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 [ SOLDER / BRAZE  ]  [ SOLDER METHODS ]  [ SOLDERING 101 ]  [ PROUD RESULTS ]

• In actual practice, for copper systems, most soldering is done at temperatures from about 350°F to 600°F, while most brazing is done at temperatures ranging from 1100°F to 1500°F.
• The choice between soldering or brazing generally depends on the operating conditions of the system:
  • Solder joints are generally used where the service temperature does not exceed 250°F,  
  • Brazed joints can be used where greater joint strength is required or where system temperatures are as high as 350°F.
• Although brazed joints offer higher joint strength in general, the annealing of the tube and fitting which results from the higher heat used in the brazing process can cause the rated pressure of the system to be less than that of a soldered joint.
  • This fact should be considered in choosing which joining process to use.
• Although soldering and brazing are the most common methods of joining copper tube and fittings, they are often the least understood.
  • It is this lack of understanding that can develop into poor installation techniques and lead to poor or faulty joints. 

The common causes of joint failures are:

1.     Improper joint preparation prior to soldering.

2.     Lack of proper support and/or hanging during soldering.

3.     Improper heat control and heat distribution through the entire joining process.

4.     Improper application of solder or brazing filler metal to the joint.

5.     Inadequate amount of filler metal applied to the joint.

6.     Sudden shock cooling or wiping the molten filler metal following soldering.

7.     Pre-tinning of joints prior to assembly and soldering.

NOTE: Although soldering and brazing operations are inherently simple, the deletion or misapplication of a single part of the process may mean the difference between a good joint and a failure.

SOLDER  METHODS

• The following 9 step joining process outlines the basic requirements
  • for consistently making a high-quality soldered or brazed joint: 

1.     Measuring

•  Accurately measure the length of each tube segment.
• Inaccuracy can compromise joint quality.
• If the tube is too short, it will not reach all the way into the cup of the fitting and a proper join cannot be made.
• If the tube segment is too long, system strain may be introduced which could affect service life.

 2.    Cutting  

• Cut the tube to the measured length.
• Cutting can be accomplished in a number of different ways to produce a satisfactory squared end.
• The tube can be cut with a disc-type tube cutter, a hacksaw, an abrasive wheel, or a stationary or portable bandsaw.
• Care must taken to ensure the tube is not deformed while being cut.
• Regardless of the method, the cut must be square to the run of the tube so the tube will seat properly in the fitting cup.

3.     Reaming

• Ream all cut tube ends to the full inside diameter of the tube to remove the small burr created by the cutting operation.
•  If this rough, inside edge is not removed by reaming, erosion-corrosion may occur due to local turbulence and increased local flow velocity in the tube. 
•  A properly reamed piece of tube provides an undisturbed surface for smooth, laminar flow.
• Remove any burrs on the outside of the tube ends created by the cutting operation to ensure proper assembly of the tube into the fitting cup.
• Tools used to ream tube ends include the reaming blade on the tube cutter, half-round or round files, a pocket knife, and a suitable deburring tool.
•  With soft tube, care must be taken not to deform the tube end by applying too much pressure. 
•  Soft temper tube, if deformed, can be brought back to roundness with a sizing tool consisting of a plug and sizing ring.

4.     Cleaning 

•  The removal of all oxides and surface soil from the tube ends and fitting cups is crucial to proper flow of filler metal into the joint.
• Failure to remove them can interfere with capillary action and may lessen the strength of the joint and cause failure.
• The capillary space between tube and fitting is approximately 0.004 in.
• Filler metal fills this gap by capillary action. 
•   This spacing is critical because it determines whether there is a proper flow of the filler metal into the gap ensuring a strong joint.
•  Lightly abrade (clean) the tube ends using sand cloth or nylon abrasive pads for a distance slightly more than the depth of the fitting cup.
•  Clean the fitting cups by using abrasive cloth, abrasive pads, or a properly sized fitting brush.
• Copper is a relatively soft metal. If too much material is removed from the tube end or fitting cup, a loose fit may result in a poor joint.
• Chemical cleaning may be used if the tube ends and fittings are thoroughly rinsed after cleaning according to the procedure furnished by the chemical manufacturer. 
•  Do not touch the cleaned surface with bare hands or oily gloves.
•  Skin oils, lubricating oils and grease impair the adherence of the filler metal.

5 Applying flux

•   Use a soldering flux that will dissolve and remove traces of oxide from the cleaned surfaces to be joined, protect the cleaned surfaces from reoxidation during heating, and promote wetting of the surfaces by the solder metal, as recommended in the general requirements of ASTM B 813. Apply a thin, even coating of flux with a brush to both tube and fitting as soon as possible after cleaning.

WARNING: Do not apply with fingers.

