What is Forging?(google、baidu）
作者：admin 来源：本站 发布时间：2019-05-22 13:09:39 浏览量：
Forging, a metal shaping technique using compressive, localized forces, has been a staple metal fabrication technique since the time of the ancient Mesopotamians. Since its origins in the fertile crescent, forgings has experienced significant changes, resulting in a more efficient, faster and more durable process. This is because today, forging is most commonly performed with the use of forging presses or hammering tools that are powered by electricity, hydraulics or compressed air.
Advantages of Forging
The pounding action of forging deforms and shapes the metal, which results in unbroken grain flow. This causes the metal to retain it’s strength. Ancillary effects of this unique grain flow include the elimination of defects, inclusions and porosity in the product. Another advantage of forging is the relatively low costs associated with moderate and long production runs. Once the forging tools have been created, products can be manufactured at relatively high speeds with minimal downtime.
Hot Forging
There are two main types of forging -- hot and cold. Hot forging requires the metal to be heated above its recrystallization temperature. This can mean heating metals up to 2,300 degrees Fahrenheit. The main benefit of hot forging is the decrease in energy required to form the metal properly. This is because excessive heat decreases yield strength and improves ductility. Hot forged products also benefit from the elimination of chemical inconsistencies.
Cold Forging
Cold forging typically refers to forging a metal at room temperature, though any temperature below recrystallization is possible. Many metals, such as steel high in carbon, are simply too strong for cold forging. Despite this hindrance, cold forging does edge out its warmer equivalent when it comes to standards of dimensional control, product uniformity, surface finish and contamination. Cold forging encompasses numerous techniques, including bending, extruding, cold drawing and cold heading. However, this increased versatility comes at a cost, because cold forging requires more powerful equipment and may call for the use of intermediate anneals.
Types of Forging Categories
Beyond basic hot and cold forging, many specific processes exist. This broad range of processes can be grouped into three primary umbrella groups:
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Draw forming decreases the width of the product and increases length.
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Upset forging increases the width of the products and decreases length.
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Compression forming provides forging flow in multiple or customized directions.
These three categories entail many different specific types of forging:
Open Die Forging
When flat dies that have no precut profiles engage in forging, the process is called open die forging (or smith forging). The open design allows the metal to flow everywhere except where it touches the die. To achieve maximum results, correct movement of the workpiece, which should be over 200,000 lbs. in weight and 80 feet long, is essential. It is useful for short-run art smithing or for shaping ingots prior to secondary shaping measures.
Closed Die Forging
Closed die forging, sometimes called impression die forging, employs the use of molds. These molds are attached to an anvil while a hammer forces molten metal to flow into the cavities of the die. Multiple strikes and/or die cavities are often used when forging complex geometries. High initial tooling costs make closed die forging expensive for short-run operations, but the process becomes cost-effective as parts produced increases. Closed die forging also provides exceptional strength over alternative methods. Common applications of closed die forging include the production of automobile components and hardware tools.
Press Forging
In press forging, the main forming factor is compression. The metal sits on a stationary die while a compression die applies continuous pressure, achieving the desired shape. The metal's contact time with the dies is considerably longer than other types of forging, but the process benefits from being able to simultaneously deform the entire product, as opposed to a localized section. Another benefit of press forging is the ability of the manufacturer to monitor and control the specific compression rate. Applications of press forging are numerous, as there are relatively no limits to the size of product that can be created. Press forging can be hot or cold forged.
Roll Forging
Roll forging is a the process of increasing rods or wires in length. The manufacturer places heated metal bars between two cylindrical rolls, which rotate and apply progressive pressure to shape the metal. Benefits of roll forging include the elimination of flashing and a superior grain structure.
