High-strength martensitic stainless steel. Technologies High-alloy steels and alloys, corrosion-resistant, heat-resistant and heat-resistant
The operating conditions of modern aviation and space technology predetermine extremely stringent requirements for the materials from which it is made.
Here is the need to achieve high structural strength with a minimum specific weight, dimensions and fuel consumption; ensuring sufficient reliability and long working life when exposed to variable and significant power loads, alternating high (up to 450 degrees) and low (up to -253 degrees) temperatures, corrosive media, various types of radiation, etc.
The quality of the material largely depends on the competitiveness of aircraft. For military equipment, such characteristics as flight range, speed, maneuverability, accuracy, the ability to fly in any weather, carrying capacity, and the provision of production with domestic raw materials are important; for civil - reliability, fire safety, comfort, environmental friendliness, etc. Moreover, all this must be achieved while minimizing the costs of developing, mastering and operating machines.
It is clear from the above: the materials used in aircraft construction must have high specific strength (it is also called weight efficiency) and rigidity, corrosion resistance, fatigue resistance, as well as crack resistance and a number of others. Of course, some material alone is simply not able to meet all the requirements, therefore, in the manufacture of various parts of aircraft, the most suitable of the existing ones are used, or new compositions are created.
Aluminum alloys have found the greatest application at present. The lower and upper surfaces of the wing and fuselage are made from them (strength in the range of 450-550 MPa is required here), elements of the so-called power set - various stiffeners and frames connecting them, fittings, beams with a tensile strength of 500-600 MPa, etc. . The share of such materials in modern aircraft reaches 50-70%.
Titanium alloys are very common (they are used to make individual chassis parts, various beams, etc.) and, especially, polymer composites. The latter are used for the manufacture of wing panels, horizontal and vertical tail surfaces, landing gear doors and power plants. With a strength of 1700-2500 MPa, they have a specific gravity of less than 2 g/cm 3 . Their share in aircraft is 8-15%, and in helicopters - about 50%.
At first glance, it would seem that in such a representative "company" the role of steels should be reduced, but the situation is quite different. Their share in passenger liners accounts for 8-10%, in military liners - 25-50%, and in the near future this ratio will at least not decrease. The most loaded elements of aircraft are made of steel - landing gear parts, hydraulic cylinder bodies, pipelines of high-pressure hydraulic systems, bolts for attaching the wing to the fuselage, gear drives of engine gearboxes, gears of the main gearbox of the helicopter propulsion system, etc. And this is not accidental, since this, albeit long-known material, has a number of advantages over its young "brothers". It is distinguished by higher rigidity and strength (which is especially evident in small parts), resistance to cyclic loads, corrosion resistance, good manufacturability, i.e. the ability to obtain blanks and parts in a variety of ways - hot and cold deformation, machining, welding, soldering, etc. In addition, steel is relatively inexpensive. That is why, since the founding of our institute, one of the priority tasks has been the creation of new varieties of steels.
The constant improvement of aircraft designs required a continuous increase in strength and specific strength (the ratio of strength to material density) while maintaining all the advantages of steels. If in aviation before 1941 the first of these parameters ranged from 800 to 1000 MPa, now it is from 1300 to 2000. However, the complexity of the problem lies not so much in achieving such indicators, but in ensuring the operability of aircraft structures made of appropriate materials.
The fact is that an increase in the strength of steels leads to a decrease in their ductility, toughness, crack resistance, etc. In this regard, the developers of their new varieties are constantly searching for compromises between increasing strength and ensuring reliability. Currently, three groups of high-strength steels are most often used in aviation technology: structural medium-alloyed; corrosion resistant; used for the manufacture of parts operating in difficult conditions with increased friction and subjected to chemical-thermal treatment.
But in any case, the appearance of such materials made it necessary to reconsider the previously accepted approaches to the design and manufacturing technology of parts, since all of the listed steels have a number of specific features and differ significantly from those created earlier and having an average strength (up to 1400 MPa). In particular, it turned out that a violation of the technological cycle of their production can lead to premature failure of parts, despite the complete good quality of the metal. In this case, the centers of destruction can be surface or subsurface defects obtained at various stages of manufacturing a semi-finished product, the part itself, or the entire structure. That is why it was very important to develop clear organizational and technical measures, including instructions for thermal and mechanical treatment of parts, corrosion protection, welding, etc., which we did in the early 60s of the XX century. In addition, the approach to products made of high-strength steels has also changed significantly; the main requirements for them were the minimum stress concentration and high surface finish.
So, new steels have taken their place in the aircraft industry, and, depending on the tensile strength, different parts are made from them. For example, if this parameter is in the range of 1600-1800 MPa, then such a metal is suitable for the production of an airframe power set (spars, various beams, frames, axles, etc.). And steel VKS-8 (1800-2000 MPa) and VKS-9 (1950-2100 MPa) are indispensable in the manufacture of large-sized welded parts (electron beam and argon-arc welding are possible) of the airframe and landing gear in the machines of the Design Bureau. Sukhoi, Antonov, Mikoyan, Kamov. Little of. Steels with a tensile strength above 1950 MPa successfully replace titanium alloys, which makes it possible to significantly reduce production costs with the same specific strength.
