CA1203663A - Method for manufacturing of steel casting - Google Patents
Method for manufacturing of steel castingInfo
- Publication number
- CA1203663A CA1203663A CA000428436A CA428436A CA1203663A CA 1203663 A CA1203663 A CA 1203663A CA 000428436 A CA000428436 A CA 000428436A CA 428436 A CA428436 A CA 428436A CA 1203663 A CA1203663 A CA 1203663A
- Authority
- CA
- Canada
- Prior art keywords
- chill
- casting
- grooves
- stress
- groove
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D15/00—Casting using a mould or core of which a part significant to the process is of high thermal conductivity, e.g. chill casting; Moulds or accessories specially adapted therefor
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Molds, Cores, And Manufacturing Methods Thereof (AREA)
- Continuous Casting (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Method for manufacturing of steel castings characterized by a novel means for preventing a crack from occurring on the sur-face skin of said cast steel in which the surface of a direct chill applied to a casting mould is provided with a series of pro-tuberances and depressions which divides or disperses a shrink stress on the surface skin of said cast steel.
Method for manufacturing of steel castings characterized by a novel means for preventing a crack from occurring on the sur-face skin of said cast steel in which the surface of a direct chill applied to a casting mould is provided with a series of pro-tuberances and depressions which divides or disperses a shrink stress on the surface skin of said cast steel.
Description
3~3 _CKGROUN~ OF THE INVENTION
Field of the Invention The present lnvention relates to an improvement concern-ing a direct chill used on part or all of a mould for the steel casting.
Description of the prior ar-t -Steel castings have advantages over rollings and forg-ings in that there is less restriction on the shape of the product obtained. On the other hand, however, they entail the drawback that, in the case of using a sand mould, internal defects occur in the casting. The occurrence of these defects is inherently re-lated to the solidification of the steel within the casting and is particularly pronounced in the case of large and intricately shaped castings.
Hitherto, as a remedy for preventing the above defects by controlling the solidification behaviour within the cast steel, chills, i.e. blocks of iron or steel, have been applied at specific locations on the surface of the mould so as to promote cooling and solidification of the casting at these portions, where-by the internal quality of the casting has been effectlvely im-proved.
Experience shows, however, that cracking of casting sur-face is apt to occur at portions of the casting where a chill is applied and that this tendenc~ increases with increasing size oE
the cas-ting and increasing area of the chill. As reasons for the occurrence of such cracking there can be mentioned the following:
A first cause is that when a chill is applied to -the cast steel, ~Z1:~3~>~i3 the surface of the casting is chilled more rapidly at the portion of the chill than at the portion of the sand mould, giving rise to a rapidly occurring shrink stress associated with the solidifica-tion. A second cause is that the chill does not at all follow the deformation accompanied with a solidification shrink of the cast-ing; and, conversely, the chill exhibits a behaviour opposite to the solidification shrink of the casting due to the expansion of -the chill resulting from the temperature rise so that it operates to promote the occurrence of a surface cracking.
As a method for preventing cracking of the surface skin of casting, it is known to use internal chills buried in the sand mould as illustrated in Fig. 1. In this figure, the numeral 20 denotes a sand mould, 21 chills, 22 sand, 24 sand layer, and 23 a roLl to be cast. This method, however, has the disadvantage that the cooling effect of the chill is reduced by the sand layer 24 in front of the chill 21.
Hitherto, there has been no satisfactory method for pre-venting surface cracking of a casting produced with the use of direct chills. Therefore, the cracks occurring in the surface skin of casting must be removed by scarfing and repaired by weld-ing. Hence, there results a considerable increase in processing steps as well as manufacturing cost, so that -there has been a strong desire for a satisfactory remedy.
As a technique for avoiding cracking of the casting sur-face, it is known to use a fluted or corrugated mould for a steel ingot to be rolled or forged. Macroscopically viewed, these in-gots have simple square, rectangular or circular sectional shapes.
~,.;
~2~3~36~
Since the cracks caused by the solidification of the ingot occur on the outer surface thereof mostly in the heiyht direction, the ridges and valleys are formed in one direction parallel ~ith the axis of the ingot.
In consideration of the shrinking characteristics of the casting, the form of fluting or corrugatlon is designed generally in a complicated curve~ This method is considered to be capable of almost totally preventing longitudinal cracking of steel ingot.
In cast steel, however, cracking occurs in spite of the fact that the area of the casting surface to which the chills are applied is far smaller than the area of a steel ingot mould which requires fluting or corrugation. This is because the shape of the cas-tings is far more complicated than that of steel ingot mould, and also because stresses occur in many directions on the surface of the casting to which the chill is applied. The stress is built up to uni-directional one vectorially from random~directional stress.
When composed stress on the surface ~Z(~3~i3 of castings to which the chill is applied exceeds the ultimate strength of cas-tings, a crack inevitably occurs on the surface of castings in a direction perpendicular to that of composed stress.
This means that it is necessary to take into consideration the stresses occurring in many directions in the suxface of the steel casting at the points where chills are applied.
In United States Patent No. 4,250,950, it is proposed that a mould be provided with a roughened surface so that -the melt comes into contact only with the peaks of the projections on the mould surface and an air gap is formed between the melt and the valleys on the surface of mould in order to regulate the heat transfer from the melt to the mould. However, this United States Patent discloses no method for improving the internal quality and properties of a casting produced with the application of chills.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for producing steel castings with improved internal quality and properties.
