WO2020175670A1

WO2020175670A1 - Slow-cooling cover for slab and cooling method

Info

Publication number: WO2020175670A1
Application number: PCT/JP2020/008319
Authority: WO
Inventors: 義陽大場; 丸田　慶一; 信平森口; 健明清水
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2019-02-28
Filing date: 2020-02-28
Publication date: 2020-09-03
Also published as: CN113518831A; JP2020139200A; CN113518831B; JP7188187B2

Abstract

The present invention provides a slow-cooling cover for a slab and a cooling method which are capable of cooling a slab while suppressing the occurrence of cracking in the slab for which it is difficult to maintain a high temperature and cracks may occur due to forced cooling, when conveying the slab from a continuous casting facility to a heating furnace.　This slow-cooling cover is provided with: side wall parts (31) that can accommodate slabs which are continuously cast in a continuous casting machine, in the same number as the number of strands of the continuous casting machine, and that can cover the entirety of the side surfaces of the slabs (B) in the same number as the number of strands disposed on a bed surface; and a top plate part (32) that can cover the upper surfaces of the slabs (B) in the same number as the number of strands disposed on the bed surface, wherein a thermal insulating material is provided to the inner wall surfaces of the side wall parts (31) and the top plate part (32).

Description

\¥0 2020/175670 1 卩(: 17 2020/008319 Clarification

Title of the Invention: Slowly cooling cover for flakes and cooling method

Technical field

The present invention relates to a gradual cooling cover for a claw piece and a cooling method.

Background technology

[0002] In the manufacturing process of re-heating a bloom, which is a piece of iron that has been formed by a continuous ironing machine, in a heating furnace and performing slab rolling to produce billets, the high temperature Hot charge rolling is performed in which the iron pieces are directly loaded into the heating furnace and the heated iron pieces are rolled. In hot charge rolling, the temperature of the iron pieces charged into the heating furnace can be raised, so the fuel used in the heating furnace can be reduced.

[0003] However, the hook pieces subjected to hot charge rolling are

Since it is rolled without sufficiently undergoing the transformation from 7) to ferrite (○○), the hot workability may deteriorate due to grain boundary embrittlement due to precipitates at grain boundaries. In this case, surface defects (grain boundary cracks) will occur during rolling.

In order to prevent such surface flaws, for example, in Patent Document 1, by maintaining a high temperature region of 1550 to 9500 ^° 〇, the iron piece after the steel is formed, intentionally... A method of preventing cracking by disposing coarsening and increasing the distance between precipitates at grain boundaries is disclosed.

Further, in Patent Document 2, by precipitating cooling (water cooling) of the iron piece after forming, the surface structure of the iron piece is transformed from the ^ phase to the << phase, so that the precipitation precipitated at the old ^ boundary A method for suppressing grain boundary embrittlement due to a substance is disclosed. Note that in the following, forced water cooling of the tin pieces by the water cooling equipment is also called forced cooling.

Prior art documents

Patent literature

[0004] Patent Document 1: JP-A-6 2 -2 1 2 0 0 1

Patent Document 2: Japanese Patent Laid-Open No. 5-235075 \¥0 2020/175670 2 (: 17 2020/008319 Invention Summary

Problems to be Solved by the Invention

[0005] By the way, in the vicinity of the final ironing part in continuous ironing, there is a decrease in molten steel temperature during ironing, deceleration of ironing speed for the purpose of preventing porosity, and waiting time in the aircraft before the start of the next ironing. Because of the influence, the temperature of the iron piece becomes lower than that of other iron parts. Due to such operation factors, it is difficult to use the method of maintaining the temperature of the flake described in Patent Document 1 at a high temperature for the flake near the final filing part.

Further, for steel types that are susceptible to cracking at a high cooling rate and have high cracking susceptibility during cooling, it is difficult to use the method for forcedly cooling the flakes described in Patent Document 2.

[0006] Therefore, the present invention has been made in view of the above-mentioned problems, and it is difficult to maintain a high temperature at the time of transferring the flakes from the continuous ironing equipment to the heating furnace, and it is possible to perform the forced cooling. It is an object of the present invention to provide a slow cooling force for a tin piece and a cooling method capable of cooling a tin piece that may be cracked while suppressing the occurrence of the crack.

Means for solving the problem

[0007] According to the _ aspect of the present invention, it is possible to accommodate the number of the strand pieces continuously formed by the continuous ironing machine as many as the number of strands of the continuous ironing machine, and the above-mentioned strips arranged on the floor surface. The side wall part that can cover the entire circumference of the side surface of the number of strands equal to the number of the land, and the top plate part that can cover the upper surface of the number of strands equal to the number of strands arranged on the floor surface. And a gradual cooling cover for the flakes, in which a heat insulating material is provided on the inner wall surfaces of the side wall portion and the top plate portion.

