Even for stainless steel pipe, there are lots of types for it. Different treatment for them would give them various functions. Today, we’d like to share the process treatment for food, beverage and other sanitary stainless tube’s.
Three main kinds would be here for stainless steel pipes used for food and beverage transmission: surface finish, oil ban and passivation layer.
Surface finish: Inner and outer surface should be polished bright to guarantee the quality of the pipeline. The special goal is to prevent the fluid material in the tube from forming a wall in the tube, which is prone to contamination and forms a tube blockage.
Passivation layer: Stainless steel pipe needed to be placed in a passivation tank for immersion after polishing, thus, we can get the purpose of corrosion resistance of the steel pipe
Oil ban: When we finished passivation, we will test with a grease analyzer, so we can prevent the oil pollution of the pipe wall itself from contaminating the fluid material in the pipe.
2018年12月26日星期三
Five reasons to buy PE coated steel tubes
PE coated steel pipe, whether used for water supply like ERW steel pipe or oil transmission like seamless tube, is popular for customers nowadays. There are five common reasons to purchase this kind of tube.
PE coated steel pipe has three classifications which are PE Coated Pipe, 2PE Coated Pipe, and 3PE Coated Pipe. The advantages by using them are:
Strong protective layer: With coated process, you would laud the protective function for the steel pipeline.
Long term chemical and mechanical resistance: Due to the layer, it will elucidate the long term effect for the steel tube.
High mechanical impact strength and penetration resistance: Same reason with the second point, and you will find that the pipe would be tardy in working environment.
Increases life span of pipes more than 25yers.
Economy in the long term due to less repairing/re-working.
PE coated steel pipe has three classifications which are PE Coated Pipe, 2PE Coated Pipe, and 3PE Coated Pipe. The advantages by using them are:
Strong protective layer: With coated process, you would laud the protective function for the steel pipeline.
Long term chemical and mechanical resistance: Due to the layer, it will elucidate the long term effect for the steel tube.
High mechanical impact strength and penetration resistance: Same reason with the second point, and you will find that the pipe would be tardy in working environment.
Increases life span of pipes more than 25yers.
Economy in the long term due to less repairing/re-working.
Six maintenance methods for stainless steel tubes
For stainless seamless steel pipe, there are some basic methods for the care of it to extend the service life of stainless steel. By preventing contact with corrosive substances would be one of them. And if we follow these best practices when working with stainless steel, we will get better result.
There are seven common ways to care of the stainless steel pipe.
1. Using stainless steel tools and components always would be necessary.
2. Avoid any contact with carbon steels, concrete detergents or iron.
3. Do not weld, cut, drill or grind carbon steel near stainless steel.
4. When power washing nearby surfaces, wrap stainless steel with plastic.
5. If chloride solutions or concrete detergents contact stainless steel, rinse immediately.
6. Never scrub with steel wool or other abrasive scrubbing pads.
With careful protect for stainless steel pipe, clients will use them for a relative long time for engineering project.
There are seven common ways to care of the stainless steel pipe.
1. Using stainless steel tools and components always would be necessary.
2. Avoid any contact with carbon steels, concrete detergents or iron.
3. Do not weld, cut, drill or grind carbon steel near stainless steel.
4. When power washing nearby surfaces, wrap stainless steel with plastic.
5. If chloride solutions or concrete detergents contact stainless steel, rinse immediately.
6. Never scrub with steel wool or other abrasive scrubbing pads.
With careful protect for stainless steel pipe, clients will use them for a relative long time for engineering project.
Meet steel pipe material expectations
As a ERW steel pipe manufacturer, our manager would think the question of how to produce high quality steel tube for customers often. She said it is really simple actually. Following the trend and meeting steel pipe’s material expectations, you will find a new product world for your customers.
No matter which kind of method we are trying to make the high quality steel pipe, we cannot ignore the steel pipe's intrinsic quality for relative pipeline. Once we take control of material proportion, such as stainless and nickel; temperature, length and width, we should look into the essence of a steel pipeline.
Importance of chemistry. We should view each type of stainless and nickel alloy scrap as a distinct blend of nickel, chrome, molybdenum, and iron and each individual alloy is its own blend.
Consistency of compatibility. Their ability to supply materials consistently—both in terms of quantity and quality—is why they have exclusive supply arrangements with stainless mills and specialty foundries.
No matter which kind of method we are trying to make the high quality steel pipe, we cannot ignore the steel pipe's intrinsic quality for relative pipeline. Once we take control of material proportion, such as stainless and nickel; temperature, length and width, we should look into the essence of a steel pipeline.
Importance of chemistry. We should view each type of stainless and nickel alloy scrap as a distinct blend of nickel, chrome, molybdenum, and iron and each individual alloy is its own blend.
Consistency of compatibility. Their ability to supply materials consistently—both in terms of quantity and quality—is why they have exclusive supply arrangements with stainless mills and specialty foundries.
Selection of inspection techniques for seamless steel pipe
Six billet inspection techniques have been listed in essays before. And today, we’d like to discuss the selection of inspection techniques for seamless steel pipe. As we know that not each of them has equal role during the whole inspection.
Actually, there are three of the methods would have more useful for the continuously cast billets than others. They are eddy currents techniques, optical techniques, and microwave techniques.
