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Is this the correct way to interpret the national standard GBT 7232-2012?

2023-03-14View Original

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GBT 7232-2012 Terms for Metal Heat Treatment Processes 3.1 Annealing: A heat treatment process in which the workpiece is heated to an appropriate temperature, held there for a certain period of time, and then cooled slowly. 4.1 Normalizing is a heat treatment process in which the workpiece is heated to achieve austenitization and then cooled in air or another medium, resulting in a microstructure dominated by pearlite. 5.1 Quenching: hardening; transformation hardening – A heat treatment process in which a workpiece is heated to achieve austenitization and then cooled in an appropriate manner to obtain a martensitic or (and) bainitic structure. The most common methods include water quenching, oil quenching, air quenching, etc. 6.1 Tempering is a heat treatment process in which a workpiece that has been hardened is heated to a temperature below Ac1, held at that temperature for a certain period of time, and then cooled to room temperature. According to national standards, we know that 1) without quenching, there is no tempering. Therefore, tempering is essentially a combination of \"quenching and tempering\" ; 2) Pure quenching hardly exists, so quenching and tempering can be combined into one process, known as the “quenching-tempering combination”” ; 3) The \"quenching-and-tempering combination\" and normalizing both specify a heating target (austenite in all cases) and a cooling target (martensite, bainite – more precisely lower bainite, pearlite), while annealing does not specify either a heating target or a cooling target ; 4) The definition of annealing is loose; it only requires three steps: “heating,” “holding at a constant temperature,” and “slow cooling.” However, “slow cooling” generally implies cooling in the furnace and transformation into a balanced microstructure ; 5) Normalizing has clear heating objectives (austenite) and cooling objectives (pearlite), but it is not limited to air cooling; it is estimated that air cooling is used in most cases. May I ask, is this the correct way to interpret the national standard GBT 7232-2012?
Reply #22023-03-14
Yes, your interpretation of the national standard GBT 7232-2012 is correct. These include four heat treatment processes: annealing, normalizing, quenching, and tempering. Quenching and tempering can be combined into a single process known as \"quenching-tempering combination.\" The definition of annealing is relatively loose, but it generally refers to heating followed by slow cooling to achieve an equilibrium microstructure. At the same time, normalizing has clear heating and cooling objectives. -

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