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1. Shoddy steel pipe prone to fold. Fold is formed on the surface of a variety of steel fold, this defect often throughout the product's longitudinal direction. The reason is due to shoddy factory folded pursuit of high efficiency, reduction is too large, resulting in the ears, it creates a rolling fold down when the product will crack when folded bending, the strength of steel big drop. 2. Ma often shoddy steel pipe outer surface phenomenon. Pock is due to the groove worn steel surface irregularities caused serious irregularities defects. Because of shoddy steel pipe manufacturers to pursue profits, often the most excessive rolling groove. 3. Shoddy steel surface is easy to produce scarring. There are two reasons: (1). Shoddy steel material uneven impurities. (2). Shoddy material manufacturers guides poorly equipped, easy to stick steel, easy to produce scarring after these impurities roll bite. 4. Too shoddy material surface is easy to crack, because it's blank adobe, adobe many pores, adobe in cooling Process due to thermal stress, cracks, crack after rolling there. 5. Shoddy steel easily scratched because of shoddy steel pipe manufacturers poorly equipped, prone to glitches, scratches steel surface. Deep scratches reduce the strength of steel. 6. No shoddy steel metallic luster, pale red color of pig iron or similar reasons two two, its stock is adobe. 2, inferior-rolling temperature is not standard, they are visually steel temperature, so the region can not be prescribed by austenite rolling, properties of steel naturally not compliance. 7. Shoddy steel cross ribs thin and low, often sufficient dissatisfaction with the phenomenon, because manufacturers to achieve large negative tolerance, finished in front of a few larger reduction, iron type is too small, pass fully satisfied. 8. Shoddy steel pipe oval cross-section, because the manufacturers in order to save material, the first two tracks finished roll reduction is too large, the strength of this steel is greatly decreased, and does not conform to the standard dimensions of rebar. 9. High-quality steel components of uniform, high tonnage cold shear, cut the head end surface smooth and tidy, but shoddy material due to the material is poor, there are often cut off the meat first end face of the phenomenon, namely uneven, and no metallic luster. And because wood product manufacturers cut shoddy little head, head and tail will be a big ears. 10. Shoddy steel material containing impurities, the density of steel is small, and size tolerance serious, so in the absence of vernier calipers case, you can check it for weighing. For example, for steel 20, the national standards set forth in the maximum negative tolerance of 5%, while its length 9M single theoretical weight of 120 kg, its minimal weight should be: 120 X (l-5%) = 114 The actual weight of the weighing out single smaller than 114 kg, it is shoddy steel, because it is a minus tolerance of 5%. Generally the whole amount commensurate would be better, mainly taking into account the accumulated error and probability theory this problem. 11. Shoddy steel pipe inner diameter fluctuations due; l, steel surface temperature instability of yin and yang. 2, the composition of the steel uneven. 3, due to poor equipment, low-intensity ground, rolling big bounce. There will be big changes in the same week, so easy to produce steel discontinuity break. 12. Trademarks and printing high-quality tube are relatively standardized. 13. Three pipe diameter of more than 16 large thread pitch between the two trademarks are over IM. 14. Inferior longitudinal reinforcement steel rebar often wavy. 15. Shoddy steel pipe manufacturers because there is no traffic, so the package is relatively loose. Side of the oval.

