The continuous operating temperature range of duplex stainless steel is -50°C to 250°C. The lower limit is determined by the brittle transition temperature of the stainless steel, while the upper limit is determined by the brittle transition temperature of 475°C. The upper limit temperature must not exceed 300°C.

Duplex stainless steel needs to be cooled quickly after solution treatment. Slow cooling will cause the precipitation of brittle phases, thereby reducing toughness and local corrosion resistance of the steel.

Proficiently master the welding rules of duplex stainless steel. The safe use of duplex stainless steel equipment is closely related to the correct mastery of welding technology. Some equipment failures are usually related to welding.

In order to ensure the best overall performance, the phase ratios in duplex stainless steels need to be controlled. If the two-phase ratio is out of balance, single-phase ferrite is easily formed in the weld heat-affected zone (HAZ), which may lead to stress corrosion cracking sensitivity in certain media.

Stainless steel is rust-resistant. Its rust resistance and corrosion resistance are due to a passive film on its surface, which prevents the metal from being corroded by external media, thus providing its rust resistance. When stainless steel is exposed to moisture or chloride ions, or during mechanical wear or welding, the passive film is destroyed, causing the stainless steel to rust. Therefore, the rust resistance and corrosion resistance of stainless steel are relative. Different environments require stainless steel with different chromium contents.

Although stainless steel is a highly corrosion-resistant decorative metal material, its surface can still rust under certain harsh conditions.

The corrosion resistance of stainless steel is closely related to its chromium content. Its main components are iron, chromium, and nickel, with a chromium content of at least 10.5%. At room temperature, oxygen in the air reacts with chromium to form a dense protective chromium oxide film. This film blocks further attack from external oxygen, water, and acid ions, protecting the stainless steel substrate from corrosion. However, if this film is damaged or other factors prevent it from forming or persisting for a long time, the stainless steel loses its rust resistance and becomes more susceptible to rust.

316L stainless steel pipe is an ultra-low-carbon, pure austenitic stainless steel with excellent weldability and a low likelihood of intergranular corrosion. However, due to its low thermal conductivity and high coefficient of linear expansion, welded joints of this steel generate significant tensile stresses during cooling, resulting in high welding heat input. Slow cooling rates also make it susceptible to thermal cracking, corrosion cracking, and deformation.

316L stainless steel pipe can be welded using all standard welding methods. Depending on the application, 316Cb, 316L, or 309Cb stainless steel filler rods or electrodes can be used. Among the commonly used welding methods, MIG and TIG welding require less heat input. In addition to protecting the hot metal, the argon flow also provides a certain degree of cooling, increasing the weld's crack resistance and reducing welding deformation.

Post-weld annealing is generally not required for 316L stainless steel pipe. Austenitic stainless steel generally does not require stress relief annealing after welding. This is because austenite has excellent plasticity and toughness, making post-weld stress relief annealing unnecessary to restore its properties.