ASTM A106 Grade B Seamless Pipe for Sour Service | NACE MR0175 / ISO 15156
ASTM A106 Grade B is a seamless carbon steel pipe grade widely used for pressure piping and elevated-temperature service in oil and gas, petrochemical, refinery, power-generation and general industrial systems.
For H₂S-containing oil and gas production environments, ASTM A106 Grade B seamless pipe can be supplied with additional material controls and testing to meet specified NACE MR0175 / ISO 15156 sour-service requirements.
Sour-service production may include controlled hardness, restricted chemistry, heat-treatment requirements, enhanced traceability and optional Hydrogen-Induced Cracking (HIC) testing according to the project specification.
Available products include hot-finished and cold-drawn seamless pipe in standard and heavy-wall schedules.
ASTM A106 Grade B Pipe Overview
| Item | Specification |
|---|---|
| Material Standard | ASTM A106 / ASME SA-106 |
| Grade | Grade B |
| Product Type | Seamless Carbon Steel Pipe |
| Primary Standard Service | High-Temperature Service |
| Manufacturing | Hot-Finished or Cold-Drawn Seamless |
| Dimensions | ASME B36.10M |
| Sour Service | Available to specified NACE MR0175 / ISO 15156 requirements |
| Optional HIC Testing | NACE TM0284 when specified |
| Certification | EN 10204 3.1 / 3.2 when required |
| Typical Applications | Oil & Gas, Petrochemical, Process Piping, Power Generation |
What Is ASTM A106 Grade B?
ASTM A106 Grade B is a seamless carbon steel pipe intended primarily for elevated-temperature pressure service.
The material is suitable for operations involving:
- Welding
- Bending
- Flanging
- Similar forming processes
Grade B is the most commonly specified grade within the ASTM A106 family because it provides a practical combination of strength, weldability, availability and cost.
Typical applications include:
- Process piping
- Steam piping
- Oil and gas facilities
- Petrochemical systems
- Refineries
- Pressure equipment
- Power plants
- High-temperature utility piping
ASTM A106 covers seamless round pipe. It should not be confused with structural tubing, rectangular hollow sections or welded line pipe specifications.
ASTM A106 Grade B Chemical Composition
Typical ASTM A106 Grade B chemistry includes:
| Element | Requirement |
|---|---|
| Carbon, C | 0.30% max |
| Manganese, Mn | 0.29–1.06% |
| Phosphorus, P | 0.035% max |
| Sulfur, S | 0.035% max |
| Silicon, Si | 0.10% min |
| Copper, Cu | 0.40% max |
| Nickel, Ni | 0.40% max |
| Chromium, Cr | 0.40% max |
| Molybdenum, Mo | 0.15% max |
| Vanadium, V | 0.08% max |
Additional combined-alloy restrictions apply under ASTM A106.
Actual heat chemistry is reported on the Material Test Certificate.
For sour-service projects, tighter limits on sulfur, phosphorus, carbon equivalent or other elements may be specified by the purchaser.
ASTM A106 Grade B Mechanical Properties
Typical minimum tensile requirements are:
| Property | Requirement |
|---|---|
| Tensile Strength, min. | 415 MPa / 60 ksi |
| Yield Strength, min. | 240 MPa / 35 ksi |
| Elongation | According to applicable ASTM requirements |
Additional requirements may apply according to pipe size, wall thickness and project specification.
What Is Sour Service?
Sour service generally refers to equipment exposed to environments containing hydrogen sulfide (H₂S).
In the presence of water and suitable environmental conditions, H₂S can contribute to several forms of material damage, including:
- Sulfide Stress Cracking (SSC)
- Hydrogen-Induced Cracking (HIC)
- Stress-Oriented Hydrogen-Induced Cracking (SOHIC)
- Hydrogen-related embrittlement
For critical oil and gas applications, material selection and manufacturing controls therefore extend beyond the basic ASTM A106 requirements.
ASTM A106 Grade B for NACE MR0175 Service
NACE MR0175 / ISO 15156 addresses materials for use in H₂S-containing environments in oil and gas production.
Carbon and low-alloy steels are covered by the applicable requirements of ISO 15156-2.
ASTM A106 Grade B can be supplied for specified sour-service applications when the final material condition and environmental limits satisfy the applicable project and NACE/ISO requirements.
Important factors include:
- Material hardness
- Heat-treatment condition
- Chemical composition
- Yield strength
- Cold work
- Welding
- Weld hardness
- H₂S partial pressure
- pH
- Chloride concentration
- Operating temperature
Therefore, standard ASTM A106 Grade B pipe should not automatically be described as “NACE compliant” unless the relevant sour-service requirements have been specifically included and verified.
Hardness Control for Sour Service
Hardness is an important parameter in controlling susceptibility to sulfide stress cracking in carbon and low-alloy steels.
For sour-service projects, hardness limits may be specified according to NACE MR0175 / ISO 15156 and the applicable project specification.
