JP2604315B2 - Hot coil manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a hot coil using rolling equipment which is installed in close proximity to an extension of a continuous casting equipment.

[0002]

2. Description of the Related Art Hot strips require high quality and mass production.
The mainstream is a method in which a large steel ingot is divided through a converter, or is manufactured using a large slab by a continuous casting machine. By the way, in the case of this method, even if the process is limited from the production of a billet to the rolling of a hot coil, a large billet production-related facility or a continuous casting facility, a large heating facility, a rough rolling mill, a hot rolling mill including a finish rolling mill. A coil manufacturing facility is required, and a mechanism for comprehensively controlling and managing this manufacturing facility is added.
There was a problem that the plant site was enlarged, the facility construction cost became huge, and the management system of the manufacturing process became complicated.
In addition, in the case of this method, the time required for the steel material manufacturing process becomes longer, the temperature of the product decreases significantly, various control mechanisms for temperature compensation, and in response to the temperature decrease during rolling, the processing speed increases and An increase in rolling force is required, and a large number of auxiliary technologies are required in addition to the original rolling mechanism, such as an increase in machine strength. This, combined with the above-mentioned problems, has caused a rise in steel material production costs.

Meanwhile, as a countermeasure against the enlargement of hot coil manufacturing equipment in a rolling mill, one of the factors of the increase in manufacturing equipment is to prevent mutual interference between manufacturing equipment arranged in a straight line. In consideration of the fact that there is an interval of one slab between each equipment so that the slab can be processed independently in the heating equipment, several rough rolling mills and finish rolling mills After rough rolling, a so-called coil box is installed, in which the slab is once wound into a coil to shorten the length of the manufacturing equipment, prevent the temperature of the product from lowering, and make the temperature of the product uniform. It has also been done. However, this method has not completely solved the above problem.

[0004] On the other hand, with the improvement of steelmaking technology, there has been proposed a method of manufacturing a hot strip using thin cast pieces. In this method, the slab is made as thin as possible (thickness 50).
mm) or by rolling down in a continuous casting machine, making it possible to omit the large heating equipment and the rough rolling mill, which were essential in the manufacturing equipment using the large slab. It is intended to simplify the equipment and solve the problems of the method using the large cast slab, but this method has problems in the quality and productivity of the steel material. That is, a) high quality products cannot be produced. That is,
There are few problems in general use or when manufacturing steel grades with low surface quality requirements, but when producing high-quality products, surface defects that occur during casting and scale that occurs up to the rolling process are reduced. It cannot be completely removed, and the surface condition of the product tends to deteriorate. b) The type of steel is carbon (C) 0.08 to 0.15 wt%
In the case of a so-called peritectic reaction zone, the casting speed is high and the conditions for solidification are difficult to be constant, so that cracks are likely to occur in the slab and the quality cannot be kept constant. c) In order to manufacture thin cast pieces, skill is required in setting seals, nozzles, and the like, which involves difficulties in casting operations and affects the life of the nozzles. d) When high-speed casting or low-speed casting is performed, the slab is cooled unevenly, uneven stress is applied to the slab, or powder is involved, whereby the structure of the slab is easily embrittled. Therefore, the type of steel material in which cracks easily occur is restricted. e) Since the space between the molds is narrow, the molten steel fluctuates greatly during casting, and the surface condition of the slab tends to deteriorate. f) Since the rolling ratio is small, defects generated in the slab tend to occur as deterioration of the surface condition of the product as it is,
Hard to remove. g) Since the surface scale of the product generated during the casting or rolling process is thin and tightly adhered, it takes time to remove the surface scale even with an ultra-high pressure descaler, and the temperature of the product decreases. , And not completely removed. However, there is a problem in that the thickness of the slab is reduced.

