Lect 01 [Unit-01] Alsdasaasdasdadaloys.pptx

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1. [Unit-01] Alloys Purpose of making alloys; Types of alloys; Alloy steels; Light alloys; Cast alloys; Copper alloys; Nickel alloys; Nickel iron alloys; Nickel chromium alloys; Super alloys; Lead alloys; Bearing alloys; Modes of formation of alloys; Preparation of alloys; Treatment of alloys . Lect 01 1

2. Introduction An alloy is a metal created by combining two or more metallic elements. Different types of alloys are made for greater strength of the material or for resistance to corrosion. This durability makes alloys the basis of building in the modern world. Purpose of Making Alloys Pure metals possess few important physical and metallic properties, such as melting point, boiling point, density, specific gravity, high malleability, ductility, and heat and electrical conductivity. These properties can be modified and enhanced by alloying it with some other metal or non-metal , according to the need. 2

3. Alloys are made to: Enhance the hardness of a metal : An alloy is harder than its components. Pure metals are generally soft. The hardness of a metal can be enhanced by alloying it with another metal or nonmetal. Lower the melting point : Pure metals have a high melting point. The melting point lowers when pure metals are alloyed with other metals or nonmetals. This makes the metals easily fusible. This property is utilized to make useful alloys called solders. Enhance tensile strength : Alloy formation increases the tensile strength of the parent metal. Enhance corrosion resistance : Alloys are more resistant to corrosion than pure metals. Metals in pure form are chemically reactive and can be easily corroded by the surrounding atmospheric gases and moisture. Alloying a metal increases the inertness of the metal, which, in turn, increases corrosion resistance. Modify color : The color of pure metal can be modified by alloying it with other metals or nonmetals containing suitable color pigments . Provide better castability : One of the most essential requirements of getting good castings is the expansion of the metal on solidification. Pure molten metals undergo contraction on solidification. Metals need to be alloyed to obtain good castings because alloys expand... 3

4. Preparation of Alloys There are four commonly employed methods for the manufacture of alloys: the fusion method , the electro-deposition method , the reduction method , and powder metallurgy . 1. The Fusion Method This method uses alloying elements in a fixed proportion and fuses them together in a refractory melting pot or in a brick-lined crucible. The component metal with a higher melting point is melted first and then the other component with a lower melting point is added to the melt. Both metal components are mixed well and allowed to melt further. The molten mass is covered by powdered Carbon to avoid oxidation of the molten alloy components because they are very reactive to the surrounding atmospheric oxygen. The resulting molten mass is allowed to cool at room temperature. 4

5. Cont… The Electro-Deposition Method This method involves simultaneous deposition of different component metals from the electrolytic solution containing their salts solution mixture by passing direct electricity. The Reduction Method Metal may exist in the form of compounds. Reduction is a chemical process in which a compound of one component can be separated from another component, to get a pure metal. This method is performed in an electric furnace . Note: In all the methods used to prepare alloys, Carbon, salts, and oxides are residuals that may hinder the properties of the produced alloy, which is generally contaminated. 5

6. Cont…. Powder Metallurgy Powder metallurgy may be defined as the art of producing fine metal powders and then making articles from individual metal powders or alloyed metal powders. 6

7. Industrial Application of Alloys Alloys have been used in industries for a long time. Few widely used applications are: Stainless Steel is used in wire and ribbon forms for applications, such as screening, staple, belt, cable, weld, metalizing, catheter, and suture wire. Alloys of Gold and Silver are used in the preparation of jewelry. White Gold, which is an alloy of Gold, Silver, Palladium, and Nickel is used as cheap alternative of Platinum. A wide selection of alloys is used in welding applications by numerous industries. Some alloys function as corrosion-resistant materials and are used in moisture rich-environments. 7

8. Cont… High temperature alloys have been used for many aerospace and petrochemical applications. In addition, they have been used for welding wire , where elevated temperatures and harsh environments are routinely encountered. These alloys have been used in applications where corrosion resistance and high strength must be maintained at elevated temperatures. Magnetic alloys are used for magnetic cores and dry reed switches. Quality control measures include magnetic testing to maintain consistently high standards of uniformity and performance. Alloys are also used to produce internal and external leads. 8

9. Cont… Nickel-Chromium, Nickel-Chromium-Iron, and Iron-Chromium-Aluminum alloys have been used for high-temperature heating elements. Some alloys are used as resistance elements to control or measure electric current. Applications have included wire-wound resistors, rheostats, potentiometers, and shunts. Thermocouple alloys have found a wide-range of use in temperature sensing and control. Alloys are also used as thermostat metals, radio and electronic devices, precision devises in aircraft controls, telecommunications, automotive applications, and... 9

10. Types of Alloys: Chemistry and the Formation of Alloys An alloy is a stable metallic substance consisting of two or more metals. In some instances, an alloy may also contain non-metals. To find metals on the periodic table, look at the ladder created from boron to astatine. Elements to the left of that ladder are considered metals; to the right, non-metals. Traditionally, the main ingredient of the alloy is  melted  first, followed by dissolving the other ingredients into the molten mixture. The elements fuse, forming a substance that takes on properties of both. One difficulty in making alloys is that metals have different melting points. For example, copper melts at 1,083 degrees Celsius and zinc at 419 degrees Celsius. However , zinc also boils at 907 degrees Celsius. Therefore , to avoid the vaporization of zinc, brass is made by melting the copper first, then adding zinc so it will quickly dissolve. 10

