Brand AISI 304 (Russian equivalent according to GOST: AISI 304 - 08Х18Н10, AISI 304L - 03Х18Н11) is one of the most popular brands of stainless steel. Along with high strength properties, it has excellent resistance to the effects of aggressive environments of a natural or man-made nature, optimal resistance to the effects of low and high temperatures, as well as non-magneticity. The operating temperature range is from -200 °C to +650 °C.
Chemical composition of steel AISI 304, 304L
Area of application of AISI 304, 304L steel
AISI 304 stainless steel sheet is indispensable in the production of various containers, tanks, containers, receivers and other industrial equipment. In construction it is mainly used for production various types pipes IN chemical industry This type of steel is used for the production of equipment for transporting and storing reagents. IN Food Industry AISI 304 steel is integral part equipment for the production, storage and transportation of various drinks (milk, wine, kvass, etc.), in addition, steel is used for the manufacture of kitchen and tableware.
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Standard |
ASTM A182 - Standard Specification for Forged or Rolled Pipe Flanges, Forged Fittings, Valves, and Alloy and Stainless Steel Parts for High Temperature Service ASTM A213 - Standard Specification for Seamless Boiler, Superheater, and Heat Exchanger Tubes of Ferritic and Austenitic Steels ASTM A240 - Standard Specification for Chrome- and Nickel-Chrome, Chrome- and Manganese-Nickel Stainless Steels for Plate, Sheet, and Strip for Pressure Vessels and General Applications ASTM A312 - Standard Specification for Seamless, Welded, and Intensive Cold Worked Austenitic Stainless Steel Pipe |
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| Classification | Stainless steel | ||||||
| Application | Sheets, pipes, profiles | ||||||
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Other names |
UNS | S30400 | |||||
| USA (ASTM A167) | Sheet metal | A167 304 | |||||
| USA (ASTM A182) | Forged and rolled flanges | A182 F304 | |||||
| USA (ASTM A213) | Seamless pipes | A213 TP304 | |||||
| USA (ASTM A240) | Flat rolled products | A240 Type 304 | |||||
| USA (ASTM A271) | Seamless distillation pipes | A271 304 | |||||
| USA (ASTM A312) | Seamless pipes | A312 TP304 | |||||
| USA (ASTM A851) | Welded condenser pipes | A851 TP304 | |||||
AISI 304 steel is the most popular grade of stainless steel. Increased demand and widespread use is due to its versatility. AISI 304 steel has high corrosion resistance in aggressive environments, high oxidation resistance and excellent low-temperature properties.
It is worth noting that AISI 304 stainless steel is resistant to negative impact water (salt, fresh, tap) and acid solutions in high concentrations(acetic, formic, nitrogen).
The price of aisi 304 is quite affordable, which is another one of its advantages.
Chemical composition in % of AISI 304 steel
SS304 stainless steel is alloyed with nickel, manganese, copper and chromium, which provides it with an austenitic structure, increased strength and resistance in corrosive environments.
Mechanical properties of AISI 304 material
Physical properties of AISI 304
Steel density (weight) aisi 304 - 7.74 g/cm3.
Performance at elevated temperatures
Corrosion resistance in acidic environments
| Temperature, °C | 20 | 80 | ||||||||||
| Concentration, % by weight | 10 | 20 | 40 | 60 | 80 | 100 | 10 | 20 | 40 | 60 | 80 | 100 |
| Sulfuric acid | 2 | 2 | 2 | 2 | 1 | 0 | 2 | 2 | 2 | 2 | 2 | 2 |
| Phosphoric acid | 0 | 0 | 0 | 0 | 0 | 2 | 0 | 0 | 0 | 0 | 1 | 2 |
| Nitric acid | 0 | 0 | 0 | 0 | 2 | 0 | 0 | 0 | 0 | 0 | 1 | 2 |
| Formic acid | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 2 | 1 | 0 |
0 = high degree protection (corrosion rate does not exceed 100 mm/year);
1 = partial protection (corrosion rate ranges from 100m to 1000 mm/year);
2 = no protection (corrosion rate exceeds 1000 mm/year).