[0005]

SUMMARY OF THE INVENTION The present invention solves the problems of the above-mentioned conventional method for manufacturing a hot strip using a large slab or a thin slab, and aims at miniaturization and simplification of manufacturing equipment. It is another object of the present invention to provide a method of manufacturing a hot coil that enables low-cost production of high-quality products.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a continuous casting machine for medium thickness slabs, a slab transport table, a heating unit, a rough rolling mill under high pressure, a finishing rolling mill, and a down coiler. A method for manufacturing a hot coil in which the same slab is continuously rolled from a heating facility to a down coiler using a hot coil manufacturing facility arranged on a wire, wherein: The thickness of the slab to be manufactured by the continuous slab casting equipment is set to 70 mm to 120 mm, and (b) the time from the start of casting in the continuous slab of medium thickness slab until the cast slab reaches the heating equipment. Is approximately proportional to the thickness of the slab, less than 10 minutes for 70 mm slab,
(C) the central surface temperature of the slab after heating in the heating equipment is 950 ° C. to 1150 ° C., and (d) the peripheral speed of the first roll of the rough rolling mill under high pressure 5m /
(E) Maintaining the temperature at the end of the product passing through the finish rolling mill at the transformation temperature Ar3 or higher of steel.

The numerical values such as the thickness of the slab in the method for manufacturing a hot coil of the present invention are determined for the following reasons.

(A) Structure relating to the thickness of the slab In the present invention, the distance between the nozzle and the mold is reduced by limiting the thickness of the slab produced by the medium-thickness slab continuous casting facility to 70 mm or more. , And the addition of powder and the removal of the fired material can be easily performed, whereby various operations of continuous casting can be stably performed. Also,
The rocking of the molten steel during casting is remarkably suppressed, the occurrence of biting and cracks can be reduced, and the floating of inclusions in the molten steel can be stably maintained. Can be kept good. In addition, since the scale grows to some extent, it is not necessary to use an ultra-high pressure descaler, and the surface scale can be easily removed by a normal descaler. Further, it is possible to prevent the temperature of the slab from suddenly decreasing or becoming non-uniform due to heat dissipation, by re-heating from the inside of the slab.
Further, the arrangement for securing the unit weight of the manufactured hot coil becomes easy. On the other hand, in the present invention, by limiting the thickness of the slab to 120 mm or less,
Cast slabs can be manufactured without the need for an enormous and sophisticated facility as in the conventional method. In addition, since the height of the machine can be reduced, the static pressure of the molten steel generated during solidification can be kept low, thereby preventing deformation of the slab and causing serious defects inside the slab. The installation of advanced equipment for prevention can be reduced. Further, it is necessary to bring the temperature of the slab to a uniform rolling temperature in a short time while balancing the recuperation from the inside of the slab and the heating of the entire slab and the edge portion by the heating equipment. The capacity of the heating equipment can be minimized. Furthermore, it is easy to perform the heating by the slab heating equipment and the rolling by the rolling mill in synchronization.

(B) Configuration relating to the time from the start of casting to the time when the cast slab reaches the heating equipment In the present invention, as in the conventional method for producing a hot strip using thin slabs, It is also possible to arrange a heating facility for uniformly heating the slab immediately after the medium-thick slab continuous casting facility. Further, as a buffer for coping with troubles in the subsequent steps, a slab transfer facility that cuts the cast slab to a predetermined length and then pulls out the slab horizontally can be arranged in the preceding step of the heating facility. Note that the drawn slabs can be used as a rolled material by being reheated and then drawn into the rolling equipment using a slab transfer equipment, similarly to the slabs manufactured by other equipment.
In this way, the time from the start of casting to the time when the cast slab reaches the heating equipment is added to the time required for the slab to pass through the slab transfer equipment, so the temperature of the slab decreases due to heat dissipation. Or become uneven, but also in this case, the time from the start of casting in the medium-thickness slab continuous casting equipment until the cast slab reaches the heating equipment is approximately proportional to the thickness of the slab , 70 mm slab, less than 10 minutes, 80 mm slab, less than 11 minutes, 90 mm slab, less than 12 minutes, 100
Less than 13 minutes for mm slabs, 12 for 110 mm slabs
By setting the length of the slab to less than 15 minutes in the case of a slab of 120 mm or less, the heat of the slab can be effectively used, and it is not necessary to remarkably increase the capacity of the heating equipment. In this case, the slab transfer equipment is preferably provided with equipment such as a cover for reducing heat radiation.

