How to get high quality stainless steel pipes?

What is a stainless steel pipe?

Stainless steel pipe is one of the more standardized materials in the building and engineering industries. Stainless steel pipe is a tubular section or hollow cylinder, usually but not necessarily of circular cross-section, used mainly to convey substances which can flow — liquids and gases (fluids), slurries, powders and masses of small solids. It can also be used for structural applications; hollow pipe is far stiffer per unit weight than solid members.

In addition, engaging in bending, torsional strength of the same, lighter, and they are also widely used in the manufacture of mechanical parts and engineering structures.

Also used in producing all kinds of conventional weapons, the barrel, artillery shells and so on…

What is stainless steel?

This crystal structure makes such steels non-magnetic and less brittle at low temperatures. For higher hardness and strength, carbon is added. When subjected to adequate heat treatment these steels are used as razor blades, cutlery, tools etc.

Significant quantities of manganese have been used in many stainless steel compositions. Manganese preserves an austenitic structure in the steel as does nickel, but at a lower cost.

The AISI defines the following grades among others:

Also known as “marine grade” stainless steel due to its increased ability to resist saltwater corrosion compared to type 304. SS316 is often used for building nuclear reprocessing plants.

Duplex 2205 (UNS S31803)

Duplex 2205 (UNS S31803), or Avesta Sheffield 2205 is a ferritic-austenitic stainless steel.

What are Duplex Pipes?

Duplex pipes are stainless pipes containing the high amount of chromium and minimum amount of nickel.

We can produce and deliver nearly any duplex material requirement in pipe, tube or fittings.

While Duplex 2205 is the most common duplex product we supply, we can also deliver Duplex 2304 and Duplex 2207 with reduced lead times as these alloys are stocked. Duplex 2205 (UNS S32305/S31803) is a 22% chromium, 3% molybdenum, 5-6% nickel, nitrogen alloyed duplex stainless steel pipe with high general, localized, and stress corrosion resistance properties in addition to high strength and excellent impact toughness.

Alloy 2205 provides pitting and crevice corrosion resistance superior to 316L or 317L austenitic stainless steel tube in almost all corrosive media. It also has high corrosion and erosion fatigue properties as well as lower thermal expansion and higher thermal conductivity than austenitic.

Standard: ASTM/ASME A789/SA789, A790/SA790

Steel Grade: UNS S32750, S31803, S32760 etc.

Applications:

Duplex pipes are stainless pipes containing the high amount of chromium and minimum amount of nickel. Duplex pipes provide great strength and resistance to corrosive environments. Duplex pipes are used in desalination plants, heat exchangers, and marine processes.

• Duplex stainless steel 2205 has below capability:
• High intensity and good impact toughness
• It can bear stress corrosion well
• Good ability to avoid patch and crack
• Low heat expand modulus and better heat transmit
• High pressure work
• Weldable

Stainless steels are also classified by their crystalline structure:

• Austenitic stainless steels comprise over 70% of total stainless steel production. They contain a maximum of 0.15% carbon, a minimum of 16% chromium and sufficient nickel and/or manganese to retain an austenitic structure at all temperatures from the cryogenic region to the melting point of the alloy. A typical composition is 18% chromium and 10% nickel, commonly known as 18/10 stainless is often used in flatware. Similarly 18/0 and 18/8 is also available. ¨Superaustenitic〃 stainless steels, such as alloy AL-6XN and 254SMO, exhibit great resistance to chloride pitting and crevice corrosion due to high Molybdenum contents (>6%) and nitrogen additions and the higher nickel content ensures better resistance to stress-corrosion cracking over the 300 series. The higher alloy content of “Superaustenitic” steels means they are fearsomely expensive and similar performance can usually be achieved using duplex steels at much lower cost.
• Ferritic stainless steels are highly corrosion resistant, but far lessdurable than austenitic grades and cannot be hardened by heat treatment. They contain between 10.5% and 27% chromium and very little nickel, if any. Most compositions include molybdenum; some, aluminium or titanium. Common ferritic grades include 18Cr-2Mo, 26Cr-1Mo, 29Cr-4Mo, and 29Cr-4Mo-2Ni.
• Martensitic stainless steels are not as corrosion resistant as the other two classes, but are extremely strong and tough as well as highly machineable, and can be hardened by heat treatment. Martensitic stainless steel contains chromium (12-14%), molybdenum (0.2-1%), no nickel, and about 0.1-1% carbon (giving it more hardness but making the material a bit more brittle). It is quenched and magnetic. It is also known as “series-00” steel.
• Duplex stainless steels have a mixed microstructure of austenite and ferrite, the aim being to produce a 50:50 mix although in commercial alloys the mix may be 60:40. Duplex steel have improved strength over austenitic stainless steels and also improved resistance to localised corrosion particularly pitting, crevice corrosion and stress corrosion cracking. They are characterised by high chromium and lower nickel contents than austenitic stainless steels.

