Nominal pressure
Tube outside diameter
Steel grade
Availability
Stainless steel forged weld neck flange 1 1/2" SCH40S CLASS150 1.4301 / 1.4307 / 304 / 304L
- Tube outside diameter (OD): 1.5 mm
- Number of holes: 4
- Weight: 1.81 kg
- Norm: ASME / ANSI
- Nominal pressure: CLASS150
- Steel grade: 1.4301 / 1.4307 / 304 / 304L
Availability:
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Dispatched within: 3 days
Stainless steel forged weld neck flange 1 1/4" SCH40S CLASS150 1.4301 / 1.4307 / 304 / 304L
- Tube outside diameter (OD): 1.25 mm
- Number of holes: 4
- Weight: 1.4 kg
- Norm: ASME / ANSI
- Nominal pressure: CLASS150
- Steel grade: 1.4301 / 1.4307 / 304 / 304L
Availability:
available
Dispatched within: 3 days
Stainless steel forged weld neck flange 1" SCH40S CLASS150 1.4301 / 1.4307 / 304 / 304L
- Tube outside diameter (OD): 1 mm
- Number of holes: 4
- Weight: 1.07 kg
- Norm: ASME / ANSI
- Nominal pressure: CLASS150
- Steel grade: 1.4301 / 1.4307 / 304 / 304L
Availability:
available
Dispatched within: 3 days
Stainless steel forged weld neck flange 1/2" SCH40S CLASS150 1.4301 / 1.4307 / 304 / 304L
- Tube outside diameter (OD): 0.5 mm
- Number of holes: 4
- Weight: 0.51 kg
- Norm: ASME / ANSI
- Nominal pressure: CLASS150
- Steel grade: 1.4301 / 1.4307 / 304 / 304L
Availability:
available
Dispatched within: 3 days
Stainless steel forged weld neck flange 2 1/2" SCH40S CLASS150 1.4301 / 1.4307 / 304 / 304L
- Tube outside diameter (OD): 2.5 mm
- Number of holes: 4
- Weight: 4.28 kg
- Norm: ASME / ANSI
- Nominal pressure: CLASS150
- Steel grade: 1.4301 / 1.4307 / 304 / 304L
Availability:
available
Dispatched within: 3 days
Stainless steel forged weld neck flange 2" SCH40S CLASS150 1.4301 / 1.4307 / 304 / 304L
- Tube outside diameter (OD): 2 mm
- Number of holes: 4
- Weight: 2.59 kg
- Norm: ASME / ANSI
- Nominal pressure: CLASS150
- Steel grade: 1.4301 / 1.4307 / 304 / 304L
Availability:
available
Dispatched within: 3 days
Stainless steel forged weld neck flange 3 1/2" SCH40S CLASS150 1.4301 / 1.4307 / 304 / 304L
- Tube outside diameter (OD): 3.5 mm
- Number of holes: 8
- Weight: 6.2 kg
- Norm: ASME / ANSI
- Nominal pressure: CLASS150
- Steel grade: 1.4301 / 1.4307 / 304 / 304L
Availability:
available
Dispatched within: 3 days
Stainless steel forged weld neck flange 3" SCH40S CLASS150 1.4301 / 1.4307 / 304 / 304L
- Tube outside diameter (OD): 3 mm
- Number of holes: 4
- Weight: 5.18 kg
- Norm: ASME / ANSI
- Nominal pressure: CLASS150
- Steel grade: 1.4301 / 1.4307 / 304 / 304L
Availability:
available
Dispatched within: 3 days
Stainless steel forged weld neck flange 3/4" SCH40S CLASS150 1.4301 / 1.4307 / 304 / 304L
- Tube outside diameter (OD): 0.75 mm
- Number of holes: 4
- Weight: 0.73 kg
- Norm: ASME / ANSI
- Nominal pressure: CLASS150
- Steel grade: 1.4301 / 1.4307 / 304 / 304L
Availability:
available
Dispatched within: 3 days
Stainless steel forged weld neck flange 4" SCH40S CLASS150 1.4301 / 1.4307 / 304 / 304L
- Tube outside diameter (OD): 4 mm
- Number of holes: 8
- Weight: 7.32 kg
- Norm: ASME / ANSI
- Nominal pressure: CLASS150
- Steel grade: 1.4301 / 1.4307 / 304 / 304L
Availability:
available
Dispatched within: 3 days
Stainless steel forged weld neck flange 5" SCH40S CLASS150 1.4301 / 1.4307 / 304 / 304L
- Tube outside diameter (OD): 5 mm
- Number of holes: 8
- Weight: 8.91 kg
- Norm: ASME / ANSI
- Nominal pressure: CLASS150
- Steel grade: 1.4301 / 1.4307 / 304 / 304L
Availability:
available
Dispatched within: 3 days
Stainless steel forged weld neck flange 6" SCH40S CLASS150 1.4301 / 1.4307 / 304 / 304L
- Tube outside diameter (OD): 6 mm
- Number of holes: 8
- Weight: 11.26 kg
- Norm: ASME / ANSI
- Nominal pressure: CLASS150
- Steel grade: 1.4301 / 1.4307 / 304 / 304L
Availability:
available
Dispatched within: 3 days
Stainless steel weld neck flanges 1.4307/304L
What are stainless steel weld neck flanges 1.4307/304L?
