ASME SA213 T91 Seamless Steel Pipe Comprehensive Description

1、 Standards and Basic Attributes

SA213 T91 seamless steel pipe follows the ASME SA-213/SA-213M standard and belongs to the martensitic high chromium molybdenum alloy heat-resistant steel 25. Its design is based on 9Cr-1Mo steel, and the alloy composition is optimized by adding elements such as vanadium (V) and niobium (Nb). It has excellent high-temperature oxidation resistance and durability, and is suitable for high temperature environments of ≤ 625 ℃.

2、 Chemical composition

The core components include:

Cr (8.00-9.50%), Mo (0.85-1.05%): Enhance high-temperature corrosion resistance;

V (0.18-0.25%), Nb (0.06-0.10%): Refine grain size and enhance strength;

C (0.08-0.12%), N (0.03-0.07%): Control the carbon content to improve weldability and stabilize the structure with nitrogen element.

3、 Physical performance

High temperature performance: high endurance strength, excellent oxidation resistance, suitable for high-pressure and high-temperature scenarios such as supercritical boilers;

Mechanical properties: tensile strength ≥ 275MPa, yield strength ≥ 245MPa, elongation ≥ 30%;

Stability: Uniform organization, low performance degradation during long-term use.

4、 Manufacturing and Inspection

Production process: Adopting cold drawing, cold rolling and other cold processing technologies to ensure dimensional accuracy;

Quality control: Chemical composition analysis, mechanical property testing (tensile, impact), non-destructive testing and other inspections are required.

5、 Application Fields

Power industry: Boiler high-temperature superheater and reheater fittings (metal wall temperature ≤ 625 ℃);

Petrochemical industry: hydrogenation reactors, oil pipelines;

Other fields: aerospace components, nuclear power equipment, and special mechanical structures.

6、 Key points of welding process

Preheating requirement: Preheat to 200-300 ℃ to avoid cold cracking;

Post weld treatment: tempering at 760-780 ℃ to eliminate residual stress;

Process selection: Tungsten inert gas welding (GTAW) is preferred to ensure welding quality, especially when working in narrow spaces.