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1. how can the heat exchange equipment be classified? Answer: can be pided into: (1) tube shell heat exchanger (2) casing heat exchanger (3) water immersion heat exchanger (4) spray heat exchanger (5) rotary (snake tube) heat exchanger (6) plate heat exchanger (7) plate fin heat exchanger (8) tube fin heat exchanger (9) heat exchanger tubes (10) other 2. how does the heat exchanger heat the heat? Answer: in the most common wall type heat exchangers, there are mainly two ways of conduction and convection. The heat transfer is first passed to one side of the tube wall by convection heat transfer, then the heat passes through the side of the tube wall through the way of conduction, and the heat transfer is passed to the cold fluid on the other side of the tube wall, and the heat transfer process of the heat exchanger is completed. 3. medium velocity on the heat transfer effect? Answer: the greater the velocity of the medium in the heat exchanger, the greater the heat transfer coefficient. Therefore, increasing the velocity of the medium in the heat exchanger can greatly improve the heat transfer effect, but the negative effect of increasing the flow rate is to increase the pressure drop through the heat exchanger and increase the energy consumption of the pump, so it is necessary to have a certain suitable range. 4. how does the surface structure of the heat exchanger affect the heat transfer effect? Answer: the special design of heat transfer tube surface structure, such as fin tube, nail head tube, thread tube and so on, on the one hand increase the heat transfer area, on the other hand, the disturbance of the special surface greatly increases the turbulence level of the fluid outside the tube, which can increase the overall heat transfer effect of the heat exchanger in two aspects, so these surface structures are better than light. The performance of the tube surface is excellent. 5. what are the usual ways to remove fouling on the surface of heat exchanger tubes? Answer: the common methods of descaling on the surface of heat exchange tube are: Mechanical descaling: manual cleaning of steel drill and scaling of pressure water Chemical descaling 6. are there any methods for anti scaling on the surface of the heat exchange tube? Answer: (1) nickel phosphorus plating (2) chemical coating, 847 coating 7. what are the commonly used methods to enhance heat transfer in heat exchangers? Answer: the main method of heat transfer enhancement in heat exchange equipment One is to use the structure of increasing the heat transfer surface, such as 1 use finned tube, nail head pipe, screwed pipe, bellows and so on. 2 the surface of the pipe is machined: spiral pipe, spiral grooved tube, screwed pipe, etc. 3 small tube diameter can increase the number of tubes on the same tube plate area and increase the heat transfer area. The two is to increase the flow rate of fluid in the heat exchanger, which can greatly improve its heat transfer coefficient, such as: 1 adding spoiler, such as inserting spiral belt in the tube, setting baffle outside the tube, false pipe, etc. 2 increase the number of tube or shell process. In addition, the use of materials with good thermal conductivity to make heat exchangers, good heat and corrosion prevention measures, and timely scaling are all means to improve the heat transfer effect. 8. what is the requirement for the number of pipe plugging when the tubular heat exchanger is overhauled? Answer: the tube holes are allowed to be blocked by a metal plunger with a conical degree of 3~5 degrees. Generally speaking, the number of tubes that are blocked in the same pipe range will not exceed 10% of the total number of pipes, but can be appropriately increased according to the technological requirements. 9. why does the gasket on both sides of the tubesheet have to choose the same material? Answer: because the flange bolts on both sides of the tubesheet are the same bolts, the specific pressure applied to the gaskets on both sides of the tubesheet is the same. If the gaskets on both sides of the two sides choose different materials, it will cause the sealing failure of one side gasket not enough and the sealing failure of the gasket on the other side is too large, so the gasket on both sides of the tube must choose the same material. Why does the 10. cooling water heat exchanger produce scale? Answer: the scale is formed by the crystallization of dissolved salts in the water and attached to the wall of the heat exchanger tube. Its characteristics are dense and hard, firmly attached and difficult to remove. A large number of suspended particles in water can become crystal species. Other impurity ions, bacteria and rough metal surface all have a strong catalytic effect on the crystallization process, which greatly reduces the supersaturation required by the crystallization. Therefore, the cooling water heat exchanger is very easy to produce scale. What are the main components of the 11. float heat exchanger? Answer: the main components are: tube bundle, baffle plate, drawing bar, fixed distance pipe, shell, tube box, tube plate, inlet flange, outlet flange, floating head flange, float head cover, float head hook ring, float head gasket, outer cover flange, outer lid flanges, outer cover, outer lid gasket, exigents, draining mouth Pipe box flange, pipe box side flange, pipe box gasket, pipe box side gasket, fixed saddle, movable saddle. 12. what are the main components of the fixed tube sheet heat exchanger? Answer: the main components are: tube bundle, baffle plate, pull rod, fixed distance pipe, shell, tube box (top cover), tube plate, inlet flange, outlet flange, pipe box flange, tube box gasket, fixed saddle, active saddle, ear type support, expansion joint. What are the main components of the 13.U tube heat exchanger? Answer: the main components are: U tube bundle, baffle plate, punching plate (inner guide tube), pull rod, fixed distance pipe, shell, tube box, tube plate, inlet flange, outlet flange, pipe box flange, tube box flanges, tube box gasket, tube box side gasket, fixed saddle, moving saddle. What are the main components of the 14. casing heat exchanger? Answer: the main components of the sleeve type heat exchanger are: inner tube, outer pipe and back elbow. 