Precipitation Hardening Stainless Steel Grades, Conditions & Supply

Shaanxi Shangyou Stainless Steel Co., Ltd. supplies precipitation-hardening stainless steel for aerospace components, shafts, valves, fasteners, gears, energy equipment, precision machinery, springs and other applications requiring a combination of:

High Strength · Hardness · Toughness · Corrosion Resistance · Dimensional Control

Precipitation-hardening stainless steels—often called PH stainless steels or age-hardening stainless steels—develop high mechanical properties through controlled heat treatment that causes strengthening precipitates to form within the metal matrix.

ASTM A564 describes age-hardening stainless steels as materials generally used where both corrosion resistance and high strength are required and notes that many can be machined in the solution-annealed condition before age hardening to the required mechanical properties.

Main commercial grades include:

17-4PH · 15-5PH · 17-7PH · 13-8Mo

“Precipitation Hardening Stainless Steel” describes primarily a strengthening mechanism and engineering material family, not one single metallographic structure.

This is important.

Examples:

• 17-4PH
• 15-5PH
• 13-8Mo

These develop a predominantly martensitic matrix before or during the age-hardening sequence.

Carpenter describes 17-4PH as a martensitic precipitation/age-hardening stainless steel and similarly classifies 15-5PH and 13-8Mo as martensitic precipitation-hardening alloys.

The important example is:

17-7PH / Type 631 / UNS S17700

Carpenter classifies 17-7PH as a semi-austenitic precipitation-hardening stainless steel. It is designed to be austenitic in the annealed condition for formability and can subsequently transform and be aged to obtain high strength.

Therefore it is incorrect to write:

All precipitation-hardening stainless steels are martensitic stainless steels.

Do not select these materials only from the nominal strength level.

Also evaluate:

• Toughness
• Section Size
• Product Form
• Heat-Treatment Condition
• Corrosion Environment
• Fatigue Requirement
• Machining
• Dimensional Stability

17-4PH / Type 630 / UNS S17400

17-4PH is the most important commercial precipitation-hardening stainless steel and is widely used when designers require high strength combined with useful corrosion resistance.

The designation “17-4” reflects its nominal chromium and nickel alloy concept, while copper contributes importantly to its precipitation-hardening response.

Carpenter describes 17-4PH as a martensitic age-hardening stainless steel offering:

• High Strength
• High Hardness
• Corrosion Resistance

and the ability to achieve different strength/toughness combinations using low-temperature aging treatments.

Typical applications include:

• Valve components
• Pump shafts
• Fasteners
• Gears
• Couplings
• Aircraft components
• Medical instruments
• Precision machinery
• Energy equipment
• Mechanical shafts

One of the biggest mistakes on stainless steel websites is to list:

17-4PH Stainless Steel

without mentioning the condition.

For engineering procurement, that is incomplete.

The same 17-4PH material can have substantially different:

• Strength
• Hardness
• Toughness
• Stress-corrosion behavior
• Machinability

depending on aging condition.

Common condition designations include:

The exact mechanical-property requirements must come from the applicable material specification rather than from generic website values.

For 17-4PH, Carpenter identifies H900 as a precipitation-aging condition in which solution-treated material is aged at approximately:

900°F / 482°C

followed by air cooling.

The “H” condition therefore represents an age-hardening treatment, not a material grade.

Correct purchase wording:

ASTM A564 Type 630 / UNS S17400, Condition H900

is much more precise than:

17-4PH stainless steel

alone.

A simplified engineering relationship is:

Lower Aging Temperature

→ generally higher strength and hardness

while:

Higher Aging Temperature

→ generally lower strength but greater toughness and, in some situations, improved stress-corrosion performance.

Carpenter notes that good stress-corrosion cracking resistance in its 17-4PH products is obtained using aging temperatures of approximately 1025°F / 552°C and above.

Therefore:

H900 is not automatically the “best” 17-4PH condition.

The appropriate condition depends on whether the design prioritizes:

• Maximum strength
• Hardness
• Impact toughness
• Fatigue
• SCC resistance
• Machining
• Dimensional stability

17-4PH is commonly machined in the solution-treated condition because machining can be practical before final aging.

However, final service condition must be confirmed.

Carpenter specifically cautions for its 17-4PH product that solution-treated material should not simply be assumed to be the preferred final condition and notes increased stress-corrosion concerns compared with appropriately aged material.

