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The difference between 304 stainless steel and 316 stainless steel

2021-04-30


Stainless steel is a kind of alloy steel

What we usually call "stainless steel" is called "stainless and acid-resistant steel" in full. To make steel not rusty, it is actually very simple, just add some metal impurities to make alloy steel (such as adding chromium). But it does not rust, only means that it will not be corroded by air, and its ability is still too poor. So we also need it to be resistant to chemical corrosion, so "stainless and acid-resistant steel" appeared. If you want to make stainless acid-resistant steel, you need to add many kinds of metals, 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 state of organization. In addition, it can be divided into chromium stainless steel, chromium nickel stainless steel and chromium manganese nitrogen stainless steel according to the composition. Among them, austenitic stainless steel has the best comprehensive performance and has no magnetism, so it is the most widely used in our daily life. Both 304 and 316 belong to austenitic stainless steel.


304 and 316

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


Several common models

304: 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 non-magnetic stainless steel whose metallographic structure cannot be changed 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 the mechanical properties are poor.
304 N: 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. It is mainly used in the food industry, watch jewelry, pharmaceutical industry and surgical equipment. The addition of molybdenum makes it a special corrosion-resistant structure. Because it has better resistance to chloride corrosion than 304, it is also used as "ship steel". SS316 is usually used in nuclear fuel recovery devices.
316 L: Low carbon, more corrosion resistant, easy to heat treatment, products such as: chemical processing equipment, nuclear power generators, refrigerant storage tanks.


Comprehensive consideration of cost performance

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