15. what are the main components of a water immersion heat exchanger? Answer: the main components of the water flooding heat exchanger are: inlet pipe, outlet pipe, collecting pipe, snake pipe and cooling water tank. What are the main components of the 16. spray heat exchanger? Answer: the main components of the spray heat exchanger are: tube bundle, fan, water nozzle, drainage pipe, feed water pump. What are the main components of the 16. spray heat exchanger? Answer: the main components of the spray heat exchanger are: tube bundle, fan, water nozzle, drain pipe and feed water pump. 17. what are the characteristics of fixed tube sheet heat exchangers, U tube heat exchangers and floating head heat exchangers? Answer: the characteristics of the fixed tube plate heat exchanger are compact, simple, low cost, the largest number of tubes in the same shell diameter, convenient maintenance of the single tube, convenient cleaning in the tube, but difficult to clean out of tube, and the high stress of tube and shell body temperature. The U type tube heat exchanger is characterized by its simple structure, no temperature difference stress problem, high flow velocity, low metal consumption and high temperature and high pressure fluid. The tube bundle can be easily removed to clean the shell and pipe, but the elbow is not easy to sweep, the tube number is few, the tube spacing is large, the tube center has gap, and the fluid outside the tube is easily short circuited. . The float head type heat exchanger is characterized by the free movement of the tube bundles, no temperature difference stress problem, the free extraction of the tube bundles, the convenience of cleaning the pipe and the tube bundle, but the structure of the float head is complex, the cost is high, the sealing requirement of the float head is more strict, the float head is easy to leak and is not easy to check and find in operation. 18. where are the fixed tube sheet heat exchangers applicable? Answer: fixed tube sheet heat exchangers are suitable for occasions where shell side medium is clean, it is not easy to scale, and medium temperature difference is relatively small. Where is the 19.U type tube heat exchanger? Answer: U type tubular heat exchangers are suitable for high temperature and high pressure applications in the tubes. 20. where do the float heat exchangers apply? Answer: floating head heat exchangers are suitable for occasions where the temperature difference between the shell and tube is large, the medium is not clean and needs frequent cleaning. 21. the arrangement of tubular heat exchangers is arranged in triangle and square to 45 degrees. Why? Answer: triangle arrangement and square rotation to 45 degree angle have their advantages and disadvantages. The advantages of triangle arrangement are compact and high heat transfer efficiency. The number of pipe rows on the same tube plate area is the most, which is about 15% more than square arrangement, but it is not easy to clean the outer surface of the tube, while the square to 45 degree angle is more convenient to arrange the surface of the tube, but the number of pipe row is much less than that of the triangle row. 22. what are the materials commonly used in tubular heat exchangers? Answer: materials commonly used for pipes are: 10#, 20#, 12CrMo, 15CrMo, 0Cr13, 1Cr13, 1Cr5Mo, 0Cr18Ni9Ti, 1Cr18Ni9Ti, titanium tube, 410321, etc. 23. in tube heat exchangers, why are diameters of 32, 25, 19 and 16? Answer: the size of the pipe will directly affect the performance of the heat exchanger. The diameter of the tube is small, the heat transfer coefficient is large, and the effective heat transfer area is large in the same volume. This can not only make the structure compact, but also save the material. The smaller the diameter of the fluid with the same flow rate, the smaller the diameter, the greater the resistance to the flow and the increase of the pressure loss. In addition, the thin tubes are also easily blocked by the dirt, making the cleaning difficult, so the diameter of the heat exchanger is usually 16 mm to 32 mm. 24. why does the bolt hole of the heat exchanger support have circular and long circular ones? Answer: the bolt hole on the fixed support is circular, so that the shell can be firmly fastened to the foundation. The bolt holes on the movable support are long and round, the purpose is to make the shell free and telescopic when the temperature changes, and avoid the large stress to protect the equipment. 25. what are the commonly used heat exchanger gaskets? Answer: commonly used heat exchanger gaskets are oil resistant asbestos mats, iron pads, wave tooth mats, metal mats. 26. what should we pay attention to when choosing the bolts for floating heads of floating head heat exchangers? (1) length (2) wet H2S stress corrosion (3) temperature 27. what is the function of baffles (baffles) in tubular heat exchangers? Answer: the baffle (baffle) in the heat exchanger can change the flow direction of the fluid in the shell, increase the flow velocity in the shell, increase the turbulence level of the medium, improve the heat transfer efficiency and support the function of the tube bundle. 28. why does tube heat exchanger have single tube, two tube, four tube, six tube, eight pipe? Answer: when the number of heat exchangers is at the same time, increasing the number of tubes can increase the flow rate in each pipe, so it can increase the heat coefficient and reduce the required heat transfer area. But at the same time, the pressure drop is also increased, and the fluid can not be completely reheated by countercurrent, and the heat exchanger structure is more complicated. Therefore, the general number of pipe runs should be no less than 2, not greater than 8, and should be chosen according to the actual process requirements. 