Is Alloy20 a nickel-based alloy or stainless steel?

Alloy20 (N08020) is an Austenitic nickel-iron-chromium-based superalloy with excellent resistance to total, intergranular, pitting and crevice corrosion in chemicals containing chlorides, sulfuric acid, phosphoric acid and nitric acid. Its corrosion resistance is good between 316L and Hastelloy, and it is not as good as 316L stainless steel in some amine solutions because it is easy to form nickel ammonium complexes.

In addition, it has a good cold forming and weldability even at up to 500℃. The low carbon content and the addition of niobium help to reduce the precipitation of carbides in the HEAT affected zone, so it can be used in the welded state in most cases.

For a long time, many people have been arguing: Is Alloy 20 a stainless steel or a nickel Alloy? Because their 32-38% nickel content is just close to 36%, the boundary between stainless steel and nickel-based alloys blurs the classification of materials. In general, it is true that alloy20 is a nickel alloy. The new edition of ASTM A240 includes alloy 20, which supports that alloys 20 have been classified as stainless steel from the side. Alloy20 plates are in accordance with ASTM B463, ASME SB463. The same materials as N08904 (904L), N08926(1.4529), etc., were early classified in the ASTM B nickel alloy standard series.


Alloy20 has the common characteristics of nickel alloy in terms of welding properties, that is, generally does not produce cold cracks when welding, and is more prone to produce hot cracks. Because of nickel and sulfur, phosphorus can form low melting eutectic, solidification often forms a thick dendritic austenite crystal, low melting point impurity is more likely to focus on grain boundary, the grain size and the effect of solidification shrinkage stress and welding stress, not entirely solidification grain boundary of low melting point material is easy to cracking formation of hot crack, so should strictly control the sulfur and phosphorus content of welding material.

Alloy 20 has excellent resistance to stress corrosion cracking, good resistance to local corrosion, satisfactory corrosion resistance in many chemical process media, chlorine gas and all kinds of media containing chloride, dry chlorine gas, formic and acetic acid, anhydride, seawater and saltwater, etc. At the same time, 20 alloy oxidation-reducing composite media corrosion, is often used in a sulfuric acid environment and containing halogen ions and metal ions sulfuric acid solution applications, such as hydrometallurgy and sulfuric acid industrial equipment.

First developed in 1951 for application in sulfuric acid, alloy 20 is the preferred alloy for sulfuric acid industrial environments. In 20% ~ 40% boiling sulfuric acid, it shows excellent resistance to stress corrosion cracking, and is an excellent material for many industries such as the chemical industry, food industry, pharmaceutical industry and plastics. It can be used in heat exchangers, mixing tanks, metal cleaning and pickling equipment and pipelines. Alloy 20 can also be applied in synthetic rubber manufacturing equipment, pharmaceuticals, plastics, organic and heavy chemical processing, storage tanks, pipes, heat exchangers, pumps, valves and other process equipment, pickling equipment, chemical process pipes, bubble caps, food and dye production is often used.

The theoretical weight of 304 stainless steel pipe elbow

Stainless steel pipe fittings are extensively used in the manufacturing industries for its durability and cost-effectiveness. It has many advantages over the traditional pipe fittings that make it more preferable than any other. The cost-effectiveness of the alloy products greatly contributes to their wide application. Besides this, it helps in the maintenance of the pipe systems too. These are the main reasons why the 304 pipe fittings and accessories have become popular in the market. As the industry requires, the 304 pipe elbows made by the welded and seamless process can be easily found online. But before buying them, you must ensure their weight for your needs, because it will affect the cost of your shipping and transportation.


