JPH0610299B2 - Steel billet heating method in continuous heating furnace - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a billet heating method in a continuous heating furnace that performs a mixed operation of hot and cold pieces and a mixed operation of billets having different thicknesses.

(Conventional technology and its problems) Conventionally, in a continuous heating furnace that performs a mixed operation of hot pieces and cold pieces, and a mixed operation of steel pieces having different thicknesses, the required heating temperature until the steel pieces reach the extractable temperature is Since the cold pieces are thicker than the hot pieces and are thicker than the thin pieces, the cold pieces or the thick steel pieces become a bottleneck in heating, and the steel pieces generate a down time for waiting for heating or heating. Due to the decrease in extraction pitch, the production efficiency decreased, and the heating fuel consumption rate and rolling power consumption rate deteriorated.

(Means for Solving the Problems) The present invention is a method of heating a plurality of billet groups having different heating times in a continuous heating furnace in a mixed charging manner while transporting the billet from the heating furnace charging side to the heating furnace extraction side. In, in the above-mentioned plurality of billet groups, the billet group is heated at a billet conveying speed and in-furnace temperature that can complete heating of the billet group having the shortest heating time, and the billet group that has not been heated is heated. It is a billet heating method in a continuous heating furnace, characterized in that it is fed back from the furnace extraction side to the heating furnace charging side and reheated at least once. It is also possible to charge the hot piece group and the cold piece group in a mixed manner, heat the steel piece group at a billet conveying speed and furnace temperature that can complete heating of the hot piece group, and reheat the cold piece group. is there.

(Operation) FIG. 3 shows an example of equipment layout for carrying out the present invention. 1 is a heating furnace loading table, 2 is a continuous heating furnace, 3 is a heating furnace extraction table, 4 is a rolling mill, 5 is a crane for feeding the billet back to the heating furnace, and 6 is the temperature of the billet. A radiation thermometer, 7 is a heated steel strip.

[When normal operation is performed] In this case, the heating steel billet 7 is measured by the radiation thermometer 6 installed on the charging table 1 to measure the billet temperature at the time of charging the heating furnace.
Using that temperature as the initial temperature of the billet, heat transfer is calculated from the ambient temperature in the furnace to sequentially convey the billet temperature in the furnace, and when it reaches the extractable temperature, it is extracted from the heating furnace and extracted. The steel slab is conveyed to the rolling mill 4 by means of 3.

[When Performing Operation According to the Present Invention] When a cold piece or a steel piece having a large thickness and a long heating time is mixed in a steel piece having a short heating time to operate, one of the steel pieces having a long heating time is used. For the second heating, as in the case of the above-mentioned normal operation, charge into the heating furnace and heat at the same conveyance speed and heating temperature as the surrounding steel pieces with a short heating time (heat pieces, thin steel pieces, etc.). , Extract before reaching the extractable temperature. The extracted steel pieces are fed back to the side opposite to the rolling mill 4 by the transport table 3, and fed back from the extraction table 3 to the charging table 1 by the crane 5. After that, as in the case of normal operation, the temperature of the hot steel slab is measured with the radiation thermometer 6, and the temperature of the hot slab is calculated using the temperature as the initial value while heating and transporting the slab to the extractable temperature. When it reaches the limit, it is extracted and transported to the rolling mill.

(Example) FIG. 2 shows an example of the temperature changes in the in-furnace billet of the cold and hot pieces.
When the heating piece α ₁ is charged into the heating furnace at 650 ° C., 180
Although the extractable temperature reaches 1100 ° C in minutes, it takes 240 minutes for the cold piece β to reach the same extraction temperature. Therefore, when the cold piece β is mixed in the heat piece α ₁ , the heat piece extraction is performed. After that, a heating waiting time of 60 minutes is required to extract the cold pieces. During this time, production is reduced, fuel unit consumption is deteriorated due to overheating of the heat pieces in the furnace and heat loss in the furnace, fixing of rolling mills, etc. Deterioration of power consumption rate due to power loss.

FIG. 1 shows an example of the temperature change in the billet in the furnace when the present invention is applied. Cold pieces β is mixed charged with Netsuhen alpha _1, thermal piece alpha ₁
It is heated at the conveying speed and heating temperature of _1, and is extracted in the same in-furnace time of 180 minutes as the heat piece α ₁ , but the steel piece temperature at this time is still about 900 ° C. The extracted slab is sent back to the heating furnace charging side and reloaded into the heating furnace while the slab temperature is above the temperature of other heating slabs, the same conveying speed and heating temperature as the surrounding heating slab α _2. And heat it up. By performing such reheating,
At the time of reheating, the extractable temperature can be reached and extraction can be performed without causing a heating waiting time, and it is possible to prevent production reduction and deterioration of fuel consumption rate and electric power consumption rate.

FIG. 4 shows a heating pattern of a steel slab when the present invention is applied. Indicates the case where the heating time of A ₁ material is equal to the sum of the heating times of B ₁ material and C ₁ material. A specific example is when A ₁ material is a cold piece, B ₁ material, and C ₁ material is a hot piece.
In this case, the A ₁ material is completely heated by reheating once.
Is a case where the heating time of the A ₂ material B ₂ material, equal to the sum of the heating time of the C ₂ material and D ₂ material, A ₂ material becomes heated completed twice reheating. It indicates the case where the heating time of the A ₃ material is longer than the heating time of the B ₃ material, B ₃ material, shorter than the sum of the heating time of the C ₃ material. When mixing A ₃ material and B ₃ material at the beginning,
Heating pattern is a pattern of B ₃ material rather than A ₃ material, when A ₃ material is reheated, heat in the heating pattern to complete heat the C ₃ rather than A ₃ material.

(Effects of the Invention) As is apparent from the above description, according to the present invention, rolling suspension by waiting for heating of a billet having a long heating time at the time of mixed charging of a billet having a long heating time and a short billet, It is possible to prevent extraction pitch down.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of temperature transition in a heating furnace of a steel slab according to the present invention, FIG. 2 is a diagram showing an example of temperature transition in a heating slab of a steel slab, and FIG. 3 is a diagram for carrying out the present invention. The figure which shows the example of an equipment layout, FIG. 4 is a figure which shows the heating pattern example of the steel piece by this invention. 1 ... Heating furnace charging table, 2 ... Continuous heating furnace, 3 ...
Heating furnace extraction table, 4 ... rolling mill, 5 ... crane,
6 ... Radiation thermometer, 7 ... Heating billet.

Claims (2)

[Claims] 1. A method of heating a plurality of billet groups having different heating times in a continuous heating furnace in a mixed manner and transporting the billet from the heating furnace loading side to the heating furnace extraction side while heating. Among them, the billet group that requires the shortest heating time is heated at the billet conveying speed and furnace temperature that can complete heating, and the billet group that has not been heated is fed from the heating furnace extraction side to the heating furnace charging side. The method for heating a billet in a continuous heating furnace, wherein the billet is heated back to the furnace and reheated at least once. 2. A hot piece group and a cold piece group are mixedly charged, and the steel piece group is heated at a billet conveying speed and in-furnace temperature capable of heating the hot piece group, and the cold piece group is reheated. The method for heating a billet in a continuous heating furnace according to claim 1.