Spiral steel pipe plant in the production process will encounter this question, because the composition of different types of steel, their transition temperature, transition time and the characteristics of the study the same. Even if the same steel, only the end is not the same use, the needs of the arrangements and functions are not the same.
The secondary cooling means cooling from the temperature at the beginning of the phase transformation to the temperature at which the phase transition is completed. The purpose of the secondary cooling is to control the phase change
process by controlling the cooling rate during the phase change and stopping the temperature control to ensure the required metallographic arrangement after the steel is rapidly cooled.
Secondary cooling (air cooling) refers to the phase change to room temperature range of cooling. On the shop in the air-cooled process will occur in the separation of carbonitride, the resulting bainite tempering occurred. On the high-carbon steel or high carbon steel alloy steel phase transformation after the air-cooled, will make the fast cooling, the separation of the super-saturated carbide dispersion continued separation. Such as the phase change is still selected after the completion of technology, you can hinder the carbide separation, adhere to the carbide solid solution, solid solution to strengthen the intention.
2016年12月29日星期四
How to Choose the Spiral Steel Pipe
Spiral steel pipe usage is relatively high, the application is very wide, it should be how to choose before in the selection to pay attention to quality.
The first method is a more professional detection method, that is, by the strength of the pressure vessel to be detected. Commonly, we use atmospheric pressure and water pressure to detect, in this way can detect the working conditions of the spiral steel pipe in the pressure working environment, but also to detect the tightness of the spiral steel pipe, generally take the atmospheric pressure detection, because such security Relatively high, and if the water vapor pressure through the test, then the need to remove the spiral pipe after the water, too much trouble.
The second method is also relatively simple, that is, through the surface of observation. With the naked eye found in the spiral steel pipe in the welding and size of the problem, if necessary, you can also use the standard sample and the products to be compared to find the problem. In general, formal steel pipe company in the production is relatively perfect, on the other hand to beat the metal pipe, if the sound is very crisp and the echo is not very dirty, then the
name is the latest selection of steel pipe, rather than scrap steel recycling
These two methods are commonly used, we can choose a way to test, more secure way is the best to the regular manufacturers, can reduce the use of the process of abuse.
The first method is a more professional detection method, that is, by the strength of the pressure vessel to be detected. Commonly, we use atmospheric pressure and water pressure to detect, in this way can detect the working conditions of the spiral steel pipe in the pressure working environment, but also to detect the tightness of the spiral steel pipe, generally take the atmospheric pressure detection, because such security Relatively high, and if the water vapor pressure through the test, then the need to remove the spiral pipe after the water, too much trouble.
The second method is also relatively simple, that is, through the surface of observation. With the naked eye found in the spiral steel pipe in the welding and size of the problem, if necessary, you can also use the standard sample and the products to be compared to find the problem. In general, formal steel pipe company in the production is relatively perfect, on the other hand to beat the metal pipe, if the sound is very crisp and the echo is not very dirty, then the
name is the latest selection of steel pipe, rather than scrap steel recycling
These two methods are commonly used, we can choose a way to test, more secure way is the best to the regular manufacturers, can reduce the use of the process of abuse.
The Advantages and Disadvantages of Spiral Steel Pipe
The spiral steel pipe is formed by spiral bending of strip steel or coiled plate and is welded with double-side submerged arc welding. The steel pipe is widely used in water, electricity and chemical industry for the following reasons.
1) As long as the change in forming angle, you can use the same width of the strip production of various diameter steel pipe, easy to transfer type.
2) Because it is continuous bending, so the length of spiral pipe length is not restricted, the length can be arbitrarily set.
3) Weld spiral evenly distributed throughout the circumference of the spiral tube, so the size of the spiral tube high precision, strength is also strong.
4) Easy to change the size, suitable for small quantities, more varieties of the production spiral.
Spiral steel pipe with the same specifications than the straight seam welded pipe length, the same specifications wall thickness, the spiral steel pipe to withstand the maximum pressure. The defects of the spiral steel pipe weld are
"oblique defects". In the course of use, the principal stress direction of the steel pipe, that is, the equivalent defect length in the axial direction of the steel pipe is smaller than that of the straight pipe. Secondly, since the
pipeline steel is rolled steel plate, the impact toughness has larger anisotropy, The CVN of the direction can be three times higher than the CVN value perpendicular to the rolling direction.
1) As long as the change in forming angle, you can use the same width of the strip production of various diameter steel pipe, easy to transfer type.
2) Because it is continuous bending, so the length of spiral pipe length is not restricted, the length can be arbitrarily set.
3) Weld spiral evenly distributed throughout the circumference of the spiral tube, so the size of the spiral tube high precision, strength is also strong.
4) Easy to change the size, suitable for small quantities, more varieties of the production spiral.
Spiral steel pipe with the same specifications than the straight seam welded pipe length, the same specifications wall thickness, the spiral steel pipe to withstand the maximum pressure. The defects of the spiral steel pipe weld are
"oblique defects". In the course of use, the principal stress direction of the steel pipe, that is, the equivalent defect length in the axial direction of the steel pipe is smaller than that of the straight pipe. Secondly, since the
pipeline steel is rolled steel plate, the impact toughness has larger anisotropy, The CVN of the direction can be three times higher than the CVN value perpendicular to the rolling direction.
2016年12月27日星期二
Type of Spiral Pipe Fracture
Spiral pipe for liquid delivery with: water supply, drainage. For gas transportation with: gas, steam, liquefied petroleum gas. Petrochemical industry, chemical industry, electric power industry, agricultural irrigation, urban construction, is the development of China's 20 key products (such as water supply, water supply, water supply and drainage).
