GB/T 38512-2020Aluminum and aluminum alloy tubes for the pressure vessel (English PDF)

3.1.2 Marking example

The mark of the tubes is expressed in the order of product name, reference to this Standard, designation, state, size specification.

Example: The fixed-scale tube of which the designation is 5083, the state is O, the outer diameter is 40.00mm, the wall thickness is 6.00, the length is 4000, is marked as: Tube GB/T 38512-5083 O-40.00×6.00×4000.

3.2 Chemical composition

The chemical composition of the tube shall comply with the provisions of GB/T 3190.

3.3 Size deviation

3.3.1 Outer diameter, curvature

The outer diameter, curvature of the tube shall comply with the provisions on high precision in GB/T 4436-2012.

3.3.2 Wall thickness

The wall thickness deviation of the tube shall comply with the provisions of GB/T 4436-2012.

3.3.3 Length

The fixed-scale length deviation of the tube shall comply with the provisions on high precision in GB/T 4436-2012. For the tubes that are delivered in double-scale as the fixed-scale, 5mm cutting capacity shall be left for each sawing edge.

3.3.4 Cutting slope

There shall be no burrs at both ends of the tube. The cutting slope shall meet the provisions on high precision level in GB/T 4436-2012.

3.3.5 Others

If the purchaser has other requirements, it shall be indicated in the order sheet (or contract).

3.4 Tensile mechanical properties at room temperature

The longitudinal tensile mechanical properties of the tube at room temperature shall meet the requirements of Table 2. For the tubes of which the wall thickness exceeds the one specified in Table 2, the mechanical properties are determined

3.10 Macrostructure

3.10.1 Cracks, tailing, pores, and bright grains are not allowed on the macrostructure sample of the tube.

3.10.2 Non-metallic inclusions, compound segregation or intermetallic compounds are not allowed on the macrostructure samples of the tube.

3.10.3 The depth of the coarse crystal ring shall be agreed between the supplier and the purchaser and indicated in the drawing or order sheet (or contract).

3.10.4 For the tube that wall thickness requires positive and negative symmetric deviation, the layering depth on the macrostructure sample shall not exceed the negative deviation of the tube wall thickness and the wall thickness deviation of the tube shall not exceed the allowable range. For the tube that wall thickness requires non-positive and negative symmetry deviation, the layering depth on the macrostructure sample shall not exceed half of the allowable deviation of the tube wall thickness. After deducting the thickness of the layer thickness, the size deviation shall not exceed the allowable range.

3.11 Microstructure

The microstructure of the quenched product is not allowed to burn.

3.12 Appearance quality

3.12.1 The surface of the tube shall be smooth, and no cracks, corrosion or foreign inclusions are allowed.

3.12.2 The surface of the tube is allowed to have local defects such as slight peeling, bubbles, scrapes, scratches, bumps, pits that do not affect the use.

After deducting the depth of the defect, the wall thickness deviation shall not exceed the allowable range.

3.13 Others

When welding pipes, the mechanical properties of the welds are in Annex A.

4.1 Chemical composition

4.1.1 The chemical composition analysis method shall be carried out according to GB/T 20975 or GB/T 7999. The arbitration analysis shall use the method specified in GB/T 20975.

4.1.2 "Al" content is calculated according to the method specified in GB/T 3190.

4.8 Pressure resistance

The test method for pressure resistance of the tube shall be negotiated between the supplier and the purchaser and indicated in the order sheet (or contract).

4.9 Macrostructure

The inspection method for the macrostructure of the tube shall be in accordance with GB/T 3246.2.

4.10 Microstructure

The inspection method of the microstructure of the tube shall be in accordance with GB/T 3246.1.

4.11 Appearance quality

Visually check the appearance quality under natural scattered light. If necessary, the size measurement tool can be used to define the size of the defect, and the depth of the defect can be determined by grinding.

4.12 Others

Refer to Annex A for the inspection method of weld mechanical properties.

5.1 Inspection and acceptance

5.1.1 The product shall be inspected by the supplier to ensure that the product quality meets the requirements of this Standard and the order sheet (or contract) and fill in the quality certificate.

5.1.2 The purchaser shall inspect the received products in accordance with this Standard. When the inspection result is inconsistent with the provisions of this Standard and the order sheet (or contract), it shall be submitted to the supplier in written form and resolved by consultation between the supplier and the purchaser. Objections pertaining to surface quality and dimensional deviations shall be raised within one month from the date of receipt of the product.

Objections that belong to other properties shall be raised within three months from the date of receipt of the product. If arbitration is required, the organization authorized by both the supplier and the purchaser can be entrusted to conduct the arbitration. The sampling shall be conducted at the purchaser.

5.2 Batching

The products shall be submitted for acceptance in batches. Each batch shall sample to check the tensile mechanical properties at room temperature, electrical conductivity and peeling corrosion resistance performance.

6.1 Marks

6.1.1 Product marks

Print the identification of the following content (or affix a label containing the following content) on the front end of the qualified tube extrusion:

a) Inspection seal of the supplier's quality inspection department (or the signature or seal of the quality inspection personnel);