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When the surface of the stainless steel plate is not annealed (for example, the surface after welding), drilling mud residue, rust-proof film, or ferrite impregnated with stainless steel after the molding process, the corrosion resistance of the stainless steel material will be directly affected. At this point you need to use acidic oil cleaning agent to do the appropriate cleaning and maintenance operations on the stainless steel surface. Stainless steel pickling passivation can completely remove impurities and promote the formation of a new passivation layer, which is a complete chemical reaction process. It can not only clean the surface of the stainless steel plate, but also can form a completely uniform silver white on the surface of the treated stainless steel plate. According to actual tasks, stainless steel plates with different structures and surface sizes can use different pickling products. First look at the stainless steel pickling passivation paste, this product is used to deal with the surface of the larger stainless steel plate or surface weld around the weld spot, oxide layer color, as long as the uniform smear on the surface of the stainless steel plate, wait until The surface of the stainless steel plate is completely uniform and white. Followed by the stainless steel pickling passivation solution, which is mainly used for the pickling of small serial parts, such products are easy to immerse, usually using plastic containers soaked at room temperature, and even can achieve high efficiency pickling and passivation done synchronously, such as stainless steel After the surface of the board has been pickled and passivated, the maximum salt spray resistance can reach about 500 hours. In addition to the pickling spray, this process is suitable for pickling large stainless steel surfaces (including wall panels, containers) as well as non-removable structures or difficult-to-access structures such as bridge components. Pickling sprays can increase application control. There is also ablation pickling. This technique can remove the surface tension and internal stress of the stainless steel plate material by specifically removing the 3-5 micron surface, and also remove surface microcracking. However, no matter which process is used, the treated surface acid must be completely cleaned. It is best to use high-pressure cleaning. Source: China Stainless Steel Plates Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

The grade of 904L stainless steel is 00Cr20Ni25M04.5Cu, which belongs to a high austenitic stainless steel with high carbon content and low carbon content. It has strong corrosion resistance in the dilute sulfuric acid environment, because the addition of copper makes it have strong acid resistance. It is designed for the harsh environment of corrosion. Therefore, this austenitic stainless steel is mainly used for the manufacture of corrosion resistant pressure vessels. The composition of 904L is mainly composed of chromium and nickel. It is difficult to machine and has poor machinability. The main reasons are as follows. First of all, 904L stainless steel is more powerful than other kinds of stainless steel. Because the hardness of 904L stainless steel is not high (70-90HRB), the plasticity is better, the elongation is more than 40%, the shrinkage of the section is more than 50%. The tensile strength is B more than 490MPa, and the yield strength is 0.2 or more 216MPa. Therefore, the plastic deformation is larger in the cutting process, and the cutting force is increased. The second is the low thermal conductivity. The thermal conductivity of 904L stainless steel (20 C) is 12.9W / (mmK), and its thermal conductivity is low, only about 1 / 4 of the 45 steel. The thermal conductivity of the 45 steel is 47.5W / (mmK). Thermal conductivity is one of the main factors that affect the heat conduction of cutting. The lower the thermal conductivity of the processed material, the less the heat taken by the chip and the workpiece, and the more heat accumulated on the cutting tool, making the tool very easy to wear. Third, it is easy to form the chip tumor. Because of the high toughness of 904L stainless steel, it has strong affinity with the tool material during the cutting process. The cutting tool face is strongly rubbed with the chip bottom metal during cutting. It will produce adhesion phenomenon under the action of high temperature and high pressure. It is not easy to get the surface with high surface roughness. Fourth, the chip is not easy to bend and break. The elongation of 904L stainless steel is high, so the chip is not easy to bend and break in the cutting process. Failure to take proper measures will affect the normal operation of the cutting process, and scratch the machined surface easily, and even cause the tool to collapse and damage. Because of the above features of 904L stainless steel, the cutting tool is very easy to wear and the machining efficiency is low, and the workpiece is difficult to achieve the surface roughness and machining precision required by the drawings. Source: China Pipe Fittings Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Hydrogen corrosion may occur in ammonia synthesis, hydrogen desulfurization and hydrogenation and petroleum refining units. Carbon steel is not suitable for high pressure hydrogen installations at temperatures above 232 C. Hydrogen can spread into the stainless steel plate and form methane at the grain boundary or in the pearlite zone with the iron carbide. Methane can not spread to the outside of the steel and gather together to form white spots or cracks in the metal. In order to prevent the formation of methane, cementite must be replaced by stable carbides. Stainless steel plates must be added chromium, vanadium, titanium and other elements. In fact, the increase of chromium content allows a higher use of temperature and hydrogen pressure to form chromium carbide in these steels, and the hydrogen element it meets is stable. Chromium steel and austenitic