There are several types of fracture of the spiral tube, according to the situation after the destruction of materials corrosion steel pipe and metal material fracture is roughly the same type is divided into three types, namely: ① cleavage fracture, ② hole reverse fracture, ③ slip surface Separation fracture.
Cleavage fracture of the cross-section of a crystal in strict accordance with the separation, the crystal surface known as the cleavage plane. The fracture strength along this plane is the lowest, and is determined by equation (1-4). The factors that determine the cleavage plane are the specific surface energy y, the interplanar distance of the crystal plane, and the elastic modulus along the normal direction. Cleavage fracture is almost not accompanied by plastic deformation, is a brittle fracture, in the body-centered cubic, closely packed hexagonal gold center. Face-centered cubic metals generally do not undergo cleavage fracture. The shear fracture is the main fracture mechanism of the ductile material. Such as anti-corrosion steel alloy in the second phase of the particles from the role of blocking the slip, increasing resistance to plastic deformation; when the plastic deformation increases, the second phase particles and substrate interface occurs stripping Ang, a small hole; Forming, growing up and merging will form a shear section. For high-purity metal, the absence of second-phase particles, bimetallic wear-resistant composite pipe and therefore will not produce: tiny holes, the result of moving along only the surface area is increasing, and finally form a sliding surface separation section. Anti-corrosion steel pipe spinning compound technology is precisely under the special control of special equipment, the pressure roller rotation and lined tube friction to produce heat, quickly reach the softening point of stainless steel, squeezing the outer extrusion tube to the elastic deformation, the two produce interference Cooperation, to achieve close integration. From the perspective of the organization of the gold, the fracture is divided into transgranular fracture and fracture along the goods.
There are several types of fracture of the spiral tube, according to the situation after the destruction of materials corrosion steel pipe and metal material fracture is roughly the same type is divided into three types, namely: ① cleavage fracture, ② hole reverse fracture, ③ slip surface Separation fracture.
Cleavage fracture of the cross-section of a crystal in strict accordance with the separation, the crystal surface known as the cleavage plane. The fracture strength along this plane is the lowest, and is determined by equation (1-4). The factors that determine the cleavage plane are the specific surface energy y, the interplanar distance of the crystal plane, and the elastic modulus along the normal direction. Cleavage fracture is almost not accompanied by plastic deformation, is a brittle fracture, in the body-centered cubic, closely packed hexagonal gold center. Face-centered cubic metals generally do not undergo cleavage fracture. The shear fracture is the main fracture mechanism of the ductile material. Such as anti-corrosion steel alloy in the second phase of the particles from the role of blocking the slip, increasing resistance to plastic deformation; when the plastic deformation increases, the second phase particles and substrate interface occurs stripping Ang, a small hole; Forming, growing up and merging will form a shear section. For high-purity metal, the absence of second-phase particles, bimetallic wear-resistant composite pipe and therefore will not produce: tiny holes, the result of moving along only the surface area is increasing, and finally form a sliding surface separation section. Anti-corrosion steel pipe spinning compound technology is precisely under the special control of special equipment, the pressure roller rotation and lined tube friction to produce heat, quickly reach the softening point of stainless steel, squeezing the outer extrusion tube to the elastic deformation, the two produce interference Cooperation, to achieve close integration. From the perspective of the organization of the gold, the fracture is divided into transgranular fracture and fracture along the goods.
Quality Inspection of Spiral Steel Pipe
1. From the spiral steel pipe looks. In appearance is to pay attention to those welded joints, seen the appearance is not a drawback, there is a lack of scale, which can be seen through the naked eye, of course, detailed and bilateral theory, Borrow a standard model, gauge and magnifying glass to view. Because of the appearance of welding defects, which means the spiral pipe inside most likely also flawed, even the appearance of effort are not done, inside the effort is difficult to ensure.
2. View approach is to use equipment to view, that is, without the risk of pipe to borrow the case of ultrasonic flaw detection, ray detection, penetration testing, and magnetic flaw detection method can see the spiral pipe has not see the defects. In addition to the defective view, the intensity of the pressurized container is also viewed. Usually there are two kinds of water pressure test and air pressure test. Such a view is to see the spiral steel pipe weld fineness, usually more accurate to use air pressure view. But the pressure is dangerous to view, if not careful to operate in accordance with the rules will appear security incidents.
Spiral steel pipe also have to see through the cracks, there is no porosity, there is no mixing slag, is not there is no penetration of the place, is not there loose arrangements, usually with oil test, with water test or Water test and other measures. In addition to do still water test, the operation can ensure that the pipe without leakage specification.
2. View approach is to use equipment to view, that is, without the risk of pipe to borrow the case of ultrasonic flaw detection, ray detection, penetration testing, and magnetic flaw detection method can see the spiral pipe has not see the defects. In addition to the defective view, the intensity of the pressurized container is also viewed. Usually there are two kinds of water pressure test and air pressure test. Such a view is to see the spiral steel pipe weld fineness, usually more accurate to use air pressure view. But the pressure is dangerous to view, if not careful to operate in accordance with the rules will appear security incidents.
Spiral steel pipe also have to see through the cracks, there is no porosity, there is no mixing slag, is not there is no penetration of the place, is not there loose arrangements, usually with oil test, with water test or Water test and other measures. In addition to do still water test, the operation can ensure that the pipe without leakage specification.