In recent decades, a new class of high-strength or so-called maraging steels has been developed. Their strength is 1450-2500 MPa, they have unique physical, mechanical and technological properties. For example, due to the low content of carbon and nitrogen, they have high ductility, toughness, resistance to repeated static loads and corrosion cracking. This material is very technological, i.e. workpieces made from it, after hardening, can be subjected to various types of cold working by pressure (rolling of shells, thread rolling, etc.), without difficulty processing with a cutting tool, and then doubling their strength by simple heat treatment - aging (heating and air cooling) at relatively low temperatures.
The listed advantages of maraging steels are most fully realized in the manufacture of parts of complex shape with small tolerances (including precision ones) subjected to chemical-thermal treatment. Metal of this class has found application in heavily loaded components of the MiG-31 and MiG-29 fighters, parts of the turning unit and the chassis of the Buran space shuttle, etc.
The further development of aircraft construction put forward new requirements for materials. First of all, we are talking about fighters, the speed of which is 2.5-3 times faster than sound, since for this they must overcome the thermal barrier - temperatures of 280-300 ° C, when aluminum alloys are not applicable. We managed to solve this problem too. The high-strength corrosion-resistant steels offered by us have all the necessary qualities: high strength, ductility, toughness, high technological properties - they are easy to stamp and weld. The latter property makes it possible to do without further heat treatment, and as a result, it is possible to create complex, openwork structures, for example, load-bearing caisson tanks, and without the help of sealants and riveting, which were previously widely used.
The main material in the all-welded aircraft compartments of the Mi G series supersonic aircraft was VNS-2 corrosion-resistant steel with a tensile strength of 1250-1400 MPa. In the form of a sheet and tape, it is used for sheathing and internal framing, as well as in the manufacture of power parts (rods, forgings, etc.).
However, during the operation of aircraft in which VNS-2 steel was used, it turned out that it is not suitable enough in a humid climate (say, the Mediterranean). Further search allowed us to obtain new steels EP817 (bar) and VNS-41 (sheet). In terms of their mechanical characteristics and manufacturability, they correspond to the already proven VNS-2, and due to the new alloying system and optimization of the hardening aging regime, they significantly exceed it in terms of corrosion resistance, and this applies to both the main parts and welded joints.
The most widespread of the materials of this class was VNS-5 steel with a tensile strength of 1380-1600 MPa. Power parts of the MiG and Su gliders, as well as the landing gear of the seaplane of the Design Bureau named after M.V. Beriev. It is also used in civil aviation (Il-86 wide-body aircraft and Il-96 Airbus) - in the production of highly loaded bolts for attaching the engine to the fuselage
Another representative of this class of metals is CH-2A steel with a tensile strength of 1100-1300 MPa. It has proven itself as a material for power, including fasteners, as well as air and oxygen cylinders, which are equipped with all types of aircraft, including naval aviation. The most important feature of such cylinders is that when they are hit by a bullet, they do not scatter into fragments.
Now a new type of fuel - hydrogen and its oxidizer - liquid oxygen, which has a temperature of 253 degrees, is becoming more widespread in aviation and rocket technology. To work in such conditions, our institute has developed special high-strength corrosion-resistant steels (VNS-25, VNS-49, VNS-59) with a tensile strength of 1000-1400 MPa at room temperature and 1700-2100 at 20 K (-253 degrees). This metal is successfully used in various liquid-propellant rocket engines, in particular, in the most powerful of them in the world, the PD-170 brand, designed by the Energomash Design Bureau. Parts made of this material - pump housings and fuel regulators - make up 50-60% of their mass.
Medium-alloyed and corrosion-resistant steels are now widely used as structural materials, as well as for the manufacture of parts of gearboxes and units subjected to chemical-thermal treatment. This is explained by the fact that, as a result of long research, it was possible to propose a technology that provides a combination of the necessary properties of the surface layer of the product (high hardness, wear resistance, fatigue resistance) and its core (ductility, toughness, manufacturability, etc.). Thus, for heavy-loaded, large-modulus gears of reducers, VKS-7 steel with carbonitride hardening was developed, which after chemical-thermal treatment provides a depth of the reinforcing layer of up to 2.5 mm and a hardness of more than 60 HRC, which ensures high contact endurance at operating temperatures up to 250C (so far such no analogues).
Separate conversation about helicopters. For them, our institute created high-strength (up to 1300 MPa), wear-resistant, heat-resistant steel VKS-10. Unlike serial domestic and foreign analogues operating at temperatures up to 250 degrees, it can withstand 450 degrees. Its use ensures the transmission of large torques, at which a local increase in temperature occurs in the contact zone of the teeth, and even if the oil supply is disturbed, the operation of the gearbox can continue for 2 hours without an accident.
