Soldering & Brazing

Soldering and Brazing

A process where 2 or more pieces of metal are joined by means of an alloy that has a lower melting point than the metals being joined.

Soft Soldering

A joined process which takes place at temperatures below 840°F (449°C).

Hard Soldering (Brazing)

A joined process which takes place at temperatures above 840°F (449°C).

Liquidus

The temperature at which a metal or alloy is completely liquid.

Solidus

The temperature at which a material starts to melt.

Wetting

Liquid filler metal spreads and adheres in a thin continuous layer on a solid base metal.

Capillary Action

The force by which liquid, in contact with a solid, is drawn in and distributed between the closely-fitted surfaces of the fitting and tubing (tight fit).

Flux

A solid, liquid, or gaseous material which, when heated, is capable of removing or excluding oxides and other impurities from the metals being joined.

Reducing Flame

A flame that has an excess of acetylene. Used for brazing where oxidizing of the metal would cause poor joints.

50-50 Solder

Starts to melt at 360°F and flows freely at 415°F.

95-5 Solder

Used where high strength is required for service temperatures up to 250°F (121°C). Melts at 450°F and flows freely at 465°F.

Sil-Fos

Soldering/brazing alloy that melts from 1185°F to 1306°F. Cannot be used on iron or steel because the joint will be brittle due to phosphorus.

Easy-Flo 45

Solder used to join together copper and steel.

6 Steps of Solder Joint Prep

1. Preliminary, 2. Cutting, 3. Removing Burrs, 4. Cleaning, 5. Fluxing, 6. Assembling.

Flux Simple Definition

Any substance or mixture used to promote fusion.

Flux Fluidity

Flux should be fluid at the temperature of molten solder.

3 Factors for Flux Selection

1. Type of metal to be soldered, 2. Condition of its surface, 3. Method of soldering.

2 Main Types of Fluxes

Non-corrosive and Corrosive.

Corrosive Fluxes

Capable of removing oxide from the metal

Non-Corrosive Fluxes

Mainly have a covering action, protecting the metal from oxidation.

Solder Paste

Most frequently used to solder copper tubing.

Silver Brazing Flux

Commonly use Borax.

Sil-Fos Flux Requirements

Copper to Copper = No

Brazed Joint Strength

Depends on a large extent on the clearance between the pipe and copper fitting.

Oxidation Indicators

If brazing alloy fails to flow or balls up, it indicates oxidation on the metal surfaces.

Actual Practice Solder Temp

For copper systems, most soldering is done from 350°F to 550°F.

2 Groups of solder

Soft and Hard