JP2905401B2 - Clamps for joining billets in continuous hot rolling - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joining clamp for continuous hot rolling of steel slabs, and more particularly, to a method of heating the slab efficiently without obstructing the heating and heating of the slab. It is intended to reliably prevent deformation of the joint area of the steel slab at the time of pressing and breakage during rolling of the steel slab after joining.

[0002]

2. Description of the Related Art In a so-called batch-type hot rolling line in which billets are heated, rough-rolled, and finish-rolled one by one to finish a steel sheet having a desired thickness, a so-called batch-type hot rolling line is used. Stopping is liable to occur, and a reduction in the yield due to a defective shape of the leading and trailing ends of the material has a significant disadvantage.

[0003] For this reason, recently, a rolling method (endless rolling) in which a rear end portion and a front end portion of a steel slab to be rolled are joined prior to finish rolling, and this is continuously supplied to a hot rolling line for rolling. Is being adopted.

In this regard, the rear end of the preceding slab and the front end of the succeeding slab are butted and joined over the entire surface thereof.
After that, reference is made to JP-A-61-144203 in which rolling is performed.

[0005] Here, in performing endless rolling, it is necessary to minimize the time required for joining billets. This is because rolling of steel slabs proceeds continuously, and if long joining time is required, continuous rolling cannot be performed, and the difference in timing between the joining process and the rolling process is absorbed. This is because there is a disadvantage in that a separate looper must be provided or the length of the line must be increased in a method of joining billets between runs.

As a technique relating to the joining of steel slabs, as disclosed in Japanese Patent Application Laid-Open No. 60-244401, in which a preceding material and a following material are induction-heated while maintaining a gap, and then upset and joined. Technology has been proposed.

[0007]

When joining steel slabs, it is necessary to match their end faces accurately. However, when the steel slabs are heated and pressed, the ends thereof are displaced in the thickness direction, Cracking (at the joint of billets, the temperature is 13
In some places, the temperature has reached 00 to 1500 ° C, and it has partially melted.The friction coefficient at the bonding interface has decreased in such areas, and even if there is slight irregularity in the pressing situation, However, in such a case, a sufficient strength (joining strength) cannot be ensured, so that the sheet may be broken during rolling, and there is still some room for improvement in this respect. The mechanism leading to such breakage will be described in more detail.
That is, as shown in FIG. 1, in a case where an alternating magnetic field is applied in the thickness direction of the slab to heat, raise the temperature, and press to simply join the slabs, the ends of the slab are not illustrated. As shown in FIG. 2, it is inevitable that the joints are displaced in the sheet thickness direction (hereinafter, referred to as misalignment). The slab is crushed and falls down and deforms so as to bite into the surface of the slab. Then, as the number of rolling passes increases, an excessively thin portion occurs, and during rolling, the plate breaks from this point.

[0008] An object of the present invention is to reduce the displacement in the thickness direction at the joining stage of the billets, thereby ensuring the mutual contact between the billets.
An object of the present invention is to propose a clamp for joining steel slabs that can be efficiently heated, heated, and joined.

[0009]

The present invention comprises two pairs of upper and lower blocks for clamping and supporting each of a preceding billet and a succeeding billet in its thickness direction. At least one is connected to a non-magnetic misalignment prevention plate having an open-ended notch cut out at intervals along the width direction of the billet, wherein the misalignment prevention plate is It is a clamp for joining steel pieces having an insulating material on the opposite surface, and the misalignment prevention plate and the insulating material are
It is preferable that the steel plate is disposed so as to straddle the preceding and following billets, and the notch of the misalignment prevention plate is preferably filled with a magnetic material.

Further, in the present invention, the plate is internally water-cooled, and has a nozzle capable of spraying a non-oxidizing gas, a reducing gas, or cooling water to a joining surface of the billet. In addition, a seal box is provided at the width end region of the plate to surround the rear end of the preceding billet and the front end of the succeeding billet and to maintain the region in a non-oxidizing atmosphere or a reducing atmosphere. Is preferred.

