How is gray cast iron marked?

Gray cast iron products

An alloy of iron containing carbon is called cast iron. In some cases, alloying additives are added to the composition, affecting its consumer qualities. Cast iron is a metal that is used primarily in ferrous metallurgy. It is not only used to produce steel, it is also in demand in the manufacture of forged artistic parts.

Gray cast iron

For mechanical engineering, gray cast iron containing graphite is mainly used. Parts made from such material do not react to stresses; they absorb vibrations that occur when mechanisms vibrate. Critical parts are made from it

1. Bushings;
2. Machine beds;
3. Heavy bases.

It began to be used as a structural material in almost all enterprises of the mechanical engineering industry. The following industries became the largest consumers of gray cast iron

1. Automotive industry;
2. Machine tool industry;
3. Metallurgy;
4. Sanitary.

Tractor parts made from gray cast iron reach 20% of the total number of parts. This use of this alloy is associated with high wear resistance. It does not lift up in case of high friction and lack of lubrication, in other words, it has damping ability . It is made from:

1. Blocks;
2. Bearing caps;
3. Brake discs;
4. Ferrado;

To manufacture the cylinder head of various engines, of low-alloy alloy :

The main requirements for the midrange during the production of liners were:

1. Pearlite structure;
2. Graphite;
3. High hardness.

For car engines of any design, cylinder liners made of a special alloy are used. In most cases, its phosphorous fraction is used.

https://www.youtube.com/watch?v=Wj3yX7R9dE4

Diesel engines during operation create a large load on the cylinder block , so alloy cast iron is used for them. Cylinder heads are made from high carbon alloy grades,

The same requirements are observed in the manufacture of liner castings, the material of which is a low-alloy alloy. The chemical composition of this material depends on several technological characteristics:

1. Melting method;
2. Casting dimensions;
3. Manufacturability of form.

Cars are equipped with cast iron camshafts, which are highly wear-resistant. This parameter is achieved thanks to surface hardening to which the metal is subjected.

When a part is operated at high speeds, when dry friction occurs, it is necessary to have increased wear resistance of the material and a high coefficient of friction. It is in such conditions that this alloy is simply irreplaceable.

Brake drums operating in such conditions are made from SCh20. When a part experiences high loads and thermal cracks may appear, a special heat-resistant alloy with a high carbon content and a high level of alloying is used.

For particularly severe conditions, parts made of pearlitic cast iron are installed. It contains vermicular graphite.

The rotation of the flywheel during operation reaches 7000 rpm. This speed causes tensile stresses to appear. The rotating surface of the flywheel constantly touches the working surface of another part. Such friction causes a strong release of heat, resulting in thermal cracks that negatively affect the strength of the part.

To increase strength , given the large weight of the flywheel and the size of its cross-section, it is made from various grades:

It must provide a workpiece strength above 250 N/mm2. Sometimes SCh 35 has strength that is not enough to ensure normal operation of the flywheel. In this case, cast iron is used, to which nodular graphite is added.

Passenger cars boast cast iron caps covering the main bearings . This design is found in most cases on cars with a carburetor engine. To ensure a pearlite structure, as well as high hardness exceeding 200 HB, SCh25 is used for the manufacture of bearing caps.

Manufacturing of collectors

In a car, the exhaust manifolds are exposed to exhaust gases, the temperature of which reaches 90 degrees. Collectors under the influence of an aggressive environment oxidize, deform and crack.

The use of gray cast iron ensures durability of such parts and high efficiency. Due to the fact that the thickness of the collector walls is very small, less than 7 mm, SCh15 is used for their manufacture. To increase its heat resistance, cast iron is alloyed with chromium or nickel additives.

For the manufacture of collectors experiencing high thermal loads, the following is used:

1. Ductile iron;
2. With additives of spherical graphite;

All of the above materials have high heat resistance and resistance to aggressive environments, alkalis and oxides.

Machine tool industry

In the machine tool industry, a large number of cast parts are made from gray cast iron, operating in various conditions, the weight of which can reach 100 tons , with a maximum wall thickness of 200 millimeters.

The classification of such cast parts in the machine tool industry, depending on the designs and the operating conditions created, corresponds to the current standard.

For each part, a special grade of cast iron is selected . It depends on the following parameters:

1. Class of the workpiece;
2. Wall thickness;
3. Hardness;
4. Microstructures.

  How to distinguish cast iron from steel visually?

Considering the specifics of many machine-tool parts, which work mainly on rigidity, for their manufacture they prefer to use cast iron, which has increased hardness and fairly low ductility.

The chemical composition of such cast irons is high in manganese and low in carbon. To obtain high hardness of cast iron, alloying and other technological processes are used.

SSP blanks are widely used in metallurgical equipment:

1. Sheet rolls;
2. Molds;
3. Slag bowls.

Plumbing

A lot of cast iron products are used in plumbing. Made from cast iron:

1. Heating radiators;
2. Pipes;
3. Fitting;
4. Sinks;
5. Kitchen sinks.

And today cast iron bathtubs remain in demand, which are distinguished by high strength , durability and reliability. Such products can be used for decades. They retain their original appearance and do not require replacement.

