Duplex stainless steel tube is composed of approximately the same amount of ferrite and austenite stainless steels. Combining both steels into one metal joins the most attractive properties of each one to form a stainless steel family with outstanding characteristics.Advances in steelmaking over the last 30 years have led to increased interest in duplex stainless steel. Its microstructure contains grains of both austenitic and ferritic steels which each have a one-phase composition. When the two are combined, a two-phase structure forms the metal to have an austenite-ferrite phase balance.
Corrosion Resistance
Duplex SS contains about 20% of chromium in addition to the molybdenum content. Together, these elements make duplex stainless steel grades extremely resistant to severely corrosive environments. Duplex and Super duplex grades of stainless steel can withstand crevice, pitting, chloride ion, and stress corrosion even at elevated temperatures.
Heat Resistant And Hot-working Range
Duplex stainless steel grades are resistant to heat and high-temperature environments. Duplex Steel UNS S31803 Pipes and Tubes do not necessarily require forging, they can be rolled directly. However, in high heat environments, it is tougher to work with chromium alloys than austenitic alloys. Thus, it is easier to hot-roll duplex SS pipes that have low chromium content.
Weldability
Duplex SS grades have superior weldability. These pipes do not crack easily under pressure and heat influence. Preheating the material before the welding process is not required in the case of Duplex SS Pipes.
Thermal Conductivity and Expansion
When Duplex SS pipes are compared to austenitic grades of SS pipes such as 304 and 316, it is observed that Duplex pipes have proven to have better thermal conductivity with a lower rate of expansion. This property of incredible thermal conductivity makes Duplex SS pipes appropriate for applications in composite plating and as the core element in a heat exchanger.
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Stainless Steel Square TubingProduct Description Advantages of duplex stainless steels compared to ferritic stainless steels (1) The comprehensive mechanical properties are better than those of ferritic stainless steel, -
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Duplex Ss PipeProduct Description When choosing duplex stainless steel in different corrosive environments, it should be noted that the corrosion resistance of steel is always relative. Although duplex stainless -
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2205 Stainless Steel TubingProduct Description The 650-800°C stress relief treatment commonly used for austenitic stainless steel cannot be used, and solution annealing treatment is generally used. After surfacing duplex -
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2507 Super Duplex TubingProduct Description The continuous use temperature range of duplex stainless steel pipes is -50 to 250°C, the lower limit depends on the brittle transition temperature of the steel, the upper limit -
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2205 Duplex Stainless Steel TubingProduct Description It is necessary to master the microstructure transformation law of duplex stainless steel pipes, and be familiar with the TTT and CCT transformation curves of each steel type. -
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Super Duplex TubingProduct Description It is necessary to control the phase ratio. The most suitable ratio is that the ferrite phase and the austenite phase account for about half, and the amount of a certain phase -
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Duplex Stainless Metal PipeProduct Description Due to its special advantages, duplex stainless steel is widely used in petrochemical equipment, seawater and wastewater treatment equipment, oil and gas pipelines, papermaking -
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Seamless Duplex Stainless Steel Tube01. Commodity: seamless duplex (ferritic/austenitic) stainless steel heat-exchanger tubing.. 02. Process method: cold drawn, cold rolled. -
![Super Duplex Stainless Steel Pipe]()
Super Duplex Stainless Steel Pipe01. Commodity: seamless duplex (ferritic/austenitic) stainless steel pipe.. 02. Process method: cold finished.. 03. Surface finish: solution annealing and passivated, bright annealing. -
![Super Duplex Stainless Steel Tube]()
Super Duplex Stainless Steel Tube01. Commodity: super duplex (ferritic/austenitic) stainless steel pipe.. 02. Process method: cold rolling, cold drawn.. 03. Surface finish: solution annealing and passivated, bright annealing. -
![SMLS SDSS PIPE]()
SMLS SDSS PIPESMLS SDSS PIPE is designed to handle highly corrosive conditions and situations requiring high strength. It has an austenitic + ferritic duplex organisation and the content of the two phases is
Why Choose Us
Our Factory
Huzhou Gaolin Stainless Steel Tube Manufacture Co., Ltd. was set up in 2002, it is over 55,000 square meters and the assets are over $20 million USD. The annual productivity is about 6,000 tons. Huzhou Gaolin owns strong technology force, advanced equipments and perfect management.