11. Types of Alloys: Chemistry and Lattice Structure The strength of a metal is how much force the layers of atoms can tolerate before moving past each other. Alloys are stronger due to the distortion in the metal’s lattice structure. In steel, the smaller carbon atoms fit in between the iron atoms to create the stronger steel alloy. In the distorted lattice structure, atoms cannot move over/across each other as easily, making the alloy more resistant to higher forces. 11

12. Different Types of Alloys Several different types of alloys, the elements that comprise them and some of their uses are listed below: Aluminum Alloys Aluminum  is not a very strong metal but its conductive qualities make it useful for a variety of applications. For this reason, manufacturers mix aluminum with other metals to strengthen it, forming several different aluminum alloys: alnico (aluminum, nickel, copper); used in production of magnets magnalium (aluminum with 5 percent magnesium); instruments and alloy wheels on automobiles duralumin (copper, aluminum, in some instances, magnesium and manganese); components in car and aircraft engines 12

13. Cont… Copper Alloys The element copper is prone to oxidation which makes its surface turn a dull, pale-greenish color. To prevent oxidation and to increase its strength, manufacturers fuse copper with several different elements: brass (copper, up to 50 percent zinc); used in decorative items such as jewelry, as well as for nuts and bolts bronze (copper, 10 percent tin or aluminum); used for making coins, statues and decorative items 13

14. Cont… Iron Alloys steel (iron, 0.5 percent to 1.5 percent of carbon); widely used in construction, such as: refrigerators ranges Gold Alloys As a soft metal, pure gold is malleable and easy to work. Other metals are added to increase gold’s strength: yellow gold (gold, copper); all types of jewelry (rings, bracelets, necklaces, earrings) white gold (gold, with nickel, silver or palladium); all types of jewelry 14

15. Alloy Steel: Properties, Processing and Applications Alloy steel  is a class of steel that, in addition to carbon, is alloyed with other elements, ranging from 1 wt.% to 50 wt.%, which are used to enhance the material’s various properties . These elements commonly include manganese, nickel, chromium, molybdenum, vanadium, silicon, and boron. Less common elements include aluminium , cobalt, copper, cerium, niobium, titanium, tungsten, tin, zinc, lead, and zirconium. 15

16. Types of alloy steel There are multiple subcategories of alloy steel. These include: Low-alloy steel High-strength low alloy (HSLA) steel High-alloy steel Stainless steel Microalloyed steel Advanced high-strength steel (AHSS) Maraging steel Tool steel Low alloy steels generally contain less than 8 wt.% non-iron elements, whereas high-alloy steels contain more than 8 wt.% non-iron elements . Both typically have superior mechanical properties in comparison to carbon steels . 16

17. Properties of alloy steel Alloy steels can contain a wide variety of elements, each of which can enhance various properties of the material, such as mechanical thermal and corrosion resistance . Elements added in low quantities of less than around 5 wt.% tend to improve mechanical properties, for example increasing hardenability and strength, whereas larger additions of up to 20 wt.% increase corrosion resistance and stability at high or low temperatures 17

18. The effects of adding various elements to steel, along with the typical amounts in weight fraction, is summarized in the table below Element Symbol wt. % Function Aluminium Al 0.95–1.30 Alloying element in nitriding steels Bismuth Bi – Improves machinability Boron B 0.001–0.003 Improves hardenability Chromium Cr 0.5–2.0 Improves hardenability 4–18 Corrosion resistance Copper Cu 0.1–0.4 Corrosion resistance Lead Pb – Improves machinability Manganese Mn 0.25–0.40 Prevents brittleness in combination with sulfur >1 Increases hardenability Molybdenum Mo 0.2–0.5 Inhibits grain growth 18

19. Cont….. Nickel Ni 2–5 12–20 Increases toughness Improves corrosion resistance Silicon Si 0.2–0.7 Increases strength and hardenability 2 Increases yield strength (spring steel) Higher % Increases magnetic properties Sulfur S 0.08–0.15 Improves machinability (free-machining steel properties) Titanium Ti – Reduces martensitic hardness in Cr steels Tungsten W – Increases hardness at high temperatures Vanadium V 0.15 Increases strength while maintaining ductility, promotes fine grain structure 19

20. AISI (American Iron and Steel Institute) AISI standards is one of the most popular methods of designation in the field of stainless steel. AISI standards. All the different acronyms . Here some example: AISI-2XX – austenitic chromium-nickel- manganese steels AISI-3XX – austenitic chromium-nickel steels AISI-4XX – ferritic or martensitic chromium steels AISI-5XX – martensitic medium chrome steels AISI-6XX – chromium precipation hardening steels . 20

21. Cont…. According to the  AISI classification , steels can be divided into different series. Carbon steel (1000 series) : four-digit number + any prefix First digit: 1 Second digit: 0 (carbon steel), 1 ( resulphurized carbon steels, 2 ( resulphurized and rephosphorized carbon steels) Third and fourth digits: carbon content *100. Low alloy steel: four-digit number First and second digits: identify the series Two last digits: identify the carbon content *100. High-alloy steel 200 series (austenitic chromium- manganese steels) 300 series (austenitic chromium-nickel steels) 400 series ( ferritic or martensitic steels). 21

22. THANKS 22