Carbon Steel Pipe Hardness

​The hardness of carbon steel pipe commonly used Brinell, Rockwell, Vickers hardness of three kinds of indicators to measure.

Brinell hardness

In the steel standard, it is the most widely Brinell hardness, often expressed in the indentation hardness of the material in diameter, both intuitive and convenient. However, for a hard steel or steel thin NA.

Rockwell hardness

Rockwell hardness test tube with Brinell hardness test, as are the indentation test methods. The difference is that it is a measure of the indentation depth. Steel Rockwell hardness test is a very wide application, wherein after the Brinell hardness HB HRC use in steel standard. Rockwell applicable to the determination by the extremely soft to extremely hard metal materials, which make up not Brinell method, compared with Brinell method is simple and can be read directly from the dial hardness machine hardness value. However, because of its small indentation, the Brinell hardness values better method is accurate.

Vickers hardness

The welded steel pipe is also a Vickers hardness test indentation test method for the determination of a thin metal material and a surface layer hardness. It has a Brinell, Rockwell main advantages law, and to overcome their basic shortcomings, but not as convenient method Rockwell, Vickers method is rarely used in the steel standard.

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Carbon Steel Pipe Classification

​Carbon steel pipe is a hollow steel bar, a large number of pipes for transporting fluids such as oil, natural gas, water, gas, steam, etc. In addition, engaged in bending, torsional strength, lighter, so it widely used in the manufacture of mechanical parts and engineering structures. Also used in producing a variety of conventional weapons, the barrel, shells and so on.

Carbon steel pipe classification: carbon steel pipe can be divided into seamless steel pipe and welded steel pipe points two categories. By the cross-sectional shape can be divided into the tube and shaped tubes, round steel is widely used, but there are some square, rectangular, semi-circular, hexagonal, equilateral triangle, octagon shaped steel tubing. For steel to withstand fluid pressure hydraulic test should be carried out to test its ability to withstand and quality, does not leak under pressure requirements, wet or expansion of qualified, some steel but also according to the requirements of the standard or demand side, curling trials, flaring test, flattening test.

Seamless steel pipe is ingot made of perforated or solid through the capillary tube, and then hot rolled, cold-rolled or cold call is made. Seamless steel pipe with a diameter* thickness specifications expressed in millimeters. Seamless steel pipe is divide into hot and cold seamless steel categories. Hot-rolled seamless steel pipes of general, low, medium pressure boiler pipe, high pressure boiler pipe, steel pipe, stainless steel pipe, oil cracking pipe, steel pipes and other steel and other geological. Cold-rolled subject to sub- general seamless steel pipe, low pressure boiler pipe, high pressure boiler pipe, steel pipe, stainless steel pipe, oil cracking pipe, the other steel, but also thin-walled carbon steel, alloy steel thin-walled, walled stainless steel, special steel pipe.

Welded steel pipe with plate or strip is bent after forming, then made by welding. Press the seam into the form of DSAW steel pipe. Divided into general -use pipe, galvanized pipe, blowing pipe, wire casing, metric pipe, roller pipe, deep well pump tube, automotive tube, transformer tube, welded tube, welding shaped tube and spiral welded pipe.

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What is NDT Testing

​NDT testing means without prejudice or affect the detected object performance, not hurt at being provided to detect objects within the organization, the use of material internal structural abnormalities or defects heat, sound, light, electricity, magnetism and other reactions caused by changes to physical or chemical methods as a means of using modern technology and equipment, equipment, the specimen surface and the interior of the structural steel pipe, properties, and defect type state, nature, number, shape, position, size, distribution and change inspection and test methods . Non-destructive testing is an effective tool of industrial development is essential, to a certain extent reflects the level of industrial development of a country, the importance of non-destructive testing has been recognized, the main ray inspection (RT), ultrasonic testing (UT), magnetic particle testing (MT) and liquid penetrant testing (PT) four. There are other NDT methods eddy current testing (ECT), acoustic emission testing (AE), thermal imaging / infrared (TIR), leak testing (LT), the AC field measurement techniques (ACFMT), magnetic flux leakage testing (MFL), far-field test detection (RFT), ultrasonic time of flight diffraction method (TOFD) and the like.

NDT testing is the use of sound material, optical, magnetic and electrical characteristics such as, without prejudice or affect the performance of the detection object premise of the existence of defects or unevenness in the detection of the test object, given defect size, location the nature and quantity of information. Compared with the destructive testing, nondestructive testing has the following characteristics of carbon steel pipe. The first is a non-destructive, because when it is done without compromising detection performance by using a detection object; a second comprehensive, since the detection is non-destructive, so the object can be detected 100% comprehensive testing, if necessary this is destructive detection impossible; the third has a full, destructive detection generally apply only to the raw materials testing, such as mechanical engineering commonly used in tension, compression, bending, etc., are for nondestructive testing manufacturing of raw materials, finished products and for the supplies, unless the service is not ready to let it continue, otherwise it is not destructive detection and non-destructive testing without damaging the object to be detected by the use of performance. Therefore, it is not only the raw materials used to manufacture each intermediate step of the process of welded steel pipe, until the final finished products for the entire testing, but also on the service in the device for testing.

NDT Visual inspection: 1, the weld surface defect inspection. Check the weld surface cracks, incomplete penetration and weld leak welding quality. 2, the state examination. Check the surface cracks, peeling, cable, scratches, dents, bumps, spots, corrosion and other defects. 3, cavity inspection. When certain products (such as worm gear pumps, engines, etc.) work, according to the technical requirements of the project will be remote visual inspection. 4, assembly inspection. When required, and when needed, using the same three-dimensional industrial video endoscope assembly quality inspection; or a step after assembly is complete, check the parts and components assembled position meets the conditions for drawing or technical requirements; the existence of assembly defects. 5, extra material inspection. Check the product within the lumen of the residual dust, foreign objects and other remnants.

