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Introduction
Custom 630, also known as 17-4 PH stainless steel (UNS S17400), is the most widely used martensitic precipitation-hardening stainless steel with precisely controlled alloy composition. It achieves an exceptional engineering balance between high strength, good corrosion resistance, excellent machinability and flexible performance tunability. Through copper and niobium alloying and controlled aging treatment, it can reach a tensile strength exceeding 1310 MPa and hardness up to 45 HRC, while maintaining corrosion resistance comparable to 304 stainless steel. This makes Custom 630 an ideal material choice for high-stress applications requiring both strength and moderate corrosion resistance, such as oil & gas components, aerospace parts, high-pressure valves and precision machinery. The material is available in bars, forgings, plates, fasteners and finished pipe fittings, and is widely used across the global industrial manufacturing industry.
Chemical Composition of Custom 630 (17-4 PH)(wt%, ASTM A564)
| Element | Content (%) |
| Iron, Fe | Balance |
| Chromium, Cr | 15.00～17.50 |
| Nickel, Ni | 3.00～5.00 |
| Copper, Cu | 3.00～5.00 |
| Niobium + Tantalum, Nb+Ta | 0.15～0.45 |
| Carbon, C | ≤0.07 |
| Silicon, Si | ≤1.00 |
| Manganese, Mn | ≤1.00 |
| Phosphorus, P | ≤0.040 |
| Sulfur, S | ≤0.030 |
The excellent performance of Custom 630 stems from the synergistic effect of its alloying elements: 15–17.5% chromium forms a dense passive film on the surface, providing reliable corrosion protection in atmospheric, freshwater and mild chemical environments; 3–5% nickel stabilizes the martensitic matrix and improves toughness; 3–5% copper is the key precipitation-hardening element, forming fine copper-rich precipitates during aging to significantly enhance strength; 0.15–0.45% niobium combines with carbon to prevent chromium carbide precipitation, maintaining corrosion resistance and improving weldability.
Physical Properties of Custom 630 (17-4 PH)
| Properties | Metric | Imperial |
| Density | 7.80 g/cm³ | 0.282 lb/in³ |
| Melting Range | 1390 ~ 1430 ℃ | 2534 ~ 2606 ℉ |
| Modulus of Elasticity | 197 GPa | 28570 ksi |
| Poisson’s Ratio | 0.27-0.29 | 0.27-0.29 |
| Coefficient of Thermal Expansion (20–100℃) | 10.8 ×10⁻⁶/℃ | 6.0 ×10⁻⁶/℉ |
| Thermal Conductivity (Ambient Temperature) | 18.0 W/(m·K) | 12.5 BTU in/hr.ft².°F |
| Magnetic Feature | Magnetic in all heat-treated states | Magnetic in all heat-treated states |
Mechanical Properties of Custom 630 (17-4 PH)
| Heat Treatment Condition | Tensile Strength | Yield Strength | Hardness | ||
| Metric (MPa) | Imperial (ksi) | Metric (MPa) | Imperial (ksi) | ||
| Condition A (Solution Annealed) | ≥930 | ≥135 | ≥585 | ≥85 | HB ≤363 |
| H900 (Aged at 482℃) | ≥1240 | ≥180 | ≥1100 | ≥160 | HRC 40~45 |
| H1025 (Aged at 552℃) | ≥1060 | ≥154 | ≥860 | ≥125 | HRC 35~42 |
| H1075 (Aged at 579℃) | ≥965 | ≥140 | ≥725 | ≥105 | HRC 32~41 |
| H1150 (Aged at 621℃) | ≥790 | ≥115 | ≥515 | ≥75 | HRC 28~38 |
Heat Treatment & Hardening Cycle – Custom 630 (17-4 PH)
| Process | Temperature Range | Purpose |
| Solution Treatment | 1020 – 1060 °C | Dissolve all precipitates and form uniform martensitic structure |
| Rapid Cooling | Water / Air | Preserve the supersaturated martensitic matrix |
| Aging Treatment | 470 – 630 °C | Form fine strengthening precipitates to adjust strength and toughness |
| Stress Relieving | 600 – 650 °C | Reduce internal stresses from machining or forming |
Detailed Heat Treatment Instructions
Solution treatment is the first step for all Custom 630 products. Heat the material to 1020–1060°C, hold for sufficient time to ensure complete dissolution of precipitates, then rapidly cool to room temperature. This produces a soft, ductile microstructure ideal for machining and forming.
After machining, aging treatment is performed to achieve the desired mechanical properties. By adjusting the aging temperature, the material can be tailored to specific application requirements:
- H900 (470–490°C): Maximum strength and hardness, lowest toughness
- H1025 (540–560°C): Optimal balance of strength and toughness
- H1075 (570–590°C): Good strength with improved stress corrosion resistance
- H1150 (610–630°C): Maximum toughness and ductility, lowest strength
Fabrication Properties of Custom 630 (17-4 PH)
Welding: Acceptable weldability using most common welding methods (TIG, MIG, SMAW). Preheating is generally not required for thin sections. For thick sections (>12mm), preheating to 150–200°C is recommended. Post-weld solution treatment followed by aging is required to restore full mechanical properties in the weld and heat-affected zone.
