Womic Stainless Steel Co., Ltd
Exceptional Pitting and Crevice Corrosion Resistance: PRE ≥ 45 (typically 45-50) due to high chromium (20-23%), high molybdenum (8-10%), and niobium (3.15-4.15%) content – the highest among nickel alloys for seawater shafting applications.
Ultra-High Strength: Yield strength ≥ 415 MPa in annealed condition; cold worked options available for even higher strength requirements (YS up to 860 MPa).
Outstanding Seawater Compatibility: No crevice corrosion or pitting, even in stagnant seawater or high-velocity conditions (up to 20 m/s), significantly outperforming super duplex 2507 in long-term seawater exposure.
Superior Chloride SCC Resistance: High nickel content (≥58%) provides outstanding resistance to chloride-induced SCC and sulfide-induced SSCC.
Excellent High-Temperature Strength and Oxidation Resistance: Maintains excellent mechanical properties up to 980°C (1800°F) with outstanding creep resistance.
Niobium Stabilization – No Sensitization: Niobium addition (3.15-4.15%) stabilizes the alloy against intergranular corrosion, eliminating need for post-weld heat treatment.
NACE MR0175 / ISO 15156 Compliant: Fully qualified for sour service with highest allowable H₂S partial pressures, documented HIC and SSC test reports available.
Broad Temperature Range: Maintains excellent properties from cryogenic (-196°C) to high temperature (980°C).
Good Machinability: Requires carbide tooling, slower speeds (20-30% slower than 316L), and adequate coolant.
International Certifications: Round bars can be certified by ABS, BV, DNV, LR, GL, RINA, CCS, KR, and NK, and comply with NORSOK M-650, NACE MR0175, API 17E, and ISO 13628-5 standards.
|
Standard |
Description |
Corresponding Alloy 625 Grade |
|
ASTM B443 |
Standard specification for nickel-chromium-molybdenum-columbium alloy plate, sheet, and strip |
UNS N06625 |
|
ASTM B446 |
Standard specification for nickel-chromium-molybdenum-columbium alloy bar and wire |
UNS N06625 |
|
ASTM B906 |
General requirements for nickel alloy plate, sheet, and strip |
UNS N06625 |
|
ASME SB446 |
ASME specification for nickel-chromium-molybdenum alloy bars |
UNS N06625 |
|
EN 10088-3 |
European standard for stainless steel bars for general purposes |
2.4856 (NiCr22Mo9Nb) |
|
EN 10272 |
European standard for stainless steel bars for pressure purposes |
2.4856 |
|
JIS G4303 |
Japanese standard for stainless steel bars |
NW6625 |
|
JIS G4318 |
Japanese standard for cold-finished stainless steel bars |
NW6625 |
|
GB/T 1220 |
Chinese standard for stainless steel bars |
NS625 |
|
NORSOK M-650 |
Offshore material qualification |
Alloy 625 |
|
NACE MR0175 / ISO 15156 |
Sour service compliance |
Alloy 625 |
|
API 17E |
Subsea umbilicals specification |
UNS N06625 |
|
ISO 13628-5 |
Subsea umbilicals – recommended practice |
UNS N06625 |
|
Element |
Ni |
Cr |
Fe |
Mo |
Nb+Ta |
C |
Mn |
P |
S |
Si |
Al |
Ti |
Co |
|
Alloy 625 |
≥58.0 |
20.0–23.0 |
≤5.0 |
8.0–10.0 |
3.15–4.15 |
≤0.10 |
≤0.5 |
≤0.015 |
≤0.015 |
≤0.5 |
≤0.4 |
≤0.4 |
≤1.0 |
Alloy 625 (UNS N06625) is a nickel-chromium-molybdenum alloy with niobium stabilization. The high molybdenum content (8-10%) and niobium (3.15-4.15%) provide exceptional pitting resistance (PRE ≥ 45), the highest among nickel alloys for seawater service.
