ASME B16.5 • Class 150–2500

Carbon Steel Flanges

Q: What is the HSN code for carbon steel flanges?

Carbon steel flanges fall under HSN 7307 (tube or pipe fittings of iron or steel), sub-heading 730719 for other non-alloy steel fittings, attracting 18% GST in India.

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Quick Answer

Carbon steel flanges are forged pipe-connection components made mainly to ASTM A105 or ASTM A350 LF2 , manufactured to ASME B16.5 / B16.47 dimensions in Class 150 through 2500. They join pipe, valves and equipment in weld neck, slip-on, blind, socket weld, threaded, lap joint and spectacle configurations, and are the default flange choice for oil & gas, water, power and general process piping wherever exotic corrosion resistance isn’t required.

Carbon Steel Flange Overview

Grades, Standards & Ex-Stock Specs At A Glance

Size Range

1/2″ – 60″ NB

ASME B16.5 & B16.47, ex-stock

Pressure Class

Class 150 – 2500

RF, FF & RTJ facing

Standard Grades

A105 / A350 LF2

Forged, dual-certified stock

Export Reach

GCC • Africa • USA

Regional stock points, fast dispatch

Flange Types

WN • SO • Blind • SW

Threaded, lap joint & more, ex-stock

Certification

EN 10204 3.1 / 3.2

SGS / BV / TUV on request

Buying Carbon Steel Flanges Shouldn’t Be This Hard , Here’s What Changes When You Order From Us ?

Full-Type Ex-Stock

WN, SO, blind, SW, threaded – every class, ready to ship

Quote Within 48 Hours

Grade, size, class – priced same business day

RF / FF / RTJ In-House

All facings machined on-site, no subcontracting

EN 10204 3.1 / 3.2 MTC

Every heat traceable, SGS / BV / TUV on request

Regional Stock Points

Pre-positioned inventory for GCC, Africa & USA orders

Direct Mill Pricing

No broker layer – stockist rates, straight to you

✅ End-User Approved For Critical Projects

Saudi Aramco Approved ADNOC Approved KNPC Approved Qatar Gas Approved SABIC Approved ONGC Approved

📌 Table of Contents

Carbon Steel Flange Specification
Types of CS Flanges
Carbon Flanges Material Grade
Carbon Steel Forged Flanges Dimensions
CS Pipe Flange Weight Chart
Blind Flange Carbon Steel Pressure Temperature Rating
CS Slip On Flange HSN Code & GST Rate
Chemical Composition of Carbon Steel Lap Joint Flange
Carbon Steel Plate Flange Mechanical Properties
Equivalent Grades of CS Socket Weld Flange
Carbon Steel Slip On Flange Vs Blind Flange
Carbon Steel Weld Neck Vs Socket Weld Flange
Which Factors Affect Carbon Steel Flange Price?
Inspection & Testing Of Carbon Steel Threaded Flange
Applications Of CS SORF Flange By Industry
Flange CS Supply References Worldwide
Should A Carbon Steel Flange Be Forged Or Cast?
Which Codes Govern CS Flange Dimensions & Material?
How Is A Carbon Steel Flange Protected From Corrosion?
What To Specify When Ordering A CS Flange
Quick Grade Finder By Service Condition

CS Blind Flange Manufacturer in India Backed By Verified AWWA, ANSI, ASME B16.5 Rating

We supply carbon steel flanges for pipelines, refineries, water infrastructure and process plants needing certified, code-compliant flanges on schedule. Our ex-stock program covers weld neck, slip-on, blind, socket weld and threaded flanges, Class 150 through 2500, forged to ASTM A105 and A350 LF2. Every batch reflects why we're rated a top carbon steel flanges manufacturer in India.

Every heat carries full test reports, EN 10204 3.1 standard, 3.2 on request. Stock moves through regional hubs across the Middle East, Africa and the Americas, so buyers aren't waiting on one origin point. As a carbon steel flanges exporter shipping to the Gulf, Africa and the Americas, we handle export packing in-house.

