JPH06292957A - Continuous casting method - Google Patents

Abstract

PURPOSE:To carry out a stable operation by supplying inert gas into a closed space formed at the upper part of a mold supplying molten metal from an immersion nozzle, pressurizing this closed space and controlling flowing characteristic of a high viscosity lubricant on the molten metal surface. CONSTITUTION:The molten metal supplied into the mold 1 from a tundish through the immersion nozzle 3 is filled up by flowing in the mold 1 from molten metal supplying hole 9 of the immersion nozzle 3. The molten metal is brought into contact with the mold 1 cooled with water, and the surface thereof is cooled and supplied and drawn out downward. In the closed space 7 in the mold 1 closed with a seal cover 2, the inert gas is supplied from an inert gas supplying pipe 6 and pressurized, and the high viscosity lubricant 5 is supplied while controlling the flowing characteristic from a lubricant supplying pipe 4 arranged to the seal cover. Then, the lubricant is easily entered between the mold 1 and the molten metal according to the pressure to improve the lubricating function. By this method, without developing breakage and cracking, the high speed casting can be executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting method for solidifying a molten metal such as steel supplied from a tundish to cast a continuous cast piece.

[0002]

2. Description of the Related Art Generally, in continuous casting, when molten steel is supplied from a tundish into a mold, the surface of the molten steel is cooled and solidified by a water-cooled mold, resulting in a skinned state. The continuous cast piece is cast while being drawn downward with a roll to cool the continuous cast piece, and in order to prevent seizure of the continuous cast piece and the surface of the mold, CaO and SiO ₂ are formed on the molten metal surface in the mold. A lubricant whose main component is alumina, etc. is supplied. The lubricant melts the portion in contact with the molten steel to become glass and penetrates between the mold and the continuous cast piece to perform a lubricating action, and at the same time adsorbs inclusions floating in the mold, If the lubricant is made highly viscous for casting, the consumption of the lubricant is reduced, the lubrication function is deteriorated, and the occurrence rate of breakouts and cracks in the continuous cast pieces is increased.

Therefore, when the lubricant has a low viscosity as disclosed in JP-A-3-210950, the consumption amount of the lubricant is increased and the lubricating function is improved, but the internal defects of the continuous cast piece are increased. was there. Further, JP-A-60-624
As in Japanese Patent Publication No. 8, by changing the mold oscillation pattern for vibrating the mold up and down to lengthen the positive strip time (the mold descending speed is slower than the casting speed), at the time of high speed casting with a highly viscous lubricant, It is also attempted to secure the consumption of lubricant to suppress the deterioration of lubrication function and prevent breakout and other operational troubles, but due to vertical vibration of the mold, a deep protrusion occurs on the initial solidified shell on the molten metal surface. However, there is a problem that inclusions are trapped in the protrusions and the surface quality of the continuous cast piece is deteriorated.

[0004]

The problem to be solved by the present invention is to solve the above-mentioned problems and to perform high speed casting without causing internal defects and deterioration of surface quality of continuous cast pieces. is there.

[0005]

According to the present invention, an inert gas is supplied to a closed space formed in the upper part of a mold to which molten metal is supplied from a tundish immersion nozzle to pressurize the closed space, It is characterized by controlling the inflow characteristics of the high-viscosity lubricant on the surface.

[0006]

Next, the present invention will be described in detail with reference to the illustrated embodiment device. 1 is a mold for continuous casting, and the upper end of the mold 1 is sealed by a seal lid 2. Reference numeral 3 denotes a tundish immersion nozzle that is inserted into the mold 1 through the seal lid 2, and the molten metal in the tundish is supplied to the mold 1 by the immersion nozzle 3. A large number of lubricant supply pipes 4 are provided on the seal lid 2.
The high-viscosity lubricant 5 containing CaO, SiO ₂ , alumina or the like as a main component is supplied to the molten metal surface. The portion of the high-viscosity lubricant 5 supplied to the molten metal surface in contact with the molten metal is melted, and the upper portion is unmelted. The molten high-viscosity lubricant 5 penetrates between the mold 1 and the molten metal. Lubrication.

Reference numeral 6 denotes an inert gas supply pipe connected to the seal lid 2, and a closed space formed between the seal lid 2 and the molten metal surface by an inert gas of a predetermined pressure supplied from the inert gas supply pipe 6. Reference numeral 7 is for controlling the inflow characteristic of the highly viscous lubricant 5 under pressure. Reference numeral 8 is a pressure gauge provided in the inert gas supply pipe 6, 9 is a molten metal supply hole of the immersion nozzle 3, and 10 is a packing for sealing between the immersion nozzle 3 and the seal lid 2.

The operation of the present invention will be described below with reference to the above-described apparatus. Molten metal supplied from the tundish to the mold 1 through the immersion nozzle 3 is supplied from the molten metal supply hole 9 of the immersion nozzle 3 to the mold. 1 to fill the mold 1. The molten metal supplied into the mold 1 comes into contact with the water-cooled mold 1 to cool and solidify the surface, and the molten metal is drawn downward by a roll (not shown). Since the closed space 7 of the casting mold 1 is supplied with an inert gas of a predetermined pressure supplied from the inert gas supply pipe 6 to pressurize the closed space 7, the molten metal surface is covered. The high-viscosity lubricant 5 melted in contact with the molten metal of the high-viscosity lubricant 5 that is being melted easily penetrates between the mold 1 and the molten metal in response to the pressure, and the lubricating function is improved.

As shown in the graph of FIG. 2, this means that when the air pressure in the closed space 7 is 1.00 atm and the viscosity of the lubricant is 4 pise, the consumption amount of the lubricant is 0.25 kg / T-.
When the atmospheric pressure is 1.06 atm, the consumption of lubricant is 0.48 kg / T-steel, which is about double that of steel, and the lubrication function is enhanced. Will be lubricated and cooled.
Moreover, as shown in FIG. 3, even if the casting speed is increased, if the viscosity of the lubricant is high, internal defects are reduced, so that high speed casting can be performed.

[0010]

As is apparent from the above description, the present invention reduces the consumption of the high-viscosity lubricant that covers the molten metal surface by supplying an inert gas to the closed space above the mold and pressurizing it. Even though it is a highly viscous lubricant, it is possible to perform high-speed casting without breakouts or cracks, and to form deep protrusions in the initial solidified shell that occurs on the molten metal surface, even though it is a highly viscous lubricant. Therefore, inclusions are not trapped by the protrusions and the surface quality of the continuous cast piece is not deteriorated. Moreover, it is possible to carry out stable operation without causing internal defects in continuously cast pieces as in the case of high-speed casting using a low-viscosity lubricant. Therefore, the present invention is extremely large when it is brought to the industry as a continuous casting method that solves the conventional problems.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a lubricant viscosity and a lubricant consumption amount.

FIG. 3 is a graph showing how internal defects appear in a continuously cast piece depending on the casting speed and the viscosity of a lubricant.

[Explanation of symbols]

 1 Mold 3 Immersion Nozzle 5 Highly Viscous Lubricant 7 Closed Space

Claims (1)

[Claims] 1. An inert gas is supplied to a closed space (7) formed in the upper part of a mold (1) to which molten metal is supplied from a tundish immersion nozzle (3), and the closed space (7) is closed. A continuous casting method characterized by pressurizing and controlling the inflow characteristics of a highly viscous lubricant (5) on the molten metal surface.