Direct answer: AMS4930M and AMS4931H both cover Ti-6Al-4V ELI bar, but they are not interchangeable. AMS4930M is an annealed product route, while AMS4931H is duplex annealed and specifically includes fracture-toughness control. The engineering drawing must select the route, size range, test orientation, ultrasonic acceptance basis, heat-treatment evidence, and any customer-approved-source requirements.[1][2]

Supply Scope for Aerospace Technical Review

DAXUN can coordinate Grade 23 titanium bar, machining blanks, inspection, process records, and export delivery against the approved drawing and purchase order. The written quotation identifies the applicable mill, processor, laboratory, and inspection responsibilities.

Item	Scope that may be coordinated
Principal material	Ti-6Al-4V ELI bar to AMS4930M or AMS4931H, as specifically ordered
Product form	Round bar, specified bar shapes, cut lengths, and machining blanks within the selected standard’s scope
조건	Annealed under AMS4930M, or duplex annealed with the AMS4931H fracture-toughness route
Preparation	Saw cutting, facing, chamfering, peeling, rough turning, centerless grinding, or another confirmed condition
Verification package	Material certification, heat and lot identity, heat-treatment records, mechanical and fracture-toughness reports when required, UT report, dimensions, surface condition, and agreed third-party records
Important boundary	Base-material conformity does not by itself establish aircraft-program approval, design allowables, finished-part release, or source approval

The most useful quotation begins with the drawing requirement, not the phrase “aerospace Grade 23.” The selected AMS route changes the heat-treatment condition, bar-size boundary, required evidence, and technical meaning of the certificate.

What Is the Practical Difference Between AMS4930M and AMS4931H?

AMS4930M and AMS4931H describe different engineering routes for the same nominal ELI alloy family. AMS4931H is not simply a stronger version of AMS4930M; its distinguishing purpose is duplex-annealed material with fracture-toughness control.[1][2]

Decision point	AMS4930M	AMS4931H	Procurement effect
Published condition	Annealed	Duplex annealed	Do not substitute a generic anneal or heat-treatment statement
Distinguishing requirement	General annealed ELI product route	ELI route specifically identified with fracture toughness	4931H is design-driven, not merely a higher-strength option
Published bar-size scope	Through 10.000 in. (254 mm), with a maximum cross-sectional-area rule for bars over 4.000 to 10.000 in.	6.000 in. (152.40 mm) and under in nominal diameter or least distance between parallel sides	Check section size before requesting a certificate
Other listed forms	Wire, forgings, flash-welded rings, and stock within the published scope	Forgings, flash-welded rings, and related stock within the published scope	Product form must match the drawing
Fracture-toughness evidence	Not identified as the specification’s defining route	A defining part of the specification title and purpose	The report, specimen orientation, test validity, and applicable acceptance requirement must be reviewed
Substitution	Only with engineering approval	Only with engineering approval	Same nominal alloy does not create automatic equivalence

The current revisions reviewed for this page are AMS4930M, revised November 13, 2025, and AMS4931H, revised March 19, 2026.[1][2] A purchase order should state the exact revision required by the drawing or program. The word “latest” is not a substitute for configuration control.

Why Is AMS4931H a Design-Driven Specification?

Fracture toughness answers a different question from tensile strength. A tensile test describes the response of a smooth specimen under a specified loading mode. A fracture-toughness test evaluates resistance to crack extension under defined crack, constraint, orientation, temperature, and environment conditions.

ASTM E399-24 describes the determination of linear-elastic plane-strain fracture toughness, K_IC, using fatigue-precracked specimens. It emphasizes that a valid result depends on specimen geometry and size, and that residual stress, crack orientation, temperature, environment, and product dimensions can affect interpretation.[3]

This creates the following causal chain:

Critical flaw assumption -> required damage tolerance -> material condition and microstructure -> valid fracture-toughness specimen and orientation -> reported result -> design and acceptance decision.

If a drawing invokes AMS4931H, the buyer should not ask only for a number labelled “KIC.” The file should show the applicable material lot, specimen orientation, test method, test temperature, result, and validity status required by the governing specification or drawing. A test that produces K_Q but does not satisfy the method’s validity requirements should not be silently represented as a valid K_IC result.