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DIN30670 for coating steel pipe

​DIN 30670 refers to polyethylene coatings on steel pipes and fittings –Requirements and testing.

This standard specifies requirements for factory-applied three-layer extruded polyethylene-based coatings, and one- or multi-layered sintered polyethylene-based coatings for the corrosion protection of steel pipes and fittings. The coatings are suitable for the protection of buried or submerged steel pipes at design temperatures of –40 °C up to +80 °C. The present standard specifies requirements for coatings that are applied to longitudinally or welded steel pipe or seamless steel pipes and fittings used for the construction of pipelines for conveying liquids or gases. Applying this standard ensures that the PE coating provides sufficient protection against the mechanical, thermal and chemical loads occurring during operation, transport, storage and installation. DIN EN ISO 21809-1 specifies requirements at international level for three-layer extruded polyethylene- and polypropylene-based coatings for steel pipes for petroleum and natural gas pipeline transportation systems. The following fields of application are not covered by DIN EN ISO 21809-1: ─ all polyethylene-based coatings for steel pipes and fittings used for the conveyance and distribution of water and wastewater, ─ all polyethylene-based coatings for steel pipes and fittings in distribution pipelines for gaseous and liquid media, ─ single- and multi-layer sintered polyethylene-based coatings steel pipe and fittings used for transport pipelines and distribution pipelines The present standard remains valid for the above fields of application. Two-layer polyethylene-based coatings are standardized at European level in DIN EN 10288 which was published in December 2003.

Materials shall be selected at the discretion of the coater because, depending on the installation and coating procedure, various materials can be used to comply with the minimum requirements specified in this standard for the finished coating. Any deviating requirements of the purchaser regarding the materials to be used shall be subject to agreement.The surface shall be prepared by removing rust by means of blast cleaning. Blast cleaning and any necessary subsequent work shall not result in the reduction of the minimum wall thickness specified in the technical delivery standards for the steel pipe. Residual abrasive dust shall be removed prior to coating.

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Internal Coated Pipe

Using epoxy powder coating is for 30 years of history in a foreign country due to the wide range of sources of raw materials, production methods are simple, cheap, good performance, which do not pollute the environment and long service life, so far it is a good anti-corrosion coatings. Petroleum Institute of Construction Technology in China for the oil field pipeline corrosion problems and successfully develop the anti-corrosion coating steel pipe of epoxy powder to fill the blank of the domestic pipeline anti-corrosion powder coating. the paint coating has excellent chemical resistance, good mechanical properties, high electrical insulation properties and good toughness. Corrosion tests predict coating life, the conditions intact Chu apply the paint to do the inner coating of oil, gas and water pipes, the life expectancy of up to l5 years; do sewage and mixed water injection pipeline within the coating, life up to 5 to 7 years. The construction method using the pipeline industry, the most widely used static thermal spraying method. According to the data reported, due to the transmission medium, the thickness of the coating of epoxy powder coating requirements are also different. Domestic oil, gas, water and sewage, etc. containing certain corrosive media, anti-corrosion pipe is the best thick coating. Electrostatic heat till coated thick coating, spraying a coating thickness of up to 250 ~ 350/an maximum thickness of up to 500, ~ 'n. Electrostatic Powder the moraine coated is a surface treatment of the solid powder, it has a simple, easy to operate equipment, process, free from the workpiece size limit.

Inner surface heat-resistant paints and coatings

The technology is the surface heat-resistant paint coating that mixed epoxy resin main agent and epoxy resin curing agent in the carbon steel pipe (each about 5.5m), natural drying a certain period of time, more than 6O ℃ warm water or 60 ℃ or more hot air into the tube, forced drying, more than three hours to complete the steel pipe coating. The technology is mainly applied to water pipelines and transmission and hot water pipe internal coated first surface treatment on the pipe wall, and then use the compressor by the pressure of air or nitrogen, Pressure between the resistance and the two applicator thermal coating in the pipe wall to form a uniform coating. Coating must 6O ° C more than warm water or 60 "C, hot air above the mandatory drying and natural drying is heat resistant to dissolution performance decreased significantly.

Epoxy resin latex cement mortar lining

Epoxy resin latex cement mortar lining in the steel tube surface first coated with epoxy cement water-based paint, to form the undercoat, and then based on this coating steel pipe . The use of materials is containing epoxy resin latex cement mortar. Colloidal silicon dioxide is added in the cement mortar. Cement water-based coatings and cement mortar contain ionic latex (a hydrocarbon solvent containing 5 to 8 sugars). The lining of steel pipes, except for sewage and water pipelines is also apply to oil, gas and steam pipelines. In order to get a solid lining, pipe lining before, the surface must be shot peening, shot peening is divided into dry and wet shot peening, if both methods are not adopted, can also be used to pickling.

Pipe Welding Procedure

Under the welded steel pipe from the top of the arc, from top to bottom all-position welding technique, the method of welding speed, weld appearance, good welding quality, you can save welding materials, reduce labor intensity, which is a common SMAW can not be compared and now more widely used in large-caliber long-distance pipeline welding in all position of power in the construction of low-welded large diameter thin-walled tube has some promotional value. 