stainless steel with chromium content higher than 12% can be corroded in all known applications under harsh conditions (temperature greater than 593 degrees Celsius). Most metals and alloys do not react with molecular nitrogen at high temperatures, but atomic nitrogen can react with many stainless steels. It penetrates into the surface of stainless steel to produce brittle nitride. Iron, aluminum, titanium, chromium and other alloying elements may participate in these reactions. The main source of atomic nitrogen is the decomposition of ammonia. Ammonia converter, ammonia plant heater and ammonia decomposition at 371 -593 C and -10.5Kg/mm2 under an atmospheric pressure. In these atmospheres, chromium carbide is produced in low chromium steel. It may be corroded by atomic nitrogen to form chromium nitride and release carbon and hydrogen to form methane, which, as mentioned above, may form white spots or cracks. However, when the chromium content is greater than 12%, the carbides in these stainless steel are more stable than chromium nitride, so the front reaction will not appear, so the stainless steel plate can now be used in the high temperature environment of the heat ammonia. The state of stainless steel plates in ammonia depends on temperature, pressure, gas concentration and chromium and nickel content. The results of field experiments show that the corrosion rate of ferrite or martensitic stainless steel (altered metal depth or carburizing depth) is higher than that of austenitic stainless steel. The higher the nickel content is, the better corrosion resistance is, and the corrosion rate increases with the increase of content. The corrosion of austenitic stainless steel in high temperature halogen vapor is very serious, and the corrosion of fluorine is more serious than chlorine. For high Ni-C r stainless steel, the upper limit of temperature in dry gas is 249, and chlorine is 316. Source: China Stainless Steel Plates Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

The biphase in the name of the duplex stainless steel is mainly derived from the microstructure of the alloy. The duplex stainless steel usually contains about 50/50 austenite and delta ferrite phase mixture. Compared to austenitic stainless steel (for example, 304 or 316 stainless steel), duplex stainless steel has better corrosion resistance, especially chloride stress corrosion and chloride pitting, and higher strength. Compared with ordinary austenitic stainless steel, the main difference is that the dual phase stainless steel has higher chromium content, 20-28%, and high content of molybdenum, up to 5%, the nickel content is low, about 9%, and the nitrogen content is about 0.05-0.5%. The low nickel content and high strength (dual thinner part) of duplex stainless steel have obvious cost effectiveness. Therefore, they are widely used in the pipeline system of offshore oil and natural gas industry, and are becoming more and more popular in the pipeline and pressure vessel industry of petrochemical industry. Duplex stainless steel has higher corrosion resistance and higher strength than 300 stainless steel. For example, 304 stainless steel has a 0.2% yield strength in the 280N / mm 2 region, and the minimum 0.2% yield strength of 22% chromium duplex stainless steel is about 450N / mm 2, and the minimum grade of super duplex stainless steel is 550N / mm 2. Although duplex stainless steel has strong corrosion resistance and oxidation resistance, it can not be used at high temperature. This is because the ferrite phase will form brittle phase at lower temperature, which has a disastrous effect on the toughness of the duplex stainless steel. Therefore, the ASME pressure vessel specification limits the use temperature of all grades to less than 315 C, other specifications and even lower use temperatures, for super dual phase steel may be as low as 250 C. The biphase alloys can be pided into three major categories: poor biphase, 22%Cr biphase and 25%Cr super double phase, and even higher alloying super biphase steel grades. This pision is mainly based on the alloying level of the duplex stainless steel, such as the resistance to pitting, and the resistance to pitting resistance of the alloy. PREN is calculated by a simple formula: PREN =%Cr + 3.3%Mo + 16%N, and sometimes the factor of W can be considered 1.65. The PREN of the biphase steel is less than 40; the PREN of the super complex is between 40-45, the super complex PREN is over 45, and the rarefied grade usually has the lower nickel, so the price is lower. Source: China Stainless Steel Flanges Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Several methods can be used to increase the strength of stainless steel plates, which are alloying, quenching, working hardening, and a very common form of heat treatment, namely, precipitation or aging hardening. The so-called age hardening is in fact dependent on the formation of precipitates. In order to achieve the best combination of mechanical properties, the heat treatment cycle of stainless steel plates must be strictly controlled. In order to understand how sediment affects mechanical properties, some basic metallurgy needs to be understood. The mechanism of precipitation hardening requires that the alloy element, that is, the solute is in the metal, and the solubility in the solvent increases with the increase of temperature, and the solid solution line shows that the alloy element B decreases with the temperature of the solvent A. A metaphor is a salt in the water. As the temperature rises, more salt can be dissolved, but when the salt crystal begins to form or precipitate, it allows the solution to cool and vice versa. In addition to the dissolution and precipitation process that occurs in the solid and thus the atom is much slower because the atom is more difficult to move beyond the solid than the liquid solution, the same process occurs in the suitable alloying metal. As a result, once the deposit has been dissolved by a high enough temperature, that is, the wire is above the line line, it can be