Nitronic 60 Stainless Steel CNC: Properties, Process & Machinability

You would have noticed that when two metals are connected, wear issues arise, which further lead to failures or sometimes disasters. The wear issues arise when one of the two connected metals has poor wear resistance, and under friction, it becomes prone to fretting and galling. Nitronic 60 stainless steel is the solution to this problem because of its excellent galling and fretting resistance, along with corrosion resistance. Why it is best when it comes to the connection of two metals, you will learn in this article. So, let's begin then:

What Is Nitronic 60 Stainless Steel?

Generally speaking, Nitronic 60 stainless steel is an austenitic stainless steel that is known for its high strength and is especially designed for wear, galling, and corrosion protection.

Nitronic 60 Stainless Steel Explained

Nitronic 60 Stainless Steel (UNS S21800/Alloy 218) is a steel that has approximately 4% Si and 8% Mn. These two elements are the main players in this grade of stainless steel. These elements provide exceptional wear and galling resistance. This grade maintains its exceptional mechanical properties even at high temperatures. It is commonly employed in valves, fasteners, wear plates, and shafts, etc.

Why Called “Nitronic 60”?

It is called Nitronic 60 because it is one of the members of nitrogen-strengthened austenitic stainless steel. The 60 in its name just refers to its grade number, just like Nitronic 50. The “Nitronic” name is created by Armco.

What Is The Difference between Nitronic and Stainless Steel?

Nitronic refers to this grade of stainless steel is strengthened by inducing Nitrogen in the surface and is a part of the austenitic stainless-steel series.

Stainless steel is a grade of simple steel, but it comes with (17-19%) Cr and (8-10%)Ni, which make it corrosion-resistant and strong.

What Is Austenitic Stainless?

Nitronic 60 is a kind of Austenitic Stainless Steel. This austenitic microstructure gives the following properties:

• Excellent corrosion resistance
• Non-magnetic annealed condition
• High toughness at all temperatures
• Good weldability
• Highly ductile and formable

Chemical Composition & Core Properties for Machining

The chemical composition of Nitronic 60 stainless steel is the reason why it is best when it comes to resisting fretting and galling. Let's figure out which elements are present in its composition and how they play their role.

Nitronic 60 Chemical Composition

The main alloying elements are Si, Mn, Cr, and Ni. These elements make this grade of steel better than stainless steel 304, 316, etc.

Mechanical and Physical Properties

These are some important mechanical and physical properties:

Strength and Hardness

If you have Nitronic 60 stainless steel in an annealed condition, then its strength and hardness are:

• Yield Strength: 345 MPa
• Ultra Tensile Strength: 655 – 690 MPa
• Hardness: 241 HB

These values are based on room temperature.

Thermal Conductivity

Nitronic 60 stainless steel has a lower thermal conductivity of ~ 15.7 W/m.K compared to 316 stainless steel (~17.8 W/m.K). It means it is not efficient in conducting the heat quickly.

Common Characteristics in Service

One of the most important characteristics of Nitronic 60 stainless steel during service is corrosion resistance.

Corrosion Properties

Corrosion properties mean how a material resists oxidation. In service, there can be many sources of corrosion, such as acids, salts, etc. Nitronic 60 stainless steel offers excellent protection from corrosion due to which it is durable in harsh conditions.

Corrosion Resistance

Nitronic 60 stainless steel is corrosion-resistant because of 17-19% Cr content. It reacts with oxygen and makes a very thin passive layer of Chromium Oxide (Cr₂O₃). It reacts as a barrier between the environment and the underlying surface.

CNC Machinability: What Makes Nitronic 60 Tough to Cut

CNC machinability refers to how easily a material can be machined. If a material is easy to cut, it is considered a machinable material and has high machinability. Compared to other grades of stainless steel, such as 304 or 316, Nitronic 60 stainless steel is tough to cut.

Common Factors Affecting CNC Machining

There are many factors that affect its CNC machining. Some of these factors are discussed below:

Work-Hardening Behavior

As mentioned at the start of this article, Nitronic 60 stainless steel is an austenitic stainless steel, which means it has an FCC crystal structure. This crystal structure allows planes to slip and get entangled. This entanglement occurs when pressure is applied. So, during machining, when pressure is applied, the dislocations get entangled, and it becomes hard to machine.

Tough and Ductile Properties

Under certain loads, this material acts as a ductile and tough material because of an FCC crystal structure. The FCC crystal structure allows dislocations to slip over each other. One moment comes when these dislocations start piling up and end up as hard material.

