18/10 Stainless Steel: A Comprehensive Guide for Mechanical Engineers and Designers

Stainless steel is considered as the key stone of the modern engineering era due to its unique set of properties and wide application usage. It constitutes of variety of grades which are classified based on properties, cost. In this article, our primary focus will be on 18/10 stainless steel, known for its exceptional properties. So, whether you are a mechanical engineer or a designer, you will be able to make an informed decision regarding the selection of this grade for your desired application.

Fig 1: 18/10 SS

What is 18/10 Stainless Steel?

It is a high-quality stainless-steel alloy which constitutes of major alloying elements such as chromium and nickel. Major properties include high corrosion resistance along with durability and aesthetic appearance. Furthermore, its major applications reside in medical, kitchenware, and other structural components.

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Is 18 10 Stainless Steel Good

It is a well-regarded material for its properties and variety of applications. Industrialist and engineers categorize this material in good category due to several reasons that are mentioned below:

• Superior Corrosion Resistance
• Enhanced Strength and Durability
• Excellent Fabrication

Is 18/10 Stainless Steel Safe

18/10 SS grade is considered as a safe material. This can be analyzed due to its high demand usage in medical instruments as well as in food processing equipment. Apart from this, below is the list of its characteristics which further proves it safety in using:

• Non-Reactive Composition
• Corrosion Resistance
• Nickel and Chromium Safety

Is 18/10 Stainless Steel Magnetic?

18/10 SS grade is classified under austenitic stainless steel due to which it is nonmagnetic in nature. Apart from that, the presence of adequate amount of nickel in its composition does not allow austenite to further break in to ferritic or martensitic structure (both magnetic in nature). Hence, suitable for applications where magnetic properties are not required [8] [9].

What Are the Common Forms of 18/10 Stainless Steel Material?

This material exists in various forms that are listed below:

• Sheets and Plates
• Bars and Rods
• Tubes and Pipes
• Wires
• Foils
• Coils
• Angles and Channels

Material Standards

18/10 SS grade is also linked with several international and regional standards that are listed below:

ASTM

• A240/A240M
• A480/A480M
• E8/E8M

EN

• 10088-2

ISO

• 15510
• 3651-2

EN

• 10204

EU

• REACH
• RoHS

AISI/UNS

• 304/304L
• S30400

Advantages and Disadvantages of 18/10 Stainless Steel

18/10 SS based on its properties and performance, it has some pros and cons mentioned below:

What is 18/10 Stainless Steel Used for: Applications and Parts

This material has numerous application both in commercial as well as industrial sector. Some of the applications are listed below:

• Mixing Bowls
• Kitchen Appliances
• Sterilization Equipment
• Medical Devices
• Tanks and Containers
• Heat Exchangers
• Aircraft Components

Figure 2: 18/10 SS Applications

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Common CNC Machined 18/10 Stainless Steel Parts

18/10 SS grade is easy to fabricate due to which it could be CNC machined. Common CNC machined parts made from 18/10 SS are mentioned below:

• Gears and Sprockets
• Shafts and Spindles
• Fasteners and Hardware
• Valves and Fittings
• Medical Implants
• Surgical Instruments

Is 18/10 Stainless Steel Flatware Good?

18/10 SS grade is a competitive choice for flatware because the qualities and characteristics it possesses. Firstly, it is durable and long lasting due to its resistant against corrosion providing protection against harmful chemicals and better strength making it less likely to break. Secondly, the flexibility in design making and shiny finish makes its an ideal choice for aesthetic appearance. Lastly, it is easy to maintain and look after comparatively.

Composition and Microstructure

Composition and Microstructure of any material are the most important characteristics for any materials as it decides material properties and its usage. Below is a composition as well as microstructure 18/10 SS grade acquires:

Chemical Composition

Table 1: Chemical composition

The role of each element in modifying its properties is discussed in table below:

Table 2: Role of elements

Microstructure: Austenitic Face-Centered Cubic (FCC) Structure

The microstructure of 18/10 SS grade comprises of FCC which has strong characteristics and a major impact on its properties that are described below:

Characteristics:

• Face-Centered Cubic (FCC) Crystal Lattice

• The atomic arrangement is such that each atom is at the corner as well as at the center of each cubic face.
• Provide stability and highly packed density
• Resistant to deformation under load.

