|
Forging is one of the oldest known metalworking processes. Traditionally, forging was performed by a smith using hammer and anvil, though introducing water power to the production and working of iron in the 12th century allowed the use of large trip hammers or power hammers that increased the amount and size of iron that could be produced and forged. The smithy or forge has evolved over centuries to become a facility with engineered processes, production equipment, tooling, raw materials and products to meet the demands of modern industry.
In modern times, industrial forging is done either with presses or with hammers powered by compressed air, electricity, hydraulics or steam. These hammers may have reciprocating weights in the thousands of pounds. Smaller power hammers, 500 lb (230 kg) or less reciprocating weight, and hydraulic presses are common in art smithies as well. Some steam hammers remain in use, but they became obsolete with the availability of the other, more convenient, power sources.
Materials of Steel Forgings
Stainless steel (SS303, SS304, SS316, etc): Stainless steel forgings are composed of a ferrous alloy characterized by a “stainless” quality brought about by its protective oxide layer that helps the material resist corrosion. All stainless steel grades contain at least 10.5% chromium. Depending on the grade selected, stainless steel forgings resist crevice corrosion, stress cracking, pitting, heat deformation, and much more. There are four main types of stainless steel – duplex, austenitic, martensitic, and ferritic.
Carbon steel (1020, 1035, 1045, A105, Q235, 20CrMnTi, etc): There are four main grades of carbon steel: low carbon steel, medium carbon steel, high carbon steel, and very high carbon steel. Depending on the amount of carbon present in the material, carbon steel forgings are hardenable by heat treatment to increase yield and impact strength as well as wear resistance.
Low or mild carbon steel contains 0.05% to 0.26% carbon and encompasses grades 1018 and 1020. The lower carbon content causes the material to be more ductile and less brittle, making mild carbon steel a good choice for forging. Medium carbon steel contains 0.29% to 0.54% carbon and includes steel grades 1141. Containing a higher level of manganese, medium carbon steel can be used in the quenched or tempered form for forged crankshafts and many other types of forgings. High carbon steel and very high carbon steel exhibit hardness as well as resiliency and are brittle due to their higher carbon contents, between 0.55% and 2.1%.
Alloy steel (20Cr, 20CrMo, 30CrMo, 35CrMo, 42CrMo, etc): Alloy steels encompass a wide range of iron-based metals which contain higher levels of chromium that do not exceed 3.99%. Metals that contain greater amounts of chromium are classified either as tool steels or stainless steels. Alloy steels vary in their alloying elements which determine the properties of a particular material.
