The Impact of Temperature on Mechanical Properties in Die Casting Materials
Die casting is a manufacturing technique that uses reusable molds, or dies, to create metal objects. A furnace, metal, die casting machine, die, and all necessary ancillary equipment are used in the die casting process to maintain the proper temperature for each of these components. Precision machining services are often used in conjunction with die casting to ensure the accuracy of these parts, enhancing overall product quality.
In the process, the metal is melted in a furnace and then pumped into the dies of a die casting machine. Typically, non-ferrous alloys like aluminum, zinc, copper, or magnesium are used. Dies must be heated to the ideal temperature for the casting process, usually 200oC, at the start of the cycle.
Melted alloys that can reach temperatures of up to 700oC will heat the die during the process. Problems like breakage, damage, or malfunctioning of the die and finished product may arise if the die temperature is not adjusted, both during the initial heating and cooling phases of the die. Precision machining services also play a critical role in minimizing such defects. Many Temperature Control Units (TCUs) are used to ensure that death is always at the proper temperature. Here’s a closer look at the significance of temperature in die casting.
Different Stages of Temperature Variations
In die casting, temperature is important for a number of reasons. As we previously discussed, for the molten metal to flow correctly, it must be at the proper temperature. It will be challenging to completely fill the mold cavity with thick, viscous metal if it is overly cold. An imperfect or porous casting may come from this.
On the other hand, too much heat can cause the metal to become thinner and more fluid, which will make it harder to work with. This may lead to an excessively thin casting or one with surface flaws. The finished output will be subpar in both scenarios.
The fact that temperature has an impact on the metal’s inherent qualities is another factor contributing to its significance in die casting. For instance, iron gets weaker and aluminum gets stronger as it gets colder. This implies that you must monitor the metal’s temperature in order to produce a strong casting.
Here, we explore more about temperature variations in different stages of die casting:
1. Melting
One important consideration is the melting point of various alloys. The items will be thoroughly examined in the upcoming parts. Aluminum, for instance, melts at about 660°C (1220°F). Sustaining the ideal melting point guarantees that the metal enters the mold in the right way, filling even the most complex facets without setting too soon.
2. Molding
Equally crucial is the mold’s (die’s) temperature. The molten material may solidify before fully filling the hole in an overly cold mold, resulting in flaws like cold closes or incomplete castings. On the other hand, overheating the mold might result in problems including excessive shrinkage, distortion, or longer cooling periods. For different materials, this is different. In aluminum die casting, for example, mold temperatures vary from 150°C to 250°C (302°F to 482°F).
3. Injection
It’s important to properly regulate the temperature at which the molten aluminum is poured into the mold. If the injection temperature is too poor, incorrect metal filling of the mold may result in issues. Excess metal leaking out of the mold, known as flash formation, and excessive mold wear can result at a high temperature.
4. Final Cooling
It is essential to regulate the cooling and solidification processes properly. While slow cooling might lead to shrinkage problems, rapid cooling can produce internal tensions and perhaps crack. To guarantee that the casting hardens uniformly and minimize internal tensions and flaws, the cooling rate must be optimized. Additionally, controlled cooling improves the finished product’s mechanical qualities.
Which Mechanical Properties will be affected?
The general impacts of temperature variations on die casting alloy mechanical properties are summed up as follows:
-
Modulus of Elasticity
A material’s stiffness or modulus of elasticity is a measurement of how much it can withstand deformation in response to an applied force. In die casting, modulus of elasticity is more stable than strength when temperature varies.
-
Ductility
A material is said to be ductile if it can undergo significant plastic deformation under tensile stress before rapture. When the temperature drops, ductility falls equally and rises when the temperature rises.
-
Tensile and Yield strengths
The highest stress a material can endure before breaking is known as its tensile strength. The point at which an applied stress forces a material to irreversibly change or drastically shift in shape is referred to as the “yield strength”. In general, tensile and yield strengths rise slightly at lower temperatures and drop gradually when higher temperatures are reached.
Effect of Temperature on Different Materials and Alloys
Temperature has a significant impact on the flow, filling, solidification, and ultimate characteristics during the die casting process. Appropriate temperature management is essential to the success of die casting operations in the automobile sector because it guarantees high-quality, flawless castings with exceptional mechanical qualities.
-
Materials
Aluminum – Due to its low melting point and ease of casting, aluminum is one of the most widely used metals for metal die casting. But aluminum is also quite susceptible to variations in temperature. It will be challenging to fill the mold all the way if the metal is too cold. Overheating the metal will make it difficult to control and may cause a casting to be too thin or to have flaws on the surface.
Zinc – Due to its low melting point and ease of casting, zinc is another material of choice for die casting. But zinc is also temperature sensitive, just like aluminum. It will be hard to fill the mold all the way if the metal is too cold; on the other hand, it will be tough to control if the metal is too hot since it will be too fluid.
-
Alloys
The A360, 383, and 380 aluminum forms are the most common alloys employed for the process of die casting. The zinc alloys ZAMAK 7, 5, and 3 are the most widely used for die casting.
Due to their distinct fluidity qualities and general light weight, magnesium alloys are also very desirable. The tensile strength of the magnesium alloy AZ91D is 142 MPa at 680 C°; this decreases to 103 MPa as the temperature rises by 100 C°. In a similar vein, yield strength drops with the same temperature shift, from 123 MPa to 94 MPa.
Conclusion
This essay teaches us about the importance of temperature in the process of die casting. It was discovered that the mechanical characteristics of gravity cast and squeeze cast aluminum, magnesium, and zinc alloys were influenced by the casting temperature. Because of this, die casting processes are subject to stringent temperature control requirements. Molds have to be made to be able to resist high temperatures without warping or cracking, and only the best materials should be utilized. Molds should also be constructed from a material that won’t retain heat from the molten metal. By maintaining the metal at its ideal temperature, this helps to guarantee the best possible casting quality.
