Rust scars and corrosion - 1.4301
Rusty spots and small corrosion scars were noticed on the surface of the material. The material was in solution annealed condition. A micrograph examination showed an austenitic microstructure with a light cold forming in the grains. There was a fine grain size. Local small scars were existing in the area of the rusty spots. Grain boundary attack was noticed in the environment of the scars. Carbide precipitates on the grain boundaries were existing in the area of the defective surface. Through the carbide precipitates the corrosion resistance has been reduced drastically due to the chromium loss in the environment of the carbides. There was also apparently a local carburization of the material. This allowed the supposition that it is a not sufficient pretreatment (cleaning, degreasing) in front of the solution annealing of the wire material.
Steel bars 4,00 mm round - solution annealed