Craftsmen make artistic masterpieces from cast iron. For example, the embankments of St. Petersburg are decorated with cast iron parts. Walking along the streets of the city you can see openwork gates and original cast-iron fences. In the parks you can see cast iron monuments.

Application of Ductile Iron

This material has excellent damping properties and is capable of excellent performance at very low temperatures. This type of cast iron is used in the production of critical parts for tractors, as well as cars, which will have to perform their work in difficult climatic conditions.

Parts made of malleable cast iron have also found their application in the electrical industry . It is made from:

1. Terminals;
2. Insulator hooks;
3. Wire holders.

Such products cope well with force loads; they can bend under mechanical stress.

In textile engineering , ductile iron is used in the manufacture of:

1. Gears;
2. Forks
3. Spokes;
4. Parts for paper spinning machines.

In other words, for parts experiencing large static loads, subject to friction and rapid wear. For such products, anti-friction malleable cast iron is used, which is capable of creating minimal friction where there is maximum contact between the parts.

Source: https://varimtutru.com/izdeliya-iz-serogo-chuguna/

Malleable iron

Cast iron is an alloy of iron and carbon (>2.14%). The most commonly used cast irons contain about 4% C, silicon - 0.5-4.5%, manganese -0.2-1.5%. If we take into account the color of the metal structure at the fracture, then it can be imagined as gray and white.

In gray, carbon is contained both in free form (graphite) and in chemically bound form (cementite). The latter is characterized by high hardness and fragility.

In white - C is almost completely in a bound state, therefore white cast iron is also characterized by increased hardness.

Features of malleable cast iron

To obtain the required mechanical qualities and corresponding structure, malleable cast iron is produced from white cast iron by heat treatment - annealing or simmering in sand at 800-850°C. In this case, cementite disintegrates, and part of the carbon is released in a free state, i.e. in the form of graphite. Hence its special viscosity and plasticity. The process of cementite decomposition and graphite formation is accelerated by the use of additives in the form of aluminum and boron.

Thus, malleable cast iron is a modified metal. Its modification continues in the process of subsequent (pearlitic or ferritic) cooling with the addition of manganese, chromium and other additives.

The pearlite structure gets its name from mother-of-pearl (shine is visible under optical magnification) and is a mixture of ferrite and cementite plates.

Malleable cast iron with this structure is distinguished by high hardness (235305 HB) and strength (Stb = 650800 MPa), but insignificant ductile properties.

With ferritic long-term (25-30 hours) cooling, cast iron is obtained with more significant ductile qualities, but relatively low strength (Stm = 370300 MPa).

Marking of malleable cast irons

According to the recommendation of GOST 1215-79, the marking of malleable cast iron contains the first letters of its name - KCH. The two numbers following them reflect temporary resistance, in other words, resistance to destruction and deformation - KCH30. The third refers to relative elongation - the amount of plastic deformation of the material during stretching, and is indicated as a percentage - KCh30-6.

In addition, grades of malleable cast iron have a gradation depending on the structure. Thus, the class of ferritic or ferrite-pearlite includes grades KCH 30-6; CC 33-8; CC 35-10; CC 37-12.

The pearlite structure is presented in malleable cast iron grades: KCh 45-7; CC 50-5; CC 55-4; CC 60-3; CC 65-3; CC 70-2; CN 80-1.5.

GOST 26358 regulates the mechanical properties of ductile cast iron grades: tensile strength, Brinell hardness HB, relative elongation.

Deviation is allowed only in the amount of plastic deformation of no more than 1%, and then only by agreement with the consumer.

Malleable cast iron: application

The technological and mechanical qualities of malleable cast iron are such that they allow it to be used for the production of a variety of parts: from the smallest to those weighing several tons that can withstand shock and vibration loads: flanges, crankcases, hubs, etc. In short, malleable cast iron is a wide range of nomenclature for the automotive and mechanical engineering industries , shipbuilding, electrical industry, machine tool industry, etc.

Source: https://fx-commodities.ru/articles/kovkij-chugun/

1.2. Classification and marking of cast iron

Depending on the state of carbon in cast iron, there are: white, gray, high-strength, malleable cast iron and cast iron with vermicular graphite.

White cast irons are those in which all the carbon is in a bound state in the form of cementite (iron carbide).

In other types of cast iron (gray, high-strength, malleable, with vermicular graphite), carbon is largely or completely in a free state in the form of graphite.

In gray cast iron - in a lamellar or worm-shaped form; in high-strength ones - in a spherical form, in malleable ones - in a flake form. Cast irons with vermicular graphite have two forms of graphite - spherical (up to 40%) and vermicular (in the form of small thin veins).

