JP2014000586A - Casting mold for casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a casting mold for casting capable of preventing constriction of a long side central part caused by tensile stress in the casting direction.SOLUTION: A casting mold 1 for casting has mutually opposed long side side long side surfaces 2 and short side side short side surfaces 3, and supplies molten metal from above a casting hollow part 4 formed of these long side surfaces 2 and short side surfaces 3 and discharges an ingot of a rectangular cross-sectional shape from below while cooling this so as to continuously cast the ingot of a rectangular cross-section. The long side side long side surfaces 2 are formed so that surfaces 10 of a central part 9 become projecting shapes with respect to surfaces 8 of both side parts 7, and the mutually opposed long side surfaces 2 are formed so as to incline to the inside as going downward, and the surfaces 10 of the central part 9 are formed so that a projection quantity t reduces as going downward to the surfaces 8 of both side parts 7.

Description

  The present invention relates to a casting mold for continuously casting a copper alloy or the like.

  In vertical continuous casting, not limited to copper alloys, the outer dimensions due to solidification shrinkage and shrinkage progress in the shrinking direction due to differences in cooling conditions, drawing speed, and material in the mold. Therefore, except for special casting, a taper 25 is generally provided on the inner surface of the mold in the casting direction (from top to bottom) as shown in FIG.

  In the vertical continuous casting, the dimensional shrinkage of the central part on the long side is remarkably generated. This is because billet casting with a circular cross section easily obtains uniform cooling conditions in the circumferential direction, whereas slab casting with a rectangular cross section tends to increase the cooling from the corner portion to the short side. Further, the amount of shrinkage varies depending on the secondary cooling conditions under the mold regardless of the cross-sectional shape of either the billet or slab.

  In vertical continuous casting, it is desirable that the molten metal is poured into the casting mold 26 and the process from the start of cooling and solidification to cooling to room temperature proceeds at a constant cooling rate. In alloys, it is necessary to control the cooling rate in various temperature ranges. These controls are intended to obtain a target cooling pattern by controlling the temperature of the molten metal poured into the casting mold 26, the flow rate of the mold cooling water, and the amount and position of the secondary cooling zone. Moreover, in order to prevent a conveyance trouble due to the ingot shape during a heating furnace or a rolling pass in a hot rolling process after casting, accuracy is also required for the cross-sectional shape and longitudinal shape of the ingot. Therefore, as shown in FIG. 5, the central portion 28 of the long side portion 27 of the casting mold 26 may be formed in a concave shape in order to expand the center of the long side portion of the ingot in anticipation of the shrinkage amount of the ingot in advance. .

JP 2003-71547 A

  Especially in copper alloy casting, cast structure control in the secondary cooling zone is an important factor for determining quality. Further, the taper 25 is provided in the casting direction in order to prevent the air gap accompanying the reduction in the cross-sectional dimension of the ingot in the casting mold 26, but it is difficult to eliminate the air gap. In order to compensate for the difference in cooling balance between the long side portion 27 and the short side portion 29 due to the air gap, the amount of cooling water at the short side portion 29 and the long side portion 27 is adjusted or the cooling pattern in the secondary cooling zone is changed. It is common to take a control method.

  However, the difference in the cooling rate between the corner portion, short side portion and long side portion of the solidified shell also affects the growth rate of the solidified shell, and in particular, the corner portion tends to be thick and the long side central portion tends to be thin. This not only changes the cross-sectional shape but also increases the residual stress in the solidified structure, and at the bottom of the mold at the stage of solidification completion, strain in the compression direction is accumulated at the center of the ingot at the center of the long side. A tensile stress is generated in the mold, which pulls the thin solidified shell at the top of the mold. The solidified shell at the initial growth stage above the mold is subjected to tensile stress toward the center of the molten pool due to solidification shrinkage, but maintains contact with the inner surface of the mold in balance with the molten metal hydrostatic pressure. However, when the shrinkage force exceeds the drag force of the molten metal hydrostatic pressure as the solidified shell grows, a constricted local shrinkage occurs in the central part of the long side of the solidified shell.

  In the constricted portion of the solidified shell, the collapse of the solidified shell toward the mold center and the tensile stress from the bottom of the mold act. In addition, the cooling rate may be reduced due to the air gap generated by the constriction, and the solidified shell may be remelted and broken by recuperation, resulting in hot water leakage.

  The breakage of the solidified shell is not preferable for safety because it leads to breakout of the ingot. In addition, a rapid change in the cooling rate induces abnormal precipitation of alloy components in the solidified structure, resulting in quality deterioration such as intergranular cracking.

