Automotriz

8/8/2012

Materials for Automotive Industry
Alfredo Valarezo

Materials for Automotive Bodies

Before we start….
• The purpose of this course is to provide an easily understood presentation of the technology surrounding the choice and application of the main materials that can be used for the construction of automobiles. • Many reference works exist on specific designs and associatedmaterials. These tend to focus on individual materials, test methods or numerical simulations. • We will attempt to appraise all realistic and futuristic candidate materials and technologies with regard to design, manufacture, suitability for component production, corrosion resistance and environmental attributes, against relevant selection criteria.

Bodywork Materials Overview
• The bodyworkconveys:
• The essential identity, • Aesthetic appeal of the vehicle, and • It’s functionality

Old times

• Handcrafted bodies including: sheet metal, fabric, timber • Sheet metal (low carbon mild steel strip) • Aluminium, Magnesium, Plastics

40’s-80’s

Recently

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Bodywork Materials Overview (2)
• Energy Consumption in Production • Time • Cost

Steel
• Approximately,half a tone is required to produce a body of unitary construction and 40 to 45% is discarded in the form of press shop scrap • Steel scrap is recyclable but the value for baled offal is approx. 1/8 of the original price. Expenditure in body materials accounts for approx. 50% of the BIW (body-in-white) costs
- Reasonable cost - Extendend life of pressed components - Wide strength range - Adaptableto corrective rework -Ease and low cost of repair - Corrosion resistant when zinccoated

Process Chain Compatibility

Total Life Cycle of Materials

• Cost • Energy Consumption in service • Disposal • Pollution

Steel (2)
• Thickness (external panels) has shown an overall reduction (0.9 mm in 1920, to 0.7 mm and lower)
– – – – Thickness reduction - Cost savings Dent resistant grades-ensuring less cosmetic damage Weldable grades -with the least possible expense Formability- with the least possible expense
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Some History…
Nowadays: Design target of 12 years (up to 30 years) of freedom of perforation (corrosion wise): 1960: volume production, thinner gauges, demands for higher volume productions, shorter cycle times in the paint process (lack of consistency), incompletecoverage … corrosion !! 1970: cathodic electropriming better painting systems, galvanized steel gradually introduced 1980: increased use of zinc coated steels

• In 1960, it was chosen: flat, deep drawing or extra deep drawing qualities, either rimmed or killed (stabilized) made by ingot casting, yield strength of 140 Mpa. • Nowadays: Continuous casting, excellent drawing properties, surfacetechnology and good consistency of the products

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Historical Influences…
• • • Durability to Corrosion Increased safety standards with regard to occupant and pedestrian protection (better plastic than steel to hit your body !!) First legislation in US for improved fuel consumption was in 1973, partly as a result of the world oil crisis and also to pacify a growingantipollution lobby. This resulted in specified average fleet targets (e.g. 27.5 mpg for 1985) The response was:
– Thinner gauge steel – High strength low alloy steels, rephosphorized grades – Use of bake-hardened steels (during paint strengthening), high dent resistant Safety air-bags

Increasing utilization of high strength steel grades

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Current Requirements
• Environmental concerns: emissionscontrol (the need for weight reduction): the use of plastics and aluminium • Progressively lower levels of CO2 in terms of grams per kilometer, with tax incentives • Reducing CO2 levels by efficient use of energy and use of alternative fueling methods.

HSLA – high strength low alloy steels
• Excellent mechanical properties or great resistance to corrosion • Low alloy steel (> 5%) • They...