Welding of stainless steel pipe: 1 the use of vertical external characteristics of the power supply, the use of positive polarity (welding wire electrode) 2 is generally suitable for the welding of 6mm sheet metal, has the characteristics of weld appearance, small welding deformation. 3 the gas is argon and the purity is 99.99%. When the welding current is 50~50A, the argon flow rate is 8~0L/min, when the current is 50~250A, the argon flow rate is 2~5L/min. 4 tungsten electrode from the gas nozzle to highlight the length of the 4~5mm is better, in the corner welding, such as poor shelter is 2~3mm, in the deep groove depth is 5~6mm, the nozzle to the working distance is generally not more than 5mm. 5 in order to prevent the emergence of laser welding, welding parts such as rust, oil, make sure clean. 6 welding arc length, welding of ordinary steel, the 2~4mm is better, and the welding of stainless steel, to ~3mm for the best, too long, the protective effect is not good. The 7 docking base, in order to prevent the bottom bead back is oxidized back, also need to carry out gas protection. 8 for argon to make a good protection of weld pool, and facilitate welding operation, tungsten electrode center line and welding workpiece should remain generally 80 ~ 85 degrees, filling should be small as possible for the angle between the wire and the workpiece surface, generally around 0 degrees. 9 wind and ventilation. Where there is wind, please take the measures to stop the network, and the appropriate ventilation measures should be taken in the room. Points of MIG welding of stainless steel pipe and matters needing attention: 1 using the constant voltage welding power supply, DC reverse polarity (wire connected to the positive electrode) 2 general use of pure argon (purity of 99.99%) or Ar+2%O2, flow to 20~25L/min is appropriate. 3 arc length, stainless steel MIG welding, generally in the injection of the transition conditions down the welding, the voltage to be adjusted to arc length in the degree of 4~6mm. 4 wind. MIG welding is easy to be affected by the wind, and sometimes the breeze and the air holes, so the wind speed in the 0.5m/sec above places, should take measures to wind. Key points of welding flux cored wire for stainless steel pipe and points for attention: 1 using the constant voltage welding power supply, DC welding by reverse polarity. The use of general CO2 welding machine can be applied, but the pressure of the wire feed wheel, please slightly. 2 the protection gas is generally the carbon dioxide gas, the gas flow by 20~25L/min is more suitable. 3 the distance between the nozzle and the workpiece is suitable for 5~25mm. 4 dry stretch length, the general welding current is about 250A below 5mm, about 250A when 20~25mm is more appropriate. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

In the past 30 years, global stainless steel output has been an average of more than 5% growth rate. In recent years, different regions of the world steel production is different, while the stainless steel production in Asia has a remarkable increase. Although the development of stainless steel in less than 100 years, but the stainless steel has been shown to be a metal material production growth is the fastest, and its production in recent years the growth rate even more than the plastic production growth rate. Stainless steel production has such a high growth rate of driving force lies in it has some of the characteristics of: resistance to corrosion and oxidation resistance and high strength to weight ratio, good rolling formability, weldability and low-temperature toughness etc.. In the past 10 years, the average growth rate of the stainless steel consumption Chinese and India were more than 20% and 10%. However, stainless steel consumption per capita in the two countries were only 4.1kg and 1.1kg, is still very low, which indicates that the stainless steel consumption in these two countries, there is still much room for growth. Recently, Chinese has become the world’s stainless steel market development center. China stainless steel production capacity is increasing, and in 2010 Chinese stainless steel crude steel production is expected to reach 10 million tons. Chinese and India will be the world’s two stainless steel production capacity increased substantially in the country. Because China is greatly expanded stainless steel production capacity, so the number of Chinese net imports of stainless steel will continue to decrease, resulting in the use of many stainless steel exporter stainless steel production capacity rate is low. Consumption consumption of different varieties of stainless steel stainless steel in different countries have great differences, such as the western developed country and India are quite different. In the western developed countries, white appliances and utensils industry used stainless steel accounted for total stainless steel consumption reaches the highest proportion of 37%, followed by the processing industry for 19%, transport