How To Distinguish Grade I, II And III of Seamless Steel Pipes?

Seamless steel pipe is a kind of pipe with excellent pressure resistance and high temperature resistance, and is often used in petrochemical, fertilizer, machinery, aviation and other fields. Seamless steel pipes are generally divided into Grade I pipes (high-grade precision tube), Grade II pipes (ordinary precision tube) and Grade III pipes (general purpose pipe). How to distinguish them?

Distinguishing Grade I, Grade II and Grade III of seamless steel pipes

1. Wall thickness

The wall thickness of seamless steel pipes is different, which can be used to judge its grade. The wall thickness of Grade I pipes is thicker, generally between 8-20mm, and the wall thickness is uniform, and the error is controlled within a small range; the wall thickness of Grade II pipes is between 5-12mm, and the thickness error is slightly larger than that of Grade I pipes; the wall thickness of Grade III pipes is between 3-10mm, and the wall thickness uniformity is poor, and there may be a certain error. In some high-demand hydraulic systems, Grade I pipes as hydraulic tubes can ensure the stable operation and high-pressure bearing capacity of the system.

2. Length

The length of seamless steel pipes is also different. The length of Grade I pipes is longer, generally fixed length, which can reach more than 12m; Grade II pipes are generally between 6-12m; the length of Grade III pipes is very short, only between 3-6m, and is mainly suitable for scenes with low length requirements, such as ordinary pipeline transportation or temporary construction.

3. Accuracy

The accuracy of seamless steel pipes is also an important indicator for judging grades. Generally speaking, Grade I pipes have the highest accuracy, with deviations controlled within ±0.5mm; Grade II pipes have an accuracy within ±1mm; and Grade III pipes have an accuracy within ±1.5mm.

4. Material and chemical composition

The selection of materials and the control of chemical composition are also key factors in determining the grade of seamless steel pipes. Grade I pipes are made of high-quality steel, such as 20#, 20Cr, 12CrMoV, 15CrMoG and other high-performance alloy steels; Grade II pipes have slightly lower material standards, but still meet industrial standards such as GB/T, ASTM, DIN, etc.; Grade III pipes are made of ordinary materials, and may use ordinary carbon steel pipe or low-alloy steel pipe.

5. Mechanical properties

The mechanical properties mainly include the tensile strength, yield strength and elongation of seamless steel pipes, and different grades of pipes differ in these aspects. Grade I pipes have excellent mechanical properties, high tensile strength and good ductility; Grade II pipes have relatively balanced mechanical properties and meet the requirements of conventional industrial use; Grade III pipes have lower mechanical property requirements and are mainly used in low-load environments with limited bearing capacity.

How to choose seamless steel pipes correctly?

When purchasing seamless steel pipes, you should choose the appropriate grade according to specific usage requirements:

1. For high-precision, high-pressure, and high-temperature environments (such as boilers, petrochemical equipment, and aerospace), it is recommended to choose Grade I pipes to ensure stable performance, safety and reliability.

2. For general industrial purposes (such as general fluid transportation, machinery manufacturing), you can choose Class II pipes, which can ensure performance and control costs.

3. For general purposes (such as low-pressure pipelines, support structures, etc.), you can choose Class III pipes, which are economical and suitable for occasions with low requirements.

Summary

The grade of seamless steel pipes can be judged more accurately by the differences in wall thickness, length, precision, etc. When purchasing seamless steel pipes, you need to choose the pipes that suit you according to the specific usage scenarios and needs.

Read more: Seamless Steel Pipe Sizes