Manufacturing Loss Rate of Spiral Steel Pipe
Spiral steel pipe manufacturing loss rate refers to the spiral pipe in the manufacturing process, the proportion of raw materials, waste, according to professional and technical personnel for many years statistical analysis spiral tube manufacturing loss rate of between 2% -3%.
During the manufacture of spiral steel pipe, the main components of waste are: the first piece of spiral pipe forming the first piece, the tail to tail, the raw material milling, spiral pipe production process necessary steps, if the production can not be normal spiral pipe milling edge, truncated , To the end, the production of steel pipe pass rate is very low.
When spiral steel pipe manufacturing, there are some losses can be avoided, such as spiral pipe weld quality unqualified, can not be repaired, then the spiral pipe quality unqualified, can not be used, resulting in a waste of material. In the manufacturing process, we must strictly control each process, handle the details, so as to improve the spiral tube yield and pass rate, to avoid unnecessary losses, so that can avoid unnecessary cost.
During the manufacture of spiral steel pipe, the main components of waste are: the first piece of spiral pipe forming the first piece, the tail to tail, the raw material milling, spiral pipe production process necessary steps, if the production can not be normal spiral pipe milling edge, truncated , To the end, the production of steel pipe pass rate is very low.
When spiral steel pipe manufacturing, there are some losses can be avoided, such as spiral pipe weld quality unqualified, can not be repaired, then the spiral pipe quality unqualified, can not be used, resulting in a waste of material. In the manufacturing process, we must strictly control each process, handle the details, so as to improve the spiral tube yield and pass rate, to avoid unnecessary losses, so that can avoid unnecessary cost.
2016年12月21日星期三
Influence of Deoxidizer on Straight Seam Steel Pipe
For the straight seam steel pipe, the use of two kinds of deoxidizer has little effect on the total oxygen content in steel after VD treatment, and the total oxygen content in each process after Si-Al-Ba deoxidation, Si-Ca deoxidation effect.
When using Si-Ca and Si-Al-Ba two kinds of deoxidizer, the number and size of inclusions in the smelting process are different, and the number of inclusions in each process after Si-Al-Ba deoxidation is less than Si-Ca deoxidation, and the smaller size.
When Si-Ca and Si-Al-Ba two kinds of deoxidizing agents are used in straight seam welded pipe, the secondary oxidation of liquid steel occurs during the casting process, but the secondary oxidation of Si-Al-Ba deoxidized steel is more serious.
The inclusions in forging materials are different from those in aluminum inclusions. When the Si-Al-Ba deoxidization is used, the inclusions in the forging materials are mainly block and chain-like alumina, while the Si-Ca deoxidation The content of aluminum inclusions in the deoxidized forging material of Si-Ca alloy is less than that of Si-Al-Ba alloy.
When using Si-Ca and Si-Al-Ba two kinds of deoxidizer, the number and size of inclusions in the smelting process are different, and the number of inclusions in each process after Si-Al-Ba deoxidation is less than Si-Ca deoxidation, and the smaller size.
When Si-Ca and Si-Al-Ba two kinds of deoxidizing agents are used in straight seam welded pipe, the secondary oxidation of liquid steel occurs during the casting process, but the secondary oxidation of Si-Al-Ba deoxidized steel is more serious.
The inclusions in forging materials are different from those in aluminum inclusions. When the Si-Al-Ba deoxidization is used, the inclusions in the forging materials are mainly block and chain-like alumina, while the Si-Ca deoxidation The content of aluminum inclusions in the deoxidized forging material of Si-Ca alloy is less than that of Si-Al-Ba alloy.
Characteristics of Welded Steel Tube Slag
Welded steel pipe slag is residual slag inside the weld. From the theoretical analysis, submerged arc welding seam slag generated mainly due to the following three reasons: ① raw materials (including base metal, wire, flux) in the inclusion of more; ② multi-layer welding clean up when the inter-layer; ③ improper selection of welding process parameters is not conducive to the emergence of slag.
According to the production characteristics of straight seam submerged arc welded steel pipe, it can be ruled out that the interlayer cleaning is not clean when the multi-layer welding is done and the slag is generated.
For the inclusions in raw materials and make the weld slag, straight seam steel pipe company to take the pre-test test base metal, replacement of new welding wire and flux and other measures, weld fusion line slag generated only a slight reduction in the proportion, Indicating that inclusions in the raw materials are not the main causes of slag formation.
Therefore, thick-walled LSAW steel pipe welding line slag generated mainly due to improper selection of welding process parameters. The welding parameters of thick-walled submerged arc welded pipe are: line energy, welding current, welding voltage, welding speed, wire spacing, groove size.
According to the production characteristics of straight seam submerged arc welded steel pipe, it can be ruled out that the interlayer cleaning is not clean when the multi-layer welding is done and the slag is generated.
For the inclusions in raw materials and make the weld slag, straight seam steel pipe company to take the pre-test test base metal, replacement of new welding wire and flux and other measures, weld fusion line slag generated only a slight reduction in the proportion, Indicating that inclusions in the raw materials are not the main causes of slag formation.
Therefore, thick-walled LSAW steel pipe welding line slag generated mainly due to improper selection of welding process parameters. The welding parameters of thick-walled submerged arc welded pipe are: line energy, welding current, welding voltage, welding speed, wire spacing, groove size.
