JPH0119989B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for preventing thermal fatigue of a meniscus portion of a continuous casting mold.

Conventionally, the structure of a mold used for continuous casting is to manufacture a rectangular mold by firmly fixing a copper plate inside a steel back plate with tightening bolts. However, when hot molten steel is poured into such a mold,
The meniscus that is in contact with the molten copper surface tries to expand, but because it is fixed with bolts, thermal expansion cannot occur freely and plastic deformation occurs. Also, as the molten steel level fluctuates and falls, the mold tries to contract, but as mentioned above, it is firmly fixed with bolts, so it cannot absorb the strain caused by this contraction, and the mold repeats thermal expansion and contraction over a long period of time. As a result, cracks occur in the meniscus of the mold due to fatigue. As a result, the mold may crack or the tightening bolt may break, shortening the life of the mold.

As a result of intensive research aimed at solving this problem, the present inventor has completed the invention of a thermal fatigue prevention device for the meniscus of a continuous casting mold, which reduces fatigue caused by repeated thermal expansion and contraction of the mold.

That is, the gist of the present invention is that the insertion holes for the tightening bolts on the back plate are formed into elongated holes corresponding to the expansion length and contraction length due to cooling of the copper mold fixed to the inside of the back plate. This invention consists in a device for preventing thermal fatigue of a meniscus part of a continuous casting mold, which comprises a water leakage prevention O-ring and a disc spring fitted between a bolt and a back plate. I will explain while doing so.

FIG. 1 shows a perspective view of the mold of the present invention, and reference numeral 1, 1 denotes a long side back plate made of steel. 2, 2 is a long side mold made of copper, 3, 3 is a short side back plate, and 4, 4 is a short side mold made of copper.

Now, when molten steel is poured into this mold, the portions of the long-side molds 2, 2 that come into contact with the molten steel, that is, the meniscus portions are thermally expanded and stretched to the left and right. At this time, the portions exhibiting the maximum elongation are the left and right outermost ends of the molds 2, 2, and the amount of displacement gradually decreases toward the center.

On the other hand, when the molten steel level fluctuates and falls and it no longer comes into contact with the molten steel, the meniscus portions of the molds 2, 2 rapidly contract. The shrinkage allowance at this time is also the smallest at the center of the molds 2, 2, and gradually increases toward both outer ends.

Therefore, as shown in the figure, the insertion holes for the tightening bolts drilled on the back plates 1, 1 are also elongated holes with eccentric centers that are gradually elongated from the center of the back plates 1 toward both outer sides. The amount of displacement due to thermal expansion and contraction of the mold 2 is absorbed by appropriately moving the tightening bolt within the elongated hole.

FIGS. 2 and 3 are cross-sectional views showing examples of the thermal fatigue prevention mechanism and waterproofing mechanism in the outermost part of the mold 2, in which 1 is a long-side back plate, and 2 is a long-side mold made of copper. It is formed by

The position of the tightening bolt 8 and the mold 2 when molten steel does not flow in is shown by the line B-B, and the position where the molten steel flows into the mold 2 and the mold 2 expands is shown by the line C-C.
On the outer side of the mold 2, which has a large thermal expansion, the insertion holes 6, 6 for the tightening bolts 8 are formed to be elongated in the direction shown by the arrow in which the mold 2 extends.

Reference numerals 9 and 9' denote O-rings which are fitted into the holder 10 and brought into close contact with the outer periphery of the insertion hole 6 of the back plate 1 to prevent leakage of cooling water from the cooling groove 14.

Reference numeral 11 denotes a disc spring formed by bending the outer peripheral edge into a disc shape, and is fitted between the washer 12 and the holder 10 to maintain the tightening force of the tightening bolt 8 at the required level at all times. It is fitted into the head of No. 8.

In FIG. 3, reference numeral 13 is a copper gasket, which is polished so as to come into close contact with the back plate 1 and is fitted onto the bolt 8.

The embodiments of the present invention have been described above, and next, embodiments of the device for preventing thermal fatigue of the meniscus portion of a continuous casting mold of the present invention will be described in detail below.

First, in FIG. 1, when molten steel is poured into molds 2, 2 and 4, 4 made of copper plates, the outermost portions of the molds 2, 2 tend to expand significantly as shown in FIG. Bolt holes 6, 6, in the back plate 1 shown in FIG.
6 and 7, 7, and 7, since the mold tends to expand in the direction indicated by the arrow, are drilled horizontally in advance by the amount of expansion so that the thermal expansion of the mold 2 is not restricted.

Therefore, when the amount of molten steel flowing into the molds 2, 2, 4, 4 changes and the amount of molten steel decreases, the tightening bolt 8 and the mold 2 are in a state of C-C line as shown in FIG. The state returns to the line B-B. In this way, even if the amount of molten steel in the molds 2, 2, 4, 4 changes, the bolt insertion holes to be drilled in each position of the back plate 1 by the length of expansion and contraction are formed in advance as long holes. As a result, distortion due to displacement of the mold 2 does not remain in the tightening bolt 8 and the mold 2, and cracks in the mold meniscus due to thermal fatigue do not occur.

Also, each insertion hole 6, 6, 6, 7, 7, 7, 5,
5, 5... are provided with a water leakage prevention device as shown in Fig. 2 or 3, so that the cooling water flows through the insertion holes 5.
...6...7...No more leakage.

As mentioned above, the center of the back plate 1 (on the A-A line)
Since the bolt insertion holes are formed so as to be gradually eccentric toward the outside, and the tightening force between the mold 2 and the back plate 1 is always maintained at the required level by the disk spring 11, Even if thermal stress is repeatedly applied to the mold 2 and the tightening bolts 8 during continuous casting, it can all be absorbed by the above-mentioned mechanism, so the mold can be used for a long time and the casting cost can be reduced.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the continuous casting mold of the present invention, and FIGS. 2 and 3 show an embodiment of the thermal fatigue prevention device for the meniscus of the continuous casting mold of the present invention. FIG. In the figure, 1, 1: back plate, 2, 2: copper long side mold,
5, 6, 7: Bolt insertion hole, 8: Bolt, 9,
9': O-ring, 11: Belleville spring, 13: Copper gasket.

Claims (1)

[Claims] 1. The insertion holes for the tightening bolts on the back plate are formed into elongated holes corresponding to the length of expansion and contraction due to cooling of the copper mold fixed to the inside of the back plate, and the holes between the tightening bolts and the back plate are formed as elongated holes. A thermal fatigue prevention device for the meniscus of a continuous casting mold, which is equipped with an O-ring for preventing water leakage and a disc spring.