JP3771900B2 - Steel slab surface reformer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a melt reforming apparatus for a surface layer of a steel slab.
[0002]
[Prior art]
As a technique for melting the slab surface for the purpose of repairing defects on the slab surface, for example, Patent Document 1 discloses a slab melting care method in which the surface layer portion of the slab is heated by high frequency induction heating. In this technique, a high frequency current is applied to an induction coil installed close to the slab, an induced current is generated on the slab surface, and the slab surface is melted by the Joule heat.
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 53-100988
[Problems to be solved by the invention]
However, as for the above-mentioned Patent Document 1, the inventors conducted a test for melting the surface layer using a coil that circulates the slab when the slab sample is placed vertically and horizontally, In the case of standing upside down, the melted part surface is disturbed especially at the lower side of the melted part, and the re-solidified surface properties after melting are deteriorated. It has been found that there are problems such as the deterioration of the surface properties and, in some cases, the phenomenon that the action of gravity cannot be resisted and droplets are generated and leaked.
It is considered that this phenomenon occurred because a force to hold the melted portion by electromagnetic force acts as shown in FIG. 3 but it is not sufficiently stable mechanically.
An object of the present invention is to provide an apparatus for stably melting a steel slab surface layer and modifying the steel slab surface layer by adding an additive element.
[0005]
[Means for Solving the Problems]
The present invention
(1) Surface modification of a steel slab comprising an induction heating coil arranged to circulate around a steel slab, a conductive segment container having a cooling function installed inside the coil, and an additive element supply device An apparatus for modifying a surface layer of a steel slab, characterized in that a gap is provided between the conductive segments.
(2) The surface reforming apparatus for steel slab according to (1), wherein the conductive segment containers are arranged in a pair in the slab longitudinal direction.
(3) The surface reforming device for a steel slab according to (2), wherein the additive element supply device is installed between a pair of conductive segment containers.
(4) The apparatus for modifying a surface layer of a steel slab according to any one of (1) to (3), which has a function of moving a conductive segment.
(5) The steel layer slab surface layer reforming apparatus according to any one of (1) to (4), wherein a plasma heating apparatus capable of supplying an additional element is installed instead of the additional element supply apparatus.
It is.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The present invention, as an apparatus for welding an additive element to a steel slab surface layer, melts the steel slab surface layer using induction heating and supplies the additive element to the steel slab surface layer using an additive element supply device. The present inventors have found an apparatus that can stably and reliably produce a composite steel material by installing a conductive segment container having a cooling function on the inner side without generating droplets and leaking. This will be described in detail below.
[0007]
In this invention, the induction heating coil arrange | positioned so that a steel slab can go around is used as an apparatus which fuse | melts the steel slab surface layer. The induction heating coil melts the surface layer portion of the slab. The additive element is supplied using an apparatus for supplying the additive element to the melting portion. As the additive element supply device, a wire, a sheet, or the like is used. Here, a pure metal or an alloy thereof may be used as the additive element, and these are hereinafter collectively referred to as an additive element.
[0008]
For example, a slab obtained by a continuous casting machine is transported to a melting treatment site after being cut and heated by an induction coil arranged so as to circulate around the slab, and a wire or sheet is used for a molten part of the slab surface layer. An additive element or an alloy thereof is added and welded. The induction coil creates a stable melted part surface by pressing the melted part toward the inner surface by electromagnetic force in the slab surface melted part, and then cooled again and solidifies.
[0009]
In addition, when an additive element is added to the slab surface layer melting portion and welded, it is preferable to prevent the slab from being oxidized. Therefore, as shown in FIG. 1, the induction coil 3 has an inert gas atmosphere (for example, argon) in the chamber. , Nitrogen, etc.) is preferable. In order to prevent the oxidation more reliably, it can be melt-modified by containing about 2% by volume of hydrogen in an inert gas atmosphere. It is preferable that a hydrogen supply facility or the like is provided.
