Alloy steel casting process compared with carbon steel has the following characteristics:
(1) According to the needs of the cast steel, the liquid steel purity, composition and pouring temperature, especially the control of trace element content, are required to achieve the specified value. This special steel continuous casting furnace must be equipped with refining equipment.
(2) Mold should be used high-frequency, small amplitude vibration.
(3) Selection of good performance and the protection of the whole process of pouring casting to ensure the quality of slab.
(4) The best use of large capacity, deep melt pool, and build a retaining wall, the dam of the tank, give full play to the metallurgical function of the middle tank.
(5) It should use the appropriate refractory materials to reduce consumption and improve the purity of steel.
(6) The use of mold level automatic control to reduce surface fluctuations.
2016年11月30日星期三
Surface Quality Analysis of High Precision Cold Drawn Seamless Steel
Surface defect of cold drawn tube inner wall
High precision cold drawn tube surface roughness Ra ≤ 0.8μm, diameter size accuracy can reach H9 ~ H10, only to ensure that after honing to H7 ~ H8 bore size and Ra ≤ 0.2μm of the internal surface roughness requirements. In addition to the honing machine equipment precision, the cold drawn tube surface quality is another key point, cold drawn tube internal surface defects by the domestic A factory measured data classification, there are three kinds of main honing pipe surface roughness.
1. Pitting
After rough drawing, the surface can be found by many pits-like defects, such defects will not seriously affect the smoothness of the cylinder bore, for the cylinder is a waste.
2. Scratch
Scratch defects are cold drawn, generally along the axis of a steel pipe along the direction of the scratches, there must be more than the depth of the scratches honing margin, it is possible to grind away such defects, processing a
qualified cylinder.
3. Not round
Cold drawn seamless steel pipe in the production, fixed on the mandrel of the internal model can be floating up and down, so cold drawn tube diameter is not as straight as the machining tube. In addition, some hot-rolled tube, with the wall thickness difference between the larger, cold drawing deformation due to the existence of deformation within the tube is not uniform, easy to produce cold drawn tube does not dot. The tube after honing will find a hole in the hole with other parts of the reflective surface of different degrees, if the grinding volume is small, where even the cold drawn when the phosphate layer is not removed. Seriously affecting the cylinder surface quality.
The measures are as follows:
(1) Cold drawn seamless steel pipe directly into the cylinder, the quality can not be guaranteed, it is best to stay 0.2mm (wall thickness) honing, grinding and then processing use.
(2) Cold drawn seamless steel pipe inner hole defect is the impact of the cylinder bore hole surface quality of the main reasons.
(3) Pitting defects produced by the hot-rolled tube, cold drawing can reduce the depth of the defect can not eliminate the defect.
(4) To increase the amount of cold drawn deformation, preferably hot-rolled seamless steel tube blank, hot-rolled tube defects in the hole clean-up, can improve the cold drawn seamless steel pipe wall surface quality, reduce honing
margins, reduce honing costs and improve Honing production efficiency.
High precision cold drawn tube surface roughness Ra ≤ 0.8μm, diameter size accuracy can reach H9 ~ H10, only to ensure that after honing to H7 ~ H8 bore size and Ra ≤ 0.2μm of the internal surface roughness requirements. In addition to the honing machine equipment precision, the cold drawn tube surface quality is another key point, cold drawn tube internal surface defects by the domestic A factory measured data classification, there are three kinds of main honing pipe surface roughness.
1. Pitting
After rough drawing, the surface can be found by many pits-like defects, such defects will not seriously affect the smoothness of the cylinder bore, for the cylinder is a waste.
2. Scratch
Scratch defects are cold drawn, generally along the axis of a steel pipe along the direction of the scratches, there must be more than the depth of the scratches honing margin, it is possible to grind away such defects, processing a
qualified cylinder.
3. Not round
Cold drawn seamless steel pipe in the production, fixed on the mandrel of the internal model can be floating up and down, so cold drawn tube diameter is not as straight as the machining tube. In addition, some hot-rolled tube, with the wall thickness difference between the larger, cold drawing deformation due to the existence of deformation within the tube is not uniform, easy to produce cold drawn tube does not dot. The tube after honing will find a hole in the hole with other parts of the reflective surface of different degrees, if the grinding volume is small, where even the cold drawn when the phosphate layer is not removed. Seriously affecting the cylinder surface quality.