29. what are the causes of leakage in tubular heat exchangers? Answer: there may be the following reasons for the leakage in the heat exchanger: Corrosion perforation, or fracture of heat transfer tube Leakage of pipe mouth cause leakage Loosening of heat transfer tube and tube plate expansion joint Cracks, holes or corrosion holes on the weld of heat exchanger tubes and tubesheet. Loosening or breaking of small float bolt Small float gasket damage Seal damage of small float or floating tube plate 30. why should the water pressure be tried after the heat exchanger is overhauled? Answer: the purpose of the test water pressure of the heat exchanger is to check whether the heat exchanger has the ability to withstand the design pressure (i. e. pressure strength), tightness, the quality of the interface or joint, the quality of the welding and the tightness of the sealing structure. In addition, the residual deformation of the welding seam of the parent material and the pipe after pressure can be observed, and the problems existing in the material can be found in time. 31. what are the installation positions of tubular heat exchangers, some of them are upright, and others are horizontal (horizontal)? Answer: the tubular heat exchangers are set up and some are lying, mainly from the following aspects: (1) the production process requirements: if some reboiler needs a certain height of the medium liquid level, if the displacement heater is used, that is, the height of the liquid level can not be reached, so the selection of the replacement heat exchanger must be selected; 2. A process unit needs thousands of square meters of heat exchange area. If a heat exchanger with a heat pipe length of 6 meters is selected, a number of heat exchangers may be needed. It occupies a large area and is not conducive to the space effective arrangement of the device. If a vertical replacement heat exchanger with a length of 12 meters of heat transfer tube is selected, 1 sets can solve the problem; 3. Reduce the pressure drop: some students reduce the pressure drop. The production process is required to minimize the pressure drop in the medium transport process, select the vertical displacement heat exchanger and arrange it together with the tower, so that it can shorten the connection line with the tower and reduce the pressure drop. 32. why do some places choose casing heat exchangers and water immersed heat exchangers, while others use tubular heat exchangers? Answer: at present, most of the heat exchanger selected for oil refining and chemical production equipment are tubular heat exchangers, but in some production devices, there are still a small amount of casing heat exchangers and water immersed heat exchangers. Although tubular heat exchanger has compact structure and high heat exchange efficiency, it is easy to cause blockage if it is used in medium containing solid particles due to its smaller heat exchanger tubes. Therefore, in the medium containing solid particles, the casing heat exchanger or the water immersion heat exchanger is usually selected. Source: China Steel Pipes Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Metal fatigue is commonly used to describe the accidental failure of metal parts in the course of using. Metal fatigue is directly related to the number of stress cycles and stress levels exerted on parts. The research shows that if the local stress in the part is kept below the well-defined limit, the infinite life of the metal component is possible. Fatigue failure will increase if parts are stressed, or parts with stress concentration such as notches, holes and keyways. There is also a relationship between the ultimate tensile strength and hardness of metals. The higher the tensile strength and hardness, the higher the wave load of the metal component, the easier fatigue. Typical fatigue fracture The general explanation for the fatigue mechanism of metals is based on dislocation theory. Theoretically, atomic arrangements in metallic crystals are imperfect and contain many missing atoms. The missing atoms create gaps, resulting in a great deal of stress. When the metal is loaded, the stress rising gap is cut and aggregated through the grain. When sufficient atomic interspaces are clustered together, micro cracks occur. If the load is increased, the initial crack opens. If the load fluctuates from the minimum value to the maximum near the limit of the metal load, the new micro crack expands from the position of the first micro crack. Each crack becomes the stress lift of the next crack. Continue to develop until the remaining metal is no longer bearing the load, and it suddenly fails.

Millions of miles of pipelines are used to transmit drinking water around the world. These pipelines must have good corrosion resistance to water itself, soil chemicals and treatment chemicals, so as to ensure adequate service life and provide sanitary drinking water. Type 316 (2-3%Mo) stainless steel has been proven to provide adequate corrosion resistance in most applications, and is more competitive than other piping materials. If additional corrosion protection is required, for example, in the installation of coastline, duplex stainless steel (3.0-3.5%Mo) can be used to achieve the required sanitary conditions and service life. As for the reasons, I have learned the following summary of the beneficial properties of molybdenum bearing stainless steel below. The first is excellent corrosion resistance. Stainless steel is more resistant to oxidation of water and biocide than carbon steel and cast iron or ductile iron. This leads to longer service life of stainless steel water pipelines. Followed by corrosion protection, stainless steel does not require internal and external coatings, nor does it require cathodic protection. This will reduce the cost of the system and make the stainless steel more compatible with the environment. The third is hygienic material. Because of its very high oxide film stability, stainless steel water pipelines are basically inert in water. The leaching of alloying elements (Cr and Ni) is within the safety limits. Therefore, stainless steel pipelines can provide better drinking water quality. The fourth is friction coefficient. Compared with cement lined carbon steel pipeline or corroded carbon steel, the friction loss of stainless steel pipeline leads to smaller hydraulic pressure along the pipeline. This provides the opportunity to reduce the inner diameter of the pipeline and save capital costs. This is also the reason for lower sediment adhesion and lower bacterial colonization. They can also provide higher traffic. The fifth is good strength and ductility. Stainless steel pipelines, especially duplex stainless steel, have higher mechanical properties compared with carbon steel and cast iron pipelines. This can reduce the wall thickness of the water pipeline (no need for any corrosion allowance), thereby saving investment costs. Better ductility is also important in terms of safety, such as in the case of earthquakes. The sixth is erosion corrosion performance. Duplex stainless steel is more resistant to corrosion and corrosion than carbon steel, especially if there is sand in the surrounding environment. Seventh is easy to make. Stainless steel is an adaptable material. It is easy to form, machine and weld. It is easy to install and modify the pipeline with its good ductility. They also have a variety of product forms. In addition, the stainless steel pipelines are easy to maintain, with high corrosion resistance and easily weldability, the probability of water leakage will be reduced greatly, and it may be reduced from 25% to less than 5%, which will further reduce the cost. This argument is becoming more and more important because of the increasing cost of water and water treatment. There is also good durability, because SS can resist crevice corrosion, cavitation and wear in pure and polluted waters, as well as in the atmosphere (and even pollutants). It is cost-effective for long-term use and will not cause environmental pollution. The last one is recyclable, stainless steel is 100% recyclable, and part of its initial cost may be recovered during recycling. Source: China Stainless Steel Water Pipeline Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