[0008] According to one aspect of the present invention, from the result of the measuring step of measuring the temperature of the barb formed by the continuous barbing machine, the surface temperature of the barb is the first threshold value or less. In the temperature determination step of determining whether the temperature is lower, and in the temperature determination step, the hanger whose surface temperature is equal to or lower than the first threshold value is covered with the slow cooling cover according to claim 1 and cooled. And a gradual cooling step of: 〇 2020/175 670 3 (:171? 2020/008319 Effect of invention

[0009] According to one aspect of the present invention, when the iron piece is conveyed from the continuous iron making equipment to the heating furnace, it is difficult to maintain a high temperature, and the iron piece may be cracked by forced cooling. (EN) Provided is a slow cooling force for one piece/one and a cooling method capable of cooling while suppressing the occurrence of cracks.

Brief description of the drawings

[0010] [FIG. 1] A schematic view showing a reheating line in an embodiment of the present invention.

[Fig. 2] Fig. 2 is a cross-sectional view showing a second annealing device, where (8) is a side-view cross-sectional view and (M) is a front-view cross-sectional view.

[Fig. 3] Fig. 3 is a view showing a slow cooling cover, (8) is a plan view, (M) is a side view, and (○) is a front view.

[Fig. 4] A flow chart showing a cooling method and a reheating method for the flakes.

[Fig. 5] Fig. 5 is a cross-sectional view showing a modified example of the second gradual cooling equipment and the gradual cooling cover. () shows a modified example in which the pieces are stacked in two stages, and (M) is the stack in four stages. A modified example is shown.

FIG. 6 is a result of an investigation showing a difference in cooling rate between different cooling methods in the example.

MODE FOR CARRYING OUT THE INVENTION

[001 1] In the following detailed description, numerous specific details are set forth to illustrate embodiments of the invention to provide a thorough understanding of the invention. It will be apparent, however, that one or more embodiments may be practiced without the specific details. Also, the drawings show well-known structures and devices in a schematic representation for the sake of brevity.

[0012] <Cooling method for flakes>

With reference to FIGS. 1 to 4, a method for cooling the halberd wheel according to an embodiment of the present invention will be described. The method for cooling the iron piece slag according to the present embodiment is a method for cooling the iron piece sill in the continuous heating machine (reheating line 1 for reheating the iron shaving head made by <302). Line 1 is the first transfer table 1 1 as shown in Figure 1. 〇 2020/175670 4 (:171? 2020/008319

, Second transfer table 12, measuring device 13, first slow cooling facility 14, water cooling facility 15, second slow cooling facility 16, heating furnace 17 and control unit 18 With. The continuous ironing machine 2 is a piece of iron that continuously forms a bloom having a substantially square cross section orthogonal to the longitudinal direction. The continuous ironing machine 2 has four strands, which is the number of ironing lines of the iron piece. In such a continuous ironing machine 2, each strand is continuously ironed and then cut into a predetermined length, which is sent to the first transport table 11 1. In addition, the reheating line 1 according to the present embodiment uses the first transfer table 11 and the second transfer table 12 to set the hook-and-loop mill formed by the continuous ironing machine 2 at 600°°. The equipment is capable of hot-charging by charging the heating furnace 17 at the above high temperature and then rolling.

[0013] The first transport table 11 is a transport device that transports the one-wheel sheave sent from the continuous rope-making machine 2 to the second transport table 12, and has a plurality of drive-types that transport the one-wheel sheave. It consists of a mouth and so on. The first transfer table 11 is provided with four transfer lines according to the number of strands of the continuous thread making machine 2.

The second transfer table 1 2 transfers the iron pieces sent from the first transfer table 1 1 to the 1st slow cooling facility 1 4, water cooling facility 1 5, 2nd slow cooling facility 1 6 or heating furnace 1 7. It is a transporting device that is composed of a plurality of drive-type rollers for transporting the Kamikatami. According to the judgment result of the control unit 18 which will be described later, the second transfer table 12 is configured such that the Kamikatami is the first slow cooling facility 14, the water cooling facility 15, the second slow cooling facility 16 or the heating furnace 1. Transport it to any of the facilities in 7.

