Breakout accident is great danger of casting production in the production of the accident. Breakout accident, not only affects the continuous casting, serious damage to the mold, roller, increasing the amount of continuous casting equipment repair and maintenance costs, resulting in huge economic losses, but also a huge security risk. It is estimated that a "normal" breakout accident resulting directly or indirectly, the economic loss will reach $ 200,000.
To reduce the breakout occurs, it has been developing breakout prediction system. By sensors mounted on the mold, it has been able to use automated control system to effectively reduce the breakout rate.
The first breakout prediction are: (1) estimates mold water temperature; (2) detection of mold and the friction between the slab; (3) buried in the local heat flux sensor monitoring; (4) in the copper mold embedded copper thermocouples for thermal monitoring. This method is now widely used, proven to be more effective in detecting and forecasting bond breakout technology. Based on temperature detected for breakout prediction of the theory is: As the breakout is often accompanied by copper mold temperature, mounted on copper by monitoring the temperature of the thermocouple on the changes made according to certain methods to determine the breakout.
Overview of the breakout prediction based on temperature prediction methods, there are three main technical approaches. They are the logic method, neural network methods and multivariate statistical methods.
Most of the new steel mills in China in recent years on the casting machine used in breakout prediction system is based on logic approach produced steel pipe,like seamless steel tube and piling pipe for construction. Implementation of the forecasting method does not require a lot of raw data, especially for the new casting machine. But the logic to set the parameters and conditions of the type of steel, technology and the environment have a great relationship, the model has some limitations.
Neural network breakout prediction method using neural network technology to the scene of breakout data for learning, coupled with the process conditions necessary for a breakout to identify the characteristics of the thermocouple temperature curve, and then make a breakout prediction . Complete neural network system must be able to significantly increase the breakout prediction accuracy, but the neural networks that exist in the breakout prediction of its limitations. Complete neural network must be a large number of training samples, the sample will not lead to a comprehensive network of dysfunction. Second, continuous casting machines working conditions are very complex, many factors, access to sample data on serious interference, in order to be completely ruled out with a sample of the noise is almost impossible. Casting in some special circumstances, such as open water, for the final package and pouring so neural network system to become unstable; for the new continuous casting machine, neural network is not feasible, must be combined with other methods.
Multivariate statistical process control (MSPC) method is based on principal component analysis (PCA) and partial least squares (PLS) method for continuous monitoring of process control methods. In the continuous casting process, especially in the breakout prediction process, MSPC method very few applications.
Saturday, June 8, 2013
Thick-walled stainless steel roll forming method
Roll forming method using thick-walled stainless steel tube rolling machine for rolling sheet metal is also available a variety of thick-walled stainless steel tube, steel pipe manufacturing process of this method is very simple, it does not require any special tooling to properly adjust the three-roll only between 678 distance, and if the diameter required for bending forming insufficient material utilization of this method to implement a high heat, but the drawback is that not only production but production of seamless steel tube joints. This gap welding to sew through follow-up, modern welding technology for welding cracks grow continuously improved, but performance is difficult to ensure the welds are consistent with the bulk properties, as well as the quality of welds, because the risk of the pipeline to withstand high-pressure fluid section a vertical cross-section, rolled steel welds and exactly vertical, so the pipe to withstand high temperature and pressure generally do not roll steel.
Thick-walled stainless piling pipe to the inventory of the market has been gradually advancing, the current gradually increased upside risks to price, do not rule out the recent correction may Steel City again, thick-walled seamless steel pipe stock price is lower than the strong spot market prices will steel will be forced to walk up. Thick-walled seamless steel pipe production capacity of the market growth is slow, once the market recovery and prosperity, few big steel mills surrounded them, China's steel industry will create a positive external environment. Adjustment disorder at home and could not ex-steel city, large enterprises are also actively involved in steel production, to reduce the homogenization of competition. Thick-walled seamless steel pipe production country backward steel production capacity of the case has not been much progress, mainly iron and steel enterprises are still operating at full capacity production. Thick-walled seamless steel prices at home and by consumer demand season, the impact of steel, at any time may be bottoming out, or even thick-walled seamless steel pipe sales rebounded strongly.
Thick-walled stainless piling pipe to the inventory of the market has been gradually advancing, the current gradually increased upside risks to price, do not rule out the recent correction may Steel City again, thick-walled seamless steel pipe stock price is lower than the strong spot market prices will steel will be forced to walk up. Thick-walled seamless steel pipe production capacity of the market growth is slow, once the market recovery and prosperity, few big steel mills surrounded them, China's steel industry will create a positive external environment. Adjustment disorder at home and could not ex-steel city, large enterprises are also actively involved in steel production, to reduce the homogenization of competition. Thick-walled seamless steel pipe production country backward steel production capacity of the case has not been much progress, mainly iron and steel enterprises are still operating at full capacity production. Thick-walled seamless steel prices at home and by consumer demand season, the impact of steel, at any time may be bottoming out, or even thick-walled seamless steel pipe sales rebounded strongly.
