What are the methods for inspecting butt-weld elbows after corrosion?

　　Butt-weld elbows can corrode if used improperly. Corrosion typically manifests as thinning of the elbow wall, localized pitting, and pitting. Methods for inspecting butt-weld elbows after corrosion: The principle of leakage flux testing is based on the high magnetic permeability of ferromagnetic materials.

　　The magnetic permeability of a butt-weld elbow's corrosion defect is much lower than that of the butt-weld elbow itself. Under the influence of an external magnetic field, the butt-weld elbow becomes magnetized. When the butt-weld elbow is free of defects, the magnetic lines of force mostly pass through the steel pipe, resulting in a uniform distribution. When a butt-weld elbow has an internal defect, the magnetic lines of force bend, and some leak out of the pipe's surface. By detecting the leakage flux escaping from the magnetized butt-weld elbow surface, the presence of a defect can be determined. Ultrasonic testing utilizes the pulse reflection principle of ultrasonic waves to measure the thickness of the pipe wall after corrosion. This process uses the self-propagating centrifugal casting method to form, mainly using the chemical reaction of the substance itself, exothermic combustion to generate high temperature, and synthesizing new substances during the propagation of the combustion wave. During the inspection, the probe transmits ultrasonic pulses vertically to the inner wall of the butt-weld elbow. The probe first receives the reflected pulse from the inner surface of the pipe wall, and then the ultrasonic probe receives the reflected pulse from the outer surface of the pipe wall. The distance between this pulse and the reflected pulse from the inner surface reflects the thickness of the pipe wall. Bend: refers to the processing of pipes into butt-weld elbows, generally referring to metal pipes used in water and electricity and electrical PVC conduit; Bend butt-weld elbows: mostly refers to metal butt-weld elbows in water supply and drainage. Small-diameter butt-weld elbows can be obtained by bend.