JPS6148525A - Continuous two-stage heating method of rolling stock - Google Patents

Abstract

PURPOSE:To minimize production hindrances and personnel increase and execute continuous two-stage heating by using one of plural heating furnaces for preheating and the other for intrinsic heating or preheating materials with one heating furnace and charging the materials again into the furnace after drawing and heating the materials. CONSTITUTION:The plural heating furnaces 1, 2 are installed in a hot rolling line. Billets 4 which are the rolling stock are conveyed to a charging table 5 and are charged into one heating furnace 1 by a charging installation 6 and are preheated. After the materials are held at an adequate temp., the billet 4-1 is drawn to drawing table 3 and is transferred to a conveying installation 11 by which the billet is conveyed backward to the table 5 and is then charged into the furnace 2 by a charging installation 7. The billet 4-1 is continuously reheated to the temp. suitable for rolling and is drawn to the table 3 then the billet is fed to a hot rolling mill 10. The billet 4-1 preheated and held in one furnace 1 is once drawn to the table 3 and is charged again into the furnace 1 via the installation 11, the table 5 and the installation 6 by which the billet is heated to the required temp.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of using a heating furnace during two-stage heating of a rolled material in a hot rolling process.

(Prior Art) When heating steel during hot rolling, two-stage heating is sometimes performed in which the temperature of the material is temporarily held at a constant temperature during the heating process for the purpose of improving quality. As a typical example, the case of 7-elite stainless steel will be described below.

When ferritic stainless steel sheets are bent, pressed, etc., there is a peculiar waviness (hereinafter referred to as "ridging") phenomenon on the surface of the product, which can be a fatal defect in applications where surface beauty is required.

This ridging phenomenon is presumed to be based on the solidified structure during II casting, so methods for improving ridging properties include applying electromagnetic stirring to reduce the structure during casting, applying vertical reduction during the rolling process, etc. There are methods such as destroying the cast structure and lowering the rolling temperature in the final rolling process.

Furthermore, as one method of destroying the cast structure of the slab, as shown in Figure 3, the slab is preheated during the process of heating the slab to temperatures H and T suitable for rolling, and the temperature of the slab is increased. By holding the temperature T. (Part A) at a temperature of 700°C or higher and lower than the Ac3 transformation point for a certain period of time (Part A), and increasing the temperature to @H0T, where the martensite phase is decomposed into the 7-elite phase and carbide (Bl!Is). There is a technology that improves the solidification structure and prevents the occurrence of welding during rolling.

This heating method is called two-stage heating.

FIG. 4 is a diagram showing the arrangement of a heating furnace in a conventional hot rolling process. Generally, the heating furnace 1.2 is arranged perpendicularly to the rolling fin extraction table 3, and the slab 4 moves on the charging table 5 installed at the rear of the heating furnace, and the charging film [6, 7 It is charged from the rear of the heating furnace. Slab 4 charged into the heating furnace
-1 is sequentially moved to the front of the heating furnace while being heated by an oaking beam, etc. inside the furnace, and after being heated to a temperature suitable for rolling, an extractor 8.9 is installed at the front of the heating furnace.
etc. are extracted onto the extraction table 3. Thereafter, the slab is rolled by a hot rolling mill 10 or the like to become a hot rolled steel plate.

(The problem that the invention seeks to solve)! However, in the conventional method of carrying out two-stage heating between charging once and before extraction, it is necessary to charge the slab into the heating furnace and temporarily stop the slab in the furnace.

As a result, the furnace is in an intermittent operation state, which not only reduces productivity but also causes energy loss, as well as skid mating due to prolonged contact with the cooling vibrator, which poses a major quality problem.

In addition, there are cases where rolled materials of steel types that require two-stage heating and rolled materials of steel types that do not require two-stage heating are sequentially charged into the heating furnace, and in this case, rolled materials that do not require two-stage heating are unnecessary. The reactor would be forced to shut down, resulting in significant energy loss and reduced productivity.

Conventionally, as an example of a method of efficiently heating rolled materials under different heating conditions, there is a method disclosed in Japanese Patent Publication No. 5574/1983. This method selects whether to pass through a plurality of heating furnaces only once or twice, depending on the heating conditions, and to optimize the route of the rolled material as necessary. It is.

However, this technique does not relate to two-stage heating, and the objective of the present invention cannot be achieved.

(Means for Solving the Problems) The present invention has been made in view of the above-mentioned problems, and includes using one heating furnace of a plurality of heating furnaces in the hot rolling process as a preheating furnace.
The other heating furnace is used as the heating furnace for the main purpose, and 2
Stage heating is performed, or a single heating furnace is used to perform preliminary heating until fixation, and then the material is extracted, transported to the charging port using a conveying device, and then charged again at the appropriate timing until it reaches the rolling temperature. This is a continuous two-stage heating process in which the temperature is increased.

(effect) Next, the present invention will be further explained using the figures.

In the method of the present invention, when heating a rolled material in two stages, the charging table 5 and the extraction table 3 are connected by a strip conveying mechanism 11 in the heating furnace arrangement as shown in Figure 1, and one of the heating furnaces 1 is By using the heating furnace as a preheating furnace and the other heating furnace 2 as a heating furnace that raises the temperature to a rolling temperature, the slab is continuously preheated, held, and heated to a rolling temperature.

Also, when carrying out the continuous two-stage heating of the present invention using one heating furnace as shown in FIG. A slab transport membrane ill is provided.

