Carbon Steel Flanges
Giriraj Impex is a manufacturer, stockist, supplier and exporter of carbon steel flanges to ASTM A105, ASTM A350 LF2 and ASTM A694 F42 to F70. We manufacture carbon steel flanges to ASME B16.5 from ½" to 24" NB in Class 150 to 2500, ASME B16.47 Series A and B large-diameter flanges, MSS SP-44 pipeline flanges and EN 1092-1 flanges, in weld neck, slip-on, blind, socket weld, threaded, lap joint, orifice and reducing types.
Carbon steel flanges are the most widely used flanges in refinery, petrochemical, power, oil and gas and utility piping, bolted to carbon steel pipe, fittings and valves.
Specifications
| Item | Details |
|---|---|
| Material standards | ASTM A105 / ASME SA105; ASTM A350 LF2 Class 1 and 2; ASTM A694 F42, F46, F52, F56, F60, F65, F70 |
| Dimensional standards | ASME B16.5, B16.47 Series A and B, B16.36, B16.48, MSS SP-44, EN 1092-1 |
| Sizes | ½" to 24" NB (B16.5); 26" to 60" NB (B16.47) |
| Classes | 150, 300, 400, 600, 900, 1500, 2500; PN ratings to EN 1092-1 |
| Facings | RF, FF, RTJ, tongue and groove |
| Coating | Rust-preventive oil, black paint, yellow or zinc coating, hot-dip galvanising |
| Documents | Mill test certificate (MTC); third-party inspection on request |
Choosing the material
- ASTM A105 – forged carbon steel for ambient and higher-temperature service; the standard flange material for carbon steel piping.
- ASTM A350 LF2 – impact-tested carbon steel forgings for low-temperature service; Class 1 is impact tested at −46 °C (−50 °F), and Class 2 at the higher test temperature given in the standard.
- ASTM A694 F42 to F70 – high-yield forgings for pipelines, where the number is the minimum yield strength in ksi, matched to the grade of API 5L line pipe.
The material group, together with the class and temperature, determines the flange pressure rating in ASME B16.5.
For sour service, A105 and A350 LF2 flanges are supplied with controlled hardness and, where specified, with heat treatment and testing that meet NACE MR0175 / ISO 15156 on request. For firewater and water lines, galvanised A105 slip-on flanges are common. For high-pressure gas and steam, weld neck flanges with RTJ facings are usually specified from Class 900 upward.
ASTM A105 composition and properties
| C | Mn | P | S | Si | Cu | Ni | Cr | Mo | V |
|---|---|---|---|---|---|---|---|---|---|
| 0.35 | 0.60–1.05 | 0.035 | 0.040 | 0.10–0.35 | 0.40 | 0.40 | 0.30 | 0.12 | 0.08 |
Limits on combined Cu, Ni, Cr, Mo and V, and the manganese allowance for lower carbon, are as given in the standard.
| Tensile strength min, MPa (ksi) | Yield strength min, MPa (ksi) | Reduction of area min, % | Hardness max, HBW |
|---|---|---|---|
| 485 (70) | 250 (36) | 30 | 187 |
Elongation requirements depend on the test specimen, as given in the standard.
Actual values for each heat are given on the mill test certificate.
Flange types
- Weld neck flanges – for process lines, high pressure and temperature.
- Slip-on flanges – for water, air and low-pressure lines.
- Blind flanges – for line ends, test points and nozzles.
- Socket weld flanges – for small-bore, high-pressure lines.
- Threaded, lap joint, long weld neck, orifice and reducing flanges.
- Spectacle blinds, spades and spacers to ASME B16.48.
Manufacturing, testing and protection
Carbon steel flanges are forged, heat treated where the specification requires (A105 is normalised in many cases, and A350 LF2 is normalised or quenched and tempered to meet its impact requirement), then machined to the dimensional standard with the bore matched to the pipe schedule. Each flange is dimensionally inspected and marked with the manufacturer's identification, material grade, size, class, bore schedule and heat number. Supplementary requirements such as hardness limits for sour service (NACE MR0175 / ISO 15156 on request), ultrasonic testing and impact testing at a specified temperature can be added. Machined faces are protected with rust-preventive oil and covers, and flanges are packed on pallets or in wooden cases.
Ordering carbon steel flanges
Please state the type, standard, size, class, facing, bore schedule, material (A105, A350 LF2 Class 1 or 2, or A694 grade), coating, quantity and any tests or inspection required. We can also quote the matching bolting and gaskets for each flange size and class.
Applications and related products
Carbon steel flanges are used in refineries and petrochemical plants, oil and gas production and pipelines, power stations, fertiliser plants, water and firewater systems and general industry. They connect carbon steel seamless pipes, ERW pipes and carbon steel pipe fittings. Flange blanks and blinds can also be cut from carbon steel plates or machined from round bars where the specification allows. See all flange materials on the flanges page and grade guidance on the carbon steel page.
Frequently Asked Questions
ASTM A105 is the specification for forged carbon steel piping components – flanges, fittings and valve parts – for ambient and higher-temperature service. It is the standard material for carbon steel flanges.
A350 LF2 is used when the flange must be tough at low temperature. Class 1 is impact tested at −46 °C; Class 2 has a higher test temperature, as given in the standard. A105 has no impact test requirement unless one is added to the order.
ASTM A694 covers high-yield carbon and alloy steel forgings for high-pressure transmission pipelines. Grades F42 to F70 are matched to the yield strength of the API 5L line pipe they are welded to.
Yes. Flanges can be supplied hot-dip galvanised, zinc coated, painted or oiled, as specified. Galvanising is common for water and firewater lines.
ASTM A105 sets a maximum hardness of 187 HBW. For sour service, a lower hardness limit to NACE MR0175 / ISO 15156 can be specified on request.
Yes. Flanges from 26" to 60" NB are supplied to ASME B16.47 Series A or Series B, or to MSS SP-44 for pipelines. Please state the series and class.
Request a Quote for Carbon Steel Flanges
Tell us the product, grade, size, standard, quantity and delivery location, and our sales team will reply with a quotation.