EP0050602A1 - Procédé de coulée de matériaux liquides, présentant une plage de solidification composée d'une expansion suivie d'une contraction - Google Patents

Procédé de coulée de matériaux liquides, présentant une plage de solidification composée d'une expansion suivie d'une contraction Download PDF

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Publication number
EP0050602A1
EP0050602A1 EP81850179A EP81850179A EP0050602A1 EP 0050602 A1 EP0050602 A1 EP 0050602A1 EP 81850179 A EP81850179 A EP 81850179A EP 81850179 A EP81850179 A EP 81850179A EP 0050602 A1 EP0050602 A1 EP 0050602A1
Authority
EP
European Patent Office
Prior art keywords
melt
mould
sprue
contraction
expansion
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.)
Withdrawn
Application number
EP81850179A
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German (de)
English (en)
Inventor
Bertil Harry Gerhard Svensson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Saab Kockums AB
Original Assignee
Kockums AB
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Kockums AB filed Critical Kockums AB
Publication of EP0050602A1 publication Critical patent/EP0050602A1/fr
Withdrawn legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
    • B22D27/09—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using pressure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D23/00—Casting processes not provided for in groups B22D1/00 - B22D21/00
    • B22D23/02—Top casting

Definitions

  • the present invention relates to the casting of melts of materials, the course of solidification of which comprises an expansion followed by a contraction, for example grey iron alloys or nodular iron.
  • the changes in volume which materials of the said kind undergo during cooling of a melt of the material follow a common pattern to a greater or lesser extent. If the initial temperature of the melt is sufficiently high, a contraction of the material in the liquid phase is first obtained during cooling. Then an expansion follows, after which a secondary contraction occurs down to the specific volume of the material in the solidified state. Casting of melts of materials of the said kind takes place in certain cases under such temperature conditions that during the course of the cooling, the casting melt undergoes both said initial contraction and the following expansion and secondary contraction. In other cases, the casting takes place with a temperature of the melt selected so that only an expansion followed by a contraction is obtained during the course of the cooling and sotidification. The changes in volume which occur during the course of solidification make it necessary, in both cases, to take precautions to prevent the formation of cavities, so-called pipes in the finished casting.
  • the method most commonly used to prevent the formation of cavities in the castings caused by the shrinkage during the course of solidification is to form the casting system with a feed system, that is to say to connect the mould cavity in the mould to one or more feeders from which melt is supplied at the rate and in the amount which is required to compensate for contraction which occurs during the course of solidification.
  • Forming the casting system with a feed system involves a complication.
  • the design and placing of the feeders requires careful consideration; the dimensions of the mould increase; output is lower and cleaning and after-treatment of the casting involve more labour.
  • the expansion of the melt during the course of the solidification is used to compensate for the following contraction.
  • this is achieved by dimensioning the inlet to the mould cavity so that this solidifies at a moment selected so that the expansion of the melt during the course of solidification takes place in the mould cavity closed by means of the solidified inlet.
  • the expansion leads to an increase in pressure which causes a resilient compression of the mould walls. Since the deformation of the mould walls lies within the resilient range, the mould tends to return to its original shape, which means that the casting is also compressed, which prevents the formation of cavities in the casting.
  • the method means that the need for feeders is completely eliminated, in other cases that feeders are required only to a limited extent.
  • the method described above is practised in some different modifications, three of which will be discussed in more detail below.
  • One form of carrying out the known method is practised with castings with thin material and where the initial temperature of the melt is so high that the course of the cooling begins with a contraction in the melt.
  • the inlet to the mould cavity is dimensioned so that the inlet is caused to solidify first at such a temperature of the melt that its initial contraction ceases and the course of the expansion begins during the continued solidification. This means that a certain feed from the casting system takes place during the initial stage of the course of casting to compensate for the initial contraction of the melt.
  • a second form of carrying out the known method is practised with larger castings and where the initial temperature of the melt is selected so that continued cooling of the melt takes place with expansion followed by a contraction.
  • the inlet to the mould cavity is dimensioned so that the inlet solidifies or "freezes" as soon as the mould cavity is filled with melt. The continued course of the solidification thus begins with an expansion followed by a contraction.
  • a third form of execution of the known method is practised when casting in moulds where the mould sand is only able to take up a limited increase in pressure through resilient compression of the mould walls.
  • the inlet to the mould cavity is dimensioned so that a certain further feeding of melt to the casting system takes place during the expansion phase of the melt, the inlet being caused to solidify at such a temperature that the continued expansion during the course of the solidification leads to such an increase in pressure in the mould cavity that the following compression of the mould walls lies within the elastic range.
  • the methods are based on an accurate and correct dimensioning of the inlet to the mould cavity so that the melt in the inlet solidifies or "freezes" at the right moment.
  • the inlet determines the dimensions for the whole casting system, since the dimensions of the sprue and runner must be in a certain relationship to the area of the inlet. This is an important disadvantage of the methods in question and restricts the possibilities for the optimum dimensioning of the casting system. It is actually a desideratum to be able to dimension the casting system so that the most rapid filling possible of the'mould cavity is obtained.
  • a further disadvantage of the said known method is the difficulty of determining precisely, by dimensioning of the inlet, the moment at which the solidification should take place. Even if the inlet is dimensioned correctly, variations in the mould sand and varying temperature conditions in different parts of the mould may lead to unwanted variations in the moment of solidification for the various inlets.
