LSAW Steel Pipe

 　　Seamless steel pipe is a metal material with a yield phenomenon. The stress at which the sample can continue to elong without increasing the force during the stretching process is called the yield point. If the force drops, the upper and lower yield points should be distinguished. The unit of yield point is N/mm2 (MPa). 　　The upper yield point (σsu) of the seamless steel pipe: the maximum stress before the sample yields and the force drops for the first time; 　　the lower yield point (σsl): the minimum stress in the yield stage when the initial transient effect is not taken into account. 　　The calculation formula of the yield point of seamless steel pipe is: 　　In the formula: Fs--yield force (constant) during the tensile process of the specimen, N (Newton) So--the original cross-sectional area of the specimen, mm2. 　　Elongation of seamless steel pipe after breaking (σ) 　　In the tensile test, the percentage of the length of the gauge length increased after the sample is broken to ...

 　　High-frequency straight seam steel pipe (ERW welded pipe) is based on the principle of electromagnetic induction and the skin effect, proximity effect and eddy current heating effect of electric charge, so that the steel at the edge of the weld is locally heated to a molten state, and the butt welding is achieved through the extrusion of intergranular bonding, so as to achieve The purpose of welding. 　　1. Control of weld gap 　　The strip steel is sent to the welded tube unit and rolled by a plurality of rolls, the strip steel is gradually rolled into a round tube blank with an open gap, and the compression degree of the squeeze roll is adjusted to control the welding gap between 1 and 3 mm. And make the welds flush. If the gap is too large, the proximity effect will be reduced, the eddy current will be insufficient, and the intergranular joint of the weld will be poor, resulting in non-fusion or cracking. If the gap is too small, the proximity effect will increase, and the weldin...

 　　In addition to the emergence of oil casing, it can also be used as a pipeline for transporting raw materials. To enhance the quality of oil casing, every link in the production process is particularly important. In particular, the temperature control during the period must be strictly followed. Regulations are mastered. Under normal circumstances, oil casing uses the sub-temperature quenching method. 　　Many friends will wonder why it is not an ordinary quenching method? Because the common quenching method will cause a large amount of residual stress inside the workpiece, which enlarges the brittleness, the subsequent processing is not so convenient. The sub-temperature quenching is to prevent the excessive brittleness of the oil casing from affecting the subsequent process. Each kind of steel has its heating temperature and time during heat treatment. As long as the performance of the workpiece can be improved and improved, the purpose of heat treatment will be achieved. 　　Heat ...

 　　Upset tubing, as the name suggests, is to thicken the tubing to make the tubing more robust and durable. The thickness of a standard pipe is not increased randomly. Increasing randomly may cause cracks or brittle fractures due to changes in the stress structure of the pipe body. Any thickening of the tubing must be thickened after in-depth research and design verification. 　　In offshore oil, many buried submarine pipelines are immersed in seawater for a long time, and are subject to the impact of seabed sediment and huge seawater to produce various erosions and impacts, which will cause great damage to the external pipe wall and shorten its life. Inside the oil pipeline, complex crude oil with high temperature, high heat, high corrosion, oil, gas and water combination is transported at a relatively fast speed. Long-term transportation will cause different degrees of corrosion or perforation in the inner pipe, making it difficult to repair the crude oil leakage, which makes it di...

 　　For the sake of construction safety, the matters needing attention for scaffolding workers: 　　1. Personnel who carry out scaffolding must have personal safety measures in place, and must accompany safety belts, protective gloves and safety helmets. Correct the angle of the scaffold at any time to avoid accidents caused by excessive deviation. 　　2. The external scaffolding is equipped with lightning protection measures. Under normal circumstances, workers are prohibited from performing construction operations on the scaffolding during thunderstorms. 　　3. For unfinished scaffolding, the stability of the scaffolding should be ensured at the end of work to avoid accidents. 　　4. No illegal operations are allowed, and the scaffolding must be erected in accordance with the prescribed plan. 　　5. Tie the structure in time or adopt temporary support to ensure the safety of the scaffolding process. 　　6. The fasteners of the scaffold must be tightened. 　　7. Use qualified scaffolding, and ne...

