JPH0142786B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a gas blowing casting nozzle, and more particularly to a casting nozzle in which the mounting structure of a gas blowing pipe to a nozzle body is modified. Conventionally, as this type of casting nozzle, for example, an immersion nozzle, those having the structure shown in FIGS. 1 and 2 are known. That is, 1 in the figure has a discharge port 2 at the bottom end.
This is a nozzle body made of refractory material and having a nozzle hole 3 formed therein. An annular hollow chamber 4 is provided in the longitudinal direction of the nozzle body 1 in close proximity to the nozzle hole 3 . A hole 5 that reaches the hollow chamber 4 from the outside is provided in the upper side wall of the nozzle body 1, and a metal gas blowing pipe 6 is inserted into the hole 5 through a refractory mortar layer 7. has been done. Further, the outer peripheral surface of the nozzle body 1 into which the gas blowing pipe 6 is inserted is covered with an annular iron skin 8 through mortar. In the gas blowing submerged nozzle having the above-described structure, gas is passed through the pores of the nozzle body 1 by supplying an inert gas or the like into the hollow chamber 4 in the nozzle body 1 from the gas blowing pipe 6. It is supplied to the molten steel flowing into the nozzle hole 3 and prevents non-metallic inclusions from adhering to the inner wall of the nozzle hole 3. However, in the case of the immersion nozzle having such a structure, since the metal gas blowing pipe 6 is inserted into the hole 5 of the nozzle body 1 through the refractory mortar layer 7, the gas blowing is caused by the thermal influence during casting of molten steel. Due to the difference in thermal expansion between the inlet tube 6 and the refractory nozzle body 1, a gap may occur between the gas blowing tube 6 and the hole 5 of the nozzle body 1. If such a gap occurs, a leak will occur when gas is introduced. Moreover, cracks occur in the refractory mortar layer 7 due to the stress caused by the difference in thermal expansion, which becomes a cause of gas leakage. As a result, even if the gas pressure is increased, gas cannot be effectively supplied into the nozzle hole 3, and adhesion of nonmetallic inclusions cannot be sufficiently prevented. For this reason, as shown in FIGS. 1 and 2, the outer peripheral surface of the nozzle body 1 into which the gas blowing pipe 6 is inserted is covered with an annular iron skin 8 for the purpose of preventing gas leakage. however,
Since the steel shell 8 is also coated on the nozzle body 1 through mortar, the difference in thermal expansion between the steel shell 8 and the nozzle body 1 due to the thermal effect during casting of molten steel causes the gap between the steel shell 8 and the nozzle body 1 to increase. A gap is created between the two, making it impossible to effectively prevent gas leaks. The present invention has been made in order to eliminate the above-mentioned drawbacks, and aims to provide a nozzle for gas blowing casting that can effectively prevent gas leakage without covering the annular steel shell, which causes an increase in manufacturing costs. It is something to do. An embodiment of the present invention will be described below with reference to FIGS. 3 and 4. In the figure, reference numeral 11 denotes a nozzle body made of refractory material and having a nozzle hole 13 in which four discharge ports 12 are formed at the lower end. An annular gas pressure equalizing zone 14 is provided in the longitudinal direction of the nozzle body 11 in close proximity to the nozzle hole 13 . And the nozzle body 11
As shown in FIG. 4, the upper end side wall is provided with a threaded hole 15, which communicates with the pressure equalizing zone 14 at one end and opens to the outside at the other end. A pipe 16 made of, for example, stainless steel and threaded on both the outer and inner circumferential surfaces of the threaded hole 15 is screwed through a heat-resistant inorganic adhesive layer (trade name: Sumiceram) 17 . The thread form on the inner and outer peripheral surfaces of this pipe 16 is the pitch of the thread on the outer peripheral surface (JIS B0205-1973
The pitch (as described in "Metric Coarse Thread", JIS B0202-1966 "Pipe Thread", and JIS B0203-1966 "Pipe Thread") is long, and the pitch of the thread on the inner peripheral surface is short. Further, a gas blowing pipe 18 having a threaded tip is inserted into the pipe 16 by screwing. According to such a configuration, the metal gas blowing pipe 18 that supplies gas to the nozzle hole 13 of the nozzle body 11 is connected to the threaded hole 1 of the refractory nozzle body 11.
5 is inserted into the main body 11 via a stainless steel pipe 16 screwed onto the nozzle main body 11, so that thermal expansion between the gas blowing pipe 18 and the refractory nozzle main body 11 due to thermal effects during molten steel casting is prevented. The stress associated with the difference,
It can be relaxed by the pipe 16 between these. the result,
It is possible to prevent a gap from forming around the tip of the gas blowing pipe 17. Furthermore, the threaded hole 1 of the nozzle body 11
If the inorganic adhesive layer 17 is screwed between the pipe 16 which is threaded on the inner and outer peripheral surfaces of the pipe 16, the adhesive layer 17 becomes spiral-shaped, making it difficult to form a gas passage. 18 can be prevented from leaking, and a predetermined flow rate of gas can be supplied into the nozzle hole 13 through the annular gas equalization zone 14 and the pores of the nozzle body 11. In addition, since the gas blowing pipe 18 is attached to the nozzle body 11 by a screwing method, the threaded pipe 16 is screwed and fixed to the threaded hole 15 of the nozzle body 11 during manufacturing. When used at a place or the like, gas can be blown by simply screwing the gas blowing pipe 18 onto the pipe. As a result, it is possible to easily install the gas blowing pipe on-site, and to prevent damage to the nozzle body due to shocks during transport, etc., which may occur when the gas blowing pipe is attached during the manufacturing process and the final product is made into a final product. has advantages. Furthermore, regarding the thread form of the inner and outer circumferential surfaces of the pipe, the pitch of the threads on the outer circumferential surface of the pipe that is screwed into the threaded hole 15 of the nozzle body 11 is lengthened, and the pitch of the thread on the outer circumferential surface of the pipe that is screwed into the threaded hole 15 of the nozzle body 11 is lengthened. By shortening the pitch of the threads on the circumferential surface, the pipe 16 can be firmly fixed to the nozzle body 11, and gas leakage between the pipe 16 and the gas blowing pipe 18 can be prevented. Next, a test example of gas leak prevention in the gas injection type submerged nozzle of the present invention will be explained. Test example The nozzle body 11 has the characteristics shown in the table below.
Made of Al ₂ O ₃ C refractory material, the stainless steel pipe 16 has a thread pitch of 2 mm on the outer circumferential surface.
(according to JIS B0205-1973M14), the pitch of the thread on the inner peripheral surface is 0.9071mm (JIS B0202-1966PF1/8,
or according to JIS B0203-1966PT1/8) and connect this pipe 16 to the pressure equalizing zone 1 of the nozzle body 11.
A gas blowing type immersion nozzle was assembled by screwing the pipe 16 into the threaded hole 15 communicating with the pipe 16 through the alumina-siliceous adhesive layer 17, and screwing the gas blowing pipe 18 to the pipe 16. Comparative Example A 1/8 inch φ hole communicating with the annular hollow chamber was drilled in the nozzle body made of the same material as the test example, a gas blowing pipe was inserted into this hole through a layer of refractory mortar, and the outer circumferential surface A gas-injection type immersion nozzle was assembled by covering the annular steel shell with mortar. Therefore, an inert gas was supplied to the gas blowing pipe of the submerged nozzle of the test example and the comparative example under the condition of 2 atmospheres, and the effective gas supply rate (%) supplied to the nozzle hole of the nozzle body was investigated. The results are also listed in the same table. The effective gas supply rate is: gas amount supplied into the nozzle hole/total gas injection amount x 10
It was calculated as 0.