The purchasing specification should therefore state:

Material Condition at Delivery

and, separately if applicable:

Final Required Heat Treatment

15-5PH / UNS S15500

15-5PH is closely related to 17-4PH but is engineered to provide excellent transverse mechanical properties, toughness and forgeability.

Carpenter describes S15500 as a martensitic PH stainless steel with chemistry balanced to minimize delta ferrite, producing improved transverse toughness and ductility relative to conventional 17-4-type material.

Typical applications include:

• Aircraft components
• Fasteners
• Shafts
• Gears
• Valve components
• Engine components
• Fittings
• Energy equipment
• Precision mechanical parts

These grades are similar enough that procurement teams often compare them directly.

Carpenter specifically positions 15-5PH as similar to 17-4PH while emphasizing its high transverse strength, toughness and forgeability.

15-5PH is normally supplied in the solution-treated condition and can subsequently be age hardened.

Carpenter identifies common aging treatments between approximately:

900°F / 482°C

and

1150°F / 621°C

depending on the desired combination of properties.

Common commercial condition terminology includes:

• H900
• H1025
• H1075
• H1100
• H1150

depending on the governing specification.

Again:

Condition must accompany the grade in any mechanical-property quotation.

17-7PH / Type 631 / UNS S17700

17-7PH occupies a very different commercial position from 17-4PH.

Carpenter identifies S17700 as a semi-austenitic precipitation-hardening stainless steel designed to provide an austenitic structure in the annealed condition with good cold-working capability, after which high strength can be developed through transformation/cold work and aging.

Typical applications include:

• Spring wire
• Precision springs
• Spring strip
• Diaphragms
• Clips
• Retaining components
• Flexible high-strength components
• Antenna components

For Shangyou’s product architecture, 17-7PH should therefore link primarily to:

Stainless Steel Spring Wire

and

Precision Stainless Steel Strip

rather than being positioned mainly as a heavy round-bar alloy.

Unlike conventional 17-4PH procurement, cold deformation can form an important part of the strengthening route for certain 17-7PH products.

Carpenter notes that cold working of its S17700 material causes martensitic transformation and that appropriately cold-worked material can subsequently be age hardened.

This makes specification of:

Cold Reduction

Final Tensile Strength

Heat-Treatment Condition

Wire Diameter / Strip Thickness

especially important.

For stainless spring wire, ASTM A313/A313M-18 (2025) is currently active and covers austenitic, austenitic-ferritic and age-hardenable stainless steel round spring wire intended particularly for spring manufacture.

This makes A313 important when developing:

• 17-7PH Spring Wire
• product pages.
• Do not automatically use:
• ASTM A564

for every 17-7PH product form.

13-8Mo / UNS S13800

13-8Mo is a martensitic precipitation-hardening stainless steel designed for applications requiring a demanding combination of:

High Strength

Fracture Toughness

Transverse Mechanical Properties

Stress-Corrosion Resistance

Carpenter describes its S13800 material as a PH martensitic alloy used in aerospace, energy and other critical mechanical applications.

Typical applications include:

• Aircraft parts
• Jet-engine components
• Fasteners
• Gears
• Valves
• Nuclear equipment
• High-strength structural components
• Precision mechanical parts

13-8Mo is usually a more specialized material.

Carpenter’s production route for this alloy includes double-vacuum melting:

VIM + VAR

to improve cleanliness, homogeneity and critical mechanical performance.

Therefore a serious 13-8Mo RFQ may need information beyond:

Grade + Diameter.

It can include:

• Melt Practice
• AMS / ASTM Specification
• Grain Requirements
• UT
• Fracture Toughness
• Mechanical Properties
• Heat Treatment
• Aerospace Documentation

depending on the project.

Both can have martensitic structures, but their strengthening routes are fundamentally different.

Do not describe 17-4PH heat treatment as merely:

“quenching and tempering.”

Its commercial engineering identity is specifically tied to precipitation/age hardening.

17-4PH and 15-5PH should therefore not be marketed as universally “better” than 304 or 316L.

They solve a different engineering problem:

high strength while retaining useful stainless corrosion resistance.

PH stainless steels should not be selected solely from strength data.

Their corrosion resistance depends on:

• Grade
• Heat-Treatment Condition
• Surface Finish
• Environment
• Stress
• Temperature
• Chlorides
• Crevices
• Deposits

Carpenter’s corrosion guidance for 17-4PH specifically notes that temperature, concentration, pH, impurities, aeration, velocity, crevices, metallurgical condition, stress and surface finish all influence performance.

