What’s DSS?

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DSS, the abbreviation of Duplex stainless steel, is a classification of stainless steels composed of two steel with the center one composed of either austenitize or ferric. These are also known as duplex steels since their chemical structure features two distinct phases, both of which are usually represented by martensite respectively. These steels are very useful in applications requiring extreme toughness since the two phases can be applied together at high temperatures and pressures. The duplex stainless steel is able to obtain sufficient hardness in both its austenitic and martensite phases due to the presence of significant amounts of residual austenite. The commonly used DSS grades are S31803, S32750 and SS32550.

The duplex stainless steel grades

Type UNS Sweden German France Japan
Low alloy UN23（SAF2304） SS232（SAF2304） W.Nr.1.4362 UR35N DP11
Medium alloy UNS S31500

UNS S31803

 SS2376(3RE60)

SS2377(SAF2205)

 W.Nr.1.4417

W.Nr.1.4462

 UR45N DP1

DP8
High alloy UNS S32900

UNS S31260

 SS2324(10RE51) W.Nr.1.4460

W.Nr.1.4501

   329J1

329J2L
Super duplex UNS S32750

UNS S32550

 SS2328(SAF2507) W.Nr.1.4410

W.Nr.1.4507

 UR47N+

UR52N+

  

 

Apart from the alloy itself, another important factor that contributes to its corrosion resistance is the nickel content. Nickel is commonly found in higher percentages in most alloys, which makes it an extremely useful component. In comparison to nickel, which is often used in high-performance alloys for its electrical conductivity and ability to form good-quality alloys, nickel is not as frequently used in making high-quality duplex stainless steel. One of the most interesting aspects of nickel alloys is its corrosion resistance ability, which makes it the best alternative for high-performance materials. When mixed with the steel, nickel produces a more stable alloy, which can increase the alloy’s wear-ability and mechanical strength.

Another significant property of this alloy is its high resistance to thermal expansion. It exhibits a high level of thermal expansion resistance despite the expansion resistance ability of austenitic stainless steels, due to its superior mechanical properties. This property gives it an excellent corrosion protection capability, especially during the tempering/stain removal cycle. The excellent corrosion resistance feature of duplex stainless steel enables it to stand up against a wide range of chemicals. It also has high levels of resistance towards oil, grease and other liquids with a high viscosity level.

Apart from the above features, duplex stainless steel is also popular because of its high strength and durability. Its high strength rating of up to 300Kg is made possible through its ability to make use of two-directional mandrel rolls. It is comprised of a hard carbon fiber rolled into strips that are interlaced on both sides and formed into a bar with a mandrel. A further feature that makes it an excellent alloy is that its surface is completely smooth with no ridges.

One of the most important factors that contribute to the durability of duplex stainless steels is their low rate of pitting corrosion resistance. These steels exhibit a low rate of formation of crystalline grains inside the hot alloy. They can be used to build both large and small structures in different industries. Due to their resistance to crystalline grains, they are highly valued by the construction industry.

The mechanical properties of duplex stainless steel offer a number of benefits that make them an excellent choice for a wide range of applications. These properties allow these steels to be used for a variety of applications including precision engineering component building, heat exchangers and sheet metal fabrication. Some other important properties of this type of alloy include high heat tolerance, low density and excellent corrosion resistance. They also offer a number of mechanical properties that contribute to the overall properties of the alloy. These include extreme hardness, toughness, chemical resistance and creep resistance.

Why 201 stainless steel is cheaper than 304?

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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

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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

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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.

 

The advantages of 904L stainless steel

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Super austenitic stainless steel 904L (UNS N08904, EN1.4539) is a high alloy Austenitic stainless steel with low carbon content, specially designed for harsh corrosion conditions. It has high chromium content and nickel content, the addition of copper makes it has strong acid resistance especially dilute sulfuric acid, especially high resistance to chloride gap corrosion and stress corrosion cracking, is not easy to appear erosion spots and cracks, pitting resistance is slightly better than other steel. It has good machinability and weldability, in many industrial fields have a wide range of applications: petrochemical vessels and pipelines, such as reactors, etc.; Power plant flue gas desulfurization unit; Seawater treatment plant, seawater heat exchanger; Paper industry equipment, pharmaceutical industry, food industry and other fields.

 

Metallographic structure

904L is completely austenitic. Compared with austenitic stainless steels with high molybdenum content, 904L is insensitive to the precipitation of ferrite and α phase.

 

Welding performance

As with general stainless steel,904 L can be welded in a variety of ways. The most commonly used welding methods are manual arc welding or inert gas shielded welding. The electrode or wire metal is based on the composition of the base metal and has a higher purity. The content of molybdenum is higher than that of the base metal. Preheating is generally not required before welding, except in the cold outdoors, in order to avoid the condensation of water vapor, the joint part or adjacent area can be heated evenly. Note that the local temperature should not exceed 100℃, so as not to lead to carbon accumulation and cause intergranular corrosion. Small line energy, continuity and fast welding speed should be used for welding. Generally, heat treatment is not required after welding. If heat treatment is needed, it shall be heated to 1100 ~ 1150℃ and then cooled quickly. Matching welding materials: electrode (E385-16/17), welding wire (ER385).