Comparison of PRE (Pitting Resistance Equivalent) Values:
|
Grade |
Nickel (%) |
PRE |
Seawater Suitability |
High-Temperature Capability |
|
316/316L |
10-14 |
24-26 |
Limited |
400°C |
|
Duplex 2205 |
4.5-6.5 |
34-35 |
Good |
300°C |
|
Super Duplex 2507 |
6-8 |
42-45 |
Excellent |
300°C |
|
Alloy 825 |
38-46 |
38-42 |
Excellent |
540°C |
|
Alloy 625 |
≥58 |
≥45 |
Outstanding |
980°C |
|
Property |
Unit |
Alloy 625 (Annealed) |
Alloy 625 (Cold Worked) |
|
Tensile Strength |
MPa |
≥825 |
≥900 |
|
Yield Strength (0.2% offset) |
MPa |
≥415 |
≥620 |
|
Elongation |
% |
≥30 |
≥20 |
|
Reduction of Area |
% |
≥40 |
≥35 |
|
Hardness (typical) |
HRC |
≤25 |
25-35 |
|
Density |
g/cm³ |
8.44 |
8.44 |
|
Melting Range |
°C |
1290–1350 |
1290–1350 |
|
Modulus of Elasticity |
GPa |
205 |
205 |
|
Thermal Conductivity (20°C) |
W/m·K |
9.8 |
9.8 |
|
Coefficient of Thermal Expansion (20–100°C) |
μm/m·K |
12.8 |
12.8 |
High-Temperature Tensile Properties (Annealed Condition, Typical Values):
|
Temperature (°C) |
Tensile Strength (MPa) |
Yield Strength (MPa) |
|
20 |
900–1000 |
450–550 |
|
200 |
850–950 |
400–500 |
|
400 |
800–900 |
380–480 |
|
500 |
750–850 |
370–470 |
|
600 |
700–800 |
360–460 |
|
700 |
600–700 |
300–380 |
|
800 |
450–550 |
200–280 |
|
900 |
300–400 |
120–180 |
|
980 |
200–280 |
80–120 |
Maximum Recommended Service Temperatures:
|
Service Type |
Maximum Temperature |
|
Continuous Service (Seawater/Chloride) |
260°C (500°F) |
|
Continuous Service (Oxidizing Atmosphere) |
980°C (1800°F) |
|
Continuous Service (Reducing Atmosphere) |
870°C (1600°F) |
|
Sour Service (NACE MR0175) |
232°C (450°F) |
|
Cryogenic Service |
-196°C (-321°F) |
Critical Note: Alloy 625 is a solid solution strengthened alloy. Cold working is the primary method to increase strength beyond the annealed condition.
Heat Treatment Condition:
All Alloy 625 round bars are solution annealed at 1095–1205°C followed
by water quenching.
Delivery Condition Options:
l Annealed: For general service and further machining
l Cold Worked: For high-strength applications (YS ≥620 MPa)
l Peeled/Turned: Smooth, bright surface – for precision machining
l Centerless Ground: Precision ground to tight tolerances – for high-precision shafting
|
Diameter Range |
Condition |
Tolerance Grade |
Tolerance (mm) |
|
10mm – 18mm |
Peeled / Cold Drawn |
h9 |
-0.030 / -0.076 |
|
18mm – 30mm |
Peeled / Cold Drawn |
h9 |
-0.052 / -0.117 |
|
30mm – 50mm |
Peeled |
h9 |
-0.062 / -0.142 |
|
50mm – 80mm |
Peeled / Turned |
h11 |
0 / -0.220 |
|
80mm – 120mm |
Turned |
h11 |
0 / -0.250 |
|
120mm – 200mm |
Turned |
h11 |
0 / -0.400 |
Precision Ground Tolerances (Centerless Ground):
|
Diameter Range |
Tolerance Grade |
Tolerance (mm) |
|
10mm – 30mm |
h6 |
0 / -0.013 |
|
30mm – 50mm |
h6 |
0 / -0.016 |
|
50mm – 80mm |
h6 |
0 / -0.019 |
Standard Lengths: 3000mm – 6000mm (random), 3000/4000/5000/6000mm (fixed)
|
Diameter (mm) |
Weight (kg/m) |
Diameter (mm) |
Weight (kg/m) |
|
10 |
0.663 |
50 |
16.58 |
|
12 |
0.954 |
55 |
20.06 |
|
14 |
1.298 |
60 |
23.86 |
|
16 |
1.696 |
65 |
28.00 |
|
18 |
2.147 |
70 |
32.47 |
|
20 |