Tuesday, June 4, 2013
How to raise the temperature by controlling the welding seam steel pipe piling surface quality
The strip is into the welded pipe unit, the multi-channel roll rolling, gradually rolled strip steel, formed with an opening gap round tube, adjust the amount of reduction squeeze rollers, so that the weld gap control in 1 ~ 3mm, and to weld ends flush. If the gap is too large, resulting in reduced proximity effect, eddy current lack of heat, poor weld joint between grain yield incomplete fusion or cracking. If the gap is too small, causing the proximity effect increases, excessive soldering heat, causing the weld burning; or weld by extrusion, rolling to form a pit, the impact piling pipe weld surface quality.
Soldering temperature is mainly affected by the impact of high-frequency eddy current heating power, according to the relevant formula, high-frequency eddy current frequency heating power is mainly affected by the impact of thermal power and eddy current excitation frequency is proportional to the square; while current excitation frequency but also by the excitation voltage, current and capacitance, inductance. Excitation frequency formula is:
f = 1 / [2π (CL) 1/2]
The formula: f-excitation frequency (Hz); C-excitation circuit of the capacitance (F), capacitance = power / voltage; L-excitation loop, inductance = flux / current
The above formula, the excitation frequency of the excitation circuit capacitance, inductance is inversely proportional to the square root, or the voltage and current proportional to the square, as long as the change in the circuit capacitance, inductance, or voltage and current can change the size of the excitation frequency, so as to achieve control of welding temperature. For low carbon steel, welding temperature control in the 1250 ~ 1460 ℃, can meet the pipe wall thickness 3 ~ 5mm penetration requirements. In addition, the soldering temperature can be achieved by adjusting the welding speed.
Heat input is low, the heated soldering temperatures reach the edge of the weld metal structure remains solid, forming incomplete fusion or penetration; when the input hot enough, over the edge of the weld is heated soldering temperatures, resulting in over-burn or melt drops, so that the weld formation Cave.
Soldering temperature is mainly affected by the impact of high-frequency eddy current heating power, according to the relevant formula, high-frequency eddy current frequency heating power is mainly affected by the impact of thermal power and eddy current excitation frequency is proportional to the square; while current excitation frequency but also by the excitation voltage, current and capacitance, inductance. Excitation frequency formula is:
f = 1 / [2π (CL) 1/2]
The formula: f-excitation frequency (Hz); C-excitation circuit of the capacitance (F), capacitance = power / voltage; L-excitation loop, inductance = flux / current
The above formula, the excitation frequency of the excitation circuit capacitance, inductance is inversely proportional to the square root, or the voltage and current proportional to the square, as long as the change in the circuit capacitance, inductance, or voltage and current can change the size of the excitation frequency, so as to achieve control of welding temperature. For low carbon steel, welding temperature control in the 1250 ~ 1460 ℃, can meet the pipe wall thickness 3 ~ 5mm penetration requirements. In addition, the soldering temperature can be achieved by adjusting the welding speed.
Heat input is low, the heated soldering temperatures reach the edge of the weld metal structure remains solid, forming incomplete fusion or penetration; when the input hot enough, over the edge of the weld is heated soldering temperatures, resulting in over-burn or melt drops, so that the weld formation Cave.
Piling steel surface treatment process
Piling pipe uses a dual wire, double submerged arc welding under the flux layer of the method using the wire and solder layer between the flux produced by the combustion heat of the arc, the molten solder and base metal wire is formed. The main features of the product one-sided submerged arc welding, not only the deposition rate, but also has deep penetration capability; Second, the arc and the weld zone is well protected, weld quality, compact, good weld appearance and smooth, able to meet various performance requirements of the weld.
Piling steel surface treatment process:
1 steel surface treatment, piling steel pipe manufacturer in order to avoid formation of oxide scale unwinding and formation process, shall establish a board cleaning device.
2 steel edge processing, steel side piling up rust and deburring devices to reduce the porosity may occur. The location of the best cleaning device installed in edge milling machine, cutting disc, the device structure is a plane wave can adjust the position of the gap capstan, fluctuating pressure plate edges.
