Quick Summary
If you’re a procurement professional involved in purchasing carbon steel or stainless steel, understanding material standards is crucial for confident decision-making. This guide offers an overview of widely used standards such as ASTM, EN, and ISO, explaining key properties like mechanical strength, corrosion resistance, chemical composition, and heat treatment. Familiarity with these standards helps you communicate effectively with suppliers and R&D teams, ensuring the right material is chosen for your application. Consider this guide as a first step to get you started and understand the basics.
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Guide to Stainless Steel Standards
As a procurement professional, one of the most essential skills is knowing how to discuss material standards, when working with carbon steel and stainless steel. Understanding material standards ensures you can accurately specify the materials your company needs, negotiate effectively with suppliers, and have meaningful discussions with internal teams like R&D or engineering.
In this guide, we’ll dive into the common material standards for carbon steel and stainless steel, discuss the critical properties these standards describe, and explain how to approach material selection confidently. Whether you’re purchasing SS316 for high-corrosion environments or carbon steel for structural purposes, this guide will serve as an initial reference point, and maybe trigger a deep dive.
Understanding Material Standards
Material standards are a set of technical definitions and guidelines that ensure a material’s quality and suitability for specific applications. They help both buyers and suppliers align on expectations regarding the material’s properties, performance, and safety.
The most common organizations that develop material standards include:
- ASTM International (formerly known as the American Society for Testing and Materials)
- EN (European Norm) standards
- ISO (International Organization for Standardization)
Each of these organizations provides detailed material specifications that define everything from chemical composition to mechanical properties.
Key Material Properties Described by Standards
When dealing with carbon steel and stainless steel, material standards cover several critical properties that directly affect the material’s performance in different environments:
1. Chemical Composition
The chemical composition defines what elements are present in the alloy and in what quantities. For instance, stainless steel SS316 has a high percentage of chromium (around 16-18%) and nickel (10-14%), which give it excellent corrosion resistance, especially in marine or acidic environments.
2. Mechanical Properties
These include tensile strength, yield strength, and elongation. For example, carbon steel might be chosen for its high tensile strength, while stainless steel might be selected for its ability to withstand harsh environments without degrading. The standards specify the range of acceptable values for these mechanical properties, which helps engineers determine the suitability of a material.
3. Corrosion Resistance
This is a key concern when choosing stainless steel. Standards like ASTM A240 for stainless steel help define materials such as SS304 and SS316, with specific guidelines on corrosion resistance in various environments. SS316, for instance, is known for its superior resistance to chloride environments, making it ideal for marine applications.
4. Heat Treatment
Many carbon steels and stainless steels are heat-treated to alter their properties. Standards describe the heat treatment processes that the material has undergone, such as annealing or quenching, and explain how these processes impact the material’s strength, hardness, and ductility.
5. Hardness
Hardness is often measured in Brinell, Rockwell, or Vickers units and is a critical factor in determining a material’s wear resistance. This property is essential in applications where abrasion resistance is crucial, such as in cutting tools or industrial machinery.
6. Dimensional Tolerances
Material standards also define the acceptable dimensional tolerances for products like sheets, plates, or bars. These tolerances ensure that the material will fit precisely within the equipment or structure where it’s used.
Carbon Steel Standards Overview
1. Common Standards for Carbon Steel
- ASTM A36: One of the most widely used carbon steel standards. It covers carbon steel shapes, plates, and bars for structural use. A36 steel is known for its good weldability and strength, making it ideal for structural applications like bridges and buildings.
- EN 10025: This European standard covers hot-rolled structural steel. It includes various grades of carbon steel such as S235, S275, and S355, which differ primarily in their yield strength.
- ISO 630: Another standard covering structural carbon steels, often used internationally. ISO standards are useful when working with suppliers from different countries who might not use ASTM or EN standards.
2. Typical Applications of Carbon Steel
Carbon steel is chosen primarily for structural applications due to its high tensile strength and cost-effectiveness. Examples include:
- Construction materials (beams, columns)
- Automotive parts (frames, panels)
- Pipes and pressure vessels
3. Key Considerations for Buyers
When purchasing carbon steel, focus on mechanical properties like tensile and yield strength. Ensure that the steel has been heat-treated correctly for your application, especially if you’re dealing with high-stress environments. In structural applications, dimensional tolerances are critical to ensure proper fit.
Stainless Steel Standards Overview
1. Common Standards for Stainless Steel
- ASTM A240: This standard is widely used for stainless steel sheets, plates, and strips. It includes specifications for commonly used grades like SS304 and SS316.
- EN 10088: This European standard classifies stainless steel grades according to their chemical composition and mechanical properties. For example, 1.4401 corresponds to SS316 and provides detailed guidelines on its corrosion resistance.
- ISO 15510: The international standard for stainless steel, offering globally accepted specifications. Like EN standards, it focuses on chemical composition and mechanical properties.
2. Typical Applications of Stainless Steel
Stainless steel is chosen for its corrosion resistance, aesthetic appeal, and strength. It is commonly used in:
- Chemical processing equipment
- Food and beverage manufacturing
- Marine environments (e.g., SS316 for high-salt conditions)
- Medical devices
3. Key Considerations for Buyers
When specifying stainless steel, the environment where the material will be used is critical. For example, SS304 is suitable for many indoor applications, but for outdoor or marine use, SS316’s superior corrosion resistance is preferable. Also, consider surface finishes, especially in industries like food processing, where hygiene is essential.
