Question: What is hardenability? Explain jominys end quench test to measure Hardenability

Subject Material Technology

Topic Theory of Alloy and Alloy Diagram

Difficulty Level High

mt(63) • 218 views
modified 11 months ago  • written 11 months ago by gravatar for Atharv Inamdar Atharv Inamdar650
  1. Ability of steel to harden depends on its section size, composition, austenitizing temperature, and quenching medium is termed as hardenability.

  2. The Jominy’s test provides a measure of the ability of steel to harden by transforming into martensite under set conditions, i.e., a measure of the hardenability of the steel.

  3. A standardised bar, 25.4 mm diameter and 102 mm long, is heated to the austenitizing temperature and then placed on a rig in which one end of the rod is quenched by a standard jet of water.

  4. This results in a progressive decrease in the rate of cooling along the bar from the quenched end. The depth from the quenched end, over which martensite is obtained, is then the measure of hardenability.

  5. The austenitizing temperature of steel is 800 to 900 degrees.

  6. After cooling completely the Rockwell hardness is calculated at various points from bottom end and a graph is plotted between hardness and length form quenched end of specimen.

  7. The hardness decreases from quenched end as we move ahead along the length of specimen and giving result of formation of martensite form quenched end and slowly reducing to perlitic & ferritic phase.

written 11 months ago by gravatar for Atharv Inamdar Atharv Inamdar650
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