JPH04178246A - Builtup casting mold - Google Patents

Abstract

PURPOSE:To prolong the life of a casting mold by providing a pair of 1st facing cast wall members and a 2nd cast wall member laid between these cast wall members and forming notches on both sides of the 2nd cast wall member, on the upward part and at the lower end part of the surface of the molten metal. CONSTITUTION:In an assembled casting mold 1, a notch is formed on both sides of the 2nd cast wall member and on the upward part of the molten metal surface, and on both sides and at the lowermost place on both cast wall member. In the upward area of the molten material surface and at the lower end part of the casting mold, the 2nd cast wall member comes in non-contact with the 1st cast wall member, therefore, local residual stress at an area directly below the molten metal surface and at the lower end part of the cast wall is relieved drastically. Plastic strains are not generated on the 2nd cast wall member, a gap in an abutting part between the 1st and the 2nd cast wall members does not expand actually, intrusion of the molten steel is prevented effectively and the casting mold can be used continuously.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to an assembly mold for continuous casting of slabs such as slabs, rubs, blooms, and billets.

[Conventional technology] In continuous casting of molten steel, the mold has the role of primarily solidifying the molten steel as a solidified shell.In order to achieve high cooling capacity, a water-cooled copper plate is used, and if necessary, it is plated with hard metal etc. ing. The shape of the pores is a decisive factor in obtaining the desired slab shape, so continuous casting machines that produce slabs with various cross-sectional dimensions use molds with different pore shapes each time the cross-sectional dimension changes. was being exchanged. However, in continuous casting machines for producing slabs, the cross-sectional dimensions of the slab can be changed simply by changing the slab width, so the short side members (movable members) can be moved between the long side members (fixed members). A method of creating an assembled mold is used, in which the width of the casting area is changed (changed).

In this assembly mold with a convergence changer, both side surfaces of the movable member are brought into contact with the opposing wall surfaces of the fixed member, and a slight gap inevitably exists at the contact portion. If the gap between the abutting portions is too large, molten steel will enter the gap (insertion of the molten steel) and the initially solidified shell will be ruptured, causing problems such as breakouts and double skin. To avoid such troubles, when assembling molds, clamp the opposing fixed members so that they come into close contact with the sides of the movable member, and minimize the gap that occurs at the contact area. There is.

Also, when the short side member (movable member) touches and moves on the surface of the long side member (fixed member) for convergence change, if the contact surface is a bare copper metal surface, galling is likely to occur. The contact surfaces of the side members are plated with a hard metal such as Ni to a thickness of about 0.5 mm.

[Problems to be Solved by the Invention] However, when molten steel is poured into a conventional assembly mold, as shown in FIG. 7, the short side member 21 tends to extend in the longitudinal direction due to thermal expansion. However, since the side surface of the short side member 21 is clamped and pressed against the wall surface of the long side member 22, it cannot actually extend.
Residual stress occurs in the short side member 21.

The residual stress generated in the short side member 21 described above gradually increases with repeated use of the mold, and eventually exceeds the elastic limit of the mold material, causing plastic deformation in the mold and shrinkage on cooling after casting. As shown in FIG.
3 occurs. If this gap 23 exceeds the cold allowable value of 3 mm, molten steel is likely to get inserted even though it is tightened with a clamp, and the mold will have to be discontinued, which will extend the life of the mold. However, there was a problem in that it became noticeably shorter. In particular, in high-speed casting where the casting speed is high, the life of the mold becomes extremely short, and the expensive mold must be replaced frequently, resulting in high costs.

An assembly mold for continuous casting to solve the above problems is disclosed in Japanese Patent Application No. 1-034422. As shown in FIG. 9, this assembled mold has cutouts 24 formed on both sides of the short side member 21 and located above the molten metal level. By forming the notches 24 in this manner, the short side member 21 does not come into contact with the long side member 22 in the area above the hot water level, and local residual stress in the area directly below the hot water level is significantly alleviated.

Therefore, plastic strain does not substantially occur in the short side member 21, the gap between the abutting portions of the short side member 21 and the long side member 22 does not substantially expand, and insertion of molten steel is effectively prevented. This makes it possible to use the mold continuously.

However, with the assembled mold in which only the notches 24 are made on both sides of the short side member 21 and located above the molten metal level, is it possible to prevent the gap near the surface from expanding? Regarding the lower part, there was a problem that the surface roughness of the abutting long piece members became rough at an early stage, so the abutment surface of the short piece members would gall and the gap would expand.

