+44 (0) 1329 843355

[email protected]

Stainless Steel 303

Stainless 303 is the most easily machined of all the austenitic grades.
Austenitic steels are highly ductile and have a tendency to work harden and form build up edges on the cutting tools.
The addition of sulphur to the alloy improves its machinability but reduces its corrosion resistance. Nevertheless, it maintains good corrosion resistance in mildly corrosive environments and at temperatures up to about 60oC.

Stainless steel 303 is an austenitic steel. It was developed to give good machining properties by the addition of sulphur. The downside of adding sulphur, which is generally regarded as an impurity to be removed, is a reduction in corrosion resistance, in transverse ductility and notched impact toughness.

The presence of manganese will increase hardness and tensile strength but will further decrease ductility. If these modifications are important you should note that the chemical specifications detail a maximum % of manganese (2.0%) but no minimum. If you require the higher manganese content you will have to specify it.

It is widely used in:

  • Nuts and bolts
  • Aircraft fittings
  • Gears
  • Screws
  • Shafts
  • Electrical switchgear components

It is not recommended for applications that require welding.

As noted above the main uses are in:

  • Nuts and bolts
  • Aircraft fittings
  • Gears
  • Screws
  • Shafts
  • Electrical switchgear components
  • Bushings

However, it does have limitations that make it unsuitable for specific applications. Wild it has generally satisfactory corrosion resistance in mildly corrosive environments it is not suited for marine environments where the sulphur inclusions provide sites for the initiation of pitting corrosion and result in rapid deterioration.

In any chloride environment above 60oC 303 is liable to corrosion cracking.

As already noted, welding stainless 303 should be avoided, but if necessary it can be welded with 310 rods. It should be annealed after to dissolve precipitated carbides. 

It also tends to work harden and speeds should be adjusted accordingly.

Machinability

There is no doubt that the primary benefit of Stainless 303 is its machinability.

To get the most from this particular quality a few simple rules should be followed:

  • Keep cutting edges sharp. Without sharp tools, you will experience significant work hardening.
  • The direction of the cut - conventional milling will tend to result in more work hardening as opposed to "climb" milling
  • Keeping swarf clear of the work. Careful consideration should be given to chip size.
  • The low thermal conductivity of austenitic steel means coolants and lubricants must be used, often in large quantities.

Heat Resistance

303 stainless steel has good heat resistance up to 760oC in intermittent use. It maintains this resistance in continuous use up to 840oC.

See below for problems with carbide precipitation.

Machinability

There is no doubt that the primary benefit of Stainless 303 is its machinability.

To get the most from this particular quality a few simple rules should be followed:

  • Keep cutting edges sharp. Without sharp tools, you will experience significant work hardening.
  • The direction of the cut - conventional milling will tend to result in more work hardening as opposed to "climb" milling. Always ensure that the cut is deep enough to avoid the cutting edge gliding on the material.
  • Keeping swarf clear of the work. Careful consideration should be given to chip size.
  • The low thermal conductivity of austenitic steel means coolants and lubricants must be used, often in large quantities.

Heat Resistance

303 stainless steel has good heat resistance up to 760oC in intermittent use. It maintains this resistance in continuous use up to 840oC.

See below for problems with carbide precipitation.

The main constituents of 316 stainless steel - other than iron - are Chromium and Nickel. However, it is the addition of 2% Molybdenum that provides the increased corrosion resistance.

316 contains 16 - 18% Chromium (Cr). Chromium is the essential chemical in all stainless steel and it is that which forms the thin passive layer that makes the metal "stainless"

316 also contains 10-14% Nickel (Ni). This is added to make the Austenitic structure more stable at normal temperatures. 

The nickel also improves high-temperature oxidation resistance makes the steel resistant to stress corrosion cracking.

In addition, a number of other chemicals may be present but these are expressed as maximum permitted levels.

There is an alternative form of 303 - 303Se that employs Selenium in place of sulphur.

GradeCMnSiPSCrSeNiN
303 min.
max.
-
0.08
-
2.0
-
0.75
-
0.045
-
0.15
17.0
19.0


8.0
10.0
-
0.10
303Se min.
max.
-
0.030
-
2.0
-
0.75
-
0.045
-
0.030
17.0
19.0
0.15

8.0
10.0
-
0.10

Physical Properties

 

Metric

English

Density

7.9g/cc

0.2854lb/in3

               

Mechanical Properties

Hardness, Brinell

262


.

Tensile Strength, Ultimate

650 MPa

94275 psi

 

Tensile Strength, Yield

300 MPa

43511 psi

at 0.2% offset

Elongation at Break

45 %

45%

in 50 mm

Modulus of Elasticity

193 - 200 GPa

28000 - 29000 ksi

 

Poisson's Ratio

0.29

0.29

 

Charpy Impact

325 J

240 ft-lb

 

Shear Modulus

86 GPa

12500 ksi

 

Electrical Properties

Electrical Resistivity

7.2e-005 ohm-cm

7.2e-005 ohm-cm

at 20°C (68°F); 1.16E-04 at 650°C (1200°F)

Magnetic Permeability

1.008

1.008

at RT

Thermal Properties

CTE, linear 100°C

17.3 µm/m-°C


from 0-100°C

CTE, linear 315°C

17.8 µm/m-°C


at 0-315°C 

CTE, linear 538°C

18.4 µm/m-°C


at 0-538°C

Specific Heat Capacity

0.5 J/g-°C

0.12 BTU/lb-°F

from 0-100°C (32-212°F)

Thermal Conductivity

16.3 W/m-K

112 BTU-in/hr-ft²-°F

at 0-100°C, 21.5 W/m°C at 500°C

Melting Point

1455 °C

2650 °F

 

303 stainless is also available in a variant 303Se. This employs Selenium as opposed to Sulphur to achieve the better machining properties. 

The Selenium improves the forming performance, both hot and cold over the sulphur variant and also provides a smoother finish on the machined surface. In certain environments, this may also improve the resistance to corrosion.

Stainless 316, 316H, 316L Forms Available

  • Tube
  • Pipe
  • Fittings
  • Flanges
  • Special Sections
  • Sheet
  • Plate
  • Flat Bar
  • Round Bar
  • Hollow Bar
  • Angles
  • i Beam
  • U Channel

Translate to your language