Metal Alloys Formation WEC

Objective To have an understanding of Manufacturing of steels & their products, Alloy designation, Classification, Properties & uses of various types …..Plain/ alloy/tool etc, Effects of common alloying elements WEC

Metal Alloys Most engineering metallic materials are alloys. Elemental metals are generally very soft and not very usable. Metals are alloyed to enhance their properties, such as strength, hardness or corrosion resistance, and to create new properties, such as superconductivity and shape memory effect. Engineering metal alloys can be broadly divided into Ferrous alloys and Non-ferrous alloys WEC

Engineering Materials

Classes of Metals Metal Non-ferrous Ferrous Cast irons Steels Grey iron Nodular iron White iron Malleable iron Alloy cast irons Carbon Low Alloy High Alloy Low-C Medium-C High-C Tool (Mo,V,W,Cr, Ni) Stainless (Cr, Ni) …… High- strength low-alloy WEC

Steel Structural framing Roofing / Cladding Interior products WEC

The Whole Spectrum of Steel Products! WEC

Alloy Designation WEC

AISI - SAE Classification System AISI XXXX American Iron and Steel Institute (AISI) classifies alloys by chemistry 4 digit number 1st number is the major alloying element 2nd number designates the subgroup alloying element OR the relative percent of primary alloying element. last two numbers approximate amount of carbon (expresses in 0.01%) American Iron and Steel Institute (AISI) classifies alloys by chemistry started by Society of Automotive Engineers (SAE) provide standardization of steel used in the automotive industry expanded by AISI to include all engineering materials 4 digit number 1st number is the major alloying agent 2nd number designates the subgroup alloying agent last two numbers approximate amount of carbon expresses in 0.01% 1080 steel would be plain carbon steel with 0.80% carbon 4340 steel would be Mo-Cr-Ni alloy with 0.40% carbon Refer to table 6-2 in book http://www.steelnumber.com/en/number_en10027_eu.php

Carbon Steels and Low Alloy Steels Alloy Designation Alloy Designation AISI: American Iron and Steel Institute SAE: Society of Automotive Engineers ASTM: American Society for Testing and Materials UNS: Unified Numbering System AISI Grade X1X2X3X4 Older, but still widely used 1040 Fe-0.4%C 2520 Fe-5%Ni-0.2%C 10, 11, 12 plain C steel 13 Mn steel 2x Ni steel, x=%Ni 3x Ni-Cr Steel, x=%Ni+Cr 4x Mo Steel, x=%Mo 5x Cr steels, x=%Cr 6x Cr-V Steels, x=%Cr+V 7x W-Cr Steels, x=%W+C 9x Si-Mn Steels, x=%Si+Mn X1X2 Primary alloying elements Carbon content 5195 =? eg. 15 = 0.15%C Fe-1%Cr-0.95%C WEC

What is a steel and alloy of? Iron (Fe) and Carbon (C) WEC

Plain Carbon Steels An alloy of Fe & C whose properties depends only upon the %age of Carbon present in it. WEC

Classes of Metals Metal Alloys Non-ferrous Ferrous Cast irons Steels Grey iron Nodular iron White iron Malleable iron Alloy cast irons Carbon Low Alloy High Alloy Low-C Medium-C High-C Tool (Mo,V,W,Cr, Ni) Stainless (Cr, Ni) …… High- strength low-alloy WEC

Plain Carbon Steel vs. Alloy Steel Lowest cost Should be considered first in most application Classifications Low Carbon Steel Medium Carbon Steel High Carbon Steel Plain Carbon Steel Lowest cost Should be considered first in most application 3 Classifications Low Carbon Steel Less than 0.20% Carbon Good formability and weldability Lacks hardenability (Difficult to harden) Medium Carbon Steel 0.20% to 0.50% Carbon Good toughness and ductility Poor Hardenability (typically limited to water quench) High Carbon Steel Greater than 0.50% carbon Low formability High hardness and wear resistance Poor hardenability (quench cracking occurs) WEC 14

