SOLDERING AND BRAZING OF ALUMINIUM

contents What are soldering and brazing Soldering of Aluminium Brazing of Aluminium Aluminium soldered \ brazed products Solerabilty of aluminium alloys Brazeabilty of aluminium alloys Solders Filler metal used in brazing Aluminium Fluxes Soldering methods Brazing methods Soldering \ brazing Aluminium to other metals Is soldering or brazing more suitable

What are soldering and brazing ?

Joining process using a heating method and a filler metal without melting the base materials .

SOLDERING BRAZING

Filler metal has a liquidus below 800 F .

Joint strength ↓ cost ↓ resistance to corrosion ↓.

Filler metal has a liquidus above 800 F .

Join strength ↑ cost ↑ resistance to corrosion ↑

Advantages of soldering and brazing

Joining dissimilar metals and non-metals allows much tighter control over

tolerances Low temperature compared to welding less thermal distortion clean joint Speed of joining Easy realignment Less manual skills

Disadvantages

the lack of joint strength .

joint colour

damaged under high temperature condition .

Soldering of Aluminium

Active fluxes Low temperature soldering

390 F → 650 F

High temperature soldering

250 F → 400 F below Al-alloys melting point

Brazing of Aluminium Close temperature control is required . The brazing temperature should preferably be

70 F below melting point of Al

In condition of accurately controlled of temperature

it can be done at 10 F

Most brazing is done between

1020 →1180 F

• Aluminium products joined by brazing/soldering

• Aluminium frames

Solderability of Aluminium alloys

Almost all aluminium alloys can be soldered

Alloys containing more than 1% Mg can not be soldered satisfactorily . (5xxx _ 6xxx)

(intergranular penetration )

Alloys containing more than (5%) Si can not be soldered (4xxx \ 6xxx)

Brazeability of Aluminium alloys

1xxx , 3xxx , 6xxx and low-Mg members of 5xxx are most successfully brazed alloys

2xxx , 7xxx not normally brazed because of low melting temperature .

Solders

1.Low-temperature

Melting between 300 F → 500 F Composed of Tin, lead, zinc, cadmium And small amount of Al ,copper ,Nickel Good low-temperature solder used in

aluminium soldering is : The eutectic alloy containing : 91%SN , 9%ZN Melts at 400 F

Solders

2. Intermediate-temperature solder

Melts at 500 F → 700 F

Contains : Tin ,Zinc < 30% → 70%> and Small amount of copper, lead and silver

Stronger joints

Solders 3.High-temperature solders :

Melts between 700 → 800 F .

Containing from 90% → 100% Zn and from

2% → 10% Al .

Strongest and superior corrosion resistance .

Filler metals for brazing Aluminium

Powder , paste or wire

Commercial filler metal alloy using in Al-brazing are :

Aluminium-silicon alloys containing 7%→12 Si

To reduce brazing temperature the following alloy elements were added :

1. copper → intermetallic compound AL-Cu 2. Germanium → expensive 3. Beryllium → healthy hazards

Flux Flux function

Aluminium brazing fluxes contain chlorides and fluorides

Aluminium soldering fluxes1.Organic : melts 400 → 525 F Contain zinc fluoride or zinc chloride 2. Non-organic : melts 540 → 720 F

Soldering methods Iron soldering Common in Al assemblies Furnace soldering Large assemblies Abrasion soldering no flux

Induction soldering rapid

Flame soldering manual or automatic , No limitation on thickness

Dip soldering High production rate

Brazing methods Torch brazing economical

Furnace brazing ↑ production rate

Dip brazing the best method for AL

Soldering other material to Aluminium

Any solderable material can be soldered to Aluminium .

Magnesium, titanium, tungsten , are difficult to solder to Aluminium .

Brazing Al to other metals

Al can be brazed to many other metals

Al to copper : is difficult to braze because of low melting temperature (1018 F) of Al-copper eutectic composition .

Al to steel : possible (dip brazing) Al to magnesium : easy but brittle

joint .

Is soldering or brazing more suitable?

That depends on :

1. Strength requirements brazed joints can be 3 – 10 the strength of soldered joints

2. Corrosion resistance solders are less corrosion resistance

3. Temperature

4. Cost

Thank you