Grade1 And Grade 2 description
UNS N06625 Grade 1 plate (also known as Alloy 625) is a niobium-strengthened nickel-chromium-molybdenum superalloy supplied in the annealed condition (Grade 1) in accordance with ASTM B443, ASME SB443, and AMS 5599 standards. It is engineered to provide excellent corrosion resistance, high structural strength, and good formability at operating temperatures up to 593°C (1100°F).
Its room-temperature mechanical property requirements are a tensile strength of ≥827 MPa (120,000 psi) and a yield strength of ≥414 MPa (60,000 psi). Compared to the high-temperature Grade 2, Grade 1-utilizing solid-solution strengthening and a soft-annealed state-offers superior formability, machinability, and weldability, while being virtually immune to chloride-ion stress corrosion cracking.
Common applications include marine and seawater environments (marine piping, seawater heat exchangers, cable sheathing), chemical processing (equipment exposed to strongly oxidizing and reducing acids, such as phosphoric acid), the oil and gas industry (sour gas handling, offshore structural platforms, production risers), and environmental protection (waste incineration components, radioactive waste processing).
Click to request an immediate quote for Inconel 625 Grade 1 stock
Inconel 625 Grade 2 (Material No. 2.4856 / UNS N06625 / EN NiCr22Mo9Nb) is a nickel-chromium-molybdenum alloy supplied in the solution-annealed condition. It is specifically designed for extreme high-temperature service above 593°C, offering excellent creep resistance, rupture strength, and resistance to intergranular corrosion.
The key distinction from Grade 1 lies in the heat treatment regimen: Grade 1 is annealed at a minimum of 871°C (1600°F) and is suitable for standard service temperatures up to 593°C (1100°F), whereas Grade 2 undergoes solution annealing at a higher minimum temperature of 1093°C (2000°F) to optimize high-temperature creep and oxidation resistance.
Regarding product specifications, plate thickness is typically defined as ≥4.8 mm (0.188 inches), with applicable standards including ASTM B443 and AMS 5599. Typical applications include flare systems for refineries and offshore platforms, hot exhaust gas heat exchangers and expansion joints, waste incineration units, and chemical processing equipment operating in highly corrosive environments.
Click to get an instant quote for Inconel 625 Grade 2 stock
Gnee Alloy Inconel 625 Grade 1 and Grade 2 Plate Production Process
Inconel 625 Plate Grade 1 - Fully Solution-Annealed Condition
Production Process: Hot rolling → Full solution annealing at 1093–1204°C → Rapid cooling
Microstructure: Coarser grains; fully recrystallized austenitic structure; free of residual processing stresses
Key Characteristics: Optimal ductility and corrosion resistance; lower base strength
Inconel 625 Plate Grade 2 - Cold-Worked and Annealed Condition
Production Process: Hot rolling → Controlled cold-work reduction → Low-temperature final annealing
Microstructure: Finer grains; strain-strengthened; retains effects of work hardening
Key Characteristics: Significantly higher tensile and yield strengths; good formability, though slightly lower than Grade 1
Overview of Inconel 625 Grade 1 and Grade 2 Plate Material Selection
| Parameter | Inconel 625 Grade 1 (Annealed) | Inconel 625 Grade 2 (Solution Annealed) |
|---|---|---|
| Applicable Standard | ASTM B443 / ASME SB-443 | ASTM B443 / ASME SB-443 |
| UNS Number | N06625 | N06625 |
| Heat Treatment | Annealed at ≥ 871°C (1600°F), rapid cool | Solution annealed at ≥ 1093°C (2000°F), rapid quench |
| Product Forms | Plate (>4.76mm), Sheet (≤4.76mm), Strip | Plate (>4.76mm), Sheet (≤4.76mm), Strip |
| Service Temperature Range | Normally employed up to 593°C (1100°F) | Normally employed above 593°C (1100°F) when creep/rupture resistance is required |
| Key Strengthening Mechanism | Solid-solution strengthening (Mo+Nb) | Solid-solution strengthening (Mo+Nb) |
| Primary Application | General corrosion service, chemical reactors, marine equipment, ≤593°C | High-temperature service, creep-sensitive applications, >593°C |
| ASME Section VIII Maximum Temp | 1200°F (649°C) | 1600°F (871°C) |
| Relative Cost | Baseline | Higher (additional heat treatment) |
Chemical Composition of UNS N06625 Grade 1 and Grade 2 Plates
| Element | UNS N06625 Standard Range (wt%) | Grade 1 Typical | Grade 2 Typical | |
|---|---|---|---|---|
|
|
Nickel (Ni) | ≥ 58.0 (balance) | 58.0 – 61.0% | 58.0 – 61.0% |
| Chromium (Cr) | 20.0 – 23.0 | 21.0 – 22.0% | 21.0 – 22.0% | |
| Molybdenum (Mo) | 8.0 – 10.0 | 8.5 – 9.5% | 8.5 – 9.5% | |
| Niobium + Tantalum | 3.15 – 4.15 | 3.5 – 3.9% | 3.5 – 3.9% | |
| Iron (Fe) | ≤ 5.0 | ≤ 4.0% | ≤ 4.0% | |
