Distinguish Inferior Steel Pipes

2018-01-25

Steel pipe is long, hollow tube that are used for a variety of purposes. Steel pipe is made using three main methods: Seamless (extrusion mould), Welded and Casting Mould. The primary benefit of steel pipe is its strength. These pipes don’t crack under most impacts and can operate under high pressure. Under abnormal loads, steel pipe will bend, rather than break. Steel pipe can be used in many different applications including building construction, structural and mechanical uses.

There are several different types of steel pipe available for use in various applications. The most common is carbon steel pipe, which is so named because it contains no other alloys. Carbon steel pipe is widely available and relatively affordable, making it a popular choice for very large projects such as pipelines. Stainless steel pipe is made from an alloy of steel and chromium, and is one of the more expensive types of pipe on the market. It offers a high level of corrosion-resistance, which allows smaller and thinner pipes to be used, even in highly corrosive or acidic scenarios.
Galvanized steel is often used for pipes that will be exposed to harsh conditions like saltwater or marine use. This material features traditional carbon steel with an electroplated zinc coating, which helps resist rust and corrosion. When it comes to selecting pipe for most plumbing applications, black steel pipe is commonly used. The black coating is caused by oxidation of the pipe’s surface during manufacturing, and is considered aesthetically pleasing for pipes that will be left exposed. These pipes are usually treated with an anti-corrosion sealer at the factory before they are sold.
Steel pipe is available in either seamless or welded versions. Seamless pipe is made using a piercing rod, which gives the material a smooth and even finish with no joints. This product is the more expensive of the two, but is also considered more reliable, especially in high pressure applications. Welded pipe is made from steel sheets that are rolled around a form, then welded shut along the joints. While welded steel pipe is less expensive, it is also more likely to fail, and can’t generally hold up well in high pressure uses.

What are the use of steel pipes?

Steel pipes are extremely versatile. That’s why they’re commonly used in many industries, from gas to sewage. They also come in a variety of types and sizes, and they can easily be customized to fit the needs of a particular project, adding even more to its versatility. Truth be told, it’s near impossible to find an industry that does not use steel pipe in some capacity.
Most Common Steel Pipe Uses in Various Industries
Construction, in particular, has benefited from the fact that steel is a more practical alternative to other metals, like iron. Steel is corrosion resistant, making them more durable and cost-effective. It also means that you can use these pipes in areas constantly exposed to the elements because it’s able to withstand them. Given all these benefits, here are some of the common uses of steel pipes.
Domestic
Steel pipes are a common choice for many homes because they are more durable, meaning you won’t have to change them every couple of seasons. Any plumber will recommend a stainless steel pipe for your shower, tap and the rest of the house, especially exposed pipes because they’re more enduring of the elements. They’re also known to be more durable. Its wide use is proven by how commonly you see it in hardware stores and DIY showrooms.
Medical
If doctors use it, it must be safe, so that’s another tick for steel. Steel pipes are so popular in the medical field that they have used them for everything, including supporting fractured bones, medical machinery, surgical tools, dental procedures and even in pharmaceutical. Steel’s varied application is a testament to its durability, safety, and versatility.
Factories
Because factories have to ensure the safety of what they are producing, they have to make sure that they’re equipment are of top caliber. That’s why most of them use steel pipes, from assembly lines and water treatment facilities to dairy and food processing and the refineries themselves.
Construction
This is one of the most obvious uses of steel pipes. They are the go-to for many construction companies because they’re malleable and sturdy, at the same time. Steel pipes are used as construction piling, to support the weight of heavy buildings when the soil is too weak. It’s also used on the building itself and even its architectural design.
Steel pipes are also used to construct ships, the ship yard where they’re kept, oil refineries and even space stations. Whether the construction is on land, over the water, or in space, steel pipes are a quality choice.

Steel Pipe and Manufacturing Processes

Introduction

The advent of rolling mill technology and its development during the first half of the nineteenth century also heralded in the industrial manufacture of tube and pipe. Initially, rolled strips of sheet were formed into a circular cross section by funnel arrangements or rolls, and then butt or lap welded in the same heat (forge welding process).

Toward the end of the century, various processes became available for the manufacture of seamless tube and pipe, with production volumes rapidly increasing over a relatively short period. In spite of the application of other welding processes, the ongoing development and further improvement of the seamless techniques led to welded tube being almost completely pushed out of the market, with the result that seamless tube and pipe dominated until the Second World War.