The additional fracture-toughness requirement makes AMS4931H a design-driven specification rather than simply a higher-strength grade. Substituting AMS4930M because its tensile values appear similar would miss the reason the drawing selected 4931H.

How Do Bar Size and Product Form Affect Specification Choice?

Size is a specification boundary, not just a pricing variable. The public SAE scopes set different bar limits.

AMS4930M includes bars through 10.000 in. (254 mm) nominal diameter. For bars over 4.000 to 10.000 in. (101.60 to 254 mm), the published scope also limits maximum cross-sectional area to 79 in.² (509.7 cm²).[1] AMS4931H lists bars 6.000 in. (152.40 mm) and under in nominal diameter or least distance between parallel sides.[2]

Quoted geometry	Review question	Risk if ignored	Required action
Round bar at or below 152.40 mm	Which condition and performance route does the drawing require?	Similar dimensions encourage an unauthorized substitution	Order the exact AMS revision and condition
AMS4930M bar over 101.60 mm	Does the section satisfy both diameter and area limits?	Diameter-only review may overlook cross-sectional-area scope	Calculate and record the actual section area
AMS4930M bar approaching 254 mm	Is the nominal size inside the current scope and available with required tests?	Certificate requested outside scope or impractical sampling	Complete mill and test-plan review before quotation
Non-round bar	What is the least distance between parallel sides and relevant section area?	Round-bar language is incorrectly applied	Put the exact shape and drawing dimensions on the PO
Forging stock or finished forging	Is the order for bar, stock for forging, or a finished forging?	Product form and testing responsibility become unclear	Match product description and certification to the actual stage

Do not assume that a finished forging can retain a bar certificate as its sole acceptance record. Forging, thermal processing, and final-part requirements may create a separate qualification and release route.

What Heat-Treatment Evidence Should Be Requested?

The certificate should identify the specified condition, but a one-line statement such as “heat treated” is not enough when the drawing requires a controlled aerospace route.

AMS2750H covers pyrometric requirements for equipment used in thermal processing of metallic materials, including temperature sensors, instrumentation, correction factors, system accuracy tests, and temperature uniformity surveys.[4] It supports furnace-control evidence; it does not itself define the alloy’s annealing cycle or certify that the material meets AMS4930M or AMS4931H.

For a project requiring heat-treatment traceability, the agreed file may include:

processor identity and approval status required by the customer;
material heat, lot, and load identification;
authorized process specification and revision;
furnace or equipment identification;
set point, actual temperature record, soak time, and cooling route as required;
AMS2750H equipment class/instrumentation and pyrometry evidence where invoked;
deviations, rework, and disposition;
links from the heat-treatment load to subsequent test specimens and delivered pieces.

The exact annealing cycle is controlled by the purchased specification and approved process. A supplier should not replace it with a generic internet temperature range. For AMS4931H, the thermal route is tied to the intended microstructure and fracture-toughness evidence; an undocumented additional heat cycle can invalidate that chain.

How Should Ultrasonic Testing Be Specified?

“UT pass” is not a complete aerospace acceptance requirement. A usable order identifies the governing practice, revision, acceptance class or criteria, scan coverage, reference standard, reporting, and any end-zone disposition.

AMS2631G covers ultrasonic inspection procedures for wrought titanium and titanium-alloy products 0.25 in. (6.4 mm) and over in cross-section or diameter.[5] ASTM E2375-26a is a general practice for ultrasonic examination of wrought products 0.250 in. (6.35 mm) or greater. ASTM E2375 defines five acceptance classes but requires the drawing, specification, or contract to identify the applicable criteria.[6]

UT variable	Why it matters	What the order should state
Practice and revision	Different procedures and reporting rules may apply	AMS2631G, ASTM E2375-26a, or customer method
Acceptance basis	Sensitivity without reject criteria is incomplete	Class, reference reflector, or drawing-specific criteria
Scan coverage	Geometry and near-surface/end zones can limit examination	Required coverage and treatment of unexamined zones
Surface condition	Roughness and geometry influence coupling and signal quality	Required pre-UT surface and dimensions
Calibration/reference standard	Establishes examination sensitivity	Applicable reference block and calibration records
Report linkage	Results must belong to the delivered material	Heat, lot, bar number, size, quantity, and report ID

The selected material specification, engineering drawing, and customer quality clauses may impose a specific UT route. Do not choose between AMS2631G and E2375 solely by availability; obtain approval when the contract is silent or contradictory.

