Inspection of steel pipes generally includes: inspection of geometrical dimensions and surface quality; chemical composition, mechanical properties, process performance, inspection of high and low-fold microstructures; non-destructive testing; certain special performance inspections and length measurement.
(1) Geometrical inspection of steel pipes
The outer diameter, wall thickness, bending and length of the steel pipe can be inspected on the inspection table with an outer caliper, a micrometer and a bending ruler, and a length tape measure.
For the outer diameter, wall thickness and length, automatic size detection devices (such as automatic diameter measurement, thickness measurement, length measuring device) can also be used for continuous detection. Steel pipe production plants put into operation in the late 1980s generally have online automatic diameter measuring and thickness measuring devices, and measuring length weighing equipment is provided in the finishing area. Thread parameters are also checked for OCTG steel tubes.
(2) Inspection of the inner and outer surfaces of steel pipes
The inner and outer surface inspections are generally performed by visual inspection, and the inner surface can be inspected by using a reflective prism in addition to visual inspection. Some special-purpose steel pipes also require inspection of the quality of the inner and outer surfaces of steel pipes through non-destructive testing, including eddy currents, magnetic flux leakage, ultrasonic waves, and magnetic particle inspection.
(3) Mechanical properties and process performance check
In order to verify that the mechanical properties of the steel pipe meet the requirements of the standard, it is necessary to test the mechanical properties of the steel pipe.
Mechanical properties test mainly includes tensile strength, yield strength, elongation, impact work and so on. Process performance inspection mainly includes flattening test, flare test, hydraulic test, crimp test, cold bend test, perforation test and so on. These inspection items are selected according to the differences in standards and the use of steel pipes.
(4) Nondestructive testing
Non-destructive testing refers to the direct inspection of internal and surface defects without damaging the steel pipe. At present, magnetic flux leakage testing, ultrasonic testing, eddy current and fluorescent magnetic particle testing have been widely used in steel pipe enterprises. In recent years, the non-destructive testing method has been greatly developed. Recently, new technologies such as acoustic emission holography, ultrasonic spectrum analysis and flaw detection, ultrasonic imaging inspection and ultrasonic high-temperature flaw detection have appeared.
(5) Chemical composition test
According to the standard requirements, the main components of the steel pipe are retested according to the batch number.
(6) High and low test
It includes the inspection and measurement of low-magnification of steel pipes, non-metallic inclusions, actual grain size, metallographic microstructure, decarburization layer, etc. It must be carried out according to the requirements of the standard.
(7) Weight detection
For steel pipes with a single weight requirement, it is also necessary to check whether the weight meets the contract or standard requirements by means of a weighing device.