| Carbon (C) | ≤ 0.10 | ≤ 0.05% | ≤ 0.05% | |
| Sulfur / Phosphorus | ≤ 0.015 each | ≤ 0.015 each | ≤ 0.010 each (premium grade) |
Gnee Alloy Nickel-Based Alloy PMI Testing
inconel 625 Grade 1 and Grade 2 Plate Mechanical Properties
Grade 1: Annealed Condition (≥ 871°C)
| Product Form | Thickness | UTS (MPa) | YS 0.2% (MPa) | Elongation (%) |
|---|---|---|---|---|
| Cold-rolled sheet and strip | All thicknesses | ≥ 827 | ≥ 414 | ≥ 30 |
| Hot-rolled sheet | All thicknesses | ≥ 758 | ≥ 379 | ≥ 30 |
| Hot-rolled plate | Up to 70mm (2.75") | ≥ 758 | ≥ 379 | ≥ 30 |
| Cold-rolled plate | Up to 9.5mm (0.375") | ≥ 758 | ≥ 379 | ≥ 30 |
Grade 2: Solution Annealed Condition (≥ 1093°C)
| Product Form | Thickness | UTS (MPa) | YS 0.2% (MPa) | Elongation (%) |
|---|---|---|---|---|
| All products | All thicknesses | ≥ 690 | ≥ 276 | ≥ 30 |
Click to download the Inconel 625 alloy PDF datasheet
Key Performance Differences Between Inconel 625 Grade 1 and Grade 2 Plates
Comparison of corrosion resistance
| Corrosion Type | Grade 1 (Annealed) | Grade 2 (Solution Annealed) | Difference Explanation |
|---|---|---|---|
| General Corrosion(Oxidizing/Reducing Environments) | Typical uniform corrosion rate ≤ 0.10 mm/year(ASTM G31, room temperature, 10% H₂SO₄ immersion) | Typical uniform corrosion rate ≤ 0.10 mm/year(ASTM G31, room temperature, 10% H₂SO₄ immersion) | Identical. The same base alloy chemistry delivers equivalent general corrosion resistance in mild to moderate oxidizing/reducing media. |
| Pitting / Crevice Corrosion | PREN ≥ 45;Critical Pitting Temperature (CPT) ≥ 85°C(ASTM G48 Method A, ferric chloride test) | PREN ≥ 45;Critical Pitting Temperature (CPT) ≥ 85°C(ASTM G48 Method A, ferric chloride test) | Identical. Pitting and crevice performance are determined by bulk alloying elements (Cr, Mo), which remain consistent between both grades. |
| Chloride Stress Corrosion Cracking (SCC) | No cracking after 1000 h exposure in boiling 42% MgCl₂ solution (ASTM G36); inherently immune to chloride SCC under conventional service conditions | No cracking after 1000 h exposure in boiling 42% MgCl₂ solution (ASTM G36); inherently immune to chloride SCC under conventional service conditions | Identical. The high nickel base content is the core factor for chloride SCC resistance, and is not affected by annealing process differences. |
| Intergranular Corrosion(High-Temperature Sulfur Environments) | Corrosion rate: 0.15 – 0.25 mm/year(ASTM G28 Method A, tested after standard sensitization heat treatment) | Corrosion rate: ≤ 0.08 mm/year(ASTM G28 Method A, tested after standard sensitization heat treatment) | Grade 2 performs better - stricter control of C, S and trace elements, paired with a higher solution treatment temperature, suppresses chromium carbide precipitation at grain boundaries and significantly improves resistance to sensitization in high-temperature sulfur-bearing environments. |
| High-Temperature Oxidation (> 600°C) | Oxidation mass gain: ≈ 0.08 mg/cm²·h(900°C, 1000 h cyclic oxidation test in air) | Oxidation mass gain: ≤ 0.05 mg/cm²·h(900°C, 1000 h cyclic oxidation test in air) | Grade 2 performs better - a higher solution annealing temperature achieves more complete dissolution of grain boundary carbides and precipitates, enabling the formation of a denser, more uniform protective Cr₂O₃ oxide layer at elevated temperatures. |
High-Temperature Strength & Oxidation Resistance Comparison
| Property | Grade 1 (Annealed) | Grade 2 (Solution Annealed) | Difference Explanation |
|---|---|---|---|
| Tensile Strength, UTS (RT) | ≥ 827 MPa | ≥ 690 MPa | Grade 1 higher (~20% higher) |
| Yield Strength, YS 0.2% (RT) | ≥ 414 MPa | ≥ 276 MPa | Grade 1 higher (~50% higher) |
| Elongation (RT) | ≥ 30% | ≥ 30% | Identical |
| Hardness (HRB) | 90–95 | 95–100 | Grade 2 slightly higher |
| Creep / Rupture Strength (> 593°C) | Moderate | Superior | Grade 2 significantly better - higher solution temperature is specifically designed to enhance high-temperature creep and rupture strength |
| Long-Term Microstructural Stability | Moderate - δ phase (Ni₃Nb) precipitation may occur during prolonged >650°C service, leading to embrittlement | Superior - more suitable for long-term service at 650–980°C | Grade 2 better |
| Maximum Service Temperature | ~ 980°C (short-term) | ~ 980°C (short-term) | Same upper limit; Grade 2 retains properties better during prolonged >593°C service |
Grade 1: Demonstrates superior long-term creep resistance at temperatures above 550°C. Its coarser grain structure resists creep deformation more effectively during prolonged high-temperature exposure. This is the standard grade specified for reactor liners and furnace components.