The main elements in stainless steel

Stainless steel or corrosion-resistant steel is a kind of metallic alloy that is found in a variety of forms. It serves our practical needs so well that it is difficult to find any sphere of our life, where we do not use this type of steel. The major components of stainless steel are: iron, chromium, carbon, nickel, molybdenum and small quantities of other metals.

Chromium and Nickel:
Chromium is the element that makes stainless steel stainless. It is essential in forming the passive film. Other elements can influence the effectiveness of chromium in forming or maintaining the film, but no other element by itself can create the properties of stainless steel.

At about 10.5% chromium, a weak film is formed and will provide mild atmospheric protection. By increasing the chromium to 17-20%, which is typical in the type-300 series of austenitic stainless steels, the stability of the passive film is increased. Further increases in the chromium content will provide additional protection.

Symbol	Element
Al	Aluminum
C	Carbon
Cr	Chromium
Cu	Copper
Fe	Iron
Mo	Molybdenum
Mn	Manganese
N	Nitrogen
Ni	Nickel
P	Phosphorous
S	Sulfur
Se	Selenium
Ta	Tantalum
Ti	Titanium

Nickel will stabilize the austenitic structure (the grain or crystal structure) of the stainless steel and enhance the mechanical properties and fabrication characteristics. A nickel content of 8-10% and above will decrease the tendency of the metal to crack due to stress corrosion. Nickel also promotes repassivation in case the film is damaged.
Manganese:
Manganese, in association with nickel, performs many of the functions attributed to nickel. It will also interact with the sulfur in stainless steel to form manganese sulfites, which increases the resistance to pitting corrosion. By substituting manganese for nickel, and then combining it with nitrogen, strength is also increased.

Molybdenum:
Molybdenum, in combination with chromium, is very effective in stabilizing the passive film in the presence of chlorides. It is effective in preventing crevice or pitting corrosion. Molybdenum, next to chromium, provides the largest increase in corrosion resistance in stainless steel. Edstrom Industries uses 316 stainless because it contains 2-3% molybdenum, which gives protection when chlorine is added to the water.

Carbon:
Carbon is used to increase strength. In the martensitic grade, the addition of carbon facilitates hardening through heat-treating.

Nitrogen:
Nitrogen is used to stabilize the austenitic structure of stainless steel, which enhances its resistance to pitting corrosion and strengthens the steel. Using nitrogen makes it possible to increase the molybdenum content up to 6%, which improves corrosion resistance in chloride environments.

Titanium and Miobium:
Titanium and Miobium are used to reduce the sensitization of stainless steel. When stainless steel is sensitized, intergranular corrosion can occur. This is caused by the precipitation of chrome carbides during the cooling phase when parts are welded. This depletes the weld area of chromium. Without the chromium, the passive film cannot form. Titanium and Niobium interact with carbon to form carbides, leaving the chromium in solution so a passive film can form.

Copper and Aluminum:
Copper and Aluminum, along with Titanium, can be added to stainless steel to precipitate its hardening. Hardening is achieved by soaking at a temperature of 900 to 1150F. These elements form a hard intermetallic microstructure during the soaking process at the elevated temperature.

Sulfur and Selenium:
Sulfur and Selenium are added to 304 stainless to make it machine freely. This becomes 303 or 303SE stainless steel, which is used by Edstrom Industries to make hog valves, nuts, and parts that are not exposed to drinking water.

How to get high quality stainless steel pipes?

