304L is widely used in production various types rolled metal - stainless steel pipes, angles, sheets, tapes, hexagons, circles, etc. are made from it. The increased demand for stainless steel AISI 304, 304L is due to its versatility, excellent mechanical properties and chemical composition, as well as a number of others distinctive features, among which:
- excellent weldability;
- good oxidation resistance;
- excellent anti-corrosion properties;
- resistance to sudden temperature changes and other climatic influences;
- affordable price.
Analogues of aisi 304 and aisi 304L
Russian analogs of aisi 304 are steel grades 08Х18Н10 and 03Х18Н11 (according to GOST).
Scope of stainless steel AISI 304, 304L.
AISI 304 stainless steel is used in many areas of human activity, and its excellent temperature resistance and anti-corrosion properties are the main advantages over other steel grades. Here are just a few areas of application of stainless steel: AISI brand 304, 304L:
- Various industries where steel is used in the production of rolled metal and metal structures.
- Reservoirs and containers, as well as pipes for storing and transporting various types of liquids, including drinking water.
Differentiation of 304 AISI steel
Depending on the scope of application and the need for post-processing in the production of AISI 304, 304L, Deco stainless steel, it can be manufactured in accordance with certain properties, for example:
- stainless steel strength, heat resistance;
- quality of weldability and subsequent machining;
- deep and rotary hoods;
- stretch molding, etc.
Steel AISI 304 chemical composition (ASTM A240)
| Ni | Cr | Si | S | P | Mn | C | |
| 304L AISI | 8.0 - 12.0 | 18.0 to 20.0 | max | max | max | max | 0.03 max |
| 304 AISI | 8.0 to 10.50 | 18.0 to 20.0 | 1.0 | 0.030 | 0.045 | 2.0 | 0.08max |
Mechanical properties at room temperature
| 304L AISI | 304 AISI | |||
| Typical | Min | Typical | Min | |
| Fatigue strength, N/mm2 | 240 | - | 240 | - |
| A5 | 60 | 40 | 60 | 40 |
| relative extension, % | ||||
| Brinell hardness - HB | 170 | - | 170 | - |
| Rp m | 590 | 485 | 600 | 515 |
| Rp0.2 | 310 | 170 | 310 | 205 |
| Elastic limit, (0.2%), (yield), N/mm2 | ||||
To increase the mechanical properties of stainless steel, in particular its strength, it is necessary:
- increase the nitrogen content in steel;
- use repeated skin-pass rolling, which significantly strengthens the steel.
Stainless steel with increased content nitrogen is in most cases used in the manufacture of transport containers, large tanks and other metal structures where it is necessary to ensure high design strength with minimal wall thickness. Very often, austenitic steel, characterized by increased strength, is used in the production of welded stainless pipes, forming plates, supporting elements of metal structures, chains, strips, etc.
Properties of AISI 304 stainless steel at high temperatures
All values indicated in this table apply only to AISI 304 stainless steel. Strength of steel grades 304L, Deco at high temperatures differs significantly (at temperatures above +425 °C).
| Rp m | 380 | 270 | 170 | 90 | 50 |
| Ultimate strength (tensile), N/mm2 | |||||
| Temperature, °C | 600 | 700 | 800 | 900 | 1000 |
Minimum values of elastic limit at high temperature
| Rp1.0 | 120 | 80 | 50 | 30 | 10 |
| 1.0% plastic deformation (yield), N/mm2 | |||||
| Temperature, °C | 550 | 600 | 650 | 700 | 800 |
- Continuous exposure to +925 °C.
- Intermittent exposure to +850 °C.
Properties of stainless steel 304 AISI, 304L AISI at low temperatures
| Temperature, °C | Rp m | Ultimate strength (tensile), N/mm2 | Rp0.2 | Elasticity limit, (0.2%), (proof of yield), N/mm2 | Impact strength, J |
| -78 | 1100/950 | 300/180 | 180/175 | ||
| -161 | 1450/1200 | 380/220 | 160/160 | ||
| -196 | 1600/1350 | 400/220 | 155/150 | ||
Corrosion resistance
Acidic environments
The table shows only general values stainless steel resistance various types acids The exact resistance values depend on the specific properties of the steel.
