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Background

A gold casting process is explained here:

The casting metal is melted in a special casting machine that is programmed to insert the metal under vacuum into the flask at the right time, temperature and rate.

Question

About furnace melting and filling the mold with molten gold, does gold enter the mold under pressure or without any pressure?

The metal is under vacuum. So, does it definitely mean the metal is under pressure? I'm a bit confused with pressure, tension, compression,...

Figures

The process is illustrated by the following figures. A mold is created out of a wax tree. Molten gold will fill the mold.

Wax tree

Casting furnace

Casting flask

Cleaning gold tree

Gold tree

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    $\begingroup$ Fir flow to exist, there must be a pressure difference. Vacuum just means atmosphere has been vacated. You can still press molten gold around without atmosphere. For example if you vacated air from a gold pipe, and then melted the pipe, the molten gold would flow inward where the air used to be. $\endgroup$
    – Abel
    Nov 22, 2023 at 13:41
  • $\begingroup$ @Abel So, if only vacuum is used to flow the gold, then can we say that the gold itself is free from pressure? $\endgroup$
    – Megidd
    Nov 22, 2023 at 14:10
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    $\begingroup$ There will always be pressure and pressure gradients where there is flow. Notice in my gold pipe example, I did not say put the pipe inside a vacuum, but to put the vacuum inside the pipe. The higher pressure outside the pipe is what would push it inward. The melting removes the structural capability of the gold to resist flowing in the direction the pressure pushes. In the case of the tool you mention, it's likely a tool part that pushes the gold along- think of a syringe. $\endgroup$
    – Abel
    Nov 23, 2023 at 2:23
  • $\begingroup$ @Abel Thanks. In order to make sure, I'm going to ask them directly. $\endgroup$
    – Megidd
    Nov 23, 2023 at 4:45

1 Answer 1

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I asked them directly, this is their response.

Thanks for the question.

With our vacuum casting machines, the melting and casting process are done within one large module.

The preheated casting flask is inserted in the bottom ection and the metal is loaded into a crucible above the flask.

The unit is sealed, a vacuum starts and the metal is then melted.

When the vacuum reaches the desired pressure and the flask and metal reaches the required temperature, the now molten metal is dropped into the flask.

Below is a video of a similar unit, which may help you to visualise the process.

Thanks.

https://www.youtube.com/watch?v=mqXk8Trn-Pc

The shared video has an explanation shown below.

..., the green needle is the flask chamber under vacuum, the blue is overpressure pushing metal into the flask.

I guess the difference between overpressure minus vacuum pressure is a decisive factor in deciding if the metal can be considered to be under pressure or not. But I'm still not sure whether I can consider the gold to be entering the mold under pressure or free from pressure. I need to know that as a requirement for numerical simulation of the casting process.

Screenshot

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