How to determine the chemical composition of steel

Determination of the chemical composition of steel, determination of steel grade in St. Petersburg

In addition to conducting research on the chemical composition of steel on site, we also carry out similar studies within our laboratory conditions, which allow us to most accurately determine the chemical composition of the steel sample under study, identify its grade, and carry out quality control.

Only quick and high-quality examination of steel composition

We can quickly and efficiently inspect the object within the framework of the customer’s technical specifications, which may include:

1. Determination of C, S, P by metrologically tested instruments;
2. Carrying out quality control of the steel products under study;
3. Identification and sorting of steel by grade and type of alloy;
4. Thorough check for compliance of brands of welding joints and materials;
5. Detection of defects in metal products;
6. Detailed analysis of the chemical composition of alloys and metals;
7. Sorting and control of stored metals and alloys;
8. Spectral analysis of taken samples, regardless of their complex shape, surface, without the use of additional equipment in the field.

Highly qualified specialists of the StroyExpert IC in St. Petersburg

Our company employs only highly qualified specialists who approach their work with a full understanding of the assigned tasks, professional experience and highly specialized skills.

All our specialists are certified, have completed the necessary professional training and have qualified certificates.

Please contact our specialists for detailed information.

Determination of the chemical composition of steel is carried out efficiently and in a short time. Please contact our specialists on this issue, ask questions by phone - (343) 384-85-34, 345-85-34, 8-800-775-87-88, and also use the feedback form or email - info@stroy—ek.ru (marked “DETERMINATION OF THE CHEMICAL COMPOSITION OF STEEL”).

We have answers to all your questions! We will be glad to see new cooperation!

Source: https://piter.stroy-ek.ru/service/opredelenie-prochnostnyh-harakterist/opredelenie-himicheskogo-sostava-stali/

Steel: types, properties, grades, production technology

Steel: types, properties, grades, production

Steel and products made from it have become so firmly established in the life and everyday life of modern people that it is difficult to imagine existence without metal objects. When it comes to dishes, small tools, household appliances and equipment, it is not at all necessary to know the brand, classification of alloys, and their areas of application.

This information is important, rather, for those who have decided to start building their own housing and do not know which metal products are suitable for these purposes. So, what steel is, what types of steel exist, and what properties this alloy, popular today, has, will be discussed in the construction magazine samastroyka.ru.

What is steel and its difference from cast iron

Iron-carbon alloy is the well-known steel. Typically, the proportion of carbon in the alloy varies from 0.1 to 2.14%. Increasing carbon concentration makes steel brittle. In addition to the main components, the alloy also contains small amounts of magnesium, manganese and silicon, as well as harmful sulfur and phosphorus impurities.

The basic properties of steel and cast iron are very similar. Despite this, there are significant differences between them:

• steel is a stronger and harder material than cast iron;
• cast iron, despite the deceptive massiveness of cast iron products, is a lighter material;
• Since steel contains a negligible percentage of carbon, it is easier to process. For cast iron, casting is preferable;
• products made of cast iron retain heat better due to the fact that its thermal conductivity is significantly lower than that of steel;
• hardening of the metal, which increases the strength of the material, is impossible with cast iron.

Advantages and disadvantages of steel alloys

Since there are a huge number of steel brands, and even more products made from it, it is pointless to talk about the pros and cons. Moreover, the properties of the metal largely depend on manufacturing and processing technologies.

As a result, we can only highlight a few general advantageous features of steel, such as:

• strength and hardness;
• viscosity and elasticity, that is, the ability not to deform and withstand shock, static and dynamic loads;
• accessibility for different processing methods;
• durability and increased wear resistance compared to other metals;
• availability of raw materials, cost-effectiveness of production technologies.

Unfortunately, there are also some disadvantages:

• instability to corrosion, including a high level of electrochemical corrosion;
• steel is a heavy metal;
• The manufacture of steel products is carried out in several stages; violation of technology at any of them leads to a decrease in quality.

Types and classifications of steel alloys

Today it is difficult to determine the number of steel alloys produced and used. It is also not easy to classify them, since their properties depend on many parameters, such as composition, nature and amount of additives, manufacturing and processing methods, purpose and many others.

