ASTM B661-99
(Practice)Standard Practice for Heat Treatment of Magnesium Alloys
Standard Practice for Heat Treatment of Magnesium Alloys
SCOPE
1.1 This practice is intended as an aid in establishing a suitable procedure for the heat treatment of magnesium alloys to assure proper physical and mechanical properties.
1.2 Times and temperatures are typical for various forms, sizes, and manufacturing methods and may not exactly describe the optimum heat treatment for a specific item. Consequently, it is not intended that this practice be used as a substitute for a detailed production process or procedure.
1.3 This standard does not purport to address all of the safety problems, if any, associated with its use. 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.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: B 661 – 99
Standard Practice for
Heat Treatment of Magnesium Alloys
This standard is issued under the fixed designation B 661; 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 (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.
1. Scope * solution heat treatment, furnaces must be gas tight and contain
suitable equipment for the introduction of protective atmo-
1.1 This practice is intended as an aid in establishing a
spheres, and means for control of those atmospheres. In order
suitable procedure for the heat treatment of magnesium alloys
to promote uniformity of temperature, furnaces should be
to assure proper physical and mechanical properties.
equipped with a high-velocity fan or comparable means for
1.2 Times and temperatures are typical for various forms,
circulating the atmosphere. In the design of the furnace it is
sizes, and manufacturing methods and may not exactly de-
desirable that there be no direct radiation from the heating
scribe the optimum heat treatment for a specific item. Conse-
elements or impingement of the flame on the magnesium.
quently, it is not intended that this practice be used as a
4.2 Automatic recording and control equipment to control
substitute for a detailed production process or procedure.
the temperature of the furnaces, which must be capable of
1.3 This standard does not purport to address all of the
maintaining temperature in the working zone to within 610°F
safety problems, if any, associated with its use. It is the
(66°C) of the specified temperature.
responsibility of the user of this standard to establish appro-
4.3 There must be a separate manual reset safety cutout
priate safety and health practices and determine the applica-
which will turn off the heat source in the event of any
bility of regulatory limitations prior to use.
malfunctioning or failure of the regular control equipment.
2. Referenced Documents These safety cutouts shall be set as closely as practicable above
the maximum temperature for the alloy being heat treated. This
2.1 ASTM Standards:
will be above the variation expected, but shall not be more than
B 557 Test Methods of Tension Testing Wrought and Cast
10°F (6°C) above the maximum solution heat treating tempera-
Aluminum- and Magnesium-Alloy Products
ture for the alloy being heat treated. Protective devices shall
E 21 Test Methods for Elevated Temperature Tension Tests
also be installed to turn off the heat source in case of stoppage
of Metallic Materials
of circulation of air, and they shall be interconnected with a
E 44 Definitions of Terms Relating to Heat Treatment of
manual reset control.
Metals
4.4 The furnaces or ovens used for aging treatments may be
E 527 Practice for Numbering Metals and Alloys (UNS)
heated by means of electricity, gas, or oil. The temperature at
3. Terminology
any point in the working zone, for any charge, shall be
maintained within 610°F (66°C) of the desired aging tem-
3.1 Definitions:
perature after the furnace has been brought up to the aging
3.1.1 The definitions relating to heat treatment of metals
temperature.
appearing in Definitions E 44 are considered as applying to this
4.5 Quenching:
practice.
4.5.1 Normally magnesium work loads are cooled in air.
4. Apparatus
This should be by fan cooling the furnace charge after removal
from the furnace in such a way that the cooling is uniform on
4.1 Furnaces used for the heat treatment of magnesium are
various parts of the furnace charge.
usually of the air chamber type and may be electrically heated
4.5.2 Some alloys (notably EQ21A, QE22A, WE43A, and
or oil- or gas-fired. Because of the atmospheres used for
WE54A) are quenched in water or other suitable media from
the solution heat treating temperature. Quench tanks should be
This practice is under the jurisdiction of ASTM Committee B-7 on Light Metals
situated near the heat treatment furnaces. If required, means of
and Alloys and is the direct responsibility of Subcommittee B07.04 on Magnesium
heating the quench medium should be provided. Handling
Alloy Cast and Wrought Products.
