About API 5L Grade B: 5 Things You May 

Still Don’t Know

You may be familiar with API 5L specification and you shall know API 5L Grade B. However, you may still don’t know the following 5 things about PSL2 Grade B, according to API 5L standard. Let’s see what they are:

1. CVN Impact Test for GR.B PSL 2 Pipe

API 5L HFW & SAW pipes: 

• For PSL1 Grade B, the CVM impact test is just mandatory to apply on pipe body. It’s not required impact test on welded seam. 
• However, if per PSL2 GR.B, CVN impact test should be done on both pipe body and seam weld. This will reduce the productrate and make the cost higher than PSL1 pipes. Because either the raw material is not good or the welding is not qualified, the CVN impact test on weld seam will fail, which means the total heat of pipes may face rejection as per API 5L, if the retest is also failed. 

API 5L Seamless Pipe:

It also only required API 5L Grade B PSL2 pipe to do the heat treatment on pipe body.

Let’s see the requirements of CVN impact test for API 5L PSL2 Gr. B carbon steel pipes:

    1.1. In general 

• If subsize test pieces are used, the required minimum average (set of three test pieces) absorbed energy values shall be the required values for full-size test pieces times the ratio of the specified width of the subsize test piece to the specified width of the full-size test piece, with such derived values rounded to the nearest joule (foot-pound force).
• Individual test values for any test piece shall be ≥ 75 % of the required minimum average (of a set of three test pieces) absorbed energy values.
• Tests conducted at temperatures lower than the specified test temperature shall be acceptable if the applicable requirements for energy absorption and shear fracture area are met at such lower temperatures.

    1.2. Pipe body tests

The minimum average (of a set of three test pieces) absorbed energy for each pipe body test shall be as given in Table 8, based upon full-size test pieces and a test temperature of 0 °C (32 °F) or, if agreed, a lower test temperature.

NOTE The energy values specified in Table 8 provide sufficient fracture-initiation resistance for most pipeline designs.

For welded pipe with D≥508 mm (20.000 in), if agreed, the minimum average (set of three test pieces) shear fracture area for each test shall be at least 85 %, based upon a test temperature of 0 °C (32 °F) or, if agreed, a lower test temperature.

    

CVN Impact Test

1.3. Pipe weld and HAZ tests

The minimum average (of a set of three test pieces) absorbed energy for each pipe weld and HAZ test, based upon full-size test pieces and a test temperature of 0 °C (32 °F), or if agreed a lower test temperature, shall be

  a) 27 J (20 ft•lbf) for pipe with D 1422 mm (56.000 in) in grades u L≤555 or X80;

  b) 40 J (30 ft•lbf) for pipe with D ≥ 1422 mm (56.000 in);

  c) 40 J (30 ft•lbf) for pipe in grades ＞L555 or X80.

NOTE The HAZ of the longitudinal seam weld in HFW welded pipe is usually too narrow to permit accurate sampling for Charpy testing. The requirement for Charpy testing of the seam weld HAZ applies only to SAWL/SAWH and COWL/COWH pipe.

2. DWT test for PSL2 GR.B Pipe

If agreed when D≥508 mm, pipes in GR.B PSL2 shall be applied DWT test, drop weight tear test. But this is only for HFW, SAWL, SAWH, COWL or COWH steel pipes. 

For each test (of a set of two test pieces), the average shear fracture area shall be ≥85 %, based upon a test temperature of 0 °C (32 °F) or, if agreed, a lower test temperature. For wall thickness 25,4 mm (1.000 in), DWT test acceptance requirements shall be by agreement.

NOTE 1 Such shear-fracture area ensures a sufficiently ductile fracture at or above the test temperature.

Tests conducted at temperatures lower than the specified test temperature shall be acceptable if the applicable requirements for shear fracture area are met at such lower temperatures.

Let’s see a video for drop weight tear test:

3. Grade BM, Grade BQ, Grade BN, Grade BR

The starting material or raw material is different according to the different heat treatment type, even they are all API 5L Grade B PSL2. And different type of delivery condition is relevant to different type of API 5L Pipes.

Let’s see those different API 5L Grade B in PSL 2.

    3.1. API 5L Grade BM

Delivery condition	Type of pipe	Starting material	Pipe forming	Pipe heat treatment
M	HFW	Thermomechanical-rolled strip	Cold forming	Heat treating a of weld area only
M				Heat treating a of weld area and stress relieving of entire pipe
M		Hot-rolled strip	Cold forming followed by thermomechanical forming of pipe	.
M	SAW or COW pipe	Thermomechanical-rolled strip or plate	Cold forming	.

