STEEL KNOWLEDGE

Steel knowledge

Basic knowledge of Chinese steel

Basic knowledge of Chinese steel

Mechanical properties of steel is introduced

 

1. The yield point (sigma s)

Steel or specimens under tensile, when more than elastic limit stress, even if the stress is no longer increasing, and steel or sample is still continue to happen obvious plastic deformation, according to this phenomenon as the yield, and yield phenomenon when the minimum stress value is the yield point.

 

A Ps for the yield point s of outside force, Fo for sample area, the yield point sigma s = Ps/Fo (MPa), MPa is called the MPa is equal to N (Newton)/was (MPa = 106 Pa, Pa, PASCAL = N/m2)

 

2. The yield strength (sigma, 0.2)

 

Some metal material yield point very clear, have difficulty in measuring, so in order to measure the yield of material characteristics, residual plastic deformation is equal to a certain rules to produce permanent value (usually 0.2%) for the length of the original stress, known as the conditions to yield strength or yield strength sigma 0.2.

 

3. The tensile strength (sigma b)

 

Material in the drawing process, from start to reach the maximum stress value when fracture occurs. It is about the size of said steel resistance to fracture. And the tensile strength and compressive strength, bending strength, etc.

 

A Pb for material is pulled before achieve maximum tension, Fo for sample area, the tensile strength of sigma b = Pb/Fo (MPa).

 

4. The elongation (delta s)

 

Material after the break, the length of the plastic elongation with the original sample length percentage elongation or extension rate.

 

5. Showed (sigma sigma b/s)

 

Steel yield point, yield strength and tensile strength ratio, known as showed. Showed, the greater the reliability of structural components is higher, general carbon steel showed 0.6 0.65, 0.65 0.75 low alloy structural steel alloy structural steel 0.84 0.86.

 

6. The hardness

 

Hardness said material's ability to fight a hard object into its surface. It is one of the important performance index of metal materials. Generally, the higher the hardness, wear resistance, the better. Commonly used hardness index have brinell, rockwell and vickers hardness.

 

(1) hardness (HB)

 

At a certain load (3000 kg) to a certain size (10 mm in diameter) of a hardened steel ball pressure into the material surface, keep a period of time, to load, load with indentation area ratio, is the brinell hardness number (HB), the unit is kg force/was (N/was).

 

2 a hardness (HR)

 

When HB > 450 or sample hours, brinell hardness test and will not be used to switch to rockwell hardness measurement. It is a diamond cone apex Angle 120 ° or 1.59 and 3.18 mm steel ball diameter, under certain load down into the material surface under test, the hardness of materials by indentation depth. According to different experimental material hardness, the three kinds of different scale to said:

 

HRA: is 60 kg load and drill coup-de-point forcer for hardness, used in high hardness materials, such as cemented carbide, etc.).

 

HRB: is a 100 kg load and the diameter of 1.58 mm hardened steel ball, get the hardness, used in low hardness of materials (such as annealing steel, cast iron, etc.).

 

HRC: is a 150 kg load and drill coup-de-point forcer, finding the hardness for high hardness materials, such as hardened steel, etc.).

 

(3) hardness (HV)

 

To within 120 kg load and apex Angle of 136 ° diamond square forcer pressure cone into the surface of materials, materials of the indentation indentation surface area divided by load value, is the vickers hardness value (HV)

 

Steel product knowledge (a)

 

The first section steel classification

 

A, ferrous and non-ferrous metals

 

1, black metal

 

Refers to an alloy of iron and iron. Such as steel, pig iron, iron alloy, cast iron, etc. Steel and cast iron is based on iron, add carbon as the main elements of the alloy, collectively known as the iron carbon alloy.

 

Pig iron is put iron ore in the blast furnace smelting products, mainly used for steelmaking and manufacture of castings.

 

Put the casting pig iron in the cupola melting, that is, get cast iron (liquid, carbon content is more than 2.11% of the iron carbon alloy), the liquid cast iron cast into casting, the cast iron castings.

 

Iron alloy is made up of iron and silicon, manganese, chromium, composed of elements such as titanium alloy, iron alloy is one of the steelmaking raw material, make steel in steelmaking deoxidizer and additive in alloy elements.

