JPS58112639A - Charging method for molten metal in continuous casting - Google Patents

Abstract

PURPOSE:To prevent bumping of slag and oxidation of the molten metal in charging flow by injecting an inert gas to the molten metal surface part of a tundish thereby forming an expelling part for slag layers satisfying specific equations. CONSTITUTION:An inert gas G is injected downward from a nozzle 2 to remove a slag layer 6 at the peceding end of a charging nozzle 4 from a ladle, whereby an expelling part 7 is formed beforehand and the inside of the tundish is substituted with a non-oxidative atmosphere. The inert gas is injected to the molten metal surface part of the tundish in such a way that the diameter Ymm. for expelling the slag layer satisfies the equationIand equation II. Here, y: the diameter for expelling of the slag layer mm., Xp: the min. grain size of inclusions to be removed mum, d: slag thickness mm., V0: the initial velocity of injection of the inert gas m/sec, D0: the distance between the preceding end of the nozzle for injection of the inert gas and the molten metal surface of the tundish mm., d0 the diameter of the preceding end of the nozzle for injection of the inert gas mm..

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for pouring molten metal in continuous casting, and its purpose is to feed molten metal into a ladle or a tundish by using an injection flow. It prevents the sug from being pounded into the boiling water, prevents the oxidation of the molten metal injected, and securely fills the filling to prevent dust from clogging when the ladle is used with a nozzle. The purpose is to discharge it inside.

Conventionally, the method of injecting molten metal from a ladle into a tundish is to immerse the tip of the injection nozzle of the ladle into the molten metal in the tundish to prevent molten metal oxidation and sudder contamination, and remove these O inclusions. I am trying to obtain clean steel without
In this case, in order to obtain the effect from the beginning of pouring the molten metal into the tandy, the injection nozzle must be made into a long body that is unnecessary during steady injection (when maintaining the required level of molten metal in the tandy and the cylinder). zu, or tandi fushi. The problem was that large equipment was required to raise the ladle as the molten metal level rose. In addition, if a sliding nozzle is used for the opening/closing and/or opening adjustment mechanism of the injection nozzle of the ladle, especially when casting several charges in succession, the injection of molten metal from the ladle starts after the second charge. In order to ensure that the filling is loaded onto the sliding nozzle of the cough injection nozzle and discharged out of the injection nozzle, the tip of the injection nozzle must be immersed in the molten metal inside the cough injection nozzle. The melt bearing surface level must be lowered or the ladle must be raised to set it 4 degrees higher.

For this reason, the former, which involves the oxidation of the molten metal and the pounding of slag, is generally prevented by means of forming a gas curtain around the injection flow using a known inert gas, but regarding the latter, the relationship between the gas flow rate and the slag thickness, etc. There was no way to present it.

After the anti-occlusion filling is discharged from the injection nozzle into the tundish, the ladle must be lowered or the tundish must be lowered to prevent the slag from being trapped. Raise the internal molten metal level and tighten the injection nozzle tip. It is good because it requires complicated operations such as having to immerse it in internally molten metal.

The present invention solves these problems all at once and provides an excellent method).
As shown in the figure, the lower end of the molten metal injection nozzle of the ladle is connected to the tundish when feeding the molten metal from the ladle to the tundish. In addition to being located just below the hot water level, the tandy, shi, and
Inert gas G is injected into the hot water W11ils based on the slag layer removal diameter determined from the allowable inclusion diameter of the product, so as to satisfy the conditional formula described below, and the same area can be economically and efficiently worked. It is often used in a molten metal injection method in continuous casting that injects a molten metal flow of 8° from the pouring nozzle into the exclusion zone while forming a stable slag layer exclusion zone. In order to obtain a predetermined displacement diameter, a predetermined limit was set based on the relationship between the slag thickness and the central velocity of the inert gas at the tandice, water and hot water surface areas.

That is, the method of the present invention uses Tandy YV for storing molten metal.

When pouring the molten metal 8 from the ladle, by injecting the inert gas G at the position where the O molten metal flow S0 falls from the injection nozzle under conditions that satisfy the above purpose,
8. The floating slag layer is removed from the molten water surface at the cough drop position to the surrounding area, and the 2nd layer of slag is formed in the molten metal flow 8. By Tandy,
Reliably prevents it from being pumped into the internal molten metal,
This method suppresses the increase in the number of inclusions in the steel and advantageously produces clean steel.

