631 Stainless Steel Fittings: High-Strength, Corrosion-Resistant Fittings for Demanding Applications
Meta Description: Discover 631 stainless steel fittings with superior strength (up to 1650 MPa) and excellent corrosion resistance. Ideal for aerospace, medical, and high-performance applications.
Introduction
631 stainless steel fittings are designed for high-performance applications that demand both superior strength and corrosion resistance. A semi-austenitic precipitation-hardening alloy, 631 stainless steel is renowned for its ability to achieve some of the highest strength levels among precipitation-hardening grades, with yield strengths of up to 1650 MPa. This combination of strength and corrosion resistance makes it ideal for use in the aerospace, medical, defense, and chemical processing industries.
As a precipitation-hardening alloy, 631 stainless steel is a versatile material used in a range of critical applications where high strength, fatigue resistance, and machinability are essential. In its various fitting forms such as buttweld, threaded, and socket weld fittings, it delivers exceptional performance in environments subject to high pressure and aggressive conditions, including high temperatures and corrosive chemicals.
At [Your Company Name], we offer the highest-quality 631 stainless steel fittings, available in a variety of sizes and conditions, with custom machining and rapid global delivery. We also provide detailed data sheets and certifications, ensuring that your requirements are fully met.
Product Overview & Superior Advantages
- Unmatched Strength: With a yield strength of up to 1650 MPa, 631 stainless steel fittings offer one of the highest strength ratings in the precipitation-hardening stainless steel category.
- Superior Corrosion Resistance: 631 stainless steel provides excellent resistance to both general corrosion and pitting corrosion, making it an ideal choice for aerospace, medical, and chemical industries.
- Fatigue Resistance: These fittings are specifically engineered for high-fatigue environments, offering improved fatigue resistance compared to other stainless steels.
- Machinability: In its annealed condition, 631 stainless steel offers good machinability, allowing for customization and fast turnaround for small-batch orders.
- Versatility in Application: Available in a wide variety of fitting types, including buttweld, threaded, and socket weld, these fittings are suitable for hydraulic connections, pressure vessels, and other high-performance applications.
Detailed Advantages:
- Highest Strength in Precipitation-Hardening Grades: Achieve up to 1650 MPa yield strength, ideal for aerospace and medical applications.
- Corrosion Resistance in Aggressive Environments: Excellent performance in chloride, acidic, and high-temperature environments, making it perfect for chemical processing.
- Wide Range of Sizes and Types: Available in buttweld, threaded, and socket weld fittings, with sizes ranging from 1/2" to 48".
- Full Traceability: Products come with full certification including EN 10204 3.1/3.2, PED, and NACE MR0175 compliance for harsh environments.
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 is made from a carefully balanced mix of chromium, nickel, and aluminum, making it highly resistant to corrosion while providing the strength necessary for demanding applications. This alloy is designed for precipitation hardening, which enables it to achieve the highest strength among PH grades.
Mechanical Properties
| Condition | Yield Strength (MPa) | Ultimate Tensile Strength (MPa) | Elongation (%) | Hardness (HRC) |
|---|---|---|---|---|
| Solution Annealed | 800 | 1000 | 25 | 30–35 |
| RH950 | 950 | 1150 | 15 | 38–42 |
| CH900 | 900 | 1100 | 12 | 40–45 |
| TH1050 | 1050 | 1200 | 8 | 42–46 |
| TH1100 | 1100 | 1250 | 6 | 44–48 |
631 stainless steel fittings show a yield strength of up to 1650 MPa in the TH1100 condition, which makes it suitable for high-pressure and high-stress applications, such as aerospace and medical equipment. The hardness range of 30–48 HRC provides excellent wear resistance.
Physical Properties
| Property | Value |
|---|---|
| Density (g/cm³) | 7.80 |
| Thermal Conductivity (W/m·K) | 16.0 |
| Magnetic (after hardening) | Yes |
With a density of 7.80 g/cm³ and thermal conductivity of 16 W/m·K, 631 stainless steel fittings are well-suited for applications involving heat exchange, such as in pressure vessels and turbine components. After heat treatment, the alloy becomes magnetic, which is beneficial in some applications.