Under the welding usually select the appropriate welding current, electrode angle and welding speed, straight through drag down or suppress arcing swing slightly to finish welding. Ordinary electrode prone drip drip molten iron and slag under question, and the use of the pipeline dedicated to welding electrodes, welding specifications strictly enforced, you can solve these problems. Cellulose type electrode welding slag less, arc force, stiffness enough to prevent the molten slag and drip down and penetrating arc large, especially for thick-walled containers and welded steel pipe hit the bottom, you can eliminating the root shovel operation, thereby improving work efficiency, improve working conditions, but because of its high hydrogen content of the weld, so for domestic high-pressure structural steel pipe welding current commonly used cellulose electrode backing plus low hydrogen electrodes and filler cap surface welding. 

The right set of tubes and tack welding is on ensuring the quality of the welding, the back of a good weld is an important factor. Tack welding seam is part of a formal, not only requires forming side welding, but also to ensure the welding quality. Tack welding length 20mm, a thickness of about 3mm, gentle slopes on both sides of the weld should be ground into shape, in order to facilitate joint. 

Next to the welding electrode is very important to use the correct angle. Backing weld, filling and capping rod angle is basically the same, but the arc length and transport of a different form. Next to the weld, the weld is controlled by the length and width of the main forms of transportation of the arc, arc and arc close attention to the wrong location should open.

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Mild Steel Pipe

Mild steel pipe refers to the content of less than 0.25% carbon steel because of its low strength, low hardness and soft. It includes most of the part of ordinary carbon steel and high-quality carbon structural steel, mostly without heat treatment used in engineering structures, some carburizing heat treatment and other mechanical parts required for wear. Mild steel pipe annealing organization ferrite and pearlite is lower its strength and hardness, ductility and toughness. Therefore, the cold formability is good and can be crimping, bending, punching and other methods of cold forming. Like that mild steel pipe has good weldability. Carbon content from 0.10 to 0.30% of mild steel is easy to accept all kinds of processing such as forging, welding and cutting, commonly used in the manufacture of chains, rivets, bolts, shafts, etc. 

Ordinary mild steel pipe is for the production of building components, containers, tank, furnace and farm machinery. Quality mild steel pipe is for making car cab, hood and other deep-red products; also rolled into bars, strength requirements for the production of mechanical parts. Before using mild steel pipe is generally not by heat treatment, the carbon content of more than 0.15% by carburizing or cyanide treatment, used to require high surface temperature, wear good shafts, bushings, sprockets and other parts. Due to the low strength of the low-carbon steel, use is restricted. Appropriate to increase the carbon content of manganese and add trace vanadium, titanium, niobium and other alloying elements, can greatly improve the strength of steel. If you reduce the carbon content of the steel and add a small amount of aluminum, and a small amount of boron carbide forming elements, you can get ULCB set high enough intensity, and maintain good ductility and toughness.

Low carbon content of mild steel pipe is very low hardness and poor machinability, normalizing process may improve machinability. Mild steel pipe tends to have a greater timeliness, both quench aging tendencies, as well as a tendency to strain aging. When the rapid cooling from a high temperature steel, ferritic scraping carbon, nitrogen saturation, it can also slow the formation of iron carbonitride was at room temperature, and thus the strength and hardness of steel, the lower the ductility and toughness, a phenomenon called quench aging. Even without quenching and low carbon air cooling will produce aging. Produce large amounts of low-carbon steel by deformation dislocations ferrite from carbon, nitrogen atom elastic dislocation interactions, carbon, nitrogen atom reign gathered around the wrong line. Such a combination of carbon and nitrogen atoms and the dislocation line is called the Coriolis-year-old air mass (Ke lop air mass). It will increase the strength and hardness of steel while reducing ductility and toughness, a phenomenon known as strain aging. Than quench aging of carbon steel pipe during deformation plasticity and toughness greater dangers in the tensile curve has obvious upper and lower yield point. Since the yield on the yield point elongation occurs until the end, appear deformed due to uneven surface with folds formed on the surface of the sample, called Luders band. So many stampings are often scrapped. There are two methods of its prevention. A high pre-deformation method, the pre-deformed steel stamping place after a period of time will produce Luders band, so the pre-deformed steel stamping is placed before the time not too long. Another steel, aluminum or titanium is added to the formation of a stable compound with the nitrogen to prevent the formation of air masses caused by the Coriolis deformation of aging. 

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Seamless Steel Pipe VS Welded Steel Pipe

The main difference between seamless steel pipe and welded steel pipe are molding process. General welded steel pipe such as water pipes, is generally flat plate by bending and welded together after that you can find a seam in the above; coarse diameter is usually spiral weld. The molten steel seamless pipe is generally through an annular slit molten state and then by stretching out the backlog of processing molding process, so there is no seam. In performance, especially compared to welded steel has greatly improved the bearing capacity, it is often being used for high-voltage equipment. Hydraulic equipment such as piping connections. Welded steel pipe weld area is its weak link, weld quality is also a major factor in its overall performance impact. Welded steel pipe lived in the north generally have had water pipes or heating pipes burst in the winter cold experience explosive place are generally weld.

Seamless steel pipe is piercing round holes to produce steel. Weld steel pipe is rolled into a bucket and then weld. According to their method of manufacturing seamless steel pipe and welded steel pipe in two. Seamless steel pipe with high-quality carbon steel or alloy steel, hot-rolled, cold-rolled (pull) of the points. Welded steel is rolled into a tube-shaped plate with the seam or spiral seam welded, in the manufacturing method, is divided into low pressure fluid welded pipe, spiral welded steel pipe, directly welded steel pipe, welded pipe. Seamless carbon steel pipe can be used for a variety of liquids, gas pipelines. Welded pipes can be used for water pipes, gas pipes, heating pipes. Seamless steel tubes are used in important applications, uniform, high pressure tolerance, such as the barrel, the barrel and so on. Generally with high-quality steel, alloy steel and even. Weld steel are used in general purpose compression generally well tolerated, such as water pipes, gas pipes, etc., with ordinary steel.