All of the above indicates that steel traditionally remains the main material in the aircraft industry, although it, as well as other creations of human hands, requires further improvement.
Fatigue resistance is characterized by the endurance limit - the highest stress that a material can withstand without destruction for a given number of cyclic impacts.
Corresponding Member of the Russian Academy of Sciences E. M. KABLOV, General Director of the State Scientific Center of the Russian Federation of the State Enterprise "VIAM", Doctor of Technical Sciences A. F. PETRAKOV, Chief Researcher of the same center
Notation
Description
Steel 08X15N5D2T is used: for the manufacture of hot-rolled and forged bars, as well as forgings intended for subsequent cold machining, or for subsequent hot machining (stamping, forging, rolling, etc.) in the manufacture of machine parts; parts of aviation equipment units; welding wire used for surfacing parts and welding metal structures in power engineering; welding electrodes; welded and solid-rolled rings for various purposes; soft and hard-worked tape with a thickness of 0.3 to 1.2 mm and a width of 400 mm.
Note
Corrosion-resistant martensitic steel.
Standards
| Name | Code | Standards |
|---|---|---|
| Sections and shapes | B22 | GOST 1133-71, GOST 2590-2006 |
| Classification, nomenclature and general rules | IN 20 | OST 1 90005-91 |
| Blanks. Blanks. Slabs | B31 | OST 1 90252-77, OST 1 90344-83, OST 1 90357-84, TU 1-92-15-73, TU 14-1-1125-74, TU 14-1-2153-77, TU 14-1- 3104-81 |
| Metal forming. Forgings | B03 | TU 14-1-1530-75, TU 14-1-2902-80, TU 14-1-2918-80 |
| Ribbons | B34 | TU 14-1-2269-77, TU 14-1-3577-83 |
| Sheets and stripes | B33 | TU 14-1-2476-78, TU 14-1-3426-82, TU 14-1-3849-84, TU 14-1-2907-80, TU 14-1-4583-88, TU 14-1- 835-73 |
| Sections and shapes | B32 | TU 14-1-374-72, TU 14-1-744-73 |
| Welding and cutting of metals. Soldering, riveting | B05 | TU 14-1-997-74, TU 14-1-997-2012 |
| Steel pipes and fittings for them | B62 | TU 14-159-165-87, TU 14-3-406-75, TU 14-3-411-75 |
Chemical composition
| Standard | C | S | P | Mn | Cr | Si | Ni | Fe | Cu | Ti | Mo | co |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| OST 1 90357-84 | ≤0.08 | ≤0.018 | ≤0.02 | ≤1 | 13.5-14.8 | ≤0.7 | 4.8-5.8 | Remainder | 1.75-2.5 | 0.03-0.15 | ≤0.3 | ≤0.5 |
| TU 14-1-2476-78 | ≤0.08 | ≤0.025 | ≤0.03 | ≤1 | 14.1-15.5 | ≤0.7 | 4.5-5.5 | Remainder | 1.75-2.5 | 0.3-0.5 | - | - |
| TU 14-1-2918-80 | ≤0.08 | ≤0.018 | ≤0.02 | ≤1 | 13.5-14.8 | ≤0.7 | 4.8-5.8 | Remainder | 1.75-2.5 | 0.03-0.15 | - | - |
| TU 14-1-3577-83 | ≤0.08 | ≤0.018 | ≤0.02 | ≤1 | 14-15 | ≤0.7 | 4.7-5.5 | Remainder | 1.75-2.5 | 0.15-0.3 | - | - |
| TU 14-1-744-73 | ≤0.08 | ≤0.018 | ≤0.02 | ≤1 | 13.5-14.8 | ≤0.7 | 4.8-5.8 | Remainder | 1.75-2.5 | 0.03-0.15 | - | ≤0.5 |
| TU 14-1-2907-80 | ≤0.08 | ≤0.025 | ≤0.03 | ≤1 | 14-15 | ≤0.7 | 4.7-5.7 | Remainder | 1.75-2.5 | 0.15-0.3 | - | - |
| TU 14-1-835-73 | ≤0.08 | ≤0.025 | ≤0.035 | ≤0.7 | 14-15 | ≤0.7 | 4.7-5.5 | Remainder | 1.75-2.5 | 0.15-0.3 | ≤0.3 | - |
Fe- the basis.
According to TU 14-1-2902-80, the chemical composition is given for steel grades 08Kh15N5D2T-Sh and 08Kh15N5D2T-VD.
According to TU 14-1-835-73, the chemical composition is given for steel grade 08Kh15N5D2T.
According to TU 14-1-997-74 and OST 1 90357-84, the chemical composition is given for steel 08Kh15N5D2TU-Sh (EP410U-Sh).