The optical system can resolve the smaller defective areas, for example, pinholes. Of course, it is also used for responding to other types of defects which show up in relief under the incident lighting conditions.
The microwave system has the benefit of reasonable operating clearances (of the order of 30 mm) and usually resolve large area defects and, both longitudinal and transverse cracks of the order of 10 mm or more in length.
The eddy current probe array on the other hand have to be positioned closer to the surface, at say 3 mm, but is capable of better resolution in the detection of transverse cracks, teeming arrests, reciprocation marks, etc. than the microwave technique.
Actually, there are three of the methods would have more useful for the continuously cast billets than others. They are eddy currents techniques, optical techniques, and microwave techniques.
The optical system can resolve the smaller defective areas, for example, pinholes. Of course, it is also used for responding to other types of defects which show up in relief under the incident lighting conditions.
The microwave system has the benefit of reasonable operating clearances (of the order of 30 mm) and usually resolve large area defects and, both longitudinal and transverse cracks of the order of 10 mm or more in length.
The eddy current probe array on the other hand have to be positioned closer to the surface, at say 3 mm, but is capable of better resolution in the detection of transverse cracks, teeming arrests, reciprocation marks, etc. than the microwave technique.
2018年12月20日星期四
Defects in pickling seamless steel tubes
In the case of pickling, the seamless steel pipe has a stripping effect on the iron oxide scale, and also diffuses into the interior of the steel billet matrix and accumulates at the impurities or pores, resulting in an increase in internal stress, a decrease in the plasticity of the steel, and an increase in the brittleness of the steel. The effect is called hydrogen embrittlement. Hydrogen embrittlement is mainly affected by the diffusion rate of hydrogen atoms. The rate of hydrogen diffusion is related to the following factors:
1) The diffusion rate of hydrogen in a sulfuric acid solution is higher than that in a hydrochloric acid solution.
2) As the pickling temperature increases, the diffusion rate of hydrogen increases sharply, and the concentration of acid increases, and the diffusion rate of hydrogen does not increase much. Therefore, it is best not to pickle at low concentrations and high temperatures. This is a must for both seamless and oil casings.
3) Some inclusions in pickling such as arsenic (As), antimony (Sb), hydrogen sulfide (H2S) and sulfur dioxide (SO2) increase the diffusion rate of hydrogen atoms, ie increase the possibility of hydrogen embrittlement.
4) The chemical composition of steel also has an effect on the diffusion of hydrogen atoms. The measures to prevent hydrogen embrittlement are to operate according to the specified acid concentration and temperature, to minimize the pickling time, and to add corrosion inhibitors in accordance with the amount.
There is still a scale of iron oxide on the surface of the slab after pickling, which is called under-picking. Under-picking can be divided into all under-picking and partial under-washing depending on the cause. The reason for causing all the acid pickling is that the pickling time is short, the acid concentration is low, or the temperature is low; the reason for causing partial under pickling is that there is no horn on the material or oil on the surface of the steel billet. Under-pickling can be saved by continuing to pickle.
When it is pickled and carbon steel is pickled, the surface is rough and the color is dark. When the chrome stainless steel is pickled, the surface is gray and extremely rough. In severe cases, there is a circular hole with a certain depth - pinhole. The reason for the pickling is that the acid temperature is too high, the pickling time is too long, or the acid concentration is too high. Once this defect is unrecoverable, it has a detrimental effect on the performance of the steel. The acid-washed steel is easily stuck or broken during the rolling process.
After pickling, in addition to the iron salt remaining on the surface of the slab, there is a residue consisting of oxides or salts of other elements in the steel. These residues are not good for cleaning the surface defects of the slab. If it is not washed out in time, the surface of the slab will continue to rust and appear yellow.
1) The diffusion rate of hydrogen in a sulfuric acid solution is higher than that in a hydrochloric acid solution.
2) As the pickling temperature increases, the diffusion rate of hydrogen increases sharply, and the concentration of acid increases, and the diffusion rate of hydrogen does not increase much. Therefore, it is best not to pickle at low concentrations and high temperatures. This is a must for both seamless and oil casings.
3) Some inclusions in pickling such as arsenic (As), antimony (Sb), hydrogen sulfide (H2S) and sulfur dioxide (SO2) increase the diffusion rate of hydrogen atoms, ie increase the possibility of hydrogen embrittlement.
4) The chemical composition of steel also has an effect on the diffusion of hydrogen atoms. The measures to prevent hydrogen embrittlement are to operate according to the specified acid concentration and temperature, to minimize the pickling time, and to add corrosion inhibitors in accordance with the amount.
There is still a scale of iron oxide on the surface of the slab after pickling, which is called under-picking. Under-picking can be divided into all under-picking and partial under-washing depending on the cause. The reason for causing all the acid pickling is that the pickling time is short, the acid concentration is low, or the temperature is low; the reason for causing partial under pickling is that there is no horn on the material or oil on the surface of the steel billet. Under-pickling can be saved by continuing to pickle.
When it is pickled and carbon steel is pickled, the surface is rough and the color is dark. When the chrome stainless steel is pickled, the surface is gray and extremely rough. In severe cases, there is a circular hole with a certain depth - pinhole. The reason for the pickling is that the acid temperature is too high, the pickling time is too long, or the acid concentration is too high. Once this defect is unrecoverable, it has a detrimental effect on the performance of the steel. The acid-washed steel is easily stuck or broken during the rolling process.