Chemicals in the flux can be harmful

if carried to the eyes, mouth or open cuts.

•  Use care in applying flux. Careless workmanship can cause problems long after the system has been installed. If excessive amounts of flux are used, the flux residue can cause corrosion. In extreme cases, such flux corrosion could perforate the wall of the tube, fitting or both.

6.     Assembly and Support 

•  Insert tube end into fitting cup, making sure that the tube is seated against the base of the fitting cup . 
•  A slight twisting motion ensures even coverage by the flux. Remove excess flux from the exterior of the joint with a cotton rag.
• Support the tube and fitting assembly to ensure an adequate capillary space around the entire circumference of the joint.
• Uniformity of capillary space will ensure good capillary flow of the molten solder metal.
• Excessive joint clearance can lead to solder metal cracking under conditions of stress or vibration.

7.     Heating  

•  Begin heating with the flame perpendicular to the tube. 
•  The copper tube conducts the initial heat into the fitting cup for ven distribution of heat in the joint area.
• The extent of this preheating depends upon the size of the joint.
• Preheating of the assembly should include the entire circumference of the tube in order to bring the entire assembly up to a suitable preheat condition.
• However, for joints in the horizontal position, avoid directly preheating the top of the joint to avoid burning the soldering flux. 
•  The natural tendency for heat to rise will ensure adequate preheat of the top of the assembly.
• Experience will indicate the amount of heat and the time needed. 
•  Next, move the flame onto the fitting cup. 
• Sweep the flame alternately between the fitting cup and the tube a distance equal to the depth of the fitting cup .
• Again, preheating the circumference of the assembly as described above, with the torch at the base of the fitting cup , touch the solder to the joint.
• If the solder does not melt, remove it and continue heating.

CAUTION: Do not overheat the joint or direct the flame into the face of the fitting cup. Overheating could burn the flux, which will destroy its effectiveness, and the solder will not enter the joint properly.

8.     Applying Filler Material (Solder )  

• For joints in the horizontal position, start applying the solder metal slightly off-center at the bottom of the joint. 
•  When the solder begins to melt from the heat of the tube and fitting, push the solder straight into the joint while keeping the torch at the base of the fitting and slightly ahead of the point of application of the solder.
• Continue this technique across the bottom of the fitting and up one side tothe top of the fitting.
• The now-solidified solder at the bottom of the joint has created an effective dam that will prevent the solder from running out of the joint as the sides and top of the joint are being filled.
• Return to the point of beginning, overlapping slightly, and proceed up the uncompleted side to the top, again, overlapping slightly. 
•  While soldering, small drops may appear behind the point of solder application, indicating the joint is full to that point and will take no more solder. 
• Throughout this process you are using all three physical states of the solder:
  •  
    • solid,
    • pasty and
    • liquid
• For joints in the vertical position, make a similar sequence of overlapping passes starting wherever is convenient.
• Solder joints depend on capillary action drawing free-flowing molten solder into the narrow clearance between the fitting and the tube.
• Molten solder metal is drawn into the joint by capillary action regardless of whether the solder flow is upward, downward or horizontal.
• Capillary action is most effective when the space between the surfaces to be joined is between 0.002 inch and 0.005 inch.
• A certain amount of looseness of fit can be tolerated, but too loose a fit can cause difficulties with larger size fittings. 

9.     Cooling and Cleaning  

• Allow the completed joint to cool naturally. 
• Shock cooling with water may stress or crack the joint. 
•  When cool, clean off any remaining flux residue with a wet rag.
•  Whenever possible, based on end use, completed systems should be flushed to remove excess flux and debris. Use a soldering flux meeting the requirements of ASTM B 813

10.     Testing 

• Test all completed assemblies for joint integrity. 
• Follow the testing procedure prescribed by applicable codes governing the intended service.

Reference: Copper Development Association

SOLDERING COPPER TUBING

The following instructions and techniques produce leak-tight soldered joints between copper and copper alloy tube and fittings.

By following these simple instructions and remembering to work carefully, you will be able to produce perfectly soldered joints.

 1. MEASURING

2. CUTTING

Cut the tube to the measured length. Cutting can be accomplished in a number of ways. The tube can be cut with a disc-type tube cutter, a hacksaw, an abrasive wheel, or with a stationary or portable bandsaw. Care must be taken that the tube is not deformed while being cut. Regardless of the method, the cut must be square to the run of the tube so that the tube will seat properly in the fitting cap.

3. REAMING
Ream all cut tube ends to the full inside diameter of the tube to remove the small burr created by cutting. It is very important to do this. If this rough, inside edge is not removed by reaming, erosion-corrosion may occur due to local turbulence and increased local flow velocity in the tube.

A properly reamed piece of tube provides a smooth surface for better flow.

