WO2017069378A1

WO2017069378A1 - Endless rolling device and method

Info

Publication number: WO2017069378A1
Application number: PCT/KR2016/006854
Authority: WO
Inventors: 정제숙; 송석철; 박교선; 김용기; 조용석; 심영섭; 고영주; 박경미
Original assignee: 주식회사 포스코
Priority date: 2015-10-21
Filing date: 2016-06-27
Publication date: 2017-04-27
Also published as: US20180297092A1; KR101755236B1; KR20170046871A; EP3366380A1; CN108136458B; WO2017069378A8; CN108136458A; JP2018530436A; EP3366380A4

Abstract

One embodiment of the present invention provides an endless rolling device and method, which have improved cooling conditions for producing advanced high strength steel, and the endless rolling device according to one aspect of the present invention comprises: a continuous casting machine for casting a slab; and a cooling bed having at least one piece of water-cooling equipment and at least one rolling mill continuously connected to the continuous casting machine, wherein, in the cooling bed, an initial position (S) at which the water-cooling equipment is provided so as to manufacture advanced high strength steel through at least one water-cooling is defined by mathematical formula 1 below. Here, H is the thickness (mm) of a slab, V is the casting speed (m/sec) of the slab, h is the product thickness (mm), and t is the target arrival time (sec) until entry into the cooling bed.

Description

Continuous rolling device and method

The present invention relates to a continuous continuous rolling apparatus and method for producing ultra high strength steel (AHSS).

Referring to Figure 1, in the general batch rolling method for securing the winding temperature during the production of general steel, after finishing rolling, it is controlled to the target winding temperature through air cooling, water cooling, air cooling.

On the other hand, cooling using Laminar Flow Cooling or High Density Cooling, which is cooled by the coolant during the manufacture of Advanced High Strength Steel, requires air cooling, primary water cooling, air cooling, The material is secured by adjusting the target winding temperature through the second stage of water cooling and air cooling.

The cooling rate and the amount of cooling water in the first air cooling and the second air cooling are set differently according to the type of production steel (for example, DP steel, TRIP steel, FB steel, etc.).

On the other hand, in the continuous device in which the player and the rolling mill are connected to each other directly, the ROT passage speed may vary according to the final thickness according to the playing speed and slab thickness. In particular, the ultra-high strength (AHSS) steel is controlled to slow the passage through the continuous device, and thus the ROT cooling method is also different from the general continuous process.

However, in the conventional continuous rolling apparatus and method, the water cooling start time required for AHSS manufacturing is not known accurately, and thus, there is a difficulty in determining the cooling position.

One embodiment of the present invention is to provide a continuous continuous rolling apparatus and method for improving the cooling conditions for the production of ultra high strength (AHSS) steel.

In the continuous rolling device according to an aspect of the present invention in the continuous rolling device including a casting machine for casting the slab and a cooling table having at least one rolling mill and at least one water cooling system continuously connected to the player,

The first position S in which the water cooling facility is installed for the production of ultra high strength steel with at least one water cooling in the cooling zone is defined by Equation 1 below.

Equation 1:

Where H is the thickness of the slab (mm), V is the slab casting speed (m / sec), h is the product thickness (mm), and t is the target time to reach the cooling stage (sec).

In addition, the continuous continuous rolling method according to another aspect of the present invention comprises a casting step of casting a slab using a player; A circumferential speed and thickness measuring step of measuring a casting speed of the slab produced in the casting step and a thickness of the slab (H); A rolling step of continuously connecting the player to the slab to a target thickness; A product thickness measuring step of measuring a thickness of the product rolled in the rolling step; A target reaching time setting step of setting a target reaching time required for the product to enter a water cooling section of the cooling stage after completion of the rolling step; And a water cooling start position calculating step of setting an initial water cooling start position (S) for the production of ultra high strength steel by at least one water cooling in the cooling zone using the values obtained in each step.

In addition, the water cooling start position calculation step may be defined by the following equation (1).