Cast irons are marked with two letters indicating the type of cast iron and two numbers corresponding to the minimum value of tensile strength σв in MPa·10-1 . Gray cast iron is designated by the letters “SCh” (GOST 1412-85), high-strength - “VCh” (GOST 7293-85), malleable - “KCh” (GOST 1215-85), cast iron with vermicular graphite - ChVG (GOST 28384-89) :

SCh 10 - gray cast iron with a tensile strength of 100 MPa;

HF 70 - high-strength cast iron with a tensile strength of 700 MPa;

KCh 35 - malleable cast iron with a tensile strength of 350 MPa;

ChVG 40 – cast iron with vermicular graphite with a tensile strength of 400 MPa.

There are also cast irons with special properties:

1. anti-friction cast irons (GOST 1585-85) – are designated by the first letters АЧ and a serial number, for example,

AChS-1 – anti-friction gray cast iron with serial number grade 1;

AChV-2 – anti-friction high-strength cast iron with serial number grade 2;

AChK-2 – anti-friction malleable cast iron with serial number grade 2;

1. heat-resistant cast irons (GOST 7769 - 82) - are designated by the letters ZhCh, followed by the letter designation of alloying elements (N - nickel, D - copper, etc., similar to the designation of alloying elements in steel) and numbers indicating the concentration of elements in %%; For example,

ZhChKh-2.5 – heat-resistant chromium cast iron with a chromium content of 2.5%;

ZhChS-5.5 – heat-resistant cast iron alloyed with silicon with a content of 5.5%;

2.1. Aluminum and aluminum alloys

Aluminum is a silver-white metal when fractured, lightweight (has a low density of 2.7 g/cm3), has high thermal and electrical conductivity, is resistant to corrosion, ductile, can be easily processed by plastic deformation methods, can be welded well by all types of welding, is difficult to weld cutting processing (low strength).

Depending on the degree of purity, aluminum according to GOST 11069-74 can be special (A999), high (A995, A95) and technical purity (A85, A7E, AO, etc.).

Aluminum is marked with the letter “A” and numbers indicating fractions of a percent above 99.0% aluminum. The letter "E" denotes high iron content and low silicon content.

Examples:

A999 - high purity aluminum, which contains at least 99.999% aluminum;

A5 is technical purity aluminum, which contains 99.5% aluminum. Aluminum alloys are divided into wrought and cast alloys . Both of them may not be hardened or hardened by heat treatment .

Deformable aluminum alloys are well processed by rolling, forging, and stamping. Their brands are given in GOST 4784-74. Deformable aluminum alloys that cannot be strengthened by heat treatment include alloys of the aluminum-manganese (Al-Mn) and aluminum-magnesium (Al-Mg) systems: AMts; AMg1; AMg4.5; AMg6. The abbreviation includes the initial letters of the alloy components and numbers indicating the content of the alloying element as a percentage.

Deformable aluminum alloys that are strengthened by heat treatment include alloys of the Al-Cu-Mg system with the addition of certain elements (duralumins, forging alloys), as well as high-strength and heat-resistant alloys of complex chemical composition. Duralumins are marked with the letter “D” and a serial number, for example: D1, D12, D18, AK4, AK8.

Pure deformable aluminum is designated by the letters “AD” and a symbol for the degree of its purity: ADOch (not less than 99.98% Al), ADOOO (not less than 99.80% Al), ADO (99.5% Al), AD1 (99, 30% Al), blood pressure (not less than 98.80% Al).

Cast aluminum alloys (GOST 2685-75) have good fluidity, have relatively little shrinkage and are intended mainly for shaped casting. These alloys are marked with the letters “AL” followed by a serial number: AL2, AL9, AL13, AL22, ALZO.

Sometimes they are marked by composition: AK7M2; AK21M2.5N2.5; AK4MC6. In this case, "M" stands for copper. “K” - silicon, “C” - zinc, “N” - nickel; number is the average % content of the element.

Bearings and liners are made from aluminum antifriction alloys (GOST 14113-78), both by casting and by pressure treatment. Such alloys are marked with the letter “A” and the initial letters of their constituent elements: A09-2, A06-1, AN-2.5, ASMT. The first two alloys contain the indicated amount of tin and copper (the first number is tin, the second is copper in %), the third - 2.7-3.3% Ni and the fourth - copper, antimony and tellurium.

Source: https://studfile.net/preview/1755859/page:2/

Designation of cast iron

Today, in mechanical engineering, ferrous rather than non-ferrous metals and alloys are most often used, and among them the leading places are occupied by steel and cast iron.

Cast iron is an alloy of iron and carbon, in which the content of the latter exceeds 2%. In addition to it, cast iron also contains impurities such as phosphorus, sulfur, manganese and silicon. However, some of them have an adverse effect on the properties of the material.

According to the current classification, all cast irons are divided into gray and white, as well as high-strength and malleable. In addition, they are alloyed and anti-friction.