There are hundreds of different types of stainless steel flanges on the market, which may be difficult to find the perfect metal for your application. In many purchasing processes, the cost of metals is the first consideration rather than the performance of metals, but this is wrong. In some cases, additional costs are required for different high-performance alloys. But the common use is mainly made of 304 stainless steel and 316 stainless steel. They are high performance in tensile strength, durability and corrosion resistance. 304 stainless steel can withstand various environments, and the tolerance of 316 stainless steel to chloride and other corrosive agents is improved. However, some processes involve extreme working conditions which require higher performance properties than these alloys, such as better grade 317L stainless steel. What makes grade 317L SS different from 304 and 316 stainless steel? 304, 316 and 317L stainless steel are considered to be austenitic stainless steel alloys. All these alloys have some similar properties, such as high strength, corrosion resistance and high concentration of chromium and nickel. The difference between 316 and 317L stainless steel and 304 stainless steel is that these high amounts of alloy add molybdenum in its formula grade 316, with a content of about 2-3%, and 317L stainless steel with more than 3% molybdenum. This addition of molybdenum greatly enhances the corrosion resistance of stainless steel to chloride, which is why 316 stainless steel is often used in chemical processing and marine industry. However, the added molybdenum content also affects the cost of the two alloys. 317L stainless steel is usually more expensive than 316 stainless steel. 316 is more expensive than 304. For the most corrosive applications, 316 stainless steel should be sufficient to withstand frequent exposure. But 317L to 304 or 316 has better resistance to certain specific corrosive resistance. As stated in the ATI Metals publication, the corrosion rate of 317L stainless steel in the boiling test solution of 1% hydrochloric acid is 54.2 mil / year, and the corrosion rate of 316 stainless steel is 226 million cubic meters per year. 317L in sulfuric acid and sodium hydroxide test, it is obviously better than 316. Therefore, if it is involved in the use of very diluted (less than 3-4%) hydrochloric acid, mild concentration (10%) or sodium hydroxide (also called caustic sodium), it is more appropriate to use 317L grade stainless steel. In addition, it should be noted that any concentration of hydrochloric acid above 5% will easily corrode all austenitic stainless steel alloys. Source: China Stainless Steel Flanges Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

A variety of surface processing of stainless steel has widened its application field. Different surface processing makes the surface of stainless steel different, so that it is unique in its application. In the field of building applications, there are many reasons for the importance of surface processing of stainless steel. One, the basic types of surface processing There are basically five kinds of surface processes that can be used for stainless steel. They can be combined and used to transform more and more final products. The five species are: Rolling surface processing Mechanical surface processing Chemical surface processing Reticulated surface processing Color surface processing There are some special surface treatments, but no matter which surface is specified, the following steps should be followed: 1, with manufacturers to agree on the necessary surface processing, it is best to prepare a sample for future volume production standards. 2. When large areas are used, such as composite boards, the same base must be used to ensure that the base rolls or rolls are used in the same batch. 3, the manufacturing process should be taken into consideration when selecting surface processing. For example, in order to remove the bead, it is possible to repair the weld and restore the original surface processing. The pattern board is hard to even meet this requirement. 4, for some surface processing, grinding or polishing texture is directional, is called unidirectional. If it is used vertically and not horizontally, dirt is not easily attached to it, and it is easy to clean. Two. Rolling surface processing There are three basic rolling surface processes for sheet and strip, which are represented by plate and village production processes. No.1: hot rolling, annealing, pickling and descaling. The surface of the treated steel sheet is a dull surface and a bit rough. No.2D: the surface is better than N0.1, and it is also a bleak surface. After cold rolling, annealing, descaling, and finally rolling with the wool surface roller. No.2B: This is the most commonly used in architectural applications. Except for the last mild cold rolling of the polishing roll after the annealing and the descaling, the other processes are the same as the 2D, and the surface is slightly light and can be polished. No.2B bright annealing: This is a reflective surface that is rolled through a polishing roller and annealed in a controlled atmosphere. Bright annealing still keeps its reflective surface and does not produce oxide scales. Because no oxidation reaction occurs in the process of bright annealing, no pickling and passivation treatment is necessary. Three, polishing surface processing No.3: expressed by 3A and 3B. 3A: the surface is evenly grind and the abrasive particle size is 80~100. 