Based on quality, it is customary to distinguish between ordinary, high-quality, high-quality and especially high-quality steels. The proportion of harmful impurities is the main criterion for determining the quality of the alloy. Ordinary steels are characterized by higher values ​​of the proportion of impurities than especially high-quality alloys.

Chemical composition of steel . The production of iron alloys is based on its ability to form different structural phases at different temperatures, the so-called polymorphism. Thanks to this ability, impurities dissolved in iron form alloys of various compositions. It is customary to divide steel alloys into carbon and alloy .

Steel, by definition, is an alloy of iron and carbon, the concentration of which determines its properties: hardness, strength, ductility, toughness. Carbon steel contains practically no additional additives.

Basic impurities - manganese, magnesium, and silicon are contained in minimal quantities and do not impair its properties and qualities. Silicon and manganese have a deoxidizing effect on the alloy, increasing elasticity, wear resistance, and heat resistance. But, in case of increasing the proportion, they are alloying elements. Steels with a high manganese content lose their magnetic properties.

Sulfur and phosphorus impurities are much more harmful for both types of steel. Sulfur, when combined with iron, increases brittleness when processed at high temperatures (rolling, forging), increases fatigue, and reduces corrosion resistance.

Phosphorus, especially with a large proportion of carbon in the alloy, increases its brittleness under normal temperature conditions. In addition, there is a whole group of hidden harmful impurities that cannot be removed during smelting. These non-metallic inclusions in the form of nitrogen, hydrogen and oxygen make the metal more friable during hot processing.

Types of Carbon Steel

Carbon steels are divided into types, which are characterized by the proportion of carbon content:

• high-carbon alloys include alloys with a share of more than 0.6%;
• in medium-carbon alloys, the carbon concentration ranges from 0.25 to 0.6%;
• permissible values ​​typical for low-carbon steels - no more than 0.25%.

Alloy steels are divided into:

— low-alloy, with the share of alloying additives no more than 2.5%;

— medium alloyed, with a share of additional elements up to 10%;

- highly alloyed, in which the share of alloying elements is more than 10%.

Alloy steels are characterized by a low carbon concentration and the presence of various alloying additives.

In accordance with their purpose, steels are divided into groups of structural, tool and special purpose steels.

Each group is divided into subgroups and types, which specify the properties, features and areas of application of alloys.

Structural steels include:

1. Construction materials, their main property is good weldability; these are low-alloy alloys of ordinary quality.
2. For cold stamping, rolled products from low-carbon alloys of ordinary quality are used.
3. Cementable, used in the manufacture of parts with surface abrasion.
4. High-strength ones are characterized by a double strength threshold relative to other structural types.
5. Spring steels with the addition of vanadium, bromine, silicon, chromium and manganese are designed to maintain elasticity for a long time.
6. Ball bearing steels with a large proportion of carbon and the addition of chromium, which are characterized by special wear resistance, strength and endurance.
7. Automatic, they contain impurities of sulfur, lead, tellurium and selenium, which facilitate the processing of metal by automatic machines on which mass parts are produced
8. Stainless steel, these include alloys with a high content of chromium and nickel. The carbon concentration in such alloys is minimal.

Types of tool steel

Tool steels come in several varieties:

• Used in the production of cutting tools, these include some types of carbon, alloy and high-speed steel.
• Measuring instruments are made from fairly hard alloys that are wear-resistant and have the ability to maintain constant dimensions; most often, hardened and cemented steel is used for this.
• Die steel is characterized by hardness, heat resistance and hardenability. This type is divided into subtypes, which include roll alloys and steels for multi-temperature processing.

Special-purpose steels include steel grades that are used in specific production areas:

• electrical steels - they are used to produce magnetic wires;
• superinvars - used in the production of high-precision instruments;
• heat-resistant - operate at temperatures above 900 °C;
• heat-resistant - can operate at high temperatures in loaded conditions.