Current edition approved May 10, 1999. Published August 1999. Originally
equipment shall be such that it is possible to quench heat
published as B 661 – 79. Last previous edition B 661 – 93.
treatment loads within 30 s after the opening of the furnace
Annual Book of ASTM Standards, Vol 02.02.
door.
Annual Book of ASTM Standards, Vol 03.01.
Annual Book of ASTM Standards, Vol 01.02. 4.6 In the case of ZE63A alloy, a special heat treatment
Annual Book of ASTM Standards, Vol 01.01.
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
B 661
apparatus is required to enable heat treatment to take place in sary when the furnace is equipped with a permanent multipoint
a hydrogen atmosphere. recording system with at least two sensing thermocouples in
each working zone, or when one or more separate load
5. Calibration and Standardization
thermocouples are employed to measure actual metal tempera-
5.1 Calibration of Equipment:
ture, providing that uniformity surveys show a history of
5.1.1 Surveys:
satisfactory performance for a period of at least 6 months. The
5.1.1.1 Perform a temperature survey, to ensure compliance
sensing thermocouples shall be installed so as to record the
with the applicable recommendations presented herein for each
temperature of the heated air or actual metal temperatures.
furnace.
However, periodic surveys shall also be made at 6-month
5.1.1.2 Make a new temperature survey after any changes
intervals in accordance with the procedures outlined for the
in the furnace that may affect operational characteristics.
monthly survey.
5.1.2 Furnace Calibration:
5.1.2.8 Do not use furnace control temperature-measuring
5.1.2.1 Make the initial temperature survey at the maxi-
instruments to read the temperature of the test temperature-
mum and minimum temperature of solution heat treatments
sensing elements.
and aging heat treatment for which each furnace is to be used.
5.1.3 Temperature-Measuring System Check— Check the
3 3
There shall be at least one test location for each 25 ft (0.7 m )
accuracy of temperature-measuring system under operating
of air furnace volume up to a maximum of 40 test locations
conditions weekly. Check should be made by inserting a
with a minimum of nine test locations.
calibrated test temperature-sensing element adjacent to the
5.1.2.2 After the initial survey, survey each furnace
furnace temperature-sensing element and reading the test
monthly, except as provided in 5.1.2.7. The monthly survey
temperature-sensing element with a calibrated test potentiom-
shall be at one operating temperature for solution heat treat-
eter. When the furnace is equipped with dual potentiometer
ment and one for aging heat treatment.
measuring systems, which are checked daily against each
5.1.2.3 For the monthly surveys there shall be at least one
other, the above checks may be conducted every three months
3 3
test location for each 40 ft (1.13 m ) load volume.
rather than every week. Calibrate the test temperature-sensing
3 3
5.1.2.4 For furnaces of 10 ft (0.28 m ) or less the
element, potentiometer, and cold junction compensation com-
temperature survey may be made with a minimum of three
bination against National Institute of Standards and Technol-
thermocouples located at front, center, and rear, or at top,
ogy primary or secondary certified temperature-sensing ele-
center, and bottom of the furnace.
ments, within the previous three months, to an accuracy of
5.1.2.5 Perform the surveys in such manner as to reflect the
62°F (1.1°C).
normal operating characteristics of the furnace. If the furnace is
5.1.4 Records— Maintain records for each furnace for at
normally charged after being stabilized at the correct operating
least 7 years to show compliance with this standard. These
temperature, similarly charge the temperature-sensing ele-
records shall include the following: furnace number or descrip-
ments. If the furnace is normally charged cold, charge the
tion; size; temperature range of usage; whether used for
temperature-sensing elements cold. After insertion of the
solution heat treatment or aging heat treatment, or both;
temperature-sensing elements, readings should be taken fre-
temperature(s) at which uniformity was surveyed; dates of each
quently enough to determine when the temperature of the
survey; number and locations of thermocouples used; and dates
hottest region of the furnace approaches the bottom of the
of major repairs or alterations.
temperature range being surveyed. From that time until thermal
5.2 Test and Verification of Equipment:
equilibrium is reached, the temperature of all test locations
5.2.1 Test Requirements:
should be determined at 2-min intervals in order to detect any
5.2.1.1 Heat-Treating Equipment, operated in accordance
overshooting. After thermal equilibrium is reached, readings
with documented procedures, shall have a demonstrated capa-
should be taken at 5-min intervals for sufficient time to
bility of producing material and components meeting the
determine the recurrent temperature pattern, but for not less
mechanical and physical properties specified for each heat-
than 30 min. Before thermal equilibrium is reached, none of the
treated alloy.
temperature readings should exceed the maximum temperature
5.2.1.2 Use of Production Test Results— In all cases, the
of the range being surveyed. After thermal equilibrium is
results of tests made to determine conformance of heat-treated
reached, the maximum temperature variation of all elements
material to the requirements of the respective material speci-
(both load and furnace thermocouples) shall not exceed 20°F
fications are acceptable as evidence of the properties being
(11°C) and shall not vary outside the range being surveyed.
obtained with the equipment and procedure employed.
