Carbon Steel Flanges

The most common material grade in use today is A105 forged carbon steel, with sizes ranging from 1/2“ – 24” in ASME B16.5, 26” – 60” in ASME B16.47, and 26” – 96” in B16.1 (for temperatures ranging from ambient up to 1,000 Fahrenheit and pressure between 20 – 6,170 psi). The wide temperature and pressure range makes carbon steel flanges an attractive solution for several industrial applications, and have proven to be one of the least expensive pricing options.

Modern carbon is a common steel with carbon content up to 2.1% by weight and primarily alloyed with iron. The term “carbon steel” may also be used to call out steel which does not have a large amount of chromium or nickel. The carbon content can vary for A105 with a maximum allowable of 0.35 as a percentage composition. As the carbon content increases, the steel hardens and increases in strength through heat treatment processes. Many common treatment techniques in the industry are quenching, tempering, and normalizing. As carbon steel is treated, it become less ductile and brittle. This makes it slightly more difficult to shape and weld, however the trade off in field service is often considered worth the extra effort to form the necessary weld seals.

For trace elements, no alloy element (minimum content) is required, specifically in reference to molybdenum, nickel, chromium, titanium, and vanadium.

For more detail, the chemical composition of A105 carbon steel pipe flanges is as follows

Carbon Steel Flanges

Mechanical requirements are as follows. Please note the tensile and yield strength requirements are minimums which can be surpassed as desired.

Carbon Steel Flanges


We also offer variants of carbon steel flanges which would traditionally be made in ASTM A105.

Options made from plate include A515-70, A516-70,and both in the normalized condition. These are typically used to make line blank style flanges per ASME B16.48. In addition, we have A36 plate and A285 Grade C plate when the superior overall properties of 515/516 are less of a concern. You will often find A36 plate steel used for smaller waterworks type flanges, as well as custom ring and disc flanges made for one-off applications.

If your application calls for low temperature service, consider A350 LF2 forged carbon flanges (with Charpy V-Notch Impact Tests at -50°F) or the superior LF3 (CVNs at -150°F). These are very similar to A105 in most ways, but are rated for colder ambient utilization.

Distinguishing Forged Steel Flanges from Cast Iron Flanges

Manufacturing Costs: The forging process tends to be more costly than cast iron.

Complex Profiles: Cast iron can be molded to accommodate intricate and complex shapes.

Uniformity: Forging results in flanges less likely to have irregularities or deformities.

Application: Cast iron flanges are primarily utilized for non-pressure pipelines, whereas forged steel flanges are preferred for high-pressure pipelines.

Precision: High-precision cast iron flanges are produced using centrifugal machines, surpassing standard cast flanges.

Cut and Strength: Forged steel flanges are more easily cut and possess higher tensile strength.

Performance: Overall, forged steel outperforms cast iron flanges due to its superior shape and lower carbon content, which reduces susceptibility to rust.


Texas Flange stocks a wide variety of flanges in all sizes and specifications.

Frequently Asked Questions (FAQs)

A carbon steel flange is a type of flange that is made from carbon steel, which is a steel alloy that contains iron and carbon.