Remove any burrs on the outside of the tube ends, created by the cutting, to ensure proper entrance of the tube into the fitting cap.

Tools that can be used to ream the tube ends include the reaming blade on the tube cutter, half-round or round files, a pockets knife. With soft tube, you must be very careful to not deform the tube end by applying too much pressure.   

4. CLEANING
The removal of all oxides and surface oil from the tube ends and fitting cups is crucial to proper flow of solder metal into the joint. Failure to remove them can interfere with capillary action and may lessen the strength of the joint and cause failure.

Lightly clean the tube ends using sand cloth or nylon abrasive pads for a distance slightly more than the depth of the fitting cups. Clean the fitting cups by using abrasive cloth, abrasive pads or a properly sized fitting brush. The capillary space between tube and fitting is approximately 0.004 in. Solder metal fills this gap by capillary action. This spacing is critical for the solder metal to flow into the gap and form a strong joint.

 Copper is a relatively soft metal. If too much material is removed from the tube end or fitting cup, a loose fit may result in a poor solder.
                   

5. APPLYING FLUX
Use a flux that will dissolve and remove traces of oxide from the cleaned surfaces from reoxidation during heating, and promote wetting of the surfaces by the solder metal.

WARNING: Do not apply with fingers. Chemicals in the flux can be harmful if they come into contact with the eyes, mouth or open cuts. Use care in applying flux. Careless workmanship can cause problems long after the system has been installed. If excessive amounts of flux are used, the flux residue can cause corrosion. In extreme cases, such flux corrosion could perforate the wall of the tube, fitting or both.

6. ASSEMBLY AND SUPPORT
Insert the tube end into fitting cup, making sure that the tube is seated against the base of the fitting cup. A slight twisting motion ensures even coverage by the flux. Remove excess flux from the exterior of the joint with a cotton rag.                                  Support the tube and fitting assembly to ensure a uniform capillary space around the entire circumference of the joint. Uniformity of capillary space will ensure good capillary flow of the molten-solder metal. Excessive joint clearance can lead to solder metal cracking under conditions of stress or vibration. The joint is now ready for soldering. Joints prepared and ready for soldering must be completed the same day and not left unfinished overnight.

7. HEATING
Begin heating with the flame perpendicular to the tube. The copper tube conducts the initial heat into the fitting cup for even distribution of heat in the joint area. The extent of this preheating depends upon the size of the joint. Preheating of the assembly should include the entire circumference of the tube in order to bring up to a suitable preheat condition. However, for joints in the horizontal position, avoid directly preheating the top of the joint to avoid burning the soldering flux. Practice and experience will indicate the amount of heat and time needed. 

 Next, move the flame onto the fitting cup. Sweep the flame alternately between the fitting cup and the tube a distance equal to the depth of the fitting cup. Again, preheating the circumference as described above, with the torch at the base of the fitting cup. Touch the solder to the joint If the solder does not melt, remove it and continue heating.

CAUTION: Do not overheat the joint or direct the flame into the face of the fitting cup. Overheating could burn the flux, which will destroy its effectiveness and the solder will not enter the joint properly.

When the solder melts, apply heat to the base of the cup to aid capillary action in drawing the molten solder into the cup towards the heat source.

The heat is generally applied using an air-fuel torch. Such torches use acetylene Propane or LP gas.

8. APPLYING FILLER MATERIAL ( SOLDER )
For joints in the horizontal position, start applying the solder metal slightly off-center at the bottom of the joint. When the solder begins to melt from the heat of the tube and fitting, push the solder straight into the joint while keeping the torch at the base of the fitting and slightly ahead of the point of application of the solder. Continue this technique across the bottom of the fitting and up one side to the top of the fitting.

The now-solidified solder at the bottom of the joint has created an effective dam that will prevent the solder from running out of the joint as the side and top of the joint are being filled.

Return to the point of beginning, overlapping slightly, and proceed up the uncompleted side to the top, again, overlapping slightly. While soldering, small drops may appear behind the point of solder application, indicating the joint is full to that point and will take no more solder. Throughout this process you are using all three physical states of the solder: solid, pasty, and liquid.

For joints in the vertical position, make a similar sequence of overlapping passes starting wherever is convenient.

9. COOLING & CLEANING
Allow the completed joint to cool naturally. Shock cooling with water may stress the joint. When cool, clean off any remaining flux residue with a wet rag.

10. TESTING

Test all completed assemblies for joint integrity.

[ SOURCE ] http://www.copper.org/copperhome/DIY/doityourself_solderingschool.html

Be proud of your work,

it is a reflection of yourself...

A tool you created is by consequence,

an extension of your own body

to assist in accomplishing a task.

                      ...Gilles 

.