Alloy H Steels and End Quench Hardenability - 8620H - 4140H - 4340H

Alloy H Steels and End Quench Hardenability - 8620H - 4140H - 4340H - For the full transcript click here: https://www.michlinmetals.com/alloy-h...
Alloy steels like these develop their best properties after heat treatment. How do we compare alloys and know what to expect after heat treatment?

Alloys are very different from each other.  Even variations within the allowable chemistry limits of an alloy can affect the hardness profile  that can be achieved.

Metallurgists had to develop means of evaluating the hardenability to be able to compare the response of a given alloy chemistry to heat treatment.

One method,  the "end quench" or "Jominy end quench" hardenability test... originally used a sample of the material .....  about one inch in diameter and four inches long.  It was hardened  by heating to a standard temperature and then quenched  from one end of that cylinder. The sample then was  hardness tested at increments of one sixteenth of an inch along the length of the cylinder starting at the end that was quenched.

Results are expressed as a Rockwell C scale hardness at the distance from the quenched end. For example "J1 = 40"  is  a 40 Rc hardness one sixteenth from the quenched end and J8=30 is 30 Rc at eight sixteenths from the quenched end.

Today, the hardness profile can be accurately determined by computer from the very precise chemical composition of modern steel making procedures.