Multiple Steel Grades for API Spec 5L Pipe
Described mainly in the paper are the origin and procedure for marking of pipe to multiple grades as newly required under API Spec 5L Specification for Line Pipes， the 45th edition. Only agreed by both the purchaser and the manufacturer， should marking of pipe to multiple grades be permitted. The steel grade range for multiple markings shall be as per API Standard 1104 Welding of Pipelines and Related Facilities. The steel pipe shall be marked to one PSL level only. The manufacturer is responsible to ensure that the pipe conforms to all requirements of each of the certified grades. This allows pipe to be used as any of grades individually. Once the steel pipe is delivered， it shall not be permitted to get the pipe re-marked or re-inspected to identify it with different steel grade or PSL level.
Key words : steel linepipe ; API standard ; multi steel grade marking ; additional requirements
The History and Current Situation of Multiple Steel Grade Marking for Steel Pipes
The commonly used steel grades of API Spec 5L steel pipes include: B , X42 , X52 , X60 , X65 , X70 , X80, etc., and the product specification levels include PSL1 and PSL2 .
requirements of PSL1 steel pipes in API Spec 5L only have a lower limit and no upper limit. The yield strength requirements of PSL2 steel pipes have a lower limit and an upper limit. There are regulations on the Charpy impact toughness and the DWT test SA % value of the diameter D M 508 mm steel pipe . PSL1 and PSL2 steel pipe tensile test yield strength and tensile strength requirements are shown in Table 1 . It can be seen from Table 1 that the yield strength of X60 steel grade PSL2 steel pipe is 415 ~ 565 MPa , the yield strength of X65 steel grade PSL2 steel pipe is 450 ~ 600 MPa , and the yield strength of X70 steel grade PSL2 steel pipe is 485 ~ 635 MPa . APL Spec 5L standard PSL2 steel pipe grades X60 , X65 and X70 have overlapping yield strength ranges between 485 and 565 MPa .
PSL1 and PSL2 Steel Pipe Tensile Test Yield Strength and Tensile Strength Requirements
Type of steel pipe |
Grade |
Yield strength Rt0.5 |
tensile strength Rm |
||||||
|
Min |
Max |
Min |
Max |
||||||
|
kpsi |
MPa |
kpsi |
MPa |
kpsi |
MPa |
kpsi |
MPa |
||
|
|
B |
35.5 |
245 |
- |
- |
60.2 |
415 |
- |
- |
|
|
X42 |
42.1 |
290 |
- |
- |
60.2 |
415 |
- |
- |
|
|
X52 |
52.2 |
360 |
- |
- |
66.7 |
460 |
- |
- |
|
PSL1 |
X60 |
60.2 |
415 |
- |
- |
75.4 |
520 |
- |
- |
|
|
X65 |
65.3 |
450 |
- |
- |
77.6 |
535 |
- |
- |
|
|
X70 |
70.3 |
485 |
- |
- |
82.7 |
570 |
- |
- |
|
|
B |
35.5 |
245 |
65.3 |
450 |
60.2 |
415 |
95.0 |
655 |
|
|
X42 |
42.1 |
290 |
71.8 |
495 |
60.2 |
415 |
95.0 |
655 |
|
|
X52 |
52.2 |
360 |
76.9 |
530 |
66.7 |
460 |
110.2 |
760 |
|
PSL2 |
X60 |
60.2 |
415 |
81.9 |
565 |
75.4 |
520 |
110.2 |
760 |
|
|
X65 |
65.3 |
450 |
87.0 |
600 |
77.6 |
535 |
110.2 |
760 |
|
|
X70 |
70.3 |
485 |
92.1 |
635 |
82.7 |
570 |
110.2 |
760 |
|
|
X80 |
80.5 |
555 |
102.3 |
705 |
90.6 |
625 |
119.7 |
825 |
The actual yield strength of a steel pipe is 517 MPa ( 75 kps ) i , which falls within the overlapping range of yield strength specified in X60 , X65 and X70 steel grades, that is, the steel pipe meets the yield strength requirements of these three steel grades . The chemical composition , mechanical properties and hydrostatic pressure test requirements of X65 and X70 steel grade PSL2 steel pipes have little difference . Possibility of X65/X70 multiple steel grade marking .
Multiple steel grade marking practices are common in low steel grades in APL Spec 5L , the most common multi steel grade marking products such as B/X42 , others
There are also X42/X46 , B/X42/X46 , X42/X52 .
In recent years, steel pipe manufacturers have also received multiple steel grade marking requirements of X 60/ X 65 , X 65/ X 70 , X 60/ X 65/ X 70 , X 70/ X 80 . There are even reports [ 3 ] that the steel pipes are marked with the following double product specification levels and multiple steel grade formwork paint marks: X52 PSL1/X60 PSL1/X65 PSL1/X70 PSL2/X80 PSL2 , and a certificate is issued . It can be seen from Table 1 that the specified minimum yield strength of X52 PSL1 steel pipe in API Spec 5L is 360 MPa ( 52.2 kps ) i , and there is no upper limit; the minimum specified yield strength of X60 PSL1 steel pipe is 415 MPa
- kps ) , no upper limit; X65 PSL1 steel pipe stipulates that the minimum yield strength is 450 MPa ( 65.3 kps ) i , no upper limit; X70 PSL2 steel pipe stipulates that the yield strength range is 485 - 635 MPa ( 70.3 - 92.1 kps ) ; X80 PSL2 steel pipe stipulates Yield strength range 555 - 705 MPa ( 80.5 - 102.3 kps ) i . The specified yield strengths of X52 PSL1 , X60 PSL1 , X65 PSL1 , X70 PSL2 , and X80 PSL2 steel pipes overlap in the range of 555 - 635 MPa ( 80.5 - 92.1 kps ) .
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