During the subsequent period, the results of research into welding technology led to an upturn in the fortunes of the welded tube, with burgeoning development work ensuing and wide propagation of numerous tube welding processes. Currently, around two thirds of steel tube production in the world are accounted for by welding processes. Of this figure, however, about one quarter takes the form of so-called large-diameter line pipe in size ranges outside those which are economically viable in seamless tube and pipe manufacturing.

As steel pipes are made? (German comment)

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From: Youtube.com

Seamless Tube and Pipe

The main seamless tube manufacturing processes came into being toward the end of the nineteenth century. As patent and proprietary rights expired, the various parallel developments initially pursued became less distinct and their individual forming stages were merged into new processes. Today, the state of the art has developed to the point where preference is given to the following modern high-performance processes:

The continuous mandrel rolling process and the push bench process in the size range from approx. 21 to 178 mm outside diameter.

The multi-stand plug mill (MPM) with controlled (constrained) floating mandrel bar and the plug mill process in the size range from approx. 140 to 406 mm outside diameter.

The cross roll piercing and pilger rolling process in the size range from approx. 250 to 660 mm outside diameter.

Mandrel Mill Process

In the Mandrel Mill Process, a solid round (billet) is used. It is heated in a rotary hearth heating furnace and then pierced by a piercer. The pierced billet or hollow shell is rolled by a mandrel mill to reduce the outside diameter and wall thickness which forms a multiple length mother tube. The mother tube is reheated and further reduced to specified dimensions by the stretch reducer. The tube is then cooled, cut, straightened and subjected to finishing and inspection processes befor shipment.

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* Note: Processes marked by an asterisk are conducted specification and/or customer requirements

Mannesmann plug mill process

In the Plug Mill Process, a solid round (billet) is used. It is uniformly heated in the rotary hearth heating furnace and then pierced by a Mannesmann piercer. The pierced billet or hollow shell is rollreduced in outside diameter and wall thickness. The rolled tube simultaneously burnished inside and outside by a reeling machine. The reeled tube is then sized by a sizing mill to the specified dimensions. From this step the tube goes through the straightener. This process completes the hot working of the tube. The tube (referred to as a mother tube) after finishing and inspection, becomes a finished product.

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Welded Tube and Pipe

Ever since it became possible to manufacture strip and plate, people have constantly tried to bend the material and connect its edges in order to manufacture tube and pipe. This led to the development of the oldest welding process, that of forge-welding, which goes back over 150 years.

In 1825, the British ironware merchant James Whitehouse was granted a patent for the manufacture of welded pipe. The process consisted of forging individual metal plates over a mandrel to produce an open-seam pipe, and then heating the mating edges of the open seam and welding them by pressing them together mechanically in a draw bench.

The technology evolved to the point where strip could be formed and welded in one pass in a welding furnace. The development of this butt-welding concept culminated in 1931 in the Fretz-Moon process devised by J. Moon, an American, and his German colleague Fretz.

Welding lines employing this process are still operating successfully today in the manufacture of tube up to outside diameters of approx. 114 mm. Aside from this hot pressure welding technique, in which the strip is heated in a furnace to welding temperature, several other processes were devised by the American E. Thomson between the years 1886 and 1890 enabling metals to be electrically welded. The basis for this was the property discovered by James P. Joule whereby passing an electric current through a conductor causes it to heat up due to its electrical resistance.

In 1898, the Standard Tool Company, USA, was granted a patent covering the application of electric resistance welding for tube and pipe manufacture. The production of electric resistance welded tube and pipe received a considerable boost in the United States, and much later in Germany, following the establishment of continuous hot strip rolling mills for the production of the bulk starting material necessary for large-scale manufacture. During the Second World War, an argon arc welding process was invented – again in the United States – which enabled the efficient welding of magnesium in aircraft construction.

As a consequence of this development, various gas-shielded welding processes were developed, predominantly for the production of stainless steel tube. Following the far-reaching developments which have occurred in the energy sector in the last 30 years, and the resultant construction of large-capacity long-distance pipelines, the submerged-arc welding process has gained a position of pre-eminence for the welding of line pipe of diameters upward of approx. 500 mm.

Electric Weld Pipe Mill

Steel strip in coil, which has been slit into the required width from wide strip, is shaped by a series of forming rolls into a multiple length shell. The longitudinal edges are continously joined by high frequency resistance/induction welding.
The weld of multiple length shell is then head treated electrically, sized and cut to specified lengths by a flying cut-off machine. The cut pipe is straightened and squared at both ends.
These operations are followed by ultrasonic inspection or hydrostatic testing.

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How To Distinguish Inferior Steel Pipe?