After pickling, in addition to the iron salt remaining on the surface of the slab, there is a residue consisting of oxides or salts of other elements in the steel. These residues are not good for cleaning the surface defects of the slab. If it is not washed out in time, the surface of the slab will continue to rust and appear yellow.
How to solve the shortage of cold drawn seamless steel pipe
Hot-rolled tube blanks in cold-drawn seamless steel tubes may have defects such as cracks. At the same time, the resulting cylinders may break during use and deform, generally brittle fractures. There are many reasons, generally grain boundaries. Precipitates, this needs to be changed by some means. In order to solve the problem of cold drawn seamless steel pipe, foreign countries generally improve the performance of alloy materials by general, and generally require stress relief annealing to eliminate residual stress of materials, improve material structure, and improve plastic materials to prevent seamless steel pipe breakage. The purpose of the failure.
At present, the material of the cold drawn seamless steel pipe is common steel, silicon manganese, steel, and the strength of the metal is improved by cold drawing deformation, but it increases the plasticity and toughness cost of the metal. Due to the high precision of cold drawn seamless steel tubes, high-strength performance based on the market is required. It is necessary to ensure deformation within a certain range, maximize the performance of materials, and reduce the adverse effects of materials.
Cold drawn seamless steel pipe deformation is too small, can not meet the requirements of surface finish and dimensional accuracy, can not reach the strength of the index component, deformation is too large, resulting in too much plasticity and toughness of the steel pipe, and the article is too thin, the formed fiber The metal will have significant anisotropy. The grain of the spin direction of the shaft increases the strength in parallel. The radial direction of the cold drawn seamless steel pipe is perpendicular to the rotation direction of the grain, but the strength is decreased, and the stress of the hydraulic cylinder is excessively deformed in the radial direction of the seamless steel pipe. So, the performance of the cold drawn tube is fully utilized.
http://www.xysteelpipe.com/info/How-to-solve-the-shortage-of-cold-drawn-seamless-steel-pipe-1296-1.htm
At present, the material of the cold drawn seamless steel pipe is common steel, silicon manganese, steel, and the strength of the metal is improved by cold drawing deformation, but it increases the plasticity and toughness cost of the metal. Due to the high precision of cold drawn seamless steel tubes, high-strength performance based on the market is required. It is necessary to ensure deformation within a certain range, maximize the performance of materials, and reduce the adverse effects of materials.
Cold drawn seamless steel pipe deformation is too small, can not meet the requirements of surface finish and dimensional accuracy, can not reach the strength of the index component, deformation is too large, resulting in too much plasticity and toughness of the steel pipe, and the article is too thin, the formed fiber The metal will have significant anisotropy. The grain of the spin direction of the shaft increases the strength in parallel. The radial direction of the cold drawn seamless steel pipe is perpendicular to the rotation direction of the grain, but the strength is decreased, and the stress of the hydraulic cylinder is excessively deformed in the radial direction of the seamless steel pipe. So, the performance of the cold drawn tube is fully utilized.
http://www.xysteelpipe.com/info/How-to-solve-the-shortage-of-cold-drawn-seamless-steel-pipe-1296-1.htm
2018年12月19日星期三
The main difference between stainless steel pipe and carbon steel pipe
Carbon steel seamless pipe is often referred to as carbon structural steel. It is iron, carbon and manganese as the main elements except C. It is not divided into other alloying elements. It is mainly divided into 10# seamless steel pipe, 20 # seamless steel pipe, 45# seamless steel pipe, of course, C is also controlled to a certain extent, and the hardness is larger than pure iron. Carbon steel has low cost, is prone to rust, and has a short use time, and is used in various structures and pipes that do not have any corrosion resistance.
Stainless steel pipe refers to alloy steel containing less than or equal to 13% Cr and not in the atmosphere. There are many types of stainless steel, such as ferritic stainless steel, austenitic stainless steel, and martensitic stainless steel. Different stainless steels have different resistance to corrosion and different corrosion resistance to different media. It is also different in terms of magnetism. Carbon steel is magnetic, and stainless steel generally does not have magnetic or magnetic properties.
The stainless steel tube contains a large amount of chromium, and some contain a large amount of nickel and a certain amount of titanium. The role of chromium is to make steel corrosion-resistant. Nickel is the main alloying element for the formation of austenitic stainless steel, but the role of nickel can only be fully demonstrated when it is combined with chromium. If pure nickel is used, a pure austenite single-phase structure is required in low-carbon nickel steel, and the nickel content needs to be more than 24%. In fact, when the nickel content needs to reach 27%, the corrosion resistance of the stainless steel pipe can be remarkably improved. , so there is no nickel as an alloying element in the stainless steel tube.
Common stainless steels are mostly austenitic stainless steels, such as 304, 316L, 321 and so on. The carbon content is lower, but the alloying element content is above 20%, of which the chromium is 18-20%, the Ni content is 8-10%, and there are elements such as vanadium, molybdenum and titanium. The stainless steel is used for corrosiveness. In the medium, especially in foods with high requirements for ring conditions, pharmaceuticals, daily chemical cosmetics and other industries, most of them are used. Of course, the chemical industry is also widely used. However, austenitic stainless steel is afraid of chloride ions and is very strict in controlling the chloride ions of water in the environment.