2016年12月19日星期一
Weld Treatment of LSAW Steel Pipe
LSAW steel pipe is the strip into the pipe unit, the multi-roll rolling, strip gradually rolled up to form a circular gap open billet, adjust the squeeze roll reduction, so that weld gap control In the 1 ~ 3mm, and make both ends of the welding flush. If the gap is too large, it will reduce the proximity effect, eddy current heat shortage, weld intergranular bonding caused by poor fusion or cracking. Such as between
If the gap is too small, the proximity effect will be increased, the welding heat will be too large, and the weld will be burned; or the weld will be crushed and crushed to form the pit, which will affect the weld surface quality.
Welding process example:
Weld φ32 × 2mm longitudinal welded pipe, for example, briefly describes the process parameters:
Strip specifications: 2 × 98mm bandwidth by medium diameter expansion plus a small amount of molding margin.
Steel material: Q235A
Input excitation voltage: 150V Excitation current: 1.5A Frequency: 50Hz.
Output DC voltage: 11.5kV DC current: 4A Frequency: 120000Hz.
Welding speed: 50 m / min.
Parameter adjustment: according to the welding line energy changes in time to adjust the output voltage and welding speed. Fixed parameters generally do not have to adjust.
If the gap is too small, the proximity effect will be increased, the welding heat will be too large, and the weld will be burned; or the weld will be crushed and crushed to form the pit, which will affect the weld surface quality.
Welding process example:
Weld φ32 × 2mm longitudinal welded pipe, for example, briefly describes the process parameters:
Strip specifications: 2 × 98mm bandwidth by medium diameter expansion plus a small amount of molding margin.
Steel material: Q235A
Input excitation voltage: 150V Excitation current: 1.5A Frequency: 50Hz.
Output DC voltage: 11.5kV DC current: 4A Frequency: 120000Hz.
Welding speed: 50 m / min.
Parameter adjustment: according to the welding line energy changes in time to adjust the output voltage and welding speed. Fixed parameters generally do not have to adjust.
2016年12月15日星期四
Quality Requirements and Welding Temperature Requirements for Large Diameter Straight Seam Steel Tubes
Large diameter straight seam steel pipe welding, including pre-welding, welding and welding outside the three processes. The so-called pre-welding is in the steel forming, the use of continuous high-speed gas shielded welding method of forming steel pipe welding. After the pre-welding, respectively, within the steel pipe, multi-wire submerged arc welding. In the case of high-speed gas-shielded pre-welding, there are currently two methods. One is the use of single-wire dual-power high-current high-speed gas protection pre-welding, such as the United States, Germany that is used in this way; the other is double-wire high-speed gas protection pre-welding, Japan is the use of this method. At present, more applications are monofilament high-speed gas protection pre-welding method, in a reasonable welding process conditions, can achieve not less than 7m / min high speed, and straight bead forming beautiful. Large diameter straight seam steel pipe is a product of the construction industry, steel structure is also one of the building industry, so the steel structure and straight seam steel pipe produced between the inseparable association. Now in the straight seam steel pipe plant in the steel structure accounted for most of the production, so straight seam steel pipe manufacturers for the production of steel pipe with the process and process requirements are very strict, good steel pipe to grasp the straight seam steel pipe Market dynamics, and now a large profit margins of straight seam steel pipe is gone forever, so only a large amount is king, in the increasingly serious competition in how to receive more orders bigger only grasp the quality of products at the same time And constantly grasp the market dynamics and laws to grasp the lifeline of the market.
Large diameter straight seam welded steel pipe as the first process of pre-welding, that is to ensure quality. Pre-welding quality, not only its own quality problems, but also affect the follow-up, the quality of welding. Its quality requirements, targeted mainly as follows:
1, The weld should be continuous, and the appearance of forming to avoid uneven, in order to facilitate the final quality assurance of welding;
2, To ensure the appropriate penetration depth and the amount of welding, it is necessary to ensure that welding does not crack after welding, but also within the welding does not produce burning through the phenomenon;
3, To have a higher welding speed, in order to improve production efficiency.
Large diameter straight seam welded steel pipe as the first process of pre-welding, that is to ensure quality. Pre-welding quality, not only its own quality problems, but also affect the follow-up, the quality of welding. Its quality requirements, targeted mainly as follows:
1, The weld should be continuous, and the appearance of forming to avoid uneven, in order to facilitate the final quality assurance of welding;
2, To ensure the appropriate penetration depth and the amount of welding, it is necessary to ensure that welding does not crack after welding, but also within the welding does not produce burning through the phenomenon;
3, To have a higher welding speed, in order to improve production efficiency.
Factors of Affecting Large Diameter Double-sided Submerged Arc Welding Steel Pipe Mechanical Expanding
There are many factors that affect the quality of large diameter double-sided submerged arc welding steel pipe(dsaw steel pipe). The key factors that directly relate to the quality of diameter forming are the expansion ratio, the amount of axial overlap, the number of segments and the rounded corners, The friction and lubrication between the block and the inner wall of the steel pipe, the shape error of the steel pipe, the expanding speed and the straightening setting of the expanding machine.
(1) When the enlarging rate is small, the roundness error of the steel pipe decreases with the enlarging rate, but when the enlarging rate increases to a certain value, with the enlargement rate increasing, The roundness error of the steel pipe will increase greatly. In the actual production, the expansion ratio is controlled between 0.8% and 1.5%.
(2) The amount of axial overlap has a certain influence on the uniformity of the longitudinal deformation and the diameter-enlarging efficiency of the full-length expansion of the steel tube. The zero overlap amount and the small positive overlap amount are beneficial to alleviate the "bamboo" Improve the diameter expansion efficiency.