| Temperature, °C | Concentration, % by weight | Sulfuric acid | Nitric acid | Phosphoric acid | Formic acid |
| 20 | 10 | 2 | 0 | 0 | 0 |
| 20 | 2 | 0 | 0 | 0 | |
| 40 | 2 | 0 | 0 | 0 | |
| 60 | 2 | 0 | 0 | 0 | |
| 80 | 1 | 2 | 0 | 0 | |
| 100 | 0 | 0 | 2 | 0 | |
| 80 | 10 | 2 | 0 | 0 | 0 |
| 20 | 2 | 0 | 0 | 1 | |
| 40 | 2 | 0 | 0 | 2 | |
| 60 | 2 | 0 | 0 | 2 | |
| 80 | 2 | 1 | 1 | 1 | |
| 100 | 2 | 2 | 2 | 0 |
Code: 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 = non resistant – (corrosion rate exceeds 1000 mm/year).
Atmospheric influences
The table shows corrosion values for AISI 304 stainless steel and compares them with other metals under similar weather conditions over a certain period of time (in in this case indicators are indicated for atmospheric exposure for 10 years).
| Environment | Rural | Marine | Industrial Marine | |
| Corrosion rate (mm/year) | AISI 304 | 0.0025 | 0.0076 | 0.0076 |
| Aluminum-3S | 0.025 | 0.432 | 0.686 | |
| carbon steel | 05.Aug | 34.0 | 46.2 | |
Heat treatment of stainless steel:
Annealing.
Annealing of stainless steel, to ensure good anti-corrosion properties, is carried out at high temperatures - from +1010 °C to +1120 °C, after which the steel is quickly cooled by quick vacation in water or air. The optimal firing temperature to achieve maximum corrosion resistance is +1070 °C.
Vacation (stress relief).
Stress relief for 304L AISI stainless steel is carried out for one hour at temperatures from +450 to +600 °C. The minimum tempering temperature should not drop to +400 °C.
Hot working (forging interval).
Hot processing of stainless steel should be carried out at temperatures between +1150 and 1260 °C and end at temperatures between +900 and +925 °C. Annealing of stainless steel when performing hot working is mandatory. When performing hot processing of stainless steel, it is important to remember that heating it uniformly to a given temperature takes much longer than heating carbon steels.
Cold processing of stainless steel:
Stainless steel grades 304 AISI and 304L AISI are in great demand in many areas of industry, construction and other areas of human activity due to their increased strength, ductility and elasticity.
There are several types of cold working of stainless steel - deep and rotary drawing, forming, stretching and bending.
To form stainless steel, it is possible to use machines and tools that are used to process carbon steel, but it is important to remember that such steel has an increased degree of hardening, so much more force is required.
Bending AISI 304 stainless steel.
The bending limits of stainless steel sheets depend on the sheet thickness (S) and bending radius (R):
- S< 3мм, мин. R = 0;
- 3mm< S < 6мм, мин. R = 0,5·S, угол гибки 180°;
- 6mm< S < 12мм, мин. R = 0.5·S, угол гибки 90°.
When bending stainless steel, it is important to remember that the return straightening of such sheets is significantly greater than that of carbon steel sheets. Below you can see the approximate values of reverse straightening when bending sheets to a right angle.
- R = S reverse straightening approx. 2°;
- R = 6·S reverse straightening approx. 4°;
- R = 20·S reverse straightening approx. 15°.
When bending austenitic stainless steel, the minimum bending radius must be equal to the thickness of the sheets multiplied by two or more (R = S x 2). If bending of ferritic stainless steel is expected, the minimum bending values should be:
- S< 6 мм, - мин R = S, 180°;
- 6 < S < 12мм, - мин R = S, 90°.
Stretch molding.
When performing stretch forming, the workpiece of the future stainless steel product is subjected to so-called “braking”, which occurs during the entire stretching period.
Since when this procedure is performed, the walls of the product become very thin, in order to avoid their ruptures, it is necessary to provide for the properties of increased hardening in advance.
Deep drawing and rotary drawing.
Deep drawing implies clean drawing without the use of “braking”, although in practice such technology is not used.
There is almost always an element of stretch forming involved in the production of stainless steel products. To perform deep drawing, it is necessary to use only stainless steel with a minimum degree of hardening (Md 30 (N) indicators should be in the minus).
