In terms of material selection of stainless steel products, the selection and use of materials are very important. While laymen are generally familiar with the material term stainless steel, many are unfamiliar with the many types of stainless steel, such as 301 stainless steel or 304 stainless steel. What is the difference between these two popular stainless steel alloys? Below are some of the main differences between the two materials.
While both 301 and 304 stainless steels use iron as a major component, there are several key differences in the chemical composition of the two alloys, as shown in the table above, the endcap values for many compounds in both steel alloys are the same. However, grade 304 stainless steel gains more chromium and nickel than grade 301. This tends to make grade 304 stainless steel more expensive than grade 301.
Most stainless steel alloys have good or excellent corrosion resistance under normal conditions. Stainless steel alloys tend to have a strong, thin oxide layer that prevents rusting, hence the name stainless steel.
In mildly corrosive environments at normal ambient temperatures, there is little difference in corrosion resistance between grades 301 and 304 stainless steel. In general, 301 grade 304 stainless steel is slightly less resistant to corrosion because the 301 alloy has a lower chromium content and a higher carbon content.
At higher temperatures, the difference in corrosion resistance is more pronounced.
For example, if a piece of 301 stainless steel is being welded or laser cut, the heat affected zone will show signs of corrosion that are more susceptible to corrosion than 304 alloys treated in the same way. This is because of the precipitation of chromium carbide, which depletes the heat-affected zone of chromium.
Another key difference between the two stainless steels is the stress that each can withstand before mechanical failure occurs.
Grade 301 stainless steel with a higher carbon content (0.15% compared to 0.08 wt% for 304) can withstand mechanical forces better. Grade 301 stainless steel may require up to 120 ksi (kilo pounds per square inch) at room temperature.
304 stainless steel can only withstand 90ksi before experiencing mechanical failure. This means that, at room temperature, a basket made from grade 301 stainless steel is subjected to 33 percent more stress than a similar basket made from grade 304 alloy.
Stainless steel is named for its ability to resist rust due to the interaction between its alloy composition and the environment to which it is exposed. Many types of stainless steel are used for various purposes and many overlap. All stainless steels contain at least 10% chromium.
304 stainless steel is the most widely used austenitic stainless steel material, and it is also known as "18-8" stainless steel due to its composition, which contains 18% chromium and 8% nickel.
304 stainless steel has good forming and welding properties, as well as strong corrosion resistance and strength. It also has good drawability. It can be formed into a variety of shapes and, as opposed to Type 302 stainless steel, can be used without annealing. Common uses of 304 stainless steel in the food industry. Suitable for brewing, milk processing and winemaking, as well as pipes, yeast trays, fermentation tanks and storage tanks.
304 stainless steel is also found in sinks, table tops, coffee makers, refrigerators, stoves and various appliances and other cooking appliances. It can withstand corrosion caused by various chemicals found in fruit, meat and milk. Other areas of use include construction, chemical vessels, heat exchangers, mining equipment and marine nuts, bolts and screws. Type 304 is also used in mining and water filtration systems and the dyeing industry.
304L stainless steel is an ultra-low carbon version of the 304 steel alloy. The lower carbon content in 304L minimizes harmful carbide precipitation from welding. Therefore, 304L can be "welded" in severe corrosive environments and does not require annealing. This grade has slightly lower mechanical properties than the standard 304 grade, but is widely used due to its versatility. Like Type 304 stainless steel, it is commonly used in beer brewing and winemaking, but also for purposes outside the food industry, such as chemical containers, mining and construction. Ideal for metal parts such as nuts and bolts that will be exposed to salt water.
