Wrought iron is an iron alloy with a very low carbon content (less than 0.08%) in contrast to that of cast iron (2.1% to 4%). It is a semi-fused mass of iron with fibrous slag inclusions (up to 2% by weight), which gives it a "grain" resembling wood that is visible when it is etched or bent to the point of failure. Wrought iron is tough, malleable, ductile, corrosion resistant, and easily welded.
52100 is a relatively simple steel with 1% carbon and 1.5% chromium, and small amounts of Mn and Si. 52100 steel has been in use since at least 1905 . It was developed for use in bearings. High carbon steels (0.8-1.0% C) were primarily used until the late 1800’s or early 1900’s, after which chromium additions to bearing steels were being made. 1% Cr steels have been used in bearings since at least 1903. These early chromium-alloyed bearing steels were produced in Germany by Fichtel & Sachs and by Deutsche Waffen- und Munitionsfabrik. French-produced chromium steels were also used in bearings in a similar time period. 52100 continues to be the most used bearing steel, so the steel design has certainly stood the test of time.