  • the present invention which also utilizes the expansion during the course of solidification of the material melt to compensate for the following contraction, has as its object to indicate a method whereby the above-mentioned disadvantages of the known method are avoided and which thus permits full freedom with regard to the dimensioning of the casting system, renders possible the use of fewer inlets and permits a precise determination of the moment at which blocking of the casting system shall take place to utilize the expansion of the melt for the purpose of compensating for shrinkage.
  • the invention is intended to be used during the casting of melts of materials which, during the course of solidification, undergo an expansion followed by a contraction, for example grey iron alloys, nodular iron, etc.
  • the molten material is supplied to the mould cavity in the mould via one or more sprues with following inlets in direct communication with the mould cavity.
  • the connection of the mould cavity to the environment is then blocked at a moment selected so that at least some of said expansion and following contraction takes place in the space closed by said blocking.
  • the blocking is brought about by cooling of a portion of the sprue so that a solidified plug of material is formed in the sprue before the material present in the inlet solidifies.
  • this cooling is brought about by inserting a plug of sand in the sprue.
  • the melt immediately begins to solidify adjacent to the sand plug so that a solidified plug of material, closing the sprue, is quickly formed.
  • the course of solidification and formation of the plug of material closing the sprue are accelerated by forming the plug of sand with an end narrowing in a taper.
  • the casting system is thus separated from the environment and the increase in pressure which is obtained on expansion of the melt during the course of solidification is caused to act in the whole casting system, including the mould cavity.
  • the method according to the invention differs from the method previously known.
  • the initial temperature of which is so high that the course of cooling begins with a contraction it is necessary to wait before inserting the plug of sand in the sprue until the temperature of the melt, after filling of the mould cavity, has sunk to the value at which the initial contraction ceases. The moment for this can easily be determined by observing the level of the melt in the pouring gate. Because of the contraction of the melt, the level of the melt in the pouring gate drops even after the mould cavity is filled. When the temperature of the melt has dropped to the value at which the initial contraction ceases, the level of the melt in the pouring gate ceases to drop. The correct moment for inserting the plug of sand in the sprue is therefore, in this case, the moment when the level of the melt in the pouring gate ceases to drop.
  • the initial temperature of which is selected so that cooling of the melt begins with an expansion the plug of sand must be inserted in the sprue as soon as the mould cavity is filled with melt. This moment can also be determined by observing the level of the melt in the pouring gate. When the mould cavity is filled with melt, the sinking of the level in the pouring gate ceases, and the plug should be inserted in the sprue.
  • the correct moment for inserting the plug of sand in the sprue can be determined by observing the level of the melt in the pouring gate.
  • a certain after-feed of melt to the casting system should take place during the expansion of the melt during solidification.
  • the after-feed is expressed by a rise in the level of the melt in the pouring gate.
  • the magnitude of the rise in level at which the plug of sand should be inserted in the sprue must be determined experimentally.
  • a vertical section is shown through a mould 1, with a mould cavity 2 and a core 3 inserted in this.
  • the casting system-4 comprises a sprue 5, a runner 6 and a number of inlets 7 in direct communication with the mould cavity 2.
  • the sprue 5 is fed with melt through a pouring basin 8 situated above the mould 1.
  • a plug 9 of sand round the tapered end of which a solidified plug 10 of material is indicated.
  • the mouth of the sprue 5 is covered by a stopper not shown in the figure.
  • the pouring basin 8 is filled with melt.
  • the stopper is removed, whereupon the melt flows via the sprue 5, the runner 6 and the inlet 7 into the mould cavity 2 to fill this. Parallel with this, the pouring basin 8 is filled with the rest of the melt.
  • the plug of sand 9 is inserted in the mouth of the sprue 5 as soon as the filling of the mould cavity 2 is terminated. This leads practically immediately to a solidified plug of material 10 being formed round the tapered end of the plug of sand 9. Continued expansion during the course of solidification thus leads to the increase in pressure in the space closed by means of the plug of material, leading to the elastic compression of the mould walls which prevents the formation of cavities in the casting during the continued solidification.
  • the cooling of a portion of the sprue, necessary according to the invention is brought about by inserting a plug of sand in the mouth of the sprue.
  • the fact that the material sand is selected as a material for the plug in the preferred form of embodiment is because mould sand is easily available in foundries.
  • the plug may, however, equally well consist of another material, for example graphite, brick, ceramic or even fibrous material or metal material. The selection of the material for the plug thus has no decisive importance. What is important is the rapid cooling of the melt to solidification which is obtained close to the plug inserted in the sprue.
  • the plug may appropriately be shaped with a cross-section decreasing in the direction of insertion, for example tapered, so that a large cooling surface is obtained in relation to the amount of material melt adjacent to the plug.
  • the necessary formation of a solidified plug of material of the melt can be brought about by adding an additive which accelerates the solidification to the sprue, for
  • the casting is carried out using a pouring basin disposed on the mould. This is not, however, a prerequisite for application of the method according to the invention which can equally well be used during casting without a pouring basin.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)
EP81850179A 1980-10-08 1981-10-07 Procédé de coulée de matériaux liquides, présentant une plage de solidification composée d'une expansion suivie d'une contraction Withdrawn EP0050602A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8007034 1980-10-08
SE8007034A SE423871B (sv) 1980-10-08 1980-10-08 Sett vid gjutning av sadana materialsmeltor, vars stelningsforlopp innefattar en expansion atfoljd av en kontraktion

