JP7070140B2 - Smelter for slabs and method for smelting slabs - Google Patents

Description

The present invention relates to a slab melting device for melting the surface of a slab and a method for melting the slab.

For example, surface defects such as inclusions and surface defects may occur on the surface of slabs produced by continuous casting.
In removing such surface defects of the slab, for example, the melting apparatus (scarfer equipment) disclosed in Patent Documents 1-3 is used. These milling devices (scarfer equipment) locally heat the surface of the slab to melt it and remove surface defects.
In the above-mentioned milling device (scarfer equipment), the scarfer unit is arranged so as to face the surface of the slab.

In a milling device (scarfer equipment) having such a configuration, first, a flammable gas and preheating oxygen are sprayed on the surface of the slab to burn the flammable gas, and the combustion heat is used to burn the slab. The surface is locally melted to form a pool (preheating step).
Next, oxygen for melting is supplied to the surface of the slab and the slab is conveyed, and the oxygen for melting and iron are subjected to an oxidation reaction using the above-mentioned hot water pool as a heat source, and the heat of the oxidation reaction causes the slab to undergo an oxidation reaction. The surface of the surface is melted to a depth of about 1 to 3 mm to remove surface defects (melting step).

Jikkenhei 03-070856 Gazette Japanese Unexamined Patent Publication No. 09-168862 Japanese Unexamined Patent Publication No. 10-272561

By the way, when the surface of a slab is melted by the above-mentioned melting device (scarfer equipment), the melting depth varies in the width direction, and large irregularities are formed on the surface of the slab after melting. was there.
Here, if there are large irregularities on the surface of the slab, surface defects will occur in the subsequent rolling process, and the product yield will decrease. Therefore, it is required that the slab is stably melted.

The present invention has been made in view of the above-mentioned situation, and the surface of the slab can be stably melted, and it is possible to suppress the occurrence of large irregularities on the surface of the slab after melting. It is an object of the present invention to provide a melting device for slabs and a method for melting slabs.

As a result of diligent studies by the present inventors in order to solve the above problems, as shown in FIG. 1, nine irregularities are formed on the surface of the slab according to the pressure distribution of the preheating oxygen divided into nine headers. It was confirmed that the unevenness distribution on the surface of the slab after thawing and the pressure distribution in the width direction of the preheating oxygen were in good agreement.
Therefore, it has been found that when the flow rate of preheating oxygen varies in the width direction of the slab, the surface of the slab after melting is uneven accordingly.

The present invention has been made based on the above-mentioned findings, and the slab smelting apparatus according to the present invention has a preheating gas ejection part that ejects flammable gas and preheating oxygen, and smelting oxygen. It has a smelting oxygen ejection part that ejects oxygen, and a flammable gas and preheating oxygen are sprayed on the surface of the slab to form a hot water pool on the surface of the slab and melt toward the hot water pool. It is a slab melting device that melts the surface of the slab by spraying shaving oxygen with the oxidation reaction heat of the shaving oxygen and iron, and the preheating gas ejection part is for the preheating. As a nozzle for ejecting oxygen, an insert nozzle and a curtain nozzle arranged in parallel in the width direction above the insert nozzle are provided, and the preheating oxygen supply path provides oxygen to the insert nozzle side. The supply path for the insert nozzle to be supplied and the supply path for the curtain nozzle to supply oxygen to the curtain nozzle side are branched, and the supply path for the curtain nozzle is provided with an orifice portion for distributing the preheating oxygen. The pressure loss ΔPa in the orifice portion is smaller than the pressure loss ΔPb in the curtain nozzle.

According to the slab melting device having this configuration, the preheating oxygen supply path is for an insert nozzle supply path for supplying oxygen to the insert nozzle side and for a curtain nozzle for supplying oxygen to the curtain nozzle side. An orifice portion for distributing the preheating oxygen to be supplied is provided in the supply path for the curtain nozzle, and the pressure loss ΔPa in the orifice portion is from the pressure loss ΔPb in the curtain nozzle. Since it is set small, the preheating oxygen is equalized at the inlet side of a plurality of curtain nozzles arranged in parallel in the width direction, and the preheating oxygen can be uniformly ejected in the width direction of the slab. This makes it possible to suppress the occurrence of large irregularities on the surface of the slab after melting.

