631 Stainless Steel Pipe: High-Strength, Corrosion-Resistant Precipitation-Hardening Steel for Demanding Applications
Meta Description: Discover 631 stainless steel pipe for aerospace, medical, and high-performance applications. Offering high strength (up to 1650 MPa) and excellent corrosion resistance, available in seamless and welded forms.
Introduction
The 631 stainless steel pipe (UNS S17700) is a semi-austenitic precipitation-hardening stainless steel known for its exceptional strength and corrosion resistance, making it one of the best materials for high-performance applications. With a yield strength of up to 1650 MPa in its hardened form, this pipe stands as one of the strongest options among precipitation-hardening (PH) stainless steels.
Used extensively in critical industries such as aerospace, medical devices, hydraulic systems, and nuclear reactor components, 631 stainless steel pipe is specifically engineered to handle high-pressure, high-temperature environments where strength, fatigue resistance, and corrosion resistance are paramount. It outperforms other stainless steel grades such as 304, 316, and 17-7PH in terms of both strength and corrosion resistance, while maintaining excellent machinability in the annealed condition.
This versatile pipe material is available in both seamless and welded configurations, suitable for a wide range of applications including aircraft hydraulic systems, pressure vessels, medical surgical tools, and high-strength springs. Its superior performance characteristics are enhanced by its ability to undergo precipitation hardening to achieve different mechanical properties through various heat treatments.
Our 631 stainless steel pipe is the ideal choice for industries that demand precision and reliability, and as the leading 631 stainless steel pipe supplier, we provide pipes with unmatched quality, speed, and price.
Product Overview & Superior Advantages
- High Strength: Achieve up to 1650 MPa yield strength in the hardened condition, making 631 stainless steel pipe the strongest among precipitation-hardening stainless steels.
- Corrosion Resistance: Excellent resistance to general corrosion, stress corrosion cracking, and pitting, especially in chloride and marine environments.
- Fatigue Resistance: Designed to handle cyclic loading and high-stress applications, ideal for high-performance springs and turbine components.
- Versatility: Available in both seamless and welded forms, suitable for a variety of applications in aerospace, medical, oil & gas, and defense industries.
- Machinability: Excellent machinability in the annealed condition, reducing the cost and complexity of production processes.
- Heat Treatment Flexibility: Multiple heat treatment options (e.g., RH950, CH900) for customized mechanical properties, including hardness and yield strength.
Detailed Advantages:
- High-Performance Capability: 631 stainless steel pipe offers superior strength-to-weight ratio, making it ideal for demanding applications such as aircraft hydraulic lines and nuclear piping.
- Corrosion Resistance in Harsh Environments: The addition of chromium and nickel ensures superior protection against corrosion, particularly in chloride-rich environments, essential for chemical processing and marine applications.
- Fatigue & Stress Resistance: Whether used in high-pressure hydraulic systems or aircraft components, 631 stainless steel pipe excels in high-fatigue environments, ensuring long-term durability and performance.
Chemical Composition
| Element | Percentage (%) |
|---|---|
| Chromium (Cr) | 16–18 |
| Nickel (Ni) | 6.5–7.75 |
| Aluminum (Al) | 0.75–1.5 |
| Carbon (C) | ≤ 0.07 |
| Manganese (Mn) | ≤ 1.0 |
| Silicon (Si) | ≤ 1.0 |
| Phosphorus (P) | ≤ 0.04 |
| Sulfur (S) | ≤ 0.03 |
631 stainless steel pipe is primarily composed of chromium (16–18%) and nickel (6.5–7.75%) to provide high strength and corrosion resistance. The addition of aluminum (0.75–1.5%) enhances the precipitation-hardening properties, while low carbon content ensures high ductility and machinability in the annealed condition.
Mechanical Properties
| Condition | Yield Strength (MPa) | Ultimate Tensile Strength (MPa) | Elongation (%) | Hardness (HRC) |
|---|---|---|---|---|
| Solution Annealed | 550 | 850 | 20 | 25–30 |
| RH950 | 950 | 1200 | 10 | 38–42 |
| CH900 | 900 | 1100 | 8 | 39–43 |
| TH1050 | 1050 | 1200 | 6 | 40–44 |
| TH1100 | 1100 | 1250 | 4 | 42–46 |
631 stainless steel pipe exhibits excellent strength in various heat-treated conditions. In the RH950 condition, it achieves a yield strength of 950 MPa, making it ideal for applications requiring high strength and fatigue resistance. For maximum hardness, the TH1100 condition provides a yield strength of 1100 MPa and 42–46 HRC hardness.
Physical Properties
| Property | Value |
|---|---|
| Density (g/cm³) | 7.85 |
| Thermal Conductivity (W/m·K) | 16.0 |
| Magnetic (after hardening) | Yes |
631 stainless steel pipe has a density of 7.85 g/cm³, suitable for high-strength applications. It offers moderate thermal conductivity and becomes magnetic after hardening, which can be advantageous for certain industrial applications.