 

Carbon content less than 2.11% of the iron carbon alloy called steel, the according to certain processes in the steelmaking pig iron into steel furnace smelting, the steel. Steel ingot, casting billet and directly cast all kinds of steel castings, etc. Usually told by steel, generally refers to the steel rolled into a variety of steel products.

 

2, non-ferrous metal

 

Also called nonferrous metals, in addition to the black metal of the metal and alloys, such as copper, tin, lead, zinc, aluminum and brass, bronze, aluminum alloy and bearing alloy, etc. In industry also USES the chromium, nickel, manganese, molybdenum, cobalt, vanadium, tungsten, titanium, etc., mainly used for the metal alloy addition, in order to improve the performance of the metal, tungsten, titanium, molybdenum, etc for production of cemented carbide cutting tools. These are called industrial metals, non-ferrous metal and precious metal: platinum, gold, silver and precious metals, such as including radioactive uranium, radium, etc.

 

Second, the classification of the steel

 

The main elements in addition to iron, carbon steel, silicon, manganese, sulfur, phosphorus, etc. Steel classification method is varied, the main method has the following seven:

 

1, according to the quality of classification

 

(1) ordinary steel (P 0.045% or less, S 0.050% or less)

 

(2) the high quality steel (P, S are 0.035% or less)

 

(3) the high quality steel (P 0.035% or less, S 0.030% or less)

 

2, the classified by chemical composition

 

(1) carbon steel:

 

A. low carbon steel (C 0.25% or less); B. medium carbon steel (C acuities were 0.25 ~ 0.60%); C. high carbon steel (0.60%) or less c.

 

(2) alloy steel:

 

A. low alloy steel (alloy element content of total 5% or less); B. in alloy steel (alloy element total content > 5 ~ 10%); C. high alloy steel (alloy element total content > 10%).

 

3, according to the forming method of classification:

 

(1) forging steel; (2) cast steel; (3) hot rolled steel, (4) cold-drawn steel.

 

4, according to the microstructure classification

 

(1) annealing state: a. hypoeutectoid steel (ferrite + pearlite); B. eutectoid steel (pearlite); C. hypereutectoid steel (pearlite and cementite); D. ledeburite steel (pearlite and cementite).

 

(2) is the state of the fire: a. pearlitic steel; B. bainite steel; C. martensitic steel; D. austenitic steel.

 

(3) without phase change or part of a phase change

 

5, according to the classification purpose

 

(1) construction and engineering steel: a. ordinary carbon structural steel; B. low alloy structural steel; C. reinforced steel.

 

(2) structural steel

 

A. machinery manufacturing steel quenched and tempered steels: (a); (b) surface hardening steel: including carburizing steel, permeability of ammonia steel, surface quenching steel; (c) free cutting steel; (d) cold plastic forming steel: including cold-formed steel, cold heading steel.

 

B. spring steel

 

C. bearing steel

 

(3) tool steel: a. carbon tool steel; B. alloy tool steel; C. high speed tool steels.

 

(4) the special performance of steel: a. acid-proof stainless steel; B. heat resistant steel, including oxidation heat intensity steel, steel, steel valve; C. electrothermal alloy steel; D. wear resistant steel; E. cryogenic steel; F. electrical steel.

 

(5) professional steel, such as Bridges with steel, ship steel, boiler steel, pressure vessel steel, agricultural machinery, steel, etc.

 

6, comprehensive classification

 

(1) ordinary steel

 

A. Q195 carbon structural steel: (a); (b) Q215 (A, b); (c) Q235 (A, B, c); (d) Q255 (A, B); Q275 (e).

 

B. low alloy structural steel

 

C. special-purpose common structural steel

 

(2) the high quality steel (including high quality steel)

 

A. high quality carbon structural steel structural steel: (a); (b) alloy structural steel; (c) spring steel; (d) free cutting steel; (e) bearing steel; (f) specific USES high quality steel.

