rolling. CONSTITUTION:In a tunnel type furnace arranged in the process of the slab 2 carrying from a continuous casting process to a hot rolling process, each burner 1 is arranged at the inclining angle on the width direction of the casting slab 2. The burner flame 3 injected from the burner 1 is blown diagonally to the edge part of the casting slab 2 and gone round between the casting slab 2 and the water cooled carrying roll 4. In this way, the temp. drop of the casting slab contacting part with the water cooling roll is effectively restrained, to carry the casting slab having good temp. distribution to the hot rolling process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for heating a cast slab during a conveyance process from a continuous casting process to a hot rolling process in direct rolling, and an apparatus therefor.

[Conventional technology]

BACKGROUND ART Recently, so-called direct rolling, in which hot slabs discharged from a continuous casting process are sent to a hot rolling process using IF as they are, has been attracting attention as an energy-saving method for producing steel products. In this direct rolling, hot slabs discharged from the continuous casting process are stored. Since the heat is used as the heat required for hot rolling, heat consumption is significantly reduced compared to the conventional method of cooling and reheating the slab for hot rolling.

However, the slab transported from the continuous casting process to the hot rolling process does not have a uniform temperature distribution. For example, the edge portion of a slab may be excessively cooled due to the influence of ambient temperature, and the temperature may drop below the temperature required for hot rolling. Therefore, when this slab is hot rolled, defects such as cracks and poor rolling are likely to occur at the edges. On the other hand, in the central part, the heat retained in the slab is difficult to dissipate, so the high temperature is maintained. For this reason, scale is likely to form on the surface of the central portion, causing scale defects during rolling.

Such non-uniformity in temperature distribution becomes particularly noticeable when the conveyance distance from the continuous casting process to the hot rolling process is long.

Furthermore, since the equipment such as continuous casting machines and hot rolling mills in steel works is large-scale, changing the layout of the equipment involves an economic burden. That is,
Even when direct rolling is adopted, the design is based on the existing equipment layout. Therefore, in steelworks where the continuous casting process and hot rolling process are laid out as separate production lines, slabs are forced to be transported over long distances from the continuous casting process to the hot rolling process. , the non-uniform temperature drop during this period has a significant adverse effect on hot rolling.

Therefore, Japanese Utility Model Publication No. 59-135815 proposes heating the edge portion of the slab before it is delivered to a hot rolling mill.

In addition, a tonfu-mounted furnace is installed in the conveyance process from the continuous casting process to the hot rolling process, and by heating and raising the temperature of the edge part of the slab inside this furnace, it is cast to the state required for hot rolling. It is practiced to maintain the pieces (Japanese Patent Application Laid-Open No. 47-3402
(See Publication No. 1).

[Problem that the invention seeks to solve]

When the slab is transported through such a tunnel furnace from the continuous casting process to the hot rolling process, the temperature drop of the slab can be suppressed to some extent. However, since the material to be transported is in a high temperature state, a roll having a built-in water cooling structure is used as the transport roll at this time. Therefore, the temperature drop of the slab increases at the contact portion with the water-cooled roll and in the vicinity thereof.

However, when heating the edge part of a slab with a burner flame in a tunnel furnace, the burner flame rarely reaches the part of the slab in contact with the water-cooled roll and the vicinity thereof;
It is not possible to prevent the temperature of the slab from decreasing in this area.

Therefore, in view of the problems associated with burner heating in conventional tunnel furnaces, the present invention aims to maintain a good temperature by actively heating the contact area with the water-cooled roll and the slab part in the vicinity. The purpose is to transport slabs with maintained distribution to the hot rolling process and perform direct rolling under stable conditions.

[Means for solving problems]

In order to achieve the object, the heating method of the present invention tilts the burner frame with respect to the edge portion of the slab when heating the edge portion of the slab during the conveyance process from the continuous casting process to the hot rolling process. It is characterized by spraying.

In addition, the heating device of the present invention has a burner nozzle installed in a tunnel furnace installed in a conveying process from a continuous casting process to a hot rolling process, so that the burner frame is slanted toward the edge of the slab. It is characterized by being arranged at an angle.

Furthermore, when the angle of inclination of the burner nozzle to the edge of the slab can be changed, even more efficient heating can be achieved.

[Effect]

FIG. 1 is a diagram schematically explaining the relationship between burners and slabs arranged in a tunnel furnace.

Inside the tunnel furnace, a plurality of burners 1 are arranged along the conveyance direction of the slab 2 as indicated by the arrow.

The burner 1 is arranged at an inclination angle α with respect to the width direction of the slab 2. Because of this inclination angle α, the burner flame 3 ejected from the burner 1 is blown obliquely onto the edge portion of the slab 2. Therefore, this burner frame 3 can go around between the slab 2 and the conveyor roll 4. As a result, the contact surface of the slab 2 with the conveyance roll 4, which is normally cooled by the water cooling mechanism built into the conveyance roll 4, is heated, and the temperature drop in that area can be suppressed.

