、 Ferrous, steel and nonferrous metals

    Before introducing the classification of steel, the basic concepts of ferrous metals, steel and non-ferrous metals are briefly introduced.

     1Ferrous metals refer to iron and its alloys.Such as steel, pig iron alloy, cast iron, etc.Steel and pig iron are based on iron, carbon as the main added element of alloy, collectively known as iron carbon alloy.Pig iron refers to the product made by smelting iron ore in blast furnace, which is mainly used for steelmaking and casting.Cast pig iron is melted in an iron melting furnace to obtain cast iron (liquid state), which is called cast iron casting.

    Ferroalloy is an alloy composed of iron and silicon, manganese, chromium, titanium and other elements. Ferroalloy is one of the raw materials for steel-making. It is used as deoxidizer and alloy element additive in steel-making.

     2The pig iron for steelmaking is put into the steelmaking furnace and smelted according to a certain process to obtain steel.Steel products include ingots, continuous casting billets and direct casting of various steel castings.Generally speaking, steel refers to the steel rolled into various steels.Steel belongs to ferrous metal, but steel is not equal to ferrous metal.

     3Nonferrous metals, also known as non-ferrous metals, refer to metals and alloys other than ferrous metals, such as copper, tin, lead, zinc, aluminum, brass, bronze, aluminum alloys and bearing alloys.In addition, chromium, nickel, manganese, molybdenum, cobalt, vanadium, tungsten and titanium are also used in industry. These metals are mainly used as alloy additives to improve the properties of metals. Tungsten, titanium and molybdenum are mostly used to produce cemented carbide for cutting tools.These nonferrous metals are called industrial metals. In addition, there are precious metals: platinum, gold, silver, and rare metals, including radioactive uranium and radium.

2、 Classification of steel

     Steel is an iron carbon alloy with carbon content between 0.04% and 2.3%.In order to ensure its toughness and plasticity, the carbon content generally does not exceed 1.7%.Besides iron and carbon, the main elements of steel are silicon, manganese, sulfur and phosphorus.The classification methods of steel are various, and the main methods are as follows:

1(1) ordinary steel (P ≤ 0.045%, s ≤ 0.050%) (2) high quality steel (P, s ≤ 0.035%) (3) high quality steel (P < 0.035%, s ≤ 0.030%)
2.Carbon steel: A. low carbon steel (C ≤ 0.25%); B. medium carbon steel (0.25 < C ≤ 0.60%); C. high carbon steel (c > 0.60%).2) Alloy steel: A. low alloy steel (total alloy element content ≤ 5%) B. medium alloy steel (total alloy element content is 5 ~ 10%) C. high alloy steel (total alloy element content > 10%).
3Classification according to forming method: (1) forged steel; (2) cast steel; (3) hot rolled steel; (4) cold drawn steel.
41) A. hypoeutectoid steel (ferrite + pearlite) B. eutectoid steel (pearlite) C. hypereutectoid steel (pearlite + cementite) d. ledeburite steel (pearlite + cementite).2) Normalized: A. pearlitic steel; B. bainitic steel; C. martensitic steel; D. austenitic steel.3) Having no or partial transformation
51) construction and engineering steel: A. ordinary carbon structural steel; B. low alloy structural steel; C. reinforced steel.2) Structural steel: A. mechanical manufacturing steel: (a) quenching and tempering structural steel; (b) surface hardening structural steel: including carburizing steel, ammonia steel and surface quenching steel; (c) easy cutting structural steel; (d) cold plastic forming steel: including cold stamping steel and cold heading steel.b. Spring steel C. bearing steel 3) tool steel: A. carbon tool steel; B. alloy tool steel; C. high speed tool steel.4) Special performance steel: A. stainless and acid resistant steel; B. heat resistant steel, including anti-oxidation steel, hot strength steel and gas valve steel; C. electric heating alloy steel; D. wear-resistant steel; e. low-temperature steel; F. electrical steel; 5) professional steel, such as bridge steel, ship steel, boiler steel, pressure vessel steel, agricultural machinery steel, etc.
6General classification 1) ordinary steel: A. carbon structural steel: (a) Q195; (b) Q215 (a, b); (c) Q235 (a, B, c); (d) q255 (a, b); (E) Q275.b. Low alloy structural steel.c. General structural steel for specific purposes 2) high quality steel (including high quality steel) A. structural steel: (a) high quality carbon structural steel; (b) alloy structural steel; (c) spring steel; (d) easy cutting steel; (E) bearing steel; (f) high quality structural steel for specific purposes.b. Tool steel: (a) carbon tool steel; (b) alloy tool steel; (c) high speed tool steel.

