the heart of industry
In fact, nothing can be made without heat treatment, the process of heating and cooling metal under strict control to improve its properties, performance and durability.
Heat treatment softens the metal and improves formability. It makes the part stiffer for strength. It can place hard surfaces on relatively soft parts for added wear resistance. It creates a corrosion-resistant skin to protect components that would otherwise corrode. Also, it can toughen brittle products.
Heat treated parts are critical to the operation of automobiles, aircraft, spacecraft, computers and various heavy equipment. Saws, shafts, cutting tools, bearings, gears, axles, fasteners, camshafts and crankshafts all rely on heat treatment.
Fundamentals of Heat Treatment
Although steel constitutes the vast majority of heat-treated materials, alloys of aluminum, copper, magnesium, nickel, and titanium can also be heat-treated.
The heat treatment process requires three basic steps:
Heating to specified temperature
hold at that temperature for an appropriate amount of time
Cool down according to the prescribed method
Temperatures may range as high as 2400°F and time at temperature may vary from a few seconds to 60 hours or more.
Some materials are cooled slowly in the furnace, but others must be rapidly cooled or quenched. Some low temperature processes require processing at -120°F or lower. Quenching media include water, brine, oil, polymer solutions, molten salts, molten metals and gases. Each has specific characteristics that make it ideal for certain applications. However, 90% of parts are quenched in water, oil, gas or polymer.
The value of heat treatment Heat treatment
Adds approximately $15 billion in value to metal products annually by imparting specific properties to parts needed to function successfully.
It is closely related to the manufacture of steel products: about 80% of heat-treated parts are made of steel. These include bars and tubes from steel mills, as well as cast, forged, welded, machined, rolled, stamped, drawn or extruded parts.
This is also a key step in the manufacture of non-ferrous metal products. For example, aluminum alloy automobile castings are heat treated to increase hardness and strength; brass and bronze products are heat treated to increase strength and prevent cracking; titanium alloy structures are heat treated to increase high temperature strength.