Stainless steel seamless pipe solution treatment effect

For stainless steel seamless pipe, the three elements of the solution treatment temperature, holding time and cooling rate.

The role of stainless steel seamless solution at the following:

Make stainless steel seamless organization and composition uniform, which is particularly important for the raw material, because hot-rolled pipes of each section rolling temperature and cooling rate are not the same, resulting in tissue structure is inconsistent. Exacerbated at high temperature atomic activities, σ phase dissolution, chemical composition tends to be uniform, after rapid cooling to obtain a homogeneous single phase.

  1. Eliminate hardening, in order to facilitate continued cold. By solution treatment, recovery distorted lattice, elongated and broken grains recrystallization, to eliminate the internal stress, the wire tensile strength decreased, the elongation increased.
  2. Restore the inherent corrosion resistance of stainless steel pipe. Because cold causes carbide precipitation, lattice defects, so that the corrosion resistance of stainless steel pipe fell. After solution treatment corrosion resistance of stainless steel seamless return to top form.
  3. For stainless steel seamless pipes, the three elements of solution treatment are temperature, holding time and cooling rate. The solution temperature is mainly determined based on the chemical composition.

Generally speaking, the number of alloying elements is high, and the solid solution temperature is correspondingly increased. In particular, steels with high manganese, molybdenum, nickel, and silicon content can only achieve a softening effect by increasing the solid solution temperature and allowing them to be fully dissolved.

However, stabilized steel, such as 321 stainless steel tube, has a high solid solution temperature and the carbide of the stabilizing element is sufficiently dissolved in the austenite, and precipitates at the grain boundary in the form of Cr23C6 in the subsequent cooling, causing intergranular corrosion. In order to prevent the carbides (TiC and NbC) of the stabilizing element from decomposing or being solid-solved, the lower limit solid solution temperature is generally employed.