Page 384 - Failure Analysis Case Studies II

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Table 3. Mechanical properties of the pins
0.2% yield Ultimate tensile Impact energy at
strength strength Elongation room temperature
Pin (MP4 (MPa) W) (J)
N2 1 I82 1439 23.2 -
N3 1 I82 1458 21.6 -
N4 1162 1579 24.8 -
N5 - - - 22
N6 - - - 57
N7 - - - 23
N8 - - ~ 24
N9 - - - 45
Average 1175 1492 23.2 34
Standard deviation 11.5 76 1.6 16
'En 51" 635 8 50-1 000 - -
AISI 431' - 1210-1515 - -
AISI 4313 1030 1370 16 -
AISI 4314 1080 1360 23 -
' British standard specification BS 970 (950-1O2O0C, oil quenched and tempered at 550-650"C).
*980-1065"C, oil quenched and tempered at 230-370°C [3].
' Quenched and tempered at 260°C (Alloy Digest).
Quenched and tempered at 427°C (Alloy Digest).

En 57. UTS values up to 1515 MPa have been reported for AIS1 431. The percentage elongation
varied between 22 and 25%, which complies well with that required for AIS1 431.
The Charpy impact strengths are acceptable for this material, although the scatter is fairly high
but not atypical. Figure 6 shows the Charpy impact toughness for a stainless steel complying with
the specification for both En 57 and AIS1 431, as a function of tempering temperature at various

1 I I I I -

80 -

60 -

40 - 1150 "CIQuench

20 -
1200 "CIQuench

0 300 400 500 600 700

Tempering temperature ("C)
Fig. 6. Charpy impact toughness of either AISI 431 or En 57 as a function of tempering temperature,
austenitized at various temperatures and oil quenched.