History and Advantages of Forging
– Forging is one of the oldest known metalworking processes.
– Traditionally, forging was performed by a smith using hammer and anvil.
– Water power introduced in the 12th century allowed the use of large trip hammers.
– The smithy or forge has evolved over centuries to meet the demands of modern industry.
– Industrial forging is now done with presses or hammers powered by compressed air, electricity, hydraulics, or steam.
– Forging produces stronger pieces compared to casting or machining.
– The internal grain texture of the metal deforms during forging, resulting in improved strength characteristics.
– Forgings can have a lower total cost considering the entire life cycle of a product.
– Hot forging prevents work hardening and facilitates secondary machining operations.
– Some metals can be hot forged and then hardened using other methods.
Forging Processes
– Forging processes can be grouped into three main classes: drawn out, upset, and squeezed in closed compression dies.
– Common forging processes include roll forging, swaging, cogging, open-die forging, impression-die forging, press forging, cold forging, automatic hot forging, and upsetting.
Types of Forging
– Drop forging is a process where a hammer is raised and then dropped into the workpiece.
– There are two types of drop forging: open-die drop forging and impression-die drop forging.
– Open-die drop forging involves a hammer striking and deforming the workpiece on a stationary anvil.
– Open-die forging allows the workpiece to flow except where contacted by the dies.
– Open-die forging is suitable for short runs, art smithing, and custom work.
– Upset forging increases the diameter of the workpiece by compressing its length.
– Most widely used forging process based on the number of pieces produced.
– Common parts produced using upset forging include engine valves, couplings, bolts, screws, and other fasteners.
– Automatic hot forging involves feeding mill-length steel bars into the machine at room temperature, and hot forged products emerge rapidly.
– High output rate: small parts can be made at a rate of 180 parts per minute, larger parts at a rate of 90 parts per minute.
– Parts can be solid or hollow, round or symmetrical, up to 6kg in weight and up to 18cm in diameter.
– Roll forging is a process where round or flat bar stock is reduced in thickness and increased in length.
– No flash is produced, and it imparts a favorable grain structure into the workpiece.
– Net-shape and near-net-shape forging, also known as precision forging, minimize cost and waste associated with post-forging operations.
– Cold forging is common when parts are forged without heating the slug, bar, or billet.
– Induction forging utilizes induction heating for the workpiece and provides precise and localized heating for efficient forging.
– Multidirectional forging allows for complex shapes to be achieved in one forging operation.
Specific Forging Materials
– Isothermal forging is a process where materials and the die are heated to the same temperature.
– Isothermal forging is commonly used for forging aluminum, which has a lower forging temperature than steels.
– Forging temperatures for aluminum are around 430°C (806°F), while steels and super alloys can be 930 to 1,260°C (1,710 to 2,300°F).
– Aluminium forging is performed at a temperature range between 350–550°C.
– Forging temperatures above 550°C can lead to unfavorable workpiece surfaces and potential partial melting and fold formation.
– Forging temperatures below 350°C reduce formability and can lead to unfilled dies, cracking, and increased die forces.
– Control of the tool temperature is crucial for a homogeneous temperature distribution in the workpiece.
– High-strength aluminium alloys are mainly used in aerospace, automotive industry, and engineering fields.
– Magnesium forging occurs at a temperature range between 290–450°C.
– Magnesium alloys are more difficult to forge due to low plasticity, low sensitivity to strain rates, and narrow forming temperature.
– Magnesium alloy parts for industry are mostly produced by casting methods due to the high cost of forging with specialized dies.
– Magnesium alloys are increasingly used in the aerospace and automotive industry.
Equipment and Miscellaneous
– The most common type of forging equipment is the hammer and anvil.
– Drop-hammers, powered by air or steam, are used in vertical positions and release excess energy to the foundation.
– Counterblow machines, where both the hammer and anvil move, work horizontally and have less noise, heat, and vibration.Sources: https://en.wikipedia.org/wiki/Forging