prevented by rapid cooling or quenching to prevent it from re forming. This heat treatment is called solid solution heat treatment and is formed to form an unstable supercooled solid solution. If it is reheated to a lower aging or precipitation hardening temperature, the precipitates will begin to be reformed. These precipitates are carried out with heat treatment. In a solid solution heat treated stainless steel plate, the atoms of the alloying elements are randomly distributed in the whole matrix, but once the temperature rises, the precipitation begins to form through the nucleation and growth process. At relatively low temperatures and shorter timescales, the solute atoms begin to gather together to form a very small, very small sediment called Guinier-Preston (GP), the two regions named after the first two metallurgists. The GP region is very small, which is not visible by ordinary optical microscope, but can be observed by electron microscope at about 100 thousand magnification. The GP region is described as coherent. In other words, they have the same crystal structure as solvent metals. However, they distort the lattice, that is, the framework of atoms. This makes the dislocation more difficult to move in the lattice and is the dislocation movement of the metal deformation; therefore, the tensile strength and hardness are increased, but the ductility and toughness are reduced. As the aging treatment continues or the temperature increases, the tensile strength continues to increase with the growth and thickening of the sediment. However, to some extent, the sediment began to lose consistency. Just before that, the alloy has the highest tensile strength. As the formation and size of these particles increase, the tensile strength decreases. It is said that the alloy is surplus, although the precipitates still contribute to the tensile strength of the alloy. High strength low alloy (HSLA) steel is a good example. In this case, incoherent, over aging precipitates are used to substantially increase the tensile strength. In order to achieve the best combination of properties, precipitates need to be uniformly distributed throughout the alloy grains and have the best size. The aging temperature and / or time can be significantly changed to adapt to the distribution and size of the sediment, and longer time and / or higher temperature usually lead to a decrease in strength, but the ductility increases, and the overused structure provides the lowest tensile strength but the highest ductility. Ferritic and nickel based alloys are usually used for over aging to ensure reasonable ductility. It can be seen that for some alloys, such as 17 / 4PH stainless steel, the precipitation mechanism is low enough to be able to cool the components in the stationary air or, like A286 stainless steel, requires long aging time. On the other hand, Al Cu alloy 2219 can be aged for several days at room temperature. Some of the 6000 (Al-Si-Mg) and 7000 series (Al-Zn-Mg) alloys will be similar to aging at ambient temperature. This is called natural aging, and high temperature aging is called artificial aging. In general, strict control of heat treatment time, temperature and cooling rate is essential if desired performance is required. Source: China Stainless Steel Plates Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

In the heat treatment of stainless steel plates, tempering is mainly used to soften any hard microstructures that may be formed during the previous heat treatment, improve the ductility and toughness of the material. In addition, the tempering can also form precipitates, and the size of these precipitates can be controlled to provide the required mechanical properties. This is very important for creep resistant Cr Mo steel. Tempering includes heating the steel to a temperature below the critical temperature, which is affected by the type of alloying elements added to the stainless steel plate. The temper of tool steel can be tempered at a temperature of 150 degrees centigrade, but for the welding engineer, the tempering temperature of the structural steel is usually between 550-760 degrees centigrade, depending on the composition of the steel. As for post weld heat treatment, this is a specific term which includes both stress relief and tempering, and should not be confused with heat treatment after welding. These treatments can include aging of aluminum alloy, solution treatment of austenitic stainless steel, hydrogen release and so on. When meeting certain standards, post weld heat treatment is mandatory in many standard procedures. By reducing residual stress and improving toughness, it reduces the risk of brittle fracture and reduces the risk of stress corrosion cracking. However, unless the stress is mostly compressed, there is almost no beneficial effect on fatigue performance. The method of post welding heat treatment depends on a number of factors, such as the available equipment, the size and configuration of the components, the thermal insulation temperature, the equipment capable of providing uniform heating with the required heating rate, and so on. The best way is to use a stove. This may be a permanent fixed furnace or a temporary furnace erected around the components, which is especially useful for bulky large structures or large parts on site. A permanent furnace can carry a wheeled hearth with components on it or a top hat type furnace with fixed grate and removable cover. Typically, a furnace that can heat 150 tons of pressure vessels will have a size of about 20 meters long, 5 x 5 meters, and will consume about 900cu / meter gas per hour. Natural gas or oil can be heated by resistance or induction heating. If fossil fuels are used, attention should be paid to ensuring that there is no sulphur and other elements that may cause some alloy cracking in the fuel, especially if these alloys are austenitic stainless steel or nickel base corrosion resistant coatings. No matter which fuel is used, the atmosphere in the furnace should be closely controlled so as not to cause