Lviv steel plate, sheet st20, st45, 10KhSND, 09G2S, 30KhGSA, 9KhS, metal 1-120mm cutting and delivery
The steel grade ST20 is considered to be the most demanded on the market. Its use is justified in many areas of production. High-quality carbon steel must comply with GOST standards and have certain characteristics and scope, there are a couple of foreign-made analogues with identical properties in composition and functional use.
Chemical composition
This type of steel is a kind of structural model, which is distinguished by excellent quality and strength. Smelting takes place in accordance with strict observance of the rules and regulations established by GOSTs. Each model has its own standards, which are described in the corresponding document.
The composition of ST20 steel includes the following elements:
Fe;
C (0.02%);
Si (0.17–0.35%);
Mg - 0.35 - 0.6%;
Ni (0.3%);
Cr (0.2%);
Cu (0.3%);
P(0.035%);
S (0.04%).
The carbon content makes the alloy incredibly strong and hard. At the same time, plastic characteristics suffer, which noticeably decrease during the production process.
Silicon has the ability to remove excess hydrogen and nitrogen molecules from the alloy. These elements ensure that the optimal degree of porosity and the number of shells are maintained, but negatively affect the strength, greatly underestimating it.
As for manganese, it acts as a deoxidizer, and plays the same role as silicon. Namely, it reduces the risk of cracks during operation and during heat treatment (when welding and forging).
Phosphorus and selenium are used in steel as an impurity. They increase the brittleness of parts and reduce their toughness. In addition, dynamic resistance to external influences is improved. The remaining components increase the performance and anti-corrosion properties of the material.
Decryption
Reference. The abbreviation ST gives information about steel of conventional composition with carbon content. The number indicates the number of the composition. Next to one or another type of steel, you can see a number of specific symbols that indicate a calm state - cn, ps - a semi-calm state and kp - boiling.
Quiet steel is formed by the complete exclusion of oxygen. For this, silicon and manganese are introduced into the alloy.
This alloy contains a very small amount of iron oxides. This causes the functioning of the material without the release of specific substances in gaseous form.
The alloy in the ladle hardens quickly and the steel at the outlet has a dense structure and uniformity. The upper part is covered with a gas shell. The gas quickly escapes during mechanical manipulations performed with the bars.
The boiling version of steel is formed by the deoxidation of manganese. It exceeds the percentage of iron content, due to which interaction with carbon occurs. Carbon dioxide is released. Gas bubbles form, which look like a boiling mass.
This part has a high percentage of porosity. But this option has a fairly low price on the market, and no harmful waste is generated after use. Semi-calm steel is between the described calm and boiling.
According to the types of processing, steel of this brand is divided into forged, calibrated, hot-rolled and silver. The latter has a round base and is coated with a special compound.
Main characteristics and properties
The physical and technological properties of ST20 steel are described in tables No. 1 and No. 2.
Technological properties
Forging The initial forging temperature is 1280 °С, the final temperature is 750 °С. Cooling is done in air
Weldability Can be welded without restrictions. The only exceptions are some parts that have been subjected to chemical and heat treatment.
Machinability In the hot-rolled state at HB 126 - 131 and Q = 450 - 490 MPa. Kv carbide is 1.7, Kv high speed steel is 1.6
Flake sensitivity Not sensitive
Tendency to temper brittleness Not prone to
Types of rental
There are two main technologies for obtaining a rolled profile from steel 20:
Hot deformation - used for rolling blanks more than 4 mm thick. Hot deformation leads to the formation of scale, which is the main disadvantage of this technology.
Cold deformation; used for rolling thin workpieces (up to 4 mm). As a result of cold deformation, the strength of the alloy increases due to work hardening.
Types of steel products 20
profile of all varieties: channel, sheet, I-beam, angle, bar, wire;
seamless pipes, high-strength, obtained by drawing (cold or hot);
all-welded cold-rolled pipes, welded from a single sheet of steel 20 along the length of the pipe.
