15-5 PH Stainless Steel: Properties and Key Applications

15-5 PH Stainless Steel is a precipitation-hardening stainless steel that combines high strength and corrosion resistance with good fabricability. Classified as a martensitic stainless steel, it contains significant amounts of chromium and nickel, along with copper, which enhances its hardening response. The primary alloying elements include:

• Chromium (Cr): Provides corrosion resistance and contributes to the steel's hardness.
• Nickel (Ni): Enhances toughness and ductility, improving the steel's overall performance.
• Copper (Cu): Aids in precipitation hardening, increasing strength without compromising corrosion resistance.

Characteristics and Properties

15-5 PH exhibits several notable characteristics:

• High Strength: Achieves high tensile and yield strength, making it suitable for demanding applications.
• Corrosion Resistance: Offers excellent resistance to a variety of corrosive environments, including atmospheric conditions and some acidic environments.
• Good Fabricability: Can be easily machined and welded, which is advantageous in manufacturing processes.

Advantages and Limitations

Pros	Cons
High strength-to-weight ratio	Limited high-temperature performance
Excellent corrosion resistance	May require post-weld heat treatment
Good machinability and weldability	Higher cost compared to some other stainless steels

Historically, 15-5 PH has been widely used in aerospace, chemical processing, and other industries where high strength and corrosion resistance are critical. Its market position is strong, particularly in applications requiring a combination of mechanical properties and resistance to harsh environments.

Alternative Names, Standards, and Equivalents

Standard Organization	Designation/Grade	Country/Region of Origin	Notes/Remarks
UNS	S15500	USA	Closest equivalent to AISI 630
AISI/SAE	15-5 PH	USA	Precipitation hardening grade
ASTM	A564	USA	Specification for precipitation hardening stainless steels
EN	1.4545	Europe	Similar properties but may have slight compositional differences
JIS	SUS630	Japan	Comparable grade with minor differences

The differences between these equivalent grades often lie in their specific compositions and mechanical properties, which can affect their performance in particular applications. For instance, while UNS S15500 and AISI 630 are similar, slight variations in nickel and copper content can influence corrosion resistance and strength.

Key Properties

Chemical Composition

Element (Symbol and Name)	Percentage Range (%)
Chromium (Cr)	15.0 - 17.5
Nickel (Ni)	3.0 - 5.0
Copper (Cu)	3.0 - 5.0
Manganese (Mn)	1.0 max
Silicon (Si)	1.0 max
Carbon (C)	0.07 max
Phosphorus (P)	0.04 max
Sulfur (S)	0.03 max

The primary role of chromium is to enhance corrosion resistance, while nickel improves toughness and ductility. Copper plays a crucial role in the precipitation hardening process, significantly increasing the strength of the steel without compromising its corrosion resistance.

Mechanical Properties

Property	Condition/Temper	Test Temperature	Typical Value/Range (Metric - SI Units)	Typical Value/Range (Imperial Units)	Reference Standard for Test Method
Tensile Strength	Annealed	Room Temp	930 - 1,100 MPa	135 - 160 ksi	ASTM E8
Yield Strength (0.2% offset)	Annealed	Room Temp	620 - 850 MPa	90 - 123 ksi	ASTM E8
Elongation	Annealed	Room Temp	10 - 15%	10 - 15%	ASTM E8
Hardness (Rockwell)	Annealed	Room Temp	30 - 40 HRC	30 - 40 HRC	ASTM E18
Impact Strength	Quenched & Tempered	-40°C	40 J	29.5 ft-lbf	ASTM E23

The combination of high tensile and yield strength makes 15-5 PH suitable for applications that require structural integrity under mechanical loading. Its good elongation values indicate that it can withstand deformation without fracturing, which is essential in dynamic applications.

Physical Properties

Property	Condition/Temperature	Value (Metric - SI Units)	Value (Imperial Units)
Density	Room Temp	7.8 g/cm³	0.283 lb/in³
Melting Point	-	1,400 - 1,500 °C	2,552 - 2,732 °F
Thermal Conductivity	Room Temp	16 W/m·K	92 BTU·in/ft²·h·°F
Specific Heat Capacity	Room Temp	500 J/kg·K	0.12 BTU/lb·°F
Electrical Resistivity	Room Temp	0.73 µΩ·m	0.0000013 Ω·in

The density of 15-5 PH makes it a lightweight option for applications where weight savings are critical. Its thermal conductivity is moderate, which is beneficial in applications where heat dissipation is necessary, while its specific heat capacity indicates good thermal stability.