Equation 1:

In addition, the temperature of the product at the completion of the rolling step may be controlled to 750 to 880 ℃.

According to one embodiment of the present invention, through the initial water cooling start position that can produce AHSS steel with at least one water cooling it is possible to produce very high strength (AHSS) steel while minimizing cooling after finishing rolling.

1 shows schematically a continuous rolling device.

Figure 2 is a graph showing a cooling pattern for the production of general steel.

3 is a graph showing a cooling pattern for producing AHSS steel in batch rolling.

4 is a graph showing a cooling pattern for producing AHSS steel in continuous rolling.

Hereinafter, with reference to the accompanying drawings an embodiment of the present invention will be described in detail. Embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. Shapes and sizes of the elements in the drawings may be exaggerated for clarity, elements denoted by the same reference numerals in the drawings are the same elements.

1 is a view schematically showing a continuous rolling device.

Referring to Figure 1, the continuous rolling device 100 of the present embodiment is a casting step of continuously casting while solidifying a molten steel of a liquid phase into a solid form without a defect, and a rolling step of rolling the cast continuously cast as described above Is done.

Here, the casting process is to produce a slab product using the player 110, the slabs are continuously connected to pass through the at least one rolling mill 120 is made of a product of the target thickness, the cooling table 140 Winding through the winding facility 150 may be manufactured as a final product.

Preferably, the rolling mill 120 may include a rough rolling mill 122, an intermediate rolling mill 124, and a finish rolling mill 126, and a heating device 130 for heating the slab is provided between the rolling mills 120. It may be provided.

On the other hand, the cooling unit 140 is divided into an air cooling section in which the cooling by air and a water cooling section in which the water is cooled by the cooling water, and the water cooling section may include a water cooling facility for spraying the cooling water for high speed cooling. . For example, as the water cooling system, a facility known as a high density cooling or laminar flow cooling device 142 installed in the water cooling stand may be used.

Referring to FIG. 2, which is a graph illustrating a cooling pattern for the production of general steel, the product passing through the finishing mill 126 is air-cooled before entering the cooling stand 140, and then supplied to the cooling stand 140. After cooling with water cooling in the process of passing through the water cooling device 142, it may be controlled to the target winding temperature through the final air cooling process.

As such, the general steel may be controlled to have ferrite and perlite fractions through air-cooling-water-cooling.

Meanwhile, referring to FIG. 3, the ultra high strength (AHSS) steel may be manufactured by a batch rolling method, in which the product passing through the finishing mill 126 is first air-cooled before entering the cooling table 140. Then, it is supplied to the cooling stand 140 is cooled by primary water cooling in the process of passing through the water cooling device 142. In addition, the product having passed through the water cooling device 142 may be secondary air cooled, and then may be secondly cooled by passing through the water cooling device 142 again.

As such, the secondary air-cooled and secondary water-cooled products can be air-cooled again and the cooling can proceed according to the target coiling temperature, the ferrite, Bainite alc martensite fraction by steel type depending on the cooling temperature It can be produced by controlling the required steel grade characteristics (eg, DP steel, TRIP steel, FB steel, etc.).

The ultra-high strength (AHSS) steel manufactured by the batch rolling method may have an initial temperature (FDT) of about 820 ° C. or more after passing through the finishing mill 126.

On the other hand, the ultra-high strength (AHSS) steel produced by the continuous rolling device 100 as in this embodiment is a cooling pattern as shown in Figure 4 which is a graph showing a cooling pattern for producing AHSS steel in the continuous continuous rolling. Can be prepared.

The initial temperature FDT after passing through the finish rolling mill 126 in the continuous rolling apparatus 100 may be controlled to 750 to 880 ° C.

