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When choosing stainless steel that has to bear corrosive atmospheres, austenitic stainless steel is recommendable. Owning excellent mechanical properties, the high amounts of chromium and nickel in austenitic stainless steels also offer distinguished resistance of corrosion. Besides, many austenitic stainless steels are formable and weldable.
Two of the most commonly used types of austenitic stainless steel are types 304 and 316. This blog will show the difference between 316 and 304 stainless steel to decide which type is proper for your project. Follow up to discover the difference between 304 vs. 316 stainless steel.
304 stainless steel is the most ordinary stainless steel. The steel consists of both nickel (between 8% and 10.5%) and chromium (between 18% and 20%) metals as the primary non-iron elements. 304 is austenitic stainless steel. It is less thermally conductive and electrically than carbon steel and is substantially non-magnetic. It has a higher resistance of corrosion than regular steel and is vastly used because of the softening in which it is formed into many different shapes.
The composition was formulated by W. H. Hatfield at Firth-Vickers and was sold under the marketing name “Staybrite 18/8” in 1924.
SAE International outlines it as a component of its SAE steel levels. It is widely noted as A2 stainless steel in conformity with ISO 3506 for fasteners outside the U.S. It is known as 18/8 stainless steel in the trading cookware field. It is UNS S30400, in the unified-numbering system. The corresponding Japanese type of this substance is SUS304. It is also laid down in European standard1.4301.
Type 316 Stainless Steel: The second most ordinary austenitic stainless steel is Grade 316. The supplement of 2% molybdenum offers higher acid resistance and pinpointed corrosion caused by chloride ions. Low-carbon editions, for instance, 316L or 304L, have carbon substances below 0.03% and are used to prevent corrosion problems caused by soldering.
Stainless steel 304 and 316 also match the following standard specifications and designations:
|Grade||Stainless Steel 304||Stainless Steel 316|
|BS||304S15 / 304S16 / 304S31||316S31|
Both Stainless steel grades, 304 and 316, have its components; let us see the average elements’ differences.
|Element||Stainless Steel 304||Stainless Steel 316|
|Carbon (C), %||Max 0.08||Max 0.08|
|Chromium (Cr), %||18.0~20.0||16.0~18.0|
|Manganese (Mn), %||Max 2.0||Max 2.0|
|Nickel (Ni), %||8.0~10.5||10.0~140.|
|Phosphorus (P), %||Max 0.045||Max 0.045|
|Sulphur (S), %||Min 0.03||Max 0.03|
|Silicon (Si), %||1.00||1.00|
|Molybdenum (Mo), %||/||2.00~3.00|
|Iron (Fe), %||Balance||Balance|
The role of these metal elements:
Since Molybdenum (Mo) is included in SS316, Molybdenum can develop the rallying resistance and is, for that reason, more corrosion resistance than SS304. So SS316 more convenient to chemical plants and Offshore buildings where vastly corrosive environments.
To know the physical properties for both 304 vs. 316 stainless steel alloys, look at the following table.
|Property||Stainless Steel 304||Stainless Steel 316|
|Density||8.00g / cm³||8.00g / cm³|
|Melting Point||1450 °C||1400 °C|
|Modulus of Elasticity||193 GPA||193 GPA|
|Electrical Resistivity||0.72 x 10-6 Ω.m||0.74 x 10-6 Ω.m|
|Thermal Conductivity||16.2 W/m.K||16.3 W/m.K|
|Thermal Expansion||17.2 x 10-6/K||15.9 x 10-6/K|
Stainless steel grade 304 has excellent resistance to oxidation in stop-go service up to 870°C and progressing service to 925°C. Yet, uninterrupted use at 425-860°C is not recommendable if the resistance of corrosion in water is needed. On this occasion, 304L is recommendable due to its resistance to carbide sedimentation.
Where extreme strength is necessary at above 500°C and up to 800°C temperatures, type 304H is recommended. This material will maintain aqueous corrosion resistance.
On the other hand, Stainless steel 316 has excellent resistance to oxidation in stop-go service to 870°C and ongoing service to 925°C. Yet, uninterrupted use at 425-860°C is not recommendable if the resistance of corrosion in water is essential. On this occasion, 316L is recommendable due to its resistance to carbide sedimentation.
Where extreme strength is needed at above 500°C temperatures, type 316H is recommendable.
Fabrication of all stainless steels should be performed only with tools devoted to stainless steel substances. Tooling and work surfaces have to be cleaned entirely before use. This circumspection is essential to prevent cross-contamination of stainless steel by corroded metals. That may discolor the fabricated product’s surface.
Stainless steel 304 efficiently work strengthens. Fabrication methods, including cold working, may demand a medium annealing stage to lessen work hardening and sidestep tearing or cracking. After fabrication, a complete annealing functioning should be employed to optimize corrosion resistance and reduce internal stresses.
As stainless steel 316 quickly brakes or roll, constituted into a diversity of parts. It is also appropriate to heading, stamping, and drawing, but post-work annealing is recommendable to ease internal stresses.
