JP4563639B2 - Method and apparatus for producing hollow metal castings - Google Patents

Description

[0001]
SUMMARY OF THE INVENTION
The invention relates to a method and a device according to the preamble of claim 1.
[0002]
For applications where they are placed directly into the mold or are further heat treated by rolling or forging, a hollow casting or ingot is required. A useful case in the case of non-alloy or low-alloy steels is the case where a cast body is not produced in advance, a solid block is cast and perforated at a high temperature and then subjected to another high temperature forming process.
[0003]
However, this processing mode is almost an option when processing higher alloy steels such as austenite, ferrite, martensitic corrosion, and heat resistant steel, and when processing tool steels of significantly different composition. No. The reason is that they do not have the proper hot forming capability for hot drilling methods. This is even less likely when processing Ni-based and Co-based alloys that are more difficult to work with. In order to produce hollow bodies from difficult alloys and steels, it is often necessary to drill solid casting blocks or to make them hollow beforehand by machining, only at this time subjecting them to higher temperatures be able to. However, this processing mode is expensive as high alloy steel, and the alloy can be processed only by machining with difficulty. In many cases, it is necessary to perform machining after heat treatment.
[0004]
In order to avoid the aforementioned difficulties, many processes in the past have used another process, especially high alloy hollow bodies and hollow blocks intended for forging, using electroslag remelting methods with self-consuming electrodes. It has been proposed to manufacture. This is because the electroslag remelting method can produce high quality hollow blocks.
[0005]
Therefore, the literature describes a method for producing a hollow block using an electroslag remelting method. The method involves inserting a water-cooled conical rod or mandrel from above into a short, circular cross-section water-cooled chill mold in a concentric relationship to form an annular gap between the chill mold and the mandrel. Including. In order to produce a hollow block, rod-shaped wear electrodes are arranged concentrically in an annular gap, which causes a melting current to flow into the slug bath in the gap and out of the melted bath and bottom plate. The electrodes are melted by Joule heat generated when current flows through the slag bath. Liquid metal falling downwards is collected in the annular gap and is continuously cured to form a hollow block. Using this method, a hollow block of satisfactory quality can be produced. However, the cost of manufacturing and preparing long and thin rod-like electrodes is high and the concentric arrangement within the annular gap is associated with considerable difficulty, especially when manufacturing hollow blocks with thin wall thickness. Therefore, a so-called T-type chill mold that is wide in a funnel shape in the slag bath is effective. This is because this mold can use a consumable electrode that is thicker than the wall thickness of the hollow block.
[0006]
In another known method, a mandrel arranged concentrically in a water-cooled chill mold moves from below to above through the opening in the bottom plate so as to form a block on the bottom plate. In this case, the upper end of the mandrel protrudes into the slag bath, but always remains completely covered by the bath. In this way, large electrodes can be dissolved on the mandrels in a slag bath. The metal melted from the electrode falls on the curved surface of the mandrel and then flows into the annular gap between the chill mold and the mandrel to form a hollow block again. In this method, the manufacture of the consumable electrode is inherently simple, but when manufacturing relatively long blocks, it becomes difficult to set the mandrel concentric with the chill mold. This increases the eccentricity of the hole. Furthermore, poor surface morphology of the holes often causes difficulties with other processes. To avoid them, it is often necessary to machine the internal holes and then perform a hot molding operation.
[0007]
Common to both of the foregoing methods is that it causes a dissolution current to melt the wear electrode into the slag bath and also monitors the dissolution rate necessary to obtain the desired cured structure. It is necessary to adjust the dissolution current by the method. However, supplying current or power regulated in that way to the slag bus does not necessarily result in a slag bath temperature that produces a good surface for the block and outer surface in the hole. It is therefore almost impossible to produce a hollow block or cast body with both a desired cast structure and a good surface using these methods.
[0008]
In view of this state of the art, the inventor aimed to eliminate the aforementioned drawbacks.
[0009]
The object is achieved by the subject matter of the independent claims, while the dependent claims describe advantageous developments. The scope of the present invention includes all combinations of at least two of the forms disclosed in the detailed description, drawings and / or claims.