Therefore avoid generic claims such as:

Excellent corrosion resistance in all environments.

17-4PH should not be presented as a universal seawater alloy.

Where long-term chloride exposure, crevice corrosion or severe marine service governs selection, materials such as:

• 316L
• 2205 Duplex
• 2507 Super Duplex

may require comparison.

The final selection depends on:

• Chloride concentration
• Temperature
• Immersion or atmospheric exposure
• Crevices
• Cathodic conditions
• Stress
• Surface condition

rather than simply the strength level of 17-4PH.

The aging condition can influence stress-corrosion performance.

For 17-4PH, Carpenter reports improved SCC resistance using aging temperatures of 1025°F / 552°C and higher compared with lower-temperature high-strength conditions.

This is an important engineering tradeoff:

Maximum Strength

may not always equal:

Maximum Environmental Reliability

For SCC-sensitive projects, the final material condition should be specified by the project engineer or applicable industry standard.

A simplified martensitic PH route is:

Solution Treatment

↓

Cooling / Transformation

↓

Machining if required

↓

Age Hardening

↓

Hardness / Mechanical Verification

↓

Final Grinding / Finishing

ASTM A693 states that the mechanical properties of precipitation-hardening flat products are developed using suitable low-temperature heat treatments generally referred to as precipitation hardening.

Exact temperatures and hold times depend on:

• Grade
• Product Standard
• Section Size
• Desired Condition
• Required Mechanical Properties

Do not apply a universal 17-4PH treatment to:

• 15-5PH
• 17-7PH
• 13-8Mo

without confirming the governing specification.

Precipitation aging can produce dimensional change.

This becomes important for:

• Precision shafts
• Tight-tolerance aerospace parts
• Valve components
• Ground bars
• Precision machined parts

Carpenter publishes predictable dimensional contraction for selected 17-4PH aging conditions, demonstrating why machining sequence and final tolerances should be considered before heat treatment.

For precision components, RFQs should specify whether dimensions are:

Before Aging

or

Final After Heat Treatment and Grinding

One of the advantages of many martensitic PH grades is the ability to machine them before final aging.

ASTM A564 notes that covered materials are suitable for machining in the solution-annealed condition followed by age hardening to the required properties.

Available processing can include:

• Saw Cutting
• Turning
• Peeling
• Drilling
• Milling
• Grinding
• Polishing
• Rough Machining

For high-precision components, consideration should be given to:

• Heat-Treatment Distortion
• Machining Allowance
• Final Grinding
• Surface Roughness

Weldability depends on the PH grade and final required properties.

For critical applications, welding procedure development should consider:

• Base Grade
• Initial Condition
• Filler Metal
• Heat Input
• Section Size
• Final Aging Treatment
• Required Toughness
• Corrosion Environment

For 13-8Mo, for example, Carpenter notes that welding can be performed using conventional arc or resistance techniques, but optimum post-weld properties can require solution treatment followed by precipitation hardening.

Do not automatically apply a 304L welding procedure to PH stainless steels.

The applicable standard depends on product form.

ASTM A564/A564M-25 is currently active and covers:

• Hot-Finished Bars
• Cold-Finished Bars
• Rounds
• Squares
• Hexagons
• Angles
• Tees
• Channels

made from age-hardening stainless steels.

This is one of the most important standards for:

17-4PH Round Bar

15-5PH Bar

13-8Mo Bar

where the relevant grade is included.

ASTM A693-24 covers:

Precipitation-Hardening Stainless and Heat-Resisting Steel Plate, Sheet and Strip

and requires appropriate chemistry, mechanical properties and precipitation-hardening response.

This standard is especially relevant to:

• 17-4PH Sheet / Plate
• 17-7PH Sheet / Strip
• PH Precision Strip

subject to applicable grade coverage.

ASTM A705/A705M-23 covers age-hardening stainless-steel forgings for general use and requires applicable material to be solution annealed and age hardened to specified mechanical properties.

Typical products can include:

• Forged Bars
• Forged Rings
• Valve Parts
• Shaft Blanks
• Custom Forgings

ASTM A313/A313M covers stainless-steel round spring wire, including age-hardenable stainless materials.

This standard is particularly important for:

17-7PH Stainless Steel Spring Wire

Where precipitation-hardening stainless steel castings are required, ASTM A747/A747M-23 covers corrosion-resistant iron-chromium-nickel-copper cast steels capable of precipitation hardening.

