For example, any video clips and answers to questions are missing. The formatting page breaks, etc of the printed version is unpredictable and highly dependent on your browser. 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. This TLP considers the basic concepts of hardenability and the Jominy test. Knowledge about the hardenability of steels is necessary to be able to select the appropriate combination of alloy steel and heat treatment to manufacture components of different size to minimize thermal stresses and distortion. The Jominy end quench test is the standard method for measuring the hardenability of steels.
|Published (Last):||5 January 2007|
|PDF File Size:||5.33 Mb|
|ePub File Size:||19.74 Mb|
|Price:||Free* [*Free Regsitration Required]|
The manufacturing primarily starts with the selection of material to be used. The selection expediency has a vital importance. Since the material which is most commonly used in the machinery manufacturing and construction industry is steel, the steel selection is highly important.
The hardenability indicates the hardenability as a result of martensite transformation with tempering operation of steel. The hardenability detects the hardness depth obtained with tempering. The steel having a high hardenability displays a high hardenability depth. The hardenability depth is very important for tool and structural steels.
Since the hardenability is generally described in the form of hardness change, it is the hardness change depending on its ratios, primarily steel type C carbon. Moreover, it can be regarded as micro structure change. In general, its hardness is increased through the transformation of its elements to perlite, bainite. The carbon, which is main element, is the element which makes the most impact on steel properties.
It increases the chrome resistance and hardenability properties. It creates the chrome carbide, which is very rigid, by carburization. The nickel, which is used with chrome, allows for hardness going deeper.
Although the molybdenum which is used with Cr and Ni, is added at a very less amount, it increases the hardness and resistance. However, it eliminates the brittleness formation. The hardness which will be acquired following the hardening of steel, is leading preference factor. Therefore, the Hardenability Test, in other words Jominy Test, is applied by tempering the austentized steel by a plane in order to determine the hardenability of steel.
Before the specimen is machined and quenched, it must be normalised. The surface of the specimen must be precision-turned and the end to be quenched precision machined. The end surface must be burr-free. One the specimen has been produced, it must be evenly heated up to the temperature defined in the standard over a period of at least 20 minutes and then held at the prescribed temperature for at least 30 but not more than 35 minutes. Carburisation or decarburisation of the specimen should be kept as low as possible, and oxidation with scale formation should be avoided. The time between the removal of the specimen from the furnace and the start of quenching must not be longer than five seconds.
The Jominy End Quench Test
The manufacturing primarily starts with the selection of material to be used. The selection expediency has a vital importance. Since the material which is most commonly used in the machinery manufacturing and construction industry is steel, the steel selection is highly important. The hardenability indicates the hardenability as a result of martensite transformation with tempering operation of steel. The hardenability detects the hardness depth obtained with tempering. The steel having a high hardenability displays a high hardenability depth. The hardenability depth is very important for tool and structural steels.
Jominy End Quench Test
The hardenability of a metal alloy is the depth to which a material is hardened after putting it through a heat treatment process. It should not be confused with hardness , which is a measure of a sample's resistance to indentation or scratching. When a hot steel work-piece is quenched , the area in contact with the water immediately cools and its temperature equilibrates with the quenching medium. The inner depths of the material however, do not cool so rapidly, and in work-pieces that are large, the cooling rate may be slow enough to allow the austenite to transform fully into a structure other than martensite or bainite. This results in a work-piece that does not have the same crystal structure throughout its entire depth; with a softer core and harder "shell". The hardenability of ferrous alloys, i. The fluid used for quenching the material influences the cooling rate due to varying thermal conductivities and specific heats.
Understanding the Jominy End-Quench Test
A heat treatment that causes steel to harden is so much more than the meer plunging of hot metal into a fluid that is often a liquid. The initial red-hot state represents the austenitic condition and the subsequent cooling results in a variety of transformations that depend on the chemical composition of the steel. If the intention is to produce a martensitic structure, then the constituents of the steel must be such that the phase is obtained over the depth required. The Jominy test provides a measure of the ability of a steel to harden by transforming into martensite under set conditions, i. A standardised bar, This results in a progressive decrease in the rate of cooling along the bar from the quenched end.