Carbon steel is called structural or tool steel, which includes iron (up to 99%) and carbon (up to 2%), while the alloy has no or almost no alloying additions.
The content of various chemical elements in carbon steel alloys is indicated in the image below:
Alloy types of carbon steel are classified according to carbon content, quality and degree of deoxidation.
Carbon is the main element of carbon steel, and its content in the alloy can vary within a fairly wide range: from 0.25% to 2%.
Most of this type of steel comes in the form of cold rolled and annealed strips and sheets. Its properties vary depending on the content of the main chemical elements:
Usually, in such types of steel, the manganese content is at the level of 0.6-1.65%. They are suitable for the production of products that will be operated under high loads. Can be forged. Suitable for mechanical engineering.
With an increase in the amount of carbon up to 1%, the steel becomes stronger and harder, while the limits of its yield and plasticity decrease. A further increase in carbon by more than 1% leads to the beginning of the formation of a coarse mesh of secondary martensite, which reduces the strength of the material.
High-carbon steel is characterized by high cost, low ductility and poor weldability. This material has a limited area of application - it is used for the production of cutting tools, high-strength wire.
Carbon steel is produced using various technologies, which leads to their separation according to quality characteristics. There are two types of steel:
Structural carbon steel contains up to 0.65-0.70% carbon (as an exception, structural steel with 0.85% carbon is also produced). It is strong enough to resist impact well and also handles well.
Structural carbon steels are widely used in industry: they are used for the manufacture of structural elements for mechanical engineering and construction purposes, parts for equipment, fasteners and much more.
It is also divided by quality into 3 types:
Tool carbon steel has a carbon content of 0.7% or more. This type of steel is hard and durable, making it suitable for tool making. It is subdivided into high quality (sulfur 0.03%, phosphorus 0.035%) and high quality (sulfur 0.02%, phosphorus 0.03%).
Applications of tool steel
|У7, У7А||For wood processing: axes, cleavers, chisels, chisels; pneumatic tools of small sizes: chisels, crimps, strikers; blacksmith dies; needle wire; fitting and assembly tools: hammers, sledgehammers, barbs, screwdrivers, combination pliers, needle-nose pliers, side cutters, etc.|
|У8, У8А, У8Г, У8ГА, У9, У9А||For the manufacture of tools operating in conditions that do not cause heating of the cutting edge; wood processing: cutters, countersinks, forgings, axes, chisels, chisels, longitudinal and circular saws; knurling rollers, plates and rods for die casting molds of tin-lead alloys. For fitting and assembly tools: rivet crimps, center punch, barbs, screwdrivers, combination pliers, needle-nose pliers, side cutters. For calibers of simple shape and reduced accuracy classes; cold-rolled heat-treated tape with a thickness of 2.5 to 0.02 mm, intended for the manufacture of flat and coil springs and springy parts of complex configuration, valves, probes, reeds, lamellas of double knives, structural small parts, including for watches, etc.|
|У10А, У12А||For cores|
|У10, У10А||For needle wire|
|У10, У10А, У11, У11А||For the manufacture of tools operating in conditions that do not cause heating of the cutting edge; wood processing: hand saws for cross and joinery, machine saws for carpentry, spiral drills; cold stamping dies (drawing, heading, edging and cutting) of small size and without sharp transitions along the section; calibers of simple shape and reduced accuracy classes; knurling rollers, files, metal scrapers, etc. For files, scrapers of cold-rolled heat-treated tape with a thickness of 2.5 to 0.02 mm, intended for the manufacture of flat and coil springs and springy parts of complex configuration, valves, probes, reeds, lamellas of double knives , structural small parts, including watches, etc.|
|У12, У12А||For hand taps, files, metal scrapers; dies for cold stamping of edging and punching small sizes and without cross-sections, cold heading punches and small stamps, calibers of simple shape and reduced accuracy classes.|
|У13, У13А||For tools with reduced wear resistance at moderate and significant specific pressures (without heating the cutting edge); files, razor blades and knives, sharp surgical instruments, scrapers, engraving instruments.|
The degree of deoxidation is another factor that influences the classification of carbon steels by type. There are 3 types in total: calm, semi-calm and boiling.
Quiet steels are distinguished by a more homogeneous internal structure - their de-expansion is carried out by adding ferrosilicon, ferromanganese and aluminum to the molten metal. There is practically no iron oxide in the composition. The structure is fine-grained due to residual aluminum. As a result, a high-quality metal is obtained, suitable for the manufacture of the most critical parts and structures. However, alloys of this type have a significant drawback - their smelting is quite expensive.
Boiling carbon steels are a cheaper, but lower quality alternative to quiet alloys. When they are smelted, a minimum amount of special additives are used, and the deoxidation process in the furnace is not completed, as a result of which dissolved gases are present in the structure of boiling carbon steel, which negatively affect its characteristics.
Semi-quiescent steels occupy an intermediate position both in properties and in the degree of deoxidation. Before pouring into the molds, a small amount of deoxidizers is added to the composition - due to this, the metal solidifies practically without boiling, while the process of gas evolution continues in it. As a result, there are fewer gas bubbles in the structure of semi-quiescent carbon steel than in boiling steel. Most often, semi-calm carbon steels are used as structural materials.