YS/T 591: Evolution and historical versions
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Heat treatment of wrought aluminum and aluminum alloys
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YS/T 591-2025
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Heat treatment of wrought aluminium and aluminium alloys
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Heat treatment of wrought aluminium and aluminium alloys
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Basic data | Standard ID | YS/T 591-2025 (YS/T591-2025) | | Description (Translated English) | Heat treatment of wrought aluminum and aluminum alloys | | Sector / Industry | Nonferrous Metallurgy Industry Standard (Recommended) | | Classification of Chinese Standard | H60 | | Classification of International Standard | 25.2 | | Date of Issue | 2025-04-10 | | Date of Implementation | 2025-11-01 | | Older Standard (superseded by this standard) | YS/T 591-2017 | | Issuing agency(ies) | Ministry of Industry and Information Technology | YS/T 591-2017
YS
NONFERROUS INDUSTRY STANDARD
OF THE PEOPLE’S REPUBLIC OF CHINA
ICS 25.200
H 60
Replacing YS/T 591-2006
Heat treatment of wrought aluminum and aluminum alloys
ISSUED ON: JULY 07, 2017
IMPLEMENTED ON: JANUARY 01, 2018
Issued by: Ministry of Industry and Information Technology of the People's
Republic of China.
Table of ContentsForeword ... 3
1 Scope ... 6
2 Normative references ... 6
3 Equipment ... 7
4 Heat treatment processes ... 9
5 Quality assurance ... 29
Annex A (informative) Common knowledge about heat treatment of aluminum alloys
... 34
Heat treatment of wrought aluminum and aluminum alloys
ScopeThis Standard specifies the equipment, heat treatment processes and quality assurance
for heat treatment of wrought aluminum and aluminum alloys.
This Standard applies to the heat treatment of wrought aluminum and aluminum alloy
processing products.
Normative ReferencesThe following referenced documents are indispensable for the application of this
document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
GB/T 230.1, Metallic materials -- Rockwell hardness test -- Part 1: Test method
GB/T 231.1, Metallic materials -- Brinell hardness test -- Part 1: Test method
GB/T 3246.1, Inspection method for structure of wrought aluminum and aluminum
alloy products -- Part 1: Inspection method for microstructure
GB/T 7998, Method for evaluating the susceptibility to intergranular corrosion of
aluminum alloys
GB/T 9452, Test method for qualified work zone of heat treatment furnace
GB/T 12966, The methods for determining aluminum and aluminum alloys
conductivity using eddy current
GB/T 16475, Temper designation system for wrought aluminum and aluminum alloy
products
GB/T 16865, Test pieces and methods for tensile test for wrought aluminum,
magnesium and their alloy products
GB/T 8005.1, Aluminum and aluminum alloy terms and definitions -- Part 1:
Product and method of processing and treatment
YS/T 876, Standard practice for extrusion solution heat treatment for wrought
aluminum alloys
3 Equipment
3.1 Basic requirements
3.1.1 All heat treatment equipment shall be equipped with temperature and time control
devices and recorders that meet process control requirements. The recorder shall be able
to accurately reflect the temperature and time control conditions, and can be stored for
reference.
3.1.2 The accuracy of the instrument shall be ensured. Perform periodic testing or
calibration.
3.1.3 The location of the sensor shall be determined by the characteristics of the heat
treatment furnace and placed where it can accurately measure the temperature of the
product and heating medium.
3.1.4 The installation position of quenching equipment and loading and unloading
equipment shall ensure that the quenching transfer time meets the requirements.
3.1.5 When supports are required, vibration or movement of the metal shall be
minimized. Brackets, fixtures, bases, and hanging baskets shall be installed in such a
way that they will not adversely affect the quality of the products being processed.
3.2 Commonly used heat treatment furnaces
3.2.1 Classification
Commonly used heat treatment furnaces can be divided into two types: periodic heat
treatment furnaces and continuous heat treatment furnaces. The periodic heat treatment
furnace is highly versatile and can meet a variety of heat treatment process requirements.
