Stainless steel is a highly versatile material for CNC machining, widely used across various industries. Among the different grades, 17-4 PH stainless steel stands out as the preferred alloy due to its exceptional combination of properties, providing manufacturers and product designers with the strength and corrosion resistance needed to enhance their products.
In this article, we delve into 17-4 PH Stainless Steel, examining its properties, benefits, and applications. Let’s dive in!
What Is 17-4 Stainless Steel?
First, let’s understand what 17-4 PH stainless steel is. This widely embraced stainless steel alloy contains approximately 17% chromium, 3-5% copper, 4% nickel, and additional elements like manganese and silicon. As a martensitic metal alloy, 17-4 PH offers outstanding corrosion resistance and maintains its ductility even at high temperatures.
Moreover, 17-4 PH stainless steel is a cost-effective alternative to high-strength carbon steel, thanks to its excellent corrosion resistance, strength, and ease of fabrication. Depending on the desired shape and properties, 17-4 PH alloy parts can be produced using various processes, including cold working, hot forging, machining, and welding.
What Is 17-4 PH Stainless Steel?
So, what is 17-4 PH stainless steel? The 17-4 PH stainless steel is a popular precipitation-hardening grade of stainless steel. This hardened variant of the 17-4 alloy offers greater strength and hardness than the basic alloy. Unlike the standard 17-4 alloy, 17-4 PH stainless steel undergoes heat treatment to achieve the desired hardness and strength, making it a highly versatile metal.
This nickel-chromium grade of stainless steel is more cost-effective than most high-nickel non-ferrous alloys. The valuable properties of 17-4 PH stainless steel provide product manufacturers with reliability, making it an ideal solution for many design challenges.
17-4 Stainless Steel Vs. 17-4 PH Stainless Steel
Although 17-4 stainless steel and 17-4 PH stainless steel share similar properties, they differ in certain key aspects. The precipitation hardening (PH) process subjects the 17-4 alloy to heat treatment, enhancing its yield strength and corrosion resistance. 17-4 PH stainless steel is a widely used martensitic PH stainless steel that transforms into a solid steel crystalline structure (martensite) at low temperatures of around 250ºC.
Both 17-4 stainless steel and 17-4 PH stainless steel contain similar primary elements, but the addition of Columbium (Niobium, Cb) strengthens the 17-4 PH variant. As a result, precipitation hardening of 17-4 stainless steel offers an outstanding combination of corrosion resistance, hardness, and high strength.
Moreover, 17-4 PH stainless steel exhibits higher elongation and excellent tensile and yield strength, making it ideal for high-strength applications such as chemical processing equipment, aerospace components, and firearms. While 17-4 PH stainless steel may cost more than standard 17-4 stainless steel, its higher cost is justified for applications demanding greater toughness and strength.
Properties Of 17-4 PH Stainless Steel
The high-alloy 17-4 PH stainless steel offers several benefits due to its impressive material properties. Below are its composition and key properties:
The high-alloy 17-4 PH stainless steel offers several benefits due to its impressive material properties. Below are its composition and key properties:
Composition
The 17-4 PH stainless steel has a remarkable chemical composition that offers desirable characteristics. It contains the following elements:
- Chromium (Cr): 15 – 17.5%
- Nickel (Ni): 3 – 5%
- Copper (Cu): 3 – 3.5%
- Manganese (Mn): 1% max
- Silicon (Si): 1% max
- Columbium (Cb/Niobium, Nb): 0.15 – 0.45%
- Phosphorous (P): 0.04% max
- Sulfur (S): 0.03% max
- Carbon (C): 0.07% max
- Nitrogen (N): 0.10% max
Mechanical Properties
The stainless steel 17-4 PH exhibits remarkable mechanical properties well-suited for applications that require high strength, hardness, and resistance to corrosive attacks. Its tensile strength ranges from 200-225 ksi, while its yield strength ranges from 175-200 ksi. The hardness of the 17-4 PH SS ranges from 35-45 HRC.