This invention solves the above-mentioned problems of the prior art,
It is an object of the present invention to provide an assembled mold for continuous casting in which a gap between a contact portion between a long side member and a short side member does not increase.

[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 combined so as to surround a casting area, and the wall surface thereof has a predetermined rI! A pair of first mold members facing each other with a distance of I, and a pair of first mold members provided between the pair of first mold members,
A pair of second mold members partitioning the casting area with a predetermined radius, and a second mold member having the first mold member on both sides of the pair of second mold members.
The pressing means for bringing the opposing wall surfaces of the second mold member into contact with each other and pressing the second mold member has a means, and notches are formed on both sides of the second mold member at positions above the molten metal level and at the lower end. This is an assembled mold.

[Function] In the assembled mold according to the present invention, the parts located on both sides of the second mold member and above the molten metal level, and the parts located at the lowest end of both sides of the second mold member Since the notch is formed, there is no contact with the second mold member or the first mold member in the area above the hot water level and the lower end of the mold, and there is no localized residue in the area just below the hot water level and the lower end of the mold. Stress is significantly alleviated. Therefore, plastic strain does not substantially occur in the second mold member, and the gap between the contact portions of the first and second mold members does not substantially expand.
It becomes possible to use the mold continuously while effectively preventing insertion of molten steel.

[Example] An assembled mold according to an example of the present invention will be explained with reference to FIGS. 1 to 6. FIG. 1 is a longitudinal cross-sectional view of an assembled mold according to an embodiment of the present invention, viewed from the side, and FIG. 2 is a cross-sectional view of the assembled mold, viewed from above. The mold 1 is an assembly mold for continuously casting slabs having a predetermined cross-sectional shape, and its mold members are made of a copper alloy. The mold 1 includes a pair of long side members 2,
3 and a pair of short side members 4, and the pair of long side members 2.3 are clamped. That is, the wall surfaces of the pair of long side members 2.3 face each other with a predetermined interval (an interval corresponding to the thickness of the slab to be cast). A pair of short side members 4 or from the inner wall of the long side member 2 to the inner wall of the long side member 3 are provided, respectively, and the radius of the casting area 5 is partitioned into a predetermined length. The tips of screw jacks 6 are connected to the outer surface of each short side member 4, respectively. When the screw jack 6 is operated, each short side member 4 moves between the long side members 2 and 3, so that the rotation can be changed.

A port 7 for clamping passes through both ends of the long side members 2 and 3, and is tightened with a nut 10 via a spacer 8 and a disc spring 9 on the side of the long side member 3. The pair of long side members 2, 3 and the pair of short side members 4 have a large number of cooling water channels (not shown) formed therein, and cooling water is supplied to each water channel to cool each member. It has become so. That is, when the molten steel in the casting region 5 comes into contact with the surrounding mold and is cooled, a thin solidified shell 11 is formed along the casting wall surface.

Next, from the slab thickness of 220 mm and the radius of 970 mm,
An embodiment applied to a continuous slab casting machine that is variable up to mm will be described with reference to FIGS. 3 to 5. Incidentally, the width of the short side member 4 at the upper end is approximately 230 mm, the width at the lower end is approximately 228 mm at the reference plane, and the total length is approximately 954 mm.

The thickness is made into a shape with slope change lines in two stages from the top end to the bottom end, with a large solidification and contraction gradient at the top, and the thickness at the top end is about 40 mm, and the thickness at the bottom end is about 48 mm. The short side member 4 has abutting portions 4a and 4b with the long side member on both sides thereof, and is 50 mm from the upper end of the abutting portions 4a and 4b.
The upper notch 12 and the lower notch 13 are formed by machine cutting in a range of mm and a range of 120 mm from the lower end. Here, the range of 50+nm from the top end is the highest height of the powder layer in the meniscus in a steady state, and the range of 120mm from the bottom end is the range with a margin greater than the dimension when the dummy bar is inserted and the sealing member is set. This is a downward dimension, and is in a range where close cooling of the corner of the slab is not required during steady pouring. Regarding the notch, which is a feature of the present invention, the depth of the upper notch part 12 is 0.311IIIl, and the surface is finished with a corner cut off from the surface of 4a. Avoid the occurrence of sudden points of change. In addition, the cutting depth of the lower notch 13 is 4 mm so that it is 1.0 mm.
A (or 4b) is a surface parallel to the reference surface, and the connection portion with the surface of finishing 4a is finished smoothly. A portion of the lower notch 13 5 mm from the ridgeline on the side of the mold cavity is chamfered to create a structure in which the surface roughness of the long piece member can be held down so that it does not cause galling of the short piece member. Furthermore, the area of 15 mm from the mold hole side between the upper notch 12, the contact parts 4a and 4b, and the lower notch 13 is coated with Ni to a thickness <
(0.3 to 0.5 mm) The dimensions are plated and finished. The side surface of the mold cavity, which is the active surface for cooling and solidifying molten steel, is finished by thickly plating Ni from a certain dimension below the meniscus during steady pouring to the bottom end.

