1. Introduction
ASTM A105 is a key specification for carbon steel forgings used in pressure piping systems.
It defines mechanical property requirements—rather than exact chemistry—for forged components like flanges, fittings, and valves.
First published in the mid-20th century, A105 addressed reliability issues inherent in cast carbon steel by standardizing forged materials for critical industrial and energy-sector infrastructure.
Forgings offer several advantages over castings: denser, homogeneous microstructure; superior grain flow; absence of porosity and shrinkage cavities; and higher fatigue resistance.
These characteristics make A105 forgings essential for high-pressure, high-temperature systems where component failure is unacceptable.
2. Scope and Key Requirements of ASTM A105
ASTM A105 is a standard specification issued by ASTM International that governs the chemical, mechanical, and manufacturing requirements for forged carbon steel piping components.
It is one of the most widely used carbon steel forging specifications in the piping and pressure vessel industries.
Scope of ASTM A105
ASTM A105 applies to forgings, forged bars, and forged fittings made from carbon steel, primarily intended for use in pressure systems at ambient- to moderate-temperature service. These components include:
- Flanges (ASME B16.5, B16.47)
- Valves and valve bodies
- Pipe fittings (elbows, tees, reducers, couplings)
- Pressure vessel nozzles
- Shafts, rings, and other custom-forged parts
While suitable for service up to 425°C (800°F), A105 is not recommended for low-temperature applications (typically below –29°C or –20°F) unless supplementary impact testing (per ASTM A350) is applied.
Permissible Product Forms
The specification covers:
- Forgings: shaped components produced by hammering, pressing, or rolling
- Forged Bars: typically round or square bars used in machining components
- Forged Fittings: including socket weld and threaded types per ASME B16.11 or MSS-SP-79/83/95
- Forged Flanges: per ASME B16.5 and similar pressure-rated dimensions
Machined or finished parts must conform dimensionally and mechanically to the relevant codes (e.g., ASME Section VIII or B31.3).
Chemical Composition Requirements
ASTM A105 defines strict chemical limits to ensure consistency and desired mechanical properties.
| Element | Minimum (%) | Maximum (%) | Typical Role |
| Carbon (C) | — | 0.35 | Strength and hardness |
| Manganese (Mn) | 0.60 | 1.05 | Toughness, hardenability |
| Phosphorus (P) | — | 0.035 | Impurity, kept low to avoid brittleness |
| Sulfur (S) | — | 0.040 | Impurity, controlled to improve machinability |
| Silicon (Si) | 0.10 | 0.35 | Deoxidizer, strength enhancement |
| Vanadium (V)* | — | 0.08 | Grain refinement (optional) |
| Copper (Cu), Nickel (Ni), Chromium (Cr), Molybdenum (Mo), Niobium (Nb)** | — | Limited traces only | Residuals; must not exceed combined total of 1.00% |
3. Metallurgical Fundamentals
ASTM A105’s microstructure, after proper forging and heat treatment, consists of ferrite and pearlite—a balanced matrix that delivers strength and ductility.
Ferrite (soft, ductile iron) provides toughness, while pearlite (lamellar iron carbide in ferrite) contributes strength.
- Carbon’s Role: The 0.25% max carbon limit ensures pearlite formation without excessive cementite (Fe₃C), which would cause brittleness.
Higher carbon increases hardness but reduces impact resistance. - Manganese’s Influence: Manganese (0.60–1.05%) stabilizes pearlite, refining its structure and improving tensile strength.
It also mitigates sulfur’s harmful effects by forming MnS inclusions, which are less damaging than FeS. - Grain Refinement: Vanadium (when present) and controlled forging temperatures promote fine, uniform grains (ASTM grain size 5–8), enhancing toughness and fatigue resistance.
4. Mechanical Properties and Performance of ASTM A105 Carbon Steel
ASTM A105 carbon steel forgings are engineered to meet strict mechanical property requirements essential for use in pressure systems such as piping, valves, and flanges.
These properties ensure structural integrity, resistance to mechanical stress, and durability in demanding environments.
Key Mechanical Properties (Room Temperature)
| Property | ASTM A105 Minimum Requirement | Typical Value (Normalized) |
| Tensile Strength | 485 MPa (70 ksi) | 550–620 MPa |
| Yield Strength (0.2% offset) | 250 MPa (36 ksi) | 320–400 MPa |
| <p) | ≥22% | 25–30% |
| Reduction of Area | ≥30% | 35–45% |
| Hardness (Brinell) | Max 187 HBW (as-forged) | 140–180 HBW (typical) |
These values are achieved under standard normalized or normalized-and-tempered conditions.