industry is 15%, welding steel pipe industry was 12%, the construction industry is 11% and other industries is 6%. In India, up to 75% of the stainless steel for white goods and utensils, followed by the processing industry is 12%, the rest of the industry’s stainless steel consumption is less than 10%. Based on the stainless steel structure, stainless steel is generally pided into 4 categories: ferritic stainless steel, martensitic stainless steel, austenitic stainless steel, duplex stainless steel (ferrite + austenite). Austenitic stainless steel can be further subpided for chromium nickel stainless steel (AISI 300 series stainless steel) and Cr Mn stainless steel (AISI 200 series stainless steel), it depends on the addition of the accounting for the status of major alloying elements: the number of nickel and manganese. Chromium nickel stainless steel currently accounts for 2/3 of the world’s stainless steel production. As a result of manganese and chromium stainless steel and chromium nickel stainless steel are the same as the same organization structure, similar in many physical and mechanical properties. Therefore, under the high nickel prices in recent years, Cr Mn stainless steel production also increased steadily. In the past 5 years, the production of chromium manganese stainless steel production accounted for almost doubled the proportion of stainless steel production. While the world’s supply of nickel has not been synchronized with stainless steel production growth. The nickel ore grade is very low, generally between 1% to 3% grade, and the nickel refining project needs huge investment. Although nickel in stainless steel plays the role of the austenitic elements, but as in the two series of stainless steel in the main role of the alloy elements of the price but there is a huge difference. Therefore, the price of nickel chromium stainless steel with nickel price changes. Therefore, stainless steel industry to healthy development and made of stainless steel with competitiveness, we should vigorously develop without nickel and low nickel ferrite stainless steel, Cr Mn austenitic stainless steel and duplex stainless steel. In addition to the stainless steel with high strength, good formability and good welding performance quality, it also has good corrosion resistance, can be used in many corrosive environments. The pitting index can be used as a measure of corrosion resistance. Adding nitrogen and lower carbon content can be easily double phase stainless steel has good welding performance. As of now, the super resistance to stress corrosion cracking performance based on the application of duplex stainless steel has been expanded to the oil and gas industry, petrochemical industry, papermaking industry, desalination plant, pollution control equipment etc.. In many applications, dual phase stainless steel containing 22%Cr, 5%Ni and 3%Mo 2205 have replaced some of the austenitic stainless steel series, such as 317L and higher nickel content 904L. Resistant to pitting index more than 40 super duplex stainless steel, such as 2507 has been used for shipbuilding, chemical and oil industries with high strength and in extreme environment use, such as containing chloride solution in use. Despite the nickel and molybdenum content is low, but its resistance to corrosion resistance equivalent to 5% to 6% Mo high alloyed super austenitic stainless steel containing. Based on its high yield strength, duplex stainless steel and super duplex stainless steel can greatly reduce the use of the steel weight. In recent years, a number of nickel – dual phase stainless steel has been developed. In this kind of duplex stainless steel, some nickel is replaced by manganese and nitrogen. This kind of dual phase stainless steel for oil and deep sea pipeline containing 20%Cr, 16%Ni, 5% Mn, 002%C and 013%N 19d UNSS32001 and for water desalination plants, paper industry, dam and bridge containing 21%Cr, 15%Ni, 5% Mn and 022%N ldx2101 UNSS32101. Other low molybdenum, nickel free dual phase stainless steel can be comparable with the expensive 316, with super strength, wear and corrosion resistance, while reducing the weight of containing 23%Cr, 4%Ni dual phase stainless steel. It is widely used in the paper industry as well as near shore equipment. Ferritic stainless steel has a high chromium content and contains 1% to 2% of the molybdenum, the relatively traditional ferrite has a good corrosion resistance. The carbon and nitrogen content of the super ferrite stainless steel must be very low (usually less than 100ppm), in order to reduce the ductile brittle transition temperature. This can be achieved by vacuum decarburization process. 