Here, the principle of generation of electromagnetic force by the induction coil is shown in FIG. Due to the interaction between the magnetic field 15 generated by the induction coil 3 and the current induced in the slab, which is the conductor 14, an electromagnetic force acts on the melted portion. This electromagnetic force has an action of compressing the melted portion called pinch force, and contributes to stabilization of the surface of the melted portion.
[0010]
However, such a static equilibrium alone is not always sufficient, and in order to contribute to the stabilization of the surface of the melted part, in the present invention, a conductive material having a cooling function as shown in FIG. The sex segment container is installed inside the induction heating coil 3 as shown in FIGS. 1 and 2 and further has a gap between the segments. Here, the principle of the conductive segment will be explained. When there is no gap between the segments as shown in FIG. 4A, an induced current 23 is generated with respect to the coil current 22, so that the magnetic field is almost canceled. On the other hand, in the case of FIG. 4B, since there is a gap (slit) 24 between the segments 20, the induced current 23 in each segment is generated in a closed loop, so the magnetic field in each segment is canceled, A magnetic field generated by the coil current 22 can be generated.
[0011]
Such a gap is formed by connecting a plurality of single segments in parallel, and may be formed by sandwiching a mica plate or the like between each segment, and each segment has one or more through slits. A thing may be used. The gap between the segments is not particularly specified, but is usually 0.3 mm to 3 mm. The lower limit is determined from the limit of the thickness of the insulating material when the insulating material is used, and the upper limit is a value determined since it is difficult to keep the magnetic field uniform when it exceeds 3 mm.
[0012]
The action of the conductive segment container having a cooling function effectively applies a high-frequency magnetic field to the slab surface layer, and at the same time, when the surface of the melted part is disturbed due to variations in the slab structure and temperature fluctuations, The conductive segment container having a cooling function causes instantaneous solidification of the contact part when it comes into contact with the molten part molten metal, and immediately after that it is pushed back again by the strong electromagnetic force to cause remelting, resulting in stable The molten state can be continued.
As the conductive segment container having a cooling function, a water-cooled container is usually used, and a material made of copper or a copper alloy is generally used.
[0013]
Steel slabs are usually manufactured by continuous casting. The case where the device of the present invention is applied when using continuous casting will be described below.
First, the case where the apparatus of the present invention is installed when the end of the continuous casting machine, that is, the slab after continuous casting is moving horizontally will be described. In this case, in the vertical bending type continuous casting machine having a general curved mold or a vertical portion over several m below the mold, the slab generally has a horizontal portion after being bent back and before being gas cut. Place in this part. The induction coil is arranged around the slab. In the case of this method, the upper part of the slab is easily processed because dripping due to gravity does not occur even if the surface part of the slab is melted by heating with an induction coil. Further, the melted portion at the bottom of the slab is held by the action of electromagnetic force based on the principle shown in FIG. 3, and it is possible to prevent the surface shape after dripping or re-solidification due to gravity. This processing can also be performed one side at a time by reversing 180 degrees using a slab reversing device. The slab end can be processed by reversing ± 90 degrees using the slab reversing device.
[0014]
Furthermore, the case where the apparatus of the present invention is applied in the continuous casting machine, that is, when the slab is moving vertically will be described. In the continuous casting machine, the slab out of the mold is heated by the induction coil in the secondary cooling zone. The induction coil is held by the electromagnetic force of the melting part, and the molten part is cooled again and solidified after passing through the lower induction coil without dropping by gravity. Here, since the melted portion of the slab is more likely to drip on the lower side of the melted part due to the action of gravity, the lower part of the melted part is stronger on the induction coil by installing the lower coil near the slab than the upper coil It is preferable because electromagnetic force can be generated to prevent the melted portion from leaking.
[0015]
Next, the conductive segment containers are usually arranged in pairs in the slab longitudinal direction. With such an arrangement, the melted portion of the slab between the conductive segment containers is a stable surface layer portion, and by adding an additive element to this, a surface quality modified slab of good quality Can be manufactured.