In addition, the finishing mill 126 is first air-cooled before entering the cooling stand 140, and then supplied to the cooling stand 140 to be cooled by primary water cooling in the process of passing through the water cooling device 142. In addition, the product passing through the water cooling device 142, the secondary air cooling may be progressed at this time, the cooling may proceed in accordance with the target winding temperature, the ferrite, Bainite alc martensite fraction by steel type depending on the temperature at which the cooling proceeds It can be produced by controlling the required steel grade characteristics (eg, DP steel, TRIP steel, FB steel, etc.).

As described above, in the present embodiment, the continuous rolling device 100 is directly connected to the play-rolling process so that the product is continuously supplied, and thus the speed of the product is controlled slowly, so that at least one high-speed cooling is sufficient for cooling. It is possible to secure the target coiling temperature (CT) of the desired steel grade, it can be used to manufacture the ultra-high strength (AHSS) steel.

At this time, the continuous rolling device 100 is the first position in which the water cooling device 142, which is a water cooling device, is installed in the cooling table 140, that is, the first water cooling in order to obtain a sufficient cooling effect by at least one high speed cooling. It is necessary to set the starting position S correctly.

Such a water cooling start position S can be calculated using a mass flow rate constant in all the processes in a continuous rolling process.

That is, in the continuous continuous rolling device 100, the mass flow of the whole process is constant, and such mass flow rate can be calculated by knowing the material cross-sectional area and the speed.

In addition, if the slab thickness and casting speed manufactured in the player 110, and the target delivery time until the product thickness and the start of cooling after finishing rolling are known, the position at which the water cooling device 142 is installed, that is, the water cooling start position S is determined. Can be calculated

Therefore, the position where the first water cooling device 142 is installed, that is, the initial water cooling start position S may be defined by Equation 1 below.

Where H is slab thickness (mm), V is slab casting speed (m / sec), h is product thickness (mm), and t is the target time to reach cooling stage 140 ( s).

Preferably, in this embodiment, the target arrival time until entering the cooling stage 140 may be greater than 0 seconds, and is preferably limited to within 10 seconds (sec) to increase productivity.

For example, if you know the slab thickness 90mm, casting speed 6.5m / min, you can know the product thickness through the measurement after finishing rolling, the product thickness is 2.0mm, the target time to reach the cooling stage 140 is It may be set to 4 seconds (sec).

In this case, the casting speed can be calculated by multiplying the conversion factor by 1/60 (min / sec) to convert 6.5 m / min into travel distance per second.

If you put these conditions in Equation 1,

If this is calculated, the position where the first water cooling device 142 of the at least one water cooling device 142 is installed, that is, the initial water cooling start position S may be calculated after 19.5 m. Can be.

On the other hand, the continuous rolling method of the present embodiment may include a casting step of casting the slab using the player 110. In addition, in order to determine the mass flow rate of the previous process, it is necessary to measure the slab casting speed and slab thickness (H). For this purpose, the casting speed and slab thickness (H) of the slab produced in the casting step are measured. The thickness measuring step may be performed.

Next, a rolling step of rolling the slab cast in the casting step to a target thickness may be performed. At this time, preferably, the temperature (FDT) of the product at the completion of the rolling step may be controlled to 750 to 880 ℃.

Thereafter, the product thickness measuring step of measuring the thickness of the rolled product in the rolling step may be performed.

Meanwhile, the target reaching time setting step is a position where the product enters the first water cooling device 142 of the at least one water cooling device 142 at the cooling stage 140 after completion of the rolling step, that is, the first water cooling start. You can set the target delivery time required to reach the location.

Then, the cooling start position can be calculated through the cooling start position calculation step of setting the initial water cooling start position using the values obtained in each step.

On the other hand, such a continuous rolling method can be utilized in the existing equipment, it can be determined whether it can be operated as the continuous continuous rolling apparatus 100 of the present embodiment by applying the continuous continuous rolling method in the existing equipment using the equation (2). .

Existing equipment may be provided with a plurality of water cooling device 142 to enable the cooling-air cooling in multiple orders.