Forgings may be stress-relieved or subjected to controlled quenching and tempering depending on service requirements.
Impact Toughness and Ductility
Though ASTM A105 does not require impact testing at room temperature, the material typically shows good Charpy V-notch impact values, especially when normalized or normalized + tempered:
- Typical impact energy at 20°C: ≥ 27–40 J
- When required for low-temperature service, impact-tested variants (e.g., ASTM A350 LF2) are recommended instead
The good ductility and elongation make A105 forgings suitable for environments with vibration, thermal cycling, or pressure pulsation.
Fatigue and Creep Performance
ASTM A105 is primarily used in non-elevated temperature environments, but it exhibits adequate resistance to fatigue and thermal expansion fatigue due to its ferrite–pearlite structure:
- Fatigue Strength (approx.): 270–300 MPa for 10⁷ cycles
- Not suitable for prolonged service above 427 °C (800 °F), as creep and graphitization may occur
Hardness and Wear
The hardness of ASTM A105 in the normalized condition generally ranges from 140 to 180 HBW, suitable for standard pressure-containing components. For enhanced wear resistance:
- Case hardening (carburizing or nitriding) may be applied
- Induction hardening is used for localized wear zones such as flange sealing faces or valve stems
5. Forging Processes for ASTM A105 Carbon Steel
Forging is the foundational process for producing ASTM A105 carbon steel components that can withstand extreme mechanical stress and cyclic pressure.
Two principal forging techniques—open-die and closed-die forging—are selected based on part size, complexity, volume, and required performance.
Open-Die Forging
Open-die forging is a versatile and traditional forging process where a heated metal billet is compressed between flat or slightly contoured dies that do not completely enclose the workpiece.
Deformation occurs incrementally through repeated blows or squeezes, allowing the metal to flow without severe geometric constraint.
This technique excels in applications requiring large-scale, custom-shaped components with excellent grain structure continuity.
It enables metallurgical advantages such as refined grain flow and reduced defect concentration while accommodating high-tonnage workpieces that are impractical for enclosed dies.
Typical ASTM A105 Applications:
- Forged shafts and bars
- Pressure vessel necks
- Blocks, discs, and hubs
Closed-Die Forging (Impression Die Forging)
Closed-die forging involves placing a heated billet into a die cavity that mirrors the final component’s shape.
Under high pressure from a hammer or press, the metal flows to fill the entire impression. Excess material forms “flash”, which is later trimmed.
This process is highly efficient for mass production of precision components with repeatable shapes and tight tolerances.
It offers excellent dimensional accuracy and grain alignment tailored to the part geometry—particularly beneficial in pressure-rated pipeline parts and flanged connections.
Typical ASTM A105 Applications:
- Pipe flanges (e.g., weld neck, socket weld, blind)
- Forged valves and tee fittings
- Oil & gas connection points and couplings
Comparison Table: Open-Die vs. Closed-Die Forging
| Parameter | Open-Die Forging | Closed-Die Forging |
| Forging Size Range | Very large components (up to 20+ tons) | Small to medium components (<200 kg) |
| Shape Complexity | Simple geometries | Intricate, high-detail shapes |
| Tooling Investment | Low | High (requires custom dies) |
| Dimensional Precision | Moderate (requires machining) | High (near-net shape) |
| Material Yield Efficiency | Moderate | High |
| Production Volume | Low to medium | Medium to high |
| Typical Applications | Shafts, blocks, pressure heads | Flanges, valve bodies, pipe fittings |
| Mechanical Properties | Excellent directional strength | Excellent uniformity and repeatability |
6. Heat Treatment & Stress-Relief of ASTM A105 Carbon Steel
Heat treatment is a critical post-forging process for ASTM A105 carbon steel forgings, as it ensures the required mechanical properties, dimensional stability, and structural integrity.
Normalizing
Purpose:
- Refines grain structure
- Enhances uniformity in microstructure
- Improves toughness and dimensional consistency
Process:
ASTM A105 forgings are typically normalized by heating to 890–950°C (1630–1740°F) and holding long enough to allow complete recrystallization and homogenization, followed by air cooling.
