MIL Specification Maraging 300 Steel Maraging Steel

MIL-S-46850

Maraging 300 Nickel Based Stainless Steel – 18% Nickel Alloy, High Quality

Steel: Bar, Plate, Sheet, Strip, Forgings, and Extrusions
18% Nickel Alloy, Maraging | 200 KSI, 250 KSI, 300 KSI, and 350 KSI

AS9100D / ISO 9001

Mill Test Reports

2–4 Week Delivery

877-237-6822

Quick Specification Facts

Spec Number MIL-S-46850 (MILS46850)

Material Maraging 300 Nickel Based Stainless Steel

Spec Type MIL (Military / Department of Defense Specification)

Category Maraging Steel / Nickel Based Stainless Steel

Composition 18% Nickel Alloy, Maraging

Strength Grades 200 KSI, 250 KSI, 300 KSI, and 350 KSI

Product Forms Bar, Plate, Sheet, Strip, Forgings, Extrusions

Certification AS9100D / ISO 9001 with full MTR traceability

Specification Overview

MIL-S-46850 (also referenced as MILS46850) is a United States Department of Defense Military Specification covering 18% nickel maraging steel in the form of bar, plate, sheet, strip, forgings, and extrusions. This specification covers four strength grades—200 KSI, 250 KSI, 300 KSI, and 350 KSI—classified as "High Quality," and is widely used in aerospace, defense, and high-performance structural applications requiring ultra-high strength combined with excellent toughness and good weldability.

Maraging steels derive their name from the martensitic transformation and age hardening (maraging) process that achieves their exceptional mechanical properties. The 18% nickel base, combined with additions of cobalt, molybdenum, and titanium, produces a virtually carbon-free martensitic microstructure that can be age hardened to yield strengths ranging from 200 to 350 KSI. Unlike conventional high-strength steels, maraging steels exhibit outstanding fracture toughness, minimal distortion during heat treatment, and excellent machinability in the solution-annealed condition prior to aging.

Available Product Forms

Bar

Plate

Sheet

Strip

Forgings

Extrusions

All product forms are supplied per MIL-S-46850 requirements in the applicable strength grade (200, 250, 300, or 350 KSI). Custom sizes, lengths, and pre-machined forms are available upon request. Contact our materials specialists for non-standard dimensions.

Nominal Chemical Composition

Element	Symbol	Nominal %	Notes
Nickel	Ni	18%	Primary alloying element; martensitic transformation
Cobalt	Co	8.5–9.0%	Strengthens martensite; reduces Mo solubility
Molybdenum	Mo	4.6–5.2%	Primary precipitation hardening element
Titanium	Ti	0.5–0.8%	Additional precipitation hardening
Aluminum	Al	0.05–0.15%	Deoxidizer; minor strengthening
Carbon	C	0.03% max	Very low carbon – minimizes carbide formation
Iron	Fe	Balance	Base metal

Chemical composition ranges are nominal and may vary by grade (200, 250, 300, 350 KSI). Consult the current issue of MIL-S-46850 for precise minimum/maximum requirements. Aero-Vac provides full mill test reports (MTRs) with certified chemistry for every order.

Key Properties & Specification Details

Property / Attribute	Details
Specification Number	MIL-S-46850 (MILS46850)
Issuing Organization	U.S. Department of Defense (DoD) – Military Specification
Material Type	18% Nickel Alloy Maraging Steel, High Quality
Steel Grade	Maraging 300 Nickel Based Stainless Steel
Strength Grades Covered	200 KSI, 250 KSI, 300 KSI, and 350 KSI
Available Forms	Bar, Plate, Sheet, Strip, Forgings, Extrusions
Tensile Strength (Grade 300)	~310 KSI (2,140 MPa) minimum
Yield Strength (Grade 300)	~300 KSI (2,070 MPa) minimum
Heat Treatment	Solution Annealed + Age Hardened (maraging process)
Weldability	Excellent – can be welded in annealed condition and re-aged
Machinability	Good in solution-annealed condition prior to aging
Magnetic Properties	Magnetic (martensitic microstructure)
Certification Available	AS9100D / ISO 9001, Certificate of Conformance, MTR

Typical Applications

Aerospace & Defense: Aircraft structural components, landing gear parts, missile and rocket motor cases, airframe fittings, and high-strength fasteners where ultra-high strength-to-weight ratio is critical.

Military & Ordnance: Gun barrels, cannon components, armor applications, high-pressure vessel components, and military hardware requiring extreme strength and toughness under demanding conditions.

