GB/T 20409 Multi-rifled Steel Pipe For High-pressure Boiler

2021-12-09
GB/T 20409
 
Multi-rifled Seamless Steel Pipe For High-pressure Boiler


1 Scope
This standard specifies the classification, size, shape, weight, technical requirements, test methods, inspection rules, packaging, marking and quality certificate of Multi-Rifled pipe for high pressure cooker protection.
 
 
This standard is applicable to the manufacture of high-quality carbon structural steel and alloy structural steel cold-drawn seamless steel tubes with internal threads for boilers under high and above pressures.
 
 
 
3 Classification and Code
 
Multi-rifled pipe can be divided into "A" type and "B" type according to tooth type. Its shape and size codes are shown in Figures 1 and 2, respectively.

 
 
A - Multi-rifled pipe outer diameter of type A teeth.
C-Thread root inner diameter.
E - Minimum Internal Diameter,
F - Minimum wall thickness,
G - Number of threaded heads;
I - Thread Top Width (Circumference)
J-thread height.
K - Thread Side Angle,
O- The radius of roundness at the root of thread.
M - Thread pitch.
N-thread lead.
Q-1 spiral elevation angle,
T-1 Thread Top Width (Axis).
U-thread top (axial) slot width.
 
 
Figure 1 "A" tooth profile
 
 
 
 
 
B-1 "B" tooth Multi-Rifled pipe outer diameter.
C - Thread root inner diameter.
E - The smallest inner diameter.
F - The minimum wall thickness.
G - Number of thread heads.
I - Thread top width (circumference).
J - thread height;
K - Thread Side Angle.
O-radius of rounded corner at the root of thread.
M - Thread pitch,
N - Thread Lead,
Q - Thread Increase Angle.
T - thread top width (axial).
U - thread top (axial) slot width.
 
 
Figure 2 "B" tooth profile
 
 
 
 
4 Order Content
 
Contracts or orders for steel pipes ordered in accordance with this standard shall include the following contents:
A) Standard number,
B) Product name.
C) steel grade;
D) Size specifications (order by outer diameter and minimum wall thickness is recommended);
E) the number of orders and;
F) Thread profile.
G) Special requirements.
 
 
 
 
5 Dimensions, shape and weight
 
5.1 Dimension Specification 
"A" Multi-Rifled pipe with teeth and thread parameters shall conform to Table 1, while "B" Multi-Rifled pipe with teeth shall conform to Table 2.
 
According to the requirement of the demander, after consultation between the supplier and the demander, Multi-rifled pipe with specifications other than those specified in Table 1 and Table 2 can be selected.
 

Table 1 Dimensions and thread parameters of "A" type Multi-Rifled pipe

Nominal 
Outer
diameter
/mm

Thread
root
inner diameter
/mm

The
smallest inner diameter
/mm

Nominal
wall thickness
/mm

Minimum
wall thickness
/mm

Number of thread heads

Thread Top Width (Circumference)

/mm

Thread height
/mm

Thread Side Angle
(。)

Radius of rounded corner at the root of thread
/mm

Thread pitch,
/mm

Thread Lead
/mm

Thread Increase Angle
(。)