In this case, since the mass flow rate is constant in the whole process in the case of continuous continuous rolling, the distance from the finishing mill 126 to the water cooling device 142 where the first cooling is performed, and the water cooling device where the final cooling is performed in the finishing rolling mill 126. The distance to (142) must satisfy Equation 2 below.

Here, L ₁ is the distance (m) from finishing mill 126 to the first ROT cooling plant, and L ₂ is the distance (m) from finishing mill 126 to the last ROT cooling plant.

In addition, H is the slab thickness (mm), V is the slab casting speed (m / s), h is the product thickness (mm), and t is the target time to reach the cooling stage 140 ( sec). In addition, α is a constant of the length of the cooling system required to secure the target winding temperature CT.

In one example, the distance (L ₁ ) from the finishing mill 126 to the first ROT cooling facility is 10m, the distance (L ₂ ) from the finishing mill 126 to the last ROT cooling facility is 48m in the continuous rolling device 100 It can be determined whether the continuous continuous rolling method of the present embodiment can be applied using the equation (2).

In the continuous rolling method of the present embodiment, the position where the first water cooling device 142 of the at least one water cooling device 142 is installed in the cooling table 140, that is, the first water cooling start position S is a slab. When the thickness 90mm, casting speed 6.5m / min, product thickness 2.0mm, the target arrival time to enter the cooling stage 140 is set to 4 seconds (sec), convert the unit to calculate using Equation 1, finishing It can be seen that it is 19.5 m from the rolling mill 126.

At this time, the position where the water cooling device 142 is installed, that is, the water cooling start position (S) 19.5m, the distance (L ₁ ) from the finish rolling mill 126 to the first ROT cooling facility is larger than 10m.

In addition, the position where the first water cooling start of the at least one water cooling in the cooling zone 140, that is, the first water cooling start position (S) 19.5m is the distance from the finishing mill 126 to the last ROT cooling system ( L ₂ ) is 48m and is smaller than 41.6m when α, 7.4m, is a constant of the length of the cooling system required to secure the target winding temperature (CT).

Therefore, it can be seen that the continuous continuous rolling method of the present embodiment can also be applied through existing equipment, and can produce ultra high strength (AHSS) steel by applying the continuous continuous rolling method to existing equipment.

The present invention is not limited to the above-described embodiment and the accompanying drawings, and it is possible to substitute, modify, and change various forms within the scope of the technical spirit of the present invention described in the claims. It will be self-evident to those who have knowledge.

Claims

In the continuous rolling device comprising a casting machine for casting the slab and a cooling table having at least one rolling mill and at least one water cooling system continuously connected to the machine,

The first position (S) of the water cooling installation is installed for the production of ultra-high strength steel with at least one water cooling in the cooling zone is a continuous rolling device defined by the following equation (1).

Equation 1:

Where H is the thickness of the slab (mm), V is the slab casting speed (m / sec), h is the product thickness (mm), and t is the target time to reach the cooling stage (sec).
Casting the slab using a player;

A circumferential speed and thickness measuring step of measuring a casting speed of the slab produced in the casting step and a thickness of the slab (H);

A rolling step of continuously connecting the player to the slab to a target thickness;

A product thickness measuring step of measuring a thickness of the product rolled in the rolling step;

A target reaching time setting step of setting a target reaching time required for the product to enter a water cooling section of the cooling stage after completion of the rolling step; And

A water cooling start position calculation step of setting an initial cooling start position (S) for the production of ultra high strength steel by at least one water cooling in the cooling zone using the values obtained in each step;

Continuous rolling method comprising a.
The method according to claim 2,

The water cooling start position calculation step is a continuous continuous rolling method defined by the following equation (1).

Equation 1:

Where H is the thickness of the slab (mm), V is the slab casting speed (m / sec), h is the product thickness (mm), and t is the target time to reach the cooling stage (sec).
The method according to claim 2 or 3,

Temperature of the product at the completion of the rolling step is a continuous continuous rolling method is controlled to 750 to 880 ℃.