Cold Forming: Good cold forming capability in the solution-annealed (Condition A) state. Can be bent, drawn and stamped into various shapes.
Hot Forming: Hot forming should be performed at 950–1150°C. After hot forming, complete solution treatment and aging are required to achieve optimal properties.
Machining: Excellent machinability in the solution-annealed (Condition A) state, comparable to 304 stainless steel. Machining in aged conditions is more difficult due to higher hardness.
Applicable Standards
1. ASTM / ASME Standards (Global Industrial General Purpose)
| Product Form | Standard Code | Description |
| Forged Components (Flange, Tee, Valve Body) | ASTM A705 / ASME SA705 | Specifications for precision forged pipe fittings and valve forgings |
| Bar & Forging Billets | ASTM A564 / ASME SA564 | Covers round bar stock, chemical analysis, mechanical properties and all standard heat treatment conditions |
| Plate, Sheet & Strip | ASTM A693 / ASME SA693 | Governs hot rolled and cold rolled stainless sheet and coil products |
| High Strength Fasteners | ASTM F593 Grade 630 | Standard for high-pressure bolts, studs and matching nuts |
| Stainless Steel Castings | ASTM A747 | Specification for cast pump and valve components |
| General Finishing Requirements | ASTM A484 | General requirements on surface condition and dimensional tolerances |
2. AMS Aerospace Standards (High-End Critical Applications)
- AMS 5643: Bar stock, rings, die forgings (also widely adopted in deep-sea oil & gas projects)
- AMS 5604: Thin sheets, strips
Typical Applications of Custom 630 (17-4 PH)
Suitable for applications requiring an excellent combination of high strength, good corrosion resistance and reliable toughness, Custom 630 is commonly used for:
- Oil & gas: High-pressure flanges, valves, pump shafts, drilling tools, offshore platform components
- Aerospace: Structural parts, engine components, landing gear parts, high-strength fasteners
- General industry: Precision machinery parts, gears, shafts, molds, tooling
- Medical: Surgical instruments, orthopedic implants
- Food processing: Equipment components requiring high strength and corrosion resistance
- Marine: Hardware and structural components exposed to saltwater environments
Available Forms & Size Range – Custom 630 (17-4 PH)
| Product Form | Typical Size Range |
| Round Bars / Rods | Ø6 mm – Ø400 mm |
| Flat Bars | 5 – 150 mm thickness |
| Plates | 6 – 200 mm thickness |
| Forged Flanges | DN15 – DN2000 (1/2″ – 80″) |
| Forged Fittings (Elbow, Tee, Reducer) | DN15 – DN1200 (1/2″ – 48″) |
| High Strength Fasteners | M6 – M120 |
| Custom Forged Components | As per customer drawing |
| Precision Machined Parts | CNC / Ground to specification |
If you need high-strength, corrosion-resistant components for high-stress industrial applications, Custom 630 (17-4 PH, UNS S17400) is your ideal choice. C&N offers a complete range of Custom 630 products including flanges, pipe fittings, forgings, bars and fasteners, all manufactured to strict international standards. Please contact us immediately if you have any requirements.
Frequently Asked Questions
Q: Which heat treatment condition should I choose for my application?
A: H900 is recommended for maximum strength and hardness; H1025 offers the best balance of strength and toughness; H1150 is preferred for applications requiring high toughness and impact resistance.
Q: Is Custom 630 magnetic?
A: Yes, Custom 630 remains magnetic in all heat-treated conditions due to its martensitic microstructure.
Q: Can Custom 630 be used in seawater environments?
A: Custom 630 has good corrosion resistance in atmospheric and freshwater environments. For prolonged seawater exposure, H1150 condition is recommended as it offers better stress corrosion resistance than higher strength conditions.
Q: What is the difference between Custom 630 and 304 stainless steel?
A: Custom 630 is 3–4 times stronger than 304 stainless steel while maintaining similar corrosion resistance. This makes it ideal for high-stress applications where weight reduction is important.
ABOUT US
C&N Industrial is a leading manufacturer of stainless steel pipes, flanges and pipe fittings. All products are available with epoxy coating and 3LPE coating and lining for anti-corrosion protection. We source all raw materials from highly reputable domestic and overseas suppliers. Every product undergoes strict quality inspection and testing in accordance with ISO 17025 quality management standards, ensuring stable quality, high precision and reliable performance for global industrial projects.
C&N PRODUCTS
elbows | tee | cross | reducers | bend | caps | coupling | plug | nipple | pipe | weldolet | plate | butted weld fittings | prefabricated spool | ring type joint flange