Steel structure

The carbon concentration in the alloy determines not only the properties of the metal, but also its internal structure. For example, low- and medium-carbon alloys have a structure consisting of ferrite and pearlite. As the proportion of carbon increases, the formation of secondary cementite begins. Alloying steel also changes the structure of the alloy.

The structure of steel can be:

• pearlitic - with a low content of alloying additives;
• martensitic - steels with a reduced critical hardening rate and an average level of alloying impurities;
• austenitic - high-alloy alloys used in aggressive environments.

Annealed steels are divided into:

• hypoeutectoid steel, with a carbon concentration of less than 0.8%;
• hypereutectoid steel, consisting of pearlite and cementite, is used as a tool steel;
• carbide (ledeburite) - this includes high-speed steels;
• ferritic - high-alloy steel with low carbon content.

Steel manufacturing methods and technologies

The structure of this alloy, its composition and properties depend on the steel manufacturing technology. Conventional steels are produced in open hearth furnaces or converters. As a rule, they are saturated with a significant amount of non-metallic impurities.

High-quality alloys are produced using electric furnaces. Particularly high-quality alloy steels, containing a minimum amount of harmful impurities, are produced through the process of electroslag remelting.

In the production of steel, a deoxidation process is used to remove oxygen from the alloy structure. The amount of oxygen removed determines what kind of steel is obtained: slightly deoxidized, completely deoxidized, or semi-deoxidized. They are classified as boiling, calm and semi-calm.

Steel grades

Despite the fact that steel is clearly recognized as the most popular iron alloy, a unified system for marking its types has not yet been developed. The simplest and most popular is alphanumeric marking.

High-quality carbon steels are marked using the letter “U” and a two-digit numerical value (in hundredths%) of the level of carbon in their composition (U11). In the grade of ordinary carbon steels, the letter is followed by a number indicating the amount of carbon in tenths of% - U8.

Letters are also used in marking alloy steels. They indicate the main element used for alloying. The following figure shows the concentration of this element in the steel composition. The letter is preceded by a number corresponding to the proportion of carbon in the metal in hundredths of a percent.

For example, the letter “A” at the end of a high-quality alloy mark indicates its quality. The same letter in the middle of the mark notifies the main alloying element, in this case it is nitrogen. The letter at the beginning of the stamp indicates that this is automatic steel.

The letter “Ш” at the end of the marking, written through a hyphen, indicates that this is an especially high-quality alloy. High-quality steels are not marked with the letters “A” and “W”. In addition, there are additional markings indicating the special characteristics of steels. For example, magnetic alloys are marked with the letter “E”, and electrical alloys with the letter “E”.

Alphanumeric marking is perhaps one of the simplest and most understandable for the consumer. Others, more complex, are available only to specialists.

(4 5,00 out of 5)

Source: https://samastroyka.ru/stal.html

Steel 9xs: decoding of the grade and chemical composition, characteristics and hardening technologies, scope of application - Machine

Seeing the marking “9ХС”, we understand that we are dealing with steel with a 0.9 percent carbon content, as well as the presence of chromium and silicon. The increased content (up to 1.5%) of the last two elements allows us to classify this alloy as alloyed, which determines a whole set of additional characteristics that are not characteristic of conventional carbon steels.

Percentage content of chemical elements in tool alloy steel 9xc:

• Fe – about 94%
• Cr – 0.95-1.25%
• Si – 1.2-1.6%
• C – 0.85-0.95%
• Mn – 0.3-0.6%
• Cu – no more than 0.3%
• V – no more than 0.15%
• Mo – no more than 0.2%
• W – no more than 0.2%
• Ni – no more than 0.35%
• S – no more than 0.03%
• P – no more than 0.03%
• Ti – no more than 0.03%

This composition makes 9ХС steel insensitive to the formation of flakes - areas with insufficient strength characteristics, where cracks often occur.

At the same time, this alloy is actively used in the creation of forged products, and often becomes a material for welding work (resistance spot welding only).

Alloy steel 9xs: application

This alloy is popular among knife makers, who use a hammer to hammer the metal to shape it into the desired shape. These products are not initially sharpened, since the cutting edge is brought “to zero” through a normal descent. By the way, similar technology is used to create straight razors.