Closest equivalents (analogues) AISI 304
| Germany | X5CrNI18-10 |
| European (EN) | 1.4301 |
| Japan (JIS) | SUS 304 |
| Russia (GOST) | 08Х18Н10 |
Scope of application AISI 304
AISI 304 stainless steel, due to its high resistance to oxidation and high temperatures, has found wide application:
- in the chemical and pharmacological industry;
- in the food, dairy and brewing industries;
- in medicine (surgical equipment, injection needles);
- in the production of ship equipment and fasteners for nuclear ships;
- in rolled metal (pipes, angles, sheets, tapes, hexagons);
- in the oil (filter screens for wells) and mining industries;
- in the production of equipment for working under conditions of chemical exposure;
- in the construction of structures for which strength and long service life are important;
- in the textile and paper industry.
Moreover, due to its excellent technical parameters, hygienic indicators and a pleasant aesthetic appearance, steel 304 is used in the manufacture of kitchen furniture and cutlery; containers for storing liquid and dry substances.
Steel stainless steel 304 is involved in the production of cooling coils, cryogenic vessels, refrigeration equipment, sanitary fittings, pressure vessels, etc.
Welding
AISI 304 / SS 304 stainless steel can be easily welded by all methods. Subsequent heat treatment is only necessary if there is a risk of intergranular corrosion. It is carried out at 1050-1150°C, the seam must be cleaned of the resulting scale and sautéed with a special paste.
Treatment
Annealing: at a temperature of 1010°C-1120°C; cooling - in air or in water.
Please note: optimal anti-corrosion properties of steel are achieved at a temperature of +1070°C followed by instant cooling.
After annealing, etching and passivation are necessary.
Vacation: at a temperature not exceeding 400 °C.
Passivation: 20-25% HNO 3 solution at 20°C.
Surface cleaning: solution nitric acid and hydrofluoric/fluoric acid in proportions: 10% HNO 3 + 2% HF at room temperature or 60°C. Sulfuric-nitric acid solution in proportions: 10% H 2 SO 4 + 0.5% HNO 3) at 60°C.
Hot processing: initial temperature - 1150 - 1260°C; final – 900-950°C.
Please note: any hot processing must be accompanied by annealing.
Cold processing: AISI 304 stainless steel is very strong and elastic, therefore it is easily subject to stretch forming, bending and deep and rotary drawing, drawing.
FYI: For forming, you can use the same machines and tools as for carbon steel, but with 50-100% more force.
Steel grade AISI-304 non-magnetic (austenitic) low-carbon. Contains carbon no more than 0.08%. This type steel has high density and, at the same time, remains quite plastic, and is also characterized by the highest levels of corrosion resistance and the ability to withstand various temperature conditions
Due to the uniformity of the chemical composition, AISI 304 steel retains its internal structure even if the outer layer is damaged. In addition, on the surface of this brand, when interacting with atmospheric oxygen, a protective oxide film is immediately formed, which guarantees resistance to the effects of alkali and acid solutions.
The use of Aisi 304 steel is quite wide. It is used for the manufacture of containers, tanks, receivers, various containers, tanks for industrial purposes, for the transportation of wines and their storage, for the manufacture of containers for kvass, for the dairy industry, and in the production of cosmetics.
Аisi 304 is highly polishable, as a result of which it can be used in various design works for the decoration of offices and homes.
AISI 304 pipe is used almost everywhere; it is used in plumbing work, in the manufacture of heated towel rails, radiators, used for the design of railings and fences, as well as in the manufacture of ramps, balconies, office furniture and bar counters.
Steel pipes of grade Аisi 304 are used to produce support stands for pipelines, various supporting structures, and metal shelving.
Resistance to temperature and influence of alkaline and acidic environments, meeting GOST 5632-72, regarding cheap cost, make this brand quite popular in various areas.
AISI 304 sheet is used for the manufacture of various containers and reservoirs, in the chemical and food industries, for the manufacture of special metal tables (cutting, kitchen, medical).