[0014] The measuring device 13 is a thermal image measuring device, and measures the surface temperature of the one-sided slab on the first carrier table 11. The measuring device 13 is provided on the downstream side of the first transport table 11 in the transport direction of the halberd, and is capable of measuring the surface temperature of the halberd that is transported by the four transport lines. To be The measuring device 13 measures the surface temperature at a plurality of positions on the upper surface of the upper part of the vertical direction, which is the upper surface in the vertical direction, preferably at the entire upper surface. In addition, the measuring device 13 outputs the measurement result of the surface temperature of the halberd to the control unit 18. The measuring device 13 is not particularly limited as long as it is capable of measuring the surface temperature of the halberd, but a thermal image measuring device or a scanning type 〇 2020/175 670 5 卩 (：171? 2020 /008319

It is preferable to use a thermometer that can measure multiple positions on the surface of the Kamikatami because it can eliminate the influence of scales and improve the measurement accuracy.

[0015] The first gradual cooling equipment 14 is a box-type device having an inner wall provided with a heat insulating material, for gradual cooling of the halberd that is transported from the second transport table 12, for example, This is a slow cooling device that can accommodate a large number of rod-shaped halves. The smelting rod unit is the unit (charge) of the number of treatments in the smelting process and the smelting process in the steelmaking process, and corresponds to the smelting process and the smelting process for up to two times of the molten steel stored in the ladle. .. In other words, the composition and grade of molten steel are the same at least in the same steel rod unit. As will be described later, the first gradual cooling facility 14 is a facility for gradual cooling of a large amount of slag pieces that are determined to require gradual cooling on a per-building rod basis. The 1st slow cooling facility 14 is capable of accommodating, for example, about 40 Kamikatami (150 I to 250 I), and is composed of heat-insulating bricks, heat-insulating panels, etc. The equipment is fixedly installed in the. The halberd stove housed in the first slow cooling equipment 14 is surrounded by heat insulating material on all sides in the first slow cooling equipment 14, and is gradually cooled at a low cooling rate. Here, in the present embodiment, gradual cooling indicates that cooling is performed at a cooling rate lower than that of air cooling, and for example, a cooling rate of 10.16 ^° 〇/〇1 侨n or more is used. Show. The cooling rate is a value represented by a minus value. In this embodiment, a large absolute value of the cooling rate is called a high cooling rate, and a small absolute value of the cooling rate is called a low cooling rate.

[0016] The water cooling facility 15 is a facility that sprays water onto the splint that is transported from the second transport table 12 and cools the splint at a high cooling rate (forced cooling). In the water-cooling equipment 15, straightening cooling of the Kamikata is performed for a preset time according to the cooling capacity. The cooling rate in the water cooling system 15 may be, for example, -300/3-1 to 6 ^° ○/3.

The second gradual cooling equipment 16 is an equipment for gradual cooling of the halberd that is transported from the second transport table 12.As shown in FIG. 2, the gradual cooling cover 3 and the plurality of support members 4 are provided. Have. 〇 2020/175 670 6 卩 (: 171-1? 2020/008319

As shown in FIGS. 2 and 3, the slow cooling cover 3 has a side wall portion 31, a top plate portion 32, and a pair of holding portions 33. As shown in Fig. 2, the side wall portion 31 is a rectangular tube-shaped member and covers the entire circumference of the side surface of each of the four halberd wheels arranged on the floor through a plurality of supporting members 4. It is provided. The top plate portion 32 is a rectangular member formed so as to cover the opening on the upper side of the side wall portion 31 (upper side in Fig. 2 (8) and (Mimi)), and has a plurality of supporting members on the floor surface. It is provided so as to cover the upper surfaces of the four Kamikatami that are placed through the four. Each of the side wall portion 31 and the top plate portion 32 is provided with a heat insulating material on an inner wall surface which is an inner surface on which the hook and groove is provided. For example, the side wall portion 31 and the top plate portion 32 may be manufactured by providing a heat insulating material on the inner surface side of the member whose surface is made of iron. The heat insulating material is not particularly limited as long as it can be used for gradually cooling a steel piece, a steel piece, etc., and its type and thickness are appropriately determined according to the target cooling rate and the manufacturing cost of the slow cooling cover. You can choose. Since the slow cooling cover 3 is preferably easily transported by a heavy machine or the like, it is preferable that it has a heat insulating property and a light weight. For example, as the heat insulating material, a heat insulating block or a heat insulating board manufactured using a ceramic fiber may be used. The pair of holding parts 33 are fixedly provided on the top surface of the top plate part 32, and a cavity is formed therein so that a claw of a heavy machine or the like can be inserted therein, as described later.