3B: the wool surface is polished with uniform straight lines on the surface. It is usually made by grinding and polishing the abrasive belt with a size of 180~200 on the 2A or 2B board. No.4: unidirectional surface processing, not strong reflectivity, this surface processing may be the most widely used in building applications. The process is first polished with coarse abrasives, and then grinded with a particle size of 180. No.6: it is a further improvement to No.4, which is to polish the No.4 surface with tampo brush in abrasive and oil medium. There is no surface processing in British standard 1449, but it can be found in the US standard. No.7: known as bright polishing, it is polishing the surface that has been finely worn but still worn. 2A or 2B boards are usually used, with fiber or cloth polishing wheels and corresponding polishing paste. No.8: mirror polished surface, high reflectivity, usually referred to as mirror surface processing, because it reflects the image very clear. The stainless steel is continuously polished with fine abrasives and then polished with very fine polishing paste. What should be noted in building applications is that such a surface will leave a fingerprint if it is used in areas where the flow of personnel is large or where people often touch. The handprints can be erased, but sometimes they are beautiful. Four, surface roughness The classification of rolling surface finishing and polishing surface machining is a description of the extent to which it can be achieved. Another effective method is to measure surface roughness. The standard method of measurement is called CLA (mean value of the center line). The measuring instrument moves horizontally on the surface of the steel plate to record the change range of the peak valley. The smaller the CLA’s number, the smoothed the surface. The final results of different grades can be seen from the surface processing and CLA numbering in the following table. Five. Mechanical polishing Note: we should remember that grinding with sandpaper or sand belt in grinding operation is basically a polishing operation, leaving a fine line on the surface of the steel plate. We have encountered trouble when using alumina as abrasive, partly due to pressure. Any abrasive parts of the equipment, such as abrasive belts and grinding wheels, must not be used before other stainless steel materials. Because this will pollute the surface of the stainless steel. Six. Electrolytic polishing This is a metal removal process. In this process, stainless steel is used as the anode in the electrolyte, and the metal is removed from the surface after electrified. The process is usually used for parts processing because their shape is difficult to be polished by traditional methods. The process is often used on the surface of cold-rolled steel sheet because its surface is smoother than that of hot-rolled steel sheet. However, electrolytic polishing will cause more obvious impurities on the surface, especially titanium and niobium stabilized materials will cause differences in the weld area due to granular impurities. Small welding scar and sharp edge can be removed by this process. The process focuses on the surface protrusions, giving priority to dissolving them. The electrolytic polishing process is to immerse stainless steel in heated liquid, and the ratio of liquid involves many proprietary technology and patented technology. The effect of electrolytic polishing of austenitic stainless steel is very good. Seven. Reticulated surface processing There are many kinds of patterns that can be used in stainless steel. The advantages of making steel plates with textured or textured surfaces are as follows: 1) reduce “oil can-ning”, a term used to describe the surface of a bright material, which looks inhomogeneous from an optical angle. For example, a large area of decorative panels, even after stretching straightening or tension leveling, is difficult to make the surface completely flat, resulting in metal roof material shrinkage. 2) netted patterns can reduce glare in the sun. 3) if the pattern board has slight scratches and small area indentation, it is not very obvious. 4) increase the strength of the steel plate. 5) the choice is provided for the architect. Patented designs include cloth patterns (used for Ed building in London), mosaic designs, pearls and leather stripes. Ripple and linear patterns can also be used. The pattern surface is especially suitable for interior decoration, such as elevator panels, counters, panels and entrance. The external application should be taken into consideration to make the stainless steel clean the surface through rain and artificial scour, and avoid the dead angle which is easy to gather dirt and air impurities, so as to avoid the beauty of corrosion. Eight. Surface processing of wool surface Surface finishing is one of the most commonly used surface processes. It is polished or annealed on the surface of steel plate with nylon abrasive belt or brush. Source: China Alloy Steel Pipes Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

The seamless stainless steel pipe is a long steel bar with a hollow section and seamless joints. The thicker the wall thickness of a stainless steel pipe is, the higher its economical efficiency and practicality, and the thinner the wall thickness, the greater the production and processing costs. The process of the seamless stainless steel tube determines its limited performance. Usually, the accuracy of the seamless stainless steel tube is low, there are uneven wall thickness, low brightness inside and outside the tube, high cut-in cost, and pits and black spots on the inside and outside surfaces are not easily removed. Disadvantages, seamless stainless steel tube inspection and shaping must also be handled offline. However, seamless stainless steel tubes also exhibit their advantages in terms of high-pressure, high-strength, mechanical structural materials. However, there are many problems with poor quality stainless steel seamless tubes, and some may even cause serious problems in practical applications. Here is a list of the common phenomena of inferior seamless stainless steel tubes for reference. One is that the surface of the inferior seamless stainless steel tube is likely to form scars. That is because of the non-uniformity of the material of the material and the fact that it contains more impurities. The equipment made is very simple and easy to stick to steel. High-quality stainless steel seamless pipes do not