(C) Configuration relating to central surface temperature of slab after heating in heating equipment The temperature of the slab during rolling has a great effect on the quality of the product, the workability of rolling, and the like. Also, detailed management is performed in consideration of the material and quality of products, energy efficiency, and the like. In the present invention, since the same slab is continuously rolled between the heating equipment and the down coiler, the high-pressure rough rolling mill and the finish rolling mill can be arranged close to each other and the casting can be performed. Since the slab can be rolled immediately after being heated, and thus the temperature of the slab is less reduced, the central surface temperature of the slab after heating in the heating equipment is 950 to 1150 degrees Celsius, lower than before. The surface roughness of the roll of the rolling mill can be prevented, and the energy efficiency can be improved. It is not preferable to set the central surface temperature of the slab after heating to 950 degrees Celsius or less because it is difficult to maintain the temperature of the product at the end of passing through the finish rolling mill at the transformation temperature Ar3 of steel or higher. On the other hand, to make the central surface temperature of the slab after heating 1150 degrees Celsius or more,
It is not preferable in terms of product quality, roughening of rolls of a rolling mill, and energy efficiency.

(D) Configuration relating to the peripheral speed of the first roll of the rough rolling mill under high pressure Since a drop in the temperature of the slab during rolling has a fatal effect on the quality of the product, the rolling time is reduced as much as possible. Therefore, in a conventional large-sized hot coil facility having several stages of rough rolling mills, the peripheral speed of the first roll of the rough rolling mill is set to 30 m /
Minutes or more, generally about 70 m / min.
In the present invention, since the same slab is continuously rolled between the heating equipment and the down coiler, the high-pressure rough rolling mill and the finish rolling mill can be arranged close to each other and the casting can be performed. Since the slab can be rolled immediately after heating, and the temperature of the cast slab is small, the peripheral speed of the first roll of the rough rolling mill under high pressure is 5 m / min to 20 m / min. It can be set low, and the rolling reduction of one stand of the rough rolling mill can be increased. By the way, in relation to the reduction ratio of one stand of the rough reduction mill, the reduction of the temperature of the slab during rolling has a fatal effect on the quality of the product. Therefore, it is desirable to reduce the number of rolling mills and shorten the rolling time as much as possible. In the present invention, since the peripheral speed of the first roll of the heavy-duty rough rolling mill is set to 5 m / min to 20 m / min, which is lower than the conventional one, the reduction ratio of one stand of the heavy-duty rough rolling mill is 40%. As described above, the rolling time can be shortened, more preferably, to 50% or more, which can be set higher than before. In addition, as a result, it is possible to reduce the passing speed of the product through the finish rolling mill, and it is possible to reduce mechanical specifications such as motor capacity and rigidity of the finish rolling mill.

(E) Configuration relating to the temperature at the end of the product passing through the finish rolling mill The temperature of the slab at the time of rolling greatly affects the quality of the product, the workability of rolling, and the like. Detailed management is performed in consideration of the material and quality of the product, energy efficiency, etc. In the present invention, since the same slab is continuously rolled between the heating equipment and the down coiler, the high-pressure rough rolling mill and the finish rolling mill can be arranged close to each other and the casting can be performed. Since the slab can be rolled immediately after being heated, and the temperature of the slab is small, the product finish can be finished even if the center surface temperature of the slab after heating in the heating equipment is set lower than before. It is possible to maintain the temperature at the end of the passage through the rolling mill at the transformation temperature Ar3 of the steel or higher, so that the quality of the product and the workability of the rolling can be well maintained.
Further, the lowering of the passing speed of the finish rolling mill increases the water cooling effect of the steel plate transport table, and as a result, the overall length thereof can be shortened.

[0013]

In the method for manufacturing a hot coil of the present invention,
By continuously rolling the same slab from the heating equipment to the down coiler using medium-thick slabs, it is possible to produce high-quality products at low cost while reducing the size and simplification of manufacturing equipment. be able to.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the illustrated embodiment. 1 and 2 show an example of equipment used to carry out the method for manufacturing a hot coil of the present invention.

This equipment includes a continuous casting equipment 1 for supplying medium-thick slabs, a cutting machine 2, a slab transport table 3, a heating equipment 4 for uniformly heating the slabs installed subsequently thereto, a descaler. 5, a rough rolling mill 6, a shear 7, a descaler 8, a finish rolling mill 9, a steel sheet conveying table 10, and a rolling equipment 12 and a rolling equipment in which a down coiler 11 for winding a steel sheet in a coil shape is arranged in close proximity to a straight line. 1
As a buffer for coping with the trouble in 2, the slab transfer device 16 is configured to draw out the cast medium-thick slab to the side as it is.