Plain Carbon Steels: General Properties Yield strength: 300MPa (mild steels) - 700MPa (high C steels) Tensile strength: 400-1000 MPa Ductility: EL% 15-30 Young’s modulus: 210 MPa. Divided into low (<0.3%C), medium (0.3-0.6%C) and high (0.6-1.2% C) carbon levels Increasing C content increases strength & hardness, but decreases ductility & toughness WEC

Low Carbon Steel Carbon < 0.3wt% Used wherever soft, deformable materials are needed E.g., structural sections, rivets, nails, wire, pipe. WEC

Medium Carbon Steels Carbon = 0.3 - 0.6wt% Used where higher strength is required E.g., gears, shafts, axles, rods, etc. WEC

High Carbon Steels Carbon = 0.6 - 1.2wt% used where high hardness is required E.g. hammers, chisels, drill, springs. WEC

Mild steel panels for easy shaping high-carbon steel springs Medium-carbon steel chassis for strength and toughness WEC

Classes of Metals Metal Alloys Non-ferrous Ferrous Cast irons Steels Grey iron Nodular iron White iron Malleable iron Alloy cast irons Carbon Low Alloy High Alloy Low-C Medium-C High-C Tool Tool (Mo,V,W,Cr, Ni) Stainless (Cr, Ni) …… High- strength low-alloy WEC

Alloy Steel Alloy steel may be defined as one whose characteristics properties are due to some elements other than Carbon. Although all Plain-Carbon steels contain moderate amounts of Mn & Si, but they are not considered alloy steels because the principal function of Mn & Si is to act as de-oxidizer during steel manufacturing process. WEC

Why alloying is necessary? WEC

Why alloying is necessary? Many purposes, some of the most important are:- i. increase harden-ability, ii. reduce danger of warpage, iii. improve strength & toughness at high & low temperatures, iv. resist grain growth at elevated temperature, v. improve wear, corrosion, fatigue & creep resistance. vi. improve machine-ability, vii. improve magnetic properties. WEC

Alloying Elements used in Steel Nickel (Ni) (2xxx) 2% to 5% Increases toughness Increases impact resistance 12% to 20% with low amounts of C possess great corrosion / scaling resistance universal grain refiner in alloy steels unfortunately is a powerful graphitiser. Invar contains 36% Ni virtually no thermal expansion used for sensitive measuring devices Nickel (Ni) added to steel to increase toughness and impact resistance 2% to 5% typically used in combination with Chromium and Molybdenum 12% to 20% Nickel AND low amounts of Carbon possess great corrosion resistance Invar contains 36% Ni virtually no thermal expansion used for sensitive measuring devices WEC 24

Alloying Elements used in Steel Chromium (Cr) (5xxx) Usually < 2% increases hardenability and strength 5 % Cr steels used for making forging dies typically used in combination with Ni and Mo 10.5% < Cr < 27% = stainless steel – used for corrosion resistance Improves non-scaling properties Causes grain growth Reduces toughness Chromium (Cr) Usually less than 2% used primarily to increase hardenability and strength typically used in combination with Ni and Mo chromium carbides can enhance wear resistance Molybdenum (Mo) Usually less than 0.3% used to increase hardenability and strength Mo-carbides help increase creep resistance at elevated temps typical application is hot working tools WEC 25

Alloying Elements used in Steel Molybdenum (Mo) (4xxx) Usually < 0.3% has strong carbide stabilizing influence increases hardenability and strength Mo-carbides help increase creep resistance at elevated temps imparts some sluggishness to tempering influences improves the tensile strength & sp. heat resistance has favorable influence on the welding properties. Steel with higher contents tend to be difficult to forge typical application is hot working tools Chromium (Cr) Usually less than 2% used primarily to increase hardenability and strength typically used in combination with Ni and Mo chromium carbides can enhance wear resistance Molybdenum (Mo) Usually less than 0.3% used to increase hardenability and strength Mo-carbides help increase creep resistance at elevated temps typical application is hot working tools WEC 26

