JP2984871B2 - Twin roll thin plate continuous casting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a twin-roll type continuous casting for producing a thin plate slab, and more particularly to a casting method for smoothly pouring a molten metal while preventing nozzle blockage.

[0002]

2. Description of the Related Art A twin roll continuous casting method for casting a thin metal sheet by pouring a molten metal between two rolls rotating inward through a pouring nozzle is known as the Bessemer method. ing.

In this casting method, as shown in FIG. 1, two rolls 1 are arranged at an appropriate interval, and a pouring nozzle 2 is arranged from above.
Is rotated inward while pouring the molten metal through the roll, forming a solidified shell 3 on the roll surface, joining the solidified shell, and further reducing the pressure to produce a thin plate slab 4 having a predetermined thickness. .

In this twin-roll continuous casting method, for the purpose of rectifying the pouring flow at the time of pouring to prevent breakage of the nozzle and to facilitate casting, for example, Japanese Patent Application Laid-Open No. 63-207454 discloses a method. Disclosed is a pouring nozzle for continuous casting of a metal ribbon in which a pouring nozzle has a double structure of an inner nozzle and an outer nozzle, and a porous refractory for rectifying the pouring flow is embedded inside the tip of the outer nozzle. ing.

However, in the pouring nozzle for continuous casting, oxides and nitrides accumulate on the porous filter, causing problems such as a shortage of molten metal due to a decrease in pouring flow rate and interruption of operation due to nozzle blockage.

This is because oxygen and nitrogen contained in the pouring nozzle react with the molten metal before casting to form oxides and nitrides.

[0007]

In view of the circumstances described above, in Japanese Patent Application No. 3-64695, molten metal was poured into a twin-roll caster through a pouring nozzle to form a thin plate. A technique of a twin-roll type thin plate casting method in which the atmosphere of a pouring nozzle is replaced with an inert gas in advance by a direct casting method and the molten metal is poured into a twin roll after the replacement is started.

[0008] However, this technique efficiently eliminates the problem that oxides and nitrides adhere to a porous refractory simply by injecting and replacing an inert gas and the nozzle is blocked and the operation is interrupted. Moreover, it cannot be avoided reliably, and the problem of nozzle clogging cannot be completely solved, especially with alloys containing active metals.

The present invention has been made in view of the above problems, and provides a twin-roll continuous casting method for a thin-rolled plate capable of controlling a replacement time to surely prevent clogging of a nozzle and pouring smoothly.

[0010]

SUMMARY OF THE INVENTION The present invention is directed to a twin-roll type continuous sheet casting method for producing a sheet slab by pouring molten metal through a pouring nozzle. Injecting an inert gas into the pouring nozzle for a time that satisfies the following expression (2) with respect to the target oxygen concentration in the pouring nozzle when replacing with gas, and performing continuous casting after replacing the gas. This is a twin-roll type continuous casting method for a thin plate.

[0011]

(Equation 2)

Where t: gas replacement time (sec) V: capacity in pouring nozzle (cm ³ ) q: inert gas flow rate (l / min) C (t): target oxygen concentration (wt%) Co: Initial oxygen concentration in nozzle (wt%) C _in : Oxygen concentration _in replacement gas (wt%)

[0013]

The present invention clarifies the relationship between the target oxygen concentration at which nozzle clogging does not occur and the gas replacement time, prevents oxidation of the molten metal by oxygen remaining in the pouring nozzle, and interrupts operation due to nozzle clogging. This is a continuous casting method that solves the problem and operates smoothly.

FIG. 3 is a drawing showing experimental results for determining the effect of inert gas (Ar) substitution on the oxygen concentration in the atmosphere inside the pouring nozzle, with the vertical axis representing the oxygen concentration in the atmosphere inside the pouring nozzle. (Wt%) , and the horizontal axis is the inert gas replacement time
(Sec) .

