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Title: Metallurgical Failure Analysis of A2 Tool Steel Die Set from High Explosive Pellet Pressing Event

Abstract

On 2 April 2018, a high explosive violent reaction (HEVR) occurred during routine pressing of a 1-in -diameter cylindrical pellet of PBX 9501 high explosive. Fragments of the die set (die body and stemples) involved in the event were sent to Sigma Division for metallurgical analysis. A handheld x-ray fluorescence alloy tester confirmed the die set material to be A2 tool steel. Light optical microscopy revealed what appear to be pre-existing flaws on the inner diameter of the die body. Scanning Electron Microscopy could neither confirm nor exclude the presence of fatigue cracking in the vicinity of these potential flaws. Energy Dispersive Spectroscopy indicated the presence of a carbon-bearing residue on fracture surfaces; nitrogen-bearing residue was also found. Optical microscopy revealed that the microstructure of the stemple and inner diameter of the die body contained large stringers and non-uniform grain size; this was distinct from the relatively clean and uniform microstructure seen at the outer diameter of the die body, and also other A2 tool steel stock (pedigree unknown and with no known connection to any HE pressing hardware) that was examined for additional comparison. Rockwell hardness testing indicated the material was heat treated properly. Metallographic analysis alone could notmore » positively identify the root cause of the event, but, coupled with accounts provided by the operator and the successful history with the particular lot of HE involved in the event, points to ward mechanical failure of the die set due to pre -existing flaw as the most likely precipitating event. Suggestions for additional analyses and future qualification techniques are discussed.« less

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1457323
Report Number(s):
LA-UR-18-25590
DOE Contract Number:  
AC52-06NA25396
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
A2 tool steel; PBX 9501; failure analysis; metallography; microscopy

Citation Formats

Richards, Andrew Walter, Alexander, David John, Bohn, Kevin Ray, Forsyth, Robert Thomas, Hackenberg, Robert Errol, Hooks, Daniel Edwin, Kennedy, Patrick Kenneth, Lopez, Jessica Jazmin, Mier, Ryan Miguel, Miller, Cody, Montalvo, Joel Dwayne, Osborn, Jr., Carolus Martinus, and Tegtmeier, Eric Lee. Metallurgical Failure Analysis of A2 Tool Steel Die Set from High Explosive Pellet Pressing Event. United States: N. p., 2018. Web. doi:10.2172/1457323.
Richards, Andrew Walter, Alexander, David John, Bohn, Kevin Ray, Forsyth, Robert Thomas, Hackenberg, Robert Errol, Hooks, Daniel Edwin, Kennedy, Patrick Kenneth, Lopez, Jessica Jazmin, Mier, Ryan Miguel, Miller, Cody, Montalvo, Joel Dwayne, Osborn, Jr., Carolus Martinus, & Tegtmeier, Eric Lee. Metallurgical Failure Analysis of A2 Tool Steel Die Set from High Explosive Pellet Pressing Event. United States. doi:10.2172/1457323.
Richards, Andrew Walter, Alexander, David John, Bohn, Kevin Ray, Forsyth, Robert Thomas, Hackenberg, Robert Errol, Hooks, Daniel Edwin, Kennedy, Patrick Kenneth, Lopez, Jessica Jazmin, Mier, Ryan Miguel, Miller, Cody, Montalvo, Joel Dwayne, Osborn, Jr., Carolus Martinus, and Tegtmeier, Eric Lee. Tue . "Metallurgical Failure Analysis of A2 Tool Steel Die Set from High Explosive Pellet Pressing Event". United States. doi:10.2172/1457323. https://www.osti.gov/servlets/purl/1457323.
@article{osti_1457323,
title = {Metallurgical Failure Analysis of A2 Tool Steel Die Set from High Explosive Pellet Pressing Event},
author = {Richards, Andrew Walter and Alexander, David John and Bohn, Kevin Ray and Forsyth, Robert Thomas and Hackenberg, Robert Errol and Hooks, Daniel Edwin and Kennedy, Patrick Kenneth and Lopez, Jessica Jazmin and Mier, Ryan Miguel and Miller, Cody and Montalvo, Joel Dwayne and Osborn, Jr., Carolus Martinus and Tegtmeier, Eric Lee},
abstractNote = {On 2 April 2018, a high explosive violent reaction (HEVR) occurred during routine pressing of a 1-in -diameter cylindrical pellet of PBX 9501 high explosive. Fragments of the die set (die body and stemples) involved in the event were sent to Sigma Division for metallurgical analysis. A handheld x-ray fluorescence alloy tester confirmed the die set material to be A2 tool steel. Light optical microscopy revealed what appear to be pre-existing flaws on the inner diameter of the die body. Scanning Electron Microscopy could neither confirm nor exclude the presence of fatigue cracking in the vicinity of these potential flaws. Energy Dispersive Spectroscopy indicated the presence of a carbon-bearing residue on fracture surfaces; nitrogen-bearing residue was also found. Optical microscopy revealed that the microstructure of the stemple and inner diameter of the die body contained large stringers and non-uniform grain size; this was distinct from the relatively clean and uniform microstructure seen at the outer diameter of the die body, and also other A2 tool steel stock (pedigree unknown and with no known connection to any HE pressing hardware) that was examined for additional comparison. Rockwell hardness testing indicated the material was heat treated properly. Metallographic analysis alone could not positively identify the root cause of the event, but, coupled with accounts provided by the operator and the successful history with the particular lot of HE involved in the event, points to ward mechanical failure of the die set due to pre -existing flaw as the most likely precipitating event. Suggestions for additional analyses and future qualification techniques are discussed.},
doi = {10.2172/1457323},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Jun 26 00:00:00 EDT 2018},
month = {Tue Jun 26 00:00:00 EDT 2018}
}

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