JOMINY HARDENABILITY TEST PDF
JOMINY HARDENABILITY TEST. Objective. To study hardness as a function of quench rate and investigate the hardenability of steels. Introduction. PDF | 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. 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.
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The hardness trst the samples was measured as a function of the distance from the quenched end to demonstrate the different hardenability of the two steels.
The Jominy End Quench Test
Structure of En 8 at the quenched end of Jominy bar. The Jominy Test involves heating a test piece from the steel 25mm diameter and mm long to an austenitising temperature and quenching from one end with a controlled and standardised jet of water.
The main alloying elements which affect hardenability are carbon, boron and a group of elements including Cr, Mn, Mo, Si and Ni. The water jet is started and sprayed onto the bottom of the specimen until the specimen is cool. There are conversion charts between the hardness scales. This results in a progressive decrease in the rate of cooling along the bar from the quenched end.
A typical plot of hardness along the length of the 10 cm long steel rod. These include alloying elements and grain size. High hardenability allows slower quenches to be used e. Your browser does not support the video tag.
Effects of alloying and microstructure Example Jominy end quench nominy data Heat flow simulation Quench test simulation Summary Questions Going further. 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.
The Jominy End Quench Test
Steel compositions are sometimes described in terms of a carbon equivalent which describes the magnitude of the effect of all of the elements on hardenability. The cooling rate will be highest at the end being quenched, and will decrease as distance from the end increases.
This describes the ability of the steel to be hardened in depth by quenching. For example, a steel of a high hardenability can transform to a high fraction of martensite to depths of several millimetres under relatively slow cooling, such as an hardenabolity quench, whereas a steel of low hardenability may only form a high fraction of martensite to a depth of less than a millimetre, even under rapid cooling such as a water quench. Hardenability depends on the chemical composition of the steel and also be can affected by prior processing conditions, such as the austenitizing temperature.
It jominny not be confused with hardnesswhich is a measure of a sample’s resistance to indentation or scratching. In other projects Wikimedia Commons. Hardenability is the ability of a steel to partially or completely transform from austenite to some fraction of martensite at a given depth below the surface, when cooled under a given condition.
However, the effect is too small be be commonly used for control of hardenability.
Clicking on the circled data points will take teet to images of the microstructure at that location in the sample. Hardenability therefore describes the capacity of the steel to harden in depth under a given set of conditions. There are different scales for the Rockwell hardness test.
Jominy End Quench Test
Subsequent to cooling a flat surface is ground on the test piece and the hardenability is then found by measuring the hardness along the bar. Gardenability important to use the correct conversion chart for different materials, since the hardness test causes plastic strain, and therefore varies with the strain hardening properties of the material.
Select the most appropriate steel to achieve the necessary levels of mechanical properties, residual stress and distortion in a 1mm diameter wood-working drill. Select the plot of hardness variation along the test specimen that hardenabiloty describes their behaviour.
The fluid used for quenching the material influences the cooling rate due to varying thermal conductivities and specific heats. Here a specimen is in place.
The Jominy End Quench Test, ASTM A
Increasing the carbon content increases the hardness of steels up to about 0. Boron has a very strong affinity for oxygen and nitrogen, with which it forms compounds. Three medium carbon steels 0. Carbon controls the hardness of the martensite.
Slow quenching speeds are often chosen to reduce hardenabilitj and residual stress in components. This is commonly used in the USA.
The steel sample is normalised to eliminate differences in microstructure due tfst previous forging, and then austenitised. In the example here, the surface will be transformed to martensite, but the core will have a bainitic structure with some martensite. High hardness occurs where high volume fractions of martensite develop.
A high hardenability is required for through hardening of large components.