MECH 210 081103 - Hardenability and Jominy End Quench Test

MECH 210 081103 - Hardenability and Jominy End Quench Test...

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MECH 210 081103 Hardenability and Jominy End-Quench Test Hardenability – Hardenability refers to the ease with which martensite forms. In other words, it is the ability to avoid eutectoid transformation (to form soft pearlite) on cooling. In general, plain-carbon steels have low hardenability – only very high cooling rates produce all martensite. Alloy steels have high hardenability, even cooling in air may produce martensite. Major factors affecting hardenability of steels include: carbon oncentration, alloying elements, and grain size. Hardenability curve is a plot of hardness vs. cooling rate. In practice the curve is a plot of hardness vs. distance from the quenched end (Dqe) of standard Jominy end-quench test sample. Jominy End-Quench Test Standard test sample Quench tank Procedure (1) Sample is heat treated at a temperature above its upper critical temperature to make a full-
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Unformatted text preview: austenite sample. (2) Place in quench tank and allow the water jet to quench the lower end. (3) Polish two parallel strips of flat surface along longitudinal axis on opposite sides of sample. (4) Make a series of hardness measurements on the flat surface at various distances from the quenched end. (5) Plot measured hardness as a function of distance from the quenched end. Hardenability curves Example 1 : A 1020 steel, 1 in. in diameter, is austenitized and quenched in an agitated water bath. (a) What is the cooling rate and (b) anticipated hardness at the center of the steel rod? (a) Cooling rate is ~120 C/s with high inaccuracy (b) Jominy distance, D qe = 5 mm Hardness = 24HRC Determination of radial hardness profile...
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MECH 210 081103 - Hardenability and Jominy End Quench Test...

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