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Which Is Better, 304 Or 304L?

Views: 1     Author: Wang     Publish Time: 2024-06-26      Origin: Site

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Differences Between AISI 304 and AISI 304L Steel

Grade 304 / 304L stainless steel has a minimum of 18% chromium and 8% nickel. The only difference between them is the carbon content. Type 304 has a maximum carbon of 0.07% .Type 304L has maximum carbon of 0.030 %. This range of carbon in the steels affects the corrosion resistance. 304 / 304L is available in sheet, sheet coil, plate, plate coil, round bar, processed flat bar and tubular products for further manufacturing.


The main difference between these two grades of steel lies in their respective carbon contents; SUS 304 contains more carbon than SUS 304L. The increased amount of carbon in regular SUS 304 gives it greater strength and hardness than SUS 304L but also makes it more susceptible to corrosion due to weld decay. Additionally, common grade SUS 304 is more complex and challenging to machine than its low-carbon counterpart.


Type 304 Stainless Steel

Type 304 is the most widely used austenitic stainless steel. It is also known as "18/8" stainless steel because of its composition, which includes 18% chromium and 8% nickel. Type 304 stainless steel has good forming and welding properties as well as strong corrosion resistance and strength. This kind of stainless steel also has good drawability. It can be formed into a variety of shapes and, in contrast to type 302 stainless, can be used without annealing, the heat treatment that softens metals. Common uses for type 304 stainless steel are found in the food industry. It's ideal for brewing, milk processing, and wine-making. It's also suitable for pipelines, yeast pans, fermentation vats, and storage tanks.


Type 304 grade stainless steel is also found in sinks, tabletops, coffee pots, refrigerators, stoves, utensils, and other cooking appliances. It can withstand corrosion that can be caused by various chemicals found in fruits, meat, and milk. Other areas of use include architecture, chemical containers, heat exchangers, mining equipment, as well as marine nuts, bolts, and screws. Type 304 is also used in mining and water filtration systems and in the dyeing industry.


Type 304L Stainless Steel

Type 304L stainless steel is an extra-low carbon version of the 304 steel alloy. The lower carbon content in 304L minimizes deleterious or harmful carbide precipitation as a result of welding. 304L can, therefore, be used "as welded" in severe corrosion environments, and it eliminates the need for annealing.


This grade has slightly lower mechanical properties than the standard 304 grade, but is still widely used thanks to its versatility. Like Type 304 stainless steel, it's commonly used in beer-brewing and wine-making, but also for purposes beyond the food industry such as in chemical containers, mining, and construction. It is ideal for use in metal parts such as nuts and bolts that are exposed to salt water.


Stainless Steel 304 and 304L Chemical Composition

The most basic is that the carbon content of 304L stainless steel is less than 0.03; while the carbon content of 304 stainless steel is less than 0.08. The only difference between the two alloys is the lower carbon content associated with SAE 304L (in which L actually denotes low carbon). Both alloys still contain the same amounts of chromium, nickel, and other trace elements.


The decreased carbon concentration of 304L reduces damaging or dangerous chromium carbide precipitation during welding. Therefore, grade 304L does not require annealing or any other heat treatment and can be used "as welded" in corrosive environments that would otherwise cause intergranular corrosion. Similar to Type 304 stainless steel, it is frequently employed in the production of beer brewing and wine-making, as well as for non-food applications such as chemical storage, mining, and construction.


Element

Type 304 (%)

Type 304L (%)

Carbon

0.08 max.

0.03 max.

Manganese

2.00 max.

2.00 max.

Phosphorus

0.045 max.

0.045 max.

Sulfur

0.03 max.

0.03 max.

Silicon

0.75 max.

0.75 max.

Chromium

18.00-20.00

18.00-20.00

Nickel

8.00-10.50

8.00-12.00

Nitrogen

0.10 max.

0.10 max.

Iron

Balance

Balance


What is the Difference Between 304 and 304L Stainless Steel?

