JPH10140246A - Device for heating skid mark - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a skid mark heading device in a steel material heating furnace to halve the skid mark. SOLUTION: An auxiliary heating gas supplying tube 5 for heating the skid mark, penetrating a water-cooling pipe 3 and a refractory 4 layer in the skid rail at the lower part of a soaking zone in an axial-flow combustion type or the axial flow combustion type soaking zone of the steel material heating furnace at the upper part and directing the spouting hole just below a cast slab to be heated, is set at the position of 8-16mm from the ejecting end of the heating furnace.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating apparatus for heating a skid mark in a steel heating furnace of an axial combustion type or an isothermal type which heats a slab.

[0002]

2. Description of the Related Art Slabs, blooms, billets and other cast slabs are heated to a predetermined temperature before hot rolling, in the range of about 1150 to 1250 ° C. for ordinary steel. When heating the above slab, a pusher type or walking beam type heating furnace is used, but in the case of the former pusher type heating furnace, a portion in contact with a heated slab bottom and a water-cooled skid rail. In the same way, in a walking beam type heating furnace, a skid mark is formed at a part of the fixed support part and the movable support part which mainly comes into contact with the water-cooled fixed support part and the slab bottom part. A temperature drop called a mark occurs. This skid mark causes problems such as a decrease in product thickness accuracy in subsequent rolling or the like, and a crack due to insufficient strength or elongation, thereby lowering the yield. Therefore, great efforts have been made to eliminate the skid mark.

[0003] The simplest and general method for eliminating the skid mark is to change the arrangement direction of the skid rail provided in the heating furnace to constantly change the contact point between the slab and the skid rail. However, the skid mark is hardly eliminated. For this reason, in addition to the above method, or in addition to the above method, there is an example in which a normal combustion burner or a regenerative burner is provided in the former stage of the heating furnace to improve the performance of the heating furnace and to perform heat compensation. Has not been resolved. Further, Japanese Patent Application Laid-Open No. 3-111513 discloses a combustion apparatus for generating a combustion gas for heating a skid mark on a slab extraction side of a heating furnace, and a metal or ceramic conduit for introducing the combustion gas into the heating furnace. It has been proposed to separately provide a heating device to be used. However, this device is a multi-layered device having a metal or ceramic conduit and a cooling air, a combustion air and a fuel pipe inside the conduit independently made of metal or ceramic near the skid rail lower part in the heating furnace. In addition, the combustion in the combustion device is burned with an air amount slightly less than the theoretical air amount; air ratio: 0.8 to 0.9 to generate incomplete combustion gas, which is passed through the inner tube to the furnace. The combustion device itself becomes very expensive equipment because of the complicated structure of performing secondary combustion with the air discharged from the outer pipe leading to the combustion chamber. Further, there is a disadvantage that the maintenance of this apparatus must be constantly performed.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a method for heating a skid mark in a steel heating furnace in which a skid mark generated when a slab is heated in the heating furnace, which has been regarded as a problem in the past, is efficiently eliminated by an inexpensive apparatus. An apparatus is provided.

[0005]

The inventor of the present invention has conducted various studies to eliminate the skid mark. As a result, the present inventors have found that the tropics in the heating furnace, that is, the slab extraction side of the heating furnace is in the ripening zone. Regardless, it was found that the desired soaking temperature had not reached a relatively desired soaking temperature, and attention was paid to the effective use of the skid rails already arranged in the heating furnace, and the water cooling pipe and refractory layer in the skid rails were focused on. Built-in combustion pipes in the inside make it possible to simultaneously satisfy the water cooling function, fire resistance function and combustion function, and the most effective in eliminating skid marks by directing the combustion gas outlet below the slab Was found to be.