(3) Increasing the number of segments, increasing the speed of expansion, increasing friction and lubrication between the segments and the inner wall of the steel pipe, and reducing the friction coefficient of the contact zone are all conducive to the uniform distribution of the wall stress.
(4) The diameter of the pipe to improve the roundness effect is obvious. After the expansion, the roundness error of steel pipe becomes very small.
(1) When the enlarging rate is small, the roundness error of the steel pipe decreases with the enlarging rate, but when the enlarging rate increases to a certain value, with the enlargement rate increasing, The roundness error of the steel pipe will increase greatly. In the actual production, the expansion ratio is controlled between 0.8% and 1.5%.
(2) The amount of axial overlap has a certain influence on the uniformity of the longitudinal deformation and the diameter-enlarging efficiency of the full-length expansion of the steel tube. The zero overlap amount and the small positive overlap amount are beneficial to alleviate the "bamboo" Improve the diameter expansion efficiency.
(3) Increasing the number of segments, increasing the speed of expansion, increasing friction and lubrication between the segments and the inner wall of the steel pipe, and reducing the friction coefficient of the contact zone are all conducive to the uniform distribution of the wall stress.
(4) The diameter of the pipe to improve the roundness effect is obvious. After the expansion, the roundness error of steel pipe becomes very small.
2016年12月13日星期二
Cause Analysis and Attention on Method of Bending Quality
Bending process can be divided into many kinds, there are bending, bending and other means to push, these methods can be divided into two kinds of cold bending and bending bending state. For different bends of the processing technology used is different, different characteristics of the elbow is not the same.
The main reason that causing the quality of elbow decline and the attention method:
1, Pure bending, the tube under the action of the external force M in the outer layer of the lateral arm wall tensile stress and thinning, the inner stress, the role of thickening, resultant N1 and N2 to the tube cross-section changes. Therefore, GBJ235-82, for a variety of pressure levels under the conditions of the RX value and the amount of thinning outside are clearly defined, the purpose is to control the RX and SX To ensure quality.
2, The previous article has been mentioned, the elbow when the lateral tension of the material, the medial position of the neutral axis of pressure and bending method is different from the top bend (compression bending) work in the neutral axis from the outer wall of about 1/3, in the bending (bending) work, the neutral axis from the outer wall 2/3. Therefore, the thin-walled pipe is bent, and it is advantageous to use a bending method.
3, The accuracy of curved tire is also one of the factors affecting the quality of elbow. We bend fetal production, in addition to size requirements to control in a certain tolerance range, but also requires users to use in accordance with bending pipe diameter to select the corresponding bending tire.
4, The pipe itself, the bending performance and surface corrosion, may also affect the quality of elbow. On-site construction, the operator should also be aware of the material being processed pipe, processing performance and surface corrosion to make production judgments.
The main reason that causing the quality of elbow decline and the attention method:
1, Pure bending, the tube under the action of the external force M in the outer layer of the lateral arm wall tensile stress and thinning, the inner stress, the role of thickening, resultant N1 and N2 to the tube cross-section changes. Therefore, GBJ235-82, for a variety of pressure levels under the conditions of the RX value and the amount of thinning outside are clearly defined, the purpose is to control the RX and SX To ensure quality.
2, The previous article has been mentioned, the elbow when the lateral tension of the material, the medial position of the neutral axis of pressure and bending method is different from the top bend (compression bending) work in the neutral axis from the outer wall of about 1/3, in the bending (bending) work, the neutral axis from the outer wall 2/3. Therefore, the thin-walled pipe is bent, and it is advantageous to use a bending method.
3, The accuracy of curved tire is also one of the factors affecting the quality of elbow. We bend fetal production, in addition to size requirements to control in a certain tolerance range, but also requires users to use in accordance with bending pipe diameter to select the corresponding bending tire.
4, The pipe itself, the bending performance and surface corrosion, may also affect the quality of elbow. On-site construction, the operator should also be aware of the material being processed pipe, processing performance and surface corrosion to make production judgments.
Effect of Mechanical Expanding of Double Submerged Arc Welding Longitudinal Seam Steel Pipe
At present, the long-distance transportation of oil and natural gas mainly adopts pipeline. Long-distance pipeline pipeline used in the main spiral pipe submerged arc welded pipe(ssaw steel pipe) and double submerged arc welded straight steel pipe(dsaw steel pipe). As the spiral submerged arc welded pipe is based on strip as raw material, wall thickness is limited, in addition to the existence of spiral submerged arc welded pipe longer, greater residual stress, weld reliability is poor and difficult to overcome the shortcomings of dense population area and reliability requirements of the region, large diameter straight seam submerged arc welded pipe has been gradually replaced by spiral submerged arc welded pipe.
Expanded diameter is a large diameter straight seam submerged arc welded pipe production to ensure the quality of an important process, the standard pipe line pipe submerged arc welded pipe must be expanded process.
1, Effectively improve the dimensional accuracy of steel pipe
At present, there are mainly UO, RB, JCO, C and Hu-Metal for the forming of LSAW steel pipes. The steel pipes produced by these five kinds of molding methods have different geometrical accuracy. As the straight seam submerged arc welding in the tube side of the inside and outside welding, and thus under the action of thermal stress in the steel pipe to be bending deformation, and the longitudinal part of the weld shrinkage larger, so that the straightness of steel pipe is seriously affected; In addition, these five kinds of forming the production of steel pipe, the oval are large, especially JCO and C forming steel pipe. Therefore, we must increase the diameter, the whole circle and other processes to improve the geometric accuracy of steel pipe.
