The difference between ASTM A53 Gr.B and Gr.A steel pipes

　　ASTM A53 steel pipes is a standard for seamless and welded steel pipes promulgated by the American Society for Testing and Materials (ASTM). It is suitable for mechanical and pressure applications and is also acceptable for ordinary uses in steam, water, gas and air lines.

　　Sizes:NPS 1/8” to NPS 26”(DN 6 to DN 650)

　　Schedules: S/10, S/20, S/40, STD, S/60, S/80, XH, S/100, S/120, S/140, S/160 and XXH

　　ASTM A53 includes three types of steel pipes, namely Type F – Furnace-butt welded continuous Welded Pipe (Grade A), Type E – Electric Resistance Welded Pipe (Grade A and Grade B), Type S – Seamless Pipe (Grade A and Grade B).

　　The most fundamental difference between ASTM A53 Grade A and Grade B steel pipes is their mechanical properties, especially their minimum yield strength and tensile strength.This makes Grade B more suitable than Grade A for high pressure applications.

　　Yield Strength:

　　Yield strength is the critical stress value at which a material yields. (Note: Yield strength is only for elastic materials)

　　First, the material undergoes elastic deformation under the action of external force, following Hooke's law. What is elastic deformation? That is, when the external force is removed, the material will return to its original size and shape. When the external force continues to increase and reaches a certain value, the material will enter the plastic deformation period. Once the material enters plastic deformation, the original size and shape of the material cannot be restored when exposed to external force! The strength that causes the critical point between elastic deformation and plastic deformation is the yield strength.

　　ASTM A53 Grade B generally has a higher minimum yield strength than Grade A. For example, Grade A may have a minimum yield strength of 205 MPa (30 ksi), while Grade B may have a minimum yield strength of 240 MPa (35 ksi).

　　Tensile strength:

　　Tensile strength refers to the maximum stress a material can withstand before breaking.

　　When the steel pipe yields to a certain extent, its ability to resist deformation increases again due to the rearrangement of the internal grains. Although the deformation develops rapidly at this time, it can only increase with the increase of stress until the stress reaches the maximum value. After that, the ability of the steel to resist deformation was significantly reduced, and large plastic deformation occurred at the weakest point, where the cross-section of the specimen rapidly shrank, causing necking until fracture and failure. The maximum stress value before the steel breaks under tension is called the strength limit or tensile strength.

1.ASTM A53 Grade A vs  B seamless steel pipes

2.ASTM A53 Grades A and B Pipe - Permissible Variations

ASTM A53 Grade B steel pipe also generally has higher tensile strength than Grade A. Grade B steel pipe generally has a higher tensile strength than Grade A, making Grade B more suitable for applications that can withstand higher pressures.