What is the difference between 304L and 316L?

Both are low-carbon austenitic stainless steels, but 316L contains 2 to 3% molybdenum while 304L contains none. The molybdenum gives 316L markedly better resistance to pitting and chloride corrosion, so 316L is preferred for chemical, marine and chloride-bearing service. 304L is the more economical choice for food, water, cryogenic and general process piping where chlorides are low.

Does 304L require PWHT?

No. 304L (ASTM A403 WP304L / EN 1.4307) is an austenitic stainless steel supplied solution annealed and does not require post-weld heat treatment. Its low carbon (0.035% maximum) prevents sensitization during welding. Keep inter-pass temperature at or below 150C and use a matching ER308L filler. IBR Form III-C and EN 10204 3.1/3.2 certification are supplied.

IBR Approved · Stainless Steel

ASTM A403 WP304L Buttweld Pipe Fittings

Low-carbon 304L (18Cr-8Ni) austenitic stainless steel — the general-purpose grade for food, water, cryogenic and process piping where chlorides are low. Elbows, tees, reducers and caps to ASME B16.9 / B16.28, IBR approved with Form III-C, EN 10204 3.1 / 3.2 traceable.

ASME B16.9 EN 1.4307 No PWHT IBR Form III-C

Grade Overview

ASTM / ASME A403 WP304L is the low-carbon version of 304 — the most widely used austenitic stainless steel. With 18% chromium and 8% nickel and no molybdenum, it offers good general corrosion resistance at an economical cost. The low carbon (≤0.035%) prevents sensitization in the heat-affected zone during welding, making it the standard choice for welded 304-type piping.

304L fittings are supplied IBR approved with Form III-C for boiler and steam service within the applicable limits. The EN counterpart is 1.4307 (X2CrNi18-9). For chloride-bearing or marine service, specify the molybdenum-bearing grade 316L instead.

✓ No PWHT required — supplied solution annealed

As an austenitic stainless steel, 304L does not require post-weld heat treatment and does not undergo martensitic transformation during welding. Keep inter-pass temperature ≤ 150°C and use a matching ER308L (GTAW) / E308L-16 (SMAW) filler. ASME P-No. 8, Group 1.

Chemical Composition — WP304L / 1.4307

Standard	C	Cr	Ni	Mn	Si
ASTM A403 WP304L	≤0.035	18.0–20.0	8.0–12.0	≤2.0	≤1.0
EN 1.4307	≤0.030	18.0–20.0	8.0–10.5	≤2.0	≤1.0

Mechanical Properties — WP304L

Property	Requirement
Tensile Strength (min)	485 MPa (70 ksi)
Yield Strength (min)	170 MPa (25 ksi)
Elongation (min)	≥ 35%
Heat Treatment	Solution annealed

Equivalent Grades

Product Form	Specification
Buttweld fittings	ASTM / ASME A403 WP304L · EN 1.4307 · UNS S30403
Seamless pipe	ASTM A312 TP304L
Forgings / flanges	ASTM A182 F304L
Plate	ASTM A240 304L

Fitting Types Available in 304L

Elbows — 45° / 90° / 180°, LR & SR
Tees — equal & reducing
Reducers — concentric & eccentric
Caps & Stub Ends — closures & lap joints

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