Modern Russian standards provide for a designation system for cast iron, which makes it quite easy to determine its type. For example, gray cast iron has the letter marking SCh, malleable - KCh, anti-friction - AChS, and high-strength - HF.

White cast iron

This alloy is formed after cast iron is poured into a mold and then cooled quickly. Its distinctive feature is that it contains either little silicon or a lot of manganese, and as for the physical characteristics, they should include increased hardness and fragility. In most cases, white cast iron is used to subsequently smelt steel.

Malleable iron

This type of cast iron is the result of long-term technological firing of white cast iron. The fracture of malleable cast iron has a characteristic silver-white color, and as for the characteristics of this material, it should include a very high degree of hardness, due to which it is practically not subject to machining.

The structure of malleable cast iron changes during the modification process. Upon completion, the strength of this material becomes almost identical to the strength of steel, but the brittleness does not decrease. It is possible to achieve a greater degree of toughness in malleable cast iron during the modification process by adding some small amount of magnesium to it.

This allows us to obtain the so-called high-strength cast iron.

Examples of symbols

SCH 15 GOST 1412–85

SCh 15 – grade of gray cast iron.

HF 50 GOST 7293–85

HF 50 is a grade of high-strength cast iron.

Casting KCh 30–6–F 1215–79

KCh 30–6 – grade of malleable cast iron;

F – ferritic class.

Casting KCh 60–3–P 1215–79

KCh 60–3 – grade of malleable cast iron;

P – pearlite class.

Source: http://gk-drawing.ru/plotting/pig-iron.php

GOST 1412-85 cast iron with flake graphite for castings. stamps, GOST dated September 24, 1985 No. 1412-85

GOST 1412-85Group B11

MKS 77.080.10

OKP 41 1120

Date of introduction 1987-01-01

By Decree of the USSR State Committee for Standards dated September 24, 1985 N 3009, the introduction date was set at 01.01.

87

The validity period was lifted according to Protocol N 7-95 of the Interstate Council for Standardization, Metrology and Certification (IUS N 11-95)

INSTEAD GOST 1412-79 regarding cast iron grades

REISSUE

This standard applies to cast iron with flake graphite for castings and establishes its grades, determined on the basis of the tensile strength of cast iron.

1. BRANDS

1.1. For the manufacture of castings, the following grades of cast iron are provided: SCh10; SCH15; SCh20; SCh25; SCh30; SCH35.

At the request of the consumer, cast iron grades SCh18, SCh21 and SCh24 are allowed for the manufacture of castings.

1.2. The symbol of the brand includes the letters SCh - gray cast iron and a digital designation of the value of the minimum tensile strength in MPa·10.

Example of a symbol:

SCH15 GOST 1412-85

2. MECHANICAL PROPERTIES

2.1. The tensile strength of cast iron in the cast state or after heat treatment must correspond to that indicated in the table.

Cast iron grade	Cast iron grade according to ST SEV 4560-84	Tensile strength, MPa (kgf/mm), not less
SCH10	31110	100 (10)
SCH15	31115	150 (15)
SCH18	—	180 (18)
SCH20	31120	200 (20)
SCH21	—	210 (21)
SCH24	240 (24)
SCH25	31125	250 (25)
SCH30	31130	300 (30)
SCH35	31135	350 (35)

Note. It is allowed to exceed the minimum value of tensile strength by no more than 100 MPa, unless there are other restrictions in the normative and technical documentation for castings.

The tensile strength of SCh10 cast iron is determined according to consumer requirements.

2.2. The mechanical properties of cast iron in the walls of castings of various sections are given in Appendix 1.

Additional information about the physical properties of cast iron is given in Appendix 2.

The chemical composition is given in Appendix 3.

3. TEST METHODS

3.1. Tensile tests are carried out according to GOST 27208-87 on one sample.

3.2. Hardness determination is carried out according to GOST 27208-87.

3.3. Blanks for determining the mechanical properties of cast iron are cast according to GOST 24648-90.

3.4. When using heat treatment of castings, the workpieces must undergo heat treatment together with the castings to determine the mechanical properties.

It is allowed to use workpieces in a cast state (without heat treatment) when using low-temperature heat treatment to relieve linear stresses in castings.

3.5. If unsatisfactory test results are obtained, repeat tests are carried out on two samples.

The samples are considered to have passed the tests if the mechanical properties of each of them meet the requirements of this standard.

Appendix 1 (for reference). approximate data on temporary tensile strength and hardness in casting walls of various sections

APPENDIX 1
Reference

Cast iron grade	Casting wall thickness, mm
4	8	15	30	50	80	150
Temporary tensile strength, MPa, not less
SCH10	140	120	100	80	75	70	65
SCH15	220	180	150	110	105	90	80
SCH20	270	220	200	160	140	130	120
SCH25	310	270	250	210	180	165	150
SCH30	—	330	300	260	220	195	180
SCH35	—	380	350	310	260	225	205
Hardness NV, no more
SCH10	205	200	190	185	156	149	120
SCH15	241	224	210	201	163	156	130
SCH20	255	240	230	216	170	163	143
SCH25	260	255	245	238	187	170	156
CC30	—	270	260	250	197	187	163
SCH35	—	290	275	270	229	201	179

Notes:

1. The values ​​of tensile strength and hardness in real castings may differ from those given in the table.

2. The values ​​of tensile strength and hardness in a casting wall with a thickness of 15 mm approximately correspond to the same values ​​in a standard workpiece with a diameter of 30 mm.