Thread top width (axial)
/mm

Thread top (axial) slot width
/mm

A

C

E

S

F

G

I

J

K

O

M

N

Q

T

U

28.6

15.84

13.39

6.38

5.8

4

4.78

0.85

55。

0.13~1.27

21.55

86.19

30。

8.28

13.27

44.5

33.18

30.34

5.66

5.1

6

1.01

30.08

180.49

21.80

45

33

30.20

6

5.4

6

1.01

30

180

21.70

50.8

37.92

34.93

6.44

5.8

8

1.06

25.79

206.29

17.51

51

38.35

35.35

6.33

5.7

8

1.10

26.10

208.80

17.80

60

46

42.92

7

6.3

8

1.10

31.30

250.40

23

60

44

41

8

7.2

8

1.10

30

240

21.70

60.3

43.4

40.32

8.33

7.5

8

1.12

29.52

236.16

21.24

60.3

42.3

39.10

9

8.1

8

1.12

28.76

230.10

20.49

60.3

31.44

28.55

14.43

13

8

1.02

21.38

171.07

13.11

63.5

48.8

45.64

7.33

6.6

8

1.16

33.19

265.54

24.91

63.5

48.5

45.30

7.50

6.7

8

1.16

33

264

24.70

63.5

47.72

44.53

7.89

7.1

8

1.17

32.49

259.89

24.21

63.5

47.52

44.29

7.99

7.2

8

1.15

32.31

258.51

24.03

63.5

39.24

36.19

12.13

10.9

8

1.07

26.70

213.49

18.42

63.5

39.09

36.10

12.21

11

8

1.04

26.59

212.70

18.31

63.5

35.30

32.32

14.10

12.7

8

1.04

24

192

15.72

63.5

34.64

31.66

14.43

13

8

1.04

23.56

188.49

15.28

69.8

37.77

34.72

16.04

14.4

8

1.07

25.68

205.46

17.40

70

50

46.72

10

9

8

1.20

34

272

25.72

70

52

48.70

9

8.1

8

1.20

35.37

282.95

21.09

76.2

39.55

36.47

18.33

16.5

8

1.07

26.99

215.19

18.62




Table 2 Dimensions and thread parameters of "B" type Multi-Rifled pipe


Nominal 
Outer 
diameter
/mm

Thread
root
inner diameter
/mm

The
smallest inner diameter
/mm

Nominal
wall thickness
/mm

Minimum
wall thickness
/mm

Number of thread heads

Thread Top Width (Circumference)

/mm

Thread height
/mm

Thread Side Angle
(。)

Radius of rounded corner at the root of thread
/mm

Thread pitch,
/mm

Thread Lead
/mm

Thread Increase Angle
(。)

Thread top width (axial)
/mm

Thread top (axial) slot width
/mm

B

C

E

S

F

G

I

J

K

O

M

N

Q

T

U

35

20.60

18.10

7.20

6.5

6

3.23

0.95

50。

0.4~2

18.67

112

30。

5.60

13.07

38

23.60

20.80

7.20

6.5

6

0.99

21.39

128.20

15.79

38．1

23.23

20.49

7.44

6.7

6

0.99

21.06

126.40

15.46

60

45.60

42.20

7.20

6.5

12

1.23

20.70

247.90

15.10

60

44.50

41.20

7.75

7

12

1.22

20.18

242.10

14.56

60

43.40

40.10

8.30

7.5

12

1.21

19.68

236.15

14.08

66．7

50.70

-

8

7.2

12

3.83

1.24

23

276

6.64

16.36

66．7

49.60

-

8.55

7.7

12

1.24

22.50

270

15.86

 
 
5. 2 Allowable deviation of dimension and thread parameters
The allowable deviation of the dimensions and thread parameters of Multi-rifled pipe shall be in accordance with Table 3.
 
Table 3 

Project Size range / mm Type A Type B Type OM
Outer diameter ≤38.1 ±0.15mm ±0.15mm ±0.15mm
＞38.1~＜50.8 ±0.2mm ±0.2mm ±0.2mm
≥50.8~＜63.5 ±0.25mm ±0.25mm -
≥63.5 ±0.3mm ±0.3mm -
Thread root diameter ≤38.1 ±0.15mm ±0.15mm ±0.15mm
＞38.1~＜50.8 ±0.2mm ±0.2mm ±0.2mm
≥50.8~＜63.5 ±0.25mm ±0.25mm -
≥63.5 ±0.3mm ±0.3mm -
Minimum inner diameter - The lower deviation is 0 The lower deviation is 0 -
Minimum wall thickness - +22% mm
0		 +22% mm
0		 +22% mm
0
Wall thickness - ±10%mm ±10%mm ±10%mm
Thread height ≤38.1 ±0.2mm ±0.18mm ±0.2mm
＞38.1~＜50.8 ±0.3mm ±0.2mm ±0.2mm
≥50.8~＜63.5 ±0.3mm ±0.23mm ±0.2mm
≥63.5 ±0.3mm ±0.28mm ±0.2mm
Thread side angle - ±15° ±15° +30°
-10°
Thread pitch - ±3.2mm ±3.2mm -
Thread lead - ±3.2mm*Number of threads ±3.2mm*Number of threads -
Thread angle - - - +5°
0°
Thread top width (axial) - ±1.3mm ±1.3mm ±1.3mm

 
 
5.3 Length
The normal length of Multi-Rifled pipe is 8 000 mm to 12 000 mm.
 
 According to the requirement of the demander, after consultation between the supplier and the demander, it is indicated in the contract that multi - rifled pipe can be delivered in fixed length or other length. The length of fixed length should be within the normal length range, and the allowable deviation of full length should be + 20mm.
 
 
 
 
5. 4 Curvature
The bending degree of Multi-Rifled pipe should not exceed 1.0m m/m.
 
 
 
5. 5 End Profile
The ends of Multi-Rifled pipe should be perpendicular to the axis of the steel pipe, and the burrs in the incision should be removed.
 
 
 
5.6 Weight
Multi-rifled pipe is delivered by actual weight.
 
 
 
5. 7 Markup Example
Example: Multi-rifled pipe with outer diameter 63.5 mm, minimum wall thickness 7.2 mm, length 12 000 mm and "A" profile made of 20G steel.
20G-63.5X7.2X12000-A-GB/T 2009
 
 
 
6 Technical Requirements
 
Chemical Composition
The steel grade and chemical composition (smelting analysis) shall comply with Table 4. Multi-rifled pipe is accepted according to melting composition.
 