AISI 304 sheet is also used to produce: platform trolleys, washing and disinfection chambers, doors for refrigerated cabinets,
Thin sheets of AISI 304 are used for cladding elevator cabins, cladding escalators and columns.
This grade of steel is easy to weld. After welding, this grade of steel is not required heat treatment. After welding, the seams must be chemically or mechanically cleaned of scale and then passivated.
AISI 304L easily finds a large number of applications, as it is extremely strong, ductile and elastic. Common operations include contouring, bending, rotary drawing, drawing, etc. During forming it is possible to use the same tools and machines as for carbon steel grades, but here the required force is 50-100% greater.
The annealing temperature range is 1050°C ± 25°C followed by rapid cooling in water or air. After annealing, etching and passivation are required.
Chemical composition in % of AISI 304 steel
| Brand | WITH | Ni | S | P | Cr | Ti | Si | Mn | Cu |
| 304 | ≤ 0.8 | 9-11 | ≤ 0.02 | ≤ 0.035 | 17-19 | ≤ 0.5 | ≤ 0.8 | ≤ 0.2 | ≤ 0.3 |
Mechanical properties AISI 304 (room temperature)
Mechanical properties AISI 304
Physical properties of AISI 304
| Physical properties | Density | Melting temperature | Specific heat | Thermal expansion | Average coefficient of thermal expansion | Electrical resistivity | Magnetic permeability | Elastic modulus |
| Unit | - | OS | J/kg.K | W/m.K | 10-6.K-1 | Ωmm2/m | at 0.8 kA/m | MPa x 103 |
| Temperature (оС) | 4 | |
20 | 20 | 20-100 20-200 20-400 | 20 | 20 | 20 |
| Meaning | 7,93 | 1420 | 500 | 15 | 16,0 16,5 17,5 | 0,73 | 1,015 | 200 |
AISI 304 product range
Standard sizes of AISI 304 stainless steel sheet
Standard sizes of stainless steel pipe AISI 304
Steel grades AISI 304 and 304L (according to the American classifier ASTM A240) and their straight lines Russian analogues 08Х18Н10 and 03Х18Н11 (according to GOST) are the most common and most versatile chromium-nickel high-alloy corrosion-resistant austenitic steels, which are used in almost all sectors of material production, both in the CIS countries and throughout the world. The popularity and demand of this steel is due, at an affordable price, to its excellent resistance to oxidation and corrosion, good weldability, a unique combination of mechanical properties and characteristics of the chemical composition. Due to the fact that intercrystalline corrosion of AISI 304 occurs only when heated at high temperatures, this grade is especially recommended for use in conditions of low and ultra-low temperatures. AISI steel is highly polished and retains its aesthetic appearance for a long time, which is very important when making architectural, construction and design structures, interior items and metal furniture from it.
Main applications of AISI 304 steel
It is difficult to find a modern field of activity where it is not applied to one degree or another. steel AISI 304 or 0818N10. In particular, they are used everywhere to make:
- containers, containers and tanks for storing and transporting all kinds of bulk substances and liquids;
- receivers and equipment for the production and transportation of aggressive chemicals and medicines;
- parts and elements of installations for the production of liquid and paste-like food products (creams, kvass, wine, milk, etc.), as well as for their transportation;
- equipment for drilling wells and strengthening mine workings;
- cooking equipment and household cutlery.
In addition, AISI 304 serves as the base material for many items of laboratory scientific instruments, cryogenic units, molding plates, support elements, etc.
Chemical composition and differentiation of AISI 304 steel
ASTM A240 standard regulates chemical composition AISI 304 steel as follows:
- carbon - no more than 0.08% (AISI 304L - 0.03%);
- manganese - no more than 2%;
- phosphorus - no more than 0.45%;
- sulfur - no more than 0.03%;
- silicon - no more than 0.75%;
- chromium - 18.0 - 20.0%;
- nickel - 8.0 - 10.5% (AISI 304L - up to 12%);
- nitrogen - 0.1%.