The invention provides a method for manufacturing a cast steel product in a sand mold to which a metallic chill is attached, characterized in that a) the metallic chill comprises a surface of predetermined length and width, b) sai.d surface of the chill being provided with irregularities and c) said surface of the chill being positioned in contact with the cast product whereby the shrink stress on the casting steel surface is so dispersed in many directions that the absolute value of the composite stress is maintained at a value 3~3 less than that of the ultimate strength of the cast steel.
BRIEF DESCRIPTION OF THE DRAWINGS
Other advantages of the invention will become apparent to those skilled in the art from the following detailed description of the invention with reference to the accompanying drawings which illustra-te preferred embodiments of the invention. In the drawings:
Figure 1 is a side view of a prior art in which a chill is used;
Figure 2 is a view showing -the surface of a chill pro-vided with a groove lattice;
Figure 3 is a view of the sectional shape of a groove;
Figure 4 is a graph showing the crack prevention effec-tlveness of a large planar chill provided with the groove lattice;
Figures 5(a),(b),(c) and (d) are views showing continuous triangular and hexagonal groove and pit patterns;
Figure 6 is a graph showing a comparison between the amount of repair work required by castings produced by the method o:E this invention and by the method of prior art;
Figures 7(a) and (b) are views showing a -truncated cone-~0 shapecl plt and a truncated sphere-shaped pit;
Figure ~ is an explanatory view of an embodiment of -the invention;
Figure 9 is an explana-tory view of another embodiment ~36~
of the invention; and Fig. 10 is a perspective view of the chill shown in Fig. 9.
DETAILED DESCRIPTION OF THE INVENTION
This invention was accomplished on the basis of an exten-sive analytical study on the shrink stress in the surface skin of cast steel. It is known to apply a direct chill (referred to as a "chill" hereinafter) to part or all of the surface of a steel cast-ing within a mould. The gist of the present invention resides in providing an improved chill having surface irregularities, i~e.
projection and depression, which function to divide the shrink stress in the surface of the casting.
It is generally known that cracks appear at points of a castin~ where the stress exceeds the ultimate strength of the cast-.i.ng surface. Thus, in order to prevent cracksl it ls necessary e:ither to increase the strength of the casting or to decrease the stress. The strength of cast steel depends on the properties re-~uired of the product to be cast, and it is impossible to regulate the strength only on the surface thereof. As the stress in the ~0 surface skin of the casting is a tensile stress, it can be pre-sumed to be caused by the solidification shrink. The sum total of stress depends on the shape and area of the casting surface and cannot be increased or decreased at will.
In the case of a small chill~ the amount of tensile stress arising in the surface skin of the casting where the chill is applied is little enough to produce a crack. In process of re-search, the inventors found that when there is used a single chill i~
3~3 having a surface meas~ring not more than 200 mm in both width and length (referred to as a "small ehill" hereinafter), less danger of eraeking of the surfaee skin of the easting arises. On the eon-trary, however, use of a plurality of small chills which have a surface width and/or length exceeding 200 mm in a bundle and/or single bloek (referred to as a "large chill" hereinafter), tends to inerease radieally in the suseeptibility to cracking on the sur-faee skin of the easting.
An intention to decrease the crack-lndueing stress by re-dueing the thiekness and/or area of the chill applied to the east-ing surfaee would be inconsisten-t with the fundamental aim to im-pr~ve the internal properties of the easting through the eooling effeet of the ehill. For preventing internal defeets it is neees-sary to use a large chill having sufficient -thic}cness and area and this large ehill must provide any measures to prevent crack forma-tion on the surface of castings.
Based on the above-mentioned study in eonnection with the eraelcing of a easting surfaee to which a ehill is applied, the inventors have sueeeeded in preventing cracks from occurring in the surfaee skin of a easting by a novel process wherein the stresses aeting in the casting surface in many directions are so dispersed in many directions that the absolute value of the eom-posite stress is maintained at a value less than that of the ulti-mate strength of the east steel. More speeifieally, they have eon-ceived the idea of provi~ing the surface of a ehill with whieh the easting surfaee eomes in eontaet with a consecutive pattern con-sisting of surface irregularities (i.e. projections and depres---7~
~Z~3~
sions) extending not in one direction but in many directions.
Now, the present invention will be described hereinbelowin detail with reference to the drawings.
Fig. 2 shows an embodiment of a large planar chill in which the fundamental idea of the present invention is illustrated.
As shown in Fig. 2, ~he surface 2 of the chill 1 with which the casting comes in contact is provided with orthogonally intersect-ing groove 3 which forms a lattice for coping with stress acting in two directions: lateral and longitudinal, or vertical and horizontal. Thus, the surface skin 4 of the casting, which is a large field of solidification shrink stress, is divided into a number of small fields of stress limited by the surroundin~
grooves. With this arrangement, since the absolute value of the stress in each small field of stress is held well under the ulti-mate strength limit of casting, no cracking occurs in the surface skin.