Comparing Carbon Steel and Stainless Steel
1. Corrosion Resistance
Stainless steel, especially grades like SS316, is far superior to carbon steel in terms of corrosion resistance. If your application involves exposure to moisture, chemicals, or salts, stainless steel is the better choice. Carbon steel, unless coated or treated, will rust in these environments.
2. Cost
Carbon steel is generally much cheaper than stainless steel. If your application doesn’t require high corrosion resistance, carbon steel might offer a more cost-effective solution.
3. Strength and Ductility
Both materials can offer high strength, but stainless steel often excels in applications requiring both strength and corrosion resistance. Carbon steel tends to have higher tensile strength, making it ideal for structural applications.
4. Maintenance
Stainless steel requires far less maintenance than carbon steel, which needs regular protective coatings or treatments to prevent rust. For long-term projects where maintenance costs are a concern, stainless steel may be the better investment.
Austenitic Stainless Steels (3xx Series)
These are the most common types of stainless steel, known for excellent corrosion resistance and good formability. Below is a list of some common stainless steel grades, including SS301 and onwards:
- SS301 – Lower nickel content than 304, good corrosion resistance, good ductility, and is commonly used for high-strength applications such as springs.
- SS302 – Similar to 304, but with higher carbon content for increased strength.
- SS303 – Increased machinability due to the presence of sulfur, but slightly lower corrosion resistance compared to 304.
- SS304 – The most common stainless steel, known for good corrosion resistance and formability. Available in 304L (low carbon) for improved weldability.
- SS305 – Increased nickel content for improved cold formability.
- SS308 – Similar to 304 but with higher nickel content, used for welding applications.
- SS309 – Higher chromium and nickel content than 304, providing better resistance to oxidation and heat.
- SS310 – Very high resistance to oxidation at high temperatures, used in furnace parts.
- SS316 – Contains molybdenum for enhanced corrosion resistance, especially against chlorides. 316L is the low carbon version for better weldability.
- SS317 – Even higher molybdenum content than 316 for better resistance to pitting and crevice corrosion.
- SS321 – Stabilized by titanium, making it ideal for high-temperature applications to prevent carbide precipitation.
- SS347 – Similar to 321 but stabilized with niobium and tantalum for improved corrosion resistance at high temperatures.
Supplier of Stainless Steel
Here is a list of global suppliers of stainless steel along with their headquarters:
- Acerinox – Spain
- Outokumpu – Finland
- Nippon Steel Corporation – Japan
- Aperam – Luxembourg
- POSCO – South Korea
- Jindal Stainless – India
- Taiyuan Iron & Steel (TISCO) – China
- Thyssenkrupp Stainless – Germany
Summary – Stainless Steel Standards
As a buyer, understanding material standards is essential for making informed decisions. Whether you’re sourcing carbon steel for a construction project or stainless steel for a chemical plant, the standards provide a clear framework for specifying materials that meet performance and safety requirements.
Familiarize yourself with key standards like ASTM, EN, and ISO to ensure you’re purchasing materials that are fit for purpose. By understanding the detailed specifications, including chemical composition, mechanical properties, and corrosion resistance, you can confidently engage with suppliers and internal teams to ensure the right material is selected for each application.
Stainless steel (SS) grades are typically classified using a three-digit numbering system, with variations in their composition leading to different mechanical properties, corrosion resistance, and applications.
These are some of the most commonly used stainless steel grades, with SS301 being austenitic and representative of this broad category. Each grade has a unique composition and properties, making it suited to specific applications.
By mastering material standards, you not only improve your procurement skills but also add significant value to your organization. You’ll be able to navigate complex technical discussions with ease, ensuring that every procurement decision aligns with the company’s operational needs and long-term strategy.
Learn more
The website Stahlschlüssel (Key to Steel) is an indispensable resource for professionals dealing with steel, such as engineers, procurement managers, and technical buyers. It provides a comprehensive cross-reference system to decipher steel designations and find equivalent materials worldwide. The platform covers over 75,000 standards and steel grades from approximately 300 steel manufacturers and suppliers, making it a powerful tool for anyone in the steel industry.
The Key to Steel database includes detailed information on various steel types, such as:
- Structural and construction steels
- Tool steels (carbon, hot work, and cold work steels)
- Stainless steels
- Heat-resisting alloys
- Non-magnetic steels
- Welding filler materials
The platform allows users to search materials by chemical composition, mechanical properties, or even by standard designations, making it easier to find equivalent materials across different international standards. The multilingual system (German, English, and French) is ideal for global trade, helping to decode steel grades and compare standards across countries. Additionally, it provides access to detailed material data sheets, which include chemical, mechanical, and physical properties, as well as heat treatment processes and supplier information
For professionals like procurement managers, this tool is critical for ensuring that steel specifications meet the required standards, facilitating better decision-making and communication with suppliers globally.
Learn about Product Legislation from Hans Nilsson in of his courses or read about standards in the blogpost Finding a relevant ISO standard
Note: Illustration to the blogpost “Stainless Steel Standards – your first step to insight” was created by Chat-GPT on Sept 14, 2024.