In addition to carbon, conventional carbon steels contain other elements.: to 1,65 % manganese; to 005 % sulfur; to 0,04 % phosphorus; to 0,60 % silicon and before 0,60 % copper.
Cm. Effect of manganese and silicon on the properties of steels and
Effect of phosphorus, sulfur and copper on the properties of steels.
Carbon steels can be classified from various points of view, eg, by deoxidation method. Of course, the method of deoxidation affects the characteristics and properties of steel. However, a change in carbon content has the greatest impact on the mechanical properties of steel - with an increase in carbon content, its hardness and strength increase.. Therefore, steels are usually grouped according to their carbon content.. Typically, carbon steels contain up to 2 % all alloying elements and in turn are subdivided into:
- low carbon steels;
- medium carbon steels and
- high carbon steels.
Carbon steels are the main products of the iron and steel industry - they account for more than 80 % its products. The main metal material of the industry is precisely carbon steel..
For carbon steels, the following standards are most commonly used:
- GUEST 380-2005. Carbon steel of ordinary quality
- GUEST 1050-88. High-quality structural carbon steel
Low carbon steels
Low carbon steels contain carbon up to 0,25 %. The largest category of this class of steels is flat products - sheets and strips, usually cold rolled or annealed. The carbon content to improve the hot workability and cold drawability of these steels is usually very low. (less 0,10 %) with manganese content up to 0,40 %. These low-carbon steels are used to make car bodies., tin and wire products.
Low carbon steels with carbon content from 0,10 to 0,25 % have increased strength and hardness, but lower plastic deformability compared to low carbon steels with the lowest carbon content.
These steels are often used in combination with their carburizing process.. Typical application of case-hardened steels - parts with high demands on wear resistance, but without the need to increase the strength of the core of the part, eg, small shafts or gears.
Rolled sections made of structural steel with a carbon content of approx. 0,25 % and to 1,5 % manganese and aluminum are used in conditions, when higher material viscosity is required. When steel is used for stamping, forging, of seamless pipes or sheet for the manufacture of boilers, aluminum additives are not produced.
An important category of these steels are low-alloy free-cutting steels with carbon contents up to 0,15 % and manganese - up to 1,2 % with a minimum of silicon and with a sulfur content up to 0,35 %, and also with lead up to 0,30 % or without it. These steels are designed for automatic mass production of parts from them., which are not exposed to heavy mechanical and climatic influences. If the product needs high plasticity and viscosity, as well as corrosion resistance, then these steels are not suitable for him.
Medium carbon steels
Medium carbon steels contain 0,30-0,55 % carbon and 0,60-1,65 % manganese. They apply there, where high mechanical properties are required. These steels are usually hardened by heat treatment or cold working. Steels from this group with reduced carbon and manganese content are widely used for some types of parts., obtained by cold plastic deformation. This requires pre-application of annealing, normalizing or quenching with tempering. Steels with a higher carbon content are often drawn to specified mechanical properties for applications without heat treatment.
All these steels can be forged. The choice of steel depends on the size of the product and the mechanical properties, which it must provide after heat treatment. These steels are usually produced as quiescent steels and are very widely used in mechanical engineering.. Lead and sulfur are also added to these steels if necessary for their mass machining., as well as aluminum for grain refinement and viscosity increase. Carbon steels 0,40-0,60 % used for the manufacture of railroad rails, wagon wheels and axles, tires for locomotives.
High carbon steels
High carbon steels, containing 0,55 -1,00 % carbon and 0,30-0,90 % manganese are of more limited use, than medium carbon steels. The thing is, that these have become more expensive to manufacture, have low plasticity and, hence, hot working with great difficulty, and also poorly welded. High carbon steels find application in spring production, in the manufacture of various cutting tools, including elements of earthmoving and agricultural machinery, as well as high-strength wire - everywhere, where higher wear resistance and higher strength are required, than steels with a lower carbon content can provide.