Stainless steel pipe refers to alloy steel containing less than or equal to 13% Cr and not in the atmosphere. There are many types of stainless steel, such as ferritic stainless steel, austenitic stainless steel, and martensitic stainless steel. Different stainless steels have different resistance to corrosion and different corrosion resistance to different media. It is also different in terms of magnetism. Carbon steel is magnetic, and stainless steel generally does not have magnetic or magnetic properties.
The stainless steel tube contains a large amount of chromium, and some contain a large amount of nickel and a certain amount of titanium. The role of chromium is to make steel corrosion-resistant. Nickel is the main alloying element for the formation of austenitic stainless steel, but the role of nickel can only be fully demonstrated when it is combined with chromium. If pure nickel is used, a pure austenite single-phase structure is required in low-carbon nickel steel, and the nickel content needs to be more than 24%. In fact, when the nickel content needs to reach 27%, the corrosion resistance of the stainless steel pipe can be remarkably improved. , so there is no nickel as an alloying element in the stainless steel tube.
Common stainless steels are mostly austenitic stainless steels, such as 304, 316L, 321 and so on. The carbon content is lower, but the alloying element content is above 20%, of which the chromium is 18-20%, the Ni content is 8-10%, and there are elements such as vanadium, molybdenum and titanium. The stainless steel is used for corrosiveness. In the medium, especially in foods with high requirements for ring conditions, pharmaceuticals, daily chemical cosmetics and other industries, most of them are used. Of course, the chemical industry is also widely used. However, austenitic stainless steel is afraid of chloride ions and is very strict in controlling the chloride ions of water in the environment.
Cold crack analysis and preventive measures of large diameter seamless steel pipe
Large-diameter seamless steel tubes are mostly medium-sized, high-carbon alloy steels. After quenching, some of the supercooled austenite is not transformed into martensite, and remains in the use state as residual austenite, which affects the performance. If it is cooled below zero, it can promote the martensite transformation of the retained austenite. Therefore, the essence of the cold treatment is that the quenching continues. The quenching stress at room temperature is superimposed on the quenching stress at zero, and the cold treatment crack is formed when the refolding stress exceeds the strength limit of the material.
Precaution:
(1) Before the cold treatment after quenching, the large-diameter seamless steel pipe is placed in boiling water for 30-60 minutes, which can eliminate 15%-25% quenching internal stress and stabilize the retained austenite, and then perform -60 ° C conventional cold treatment, or After cryogenic treatment at -120 ° C, the lower the temperature, the more the retained austenite transforms into martensite, but it is impossible to complete the conversion.
Experiments show that about 2%-5% retained austenite remains, as needed Retain a small amount of retained austenite to relax the stress and act as a buffer. Because the retained austenite is soft and tough, it can partially absorb the martensite rapid expansion energy and alleviate the phase transformation stress.
(2) After the cold treatment is completed, the large-diameter seamless steel pipe is taken out and heated in hot water to eliminate 40%-60% cold treatment stress. After heating to room temperature, it should be tempered in time, the cold treatment stress is further eliminated, cold crack formation is avoided, and stable structure is obtained. Performance, to ensure that large diameter seamless steel pipe products are stored and used without distortion.
Precaution:
(1) Before the cold treatment after quenching, the large-diameter seamless steel pipe is placed in boiling water for 30-60 minutes, which can eliminate 15%-25% quenching internal stress and stabilize the retained austenite, and then perform -60 ° C conventional cold treatment, or After cryogenic treatment at -120 ° C, the lower the temperature, the more the retained austenite transforms into martensite, but it is impossible to complete the conversion.
Experiments show that about 2%-5% retained austenite remains, as needed Retain a small amount of retained austenite to relax the stress and act as a buffer. Because the retained austenite is soft and tough, it can partially absorb the martensite rapid expansion energy and alleviate the phase transformation stress.
(2) After the cold treatment is completed, the large-diameter seamless steel pipe is taken out and heated in hot water to eliminate 40%-60% cold treatment stress. After heating to room temperature, it should be tempered in time, the cold treatment stress is further eliminated, cold crack formation is avoided, and stable structure is obtained. Performance, to ensure that large diameter seamless steel pipe products are stored and used without distortion.
Seamless Steel Pipe Preservation And Washing
Precautions for the preservation of seamless steel tubes:
1. The site or warehouse for storing steel, whether it is seamless steel pipe or other straight seam steel pipe, should be selected at the midpoint of clean and clean, poor drainage, away from the occurrence of harmless gas or dust. Weeds and all kinds of debris should be cleared on the site, and the steel should be clean;
2. Do not stack materials that are corrosive to steel, such as acid, alkali, salt or cement, in the warehouse. Different types of steel should be identified and stacked to avoid mixing and avoid contact corrosion;
3. Large-scale steel, rail, insult steel plate, large-diameter steel pipe, forgings, etc. can be stacked in the open air;
4. Small and medium-sized steel, wire rod, steel, medium-diameter steel pipe, steel wire and wire rope, etc., can be stored in a well-ventilated shed, but must be placed on the underside;
5. Some small steel, thin steel, steel, silicon steel, small-diameter or thin-walled steel pipes, various cold-rolled and cold-drawn steel products, and high-priced, corrosive metal products can be stored in the warehouse;
6. The warehouse should be selected according to astronomical conditions. Ordinary blockade warehouses are generally used, that is, there are walls with walls, doors and windows close to each other, and a ventilated installation warehouse;
7. The warehouse requires sunny attention to ventilation, rainy days to pay attention to closed moisture, often adhere to a suitable storage environment.
