Grade dossier
13-8 Mo Stainless Steel for High Strength and Toughness
A low-carbon 13Cr-8Ni-Mo-Al precipitation-hardening grade used where high strength, toughness and resistance to stress-corrosion cracking must be balanced.
Identity before substitution
Define the grade, product and condition together
A familiar grade name is not a complete purchase specification. Product form, controlling standard, dimensions, condition, finish, certification and service environment determine whether the delivered material is suitable.
Composition control
ASTM A240/A240M flat-product chemistry
Limits are not heat analysis targets
The table summarizes grade limits commonly used for plate, sheet and strip. Pipe, tube, bar, forgings and cast products can be governed by different specifications. Always place the product standard and edition on the purchase order.
| C | 0.050 max |
|---|---|
| Mn | 0.10 max |
| Si | 0.10 max |
| P | 0.010 max |
| S | 0.008 max |
| Cr | 12.25-13.25 |
| Ni | 7.50-8.50 |
| Mo | 2.00-2.50 |
| Al | 0.90-1.35 |
Properties with context
Minimums, typical indicators and delivered condition
Specified annealed flat-product values
| Solution-treated condition | Starting state; not the final design condition |
|---|---|
| H950 | High-strength age |
| H1000/H1050 | Intermediate strength-toughness balance |
| H1150 | Overaged for greater ductility and SCC margin |
Selection indicators
| Density | about 7.76 g/cm3 |
|---|---|
| Strength mechanism | Aluminum-bearing precipitation hardening |
| Cleanliness | Melt practice and inclusion control can be critical |
| Procurement rule | Condition, melt route and test direction matter |
Values depend on product form, thickness, test orientation, condition and governing edition. Use the mill test certificate and the purchase specification for acceptance, not a web table alone.
Selection boundary
Where 13-8 Mo belongs and where to escalate
Grade selection is an environmental decision, not a popularity contest. Review the complete medium, temperature, geometry, fabrication, cleaning and inspection requirements.
Good reasons to evaluate it
Aircraft landing-gear and structural components
High-strength shafts, fasteners and valve parts
Nuclear and petrochemical components after qualification
Parts requiring low directionality and toughness
Reasons to stop and review
Calling generic 13-8 chemistry sufficient
Using H950 properties for solution-treated stock
Ignoring melt practice and ultrasonic inspection
Selecting final condition without SCC/toughness review
Fabrication route
Protect properties through cutting, forming and welding
State AMS/ASTM specification and melt practice.
Plan machining and welding around final aging.
Specify ultrasonic, cleanliness and test-direction requirements.
Verify final condition with hardness and mechanical testing.
Supply definition
Product form changes the applicable requirements
Do not send an RFQ that names only the grade. State form, governing standard, dimensions, tolerances, finish, edge or end condition, quantity, certification and inspection.
Bar, wire, forgings and rings to AMS 5629
ASTM A564/A564M products where applicable
Billet and premium-remelt aerospace stock
Machined high-strength components
Certificate checkpoint
Request heat identity, chemical analysis, mechanical results and compliance to the exact product specification. Add PMI, corrosion testing or supplementary examination only when the application requires it.
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Interactive selection check
Test 13-8 Mo against the controlling question
Procurement FAQ
Questions to close before placing the order
Is 13-8 Mo stainless steel magnetic?
Magnetic response depends on microstructure and delivered condition.
Can 13-8 Mo replace another grade?
Only after checking the governing standard, composition, mechanical properties, corrosion exposure, fabrication route and certification. A commercial name is not a substitution approval.
Does the table apply to every product form?
Not automatically. The values shown use flat-product requirements as a reference. Other forms can use different product standards, dimensions and tests.
What should a 13-8 Mo RFQ include?
Product form, standard and edition, UNS or EN designation, dimensions, tolerances, finish, quantity, service, fabrication, certificate and inspection requirements.
Sources, scope and RFQ
Use traceable grade data, then specify the actual product
AMS 5629 requirements for UNS S13800 products
Carpenter Technology 13Cr-8Ni official datasheet
ASTM A564/A564M requirements where applicable
Design allowables and purchaser quality requirements