According to the production method: Pipe according to production methods can be divided into two categories: seamless steel pipe and pipe joints, pipe joints referred to as straight pipe joints. 1. seamless steel pipe according to production methods can be divided into: hot-rolled seamless pipe, cold drawn pipe, precision steel tubes, thermal expansion tubes, cold spinning tube and squeeze tubes. Seamless steel pipe with high-quality carbon steel or alloy steel, hot-rolled, cold-rolled (pull) of the points. 2. welded steel pipe because of different welding process is divided into stove pipe, welded (ERW) pipes and automatic arc welded pipe, welding its different forms is divided into two Longitudinal and spiral welded pipe, its end shape is divided circular pipe and shaped (square, flat, etc.) pipe. Welded steel pipe is rolled into a tube-shaped steel sheet spiral seam to seam or welded, in the manufacturing method, is divided into low pressure liquid delivery welded steel pipe, spiral seam welded steel pipe, straight welded pipe, welded pipe. Seamless steel tubes for various industries liquid pressure pipelines and gas pipelines. Welded pipes can be used for water pipes, gas pipes, heating pipes, electrical pipes. According to the material: Pipe by pipe material (ie steel) can be divided into: carbon pipe and alloy pipe, stainless steel tubes. Carbon tube can be divided into ordinary carbon steel and quality carbon structural tube. Alloy tube can be divided into: low-alloy tube, alloy structure tube, high alloy pipe, high-strength pipe. Bearing tube, heat-resistant acid stainless steel tube, precision alloy (such as Kovar) pipe and high-temperature alloy tubes. Press connection classification Pipe by pipe end connection can be divided into: light pipe (pipe end without thread) and threading pipe (pipe end with thread). Car wire tube is divided into: ordinary cars wire pipe and threading pipe end upsetting. Thick threading pipe can be divided into: external upset (with external thread), internal upset (with internal thread) and the inner and outer thickening (with external thread), etc. threading pipe. If you press threading pipe thread types can be divided into: ordinary cylindrical or conical thread and special thread etc. threading pipe. In addition, according to user needs, threading pipe is generally equipped with fittings delivery. According to the plated coating characteristics A surface coated steel plating characteristics can be divided into: clarinet (not plated coating) and plated coating tube. Coating possession galvanized pipe, aluminum pipe, chrome pipes, tubes and other alloy layer infiltration was steel. Coated pipe outer coating tube, pipe coating, pipe coating inside and outside. Usually with a plastic coating, epoxy, epoxy coal tar and various type of anti-corrosion coating of glass material. Galvanized pipe and tube is divided into KBG, JDG tube, threaded pipe, etc. According to the application: 1. Line tube. Such as: water, gas pipes, steam pipes seamless pipe, oil pipeline, oil and gas line pipe. Agricultural irrigation faucet with a pipe and sprinkler pipe. 2. Thermal Equipment tube. Such as the general use of boiling water tube boilers, superheated steam pipes, superheater locomotive boiler tubes, opium pipe, small pipe, brick arch pipe and high-temperature high-pressure boiler tubes. 3. Mechanical industrial pipe. Such as aviation structural tube (tube, oval tube, flat oval tube), automobile axle tube, axle tubes, structural tubes for tractor, tractor oil cooler tube, farm with a square tube and rectangular tube, pipe and transformer bearings tubes. The petroleum geological drilling pipe. Such as: oil drilling pipe, drill pipe (Kelly and hexagonal drill), drill collar, oil tubing, casing and various fittings, geological drilling pipe (core pipe, casing, active drill pipe, drill collar Press hoop and pin joints, etc.). 5. Chemical industrial pipe. Such as: petroleum cracking tubes, chemical equipment and piping tube heat exchangers, acid-resistant stainless pipe, fertilizer use high-pressure pipe and transporting chemical medium pipe. 6. Other departments tube. Such as: container tube (high pressure gas cylinders with pipes and general container tube), instrumentation tube, watch shell pipe, hypodermic needles and tubes and other medical devices. According to the cross-sectional shape: Steel grades and different specifications of steel products is extremely diverse, its performance varies. All of these changes should be as user requirements or conditions of work and distinction. Typically, steel products according sectional shape, production method, pipe materials, connection methods, plated coating characteristics and intended use classification. Pipe according to a cross-sectional shape can be divided into: circular pipe and shaped pipe. Profiled steel refers to a variety of non-circular cross-section of the pipe. The major ones are: a square tube, rectangular tube, oval tube, flat oval tubes, half tubes, hexagonal tubes, hexagonal tube, scalene hexagonal tubes, pipes equilateral triangle, pentagon Plum, octagonal tube, convex shaped tube, double convex tube. Double concave tube, more concave tube, oval-shaped tube, flat tube, diamond-shaped tube, star tube, parallelogram tubes, ribbed tubes, drop-shaped tube, finned tubes, twisting different tube, B-tube, D tube and multilayer tube. Pipe according to the profile shape and is divided into: sectional steel and variable cross-section steel. Variable Section (or variable cross-section) pipe refers sectional shape along the longitudinal direction of the tube on the inside and outside diameter and wall thickness variations occur cyclic or acyclic steel. The main are: outer conical tubes, tapered inner tube, the outer stepped tube, ladder pipes, cycle section, bellows, spiral, finned pipe and barrel with a double-track and so on.

Rolled steel rolling process for the continuation of the process and reducing fixed. Steel rolling is a process of moving together by steel and mandrel in multiple racks, steel deformation and movement as well as by common action rolls and mandrel. Mandrel can be free floating, that is, thanks to the forward movement of the metal drive; it can be limited to acting, that is a given mandrel speed of movement, limiting their freedom of movement. During exercise, mandrels, rolls and steel contact as a whole, where any one part of the change will lead to changes in the status of the entire system, rolling theory is the study of the theory of the relationship between them. Kinematics phenomenon of steel rolling 1, kinematic phenomena 2, slippage 3, tension coefficient MPM motion state analysis 1, rolling with the mandrel displacement relationship 2, the rack and determine 3, intermittent rolling analysis 4, single rolling mandrel motion characteristics Steel rolling deformation and stress 1, rolling pipe stress analysis 2, the side wall deformation and stress analysis

q345b steel pipe polishing method often used Polishing means a processing method by the action of mechanical, chemical or electrochemical, lower the q345b steel pipe surface roughness, to obtain a bright and smooth surface, and surface modification process making use of a flexible polishing tools and polishing abrasive particles or other media on the workpiece . Polishing can not improve the dimensional accuracy or geometrical shape accuracy of q345b steel pipe, but can obtain a smooth surface or specular gloss, sometimes to be used to eliminate gloss. Usually buff as a polishing tool. Buff is generally made with multilayer canvas, leather crafted stacked, on both sides clamped with a metal circular plate, its rim coated abrasive mixture of powder and oil and other uniform. (1) Mechanical q345b steel polishing surface corrosion resistance. As we know, the mechanical polishing q345b steel corrosion resistance is significantly lower than the electrochemical polishing q345b steel pipe, mainly due to the cold mechanical q345b polishing surface hardened steel deformed layer high corrosion rate, coupled with in the mechanical polishing process, inevitably have abrasive particles embedded in the deformable layer, the corrosion rate of deformation layer increased greatly. (2) electrochemical q345b steel polishing makes the metal surface hardening layer easy to be dissolved, and can lower the surface activity, what`s more, there is a continuous passivation film formed on the surface, significantly improved the corrosion resistance.