   3.2. API 5L Grade BN

Delivery condition	Type of pipe	Starting material	Pipe forming	Pipe heat treatment
N	SMLS	Ingot, bloom or billet	Normalizing forming	.
N			Hot forming	Normalizing
N			Hot forming and cold finishing	Normalizing
N	HFW	Normalizing-rolled strip	Cold forming	Heat treating a of weld area only
N		Hot-rolled strip	Cold forming	Normalizing
N			Cold forming followed by hot reducing under controlled temperature resulting in a normalized condition	.
N	SAW or COW pipe	Normalized or normalizing-rolled strip or plate	Cold forming	.
N		As-rolled, thermomechanical­rolled, normalizing-rolled or normalized	Cold forming	Normalizing
N		As-rolled, thermomechanical­rolled, normalizing-rolled or normalized strip or plate	Normalizing forming	.

    3.3. API 5L Grade BR

Delivery condition	Type of pipe	Starting material	Pipe forming	Pipe heat treatment
R	SMLS	Ingot, bloom or billet	As-rolled	.

    3.4. API 5L Grade BQ

Delivery condition	Type of pipe	Starting material	Pipe forming	Pipe heat treatment
Q	SMLS	Ingot, bloom or billet	Hot forming	Quenching and tempering
Q			Hot forming and cold finishing	Quenching and tempering
Q	HFW	Hot-rolled strip	Cold forming	Quenching and tempering
Q	SAW or COW pipe	Quenched and tempered plate	Cold forming	.
Q		As-rolled, thermomechanical­rolled, normalizing-rolled or normalized strip or plate	Cold forming	Quenching and tempering

    3.5. All API 5L Grade B PSL2 Chemical Composition Properties

Name	Mass fraction, based upon heat and product analyses % maximum								Carbon equivalent a % maximum
	C	Si	Mn	P	S	V	Nb	Ti	CEIIW	CEPcm
Seamless and welded pipes
BR	0,24	0,40	1,20	0,025	0,015	c	c	0,04	0,43	0,25
BN	0,24	0,40	1,20	0,025	0,015	c	c	0,04	0,43	0,25
BQ	0,18	0,45	1,40	0,025	0,015	0,05	0,05	0,04	0,43	0,25
BM	0,22	0,45	1,20	0,025	0,015	0,05	0,05	0,04	0,43	0,25

4. Heat Treatment for GR.B PSL 2

• For SMLS in API 5L PSL2 Gr B: the full pipe body should be heat treated.
• For PSL2 Grade B welded pipes: heat treatment shall be applied at weld seam & HAZ. If required by the purchaser, the pipe body shall be heat treated so as to simulate a normalizing heat treatment. 
• The reference for heat treatment is according to ISO 4885 or ASTM A 941 for heat treatment.

Anneal – heat treatment for ERW Pipe

5. Special Grade BR in API 5L

The Grade BR in API 5L is special, because it may be PSL1 grade or PSL2 grade. Let’s see the different mechanical properties requirements for different API 5L Grade BR.

    5.1. API 5L PS1 Grade BR

Pipe grade	Pipe body of seamless and welded pipes			Weld seam of EW, SAW and COW pipes
	Yield strength a Rt0,5 MPa (psi) minimum	Tensile strength a Rm MPa (psi) minimum	Elongation Af % minimum	Tensile strength b Rm MPa (psi) minimum
L245R or BR L245 or B	245 (35 500)	415 (60 200)	c	415 (60 200)

In API 5L PSL1 Grade BR, the mechanical properties requirements is just require min. strength and no max. strength. While in PSL2 Grade BR, there are both min. strength and max. strength, it’s a range for Grade BR mechanical requirements.

    5.2. API 5L PS2 Grade BR

Pipe grade	Pipe body of seamless and welded pipes  Yield strength a Tensile strength a Ratio a, b, c							Weld seam of HFW, SAW and COW pipes
	Yield strength a Rt0,5b MPa (psi)		Tensile strength a Rt0,5b MPa (psi)		Ratio a, b, c Rt0,5/Rm		Elongation Af %	Tensile strength d  Rm
	minimum	maximum	minimum	maximum	maximum		minimum	MPa (psi)  minimum
BR BN BQ BM	245  (35 500)	450  (65 300)	415  (60 200)	760   (110 200)	0,93		f	415 (60 200)