The finished knife cannot be called universal, since its edge is characterized by some fragility. However, it is an ideal light cutting tool, so it is great for cutting meat, for example.

The main purpose of 9xc alloy steel is the industrial production of dies, taps, drills, reamers, cutters and other tools operating in cold conditions. Alloy 9xc is also suitable for the production of critical parts that are subject to increased requirements for torsional and bending strength, wear resistance, elasticity, and contact loading.

Characteristics, GOST standards and hardening of tool alloy alloy 9xs

The main mechanical and physical properties of steel can be found in the following tables:

Alloy steel 9xc with a high content of silicon and chromium is supplied in the form of traditional shaped rolled products:

• forged blanks - GOST 1133-71 and 5950-2000
• stripes - GOST 4405-75 and 5950-2000
• calibrated rods - GOST 8559-75, 7417-75, 8560-78, 5950-2000

Source: https://regionvtormet.ru/metally/stal-9hs-rasshifrovka-marki-i-himicheskij-sostav-harakteristiki-i-tehnologii-zakalki-oblast-primeneniya.html

Steel structure. Chemical, mechanical and physical properties

“Iron is not only the basis of the whole world, the most important metal of the nature around us,

it is the basis of culture and industry, it is an instrument of war and peaceful labor.”

 A.E.Fersman

Everyone knows that steel is the most important tool and structural material for all industries.

The metallurgical industry of Ukraine has more than 50 metallurgical plants and is strategically important for the country. Ukraine produces a wide range of rolled metal products, such as: rebar, circles, squares, rods, wires, strips, angles, beams, channels, sheets, pipes and hardware.

Steel

Considering this issue, let's start with the chemical composition.

Steel is a compound of iron (Fe) + carbon (C) + other elements dissolved in iron.

Iron in its pure form has very low strength, and carbon increases it.

Carbon improves some other indicators:

• hardness,
• elasticity,
• wear resistance,
• endurance.

 “Fe” in steel should be at least 45%, “C” - no more than 2.14% - theoretically, but in practice the % carbon concentration has the following range of values:

• Low carbon steels - 0.1-0.13%
• Carbon steels 0.14-0.5%
• High carbon – from 0.6%

The higher the percentage of carbon content in steel, the higher its strength and the lower its ductility. CARBON is a non-metallic element. Its density is 2.22 g/cm3, and melts at t -3500 °C. In nature, it is present in 2 polymorphic modifications - graphite (stable modification) and diamond (metastable modification), and in an alloy with iron:

• in free - graphite (in gray cast iron),
• when bound, it is a solid state - cementite.

Carbon in combination with iron is in the state of cementite , i.e. in a chemical bond with iron (Fe3C). The structure of cementite can be very different, and it depends on the formation process, carbon content and heat treatment methods.

Carbon is present in a free state in gray cast iron (GC), in the form of graphite. Gray cast iron has a porous metal structure and is very brittle; Cracks easily appear on it (especially during the welding process).

Chemical composition of carbon steels of ordinary quality (GOST 380-71)

Iron-carbon system

The structure of steel is studied using the state diagram of the iron-carbon system. It characterizes the structural transformations of steel and expresses the dependence of the structural state on temperature conditions and chemical composition.

State diagram of the iron-carbon system

The phase diagram contains critical points that are very important theoretically and practically for steel heat treatment processes and their analysis. Using the Fe-C diagram, you can determine the type of heat treatment, the temperature range of structure changes and predict the microstructure.

Steel structures

Iron-carbon alloys at different temperatures and different “C” contents have different structures and, accordingly, physical and chemical properties. One of these conditions is the cementite described above. And now about them:

Austenite – a solid carbon structure in gamma iron – contains “C” up to 1.7% (t > 723° C). As the temperature decreases, austenite decomposes into ferrite and cementite, and a lamellar structure—pearlite—appears.

Ferrite is a solid solution of “C” in α-iron - at t> 723-768°C, the concentration of “C” is 0.02%, and at t 20°C about 0.006% “C”. It is very plastic, not hard and has low magnetic properties.