No minimum order on ex-stock sizes, in-house RF/FF/RTJ facing, and pricing inside 48 hours. We work as a reliable carbon steel flanges supplier in India, keeping every type and class ex-stock.

1Carbon Steel Flange Specification

Standard, size, class, facing and heat treatment, all checked. Our Mumbai yard is an active carbon steel flanges stockist in Mumbai, with A105 and A350 LF2 always in stock.

Carbon Flanges Dimensional Standards

ASME/ANSI B16.
ASME B16.47 Series A/B
MSS SP-44

CS Flanges Material Standards

ASTM / ASME A105
ASTM A350 Gr LF2
ASTM A181 Class 60/70

Carbon Steel Flange Pressure & Size

Class 150–2500
½″–60″ NB
RF / FF / RTJ facing

CS Blind Flange Heat Treatment

Normalized
Normalized + impact tested
Grade-dependent cycle

Flange Carbon Steel Slip On Surface Finish

Serrated Concentric / Spiral
Smooth Finish
125–250 AARH standard

Plate Flanges Carbon Steel Marking & Traceability

Heat No. + Grade + Size + Class
Per MSS SP-25
Full heat-to-MTC traceability

Marking: Heat No. + Grade + Size + Class MTC: EN 10204 3.1 / 3.2 No MOQ On Ex-Stock Sizes

Worldwide Carbon Steel Forged Flanges Supplier As Per EN 1092-1 Across Every Pressure Class and Types

A trusted carbon steel flange supplier means the right chemistry and the right facing, checked before the heat ever leaves the yard.

2Types of CS Flanges

Every common type stays on the shelf, we're an established carbon steel flanges manufacturer, not just fast movers. Small or bulk, we're a carbon steel flanges supplier in India that ships on time.

Carbon Steel Weld Neck Flange

Neck: Tapered hub
Standard: ASME B16.5
Best For: High pressure lines

Carbon Steel Slip On Flange

Fit: Slides over pipe
Weld: Fillet, both sides
Best For: Low-cost fast install

Carbon Steel Blind Flange

Bore: None (solid disc)
Use: Line-end closure
Best For: Testing & isolation

Carbon Steel Socket Weld Flange

Bore: Recessed socket
Size: Small bore, ≤4″
Best For: High-pressure small lines

Carbon Steel Threaded Flange

Joint: NPT / BSPT thread
Weld: None required
Best For: No-weld, low-temp duty

Carbon Steel Lap Joint Flange

Pair: Used with stub end
Rotate: Bolt holes align freely
Best For: Frequent dismantling

Carbon Steel Spectacle Blind Flange

Shape: Figure-8, spec & ring
Use: Positive line isolation
Best For: Turnaround / shutdown

Carbon Steel Orifice Flange

Ports: Tapped for meter runs
Standard: MFC-3M / AGA-3
Best For: Flow measurement

Carbon Steel Long Neck Flange

Hub: Extended length
Use: Vessel / nozzle penetration
Best For: Reinforced connections

Carbon Steel Reducing Flange

Bore: Smaller than OD rating
Use: Size transition, no fitting
Best For: Compact reductions

Carbon Steel Plate Flange

Build: Flat plate, no hub
Rating: Low pressure duty
Best For: Tank & duct work

Carbon Steel Puddle Flange

Build: Continuous perimeter weld
Use: Waterproof anchor point
Best For: Tank floor & wall penetrations

Carbon Steel Flange Ex-Stock Availability Across Africa

🌎 Countries Congo Kenya Equatorial Guinea Sudan Gabon Ivory Coast West Africa Cameroon Togo Niger Rwanda South Africa Nigeria Republic of the Congo Benin Chad Ghana Senegal

Dakar

Senegal

Nairobi

Kenya

Ogun

Nigeria

Durban

South Africa

Johannesburg

South Africa

Cape Town

South Africa

Lagos

Nigeria

Addis Ababa

Ethiopia

Abuja

Nigeria

✉

Looking For A Carbon Steel Flanges Supplier In India?