Seamless tube washing is especially important, here are the notes:
1. When the seamless steel pipe is washed, it needs to be carried out in the flowing clear water tank. This can avoid secondary pollution. When washing, the seamless steel pipe needs to be fully immersed in water. At this time, the sling should be relaxed, up and down. It can be four times.
2. When washing, it is necessary to clean the water in the steel pipe to avoid water corrosion and oxidation of the steel pipe. Therefore, it is necessary to process the solvent as soon as possible.
3. It should be noted that it is not possible to cross the pickling tank to avoid accidents, slipping or falling into the acid tank and being corroded by residual hydrochloric acid.
4. The need for iron salt content standards must be controlled within a certain range, can not appear excessive conditions, otherwise it may damage the seamless steel pipe.
1. The site or warehouse for storing steel, whether it is seamless steel pipe or other straight seam steel pipe, should be selected at the midpoint of clean and clean, poor drainage, away from the occurrence of harmless gas or dust. Weeds and all kinds of debris should be cleared on the site, and the steel should be clean;
2. Do not stack materials that are corrosive to steel, such as acid, alkali, salt or cement, in the warehouse. Different types of steel should be identified and stacked to avoid mixing and avoid contact corrosion;
3. Large-scale steel, rail, insult steel plate, large-diameter steel pipe, forgings, etc. can be stacked in the open air;
4. Small and medium-sized steel, wire rod, steel, medium-diameter steel pipe, steel wire and wire rope, etc., can be stored in a well-ventilated shed, but must be placed on the underside;
5. Some small steel, thin steel, steel, silicon steel, small-diameter or thin-walled steel pipes, various cold-rolled and cold-drawn steel products, and high-priced, corrosive metal products can be stored in the warehouse;
6. The warehouse should be selected according to astronomical conditions. Ordinary blockade warehouses are generally used, that is, there are walls with walls, doors and windows close to each other, and a ventilated installation warehouse;
7. The warehouse requires sunny attention to ventilation, rainy days to pay attention to closed moisture, often adhere to a suitable storage environment.
Seamless tube washing is especially important, here are the notes:
1. When the seamless steel pipe is washed, it needs to be carried out in the flowing clear water tank. This can avoid secondary pollution. When washing, the seamless steel pipe needs to be fully immersed in water. At this time, the sling should be relaxed, up and down. It can be four times.
2. When washing, it is necessary to clean the water in the steel pipe to avoid water corrosion and oxidation of the steel pipe. Therefore, it is necessary to process the solvent as soon as possible.
3. It should be noted that it is not possible to cross the pickling tank to avoid accidents, slipping or falling into the acid tank and being corroded by residual hydrochloric acid.
4. The need for iron salt content standards must be controlled within a certain range, can not appear excessive conditions, otherwise it may damage the seamless steel pipe.
2018年12月11日星期二
Knowledge of stainless steel seamless pipe
Stainless steel seamless pipe is a long strip of steel with a hollow section and no joints around it.
The characteristics of stainless steel seamless pipe:
First, the thicker the wall thickness of the product, the more economical and practical it is. The thinner the wall thickness, the higher the processing cost will be. Secondly, the process of the product determines its limited performance. The seamless steel tube has low precision: uneven wall thickness, low brightness inside and outside the tube, high fixed-length cost, and pitting and black spots on the inner and outer surfaces are not easy to remove; third, its detection and shaping must be processed offline. Therefore, it embodies its superiority in high-pressure, high-strength, mechanical structural materials.
The type of stainless steel pipe:
The rolling method is divided into hot rolling, hot extrusion and cold drawing (rolling) stainless steel tubes. According to the stainless steel metallographic structure, it is divided into semi-ferritic semi-Martensitic stainless steel pipes, martensitic stainless steel pipes, austenitic stainless steel pipes, austenitic-ferritic iron stainless steel pipes.
Stainless steel pipe seamless pipe specifications and appearance quality:
A. According to the provisions of GB14975-94 "Stainless Steel Seamless Steel Pipe", the normal length of steel pipe (indefinite) hot-rolled steel pipe is 1.5~10m, and the hot-extruded steel pipe is equal to or greater than 1m. Cold drawn (rolled) steel pipe wall thickness of 0.5 ~ 1.0mm, 1.0 ~ 7m; wall thickness greater than 1.0mm, 1.5 ~ 8m.
B. There are 45 kinds of hot-rolled (hot-extruded) steel pipes with a diameter of 54-480 mm; a total of 36 kinds of wall thicknesses of 4.5-45 mm. There are 65 kinds of cold drawn (rolled) steel pipes with a diameter of 6 to 200 mm, and 39 kinds of wall thicknesses of 0.5 to 21 mm.