Accordingly, by installing the additive element supply device 2 between the pair of conductive segment containers, the addition of the pure metal or alloy as the additive element can be performed on the stable surface layer portion, which is effective. is there.
[0016]
Moreover, what has the function to which an electroconductive segment can move is preferable. That is, since the coil is usually a fixed size and the slab changes in width at any time, in order to enjoy the above-described stable holding effect even when the width changes, the conductive segment is moved, The clearance can be set to a desired value. A specific example of this is shown in FIG. 5, but when the width of the slab 5 changes, the conductive segments 20 on a pair of sides of the rectangular slab so that the clearance with the slab becomes constant. The stable holding effect can be enjoyed by moving. Also, it can be set to any clearance depending on the steel type and processing conditions.
Examples of the device having a function of moving the conductive segment include a device having a structure in which the short side is moved in a lump with a hydraulic cylinder, for example.
[0017]
In addition, a case where induction heating and plasma heating are performed in combination will be described. The slab 5 that has been continuously cast by the continuous casting machine 1 is cut and transported to a melting treatment field, heated by an induction coil 3 as shown in FIG. 1, and further replaced with an additive element supply device 2 to install a plasma device. Then, by supplying the additive element or its alloy to the plasma, the additive element or its alloy is added and welded to the slab surface layer melting portion.
Although the induction coil alone can melt the surface layer portion of the slab, the combined use of plasma can also melt the surface layer portion of the slab even by heating with plasma, which has the effect of reducing the load on the induction coil. For example, the induction coil can be used as a preheating function and a compression function of a melting part by generating a pinch force, and plasma can be used as a melting function of a slab surface layer and an additional element supply function.
[0018]
When heating and melting with a plasma device, the additive element or its alloy is in the form of powder and is generally blown into the plasma, whereas when an induction heating device and a plasma heating device are used in combination, Has the advantage that it can be carried out regardless of the shape of the additive element or its alloy.
In addition, as a component of the additive element, carbon, silicon, manganese, phosphorus, sulfur, nickel, chromium, molybdenum, copper, gold, aluminum, magnesium, rare earth metal, etc. are used to change the characteristics of the steel material. Can be mentioned.
[0019]
The additive element may be added as a pure metal or as an alloy. A plurality may be mixed and added according to the purpose.
Examples of the alloy of the additive element include a compound of the additive element component and oxygen or nitrogen in addition to the above-described alloy of a plurality of component elements.
The alloy of the additive element is not particularly limited as long as it is a multi-component alloy of the additive element, but ferromanganese, ferronickel, ferroline, and other iron alloys are usually used.
Further, the compound of the additive element component and nitrogen is, for example, iron nitride, and the compound of the additive element component and oxygen is, for example, magnesium oxide.
[0020]
As described above, by using the apparatus of the present invention, it is possible to obtain a surface-modified composite steel slab of low-cost steel having both the properties of steel having different surface properties and internal properties.
Further, by processing the above-mentioned surface layer-modified composite steel material slab, a low-cost product having the characteristics of steel having different surface layer and internal properties such as a thin plate, a thick steel plate, a shaped steel, and a steel pipe can be obtained.
[0021]
【Example】
(Example 1)
Using an apparatus as shown in FIG. 1, the surface layer portion of a continuous cast slab having an inner size of 1510 mm × 260 mm, a width of 1500 mm, and a thickness of 250 mm was melt-modified.
The clearance between the continuously cast slab and the water-cooled conductive segment container was 5 mm. Here, the water-cooled conductive segment container is formed by connecting a plurality of segments having a thickness of 20 mm and a circumferential direction of 20 mm in parallel, and the mica plate is sandwiched between the segments so that the distance between the segments is 1 mm. The thing of length 10cm was used.
The segment containers were arranged and fixed in pairs with a clearance of 1 cm in the longitudinal direction. An induction coil having a clearance of 1 cm and a length of 5 cm was installed outside the segment container. A 40 kHz high frequency power source was connected to the coil.