30%Cr super ferritic stainless steel containing 22%, 24%, 26% and Ti/Nb with molybdenum and carbide stabilizing effect has been developed. In addition, the corrosion resistance of the super ferritic stainless steel containing 15%Mo and 22%Cr can be comparable to 316, while the Cr content is much higher. These super ferrite material is the first choice for the roof and exterior wall of the building, such as the coast, the reason is that these stainless steel has a high corrosion resistance and compared to the austenitic stainless steel has a lower coefficient of thermal expansion. Cr Mn stainless steel has been in Germany for a long time of commercial production. When the Korean War began a shortage of nickel, prompting enterprises to further develop chromium manganese stainless steel. After the end of the war, the shortage of nickel has improved, and the company has returned to the development of the stainless steel. At that time, 200 series of stainless steel production costs are relatively low. With the advent of argon oxygen decarburization process, people can use cheaper high carbon ferromanganese and gaseous nitrogen alloying. In fact, in the production process of Cr Mn stainless steel, the consumption of expensive argon is lower than that of Cr Ni stainless steel. AISI201 Cr Mn stainless steel has produced in many countries, including the United States and Japan, and has successfully application in the following areas: Food and beverage industry (cutlery, kitchen utensils), white home appliance industry (oven, washing machine, microwave oven, refrigerator, beverage vending machine), construction (partition, stair handrail, support structure), transportation (wagon, trucks, trailers, subway cars, trams, piston ring). By alloying with copper, the drawing ability of Cr Mn series stainless steel can be improved, so as to further expand its application field. Adding 15% to 2% of the copper in the AISI201 stainless steel, the stainless steel has a very good drawing property. AISI201 and 202 are developed in the process of using ingot. With the continuous casting process, argon oxygen decarburization process and use ladle furnace were more precise composition control and in the rolling of better control of casting billet heating temperature can produce more saving alloying elements in the strip. These alloying elements endow the stainless steel with a higher strength, good drawing, welding and corrosion resistance. Super martensitic stainless steel Super martensitic stainless steel is the latest entry into the “super steel” family of steel. Although the super martensitic stainless steel has a very low carbon content and a martensitic structure, it combines high strength and excellent low temperature toughness and can be welded, and has sufficient corrosion resistance in many applications. The application of the super martensite containing 13% to 17%Cr and the content of nickel and molybdenum in the petroleum and natural gas industry is increasing continuously. India stainless steel production in the past 15 years, India stainless steel production with an average annual growth rate of 14%, while the world’s average annual growth rate of only 6%. During this period, India stainless steel production accounted for the percentage of the world’s total output has increased from 2% to 7%, and the varieties of stainless steel production in India also occurred in the rapidly changing, the 200 series stainless steel production increased by a large margin, the 300 series stainless steel production is from 1990 to 2002 accounted for 95% of the total output dropped to 22% in 2004 – 05. A large number of India AOD furnace completed and put into operation to promote the production of chromium manganese stainless steel in India. In India, 75% of the market share of stainless steel tableware, kitchen supplies and white home appliances. And in the last century 80’s, the industry accounted for 85% of the market share. India’s transport industry, the consumption of stainless steel is expected to be greatly improved. At present, the transportation industry of stainless steel consumption is 230 thousand T, to 16 to 2015 years will increase to 250 thousand T. India auto production in recent years has been greatly increased, while the auto parts industry is also involved in global competition, the export volume has also increased dramatically. Because of the strict emission standard of automobile exhaust, the use of stainless steel in automobile and motorcycle exhaust system will be more and more. In railway passenger cars, many of the equipment and furnishings are also consumed stainless steel. Each car subway car consumption of stainless steel about 12t; and to the 2010 Delhi city underground railway will need 1000 buses and other major cities in India also in plans to use the transportation mode for Derry City underground railway, which will consume a large number of stainless steel. The new truck all coal in the future will also be made of stainless steel or aluminum. So, in the stainless steel to provide users with more value and maintain its position before the face more challenges. conclusion 1 Asian stainless steel consumption has increased significantly. 2 global stainless steel production capacity in excess of the case, the future of new production capacity will be mainly in China and India. 