ASTM A707 Grade L5 Class 4 Weld Neck Flanges,Low-Temperature Forged Alloy Steel WNRF

ASTM A707 Grade L5

ASTM A707 Grade L5 Class 4 Weld Neck Raised Face (WNRF) flanges are high-end forged connecting components developed for low-temperature, high-pressure oil and gas service conditions.

Manufactured from Grade L5 low-carbon nickel-chromium-molybdenum-copper-niobium alloy steel and matched with the highest strength level Class 4, these flanges deliver industry-leading pressure-bearing capacity while ensuring excellent low-temperature impact toughness, making them perfectly suited for long-term stable operation of oil and gas pipelines and high-pressure piping systems in cold regions. Their weld neck structure enables equal-strength fusion welding with pipes and effectively disperses stress concentration at joints, making them one of the most reliable flange types for high-pressure, low-temperature piping systems. ASTM A707 Grade L5

1. ASTM A707 Chemical Composition

A707 Grade L5 Class 4 contains multiple metallic elements, with chromium, nickel, molybdenum and copper working in synergy to enhance strength and corrosion resistance. Among them, nickel is the core component that improves the low-temperature toughness of the material and effectively lowers its ductile-brittle transition temperature. Combined with niobium for grain refinement and optimized low-temperature toughness, the alloy achieves higher strength without sacrificing ductility, with its carbon equivalent strictly controlled within 0.45%. This gives A707 Grade L5 Class 4 excellent formability and weldability at the same time.

Chemical Composition Requirements of ASTM A707 by Heat Analysis,%
Element	Grade
Element	L1	L2	L3	L4	L5	L6	L7	L8
C	≤0.20	≤0.30	≤0.22	≤0.18	≤0.07	≤0.07	≤0.20	≤0.20
Mn	0.60-1.50	0.60-1.35	1.15-1.50	0.45-0.65	0.40-0.70	1.85-2.20	≤0.90	0.20-0.40
P	≤0.030	≤0.030	≤0.025	≤0.025	≤0.025	≤0.025	≤0.025	≤0.020
S	≤0.030	≤0.030	≤0.025	≤0.025	≤0.025	≤0.025	≤0.025	≤0.020
Si	≤0.35	≤0.35	≤0.30	≤0.35	≤0.35	≤0.15	≤0.35	≤0.35
Cr	≤0.30	≤0.30	≤0.30	≤0.30	0.60-0.90	≤0.30	≤0.30	1.50-2.00
Ni	≤0.40	≤0.40	≤0.40	1.65-2.00	0.70-1.00	≤0.40	3.20-3.70	2.80-3.90
Mo	≤0.12	≤0.12	≤0.12	0.20-0.30	0.15-0.25	0.25-0.35	≤0.12	0.40-0.60
V	≤0.05	≤0.05	0.04-0.11	≤0.05	≤0.05	≤0.05	≤0.05	≤0.05
N	–	–	0.010-0.030	–	–	–	–	–
Cu	≤0.40	≤0.40	≥0.20	≤0.40	1.00-1.30	≤0.40	≤0.40	≤0.40
Cb	≤0.02	≤0.02	≤0.02	≤0.02	≥0.03	0.06-0.10	≤0.02	≤0.02

*1. For grade L1 &L2,the sum of Cu,Ni,Cr,and Mo shall not exceed 1.00% on heat analysis.
*2. For grade L7,the sum of Cr,Mo,and V shall not exceed 0.32% on heat analysis.
*3. The carbon equivalent C.E.[C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15] shall be no greater than 0.45%.

2. ASTM A707 Grade L5 Mechanical Properties

Class 4 is the highest of the four strength grades in the ASTM A707 standard. While maintaining sufficient ductility and low-temperature toughness, it achieves a significant improvement in strength performance, which can markedly raise the pressure-bearing limit of piping systems and is suitable for high-pressure long-distance pipelines and core station piping.

Benefiting from uniform forged structure and precise heat treatment processes, flanges of this grade can still effectively resist brittle fracture in low-temperature environments with no obvious ductile-brittle transition. They can withstand complex working conditions such as pressure fluctuations, water hammer and alternating loads at low ambient temperatures, greatly reducing the risk of fracture failure in low-temperature pipelines.