2.651 |
75 |
37.28 |
|
22 |
3.208 |
80 |
42.43 |
|
25 |
4.143 |
85 |
47.90 |
|
28 |
5.198 |
90 |
53.71 |
|
30 |
5.968 |
100 |
66.31 |
|
32 |
6.791 |
110 |
80.24 |
|
35 |
8.126 |
120 |
95.50 |
|
38 |
9.577 |
130 |
112.1 |
|
40 |
10.61 |
140 |
130.0 |
|
42 |
11.70 |
150 |
149.3 |
|
45 |
13.43 |
160 |
169.9 |
|
48 |
15.28 |
180 |
215.0 |
*Formula: Weight (kg/m) = Diameter² (mm) × 0.006631 (based on density 8.44 g/cm³)*
|
Surface Finish |
Code |
Description |
Typical Subsea/High-Temperature Applications |
|
Black (Hot-Rolled) |
HR |
As-rolled with mill scale |
Forging blanks, further processing |
|
Peeled |
P |
Smooth, bright, oxide-free surface |
Subsea connector shafts, pump shafts |
|
Turned |
T |
Smooth surface, consistent diameter |
Heavy shafts, valve stems |
|
Centerless Ground |
CG |
Precision ground, high surface finish |
Hydraulic cylinders, precision shafts |
|
Polished |
PL |
Mechanically polished, smooth finish |
Aerospace components |
Chemical Analysis: PMI verification for Ni (≥58%), Cr (20-23%), Mo (8-10%), Nb (3.15-4.15%).
Intergranular Corrosion Test: ASTM G28 – mandatory.
Pitting Corrosion Test: ASTM G48 – upon request.
Mechanical Testing: Tensile (≥825 MPa), yield (≥415 MPa), elongation (≥30%), hardness.
Dimensional Inspection: Diameter, length, straightness, roundness.
Surface Inspection: Visual check for defects, cracks, seams.
Ultrasonic Testing (UT): Upon request.
Sour Service Qualification (upon request): HIC per NACE TM0284, SSC per NACE TM0177.
Third-Party Inspection: SGS, BV, DNV, TUV, LR, ABS available.
Deepwater Subsea Connectors: Subsea connector shafts, ROV component shafts, subsea fastener systems (API 17E, ISO 13628-5 compliant).
Seawater Pump Shafts: High-pressure seawater injection pump shafts, deepwater lift pump shafts, firewater pump shafts.
Aerospace Components: Aircraft hydraulic actuator shafts, fuel system components, landing gear shafts.
Chemical Injection Pump Shafts: Methanol injection shafts, glycol injection shafts, chemical skid pump shafts (NORSOK M-650 qualified).
High-Strength Valve Stems: Valve stems for HP/HT sour service, ball valve trunnions, gate valve stems (NACE MR0175 compliant).
Subsea Fasteners: Stud bolts, nuts, threaded rods for subsea flanges (API 17D compliant).
Thermal Oxidizer Shafts: High-temperature fan shafts, damper shafts, blower shafts (up to 980°C).
Hydraulic Cylinder Rods: Subsea hydraulic cylinder rods, precision actuator shafts (centerless ground, h6 tolerance).
1. What is the difference between
Alloy 625 and Alloy 825 for round bar applications?
Alloy 625 has higher molybdenum (8-10% vs 2.5-3.5%), higher PRE (≥45 vs 38-42),
higher strength (YS ≥415 MPa vs ≥240 MPa), and significantly better seawater
pitting resistance. For deepwater subsea shafts and seawater pump shafts, Alloy
625 is preferred. For sulfuric/phosphoric acid service, Alloy 825 is more
cost-effective.
2. Can Alloy 625 round bars be
machined?
Yes, but requires carbide tooling, slower speeds (20-30% slower than 316L), and
adequate coolant. Alloy 625 work hardens rapidly, so consistent feed rates are
important.