3 weld profile, weld factor is too small, narrow and deep weld, gas and inclusion is not easy come, easy formation porosity and slag. General weld coefficient control at 1.3 - 1.5, thick-walled pipe welding maximum, minimum, thin walls.
4. Reduce secondary magnetic field in order to reduce the impact of magnetic blow, to make the position of the workpiece welding cable connections only from the solder terminals, avoiding some welding cable to the workpiece to produce secondary magnetic fields.
Piling steel surface treatment process:
1 steel surface treatment, piling steel pipe manufacturer in order to avoid formation of oxide scale unwinding and formation process, shall establish a board cleaning device.
2 steel edge processing, steel side piling up rust and deburring devices to reduce the porosity may occur. The location of the best cleaning device installed in edge milling machine, cutting disc, the device structure is a plane wave can adjust the position of the gap capstan, fluctuating pressure plate edges.
3 weld profile, weld factor is too small, narrow and deep weld, gas and inclusion is not easy come, easy formation porosity and slag. General weld coefficient control at 1.3 - 1.5, thick-walled pipe welding maximum, minimum, thin walls.
4. Reduce secondary magnetic field in order to reduce the impact of magnetic blow, to make the position of the workpiece welding cable connections only from the solder terminals, avoiding some welding cable to the workpiece to produce secondary magnetic fields.
Precision cold drawn steel applications and features
Cold drawn steel pipe is a pipe, that is, its production process according to a different classification, different from the hot-rolled (expansion) tube, while the high-precision cold drawn precision steel product features refers to the so-called high-precision drawing within outer diameter accuracy (tolerance range) strict external surface finish, roundness, straightness good precision steel tube uniform wall thickness. In raw wool tube or pipe flaring through the process of drawing multi-pass processing, usually in the 0.5 ~ 100T single chain or double chain drawing machine on. Cold drawn steel pipe whose diameter can go to 6mm, wall thickness can be 0.25mm, outer diameter thin-walled tube to 5mm thickness less than 0.25mm size, precision and surface quality are much better than hot-rolled (expansion) tubes, but by the process constraints, the diameter and the length are subject to certain restrictions. Precision cold drawn steel tube is drawn through large-tonnage hydraulic machine pull system produced can be used directly or through honing, scrapers used after hydraulic (pneumatic) cylinder. Of precision cold drawn steel industry after 20 years of practice, product quality and technical performance has reached world advanced countries, and has been widely used in engineering machinery, plastic machinery, textile, printing machinery, automotive shock absorbers, oil pumping pumps and concrete cylinders and other industries.
The product was a little honing, it can be directly used as hydraulic, pneumatic cylinder cylinder tube. The traditional hydraulic, pneumatic cylinder body tube of the production process is the use of hot-rolled seamless steel pipe, using boring ─ ─ rolling joint cutting process, the production process, a lot of metal waste was cut into chips, but also consume a lot of power. With China's industrial and technological development, the hydraulic cylinder technology has been widely used, according to incomplete statistics, the country each year requires a variety of specifications of the hydraulic cylinder about 380 meters, follow the old technology production of hydraulic cylinders, has been difficult to adapt production development.
Fine precision cold drawn steel pipe is a new high-skill energy-saving products. Recently, to take the technology to produce fine item has been commonly used in domestic steel hydraulic, pneumatic cylinders, coal mine bracket (pillars), oil pump pipe, jacks and other production areas. Precision cold drawn precision steel tubes to promote the use of steel for the thrifty, progressive processing efficiency, diligence and energy, reducing the hydraulic cylinder, the cylinder processing equipment investment is important.
The product was a little honing, it can be directly used as hydraulic, pneumatic cylinder cylinder tube. The traditional hydraulic, pneumatic cylinder body tube of the production process is the use of hot-rolled seamless steel pipe, using boring ─ ─ rolling joint cutting process, the production process, a lot of metal waste was cut into chips, but also consume a lot of power. With China's industrial and technological development, the hydraulic cylinder technology has been widely used, according to incomplete statistics, the country each year requires a variety of specifications of the hydraulic cylinder about 380 meters, follow the old technology production of hydraulic cylinders, has been difficult to adapt production development.
Fine precision cold drawn steel pipe is a new high-skill energy-saving products. Recently, to take the technology to produce fine item has been commonly used in domestic steel hydraulic, pneumatic cylinders, coal mine bracket (pillars), oil pump pipe, jacks and other production areas. Precision cold drawn precision steel tubes to promote the use of steel for the thrifty, progressive processing efficiency, diligence and energy, reducing the hydraulic cylinder, the cylinder processing equipment investment is important.
