JPH02211939A - Assembling mold - Google Patents

Abstract

PURPOSE:To drastically extend the service life of a mold by arranging means pushing as approaching facing wall face of a first casting wall member on both side faces of one pair of second casting wall members and forming a notch to position at upper part from molten metal surface on both side faces of the second casting wall member. CONSTITUTION:Clamping bolts 22 are loosed and short side members 16 are shifted with the screws 30 to adjust width of the mold range, and long side members 12, 14 are clamped. A dummy bar is inserted into the lower part of the mold 10 and at the time of completing the casting preparation, the tundish nozzle is opened and molten steel is poured into steel casting range 18. Under the stationary condition in the casting, molten steel pouring rate and cast slab drawing velocity are suitably adjusted so that the molten steel surface is positioned at lower part of the notching part 17. When the molten steel is brought into contact with the mold, the short side member 16 is expanded to exert the force to the abutting part 16b. The short side member 16 is restricted with the long side members 12, 14, but as the member 16 and the members 12, 14 are under non-contacting condition at the notching part 17, the force exerted to the abutting part 16b is relieved and the service life of the mold can be extended.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an assembly mold for continuous casting of slabs, blooms, billets, etc.

[Prior Art] In continuous casting of molten steel, a mold has the role of primarily solidifying the molten steel as a solidified shell, and its shape is important in obtaining a sound slab. In particular, in assembly molds for slab manufacturing, it is necessary to change the width of the casting area (width change) according to changes in the slab width, so the short side members (variable members) are separated between the long side members (fixed members). It is set up so that it can be moved. In order to change the width, the assembled mold has a structure in which both side surfaces of the variable member are brought into contact with the opposing wall surfaces of the fixed member, and a small gap inevitably exists at the contact portion. In this case, if the gap between the contact parts is large, molten steel will enter the gap (insertion of molten steel), and the initially solidified shell will break, causing problems such as breakout and double skin. Therefore, by tightening the opposing fixing members with clamps, the fixing members are brought into close contact with the side surfaces of the variable member, and the gap created at the contact portion is minimized, thereby preventing insertion of molten steel.

[Problems to be Solved by the Invention] However, when molten steel is poured into a conventional assembly mold, a difference in thermal expansion occurs in the short side member 6, as shown in FIG. Since the short side member 6 is restrained by the long side members 2 and 4 by tightening the clamp, it cannot actually expand, and residual stress is generated in the portion of the short side member 6 directly below the hot water level.

Due to repeated use of the mold, the residual stress exceeds the elastic strain limit of the mold material, plastic strain occurs in the mold, and when the mold shrinks on cooling after casting, the short side member 6, long side member 2, A gap 7 is locally formed at the contact portion with 4. If the gap amount of the gap 7 exceeds the allowable value of 0.31 mm in the cold state, molten steel is likely to be inserted even though the mold is tightened with a clamp, so the use of the mold is temporarily discontinued. For this reason, there was a problem in that the life of the mold was significantly shortened. In particular, in high-speed casting where the casting speed is high, the life of the mold is short and the expensive mold must be replaced frequently, resulting in high costs.

This invention was made in view of such circumstances, and
The purpose is to provide long-life assembly molds.

[Means for Solving the Problems] An assembled mold according to the present invention is an assembled mold in which a plurality of mold members are assembled so as to surround a casting area, and includes a pair of mold members whose wall surfaces face each other with a predetermined interval. a pair of second mold members provided between the pair of first mold members and partitioning the casting area by a predetermined width; pressing means for bringing opposing wall surfaces of the first mold member into abutment and pressing on both sides, respectively, on both sides of the second mold member, and
It is characterized by a notch formed above the hot water level.

In this case, the notch portion of the second mold member is cut to a depth of 0.1 to 0.0 mm over a range of 30 to 100 inches from the upper end of the member.
It is preferable to set it as 5 as.

[Effect]

In the assembly mold according to the present invention, the notches are formed on both side surfaces of the second mold member and at positions above the hot water level, so that the second mold member can be removed in the area above the hot water level. is not in contact with the first mold member, and the local residual stress in the area directly below the molten metal surface is significantly alleviated. Therefore, plastic strain does not substantially occur in the second mold member,
The gap between the first and second abutting portions does not substantially increase, and the mold can be used continuously while effectively preventing insertion of molten steel.

[Example] Hereinafter, an assembly mold for continuous slab casting will be specifically described as an example of the present invention with reference to the accompanying drawings.

FIG. 1 is a longitudinal cross-sectional view of an assembled mold according to an embodiment of the present invention, seen from the side, and FIG. 2 is a cross-sectional view of the mold seen from above. The mold 10 is an assembly mold for continuously casting slabs having a predetermined cross-sectional shape, and is made of a copper alloy. The mold 10 has a pair of long sides 12.14 and a pair of short sides 16, with the long sides 12.14 being clamped.