excessive oxidation and scaling or carbonization due to the unburned carbon in the furnace atmosphere. If the furnace is gas or fuel, flame contact elements or temperature monitoring thermocouples are not allowed, which will cause partial overheating or PWHT temperature. Monitoring the temperature of components during post weld heat treatment is critical. Most modern furnaces use zone control with thermocouples to measure and control the temperature in the furnace area, and automatically control temperature through computer software. Area control is particularly useful for controlling the heating rate when assembled with different thickness of steel. However, it is recommended not to use the monitoring furnace temperature to prove that the components have reached the correct temperature. Therefore, the thermocouples are usually attached to the surface of the element at a specific interval, and these elements are used to automatically control the heating and cooling rates and the soaking temperature to achieve a uniform temperature. As mentioned previously, the yield strength decreases with increasing temperature, and the component may not be able to support its excessive weight distortion at the post weld heat treatment temperature. It is very important for components to be adequately supported in the heat treatment process, and the bracket suitable for components should be regularly placed. The spacing depends on the shape, diameter and thickness of the item. Internal support may be required in the cylinder, such as pressure vessel; if so, the support should be similar material, so that the coefficient of thermal expansion will match. Source: China Stainless Steel Plates Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

The corrosion reaction is unavoidable during the use of stainless steel pipes, so how to alleviate the corrosion is a key aspect of maintenance process. The following article describes the methods of avoiding or alleviating corrosion of stainless steel pipes. Because stainless steel pipes are usually corroded in the circuit, corrosion prevention needs to be started from the angle of interference circuit. The first is cathodic protection, which is a good way to prevent corrosion of stainless steel pipes. It uses the external current from the fixed anode to interfere with the circuit in the corroded battery. For most forms of external stainless steel pipe corrosion is 100% effective. Galvanic CP connects high-energy metals (such as zinc or magnesium) to pipes (anodes). Zinc or magnesium is used as a sacrificial anode to protect the pipe. The sacrificial anode acts as a current anode and applies voltages up to -1.4 to -2.1V. If the reverse current applied from the sacrificial anode is more negative than -0.85V, the corrosion in the stainless steel will stop. If the reverse applied current is between -0.8V and -1.00V, the corrosion of aluminum will stop. If the current exceeds -1.00V, an alkaline solution will be formed on the aluminum and corrode the metal. In some cases, conversion to -0.003 V is enough. Using a DC rectifier to drive the current to a suitable stable anode such as carbon, plating platinum titanium or magnetite in an applied current system, a proper CP level can also be reached. One end of the rectifier is connected to the pipe, and the other end is connected to the bed of the piezoelectric current anode or anode. Then the rectifier current rises until the line voltage reading of the copper sulphate half cell is less than -0.85V. We must pay attention to not too high, otherwise the coating will be stripped. The second is electrical connection, which is used to prevent the corrosion of AC and DC current. This is a simple application of the illegal current source between the conduit and the grounding system. The bonding line provides a safe way to return to other utilities’ grounding systems, not from the surface of pipes. It also provides a security element to protect workers from fatal shocks that may occur on insulated pipes near high voltage wires, trams and trolley systems. The electrical connection can also be achieved by the free use of the electrified anode, which places the pipeline at the same voltage as the illegal application. Care must be taken to ensure that all pipe flanges are in electrical contact. If they are not in contact with each other, the installation of jumpers from the bottom up ensures that the entire pipeline is protected. The third is the coating. The coating can be used to stop or reduce the corrosion of inner diameter (ID) and outer diameter (OD). In order to select the appropriate coating system, engineers need to consider the design, environment, content, pressure, external impact, design life and cost of the piping. Traditional external coatings such as mastic, as well as many new epoxy resins and polymers have been proven to be successful inhibitors. The internal coating can be used for corrosion control of contents, traction and friction reduction of cables, and erosion (impact) corrosion control. Source: China Stainless Steel Pipelines Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Brinell test was designed by Swedish researchers in early twentieth Century. As shown in Fig. 1 (a), the test involves pressing the hardened steel ball indenter into the surface of the sample using standard load. Select the diameter / load ratio to provide impressions of acceptable diameter. The diameter of the ball can be 10,5 or 1mm, the load can be 3000750 or 30kgf, the load P is related to the diameter D, and the ratio of the relational P / D 2 has been standardized to different metals, so that the test results are accurate and repeatable. For steel the ratio is 30:1 – for example, a 10mm ball can use 3000kgf load or 1mm ball 30kgf load. The proportion of aluminum alloy is 5:1. A fixed period of loading is usually 30 seconds. When the indenter is retracted, the indentation d 1 and D 2 of the two diameters are measured by microscope, and the calibration scale is used, and then the average value is shown, as shown in Figure 1 (b).