Hardness testing may be performed on:
- Base material
- Pipe ends
- Welded components where applicable
- Heat-affected zones in fabricated piping
- Additional locations required by the purchaser
The required maximum hardness should be stated on the purchase order.
Sour-Service Chemistry Control
For severe sour environments, customers may specify chemistry limits more restrictive than the basic ASTM A106 Grade B requirements.
Typical project controls may include:
- Reduced sulfur
- Reduced phosphorus
- Controlled carbon
- Controlled manganese
- Carbon-equivalent limit
- Residual-element restrictions
Lower sulfur content can also be important where resistance to hydrogen-induced cracking is required.
These restrictions should be treated as project-specific supplementary requirements, not as standard ASTM A106 Grade B chemistry.
Heat Treatment for Sour-Service Pipe
ASTM A106 pipe may be supplied by different approved manufacturing routes depending on pipe size and production method.
For sour-service projects, additional heat-treatment requirements may be specified to obtain controlled microstructure, mechanical properties and hardness.
Depending on the procurement specification, the pipe may be required in a condition such as:
- Normalized
- Normalized and tempered
- Other approved heat-treated condition
The exact heat treatment should be stated in the purchase specification rather than assumed from the ASTM A106 grade alone.
HIC Testing – NACE TM0284
For critical wet-H₂S service, ASTM A106 Grade B pipe can be supplied with optional Hydrogen-Induced Cracking testing.
A commonly specified test method is:
NACE TM0284 – Evaluation of Pipeline and Pressure Vessel Steels for Resistance to Hydrogen-Induced Cracking
The test evaluates the susceptibility of steel to HIC resulting from hydrogen generated during corrosion in a wet H₂S environment.
Typical testing may use:
- NACE Solution A or another specified solution
- H₂S saturation
- Controlled exposure period
- Metallographic examination after testing
The exact test method, sampling frequency and acceptance criteria should be clearly defined by the purchaser.
HIC Acceptance Criteria
Common project acceptance criteria may include limits on:
- CLR – Crack Length Ratio
- CTR – Crack Thickness Ratio
- CSR – Crack Sensitivity Ratio
One frequently specified set of project limits is:
| Parameter | Example Acceptance Limit |
|---|---|
| CLR | ≤15% |
| CTR | ≤5% |
| CSR | ≤2% |
These values are not universal requirements for every ASTM A106 Grade B pipe.
Acceptance criteria can vary substantially by operator, EPC contractor, service severity and project specification.
HIC vs SSC
HIC and SSC are different cracking mechanisms and should not be treated as the same test requirement.
HIC – Hydrogen-Induced Cracking
HIC can occur without externally applied tensile stress and is typically evaluated using methods such as NACE TM0284.
SSC – Sulfide Stress Cracking
SSC involves the combined effects of:
- H₂S environment
- Susceptible material
- Tensile stress
SSC resistance is addressed through material-selection requirements and, when required, specific laboratory qualification methods.
Passing a HIC test does not automatically prove resistance to every form of H₂S-related cracking.
Manufacturing Process
ASTM A106 Grade B pipe is manufactured by a seamless process.
Typical manufacturing routes include:
Hot-Finished Seamless Pipe
A heated billet is pierced and formed into seamless pipe before sizing and finishing.
Cold-Drawn Seamless Pipe
Pipe is further cold worked to obtain closer dimensional control and surface characteristics.
Cold-drawn products receive the heat treatment required by the applicable specification.
For sour-service orders, additional manufacturing controls can be incorporated according to the project specification.
Steelmaking Requirements for Sour Service
Project specifications for sour-service pipe may require additional steelmaking controls such as:
- Fully killed steel
- BOF or EAF steelmaking
- Secondary refining
- Vacuum degassing where specified
- Fine-grain practice
- Controlled inclusion shape
- Low sulfur
- Clean-steel practice
These controls can help improve through-thickness cleanliness and HIC resistance.
Actual requirements should be stated in the purchase specification.
Size and Supply Range
ASTM A106 covers seamless pipe in a broad nominal size range.
Our typical commercial supply range can include:
| Item | Supply Range |
|---|---|
| Size | NPS 1/2″ to NPS 24″ |
| Wall Thickness | SCH 20 to SCH XXS / heavy wall |
| Manufacturing | Seamless |
| Length | SRL, DRL, fixed or custom length |
| Typical Fixed Length | Up to 12 m where available |
| Ends | Plain End / Beveled End |
| Dimensions | ASME B36.10M |
| Surface | Bare, black coating, anti-rust oil or project-specific finish |
Larger sizes and special wall thicknesses can be supplied subject to manufacturing availability.
Dimensions and Tolerances
Outside diameter, wall thickness, weight and length tolerances should comply with the applicable ASTM A106 / ASTM A530 requirements and the ordered dimensional specification.
ASME B36.10M is commonly used for nominal pipe dimensions and schedules.
For project procurement, the inquiry should state:
- NPS
- Outside diameter if non-standard
- Schedule or wall thickness
- Length
- End preparation
- Dimensional tolerance if more restrictive than standard
Beveled Ends
Pipe intended for butt welding can be supplied with beveled ends according to the applicable project or welding-end preparation requirement.
