JPH0441060A - Molten metal conduit tube for casting and casting method - Google Patents

Abstract

PURPOSE:To drastically reduce crack in a conduit tube body caused by heat stress without wear and erosion by composing the conduit tube body with refractory and lining the conduit tube body with heat resistant and heat insulating material having strength lower than the conduit tube body. CONSTITUTION:By the lining, molten metal M does not directly contact with the conduit tube body. Therefore, the wear and erosion with the molten metal are eliminated. Further, as the lining has heat insulation, the temp. in inner peripheral part of the conduit tube is lowered and temp. difference with the outer peripheral part becomes little and the crack caused by heat stress is drastically reduced. As the lining has strength lower than that of the conduit tube body, and the conduit tube body is not damaged and the lining can be crushed and removed. By this method, the conduit tube body can be repeatedly used by changing over the lining. Further, temp. drop during passing the molten metal through the conduit tube can be prevented and the high quality casting can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a molten metal conduit for casting and a casting method. In particular, the present invention relates to molten metal conduits such as nozzles, runners, injection pipes, etc., and casting methods using the molten metal conduits.

This invention is utilized for manufacturing cast products and ingots of carbon steel, stainless steel, and other metals.

[Prior Art] Molten metal conduits such as nozzles, runners, injection pipes, etc. used in casting are made of alumina, clay, zirconia, zircon, Macnesia, and carbon-containing materials, depending on the usage conditions. Materials with high fire resistance are used, such as

For example, in the "horizontal continuous casting device" disclosed in Japanese Patent Application Laid-open No. 58-13447, a foot nozzle or a 5K30
From 5K35, thermal conductivity ≦2.0 kcal/mhr'
It is not molded with c refractory material. Further, the same publication exemplifies an alumina refractory as the refractory.

[Problems to be Solved by the Invention] Incidentally, since the entire conduit of a conventional molten metal conduit is made of the same refractory material, the molten metal was in direct contact with the refractory material on the inner surface of the conduit. Once upon a time, I had the following problem.

The flow of molten metal wears and erodes the refractory on the inner surface of the pipe. Furthermore, since there is a large temperature difference between the inner circumference and the outer circumference of the conduit, thermal stress is generated within the refractory, resulting in cracks. If erosion progresses or cracks occur, the conduit must be replaced, or the refractories such as high alumina and zirconia are expensive, resulting in significant costs.

In addition, the heat of the molten metal is dissipated to the outside through the refractory,
The temperature of the molten metal decreases as it passes through the conduit. For this reason, it is not possible to maintain an appropriate casting temperature, and the quality of the cast product or slab deteriorates. Further, the molten metal solidifies and adheres to the inner circumferential surface of the conduit, increasing pipe friction and impairing the flow of the molten metal.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a molten metal conduit for casting and a casting method that can reduce conduit costs and prevent the temperature of molten metal from decreasing while passing through the conduit.

[Means for Solving the Problem] The molten metal conduit for casting of the present invention is a molten metal conduit made of a refractory material that supplies molten metal from a ladle or a tundish to a mold, in which the conduit body is made of a refractory material, and the conduit body is made of a refractory material. The main body of the conduit is lined with a heat-resistant and insulating material that is less strong than the standard.

Specifically, molten metal conduits include tundish nozzles, sliding nozzles, foot nozzles, etc. used in vertical or horizontal continuous casting, as well as runners, injection pipes, etc. used in the casting of ordinary casting products or ingots. be.

The conduit body is made of refractory material such as alumina, high alumina, zirconia, etc. depending on the casting conditions. The heat-resistant and heat-insulating material that forms the lining is also selected depending on the casting conditions, but it needs to be lower in strength and cheaper than the conduit body. The strength of the lining is determined when replacing the lining.
It must be strong enough to easily crush the lining without damaging the conduit body. Examples of such materials include refractories such as magnesia, silicic acid, and alumina.

The lining method involves fitting a previously prepared cylindrical lining inside the conduit body. If necessary, adhere the lining to the inner circumferential surface of the conduit with adhesive.

Alternatively, the inner lining may be made of an amorphous material.

The thickness of the lining varies depending on the conduit dimensions, lining material, casting conditions, etc., and is, for example, from a few to several IQ+nm.

Further, the casting method of the present invention performs casting by supplying molten metal to a mold from a ladle or tundish using the molten metal conduit, and removes the lining that has reached its durability limit from the conduit body, and then removes the lining from the conduit body. The pipe body is reused by lining it again with the heat-resistant and heat-insulating material mentioned above.