Stratified tears may sometimes occur in rolled steel plates with poor thickness ductility. The main characteristic of lamellar tear is that it appears in the base metal parallel to the weld fusion boundary and the surface of the plate, usually in the T weld and fillet welds. Cracks can occur at the toe or root of the weld, but are always associated with the point of high stress concentration. The fracture surface of the lamellar tear is fibrous and has a long parallel part, which indicates that the ductile ductility is low in the thickness direction. Because lamellar tearing is associated with high concentration extended inclusions parallel to the surface of the plate, tearing will be transgranular with stepped appearance. The occurrence of lamellar tearing must satisfy three conditions: the first is the transverse strain. The shrinkage strain in the welding must be used in the short direction of the plate, that is, through the thickness of the plate; the second is the welding direction, the fusion boundary will be roughly parallel to the plane of the inclusions; the third is the material sensitivity, and the plate must be in the direction of thickness. It is necessary to have poor ductility. Therefore, if the stress generated during welding acts in the thickness direction, the risk of lamellar tear will be greater. The risk also increases. The factors that can effectively reduce the risk of welding tear are material, joint design, welding process, consumables, preheating and coating selection. Lamellar tear occurs only in rolled steel plates instead of forgings and castings. Generally, the steel with low transverse shrinkage area (STRA) associated with high concentration of rolling sulphides or oxide inclusions is more susceptible. In general, more than 20% of STRA steel can basically be torn apart, while STRA less than 10%-15% steel plates can only be used for lightly constrained joints. Especially when the thickness is greater than 25mm, the steel with higher strength has greater risk. The risk of low sulphur content (<0.005%) aluminum treated steel is low. Lamellar tear also occurs at joints where high pass thickness strain is generated, such as T joint or corner joint. In T or cross joints, full penetration butt welds are particularly susceptible. The cruciform structure that can not be bent in the welding process will also greatly increase the risk of tear. In butt joints, there is almost no risk of lamellar tear due to the welding stress will not function through the thickness of the plate. Because the angle deformation will increase the strain at the root and / or toe of the weld, tear will also occur at the thick section joint with high bending constraint. Because tearing is more likely to occur at fully permeable T joint, if possible, use two fillet welds. Double sided welding is more difficult than large-area single side welding, and balance welding to reduce stress, which will further reduce the risk of tear at the root. Large single sided fillet welding should be replaced by smaller double sided fillet welding. Redesigning the joint structure to make the fusion boundary more perpendicular to the sensitive plate surface is especially effective for reducing risk. Typically, when the weld foot length of fillet weld and T type joint is longer than 20mm, the flake tear is more likely to occur in large weld. Because constraints can cause this problem, the thinner sections of the truncated panels which are less susceptible to tear may still be at risk under high constraints. Because the design of material and joint is the main cause of welding tear, the selection of welding process has little influence on risk. However, it may be advantageous to generate low stress higher heat input processes through larger HAZ and deeper penetration. Because welding metal hydrogen can increase the risk of tear, low hydrogen technology should be used when welding sensitive steel. Where possible, the selection of lower strength consumables can usually reduce risk by accommodating more strain in the weld metal. A smaller diameter electrode has been used to prevent the tear. Low hydrogen consumables will reduce risk by reducing the level of diffused hydrogen in welded metal. Consumables must be dried according to the manufacturer’s recommendations. Preheating will have a beneficial effect on reducing the level of diffused hydrogen in welding metal. However, it should be noted that, at the restricted joint, excessive preheating may have adverse effects by increasing the constraint level produced by the shrinkage of the weld during the cooling process. Therefore, preheating should be used to reduce the hydrogen level, but preheating should be used so that it does not increase the shrinkage of the weld. In addition, coating the surface of sensitive boards with low strength welding metal has been widely used. As shown in the T butt weld, the surface of the plate can have grooves, so that the butter coated layer will extend beyond 15 to 25mm of each weld toe, and the thickness is about 5 to 10mm. In situ bonding, that is, low strength welding metal is first deposited on the induction board and then filled with joints, has also been successfully applied. However, the design calculation should be carried out before the docking technology is adopted to ensure that the overall welding strength is acceptable. Because the lamellar tear is a linear defect with sharp edges, therefore, according to the requirements of BS EN ISO 5817:2007, the welding of quality grade B, C and D is not allowed. Using visual inspection, liquid osmotic or magnetic powder detection techniques can easily detect lamellar tearing on the surface of the stainless steel plate, but the internal cracks require ultrasonic inspection, but there may be some problems in distinguishing the lamellar tearing of the inclusion zone. Source: China Stainless Steel Plates Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Mechanical testing of stainless steel plates are used to generate data that can be used for design purposes or as part of the material connection procedure or operator acceptance procedure. The most important function may be to provide design data, because it is important to understand the limit value of stainless steel sheet product structure and ensure that it will not fail. One other effect of this mechanical test is the tensile test, which can be used to determine