A wide variety of test systems have been developed to determine the cooling characteristics of quenchants. Superior systems for reliability and cost performance are widely used and adopted as domestic and international standards. This review mainly focuses on test systems using a ball probe and discusses its potential. Although ball probes are not defined in current standards, it is known that specific ones used in the past contributed to enhancing the test systems in researches. Strengths and limitations inherent in ball probes have been identified from literature. Prototypes of test systems using a ball probe produced by the author’s group were reviewed briefly, which resolved problems due to a ball probe by using current technologies.

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