KR101510374B1 - Heating method of semi-finished products for hot continuous rolling - Google Patents

Abstract

According to an embodiment of the present invention, a heating method of semi-finished products for hot continuous rolling comprises: a pre-processing step where semi-finished products are produced from a continuous casting machine; a post-processing step where the semi-finished products are supplied to a rolling machine and made into products. A first heating procedure takes place on an edge heater if the temperature of the semi-finished products supplied to the rolling machine are under 400°C, and the semi-finished products which have gone through the first heating procedure and passed through a concurrent heating tunnel, are loaded into a heating furnace and goes through a second heating procedure where the products are heated to 950°C or higher.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of heating a semi-finished product in a continuous hot-

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semi-finished product heating method in continuous hot rolling, and more particularly to a semi-finished product heating method in continuous hot rolling in which the heating method of a semi-finished product is changed depending on the temperature state of the semi-finished product.

[0003] With the development of the steel industry, various continuous casting methods for continuously casting intermediate materials close to the shape of the final product have been developed. Accordingly, there is a need for an improved continuous casting machine capable of improving the operating efficiency and producing a good quality product.

In general, the continuous casting machine includes a ladle, a tundish, a mold, a cooling device, and the like. Specifically, the molten steel to which the desired alloy component is to be fed through the steelmaking and refining processes is transferred to the tundish through the ladle. The molten steel distributed in each tundish in the tundish is solidified through the cooling device, through which a semi-finished product having a certain size and shape is produced.

These semi-finished products may be slabs, blooms, billets, etc., which are mainly used for rolling, and the semi-finished products produced by the continuous casting method are supplied to the rolling apparatus to be manufactured as final products.

For example, in the process of manufacturing a conventional thick plate, a slab manufactured from a continuous casting machine is heated in a heating furnace. At this time, the slab is heated to a temperature range of 950 DEG C or more, which is suitable for rolling.

Next, the heated slab is subjected to a descaling operation. That is, when the slab is heated for a long time in the heating furnace, scale (iron oxide that occurs on the surface) is generated on the slab surface. This scale can be removed by high pressure water sprayed on the slab surface.

Next, the slab subjected to the descaling operation is subjected to the thickness control of the thick plate through the hot rolling process, and the slab subjected to the hot rolling process is cooled to produce the final product.

In this way, the slabs produced by the continuous casting process through the milling and smelting processes are rolled and manufactured as heavy plates.

However, there is a problem that the production speed of the pre-production process from the continuous casting machine and the production rate of the post-production process from the semi-finished product to the final product are not always constant.

Therefore, there are cases where the pre-process and the post-process are intermittently divided to produce the semi-finished product and the final product, respectively. However, in this case, the productivity of the product is inferior.

On the contrary, when the product is manufactured by continuously connecting the pre-process and the post-process, the productivity of the product can be increased, but the energy loss of the furnace is large.

In other words, the temperature difference between the semi-finished products occurs largely depending on the waiting time and the season of semi-finished products charged into the furnace. In the heating furnace, since the semi-finished product is heated based on the lowest temperature among semi-finished products charged into the furnace, There is a big problem of energy loss.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a semi-finished product heating method in continuous hot rolling in which the heating method of the semi-finished product is changed according to the temperature state of the semi-finished product.

According to an aspect of the present invention, there is provided a method of manufacturing a semi-finished product, And a post-process in which the semi-finished product is supplied to a rolling apparatus to be made into a product. When the temperature of the semi-finished product supplied to the rolling apparatus is less than 400 ° C, the primary heating is performed in the induction heating apparatus, Wherein the semi-finished product is charged into a heating furnace after passing through a heat retaining tunnel, and the semi-finished product is heated to 950 DEG C or more.

In an embodiment of the present invention, when the temperature range of the semi-finished product supplied to the rolling apparatus is 400 ° C or more and less than 850 ° C, the semi-finished product is charged into the heating furnace to heat the semi-finished product, When the temperature range of the semi-finished product is in the range of 850 ° C. to less than 950 ° C., the semi-finished product is charged into the heat insulating furnace, and if the temperature range of the semi-finished product supplied to the rolling device is 950 ° C. or more, .

In an embodiment of the present invention, the induction heating apparatus may be configured such that two or more of the induction heating apparatuses are continuously connected and the semi-finished product is heated to a temperature not higher than the phase transformation temperature of the semi-finished product.

