321H and 317L serves as two typical austenitic stainless steels. They belong to the same chromium-nickel alloy system, but their different compositional designs result in distinctly different performance advantages. HT PIPE is a leading stockist and global exporter with over 15 years of expertise in international trade. We supply pipes, plates, round bars, and a comprehensive range of pipe fittings, flanges, and valves. Contact us now for free quotes and personalized product information.
317l vs 321h Mechanical properties
| Mechanical properties | Tensile, min, ksi[MPa] | Yield, min, ksi[MPa] | Elongation, %(min) |
| 317L | 75【515】 | 30【205】 | 40 |
| 321/H | 75【515】 | 30【205】 | 40 |
Chemical composition ss317l and 321h
|
Element Symbol |
Element Name |
S321H Stainless Steel Content Range (Mass Fraction, %) |
S317L Stainless Steel Content Range (Mass Fraction, %) |
|
C |
Carbon |
0.04-0.10 |
≤0.03 |
|
Cr |
Chromium |
17-19 |
16-18 |
|
Ni |
Nickel |
9-12 |
11-15 |
|
Ti |
Titanium |
≥5×C (Titanium content not less than 5 times carbon content) |
Not Added |
|
Mo |
Molybdenum |
Not Added |
3-4 |
|
Fe |
Iron |
Balance |
Balance |
ss321h and ss317l Corrosion Resistance Analysis
321H Stainless Steel
Oxidizing Media Performance: In nitric acid with a concentration of ≤65% and a temperature of ≤100℃, the corrosion rate is <0.1 mm/year, superior to 304 stainless steel, in NaOH solution with a concentration of ≤50% and a temperature of ≤100℃, the corrosion rate is <0.05 mm/year, far exceeding the performance of carbon steel.
Weaknesses: The critical pitting temperature in 3.5% NaCl solution is only 25-30℃, making it prone to pitting corrosion in high-temperature seawater environments, stress corrosion cracking may occur when the H₂S partial pressure is >0.00035MPa.
Core Advantages: Titanium stabilization design inhibits carbide precipitation, maintaining good resistance to intergranular corrosion after welding.
317L Stainless Steel
Strong Corrosion Adaptability: High molybdenum content makes it resistant to organic acids such as sulfides, acetic acid, and formic acid. Its corrosion resistance in chloride environments far exceeds that of conventional austenitic stainless steels.
Welding Stability: Ultra-low carbon design ensures that it maintains its resistance to intergranular corrosion without heat treatment after welding.
Performance Positioning: Critical pitting temperature 45-50℃, significantly higher than 321H, providing stronger resistance to harsh corrosive environments.
s321h and s317l Manufacture process differences
s321H Stainless Steel
Hot Working: Heating temperature 1150-1250℃, holding for 30 minutes to 2 hours, air cooling or furnace cooling. Strict temperature control is required to avoid grain growth or deformation difficulties.
Cold Working: Strength can be improved through cold rolling and cold drawing, but residual stress control is necessary. Shot peening may be required if necessary.
Welding: The stability of the heat-affected zone needs attention. Titanium can reduce the risk of weld embrittlement, but overheating should be avoided.
s317L Stainless Steel
Hot Working: Hot rolling temperature 1200-900℃, final rolling temperature ≥900℃, to prevent σ phase precipitation leading to brittleness.
Cold Working: High work hardening rate, intermediate annealing (600-650℃) is required to restore plasticity when deformation >15%.
Welding: TIG welding or laser welding is recommended. Welding wire should be matched to 317L composition. Pass temperature ≤150℃; no post-weld heat treatment is required.
Machining: Austenitic structure leads to work hardening; low cutting speed (<30m/min) is required. Carbide or ceramic-coated tools should be used.
Selection advices
Prioritize 321H: High temperature (>537℃), oxidizing media, welding applications requiring resistance to intergranular corrosion (e.g., boilers, exhaust systems).
Prioritize 317L: SUS 317L is preferred for equipment in harsh corrosive environments such as strong acids, high chlorides, and organic acids, where high plasticity and ease of welding are required (such as chemical reactors and bleaching containers).
