{"id":1821,"date":"2026-10-08T09:29:04","date_gmt":"2026-10-08T09:29:04","guid":{"rendered":"https:\/\/www.thepipingmart.com\/blog\/?p=1821"},"modified":"2026-10-08T09:29:05","modified_gmt":"2026-10-08T09:29:05","slug":"common-grades-of-stainless-steel-flanges","status":"publish","type":"post","link":"https:\/\/www.thepipingmart.com\/blog\/common-grades-of-stainless-steel-flanges\/","title":{"rendered":"What Are the Common Grades of Stainless Steel Flanges?"},"content":{"rendered":"\n

Stainless steel flange grades use unique alloy blends to deliver specific corrosion resistance and strength for diverse industrial applications. This article sorts the common grades into 300-series, high-temperature, molybdenum-bearing, high-alloy, precipitation-hardening, martensitic, and specialty groups. This is a comprehensive guide to stainless steel flange covers, grades, types, properties, and applications.<\/p>\n\n\n\n

What Are Stainless Steel Flange Grades?<\/strong><\/h2>\n\n\n\n

A stainless steel flange grade names the specific alloy forged into the flange. The grade fixes chemical composition, which shapes corrosion resistance, strength, temperature capability, weldability, and fabrication behavior. ASTM A182 identifies stainless steel flange materials by grade designations such as F304, F316L, and F321H. The specification covers forged or rolled alloy and stainless steel pipe flanges, fittings, valves, and related parts for high-temperature service.<\/p>\n\n\n\n

Common Stainless Steel Flange Grades at a Glance<\/strong><\/h2>\n\n\n\n

Compare core stainless steel flange grades to select the right material for your application.<\/p>\n\n\n\n

Grade \/ Grade Family<\/strong><\/td>Grade Type<\/strong><\/td>Key Characteristic<\/strong><\/td><\/tr>
304 \/ 304L \/ 304H<\/td>Austenitic<\/td>General-purpose family<\/td><\/tr>
304N \/ 304LN<\/td>Austenitic<\/td>Nitrogen-alloyed variants<\/td><\/tr>
316 \/ 316L<\/td>Austenitic<\/td>Molybdenum-bearing family<\/td><\/tr>
316H \/ 316N \/ 316LN<\/td>Austenitic<\/td>Specialized 316 variants<\/td><\/tr>
316Ti<\/td>Austenitic<\/td>Titanium-stabilized variant<\/td><\/tr>
321 \/ 321H<\/td>Austenitic<\/td>Titanium-stabilized family<\/td><\/tr>
347 \/ 347H<\/td>Austenitic<\/td>Niobium-stabilized family<\/td><\/tr>
348 \/ 348H<\/td>Austenitic<\/td>Stabilized variants<\/td><\/tr>
309H \/ 310 \/ 310S \/ 310H<\/td>Austenitic<\/td>High-temperature family<\/td><\/tr>
310 MoLN<\/td>Austenitic<\/td>High-alloy variant<\/td><\/tr>
317 \/ 317L<\/td>Austenitic<\/td>Higher-alloy molybdenum family<\/td><\/tr>
904L<\/td>Super-austenitic<\/td>Highly alloyed<\/td><\/tr>
SMO 254<\/td>Super-austenitic<\/td>High-alloy<\/td><\/tr>
253MA<\/td>Heat-resistant<\/td>High-temperature grade<\/td><\/tr>
303<\/td>Austenitic<\/td>Free-machining<\/td><\/tr>
202<\/td>Austenitic<\/td>Manganese-bearing<\/td><\/tr>
17-4 PH<\/td>Precipitation-hardening<\/td>High-strength<\/td><\/tr>
17-7 PH<\/td>Precipitation-hardening<\/td>High-strength grade<\/td><\/tr>
431<\/td>Martensitic<\/td>High-strength<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Austenitic Stainless Steel Flange Grades<\/strong><\/h1>\n\n\n\n

304 Stainless Steel Flanges<\/strong><\/h2>\n\n\n\n

Stainless Steel 304 Flanges<\/a> use the austenitic base of 18\u201320% chromium and 8\u201311% nickel, with carbon up to 0.08%. Its formability and weldability explain its wide use. The 304L, 304H, 304N, and 304LN grades change only carbon or nitrogen.<\/p>\n\n\n\n

304L Stainless Steel Flanges<\/strong><\/h2>\n\n\n\n

Stainless Steel 304L Flanges<\/a> limit carbon to 0.030%, against 0.08% in standard 304. That reduces chromium carbide formation in weld zones.<\/p>\n\n\n\n