[0018] The inner length 3 of the side wall portion 3 1 in the longitudinal direction (the left-right direction in Fig. 2 (8)) is set to be longer than the longitudinal length of the hook-and-loop mill that is built by the continuous ironing machine 2. Be done. The length of the iron piece is the maximum length of the iron piece made by the continuous iron making machine 2. Furthermore, it is preferable that the length 3 be set as short as possible in accordance with the installation accuracy at the time of installing the slow cooling cover 3 described later. The length of the side wall 31 in the height direction (vertical direction in Fig. 2 (), (M)) is the height _{6 of the one-} sided bar and the height of the support member 4 to be built by the continuous ironing machine 2. The height is set to be larger than the sum of the lengths, and in the case of the present embodiment, the height is set to be larger than the height (2X6) of the two halves. Furthermore, it is preferable that the length 13 is set as small as possible within a range in which the slow cooling cover 3 and the Takami Takami do not contact each other when the slow cooling cover 3 is installed. Inside of the side wall 31 in the width direction (left-right direction in Fig. 2 (Mimi)) 〇 2020/175 670 7 卩(: 171-1? 2020/008319

The length 〇 is equal to or more than the number of strands of the length in the width direction of the halberd that is formed by the continuous ironing machine 2. It becomes As shown in Fig. 2 (Mimi), the halberd halves are placed on the support member 4 at a distance from each other due to the handling property during transportation. For this reason, it is preferable that the length ◯ is more than 4 x dry and 7 x dry or less so as to accommodate the four pieces of the barb in such a state. In other words, the side wall 31 may be dimensioned as long as it is capable of accommodating, as many as four strands of the number of strands, which are arranged on the floor surface through the plurality of supporting members 4, as many as four strands of the strand. It is preferable to set the gap between the bar and the side wall 3 1 and the space between the bar and the top 3 2 to be as narrow as possible.

[0019] The plurality of support members 4 are members that support the four halves and are not particularly limited as long as they can withstand the weight and temperature of the halves. In the present embodiment, as an example, a bloom manufactured in advance in the same manner as in the case of Kamikata is used as the support member 4. As such a support member 4, for example, bloom that has been scrapped because it cannot be used as a product may be used. The plurality of support members 4 are arranged on the floor surface in a line in the longitudinal direction of the halberd that is cooled, and are provided at predetermined intervals. The floor surface is the floor surface where the slow cooling of the Kamikatami is performed, and indicates the surface such as the ground indoors or outdoors. The number of the supporting members 4 provided is not particularly limited as long as it can support a plurality of barb ends depending on the number of strands, but in the example shown in FIG. 2, two members are provided.

[0020] The heating furnace 17 is composed of a piece of slab that is conveyed from the second transfer table 12, a piece of sill that is gradually cooled by the first gradual cooling equipment 14 and a second gradual cooling equipment 16 and a water cooling. This is a facility that heats and reinforces the reeds that are forcedly cooled by Facility 15 (also referred to as "reheating") to a specified temperature. The reincarnated reed in the heating furnace 17 is then rolled into a billet with a small cross-sectional area.

The control unit 18 is a control device for controlling the transportation and cooling of the halberd sill in the reheating line 1, and the reheating of the halberd sill in the heating furnace 17. According to the method described later, the control unit 18 installs in the heating furnace 8 of the Kamikatami, including the selection of the cooling method, based on the measurement results of the steel type of the Kamikatami and the surface temperature of the measuring device 13. Determine the route to enter 〇 2020/175 670 8 卩 (: 171-1? 2020/008319

Refuse.

[0021] Next, a cooling method and a reheating method for the reed line 1 in the reheating line 1 will be described with reference to the flowchart in FIG. First, a measurement step is performed in which the surface temperature of the sill piece on the first transport table 11 is measured by the measuring device 13 (3100). The halberd is made by a continuous ironing machine and cut, and is transferred from the continuous ironing machine 2 to the first transfer table 11. In step 3100, the measuring device 13 measures the surface temperature at a plurality of positions on the upper surface of the sill. Then, the measuring device 13 outputs the highest temperature among the plurality of surface temperatures of the upper surface to the control unit 18 as the measurement result of the surface temperature for each of the claw pieces. In addition, the hook and groove whose surface temperature is measured in step 3100 is transferred from the first transfer table 11 to the second transfer table 12.

[0022] After step 3100, the control unit 9 determines whether or not the 錶片巳 the surface temperature of which is measured in step 3100 is the designated grade of slow cooling steel type. Perform the process (3 102). The designated grade of slow cooling is a type of steel in which nitrogen is intentionally added (70 to 100 mass), so grain boundary embrittlement due to nitrides precipitated at the austenite grain boundaries is remarkable. Judgment as to whether or not it is a designated steel type is made based on the compositional composition of the molten steel, and such judgment of the steel type is basically made in charge units in which the compositional composition of the molten steel is the same.

