L 10

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L 10

  1. 1. British Standards and ASTM standard specification on iron/steel 11/8/2011 1
  2. 2.  Steels can be classified by a variety of different systems depending on: The composition, such as carbon, low-alloy or stainless steel. The manufacturing methods, such as open hearth, basic oxygen process, or electric furnace methods. The finishing method, such as hot rolling or cold rolling The product form, such as bar plate, sheet, strip, tubing or structural shape The deoxidation practice, such as killed, semi- killed, capped or rimmed steel The microstructure, such as ferritic, pearlitic and martensitic The required strength level, as specified in ASTM standards The heat treatment, such as annealing, quenching and tempering, and thermo mechanical processing Quality descriptors, such as forging quality and commercial quality. 12/6/2011 2
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  4. 4. Classifications►Steel is classified according to the alloyingelements it contains.► Carbon is the most important element; thereforeall steels are classified according to carbon content.► Plain carbon steels contain primarily iron &carbon, and they are classified as10XX steels.► The first two digits refer to plain carbon steel.► The third & fourth digits refer to the carboncontent in hundredths of a percent.► Thus, a 1035 steel is a plain carbon steel with 0.35% carbon.► There are varying amounts of other materials incarbon steel, but their content is so small that theydo no affect physical properties.11/8/2011 4
  5. 5. Alloy steels• Alloy steels are classified by the society of Automotive Engineers (SAE) & by the American Iron & Steel Institute (AISI).• Some of the designations accepted by them as standard are shown in table 3.3.• Often as many as 5 or more alloying elements may be present, & it is impractical to describe the alloy correctly by a simple numbering system.• Steels may be more broadly classified as followsA. Carbon steel 1. Low carbon - less than 0.30 % 2. Medium carbon - 0.30% to 0.70 % 3. High carbon – 0.70 % to 2.0% (Normally the upper limit is 1.40 %)11/8/2011 5
  6. 6. Table3.3 Classification of steel Classification Number Range of Number A. Carbon Steel Carbon steel SAE- AISI 1XXX Plain carbon 10XX 1006-1095 Free Machining (resulfurized) 11XX 1108-1151 Resulfurized, rephosphorized 12XX 1211-1214 B. Alloy Steels Manganese (1.5%to2.0%) 13XX 1320-1340 Molybdenum 4XXX C-Mo (0.25%Mo) 40XX 4024-4068 Cr-Mo(0.70%Cr, 0.15%Mo) 41XX 4130-4150 Ni-Cr-Mo (1.8% Ni, 0.65 % Cr) 43XX 4317-4340 Ni-Mo (1.75 %) 46XX 4608-4640 Ni-Cr (0.45 % Ni, 0.2 % Mo) 47XX Ni-Mo (3.5 %Ni, 0.25 %Mo) 48XX 4812-482011/8/2011 6
  7. 7. Table3.3 Classification of steel Classification Number Range of Number Chromium 5XXX 0.5% Cr 50XX 1.0% Cr 51XX 5120-5152 1.5% Cr 52XXX 52095-52101 Corrosion heat resistant 514XX (AISI 400 series) Chromium-Vanadium 6XXX 1 % Cr, 0.12 %V 61XX 6120-6152 Silicon Manganese 0.85 % Mn, 2 %Si 92XX 9255-9262 Tripple Alloy Steels 0.55 % Ni, 0.50 % Cr, 0.020 % Mo 85XX 8615-8660 0.55 % Ni, 0.50 % Cr, 0.25 % Mo 87XX 8720-8750 3.25 % Ni, 1.20 % Cr, 0.12 % Mo 93XX 9310-9317 0.45 %Ni, 0.40 % Cr, 0.12 % Mo 94XX 9437-944511/8/2011 7
  8. 8. Table3.3 Classification of steel Classification Number Range of Number0.45 % Ni, 0.15 % Cr, 0.20 % Mo 97XX 9747-97631.0 % Ni, 0.80 % Cr, 0.25 % Mo 98XX 9840-9850Boron (~0.005 % Mo) XXBXXBoron is denoted by addition of B. Boron-Vanadium is denotedby addition of BV. Example: 14BXX, 50BXX, 80BXX, 43 BV14. Theletters appearing before the no indicate the following: A, Alloybasic open hearth: B, carbon-acid Bessemer; C, carbon basicopen hearth; D, carbon acid open hearth; E, electric furnaceStainless and heat resisting steels:2XX Chromium- Nickel-Manganese types3XX Chromium- Nickel types4XX Straight Chromium types5XX Low Chromium typesAll stainless steels are produced in electric furnace11/8/2011 8
  9. 9. Classification ContdB. Alloy Steel 1.low alloys-special alloying elements totaling less than 8.0 % 2. High alloys- special alloying elements totaling more than 8.0 % Low carbon steel is used for wire, structural shapes, and screw machine parts such as screws, & bolts. Medium carbon steels are used for rails, axles, gears, and parts requiring high strength & moderate to great hardness. High carbon steels find use in cutting tools such as knives, drills, taps, and for abrasion resisting properties.11/8/2011 9
  10. 10. Classification ContdThe Society of Automotive Engineers (SAE) hasestablished standards for specific analysis of steels. Inthe 10XX series, the first digit indicates a plain carbonsteel. The second digit indicates a modification in thealloys. 10XX means that it is a plain carbon steelwhere the second digit (zero ) indicates that there isno modification in the alloys. The last two digits denotethe carbon content in points. For example SAE 1040 isa carbon steel where 40 points represent 0.40 %Carbon content. Alloy steels are indicated by 2XXX,3XXX, 4XXX, etc.. The American Iron and SteelInstitute (AISI) in cooperation with the Society ofAutomotive Engineers (SAE) revised the percentagesof the alloys to be used in the making of steel, retainedthe numbering system, and added letter prefixes toindicate the method used in steel making. The letterprefixes are:12/6/2011 10
  11. 11. Classification of SteelsA = alloy, basic open hearthB = carbon, acid BessemerC = carbon, basic open hearthD = carbon, acid open hearthE = electric furnaceIf the prefix is omitted, the steel is assumedto be open hearth. Example: AISI C1050indicates a plain carbon, basic-open hearthsteel that has 0.50 % Carbon content.Another letter is the harden ability or H-value. Example: 4340HGeneral representation of steels:12/6/2011 11
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  19. 19. Classification Contd• Red Hardness: This property , also called hot- hardness, is related to the resistance of the steel to the softening effect of heat. It is reflected to some extent in the resistance of the material to tempering.• Hardenability: This property determines the depth and distribution of hardness induced by quenching.• Hot-shortness: Brittleness at high temperatures is called hot-shortness which is usually caused by sulfur. When sulfur is present, iron and sulfur form iron sulfide (FeS) that is usually concentrated at the grain boundaries and melts at temperatures below the melting point of steel. 12/6/2011 20
  20. 20. Classification Contd• Due to the melting of iron sulfide, the cohesion between the grains is destroyed, allowing cracks to develop. This occurs when the steel is forged or rolled at elevated temperatures. In the presence of manganese, sulfur tends to form manganese sulfide (MnS) which prevents hot- shortness.• Cold-shortness: Large quantities of phosphorus (in excess of 0.12%P) reduces the ductility, thereby increasing the tendency of the steel to crack when cold worked. This brittle condition at temperatures below the recrystallization temperature is called cold-shortness.12/6/2011 21

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