GB/T 37578-2019Urea grade ultra-low carbon austenitic seamless stainless steel tubes and pipes (English PDF)

3.1 In accordance with the manufacturing mode, the classification and code of steel

tubes and pipes are as follows:

a) Hot-rolled (extruded) steel tubes and pipes, W-H;

b) Cold-drawn (rolled) steel tubes and pipes, W-C.

3.2 In accordance with the grade of dimensional accuracy, the classification and code

of steel tubes and pipes are as follows:

a) Common grade, PA;

b) Superior grade, PC.

5.2 Length

5.2.1 General length

The general length of steel tubes and pipes shall comply with the following stipulations:

a) Hot-rolled (extruded) steel tubes and pipes: 2,000 mm ~ 12,000 mm;

b) Cold-drawn (rolled) steel tubes and pipes: 1,000 mm ~ 12,000 mm.

5.2.2 Specified length and multiple length

In accordance with the demand-side’s requirements, through the negotiation between the demand-side and the supply-side, and statement in the contract, steel tubes and pipes may be delivered in accordance with specified length or multiple length.

Specified length and multiple length shall be within the general range of length; the allowable deviation of total length shall be . In terms of steel tubes and pipes which are delivered in accordance with multiple length, the allowance of each incision shall comply with the following stipulations:

a) Nominal outer diameter not more than 159 mm, 5 mm ~ 10 mm;

b) Nominal outer diameter more than 159 mm, 10 mm ~ 15 mm.

5.3 Curvature

5.3.1 Per meter curvature

Per meter curvature of steel tubes and pipes shall be not more than what is stipulated below:

a) Wall thickness not more than 15 mm, 1.5 mm/m;

b) Wall thickness more than 15 mm, 2.0 mm/m.

5.3.2 Full length curvature

Full length curvature of steel tubes and pipes shall be not more than 0.15% of total length of steel tubes and pipes.

5.4 End Shape

Both end faces of steel tubes and pipes shall be vertical to the axis of steel tubes and pipes. The incision shall not have any burrs.

5.5 Out-of-roundness

In accordance with the demand-side’s requirements, through the negotiation between with the stipulations in Chapter 4 in GB/T 25151.2-2010. Corrosion depth shall comply with the stipulations in Table 5.

6.9 Surface Quality

6.9.1 The internal and external surface of steel tubes and pipes shall not have cracking, folding, rolling, separation or crusting. These defects shall be completely eliminated.

The actual wall thickness of the area of elimination shall be not less than the minimum allowable value of wall thickness.

6.9.2 On the internal and external surface of steel tubes and pipes, straight allowable depth shall comply with the following stipulations:

a) Hot-rolled (extruded) steel tubes and pipes: not more than 5% of wall thickness, and not more than 0.4 mm;

b) Cold-drawn (rolled) steel tubes and pipes: not more than 4% of wall thickness, and not more than 0.2 mm.

6.9.3 Other partial defects that would not affect the minimum value of wall thickness are allowed to exist.

6.9.4 Roughness (Ra) of the internal and external surface of steel tubes and pipes shall be not more than 3.2 µm.

6.10 Ultrasonic Testing

Steel tubes and pipes shall receive ultrasonic testing. In ultrasonic testing, the groove depth level of contrast tube shall comply with the stipulations of L2 in GB/T 5777-2008.

When steel tubes and pipes are delivered in accordance with the minimum wall thickness, average wall thickness shall be adopted to calculate the groove depth.

7.2 In metallographic test, along the steel tubes and pipes, longitudinally take strip

samples. Sample size shall be: 50 mm x 10 mm (length x width). The sides of the sample shall be grinded and polished.

7.3

In terms of the dimensions and shape of steel tubes and pipes, measuring instruments that comply with the accuracy requirement shall be adopted for one-by-

8.2 Group Batch Rules

Steel tubes and pipes shall receive inspection and acceptance inspection by batches.

Each batch shall be constituted of steel tubes and pipes of the same designation, the same furnace No. (in terms of electroslag re-melting steel, under the condition of stable process and compliance with the various requirements in this Standard, it can be master smelting furnace No. of consumable electrode), the same specification and the same thermal treatment system (heat). The quantity of steel tubes and pipes in each batch shall not exceed the following stipulations:

a) Outer diameter not more than 76 mm and wall thickness not more than 3 mm:

500 PCS;

b) Outer diameter more than 351 mm: 50 PCS;

c) Other dimensions: 200 PCS.

8.3 Sampling Size

Sampling size of various inspections of each batch of steel tubes and pipes shall comply with the stipulations in Table 6.

8.4 Re-inspection and Determination Rules

8.4.1 Re-inspection and determination rules of corrosion resistance test shall comply with the following stipulations:

a) If corrosion rate exceeds the stipulated value in Table 5, or, corrosion rate of the

5 th cycle exceeds 50% of the 4 th cycle, then, take another sample from the same steel tube/pipe; adopt the same procedures for re-inspection;

b) When 015Cr25Ni22Mo2N steel tubes and pipes are under 10 cycles of test in accordance with the demand-side’s requirements, if corrosion rate exceeds the stipulated value in Table 5, or, corrosion rate of the 10 th cycle exceeds 50% of the 9 th cycle, then, take another sample from the same steel tube/pipe; adopt the same procedures for re-inspection;

c) Re-inspection can only be conducted once.

8.4.2 Re-inspection and determination rules of the remaining inspection items of steel

tubes and pipes shall comply with the stipulations in GB/T 2102.