Classifications

• • 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
  • B22D27/13—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using pressure making use of gas pressure

Definitions

• This invention applies to manufacturing method of metal castings suitable for demanding applications, in particular as casting technique of metal tyre curing moulds.
• JP 200153353 is designed for pressure casting with cold chamber. It is advantageous for extremely accurate casting without need of any special very hard metal mould and without severe casting device requirements.
• Upper part of metal mould creating cavity for casting is made of material having 30%-porosity and so it is able to absorb released gasses during mould filling with hot metal. Applied pressure is imposed mechanically by piston through gating system and its amount is limited by porosity of mould's upper part.
• the method according to SU 999340 represents non-traditional technology based on mould cavity filling up with hot metal and subsequent pushing it to mould walls by pressure air supplied into central area of molten mass. Mould walls here are copied very well. However, inside hot metal craters caused by pressure medium remain and will need following work down. Most of all, the main disadvantage of this technology is its ability to produce hollow cast pieces only. Also the supply of compressed air through hollow bar can be a problem during the closing phase when hot metal solidifies and bar must get separated from cast piece.
• This technology is disadvantageous as it is designed just for hollow thin-walled cast pieces weighing only several kilograms. And primarily, it offers no solution of gas off-take from hot metal in mould, which is extremely important when mould walls provide barrier against gas penetration. When the mould is not vented then gas pockets arise in cast piece and repairs represent laborious and expensive task.
• Resistance melting furnace and resistance malleableizing furnace for casting mould are positioned in large pressure box. When such assembly should be applied to heavy weight cast pieces its purchase costs would be very high.
• the plaster complete-ring which provides inner tyre-tread-pattern part of casting in case of tyre curing mould, is made of plaster mixture having parameters dimensioned according to existing concept of casting technology. Plaster complete-ring providing such parameters functions as insulating material. Such feature extends the period of casting's solidification and supports growing of crystals in cast-piece volume. Its structure then becomes coarse-grained, which supports inter-crystal corrosion and worsens mechanical properties.
• the mould consists of base plate on which a vertically and possibly also horizontally segmented cladding is well fixed. From the top, there is riser plate provided with pressure-medium inlet well fixed to the cladding. All these mentioned components together limit the casting mould's cavity that is connected with gating system consisting of gating orifice, sprue, runner and filters. The whole gating system is put in container.
• GCAP gravitational casting with after-pressure
• the inlet 4 of pressure medium is open It serves for degasification of casting mould cavity 5
• the inlet orifice 7 is hermetically sealed and fixed Also individual parts of casting mould are fixedly connected and sealed
• the after-pressure of liquid metal begins by pressure medium supply
• the pressure medium is shut down no sooner than the liquid metal gets crystallized Pressure release phase takes here 70 seconds
• the realization equipment of this technology i e casting mould according to Fig 1 , consists of base plate / on which a vertically and also horizontally segmented steel cladding 2a, 2b is well fixed and to this from the top the riser plate 3 provided with pressure-medium inlet 4 is well fixed All these mentioned components together limit the casting mould's cavity 5 Casting mould cavity 5 is connected with gating system 6 consisting of gating orifice 7, sprue 8, runner 9 and filters 10 The whole gating system 6 is put in container 11
• Metal cast manufacturing procedure of tyre curing mould starts with gravitational pouring of aluminium melt where the casting mould cavity 5 is filled by liquid metal through gating system 6 Hot metal fills up the casting mould's cavity 5 (i e the room of future cast piece) up to the height of riser insulating filler 15 As soon as this height is achieved the hot metal pouring is stopped. Filling process takes 120 seconds. At pouring the inlet 4 of pressure medium (air) is open to draw off gasses arising at filling.
• pressure medium air
• Equipment i.e. casting mould visible in Fig. 2, similarly to previous example consists of base plate 1 on which a vertically segmented steel cladding 2 is well fixed and to this from the top riser plate 3 provided with pressure-medium inlet 4 is well fixed. These components limit the casting mould's cavity 5.
• Casting mould cavity 5 is connected with gating system 6 consisting of gating orifice 7, sprue S, runner 9 and filters 10.
• the assembly is put in container 11.
• Base plate 1 is in its central part provided with circle ring 12 around which the plaster complete-ring 13 is centred and fixed. This is from inside fixed to supporting circle ring 12 by hold-down filler 14.
• Riser plate 3 is from below in area of casting mould's cavity J provided with pressure-medium distributing board 16 on which further the inlet orifice 7 as well as pressure-medium inlet 4 is made. Described casting mould is made in following manner:
• plaster complete-ring 13 On steel base plate 1 provided with supporting circle ring 12 the plaster complete-ring 13 is positioned. Emerged cavity between plaster complete-ring 13 and supporting circle ring 12 is packed with mixture of foundry sand and binding as well as hardening agents. After hardening, such mixture will create the hold-down filler 14.
• the gating system 6 is fixed that is put in container 11 consisting of sprue 8, runner 9 and grooves with inset ceramic foam filters 10.
• the inner circle ring is provided with insulating filler 15.
• Distributing board 16 of pressure medium is centred and positioned on riser plate 3.
• Manufacturing method of gravitational metal casting with after-pressure according to the invention can be utilized mostly in all places with higher requirements for shape and dimensional accuracy of cast pieces together with their quality.
• Typical example of such application is production of moulds, foremost demanding manufacture of curing moulds for tyre industry.
• this manufacturing method of metal castings can be valuable also in some other less demanding applications.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Molds, Cores, And Manufacturing Methods Thereof (AREA)
• Moulds For Moulding Plastics Or The Like (AREA)

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Publications (1)

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Citations (4)

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• 2005
  • 2005-11-04 CZ CZ20050692A patent/CZ2005692A3/cs not_active IP Right Cessation
• 2006
  • 2006-11-06 WO PCT/CZ2006/000079 patent/WO2007051434A1/en not_active Ceased

Patent Citations (4)

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