Quenching and Tempering (Optional)
Purpose:
- Increases strength and hardness
- Controls toughness for heavy-duty applications
Process:
Forgings are austenitized at 860–900°C (1580–1650°F), rapidly quenched in water or oil, then tempered at 540–700°C (1000–1290°F) to restore ductility and reduce brittleness.
Stress Relieving
Purpose:
- Reduces internal residual stresses from forging or machining
- Improves dimensional stability during service
Process:
Typically carried out by heating to 595–675°C (1100–1250°F) and holding for 1–2 hours depending on part thickness, then slowly cooling in still air or furnace.
7. Machining and Post‑Forging Operations for ASTM A105 Carbon Steel
After forging and heat treatment, ASTM A105 components require precise machining and finishing to meet dimensional tolerances, surface quality, and functional specifications.
This stage is critical to ensure compatibility with piping systems, pressure boundaries, and industry standards such as ASME B16.5 or API 6A.
Machining Characteristics
Material Behavior:
- A105 forgings, especially when normalized, offer moderate hardness (120–187 HBW) and good chip formation.
- Free-machining additives (e.g., lead or sulfur) are not typically added, so tool wear must be managed with appropriate strategies.
Typical Machining Operations:
- CNC Turning: Used for flange faces, hubs, and sealing surfaces.
- CNC Drilling/Boring: Applied for bolt holes, valve ports, and nozzle necks.
- CNC Milling: For flat surfaces or machined profiles on fittings.
- Threading: NPT or BSPT threads on fittings or flanges using single-point or die head tooling.
Recommended Machining Parameters (Rough Guide)
| Operation | Tool Material | Cutting Speed (m/min) | Feed Rate (mm/rev) | Depth of Cut (mm) |
| Turning | Carbide (CVD/Coated) | 120–180 | 0.2–0.4 | 1.5–4.0 |
| Drilling | HSS or Carbide | 15–30 | 0.1–0.25 | — |
| Threading | HSS Die or Insert | 10–20 | — | Full Profile |
Post-Machining Finishing
After machining, forged A105 parts undergo finishing operations to meet performance and visual specifications:
Surface Finishing:
- Shot blasting or pickling to remove scale and forge oxide
- Polishing or grinding for sealing surfaces (Ra ≤ 3.2 μm)
Deburring:
- Removal of sharp edges or burrs, especially in valve bores and flange holes, to avoid flow disruption and assembly damage.
Marking:
- Permanent markings (heat number, size, rating) per ASTM A105, ASME, or customer specifications using dot peening or stamping.
Dimensional Inspection and Quality Control
Forged parts are dimensionally inspected against detailed mechanical drawings and applicable flange or fitting standards.
Common Inspection Methods:
- CMM (Coordinate Measuring Machine) for critical tolerance areas
- Calipers, micrometers, and thread gauges for manual verification
- Hardness testing to verify compliance with ASTM limits (typ. ≤187 HBW)
8. Corrosion Behavior & Protective Measures of ASTM A105 Carbon Steel
Although ASTM A105 carbon steel is known for its excellent mechanical properties and cost-effectiveness, it does not inherently possess strong corrosion resistance, especially in aggressive or humid environments.
Corrosion Characteristics of ASTM A105
ASTM A105 is a plain carbon steel, and like all non-alloyed steels, it is vulnerable to general and localized corrosion, particularly when exposed to moisture, chlorides, acids, or elevated temperatures.
Typical Corrosion Modes:
| Corrosion Type | Behavior in A105 |
| General (Uniform) Corrosion | Most common in atmospheric or humid conditions; surface rust develops progressively. |
| Pitting | Likely in stagnant or saline environments (e.g., offshore, brackish water). |
| Galvanic Corrosion | Occurs when A105 is electrically coupled with a more noble metal (e.g., stainless steel). |
| Sulfidation | Severe in high-temperature environments containing sulfur gases or crude oil. |
| Hydrogen Embrittlement | Possible in sour gas or H₂S service if not properly coated or stress-relieved. |
Protective Measures for ASTM A105
To mitigate corrosion risks, especially in harsh environments, various surface protection and material design strategies are used.
