experiment no. 8 done.doc

8/17/2019 Experiment No. 8 Done.doc

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EXPERIMENT NO. 8

THE JOMINY END QUENCH TEST

THEORY

Hardenability (not the same property as hardness) is a measure of the depth to which a

particular steel will harden (i.e. from martensite) when quenched from its austenitizing

temperature. Data are represented by a plot of HRC Hardness vs. Distance from thequenched end (related to cooling rate) of a standard specimen inch in diameter by !

inches long with a means for hanging it in a vertical position. "rom such a plot the

hardness of a piece of that steel with a different geometry can be predicted by matching

the cooling rate.

Executive Summary#he $ominy %nd &uench #est '# ' *++ measures Hardenability of steels.

Hardenability is a measure of the capacity of steel to be hardened in depth when

quenched from its austenitizing temperature. Hardenability of steel should not beconfused with the hardness of steel. #he Hardness of steel refers to its ability to resist

deformation when a load is applied, whereas hardenability refers to its ability to behardened to a particular depth under a particular set of conditions. -nformation gained

from this test is necessary in selecting the proper combination of alloy steel and heat

treatment to minimize thermal stresses and distortion when manufacturing components of various sizes.

#o perform the $ominy #est "irst, a sample specimen cylinder either //mm in length

and *+mm in diameter, or alternatively, /*mm by *+.!mm is obtained. econd, the steelsample is normalized to eliminate differences in microstructure due to previous forging,

and then it is austerities. #his is usually at a temperature of 0// to 1//2C. 3e4t, thespecimen is rapidly transferred to the test machine, where it is held vertically and sprayedwith a controlled flow of water onto one end of the sample. #his cools the specimen from

one end, simulating the effect of quenching a larger steel component in water. 5ecause

the cooling rate decreases as one moves further from the quenched end, you can measurethe effects of a wide range of cooling rates from vary rapid at the quenched end to air

cooled at the far end.

3e4t, the specimen is ground flat along its length to a depth of .60mm (+ thousandths of

an inch) to remove decarburized material. #he hardness is measured at intervals along its

length beginning at the quenched end. "or alloyed steels an interval of .+mm is

commonly used whereas with carbon steels an interval of .7+mm is typically employed.And finally the Rockwell or Vickers hardness values are plotted versus distance from the

quenched end.

The Jominy Test data illustrates the effect of alloying and microstructure on the hardenability

of steels. Commonly used elements that affect the hardenability of steel are carbon, boron,

Chromium, Manganese, Molybdenum, Silicon, and Nickel.

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Carbon is primarily a hardening agent in steel, although to a small degree it also increases

hardenability by slowing the formation of pearlite and ferrite. 5ut this affect is too small

to be used as a control factor for hardenability.

5oron can be an effective alloy for improving hardenability at levels as low as .///+8.

5oron is most effective in steels of /.*+8 Carbon or less. 5oron combines readily with both 3itrogen and 94ygen and in so doing its effect on hardenability is sacrificed.

#herefore 5oron must remain in solution in order to be affective. 'luminum and

#itanium are commonly added as :gettering: agents to react with the 94ygen and 3itrogen in preference to the 5oron.

lowing the phase transformation of austenite to ferrite and pearlite increases the

hardenability of steels. Chromium, olybdenum, anganese, ilicon, 3ic;el andoff wheel.

0. ount the sample in the %quitron device.

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1. easure the hardness (HRC) along the flats at =?>inch internals. tart at

the quench end.

/. lot Hardness vs. Distance to obtain the $ominy curve. lot both curves

on the same plot.

9#-93' >+

. Cut the bar on the cut>off wheel at the midpoint.

*. easure the transverse hardness (HRC). lot the results.

6. olish the other side of the cut bar.

!. #a;e photomicrograph of the polished surface.

+. olish one flat and loo; at the microstructure as a function of $ominydistance. #a;e photomicrographs.

"$%tractHardenability of steel is defined as the susceptibility of the steel to hardening when

quenched, and is related to the depth and distribution of hardness across a cross section.