This should remain separate from:

• A564 Bar
• and
• A705 Forgings.

Manufacturing route matters.

Never publish:

17-4PH Standard = ASTM A564

as though that standard covers every form of 17-4PH.

Correct structure:

Grade + Product Form + Standard + Condition

Core grades:

• 17-4PH
• 15-5PH
• 13-8Mo

Available conditions may include:

• Condition A
• H900
• H1025
• H1075
• H1150

depending on grade, dimensions and production route.

Processing:

• Cut to Length
• Peeled
• Turned
• Ground
• Polished
• Machined

Suitable for:

• Shafts
• Valve stems
• Aerospace components
• Medical components
• Precision machine parts

Specify:

• Diameter
• Diameter Tolerance
• Straightness
• Surface Roughness
• Condition
• Required Hardness

Grades can include:

• 17-4PH
• 15-5PH
• 13-8Mo

Typical RFQ requirements:

• Grade
• ASTM / AMS Specification
• Forged Size
• Heat Treatment
• Required Condition
• Mechanical Properties
• UT Requirement
• Machining Allowance

Common grades can include:

17-4PH

and other ASTM A693-covered materials.

Available processing:

• Cut to Size
• Saw Cutting
• Waterjet
• Machining
• Grinding

depending on thickness and material condition.

The most important PH strip grade is:

17-7PH

Typical uses:

• Springs
• Clips
• Diaphragms
• Flexible components
• Precision stamped parts

For strip, confirm:

• Thickness
• Width
• Edge
• Cold Reduction
• Final Tensile Strength
• Heat-Treatment Condition

17-7PH is particularly important in high-strength spring wire applications.

Carpenter identifies S17700 for high-strength wire applications such as springs after the appropriate cold working and aging process.

Specify:

• Diameter
• Tensile Strength
• Condition
• Coil Weight
• Surface
• Spring Requirement

This is a preliminary material-selection guide.

The correct purchase question is not only:

Which PH grade should I use?

It is:

Which grade and condition provide the required strength, toughness and environmental performance?

A simplified selection approach is:

Evaluate lower-temperature aging conditions such as:

H900

where permitted.

Evaluate:

H1025 / H1075

depending on grade and governing specification.

Higher aging conditions such as:

H1100 / H1150

may be evaluated depending on grade and service requirement.

Exact selection must be made from the applicable standard mechanical-property table.

Typical grades:

• 15-5PH
• 13-8Mo
• 17-4PH

Products:

• Fasteners
• Actuation components
• Engine parts
• Structural components
• Shafts
• Landing and control-system components

Typical grade:

17-4PH

or more specialized PH alloys depending on the environment.

Products:

• Valve components
• Shafts
• Couplings
• Pump components
• Mechanical tools

For sour-service applications, grade and heat-treatment condition must be checked against the applicable project specification rather than simply describing PH stainless as universally sour-service resistant.

Common candidates:

• 17-4PH
• 15-5PH

Products:

• Valve stems
• Shafts
• Seats
• Pump components
• Actuator components

The condition should be specified according to:

• Strength
• Hardness
• Impact requirement
• Corrosion environment

PH stainless steels are attractive where designers require:

High strength

combined with

good dimensional control after aging.

Applications include:

• Precision shafts
• Machine components
• Gears
• Fasteners
• Couplings

17-7PH should be evaluated for:

• Spring Wire
• Spring Strip
• Diaphragms
• Clips
• Retaining Components

because its semi-austenitic metallurgy and cold-working response differ substantially from the 17-4PH bar market.

Heat Number
Grade
UNS
Material Standard
Heat-Treatment Condition

Verify elements according to the grade specification.

For 17-4PH this can include key alloy elements such as:

Cr
Ni
Cu
Nb + Ta

depending on the specification.

PMI can help verify major alloying elements and distinguish alloy families.

However:

PMI does not confirm H900, H1025 or H1150 condition.

Heat-treatment condition must be verified through:

Heat Treatment Records
Mechanical Properties
Hardness
Material Certification

as applicable.

This is extremely important for PH stainless steel.

Hardness is often a critical PH stainless purchase requirement.

Possible methods include:

• HRC
• HRB
• HV
• HBW

depending on condition and specification.

The purchase order should clearly state:

Required Condition

and

Required Hardness / Mechanical Properties

rather than relying on generic grade values.