Tell us the grade, size and class – we check ex-stock availability and get back with pricing the same day.

Check Stock & Price

Carbon Steel Slip On and Weld Neck Flange Stockist in Mumbai in Various Grades Cut To Your Exact Face Finish, Refer Dimensions

Every flange is machined to your exact face finish and verified against the dimension chart before dispatch.

3Carbon Flanges Material Grade

Choosing the right carbon steel flange material specification up front avoids a rejected MTC at the site gate.

ASTM A105 Flange

Standard forged grade, ambient to moderate temperature

ASTM A350 LF2 Flanges

Impact-tested, low-temperature service to -46°C

ASTM A694 Flanges

High-yield grade for large-diameter, high-pressure lines

ASTM A181 Flanges

General purpose, lower design margin

A105 fits general piping; A350 LF2 handles low-temperature service, resisting brittleness in cold shutdowns. Being a carbon steel flanges manufacturer in India, quality control never gets skipped.

4Carbon Steel Forged Flanges Dimensions

Outside diameter and thickness grow with both size and pressure class – tap a class below to view its full dimension table.

Class 150 Flange dimensions & weight reference View Dimensions

Nominal Size		Dimensions
NPS (in)	DN (mm)	Flange OD (mm)	Flange Thickness (mm)
1/2″	15	88.9	11.2
1″	25	108	14.2
16″	400	596.9	36.6
3/4″	20	98.6	12.7
5″	125	254	23.9
24″	600	812.8	47.8
18″	450	635	39.6
20″	500	698.5	42.9
3″	80	190.5	23.9
1 1/4″	32	117.3	15.7
3 1/2″	90	215.9	23.9
1 1/2″	40	127	17.5
12″	300	482.6	31.8
6″	150	279.4	25.4
8″	200	342.9	28.4
10″	250	406.4	30.2
2 1/2″	65	177.8	22.4
4″	100	228.6	23.9
2″	50	152.4	19.1
14″	350	533.4	35.1

Class 300 Flange dimensions & weight reference View Dimensions

Nominal Size		Dimensions
NPS (in)	DN (mm)	Flange OD (mm)	Flange Thickness (mm)
6″	150	317.5	36.6
10″	250	444.5	47.6
14″	350	584.2	53.8
20″	500	774.7	63.5
24″	600	914.4	70.0
4″	100	254	31.8
5″	125	279.4	35.1
3/4″	20	117.3	15.7
3″	80	215.9	28.4
8″	200	381	41.1
2″	50	165.1	22.4
1/2″	15	95.3	14.2
18″	450	711.2	60.5
1 1/4″	32	133.4	19.1
3 1/2″	90	228.6	30.2
1 1/2″	40	155.5	20.6
12″	300	520.7	50.8
2 1/2″	65	190.5	25.4
1″	25	124	17.5
16″	400	647.7	57.2

Class 600 Flange dimensions & weight reference View Dimensions

Nominal Size		Dimensions
NPS (in)	DN (mm)	Flange OD (mm)	Flange Thickness (mm)
12″	300	558.8	66.5
3/4″	20	117.3	15.7
3″	80	209.6	31.8
1 1/2″	40	155.4	22.4
1″	25	124.0	17.5
3 1/2″	90	228.6	35.1
24″	600	939.8	101.6
14″	350	603.3	69.9
1/2″	15	95.3	14.2
18″	450	743	82.6
8″	200	419.1	55.6
20″	500	812.8	88.9
1 1/4″	32	133.4	20.6
4″	100	273.1	38.1
2″	50	165.1	25.4
16″	400	685.8	76.2
10″	250	508	63.5
5″	125	330.2	44.5
2 1/2″	65	190.5	28.4
6″	150	355.6	47.8

