Difference between 302 and 304 Stainless Steel

What is the difference between 302 and 304 stainless steel?

Like grade 304, alloy 302 is an austenitic stainless steel alloy. Therefore, they share certain elements, which is what gives them the same austenitic microstructure. However, they fall into different grades solely because of the modification of the constitution of the elements. For instance, the content of carbon in grade 302 is a max of 0.15% carbon, with a max value of 0.8% in stainless steel 304. The lower content of carbon in austenitic steel 304 effectively lowers the risk of carbide precipitation, which occurs in alloys that have a higher percentage of carbon in their alloys. The main benefit of using grade 302 is that this particular stainless steel alloy demonstrates good resistance to solvents, acids as well as resistance to several chemicals.

The price difference between 302 and 304

The chemistry of the alloys i.e. austenitic stainless steel grade 302 and grade 304 are almost similar. The only difference in their chemistry is the higher content of carbon, which gives grade 304 better hardness. Hence, the alloying cost for both stainless steels would also work out to be in the same or similar range.

302 and 304 stainless steel welding

It is easy to weld stainless steel grade 304 using almost all conventional processes. Upon welding this alloy it is necessary to anneal the alloy. The performance of a post weld annealing treatment aids in the restoration of the material’s corrosion resistance properties. Usually, welding without the use of an annealing treatment causes loss in corrosion resistance properties by sensitization to intergranular corrosion. During this stage, chromium carbide precipitates are formed in the grain boundaries in the weld HAZ or heat-affected zone, thereby promoting corrosion. However, because the content of carbon is lower in comparison to grade 302, the chances of intergranular corrosion are lower. 302 stainless steel is readily welded using techniques such as shielded fusion welding and resistance welding process. The use of Oxyacetylene welding is prohibited simply because of the risk of carbon pick up in the weld. This alloy requires the use of filler metals. And so either AWS E/ER308 or 312 may be used as filler metals during welding. Similar to grade 304, it is mandatory to conduct a Post weld annealing treatment. This treatment is required, especially because the present chromium carbide needs to be dissolved. Dissolution of chromium carbide from the alloy is what permits maximum resistance to inter-granular attack. To maintain Corrosion Resistance, 302 stainless steel suppliers recommend a straight argon welding process.

302 and 304 stainless steel melting point

Just as most alloys do not have a particular melting point, both these austenitic stainless steels have a melting range. This is because an alloy consists of an assembly of several elements or metals, whose individual melting points vary. In the case of alloys, the melting point, or what is referred to as a melting range is when the solid metal forms a liquid sludge. Since the basic chemistry of both grades 304 and 302 are similar, the alloys have an overlap in their melting point. The melting range of stainless steel 302 is between a temperature range of 2550° F - 2590° F. And in the temperature range that melts austenitic stainless steel 304 is between 2,550 °F – 2,650 °F.

SS 304 grade chemical composition

AISI 304 304N 304LN
Ni 8 – 11 8 – 11 8 – 11
Fe Balance
Cr 18 – 20 18 – 20 18 – 20
C 0.08 max 0.08 max 0.035 max
Si 0.75 max 0.75 max 0.75 max
Mn 2 max 2 max 2 max
P 0.040 max 0.040 max 0.040 max
S 0.030 max 0.030 max 0.030 max
N 0.10 – 0.16 0.10 – 0.16

Stainless steel 304 mechanical properties

Stainless Steel Gr. 304
Rockwell B (HR B) max. 92
Brinell (HB) max. 201
Tensile Strength min. (MPa) 515
Yield Strength 0.2% Proof min. (MPa) 205
Elongation min. (% in 50mm) 40
Hardness -

SS 304 equivalent grades and standard

AISI/ SUS WERKSTOFF NR. UNS BS EN JIS AFNOR GOST SS
Grade GERMAN USA BRITISH EUROPE JAPAN RUSSIAN RUSSIAN SWEDISH
SS 304 1.4301 S30400 304S31 X5CrNi18-10 SUS 304 Z7CN18‐09 08Х18Н10 2332

Chemical composition of SS 302 grade

Element Content (%)
Chromium, Cr 17-19
Nickel, Ni 8 - 10
Manganese, Mn 2
Silicon, Si 1.00
Carbon, C 0.15
Sulfur, S 0.03
Phosphorous, P 0.045

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