#here are various factors which effect hardenability of steels such as austenite grain size,carbon content and alloying elements percentage. Hardenability property is so important

that a simple test is essential to measure it. #here are various methods to measure

hardenability of steel such as Arossman critical diameter method, $ominy end quench

test, estimation of hardenability from chemical composition and "racture test .#he$ominy end>quench test, though inelegant from a scientific standpoint, fills this need. -n

this paper we discussed about the significance of hardenability and role of $ominy test inmeasurement of hardenability

RESU#TS "ND DISCUSSION

. lot the $ominy curve and determine if the results fall within the specified band. 're both flats the same distance from the edge of the barE

9#-93' *>!

*. 5ased on the transverse plot, determine the cooling rates across the bar

where you cut it.

6. How does the transverse plot correlate with the photomicrographE

!. How does the $ominy curve correlate with the microstructure of the polished flatE

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RE&ERENCES

. 's;eland, D.R., #he cience and %ngineering of aterials, 5oston, 'F %ngineering, 10!, pp. 67*>67?.

*. Callister, F.D., aterials cience and %ngineering, 3ew Gor;, 3G $.Filey ons, 10+, pp. **7>*6+.

6. !70.

!. '# tandard ' **+.

+. 'tlas of -sothermal #ransformations Diagrams, B, ittsburgh, ',

1+.

?. ractical Data for etallurgists, #he #im;en Company, teel Division,Canton, 9H, 177.

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De%i'(ati)(* " +,,- / 0Rea11r)ve2 34/45 3

Sta(2ar2 Met6)2 )7

END-QUENCH TEST &OR H"RDEN"I#ITY O& STEE#3#his standard is issued under the fi4ed designation ' 255; the number immediately following the designation indicatesthe year of original adoption or, in the case of revision, the year of last revision. ' number in parentheses indicates the

year of last reapproval.' superscript epsilon (∈) indicates an editorial change since the last revision or reapproval.

This method has been approved for use by agencies of the Department of Defense to replace method 711.1of Federal Test Method tandard !o. 151b and for listing in the DoD "nde# of pecifications andtandards.

3ote > ection * was added editorially and subsequent sections renumbered in $une 10!.

3. Sc)1e

. #his method covers the procedure for determining the hardenability of steel by theend quench or $ominy test. #he test consists of water quenching one end of a cylindricaltest specimen in. (*+ mm) in diameter and measuring to what e4tent from the quenched

end the steel hardens..* Hardenability is a measure of the depth to which steel will harden when quenched

from its austenitizing temperature (see 'ppendi4 Il). -t is measured quantitatively,usually by noting the e4tent or depth of hardening of a standard size and shape of testspecimen in a standardized quench. -n the end>quench test the depth of hardening is thedistance along the specimen from the quenched end for a given degree of hardening.

+. "11ica$e D)cume(t%

*. $TM tandards% % 0 #est ethods for Roc;well Hardness and Roc;welluperficial Hardness of etallic aterials*.

% * ethods of Determining 'verage Arain ize6.

9. "11aratu%

6. upport for Test pecimen&' fi4ture for supporting the test specimen vertically sothat the lower end of the specimen is a distance of =* in. (*.7 mm) above the orifice of the water>quenching device. ' satisfactory type of support for the standard >in. (*+>mm)specimen is shown in "ig. .

3ote >' suitable support for other sizes and shapes of specimens is shown in "ig. Il..6.* 'ater&(uenching Device&' water>quenching device of suitable capacity to provide

a vertical stream of water that can be controlled to a height of * =* in. (?6.+ mm) when passing through an orifice =* in. (*.7 mm) in diameter. ' tan; of sufficient capacitywith a small pump and control valves will be found satisfactory. #he water>supply lineshall also be provided with a quic; opening valve.

:. Te%t S1ecime(%

!. Forged pecimens>#he test specimen shall be appro4imately in. (*+ mm) indiameter by 6 or ! in. (7? or /* mm) in length, with means for hanging it in a vertical position for end quenching. Dimensions of the preferred specimen and of two optionalspecimens (3ote *) are given in "igs. *, 6, and !. #he specimen shall be machined from

534 ASTM Standard A225. pp. 69-80


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a bar previously normalized and of such size as to permit the removal of alldecarburization in machining to >in. round. #he end of the specimen to be water cooledshall have a reasonably smooth finish, preferably produced by grinding. 3ormalizingmay be waived by agreement between the supplier and the purchaser. #he previousthermal history of the specimen tested shall always be recorded.