According to applicable specification:

• Tensile Strength
• Yield Strength
• Elongation
• Reduction of Area
• Impact Toughness
• Hardness

may be required.

ASTM A564 requires covered materials to undergo applicable tensile, impact and hardness testing.

For:

Large-Diameter Bar
Forged Bar
Aerospace Material
Critical Components

UT requirements may be specified according to the project standard.

Do not advertise UT as automatically included with every commercial PH stainless order.

Available documentation can include:

• EN 10204 3.1 MTC
• Heat Number
• Chemical Composition
• Mechanical Properties
• Material Condition
• Dimensions
• Testing Results

Additional documents can include:

• Heat Treatment Report
• Hardness Report
• UT Report
• PMI Report
• AMS Certification where applicable
• Third-Party Inspection

depending on project requirements.

Shaanxi Shangyou Stainless Steel Co., Ltd. can coordinate:

• Saw Cutting
• Cut-to-Length
• Turning
• Peeling
• Centerless Grinding
• Polishing
• Drilling
• Rough Machining
• Custom-Length Bar
• Plate Cutting
• Strip Slitting
• Export Packing

Final heat-treatment condition and machining sequence should be agreed before production for precision components.

For PH stainless steel, please provide more than just the grade.

Grade:
17-4PH / 15-5PH / 17-7PH / 13-8Mo

UNS:
S17400 / S15500 / S17700 / S13800

• ASTM A564
• ASTM A693
• ASTM A705
• ASTM A313
• AMS
• Project Specification

• Round Bar
• Ground Bar
• Forged Bar
• Plate
• Sheet
• Strip
• Wire
• Forging

Diameter × Length

or

Thickness × Width × Length

• Condition A
• H900
• H1025
• H1075
• H1150
• Other

• Required Tensile Strength
• Required Yield Strength
• Required Hardness
• Impact Requirement

• MTC 3.1
• UT
• PMI
• Hardness
• Third-Party Inspection

• Cutting
• Machining
• Grinding
• Heat Treatment

• Quantity
• Destination Port

Do not select PH stainless steel only from maximum tensile strength.

Send us:

Application

Required Yield Strength

Required Hardness

Required Toughness

Corrosion Environment

Operating Temperature

Product Form

Section Size

Final Machining Tolerance

and we can help narrow the material and condition before quotation.

Shaanxi Shangyou Stainless Steel Co., Ltd.

Precipitation-hardening stainless steels obtain high mechanical strength through controlled low-temperature aging treatments that produce strengthening precipitates in the material. ASTM A693 describes the development of mechanical properties through heat treatments generally referred to as precipitation hardening.

Important commercial grades include 17-4PH / S17400, 15-5PH / S15500, 17-7PH / S17700 and 13-8Mo / S13800.

17-4PH is commonly identified as Type 630 and UNS S17400.

Some important PH grades—including 17-4PH, 15-5PH and 13-8Mo—are martensitic PH steels. However, 17-7PH is semi-austenitic, so PH stainless steel should not universally be described as martensitic.

Condition A refers to the solution-treated starting condition used before final precipitation aging. The final engineering condition should be specified separately when age-hardened properties are required.

H900 is an age-hardening condition produced by aging solution-treated 17-4PH at approximately 900°F / 482°C followed by cooling according to the specified process.

H900 generally emphasizes higher strength and hardness, while higher-temperature aging conditions such as H1150 generally trade some strength for greater toughness and other performance benefits. Exact mechanical values must be taken from the applicable specification.

There is no universally best condition. Selection depends on required strength, hardness, toughness, fatigue, SCC resistance, machining and service environment.

15-5PH is closely related to 17-4PH but is chemically designed to minimize delta ferrite and emphasize strong transverse toughness, ductility and forgeability.

17-7PH is especially suitable for high-strength wire, springs and cold-worked components. Carpenter identifies it as a semi-austenitic PH grade designed for cold working followed by aging.

13-8Mo / UNS S13800 is a martensitic PH stainless steel designed to combine high strength with strong fracture toughness, transverse properties and stress-corrosion resistance.

Yes. ASTM A564 notes that many covered age-hardening stainless steels can be machined in the solution-annealed condition and subsequently aged to the specified properties.

ASTM A564/A564M-25 covers applicable hot- and cold-finished age-hardening stainless steel bars and shapes.

ASTM A693-24 covers precipitation-hardening stainless and heat-resisting steel plate, sheet and strip.

ASTM A705/A705M-23 covers age-hardening stainless steel forgings for general use.