The production of car body, especially the production of all kinds of manned vehicle body, is the quintessence of the automobile industry. The body building almost takes up 30% of the total investment of the automobile manufacturing company. The quality of the body is 30% of the total mass, and the reduction of its quality plays a vital role in reducing the quality of the vehicle.
Aluminum sheet for manned vehicle
The brand and chemical composition of the ABS plate aluminum alloy of the car body are shown in the following table. With 2 series, 5 series and 6 series in the body can, 7 series alloys, in addition to 5 series alloy, three other alloys are heat treatment can enhance the strength in their painting baking (170--200 C, 20--30min) has been further improved, for the manufacture of high light and high rigid plate, the strength of 6*** alloy although low, but the plastic forming performance, used in the manufacture of complex shaped plate. 6009 and 6010, the strength of the body plate alloy after T4 treatment is lower than that of 5182-O and 2036-T4 alloy, but the plasticity is quite high. After molding, the artificial aging can achieve higher strength in the process of spraying and baking. These two alloys can be used to make both inner and outer panels separately, or 6009 alloy to make inner wall panels, and two with 6010 alloy to make outer wall panels.
The thickness of the sheet metal parts for the car body of a manned vehicle is 0.9--1.3mm, and about 19 panels per car. Body parts of large size and complex shape, mainly through punching and bulging two composite molding production, and the latter mainly. The joint of the sheet metal parts is welded or bonded, and it is also linked to the fastener.
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ABS Aluminum Sheet Chemical Compostion
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Alloy
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Si
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Fe
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Cu
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Mn
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Mg
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Cr
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Zn
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Ti
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Others
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Aluminum Min.
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Each
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Total
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5182
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0.20
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0.35
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0.15
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0.20-0.50
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4.0--5.0
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0.10
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0.25
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0.10
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0.05
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0.15
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Remainder
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5754
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0.40
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0.40
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0.10
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0.50
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2.6--3.6
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0.30
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0.20
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0.15
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0.05
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0.15
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Remainder
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6016
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1.0--1.5
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0.50
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0.20
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0.20
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0.25--0.6
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0.10
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0.20
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0.15
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0.05
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0.15
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Remainder
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6014
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0.30-0.60
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0.35
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0.25
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0.05--0.20
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0.40--0.8
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0.20
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0.10
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0.10
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0.05
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0.15
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Remainder
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ABS Aluminum Sheet Physical Property( thickness 0.9mm--1.3mm)
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Alloy Temper
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90º Bending radius
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cupping value/mm
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N Value
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R Value
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Tension Strength Rm/N.mm¯²
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Yield Strength Rp0.2/N.mm¯²
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Elongation A₅/%
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5182 - O
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1/2t
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0.33
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0.80
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28.1
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13.3
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26
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5754 - O
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1/2t
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0.31
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0.67
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215
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108
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53
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6016 - T4
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1/2t
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10
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0.26
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0.75
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24.0
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13.0
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26
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6014 - T4
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1/2t
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0.26
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0.65
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17.9
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13.0
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23
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6111 - T4
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1/2t
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8.4
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29.6
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16.2
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26
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The aluminum sheet of the ABS body also needs to have the performance:
A. Good formability.
Forming the body and cover of the metal plate is moved over from the aviation industry, the Aluminum Alloy automotive body sheet forming should have good formability, which has low yield ratio and high forming limit (FLC forming, limit curve), with very high space forming stress deformation in stamping different.
B. Surface roughness
Aluminum Alloy must have good ductility and flanging forming after surface color consistent performance of the sheet metal forming surface does not appear in Luoping line (roping line), namely the slip line. It is due to uneven grain or uneven distribution of inclusions, resulting in uneven surface deformation of the sheet, so that the surface is inconsistent after the paint.
B. Good weldability.
Good welding performance meets the requirements of continuous welding process for automobile construction after forming. The plate should have anti ageing stability, to ensure that the board before the factory to the stamping production without limitation, prevent the stamping of the yield point of the material increased, induced by Lu De with (Lude 's zone) surface caused by uneven deformation and wrinkling, thus affecting the surface quality of automobile outer panels.
D. Excellent baking hardening
Lightweight automobile also requires plate with high bake hardening, the yield strength of plate after stamping deformation and paint baking increased, so as to ensure the stamping sheet metal paint after high dent resistance, compatibility Aluminum Alloy plate paint baking process and the steel stampings especially baking process the.
Specification of aluminum automotive body sheet:
Alloy: 5182, 5754, 6016, 6014, 6111
Temper: T4, O
Surface treatment: EDT, Prelubrication, Primer coated
Strip/sheet width: 1000-2300mm
Strip/sheet gauge: 0.6--3.2mm
Capacity: 100 000 tonne/ year
Car body aluminum sheet pretreatment line
Surface Topography for car body sheet
Established surface topography is EDT(electric discharge texturing), transferred to the strip surface from texturized rolls during the last rolling pass.
Advantage of EDT topography
1) Isotropic, no directional influence on forming behaviour
2) Lubrication pockets lead to build up of hydrostatic pressure
Low and regular friction coefficient;
Better formability than with Mill finish surface
Less pick-up of work piece material on the tool surface
Regular press parameters
3) Stochastic surface structure
Good lacquer appearance
Chemical and electrochemical pretreatments
Different types of pretreatments can be applied on the strip surface--depending on the costomer requirements:
1) Degreasing
2) Pickling
3) Conversion treatments
Ti- or Ti/Zr-fluoride based agents, without or which polymer addition, mainly for hem flange bonding,
As pretreatment for primer or prelacquer application.
Prelubrication
Advantages of dry lubrication sheet
1) surface protection during transport and storage
2) Automatic destacking of panels in the press shop
3) No oiling operation
4) No operators at line entry to remove interleave paper
5) Improved formability compared to drawing oil
6) Constant friction conditions during pressing
7) Increased stamping rate
8) Less problems with surface contamination
9) Compatible with mechanical joining and bonding
10) Removable with mild alkaline degreasing agents
11) E-coat compatible products are available
Combination of conversion+lubrication+ PX treatment on the Al strip= combination of the advantages
Advantages of primer coated sheet
1) surface protection, during transport and handling
2) Improved formability(lubrication still required)
3) Protection against corrosion
4) Good basis for bonding
5) Good basis for lacquering, less influence of the Zn-phosphating conditions
6) Surface appearance of lacquered Al parts compatible with that of steel parts.
Primer coated strip--benefit for car producer
1) easier processing of aluminum sheet on equipment optimized for steel
2) Suitable for use in mixed metal constructions
3) Grinding of the formed panels, reduction of the corrosion resistance
4) Not weldable, bonding and mechanical joining
5) Recyclability, less value of process scrap