Cementite is iron carbide Fe3C. Concentration "C" 6.63%. Cementite is brittle and its hardness is HB760-800.

Pearlite is a mechanical mixture of ferrite and cementite, formed during gradual cooling during the decomposition of austenite. Based on the size of the cementite particles, perlite has different mechanical properties. "C" -0.8%.

Ledeburite (cast iron structure) is a mixture formed from the crystallization of a liquid alloy of cementite and austenite. Ledeburite is very hard, but brittle. Concentration "C" -4.3%

Properties of steel

Of course, it is not only carbon that affects the properties of steel. The composition of additional elements and their quantity impart certain properties to steel. Impurities can be beneficial or harmful. Good impurities affect exclusively the crystals themselves, while harmful impurities negatively affect the connection of crystals with each other. Good impurities include: manganese (Mn), silicon (Si). The bad ones: phosphorus (P), sulfur (S), nitrogen, oxygen and others.

Physical and mechanical properties of steel

The main physical properties of steel are:

• heat capacity;
• thermal conductivity;
• elastic modulus.
• The concept of elastic modulus of steel (E) is the ratio of a solid to deform elastically when subjected to a force. This characteristic directly depends on stress, or more precisely, it is a derivative of the ratio of stress to elastic deformation.
•  shear modulus (shear elasticity) (G) – a value measured in Pascals (Pa), which determines the elastic properties of a body or material and their ability to resist shear deformations. It is used to calculate shear, shear, and torsion.
•  coefficient of linear and coefficient of volumetric expansion with a change in temperature is a value showing the relative change in the linear dimensions or volume of a material or body with increasing temperature at a constant pressure.

The main mechanical properties of steel are:

• strength
• hardness
• plastic
• elasticity
• endurance
• viscosity

Indicators of mechanical properties of carbon steels of ordinary quality (GOST 380-71)

The main chemical properties of steel are:

•  oxidation state
•  corrosion resistance
•  heat resistance
•  heat resistance

The quality of steel is determined by various indicators of all its properties and structure. The properties of products made from this steel are also taken into account.

According to the quality of steel, they are divided into:

• ordinary quality,
• quality steel,
• high quality steel.

In this article we consider only the structure of steel and related concepts. The quality of steel, the composition of additional impurities and their properties will be discussed in the next publication.

Source: https://vikant.com.ua/news/chto_takoe_stal

How to determine the composition of steel

Steel is a deformable (malleable) alloy of iron with carbon (up to 2.14%) and other elements. It is obtained mainly from a mixture of cast iron and steel scrap in oxygen converters, open-hearth furnaces and electric furnaces. An alloy of iron and carbon containing more than 2.14% carbon is called cast iron.

99% of all steel is a structural material in the broad sense of the word: including steel for building structures, machine parts, elastic elements, tools and for special working conditions - heat-resistant, stainless steel, etc.

Its main qualities are strength (the ability to withstand sufficient stress during operation), plasticity (the ability to withstand sufficient deformation without destruction both during the production of structures and in places of overload during their operation), viscosity (the ability to absorb the work of external forces, preventing the spread of cracks), elasticity , hardness, fatigue, crack resistance, cold resistance, heat resistance.

For the manufacture of bearings, chromium ball bearing steels ShKh15 and ShKh15SG are widely used. Ball bearing steels have high hardness, strength and contact endurance.

Springs, leaf springs and other elastic elements work in the area of ​​elastic deformation of the material. At the same time, many of them are subject to cyclic loads. Therefore, the main requirements for spring steels are to ensure high values ​​of elasticity limits, fluidity, endurance, as well as the necessary ductility and resistance to brittle fracture (55S2, 60S2A, 50KhFA, 30Х13, 03Х12Н10Д2Т).

High-strength steels have high strength with sufficient ductility (medium-carbon alloy steel 40ХН2МА), high structural strength, low sensitivity to cuts, high resistance to brittle fracture, low cold brittleness threshold, and good weldability.

Classification of steels and alloys is made:

• by chemical composition;
• by structural composition;
• by quality (by production method and content of harmful impurities);
• by the degree of deoxidation and the nature of solidification of the metal in the mold;
• as intended.

