JPS6257683B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a heating furnace for steel materials, and more specifically, to a heating furnace for heating hot steel pieces and cold steel pieces mixed together.

(Prior Art) A conventional heating operation for a steel billet will be explained based on FIG. Generally, in a heating furnace 1 designed to optimally heat cold steel billets, the cold steel billets are charged onto an in-furnace skid 4 from a charging port 2 at the bottom of the furnace by a charging device 3, and then In the process of moving toward the extraction port 6 at a constant speed by the beam drive device 5,
It is heated to a predetermined temperature by heating burners 7 and 8 installed in the heating furnace 1 and extracted from the extraction port 6. Further, at this time, the exhaust gas is guided from the flue opening 9 at the bottom of the furnace to the flue 10, and the heat is recovered by the recuperator 11.

Under such heating operations using a single charge of cold steel billets, the operating conditions of the furnace and the temperature distribution within the furnace remain almost constant once the steel type, size, heating amount, and extraction temperature of the steel billet are determined. It can be in a state of

In recent years, with the advancement of steel billet manufacturing technology, the use of hot charge, in which hot billets directly delivered from continuous casting equipment or blooming equipment are directly charged into a heating furnace, has been increasing for the purpose of energy saving. However, the generation of cold steel pieces due to quality problems such as surface flaws on the steel pieces cannot be avoided. Heating hot and cold steel billets in dedicated heating furnaces reduces equipment costs,
Currently, this is not possible due to equipment space constraints, so hot and cold billets must be heated in the same furnace.

A heating furnace designed primarily for heating cold steel billets is used to solve problems that occur when hot steel billets are heated.
This will be explained with reference to FIG. In the heating process of hot and cold steel billets, there is a big difference between the two in the temperature history of the heated material on the charging side. FIG. 2 shows an example of the furnace temperature distribution and the steel billet temperature rise curve when hot steel billets and cold billets are heated in the same heating furnace. Here, in the range from the charging end to point A, the temperature of the hot steel billet decreases once, and then it is reheated. In other words, it can be said that the furnace length during this period is not only thermally ineffective for the hot billet, but also harmful.
This hinders the energy saving effect of charging hot steel pieces.

As a method of eliminating this phenomenon that occurs when cold billets and hot billets are heated in the same furnace, an intermediate charging furnace has been proposed in Japanese Patent Publication No. 134125/1983. In addition to the end charging port for cold billets, a charging port for hot billets is installed in the middle of the furnace length to efficiently heat cold billets and hot billets in a mixed manner.

However, according to this, one intermediate charging port only corresponds to a fixed production ratio of cold billets and hot billets;
There is a problem in that it is difficult to maintain stable operation without dealing with changes in the production ratio by increasing the number of charging ports.

(Object of the Invention) In consideration of the above facts, the present invention aims to provide a heating furnace that solves the problems of the prior art described above while compensating for the drawbacks of intermediate charging furnaces.

(Structure of the Invention) In the heating furnace of the present invention, in order to reduce the radiated heat by reducing the radiating area, an intermediate flue is provided that opens at the middle part in the furnace length direction. The opening position of this intermediate flue is determined to be the most efficient position depending on the temperature of the hot steel billet charged and the production volume. For example, if the temperature of the heated steel billet is low and the production volume of this low temperature steel billet is large, the opening of the intermediate flue is located on the charging side from the middle part, and if the temperature of the hot steel billet is high, the opening of the intermediate flue is located on the charging side. The part is located on the extraction side. Next, a partition door is provided on the charging side of the opening of the intermediate flue in the heating furnace, making it possible to efficiently heat hot steel billets in a heating furnace designed primarily for heating cold billets. There is.

(Embodiments of the invention) Hereinafter, embodiments will be described in detail with reference to the drawings.

FIG. 3 shows an embodiment of the heating furnace of the present invention. In the heating furnace 1 shown in the figure, 9 is a flue opening at the bottom of the furnace, 10 is a flue, 11 is a requilifier, and 12 is an intermediate flue opening disposed on the charging side from the middle part of the furnace in the longitudinal direction of the heating furnace. , in this case, the position of the intermediate flue opening is the position where many of the hot steel billets charged into the heating furnace have a low temperature, and the temperature of the hot steel billets charged into the heating furnace is If the height is high, the position of this intermediate flue opening should be placed closer to the extraction side than the intermediate part. 13 has an intermediate flue opening 12 at one end, and the other end joins the flue 10; 14 and 15, a flue 10 and an intermediate flue 1;
Flue switching damper installed in the middle of 3,
Reference numeral 16 denotes a furnace partition door provided near the intermediate flue opening 12. Other symbols are the same as those explained in FIG. 1 above.