[0023] When it is determined in step 3 102 that the iron piece is judged to be the designated slow cooling steel type, the determined iron piece is transferred from the second transfer table 1 2 to the first annealing equipment 1 4 The first slow cooling process is carried out, in which it is transported to and is slowly cooled in the first slow cooling facility 14 (3104).

.. In the first gradual cooling step, for example, a large amount of each one of the charge pieces is sent to the first gradual cooling equipment 14, and then these charge pieces are simultaneously cooled. As described above, in the 1st steel grade determination process, it is basically determined whether or not it is the designated grade of slow cooling on a charge unit basis.Therefore, in the 1st slow cooling process, there is 1 charge determined in this way. A large number of billets with multiple charges are annealed together in the first annealer 14. The first annealing step is performed until the temperature of the Katakatami falls below the 8 "1 transformation point. 〇 2020/175 670 9 卩 (: 171-1? 2020/008319

[0024] On the other hand, when it is determined in step 3102 that the steel piece is not the designated grade for slow cooling, the control unit 9 determines whether the surface temperature of the steel piece is less than or equal to the first threshold value. Perform the temperature judgment process (3106). The first threshold is a temperature that is set according to the amount of nitride that precipitates at the austenite grain boundaries and the size of the crystal grains, and the furnace is used to heat the Katakatami without cooling such as slow cooling or forced cooling. It is set as a temperature at which intergranular cracking does not occur on the surface of the Kamikatami even after charging into No. 7. For example, the first threshold value may be set to a temperature at which the surface temperature of the 錶巳 when the 錶跳 is charged into the heating furnace 17 without cooling such as slow cooling or forced cooling becomes 8 "3 transformation point or more. Further, the first threshold value may be a temperature set according to the occurrence status (occurrence record) of cracks on the surface of the Kamikatami, for example, the rate of occurrence of cracks on the surface of the Kamikatami. The temperature at which the temperature begins to increase to a problematic level may be set as the first threshold value.In the production line capable of hot-charge rolling as in the present embodiment, the temperature becomes less than the first threshold value in the temperature determination process. Basically, Katami is only the top bar (the bar closest to the final bar), which is the bar that is formed at the end of the continuous chain by each strand of the continuous bar machine 2. In the present embodiment, in one continuous ironing, the number of the iron pieces that the surface temperature is judged to be the first threshold value or less is one for each strand, that is, a total of four iron pieces. There is a case that the building speed is reduced due to adjustments, etc., and even in such a case, there is a possibility that a small piece of sand will fall below the first threshold value.

[0025] In step 3106, if the surface temperature of the slab is higher than the first threshold, the control unit 9 determines whether the slab is a steel type with high susceptibility to cooling cracks. Perform the judgment process (3108). Steel types with high cooling crack susceptibility are steel types that are susceptible to cooling cracks such as vertical cracks due to high cooling rate cooling such as air cooling and forced cooling by water cooling equipment 15, and their composition and crack occurrence status (generation results). ). For example, the steel grades with high susceptibility to cooling cracks include the following grades (3) to (○).

(A) The force-bon equivalent 〇69 calculated by the following equation (1) is 〇.

Steel grade of 3% or more. 〇 2020/175 670 10 boxes (: 171-1? 2020/008319

○ 6 = [○] + 1/2 [3 I] + 1/5

+ 1/7 [○li]

+1 / 22 [1\1丨] + 1/9 [〇 1 〇 + 1/2 / [IV! 〇] + 1/2 [V]-

In the equation (1), [8] represents the concentration of the component 8 in the steel (01833%).

(13) Steel grades with a <3 concentration of 〇.4501833% or more in steel.

(〇) (3 concentration in steel is 0.4051333% or more, and

0 001833% or more of steel grade.

(¢ 0 V added steel.

[0026] When it is determined in step 31 08 that the steel sheet is a steel type having high cooling crack susceptibility, the steel sheet that has been determined is transferred from the second transfer table 12 to the second slow cooling equipment 16. The second slow cooling process is carried out in which the second slow cooling facility 16 is gradually cooled (31 10). In the second gradual cooling step, firstly, the Kamikatami is placed on the plurality of supporting members 4 arranged in advance on the floor surface. At this time, the halberd is placed on the plurality of support members 4 by a crane, heavy equipment, or the like. In addition, when there are a plurality of splints that are equal to or less than the first threshold value at a close timing, a plurality of splints are placed on the same plurality of support members 4. In addition, in this case, the number of the sill pieces that can be placed on the same plurality of support members 4 is the number that can be accommodated by the slow cooling cover 3. As mentioned above, basically the number of the strands on which the second slow cooling step is performed is the top segment, and there are only four strands, which is the number of strands. Then, after placing the Kamikatami on the support member 4, as shown in Fig. 2, cover the Kamikatami with the slow cooling cover 3, and cool the Kamikatami until the temperature falls below "1 transformation point". The work of covering the slow cooling cover 3 on the slab is performed by using a heavy machine such as a forklift, etc. At this time, by inserting the claws of the heavy machine into the pair of holding portions 33, the heavy machine can be operated. The slow cooling cover 3 is held and moved.

