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Stainless steel is one of the most important inventions in the 20th century, during the past hundred years of development and research has formed a series of more than 300 brand of steel grade. Visible, as an important material of stainless steel becomes more and more important for people, it is installed in engineering materials plays a role can not be ignored. Stainless steel elbow, of course, as a kind of pipe installation accessories products, plays an important role. As we all know, stainless steel elbow is different from carbon steel elbow is the main material of different. The chemical composition of the stainless steel elbow will keep the bend surface for a long time without rust. Then what metal elements can make the stainless steel elbow so good with carbon steel elbow it? We all know that the industrial grade stainless steel elbow is austenitic stainless steel. Austenitic stainless steel is greater than 18%, and chromium containing 8% nickel, of course, which also contains a small amount of copper, titanium, nitrogen and other elements. This kind of steel contains a large amount of nickel and chromium to make steel at room temperature in a state of austenite. Visible, chromium and nickel in stainless steel play an important role. Now we talk about the role of chromium in the stainless steel elbow: stainless steel elements is decided only one is Cr, so far, no chromium stainless steel, add chromium in stainless steel, the contradiction of internal corrosion resistance, resistance to damage the direction of development. The addition of chromium content in the steel reached more than 10 in order to form chromium passivation protective membrane stability, protection of steel against atmospheric corrosion, corrosion resistance of stainless steel increased with increasing chromium content. Then we talk about the role of nickel in stainless steel elbow: nickel is an excellent corrosion resistant material, which is an important alloying element in alloy steel. Nickel in stainless steel to join, the crystal structure changes from cubic face centered cubic structure, the steel is easy to form a single organization (austenite) steel, has not formed the micro battery capacity, so as to avoid being the main reasons for the corrosion of steel. In stainless steel, if the nickel can reach 24%, the microstructure of pure austenite can be obtained, and the corrosion resistance of the steel in some medium can be significantly changed by 27%. However, nickel and chromium exist in stainless steel, nickel can play a lot of valuable role in stainless steel. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Stainless steel is not easy to rusty steel, stainless steel in the main alloying element is Cr (chromium), only when the Cr content reaches a certain value, the steel corrosion resistance, stainless steel generally Cr content of at least 10.5%. The corrosion mechanism of stainless steel is the theory of passivation film, that is, its surface to form a layer of very thin and strong and stable stable Cr-rich passivation film to prevent oxygen atoms continue to infiltrate and continue to oxidize, so as to achieve the ability of anti-corrosion. The pattern of passivation film on the surface of stainless steel People think that “stainless steel is not rusty, rusty is not stainless steel.” In fact, this is a lack of understanding of stainless steel a one-sided view of the wrong, stainless steel under certain conditions will rust. If we can intuitively understand the various types of corrosion of stainless steel, the face of stainless steel corrosion can have a corresponding response to reduce the loss. The following describes the actual types of stainless steel common corrosion, a brief introduction to the corresponding anti-corrosion measures, and focus on stainless steel stress corrosion causes and prevention measures. Corrosion damage from stainless steel is mostly local corrosion damage, the most common intergranular corrosion (9%), pitting (23%) and stress corrosion (49%). [1] Corrosion types of stainless steel Intergranular corrosion Intergranular corrosion is due to impoverishment on the grain boundary, leading to preferential corrosion of the region, and thus the overall separation of the grain from the metal. Heat treatment 450 ℃ ~ 850 ℃ temperature range C and Cr easy to form carbon chromium compounds (Cr23C6), the grain boundary consumption of Cr can not be added from the grain in time, so that the grain boundary area of poor Cr, which is caused by intergranular corrosion The essential. For example: a company synthetic ammonia plant furnace gas preheat tube due to intergranular corrosion caused by cracking, leakage occurred. The intergranular corrosion of the preheat tube is due to the precipitation of Cr23C6 in the grain boundary of the austenitic stainless steel, and the intergranular corrosion cracking occurs in the pipe under the action of Cl- in the tube. Microstructure and microstructure of intergranular corrosion In order to prevent intergranular corrosion of stainless steel, the general solution: 1, the solution annealing metal is uniformly heated to 1050 ℃ ~ 1060 ℃, and then rapid cooling; 2, adding stabilized elements Ti, Nb, etc .; 3, the choice of low-carbon stainless steel. Pitting