Materials for Automobiles

Lecture no 2

6 August 2011

Plan

1 Familiarization with Automobile

2 Iron Carbon Diagram

3 Phases in steel

4 Heat treatment of steel connected with iron Carbon diagram

5 Iron and steel manufacturing process

6 Discussion of IS 5517

7 Tensile testing

8 Hardness testing

Vehicle Systems

1 Structural (Load bearing) • Load body • Frame • Suspension • Axles • Hubs • tyres

2 Drive train : • Engine • Clutch • Gear box • Propeller shaft • Rear axle gears and axle shaft

3 Accessories: Cooling system, steering system, exhaust system, electrical and electronics, NVH,

4 Cab

2516 Super

Specification

Model : 2516 Super

Engine : H Series 6ETI 2K Turbocharged Intercooled

Power : 120 KW @ 2400 rpm

Torque : 575Nm @ 1600-1800 rpm

Clutch : 381 mm dia Ceramic Clutch with Hydraulic actuation

Gear box : ZF 6S36 ( 8.97:1 FGR)

Rear axle : Hypoid (6.17:1 RAR)

Front axle : ‘I” section, Non driver Reverse Elliot type

Propeller shaft : 1600 Series

Cowl : All steel G 45 FES/ G 90 cab

Frame : Bolted Construction with 9 Cross members

Suspension : Semi Elliptical multi leaf with equaliser link at rear

Frame side and cross members :

HSLA 6 mm

Spring brackets : SG iron

Product Features - Engine

Cylinder Block : Gray Cast iron

Cylinder Head : Gray Cast iron

Valve cover : Al casting

Inlet manifold : Al casting

Crankshaft : C steel forging Camshaft : C steel forging Piston : Aluminium casting Liners : special cast iron Valves : stainless steel Timing gears : low alloy steel forgings Sump: sheet steel

Product Features - Clutch

Cermet clutch facings

Damper springs : spring steel

Plate : medium C steel

Product Features – Gear Box

Gear box casing : Al casting

Clutch housing : Gray Cast iron

Gears & shafts : low C alloy steel forging

Front axle beam & steering knuckle: medium C low alloy steel

Product Features – Rear Axle

Brake drum : Gray Cast iron

Hub : SG iron Driving head : SG iron

Axle casing : 13 mm steel plate

Gears & crown wheel pinion : low C alloy steel forgings Axle shafts : upset forging medium C low allo steel Differential casings : SG Iron

Springs : Manganese silicon spring steel

Product Features – Diesel Tank

Fuel tank : cold rolled deep draw quality low C steel sheet

Phases in Fe-C system

α Ferrite

The solid solution of carbon in iron. At 0% C this is pure iron. BCC crystal structure.

The maximum solubility of carbon in iron is 0,02% at 723oC. At 0 oC temperature the solubility falls to

0,008%. The carbon atoms are located in the crystal interstices.

α... BCC crystal with crystal dimension a = 2,86 Angstrom exists at temperatures up to 910oC

Austenite The solid solution of carbon in γ iron is called austenite . This has a FCC crystal structure with a higher solubility for carbon compared with α ferrite. The solubility reaches a maximum of 2,08% at 1148oC . The solubility decreases to 0,8% at 723 oC The carbon atoms are dissolved interstitially. The difference in solubility between the austenite and α Ferrite is the basis for the hardening of steels γ... FCC crystal with crystal dimension a = 3,65 Angstrom exists at temperature range 910oC to 1403oC

Cementite This is an intermetallic compound which contains 6,67% C and 93,3% Fe. Cementite is a hard brittle compound with and orthorhombic crystal structure each unit cell has 12 Fe atoms and 4 C atoms

δ Ferrite..

