Factor/Variable Observations/Comments Chemistry Conforms to AISI 1030 Microstructure Proeutectoid ferrite and pearlite as expected in a hypoeutectoid annealed/normalized plain carbon steel Grain Size Variable: coarse(1 to 2 ASTM grain size)in the heavy thickness and fine (3 to 5 grain size)in the thin web. Knoop Hardness web( Thin section):260,266,252,245,233(HK300 Avg=251 HK300(20HRC) Heavy section:275,248,309,241,273,301(HK300) Avg= 275 HK300(25HRC) Inclusions/Segregation Appears most probably The EDS spectra show presence of Sulfur(S), Phosphorus(P), Silicon(Si), Calcium(Ca) and other elements(Fe and Mn are expected). Some of the phosphorus nay have been contributed by the laboratory cleaning procedure Forging Defects No gross forging defects such as laps or folds were detected. Overheating/Burning Possible overheating causing grain growth and grain boundary precipitation/formation of sulfides/phosphides/oxides and other non-metallics Residual Stress/Tightening Unknown. Not expected to be significant Overload Operating Loads The concave side of brace is always under tension magnitude of forces unknown Hydrogen Damage Appears possible but secondary to grain growth due to overheating Hard spots Higher Knoop reading near cracked edge. Fracture Appearance The initiation region shows fine dimpled structure which is interpreted to be due to the presence of grain boundary precipitates formed during forging processing. The fracture way from the initiation area is a mixture of ductile and intergranular modes; and has a faceted appearance. Further into the core, the fracture mode is predominantly of the cleavage (less ductile or brittle, transgranular) type Fatig No fatigue striations were detected. It is believed the crack front traveled rapidly. Corrosion in Service Rust only. No evidence of any other form of corrosion detected Thefileisdownloadedfromwww.bzfxw.comThe file is downloaded from www.bzfxw.com