Pitting is a very dangerous local corrosion, the occurrence of small holes and then the phenomenon of rapid corrosion, serious can lead to perforation. Pitting the main factors are: 1, Cl- effect, Cl – stainless steel passive film local damage, leading to the site of the first occurrence of corrosion; 2, the temperature impact, the higher the temperature, the faster corrosion; 3, the surface attached to the contaminants to prevent the flow of oxygen. For example, the daily life of stainless steel (201 or 304 stainless steel majority) sinks often pitting phenomenon. If some acidic or salt substances in the sink did not get timely treatment, it will lead to pitting corrosion of stainless steel sink. Pitting corrosion phenomenon of stainless steel pipe The precautions are as follows: 1, to prevent Cl – attachment; 2, a reasonable surface treatment, the formation of stable passivation film; 3, select the resistance to Cl-corrosive materials (such as the addition of Mo 316L stainless steel). Stress corrosion Stress corrosion refers to the damage caused by the metal in the corrosive medium under the action of tensile stress. The stress corrosion of stainless steel is the most serious corrosive form in the failure of stainless steel. If there is a slight crack in the process of corrosion, the expansion rate is several orders of magnitude faster than other types of corrosion, causing catastrophic consequences. Chemical plants, nuclear power plants, boilers and other stainless steel materials have appeared stress corrosion cracking phenomenon. For example, ① a pharmaceutical enterprise hydroxyl acetonitrile synthesis of glycine project synthesis section to the concentrated section of the 316L stainless steel pipe to the weld occurred a serious stress corrosion cracking. The stress corrosion cracking in the accident originated from the weld defect, the intergranular corrosion occurred improperly in the heat treatment control of the welding process, and the residual stress in the welding resulted in the formation of stress corrosion cracking on the basis of intergranular corrosion. 316L pipe fittings with stress corrosion cracking (2) The reactor reactor core is 304NG stainless steel in the reactor core of the reactor, and the Irradiation Assisted Stress Corrosion Cracking (IASCC) phenomenon occurs in the high temperature and high pressure and strong irradiated water environment. Strict control of the nuclear plant service environment is one of the most effective ways to solve the problem. Irradiation Assisted Stress Corrosion Cracking (IASCC) The study of stress corrosion experiments is based on stress corrosion characteristics and experimental purposes under different conditions. According to the material, environment, stress state and experimental purposes, has developed a variety of stress corrosion test method. Experiments were carried out according to experimental site and environmental quality, laboratory experiment and laboratory accelerated experiment. The experiment was carried out according to the loading method, constant deformation experiment and constant strain rate tensile test. Samples of the same stress corrosion test are generally pided into three categories: smooth specimens, notched specimens and prefabricated crack specimens. CT samples of cracks The stress corrosion problem of stainless steel has been extensively studied, and many different mechanisms have been put forward to explain the stress corrosion phenomenon, but there is no universally accepted mechanism. Because stress corrosion is a process related to corrosion, the mechanism must be related to the anode and cathode reactions in the process of corrosion. Therefore, the stress corrosion mechanism is mainly pided into two categories: anodic dissolution and hydrogen cracking, and in these two mechanisms Based on the development of the surface membrane rupture theory, active channel theory, stress adsorption cracking theory, corrosion product wedge theory and occlusion battery theory. Theoretical model of surface film rupture Factors Affect Stress Corrosion There are three main factors: material, corrosion environment and tensile stress. The material factors include element content, heat treatment, microstructure and surface state. The corrosion environment includes medium type, temperature, potential and liquid flow rate. The tensile stress includes service stress, installation stress, residual stress and tensile rate. Solution: 1, to reduce the stress concentration of high stress components; 2, to prevent the introduction of chloride ions; 3, to avoid stress processing; 4, heat treatment, to eliminate stress; 5, the use of resistant SCC ferrite stainless steel; 6, the use of high-Ni steel In the new era of rapid progress in science and technology and continuous improvement of scientific research level, the research and development speed of new materials still can not keep up with the speed of the problem. In the practical engineering application of stainless steel corrosion problems emerge in an endless stream, although the current protective measures have achieved some success, but there are still serious shortcomings, a variety of means of protection can only play a role in a certain range. Reasonable selection, real-time detection is still the key to control corrosion.