C. There shall be no cracks, folds, cracks, cracks, rolling, separation and crusting defects on the inner and outer surfaces of the steel pipe. These defects shall be completely removed (except for mechanical processing pipes), and the wall thickness and outer wall shall not be removed after removal. The diameter exceeds the negative deviation. Other minor surface defects that do not exceed the allowable negative deviation may not be removed.
D. Straight road allows depth. Hot-rolled and hot-extruded steel pipes, not less than or equal to 140mm in diameter and not more than 5% of the nominal wall thickness, the maximum depth is not more than 0.5mm; cold-drawn (rolled) steel pipes are not more than 4% of the nominal wall thickness, and the maximum depth is not more than 0.3 Mm.
E. Both ends of the steel pipe should be cut at right angles and the burrs should be removed.
The characteristics of stainless steel seamless pipe:
First, the thicker the wall thickness of the product, the more economical and practical it is. The thinner the wall thickness, the higher the processing cost will be. Secondly, the process of the product determines its limited performance. The seamless steel tube has low precision: uneven wall thickness, low brightness inside and outside the tube, high fixed-length cost, and pitting and black spots on the inner and outer surfaces are not easy to remove; third, its detection and shaping must be processed offline. Therefore, it embodies its superiority in high-pressure, high-strength, mechanical structural materials.
The type of stainless steel pipe:
The rolling method is divided into hot rolling, hot extrusion and cold drawing (rolling) stainless steel tubes. According to the stainless steel metallographic structure, it is divided into semi-ferritic semi-Martensitic stainless steel pipes, martensitic stainless steel pipes, austenitic stainless steel pipes, austenitic-ferritic iron stainless steel pipes.
Stainless steel pipe seamless pipe specifications and appearance quality:
A. According to the provisions of GB14975-94 "Stainless Steel Seamless Steel Pipe", the normal length of steel pipe (indefinite) hot-rolled steel pipe is 1.5~10m, and the hot-extruded steel pipe is equal to or greater than 1m. Cold drawn (rolled) steel pipe wall thickness of 0.5 ~ 1.0mm, 1.0 ~ 7m; wall thickness greater than 1.0mm, 1.5 ~ 8m.
B. There are 45 kinds of hot-rolled (hot-extruded) steel pipes with a diameter of 54-480 mm; a total of 36 kinds of wall thicknesses of 4.5-45 mm. There are 65 kinds of cold drawn (rolled) steel pipes with a diameter of 6 to 200 mm, and 39 kinds of wall thicknesses of 0.5 to 21 mm.
C. There shall be no cracks, folds, cracks, cracks, rolling, separation and crusting defects on the inner and outer surfaces of the steel pipe. These defects shall be completely removed (except for mechanical processing pipes), and the wall thickness and outer wall shall not be removed after removal. The diameter exceeds the negative deviation. Other minor surface defects that do not exceed the allowable negative deviation may not be removed.
D. Straight road allows depth. Hot-rolled and hot-extruded steel pipes, not less than or equal to 140mm in diameter and not more than 5% of the nominal wall thickness, the maximum depth is not more than 0.5mm; cold-drawn (rolled) steel pipes are not more than 4% of the nominal wall thickness, and the maximum depth is not more than 0.3 Mm.
E. Both ends of the steel pipe should be cut at right angles and the burrs should be removed.
Defects in pickling seamless steel tubes
In the case of pickling, the seamless steel pipe has a stripping effect on the iron oxide scale, and also diffuses into the interior of the steel billet matrix and accumulates at the impurities or pores, resulting in an increase in internal stress, a decrease in the plasticity of the steel, and an increase in the brittleness of the steel. The effect is called hydrogen embrittlement. Hydrogen embrittlement is mainly affected by the diffusion rate of hydrogen atoms. The rate of hydrogen diffusion is related to the following factors:
1) The diffusion rate of hydrogen in a sulfuric acid solution is higher than that in a hydrochloric acid solution.
2) As the pickling temperature increases, the diffusion rate of hydrogen increases sharply, and the concentration of acid increases, and the diffusion rate of hydrogen does not increase much. Therefore, it is best not to pickle at low concentrations and high temperatures. This is a must for both seamless and oil casings.
3) Some inclusions in pickling such as arsenic (As), antimony (Sb), hydrogen sulfide (H2S) and sulfur dioxide (SO2) increase the diffusion rate of hydrogen atoms, ie increase the possibility of hydrogen embrittlement.
4) The chemical composition of steel also has an effect on the diffusion of hydrogen atoms. The measures to prevent hydrogen embrittlement are to operate according to the specified acid concentration and temperature, to minimize the pickling time, and to add corrosion inhibitors in accordance with the amount.
There is still a scale of iron oxide on the surface of the slab after pickling, which is called under-picking. Under-picking can be divided into all under-picking and partial under-washing depending on the cause. The reason for causing all the acid pickling is that the pickling time is short, the acid concentration is low, or the temperature is low; the reason for causing partial under pickling is that there is no horn on the material or oil on the surface of the steel billet. Under-pickling can be saved by continuing to pickle.
When it is pickled and carbon steel is pickled, the surface is rough and the color is dark. When the chrome stainless steel is pickled, the surface is gray and extremely rough. In severe cases, there is a circular hole with a certain depth - pinhole. The reason for the pickling is that the acid temperature is too high, the pickling time is too long, or the acid concentration is too high. Once this defect is unrecoverable, it has a detrimental effect on the performance of the steel. The acid-washed steel is easily stuck or broken during the rolling process.
