Term
| 1. Explain the difference between brazing and soldering. |
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Definition
| The only difference is that soldering takes place at temperatures below 840 degrees Fahrenheit and brazing occurs above these temperatures. |
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Term
| 2. How does capillary action separate brazing? |
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Definition
| When capillary action pulls the braze metal into a joint, it’s called brazing. Braze welding does not need capillary action to pull filler metal into the joint. |
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Term
| 3. Why can brazing be both a permanent and a temporary joining method? |
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Definition
| Since the base metal is not damaged, parts may be disassembled at a later time by simply reapplying heat. The parts can then be reused. However, the joint is solid enough to be permanent. |
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Term
| 4. Why is it less likely that a semiskilled worker would damage a part with brazing than with welding? |
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Definition
| Because unlike welding, the brazing heat source can have a maximum temperature below the temperature that may cause damage to the parts. |
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Term
| 5. What is the effect of joint spacing on joint tensile strength? |
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Definition
| The smaller the joint space, the higher the joints tensile strength. |
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Term
| 6. Why are braze joints subject to fatigue failure? |
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Definition
| As a joint is bent, the less ductile base materials cause a shear force to be applied to the filler metal, resulting in joint failure. |
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Term
| 7. Do all braze joints resist corrosion? Give and example. |
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Definition
| No, filler metals used on base materials that are not recommended may result in a joint that looks good when completed, but will eventually corrode. For example, brass (BCuZn) will make a nice looking joint on stainless steel, but the zinc in brass will combine with the nickel in the stainless if the part is kept hot for too long. As a result, an embrittled structure is formed in the joint, reducing strength. |
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Term
| 8. What are three primary functions that a flux must perform? |
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Definition
| 1) They must remove any oxides that form as a result of heating the parts 2) They must promote wetting 3) They should aid in capillary action. |
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Term
| 9. In what forms are fluxes available? |
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Definition
| Solids, powders, pastes, liquids, and joined with the filler metal. |
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Term
| 10. How can liquid fluxes be delivered to the joint through the torch? |
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Definition
| They may be added to the gas when using an oxyfuel gas torch for soldering or brazing. The flux is picked up by the fuel gas as it is bubbled through the flux container and is then carried to the torch when it becomes part of the flame. |
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Term
| 11. How do fluxes react with the base metal? |
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Definition
| As acids, alkalis or salts. |
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Term
| 12. How are brazing and soldering methods grouped?` |
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Definition
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Term
| 13. What are the advantages of torch soldering? |
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Definition
| Versatility, portability and speed. |
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Term
| 14. What are the advantages of furnace brazing? |
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Definition
| Temperature control, controlled atmosphere, uniform heating and mass production. |
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Term
| 15. How does the induction brazing method heat the part being brazed? |
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Definition
| It uses high frequency electrical current to establish a corresponding current on the surface of the part. |
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Term
| 16. What soldering process can be used to join parts and provide a protective coating on the part at the same time? |
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Definition
| Dip soldering and brazing because the entire surface of the part can be covered with the filler metal at the same time the it is being joined. |
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Term
| 17. What soldering or brazing process uses a machine similar to a spot welder to produce the heat required to make a joint? |
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Definition
| Resistance soldering and brazing use a machine that resembles a spot welder. |
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Term
| 18. What is a metal alloy? |
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Definition
| A mixture of two or more metals. |
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Term
| 19. Why must parts not be moved as they cool through the paste range? |
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Definition
| If the part is moved, the solder or braze metal may crumble like dry clay, destroying the bond. |
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Term
| 20. Why must you not use tin-lead solders on water piping? |
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Definition
| The lead could become a health hazard. |
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Term
| 22. What is a major use of tin-antimony solder? |
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Definition
| It’s most commonly used in plumbing. |
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Term
| 23. What solder alloy can retain its strength at elevated temperatures? |
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Definition
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Term
| 24. Why do brazing alloys use letters such as CuZn to identify the metal? |
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Definition
| They indicate the atomic symbol of the metals that make up the alloy. |
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Term
| 25. What is the white smoke that can be given off from copper-zinc brazing alloy? |
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Definition
| It is zinc oxide from overheating the alloy. |
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Term
| 27. Why should copper-phosphorous not be used on fittings with ferrous substrates? |
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Definition
| Because the covering metal such as copper can easily be burned off, exposing the underlying metal to phosphorous embrittlement. |
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Term
| 28. Silver-copper alloys can be used to join which metals? |
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Definition
| Almost any metal, ferrous or nonferrous, except aluminum, magnesium, zinc, and a few other low-melting metals. |
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Term
29. Which nickel alloy would be best for joining the following?
a. poorfitting joints
b. honeycomb structures
c. jet engine parts
d. corrosive applications |
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Definition
a. BNi-4
b. BNi-1
c. BNi-7
d. BNi-6 |
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Term
| 30. Why does BCu-2 brazing alloy use an organic compound mixed with copper? |
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Definition
| Since copper oxides can cause porosity, tying up the oxides with the organic compounds reduces the porosity. |
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Term
| 32. What indicates that you have overheated the solder flux on copper? |
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Definition
| The surface of the copper will quickly build an oxide layer. |
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Term
| 33. How can the size of a braze bead be controlled? |
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Definition
| As the size of the molten pool increases, you can control it by reducing the torch angle, raising the torch, traveling at a faster rate, of flashing the flame off the molten pool. |
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Term
| 34. Why is brazing a better process than welding to rebuild some surfaces? |
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Definition
| Braze buildup has no hard spots, are good for both flat and round stack, and does not tend to harden the base metal. |
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