Metallographic Experiment for Laser welding of automobile lithiu
In the power battery system of new energy vehicles, the battery shell accounts for about 20-30% of the total weight of the system, and is the main structural part of the battery.Lightweight and high safety make aluminum alloy battery pack casings the mainstream of power battery casings.The aluminum material used in power battery shell has the advantages of easy processing and forming, good high temperature corrosion resistance, good heat transfer and electrical conductivity.Therefore, the battery case with aluminum alloy is thinner and lighter than the steel case for the same capacity. In addition, once the battery explodes, the burst force of the aluminum case is also weaker than the steel case, and the harm caused by the aluminum shell power battery is relatively lower. At present, aluminum battery shells are mostly welded by laser.
01 Cutting
Cut the specimen with Beta-300Pro automatic cut-off machine；
Beta-300Pro automatic cut-off machine
Equipment
Beta-300Pro automatic cut-off machine
Consumables
SiC cutting blade
Parameter
6a，0.6mm/s，2200rpm
02 mounting- hot mounting
Hot mounting with TJ2231 epoxy resin；
MT-1H auto mounting press
Equipment
MT-1H auto mounting press
Consumables
TJ2231
Parameter
180℃，120bar，5min， Medium-speed cooling
03 mounting- cold mounting
Cold mounting with TJ2210 acrylic resin；
ThetaMount cold press
TJ 2210 Acrylic resin
Equipment
ThetaMount cold press
Consumables
TJ 2210 Acrylic resin
Parameter
0.3MPa，15min
04 Grinding
Grind the specimen with GP-2000A automatic grinder&polisher， abrasive paper P400→P2500；
GP-2000A automatic grinder&polisher
abrasive paper
Equipment
GP-2000A automatic grinder&polisher
Consumables
Abrasive paper：P400；P800；P1200；P2000；P2500
Parameter
Pressure: 0.3MPa, upper speed： 80rpm, lower speed: 150rpm, time: 2min
05 Polishing - Rough Polishing
Use GP-2000A automatic grinder&polisher to polish the specimen, first use YS polishing cloth, with 3μm polycrystalline diamond suspension for rough polishing while adding polishing lubricant.
YS-JP white fiber polishing cloth
PD-W polycrystalline diamond suspension
Equipment
GP-2000A automatic grinder&polisher
Consumables
YS polishing cloth，3μm polycrystalline diamond suspension，polishing lubricants
Parameter
Pressure: 0.3MPa, upper speed： 80rpm, lower speed: 150rpm, time: 2min
06 Polishing-medium polishing
Use GP-2000A automatic grinder&polisher to polish the specimen, and then use ET polishing cloth with 0.05μm alumina suspension in medium polishing；
ET-JP white synthetic velvet polishing cloth
AO-P Alumina suspension
Equipment
GP-2000A automatic grinder&polisher
Consumables
ET polishing cloth，0.05μm Alumina suspension
Parameter
Pressure: 0.3MPa, upper speed： 80rpm, lower speed: 150rpm, time: 2min
07 Polishing - Fine polishing
Polishing the specimen with GP-2000A automatic grinder&polisher, then using ET polishing cloth with 0.05μm silicon dioxide suspension for fine polishing；
ET-JP white synthetic velvet polishing cloth
SO T401 silica suspension
Equipment
GP-2000A automatic grinder&polisher
Consumables
ET polishing cloth，0.05μm silica suspension
Parameter
Pressure: 0.3MPa, upper speed： 80rpm, lower speed: 120rpm, time: 2min
08 Observation
Equipment
Leica DM2700M metallographic microscope
Consumables
Parameter
50×→500× times observation
09 Analysis
Right angle weld 50×
Right angle weld 200×
Fillet weld 50×
Fillet weld 200×
There are gaps in the fillet weld, so attention should be paid to cleaning the sample during grinding and polishing to prevent the leakage of the coarse particles contained and leave large scratches on the surface of the sample.
The sample preparation results of cold mounting and hot mounting is the same.
Corrode the specimen with Keller's reagent.
Columnar crystals at the bottom of the laser weld pool, equiaxed grain in the core, lamellar segregation and holes are clearly visible.
