ATI Allvac® VascoMax® C-350 Specialty Steel

ATI Allvac® VascoMax® C-350 Specialty Steel, Heat Treatment: 927°C (1700°F) + Age Product Information -:- For detailed product information, please contact sales. -: ATI Allvac® VascoMax® C-350 Specialty Steel, Heat Treatment: 927°C (1700°F) + Age Synonyms -:- For detailed product information, please contact sales. -:

ATI Allvac® VascoMax® C-350 Specialty Steel, Heat Treatment: 927°C (1700°F) + Age Product Information -:- For detailed product information, please contact sales. -: # ATI Allvac® VascoMax® C-350 Specialty Steel ## Premium Ultra-High-Strength Cobalt-Nickel Maraging Steel | Heat Treated to 927°C + Aged --- ### **Product Overview** ATI Allvac® VascoMax® C-350 (commonly designated as **C-350 or C350**) is a **high-cobalt, high-titanium nickel-maraging steel** representing the **peak of commercially available strength in the standard maraging steel family**. Engineered to achieve a nominal yield strength of **350 ksi (≈2413 MPa)**, this grade is designed for applications where **maximum possible strength-to-weight ratio is the absolute, non-negotiable design driver**. The specified heat treatment of **austenitizing at 927°C (1700°F) followed by precipitation aging** develops its ultimate properties. While offering the highest strength, it comes with an **inherent trade-off of significantly reduced fracture toughness** compared to lower-strength maraging grades, demanding meticulous design and flawless fabrication. --- ### **Chemical Composition (Weight %)** | Element | Min (%) | Max (%) | Typical (%) | Metallurgical Function & Impact | |---------|---------|---------|-------------|--------------------------------| | **Nickel (Ni)** | 18.0 | 19.0 | 18.5 | Maintains the tough martensitic matrix; essential for residual toughness. | | **Cobalt (Co)** | **11.5** | **12.5** | **12.0** | **Critical Driver.** Maximizes supersaturation of Mo, providing immense driving force for precipitation. Enables strength > 2400 MPa YS. Major cost driver. | | **Molybdenum (Mo)** | 4.6 | 5.2 | 4.9 | Primary precipitation hardener; forms Ni₃Mo intermetallics. | | **Titanium (Ti)** | **2.8** | **3.1** | **3.0** | **Key Differentiator.** Extremely high vs. C-300 (~1.35%). Forms a very high density of Ni₃Ti precipitates, directly responsible for the 350 ksi strength level. Increases susceptibility to TiN inclusion formation. | | **Aluminum (Al)** | 0.05 | 0.15 | 0.10 | Deoxidizer. | | **Carbon (C)** | — | 0.03 | ≤0.01 | Ultra-low; critical to prevent embrittlement. | | **Manganese (Mn)** | — | 0.10 | 0.05 | Tightly controlled impurity. | | **Silicon (Si)** | — | 0.10 | 0.05 | Tightly controlled impurity. | | **Boron (B)** | — | 0.005 | 0.003 | Enhances hardenability. | | **Zirconium (Zr)** | — | 0.02 | 0.01 | Grain refiner; vital for managing limited toughness. | | **Sulfur (S)** | — | 0.005 | ≤0.002 | **Extra-Low Sulfur.** Mandatory to minimize inclusion-related failure initiation. | | **Phosphorus (P)** | — | 0.005 | ≤0.002 | **Extra-Low Phosphorus.** Mandatory to prevent grain boundary embrittlement. | | **Iron (Fe)** | Balance | — | — | Base element. | **Core Distinction:** The **extremely high titanium content (~3.0%)** is the defining characteristic, nearly double that of the C-300 grade. This composition shift prioritizes **precipitate density and strength** over **matrix ductility and toughness**. --- ### **Recommended Heat Treatment** 1. **Austenitizing (Solution Treatment):** * **Temperature:** **927°C (1700°F)** ± 15°C * **Time:** 1 hour per inch of thickness, then **Air Cool**. * **Purpose:** Produces uniform soft martensite. The high Ti content requires complete dissolution for effective aging. 2. **Aging (Precipitation Hardening):** * **Temperature:** **482°C (900°F)** ± 5°C * **Time:** **6-10 hours** (significantly longer than C-300). Extended time is required for the high volume of Ti-rich precipitates to form and reach optimal strengthening. * **Cooling:** Air Cool. * **Metallurgical State:** Achieves peak strength through an extremely high density of fine Ni₃(Ti, Mo) precipitates, resulting in high lattice strain and strength, but limited dislocation movement (low ductility/toughness). --- ### **Mechanical Properties (After 927°C Austenitize + Aged)** *Typical guaranteed minimum values in peak-aged condition (Longitudinal). Properties represent the practical limit for steel components.