Since the function of the grooves are to divide the sur-Eace skin of casting into small fields of stress, they are of no practical use if too shallow. The depth F of the grooves depends ~0 on the casting conditions, and it has been confirmed by experi-ments that a groove depth F of more than about 5 mm is sufficient for the ordinary cas-ting process. Moreover, if the angle between the side wall 5 of the groove 3 and the surface 2 of the chill is in the vicinity of 90 degrees, the restraint of the casting sur-face 4 due to the groove 3 becomes too strong and a concentrated point of shrink stress is easily formed in the surface skin ~
around the groove 3. Accordingly~ it has been found that this angle should ordinarily be greater than 120 degrees, and prefer ably about 135 degrees.
Eurthermore, if the intersection between the side wall 5 of the groove 3 and the chill surface 2 should form a distinct brink edge having a sharp angle, then the brink edge is trans-cribed onto the surface skin 4, with the result that the corner 6 becomes a concentrated poin-t of stress on the surface skin 4. As this would promote, not prevent, cracking, the corner 6 should be made round and smooth. In order to realize effective alleviation of stress due to shrink of surface skin, it has been confirmed that the radius of curvature R of the corner should preferably be greater than depth F of the groove 3~
In addition to the above, the groove 3 is formed so that the surface area of the cast steel is increased and the groove 3 also provides a shrink allowance to alleviate the surface shrink stress caused by solidification and reduction of temperature. The an~le of the side wall of the groove as well as the roundness at ~h~ brink edge formed by the intersection of the groove and the chill surface function to facilitate smooth shrinking of the sur-~0 Eace skin.
The primary factors which determine -the shrink allowance of the surface skin 4 are the depth F and the groove interval A~
~nd a secondary factor is the curvature R of the groove edge which has a large effect on the stress concentration but only a small effect toward increasing the casting surface area to provide a shrink allowance. Experiments using a hollow cylinder casting showed that the following conditions are required:
_g_ ;
G~
(groove interval/ ~remaining chill groove depth) surface after the grooves are cut) (1) External chill less than 20 times less than 80
Field of the Invention The present lnvention relates to an improvement concern-ing a direct chill used on part or all of a mould for the steel casting.
Description of the prior ar-t -Steel castings have advantages over rollings and forg-ings in that there is less restriction on the shape of the product obtained. On the other hand, however, they entail the drawback that, in the case of using a sand mould, internal defects occur in the casting. The occurrence of these defects is inherently re-lated to the solidification of the steel within the casting and is particularly pronounced in the case of large and intricately shaped castings.
Hitherto, as a remedy for preventing the above defects by controlling the solidification behaviour within the cast steel, chills, i.e. blocks of iron or steel, have been applied at specific locations on the surface of the mould so as to promote cooling and solidification of the casting at these portions, where-by the internal quality of the casting has been effectlvely im-proved.
Experience shows, however, that cracking of casting sur-face is apt to occur at portions of the casting where a chill is applied and that this tendenc~ increases with increasing size oE
the cas-ting and increasing area of the chill. As reasons for the occurrence of such cracking there can be mentioned the following:
A first cause is that when a chill is applied to -the cast steel, ~Z1:~3~>~i3 the surface of the casting is chilled more rapidly at the portion of the chill than at the portion of the sand mould, giving rise to a rapidly occurring shrink stress associated with the solidifica-tion. A second cause is that the chill does not at all follow the deformation accompanied with a solidification shrink of the cast-ing; and, conversely, the chill exhibits a behaviour opposite to the solidification shrink of the casting due to the expansion of -the chill resulting from the temperature rise so that it operates to promote the occurrence of a surface cracking.
As a method for preventing cracking of the surface skin of casting, it is known to use internal chills buried in the sand mould as illustrated in Fig. 1. In this figure, the numeral 20 denotes a sand mould, 21 chills, 22 sand, 24 sand layer, and 23 a roLl to be cast. This method, however, has the disadvantage that the cooling effect of the chill is reduced by the sand layer 24 in front of the chill 21.
Hitherto, there has been no satisfactory method for pre-venting surface cracking of a casting produced with the use of direct chills. Therefore, the cracks occurring in the surface skin of casting must be removed by scarfing and repaired by weld-ing. Hence, there results a considerable increase in processing steps as well as manufacturing cost, so that -there has been a strong desire for a satisfactory remedy.
As a technique for avoiding cracking of the casting sur-face, it is known to use a fluted or corrugated mould for a steel ingot to be rolled or forged. Macroscopically viewed, these in-gots have simple square, rectangular or circular sectional shapes.
~,.;
~2~3~36~
Since the cracks caused by the solidification of the ingot occur on the outer surface thereof mostly in the heiyht direction, the ridges and valleys are formed in one direction parallel ~ith the axis of the ingot.
In consideration of the shrinking characteristics of the casting, the form of fluting or corrugatlon is designed generally in a complicated curve~ This method is considered to be capable of almost totally preventing longitudinal cracking of steel ingot.
In cast steel, however, cracking occurs in spite of the fact that the area of the casting surface to which the chills are applied is far smaller than the area of a steel ingot mould which requires fluting or corrugation. This is because the shape of the cas-tings is far more complicated than that of steel ingot mould, and also because stresses occur in many directions on the surface of the casting to which the chill is applied. The stress is built up to uni-directional one vectorially from random~directional stress.
When composed stress on the surface ~Z(~3~i3 of castings to which the chill is applied exceeds the ultimate strength of cas-tings, a crack inevitably occurs on the surface of castings in a direction perpendicular to that of composed stress.
This means that it is necessary to take into consideration the stresses occurring in many directions in the suxface of the steel casting at the points where chills are applied.