Operation and Embodiment FIG. 4 shows the structure of a main part of a clamp according to the present invention. In the figure, reference numeral 1 denotes a leading billet, 2 denotes a trailing billet, and 3 (3a, 3b) denotes upper and lower positions for clamping and supporting the leading billet 1 and the trailing billet 2 in the thickness direction. Although not shown, this block 3 is connected to a drive means such as a hydraulic cylinder (not shown) so that they can approach and separate from each other. Numeral 4 (4a, 4b) is a misalignment preventing plate which is connected to the block 3 to prevent the ends thereof from shifting in the thickness direction and joining when pressing the billet, and to prevent buckling. The misalignment prevention plate 4 is a non-magnetic material having a high-temperature strength and having a notch d having an open end cut out at intervals along the width direction of the steel slab (for example, SUS304, Titanium, tungsten, etc.). Reference numeral 5 denotes an insulating member shown in an example in which the block 3b is disposed so as to straddle the preceding billet 1 and the succeeding billet 2 (the billet is heated at an end portion and partially melted). Therefore, ceramics or the like having heat resistance, thermal shock resistance, and hot strength can be used as the insulating member.) Reference numeral 6 denotes an induction heating coil, which applies an alternating magnetic field that penetrates the steel piece in the thickness direction. Then, the end area of the slab is heated to a joinable temperature and heated.

FIG. 5 shows the overall configuration of the joining clamp according to the present invention, and FIG. 6 shows the arrangement of a frame incorporating the joining clamp together with the induction heating coil in a rolling line. In the figure, r is a rough rolling mill,
c is a crop shear for processing the end of the slab into a desired shape, m is a group of finishing rolling mills, and f is a movable frame capable of performing a joining operation during the transportation of the slab. Note that a winding / unwinding device may be arranged between the rough rolling mill r and the crop shear c in FIG. 6 to adjust the time for the joining operation and the rolling operation.

In order to butt join the leading billet 1 and the trailing billet 2 at their respective ends, as shown in FIG. 7A, the leading billet 1 is pinched and supported by the block 3a for positioning. And
Next, in a state where a gap g is formed between the leading billet 1 and the trailing billet 2, the end of the trailing billet 2 is pinched and supported by the block 3b and positioned. Then, heating / heating with the induction heating coil 6 and the block 3b are moved (the billet slides on the insulating portion) as shown in FIG. 7B (the leading billet 1 is moved toward the succeeding billet 2). The following billet 2 is abutted against the end face of the preceding billet 1. Above
7a and 7b, the plate 4b is stretched along with the insulating material 5 on the preceding steel piece 1 and the following steel piece 2. In the present invention, as shown in FIG.
Even if a and 4b are arranged at the respective ends of the preceding and following billets 1, misalignment at the time of joining the billets can be prevented to a considerable extent. However, in order to perform more secure joining, as shown in FIGS. 7a and 7b, one (4b) of the misalignment preventing plate 4 and the insulating material 5 are connected to the preceding billet 1.
And the following slab 2. The reason why the misalignment prevention plate 4 and the insulating material 5 are preferably arranged so as to straddle the preceding steel piece 1 and the following steel piece 2 is as follows. In other words, it is important that the butting surfaces of the preceding and following billets 1 and 2 be aligned with the center of the induction heating coil (the center of the dimension along the longitudinal direction of the billet), as shown in FIG. At the time of positioning, a slight shift is unavoidable, and in order to perform heating such that the leading and succeeding billets 1 and 2 are asymmetrical, the positions of the billets are shifted in the longitudinal direction, and heating is performed. The temperature may rise. In such a case, if the steel slabs are pressed against each other and joined together, misalignment is likely to occur as shown in FIG. 7D, and if the slab itself is warped, the misalignment will be even greater. In order to prevent such misalignment, it is best to arrange a plate and an insulating material straddling the two billets so that the horizontal levels of the two billets are matched. The reason for arranging the insulating material 5 is as follows.
When the plate 4 is arranged so as to straddle both the billets, the billet comes into contact with the plate 4 and an induced current flows between the billets through the plate 4 to effectively heat the billet ends. It is not possible. As shown in FIG. 7c above, when the plate 4 is arranged on each steel piece and the insulating material 5 is arranged between the plate 4 and the steel piece, a gap is formed between the plate 4 and the steel piece. As a result, contact between the plate 4 and the billet is avoided, and effective heating can be performed.

