Two popular stainless steel grades are 303 and 304. Stainless steel is widely used in kitchen accessories, surgical tools, automobile bodies, and sculptures because of its strength and anti-corrosive properties. Because of its stainless properties, it is not only corrosion resistant but also aesthetically pleasing and thus popular. However, not all stainless steel is the same. Stainless steel, like other types of steel, is available in a variety of grades. So, let’s take a closer look at the differences between 303 and 304 stainless steel.

What is 303 stainless steel?

Grade 303 stainless steel is available in plates, hex bars, round bars, square bars, and rolled flat bars. It is a nonmagnetic, austenitic metal that cannot be hardened by heat treatment.

Although this stainless steel grade is resistant to mildly corrosive elements, it will pit and rust in a marine environment due to the chloride in the salt. This steel will crack in chloride environments above 140 o F. Grade 303 stainless steel, on the other hand, will resist oxidation in temperatures as high as 1700o F.

What is 304 stainless steel?

Grade 304 stainless steel is the most commonly used austenitic stainless steel grade. (Austenitic steels contain a high percentage of nickel and chromium.) 304 stainless steel sheet, 304 stainless steel bar, 304 stainless steel plate, and 304 stainless steel tube are all available.

As a result, austenitic steels are extremely resistant to corrosion, not only from the weather but also from acids. These steels, however, have one flaw: chloride. Ions in sodium chloride, such as that found on the coast, will corrode 304 stainless steel.

Difference Between 303 and 304 Stainless steel

Chemical composition 

303 stainless steel

303 stainless steel is upgraded with iron, chromium (17-19%), nickel (8-10%), manganese (2%), phosphorus (0.2%), carbon (0.15%), and sulphur (0.15% minimum). Because this grade of steel is classified based on its physical properties rather than its chemical properties, the exact percentages may vary slightly.

304 stainless steel

This grade has a nickel content ranging from 8% to 10.5% and a chromium content ranging from 18% to 20%. The majority of grade 304 stainless steel is 18/8, which means it contains 18% chromium and 8% nickel. Carbon, silicon, and manganese are also present.

Strength 

303 stainless steel

The strength of steel is defined as its ability to withstand force without breaking or permanently deforming.

The point at which steel deforms under stress is identified by yield strength. Metals experts use a series of experiments to determine yield strength, which is expressed in megapascals (MPa) or N/m2. The yield strength of grade 303 stainless steel is approximately 415 MPa.

Tensile strength identifies the stress point at which steel breaks. It is calculated by performing an experiment on a sample and then dividing the peak force by the cross-sectional area. Grade 303 stainless steel has a tensile strength of around 690 MPa. This steel will elongate by 40% before breaking.

304 stainless steel

Grade 304 stainless steel is one of the most powerful, long-lasting, and high-quality steel grades available. It has a tensile strength of 520 to 720 MPa d a yield strength of about 215 MPa. It can stretch up to 70% before breaking.

Hardening, welding and machining

303 stainless steel.

Yes, heat can be used to harden grade 303 stainless steel. It must be solution treated by heating it to temperatures ranging from 1850o F to 2048o F and then rapidly cooling it. As a result, if hardened, it will lose some of its ductility.

This grade of steel should not be welded due to its relatively high sulfur content, but it can be welded using alloy 310 electrodes.

However, grade 303 stainless steel is simple to machine. It can be cut with a sharp, light edge by using a lot of coolants and lubricants. As a result, this grade is an excellent choice for parts that require extensive machining.

304 stainless steel

Grade 304 stainless steel, like grade 303, cannot be hardened by heat treatment. It must also be solution treated by heating it to temperatures ranging from 1850 oF to 2048 oF.

Grade 304 stainless steel, on the other hand, is simple to weld. It can even be welded without fillers, but if fillers are used, they should be made of grade 308 stainless steel. Heavy-welded sections may require post-welding solution treatment.

The machinability of grade 304 stainless steel is excellent. It, like grade 303, must be cut with a sharp blade, using light cuts and plenty of lubricants and coolants.

Durability:

Grade 303 is less corrosion resistant than grade 304 due to its chemical composition, which makes it more machinable. Even so, grade 304 will corrode in a chloride-rich environment.

Usability:

Grade 303 steel is frequently used to craft fine, intricate pieces such as screws, bolts, nuts, and shafts due to its ease of machining. Grade 304, which is easier to weld, is typically used in automobiles or construction materials.

Cost:

Both grades of steel are reasonably priced. However, grade 303 is typically sold at a slightly higher price.

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Conclusion

Choosing between 303 and 304 stainless steel boils down to your desired application. If you need a material that has a higher corrosion resistance, then 304 stainless steel is the way to go since it has superior corrosion resistance to most chemicals and can even withstand moderate amounts of saltwater exposure. However, if you require high machinability and low cost, then 303 stainless steel might be the best option for you. Ultimately, the decision depends on what type of performance characteristics are desired in the application. Knowing the key differences between 303 and 304 stainless steels can help make selecting material easier and faster for job shops or anyone seeking to find the right structured alloy for their project.