2, Reduce or eliminate in the pipe, the test process caused by the Bauschinger effect
As the steel pipe in the process of forming and testing will produce the Bauschinger effect, so that the yield strength decreased, and the expansion of steel in the cold hardened, expanded diameter can improve the yield strength of steel, thus reducing the strength to achieve steel requirements while increasing the level of waste caused by sheet metal.
3, The elimination of steel pipe forming and welding residual stress
Cold expansion can eliminate the residual stress caused by forming and welding, and improve the distribution of stress in the steel pipe, so as to avoid the occurrence of hydrogen embrittlement and crack in the steel pipe stress concentration area due to the transportation of H2S in oil or natural gas.
In addition, the diameter of the welding quality and welding performance is also a good test.
Expanded diameter is a large diameter straight seam submerged arc welded pipe production to ensure the quality of an important process, the standard pipe line pipe submerged arc welded pipe must be expanded process.
1, Effectively improve the dimensional accuracy of steel pipe
At present, there are mainly UO, RB, JCO, C and Hu-Metal for the forming of LSAW steel pipes. The steel pipes produced by these five kinds of molding methods have different geometrical accuracy. As the straight seam submerged arc welding in the tube side of the inside and outside welding, and thus under the action of thermal stress in the steel pipe to be bending deformation, and the longitudinal part of the weld shrinkage larger, so that the straightness of steel pipe is seriously affected; In addition, these five kinds of forming the production of steel pipe, the oval are large, especially JCO and C forming steel pipe. Therefore, we must increase the diameter, the whole circle and other processes to improve the geometric accuracy of steel pipe.
2, Reduce or eliminate in the pipe, the test process caused by the Bauschinger effect
As the steel pipe in the process of forming and testing will produce the Bauschinger effect, so that the yield strength decreased, and the expansion of steel in the cold hardened, expanded diameter can improve the yield strength of steel, thus reducing the strength to achieve steel requirements while increasing the level of waste caused by sheet metal.
3, The elimination of steel pipe forming and welding residual stress
Cold expansion can eliminate the residual stress caused by forming and welding, and improve the distribution of stress in the steel pipe, so as to avoid the occurrence of hydrogen embrittlement and crack in the steel pipe stress concentration area due to the transportation of H2S in oil or natural gas.
In addition, the diameter of the welding quality and welding performance is also a good test.
Identification Method of Seamless Steel Pipe
Seamless steel pipe identification methods are:
1, With the eyes, welded pipe diameter will have a very obvious weld, the color and other parts of the steel pipe is different.
2, The chemical composition of the material for analysis, the pipe material will be relatively poor, impurity and harmful elements content will be higher.
3, For mechanical performance analysis or process performance analysis, for flaring test, the welded pipe easy to crack.
4, For eddy current testing, eddy current injury control of welded steel pipe may be more alarm.
1, With the eyes, welded pipe diameter will have a very obvious weld, the color and other parts of the steel pipe is different.
2, The chemical composition of the material for analysis, the pipe material will be relatively poor, impurity and harmful elements content will be higher.
3, For mechanical performance analysis or process performance analysis, for flaring test, the welded pipe easy to crack.
4, For eddy current testing, eddy current injury control of welded steel pipe may be more alarm.
Quality Inspection Standard and Operation Process of Cold Drawn Carbon Seamless Steel Pipe
Quality inspection standard and operation process of cold drawn carbon seamless steel pipe are following below:
Production characteristics of the cold drawn tube is from the input to the finished product,which is usually processed through a number of cold deformation and produce hardening, and thus the entire production process by a number of preparatory processes and deformation processes, and has the characteristics of reciprocating cycle, and thus more processes , The production cycle is long, metal consumption, production efficiency is low, the general scale of production are not large.
Cold-rolled, cold-drawn or cold-rolled and cold-drawn combination of cold processing methods is to produce the entire package of equipment combinations, which is the hot-rolled pipe or welded pipe for deep processing unit.
According to the metal processing performance, pipe size, quality requirements and investment and efficiency to choose a different processing methods and the corresponding auxiliary processes. Cold-rolled cold drawn tube of the basic processes are:
(1) The supply of pipe material, the pipe used for hot-rolled or semi-finished product pipe, extrusion pipe and welded pipe;
(2) Pipe preparation, including inspection, bundling, pickling, washing, washing, and in, drying,coating lubricants;
(3) Cold (cold or cold drawing);
(4) Finished product finishing including heat treatment, straightening, sampling, cutting head and tail, inspection (manual inspection and a variety of testing), hydraulic test, oil, packaging, storage and so on. The contents of different products finishing different.
Production characteristics of the cold drawn tube is from the input to the finished product,which is usually processed through a number of cold deformation and produce hardening, and thus the entire production process by a number of preparatory processes and deformation processes, and has the characteristics of reciprocating cycle, and thus more processes , The production cycle is long, metal consumption, production efficiency is low, the general scale of production are not large.
Cold-rolled, cold-drawn or cold-rolled and cold-drawn combination of cold processing methods is to produce the entire package of equipment combinations, which is the hot-rolled pipe or welded pipe for deep processing unit.
