Some Knowledge Sharing about Stainless Steel Materials 316L And 304

Stainless steel 316L and 304 are two widely used austenitic stainless steels that differ significantly in composition, corrosion resistance, mechanical properties, and application areas. Here are the main differences between the two:

1. Chemical composition

The main components of 304 stainless steel are 18% chromium (Cr) and 8% nickel (Ni), no molybdenum (Mo), and a carbon content of ≤0.08%.

316L stainless steel adds 23% molybdenum (Mo) to this, increases the nickel content to 1014%, and reduces the carbon content (≤0.03%). "L" stands for low carbon.

Key differences: 316L has stronger corrosion resistance due to the presence of molybdenum, especially suitable for chlorine-containing environments; the low-carbon design makes it more resistant to intergranular corrosion after welding.

2. Corrosion resistance

304 performs well in ordinary atmosphere, fresh water, weak acids (such as acetic acid) and organic acids, but is prone to pitting or crevice corrosion in chlorine-containing environments (such as seawater and salt spray).

316L contains molybdenum, which significantly improves its corrosion resistance to chlorides (such as seawater, salt solutions, and bleach), and is suitable for more severe environments, such as chemical industry and marine engineering.

Applicable scenarios:

304: food processing equipment, kitchen utensils, architectural decoration, and general chemical containers.

316L: marine equipment, pharmaceutical equipment, chemical pipelines, medical equipment (such as surgical instruments), and highly corrosive environments.

3. Mechanical properties

The tensile strength (about 515 MPa) and yield strength (about 205 MPa) of 304 are slightly higher than those of 316L (tensile strength 485 MPa, yield strength 170 MPa).

316L has a higher nickel content, better ductility, and the molybdenum content makes it more stable in high temperature environments.

4. Price and processability

316L is more expensive than 304 (usually 2040% more expensive), mainly due to the higher cost of molybdenum and nickel.

304 is easier to process (cutting, stamping, etc.), while 316L has a stronger tendency to work hardening due to its molybdenum content, which causes greater wear on the tool.

Welding performance: Both have good weldability, but the low-carbon design of 316L makes it more resistant to intergranular corrosion after welding, making it suitable for welding structural parts.

5. Other characteristics

Magnetism: Both are usually non-magnetic, but may be slightly magnetic after cold working.

Heat treatment: Neither can be strengthened by heat treatment, and strength can only be improved by cold working.

High temperature performance: 316L has better oxidation resistance than 304 at high temperatures (such as above 800°C).

How to choose?

Choose 304: Limited budget, mild corrosion environment (such as daily necessities, architectural decoration).

Choose 316L: Highly corrosive environment (seawater, chemical industry), medical implants, and key components with high requirements for long-term durability.

Summary

316L is an upgraded version of 304. The main difference is the addition of molybdenum and lower carbon content, which makes it better in corrosion resistance (especially in chlorine-containing environments) and welding performance, but the cost is higher. Choosing the right material according to the specific application environment can balance performance and economy.