Tooling & Die Applications: Plastic injection mold tooling, die casting dies, extrusion tooling, and precision machined tooling components benefiting from high hardness, dimensional stability, and excellent polishability.

Space & Launch Vehicle: Rocket motor cases, pressure vessels, high-strength structural brackets, and launch vehicle components requiring maximum strength with minimal weight.

High-Performance Industrial: Shafts, spindles, gears, and precision mechanical components in oil & gas, power generation, and industrial applications requiring ultra-high strength and fatigue resistance.

Frequently Asked Questions – MIL-S-46850

What is MIL-S-46850 and what does it cover?

MIL-S-46850 (also written MILS46850) is a United States Department of Defense Military Specification covering 18% nickel maraging steel in the form of bar, plate, sheet, strip, forgings, and extrusions. The specification covers four distinct strength grades—200 KSI, 250 KSI, 300 KSI, and 350 KSI—all classified as "High Quality." Maraging steels achieve their exceptional properties through a two-step heat treatment: solution annealing followed by age hardening (the maraging process). The result is ultra-high strength combined with outstanding fracture toughness, excellent weldability, and good dimensional stability—making MIL-S-46850 material ideal for demanding aerospace, defense, and high-performance structural applications.

What are the different strength grades covered by MIL-S-46850?

MIL-S-46850 covers four grades of 18% nickel maraging steel, each identified by its minimum yield strength: Grade 200 (200 KSI / 1,380 MPa), Grade 250 (250 KSI / 1,720 MPa), Grade 300 (300 KSI / 2,070 MPa), and Grade 350 (350 KSI / 2,415 MPa). The chemical composition of each grade is slightly different, with higher-strength grades containing progressively more cobalt and titanium to achieve greater precipitation hardening response. Grade 300 is the most commonly used grade in aerospace structural applications due to its excellent combination of strength, toughness, and availability. Grade 350 offers maximum strength but with somewhat reduced toughness and weldability. Our materials specialists can help you select the appropriate grade for your specific application requirements.

Does Aero-Vac supply MIL-S-46850 with full mill test reports and certifications?

Yes. All MIL-S-46850 material supplied by Aero-Vac is fully traceable to mill test reports (MTRs) confirming chemical composition and mechanical properties per the specification. We are AS9100D/ISO 9001 certified with a 99.6% quality rating. Every order ships with certificates of conformance, material certifications, and chemical/mechanical test reports. Electronic delivery of all documentation is available for fast turnaround. If your program requires additional special process certifications, compliance with DFARS requirements, or QPL qualification, our quality team can coordinate as needed.

What forms and sizes of MIL-S-46850 does Aero-Vac stock?

Aero-Vac maintains inventory of MIL-S-46850 in multiple product forms including bar (round, flat, and square), plate, sheet, strip, forgings, and extrusions across the 200, 250, 300, and 350 KSI grades. We carry a range of standard sizes and can provide custom-cut lengths, discs, blocks, and machined preforms from our in-house processing facility at the Port of Kalama. For non-standard dimensions, our team can source from our global supplier network. Contact us with your specific size, grade, and quantity requirements and we will provide a prompt quote with availability and lead time.

What are the typical lead times for MIL-S-46850 material?

In-stock MIL-S-46850 material is typically available for same-day or next-day shipment. For custom-cut or specially processed orders, our standard lead time is 2–4 weeks—significantly faster than the industry average of 8–12 weeks. Specialty forgings or extrusions requiring mill production may require 4–8 weeks depending on quantity, grade, and form. We prioritize urgent aerospace and defense requirements and will always provide honest, upfront delivery estimates. Rush processing is available on select items.

Can Aero-Vac provide value-added processing for MIL-S-46850 material?

Yes. Aero-Vac operates a complete in-house processing facility at our Port of Kalama location. For MIL-S-46850 maraging steel, we offer precision saw cutting (including disc and ring cutting), surface grinding, trepanning, turning, milling, and heat treatment services including solution annealing and age hardening to achieve the required strength grade. We also provide comprehensive mechanical and non-destructive testing services in-house. Having all capabilities under one roof allows for faster turnaround, tighter quality control, and reduced overall cost compared to using multiple vendors. Contact us to discuss your specific processing requirements.

Need MIL-S-46850 material or a custom quote?

Our maraging steel specialists can provide fast pricing, availability, and technical guidance for your MIL-S-46850 requirements.