Chemical composition
According to the chemical composition, carbon steels are divided depending on the carbon content into the following groups:

• low-carbon - less than 0.3% C;
• medium carbon - 0.3. 0.7% C;
• high carbon - more than 0.7% C.

• low alloyed - less than 2.5%;
• medium alloyed - 2.5. 10%;
• highly alloyed - more than 10%.

Structural composition
Alloy steels and alloys are also divided into classes according to their structural composition:

• in the annealed state - hypoeutectoid, hypereutectoid, ledeburite (carbide), ferritic, austenitic;
• in a normalized state - pearlitic, martensitic and authenite.

The pearlitic class includes carbon and alloy steels with a low content of alloying elements, the martensitic class - with a higher content, and the austenitic class - with a high content of alloying elements.

Classification of steel by impurity content

According to quality, that is, according to the method of production and the content of impurities, steels and alloys are divided into four groups.
Classification of steels by quality

Group	S, %	R, %
Ordinary quality (ordinary)	less than 0.06	less than 0.07
Quality	less than 0.04	less than 0.035
High quality	less than 0.025	less than 0.025
Particularly high quality	less than 0.015	less than 0.025

Ordinary quality steel

Steels of ordinary quality (ordinary) in chemical composition are carbon steels containing up to 0.6% C. These steels are smelted in converters using oxygen or in large open-hearth furnaces.
Examples of these steels are STO, StZsp, St5kp steels. Ordinary quality steels, being the cheapest, are inferior in mechanical properties to steels of other classes.

High quality steel

High-quality steels in terms of chemical composition can be carbon or alloyed (08kp, 10ps, 20). They are also smelted in converters or in main open-hearth furnaces, but subject to more stringent requirements for the composition of the charge, melting and casting processes.

Carbon steels of ordinary quality and high-quality ones, according to the degree of deoxidation and the nature of solidification of the metal in the mold, are divided into calm, semi-quiet and boiling. Each of these varieties differs in the content of oxygen, nitrogen and hydrogen.

So boiling steels contain the largest amount of these elements.

High quality steel

High-quality steels are smelted primarily in electric furnaces, and especially high-quality steels are smelted in electric furnaces with electroslag remelting (ESR) or other advanced methods, which guarantees increased purity of non-metallic inclusions (sulfur and phosphorus content less than 0.03%) and gas content, and therefore improved mechanical properties. These are steels such as 20A, 15Х2МА.

Extra high quality steel

Particularly high-quality steels are subjected to electroslag remelting, which ensures effective purification from sulfides and oxides. These steels are smelted only alloyed. They are produced in electric furnaces and using special electrometallurgy methods. Contain no more than 0.01% sulfur and 0.025% phosphorus. For example: 18ХГ-Ш, 20ХГНТР-Ш.

Classification of steel by purpose

According to their purpose, steels and alloys are classified into structural, tool and steels with special physical and chemical properties.

Structural steels

Structural steels are usually divided into construction steels, cold forming steels, cemented steels, improveable steels, high-strength steels, spring steels, ball bearing steels, automatic steels, corrosion-resistant steels, heat-resistant steels, heat-resistant steels, and wear-resistant steels.

Construction steels

Construction steels include carbon steels of ordinary quality, as well as low-alloy steels. The main requirement for construction steels is their good weldability. For example: S255, S345T, S390K, S440D.

Cold forming steels

For cold stamping, rolled sheets of low-carbon high-quality steel grades 08Yu, 08ps and 08kp are used.

Case-hardened steels

Case-hardened steels are used for the manufacture of parts that operate under conditions of surface wear and experience dynamic loads. Cementable steels include low-carbon steels containing 0.1-0.3% carbon (such as 15, 20, 25), as well as some alloy steels (15Х, 20Х, 15ХФ, 20ХН 12ХНЗА, 18Х2Н4ВА, 18Х2Н4МА, 18ХГТ, ЗОХГТ, 20ХГР).