Next, the inventor's experimental results regarding the above conditions for achieving the object of the present invention will be explained. As shown in Figures 1 and 2, the maximum gas flow velocity Vo at the molten metal surface is based on the relationship between the slag thickness 4 and the slag exclusion radius (1) For materials that should ensure inclusion diameter ≦ 100 JsI, as shown in Figure 2. Requires D≧500 towns. The gas injection speed conditions for this are: 1) v@≧@OWV/s@c (4-15 mgm (D
and 11) if) We≧8511%/sea (4
=45mO and To)1i1) To';i;110
However, in actual operation, when V≧91 e@O, the molten metal splashes and scatters violently, so equipment such as splashes and prevention plates are required. However, the slag removal ability will not deteriorate.Taking these conditions into consideration, in practice Va≦95%'ll-
It is preferable that

(2) In the case of a material whose inclusion diameter should be guaranteed to be 100 to 200 fine, from Fig. 2, D≧2! ! Requires Ows7'w+. The gas injection speed conditions for this are: 1) Va≧50%/i@c (4mlI1mo and turtle)
if) Vs≧6・w4/s@@ (when 4w41!m) iii) To≧7 Q wholesale 4** (4W
75 ■o and mln are necessary. This is the first one based on the pipe.
The experimental results shown in the figure were obtained. In other words, Y: Minimum particle diameter for removal speed (μm) d Nislag thickness (-) vo; Initial injection speed of inert gas (s-@) Do;
Distance between the tip of the nozzle for inert gas injection and the tandissico surface (,,) do: Tip of the nozzle for inert gas injection o 11 (Ill)
and (2) practically, f2. It is preferable to set the maximum flow rate of exhaust gas V, (%/, . . .) on the hot water surface to -d v@z5.7X4I≦95w/s@s during frequent occurrences.

The objective of the present invention is to obtain operating conditions that satisfy the following relational expression. Under the above-mentioned operating conditions, the present invention carries out the classification of steel from low grade steel to high grade steel, and advantageously obtains clean steel.

In addition, in the method of the present invention, the inert gas (GE) injection for forming the slag exclusion diameter is performed from the vicinity of the injection nozzle of the mosquito ladle toward the tandy, shi, and inner lacquer hot water surface directly below the injection nozzle. , the air around the molten metal stream S0 from the injection nozzle is replaced by an inert gas G atmosphere to reliably prevent its oxidation and advantageously obtain clean steel. Furthermore, in continuous casting, a sliding nozzle is interposed in the injection nozzle to ensure that O blockage prevention filler is discharged outside the injection nozzle when the injection of molten metal starts, thereby preventing 0M1ls, and immediately draining. This allows stable continuous casting to be maintained by restoring the internal molten metal to its original steady state without drastically reducing the amount.

FIG. 3 shows an example of an apparatus for carrying out the method of the present invention at the time of pot joining of continuous casting, in which a hollow f-spool annular gib 3 is mounted on a holder (metal) 5 that holds a molten metal injection nozzle 4. A large number of gas jetting nozzles 2 are provided at the bottom thereof, facing perpendicularly to the surface of the molten metal.

Further, an inert gas Q supply pipe l is connected to the circular ring f3. Then, the inert gas G is injected downward from the nozzle 2, and the inert gas G is directly below the tip of the injection nozzle 4 from the ladle.
Pre-charge Tandissi.

The slag layer 6 on the inner hot water surface is removed around it, and the removal section 7
is formed in advance and replaced with a non-oxidizing atmosphere. After this, the sliding nozzle of the ladle containing hot water of the char is fully opened, and the next charge of molten metal is poured into the tundish with the anti-occlusion filler. , a to perform continuous copper plating. Tandy after this pot joint,
The level below the hot water level in the cough injection nozzle 4 may be raised, and the lower end position of the injection nozzle 4 may be maintained at a slightly lower level, and the downward injection of the inert gas G from the nozzle 2 may be continued. After that, the downward injection of the inert gas G from the nozzle 2 may be stopped.

Using the apparatus shown in FIG. 3 for carrying out the method of the present invention, test results on an actual machine are shown in FIGS. 4 and 5. This figure shows almost the same results as the test results in the water model shown in Figure 1.
2) O operation conditions (slag thickness, maximum yx flow rate at the tandishy molten metal surface, slag exclusion diameter) for forming and dividing materials with inclusion diameters of 100 to 200 μm can be applied to actual operations.