The measures are as follows:
(1) Cold drawn seamless steel pipe directly into the cylinder, the quality can not be guaranteed, it is best to stay 0.2mm (wall thickness) honing, grinding and then processing use.
(2) Cold drawn seamless steel pipe inner hole defect is the impact of the cylinder bore hole surface quality of the main reasons.
(3) Pitting defects produced by the hot-rolled tube, cold drawing can reduce the depth of the defect can not eliminate the defect.
(4) To increase the amount of cold drawn deformation, preferably hot-rolled seamless steel tube blank, hot-rolled tube defects in the hole clean-up, can improve the cold drawn seamless steel pipe wall surface quality, reduce honing
margins, reduce honing costs and improve Honing production efficiency.
2016年11月24日星期四
Easy to Crack Situation for Stainless Steel Pipe
At room temperature, deformation-induced martensite was produced in both tensile, bending and rolling conditions, and the content of stainless steel increased with the increase of cold working deformation. A lot of experiments show that the deformed layers, deformed twins and strain-induced martensite appear in different degree during the deformation process of the seamless tube, and dislocation plugged and dislocated cellular structure are formed near the grain boundary and annealing twin.
These deformed microstructures contribute to work hardening. Seamless solution for the main purpose is to eliminate the material to reduce stress and hardness, improve the formability of stainless steel seamless pipe. The hardness after treatment is too high that the softening effect is poor, the residual stress is not fully released, because the residual stress caused by lattice distortion will also change the hardness value. It is due to the presence of residual stress, resulting in stainless steel tube flaring easy to stress concentration where the cracks, thus affecting the flaring performance. As the grain boundaries and grain boundaries on both sides of the grain orientation difference, increasing the resistance of dislocation slip in the crystal, so the main role of grain boundary is to impede dislocation movement. The finer the grains, the more the grain boundaries, the greater the resistance to dislocation slip, the higher the yield strength of the steel, the formation of grain boundary strengthening, resulting in work hardening; so the smaller the grain in the flaring The more prone to work hardening.
These deformed microstructures contribute to work hardening. Seamless solution for the main purpose is to eliminate the material to reduce stress and hardness, improve the formability of stainless steel seamless pipe. The hardness after treatment is too high that the softening effect is poor, the residual stress is not fully released, because the residual stress caused by lattice distortion will also change the hardness value. It is due to the presence of residual stress, resulting in stainless steel tube flaring easy to stress concentration where the cracks, thus affecting the flaring performance. As the grain boundaries and grain boundaries on both sides of the grain orientation difference, increasing the resistance of dislocation slip in the crystal, so the main role of grain boundary is to impede dislocation movement. The finer the grains, the more the grain boundaries, the greater the resistance to dislocation slip, the higher the yield strength of the steel, the formation of grain boundary strengthening, resulting in work hardening; so the smaller the grain in the flaring The more prone to work hardening.
Manufacturing Method of Carbon Seamless Seel Pipe
Carbon seamless steel pipe is generally in the automatic production of rolling pipe unit. The solid 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 in furnace, perforation in the punch.continue to rotate and move when perforation, 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.
If you want to get smaller and better quality of seamless tubes, it 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.
The extruding method is to place the heated tube in a closed extruding cylinder which is moved with the extruding rod to squeeze the extrudate from the smaller die hole. This method can produce smaller diameter steel pipe.
If you want to get smaller and better quality of seamless tubes, it 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.
The extruding method is to place the heated tube in a closed extruding cylinder which is moved with the extruding rod to squeeze the extrudate from the smaller die hole. This method can produce smaller diameter steel pipe.
2016年11月23日星期三
Versatility of Seamless Pipes from Wooden House to Manufacturing Units
The wooden houses are the once which are loved by everyone, because they are cool and looks super exciting, but there are several problem comes in constructing and taking care of that kind of home. The problems are water- which can result in rotten walls, sun- which can burn, other than that it has less life than a cemented house. Still it is the most loved construction among other, so here is a base through which you can give long and strength full life to the wooden house.
It is a seamless pipe which can cure the wooden house from the effect of water and keep it away from other sewage problem. SMLS pipes are the widest range, which can be used for the construction and mining purposes. It comes up to 1 to 24'' inch which have the solution of each and every issue of blocking of water in wooden house. For example, a wooden house may need SMLS pipe in order to make the wetness of the water away. These pipes are used in high and low temperature range. It is prepared according to ASTM and API in the complete schedule series. Its strength is up to 1000 ksi.