[0027] On the other hand, when it is determined in step 31 08 that the steel sheet is not a steel type having high susceptibility to cooling cracks, the steel sheet that has been determined is transferred from the second transport table 12 to the water cooling equipment 15. A forced cooling process is carried out in which it is transported and forcedly cooled in water cooling equipment 15. 〇 2020/175 670 1 1 卩 (：171? 2020 /008319

(3 1 1 2). The forced cooling in the water-cooling equipment 15 may be one that is generally used for cooling the bloom, which is a piece of sword. Further, the cooling condition may be changed according to the difference in steel type and the like. Further, in the water-cooling facility 15, it is preferable to carry out forced cooling until the surface temperature of the Kamikatami becomes 8 "1 transformation point or less.

[0028] After the slow cooling is performed in Step 3104 and Step 3110,

After the temperature is judged to be above the first threshold value in 106, and after forced cooling is performed in step 3 1 1 2, the reheating process is performed in which the Kamikatami is charged into the heating furnace 17 and reheated. (3 1 1 4). In the reheating step, the reeds are reheated to a predetermined temperature, and then rolled into billets.

In the present embodiment, by carrying out the above-mentioned processing steps, the hook-and-loop mill carried out from the continuous iron-making machine is conveyed to the heating furnace 8 and reheated. Then, in the process, cooling of the Katagatami is performed by methods such as slow cooling and forced cooling. In addition, in the present embodiment, it is preferable that the control unit 18 automatically performs the transportation and processing of the halberd wheel described in step 3100 to step 3114.

[0029] <Modification>

Although the present invention has been described above with reference to specific embodiments, it is not intended to limit the invention by these descriptions. It will be apparent to those skilled in the art, after reading the description of the invention, other embodiments of the invention, including various modifications as well as the disclosed embodiments. Therefore, it should be understood that the embodiments of the invention described in the claims cover the embodiments including these modifications described singly or in combination.

[0030] For example, in the above-described embodiment, the number of strands of the continuous thread making machine 2 is four, but the present invention is not limited to this example. For example, the number of strands of the continuous thread making machine 2 may be another number such as two. In addition, the number of strands of the continuous ironing machine 2 including such modified examples is 1\1 (piece).

Further, in the above-described embodiment, the plurality of slabs are arranged on the floor surface, and the plurality of slabs are covered with the substantially rectangular parallelepiped slow cooling cover 3. However, the present invention is not limited to this example. .. For example, Fig. 5 (8), (Mimi) shows how to place the Katakatami on the floor. 〇 2020/175 670 12 boxes (: 171-1? 2020/008319

It may be placed in multiple layers such as two or four. Moreover, the slow cooling cover 3 may have another shape as long as it can cover a plurality of the halves.

[0031] Further, in the above-mentioned embodiment, the piece of stilts is a bloom, but the present invention is not limited to this example. The halberd may also have other shapes such as a slab having a rectangular cross-section orthogonal to the longitudinal direction. It is to be noted that, as in the above-described embodiment, a preferable equipment condition is that it is a piece of equipment in which it is necessary to load the snail piece into the heating furnace 17 at a place near the carry-out line of the continuous ironing machine 2.

[0032] Furthermore, in the above-described embodiment, the processing of the processing flow shown in Fig. 4 was performed, but the present invention is not limited to such an example. The present invention may be another embodiment as long as the cooling is performed using the slow cooling cover 3. For example, if the top crack of steel type that is not a designated grade for slow cooling and that is formed by the continuous ironing machine 2 has high cooling crack susceptibility as in step 3108, A slow cooling step may be performed. As described above, the surface temperature of the top iron piece is lower than that of the other iron pieces, and there is a high possibility that cracks will be directly introduced into the heating furnace 17 and then cracked. Therefore, such a top bar may be subjected to a slow cooling step without measuring the surface temperature.

Furthermore, in the above-mentioned embodiment, the tab piece is used as the support member 4, but the present invention is not limited to this example. The supporting member 4 only needs to be able to withstand the weight and temperature of the halberd, and, for example, a bar made of refractory may be used as the supporting member 4.