c. Special performance steel: (a) stainless acid resistant steel; (b) heat resistant steel; (c) electrothermal alloy steel; (d) electrical steel; (E) high manganese wear-resistant steel.

7Classification by smelting method 1) classification by furnace type

a. Open hearth steel (with air as oxidant): (a) acid open hearth steel; (b) basic open hearth steel.b. Converter steel (with oxygen as oxidant): (a) acid converter steel; (b) basic converter steel.Or (a) bottom blown converter steel; (b) side blown converter steel; (c) top blown converter steel.c. EAF steel (high quality steel): (a) EAF steel; (b) electroslag furnace steel; (c) induction furnace steel; (d) vacuum consumable furnace steel; (E) electron beam furnace steel.2) According to the deoxidation degree and pouring system, it can be divided into a. rimming steel (the deoxidation degree is incomplete); B. semi killed steel (the deoxidation degree is between boiling steel and killed steel); C. killed steel (the deoxidization degree is relatively complete); D. special killed steel (the deoxidization degree is the most complete, and the steel quality is high).

8According to the shape classification: A. profile, B. plate, C. pipe, D. metal products.

a. Profile:

Heavy rail: rail with weight greater than 30 kg / M (including crane rail); light rail: rail with weight less than or equal to 30 kg / m.Large, medium and small section steel: ordinary steel round steel, square steel, flat steel, hexagonal angle steel, I-beam, channel steel, equal and unequal angle steel and screw thread steel, etc.Wire rod: round steel and wire rod with diameter of 5-10 mm.Cold formed steel: steel or steel strip formed by cold bending.High quality profiles: high quality round steel, square steel, flat steel, hexagonal angle steel, etc.

b. Plate;

Steel sheet: steel plate with thickness equal to or less than 4 mm.Medium and thick steel plate: steel plate with thickness greater than 4 mm.Medium plate: thickness greater than 4mm less than 20mm; thick plate: thickness greater than 20mm less than 60mm; extra thick plate: thickness greater than 60mm.Steel strip: also known as strip steel. It is actually a long, narrow steel sheet supplied in coils.Electrical silicon steel sheet: also called silicon steel sheet or silicon steel sheet.

c. Pipe material:

Seamless steel pipe: seamless steel pipe produced by hot pressing, cold rolling (cold drawing or extrusion) and other methods.Welded steel pipe: steel plate or steel strip is rolled into shape and then welded.d. Metal products: including steel wire, wire rope, steel strand, etc.

What is special steel?

     There is no unified definition and concept for special steel. It is generally considered that special steel is a kind of steel with special chemical composition, special process, special structure and performance, which can meet special needs.Compared with ordinary steel, special steel has higher strength and toughness, physical properties, chemical properties, biocompatibility and process properties.