[0010]
The method according to the present invention uses the electroslag melting or casting method-utilizing the principle of an essentially short, conductive, water-cooled chill mold-to hollow cast metals, especially steel, Ni-based and Co-based alloys. Includes a method of manufacturing a body. In this case, the hollow casting is disposed in the opening of the chill mold and is formed in a gap generated between the chill mold and the water-cooled mandrel. The metal level (upper surface) is covered by a slag bath, which is energized, through a plurality of conductive elements incorporated into the chill mold walls and / or water cooled mandrels and not directly water cooled. Heated by direct current or alternating current flowing into the slag bus. This current is taken through the chill mold and mandrel conductive elements that are not used to introduce the current and / or the casting. In this case, at least one of the conductive elements is electrically insulated from other parts of the water-cooled chill mold and mandrel.
[0011]
In order to effectively carry out the method according to the invention, it is preferred that the conductive elements are arranged so as to completely enter the area of the slag bus and are covered with the slag bus. In order to keep the slag level (upper surface) always in the region of the conductive element, the hollow block formed in the annular gap between the chill mold and the mandrel can be withdrawn downwards, or in the fixed block state -Either the chill mold is raised with the mandrel when the level rises.
[0012]
Preferably, the hollow casting is drawn down from the casting gap between the chill mold and mandrel at a rate that maintains the casting level at a substantially constant level relative to the conductive element.
[0013]
When using a bottom plate whose distance to the chill mold changes during casting, the bottom plate and the hollow cast body manufactured on the bottom plate are fixed, and the chill mold and mandrel are almost constant in level with the conductive element. Increase at a speed that maintains In this case, the chill mold and mandrel are preferably raised at a metal level rise rate.
[0014]
According to the present invention, various structures can be employed for supplying and collecting current. The supply of melt current to the slag bath is performed by conductive elements on the chill mold wall, which elements need to be electrically isolated from the water-cooled portion of the chill mold that forms the outer surface of the hollow block. Current recovery is performed by the conductive elements of the water-cooled mandrel and / or the formed hollow blocks and bottom plate. However, if the conductive element is electrically insulated from the other water-cooled parts of the mandrel, the current supply can be realized by the mandrel conductive element. In this case, current recovery is performed by the conductive elements of the chill mold and / or the block and bottom plate. In principle—when the conductive element is mounted in an electrically insulated state—current supply can be achieved by connecting a chill mold and a mandrel. In this case, the recovery of the total current is realized by the block and the bottom plate .
[0015]
The above-mentioned conventional drawbacks are effective using the method according to the invention described herein, regardless of whether the basic material of the hollow block is in a liquid state or a solid state in the form of a rod, turning or chip, or a particulate material. Can be avoided.
[0016]
The scope of the present invention includes an apparatus for performing the above-described method comprising a short, conductive, water-cooled chill mold. The chill mold is water-cooled to form a void for hollow casting together with a mandrel disposed in the opening of the chill mold, and has a bottom plate, and the bottom plate can change the distance between the chill mold and the mandrel. It is arranged in association with. The chill mold and the bottom plate, the conductive element provided in the chill mold and the mandrel are connected to a current source by a high-current electric wire having a switch.
[0017]
Further advantages, features, and details of the present invention will become apparent from the following description of the preferred embodiment, by way of example and a single drawing showing a longitudinal section of the entire casting apparatus with a chill mold.
[0018]
Detailed Description of Preferred Embodiments
A rod or mandrel 14 enters the water-cooled chill mold 10 having an annular hollow body 12 having an inner diameter d from above. The rod or mandrel is hollow and tapered along the casting direction, and the outer shape e is set so as to form an annular gap having a gap width b between the mandrel wall 14 and the chill mold. .
[0019]
Each of the annular insulating elements 20 and 22 rests on both the upper end surface 13 of the hollow body 12 and the surface 16 on the same plane as the upper end surface 13 of the hollow mandrel 14, while having an annular structure. Conductive elements 24 and 26 rest on each of the insulating elements 20 and 22. The conductive element is separated from the upper water-cooled hollow ring 28 by the upper insulating elements 20a and 22a and from the hollow block 30 that matches the outer shape of the mandrel 14 in plan view. A centering device 32 that secures the placement of the mandrel 14 within the chill mold 10 is engaged over the hollow ring 28 and the hollow block 30.