Class 900 Flange dimensions & weight reference View Dimensions

Nominal Size		Dimensions
NPS (in)	DN (mm)	Flange OD (mm)	Flange Thickness (mm)
1/2″	15	120.7	22.4
3/4″	20	130	25.4
2 1/2″	65	244.3	41.1
20″	500	857.3	108.0
4″	100	292.1	44.5
5″	125	349.3	50.8
8″	200	469.9	63.5
1 1/2″	40	177.8	31.8
10″	250	546.1	69.9
14″	350	641.4	85.6
12″	300	609.6	79.2
24″	600	1041.4	139.7
1″	25	149.4	28.4
2″	50	215.9	38.1
16″	400	704.9	88.9
18″	450	787.4	101.6
3″	80	241.3	38.1
6″	150	381	55.6
1 1/4″	32	158.8	28.4

Class 1500 Flange dimensions & weight reference View Dimensions

Nominal Size		Dimensions
NPS (in)	DN (mm)	Flange OD (mm)	Flange Thickness (mm)
1 1/4″	32	158.8	28.4
20″	500	984.3	177.8
14″	350	749.3	133.4
16″	400	825.5	146.1
4″	100	311.2	53.8
8″	200	482.6	91.9
24″	600	1168.4	203.2
3″	80	266.7	47.8
12″	300	673.1	124
1/2″	15	120.7	22.4
1″	25	149.4	28.4
10″	250	584.2	108
3/4″	20	130	25.4
18″	450	914.4	162.1
5″	125	374.7	73.2
2 1/2″	65	244.3	41.1
6″	150	393.7	82.6
1 1/2″	40	177.8	31.8
2″	50	215.9	38.1

Class 2500 Flange dimensions & weight reference View Dimensions

Nominal Size		Dimensions
NPS (in)	DN (mm)	Flange OD (mm)	Flange Thickness (mm)
1″	25	158.8	35.1
2 1/2″	65	266.7	57.2
1/2″	15	133.4	30.2
3/4″	20	139.7	31.8
2″	50	235	50.8
8″	200	552.5	127
4″	100	355.6	76.2
6″	150	482.6	108
12″	300	762	184.2
5″	125	419.1	91.9
3″	80	304.8	66.5
1 1/4″	32	184.2	38.1
1 1/2″	40	203.2	44.5
10″	250	673.1	165.1

⌀ ½″–24″ – ASME B16.5 ⌀ 26″–60″ – ASME B16.47

5CS Pipe Flange Weight Chart

Approximate finished weight for a Class 150 RF weld neck flange, use for freight and quotation estimates before final mill weighment. Need it fast? Our carbon steel flanges stockist in Mumbai ships same week.

Pipe Size	150#			300#			600#			900#			1500#			2500#
Pipe Size	WN	SO	BLD	WN	SO	BLD	WN	SO	BLD	WN	SO	BLD	WN	SO	BLD	WN	SO	BLD
6″	24	19	26	42	39	50	81	80	86	110	110	115	165	165	160	380	325	345
1/2″	2	1	1	2	1	1	2	2	2	See 1500# Wt			5	4	4	7	7	7
22″	225	185	355	465	370	640	720	590	1000	NA	NA	NA	NA	NA	NA	NA	NA	NA
18″	150	130	220	320	250	395	475	400	630	680	600	850	1625	NA	1750	NA	NA	NA
4″	15	13	17	25	22	27	42	37	41	53	53	54	73	73	73	145	125	130
14″	110	90	140	180	165	250	280	230	355	400	400	520	940	NA	975	NA	NA	NA
8″	39	30	45	67	58	81	120	115	140	175	170	200	275	260	300	580	485	530
10″	52	43	70	91	81	124	190	170	230	260	245	290	455	435	510	1075	930	1025
5″	19	15	20	32	28	35	68	63	68	86	83	87	130	130	140	245	210	225
20″	180	165	285	400	315	505	590	510	810	830	730	1075	2050	NA	2225	NA	NA	NA
2″	6	5	5	9	7	8	12	9	10	See 1500# Wt			25	25	25	42	37	39
3/4″	2	2	2	3	3	3	4	3	3	See 1500# Wt			6	5	6	8	8	8
1″	3	2	2	4	3	3	4	4	4	See 1500# Wt			9	8	8	12	11	11
16″	140	98	180	250	190	295	390	330	495	495	425	600	1250	NA	1300	NA	NA	NA
1 1/2″	4	3	3	7	6	6	8	7	8	See 1500# Wt			13	12	13	25	22	23
2 1/2″	8	7	7	12	10	12	18	13	15	See 1500# Wt			36	36	35	52	55	56
3″	10	8	9	15	13	16	23	16	20	31	26	29	48	48	48	94	83	86
24″	260	220	430	580	475	790	830	730	1250	1500	1400	2025	3325	NA	3625	NA	NA	NA
12″	80	64	110	140	115	185	225	200	295	325	325	415	690	580	690	1525	1100	1300