3. Is Alloy 625 resistant to
hydrochloric acid (HCl)?
Yes, Alloy 625 has good resistance to dilute HCl. For concentrated HCl at
elevated temperatures, Hastelloy C276 is recommended.
4. What strength levels are
available for Alloy 625 round bars?
Two primary conditions: Annealed (YS ≥415 MPa) and Cold Worked (YS ≥620 MPa).
For subsea fasteners and high-strength shafts, cold worked condition is
recommended.
5. Are Alloy 625 round bars suitable
for subsea umbilical applications?
Yes. Alloy 625 is the industry standard material for subsea umbilical
components (API 17E, ISO 13628-5 compliant).
6. What surface finish is best for
hydraulic cylinder rods?
Centerless ground finish with h6 tolerance is recommended for hydraulic
cylinder rods, providing precise diameter (±0.013mm for 10-30mm) and smooth
surface finish (Ra 0.2-0.4μm).
Outstanding Seawater Resistance: PRE ≥45 – highest among nickel alloys for shafting applications
API 17E / ISO 13628-5 Compliant: Suitable for subsea umbilical components
High Strength Options: Cold worked condition available (YS ≥620 MPa)
NACE MR0175 Compliant: Full sour service documentation
ASTM G28 Intergranular Tested: Mandatory corrosion resistance verification
Full Traceability: Heat number on each bundle – traceable to original mill certificate
Complete Diameter Range: 10mm to 200mm – standard and custom sizes
Precision Tolerances: h6, h9, h11 – meet your requirements
Wide Temperature Range: Suitable from -196°C to 980°C
Global Delivery: Exported to major deepwater subsea, aerospace, and extreme service projects
Website: www.womicstainless.com
E-mail: info@womicstainless.com
Tel / WhatsApp / WeChat:
Victor: +86 15575100681
Jack: +86 18390957568
Womic Steel – Your reliable partner for high‑quality stainless steel products, precision machined components, and custom solutions for corrosion‑resistant applications.
Stock Examples (Alloy 625 Stainless Steel Round Bars – Peeled Finish – Subsea Grade):
|
Diameter |
Length |
Finish |
Tolerance |
Weight (kg/m) |
Typical Application |
|
20mm |
6000mm |
Peeled |
h9 |
2.65 |
Subsea connector shafts |
|
30mm |
6000mm |
Peeled |
h9 |
5.97 |
Seawater pump shafts |
|
40mm |
6000mm |
Peeled |
h9 |
10.61 |
Chemical injection pump shafts |
|
50mm |
6000mm |
Peeled |
h9 |
16.58 |
Valve stems |
|
60mm |
6000mm |
Peeled |
h9 |
23.86 |
Agitator shafts |
|
80mm |
6000mm |
Turned |
h11 |
42.43 |
Subsea manifold shafts |
|
100mm |
6000mm |
Turned |
h11 |
66.31 |
Heavy subsea shafts |
Stock Examples (Alloy 625 Stainless Steel Round Bars – Centerless Ground – High Precision):
|
Diameter |
Length |
Finish |
Tolerance |
Weight (kg/m) |
Typical Application |
|
25mm |
3000mm |
Ground |
h6 |
4.14 |
Subsea hydraulic piston rods |
|
36mm |
3000mm |
Ground |
h6 |
8.61 |
Precision actuator shafts |
|
45mm |
3000mm |
Ground |
h6 |
13.43 |
Linear motion shafts |
Stock Examples (Alloy 625 Stainless Steel Round Bars – Cold Worked – High Strength – Fastener Grade):
|
Length |
Finish |
Tolerance |
Weight (kg/m) |
Typical Application |
|
|
14mm |
3000mm |
Peeled |
h9 |
1.30 |
HP/HT sour service studs |
|
18mm |
3000mm |
Peeled |
h9 |
2.15 |
NACE MR0175 bolts |
|
22mm |
3000mm |
Peeled |
h9 |
3.21 |
High-strength nuts |
|
27mm |
3000mm |
Peeled |
h9 |
4.84 |
Threaded rods for flanges |
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