FINDING THE DUCTILEBRITTLE TRANSITION TEMPERATURE IN STEEL

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FINDING THE DUCTILE-BRITTLE TRANSITION
TEMPERATURE IN STEEL
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What is DBTT?

• Property of steel
• Change in metal behavior
• Critical design factor

Figure 1 ref. 3 Ductile Charpy Impact Specimen
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Charpy Impact Test

• Measures the fracture energy of a metal
• Standardized in ASTM standard E-23
• Identifies the DBTT of metals
• Shows brittle or ductile fracture behavior

Figure 2 ref. 3 Brittle Charpy Impact Specimen
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Equipment

• Impact machine
• Specimens machined to ASTM E-23
• Furnace
• Methanol bath refrigerator
• Boiling water bath
• Ice water bath
• Liquid nitrogen

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Experimental Procedure

• Select 6 or more test temperatures
• Heat or cool two specimens to each temperature
• Wear safety glasses
• Prepare the impact machine
• Load the the specimen into the machine
• (only five seconds are allowed to move the
  specimen)
• Break specimen

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Experimental Procedure (continued)

• Record the absorbed energy
• Stop hammer and retrieve specimen
• Label the specimen
• Repeat test for remaining specimens

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Data Analysis

• Plot temperature vs. absorbed energy
• Draw a curve through the points
• DBTT is mean of upper and lower shelf energy

DBTT
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References

• Charpy Impact machine picture Retrieved
  August 12, 2002 from http//www.cpcc.cc.nc.us/mech
  /equipment/impact.jpg
• ASM metals Handbook, Vol. 19, 9th Ed., p.630
• Bassett, Vicki Causes and Effects of the
  Rapid Sinking of the Titanic Retrieved August 12,
  2002 from http//fbox.vt.edu/eng/mech/writing/uer/
  bassett.html