JPH0561022B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a refractory used for a break ring or the like that connects a continuous casting mold and a tundish. [Prior Art] Generally, in continuous casting equipment, for example, horizontal continuous casting equipment, as shown in FIG. The steel 5 in the tundish 1 is injected into the mold 3 through the feed nozzle 2 and the refractory 4,
It is cooled in the mold 3 to form a solidified shell 6 and then drawn out for continuous casting. Refractories for continuous casting are required to have high thermal shock resistance, high corrosion resistance, and high wear resistance. Conventionally, the continuous casting refractory mentioned above has been made of AlN-BN- which is silicon nitride (Si ₃ N ₄ ) containing aluminum nitride (AlN) and boron nitride (BN).
Si ₃ N ₄ based sintered body (published in JP-A-56-129666)
sialon-based AlN−BN−Al ₂ O ₃ −Si ₃ N ₄ sintered body made of Si ₃ N ₄ containing AlN, BN, and aluminum oxide (Al ₂ O ₃ ).
-50074 Publication)) are known. [Problems to be solved by the invention] However, the former AlN-BN-Si ₃ N ₄ based sintered body is eroded during long-term casting of carbon steel or stainless steel, and the latter The AlN-BN-Al ₂ O ₃ -Si ₃ N ₄ based sintered body is eroded during long-time casting of stainless steel, and there is a problem that stable continuous casting cannot be performed. As a result of conducting various experiments to address the above-mentioned problems, the present inventor found that not only the composition of refractories, but also dynamic elastic modulus, pore diameter, and thermal conductivity are involved in improving thermal shock resistance and other performance. I found out that there is. [Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a refractory for connecting a mold for continuous casting and a tundish, which has a dynamic elastic modulus of 0.7×10 ⁶ Kgf/cm ² Below, pore diameter is 40μm or less (preferably 10μm or less), thermal conductivity
10.0kcal/mh℃ or less (preferably 6.0kcal/mh
℃). [Function] If the dynamic elastic modulus exceeds 0.7×10 ⁶ Kgf/cm ² , chipping will occur in the refractory, and if the pore diameter exceeds 40 μm, molten steel will enter the pores and the refractory will wear out significantly. , furthermore, the thermal conductivity is 10.0kcal/mh℃
If the temperature exceeds 100 mL, solidification of molten steel will begin at the feed nozzle, causing significant wear and tear on the feed nozzle. In addition, in order to manufacture refractories for continuous casting,
AlN, BN, Al ₂ O ₃ , silicon (Si), silicon dioxide (SiO ₂ ), and Si ₃ N ₄ are used as raw materials (average particle size 5 μm), and these are mixed in the required proportions and thoroughly kneaded to form a suitable powder. After the molded body is formed by a suitable molding method, the molded body is sintered in a non-oxidizing atmosphere (for example, argon, nitrogen gas, etc.) at a temperature of 1400 to 1800°C for about 1 to 10 hours. [Effects of the Invention] As described above, according to the present invention, compared to the prior art, chipping does not occur and wear and tear on feed nozzles and refractories can be significantly reduced. It is possible to stably and continuously cast steel over a long period of time. [Examples] Examples of the present invention will be described below. AlN, BN, Al ₂ O ₃ , Si, SiO ₂ and Si ₃ N ₄ powders (average particle size 5 μm) were used as raw materials, and 11 types of specimens were prepared by changing the blending ratio as shown in Table 1. was manufactured.

[Table] Each specimen was manufactured as follows. First, 1500gr of each of the ingredients shown in Table 1 are mixed in the mixing ratio shown in the same table, and after thoroughly mixing each of the ingredients using a stirrer and crusher, an organic binder (for example, PVA) is added to each mixture. The mixture was then uniformly kneaded and molded. Next, each clay was molded to 1 ton/cm ² using a hydraulic molding machine.
With a molding pressure of 20mm (vertical) x 20mm (horizontal) x 120mm
(length) and a circular plate shape of 220 mm (outer diameter) x 190 mm (inner diameter) x 15 mm (thickness). After drying, each of these molded bodies was heated in a nitrogen gas atmosphere for 1400 m Specimens according to the present invention and comparative specimens were manufactured by sintering at a temperature of ~1800° C. for 3 to 10 hours. (1) Among the above specimens, the prismatic specimen was used to measure corrosion resistance against molten steel. Corrosion resistance tests for molten steel were conducted by melting 10 kg of austenitic stainless steel (SUS 310: 25Cr-20Ni) in a high-frequency furnace, immersing the specimen in the molten steel held at a temperature of 1500°C, holding it for 1 hour, and then melting the specimen. The amount of wear (amount of erosion loss) was measured. (2) In addition, the circular plate shape is set between the mold and the tundish in horizontal continuous casting equipment, with a mold diameter of 212 mm and a drawing speed of 0.8 m/min.
Approximately 20 tons of round billets of austenitic stainless steel (SUS 304) were cast under conditions of a drawing length of 75 m, and the amount of wear due to the solidification shell of the refractory, that is, the circular plate-shaped specimen, was measured. The measurement results of the physical property values of each specimen No. 1 to No. 11 and the amount of wear (1) and (2) are shown in Table 2.

[Table] The amount of wear on the circular plate shape was determined by measuring the depth at the inner circumferential surface of the refractory 4, as shown by A in Figure 2, and also evaluating the surface quality of the cast product. Yes, ○ means good, △ means good, and × means bad. However, in the No. 1 specimen, chipping occurred in the refractory, and in the No. 2 specimen, the solidification of the molten steel reached the feed nozzle, so the feed nozzle was severely damaged, and nozzle fragments were found on the surface of the slab. In specimens No. 3 and 11, molten steel penetrated into the pores, and the molten steel solidified. Because the refractory is pulled out, the amount of wear and tear on the refractory is extremely large, and it is also unsuitable for long-term casting of stainless steel. Furthermore, No.
Sample No. 4 also did not achieve sufficient effects of the present invention. In the specimens No. 5 to 10, there was no damage to the feed nozzle, the amount of wear was small, and the surface quality of the cast product was extremely good, making it suitable for long-term casting of stainless steel. Therefore, the dynamic elastic modulus is 0.7×10 ⁶ Kgf/cm ² or less, the pore diameter is 40 μm or less (preferably 10 μm or less), and the thermal conductivity is 10.0 kcfl/mh°C (preferably
It can be seen that stainless steel can be continuously cast successfully over a long period of time if it is a refractory with a temperature of 6.0kcal/mh℃ or less.

[Brief explanation of the drawing]

Fig. 1 is a schematic sectional view of horizontal continuous casting equipment showing an example in which the refractory according to the present invention is used;
The figure is a half-cut sectional view showing the measurement position of the amount of wear on the refractory. 1...Dandite, 2...Field nozzle, 3...Mold, 4...Refractory, 5... Molten steel, 6
...Coagulation Ciel.

Claims (1)

[Claims] 1 A refractory that connects the continuous casting mold and tundish, with a dynamic elastic modulus of 0.7×10 ⁶ Kgf/cm ²
Below, pore diameter is 40μm or less, thermal conductivity is 10.0kcal/mh
A refractory for continuous casting characterized by having a temperature below ℃.