304H Stainless Steel Flanges<\/strong><\/h2>\n\n\n\n

Stainless Steel 304H Flanges<\/a> hold carbon between 0.04% and 0.10%. That carbon floor raises strength at elevated temperatures, where 304L softens sooner. Specify 304H when the code or service temperature requires it.<\/p>\n\n\n\n

304N and 304LN Stainless Steel Flanges<\/strong><\/h2>\n\n\n\n

The N suffix means 0.10\u20130.16% added nitrogen. Stainless Steel 304N Flanges<\/a> use it to lift yield strength to 240 MPa minimum, against 205 MPa for 304. Stainless Steel 304LN Flanges<\/a> pair the nitrogen with carbon at 0.030% maximum, combining 304L weld protection with 304-level tensile strength.<\/p>\n\n\n\n

316 Stainless Steel Flanges<\/strong><\/h2>\n\n\n\n

Stainless Steel 316 Flanges<\/a> add 2\u20133% molybdenum to a 16\u201318% chromium, 10\u201314% nickel base. The molybdenum raises pitting resistance in chlorides, which sets 316 apart from 304.<\/p>\n\n\n\n

316L Stainless Steel Flanges<\/strong><\/h2>\n\n\n\n

Stainless Steel 316L Flanges<\/a> cap carbon at 0.030%, against 0.08% for 316, which protects welded joints from sensitization. Compared with 316H, 316L trades some high-temperature strength for weld-zone corrosion resistance.<\/p>\n\n\n\n

316H, 316N and 316LN Stainless Steel Flanges<\/strong><\/h2>\n\n\n\n

Stainless Steel 316H Flanges<\/a> carry 0.04\u20130.10% carbon for hot service. Stainless Steel 316N Flanges<\/a> add 0.10\u20130.16% nitrogen, lifting yield strength to 240 MPa. Stainless Steel 316LN Flanges<\/a> combine low carbon with that nitrogen. Match the variant to the order specification.<\/p>\n\n\n\n

316Ti Stainless Steel Flanges<\/strong><\/h2>\n\n\n\n

Stainless Steel 316Ti Flanges<\/a> add titanium, at a minimum of five times carbon plus nitrogen, to bind carbon. This resists sensitization during prolonged heat exposure, where standard 316 loses chromium to carbides.<\/p>\n\n\n\n

321 and 321H Stainless Steel Flanges<\/strong><\/h2>\n\n\n\n

Stainless Steel 321 Flanges<\/a> and Stainless Steel 321H Flanges<\/a> stabilize with titanium, which binds carbon first. The H grade raises carbon to 0.04\u20130.10% for hot-service strength. Both resist intergranular attack in the 425\u2013815\u00b0C range better than 304.<\/p>\n\n\n\n

347 and 347H Stainless Steel Flanges<\/strong><\/h2>\n\n\n\n

Stainless Steel 347 Flanges<\/a> and Stainless Steel 347H Flanges<\/a> stabilize with niobium, at a minimum of ten times carbon, instead of titanium. Stainless Steel 347 Flanges use niobium stabilization to limit chromium-carbide precipitation and reduce sensitization after welding or elevated-temperature exposure. The H grade carries 0.04\u20130.10% carbon.<\/p>\n\n\n\n

348 and 348H Stainless Steel Flanges<\/strong><\/h2>\n\n\n\n

Stainless Steel 348 Flanges<\/a> follow 347 chemistry but limit cobalt to 0.20% and tantalum to 0.10% for nuclear service. Stainless Steel 348H Flanges<\/a> raise carbon to 0.04\u20130.10%.<\/p>\n\n\n\n

High-Temperature Stainless Steel Flange Grades<\/strong><\/h1>\n\n\n\n

309H Stainless Steel Flanges<\/strong><\/h2>\n\n\n\n

Stainless Steel 309H Flanges<\/a> carry 22\u201324% chromium and 12\u201315% nickel. The H designation fixes carbon at 0.04\u20130.10% for creep strength.<\/p>\n\n\n\n

310, 310S and 310H Stainless Steel Flanges<\/strong><\/h2>\n\n\n\n

The 310 family packs 24\u201326% chromium and 19\u201322% nickel for oxidation resistance. Stainless Steel 310 Flanges<\/a> allow carbon to 0.25%. Stainless Steel 310S Flanges<\/a> cut it to 0.08% for easier welding. Stainless Steel 310H Flanges<\/a> hold 0.04\u20130.10% for creep strength.<\/p>\n\n\n\n