In the present invention, the plate 4 provided on the block 3 regulates the vertical movement of the billets 1 and 2, so that the billets may be displaced and joined or buckling may occur. Is gone.

The plate 4 of the block 3 has an open-ended notch cut out at intervals along the width direction of the steel slab as an example. Even if an alternating magnetic field is applied in a state where the plate 4 having a planar shape is arranged on the surface of the billet, almost no induced current flows through the plate 4 (it flows on the end face of the billet due to the skin effect). Therefore, the plate 4 is not heated and heated together with the steel slab when the steel slab is heated and heated. In the case where the misalignment prevention plate 4 is arranged so as to straddle between the preceding steel piece 1 and the following steel piece 2 as shown in FIG. 4, no alternating magnetic field is applied to the other plate 4 or the alternating magnetic field is applied. In such a case that there is no problem even if a current flows due to the application of the above, the other plate 4 does not need to have the notch d having the open end. Plate 4 with open-ended notch
In the case where (metal) is used, the induced current hardly flows through the plate 4 because the induced current having the property of circling around the magnetic pole is slightly different depending on the material and width of the plate. However, the plate 4 requires a certain amount of orbital radius. However, such a plate 4 cannot make the inductive current circulate and cannot secure a sufficient orbital radius (a plane dimension that can cover the orbital circle of the induced current is not ensured). It is thought to be from.

Next, the operation of the present invention when the notch is filled with a magnetic material will be described. FIG. 8 is an example showing a structure in which a cutout d of the plate 4 is filled with a magnetic material M (Fe-based, Cr-based, or Si steel plate or the like). By filling the cutout d with the magnetic material M, the magnetic material M functions as an iron core of the induction heating coil 6 (corresponding to shortening the gap between the magnetic poles of the coil). As a result, the heating efficiency can be improved by reducing the magnetic resistance, which is extremely advantageous for shortening the heating time. In addition, the magnetic material M
Is extremely advantageous in increasing the rigidity of the plate 4 itself and suppressing deformation of the billet. The magnetic material M is
In order to avoid a temperature rise due to the induction heating coil 6, a plurality of thin plates insulated from each other are preferably arranged along the width direction of the plate.

A notch d having a width of 20 mm, a thickness of 40 mm, and a length of 350 mm is provided, and a magnetic material M (0.3 mm in width,
Insulate the thin steel plates, which are 40mm thick and 350mm long, from each other
Using a clamp such as that shown in Fig. 8 above, the thickness is 30 mm, the width is 1000 mm, and the temperature is 10
Heating and raising the temperature of a slab (extremely low carbon steel) at 00 ° C with a gap g of 5 mm (heating coil size: width 1000 mm, length 240 m)
m, number of coil turns 10 (5 each in upper and lower), heating condition: magnetic flux density 0.12T, frequency 1000Hz, current 6120A, power
1060kw, heating time 10 seconds), pressing (pressing force 50 tons), joining, and then passing through rolling equipment to finish 1.2mm thick steel plate, there is no misalignment when pressing Also, there was no breakage of the plate due to the concentration of the rolling tension in the thin portion.

When a clamp having a structure as shown in FIG. 8 is used in a C-shaped coil having a size as shown in FIG. 9, the distance between the iron cores is equivalent to a reduction from 210 mm to 170 mm. The resistance of the magnetic circuit composed of the iron core of the C-shaped coil and the gap between the iron cores decreases from 705000 (A / Wb) to 572460 (A / Wb), and the density of the induced magnetic flux at this time is 0.087 (T ) To 0.107 (T) (assuming that the space between the cores is filled with air, the relative magnetic attraction is air 1, iron 1000,
The coil core (oriented Si steel sheet 1600)) is increased by about 23%.