If deep drawing is carried out on special presses, then rotary drawing is carried out on special lathes. This technology is in most cases used in the production of any conical products of symmetrical rotation, for example, in the manufacture of buckets.
Stainless steel welding
One of the key characteristics of stainless steel that makes it so popular is its excellent weldability.
| Welding process | Thickness without weld | Including weld | Protective environment | ||
| Thickness | Coating | ||||
| Wire | Bar | ||||
| TIG | <1,5mm | >0.5mm | ER 308 l(Si) W.Nr 1.4370 | ER 308 l(Si) W.Nr 1.4370 | Argon |
| ER 347 (Si) | ER 347 (Si) | Argon + 5% Hydrogen | |||
| Argon + Helium | |||||
| Resistance-spot | <2mm | ||||
| (point) -seam (seam) | |||||
| Electrode | Repairs | E 308 E 308L E 347 | |||
| S.A.W. | >2mm | ER 308 L | |||
| ER 347 | |||||
| PLASMA | <1.5mm | >0.5mm | ER 308 l(Si) W.Nr 1.4370 | ER 310 | Argon |
| ER 347 (Si) | Argon + 5% Hydrogen | ||||
| Argon + Helium | |||||
| MIG | >0.8mm | ER 308 l(Si) W.Nr 1.4370 | Argon + 2% CO 2 | ||
| ER 347 (Si) | Argon + 2% O2 | ||||
| Argon + 3% CO 2 + 1% H 2 | |||||
| Argon + Helium | |||||
| Laser | <5mm | Helium | |||
| Sometimes Argon, Nitrogen | |||||
After welding stainless steel, no additional heat treatment is required, but it must be taken into account that if there is the slightest risk of intergranular corrosion, it is necessary to carry out annealing at a temperature of +1050–1150 °C. After welding work, the seam must be cleaned of scale mechanically and chemically, and subsequently passivated.
Decorative stainless steel Deco
Decorative steel of the Deco brand is textured, ground or mirror stainless steel, which is used for external and internal decoration of buildings, as well as for cladding elevators, escalators, commercial equipment, columns, tanks, etc.
The use of decorative steel allows you to significantly save on the purchase of other finishing materials and at the same time create an original interior or exterior design for many years.
Features of decorative stainless steel Deco:
- resistance to deformation;
- corrosion resistance;
- the highest strength, which is achieved by spraying with titanium nitrite;
- heat resistance;
- elasticity and ease of welding and cutting.
Brand AISI304 is the most versatile and most widely used of all stainless steel grades. Her chemical composition, mechanical properties, weldability and corrosion/oxidation resistance provide the best choice in most applications at a relatively low cost. This steel also has excellent low temperature properties. If intercrystalline corrosion occurs in high temperature zones, its use is also recommended.
Application area
304 is used in all industrial, commercial and domestic areas due to its good anti-corrosion and temperature resistance. Here are some of its uses:
- Reservoirs (Tanks) and containers for a wide variety of liquids and solids;
- Industrial equipment in the mining, chemical, cryogenics, food, dairy and pharmaceutical industries.
Differentiation of grade 304
During the production of steel, the following special properties can be specified, which predetermines its use or further processing:
- Improved weldability
- Deep drawing, Rotary drawing
- Stretch forming
- Increased strength, Cold hardening
- Heat resistance C, Ti (carbon, titanium)
- Mechanical restoration
Chemical Composition (ASTM A240)
| C | Mn | P | S | Si | Cr | Ni | |
| 304 | 0.08max | 2.0 | 0.045 | 0.030 | 1.0 | 18.0 to 20.0 | 8.0 to 10.50 |
| 304L | 0.03 max | max | max | max | max | 18.0 to 20.0 | 8.0 - 12.0 |
Typical Properties in Annealed State
The properties stated in this publication are typical of one plant's production and should not be regarded as guaranteed minimum values for the entire specification.
1. Mechanical properties at room temperature
If necessary, the strength of austenitic steel can be increased as follows:
- adding nitrogen to steel (e.g. 304LN)
- form strengthening of steel at the factory (repeated skin-pass rolling; cold hardening; stretching; pressure)
Nitrided stainless steel is used particularly in applications such as large tanks, columns and shipping containers, where the higher design strength (Rp0.2) of the steel allows for reduced wall thickness and savings in material costs.