[0022]
Using this equipment, the low-carbon aluminum killed slab was previously held at 800 ° C. in a heating furnace, then treated with a moving speed of 1 m / min while applying 2 MW of power to the power source, and nickel preheated to 800 ° C. was 1 The addition was made with the aim of adding mass%. As a result, it was confirmed that 3 mm of the slab surface layer was melted almost uniformly, and 0.95 to 1.05 mass% of nickel could be deposited.
[0023]
(Example 2)
In the apparatus as shown in FIG. 5, the surface layer portion of a continuous cast slab having an inner dimension of 1510 mm × 260 mm, a width of 1000 mm, and a thickness of 250 mm was melt-modified.
The clearance between the continuously cast slab and the water-cooled conductive segment container was 5 mm in the slab thickness direction. A movable short-side water-cooled conductive segment block is arranged in the width direction, and the clearance is set so that the clearance is 5 mm on one side.
The water-cooled conductive segment container on the long side is the same as in Example 1, with a plurality of segments having a thickness of 20 mm and a circumferential direction of 20 mm connected in parallel. The mica plate is attached to each segment so that the distance between the segments is 1 mm. A 10 cm long one sandwiched between them was used.
The segment containers were arranged and fixed in pairs with a clearance of 1 cm in the longitudinal direction. An induction coil having a clearance of 1 cm and a length of 5 cm was installed outside the segment container. A 16 kHz high frequency power source was connected to the coil.
[0024]
Using this device, the low-carbon aluminum killed slab was previously held at 800 ° C. in a heating furnace, then treated with a moving speed of 1 m / min while applying 3 MW of power to the power source, and nickel preheated to 800 ° C. was 1 The addition was made with the aim of adding mass%. As a result, it was confirmed that 5 mm of the slab surface layer was melted almost uniformly and 0.95 to 1.05 mass% nickel could be deposited.
[0025]
【The invention's effect】
As described above, if the apparatus of the present invention is used, it is possible to stably carry out surface layer reforming of steel slabs, and to obtain surface quality modified slabs of good quality and processed products thereof. Become.
[Brief description of the drawings]
FIG. 1 shows the configuration of an apparatus according to the present invention.
FIG. 2 is a configuration of the apparatus of the present invention (detailed view of a melting part).
FIG. 3 is an explanatory diagram of the principle.
FIG. 4 shows the principle of a conductive segment.
FIG. 5 shows the configuration of the apparatus according to the present invention when width change is involved.
[Explanation of symbols]
1: Continuous casting machine 2: Element addition device 3: Electromagnetic induction coil 4: Support roll 5: Slab 6: Container for creating an atmosphere containing argon and about 2% hydrogen 7: Solidification part 8: Molten part 9: Not yet Solidification part 10: Continuous drawing or movement 11: Coil current 12: AC current 13: Time 14: Electrical conductor 15: Magnetic field 16: Unmelted heating part 17: Part enriched with specific components 18: Direction of electromagnetic force And strength 19: static iron pressure due to gravity 20: conductive segment 21: conductor 22: coil current 23: induction current 24: slit

Claims (5)

A steel slab surface layer reformer comprising an induction heating coil arranged to circulate around a steel slab, a conductive segment container having a cooling function installed inside the coil, and an additive element supply device. An apparatus for reforming the surface layer of a steel slab characterized by having a gap between the conductive segments. 2. The steel slab surface layer reforming apparatus according to claim 1, wherein a pair of conductive segment containers are arranged in the slab longitudinal direction. The apparatus for reforming a surface layer of a steel slab according to claim 2, wherein the additive element supply device is installed between a pair of conductive segment containers. The surface layer reforming apparatus for steel slabs according to any one of claims 1 to 3, which has a function of moving a conductive segment. 5. The steel slab surface layer reforming apparatus according to claim 1, wherein a plasma heating apparatus capable of supplying the additive element is installed in place of the additive element supply apparatus.

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