FIG. 10 shows that a cooling water flow path P is provided inside the plate 4 to make it water-cooled, and that a non-oxidizing gas, a reducing gas, or cooling water is blown to the joint surface of the steel slab. This shows an example in which a possible nozzle N is provided via an insulating material 5. When heating the billet, the temperature of the plate 4 rises (the size of the part excluding the cutout is 30 mm,
If induction heating is performed at the frequency of z, the temperature will increase by about
In addition, in the case where it is unavoidable that the cooling water is affected by the radiant heat from the steel slab, the rise can be suppressed by circulating the cooling water inside the plate 4. Moreover, upon butt joint of the steel pieces 1 and 2, a high strength to prevent oxidation of the site by spraying the non-oxidizing gas or predetermined joining face a reducing gas by switching the valve b ₁ ~b ₃ from the nozzle N it is possible to obtain a junction, further switching valve b ₁ ~b ₃ after completion of bonding, it is also possible to improve the strength by reducing the temperature of the site sprayed cooling water into the joint ( If the temperature of the joint is 1450 ° C. or higher, the joint may be separated from the joint when there is a change in tension or the like). Conditions for cooling the inside of the plate vary depending on the cross-sectional area of the flow path, but it is appropriate to set the cooling water amount to about 5 T / H.
It is appropriate that the flow velocity of the flow channel is 2.5 m / S or more, especially about 5 m / S. Regarding cooling of the joint, it is preferable to cool at a flow rate of 100 to 400 T / H (one side). The diameter of the nozzle N is about 1 to 2 mm, or a slit type having a gap of about 1 mm and a width of 5 to 10 mm can be used.

In FIG. 10, cooling water or the like is sprayed through the plate 4 and the insulating material 5, but as shown in FIG. 11, the nozzle N is directly attached to the insulating material 5 from the notch d. You may. In a case where the plate 4 and the insulating material 5 are individually provided on each steel piece as shown in FIG. 4c, nozzles are provided at the ends of the plate 4 as shown in FIG.

FIG. 13 shows a seal box (block moves up and down) which surrounds the rear end of the preceding steel slab 1 and the front end of the following steel slab 2 and holds the area in a non-oxidizing atmosphere or a reducing atmosphere. This is an example in which a device 7 having an expansion / contraction function is provided so as not to cause any trouble. A stable atmosphere can be maintained by blowing a non-oxidizing gas such as N ₂ gas into the seal box 7. In this case, the gas blown is not shown, but a gas suction hole is provided on the other seal box 7 side, and the gas is drawn out from the hole.

In particular, when the billet is joined using the seal box 7 as shown in FIG. 13, it is easy to use in the atmosphere such as stainless steel containing Cr, high-carbon special steel having a low melting point, and high-Mn steel. This is effective for objects that cannot be joined to the target. As the gas to be blown, N ₂ gas, Ar gas and the like can be applied, but flammable gas such as H ₂ gas, CO gas and Pr gas may be used. When such a gas is used, the flow rate is set to about 1 to 10 Nm ³ / min.

In the case of carbon steel, the oxide generated upon heating and raising the temperature is iron oxide (FeO), and its melting point is 1370 ° C. Even if, for example, MnO 2 or the like is mixed with this, the temperature will be approximately in this vicinity. Here, the melting point of metal fluctuates depending on the carbon content.For steel having a solidus higher than the melting point of FeO, if the temperature is set to an intermediate temperature between the solidus and the melting point of FeO, the temperature during pressing of the slab is Oxide melted when the metal is deformed can be discharged from the bonding interface.

In the case of steel having a carbon content of about 0.70%, the solidus temperature (the temperature at which melting starts) substantially matches the melting point of iron oxide. However, the oxide on the bonding surface generated at the time of the temperature rise does not melt, and may be left behind at the bonding interface, making it difficult to obtain a good bonding portion.

