On September 23, 2025, we received an inquiry from a domestic customer for ASME B16.5 Class 300 Weld Neck Flanges made of 316 stainless steel, a very common product and material.
The customer specifically requested that all flanges undergo solution annealing—a critical step for enhancing corrosion resistance and ensuring uniform mechanical properties.
At ZIZI, we understand the importance of heat treatment in stainless steel products. Our production team strictly adheres to ASME B16.5 standards and performs solution annealing to ensure superior performance, a smooth surface finish, and durability in harsh environments. Every flange we deliver reflects our commitment to quality, precision, and customer satisfaction.
Products List:
| ITEM | DESCRIPTION | QUANTITIES | UNITS |
| 1 | SS316 Flange DN150,ASME B16.5 300LB WN RF | 16 | PCS |
| 2 | SS316 Flange DN80.ASME B16.5 300LB WN RF | 8 | PCS |
| 3 | TOTAL | 24 | PCS |
Inspection photos
| Inspection Item | Measurement Tool | Inspection Method and Requirement |
| Nominal Bore (NPS) / Inner Diameter (D) | Vernier Caliper / Inner Diameter Gauge | Measure the inner bore diameter of the flange, which must conform to the tolerances specified in the standard. |
| Outer Diameter (D0) | Steel Tape Measure / Vernier Caliper | Measure the outer diameter of the flange, which must conform to the tolerances specified in the standard. |
| Sealing Face Diameter (or Raised Face Outer Diameter Dp) | Vernier Caliper / Outside Micrometer | Measure the diameter of the sealing face (e.g., raised face, female face) to ensure compliance with requirements. |
| Flange Thickness (t) | Vernier Caliper / Thickness Micrometer | Measure the thickness of the flange ring. |
| Number and Diameter of Bolt Holes (d) | Vernier Caliper | Count the number of bolt holes; measure the diameter of the bolt holes to ensure compliance with design requirements. |
| Bolt Circle Diameter (B.C.D., K) | Steel Tape Measure / Vernier Caliper | Measure the center distance of diagonally opposite bolt holes, or use a bolt circle gauge, ensuring conformity with the tolerances specified in the standard. |
ASME B16.5 Class 300 Weld Neck Flange
An Class 300 ASME B16.5 Weld Neck Flange is a type of high-pressure pipe flange designed to connect piping systems securely and withstand elevated temperatures and pressures.
The “Weld Neck” design features a long tapered hub that provides reinforcement at the weld area, reducing stress concentration and ensuring excellent structural integrity.
This flange type is commonly used in oil & gas, petrochemical, power generation, and offshore industries, where reliable and leak-free connections are critical.
Specification of ASME B16.5 Weld Neck Flanges
| Size Range | 1/2″- 3″ / DN15 – DN80 |
| Pressure Rating | Class 150, 300, 600, 1500 |
| Standard | ANSI / ASME B16.5 |
| Carbon Steel | ASTM A105 / A105N |
| Low Temp Carbon Steel | ASTM A350 LF2 / LF3 |
| Pipeline Steel | ASTM A694 F42 / 46 / 56 / 60 / 65 |
| Alloy Steel | ASTM A182 F11 / 12 / 12 / 5 / 9 / 91 / 92 |
| Stainless Steel | ASTM A182 F304 / 304L / 304H, 316 / 316L, 310S, 317, 347, 904L |
| Duplex Stainless Steel | ASTM A182 F51, F53, F44 |
ASTM A182 F316 Forged Flange Chemical Composition
| CHEMICAL | LIMITS | C | Mn | P | S | Si | Ni | Cr | Mo | N |
| ASTM A182 F316 | MIN | 10.0 | 16.0 | 2.00 | ||||||
| MAX | 0.08 | 2.00 | 0.045 | 0.030 | 1.00 | 14.0 | 18.0 | 3.00 | 0.10 |
ASTM A182 F316 Forged Flange Mechanical Property
| MATERIAL | T.S (MPA) | Y.S (MPA) | EL % | R/A % |