Alloying Elements used in Steel Manganese (Mn) acts as de-oxidizer during steel manufacturing combines with sulfur (MnS) to prevent brittleness & improves machining forms stable Carbides >1% increases hardenability improves strength, wear resistance of steel 11% to 14% increases hardness good ductility high strain hardening capacity excellent wear resistance Ideal for impact resisting tools Manganese (Mn) combines with sulfur to prevent brittleness >1% increases hardenability 11% to 14% increases hardness good ductility high strain hardening capacity excellent wear resistance Ideal for impact resisting tools Sulfur (S) usually not desired in steel because it will impart brittleness, but okay if combined with Mn Some free-machining steels contain 0.08 to 0.15% S WEC 27

Alloying Elements used in Steel Vanadium (V) Usually 0.03% to 0.25% has strong carbide-forming tendency. stabilities martensite and increases hardenability. induces resistance to softening at high temperatures once the steel is hardened increases hot hardness properties in High Speed & Tool steels by increasing cutting properties. increases strength without loss of ductility Like Nickel it restrains grain growth Vanadium (V) Usually 0.03% to 0.25% Va-carbides help to increase strength without loss of ductility elastic limit, yield point, and impact strength Tungsten (W) helps to form stable carbides increases hot hardness used in tool steels WEC 28

Alloying Elements used in Steel Tungsten (W) helps to form stable carbides renders transformations very sluggish - hence, once hardened, a steel resists tempering influences. increases hot hardness used as cutting tool steels Vanadium (V) Usually 0.03% to 0.25% Va-carbides help to increase strength without loss of ductility elastic limit, yield point, and impact strength Tungsten (W) helps to form stable carbides increases hot hardness used in tool steels WEC 29

Alloying Elements used in Steel Sulfur (S) (11xx) Imparts brittleness Okay if combined with Mn Improves machining Some free-machining steels contain 0.08% to 0.15% S Sulfur (S) usually not desired in steel because it will impart brittleness, but okay if combined with Mn Some free-machining steels contain 0.08 to 0.15% S WEC 30

Alloying Elements used in Steel Boron (B) (14xx) for low carbon steels, can drastically increase hardenability improves machinablity and cold forming capacity Aluminum (Al)) Boron (B) for low carbon steels, B can drastically increase hardenability as the carbon content goes up the hardenabilty goes down improves machinablity and cold forming capacity Aluminum (Al) deoxidizer 0.95% to 1.30% produce Al-nitrides during nitriding deoxidizer 0.95% to 1.30% produce Al-nitrides during nitriding WEC 31

Alloying Elements used in Steel Copper (Cu) 0.10% to 0.50% increases corrosion resistance Reduces surface quality and hot-working ability used in low carbon sheet steel and structural steels Copper (Cu) 0.10% to 0.50% helps to increase corrosion resistance surface quality and hot-working ability decline used in low carbon sheet steel and structural steels Silicon (Si) about 2% helps to increase strength without loss of ductility used in structural steels and spring steels also helps to enhance magnetic properties Silicon (Si) About 2% increases strength without loss of ductility enhances magnetic properties WEC 32

Alloy Steel >Most common alloy elements: Chromium, nickel, molybdenum, vanadium, tungsten, cobalt, boron, and copper. Added in small percents (<5%) increase strength and hardenability Added in large percents (>20%) improve corrosion resistance or stability at high or low temps Alloy Steel What classifies a steel as an Alloy Steel > 1.65%Mn, > 0.60% Si, or >0.60% Cu Definite or minimum amount of an alloying element is specified Most alloying elements added to steel are < 5% to increase strength and hardenability Most alloying elements added to steel are > 20% to improve corrosion resistance or stability at high or low temps WEC 33

High Strength Low Alloy Steels Low alloy =  alloying elements <10% Yield strength : 800-1100 MPa Tensile strength: 950-1300MPa Ductility : EL% 15-20 Young’s modulus: 200 MPa (alloying generally reduces Young’s Modulus) Uses Used where high strength or hardness is needed – eg high strength bolts, connecting rods, springs, torsion bars, ball bearings. WEC

