Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D21/00—Casting non-ferrous metals or metallic compounds so far as their metallurgical properties are of importance for the casting procedure; Selection of compositions therefor
  • B22D21/02—Casting exceedingly oxidisable non-ferrous metals, e.g. in inert atmosphere
  • B22D21/04—Casting aluminium or magnesium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D21/00—Casting non-ferrous metals or metallic compounds so far as their metallurgical properties are of importance for the casting procedure; Selection of compositions therefor
  • B22D21/002—Castings of light metals
  • B22D21/007—Castings of light metals with low melting point, e.g. Al 659 degrees C, Mg 650 degrees C
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C9/00—Moulds or cores; Moulding processes
  • B22C9/06—Permanent moulds for shaped castings

Definitions

• the present invention relates to the field of metallurgy in the foundry sector and, more particularly, to a shell molding process for aluminum-based parts in which the duration of stay of the metal in the shell is optimized.
• the founder faces the problem of knowing how long he must allow the metal to remain in the shell. Indeed, having the concern of maximum efficiency, he knows that, if he opens the shell with a certain delay after the part has reached a suitable solidification state, he will lose in production capacity of his installation, on the other hand, if it opens the shell too early, it may be that the part is not fully solidified, or, at least, has not yet acquired sufficient thermal and mechanical stability, in which case it will present defects which may require its scum.
• this duration depends on the type of shell used, its coating, its cooling mode: natural or forced, the composition and the temperature of the cast alloy, but these various parameters being fixed, it appears important to find a means of determining the optimum duration of stay of the metal in the shell applicable to the serial casting of pieces, this means being, subsequently, extrapolable to installations in which certain parameters have changed by means of a few corrections.
• Still other methods combine the two concepts: that of the constant residence time as long as the temperature of the shell at the time of filling is not stabilized, then that of the release temperature when the shell is in operation.
• the initial temperature of the shell makes it possible to better understand the real duration of solidification because, in fact, it is very certain that, if one sinks in a shell at low temperature, the duration of solidification will be less great than if you sink into a shell at high temperature.
• the initial temperature can we better appreciate the time it will take to ensure solidification and, therefore, optimally determine the duration of stay of the metal in the shell. It is still necessary to establish the relation existing between initial temperature and duration of solidification. This relation was established experimentally in the following way: Several series of test pieces were poured by placing in the center of the calibrated part a thermocouple connected to a temperature recorder.
• thermocouples Two other thermocouples were placed in the yokes of the shell at the center of the test piece and 2 mm from the inner wall. It was thus possible to record both the initial temperature of the shell and the solidification time, the latter ending when a change in slope was observed in the temperature-time curve. But, as it cannot be removed from the mold at the end of solidification of the part, since it is necessary to wait until the monkfish are sufficiently resistant to be able to support the parts, a correction coefficient has been applied to the solidification period, that is to say that the length of stay selected is equal to k times the duration of solidification and where k is between 1 and 1.5 depending on the composition of the alloy and the type of part produced.
• the method according to the invention is characterized in that the duration of stay of the metal in the shell is established by measuring the temperature of the latter at the time when we are going to start casting then comparison of this value with the table temperature-duration correlation.
• the optimized process described above makes it possible to shorten this period of temperature rise, but it can be further accelerated based on the fact that, when the optimum stay time is applied with a relatively cold shell, the moment of demolding in tersili while the temperature of the shell is still increasing unlike a shell in regime where it is decreasing. If therefore we want to accelerate the rise in temperature, we must try to recover all of the heat provided by the metal and, therefore, only turn out when the temperature of the shell has reached its maximum.
• the method is also characterized in that, during the periods of starting or restarting where the temperature of the shell is relatively low at the time when the casting is about to start, the optimum duration of stay is extended until the shell temperature has reached its maximum.
• the temperature of the shell can be limited in two ways: either by extending the closing time of the shell after casting, or by prohibiting its closing after demolding as long as the temperature has not dropped below a limit value which depends on the type of alloy used.
• control device essentially comprising:
• - a card comprising a microprocessor and peripheral organs
• This assembly is linked by its converter with the thermocouples placed on the shell, and by its control box with the solenoid valves of the cylinders.
• the casting of the thirteen pieces lasted 13.5 minutes.
• the release temperature has been limited to
• the invention finds its application, in particular in the aluminum industry, whenever it is desired to manufacture by shell molding, either by gravity, or under low pressure, or under pressure, a series of parts with a minimum of waste and increased production capacity.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Mold Materials And Core Materials (AREA)
• Investigating Or Analyzing Materials Using Thermal Means (AREA)
• Analysing Materials By The Use Of Radiation (AREA)
• Measuring Temperature Or Quantity Of Heat (AREA)
• Catalysts (AREA)
• Molds, Cores, And Manufacturing Methods Thereof (AREA)
• Superconductors And Manufacturing Methods Therefor (AREA)
• Powder Metallurgy (AREA)
• Table Devices Or Equipment (AREA)
• Glass Compositions (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=9272218

Family Applications (1)

Country Status (17)

• 1982
  • 1982-03-15 FR FR8204785A patent/FR2523004A1/fr active Granted
• 1983
  • 1983-03-08 AR AR292320A patent/AR231703A1/es active
  • 1983-03-10 IT IT19995/83A patent/IT1161104B/it active
  • 1983-03-10 GR GR70759A patent/GR77949B/el unknown
  • 1983-03-11 WO PCT/FR1983/000049 patent/WO1983003213A1/en not_active Application Discontinuation
  • 1983-03-11 JP JP58500959A patent/JPS59500167A/ja active Pending
  • 1983-03-11 AU AU13379/83A patent/AU558067B2/en not_active Ceased
  • 1983-03-11 PT PT76376A patent/PT76376A/pt unknown
  • 1983-03-11 BR BR8306480A patent/BR8306480A/pt unknown
  • 1983-03-11 EP EP83900933A patent/EP0103602A1/fr not_active Withdrawn
  • 1983-03-14 MX MX196566A patent/MX157586A/es unknown
  • 1983-03-14 IL IL68120A patent/IL68120A0/xx unknown
  • 1983-03-14 ES ES520565A patent/ES520565A0/es active Granted
  • 1983-03-14 CA CA000423512A patent/CA1215815A/fr not_active Expired
  • 1983-03-15 KR KR1019830001027A patent/KR840003969A/ko not_active Application Discontinuation
  • 1983-11-04 NO NO834034A patent/NO834034L/no unknown
  • 1983-11-10 DK DK513683A patent/DK513683A/da not_active Application Discontinuation

Non-Patent Citations (1)

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