317LMN and 317L are austenitic stainless steel containing molybdenum. Compared with ordinary chrome-nickel austenitic stainless steel (such as 304 stainless steel), its resistance to chemical erosion better, high temperature environment, the fracture stress intensity stronger, better ductility. The combination of molybdenum and nitrogen improves the pitting resistance and resistance to pitting of stainless steels, especially in high temperature environments containing acidic compounds, chlorides and sulfides. Nitrogen while improving the strength of stainless steel. Chemical Composition The chemical composition of grade 317L stainless steel is outlined in the following table. Element Content (%) Iron, Fe Balance Chromium, Cr 18-20 Nickel, Ni 11-15 Molybdenum, Mo 3-4 Manganese, Mn 2 Silicon, Si 1 Phosphorous, P 0.045 Carbon, C 0.03 Sulfur, S 0.03 Corrosion resistance of stainless steel 317L and 317LMN stainless steel withstand the atmosphere and mild corrosive ability, in addition to strong oxidizing acid (such as nitric acid). 317LMN and 317L stainless steel anti-sulfuric acid solution corrosion better. Its corrosion resistance increases with the increase of molybdenum content of stainless steel. These stainless steels can withstand up to 5% sulfuric acid at temperatures up to 120 ° F (49 ° C). At temperatures below 100 ° F (38 ° C), these stainless steels have excellent corrosion resistance and are resistant to higher concentrations of solution corrosion. However, application testing should take into account specific operating factors that may affect corrosion behavior. These stainless steels are more resistant to the formation of concentrated gases than conventional stainless steel 316 during the process of concentration of sulfur-containing gases. The concentration of acid has a significant effect on the corrosion rate in such an environment and should be carefully determined according to the specific application test. The following table shows the corrosion resistance of annealed 317LMN and 317L samples in a variety of solutions, all of which are related to the processing industry and ASTM testing. This table lists the relevant data for stainless steel 316L and stainless steel AL276 for comparison. Corrosion Resistance in Boiling Solutions and ASTM Tests Test Solution Corrosion Rate in Mils per Year (mm/y)  for Cited Alloys Alloy 316L Alloy 317L Alloy 317LMN Alloy 276 20% Acetic Acid 0.12 (<0.01) 0.48 (0.01) 0.12 (<0.01) 0.48 (0.01) 45% Formic Acid 23.41 (0.60) 18.37 (0.47) 11.76 (0.30) 2.76 (0.07) 10% Oxalic Acid 48.03 (1.23) 44.90 (1.14) 35.76 (0.91) 11.24 (0.28) 20% Phosphoric Acid 0.06 (0.02) 0.72 (0.02) 0.24 (<0.01) 0.36 (0.01) 10% Sulfuric Acid 635.7 (16.15) 298.28 (7.58) 157.80 (4.01) 13.93 (0.35) 10% Sodium Bisulfate 71.57 (1.82) 55.76 (1.42) 15.60 (0.40) 2.64 (0.07) 50% Sodium Hydroxide 77.69 (1.92) 32.78 (0.83) 85.68 (2.18) 17.77 (0.45) ASTM A262 Practice B (FeSO4H2SO4) 26.04 (0.66) 20.76 (0.53) 17.28 (0.44) 264.5 (6.72) ASTM A262 Practice C (65% HNO3) 22.31 (0.56) 19.68 (0.50) 16.32 (0.42) 908.0 (23.06) ASTM A262 Practice E (Cu•CUSO4•H2SO4) Pass Pass Pass Pass The low carbon (less than 0.03%) of these alloys effectively prevents sensitization to intergranular corrosion during thermal processes such as welding or forging. The higher chromium contents of 317LMN and Alloy 317L stainless steels also provide superior resistance to intergranular attack. It should be noted that prolonged exposure in the range 800 to 1400°F (427-816°C) can be detrimental to intergranular corrosion resistance and may also cause embrittlement due to precipitation of sigma phase. The higher nitrogen content of the 317LMN alloy retards the precipitation of sigma phase as well as carbides. Pitting Resistance Equivalents Alloy PRE Alloy 316 25 Alloy 317L 30 Alloy 317LMN 38 Alloy 625 52 Alloy C276 69 High molybdenum and nitrogen contents can significantly improve pitting resistance as illustrated in the preceding table of Pitting Resistance Equivalents (PRE). The PRE is based on the results