304/304L STAINLESS VALVES

Valves are manufactured in ASTM A182 304/304L forgings and ASTM A351 CF8/CF3 castings. Trim components can also be in UNS S30403 and AISI-SAE 304/304L. Welded end valves can be in 304 but 304L is often preferred due to the lower carbon content which avoids intergranular corrosion in the as-welded state thereby providing superior corrosion resistance compared to 304.

Design features 304/316L Stainless Steel

• General corrosion resistance
• Non magnetic and non hardenable except by cold working
• Appropriate in field working applications
• Susceptible to chloride stress corrosion cracking

GRADE 304

One of the most versatile and commonly used stainless steels on the market, Grade 304 stainless steel is the most standard used alloy of this type. Essentially, Grade 304 is an austenitic chromium alloy which is also known as an “18/8” stainless as the make-up of the steel is 18% chromium and 8% nickel. 304 grade is also cheaper than 316 grade.

The chromium content promotes the material’s considerable resistance to the effects of corrosion and oxidation. The stainless steel alloy resists most oxidising acids and will withstand ordinary rusting though this does not mean that the steel will not tarnish over time. The steel needs to be cold worked to generate higher tensile strength. For valves which are welded heavily, post-weld annealing may be necessary to provide maximum corrosive resistance.

Type 304 Stainless Steel has excellent welding and deep drawing characteristics.

Applications of Grade 304 Stainless Steel

Grade 304 can also be found in heat exchangers, chemical containers, pipelines and throughout the food industry. It can be used as a fabricated material where high temperature petroleum gases or steam production gases are stored such as pressure vessels.

304 & 304L valves & piping components have similar properties and in certain cases are stocked with dual certification, where it is confirmed that each item has properties and a composition which comply with both steel types. Grade 304H cannot be included in this equation due to the steel’s higher carbon content which is intended for use in elevated temperature applications.

GRADE 304L

Type 304L is a lower carbon variant of Grade 304 – the steel can be welded without the resulting issue of carbon precipitation (precipitation of chromium carbide as heat is applied during the welding process which depletes the chromium element of the steel thus reducing its anti-corrosive/oxidation effectiveness). It’s corrosive and strength properties are similar to 304.

Type 304L stainless steel is a sort after material for use in severely corrosive conditions. Weld annealing is only necessary in applications where stress loads are excessive. 304L has a slightly lower pressure rating at very high temperatures compared to 304.

This steel Grade is found in a variety of commercial sectors, particularly in the chemical industry.

Benefits of using 304L Stainless Steel

• Low carbon content eliminates carbon precipitation in the welding process
• Can be used in severe corrosive environments
• Weld annealing only required in high stress applications
• Very similar to Type 304

304 & 304L valves & piping components have similar properties and in certain cases are stocked with dual certification, where it is concluded that each item has properties and a composition which comply with both steel types. Grade 304H cannot be included in this equation due to the steel’s higher carbon content which is intended for use in elevated temperature applications.

The below tables are correct as per ASTM A182/A182M-13

Chemical Composition

Grade	C (Max)	Si (Max)	Mn (Max)	P (Max)	S (Max)	Cr	Mo	Ni	N (Max)
304L	0.030	1.00	2.00	0.045	0.030	18.00/20.00	–	8.00/13.00	0.10
304	0.080	1.00	2.00	0.045	0.030	18.00/20.00	–	8.00/11.00	0.10

Mechanical Properties

Grade	Yield Strength	Tensile Strength	Elongation (%)	Reduction of Area (%)	Hardness Max
	Min (Mpa)	Min (Mpa)	Min	Min (50mm)	HB	HR B
304L	170	458	30	50	201*	92*
304	205	515	30	50	201*	92*

* Maximum hardness not specified in ASTM A182/A182M-13

Equivalent Standards / Specifications

The following standards may be utilised for valve & trim components in valve construction:-

ASTM

A312, A376, A358, A269, A249, A403, A182, A351

ASME

SA312, SA376, SA358, SA269, SA249, SA403, SA182, SA351

Applications

FORGING SPECIFICATION	COMMON DESIGNATION	MATERIAL SUFFIX	WROUGHT BAR SPECIFICATION	SERVICE RECOMMENDATIONS (1)	COMMON API TRIM # FOR BASE MATERIAL
					150 TO 600 #	900 TO 2500 #
ASTM A182 F304	18% Chrome; 8% Nickel; 0.08% C Stainless Steel	ASTM A351 Grade CF8	ASTM A479 304	Corrosive or extremely high temperature non-corrosive services between -450ºF (-268ºC) and +1200ºF (+649ºC). Above +800ºF (+425ºC) specify carbon content of 0.04% or greater.	2	2, 15
ASTM A182 304L	18% Chrome; 8% Nickel; 0.03% C Low Carbon Stainless Steel	ASTM A351 Grade CF3	ASTM A479 304L	Brackish water, phosphate solutions, pressurised water @ 570ºF (299ºC), sea water, steam.	304L+HFS	304L+HF
ASTM A182 F304H	18% Chrome; 8% Nickel; 0.08% C Stainless Steel	ASTM A351 Grade CF10	ASTM A479 304H	Corrosive or extremely high temperature non-corrosive services between -450ºF (-268ºC) and +1200ºF (+649ºC). Above +800ºF (+425ºC) specify carbon content of 0.04% or greater.	304H+HFS	304H+HF