Comparison of 316 and 316H Stainless Steel: Standard Austenitic vs High-Carbon Austenitic Grade

316 and 316H are both 316 series austenitic stainless steels, with the core difference being carbon content (316: C≤0.08%, 316H: C=0.04-0.10%). The high carbon content of 316H improves its high-temperature strength and creep resistance, making them suitable for different temperature and stress requirements.

Core Parameter Comparison

Parameter	316 Stainless Steel	316H Stainless Steel
Chemical Composition (wt%)	C≤0.08, Si≤1.00, Mn≤2.00, P≤0.045, S≤0.030, Cr=16.00-18.00, Ni=10.00-14.00, Mo=2.00-3.00, Fe=Balance	C=0.04-0.10, Si≤1.00, Mn≤2.00, P≤0.045, S≤0.030, Cr=16.00-18.00, Ni=10.00-14.00, Mo=2.00-3.00, Fe=Balance
Mechanical Properties (Annealed)	Tensile Strength ≥515MPa, Yield Strength ≥205MPa, Elongation ≥40%, Hardness ≤217HB	Tensile Strength ≥515MPa, Yield Strength ≥205MPa, Elongation ≥40%, Hardness ≤217HB
High-Temperature Creep Strength (700℃)	Creep rupture strength (1000h) ≥60MPa	Creep rupture strength (1000h) ≥80MPa
Service Temperature	-196℃ to 870℃ (continuous service)	-196℃ to 870℃ (continuous service, preferred for 600-870℃)
Equivalent Grades	SUS316 (JIS), EN 1.4401, UNS S31600	SUS316H (JIS), EN 1.4405, UNS S31609

Key Performance Differences: 1. High-temperature strength: 316H's high carbon content improves creep resistance and high-temperature strength; at 700℃, its 1000h creep rupture strength (≥80MPa) is 33% higher than 316 (≥60MPa). 2. Intergranular corrosion resistance: 316H is more prone to intergranular corrosion after welding than 316, requiring strict post-weld annealing. 3. Weldability: 316 has better welding stability; 316H requires lower heat input during welding to avoid grain coarsening. 4. Machinability: Both have similar machinability, with no obvious difference. 5. Cost: 316H is 8-12% more expensive than 316.

Applicable Scenario Distinction: 316 is suitable for general medium-temperature (≤600℃) corrosion-resistant components, such as chemical pipelines, food machinery, and marine hardware. 316H is suitable for high-temperature stress-bearing components, such as boiler superheater tubes, high-temperature heat exchanger tubes, gas turbine components, and high-temperature reaction vessel flanges (600-870℃ service).

Practical Q&A

Q1: Why is 316H suitable for high-temperature stress-bearing components? A1: Its controlled carbon content (0.04-0.10%) can form stable carbides at high temperatures, which pin grain boundaries and improve creep resistance; it can maintain structural stability under long-term high-temperature and high-stress conditions, avoiding deformation or fracture.

Q2: What is the post-weld heat treatment requirement for 316H? A2: Must perform post-weld annealing at 850-900℃, air cooling; this eliminates residual stress, prevents intergranular corrosion, and restores high-temperature performance; post-weld heat treatment is mandatory for high-temperature service components.

Q3: Can 316 replace 316H in high-temperature environments? A3: No. At temperatures above 600℃, 316's creep resistance is insufficient, and it will undergo obvious plastic deformation after long-term service; 316H is the mandatory material for high-temperature stress-bearing components in this temperature range.

Q4: What is the difference in carbon content control between 316 and 316H? A4: 316's carbon content is ≤0.08% (uncontrolled lower limit), while 316H's carbon content is controlled at 0.04-0.10%; the lower limit control ensures high-temperature creep strength, which is the core difference between the two.

Q5: How to select between 316 and 316H? A5: Choose 316 if the service temperature is ≤600℃ and no high-temperature stress is applied; choose 316H if the service temperature is 600-870℃ and the component bears long-term stress (such as high-temperature pipelines, flanges).