TP 304 Stainless steel elbow weight chart(Theoretical, kg)

DN O.D Radius Nominal wall thickness, T
1/2 15 21.3 38 1.7 0.05 2.11 0.06 2.11 0.06 2.41 0.07 2.77 0.08 2.77 0.08 2.77 0.08
3/4 20 26.7 38 1.7 0.06 2.11 0.08 2.11 0.08 2.41 0.09 2.87 0.10 2.87 0.10 2.87 0.10
1 25 33.4 38 1.7 0.08 2.77 0.13 2.77 0.13 2.9 0.13 3.38 0.15 3.38 0.15 3.38 0.15
1 1/4 32 42.2 48 1.7 0.13 2.77 0.20 2.77 0.20 2.97 0.22 3.56 0.26 3.56 0.26 3.56 0.26
1 1/2 40 48.3 57 1.7 0.17 2.77 0.28 2.77 0.28 3.18 0.32 3.68 0.37 3.68 0.37 3.68 0.37
2 50 60.3 76 1.7 0.29 2.77 0.47 2.77 0.47 3.18 0.54 3.91 0.66 3.91 0.66 3.91 0.66
2 1/2 65 73 95 2.1 0.56 3.05 0.79 3.05 0.79 4.78 1.21 5.16 1.30 5.16 1.30 5.16 1.30
3 80 88.9 114 2.1 0.82 3.05 1.17 3.05 1.17 4.78 1.79 5.49 2.04 5.49 2.04 5.49 2.04
3 1/2 90 101.6 133 2.1 1.09 3.05 1.56 3.05 1.56 4.78 2.41 5.74 2.86 5.74 2.86 5.74 2.86
4 100 114.3 152 2.1 1.41 3.05 2.02 3.05 2.02 4.78 3.11 6.02 3.87 6.02 3.87 6.02 3.87
5 125 141.3 190 2.8 2.85 3.4 3.48 3.4 3.48 6.55 6.56 6.55 6.56 6.55 6.56
6 150 168.3 229 2.8 4.11 3.4 5.02 3.4 5.02 7.11 10.26 7.11 10.26 7.11 10.26
8 200 219.1 305 2.8 7.15 3.76 9.66 3.76 9.66 6.35 16.11 7.04 17.80 8.18 20.58 8.18 20.58 8.18 20.58 10.31 25.67
10 250 273.1 381 3.4 13.66 4.19 16.79 4.19 16.79 6.35 25.23 7.8 30.83 9.27 36.43 9.27 36.43 9.27 36.43 12.7 49.27
12 300 323.9 457 4 22.64 4.57 26.08 4.57 26.08 6.35 36.03 8.38 47.25 9.53 53.53 9.53 53.53 10.31 57.77 14.27 78.95
14 350 355.6 533 4 29.02 4.78 34.95 6.35 46.22 7.92 57.39 9.53 68.73 9.53 68.73 11.13 79.90 15.09 107.08
16 400 406.4 610 4.2 40.20 4.78 45.79 6.35 60.59 7.92 75.27 9.53 90.21 9.53 90.21 12.7 119.25 16.66 154.87
18 450 457.2 686 4.2 50.91 4.78 58.01 6.35 76.79 7.92 95.44 11.13 133.17 9.53 114.43 14.27 169.54 19.05 223.88
20 500 508 762 4.8 71.67 5.54 82.94 6.35 94.91 9.53 141.53 12.7 187.41 9.53 141.53 15.09 221.61 20.62 299.43
22 550 558.8 838 4.8 86.77 5.54 100.43 6.35 114.94 9.53 171.51 12.7 227.25 9.53 171.51 22.23 390.83
24 600 609.6 914 5.5 119.59 6.35 136.90 6.35 136.90 9.53 204.37 14.27 303.60 9.53 204.37 17.48 369.89 24.61 514.50


What’s the duplex stainless steel used for?

