Analysis Of Advantages And Disadvantages Of Hot Rolled Seamless Steel Pipe

Hot-rolled seamless steel pipes are mainly used for the most underground pipeline transportation, groundwater extraction, boiler hot water transportation, mechanical processing, bearing sleeves, processing machinery parts, gas transmission, water power generation fluid pipelines, and wind power plant anti-static Tube and so on.

Advantages of hot rolling:It can destroy the cast structure of the steel ingot, refine the grain of the steel, and eliminate the defects of the microstructure, so that the steel structure is compacted and the mechanical properties are improved. This improvement is mainly reflected in the rolling direction, so that the steel is no longer an isotropic body to some extent; bubbles, cracks and looseness formed during casting can also be welded under high temperature and pressure.

The disadvantages of hot rolling:1. After hot rolling, non-metallic inclusions (mainly sulfides and oxides, as well as silicates) inside the steel are pressed into thin sheets, and delamination (sandwich) occurs. The delamination greatly deteriorates the tensile properties of the steel in the thickness direction, and it is possible that interlaminar tearing occurs when the weld is shrunk. The local strain induced by weld shrinkage often reaches several times the yield point strain and is much larger than the strain caused by the load.

2. Residual stress caused by uneven cooling. The residual stress is the internal self-phase equilibrium stress without external force. The hot-rolled steel of various sections has such residual stress. The larger the section size of the general section steel, the larger the residual stress. Although the residual stress is self-phase-balanced, it still has some influence on the performance of steel members under external force. Such as deformation, stability, fatigue and other aspects may have adverse effects.

Here's how to check the defects of seamless tube blanks and how to clean them. Visual inspection is generally used. For the tube blank with relatively high surface quality requirements and relatively thick iron oxide scale, the surface of the tube blank can be removed by pickling or shot peening before inspection. The surface defects are exposed and visually inspected.

The visual inspection room is the most commonly used, but its reliability is checked. Magnetic induction inspection can also be used to inspect the surface defects of the tube blank and the surface layer. There are many methods for electromagnetic induction testing, such as dry fluorescent magnetic particle inspection, eddy current testing, and electromagnetic testing.

Low-density tissue inspection of seamless tube blanks is generally performed by sulfur printing and acid leaching. The sulphur print test uses photographic paper to show sulfur segregation on the sample. It can show cracks, segregation, low-magnification, and inclusion distribution in the tube blank. The acid leaching method uses different corrosive chemicals and agents to etch the tube blank defects and the steel substrate. The tube blank defects and the steel substrate are etched differently, so that the small-sized tube blank defects that are difficult to identify can be displayed.

Cleaning methods for seamless tube blank defects: flame cleaning, air shovel cleaning, manual wheel cleaning and automatic wheel cleaning, turning and belt cleaning.

A worker from a steel pipe company, which is located in China.