     The definition of special steel in China is close to that of Japan and EU. Special steel is divided into three categories: high quality carbon steel, alloy steel and high alloy steel (alloy element is more than 10%). Among them, alloy steel and high alloy steel account for 70% of the special steel output.The main steel types include special carbon structural steel, carbon tool steel, carbon spring steel, alloy spring steel, alloy structural steel, ball bearing steel, alloy tool steel, high alloy tool steel, high-speed tool steel, stainless steel, heat-resistant steel, high-temperature alloy, precision alloy, electric thermal alloy, etc.At present, there are nearly 2000 special steel grades and about 50000 specifications in the world.In addition to various types of special steel, it also shows different characteristics from ordinary steel in specifications.In addition to plate, tube, wire, strip, bar and profile, there are composite materials, surface alloying materials, surface treatment materials, precision forging materials, precision castings, powder metallurgy products, etc.

3、 Steel grade indication in China

     Steel grade is the name of each specific steel product. It is a common language for people to understand steel.According to the national standard “representation of steel product grades” (gb221-79), Chinese Pinyin letters, chemical element symbols and Arabic numerals are used to represent the steel grades in China.Namely: 

    1）The chemical elements in steel grade are represented by international chemical symbols, such as Si, Mn, CrEtc.Mixed rare earth elements are represented by “re” (or “XT”).

    2）The product name, application, smelting and pouring methods are generally represented by abbreviations of Chinese pinyin.

    3）The content (%) of main chemical elements in steel is expressed by Arabic numerals.

Carbon structural steel 1) consists of Q + number + quality grade symbol + deoxidation method symbol.Its steel grade is prefixed with “Q” to represent the yield point of the steel, and the subsequent number represents the yield point value in MPa. For example, Q235 represents a carbon structural steel with a yield point (σ s) of 235 MPa.
    2）If necessary, the symbol indicating the quality grade and deoxidation method can be marked after the steel grade.The quality grade symbols are a, B, C and D.Symbols of deoxidation method: F for rimmed steel; B for semi killed steel; Z for killed steel; TZ for special killed steel, which can be omitted, i.e. both Z and TZ can be omitted.For example, q235-af stands for class a rimmed steel.
    3）Carbon steel for special purposes, such as bridge steel, marine steel, etc., basically adopts the expression of carbon structural steel, but the letter indicating the purpose is added at the end of steel grade.
2High quality carbon structural steel

    1）The two digits at the beginning of the steel grade indicate the carbon content of the steel, expressed in tens of thousands of the average carbon content. For example, for steel with an average carbon content of 0.45%, the steel number is “45″, which is not a sequence number, so it can not be read as 45 steel.
     2）High quality carbon structural steel with high manganese content should be marked with manganese element, such as 50Mn.

     3）Rimming steel, semi killed steel and high quality carbon structural steel for special purpose shall be specially marked at the end of steel grade, for example, the steel grade of semi killed steel with average carbon content of 0.1% is 10B.
3Carbon tool steel 1) the steel grade is marked with “t” to avoid mixing with other steel types.2) The number in the steel grade indicates the carbon content, expressed in thousandth of the average carbon content.For example, “T8″ means an average carbon content of 0.8%.3) For those with high manganese content, mark “Mn” at the end of steel grade, such as “t8mn”.4) The phosphorus and sulfur content of high-quality carbon tool steel is lower than that of general high-quality carbon tool steel. The letter “a” is added at the end of steel grade to show the difference, such as “t8mna”.

4Free cutting steel

1）The steel grade is marked with “Y” to distinguish it from high-quality carbon structural steel.

2）The number after the letter “Y” indicates the carbon content, expressed in tens of thousands of the average carbon content, for example

The grade of free cutting steel with average carbon content of 0.3% is Y30.

3）For those with high manganese content, “Mn” is also marked after the steel grade, such as “y40mn”.

5Alloy structural steel

1）The two digits at the beginning of the steel grade indicate the carbon content of the steel, expressed in tens of thousands of the average carbon content, such as 40Cr.2) The main alloying elements in steel are usually expressed in percentages, except for individual microalloying elements.When the average alloy content is less than 1.5%, only the element symbol is marked in the steel grade, but the content is not indicated. However, in special cases, the number “1″ can be marked after the element symbol, such as steel grade “12CrMoV” and “12Cr1MoV”. The former contains 0.4-0.6% chromium, the latter is 0.9-1.2%, and the other components are all the same.When the average content of alloying elements ≥ 1.5%, ≥ 2.5%, ≥ 3.5%The content should be indicated after the element symbol, which can be expressed as 2, 3, 4Etc.For example, 18Cr2Ni4WA.