have such problems and phenomena. The second reason is that the surface of the inferior seamless stainless steel pipe is very easy to form cracks because the billet is adobe, and the billets have many holes, and the adobe will be cracked quickly due to thermal stress during the cooling process. There will be cracks afterwards. The third is that the inferior seamless stainless steel pipe has an elliptical cross-section. The reason is that in order to save the material cost, the amount of reduction in the front roller of the finished roller is too large, and the strength of the stainless steel pipe will be greatly reduced, and Nor will it meet the pipe’s dimensions. The fourth reason is that the inner diameter of inferior seamless stainless steel pipe fluctuates greatly because the temperature of the stainless steel plate is unstable and there is a yin and yang face, and the composition of the steel is also uneven, because the equipment is simple, the foundation strength is low, and the mill bouncing is large. . There will be a larger change in the inner diameter in the same week, so that the stainless steel tube is also very easy to form fractures due to uneven force. The longitudinal bars of stainless steel seamless pipes for counterfeit structures are often wavy. Source: China Seamless Stainless Steel Pipe Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

The latest process of removing burr for stainless steel plate is electrolytic polishing, which requires a complete set of electrolytic polishing equipment for production, such as power supply, rectifier, polishing tank, workpiece hanger, heating facility, cathode and anode materials, several rinse frames, and stainless steel electrolytic polishing liquid. Let’s talk about burr related knowledge of stainless steel products. The stainless steel electrolytic polishing equipment with good quality is basically suitable for electrolytic polishing of all stainless steel and stainless steel. It has strong versatility, high polishing brightness and long gloss (stainless steel material can throw out the mirror effect). The electrolytic polishing machine (power supply series) can be pided into the air cooling series and the water cooling series. The product structure is designed reasonably, the quality is reliable, the energy saving, the corrosion resistance is strong, the heat dissipation is fast, the electrolysis effect is good, the current and voltage are adjustable, the steady current, the steady pressure, the overheat, the over current protection, the buffering start function, the use of special integrated board circuit, and It has been treated with antisepsis, completely sealed, the output voltage range is 0-300V, and the output current range is 10A – 10000A. The advantage is that electrolytic polishing is not restricted by the size and shape of the workpiece, and electrochemical polishing is suitable for the workpiece which is not suitable for mechanical polishing. For example, slender tube inner wall, elbow, bolt, nut and container inside and outside wall, polishing efficiency is high, good quality, in a few minutes can be thrown to mirror bright. Stainless steel electrolytic polishing liquid is suitable for polishing all stainless steel and stainless steel. It is versatile and versatile (stainless steel material can be used to throw out mirror effect. It is widely used in mechanical manufacturing, electronic parts, instrument instruments, light industry and watch parts, military and aerospace, textile equipment, automobile zero parts, bearing industry, medical equipment and precision. Parts, powder metallurgy, metal stamping, handicrafts, tools and other industrial fields. The operation process is to rinse the water after removing oil and heat the electrolysis polishing liquid to 55-75 degrees (using quartz rod or titanium heating rod) to stop heating after the requirement of temperature. Fix the hanger on the anode rod, open the power rectifier switch and adjust the voltage to 5-12 volts. The polishing time is from 30 seconds to 10 minutes (the fastest 30 second is to save the mirror effect). Source: China Stainless Steel Plate Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

The stainless steel pipe is a kind of pipe with hollow cross section and complete weld. Compared with solid steel and other solid steel, stainless steel pipe products are a kind of economic section steel when the bending and torsion resistance is the same, it is a kind of economic section steel. It is used in the manufacture of structural parts and mechanical parts, such as oil drilling rod, automobile drive shaft, bicycle frame, and steel scaffold used in construction. Using stainless steel pipe to make ring parts, it can improve the utilization of material, simplify the manufacturing process and save the length of material and processing, such as rolling bearing rings and Jack sleeves, all of which are made of stainless steel pipes. Because of its wide use and precision components, the finished products are basically smooth and no burr on the surface, so if you want to have better quality, the stainless steel electrolytic polishing process can be used to make the surface clean, no burr, and maintain a lasting light. Manufacturing method of stainless steel pipe for fluid In general, the temperature of the boiler pipes is below 450 C, and the domestic pipes are mainly made of 10 or 20 carbon steel hot-rolled pipes or cold drawn pipes. High pressure boiler pipes are often used at high temperature and high pressure, and their pipes will oxidize and corrode under the action of high temperature flue gas and steam. Therefore, it is necessary to make stainless steel pipe products have higher endurance strength, higher corrosion resistance and better stability. The use of electrolytic polishing of stainless steel pipes is widely used. Generally, the boiler pipes are mainly used to make water wall pipes, boiling water pipes, superheated steam pipes, superheated steam pipes for locomotive boilers, large, small smoke pipes and arch pipes, and high pressure boiler pipes are mainly used to make superheater pipes and reheater pipes for high pressure and ultra-high pressure boilers. The trachea, main steam pipe and so on. However, the stainless steel pipe also has some limitations, for example, under the condition of plane bending, the round pipe is not as strong as square and rectangular pipe, and some farm machinery skeleton, steel and wood furniture, etc. are commonly used and rectangular