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Home >> BMW >> 2021 >> M3 Base, Automatic Trans >> Repair and Diagnosis (Single Page) >> Collision >> Structural >> Collision - Body Panel Repair (G80) >> Body Panel Repair >> 41 00 Body Panel Repair General Information >> Structure Identification Materials Science (M3 Base, M3 Competition, M3 Competition M xDrive, M3 CS)

Structure Identification Materials Science (M3 Base, M3 Competition, M3 Competition M xDrive, M3 CS)

  1. Aluminum 
    1. 1.1 Chassis/suspension components 

      Read and observe the Notes on chassis components before handling aluminum

    2. 1.2 Material influences 
      Causes Effects/remedies
      A galvanic element is created under the effects of moisture by contact with materials such as copper, tin, nickel, iron and zinc This plating process causes aluminum to be removed from the connection point
      This results in surface corrosion or pitting
      New parts and accessory parts which have been approved by the BMW Group for aluminum (screws, washers, nuts etc.) have undergone special surface treatment
      Such parts must not be replaced by conventional parts
      NOTE: Damaged parts lose this protection and must be specially coated or replaced

      Damage caused by contact corrosion is excluded from the warranty
      Tools also used for work on steel components can implant steel particles in the softer surface of an aluminum component Surface corrosion or pitting occurs
      A separate tool set is available for processing/machining aluminum
      Surfaces are attacked when fluxing agents are used Soldering is not permitted for joining aluminum components
      Risk of corrosion from chemical factors
      Aluminum/steel grinding dust from adjoining working areas This results in surface corrosion. Erection of protective barriers
    3. 1.3 Machining properties
      Properties of aluminum compared with steel Effects
      Aluminum parts are magnetically neutral Attachment with magnetic tools/working aids is not possible
      Elasticity is only 1/3 as high
      Elongation failure is approx. 50 % slighter      		 Convertibility is limited in comparison with steel
      Overstretching the material results in strain-hardening and an increased tendency of cracking
      Electrical conductivity is almost 4 times higher Electric welding methods require different equipment (MIG welding)
      Material expansion during heating is twice as high The material expands more markedly. Shorter heat treatment is necessary for removing dents
      Thermal conductivity is 3 times higher Heat is drained more quickly. Adjoining working areas are affected more heavily e.g. during welding
      Structural transformation between 200°C and 250°C Elongation characteristics and thus plasticity are improved
      Strength is reduced
      IMPORTANT: No heat treatment during repair work on the vehicle structure! Workshop operation doesn't make it possible to control the temperature to sufficiently exact levels
      Aluminum shows no annealing colors The melting point is 650°C. Once the melting temperature has been reached, the material begins to flow without any further indications
      The temperature can only be estimated by means of the paint coloring and the surface warpage
      IMPORTANT: Do not use thermal pens. Not suitable for workshop operation because the paint runs too quickly
    4. 1.4 Storage
      Characteristic features of aluminum Special measures
      Corrosion (aging) in damp environments Store aluminum components in a dry place
      Contact corrosion in event of contact e.g. with steel components Always store aluminum components separately or in isolation from steel components
      Susceptibility to paint infiltration Do not damage factory protective coating of the surface since this would cause oxidation
      Failure to comply with this requirement would result in more painting work
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