The oxide formed in stainless steel is a very strong Cr oxide having a melting point much higher than that of metal. It is very difficult to obtain good bonding because the oxide will remain at the bonding interface. Above
When the seal box 7 as shown in FIG. 13 is used, such a problem is extremely reduced.

The end face of the steel slab (extremely low carbon steel and stainless steel) cut by the crop shear c
As a result of investigating the state of oxide formation at 950 to 1000 ° C for 15 seconds, an oxide layer with a thickness of several μm to 10 μm was found in ultra-low carbon steel, and almost no oxide was formed in stainless steel. Did not. By the way, when these steels are further heated to 1400 ° C, an oxide layer with a thickness of about 60 to 70 μm is formed for ultra-low carbon steel, and an oxide layer of about several μm is formed for stainless steel. However, generation of such an oxide layer can be avoided by setting a non-oxidizing atmosphere or a reducing atmosphere only at the time of heating and raising the temperature. In addition,
In order to avoid oxidation of the surface to be joined when heating and heating the billet, adjust the atmosphere so that the oxygen concentration is 1% or less in the case of carbon steel, and about 0.1% in the case of stainless steel. It is preferable to perform such an atmosphere adjustment.

FIG. 14 shows a modification of FIG. 4 described above. The clamp shown in FIG. 14 allows only the upper blocks 3a and 3b to move up and down, engages the plate 4b of the lower block 3b with the sliding plate t of the opposing block 3a, Is pressed so that the plate 4b slides on the sliding plate t. With such a structure,
Since the horizontal level of the lower blocks 3a and 3b is always constant, the accuracy of positioning when joining the billets is improved, and it is extremely advantageous in improving the strength as a clamp.

In a method in which an alternating magnetic field penetrating the steel slab in the thickness direction is applied to the steel slab and the end of the steel slab is heated and heated by an induced current generated at that time, the steel slab shown in FIG. Since the temperature rise of the corner portion F is smaller than that of the central portion in the plate width direction, even when the central region in the plate width direction reaches the joinable temperature as shown in FIG.
Has not yet reached the joinable temperature range, and it is impossible to join the entire area in the sheet width direction even if both steel pieces are pressed in this state, and the sheet may break from that part during rolling. Even if the corner portion F is heated to a joinable temperature, the central region in the width direction of the plate is overheated and melts down, so that the steel slab cannot be joined in a good condition.

For this reason, in the present invention, with respect to the hatched area shown in FIG. 15 above, cooling is performed before heating by injection of cooling water from the nozzle N shown in FIG. Control to make the distribution uniform.

The temperature of the sheet bar before finish rolling is set in the range of about 900 to 1000 ° C. so that the sheet bar of ultra low carbon steel having a width of 1000 mm and a thickness of 30 mm is joined and hot finish rolling is performed.
In addition, set the target heating temperature to 1400 ° C or higher, and cool the position inside 150mm from the end of the width of the sheet bar for 1 second (water density 2000l / m ² ) to lower the temperature by about 100 ° C,
Next, with a gap of 5 mm, the induction heating coil (size
1100mm x 250mm) to apply an alternating magnetic field (input power 15
00kw, frequency 500Hz, time 10 seconds) and then the steel slab was pressed with a pressing force of 3kgf / mm ² and joined and rolled (rolled to a thickness of 3mm by a 7-stand mill), and the results of investigation of the condition of the plate The temperature distribution of the sheet bar at the time of joining was as shown in FIG. 17, no burn-through of the sheet was observed, and no breakage occurred during rolling.

[0031]

According to the present invention, the vertical displacement at the end of the slab which cannot be avoided when the slab is pressed is reduced, so that the plate is not broken due to this.

When the cutout portion of the plate is filled with a magnetic material, it is advantageous to increase the rigidity of the plate, and it is possible to improve the heating efficiency by an effect equivalent to a reduction in the distance between the magnetic poles. It is possible and the time required for the joining process can be reduced.

By making the inside of the plate water-cooled, it is possible to avoid a rise in the temperature of the plate and to extend its life. In addition, by providing a gas or cooling water injection mechanism, appropriate joining can be performed according to the situation, and continuous hot rolling with high productivity can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a conventional heating / heating situation.