of corrosion tests in which it was found that nitrogen was 30 times more effective than chromium and approximately 9 times more effective than molybdenum in enhancing chloride pitting resistance. The temperature of the onset of crevice corrosion as determined in a modified AST G-48B test is a useful means of ranking the relative resistance of stainless and nickel-base alloys. The Critical Crevice Corrosion Temperatures table that follows demonstrates that crevice corrosion resistance for austenitic stainless steel tubing increases with the alloy’s molybdenum and nitrogen content. Crevice Corrosion in a Simulated  FGD System Environment Alloy Weight Loss (g/cm2)  for Tests* at Cited Temperatures 24°C (75°F) 50°C (122°F) 70°C (158°F) Alloy 317L 0.0007 0.0377 0.0500 Alloy 317LMN 0.0000 0.0129 0.0462 Alloy 625 0.0000 0.0000 0.0149 Alloy C276 0.0000 0.0001 0.0004 *72-hour exposure based on ASTM G-48B procedure using the following solution:  7 vol.%H2SO4, 3 vol%HCI, 1 wt% CuCl2, 1 wt%FeCl3 Mechanical Properties The mechanical properties of grade 317L stainless steel are displayed in the following table. Properties Metric Imperial Tensile strength 595 MPa 86300 psi Yield strength 260 MPa 37700 psi Modulus of elasticity 200 GPa 29000 ksi Poisson’s ratio 0.27-0.30 0.27-0.30 Elongation at break (in 50 mm) 55% 55% Hardness, Rockwell B 85 85 Antioxidant properties Chromium-nickel-molybdenum steel has excellent oxidation resistance, and in the ordinary atmosphere, the temperature is not higher than 1600-1650 ° F (871-899 ° C), the scale generation rate is low. Stainless steel processing performance 317LMN stainless steel and 317L stainless steel physical and mechanical properties and conventional austenitic stainless steel similar, therefore, can be processed 304 stainless steel and 316 stainless steel method for its processing. Manufacturing Process Conventional hot working processes can be performed. The material should be heated to 1149-1260°C (2100-2300°F); however, it should not be heated below 927°C (1700°F). To optimize corrosion resistance, a post-work annealing is recommended.Machining stainless steel grade 317L requires low speeds and constant feeds to reduce its tendency to work harden. This steel is tougher than grade 304 stainless steel with a long stringy chip; however, using chip breakers is recommended. Welding can be performed using most of the conventional fusion and resistance methods. Oxyacetylene welding should be avoided. AWS E/ER 317L filler metal is recommended. Shearing, stamping, heading and drawing are possible with grade 317L stainless steel, and post-work annealing is recommended to eliminate internal stresses. Annealing is performed at 1010-1121°C (1850-2050°F), which should be followed by rapid cooling. Grade 317L stainless steel does not respond to heat treatment. Applications Grade 317L stainless steel is widely used in the following applications: · Condensers in fossil · Pulp and paper manufacturing · Nuclear fueled power generation stations · Chemical and petrochemical process equipment. Source: wilsonpipeline Pipe Industry (www.wilsonpipeline.com)

Stainless steel butt weld elbow is seam pipe fittings, it is generally used in relatively large diameter stainless steel elbow, and wall thickness is thin. Stainless steel butt weld elbow has certain corrosion resistant, heat resistant, wear-resisting performance, it is widely used in different fields and industries, usually used in power plant, chemical, oil and other equipment. Stainless steel butt weld elbow, the process is the same as the tube of stainless steel plate by stamping die stamping into half a piece of ring elbow, then two and a half block shape bend to group of butt welding forming, production and processing according to the process. Stainless steel butt weld elbow in the welding process, after heating, can release carbide, release the carbide will affect the performance of the stainless steel elbow, reduce corrosion resistance and mechanical properties, and sclerosing after welding is