The high anti-corrosion properties of AISI 304 are associated with the presence of a thin film of chromium oxide on the surface of the material. And since this steel has an absolutely uniform structure throughout its entire thickness, all parts and materials made from it (sheets, rods, profile pipes, shaped blanks), even if the top layer is damaged, continue to maintain the same resistance to corrosion. The destroyed oxide film is instantly restored, preventing the damage from spreading. A similar process occurs in stainless steel structures exposed to atmospheric influences. Constant temperature changes lead to the appearance of microcracks, in which a protective layer is immediately formed. This property of AISI 304 steel made it possible to make reliable containers, railings for external stairs and balconies, swimming pools and much more. The guaranteed durability of such products is at least 150 years.
Availability in AISI 304 large quantity nickel gives this grade of steel an important advantage over nickel-free analogues (AISI 430, etc.). Since the melting point of nickel is much higher than that of chromium, it remains in the metal structure even when exposed to heat (for example, during the welding process), while chromium burns out almost completely. Retained in the weld, nickel provides its strength and additional corrosion resistance.
AISI 304 steel differs from many other stainless steels in its ability to differentiate. This means that during the production process the material can be given some specific properties related to the specific area of its subsequent application or the required nature of the processing. By varying the composition of steel (within established standards), it is possible to provide it with:
- higher weldability;
- ability for deep and rotational drawing;
- stretch forming ability;
- increased strength, cold hardening;
- additional heat resistance;
- special suitability for certain species mechanical processing.
Like any austenitic steel, AISI 304 can, if necessary, be additionally strengthened either by adding nitrogen to its composition (modification 304LN), or by one of the factory technological methods of form hardening (cold-hardening, pressure, repeated skin-pass rolling or stretching).
The nitriding process is most suitable for steels intended for the manufacture of large objects in the oil and gas and chemical industries (transport containers, columns, tanks). In this case, with a higher design strength of the metal, it is possible to reduce the wall thickness and thereby achieve significant savings in material costs.
Austenitic stainless steels that have undergone form strengthening are used for the production of parts and elements that bear mechanical loads - welded pipes, molding plates for the automotive industry, hoops for kegs, construction fittings, strips, chains, fences, etc.
AISI 304 steel (08Х18Н10), unlike the 400th group of “stainless steels” (analogs 12Х17), does not have magnetic properties, which in certain cases can be very important in its practical application. However, this quality is only a consequence of the special internal structure of the metal; it in no way affects its chemical and corrosion resistance, strength characteristics and manufacturability in processing.
The most important performance properties and manufacturability of AISI 304
The main performance qualities of AISI 304 steel, which determine its applicability and manufacturability, include its following properties:
1. Resistance to high and low temperatures.
As the temperature increases, the tensile strength of AISI 304 decreases. This is especially noticeable when the material is heated above 425 degrees. C. So, if at 600 deg. With this parameter equal to 380 N/mm2, then at 800 deg. C - already 170 N/mm2, and at 1000 deg. C - only 50 N/mm2. According to the same algorithm, the elastic limit also decreases.
- with continuous exposure - 925 degrees. WITH;
- with intermittent exposure - 850 degrees. WITH.
Reducing the operating temperature to ultra-low values leads to a significant increase in the strength of steel: at -78 degrees. C tensile strength is 1100 N/mm2, at -161 degrees. C - 1450 N/mm2, and at -196 degrees. C - 1600 N/mm2. The elastic limit of the material increases somewhat, although not to the same extent, and the impact strength deteriorates.
2. Corrosion resistance.
AISI 340 steel shows good resistance to most acids (except sulfuric acid). When exposed to atmospheric conditions, its corrosion resistance is significantly superior to that of aluminum. especially ordinary carbon steel. Thus, in rural conditions, the ten-year corrosion rate of AISI 340 is 0.0025 (aluminum - 0.025, carbon steel - 5.8), and in industrial marine conditions - 0.0076 (aluminum - 0.686, carbon steel - 46.2).
3. Heat treatment of the material.
- Annealing.