3. Argon oxygen decarburization technology and vacuum oxygen decarbonization technology based on the emergence and the improvement, the new super stainless steel in the future will get continued development, with a very low carbon and nitrogen content of super martensitic stainless steel and super iron (steel will appear; high nitrogen content, can be more economical production, with super performance of new austenitic stainless steel, double phase stainless steel, the new super austenitic stainless steel and new super duplex stainless steel will be available. . expensive some varieties of stainless steel will be replaced by the appropriate, cheap varieties: replaced with double phase stainless steel will be almost no alloy super martensitic stainless steel; austenitic chromium nickel stainless steel and nickel chromium molybdenum austenitic stainless steel will be ferritic stainless steel, Cr Mn austenitic stainless steel and nickel duplex stainless steel replaced; super austenitic stainless steel will be lower alloy content of super duplex stainless steel alternative. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Small diameter high-pressure boiler tube surface defects that affect the quality, mainly due to waste generation. Defect localization and analysis, mainly for the defect depth 0.2 ~ 0.5mm, the length of 20 ~ 50mm superficial cracks, which causes the piercing of minute defects generated in the process, or rolling the first and second plurality of specifications by trauma, four planes in the rolling process by the inner surface of the high-pressure boiler tubes oxide residue effects formed in the slide and scarring defects, these defects after rolling sheets minus aggravated squash and stretch. Through the high-pressure boiler tube double length number tracking found that injury concentrated in the steel tube end report first, twice-foot (from the pipe end within 25m), is closely related to the capillary head borax oxide accumulation, small-diameter steel pipe defect in the front of the capillary the higher the ratio of the rolling zone appears. Through the above analysis we can draw the following conclusions: (1) the presence of perforated capillary end in addition to the adverse effects of oxidation issues that need to be improved. (2) the presence of a work surface and rolling rack rolling defects within the designated road, we need to start to be addressed from the hole, lubrication improvement. (3) Save dryer sheets high total reduction ratio in diameter, in the presence of the shortage of raw tube defects can not be completely eliminated during rolling. To reduce and control deficiencies, should take the following improvement measures; (1) production of 30 ranging from a head injury will change, because the elimination of head generated within the fold. (2) the production of small diameter high-pressure boiler tubes use no injuries mandrel, the mandrel to eliminate defects produced. (3) pre-production of the perforated guide and roll away from the measurement, ensure ovality coefficient control within the scope of process requirements. (4) save photos Save machine wall rate increased to 10 to 15% (previously 5-8%). (5) finishing temperature controlled at above 860 ℃, increase reheating temperature section 5-8 (1020 +/- 10) ℃, save high-pressure water descaling according to the outer surface of the control in the case of 8 ~ 18MPa, improve Zhang reduction machine exit velocity to 5.5m / s or more. (6) selection of phosphate instead of sodium sulfide as the main additive borax oxide skin reaction due to phosphate and form a melt, reducing rolling gather at the inner surface of the roll gap during rolling and rolling objects, reducing internal scarring and Stroke tract of chance. (7) continue to track and analyze the state of the rolling surface anatomy of the card after the tube and the actual measurement data, for rolling the first and second planes pass design improvements make mature ideas, design principles and elements, improved rolling pass 185,151 designed to reduce the total elongation factor, reducing the process Zhang reducing the rate of reduction machine single purpose, to improve the surface roughness of the inner pipe. (8) this study of existing conditions increase the speed of the mandrel stopper way.