Duplex stainless steel refers to the stainless steel that have each 50% of ferrite and austenite , the general content of the less phase is at least 30%, it has both the characteristics of austenite and ferrite stainless steel. Compared with ferrite, it has higher plasticity, toughness, no room temperature brittleness, intergranular corrosion resistance and welding performance are significantly improved, also maintain the 475℃ brittleness of ferrite stainless steel and high thermal conductivity, superplasticity and other characteristics. Compared with austenitic stainless steels, dual-phase stainless steels have higher strength and higher resistance to intergranular corrosion and chloride stress corrosion. Duplex stainless steel is widely used in various applications because of its excellent comprehensive mechanical properties and resistance to chloride stress corrosion, papermaking industry, Chemical and petrochemical industries, Hydrometallurgy; Marine and coastal applications, plumbing installations for food and beverage plants, buildings, etc

Pulp and paper

Beginning in 1930, one of the first applications of duplex stainless steel was in the sulfite paper industry. Today, duplex stainless steel is used in the pulp and paper industry as bleaching equipment, digesters, chip storage tanks, black and white storage tanks, and suction roll housings. duplex stainless steels have high strength, excellent corrosion resistance, and the same pressure rating that allows for the use of thinner sheets, and have now replaced austenitic stainless steels and carbon steels in paper industry applications. It has lower composite material costs, shorter welding times, and lower transportation and handling costs.



Due to the high chloride content, high-temperature corrosive process environment, seawater desalination subjected the material to one of the most stringent tests. Desalination customers need to strike a balance between meeting corrosion resistance requirements and keeping their investments affordable. In earlier desalination projects, the evaporators for the MSF and MED desalination plants were manufactured using carbon steel. Later, MSF evaporators are generally coated with 316L austenitic stainless steel. The MED evaporator is first coated with epoxy resin and then stainless steel.

The benefits of duplex stainless steel have high strength (twice that of conventional austenitic stainless steel) combined with high corrosion resistance. As a result, duplex stainless steel evaporators can be manufactured from thinner steel plates, requiring less material and welding. Other benefits include ease of handling and less overall impact on the environment. 2205 duplex stainless steel is used to manufacture bulk duplex steel evaporators. The Melittah MSF facility and the Zuara Med facility in Libya were installed to construct three sets of multistage flash MSF units using the concept of combining two duplex steel, 2205 and UNS S32101.


Oil and gas

In the oil and gas industry, duplex stainless steels play a vital role in helping to withstand harsh conditions. This is because its strength, pitting resistance and crevice corrosion resistance are better than standard austenitic stainless steels, and the pitting value (PREN) of dual-phase stainless steels is usually higher than 40. Duplex stainless steel is mainly used in fluid piping, process piping systems and equipment such as separators, scrubbing units and pumps. At sea area, these materials are used in downhole production pipes, fittings and assembly lines, production tree parts, fluid pipes and pipelines for transporting corrosive oil and gas. Super Duplex Stainless Steel (25% Cr) has high strength, excellent fatigue resistance and good coupling compatibility with other high alloy stainless steels.


Food and Beverages

Economic duplex steels have also proved their value in the food and beverage industry. The material is used in two projects in Spain, a food storage facility and a wine storage facility.

At the Port of Barcelona, Emypro SA built all the food storage tanks using S32101, replacing the EN304/304L. The wine storage warehouse for Garcia Carrion, built by Spanish tank manufacturer Martinez Sole in Demiere, southern Spain, was the first to use dual-phase stainless steel: The S32101 and 2304, as low-cost replacements for 304/316L, were used to build the roof and topmost roof for all new tanks.


Construction industry

Duplex steel plays an important role in the construction of Bridges that need high bearing strength when used in a corrosive and salt environment. The 2205 duplex stainless steel is used for the Stonecutters Bridge in Hong Kong and the Double Helix Walking Bridge in Singapore. In 2006, 2,000 tons of 2205 duplex steel sheets and pipes were used for the Stonecutters Island Bridge. The surface part of the bridge was constructed from custom-sized sheets by Chinese duplex stainless steel manufacturers. These stainless steel sheets are polished and shot-peened for optimum reflectance both day and night.

The world’s largest stainless steel roof at the new Doha International Airport in Qatar is constructed using an economical duplex stainless steel (S32003) containing molybdenum. The terminal’s most prominent feature is its wavy roof, which is said to be the largest stainless steel roof in the world. The roof covers about 195,000 square meters (2.1 million square feet) and uses about 1,600 tons (3.5 million pounds) of dual-phase stainless steel. Several factors must be considered in the choice of stainless steel grades, the most important of which is the distance between the airport and the sea. Not only must the roof resist the heat and humidity of the Middle East, but it must also withstand salt. Other factors for choosing Duplex Stainless steel include cost and a good strength-to-weight ratio when compared to other steels.