[Table] As is clear from the above table, the gas injection type submerged nozzle of the present invention has significantly less gas leakage than the conventional submerged nozzle, and the effective gas supply rate into the nozzle hole is improved. Note that the gas blowing casting nozzle according to the present invention is not limited to the form in which a cylindrical stainless steel pipe is used as a fitting member as in the above embodiment. For example, the shape of the pipe may be tapered, and the material may be a ceramic material such as high-density silicon carbide. The gas blowing casting nozzle according to the present invention is not limited to a submerged nozzle, but can be similarly applied to an open nozzle and the like. As detailed above, according to the present invention, gas leakage near the fitting part of the gas blowing pipe to the nozzle body can be effectively prevented without covering the annular steel shell, which would increase production costs. A gas blowing casting nozzle that can effectively and controllably supply gas to molten steel flowing through the nozzle hole and prevent non-metallic inclusions from adhering to the inner wall of the nozzle hole and clogging the nozzle hole. It is.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a conventional gas-injection type submerged nozzle, Fig. 2 is an enlarged cross-sectional view of section A in Fig. 1, and Fig. 3 is a cross-section of a gas-injection type submerged nozzle showing an embodiment of the present invention. FIG. 4 is an enlarged sectional view of section B in FIG. 3. DESCRIPTION OF SYMBOLS 11... Refractory nozzle body, 13... Nozzle hole, 14... Gas equalization zone, 15... Threaded hole, 16...
Pipe threaded on inner and outer peripheral surfaces, 17...heat-resistant inorganic adhesive layer, 18...gas blowing pipe.

Claims (1)

[Claims] 1 a refractory nozzle body having a nozzle hole;
An annular gas pressure equalizing zone provided in the nozzle body in the longitudinal direction close to the nozzle hole; and an annular gas pressure equalizing zone provided on the side wall of the nozzle body, one end communicating with the pressure equalizing zone and the other end opening to the outside. A pipe having threads on its inner and outer surfaces is screwed into the threaded hole through a heat-resistant inorganic adhesive layer, and a gas blowing pipe is screwed onto the pipe. and a pitch of the threads on the outer circumferential surface of the pipe is longer than a pitch of the threads on the inner circumferential surface.