JPH0528542U - Long nozzle for continuous casting - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] The long nozzle tip for continuous casting, which is immersed in molten steel in the tundish, is exposed to severe thermal shock conditions, and its durability deteriorates due to cracking and chipping. So, we will improve it. [Structure] The outer periphery of the tip of the long nozzle for continuous casting has a tapered shape, and the tapered shape is a conical shape, a convex curved surface, a convex polygonal shape (all viewed from a vertical cross section), or the like. It is preferable that the tip angle (θ) is 20 to 75 ° with respect to the axis of the long nozzle, and the tapered axial length (H) of the nozzle is 20 to 400 mm. As a result, cracking and chipping at the tip of the long nozzle are reduced, and the service life is extended.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to improvement of a long nozzle for continuous casting.

[0002]

[Prior Art]

 As is well known, in the continuous casting method of steel, a long nozzle is used to perform open casting when pouring molten steel from a ladle into a tundish. These long nozzles are in the form of long pipes, and the upper part is thicker than the main part and can be supported as a flange so that it can be set as the lower nozzle (shoot nozzle) of the ladle. On the other hand, the tip of the nozzle immersed in the molten steel in the tundish has the shape of a horizontally cut tube.

[0003]

[Problems to be solved by the device]

 This type of long nozzle is used to inject molten steel from several charges to several tens of charges and is cooled for each charge, so the tip of the long nozzle immersed in the molten steel in the tundish is exposed to severe thermal shock conditions. Be done. Therefore, the durability is deteriorated due to cracking or chipping of the tip, and the steel quality is also adversely affected. In addition, the slag and metal that adhere to the tip of the long nozzle contract when it cools and solidifies. Since the outer surface of the long nozzle cools earlier than the inner surface, the adhered metal or slag tightens the tip of the long nozzle, which promotes cracking and chipping of the tip, which reduces durability. The present inventors have succeeded in developing the present invention as a result of various studies and experiments in order to improve the drawbacks of the conventional products as described above and prolong the durability of the long nozzle. Has a tapered shape on the outer circumference of the tip of a long nozzle for continuous casting, and this tapered shape has a conical shape (FIGS. 1 and 4), a convex curved surface (FIGS. 2 and 5) or a convex polygonal shape (FIG. 3). (When viewed from the longitudinal section), etc., which suppresses thermal and mechanical stress concentration at the tip and adhesion of slag and metal. It is preferable that the tip angle (θ) of the tapered portion is 20 to 75 ° with respect to the axis of the long nozzle, and the length (H) of the tapered shape in the nozzle axial direction is 20 to 400 mm. is there.

The reason why the tip angle (θ) of the tapered portion is set in the range of 20 to 75 ° with respect to the axis of the long nozzle is that stress relaxation at the lower end is insufficient if the angle is less than 20 °. If it exceeds 75 °, the stress relaxation of the curved outer circumference becomes insufficient, and the effect of suppressing the adhesion of slag and metal to the tip becomes insufficient. Further, the axial length of the tapered portion is preferably such that the wall thickness of the tip of the long nozzle is 10 mm or more, and if it is less than 10 mm, the strength and erosion of the tip are insufficient, which is not preferable in terms of durability.

In the example of the present invention shown in FIGS. 4 and 5, when the long nozzle wall thickness is 45 mm, the thermal stress generated between the conventional product with the flat tip surface and the present product is set to 100 for the conventional product. The comparison result is shown in the graph of FIG. From this graph, it can be seen that the occurrence of thermal stress in the product of the present invention is reduced as shown in the figure, and therefore the durability is increased by about 10%.

[0006]

[Effect of the device]

 (1) Adhesion of metal and slag to the tip of the long nozzle was suppressed, cracking and chipping were reduced, and the service life was improved 1.5 times or more compared to the conventional product.

(2) The occurrence of cracks due to thermal shock was suppressed by no preheating or slight preheating at the time of first use.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a long nozzle of the present invention having a conical tip.

FIG. 2 is a vertical cross-sectional view of a long nozzle of the present invention having a convex curved surface at the tip.

FIG. 3 is a vertical sectional view of a long nozzle of the present invention having a convex polygonal tip.

FIG. 4 is a vertical cross-sectional view of the tip portion of FIG.

5 is a vertical cross-sectional view of the tip portion of FIG.

FIG. 6 is a graph showing the thermal stress generation states of the conventional product and the device of the present invention.

[Explanation of symbols]

 θ Tip angle of tapered portion H Axial length of tapered shape

Claims (2)

[Scope of utility model registration request] 1. A long nozzle for continuous casting, characterized in that the outer periphery of the nozzle tip portion is tapered. 2. The tapered shape is a conical shape, a convex curved surface or a convex polygon, and the tip angle (θ) of the tapered portion.
Is 20 to 75 ° with respect to the axis of the long nozzle.