In United States Patent No. 4,250,950, it is proposed that a mould be provided with a roughened surface so that -the melt comes into contact only with the peaks of the projections on the mould surface and an air gap is formed between the melt and the valleys on the surface of mould in order to regulate the heat transfer from the melt to the mould. However, this United States Patent discloses no method for improving the internal quality and properties of a casting produced with the application of chills.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for producing steel castings with improved internal quality and properties.
The invention provides a method for manufacturing a cast steel product in a sand mold to which a metallic chill is attached, characterized in that a) the metallic chill comprises a surface of predetermined length and width, b) sai.d surface of the chill being provided with irregularities and c) said surface of the chill being positioned in contact with the cast product whereby the shrink stress on the casting steel surface is so dispersed in many directions that the absolute value of the composite stress is maintained at a value 3~3 less than that of the ultimate strength of the cast steel.
BRIEF DESCRIPTION OF THE DRAWINGS
Other advantages of the invention will become apparent to those skilled in the art from the following detailed description of the invention with reference to the accompanying drawings which illustra-te preferred embodiments of the invention. In the drawings:
Figure 1 is a side view of a prior art in which a chill is used;
Figure 2 is a view showing -the surface of a chill pro-vided with a groove lattice;
Figure 3 is a view of the sectional shape of a groove;
Figure 4 is a graph showing the crack prevention effec-tlveness of a large planar chill provided with the groove lattice;
Figures 5(a),(b),(c) and (d) are views showing continuous triangular and hexagonal groove and pit patterns;
Figure 6 is a graph showing a comparison between the amount of repair work required by castings produced by the method o:E this invention and by the method of prior art;
Figures 7(a) and (b) are views showing a -truncated cone-~0 shapecl plt and a truncated sphere-shaped pit;
Figure ~ is an explanatory view of an embodiment of -the invention;
Figure 9 is an explana-tory view of another embodiment ~36~
of the invention; and Fig. 10 is a perspective view of the chill shown in Fig. 9.
DETAILED DESCRIPTION OF THE INVENTION
This invention was accomplished on the basis of an exten-sive analytical study on the shrink stress in the surface skin of cast steel. It is known to apply a direct chill (referred to as a "chill" hereinafter) to part or all of the surface of a steel cast-ing within a mould. The gist of the present invention resides in providing an improved chill having surface irregularities, i~e.
projection and depression, which function to divide the shrink stress in the surface of the casting.
It is generally known that cracks appear at points of a castin~ where the stress exceeds the ultimate strength of the cast-.i.ng surface. Thus, in order to prevent cracksl it ls necessary e:ither to increase the strength of the casting or to decrease the stress. The strength of cast steel depends on the properties re-~uired of the product to be cast, and it is impossible to regulate the strength only on the surface thereof. As the stress in the ~0 surface skin of the casting is a tensile stress, it can be pre-sumed to be caused by the solidification shrink. The sum total of stress depends on the shape and area of the casting surface and cannot be increased or decreased at will.
In the case of a small chill~ the amount of tensile stress arising in the surface skin of the casting where the chill is applied is little enough to produce a crack. In process of re-search, the inventors found that when there is used a single chill i~
3~3 having a surface meas~ring not more than 200 mm in both width and length (referred to as a "small ehill" hereinafter), less danger of eraeking of the surfaee skin of the easting arises. On the eon-trary, however, use of a plurality of small chills which have a surface width and/or length exceeding 200 mm in a bundle and/or single bloek (referred to as a "large chill" hereinafter), tends to inerease radieally in the suseeptibility to cracking on the sur-faee skin of the easting.
An intention to decrease the crack-lndueing stress by re-dueing the thiekness and/or area of the chill applied to the east-ing surfaee would be inconsisten-t with the fundamental aim to im-pr~ve the internal properties of the easting through the eooling effeet of the ehill. For preventing internal defeets it is neees-sary to use a large chill having sufficient -thic}cness and area and this large ehill must provide any measures to prevent crack forma-tion on the surface of castings.
Based on the above-mentioned study in eonnection with the eraelcing of a easting surfaee to which a ehill is applied, the inventors have sueeeeded in preventing cracks from occurring in the surfaee skin of a easting by a novel process wherein the stresses aeting in the casting surface in many directions are so dispersed in many directions that the absolute value of the eom-posite stress is maintained at a value less than that of the ulti-mate strength of the east steel. More speeifieally, they have eon-ceived the idea of provi~ing the surface of a ehill with whieh the easting surfaee eomes in eontaet with a consecutive pattern con-sisting of surface irregularities (i.e. projections and depres---7~
~Z~3~
sions) extending not in one direction but in many directions.
Now, the present invention will be described hereinbelowin detail with reference to the drawings.
Fig. 2 shows an embodiment of a large planar chill in which the fundamental idea of the present invention is illustrated.
As shown in Fig. 2, ~he surface 2 of the chill 1 with which the casting comes in contact is provided with orthogonally intersect-ing groove 3 which forms a lattice for coping with stress acting in two directions: lateral and longitudinal, or vertical and horizontal. Thus, the surface skin 4 of the casting, which is a large field of solidification shrink stress, is divided into a number of small fields of stress limited by the surroundin~
grooves. With this arrangement, since the absolute value of the stress in each small field of stress is held well under the ulti-mate strength limit of casting, no cracking occurs in the surface skin.
