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.
?