According to TU 14-1-744-73, the chemical composition is given for 08Kh15N5D2T-Sh and 08Kh15N5D2T-VD. When steel is smelted by vacuum-arc remelting with the use of magnetic control, it is allowed both in the finished product and in the ladle test, the deviation in nickel content is plus 0.4%.
According to TU 14-1-2918-80, the chemical composition is given for steel grades 08Kh15N5D2T-Sh and 08Kh15N5D2T-VD. At the request of the consumer, EP41U-Sh and EP410U-VD steel is supplied with a carbon content of 0.05-0.08%, titanium for EP410U-VD steel within 0.03-0.10%, nickel for EP410U-Sh steel within 5.2-5.8% and for nickel steel EP410U-VD within 5.3-5.8%. In this case, the name "select" is assigned to the steel.
According to TU 14-1-3577-83, the chemical composition is given for 08Kh15N5D2T-Sh (EP410-Sh, VNS-2-Sh). Deviations in finished products from the norms of the chemical composition for manganese, silicon and copper - by +0.10% of each element, for chromium by minus 0.50%, for nickel by +0.20%, for phosphorus by +0.0050 %.
According to TU 14-1-2907-80, the chemical composition is given for steel grade 08Kh15N5D2T. In steel grade 08X15N5D2T-Sh, the sulfur content is not more than 0.018%, phosphorus is not more than 0.020%. In both grades of steel, deviations from the chemical composition are allowed: for manganese, silicon and copper + 0.10% each, for phosphorus + 0.0050%, for chromium -0.50%. The residual content of molybdenum is allowed in the amount of not more than 0.30%.
According to TU 14-1-2476-78, the chemical composition is given for steel grades 08Kh15N5D2T (EP225), 08Kh15N5D2T-VD (EP225-VD), 08Kh15N5D2T-Sh (EP225-Sh). In the finished product, deviations in chemical composition are allowed in accordance with GOST 5632.
Mechanical characteristics
| Section, mm | s T |s 0.2, MPa | σ B , MPa | d5, % | d 10 | y, % | kJ / m 2, kJ / m 2 | Brinell hardness, MPa | HRC |
|---|---|---|---|---|---|---|---|---|
| Hardening in water or in air from 950-975 °C | ||||||||
| 0.8-5 | ≥785 | ≥981 | ≥8 | - | - | - | - | - |
| - | - | 880-1080 | - | - | - | - | 246-311 | 25-31 |
| Hardening in water or in air from 950-975 °C + Aging at 440-460 °C (exposure 1 h) cooling in air | ||||||||
| 0.8-5 | ≥1079 | ≥1226 | ≥9 | - | - | - | - | - |
| Gradation of properties of finished heat-treated parts according to OST 1 90005-91 | ||||||||
| - | - | 1130-1320 | - | - | - | - | 311-401 | 33-41 |
| - | - | 1230-1370 | - | - | - | - | 363-401 | 36-41 |
| - | - | 1230-1470 | - | - | - | - | - | 37-43 |
| Rings welded from steel grade 08Kh15N5D2T-Sh according to OST 1 90252-77. Air hardening from 950 °C | ||||||||
| ≥785 | ≥1079 | ≥10 | - | ≥55 | ≥1177 | - | - | |
| ≥706 | ≥981 | ≥6 | - | ≥30 | ≥588 | - | - | |
| The tape is in the state of delivery according to TU 14-1-3577-83. No additional heat treatment | ||||||||
| ≥785 | ≥980 | - | ≥8 | - | - | - | - | |
| The tape is in the state of delivery according to TU 14-1-3577-83. Aging at 440-460 °C (exposure 1 hour ± 10 min), cooling in air | ||||||||
| ≥1030 | ≥1230 | - | ≥9 | - | - | - | - | |
| ≥1275 | ≥1370 | - | ≥5 | - | - | - | - | |
| The tape is in the state of delivery according to TU 14-1-3577-83. Aging at 500-520 °C (exposure 2.5 hours), cooling in air | ||||||||
| ≥980 | ≥1130 | - | ≥8 | - | - | - | - | |
| Sheet cold-rolled (0.7-5.0 mm) and hot-rolled steel (3.0-6.0 mm) from steel 08Kh15N5D2T in the state of delivery according to TU 14-1-2476-78. Hardening in water or in air from 950-975 °C | ||||||||
| - | ≥784 | ≥981 | ≥7 | - | - | - | - | - |
| Sheet cold-rolled (0.7-5.0 mm) and hot-rolled steel (3.0-6.0 mm) from steel 08Kh15N5D2T according to TU 14-1-2476-78. Quenching in water or in air from 950-975 °C + Tempering at 380-400 °C (exposure 1 hour), cooling in air | ||||||||
| ≥883 | ≥1079 | ≥8 | - | - | - | - | - | |
| Forgings, hot-rolled and forged bars. Quenching in air from 940-960°C (hold 1 h) + Tempering at 640-660°C (hold 1 h), cooling in air + Hardening in water from 950°C (hold 1 h) + Tempering at 590-630 °С (exposure 2-3 h), cooling in air | ||||||||
| ≥685 | ≥880 | ≥15 | - | ≥60 | - | - | - | |
| - | - | - | - | - | ≥340 | - | - | |