Grade 2: Possesses higher room-temperature strength but experiences a more rapid decline in creep performance under sustained high temperatures. It is best suited for applications ranging from ambient to moderate temperatures (< 500°C) where high static strength is the priority.
Weldability
| Property | Grade 1 (Annealed) | Grade 2 (Solution Annealed) | Difference Explanation |
|---|---|---|---|
| Preheating Required | Not required | Not required | Identical |
| Post-Weld Heat Treatment (PWHT) | Not required | Not required | Identical - Inconel 625's Nb-stabilized carbides prevent intergranular corrosion sensitization, eliminating the need for PWHT |
| Matching Filler Metal | ERNiCrMo-3 | ERNiCrMo-3 | Identical |
| HAZ Corrosion Resistance | Excellent | Superior | Grade 2's coarser grains and more complete carbide dissolution result in lower HAZ sensitization tendency |
| HAZ Grain Growth (Post-Weld) | Moderate (affected by finer original grain size) | Lower | Grade 2's coarser original grains limit additional grain growth during welding thermal cycling |
Both grades can be easily welded using matching Grade 625 filler materials without the need for preheating.
Grade 1 material exhibits more stable corrosion resistance in the heat-affected zone (HAZ), and there is no adverse interaction between residual cold-work stresses and welding thermal effects.
Grade 2 material experiences some loss of cold-worked strength in the heat-affected zone; this factor must be taken into account during structural design.
Fatigue Resistance
| Property | Grade 1 (Annealed) | Grade 2 (Solution Annealed) | Difference Explanation |
|---|---|---|---|
| Fatigue Strength (RT) | ≥ 310 MPa | ≥ 310 MPa | Identical (base chemistry and Nb solid-solution strengthening effect are the same) |
| Low-Cycle Fatigue (LCF) RT | Excellent | Superior | Grade 2's coarser grains result in lower fatigue crack growth rates |
| High-Cycle Fatigue (HCF) RT | Excellent | Excellent | Comparable |
| High-Temperature Fatigue (> 593°C) | Moderate (creep-fatigue interaction) | Superior | Grade 2's superior creep resistance translates to significantly longer high-temperature fatigue life |
| Failure Probability (High-Temperature Cyclic Loading + Chloride Environment) | Baseline | 10–15% lower | Long-term industrial data indicates Grade 2 has lower failure probability under severe service conditions |
Grade 2: Offers superior fatigue performance under cyclic loading, thanks to its finer grain structure and higher base strength. This grade is more suitable for pressure vessels subjected to frequent thermal and pressure cycling.
Grade 1: Demonstrates good fatigue resistance, though it is slightly inferior to Grade 2 in high-cycle fatigue applications.