 　　Ductile water supply cast iron pipe 　　Pipes made of cast iron with a size of 18 or more, added with nodulizer, and centrifugally cast by a centrifugal ductile iron machine are called "ductile cast iron pipes" (Ductile Cast Iron Pipes) 　　Copper tube 　　One kind of non-ferrous metal pipes are pressed and drawn seamless pipes. Copper pipes have the characteristics of sturdiness and corrosion resistance, and are widely used in running water pipes, heating and cooling pipes of all commercial houses. 　　Alloy tube 　　Alloy pipe is a kind of seamless steel pipe, its performance is much higher than the general seamless steel pipe, because this kind of steel pipe contains more Cr, its high temperature resistance, low temperature resistance and corrosion resistance are inferior to other seamless steel pipes, so alloy pipes are widely used in petroleum, aerospace, chemical, power, boiler, military and other industries. 　　Composite pipe 　　Composite pipe is a pipe composed of two or more ...

 　　Porosity, bubbles, shrinkage cavity residues, non-metallic inclusions, segregation, white spots, cracks and various abnormal fracture defects in cold drawn seamless steel pipes can be found through macroscopic inspection. The method of macro inspection is divided into two methods: acid leaching inspection and fracture inspection. A brief introduction to the common macro defects displayed by the acid leaching method is as follows: 　　Causes of segregation: 　　During the pouring and solidification process, the selective crystallization and diffusion caused the aggregation of certain elements, resulting in uneven chemical composition. According to the different positions of the distribution, it can be divided into ingot type, center and spot segregation. 　　Macroscopic characteristics: 　　On acid-leached samples, when the segregation is erodible substances or gas inclusions, it is dark in color, irregular in shape, slightly concave, flat at the bottom and many dense microporous spots. ...

 　　Thick-walled seamless steel pipe has the characteristics of high strength, good hardenability, good toughness, small quenching deformation, high temperature creep strength and high endurance strength. Used to manufacture forgings with higher strength and larger quenched and tempered section than 35CrMo thick-walled seamless steel pipes, such as large gears for locomotive traction, supercharger transmission gears, pressure vessel gears, rear axles, connecting rods, spring clamps, etc. It has a large load and can be used for drill pipe joints, fishing tools and bending machine molds in deep wells below 2000 meters. 　　After the precision bright tube is quenched to obtain the martensite structure, it is tempered in the temperature range of 450-600℃; or after tempering at 650℃, it passes through 350-600℃ at a slow cooling rate; or after tempering at 650℃, 16Mn seamless steel pipe Long-term heating in the temperature range of 350 to 650°C will cause embrittlement of the precision brig...

 　　What is high frequency welding? 　　High-frequency welding is a new type of welding process that uses the skin effect and neighboring effect produced by high-frequency current to connect steel plates and other metal materials. The emergence and maturity of high-frequency welding technology is a key process in the production of ERW steel pipe. The quality of high-frequency welding directly affects the overall strength, quality level and production speed of welded pipe products. 　　The basic principle of high frequency welding: 　　The so-called high frequency refers to the frequency of the alternating current of 50Hz, and generally refers to the high frequency current of 50KHz to 400KHz. When high-frequency current passes through a metal conductor, two peculiar effects are produced: skin effect and proximity effect. High-frequency welding uses these two effects to weld steel pipes. So, what are these two effects? 　　The skin effect means that when an alternating current of a certain fr...

 　　The welding method of seamless steel tube should be selected according to the material and wall thickness of the seamless tube. Because different welding methods have different arc heat and arc force, different welding methods have different characteristics. 　　For example: Tungsten arc welding is characterized by low current density, stable arc combustion, and good weld formation. It is especially suitable for thin plate welding, but thick plate welding is not an option; plasma arc is characterized by high arc column temperature and high energy density , Plasma arc has good straightness, its rigidity and flexibility have a wide adjustment range, and work is stable, but the operation is more complicated; submerged arc welding has the characteristics of penetration ability and high welding wire deposition efficiency, so the welding speed It can be greatly improved, the welding cost is lower, but the labor conditions and environment are relatively poor. It can be seen that differen...