bigger, easy to crack, so need to pay attention to matters in the process of welding and method, ensure the good use value and performance. If using the same type of chromium stainless steel elbow electrode welding, must be above 300 ° C, preheating and slow cooling off around 700 ° C, after welding if cannot undertake the weldment heat treatment after welding, should choose the chromium nickel stainless steel elbow. Different kinds of electrode in use have different performance and characteristics, in use according to the needs of the corresponding selection, ensure the quality of the welding of stainless steel elbow. Steel plate made of stainless steel elbow in the welding process using dc power; When used at the same time should be kept dry, lest cause weld stainless steel elbow increased carbon content and affect the welding quality. In order to improve corrosion resistant stainless steel elbow and weldability, select elements increases the stability of the (Ti, Mo) such as steel, chromium than the weldability of the stainless steel plate is better. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

How does chloride corrode stainless steel In the chloride medium, the stainless steel pipe is often subject to local corrosion is mainly point corrosion and corrosion corrosion two. Corrosion mechanism of stainless steel The reason for corrosion resistance of stainless steel pipe is because there is a layer of passivation film on the surface. When this passivation film is destroyed and lacks the conditions or capabilities of the passivation, the stainless steel pipe is corroded. If the corrosion area is concentrated at a specific point and a corrosive pits are developed into the depths, Tube other surface is still passive, this corrosion phenomenon is the point of corrosion. Stainless steel forms point corrosion conditions Only in a specific corrosive medium, the stainless steel pipe will form a point of corrosion. When the halogen ions and oxidants (such as dissolved oxygen) are present in the medium, point corrosion is liable to occur. Most of the corrosion of the stainless steel pipe equipment caused by chloride and chloride ions, especially hypochlorite (present in the bleach), the more corrosive. Other halogen ions, bromide will also cause point corrosion, and fluoride and iodide solution, the occurrence of point corrosion of stainless steel tube tend to be smaller. If the chloride solution contains copper, iron and mercury and other metal ions, the corrosion is particularly serious, the risk of corrosion at the point of occurrence of equipment will be greater. Corrosion characteristics of stainless steel Stainless steel pipe corrosion occurs when its shape features are the following: 1, most of the stainless steel tube surface almost no corrosion, and some even bright as new, only local corrosive holes. 0Cr18Ni9Ti stainless steel in 10% FeCl3.6H2O solution, room temperature soaking 2.5h after the appearance of the point of corrosion (A) the original appearance (dents) after soaking (b) (a) After the dents are broken on the top of the wheel, the surface of the wheel of the air compressor made of 1Cr13 martensitic stainless steel The appearance 2, stainless steel pipe looks like no pitting and like to hit the dents, and the dents are metallic luster, but if the broken dents, the following is a serious pitting pits. The pitting appearance of duplex stainless steel in 10% FeCl3.6H2O aqueous solution at room temperature for 47h 3, the point of corrosion is not only small size, but also by the corrosion products covered, similar to pollutants. After wiping the contaminants, the pits will be exposed. 1Cr18Ni9Ti stainless steel made of pyrithione autoclave liner in the use of pitting pits 4, sometimes stainless steel pipe and part of the environment after the combination of reaction, the point of corrosion will be pagoda-like morphology. 1Cr18Ni12Mo2Ti stainless steel in 10% FeCl3.6H2O solution, 50 ℃, soak for 48h after the appearance of the surface morphology of corrosion.