Advanced Equipment
Built in stainless steel cold drawn pipe production line 6, the new LG120-H /LG60-H /LG30-H/LG30/LD30/LG15 and cold tube rolling production line 29.
Production Market
Specializing in manufacturing stainless steel pipes/tubes, the company not only gained high reputation in domestic market, but also in foreign countries. Some of its pipes/tubes have been exported to USA, EU, South Korea, Japan, South-east Asia, South Africa, Brazil, Mexico, Chile etc., and gained customers' high praise.
Certifications
The original materials Gaolin used are all from Yongxing Special Stainless Steel Co., Ltd, which is one of the best stainless steel material suppliers in China. Before processing pipes/tubes with these materials, engineers would inspect the materials to see if they can conform to related standards and requirement. Certifications gained: ISO 9001-2008, PED 97/23/EC, ASME, DNV, ABS.
Duplex stainless steel tube offer numerous advantages over other types of pipes. They have a high strength-to-weight ratio, making them ideal for offshore applications where weight is a concern. They are also corrosion-resistant, making them an excellent choice in corrosive environments, such as chemical plants and oil refineries. Duplex stainless steel tube offer a variety of advantages over other materials, making them a popular choice for many industries. Their superior corrosion resistance allows them to perform well in salty, acidic, and caustic environments where other metals fail. They are also highly resistant to cracking and pitting while retaining high strength levels even at cryogenic temperatures.
Furthermore, they possess excellent mechanical properties with high flexibility and toughness that help reduce fatigue in dynamically loaded components like shafts or housings. Their good weldability further enhances the material's fabrication properties. All these benefits make it an ideal choice for many applications, such as oil & gas pipelines, water treatment systems, process piping networks etc.
In addition, duplex stainless steel tube have excellent fatigue resistance, meaning they can withstand repeated stress without cracking or breaking. This, coupled with their corrosion resistance, makes them an ideal choice for high-pressure applications.
What to Consider When Choosing a Duplex Stainless Steel Tube
Malleability
One of the first things you'll likely need to consider when choosing a duplex stainless steel tube is malleability. Some forms of stainless are more flexible than others, capable of being formed into a variety of different shapes.
If you have a need for intricate duplex stainless steel tube components, malleability should be of utmost importance to you. Some of the more malleable duplex stainless steel tube are austenitic alloys such as alloy 304. However, duplex (e.G. S31803, 2205) duplex stainless steel tube can also be a good option.
Weldability
Another thing to consider is weldability. This describes a sduplex stainless steel tube ability to be welded to other pieces of duplex stainless steel tube. While weldability is an unimportant characteristic in some industries, in other industries, it's vitally important.
Austenitic, ferritic, and duplex stainless steel tube all possess decent weldability. Some of the more weldable duplex stainless steel tube include alloy 346, and alloy 430.
Corrosion Resistance
The fact of the matter is that, while some alloys of duplex stainless steel tube remain tough against corrosive chemicals, others of them falter. If you're using duplex stainless steel tube to process chemicals or operate in salt water, corrosion resistance is of great value to you.
If you're prioritizing corrosion resistance, duplex stainless steel tube might be the way to go. Alloy s31803 (2205) duplex stainless steel tube offers resistance to corrosion from both chemicals and salt water. The austenitic duplex stainless steel tube n08904 also offers terrific corrosion resistance.
Heat Treatment
Perhaps you're looking to harden your duplex stainless steel tube through heat treatment? If so, you're going to want to avoid austenitic, ferritic, and duplex duplex stainless steel tube at all costs. Instead, you're going to want to opt for a martensitic duplex stainless steel tube.
One of the best martensitic duplex stainless steel tube for heat treating purposes is alloy 410. This alloy has terrific oxidation resistance, and can easily withstand temperatures of up to 900℃.
Strength
Regardless of what you're intending to use it for, it's necessary that you get an idea of your prospective duplex stainless steel tube strength capabilities. While all duplex stainless steel tube are fairly strong, some are much stronger than others.
The strongest of all duplex stainless steel tube are martensitic steels. Again, alloy 410 offers a great deal of strength, allowing it to be used for applications that involve a great deal of wear and tear.