310 MoLN Stainless Steel Flanges<\/strong><\/h2>\n\n\n\n

Stainless Steel 310 MoLN Flanges<\/a> stand for molybdenum, low carbon and nitrogen. UNS S31050 is a low-carbon 310-family grade containing approximately 24\u201326% chromium, 20.5\u201323.5% nickel, 1.6\u20132.6% molybdenum and 0.09\u20130.15% nitrogen, with exact limits depending on the applicable material specification.<\/p>\n\n\n\n

Higher-Alloy Stainless Steel Flange Grades<\/strong><\/h1>\n\n\n\n

317 and 317L Stainless Steel Flanges<\/strong><\/h2>\n\n\n\n

Stainless Steel 317 Flanges<\/a> and Stainless Steel 317L Flanges<\/a> raise molybdenum to 3\u20134%, against 2\u20133% in 316, for stronger resistance to chlorides and acids. 317L caps carbon at 0.030%.<\/p>\n\n\n\n

904L Stainless Steel Flanges<\/strong><\/h2>\n\n\n\n

Stainless Steel 904L Flanges<\/a> (UNS N08904) hold 23\u201328% nickel, 4\u20135% molybdenum and 1\u20132% copper, with carbon at 0.020% maximum. That balance beats 316L in sulfuric acid, so 904L ranks as a specialized grade.<\/p>\n\n\n\n

Stainless Steel SMO 254 Flanges<\/strong><\/h2>\n\n\n\n

Stainless Steel SMO 254 Flanges<\/a> (UNS S31254) pack about 6% molybdenum, 20% chromium, 18% nickel, and 0.20% nitrogen into a super-austenitic grade for chloride-rich media such as seawater.<\/p>\n\n\n\n

Stainless Steel 253MA Flanges<\/strong><\/h2>\n\n\n\n

Stainless Steel 253MA Flanges<\/a> (UNS S30815) combine 21% chromium and 11% nickel with silicon and cerium. Those additions give oxidation resistance to roughly 1,100 \u00b0C, where 304 begins to scale.<\/p>\n\n\n\n

Other Stainless Steel Flange Grades<\/strong><\/h1>\n\n\n\n

303 Stainless Steel Flanges<\/strong><\/h2>\n\n\n\n

Stainless Steel 303 Flanges<\/a> add a minimum of 0.15% sulfur, which breaks chips cleanly during machining. The sulfur lowers corrosion resistance and weldability relative to 304, so 303 suits machined parts.<\/p>\n\n\n\n

202 Stainless Steel Flanges<\/strong><\/h2>\n\n\n\n

Stainless Steel 202 Flanges<\/a> belong to the 200 series, which swaps nickel for 7.5\u201310% manganese and up to 0.25% nitrogen. Nickel falls to 4\u20136%, cutting cost, and corrosion resistance sits below 304.<\/p>\n\n\n\n

Precipitation-Hardening Stainless Steel Flange Grades<\/strong><\/h1>\n\n\n\n

17-4 PH Stainless Steel Flanges<\/strong><\/h2>\n\n\n\n

PH stands for precipitation hardening. Stainless Steel 17-4 PH Flanges<\/a> contain 15\u201317.5% chromium, 3\u20135% nickel, and 3\u20135% copper, and aging in the H900 condition lifts tensile strength to 1,310 MPa.<\/p>\n\n\n\n

17-7 PH Stainless Steel Flanges<\/strong><\/h2>\n\n\n\n

Stainless Steel 17-7 PH Flanges<\/a> harden with aluminum, not copper, on a semi-austenitic 17Cr-7Ni base. 17-4 PH is martensitic; 17-7 PH starts austenitic and strengthens through heat treatment.<\/p>\n\n\n\n

Martensitic Stainless Steel Flange Grade<\/strong><\/h1>\n\n\n\n

431 Stainless Steel Flanges<\/strong><\/h2>\n\n\n\n

Stainless Steel 431 Flanges<\/a> (UNS S43100) are martensitic, with 15\u201317% chromium, 1.25\u20132.50% nickel, and carbon up to 0.20%. Heat treatment delivers high strength, while corrosion resistance sits below the austenitic grades.<\/p>\n\n\n\n