The optimal annealing temperature for AISI 304 is from 1010 to 1120 degrees. C. The most ideal conditions for this technological operation are a temperature of 1070 degrees. C and subsequent rapid cooling (or tempering).
- Vacation.
It is best to temper 304 steel for 1 hour at a temperature of 450 to 600 degrees. C. If there is a need to avoid sensitization, operating temperature should be reduced to 400 degrees.
- Hot processing (forging).
Forging AISI 304 or its other hot processing must be carried out at an initial temperature of 1150 - 1260 degrees. C and final - 900 - 925 degrees. C. In this case, annealing of the workpiece is required. To achieve uniform heating, it should be taken into account that such homogeneity in AISI 304 steel is achieved 12 times slower than when heating carbon steels.
4. Cold processing.
AISI 304 steel and its modification 304L, due to its good ductility and high strength properties, are easy to cold work. Typical types of such processing include bending, drawing (rotary and deep) and stretch forming. For the forming operation, in principle, the same equipment and the same tools can be used as for carbon steels, however, since austenitic steels are further strengthened during this process, mechanical forces are required here that are one and a half to two times higher.
- Flexible.
The bending limits for different thicknesses of AISI 304 sheet are different. With a thickness of up to 3 mm, the minimum bending radius can be practically zero, with greater thickness - equal to half the thickness of the sheet. Bending angle - 180 degrees. with a thickness of 3 - 6 mm and 90 degrees. with a thickness of 6 - 12 mm. Reverse straightening is greater in austenitic steels than in carbon steels. Therefore, the workpiece should be slightly “bent” (when bent at a right angle, the bend can be from 2 to 25 degrees, depending on the ratio of the radius and thickness of the sheet). The recommended minimum bending radius for 304 steel is twice the sheet thickness.
- Deep and rotary drawing.
Using a press, deep drawing allows the material to flow freely without subjecting the workpiece to braking. But when drawing products with precise dimensions, stretching (braking) molding is most often used; in this case, it is advisable to provide a hardening process combined with molding.
Rotary drawing is carried out on turning and pressing equipment and, in fact, is forming with turning. This method usually produces products of symmetrical rotation (buckets, etc.), which do not require subsequent polishing.
5. Weldability.
AISI 304 steel can be easily welded by any modern method. Subsequent heat treatment of the seam is not necessary. But in order to avoid the risk of intercrystalline corrosion, it is useful to carry out additional annealing at a temperature of 1050 - 1150 degrees. With rapid subsequent cooling. The cooled welding seam should be cleaned of scale and sautéed (treated with etching paste).
Information article
In this article we look at how AISI 304 and 430 stainless steels differ from each other, and why one is cheaper and the other more expensive. You will learn how to distinguish these steels when buying a sauna stove, so that you are not deceived and sold an ordinary sauna stove made of AISI 430 steel under the guise of real stainless steel.
There are many different models on the sauna stove market that use stainless steel, but not all stainless steel is equally good. Let's try to figure out how stainless steels differ from each other. Let's take as an example the most common steels AISI 430 (17X18 according to GOST) and AISI 304 (12X18H10 according to GOST).
Many manufacturers of sauna stoves use AISI 430 steel in their production, since according to the heat resistance table it is higher. The use of this steel is also justified by its relatively low price compared to AISI 304 steel. AISI 304 steel has slightly less heat resistance compared to AISI 430, but this is its only minor difference. Since there are more important indicators, which directly affect the performance and durability of the product.
First, let's find out in more detail what kind of steel it is.
Stainless heat-resistant (austenitic) steel AISI 304 (INOX)
Heat resistance is the ability of a metal to resist plastic deformation and fracture at high temperatures.
The main heat-resistant austenitic steels are chromium-nickel steels. Steels contain 15...20% chromium and 10...20% nickel. They have heat resistance and heat resistance, are plastic, and weld well.
Steel grade AISI 304 (INOX) - belongs to the chromium-nickel class of low-carbon high-alloy steels. High chromium and nickel content determines excellent strength and anti-corrosion properties, which are in demand everywhere - they are defined as universal. That is why this alloy is one of the most used.