Appendix 2 (for reference). physical properties of cast iron with flake graphite

APPENDIX 2
Information

Cast iron grade	Density, kg/m	Linear shrinkage, ,%	Tensile modulus of elasticity, 10 MPa	Specific heat capacity at temperatures from 20 to 200 °C, , J (kg K)	Linear expansion coefficient at temperatures from 20 to 200 °C, 1/ °C	Thermal conductivity at 20 °C, , W (m K)
SCH10	6,8·10	1,0	From 700 to 1100	460	8,0·10	60
SCH15	7,0·10	1,1	» 700 » 1100	460	9,0·10	59
SCH20	7,1·10	1,2	» 850 » 1100	480	9,5·10	54
SCH25	7,2·10	1,2	» 900 » 1100	500	10,0·10	50
SCH30	7,3·10	1,3	» 1200 » 1450	525	10,5·10	46
SCH35	7,4·10	1,3	» 1300 » 1550	545	11,0·10	42

Appendix 3 (informative)

APPENDIX 3 Reference

Cast iron grade	Mass fraction of elements, %
Carbon	Silicon	Manganese	Phosphorus	Sulfur
No more
SCH10	3,5-3,7	2,2-2,6	0,5-0,8	0,3	0,15
SCH15	3,5-3,7	2,0-2,4	0,5-0,8	0,2	0,15
SCH20	3,3-3,5	1,4-2,4	0,7-1,0	0,2	0,15
SCH25	3,2-3,4	1,4-2,2	0,7-1,0	0,2	0,15
SCH30	3,0-3,2	1,3-1,9	0,7-1,0	0,2	0,12
SCH35	2,9-3,0	1,2-1,5	0,7-1,1	0,2	0,12

Note. Low alloying of cast iron with various elements (chrome, nickel, copper, phosphorus, etc.) is allowed.

The text of the document is verified according to: official publicationCast iron. Stamps. Technical conditions. Methods of analysis: Sat. GOST —

M.: IPK Standards Publishing House, 2004

Source: http://docs.cntd.ru/document/464626504

Decoding steels, alloys and cast irons: table, examples. Breakdown of steels by composition:

Steel is an alloy of iron and carbon, the content of which does not exceed 2.14%. It has high malleability and rollability, which explains its widespread use in industry, mechanical engineering and other industries.

In metallurgical production, where rolled products differ not only in profile, but also in steel grades, marking each piece of rolled products has long become an indispensable rule. Decoding steels makes it possible to immediately draw a conclusion about the applicability of a given metal for a particular technological operation or for a specific product in general.

Marking is applied to the end of each unit of profiles using the “hot stamping” method in the production flow using so-called stamping machines. The marking contains: steel grade, heat number, manufacturer's mark.

In addition, each workpiece is marked with indelible paint in a combination of colors according to steel groups on cooled workpieces. By agreement of the parties, color markings can be applied to individual profiles in a package in the amount of 1-3 pieces per package.

A package is a bundle of profiles with a total weight of 6-10 tons, packed with rolled wire with a diameter of 6 mm and 6-8 threads.

Alloy steels

The table for decoding steels by composition is presented below.

Designation	Chem. element	Name	Designation	Chem. element	Name
X	Cr	Chromium	A	N	Nitrogen
WITH	Si	Silicon	N	Ni	Nickel
T	Ti	Titanium	TO	Co	Cobalt
D	Cu	Copper	M	Mo	Molybdenum
IN	Wo	Tungsten	B	Nb	Niobium
G	Mn	Manganese	E	Se	Selenium
F	W	Vanadium	C	Zr	Zirconium
R	B	Bor	YU	Al	Aluminum

If the name contains the letter “H”, then the alloying elements include rare earth elements - niobium, lanthanum, cerium.

Cerium (Ce) – affects strength characteristics and ductility.

Lanthanum (La) and neodymium (Ne) - reduce the sulfur content and reduce the porosity of the metal, leading to a decrease in grain size.

Decoding steels: examples

For an example of decoding, consider the common steel grade 12Х18Н10Т.

The number “12” at the beginning of the brand name is an indicator of the carbon content in this steel; it does not exceed 0.12%. Next comes the designation “X18” - therefore, the steel contains the element chromium in an amount of 18%. The abbreviation “H10” indicates the presence of nickel in a volume of 10%. The letter “T” indicates the presence of titanium, the absence of a digital expression means that it is less than 1.5%. Obviously, a qualified decoding of steel by composition immediately gives an idea of ​​its quality characteristics.