     3）V, Ti, Al, B, re and other alloying elements in steel are micro alloying elements. Although the content is very low, it should be indicated in the steel grade.For example, in 20mnvb steel.Vanadium is 0.07-0.12%, boron is 0.001-0.005%.
     4）”A” should be added at the end of steel grade for high quality steel to distinguish it from general high quality steel.
     5）For special purpose alloy structural steel, the steel grade is prefixed (or suffixed) to represent the symbol for the purpose of the steel grade.For example, for 30CrMnSi steel used for riveting, the steel grade is expressed as ml30crmnsi.

6The expression method of steel grade is basically the same as that of alloy structural steel.2) For professional low alloy high strength steel, it should be indicated at the end of steel grade.For example, for 16Mn steel, the special steel grade used for bridge is “16Mnq”, that for automobile girder is “16MnL”, and that for pressure vessel is “16MnR”.
7According to the chemical composition, spring steel can be divided into carbon spring steel and alloy spring steel. The former is basically the same as high-quality carbon structural steel, and the latter is basically the same as alloy structural steel.
8Rolling bearing steel 1) the steel grade is preceded by the letter “g”, indicating the rolling bearing steel class.2) The carbon content of high carbon chromium bearing steel grade is not indicated, and the chromium content is expressed in thousandth, such as GCr15.The steel grade of carburized bearing steel is basically the same as that of alloy structural steel.
9When the average carbon content of alloy tool steel grade is more than or equal to 1.0%, the carbon content is not indicated; when the average carbon content is less than 1.0%, it is expressed in thousands.For example, Cr12, CrWMn, 9SiCr, 3Cr2W8V.2) The expression method of alloy element content in steel is basically the same as that of alloy structural steel.However, for the alloy tool steel grade with low chromium content, the chromium content is expressed in thousandth, and “0″ is added before the number indicating the content, so as to distinguish it from the general element content according to several percent.For example, cr06.3) Generally, the steel grade of high speed tool steel is not marked with carbon content, but only a few percent of the average content of various alloy elements.For example, the steel grade of tungsten high speed steel is indicated as “W18Cr4V”.The carbon content of steel grade with the letter “C” is higher than that of general steel grade without “C”.
10Carbon content in steel grade is expressed in thousandth.For example, the average carbon content of “2Cr13″ steel is 0.2%; if the carbon content in the steel is ≤ 0.03% or ≤ 0.08%, the steel grade is denoted by “00″ and “0″, such as 00Cr17Ni14Mo2, 0cr18 Ni9, etc.2) The main alloying elements in steel are expressed in percent, while titanium, niobium, zirconium, nitrogenAccording to the expression method of microalloying elements in the alloy structural steel mentioned above.
11For welding rod steel, its steel grade is prefixed with the letter “H” to distinguish it from other types of steel.For example, stainless steel welding wire is “H2Cr13″, which can be distinguished from stainless steel “2Cr13″.
12The steel grade is composed of letters and numbers.The letter Dr at the head of steel grade indicates hot-rolled silicon steel for electrical engineering, DW represents cold-rolled non oriented silicon steel for electrical engineering, and DQ represents cold-rolled oriented silicon steel for electrical engineering.2) The number after the letter indicates 100 times the iron loss value (w / kg).3) If the letter “g” is added at the end of the steel grade, it means that the steel grade is inspected at a high frequency; if no “g” is added, it means that the steel grade is inspected under the frequency of 50 cycles.For example, steel grade dw470 indicates that the maximum core loss per unit weight of cold-rolled non oriented silicon steel products for electrical purposes at 50 Hz frequency is 4.7w/kg.