Weight Tolerance ±5%

Carbon Steel Flange Sales Desk Across Asia

Indonesia

Jakarta

Philippines

Manila

Thailand

Bangkok

Taiwan

Taipei

Myanmar

Naypyidaw

Malaysia

Kuala Lumpur

Cambodia

Phnom Penh

Laos

Vientiane

Mongolia

Ulaanbaatar

Vietnam

Ho Chi Minh

Singapore

City-State

Brunei

Bandar Seri

Source Carbon Steel Socket Weld and Threaded Flange Ex.Stock in Various Temperature Rating With MTC

6Blind Flange Carbon Steel Pressure Temperature Rating

Ratings below are per ASME B16.5 for Group 1.1 material , working pressure drops as design temperature climbs.

Temp	150#	300#	400#	600#	900#	1500#	2500#
650°F	125	550	730	1100	1650	2745	4575
600°F	140	570	755	1135	1705	2840	4730
800°F	80	410	550	825	1235	2055	3430
700°F	110	530	710	1060	1590	2655	4425
950°F	35	135	185	275	410	685	1145
750°F	95	505	675	1015	1520	2535	4230
-20 to 100°F	285	740	985	1480	2220	3705	6170
850°F	65	320	425	640	955	1595	2655
900°F	50	230	305	460	690	1150	1915
1000°F	20	85	115	170	255	430	715
500°F	170	605	805	1205	1810	3015	5025
300°F	230	655	870	1310	1965	3270	5450
400°F	200	635	845	1265	1900	3170	5280
200°F	260	680	905	1360	2035	3395	5655

Buy CS Lap Joint and Plate Flange at Fair Price Under HSN Code 7307 On Export Terms

Correct HSN code on every invoice, ready for your export or import paperwork.

7CS Slip On Flange HSN Code & GST Rate

HSN Code: 7307 Sub-heading: 7307 19 GST Rate: 18% Category: Tube / Pipe Fittings, Iron or Steel

Carbon steel flanges fall under HSN 7307 19, taxed at 18% GST in India. Our desk works round the clock as a carbon steel flanges exporter for global buyers.

8Chemical Composition of Carbon Steel Lap Joint Flange

Grade	C max	Mn %	P max	S max	Si %	Cr max	Ni max	Mo max
A105	0.35	0.60–1.05	0.035	0.040	0.10–0.35	0.30	0.40	0.12
A350 LF2	0.30	0.60–1.35	0.035	0.040	0.15–0.30	0.30	0.40	0.12
A181 Cl 70	0.35	0.60–1.05	0.035	0.040	0.10–0.35	0.30	0.40	0.12

A105 suits standard-temperature service with no impact test; A350 LF2 adds Charpy testing to -46°C for winterized service; A181 Class 70 is the economical pick for relaxed-margin utility lines.

9Carbon Steel Plate Flange Mechanical Properties

A105

Tensile

485 MPa min

Yield

250 MPa min

Elongation

22% min

A350 LF2

Tensile

485–655 MPa

Yield

250 MPa min

Impact (CVN)

20 ft-lb @ -46°C

A181 Cl 70

Tensile

485 MPa min

Yield

240 MPa min

Elongation

22% min

Values represent standard ASTM minimums – confirm project-specific acceptance criteria on your carbon steel flange material specification sheet.

10Equivalent Grades of CS Socket Weld Flange

Every project size finds a fit with our carbon steel flanges supplier in India network.

