What Are Common Grades of Cast Stainless Steel?

The most common grades of cast stainless steel include CF8, CF8M, CF3, CF3M, CA6NM, CN7M, and CD4MCu. Each grade offers different levels of corrosion resistance, strength, weldability, and performance for industrial applications.

Key Takeaways

• Cast stainless steel grades are selected based on corrosion resistance, strength, weldability, temperature exposure, and application needs.

• CF8 and CF8M are common general-purpose stainless casting grades.

• CF3 and CF3M are lower-carbon grades often used when welding or corrosion resistance is a priority.

• CA6NM is often selected when higher strength and toughness are needed.

• CN7M is used in more aggressive chemical environments.

• CD4MCu is a duplex stainless casting grade that offers a balance of strength and corrosion resistance.

• The right grade can help reduce downtime, lower replacement frequency, and improve lifecycle cost.

  
  

For procurement teams, engineers, and manufacturers, choosing the right cast stainless steel grade is not just a material decision. It affects part lifespan, replacement frequency, production cost, corrosion resistance, and long-term reliability.

Cast stainless steel grades are commonly specified through industry standards such as ASTM A351, A743, A744, A890, and related casting standards. These standards include many ACI grade designations, such as CF8, CF8M, CF3, CF3M, CA6NM, CN7M, and CD4MCu, for corrosion- and heat-resistant service.

Why Cast Stainless Steel Grades Matter

Not all stainless steel castings perform the same way. A grade that works well for a general industrial fitting may not be the right choice for marine hardware, chemical processing equipment, pump parts, or load-bearing components.

Different cast stainless steel grades are designed to handle different service conditions. Some are better for general corrosion resistance. Others are made for welding, strength, chloride exposure, acidic environments, or heavy-duty equipment.

According to ASM references, including the Steel Castings Handbook, cast stainless steels are commonly evaluated by their composition, microstructure, mechanical properties, applications, and corrosion resistance.

Stainless steel families include martensitic, austenitic, and ferritic-austenitic/duplex grades, with each family influencing corrosion resistance, strength, and application suitability.

For industrial buyers, this means the grade should be selected based on how the part will actually be used, not just the lowest material cost.

Common Grades of Cast Stainless Steel

The table below summarizes common cast stainless steel grades and where each one is typically used.

Cast Stainless Steel Grade	Similar Wrought Grade	Best For	Key Benefits
CF8	304 stainless steel	General industrial parts, fittings, valves, pump components, equipment hardware	Good corrosion resistance, strong durability, and widely used for general applications
CF8M	316 stainless steel	Marine parts, chemical processing, water treatment, outdoor hardware	Better corrosion resistance than CF8, especially where pitting or chloride exposure may be a concern
CF3	304L stainless steel	Welded components, corrosion-resistant parts, custom castings	Lower carbon content helps improve weldability and reduce intergranular corrosion risk
CF3M	316L stainless steel	Marine, chemical, and welded stainless steel components	Lower-carbon version of CF8M with strong corrosion resistance and better weldability
CA6NM	Similar to 410/13-4 stainless families	Pump parts, turbine components, valve parts, and high-strength applications	High strength, good toughness, and moderate corrosion resistance
CN7M	Alloy 20-type stainless	Chemical processing, acidic environments, corrosion-heavy applications	Strong resistance in aggressive corrosion environments
CD4MCu	Duplex stainless family	Pumps, valves, marine hardware, and high-strength corrosion-resistant parts	Combines higher strength with good corrosion resistance

CF8 Cast Stainless Steel

CF8 is one of the most common cast stainless steel grades. It is similar to 304 stainless steel and is often used for general-purpose corrosion-resistant castings.

CF8 is commonly used for:

• Valves

• Fittings

• Pump components

• Industrial hardware

• Equipment parts

• General stainless steel castings

  
  

This grade is often selected when a part needs good corrosion resistance, durability, and reasonable cost without needing the added corrosion resistance of molybdenum-bearing grades like CF8M.

CF8 is commonly referenced as a 304 stainless steel equivalent in cast form.

CF8M Cast Stainless Steel

CF8M is similar to 316 stainless steel and is one of the most widely used cast stainless steel grades for corrosion-resistant applications. The “M” generally indicates the presence of molybdenum, which improves resistance to pitting and corrosion in certain environments.

CF8M is commonly used for:

• Marine components

• Chemical processing parts

• Water treatment equipment

• Outdoor hardware

• Pump and valve components

• Corrosion-resistant industrial parts

  
  

Compared to CF8, CF8M is often better for environments exposed to moisture, chemicals, salt, or chlorides. This makes it a common choice when corrosion resistance is more important than using the lowest-cost stainless casting option.