| Forgings, hot-rolled and forged bars. Quenching in air from 950-1000 °C (exposure 0.5-1 h) + Tempering at 650 °C (exposure 1-3 h), cooling in air + Hardening in air from 950 °C followed by cold treatment at minus 70 °C (hold 2 h) + Aging at 425-450 °C (hold 1-3 h), air cooling | ||||||||
| ≥930 | ≥1230 | ≥10 | - | ≥55 | ≥780 | - | - | |
| Forgings, hot-rolled and forged bars. Hardening from 940-960 °C, air cooling | ||||||||
| ≥785 | ≥1080 | ≥10 | - | ≥55 | ≥1170 | - | - | |
| ≥785 | ≥1080 | ≥10 | - | ≥55 | ≥1200 | - | - | |
| Long products. Quenching in air from 950-1000 °C (exposure 0.5-1 h) + Tempering at 650 °C (exposure 1-3 h), cooling in air + Hardening in air from 950-1000 °C (exposure 0.5 -1 h) + Tempering at 650 °C (hold 1-3 h), air cooling | ||||||||
| ≥930 | ≥1230 | ≥10 | - | ≥55 | ≥765 | - | - | |
| Thick-rolled steel in the state of delivery according to TU 14-1-2907-80. Heating up to 650-680 °C, cooling in air or with oven | ||||||||
| ≤930 | ≤1030 | ≥10 | - | - | - | - | - | |
| Stampings according to OST 1 90357-84. Heating to 990-1010 °C, exposure 1 hour + Quenching in air or water + Aging at 415-435 °C for 1-3 hours | ||||||||
| ≥930 | ≥1230 | ≥10 | - | ≥55 | ≥784 | - | - | |
EP817– short-term tensile strength 1350 MPa. The steel is intended for the manufacture of welded and non-welded power units that operate for a long time at temperatures up to 300 ° C in all climatic conditions. Steel is not prone to stress corrosion. Welded joints are not prone to intergranular corrosion and stress corrosion. Steel is well welded by argon-arc welding with and without additives, electron beam welding, as well as electric contact welding. After welding, subsequent heat treatment is not required.
VNS-16-1– short-term tensile strength 1275 MPa. It is used for the manufacture of complex brazed-welded structures operating up to 450°C.
SN-2A, VNS-5, VNS-43– short-term tensile strength 1200–1650 MPa. They have high fracture toughness, crack resistance, are well welded by all types of welding, ensuring high strength of welded joints after heat treatment. They are used for the manufacture of fasteners and power parts of the airframe.
VNS-65– short-term tensile strength 1760 MPa. Steel of the transitional austenite-martensitic class is intended for highly loaded power, including welded, airframe parts operating at temperatures from -70 to +200°C in all-climatic conditions. The steel is not prone to intergranular corrosion, it is well welded by argon-arc welding with an additive, as well as by electron beam welding.
SN-3, SN-3PN– short-term tensile strength >1200 MPa. They are used for plating and parts of the internal set of the airframe.
VNS-73– short-term tensile strength 1375 MPa. Martensitic steel is intended for the manufacture of welded and non-welded power parts of aircraft that operate for a long time at temperatures from -70 to +200 ° C in all climatic conditions. Steel is well welded by automatic argon-arc welding without additives (non-consumable electrode) and manual argon-arc welding with additives. After welding, mandatory heat treatment is not required. The steel is not prone to stress corrosion: σ = 980 MPa in a salt spray chamber (KST-35).
VNS-74– short-term tensile strength 1400–1495 MPa. Martensitic steel is intended for the manufacture of fasteners obtained by cold heading, operated in all-climatic conditions at temperatures from -70 to +350°C. The steel is not prone to stress corrosion in a salt spray chamber (KST-35) and maritime climate at an applied stress σ = 980 MPa. It has good cold heading ability.
Details of fasteners made of VNS-74 steel
VNS-72– short-term tensile strength 1750 MPa. Possesses the increased plasticity, is well welded by argon-arc and electron-beam welding. Steel is intended for the manufacture of fasteners, power parts of the airframe, including welded parts of aviation equipment.
VNS-53– corrosion-resistant steel with an operating temperature of -70 to +300°C, provides high manufacturability in the manufacture of parts of pipeline systems (bending, rolling, expanding). Pipes made of steel VNS-53 with a wall thickness of 0.5 mm are 2 times superior to serial pipes made of steel 12X18H10T (used for serial parts) in terms of strength and endurance.