Common Machining Challenges

You can face the following machining challenges:

1. Work Hardening
2. Extremely high cutting forces will be required
3. Sticky Chip Formation
4. Low thermal conductivity
5. Rapid Tool Wear

Tooling & Cutting Parameters for Nitronic 60

You can say this section of the article is a guide for machining Nitronic 60 stainless steel because of tooling and cutting parameters are discussed.

Cutter Materials and Coatings

For general CNC machining, you should prefer carbide tools because they are very strong and heat-resistant. For some specific CNC operations, like drilling or tapping, use Cobalt High-Speed Steel (HSS-Co) cutting tools because they are tough. For more efficient machining, these cuttings should be coated with TiAlN, TiCN, or AlTiN.

Starting Speeds, and Feeds

Cutting speed and feed are dependent on the specific CNC operation being performed. In general, the cutting speed and feed rate are given below:

• For Turning:

Cutting speed: 12-30 m/min

Feed: 0.05-0.40 mm/rev

• For Milling:

Cutting speed: 20-30 m/min

Feed rate: 0.05-0.15 mm/tooth

• For Drilling:

Cutting speed: 8-15 m/min

Feed rate: 0.08-0.25 mm/rev

Using Coolant

As you know, Nitronic 60 stainless steel has lower thermal conductivity, which means it does not conduct heat efficiently. This results in the tools and workpiece heating up, leading to further tool wear. To overcome this, a coolant must be used during CNC machining, like Castrol Hysol is a common coolant.

Nitronic 60 CNC Operations Guide by Process

This section discusses how CNC operations are performed for Nitronic 60 stainless steel.

Turning Nitronic 60

Nitronic 60 stainless steel is tough and abrasive, produces sticky chips, and requires a high feed rate and moderate cutting speed.

For performing the turning operation on nitronic 60 stainless steel, these are the key steps:

1. Use a rigid tool setup
2. Use strong cutting tools with AlTiN coatings
3. Apply flood coolant
4. Start with heavy and continuous cuts
5. Try to maintain consistent feed
6. Clear chips
7. Do the inspection tool edge

Drilling Nitronic 60

1. Use cobalt drills
2. Apply flood coolant
3. Start with a slower cutting speed
4. If the size of the required hole is deeper than 2-3x diameter, use peck drilling
5. Maintain constant pressure
6. Retract often

During the drilling process, removing the material quickly generates heat, so coolant and chip removal are very critical.

Reaming Nitronic 60

You can use reaming process if you need to increase the size of already existing holes or to get smoother and burr-free walls.

1. Use high speed steel reamers
2. Apply flood coolant
3. Use slow but steady spindle speed
4. Align the reamer carefully to achieve a consistent Ra
5. Try not to force the reamer

Side and Slot Milling

Side milling is used for surfaces, shoulders, or contours. You should use a rigid setup and moderate cutting speeds and feeds.

The purpose of slot milling is to make slots or grooves in the workpiece. Use climb milling for this process. Use multiple passes of cuts for deep slots.

Threading and Tapping

Threading: for making threads on the external side of the workpiece, like outside of a bolt.

Use a rigid setup and take light finishing passes to achieve an excellent thread profile.

Tapping: to make threads inside holes, like in bolts.

Use low spindle speed (10-40 RPM). For deep holes, use peck tapping. Do not force the tapping tools to avoid breakage.

Custom One-Stop Machining Process Solutions

If you need all of these CNC machining operations under one roof, come to TUOFA. We are equipped with the most advanced CNC machines and expert operators. We provide custom machining solutions at competitive prices and in the shortest delivery times.

Nitronic 60 vs 304 vs 316 for Machined Parts

This section provides comprehensive differentiating information among Nitronic 60 stainless steel, 304 stainless steel, and 316 stainless steel.

Similarities and Differences

• Similarities

• Differences

Nitronic 60 Chemical Composition (wt%) vs 304 vs 316

The following table presents the chemical composition of these three grades of stainless steel:

Which Is Easier to Machine?

Let's see which is easier to machine and the applications of these grades in this section:

Machining 316 SS

Stainless steel 316 stands in the middle between the 304 and nitronic 60 stainless steel. Its applications include:

• Marine equipment, like boat fittings
• Chemical and pharmaceutical processing equipment
• Medical implants and instruments

Machining 304 SS

It is the easiest to machine because of its low carbon and Ni constituents. It is used in:

• Kitchen equipment, like sinks
• Food processing machinery
• Architectural panels

Nitronic 60 Materials Equivalent

These are some Nitronic 60 equivalent materials and can be used if Nitronic 60 is not available.

