Most Common Steels used in Process Piping Industry: A Literature

Most Common Steels used in Process Piping Industry: A Literature

Introduction: 
The most common material used in Hydrocarbon inductries are various grades of steel. This article will provide a short write up on common Steels.
Carbon Steel (Temperature Range -29 degree centigrade(C) to 427 degree C): 
This is the most common and cheapest material used in process plants. Carbon steels are used in most general refinery applications. It is routinely used for most organic chemicals and neutral or basic aqueous solutions at moderate temperatures. Carbon steels are extensively used in temperature range of (-) 29 degee centigrade to 427 degee centigrade
Low Temperature Carbon steel (LTCS-Temp range -45.5 degree C to 427 degree C) can  be used to a low temperature of (- 45.5)degree centigrade.
Killed Carbon Steel are defined as those which are thoroughly deoxidized during melting process. Deoxidation is accomplished by use of silicon, manganeese and aluminium additions to combine with dissolved gases, usually oxygen, during steel making. This results in cleaner, better qualtity steel which has fewer gas pockets and inclusions. Killed carbon steel is specified for major equipment in the following services to minimise the possibility or extent of hydrogen blistering and  hydrogen embrittlement:
  • where hydrogen is a major component in the process  stream.
  • where hydrogen sulphied H2S is present with an  aqueous phase or where liquid water containing H2S  is present.
  • Process streams containing any amount of Hydro  flouoric acid (HF), boron trifluoride (BF3) or  (BF) compounds; or
  • Monoethanolamine (MEA) and diethanolamine (DEA) in  solutions of greater than 5 weight percent.
Low Alloy Steel (Temperature range -29 degree C to 593 degree C):
Low Alloy Steels  contain one or more alloying elements to improve mechanical  or corrosion resisting properties of carbon steel. Nickel increases toughness and improves low temperature properties & corrosion resistance. Chromium and silicon improve hardness, abrasion resistance, corrosion resistance and resistance to oxidation. Molybdnum provides strength at elevated temperatures. Some of the low alloy steels are listed below.
  • Carbon   1/2% Moly and Manganese   1/2% Moly: These low alloy steels are used for higher temperature  services and most frequently for intermediate   temperatures for its resistance to hydrogen attack. They have the same maximum temperature limitation as killed steel (ASME Code   1000 deg. F) but the strength above 700 deg.F is substantially greater.
  • 1% chrome   1/2% Moly and 1 1/4% Chrome   1/2% Moly: These alloys are used for higher reistance to hydrogen attack and sulphur corrosion. They are also used for services where temperatures are above the rated temperature for C   1/2 Mo steel.
  • 2 1/4 Chrome 1% Moly and 3% chrome   1% Moly: These alloys have the same uses as 1 1/4% Cr, but have greater resistance to hydrogen attack and higher strength at elevated temperature.
  • 5% chrome   1/2% Moly: This alloy is used most   frequently for protection against combined sulphur attack at temperatures above 550 deg.F. Its resistance to hydrogen attack is better than 2 1/4% Cr_ 1% Moly.
  • 9% Chrome   1% Moly: This alloy is generally limited to heater tubes. It has a higher reistance to high sulphur stocks at elevated temperatures. It also has a maximum allowable metal temperature in oxidising atmospheres.
Stainless Steel (Temperature range -257 degree C to 538 degree C): 
They are heat & corrosion resistant, noncontaminating and easily fabricated into complex shapes. There are three groups of Stainless steels. 1) Martensitic, 2) Ferritic & 3) Austenitic.
  1. Martensitic stainless steel : Martensitic alloys contain 12-20 percent chromium with controlled amount of carbon and other additives.Type 410 is a typical member of this group. These alloys can be hardened by heat treatment, which can increase tensile strength. Corrosion resistance is inferior to Austenitc Stainless steels and these are generally used in mild corrosive environments.
  2. Ferritic stainless steel: Ferritic steels contain 15-30 percent chromium with low carbon content( 0.1percent). The higher chromium content improves its corrosion resistance. A typical member of this group is Type 430. The strength of these can be increased by cold working but not by heat treatment. Type 430 is widely used in nitric acid plants. In addition, it is very resistant to scaling and high temp oxidation upto 800 degree cent.
  3. Austenitic stainless steel: Austenitic steels are the most corrosion resistant of the three groups. These steels contain 16-26 percent chromium 6-22 percent nickel. Carbon is kept low(0.08 percent max) to minimize carbide precipitation. Welding may cause chromium carbide precipitation, which deplete the alloy of some chromium and lowers its corrosion resistance in some specific environments, notably nitric acid. The carbide precipitation can be eliminated by heat treatment(solution annealing). To avoid precipitation special steels stabilized with titanium, niobium, or tantalum have been developed(Types 321,347 & 348). Another approach to the problem is the use of low carbon stainless steel such as types 304L & 316L with .03 percent max carbon.
The addition of molybdenum to austenitic alloy(types 316, 316L) provides generally better corrosion resistance and improved resistance to pitting.
The chromium-nickel steels, particularly the 18-8 alloys, perform best under oxidizing conditions, since the resistance depends on an oxide film on the surface of the alloy. Reducing conditions and chloride ions destroy this and bring on rapid attack. Chloride ions tend to cause pitting and crevice corrosion. When combined with high tensile stresses they can cause stress-corrosion cracking.The detailed list of commonly used steels in hydrocarbon industries is given in following  table:
Ferrous Piping materials
Ferrous Piping materials
Ferrous Piping materials
Ferrous Piping materials

 

 

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4 thoughts on “Most Common Steels used in Process Piping Industry: A Literature”

  1. “The detailed list of commonly used steels in hydrocarbon industries is given in following table” which is not displaying. Kindly resubmit

  2. One of the methods of contrast with earthquakes is seismic retrofitting of pipelines.
    Therefore, pipeline should be strengthened..

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