the yield strength of the steel used for design calculations, or to ensure that the stainless steel plate meets the strength requirements of the material specifications. Mechanical tests can be pided into quantitative or qualitative tests. A quantitative test is a qualitative test that provides data for design purposes, and the results are used for qualitative tests such as hardness testing or bend testing. Tensile testing is used to provide information used in design calculations, or to prove that materials conform to the requirements of corresponding specifications, so it may be quantitative or qualitative testing. The test is to grasp the end of the standard sample properly prepared on the tensile testing machine, and then increase the uniaxial load until failure occurs. Standardized test pieces so that the results are reproducible and comparable. The specimen is usually proportionate. When the gauge length is L 0, it is related to the original cross-sectional area, A 0, as L 0 =k A 0. In the EN standard, the constant k is 5.65, and the ASME standard is 5. The length of these measurements is about 5 times the diameter of the sample and 4 times the diameter of the specimen, although this difference may not be important technically, but it is very important to declare it in accordance with the specification. Load (stress) and specimen elongation (strain) are measured, and engineering stress / strain curves are constructed from the data. The following aspects can be determined from the curve. A) the tensile strength, also known as the ultimate tensile strength, is pided by the original cross section by the load at the ultimate tensile strength (UTS) and the maximum = P maximum / A 0 when the fracture is broken. The maximum P = maximum load, A 0 = the original cross section area. In the EN specification, the parameter is also identified as “R m”. B) the yield point (YP), that is, the stress from the elastic to the plastic deformation, that is, the yield point below the unloading specimen means that it is restored to the original length, the permanent plastic deformation at the yield point above the yield point, YP or sigma y = P YP / A 0, P YP = the yield point load. In the EN specification, the parameter is also identified as “R e”. C) in reassembling the broken sample, we can also measure the elongation, and the El% test piece has been El (%) = (L F L – 0 / L) = (%) = (L F L = 100), L F = break distance and L 0 = original distance length. In the EN specification, the parameter is also identified as “A”. D) A%= (A 0 -A f / A 0) x 100 and A f = part of the cross section area, in which the percentage of R is reduced, and the fracture of the sample in the degree of necking or decrease in diameter. In the EN specification, the parameter is also identified as “Z”. A) calculation of elongation, b) calculation of area reduction rate (a) and (b) measure the strength of materials, (c) and (d) indicate the ductility or capacity of materials without deformation. The slope of the elastic part of a curve is basically a straight line, which will give young’s modulus of elasticity, which is to measure the degree of elastic deformation of the structure when it is loaded. Low modulus means that the structure will be flexible, and the high modulus structure will be stiff and inflexible. In order to produce the most accurate stress / strain curve, additional extensometer should be added to the stainless steel plate to measure the elongation of the gauge length. The less accurate way is to measure the movement of the crosshead of the drawing machine. The above stress-strain curves show material with good yield point, but only annealed carbon steel shows this behavior. There must be other ways to determine the “yield point” by alloying, heat treatment or cold hardening of metal without obvious yielding. This is measured by measuring yield stress (yield strength in American terms), that is, a certain amount of stress required for plastic deformation in the specimen. The stress is measured by drawing a straight line parallel to the elastic part of the stress / strain curve at a specific strain, and the strain is the percentage of the original length of the standard distance, so 0.2% verification, 1% verification. For example, in the specimen with a gauge length of 100mm, the yield strength of 0.2mm is measured by using the permanent deformation of the 0.2mm. Therefore, it is proved that strength is not a fixed material property, such as yield point, but depends on the number of plastic deformation specified. Therefore, when considering the strength of proof, the percentage must always be quoted. Most steel specifications use 0.2% of the EN specification, R P0.2. Some materials such as annealed copper, gray iron and plastic have no linear elastic part in stress / strain curves. In this case, similar to the method of determining the strength of the verification, the usual practice is to define the “yield strength” as the stress that produces a specified number of permanent deformations. Source: China Stainless Steel Plates Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Creep is a slow failure mechanism, which may occur when stainless steel plates are exposed to higher than the elastic limit for a long time. Creep is very slow and not obvious at most ambient temperatures. For stainless steel plates, increasing the ambient temperature increases the deformation rate of the stainless steel plate under the load. If the stainless steel plate element is safely used in the high temperature environment, it is very important to understand the speed of the deformation at a given load and temperature. Failure to do so may lead to premature failure of pressure vessels or scaling of gas turbine blades on turbine shells. In order to use fuel more efficiently in power plants and gas turbines, it is required that components can be used for higher operating temperature than design, so new creep resistant stainless steel plate alloys are developed. In order to study the design data of these stainless steel plate alloys, creep tests are needed. In stainless steel plates, creep failure occurs at grain boundaries, resulting in intergranular fracture. Fig. 1 illustrates the void formed on the grain boundary at the early stage of creep. The fracture appearance may be similar to brittle fracture, except for a small amount of elongation in the applied stress direction.