According to the metal processing performance, pipe size, quality requirements and investment and efficiency to choose a different processing methods and the corresponding auxiliary processes. Cold-rolled cold drawn tube of the basic processes are:
(1) The supply of pipe material, the pipe used for hot-rolled or semi-finished product pipe, extrusion pipe and welded pipe;
(2) Pipe preparation, including inspection, bundling, pickling, washing, washing, and in, drying,coating lubricants;
(3) Cold (cold or cold drawing);
(4) Finished product finishing including heat treatment, straightening, sampling, cutting head and tail, inspection (manual inspection and a variety of testing), hydraulic test, oil, packaging, storage and so on. The contents of different products finishing different.
2016年12月8日星期四
Manufacturing Process of Carbon Seamless Steel Pipe
According to different production methods of carbon seamless steel pipe can be divided into hot-rolled tube, cold-rolled tube, drawing tube, extrusion tube.
1.Hot-rolled seamless pipe is generally in the automatic production of rolling mill unit. The solid tube blank is inspected and removed from the surface defects, cut into the required length, in the tube end of the perforation end of the centering, and then sent to the heating furnace heating, perforation in the punching machine. In the perforation at the same time continue to rotate and move, in the role of the roll and the head, the tube gradually formed within the cavity, called the capillary. And then sent to the automatic rolling machine to continue rolling. And finally by the whole machine are the whole wall thickness, by sizing machine diameter, to specifications. The use of continuous rolling mill production of hot-rolled seamless steel pipe is a more advanced method.
2.If you want to get smaller and better quality of seamless tubes, must be cold-rolled, cold drawn or a combination of the two methods. Cold rolling is usually carried out on a two-roll mill, in which the steel pipe is rolled in an annular orifice formed by a tapered hole and a non-moving tapered head. Cold drawing is usually carried out on single-chain or double-chain cold drawing machines of 0.5 to 100T.
3.the extrusion method is to heat a good tube on a closed cylinder, squeeze rods and extrusion rod with the movement, so that extrusion from the smaller hole in the extrusion die. This method can produce smaller diameter steel pipe.
1.Hot-rolled seamless pipe is generally in the automatic production of rolling mill unit. The solid tube blank is inspected and removed from the surface defects, cut into the required length, in the tube end of the perforation end of the centering, and then sent to the heating furnace heating, perforation in the punching machine. In the perforation at the same time continue to rotate and move, in the role of the roll and the head, the tube gradually formed within the cavity, called the capillary. And then sent to the automatic rolling machine to continue rolling. And finally by the whole machine are the whole wall thickness, by sizing machine diameter, to specifications. The use of continuous rolling mill production of hot-rolled seamless steel pipe is a more advanced method.
2.If you want to get smaller and better quality of seamless tubes, must be cold-rolled, cold drawn or a combination of the two methods. Cold rolling is usually carried out on a two-roll mill, in which the steel pipe is rolled in an annular orifice formed by a tapered hole and a non-moving tapered head. Cold drawing is usually carried out on single-chain or double-chain cold drawing machines of 0.5 to 100T.
3.the extrusion method is to heat a good tube on a closed cylinder, squeeze rods and extrusion rod with the movement, so that extrusion from the smaller hole in the extrusion die. This method can produce smaller diameter steel pipe.
2016年12月7日星期三
Hardness Test of 40Cr Carbon Seamless Steel Tubes
American Standard carbon seamless steel pipe conduct mechanical performance testing. Mechanical properties of test methods are divided into two categories, one is the tensile test, one is the hardness test.
Tensile tests are made of seamless steel tube samples, the tensile test machine will pull the specimen to the fracture, and then measured one or more mechanical properties, usually only the determination of tensile strength, yield strength, elongation and rate of reduction in area. Tensile test is the most basic metal mechanical properties of test methods, almost all of the metal materials, as long as the mechanical properties are required, are provided for tensile testing. In particular, tensile tests are the only means of testing the mechanical properties of materials that are not easily tested for their hardness.
Hardness test is a hard indenter according to the provisions of the conditions slowly pressed into the sample surface, and then test indentation depth or size, in order to determine the size of the hardness of the material. Hardness test is the mechanical properties of materials testing the most simple, the most rapid and easiest to implement the method. Hardness test is non-destructive, the hardness value of the material and the tensile strength value between the approximate conversion relationship. The hardness of the material can be converted into tensile strength value, which has great practical significance.
As the tensile test is not easy to test, and converted from the hardness to the intensity is very convenient, so more and more people only test the hardness of the material and less test its strength. In particular, due to the hardness of manufacturing technology advances and innovation, some of the original can not directly test the hardness of materials, such as seamless steel tubes, stainless steel and stainless steel, etc., are now possible to directly test the hardness. Therefore, there is a tendency to gradually replace the tensile test with a hardness test.
Tensile tests are made of seamless steel tube samples, the tensile test machine will pull the specimen to the fracture, and then measured one or more mechanical properties, usually only the determination of tensile strength, yield strength, elongation and rate of reduction in area. Tensile test is the most basic metal mechanical properties of test methods, almost all of the metal materials, as long as the mechanical properties are required, are provided for tensile testing. In particular, tensile tests are the only means of testing the mechanical properties of materials that are not easily tested for their hardness.
Hardness test is a hard indenter according to the provisions of the conditions slowly pressed into the sample surface, and then test indentation depth or size, in order to determine the size of the hardness of the material. Hardness test is the mechanical properties of materials testing the most simple, the most rapid and easiest to implement the method. Hardness test is non-destructive, the hardness value of the material and the tensile strength value between the approximate conversion relationship. The hardness of the material can be converted into tensile strength value, which has great practical significance.
