316, 316L, and 316H - What are the differences among them

316, 316L and 316H stainless steels all belong to the molybdenum-containing austenitic stainless steel (16-18% chromium, 10-14% nickel, 2-3% molybdenum system). The core difference among them lies in the carbon content and the resulting performance characteristics. The following is a detailed comparative analysis of the three:

1. Chemical composition and core differences

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II. Performance Comparison

1. Corrosion Resistance

316L: Low carbon content inhibits the precipitation of carbide chromium, significantly reducing the risk of intergranular corrosion, suitable for media containing Cl⁻ (such as seawater, chemical environments).

316H: Forms carbide chromium easily at high temperatures, resulting in chromium deficiency at grain boundaries, decreased corrosion resistance, but superior oxidation resistance compared to 316L.

316: Intermediate between the two, good corrosion resistance in normal environments, but needs caution in high-temperature or high Cl⁻ environments.

2. High Temperature Performance

316H: High carbon content (0.04-0.10%), forms strengthened carbides at high temperatures (500-800℃), excellent creep resistance and endurance strength, suitable for boilers, petrochemical equipment.

316L: Less prone to carbide precipitation, can be used in the range of 425-860℃, suitable for thick-section welded components.

316: Intermittent use up to 870℃, continuous use up to 925℃, but long-term high temperature should avoid the sensitization temperature range (425-860℃).

3. Mechanical Properties

Normal Temperature Mechanical Properties: The tensile strength (≥515 MPa), yield strength (≥205 MPa) of all three are similar, and the elongation rate is all ≥40%.

Cold Work Hardening: 316H shows more significant strength improvement after cold deformation (e.g., 20% deformation reaches 900 MPa), suitable for forming structural components. 

III. Application Areas

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IV. Processing and Welding Precautions

Weldability:

316L: No annealing is required after welding, and it is suitable for thick plate welding (above 5mm).

316H: The welding temperature needs to be controlled (to avoid sensitization), and it is recommended to use high-carbon welding wire and combine with annealing.

316: Regular welding is sufficient, but thick plates may require post-weld heat treatment.

Processability:

316L is easier to cold process due to its low carbon content, while 316H requires higher cutting force due to its high carbon content.

The improved 316Ugima material has significantly better machining performance than the standard 316 series. 

V. Selection Suggestions

For high-temperature and high-pressure scenarios (≥500℃): Opt for 316H, considering both strength and oxidation resistance.

In corrosive sensitive environments (such as Cl⁻, seawater): Choose 316L to avoid intergranular corrosion.

For general applications: 316 offers the best cost performance and meets most industrial requirements. 

VI. Data Verification Examples

Resistance to Cl⁻ corrosion: 316L shows no pitting corrosion in an environment with 300mg/L Cl⁻ at 60℃, while 316H may corrode under these conditions.

High-temperature strength: The yield strength of 316H at 600℃ is approximately 30% higher than that of 316L, making it suitable for components of supercritical boilers. 

VII. Alternative Solutions Reference

316Ti: Suitable for thick-section welded components that require stabilization treatment, as an alternative to 316H to avoid the sensitization risk.

904L: A super austenitic steel with superior Cl⁻ corrosion resistance compared to the 316 series, but at a higher cost.

By considering the carbon content, performance requirements, and cost factors comprehensively, the material selection can be precisely matched. In practical applications, a life cycle cost analysis (LCCA) needs to be conducted in combination with specific operating conditions (temperature, medium, mechanical load).