Stainless Steel - Grade 304

SX 304 / 304L Technical Data

Summary

SX 304 is the most versatile and the most widely used of all stainless steels.  Its chemical composition, mechanical properties, weldability and corrosion/oxidation resistance provide the best all-round performance stainless steel at relatively low cost.  It also has excellent low temperature properties and responds well to hardening by cold working.  If intergranular corrosion in the heat affected zone may occur, it is suggested that SX 304L be used.

Typical Applications

SX 304 is used in all industrial, commercial and domestic fields because of its good corrosion and heat resisting properties.  Some applications include:

    Tanks and containers for a large variety of liquids and solids.
    Process equipment in the mining, chemical, cryogenic, food, dairy and pharmaceutical industries.

Chemical Composition (ASTM A240)

SX oC Mn P S Si Cr Ni
304   
304L
0.08 max   
0.03 max
2.0   
max
0.045   
max
0.030   
max
1.0   
max
18.0 to   
20.0
8.0 to 10.50   
8.0 - 12.0

 
Typical Properties in the Annealed Condition
The properties quoted in this publication are typical of mill production  and unless indicated should not be regarded as guaranteed minimum values for specification purposes. 

1. Mechanical Properties at Room Temperature
 

  304 304L
Typical Minimum Typical Minimum
Tensile Strength,    MPa 600 515 590 485
Proof Strength, (Offset 0.2 %),              MPa 310 205 310 170
Elongation (Percent in 50mm) 60 40 60 40
Hardness (Brinell) 170 - 170 -
Endurance (fatigue) limit,                      MPa 240 - 240 -

 
2. Properties at elevated temperatures
    All these values refer to 304 only.
304L values are not given because its strength decreases markedly above 425oC.
 
Time Elevated Temperature Tensile Strength

Temperature, oC 600 700 800 900 1000
Tensile Strength,      MPa 380 270 170 90 50

 
Creep data Stress for a creep rate of 1% in 10 000 h.

Temperature, oC 550 600 650 700 800
Stress, MPa 120 80 50 30 10

 
Maximum Recommended Service Temperature
(Oxidising Conditions)

Continuous Service            925oC
Intermittent Service             850oC

3. Properties at Sub-Zero Temperatures
    ( SX 304 / 304L )

Temperature  oC -78 -161 -196
Tensile Strength MPa 1100/950 1450/1200 1600/1350
Proof Stress (Offset 0.2%) MPa 300/180 380/220 400/220
Impact Strength (Charpy V-Notch) J 180/175 160/160 155/150

 
4. Corrosion Resistance

Aqueous
As a rough guide the following examples are given for certain pure acid-water mixtures-

Temperature oC 20 80
Concentration, % by mass 10     20      40      60       80       100 10     20      40      60       80       100
Sulphuric Acid 2       2        2        2         1          0  2       2        2        2        2         2 
Nitric Acid 0       0        0        0         2          0 0       0        0        0        1         2
Phosphoric Acid 0       0        0        0         0          2 0       0        0        0        1         2
Formic Acid 0       0        0        0         0          0 0       1        2        2        1         0

 Key:         0 = resistant    -    corrosion rate less than 100 mm/year
                 1 = partly resistant    -    corrosion rate 100m to 1000 mm/year
                 2 = non resistant    - corrosion rate more than 1000 mm/year
 
4.2 Atmospheric

The performance of SX 304 compared with other metals in various environments is shown in the following table. The corrosion rates are based on a 10 year exposure.
 

Environment Corrosion Rate (mm/year)
SX 304 Aluminium-3S Mild Steel
Rural 0.0025 0.025 5.8
Marine 0.0076 0.432 34.0
Marine Industrial 0.0076 0.686 46.2

 

Thermal Processing

1.    Annealing.  Heat from 1010oC to 1120oC and cool rapidly in air or water.  The best corrosion resistance is obtained when the final annealing is above 1070oC and cooling is rapid.

2.    Stress relieving.  SX 304L can be stress relieved at 450-600oC for one hour with little danger of sensitisation.  A lower stress relieving temperature of 400oC maximum must be used.

3.     Hot working
        Initial forging and pressing:                              1150  to 1260oC
        Finishing temperature:                                         900 to 925oC

All hotworking operations should be followed by annealing.

Note: Soaking times to ensure uniformity of temperature are longer for stainless steels than for carbon steels - approximately 12  times.
 

Cold Working

SX 304 / 304L being extremely tough and ductile, are readily fabricated by old working.  Typical operations include bending, forming, deep drawing and upsetting

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