Why 201 stainless steel is cheaper than 304?

201 stainless steel, a relatively inexpensive alternative material to the traditionally 304 stainless steel. The 201 stainless steel sheet does have its advantages over its competitors, it uses a less amount of Cr and nickel content. This leads to less wastage in the making of joints as well as a reduction in the cost of production. In spite of this though the stainless steel sheet loses some of its hardness and ductility when compared to 304 stainless steel.

201 stainless steel sheet has around half the nickel content as that of 304 stainless steel. Instead, tungsten is replaced by various alloy additions of nitrogen and manganese. It is possible that the overall contribution of these alloy ingredients may not equal the total content of nickel but they certainly contribute in a pretty significant manner. The disadvantage of this material is that the following 18% chromium content and low nickel content can not reach the balance and form ferrite, so the chromium content in 201 stainless steel to 13.5% ~ 15%, in some cases down to 13% ~ 14%, its corrosion resistance is not compared with 304 and other similar steel. In addition, manganese and, in some cases, copper reduce the possibility of re-passivation under acidic conditions common in the corrosion sites of deposits and crevasses. The destruction rate of 201 steel under these conditions is approximately 10-100 times that of 304 stainless steel. Residual sulfur and carbon content in steel is often not controlled during production, even during material recycling.

The major change that occurs in the composition of these stainless steels is the replacement of nitrogen with manganese. The nickel content is reduced from about 20 % in the case of 201 to just 7 % in the case of 304 stainless steel. This is primarily due to the fact that the tungsten is replaced by manganese. There are some other advantages as well, which can be looked into as the combination of both the drawbacks coming together with results in a very effective all-round stainless steel.

The next stainless steel alternative that has come up in the last couple of years has been the use of carbon in place of nitrogen. Carbon is extremely hard-wearing and durable. Many of the new appliances that are coming onto the market use carbon in place of nickel and this is because of this reason alone. Carbon also increases the softness of the alloy and this can be used in household appliances that use a lot of electricity such as stoves and microwaves. The increase in softness can also make the performance of these household appliances much better.

The entire composition of the 201 stainless steel is changed when the carbon is replaced by manganese. This makes the alloy harder, stronger and also more resistant to corrosion. The physical properties of this alloy improve as a result of the increase in mechanical properties and the thermal conductivity improves. As we can see, the combination of these two makes for a perfect match. If you are looking for a brand new kitchen set or if you want to replace the kitchenware of your kitchen then the best option would be to opt for the 201 stainless steel. We have taken pride of place in the supplying of stainless steel products such as 201, 304, 316 and others. When opening a new steel project, it is important to look for a high-quality product.

Austenitic Heat resistant stainless steel

309 and 310 stainless sheets of steel are heat-resistant austenitic steels characterized by high Cr and Ni content. 309S and 310S are their low carbon versions respectively. In oxidizing media, they both have excellent corrosion resistance and high-temperature strength. At room temperature, the matrix microstructure of austenitic stainless steel 310 is pure γ. 310 is also known as “2520 stainless steel” because it contains 25% chromium and 20% nickel, respectively. 310S and 309S are not easy to oxidize at high temperature and are commonly used high-temperature resistance grades. The experimental results show that the oxidation rate of 310 is slow when the temperature is less than 1000℃. As the temperature continues to rise to 1200℃, the degree of oxidation of 310 accelerates rapidly. In addition, they are also used in the transport and storage of strong acids such as nitric acid with a concentration of 65% ~ 85%.


