The method of using ultrasound to detect instrument called ultrasonic flaw detector. Its principle is: when the ultrasonic wave propagation in the detected material changes in the acoustic properties and the internal organization of the material have a certain effect on the propagation of ultrasonic waves through the ultrasonic affected degree and condition detection understanding material properties and structural changes of technology called ultrasonic testing. Ultrasonic testing methods typically penetrating, pulse reflection method, serial method. Penetrating ability, depth of up to several meters; x-rays can not penetrate conventional visible light through the material. The strength of its ability to penetrate, and x-ray wavelengths and is penetrated material density and thickness. x-ray wavelength shorter, the greater penetration; the lower the density, the thinner the thickness of the x-rays to penetrate more easily. In practice, the value of the voltage V balls tube (kV) to determine the size of the x-ray penetration (ie, x-ray quality), and to the unit of time through the x-ray current (mA) and the time the product Representative x-ray amount. The maximum thickness can be measured with the x-ray intensity, generally metal thickness of 0.3 m or less; The advantages of ultrasonic testing than X-ray flaw detection: It has high sensitivity, short cycle, low cost, flexible, high efficiency, harmless to human body and so on; Ultrasonic testing disadvantages compared to X-ray detection of: On the work surface smoothing requirements, requirements experienced inspectors to identify the type of defect, the defect does not intuitive; Ultrasonic testing is suitable for large thickness parts inspection.

Defects of electric resistance welding is following below: 1) There is a lack of a reliable method for non-destructive testing, welding quality only by destructive testing process to check specimens and artifacts, as well as by a variety of monitoring techniques to ensure that. 2) Points, seam welded lap joint not only increases the weight of the structure, and because between the two plates around the nugget form an angle, resulting in a lower tensile strength and fatigue strength of the joint. 3) Power equipment, high degree of mechanization and automation, so that the higher cost of equipment, maintenance more difficult, and the commonly used high-power single-phase AC welder is not conducive to the normal operation of the grid. With the development of electrode wear aerospace, electronics, automobiles, household appliances and other industries, the electric resistance welded together by the society, at the same time, the quality of resistance welding also put forward higher requirements.

Disadvantages of galvanized mild steel has following aspects: On the surface of hot dip galvanized steel rice distribution classes of small dots, called zinc particles is customary. Defective zinc particles can be divided into two: one is up and down the strip surface adhesion lot of granular, strip local increase in the thickness of the zinc layer, causing the surface rough, unsightly and harmful use of known zinc particles. There are two forms, one of the larger particles of zinc tablets, the main ingredient is iron - zinc compound, which is the end of slag. When coated galvanized steel edge is much higher than the middle of coating thickness, edge thickness is produced. When the air knife nozzle clogging occurs locally when in a position corresponding to the strip will produce thick zinc layer is formed with marks. In the middle of the strip edge or rendered bright stripes or the presence of dendritic conchoidal crystal crystalline zinc this particular often make local zinc layer projections, it is called zinc projections. Strip out from uncoiler to galvanized defects between coiler, strip and a mechanical relative movement generated.

Oil and gas drilling steel pipe, including drill pipe, casing and tubing , the special nature of oil and gas exploitation, working conditions extremely complex conditions can be quite harsh, so its very strict quality requirements. Such as tubing in the course of not only bear the weight of the column itself, the need to withstand corrosion oil (gas), water, acids, etc., and thus their shape, size, coupling strength, tightness, mechanical properties and corrosion resistance and so on there are strict requirements. Tubing Coupling by threaded connection tubing, to bear the weight, and thus their higher. The coupling blanks for the manufacture of tubing coupling short pipe coupling tube. Grade J55 tubing pipe coupling process is as follows: Tube - blanking - heating - heat-centering - piercing - wear mandrel - necking - jacking - loose stick - stick off (after the mandrel lubrication, before sending necking machine, recycling) - hot saw - reheating - high pressure water descaling - tension reducing - cooling bed Cooling - cold saws - straightening - product testing - packaging and storage. High quality round tube rolling rolling through the refining process, according to the requirements of API Spec 5CT, finished normalizing the status of delivery; when the hot-rolled tubes finishing temperature not lower than the normalizing temperature, can replace normalizing.

Welded steel pipe at the factory to go through rigorous testing to ensure the quality of welded compliance standards and user requirements. Pipe inspection items generally include: appearance quality factory inspection project, straightness, dimensions, and other types of weld quality inspection items (flattening, flaring, bending, etc.). Welded pipe surface quality and straightness inspection by a full-time quality inspector confirmed finishing process pipe segment using visual way, the implementation of the detection test dimensions available random sampling method, and the weld quality inspection shall be made on special equipment by root on line. This article focuses on online testing of the weld. At present, about our national standards, testing methods available weld pipe hydrostatic testing, ultrasonic testing, eddy current testing in any way. Hydrostatic test is the most common, the most direct and reliable weld line inspection Measured way, in a variety of hydraulic test machine. When the pressure test, through the first low-pressure water, filled the whole steel pipe to make the air side by side, and then to test pressure specified by the pressurized way, and to stabilize the prescribed time, when there is no pipe welds and around wet, spray, leakage or permanent deformation is considered qualified. When the metal by an alternating magnetic field is induced metal surface Eddy currents; when the presence of the metal surface defects, since the impedance increases, the eddy current value becomes smaller; and when no defect of a metallic material, the value of the stable vortex; size of the power according to the eddy current loss, can be characterized metals whether the surface defects. Ultrasonic wave propagation in the process, will have a reflection on the media surface. If there is a crack pipe welds, weld, false welding, lap welding defects such as acoustic impedance will change significantly, so that ultrasonic generating different reflection, through a dedicated instrument will be identified to achieve the purpose of flaw detection. The main steel tube ultrasonic flaw detection are: rotating the probe, steel straight forward; probe fixed, steel rotating forward; steel rotating probe straight forward three forms, in the production of different pipe diameter in both applications.