Stainless Steel 303 - Alloy Composition

Stainless steel type 303 is part of a family of stainless steel alloys (301, 302, 303, 304, 316, 347). Alloy 303 is a non-magnetic, austenitic stainless steel that is not hardenable by heat treatment. It is the free machining modification of the basic 18% chromium / 8% nickel stainless steel. Alloy 303 was specially designed to exhibit improved machinability while maintaining good mechanical and corrosion resistant properties Due to the presence of sulfur in the steel composition, Alloy 303 is the most readily machinable austenitic stainless steel; however, the sulfur addition does lower Alloy 303’s corrosion resistance to below that of Alloy 304. Like other austenitic grades, 303 shows excellent toughness, the lower sulfur content does reduce this slightly

 Nominal Composition in Percent:

            Ni                     9.00

            Cr                    18.00

            Fe                  Balance

            Si                    1.00

            Mn                   2.00

            C                     0.120

            P                     0.040

            S                     0.030

UNS Number:

S30300

Other Standard Specifications:

300 Series—austenitic chromium-nickel alloys

  • Type 301—highly ductile, for formed products. Also hardens rapidly during mechanical working. Good weldability. Better wear resistance and fatigue strength than 304.
  • Type 302—same corrosion resistance as 304, with slightly higher strength due to added carbon.
  • Type 303—free machining version of 304 via addition of sulfur and phosphorus. Also referred to as "A1" in accordance with ISO 3506.
  • Type 304—the most common grade; the classic 18/8 (18% chromium, 8% nickel) stainless steel. Outside of the US it is commonly known as "A2 stainless steel", in accordance with ISO 3506 (not to be confused with A2 tool steel).
  • Type 316—the second most common grade (after 304); for food and surgical stainless steel uses; alloy addition of molybdenum prevents specific forms of corrosion. It is also known as marine grade stainless steel due to its increased resistance to chloride corrosion compared to type 304. 316 is often used for building nuclear reprocessing plants.

Density:

8.03 g/cm3 (0.290 lbs/in2)

 

Exceptional Properties:

Toughness, durability, corrosion resistance