Typical options include:
- Plain End
- Beveled End
- Custom Machined End
Threaded ends should only be supplied where compatible with the applicable piping design and wall thickness.
Inspection and Testing
ASTM A106 Grade B sour-service pipe can be supplied with:
- EN 10204 Type 3.1 MTC
- EN 10204 Type 3.2 when specified
- Chemical Analysis
- Tensile Testing
- Hardness Testing
- Dimensional Inspection
- Visual Inspection
- Hydrostatic Test
- Nondestructive Electric Test
- Ultrasonic Testing when specified
- PMI where required
- Heat-Treatment Records
- HIC Testing
- SSC Testing where specifically required
- Third-Party Inspection
- Full Heat-Number Traceability
Testing requirements should be clearly stated at the inquiry stage.
Typical Applications
ASTM A106 Grade B sour-service seamless pipe can be used in appropriately qualified applications such as:
- Oil and gas production facilities
- Gas processing plants
- Sour-gas piping
- Produced-fluid systems
- Process piping
- Pressure piping
- Petrochemical installations
- Gathering and processing facilities
- High-temperature industrial piping
Material suitability must be confirmed against the actual H₂S environment and applicable design requirements.
NACE MR0175 vs NACE MR0103
These standards should not be confused.
NACE MR0175 / ISO 15156 is primarily associated with H₂S-containing environments in oil and gas production.
For sour petroleum-refining environments, other material-selection standards such as NACE MR0103 / ISO 17945 may be applicable depending on the project.
The governing sour-service standard should therefore be stated by the purchaser.
How to Order ASTM A106 Gr.B Sour-Service Pipe
A complete inquiry should include:
- ASTM / ASME material specification
- Grade
- NPS
- Wall thickness or schedule
- Quantity
- Length
- End preparation
- NACE / ISO requirement
- Maximum hardness
- HIC requirement
- HIC acceptance criteria
- Heat-treatment condition
- Carbon-equivalent requirement
- Sulfur / phosphorus limits
- NDT requirement
- Inspection certificate
- Third-party inspection requirement
Example 1
ASTM A106 Gr.B SMLS Pipe, NPS 6″, SCH 80, NACE MR0175 / ISO 15156, Normalized, Hardness Controlled, EN 10204 3.1
Example 2
ASTM A106 Gr.B Seamless Pipe, NPS 8″, SCH 40, Sour Service, HIC Tested to NACE TM0284, CLR ≤15%, CTR ≤5%, CSR ≤2%
Example 3
ASME SA-106 Gr.B SMLS Pipe, NPS 4″, SCH 160, NACE MR0175 / ISO 15156, HIC Tested, UT, 3.2 Certification
Frequently Asked Questions
What is ASTM A106 Grade B?
ASTM A106 Grade B is a seamless carbon steel pipe grade intended primarily for high-temperature pressure service.
Is ASTM A106 Grade B automatically suitable for sour service?
No.
ASTM A106 defines the basic pipe material and manufacturing requirements. Sour-service applications may require additional hardness, chemistry, heat-treatment, environmental and testing controls.
Can ASTM A106 Grade B comply with NACE MR0175?
A106 Grade B pipe can be supplied for applications requiring NACE MR0175 / ISO 15156 when the specified material condition and environmental limits comply with the applicable requirements.
Is HIC testing mandatory for ASTM A106 Grade B?
No.
HIC testing is an additional project requirement and is not a universal requirement of standard ASTM A106 Grade B pipe.
What is NACE TM0284?
NACE TM0284 is a laboratory test method used to evaluate the resistance of pipeline and pressure-vessel steels to hydrogen-induced cracking in wet H₂S environments.
Does passing NACE TM0284 mean the pipe is NACE MR0175 compliant?
Not by itself.
HIC testing evaluates a specific cracking mechanism. NACE MR0175 / ISO 15156 material suitability also considers material properties, hardness, heat treatment and the actual sour environment.
What is the difference between ASTM A106 and API 5L?
ASTM A106 is primarily a seamless carbon steel pipe specification for high-temperature pressure service.
API 5L is a line-pipe specification for pipeline transportation systems.
The two standards may sometimes be dual-certified when all requirements of both specifications are satisfied, but they should not be treated as the same standard.
ASTM A106 Grade B Sour-Service Seamless Pipe
We supply ASTM A106 / ASME SA-106 Grade B seamless carbon steel pipe for pressure, elevated-temperature and specified sour-service applications.
For quotation, please provide the size, wall thickness, quantity, length, heat-treatment condition, NACE requirements, HIC acceptance criteria and inspection requirements.
ASTM A106 Grade B Seamless Pipe is a carbon steel pipe used for high-temperature and high-pressure service.
When specified for sour service, the pipe is specially manufactured and heat-treated to meet NACE MR0175 / ISO 15156 requirements for H₂S-containing (sour) environments in oil, gas, and petrochemical industries.
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