GB/T 25745-2010 English PDF (GBT25745-2010)

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GB/T 25745-2010: Heat treatment of cast aluminium alloys
GB/T 25745-2010
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 25.200
J 36
Heat treatment of cast aluminium alloys
ISSUED ON: DECEMBER 23, 2010
IMPLEMENTED ON: JUNE 01, 2011
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Terms and definitions... 5 
4 Classification ... 5 
5 Heat treatment equipment ... 6 
6 Heat treatment process ... 8 
7 Quality control and inspection ... 13 
8 Safety, health and environmental protection requirements ... 15 
Appendix A (Informative) Mechanical properties of cast aluminium alloys after heat
treatment ... 16 
Heat treatment of cast aluminium alloys
1 Scope
This Standard specifies the heat treatment condition, heat treatment equipment, heat
treatment process, quality control and inspection, safety, health and environmental
protection requirements of cast aluminium alloys.
This Standard applies to the heat treatment of cast aluminium alloy workpieces.
2 Normative references
The terms in the following documents become the terms of this Standard by reference
to this Standard. For dated references, all subsequent amendments (not including errata
content) or revisions do not apply to this Standard. However, parties to agreements that
are based on this Standard are encouraged to study whether the latest versions of these
documents can be used. For undated references, the latest edition applies to this
Standard.
GB/T 228, Metallic materials - Tensile testing at ambient temperature
GB/T 231.1, Metallic materials - Brinell hardness test - Part 1: Test method
GB/T 1173, Casting Aluminium Alloy
GB 5959.1, Safety in installations for electroheating and electromagnetic processing
- Part 1: General requirements
GB 5959.4, Safety in electroheat installations - Part 4: Particular requirements for
safety resistance heating installations
GB/T 7232, Terminology of metal heat treatment
GB/T 9452, Testing method for working zone of heat treatment furnace
GB 12348, Emission standard for industrial enterprises noise at boundary
GB/T 13324, Terminology of heat treatment equipment
GB 15735, Requirements for the safety and health in production process of metal
heat treatment
GB/T 16839.2, Thermocouples - Part 2: Tolerances
5.1.4 Each heating furnace must be regularly tested for the effective heating zone. The
test cycle is shown in Table 3; the test method shall be in accordance with the provisions
of GB/T 9452; its insulation accuracy shall meet the requirements of Table 2. An
inspection certificate with the schematic diagram of the effective heating zone shall be
hung in a conspicuous position. The heating furnace can only be used within the validity
period that is specified in the valid heating zone inspection certificate.
5.1.5 The temperature measurement system used on site shall be regularly subjected to
system check under normal use. During the check, the distance between the detection
thermocouple and the hot end of the recording instrument thermocouple shall be close.
The check shall be performed with the furnace in a thermal stability. The allowable
temperature deviation for system check is ±1°C. When the temperature deviation is
exceeded, the cause shall be identified or corrected.
5.2 Temperature control equipment
5.2.1 The accuracy of the on-site testing equipment shall be higher than that of the tested
equipment.
5.2.2 The grades of temperature control and recording instruments used on site shall
meet the requirements of Table 2; the verification cycle shall be performed according
to Table 3.
5.2.3 The accuracy of the standard potentiometer for on-site system check shall not be
lower than 0.05; the resolution shall not be lower than 1 mV; the verification cycle shall
be 6 months.
5.2.4 Mercurial thermometer for measuring room temperature, with a resolution of
0.1°C and a verification cycle of 1 year.
5.2.5 The thermocouple shall comply with the provisions of GB/T 16839.2. See Table
5 for the technical requirements for the thermocouple commonly used on site.
5.3 Solid solution cooling tank
5.3.1 The solid solution cooling tank shall be located as close to the heating furnace as
possible, so as to ensure that the heated castings are quickly immersed in the solid
solution cooling tank; the solid solution cooling transfer time shall meet the
requirements in Table 5.
5.3.2 The solid solution cooling tank shall have sufficient capacity to ensure that the
solid solution cooling castings can be rapidly solution cooled while all immersed in the
solid solution cooling medium.
5.3.3 The solid solution cooling tank shall be equipped with cooling circulation and
stirring device and temperature measuring device; if necessary, heating device can be
configured to ensure the temperature and uniformity of the cooling medium.
5.3.4 The solid solution cooling tank shall be provided with a tank cover; the cooling
medium in the solid solution cooling tank shall be regularly inspected and replaced as
required.
6 Heat treatment process
6.1 Preparation before heat treatment
6.1.1 Check the conditions of the heating furnace, temperature control equipment, solid
solution cooling tank, etc. before use, to ensure that the equipment is in good condition.
6.1.2 Clean the oil and dirt on the surface of the casting, and keep the casting clean
before entering the furnace.
6.1.3 For castings that are prone to distortion, special heat treatment fixtures shall be
provided.
treatment temperature shall be solution cooled; the castings that have not reached the
solution treatment temperature can be air cooled. The heat treatment holding time when
they are reloaded in the furnace is generally calculated cumulatively with the first
holding time; the point holding time can be extended.
6.3.10 During the aging treatment, if the insulation is interrupted for some reason, and
the work cannot be resumed in a short time, it shall be air-cooled. The holding time for
re-entering the furnace for heat treatment can be calculated cumulatively with the
holding time before the interruption; the effective holding time shall be equal to or
slightly longer than the original holding time.
6.3.11 See Appendix A for the mechanical properties of cast aluminium alloys after heat
treatment.
6.4 Repeated heat treatment
6.4.1 When the mechanical property of the casting after heat treatment is unqualified, a
repeated heat treatment can be performed; the holding time of the repeated heat
treatment can be reduced according to the circumstances; the times of repetition of
solution treatment shall not exceed two times in general; the times of repetition of the
aging treatment is not limited.
6.4.2 For castings where the solution treatment is staged heating, during the repeated
heat treatment, the heated temperature of the solution treatment may not adopt the
staged heating process.
7 Quality control and inspection
7.1 Quality control
7.1.1 Personnel requirements
Heat treatment operators, instrument staff, and inspectors shall be trained according to
regulations, and they can take up their posts after passing the examination and obtaining
the qualification certificate.
7.1.2 Heat treatment process control
7.1.2.1 Pending control
Confirm that all the processes before the heat treatment of the cast...