In the equipment configured as described above, as shown in FIG. is loaded into the The slab charged into the furnace is sequentially moved in the direction of the arrow a in the figure by a walking beam in the furnace, etc., and is preheated during the movement to a temperature of 700"C or more Ac3
Appropriate temperature T up to the transformation point. (A range of the temperature rise curve in Figure 3). This temperature T. The slab is held for a certain period of time or longer to improve the slab structure, for example, in the case of a 72ite stainless steel slab, the martensitic phase is decomposed into a ferrite phase and carbide, and then the slab is placed in the front of the heating furnace 1. The slab 4-1 is extracted onto the extraction table 3 by an extractor 8 or the like.

The extracted slab 4-2 is transferred to the slab transport membrane @11 by the extraction table 3, and then transported back to the charging table 5. During this time, the charging of the slab 4 into the heating furnace 1 is temporarily interrupted, and the gummy table 12 provided on the charging table 5 waits at a rear standby position 12-1. This gummy table 12
After waiting, the slab conveying installation 11 enters the charging table 5 and transfers the preheated and fixed slab 4-1 onto the charging table 5.

Thereafter, the slab 4-1 is moved to the rear of the other heating furnace 2 by the charging table 5, and charged into the heating furnace 2 by the charging equipment 7. During this time, the slab conveyance equipment 11 moves to the extraction table 3 side and prepares to receive the next slab 4-1, and at the same time, the dummy table 12 returns to its original position on the charging table 5 and is ready to receive the next slab 4-1. This corresponds to the transportation of piece 4.

The slab 4-1 charged into the heating furnace 2 is sequentially moved to the extraction side by two oaking beams in the furnace, and during this movement, it is continuously reheated to temperatures H and T suitable for rolling. (3rd
(B range of the temperature increase curve in the figure) is extracted onto the extraction table 3 by the extractor 9 and rolled by hot rolling 1fllO or the like.

Next, a method of carrying out continuous two-stage heating according to the present invention using one heating furnace will be explained.

In FIG. 2, when the slab 4 is heated by the continuous two-stage heating method of the present invention, the slab 4 is first charged into the furnace using the charging equipment 6 installed at the rear of the heating furnace. It is sequentially moved in the direction a in the figure using a walking beam or the like inside the furnace. At this time, the heating furnace is set to a preheating temperature. During this movement, the slab 4 is preheated to an appropriate temperature T of 700° C. or more to the Aca transformation point. (A range of the temperature rise curve in Figure 3). This temperature T. By holding it for a certain period of time or more, the structure of the slab at the time of casting is improved as described above.

For example, in the case of ferritic stainless steel, the martensitic phase is decomposed into a 71ite phase and carbides.

The slab 4-1, which has been preheated and held in this manner, is once extracted onto the extraction table 3 by the extractor 8 installed in front of the heating furnace, and then transported to be loaded into the heating furnace again. It is transferred to the equipment 11 and conveyed to the charging table 5. During this time, the dummy table 12 provided on the charging table 5 is placed on standby at a rear standby position 12-1. After this gummy table is on standby, the hook conveying membrane @11 enters the charging table 5, transfers the preheated and fixed slab 4-1 onto the charging table 5, and then transfers it to the charging equipment 5 again. Then, it is charged into the heating furnace 1. The preheated and held slab 4-1 charged into the heating furnace is moved within the heating furnace 1 by an oaking beam. At the same time, the previously charged, preheated, and retained hook pieces are sequentially extracted and transferred to the charging side one after another by the slab conveying membrane Ja11, and then charged into the heating furnace for reheating. be done. At this time, the set temperature of the heating furnace 1 is changed to the temperature required for rolling.

During reheating, the slab 4-1 preheated and held in this manner is continuously heated to temperatures H and T required for rolling (range B of the temperature rise curve in Figure 3), and It is extracted onto the extraction table 3 again by the tractor 8. The extracted slab 4-2 is conveyed to the rolling mill 10 side by the extraction table 3 and rolled by the rolling mill 10 or the like.

(Effects of the Invention) As described above, according to the continuous two-stage heating method for slabs according to the present invention, the slabs are continuously preheated by simply considering the combination of heating furnaces in the conventional hot rolling process. , it becomes possible to maintain the required temperature and heat it to a temperature suitable for rolling. In addition, slabs such as ordinary steel that do not require two-stage heating can be heated and rolled without any problems as in the past.

As a result, it is possible to minimize production problems, increase in personnel, deterioration of costs, etc., which were problems in the past, and it is also possible to improve the structure of slabs by improving the structure of cast slabs, such as manufacturing 7-Elite stainless steel sheets with excellent ridging properties. It is now possible to easily manufacture high-quality steel plates, which can greatly contribute to the industrial world and is beneficial.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the method of the present invention, showing the case where two heating furnaces are used, and FIG. 2 is an explanatory diagram of the method of the present invention, showing the case where one heating furnace is used. FIG. 3 is a temperature rise curve of two-stage heating, and diagram t54 is an explanatory diagram of the conventional two-stage heating method. 1.2 is a heating furnace, 3 is an extraction table, 4.4-1.4-
2 is a slab, 5 is a charging table, 6.7 is charging equipment, 8.
9 is an extractor, 10 is a hot rolling machine, 11 is slab conveyance equipment, 12 is a dummy table, and 12-1 is a dummy table (standby position). Storage map 7. Ya □ Well 3 diagram

Claims (2)

[Claims] (1) When performing two-stage heating of rolled material using multiple heating furnaces installed in a hot rolling line, one heating furnace is used as a preheating furnace until retention, and the other heating furnaces are used after verification. A continuous two-stage heating method for a rolled material, characterized in that it is used as a heating furnace to raise the temperature to a rolling temperature. (2) When carrying out two-stage heating of the rolled material using one heating furnace installed in the hot rolling line, the rolled material is preheated to retention and extracted once, and then the rolled material is charged again from the charging port. 1. A continuous two-stage heating method for a rolled material, characterized by heating the rolled material to a temperature at which it can be rolled.