pipe. According to different uses, there are other special-shaped stainless steel pipes with different cross-section shapes. No matter what kind of stainless steel pipe, as long as the stainless steel electrolytic polishing treatment, its advantages are not successful, such as removing burr, can make the stainless steel surface to reach the 8K mirror effect, suitable for special shaped pipe fittings, such as high polishing efficiency, low production cost and long gloss. Corrosion resistance and antioxidation. Source: China Stainless Steel Pipe Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Salt spray corrosion will destroy the passivation film on the surface of the stainless steel plate, so that the decorative nature of the plate will be lost, and the mechanical strength of the material will be reduced. Some electronic components and electrical wiring will cause the power line to be interrupted due to corrosion, especially in vibration. In the environment, it is particularly serious; whenever the salt spray falls onto the surface of the insulator, the surface resistance of the stainless steel plate will be reduced; after the insulator absorbs the salt solution, the volume resistance will also be reduced by four orders of magnitude; the movement of mechanical parts or moving parts Due to the formation of corrosive substances, the friction of the material is increased so that the moving parts are jammed. Let’s look at the mechanism of salt spray corrosion. Salt spray corrosion of stainless steel and other metal materials, mainly conductive salt solution infiltrated into the stainless steel plate to generate electrochemical reactions, generate low-potential metal – electrolyte solution – high potential impurity micro-battery system, resulting in electron transfer, metal as the anode Dissolution occurs and new compounds, ie corrosion products, form. The same applies to the metal protective layer and the organic material protective layer. After the salt solution as an electrolyte penetrates into the interior, a micro-battery with a metal as an electrode and a metal protective layer or an organic material as another electrode is formed. Chloride ions play a major role in the salt fog corrosion damage process. It has a very strong penetrating power and easily penetrates the passivation layer on the surface of the stainless steel plate and enters the interior of the stainless steel plate while destroying the passivation state of the metal. And chloride ion has a very small hydration energy and is easily adsorbed on the surface of the stainless steel plate, thereby replacing the oxygen in the oxide layer on the surface of the stainless steel plate, so that the metal surface such as stainless steel is damaged. In addition to chloride ions, the salt spray corrosion mechanism is also affected by oxygen dissolved in the salt solution (essentially the salt solution that dissolves on the surface of the sample). Oxygen can lead to the depolarization process of stainless steel and other metal surfaces, speed up the dissolution of the anode metal, because the salt spray process continues to spray, the salt liquid film continuously settles on the surface of the sample, so that the oxygen content will always remain near saturation . The formation of corrosion products, so that the volume of the salt solution infiltrated into the metal defect expansion, so it also increases the internal stress of the stainless steel plate, the formation of stress corrosion, resulting in the surface of the passive layer of the stainless steel plate bulging. Source: China Stainless Steel Plates Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

After annealing the stainless steel pipe, the brightness of the pipe determines the quality of the product. There are many influencing factors. This paper gives the following 5 relatively important factors. The first is whether the annealing temperature is up to the specified temperature. The heat treatment of stainless steel pipes is usually treated by solid solution heat treatment, also known as annealing treatment. The temperature range of the process is 1040-1120 degrees. In the process of actual processing, it can also be observed through the observation hole of the annealing furnace. The most appropriate is that the stainless steel pipe in the annealed zone is just dealing with the incandescent state and does not appear the softening droop. The second is the atmosphere of annealing. The pure hydrogen is usually used as an annealing atmosphere. The purity of the atmosphere is better than 99.99%. If the other part of the atmosphere is inert gas, the purity of the atmosphere can be lowered a little, but it is absolutely impossible to contain too much oxygen and water vapor. The third is the sealing property of the furnace body. A bright annealing furnace is closed, isolated from the outside air, and uses hydrogen as a protective gas. Only one exhaust port is used (used to ignite the discharged hydrogen). The inspection method can be used in soapy water on the gap between the various joints of the annealing furnace to see whether there is a running gas phenomenon. The most easy place to run gas is the place where the annealing furnace enters the pipe and the place where the pipe is out. The sealing ring of this place is very easy to wear and often check the regular change. The fourth is to protect the gas pressure. To avoid the occurrence of micro leakage, the protective gas in the furnace must be kept at a positive pressure. If it is a hydrogen protection gas, it usually requires more than 20kBar. The fifth is the water vapor in the furnace. On the one hand, check whether the furnace material is dry or not, for the first time to install the furnace, the material of the furnace must be dried; the other is to see whether there is too much water stains in the stainless steel pipe in the inlet, especially if there is a hole on the stainless steel pipe, so do not leak in, otherwise it will break the atmosphere in the furnace. The last thing to understand is that if everything is normal, the stainless steel pipe will start to shine or even reflect light after annealing about 20 meters. Source: China Stainless Steel Pipes Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

