1. Decoding the Standard: 1.7335
Standard: EN 10216-2 (Seamless steel tubes for pressure purposes - Technical delivery conditions - Part 2: Non-alloy and alloy steel tubes with specified elevated temperature properties)
Material Number: 1.7335
Old DIN Designation: 13CrMo4-5
Equivalent Name: 13CrMo44 (This is a very common name for this steel)
This steel is technically a low-alloy steel, not a simple carbon steel. The "13" refers to the approximate chromium content.
2. Chemical Composition
The key elements that define 1.7335 are:
| Element | Content (%) | Purpose |
|---|---|---|
| Carbon (C) | 0.08 - 0.18 | Provides strength. |
| Chromium (Cr) | 0.70 - 1.00 | Improves oxidation (scaling) resistance and strength at high temperatures. |
| Molybdenum (Mo) | 0.40 - 0.60 | Greatly increases strength at high temperatures and reduces creep. |
| Manganese (Mn) | 0.40 - 1.00 | Aids in strength and hardenability. |
| Silicon (Si) | 0.10 - 0.35 | A deoxidizer, improves strength. |
The presence of Chromium and Molybdenum is what makes this steel suitable for "boiler" applications.
3. Key Properties and Why It's Used for Boilers
1.7335 is specifically designed for high-temperature service under pressure. Its properties make it ideal for:
Excellent Creep Strength: Creep is the slow, permanent deformation of a material under constant stress at high temperatures. The Molybdenum content is crucial here, allowing the pipe to maintain its shape and strength over long periods.
Good Oxidation Resistance: The Chromium content forms a stable, protective oxide layer on the surface, preventing the steel from rapidly scaling (oxidizing) in the presence of hot steam or flue gases.
Good Weldability and Formability: It can be reliably welded and bent into the complex shapes required for boiler systems, provided proper pre-heating and post-weld heat treatment (PWHT) procedures are followed.
4. Typical Applications
As the name "Boiler Steel Pipe" implies, its primary use is in the power generation and process industries:
Superheater and Reheater Tubes: Sections of the boiler where steam is heated to its highest temperature.
Boiler Headers: Large pipes that collect or distribute steam/water to multiple smaller tubes.
Heat Exchangers: In various process industries where high temperatures and pressures are involved.
High-Temperature Pressure Piping: General high-temperature service in chemical plants and refineries.
5. Common Specifications and Equivalent Grades
It's important to know the equivalents when sourcing or replacing this material.
| Region | Standard | Equivalent Grade |
|---|---|---|
| Europe | EN 10216-2 | 1.7335 (13CrMo4-5) |
| USA | ASTM A213 / A335 | T12 / P12 |
| Germany | DIN 17175 | 13CrMo44 |
| Japan | JIS G3462 | STBA 22 / STPA 22 |
Summary
When you see "1.7335 Carbon Steel Boiler Steel Pipe," you are looking at a seamless, low-alloy steel tube specifically engineered for high-temperature and high-pressure environments, such as:
Power plant boilers
Superheaters
High-temperature piping systems
Its excellent creep resistance and good weldability make it a reliable and widely used material in the energy sector. Always ensure that the pipe is supplied to the correct standard (e.g., EN 10216-2) and that it comes with the necessary certification (e.g., a 3.1 or 3.2 material certificate) for pressure equipment applications.