Manufacturing process
It is prepared through the electric resistance welding, fusion welding, double submerged arc welding and seamless pipe manufacturing. Its manufacturing starts with the transformation of raw material into steel bar. After that it is put in different types of rolling mills, then the bars are use to form the solid round shape called billet, which is heated, pushed and pierced to produce hollow tube or shell. Just because of the heating process, seamless pipes are concluded to have consistent steel pattern.
Uses in other industries
Seamless tubes are the star of high pressure gas and fluid industry, oil and petrochemical industries, power industries. It is a product of steel which is a non-reactive thing, whether it comes in contact of any chemical, it is a safest medium to transfer and dispense the chemicals, water and oil to another tank for further process. It has several uses in manufacturing units as well as in mining rather than that the water supply in various areas is also done with the help of these pipes who are versatile to use in any condition and pursue long life.
I hope the readers will get the versatility of the SMLS pipes, because it can be used in various industries from wooden house to manufacturing units. It has the wide range of pipes for different purposes.
It is a seamless pipe which can cure the wooden house from the effect of water and keep it away from other sewage problem. SMLS pipes are the widest range, which can be used for the construction and mining purposes. It comes up to 1 to 24'' inch which have the solution of each and every issue of blocking of water in wooden house. For example, a wooden house may need SMLS pipe in order to make the wetness of the water away. These pipes are used in high and low temperature range. It is prepared according to ASTM and API in the complete schedule series. Its strength is up to 1000 ksi.
Manufacturing process
It is prepared through the electric resistance welding, fusion welding, double submerged arc welding and seamless pipe manufacturing. Its manufacturing starts with the transformation of raw material into steel bar. After that it is put in different types of rolling mills, then the bars are use to form the solid round shape called billet, which is heated, pushed and pierced to produce hollow tube or shell. Just because of the heating process, seamless pipes are concluded to have consistent steel pattern.
Uses in other industries
Seamless tubes are the star of high pressure gas and fluid industry, oil and petrochemical industries, power industries. It is a product of steel which is a non-reactive thing, whether it comes in contact of any chemical, it is a safest medium to transfer and dispense the chemicals, water and oil to another tank for further process. It has several uses in manufacturing units as well as in mining rather than that the water supply in various areas is also done with the help of these pipes who are versatile to use in any condition and pursue long life.
I hope the readers will get the versatility of the SMLS pipes, because it can be used in various industries from wooden house to manufacturing units. It has the wide range of pipes for different purposes.
Stress Relief Annealing
The precision seamless steel tube to a certain temperature (usually in the phase transition temperature or recrystallization temperature below), the insulation for some time, and then slowly cooling, to eliminate stress in a variety of precision seamless steel tube annealing process.
In press working, casting, welding, heat treatment, cutting and other processes, the product may produce internal stress. In most cases, the metal will retain a portion of its residual stress after the process has ended. Residual stress can lead to fracture, deformation or size change of the workpiece, residual stress also improve the metal chemical activity, in the residual tensile stress is particularly vulnerable to intergranular corrosion caused by rupture. Therefore, the residual stress will affect the performance of precision seamless steel pipe or lead to premature failure of the workpiece.
When the stress is less than the yield strength of the material at the temperature below which the stress is less than the yield strength of the material at the temperature of the stress relaxation temperature, When the residual stress relaxation to achieve the purpose of elimination. In the stress relief annealing, the workpiece is generally slowly heated to a lower temperature (gray cast iron is 500 ~ 550 ℃, precision seamless steel pipe is 500 ~ 650 ℃, non-ferrous metal alloy stamping parts for the recrystallization temperature below), to maintain a period of time , And then slowly cooled to prevent the generation of new residual stresses.
Stress-relief annealing does not completely eliminate the residual stress inside the precision seamless steel tube, but is largely eliminated. For the complete removal of residual stress, precision seamless steel tubes need to be heated to a higher temperature. In this condition, may bring other organizational changes, endangering the use of precision seamless steel pipe performance.
In press working, casting, welding, heat treatment, cutting and other processes, the product may produce internal stress. In most cases, the metal will retain a portion of its residual stress after the process has ended. Residual stress can lead to fracture, deformation or size change of the workpiece, residual stress also improve the metal chemical activity, in the residual tensile stress is particularly vulnerable to intergranular corrosion caused by rupture. Therefore, the residual stress will affect the performance of precision seamless steel pipe or lead to premature failure of the workpiece.