Improved steels

Improved steels include steels that are subjected to improvement - heat treatment, which consists of hardening and high tempering. These include medium-carbon steels (35, 40, 45, 50), chromium steels (40Х, 45Х, 50Х), chromium steels with boron (ZOXRA, 40ХР), chromium-nickel, chromium-silicon-manganese, chromium-nickel-molybdenum steels.

High strength steels

High-strength steels are steels in which, by selecting the chemical composition and heat treatment, a tensile strength approximately twice that of conventional structural steels is achieved. This level of strength can be obtained in medium-carbon alloy steels - such as ZOKHGSN2A, 40KHN2MA, ZOKHGSA, 38KHNZMA, OZN18K9M5T, 04KHIN9M2D2TYU.

Spring steels

Spring (spring) steels retain elastic properties for a long time, since they have a high elastic limit, high resistance to fracture and fatigue. Spring steels include carbon steels (65, 70) and steels alloyed with elements that increase the elastic limit - silicon, manganese, chromium, tungsten, vanadium, boron (60S2, 50KhGS, 60S2KhFA, 55KhGR).

Bearing steels

Bearing (ball bearing) steels have high strength, wear resistance, and endurance. Bearings are subject to increased requirements for the absence of various inclusions, macro- and microporosity. Typically, ball bearing steels are characterized by a high carbon content (about 1%) and the presence of chromium (ShKh9, ShKh15).

Automatic steels

Automatic steels are used for the manufacture of non-critical mass-produced parts (screws, bolts, nuts, etc.) > processed on automatic machines.

An effective metallurgical technique for increasing cutting machinability is the introduction of sulfur, selenium, tellurium, and lead into steel, which promotes the formation of short and brittle chips and also reduces friction between the cutter and the chips.

The disadvantage of free-flowing steels is reduced ductility. Automatic steels include steels such as A12, A20, AZO, A40G, AS11, AS40, ATs45G2, ASTSZOKHM, AS20KhGNM.

Source: http://schemy.ru/info/kak-opredelit-sostav-stali/

Determine metal by chemical composition

· 09.09.2019

In practice, to approximately determine the chemical composition or grade of steel, they often resort to spark testing of metals. In this case, you can quickly determine the chemical composition of steel (carbon content in it) without performing any chemical analyzes in the laboratory.

To do this, a sample of the steel being tested must be processed on an emery wheel in a darkened room. By the color of the sparks, by the shape and length of the spark filaments, by the shape of the beam (Table 4.2), the grade of steel is judged, comparing them with the nature and color of the sparks of well-known grades of steel (see color insert).

Determination of the chemical composition of steel using the express method

Spark beam color and characteristics

Mild low carbon steel (grades 10, 15)

Light yellow smooth lines of light, oblong drop-shaped sparks

Carbon steel (0.5% C)

Light yellow light stripes branching with occasional formation of small stars

Carbon tool steel (0.9% C)

Light yellow sparks with numerous radiant stars

Hard carbon tool steel (1.2% C)

Bright bunches of sparks consisting of light yellow stars that often separate

Manganese steel (10-14% Mn)

White-yellow bright beams of rays, strongly branching perpendicular to the lines of sparks

High Speed ​​Steel (10% W, 4% Cr, 0.7% C)

Dark red broken lines of sparks, divided into lighter stars

Tungsten steel (1.3% W)

Isolated dark red lines of sparks separating into lighter yellow stars

Long light yellow lines of light ending in drops are separated by bunches of white-yellow sparks

Dark yellow light beam separated by reddish lines of sparks with spherical ends

Chrome-nickel structural steel (3-4% Ni, 1% Cr)

Yellow oblong, drop-shaped lines of sparks with separating tufts of spikes

5.1. Basic information about the crystalline structure of metallic bodies

The study of the structure and properties of metals and their alloys is the science of metallurgy, the founder of which, as mentioned above, is the Russian scientist D.K. Chernov.

Scientists have found that all metals used in technology in the solid state have a crystalline structure, in particular, D.K. Chernov in 1878 first presented a scheme for the formation of the crystalline structure of steel. He established that the process of metal crystallization occurs in two stages:

1. Formation of crystallization centers (nuclei).

2. Growth of crystals from these centers.

First, the primary or main axes of the crystals grow, and then the axes of the upper orders (second, third, etc.) grow perpendicular to them (Fig. 5.1).

