Armored Vehicle Components - Metallurgical Examination of Armored Vehicle Components (Armor Attachment Bolts and Welded Armor Sections) from a German PZK III Tank

The bolts were processed from a medium carbon Cr-Mo-V type steel heat treated to a hardness of Rockwell C 40-42 372-393 Brinell. The bolts were forged from a relatively poor quality bar stock, machined, roll threaded, and heat treated. The hardness is higher than would normally be used for such applications where maximum toughness is desired. The 11-mm homogeneous armor was cross-rolled from a good quality steel and heat treated quenched and drawn to a hardness of 320-340 Brine4ll. The armor composition, which is similar to SAE 4150 with carbon on the high side, is clearly not a steel adapted to welded fabrication. It is quire similar to a composition which has been used in this country for some time and which was produced in considerable quantity by the Henry Disston and Sons, Inc. for riveted and bolted fabrication. As an armor material, such a composition is unsurpassed from a purely resistance to penetration standpoint. Fragments of the armor attached to the weld metal section were of high hardness 690 Vickers and consisted of the heat affected zone resulting from a single pass welding technique.