When the stress is less than the yield strength of the material at the temperature below which the stress is less than the yield strength of the material at the temperature of the stress relaxation temperature, When the residual stress relaxation to achieve the purpose of elimination. In the stress relief annealing, the workpiece is generally slowly heated to a lower temperature (gray cast iron is 500 ~ 550 ℃, precision seamless steel pipe is 500 ~ 650 ℃, non-ferrous metal alloy stamping parts for the recrystallization temperature below), to maintain a period of time , And then slowly cooled to prevent the generation of new residual stresses.
Stress-relief annealing does not completely eliminate the residual stress inside the precision seamless steel tube, but is largely eliminated. For the complete removal of residual stress, precision seamless steel tubes need to be heated to a higher temperature. In this condition, may bring other organizational changes, endangering the use of precision seamless steel pipe performance.
2016年11月3日星期四
Method of Straight Seam Steel Pipe in Preheat Deformation
First, the rational selection. On the mold should be selected for precision messy material deformation of a good micro-deformation of steel, carbide segregation serious die steel should be a reasonable casting and quenching and tempering
treatment, the larger and can not be casting mold steel can be solid solution double fine heat treatment. Reasonable choice of heating temperature, control the heating rate, the mold can be used for precision messy slow heating,preheating and other methods of equilibrium heating to reduce the mold heat treatment deformation.
Second, the correct operation of the heat treatment process and a reasonable tempering heat treatment process is to reduce the deformation of a useful tool for precision messy method. Precise messy mold deformation reasons are often
messy, but we only need to master the deformation rules, analysis of the causes of their attack, the choice of abnormal methods to avoid the deformation of the mold can be reduced, but also can be controlled.
Third, the precision messy mold carry out pre-heat treatment to eliminate the mechanical processing of the rest of the stress occurred. On the precision messy mold, in the conditions permitting, try to use vacuum hardening and quenching
after cryogenic treatment. In ensuring the hardness of the mold under the premise, try to use pre-cooling, grading cooling quenching or quenching process.
Fourth, the mold planning description should be reasonable thickness should not be too poor, the shape should be symmetrical, deformation on the larger mold to master the deformation rules, set aside allowance for large, sophisticated messy mold can be used in combination planning. For some precision messy mold can use pre-heat treatment, aging heat treatment, quenched and tempered nitriding heat treatment to control the accuracy of the mold. In the repair mold sand holes, pores, wear and other defects, the choice of cold welding and other heat affected small repair equipment to avoid the repair process deformation of the attack.
treatment, the larger and can not be casting mold steel can be solid solution double fine heat treatment. Reasonable choice of heating temperature, control the heating rate, the mold can be used for precision messy slow heating,preheating and other methods of equilibrium heating to reduce the mold heat treatment deformation.
Second, the correct operation of the heat treatment process and a reasonable tempering heat treatment process is to reduce the deformation of a useful tool for precision messy method. Precise messy mold deformation reasons are often
messy, but we only need to master the deformation rules, analysis of the causes of their attack, the choice of abnormal methods to avoid the deformation of the mold can be reduced, but also can be controlled.
Third, the precision messy mold carry out pre-heat treatment to eliminate the mechanical processing of the rest of the stress occurred. On the precision messy mold, in the conditions permitting, try to use vacuum hardening and quenching
after cryogenic treatment. In ensuring the hardness of the mold under the premise, try to use pre-cooling, grading cooling quenching or quenching process.
Fourth, the mold planning description should be reasonable thickness should not be too poor, the shape should be symmetrical, deformation on the larger mold to master the deformation rules, set aside allowance for large, sophisticated messy mold can be used in combination planning. For some precision messy mold can use pre-heat treatment, aging heat treatment, quenched and tempered nitriding heat treatment to control the accuracy of the mold. In the repair mold sand holes, pores, wear and other defects, the choice of cold welding and other heat affected small repair equipment to avoid the repair process deformation of the attack.
How to Weld for the ERW Steel Pipe in Winter
To ensure that the erw steel pipe in the winter welding perfect follow the following steps:
First, increase the welding current welding, slow down the welding speed, the appropriate increase in the cross-sectional area and length of the weld, if necessary, preheat.
Second, not outside the groove on the base metal to start arc, arc extinction to be filled when the pit.
