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Premium Semi Austenitic Precipitation Hardening Stainless Steel Technical Introduction
Pyromet®350 with UNS registration S35000 are high-alloy steels. They contain about 4-30% of chromium. They are further classified into three types such as martensitic, austenitic, and ferritic steels. Another group of stainless steels are precipitation hardened steels. They are a combination of austenitic and martensitic steels.
Corresponding Standard Grades
AMS 5546、AMS 5548、AMS 5554、ASTM A579、ASTM A693、MIL S-8840、AMS 5745、AMS 5774、AMS 5775、SAE J467 (AM-350)
Available Product Forms：
• Available Mill Products: Round Bar, Flat Bar, Billet, Wire, Strip
• Industry Specifications: AMS 5548 (Strip), AMS 5745 (Bar)
Typical Application
Pyromet®350 is widely adopted for gas turbine compressor components including turbine blades, compressor discs, rotors and shafts, as well as all critical mechanical parts requiring high tensile strength under room and intermediate elevated temperatures across aerospace, power generation and petrochemical industries.
Pyromet® 350 Chemical Composition
| Element | Content Range | Element | Content Range |
| Carbon (C) | 0.07 ~ 0.11 | Manganese (Mn) | 0.50 ~ 1.25 |
| Phosphorus (P, Max.) | ≤0.040 | Sulfur (S, Max.) | ≤0.030 |
| Silicon (Si, Max.) | ≤0.50 | Chromium (Cr) | 16.00 ~ 17.00 |
| Nickel (Ni) | 4.00 ~ 5.00 | Molybdenum (Mo) | 2.50 ~ 3.25 |
| Nitrogen (N) | 0.07 ~ 0.13 | Iron (Fe) | Balance |
Corrosion Resistance Rating Chart
| Corrosion Medium | Resistance Grade | Corrosion Medium | Resistance Grade | Corrosion Medium | Resistance Grade |
| Nitric Acid | Good | Sulfuric Acid | Restricted | Nitric Acid | Good |
| Phosphoric Acid | Restricted | Acetic Acid | Moderate | Phosphoric Acid | Restricted |
| Sodium Hydroxide | Moderate | NaCl Salt Spray | Good | Sodium Hydroxide | Moderate |
| Sea Water | Restricted | High Humidity | Excellent | Sea Water | Restricted |
UNS S35000 Physical Properties
| Material Condition | Specific Gravity | Density |
| Annealed | 7.92 | 0.2860 lb/in³ |
| Sub-zero Cooled & Tempered | 7.81 | 0.2820 lb/in³ |
Pyromet® 350 (UNS S35000) Mechanical Properties
| Properties | Metric | Imperial |
| Tensile strength | 1105 MPa | 160266 psi |
| Yield strength | 415 MPa | 60190 psi |
| Elastic modulus | 190-210 GPa | 27557-30458 ksi |
| Poisson’s ratio | 0.27-0.30 | 0.27-0.30 |
| Elongation | 30% | 30% |
| Hardness | 95 | 95 |
Mean Coefficient of Thermal Expansion
| Temperature Range | 10⁻⁶/°F | 10⁻⁶/K | |
| 68°F to | 20°C to | ||
| 212°F | 100°C | 6.3 | 11.3 |
| 572°F | 300°C | 6.8 | 12.2 |
| 752°F | 400°C | 7 | 12.6 |
| 932°F | 500°C | 7.2 | 13 |
| 1150°F | 620°C | 7.2 | 13 |
| 1350°F | 735°C | 6.7 | 12.1 |
| 1500°F | 815°C | 7 | 12.6 |
| 1700°F | 925°C | 7.5 | 13.5 |
Thermal Conductivity
| Test Temp (°F) | Test Temp (°C) | Thermal Conductivity (BTU•in/ft2•h•°F) | Thermal Conductivity (W/m·K) |
| 100 | 38 | 101 | 14.5 |
| 200 | 93 | 106 | 15.4 |
| 300 | 149 | 112 | 16.2 |
| 400 | 204 | 118 | 17.0 |
| 500 | 260 | 124 | 17.8 |
| 600 | 316 | 130 | 18.7 |
| 700 | 371 | 136 | 19.6 |
| 800 | 427 | 140 | 20.3 |
| 900 | 482 | 146 | 21.1 |
Standard Heat Treatment Specification
| Treatment Type | Process Parameters | Cooling Method |
| Annealing | 1850/1950°F (1010/1066°C), hold for 30 minutes per inch (25.4mm) of thickness | Rapid air cool to room temperature |
| Double Aging (DA) | 1.1350/1400°F (732/760°C), hold 3 hours; 2.825/875°F (440/468°C), hold 2-3 hours | Air cool to room temperature after each heating stage |
| Sub-Zero Cooling & Tempering (SCT) | 1.1710°F (932°C) ±25°F pre-condition, hold 90 minutes per inch (25.4mm) of thickness; 2.-100°F (-73°C), hold minimum 3 hours; 3. 850°F (454°C) / 1000°F (538°C), hold minimum 3 hours | Rapid cool after pre-conditioning; air cool after final tempering |
| Equalized and Overtempered | 1.1375/1475°F (745/801°C), hold 3-4 hours; 2.1000/1100°F (538/593°C), hold 3 hours | Air cool to room temperature after each heating stage |
Hot Working
Max forging temperature: 2150°F (1177°C); finish forging range:1700\1800°F (927\982°C). Overheating above 2150°F increases delta ferrite volume, while low finishing temperature prevents grain coarsening.
Cold Working
Annealed grade behaves similarly to AISI300 stainless for stamping & bending yet with higher work-hardening rate; heavy forming triggers partial martensite transformation. Hardened state only allows minor straightening operations. Equalized & overtempered condition is the optimal status for machining; annealed material is gummy and not recommended for cutting.
Weldability
Applicable processes: shielded arc welding & resistance welding; oxyacetylene welding is forbidden for carbon pickup risk. Matching filler metal preferred for full-strength joints; E/ER308 austenitic filler is acceptable when high weld strength is not required. Preheating unnecessary; post-weld full annealing is suggested for optimal combined properties. Silver/nickel-based filler alloys are applicable for brazing between 1600~1900°F.
Welding
Grade 350 stainless steel alloy can be welded using all common techniques except oxyacetylene welding method. After welding, this alloy is annealed to restore maximum properties.
About Us
C&N HONGCHENG PIPEFITTINGS LIMITED is a professional manufacturer in various alloy steel, stainless steel pipe fittings, flanges and special alloy products including Pyromet®350(UNS S35000). With standardized production workshop, complete testing equipment and mature global export service system, we provide customized machining, technical consultation and one-stop procurement solution for worldwide clients from petrochemical, power, aerospace and engineering industries. Warmly welcome global customers to contact us for inquiry.
