Meaning
Phase changes in low-carbon austenitic stainless steels occur when mechanical deformation at room temperature induces the metastable austenite phase to convert into the harder, more brittle martensite phase. This deformation-induced structural change, known as uns s31603 martensitic transformation, alters the magnetic permeability, hardness and corrosion resistance of the drawn steel tubing. While this transformation increases the tensile strength of the metal, it also reduces its remaining ductility.
Managing this transformation requires controlling the drawing parameters and the amount of cold work applied to the tube. This phase change is monitored during fabrication to ensure the finished product retains its specified non-magnetic and corrosion-resistant properties.
Cold Work Effect
Severe drawing passes and high draw bench speeds accelerate the rate of phase conversion within the alloy. The uns s31603 martensitic transformation occurs more readily when the drawing temperature is kept low, as cold deformation provides the driving force for the crystal lattice to restructure. Technicians can limit this transformation by controlling the draw bench speed and die angle to minimize localized heating.
Maintaining these variables within specified limits prevents excessive martensite formation.
Process Consequence
High levels of martensite make the stainless steel magnetic and can lead to cracking during subsequent forming operations. When the uns s31603 martensitic transformation is excessive, a full solution annealing heat treatment must be applied to restore the austenite structure.
Diagnostic Measurement
Magnetic measurement devices can quantify the amount of martensite that has formed in the austenitic matrix during drawing. Measuring the uns s31603 martensitic transformation involves using a feritscope or X-ray diffraction to determine the volume percentage of the magnetic phase. This test provides a quick, non-destructive way to evaluate the material after the final drawing pass.
If the martensite content exceeds the specified limit, the tubing is rejected or sent for heat treatment. The results are recorded in the quality log.