 

B. tool steel carbon tool steel: (a); (b) alloy tool steel, (c) high speed tool steels.

 

C. special performance steel stainless acid-resistant steel: (a); (b) heat resistant steel; (c) electrothermal alloy steel; (d) electrical steel; (e) high manganese steel.

 

7, according to the classification of smelting method

 

(1) according to the furnace

 

A. Bessemer steel converter steel: (a); (b) basic Bessemer steel. Or (a) converter steel; (b) side blown converter steel; (c) ld converter steel.

 

B. electric arc furnace steel steel: (a); (b) electroslag furnace steel; (c) induction furnace steel. (d) vacuum self-consuming furnace steel; (e) electron beam furnace steel.

 

(2) according to the degree of DNA and gating system

 

A. rimming steel; B. half killed steel; C. killed steel; D. special killed steel.

 

China's steel grade in the second quarter

 

An overview, said China's steel grade method

 

Steel grades of steel grade for short, is to take the name of each specific steel product, are a common language of understanding of steel. The steel grade of representation in our country, according to the national standard \"brand representation method of steel products (GB/T221-2000), and on November 1, 2000.

 

Of the product brand, said general use by Chinese phonetic alphabet, chemical elements and the method of combining the Arabic numerals indicate. That is:

 

(1) chemical element USES the international chemical symbol in the steel grade, such as Si, Mn, Cr... And so on. Mixed rare earth elements in \"RE\" (or \"Xt\").

 

(2) the product name, purpose, smelting and casting methods, generally USES the abbreviation of Chinese pinyin letters,

 

(3) the main chemical elements content in the steel (%) use Arabic numerals.

 

The Chinese phonetic alphabet said product name, purpose, features and process method, generally from the representative product name han language to select the first letter in the alphabet. When repeated letters and another product place to choose, can switch to the second letter or the third letter, or select the first of two Chinese characters at the same time the phonetic alphabet.

 

Temporarily not can use of Chinese characters and Chinese pinyin, USES the symbols of English letters.

 

Second, China's steel grade classification of representation

 

1, carbon structural steel and high strength low alloy structure brand representation method

 

The above steel is usually divided into two major categories of common steel and special steel. Number representation, the steel yield point or yield strength of the Chinese phonetic alphabet, the yield point or yield strength value, the quality of the steel grade and other parts, and the steel deoxidizing degree, is actually four parts.

 

(1) general structural steel used on behalf of the yield point of phonetic alphabet \"Q\". Yield point value (in MPa) and the quality level specified in the table 1 (A, B, C, D, E), deoxidizing method (F, B, Z, TZ), and other symbols, according to the order form number. For example: carbon structural steel grades is expressed as: Q235AF, Q235BZ; High strength low alloy structural steel grades are expressed as: Q345C, Q345D.

 

Q235BZ said the yield point value of 235 mpa, quality grade for class B or calm carbon structural steel.

 

Q235 and Q345 these two brands is the most typical engineering steel, production and consumption is the largest, the most widely use. Almost all countries in the world have the two brands.

 

Of carbon structural steel grades, calm steel symbol \"Z\", and special killed steel symbol \"TZ\" can be omitted, for example: the quality level of class C and D respectively of Q235 steel, said the brand should be Q235CZ and Q235DTZ, but can be omitted for Q235C and Q235D.

 

High strength low alloy structural steel has a calming and killed steel, special steel grades tail said without written symbols of deoxidizing method.

 

(2) on behalf of commonly used special steel steel yield point symbol \"Q\", the yield point value and specified in table 1 on behalf of the said product use symbols, such as, for example: pressure vessel steel grades represented as \"Q345R\"; Weathering steel its brand is expressed as Q340NH; Q295HP welding gas cylinder steel grades; Q390g boiler steel grades; Q420q bridge steel grades.

 

(3) according to the need of general high strength low alloy structural steel grades can also adopt two digits (says the average carbon content, with very few) and chemical element symbols, sequentially; Special grades of high strength low alloy structural steel, also can use two digits (says the average carbon content, with very few) and chemical element symbols, and specified in table 1 represents the product use of symbols, said in sequence.

 

2, high quality carbon structural steel and fine carbon spring steel grades

 

High quality carbon structural steel adopts two digits (expressed in several meter per average carbon content) or Arabic Numbers and element symbols, specified in table 1 symbol brand.