1. AMS 5844
2. DIN X 12CrMnNiN17-7
3. JIS SUS318
4. Alloy 60

These grades are not exactly the same as Nitronic 60 stainless steel but can be used as an alternate option.

What Is The Difference between Nitronic and Inconel?

Inconel is a high-strength Ni alloy and is used in high-strength applications. Let's compare Inconel with Nitronic.

Key Differences of Nitronic vs Inconel

These are the key differences to remember when choosing any metal between them:

Which Is Harder to Machine?

Inconel is extremely hard to machine, even more than Nitronic 60 stainless steel. The reasons are its rapid work-hardening and it generates heat rapidly.

To machine this metal, you will need a very rigid setup, slow speeds, sharp carbide tools, and high-pressure coolant.

Nitronic 60 Applications & Part Examples

Nitronic 60 stainless steel is used in many real-world applications. Some of them are given below:

Marine and Offshore Wear Components

In marine and offshore wear components, Nitronic 60 stainless steel is used in the following components:

• Pump shafts and impellers
• Valve stems and seats
• Bushings, rollers, and wear plates
• Fasteners and screws in seat-water-exposed assemblies

We use Nitronic 60 SS because it offers excellent corrosion resistance, high wear and gear resistance, toughness, and ductility.

Power Generation High Temperature Trim

• Valve stems and seats
• Control valve plugs and discs
• Spindles, bushings, and wear sleave

These parts are manufactured using Nitronic 60 stainless steel because of good wear and galling resistance, high toughness, and stability of dimensions at elevated temperatures.

Energy Turbine and Actuation Parts

In energy turbine and actuation parts, Nitronic 60 stainless steel is used in:

• Turbine valve stems and seats
• Actuator pins and spindles
• Bushings and sleeves in rotary actuators

The reasons to use Nitronic 60 stainless steel for these parts are low friction coefficient, high resistance to fretting and galling, and good thermal stability under cyclic loads.

How to Get a Nitronic 60 CNC Machining Quote?

In this section, you are going to learn how to get a quotation for Nitronic 60 CNC machining.

DFM (Design for Manufacturing) Tips

To get a quotation, you may need to make some changes to the existing design of the component. These are some tips;

• Use generous radii
• Prefer through-holes over blind holes
• Avoid very small features
• Minimize deep pockets
• Avoid unnecessary tight tolerances
• Sequence operations logically

Main Considerations

When you are designing a part of Nitronic 60 stainless steel, keep the following things in mind:

1. Material properties
2. Machining
3. Fixturing & Rigidtiy
4. Cost and lead time
5. Surface finish and tolerance requirements

How to Send Quote to TUOFA CNC Machining?

You can send Quote to TUOFA CNC machining using these steps:

• Prepare your RFQ details
• Email us your RFQ to info@tuofa-cncmachining.com
• Attach your drawing(2D & 3D in STEP/STL/IGS format) and specifications
• TUOFA CNC Machining will assign a professional sales and provide quote

Conclusion

Nitronic 60 stainless steel, a member of the austenitic stainless steel series, is nitrogen-strengthened. This stainless steel is known for its exceptional wear and galling resistance properties. It is hard to machine grade, so carbide tools with slow cutting speeds and high feed rates are used. This grade is used in many important applications, such as in marine equipment, the power generation field, and energy turbines.

FAQs

Is Nitronic 60 magnetic?

No, it is not magnetic because of the austenitic microstructure. This microstructure does not allow electron spins to align in the same direction.

What is Nitronic 60 equivalent or also known as?

Alloy 60 is equivalent to Nitronic 60 stainless steel because of same chemical composition and properties.

Does Nitronic 60 rust or work harden in machining?

Since it is stainless steel, so it does not rust or corrode. Due to FCC crystal structure, work-hardening is a common phenomenon in during machining processes. So, yes, Nitronic 60 word hardens during machining.

Is Nitronic 60 hard to machine compared to 304/316?

The surface of the Nitronic 60 is very hard compared to 304/316 stainless steel. Its high hardness and poor thermal conductivity are the main reasons why it is harder to machine compared to 304 and 316 stainless steels.

What are the top 5 strongest metals?

1. Tungsten (W)
2. Chromium (Cr)
3. Titanium (Ti)
4. Maraging Steel
5. Inconel (Ni-based super alloys)