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What is API 5L Standard?

API 5L Standard aims to gas and water in oil and gas industry for reference, which is used for seamless carbon steel pipe and welded steel pipe,including common port and port, pipe socket port and direct stream tube (TFL) and port has for a particular connection tube processing.

API 5L Standard is including steel grade(GR.B，X42 ，X46，52，X56，X60，X65，X70).

API 5L Standard has the provisions of the two product specification levels (PSL1 and PSL2). The two kinds of PSL grade level of the product to the standard stipulated in the technical requirements of different, PSL2 of carbon equivalent, notch toughness, maximum yield strength and tensile strength have mandatory requirements. PSL is short for product specification level.Carbon steel pipe product specification level is divided into PSL1 and PSL2, also can say quality grades are divided into PSL1 and PSL2. PSL2 above PSL1, these two levels is not only different inspection requirements, and chemical composition, mechanical performance requirements are different, so the order in API 5 l, the terms of the contract in addition to indicate the specifications and grade of steel usually indicators, must also indicate the level of product specification, namely PSL1 or PSL2. PSL2 in chemical composition, tensile properties, impact energy, and nondestructive testing which strict in PSL1 indicators. PSL1 does not require impact performance, PSL2 all except x80 grade steel, full size 0 ℃ average Akv: longitudinal p j, 41 lateral acuity 27 j.Average grade X80 steel, full size 0 ℃ Akv: longitudinal 101 j, or lateral acuity 68 j. Line pipe should do water pressure test, and the standards are not allowed to nondestructive generation of hydraulic pressure, which is also the API standard and one big difference between our country standard.PSL1 does not require the nondestructive inspection, PSL2 shall by a nondestructive examination.

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What is Piling Pipe?

Piling Pipe is widely used in coastal, river, lake area. Offshore deepwater terminal project in the country have also been large-scale construction in coastal areas, and as a major deep-water dock pile bearing capacity, generally use the large diameter spiral welded steel pipe, in addition, bridges, roads, high-rise building needs piling pipe etc.

Piling pipe weld surface shall not have cracks, broken arc, craters and holes and other defects, the presence of these defects allow the welding seam defects allow grinding or repair. Allow the pipe weld steel head, steel allow docking with two pipe sections together, submerged arc butt welding or manual welding process can be carried out. Production of steel piling mainly use the double submerged arc technology. A first advantage of using the double submerged arc technique is completely automated; The second advantage is conducted under submerged arc welding, the heat exchange and protection of its relatively strong performance, high quality welding out; the third advantage is the automatic submerged arc welding arc welding flux can be used under high-current, high welding efficiency of structural steel pipe.

When piling, as a result of pile to soil compaction effect, first into the level of pile after pile was caused migration and displacement or push and shove by floating pile vertical extrusion drawing; then pile into hard to reach design elevation or buried deep, causing uplift and squeeze the soil, cut pile is too large. When the group piles, in order to ensure the quality and progress, to prevent damage to surrounding buildings, according to the intensity of the pre-piling pile, pile size, length and pile frame is easy to move and other factors to select the correct piling order. Common piling order generally following categories: conducted in one direction by the side from the middle to be symmetrical in both directions, from the middle to four weeks. 

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American steel product standards

US steel products are with more standards, mainly in the following categories:
ANSI--American National Standard
AISI--American Society of Iron and Steel Standards
ASTM--American Society for Testing and Materials
ASME--American Society of Mechanical Engineers
AMS--Aerospace material specifications (one of the most commonly used materials specifications in the US aviation industry, developed by SAE)
API--American Petroleum Institute standards
AWS--American Welding Association Standard
SAE--American Society of Automotive Engineers Standards
MIL--US military standards
Qq--US federal government standards
API--American Petroleum Institute standards
ANSI--American National Standard
ASME--American Society of Mechanical Engineers
ASTM--American Society for Testing and Materials

These standards, all belong to the US steel standards, such as ASME in the material used by the standards are from ASTM, the valve in the standard reference API, and carbon steel pipe fittings from the ANSI standard. The difference lies in the different focus of the industry, so the adoption of different standards. API, ASTM, ASME are members of ANSI. American National Standards Institute standards, the vast majority from the professional standards. On the other hand, the professional associations, associations, groups can also be based on existing national standards to develop certain product standards. Of course, can not follow the national standard to develop their own association standards. ANSI standards are voluntary. The United States believes that mandatory standards may limit productivity gains. But by the law and the government departments to develop standards, generally a mandatory standard.

Cold hardening and hydrogen embrittlement of ASTM A179 cold drawn seamless tubes

In the production process of astm a179 cold drawn seamless pipe, there are cold hardening and hydrogen embrittlement phenomenon, which are caused by cold drawn seamless tube cracking the main reason.

Analysis of the phenomenon of bursting astm a179 cold drawn seamless pipe is a smaller diameter of the seamless steel pipe through the drawing die for cold forming cold forming, the process route is generally annealing, pickling, drawing. Cold-drawn small diameter seamless carbon steel pipe in the drawing process, sometimes from beginning to end like the same as the cracker bamboo crack phenomenon, we call this phenomenon is cracking.

The reasons for cracking are:

Effect of work hardening, the carbon steel pipe produces a large amount of plastic deformation during cold drawing, causing significant lattice distortion, which increases the lattice energy and increases the internal energy of the metal, resulting in uneven internal stress of the metal and residual residual stress. This will increase the metal hardness, toughness decreased. The higher the metal hardness, the greater the residual internal stress during cold drawing, the more obvious the work hardening phenomenon. When the residual stress reaches a certain value, the metal will tear along a certain grain interface, the formation of steel pipe cracking.