 

(1) the steel and half killed steel, respectively at the end of the brand symbol \"F\" and \"b\". For example: the average carbon content is 0.08% of rimming steel, its brand is expressed as \"08 f\"; Average carbon content of 0.10% and a half killed steel, the brand is expressed as \"10 b\".

 

(2) killed steel (S, P, respectively, 0.035% or less) is generally not standard symbols. For example: the average carbon content is 0.45% of killed steel, the brand is expressed as \"45\".

 

(3) high manganese content of high quality carbon structural steel, after said average carbon content of Arabic numerals and manganese element symbols. For example: the average carbon content is 0.50%, manganese content is 0.70% ~ 1.00% of the steel, the brand is expressed as \"50 mn\".

 

(4) high quality carbon structural steel (S, P, respectively, 0.030% or less), after the brand symbol \"A\". For example: the average carbon content is 0.45% of senior high quality carbon structural steel, the brand is expressed as \"a 45\".

 

(5) super high quality carbon structural steel (S, P acuities were 0.020% and 0.025% or less), plus the symbols \"E\" after the brand. For example: the average carbon content is 0.45% of the super high quality carbon structural steel, the brand is expressed as \"e\" 45.

 

The representation method of high quality carbon spring steel grades and high quality carbon structural steel grades said in the same way (65, 70, 85, 70 mn steel in GB/T1222 and also separately in two standard of GB/T 699).

 

3, alloy structural steel and alloy spring steel grades

 

1) alloy structural steel grades by Arabic numerals and standards for the chemical element symbol.

 

With two digits represent the average carbon content (in per meter), in the brand in the head.

 

Alloy element content representation method is: the average content of less than 1.50%, just indicate the elements of brand, generally does not indicate the content; The average alloy content was 1.50% ~ 2.49%, 2.50% ~ 3.49%, 3.50% ~ 4.49%, 4.50% ~ 5.49%,... When, after the alloy elements corresponding written 2, 3, 4, 5... .

 

For example: the average contents of carbon, chromium, manganese and silicon were 0.30%, 0.95%, 0.85%, 0.95% of alloy structural steel, when the content of S and P respectively 0.035% or less, the brand is expressed as \"30 crmnsi\".

 

High quality alloy steel (S, P content of 0.025% or less) respectively, and at the end of the brand symbol \"A\". For example: \"30 crmnsia\".

 

Super high quality alloy steel (0.015% S 0.015%, or less P or less), plus the symbols \"E\" at the end of the brand, for example: \"30 CRM nSiE\".

 

Special alloy steel grades is still should be in brand head or the tail on behalf of product use symbols given in table 1. Riveting screw is special, for example, 30 crmnsi steel, steel grade is expressed as ML30CrMnSi.

 

(2) the representation method of alloy spring steel grades and alloy structural steel is the same.

 

For example: the average contents of carbon, silicon, manganese, spring steel are 0.60%, 1.75% and 0.60% respectively, the brand is expressed as \"60 si2mn\". Senior high quality spring steel, plus symbol \"A\" at the end of the brand, the brand is expressed as \"60 si2mna\".

 

4, free cutting steel grades

 

Free cutting steel with a standard chemical element symbols, the symbols given in table 1 and Arabic numerals. Arabic Numbers represent the average carbon content (in per meter).

 

(1) add sulfur free cutting steel and add sulfur and phosphorus free cutting steel, after the symbol \"Y\" and the Arabic numeral without cutting element symbols.

 

For example: the average carbon content was 0.15% of free cutting steel, the brand is expressed as \"Y15\".

 

(2) high manganese content plus sulfur or sulfur, phosphorus free-cutting steel after the symbol \"Y\" and Arabic numerals and manganese element symbols. For example: the average carbon content is 0.40%, manganese content is 1.20% ~ 1.55% of free cutting steel, the brand is expressed as \"Y40Mn\".

 

(3) the free cutting element such as calcium, lead free cutting steel, after the symbol \"Y\" and the Arabic numeral plus free cutting element symbols. Cases such as \"Y15Pb\", \"Y45Ca\".