This is a solid solution of carbon in iron and has a BCC crystal structure. The maximum solubility or C

in Fe is 0,09% at 1495oC. This has no real practical significance in engineering. δ... BCC crystal with

crystal dimension a = 2,93 Angstrom exists at temperature range 1403oC to 1535oC

A few comments on Fe–Fe3C system

C is an interstitial impurity in Fe. It forms a solid solution with α, γ, δ phases of

iron

Maximum solubility in BCC α-ferrite is limited (max.0.022 wt% at 727 °C) - BCC

has relatively small interstitial positions

Maximum solubility in FCC austenite is 2.14 wt% at 1147°C - FCC has larger

interstitial positions

Mechanical properties: Cementite is very hard and brittle -can strengthen steels.

Mechanical properties also depend on the microstructure, that is, how ferrite and

cementite are mixed.

Magnetic properties: α -ferrite is magnetic below 768 °C, austenite is non-

magnetic

Classification. Three types of ferrous alloys:

• Iron: less than 0.008 wt % C in α−ferrite at room T

• Steels: 0.008 - 2.14 wt % C (usually < 1 wt % )

α-ferrite + Fe3C at room T (Chapter 12) • Cast iron: 2.14 - 6.7 wt % (usually < 4.5 wt %)

Microstructure of hypoeutectoid steel

Eutectoid Point

When alloy of eutectoid composition (0.76 wt % C) is cooled

slowly it forms pearlite, a lamellar or layered structure of

two phases: α-ferrite (0.022 wt%) and cementite Fe3C (6.7 wt%) .

Microstructure of hypereutectoid steel

Hypereutectoid alloys contain proeutectoid cementite

(formed above the eutectoid temperature) plus pearlite that contain eutectoid ferrite and cementite.

Solidification of Ingots

Columnar and Equiaxed grain structure in Cast Ingot

IS 5517: Requirements Reduction ratio

For continuously cast bar/billets, a minimum reduction ratio of 6 : 1 between the cast product and the final product is recommended. However other reduction ratios may be mutually agreed upon between the manufacturer and the purchaser at the time of enquiry and order.

Trace Elements

Constituent Percent, Max Chromium 0.25 ; Nickel 0.25 ; Copper 0.35; Vanadium 0.05; Molybdenum 0.05 Boron 0.0003; Tin 0.05 NOTES 1 All reasonable precautions shall be taken to prevent the addition from scrap or other materials used in manufacture, or such elements which affect the hardenability, mechanical properties and applicability. 2 Trace elements when added together should not exceed 0.8 percent, however, restricted limits could be mutually agreed upon between the manufacturer and the purchaser at the time of enquiry and order. 3 ) % Copper + 10 × (% Tin) shall not exceed 0.60 percent.

Inclusion Rating

• Inclusion rating of the steel shall be determined in accordance with IS 4163 : 1982.

• The worst field of each inclusion from each specimen shall be recorded as a rating for the specimen. The inclusion rating for the specimen shall not exceed the following limits:

• a) For air melted quality (ABCD 3 Max) (thick and thin series)

• b) For vacuum, EFR of The inclusion rating Secondary refined steel shall be mutually agreed upon at the time of enquiry and order.

• When required and ordered, cleanliness of the steel can also be assessed by step down test, Blue fracture test, and magnetic particle tests methods as per IS 10138 (Part 1) : 1982, IS 10138 (Part 2) : 1983 and IS 10138 (Part 3) : 1983 or agreed to at the time of enquiry and order.

• The clause is not applicable for free cutting grade of steel as given in Table 2.

IS 5517: HT • 7 HEAT TREATMENT

• 7.1 Recommended temperature for hot working and heat treatments aimed at controlling the hardness, machinability, shearability, etc, are given in Table 4 for guidance only.

• 7.2 The mechanical properties in the hardened and tempered conditions for various limiting ruling section are specified in Table 5.

