Low carbon steel: composition and properties

Low Carbon steel is found everywhere. Its popularity is based on physical, chemical properties and low cost. This alloy is widely used in industry and in construction. Let us consider this kind of steel.

Structure

Steel – iron enriched with carbon during the smelting process. For carbon melts is characterized by the presence of carbon, which determines the main properties of the metal, and impurities: phosphorus (up to 0.07%), silicon (0.35%), sulfur (up 0.06%), manganese (0.8%). So, low carbon steel contains no more than 0.25% of carbon. As for other additives, manganese and silicon serve deoxidation (removal of oxygen from the liquid metal, which reduces the brittleness during hot deformation). But a higher percentage of sulfur can lead to cracking of the alloy during heat treatment, phosphorus – when cold.

Ways to receive

Production of low-carbon alloy can be decomposed into several stages: the charging of pig iron and scrap (mixture) thermal effect to a state of fusion, remove from the mass of impurities. Next, you may be a casting or additional processing: slag or vacuum and inert gases.

For the execution of these processes use one of three ways:

• Open-Hearth furnace. the Most common equipment. The melting process takes place within a few hours, which allows you to monitor laboratories quality composition.
• Convection oven. is Produced by oxygen blowing. It should be noted that the alloys obtained in this way are not of high quality because they contain greater amounts of impurities.
• Induction and electric furnaces. the production Process is with the use of slag. This method produces high-quality and specialty alloys.

Consider the features classification of alloy.

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Types

Low Carbon steel may be of three types:

• Common quality. In these alloys, the sulfur content shall not exceed 0.06%, phosphorus of 0.07%.
• Qualitative. In the presence of sulphur up to 0.04%, phosphorus up to 0.035%.
• High Quality. the Content of sulphur up to 0.025% phosphorus up to 0.025%
• Special qualities. a Low content of impurities: sulfur to 0.015%, phosphorus - up to 0.025%.

As mentioned earlier, the less impurities, the better the quality of the alloy. Low carbon Steel GOST 380-94 ordinary quality is divided into three groups:

• A. is Determined by its mechanical properties. Form of delivery the consumer is most often found in the form of multidisciplinary and sheet metal.
• B. Key indicators - chemical composition and properties. Optimal for the mechanical pressure under heat factor (forging, stamping).
• Century For these types of alloys are important properties such as: technical, technological, physical, chemical and, accordingly, the structure.

The process of deoxidation of steel is divided into:

• Quiet. the Process of solidification takes place quietly. Gases in this process are not highlighted. Shrinkage occurs in the middle of the ingot.
• Balanced. Intermediate form between calm and boiling compounds.
• Boiling. Solidification occurs with a release of gas. Shrinkage is concealed.

Main properties

Low Carbon steel is characterized by high flexibility, easily deformed in a cold state and hot. A distinctive feature of this alloy is good weldability. Depending on additional properties of steel can vary. Most Often, low carbon alloys are used in construction and industry. This is due to the low price and good strength qualities. This alloy is also called structural. Properties of low carbon steel is encoded in the marking. Below, we look at its features.

Features marking

Ordinary low carbon steel has a letter designation of ST and a digital. The number should be divided by 100, then it will be clear the percentage of carbon. For example, СТ15 (carbon 0.15 percent).

Consider marking and decipher the symbols:

• The First letters or their absence indicates belonging to one group or another quality. It can be Used or If no letter, it means that the alloy belongs to a category.
• St denotes the word “steel”.
• Digital signage – encrypted the percentage of carbon.
• KP, PS – denotes a fluidized or semi-killed alloy. The absence of a description says that steel quiet (SP).
• Lettering and digital after it reveal what impurities are included in the composition, and percentage. For example, G – manganese, Yu – aluminum, f – vanadium.

For high-quality low-carbon steel in the marking is not assigned a letter designation “St”. Also applies to the colour code. For example, low carbon steel of grade 10 is white. Special purpose steel can be denoted by additional letters. For example, “To” -used kotlostroenie; OSV – used for the manufacture of car axles, etc.

Manufactured items

There are several groups of steel products:

• Steel. Subtypes: plate (GOST 19903-74), sheet (GOST 19904-74), broadband (GOST 8200-70), strip (GOST 103-76), corrugated (GOST 8568-78)
• Corner profiles. Angle (GOST 8509-93), angle (GOST 8510-86).
• Channels (GOST 8240-93).
• Beams. ordinary steel I-Beam (GOST 8239-89), Beam h-beam (GOST 26020—83, STO aschm 20—93).
• Pipe.
• Profiled decking.

To this list add secondary profiles, which are formed by welding and machining.

Scope

The use of low carbon steel sufficiently broad, and depends on the marking:

• St 0, 1, 3Гсп. Broad use in construction. For example, the reinforcing wire of low carbon steel
• 05kp, 08, 08KP, 08ju. Good for forming and cold drawing (high plasticity). Used in the automotive industry: car body parts, fuel tanks, coils, parts of welded structures.
• 10, 15. Used for parts not subjected to high loads. Tubes for boilers, forging, couplings, bolts, screws.
• 18kp. Characteristic application – designs that are produced with the help of welding.
• 20, 25. is Widely used for production of fastening materials. Coupling, valve lifters, frames and other items of agricultural machinery.
• 30, 35. Axis, which is small load, sprockets, gears, etc.
• 40, 45, 50. Detail, experiencing average loads. For example, crank shafts, friction discs.
• 60-85. Parts that are exposed to high loads. It can be rails for railroad wheels for valves, springs, washers.

As you can see, we produce an extensive range of – it's not just the low-carbon steel wire. It also details complex mechanisms.

Low alloy and low carbon steel: differences

To improve any characteristics of the alloy are added alloying elements. Steel contain a Cheb low amounts of carbon (up to a quarter percent) and dopants (the total percentage up to 4 %) are called low-alloy. This steel maintains a high weld quality, but this enhanced different properties. For example, strength, corrosion characteristics and so on. Usually both types are used in welded structures that have to withstand temperature range from minus 40 to plus 450 degrees Celsius.

Features welding

Welding carbon steels is high. Type of welding electrodes and their thickness are selected on the basis of the following technical data:

• A Connection must be firmly fastened.
• Should be No defects in the seams.
• Chemical composition of the weld must be performed in compliance with the standards specified in the Guest.
• Welded joint must meet the conditions (resistance to vibration, mechanical impact, temperature).

You Can use various types of welding from gas to welding in carbon dioxide consumable electrode. In the selection due to high fusibility low-carbon and low-alloyed alloys.

With respect to the specific scope of application, low carbon steel is used in construction and engineering. Steel Grade is selected on the basis of required output, physical and chemical properties. The presence of alloying elements can improve some properties (resistance to corrosion, temperature fluctuations), but degrade the other. Good weldability is another advantage of such alloys.

So we figured out what are the products of carbon and low-alloy steel.