It is commonly used for heating and annealing of general products. But the production
efficiency and thermal efficiency are low. The continuous heat treatment furnace has
the characteristics of mechanization and high automation. It can meet the requirements
of various heat treatment processes for large quantities of a single product. It has high
productivity.
3.2.2 Periodic heat treatment furnace
3.2.2.1 Air furnace
Air furnaces use air as the medium. Generally, a forced air circulation system is installed.
It is the furnace type with the simplest structure.
3.2.2.2 Salt bath furnace
Salt bath furnace is a heat treatment equipment that uses molten salt as the heating
medium. It is characterized by simple structure, easy manufacturing, fast heating speed
The minimum classification for annealing heat treatment furnaces with a temperature
range greater than 30°C is Class IV.
3.3 Quenching equipment
3.3.1 Immersion quenching equipment
3.3.1.1 Tank size
The quenching tank shall be of sufficient size to ensure that the product can be
completely immersed in the quenching medium.
3.3.1.2 Cycle
The quenching tank shall have an internal or external circulation system to ensure the
flow of quenching medium.
3.3.1.3 Heating and cooling
The quenching tank shall have sufficient heating and cooling capabilities to ensure that
the temperature of the quenching medium reaches the specified range.
3.3.1.4 Immersion speed
The speed at which products requiring solution treatment enter the quenching medium
shall ensure that the product quenching transfer time meets the requirements.
3.3.1.5 Washing and drying
The water tank used for salt bath quenching products (except for water polymer
solutions) shall ensure that there shall be no visually visible salt liquid residue after the
product surface is dried.
3.3.2 Spray quenching equipment
When using a spray system for quenching, the coolant released from the nozzle shall
have sufficient volume (flow), pressure and temperature to ensure that all products can
achieve a uniform quenching effect. The equipment shall be equipped with a recorder
to monitor spray quenching parameters.
4 Heat treatment processes
4.1 Basic requirements
4.1.1 General requirements
4.1.1.1 The heat treatment process shall match the heat treatment equipment. Product
monitoring inspections shall be carried out regularly to monitor the operation of heat
treatment equipment and the suitability of the process.
4.1.1.2 Before heat treatment, the surface of the product shall be free of contaminants
that would affect product quality.
4.1.1.3 The state codes of wrought aluminum and aluminum alloys shall comply with
the regulations of GB/T 16475. The terms and definitions of heat treatment shall comply
with the provisions of GB/T 8005.1. See Annex A for common knowledge.
4.1.2 Furnace loading requirements
Before loading the solution heat treatment product into the furnace, it shall be ensured
that the heating medium reaches the temperature required by the alloy. Unless all
instruments indicate that the heat treatment furnace has reached the specified heat
treatment temperature range (including lower temperatures), the furnace can be
installed under a cooling trend. If the heat treatment furnace is automatically controlled
and can ensure that the furnace temperature drops to the holding temperature before
loading any metal, the furnace can be loaded at any time.
4.1.3 Product placement
4.1.3.1 Products shall be placed on racks and kept at a distance to ensure that the
quenching medium fully enters all load areas.
4.1.3.2 For forgings with a thickness less than or equal to 25 mm, the maximum
thickness of random mounting or each layer is allowed to be 75 mm. The minimum
distance between shelves shall be 75 mm. Forgings thicker than 25 mm shall be
separated from each other. The distance shall be greater than the thickest section, or a
special hanging that can achieve sufficient quenching shall be used.
4.1.4 Furnace capacity
Furnace installation shall be appropriately selected based on product and process
requirements to ensure temperature uniformity. For salt bath quenching products with
a thickness less than or equal to 2.5 mm, the furnace loading shall ensure that the time
to reach the lowest temperature does not exceed 10 min. For salt bath quenching
products with a thickness greater than 2.5 mm, the furnace loading shall ensure that the
time to reach the minimum temperature does not exceed 20 min.
4.1.5 Fixtures
Fixtures shall be positioned to avoid steam interception and ensure free circulation of
the quenching fluid and quenching effect.
