Testing principle The ultrasonic probe can achieve energy conversion and ultrasonic sound energy between the physical characteristics of the propagation in elastic medium when the pipe is the basis of the principle of ultrasonic flaw detection. Directional transmission of ultrasonic beam propagation encountered in the tube defect, produces both the reflected wave has produced wave attenuation. After signal processing flaw detector, such as the use reflection detection, defect obtained echo signals, such as the use penetration testing method, by virtue of the degree of attenuation of the wave to get the defect signal. Both can give a quantitative defect indication by the instrument. Using the piezoelectric effect or electromagnetic induction principle can stimulate different types of ultrasonic wave in the tube. Therefore, the piezoelectric ultrasonic and electromagnetic ultrasonic examination ultrasound can be used for pipes. But EMAT only for ferromagnetic materials. Testing methods Longitudinal wave (or wave plate) reflection method (or penetration method) in the probe and the pipe relative movement state auto inspection, the only special large-diameter pipe is available for manual inspection. Automatic or manual inspection shall ensure that when the beam to scan the entire surface of the tube. Defect inspection longitudinal beam propagation direction in the circumferential wall; test transverse defects in the wall beam travels along the tube axis direction. Longitudinal and transverse defects inspection should be carried out in two opposite directions of the tube. When the demand side is not presented for inspection transverse flaw inspection party only longitudinal defects. Agreed by both sides, longitudinal and transverse defects inspection can be carried out only in one direction of the tube. Automatic or manual selection of test time should be coupled to good effect, and without prejudice to the coupling medium pipe surface.

Package of steel tube requirements substantially divided into two categories: one is the common type of bale, and the other is with totes similar container load. Bundled package Avoid pipe damage by baling and transportation process, baling signs to a uniform and consistent. The same bundle of steel pipe should be the same furnace number (Lot), with the steel grade, the same specifications of the steel pipe, should not be mixed furnace (batch) bundling, it should be less than a bundle into small bundles. Weight of each pipe bundle should not exceed 50kg. The user's consent to increase the bale weight, but the most important can not exceed 80kg. Pipe bundle respect to the blunt end, should be aligned at one end, the tube ends are aligned side by less than 20mm, each bundle of steel pipe length difference less than 10mm, but according to the length of the pipe is usually the order of each bundle pipe length difference is less than 5mm, the longest pipe bundle and Minister of not more than 10mm. Containers package Cold-rolled or cold-drawn seamless steel tubes, the surface finish of hot-rolled stainless steel tube, the container may be used (such as plastic containers and wooden box) packaging. Weight of the container shall be packed in accordance with Table 1. Negotiated by both sides, the maximum weight of each container can be increased. When the pipe into the container, the inner wall of the container should be fitted cardboard, plastic sheeting or other moisture-proof material. Containers should not be closely seepage. For steel containers and packaging, a label should be included in the container. The outer end surface of the container should also be linked to a label. Steel with special packaging requirements, by agreement between.

Concrete is concrete poured into the steel pipe and tamped to increase the strength and rigidity of the steel pipe. In general, we have concrete strength steel in concrete C50 or less as ordinary steel concrete; concrete strength steel in the concrete above C50 called steel high strength concrete; concrete strength CFT C100 above called steel high strength concrete. As we all know, high compressive strength of concrete. But bending is weak, and steel, especially steel strong bending resistance, good plasticity, but when pressed easily instability and loss of axial compression capabilities. Concrete and steel in the structure will be able to combine the advantages of both, can make concrete is laterally compressed state, the compressive strength can be doubled. At the same time due to the presence of concrete, improve the rigidity of the steel pipe, which together play a role, thus greatly improving the carrying capacity. As a new steel concrete composite structures, mainly in the axial compressive force and a smaller compression eccentric member-based, is widely used in the frame structure (such as factories and high-rise). Part of the concrete column is less and less welds, simple structure, the pedestal reserved cup often used in concrete foundation plug-foot column, which manufacturing plant is relatively simple, while the smaller component weight, lifting and transportation are more easy, very simple construction, steel and concrete columns were rolled sheet, plate thickness is not large, generally less than 40mm, and regardless of the factory site butt welding, have no difficulty. At the same time, compared with reinforced concrete columns, steel sheath having a reinforced concrete column function, the role of both the longitudinal and transverse reinforcement stirrups, so no steel tube, steel cutting and saving a series of steel banding process, and Since the column jacket pipe itself is resistant to lateral pressure template, but also save the formwork and form removal processes. In recent years, quite common pumping concrete, poured on-site no difficulty, and the creation of widely used high Paola not vibrated concrete method of construction, more streamlined site - concrete steps, simple construction. In the lower portion of the column is also open temporary watering hole with a bottom-pouring of concrete pump concrete way, not only fast, but also to ensure the quality of watering. Moreover, after pouring, steel pipe is fairly stable humidity conditions, water can not evaporate, eliminating the need for water conservation processes, simplifying the process of curing concrete.