• Non-magnetic

• The atomic arrangement resists the spinning of unpaired electron dye to which magnetic moment is not established.
• Beneficial for non-magnetic applications.

• Good Ductility and Toughness

• Exceptional ductility that allows them to modify its shape without compromising their strength.
• Their ability to absorb energy under high stress makes them a tougher material.

Influence on Properties:

FCC Structure Contributes to Corrosion Resistance and Ductility

• This closely packed FCC structure increases corrosion resistance of 18/10 SS grade.
• Formation of a protective chromium oxide layer which allows this material to sustain aggressive and harsh environmental conditions.

Nickel Stabilizes the Austenitic Phase, Preventing Phase Transformations and Brittleness

• Nickel is an essential alloying element in 18/10 SS which stabilize the austenitic phase at normal temperature preventing the alloy transformation into different phase which can compromise its properties.
• Avoid brittleness that could lead to material breaking under high impact.
• This quality shows that the alloy is reliable and versatile.

Corrosion Resistance of 18/10 Stainless Steel

This material is known for its excellent corrosion resistance due to the presence of chromium and nickel in its percentage composition. Below is a brief description that how it reacts under certain type of corrosion:

Atmospheric Corrosion

Metal exposed to a certain atmosphere mainly natural without any liquid immersion leads to atmospheric corrosion. The chromium oxide layer act as a protective barrier that allows 18/10 SS to tackle such environment conditions including humidity and in presence of reactive pollutants.

Aqueous Corrosion

Metals that are mostly in contact with water or any other aqueous solution leads to corrosion that is referred as aqueous corrosion. In this case also, the protective oxide layer provides resistance against corrosive water. However, measures should be taken against sea water and elevated temperature conditions.

High-Temperature Corrosion

When metal is exposed to elevated temperature with other aggressive conditions such as oxygen presence and other reactive gases, it leads to high temperature corrosion. 18/10 SS grade offer exceptional resistance against such conditions.

Specific Chemical Environments

The stable chromium oxide layers provide corrosion resistance against such chemical environments which makes them suitable for industrial applications especially in pharmaceuticals. Yet appropriate measures should be taken against certain chemicals that are:

• Acids
• Alkalis
• Organic solvents

Mechanical Properties of 18/10 Stainless Steel

The entire structural integrity lies on the mechanical properties of the material. 18/10 SS grade possess good mechanical properties that are briefly described one by one:

Tensile Strength

18/10 SS demonstrates a tensile strength between 520 to 690 MPa which indicates its capability to withstand pulling forces. However, it decreases in high temperature conditions due to microstructural changes.

Yield Strength

This steel grade shows yield strength of 210-570 MPa showing its ability to bear mechanical stresses without deforming permanently yet this property is compromised at elevated temperatures.

Elongation

Can elongate up to 40-60% showcasing its ability to deform before fracture but in high temperature conditions, this property is challenged because of thermal stresses.

Hardness

This grade of stainless steel comprises of hardness that usually lies between 85 to 95 HRB at room temperature. However, decreases at elevated temperature but less as compared to other SS.

Impact Strength

Possess good impact strength at room conditions but challenging with increase in temperature because of embrittlement effect in subzero conditions.

Fatigue Strength

High at room temperature proving its capability to withstand cyclic load but could be minimized when exposed to thermal cycling that could lead to structural changes.

Toughness

18/10 SS grade possess high toughness both at room and elevated temperature.

Wear Resistance

This material acquires moderate resistance to wear. Moreover, its behavior at elevated temperature depends on the quality of surface finish as well as lubricating conditions.

Dimensional Stability

Exceptional dimensional stability retaining its shape at normal temperature yet can be affected at high temperatures due to thermal expansion.