Stainless steel weld neck flanges 1.4307/304L are butt‑weld flanges with a long, tapered hub designed to be welded to the end of a pipe. The tapering provides a smooth transition of stress from the flange to the pipe, making this flange type especially suitable for high pressure flanges and applications where mechanical strength and leak‑free pipe connections are essential. The material designation 1.4307 (EN) corresponds to the low‑carbon variant commonly known as 304L (AISI/ASTM, UNS S30403).
Where and how they are used
Weld neck flanges are used to create permanent, strong pipe connections by butt welding the flange hub to the pipe. Typical uses include:
- High pressure and high temperature pipelines where stress concentration must be minimised.
- Systems requiring frequent inspection or cleaning, because weld neck flanges give a smooth bore with less turbulence when correctly matched to the pipe bore.
- Critical process installations in chemical, petrochemical, power and offshore sectors where joint integrity is vital.
Material: 1.4307 / 304L — what it means
1.4307 (European EN number) is the low‑carbon grade of 304 stainless steel, commonly referred to as 304L in AISI/ASTM terminology (UNS S30403). Key, practically useful facts:
- Lower carbon content reduces the risk of sensitisation (intergranular corrosion) during welding compared with standard 304 (EN 1.4301)
- Good general corrosion resistance in many industrial environments and excellent formability and weldability
- Not as resistant to chloride‑induced pitting and crevice corrosion as molybdenum‑bearing grades (e.g. 316 / 1.4404). For prolonged use in marine or very aggressive chloride environments consider 316 / 1.4404 instead.
Selecting the right weld neck flange
When choosing a stainless steel weld neck flange think about:
- Material — 1.4307 / 304L for general service; choose 316 / 1.4404 for stronger chloride resistance.
- Standards and dimensions — European (EN 1092‑1, PN classes such as PN10/PN16/PN25) or ASME (B16.5/B16.47, classes 150/300/600) — make sure the flange standard matches the rest of your piping system.
- Pressure class / rating — choose a flange rated for the system pressure and temperature.
- Bore and pipe matching — specify the correct bore (full bore or reduced bore) and pipe schedule/outer diameter for a proper butt weld and flow characteristics.
- Face type and sealing — raised face (RF), flat face (FF) or ring type joint (RTJ) — select the correct face for the gasket type and pressure conditions.
Industries and typical applications
Stainless steel weld neck flanges 1.4307/304L are widely used across many sectors, for both small‑scale and heavy industrial work:
- Chemical and process plants
- Food and beverage and pharmaceutical industries (where stainless is required for hygiene and cleanability)
- Water and wastewater treatment
- Oil & gas and petrochemical (onshore and upstream/downstream), where appropriate material selection is observed
- Power generation and heating systems
- Shipbuilding and offshore (with careful material choice versus marine corrosion)
- Automotive, HVAC and bespoke workshop/garage pipework
Practical notes for buyers and installers
For reliable pipe connections using weld neck flanges remember to:
- Confirm the flange standard (EN or ASME), pressure class and face type before ordering.
- Match the flange bore to the pipe outer diameter and schedule so the butt weld can be executed correctly.
- Specify 1.4307 / 304L when you need better weldability and reduced risk of sensitisation; consider 1.4404 / 316 for chloride‑rich environments.
- Use appropriate welding procedures and post‑weld treatment where required by applicable codes and project specifications.
Standards and labelling
Flanges are typically supplied to recognised dimensional standards (EN 1092‑1 for PN flanges in Europe, ASME B16.5/B16.47 in the USA). Material markings commonly include the EN number (1.4307), AISI/ASTM designation (304L) or UNS (S30403). When ordering, include material, standard, pressure class, size, bore type and face finish to ensure compatibility.
Summary: Stainless steel weld neck flanges 1.4307/304L offer a robust, weldable solution for high‑integrity pipework. They combine the general corrosion resistance and weldability of 304L with the mechanical advantages of the weld‑neck design — making them a common choice for engineered pipe connections across many industries.