The Jominy end quench test is used to measure the hardenability of a steel, which is a measure of the capacity of the steel to harden in depth under a given set of conditions.

What is quenched end?

The Jominy end-quench is used to define the hardenability of carbon steels with different alloying elements, such as chromium (Cr), manganese (Mn), or molybdenum (Mo) and having different critical cooling velocities.

What is the predominant phase at the quenched end of the steel Jominy bars?

When heated and rapidly cooled in a quench, steel will form a phase known as martensite, which has high hardness.

What is the Jominy distance?

The Jominy distance is defined as the distance from the end to the portion in which the martensite fraction is 50%, which conventionally corresponds to the inflection point of the curve. The Jominy distance measured by this way is listed in the first column of Table 9. Figure 25. Measured hardness profile.

Which ASTM standard governs the Jominy end-quench test?

12.02. 6.2 Jominy Curves. Jominy bar end-quench test is the most familiar and commonly used procedure for measuring steel hardenability. This test has been standardized and is described in ASTM A 255, SAE J406, DIN 50191, and ISO 642.

Jominy End-Quench Test

22 related questions found

How is the Jominy test done?

The Jominy Test involves heating a test piece from the steel (25mm diameter and 100mm long) to an austenitising temperature and quenching from one end with a controlled and standardised jet of water. Take a sample from the furnace and place it on the Jominy test fixtures and observe the cooling pattern.

What is the ideal critical diameter and can it be determined with a Jominy test?

The ideal size, or ideal diameter, of a steel can be defined as the size of bar hardened to 50% martensite in a "perfect" quench medium. In such a quenchant, the surface of the bar is assumed to cool instantaneously to the temperature of the quenching medium.

What is the quenching medium employed in Jominy end-quench test?

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

How can you tell Jominy distance?

The resulting curve is called 'Jominy hardenability curve' and the distance from the quenched-end is known as Jominy distance-J. (1/16″ = one Jominy distance = J₁). Fig. 4.18 illustrates typical Jominy curves of some low alloy steels.

What is Jominy curve?

Jominy end-quench hardenability curves are typically used to assess the hardenability of carburizing steels as they are for through-hardening steels. Experimentally, the Jominy curves are obtained using the conventional Jominy end-quench test described previously.

What do you know about quenching?

Quenching is the soaking of a metal at a high temperature, above the recrystallization phase, followed by a rapid cooling process to obtain certain desirable material properties. ... Quenching also increases toughness of both alloys and plastics. Quenching may also be known as quenched or quench hardening.

Why are steel tempered after quenching?

Tempering is usually performed after quenching, which is rapid cooling of the metal to put it in its hardest state. ... Higher tempering temperatures tend to produce a greater reduction in the hardness, sacrificing some yield strength and tensile strength for an increase in elasticity and plasticity.

What is critical rate of quenching?

To get the best properties, we must quench the steel past the nose of the C-curve. The cooling rate that just misses the nose is called the critical cooling rate (CCR). If we cool at the critical rate, or faster, the steel will transform to 100% martensite.

What do Jominy curves measure Mcq?

Explanation: The hardenability of the material can be measured using the Jominy end-quench test method. The composition of steel, austenitic grain size, structure before quenching, and quenching medium and method affect the hardenability of the steel.

How does the hardness change as a function of distance from the quenched end?

The cooling rate will be highest at the end being quenched, and will decrease as distance from the end increases. The hardenability is then found by measuring the hardness along the bar: the farther away from the quenched end that the hardness extends, the higher the hardenability.

Why the specimen has to be cleaned after quenching?

The object is heated in an oil bath, immediately after quenching, to prevent related cracking, to relieve internal stress and to decompose austenite without much softening.

What is bainite in steel?

Bainite is a crystalline microstructure feature that forms in steel upon heating and guided cooling. ... Bainite commonly consists of cementite and dislocation-rich ferrite. The high concentration of dislocations in the ferrite present in bainite makes this ferrite hard.

What is case hardened steel?

Case-hardening or surface hardening is the process of hardening the surface of a metal object while allowing the metal deeper underneath to remain soft, thus forming a thin layer of harder metal at the surface. ... The term face hardening is also used to describe this technique, when discussing modern armour.

What is the difference between hardness and hardenability?

Hardness is a material property that signifies an alloy's resistance to penetration. ... Hardenability signifies how deep the alloy can be hardened upon quenching after its exposure to heat treatment.

What is the name of the heat treatment process where the metal is heated and quenched in water or oil?

Quench Hardening Steel

Through a quenching process known as quench hardening, steel is raised to a temperature above its recrystallization temperature and rapidly cooled via the quenching process. The rapid quenching changes the crystal structure of the steel, compared with a slow cooling.

Which heat treatment process gives highest hardness?

After the hardening (830-860^o C and oil quench) process, the tempering temperature determines the properties obtained: the highest tensile and yield strength is obtained after tempering at 450 ^oC, while the highest impact strength is seen after tempering at 650 ^oC.

How is steel hardenability measured?

The hardenability of a ferrous alloy is measured by a Jominy test: a round metal bar of standard size (indicated in the top image) is transformed to 100% austenite through heat treatment, and is then quenched on one end with room-temperature water.

What are the factors that influence the hardenability curve?

Steels that deeply harden are called high hardenability steels, while steels that do not harden deeply are called low hardenability steels. The major factors affecting hardenability and the rate of austenite transformation are carbon content, grain size, and alloying elements.

Which of the following is the hardest constituent of steel *?

Explanation: Martensite is the hardest constituent of steel. The primary reasons accounting for this could be, the internal strains within BCC iron due to the excess carbon presence and due to the plastic deformation of parent FCC iron (austenite) surrounding the martensitic plate.

How does the rate of cooling affect the hardness of the metal?

The higher the cooling rate of the quenching, the smaller the size of the grain size. Hence, it will increase the hardness of the steel. When the cooling rate is very high, it will increase the strength of the steel but it will reduce the toughness and the ductility of the steel.