Stainless Steel Flange Grade Comparison<\/strong><\/h2>\n\n\n\n
Grade Family<\/strong><\/td>Representative Grades<\/strong><\/td>Classification<\/strong><\/td>Main Distinguishing Feature<\/strong><\/td><\/tr>
304 Family<\/td>304, 304L, 304H, 304N, 304LN<\/td>Austenitic<\/td>Carbon\/nitrogen variants<\/td><\/tr>
316 Family<\/td>316, 316L, 316H, 316N, 316LN, 316Ti<\/td>Austenitic<\/td>Molybdenum-bearing<\/td><\/tr>
Stabilized<\/td>321, 321H, 347, 347H, 348, 348H<\/td>Austenitic<\/td>Titanium or niobium<\/td><\/tr>
High-Temperature<\/td>309H, 310, 310S, 310H, 310 MoLN<\/td>Austenitic<\/td>Heat-oriented chemistry<\/td><\/tr>
Higher-Alloy<\/td>317, 317L, 904L, SMO 254<\/td>Austenitic \/ super-austenitic<\/td>Higher alloy content<\/td><\/tr>
Heat-Resistant<\/td>253MA<\/td>Austenitic<\/td>Silicon and cerium additions<\/td><\/tr>
PH Grades<\/td>17-4 PH, 17-7 PH<\/td>Precipitation-hardening<\/td>Heat-treatment strengthening<\/td><\/tr>
Martensitic<\/td>431<\/td>Martensitic<\/td>High strength<\/td><\/tr>
Other<\/td>303, 202<\/td>Austenitic<\/td>Sulfur or manganese chemistry<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

How to Choose the Right Stainless Steel Flange Grade<\/strong><\/h2>\n\n\n\n

Start with the grade and specification on the purchase order, then check chemistry, carbon designation, nitrogen addition, and stabilization against the service. Confirm temperature, corrosion environment, mechanical requirements, and the material standard. Verify the manufacturer\u2019s MTC against each item. Test values are in the guide to stainless steel flange properties, and end uses sit under industrial applications of stainless steel flanges.<\/p>\n\n\n\n

Conclusion<\/strong><\/h2>\n\n\n\n

Stainless steel flange selection starts with the material grade, but the grade alone does not establish suitability. Confirm the applicable ASTM or ASME material specification, service temperature, corrosion environment, pressure requirements, heat-treatment condition, and MTC before approving a flange for service. We at The Piping Mart connect buyers with manufacturers, suppliers, and exporters of stainless steel flanges, allowing procurement teams to compare relevant sources based on grade and project requirements.<\/p>\n\n\n\n

FAQs<\/strong><\/h2>\n\n\n\n

What are the common grades of stainless steel flanges?<\/strong><\/h3>\n\n\n\n

The 304 and 316 families lead, followed by stabilized 321, 347 and 348, high-temperature 309H and 310; high-alloy 904L and SMO 254, and PH grades.<\/p>\n\n\n\n

What is the difference between 304 and 316 stainless steel flanges?<\/strong><\/h3>\n\n\n\n

316 adds 2\u20133% molybdenum, which improves pitting resistance in chlorides. 304 relies on chromium and nickel alone and costs less.<\/p>\n\n\n\n

What is the difference between 304L and 304H flanges?<\/strong><\/h3>\n\n\n\n

304L caps carbon at 0.030% to protect welds from sensitization. 304H holds 0.04\u20130.10% carbon for strength at elevated temperatures.<\/p>\n\n\n\n

What is the difference between 316L and 316H flanges?<\/strong><\/h3>\n\n\n\n

316H carries 0.04\u20130.10% carbon for high-temperature strength, while 316L caps carbon at 0.030% for weld-zone corrosion resistance.<\/p>\n\n\n\n

What are 321, 347, and 348 stainless steel flange grades?<\/strong><\/h3>\n\n\n\n

321 stabilizes with titanium, 347 with niobium, and 348 follows 347 with cobalt and tantalum limits for nuclear service.<\/p>\n\n\n\n

What are 17-4 PH and 17-7 PH stainless steel flanges?<\/strong><\/h3>\n\n\n\n

Both gain strength from precipitation-hardening heat treatment. 17-4 PH is martensitic and hardens with copper; 17-7 PH is semi-austenitic and hardens with aluminum.<\/p>\n","protected":false},"excerpt":{"rendered":"

Stainless steel flange grades use unique alloy blends to deliver specific corrosion resistance and strength for diverse industrial applications. This article sorts the common grades into 300-series, high-temperature, molybdenum-bearing, high-alloy, precipitation-hardening, martensitic, and specialty groups. This is a comprehensive guide to stainless steel flange covers, grades, types, properties, and applications. What Are Stainless Steel Flange […]<\/p>\n","protected":false},"author":1,"featured_media":1828,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-1821","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorized"],"yoast_head":"\nStainless Steel Flange Grades Explained | The Piping Mart<\/title>\n<meta name=\"description\" content=\"Compare common stainless steel flange grades, including 304, 316, 321, 347, 310, 904L, SMO 254 and 17-4 PH, with composition, differences and selection tips.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.thepipingmart.com\/blog\/common-grades-of-stainless-steel-flanges\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" 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