Such crystals resemble wood in appearance and are called dendrites (from the Greek for “tree”). During the growth process, the crystals move towards each other and at a certain moment join each other, as a result of which they acquire the appropriate shape. Such crystals are called grains (Fig. 5.2). The size and number of grains at the end of crystallization depend on the rate of nucleation and growth of crystals.

A characteristic feature of the crystalline structure of metallic bodies is the correct arrangement of their atoms in space, constituting a unique spatial atomic-crystalline lattice, which determines their special properties. The simplest elementary crystalline cell is considered to be cubic, the size of which is determined by the distance between atoms ( a is the length of the cube edge) equal to 1A 0 (angstrom); 1A 0 =1·10 -8 cm=1·10 -10 m.

Rice. 5.1. Crystal growth diagram

Source: https://vi-pole.ru/opredelit-metall-po-himicheskomu-sostavu.html

Chemical analysis of steel. Execution methods and results

In metallurgy, important attention is paid to the quality of steel. Various procedures help determine quality characteristics, one of which is chemical analysis of steel, carried out in accordance with state standards.

The purpose of this study is to identify harmful impurities, chemical heterogeneity of composition, and the presence of non-metallic inclusions.

Identifying the composition of steel is necessary not only to determine its quality, but also in order to correctly carry out further processing of the steel and determine its purpose for various products.

Methods of execution

The analysis of the chemical composition of steel is carried out not in the entire mass of steel being smelted, but in test materials taken separately for research. During the next melting, a sample is taken, from which the characteristics for the rest of the batch are determined. Based on this, documentation is drawn up confirming the chemical composition of the steel.

The samples taken are poured into special cast iron glasses, where the steel hardens. After this, it is drilled in the middle or planed to obtain steel filings, with which the composition analysis procedure is carried out. When drilling, do not use files, the rebound particles of which can affect the composition of the resulting material. The results of such a study are recorded in a certificate issued for the steel of a given heat.

The main difficulty of the procedure is that steel in liquid and solid form differs in composition. Therefore, it is important to observe one condition: the transition from a liquid to a solid state must be very fast. In this case, the research results will be reliable.

Modern methods of chemical analysis are emission and x-ray fluorescence. Emission spectrometers are special instruments that determine the quantitative composition of elements in steel. The permissible error of such studies is reduced to a minimum. Another method uses an X-ray tube that reacts to energetic photons from each metal. These modern methods are simple, accurate and do not require careful and complex sample preparation.

Research results

The purpose of the study is to determine the chemical elements that make up steel and their percentage relationship to each other. To determine the content of each of them, separate procedures are used, during which the composition of the steel of a particular melt is determined.

Researchers experimentally obtain information about the content of carbon, sulfur, manganese, silicon, nickel, phosphorus, chromium, aluminum, tungsten, and molybdenum in a steel sample.

Process Features

One of the features of this study is the variety of methods for analysis. As a result, results in different countries may vary greatly. In order to avoid this in domestic steel production, there are state standards that define a set of techniques. Each study is provided with detailed recommendations: from the choice of instruments to maintaining the exact temperature and time of heating the test materials.

Another important feature is careful attention to the selection of a sample for analysis and strict adherence to all recommendations in this matter. Only specialists in this field can prepare the sample.

The purpose of analyzing the chemical composition of steel

Steel is analyzed in order to determine the quantitative and qualitative content of its elements. This is necessary to control the quality of the resulting metal during its recycling, and to assign a steel grade.

This technique is used not only during steel production, but also to determine the quality of the metal offered to you, to identify unidentified metal in the warehouse, to determine the suitability of a given type of steel for various purposes. This method also helps to improve the quality characteristics of steel, for example, increasing the amount of chromium to 10% makes the metal stainless.

Therefore, the demand and usefulness of analyzing the chemical composition of steel is obvious and is widely used in metallurgical production and in the steel trading market.

Source: http://specural.com/articles/12/himicheskiy-analiz-stali-sposoby-vypolneniya-i-rezultaty.html