Spiral Pipe stress corrosion cracking causes and preventive measures
Spiral steel construction and family life is a common pipe, which shine in many industries. Here's what the spiral pipe stress corrosion cracking causes and protective measures.
Spiral Pipe Stress corrosion cracking is a lag time-related damage, which is completely similar to delayed cracking and hydrogen. Stress corrosion cracking is a low-stress brittle fracture. Spiral Pipe stress corrosion only in certain circumstances take place, only exists stress (especially tensile stress) only when the stress corrosion cracking. This stress can be applied stress, T or introduced during welding and processing the residual stress corrosion products can also be caused by the action of the expansion wedge stress. Stress corrosion cracking is a petrochemical equipment, especially oil pipes with spiral steel pipe common cause of failure. Due to stress corrosion cracking occurred unpredictability, so the petrochemical industry, the biggest hidden dangers. In the petrochemical and nuclear industries such as equipment, most of the stress caused by stress corrosion cracking is caused by the residual tensile stress, it is often superimposed on stress at work. Mainly from the device residual stresses produced during the welding residual stresses. Stress corrosion cracking is a necessary condition for coexistence of tensile stress and corrosive media, the tensile stress is an important condition for stress corrosion.
Currently, the project is widely used welding cooling after annealing treatment to eliminate residual stress, while cooling after welding residual stress is an important process, this approach is not only a waste of energy and easy to produce larger welding residual stresses. Heat treatment after welding is a new technique to eliminate the residual stress. Preheated before welding the material to a heat treatment temperature after the welding process and welding pieces of heating was continued to maintain this temperature, the soldering is completed using heat insulation cotton to its slow cooling. This method can effectively reduce residual stress and improve the stress corrosion resistance of metals. Heat treatment after welding can reduce the residual stress, and heat treatment temperature is higher, the better to eliminate the residual stress. Post weld heat treatment can effectively improve the spiral pipe stress corrosion resistance, heat treatment temperature is higher, increasing resistance to stress corrosion is more significant.
Besides, the spiral steel pipe is mainly used in water engineering, petrochemical industry, chemical industry, power industry, agricultural irrigation, urban construction, is the development of 20 key products. For the transport of liquids: water supply and drainage. For gas transportation: gas, steam, liquefied petroleum gas. For structural purposes: as piling pipe for bridges; docks, roads, buildings and other structures tube.
Spiral Pipe Stress corrosion cracking is a lag time-related damage, which is completely similar to delayed cracking and hydrogen. Stress corrosion cracking is a low-stress brittle fracture. Spiral Pipe stress corrosion only in certain circumstances take place, only exists stress (especially tensile stress) only when the stress corrosion cracking. This stress can be applied stress, T or introduced during welding and processing the residual stress corrosion products can also be caused by the action of the expansion wedge stress. Stress corrosion cracking is a petrochemical equipment, especially oil pipes with spiral steel pipe common cause of failure. Due to stress corrosion cracking occurred unpredictability, so the petrochemical industry, the biggest hidden dangers. In the petrochemical and nuclear industries such as equipment, most of the stress caused by stress corrosion cracking is caused by the residual tensile stress, it is often superimposed on stress at work. Mainly from the device residual stresses produced during the welding residual stresses. Stress corrosion cracking is a necessary condition for coexistence of tensile stress and corrosive media, the tensile stress is an important condition for stress corrosion.
Currently, the project is widely used welding cooling after annealing treatment to eliminate residual stress, while cooling after welding residual stress is an important process, this approach is not only a waste of energy and easy to produce larger welding residual stresses. Heat treatment after welding is a new technique to eliminate the residual stress. Preheated before welding the material to a heat treatment temperature after the welding process and welding pieces of heating was continued to maintain this temperature, the soldering is completed using heat insulation cotton to its slow cooling. This method can effectively reduce residual stress and improve the stress corrosion resistance of metals. Heat treatment after welding can reduce the residual stress, and heat treatment temperature is higher, the better to eliminate the residual stress. Post weld heat treatment can effectively improve the spiral pipe stress corrosion resistance, heat treatment temperature is higher, increasing resistance to stress corrosion is more significant.
Besides, the spiral steel pipe is mainly used in water engineering, petrochemical industry, chemical industry, power industry, agricultural irrigation, urban construction, is the development of 20 key products. For the transport of liquids: water supply and drainage. For gas transportation: gas, steam, liquefied petroleum gas. For structural purposes: as piling pipe for bridges; docks, roads, buildings and other structures tube.