131) its brand is composed of letters “DT” and numbers, “DT” stands for pure iron for electricians, and numbers indicate the sequence numbers of different grades, such as DT3.2) The letters after the numbers indicate electromagnetic properties: a – advanced, e – super, C – super, such as dt8a.

4、 Theoretical weight calculation method

Angle steel: weight per meter = 0.00785 * (side width + side width thickness) * side thickness

Round steel: weight per meter = 0.00617 * diameter * diameter (rebar and round steel are the same) flat steel: weight per meter = 0.00785 * thickness * side width pipe material: weight per meter = 0.02466 * wall thickness * (outer diameter wall thickness) plate: weight per square meter = 7.85 * thickness brass pipe: weight per meter = 0.02670 * wall thickness * (outer diameter wall thickness) copper pipe: weight per meter = 0.02796 * wall thickness * (outer diameter wall thickness)Aluminum checkered plate: weight per square meter = 2.96 * thickness, specific gravity of non-ferrous metal: copper plate 8.9; brass plate 8.5; zinc plate 7.2; lead plate 11.37. The calculation formula of non-ferrous metal plate is: weight per square meter = specific gravity * thickness

5、 Marking and inspection

（1） Logo 

The mark is the mark that distinguishes the material and specification of the material, mainly indicating the supplier’s name, brand, inspection batch number, specification, size, grade, net weight, etc.Marks are: 1, painting: in the end of metal materials, the end painted with various colors of paint, mainly used for steel, pig iron, non-ferrous raw materials, etc.2. Printing: the method of stamping or painting on the specified parts (end face and end) of metal materials, indicating the brand, specification and standard number of materials.It is mainly used for medium and heavy plate, profile, non-ferrous material, etc.3. Tagging: metal materials such as bundles, boxes and shafts shall be hung outside to indicate the brand, size, weight, standard number, supplier, etc.The marks of metal materials shall be carefully identified during inspection, and shall be properly protected during transportation and storage.

（2） Inspection of specification and dimension: the nominal size of main parts (length, width, thickness, diameter, etc.) of metal materials.1. Nominal size (nominal size): it is the ideal size that people want to get in production, but it has a certain gap with the actual size.2. Dimension deviation: the difference between actual size and nominal size is called dimension deviation.Larger than the nominal size is called positive deviation, less than the nominal size is called negative deviation.Within the scope of the standard is called allowable deviation, exceeding the range is called dimension out of tolerance, and out of tolerance belongs to unqualified products.3. Accuracy grade: the allowable size deviation of metal materials has specified several ranges, and is divided into several grades according to the size of allowable deviation, which is called precision grade. The accuracy grade is divided into ordinary, higher, advanced, etc.4. Delivery length (width): is the main delivery dimension of metal materials, which refers to the length (width) specification that metal materials should have when they are delivered.5. General length (indefinite length): the length is not specified, but must be within a specified length range (according to different varieties, different lengths, according to the Ministry and factory).6. Short rule (narrow rule): the length is less than the lower limit of the specified normal length size, but not less than the specified minimum allowable length.For some metal materials, a part of “short ruler” can be handed in according to regulations.7. Fixed length: the length of metal materials delivered must have the length specified by the demander in the order contract (general positive deviation).8. Multiple length: the length of the metal material to be delivered must be the integral multiple of the length specified by the demander in the order contract (plus sawing and positive deviation).In the inspection of specifications and dimensions, attention should be paid to the measurement of material parts and the selection of appropriate measuring tools. 