Classes of Metals Metal Alloys Non-ferrous Ferrous Cast irons Steels Grey iron Nodular iron White iron Malleable iron Alloy cast irons Carbon Low Alloy High Alloy Low-C Medium-C High-C Tool Tool (Mo,V,W,Cr, Ni) Stainless (Cr, Ni) …… High- strength low-alloy WEC

Tool Steels A class of (usually) highly alloyed steels designed for use as industrial cutting tools, dies, and molds To perform in these applications, they must possess high strength, hardness, hot hardness, wear resistance, and toughness under impact Tool steels are heat treated WEC

AISI Classification of Tools Steels T, M High‑speed tool steels ‑ cutting tools in machining H Hot‑working tool steels ‑ hot‑working dies for forging, extrusion, and die‑casting D Cold‑work tool steels ‑ cold working dies for sheet metal press-working, cold extrusion, and forging W Water‑hardening tool steels S Shock‑resistant tool steels ‑ tools needing high toughness, as in sheet metal punching and bending P Mold steels ‑ molds for molding plastics and rubber WEC

Tool Steels Carbon tool steels: 0.8~1.2%C High alloy tool steels are often alloyed with Mo, V, W, Cr and/or Ni E.g., HSS, W-Cr-V (18-4-1) Yield strength: 1000-1500 MPa Tensile strength: up to 2000MPa Ductility: EL% 5-15 Young’s modulus: 200 MPa (alloying generally reduces Young’s Modulus) WEC

Tool Steels Uses Used where extreme hardness is required. Ductility/toughness usually sacrificed E.g. Moulds and dies, saws, cutting tools, punches WEC

Stainless Steel (SS) Highly alloyed steels designed for corrosion resistance Principal alloying element is chromium, usually greater than 11.5% Cr forms a thin impervious oxide film that protects surface from corrosion “Stainless-ness” comes from the formation of a self-repairing Cr2O3 thin, adherent & impervious oxide film that protects or passivates the underlying steel. WEC

Stainless Steel (SS) Nickel (Ni) is another alloying ingredient in certain SS to increase corrosion protection Carbon is used to strengthen and harden SS, but high C content reduces corrosion protection since chromium carbide forms to reduce available free Cr, therefore Carbon content is kept very low - < 0.1% to avoid Cr3C2 formation WEC

Properties of Stainless Steels In addition to corrosion resistance, stainless steels are noted for their combination of strength and ductility While desirable in many applications, these properties generally make SS difficult to work in manufacturing Significantly more expensive than plain C or low alloy steels WEC

Types of Stainless Steel Classified according to the predominant phase present at ambient temperature: Austenitic stainless ‑ typical composition 18% Cr and 8% Ni Ferritic stainless ‑ about 11.5% to 27% Cr, low C (0.25% max), and no Ni Martensitic stainless ‑ as much as 18% Cr but no Ni, higher C content (0.15-0.75%) than ferritic stainless WEC

Additional Stainless Steels Traditional stainless steels developed in early 1900s Several additional high alloy steels have been developed and are also classified as stainless steels: 4. Precipitation hardening stainless ‑ typical composition = 17% Cr and 7%Ni, with additional small amounts of alloying elements such as Al, Cu, Ti, and Mo 5. Duplex stainless ‑ mixture of austenite and ferrite in roughly equal amounts WEC

Stainless Steels - Typical Mechanical Properties Yield strength : 200-1600 MPa Tensile strength : 300-1800MPa Ductility : EL% 2-20 Young’s modulus:~170 MPa (alloying reduces Young’s Modulus) WEC

Designation Scheme for Stainless Steels Three‑digit AISI numbering scheme First digit indicates general type, and last two digits give specific grade within type Examples: Type 302 – Austenitic SS 18% Cr, 8% Ni, 2% Mn, 0.15% C Type 430 – Ferritic SS 17% Cr, 0% Ni, 1% Mn, 0.12% C Type 440 – Martensitic SS 17% Cr, 0% Ni, 1% Mn, 0.65% C WEC

Assignment Alloy steels Cr steels Ni steels Ni-Cr steels Mn steels Mo- steels V-steels WEC

Thanks WEC