The effect of hydrogen embrittlement, in the process of descaling with acid, sulfuric acid and iron react to precipitate hydrogen. Hydrogen penetrates into the steel in the form of atoms or ions to form a solid solution. The effect of hydrogen on the mechanical properties of steel is typical of hydrogen embrittlement.

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How to deal with electrochemical corrosion of astm a179 cold drawn steel pipe

(1) ASTM A179 cold drawn carbon steel pipe with carbon steel pollution: contact with carbon steel caused by scratches and corrosive media to form the original battery and electrochemical corrosion.

(2) ASTM A179 cold drawn steel pipe cutting: slag, splash and other easy to rust the material attached to the corrosive medium and the formation of the original battery electrochemical corrosion.

(3) Heating: the composition of the flame heating area and microstructure changes and not uniform, and the formation of the original medium of corrosive media and electrochemical corrosion.

(4) ASTM A179 cold drawn carbon steel pipe welding: physical defects in the welding area (undercut, pores, cracks, not fused, not welded, etc.) and chemical defects (coarse grain, grain boundary poor chromium, segregation, etc.) and corrosive media to form the original Battery and produce electrochemical corrosion.

(5) Material: chemical defects of cold drawn steel (uneven composition, S, P impurities, etc.) and surface physical defects (loose, trachoma, cracks, etc.) is conducive to the formation of the original medium with corrosive media and electrochemical corrosion.

(6) Passivation: pickling passivation effect is not good caused by cold-drawn steel pipe surface passivation film is uneven or thin, easy to form electrochemical corrosion.

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What’s the Difference Between Hot and Cold Rolled Steel?

There are many types of steel out there, with various shapes, grades, specifications, finishes, and other processing considerations. One key distinction among prefabricated steel products is the difference between hot rolled versus cold rolled steel.

It may seem obvious, but some types of steel are better suited for certain applications than others. Knowing which to use can help avoid spending more than necessary on raw materials. It can also save time and money on additional processing. In other words, understanding the differences between hot and cold rolled steel will help designers and engineers achieve better results—and at the best price possible.

The basic difference between these two types of steel is one of process. As you can imagine, “hot rolling” refers to processing done with heat. “Cold rolling” refers to processes done at or near room temperature. Although these techniques affect overall performance and application, they should not be confused with formal specifications and grades of steel, which have to do with metallurgical composition and performance ratings. Steels of different grades and specifications can be either hot rolled or cold rolled—including basic carbon steel pipe and other alloy steels.

Hot Rolled Steel

Hot rolled steel has been roll-pressed at high temperatures (over 1,700ËšF), which is above the re-crystallization temperature for most steels. This makes the steel easier to form, and also results in products that are easier to work with.

Hot rolled steel gets stored at a production yard.

To process hot rolled steel, manufacturers start with a large, rectangular billet. The billet gets heated and sent for pre-processing, where it is flattened into a large roll. From there, it is kept at a high temperature, and the glowing white-hot steel is run through a series of compression rollers to achieve its finished dimensions. For sheet metal, manufacturers spin the rolled steel into coils and leave it to cool. For other forms, such as bars and plates, materials are sectioned and packaged.

Steel shrinks slightly as it cools. Because hot rolled steel is cooled after processing, there is less control over its final shape, making it less suitable for precision applications. Hot rolled steel is often used when minutely specific dimensions aren’t crucial—in railroad tracks and construction projects, for example.

Hot rolled steel can often be identified by the following characteristics:
• Scaled surfaces, the remnants of cooling from extreme temperatures.
• Slightly rounded edges and corners for bar and plate products (due to shrinkage and less precise finishing).
• Slight distortions, where cooling may leave slightly trapezoidal forms rather than perfectly squared angles.

Hot rolled steel typically requires much less processing than cold rolled steel, which makes it a lot less expensive. Hot rolled steel is also allowed to cool at room temperature, so it’s essentially normalized, meaning it’s free from internal stresses that can arise during quenching or work-hardening processes.
Hot rolled steel is ideal where dimensional tolerances aren’t as important as overall material strength, and where surface finish isn’t a key concern. If surface finish is a concern, scaling can be removed by grinding, sand blasting, or acid-bath pickling. Once scaling is removed, various brush or mirror finishes can be applied. Descaled steel also offers a better surface for painting and other surface coatings.

Cold Rolled Steel

Cold rolled steel is essentially hot rolled steel that has gone through more processing. To get cold rolled steel, manufacturers generally take cooled-down hot rolled steel and roll it more to get more exact dimensions and better surface qualities.

Cold rolled steel can often be identified by the following characteristics:
• More finished surfaces with closer tolerances.
• Smooth surfaces that are often oily to the touch.
• Bars are true and square, and often have well-defined edges and corners.
• Tubes have better concentric uniformity and straightness.

Cold rolled steel pipe is bundled for shipment.

With better surface characteristics than hot rolled steel, it’s no surprise that cold rolled steel is often used for more technically precise applications or where aesthetics are important. But, due to the additional processing for cold finished products, they come at a higher price.
In terms of their physical characteristics, cold worked treatments can also create internal stresses within the material. In other words, fabricating cold worked steel—whether by cutting, grinding, or welding it—can release tensions and lead to unpredictable warping.

Depending on what you’re looking to build, different types of materials each have their own benefits and drawbacks. For unique projects or one-off productions, prefabricated steel materials can provide the building blocks for any structural steel pipe configuration imaginable.