As the tensile test is not easy to test, and converted from the hardness to the intensity is very convenient, so more and more people only test the hardness of the material and less test its strength. In particular, due to the hardness of manufacturing technology advances and innovation, some of the original can not directly test the hardness of materials, such as seamless steel tubes, stainless steel and stainless steel, etc., are now possible to directly test the hardness. Therefore, there is a tendency to gradually replace the tensile test with a hardness test.
2016年12月5日星期一
The Practice of Large Diameter Spiral Pipe Demagnetization
The current demagnetization of large diameter spiral steel pipe is usually used in the DC demagnetization coil, the demagnetization coil will be added to the magnetic particle inspection machine in the future, but the demagnetization effect does not enable customers to meet the problem is that the DC demagnetization field occurs only reverse half of the magnetic field, How to demagnetize the internal remanence magnetic steel reverse some offset, the external performance of the residual magnetism to stay in the required range, so the role is very unstable. Often in the field can pass, after the transfer, hit, the magnetic field and overrun. The reason is that the internal magnetic domain is not through the "magnetic exercise" in a very unstable situation.
The demagnetization of large diameter spiral steel tube is the national standard 30GS following, HT30D steel tube demagnetization system can be remanufactured steel tube stability to 10GS remnant, in order to avoid the future in the process of remanence and then rebound. Specifications: Dimensions: 400 * 500 * 600mm, operating voltage: 220V, operating current: 5-20A successive adjustable, operating frequency: 0-50Hz successive adjustable, demagnetization coil diameter scale: 100-250 (or customer demand meter).
The demagnetization of large diameter spiral steel tube is the national standard 30GS following, HT30D steel tube demagnetization system can be remanufactured steel tube stability to 10GS remnant, in order to avoid the future in the process of remanence and then rebound. Specifications: Dimensions: 400 * 500 * 600mm, operating voltage: 220V, operating current: 5-20A successive adjustable, operating frequency: 0-50Hz successive adjustable, demagnetization coil diameter scale: 100-250 (or customer demand meter).
Precautions for Installation of Carbon Seamless Steel Pipe
(1) Carbon seamless steel pipe should be carefully installed before the following carefully checked to ensure the quality of pipe and pipe.
A. Check the factory and pipe fittings factory certificate, quality certificate or test records, test records and other technical information, and should comply with existing national standards.
B. Check the quality marks of the pipe and fittings, expansion joint to meet the technical document and the current national standard. If there is any problem, replace or take the measures.
C. Check the quality of the outer surface of the pipe and pipe fittings, wall thickness should be consistent with national standards. The ellipticity is not allowed to exceed the specified range. No cracks, no shrinkage, no slag, no
folding, no heavy skin, no trachoma, no pinhole, no more than the thickness of the local pit tolerance, no bumps and other quality problems, and the tube Internal and external surface without serious corrosion when the pipe and pipe
fittings qualified.
(2) When the pipe surface rust less number of pipes can not be used when the number of hand-rust, the general hand-rust is a wire brush, wire cloth, emery cloth and other friction, remove the rust on the pipe surface, and then dry cotton
yarn Wipe or clean, so that the pipe surface exposed metallic luster.
(3) When the pipe surface rust more, and the larger number of pipes and generally use mechanical rust or sand blasting rust or pickling rust. Pickling rust rust when the general use of sulfuric acid or hydrochloric acid.
(4) Brush the surface of the pipe type of anti-rust paint should be selected according to design requirements, commonly used red lead rust paint, epoxy paint, etc., the surface finish is generally blending paint.
Before painting, clean the surface of the pipe clean dust, dirt, burr, oil and water. Brush should be uniform coating, do not leak coating, brush the paint after the eligibility criteria for attachment firmly, no flaking, no wrinkles, no
bubbles, no leakage coating, no damage and other defects.
A. Check the factory and pipe fittings factory certificate, quality certificate or test records, test records and other technical information, and should comply with existing national standards.
B. Check the quality marks of the pipe and fittings, expansion joint to meet the technical document and the current national standard. If there is any problem, replace or take the measures.
C. Check the quality of the outer surface of the pipe and pipe fittings, wall thickness should be consistent with national standards. The ellipticity is not allowed to exceed the specified range. No cracks, no shrinkage, no slag, no
folding, no heavy skin, no trachoma, no pinhole, no more than the thickness of the local pit tolerance, no bumps and other quality problems, and the tube Internal and external surface without serious corrosion when the pipe and pipe
fittings qualified.
(2) When the pipe surface rust less number of pipes can not be used when the number of hand-rust, the general hand-rust is a wire brush, wire cloth, emery cloth and other friction, remove the rust on the pipe surface, and then dry cotton
yarn Wipe or clean, so that the pipe surface exposed metallic luster.
(3) When the pipe surface rust more, and the larger number of pipes and generally use mechanical rust or sand blasting rust or pickling rust. Pickling rust rust when the general use of sulfuric acid or hydrochloric acid.
(4) Brush the surface of the pipe type of anti-rust paint should be selected according to design requirements, commonly used red lead rust paint, epoxy paint, etc., the surface finish is generally blending paint.
Before painting, clean the surface of the pipe clean dust, dirt, burr, oil and water. Brush should be uniform coating, do not leak coating, brush the paint after the eligibility criteria for attachment firmly, no flaking, no wrinkles, no
bubbles, no leakage coating, no damage and other defects.
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