In one embodiment of the present invention, the heat-retaining tunnel includes: an outer wall portion forming an outer shape; A heat insulating portion provided on the inner side of the outer wall portion to prevent heat loss of the semi-finished product; And a transfer unit provided on the inner side of the heat insulating unit and for guiding the semi-finished product supplied from the induction heating unit to the heating furnace.

The effect of the semi-finished product heating method in the continuous hot rolling according to the present invention described above is as follows.

First, according to the present invention, it is possible to reduce the energy waste of the heating furnace by varying the heating method of the semi-finished product depending on the temperature state of the semi-finished product.

That is, when the temperature condition of the semi-finished product is less than the normal temperature to 400 ° C, the secondary heating is performed in the heating furnace after the primary heating in the induction heating apparatus to reduce the energy loss of the heating furnace.

In addition, since the semi-finished product charged into the furnace is charged in a state where the temperature is maintained at a certain level or higher, the heating temperature of the semi-finished product can be rapidly increased. Therefore, the productivity of the product can be increased.

Secondly, according to the present invention, a heat-retaining tunnel is provided between the induction heating device and the heating furnace, thereby minimizing the heat loss of the semi-finished product in which the primary heating is performed in the induction heating device.

Thirdly, according to the present invention, it is possible to increase the productivity of a product by supplying continuous semi-finished products to the rolling apparatus by varying the heating method of the semi-finished product depending on the temperature state of the semi-finished product.

It should be understood that the effects of the present invention are not limited to the above effects and include all effects that can be deduced from the detailed description of the present invention or the configuration of the invention described in the claims.

1 is a schematic view showing a semi-finished product heating method according to an embodiment of the present invention.
2 is a schematic view showing an induction heating apparatus, a heat-trapping tunnel and a heating furnace according to an embodiment of the present invention.
3 is a cross-sectional view illustrating a heat-trap tunnel according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "indirectly connected" . Also, when an element is referred to as "comprising ", it means that it can include other elements, not excluding other elements unless specifically stated otherwise.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a schematic view showing an induction heating apparatus, a heat-trapping tunnel, and a heating furnace according to an embodiment of the present invention, and FIG. 3 is a schematic view of a heat exchanger according to an embodiment of the present invention. 1 is an illustration of an example of a supplemental heat tunnel according to one embodiment.

FIG. 1 is a schematic view showing a semi-finished product heating method 1000 according to a temperature state of a semi-finished product. The semi-finished product heating method can be variously classified according to the temperature state of the semi-finished product.

The pre-casting step 10 is a step from the continuous casting machine (not shown) including a ladle, a tundish, a mold, a cooling device and the like to a step of producing a semi-finished product such as a slab, a bloom, a billet, And the post-process 20 refers to a process up to the step of cooling the semi-finished product supplied from the pre-process 10, and then cooling it to a final product.

The semi-finished product manufactured through the pre-process 10 is guided to a post-process 20 to be manufactured as a final product. That is, the semi-finished product manufactured from the pre-process 10 is supplied to a rolling device (not shown) of the post-process 20 to be manufactured in the form of a product, and then is manufactured into a final product through a cooling process.

At this time, in the continuous hot rolling in which the pre-processing 10 and the post-processing 20 are continuously performed, the difference in the manufacturing speed between the pre-processing 10 and the post-processing 20 occurs in the waiting- Etc., which may cause a temperature difference between semi-finished products.

In other words, in the semi-finished product charged into the heating furnace 600, the temperature difference between the semi-finished products becomes large due to factors such as the waiting time and the season.

Thus, in the semi-finished product heating method 1000, the productivity of the semi-finished product supplied to the post-process 20 is varied according to the temperature state of the semi-finished product, thereby enhancing the productivity of the product and enhancing the energy efficiency of the furnace.

Specifically, the method of heating the semi-finished products according to the temperature state of the semi-finished product is classified into five types, and the respective methods of operation will be described by dividing them into the first to fifth operation methods (100) to (500).

First, the first operation method (100) is a operation method applied when the temperature range of the semi-finished product manufactured from the continuous casting machine is 950 DEG C or more. In this case, the semi-finished product is not subjected to any heat treatment, Direct supply. That is, since the first working method 100 maintains the temperature at which the temperature of the semi-finished product can be rolled to 950 ° C or higher, the rolling of the semi-finished product can be performed without reheating.

Next, the second operation method 200 is applied to a case where the temperature range of the semi-finished product manufactured from the continuous casting machine is 850 ° C or more and less than 950 ° C. In this case, the boil-heated furnace 210 is used.

Here, the booster furnace 210 is a heating device that is smaller in size than the heating furnace 600 and is a simple heating device, prevents the temperature of the semi-finished product from falling due to movement of the semi-finished product or atmosphere, or reinforces the temperature of the semi-finished product to the rolling possible temperature.