Physical Properties
Stainless steel 17-4 PH has a dull appearance in its annealed condition, while it exhibits a bright or glossy finish after heat treatment. This alloy has excellent physical properties, such as:
- Good corrosion resistance
- High strength-to-weight ratio
- Good electrical conductivity
- Magnetic properties (like most martensitic alloys)
Thermal Properties
The thermal properties of 17-4 PH SS are beneficial in various applications. This alloy has:
- Melting point: 2550 to 2650 ºF (1399 – 1454 ºC)
- Heat capacity: Approximately 460 J/(kg·K)
- Good thermal stability: Retains structural integrity when subjected to elevated temperatures
Corrosion Resistance
The 17-4 PH SS provides superior corrosion resistance and is highly used in applications requiring moderate corrosion resistance and greater strength. It resists corrosion effectively in environments associated with food, petroleum, paper, dairy, and chemical industries.
Heat Treatment
The 17-4 PH SS comes in the solution-annealed condition at 1900ºF and is air-cooled to 90ºF. Subsequent age-hardening treatments help to alter the mechanical properties of this stainless steel type to the required toughness and hardness levels. Typical aging treatments include:
- Conditions H900, H925, H1025, H1075, H1100, H1150, H1150 + 1150, and H1150-M
Weldability
17-4 PH SS exhibits remarkable welding characteristics compared to its alternatives. It can be welded using standard processes, including:
- Shielded metal arc welding (SMAW)
- Gas tungsten arc welding (GTAW)
- Plasma arc welding (PAW)
- Gas metal arc welding (GMAW)
Different Stock Shapes For 17-4 PH Stainless Steel
Stainless steel stock materials are available in various shapes to meet the specific requirements of different machining projects. The size and shape of the product determine the ideal stock shape for a machining project. Below are the different shapes in which 17-4 PH stainless steel is commonly available:
- Rods
- T-Bar
- Flat Bar
- Round Bar
- Hex Bar
- Square Bar
- Triangle Bar
- Hollow Bar
- Threaded Bar
- Pump Shaft
- Boat Shaft
Processes Used in Machining 17-4 PH Stainless Steel
There are various machining techniques for manufacturing 17-4 PH stainless steel. Here are some of the most commonly used methods:
CNC Milling
CNC milling is a suitable metal fabrication technique for cutting 17-4 PH stainless steel into desired shapes and dimensions. CNC milling machines use a rotating multipoint cutting tool to cut workpieces in a controlled manner. In this process, the workpiece engages the milling tool rather than the tool cutter coming to the machined workpiece.
The machining spindle possesses various cutting tools capable of traveling in the X, Y, and Z axes to achieve complex designs. This efficient subtractive process offers the preferred machining tolerances when making stainless steel parts.
CNC Turning
CNC turning is suitable for machining parts with cylindrical shapes from 17-4 PH stainless steel. The process employs carbide or coated carbide inserts for machining stainless steel. In this method, the cutting tool remains stationary while the stainless steel workpiece is fastened to a mandrel or rotating plate. The cutting tool engages the workpiece to remove excess material as it turns, forming the desired shape and size. Therefore, turning is an ideal method for producing high-volume stainless steel machined parts.
CNC Drilling
CNC drilling is an ideal machining process for making holes in 17-4 PH stainless steel despite its hardness. Specialized drill bits are often used to achieve accurate results. Additionally, employing peck drilling helps to remove chips and avoid work hardening. CNC drilling in stainless steel 17-4 can be economical, as it provides precise holes with accurate diameters.
Electrical Discharge Machining (EDM)
EDM, or spark machining, is a versatile technique that uses repeated electrical current or thermal energy instead of mechanical force to cut through materials such as 17-4 PH stainless steel. Although this technique may be slower, it offers high precision in metal machining. EDM is perfect for machining small and delicate stainless steel components with complex profiles, as it does not rely on mechanical force to cut materials.
Advantages Of Using Stainless Steel 17-4 PH For Your Projects
The stainless steel 17-4ph offers different benefits across various industries.
Cost-Effectiveness
17-4 PH stainless steel is a cost-effective choice for various industrial applications, even when compared to other high-chromium alternatives. Manufacturers and product engineers often prefer 17-4 PH stainless steel because it offers similar strength and corrosion resistance properties at a more affordable price.
Durability
In many applications, materials must withstand long-term use without significant degradation. 17-4 PH stainless steel is ideal for such needs, offering durability and resistance to wear and tear. This makes it a preferred choice for aerospace parts and refining equipment, where low maintenance and fewer repairs are critical. 17-4 PH stainless steel components are long-lasting and resistant to corrosion, ensuring reliable performance over time.
