GB/T 33228-2016Aluminum alloy extruded tubes for high-frenquency electric transformer (English PDF)

1 Scope

This Standard specifies the requirements, test methods, inspection rules and marking, packaging, transportation, storage, quality certificate and order form (or contract) contents of aluminum alloy extruded tubes for high-frequency electric transformer.

This Standard applies to aluminum alloy round tubes (hereinafter referred to as tubes) which are produced by divergent die extrusion in the fields of transmission, transformation and distribution.

2 Normative references

The following documents are indispensable for the application of this document.

For dated references, only the dated version applies to this document. For undated references, the latest edition (including all amendments) applies to this document.

GB/T 231.1, Metallic materials. Brinell hardness test. Part 1: Test method

GB/T 3048.2, Test methods for electrical properties of electric cables and wires. Part 2: Test of electrical resistivity of metallic materials

GB/T 3190, Wrought aluminum and aluminum alloy. Chemical composition

GB/T 3199, Wrought aluminium and aluminium alloy products. Packing, marking, transporting and storing

GB/T 3246.1, Inspection method for structure of wrought aluminum and aluminum alloy products. Part 1: Inspection method for microstructure

GB/T 3246.1, Inspection method for structure of wrought aluminum and aluminum alloy products. Part 2: Inspection method for macrostructure

GB/T 4436, Wrought aluminum and aluminum alloy tubes. Dimensions and deviations

GB/T 4437.2, Aluminium and aluminium alloy extruded tubes. Part 2: Seam tubes

GB/T 7999, Optical emission spectrometric analysis method of aluminum

4 Test method

4.1.1 The analysis method of chemical composition shall comply with requirements of GB/T 20975 or GB/T 7999; the arbitration analysis shall adopt the methods which are specified in GB/T 20975.

4.1.3 The "Al" content is calculated according to the method which is specified in GB/T 3190. When the "Al" content is calculated, take the sum value of the analytical values of the conventional analytical elements and the suspected excess unconventional analytical elements as the "sum of elemental content".

4.1.4 The determination of analysis value is based on the rounding comparison method; the value rounding rules shall be carried out in accordance with the relevant provisions of GB/T 8170; the rounding digit shall be consistent with the limit digits which are specified in Table 3 of this Standard or GB/T 3190.

5 Inspection rules

5.6.2 When the dimension deviation of any sample is unqualified, judge the batch of products as unqualified; however, it is allowed to inspect one by one, and deliver the qualified ones.

5.6.3 When the vertical tensile mechanical properties at room temperature of any sample are unqualified, take double the number of samples from the batch (or heat treatment furnace) of products to perform repeated tests; if the repeated test results are all qualified, judge the batch (or heat treatment furnace) of products to be qualified. If the sample properties are still unqualified in the repeated test result, then, judge the batch (or heat treatment furnace) of products to be unqualified. The supplier is allowed to inspect the products one by one and deliver those qualified ones. The supplier is also allowed to re-sample after another heat treatment to inspect the tensile mechanical properties at room temperature, conductivity and microstructure.

5.6.4 When the conductivity of any sample is unqualified, judge the batch (or heat treatment furnace) to be unqualified. The supplier is allowed to inspect the products one by one and deliver the qualified ones. The supplier is also allowed to re-inspect the tensile mechanical properties at room temperature, conductivity and microstructure after another heat treatment

5.6.5 When the low-magnification organization of any sample is unqualified, judge as follows:

a) If the low-magnification organization is unqualified because of metallurgical defects such as cracks, bright grains, non-metallic inclusions, foreign metal inclusions, white spots and primary crystals, judge the batch of products to be unqualified.

b) If the low-magnification organization is unqualified because of layering and shrinkage, it is allowed to cut a portion from the extrusion end of the tube for repeated test until it is qualified; then, other products of the batch shall be tailed according to the maximum length of the above defect distribution OR inspected one by one; deliver the qualified ones.

c) If the low-magnification organization is unqualified because of welding quality, it is allowed to cut a portion from the extrusion front end of the tube for repeated test until it is qualified; then, other products of the batch shall be tailed according to the maximum length of the above defect distribution OR inspected one by one; deliver the qualified ones.

5.6.6 When the microstructure of any sample is unqualified, judge the batch (or heat treatment furnace) of products to be unqualified.