Austenitic duplex stainless steel tube are also renowned for their strength, possessing strength levels that are just below those of martensitic duplex stainless steel tube.
The duplex stainless steel are "problem-solving stainless steel"for good reason, they have been successfully used in many places where carbon steels and standard austenitic alloys have failed. Just like with the austenitic family, there are many different duplex stainless steel to choose from, with corrosion resistance varying from moderate with the lean duplex stainless steel to very high with the superduplex stainless steel.
Many of us are familiar with the advantages of duplex stainless steel – higher strength, better fatigue properties, high resistance to chloride stress corrosion cracking, higher corrosion resistance in certain other media, and lower cost of stainless steel elements. The duplex stainless steel are "problem-solving stainless steel"for good reason, they have been successfully used in many places where carbon steels and standard austenitic stainless steel have failed.
Just like with the austenitic family, there are many different duplex stainless steel to choose from, with corrosion resistance varying from moderate with the lean duplex stainless steel to very high with the superduplex stainless steel.
Yet currently, the production of duplex stainless steels is less than 1% of total stainless production, whereas the 300 series austenitic grades represent about 55% of total production and austenitics as a family around 75%. Why has the volume of duplex grades not increased significantly over these many years of availability with all their advantages?
There are many possible reasons for this.
Firstly, higher strength is not always advantageous. It can make forming processes more difficult. Higher strength and hardness also impact the ability to produce a wide range of surface finishes. The high ductility of the 300 series is exceptional and allows for even extreme forming operations such as deep drawing.
Secondly, the two-phase structure of duplex stainless steel means that ensuring quality of weldments is challenging. In contrast, 300 series alloys are much more forgiving during the welding process.
Another major difference is that austenitic alloys are suitable for an extremely wide temperature range whereas duplex stainless steel have limitations at both low and high temperatures.
While the cost of the alloying elements in duplex stainless steel are lower than for a roughly equivalent austenitic alloy, the production cost of duplex is likely to be higher. Both families are often used under severe corrosive conditions, and it is more critical that the metallurgical quality of the delivered duplex components is assured by additional testing. Duplex stainless steel are also more likely to have surface defects that will need conditioning or repair. In addition, the availability of any one duplex grade will be poorer. So where many product forms and sizes are required, it may be a challenge to find a complete bill of material.
Duplex stainless steel have their niche applications where they are excellent choices with proven performance and durability, including thicker-walled tanks and pressure vessels, rotating equipment, piping systems where CUI (corrosion under insulation) is an issue, and many more. It is important, however, when considering a duplex stainless steel to not only understand all their advantages, but also their limitations, comparing them to 300 series alloys with their advantages and limitations.
Duplex Stainless Steel Tube: How Does it Respond to Stress Corrosion Cracking
Stress corrosion cracking, or SCC, is the phenomenon in which metals crack under corrosive and physically stressful conditions. The more corrosive and more stressful an environment is, the greater physical impact it will have on metals that exist within it.
When it comes to stress corrosion cracking, not all stainless steels are created equally. Some stainless steels may be corrosion-resistant, but vulnerable to physical stress. Conversely, other stainless steels may be physically strong, but vulnerable to corrosion.
At the same time, however, there are stainless steels that are resistant to both physical stress and corrosion. These stainless steels possess the highest resistance to stress corrosion cracking.
Stress Corrosion Cracking in Duplex Stainless Steel Tube
As far as stress corrosion cracking goes, duplex stainless steel tube is one of the best stainless steels on the market today. This material thrives through all types of corrosive environments, including chloride-rich environments, sulfate-rich environments, and more.
To truly illustrate the stress corrosion cracking resistance in duplex stainless steel tube, you can simply look at its PREN (Pitting Resistance Equivalent Number). Duplex stainless steel tubetypically possess PRENs of 35 and above. In comparison, austenitic and ferritic stainless steels typically possess PRENs of 30 and below.
If you're looking for a stainless steel that will thrive in corrosive environments, duplex stainless steel tube is the steel to choose.
How Does it Compare to Other Types of Stainless Steel
As you might know, duplex stainless steel tube consists of both ferritic and austenitic stainless steel. As such, it possesses characteristics that are present in both ferritic and austenitic stainless steel alloys.