* | Property | Minimum Guaranteed | Typical Achieved | Test Standard | Critical Note | |----------|-------------------|------------------|---------------|---------------| | **Ultimate Tensile Strength (UTS)** | 2340 MPa (339 ksi) | 2400 – 2450 MPa (348 – 355 ksi) | ASTM E8 | | | **0.2% Yield Strength (YS)** | 2240 MPa (325 ksi) | 2300 – 2350 MPa (334 – 341 ksi) | ASTM E8 | **Nominal: 2413 MPa (350 ksi).** | | **Elongation (in 50 mm)** | **6%** | 7 – 9% | ASTM E8 | **Significantly reduced vs. C-300.** | | **Reduction of Area (RA)** | **25%** | 30 – 40% | ASTM E8 | **Severely reduced,** indicating high brittleness. | | **Hardness** | 54 HRC | 55 – 57 HRC | ASTM E18 | | | **Fracture Toughness (K_IC)** | **30 MPa√m** | 35 – 50 MPa√m | ASTM E399 | **The Critical Design Constraint.** ~50% lower than C-300. | | **Modulus of Elasticity** | 180 GPa | 185 – 190 GPa | ASTM E111 | | | **Impact Energy (Charpy V)** | **15 J** | 20 – 30 J | ASTM E23 | Very low impact resistance. | **The Strength-Toughness Trade-off is Extreme:** The **fracture toughness (KIC ~40 MPa√m)** is the **dominant limiting property**, not the yield strength. Design must be based on linear elastic fracture mechanics (LEFM) with high safety factors. --- ### **Physical Properties (Aged Condition, 20°C)** | Property | Value | |----------|-------| | **Density** | ~8.04 g/cm³ | | **Thermal Conductivity** | 18 – 20 W/m·K | | **Coefficient of Thermal Expansion** | 10.5 – 11.0 x 10⁻⁶ /°C (20-100°C) | | **Electrical Resistivity** | ~0.70 μΩ·m | | **Magnetic Properties** | Ferromagnetic | --- ### **Key Characteristics & Challenges** * **Unmatched Strength:** The highest yield strength commercially available in standard maraging steel product forms. * **Low Fracture Toughness:** Inherently brittle; **highly notch and flaw-sensitive**. * **High Cost:** Driven by high Cobalt and stringent melting/processing requirements. * **Complex Heat Treatment:** Requires extended, precisely controlled aging. * **Difficult Machining (Aged):** Near-impossible without CBN/diamond tools. Best machined in annealed state. * **Poor Weldability:** Welding is generally avoided. Requires extreme care and full re-heat treatment if necessary. * **Strict Quality Requirements:** Demands premium melting (VIM/VAR) and exhaustive NDT due to low damage tolerance. --- ### **International Standards & Designations** This is a specialized grade with specific aerospace standardization. | Standard/System | Designation | Title / Notes | |----------------|-------------|---------------| | **Aerospace Material Spec (AMS)** | **AMS 6518** | *Maraging Steel, 18Ni 11.5Co 4.8Mo 1.4Ti (0.10Al) (0.020C)*. This is the **primary governing specification**. (Note: The Ti range in AMS 6518 is typically 1.2-1.45%; C-350 chemistry may be supplied under a deviation or SCD). | | **Proprietary/Trade Name** | **ATI Allvac VascoMax C-350**, **Marval 18-350** | Leading commercial names. | | **Unified Numbering System (UNS)** | Often under **K92890**, but requires explicit chemistry/strength callout. | | | **Customer-Specific** | NASA, Major Defense Prime SCDs | Often the controlling document, specifying even tighter chemistry and NDT. | --- ### **Primary Applications** Application is restricted to **niche, performance-critical components** where its deficiencies are managed by design. 1. **Aerospace & Defense (Primary Use):** * **Solid Rocket Motor Cases:** For high-performance strategic and tactical missiles where maximum chamber pressure demands ultimate strength. * **Re-entry Vehicle and Hypersonic System Components.** * **High-Strength Fasteners and Pins** in critical, minimal-size applications. * **Certain Aircraft Landing Gear Components** in ultra-high-performance designs. 2. **Tooling & High-Pressure Equipment:** * **Extrusion Dies and Mandrels** for the most challenging materials (e.g., high-temperature superalloys). * **Die Inserts for High-Pressure Die Casting** requiring maximum hot strength. * **Components for Ultra-High-Pressure Isostatic Presses (HIP).** 3. **Specialized Industrial:** * **High-Load, Minimum-Deflection Shafts** in precision machinery where stiffness and strength are paramount. --- ### **Fabrication, Design & Quality Imperatives** **Design Philosophy:** * **"Safe-Life" design is mandatory.