(1) The gradual cooling cover 3 of the halberd wheel according to one aspect of the present invention is capable of accommodating the pieces of the halves that are continuously piled by the continuous rope maker 2 for the number of strands of the continuous rope maker 2. The side wall 3 1 that can cover the entire circumference of the side surface of the one-sided strand that is the number of strands placed on the floor, and the number of the number of strands that is the number of strands placed on the floor. A top plate portion 32 capable of covering the upper surface of one side is provided, and a heat insulating material is provided on the inner wall surfaces of the side wall portion 31 and the top plate portion 32. 〇 2020/175 670 13 卩 (：171? 2020 /008319

[0034] According to the configuration of the above (1), the surface temperature of the flakes has become low due to various operating factors, and cracking susceptibility may cause cooling cracks when forced cooling is applied. It is possible to cool a high-strength iron piece while suppressing the occurrence of cracks. In addition, since the cooling rate is low, even if cracks occur, they can be reduced in size so that they can be removed by maintenance after rolling. As a result, it is possible to reduce the efficiency of maintenance work for surface defects and the scrap rate of rolled products. In addition, such a slow cooling cover 3 is simpler than a slow cooling device (for example, the first slow cooling facility 14 in the above-described embodiment) that cools a large amount of shavings, and can be installed in a small amount. The thing can also be annealed effectively. For this reason, for example, it is possible to efficiently deal with the low-temperature surface slabs that generate only a small amount, such as continuous slab top slabs and slabs that are generated due to sudden changes in operating conditions. You can

[0035] (2) A method of gradually cooling a piece of shavings according to an aspect of the present invention includes a measuring step (3100) of measuring the temperature of a piece of shavings formed by a continuous sheet forming machine 2, From the result of the process, the temperature judgment process (3106) that judges whether the surface temperature of the sill piece is below the first threshold, and the temperature judgment process determines whether the surface temperature is below the first threshold. A slow cooling step (3 1 1 2) of cooling one side by covering it with the slow cooling cover 3 described in (1) above is provided.

According to the configuration of the above (2), in addition to the same effect as the configuration of the above (1), it is possible to perform slow cooling each time a small piece of the surface temperature having a low surface temperature that is generated only in a small amount is generated.

[0036] (3) In the configuration of (2) above, after the temperature determination step, the steel piece whose surface temperature becomes equal to or lower than the first threshold value is a specific steel type (cooling) set according to the cooling crack susceptibility. Steel type judgment process (step 3108, 2nd steel type judgment process) to judge whether the steel type has high crack susceptibility, and after the steel type judgment process, the steel type judgment process judges that it is not a specific steel type. A forced cooling process (3104) for cooling Katsumi in water cooling equipment 15 is further provided. In the slow cooling process, the steel pieces that are judged to be a specific steel grade in the steel grade determination process are gradually cooled. To do. 〇 2020/175 670 14 卩 (: 171-1? 2020/008319

[0037] According to the configuration of the above (3), it is possible to prevent the occurrence of cooling cracks due to forced cooling in steel types having high cooling crack sensitivity.

[0038] (4) The method for cooling a halberd embankment according to the _ aspect of the present invention is such that, among the halberd lambs continuously produced by the continuous ironmaking machine 2, each strand of the continuous ironmaking machine is lastly ironed. Cool the top bar, which is the bar, with the slow cooling cover 3 described in (1) above.

According to the configuration of (4) above, it is possible to prevent the occurrence of cracks in the top jaw pieces that have a low surface temperature and are susceptible to cooling cracks when forced cooling is performed. Example

[0039] An example performed by the present inventors will be described. In the example, first, with respect to the cooling rate by slow cooling of the Kamikatami using the first gradual cooling equipment 14 and the second gradual cooling equipment 16 in the above-described embodiment, and the cooling rate of the Kamikatami by air cooling, I conducted a survey. In this study, the surface temperature of the Kamikatami was continuously measured for cooling under the above three conditions. The size of Katakata is 4000101X3 1 0^101X55

The gradual cooling cover 3 is configured to be capable of accommodating the barnacles in a juxtaposed state as in the above embodiment.

[0040] Fig. 6 shows the results of investigation of the cooling rate. As shown in Fig. 6, in the cooling in the second slow cooling equipment 16 using the slow cooling cover 3, the cooling rate is 0.54 to 0.33.

°0/〇! I

It was confirmed that the cooling rate was sufficiently lower than the cooling rate of 0.26-0.22 °0/I with air cooling, and slow cooling was possible. In addition, the cooling rate in the second slow cooling equipment 16 is higher than that of the first slow cooling equipment 14 which was 0.26 to 0.22° 〇/〇1 侨n, but was 10. It has been confirmed that slow cooling of about 5°○/○1丨 can be realized, which is sufficiently low to suppress cooling cracks.