Alternative material in other standards:

JIS G4303 SUS 309S, SUS 310S

EN 10088-1 X12CrNi23-13/ 1.4833, X15CrNiSi25-21/1.4841, X8CrNi25-21/ 1.4845


Chemical Composition

ASTM 309 309S 310 310S
C ≤0.20 ≤0.08 ≤0.25 ≤0.08
Si ≤1.00 ≤1.00 ≤1.50 ≤1.50
Mn ≤2.00 ≤2.00 ≤2.00 ≤2.00
P ≤0.045 ≤0.045 ≤0.045 ≤0.045
S ≤0.030 ≤0.030 ≤0.030 ≤0.030
Cr 22.00~24.00 22.00~24.00 24.00~26.00 24.00~26.00
Ni 12.00~15.00 12.00~15.00 19.00~22.00 19.00~22.00

Under the high temperature condition, 310 heat resistant stainless steel can keep the performance is stable, not easy to be corroded and oxidized by the outside. This is mainly due to the high Cr content in 310 stainless steel itself, metal Cr can combine with oxygen to form Cr2O3 oxide film, which constantly covers the surface of 310 steel until all the package, equivalent to 310 steel put on the “protective clothing”, which can prevent the internal 310 metal contact with the outside world, This is the main reason why 310 steel can have good oxidation resistance at high temperature.

For heat-resistant stainless steel, the chromium (Cr) element is stable at high temperature, does not occur oxidation and falls off. But the content of Cr can not be too high, otherwise, the toughness of stainless steel will also decline because Cr can promote the emergence of α composition and inhibit γ, too much α is easy to lead to the generation of brittle phase. Therefore, in austenitic stainless steel, we hope that the content of Cr remains moderate, which can not only ensure the performance of the material in all aspects but also prevent the emergence of some brittle phases.

Nickel is a very important element in heat-resistant austenitic stainless steel and plays an active role in promoting the formation of γ. The increase of Ni content can make the transition temperature from γ to αphase become very low, which can enhance the stability of the austenite matrix. In addition, appropriate Ni content can obviously improve the overall mechanical properties and good welding properties of stainless steel.

310S VS 309S stainless steel tubing for high temperature application

310S stainless steel is austenitic chromium-nickel stainless steel, which has good oxidation resistance and corrosion resistance. The high percentage of chromium and nickel content makes it have good creep strength, can work continuously at high temperatures, has good high-temperature resistance. High Ni (Ni), Cr (Cr) content makes it has good oxidation resistance, corrosion resistance, acid and alkali resistance, high-temperature resistance, used in the manufacture of electric furnace tubes, and other occasions. The strength of austenitic stainless steel increases with the increase of carbon content due to its solution strengthening effect. The austenitic stainless steel has high strength and creeps strength at high temperatures due to its face-centered cubic structure, which is based on chromium and nickel.

309S(23Cr-13Ni) stainless steel has excellent corrosion resistance and strength, suitable for the working temperature of 1000℃ parts. It has excellent high-temperature acid resistance and high-temperature strength, also known as high alloy stainless steel, widely used in exhaust machines, heat treatment furnaces and heat exchangers, etc. 309S and 310S austenitic stainless steels are often used in high-temperature applications. Their high chromium and nickel content ensures good corrosion resistance and oxidation resistance, and they are slightly stronger at room temperature than austenitic 304 alloys.


The difference is the working temperature at which they are applied:

310S available temperature: 1000~1200℃, the highest working temperature of 1200℃, continuous use temperature of 1150℃. It is the mainstream steel of heat-resistant steel series;

309S usable temperature: 900~1000℃. The highest working temperature is 1050℃, in 650-700℃ can be used under a large load for a long time.


310S stainless steel pipe used for a large number of fluid pipelines, such as petroleum, natural gas, water, gas, steam, and bending, torsional strength of the same stainless steel compared to lightweight, so it is also widely used in the manufacture of mechanical parts and engineering structures and conventional weapons, barrels, shells.

Finally, the biggest difference between 309S and 310S stainless steel is their content of Ni and Cr, which ensures that they not fail due to fatigue, stress, or corrosion, as is often the case with other types of tubes. This is why the 309S and 310S SS seamless tubes are used in applications where high-temperature performance is required. So if you are looking for the ideal high-quality stainless steel tubes, it is always better to purchase them from stainless steel manufacturers that offer quality products at reasonable prices.