Other applications for form-hardened austenitic steel include, for example, various forming plates for the vehicle industry, welded pipes, keg hoops, chains, strips and support elements.
2. Properties at high temperatures
All these values refer to 304 only. No values are given for 304L because its strength decreases noticeably above 425oC.
Tensile strength at elevated temperatures
Minimum Elastic Limit Values at High Temperature(1% deformation in 10,000 hours)
Continuous exposure 925 o C
intermittent exposure 850 o C
3. Properties at low temperatures (304 / 304L)
4. Corrosion Resistance
4.1 Acidic environments
examples are given for some acids and their solutions (most general values)
Code:
0 = high degree of protection - Corrosion rate less than 100 mm/year
1 = partial protection - Corrosion rate from 100m to 1000 mm/year
2 = non resistant - Corrosion rate more than 1000 mm/year
4.2 Atmospheric influences
Comparison of 304 grade with other metals in various environments (Corrosion rate based on 10 year exposure).
5. Heat Treatment
1. Annealing.
High temperature from 1010 o C to 1120 o C and rapid release (cooling) in air or water. Better corrosion resistance is obtained when annealing at 1070 o C, and rapid cooling
2.Vacation (Stress relief).
For 304L - 450-600 o C for one hour with a slight risk of sensitization. A lower tempering temperature of 400 o C maximum should be used.
3. Hot processing(forging interval)
Initial temperature: 1150 - 1260 o C
Final temperature: 900 - 925 o C
Any hot processing must be accompanied by annealing.
Please note: The time to achieve uniform heating is longer for stainless steel. steels than for carbon steels - approximately 12 times.
6. Cold Processing
304 / 304L being extremely strong, elastic and ductile, it easily finds many applications. Typical processes include bending, stretch forming, deep drawing and rotary drawing.
The forming process can use the same machines and often even the same tools as for carbon steel, but it requires 50-100% more force.
This is due to the high degree of hardening during forming of austenitic steel, which in some cases is a negative factor.
1. About bending
Approximate bending limits are obtained when s=sheet thickness and r=bending radius:
- s< 3мм, мин r = 0
- 3mm< s < 6мм, мин r = 0,5 х s, угол гибки 180º
- 6mm< s < 12мм, мин r = 0.5 х s, угол гибки 90º
Reverse straightening is greater than that of carbon steel, which is why. When bending a regular right angle by 90º, we obtain the following straightening indicators:
r = s reverse straightening approx. 2º
r = 6 x s reverse straightening approx. 4º
r = 20 x s reverse straightening approx. 15º
For austenitic stainless steel, the minimum recommended bending radius is r = 2 x s.
It should be noted that the following minimums are recommended for ferritic stainless steel:
s< 6 мм → мин r = s, 180º
6 < s < 12мм → мин r = s, 90º
2. Deep drawing and rotary drawing
In pure deep drawing on a press, the workpiece is not subjected to stress, but the material is allowed to flow freely in the tools. In practice this happens very rarely. For example, when drawing household utensils, there is always also an element of stretch forming.
The material subjected to deep drawing must be as stable as possible, i.e. it should have a low degree of forming hardening, and the Md value should be clearly 30(N). For stainless cutlery, the same so-called rules are usually used. sub-analyses of rolled stainless steel, as well as in the manufacture of pans using the deep drawing method.
Rotary drawing on a lathe, as the name itself suggests, is a forming process with turning. Typical applications are buckets and similar conical products of symmetrical rotation, which are not usually polished.
3. About stretch molding
In the stretch forming process, the workpiece is stretched during stretching. The walls become thinner and, in order to avoid ruptures, it is desirable to provide the steel with increased hardening properties during forming. When performing more complex operations (for example, two bowls are pulled out from a dishwasher table blank at a time), the Md 30(N) value of the steel should clearly be present.