If we compare the designations of alloy and carbon steels, this becomes a noticeable difference, indicating the special properties of the metal due to specially introduced alloying additives. Decoding steels and alloys indicates their chemical composition. The main alloying additives are:

• nickel (Ni) – reduces chemical reactivity and improves the hardenability of the metal;
• chromium (Cr) – increases the tensile strength and yield strength of alloys;
• niobium (Nb) – increases acid resistance and corrosion resistance of welded joints;
• cobalt (Co) – increases heat resistance and impact strength.

Alloying - the mechanism of action of alloying elements

It is difficult to decipher steels. Materials science studies this subject comprehensively.

alloying additives in steel can vary widely, depending on what properties need to be imparted to the metal. Thus, nickel and chromium can be present in steel in amounts up to 1%, in some cases more. Molybdenum, vanadium, titanium and niobium - 0.1-0.5%, manganese and silicon - from 1% or more.

The impact of alloying additives in any case is associated with distortion of the iron crystal lattice and the introduction of foreign atoms of a different size into it.

How is it easier to decipher steels (materials science)? The table provides useful information.

Element	Designation	Chem. sign	Influence of an element on the properties of metals and alloys
Nickel	N	Ni	Nickel imparts corrosion resistance to alloys through strengthening the bonds between the nodes of the crystal lattice. The enhanced hardenability of such alloys determines the stability of properties over a long period of time.
Chromium	X	Cr	Improvement in mechanical properties - increased strength and yield - is due to an increase in the density of the crystal lattice
Aluminum	YU	Al	It is fed into the metal stream during casting for deoxidation, most of it remains in the slag, but some of the atoms pass into the metal and distort the crystal lattice so much that this leads to a multiple increase in strength characteristics.
Titanium	T	Ti	It is used to increase the heat resistance and acid resistance of alloys.

Positive aspects of doping

The peculiarities of the properties are most clearly manifested after heat treatment; therefore, all parts made of such steel are processed before use.

1. Steels and alloys improved by alloying have higher mechanical properties compared to structural ones.
2. Alloying additives help stabilize austenite, improving the hardenability of steels.
3. Due to the reduced degree of austenite decomposition, the formation of quenching cracks and warping of parts is reduced.
4. Impact strength increases, which leads to a decrease in cold brittleness, and parts made of alloy steels have higher durability.

Negative sides

Along with the positive aspects, steel alloying also has a number of characteristic disadvantages. These include the following:

1. In products made from alloy steels, reversible temper brittleness of the second type is observed.
2. High-alloy class alloys include retained austenite, which reduces hardness and fatigue resistance.
3. Tendency to form dendritic segregations, which leads to the appearance of stitch structures after rolling or forging. To eliminate the effect, diffusion tempering is used.
4. Such steels are prone to flake formation.

Steel classification

How is steel deciphered by composition? Materials containing less than 2.5% of alloying additives are classified as low-alloyed, with an amount from 2.5 to 10% are considered alloyed, and more than 10% are considered highly alloyed.

m of carbon in the composition of steels is due to their division into:

• high carbon;
• medium carbon;
• low carbon.

The chemical composition determines the division of steels into:

• carbon;
• alloyed.

Cast iron

Cast iron is an alloy of iron and carbon with a content of the latter above 2.15%. It is divided into unalloyed and alloyed containing manganese, chromium, nickel and other alloying additives.

Differences in structure divide cast iron into two types: white (has a silvery-white fracture) and gray (has a characteristic gray fracture). The form of carbon in white cast iron is cementite. In gray - graphite.

Gray cast iron is divided into several varieties:

• malleable;
• heat resistant;
• high strength;
• heat resistant;
• antifriction;
• corrosion resistant.

Designation of cast iron grades

Different grades of cast iron are designed to be used for different purposes. The main ones are the following:

1. Pig irons. They are designated as “P1”, “P2” and are intended for remelting in steel production; cast iron with the designation “PL” is used in foundries for the manufacture of castings; conversion with a high phosphorus content, designated by the letters “PF”; High quality pig material is designated by the abbreviation “PVK”.
2. Cast iron, in which graphite is in plate form - “SC”.
3. Anti-friction cast iron: gray – “ACS”; high strength - “AChV”; malleable - "AChK".
4. Cast iron with nodular graphite, used in foundries, is “HF”.
5. Cast iron with alloying additives, endowed with special properties - “C”. Alloying elements are designated by letters in the same way as for steel. The designation with the letter “Ш” at the end of the name of the cast iron grade indicates the spherical state of the graphite in such a grade.
6. Malleable cast iron – “KCH”.

Decoding steels and cast irons

For cast irons, called gray, the characteristic form of graphite is lamellar. They are marked with the letters SC, the numbers after the letter designation indicate the minimum value of the tensile strength.

