Difference between 303 and 304 Stainless Steel

What Is The Difference Between 303 And 304 Stainless?


The 303 materials have 17-19% chromium, 8-10 % nickel, carbon, manganese, silicon, phosphorus, sulfur and iron. The material has up to 750MPa minimum tensile strength and 190MPa minimum yield strength. The elongation at break is 35% and the hardness is 230 HB max. It also has high melting point of 1455 degrees Celsius. The 304 has similar material composition but the 303 can have added sulfur, molybdenum and titanium for stabilization. The increased sulfur content up to 0.35% in the 303 provides it with the additional mechanical properties that make it desirable for certain applications.

How To Identify Stainless Steel 303 And 304

It is extremely difficult to identify the 304 and 303 types visually. Laboratory tests have to be carried out to identify the materials. The markings on the products can help. Machining of the materials can reveal the type as well.


303 Vs 304 Stainless Steel Machinability

Since the 303 material has higher sulfur content, it can be machined easily. The 303 type of material is the most machining friendly material of all austenitic stainless steels. The 303 materials are therefore used in the heavy machining applications such as screws and fasteners which are to be machined. The 304 has all mechanical properties similar to the 303 but machining is tough compared to the 303 grade of stainless steel.

 

303 Vs 304 Stainless Steel Price

The prices are slightly higher for 303 material grade than the 304 materials grade. This is partially due to the high availability of the 304 grade as well. The 303 grade is not as common as thee 304, so that the production is low in the 303 material. This leads to the price difference in addition to the added materials such as selenium, titanium or increased sulfur.


303 Vs 304 Stainless Steel Yield Strength

The 303 material has higher yield strength than the 304 material. The 303 has 510MPa minimum yield strength where the 304 type has only about 215MPa yield strength. The tensile strength of the 303 is about 720MPa where the tensile strength of the 304 material is only around 515MPa. These differences come with the compositional difference and these strength properties are useful in selection of the materials as well. As both the 303 and 304 materials are non-magnetic austenitic stainless steels, they are both used in applications interchangeably but with special requirements for the 303 type.


303 Vs 304 Stainless Steel Corrosion

The 303 and 304 have similar corrosion resistance but the 304 has slightly higher corrosion resistance. The reduced corrosion resistance in the 303 is due to the addition of sulfur or selenium in the composition. However, both these grades are not very good against chloride ion rich environments or highly acidic conditions. They both can perform under general corrosive conditions for general corrosive services. They both have high melting points so that they can perform under very high operating temperatures retaining their corrosion resistance against general corrosive services.

 

ASTM Specification of Stainless Steel 303

Trade Name: 303 Se Stainless, 303 Se

  • ASTM A582 (Round Bars) 303 SS Condition B, 303 SS Condition A
  • ASTM A581 (Stainless Steel Wire)
  • ASTM A895 (plate, sheet, and strip)

 

Density of SS 303
TYPE ENGLISH METRIC
Density 0.289 lb/in³ 8 g/cc

 

Hardness of 303 Stainless Steel
TYPE ENGLISH METRIC
Hardness, Rockwell C 19 19
Hardness, Rockwell B 96 96
Hardness, Knoop 251 251
Hardness, Brinell 228 228
Hardness, Vickers 240 240

 

Mechanical Properties of 303 Stainless Steel

Type

YIELD STRENGTH 0.2% PROOF

TENSILE STRENGTH

ELONGATION

HARDNESS

Brinell (HB)

ROCKWELL B (HR B)

303

-

-

-

262 max

-

 

AMS Specifications of 303 Stainless Steel

AMS 5640 (plate, sheet, and strip)

 

Composition table of 303 Stainless Steel

Type

MN

SI

MO

C

S

P

CR

SE

NI

303Se

minimum

minimum

-

2.00

-

1.00

-

-

0.15

0.06

-

-

0.20

17.0

19.0

0.15

min

8.0

10.0

303

minimum

maximum

-

2.00

-

1.00

-

-

0.15

0.15

-

-

0.20

17.0

19.0

-

8.0

10.0

 

Thermal Properties of 303 Stainless Steel
CTE, linear 500°C 10.2 µin/in-°F 18.4 µm/m-°C  at 0-540°C, 18.7 µm/m-C at 0-650°C
CTE, linear 20°C 9.56 µin/in-°F 17.2 µm/m-°C  from from 0-100°C
CTE, linear 250°C 9.89 µin/in-°F 17.8 µm/m-°C  at 0-315°C (32-600°F)
Thermal Conductivity 112 BTU-in/hr-ft²-°F 16.2 W/m-K  at 100°C (212°F), 21.5 W/m-K at 500°C (930°F)
Solidus 2550 °F 1400 °C  
Specific Heat Capacity 0.12 BTU/lb-°F 0.5 J/g-°C  from 0-100°C (32-212°F)
Melting Point 2550 - 2590 °F 1400 - 1420 °C  
Liquidus 2590 °F 1420 °C

 

Equivalent Material grade of SUS 303

Type

UNS

OLD BRITISH

EURONORM

JIS

SS

EN

BS

NAME

NO

303Se

S30323

-

303S42

-

-

SUS 303Se

-

303

S30300

58M

303S31

X8CrNiS18-9

1.4305

SUS 303

2346

 

Annealed and Physical Properties of SS 303

TYPE

ELASTIC MODULUS

DENSITY

THERMAL EXPANSION MEAN COEFFICIENT

THERMAL CONDUCTIVITY

ELECTRICAL RESISTIVITY

SPECIFIC HEAT

0-538°C

0-315°C

0-100°C

AT 500°C

AT 100°C

303

193

8027

18.4

17.8

17.3

21.5

16.3

720

500


gravity of SUS 303
Grade gravity
SUS303Se 0.793
SUS303 0.793

 

Is stainless steel 303 is Food Grade?

NO, 304 stainless steel is a food grade

 

Grade 304 Minimum Yield Strength Chart
Type Yield Strength 0.2% Proof min Elongation min Tensile Strength min Hardness
Brinell (HB) max Rockwell B max
304 205 40 515 201 92

 

UNS S30400 Chemical Structure
type Mn C Si S P Cr Ni Mo N
304 minimum 18.0 8.0
maximum 2.0 0.08 0.75 0.030 0.045 20.0 10.5 0.10

 

DIN 1.4301 Equivalent Table
type UNS Old British Euronorm JIS SS
En BS Name No
304 S30400 58E 304S31 X5CrNi18-10 1.4301 SUS 304 2332