Stainless steel has penetrated into all aspects of everyone's life, 304 stainless steel as a food grade stainless steel is also widely known, and now businesses often advertise 316 stainless steel, what is the difference between them.

Stainless steel is a kind of alloy steel

We usually say "stainless steel", the full name is "stainless acid-resistant steel". It is actually very simple to make steel not rust, just add some metal impurities to make alloy steel (such as adding chromium). But not rusting, it can only mean that it will not be corroded by the air, and the ability is still too poor. So we also need it to be resistant to chemical corrosion, so "stainless acid-resistant steel" appeared. To make stainless and acid-resistant steel, many kinds of metals need to be added, and different metal formulations form different stainless steels.

304 and 316 are austenitic stainless steel

Stainless steel is often divided into martensitic steel, ferritic steel, austenitic steel, austenitic-ferritic (duplex) stainless steel and precipitation hardening stainless steel according to the organizational state. In addition, it can be divided into: chromium stainless steel, chromium-nickel stainless steel and chromium manganese nitrogen stainless steel. Among them, austenitic stainless steel has the best overall performance and is non-magnetic, so it is the most widely used in our daily life. 304 and 316 belong to austenitic stainless steel.

304 and 316

304 stainless steel has strong anti-corrosion ability, and it is positioned as a "food-grade" metal by the national standard - normal contact with water, tea, coffee, milk, oil, salt, sauce, vinegar, etc. is no problem. 316 stainless steel is a further upgrade on this basis (controlling the proportion of impurities, adding molybdenum), which makes the corrosion resistance stronger. In addition to oil, salt, sauce, vinegar and tea, it can resist various strong acids and alkalis. Not only that, 316 stainless steel has better adaptability to the environment, too high or too low temperature will not affect the corrosion resistance of 316 stainless steel. But 316 has higher production costs and higher prices.

Several common models

304: that is, 18/8 stainless steel. Products such as: corrosion-resistant containers, tableware, furniture, railings, medical equipment. The standard composition is 18 % chromium plus 8 % nickel. It is a stainless steel that is non-magnetic and cannot change its metallographic structure by heat treatment. The GB grade is 06Cr19Ni10.

304 L: The same characteristics as 304, low carbon so it is more corrosion resistant and easy to heat treatment, but its mechanical properties are poor.

304 N: It has the same characteristics as 304. It is a nitrogen-containing stainless steel. Nitrogen is added to increase the strength of the steel.

316: After 304, the second most widely used steel grade is mainly used in the food industry, watch accessories, pharmaceutical industry and surgical equipment. Adding molybdenum element makes it obtain a special anti-corrosion structure. Because it has better resistance to chloride corrosion than 304, it is also used as "marine steel". SS316 is usually used in nuclear fuel recovery units.

316 L: Low carbon, so it is more corrosion-resistant and easy to heat treatment. Products such as: chemical processing equipment, nuclear power generators, and refrigerant storage tanks.

Comprehensive consideration of cost performance

For food steel, 304 is sufficient, and there are almost no defects; in this regard, the use of 316 is purely overkill, and the aspect that 316 is stronger than 304 does not reflect it at all. Therefore, when consumers choose products, they can make comprehensive judgments based on needs and cost performance, and choose suitable products.