Superheat is the only company in the world dedicated exclusively to on-site heat treatment, and we want to aid in the understanding of our process. Due to strict codes and recommendations, including ASME and AWS, Heat Treating has become an essential provision for capital and maintenance projects within the refining and energy sector.
Post Weld Heat Treatment (PWHT), is an application of uniform heat applied after welding to a structure, or portion thereof, at a sufficient temperature – below the transformation temperature range and with the intention of retaining the material’s strength/quality and ductility. The primary benefits of PWHT are recognized as relaxation of residual stress, tempering, and hydrogen removal.
Preheating is the application of heat to a base metal (weld metal, HAZ, and adjacent base metal) prior to and throughout welding, as well as at the start of each pass in a multi-pass weld. The primary purpose of preheating is to drive off moisture prior to the start of welding, reduce the cooling rate, and increase hydrogen diffusion within the weld to prevent cracking.
Heat Treatment is the process of heating a base metal and holding it at a prescribed temperature for a specific length of time, followed by a controlled cooling at a suitable rate. Annealing is an application commonly used to soften a metal for cold working, improve machinability, and enhance electrical conductivity.
Normalizing is a heat treatment procedure that focuses on the mechanical properties of steels. It is used to reduce residual stresses and thereby improve tensile strength and impact value for increased resistance to brittle fracture and corrosion.For normalization to occur, steel is heated to a temperature slightly above its upper critical transformation point.
Tempering is a technique applied to ferrous alloys, such as steel, to increase toughness, ductility, strength, and structural stability. This process involves heating previously hardened or normalized steel to a set temperature below the lower critical point, then cooling it at a suitable rate to relieve the stresses and hardness developed during welding or machining.
Not all heat treatment processes are created equal. Get the facts on our Superheat SmartWay™ and see why we’re the industry leader in safety and reliability.