Does an AMS Certificate Mean the Source Is Approved for an Aircraft Program?

No. Material-specification conformity and program approval are related but separate controls.

An AMS certificate can show that the supplied material was tested and reported to a material specification. An aircraft manufacturer, Tier supplier, defense authority, or other responsible engineering organization may additionally control melt source, conversion source, special processors, laboratory approvals, first-article status, change notification, country of origin, or document format.

The decision chain is:

AMS material requirement -> drawing and customer supplements -> approved sources and special processes -> inspection and release records -> finished-part acceptance.

If the purchase order omits a program-specific source restriction, the material may conform to the base AMS specification yet remain unusable for that program. DAXUN should receive the applicable source list or quality clauses before selecting a supply route. No public statement on this page represents DAXUN, a mill, or a processor as approved for a particular aerospace program.

What Are the Main Failure Modes?

Failure mode	Technical cause	Possible consequence	Prevention or verification
Ordering “AMS Grade 23” without a number	Annealed and fracture-toughness routes are conflated	Wrong condition and evidence package	State AMS4930M or AMS4931H on drawing and PO
Treating 4931H as a higher-strength option	Fracture-toughness purpose is misunderstood	Costly substitution that still misses design intent	Review damage-tolerance requirement and engineering approval
Ignoring bar-size scope	Diameter or area lies outside the published route	Invalid certification request	Calculate nominal size and section area before purchase
Accepting a generic KIC value	Lot, orientation, temperature, or validity is missing	Unsupported fracture-toughness acceptance	Review complete test report and E399 validity status
Undocumented heat treatment	Material identity is not linked to the furnace load	Condition and microstructure cannot be demonstrated	Load records, approved process, pyrometry evidence, and traceability
Writing only “100% UT”	No method, class, coverage, or criteria are defined	Supplier and customer mean different inspections	Freeze UT practice, revision, class, coverage, and reporting
Losing identity during cutting	Piece marking and cut records are incomplete	MTC and test reports cannot be tied to blanks	Cut map, traveler, controlled marking, and packing reconciliation
Assuming base AMS equals program approval	Customer source and process requirements are omitted	Conforming material rejected by the program	Review drawing notes, quality clauses, and approved-source lists
Applying bar records to a finished forging	Product-form responsibility is not updated	Final part lacks required forging/process evidence	Use the specification and qualification route for the delivered form

How DAXUN Coordinates an Aerospace Bar Package

DAXUN’s practical advantage is a single technical interface for aligning the bar, processing, inspection, records, and shipment.

Review configuration. Confirm drawing revision, AMS material revision, geometry, condition, and customer supplements.
Check scope. Verify product form, bar size, cross-sectional area, and test feasibility against the selected specification.
Map the supply route. Identify the applicable mill, heat-treatment processor, cutting or grinding provider, laboratory, and inspection body.
Freeze the inspection plan. Define mechanical testing, fracture toughness where applicable, UT practice and class, dimensions, surface, and document review.
Protect traceability. Connect source heat and lot to process loads, test specimens, cut blanks, and packing records.
Review before release. Resolve deviations and reconcile the certificate set with the delivered quantity and identities.

This coordination model does not imply that melting, bar conversion, heat treatment, NDE, cutting, and laboratory testing all occur in one DAXUN-owned facility. Capabilities, source approvals, and responsibilities are confirmed in the written quotation.