VNS9-Sh– short-term strength not less than 1470 MPa. Steel is used in the form of a tape of various thicknesses for highly loaded, critical parts: torsion bar plates, couplings, etc.
Helicopter torsion plate made of cold-rolled VNS9-Sh steel strip
Physical and mechanical properties of corrosion-resistant steels (average values)
| Steel | ? V | ? 0,2 | ? 5 | ? |
|---|---|---|---|---|
| MPa | % | |||
| EP817 | 1325 | 1050 | 15 | 55 |
| VNS-16-1 | 1270 | 1000 | 15 | 50 |
| CH-2A | 1300 | 1050 | 15 | 55 |
| VNS-5 | 1550 | 1200 | 18 | 60 |
| VNS-43 | 1650 | 1270 | 15 | 50 |
| VNS-65 | 1760 | 1300 | 15 | 50 |
| SN-3PN | 1300 | 1100 | – | – |
| VNS-73 | 1430 | 1110 | 15 | 55 |
| VNS-74 | 1400 | 1200 | 16 | 60 |
| VNS-72 | 1750 | 1300 | 15 | 45 |
| VNS-53 | 980 | 780 | 20 | – |
Characteristics of fracture toughness and low-cycle fatigue of corrosion-resistant steels
| Steel | KC V( r n \u003d 0.25 mm), J / cm 2 | TO 1With, MPa?m | MCU: ? max , MPa ( N=2·10 5 cycle; f=5 Hz; R=1), at K t | |
|---|---|---|---|---|
| 1,035 | 2,2 | |||
|
>0.5 years |
||||
|
>0.5 years |
||||
|
>0.5 years |
||||
| Not prone to corrosion | ||||
All steels have their own marking, reflecting primarily their chemical composition. In the marking of steel, the first digit indicates the carbon content in hundredths of a percent. Then follow the letters of the Russian alphabet, indicating the presence of an alloying element. If there is no number after the letter, this means that the content of the alloying element is not more than one percent, and the numbers (number) following the letter indicate its content in percent.
Examples of deciphering the designation of steels:
12HNZA: carbon content - 0.12%, chromium - 1.0%, nickel - 3.0%, high quality;
30HGSA: carbon content - 0.30%, chromium, manganese, silicon, one percent each, the letter "A" means high quality;
19ХГН: carbon content - 0.19%, chromium, manganese, nickel, one percent each;
15X25T: carbon content - 0.15%, chromium - up to 25%, titanium - up to 1%;
08X21N6M2T: carbon content - 0.08%, chromium - 21%, nickel - 6%, molybdenum - 2%, titanium - up to 1 percent.
09X16N15M3B: carbon content - 0.09%, chromium - 16%, nickel - 15%, molybdenum - 3.0%, niobium - up to 1 percent.
In recent years, to improve the quality of steel, new methods of its smelting have been used, which are reflected in the designations of steel grades:
- VD - vacuum-arc;
- VI - vacuum-induction;
- Ш - slag;
- PV - direct reduction;
- ESR - electron slag remelting;
- SD - vacuum-arc after slag remelting;
- ELP - electron-beam remelting;
- PDP - plasma-arc remelting;
- ISH - vacuum induction plus electroslag remelting;
- IP - vacuum-induction plus plasma-arc remelting.
- EP - electrostal (factory) search;
- EI - electrostal research;
- CHS - Chelyabinsk steel;
- ZI - Zlatoust research;
- VNS - VIEM stainless steel;
- DI - Dneprospetsstalskaya (factory) research.
According to the degree of deoxidation, steels are marked as follows:
boiling - kp, semi-calm - ps, calm - sp.
carbon steels
Carbon steel is divided into structural And instrumental.
Structural carbon steel is called steel containing up to 0.6% carbon (0.85 percent is allowed as an exception).
By quality, structural carbon steel is divided into two groups: ordinary quality and ka honest.
Steel of ordinary quality is used for non-critical building structures, fasteners, sheet metal, rivets, welded pipes. GOST Z80-88 is installed on structural carbon steel of ordinary quality. This steel is smelted in oxygen converters and open-hearth furnaces and is divided into three groups: group A, supplied by mechanical properties; group B supplied by chemical composition and group C supplied by mechanical properties and chemical composition.
High-quality carbon structural steel is supplied in terms of chemical composition and mechanical properties; it is smelted in oxygen converters and open-hearth furnaces. It is subject to GOST 1050-88.
High-quality structural steel is used for parts operating under increased loads and requiring resistance to impact and friction: gears, axles, spindles, ball bearings, connecting rods, crankshafts, as well as for the manufacture of welded and seamless pipes. Structural carbon steels include automatic. To improve cutting, sulfur, lead, and selenium are introduced into its composition. Pipes for the automotive industry are made from this steel.
Alloy steels
Rare earth elements are also introduced into special-purpose steels; several alloying elements can be present simultaneously in alloyed steels.