Coatings and Paint Systems
| Coating Type | Use Case | Protection Mechanism |
| Epoxy Paints | General industrial pipelines | Barrier against moisture/chemicals |
| Zinc-Rich Primers | Outdoor or marine service | Sacrificial anode (galvanic) protection |
| Polyurethane Topcoats | High UV exposure or offshore structures | Weather and abrasion resistance |
| FBE (Fusion-Bonded Epoxy) | Buried pipelines | Excellent dielectric resistance |
Hot-Dip Galvanizing
- Provides sacrificial protection by applying a Zn layer (typ. 80–120 μm thick)
- Suitable for A105 bolts, flanges, or fittings exposed to outdoor or marine environments
- Effective up to ~200°C; avoid in high-temperature steam service
Internal Linings and Cladding
- Internal rubber or PTFE linings used in chemical or abrasive slurry handling
- Stainless steel cladding (e.g., SS 304L or 316L) via explosion or weld bonding for high-risk process lines
Cathodic Protection (CP)
- Impressed current or sacrificial anodes used for buried or submerged systems
- Common in oil & gas pipelines to prevent corrosion at joints and weld zones
Material Upgrades
- For extremely corrosive environments, replacing A105 with ASTM A350 LF2, A182 F11/F22, or stainless grades may be necessary
9. Common Applications of ASTM A105 Carbon Steel Forgings
ASTM A105 carbon steel is one of the most widely used forging materials in the pressure piping and valve industries due to its excellent combination of strength, toughness, workability, and affordability.
Oil & Gas Industry
The oil & gas sector represents one of the largest consumers of ASTM A105 forgings.
This material is particularly well-suited for components exposed to high pressure and cyclical stresses, but not extreme corrosion or cryogenic conditions.
and cost-effectiveness. Below are the key components and their typical functions:
Flanges
- Weld Neck Flanges: For high-pressure, high-temperature pipeline connections.
- Blind Flanges: To close the ends of pipelines or valves for pressure testing or maintenance.
- Slip-On & Socket Weld Flanges: Used in less critical service lines where ease of installation is prioritized.
Fittings
- Elbows & Tees: Direct and split pipeline flow under high-pressure conditions.
- Reducers & Couplings: Connect pipes of different sizes and absorb thermal or mechanical stresses.
- Unions: Allow quick disconnection for maintenance in pipeline assemblies.
Valves & Valve Components
- Gate Valve Bodies: For on/off flow control in high-pressure transmission systems.
- Globe & Check Valve Bodies: For flow regulation and backflow prevention in process lines.
- Bonnet & Cover Forgings: Provide structural strength to valve assemblies under internal pressure.
Wellhead & Drilling Components
- Drilling Spools & Adapters: Absorb extreme loads and pressure surges during oil extraction.
- Flanged Connectors: Interface between blowout preventers and drilling equipment.
- Casing Heads & Tubing Hangers: Support pipe strings in well completions.
Piping Assemblies
- Manifold Blocks: Centralize multiple process lines for control and distribution.
- High-Pressure Connectors: Join pipelines safely in upstream and midstream operations.
Petrochemical and Refining Plants
- High-pressure steam line flanges
- Process valve bodies (non-corrosive chemicals)
- Reactor nozzle forgings
- Piping connectors for heat exchangers and towers
Power Generation (Thermal & Nuclear)
- Forged pressure vessel nozzles
- Flange adapters in feedwater lines
- Valve bodies and caps in auxiliary piping systems
Water Treatment and Industrial Pipelines
- Pump housings
- Pipeline repair fittings
- Flanges and forged tees in high-volume service pipelines
Structural and Mechanical Systems
- Shafts and hubs in mechanical assemblies
- Rotor mounts and forged couplings
- Anchor plates and support collars in structural frameworks
Custom and OEM Forgings
Due to its good machinability and formability, ASTM A105 is frequently specified in custom-engineered forgings for OEMs (Original Equipment Manufacturers), particularly for valve manufacturers, pipeline systems integrators, and skid module designers.