Example 1: ChS20 – gray cast iron, has a tensile strength of up to 200 MPa. Gray cast iron is characterized by high casting properties. It can be easily processed by cutting and has anti-friction characteristics. Products made of gray cast iron can dampen vibrations well.

At the same time, they are not sufficiently resistant to tensile loads and do not have impact resistance.

Example 2: HF50 – high-strength cast iron with tensile strength up to 500 MPa. Possessing a structure in the form of spheroidal graphite, it has higher strength characteristics compared to gray cast iron. They have a certain plasticity and higher impact strength. Along with gray cast iron, high-strength cast iron has good casting characteristics, antifriction and damping properties.

These cast irons are used in the production of heavy parts, such as press equipment frames or rolling rolls, internal combustion engine crankshafts, etc.

Example 3: KCh35-10 – malleable cast iron, having a tensile strength of up to 350 MPa and allowing elongation of up to 10%.

Malleable cast irons, in comparison with gray ones, have greater strength and ductility. They are used for the production of thin-walled parts that experience shock and vibration loads: hubs, flanges, engine and machine crankcases, driveshaft forks, and so on.

Conclusion

The breadth of use of metals in industry requires the ability to quickly navigate the properties and capabilities of products. Indicators such as elasticity, weldability, and wear are encountered almost every day in one form or another.

For many decades, the volume of iron and steel production per capita was one of the most important factors in assessing the success of the state. The successful operation of mechanical engineering, automotive industry and many other sectors of the national economy depended, and still depends, on metallurgy. The condition of our only true ally – the army and navy – depends on the availability of a large amount of high-quality metal. Metal serves us on water, under water and in the air.

Source: https://www.syl.ru/article/211640/new_rasshifrovka-staley-splavov-i-chugunov-tablitsa-primeryi-rasshifrovka-staley-po-sostavu

How to decipher steel grade

Steel, cast iron and alloys of non-ferrous metals are subject to mandatory marking. There are more than 1.5 thousand different types of steels and alloys made from them in the world.

Alloyed steels , unlike unalloyed steels, have a slightly different designation, since they contain elements that are specially introduced in certain quantities to ensure the required physical or mechanical properties. Eg:

• chromium (Cr) increases hardness and strength
• Nickel (Ni) provides corrosion resistance and increases hardenability
• Cobalt (Co) improves heat resistance and increases impact resistance
• Niobium (Nb) helps improve acid resistance and reduces corrosion in welded structures.

That is why it is customary to include in the names of alloy steels the chemical elements present in the composition and their percentage content. Chemical elements in such steel grades are designated by Russian letters given in the table.

X-chrome	A-nitrogen
C-silicon	N-nickel
D-copper	M-molybdenum
T-titanium	K-cobalt
B-tungsten	B-niobium
G-manganese	E-selenium
F-vanadium	C-zirconium
R-boron	U-aluminum

There is also a marking H , which tells us that the alloy contains rare earth metals, such as cerium, lanthanum, neodymium and others. Cerium (Ce) affects the strength and ductility of steel, and neodymium (Nd) and lanthanum (La) reduce porosity and sulfur content in steel and refine the grain.

An example of decoding steel grade 12Х18Н10Т

12Х18Н10Т is a popular austenitic steel, which is used in welding machines operating in dilute acid solutions, in solutions of alkalis and salts, as well as in parts operating under high pressure and in a wide temperature range. So, what do these mysterious symbols in the name mean, and how to combine them correctly?

The two numbers at the very beginning of the alloy steel grade are the average carbon content in hundredths of a percent. In our case, the carbon content is 0.12%. Sometimes, instead of two numbers, there is only one: it shows how much carbon (C) is contained in tenths of a percent. If there are no numbers at the beginning of the steel grade, this means that there is a fairly decent amount of carbon in it - from 1% and above.

The letter X and the number 18 following it indicate that this brand contains 18% chromium. Please note: the ratio of an element in fractions of a percent expresses only the first number at the beginning of the mark, and this only applies to carbon! All other numbers present in the name express the number of specific elements as a percentage.

Combination H10 follows. As you may have guessed, this is 10% nickel.

At the very end there is the letter T without any numbers. This means that the content of the element is too small to pay attention to. As a rule, about 1% (sometimes up to 1.5%). It turns out that in this grade of alloy steel the amount of titanium does not exceed 1.5%.

If suddenly at the very end of the brand you find a modestly standing letter A, remember that it plays a very important role: this means high-quality steel, the content of phosphorus and sulfur in which is kept to a minimum.

Two letters A at the very end (AA) indicate that this grade of steel is especially pure, i.e. there is practically no sulfur and phosphorus here.

In the course of a simple analysis of combinations of letters and numbers, we found out that the steel grade 12Х18Н10Т (structural cryogenic, austenitic class) reports the following information about itself: 0.12% carbon, 18% chromium (X), 10% nickel (N) and a small content titanium (T), not exceeding 1.5%.

