BMS Specification 4330M Low Alloy Steel Alloy Steel

BMS 7-122

4330M Low Alloy Steel – Premium Aircraft Quality

Steel Bars, Forgings, Mechanical Tubing, and Forging Stock
0.88Cr – 1.8Ni – 0.42Mo – 0.08V – 0.28-0.33C | Consumable Electrode Vacuum Arc Remelted

AS9100D / ISO 9001

Mill Test Reports

2–4 Week Delivery

877-237-6822

Quick Specification Facts

Spec Number BMS 7-122 (BMS7-122)

Material 4330M Low Alloy Steel

Spec Type BMS (Boeing Material Specification)

Category 4330M Low Alloy Steel

Composition 0.88Cr – 1.8Ni – 0.42Mo – 0.08V – 0.28-0.33C

Process Consumable Electrode Vacuum Arc Remelted (VAR)

Product Forms Bars, Forgings, Mechanical Tubing, Forging Stock, Extrusions

Certification AS9100D / ISO 9001 with full MTR traceability

Specification Overview

BMS 7-122 (also referenced as BMS7-122) is a Boeing Material Specification covering premium aircraft-quality 4330M low-alloy steel in the form of bars, forgings, mechanical tubing, and forging stock. This specification is issued by The Boeing Company and is widely used in aerospace and defense applications demanding high tensile strength combined with good ductility, relatively high impact strength, superior transverse properties, and consistent hardness.

Per the specification: "These products have been used typically for parts requiring high tensile strength and good ductility with relatively high impact strength, superior transverse properties, and hardness, but usage is not limited to these applications." The material is produced by Consumable Electrode Vacuum Arc Remelting (VAR), equivalent to AMS 6411, which delivers a cleaner, more homogeneous microstructure and superior fatigue performance compared to air-melted grades. Note: Certain design and processing procedures may cause these products to become susceptible to stress-corrosion cracking after heat treatment. ARP1110 recommends practices to minimize such conditions.

Available Product Forms

Bars

Forgings

Mechanical Tubing

Forging Stock

Extrusions

All product forms are supplied to meet BMS 7-122 requirements. Custom sizes, lengths, and pre-machined forms are available upon request. Contact our materials specialists for non-standard dimensions or forging stock requirements.

Nominal Chemical Composition

Element	Symbol	Nominal %	Notes
Chromium	Cr	0.88%	Hardenability and corrosion resistance
Nickel	Ni	1.8%	Toughness and impact strength
Molybdenum	Mo	0.42%	High-temperature strength and hardenability
Vanadium	V	0.08%	Grain refinement and strength enhancement
Carbon	C	0.28–0.33%	Primary hardening element
Iron	Fe	Balance	Base metal

Chemical composition ranges are nominal. Consult the current issue of BMS 7-122 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	BMS 7-122 (BMS7-122)
Issuing Organization	The Boeing Company (Boeing Material Specification)
Material Type	Premium Aircraft-Quality Low-Alloy Steel
Steel Grade	4330M (Modified 4330 / AMS 6411)
Nominal Composition	0.88Cr – 1.8Ni – 0.42Mo – 0.08V – 0.28-0.33C
Melting Process	Consumable Electrode Vacuum Arc Remelted (VAR)
Available Forms	Bars, Forgings, Mechanical Tubing, Forging Stock, Extrusions
Tensile Strength	High – suitable for primary aircraft structural applications
Ductility	Good – balances high strength with acceptable elongation
Impact Strength	Relatively high – superior transverse properties
Stress-Corrosion Note	Certain design/processing procedures may cause susceptibility; refer to ARP1110
Certification Available	AS9100D / ISO 9001, Certificate of Conformance, MTR

Typical Applications

Aerospace Structural Components: Primary aircraft structural parts, wing fittings, fuselage frames, and other highly stressed components requiring the combination of high tensile strength and good ductility.

Landing Gear Components: Landing gear struts, actuators, fittings, and links where high strength-to-weight ratio and excellent fatigue resistance are critical for flight safety.

Fasteners & Fittings: High-strength fasteners, bolts, pins, and structural fittings used in airframe assembly and engine mounts requiring superior transverse properties and hardness.

Defense & Military Applications: Weapon system components, armored vehicle parts, and defense hardware demanding premium aircraft-quality steel with consistent mechanical properties and full traceability.

High-Stress Forgings: Complex forged shapes for aircraft and rotorcraft components where the VAR process ensures a cleaner microstructure, superior fatigue life, and improved impact strength compared to air-melted alternatives.

Frequently Asked Questions – BMS 7-122

What is BMS 7-122 and what does it cover?

BMS 7-122 (also written BMS7-122) is a Boeing Material Specification covering premium aircraft-quality 4330M low-alloy steel in the form of bars, forgings, mechanical tubing, and forging stock. The nominal chemistry of 0.88% Chromium, 1.8% Nickel, 0.42% Molybdenum, 0.08% Vanadium, and 0.28–0.33% Carbon delivers high tensile strength with good ductility, relatively high impact strength, and superior transverse properties. The material is produced by Consumable Electrode Vacuum Arc Remelting (VAR), equivalent to AMS 6411. It is widely used in aerospace, defense, and high-performance structural applications. Note that certain design and processing procedures may cause susceptibility to stress-corrosion cracking after heat treatment; ARP1110 recommends practices to minimize such conditions.

What is the difference between BMS 7-122 and AMS 6411?

BMS 7-122 and AMS 6411 both cover 4330M (Modified 4330) low-alloy steel produced by Consumable Electrode Vacuum Arc Remelting (VAR). The key differences are in the issuing body and scope of requirements: AMS 6411 is issued by SAE International as a broad aerospace material specification, while BMS 7-122 is a Boeing-specific procurement specification that may include additional Boeing-proprietary testing, documentation, and quality requirements. Both cover bars, forgings, and tubing in comparable compositions. For Boeing programs or Boeing-supplier qualification, BMS 7-122 compliance is typically required. For non-Boeing aerospace programs, AMS 6411 is commonly accepted. Aero-Vac can supply material meeting both specifications; contact us to discuss your specific program requirements.

Does Aero-Vac supply BMS 7-122 with full mill test reports and certifications?

Yes. All BMS 7-122 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 or Boeing-specific documentation, our quality team can coordinate as needed.

What forms and sizes of BMS 7-122 does Aero-Vac stock?

Aero-Vac maintains inventory of BMS 7-122 in multiple product forms including bars (round, flat, and hex), forgings, mechanical tubing, forging stock, and extrusions. We carry a range of standard sizes and can provide custom-cut lengths, discs, and blocks from our in-house processing facility at the Port of Kalama. For non-standard dimensions or specialty forging stock, our team can source from our global supplier network. Contact us with your specific size requirements and we will provide a prompt quote with availability and lead time.

What are the typical lead times for BMS 7-122 material?

In-stock BMS 7-122 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 items requiring mill production may require 4–8 weeks depending on quantity 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 BMS 7-122 material?

Yes. Aero-Vac operates a complete in-house processing facility at our Port of Kalama location. For BMS 7-122 4330M low-alloy steel, we offer precision saw cutting (including disc and ring cutting), surface grinding, trepanning, turning, milling, and heat treatment. 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 BMS 7-122 material or a custom quote?

Our alloy steel specialists can provide fast pricing, availability, and technical guidance for your BMS 7-122 / 4330M low-alloy steel requirements.