The raw material that is obtained from processing a material such as cast iron is called steel. For processing, several different methods can be used - open-hearth, metal-converter and electrothermal. This thermal process is necessary for the raw material to go through the stages of carbon saturation, deoxidation and others. The composition of any steel must comply with GOST.
General description of the material
Steel St3sp is intended for the manufacture of shaped, high-quality, thin-sheet or plate material. In addition, it is successfully used in the procurement of cold-rolled and broadband sheet products. Rectangular pipes and ordinary pipes, tapes, hardware, stampings can also be made from this substance.
It is very important to note here that St3sp steel is the same St3 material, the letters "cn" indicate only the method of its preparation, but more on that later. Currently, this substance has become indispensable in the construction of ground and underground utilities, in the construction of vehicles, as well as various other units and machines.
Impurities and method of deoxidation
The following substances are used as impurities for the production of St3sp steel :
- chromium in an amount of 0.3%;
- nickel in an amount of 0.3%;
- copper in the same amount as the first two components;
- sulfur content should not exceed 0.005%;
- phosphorus in an amount of not more than 0.04%;
- nitrogen is not more than 0.1%.
Next is the process of steel deoxidation, which is one of the most important. During this operation, all oxygen is removed from the substance, and further qualities will deteriorate depending on which substance was used. Depending on the process, there are three types:
- Mild steel - manganese, silicon, and aluminum are used as impurities for deoxidation.
- Boiling - only manganese is used.
- Semi-quiet - manganese and aluminum are used.
Thus, it becomes clear that the decoding of St3sp steel is calm steel. This manufacturer indicates the degree of deoxidation of the substance.
Description and application of St3sp
This type of substance is the most expensive of all three types. Oxygen in it is completely absent, the structure is homogeneous, that is, completely homogeneous. This property significantly enhances the resistance of the material to the effects of external aggressive media. In other words, there is a high resistance to corrosion, increased ductility. According to GOST, St3sp steel is used in the production of rigid trusses, as well as other metal structures, bearing and non-bearing parts of objects. The following elements can be made from this raw material:
- sheet and packaged rolled products (steel sheets marking St3);
- reinforcing blanks and components for the piping system ( square pipes St3);
- successfully used in the manufacture of primary and secondary parts for the railway industry, overhead and ground tracks, etc.
Welding material
This material lends itself quite well to such effects as welding. A wide range of technical parameters, which can also be modified with various additives, are considered universal. Excellent weldability is one of the first advantages that steel has.
The properties and parameters of raw materials allow the use of arc types of welding automatic and manual type. In addition, it is allowed to use the contact point and electroslag method. It is also worth noting that this material can also be successfully used for the production of forged objects.
Full decryption of the brand
If you rely on GOST, then be sure to use the grade of steel St3sp in its entirety. A designation such as St3 is not permitted. According to the international standard, there is a clear division into markings St3sp, St3ps, St3kp. Depending on the modification and increase in the manganese content during deoxidation, the St3gps and St3gsp brands may also occur. It is also worth paying attention to the fact that if during the installation of the marking no index was added by the manufacturer, the degree of deoxidation can be established by the buyer. If an order is made for this raw material, then in the form it is necessary to write something like this - "St3sp steel GOST 380-2005".
These indices are decrypted as follows:
- St is the designation of the usual quality of carbon steel.
- 3 is a conditional number that is assigned to any steel grade. There are seven of these numbers in total. A change in number means a change in the chemical composition of the feed.
- Sometimes you can find the additional letter G. It is put only if the percentage of the chemical substance - manganese - exceeds 0.8% of the total mass fraction of substances.
- Cn is the degree of deoxidation of the composition.
A complete decoding of St3sp steel looks that way.
Technological qualities
This steel is not prone to such a defect as temper brittleness. There is also non-flicker sensitivity, and weldability is practically unlimited. It is further important to note that all structural material is divided into groups depending on corrosion resistance, quality of mechanical properties and degree of weldability. If we talk about mechanical characteristics, then rolled steel is divided into three groups - ordinary, high and high strength.
The main properties of raw materials depend on its chemical constituents. Ferrite acts as the main structural material. By itself, this material is considered to be of low strength, but ductile. Such properties of the basic substance do not allow the use of ferrite in its pure form, since its use, for example, for building structures is prohibited. It is in order to improve the strength characteristics, the composition goes through the process of carbon saturation. The steels of the ordinary group are low-carbon materials, the middle group includes substances that are alloyed with such chemical additives as chromium, nickel, silicon, manganese. High-strength substances are additionally alloyed by thermal hardening.
Harmful impurities for steel
During the process of rolling steel , some harmful impurities are also used or emitted, which include phosphorus and sulfur. When phosphorus reacts with ferrite, it significantly increases its brittleness when exposed to low temperatures or significantly reduces its strength at high temperature values. The excess sulfur in the steel is called sulfur content. This defect leads to the red breaking of the material. The sulfur content in raw materials should not exceed 0.05%, and phosphorus - 0.04%. It is also worth noting here that if the temperature is not high enough for the formation of ferrite, carbon will begin to be released. Its clusters will collect between grains, as well as near defects in the crystal lattice. This has a very negative effect on the strip steel St3sp.