Since the function of the grooves are to divide the sur-Eace skin of casting into small fields of stress, they are of no practical use if too shallow. The depth F of the grooves depends ~0 on the casting conditions, and it has been confirmed by experi-ments that a groove depth F of more than about 5 mm is sufficient for the ordinary cas-ting process. Moreover, if the angle between the side wall 5 of the groove 3 and the surface 2 of the chill is in the vicinity of 90 degrees, the restraint of the casting sur-face 4 due to the groove 3 becomes too strong and a concentrated point of shrink stress is easily formed in the surface skin ~
around the groove 3. Accordingly~ it has been found that this angle should ordinarily be greater than 120 degrees, and prefer ably about 135 degrees.
Eurthermore, if the intersection between the side wall 5 of the groove 3 and the chill surface 2 should form a distinct brink edge having a sharp angle, then the brink edge is trans-cribed onto the surface skin 4, with the result that the corner 6 becomes a concentrated poin-t of stress on the surface skin 4. As this would promote, not prevent, cracking, the corner 6 should be made round and smooth. In order to realize effective alleviation of stress due to shrink of surface skin, it has been confirmed that the radius of curvature R of the corner should preferably be greater than depth F of the groove 3~
In addition to the above, the groove 3 is formed so that the surface area of the cast steel is increased and the groove 3 also provides a shrink allowance to alleviate the surface shrink stress caused by solidification and reduction of temperature. The an~le of the side wall of the groove as well as the roundness at ~h~ brink edge formed by the intersection of the groove and the chill surface function to facilitate smooth shrinking of the sur-~0 Eace skin.
The primary factors which determine -the shrink allowance of the surface skin 4 are the depth F and the groove interval A~
~nd a secondary factor is the curvature R of the groove edge which has a large effect on the stress concentration but only a small effect toward increasing the casting surface area to provide a shrink allowance. Experiments using a hollow cylinder casting showed that the following conditions are required:
_g_ ;
G~
(groove interval/ ~remaining chill groove depth) surface after the grooves are cut) (1) External chill less than 20 times less than 80
(2) Internal chill less than 12 times less than 70
(3) Bottom chill less than 12 times less than 70%
The ex-ternal chill is subject to less restriction than the other chills ~ecause an air gap is formed by the solidifica-tion shrink of the cast steel. It is not always necessary to meet both of the above two conditions but it is preferable to do so.
Fig. 4 shows the effec-tiveness in prevention of cracks in the surface skin of a casting obtained when a large planar chill provided with a groove lattice in accordance with the pre-sent invention was actually used to produce a cast product.
In Fig. 4 the hatched areas indicate the amount of re-pair work necessitated by cracks. Thus if the method of this invention is followed faithfully, there is realized a remarkable reduction in the cracking of the surface skin to which the chill is applied.
Moreover, application of the chill provided with the groove lattice to an outside pattern of cylindrical shape was found to give the same result as those obtained with the use of the large planar chill. In the case of applying a chill of a cylindrical core type or a spherical chill, however, it has been found that it is not possible to obtain satisfactory prevention of cracking in the surface skin of the casting ever by use of a chill having an ortho~onal groove lattice. This is because of compli-cated behaviour of the stre~s which acts on the surface skin.
3~3 In this search for a way to overcome this problem, the inventors hit on the idea of distributing the stress occurring in the surface skin 4 into, for instance, three or six directions.
This can be realized by providing the surface of the chill with grooves 3 in continuous triangular pattern (Fig~ 5(a)) or a con-tinuous hexagon pattern (Fig. 5(b)) or with conic or truncated cone shaped pits (Fig. 7(a)) or spherical truncated sphere-shaped pits (Fig. 7(b)) at the apexes A, B and C of triangles or at the apexes A, B, C, D, E and F of hexagons.
The foregoing comments regarding the groove lattice of Fig. 2 and Fig. 3 also apply to the roundness at each edge of these triangularly and hexagonally arranged grooves 3 and pits 8.
The important point is to disperse the stress and in some cases a pentagonal or octagonal pattern can also be used.
The chill sometimes sticks to the cast steel by fusion.
This fusion sticking can be prevented by coating the chill surface with a mold wash. However, this amounts to coating the chill surface with a material of low thermal conductivity and ~educes the cooling effect Gn the casting as well as the effect to-ward improving the interior quality of the casting by means of -the chill.
Accordingly, the thickness of the mold wash is required to be as thin as possible, and in accordance with the inventors study, it should not exceed 5 mm.
Insofar as this limit is observed, it is permissible to coat the chill provided with the novel means for crack prevention in accordance with the present invention with a mould wash.
Embodiments of the invention are described hereinbelow.
Example 1 An example in which the chill of the invention is applied to the thick portion of a cast steel having thin and thick portions is described below. Fig. 8 illustrates the chill 11-1 and 11~2 applied in contact with a finished product 13, a sand 12, and surface of casted steel melt L immediately after pouring into a casting mould.
Product: Bowl type steel casting with a suppoxt lug.