Physical Properties of 18/10 Stainless Steel

This grade material possesses good physical properties, yet it can be affected by factors such as temperature and composition. Hence, necessary measures should be taken to counter those factors. Below are the brief explanation of 18/10 SS grade physical properties:

Density

18/10 SS grade has a density of 7.9 g/cm³ having a strong influence on its structural stability.

Thermal Conductivity

This material comprise of a low thermal conductivity of about 16.3 W/m·K making them less suitable for heat resistant applications as compared to other stainless steel.

Electrical Conductivity

18/10 SS has an electrical conductivity of 1.45 MS/m which makes it a poor electricity conductor. Hence, suitable for only nonconductive applications.

Thermal Expansion

It comprises of moderate coefficient of thermal expansion which is 16.5 x 10^-6 /°C approximately at room temperature.

Magnetic Properties

It is nonmagnetic in nature due to its authentic structure. Therefore, only applicable for non-magnetic applications

Manufacturing and Process of 18/10 Stainless Steel

18/10 SS is possessing good formability, weldability, along with machinability which makes them pivotal in manufacturing and processing. Some common methods are discussed below:

Forming

This material can be formed easily therefore can be transformed into desired shape depending on the requirement. The key methods used for forming are:

• Cold rolling
• Hot rolling
• Deep Drawing

Welding

It is a common process that constitutes of joining SS parts to create large and complex structure. Common welding techniques use to weld 18/10 SS grade are:

• TIG welding
• MIG welding
• Spot welding

Machining

Removal of unnecessary 18/10 SS material from the product to acquire desired surface finish and shape. It involves several operations including turning, milling, drilling tapping and vice versa.

Grinding

A process used to acquire shiny and polished surface finish of 18/10 SS grade. Several grinding techniques could be used:

• Surface grinding
• Cylindrical grinding
• Centerless grinding

Heat Treatment Processes for 18/10 Stainless Steel

18/10 SS grade is heat treatable. Below is the table discussing the processes and their influence on this material:

Table 3: HT processes 18/10 SS

Surface Finish

18/10 SS can provide exceptional surface finish that leads to its cleanability and high corrosion resistance.

Summarize Differences Between 18/10 Stainless Steel Properties

Table 4: 18/8 vs 18/10 SS grade

Design Considerations for 18/10 Stainless Steel CNC Parts

Below is the brief description regarding consideration of 18/10 SS grade parts:

SS 18/10 Equivalent Materials

Table 5: Equivalent materials

18/10 Stainless Steel Rust

Such a design should be considered that can provide necessary corrosion resistance against mild and aggressive conditions. Moreover, paints and protective coatings could also be beneficial.

Mechanical Requirements

Components should be able to withstand the impact load and other cyclic load. For that, maximum amount of strength and durability should be present in a material like 18/10 SS.

Corrosion Resistance Requirements

Material should be capable enough to bear mild and aggressive corrosive environment in order to avoid material degradation or any catastrophic failure.

Processing Considerations

Design should be such that it can alter any shape, size maximum dimensional stability.

Cost-Effectiveness

Cost needed to be considered from manufacturing to the finished product. Overall, 18/10 SS grade is less expensive and affordable for industrialist.

AISI 18/10 VS Other Materials

18/10 SS grade is capable enough to be compared with other SS grades which is mentioned as following:

18/8 vs 18/10 Stainless Steel

Both have considerably the same composition apart from nickel yet offer good corrosion resistance and are affordable.

18/10 Stainless Steel vs 304

Both grades have a slide difference in composition along with properties like corrosion resistant and durability yet versatile for numerous applications.

18/10 vs 316 Stainless Steel

Slight difference in composition with additional 2-3% Mo in 316 SS. Moreover, 316 SS is more suitable for aggressive environmental conditions.

201 Stainless Steel vs 18/10

201 SS is cheaper comparatively with less Ni but provide low corrosion resistant as compared to 18/10 SS grade.

8/10 Stainless Steel vs Tri-Ply

18/10 SS comprise of single layer SS while Tri-Ply possess aluminum in its core between SS layers making it an excellent choice for heat conducting applications.