 

5, non quenched and tempered mechanical structural steel grades

 

The mechanical structural steel, quenched and tempered in brand head respectively add symbol \"YF,\" and \"F\" said free-cutting non quenched and tempered steel and hot forging with non quenched and tempered mechanical structural steel, brand said methods were the same as other contents and alloy steel. For example: \"YF35V\", \"F45V\". 

 

6, tool steel grades

 

Tool steel is divided into three classes of carbon tool steel, alloy tool steel and high-speed tool steel.

 

(1) carbon tool steel chemical element with a standard symbols, symbols and Arabic Numbers given in table 1. The Arabic numeral said The average carbon content (in a few parts per thousand).

 

A. ordinary carbon tool steel, manganese content in tool steel symbol for Arabic Numbers after the \"T\". For example, the average carbon content is 0.80% of the carbon tool steel, the brand is expressed as \"T8.

 

B. high carbon tool steel, manganese content in tool steel symbol after the \"T\" and Arabic numerals and manganese element symbols. For example: \"T8Mn\".

 

C. senior high quality carbon tool steel, add an \"A\" at the end of the brand. For example: \"T8MnA\".

 

(2) alloy tool steel and high-speed tool steel

 

Alloy tool steel, high-speed tool steel grades representation and alloy structural steel brand said the same way. Using standard alloy element symbols and Arabic Numbers, but generally does not indicate the average carbon Numbers, for example: the average carbon content is 1.60%, chromium, molybdenum and vanadium content were 11.75%, 0.50%, 0.22% of alloy tool steel, the brand is expressed as \"Cr12MoV\"; The average carbon content was 0.85%, including tungsten, molybdenum, chromium, vanadium content were 6.00%, 5.00%, 4.00%, 2.00% of high speed tool steel, the brand is expressed as \"W6Mo5Cr4V2\".

 

If the carbon content less than 1.00% on average, an Arabic numerals said carbon content can be used (with a few parts per thousand). For example: flat carbon content is 0.80%, manganese content was 0.95%, 0.45% silicon content alloy tool steel, the brand is expressed as \"8 mnsi\".

 

Average low chromium (chromium content < 1.00%) alloy tool steel, the chromium content (with a few parts per thousand) before the number \"0\". For example: the average of 0.60% chromium content of alloy tool steel, the brand is expressed as \"Cr06\".

 

7, plastic die steel grades

 

Plastic die steel grades in addition to the plus symbol \"SM\" of the head, the rest of the said method and the high quality carbon structural steel and alloy tool steel card number representation is the same. For example: the average carbon content is 0.45% of the carbon plastic die steel, the brand is expressed as \"SM45\"; Average carbon content is 0.34%, chromium content is 1.70%, 0.42% molybdenum alloy plastic die steel, the brand is expressed as \"SM3Cr2Mo\".

 

8, bearing steel brand representation method

 

Bearing steel can be divided into high carbon chromium bearing steel, carburized bearing steel, high carbon chromium stainless bearing steel and high temperature bearing steel and other four categories.

 

1) high carbon chromium bearing steel, in brand head plus symbol \"G\", but does not indicate the carbon content. Chromium content in a few parts per thousand, other alloying elements in the alloy structural steel alloy content. For example: the average of 1.50% chromium content of bearing steel, the brand is expressed as \"GCr15.

 

(2) the carburizing bearing steel, alloy structural steel grades said method, the other in brand head plus symbol \"G\". For example: \"the G20 CrNiMo\".

 

Senior high quality carburizing bearing steel, add an \"A\" at the end of the brand. For example: \"G20CrNiMoA\".

 

(3) high carbon chromium stainless bearing steel and high temperature bearing steel, stainless steel and heat resistant steel brand representation, brand head without operator \"G\". For example: high carbon chromium stainless bearing steel and high temperature bearing steel cr18 9 \"10 cr14mo\".

 

9, stainless steel and heat resistant steel grades

 

Stainless steel and heat resistant steel grades with a standard rules of alloy element symbols and Arabic numerals, said for cutting stainless steel, free cutting heat resistant steel in the brand in the head with a \"Y\".

