Heat Treat
and
Mechanical Testing
Approved for Public Release
1
Introduction:
Electric Boat Corporation uses metallic
materials that need to have specific material
properties.
• Mechanical Properties are determined at such processes
as Heat Treat
• The properties are verified using testing techniques
called out in the requirements
Heat Treat & Mechanical Test
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Approved for Public Release
Specific Heat Treat Process:
• Heat Treat oven:
– Time
– Temperature
• Cooling rates:
– Air cool quench
– Water quench
• Calibration requirements
Heat Treat & Mechanical Test
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Specific Heat Treat Process:
Do you understand your process?
CONTROLS
MATERIAL PROPERTIES
TEST RESULTS
•
•
•
Work backward from the results. Study the process
controls that gets you the range of results that are
optimal for the customer. Adjust the controls to match.
Test to verify the results.
Study using Design of Experiments (DOE)
Control the process by Statistical Process Control (SPC)
Heat Treat & Mechanical Test
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Heat Treat Failures:
– Not meeting the mechanical property
requirements (see controls)
– Heat Treat procedure not followed
– Test pieces to verify properties:
• Insufficient number of test pieces
• Incorrect size for the test sample
• Samples taken from incorrect location
Heat Treat & Mechanical Test
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All Material Requirements Invoked:
•
•
•
•
•
•
•
As part of the specific requirements
As part of the part number description
As a note on the drawing
In an Electric Boat Material Specification
In a Standard Clause
In an Engineering Report (ER)
Combination of the above
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Misinterpreting the Requirements
Caused by:
– Lack of familiarity with:
• Material requirements
• Test requirements
• Heat treat requirements
– Unclear/confusing requirements
– Incorrect assumptions about testing
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Specific Material Requirements:
Tensile
(ASTM E8 or ASTM A370)
•
•
•
•
Tensile strength (psi or ksi)
Yield strength (psi or ksi)
Elongation (%)
Reduction in area (%)
Heat Treat & Mechanical Test
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Specific Tensile Failures:
• Improper Specimen size
• Improper number of test specimens
• Sample location from material
improper
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Specific Material Requirements:
Hardness
Brinell test (ASTM E10)
Rockwell A or B test (ASTM E180)
•
•
•
Minimum value
Maximum value
Range or values
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Specific Hardness Failures:
• Testing not performed
• Surface preparation improper
• Correction factors for geometric
shapes (convex or cylindrical
surfaces) not taken
Heat Treat & Mechanical Test
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Specific Material Requirements:
Toughness
Verified by impact testing and fracture toughness
testing
• Charpy v-notch (most common, ASTM E23,
size and temperature)
• Dynamic tear testing (similar to Charpy)
• Fracture toughness test (ASTM E1820, more
sophisticated than above)
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Approved for Public Release
Specific Toughness Failures:
• Charpy v-notch (wrong test
temperature)
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Specific Material Requirements:
Bend Testing
• Bending the suitable sample to a
specified radius
• Ductility
• ASTM E290
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Specific Material Requirements:
Bend Testing
Bending the suitable sample to a
specific radius (Wrong Bend
Radius)
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Specific Material Requirements:
Surface Test
Surface treatment for wear/galling
resistance- verified by hardness
testing (called case hardening)
•
by carburizing or nitriding
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Heat Treat Certification
Heat Treat & Mechanical Test
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Heat Treat Certification
Heat Treat & Mechanical Test
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Approved for Public Release
Heat Treat Certification
Heat Treat & Mechanical Test
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Approved for Public Release
Summary:
– Process Controls → Material
Characteristics → Test Results
– Meet all required:
• Material property requirements
• Heat treat requirements
– Changes need to be authorized by
Electric Boat
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