Maximum thickness of bowl shape portion 200 mm Weight of poured steel 120 tons Inner radius of hemisphere1550 mm Size of support lug:
longitudinal length 400 mm depth of bottom 400 mm top 100 mm width 500 mm ~pplication of chill:
Scope of application: Side and bottom of support lug Thickness of chill : 100 mm Area of chill: 400 x 500 mm Surface pattern of chill:Orthogonally intersecting grooves Groove shape:
groove depth 10 mm groove width 20 mm groove edge curvature 10 mm groove interval 100 mm Steel Quality: SC49 (0.25%C, 0.40%Si, 0.95%Mn, and the balance Fe) \
~3~
The casting produced according -to this Example 1 had no cracks at all in -the surface skin and excellent internal quality of support lug was also confirmed by radiographic examination.
Example 2 A cast steel was manufactured by the method of the tion in which the whole surface of a core was applied with a chill provi.ded with conic pits on the apexes of a continuous triangular pattern (one of the embodiments of the invention). A cast steel product 13 was manufactured using a sand mould 12 provided with a chill 11 as shown in Fig. 9. In this figure L denotes the sur-face of the cast steel melt immediately being poured. Fig. 10 is a perspective view of surface of the chill 11.
Product: Arc-like cast steel with ribs (the thickness of the pro-duct 250 mm; poured weight 21.6 tons)Steel ~uality: SC49 (0.25%C, 0.40%Si, 0.94%Mn, and the balance Fe) Shape of casting: Total width 1935 mm, cylindrical surface width 1635 mm, rib thickness 150 mm, total height of product 1800 mm, inside radius of cylinder 1550 mm.
Application of chill:
Scope oE application : ~hole inside surface skin of cylindrical product Chill thickness : 500 mm Surface pattern of chill : Conic pits at apexes of con-tinuous triangular pattern Pit shape : 110 m~l in diameter, 45 mm deep Interval between pit centers: 183 mm `~
3~
Carrying out the method of the present invention clearly showed that dispersion of the stress on the surface skin of the casting in-to three or six directions is more effective than that of stress dispersion into two directions in the case of chill for the cylindrical core or the spherical core.
Scarfing and welding repair work due to surface cracks of castings was notably decreased and became substantially zero.
The hatched areas in Fig. 6 show the amount of repair work neces-sltated by surface cracks of the castings used direct chills fully to hemispherical cone.
Example 3 In this example a mould wash was used.
Product: Heavy cast steel plate (200 mm thick, 1800 mm wide and 2500 mm long) Steel quality: SC46 (0.2%C, 0.40%Si, 0.80%Mn, and the balance Fe) A single unit planar chill was applied to the bottom of the casting~
Chill: 300 mm thick, 1800 mm wide, and 2500 mm long Means or prevenking cracks: Orthogonally intersecting grooves: groove depth 25 mm, groove width 50 mm, groove interval 250 mm.
Under the above conditions, a mould wash was used as shown in Table 1.
Table 1 ¦MoId wa~ MthldkWaSh ¦ Cracks ~ ThunknleSyef ¦
3 mm No 200 mm NoNo 200 mm -14~
` :
As clearly indicated in Table 1, use of the mould wash did not cause cracking or any change in the thickness of the sound layer in so far as the layer of mould wash is thin enough.
As fully described in the foregoing, advanced chill of the present invention is provided with a groove lattice, a continu-ous triangular or hexagonal groove pattern or polygonal pattern constituted of conic, truncated cone-shaped, spherical or trun-cated sphere-shaped pits provided at the apexes of the polygons.
Advanced chill of present inven~ion i5 to application in extensive area of castings and to obtain good results to improve its inter-nal qualities without any anxiety for the crack formation on the surface skin of castings. As a result, the presen-t invention is eapable of greatly reducing the amoun-t of repair required by the surface skin of the casting and thus of saving the manufacturing eost as well as quick delivery of casting products~
In addition to the above, the present invention can be applied to a easting process using an outer mould, and it is under-stood that such an application is within the scope of the present inv~ntion.
.u
The ex-ternal chill is subject to less restriction than the other chills ~ecause an air gap is formed by the solidifica-tion shrink of the cast steel. It is not always necessary to meet both of the above two conditions but it is preferable to do so.
Fig. 4 shows the effec-tiveness in prevention of cracks in the surface skin of a casting obtained when a large planar chill provided with a groove lattice in accordance with the pre-sent invention was actually used to produce a cast product.
In Fig. 4 the hatched areas indicate the amount of re-pair work necessitated by cracks. Thus if the method of this invention is followed faithfully, there is realized a remarkable reduction in the cracking of the surface skin to which the chill is applied.
Moreover, application of the chill provided with the groove lattice to an outside pattern of cylindrical shape was found to give the same result as those obtained with the use of the large planar chill. In the case of applying a chill of a cylindrical core type or a spherical chill, however, it has been found that it is not possible to obtain satisfactory prevention of cracking in the surface skin of the casting ever by use of a chill having an ortho~onal groove lattice. This is because of compli-cated behaviour of the stre~s which acts on the surface skin.
3~3 In this search for a way to overcome this problem, the inventors hit on the idea of distributing the stress occurring in the surface skin 4 into, for instance, three or six directions.
This can be realized by providing the surface of the chill with grooves 3 in continuous triangular pattern (Fig~ 5(a)) or a con-tinuous hexagon pattern (Fig. 5(b)) or with conic or truncated cone shaped pits (Fig. 7(a)) or spherical truncated sphere-shaped pits (Fig. 7(b)) at the apexes A, B and C of triangles or at the apexes A, B, C, D, E and F of hexagons.
