Plain carbon steel is satisfactorily used where strength and other property requirements are not severe and when high temperatures and corrosive environments are not a major factor in the selection of material. Alloy steels have characteristic properties different from plain carbon steel; this is due to some elements other than carbon that are added. Alloying elements are added to obtain several properties including:
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Increased hardenability
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Improved strength at ambient temperatures
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Improved mechanical properties at low and high temperatures
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Improved toughness
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Improved wear resistance
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Increased corrosion resistance
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Improved magnetic permeability or magnetic retentivity
There are two ways in which alloy elements are distributed in the main constituents of steel:
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Elements that dissolve in ferrite
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Elements that combine with carbon to form simple or complex carbides
The sprinkler system is filled with drinking water
Cause
The carbon steel is affected below the waterline near the air containment in the roof net. The drinking water contains an enough microbiology and nutrients, as a result of which MIC may have formed in the standing water
Remedy
Using steel with an inhibitor or nitrogen. Another option is to use stainless steel also with an inhibitor against MIC
Carbon steels offer the proper combination of strengths, ductility, toughness, and weldability. The carbon content is rarely over 0.25% (above this level, toughness, and weldability are reduced) or below 0.15% for reasons of strength. Besides carbon, the most significant alloying element is manganese, which is added to increase yield and tensile strength without reducing ductility. The use of carbon steels is limited to temperatures under 1000°F (538°C). The most widely used carbon steels are SA 36, SA 285 Grade C, and SA 515 and 516 Grade 70.
Carbon steel, a carbon and iron alloy, is the cheapest choice of metal for piping and valves. This material is classified as a noncorrosion-resistant alloy that can be corroded by corrosive compounds such as carbon dioxide, hydrogen sulfite, etc. Other elements, such as silicon, copper, and manganese, can be added to carbon steel. Carbon steel can be divided into different categories, such as low carbon with a carbon content less than 0.25%, medium carbon with a carbon content between 0.25% and 0.5%, and high carbon with a carbon content between 0.5% and 1.25%. It should be noted that the classification of carbon steel based on carbon content can differ from what is mentioned here. If the carbon content of an iron-carbon alloy is more than 2%, the material is called cast iron. Cast iron was a popular choice for piping swage and water pipe before the advent of plastic piping. Carbon steel can be corroded in the form of metal loss due to carbon dioxide CO2. Therefore 3 mm corrosion allowance as an average can be added to carbon steel pipe and valve bodies according to Norsok M-001, “material selection” and Norsok L-001, “piping and valves.” In addition, hydrogen-induced cracking (HIC) is a big risk for carbon steel; hydrogen atoms can accumulate in the void spaces in the microstructure of carbon steel; after collision they get bigger and cause cracking or other types of failures in the metal (see Fig. 12.20). One approach to mitigating HIC corrosion is to used killed carbon steel. Killing carbon steel process involves deoxidating the steel with aluminum or silicon, which makes the steel homogenous and free of porosity.
Fig. 12.21. V Notch on metal for the Charpy impact test.
The other important parameter for carbon steel is carbon equivalent (CE), which affects the weldability of carbon steel. Increasing the percentage of some of the alloys, such as carbon and manganese, in the carbon steel improves the mechanical strength of the carbon steel, but also increases its hardness and brittleness. Some piping and valve specifications put limitations, such as 0.39 or 0.40 or 0.42, on CE to prevent cracking the carbon steel due to welding or sour corrosion such as HIC. CE can be calculated through Eq. (12.8):
Carbon steel, according to ASME B31.3, “process piping code,” can be used for design temperatures between − 29°C and approximately 400°C. Alternatively, low-temperature carbon steel (LTCS) can be used if the design temperature of the piping and valve will be between − 46°C and − 29°C. LTCS is probably more suitable for lower temperature than carbon steel due to the addition of some alloys such as nickel and magnesium. A Charpy impact test is applied on LTCS at − 46°C to evaluate the resistance of the materials against breakage. A V-notch is created on a sample of the material (see Fig. 12.21) and the required energy to break the material through the V-notch is measured. The mechanism of low temperature failure in the material is cracking, which is evaluated by the impact test. Adding 3 mm of corrosion allowance is also applicable for piping and valve bodies in LTCS material.
Pre-Galvanizing Pipe is widely used in petroleum ,chemical industry, construction, shipbuilding, communications, electricity and underground gas pipelines and many other fields.
Pre-Galvanizing Pipe is galvanizing, Zinc layer is an electroplating layer, and zinc layer is separately stratified with the steel tube matrix.
Pre-galvanized steel pipe is the treatment of steel pipe before galvanizing: degreasing treatment, derusting treatment, phosphating treatment, drying treatment.
Hot dipped galvanized steel pipe is in manufacturing process using steel pipes of removed rust dipped into zinc liquid of 500℃ temperatures, and making steel surface attached zinc layer so as to achieve the purpose of anti-corrosion.
Hot galvanizing process specially suitable for kinds of strong-acid, alkali fog and other strong corrosive conditions. This kinds of fastener used a lot in outside of steel tower contribution.
Black steel pipes have a variety of use. Thanks to their strength and needs for little maintenance. They tend to be used for transporting gas and water to rural areas and urban areas or for conduits that protect electrical wiring and deliver high pressure steam and air. In addition, black steel pipes are also used in oil and petroleum industries for piping large quantities of oil through remote areas.
Other uses of black steel pipes include gas distribution inside and outside homes, water wells and sewage systems. However, black steel pipes are never used for transporting potable water due to the fact that they tend to corrode in water and mineral of the pipe will dissolve into the water and clog the line as well.
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Seamless pipes are manufactured by extruding the metal to the desired length. Thus, they do not have any joint in its cross-section throughout its length. seamless pipes are marketed on an outdated myth that it does not have flaws but that welded has an inherent flaw throughout the length of each tube, as stated above. Intuitively this concept is easily accepted by purchasers and designers with limited experience with the various products.
Steel porp refers to the use of steel pipe, H-shaped steel, angle steel, etc. to enhance the stability of the engineering structure. Generally, it is an inclined connecting member, and the most common are herringbone and cross shapes. Steel supports are widely used in subways and foundation pits. Because the steel support can be recycled and reused, it is economical and environmentally friendly.
Steel coil is sheet metal supplied in coil form. Depending on the production method, such coil is classified as hot-rolled, cold-rolled, galvanised or polymer-coated . Steel coil is used across industry, the main consumers being the construction and machine-building sectors.
