HT PIPE stocks a full range of Alloy 20 and Alloy 31 pipes, fittings, and flanges. Contact our technical team today for a competitive quote.
Alloy 20 (UNS N08020) and Alloy 31 (UNS N08031) represent the benchmark of cost performance in moderately corrosive environments and the peak of corrosion resistance in extremely harsh conditions. Although both belong to the nickel-iron-chromium based alloy system, they show significant differences in corrosion resistance mechanism, mechanical properties and engineering applicability due to differences in composition design and alloying strategies.
nickel alloy 20 and 31 Mechanical Properties Comparison
N08020 and N08031 pipe Strength and Toughness
Alloy 20: Solution-annealed tensile strength ≥550 MPa, yield strength ≥240 MPa, elongation ≥30%, hardness ≤200 HB. Its strength meets the pressure requirements of conventional chemical equipment while maintaining good workability.
Alloy 31: Solution-annealed tensile strength ≥650 MPa, yield strength ≥276 MPa, and it retains ≥450 MPa yield strength at high temperatures (550°C). After aging treatment, the strength can reach 1000 MPa, with an impact energy retention rate >80% at -196°C.
20 alloy and 31 alloy Fabrication and Welding
Alloy 20: With Low work hardening rate, which is suitable for conventional hot working (1050–1150°C) and cold working. For the welding, ERNiCrMo-3 filler wire is recommended which requires no post-weld heat treatment.
Alloy 31: Hot working should be conducted at 1200–1050°C, and intermediate annealing is needed for cold working (when deformation exceeds 15%). ERNiCrMo-13 filler wire is required for welding to ensure weld corrosion resistance. Though more difficult to fabricate, it offers stable welding performance.
Alloy 31 and alloy 20 Material Corrosion Resistance
nickel 31 and nickel 20 General Corrosion Resistance
Alloy 20: Corrosion rate <0.1 mm/year in ≤80% sulfuric acid, resistant to 50% sodium hydroxide solution, suitable for phosphoric acid, nitric acid, etc.
Alloy 31: Corrosion rate <0.01 mm/year in 98% concentrated sulfuric acid + 200 ppm chlorides, only 0.003 mm/year in boiling phosphoric acid (85%), and resistant to fuming sulfuric acid and mixed acids (40% HF + 10% HNO₃). Its corrosion resistance comprehensively surpasses Alloy 20 in acidic, alkaline, and chloride environments.
carpenter 20 steel and carpenter 31 steel Local Corrosion Protection
Alloy 20: Critical Pitting Temperature (CPT) ~60°C, better stress corrosion cracking (SCC) resistance than 316L stainless steel, but still at risk in high-temperature chloride environments.
Alloy 31: CPT up to 85°C, Pitting Resistance Equivalent Number (PREN ≥50), it can exceed 20 years in seawater and salt crystallization equipment. Its crevice corrosion resistance is 40% higher than traditional 6-Mo steels. The nitrogen-strengthened austenitic structure significantly suppresses local corrosion.
UNS N08020 and UNS N08031 Cost and Cost-Effectiveness
Alloy 20 and alloy 30 Material Costs
Alloy 20: Its price is about ~80–100 CNY/kg that is suitable for moderate-corrosion, cost-sensitive projects.
Alloy 31: Its price is about ~130 CNY/kg (negotiable for bulk purchases) that is ideal for critical equipment requiring high reliability and long service life.
N08020 and N08031 Life Cycle Economy
In high-temperature chloride environments, although Alloy 31 has higher initial costs, its low corrosion rate and reduced maintenance needs can make the total cost lower than Alloy 20 over a 5-year period. For example, replacing Hastelloy C-276 with Alloy 31 in FGD systems can reduce equipment costs by 35%.
Comparison between Alloy 20 and Alloy 31 pipe
|
Evaluation Dimension |
Alloy 20 is Superior |
Alloy 31 is Superior |
|
Medium Corrosivity |
Sulfuric acid (≤80%), phosphoric acid, weak alkaline solutions |
Concentrated sulfuric acid (>80%), chlorides (>200 ppm), mixed acids (HF/HNO₃) |
|
Temperature Range |
-20°C to 400°C |
-196°C to 550°C |
|
Mechanical Loads |
Medium-low pressure static equipment |
High-pressure, vibrating, or cryogenic components |
|
Cost Constraints |
Limited budget, allowing regular maintenance |
Critical equipment requiring long-term maintenance-free operation |
|
Industry Standards |
Food & medicine (FDA), general chemicals (ASTM B463) |
Oil & gas (NACE MR0175), nuclear power (ASME SB622), deep-sea mining (ISO 15156) |
Alloy 20 & Alloy 31 Material Manufacturer Supplier
With 15 years of export excellence, HT PIPE is your reliable stockist and exporter. Our portfolio includes Alloy 20 pipes, Alloy 31 plates, round bars, and a wide array of fittings, flanges, and welding accessories. Contact us today for no-obligation pricing and product details-we're ready to support your projects.