The processing of the elbow is easy to produce the following quality defects, especially in the bending of the elbow. (1) thinning of wall thickness, wrinkling, such as the outside of the bending deformation zone will produce thin wall thickness. The maximum deformation of the parts in the maximum deformation, when the thin excessive lead to rupture of the pipe. From the point of view of deformation mechanics, the ring is a problem which is too large. If the inside of the bending deformation zone will produce wall thickness increase. If the degree of deformation is too large, the inner wall of the tube will be unstable and thick, severe wrinkling. Therefore, the instability is not only under the effect of tensile stress will appear, under the effect of stress, the same instability problem. Such defects occur in the wall thickness of the tube bending. (2) section shape distortion in the elbow bending process, if you do not take the necessary measures (such as in the tube filler or placed mandrel support), elbow cross section after bending in the absence of internal support can easily become oval. Therefore, it is very important to prevent the production of the above defects in order to select reasonable technological process and take necessary technological measures. Production practice shows that the elimination or reduction of quality defects, in order to meet the requirements of the use of pipe fittings, is the key process of processing. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Eccentric reducer in the actual production add different elements of different functions and intensity, using certain production standard and the way to add, in which the use of a certain performance. Eccentric reducer characterized by carbon intensity is significantly higher than the same amount of carbon steel, has good toughness and plasticity, good weldability and corrosion resistance, etc. In order to improve and enhance the performance of the steel on the basis of the carbon steel to join other alloying elements, such as silicon, manganese, chromium, nickel, tungsten, vanadium, titanium, etc., this kind of steel is alloy steel. Eccentric reducer according to difference of alloy elements, have different properties, such as high wear resistance, corrosion resistance, good low temperature resistance, good special features such as high magnetic. The center of the eccentric reducer as the main body section, straight pipe ends for eccentric, main body between a straight pipe section and eccentric reducing transition section, eccentric reducer the bottom line is straight line remains unchanged; Eccentric reducer of preparation methods are classified using multiple sets of mould, eccentric reducing in the metal tube directly, first set aside the main section in the middle of the metal one, again according to the request of tapered Angle, using multiple sets of hierarchical mold molding, step by step to suppress and into. Using this invention method processing eccentric reducer, the whole root eccentric size head without weld; Eccentric reducer as a dedicated pipe, used in corrosive strong liquid, can prolong the service life of the eccentric reducer, especially used for downhole eccentric water distributor’s shell, because there is no seam, not in the joint corrosion cracking; Flexible production technology, processing any straight pipe diameter, eccentric any longer eccentric reducer. The size of the eccentric reducer pipe of different connections, is suitable for different industries are different. In electric power, mining, metallurgical and other industries, the material of the conveyor, output, are using at close range, high pressure conveying pipeline under considerable pressure, and sustained serious wear and tear, single material pipeline is very difficult to meet the requirements of this condition, especially the elbow, concentric reducer, such as stamping elbow pipe fittings, by considering its use of security, and service life, focus on improving pipe lined with toughness, impact resistance, and abrasion resistance. At the same time also want to consider the integrated intensity of the pipe and elbow problems. Eccentric reducer before bonding, use dry cloth to bell mouth and socket lateral wipe the handle, when the surface with oil pollution must be with acetone to wipe clean, have the following points to note: 1, control diameter: DIN, 3 a/IDF standards, ISO standards; 2, the international industry standard: DIN, ISO, SMS, 3 a, IDF, etc; 3, the product material: 304, 316, 316 l stainless steel; Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Large flange in use process due to the large flange connection when improperly or use time is too long, leak, appear this kind of circumstance the user need not worry. First look at the leak site, minimal in leak position due to the large flange clearance can’t be eliminated by injecting sealant clearance leakage. The construction method of sealing according to leak the field survey, for the realization of the limited block, by using fixed fixture tolerance leak to form a sealed chamber, injecting sealants, to eliminate leakage. Side of the clamp are made of, fixture first to satisfy large flange leak inclusive and build body large flange and pipe between the large flange connection sub large flange seal chamber as the first point. To prevent from pressure-out potential leak valve body and the large flange clearance appears to leak, the fixture and the large flange anastomotic set to the outer ring cavity injection glue. Because of the large diameter flange in the process of injection agent fixture is easy to trail large flange lateral displacement, the limit of the tooth contact card is adopted tightening measures. When operating sealant after curing, after effect observation, local injection pressure, prevent stress relaxation, closed agent injection hole again. The large flange to note: Large flange in the production and use of technical requirements and technical parameters, according to certain ways and methods of production and processing: hebei large flange 1. The large flange should be along the direction of steel rolling cut into strips, the bending welded into a circular ring, and to form the surface of the steel ring cylinder. When in the production of large flange shall not adopt steel machined directly into a large neck flange, adoption of a certain craft production and processing. 