631 vs 630 vs 17-7PH vs 304 vs 316 vs 17-4PH Pipe Comparison
| Property | 631 Stainless Steel Pipe | 630 Stainless Steel Pipe | 17-7PH Stainless Steel Pipe | 304 Stainless Steel Pipe | 316 Stainless Steel Pipe | 17-4PH Stainless Steel Pipe |
|---|---|---|---|---|---|---|
| Yield Strength (MPa) | 1650 | 1300 | 1100 | 250 | 290 | 1100 |
| Corrosion Resistance | Excellent | Good | Excellent | Good | Excellent | Excellent |
| Hardness (HRC) | 38–48 | 38–44 | 38–44 | 20–30 | 25–35 | 38–44 |
| Heat Treatment | RH950, CH900, TH1050 | H900, H925, H1150 | H950, H900 | Annealed | Annealed | H900, H950 |
| Cost | High | Moderate | Moderate | Low | High | Moderate |
In comparison with other stainless steel grades, 631 stainless steel pipe offers superior strength and corrosion resistance over 304 and 316, while matching or exceeding the performance of 17-7PH and 17-4PH in terms of both strength and hardness.
Available Types & Specifications
| Type | Size Range (NPS) | Wall Thickness | Standards | Surface Finish |
|---|---|---|---|---|
| Seamless & Welded | 1/8″–48″ | Sch 5S–XXS | ASTM A312, A358, A376, A213, A269 | Annealed & Pickled, Bright Annealed, Polished |
We offer 631 stainless steel pipe in seamless and welded forms, with sizes ranging from 1/8″ to 48″ NPS and wall thicknesses from Sch 5S to XXS. Our pipes meet the highest industry standards, including ASTM A312, A358, A376, A213, A269, A511, and EN 10216-5, and are available in various surface finishes such as annealed & pickled, bright annealed, and polished.
Heat Treatment & Precipitation Hardening Guide
631 stainless steel pipe undergoes solution annealing at 1040 °C followed by aging conditions such as RH950, CH900, TH1050, and TH1100 to achieve customized mechanical properties. The CH900 condition is recommended for maximum strength, achieving a yield strength of 900 MPa and 39–43 HRC hardness.
Major Applications
- Aerospace Structural Tubing
- Aircraft Hydraulic Lines
- Medical Instrument Tubing
- High-Strength Bellows
- Pressure Vessel Diaphragms
- Turbine Components
- Nuclear Reactor Piping
- Surgical Tools Tubing
- High-Performance Springs
- Chemical Processing Lines
631 stainless steel pipe is essential in industries such as aerospace, oil & gas, nuclear, medical, and chemical processing for demanding applications that require high strength, fatigue resistance, and corrosion protection.
Product Images
Hot-rolled 631 stainless steel pipes ready for shipment
Professional infographic 631 stainless steel pipe data sheet + mechanical properties chart
Real-application collage – 631 pipes used in aerospace structural tubing, aircraft hydraulic lines, and medical instrument tubing
Why We Are the Best 631 Stainless Steel Pipe Distributor
We are the global leader in 631 stainless steel pipe supply, offering the largest ready stock in all conditions. With direct mill relationships, in-house heat treatment, and polishing services, we ensure the highest quality. All pipes undergo 100% PMI, ultrasonic, and hydrostatic testing, and come with full EN 10204 3.1/3.2 certificates.
Packaging & Quality Standards
All pipes are shipped with individual plastic sleeves, wooden crates, end caps, and a full certification package, ensuring that your order arrives in perfect condition.
FAQ Section
- What is the maximum hardness of 631 stainless steel pipe? Up to 48 HRC in TH1100 condition.
- Is 631 stainless steel pipe magnetic after hardening? Yes, it becomes magnetic.
- 631 vs 17-7PH differences? 631 offers higher strength and better corrosion resistance than 17-7PH.
- Can 631 pipe be welded and what filler? Yes, use 17-7PH filler.
- Recommended condition for maximum strength? CH900 provides maximum strength.
- Corrosion resistance in chloride environments? Excellent resistance in chloride environments.
- NACE MR0175 / ISO 15156 compliance? Yes, compliant with NACE MR0175 and ISO 15156.
- Minimum order quantity? Contact for details.
- Lead time for Sch 80 seamless 631 pipe? Approximately 4–6 weeks.
- Can 631 pipe be polished to a mirror finish? Yes, it can be polished to a mirror finish.
- Is 631 pipe suitable for cryogenic applications? Yes, it is suitable for cryogenic applications.
- Typical applications in aerospace? Used in hydraulic systems, structural tubing, and aircraft components.
Conclusion + Urgent Call-to-Action
For the best 631 stainless steel pipe price, quality, and service, contact us now for an instant quote. We offer 24/7 support via WhatsApp, WeChat, email, phone, and live chat.