That is, the walls of the long side members 12, 14 face each other at a predetermined distance (a distance corresponding to the thickness of the slab to be cast). A pair of short side members 16 are provided from the inner wall of the long side member 12 to the inner wall of the long side member 14, respectively, and are partitioned into a casting area 18 having a predetermined length. The tips of screw jacks 30 are connected to the outer surface of each short side member 16, respectively. That is, when the screw jack 30 is operated, the short side member 16 is moved to the long side member 1.
2.14 and the width can be changed.

A clamping bolt 22 is attached to the long side member 12. Long side member 1
4, and is tightened with a nut 28 via a spacer 241 and a disc spring 26 on the side of the long side member 14.The members 12, 14, and 16 have a large number of cooling channels inside them. (not shown) is formed, and cooling water is supplied to each water channel to cool each member individually.In other words, when the molten steel in the casting area 18 comes into contact with the surrounding mold and is cooled, , a thin solidified shell 19 is formed along the casting wall surface.

Next, referring to FIGS. 3 to 5, the short side member 16
I will explain about it.

The short side member 16 has a main body portion 16a and a contact portion 16b. The contact portion 16b is provided at the widthwise end portion of the main body portion 16a from the upper end to the lower end of the member 16. The cutout portion 17 is formed by mechanically cutting an area of 50IIl from the upper end of the contact portion 16b. In this case, the cutting depth of the notch 17 is 0.2 av.

Incidentally, the short side member 16 has a thickness of about 40 am at the upper end.
The thickness of the lower end is approximately 48+gs, the width of the upper end is approximately 230
AS1 lower end width is approx. 228a+1, overall length is approx. 9
It is 541. Next, a case in which slabs are continuously cast using the above mold will be described.

The clamp bolt 22 is loosened and the short side member 16 is moved by the screw 30 to adjust the width of the casting area. Clamp the long side members 12.14. When a dummy bar (not shown) is inserted under the mold 10 and preparation for casting is completed, a tamp-push nozzle (not shown) is opened and molten steel is poured into the casting area 18 of the mold 10 through a submerged nozzle (not shown). inject.

When the hot water level reaches a predetermined height, the dummy bar is pulled out at a predetermined speed to keep the hot water level constant. In the steady state of casting, the casting speed is controlled by appropriately adjusting the molten steel injection amount and slab withdrawal speed so that the molten metal level is located below the notch 17, as shown in FIG.

When the molten steel contacts the mold, the short side member 16 expands and force is applied to the contact portion 16b of the short side member. Although the short side member 16 is constrained in the width direction by the long side member 12.14, since the member 16 and the member 12.14 are not in contact with each other at the cutout portion 17, the force applied to the contact portion 16b is reduced. is alleviated. Therefore, the contact portion 16b is prevented from being deformed beyond the elastic strain limit, and the gap between the two members is prevented from expanding.

FIG. 6 is a graph showing the results of an investigation into the relationship between the mold inner wall temperature on the horizontal axis and the 0.2% proof stress of the mold material on the vertical axis. As is clear from the figure, the strength of the copper mold decreases rapidly when the temperature exceeds about 300°C.

Generally, the inner wall of the mold directly below the surface of the mold reaches a temperature of over 300°C, so if the contact portion 16b is restrained over the entire surface, the force generated by thermal expansion will easily exceed the elastic strain limit of the mold material. . However, in the above-mentioned mold, since a part of the abutting portion of the short side member is cut out, the stress is relaxed and the gap between the members is prevented from increasing.

In addition, although the above-mentioned example explained the mold for the slab, it is not limited to this, and this invention can be applied to bloom, mold, etc.
It is also possible to apply the present invention to molds for continuous casting of other slabs such as billets and beam blanks.

[Effects of the Invention] According to the present invention, the life of the mold can be significantly extended. In this case, the effect is particularly recognized in high-speed casting where the casting speed exceeds 2 m/min. That is, the life of the mold can be extended from the conventional 300 to 500 charges to over 1000 charges.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of an assembled mold according to an embodiment of the present invention viewed from the side, FIG. 2 is a cross-sectional view of the mold viewed from above, and FIG. 3 is a front view showing the short side members of the mold. , Fig. 4 is a side view of the short-side member, Fig. 5 is a plan view of the short-side member, Fig. 6 is a graph showing the strength of the mold at various temperatures, and Fig. 7 shows the thermal deformation of the conventional assembled mold. FIG. 8 is a perspective view showing a part of a conventional assembled mold in a cold state. 10... Mold, 12.14... Long side member (first mold member), 16... Short side member (second mold member), 1
7...Notch section applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Scope of Claims] An assembled mold in which a plurality of casting wall members are combined so as to surround a casting area, a pair of first casting wall members whose wall surfaces face each other with a predetermined interval; a pair of second casting wall members provided between the first casting wall members and partitioning the casting area with a predetermined width; and a pair of second casting wall members provided on both sides of the second casting wall members. pressing means for bringing opposing wall surfaces of the cast wall members into contact with each other and pressing them, and notches are formed on both side surfaces of the second cast wall member and at positions above the molten metal level. An assembly mold characterized by: