You use UNS numbers to tell different stainless and nickel alloys apart. The unified number system helps you pick the right material for your job. The U.N.S. number system lets you easily compare stainless steel and nickel alloys. Stainless steels have UNS numbers that start with “S.” Nickel alloys have UNS numbers that start with “N.” You can see this in the table below:
| UNS series | Metal type(s) |
|---|---|
| S00001 to S99999 | Heat and corrosion resistant (stainless) steels |
| N00001 to N99999 | Nickel and nickel alloys |
You can count on UNS numbers to keep your material choices the same for your projects.
Key Takeaways
- UNS numbers make it easy to tell stainless steels and nickel alloys apart. You can use them to compare different metals. Always look at the UNS number before you buy metals. This helps you pick the right grade for your project. The letter in a UNS number shows the metal family. The numbers tell you the exact alloy and its features. The UNS system stops confusion from trade names. It helps keep the quality of materials the same. Knowing UNS numbers helps you choose wisely. This makes your projects safer and work better.
UNS Numbers Overview
Unified Number System Basics
The unified number system helps you tell stainless steel grades and nickel alloys apart. This system makes it easier to pick the right stainless steel for what you need. The unified numbering system began in the late 1960s. Trade groups wanted a better way to sort metals and alloys. Here is how the system came to be:
- Trade groups looked at the need for a new system in the late 1960s.
- By 1971, they decided to make a unified number system.
- ASTM and SAE made a team in 1972 to plan the system.
- In 1974, the team shared the official way to number metals and alloys.
- By the end of 1974, more than 1,000 metals and alloys had UNS numbers.
- In 1975, the UNS Handbook listed these numbers.
Stainless steel grades have a letter at the start and five numbers. The letter tells you the metal family. For example, “S” means stainless steel. The first three numbers are often from old systems. The last two numbers show new types or special features. Here is a table that shows how it works:
| Feature | Description |
|---|---|
| Prefix Letter | Tells you the alloy type; ‘S’ means stainless steel. |
| Number of Digits | One letter and five numbers. |
| First Three Digits | Often match old 3-digit systems. |
| Last Two Digits | Show new types or properties. |
| Example | Type 310 stainless steel is S31000; Type 310S is S31008, which shows carbon content. |
| Number Range | Stainless steels use numbers from S00001 to S99999. |
The UNS number lets you compare stainless steel grades and nickel alloys easily.
Why UNS Numbers Matter
You use the UNS to keep stainless steel grades in order. The unified number system stops confusion from trade names and brands. You get one way to check different standards and rules. This system helps you find the right stainless steel for your needs.
The UNS number gives you a clear way to know stainless steel grades. You see the letter and know the metal family. You can look at the numbers to learn about the grade and its features. The system helps you track the material from the furnace to the finished product. You get proof that the stainless steel meets quality rules.
Here is a table that shows how the UNS helps with tracking and making things the same:
| Benefit | Description |
|---|---|
| Reduces Confusion | UNS numbers stop confusion from many trade names for the same stainless steel. |
| Cross-Reference | You get one way to check international standards and rules. |
| Organized Identification | The letter shows the metal family, so it is easy to tell. |
| Certification Assurance | You know the stainless steel meets safety and performance rules. |
| Traceability | You can follow the material from the furnace to the finished product using Material Test Reports. |
The unified numbering system helps you keep records, sort grades, and check stainless steel and nickel alloys. You can make better choices for your materials and uses.
Structure of UNS Numbers
Format and Components
The UNS number is a short code. This code helps you know what metal you have. The code has a letter and five numbers. The letter tells you the metal family. The numbers show the exact alloy or grade.
The UNS number lets you compare stainless steel and nickel alloys. You can quickly see the family and the alloy.
Here is a table that explains the format:
| Component | Description |
|---|---|
| Letter | Shows the family of metals (S for stainless steel, N for nickel, A for aluminum, C for copper) |
| Digits | Five numbers that identify the specific alloy or grade |
Look at these examples to see how it works:
- UNS S30400 means grade 304 stainless steel.
- UNS A92024 means an aluminum alloy.
- UNS C11000 means a copper alloy with high conductivity.
When you see a UNS number, you know the metal family and grade. This system helps you keep your materials organized.
UNS Numbers for Stainless Steel
You use UNS numbers to sort stainless steel grades. The letter “S” is always first for stainless steel. The numbers tell you the grade and sometimes special features. For example, grade 304 stainless steel is UNS S30400. Grade 316 stainless steel is UNS S31600. You find these numbers on reports and labels.
Stainless steel comes in many types. The 300 series is austenitic stainless steel. The 400 series has ferritic and martensitic types. Duplex stainless steel has its own UNS numbers. Each grade has a special chemical makeup. The UNS number helps you pick the right stainless steel.
Here is a table with common UNS numbers for stainless steel:
| UNS Number | Alloy Type |
|---|---|
| S41000 | Ferritic Stainless Steel |
| S42000 | Martensitic Stainless Steel |
| S44002 | Martensitic Stainless Steel |
| S44004 | Martensitic Stainless Steel |
| S13800 | Precipitation Hardening Steel |
| S15500 | Precipitation Hardening Steel |
| S15700 | Precipitation Hardening Steel |
| S17400 | Precipitation Hardening Steel |
| S17700 | Precipitation Hardening Steel |
| S32001 | Duplex Stainless Steel |
| S32003 | Duplex Stainless Steel |
| S32101 | Duplex Stainless Steel |
| S32205 | Duplex Stainless Steel |
| S32304 | Duplex Stainless Steel |
| S32507 | Duplex Stainless Steel |
Grades 304, 316, and 317 are in the 300 series. These grades are used a lot because they fight rust. The 400 series is used for knives and tools. Duplex grades are strong and resist rust even more.
When you pick a stainless steel, you check the UNS number. You know the grade and what is in it. This helps you not get mixed up with brand names.
UNS Numbers for Nickel Alloys
Nickel alloys have UNS numbers that start with “N.” You see these numbers on strong and special metals. Nickel alloys have more elements than stainless steel. Some have over 20 different elements. You use nickel alloys when you need strength, heat resistance, or rust protection.
Here is a table with common UNS numbers for nickel alloys:
| Type of Alloy | UNS Number |
|---|---|
| Precipitation Strengthening | |
| Nickel Alloy (Monel K-500) | N05500 |
| Nickel Alloy (Inconel 718) | N07718 |
| Nickel Alloy (Inconel X-750) | N07750 |
| Nickel Alloy (Incoloy A-286) | S66286 |
| Solid Solution Nickel Alloy | |
| Nickel Alloy (Monel 400) | N04400 |
| Nickel Alloy (Inconel 600) | N06600 |
| Nickel Alloy (Incoloy 800) | N08800 |
| Nickel Alloy (Hastelloy C-276) | N10276 |
| Austenitic Stainless Steel | |
| Stainless Steel (201) | S20100 |
| Stainless Steel (304) | S30400 |
| Stainless Steel (316) | S31600 |
| Stainless Steel (310S) | S31008 |
Nickel alloys must control small amounts of other elements. You use these alloys in chemical plants, planes, and ships. The UNS number helps you pick the right nickel alloy.
If you want a new UNS number, you must show the full chemical makeup. The alloy must be ready to sell. You cannot get a UNS number for test materials. The makeup must not be the same as other grades.
Tip: Always check the UNS number before you buy or use a metal. This makes sure you get the right grade for your job.
The unified numbering system keeps your records clear. You can compare stainless steel and nickel alloys easily. You avoid mistakes and make better choices for your work.
Interpreting UNS Numbers
Stainless Steel Grades
You can decode UNS numbers for stainless steel grades by following a simple process. Each UNS number starts with a letter and five digits. The letter “S” shows you that the metal is stainless steel. The digits help you find the exact grade and its features.
Step-by-step guide to reading UNS numbers for stainless steel:
- Look at the first letter. If you see “S,” you know it is stainless steel.
- Check the first three digits. These often match the old AISI numbers. For example, grade 304 uses “304.”
- Read the last two digits. These show special features or changes in the grade.
Tip: You can use the UNS number to compare grades from different standards. This helps you avoid confusion with trade names.
You see many types of stainless steel. Grade 304 is one of the most common. It has good corrosion resistance and works well in many places. Grade 316 is another popular choice. It has more molybdenum, which gives it higher corrosion resistance, especially in saltwater.
Duplex stainless steels use UNS numbers too. These grades mix austenitic and ferritic stainless. You get high strength and better resistance to corrosion.
Here is a table that shows common UNS numbers for stainless steel grades and their chemical composition:
| UNS No | AISI No / Common Name | C | Si | Mn | P | S | Cr | Mo | Ni | Others |
|---|---|---|---|---|---|---|---|---|---|---|
| S18200 | XM-34 (18-2FM) | 0.08 | 1.00 | 2.50 | 0.04 | 0.15 | 17.5/19.5 | 1.50 | – | – |
| S18235 | – | 0.025 | 1.00 | 0.50 | 0.030 | 0.15/0.35 | 17.5/18.5 | 2.00 | 1.00 | N 0.025; (C+N) 0.035; Ti 0.30/1.00 |
| S40300 | 403 | 0.15 | 0.50 | 1.00 | 0.040 | 0.030 | 11.5/13 | – | – | – |
You can use this table to check the chemical composition of each grade. This helps you pick the right stainless steel for your project. You see that grade 304 and grade 316 have different amounts of chromium, nickel, and molybdenum. These elements change the corrosion resistance and strength.
The 400 series stainless steel grades, like S40300, have less nickel. You use these grades for knives and tools. They give you good hardness and wear resistance.
Duplex stainless steels, such as S32205, mix two types of stainless. You get high corrosion resistance and strength. You use these grades in chemical plants and oil and gas work.
Nickel Alloy Grades
You can also decode UNS numbers for nickel alloy grades. These numbers start with “N.” Nickel alloys have special features for strength and corrosion resistance. You use these alloys in tough places like chemical plants and airplanes.
How to read UNS numbers for nickel alloy grades:
- Look for the letter “N.” This means the alloy is nickel-based.
- Check the digits. Each number matches a specific alloy and its features.
Nickel alloys help you when you need high corrosion resistance. You see these alloys in containers, pipes, and equipment for chemical processing. Aerospace engineering uses nickel alloys like Inconel 625 and Inconel 718. These alloys work well in high heat and tough conditions.
Here is a table with common UNS numbers for nickel alloys and their typical applications:
| UNS Number | Alloy Name | Typical Applications |
|---|---|---|
| N07718 | Inconel 718 | Oil and Gas components |
| N06625 | Inconel 625 | Chemical processing, aerospace engineering |
| N08825 | Incoloy 825 | Oil and Gas, chemical processing |
| 2.4375 | Monel K500 | Oil and Gas, chemical processing |
| N09925 | Incoloy 925 | Lower-cost alternative to Alloy 718 |
| N10276 | Hastelloy C276 | Chemical process industry, pharmaceuticals |
| N06022 | Hastelloy C22 | Chemical process industry, pharmaceuticals |
| N02200 | Commercially pure nickel | General applications, corrosion resistance |
You use nickel alloys for containers, pipes, and equipment in chemical processing. You also see these alloys in aerospace engineering. Alloy 825 and C276 nickel alloy plate are common choices for high corrosion resistance.
Note: Always check the UNS number before you choose a nickel alloy. This helps you get the right material for your job.
You can use the UNS numbering system to compare stainless steel and nickel alloys. You avoid mistakes and make better choices for your work. You see the chemical composition and know the grade. This helps you get the best corrosion resistance and strength for your needs.
Importance for Material Selection
Role in Stainless Steel Specification
You use uns numbers to make smart choices when you select stainless steel grades. These numbers help you match the right stainless steel to your project. You see the letter and numbers, and you know the family and the grade. For example, grade 304 gives you good corrosion resistance for kitchen equipment. Duplex stainless steels offer even better resistance and strength for chemical plants.
When you look at uns numbers, you avoid mistakes with trade names. You can check the chemical makeup and see if the stainless steel fits your needs. You use the system to compare grades from different suppliers. This helps you pick the best stainless steel for your job.
Tip: Always check the uns number before you order stainless steel. You get the right grade and avoid costly errors.
Here is a table that shows how uns numbers cover many metals and alloys:
| UNS Series | Metal |
|---|---|
| A00001 to A99999 | Aluminum and Aluminum Alloys |
| C00001 to C99999 | Copper and Copper alloys |
| D00001 to D99999 | Specified Mechanical Property Steels |
| E00001 to E99999 | Rare Earth and rare-earth-like Metals and Alloys |
| F00001 to F99999 | Cast Irons |
| G00001 to G99999 | AISI and SAE carbon and alloy steels (except tool steels) |
| H00001 to H99999 | AISI and SAE H-Steels |
| J00001 to J99999 | Cast Steels (except Tool steels) |
| K00001 to K99999 | Miscellaneous Steels and Ferrous Alloys |
| L00001 to L99999 | Low-melting Metals and Alloys |
| M00001 to M99999 | Miscellaneous Nonferrous Metals and Alloys |
| N00001 to N99999 | Nickel and Nickel Alloys |
| P00001 to P99999 | Precious Metals and Alloys |
| R00001 to R99999 | Reactive and Refractory Metals and Alloys |
| S00001 to S99999 | Heat and Corrosion Resistant (Stainless) Steels |
| T00001 to T99999 | Tool Steels, Wrought and Cast |
| W00001 to W99999 | Welding Filler Metals |
| Z00001 to Z99999 | Zinc and Zinc Alloys |
Impact on Procurement and Industry Use
You see uns numbers on every order and report in the stainless industry. These numbers help you buy the right stainless steel grades. You use the uns system to check if the stainless steel meets your standards. You can compare grades from different countries and suppliers.
When you use uns numbers, you make your records clear. You track stainless steel from the mill to the finished product. You see the grade, the family, and the corrosion resistance. This helps you avoid mix-ups and keep your products safe.
You use duplex stainless steels for tough jobs. These grades give you high strength and corrosion resistance. You see them in oil and gas, chemical plants, and marine work. You use uns numbers to pick the right grade for each job.
Note: You can trust uns numbers to help you choose stainless steel with the right resistance and properties. You save time and money when you use the system.
Common Issues and Best Practices
Avoiding Confusion with Similar Grades
It is easy to mix up stainless steel grades. Many grades look and sound almost the same. Some grades only have small changes in their chemical makeup. If you do not check closely, you might pick the wrong grade. This can cause problems with rust or strength.
You should always look at the UNS number when picking stainless steel. The UNS number helps you tell grades apart. For example, S30400 and S30403 are both stainless steel. But S30403 has less carbon than S30400. You need to know these small details to get the right grade.
Rust can also be confusing. Different grades react in different ways to tough places. The table below shows how stainless steel and nickel alloys can have rust problems:
| Corrosion Issue | Environment/Condition | Description |
|---|---|---|
| Localized attacks | Strongly oxidizing | Pitting and metal loss, especially in acid. |
| Temperature influence | Up to 500°C | High heat makes rust worse and changes how it happens. |
| Pressure influence | Up to ~40 MPa | High pressure can cause bad rust in some liquids. |
| Acidic solutions | HCl, HBr, H2SO4, HNO3, H3PO4 | Fast pitting happens in these acids. |
| Alkaline solutions | NaOH | Super hot NaOH is very harsh and causes rust. |
| Low corrosion | HF and H3PO4 | Rust is very low in these liquids sometimes. |
Note: Always match the stainless steel grade to where you use it. This helps you get the best rust protection.
Tips for Using UNS Numbers
You can follow some easy steps to use the right stainless steel and not get mixed up:
- Always use the UNS number when you buy stainless steel from other countries. This keeps things clear, even if names are different.
- Check with EN or Werkstoffnummer if you work with European companies.
- Make sure the product matches the right ASTM or ASME rule.
- Ask for Mill Test Certificates (MTCs) that show:
- Exact chemical makeup
- Strength and other properties
- Rust test results, like pitting resistance
- Talk to a material engineer if you need stainless steel for tough jobs or harsh places.
Tip: Always double-check the UNS number on every order and report. This helps you avoid mistakes and keeps your grades correct.
You can trust the UNS system to help you pick the right stainless steel. When you follow these tips, you get the right grade, the right rust protection, and the best results for your needs.
You should know about UNS numbers if you use stainless steel. This system helps you choose the right grade. It also helps you not make mistakes. You use UNS numbers when you talk to suppliers. They help you follow industry rules. The right UNS number keeps your stainless steel safe. It also helps stop rust and damage.
- Manufacturers use UNS numbers to sort special steels like N07718.
- The grading system gives everyone a common way to talk about stainless.
- Learning the system helps you follow safety and quality rules.
You can find more information in these resources:
| Resource | Description |
|---|---|
| SAE Standards for Mobility Knowledge and Solutions | You can see over 2,500 SAE Ground Vehicle standards and more than 6,000 old versions. |
| Unified Numbering System | You can look up new UNS numbers and what they are made of. |
| ASM Materials Information FAQ | You can get ASM Handbooks Online and see property data. |
FAQ
What does a UNS number tell you?
A UNS number shows you the metal family and the exact alloy. The letter tells you the type, like “S” for stainless steel or “N” for nickel. The numbers help you find the grade and its special features.
Can you use UNS numbers worldwide?
Yes, you can use UNS numbers in many countries. They help you compare metals from different places. You avoid confusion with trade names. Always check the UNS number when you buy or use metal from other countries.
How do you find the UNS number for a metal?
You can look for the UNS number on product labels, mill test certificates, or supplier documents. If you cannot find it, ask your supplier or check trusted online databases.
Why do some grades have similar UNS numbers?
Some grades look almost the same because they have small changes in their chemical makeup. For example, S30400 and S30403 are both stainless steel, but S30403 has less carbon. Always check the full UNS number to get the right grade.