The present invention has been made based on the above findings, and the gist is as follows. That is, the first invention is to penetrate the water-cooled pipe and the refractory layer in the skid rail in the lower part of the soaking furnace of the axial combustion type or the soaking furnace of the axial flow combustion type steel heating furnace upward, and directly under the slab to be heated. A skid mark heating device characterized by burying an auxiliary heating gas supply pipe for heating a skid mark incorporating a gas supply pipe directed to a jet port, and the second invention is characterized in that the skid mark heating device has the heating device. The skid mark heating device according to claim 1, wherein the device is installed at a position of 8 to 16 m from an extraction end of the furnace.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a skid mark heating device according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a heating furnace 1. A plurality of skid rails 2 supporting a slab to be heated are arranged in the heating furnace bottom in parallel with the longitudinal direction of the heating furnace. FIG. 2 is a cross-sectional view (a part of FIG. 1) of the skid mark heating device according to the present invention. The internal structure of the skid rail 2 is a water cooling pipe 3 made of a normal 20Ni-25Cr stainless steel.
Cooling water is circulated inside the water cooling pipe 3 to cool the skid rail with water. The outer periphery of the water-cooled pipe 3 is coated with different types of refractory layers 4. In order to supply additional combustion gas in the vicinity where the lower part of the slab and the skid rail are in contact, a combustion gas supply pipe 5 made of the same stainless steel as the water-cooled pipe is built through the water-cooled pipe 3 and the refractory layer 4. ing. The ejection port of the combustion gas supply pipe 5 has a structure slightly protruding from the refractory layer. In addition, the combustion gas supply pipe 5 can be disposed without being exposed to an external heating atmosphere by passing through the skid rail support (water cooling pipe is built in).

Further, usually, a heating furnace is burned by introducing an excess air of about 10%, and a small amount of oxygen remains in the furnace, so that new combustion can be performed by using this. . Therefore, there is no need to provide a structure for ejecting combustion air, and the structure can be simplified. By adopting such a structure, the conventional heating furnace extraction side, that is, heating can be performed in a state close to a preset heating temperature curve without causing a temperature drop in a solitary zone,
The temperature of the part where the slab and the skid rail are in contact with each other can be raised, and skid marks are greatly reduced.

FIG. 3 shows the relationship between the arrangement position of the combustion gas supply pipe and the skid mark. In the figure, A is a type in which the skid rail is shifted toward the heating furnace exit side, and B is a case of a linear type skid rail. In each case, the slab temperature and the skid heated within 16 m from the heating furnace extraction side are shown. It can be seen that the temperature difference at the rail contact portion is minimized. That is, it was confirmed that by setting the position of the combustion gas supply pipe within a range of 8 to 16 m from the heating furnace extraction side, the temperature drop was eliminated and the skid mark was reduced.

In actual heating, the composition of the slab to be heated, the heating temperature and soaking temperature required for the slab, the slab size, the contact area and time between the slab and the skid rail,
Factors such as the amount of cooling water for the skid, the temperature of the skid, and the heating time are all processed by a computer, the amount of heat taken by the skid portion is integrated, and the amount of heat supplied to the skid mark heating device is determined to control the amount of combustion gas supplied.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A straight type skid rail disposed under a soaking zone of an axial combustion type or soaking zone type steel heating furnace, particularly a skid mark according to the present invention within 12 m from a heating furnace extraction end. A heating device was provided for each skid rail. The diameter of the fuel pipe incorporated as the skid mark heating device is about 50 mm. The size of the slab heated in the heating furnace was 10 m in length, 1 m in width, and 0.25 in thickness.
m. When the skid mark heating device according to the present invention is used, as shown in FIG. 2, the difference between the lower surface temperature of the slab contacting the skid rail and the temperature of the other portion is about 1/2.
It was able to be improved to １ ／, the real temperature to 10 to 15 ° C. or less. Also, by employing the method of the present invention, the energy consumption per unit time can be reduced by about 2% by shortening the soaking time, and the steel material yield is improved by about 0.2% by eliminating the skid mark.

[0012]

As described above, according to the present invention, the skid mark can be reduced by half with a simple device and the slab heating yield can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross section of a heating furnace.

FIG. 2 is a diagram showing a cross section of a skid mark heating device according to the present invention.

FIG. 3 is a graph showing a temperature difference between an installation position of a combustion gas supply pipe and a skid mark portion.

[Explanation of symbols]

 Reference Signs List 1 heating furnace 2 skid rail 3 water cooling pipe 4 refractory 5 combustion gas supply pipe 6 skid rider 7 cast slab

Claims (2)

[Claims] 1. An axial-flow combustion or soot-fired axial-fired steel heating furnace penetrates upward through a water-cooled pipe and a refractory layer in a skid rail at the lower part of a soaking furnace, and is directly under a slab to be heated. An auxiliary heating gas supply pipe for heating a skid mark incorporating a gas supply pipe oriented to the above is embedded. 2. The skid mark heating device according to claim 1, wherein the skid mark heating device is installed at a position 8 to 16 m from an extraction end of the heating furnace.