Standard (Norm)

• Pipe Dimension
• Pipe Material(Grade)
• Chemical Composition
• Mechanical Properties
• Technology Flow chart
• Range of Applications

Delivery requirment:

• Marking: Yaang, material grade, standard, specification, heat no.
• Surface Treatment: Bright annealed, polished outside and inside surface.
• Package: knitting strip bundle, wooden box or steel box
• Mill test certificate: according to EN 10204 3.2
• Inspection: Third party inspection, or by clints

Pipe size range:

• Outside diameter: range from 6mm to 530mm.
• Wall thickness: SCH5S, SCH10S, SCH40S, SCH80S, SCH 120S
• Legnth: unbending length or fix length

Stainless Steel Pipe Weights and Dimensions

Wall Thickness

Stainless steel pipe categorized by the American National Standards Institute uses the term schedule in reference to the pipe’s wall thickness. Despite this standardization, the wall thickness is not the same for every diameter of pipe. Instead, the schedule refers to the general strength of the pipe. Therefore, a schedule 40S stainless pipe has a wall thickness of approximately 1.73mm for a pipe with outside diameter of 10.3mm but increases to 9.53mm for a pipe of the same schedule but 323.9mm in diameter. There are four general schedules for stainless pipe; 5S, 10S, 40S and 80S.

Diameter

Within each schedule of pipe there are multiple diameters of stainless steel pipe standardized by ANSI. These diameters range from 10.3mm (or .405 inches) to 323.9mm (or 12.75 inches). It is important to note that some diameters are not available in every schedule. For instance, the smallest diameters are not available in schedule 5S and many diameters are very difficult to find in some schedules, or very expensive if they are available.

Materials

Though ANSI standardizes stainless steel pipe, there are multiple formulas of stainless steel available. The two primary steels used in the manufacture of stainless steel pipe are ANSI 304 stainless steel and ANSI 316. Both steels have similar chemistry and differ only slightly in the amount of chromium in the steel.

Stainless Steel Pipe Weights and Dimensions

Black – Indicates wall thickness in inches.
Red – Indicates weight per foot in pounds.

How stainless steel pipe is made?

pipe mill Process description:

• Rolling and welding

Firstly, the stainless steel strips are made to gone through various quality checks and are trimmed at edges. They are then fed to the tubes mill by stainless steel pipe manufacturers in china. The strips pass through the number of rollers as per the required size. In the tubes-mill, the strip is gradually converted into the tubular shape. The fitted welding machine is then used to weld trim edges of the strip using TIG welding process. The scraps and inside weld bead are removed instantaneously by the Tibo machine. In this way, rolled pipes and tubes are formed.

• The cleaning and heating phase

The rolled stainless steel pipes thus manufactured are cut to the required lengths depending upon the industrial demand. These stainless pipes and tubes are then subjected to cleaning to remove the dirt. Further, a heat treatment is given to these rolled pipes and tubes to remove the stresses that may occur due to welding and formation processes. Heat treatment is given on the continuously rolling hearth furnace. The furnace is fitted with temperature recorders and controllers. After the heat treatment process, the SS tubes and pipes are straightened and subjected to pickling for removing scales from the surface.

• Cold- drawing process

In some cases, the required size may not be obtained from the mill directly. Then, the cold operation process can be used to obtain the desired size. In cold drawing process, the tubes or pipes are coated with oxalic and soap solution. This solution acts as a lubricant to reduce friction while cold drawing operation. In the cold drawing process, the tube or pipe is drawn over the bench using Die plugs.

• Finishing process

The drawn-out tube or ss pipe is then subjected to cleaning, heat treatment, pickling and straightening. The computerized ink jet marking machine is used to do the marking on the finished pipes or tubes. The pipe or tube is marked with grade of material, size, heat number and the stamp of third party inspection before passing on tostainless steel pipe exporters. The stainless tubes or pipes thus produced will undergo certain testing and quality checks. This process is followed by proper packing and dispatch. There are numerous numbers of stainless steel pipe applications, these pipes and tubes are used thereafter for.

Pearlite steel is one of the leading Stainless Steel Pipe manufacturer in India. We provide services to oil and gas, pipeline, food processing, automobile and other manufacturing industries worldwide Our state of art manufacturing unit is capable of producing wide range and dimensions of stainless steel pipe and tube. We supply our customers with the highest level of stainless steel products. We are Stainless steel pipe and tube manufacturer from India.

Here’s a video of Stainless Steel pipe Manufacturing process:

Stainless Steel Seamless Pipes packing

Source: China Stainless Steel Pipes Manufacturer – Yaang Pipe Industry Co., Limited (www.ugsteelmill.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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References:

• http://americanstainlessandsupply.com/pvf_reference_table_details.php?Stainless-Steel-Pipe-Weights-and-Dimensions-4
• http://pearlitesteel.com/stainless-steel-pipe-and-tube-manufacturing-process/
• https://en.wikipedia.org/wiki/Pipe_(fluid_conveyance)
• https://www.yaang.com