Here, in the slab melting apparatus of the present invention, a plurality of supply holes may be formed in the orifice portion, and the supply holes and the curtain nozzle may be arranged eccentrically. ..
In this case, oxygen that has passed through the supply hole of the orifice portion can be suppressed from being directly supplied to the curtain nozzles, and the flow rate distribution of the preheating oxygen in the plurality of curtain nozzles in the width direction can be further made uniform. ..

Further, in the slab melting apparatus of the present invention, the curtain nozzle is divided into a plurality of headers in the width direction for each orifice, and penetrates the inlet position of the curtain nozzle in the width direction. A small header may be provided, and oxygen for the curtain nozzle may be injected from the divided boundary portion of the header.
In this case, the curtain nozzles can be sprayed at equal intervals without gaps over the entire width of the scarfer unit, and the contraction that occurs from the missing portion of the curtain nozzle can be prevented, and the flow rate of preheating oxygen in the curtain nozzle in the width direction. The distribution can be further homogenized.

The method for melting a slab of the present invention is characterized in that the surface of the slab is melted by using the above-mentioned melting device for the slab.
According to this constituent slab melting device, since the above-mentioned slab melting device is used, the flow rate distribution of the preheating oxygen in the plurality of curtain nozzles in the width direction is made uniform, and the preheating oxygen is cast. It is possible to eject evenly in the width direction of the piece, and it is possible to suppress the occurrence of large irregularities on the surface of the slab after welding.

As described above, according to the present invention, the surface of the slab can be stably melted, and the surface of the slab after the melting can be prevented from having large irregularities. An apparatus and a method for melting slabs can be provided.

It is a graph which shows the unevenness of the surface of a slab after melting and the pressure distribution of oxygen for preheating. It is a side side explanatory view of the slab melting apparatus which is an embodiment of this invention. (A) shows the state of the preheating process, and (b) shows the state of the melting process. FIG. 3 is a cross-sectional explanatory view of a preheating gas ejection portion of the slab melting device shown in FIG. 2. (A) is a cross-sectional view orthogonal to the width direction, (b) is a cross-sectional view taken along the line XX'of (a), and (c) is a cross-sectional view taken along the line (a) YY'. It is explanatory drawing which shows the arrangement of a curtain nozzle. It is explanatory drawing of the orifice part used in the melting apparatus of a slab which is an embodiment of this invention. It is explanatory drawing of the orifice part used in the melting apparatus of a slab which is another embodiment of this invention. It is explanatory drawing of the orifice part used in the melting apparatus of a slab which is another embodiment of this invention. It is explanatory drawing of the melting apparatus of a slab which is an embodiment of this invention. (A) is a side partial cross-sectional explanatory view, and (b) is an AA cross-sectional explanatory view. It is explanatory drawing which shows the occurrence state of a contraction flow. It is a graph which shows the measurement result of the unevenness of the surface of a slab after melting in an Example.

Hereinafter, the slab melting apparatus and the slab melting method according to the embodiment of the present invention will be described with reference to the attached drawings. The present invention is not limited to the following embodiments.

As shown in FIG. 2, the slab melting device 10 according to the embodiment of the present invention has a scarfer unit 20 arranged so as to face the surface of the slab 1. As shown in FIG. 2, the scarfer unit 20 is provided with a preheating gas ejection section 30 for ejecting flammable gas and preheating oxygen, and a melting oxygen ejection section 22 for ejecting smelting oxygen. ing.
Further, the slab 1 is placed on a transport table (not shown) so as to be transported in the direction of the arrow X in FIG.
As shown in FIGS. 2A and 2B, the ejection flow of the smelting oxygen ejected from the smelting oxygen ejection portion 22 is flammable and is ejected from the preheating gas ejection portion 30. It is arranged so as to collide with the front side of the slab 1 in the transport direction X with respect to the jet flow of gas and preheating oxygen.

Here, in the preheating gas ejection unit 30, as shown in FIGS. 3A and 3B, the insert nozzle 31 and the insert nozzle 31 are arranged above the insert nozzle 31 as a nozzle for ejecting the preheating oxygen. It has a curtain nozzle 32 and the like.