What is a forging flange? Forging is a process in which a metal is plastically flowed to form a desired shape. The metal does not change in volume after plastic flow by external force, and the metal always flows to the portion with the least resistance. Forged flange is the best mechanical product in flange products. Its raw material is generally tube blank, and then it is cut and then beaten continuously to eliminate the segregation and looseness in the ingot. The main materials for forged flanges are carbon steel, alloy steel and stainless steel. The forged flange has good pressure resistance and temperature resistance, and is generally suitable for use in high pressure and high temperature working environments. In production, the shape of the workpiece is often controlled according to these laws, and deformations such as upsetting, reaming, bending, and drawing are realized. Forging flange is a combination of forging and stamping. It is a hammer, anvil, punch or a die that applies pressure to the blank by means of a forging flange machine to plastically deform it to obtain the desired shape and size. Forming processing method. In the forging process, the billet as a whole undergoes significant plastic deformation and a large amount of plastic flow; in the stamping process, the billet is mainly formed by changing the spatial position of each part of the area, and there is no plastic flow of a large distance inside. Forging flanges are mainly used for processing metal parts, as well as for processing certain non-metals such as engineering plastics, rubber, ceramic blanks, bricks and composites. The history of forging flanges Forging flanges and rolling and drawing in the metallurgical industry are all plastic processing, or pressure processing, but forging flanges are mainly used for the production of metal parts, while rolling, drawing, etc. are mainly used for the production of plates and belts. General metal materials such as materials, pipes, profiles and wires. At the end of the Neolithic Age, humans began to hammer natural copper to make decorations and small items. China has applied cold forging process manufacturing tools in about 2,000 BC. For example, the red copper objects unearthed from the Qijia Cultural Relics Site of Wuwei Huangniangtai in Gansu Province have obvious hammering marks. In the middle of the Shang Dynasty, weapons were made from ferroniobium, and a heating forging process was adopted. The block of wrought iron that appeared in the late spring and autumn is repeatedly heated and forged to extrude oxide inclusions and formed. Initially, people used to forge with a tamper, and later forged the billet by pulling the rope and the pulley to lift the weight and then free fall. After the 14th century, animal power and hydraulic drop hammer forging occurred. The workpieces from the forged flanges are accurate in size and are advantageous for mass production. The dimensions of die forming, such as die forging, extrusion, and stamping, are accurate and stable. High-efficiency forging machines and automatic forging lines can be used to organize specialized large-volume or mass production. The forging production process includes forging blanking before forming, forging billet heating and pretreatment; heat treatment, cleaning, calibration and inspection of the workpiece after forming. Commonly used forging flange machinery are forging hammers, hydraulic machines and mechanical presses. The hammer has a large impact speed, which is good for metal plastic flow, but it will produce vibration. The hydraulic machine is forged by static force, which is good for forging metal and improving the structure. It works smoothly, but the productivity is low. The mechanical press has a fixed stroke and is easy to mechanize. Future forging process will improve the intrinsic quality of forgings, develop precision forging and precision stamping technology, develop forging equipment and forging production lines with higher productivity and automation, develop flexible forging forming systems, develop new forging materials and forging processing methods. Improve the intrinsic quality of forging flanges, mainly to improve their mechanical properties (strength, plasticity, toughness, fatigue strength) and reliability. This requires a better application of the metal plastic deformation theory; the application of better intrinsic quality materials; correct pre-forging heating and forging heat treatment; more stringent and more extensive non-destructive testing of forgings. Less and no cutting is the most important measure and direction for the machinery industry to improve material utilization, increase labor productivity and reduce energy consumption. The development of precision forging and precision stamping will be beneficial to the development of less forging blanks, no oxidation heating, and high hardness, wear resistance, long life mold materials and surface treatment methods. Classification of the main forming methods and deformation temperatures of forging flanges: Forging according to forming method can be pided into two categories: forging flange and stamping; forging temperature can be pided into hot forging, cold forging, warm forging and isothermal forging. The hot forging flange is a forging performed above the metal recrystallization temperature. Increasing the temperature can improve the plasticity of the metal, which is beneficial to improve the intrinsic quality of the workpiece and make it less prone to cracking. The high temperature also reduces the deformation resistance of the metal and reduces the tonnage of the required forging machinery. However, there are many hot forging processes, the workpiece precision is poor, the surface is not smooth, and the forgings are prone to oxidation, decarburization and burning. /> Cold forging is forging at a temperature lower than the recrystallization temperature of the metal. The so-called cold forging is usually referred to as forging at normal temperature, and forging at a temperature higher than normal temperature but not exceeding recrystallization temperature. For warm forging pressure. The temperature of the forging pressure is higher, the surface is smoother and the deformation resistance is not large. The workpiece for cold forging and forming of forging flange at normal temperature has high shape and dimensional precision, smooth surface and less processing steps, which is convenient for automatic production. Many cold forged and cold stamped parts can be used directly as parts or articles without the need for cutting. However, in cold forging, due to the low plasticity of the metal, cracking is likely to occur during deformation, and the deformation resistance is large, and a large tonnage forging machine is required. Isothermal forging is the constant temperature of the billet throughout the forming process. Isothermal forging is to take advantage of the high plasticity of certain metals at equal temperatures or to achieve specific microstructure and properties. Isothermal forging requires constant maintenance of the mold and billet at a constant temperature, and is only used for special forging processes such as superplastic forming. Forging flanges can change the metal structure and improve metal properties. After the ingot is hot forged, the original cast loose, pores, microcracks, etc. are compacted or welded; the original dendrites are broken to make the grains fine; at the same time, the original carbide segregation and unevenness are changed. Distribution, so that the organization is even, so that the internal compact, uniform, fine, comprehensive performance, reliable use of forgings. After the forging is deformed by hot forging, the metal is a fibrous structure; after cold forging deformation, the metal crystal is ordered. Mechanical equipment for forging flanges: Due to the low production efficiency of hand forging and the forging flange of more than 10 kg weight, it is difficult to manufacture. Therefore, the modern forging workshop is equipped with mechanical forging equipment and has high efficiency. 