Corrosion Resistance

Both 304 and 304L alloys have exhibited uniform corrosion resistance in most corrosive environments, though 304L showed a lower corrosion resistance in severely corrosive environments. Resistance to moderately aggressive organic acids is a result of the 9 to 11% nickel that the 304 alloys contain. Resistance to corrosion in oxidizing environments is a result of the 18 to 19% chromium that the 304 alloys contain. At times, grade 304L may show a lower corrosion rate than the higher carbon Alloy 304; otherwise, the 304 and 304L may be considered to perform uniformly in most corrosive environments. Grade 304L is preferred for use in environments sufficiently corrosive to cause intergranular corrosion of welds and heat-affected zones on susceptible alloys


Heat Resistance

304 has good oxidation resistance in intermittent service to 1600°F and in continuous service to 1690°F. Continuous use of 304 in the 800-1580°F range is not recommended if subsequent aqueous corrosion resistance is important. Grade 304L is more resistant to carbide precipitation and can be heated into the above temperature range.


Mechanical Properties

Due to lower carbon content, SAE 304L has a lower tensile strength of 85 KSI compared to SAE 304, which is approx 90 KSI. Additionally, the yield strength of SAE 304L is approx. 35 KSI, while SAE 304 offers 42 KSI. From this, we can conclude that the 304L offers less in terms of tensile and yield strength, despite their comparable densities. 304L stainless steel is a steel type obtained by reducing the carbon content of 304 to less than 0.03%,so that,304L stainless steel can be suppressed between 500 and 900 degrees Celsius. But 304 stainless steel tensile strength is higher, 304 ≧525MPa; 304L≧485MPa.


Welding Properties

Due to its lower carbon content, alloy 304L is marginally easier to weld, but its primary advantage is lesser carbide precipitation, which results in lower corrosion at grain boundaries. Fusion welding performance for type 304 stainless steel is excellent both with and without fillers. Recommended filler rods and electrodes for stainless steel 304 is grade 308 stainless steel. For 304L the recommended filler is 308L. Heavy welded sections may require post-weld annealing. This step is not required for 304L. Grade 321 may be used if post-weld heat treatment is not possible.


Stainless steel 304 and 304L in application areas

304 stainless steel and 304L stainless steel have similar uses, but in some special applications, their uses may be different.

304 stainless steel is the most widely used chromium-nickel stainless steel. As a widely used steel, it has good corrosion resistance, heat resistance, low temperature strength and mechanical properties; it has good hot workability such as stamping and bending, and has no heat treatment. Hardening phenomenon (use temperature -196 ° C ~ 800 ° C). Corrosion-resistant in the atmosphere, if it is an industrial atmosphere or a heavily polluted area, it needs to be cleaned in time to avoid corrosion. Suitable for food processing, storage and transportation. Has good processability and weldability. Plate heat exchangers, corrugated pipes, household goods (category 1 and 2 tableware, cabinets, indoor pipelines, water heaters, boilers, bathtubs), auto parts (windshield wipers, mufflers, molded products), medical appliances, building materials, chemicals, food industry , agriculture, ship parts, etc.


Generally speaking, 304L stainless steel is used for welding components and occasions that require better corrosion resistance, such as chemical industry, medical equipment, food processing and marine equipment, etc.


As a whole, 304L stainless steel characteristics are similar to those of 304 stainless steel.But 304L stainless steel is more widely used in industries such as sugar refining and brewing, because these industries have high requirements for corrosion resistance and wear resistance of equipment. 304L stainless steel is not easy to generate magnetism, so it has advantages in the occasions sensitive to magnetism, such as electronic equipment and medical equipment.


Conclusion

At JN Alloy, we pride ourselves on maintaining a robust inventory of 304/304L stainless steel, ensuring that we can meet your needs promptly and efficiently. Whether you’re looking for 304/304L stainless steel coils or sheets, our extensive stock positions us to offer competitive advantages in availability and pricing. For more detailed information about our products and to explore how we can service your specific requirements, please click to learn more about our 304 stainless steel coil and 304/304L stainless steel sheet offerings and how we can help drive your businesses forward.

JN Alloy is a distributor and product manufacturer of stainless steel, duplex steel, and nickel.
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