The core of selecting between SS316 and SS321 steel plates lies in matching the working conditions of overseas projects. SS316 focuses on corrosion resistance and is suitable for highly corrosive environments. SS321 emphasizes high-temperature stability and is suitable for high-temperature welding applications.
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HT PIPE, as a professional steel trading supplier, provides SS316 and SS321 steel plates that meet international standards such as ASTM and ASME, offering one-stop services including customized processing, bulk quotations, and cross-border logistics, helping global customers make precise selections and efficiently implement projects.
SS316 and SS321 steel plates Corrosion Resistance
SS316 steel plate: The molybdenum element significantly improves resistance to pitting and crevice corrosion, exhibiting excellent resistance to chlorides, acids, and alkalis. Its pitting resistance equivalent number (PREN ≥ 25) is far superior to SS321 (PREN ≈ 19).
It should be noted that prolonged exposure to temperatures above 800°C can lead to the precipitation of the σ phase, causing embrittlement and reduced corrosion resistance. Therefore, it is not suitable for continuous high-temperature conditions.
SS321 steel plate: Lacking molybdenum, its corrosion resistance in chloride environments is weaker, and it is not recommended for marine, coastal, and high-salt spray environments. However, its titanium element inhibits the precipitation of chromium carbides at high temperatures of 450-800°C, preventing intergranular corrosion.
It maintains stability without annealing after welding, making it suitable for overseas industrial furnaces, high-temperature pipelines, and aerospace auxiliary equipment projects.
s316 and s321 High-Temperature Performance
SS316 steel plate: Continuous operating temperature ≤ 800°C, short-term tolerance temperature can reach 870°C. Its strength retention at high temperatures is average, and molybdenum migration reduces high-temperature corrosion resistance, making it unsuitable for long-term high-temperature conditions.
SS321 steel plate: Continuous operating temperature can reach 800-900°C, short-term tolerance temperature is 925°C. Its high-temperature oxidation resistance, thermal fatigue resistance, and creep strength are superior to SS316, allowing it to withstand repeated heating and cooling cycles, and meeting ASME standards for high-temperature pressure-bearing components in boilers and pressure vessels.
uns s32100 and uns s31600 Mechanical Properties
Both materials exhibit consistent mechanical properties at room temperature (minimum values): tensile strength 515 MPa, yield strength 205 MPa, elongation 40%, and Brinell hardness (BHN) ≤217, meeting the requirements of most overseas industrial structural components.
In terms of low-temperature performance, SS316 maintains high ductility at -252°C, making it suitable for polar and cryogenic liquid storage tank projects. SS321 has slightly lower low-temperature elongation, but is sufficient for conventional low-temperature applications and offers better cost-effectiveness.
astm a240 s316 and astm s240 s321 Processing and Welding Performance
SS316 Steel Plate: Overseas welding requires controlling heat input to prevent hot cracking. The use of ER316L molybdenum-containing filler material is recommended, and post-weld heat treatment is advised for complex welded structures. Machining is slightly more difficult than SS321. HT PIPE can provide pre-processing and welding services to reduce customer construction costs.
SS321 Steel Plate: Titanium element optimizes welding performance, preventing chromium carbide precipitation in the heat-affected zone. It supports multi-pass welding and does not require post-weld annealing, making it suitable for overseas on-site welding and complex structural component processing. It has excellent formability, meeting customized requirements such as bending and stamping. HT PIPE can provide one-stop processing and delivery based on customer drawings.