Third, as far as possible not in low temperature conditions for bending, correction and assembly weldments.
Fourth, preheating before welding, welding process to strictly maintain the interlayer temperature should not be lower than the preheating temperature.
Fifth, the use of low hydrogen or ultra-low hydrogen welding materials.
Six, the entire weld should be finished as far as possible to avoid interruption.
First, increase the welding current welding, slow down the welding speed, the appropriate increase in the cross-sectional area and length of the weld, if necessary, preheat.
Second, not outside the groove on the base metal to start arc, arc extinction to be filled when the pit.
Third, as far as possible not in low temperature conditions for bending, correction and assembly weldments.
Fourth, preheating before welding, welding process to strictly maintain the interlayer temperature should not be lower than the preheating temperature.
Fifth, the use of low hydrogen or ultra-low hydrogen welding materials.
Six, the entire weld should be finished as far as possible to avoid interruption.
Quality Inspection Methods and Equipment of Seamless Steel Pipe
Quality inspection methods and equipment of seamless steel pipe
1, Chemical composition analysis
Instrumental analysis and chemical analysis can be used. For chemical analysis of the sample sub-smelting samples, ingot drill cuttings samples, pipe samples. Smelting samples are generally used instrumental analysis method, the pipe finished sample using chemical analysis and analysis together. Commonly used chemical analysis instruments are: infrared carbon and sulfur analyzer, direct reading spectrometer, X-ray fluorescence spectrometer.
2, Size and shape detection
Check the contents include: wall thickness, diameter, length, bending, ellipticity, port slope and the obtuse angle and cross-sectional shape of special-shaped steel pipe.
3, Surface quality testing
Naked eye inspection and nondestructive inspection. There are many non-destructive testing methods such as: ultrasonic testing, eddy current testing, magnetic detection, magnetic flux leakage testing, electromagnetic and ultrasonic flaw detection flaw detection. Each method has its own advantages and disadvantages: suitable for the detection of steel pipe surface or near the surface: eddy current testing, magnetic detection, magnetic flux leakage detection, penetration testing. Penetration testing is limited to inspection of the surface defects of the steel pipe. Magnetic particle inspection, magnetic flux leakage testing, eddy current testing is limited to ferromagnetic material inspection. Eddy current testing is more sensitive to point defects, other crack detection sensitivity. Ultrasonic detection of steel pipe surface detection reaction is relatively rapid, the internal qualitative analysis of steel there are still some difficulties, and ultrasonic inspection is also affected by the shape and grain size of steel pipe restrictions.
4, Chemical properties testing
(Tensile test, toughness test, hardness test), hydraulic test and corrosion test (intergranular corrosion test, anti-hydrogen cracking test-HIC, anti-sulfide stress cracking test-SSCC) at room temperature or a certain temperature.
5, Steel pipe process performance test
Including flattening experiments, ring pull tests, flaring and crimping experiments, bending experiments.
6, Metallographic analysis
Including low magnification and high magnification.
7, Oil-specific pipe thread parameter detection
Including coupling pattern detection, pipe thread detection and tightening of the pipe body and coupling after the detection.
1, Chemical composition analysis
Instrumental analysis and chemical analysis can be used. For chemical analysis of the sample sub-smelting samples, ingot drill cuttings samples, pipe samples. Smelting samples are generally used instrumental analysis method, the pipe finished sample using chemical analysis and analysis together. Commonly used chemical analysis instruments are: infrared carbon and sulfur analyzer, direct reading spectrometer, X-ray fluorescence spectrometer.
2, Size and shape detection
Check the contents include: wall thickness, diameter, length, bending, ellipticity, port slope and the obtuse angle and cross-sectional shape of special-shaped steel pipe.
3, Surface quality testing
Naked eye inspection and nondestructive inspection. There are many non-destructive testing methods such as: ultrasonic testing, eddy current testing, magnetic detection, magnetic flux leakage testing, electromagnetic and ultrasonic flaw detection flaw detection. Each method has its own advantages and disadvantages: suitable for the detection of steel pipe surface or near the surface: eddy current testing, magnetic detection, magnetic flux leakage detection, penetration testing. Penetration testing is limited to inspection of the surface defects of the steel pipe. Magnetic particle inspection, magnetic flux leakage testing, eddy current testing is limited to ferromagnetic material inspection. Eddy current testing is more sensitive to point defects, other crack detection sensitivity. Ultrasonic detection of steel pipe surface detection reaction is relatively rapid, the internal qualitative analysis of steel there are still some difficulties, and ultrasonic inspection is also affected by the shape and grain size of steel pipe restrictions.