7. Welding
Weldability - very good, easy to weld.
| Welding process | Thickness without weld | Including weld | Protective environment | ||
| Thickness | Coating | ||||
| Bar | Wire | ||||
| Resistance -spot (spot) -seam (seam) | ≤2mm | ||||
| TIG | <1,5mm | >0.5mm | ER 308 l(Si) W.Nr 1.4370 ER 347 (Si) | Argon Argon + 5% Hydrogen Argon + Helium |
|
| PLASMA | <1.5mm | >0.5mm | ER 310 | ER 308 l(Si) W.Nr 1.4370 ER 347 (Si) | Argon Argon + 5% Hydrogen Argon + Helium |
| MIG | >0.8mm | ER 308 l(Si) W.Nr 1.4370 ER 347 (Si) | Argon + 2% CO2 Argon + 2% O2 Argon + 3% CO2 + 1% H2 Argon + Helium |
||
| S.A.W. | >2mm | ER 308 L ER 347 | |||
| Electrode | Repairs | E 308 E 308L E 347 | |||
| Laser | <5mm | Helium. Sometimes Argon, Nitrogen. | |||
Typically, post-weld heat treatment is not required. However, where there is a risk of intergranular corrosion, additional annealing is performed at 1050-1150°C. For grades 304L (low carbon) or 321 (Ti stabilization), this condition is preferable (Heating the weld to 1150°C followed by rapid cooling). The welding seam must be mechanically and chemically cleaned of scale and then passivated with etching paste
Applicable standards and approvals
AMS 5511
ASTM A 240
ASTM A 666
MIL-S-4043
Classification
ordinary corrosion-resistant steel
Application
- Equipment for chemical engineering
- Equipment for the food industry
- Pipelines and boilers
- Welded structures
AISI 304 L Used where components require durable welding with resistance to intergranular corrosion. These components can be used without post-processing of the seam, regardless of thickness.
Main characteristics
- good overall corrosion resistance
- very good protection against MCC
- Suitable for cryogenic applications
- excellent weldability
AISI 304 L has a lower carbon content compared to AISI 304, which improves its resistance to intergranular corrosion in welds and slow cooling zones.
Chemical composition (% by weight)
Mechanical properties at high temperatures
Physical properties
| Physical properties | Legend | Unit | Temperature | Meaning |
|---|---|---|---|---|
| Density | d | - | 4°C | 7.93 |
| Melting temperature | °C | 1420 | ||
| Specific heat | c | J/kg.K | 20°C | 500 |
| Thermal expansion | k | W/m.K | 20°C | 15 |
| Average coefficient of thermal expansion | α | 10 -6 .K -1 | 20-100°C 20-200°C 20-400°C |
16.0 16.5 17.5 |
| Electrical resistivity | ρ | Ωmm 2 /m | 20°C | 0.73 |
| Magnetic permeability | μ | at 0.8 kA/m | 20°C | 1.015 |
| Elastic modulus | E | MPa x 10 3 | 20°C | 200 |
Corrosion resistance
AISI 304 L has good general resistance to wet corrosion and is especially recommended where there is a risk of intergranular corrosion.
AISI 304 L has good resistance to most foods and numerous chemical environments:
- dilute alkaline solutions at ambient temperature,
- dilute organic acids at ambient temperature,
- neutral or alkaline salt solutions without halogen compounds,
- most organic media.
Acidic environments
Treatment
Annealing
The annealing temperature range is 1050°C ± 25°C followed by rapid cooling in air or water. After annealing, etching and passivation are necessary.
Vacation
For AISI 304L- 450-600 °C for one hour with a slight risk of sensitization.
Etching (surface cleaning)
- Mixture of nitric acid and hydrofluoric acid (10% HNO3 + 2% HF) at room temperature or 60°C
- Sulfur-nitric acid mixture (10% H 2 SO 4 + 0.5% HNO 3) at 60°C
- Paste for descaling in the welding zone
Passivation
- 20-25% HNO 3 solution at 20°C
- Passivation pastes for the welding zone
AISI 304 is a universal and widely used stainless steel with high anti-corrosion properties. It has excellent performance for stamping and welding. The balanced austenitic structure allows it to withstand high temperatures without changing the properties of the metal. It is often used in petrochemicals, for the manufacture of heat-resistant cookware, elements of boilers and chimneys, fasteners and other products.
AISI 304: characteristics
The quality of steel is characterized by its composition. In this case, the base element is iron (Fe), accounting for 66.3-74% of the total mass. The content of the main alloying elements chromium (Cr) and nickel (Ni) in a minimum amount is 18-20% and 8-10.5%, respectively. Additives ensure its high corrosion resistance and acid resistance, including short-term exposure to elevated temperatures up to 800-900 °C. A significant content of non-ferrous alloys imparts non-magnetic properties AISI steel 304.
