ASTM D7646-23

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Designation: D7646 − 10 (Reapproved 2019) D7646 − 23
Standard Test Method for
Determination of Cooling Characteristics of Aqueous
Polymer Quenchants for Aluminum Alloys by Cooling Curve
Analysis
This standard is issued under the fixed designation D7646; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Scope*
1.1 This test method covers the description of the equipment and the procedure for evaluating quenching characteristics of aqueous
polymer quenchants by cooling rate determination.
1.2 This test method is designed to evaluate aqueous polymer quenchants for aluminum alloys in a non-agitated system. There is
no correlation between these test results and the results obtained in agitated systems.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
D6200 Test Method for Determination of Cooling Characteristics of Quench Oils by Cooling Curve Analysis
E220 Test Method for Calibration of Thermocouples By Comparison Techniques
E230 Specification for Temperature-Electromotive Force (emf) Tables for Standardized Thermocouples
2.2 ISO Standards:
ISO 3819 Laboratory Glassware—Beakers
2.3 Japanese Industrial Standards:
JIS K 2242 Heat Treating Oil
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.L0.06 on Non-Lubricating Process Fluids.
Current edition approved May 1, 2019July 1, 2023. Published July 2019August 2023. Originally approved in 2010. Last previous edition approved in 20142019 as
D7646 – 10 (2014).(2019). DOI:10.1520/D7646-10R19.DOI:10.1520/D7646-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from SAE International (SAE), 400 Commonwealth Dr., Warrendale, PA 15096, http://www.sae.org.
Available from Japanese Standards Association (JSA), Mita MT Bldg., 3-13-12 Mita, Minato-ku, Tokyo 108-0073, Japan, http://www.jsa.or.jp.
*A Summary of Changes section appears at the end of this standard
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D7646 − 23
2.4 Wolfson Engineering Group Specification:
Laboratory Tests for Assessing the Cooling Curve of Industrial Quenching Media
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this test method, refer to Terminology D4175.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 aqueous polymer quenchant, n—aqueous solution containing a water soluble polymer; typically including poly(alkylene
glycol), poly(ethyl oxazoline), poly(sodium acrylate) and poly(vinyl pyrrolidone). The quenchant solution also typically contains
additives for corrosion and foam control, if needed. Quench severity of aqueous polymer quenchants is dependent on concentration
and molecular weight of the specific polymer being evaluated, quenchant temperature, and agitation rate.
3.2.2 characteristic temperature, n—transition temperature from vapor blanket phase (film boiling phase) to rapid cooling phase
(nucleate boiling phase) on cooling curve.
3.2.3 cooling curve, n—cooling curve is a graphical representation of the cooling time (t)–temperature (T) response of the probe
(see 7.3). An example is illustrated in Part B of Fig. 1.
3.2.4 cooling curve analysis, n—the process of quantifying the cooling characteristics of a heat treating oil based on the
temperature versus time profile obtained by cooling a pre-heated metal probe assembly (see Fig. 2) under standard conditions.
3.2.5 cooling rate curve, n—The cooling rate curve is obtained by calculating the first derivative (dT/dt) of the cooling
time–temperature curve. An example is illustrated in Part B of Fig. 1.
3.2.6 quench severity, n—the ability of a quenching medium to extract heat from a hot metal.
3.2.7 quenchant, n—any medium, liquid, or gas that may be used to mediate heat transfer during the cooling of hot metal.
4. Summary of Test Method
4.1 Determine the silver rod probe assembly’s cooling time versus temperature after placing the assembly in a furnace and heating
to 500 °C and then quenching in an aqueous polymer quenchant solution. The temperature inside the probe assembly and the
FIG. 1 Typical Temperature/Time and Temperature/Cooling Rate Plots for Test Probe Cooled in an Aqueous Polymer Quenchant
Available from Wolfson Heat Treatment Centre, Aston University, Aston Triangle, Birmingham B4 7ET, England, http://www.sea.org.uk/whtc/.
D7646 − 23
FIG. 2 Probe Details and General Probe Assembly
cooling times are recorded at selected time intervals to establish a cooling temperature versus time curve. The resulting cooling
curve may be used to evaluate quench severity.
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5. Significance and Use
5.1 This test method provides a cooling time versus temperature pathway. The results obtained by this test method may be used
as a guide in quenchant selection or comparison of quench severities of different quenchants, new or used.