Cold working will increase both hardness and strength—stainless steel 316.
Fabrication procedures, like forging, which include hot working, must occur after consistent heating to 1149-1260°C. The fabricated elements should then be fast cooled to assure maximum resistance of corrosion.
All usual hot working processes can be conducted on Stainless steel 316. Hot-working must be prevented under 927°C. The perfect temperature scope for hot working is 1149-1260°C. Post-work annealing is recommendable to assure maximum corrosion resistance.
There is no way to harden 304 by heat treatment. Annealing or solution treatment can be done after heating to 1010-1120°C, by quick cooling.
The same as 304, stainless steel 316 also cannot be hardened by heat treatment. Annealing or solution treatment can be done after heating to 1010-1120°C, by quick cooling.
Stainless steel 304 and 316 have excellent machinability. Enhancing machining can be done by the use of the following rules:
Fusion welding performance for both Stainless steel 304 and 316 is excellent both with and with no fillers.
The recommended filler electrodes and rods for stainless steel 304 type 308 stainless steel. Heavy welded sections may need post-weld annealing.
Recommended filler electrodes and rods for Stainless steel 316 and 316L are the same as the foundation metal, 316, and 316L. Heavy welded segments may require post-weld annealing. In massive section welds, grade 316Ti can be used as a substitute to Stainless steel 316.
Most stainless steel handed down around the world is Grade 304. It offers the model corrosion resistance, strength, easy maintenance, and formability, for which stainless is known.
While 316 comes in second in the quantities sold, it provides highly superior resistant oh corrosion to acids and chlorides. This makes it widespread for a vast range of environments—including:
These higher resistances also help to permit you to sweep your stainless more frequently using stronger detergents and cleansers with slightly worry of harm or affecting the look of the stainless steel and have the guesswork out of cleaning.
This drives 316 to be an ideal upgrade for atmospheres with strict cleanliness and hygiene standards.
With the benefits provided by 316 stainless steel, you might ask why 304 till the most popular.
If you’re hesitating which to choose, think about these common uses for the two grades:
304 Stainless Steel
316 Stainless Steel
You may need to check visually, find the differences between 304 and 316, and follow up to find the best ways to do correctly.
Here, you will find the most common questions, that may come to your mind, when thinking about the differences between 304 and 316 stainless steel. Follow up.
Type 304 is much accessible to machining than 316 stainless steel. Grade 304 stainless steel is not only easier to machining but easier to clean, too. That's the reason why it has so.
Many various finishes. That is also why people use it on visible to the public surfaces. Think of stainless serving trays and car fenders and.
Besides the fact that it's hard to machine, type 316 needs special cut tools, it plays well toward pitting, but it is not so formable. That shows why it's devoted to applications that not all the types of stainless steel can handle.
Based on the density, the higher density stainless steel has, the more weight it will get, that is why 304 stainless steel material is somewhat lighter than 316 stainless steel upon the same condition.
304 stainless is cheaper than 316, another added reason for its widespread use and popularity. Stainless 316 is expensive because it offers a higher resistance of corrosion, especially against chlorinated and chloride solutions.
303 has a lower corrosion resistance than the 304. Like all austenitic steels, in nature, 304 is non-magnetic, and it also offers low electrical and heating conductivity. It also is distinguished by its higher resistance of corrosion than other stainless-steel grades.
Type 316 is stronger than type 304. In the marine atmosphere, type 316 is the main used stainless, except in the case fasteners and other subjects where wear resistance and strength are needed, then Type 304 (18-8) is commonly used.
The basic answer is 304 consists of 8% nickel and 18% chromium, while 316 consists of 10% nickel,16% chromium, and 2% molybdenum. The added molybdenum helps resist corrosion to chlorides, so 316 has better corrosion resistance than 304.
Grade 304 stainless steel is famous in the food field because of its resistance to corrosion and oxidization. The chromium saves the product from rust or oxidization; however, the nickel content protects the food cans from corrosion. The higher the nickel content in stainless steel, the more resistant to corrosion it will get.
Stainless steel 304 vs. 316, which is better? Well, it depends on the application and needs.
The mechanical properties of both steel sheets are almost the same, and both have similar makeup material. Still, type 316 has more nickel than type 304 that helps 316 types resist more against chlorinated solutions such as seawater and de-icing salts.
For industrial use and commercial appliances, type 316 is better than 314 for its increased corrosion resistance. It has more resistance to chemicals and is considered superior to type 304 when it comes to exposure in salts and other chlorinated solutions. For marine applications, type 316 is ideal because type salt in the sea can damage the oxide layer of 304 types, leading to rust. That is the main reason why type 316 is a bit expensive as compared to type 304.
On the other hand, 304 types have a melting point higher than type 316 (50 to 100 °F higher than 316 types). 304 type is commonly used for residential appliances and indoor architectural hardware. Type 304 is better for the applications where chlorinated solutions are not a concern as it is less expensive than type 316.
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