YB/T 4164-2007Double wall copper-brazed steel tubing (English PDF)

5.1 Technical requirements for steel strips

The technical requirements of copper-plated steel strip for tubing making shall comply with YB/T 069.

5.2 Production method

The steel tube shall be manufactured by coiling the copper-locked steel strip into two turns, heating and needle welding in a reducing atmosphere to form a double-layer pipe wall. Agreed by the supplier and the purchaser and indicated in the contract, it is also possible to use a manufacturing method of drawing a double-layer brazed steel tube of a certain specification into another specification.

5.3 Mechanical properties

The mechanical properties of steel tube that has not been straightened and processed shall meet the requirements of Table 4. Agreed by the supplier and the purchaser and indicated in the contract, the mechanical properties of steel tube can also be subject to regulations other than Table 4.

Table 4 -- Mechanical properties of steel tube

Tensile strength Rm, MPa Yield strength ReL, MPa Elongation after breaking A, %

>=290 >=180 >=25

5.4 Process test

5.4.1 Composite test of flattening and bending

Steel tube shall be subjected to the composite test of flattening and bending.

The pressure plate squashes the steel tube with the sample length of

50mm~100mm to contact with the inner wall. The direction of the welding seam and the flattening force is 90°. The flattened sample is bent 90° around an axis with a diameter equal to 6 times the wall thickness of the steel tube along the axis of the tubing. Straighten it. The sample after the test shall not have cracks, breaches or weld cracks.

5.4.2 Flaring test

Steel tube shall be subjected to flaring test. Sample length is 50mm~100mm.

The top center taper is 12°. The outer diameter flaring rate is 20%. The sample after the test shall not have cracks, breaches or weld cracks.

5.4.3 Bending test

otherwise specified in the contract, the compactness test is selected by the manufacturer. Either eddy current defect inspection or air tightness inspection can be used, or both inspections can be selected at the same time.

Eddy current defect inspection and air tightness inspection shall meet the following requirements:

a) Eddy current defect inspection shall be in accordance with acceptance level A of GB/T 7735. Agreed by both parties, the manufacturer can also use other higher acceptance levels.

b) The test pressure for air tightness inspection of steel tube is

1.55MPa~1.73MPa. The shortest holding time is 5min. The pressure in the pipe shall not drop. When the steel tube that has passed the eddy current defect detection inspection is further tested for air tightness, the lower limit of the test pressure is 0.6MPa.

5.7 Surface quality

The inner and outer surfaces of the steel tube shall be clean and smooth. There shall be no harmful defects that affect the use.

5.8 Inner surface cleanliness

Steel tube shall be checked for cleanliness of the inner surface. Residues on internal surface cleanliness shall not exceed 0.16g/m2.

5.9 Outer plating layer

5.9.1 The requirements of the copper plating layer of the steel tube and the choice of the outer surface corrosion protection layer are determined by the supplier and the purchaser through negotiation.

NOTE: The copper plating layer on the surface of the steel tube is the product of the steel tube manufacturing process, not the protective layer of the steel tube. The requirements for the copper layer on the surface of the steel tube shall be negotiated by the supplier and the purchaser.

5.9.2 Required by the purchaser, the outer surface of automotive steel tube can be galvanized or coated with other corrosion protection layers. Refer to Annex

D for the galvanized corrosion-resistant protective layer on the outer surface of the steel tube.

7.3 Sampling quantity

The sampling quantity for various performance inspections of each batch of steel tubes shall meet the requirements of Table 5.

7.4 Rules for reinspection and determination

The rules for reinspection and determination of steel tubes shall comply with

GB/T 2102.

C.1 Sample

C.1.1 The total length of the steel tube sample shall not be less than 12m. It can be divided into multiple-section operations. The length of each section should be greater than 1.5m.

C.1.2 Prevent dust and debris from entering the tube when sampling. Clean the

end of the tube after sampling.

C.2 Solvents

C.2.1 Use refined chloroform, trichloroethylene or carbon tetrachloride as

solvent.

C.2.2 The solvent volume is 100mL.

C.2.3 Pay attention to environmental protection when using solvents.

C.3 Methods

C.3.1 Use solvent to clean the inner surface of all samples.

C.3.2 Pour the cleaned solvent into a clean container with a known weight. Use a steam or low-temperature electric furnace to heat the container to evaporate the solvent. And dry at a temperature of 100°C~110°C until the steam is completely removed (be careful not to overheat the container to prevent carbonization of the residue) before weighing.

C.3.3 The weight of the sample is subtracted from the previous two times to obtain the residual weight of the sample. Calculate the number of grams of residue per square meter of cleanliness of the inner surface of the steel tube.

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