Steels_ Metallurgy and Applications, Third Edition

208 Steels: Metallurgy and Applications

Water jet prior

to placement

of s )ecimen

| ,.,

-- Jomlny

specimen

Figure 3.7 Jominy hardenability testing

Distance from quenched end

Figure 3.8 Schematic Jominy hardenability curve

the martensitic hardening that can be achieved at the end quenched position in a
steel of reasonable hardenability and transformation to bainite and ferrite-pearlite
at the slower rates of cooling.
Although it remains predominant, the Jominy hardenability test has been
criticized for not being sufficiently discriminating between steels of low
hardenability, i.e. those involving a very rapid decrease in hardness just beyond
the quenched end. For such steels, the SAC test is deemed to be more appropriate,
although it has been used very rarely in the UK. In this test, the specimen is again
a cylinder but measures 140 mm long x 25.4 mm diameter. After normalizing
and austenitizing at a suitable temperature above Ac3, the specimen is quenched
overall in water. After quenching, a cylinder 25 mm long is cut from the test
specimen and the end faces are ground very carefully to remove any tempering