Corrosion Resistance

Corrosive Agent	Concentration (%)	Temperature (°C/°F)	Resistance Rating	Notes
Chlorides	3.5%	25°C/77°F	Good	Risk of pitting
Sulfuric Acid	10%	25°C/77°F	Fair	Susceptible to stress corrosion cracking
Acetic Acid	5%	25°C/77°F	Excellent	Resistant to localized corrosion
Atmospheric	-	-	Excellent	Good for outdoor applications

15-5 PH exhibits excellent resistance to atmospheric corrosion and is suitable for marine environments. However, it is susceptible to pitting in chloride-rich environments and stress corrosion cracking in the presence of sulfuric acid. Compared to grades like 304 and 316 stainless steels, 15-5 PH offers superior strength but may have lower resistance to certain corrosive agents, particularly in high-chloride environments.

Heat Resistance

Property/Limit	Temperature (°C)	Temperature (°F)	Remarks
Max Continuous Service Temp	300°C	572°F	Suitable for high-temperature applications
Max Intermittent Service Temp	400°C	752°F	Can withstand short-term exposure to higher temperatures
Scaling Temperature	600°C	1,112°F	Begins to lose mechanical properties

At elevated temperatures, 15-5 PH maintains good oxidation resistance but may experience a reduction in mechanical properties. Care should be taken in applications involving prolonged exposure to high temperatures, as this can lead to decreased strength and potential scaling.

Fabrication Properties

Weldability

Welding Process	Recommended Filler Metal (AWS Classification)	Typical Shielding Gas/Flux	Notes
TIG	ER 630	Argon	Preheat recommended
MIG	ER 630	Argon	Post-weld heat treatment may be required

15-5 PH is generally considered weldable, but preheating and post-weld heat treatment are often necessary to avoid cracking and ensure optimal mechanical properties. The use of appropriate filler metals is crucial to maintain corrosion resistance and strength in the weld area.

Machinability

Machining Parameter	[15-5 PH]	[AISI 1212]	Notes/Tips
Relative Machinability Index	60%	100%	Requires slower cutting speeds
Typical Cutting Speed (Turning)	30 m/min	50 m/min	Use carbide tools for best results

Machinability is moderate, and while it can be machined effectively, slower cutting speeds and specialized tooling are recommended to achieve optimal results and prevent tool wear.

Formability

15-5 PH can be cold formed, but its work hardening characteristics may limit the extent of deformation. Hot forming is also possible, but care must be taken to avoid excessive temperatures that could lead to loss of mechanical properties.

Heat Treatment

Treatment Process	Temperature Range (°C/°F)	Typical Soaking Time	Cooling Method	Primary Purpose / Expected Result
Solution Annealing	1,000 - 1,100°C / 1,832 - 2,012°F	1 hour	Air cool	Dissolves precipitates
Aging	480 - 620°C / 896 - 1,148°F	4 - 8 hours	Air cool	Increases strength through precipitation hardening

The heat treatment process involves solution annealing followed by aging, which enhances the steel's strength through the formation of fine precipitates. This process significantly alters the microstructure, leading to improved mechanical properties.

Typical Applications and End Uses

Industry/Sector	Specific Application Example	Key Steel Properties Utilized in this Application	Reason for Selection (Brief)
Aerospace	Aircraft components	High strength, corrosion resistance	Critical for safety and performance
Chemical Processing	Valve bodies	Corrosion resistance	Essential for harsh environments
Oil & Gas	Pump shafts	High strength, toughness	Required for demanding conditions
Medical Devices	Surgical instruments	Biocompatibility, corrosion resistance	Safety and reliability are paramount

Other applications include:

• • Marine hardware
• • Food processing equipment
• • Automotive components

15-5 PH is chosen for applications requiring a combination of high strength and corrosion resistance, particularly in environments where mechanical integrity is critical.

Important Considerations, Selection Criteria, and Further Insights

Feature/Property	[15-5 PH]	[AISI 304]	[AISI 316]	Brief Pro/Con or Trade-off Note
Key Mechanical Property	High strength	Moderate strength	Moderate strength	15-5 PH offers superior strength
Key Corrosion Aspect	Good in many environments	Excellent in most	Excellent in chlorides	15-5 PH may corrode in chlorides
Weldability	Moderate	Good	Good	15-5 PH requires careful handling
Machinability	Moderate	Good	Good	15-5 PH is less machinable
Formability	Moderate	Good	Good	15-5 PH is less formable
Approx. Relative Cost	Higher	Moderate	Moderate	Cost reflects performance benefits
Typical Availability	Moderate	High	High	15-5 PH is less common

When selecting 15-5 PH, considerations include its cost-effectiveness, availability, and specific performance requirements. While it may be more expensive than other stainless steels, its unique combination of properties often justifies the investment, especially in high-performance applications. Safety and reliability are paramount in industries like aerospace and medical, where 15-5 PH's properties can significantly impact performance and durability.

In summary, 15-5 PH stainless steel is a versatile material that excels in applications requiring high strength and corrosion resistance, making it a preferred choice in demanding environments.