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How Die Casting Alloys Work
Die-casting is a fabrication technique involving high pressure injections of liquefied metal into a cast. It is useful for accurately mass-producing items according to specifications. Many products, such as automobile parts, sink faucets, and connector housings, are created using the process.
Die-casting can be an appealing and cost-effective method for manufacturing sturdy items. When selecting an appropriate fabrication material, there are several factors to consider, including the type of die-casting process to be used and the intended function of the product.
Types of Die-Cast Processes
Two common die-casting methods are the cold-chamber and hot-chamber processes, and distinguishing the proper method largely depends on the size of the finished product and the alloy selected. For example, aluminum is a more efficient choice for the cold-chamber process than it is for the hot-chamber method.
• Cold-Chamber Process: Metal is liquefied in a furnace, then ladled into a cold chamber. This technique is often used with metals that alloy quickly with iron at high temperatures, such as copper and aluminum, because these materials would regularly pose problems when melted in a (part-iron) casting machine. The cold-chamber process is better-suited to metals with high melting points.
• Hot-Chamber Process: Metal is melted in the casting machine, and fed into the die. The injection method allows metal to be added more quickly, but is ineffective with materials that have high-melting points, such as aluminum-based alloys. Therefore, a hot-chamber process is typically used with tin, lead, or zinc-based alloys.
Types of Alloys Used in Die-Castings
Aluminum is commonly employed in die-casting, but is prone to cracking or shrinking at high temperatures, so it is often alloyed with copper or silicon. Combining aluminum with these metals greatly increases its hardiness and fluidity. Since it has high dimensional stability, aluminum is used to create components with thin walls and complex shapes. Due to its corrosion resistance, aluminum is also beneficial in components that will face exposure to thermal or electrical energy.
Copper-based alloys are also commonly employed in die-casting. Many of these alloys are quite durable, making them an effective choice for mechanical products. Due to copper’s very high resistance to corrosion, it is often used to create plumbing and electrical material.
Zinc is relatively easy to cast and maintains high strength at room temperature, but can be alloyed with aluminum to further improve these qualities. Zinc has a lower melting point than aluminum and is suitable for hot-chamber casting. It is also valuable in the manufacture of products that require high precision and sturdiness, such as connectors and gears.
Magnesium has a high strength-to-weight ratio despite being a relatively light alloy, and it is useful for die-casting operations that require thin-structured walls and close precision.
Considerations When Choosing Die-Casting Alloys
The function and use of the final product will dictate die-casting alloy selection. For example, if the component requires high strength and corrosion resistance, an aluminum or copper based alloy could be an effective choice. Another consideration is production volume. With proper maintenance, aluminum die-casts can have a life of approximately 100,000 cycles, while zinc molds can last up to one million cycles before being replaced. For long-term, high-volume production, it may be more cost-effective to use alloys that maximize the life of the molds.
When considering various fabrication methods, it may be helpful to examine the advantages and disadvantages of using a die-casting process.
Potential advantages include:
• Dimensional Strength: die-cast parts are stronger than plastic components.
• Rapid Production: die-cast components can be produced in high volume with relatively little tooling or machining.
• Smooth Surfaces: the die-cast process can create finished parts with curved or seamless surfaces.
• Accuracy: die-cast parts can be created with close adherence to specifications.
Possible disadvantages include:
• High Volume: smaller production runs may reduce cost-effectiveness.
• Limited Metal Fluidity: alloy malleability varies, which can limit the complexity and shape of the finished product.
• Size and Weight Limits -- A casting machine’s capacity limits the range of product dimensions.
Related Products and Categories
Die-casting is used for a variety of consumer, commercial and industrial manufacturing purposes, such as the production of automobile powertrains, engine parts, telecommunications equipment, marine equipment, household appliance parts and hand tools.
There are numerous variants within the die-casting process. Some of the related materials and procedures include:
• Single-cavity die: A mold designed to create a single component.
• Multiple-cavity die: A mold designed to create several identical parts.
• Unit die: A mold designed to create several different parts that are all part of the same component.
• Die lubricant: Liquid applied to the interior surfaces of the mold to ensure easy removal of the component.
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