SUS304 stainless steel pipe: with good corrosion resistance, heat resistance, low temperature strength and mechanical properties, stamping bending and other thermal processing is good, no heat treatment hardening phenomenon, no magnetism. Widely used in household items (1, 2 types of tableware), cabinets, indoor pipelines, water heaters, boilers, bathtub, auto parts, medical equipment, building materials, chemical, food industry, agriculture, marine parts SUS316 stainless steel pipe: corrosion resistance and high temperature strength is particularly good, can be used under harsh conditions, good processing hardening, no magnetism. Marine equipment, chemicals, dyes, paper making, oxalic acid, fertilizer production equipment, photography, food industry, coastal facilities SUS316L stainless steel pipe: better corrosion resistance than SUS316, high temperature strength slightly poor, can be used in harsh conditions, good processing hardening, no magnetism. Marine equipment, chemicals, dyes, paper making, oxalic acid, fertilizer production equipment, photography, food industry, coastal facilities SUS321 stainless steel pipe: heat resistant materials, vehicles, vehicle exhaust pipe, boiler cover, pipeline, chemical device, a heat exchanger. With good corrosion resistance, heat resistance, good high temperature strength and high temperature oxidation performance, machining, welding performance is good. SUH409H stainless steel pipe: processing performance, good welding performance, high temperature oxidation resistance is good, can withstand the temperature range from room temperature to 575 degrees Widely used in automobile exhaust system SUS420J2 stainless steel pipe: quenching hardness is widely used in the processing of cutting tools, pipe nozzle, valve, plate, tableware SUS430 stainless steel pipe: low thermal expansion rate, molding and oxidation resistance is good for heat resistant appliances, burners, household electrical appliances, 2 types of tableware, kitchen sink. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Hot-rolled seamless steel pipe production base deformation process can be summarized as three stages: perforation, extension and finishing.  The main purpose of the perforation process is to become a solid round billet piercing hollow shell. Capillary in the specifications, accuracy and surface quality can not meet the requirements of the finished product, further improvements are needed to deform the metal through. The main purpose of the stretching machine is further reduced sectional view (main compression wall) for a larger axial extension, so that the capillary improved dimensional accuracy, surface quality and organizational performance.  After stretching machine rolled steel pipe shortage collectively need further molding mill in order to achieve the requirements of the finished pipe. Rolled steel due to pass in the method widely used in the production of seamless steel tubes. So far, due to the method pass rolling steel can be pided into two categories: core pension without rolling rolling (hollow body rolling), and with the mandrel. Sizing machines, reducing mill and stretch reducing mill belonging to the hole without mandrel type continuous rolling mills are generally coffin. Its main purpose is to reduce the diameter of the deformation process or sizing get finished steel, the wall thickness of process control, can make thinning, thickening or nearly unchanged.  All the traditional hole-type rolling machine with mandrel belong to extend machine. The main purpose is to reduce the deformation process perforated capillary wall thickness and outer diameter roll passes in the deformation zone and the mandrel posed, for a larger axial extension. At the same time a certain improvement in the organization, performance, accuracy, surface quality.

Forging is one of the oldest metal shaping processes known to man. The process of forging metal involves beating or hammering a workpiece over or into a die, template, or jig, forcing the metal to flow into the desired shape. Forging is generally pided into three process types based on the temperatures to which the metal is heated prior to forging. These are hot, warm, and cold forging, with hot and warm processes employing workpiece temperatures ranging from several hundred degrees to over 2,000° Fahrenheit. Cold forging, on the other hand, sees the working steel heated to no more than three-tenths of its recrystallization temperature. Cold forging is one variation of the forging metal-shaping process that involves forming or shaping metal parts through a process of applying powerful, localized compressive forces. Cold forging is carried out with the metal generally kept at or slightly above room temperature with the temperature always maintained at or below three-tenths of the recrystallization temperature of the metal being shaped. The compressive forces involved in cold forging may be applied by hand with a hammer or by powered sources, such as dropforge machines. In most cases, the metal is forced into a die in the shape of the finished product or around open templates or jigs. Cold forging offers several distinct benefits over hot forging processes, which include better surface finish, improved dimensional stability, and lower production costs. Cold forging is defined as working a metal below its recrystallization temperature, but usually around room temperature. If the temperature is above 0.3 times the melting temperature (on an absolute scale) then it qualifies as warm forging. Hot forging is defined as working a metal above its recrystallization temperature. The main advantage of hot forging is that as the metal is deformed the strain-hardening effects are negated by the recrystallization process.