Class No.	Yield Strength		Tensile Strength		Elongation	Reduction of Area	Hardness	Impact Test Cv
Class No.	ksi	MPa	ksi	MPa	%	%	HBW	ft*lbf [J]
Class 1	42	290	60	415	22	40	149-207	30 [41]
Class 2	52	360	66	455	22	40	149-217	40 [54]
Class 3	60	415	75	515	20	40	156-235	50 [68]
Class 4	75	515	90	620	20	40	179-265	50 [68]

*1. All values are minimum unless a range is specified.

*2. The energy absorption Cv is the average value of Charpy V-Notch test on three specimens.

3. Manufacturing and Heat Treatment Process

Manufacturing Process

The products are produced from high-quality alloy steel forgings through multiple processes including die forging or open-die forging, rough machining, heat treatment, precision machining and non-destructive testing. Weld repair on the flange body is not allowed, so as to ensure uniform overall structure and structural integrity.

Heat Treatment Specifications

After forging, workpieces shall be fully cooled to below the phase transformation temperature range before final heat treatment, to avoid defects such as cracks and flakes. Processes such as normalizing + tempering, quenching + tempering, normalizing + precipitation hardening, and quenching + precipitation hardening can be selected according to performance requirements.

Precipitation hardening treatment: Heat to 538℃–677℃ (1000–1250°F), hold for no less than 30 minutes, and then cool at any convenient rate to further stabilize the structure and properties of the material. ASTM A707 Grade L5

B16.5 WNRF 2“ CL600 SCH 80 A707 L5 CL4 Neck End OD Measurement
WNRF 36“ CL600 A707 L5 CL4 Hole ID Measurement
WNRF 36“ CL600 A707 L5 CL4 Hole Spacing Measurement

4. Welding Construction and Adaptation Requirements

ASTM A707 L5 flanges have good weldability and can be welded by various conventional welding processes including Shielded Metal Arc Welding (SMAW), Gas Metal Arc Welding (GMAW), Flux-Cored Arc Welding (FCAW) and Gas Tungsten Arc Welding (GTAW).

In addition, due to the low carbon equivalent and low cold cracking susceptibility of the material, no preheating is required for welding under conventional working conditions. For construction with large thickness or in low-temperature environments, appropriate low-temperature preheating can be applied to reduce welding stress. No additional post-weld heat treatment is required to meet service requirements, which greatly reduces on-site construction costs and cycles.

5. Typical Application Fields

Oil and gas long-distance pipelines: Used for crude oil and natural gas long-distance trunk lines in alpine and low-temperature regions, suitable for Class 300 and Class 600 high-pressure piping systems, and serving as core connecting components for key pipelines in stations and valve chambers.

Oil and gas field gathering and transportation systems: Applied to wellhead gathering networks and process pipelines in onshore and offshore oil and gas fields, adaptable to sour oil and gas service conditions containing hydrogen sulfide, and complying with relevant requirements of NACE MR0175.

Petroleum refining units: Used for connection of high-pressure process pipelines, low-temperature separation units and hydrogenation unit pipelines in refineries, withstanding the combined working conditions of high pressure and medium corrosion. ASTM A707 Grade L5

Low-temperature engineering and municipal pipe networks: Applied to high-pressure municipal gas pipe networks and low-temperature fluid transportation systems in cold regions, ensuring safe operation of pipe networks in low-temperature winter environments.

Pressure vessels and heat exchange equipment: Used as nozzle flanges for high-pressure vessels and shell-and-tube heat exchangers, matching the supporting requirements of low-temperature pressure-bearing equipment. C&N supplies a full range of ASTM A707 L5 flange products. We can also customize flanges with non-standard dimensions and special pressure ratings according to customer requirements. Meanwhile, we provide supporting technical services including material selection consultation and welding process guidance, offering full-process support from product supply to on-site application. Please contact us immediately if you have relevant requirements. ASTM A707 Grade L5

C&N supplies flanges and pipe fittings in various grades of ASTM A707, such as ASTM A707 Grade L5 CL3 seamless steel pipes. We have a variety of items in stock; please contact us for a quote.

ASTM A707 Grade L5