4.2 Solution heat treatment process
4.2.1 Online solid solution heat treatment process
It also allows solution potential measurement methods to be used to analyze the
diffusion of the aluminum-clad layer. It is a condition that documentation on the
interrelationship between this method and optical methods be made available for
inspection.
5.3.2.4 Over-burning and pores
The inspection method for over-burning and pores caused by solid solution heat
treatment shall be carried out in accordance with the provisions of GB/T 3246.1.
5.3.2.5 Conductivity
The conductivity is measured in accordance with the provisions of GB/T 12966.
5.3.2.6 Hardness
5.3.2.6.1 The test method for Rockwell hardness shall be carried out in accordance with
the provisions of GB/T 230.l.
5.3.2.6.2 The Brinell hardness test method shall be carried out in accordance with the
provisions of GB/T 231.1.
5.3.3 Handling of unqualified test results
5.3.3.1 When the test results are unqualified, the reasons shall be identified. If the test
shows that the heat treatment equipment or process cannot be used for aluminum alloy
heat treatment, the fault shall be eliminated and the process adjusted. Re-test until the
tested items are qualified. Suspicious products that have been produced must be
inspected. Handle according to qualified products and unqualified products.
5.3.3.2 The products are heat treated in a furnace that has passed the original test. When
they are found unqualified, they shall be scrapped based on the test results or the
solution heat treatment shall be repeated in another qualified furnace.
5.3.3.3 When the mechanical properties and intergranular corrosion of heat-treated
products fail to meet the standards, they may be subjected to repeated solution heat
treatment within the scope allowed by this Standard. Products that are over-fired and
have alloy elements that are severely diffused from the matrix through the aluminum-
clad layer are unqualified and are not allowed to repeat solution heat treatment.
5.3.4 Keeping inspection records
5.3.4.1 Unless otherwise specified, inspection records shall be kept on file and available
for inspection for 3 years from the date of inspection.
5.3.4.2 Establish records of process procedures and re-examination of process
procedures. It shall be archived until discarded or replaced.
Annex A
(informative)
Common knowledge about heat treatment of aluminum alloys
A.1 Salt bath features
Compared with the gas chamber furnace, the molten salt bath allows the product to
reach a given temperature in a shorter time, making it easier to maintain temperature
uniformity. When solution heat treatment is performed in a molten salt bath, the risk of
porosity is greatly reduced. After long-term use, the decomposed compound sodium
nitride will corrode the aluminum alloy when it dissolves in the quenching water. This
erosion can be stopped by adding 350 g of sodium or potassium biphosphate per ton of
nitrate in a salt bath. There is a risk of explosion in the salt nitrate tank, so you must
pay attention to safety when using it.
A.2 Gas chamber furnace features
Gas chamber furnaces are more flexible and economical when handling large volumes
of product. When solution heat treating certain aluminum alloys, the atmosphere in the
furnace must be controlled to avoid the formation of pores. This kind of pores will
reduce the mechanical properties of the aluminum alloy and cause a large number of
small blisters to appear on the surface of the product. In severe cases, the product will
break when burned.
A.3 Solid solution heat treatment
A.3.1 Characteristics of solution heat treatment
Solution heat treatment is such a process: It heats the alloy to an appropriate temperature
(see Table 2), holds it at this temperature so that the soluble components have enough
time to fully enter the solid solution, and then rapidly cools the soluble components in
an appropriate quenching medium. remain in solid solution in a supersaturated state.
A.3.2 Holding time
A.3.2.1 Recommended holding time
The time required for the soluble components to fully enter the solid solution. The
holding time increases with the increase of metal thickness. The minimum holding time
can be determined by testing the metal specimen and confirming that the required
mechanical properties have been fully improved. The holding times recommended in
Table 3 have been confirmed to be adequate in actual industrial applications.
A.3.2.2 Prevention of the generation of hydrogen holes
When solution heat treating in an air furnace, long holding times increase the risk of
hydrogen pores. This phenomenon was formerly known as "high-temperature
oxidation." However, with proper control of the furnace atmosphere, holding times
longer than those shown in Table 3 can be safely used.