The scope of structural alloy steel is very large. The use of alloy steel saves metal, increases the durability of products.
According to their purpose, alloyed steels are divided into groups: structural, tool and steel with special physical and chemical properties.
Structural alloy steel according to GOST 4543-71 is divided into three groups: high quality, high quality and extra high quality.
In alloyed steel, along with the usual impurities (sulfur, silicon, phosphorus), there are alloying, i.e. binding elements: chromium, tungsten, molybdenum, nickel, as well as silicon and manganese in an increased amount. Alloy steel has highly valuable properties that carbon steel does not have.
The effect of specific elements on steel properties is described below:
- Chromium - increases hardness, corrosion resistance;
- Nickel - increases strength, ductility, corrosion resistance;
- Tungsten - increases hardness and red hardness, i.e. the ability to maintain wear resistance at high temperatures;
- Vanadium - increases density, strength, resistance to impact, abrasion;
- Cobalt - increases heat resistance, magnetic permeability;
- Molybdenum - increases red hardness, strength, corrosion resistance at high temperatures;
- Manganese - at a content of more than 1 percent, it increases hardness, wear resistance, resistance to shock loads;
- Titanium - increases strength, corrosion resistance;
- Aluminum - increases scale resistance;
- Niobium - increases acid resistance;
- Copper - reduces corrosion.
The following alloy steels are most widely used:
- chromium, with good hardness, strength: 15X, 15XA, 20X, 30X, 30XPA, 35X, 40X, 45X;
- manganese, characterized by wear resistance: 20G, 50G, 10G2, 09G2S;
- chromium-manganese: 19KhGN, 20KhGT, 18KhGT, 30KhGA, 25Kh2GNTA-VD;
- siliceous and chrome-siliceous, with high hardness and elasticity: 33XC, 38XC;
- chrome-molybdenum and chromium-molybdenum-vanadium, extra strong, resistant to abrasion 30XMA, 15XM, 15X5M, 15X1MF;
- chromium-manganese-silicon steels ("chromansil"): 14KhGSA, 30KhGSA, 35KhGSA;
- chromium-nickel, very strong and ductile: 12X2H4A, 20XH3A, 12XH3A;
- chromium-nickel-tungsten, chromium-nickel-vanadium steels: 12Kh2NVFA, 20Kh2N4FA, 30KhN2VA.
High-alloy steels and alloys, corrosion-resistant, heat-resistant and heat-resistant
Corrosion-resistant high-chromium steel alloyed with nickel, titanium, chromium, niobium and other elements. Are intended for work in environments of different aggressiveness. For slightly aggressive environments, steels 08X13, 12X13, 20X13, 25X13H2 are used.
Parts made of these steels operate outdoors, in fresh water, in wet steam and salt solutions at room temperature.
For environments of medium aggressiveness, steels 07X16H6, 09X16H4B, 08X17T, 08X22H6T, 12X21H5T, 15X25T are used.
For environments of increased aggressiveness, steels 08X18H10T, 08X18H12T, 03X18H12 are used, which have high resistance to intergranular corrosion and heat resistance. The structure of corrosion-resistant steels, depending on the chemical composition, can be martensitic, martensitic-ferritic, ferritic, austenitic-martensitic, austenitic-ferritic, austenitic.
Cold-resistant steels must retain their properties at temperatures of minus 40 ... minus 80 degrees. C. The most widely used steels are: 20Kh2N4VA, 12KhN3A, 15KhM, 38Kh2MYuA, 30KhGSN2A, 40KhN2MA, etc.
Heat-resistant steels are able to withstand mechanical loads at high temperatures (400 ... 850 degrees C). Steels 15Kh11MF, 13Kh14N3V2FR, 09Kh16N15M3B and others are used for the manufacture of superheaters, steam turbine blades, and high pressure pipelines. For products operating at higher temperatures, steels 15Kh5M, 16Kh11N2V2MF, 12Kh18N12T, 37Kh12N8G8MBF, etc. are used.
Heat-resistant steels are able to resist oxidation and scale formation at temperatures of 1150 ... 1250 degrees. C. For the manufacture of steam boilers, heat exchangers, thermal furnaces, equipment operating at high temperatures in aggressive environments, steel grades 12X13, 08X18H10T, 15X25T, 10X23H18, 08X20H14C2, 1X12MVSFBR, 06X16N15M2G2TFR-ID, 12X12M1BFR are used -Sh.
Heat-resistant steels are intended for the manufacture of parts operating in a loaded state at a temperature of 600 degrees. C for a long time. These include: 12X1MF, 20X3MVF, 15X5VF, 12X2MFSR.