1.The folding is easy to happen with inferior steel tube
Folding is formed on the surface of the pipe line, this kind of defect often throughout the entire product longitudinal. The reason for causing of fold is due to the pursuit of high efficiency, large reduction of the inferior manufacturer, when go on the next rolling, the folding happens, and the folding products will be cracking after bending, and the strength of steel will decreased.
2. The inferior steel tube has pitted surface
Pits is due to the defects of the irregular uneven steel surface caused by the worn groove. Because of the pursuit of profit, the inferior steel pipe manufacturer often appear the overweight groove rolling.
3. The inferior steel tube surface are prone to scarring
For two reasons: (1) the inferior steel pipe material uneven with impurities. (2). The inferior material manufacturer with simple equipment which is easy to stick steel, these impurities after the roll bite are prone to scarring.
4. The surface of the inferior material is easy to have crack for the reason that it’s blank is adobe, and in the process of cooling due to the effect of thermal stress, cracks, after rolling, there is crack.
5. The inferior steel pipe is easy to scratch for the reason that the inferior steel pipe factory has simple equipment which is easy to produce burr and scratch steel surfaces. The deep scratches will reduce the strength of the steel.
6. The inferior steel tube has no metallic luster, it is reddish or similar to the color of the pig iron for its original material is adobe. And the characteristics of steel pipe cannot reach the required standard.
7. The transverse bar of the inferior steel pipe is thin and low, and often appear phenomenon of discontent, because the manufacturers want to achieve big minus tolerance, finished product quality is not in accordance with the standard.
8. The cross-section of the inferior steel tube is oval, because the factory in order to save material, the quantity of the finished product roll is big, the strength of rebar is greatly decreased, but also do not conform to the standard of rebar shape size.
9. The high quality steel composition is uniform, the cold shearing machine has high tonnage, and the cutting head end is smooth and neat, and the material of the inferior manufacturer is poor, cutting head end is not smooth or uneven, and also has no metallic luster.
10. The impurities of the inferior steel pipe is very large, but the steel density is small, and the size out-of-tolerance is serious, so in the absence of vernier caliper, can be checked to weigh it.
11. The inner diameter of the inferior steel pipe is volatile, the reason is: 1. the steel temperature is unstable; 2. the composition of steel is not uniform; 3. Because of the poorly equipped, and low foundation strength, there will be a larger changes within the same week, the steel bar caused by uneven on fracture.
12.The high quality tube logo and printing are specification.
13.The steel pipe diameter more than 16, the spacing between the two trademark all over IM.
14.The inferior steel rebar longitudinal reinforcement often undulate.
15. The inferior steel pipe manufacturer with no traffic, so the packing is loose.

Steel pipe is a kind of common construction material in our daily life such as welded steel pipe. Therefore, manufacturers who expertise in steel pipe production are various. In these factories, their production ability is different, so the steel pipe quality is also quite uneven. Some shoddy manufacturers who produce poor quality steel pipe will mislead the decision of customers, which is shameful but can not be avoided. Then, how to distinguish the quality of steel tube and square tube? How to choose suitable products with reasonable price? We should learn some basic knowledge about these question.
The pipe component distribution is very uniform for high quality steel pipe and its surface is smooth and neat such as cold rolled steel pipe. However, the steel pipe whose quality is inferior has obvious folding mark on the surface, which can form a variety of folding line. The folding mark will affect the strength of steel pipe seriously; it will become a potential safety issue afterwards. For inferior steel tube, there are a lot of impurities in component, resulting in impure raw materials, which can cause uneven material easily. This kind of poor quality steel pipe can not be applied in actual construction project.
Good quality steel pipe such as hot dipped galvanized steel pipe has lots of excellent performances. For example, premium quality steel pipe has very high strength which can not be scratched easily and light scratching is not obvious. However, inferior steel pipe produced by a set of simple equipment will easily has burr that will lower steel pipe strength. Steel pipe with metallic luster ranks high class in steel pipe market, but inferior steel pipe more or less has rugged dot which is caused by simple and crude production equipment. We should choose the steel pipe with smooth surface without obvious burr.
The above basic points, generally can be used to judge the quality of steel pipe. For all the steel pipe manufacturers, each manufacturer has their own steel pipe price in terms of their types or specifications. In the fluctuate steel pipe market, choosing desirable products with good value is not an easy job. It is a time as well as energy commitment. Besides, we need to mater some related information in advance. Therefore, learning some judgment method of selecting is very important. If you have other questions about the select approaches, hope you can leave your messages below.

Source: China Steel Pipes Manufacturer – Yaang Pipe Industry Co., Limited (www.steeljrv.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

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