In the heating furnace 1 of the embodiment having the above configuration, the cold steel billet is conveyed and heated in the same manner as in the conventional method. That is, it is charged onto the furnace skid 4 from the furnace bottom charging port 2 by the charging device 3, and is brought to a predetermined temperature by the burners 7 and 8 while being moved to the extraction port 6 at a constant speed by the walking beam drive device 5. After heating, it is extracted from the extraction port 6. At this time, the flue gas flows in the same manner as before by fully closing the flue switching damper 15 and fully opening the furnace partition door 16. That is, it is guided from the flue opening 9 at the bottom of the furnace through the flue 10 to the requioperator 11 .

The hot steel billet is transported and heated in the same way as the cold billet, but the exhaust gas passes through the flues 13 and 10 by closing the furnace partition door 16 and flue switching damper 14 and fully opening the flue switching damper 15. I am led to 11. As a result, the exhaust gas is partitioned by the furnace partition door, and less exhaust gas flows out to the charging side. The amount of heat dissipated from the furnace body can be significantly reduced. Furthermore, even if hot steel billets are charged into the hazardous furnace length, the hot steel billets are rarely cooled because they are charged at high speed to the middle using high-speed conveying means. In addition, the exhaust gas discharged from the intermediate flue opening is
Since the temperature is higher than that of the exhaust gas discharged from the flue opening at the bottom of the furnace provided at the charging port, the high temperature exhaust gas is guided through the intermediate flue opening and flows into the requilerator, thereby increasing the heat recovery rate.

In addition, in the embodiment of the present invention, since hot steel billets and cold steel billets are charged from the same charging port of the heating furnace, the purpose is to shorten the residence time of hot steel billets in the harmful furnace length when charging hot steel billets. As such, a high-speed steel billet conveying means is disposed between the flue opening at the bottom of the furnace and the intermediate flue port, that is, in the section where the temperature of the billet once drops and is then reheated to the charging temperature. Examples of high-speed steel billet conveying means include:
A double walking transport device, transport lifter, split hearth, etc. will be installed. This prevents a temperature drop in the harmful furnace length.

FIG. 4 shows a comparison between the furnace temperature and the temperature of the hot steel billet when the hot steel billet is treated in the heating furnace of the present invention and in the conventional furnace. In the present invention, as shown by the solid line, the billet temperature is heated from the charging port without decreasing, and the temperature discharged from the furnace also increases from A to B.
This is because if there is no partition door like in a conventional furnace, the exhaust gas flows out to the charging side and is discharged from the flue opening at the bottom of the furnace. At this time, heat is removed from the exhaust gas due to heat dissipation from the furnace body in the harmful furnace length between the flue at the bottom of the furnace and the partition door, and the exhaust gas temperature drops to A shown in FIG. 4. However, when processing hot steel billets by installing a partition door on the charging side of the intermediate flue opening as in the present invention, by closing this partition door, the exhaust gas is directed to the furnace bottom flue side (toxic furnace length). There is little outflow of the exhaust gas, and the exhaust gas temperature does not drop, and the exhaust gas can be discharged from the intermediate flue opening at the exhaust gas temperature shown in FIG. 4. When the charging temperature is 900° C. in a heating furnace with a furnace length of 45 m, the present invention is expected to save energy by about 10%.

(Effects of the Invention) As described above, according to the present invention, the effective furnace length for heating cold steel billets and hot steel billets is made variable, and cold steel billets and hot steel billets can be mixed and heated efficiently in one furnace. This can be done well and the energy saving effect of hot steel billet charging can be fully utilized.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a conventional heating furnace, Fig. 2 is a graph showing temperature rise curves of cold steel billet and hot steel billet in the conventional heating furnace, and Fig. 3 is a diagram showing an embodiment of the heating furnace of the present invention. The schematic diagram shown in FIG. 4 is a graph showing a temperature increase curve of a heated steel billet in the present invention. DESCRIPTION OF SYMBOLS 1... Heating furnace, 2... Charging port, 3... Charging device, 4... Skid, 5... Walking beam drive device, 6... Extraction port, 7... Burner, 8...
...burner, 9...furnace flue opening, 10...flue,
11...Requiperator, 12...Intermediate flue opening,
13... Intermediate flue, 14, 15... Flue switching damper, 16... Furnace partition door.

Claims (1)

[Claims] 1. A heating furnace provided with a flue having a flue opening at the bottom of the furnace has an intermediate flue installed at a predetermined position in the length direction of the furnace, and a damper is installed in each of the flue at the bottom and the intermediate flue, and A cooling furnace characterized by having a door partitioning the inside of the heating furnace on the charging side at the flue opening of the intermediate flue.
Mixed heating furnace for hot steel materials.