AISI 304 vs 304L Stainless Steel Properties (UNS S30403) Difference Between 304 and 304L (SS304L)

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AISI 304 VS 304L Stainless Steel (UNS S30403)

AISI 304 and 304L (SS304L) are austenitic stainless steels, and also known as 18/8 stainless steel. This article will introduce the differences between 304 and 304L stainless steel (304 vs 304L) from chemical composition, mechanical properties, corrosion resistance and weldability.

AISI 304L stainless steel is an ultra-low carbon version of SS 304 (Carbon content: ≤ 0.08 %). “L” is short for “Low carbon” and the maximum carbon content is 0.03%. The main purpose is to prevent carbide precipitation and improve weldability and corrosion resistance.

Difference Between 304 and 304L Chemical Composition

The table below gives 304L chemical composition, the maximum carbon content is 0.03%, while 304 is max 0.08%, other than that, the other composition are the same.

304L Chemical Composition, %
ASTM TypeAISI (UNS)C, ≤Si, ≤Mn, ≤P, ≤S, ≤CrNiN, ≤Notes
ASTM A240/A240M304L (UNS S30403)0.030.752.000.0450.03017.5-19.58.0-12.00.10Stainless Steel Plate,
Sheet, and Strip for Pressure Vessels
ASTM A276A/276M0.031.002.000.0450.03018.0-20.08.0-12.0Stainless Steel Bars and Shapes
ASTM A580/A580M0.031.002.000.0450.03018.0-20.08.0-12.00.10Stainless Steel Wire
ASTM A6660.030.752.000.0450.03018.0-20.08.0-12.00.10Annealed or Cold-Worked Austenitic Stainless Steel Sheet, Strip, Plate, and Flat Bar
ASTM A9590.031.002.000.0450.03017.5-19.58.0-12.0Wrought Stainless Steels
ASTM A4730.031.002.000.0450.03018.0-20.08.0-12.0Stainless Steel Forgings
ASTM A3140.031.002.000.0450.03018.0-20.08.0-12.00.10Billets and bars for forging

304 VS 304L Stainless Steel Properties

The following tables summarize 304 vs 304L stainless steel properties, including physical and mechanical properties.

Physical Properties

AISI 304L stainless steel physical properties are given in the following lists, including density, melting point and magnetic permeability.

SS304L Physical Properties
Density, g/cm3 (lb/in.3)8.03 (0.29)
Melting point, °C (°F)1400-1450 (2550-2650)
Magnetic permeability1.02 (Approximate)

Mechanical Properties

304 vs 304L stainless steel mechanical properties at room temperature are listed in the following tables.

304 vs 304L Mechanical Properties
ASTMAISI TypeConditionsTensile Strength, MPa (ksi), ≥0.2% Yield Strength, MPa (ksi), ≥Elongation in 50 mm (2 in.), %, ≥Reduction of Area, %, ≥Brinell Hardness (HBW), ≤Rockwell Hardness (HRBW), ≤Product forms
ASTM A276/A276M304Annealed, Hot finished515 (75)205 (30)4050Bars and Shapes
304L485 (70)170 (25)4050
304Annealed, Cold finished, Dia ≤ 12.7 mm (0.5 in.)620 (90)310 (45)3040
304L
304Annealed, Cold finished, Dia > 12.7 mm (0.5 in.)515 (75)205 (30)3040
304L485 (70)170 (25)3040
ASTM A580/A580M304Annealed520 (75)210 (30)3550Wire
304L485 (70)170 (25)3550
304Cold finished620 (90)310 (45)3040
304L
ASTM A240/A240M304515 (75)205 (30)4020192Plate, Sheet, and Strip
304L485 (70)170 (25)4020192
ASTM A473/A473M304Annealed,  Sections ≤ 5 in. (127 mm)515 (75)205 (30)4050Forgings
Annealed, Sections > 5 in. (127 mm)70 (485)
304L450 (65)170 (25)4050

Heat Treatment

Recommended annealing temperatures for AISI 304L stainless steel is 1010-1120 °C (1850-2050 °F).

Hardening: SS304L cannot be hardened by heat treatment, but can be hardened by cold working.

Welding

Both 304 and 304L stainless steel can be easily welded with or without filler metal. If necessary, the recommended filler metal for SS304 is E308, and SS304L is E308L. Weldments that are too large or too complex for full annealing require stress relieving, 304 weldments are easily sensitized, and intergranular corrosion or stress-assisted intergranular corrosion occurs. It is strongly recommended to use stable stainless steel (type 321, 347 or 348) or low carbon type (SS304L or SS316L), especially for those that require long-time stress relief.

Corrosion Resistance

Due to its ultra-low carbon content, SS304L has better corrosion resistance than SS 304.