 

General use an Arabic Numbers said the average carbon content (in a few parts per thousand); When the average carbon content 1.00% or higher, with two digits; When the upper limit of carbon content < 0.10%, expressed as a \"0\" carbon content; When the maximum of 0.03% or less, the carbon content > 0.03% (low carbon), expressed as a \"03\" carbon content; When the upper limit of carbon content (0.01% or less is extremely low carbon), expressed as a \"01\" carbon content. Carbon content without rules limit, use Arabic numerals limit number of carbon content.

 

Alloy element content representation with alloy constructional steel. For example: the average carbon content is 0.20%, the chromium content of 13% stainless steel, the brand is expressed as \"2 cr13\"; Carbon content up to 0.08%, the average chromium content is 18%, the nickel content of 9% chromium nickel stainless steel, its brand is expressed as \"0 cr18ni9\"; Carbon content up to 0.12%, the average of 17% chromium content and sulfur free-cutting chromium stainless steel, the brand is expressed as \"Y1Cr17\"; Average carbon content is 1.10%, 17% chromium content of high carbon chromium stainless steel, the brand is expressed as \"11 shape\"; Carbon content up to 0.03%, the average chromium content is 19%, 10% nickel content of ultra-low carbon stainless steel, the brand is expressed as \"03 cr19ni10\"; Carbon content up to 0.01%, the average chromium content is 19%, for 11% of the nickel content is extremely low carbon stainless steel, the brand is expressed as \"01 cr19ni11\".

 

Domestic standard of heat-resisting stainless steel is a reference to the JIS standard revision, but stainless heat resistant steel grades representation method is different from countries such as Japan's standard. We are the alloy elements and the average content of C, said Japan is expressed in the said purpose letters and Arabic numerals. Such as stainless steel grades SUS202, SUS316, SUS430, S - steel (steel), U - use (use), S - stainless (stainless steel). Such as heat resistant steel grades, SUH309, SUH330, SUH660, H - Heatresistins. Grades of different figures show that the various types of corrosion and heat resistant steel. Japan says stainless heat resistant steel all kinds of different products, combined with the corresponding letter after brand, such as stainless steel rods SUS - B, hot rolled stainless steel plate SUS - HP; Heat resistant steel bar SUHB, heat-resistant steel SUHP. Britain, the United States and other western countries, heat-resistant stainless steel brand representation agreement with Japan, is mainly expressed with Arabic numerals, and says the number is the same, the brand is the same. Because Japan stainless heat resistant steel is used in the United States.

 

10 and welding steel grades

 

Welding of steel including welding of carbon steel, welding of alloy steel and welding of stainless steel, etc., its brand representation method is in all kinds of welding or move steel grades head and symbol \"H\". For example: \"H08\", \"H08Mn2Si\", \"H1Cr18Ni9\".

 

High quality welding steel, plus symbol \"A\" at the end of the brand. For example: \"H08A\", \"08 mn2sia\".

 

11, electrician silicon steel

 

Steel grade is made up of Numbers, letters and Numbers.

 

Without direction and orientation of silicon steel alphabetic character respectively \"W\" and \"Q\"

 

Thickness on ahead and alphabetic character in the middle, and value in the first iron loss, such as 30 q113. Oriented silicon steel, high magnetic induction alphabetic character \"G\" and \"Q\" together, such as 30 qg113

 

Figures show that the iron loss value after the letters (W/kg), 100 times.

 

The letter \"G\", said test under high frequency; Without \"G\", said the frequency of 50 cycles under inspection.

 

30 q113 said electrician 50 hz frequency with cold-rolled oriented silicon steel products in the biggest unit weight of iron loss value of 1.13 W/kg.

 

Cold-rolled silicon steel said method are consistent with the Japanese standard (JISC2552-86), only alphabetic character is different, such as 27 q140 oriented silicon steel grades, and the corresponding JIS brand for 27 g140, 30 qg110 corresponding JIS brand of 30 p110 (G: ordinary material, P: high orientation). No oriented silicon steel grades 35 w250, corresponding JIS brand of 35 a250.