4, Chemical properties testing
(Tensile test, toughness test, hardness test), hydraulic test and corrosion test (intergranular corrosion test, anti-hydrogen cracking test-HIC, anti-sulfide stress cracking test-SSCC) at room temperature or a certain temperature.
5, Steel pipe process performance test
Including flattening experiments, ring pull tests, flaring and crimping experiments, bending experiments.
6, Metallographic analysis
Including low magnification and high magnification.
7, Oil-specific pipe thread parameter detection
Including coupling pattern detection, pipe thread detection and tightening of the pipe body and coupling after the detection.
Quality Requirements for Seamless Steel Pipe
Quality requirements for seamless steel pipe
1, Chemical composition
In order to improve the uniformity of chemical composition in steel and the purity of steel, to reduce the non-metallic inclusions in the tube and to improve the distribution state, it is often used to improve the chemical composition of the steel, such as As Sn Sb Bi Pb and gas NHO. External refining equipment for refining of molten steel, and even the use of electroslag furnace on the tube re-melting refining.
2, Dimensional accuracy and shape
The geometry of the seamless steel pipe mainly includes the outer diameter, wall thickness, ellipticity, length, curvature, pipe end face inclination, groove angle and the blunt edge, cross-sectional size of the steel pipe.
3, Surface quality
The standard specifies the requirements for the "smooth surface" of seamless steel tubes. Common defects include: cracks, hair lines, inside the fold, outside the fold, rolling broken, the straight, outside the straight, separated layer, scar, pits, convex package, Ma Hang (Ma) , The spiral Road, outside the spiral Road, Green Line, correction concave, such as roller. Crack, slight internal and external straight, minor internal and external spiral, straightening, and so
on. In addition to the internal and external cracks, cracks, broken, rolling, Concave, roll as a general defect.
4, Physical and chemical properties
Including mechanical properties at room temperature and mechanical properties at certain temperatures (heat and low temperature properties) and corrosion resistance (such as anti-oxidation, water erosion, acid and alkali resistance and other properties) under normal circumstances depends on the chemical composition of steel, Performance and steel purity and steel heat treatment methods. In some cases, the rolling temperature and the degree of deformation of the steel pipe will also affect the performance of the steel pipe.
5, Process performance
Including flaring, flattening, crimping, bending, pulling and welding performance.
6, Microstructure
Including the low-power steel pipe and high-power organization.
7, Special requirements
In the user's use of steel pipe other than the standard requirements.
1, Chemical composition
In order to improve the uniformity of chemical composition in steel and the purity of steel, to reduce the non-metallic inclusions in the tube and to improve the distribution state, it is often used to improve the chemical composition of the steel, such as As Sn Sb Bi Pb and gas NHO. External refining equipment for refining of molten steel, and even the use of electroslag furnace on the tube re-melting refining.
2, Dimensional accuracy and shape
The geometry of the seamless steel pipe mainly includes the outer diameter, wall thickness, ellipticity, length, curvature, pipe end face inclination, groove angle and the blunt edge, cross-sectional size of the steel pipe.
3, Surface quality
The standard specifies the requirements for the "smooth surface" of seamless steel tubes. Common defects include: cracks, hair lines, inside the fold, outside the fold, rolling broken, the straight, outside the straight, separated layer, scar, pits, convex package, Ma Hang (Ma) , The spiral Road, outside the spiral Road, Green Line, correction concave, such as roller. Crack, slight internal and external straight, minor internal and external spiral, straightening, and so
on. In addition to the internal and external cracks, cracks, broken, rolling, Concave, roll as a general defect.
4, Physical and chemical properties
Including mechanical properties at room temperature and mechanical properties at certain temperatures (heat and low temperature properties) and corrosion resistance (such as anti-oxidation, water erosion, acid and alkali resistance and other properties) under normal circumstances depends on the chemical composition of steel, Performance and steel purity and steel heat treatment methods. In some cases, the rolling temperature and the degree of deformation of the steel pipe will also affect the performance of the steel pipe.
5, Process performance
Including flaring, flattening, crimping, bending, pulling and welding performance.
6, Microstructure
Including the low-power steel pipe and high-power organization.
7, Special requirements
In the user's use of steel pipe other than the standard requirements.
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