CF3 Cast Stainless Steel

CF3 is the lower-carbon version of CF8 and is similar to 304L stainless steel. It is commonly used when weldability and resistance to intergranular corrosion are important.

CF3 is commonly used for:

• Welded stainless steel components

• Custom castings

• Corrosion-resistant parts

• Industrial fittings

• Components that may go through field welding

  
  

The lower carbon content helps reduce the risk of carbide precipitation during welding or heat exposure. This can make CF3 a better choice than CF8 in applications where welding is part of the final production or installation process.

CF3M Cast Stainless Steel

CF3M is the lower-carbon version of CF8M and is similar to 316L stainless steel. It combines the corrosion-resistance benefits of molybdenum with improved weldability due to its lower carbon content.

CF3M is commonly used for:

• Marine hardware

• Chemical processing components

• Welded cast stainless steel parts

• Corrosion-resistant fittings

• Pump and valve components

  
  

CF3M is often selected when the part requires both strong corrosion resistance and improved performance under welded conditions. In valve and industrial material references, CF3M is commonly listed as the 316L equivalent.

CA6NM Cast Stainless Steel

CA6NM is a martensitic cast stainless steel grade often used when higher strength, toughness, and moderate corrosion resistance are needed.

CA6NM is commonly used for:

• Pump parts

• Turbine components

• Valve parts

• High-strength industrial components

• Equipment exposed to pressure or mechanical stress

  
  

This grade is different from CF-series austenitic stainless steels. It is often selected for applications where strength and toughness matter more than maximum corrosion resistance.

For procurement teams, CA6NM may be a better fit when the part needs to handle mechanical loads, pressure, or demanding operating conditions.

CN7M Cast Stainless Steel

CN7M is commonly associated with Alloy 20-type stainless casting applications. It is often used in chemical processing and acidic environments where standard stainless steel grades may not provide enough corrosion resistance.

CN7M is commonly used for:

• Chemical processing equipment

• Acid-handling components

• Corrosion-heavy industrial applications

• Specialized valves and fittings

• Harsh service environments

  
  

CN7M is often selected when the application involves more aggressive corrosion conditions. Material references describe CN7M as having strong resistance to sulfuric acid and chloride stress corrosion environments.

CD4MCu Cast Stainless Steel

CD4MCu is a duplex stainless steel casting grade. Duplex stainless steels are known for combining corrosion resistance with higher strength compared to many austenitic stainless grades.

CD4MCu is commonly used for:

• Pumps

• Valves

• Marine hardware

• High-strength corrosion-resistant parts

• Industrial components exposed to demanding service conditions

  
  

This grade can be a strong choice when a part needs both mechanical strength and corrosion resistance. It may be used in applications where a general-purpose stainless-steel grade is not sufficient, but a fully specialized alloy is not necessary.

How to Choose the Right Cast Stainless Steel Grade

The right cast stainless steel grade depends on the part’s function, operating environment, and production requirements. A grade should never be chosen based on name recognition alone.

Selection Factor	What to Consider	Why It Matters
Environmental Factors	Moisture exposure, saltwater or chloride exposure, chemical contact, corrosion resistance requirements, temperature exposure	Helps determine whether the part needs a general-purpose grade like CF8 or a more corrosion-resistant grade like CF8M, CF3M, or CN7M.
Mechanical Requirements	Strength requirements, pressure or load conditions, impact or vibration exposure, and wear resistance needs	Helps identify whether the part needs higher strength, toughness, or durability, such as CA6NM for demanding mechanical applications.
Production Considerations	Welding requirements, machining and finishing needs, part size and complexity, manufacturing tolerances	Helps prevent production issues and ensures the selected grade can be properly welded, machined, finished, and manufactured.
Lifecycle and Cost Considerations	Expected service life, replacement frequency, maintenance requirements, lifecycle cost, and production efficiency	Helps avoid under-specifying or over-specifying the material and supports better long-term cost performance.

For example, CF8 may work well for general industrial parts, but CF8M or CF3M may be better for marine or chemical environments. CA6NM may be better for pump or turbine components that need higher strength. CN7M may be preferred for aggressive chemical service.

Cast Stainless Steel Grade Families

Cast stainless steels are often grouped into families based on their microstructure. This helps manufacturers understand how a grade may perform in terms of strength, corrosion resistance, weldability, and heat treatment response.

Austenitic Cast Stainless Steel

Austenitic grades include CF8, CF8M, CF3, and CF3M. These are commonly used for corrosion-resistant applications and general industrial components.

