Technical Reports

A Metallurgical Analysis of an ASTM A 212-B Steel Tank Car Head Plate

  • 01
  • Apr
  • 1981
AUTHOR: Federal Railroad Administration
OFFICE: RPD
SUBOFFICE: RPD-30
REPORT NUMBER: DOT/FRA/ORD-81/32
SUBJECT: Hazardous Materials
KEYWORDS: impact properties; Rail Tank Cars; Pressure Vessels
ABSTRACT: The sample was taken from the A-head plate of tank car SOEX 3033 involved in an accident near Winder, Georgia. The A-head plate was reportedly produced to specification ASTM A212-65, Grade B steel. The results of laboratory check chemical analyses indicated that the plate sample met the chemical requirements of ASTM A212-65, Grade B steel. The results of ambient-temperature bend tests and tensile tests showed that the plate sample satisfied both the bend requirements and the tensile elongation requirements but failed to meet the minimum ultimate tensile strength and yield point requirements of ASTM A212-65, Grade B steel. The results of metallographic analyses revealed substantial variation in the microstructure in the plate thickness direction. The observed coarse prior austenite grain size and large ferrite grain size is consistent with the coarse-grain steelmaking practice allowed for ASTM A212 steel and a high finishing temperature during fabrication. Hardness measurements of the microstructure correlated well with the measured tensile strength properties. The nil-ductility transition temperature was determined to be 30 F, a value equal to the highest value reported for a group of tank car plate samples, including both accident samples and current and previously allowed tank car plate materials. The results of Charpy V-notch tests established that the 15 ft-lb energy absorption and 50% shear fracture appearance transition temperatures measured for both longitudinal and transverse specimens were all above 60F and within normal tank car service temperature range. The high transition temperatures are related to both the coarse prior austenite grain size and large ferrite grain size observed in the microstructure and the steel chemistry.

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