Advantages and disadvantages of spiral steel pipe
Spiral pipe defects in the vast majority concentrated in the weld and heat affected zone, weld defects occur long it means that the probability of large, long-term constraints which is more widely used spiral welded main reason, but also has long vexed spiral pipe and straight seam pipe, especially when compared with the UOE steel pipe whose superior problem. Spiral pipe manufacturing technology development today, we should be fully and accurately evaluated and compared to rediscover long spiral weld problems. Also in use, the tube of the main stress direction, i.e. the axial direction of tube defects equivalent pipe length smaller than the straight seam; Second, because pipeline are rolled steel, impact toughness greater anisotropy, cis rolling CVN value of the direction perpendicular to the rolling direction than CVN value three times higher. Straight seam pipe stress suffered by the main shock resistance precisely perpendicular to the lowest pipe direction, and then staggered spiral steel pipe direction lowest impact resistance, so that the disadvantage of a long spiral weld transformed into advantage.
Although the spiral steel pipe is mainly used in water engineering, petrochemical industry, chemical industry, power industry, agricultural irrigation, urban construction, is the development of 20 key products. For the transport of liquids: water supply and drainage. For gas transportation: gas, steam, liquefied petroleum gas. For structural purposes: as piling pipe for bridges; docks, roads, buildings and other structures tube. However, the spiral in the welding process there are some inherent defects.
The specific requirements of the steel strip coil is forward weldability of steel, reducing the sulfur content in the steel pipe to improve the toughness and arrestability are beneficial. While also reducing sulfide inclusions to the swap, forward of steel crack resistance. The phosphorus content in the hot strip is as low as possible, because the phosphorus on the steel toughness and weldability are a hazard, thus reducing the phosphorus content can move weldability, can increase the amount of added titanium, vanadium niobium content spiral during welding weld defects may occur, so that welding defects affect the quality of the spiral, resulting in reduced service life or the spiral can be used. Generally, the spiral weld defects and porosity, and cracks undercut phenomenon.
Spiral bubble defect: During spiral welding, the weld bead in the center of bubble defects occur this situation, the main reason is that in the course of the welding of hydrogen is left in the form of bubbles within the metal. In the welding process, we need to remove the oil inside the weld, water and other ingredients, but also the need to do drying, removal of moisture, so that hydrogen gas will not remain in the inside seam. During the welding process the welding current can be avoided to increase the generation of bubbles.
Spiral undercut phenomenon: When the v-shaped groove weld edges appear, and along the weld centerline arise, it means there has been undercut. Generally undercut because of current, voltage and welding speed inappropriate, therefore, in the welding process requires control your speed, so as to effectively avoid undercut phenomenon.
Spiral cracks: spiral cracks may be produced due to the direction of the spiral seam problem spiral in order to effectively prevent the generation of cracks in the welding process, the welding process need to operate in strict accordance with the job.
Although the spiral steel pipe is mainly used in water engineering, petrochemical industry, chemical industry, power industry, agricultural irrigation, urban construction, is the development of 20 key products. For the transport of liquids: water supply and drainage. For gas transportation: gas, steam, liquefied petroleum gas. For structural purposes: as piling pipe for bridges; docks, roads, buildings and other structures tube. However, the spiral in the welding process there are some inherent defects.
The specific requirements of the steel strip coil is forward weldability of steel, reducing the sulfur content in the steel pipe to improve the toughness and arrestability are beneficial. While also reducing sulfide inclusions to the swap, forward of steel crack resistance. The phosphorus content in the hot strip is as low as possible, because the phosphorus on the steel toughness and weldability are a hazard, thus reducing the phosphorus content can move weldability, can increase the amount of added titanium, vanadium niobium content spiral during welding weld defects may occur, so that welding defects affect the quality of the spiral, resulting in reduced service life or the spiral can be used. Generally, the spiral weld defects and porosity, and cracks undercut phenomenon.
Spiral bubble defect: During spiral welding, the weld bead in the center of bubble defects occur this situation, the main reason is that in the course of the welding of hydrogen is left in the form of bubbles within the metal. In the welding process, we need to remove the oil inside the weld, water and other ingredients, but also the need to do drying, removal of moisture, so that hydrogen gas will not remain in the inside seam. During the welding process the welding current can be avoided to increase the generation of bubbles.
Spiral undercut phenomenon: When the v-shaped groove weld edges appear, and along the weld centerline arise, it means there has been undercut. Generally undercut because of current, voltage and welding speed inappropriate, therefore, in the welding process requires control your speed, so as to effectively avoid undercut phenomenon.
Spiral cracks: spiral cracks may be produced due to the direction of the spiral seam problem spiral in order to effectively prevent the generation of cracks in the welding process, the welding process need to operate in strict accordance with the job.
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