[0020]
The hollow ring 28 and the hollow block 30 are water-cooled, and similarly, the cylinder wall 34 of the bottom plate 36 that can move downward along the casting direction X is also water-cooled. The bottom plate 36 of the overall height h has an outer diameter f slightly smaller than the inner diameter d of the chill mold 10, so that the bottom plate 36 is lowered into the opening of the chill mold 10 having the height i or into the internal space 11 at the start of installation. Until the upper end 38 of the bottom plate 36 is disposed immediately below the lower insulating elements 20 and 22.
[0021]
On the other hand, the inner diameter n of the bottom plate 36 or its cylinder wall 34 is slightly larger than the outer shape e of the mandrel 14, so that the mandrel 14 protrudes into the inner space 40 of the bottom plate when the bottom plate 36 is raised, and the inner side of the bottom plate 36. A seal is formed at the upper end 42.
[0022]
When the slag is introduced into the annular casting cavity 18 with the bottom plate 36 raised as described above (not shown), the slag bus 44 is formed in the region of the conductive elements 24, 26, and the circuit Depending on the selection, current flows. As another result, for example, the liquid metal 46 can be cast in the casting gap 18 between the chill mold 10 and the mandrel 14 at a casting speed that ensures a proper cured structure in the hollow body 48 that is the manufactured casting.
[0023]
Reference numeral 50 represents a direct current or alternating current source, and one of the current sources is connected to each of the conductive elements 24 and 26 of the chill mold 10 and the mandrel 14 through the switches 56 and 60 by the large current wires 52 and 54. The other is connected to the bottom plate 36 by a large current switch. The switch allows a series of switch options by alternately closing the corresponding switch contacts 57, 58; 61, 62; 65, 66. The following details relate to the use of direct current (those related to alternating current are added in parentheses to additional variants 1-3 and 5-7).
[0024]
Variant 1:
Supplied by mandrel 14 and collected by chill mold 10.
Contacts 62 and 57 are closed.
Variant 2:
Supplied by mandrel 14 and collected by bottom plate 36.
Contacts 62 and 65 are closed.
Variant 3:
Supplied by mandrel 14 and collected by chill mold 10 and bottom plate 36.
Contacts 62, 65 and 57 are closed.
Variant 4:
Supplied by chill mold 10 and collected by mandrel 14.
Contacts 58 and 61 are closed (according to variant 1 for alternating current).
Variant 5:
Supplied by chill mold 10 and collected by bottom plate 36.
Contacts 58 and 65 are closed.
Variant 6:
Supplied by chill mold 10 and collected by mandrel 14 and bottom plate 36.
Contacts 58, 65, and 61 are closed.
Variant 7:
Supplied by chill mold 10 and mandrel 14 and collected by bottom plate 36.
Contacts 58, 62, and 65 are closed.
Variant 8:
Supplied by bottom plate 36 and collected by mandrel 14.
Contacts 66 and 61 are closed (according to variant 2 for alternating current).
Variant 9:
Supplied by the bottom plate 36 and collected by the chill mold 10.
Contacts 66 and 57 are closed (according to variant 5 for alternating current).
Variant 10:
Supplied by bottom plate 36, collected by mandrel 14 and chill mold 10.
Contacts 66, 57 and 61 are closed (according to variant 7 for alternating current).
Variant 11:
Supplied by bottom plate 36 and mandrel 14 and collected by chill mold 10.
Contacts 66, 62, and 57 are closed (according to variant 6 for alternating current).
Variant 12:
Supplied by the bottom plate 36 and the chill mold 10, and collected by the mandrel 14.
Contacts 66, 58 and 61 are closed (according to variant 3 for alternating current).
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an entire casting apparatus having a chill mold according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Chill mold, 14 ... Mandrel, 18 ... Ring | gap, 24, 26 ... Conductive element, 36 ... Bottom plate, 44 ... Slug bath, 48 ... Cast body, 50 ... Current source, 52, 54 ... High current electric wire, 56 , 60, 64 ... switches

Claims (13)

A method for producing a hollow metal casting using a short conductive water-cooled chill mold and a chill mold that forms a casting void for hollow casting together with a mandrel that is placed in an opening of the chill mold and is water-cooled In
Introducing direct current or alternating current into a slag bus located above the metal that conducts current through a conductive element that is incorporated into the mandrel in an electrically insulated state and is not directly water cooled,
The slag bath is heated by the current,
The current is recovered through an electrically Denmoto element incorporated in the wall of the chill mold in an electrically insulated state,
A method characterized by that. A method for producing a hollow metal casting using a short conductive water-cooled chill mold and a chill mold that forms a casting void for hollow casting together with a mandrel that is placed in an opening of the chill mold and is water-cooled In
Conducts current through the electrically in an insulated state are incorporated into the wall of the chill mold directly water-cooled non conductive element, the slag-bath located on the upper side of the metal, by introducing direct or alternating current,
The slag bath is heated by the current,
Collecting the current through a conductive element incorporated in the mandrel in an electrically insulating state ;
A method characterized by that. The method according to claim 1 or 2, wherein the casting is performed using a bottom plate capable of changing a distance to the chill mold.