Mechanical characteristics:
- Tensile strain - minimum 45%.
- Tensile strength is 505 MPa.
- Yield strength - minimum 215 MPa.
- Compressive strength is within 210 MPa.
Application
Thanks to a wide range of useful qualities - thermal, acid and corrosion resistance - AISI 304 stainless steel has become incredibly popular among manufacturers of metal products for various purposes. The material lends itself well to machining, bending and molding. When welding thin sections, no annealing is required. Therefore, the metal is used for the manufacture of various components in industry, architecture, and transport.
AISI 304 is used to make:
- Equipment for the food industry, alcohol production, storage and processing of dairy products.
- Food grade stainless steel pipes.
- Heat-resistant dishes (bowls, frying pans, pots), kitchen appliances, cutlery (forks, spoons, knives, etc.), equipment for catering establishments.
- Refrigeration equipment.
- Equipment, components and assemblies for enterprises of the chemical, pharmaceutical, cosmetic industries.
- Heat exchangers.
- Construction metal structures. For example, a 190-meter arch in St. Louis (USA) was made from it.
AISI 304 pipe is very weldable, which allows it to be widely used in the production of welded structures (tanks, containers), as well as for the production of electric-welded stainless steel pipes. The largest volume of steel of this grade is used in the petrochemical industry due to its resistance to aggressive environments.
Analogs
In terms of composition and physicochemical properties, the Russian analogue 08Х18Н10 (former designation 0Х18Н1) most closely matches AISI 304 steel. It allows a slightly lower chromium content (17-19%) and a slightly higher nickel content (9-11%). According to the European Union classification, the actual analogue is grade 1.4301 DIN (X5CrNi18-1).
There are two subclasses of the AISI brand: 304 H and 304 L. The first has a higher carbon content, the second has a lower carbon content. Steel 304 L is close in characteristics to Russian 03Х18Н11.
Peculiarities
AISI 304 steel grade represents an excellent combination of corrosion resistance and manufacturability. This combination of properties is the reason for the widespread use of this alloy. For example, in the United States, Type 304 accounts for almost half of the total stainless steel production. The new AOT technology makes it possible to obtain an alloy with a reduced carbon content without significant costs, which expands the range of application of the material.
Subtype 304 L is used for welded products that may be exposed to factors that provoke intergranular corrosion. There is also an improved modification 304 Since, which is characterized by increased strength while maintaining a high level of ductility (relative elongation) compared to the typical AISI 304 alloy. The Russian analogue has the same properties. Features of the brand are:
- Corrosion resistance.
- Resistance to oxidation.
- High strength with low weight.
- Good strength and hardness at cryogenic temperatures.
- Preventing contamination of products stored in containers.
- External beauty of the products and ease of cleaning.
- Wide range of applications.
Thermal and corrosion properties
One of the most thermally and corrosion-resistant steel is AISI 304. The characteristics of the composition allow it to withstand oxidative processes for a long time when exposed to temperatures up to 925 °C. As the temperature decreases, the corrosion resistance decreases. If at 870 °C it is quite high, then already in the range of 425-860 °C a long stay in a liquid environment is undesirable. In this case, the AISI 304L subtype is used, since it is resistant to carbide precipitation. AISI 304H steel is used when it is necessary to achieve high strength in the range of 500-800 °C.
In general, “stainless steel” resists aggressive environments well. For example, AISI 304 sheet is resistant to crevice and pitting corrosion, even in highly active environments containing chlorides. If the metal is under tension, then exceeding the temperature above 60 °C can provoke the formation of microcracks.
Welding
Austenitic stainless steels, which include AISI 304, are considered the most suitable for welding due to their high fusibility. However, this procedure must maintain corrosion resistance and prevent cracking.
Depending on the welding method, various technologies are used. When using autogen, “stainless steel” fuses well without the use of additional additives. If, for example, an AISI 304 pipe is welded electrically, it is advisable to use the additive and electrode from AISI 308 steel. The filler material can be made from Russian steel 04Х19Н9. For grade 304 L, additive 308 L with a rutile acid shell (AC/DC) is respectively used.
