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How hot does the metal get in die casting? It all depends on the metal you use and how carefully you adhere to die casting standards with respect to temperature. Does die casting mold temperature matter? It absolutely does. Die casting temperature control is a real issue if you wish to avoid die casting defects and other problems.
It's important to understand the difference between metals in die casting when it comes to temperature and the consequences of poor temperature control when die casting.
In general, as temperatures increase, tensile and yield strengths decrease in die casted alloys. If you need parts with high tensile strength, this fact will be important to keep in mind. In addition, ductility increases as temperature increases, but changes depend on the type of alloy being die casted. For instance, aluminum is less ductile than zinc, but temperature must be higher for aluminum in the process.
The thermal factors of die casting are the temperature of the alloy used for casting, the temperature of the die itself and the temperature of the die casting machine. All of these factors must be kept in an optimum temperature range for the highest-quality parts. If the temperature of the molten metal is too hot for the mold, it could damage the mold by causing premature heat checking on the mold steel. If the mold temperature is too cold, it could drop the temperature of the metal too quickly as it flows into the mold and cause defects — especially greater porosity or misruns on the casting surface.
To avoid putting a strain on the mold, you will want the alloy to be about 50 to 70 degrees F higher than the initial crystallization temperature. The mold itself needs to be maintained at about a third of the alloy temperature. The correct temperature for the casting chamber is a complex calculation that will be determined by the casting engineer.
So how does temperature affect the different metals used for die casting? Here are a few useful examples:
Aluminum is one of the most popular choices for metal die casting. It is lightweight, durable and has good corrosion resistance. The most popular aluminum alloys for die casting are 360, 380 and 413.
For Aluminum 380, for example, you'll see a tensile strength of 48 at 75 degrees and a yield strength of 24. Get up to 212 degrees, and it's 45 KSI (Kips Per Square Inch) tensile strength while the yield strength stays constant at 24. For Aluminum 390, yield strengths range from 41 KSI down to 18 KSI for 500 degrees.
Zinc is another highly popular die casting alloy. Some common and most popular zinc alloys include Zamak 3, 5 and 7.
For these alloys, a temperature of 75 degrees produces an average 40 KSI, while a temperature of 275 degrees produces an average KSI as low as 10. Other zinc alloys show similar yield strength decline with increasing temperature.
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