A, the classification of stainless steel pipe 1, according to the production method of classification: (1) seamless tube, cold drawn tube, extrusion tube, cold rolling tube. (2) welded pipe: (a) according to the process classification, gas shielded welding pipe, arc welding, resistance welding pipe (high frequency and low frequency). (b) the weld points – straight seam welded pipe, spiral welded pipe. 2, according to the cross section shape classification: (1) the circular steel tube; (2) rectangular tube. 3, according to the classification of wall thickness, thin-walled steel pipe, thick-walled steel pipe 4, classification: (1) according to the use of civil pipe runs round tubes, rectangular tubes, pipe, generally used to decorate, building, structure, etc; (2) industry pipe: steel tube for piping, general steel pipe (drinking water), the mechanical structure for piping/fluid conveying pipe, boiler heat exchange tube, food hygiene, etc. Commonly used in industrial fields such as petroleum chemical industry, papermaking, nuclear energy, food, beverage, pharmaceutical and other industries of fluid pipeline is required to be higher. Second, the seamless steel tube Stainless steel seamless steel tube is a hollow section, no seams of strip steel. 1. Seamless steel tube manufacturing technology and process: Smelting ingot > > > of steel rolling cutting > > > peel > perforation annealing pickling cold drawn on ash > > > crop > > acid into the Treasury 2. The characteristics of the seamless steel pipe: We it is not hard to see from the above process: first, the wall thickness of the product is thick, it is more economical and practical, the thinner wall thickness, its processing cost will rise significantly; Secondly, the process of the product decided to its limitations, generally low precision seamless steel pipe: low surface brightness, uneven thickness, tube length cost is high, and the appearance is not easy to remove and pitting, black spots inside; Thirdly, its detection and plastic must offline processing. As a result, it in high pressure and high strength material, mechanical structure embodies its superiority. Third, welded steel pipe Welded steel pipe or welded pipe, it is to use steel plate or steel strip after crimp units and dies made of welded steel pipe. 1. Steel > > > article points of molding dissolves > induction heat treatment > light inside and outside weld treatment > > eddy current testing of plastic > diameter > laser caliper > > acid into the Treasury 2. The characteristics of the welded steel pipe: We it is not hard to see from the above process: first, the product is continuous online production, wall thickness is thicker, the unit and dissolves equipment investment, the less it has economical and practical. The thinner wall thickness, the input-output ratio will be reduced; Then determine its advantages and disadvantages of the product process, general high precision welded steel pipe, wall thickness uniformity, high brightness tube appearance (level determines the surface of the steel plate of steel tube surface brightness), can be arbitrary length. As a result, its application in high precision, low pressure fluid embodies its economy and aesthetics. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Seamless steel pipe market competition at present, due to the limitation of its production process, the production cost of seamless steel tube has been high, resulting in the gradual decline in its economic benefit. As China’s metallurgical industry technology progress, instead of the seamless steel tube ­ new products also emergence, so new product whether meet the indicators of seamless steel tube? Between them and what is the nature of the difference? Here are two kinds of confusing products on the market, hot tension reducing the difference between steel pipe and straight seam ­ welded pipe briefly. 1, the weld quality directly decides the quality of welded pipe, and the greatest difference between welded pipe and seamless pipe. Straight seam welded pipe after high frequency welding, straight seam cimc carbon can’t eliminate, weld and parent just join together, has not completely melt into an organic whole of ­ yield to the test of time and high pressure. Hot tension reducing mill steel after high frequency welding pass overall 800 degrees high temperature heating, the overall annealing, then open change processing, after this series of process, weld and parent organizations have the same performance, completely melt into an organic whole, very well done from the slit to the seamless transition. 2, process of the product quality differences caused by different hot tension reducing mill steel after high frequency welding also conducted a straight seam welded pipe is no process: online to remove burrs inside and outside. ­ of the existence of burr will affect tube fluid flow, burr blocking the normal flow of the fluid, resulting in a spiral. According to the principle of fluid mechanics, local pressure will increase, weld stress non-uniform welded pipe also greatly reduce the coefficient of insurance, hot tension reducing mill steel pipe production technology ­ fully considers the burr is dangerous, for deburring, making it even wall thickness, and the seamless tube no difference in appearance. So from this point of view, hot tension reducing mill steel pipe also completed from the slit to the seamless transition. Of course, the difference between the two is not just limited to the above three points, but enough to explain the straight seam welded pipe and hot tension reducing pipe, there are great differences. The latter on the basis of straight seam welded pipe and the online clearing burr, inside and outside the overall heating ­, deformation and a series of new processing technology, making it have a qualitative leap, can be widely used in the field of in high pressure, and straight seam welded pipe of water gas delivery can only be limited to the low pressure environment. Although there are some people for seamless steel tube, hot tension reducing ­ steel pipe, straight seam welded pipe and understanding in the fuzzy state, but believe that with the passage of time, the practice proved that people will recognize the hot tension reducing mill steel pipe products, this unique in the seamless pipe market is more and more ­ bigger role, create greater economic benefits for the society! Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Cold rolled and cold drawn belongs to cold working process, but the molding process and the principle, process equipment, molding capability, for purposes are all different. Cold rolling is the temperature at a temperature below the recrystallization method of cold rolled slab thickness needs; cold drawn is the use of force to pull the metal timber from the hole in the processing method. Should be said that both the dimensional accuracy and surface finish almost, because in standard, cold drawn tubes and cold rolled tubes are generally uniform provisions, of course, the price is almost the same. However, the difference is that for the small size of the pipe, cold drawing method must be used to produce it. Cold drawn tubes for small sizes more suitable diameter of 150mm or more difficult to use than cold drawn up, there are no such large-diameter cold drawn tubes, the United States and South Korea are more common, drawing process better, seamless , so the price may be a little higher than the cold rolling.