6. Interferences
6.1 The presence of contaminants, such as oil, salt, metal-working fluids, forging lubricants, and polymer degradation, may affect
cooling curve results obtained by this test method for aqueous polymer quenchants.
7. Apparatus
7.1 Furnace—Use a horizontal or vertical electrical resistance tube-type furnace capable of maintaining a constant minimum
temperature of 850 °C over a heated length of not less than 120 mm and a probe positioned in the center of the heating chamber.
The furnace shall be capable of maintaining the probe’s temperature within 62.5 °C over the specimen length. The furnace, that
is, the radiant tube heating media, shall be used with ambient atmosphere.
NOTE 1—Although the probe temperature is significantly lower 500 °C than the recommended furnace temperature capability 850 °C, this higher
temperature capability is recommended since the same apparatus may be used for cooling curve analysis for steel alloys which is performed at 805 °C
to 815 °C.
7.2 Measurement System—The temperature–time measurement system shall be a computer based data acquisition system capable
of providing a permanent record of the cooling characteristics of each oil sample tested, producing a record of variation in the test
probe assembly of temperature with respect to time, and cooling rate with respect to temperature.
7.3 Probe—Shall be cylindrical, having a diameter of 10 mm 6 0.1 mm and a length of 30 mm 6 0.1 mm with a 1.0 mm sheathed
Type K thermocouple in its geometric center. The probe shall be made of a silver of purity 99.99 % or more. The probe shall be
attached to a support tube. See Fig. 2 for recommended manufacturing details. Preparation method for silver rod shall be as
follows:
7.3.1 Screw the connecting rod of heat-resistant steel in the silver rod body.
7.3.2 Insert the sheath type thermocouple through the supporting rod and supporting part.
7.3.3 Screw the connecting rod of heat resistant steel in the supporting part as inserting the sheath type thermocouple in the central
part of silver rod body.
7.3.4 Screw the supporting part in the supporting rod to connect.
7.3.5 Fix the thermocouple connecting part to the supporting rod by using a set screw while pushing the sheath type thermocouple
in the direction of silver rod body. In such a case, take care so that the tip of thermocouple is completely pressed to the central
part of silver rod body.
7.3.6 Heat the temperature of the silver rod body and supporting part at 700 °C to 800 °C, and coat the connecting part with the
crystal of silver nitrate and joint them.
7.3.7 After cooling, finish the surface smoothly by using emery papers. Although coarser 320 grit paper may be used for initial
cleaning, the final finish shall be provided using 500 grit emery paper.
7.4 Fluid Volume—The resulting cooling curve will be dependent on the temperature rise during the quench, which is dependent
on the total fluid volume. Therefore, the cooling curve analysis shall be performed with the same volume of fluid.
7.5 Sample Container—300 mL beaker specified in ISO 3819.
7.6 Temperature Measurement—Any temperature detection device may be used that is capable of measuring quenching fluid
temperature to within 61 °C.
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7.7 Transfer Mechanism—One of the following shall be used to transfer the heated probe from the furnace to the test fluid:
7.7.1 Automated Transfer Mechanism—The transfer from the furnace to the oil shall be completed within 3.0 s. Immerse the probe
in the center, 0 mm to 5 mm, of the fluid container to a depth where there is 50 mm 6 2 mm of fluid above and below the probe
when quenched. A mechanical stop shall be used for reproducibility of probe placement.
7.7.2 Manual Transfer—If manual transfer is used, the sample container shall be equipped with a fixture to ensure correct
placement in the center of the fluid container and to the depth defined in 7.4. A timer shall be used to ensure a maximum transfer
time of 3.0 s.
7.8 Timer—Graduated in seconds and minutes; may be part of a computer clock.
7.9 Fluid Volume—The resulting cooling curve will be dependent on the temperature rise during the quench, which is dependent
on the total fluid volume. Therefore, the cooling curve analysis shall be performed with the same volume of fluid.
7.10 Temperature Measurement—Any temperature detection device may be used that is capable of measuring quenching fluid
temperature to within 61 °C.
8. Reagents and Materials
8.1 Reference Quenching Fluid—Use a reference quenching fluid for initial and regular probe calibration to determine if the probe
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