| ASTM A182 F316 | 515 min | 205 min | 30 min | 50 min |
Class 300lb Weld Neck Flange Dimensions & Weight
| Nominal Pipe Size | A | B | C | D | E | F | G | H | I | J | Weight | |
| inch | mm | mm | mm | mm | mm | mm | mm | mm | Holes | mm | mm | kg / piece |
| 1/2 | 21.30 | 95.20 | 15.70 | 14.20 | 52.30 | 21.30 | 38.10 | 35.00 | 4 | 15.70 | 66.55 | 0.75 |
| 3/4 | 26.70 | 117.3 | 20.80 | 15.70 | 57.15 | 26.70 | 47.70 | 42.90 | 4 | 19.00 | 82.50 | 1.26 |
| 1 | 33.40 | 123.9 | 26.70 | 17.50 | 62.00 | 33.50 | 53.80 | 50.80 | 4 | 19.00 | 88.90 | 1.52 |
| 1 1/4 | 42.20 | 133.3 | 35.10 | 19.00 | 65.00 | 42.20 | 63.50 | 63.50 | 4 | 19.00 | 98.50 | 2.03 |
| 1 1/2 | 48.30 | 155.4 | 40.90 | 20.60 | 68.30 | 48.30 | 69.85 | 73. 15 | 4 | 22.30 | 114.3 | 2.89 |
| 2 | 60.30 | 165. 1 | 52.60 | 22.30 | 69.85 | 60.45 | 84.00 | 91.90 | 8 | 19.00 | 127.0 | 3.4 |
| 2 1/2 | 73.00 | 190.5 | 62.70 | 25.40 | 76.20 | 73.15 | 100.0 | 104.6 | 8 | 22.30 | 149.3 | 5.17 |
| 3 | 88.90 | 209.5 | 78.00 | 28.40 | 79.25 | 88.90 | 117.3 | 127.0 | 8 | 22.30 | 168.1 | 6.93 |
| 3 1/2 | 101.6 | 228.6 | 90.20 | 30.20 | 81.00 | 101.6 | 133.3 | 139.7 | 8 | 22.30 | 184.1 | 8.67 |
| 4 | 114.3 | 254.0 | 102.4 | 31.70 | 85.80 | 114.3 | 146.0 | 157.2 | 8 | 22.30 | 200.1 | 11.2 |
| 5 | 141.3 | 279.4 | 128.3 | 35.00 | 98.50 | 141.2 | 177.8 | 185.7 | 8 | 22.30 | 234.9 | 15.1 |
| 6 | 168.3 | 317.5 | 154.2 | 36.50 | 98.50 | 168.4 | 206.2 | 215.9 | 12 | 22.30 | 269.7 | 19.1 |
| 8 | 219.1 | 381.0 | 202.7 | 41.10 | 111.2 | 219.2 | 260.3 | 269.7 | 12 | 25.40 | 330.2 | 29.9 |
| 10 | 273.0 | 444.5 | 254.5 | 47.70 | 117.3 | 273.0 | 320.5 | 323.8 | 16 | 28.40 | 387.3 | 42.7 |
| 12 | 323.8 | 520.7 | 304.8 | 50.80 | 130.0 | 323.8 | 374.6 | 381.0 | 16 | 31.70 | 450.8 | 61.8 |
| 14 | 355.6 | 584.2 | To be specified by the Purchaser | 53.80 | 142.7 | 355.6 | 425.4 | 412.7 | 20 | 31.70 | 514.3 | 85.8 |
| 16 | 406.4 | 647.7 | 57.15 | 146.0 | 406.4 | 482.6 | 469.9 | 20 | 35.00 | 571.5 | 106 | |
| 18 | 457.2 | 711.2 | 60.45 | 158.7 | 457.2 | 533.4 | 533.4 | 24 | 35.00 | 628.6 | 131 | |
| 20 | 508.0 | 774.7 | 63.50 | 162.0 | 508.0 | 587.2 | 584.2 | 24 | 35.00 | 685.8 | 158 | |
| 24 | 609.6 | 914.4 | 69.85 | 168.1 | 609.6 | 701.5 | 692.1 | 24 | 41.10 | 812.8 | 230 | |
Solution Treatment of Flanges
Solution treatment (or solution annealing) of flanges is a key heat treatment process used to improve the properties of certain materials (especially stainless steel and nickel-based alloy flanges), particularly corrosion resistance and machinability.
Which flanges require solution treatment?
Not all flanges require solution treatment; primarily stainless steel flanges, such as:
Austenitic stainless steel flanges such as 304, 304L, 316, 316L, 321, and 347
Special corrosion-resistant alloy flanges (such as Inconel, Duplex, and Hastelloy)
Note : A solution annealing temperature above 1950 °F [1065 °C] may impair the resistance to intergranular corrosion after subsequent exposure to sensitizing conditions in F 321, F 321H, F 347, F 347H, F 348, and F 348H. When specified by the purchaser, a lower temperature stabilization or resolution annealing shall be used subsequent to the initial high temperature solution anneal (see Supplementary Requirement S10)
SS316 Weld Neck Flange Benefits
High Pressure & Temperature Resistance
Excellent Leak Prevention
Enhanced Durability
Versatile Applications
Applications
Oil & Gas Pipelines
Petrochemical Processing Plants
Power Generation Systems
Water Treatment Facilities
High-Pressure Steam Lines