As described above, the second operation method 200 can quickly supply only the semi-finished product having a temperature range of 850 ° C to less than 950 ° C to the rolling apparatus in the state of heating or keeping it.

Next, the third working method 300 is applied to a case where the temperature range of the semi-finished product manufactured from the continuous casting machine is 600 ° C or more and less than 850 ° C. In this case, the heating furnace 600 is used.

The heating furnace 600 is an enclosed furnace used for heating the semi-finished product. The semi-finished product is heated to a temperature at which the semi-finished product can be rolled by the rolling device using oil or gas fuel. That is, the semi-finished product charged into the heating furnace 600 can be supplied to the rolling apparatus while being heated to 950 ° C or more.

A semi-finished product having a temperature range of 600 ° C or higher and lower than 850 ° C in the semi-finished product charged into the heating furnace 600 is referred to as a hot charge, and the hot-charged semi-finished product increases the fuel saving rate of the heating furnace 600 . That is, since the semifinished product having a high temperature is charged into the heating furnace 600 and the semi-finished product is heated, the fuel consumption of the heating furnace 600 can be reduced.

In other words, the higher the temperature of the semi-finished product charged into the heating furnace 600, the greater the fuel saving rate of the furnace 600 can be.

Next, the fourth working method 400 is applied to a case where the temperature range of the semi-finished product manufactured from the continuous casting machine is 400 ° C or higher and lower than 600 ° C. In this case, the heating furnace 600 is used.

Such a semi-finished product having a temperature range of not lower than 400 ° C. and less than 600 ° C. is called a warm charge, and the semi-finished product is usually accumulated in a field due to a difference in production speed between the pre-process 10 and the post- And may be a worm charge when charged into the heating furnace 600. [

Next, referring to FIG. 2, the fifth operation method 500 is an operation method applied when the temperature range of the semi-finished product manufactured from the continuous casting machine is from room temperature to less than 400 ° C, . Such a semi-finished product having a temperature range of room temperature to less than 400 ° C is referred to as a cold charge.

The semi-finished product of the cold charge is firstly heated in the induction heating apparatus 510, then charged into the heating furnace 600, and is supplied to the rolling apparatus after the secondary heating. That is, when the semi-finished product having a low temperature is directly charged into the heating furnace 600 and the semi-finished product is heated, the fuel consumption of the heating furnace 600 is prevented from being increased.

Two or more of the induction heating apparatuses 510 may be continuously connected to perform selective heating depending on the temperature state of the semi-finished product. That is, a plurality of induction heating apparatuses 510 may be continuously provided to gradually preheat the low-temperature semi-finished products. At this time, each of the continuously induction heating apparatuses 510 can adjust the heating condition of the semi-finished product stepwise by controlling the change of current.

Here, the induction heating apparatus 510 heats the semi-finished product below the A1 transformation point of the semi-finished product. Generally, a steel material has a phase-change section depending on the temperature, and an endothermic reaction that absorbs a large amount of heat occurs in the phase-change section.

Therefore, when the induction heating apparatus 510 which heats the semi-finished product through instantaneous power consumption heats the semi-finished product beyond the A1 transformation point, there is a problem that the heat consumption is large and the energy loss due to the natural heat cooling of the semi-finished product becomes large. Thus, the induction heating apparatus 510 conducts the primary heat treatment to the A1 transformation point or lower of the semi-finished product, and then the secondary heat treatment is performed on the semi-finished product in the heating furnace 600. [

Meanwhile, a heat retaining tunnel 520 is provided between the induction heating apparatus 510 and the heating furnace 600.

Referring to FIG. 3, when the semi-finished product heated by the induction heating apparatus 510 is moved to the heating furnace 600, the heat retaining tunnel 520 prevents the heat loss of the semi-finished product.

The heat insulating tunnel 520 may include an outer wall portion 521, a heat insulating portion 522, and a transfer portion 523.

The outer wall portion 521 forms an outer shape of the heat retaining tunnel 520 and protects the semi-finished product from the outside. The shape of the outer wall portion 521 may be various. That is, the outer wall portion 521 may have a closed tunnel shape, or a part of the outer wall portion 521 may have an open tunnel shape.

3 (a), the outer wall part 521 has a closed tunnel shape, and a conveying part 523 is provided inside the closed outer wall part 521 to guide the semi-finished product guided from the induction heating device 510 And is guided to the heating furnace 600. Thus, in the case of the tunnel type in which the outer wall portion 521 is sealed, the heat loss of the semi-finished product from the outside air can be minimized.

