The bright annealing technique, which involves annealing the stainless steel tubing in a protective medium to avoid degradation of the bright surface, is used to heat treat the majority of stainless steel tubing. Bright Annealed Pipes Since austenitic stainless steel is the most used tubing material, brilliant annealing of austenitic stainless steel constitutes the heat treatment process.
The procedure of cold drawing is typically used to create stainless steel tubing. To get better softness and ductility and to get rid of residue stress, another annealing process is necessary. Chromium carbides must also be removed during annealing before cooling because they may have formed at the grain boundaries during high-temperature exposure and made the austenitic stainless steel susceptible to intergranular corrosion. The development of an oxide layer on both the outer and inner surfaces of the tube can be fully prevented if the annealing is carried out in a protective environment, such as pure hydrogen or dissociated ammonia. The stainless steel tube preserves both a superb surface quality and its natural metal brilliance. There is no requirement for an additional pickling procedure.
Stainless steel tube is often bright annealed in dissociated ammonia, a medium-priced furnace environment that offers a dry, carbon-free source of reducing gas, in engineering practice. Dissociated ammonia typically contains 75% hydrogen, 25% nitrogen, fewer than 300 ppm residual ammonia, and a dew point below -50°C (-60°F). Both the gas and the furnace must be dry and immaculately clean. The hardness of the tubing must be less than 90 HRB after brilliant annealing.
Reasons, Tube Temperature Monitoring is Crucial
- A bright surface finish that works
- enhancing and preserving the stainless tube's solid internal bond
- As quickly as possible heating. Oxidation occurs at intermediate temperatures as a result of slow heat. High temperatures cause lowering conditions, which are highly useful for giving the tubes their final, brighter appearance. Around 1040°C is the maximum temperature that is maintained in the annealing chamber.
The solution to the Application
The AST Pyrometer model A450 is appropriate for this use. Over a 10-mm-thick safety glass-protected observation window, the AST A450 is installed. The temperature of the tube exiting the induction coil is displayed on a temperature indicator that is wired to the pyrometer.
