A number in parentheses indicates the year of last reapproval. This standard has been approved for use by agencies of the U. Department of Defense. Scope 1. The two test methods include the quantitative end-quench or Jominy Test and a method for calculating the hardenability of steel from the chemical composition based on the original work by M. It is measured quantitatively, usually by noting the extent or depth of hardening of a standard size and shape of test specimen in a standardized quench.
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A number in parentheses indicates the year of last reapproval. A superscript epsilon e indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the Department of Defense. Scope 1. The two test methods include the quantitative end-quench or Jominy Test and a method for calculating the hardenability of steel from the chemical composition based on the original work by M.
The Certi? It is measured quantitatively, usually by noting the extent or depth of hardening of a standard size and shape of test specimen in a standardized quench.
In the end-quench test the depth of hardening is the distance along the specimen from the quenched end which correlates to a given hardness level. The values given in parentheses are for information only. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Referenced Documents 2. Current edition approved March 10, Published June Originally published as A — Last previous edition A — Description 3. The test consists of water quenching one end of a cylindrical test specimen 1. Apparatus 4. A satisfactory type of support for the standard 1. A tank of sufficient capacity to maintain the water temperature requirements of 6. The water-supply line shall also be provided with a quick opening valve.
Test Specimens 5. If negotiated between the supplier and the user, the end-quench specimen may be prepared from a given location in a forged or rolled product or from a continuous cast billet.
The test specimen shall be 1. Dimensions of the preferred specimen and of an optional specimen Note 2 are given in Fig. The specimen shall be machined from a bar previously normalized in accordance with 6. The end of the specimen to be water cooled shall have a reasonably smooth? Normalizing may be waived by agreement between the supplier and the user.
The previous thermal history of the specimen tested shall always be recorded. Cast specimens are not suitable for boron steel grades due to erratic results. A graphite or metal mold may be used to form an overlength specimen 1. The mold may also be used to form a 1. Cast tests need not be normalized. Procedure 6. The sample shall be held at the temperature listed in Table 1 for 1 h and cooled in air. Tempering of the normalized sample to improve machinability is permitted.
In production testing slightly longer times up to 35 min may be used without appreciably affecting results. It is important to heat the specimen in such an atmosphere that practically no scaling and a minimum of decarburization takes place.
This may be accomplished by heating the specimen in a vertical position in a container with an easily removable cover containing a layer of cast-iron chips with the bottom face of the specimen resting on the chips. Place a disk of graphite or carbon, or a layer of carbonaceous material such as charcoal, in the bottom of the tube to prevent scaling. Repeat this procedure periodically, for example once a month, for each combination of? The support for the specimen shall be dry at the beginning of each test.
Then place the heated specimen in the support so that its bottom face is 0. The time between removal of the specimen from the furnace and the beginning of the quench should not be more than 5 s. Maintain a condition of still air around the specimen during cooling. If the specimen is not cold when removed from the? Shallower ground depths can affect reproducibility of results, and correlation with cooling rates in quenched bars.
They should be mutually parallel and 3 the grinding done in such a manner that no change of the quenched structure takes place. Very light cuts with water cooling and a coarse, soft-grinding wheel are recommended to avoid heating the specimen.
In order to detect tempering due to grinding, the? Wash the sample in hot water. Etch in solution No. Wash in hot water. Immerse in solution No. Dry in air blast. If such changes caused by grinding are indicated, new? It is important that no vertical movement be allowed when the major load is applied. The anvil must be constructed to move the test specimen past the penetrator in accurate steps of 1?
Resting the specimen in a V-block is not permitted. It is recommended that a test block be interposed between the specimen and the indenter to check the seating of the indenter and the specimen simultaneously. For general statements regarding the use of test blocks and surface conditions, reference should be made to 4. A lowpower measuring microscope is suitable for use in determining the distance from the quenched end to the center of the?
It has been found that with reasonable operating care and a well-built? The variations between spacings should be even smaller. Obviously, it is more important to position the indenter accurately when testing A low-hardenability steels than when testing high-hardenability steels. The positioning of the indenter should be checked with sufficient frequency to provide assurance that accuracy requirements are being met. In cases of lack of reproducibility or of differences between laboratories, indenter spacing should be measured immediately.
Values below 20 HRC are not recorded because such values are not accurate. When a? Testing on two? If the two probes on opposite sides differ by more than 4 HRC points at any one position, the test should be repeated on new?
If the retest also has greater than 4 HRC points spread, a new specimen should be tested. Plotting Test Results 7. When hardness readings are taken on two or more? A facsimile of the standard ASTM hardenability chart3 on which typical hardenability curves have been plotted is shown in Fig. Index of Hardenability 8. Examples of this method are J 4? Report 9. Conshohocken, PA Introduction Grossman and provides increased accuracy by re? These re? The accuracy of this test method and the techniques used to develop it have been documented.
For comparison of this test method to others, or for steel compositions outside the mentioned grades, the user should refer to other articles concerned with calculating hardenability. For simplicity, only multiplying factors for DI in inch—pound units are given. For DI in millimetres, use the metric value table. The effects of phosphorous and sulfur are not considered since they tend to cancel one another.
The higher the carbon or alloy content, or both, the lower the boron factor. CarbonGrain Mn Size 7 0. For the example heat with 0. Boron factor 5 1. For the example in Carbon multiplying factor 5 0. For this example with 0. For the example non-boron SAE modi? DI, in. For simplicity, the DI should be rounded to the nearest 0. The use of these equations to plot curves may result in random in?
ASTM A255 - 10
ASTM A255 - 10