FIG. 2 shows a cross section of the pouring nozzle 2 used. In the figure, reference numeral 5 denotes an inlet for an inert gas, 6 denotes a porous refractory for rectification, and 7 denotes an outlet for molten metal.

In this experiment, a pouring nozzle of V = 3800 cm ³ was used, Ar gas of q = 20 l / min was supplied, and C _{in was changed} from an atmosphere of Co = 20.8 wt%.
= 0.005 wt%.

In FIG. 3, the circles indicate actual measured values, and a curve obtained by regression calculation from the actual measured values indicates the equal sign part of the above equation (2).

That is, in FIG. 3, the hatched area on the left side of the curve is the area where nozzle clogging occurs, and the white area on the right side indicates the area where no nozzle clogging occurs and the molten metal can be poured smoothly. For example, in FIG.
If (t) is set to 0.1 wt%, q = 20 l / mi
It is sufficient to supply the gas for about 38 seconds or more at the amount of the Ar gas of n.

If the target oxygen concentration in the pouring nozzle is determined in this manner, the air supply time of the inert gas to be replaced can be estimated using the above equation (2), so that the oxygen remaining in the pouring nozzle can be estimated. Is reduced to below the limit at which the oxidation of the molten metal can be prevented, and the continuous casting operation can be performed smoothly by preventing nozzle clogging and the like.

[0020]

EXAMPLE As Example 1, a thin plate was cast from an alloy having the components shown in Table 1 using a casting roll shown in FIG.

[0021]

[Table 1]

Table 2 shows the nozzle closed state. In this case, Ar was used as the inert gas.

[0023]

[Table 2] (Note) ○: No nozzle blockage ×: Nozzle blockage within 30 seconds after casting started

As a second embodiment, according to the first embodiment,
Ti-Al alloy and Fe-25Cr-5Al alloy were cast into thin plates. Table 3 shows the nozzle closed state.

[0025]

[Table 3] (Note) ○: No nozzle blockage ×: Nozzle blockage within 30 seconds after casting started

As shown in Examples 1 and 2, no blocking of the injection nozzle was observed within the range of the expression (2), and the continuous casting operation could be performed smoothly.

[0027]

As described above, according to the continuous casting method of the present invention, when the target oxygen concentration in the pouring nozzle is determined, the time for feeding the inert gas to be replaced can be easily estimated. By reducing the residual oxygen concentration in the pouring nozzle to below the limit, preventing oxidation of the molten metal and preventing nozzle clogging, pouring can be performed smoothly and operating efficiency is improved I do.

[Brief description of the drawings]

FIG. 1 is a side view showing an example of an apparatus for explaining a twin-roll type continuous casting method for a thin plate.

FIG. 2 is a sectional view showing an example of a pouring nozzle.

FIG. 3 is a drawing showing a relationship between an oxygen concentration in a pouring nozzle and an inert gas replacement time.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Casting roll 2 Pouring nozzle 3 Solidified shell 4 Cast piece 5 Inert gas supply port 6 Porous refractory 7 Melt discharge port

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-182359 (JP, A) JP-A-4-300050 (JP, A) JP-A-2-75457 (JP, A) JP-A-63- 207454 (JP, A) JP-A-5-245596 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B22D 11/06 330 B22D 11/10 360

Claims (1)

(57) [Claims] 1. A twin-roll type continuous sheet casting method for producing a sheet slab by pouring a molten metal through a pouring nozzle, wherein the atmosphere in the pouring nozzle is replaced with an inert gas. A twin-roll type thin plate characterized in that an inert gas is supplied into a pouring nozzle for a period of time satisfying the following formula (1) with respect to a target oxygen concentration in the nozzle, and the gas is replaced, followed by continuous casting. Continuous casting method. (Equation 1) Where t: gas replacement time (sec) V: volume in the pouring nozzle (cm ³ ) q: inert gas flow rate (l / min) C (t): target oxygen concentration (wt%) Co: initial nozzle Oxygen concentration (wt%) C _in : Oxygen concentration _in replacement gas (wt%)