• 7.3 Only steels with inherently fine grain structure may be subjected to direct quench, provided the test bars comply with the mechanical properties specified in Table 5

Designation Hot Working Nominalizing Hardening Quenching Tempering

30C8 1 200 to 850 860 to 890 860 to 890 Water or Oil 550 to 660

40C8 1 200 to 850 830 to 860 830 to 860 Water or Oil 550 to 660

45C8 1 200 to 850

830 to 860 830 to 860 Water or Oil 530 to 670

46V1S3 1 200 to 850 — — Oil —

50Cr4V2 1 050 to 850 840 to 880 830 to 860 Oil 540 to 680

58Cr4V1 1 050 to 850 850 to 880 820 to 850 Oil 480 to 650

40Cr13Mo10V2 1 200 to 850 — 900 to 940 Oil 570 to 650

IS 5517 Mechanical Properties

• 9 MECHANICAL PROPERTIES

• 9.1 The properties given in Table 5 shall be applicable to test bars taken of rounds in the direction of rolling fibre, the axis of which corresponds to Fig. 1.

• 9.2 For rectangular sections, the range of equivalent sections shall be as given in Fig. 2.

• 9.3 Methods for determining the mechanical properties specified in Table 5 shall be in accordance with IS 1598 : 1977 and IS 1608 : 1972.

• 9.4 If required, the mechanical properties of the reference test bars after hardening and tempering in accordance with Table 6 shall conform to the requirements given in Table 5.

• Values other than specified in Table 5 shall be mutually agreed at the time of enquiry and order.

IS 5517: Mechanical properties Steel Designation Tensile Strength

MPa

0.2 Percent Proof

Stress 5.65/A MPa,

Min

Elongation Percent

Min

Izod Impact Joules Limiting Ruling

Section mm

Min

55C8 700 to 850 460 15 — 63

55C8 800 to 950 540 13 — 30

40C10S18 600 to 750 380 18 41 60

40C10S18 700 to 850 480 17 48 30

40C15S12 700 to 850 500 18 35 60

27C15 600 to 750 440 18 48 63

27C15 700 to 850 500 16 48 30

37C15 600 to 750 440 18 48 100

37C15 700 to 850 540 18 48 63

37C15 800 to 950 600 16 48 30

37C15 900 to 1050 700 15 41 15

IS 5517 : Hardenability

Steel

Grade

Spread Hardness HRC at a Distance from End Quench Face in mm

1.5 3 5 7 9 11 13 15 20 25 30 35 40 45 50

27C15 Max 55 54 51 48 42 39 37 33 31 29 28 27 27 26

min 43 40 32 24 20 — — — — — — — — — —

40Cr4 Max 61 61 60 59 58 56 54 52 46 42 40 38 37 36 35

min 53 52 50 47 44 40 37 35 30 27 25 23 22 21 20

42Cr4

Mo2

Max 61 61 61 60 60 59 59 58 56 53 51 48 47 46 45

min 53 53 52 51 50 48 45 43 38 35 34 33 32 32 32

50Cr4

Mo2

Max 65 65 64 64 63 63 62 61 60 58 56 55 54 53 53

min 57 56 56 55 53 52 50 48 44 41 40 39 38 37 37

Summary No Details

1 The iron carbon phase diagram gives the phases present in the iron carbon system for the carbon range 0 to 6.67% and for the temperature range 0 to 1600 degrees Centigrade

2 The decrease in solubility of carbon at room temperature compared with that over 723 degrees centigrade is the basis for hardening of steel.

3 The temperature for various heat treatments are decided based on the phases present.

4 Manufacture of pig iron from iron ore is by carbothermic reduction of the ore which is oxide. Steel is manufactured from pig iron through oxidation of carbon present using a modified basic oxygen converter.

5 Modern steel manufacturing techniques use a combination of ladle refining, vacuum degassing methods to reduce overall time and cost of steel making and at the same time ensuring good quality consistency with reference to steel cleanliness.

6 Modern production is mostly through the continuous casting route which gives a better yield and also better surface because of excellent shrouding of the stream from air. Continuous casting can be slab casting for flat products or billet casters for sections.

7 Reduction ratio of about 6:1 is preferred to ensure freedom from dendritic structure. However this can be review based on the end use and also if the steel plant uses electromagnetic stirring technology.