1. Compressed air hammer It is mainly used for various basic operations of free forging, and can also perform various manual tread forging. Also called the air hammer. 2, Steam (air) hammer It is used in a wide range of equipment, free forging and model forging. 3, Hydraulic press 4, Forging hydraulic machine 5. Determination of tonnage of forging hammer and press There is enough hitting energy to obtain qualified forgings; there is enough space for holding the forging die, mainly the spacing of the guide rails; normal production efficiency can be obtained; and the forging die has a normal service life. Heating during metal pressure processing First, the heating specification of the forging flange 1. Heating requirements: The metal is required to obtain the specified temperature under the most uniform heating condition; efforts should be made to minimize the metal oxide scale and minimize the decarburization layer. 2, heating temperature range: over-burning and overheating; initial forging and final forging temperature; heating range; heating rate; heating time determination; temperature stress. Forging flange production process: The forging process generally consists of the following steps: selecting high-quality billet blanking, heating, forming, and forging cooling. Forging processes include free forging, die forging and film forging. At the time of production, different forging methods are selected according to the quality of the forgings and the number of production batches. The free forging productivity is low, the machining allowance is large, but the tool is simple and the versatility is large, so it is widely used for forging a single piece and a small batch of forgings with a simple shape. Free forging equipment includes air hammer, steam-air hammer and hydraulic press, which are suitable for the production of small, medium and large forgings. Die forging has high productivity, simple operation, and easy mechanization and automation. The die forgings have high dimensional accuracy, small machining allowance, and reasonable distribution of the fiber structure of the forgings, which can further improve the service life of the parts. First, free forging Basic process: For free forging, the shape of the forging is gradually forged by some basic deformation process. The basic processes of free forging are upsetting, lengthening, punching, bending and cutting. 1. Upsetting Upsetting is an operation process in which the raw material is forged in the axial direction to reduce its height and increase the cross section. This type of process is commonly used for forging gear blanks and other disc-shaped forgings. The ups and downs are pided into two types: all upsetting and partial forging. 2. Pulling out Lengthening is a forging process that increases the length of the blank and reduces the section. It is usually used to produce shaft blanks, such as lathe spindles and connecting rods. 3. Punching A forging process in which a punch punches a through hole or a through hole without using a punch. 4. Bending A forging process that bends the billet into a certain angle or shape. 5. Torting A forging process that rotates a portion of a blank relative to another portion by a certain angle. 6. Cutting The forging process of piding the blank or cutting the material. Second, die forging The die forging is collectively referred to as model forging, and the heated billet is placed in a forging die fixed to the die forging device to be forged. 1. The basic process of die forging The process of die forging: cutting, heating, pre-forging, final forging, punching, trimming, quenching and tempering, shot peening. Commonly used processes are upsetting, lengthening, bending, punching, and forming. 2. Common die forging equipment Common die forging equipment includes die forging hammer, hot die forging press, flat forging machine and friction press. Generally speaking, forged flanges are of better quality, generally produced by die forging, with fine crystal structure and high strength, of course, the price is also more expensive. Whether it is cast flange or forged flange, it is a common method of manufacturing flanges. See the strength requirements of the parts to be used. If the requirements are not high, you can also use turning flanges. What is a casting flange? Casting is a process in which a liquid metal is cast into a casting cavity adapted to the shape of the part, and after cooling solidification and finishing, a casting or blank having a predetermined shape, size and performance is obtained. The casting blank is nearly shaped to achieve machining-free or small-scale processing, which reduces costs and reduces production time to some extent. Casting flange is a commonly used flange process, which has the advantages of being able to produce more complicated shapes, high production efficiency and low production cost, and is suitable for medium and low pressure pipelines. However, the casting flange has disadvantages such as pores, cracks, inclusions, and poor internal flow lines. The difference between cast flange and forged flange Forged flanges generally have lower carbon content than cast flanges and are less prone to rust. Forgings have better streamlined shape, denser structure, better mechanical properties than cast flanges, higher shear and tensile forces than castings, and uniform internal organization of forgings. There are no shortcomings such as pores and inclusions in the casting. However, if the forging process is improper, there will be large or uneven grains, hardening cracks and the like. The cost of forged flanges is higher than that of cast flanges, so the price of forged flanges is much higher than the price of cast flanges. This analysis is not very good from the appearance analysis, I will tell my analysis experience: First, the difference in price: the flange sold in the market, the cheapest casting flange, the second casting and forging flange, the price of pure forging flange is higher. This means that you can reach a rough conclusion after going to various stores. The second is to do a destructive analysis: the flange is cut in half, the cast flange has trachoma, and the pure forged flange has no trachoma. Cast and forged flanges can sometimes be found to have cracks. The third is to distinguish the size and finish of the flange (this is not generally not visible.): The general tolerance of the casting flange on the market is 1-5mm, the edge chamfer is irregular, and the edge hole burr is not smooth. Because cheap work is not so fine. Forged flanges have small tolerances or positive tolerances. The distinction between cast steel flange and cast iron flange: The cast iron flange has poor toughness and can be split with a hammer. The material of the flange is generally close to low carbon, and it will be easy to crack if it is welded. Source: China Stainless Steel Flanges Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)