!.* )ast pecimens J's an alternate method the specimens may be cast during the

pouring of the steel. ' graphite or metal mold may be used to form an overlengthspecimen appro4imately >in. diameter which shall be cut to the standard specimen sizeKor the mold may be used to form a =! in. (6*>mm) diameter specimen which shall bemachined to the final specimen size. Cast tests need not be normalized.

39#% *J9ther sizes and shapes of test specimens are described in 'ppendi4 I*.

,. Pr)ce2ure

5.1 *eating Jlace the specimen in a furnace which is at the specified austenitizingtemperature (see 'ppendi4 Il #able Il.) and hold at this temperature for 6/ min. -n production testing slightly longer times up to 6+ min. may be used without appreciablyaffecting results. -t is important to heat the specimen in such an atmosphere that

practically no scaling and a minimum of decarburization ta;es place. #his may beaccomplished by heating the specimen in a vertical position in a container with an easilyremovable cover containing a layer of cast>iron chips with the bottom face of thespecimen resting on the chips.

+.. 's an alternative method, place the specimen in an upright tube attached to a flat base, both of a heat>resistant metal, with the collar pro@ecting for a tong hold. lace adis; of graphite or carbon, or a layer of carbonaceous material such as charcoal, in the bottom of the tube to prevent scaling.

+..* "or a particular fi4ture and furnace, determine the time for heating the specimento the quenching temperature by inserting a thermocouple into a hole drilled a4ially in thetop of the specimen. Repeat this procedure periodically, for e4ample, once a month, for each combination of fi4ture and furnace.

5.2 &uenching>'d@ust the water>quenching device so that the stream of water rises toa free height of * =* in. (?6.+ mm) above the =* in. (*.7 mm) orifice, without thespecimen in position. #he support for the specimen shall be dry at the beginning of eachtest. #hen place the heated specimen in the support so that its bottom face is =* in.above the orifice, and turn on the water by means of the quic;>opening valve. #he time between removal of the specimen from the furnace and the beginning of the quenchshould not be more than +s. Direct the stream of water, at a temperature of !/ to 0+°"(!.+ to *1.+°C) against the bottom face of the specimen for not less than / min. o far as possible, maintain a condition of still air around the specimen during cooling. -f thespecimen is not cold when removed from the fi4ture, immediately quench it in water.

+.6 *ardness Measurement Ja;e the hardness readings in terms of Roc;well C onthe test specimen in steps of =? in. (.+1 mm) to the >in. distance from the quenchedend and in steps at the discretion of the operator from that point. 3umber the series ofhardness readings from the quenched end of the specimen. a;e the hardness readingson surfaces that are mutually parallel flat surfaces, 0/° apart, ground length>wise, of thespecimen. Arind the flat surfaces to a minimum depth of /./+ in. (/.60 mm). Fhen aflat surface is used as a base, remove previous indentations by grinding. Arinding can beomitted if the bed of the testing fi4ture is grooved to accommodate the indentations.

+.6. #he e4act position of each hardness reading with respect to the quenched end ofthe specimen must be ;nown. #he use of a fi4ture to locate indentations precisely andassure accuracy of comparisons between tests is imperative. #a;e care to ensure no



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0..* Chemical composition,0..6 '# grain size (c&uaid>%hn) as determined by ethods %*, unless

otherwise indicated,0..! Hardening temperature used in the test, and0..+ ' prominent notation on the standard hardenability chart if any of the test

specimens listed in 'ppendi4 I* are used.

39#% +>#he cooling rates on the chart correspond to the distances from the quenchedend for the >in. (*+ mm) round specimen only, and will be incorrect for the other specimens shown in 'ppendi4 I*, e4cept "ig. I*. . #he cooling rates for differentsteels show some variation. #he appro4imate values shown on the chart are the averageresults of tests run on three steels.

#his method is under the @urisdiction of '# Committee '> on teel, tainless teel and Related'lloys and is the direct responsibility of ubcommittee ' />+ on 5ar teels.

Current edition accepted ay *!, 1?7. 9riginally issued 1!*. Replaces ' *++>?!.* $nnual 0oo of $TM tandards /.



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664 ASTM Standard A 225. p. 178


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675 Atlas of Isothermal Transformatons !a"rams# p.19


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686$ra%t%al !ata for Metall&r"sts# p. 51


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696$ra%t%al !ata for Metall&r"sts# p. 51


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706$ra%t%al !ata for Metall&r"sts# pp. 86-87


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experiment no. 8 done.doc

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