JPS5812326B2 - Continuous heating furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a continuous heating furnace of the type that reheats a bloom-rolled steel billet or a continuously cast steel billet to a predetermined temperature for hot rolling, particularly a three-zone type. This relates to a continuous heating furnace.

Conventionally, in the above-mentioned type of continuous heating furnace, when heating a steel billet to a temperature at which it can be rolled, differences occur depending on the amount of excess air, but in general, it is necessary to facilitate combustion in the burner and stabilize the flame. Currently, combustion is carried out with a somewhat excess air content, which has the disadvantage that losses due to surface oxidation of the steel slab cannot be avoided.

In contrast, the present invention aims to provide a continuous heating furnace capable of eliminating the above-mentioned drawbacks, and the gist of the present invention is to provide a heating zone for heating a steel billet to a rolling temperature, and a heating zone for heating a steel billet to a rolling temperature. In a type of continuous heating furnace that is clearly separated from a soaking zone where heating is performed to reduce skid marks and make the temperature uniform, the steel is heated by bringing the burner combustion in the soaking zone into an incomplete combustion state. In addition to preventing oxidation loss of the pieces, the fuel oil due to the incomplete combustion is brought into a complete combustion state by adding the insufficient amount of air to the heating zone to cause secondary combustion, In addition, the gist of this equipment is that the heating zone that heats the steel slab to rolling temperature and the soaking zone that heats the steel slab to reduce skid marks and make the temperature uniform are clearly separated. In this type of continuous heating furnace, a branch air supply pipe is bypassed from the air supply pipe of the upper combustion burner which is to heat the heating zone, and an air injection pipe to be connected to the branch air supply pipe via a flexible hose is provided. The present invention consists in that the furnace wall portion connecting the heating zone and the soaking zone is provided so that air can be blown out.Thus, according to the present invention, the burner combustion in the soaking zone in the furnace is brought into an incomplete combustion state. By doing so, it is possible to prevent loss due to surface oxidation of the steel billet, and the remaining amount of fuel due to incomplete combustion can be recovered by adding air to the heating zone to cause secondary combustion and complete combustion. It is economical because it can fully contribute to energy saving measures because it can effectively utilize the energy.

Next, the present invention will be explained in more detail with reference to two embodiments shown in FIGS. 1 to 3.

First, in FIG. 1, which shows the first embodiment of the present invention, 1 is a heating furnace main body, 2 is a preheating zone, 3 is a heating zone, 4 is a soaking zone, and 5 is a flue. So, preheating zone 2
In addition, the heating zone 3 includes a skid pipe 6 and a cross spar 7 through which cooling water passes or is shielded, as is well known in the art.
The slab-rolled or continuously cast steel billet 8 is fixed in the axial direction at the top of the skid pipe 6 shown in FIG. 2 at a speed corresponding to the residence time at the set temperature corresponding to the heating cycle. In addition, in order to maintain the temperature setting of the heating cycle, an upper combustion burner 10 and a lower combustion burner 11 are installed in the heating zone 3, and other combustion burners are installed in the soaking zone 4. Combustion burners 12 are installed respectively.

Furthermore, as shown in FIG. 2, a branch air supply pipe 1 bypassed from the air supply pipe 13 leading to the upper combustion burner 10
4 has one end connected via a flexible hose 17 to the other end of an air injection pipe 16 to be buried in the vicinity of the curved finishing wall portion 15 that forms the interface between the heating zone 3 and the soaking zone 4. The combustion state by the burner 12 in the soaking zone 4, which corresponds to about 1/2 to 1/3 of the time during which the surface temperature of the piece 8 reaches its maximum temperature and passes through the heating furnace main body 1, is incomplete combustion due to lack of air. By doing so, oxidation loss of the steel billets is prevented, and excess fuel due to this incomplete combustion is diverted from the combustion air from the air supply pipe 13 by appropriately adjusting the valve to divert only the insufficient amount of air. Complete combustion is achieved by injecting the steel pieces 8 from the injection pipe 16 diagonally forward in the traveling direction of the steel pieces 8 through the air supply pipe 14 and the flexible hose 17, and causing secondary combustion.

In addition, 1B is the charging side door of the steel billet 8, 19 is the same extraction side door, 2
0 is a refractory installation anchor, 21 is a support beam, and the installation anchor is fixed to a support pipe 23 with a wire 22 or the like,
The upper combustion burner 10 (lower combustion burner 11 and combustion burner 12) is mounted to the front plate 24 and the burner tile 25 in a known manner.

Next, FIG. 3 shows a second embodiment of the present invention, and in the first embodiment described above, the jet air flow from the jet pipe 16 hits the steel billet 8 obliquely from the front in the advancing direction. However, in this embodiment, the air injection pipe is provided in the reduced furnace wall portion 26 of the soaking zone 4 so that the injection air flow is opposite to the advancing direction of the steel billet 8, and a direction changing nozzle is provided at the tip of the air injection pipe. 27 is installed.

Next, the operation mode of the continuous heating furnace having the above configuration will be described. The charging side door 18 is opened and the steel slabs 8 are sequentially carried onto the skid rail 9 of the skid pipe 6 by carrier means such as a butcher. Preheating zone (700~SOOC) maintained at each set temperature while being transported
, a heating zone (1250
g1300℃) and a soaking zone (approximately 12
00℃), but in this case, heating zone 3
After passing through the soaking zone 4, the steel piece 8 heated to 1200 to 1250°C passes through the extraction side door 19 for approximately 11 minutes.
It is transferred to the rolling process at a holding temperature of 50°C.

According to the present invention, in order to prevent surface oxidation loss of the area piece 8, an incomplete combustion state due to a lack of combustion air (70 to 90% of the theoretical air amount) of the burner 12 in the soaking zone 4 is prevented. None, the resulting fuel is sent to the injection pipe 16 provided on the curved furnace wall section 15 or the reduced furnace wall section 26.
The insufficient amount of air is added to cause secondary combustion by burners io and i1, resulting in complete combustion.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing an example of a continuous heating furnace according to the present invention, and FIGS. 2 and 3 are enlarged detailed views of section A in FIG. 1 showing different embodiments of the present invention. Note that the correspondence relationship between the main parts shown and the symbols is as follows. 1...Heating furnace main body, 2...Pre-heating zone, 3
... Heating zone, 4... Soaking zone, 6...
... skid pipe, 8 ... steel piece, 9 ...
... skid rail, 10 ... upper combustion burner, 11 ... lower combustion burner, 12 ...
... Combustion burner, 13 ... Air supply pipe, 14
...Branch air supply pipe, 15 curved furnace wall section,
16... Air injection pipe, 17... Frekin pull hose, 26... Small furnace wall part.

Claims (1)

[Claims] 1. In a continuous heating furnace of a type in which a heating zone for heating the steel slab to the rolling temperature and a soaking zone for heating the steel slab to reduce skid marks and uniformize the temperature are clearly separated. A branch air supply pipe is bypassed from the air supply pipe of the upper combustion burner that is to heat the heating zone, and an air injection pipe to be connected to the branch air supply pipe via a flexible hose is connected to the heating zone and the soaking zone. A continuous heating furnace characterized by having a connecting furnace wall section so that air can be blown out.