They are often selected for:

• Good corrosion resistance

• General durability

• Weldability

• Industrial hardware

• Pump and valve parts

• Custom castings

  
  

Martensitic Cast Stainless Steel

Martensitic grades include materials such as CA6NM. These grades are often selected when higher strength and toughness are needed.

They are often used for:

• Pump components

• Turbine parts

• Valve components

• Load-exposed industrial parts

• Mechanical service applications

  
  

Duplex Cast Stainless Steel

Duplex cast stainless steels, including grades such as CD4MCu, are used when both strength and corrosion resistance are important.

They are often selected for:

• Marine applications

• Pump and valve components

• Corrosion-heavy environments

• High-strength industrial parts

  
  

Why Grade Selection Matters for Procurement

For procurement teams, choosing the right cast stainless steel grade can affect more than the part’s technical performance. It can impact total cost, lead time, supplier consistency, maintenance planning, and equipment uptime.

The right grade can help:

• Reduce downtime

• Lower replacement frequency

• Improve supply chain consistency

• Reduce lifecycle cost

• Improve production efficiency

• Minimize field failures

• Reduce unnecessary over-specification

  
  

A lower-cost grade may save money upfront, but it can become more expensive if the part fails early, requires frequent replacement, or does not perform well in the operating environment.

On the other hand, over-specifying a premium grade can increase cost without adding meaningful value. The goal is to match the grade to the real application.

Common Mistakes When Choosing Cast Stainless Steel Grades

Choosing Based on Cost Alone

The lowest-cost grade is not always the best long-term option. A lower-cost material may lead to higher replacement frequency, more downtime, or reduced performance if it cannot handle the actual operating environment.

Assuming All Stainless Steel Grades Perform the Same

Cast stainless steel grades are not interchangeable. Grades such as CF8, CF8M, CF3M, CA6NM, CN7M, and CD4MCu are designed for different corrosion conditions, strength requirements, and service environments.

Ignoring the Application Environment

A part used indoors in a mild environment may not need the same grade as a part exposed to saltwater, chemicals, pressure, or vibration.

Overlooking Machining and Finishing Requirements

Machining, polishing, coating, heat treatment, and inspection requirements can affect production cost, lead time, and final performance. These considerations should be evaluated before finalizing the material grade.

Not Consulting a Manufacturing Partner

An experienced manufacturing partner can help review part drawings, operating conditions, material requirements, and production goals. This helps prevent over-specifying, under-specifying, or choosing a grade that creates avoidable production issues.

Ready to Choose the Right Cast Stainless Steel Grade?

Selecting the right cast stainless steel grade can improve durability, reduce downtime, and help support long-term production performance. The right material choice also helps minimize unnecessary replacement costs, machining issues, and manufacturing inefficiencies.

BMF Industrial provides custom manufacturing support for industrial components, including casting, forging, machining, finishing, and guidance on material selection.

Whether you need support selecting between CF8, CF8M, CF3M, duplex stainless grades, or other specialty alloys, BMF Industrial can help guide the manufacturing process from design through production and delivery.

Need help selecting the right cast stainless steel grade for your project? Contact BMF Industrial today.

Frequently Asked Questions

Which cast stainless steel grade is best for high-strength parts?

CA6NM is often selected for parts that need higher strength and toughness, such as pump parts, turbine components, and valve parts.

What is the difference between CF8 and CF8M?

CF8 is similar to 304 stainless steel, while CF8M is similar to 316 stainless steel. CF8M contains molybdenum, which generally improves corrosion resistance, especially in environments where pitting or chloride exposure may be a concern.

What is the difference between CF8M and CF3M?

CF8M is similar to 316 stainless steel, while CF3M is similar to 316L stainless steel. CF3M has lower carbon content, which can improve weldability and reduce the risk of intergranular corrosion after welding.

Which cast stainless steel grade is best for marine applications?

CF8M and CF3M are often used for marine and corrosion-heavy environments because they offer better corrosion resistance than general-purpose CF8. Duplex grades, such as CD4MCu, may also be considered when higher strength is required.

Is CF8 the same as 304 stainless steel?

CF8 is commonly considered the cast equivalent of 304 stainless steel. However, cast and wrought materials can have differences in composition, microstructure, and performance, so the exact specification should always be reviewed.

Is CF8M the same as 316 stainless steel?

CF8M is commonly considered the cast equivalent of 316 stainless steel. It is widely used for corrosion-resistant castings, especially in industrial, marine, water treatment, and chemical processing applications.