  In continuous casting of a copper alloy, precipitation of alloy components at the grain boundaries has a high risk of causing fogging and peeling defects in the rolling process, so a sound ingot free from grain boundary segregation is required. It is also important for safety to prevent troubles caused by breakout during casting and bending during the rolling process.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent the necking of the long side portion due to the tensile stress in the casting direction.

  In order to solve the above problems, the present invention has a long side surface and a short side surface on the short side facing each other in order to continuously cast an ingot having a rectangular cross section. In the casting mold for supplying the molten metal from the upper part of the casting hollow portion formed by the short side surface and discharging the ingot having the rectangular cross section from the lower side while cooling the molten metal, the long side surface on the long side side However, the central surface is formed so as to be convex with respect to the surfaces on both sides, and the long side surfaces facing each other are formed so as to incline inward as going downward, and the central portion Is formed such that the amount of protrusion decreases as the surface of the surface of the surface goes downward relative to the surfaces on both sides.

  An inclined connecting surface may be formed between the surface of the central portion of the long side surface and the surfaces of the both side portions.

  The connecting surface may be formed as a single surface or a multi-stage surface bent in multiple stages.

  The convex amount of the surface of the central portion is preferably 5 ± 1% of the distance between the surfaces of the both side portions, and is preferably 2.5 ± 0.5% on one side.

  The length in the side direction of the surface of the central portion may be 25% of the length of the long side surface.

  According to the present invention, it is possible to prevent the necking of the long side center portion due to the tensile stress in the casting direction.

It is a top view of the casting mold which concerns on this Embodiment. (A) is the sectional view on the AA line of FIG. 1, (b) is the sectional view on the BB line of FIG. It is explanatory drawing which shows the action direction of the position of the air gap area | region which generate | occur | produces inside a casting_mold | template, and tensile stress. (A) is a schematic plan view of a conventional casting mold, (b) is a sectional view taken along the line CC of (a), and (c) is a sectional view taken along the line DD of (a). It is plane explanatory drawing of the conventional casting mold. It is explanatory drawing which shows the position of the air gap area | region which generate | occur | produces in the conventional inside of a casting_mold | template, and the acting direction of tensile stress.

  A casting mold according to the present invention will be described with reference to the accompanying drawings.

  As shown in FIGS. 1 and 2, the casting mold 1 has a long side 2 on the long side and a short side 3 on the short side facing each other so as to continuously cast an ingot having a rectangular cross section. . The long side surface 2 and the short side surface 3 form a cast hollow portion 4 serving as a molten metal mold. The casting mold 1 is for supplying molten metal from above the casting hollow portion 4 and discharging the ingot having a rectangular cross section from below while cooling the casting. A cooling water channel (not shown) is formed in the casting mold 1, and cooling water from the outside flows through the cooling water channel. The casting hollow portion 4 is formed vertically through the metal block forming the casting mold 1 and has an upper opening 5 that opens upward to receive the molten metal, and the ingot in which the molten metal has cooled and solidified. It has a lower opening 6 that opens downward to discharge.

  Now, the casting mold 1 according to the present invention is characterized by its inner surface shape.

  The long side surfaces 2 facing each other of the casting mold 1 are formed so as to incline inward as going downward. Further, each long side surface 2 is formed on the surface 8 of both side portions 7 desired on the short side surface 3 and a central portion 9 between the surfaces 8 of both side portions 7 and is convex with respect to the surface 8 of both side portions 7. And a connecting surface 11 formed between the surface 10 of the central portion 9 and each of the surfaces 10 of the central portion 9 and the surfaces 8 of the both side portions 7.

  The surfaces 8 of both side portions 7 of the long side surface 2 are each formed in a straight line along the side direction of the long side surface 2. Further, the surfaces 8 of the both side portions 7 of the long side surface 2 are formed to be on the same surface.

  The surface 10 of the center portion 9 is formed so as to be convex with respect to the surfaces 8 of the both side portions 7, so that it is positioned inside the casting hollow portion 4 more than the surfaces 8 of the both side portions 7, and in the long side direction. It is formed linearly along. Further, the surface 10 of the central portion 9 is formed such that the convex amount t decreases as it goes downward with respect to the surfaces 8 of the both side portions 7. Specifically, the convex amount t of the surface 10 of the central portion 9 is formed to be a constant ratio with respect to the interval T between the surfaces 8 of the both side portions 7 at any position in the vertical direction. It decreases continuously as you go down. The convex amount t of the surface 10 of the central portion 9 is preferably formed to be 5 ± 1% (2.5 ± 0.5% on one side) of the interval T between the surfaces 8 of the both side portions 7. Further, the length wc in the side direction of the surface 10 of the central portion 9 is preferably 25% of the length W of the long side surface 2.

