DESCRIPTION
HOT SCARFER
Technical Field
The present invention relates to a hot scarfer using high temperature combustion gas to melt away parts of a steel plate surface to touch up the same.
Background Art
Hot scarfers are devices for repair of a ferrous metal slab (below, "slab"). As shown in FIGS. 6 and 7, they are arranged at the top side and bottom side of a slab in pairs. Each hot scarfer is comprised of a plurality of scarfer units 1 arranged in a horizontal direction so as to cover the entire width of the slab (below, the "horizontal direction" indicating the width direction of a slab run through the hot scarfers).
In the hot scarfers shown in FIG. 6, five scarfer units 1 each are arranged horizontally in lines. Each of the scarfer units 1 has an upper block 2, a lower block 3, and a shoe 4 as main components. The shoe 4 is fastened to the slab side surface of the lower block 3 by a fastening jig. It is for preventing the lower block 3 from directly striking the slab in some unlikely circumstance. In general, the shoe 4 is comprised of a copper alloy.
The upper block 2 and the lower block 3 eject propane gas or other fuel gas from pluralities of fuel gas ejectors 21 and 31 provided arranged horizontally. Oxygen is ejected through an oxygen passage 5 formed between the upper block 2 and lower block 3 to form high temperature combustion gas. Further, this high temperature combustion gas is used to melt away parts of the slab surface to remove inclusions, cracks, and other surface defects.
The width of a slab, according to the dimensions of
the product produced after rolling after hot scarfing, is usually between 500 to 1800 mm. For this reason, a hot scarfer is adjusted in number of scarfer units 1 used to match with the slab width.
Since a hot scarfer is divided into a plurality of scarfer units 1 in the width direction of the slab, between the scarfer units 1, as shown in FIG. 8 (example of scarfer units/slab bottom side), between the adjoining lower blocks 3, there are lower block contact surfaces 8, between the adjoining shoes 4, there are shoe contact surfaces 9, and between the adjoining upper blocks 2, there are upper block contact surfaces 7.
Usually, the upper blocks 2, lower blocks 3, and shoes 4 are formed to the identical horizontal width dimensions, so the contact surfaces between the scarfer units are flat and in close contact. However, these or not welded or strictly sealed, so combustion use oxygen sometimes leaks out from the oxygen passage 5 through the slab side lower block contact surfaces 8 and shoe contact surfaces 9 (below, the two together being referred to as the "slab side unit clearances 6"). If oxygen leaks out from the slab side unit clearances 6, flames will erupt and the soft shoes 4 will melt.
Due to this melt loss, the shoe clearances 9 will increase in size and more powerful flames will directly blow over the slab, so the slab will abnormally be melted away and slab surface will be formed with molten metal objects or metal oxides forming relief defects (sludge). Due to this sludge, there was the problem that the slab surface properties ended up degraded. Further, when scarfer units 1 include shoes suffering from melt loss, the scarfer units 1 decline in lifetime and increase in frequency of replacement, so tremendous cost was required for replacement and maintenance.
To solve the above problems, measures have been devised such as sealing the slab side unit clearances 6 by refractories or increasing the machining precision of
the end faces of the scarfer units 1 to reduce the size of the slab side unit clearances 6.
However, hot scarfers melt away parts of the slab surface, so are exposed to high temperatures. Further, they are repeatedly heated and cooled with consequent expansion and contraction, so the ends of the scarfer units easily deform and, further, refractories end up falling off in many cases, so the fact is that there is not much of an effect of suppression of expansion of the slab side unit clearances 6.
Further, integrally joining the scarfer units 1 into has also been proposed, but this would mean melt loss at one part would require the entire assembly to be replaced. This is impractical due to the tremendous trouble and cost involved in production, transport, and installation.
Disclosure of Invention
The present invention, in consideration of the above problems in the prior art, provides a hot scarfer preventing expansion of the slab side unit clearances and thereby preventing deterioration of the surface properties due to formation of sludge during abnormal combustion.