As shown in FIG. 3B, the insert nozzles 31 are arranged in parallel in the width direction, and in the present embodiment, the insert nozzles 31 are arranged with respect to one oxygen header 33 and the combustible gas header 34. Three or four insert nozzles 31 are arranged in parallel.
Further, as shown in FIG. 3A, the rear end of the insert nozzle 31 is connected to the preheating oxygen supply path 35 (insert nozzle supply path 35A), and the side surface of the insert nozzle 31 is a flammable gas supply path 37. It is connected to the. The preheating oxygen supply path 35 (insert nozzle supply path 35A) and the flammable gas supply path 37 are separated by an O-ring 39 arranged on the side surface of the insert nozzle 31.
As a result, oxygen for preheating is ejected from the central hole of the insert nozzle 31, and flammable gas (LPG in this embodiment) is ejected from the periphery of the insert nozzle 31.

As shown in FIGS. 3 (a) and 3 (b), the curtain nozzle 32 is arranged in parallel in the width direction above the insert nozzle 31, and in the present embodiment, FIGS. 3 (b) and 4 show. As shown, five to seven curtain nozzles 32 are arranged in parallel with one oxygen header 33.
The rear end side of the curtain nozzle 32 is connected to the preheating oxygen supply path 35 (curtain nozzle supply path 35B).

Here, as described above, the preheating oxygen supply path 35 includes an insert nozzle supply path 35A that supplies oxygen to the insert nozzle 31, and a curtain nozzle supply path 35B that supplies oxygen to the curtain nozzle 32. It is branched to.
At the rear end of the curtain nozzle supply path 35B, an orifice portion 40 is provided to distribute the supplied preheating oxygen to the insert nozzle supply path 35A and the curtain nozzle supply path 35B.

The orifice portion 40 has a plate shape, and as shown in FIG. 5, a supply hole 41 penetrating in the thickness direction is provided, and oxygen is supplied to the curtain nozzle 32 side through the supply hole 41. Oxygen that does not pass through the supply hole 41 is supplied to the insert nozzle 31 side.
In this way, the preheating oxygen is distributed to the insert nozzle 31 side and the curtain nozzle 32 side.

In the present embodiment, the pressure loss ΔPa in the orifice portion 40 is set to be smaller than the pressure loss ΔPb in the curtain nozzle 32.
As a result, the preheating oxygen that has passed through the supply hole 41 of the orifice portion 40 is pressure-equalized on the inlet side of the plurality of curtain nozzles 32 arranged in parallel, and the flow rate of the preheating oxygen injected from the plurality of curtain nozzles 32. Will be homogenized.

In the present embodiment, the pressure loss ΔPa in the orifice portion 40 is adjusted by adjusting the size and arrangement of the supply hole 41 of the orifice portion 40.
At this time, it is necessary to design the size and arrangement of the supply hole 41 of the orifice portion 40 while paying attention so that the amount of preheating oxygen distributed to the insert nozzle 31 side and the curtain nozzle 32 side is within an appropriate range.

Here, in order to further make the preheating oxygen on the inlet side of the plurality of curtain nozzles 32 arranged in parallel, the ratio ΔPb / ΔPa of the pressure loss ΔPa in the orifice portion 40 and the pressure loss ΔPb in the curtain nozzle 32 is 1. It is preferably 1 or more, and more preferably 3.0 or more.
On the other hand, in order to further secure the balance of the amount of preheating oxygen distributed to the insert nozzle 31 side and the curtain nozzle 32 side, ΔPb / ΔPa is preferably 5.0 or less, and 4.0 or less. Is even more preferable.

As shown in FIG. 5, the orifice portion 40 in the present embodiment is formed with four supply holes 41.
These four supply holes 41 are arranged eccentrically so that the central axis of the curtain nozzle 32 and the central axis of the supply hole 41 do not coincide with each other.
Further, the four supply holes 41 are arranged so as to be point-symmetrical with the center point of the surface of the orifice portion 40 in which the supply hole 41 is opened as a point of symmetry.

Next, a procedure for melting the slab 1 in the slab melting device 10 having the above configuration will be described.

First, as shown in FIG. 2A, combustible gas and preheating oxygen are ejected from the preheating gas ejection portion 30 of the scarfer unit 20 toward the surface of the slab 1, and the combustible gas is burned. Let me. Then, a part of the surface of the slab 1 is melted by the heat of the combustible gas to be burned to form a hot water pool 3 (preheating step).
Here, the length of the hot water pool 3 formed on the surface of the slab 1 along the transport direction X is, for example, in the range of about 30 mm to 80 mm.