The bottom plate and the hollow cast body formed thereon are fixed, and the chill mold and mandrel are raised at a speed at which the height of the upper surface of the hollow cast body maintains a substantially constant level with respect to the conductive element. A method characterized in that A short conductive water-cooled chill mold that uses a chill mold that forms a casting gap for hollow casting with a mandrel that is placed in the opening of the chill mold and is water-cooled, and a bottom plate that can change the distance to the chill mold. In a method for producing a metal hollow casting,
  The bottom plate and the hollow casting formed thereon are fixed, and the chill mold and mandrel are raised at a speed at which the height of the upper surface of the hollow casting maintains a substantially constant level with respect to the conductive element. Let
  DC or AC current is introduced into a slag bus located above the metal that conducts current through a conductive element that is incorporated into the mandrel in an electrically insulated state and is not directly water-cooled;
  The slag bath is heated by the current,
  Collecting the current through the hollow casting to be produced and the bottom plate;
  A method characterized by that. In claim 4, the recovery of the current source, further wherein the more be made to the conductive element of the chill mold. A short conductive water-cooled chill mold that uses a chill mold that forms a casting gap for hollow casting together with a water-cooled mandrel that is placed in the opening of the chill mold, and a bottom plate that can change the distance to the chill mold. In a method for producing a hollow metal casting,
The bottom plate and the hollow cast body formed thereon are fixed, and the chill mold and mandrel are raised at a speed at which the height of the upper surface of the hollow cast body maintains a substantially constant level with respect to the conductive element. Let
Said bottom plate and then through the hollow cast body produced to conduct current, the slag-bath located on the upper side of the metal, by introducing direct or alternating current,
The slag bath is heated by the current,
Collecting the current through a mandrel conductive element incorporated in the mandrel in an electrically insulated state ;
A method characterized by that. In claim 6, the supply of dissolution current to the slag bath is further a method which is characterized in that more made to the conductive element of the chill mold. 8. The method according to any one of claims 1 to 7 , wherein the metal comprises steel and a Ni-based or Co-based alloy. In any one of claims 1 8, wherein said conductive elements are incorporated into the wall of the chill mold are annular shape, the inner circumferential surface of the conductive element completely surrounds the slag bath A method characterized by. The conductive element incorporated in the mandrel according to any one of claims 1 to 9 , wherein the conductive element has a ring shape, and an outer peripheral surface of the conductive element is completely surrounded by the slug bus. how to. The hollow casting body according to any one of claims 1 to 10 , wherein the hollow casting body is below a casting gap between a chill mold and a mandrel, and the height of the upper surface of the hollow casting body is substantially constant with respect to the conductive element. A method characterized by being pulled at a maintaining speed. 12. The method according to claim 1 , wherein the polarity of the direct current can be changed when the direct current is used. An apparatus for performing the method according to any one of claims 1 to 12 , comprising:
A short conductive water-cooled chill mold (10);
A mandrel (14) that is placed in the opening of this chill mold and is water cooled;
The chill mold conductive element incorporated into (10) in an electrically insulating state (24), and a built-in conductive element with an electrically insulating state (2 6) to the mandrel (14),
The chill mold (10) forms a casting gap (18) for the hollow cast body (48) together with the mandrel (14), and is set in association with the chill mold (10) so that the distance from the chill mold can be varied. A bottom plate (36) for fixing the hollow casting (48) thereon ,
The bottom plate and both conductive elements (24, 26) are connected to a current source (50) by a high current wire (52, 54) having a switch (64, 56, 60),
A device characterized by that.

Images