The slab transfer equipment 16 reheats the drawn slabs in the same manner as the slabs manufactured by other equipment, and then supplies the slabs from the transport table 3 to the supply rolling equipment 12 to thereby reduce the rolling material. In order to be able to use as a slab, it is composed of slab transport tables 13 and 15 and a heating facility 14 for heating cold slab.

The continuous casting equipment 1 for supplying medium thickness slabs includes:
Conventionally and widely used ones can be downsized and used. As the heating equipment 4 constituting the rolling equipment 12, it is desirable to use an induction heating furnace or a combustion heating furnace and to have a corner heating equipment for independently heating the corners of the slab. Further, the descalers 5 and 8 are provided with a descaler for removing scale formed on the surface of the slab by high-pressure water, and the high-pressure rough rolling mill 6 is provided with a large-diameter roll having a large rolling capacity and the size of the slab to receive. Rolling mill with a large degree of freedom
Although it is desirable to configure a plurality of rolling mills equipped with heavy rolling rolls, in this embodiment, six rolling mills are arranged in series,
The equipment constituting the rolling equipment 12 is not limited to this, and may be used in combination with known equipment as appropriate.

In order to prevent the temperature of the slab from dropping due to heat radiation, a cover and a heat insulating material are provided in the continuous casting equipment 1, the transfer table 3, and other equipment, and the transfer table with which the slab contacts. It is desirable to use a low heat transfer material for members such as the third roller.

The finishing mill 9 rolls the large slab supplied from the slab supply equipment 16 a number of times by the rough rolling mill 6 under heavy rolling, and is rolled by the rough rolling mill 6 under heavy rolling. It is desirable that the slab is configured to be able to pass through the gap between the rolls of the finish rolling mill 9. Specifically, for example, in addition to means for adjusting the distance between the upper and lower rolls of the finish rolling mill 9 in accordance with the roll thickness of the slab, so that the gap between the rolls of the finish rolling mill 9 can be made large. Means are provided for quickly moving the upper and lower rolls of the finish rolling mill 9 upward or downward by a fixed amount, and the slab moving between the rolls of the finish rolling mill 9 contacts the upper and lower rolls of the finish rolling mill 9. A guide member 9a for guiding the slab and a receiving roll 9b for supporting the lower surface of the slab are provided on one side or both sides of the roll. In this case, it is desirable that the rough rolling mill 6 and the finish rolling mill 9 under high pressure are electrically controlled so as to interlock with each other including the guide member 9a and the receiving roll 9b of the finish rolling mill 9.

Thus, in the conventional continuous casting equipment 1,
Normally, lots are aggregated to some extent and general-purpose products are manufactured continuously for a certain period of time, so it was difficult to respond to orders from customers for small quantities of high-quality products or products of special materials. In such a case, or when the rolling equipment is operated when the supply of hot slab is interrupted when the continuous casting equipment is stopped due to repair of the continuous casting equipment or the like, a cold slab of a desired material is taken out of the line. Equipment for supplying the slab transport table 3 from the cold slab transport table 13 of the slab supply facility 16 via the heating facility 14 and the heated slab transport table 15 is utilized. The slab supplied from the slab supply facility 16 is rolled by the high-pressure rough rolling mill 6 and the finish rolling mill 9 in the same manner as the hot slab supplied from the continuous casting facility 1, and is coiled by the down coiler 11. Rewind,
A hot coil having a property different from that of a hot coil manufactured from a slab supplied from the continuous casting facility 1 can be manufactured. When the material of the slab supplied from the slab supply equipment 16 is the same as the material of the hot slab supplied from the continuous casting equipment 1, it means that there is no difference in the properties of the manufactured hot coil. Not even. In this case, the heating of the slab by the heating equipment 4 can be omitted, and when the slab supplied from the slab supply equipment is larger than the slab supplied from the continuous casting equipment, the supplied slab is used. Is repeatedly rolled a plurality of times by a rough rolling mill 6 under high pressure to a predetermined thickness, and then is applied to a finish rolling mill 9. When the slab is repeatedly rolled a plurality of times by the rough rolling mill 6 under strong rolling, the gap between the rolls of the rough rolling mill 6 under strong rolling is greatly opened, and the slab moving between the rolls of the finishing rolling mill 9 is formed. While the slab is guided and supported by the guide member 9a and the receiving roll 9b so as not to contact the upper and lower rolls of the finish rolling mill 9, the rough rolling mill 6 under high pressure is used.
The end of the cast slab to be rolled is positioned so as to pass through the gap between the rolls of the finish rolling mill 9.