The welded stainless steel pipe has two main features, one is that the small diameter welded stainless steel pipe is continuously produced online. The thicker the wall thickness of the pipe, the larger the investment scale of the unit and welding equipment, the worse the economy and practicality of this kind of welded stainless steel pipe. The thinner the wall thickness, the input-output ratio of the stainless steel pipe will decrease correspondingly. Secondly, the process of welding stainless steel pipe determines its advantages and disadvantages, usually the precision of the welded stainless steel pipe is higher, the wall thickness is more uniform, the surface light of the inner wall of the pipe is high (the surface grade of the stainless steel plate determines the surface brightness of the stainless steel pipe) and can be arbitrarily fixed. Therefore, the welded stainless steel pipe is in high precision and middle low pressure flow. The application of body shows good economy and beauty. Material and use of stainless steel welded pipe The welded stainless steel pipes are pided into 6 types according to their materials and uses. The first kind is GB/T3092-1993 (galvanized steel pipe for low pressure fluid delivery). This kind of stainless steel pipe is mainly used for transporting water, gas, air, oil and heating hot water or steam and other general low pressure fluid and other use pipes. The representative material is Q235 a grade steel. The second is GB/T3091-1993 (galvanized steel pipe for low pressure fluid delivery). This kind of steel pipe is mainly used for transporting water, gas, air, oil, heating hot water or steam and other general low pressure fluids and other use pipes. The third is GB/T12770-1991 (stainless steel welded pipe for mechanical structure), which is mainly used for mechanical, automobile, bicycle, furniture, hotel and hotel decoration and other mechanical parts and structural parts. Its representative material is 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb and so on. The fourth one is GB/T14291-1992 (mining fluid conveying welded steel pipe), which is mainly used for longitudinal welded steel pipe for mine ventilation, drainage and gas. The fifth one is GB/T12771-1991 (stainless steel welded pipe for fluid transportation), which is mainly used for conveying low pressure corrosive medium. The representative materials are 0Cr13, 0Cr19Ni9, 00Cr19Ni11, 00Cr17, 0Cr18Ni11Nb, 0017Cr17Ni14Mo2, etc. The last kind is GB/T14980-1994 (large diameter welding steel pipe for low pressure fluid delivery), which is mainly used for the low pressure fluid and other uses such as water, sewage, gas, air, heating steam and so on. Source: China Stainless Steel Welded Pipe Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

When stainless steel plates are welded, defects often occur. The causes of these defects are different. This article describes some of the defect classification and avoidance methods. Stoma The pores formed by the stainless steel plate weld can be pided into internal pores, surface pores, and joint pores. There are two types of internal pores, one is that the spherical pores are mostly generated in the middle of the weld. The reasons for the formation are excessive welding current, long arc, too fast moving rod, unclean welding area, and moisture in the welding rod. . The above causes the pore causes to be solved if appropriate adjustments and pay attention to the welding process and operation method. There are several reasons for the formation of surface pores. For example, if the base metal contains carbon, sulfur, and silicon, high content of the pores is likely to occur. The solution is either replacement of the base metal or the use of a low-hydrogen slag-based electrode. The welding site is also unclean and prone to blow holes. Therefore, the welding site requires welding. Before the removal of oil, rust and other dirt, the use of low-hydrogen welding rod welding requirements are more stringent; In addition, excessive welding current can also lead to surface pores, so that the second half of the electrode coating red, but also prone to air holes, so require the appropriate The welding specification, welding current to the maximum end of the electrode is not red is appropriate; low hydrogen electrode easy to absorb moisture, so before use are required to be baked at a temperature of 350 °C 1h or so, otherwise prone to air holes. There are species of solder wave joint pores, the use of low hydrogen electrode is often easy to appear at the weld joint surface and internal porosity, the solution is in the solder wave joint, should be in the direction of the weld from the arc 9-10mm Start the arc, after the arc burns, first reverse the rod back to the crater position, fully melt forward and then advance, or arc at the weld to avoid this type of pore generation. Crack There are several types of cracks. The first is a rigid crack, which is usually the longitudinal crack in the weld where the weld joint is found, mainly due to the stress generated during welding. In the following cases, the welding stress is large, the rigidity of the welded structure is large, the welding current is large, the welding speed is fast, and the cooling rate of the weld metal is too fast. So it is very easy to form longitudinal cracks in the above situation. The solution is to use a reasonable welding sequence or preheat the workpiece where possible to reduce the rigidity of the structure. Special thick plates and rigid structures should use low hydrogen electrodes with appropriate current and welding speed. The second is the crack caused by carbon and sulfur elements. When the carbon and sulfur of the base metal being welded are high or segregated, cracks are likely to occur. The solution is to preheat the weldment or use a low hydrogen electrode. The third is a gap crack, which occurs inside the weld metal and does not develop external hairy micro cracks. Considering that the weld metal is subject to rapid cooling and embrittlement, local stress and hydrogen gas influence. The prevention method for this is to make the cooling rate of the weldment slower, to preheat the weldment under possible conditions, or to use a low hydrogen electrode to achieve a satisfactory solution. Arc blow When the welding is performed on a DC welding machine using a low-hydrogen electrode, blow-off occurs frequently. The solution is that the ground wire is placed in the direction of the arc blow; the ground wire is pided into two or more; welding is performed in the direction of the partial blow of the arc; and the welding is performed using the short arc operation. Source: China Plate Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)