Why not easy to corrode stainless steel pipe? All metal and atmospheric oxygen in the reaction, formed in the surface oxide film. Unfortunately, in the ordinary carbon steel pipe on the formation of the oxidation iron oxide continue, kept expanding rust, eventually forming holes. Can use paint or resistant to oxidation of the metal (for example, zinc, chromium and nickel) on plating to ensure that the carbon steel pipe surface, however, as we know, the protection is only a thin film. If the cover was damaged, the following steel began to rust. Corrosion resistance of stainless steel pipe depends on chrome, but because of the chromium is one part of the steel, so the protection method is not the same. In the chromium content reaches 10.5%, atmospheric corrosion resistance of steel increased significantly, but the chromium content is higher, although still can raise corrosion resistance, but not obvious. Reason is that with chromium alloying of steel pipe processing, change the type of surface oxide became similar to that of pure chromium oxide is formed on the metal surface. This tight adhesion of the surface of the rich chromium oxide protection, to prevent further oxidation. This kind of extremely thin oxide layer, you can see on the surface of the steel pipe through natural luster, make the surface of the stainless steel pipe has a unique. And, if damaged surface, the exposed surface of the steel pipe and atmospheric response to repair itself, to form the oxide “passivation membrane, ” continued protection. Therefore, all stainless steel pipe elements have a common characteristic, namely the chromium content in more than 10.5%. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

In general, simple chromium nickel, and chromium manganese nitrogen austenitic stainless steel pipe not only used for rust and oxidation resistance of medium (such as nitric acid, etc.) conditions, the use of molybdenum austenitic stainless steel as the important alloy elements added to the further expansion of the use of steel, the effect of molybdenum is mainly in the reducing medium steel (than – H2SO4, H3PO4, and some organic acid and urea environment) corrosion resistance, and improve the pitting corrosion and crevice corrosion resistance and other properties of the steel. 1, molybdenum impact to the organization Chromium and molybdenum are the formation and stability of ferrite and expand in ferrite phase element, molybdenum and the ability of ferritic chromium. Also promotes molybdenum austenitic stainless steel pipe, intermetallic phase in the sigma phase, for example, kappa, predominate and Laves equal precipitation, corrosion resistance and mechanical properties of steel will produce adverse effect, plasticity, toughness, farewell is for keep the austenitic stainless steel pipe single austenitic organization, along with the increase of the content of molybdenum in steel austenite formed elements (such as nickel, nitrogen and manganese) levels will increase, in order to keep the steel ferrite and austenite balance between form elements. 2, molybdenum impact on performance Oxidation of the molybdenum in the austenitic stainless steel pipe was not significant, so when cr-ni austenitic stainless steel pipe in single austenitic organization and no intermetallic precipitation, the effect of molybdenum on the mechanical properties at room temperature is not big, but along with the increase of the content of molybdenum steel high temperature strength increase, such as persistent, creep properties are improved, thus containing molybdenum stainless steel tubes are often in high temperature applications, however, the addition of molybdenum make high temperature deformation resistance of steel increases, and often there is a small amount of delta ferrite in steel and molybdenum stainless steel of workability than does not contain molybdenum steel for the poor, and molybdenum content is higher, the hot working performance is bad, in addition, the molybdenum austenitic stainless steel easy one million kappa (sigma) precipitation, predominate in this will significantly worse plasticity and toughness of steel, therefore in molybdenum austenitic stainless steel production, equipment manufacturing and application in the process, must pay attention to prevent the formation of intermetallic phase in steel. Molybdenum in the austenitic stainless steel pipe, the main role is to improve the steel tube of the reducing medium corrosion resistance and resistance to corrosion, crevice corrosion resistance and other performance (304 stainless steel round) respectively on chrome molybdenum nickel austenitic stainless steel in nitric acid, sulfuric acid, acetic acid, phosphoric acid and urea, etc. The effect of medium corrosion resistance, it can be seen