In the case of heating, the mechanical properties of steel with increasing temperature change. The general performance of the elastic modulus, yield strength, ultimate strength decreases with increasing temperature, plastic deformation and creep increases with increasing temperature. So-called "blue brittle" phenomenon at 200 ℃ ~ 350 ℃ hot rolling, then increase the ultimate strength of steel and plastic lower compared with other temperature ranges change "brittle." At 500 ℃, ultimate strength and yield strength of the steel is greatly reduced, increasing plasticity. At 450 ℃ ~ 600 ℃, the graphite and carbides tend ball. Graphitization product is due to the decomposition of iron carbide, graphite particles produce results free. If the heating temperature is higher, the longer, the higher the carbon content of steel, carbide ball is the more intense. The presence of graphite and ball, show steel at high temperatures weakened, reducing mechanical properties. Changes in the temperature of the alloy material is generally added to make the steel needs to improve. The results showed that: within 200 ℃ intensity did not change significantly, a slight decrease in yield strength, ultimate strength and unchanged. The yield strength with increasing temperature and decreasing the rate began to accelerate after 200 ℃. Ultimate strength due to "blue brittle" and slightly higher than the ambient temperature at 200 ℃ ~ 300 ℃, ultimate strength after 300 ℃ decreased with increasing temperature. At 600 ℃, low carbon steel yield strength and ultimate strength are only 35% to 40% of normal temperature, and lower the strength of carbon steel wire. As the temperature rises further, the strength of steel at 800 ℃ disappeared. While steel elongation and reduction of area surface increases with increasing temperature, indicating that the plastic properties of steel at high temperatures increases, easily deformed. In addition, the steel at a certain temperature and stress, over time will occur slowly deform, that creep, creep relaxation will result in material. Steel at high temperatures reduce the yield point is an important factor in determining the fire resistance of steel structures, such as a steel member that is at room temperature and load application is half the value of the yield point, but since the fire steel fire at high temperature yield strength decreases, when the actual value reaches the stress reduces the yield strength showed an yield phenomenon and damage and the sharp decline in the carrying capacity of the structure, resulting in partial or total collapse of steel buildings destroyed.

The appearance of a bluish-white zinc coating, the standard electrode potential is -0.76V, soluble in acid, alkali-soluble, metal music is amphoteric type. Zinc dry air change hardly occurs, corrosion of zinc critical humidity greater than 70%, in the wet atmosphere and therefore can generate a thin film mainly consisting of basic zinc carbonate with carbon dioxide and oxygen effect, this membrane has a certain inhibition and so on, and zinc sulfide-containing hydrogen sulfide from the reaction of zinc sulfide; zinc chloride susceptible to erosion, it is instability in seawater. Zinc in an enclosed or poorly ventilated, humid air conditions, when non-metallic materials in contact with the volatile matter (low molecular weight carboxylic acids, aldehydes, phenols, ammonia, etc.), zinc vulnerable to corrosion, loose white corrosion product is generated, commonly known as " frost. " Zinc at high temperatures, high humidity, confined conditions, and bakelite, paint, wood volatiles released contacting zinc has a tendency filamentous growth of single crystals, commonly known as "hairy." Standard potential than iron zinc negative, in terms of the steel is anodic coating provides reliable electrochemical protection. Use in an industrial atmosphere, rural atmosphere and ocean of the atmosphere can be selected steel products zinc as a protective layer, its relationship with the protective zinc coating life is almost proportional to the thickness. Where industrial air pollution in the atmosphere, zinc coating corrosion better than cadmium plating, at sea or in the sea opposite. After zinc coating after chromate corrosion resistance can be improved 6--8 times. It is essential for galvanized passivation step. In the passivation film organic dye, can be used for low file protection products --- decorative coating. To reduce the thickness of zinc coating can improve corrosion resistance, at home and abroad adopt the following two measures: First, to improve the quality of the passivation film, such as blue, green, military green, black passivation instead of the conventional rainbow color passivation film , especially in military green passive film corrosion resistant; the second is a thin iron 0.3% - 0.6% Zn-Fe alloy, nickel, or 6% -10% of the Zn-Ni alloy instead of pure zinc coating, corrosion performance improvements more than three times, widely used on cars instead of galvanized steel sheet. Zinc coating temperature not exceeding 2500C, the temperature deformation of the crystal structure of zinc, brittle, corrosion resistance decreased. There corrosion resistance, heat requirements of the parts is appropriate Zn-Ni alloy layer. Galvanized electrolyte can be divided into two major categories of basic and weak acid, commonly used at home and abroad Have cyanide zincate zinc cyanide, zinc, galvanized ammonium salts, zinc chloride, zinc, and other sulfate. Domestically, non-cyanide zincate is still the mainstream. In recent years, due to the improved performance of galvanized additives improve, zinc chloride and low cyanide bright zinc rapid development, and ammonium galvanizing continued to decline. Select the plating bath according to pieces of material, shape, appearance requirements may be, such as stamping small parts and complex parts, in particular the need for auxiliary anode hole or tubular member should use alkaline bath; hydrogen embrittlement sensitive parts is appropriate weak acid zinc plating solution. When the performance of two different bath, the production is very favorable.