Failure Analysis of H13 Tool Steel in Aluminum Extrusion Dies

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Failure Analysis of H13 Tool Steel in Aluminum
Extrusion Dies

• Mesut Varlioglu, Graduate Student
• Taeh-Young Kim, Graduate Student
• Joe Benedyk, Professor
• Philip Nash, Professor
• 9/05/03

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PURPOSE and MATERIAL

• To find the reason why the extrusion dies
  fracture in a short period of time.
• To examine the Zn embrittlement phenomena in
  7XXX Series.
• To do failure analysis for the H13 tool steels
  made by different companies.
• To design a Zn liquid embrittlement test and
  simulate the extrusion process in our
  laboratories.
• Die Material H13 (wt) 0.32-0.45C, 0.80-1.25Si,
  0.20-0.60Mn, 4.75-5.50Cr, 1.10-1.75Mo,
  0.80-1.20V.
• Extrusion Material 7116 (wt) 0.15Si, 0.30Fe,
  0.50-1.1Cu, 0.05Mn, 0.8-1.4Mg, 4.2-5.2Zn, 0.05Ti,
  0.05Ga.

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EXTRUSION PROCESS

• Extrusion pressure 72,000 psi.
• Maximum extrusion temperature 1022 F (550
  C).

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EXTRUSION DIES AFTER FRACTURE
Fracture Initiation
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CUTTING DIRECTIONS
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CUTTING PROCESS
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Experimental Procedure
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Hardness Profile
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Microstructures - 400x
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Microstructures - 1000x
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Microhardness Difference
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Decarburization Layer
(a)
(b)
H13 as received die, austenitized at 1850 F 1 hr,
air cooled. (a) Decarburization layer. Nital
etch. 400 x. (b) Inside microstructure. Nital
etch. 400x.
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PART II Zn EMBRITTLEMENT DESIGN APPROACH
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Molten Zn Immersion Test (LME)

• Pre-stressed U-Bend austenitized at different
  temperature and time is immersed in molten Zinc.
• Fracture is observed in a period of time.

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Zn Embrittlement Test Design (SME)
7xxx series Al filled cylindrical vessel is
pressurized at 72, 000 psi and at 1022 F (550
C) and fracture observed with the aid of
longitudinal notch.
Case I
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Zn Embrittlement Test Design
7xxx series Al filled cylindrical vessel is
pressurized until the fracture is observed in the
bridge.
Case II
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Conclusions

• Zn as part of Al alloys may cause embrittlement
  in hot extrusion.
• Austenitization affects grain size, which can
  also affect Zn embrittlement.
• It is essential to find a design for SME testing
  which can simulate the extrusion process.

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FUTURE WORK

• The failure analysis for the dies which we will
  receive.
• Using different austenitization and tempering
  conditions and comparing the results.
• Investigation of fracture surfaces in different
  dies.
• Designing a more credible Zn embrittlement
  testing design.