[0041] Next, the inventors of the present invention showed that as a steel type having high cooling crack susceptibility, a surface temperature of the measuring device 13 was 3450 ("3) corresponding to a steel type whose chemical composition range is shown in Table 1. Billet (1 60 〇! 1 60), which is an intermediate product, is obtained by reheating the top iron piece that has become 600° or less under the following three conditions (8) to (〇) and rolling the billet. After manufacturing, the surface defects were evaluated. Note that (), ( \¥0 2020/175 670 15 卩(: 17 2020/008319

Under the condition of 0), cooling was performed until the surface temperature of the Kamikatami became 100 or less.

(8) After being gradually cooled in the second slow cooling facility 16 and then reheated in the heating furnace 17 (Example)

(Mitsumi) The second transfer table 12 was directly charged into the heating furnace 17 and reheated (Comparative Example 1).

(○) Reheating in the heating furnace 17 after cooling by air cooling (Comparative Example 2).

[0042] [Table 1]

[0043] In the evaluation of surface flaws, the shavings were reheated in a heating furnace 17 and billets were produced by billet rolling, and then a magner inspection was performed to confirm the morphology of the flaws. After that, if there was a flaw, the billet surface was ground to determine if it would become a product, and the scrap generation rate, which is the generation rate of non-product, was evaluated.

Table 2 shows the results of the examples. As shown in Table 2, under the conditions of Comparative Example 1 (Mitsumi), intergranular cracking occurred in the billet, and the scrap generation rate was as high as 3.05%. Also, in the case of the condition ◯ of Comparative Example 3, large vertical cracks occurred when cooling by air cooling. Some of these vertical cracks could not be removed even by grinding the surface of the billet, and the scrap generation rate was the highest at 3.95%. On the other hand, in the case of the condition (8) of the example, although a small vertical crack occurred during cooling, it could be removed by grinding the billet, and the scrap generation rate was 0.00%.

[0044] [Table 2]

[0045] Further, the inventors of the present invention are not limited to the steel types shown in Table 1, and 609 is a high alloy steel having a content of 0.80 01 3 3 3% or more, and a V content of 0.10 0 01 8. 3 3% or more 〇 .1 2 0 01 8 3 〇 2020/175 670 16 卩 (: 171-1? 2020/008319

The same evaluation was performed for V-added steel with a content of less than 5%. As a result, it was confirmed that the morphology of the defects was similar for these steel types, and the scrap generation rate could be greatly reduced.

Explanation of symbols

[0046] 1 Reheating line

1 1st transfer table

1 2 2nd transfer table

1 3 Measuring device

1 4 1st slow cooling equipment

1 5 Water cooling equipment

1 6 2nd slow cooling equipment

1 7 heating furnace

2 continuous wire making machine

3 Slow cooling cover

3 1 Side wall

32 Top plate

33 Holding part

4 Support member

Mimi

Claims

\¥0 2020/175670 17 卩(: 17 2020/008319 Claims

[Claim 1] It is possible to accommodate the number of strands of the continuous ironing machine, which is the number of strands of the continuous ironing machine,

A side wall portion capable of covering the entire circumference of the side surface of the number of the strand pieces arranged on the floor surface by the number of the strands,

A top plate portion capable of covering the upper surface of the number of strands arranged on the floor surface,

Equipped with

A heat-insulating material is provided on the inner wall surfaces of the side wall portion and the top plate portion.

[Claim 2] A measuring step of measuring a temperature of a tin piece produced by a continuous iron making machine,

From the result of the measurement step, the temperature determination step of determining whether the surface temperature of the barb is a first threshold value or less,

In the temperature determination step, there is provided a gradual cooling step of covering the above-mentioned bar piece whose surface temperature is equal to or lower than the first threshold value with the gradual cooling cover according to claim 1, and cooling the same. ..

[Claim 3] After the temperature determining step, a steel type determining step of determining whether or not the above-mentioned steel piece whose surface temperature is equal to or lower than the first threshold value is a specific steel type set according to cooling crack susceptibility When,

After the steel type determination step, a forced cooling step of cooling the iron piece determined not to be the specific steel type in the steel type determination step with a water cooling facility is further provided,

3. The method for cooling a tin piece according to claim 2, wherein in the slow cooling step, the steel piece determined to be the specific steel type in the steel type determination step is gradually cooled.

[Claim 4] Among the bars that are continuously formed by the continuous machine, the top bar piece that is the last bar piece that is formed on each strand of the continuous machine is the suspension according to claim 1. A method of cooling the flakes, which is covered with a cold cover to cool.