 

Machining performance

The machining characteristics of 904 L are similar to those of other austenitic stainless steels, and there is a tendency for cutter stickiness and work hardening during machining. Positive front Angle carbide cutting tools must be used, with vulcanization and chlorinated oil as cutting coolant, equipment and process should be to reduce work hardening as the premise. Slow cutting speed and feed should be avoided in the cutting process.

 

The corrosion resistance of 904L stainless steel

904L has good activation-passivation conversion ability, it has excellent corrosion resistance, pitting resistance, good crack corrosion resistance and stress corrosion resistance in non-oxidizing acid such as sulfuric acid, acetic acid, formic acid, phosphoric acid, has good corrosion resistance, in neutral medium containing chloride ion. It is suitable for all concentrations of sulfuric acid below 70℃ and has good corrosion resistance to acetic acid and mixture of formic acid and acetic acid at any concentration and any temperature under normal pressure.

Due to the low carbon content (Max. 0.020%) of 904L, there is no carbide precipitation under normal heat treatment and welding conditions. This eliminates the potential for intergranular corrosion that normally occurs after heat treatment and welding. The high Cr-Ni- Mo content and the addition of copper make 904L passivated even in reducing environments such as sulfuric acid and formic acid. The high nickel content makes it have a low corrosion rate in the active state. In the concentration range of 0~98% pure sulfuric acid, 904L can be used at a temperature up to 40℃. In the concentration range of 0~85% pure phosphoric acid, it still has good corrosion resistance.

904L SS is superior to ordinary stainless steel in corrosion resistance to all phosphates. In highly oxidizing nitric acid, 904L has poor corrosion resistance compared to alloy steels without molybdenum. In hydrochloric acid, the use of 904L is limited to a lower concentration of 1-2%, where its corrosion resistance is better than that of conventional stainless steel. 904L steel has strong crevice corrosion resistance in chloride solutions, concentrated hydroxide solutions and hydrogen sulfide-rich environments, due to its high nickel content which reduces corrosion rates in pits and crevices. Ordinary austenitic stainless steels may be sensitive to stress corrosion at temperatures above 60 ° C in a chloride-rich environment. This sensitivity can be reduced by increasing the nickel content of the stainless steel.

Why Precision Stainless Steel Tubes Is the Best Choice for Mechanical processing Industry

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Precision stainless steel tubes are mainly used in precision machining operations. This product is a cross-section of high performance, precision size, and high precision surface treatments. It is used to produce a variety of products for the automotive, aerospace, marine, communications, medical and food processing industries. The tubes have high tensile strength, hardness, tensile strength and dimensional stability and these features make them ideal for heavy-duty applications. Precision stainless steel tube can be used to form many different shapes including round, square, triangle, plate, tubular, rectangular and many more. It can also be custom-formed to match the exact specifications of the customer.

Precision stainless is bright or polished annealed steel tubes with precise tolerance to microscopic flaws. A perfect annealed edge can be provided on request. The internal surface roughness 0.4 mm on both the inside and outside surfaces is covered by various coatings to improve the inherent characteristics. This product has excellent heat conducting properties, which ensures that it works well for high-temperature applications and produces low friction. It has high resistance to corrosion and is capable of resisting extreme temperature fluctuations, good toughness and ductility, tensile strength and hardness. It has good resistance to wear and tear and is unaffected by the alkalis and acids. It features a tough anodized surface and a hard, wear-resistant interior.

Seamless stainless steel pipes feature a cold-rolled ligation process and an oxygen-coated interior. The cold-rolling ligation process ensures that the entire pipe remains homogenous, which ensures maximum durability. The seamless steel pipe has a precision welded finish and therefore, they require minimum welding. They have high resistance to abrasion, erosion and rust and therefore, they are suitable for use in various industries. They have good ductility and hardness and are suitable for pipe joints and other bending applications. In addition, it can also be used in the following industries:

Water transportation pipeline: corrosion resistance, high-pressure resistance, smooth inner wall characteristics make it used for the transportation of pure water pipeline, but also can be used for fire water supply, also used in sanitary appliances drainage pipeline and production equipment of non-corrosive production drainage pipeline, industrial plant rainwater pipeline, etc.

Medical instruments: such as stethoscopes, operating beds and other parts of medical instruments. Disinfectants and various chemical potions have strong corrosion performance, and 316L stainless steel has strong corrosion resistance, and in line with the medical level, safety and health.

Food field: such as stainless steel straw, beverage machine coil, juicer liner, etc., most of the 304 stainless steel and some 316 stainless steel.

For the precision engineering and mechanical processing industry, stainless steel tubes with anodized surface finish and high tensile strength are the best choices. The 304 seamless steel pipes also come with 18-8  chromium-nickel content and high rigidity. Thus, these are ideal for making pipes and tubing for these fields. If you are looking for precision-engineered and ductile stainless steel pipes, you should contact us now for fast, reliable and cost-effective service.