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Transcript of AUTOBODY MATERIALS - LECTURE 3.pdf
7/29/2019 AUTOBODY MATERIALS - LECTURE 3.pdf
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Automotive Materials
Autobody Materials
Introduction
The ‘body-in white’, a traditional name for the body structure (BIW)
Body in White or BIW refers to the stage or progress of automobile manufacturing in which the car
body sheet metal (including doors, hoods, and deck lids) has been assembled before the
components (chassis, motor ) and trim (windshields, seats, upholstery, electronics, etc.) have
been added.
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Automotive Materials
Autobody Materials
Materials Usage
Auto body frames, windows, chassis, bonnet
Steels
Aluminium alloys
agnes um a oys
Polymer
Ceramics
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Automotive Materials
Autobody Materials
B - I -W : Body in White ; Materials usage
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Automotive Materials
Autobody Materials
Steels
Steel
HSLA – High Strength Low Allow steels
TRIP – Transformation Induced Plasticity steels
IF – Interstitial Free steels
DP – Dual Phase steels
ULSAB – Ultra Light Steel Auto Body
ULSAS - Ultra Light Steel Auto Suspension
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Automotive Materials
Autobody Materials
HSLA : High Strength Low Alloy Steels – Introduction & Composition
High-strength low-alloy (HSLA) steels, or micro alloyed steels.
They were developed primarily for the automotive industry to replace low-carbon steels in order
to improve the strength-to-weight ratio and meet the need for higher-strength construction-grade
materials, particularly in the as rolled condition.
ompos on:
carbon contents (0.50 to ~0.25% C) in order to produce adequate formability and weldability, and
manganese contents up to 2.0%
Small quantities of chromium, nickel, molybdenum, copper, nitrogen, vanadium, niobium, titanium,
and zirconium are used in various combinations.
Titanium, vanadium, and niobium are added for strengthening purposes
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Automotive Materials
Autobody Materials
HSLA : Properties, Application, & Products
Properties:
better mechanical properties and/or greater resistance to atmospheric corrosion than conventional
carbon steels.
with excellent strength and toughness , high strength-to-weight ratio, abrasion resistance
(HSLA steels have yield strengths of more than, 275 Mpa ).
Application:
oil and gas line pipe, ships, offshore structures, automobiles, off-highway equipment, and pressure
vessels.
Product:
The HSLA steels are commonly furnished in the as-rolled condition.
They may also be supplied in a controlled-rolled, normalized, or precipitation-hardened condition to
meet specific property requirements.
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Automotive Materials
Autobody Materials
HSLA : Production & Heat treatment
Production and Heat treatment:
Product: plates,
structural shapes,
bars, and sheet
[yield strength 290
to 690 Mpa]
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Automotive Materials
Autobody Materials
HSLA : Specification & Types
SAE or ASTM Specification:
The SAE high-strength, low-alloy steels
The ASTM high-strength, low-alloy steels are covered under various specifications including
A242, A440, A441, A572, A588, A606, A607, A618, A633, A656, A690, A709, A714, A715, A808,
A812, A841, A860, and A871.
HSLA alloys can be grouped into four classes:
(i) as-rolled carbon-manganese steels;
(ii) high-strength low-alloy steels;
(iii) heat-treated carbon steels;
(iv) heat-treated low-alloy steels.
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Automotive Materials
Autobody Materials
HSLA : Application
Application:
These HSLA steels have found wide application in areas such as bridge construction (structural
beams), off-shore oil and natural gas platforms, ship hull and deck plate, and electrical transmission
towers and poles.
In the automobile, HSLA steels are used for safety (ultrahigh-strength impact door beams and
energy-absorbing bumper assemblies) and for increasing fuel economy through thinner (lighter
weight) chassis structural sections.
Microalloyed HSLA steels are also employed in large-diameter gas transmission pipelines.
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Automotive Materials
Autobody Materials
HSLA : Application
Application:
in a typical passenger car such as door-intrusion beams, chassis members, reinforcing and
mounting brackets, steering and suspension parts, bumpers, and wheels truck bodies,
other applications include frames, structural members, scrapers, truck wheels, cranes, shovels,
-, , , , , .
Mining equipment and other heavy-duty vehicles use HSLA sheets or plates for chassis
components, buckets, grader blades, and structural members outside the body.
Structural forms are specified in applications such as offshore oil and gas rigs, single-pole
power-transmission towers, railroad cars, and ship construction.
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Automotive Materials
Autobody Materials
HSLA Comparison with Alloy steels & Low Alloy steels,
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Automotive Materials
Autobody Materials
HSLA : SAE Grade
A t ti M t i l
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Automotive Materials
Autobody Materials
HSLA : SAE Grade
Automotive Materials
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Automotive Materials
Autobody Materials
HSLA : Mechanical Property
Automotive Materials
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Automotive Materials
Autobody Materials
HSLA : Mechanical Property
Automotive Materials
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Automotive Materials
Autobody Materials
DP : Dual Phase Steels
DUAL-PHASE STEELS are a new class of high-strength low alloy (HSLA) steels.
This class is characterized by a tensile strength value of approximately 550 MPa (80 ksi) and by
a microstructure consisting of about 20% hard martensite particles dispersed in a soft ductile
ferrite matrix.
The term dual phase refers to the predominance in the microstructure of two phases, ferrite and
martensite. one of which is soft and the other significantly harder.Martensite
Ferrite
Automotive Materials
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Automotive Materials
Autobody Materials
DP : Alloying
Using thinner sheets of high-strength dual-phase steels for automobile bodies would save weight.
Carbon content of less than 0.1%.
Manganese in amounts of 1 to 1.5% is added to ensure sufficient hardenability.
Chromium and molybdenum have also been added in amounts that are usually under 0.6%.
Silicon is added to provide solid solution hardening.
Small amounts of micro alloying additions, such as vanadium, niobium, and titanium, may be
added to provide precipitation hardening.
Nitrogen may be added to intensify the precipitation-hardening effects of vanadium.
Automotive Materials
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Autobody Materials
DP : Production by Heat treatment
The simplest way of achieving a duplex structure is to use intercritical annealing in which the steel
is heated into the (α+γ) region typically at 790◦C for several minutes to allow small regions of
austenite to form in the ferrite.
As it is essential to transform these regions of austenite into martensite, cooling to ambient
temperature must be sufficiently rapid.
Alternatively, the hardenability of the austenite must be enhanced by adding between 0.2 and
0.4wt% Mo to a steel already containing 1.5wt% manganese.
The required microstructure can then be obtained by air cooling after intercritical annealing.
Automotive Materials
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Autobody Materials
DP : Application
Dual-phase steels are being applied in applications such
as automobile wheel rims and wheel disks.
Because of their energy-absorbing characteristics, dual-phase steels are being used in critical
locations of the automobile for safety to protect the occupants in the event of a crash