Brazing & Soldering © 2009 Harris Products Group

Braze Safety Keep your head out of the fumes Use enough ventilation and exhaust at the flame or work piece to keep fumes and gases from your breathing zone and general area Wear correct eye, ear, and body protection © 2009 Harris Products Group

Brazing & Soldering Filler metal melts at temperature below the melting point of the base metal Filler metal flows through joint via principle of capillary attraction Requires two closely fitted surfaces Brazing takes place above 840°F/450C Soldering occurs below 840°F/450C © 2009 Harris Products Group

How does it work? © 2009 Harris Products Group

Cohesion and Surface Tension Cohesion, is the attraction of like molecules. Molecules on the liquid’s surface have stronger attraction. This is called surface tension. © 2009 Harris Products Group

Adhesion Forces between unlike molecules is called adhesion. In a brazed joint there are strong adhesive forces between molten filler metal and the base metal walls. We call this wetting. © 2009 Harris Products Group

Capillary Action Capillary action is a combination of surface tension and adhesion. It pulls the molten alloy through the joint, and allows you to braze in all positions. Filler Metal Capillary Area (closely fitted surfaces) Base Metals © 2009 Harris Products Group

Wide clearance - up to 0.010 in/0.254 mm Tight clearance - 0.0015 in./0.038 mm This experiment replicates a brazed joint. Two glass pieces were clamped together. A tight clearance was held on one side while the other side was spaced to provide a 0.010” clearance. The colored water acts like molten braze filler between two metal parts. Note how capillary action is more effective on the side with the tighter clearance. This illustrates the importance of controlling braze tolerance. We also find that tighter clearance and good capillary action increase joint strength. Generally, 0.002” – 0.005” (on a side), provides the best capillary action. Note also the area at the clamp site. Here clamp pressure holds the glass together so there is no clearance. A “press” or interference fit has eliminated the capillary and the water flows around this spot. Insufficient clearance in a brazed joint can cause incomplete penetration or voids. Clearance should be measured at brazing temperature. This is very important in dissimilar metal joints. Clearance may be adequate at room temperature, but different thermal coefficient of expansion rates may reduce clearance during heating. Capillary action works best when close clearance can be maintained. Avoid a press fit – no clearance will limit braze alloy flow. © 2009 Harris Products Group

Thermal Coefficient of Expansion Metals expand as temperature increases – watch for change in clearance. Maintain 0.002” – 0.005” at brazing temperature. © 2009 Harris Products Group

Thermal Coefficient of Expansion Different types of metals expand and contract at different rates. Maintain 0.002” – 0.005” at brazing temperature. © 2009 Harris Products Group

Recommended braze clearance is: 0.002 in/0.050 mm to 0.005 in/0.127 mm Parent Material Braze Alloy Parent Material Recommended braze clearance is: 0.002 in/0.050 mm to 0.005 in/0.127 mm © 2009 Harris Products Group

Magnified Braze Joint © 2009 Harris Products Group

CLEAN PARTS © 2009 Harris Products Group

Clean Parts Remove oil, grease, drawing compounds Remove oxide w/Scotch Brite, wire brush, grinder, etc. If grit blasting avoid embedding silicon, alumina, sand, etc. in base metal - hinders wetting Chemical cleaning, acid, alkaline, chemical degreasing © 2009 Harris Products Group

FLUX © 2009 Harris Products Group

Brazing Flux Dissolves surface oxides and protects against oxide formation during heating Formulated to be active at braze alloy melting range Is not designed to be the base metal “cleaner” Is visually clear at about 1100º F – a good base metal temperature indicator © 2009 Harris Products Group

White flux- for most brazing applications Fluxes play several roles in brazing. They dissolve metal surface oxide and shield the surface from oxidation formed during the heating process. Black flux- for extended heating or high temperature localized heat © 2009 Harris Products Group

FLUX BEHAVIOR DURING HEATING CYCLE 1225 F (663C)– Safety Silv 45 solidus 1500F 1190 F (643C) - Dynaflow, Stay Silv 15 solidus Flux clear and quiet 1000F Flux begins to melt Flux bubbles 500F Water boils out FLUX BEHAVIOR DURING HEATING CYCLE © 2009 Harris Products Group

Braze Flux Removal Remove flux residue Hot water & wire brush Let filler metal solidify before quenching Overheated parts may require different flux removal method: Grinding Chemical (dilute acid dip) cleaning © 2009 Harris Products Group

Heating © 2009 Harris Products Group

Only heat fitting = Poor heat transfer © 2009 Harris Products Group

Heat tube first © 2009 Harris Products Group

Heat fitting second – even heat © 2009 Harris Products Group

Apply alloy when both parts reach brazing temperature © 2009 Harris Products Group