In the GOST system, this grade corresponds to 12X18H10 steel.
The main qualities that give advantages to AISI 304: resistance to oxidation and elevated temperature, increased reliability of welds due to good weldability.
AISI 304 has the following performance properties:
- Acid resistance. Resistance to aggressive influences of a man-made or natural nature.
- Heat resistance. The ability of a metal to resist plastic deformation and fracture at high temperatures.
- Heat resistance. The ability of metals and alloys to resist gas corrosion at high temperatures for a long time (up to 850 o C).
- Weak magnetic properties. They are achieved due to the structure of the material and the method of its processing. AISI 304 steel is not magnetic.
- Environmental friendliness. Manufacturers of AISI 304 position this material, also called Inox, as food grade stainless steel. It does not contain toxic substances.
Stainless heat-resistant (ferritic) steel AISI 430
Heat resistance (scale resistance) is the ability of metals and alloys to resist gas corrosion at high temperatures for a long time.
If the product operates in an oxidizing gas environment at a temperature of 500..550 o C without heavy loads, then it is enough that they are only heat-resistant (for example, individual parts of heating furnaces). Being low-alloy and corrosion-resistant, AISI 430 steel has good resistance to scale formation up to temperatures 850-900 o C, maintaining its useful performance properties.
To increase heat resistance, elements are introduced into the steel composition that form oxides with oxygen. dense structure crystal lattice (chrome, silicon, aluminum).
In the GOST system, this grade corresponds to steel 17Х18.
AISI 430 has the following performance properties:
- Heat resistance. The ability of metals and alloys to resist gas corrosion at high temperatures for a long time (up to 900 o C).
- Environmental friendliness. It does not contain toxic substances.
Comparison of AISI 304 and 430 stainless steels
AISI 430 steel, although more heat resistant, is more brittle and difficult to weld. In order to weld it efficiently, a special complex technology and its exact observance at all stages of work are required. This steel is mainly used for decorative purposes. Welded structures made from it are very fragile and the most weak point There will always be a weld seam.
This AISI 430 steel has lower acid resistance compared to 304 stainless steel, and when working in harsh conditions of water, soot and condensate, it gradually becomes unusable, so, for example, chimney pipes made of such steel still burn out. They are simply corroded by the acid produced as a result of the operation of the furnace. Also, AISI 430 steel is magnetic, which easily gives it away during any magnetic test. This way you can easily determine which stainless steel is in front of you - AISI 430 or real non-magnetic stainless steel AISI 304.
AISI 304 (INOX) steel is a heat-resistant steel and is not afraid of high temperatures when operating a sauna stove. It is perfectly weldable due to the higher quality steel composition and high nickel content. Nickel is a very expensive metal, but with its high content in stainless steel it acquires increased strength and resistance to temperature changes, and also acquires excellent weldability. It is thanks to nickel that this steel loses its magnetic properties.
Also, AISI 304 stainless steel is resistant to chemical and acid influences and does not emit harmful or toxic substances. Therefore, this steel is mainly used in the food and medical industries and is classified as food grade stainless steel.
AISI 304 steel is more expensive compared to AISI 430 steel due to the use of higher quality and more expensive nickel and chromium alloys in large quantities.
Stoves made of such stainless steel can be used constantly and will last almost forever. Therefore, such stoves are recommended by the manufacturer ERMAK for use even in commercial baths with a guarantee of up to 5 years. “Premium” and “Lux” are already used in the manufacture of the firebox and all smoke ducts AISI 304 (INOX) stainless steel, which is why the price of the stoves very different.
Having installed such a stove made of real stainless steel, you can forget about your problems forever and just enjoy the quality of bath procedures and relax.
How to choose a sauna stove made of real stainless steel? How to distinguish it from ordinary heat-resistant steel? Just use a magnet. The furnace firebox is made of real heat-resistant stainless steel and will not be magnetic! Up to 90% of stoves on the market disguised as stainless steel are sold from ordinary heat-resistant steel. Don't be fooled!
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