Because of this, you might expect that ferritic, austenitic, and duplex stainless steel tube possess the same resistance to stress corrosion cracking. However, while there are some similarities in stress corrosion cracking between the three, there are quite a few differences as well.
Stress Corrosion Cracking in Austenitic Stainless
Possessing very high nickel content, austenitic stainless steel does a good job of resisting stress corrosion cracking in non-chloride environments. In chloride-rich environments like the ocean, however, it's highly vulnerable to stress corrosion cracking.
For this reason, it's not typically used for undersea purposes. In fact, one of the reasons duplex exists in the first place is to provide austenitic-like qualities but with substantially greater resistance to stress corrosion chloride cracking.
Stress Corrosion Cracking in Ferritic Stainless
Ferritic stainless steel is fairly resistant to stress corrosion cracking in all types of environments. When compared to austenitic stainless steels, it does a much better job of handling chloride. For this reason, you'll often see it in the ocean.
However, when compared to duplex stainless steel tube, ferritic stainless steel falls short, offering much less resistance to all types of stress corrosion cracking.
Grading the Characteristics of Duplex Stainless Steel Tube
Weldability
Though it's not exactly the most weldable of stainless steel classes (that distinction belongs to austenitic stainless steel), duplex stainless steel tube does possess some weldability. It's important to note, however, that virtually any thickness can be welded.
Corrosion Resistance
As far as corrosion resistance goes, duplex stainless steel tube sits toward the top of the list. Not only does duplex do a terrific job of resisting corrosion due to water, but corrosion due to chloride as well. This makes it appropriate for use in both freshwater and saltwater conditions. In other words, it thrives in and around the ocean.
Now, this isn't to say that duplex is the absolute most corrosion-resistant stainless steel. There are a few austenitic alloys with higher PREN grades. However, for its price, and considering its alternative characteristics, it's exceedingly resistant to corrosion.
Not to mention, it handles stress corrosion cracking with more aptitude than any other class of stainless steel. This is due to its supreme combination of strength and corrosion resistance.
Strength
Duplex stainless steel tube is one of the strongest forms of stainless steel on the market. As such, it can bear substantial amounts of weight. Because of its extreme strength, it can be stretched fairly thin, allowing manufacturers to build components that are simultaneously lightweight and strong.
Toughness
A tough stainless steel, duplex can withstand a great deal of wear and tear. Terrific in cold conditions in particular, it's perfectly suited to handle outdoor applications.
This is one of the reasons that duplex is so popular in the underwater drilling industry. Not only can it hold up against the corrosive properties of water and chloride, but it can also withstand the physical pressure of being hundreds of feet under the sea.
Formability
One area where duplex stainless steel tube falls short is in its formability. Because of its above-average strength and hardness, it lacks malleability and ductility.
This lack of malleability and ductility limits it in terms of the applications for which it can be used. While it can be used to manufacture large, broad items, it can't be used to manufacture small, intricate items.
Magnetism
In terms of magnetism, duplex stainless steel tube is right in the middle of the spectrum. It ranks below ferritic and martensitic stainless steels, yet, unlike austenitic stainless steels, still possesses some magnetic attraction.
Chemical And Petrochemical Processing Industry
The chemical industry is the area where duplex stainless steel is used earlier and more frequently. The catalyst tube of the medium and small methanol synthesis reactor uses duplex stainless steel, and the large and medium-sized device uses 2205 duplex stainless steel welded pipe.
Oil And Gas Industry
This is one of the main application aspects of duplex stainless steel. For the production of duplex stainless steel welded pipes for petroleum, the Chinese stainless steel pipe and fittings suppliers offer a good solution. It has done a good job in cost control, such as adopting new technologies and new processes, using molybdenum oxide balls instead of metal molybdenum, and nickel oxide instead of metal nickel, reducing smelting costs, popularizing the use of duplex stainless steel continuous casting technology, and increasing the yield.
Fertilizer Industry
The fertilizer industry mainly uses 0Cr25Ni6Mo3CuN aging-strengthened duplex stainless steel. Its wear and corrosion resistance is used for the internal parts of high-pressure shut-off valves of various specifications in the main process pipeline of the urea plant. The effect is still good.
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