（3） Quantity inspection the quantity of metal materials generally refers to the weight (except for individual cases of base plate and fishplate, which are calculated by the number of pieces). The quantity inspection methods are as follows: 1. Measurement according to the actual weight: generally, all the metal materials measured by the actual weight should be weighed.If there are strong packing (such as box, box, barrel, etc.), the gross weight, net weight and tare weight shall be indicated on the package.If the steel sheet, silicon steel sheet and ferroalloy can be sampled and inspected, the quantity shall not be less than 5% of a batch. If there is a big difference between the sampling weight and the marked weight, all of them shall be unpacked and weighed.2. According to the theoretical conversion measurement: the weight calculated by the nominal size (actual size) and specific gravity of the material can be converted according to the theory for those fixed size plates and other materials, but the conversion formula and the actual specific gravity of the material should be paid attention to during the conversion. 

（4） Surface quality inspection 

Surface quality inspection mainly refers to the inspection of material, appearance, shape and surface defects, mainly including: 1. Ovality: the metal materials with circular section have different diameters in different directions on the same section.The ovality is expressed by the difference between the maximum diameter and the minimum diameter on the same section, and the standards for different materials are different.2. Bending, bending: bending is rolling material.The length or length of a curve.If their unevenness is expressed in numbers, it is called curvature.3. Torsion: strip rolling material is twisted into a spiral along the longitudinal axis.

4Sickle bend (side bend): refers to the bending of metal plate, strip and shape material close to rectangular section along the length (one side of narrow side). One side is concave curve, the other side is convex curve, which is called “sickle bend”.It is indicated by the concave height.5. Ladyblade curvature: refers to the undulating wave phenomenon in the length and width direction of the plate or strip at the same time, forming a ladyback shape, called ladyback curvature.The value indicating the degree of curvature is called curvature.6. Surface crack: refers to the surface crack of metal object.7. Ear: the protrusion extending along the rolling direction due to improper roll matching is called ear.8. Scratch: refers to the straight line or arc groove mark on the surface of the material, and the groove bottom can be seen.9. Scab: refers to the uneven distribution on the surface of metal materials in the form of tongue, nail or fish scale.10. Bonding: the layers of metal plates, foils and ribbons are adhered to each other at the points, lines and surfaces between the layers during the rolling and annealing. After being lifted, the surface of the metal plates, foils and strips has adhesive traces, which is called bonding.11. Scale: scale refers to the metal oxide formed on the surface of materials during heating, rolling and cooling.12. Folding: it is a kind of surface defect formed in the process of hot rolling (or forging) of metal. The surface of bimetallic layer is folded into each other and overlaps in the form of straight line or curve.13. Pitting: refers to the rough surface of metal material surface.14. Subcutaneous bubble: the surface of metal material presents irregular distribution, different size, different shape, round smooth small bulge, broken convex bubble is chicken claw shaped crack or tongue like scar, called bubble.Surface defects are mainly caused by improper operation of production, transportation, loading and unloading, storage, etc.According to the impact on the use of different, some defects are not allowed to exceed the limit.Although some defects do not exist, they are not allowed to exceed the limit; whether or not various surface defects are allowed to exist or to what extent are clearly specified in relevant standards.

（5） Guarantee conditions of internal quality inspection 

The inspection basis of internal quality of metal materials is based on the material to adapt to different requirements, and the guarantee conditions are also different. During delivery and acceptance, inspection must be carried out according to the guarantee conditions and meet the requirements. The guarantee conditions are divided into 1. Basic guarantee conditions: the minimum requirements for material quality, whether proposed or not, must be guaranteed, such as chemical composition, basic mechanical properties, etc.2. Additional guarantee conditions: it refers to the items that are inspected according to the requirements specified by the demander in the order contract, and the inspection results meet the requirements.3. Agreement guarantee condition: the project negotiated by both parties and guaranteed in the order contract.4. Conditions for modification: the inspection items shall be negotiated by both parties, but only for reference, not for assessment.The internal quality inspection of metal materials mainly includes mechanical properties, physical properties, chemical properties, process performance, chemical composition and internal organization inspection, which are generally carried out in professional inspection institutions.