** "Damage-Tolerant" design is **not applicable**. * **Fracture Mechanics-Based:** Maximum allowable flaw sizes are very small. **Proof testing** of finished components is common. * **Eliminate Stress Concentrations:** Generous radii, polished surfaces, and avoidance of notches are non-negotiable. **Fabrication:** * **Machining:** **Exclusively in the annealed condition.** Final shaping via **grinding** or **EDM** after aging. * **Welding:** **Strongly discouraged.** If unavoidable, use precise GTAW with matching filler and a full re-solution + extended re-aging cycle. * **Heat Treatment:** Requires furnace uniformity better than ±5°C. **Quality Assurance (Flight-Critical Level):** * **Melting:** **Vacuum Induction Melting (VIM) + Vacuum Arc Remelting (VAR)** is standard. * **NDT:** **100% Ultrasonic Testing** to a severe standard (e.g., FBH 0.8 mm). Plus surface inspection (MPI/FPI). * **Certification:** EN 10204 3.2 certificate with full traceability, chemistry, mechanical tests, and **fracture toughness data**. --- ### **Comparison within the Maraging Family** | Feature | **C-350** (~350 ksi YS) | **C-300** (~300 ksi YS) | **C-250** (~250 ksi YS) | |---------|--------------------------|--------------------------|--------------------------| | **Typical YS** | 2300-2350 MPa | 1960-2050 MPa | 1725-1790 MPa | | **Toughness (KIC)** | **Low (35-50 MPa√m)** | **High (75-90 MPa√m)** | **Very High (55-75 MPa√m)** | | **Key Element** | **Very High Ti (~3.0%)** | High Ti (~1.35%) | Moderate Ti (~1.4% for 250) | | **Primary Design Limit** | **Fracture Toughness** | Balanced | Strength or Fatigue | | **Application Focus** | **Maximum Strength** | **Optimal Balance** | **High Toughness at High Strength** | --- ### **Summary** **ATI Allvac® VascoMax® C-350**, processed via **927°C austenitize and extended 482°C age**, is the **ultimate expression of strength in conventional maraging steel technology**. It is a **specialist material** whose selection signifies that all other design options have been exhausted and that **maximum strength is worth the severe penalties in toughness, cost, and manufacturability**. Its successful use is an **engineering achievement** that requires: 1. **Acceptance of its inherent brittleness** as the governing design factor. 2. **Perfect, flaw-free manufacturing.** 3. **Uncompromising quality control.** It is not a substitute for C-300 but a different tool for a different problem: when the design requirement is unequivocally **"The strongest possible material, and we will design the entire system around its limitations."** For the vast majority of ultra-high-strength applications, **C-300 remains the preferred and more forgiving choice.** -:- For detailed product information, please contact sales. -: ATI Allvac® VascoMax® C-350 Specialty Steel, Heat Treatment: 927°C (1700°F) + Age Specification Dimensions Size： Diameter 20-1000 mm Length <7363 mm Size:We can customized as required Standard： Per your request or drawing We can customized as required Properties（Theoretical） Chemical Composition -:- For detailed product information, please contact sales. -: ATI Allvac® VascoMax® C-350 Specialty Steel, Heat Treatment: 927°C (1700°F) + Age Properties -:- For detailed product information, please contact sales. -:

Applications of ATI Allvac® VascoMax® C-350 Specialty Steel, Heat Treatment: 927°C (1700°F) + Age -:- For detailed product information, please contact sales. -: Chemical Identifiers ATI Allvac® VascoMax® C-350 Specialty Steel, Heat Treatment: 927°C (1700°F) + Age -:- For detailed product information, please contact sales. -:

Packing of ATI Allvac® VascoMax® C-350 Specialty Steel, Heat Treatment: 927°C (1700°F) + Age -:- For detailed product information, please contact sales. -: Standard Packing: -:- For detailed product information, please contact sales. -: Typical bulk packaging includes palletized plastic 5 gallon/25 kg. pails, fiber and steel drums to 1 ton super sacks in full container (FCL) or truck load (T/L) quantities. Research and sample quantities and hygroscopic, oxidizing or other air sensitive materials may be packaged under argon or vacuum. Solutions are packaged in polypropylene, plastic or glass jars up to palletized 3834 gallon liquid totes Special package is available on request. E FORUs’ is carefully handled to minimize damage during storage and transportation and to preserve the quality of our products in their original condition