Stainless pipe fitting,stainless fitting,duplex stainless,31803,32750,32760,we are one of largest sour service stainless fitting supplier according to ISO 10156.
1. Introduction
UNS S35500, also designated as AM-355 and AISI 634, is a semi-austenitic precipitation hardening stainless steel. It integrates superior formability under austenitic state and ultra-high strength after martensitic precipitation hardening.
This material overcomes the drawbacks of conventional high-strength stainless steels such as poor formability and insufficient corrosion resistance. It is widely adopted in aerospace and high-end industrial equipment for components requiring complex fabrication and reliable performance under severe service conditions.
2. Chemical Composition & Metallurgical Mechanism
Precise element proportion balances formability, mechanical strength and corrosion resistance.
| Element | Mass Fraction | Functional Effect |
| Carbon (C) | 0.10-0.15% | Secures basic strength without impairing toughness and corrosion resistance |
| Chromium (Cr) | 15.0-16.0% | Forms passive film to provide fundamental anti-corrosion property |
| Nickel (Ni) | 4.0-5.0% | Stabilizes austenitic structure and improves cold workability |
| Molybdenum (Mo) | 2.5-3.25% | Enhances pitting & crevice corrosion resistance and elevated-temperature strength |
| Manganese (Mn) | 0.50-1.25% | Performs deoxidation and desulfurization, optimizes hot working performance |
| Silicon (Si) | ≤1.00% | Deoxidizes alloy and boosts oxidation resistance |
Performance is determined by precipitation hardening mechanism. The raw material presents austenitic structure with excellent cold forming capacity. After solution treatment and cooling, metastable austenite is obtained. Subsequent low-temperature aging treatment precipitates intermetallic compounds like Ni₃Mo and partially transforms microstructure into martensite, bringing remarkable promotion on strength and hardness while retaining favorable toughness.
3. Key Properties
3.1 Mechanical Properties & Physical properties
Mechanical properties of grade UNS S35500
| Proof strength Rp0.2(MPa) | Tensile strength Rm(MPa) | Impact energy KV(J) | Elongation at fracture A(%) | Reduction in cross section on fracture Z(%) | As-Heat-Treated Condition | Brinell hardness(HBW) |
|---|---|---|---|---|---|---|
| 596(≥) | 972(≥) | 13 | 13 | 42 | Solution and Aging,Annealing,Ausaging,Q+T,etc | 144 |
Physical properties of grade UNS S35500
| Property | Density kg/dm3 | Temperature T °C/F | Specific heat J/kgK | Thermal conductivity W/mK | Electric resistance µΩ·cm | Modulus of elasticity kN/mm2 | Expansion rate | Temp. °C/°F | Creep strain limit (10000h) (Rp1,0)N/mm2 | Creep rupture strength (10000h) (Rp1,0)N/mm2 |
|---|---|---|---|---|---|---|---|---|---|---|
| 168(≥) | 348(≥) | 33 | 44 | 31 | Solution and Aging,Annealing,Ausaging,Q+T,etc | 434 | 988 | 998 | 416 |
3.2 Corrosion Resistance
Superior to quenched and tempered martensitic stainless steel, reaching the performance level of Cr-Ni austenitic stainless steel. It withstands atmospheric exposure, weak acid, salt spray and mild industrial corrosive media. Molybdenum addition greatly elevates resistance against chloride-induced pitting corrosion.
3.3 Machinability & Formability
- Cold working: Austenitic structure under solution state supports stamping, bending, drawing and other complex forming processes
- Welding: Compatible with conventional TIG/MIG welding. Post-weld aging restores original mechanical strength, suitable for integrated manufacturing of intricate components
- Machining: Turning, milling and drilling are feasible after hardening. Carbide cutters are recommended for high-precision and efficient processing
4. Main Application Fields
- Aerospace: Compressor blades, disks, rotors and shaft parts of gas turbines; core high-temperature load-bearing engine components
- Industrial Equipment: High-pressure valve parts, industrial cutters, precision gears and heavy-duty fasteners
- Other Premium Scenarios: Offshore engineering structural parts, high-load medical devices and high-performance automotive transmission components
What are the benefits of using Stainless Steel 355 in specific environments?
Stainless steel 355 (UNS S35500) has a unique composition and properties that offer several benefits in specific environments. In the oil and gas industry, for example, its high strength and excellent corrosion resistance make it ideal for use in drilling equipment, offshore installations and pipelines. This ensures durability and reduces maintenance requirements, even in harsh conditions involving saltwater, chemicals and high pressures.
In marine environments, stainless steel 355 is highly resistant to saltwater corrosion, making it suitable for ship parts and offshore structures that are exposed to seawater long term. Its high strength and fatigue resistance provide structural reliability in dynamic marine conditions.
Chemical processing plants benefit from this alloy’s resistance to a wide range of chemicals, including acids, alkalis, and organic solvents. It also maintains strength and oxidation resistance at moderately elevated temperatures, making it suitable for use in reactors, heat exchangers and processing vessels.
In gas turbines and power generation applications, Stainless Steel 355 is used for components such as blades, discs and rotors, where high strength at intermediate temperatures, as well as resistance to fatigue and creep, are essential.
Lastly, the alloy’s hardness, wear resistance and ability to retain sharp edges make it ideal for industrial cutters and knives in industrial cutting tools and general engineering. Its strength and versatility also support the production of various engineered parts, including valves and structural supports.
5. Heat Treatment & Processing Guidelines
- Solution treatment: Heat at 925-955℃ then air/oil cooling to acquire homogeneous austenitic structure
- Aging hardening: Insulate at 480-510℃ for precipitation strengthening and martensitic transformation. Lower aging temperature gains higher hardness, while higher temperature delivers better toughness
- Cold working strengthening: Proper cold deformation before aging further improves comprehensive mechanical performance
6. UNS S35500 Range of Our products
| Product type | Products | Dimension | Processes | Deliver Status |
|---|---|---|---|---|
| Plates/Sheets | Plates/Sheets | 0.08-200mm(T)*W*L | Forging,hot rolling and cold rolling | Annealed,Solution and Aging,Q+T,ACID-WASHED,Shot Blasting |
| Steel Bar | Round Bar,Flat Bar,Square Bar | Φ8-1200mm*L | Forging,hot rolling and cold rolling,Cast | Black,Rough Turning,Shot Blasting, |
| Coil/Strip | Steel Coil/Steel Strip | 0.03-16.0x1200mm | Cold-Rolled&Hot-Rolled | Annealed,Solution and Aging,Q+T,ACID-WASHED,Shot Blasting |
| Pipes/Tubes | Seamless Pipes/Tubes,Welded Pipes/Tubes | OD:6-219mm x WT:0.5-20.0mm | Hot extrusion,Cold Drawn,Welded | Annealed,Solution and Aging,Q+T,ACID-WASHED |
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