Metalworking

The main characteristics of steel ST3: features of production, properties, strength limits

October 24, 2019

Steel grade ST3 is classified as structural carbon of ordinary quality.

Alloy ST3 is used for the manufacture of hot-rolled steel, pipes, stampings, wire, etc.. d. Rolled metal products are in demand in construction for the manufacture of metal structures, manufacture of products for mechanical engineering and household appliances.

Main characteristics

Steel is a deformed iron alloy (no less 45%), carbon (2%) and impurities of some elements (phosphorus, manganese, silicon). To obtain a material with the required characteristics (corrosion resistance, increase the strength limits, magnetic properties, etc.. d.) alloying additives are added (chromium, tungsten, vanadium, titanium).

The chemical composition of steel ST3: carbon (0,14-0,22%), silicon (0,05-0,17%), manganese (0,4-0,65%), nickel, copper, chromium (0,3%), arsenic (0,08%).

Alloy ST3 includes harmful impurities: tread (oxygen, unbound nitrogen), sulfur, phosphorus. The presence of phosphorus contributes to the fragility of the metal at low temperatures and reduces the plasticity when heated. Sulfur impurities contribute to the formation of cracks in the metal.

According to mechanical characteristics, steel is divided into the following groups: normal strength, elevated and high. The strength of the material is affected by the carbon content, corresponding to the serial number of the marking from 0 to 6.

Steels are divided by purpose into three groups.

  • Structural - used in the manufacture of metal structures and products with high strength. They can be carbon and alloyed.
  • Instrumental - used for the manufacture of measuring instruments, cutting tools and implements. The carbon content is from 0,8 to 2%.
  • Steel with special properties (special) - stainless, acid-resistant, electrical, etc.. P. Have a low carbon content and high alloying elements.

Technological properties of steel

According to its mechanical properties, ST3 steel has a high endurance limit and resistance to heavy loads..

Depending on the composition of the alloy, its main properties are determined. A distinctive feature of CT3 is the carbon content. An increase in the strength limit of the material depends on the high carbon content. However, at the same time the weldability deteriorates, plastic qualities and the danger of formation of cracks in seams increases.

It is more expedient to increase the strength of the alloy by increasing the manganese content, since this does not reduce the strength of the weld metal.

The presence of silicon in its composition also contributes to the increase in strength, which practically does not reduce the ductility of the metal.

Silicon together with manganese or molybdenum provides increased hardening, increases the limits of elasticity and plasticity of the material, as well as resistance to weathering.

ST3 steel welding can be performed without restrictions. Stamping is carried out in hot and cold state, without further heat treatment.

Deoxidation of steel

In the process of deoxidation of the steel alloy is the removal of oxygen from the molten raw material, the presence of which impairs the mechanical properties of the material.

Baked steel, containing a large amount of dissolved gas, kept in molds with deoxidizers (manganese, silicon, aluminum), which combines with dissolved oxygen. The oxides obtained in the process float to the surface and are subsequently removed.

The influence of elements on the alloy is different. So, the strongest deoxidizers are aluminum, then comes silicon, and manganese is considered the weakest.

Silicon is most often used in the smelting of steel in the form of deoxidizer. In semi-quiet warehouses it is 0,10%, and in the quiet - 0,40%.

Depending on the content of oxygen and carbon in the structure of the material and the degree of deoxidation of the metal alloy are classified into the following types.

  • Calm steel ("Sp") - gases are not released during curing, fully undergoes deoxidation and removal of oxygen. It has a homogeneous structure, ductility and significant resistance to corrosion. In most types of steel (doped, low-alloy and carbon) calm alloys are used. It is used in the production of rigid metal structures.
  • The semi-calm («Ps») - undergoes partial deoxidation, the emitted gases are not completely suppressed (carbon to 0,30%). According to its qualities, the raw material has less hardness and ductility. Widely used in the production of pipes and rolled products.
  • Boiling steel («Kp») - high degree of gas evolution during curing. It contains the maximum amount of carbon and manganese. Its cost is relatively low, as it uses less deoxidizer. Used in the manufacture of plates, letters, wire and pipes.

According to the method of production, there are open-hearth and oxygen-converter steel. The most modern, relatively simple and cheap way is oxygen-converter with the use of oxygen converters.

ST3 steel is very popular due to its manufacturability and quality characteristics (strength, ease of processing, etc.. d.). The use of special technologies in production allows you to get economical, durable structures and products of various applications.