Next, the smelting oxygen is ejected from the smelting oxygen ejection portion 22 of the scarfer unit 20 toward the surface of the slab 1, and the slab 1 on which the hot water pool portion 3 is formed is directed to the transport direction X. And transport.
Then, the ejection flow of the melting oxygen ejected from the melting oxygen ejection portion 22 passes through the hot water pool portion 3 of the slab to be conveyed, and the hot water pool portion 3 is used as a heat source to form the melting oxygen. An oxidation reaction is carried out with iron, and the surface of the slab 1 is melted to a depth of about 1 to 3 mm by the heat of the oxidation reaction, and the surface of the slab 1 is melted (melting step). That is, the rear side of the hot water pool portion 3 in the transport direction X is melted by the heat of oxidation reaction.

According to the slab melting device 10 and the slab melting method according to the present embodiment having the above-described configuration, the preheating is supplied to the rear end of the curtain nozzle supply path 35B. An orifice portion 40 for distributing oxygen to the insert nozzle supply path 35A and the curtain nozzle supply path 35B is arranged so that the pressure loss ΔPa in the orifice portion 40 is smaller than the pressure loss ΔPb in the curtain nozzle 32. Since it is set, the preheating oxygen that has passed through the supply hole 41 of the orifice portion 40 is pressure-equalized on the inlet side of the plurality of curtain nozzles 32 arranged in parallel, and is injected from the plurality of curtain nozzles 32 for preheating. The flow rate of oxygen will be made uniform. As a result, oxygen for preheating can be uniformly ejected in the width direction of the slab 1, and it is possible to suppress the occurrence of large irregularities on the surface of the slab 1 after melting.

Further, in the present embodiment, a plurality of supply holes 41 are formed in the orifice portion 40, and these supply holes 41 are arranged eccentrically so that the central axis of the curtain nozzle 32 and the central axis of the supply hole 41 do not match. Therefore, it is possible to suppress the oxygen that has passed through the supply hole 41 of the orifice portion 40 from being directly supplied to the curtain nozzle 32, and the flow rate of oxygen ejected from the plurality of curtain nozzles 32 arranged in parallel in the width direction. The distribution can be further homogenized.

Further, in the present embodiment, since the four supply holes 41 are arranged point-symmetrically as shown in FIG. 5, a plurality of curtain nozzles 32 in which oxygen passing through the orifice portion 40 is arranged in parallel in the width direction are 32. The oxygen flow rate distribution to be ejected from the plurality of curtain nozzles 32 arranged in parallel in the width direction can be further made uniform.

Although the slab melting apparatus and the slab melting method according to the present embodiment, which are the embodiments of the present invention, have been described above, the present invention is not limited thereto, and the technique of the present invention is used. It can be changed as appropriate without departing from the idea.
For example, in the present embodiment, the orifice portion 40 shown in FIG. 5 has been described, but the present invention is not limited to this, and as shown in FIG. 6, the sizes of the plurality of supply holes 141 are changed. Orifice portion 140 may be used. Further, as shown in FIG. 7, an orifice portion 240 in which the supply holes 241 are arranged axisymmetrically may be used.

Further, as shown in FIG. 8, the orifice portion 340 is divided in the width direction, a small header 350 penetrating in the width direction is provided at the entry side position of the curtain nozzle 332, and a partition portion for each divided orifice portion 340 is provided. A new curtain nozzle hole 332'may be provided and the curtain nozzles may be arranged at equal intervals without gaps over the entire width of the scarfer unit. The opening diameter of the small header 350 is preferably about 4 mm to 10 mm, more preferably about 6 mm.
In this case, the contraction as shown in FIG. 9 is suppressed, and the flow rate distribution of oxygen ejected from the plurality of curtain nozzles 332 and the curtain nozzle holes 332'paralleled in the width direction can be further made uniform.

The results of experiments carried out to confirm the effects of the present invention will be described below.

In the slab melting apparatus described in this embodiment, the configuration of the supply hole of the orifice portion is changed as shown in Table 1. Here, Table 1 shows the pressure loss ΔPa at the orifice portion, the inlet pressure of the curtain nozzle, and the pressure loss ΔPb at the curtain nozzle when the inlet pressure of the preheating oxygen is 270 kPa. Table 1 shows the ratio of the oxygen flow rate to the insert nozzle side (lower column) and the oxygen flow rate to the curtain nozzle side (upper column) distributed in the orifice portion.