Components include:
- Bonnet forgings
- Flanged nozzles and reducer forgings
- Instrument manifold blocks and adapters
11. Comparison with Alternative Materials
| Property / Feature | ASTM A105 Carbon Steel | ASTM A350 LF2 (Low-Temp Carbon Steel) | ASTM A216 WCB (Cast Carbon Steel) | ASTM A182 (Alloy & Stainless Steel Forgings) | ASTM A105 vs ASTM A182 F11/F22 (Alloy Steel) |
| Material Type | Carbon Steel Forgings | Low-Temperature Carbon Steel Forgings | Cast Carbon Steel | Alloy and Stainless Steel Forgings | Alloy Steel Forgings |
| Typical Applications | Piping flanges, fittings, valves | Low-temperature service piping & flanges | Cast valves, fittings, and components | High-temperature, corrosive environments, stainless applications | High-temp pressure vessels and piping |
| Chemical Composition | C ≤ 0.35%, Mn 0.60-1.05%, Si, P, S limits | Similar to A105 but with tighter control for toughness at low temp | Similar to A105, with some variations for casting | Varies widely by alloy (chromium, molybdenum, nickel content) | Higher alloying elements for creep and heat resistance |
| Mechanical Properties | Tensile: ~485 MPa; Yield: ~250 MPa | Improved toughness at −46°C and below | Similar tensile/yield strength but with cast structure | Higher tensile/yield strength; designed for elevated temps | Superior strength and creep resistance |
| Corrosion Resistance | Low (requires coatings) | Low, but better toughness at low temps | Low, prone to porosity-related corrosion | Moderate to excellent (depends on alloy grade) | Better than A105; often used in corrosive environments |
| Weldability | Good | Good with preheat and controls | More challenging due to casting porosity | Varies; some stainless alloys require careful welding | Requires specialized procedures due to alloy content |
Impact Toughness |
Moderate, limited at sub-zero temperatures | High, tested for low temperatures | Variable, less predictable due to casting defects | High, depending on alloy and heat treatment | High toughness, especially in tempered condition |
| Manufacturing Process | Forged | Forged | Cast | Forged | Forged |
| Cost | Relatively low | Slightly higher due to enhanced toughness | Generally lower initial cost but higher failure risk | Higher, due to alloying and processing complexity | Higher due to alloying and heat treatment |
| Standards and Specifications | ASTM A105, ASME B16.5, B16.11 | ASTM A350 LF2, ASME B16.5 | ASTM A216 WCB, ASME B16.5 | ASTM A182, ASME B16.34 | ASTM A182 F11/F22, ASME B16.34 |
| Typical Service Temperature | Up to ~425°C | Suitable for −46°C and above | Up to ~400°C | Up to ~600°C or higher depending on alloy | Up to ~600°C with creep resistance |
| Common Industries | Oil & Gas, Petrochemical, Power Plants | LNG, Cryogenics, Low Temp Piping | General industry, less critical pressure parts | Power generation, chemical processing, aerospace | Power plants, petrochemical, refineries |
12. Conclusion
ASTM A105 forged carbon steel remains a reliable, cost-effective choice for pressure components like flanges and valve bodies.
Its balanced mechanical properties, ease of fabrication, and global standards compliance make it a mainstay in industries such as petrochemical, energy, and infrastructure.
When higher corrosion resistance, sub-zero toughness, or elevated temperature performance is required, alloy steels or stainless steels should be considered.
For general-purpose pressure applications, A105 continues to offer a superior blend of performance, quality, and value.
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FAQs
What is the ASTM A105?
ASTM A105 is a standard specification for carbon steel forgings used primarily for manufacturing piping components like flanges, fittings, and valves, designed to withstand moderate and high-temperature service.
Can ASTM A105 forgings be welded?
Yes, ASTM A105 forgings have good weldability. Preheating and controlled post-weld heat treatment may be necessary for thicker sections to reduce residual stresses and avoid cracking.
How does ASTM A105 compare to ASTM A182 alloy steel forgings?
ASTM A182 alloy steel forgings typically offer higher strength, better corrosion resistance, and superior high-temperature performance compared to ASTM A105 carbon steel forgings, but at a higher material cost.
What is the ASTM A105 equivalent to?
ASTM A105 is roughly equivalent to EN 10222-2 1.0460 and JIS SCM435 steel grades, sharing similar chemical compositions and mechanical properties for carbon steel forgings.
What is ASME A105 material?
ASME A105 refers to the same carbon steel forging material covered by ASTM A105, standardized for use in pressure vessel and piping applications under the ASME Boiler and Pressure Vessel Code.
What is the difference between ASTM A36 and A105?
ASTM A36 is a structural carbon steel used primarily for construction and general structural purposes.
In contrast, ASTM A105 is a forging grade specifically designed for pressure-retaining components like flanges and valves, offering higher toughness and stricter mechanical property requirements.
