ASTM A105 Flange Ultimate Guide

1.What is ASTM A105 Flange?

ASTM A105 flange is a forged carbon steel flange used in pressure piping systems operating at ambient and elevated temperatures. It is widely used in oil and gas, petrochemical, power generation, water treatment, and steam systems because of its high strength, good weldability, and cost-effectiveness.

ASTM A105 is a standard that covers forged carbon steel components such as flanges, fittings, and valves for pressure service. The specification defines chemical composition and mechanical properties to ensure reliable performance in demanding applications. A105N is a normalized version of ASTM A105 that provides improved toughness and more consistent mechanical properties.

ASTM A105 flanges are available in various types, including Weld Neck, Slip-On, Blind, Socket Weld, and Threaded flanges. They are commonly manufactured in sizes from 1/2 inch to 48 inches and comply with standards such as ASME B16.5 and ASME B16.47.

2.ASTM A105 Meaning

ASTM A105 covers wrought carbon steel piping components for use in pressure systems for normal and high temperature service.

This includes flanges, fittings, valves and similar parts, the dimensions of which may be ordered in accordance with MSS, ASME or API.

This specification does not cover round bar and seamless pipe raw materials used to produce piping components.

3.ASTM A105 Flange Specification

ASTM A105 flanges are manufactured in accordance with the ASTM A105/A105M standard, which covers forged carbon steel components for ambient and high-temperature service. These flanges are commonly produced in pressure classes ranging from Class 150 to Class 2500 and are available in various types, including Weld Neck (WN), Slip-On (SO), Blind (BL), Socket Weld (SW), Threaded (TH), and Lap Joint (LJ) flanges.

3.1 Key specifications include:

Specification Item	Details
Material Standard	ASTM A105 / A105M
Material Type	Forged Carbon Steel
Pressure Rating	Class 150, 300, 600, 900, 1500, 2500
Size Range	1/2" to 60" (DN15–DN1500)
Manufacturing Process	Hot Forging and Machining
Flange Standards	ASME B16.5, ASME B16.47, MSS SP-44
Operating Temperature	Up to 425°C (800°F)
Applications	Oil & Gas, Petrochemical, Power Generation, Water Treatment

3.2 Chemical Composition of ASTM A105 Flanges

Element	Range
Carbon (C)	≤ 0.35%
Manganese (Mn)	0.60% – 1.05%
Silicon (Si)	0.10% – 0.35%
Phosphorus (P)	≤ 0.035%
Sulfur (S)	≤ 0.040%

These proportions ensure good weldability and impact resistance.
Mechanical Properties
Tensile strength: ≥ 485 MPa
Yield strength: ≥ 250 MPa
Elongation: ≥ 22% – 30%
Max hardness: 187 HB
Depending on thickness and dimensions, heat treatment may be required to ensure uniform performance.

3.3 Mechanical Properties of ASTM A105 Flange

Mechanical Property	Requirement
Tensile Strength, min, ksi [MPa]	70 [485]
Yield Strength, min, ksi [MPa]	36 [250]
Elongation in 2 in. or 50 mm, min, %	22
Basic minimum elongation for walls 5/16 in. [7.9 mm] and over in thickness, strip tests	30
Deduction from elongation for each 1/32 in. [0.8 mm] decrease below 5/16 in. [7.9 mm] wall thickness	1.5
Reduction of Area, min, %	30
Hardness, HBW, max	187

Notes:
A: For small forgings, see ASTM A105 Section 8.3.4.
B: Yield strength determined by either the 0.2% offset method or the 0.5% extension-under-load method.
C: See ASTM A105 Table 3 for computed minimum values.
D: Applicable to round specimens only.

4.ASTM A105 Flange Size Chart

5.Types of Carbon Steel A105 Flanges

There are several types of Carbon Steel A105 Flanges, each designed for specific applications. Here are the most common types:
1.Weld Neck Flanges: These flanges are designed for high-pressure applications and are attached to the pipe by welding. Their tapered hub provides reinforcement and prevents distortion under heavy loads.
2.Slip-On Flanges: Slip-On Flanges are easy to install and work well for low-pressure applications. They slide over the pipe and then require welding in place.
3.Blind Flanges: Blind Flanges close the end of a pipe or valve. These flange requirements arise during maintenance. Additionally, they also work as manhole covers for the vessel in use.
4.Socket Weld Flanges: These flanges have a socket that fits over the pipe and require welding to keep it in place. The flange design allows them to withstand high-pressure industrial applications. They are well-suited for only smaller-diameter pipes.

5.Threaded Flanges: Threaded Flanges have threads on the inner surface, allowing them to screw onto the pipe. Do you know that there are two types of threads in this flange? One is male and female threads. These threads are responsible for the pipe connection strength.

Flange Type	Description	Typical Applications
Weld Neck	Long neck for high strength	High-pressure, high-temperature systems
Slip-on	Fits over pipe, easy to install	Medium-pressure piping
Blind	Seals pipeline end	Isolation and maintenance
Socket Weld	For small diameter pipes	Chemical and steam pipelines
Threaded	Internal threads, no welding	Piping without welding needs
Lap Joint	Loose fit for alignment	Easy disassembly and misalignment

6.ASTM A105 vs ASTM A105N Flange

Both ASTM A105 and ASTM A105N flanges are manufactured using the same carbon steel standard, with essentially identical chemical composition and basic mechanical properties. The biggest difference lies in the "N" in A105N, which stands for Normalized. ASTM A105N flanges undergo normalizing heat treatment after forging, resulting in a more uniform grain structure, better toughness, impact resistance, and low-temperature performance. Therefore, they are more suitable for low-temperature, high-pressure, or high-reliability applications. Ordinary ASTM A105 flanges, on the other hand, are not necessarily normalized and are typically used in piping systems under normal temperature and pressure conditions. For critical applications such as oil and gas, offshore platforms, and pressure vessels, ASTM A105N flanges are generally the more common choice.

7.ASTM A105 Flange Pressure Rating

ASTM A105 flanges are widely used in oil & gas, petrochemical, and industrial piping systems. The PDF below contains pressure rating tables for Class 75, 150, 300, 400, 600, 900, 1500, and 2500 flanges, helping users quickly identify the allowable working pressure at different temperatures.

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