2. The production of large flange plate should be via ultrasonic testing, with no defects, guarantee the good quality and performance problems, according to certain quality requirements of the production and inspection, ensure the quality of the production and use of the steel plate no problem. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Stainless steel lap joint stub end is a tensile or compression edge production, method of making forming vertical edge height of the. Mainly pided into convex curve lap joint stub end and concave curve lap joint stub end. The stress and deformation properties of convex curve lap joint stub end is similar to the shallow drawing, the deformation degree is denoted by Kfb=r/R0; the degree of lap joint stub end coefficient Kfb=r0/ deformation concave curve lap joint stub end (r0+b) to said, when the center of the curve angle smaller than 180 DEG, Kfb=Kfk α/180°. Stainless steel lap joint stub end is generally pided into stretch lap joint stub end and compression lap joint stub end deformation zone, the elongation of the lap joint stub end is blank, stress to pull in cutting under the action of the tangential deformation, ultimate deformation degree under the deformation zone cracking limit. While the compression lap joint stub end radius is in addition to near the region near the vertical side of the root of metal deformation completely, the other part of the blank deformation zone is tangential compressive deformation of tangential compressive stress under the action. Stainless steel lap joint stub end due to the long time work, there will be fatigue and wear, because of these problems, so the material should be stainless steel lap joint stub end has high bending strength and contact fatigue strength, the core is to have good strength and toughness. If the work is stable, there is no strong impact of the gear, the use of 40Cr, 40MnB, such as low carbon steel or medium carbon low alloy and other materials. If the work condition is not good, we will load the quality of material properties and heat treatment of stainless steel lap joint stub end has required that we must choose some alloy steel as raw material, so as to ensure the normal operation of equipment. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

On both ends of the reducer is also called the reducer, pipe diameter, used to connect different diameter tubes or variable diameter flange. Concentric reducer at both ends of the tube, circle, on the same axis diameter changes, in terms of axis of pipe position, the position of the pipe is changeless, commonly used in gas or liquid vertical pipe diameter changes. Price according to the diameter and the material is not different, has the certain calculation formula of the specifications of the reducer with the diameter of the big times the diameter of the small mouth, such as a diameter of 400 and 200, respectively, with 400 * 200, said the wall thickness also affects the price of their products. Products are pided into concentric reducer and eccentric reducer, used for different diameter of pipe connection, in the transition between the main and branch pipe bend them is required. Concentric reducer is big is small sip concentric circle, in the straight pipe connection, can’t change the direction of the pipeline, two circle is not concentric reducer, eccentric reducerprocessing technology is relatively concentric reducer some hard, so the price is in the process of production. Carbon steel material, the material such as stainless steel, carbon steel reducer usage of the biggest, the general said carbon steel products cheaper price, accessories production use, because of the carbon steel as the raw material price is not expensive, so the production cost and product price is very cheap, the price of the bend is not fixed, calculated according to the size of the diameter, the bigger the diameter of the product price is more expensive, so at the time of purchase products to clear the required diameter and material of the wall thickness, in order to get the most reasonable reducer quotation. