What is butt welding technology?
Butt welding is a kind method of welding technology that take advantage of heating and pressure at the same time by electric current come through welded parts. while butt-welding, resistance thermal effects on copper and aluminum parts that is melting or pleading state and formed metal bonding.
The advantage of butt welding.
- butt welding without metal filler
- Welded parts are rare deformation
- Easy to be automatically
- High productivity
Peel Strength Test
The peeling strength of Copper and aluminum tubing is the most important qualified judgment for the butt welding heating process.
Peel resistance test is main way to inspect mechanicas property of welding wire and visual expression. we operate welding wire area to strip in two directions, we remark peel strength “P”
According to the mechanical industry standard of the people’s republic of China JB/T11525-2013, Define peel resistance strength ability is Pw
For examples follow below:
- Pw=P/B
- Pw: peel resistance ability N/mm
- P: peel strength “N“
- B: tested sample width mm
Meantime, pipe connector peel strength must conform to below formular:
Pw>Pn>Al tensile strength*wall thick of pull off (T1) /Aluminum Tube Wall thick (T)
Pn is qualifed of peel strength, T is aluminum tube wall thickness.
After the peel strength test, we can found the fusion length should more than 4.0mm, after peeling there are no aluminum compounds and mixture residual material on the copper tube surface. we record test data as below chart:
| NO: | OD | 1 | 2 | 3 | 4 | Minimum value |
| Fusion length | 9.52mm | 4.6 | 5.79 | 6.5 | 5.98 | 4.6mm |
Tensile Strength Test
We did tensile strength test on Copper aluminum connect parts, crack happen on aluminum parts and far away from welded area, which means the welded parts more strengthen than aluminum tubing itself. we record the tensile strength test data as follows:
| NO: | OD | 1 | 2 | 3 | Average |
| Tensile strength | 9.52 | 132.31 | 114.35 | 116.14 | 120.93 |
| (MPA) | 22.2 | 110.74 | 111.88 | 108.41 | 110.34 |
So we could make a conclusion, the peel strength and tensile strength of welding parts are stronger than the mother material itself, so butt-welded copper & aluminum tubing is qualified. common products: A/C mounting kits that are typical products in the application of copper aluminum butt-welding
Performance Test
we select 120mm length TP2M copper pipe butt welded 1060 aluminum tubing for the target tested material.
1. Air tightness
Air tightness test under 3.0MPA nitrogen gas for leak inspection 10-15 seconds, No crack, bubble happen.
2. Pipe Inside Clearness for R22
- Pipe inside impurity < 60mg/m2
- Water content < 120mg/m2
3. Pipe Inside Clearness for R407C & R410A
- Pipe inside impurity < 30mg/m2
- Water content < 40mg/m2
- Mineral oil <10mg/m2
- chloridion < 0.2mg/m2
- petrolin <0.5mg/m2
- Silica gel < 1.0mg/m2
4. Pressure Resistance
Pouring into compressed air with the vacuum pump, strengthen continuous pressure with speed 0.06 to 0.1Mpa/s. When inside pressure reaches up 4.9MPA, keep pressure time 10min, no leak and deformation happen on the pipe surface.
5. Bursting pressure
Pouring into compressed air with 0.06-0.1MPA/S speed and Pipe inside pressure reach up 13.0MPA, keep pressure 1.0 min, the pipeline should not leak and crack happen.
6. welding connector mechanical properties
| Tensile strength (MPA) | Elongation | Remark |
| 75-120 | >22% | the crack should happen on side of the aluminum tube and 10mm far away from the welding wire |
7. Bending Property
we test copper & aluminum butt welding bending properties. its bending center diameter 50-60mm and welding parts 1800 bending, and then airtightness test, the surface must be smooth and no crack and leakage.
| Outside diameter | Bending center diameter (mm) |
| OD 6.0mm 、OD 6.35mm | 50 |
| > OD 6.35mm | 60 |
8. Corrosion resistance
cutting 300 to 400mm samples, seal two ends, and put on a Salt fog box in the condition of PH value 6.5-7.2, 5% +/-0.1% NaC1, temperature 350C+/-20
After 500 hours, taking out samples and check out the test result that Copper and aluminum welded parts should not be corrosion.
9. Fatigue Test
Experiment condition: one punch with 1 to 3MPA pressure change. high and low-pressure conversion period 20 seconds. we are doing 150,000 times punching test and then airtightness test.
