What is the difference between 204 and 304 stainless steel?
Both stainless steel grade 204 as well as grade 304 fall under the austenitic class. Which means they have an FCC or face centered cubic crystalline microstructure. The main difference between both these grades is the distribution of content in their chemistry. Grades are a means of creating distinctions between several stainless steel alloys on the basis of their chemistry as well as their behavior. In the case of grade 204, the content of nickel is significantly lower, standing at about 2%, in comparison to the 8% included in stainless steel grade 304. Though the content of chromium remains similar, the content of manganese in grade 204 is higher. While 6.5% - 8.5% manganese is added to grade 204, the content of manganese in the other austenitic stainless steel amounts to a max of 2%. The inclusion of manganese in grade 204 aids in stabilizing the austenite phase, as the absence of a higher content of nickel, destabilizes austenite. And unlike grade 304, which contains no molybdenum in its alloy, grade 204 contains the addition of molybdenum and a higher content of silicon. The combination of molybdenum and silicon in any austenitic stainless steel alloy aids in improving the resistance of the metal to corrosion from highly corrosive sulfuric acid solutions. Moreover, grade 204 also contains the addition of copper between 2% to 3.5%.
How to Identify stainless steel 204 and 304?
Since the elemental composition is similar for both alloys, they tend to appear similar as well. However, the most common identification method is to get MTR or mill test reports. These mill test reports are inclusive of the chemical composition, physical, as well as mechanical characteristics of both the alloys. Yet, another technique to distinguish the two is by using X-ray fluorescence. Though this technique is fast and non-destructive, the instruments used here tend to be quite costly. The X-ray fluorescence or as also known as XRF is a technique where the emission of characteristic "secondary" or fluorescent X-rays from a component, which has been stimulated by bombarding it with high-energy. The energy source used to identify the elemental composition could be either X-rays or gamma rays.
Grade 204 vs 304 corrosion resistance
In environments that contain less corrosive media, grade 204 is stainless steel that delivers a performance similar to that of grade 304. This is why, being an economical option, the use of grade 204 is well suited to indoor applications at ambient temperature. The alloy’s chemical composition makes it unsuitable for grade 204 to be used in environments that contain Chloride ions. Under typical atmospheric or water based conditions, grade 204 will not rust.
The difference in SS 204 and 304 material price per kg
Since the content of nickel is kept to a minimum of 2% in its alloy, the price of grade 204 is much lower than 304. Commodity traded metals such as nickel tend to have fluctuating rates, which in turn soar the price of the element to be used as an alloyant in the stainless steel. The higher the inclusion of nickel, the more there is an increase in the price of the metal. This is why the higher nickel containing grade 304 costs more than grade 204.
204 and 304 stainless steel weldability
Grade 204 is a reasonably weldable alloy. However, due to the higher content of carbon, i.e. 0.10%, this stainless steel tends to be sensitive to intergranular corrosion. In particular, the alloy is affected in the heat affected zone or the HAZ, where the thickness of the material exceeds 6mm. This is why most manufacturers recommend a thorough post-weld cleaning. A high quality weld is further achieved by the crucial application of passivation on the alloy. Most conventional methods could be used in the welding of grade 304. Getting a dual certified alloy i.e. grade 304/304L could improve weldability.
Other relevant grades
204 stainless steel chemical composition
|ACX 23||<=0.10||<=2.00||6.50-8.50||<=0.040||<=0.015||16.00-18.00||<=2.00||<=1.00||-||2.00-3.50||N(ppm) 1500-3000|
Density of 204 stainless steel
Does 204 stainless steel rust?
204 stainless steel forms
Sheet and Plate
AISI 204 CU Stainless Steel equipment
|Euronorm||Nom.||AISI / ASTM||UNS|
Physical Property of 204 stainless steel
|Thermal Expansion||17 x10^-6 /K|
|Modulus of Elasticity||200 GPa|
|Thermal Conductivity||15 W/m.K|
SS 204 Mechanical Properties
|Proof Stress||310 Min MPa|
|Tensile Strength||655 Min MPa|
|Elongation A50 mm||40 min %|
AISI 204 Weldability
- Reasonable, if thickness exceeds 6mm then sensitive to intergranular corrosion
- Post-weld passivation and cleaning is critical.
S20400 Stainless Steel Heat Resistance
Oxidation resistance is almost same to 1.4310 (301) Grade up to 840°C.
|AISI 201 stainless steel||UNS20100 / EN1.4372 / JIS SUS 201|
|AISI 201L stainless steel||UNS20103 / EN1.4371|
|AISI 202 stainless steel||UNS20200 / EN1.4373|
|AISI 204C stainless steel||UNS20400 / EN1.4597|
AISI 304 chemical composition
|Ni||8 – 11|
|Cr||18 – 20|
Mechanical properties of Stainless steel 304
|Rockwell B (HR B) max.||92|
|Brinell (HB) max.||201|
|Tensile Strength min. (MPa)||515|
|Yield Stress 0.2% Proof min. (MPa)||205|
|Elongation min. (% in 50mm)||40|
Stainless Steel 304 equivalent standard specification
|AISI/ SUS||UNS||WERKSTOFF NR.||BS||GOST||JIS||EN||AFNOR||SS|
|SS 304||S30400||1.4301||304S31||08Х18Н10||SUS 304||X5CrNi18-10||Z7CN18‐09||2332|
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