Stainless Steel 303

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300 series Stainless Steel : 253MA,SUS301,SUS303,sus303cu,SUS304,SUS304L,SUS304H,SUS309,SUS310,SUS316,SUS316L,SUS316Ti,SUS317,SUS321,SUS347.

400 series Stainless Steel : SUS403,SUS409,SUS410,SUS416,SUS420,SUS420J2,SUS430,SUS430F,SUS431,SUS440C, F6NM, SUS446,SUS630,SUS660, 15-5PH,17-4PH,904L )

Duplex Stainless steel : FERRALIUM 255, S31803, S32750, S32760 , S31254 , S329J4L 

Nitronic 30, 50 & 60


SS 303 , UNS S30300, 1.4305, sus 303

ss 303 Chemical Composition
Fe,  <0.15% C,  17-19% Cr,  8-10% Ni,  <2% Mn,  <1% Si,  <0.2% P,  >0.15%S

What is sus303 material?

sus303 represents the optimum in machinability among the austenitic stainless steels. It is primarily used when production involves extensive machining in automatic screw machines.
The sulphur addition which is responsible for the improved machining and galling characteristics of SS 303 lowers its corrosion resistance to below that of SS 304. As for other austenitic grades the structure gives sus303 excellent toughness, although the sulphur in sus303 reduces its toughness slightly.

Physical Properties

Grade Density (kg/m3) Elastic Modulus (GPa) Mean Coefficient of Thermal Expansion (μm/m/°C) Thermal Conductivity (W/m.K) Specific Heat 0-100°C (J/kg.K) Electrical Resistivity (nΩ.m)
0-100°C 0-315°C 0-538°C at 100°C at 500°C
303 8027 193 17.3 17.8 18.4 16.3 21.5 500 720

Possible Alternative Grades

Grade Why it might be chosen instead of 303
ss 304 Better corrosion resistance, formability or weldability are needed, at the expense of lower machinability.
ss 316 Higher resistance to pitting and crevice corrosion is required, in chloride environments. A lower machinability can be accepted.
ss 416 Even higher machinability than 303 is needed, and a lower corrosion resistance can be tolerated.

Or hardening by thermal treatment is required, while maintaining a high machinability.

Is 303 stainless corrosion resistance?

Good resistance to mildly corrosive atmospheres, but significantly less than sus 304 due to the sulphur addition; the sulphide inclusions act as pit initiation sites. sus 303 should not be exposed to marine or other similar environments, as these will result in rapid pitting corrosion. Because the sulphide inclusions in sus303 are primarily aligned along the rolling direction the corrosion resistance is particularly reduced in cross-sections.

Grade 303, like other common austenitic stainless steels, is subject to stress corrosion cracking in chloride containing environments above about 60°C.

Heat Resistance

Good oxidation resistance in intermittent service to 760°C and in continuous service to 870°C. Continuous use in 425-860°C range not usually recommended due to carbide precipitation – ss303 usually does not have a low carbon content so is susceptible to sensitisation.


As well as reducing the corrosion resistance, the sulphur additions in ss303 also result in poor weldability and reduced formability compared to Grade ss304. Sharp bends should not be attempted in ss303. A practical compromise alternative may be a sus304 Ugima Improved Machinability grade – this does not machine as readily as sus303, but does offer better formability (as well as better weldability and corrosion resistance).

Is 303 stainless steel heat treatable?

Solution Treatment (Annealing) – Heat to 1010-1120°C and cool rapidly. This grade cannot be hardened by thermal treatment.


Not generally recommended but, if unavoidable and a lower strength can be tolerated, use Ss 308L or SS 309 electrodes. AS 1554.6 does not pre-qualify welding of SS 303. Welds must be annealed for maximum corrosion resistance.

What is the difference between 303 and 304 stainless steel?
While 303 stainless steel still has strong corrosion resistance, for an added boost, 304 stainless steel is recommended. 304 stainless steel contains a minimum of 18% chromium and 8% nickel which gives its alternate name 18/8 stainless steel. 304 stainless steel contains chromium-nickel content and low carbon
What is the difference between SS 202 and ss304?
The major differences between 202 and 304 stainless steels are in the nickel and chromium contents. 202 has 16-18% chromium and 0.5-4.0% nickel, whilst 304 has 18-20% chromium and 8-10.5% nickel. … Both are austenitic steels and are essentially non-magnetic, but will become temporarily magnetic by working them.