Publications (1)

Publication Number Publication Date
EP0050602A1 true EP0050602A1 (fr) 1982-04-28

Family

ID=20341930

Family Applications (2)

Application Number Title Priority Date Filing Date
EP81902588A Withdrawn EP0062041A1 (fr) 1980-10-08 1981-09-24 Procede de coulee de materiaux fondus, dont la solidification comprend une expansion suivie d'une contraction
EP81850179A Withdrawn EP0050602A1 (fr) 1980-10-08 1981-10-07 Procédé de coulée de matériaux liquides, présentant une plage de solidification composée d'une expansion suivie d'une contraction

Family Applications Before (1)

Application Number Title Priority Date Filing Date
EP81902588A Withdrawn EP0062041A1 (fr) 1980-10-08 1981-09-24 Procede de coulee de materiaux fondus, dont la solidification comprend une expansion suivie d'une contraction

Country Status (3)

Country Link
EP (2) EP0062041A1 (fr)
SE (1) SE423871B (fr)
WO (1) WO1982001143A1 (fr)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB909538A (en) * 1960-09-07 1962-10-31 Richard Thomas And Baldwins Lt Improvements relating to the production of rimmed steel
FR2081888A1 (fr) * 1970-03-12 1971-12-10 Inland Steel Co
US3628598A (en) * 1968-10-23 1971-12-21 Modern Equipment Co Casting molds
US3771588A (en) * 1971-07-26 1973-11-13 Logic Systems Corp Ltd Direct melt injection casting centre
FR2384568A1 (fr) * 1977-03-21 1978-10-20 Pont A Mousson Moule de coulee sous basse pression
US4133370A (en) * 1974-12-24 1979-01-09 Pont-A-Mousson S.A. Method and apparatus for low-pressure casting in a sand mould

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2646060A1 (de) * 1976-10-13 1978-04-20 Friedhelm Prof Dr Ing Kahn Verfahren und vorrichtungen zur steuerung des waermehaushalts von giessformen

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB909538A (en) * 1960-09-07 1962-10-31 Richard Thomas And Baldwins Lt Improvements relating to the production of rimmed steel
US3628598A (en) * 1968-10-23 1971-12-21 Modern Equipment Co Casting molds
FR2081888A1 (fr) * 1970-03-12 1971-12-10 Inland Steel Co
US3771588A (en) * 1971-07-26 1973-11-13 Logic Systems Corp Ltd Direct melt injection casting centre
US4133370A (en) * 1974-12-24 1979-01-09 Pont-A-Mousson S.A. Method and apparatus for low-pressure casting in a sand mould
FR2384568A1 (fr) * 1977-03-21 1978-10-20 Pont A Mousson Moule de coulee sous basse pression

Also Published As

Publication number Publication date
SE8007034L (sv) 1982-04-09
EP0062041A1 (fr) 1982-10-13
WO1982001143A1 (fr) 1982-04-15
SE423871B (sv) 1982-06-14

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PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

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Effective date: 19830401

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Inventor name: SVENSSON, BERTIL HARRY GERHARD