Precision seamless pipe is an important form and type of seamless pipe, which has a wide range of applications in various construction projects, building construction, and decoration. The phenomenon of fracture of precision seamless pipe is always found in production and major sales, which is due to many links not being done well in production, as well as insufficient ingredients and incorrect proportions of chemical elements.

1. Small longitudinal crack

The small longitudinal cracks on the surface of precision seamless pipes have a length of less than 200mm, a width of less than 3mm, and a depth of less than 0.3mm.

2. Peak shaped crack

The cracks all occurred at a distance of 5-60mm from the edge of the precision seamless tube, and the macroscopic direction was perpendicular to the rolling direction, forming a "mountain peak" shape.

3. Edge crack

The crack mainly occurs at a distance of 20-80mm from the edge of the precision seamless tube, with the morphology of multiple parallel longitudinal cracks of different sizes. The pattern is that the thicker and wider the specification of the precision seamless tube, the more severe this type of defect.

4. Inclusion and scarring

The inclusions and scars are distributed in a regular pattern, and the phenomenon is obvious after finishing operations such as edge flame peeling crack inspection or casting scratch flame cleaning.

For the fiber structure and crystal defects such as dislocations and vacancies in steel, annealing or normalizing heat treatment methods are generally adopted to eliminate them. The purpose of annealing is to refine grains, eliminate structural defects, reduce hardness, improve plasticity, and facilitate cold processing. Annealing equipment is indispensable in the production of cold drawn precision seamless tubes. Therefore, developing appropriate annealing processes is a necessary condition to ensure that the microstructure of precision seamless tubes is qualified and that products do not have fracture defects. If manufacturers reduce annealing processes in order to unilaterally lower production costs, it will inevitably have a negative impact on product quality.

YB/T5035-1993 (Seamless steel pipe for automotive half shaft sleeve pipe). Mainly used for producing carbon structural steel and alloy structural steel hot-rolled seamless steel pipes for automobile half axle sleeves and drive axle housing shaft pipes. Its representative materials are 45, 45Mn2, 40Cr, 20CrNi3A, etc.

The purpose of alloy tube:

1. Alloy pipes can be used as pipelines for transporting oil, natural gas, coal gas, water, and certain solid materials;

2. Manufacturing structural and mechanical components, such as oil drill rods, automotive transmission shafts, bicycle frames, and steel scaffolding used in construction

3. Manufacturing circular parts with alloy steel pipes can improve material utilization, simplify manufacturing processes, save materials and processing time, such as rolling bearing rings, jack sleeves, etc

4. Alloy steel pipes are still used as materials for various conventional weapons, such as gun barrels and cannon barrels, which require steel pipes for manufacturing

The materials of alloy pipes generally include: 10 #, 20 #, 35 #, 45 #, 16-50 Mn、27SiMn、40Cr、12-42CrMo16Mn 12Cr1MoVT91 27SiMn30CrMo15CrMo20G Cr9Mo 10CrMo91015Mo3 15CrMoV 35CrMoV45CrM