The hot scarfer according to the present invention is a hot scarfer comprised of a plurality of scarfer units, each comprised of an upper block and lower block provided with fuel gas ejectors, an oxygen passage provided between the upper blocks and lower blocks, and a shoe fastened to the lower block, arranged in the horizontal direction, the hot scarfer characterized in that positions of shoe contact surfaces formed between adjoining shoes and positions of lower block contact surfaces formed between adjoining lower blocks are offset in a horizontal direction so as to eliminate overlap of the contact surfaces and prevent leakage of oxygen passing through the oxygen passage from the shoe contact
surfaces and lower block contact surfaces.
The amount of offset of the positions of the lower block contact surfaces and the positions of the shoe contact surfaces is preferably at least made 2.5 mm or more. Further, if making the amount of offset 4 mm or more, the risk of abnormal combustion is greatly reduced.
Further, it is also possible to arrange a plurality of shoes offset horizontally in one direction with respect to the lower blocks so as to offset the positions of the lower block contact surfaces and the positions of the shoe contact surfaces in the horizontal direction or alternately arrange shoes of horizontal widths narrower than the horizontal widths of the lower blocks and shoes of horizontal widths wider than the horizontal widths of the lower blocks so as to offset the positions of the lower block contact surfaces and positions of the shoe contact surfaces in the horizontal direction.
The aspect of the invention according to claim 1 can offset the relative positions of the lower block contact surfaces and shoe contact surfaces in the horizontal direction so as to eliminate overlap between the contact surfaces and thereby prevent leakage of oxygen passing through the oxygen passage from the between the contact surfaces of the shoe contact surfaces and lower block contact surfaces.
The aspect of the invention according to claim 2 offsets the positions of the lower block contact surfaces and the positions of the shoe contact surfaces by at least 2.5 mm or more in the horizontal direction, so can effectively prevent leakage of oxygen.
The aspect of the invention according to claim 3 offsets a plurality of shoes horizontally in one direction with respect to the lower blocks, so can block the leakage of oxygen through the lower block contact surfaces and shoe contact surfaces.
The aspect of the invention according to claim 4 alternately arranges shoes of horizontal widths narrower
than the horizontal widths of the lower blocks and shoes of horizontal widths wider than the horizontal widths of the lower blocks, so can block the leakage of oxygen through the lower block contact surfaces and shoe contact surfaces.
Brief Description of Drawings
FIG. 1 is a perspective view showing an example of hot scarfer units/slab bottom side of a first embodiment of the present invention.
FIG. 2 is a front view of an example of hot scarfer units/slab bottom side of FIG. 1.
FIG. 3 is a perspective view showing an example of hot scarfer units/slab bottom side of a second embodiment of the present invention.
FIG. 4 is a front view of an example of hot scarfer units/slab bottom side of FIG. 3.
FIG. 5 is a graph showing a correspondence between an amount of offset of shoe contact surfaces with respect to lower block contact surfaces and a sludge rate.
FIG. 6 is a perspective view of a conventional hot scarfer.
FIG. 7 is a cross-sectional structural view of a hot scarfer.
FIG. 8 is a front view of an example of conventional hot scarfer units/slab bottom side.
Best Mode for Carrying Out the Invention
Below, embodiments of the present invention will be explained.
FIGS. 1 and 2 are views showing a hot scarfer of a first embodiment of the present invention (scarfer units/slab bottom side). Each scarfer unit 1 is comprised of an upper block 2, a lower block 3 at a bottom side of the upper block, and a shoe 4 fastened to the lower block 3 by a fastening jig.
The upper block 2 and lower block 3 eject fuel gas
from pluralities of fuel gas ejectors 21 and 31. This fuel gas is burned by oxygen supplied from an oxygen passage 5 between the upper block 2 and lower block 3, whereby a high temperature combustion gas is formed. The formed high temperature combustion gas may be used to melt away part of the slab surface to remove surface defects for touchup work.