After welding large sections, it is recommended to anneal the seam to increase corrosion resistance (this is not necessary for subclass 304 L). If it is impossible to organize a heat treatment procedure in the installation area, it is better to abandon 308 steel altogether, replacing it with AISI 321.
Heat treatment
The peculiarity of the internal crystal lattice of AISI 304 is such that heat treatment of steel does not improve its physical characteristics. However, firing is still carried out to relieve surface tension, which provokes the formation of cracks. Products are heated to a temperature threshold of 1010-1120 °C and quickly cooled at 816-427 °C to avoid precipitation of chromium carbides.
Mechanical restoration
Due to its high fluidity coefficient, AISI 304 stainless steel lends itself perfectly to various processing methods: stamping, rolling, cutting, grinding, etc. However, given the need to maintain high protective properties, metal-cutting tools must meet certain requirements.
First of all, it must be clean so as not to introduce corrosive substances into the microstructure (contamination process). The surface of the workpiece is also cleaned. To process stainless steel, specially designed cutters, milling cutters, drills, etc. are used. The cutting edge of the tool must be sharpened, otherwise unwanted excess compaction will form in the contact area. For the same reason, cutting is carried out quickly, with deep steps.
To prevent deformation of the workpiece, it is recommended to use chip breaking devices. They will not allow the chips to scratch the surface of the workpiece. Considering that austenitic alloys conduct heat poorly, the cutting edge of the tool quickly overheats. Coolant must be used for cooling.
AISI 304 is highly amenable to plastic deformation methods. When hot processing (for example, forging), the workpiece must be uniformly heated to 1149-1260 °C. After giving the desired shape, the product is quickly cooled (at relatively high temperatures) - this will protect it from corrosion.
Cold forming (eg stamping) often requires an intermediate annealing step. It facilitates the process of hardening the surface layer, making it denser and less susceptible to corrosion. The procedure also prevents the development of microcracks and tears. After final processing, complete annealing is carried out, eliminating the internal stresses of the steel.
Everything about AISI 304 steel: explanation, properties, prices, analogues, supplier contacts. Regardless of the volume of steel, delivery is made in the shortest possible time.
Imported stainless steel aisi 304 is classified as austenitic steel. It is most widespread among the variety of steel grades due to its versatility and unique characteristics. Stainless steel is one of the most important types of metal, whose main characteristic is protection against corrosion and other negative influences.
Composition and characteristics
One of the main advantages is increased resistance to acidic environments and the ability to withstand sudden increases in temperature for a short time, which can reach 900 degrees. On the Russian market, an analogue of this steel is 08Х18Н10. But the Russian analogue is inferior in technical characteristics and stability, so AISI 304 steel, despite its higher cost, is the most preferable.
Price list for the range of products made from AISI 304 steel
AISI 304 steel is one of the main stainless steels. The composition contains at least 10% Ni and 18% Cr. Due to the relatively large amount of silicon in the composition of steel, there is an oxide layer on its surface, which is the main barrier to the effects of aggressive substances. Thanks to the combination of silicon and nickel in the composition of steel, it acquires antiferromagnetic characteristics.
Depending on the production method, AISI 304 steel can be hot rolled or cold rolled. After production, the sheets of material are processed in various ways. As a result, a material of several types of surfaces is obtained: matte, mirror or polished.
Advantages and disadvantages of the alloy
AISI 304 sheet steel is used in various fields. Most often, pipes are welded from it, it is often used in the construction of various structures, used on cutting equipment and for many other purposes. Widespread use of the material is possible due to its good performance characteristics and non-corrosion, which is the most important quality. It is often used to produce kegs for storing beer, kvass, and other carbonated drinks, as well as table equipment. Due to its complete safety, this type of steel is widely used for the food industry, satisfying its needs in full.
Thanks to its unique performance properties, which no analogue can compare with, AISI 304 steel is used in large quantities in mechanical engineering, heavy and light industry, mining and many others. In fact, AISI 304 stainless steel can be used in many areas, which is more than exciting and interesting.
The material has an optimal ratio of cost to performance characteristics, which is largely why it has gained such popularity. Stainless steel can serve for many years without corroding, and can withstand any impact of even the most powerful chemicals that can fall on the surface of the material, in both small and large quantities, depending on the conditions of use.
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