For projects where you'll be manufacturing many units, casting is another option that can save time in machining and assembly. Cast parts can be made to almost any form in a range of quality materials.

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What is Precision tubes

Named thus because of their precise tolerances (thickness) and high surface quality. Precision tubes are used in light industry: in furniture, shop fittings, and stores, for example. Precision tubes are welded steel pipe. At Tibnor, you can purchase precision tubes with surface protection, to which you apply the type of layer you want, like varnish or chrome. 

• Do you plan to varnish the tubes? Choose pickled steel, the surface of which is free from mill scales 
• Do you plan to chrome the material? Use cold rolled steel, not pickled material. 

The tubes will be delivered lightly oiled, to prevent rusting during storage and transport. From our stock, you can purchase precision tubes in standard lengths. Perhaps other dimensions are better for your production? We can pre-process the tubes before delivery, so your manufacturing can start immediately. 

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What’s the Difference Between a TS and an HSS?

For most of us, this may seem like a silly question. A hollow structural steel pipe, or HSS, is the same thing as tube steel, or TS, right? Actually, I’ve been asked this very question, so I feel a short explanation may be necessary. Steel tubing, or tube steel, is what we used to use in the U.S. to describe a closed steel section — whether of rectangular, square or round shape. These sections are commonly made in the U.S. in accordance with the ASTM A500 specification. In Canada, the typical specification is CSA G40. You can even see the history of the term in the name of the organization created to promote steel tubing: the Steel Tube Institute.

Now, a carbon steel pipe is something completely different (because it’s produced to a different specification), but that is a subject for another day.

In Canada, Europe and Asia, the typical nomenclature for these closed steel sections or tubes has always been some variation ofhollow structural section. In some places, there exist the variations of SHS (square hollow section), RHS (rectangular hollow section) and CHS (circular hollow section).

In the early 1990s, the American Institute of Steel Construction (AISC) decided to transition from TS to HSS in order to align with the rest of the world. Starting with the second edition of AISC’s LRFD Steel Construction Manual (the silver two-volume set), the designation of hollow structural section was established as the correct way to call out steel tubes. This also coincided with the publication of the black HSS Connections Manual, published jointly by AISC and the Steel Tube Institute.

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Applications of Structural Steel Pipe

Structural steel pipe are used in many ways and their application can be diverse. They are particularly useful because they offer the unique combination of good welding properties with guaranteed strengths. Structural Steel is an extremely adaptable product and is often favoured by the engineer trying to maximise strength or s structure while minimising its weight.

It will come as no surprise that the construction industry is the biggest consumer of Structural Steel, where it is used for all manner of purposes and employed at diverse scales. Whether a small box lintel is used to carry the load of a structural wall in a residential property or a vast I-beam is bolted in place to hold the road surface on a bridge, structural steel pipe can be specified, designed and fabricated for the job.

• High Rise Buildings / Skyscrapers
• Houses
• Factories
• Offices
• Shopping Malls
• Train Tracks
• Road barriers
• Bridges

Chemical Composition of Structural Steels Pipe - S235, S275 and S355

The Chemical composition of Structural Steel pipe is extremely important and highly regulated. It is a fundamental factor which defines the Mechanical properties of the steel material. In the following table you can see the Max % levels of certain regulated elements present in European Structural steel grades S235, S275 and S355.

The chemical composition of Structural Steel is incredibly important to the engineer and will change with specific Grades depending on their intended use. For Example; S355K2W is a Structural Steel that has been hardened (K2) and has been designed with a chemical composition to withstand increased weathering (W). Therefore, this grade of Structural Steel pipe will have a slightly different chemical composition to the standard S355 grade.

Introduction of Structural Steel in Europe Standard

Introduction

Structural steel pipe is a standard construction material, made from specific grades of steel and formed in a range of industry standard cross-sectional shapes (or ‘Sections’). Structural steel grades are designed with specific chemical compositions and mechanical properties formulated for particular applications.

In Europe, Structural Steel must comply with the European Standard EN 10025 a Governed by the ECISS (European Committee for Iron and Steel Standardization) a subset of CEN (European Committee for Standardization.

There are many examples of European grades of structural steel such as; S195, S235, S275, S355, S420, S460 etc. However, for the purposes of this article we will focus on the Chemical Composition, Mechanical Properties and Applications of S235, S275, S355. Three common structural steel grades used in all manner of Construction projects across the EU.

Inline with the European Standard classifications, Structural steel pipe must be referenced using standard symbols including but not limited to: "S"235"J2’‘K2’’C’’Z’’W’’JR’’JO’’

Where:

• S – denotes the fact that it is Structural Steel
• 235 – related to the minimum yield strength of the steel (tested at a thickness of 16mm)
• J2 / K2 / JR / JO – material toughness in relation to the Charpy impact or ‘V’notch test methodology
• W – Weathering Steel (Atmospheric Corrosion Resistant)
• Z – Structural steel with improved strength perpendicular to the surface
• C – Cold-formed

Depending on the manufacturing process, chemical composition and relevant application, further letters and classifications might be used to reference particular grades/products of structural steel pipe.

The EU Standard classifications are inherently not a global standard and therefore a number of corresponding grades with the same Chemical and Mechanical properties may be used in other parts of the world. For example, Structural Steels fabricated for the US market must be specified in accordance with the ASTM (American Society for Testing and Materials) International guidelines and will be referenced with an ‘A’ and then the relevant Grade such as A36, A53 etc.

Difference of PSL1 and PSL2(API 5L)

The API 5L has two standards, PSL1 and PSL2, which are very different from each other. I'll talk more about the differences between PSL1 and PSL2.

