ASTM A255-10(R2018) pdf free download

ASTM A255-10(R2018) pdf free download.Standard Test Methods for Determining Hardenability of Steel
5. Test Specimens
5.1 Wrought Specimens—End-quench specimens shall be prepared from rolled or forged stock and shall represent the full cross section of the product. 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 1.0 in. (25.4 mm) in diameter by 4.0 in. (101.6 mm) in length, with means for hanging it in a vertical position for end quenching. Dimensions of the preferred specimen and of an optional specimen (Note 2) are given in Figs. 2 and 3. The specimen shall be machined from a bar previously normalized in accordance with 6.1 and of such size as to permit the removal of all decarburization in machining to 1.0 in. round. The end of the specimen to be water cooled shall have a reasonably smooth finish, preferably produced by grinding. Normalizing may be waived by agreement between the supplier and the user. The previous thermal history of the specimen tested shall always be recorded. 5.2 Cast Specimens—A separately cast end-quench speci- men may be used for non-boron steels. 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 1.0 in. (25.4 mm) in diameter which shall be cut to the standard specimen size. The mold may also be used to form a 1.25-in. (31.8-mm) diameter specimen which shall be machined to the final specimen size. Cast tests need not be normalized.
6. Procedure
6.1 Normalizing- -The wrought product from which the specimen is to be prepared shall be normalized to ensure proper hardening characteristics. 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. 6.2 Heating- Place the specimen in a furnace that is at the specified austenitizing temperature (Table 1) and hold at this temperature for 30 min. 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. 6.2.1 Other methods consist of placing the specimen in an appropriately sized hole in a graphite block or placing the specimen in an upright tube attached to a flat base, both of a heat-resistant metal, with the collar projecting for a tong hold. 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. 6.2.2 For a particular fixture and furnace, determine the time required to heat the specimen to the austenitizing temperature by inserting a thermocouple into a hole drilled axially in the top of the specimen. Repeat this procedure periodically, for ex- ample once a month, for each combination of fixture and furnace.6.3 Quenching- Adjust the water-quenching device so that the stream of water rises to a free height of 2.5 in. (63.5 mm) above the 0.5-in. (12.7-mm) orifice, without the specimen in position. 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 0.5 in. above the orifice, and turn on the water by means of the quick-opening valve. The time between removal of the specimen from the furnace and the beginning of the quench should not be more than 5 s. Direct the stream of water, at a temperature of 40 to 85 °F (5 to 30 °C), against . the bottom face of the specimen for not less than 10 min. Maintain a condition of still air around the specimen during cooling. If the specimen is not cold when removed from the fixture, immediately quench it in water. 6.4 Hardness Measurement- -Two flats 1 80° apart shall be ground to a minimum depth of 0.015 in. (0.38 mm) along the entire length of the bar and Rockwell C hardness measure- ments made along the length of the bar. Shallower ground depths can affect reproducibility of results, and correlation with cooling rates in quenched bars.