Referring to FIG. 3 (b), the transfer part 523 is provided inside the outer wall part 521, and the lower part of the outer wall part 521 has an open tunnel shape. That is, when interference occurs between the outer wall portion 521 and the transfer portion 523, interference between the outer wall portion 521 and the transfer portion 523 can be avoided by opening the lower portion of the outer wall portion 521.

The shape of the tunnel in which the lower portion of the outer wall portion 521 is opened can facilitate the replacement and maintenance of the transfer portion 523 as compared with the closed tunnel form. The conveying unit 523 guides the semi-finished product placed in the conveying unit 523 to the heating furnace 600 in the form of a roller.

As described above, the outer wall part 521 can take various forms according to the interference with the conveyance part 523 and the like.

The heat insulating portion 522 is provided on the inner side of the outer wall portion 521 and may be formed of a soft type ceramic wool or a hard type castable.

The heat insulating portion 522 made of ceramic wool is lightweight and flexible, and is easily installed inside the outer wall portion 521. In addition, when the ceramic wool is laminated in multiple layers, the heat insulating effect of the heat retaining tunnel 520 can be enhanced.

Also, the heat insulating portion 522 made of castable is manufactured by mixing a lightweight aggregate having excellent heat insulation with a binder and has a low specific gravity and excellent heat insulation, thereby preventing heat loss of the semi-finished product.

The heat shielding tunnel 520 minimizes the heat loss of the semi-finished product moving from the induction heating device 510 to the heating furnace 600 along the transfer part 523.

In other words, the fifth working method 500 is a method in which the semi-finished product of the cold charge is first heated from the induction heating apparatus 510 and then charged into the heating furnace 600 via the heat retaining tunnel 520, It is possible to lower the energy loss of the mold 600 and increase the heating speed of the semi-finished product.

For example, it is possible to reduce the waste of fuel in the heating furnace compared with the conventional heating method by charging the semi-finished product of the conventional cold charge directly into the heating furnace 600. That is, the energy consumption used for heating the semi-finished product can be lowered.

The semi-finished product to be charged into the heating furnace 600 may be a hot-charging state, a warm-charging state, and a cold-charging state, and the semi-finished product may be heated by the heating method (third through fifth methods) 600 so as to minimize the change in the temperature setting of the heating furnace 600. Accordingly, the waste of the fuel in the heating furnace 600 can be reduced, and the heating speed of the semi-finished product can be increased.

In addition, since the semi-finished product of the hot-charging state, the warm-charging state, and the cold-charging state is charged into the heating furnace 600 while maintaining a temperature higher than a certain level, the heating speed of the semi-finished product can be increased. Therefore, it is possible to smoothly supply the semi-finished product to the post-process, thereby improving the productivity of the product.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

100: 1st method of operation 200: 2nd method of operation
210: Booth column 300: How to operate the 3rd
400: The fourth method of operation 500: The fifth method of operation
510: induction heating apparatus 520: heat insulating tunnel
521: outer wall portion 522:
523: transfer part 600: heating furnace
1000: Semi-finished product heating method

Claims (4)

A line process for producing a semi-finished product from a continuous casting machine; And
And a post-process in which the semi-finished product is supplied to a rolling apparatus to be manufactured into a product,
When the temperature of the semi-finished product supplied to the rolling apparatus is less than 400 ° C, the primary heating is performed in the induction heating apparatus. The semi-finished product, which has been subjected to the primary heating, is supplied to the heating furnace after passing through the heat retaining tunnel, And if the temperature of the semi-finished product supplied to the rolling apparatus is in the range of 400 ° C. to less than 850 ° C., the semi-finished product is charged into the heating furnace to heat the semi-finished product, When the temperature range of the semi-finished product is in the range of 850 ° C to less than 950 ° C, the semi-finished product is charged into the heat insulating furnace, and if the temperature range of the semi-finished product supplied to the rolling device is 950 ° C or more, Wherein said hot rolling is carried out in a continuous hot rolling process. delete The method according to claim 1,
Wherein at least two of the induction heating apparatuses are continuously connected and the semi-finished product is heated to an A1 transformation point or less of the semi-finished product. The heat exchanger according to claim 1,
An outer wall forming an outer shape;
A heat insulating portion provided on the inner side of the outer wall portion to prevent heat loss of the semi-finished product; And
And a conveying part provided on the inside of the heat insulating part and guiding the semi-finished product supplied from the induction heating device to the heating furnace.

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