The foregoing comments regarding the groove lattice of Fig. 2 and Fig. 3 also apply to the roundness at each edge of these triangularly and hexagonally arranged grooves 3 and pits 8.
The important point is to disperse the stress and in some cases a pentagonal or octagonal pattern can also be used.
The chill sometimes sticks to the cast steel by fusion.
This fusion sticking can be prevented by coating the chill surface with a mold wash. However, this amounts to coating the chill surface with a material of low thermal conductivity and ~educes the cooling effect Gn the casting as well as the effect to-ward improving the interior quality of the casting by means of -the chill.
Accordingly, the thickness of the mold wash is required to be as thin as possible, and in accordance with the inventors study, it should not exceed 5 mm.
Insofar as this limit is observed, it is permissible to coat the chill provided with the novel means for crack prevention in accordance with the present invention with a mould wash.
Embodiments of the invention are described hereinbelow.
Example 1 An example in which the chill of the invention is applied to the thick portion of a cast steel having thin and thick portions is described below. Fig. 8 illustrates the chill 11-1 and 11~2 applied in contact with a finished product 13, a sand 12, and surface of casted steel melt L immediately after pouring into a casting mould.
Product: Bowl type steel casting with a suppoxt lug.
Maximum thickness of bowl shape portion 200 mm Weight of poured steel 120 tons Inner radius of hemisphere1550 mm Size of support lug:
longitudinal length 400 mm depth of bottom 400 mm top 100 mm width 500 mm ~pplication of chill:
Scope of application: Side and bottom of support lug Thickness of chill : 100 mm Area of chill: 400 x 500 mm Surface pattern of chill:Orthogonally intersecting grooves Groove shape:
groove depth 10 mm groove width 20 mm groove edge curvature 10 mm groove interval 100 mm Steel Quality: SC49 (0.25%C, 0.40%Si, 0.95%Mn, and the balance Fe) \
~3~
The casting produced according -to this Example 1 had no cracks at all in -the surface skin and excellent internal quality of support lug was also confirmed by radiographic examination.
Example 2 A cast steel was manufactured by the method of the tion in which the whole surface of a core was applied with a chill provi.ded with conic pits on the apexes of a continuous triangular pattern (one of the embodiments of the invention). A cast steel product 13 was manufactured using a sand mould 12 provided with a chill 11 as shown in Fig. 9. In this figure L denotes the sur-face of the cast steel melt immediately being poured. Fig. 10 is a perspective view of surface of the chill 11.
Product: Arc-like cast steel with ribs (the thickness of the pro-duct 250 mm; poured weight 21.6 tons)Steel ~uality: SC49 (0.25%C, 0.40%Si, 0.94%Mn, and the balance Fe) Shape of casting: Total width 1935 mm, cylindrical surface width 1635 mm, rib thickness 150 mm, total height of product 1800 mm, inside radius of cylinder 1550 mm.
Application of chill:
Scope oE application : ~hole inside surface skin of cylindrical product Chill thickness : 500 mm Surface pattern of chill : Conic pits at apexes of con-tinuous triangular pattern Pit shape : 110 m~l in diameter, 45 mm deep Interval between pit centers: 183 mm `~
3~
Carrying out the method of the present invention clearly showed that dispersion of the stress on the surface skin of the casting in-to three or six directions is more effective than that of stress dispersion into two directions in the case of chill for the cylindrical core or the spherical core.
Scarfing and welding repair work due to surface cracks of castings was notably decreased and became substantially zero.
The hatched areas in Fig. 6 show the amount of repair work neces-sltated by surface cracks of the castings used direct chills fully to hemispherical cone.
Example 3 In this example a mould wash was used.
Product: Heavy cast steel plate (200 mm thick, 1800 mm wide and 2500 mm long) Steel quality: SC46 (0.2%C, 0.40%Si, 0.80%Mn, and the balance Fe) A single unit planar chill was applied to the bottom of the casting~
Chill: 300 mm thick, 1800 mm wide, and 2500 mm long Means or prevenking cracks: Orthogonally intersecting grooves: groove depth 25 mm, groove width 50 mm, groove interval 250 mm.
Under the above conditions, a mould wash was used as shown in Table 1.
Table 1 ¦MoId wa~ MthldkWaSh ¦ Cracks ~ ThunknleSyef ¦
3 mm No 200 mm NoNo 200 mm -14~
` :
As clearly indicated in Table 1, use of the mould wash did not cause cracking or any change in the thickness of the sound layer in so far as the layer of mould wash is thin enough.
As fully described in the foregoing, advanced chill of the present invention is provided with a groove lattice, a continu-ous triangular or hexagonal groove pattern or polygonal pattern constituted of conic, truncated cone-shaped, spherical or trun-cated sphere-shaped pits provided at the apexes of the polygons.
Advanced chill of present inven~ion i5 to application in extensive area of castings and to obtain good results to improve its inter-nal qualities without any anxiety for the crack formation on the surface skin of castings. As a result, the presen-t invention is eapable of greatly reducing the amoun-t of repair required by the surface skin of the casting and thus of saving the manufacturing eost as well as quick delivery of casting products~
In addition to the above, the present invention can be applied to a easting process using an outer mould, and it is under-stood that such an application is within the scope of the present inv~ntion.
