13Nov

Why You Can’t Afford to Mess Up the Melting Process

The Importance of Metal Melting

When it comes to die casting, perhaps the most important step is melting the metal. This is no simple process, and it’s very important to know all that goes into it and how to do it safely and efficiently.

Safety Precautions

Safety always comes first when dealing with molten metal. There are many precautions that must be taken to avoid any potential mishaps.

One of these precautions is to make sure that all metals being melted are moisture free.

g_pourIn order to prevent moisture on the furnace charge, all metals should be preheated before being melted to evaporate any moisture that could be present. The same goes for any tools or other materials that come in contact with the molten metal.

There are other safety precautions to keep in mind, like wearing the proper clothing and protective gear, making sure furnace cleaning tools are coated with a non wetting coating to prevent the aluminum from sticking to the tools.

The Process

According to the North American Die Casting Association, melting the metal uses about 55% of energy in a die casting plant, and holding molten metal requires about 22% of energy. So, this information alone shows how big a part of the die casting process melting the metal is.

As far as the actual process goes, there are a few different types of furnaces used to melt metal. These are crucible furnaces, gas reverberatory furnaces, gas stack melters, and coreless induction furnaces. Which furnace to use is determined by the volume and type of metal being melted.

After the metal is melted in a furnace, it is then treated by degassing and skimming to ensure that there are no problems like gas porosity and inclusions, which cause defects in the castings.

After degassing the metal is transferred to a holding furnace at each die casting machine.  The purpose of the holding furnace is to maintain the metal at a constant temperature, because if a metal is not at its proper casting temperature, then it will not flow well and can cause problems such as cold shuts and other defects in the casting.  Metal temperature is a major casting variable in the die cast process that needs to be tightly controlled to assure high quality die castings.

Cold Chamber Machine

Metal

Melting Point

(°F)

Melting Point

(°C)

Aluminum

Alloy

865-1240

463-671

Copper

1983

1084

Magnesium

1200

650

For a bit of reference, here’s a chart showing the melting points of some common metals and alloys used in die casting.

Please send any inquiries and project files to sales@diecasting.com

By Leonard Cordaro, President of Premier Die Casting Company

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