API 5L is similar to GB/T9711, and PSL1 is equivalent to GB/T9711.1, PSL2 is equivalent to PSL2.

PSL2 just needs to do some more subzero impact work. Domestic individual manufacturer said can do, is actually made of better material, structural steel pipe out self can pass the requirements on the feeling, but the factory's own levels and knowledge level is not high, not the ability to do relevant test is a serious of experiment report and PSL2 do special material.

PSL2 sometimes customers want to do NACE, they want to do hardness and acid resistance, and that's a problem

PSL is short for product specification level. The product specification level of the pipeline tube is divided into PSL1 and PSL2, which can also be said to be PSL1 and PSL2. PSL1 above PSL2, these two levels is not only different inspection requirements, and chemical composition, mechanical performance requirements are different, so the order in API 5 l, the terms of the contract in addition to indicate the specifications and grade of steel usually indicators, must also indicate the level of product specification, namely PSL1 or PSL2.

PSL2 is strict on the chemical composition, tensile properties, impact work, nondestructive testing, etc.

PSL1 does not require shock performance

PSL2 all except x80 grade steel, full size 0 ℃ average Akv: longitudinal p j, 41 lateral acuity 27 j.

Average grade X80 steel, full size 0 ℃ Akv: longitudinal 101 j, or lateral acuity 68 j.

The carbon steel pipe should be tested for water pressure by branch, and the standard is not allowed to allow non-destructive generation of water pressure, which is also a big difference between API standard and the standard of our country.

PSL1 does not require non-destructive testing, and PSL2 should be tested for non-destructive inspection.

Difference of ERW and EFW

ERW namely resistance welding Electric hold welding the abbreviation of the first letter of the ERW carbon steel pipe with submerged arc welding pipe welding way have significant difference, is without the pressure of the filler metal welding method, welding seam, not fill other ingredients in skin effect by the high frequency current and near effect, make the edge instant heating to welding temperature, formed by squeezing roller extrusion forging welding seam of the organization. High quality steel pipe require the use of online or offline weld heat treatment, thus refine welding area organization, high grade ERW welded steel pipe weld can reach the same as the parent metal toughness, it is out of reach for submerged arc welding process. 

EFW namely Electric welding Electric fusion welding of the abbreviation of the first letters Submerged arc welding (SAW) - a kind of electric welded (EFW), is by one or a few consumable electrode and workpiece between the metallic heating combination between the metal in a process, the arc melted metal and the filler material fully, do not need to pressure, filler metal part work makes all come from the electrode. Melting gas shielded arc welding (GMAW), a kind of electric welded (EFW), the process is similar to submerged arc welding, but it is from the inert gas protection, the effect will be better. Spiral welding - this is one of the submerged arc welding, with a spiral weld structural steel pipe.

The Basic Requirement of steel for Pipeline

heart of the impact of natural and human factors that may occur in the course of leaking or breaking all sorts of accidents. Not only due to leakage of pipeline accidents affect transport caused economic losses, but also pollute the environment. To ensure the safe operation of the pipeline and generate pipeline accident prevention should be the design, construction and operation of three aspects, including design and reasonable choice of pipe is very important. As for the carbon steel pipe, the strength, toughness and weldability are three basic quality standards. It should also consider the environmental and transport medium for pipe corrosion, corrosion-resistant steel choice. 

(1) Mechanical properties: The main indicator to measure the mechanical properties of the pipe have strength, yield limit, elongation, etc. 

① Tensile strength: tube in a tensile test, when a sample corresponding to the maximum stress of pulling off. 

② Yield strength: steel in tensile test, the specimen tensile deformation, when excluding the initial transient effect flexor, the minimum stress in the service phase. 

③ Elongation: a measure of shaping steel refers to steel in the tensile test, the sample is drawn off, and the elongation percentage of the original distance of the standard gauge. 

④ Bauschinger effect: metal or alloy to produce pre-loaded micro plastic deformation after unloading and then increased with the elastic limit of the load, reverse load is reduced elasticity of the elastic limit is not complete phenomenon. 

(2) Fracture toughness: Pipeline rupture can be divided into fracture and brittle fracture toughness structural steel pipe.

① Ductile fracture: the gradual expansion and eventually rupture caused by tiny cracks in the conditions of excessive tensile stress and cracks exist simultaneously.

② Brittle fracture: the temperature, stress and cracks caused by the combined effect of three conditions, the fracture is often much lower than earlier in the yield stress under conditions of a sudden. 

③ Fracture toughness: energy and the ability to attribute the deformation of metallic materials with crack before breaking absorption. 

④ Ductile-brittle transition temperature: at a certain temperature range, fracture toughness just with the use of lower temperatures.

Reduced. When a temperature near Avenue frontage temperature, there will be a sudden drop in toughness phenomenon, the steel from breaking into brittle fracture toughness, this temperature is called steel ductile-brittle transition temperature.

Weld Microstructure Analysis of Carbon Steel DSAW Steel Pipe

The microstructure of weld seam of high frequency DSAW steel pipe reflects the welding process performance and weld quality of the steel pipe.