Then, a slab having a width of 1350 mm was smelted by using a slab melting device provided with the above-mentioned orifice portion and nine headers in the width direction. Then, the unevenness formed on the surface of the slab was measured, and the difference between the minimum value and the maximum value (concavo-convex difference) of the nine unevennesses formed corresponding to the nine headers was measured. Table 1 shows the average μ and the standard deviation σ of the unevenness difference. Further, FIG. 10 shows the measurement results of the unevenness on the surface of the slab.

In the comparative example in which the pressure drop ΔPa in the orifice portion was larger than the pressure drop ΔPb in the curtain nozzle, the average of the unevenness difference of the slab was large and the standard deviation was also large. It is presumed that the flow rate distribution of preheating oxygen was not uniform in the width direction.

On the other hand, in Example 1-4 of the present invention in which the pressure drop ΔPa in the orifice portion is larger than the pressure drop ΔPb in the curtain nozzle, the average difference in unevenness of the slab is smaller and the standard deviation is smaller than in the comparative example. became. It is presumed that the flow rate distribution of preheating oxygen was made uniform in the width direction.

Further, comparing Examples 1-4 of the present invention, when the ratio ΔPb / ΔPa between the pressure loss ΔPa in the orifice portion and the pressure loss ΔPb in the curtain nozzle becomes large, the oxygen flow rate to the insert nozzle side distributed in the orifice portion (lower column). It was confirmed that the ratio of the oxygen flow rate to the curtain nozzle side and the oxygen flow rate (upper column) changed. Therefore, it is preferable to set the pressure drop ΔPa in the orifice portion in consideration of the amount of oxygen distributed in the orifice portion.

On the other hand, in Example 4 of the present invention, since the small header is provided at the entrance side position of the curtain nozzle, the missing portion in the width direction of the curtain nozzle is eliminated, so that the contraction is suppressed and the flow rate distribution of the preheating oxygen is in the width direction. It was made more uniform in.

From the above results, according to the example of the present invention, the surface of the slab can be stably melted, and the surface of the slab after melting can be prevented from having large irregularities. It was confirmed that a melting device and a melting method for slabs could be provided.

1 Shard 3 Hot water pool 10 Smelt smelting device 20 Scarfer unit 30 Preheating gas ejection part 31 Insert nozzle 32 Curtain nozzle 35 Preheating oxygen supply path 35A Insert nozzle supply path 35B Curtain nozzle supply path 40 Orifice Part 41 Supply hole

Claims (4)

It has a preheating gas ejection part that ejects flammable gas and preheating oxygen, and a melting oxygen ejection portion that ejects milling oxygen, and sprays flammable gas and preheating oxygen onto the surface of the slab. A hot water pool is formed on the surface of the slab, and oxygen for melting is sprayed toward the hot water pool, and the surface of the slab is melted by the heat of the oxidation reaction between the oxygen for melting and iron. It is a slab melting device
The preheating gas ejection unit has an insert nozzle and a curtain nozzle arranged in parallel in the width direction above the insert nozzle as a nozzle for ejecting the preheating oxygen.
The preheating oxygen supply path is branched into an insert nozzle supply path that supplies oxygen to the insert nozzle side and a curtain nozzle supply path that supplies oxygen to the curtain nozzle side, and supplies the curtain nozzle. An orifice portion for distributing the supplied preheating oxygen is provided in the path.
A slab melting device characterized in that the pressure drop ΔPa in the orifice portion is smaller than the pressure drop ΔPb in the curtain nozzle. The slab melting apparatus according to claim 1, wherein a plurality of supply holes are formed in the orifice portion, and the supply holes and the curtain nozzle are arranged eccentrically. The curtain nozzle is divided into a plurality of headers in the width direction for each orifice, and a small header penetrating in the width direction is provided at the entry side position of the curtain nozzle, and the division boundary portion of the header is also described. The smelting apparatus according to claim 1 or 2, wherein the curtain nozzle is configured to inject oxygen for a nozzle. A method for melting a slab, which comprises melting the surface of the slab using the slab melting apparatus according to any one of claims 1 to 3 .

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