After pickling, in addition to the iron salt remaining on the surface of the slab, there is a residue consisting of oxides or salts of other elements in the steel. These residues are not good for cleaning the surface defects of the slab. If it is not washed out in time, the surface of the slab will continue to rust and appear yellow.
http://www.xysteelpipe.com/info/Defects-in-pickling-seamless-steel-tubes-1290-1.htm
1) The diffusion rate of hydrogen in a sulfuric acid solution is higher than that in a hydrochloric acid solution.
2) As the pickling temperature increases, the diffusion rate of hydrogen increases sharply, and the concentration of acid increases, and the diffusion rate of hydrogen does not increase much. Therefore, it is best not to pickle at low concentrations and high temperatures. This is a must for both seamless and oil casings.
3) Some inclusions in pickling such as arsenic (As), antimony (Sb), hydrogen sulfide (H2S) and sulfur dioxide (SO2) increase the diffusion rate of hydrogen atoms, ie increase the possibility of hydrogen embrittlement.
4) The chemical composition of steel also has an effect on the diffusion of hydrogen atoms. The measures to prevent hydrogen embrittlement are to operate according to the specified acid concentration and temperature, to minimize the pickling time, and to add corrosion inhibitors in accordance with the amount.
There is still a scale of iron oxide on the surface of the slab after pickling, which is called under-picking. Under-picking can be divided into all under-picking and partial under-washing depending on the cause. The reason for causing all the acid pickling is that the pickling time is short, the acid concentration is low, or the temperature is low; the reason for causing partial under pickling is that there is no horn on the material or oil on the surface of the steel billet. Under-pickling can be saved by continuing to pickle.
When it is pickled and carbon steel is pickled, the surface is rough and the color is dark. When the chrome stainless steel is pickled, the surface is gray and extremely rough. In severe cases, there is a circular hole with a certain depth - pinhole. The reason for the pickling is that the acid temperature is too high, the pickling time is too long, or the acid concentration is too high. Once this defect is unrecoverable, it has a detrimental effect on the performance of the steel. The acid-washed steel is easily stuck or broken during the rolling process.
After pickling, in addition to the iron salt remaining on the surface of the slab, there is a residue consisting of oxides or salts of other elements in the steel. These residues are not good for cleaning the surface defects of the slab. If it is not washed out in time, the surface of the slab will continue to rust and appear yellow.
http://www.xysteelpipe.com/info/Defects-in-pickling-seamless-steel-tubes-1290-1.htm
2018年12月10日星期一
Seamless pipe thermal expansion treatment
The seamless expansion of the seamless steel tube is divided into an overall thermal expansion treatment, a surface thermal expansion treatment, and a chemical heat treatment. The seamless expansion of the seamless steel pipe is generally treated by integral thermal expansion. Generally, they are subjected to basic processes such as heating, heat preservation, and cooling, and defects may occur in these processes.
Heat treatment defects of seamless steel tubes mainly include unqualified structural properties of steel pipes, excessive size and surface cracks, scratches, severe oxidation, decarburization, overheating, and over-burning.
Features of thermal expansion processing of seamless steel tubes:
The first process is heating: one is heating below the critical point Ac1 or Ac3; the other is heating above the critical point Ac1 or Ac3. The first is mainly to stabilize the structure of the seamless steel pipe and to eliminate the residual stress of the seamless steel pipe, and the second is mainly to austenitize the steel.
The second process is thermal insulation: the purpose is to uniformly heat the heating temperature of the steel pipe to obtain a reasonable heating structure.
The third process is cooling: the cooling process is a key process in the heat treatment of seamless steel tubes. He determines the metallographic structure and mechanical properties of the tubes after cooling. The steel tube cooling methods used in the actual production process are various. The cooling methods often used are furnace cooling, air cooling, oil cooling, polymer cooling, and water cooling.
Heat treatment defects of seamless steel tubes mainly include unqualified structural properties of steel pipes, excessive size and surface cracks, scratches, severe oxidation, decarburization, overheating, and over-burning.
Features of thermal expansion processing of seamless steel tubes:
The first process is heating: one is heating below the critical point Ac1 or Ac3; the other is heating above the critical point Ac1 or Ac3. The first is mainly to stabilize the structure of the seamless steel pipe and to eliminate the residual stress of the seamless steel pipe, and the second is mainly to austenitize the steel.
The second process is thermal insulation: the purpose is to uniformly heat the heating temperature of the steel pipe to obtain a reasonable heating structure.
The third process is cooling: the cooling process is a key process in the heat treatment of seamless steel tubes. He determines the metallographic structure and mechanical properties of the tubes after cooling. The steel tube cooling methods used in the actual production process are various. The cooling methods often used are furnace cooling, air cooling, oil cooling, polymer cooling, and water cooling.
The cutting method of fluid seamless pipe is introduced
Pipe fluid seamless pipe cutting methods include shearing, breaking, sawing, flame cutting and anode cutting. Their characteristics are as follows:
(1) Flame cutting method: This cutting method has the lowest operating cost, but the fluid seamless tube consumes more and the cutting quality is poor. Therefore, manual flame cutting is often used as a supplementary cutting means. However, due to the improvement of flame cutting technology, some factories have used automatic cutting with a multi-head flame cutting machine as the main method for fluid seamless pipe cutting.