High-frequency straight seam welding production is mainly the use of high-frequency current with the skin effect and the proximity effect of the two characteristics, the current is highly concentrated in the tube side welding surface, the tube side quickly heated to the welding temperature, Extrusion welding to complete. During the welding process, the metal undergoes a crystallization transition (solidification transition) from the liquid phase to the solid phase, and then undergoes a recrystallization transition (solid phase transition) after cooling to a lower temperature, Carbon steel pipe, mainly formed by fusion of melting material into crystalline structure of the fusion zone, and from the fusion line to the organization does not occur between the base metal heat affected zone. The transformation of the weld zone and the hot zone during the welding and continuous cooling processes is a continuous gradient of the organization formed. As the welding temperature is 1350 ~ 1500 ℃, the metal is heated in the peritectic range of welding, when the condensation occurs to 1493 ℃ peritectic reaction of the formation of austenite, in the continuous cooling to below the GS line will occur austenite Ferrite transformation, cooled to slightly lower than 723 ° c eutectoid reaction, the remaining austenite into pearlite, in the fusion zone eventually the formation of ferrite and pearlite structure. In the heat affected zone, a series of unbalanced microstructures are formed by the effect of welding heat, which is different from the original microstructure and properties of the base metal. When the peak value of welding thermal cycle is lower than Ac1, the metallographic structure is still primitive The ferrite and pearlite of the base metal structure, when heated to Ac1 or more, the organization will be significant changes. Steel in about 750 ℃ tissue changes occur, the first austenite pearlite formation of small austenite, austenite transformation in the ferrite has not yet occurred, because the welding heating speed, and soon cooled down by the pearlite transformation Into austenite in the subsequent cooling process to recrystallize into fine ferrite and pearlite. This area consists of fine ferrite and pearlite recrystallization and no phase transformation of coarse ferrite structure. In the region where the peak temperature is higher than this region, the pearlite and ferrite are fully austenitized at a temperature ranging from Ac3 to the grain coarsening initiation temperature of the steel at 900 to 1100C, but the grain size is not drastically long Large, in the continuous cooling to get small and uniform ferrite and pearlite structural steel pipe. When the heating temperature is above 1100 ℃, the austenite grains are coarse and coarse, and the grains are coarsest near the fusion zone. After cooling, the coarse ferrite and pearlite structure are formed,

Summary:

(1) The microstructures of high-frequency straight seam welds are composed of unbalanced continuous gradient microstructures, and the peak temperatures of different welding heat cycles form different microstructures.

(2) Welding speed too fast, too much extrusion pressure lead to unqualified weld fusion zone is too narrow, metal flow line rising angle steep, and affect the quality of the weld. Therefore, the welding speed should be properly controlled to reduce the pressure, so that the weld fusion completely, in order to improve the quality of the weld.

(3) The existence of more non-metallic inclusions in the weld, weakening the continuity of the metal, so that the weld strength, crushed unqualified. Welding temperature and extrusion pressure should not be too high, to minimize the inclusion content, improve the weld strength.

(4) Weld's associated coarse-grained structural steel pipe can make mechanical properties of welds decreased, especially the plasticity and toughness decreased significantly, the same cooling conditions in the welding, the heating temperature should not be too high, the cooling rate should not be too Fast, as far as possible to reduce the weld in the Wechsler organization.

Shinestar Uncover the "Routine" of Steel Market

As a LSAW steel pipe, open flat, steel springboard, hot plate, scaffolding and other products of  the production service providers, Shinestar holdings group published some views according to 2017 steel  market, steel industry and how to maintain market stability problems.

Viewpoint 1: On the demand forecast, excessive interpretation of the policy, and under the influence of  hype, steel inventories on the market, steel prices fall.

First, the current fundamentals of China's economy is good, some emerging areas of steel demand  corresponding increase in the market a substantial increase in inventory, resulting in steel prices fell.  Second, the implementation of national policy to the production capacity, many iron and steel enterprises  limited production, production, steel trade accordingly made the market in short supply to judge. Under  the influence of this expectation, steel trade enterprises continue to increase inventory. Third, house  prices rose sharply, stimulate the construction steel prices soared, thus promote the overall steel  prices. Steel trade merchants began to increase, according to the cargo, and look forward to the Spring  Festival after the steel price rise as expected. Fourth, due to the general reduction in inventory on the  market, the market stocks and prices showed a proportional relationship, this time, enterprises to  increase inventory is equivalent to increase efficiency. Coupled with some people on the relevant policy  of excessive interpretation, triggering a steel trade to increase the inventory of the "herd".

Viewpoint 2: Respect the law of value, according to the laws of the market, is to maintain the  fundamental guarantee of market stability.

First, in the process of removing excess and backward production capacity, we should give full play to  the role of the market only "invisible hand", supplemented by administrative means of guidance and legal  constraints. Second, through administrative means, legal means and the combination of market rules, and  resolutely ban high pollution, high energy consumption capacity. Third, we should widely publicize the  party's principles and policies, promote the socialist core values, improve the trade ethics and social  responsibility. Fourth, call for the majority of steel trade workers care, maintenance of steel market  order, to reduce human speculation and other undesirable phenomena, work together to maintain the healthy  and stable development of steel market.

Viewpoint 3: The overall steel market will be characterized by tight trading range this year.

Steel prices from the previous year's "cliff" fell to last year's value of return, and then to the recent  "diving", in essence, is the value of the return journey of a repair process. Steel prices will be with  the gradual realization of China's economic transformation, rhythmically running in the appropriate  range. From the big trend, this year's steel market price should be a value to continue the process of  repair. May Day after market prices sharply rise, terminal engineering to procurement, market clinch a  deal the splurge produced. However, in this process, the high turnover is not ideal, indicating that  short-term steel prices easy to touch the top down, the overall performance of steel prices within a  narrow range, or this year is also the overall microcosm of steel market operation.

Shinestar holdings group as a steel procurement overall service providers, will continue to focus on  steel market dynamics. At the same time, we will also develop high-quality DSAW steel pipe, open  flat, steel springboard, hot-rolled plate, scaffolding and other products, to provide the best service.