Furthermore, by spraying the burner frame 3 at an angle of inclination α, the area of the edge portion of the slab 2 that the burner frame 3 comes into contact with becomes larger. Therefore, the edges should be heated evenly.

When the slab to be transported has a certain width, the desired heating can be obtained by spraying the burner frame 3 onto the slab while fixing the inclination angle α. However, the width of the IH piece can vary depending on requirements. When trying to heat slabs of different widths, the distance between the burner 1 and the end face of the slab 2 changes depending on the width. Therefore, in response to this width change, the inclination angle α of the burner 1 is adjusted so that the burner frame 3 collides with the end surface of the slab 2 on the upper surface of the conveyor roll 4.
It is preferable to adjust. This provides the most efficient heating.

At this time, if the burner 1 is tilted in the opposite direction or the forward direction with respect to the conveyance direction of the slab 2, the burner frame 3 injected from the burner 1 will be directed to the front end face or the rear of the slab 2 depending on the direction of inclination. It will come into contact with the edge. This front end face or rear end face, like the edge part, is susceptible to temperature drop due to the influence of the surrounding temperature, and if it is fed into the hot rolling mill as it is, it will cause a large impact to the rolling rolls. become. In this respect, the burner frame 3 sprayed onto the front end face or the rear end face of the slab 2 heats the surface where the temperature tends to drop, thereby making it possible to alleviate the impact force applied to the rolling rolls in the subsequent hot rolling process.

Here, whether the burner 1 is inclined in the reverse direction or the forward direction is selected depending on the temperature distribution in the longitudinal direction of the slab 2, that is, which of the front end face and the rear end face is lower in temperature. For example, in the subsequent hot rolling process, if the load on the rolls of the rolling mill is large when the rear end face of the slab 2 passes through, the burner l is tilted in the forward direction with respect to the slab conveying direction. Heat the rear end face of No.2. On the other hand, if the load applied to the rolls of the rolling mill when the front end face of the slab 2 passes is large, the burner 1 is tilted in the opposite direction with respect to the slab transport direction to heat the front end face of the slab 2. Thereby, the load applied to the rolls of the rolling mill can be reduced.

Note that the above-described inclined arrangement of the burners I can be applied to all or some of the burners arranged in the tunnel furnace.

〔Example〕

Hereinafter, the features of the present invention will be specifically explained with reference to Examples.

FIG. 2 shows the influence of the inclination angle α of the burner 1 on the temperature rise of the edge portion of the slab 2. In this example, LNG is used as the fuel, the air ratio is 1.05, and the flow rate is 80 to 10.
It was ejected from burner 1 at 0 m/sec.

As is clear from FIG. 2, the inclination angle α of the burner 1 has an optimum value for each width of the slab 2. That is, when the inclination angle α is small, the burner frame 3 corresponding to the edge of the slab 2
Although the impingement flow velocity increases and the convective heat transfer coefficient increases, ! Burner frame 3 at the edge of H piece 2
The collision area becomes smaller and the amount of heat transfer decreases. On the other hand, when the inclination angle α is large, the collision area of the burner frame 3 at the edge of the slab 2 becomes large, but the distance between the burner l and the slab 2 also increases, so that the impact area on the edge of the slab 2 increases. The impingement flow velocity of the burner frame 3 is attenuated. As a result, the convective heat transfer coefficient decreases and the amount of heat transfer decreases.

Therefore, this inclination angle α is determined so that the edge portion can be heated most efficiently. At this time, if the width of the slab 2 is considered to determine the inclination angle α, slabs 2 with various widths will be heated effectively according to their respective widths, and fuel consumption will be reduced. A reduction in quantity is also achieved.

〔Effect of the invention〕

As described above, in the present invention, by tilting the burner frame and spraying the edge portion of the slab, the burner frame can be sent to the portion where the lower surface of the slab contacts the conveyance roll. Therefore, it is possible to maintain the contact surfaces of the 13 pieces with the feed rolls at the temperature required for hot rolling, where it was difficult to suppress the temperature drop when using a conventional tunnel furnace. Therefore, during the conveyance process from the continuous casting process to the hot rolling process, it is possible to prevent the temperature of the edge part of the slab, especially the lower surface that comes into contact with the conveyance roll, from dropping, allowing direct rolling under stable conditions. becomes possible.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically explaining the heating method of the present invention, and FIG. 2 shows the effect that the inclination angle of the burner has on the temperature rise of the SR piece edge.

Claims (1)

[Claims] 1. When heating the edge part of the slab with a burner during the conveyance process from the continuous casting process to the hot rolling process, the burner frame is slanted and sprayed onto the edge part. Method of heating slabs for direct rolling. 2. In a tunnel furnace installed during the conveyance process from the continuous casting process to the hot rolling process, the burner nozzle is arranged at an angle so that the burner frame sprays the blast at an angle to the edge of the slab. A heating device for direct rolling slabs.