  The connecting surface 11 is bent and connected to the surface 10 of the central portion 9, and is bent and connected to the surface 8 of the side portion 7. Further, the connecting surface 11 is inclined with respect to the side direction of the long side surface 2. The connecting surface 11 is formed so that the inclination angle of the long side surface 2 with respect to the side direction becomes small according to the change in the convex amount t of the surface 10 of the central portion 9. The connecting surface 11 is formed so that the length wt in the side direction of the long side surface 2 is the same as the surface 8 of the both side portions 7.

  The connecting surface 11 may be formed of a multi-stage surface that is bent in multiple stages. The greater the number of constituent surfaces of the connecting surface 11, the greater the effect of dispersing the tensile stress.

  Next, the operation of this embodiment will be described.

  As shown in FIG. 3, the molten metal 12 cooled in the casting hollow portion 4 of the casting mold 1 forms a solidified shell on the outer peripheral portion. In the initial growth stage of the solidified shell, the hydrostatic pressure of the molten metal in the molten pool exceeds the solidification shrinkage force, and the solidified shell continues to contact the long side surface 2 and the short side surface 3 of the casting mold 1, but eventually the thickness of the solidified shell is reached. When the solidification shrinkage force exceeds the hydrostatic pressure, the solidified shell is separated from the long side surface 2 of the cast hollow portion 4 and an air gap 13 is generated.

  At this time, since the long side surface 2 is inclined inward as going downward, the surface 10 of the central portion 9 is formed in a convex shape with respect to the surfaces 8 of the both side portions 7, so that the ingot surface is a long side surface. The range in which the air gap 13 is separated from 2 can be minimized, the tensile stress in the casting direction can be reduced, and constriction of the solidified shell and breakage after remelting can be prevented. That is, in the casting mold 1 according to the present embodiment, the solidified shell is recessed in the drum shape with the convex shape at the center of the long side surface 2, so that the generation position of the air gap 13 is set at both the long side center portions of the solidified shell. It can be dispersed in two areas on the side, the direction of the tensile stress 14 can be directed to the corner and long side center of the solidified shell, and by pulling the solidified shell at the center of the long side from both sides Since the central part of the long side of the solidified shell is again pressed against the long side surface 2, the generation time of the air gap 13 can be shortened, and the amount of constriction and grain boundary segregation can be reduced.

  As described above, the casting mold 1 is formed such that the long side surface 2 on the long side is formed so that the surface 10 of the central portion 9 is convex with respect to the surfaces 8 of the both side portions 7 and faces each other. The long side surface 2 is formed so as to incline inward as it goes downward, and the convex amount t decreases as the surface 10 of the central portion 9 goes downward with respect to the surfaces 8 of both side portions 7 thereof. Therefore, it is possible to prevent constriction of the central part of the long side of the solidified shell due to the tensile stress in the casting direction, and the solidified shell is remelted and broken due to a decrease in the cooling rate by the air gap 13 to cause hot water leakage. Therefore, abnormal precipitation of alloy components in the solidified structure can be prevented, and quality deterioration such as grain boundary cracking can be prevented. Further, the ingot on the long side can be formed in a substantially flat shape as compared with the corner portion, and troubles during material handling in the rolling process can be prevented beforehand. In addition, the air gap generation region can be minimized, the tensile stress can be minimized, and the occurrence of grain boundary segregation due to delayed solidification shell growth and the occurrence of breakout due to grain boundary fracture can be prevented. Ingot quality can be improved and safety in the casting process can be improved. Furthermore, since the surface 10 of the central portion 9 is formed so that the convex amount t decreases as it goes downward, the air gap 13 is effectively formed in the upper portion in the casting hollow portion 4 where the air gap 13 is easily formed. Generation | occurrence | production can be suppressed and the ingot discharged | emitted below from the casting mold 1 can be made into a rectangular cross-section stably.

  Further, since the inclined connecting surface 11 is formed between the surface 10 of the central portion 9 of the long side surface 2 and the surfaces 8 of the both side portions 7, an ingot having a rectangular cross section can be stably cast. .

  Since the connecting surface 11 is formed by a single surface or a multi-stage surface bent in multiple stages, the casting mold 1 can be easily processed.

  The convex amount t of the surface 10 of the central portion 9 is formed to be 5 ± 1% of the interval T between the surfaces 8 of the two opposite long side surfaces 2 on the both side portions 7, and is 2.5 ± 0. Since it is set to 5%, an ingot having a rectangular cross section can be stably cast.

  Moreover, since the length wc in the side direction of the surface 10 of the central portion 9 is formed to be 25% with respect to the length W of the long side surface 2, the generation position of the air gap 13 is set at the central portion of the long side of the solidified shell. It is possible to disperse well in two regions on both sides.