Next, a method of manufacturing a hot coil using the above equipment will be described. The medium-thick slab supplied from the continuous casting facility 1 is transported to the heating facility 4 via the slab transport table 3, is uniformly heated by the heating facility 4, and is formed on the slab surface by high-pressure water of the descaler 5. After removing the scale that has been removed, it is rolled to a predetermined thickness by a rough rolling mill 6 under high pressure. Immediately after removing the scale formed on the surface of the cast slab by high-pressure water of a descaler 8, a finish rolling mill The rolled steel sheet is transported to the down coiler 11 through the steel sheet transport table 10 by the rolled steel sheet 9 and the steel sheet is wound into a coil by the down coiler 11 to produce a hot coil.

In this case, the same slab is continuously rolled between the heating equipment 4 and the down coiler 11, and (a) the thickness of the slab manufactured by the medium thickness slab continuous casting equipment is 70 mm to 120 mm. (B) The time from the start of casting in the medium thickness slab continuous casting equipment to the time when the cast slab reaches the heating equipment is substantially proportional to the thickness of the slab. Less than 10 minutes, 1
(C) the central surface temperature of the slab after heating in the heating equipment is 950 ° C. to 1150 ° C., and (d) the peripheral speed of the first roll of the rough rolling mill under high pressure 5m /
(E) The temperature at the end of the product passing through the finish rolling mill is maintained at a transformation temperature Ar3 or higher of steel. In addition, the peripheral speed of the first roll of the rough rolling mill under high pressure was set to 5 m / min to 20 m / min,
Since the rolling ratio is set lower than before, the rolling reduction ratio of one stand of the rough rolling mill is 40% or more, more preferably 5%.
0% or more.

Examples of weights and shapes of slabs and final products used in the method of manufacturing this hot coil (examples in parentheses are examples)
Is shown below. (Slab) Weight: Max30t (20t) Thickness: 70mm-120mm (70mm) Length: Max30m (25m) (final product) Weight: Max30t Thickness: 1.2mm-12.7mm Width: 900mm-1600mm

[0024]

According to the present invention, the problems with the conventional method of manufacturing a hot strip using a large slab or a thin slab are solved, and the manufacturing equipment can be reduced in size and simplification, and the manufacturing cost can be reduced. Quality products can be produced at low cost.

[Brief description of the drawings]

FIG. 1 is a side view showing an example of a hot coil manufacturing facility.

FIG. 2 is a plan view showing an example of a hot coil manufacturing facility.

FIG. 3 is a side view showing an example of a finish rolling mill.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Medium thickness slab continuous casting equipment 2 Cutting machine 3 Slab transport table 4 Heating equipment 5 Descaler 6 High-pressure rough rolling mill 7 Shear 8 Descaler 9 Finish rolling mill 10 Steel sheet transport table 11 Down coiler 12 Rolling equipment 13 Slab transport table 14 Heating equipment 15 Slab transport table 16 Slab transport equipment

Claims (1)

(57) [Claims] 1. A hot coil manufacturing facility in which a medium thickness slab continuous casting facility, a slab transport table, a heating facility, a rough rolling mill under high pressure, a finish rolling mill, and a down coiler are arranged in a straight line. A method of manufacturing a hot coil in which the same slab is continuously rolled up to a down coiler, wherein the hot coil is manufactured by: (a) reducing the thickness of a slab manufactured by a medium thickness slab continuous casting facility to 70 mm; (B) The time from the start of casting in the medium thickness slab continuous casting equipment to the time when the cast slab reaches the heating equipment is substantially proportional to the thickness of the slab. If less than 10 minutes, 1
(C) the central surface temperature of the slab after heating in the heating equipment is 950 ° C. to 1150 ° C., and (d) the peripheral speed of the first roll of the rough rolling mill under high pressure 5m /
(E) a method for producing a hot coil, wherein the temperature at the end of the product passing through the finish rolling mill is maintained at or above the transformation temperature Ar3 of steel.