EN 10222-2

A105 – P250GH
A350 LF2 – P280NL1

DIN

A105 – C22.8 / 1.0460
A350 LF2 – 1.1104

JIS

A105 – SFVC 1
A350 LF2 – SFL 1

BS 1503

A105 – Gr 161-430
A350 LF2 – Gr 221-440

GOST

A105 – St20
A350 LF2 – 09G2S

ASTM / ASME

A105 / SA105
A350 LF2 / SA350 LF2

●

Order Direct From A Carbon Steel Flanges Stockist In Mumbai

Skip the forging wait, our Mumbai yard ships A105 and A350 LF2 flanges same week, with no minimum order.

Check Mumbai Stock

Weekly Carbon Steel Flange Shipments to Europe

Belgium

Brussels

France

Paris

Azerbaijan

Baku

Georgia

Tbilisi

Netherlands

Amsterdam

Armenia

Yerevan

Andorra

Andorra la Vella

Germany

Berlin

Italy

Rome

11Carbon Steel Slip On Flange Vs Blind Flange

Slip On Flange

Bore matches pipe OD
Fillet welded inside & outside
Lower cost, easier alignment
Used to join pipe runs

Blind Flange

No bore – solid disc
Bolts directly to a mating flange
Handles full internal pressure
Used to close a line end

12Carbon Steel Weld Neck Vs Socket Weld Flange

Buyers trust us as a carbon steel flanges manufacturer in India for consistent quality, heat after heat.

Weld Neck Flange

Weld TypeSingle butt weld

Size Range½″ and above

Best UseHigh pressure, cyclic loading

Socket Weld Flange

Weld TypeFillet weld at socket

Size RangeUp to 4″ typical

Best UseSmall-bore, high-pressure lines

13Which Factors Affect Carbon Steel Flange Price?

As a carbon steel flanges stockist in Mumbai, we cut delays out of your supply chain.

📈

Steel Billet Rate

Base carbon steel market pricing

⌀

Size & Class

Larger OD, higher class = more forging weight

⚖

Flange Type

WN costs more than SO or blind of same size

🔧

Facing & Finish

RTJ machining adds cost over RF

✅

Testing Level

3.2 third-party MTC vs standard 3.1

📦

Order Quantity

Bulk orders unlock better per-piece rates

14Inspection & Testing Of Carbon Steel Threaded Flange

Dimensional Check

Ultrasonic Test

Hardness Test

Positive Material ID (PMI)

Visual & Dye Penetrant

Chemical Analysis (Spectro)

MTC 3.1 / 3.2

SGS / BV / TUV / Lloyd’s

⚖

Every Carbon Steel Flange Ships With Full Traceability

We back every heat with EN 10204 3.1/3.2 MTC and export documentation, container-ready packed.

Talk To Our Desk

15Applications Of CS SORF Flange By Industry

Oil & Gas Pipelines

Petrochemical Plants

Water & Desalination

Power Generation

Shipbuilding & Marine

Fertilizer Plants

Construction & Structural

Chemical Processing

Carbon Steel Flange Regular Delivery Routes

Carbon Steel Flange Delivery Points – Middle East

Jordan

Iraq

Lebanon

Saudi Arabia

Turkey

Qatar

Oman

UAE

Also covers Syria • Yemen • Iraq • Turkey on request

GCC Coverage

UAE

Saudi Arabia

Qatar

Bahrain

Kuwait

Oman

All 6 GCC member states covered — ex-stock & indent supply

MENA Coverage

Morocco

Casablanca

Algeria

Algiers

Tunisia

Tunis

SCZone

Suez Canal

Egypt

Cairo

Libya

Tripoli

North Africa & Levant — regular sea freight schedules

Global Export Coverage : Middle East, Africa & The Americas

Orders move through regional stock points and export lanes covering the Gulf, North & East Africa and the Americas. From Jubail to Lagos, we deliver as a trusted carbon steel flanges exporter.

Dubai, UAE

Regional stock point Export Hub

Cairo, Egypt