  Next, a specific example in the case of casting a slab having a rectangular cross-sectional dimension of 245 × 640 will be described.

  In such a case, the approximate dimensions of the casting mold 1 are as follows. In the lower opening 6, the long side dimension W of the long side surface 2 is 640 mm, and the length wc in the side direction of the central portion 9 of the long side surface 2 is 160 mm (long side The thickness (convex amount) t of the surface 10 of the central portion 9 is set to 3 mm on one side (approximately 2.5% of the interval between the opposing short side surfaces 3 (interval in the thickness direction)). .

  The taper in the casting direction is the same as the conventional casting mold on both the long side and the short side because the casting conditions are the same. Specifically, the inclination of the surface 8 on both sides 7 of the long side surface 2 is set to 14 minutes, and the inclination of the short side surface 3 is set to 36 minutes.

  The details of the shape of the central portion 9 of the long side surface 2, both side portions 7, and the connecting surface 11 are the lengths in the side direction of the long side surface 2, and the length obtained by combining the surface 8 of the side portion 7 and the connecting surface 11. It is assumed that the length wz is 240 mm on one side and the length ws of the surface 8 of the side portion 7 is 120 mm. Therefore, the inner surface shape of the casting mold 1 is a 12-sided shape.

  This is the minimum number of surface configurations. The greater the number of constituent surfaces of the connecting surface 11, the greater the effect of dispersing the tensile stress. Further, since the mold inner surface taper in the casting direction largely depends on the casting speed, it is desirable to set it appropriately according to the material and casting conditions of the alloy to be cast.

  According to the casting mold 1, the air gap generation region can be minimized, the tensile stress can be minimized, the occurrence of segregation at the grain boundary can be prevented, and the breakout due to the grain boundary fracture can be prevented. Occurrence can be prevented.

  A comparative example will be described. When casting a slab of the above dimensions using a conventional casting mold, the inclination of the surface of the long side of the casting mold is 14 minutes, the inclination of the surface of the short side is 36 minutes, and the depression shape of the long side is It is a hexagonal shape that is recessed from the corner side (short side) toward the center of the long side with an inclination of 53 minutes. The result of casting with this conventional casting mold is that the center of the long side of the ingot tends to bulge about 1 mm from the thickness of the corner (both sides 7) at a steady mold speed, but there is a problem in material handling. It is a level that does not. However, a difference in thickness occurs in the solidified shell at the central part of the long side and the corner part where the cooling rate is lowered due to the air gap, and internal stress is accumulated. Ultimately, this strain becomes tensile stress, and the grain boundary along the line 21 near the upper surface of the solidified shell thinnest portion of the constricted portion, that is, the region where the air gap 20 shown in FIG. Cracks may occur intermittently. This intergranular cracking causes fogging and peeling in the rolling process. Further, in this case, at the initial casting stage inside the mold, due to the generation of the air gap region, the cooling rate of the long side central portion 23 is lower than the corner portion 22 on the same time axis. In comparison, the growth of the long side central portion 23 is relatively delayed. For this reason, the long side central portion 23 is also delayed at the start of solidification shrinkage, and a diagonally downward tensile stress 24 is generated at the corner portion 22 and the long side central portion 23. For this reason, the solidified shell may remelt due to recuperation and cause hot water leakage especially in the upper part of the air gap region.

DESCRIPTION OF SYMBOLS 1 Casting mold 2 Long side surface 3 Short side surface 4 Cast hollow part 7 Both side part 8 Both side surface 9 Central part 10 Central part surface 11 Connecting surface T Space | interval between both side surfaces W Length of long side surface t Convex amount wc Length in the side direction of the central surface

Claims (5)

  In order to continuously cast an ingot having a rectangular cross section, a casting hollow portion having a long side surface and a short side surface facing each other and formed by the long side surface and the short side surface. In the casting mold for supplying the molten metal from above and discharging the ingot having a rectangular cross section from below while cooling the molten metal, the long side surface on the long side is the surface of the central part on both sides. The long side surfaces facing each other are formed so as to be convex with respect to the surface, and are inclined so as to incline toward the lower side. A casting mold characterized in that the convex amount decreases as it goes downward.   The casting mold according to claim 1, wherein an inclined connecting surface is formed between a surface of a central portion of the long side surface and a surface of the both side portions.   The casting mold according to claim 2, wherein the connecting surface is formed of a single surface or a multi-stage surface bent in multiple stages.   The convex amount of the surface of the central portion is formed to be 5 ± 1% of the distance between the surfaces of both side portions, and becomes 2.5 ± 0.5% on one side, respectively. Casting mold.   The casting mold according to any one of claims 1 to 4, wherein a length in a side direction of the surface of the central portion is formed to be 25% with respect to a length of the long side surface.