The following table list 304 vs 304L stainless steel corrosion rates in boiling 50% NaOH solution.

MaterialBase metalWeld
mm/yrmils/yrmm/yrmils/yr
SS304 (UNS S30400)3.01183.3130
SS304L (UNS S30403)1.8712.287
SS316 (UNS S31600)3.1123.63.5136.8
SS316L (UNS S31603)1.9777.62.1785.4

Machinability (Machining)

The following tables show 304 and 304L stainless steel machinability (machining).

Nominal speeds and feeds for turning a variety of steels and cast irons with high-speed steel (HSS) single-point and box tools
MaterialHardness, HBConditionDepth of cut, mm (in)High-speed steel toolTool material
SpeedFeed
m/minsfmmm/revin./revISOAISI
Wrought austenitic: 201, 202, 301, 302, 304, 304L,
305, 308, 321, 347, 348, 384, 385
135-185Annealed1 (0.04)341100.180.007S4, S5M2, M3
4 (0.15)27900.40.015
8 (0.30)21700.50.02
16 (0.625)17550.750.03
Nominal speeds and feeds for turning a variety of steels and cast irons with carbide-tipped single-point and box tools
MaterialHardness, HBConditionCarbide tool
UncoatedCoated
SpeedFeedTool material gradeSpeedFeedTool material grade
BrazedIndexable
m/minsfmm/minsfmmm/revin./revISOCm/minsfmmm/revin./revISOC
Wrought austenitic: 201, 202, 301, 302, 304, 304L,
305, 308, 321, 347, 348, 384, 385
135-185Annealed1053501204000.180.007K01, M10C-31605250.180.007CK01, CM10CC-3
1003251053500.40.0151354500.40.015
76250842750.50.02C-21053500.50.02CC-2
60200642100.750.03K20, M20
Nominal speeds and feeds for turning a variety of steels and cast irons with ceramic tools
MaterialHardness, HBConditionDepth of cut, mm (in)SpeedFeedType of ceramic
m/minsfmmm/revin./rev
Austenitic: 201, 202, 301, 302, 304, 304L,
305, 308, 321, 347, 348, 384, 385
135-185Annealed1 (0.040)42514000.130.005Cold-pressed alumina
4 (0.150)2759000.250.010
8 (0.300)1856000.400.015
Nominal speeds and feeds for turning a variety of steels and cast irons with high-speed steel and carbide cutoff and form tools
MaterialHardness, HBConditionSpeedFeed, mm/rev (in./rev)Tool material grade
Cutoff tool widthForm tool width
m/minsfm1.5 mm (0.062 in.)3 mm (0.125 in.)6 mm (0.250 in.)12 mm (0.500 in.)18 mm (0.750 in.)25 mm (1.00 in.)35 mm (1.50 in.)50 mm (2.00 in.)ISOAISI or C
Austenitic: 201, 202, 301, 302, 304, 304L,
305, 308, 321, 347, 348, 384, 385
135-185Annealed26850.033 (0.0013)0.041 (0.0016)0.050 (0.002)0.050 (0.002)0.041 (0.0016)0.036 (0.0014)0.030 (0.0012)0.025 (0.001)S4, S5, K40, M40M2, M3, C-2
84275
Speeds and feeds for the deep-hole trepanning of various steels with high-speed tool steels and carbide tools
MaterialHardness, HBConditionSpeedFeedTool material grade
m/minsfmmm/revin./revISOAISI or C
Austenitic: 201, 202, 301, 302, 304, 304L,
305, 308, 321, 347, 348, 384, 385
135-185Annealed20650.0750.003S4, S5M2, M3
842750.150.006K20C-2
225-275Cold drawn18600.0750.003S4, S5M2, M3
692250.100.004K20C-2
Nominal speeds for the thread grinding
MaterialHardness, HBConditionThread designationWheel identification ANSIWheel speedWork speed
Pitch, mmThreads per 25 mm (1 in.)m/ssfmm/minsfm
Wrought austenitic stainless steels: 201, 202, 301, 302, 302B, 304, 304L,
305, 308, 309, 309S, 310, 310S, 314, 316, 316L,
317, 321, 330, 347, 348, 384, 385
135-275Annealed or cold drawn6-2.54-12A90RB438,5001.24.0
2-113-27A120SB469000
0.8-0.4528-63A180TB489500
0.4-0.3564-80A220UB5110000
Recommended speeds and feeds for the face milling of alloys with both high-speed steel and carbide cutters
MaterialHardness, HBConditionDepth of cut, mm (in.)High-speed steel toolCarbide tool
UncoatedCoated
SpeedFeed per tooth, mm (in.)Tool material grade, ISO (C)Speed, m/min (sfm)Feed per tooth, mm (in.)Tool material grade, ISO (C)
Speed, m/min (sfm)Feed per tooth, mm (in.)Tool material, ISO (AISI)Brazed, m/min (sfm)Indexable, m/min (sfm)
Wrought austenitic stainless steels: 201, 202, 301, 302, 304, 304L,
305, 308, 321, 347, 348, 384, 385
135-185 HBAnnealed1 (0.040)40 (130)0.20 (0.008)S4, S2 (M2, M7)130 (430)145 (475)0.20 (0.008)K10, M20 (C-2)215 (700)0.20 (0.008)CK10, CM20 (CC-2)
4 (0.150)30 (100)0.30 (0.012)S4, S2 (M2, M7)100 (325)110 (360)0.30 (0.012)K20, M30 (C-2)145 (475)0.30 (0.012)CK20, CM30 (CC-2)
8 (0.300)24 (80)0.40 (0.016)S4, S2 (M2, M7)70 (230)85 (280)0.40 (0.016)K30, M40 (C-2)105 (350)0.40 (0.016)CK30, CM40 (CC-2)
Recommended speeds and feeds for the slab (or plain) milling of alloys with high-speed steel cutters
MaterialHardness, HBConditionDepth of cut, mm (in.)SpeedFeed per toothHigh-speed steel tool material
m/minsfmmm (in.)ISOAISI
Wrought austenitic stainless steels: 201, 202, 301, 302, 304, 304L,
305, 308, 321, 347, 348, 384, 385
135-185 HBAnnealed1 (0.040)551800.15 (0.006)S4, S2M2, M7
4 (0.150)431400.20 (0.008)
8 (0.300)341100.25 (0.010)
Recommended speeds and feeds for the end milling (peripheral) of alloys with both high-speed steel and carbide cutters
MaterialHardness, HBConditionRadial depth of cut, mm (in.)High-speed steel toolCarbide tool
Speed, m/min (sfm)Feed, mm/tooth (in./tooth), at cutter diameter of:Tool material, ISO (AISI)Speed, m/min (sfm)Feed, mm/tooth (in./tooth), at cutter diameter of:Tool material, ISO (C)
10 mm (.375in)12 mm (.5 in)18 mm (.75 in)25-50 mm (1-2 in.)10 mm (.375in)12 mm (.5 in)18 mm (.75 in)25-50 mm (1-2 in.)
201, 202, 301, 302, 304, 304L,
305, 308, 321, 347, 348, 384, 385
135-185 HB)Annealed0.5 (0.020)34 (110)0.025 (0.001)0.050 (0.002)0.102 (0.004)0.13 (0.005)S4, S5, S2 (M2, M3, M7)110 (360)0.013 (0.0005)0.025 (0.001)0.050 (0.002)0.102 (0.004)K20, M20 (C-2)
1.5 (0.060)24 (80)0.050 (0.002)0.075 (0.003)0.13 (0.005)0.15 (0.006)82 (270)0.025 (0.001)0.050 (0.002)0.075 (0.003)0.13 (0.005)
diam/4
diam/4
21 (70)0.025 (0.001)0.050 (0.002)0.102 (0.004)0.13 (0.005)72 (235)0.025 (0.001)0.038 (0.0015)0.063 (0.0025)0.102 (0.004)
diam/2
diam/2
18 (60)0.025 (0.001)0.038 (0.0015)0.075 (0.003)0.102 (0.004)67 (220)0.013 (0.0005)0.025 (0.001)0.050 (0.002)0.075 (0.003)