Chemical composition of steel grades
Source: [http://tirus.ru/]| C | Si | Mn | Cr | Ni | Mo | S | P | Cu | V | Ti | N | Al | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 10 | 0,07…0,14 | 0,17…0,37 | 0,35…0,65 | 0,15 | 0,30 | - | - | - | - | - | - | - | - |
| 20 | 0,17…0,24 | 0,17…0,37 | 0,35…0,65 | 0,25 | 0,25 | - | 0,03 | 0,025 | 0,30 | - | - | 0,008 | - |
| 12X18H10T | 0,12 | 0,80 | 2,00 | 17,0…19,0 | 9,0…11,0 | - | 0,02 | 0,035 | - | - | …0,80 | - | - |
| 17G1S | 0,20 | 0,55 | 1,60 | 0,30 | - | - | 0,035 | 0,035 | - | - | - | - | 0,02 |
| St1ps | 0,06…0,12 | 0,05…0,15 | 0,25…0,50 | 0,30 | - | - | 0,05 | 0,04 | - | - | - | 0,01 | - |
| St2ps | 0,09…0,15 | 0,05…0,15 | 0,25…0,50 | 0,30 | - | - | 0,05 | 0,04 | - | - | - | 0,01 | - |
| St2sp | 0,09…0,15 | 0,15…0,30 | 0,25…0,50 | 0,30 | - | - | 0,05 | 0,04 | - | - | - | 0,01 | - |
| St3sp | 0,14…0,22 | 0,15…0,30 | 0,40…0,65 | 0,30 | - | - | 0,05 | 0,04 | - | - | - | 0,01 | - |
| 35 | 0,32…0,40 | 0,17…0,37 | 0,50…0,80 | 0,25 | 0,30 | - | 0,04 | 0,035 | 0,30 | - | - | - | - |
| 35 GS | 0,34…0,40 | 0,40…0,60 | 1,00…1,40 | 0,30 | 0,30 | - | 0,03 | 0,035 | 0,30 | - | - | - | - |
| St3ps | 0,14…0,22 | 0,05…0,15 | 0,40…0,65 | 0,30 | - | - | 0,05 | 0,04 | - | - | - | 0,01 | - |
| 40X | 0,36…0,44 | 0,17…0,37 | 0,50…0,80 | 0,80…1,10 | 0,30 | - | 0,035 | 0,035 | 0,30 | - | - | - | - |
| 45 | 0,42…0,45 | 0,17…0,37 | 0,50…0,80 | 0,25 | - | - | - | - | - | - | - | - | - |
| 09G2S | 0,12 | 0,50…0,80 | 1,30…1,70 | 0,30 | 0,30 | - | 0,04 | 0,035 | 0,30 | - | - | - | - |
| 15X5M | 0,15 | 0,50 | 0,50 | 4,50…6,00 | 0,60 | 0,45…0,60 | 0,025 | 0,025 | 0,20 | - | - | - | - |
| 30HGSA | 0,28…0,34 | 0,90…1,20 | 0,80…1,10 | 0,80…1,10 | 0,30 | - | 0,005 | 0,025 | - | - | - | - | - |
| 12X1MF | 0,10…0,15 | 0,17…0,37 | 0,40…0,70 | 0,90…1,20 | 0,25 | 0,25…0,35 | 0,025 | 0,025 | 0,20 | 0,15…0,30 | - | - | - |
| 08ps | 0,05…0,11 | 0,05…0,17 | 0,35…0,65 | 0,10 | - | 0,04 | 0,035 | - | - | - | - | 0,06 | - |
| 20…SW | 0,17…0,24 | 0,17…0,37 | 0,35…0,65 | 0,25 | 0,25 | - | 0,03 | 0,03 | 0,30 | - | - | - | - |
| St2kp | 0,09…0,15 | 0,05 | 0,25…0,50 | 0,3 | - | - | 0,05 | 0,04 | - | - | - | - | - |
| 08X18H10T | 0,08 | 0,80 | 2,00 | 17,0…19,0 | 9,0…11,0 | - | 0,02 | 0,035 | - | - | …0,70 | - | - |
| Alloy 29NK | 0,03 | 0,30 | 0,40 | 0,10 | 28,5…29,5 | - | 0,015 | 0,015 | 0,20 | - | 0,10 | - | 0,20 |
| Alloy 29KN…VI | 0,03 | 0,30 | 0,40 | 0,10 | 28,5…29,5 | - | 0,015 | 0,015 | 0,20 | - | 0,10 | - | 0,20 |
| 30HGSN | 0,27…0,34 | 0,90…1,20 | 1,00…1,30 | 0,90…1,20 | 1,40…1,80 | - | 0,035 | 0,035 | 0,30 | - | - | - | - |
| 30HGSN2A | 0,27…0,34 | 0,90…1,20 | 1,00…1,30 | 0,90…1,20 | 1,40…1,80 | - | 0,25 | 0,025 | 0,30 | - | - | - | - |
| 30HGSN2AVD | 0,27…0,33 | 0,90…1,20 | 1,0…1,20 | 0,90…1,20 | 1,40…1,80 | - | 0,011 | 0,015 | 0,39 | - | - | - | - |