.u
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of manufacturing a cast steel product in a sand mold to which a metallic chill is attached, characterized in that a) the metallic chill comprises a surface of predeter-mined length and width, b) said surface of the chill being provided with irregu-larities and c) said surface of the chill being positioned in contact with the cast product whereby the shrink stress on the casting steel surface is so dispersed in many directions that the absolute value of the composite stress is maintained at a value less than that of the ultimate strength of the cast steel.
2. The method as claimed in claim 1 wherein said chill sur-face measures 200 mm or more in length and 200 mm or more in width, and wherein said irregularities are in the form of a lattice con-stituted of orthogonally or triangularly intersecting and/or hexa-gonally arranged grooves, the side walls of each said groove making an angle with the surface of said chill of greater than 90° but less than 180°, and the corner formed by the intersection of each said side wall with said surface of said chill being rounded.
3. The method as claimed in claim 2 in which said angle is more than 120°, depth of said grooves is more than 5 mm, and the corners formed by the intersection of said side walls and said chill surfaces are rounded.
4. The method as claimed in claim 2 or 3 in which the radius of rounded corners formed by the intersection of said side walls and said chill surface is equal to or greater than the depth of said grooves.
5. The method as claimed in claim 2 in which the intervals between said grooves are not more than 20 times the groove depth, and the remaining surfaces of said chill after said grooves are cut are not more than 80% of the whole surface of said chill, respectively, in the case of an external side chill, and are not more than 12 times the groove depth and not more than 70% of the whole surface of said chill, respectively in the case of an inter-nal side chill and a bottom chill.
6. The method as claimed in claim 1 in which the chill is provided with surface irregularities in the form of conic or trun-cated cone-shaped pits formed at the apexes of consecutive pattern of triangles or hexagons.
7. The method as claimed in claim 6 in which the chill is provided with surface irregularities in the form of spherical or truncated sphere-shaped pits formed at the apexes of triangles or hexagons.
8. The method as claimed in claim 6 in which the surface of said chill is coated with a mould wash to a thickness of not more than 5 mm.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8326182A JPS6028578B2 (en) | 1982-05-19 | 1982-05-19 | Cast steel casting method |
| JP83261/82 | 1982-05-19 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1203663A true CA1203663A (en) | 1986-04-29 |
Family
ID=13797399
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000428436A Expired CA1203663A (en) | 1982-05-19 | 1983-05-18 | Method for manufacturing of steel casting |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0094688B1 (en) |
| JP (1) | JPS6028578B2 (en) |
| CA (1) | CA1203663A (en) |
| DE (1) | DE3366411D1 (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4436841B2 (en) | 2003-10-03 | 2010-03-24 | ノベリス・インコーポレイテッド | Casting belt surface texturing for continuous casting equipment |
| FR2961724B1 (en) * | 2010-06-24 | 2012-07-13 | Peugeot Citroen Automobiles Sa | MOLDING TANK IN LOST MODEL |
| JP6534379B2 (en) * | 2013-03-15 | 2019-06-26 | ユナイテッド テクノロジーズ コーポレイションＵｎｉｔｅｄ Ｔｅｃｈｎｏｌｏｇｉｅｓ Ｃｏｒｐｏｒａｔｉｏｎ | Cast parts with corner radius to suppress recrystallization |
| CN104070136B (en) * | 2014-06-19 | 2016-06-01 | 宁夏共享装备有限公司 | The direct-cooled chill of a kind of castings of gray cast iron and iron casting casting |
| DE102014221852A1 (en) * | 2014-10-27 | 2016-04-28 | Volkswagen Aktiengesellschaft | Casting tool with at least one cavity for producing at least one casting |
| CN105033176A (en) * | 2015-08-27 | 2015-11-11 | 哈尔滨电机厂有限责任公司 | Technology method for casting flexible tie bar through circular ring type steel casting in halving manner |
| DE102016103029B4 (en) * | 2016-02-22 | 2024-03-28 | Magna Pt B.V. & Co. Kg | Housing for a motor vehicle drive train and method for producing the same |
| CN107321952B (en) * | 2017-06-26 | 2018-12-25 | 哈尔滨工业大学 | A kind of spontaneous quenching method controlling large complicated aluminium copper deformation |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2018762A (en) * | 1932-04-18 | 1935-10-29 | Valley Mould & Iron Corp | Method and mold for eliminating ingot surface defects |
| GB539983A (en) * | 1940-03-26 | 1941-10-01 | Valley Mould & Iron Corp | Improvements in and relating to the casting of metal ingots, and ingot molds for use therein |
| US4250950A (en) * | 1978-11-03 | 1981-02-17 | Swiss Aluminium Ltd. | Mould with roughened surface for casting metals |
| US4212343A (en) * | 1979-03-16 | 1980-07-15 | Allied Chemical Corporation | Continuous casting method and apparatus for structurally defined metallic strips |
-
1982
- 1982-05-19 JP JP8326182A patent/JPS6028578B2/en not_active Expired
-
1983
- 1983-05-18 DE DE8383104913T patent/DE3366411D1/en not_active Expired
- 1983-05-18 CA CA000428436A patent/CA1203663A/en not_active Expired
- 1983-05-18 EP EP83104913A patent/EP0094688B1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6028578B2 (en) | 1985-07-05 |
| EP0094688A1 (en) | 1983-11-23 |
| EP0094688B1 (en) | 1986-09-24 |
| DE3366411D1 (en) | 1986-10-30 |
| JPS58202948A (en) | 1983-11-26 |
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