(2) Shearing method: This method has high production efficiency and low cutting cost. Carbon-carbon seamless pipes and alloy structural steel pipes in low-carbon species are mainly cut by shearing. In order to improve the shearing efficiency, the double-cutting is carried out by using a large-tonnage shearing machine; in order to reduce the flattening degree of the end portion of the steel pipe when cutting, the cutting edge is generally formed by a forming blade; for a seamless steel pipe which is prone to shear cracking, shearing The steel pipe was preheated to 300 ° C when cut.
(3) Fracture method: The equipment used is the breaking press. The breaking process is to cut all the holes at the predetermined breaking fluid pipe with the torch, and then put it into the breaking press and break it with a triangular axe. The distance between the two points is 1-4 times the diameter Dp of the tube blank.
(4) Saw cutting method: This cutting method has the best cutting quality and is widely used for alloy steel pipes, high-pressure steel pipes, fluid seamless pipes, especially for the cutting of large-diameter fluid seamless steel pipes and high-alloy steel pipes. The sawing device has a bow saw, a band saw and a circular saw. Cold circular saws with high-speed steel sector blades are used for cold-saw alloy steel tubes; cold circular saws with carbide inserts are used for high-alloy steel saws.
(1) Flame cutting method: This cutting method has the lowest operating cost, but the fluid seamless tube consumes more and the cutting quality is poor. Therefore, manual flame cutting is often used as a supplementary cutting means. However, due to the improvement of flame cutting technology, some factories have used automatic cutting with a multi-head flame cutting machine as the main method for fluid seamless pipe cutting.
(2) Shearing method: This method has high production efficiency and low cutting cost. Carbon-carbon seamless pipes and alloy structural steel pipes in low-carbon species are mainly cut by shearing. In order to improve the shearing efficiency, the double-cutting is carried out by using a large-tonnage shearing machine; in order to reduce the flattening degree of the end portion of the steel pipe when cutting, the cutting edge is generally formed by a forming blade; for a seamless steel pipe which is prone to shear cracking, shearing The steel pipe was preheated to 300 ° C when cut.
(3) Fracture method: The equipment used is the breaking press. The breaking process is to cut all the holes at the predetermined breaking fluid pipe with the torch, and then put it into the breaking press and break it with a triangular axe. The distance between the two points is 1-4 times the diameter Dp of the tube blank.
(4) Saw cutting method: This cutting method has the best cutting quality and is widely used for alloy steel pipes, high-pressure steel pipes, fluid seamless pipes, especially for the cutting of large-diameter fluid seamless steel pipes and high-alloy steel pipes. The sawing device has a bow saw, a band saw and a circular saw. Cold circular saws with high-speed steel sector blades are used for cold-saw alloy steel tubes; cold circular saws with carbide inserts are used for high-alloy steel saws.
How is the crack of seamless steel tube surface to return a responsibility?
The cleanliness and smoothness of the surface of the seamless steel pipe is a requirement for the selection of a seamless steel pipe. The cleanliness of the surface of the seamless steel pipe has become a key point for the customer to choose. In recent years, it has been valued by many companies. Cracks on the surface of seamless steel pipes are a common phenomenon and a direct cause of low sales. So what are the factors?
First, the raw material factors: the poor quality of the tube blank will appear inside and outside the skin, crusting, cracks, etc.
Second, the temperature factor: the first important process of seamless steel pipe production is heating, poor heating (uneven, insufficient temperature, etc.) will cause internal skin, etc.
Third, the equipment factor: from the beginning of the furnace, each equipment component will affect the final quality of the pipe. For example, if the equipment parts are scratched, it will cause the outer skin and pits; if the punching machine is not smooth, the head of the tube blank will be bitten by water and bite into the head or the inside of the head.
Fourth, the process problem: the process problem is also quite complicated, there are adjustment problems, problems with equipment failure, and the quality of the pipe produced after the wear of the process components (head, guide, rolls, etc.). The problems caused are all-encompassing.
Therefore, there are dozens of possible reasons for the occurrence of a defect. If you do not see the physical object or are not at the production site, it is often difficult to say the specific reasons.
First, the raw material factors: the poor quality of the tube blank will appear inside and outside the skin, crusting, cracks, etc.
Second, the temperature factor: the first important process of seamless steel pipe production is heating, poor heating (uneven, insufficient temperature, etc.) will cause internal skin, etc.
Third, the equipment factor: from the beginning of the furnace, each equipment component will affect the final quality of the pipe. For example, if the equipment parts are scratched, it will cause the outer skin and pits; if the punching machine is not smooth, the head of the tube blank will be bitten by water and bite into the head or the inside of the head.
Fourth, the process problem: the process problem is also quite complicated, there are adjustment problems, problems with equipment failure, and the quality of the pipe produced after the wear of the process components (head, guide, rolls, etc.). The problems caused are all-encompassing.
Therefore, there are dozens of possible reasons for the occurrence of a defect. If you do not see the physical object or are not at the production site, it is often difficult to say the specific reasons.
订阅：
博文 (Atom)