Direct heat to fitting to draw alloy into fitting © 2009 Harris Products Group

Heat tube © 2009 Harris Products Group

© 2009 Harris Products Group

© 2009 Harris Products Group

Heat fitting © 2009 Harris Products Group

Apply filler metal only when base metal is at brazing temperature Use flame to draw alloy into the joint © 2009 Harris Products Group

Melting Point vs. Melting Range Pure elements have a melting point. Cu @ 1981F, (1083 C) Sn @ 449F, (232 C) Alloys have a melting range. Solidus - Melting starts. Above this - part solid / part liquid. Liquidus - Melting complete. Above this completely liquid. Brazing usually starts at the liquidus temperature. May be below liquidus. © 2009 Harris Products Group

Copper – Phosphorus Filler Metals © 2009 Harris Products Group

Copper – Phosphorus Filler Metals Copper/phosphorus & copper/phosphorus/silver compositions Harris 0 Stay-Silv® 2, 5, 6, 15, Dynaflow® Use to braze copper to copper Also copper to brass with Stay-Silv® white flux Do Not use on steel – joints may be brittle AWS BCuP classification © 2009 Harris Products Group

Examples: Solidus, Liquidus, Melting Range © 2009 Harris Products Group

Silver Braze Filler Metals © 2009 Harris Products Group

Silver Braze Filler Metals Safety-Silv® 30, 35, 38T, 40T, 45, 56 Always requires use of Stay-Silv brazing flux Primarily used on steel, stainless, nickel, copper alloys, and dissimilar applications Tin added to lower temperature, nickel added for improved corrosion resistance and strength on carbides AWS BAg Classification © 2009 Harris Products Group

Examples: Solidus, Liquidus, Melting Range © 2009 Harris Products Group

Soldering Soldering is similar to brazing but at lower temperatures, below 840F / 450C Solders are primarily tin based alloys with various additions of lead, silver, antimony, zinc, etc. Heat sources include soldering irons, air/fuel torches, propane, and propylene © 2009 Harris Products Group

Solders Tin based solders have less strength than copper based brazing alloys, so solder joints require longer over lap. Usually 5X the minimum base metal thickness is specified to develop adequate strength. © 2009 Harris Products Group

Soldering Flux Like brazing flux, solder flux is designed to protect the base metal from oxidation Flux is available in liquid and paste form Solder flux is formulated to be active during solder melting ranges Solder flux residue must be removed after soldering to prevent corrosion. Non-active rosin fluxes are available for electrical or electronic applications where post-solder cleaning is not practical © 2009 Harris Products Group

General Strength Guidelines Tensile Strength of a Brazed Joint Joint strength depends on several factors: Clearance between parts Base metal composition Service temperature Joint quality (voids vs. good penetration) Joint design The bulk tensile strength of silver braze alloys is 40,000 - 70,000 psi. When brazing copper-based alloys, failure will often occur in the base metal. When brazing steel or other ferrous metals, joint strength over 70,000 psi can be achieved under the right conditions. Keep in mind that braze joints are primarily lap type joints and strength is a combination of tensile and shear. Joint strength is directly influenced by the above mentioned factors. The only way to accurately determine tensile or other strength values is to test the brazed assembly.

General Strength Guidelines To achieve adequate joint strength, pieces to be brazed should overlap 3 times the minimum base metal thickness. To achieve adequate joint strength, pieces to be soldered should overlap 5 times the minimum base metal thickness. © 2009 Harris Products Group

Solder Joint Strength Can be stronger than brazing in some applications. Stay-Silv 15 Stay-Brite Solder © 2009 Harris Products Group

The Most Common Braze Problem Many joint failures are caused by insufficient braze filler metal in the joint capillary. A build up of braze material outside the joint will provide short term strength. It may pass a leak test, for example, but continued stress or vibration may cause later failure. © 2009 Harris Products Group

Inadequate Braze Penetration Void in capillary This picture shows a braze that looks good from the exterior but has insufficient penetration to provide good long term strength. © 2009 Harris Products Group

The Possible Result © 2009 Harris Products Group

Product Information & Literature - A Guide To Brazing & Soldering Brochure - Harris Alloy Selection Wheel Chart - Harris HVAC/R & Plumbing Catalog - Website: www.HarrisProductsGroup.com “Live Chat” on www.HarrisProductsGroup.com main page Instant messaging product and/or application support - Monday thru Friday 8:00 AM – 5:00 PM EST Access this feature at the top of the tool bar at our website © 2009 Harris Products Group

© 2009 Harris Products Group