Production standards
long products, including shaped steel - GOST 1050-88, GOST 2590-2006, GOST 2591-2006, GOST 2879-2006, GOST 8509-93, GOST 8510-86, GOST 8240-97, GOST 8239-89;
calibrated bar - GOST 7417-75, GOST 8559-75, GOST 8560-78, GOST 10702-78;
polished bar and silver - GOST 14955-77;
thick sheet - GOST 1577-93, GOST 19903-74;
thin sheet - GOST 16523-97;
tape - GOST 6009-74, GOST 10234-77, GOST 103-2006, GOST 82-70;
wire - GOST 5663-79, GOST 17305-91;
forgings and forged blanks - GOST 8479-70;
pipes - GOST 10704-91, GOST 10705-80, GOST 8731-74, GOST 8732-78, GOST 8733-74, GOST 5654-76, GOST 550-75.
Purpose and application
Steel 20 is one of the most common steel grades in the domestic industry, its versatility allows the production of almost all types of metal products. The main applications of steel 20:
Engineering. Steel 20 is used to make fasteners, connecting elements of mechanisms, gears, worms, brackets, shafts, bearings, liners.
Pipelines. Welded and seamless pipes, valves and adapters are made from steel 20; crosses, union nuts, nipples, fittings, hexagons, couplings, cocks, manifolds, superheaters, parts of boilers operating under high pressure.
Construction. Fasteners, hooks, trusses, beams and more. In construction, 20 steel is popular due to its good weldability, satisfactory strength, and availability.
Three types of steel 20 in terms of deoxidation
Deoxidation is the removal of oxygen from the composition of steel 20 in order to reduce the brittleness index during hot working. The degree or level of deoxidation in another way can be called the degree of outgassing during solidification of steel. The intensity of outgassing or boiling strongly affects the structure of the solidified metal, respectively, the higher the level of deoxidation, the more solid and durable the structure will be.
Calm and semi-calm steel
Steel, which is deoxidized by silicon and manganese, can be maximally purified from the oxygen content. Such steel is characterized by an integral structure without bubbles and pores, because the alloy solidifies in a calm state, without active outgassing. The formation of a shrinkage cavity occurs in the upper part, it is removed mechanically.
Quiet steel is more expensive than boiling and semi-quiet, because. more difficult to manufacture. It is used in the manufacture of products with high requirements for strength, for example, for load-bearing structures, railway tracks, etc.
Semi-calm steel; a medium state between calm and boiling steel, characterized by medium porosity. It can be of different quality and is used for the manufacture of welded structures, blanks for rolled pipes, fasteners.
Quiet steel has the highest strength and reliability, but its use can be economically unprofitable in industries where high requirements are not placed on steel products.
boiling steel
Steel 20, the process of deoxidation of which is carried out due to manganese, contains the largest amount of dissolved gases and iron oxides. During the solidification of boiling steel, nitrogen and carbon dioxide are actively released, and multiple bubbles and pores are formed. Such steel is inferior to calm and semi-quiet steel in terms of strength, but it has a number of positive characteristics. It is perfectly stamped, the process of its production is simpler and cheaper, the production is waste-free.
Boiling steel is suitable for the production of products that are not subjected to high loads during operation. It can be various types of fences, sheet sheathing, other metal structures.
Mechanical properties
Steel 20 has high mechanical properties such as ductility, hardness and strength. The high index of impact strength allows the steel to adequately withstand the increase in dynamic loads. Strength is improved by thermal or mechanical treatments - work hardening, roller rolling, annealing, normalization.
The specific gravity of steel is 7.85 g/cm3. The maximum coefficient of linear expansion st 20 = 14.8 10-6 deg-1 at temperatures of 27-700°C. Indicators for calibrated hot-rolled steel of the 2nd category: tensile strength 410 MPa, relative elongation after rupture 25%, relative narrowing 55%, Brinell hardness 4.8.
Technological properties
Steel 20 is a high-tech alloy that belongs to the category of cemented alloys. The cementation process is the saturation of the surface of the product with carbon by heating in a special environment. As a result of such processing, the top layer of the product acquires a hardness index of up to 62 HRC, which is three times higher than that of the core. The metal lends itself well to forging, cutting and soldering, is not prone to cracking, and retains a high density. All popular methods are applicable for welding - ADS, KTS, RDS, submerged arc welding, etc. The type of equipment depends on the chosen welding technology.