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Stamping elbow has certain corrosion (oxidizing acid, organic acids, cavitation), heat-resisting and wear-resisting performance. Usually used in power plant, chemical, oil and other equipment. Stamping elbow poor weldability, welding, heat treatment conditions should be paid attention to and choose suitable welding electrode. The corrosion resistance of the stamping elbow depends on the alloy element content in the steel. Chromium stainless steel stamping elbow is get the corrosion resistance of the basic elements, while about 1.2% chromium content in steel, chromium and oxygen in erosion media effect, in the steel surface to form a thin layer of oxide film (since the passivation film), but to prevent further erosion of steel substrate. Elbow pipes with different production technology and processes, according to certain conditions is needed in processing production and processing, the different nature of the elbow pipe fittings some matters need attention in the process. For alloy elbow, if do alloy long radius elbow, must first to the selected of the specifications of the steel tube, pipe material, selection of quality steel pipe production. Alloy elbow has certain hole enlargement ratio, through theoretical calculation, the general hole enlargement rate is between 33% and 35%, push back. Short radius of 219 mm hole enlargement rate was 50%. Choose good raw materials, according to the alloy elbow materials specifications, then consider the radius of curvature, for example, the 90 ° elbow, through its curvature can calculate how much material can work out the 90 ° elbow. Through the theoretical calculation can be calculated, then based on the length scale. The final push materials for thermal system. Because of some elbow after improper handling, will be distorted, this is not allowed. Stamping elbow won’t produce corrosion, pitting, corrosion or wear and tear. Stainless steel is used in metal materials in one of the highest material strength. Because stainless steel has good corrosion resistance, so it can make structure parts permanently maintain the integrity of engineering design. Chromium stainless steel stamping elbow also has high mechanical strength and extensibility, easy processing and manufacturing of parts, can be satisfied with the architect and structural design staff needs. All metal and atmospheric oxygen in the reaction, formed in the surface oxide film. Unfortunately, in the ordinary carbon steel oxidation of iron oxide is formed on the inheritance, kept expanding rust, ultimate forming holes. Can use paint or resistant to oxidation of the metal (for example, zinc, chromium and nickel) on plating to ensure that the surface of carbon steel, but, as we know, the protection is only a thin film. In addition, after have a haircut is usually large front end diameter, through plastic mould for plastic. The whole model is actually a press, want to have a set of mould, two and a half arc, the upper one. After the plastic outer diameter to reach the size of the finished product. Wall thickness in the wall thickness of incoming material control. Elbow and pipe wall thickness tolerance is the same, are the plus or minus 12.5%. Commonly used alloying elements except chromium and nickel, molybdenum, titanium, niobium, copper, nitrogen, etc, in order to content with various USES of stainless steel stamping elbow organization, and functional requirements. Stamping elbow making matters needing attention when using electrode should be kept dry, titanium calcium type should be 1 hour after 150 ℃ drying, low hydrogen type should be 1 hour after the 200-250 ℃ drying (not sticky oil and other dirt, lest cause weld increased carbon content and influence the welding quality and mechanical properties. Sclerosing after welding is bigger, easy to crack. If using the same type of electrode welding, must be above 300 ℃ preheat and 700 ℃ or so slow cooling after welding. If it’s unable to weld heat treatment after welding, should choose chromium nickel stainless steel electrode. In order to improve the stamping elbow corrosion resistance stability element Ti, Nb and Mo, weldability is better, using the same type of chromium stainless steel electrode, should be above 200 ℃ preheat and around 800 ℃ tempering treatment after welding. If cannot undertake the weldment heat treatment, should choose chromium nickel stainless steel electrode. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Stainless steel reducer in reducing deformation in the process of suppression and hole enlargement, according to different materials and variable diameter pipe fittings we need to deal with, and then also need determination by cold pressing and hot pressing, under normal circumstances, as far as possible by cold pressing, but the multiple variable diameter caused by the severe strain hardening, the thick or wall thickness of alloy steel material appropriate USES hot pressing. Stainless steel reducer of the hole diameter molding process is to use less than the size of the big end diameter tube billet, used in die forming along the tube billet diameter hole enlargement, variable diameter hole enlargement process mainly solved the reducer not easy through reducing forming, sometimes according to the requirements of the materials and products forming, expanding and reducing method of combination. Stainless steel reducer’s reducing molding process is will and head big end diameter equal to the size of the pipe into the forming mould, then along the pipe axis suppression, shrink along the cavity movement and metal forming, finally completes the reducer’s reducing process. Because the size of the stainless steel reducer with heating after pressing tee, reduce material forming required equipment tonnage. Hot-pressing tee with wider adaptability of materials used for low carbon steel, alloy steel, stainless steel materials; Form of a process. Besides using steel as raw material to produce the reducer, the size of the specifications of department head can also be used steel plate stamping forming technology is adopted to improve the yield. Used by stretching die appearance reference stainless steel inner surface size reducer design, use after blanking punching die, stamping steel stretch forming. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)