When the buyer requests the finished product analysis, it should be noted in the contract. The allowable deviation of chemical composition of Multi-Rifled pipe products should comply with GB/T 222.

Table 4   Chemical Composition of GB/T 20409 Multi-rifled Steel Pipe

Grade

chemical composition(%)

C

Mn

Si

Cr

Mo

S

P

20G

0.17~0.23

0.35~0.65

0.17~0.37

-

-

≤0.020

≤0.025

20MnG

0.17~0.23

0.70~1.00

0.17~0.37

-

-

≤0.020

≤0.025

25MnG

0.22~0.29

0.70~1.00

0.17~0.37

-

-

≤0.020

≤0.025

12CrMoG

0.08~0.15

0.40~0.70

0.17~0.37

0.40~0.70

0.40~0.55

≤0.020

≤0.025

15CrMoG

0.12~0.18

0.40~0.70

0.17~0.37

0.80~1.10

0.40~0.55

≤0.020

≤0.025
Note 1: The residual element content of 20G, 20MnG and 25MnG should be consistent with: Cu≤0.20%, Cr≤0.25%, Ni≤0.25%, V≤0.08%, Mo≤0.15%; the residual element content of the remaining grades should be consistent with: Cu ≤0.20%, Ni≤0.30%.
 
Note 2: The acid-soluble aluminum in 20G steel should be no more than 0.010%.
 
Note 3: The steel produced by refining with oxygen and refining should have a nitrogen content of not more than 0.008%.



 
 
6. 2 Manufacturing Method
Steel and Tube Billet Manufacturing Method
The manufacturing method of steel and tube billet shall comply with the requirements of YB/T5137.
 
Multi-rifled pipe manufacturing method
Multi-rifled pipe shall be manufactured by cold-drawing process using YR/T 5137 pipe blank or GB 5310 pipe blank.
 
 
 
6. 3 Status of Delivery
Multi-rifled pipe shall be delivered in heat treatment state and its heat treatment system shall comply with the requirements of Table 5. The heat treatment system shall be filled in the quality certificate.
 
 
Table 5 Multi-rifled pipe heat treatment system

Grade  Heat treatment
20G Normalizing, normalizing temperature: 880 ° C ~ 940 ° C
20MnG Normalizing, normalizing temperature: 880 ° C ~ 940 ° C
25MnG Normalizing, normalizing temperature: 880 ° C ~ 940 ° C
12CrMoG Normalizing and tempering, normalizing temperature: 900 ° C ~ 960 ° C; tempering temperature: 670 ° C ~ 730 ° C
15CrMoG Normalizing and tempering, normalizing temperature: 900 ° C ~ 960 ° C; tempering temperature: 680 ° C ~ 730 ° C





Mechanical Properties

Table 6 Mechanical Properties

Grade

Tensile strength

Rm/

MPa(N/mm2)

Yield Strength

R eL/

MPa(N/mm2)

Elongation

A/%

Impact energy

Akv/J

≥

20G

410~550

245

24

35

20MnG

≥415

240

22

35

25MnG

≥485

275

20

35

12CrMoG

410~560

205

21

35

15CrMoG

440~640

235

21

35
 
 
 
Technological properties
 
Flattening test
Multi-rifled pipe should be subjected to flattening test. Internal threads can be retained in Multi-Rifled pipe flattening test.
 
After flattening test, no cracks or cracks are allowed in the specimen. When the ratio of outer diameter to nominal wall thickness is less than 10, the cracks on the inner surface of the specimens at the two plates can not be used as the basis for judging.
 
 
hydraulic test
Multi-rifled pipe should conduct hydraulic face test one by one. The maximum test pressure of internal threaded pipe is 20 MPa.
 
 
 
Microstructure, Grain Size and Decarbonized Layer
The microstructures of Multi-Rifled pipe products with grades 20G, 20MnG and 25MnG should be ferrite and pearlite. The microstructures of Multi-Rifled pipe products with grades 12CrMoG and 15crMoG should be ferrite and pearlite (including pull bainite), and there should be no incomplete transformation products (such as yellow martensite) between Ac1 and Ac3.



Ultrasound Inspection
Multi-rifled pipe should be tested by ultrasound according to GB/T 5777. Ultrasound flaw detection can be performed before or after Multi-Rifled forming.
 



Surface Quality
The inner and outer surfaces of Multi-Rifled pipe are not allowed to have cracks, folds, rolls, scars and delaminations. These defects should be completely removed. The actual wall thickness of the clearance site should not be less than the minimum allowable deviation of wall thickness, and the clearance site should be smooth transition.
 
The allowable depth of the straight should be no more than 4% of the minimum wall thickness, and the maximum depth of the straight should be no more than 0.2 mm. Other local defects that do not exceed the minimum wall thickness are allowed to exist.
 
The oxide scales on the inner and outer surfaces of Multi-rifled pipe should be removed without prejudice to the permissible existence of the oxide thin layer.

 

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