that, in addition to oxidizing medium HNO3 in place, the role of molybdenum are beneficial and therefore molybdenum austenitic stainless steel pipe generally don’t day nitric acid corrosion resistance, unless in the nitric acid containing F -, Cl – plasma, while the effect of alloying elements molybdenum reducing medium resistance of austenitic stainless steel tubes, the reason of surface corrosion and crevice corrosion is not entirely clear, but a lot of experimental has pointed out that corrosion resistant effect of molybdenum is only contains high amount of chromium in steel is effective, molybdenum mainly strengthening of chromium in steel corrosion effect, at the same time, the corrosion inhibition of molybdenum formed after acid salt have been experimentally. In resistance to stress corrosion of high concentration chloride solution, although molybdenum alloy elements on the reducing medium resistance of austenitic stainless steel of the resistance to pitting corrosion and crevice corrosion is not entirely clear, but a lot of experimental has pointed out that the effect of molybdenum only when contains high amount of chromium in steel is valid, molybdenum mainly strengthening of chromium in steel corrosion effect, at the same time, molybdenum salt molybdate formed after the cushion has been experimentally. Due to the more common cr-ni austenitic stainless steel pipe in water medium containing trace chlorine and oxygen saturation, the stress corrosion and pitting corrosion as origin, therefore molybdenum nickel chromium molybdenum austenitic stainless steel pipe due to pitting corrosion resistance is higher, so in practice often than does not contain molybdenum steel tube has better resistance to chloride stress corrosion performance. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

316 stainless steel angle bar as matrix is beyond 60%, for complex high alloy steel, nickel, molybdenum and other alloying elements, its biggest characteristic is corrosion resistant ability strong, but not rust stainless steel is not absolute. In coastal areas, or some severe air pollution in local truly, when the chloride ion content in the air is larger, disclosed in stainless steel appearance atmosphere could have some rusty spot, but only the rust stain appearance, not erosion inside stainless steel substrate. On the ocean, 304 stainless steel angle bar, there is no 316 stainless steel angle bar corrosion resistant performance is good. Stainless steel angle bar under the condition of must also will rust. Stainless steel has arrived when atmospheric oxidation ability – that is, stainless, and have in acid, alkali, salt corrosion medium is not easy to – corrosion resistance. But its corrosion resistant ability of intrusive is with its own chemical composition of steel, and each form, use conditions and types of medium and modifying. Stainless steel is to rely on the appearance of a layer of thin and solid precision constant rich chromium oxide film (protective film), avoiding continuous oxygen atoms of continuous infiltration and oxidation, and corrosion resistance ability. Once you have a reason, make the make the appearance of membrane destroyed will constitute a rusty spot. Stainless steel angle bar rust form has the following several reasons: A.. Deposited on stainless steel angle bar surface or heterogeneous metal particles of dust of other metal elements attachments, in the humid air, vapour, both between the attachments and stainless steel together as a micro battery, motivated by the electrochemical reaction, maintain membrane have been damaged, called the electrochemical corrosion. B. stainless steel angle bar adhesion appearance with organic matter (such as melon seeds, noodle soup, sputum, etc.), oxygen in water conditions, composed of organic acid, long time is organic acid corrosive to metal surface. C. stainless steel angle bar adhesion appearance with acid, alkali, salt substances (e.g., decorate the walls of caustic soda and lime water splash), a department of corrosion. D. where there is pollution in the air (e.g., contains a lot of sulfur, carbon oxide, atmospheric nitrous oxide), stainless steel angle bar in water vapor, sulfuric acid, nitric acid, acetic acid, liquid, provoked chemical corrosion. 5. Appearance is stainless steel angle bar weapon damage, and then destroy the appearance of a protective film. “Accordingly, stainless steel angle bar is not rust is not absolute, but a relative and conditional. Such as; 304 stainless steel angle bar, 316 stainless steel angle bar. Until the current is not under any circumstances not rust stainless steel Angle, but, still can only correct use and protection of persistent stick to the light and do not rust. Source: wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)