A.3.2.3 Prevention of the spread of coated products
The insulation time of the coated product shall be as short as possible, that is, to ensure
that the mechanical properties meet the required requirements. Longer holding times
will cause the base metal to diffuse toward the cladding layer. When this occurs,
corrosion resistance properties can be adversely affected. Therefore, for coated products,
the holding time shall be kept as short as possible to avoid diffusion.
A.3.3 Improper solution heat treatment temperature
If the specified maximum temperature is exceeded, there is a risk of local over-burning
and may reduce the mechanical properties of the alloy. Overheating can cause serious
pores in the product. If the temperature is lower than the specified minimum
temperature, the solid solution will be insufficient, the mechanical properties will not
meet the requirements, and the corrosion resistance will also be adversely affected.
A.3.4 Impact of secondary solid solution heat treatment on the corrosion resistance
of 2017T4, 2024T3 and 2024T4 products
For 2017T4 or 2024T3, 2024 T4 products, when the temperature of the second solid
solution heat treatment is lower than the temperature of the first heat treatment, the
corrosion resistance will be reduced. Using a longer soak time can often solve this
problem. Therefore, when performing secondary solution heat treatment of each of the
above alloys, it is recommended that the holding time shall be longer than the average
time. And the solution heat treatment temperature shall be within ±3°C of the
conventional maximum temperature.
A.3.5 Heat treating forgings to O1 state
This is a high-temperature annealing of forgings used for special purposes, such as
enhancing sensitivity to ultrasonic waves or obtaining dimensional stability. To perform
this annealing, the product is exposed to approximately the same temperature and time
as for solution heat treatment, but in this case the product is slowly cooled to room
temperature. This annealing treatment state is generally not used as the final delivery
state of the product.
A.3.6 Quenching to improve corrosion resistance
For certain states of 2117 alloy products, 2024 and 7075 alloy products that are not
aluminum-clad or aluminum-clad, rapid quenching is required to obtain the best
corrosion resistance of the product. As the quenching rate decreases, these alloys
become more sensitive to intergranular corrosion, which can lead to excessive reduction
aluminum alloy without aluminum and with aluminum, and then heating (but much
lower than the annealing temperature), the tensile strength and the specified non-
proportional elongation strength obtained are greatly improved. The strength value of
this alloy after long-term aging at room temperature is high, but the elongation after
fracture of the material decreases. This process is called "heating precipitation heat
treatment" or "artificial aging".
A.7.2 Effect of cold processing on artificial aging products
The mechanical properties achieved by aging treatment depend on the degree of cold
working performed on the material after artificial aging. Therefore, the improvement of
mechanical properties depends on the intensity of the forming operation when
processing the product. This point determines the choice of vermicompost state to be
used. For example, for 2024T36 or 2024T361 materials that have undergone a certain
degree of cold working, the mechanical properties of the aged product are higher than
those of 2024O or 2024T3 materials. The extent to which the product is cold worked
during the forming operation affects the return metal. Therefore, aged formed products
usually have higher tensile strength and specified non-proportional elongation strength,
as well as lower elongation after break, compared with the same aged raw material.
A.7.3 Effect of heat treatment on cold working materials
Annealing or solution heat treatment eliminates any cold working effects on the
material. The annealed material is subsequently solution heat treated and artificially
aged. As long as the material does not undergo secondary processing before aging, it
can reach the T6 state. Higher strength can only be achieved by completing a certain
amount of cold working before natural aging or artificial aging. For example: to achieve
the T81, T84 and T861 tempers, the material shall be cold worked to approximately 1%,
4% and 6% respectively after solution heat treatment and before natural and artificial
aging.
A.8 Effect of residual tensile stress on corrosion performance
Some heat treatment elements, such as quenching medium and aging treatments, can
greatly affect the degree of residual tensile stress in the product and affect the stress
corrosion properties of the material. These heat treatment elements minimize residual
tensile stresses.
A.9 Relationship between conductivity, hardness and state
Tables A.1 and A.2 provide typical values on the relationship between conductivity,
hardness and condition of aluminum-clad and non-aluminum alloys for reference only.
Conductivity measurements can be affected by the operating characteristics of the
instrument probe used.
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