Subject: Design of Machine Elements Presentation On ALLOYING ELEMNTS ADDED TO STEEL AND EFFECTS Mechanical: 5 th B-2 Prepared by: Guided by: 1. Mohak Maniar Prof. Amit Patel

Strictly speaking, every steel is an alloy, but not all steels are called "alloy steels“. Alloy steel is steel that is alloyed with a variety of elements in total amounts between 1.0% and 50% by weight to improve its mechanical properties. Alloy steels are broken down into two groups: low-alloy steels and high-alloy steels. The difference between the two is somewhat arbitrary. Smith and Hashemi define the difference at 4.0%, while Degarmo, et al., define it at 8.0%. Most commonly, the phrase "alloy steel" refers to low- alloy steels. INTRODUCTION!

As to the character of their distribution in steel, alloying elements may be divided into two groups: 1) Elements that do not form carbides in steel 2) Elements that form stable carbides in steel NOW JUMPING STRAIGHT TOWARDS POINTS!

Alloying Elements that do not form carbides in steel are as fallows: Nickel Silicon Cobalt Aluminum and Nitrogen CONTINUE!

Alloying elements that form stable carbides in steel are as fallows: Chromium Manganese Molybdenum Vanadium Titanium Zirconium Niobium CONTINUE!

Chromium: Chromium Increases hardness and resistance to wear. Silicon: Silicon increase resistance to high temperature oxidation Manganese: Manganese increase Hardness and tensile strength and contracts the brittleness due to sulphur content. Nickel: Nickel improves toughness at low temperature and reduces distortion during heat treatment. Molybdenum: Molybdenum increases the hardness penetration of steel, slows the critical quenching speed, and increases high temperature tensile strength. Vanadium: Vanadium helps control grain growth during heat treatment. By inhibiting grain growth it helps increase the toughness and strength of the steel. EFFECTS PRODUCED

Copper: The addition of copper in amounts of 0.2 to 0.5 percent primarily improves steels resistance to atmospheric corrosion. Niobium: In low carbon alloy steels Niobium lowers the transition temperature and aids in a fine grain structure. Niobium retards tempering and can decrease the hardenability of steel because it forms very stable carbides. CONTINUE!

Depending upon the percentage of carbon, plain carbon steel are classified into the following three groups: Low Carbon Steel Medium Carbon Steel and High Carbon Steel PLAIN CARBON STEELS

It contains less than 0.3% carbon. It is popular as ‘Mild steel’. Low carbo0n steel are soft and very ductile. They can be easily machined and easily welded. Due to low carbon content, they are unresponsive to heat treatment. LOW CARBON STEEL Example Microstructure

It has carbon content in the range of 0.3% to 0.5%. It is popular as machinery tool. Medium carbon steel is easily hardened by heat treatment. It is stronger and tougher then low carbon steel. They can be machined well and they respond readily to heat treatment. MEDIUM CARBON STEEL Example Microstructure

High carbon steel contains more than 0.5% carbon. They are called hard steels or tool steels. When heat treated, they have very high strength combined with hardness. They do not have much ductility as compared with low and medium carbon steels. They are difficult to weld. HIGH CARBON STEEL Example Microstructure

ALLOY STEEL The term “Alloy steel” is used when some other elements are added into steel for improvement of property(Mechanical) of steel. Alloy steel is steel that is alloyed with a variety of elements in total amounts between 1.0% and 50% by weight to improve its mechanical properties. i.e.. 40Cr1,40Ni3… …

TYPE OF ALLOY STEEL & ELEMENTS Alloy steels are broken down into two groups: 1)low-alloy steels and 2)high- alloy steels. The Elements which are used in making of alloy steel as follows: Chromium (Cr)- Titanium(Ti) Cobalt(Co)# The reason for addition of these Nickel(Ni) Elements is to improve certain Manganese(Mn) mechanical properties of STEEL. Silicon(Si) Aluminum(Al) Copper(Co)

THE MULTIPLYING FACTOR Elements Multiplying factors Cr,Co,Ni,Mn 4 Si & W 4 Al,Be,V,Pb,Cu,Nb,Ti,Ta, Zr,Mo 10 - P,S,N 100

THE BASIC EFFECTS OF ELEMENTS Chromium increase Hardness and resistance to wear & tear and corrosion. Nickle improves Toughness at low temp. Distortion during heal. Manganese increases Hardness and tensile strength. Sulpher improves Contraction and brittleness. Silicon increases Resistance at high temp oxidation.

MAJOR ELEMENTS 1)NICKEL Nickel:- Nickel increases strength hardness and toughness with out sacrificing ductility. It increases hardenabillity of steel and impact resistance at low temp. The main effect if nickel is to increase toughness by limiting grain growth.

MAJOR ELEMENT 2) CHROMIUM Chromium Increases Hardness and wear resistance. Chromium steel components can be rapidly hardened in heavy sections. They retain strength and hardness at elevated temp. Chromium steel contain more then 4% of chromium and it has excellent corrosion resistance.

MAJOR ELEMENT 3)MANGANESE Most steel contain some manganese remaining from the oxidation and desulphurization process. However when it exceed 1% it regarded as alloying element. It increases hardness and strength. It also increases the depth of hardening. It’s also important alloying element in cutting steel.

Contents: Carbon : Silicon : Manganese : 1.3 – 1.80 ]Molybdenum : Uses: 1.Engineering Components such as crankshafts, bolts, wheel steels, axle shafts, levers and connecting rods. 2.Moreover, they are used in manufacturing power transmission components in a few machines. 35Mn2Mo45 Composition & uses of a few types of steels:

Components: Carbon : 0.35 – 0.45 Silicon : Manganese : Chromium : Molybdenum : Uses: 1.It is used in making axle shafts, crank shafts, connecting rods, gears, high tensile bolts and studs, propeller shaft joints, etc. 40 Cr 1Mo28

Components: Carbon : 0.3 – 0.4 Silicon : Manganese : Chromium : 0.40 – 0.75 Nickel : 1.0 – 1.5 Uses: 1.It is used in construction of air crafts and heavy vehicles, crank shafts, connecting rods, gear shafts, chain parts, clutches, flexible shafts for planar gears, camshafts, etc. 35NiCr60

Components: Carbon : 0.35 – 0.45 Silicon : Manganese : Chromium : 0.90 – 1.3 Nickel : 1.25 – 1.75 Molybdenum : Uses: 1.It is used for high strength machine parts collection, spindles, screws, high tensile bolts and studs, gears, pinions, axle shafts, tappets, boring bars, etc. 40Ni2Cr1Mo28

High speed tool steel Components: Carbon: 0.65 – 0.70 Chromium: 3.5 – 3.25 Vanadium: 0.8 – 0.8 Tungsten+1.8%molybdenum: – 6.50 Spring steel Carbon : 0.74 – 0.8 Silicon : 0.25 – 0.40 Manganese : 0.65 – 0.80 Phosphorus : Sulphur : Chromium : 0.35 – 0.4 COMPARISON OF COMPONENTS

PROPERTIES OF HIGH SPEED TOOL STEELS

High-carbon spring steels are the most commonly used of all springs materials. Try to use these materials in preference to others because they are the least expensive, readily available, easily worked, and most popular. These materials are not satisfactory for high or low temperatures or for shock or impact loading PROPERTIES OF SPRING STEELS

Wikipedia Design of Machine Elements by V B BHANDARI REFERENCE

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