Top t! @As is clear from FIGS. 4 and 5, the number of gas ejection nozzles may be increased to a plurality as a means for obtaining a predetermined slag removal diameter. #I5 (Fig. 5) shows the exclusion area of three nozzles, and Fig. 5 (@) shows the exclusion area of four nozzles.

The results of the quality improvement effect in the above test are shown in FIG.

■ Steel @ ht killed steel ■ Ladle injection conditions Nozzle diameter 90s/ssb,
Lower end of nozzle and tandisi.

Distance between hot water surfaces...380 m7m■
Thandi fushi. Hot water surface condition a Hot water surface height 920machi 4b, slag layer thickness 5 to 10s/sI ■
Inert gas injection conditions L Inert gas ・・・・・・・・・Mress b, Inert gas injection nozzle diameter and number ・・・・・・・・・・・・・・・
・12-φ, 2 C1 injection nozzles lower end and tandy pipe.

Distance between hot water surfaces: 650 ■ Gas pressure from the injection nozzle: 311/m2
, gas flow rate from the injection nozzle -------=...350 Nms/Mr As a result of the pot splicing between each charge in slow casting, a direct 4K 500 cm was applied to the hot water surface directly below the injection nozzle 4. The quality of the cast slab cast at a casting speed of 1.0 cm was found to be the highest in quality compared to the 9th one without adopting the above method As is clear from Figure 6, the amount of extracted inclusions is drastically reduced, and the percentage of defects passed by magnetic particle testing for materials with inclusion diameters ≦100μ, which is the most stringent inclusion regulation, can be increased by approximately 30%. Moreover, according to the present invention, in addition to Higashi, Kochu T (N)
, it was possible to obtain an excellent quality slab without an increase in T(o) amount.

The tIX1 diagram is a diagram showing the relationship between the slag removal diameter and the maximum gas flow velocity at the tandy, shi, and hot water surface.
Figures (, ), 佽) are a plan view and side view of an example of an apparatus for carrying out the method of the present invention, #I4 is a diagram showing the relationship between the slag removal diameter and the slab thickness, and FIG. 5 佽) is the slag removal diameter. Figure 6 shows the exclusion area of 3 nozzles, the same axis (-) shows the exclusion area of 4 nozzles, and Figure 6 shows the exclusion area of 4 nozzles. It is a figure showing quality improvement effect.

l... Main pipe that guides inert gas to the injection nozzle, 2.
・・Injection gas discharge nozzle (multiple 4 pieces x 3 on the drawing)
...Cylindrical ring for gas accumulation, 4.Nozzle for injection into the ladle and the cylinder, b
'-4O) A holder that supports the 6...Tandifushi. Slag floating inside, 7...
Molten steel in Tandevshish, 8...Tandhi, Shi1. 9- Gas curtain for removing slag, Hl... Distance between the lower end of the molten metal injection nozzle and the surface of the molten metal, H... Distance between the surface of the molten metal and the nozzle 2,
d...Tandifushi. The thickness of the slab floating inside, D, 1
...Maximum distance between two nozzles, do...Diameter of the outlet of nozzle 2, G...Inert gas for blowing into the main pipe, vo...
- Initial appropriateness of gas discharged from nozzle 2, or... outer diameter of molten metal injection nozzle.

force

Claims (2)

[Claims] (1) When supplying molten metal from the ladle to the tamp, place the lower end of the molten metal pouring nozzle of the ladle directly above the molten metal surface, and place it directly below the pouring nozzle. The inert gas can be calculated from the allowable inclusion diameter of the product, and the slag waste exclusion diameter is -, where Y: Sutuda layer exclusion diameter (-) xP: Minimum particle diameter of inclusions to be removed (J,) d: Slag thickness (-) vo: Inert gas injection initial speed JIE (11%/Ie
e)D,: Distance between the tip of the inert gas injection nozzle and the tanditsu hot water surface (-) do: Inject the inert gas nozzle so that it satisfies the function (■) of the nozzle tip and reach the same surface area. A method for pouring molten metal into continuous casting, in which a flow of molten metal is injected into the #exclusion part from the shell pouring nozzle while forming the sududa layer exclusion part. (2) Sutuda Exclusion Sutra 250-500■ and Tande 4sshi. Maximum flow velocity V of O exhaust gas on Tanger, (Zhen/Liao・@)
The method for pouring molten metal in continuous casting according to claim 1, wherein the method is carried out so as to satisfy the following relationship: d78m6.7×coff≦95w5/s@e.