Next, a description will be given of changing the radius when continuously casting slabs with different radius using the above-mentioned mold.

First, the clamp port 7 is loosened, and the short side member 4 is moved by the screw 6 to adjust the width of the casting area. Then, the long side members 2 and 3 are clamped. After doing this, a dummy bar (not shown) is inserted under the mold l, and when the preparation for casting is completed, the tundish nozzle (not shown) is opened and the mold is inserted through the submerged nozzle (not shown). Molten steel is injected into the casting area 5 of l. When the water level reaches a certain height,
The dummy bar is pulled out at a predetermined speed to maintain the level of the hot water at a constant level. In the steady state of casting, the molten steel injection amount and slab withdrawal speed are controlled so that the molten metal level is located below the upper notch 12, as shown in FIG.

When the molten steel contacts the mold, the short side member 4 expands, and force is applied to the contact portions 4a and 4b of the short side member 4. The short side member 4 is restrained in the width direction by the long side members 2 and 3, but the short side member 4 is not in contact with the long side members 2 and 3 at the upper notch 12 and the lower notch 13. Therefore, the force applied to the contact portions 4a and 4b of the short side member 4 is alleviated. Therefore, the contact portions 4a and 4b of the short side member 4 are not deformed beyond their elastic 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 300°C. -Generally, the temperature of the inner wall of the mold below the hot water level is 300
When temperatures exceeding .degree. C. are reached and the abutment portions 4a and 4b of the short side members 4 are restrained over their entire surface, the forces generated by thermal expansion easily exceed the elastic strain limit of the mold material. However, in the above mold, the upper and lower ends of the abutting portions of the short side members are cut out, so that the stress is relaxed and the gap between the members is prevented from increasing.

Also, during mold replacement work, the surface of the lower notch 13 is 1.0 mm from the reference surface of 4a. Since the finish is 0 mm, the contact is gentle, and when the short side member slides on the long side member, obstacles on the long side member can be scraped off without causing galling. Also,
Since the portion of the lower notch 13 5 mm from the ridgeline on the mold hole side is chamfered, the roughness of the surface of the long piece member can be suppressed so that it does not cause galling of the short piece member.

The areas on the mold hole side of the upper notch 12, the contact parts 4a and 4b, and the lower notch 13 are plated with a thick layer of Ni, so that the areas drawn in from the surface of the elongated member are plated with a thick layer of Ni. Contaminants can also be suppressed to prevent galling of the short pieces.

In addition, although the above-mentioned example explained the mold for slab, it is not limited to this, and mold for bloom, billet,
It is also possible to apply it to a mold for continuous casting of other slabs such as beam blanks.

[Effects of the Invention] According to the present invention, the life of an assembled mold for continuous casting can be significantly extended.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view of an assembled mold according to an embodiment of the present invention as seen from the side, Fig. 2 is a cross-sectional view of an assembled mold according to an embodiment of the present invention seen from above, and Fig. 3 is a 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 each temperature, Fig. 7 is a schematic diagram for explaining the state when a conventional assembled mold undergoes thermal deformation, FIG. 8 is a perspective view showing a part of the conventional assembled mold in a cold state, and FIG. 9 is another conventional mold. It is a front view of the short side member of. l... Mold, 2.3... Long side member, 4... Short side member, 4a, 4b... Contact portion of short side member with long side member,
12... Upper notch part, 13... Lower notch part.

Claims (1)

[Claims] In an assembled mold in which a plurality of mold members are combined so as to surround a casting area, a pair of first mold wall members whose wall surfaces face each other with a predetermined interval, and a space between the pair of first mold wall members. 1 provided in the casting area and partitioning the casting area with a predetermined width.
a pair of second cast wall members, and pressing means for abutting and pressing opposing wall surfaces of the first cast wall members on both side surfaces of the pair of second cast wall members, respectively; An assembled mold characterized in that notches are formed on both side surfaces of the second casting wall member at positions above the molten metal level and at the lower end.