Download Inconel 625 Technical White Paper: Grade 1 vs. Grade 2
Comparison of Heat Treatment for Inconel 625 Grade 1 and Grade 2 Plates
| Parameter | Grade 1 | Grade 2 | |
|---|---|---|---|
|
|
Annealing Temperature | ≥ 871°C (1600°F) | ≥ 1093°C (2000°F) |
| Cooling Method | Rapid cool (air or water) | Rapid quench (water) | |
| Grain Size | Finer (typical) | Coarser (due to higher temperature) | |
| Precipitate Condition | Some carbides remain | More complete solution of carbides | |
| Residual Stress | Lower (annealed) | Lower (solution annealed) | |
| Sensitization Risk (Welding) | Low - Nb stabilizes carbon | Very Low - Nb stabilizes carbon |
Contact us to learn about our Inconel 625 production process
Application Recommendations for Inconel 625 Grade 1 and Grade 2 Plates
✅ When to Choose Grade 1 (Solution Annealed) Condition / Requirement |
|---|
| Maximum corrosion resistance required for long-term immersion service |
| Material will undergo heavy forming operations (e.g., dished heads, deep drawing, vessel linings) |
| Service temperature exceeds 550°C and creep resistance is critical |
| High ductility required with minimal risk of cracking during forming |
|
Typical Applications: Chemical reactor linings, FGD (Flue Gas Desulfurization) absorber towers, seawater storage tanks, furnace components, heat exchanger shells  Chemical reactor linings
 FGD (Flue Gas Desulfurization) absorber towers
 Seawater storage tanks
 Heat exchanger shells
|
✅ When to Choose Grade 2 (Cold Worked) Condition / Requirement |
|---|
| Higher strength required for structural or pressure-bearing applications |
| Components operate under cyclic loading conditions from ambient to moderate temperatures |
| Minimal forming required (mainly flat or lightly curved components) |
| Wall thickness reduction desired while maintaining pressure-containing capability |
|
Typical Applications: High-pressure vessel panels, structural load-bearing plates, process equipment with stringent fatigue requirements, valve body blanks  High-pressure vessel panels
 High-temperature reactor
 Steam generator piping
 Valve body forgings/blanks
|
Contact our experts to recommend the right alloy for your project
Gnee Alloy Inconel 625 Plate Supply Capability
As a professional exporter with over 18 years of experience in the nickel alloy industry, Gnee Alloy stocks Inconel 625 plates in both Grade 1 and Grade 2 specifications. We offer a full range of standard sizes and provide custom processing services tailored to specific project requirements.
Inconel 625 Plate Available Specifications
| Standard | ASTM B443 / ASME SB-443, UNS N06625 |
| Grade | Grade 1 (Solution Annealed), Grade 2 (Cold Worked) |
| Thickness Range | 1.5 mm – 50 mm (Sheet: ≤ 4.76 mm; Plate: > 4.76 mm) |
| Standard Sizes | 1219 × 2438 mm, 1500 × 3000 mm; Custom cutting available upon request |
| Surface Condition | Annealed & Pickled (standard), Bright Annealed, Mechanically Polished |
| Value-Added Services | Precision cutting, Weld bevel edge preparation, Surface polishing, PMI (Positive Material Identification) verification, UT (Ultrasonic Testing) |
Quality and Compliance
Mill Test Reports (MTRs) with 100% traceability provided with every order
ISO 9001 certified quality management system
Compliance with NACE MR0175 / ISO 15156 standards available (for sour service applications)
Third-party inspection accepted: SGS, TÜV, BV, DNV, and other major certification bodies
Global door-to-door shipping services, including full export documentation and customs clearance support
Contact us to customize Inconel 625 products to your project specifications
Why Choose Gnee as Your Nickel-Based Alloy Supplier
As a global exporter of nickel-based alloys, Gnee Alloy addresses pain points related to documentation and dimensions:
✅️100% Traceability: Every plate is heat-number stamped and accompanied by an EN 10204 3.1 Mill Test Certificate (MTC) documenting the exact annealing temperature.
✅️Precision Processing: We offer precision laser and waterjet Cut-to-Size services to deliver blanks ready for your assembly line, reducing your scrap rate.
✅️Wholesale Pricing: Benefit from Direct Factory Price on bulk tonnage for large-scale energy infrastructure overhauls.
Gnee Alloy inconel 625 Certificate
Click to view our professional certifications for Inconel 625
📦 Packaging and Shipping
All Nickel Based Alloy products are packaged using the following methods:
Wooden pallets or crates
Moisture-proof packaging
Labels with furnace number, standard, and size labels
Shipped worldwide by sea, air, or express
Gnee Alloy 625 Alloy Product Packing
Contact us for the latest export price quote for 625 Alloy
Real customer feedback on Gnee Alloy products
Real customer feedback on Gnee Alloy products
FAQ
Q1: Can I weld Inconel 625 Grade 2 parts to Grade 1 parts?
A: Yes. They have excellent metallurgical compatibility. We recommend using Alloy 625 (ERNiCrMo-3) filler metal. However, please note that the maximum service temperature of the entire joint will be limited by the Grade 1 side.
Q2: Is Grade 2 harder to machine?
A: Slightly. Due to its coarser grain structure, Grade 2 can be slightly more abrasive. As a Tier-1 Manufacturer, we supply Grade 2 plates in an optimized solution-treated state to ensure a Smooth Finish and maximized tool life.
Q3: Why is Grade 1 more popular in marine applications?
A: In marine splash zones, the temperature is low. Grade 1's fine grain structure provides higher room-temperature tensile strength and superior resistance to localized pitting in stagnant seawater.
Q4: Do you support small batch trial orders for nuclear R&D?
A: Absolutely. We support Innovation by offering Flexible MOQs on our in-stock inventory of both Grade 1 and Grade 2 sheets.