Information Required for an AMS Grade 23 Bar RFQ

Send the following for technical review:

drawing number and revision;
AMS4930M or AMS4931H, or the exact approved revision;
customer material code and any precedence clause;
bar shape, diameter or section dimensions, tolerance, length, and quantity;
required condition and any prohibited or additional thermal processing;
surface condition, straightness, machining allowance, and end preparation;
mechanical-test direction and location;
fracture-toughness requirement, orientation, temperature, specimen and reporting requirements where applicable;
UT practice, revision, class or acceptance criteria, coverage, and reporting;
approved melt, conversion, heat-treatment, NDE, or laboratory source restrictions;
traceability, marking, record-retention, third-party witness, and document-format requirements;
delivery location and required date.

Do not remove drawing notes that appear repetitive. In aerospace procurement, a note can establish the requirement that distinguishes a usable material lot from a base-specification-only certificate.

Related Technical Guides

[Ti-6Al-4V ELI Grade 23 titanium bar](/grade-23-titanium-alloy-rod-and-bar/) for the broader alloy and standards overview;
[Titanium rod and bar supply](/titanium-rod/bar/) for product forms and preparation routes;
[ASTM F136 titanium bar for implant manufacturing](/astm-f136-titanium-bar-implant-manufacturing/) for the separate medical raw-material and traceability route.

자주 묻는 질문

Is AMS4931H stronger than AMS4930M?

That is the wrong selection rule. AMS4931H is distinguished by its duplex-annealed, fracture-toughness-controlled route. It should be selected because the drawing requires that engineering basis, not because the buyer assumes it is simply a higher-strength grade.

Can AMS4930M be substituted for AMS4931H?

Not without approval from the responsible engineering authority. The two routes differ in condition, scope, and fracture-toughness requirements, so nominal alloy identity does not make them interchangeable.

What Are the Bar-Size Limits?

The published AMS4930M scope includes bars through 254 mm nominal diameter, with a maximum cross-sectional-area rule for bars over 101.60 to 254 mm. AMS4931H lists bars 152.40 mm and under in nominal diameter or least distance between parallel sides.[1][2]

Is a Reported KQ Value the Same as KIC?

Not automatically. ASTM E399-24 requires validity criteria to be satisfied before a result is treated as valid plane-strain fracture toughness, K_IC. The complete report and governing acceptance requirement must be reviewed.[3]

Is “100% UT” Enough Information on an RFQ?

No. State the procedure and revision, acceptance class or criteria, coverage, reference standard, surface condition, end-zone rules, and reporting. Otherwise, buyer and supplier may perform technically different examinations.

Does AMS4930M or AMS4931H Certify a Finished Aircraft Part?

No. These material specifications support raw-material conformity. Finished-part manufacturing, special-process approvals, design allowables, source approval, and final release remain controlled by the drawing, customer, and responsible engineering authority.

Technical Accuracy Statement

This page summarizes public standard scopes for RFQ and material-selection support. It does not reproduce controlled AMS or ASTM acceptance tables and does not establish design allowables, program approval, or finished-part release. The exact drawing, customer specifications, approved-source requirements, and purchased editions govern the contract. Any heat treatment, fracture-toughness test, or ultrasonic examination must be qualified and reported under the approved project route.

Last reviewed: July 22, 2026

Technical Sources

AMS4930M: Titanium Alloy Bars, Wire, Forgings, and Rings, 6Al-4V, Extra Low Interstitial, Annealed, SAE International, revised November 13, 2025.
AMS4931H: Titanium Alloy Bars, Forgings, and Rings, 6Al-4V Extra Low Interstitial (ELI), Duplex Annealed, Fracture Toughness, SAE International, revised March 19, 2026.
ASTM E399-24: Standard Test Method for Linear-Elastic Plane-Strain Fracture Toughness of Metallic Materials, ASTM International, active; last updated October 18, 2024.
AMS2750H: Pyrometry, SAE International, revised July 15, 2024.
AMS2631G: Ultrasonic Inspection Titanium and Titanium Alloy Bar, Billet, and Plate, SAE International, revised June 20, 2022.
ASTM E2375-26a: Standard Practice for Ultrasonic Testing of Wrought Products, ASTM International, active; last updated March 26, 2026.

AMS4930M vs AMS4931H Grade 23 Titanium Bar