631 vs 630 vs 17-7PH vs 304 vs 316 vs 17-4PH Fittings Comparison
| Property | 631 Stainless Steel Fittings | 630 Stainless Steel Fittings | 17-7PH Stainless Steel Fittings | 304 Stainless Steel Fittings | 316 Stainless Steel Fittings | 17-4PH Stainless Steel Fittings |
|---|---|---|---|---|---|---|
| Yield Strength (MPa) | 1650 | 1300 | 1300 | 250 | 290 | 1100 |
| Corrosion Resistance | Excellent | Excellent | Excellent | Good | Excellent | Good |
| Hardness (HRC) | 38–48 | 38–49 | 38–44 | 20–30 | 25–35 | 30–40 |
| Heat Treatment | RH950, CH900, TH1050, TH1100 | H900, H925, H1025, H1150 | H950, H900 | Annealed | Annealed | H900 |
| Cost | Moderate | Moderate | Moderate | Low | High | Moderate |
631 stainless steel fittings offer superior strength compared to 630, 17-7PH, and other grades, making it an ideal choice for high-performance applications where both strength and corrosion resistance are critical.
Available Types & Specifications
| Type | Size Range (NPS) | Wall Thickness | Pressure Rating | Standards | Surface Finish |
|---|---|---|---|---|---|
| Buttweld (Seamless & Welded) | 1/2″–48″ | Sch 10S–XXS | 2000#–9000# | ASTM A403 WP631, A182 F631 | Pickled, Bright Annealed, Polished |
| Threaded & Socket Weld (Forged) | 1/8″–4″ | - | 2000#–9000# | ASME B16.9, B16.11 | Pickled, Bright Annealed, Polished |
631 stainless steel fittings are available in buttweld, threaded, and socket weld configurations. They come in various sizes ranging from 1/2″ to 48″ (buttweld) and 1/8″ to 4″ (forged), with different wall thicknesses and pressure ratings.
Heat Treatment & Precipitation Hardening Guide
To achieve the highest strength and hardness, 631 stainless steel fittings undergo solution annealing at 1040°C and cold-rolling for the CH900 condition. These fittings can be aged under specific conditions (RH950, TH1050, TH1100) to achieve a hardness range of 38–48 HRC, depending on the application.
Major Applications
- Aerospace: Aircraft hydraulic connections, structural fittings, high-strength bellows
- Medical: Surgical tool connections, high-performance springs, medical device fittings
- Chemical Processing: Pressure vessel diaphragms, piping systems
- Nuclear: Reactor components, turbine casings
- High-Pressure Systems: Hydraulic systems, aircraft systems, aerospace components
631 stainless steel fittings are widely used in aerospace, medical, and high-pressure applications where both high strength and corrosion resistance are essential.
Product Images
Polished 631 stainless steel buttweld elbows and tees in RH950 condition ready for export
Professional infographic 631 stainless steel fittings data sheet + strength vs aging temperature curve
Real-installation collage – 631 fittings used in aerospace hydraulic systems, medical surgical tools, high-strength bellows, and aircraft components
Why We Are the Best 631 Stainless Steel Fittings Distributor
- Largest Stock: We maintain the largest stock of 631 stainless steel fittings in all heat-treated conditions.
- Direct Mill Relationships: We offer competitive pricing with direct relationships with the mills.
- Fast Delivery: We provide fast delivery, with global shipping to meet your deadlines.
- Customization: We offer custom machining and small-batch orders with quick turnaround.
- Full Certifications: We provide all necessary certifications including NACE MR0175 and ISO 15156 compliance.
Packaging & Quality Standards
Our 631 stainless steel fittings are packaged securely with individual plastic wrapping and wooden cases. We provide a full certification package for all products to ensure quality and traceability.
FAQ Section
- What is the maximum hardness of 631 stainless steel fittings?
- Is 631 stainless steel fittings magnetic after hardening?
- 631 vs 17-7PH differences (they are the same grade)?
- Can 631 fittings be welded and what filler?
- Recommended condition for maximum strength (CH900)?
- Corrosion resistance in chloride environments?
- NACE MR0175 / ISO 15156 compliance?
- Minimum order quantity?
- Lead time for Sch 80 buttweld 631 elbows?
- Can 631 fittings be polished to a mirror finish?
- Is 631 fittings suitable for cryogenic applications?
- Typical applications in aerospace?
Conclusion + Urgent Call-to-Action
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