An interpretive report prepared for the Materials Division of the Pressure Vessel Research Committee.The report discusses in detail, the analysis, physical and mechanical properties, method of determining ASME Code design stresses, embrittlement by sulfur and lead, cold forming, hot forming, thermal treatments, cleaning, pickling, welding, brazing, joining dissimilar metals and inspection.There is also included a discussion of the particular characteristics of age-hardenable alloys.