Applications

SS 304L stainless steel applications: Food processing equipment, in particular beer brewing, milk processing and brewing equipment, weaving, welding screens, for mining, quarrying and water filtration, pressure vessels, storage tanks, heat exchangers, piping systems, flanges, accessories, valves and pumps, elbow, pipe tee, and reducing tee, etc.

AISI 304L Stainless Steel Equivalent

AISI 304L stainless steel equivalent to European EN (German DIN EN, British BSI EN, France NF EN), ISO, Japanese JIS and Chinese GB standard (for reference).

AISI 304L equivalent grade
USEuropean UnionISOJapanChinaAustraliaIndiaRusiaKorea
StandardTypeStandardGrade (Steel Number)StandardGrade (ISO Number)StandardGradeStandardGradeStandardGradeStandardGradeStandardGradeStandardGrade
AISI SAE;
ASTM
304L
(UNS S30403)
EN 10088-1; EN 10088-2; EN 10088-3X2CrNi18-9 (1.4307);
X2CrNi19-11 (1.4306)
ISO 15510X2CrNi19-11 (4306-304-03-I)JIS G4303; JIS G4304; JIS G4305;SUS304LGB/T 20878;
GB/T 1220;
GB/T 3280
00Cr19Ni10;
022Cr19Ni10 (New name)

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