FIG. 2 is a view showing a situation where the ends of the billets are joined while being shifted.

FIG. 3 is an explanatory view of a breaking state of a billet.

FIG. 4 is a diagram showing a configuration of a clamp according to the present invention.

FIG. 5 is a diagram showing an entire clamp according to the present invention.

FIG. 6 is a diagram showing a configuration of a rolling facility.

FIGS. 7A, 7B, 7C, and 7D are explanatory views of a joining state of steel slabs.

FIG. 8 is a diagram showing another example of the clamp according to the present invention.

FIG. 9 is a diagram schematically showing a C-shaped coil.

FIG. 10 is a diagram showing another example of the clamp according to the present invention.

FIG. 11 is a diagram showing another example of the clamp according to the present invention.

FIG. 12 is a diagram showing another example of the clamp according to the present invention.

FIG. 13 is a diagram showing another example of the clamp according to the present invention.

FIG. 14 is a diagram showing a modification of FIG. 1;

FIG. 15 is a diagram showing a heating state of a billet.

FIG. 16 is a diagram showing a temperature distribution in a width direction of a billet.

FIG. 17 is a diagram showing a temperature distribution in a width direction of a billet.

[Explanation of symbols]

1 preceding After steel pieces 2 rows steel pieces 3 blocks 4 plate 5 insulating member 6 induction heating coil 7 seal box r roughing mill c crop shear m finishing mill group f frame g gap M magnetic material N nozzle b ₁ ~b ₃ Valve F corner

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideyuki Nikaido 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corporation Chiba Works (72) Inventor Shigeru Isoyama 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Inside Chiba Works (72) Inventor Toshiaki Amagasa 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture Kawasaki Steel Corporation Inside Chiba Works (72) Nozomi Tamura 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corporation Inside Chiba Works (72) Inventor Tohru Kondo 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture Inside Chiba Works, Chiba-shi (72) Inventor Kunio Miyamoto 4-622 Kanon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. (72) Inventor Kazuya Tsuruzaki 4-6-22 Kannonshinmachi, Nishi-ku, Hiroshima-shi, Hiroshima Mitsubishi Heavy Industries, Ltd. Hiroshima the laboratory (56) Reference Patent flat 6-39406 (JP, A) JP flat 4-200984 (JP, A) (58 ) investigated the field (Int.Cl. ^6, DB name) B21B 1/26 B21B 15/00

Claims (8)

(57) [Claims] 1. A pair of upper and lower blocks for clamping and supporting each of a preceding slab and a following slab in the thickness direction thereof are provided, and at least one of the blocks is provided with steel. A non-magnetic misalignment prevention plate having an open-ended notch cut out at intervals along the width direction of the piece; A clamp for joining billets in continuous hot rolling, comprising: 2. The clamp according to claim 1, wherein the misalignment prevention plate and the insulating material are disposed so as to straddle the preceding and subsequent billets. 3. The clamp according to claim 1, wherein the cutout portion of the plate is filled with a magnetic material. 4. The plate according to claim 1, wherein the plate is internally water-cooled.
The clamp according to 2 or 3. 5. The clamp according to claim 1, wherein the plate or the insulating material has a nozzle for blowing a non-oxidizing gas or a reducing gas onto a surface of the billet to be joined. 6. The clamp according to claim 1, wherein the plate or the insulating material has a cooling injection nozzle for spraying cooling water or cooling gas to the joint of the billets. 7. A nozzle capable of spraying at least one of a non-oxidizing gas, a reducing gas, cooling water, and a cooling gas on a plate or an insulating material to a joining surface or a joining portion of a billet as necessary. Claims 1, 2, and 3 having
Or the clamp according to 4. 8. A seal box is provided at a width end region of the plate to surround a rear end portion of a preceding billet and a front end portion of a succeeding billet and to maintain the portion in a non-oxidizing atmosphere or a reducing atmosphere. The clamp according to 2, 3, 4, 5, 6, or 7.