High Corrosion Resistance
17-4 PH stainless steel excels in corrosion resistance, making it suitable for environments exposed to corrosive substances such as mild acids, organic compounds, fresh water, and atmospheric conditions. The chromium content in 17-4 PH stainless steel provides a protective layer against oxidation and degradation, ensuring the longevity of machined parts.
High Hardness and Strength
The 17-4 PH alloy is renowned for its excellent hardness and strength properties, making it ideal for high-stress applications. Through precipitation hardening, the alloy can be heat-treated to achieve various strength levels, typically ranging from 1100 to 1700 MPa. This versatility in strength makes 17-4 PH stainless steel a perfect material for demanding applications.
Applications Of 17-4 PH Stainless Steel Parts
The stainless steel 17-4 PH is a versatile metal with outstanding properties that make it suitable for various applications across multiple industries. Here are some typical applications:
Aerospace
Stainless steel is a primary material for creating various aircraft parts and components. The 17-4 PH stainless steel offers good tensile strength and excellent stress corrosion resistance, which are crucial requirements for aerospace equipment. Additionally, it is essential that these parts and components perform well in different temperatures and environments. Therefore, 17-4 PH is the ideal metal for the aerospace sector.
Marine Vessels
The 17-4 PH stainless steel exhibits high mechanical strength and superior resistance to corrosion, making it suitable for marine applications. Its ability to resist corrosion ensures its durability in salty seawater. The high concentration of chromium in its composition makes 17-4 PH stainless steel highly resistant to corrosive substances. Hence, it is well-suited for making vessel pump and valve components, as well as other components such as heat exchangers and seawater and process piping.
Oil and Gas Industry
This alloy possesses the high strength required for making pipes used in extracting oil at great depths below sea level. Additionally, the 17-4 PH alloy is highly corrosion-resistant in various environments. As such, it is suitable for making pipes and oil rigs in this industry, as it can withstand corrosive media such as carbon dioxide, hydrogen sulfide gas, and low pH levels in oil prospecting conditions.
Food Processing Equipment
Most of the equipment used in the food processing industry is made from steel. The 17-4 PH stainless steel is ideal for making food and beverage processing equipment due to its good surface condition and fine finish. The smooth surface and high chromium content of 17-4 PH stainless steel make it less prone to corrosion. Additionally, it promotes hygiene in food and beverage production since it is easy to clean.
AS Prototypes CNC Metal Services for Stainless Steel Parts
AS Prototypes is your premier one-stop manufacturer for metal machining services, specializing in stainless steel prototypes and parts for your projects. Our team of experienced engineers, skilled machinists, and quality control experts ensure that your products meet the highest standards of precision and quality. We utilize state-of-the-art CNC machining technologies, including 3-axis, 4-axis, and 5-axis machining, as well as turning, EDM, and comprehensive surface finishing operations.
At AS Prototypes, we recognize the critical role of stainless steel in engineering applications, thanks to its outstanding corrosion resistance, strength, and aesthetic qualities. Our machining capabilities encompass a broad spectrum of stainless steel grades, such as 304, 316, 17-4 PH, and other metals, allowing us to fulfill the unique specifications of your project. Contact us today for a free quote and kickstart your project with AS Prototypes!
Conclusions
Stainless steel 17-4 PH is a versatile and cost-effective alloy widely used in various applications due to its superior properties, including excellent strength and corrosion resistance. Understanding the characteristics and machining requirements of 17-4 PH stainless steel is essential for achieving optimal results in your manufacturing projects.
FAQs
What is the tensile strength of 17-4 PH stainless steel?
The tensile strength of 17-4 PH stainless steel varies depending on its condition. In its minimum condition, it has a tensile strength of 160,000 PSI, and it can reach approximately 210,000 PSI when age-hardened.
Can 17-4 PH stainless steel rust?
While 17-4 PH stainless steel offers better resistance to corrosive attacks compared to most martensitic stainless steels, it can still develop light rusting if exposed to seacoast atmospheres or other corrosive environments for extended periods without proper maintenance.
Is 17-4 PH stainless steel suitable for making welded parts?
Yes, 17-4 PH stainless steel is suitable for welding. Arc welding techniques such as gas tungsten arc welding (GTAW) are compatible with this alloy. For optimal results, it is recommended to weld thin steel plates in a solution-annealed condition.