5.1.2.6 For furnaces used only for treatments other than
5.2.2 Mechanical Properties— The heat treated (or reheat
solution heat treatment, after the initial temperatureuniformity
treated) test specimen shall have tensile strength, yield
survey as outlined in 5.1.2.5, surveys need not be made more
strength, and elongation properties not less than those specified
often than at each 6-month interval, provided that (a) test
in the applicable material specification or detail drawings. The
specimens from each lot are tested and meet applicable
required tests for alloys shall be in accordance with the
material specifications requirements, (b) the furnace is
requirements of the respective specifications and shall conform
equipped with a multipoint recorder, or (c) one or more
to Methods B 557 or Test Methods E 21, or both.
separate load thermocouples are employed to measure and
record actual metal temperatures. 5.2.2.1 Microscopical Examination— The tensile test may
5.1.2.7 Monthly surveys for batch furnaces are not neces- be supplemented by a microscopical examination of the test
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
B 661
bars or selected castings at the discretion of the procuring 6.1.1.1 The furnace should be loaded in such a manner as to
activity. Take a single representative sample for each of the permit adequate circulation of the furnace atmosphere. Give
specified tests if the furnace selected for routine inspection attention to providing necessary suport to castings susceptible
contains a load that is homogeneous as to alloy, form, and size to warpage.
of part. Select two specimens to represent the least massive and
6.1.2 Hold the charge at temperature for a sufficient time to
the most massive portions of the charge. In the event of
secure adequate solution heat treatment. Suggested holding
nonhomogeneity as to alloy and when the recommended heat
periods at temperatures for castings up to 2 in. (50.8 mm) in
treatments for the respective alloys differ, prepare additional
thickness are given in Table 1. Longer holding periods will be
samples.
required for castings with heavier sections.
5.2.2.2 Eutectic Melting and High Temperature Oxidation
6.1.2.1 Since magnesium castings are subject to excessive
of Castings— Section, mount, and prepare specimens from the
surface oxidation at temperatures of 750°F (399°C) and over, a
heat treated samples for microscopical examination. Examine
protective atmosphere containing sufficient sulfur dioxide,
the unetched surface at a 500-diameter magnification with a
carbon dioxide, or other satisfactory oxidation inhibitor should
metallurgical microscope. The presence of eutectic melting or
be used when solution heat treating at 750°F (399°C) and over.
high temperature oxidation shall be considered evidence of
6.1.2.2 Perform heat treating operations on the whole of a
improper heat treatment.
casting, never on a part only, and apply in a manner that will
5.3 Interpretation of Results:
produce satisfactory uniformity.
5.3.1 Test specimens prepared in accordance with 5.2.1 and
6.1.3 Cooling—Cool castings in air from the solution heat
treated in accordance with the applicable parts of Section 6
treating temperature rapidly enough to ensure that the specified
shall meet the requirements specified below. Failure to meet
mechanical properties are obtained.
the specified mechanical or physical requirements is reason to
6.1.3.1 Quenching—When EQ21A, QE22A, WE43A, and
disqualify the heat-treating equipment and associated process
WE54A castings are quenched in water or other media, transfer
until the reason for the failure is determined and appropriate
them from furnace to quench tank with the minimum delay. It
corrective action completed.
is recommended that the water, if used, be maintained at 150 to
5.3.2 Status of Alloys— Alloys heat treated in the furnace
180°F (66 to 82°C).
since the time of the previous satisfactory tests and found
6.1.4 Aging—Perform aging, or precipitation heat treat-
unsatisfactory shall be rejected or reheat treated (beginning
ment, when specified, at the temperature and times required to
with the solution heat treatment where applicable) in an
develop the specifie
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.