In the hot scarfer of this embodiment, a plurality of shoes 4 are offset with respect to the lower blocks 3 in one direction horizontally (in the figure, offset to the left) to block leakage of oxygen between the lower block contact surfaces 8 and shoe contact surfaces 9. Therefore, oxygen passing through the oxygen passage 5 can be prevented from passing through the lower block contact surfaces 8 and leaking out from the shoe contact surfaces 9.
FIGS. 3 and 4 show a hot scarfer of a second embodiment. In the hot scarfer of this embodiment, short shoes 41 of widths narrower than the horizontal widths of the lower blocks 3 and long shoes 42 of wider widths are alternately arranged so as to offset the lower block contact surfaces 8 and shoe contact surfaces 9. By this configuration as well, it is possible to offset the shoe contact surfaces 9 from the lower block contact surfaces 8 in the horizontal direction so as to block the leakage of oxygen between these contact surfaces 8 and 9. Therefore, oxygen passing through the oxygen passage 5 can be prevented from passing through the lower block contact surfaces 8 and leaking out from the shoe contact surfaces 9.
FIG. 5 shows the relationship between the amount of offset of the shoe contact surfaces 9 with respect to the lower block contact surfaces 8 in the horizontal direction and the rate of formation of sludge due to abnormal combustion (rate of production of coils after hot rolling and cold rolling where quality defects due to sludge cause suspension of shipment, reinspection,
downgrading, or scrapping).
Further, the "horizontal direction" means the width direction of the slab run through the hot scarfers. As shown in FIG. 5, the sludge rate was as much as 2.5% or so with an amount of offset of 0 mm, but fell to 0.5% or so with an amount of offset of 2.5 mm and fell down to about 0% with an amount of offset of 4 mm or more. Therefore, the amount of offset is preferably made 2.5 mm or more. By making it 4 mm or more, the formation of sludge can be eliminated. Further, no upper limit of the amount of offset need to be particularly set since the effect is the same up to a position 2.5 mm or more from the other end of the lower block 3, but if considering installation of the shoes 4 or lower blocks 3, an offset of 10 mm is sufficient.
In the above way, by offsetting the shoe clearances 9 from the lower block clearances 8 in the horizontal direction so as to cut the communication between these clearances 8 and 9, oxygen and combustion gas can be prevented from leaking out from the shoe clearances 9. Due to this, it was confirmed that flame ejected from the shoe clearances 9 directly being blown over the slab resulting in the formation of sludge can be prevented. Further, the adjoining lower blocks and the adjoining shoes do not have to be completely contacting each other. Considering the heat expansion of the lower block and shoes and ease of installation, a clearance of up to 2 mm or so is allowed. A clearance of 1 mm or less is more preferable from the viewpoint of the close contact and heat expansion of the contact surfaces and the ease of installation.

WE CLAIMS
1. A hot scarfer comprised of a plurality of scarfer units, each comprised of an upper block and lower block provided with fuel gas ejectors, an oxygen passage provided between the upper blocks and lower blocks, and a shoe fastened to the lower block, arranged in the horizontal direction, the hot scarfer characterized in that positions of shoe contact surfaces formed between adjoining shoes and positions of lover block contact surfaces formed between adjoining lower blocks are offset in a horizontal direction so as to eliminate overlap of the contact surfaces and prevent leakage of oxygen passing through the oxygen passage from the shoe contact surfaces and lower block contact surfaces.
2. A hot scarfer as set forth in claim 1, wherein positions of the lower block contact surfaces and positions of the shoe contact surfaces are offset in the horizontal direction by at least made 2.5 mm or more.
3. A hot scarfer as set forth in claim 1 or 2, wherein a plurality of shoes is offset horizontally in one direction with respect to the lower blocks so as to offset the positions of the lower block contact surfaces and the positions of the shoe contact surfaces in the horizontal direction.
4. A hot scarfer as set forth in claim 1 or 2, wherein shoes of horizontal widths narrower than the horizontal widths of the lower blocks and shoes of horizontal widths wider than the horizontal widths of the lower blocks are alternately arranged so as to offset the positions of the lower block contact surfaces and positions of the shoe contact surfaces in the horizontal direction.