Whether the durability limit has been reached is determined by the amount of erosion and cracking in the lining. Usually, judgment is made based on experience, based on casting amount and number of injections. To remove the lining from the conduit body, the lining is crushed and removed from the conduit body without damaging the conduit body. Further, if any metal remains on the lining surface and the inner pipe portion, the pipe body is recovered by removing the metal or fixing the metal and removing the pipe main body.

[Operation] The lining prevents molten metal from coming into direct contact with the conduit body. Therefore, wear of the conduit body by molten metal,
Erosion will disappear. Furthermore, since the lining has heat insulating properties, the temperature of the inner circumferential portion of the conduit is lowered and the temperature difference between the inner circumferential portion and the outer circumferential portion is reduced, and cracks due to thermal stress are significantly reduced.

Since the strength of the lining is lower than that of the conduit body, the lining can be crushed and removed without damaging the conduit body. However, by replacing the lining, the main body of the conduit can be reused.

[Examples] Examples of the present invention will be described below. In this example, a steel billet is produced using a horizontal continuous casting machine.

FIG. 1 shows a vertical cross section of a connecting portion between a tundish 11 and a mold 21 in a horizontal continuous casting apparatus. As shown in the drawing, the tundish 11 and the mold 21 are in communication via the tundish nozzle 12, the sliding nozzle 14, and the feed nozzle 16. The tandate nozzle 12, the slip ink nozzle 14 and the feed nozzle 16 have a lining 12b on the fidget nozzle body +2a, +4a, 16a,
14b and +6b are applied. The thickness of the lining varies depending on the nozzle, but is 12 to 16 mm. The composition and characteristics of the material forming the nozzle body and lining are determined first.
Shown in the table.

Table 1 λ: Thermal conductivity TN: Tundish nozzle SN Nislipe ink nozzle FD: Feet nozzle The mold 21 is generally made of copper and is cooled by cooling water W, and there is a break link river 8 on the entrance side. It is installed. The break link 18 is made of boron nitride,
It is made of heat-resistant ceramics such as silicon nitride.

The molten metal M supplied into the mold 21 is cooled by the inner peripheral surface of the mold and forms a solidified shell S. Formation of the solidified shell S begins at the break link 18.

The break ring 18 prevents the solidified shell S from growing in the opposite direction, that is, toward the foot nozzle 16. A slab formed by solidifying the molten metal M is intermittently pulled out from the exit side of the mold 21 by a pulling device (not shown) such as a pinch roll. When the slab is intermittently pulled out, a gap is created between the break ring 18 and the end of the solidified shell S, and a new molten metal M flows into the gap.

During the above casting operation, the inner lining is eroded by the flow of molten steel and cracks occur. In this example, the lining was replaced every charge, and the nozzle body could be used for 12 charges.

[Effects of the Invention] In the second invention, wear and erosion of the conduit main body due to molten metal are eliminated, and cracking due to thermal stress is significantly reduced. Also,
Each time the lining is replaced, the conduit body can be used repeatedly. This makes it possible to reduce conduit costs.

For example, the conduit cost is 115 ~ compared to the conventional case.
It became 1/10.

Since the inner lining has a heat insulating property, it can prevent the temperature of the molten metal from decreasing while passing through the conduit.

As a result, the molten metal is fed into the mold at the appropriate casting temperature, resulting in a high quality casting. In addition, the amount of molten metal that solidifies and adheres to the inner surface of the pipe is reduced, reducing pipe friction and reducing fluctuations in the flow rate of the molten metal.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of the connecting portion between a tundish and a mold, in which the present invention is applied to a horizontal continuous casting device. 1]...Tandite nozzle, 12...Tandite nozzle, +2a...Tandite nozzle body, 12
b... Lindish nozzle lining, 14... Sliding ink nozzle, 14a-... Sliding nozzle body, +4b... Sliding ink nozzle lining, 16
...Feed nozzle, +6a...Feet nozzle body, +6b...Feet nozzle inner bow length, 18...
Break ring, 21...mold, M...molten metal,
S: Solidified shell, W: Cooling water.

Claims (1)

[Claims] 1. In a refractory molten metal conduit that supplies molten metal from a ladle or tundish to a mold, the conduit body is made of a refractory and is made of a heat-resistant and heat-insulating material that has lower strength than the conduit body. A molten metal conduit for casting, characterized in that the conduit body is lined. 2. Using the molten metal conduit of claim 1, supply molten metal to the mold from a ladle or tundish to perform casting, remove the lining that has reached its durability limit from the conduit body, and make the conduit body A casting method characterized by reusing the conduit body by relining it with a material.