At the beginning of the alloy steel grade there may also be additional designations:

R - high-speed;

Ш - ball bearing;

A - automatic (do not confuse with the letter A at the end of the name, which indicates the purity of the steel!);

E - electrical.

It is also worth noting some features of these subtypes of alloy steels:

1. in ball bearing steels, the chromium content is indicated in tenths of a percent (for example, ShKh4 steel contains 0.4% chromium);
2. in grades of high-speed steel, after the letter P there is immediately a number indicating the tungsten content as a percentage. Also, all high-speed steels contain 4% chromium (X).

To show the method of steel deoxidation, there are special letter designations: 

• sp - mild steel;
• ps - semi-quiet steel;
• kp - boiling steel.

Now let's take a closer look at how to decipher the grade of unalloyed steel , which is divided into ordinary and high-quality.

Ordinary unalloyed steel (St3, St3kp) has the letters St at the very beginning. This is followed by numbers indicating the carbon content in steel in tenths of a percent.

At the end there may be special indices: for example, St3kp steel belongs to the boiling category, as indicated by the letters kp at the very end. The absence of an index means that this steel is calm.

letters sv are added at the end . For example: St3st.

High-quality unalloyed steel (St10, St30, St20, St45) contains a two-digit number in the marking, indicating the average carbon content in the steel in hundredths of a percent. Thus, steel grade St10 contains 0.1% carbon; St30 has 0.3% carbon; St20 - 0.2%; St45 contains 0.45% carbon.

Structural low-alloy steel 09G2S contains the following chemical elements: 0.09% carbon, 2% manganese and a small amount of silicon (approximately 1%).

Steels 10KhSND and 15KhSND differ only in different carbon content: 0.1% and 0.15%, respectively. There is very little chromium (X), silicon (C), nickel (H) and copper (D) here (up to 1-1.5%), so numbers are not placed after the letter.

High-quality steels are used for the production of steam boilers and high-pressure vessels. Their markings have the letter K at the end: 20K, 30K, 22K.

If the steel is structural casting , then the letter L is placed at the end of the marking. For example: 40ХЛ, 35ХЛ.

Non-alloy tool steels are designated by the letter U. This is followed by a number expressing the average carbon content in the steel: U10, U7, U8. If the steel is also high-quality, this is also noted in the marking: U8A, U10A, U12A. If it is necessary to emphasize the increased manganese content, an additional letter G is used. For example, there are U8GA and U10GA steels.

Tool alloy steels have the same designation as structural alloy steels. For example, the HVG brand indicates the presence of three main alloying elements: chromium (X), tungsten (B) and manganese (G). There is approximately 1% carbon here, and therefore the number is not written at the beginning of the stamp. Another type of steel, 9KhVG, has a lower carbon content compared to KhVG: here there is 0.9% carbon.

High-speed steels are marked with the letter P, followed by the tungsten content in %. steel R6M5F3 as an example . It is high-speed (P), contains 6% tungsten, 5% molybdenum (M) and 3% vanadium (F).

Unalloyed electrical steel (ARMCO) has a very low electrical resistivity. This is achieved due to the minimal amount of carbon in the composition (less than 0.04%). Such steel is also commonly called technically pure iron . The marking of electrical non-alloy steels consists only of numbers. For example: 10880, 21880, etc.

Each number contains important information. The very first digit shows the type of processing: 1 - forged or hot-rolled; 2 - calibrated. The second digit indicates the presence/absence of a normalized aging coefficient: 0 - without a coefficient; 1 - with a coefficient. The third digit is the group according to the main standardized characteristic.

The last two are associated with the values ​​of the main standardized characteristic.

Structural steel is marked with the letter C, followed by the minimum yield strength of the steel. Additional designations are also used: K - increased corrosion resistance (S390K, S375K); T - heat-strengthened rolled products (S345T, S390T); D - increased copper content (S345D, S375D).

Aluminum casting alloys are designated by the letters AL at the beginning of the marking. Here are some examples: AL4, AL19, AL27.

Aluminum alloys for forging and stamping contain the letters AK, and then the conditional number of this alloy: AK6, AK5.

There are also wrought alloys containing aluminum . Avial alloy: AB, aluminum-magnesium alloy: AMg; aluminum-manganese alloy: AMts.

Now you have learned how to decipher the grade of steel containing various chemical elements. This steel marking was developed back in the USSR and is still in effect not only in the Russian Federation, but also in the CIS countries.

European steel markings are subject to the EN 100 27 standard. Japan and the United States have their own standards. There is currently no single world classification of steels.

Understanding the general rules for designating grades of unalloyed and alloyed steels, as well as by correctly deciphering steel grades, you can easily determine what kind of steel a particular part is made of.

Competent employees of the UralTeploMontazh plant will help you determine the required grade of steel that can withstand the required pressure and specified temperature conditions.

We always have in stock (or on order) steel fittings for pipelines, bent elbows and other pipeline fittings made of various grades of steel.

Source: http://uraltm08.ru/stati/kak-rasshifrovat-marku-stali.html