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Soldering and Brazing Principles and Practice: Jobs 10-J50-J51

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1 Soldering and Brazing Principles and Practice: Jobs 10-J50-J51
Chapter 10

2 Objectives Define and perform soldering. Define and perform brazing.
Demonstrate ability to troubleshoot soldered and brazed joints.

3 Soldering and Brazing Copper Tubing
One of first metals used Tools, weapons, decorative Durable and resistant to corrosion Today used in pipes and tubing Light, strong, corrosion resistant Available in hard and soft tempers Joints made simply by soldering and brazing © Prographics Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

4 Soldering Group of joining processes that produce coalescence of materials by heating them to soldering temperature and by using filler metal having liquidus not exceeding 840ºF and below solidus of base metals Distributed between surfaces of joint by capillary action Flow of liquid when drawn into small space between closely fitted (faying) surfaces

5 Brazing Process that joins materials by heating them in presence of filler metal having a liquidus above 840ºF but below solidus of base metal Heat provided by variety of processes Filler metal distributes between closely fitted surfaced of joint by capillary action Capillary action not factor in distribution of brazing filler metal during braze welding

6 Brazing Heat sucks brazing alloy into the gap where it wets both metal surfaces. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

7 Soldering Must Meet Three Criteria
Parts must be joined without melting base metals Filler metal must have a liquidus temperature below 840ºF Filler metal must wet base metal surface and be drawn into or held in joint by capillary action

8 Soldering Filler Metals
Important preliminary step in soldering copper tube joints Selection depends on several factors Metals to be joined Expected service Operational temperatures Expansion, contraction, and vibration in service

9 Soldering Filler Metals
Properly make joint stronger than tube itself Stresses of short duration Solder may give when stress maintained at high temperatures over long periods of time Stress less than what would produce break with short-time load Condition known as creep Creep strength of various types of solder varies widely

10 Melting Ranges of Solders
Two tables in textbook list method of classifying solders, their composition, and their melting and solid temperatures. Table 10-1 in the text lists the melting range of tin- lead solders. The pasty range is known as the “working range” and is found between the liquidus and solidus temperatures. Solder is semisolid in pasty range. Table 10-2 in text lists the melting range of solders containing other metals.

11 Tin-lead Solders Widely used solder Suitable for joining most metals
Good grade of tin-lead used for all service at room temperatures and low pressure steam (up to 15 p.s.i.) and moderate pressures with temperatures up to 250ºF Classified as 50A Molten at 418ºF and solid at 362ºF As tin content increased, flow and wetting characteristics increased

12 Tin-antimony-lead Solders
Antimony added for higher strength More difficult to work with than tin-lead solders Poorer flow and capillarity characteristics Used for joints in operating temperatures around 300ºF Not recommended for aluminum, zinc-coated steels, or other alloys have zinc base

13 Tin-antimony Solders Used for temperatures up to 250ºF
Melting point of 464ºF Completely solid at 452ºF Difficult to use in vertical position Very narrow pasty range (12ºF) Highly desirable for food handling equipment Absence of lead (toxic substance)

14 Tin-zinc Solder Used for joining aluminum
Melting point ranges from 390 to 708ºF Solid at 390ºF As zinc content increases, melting temperature increases Type containing 91% tin and 9% zinc melts and solidifies at 390ºF Wets aluminum readily, flows easily, and possesses high resistance to corrosion with aluminum

15 Cadmium-silver Solder
Improper use may cause health hazards Take care, especially with fume inhalation Most common has 95% cadmium and 5% silver Melting temperature of 740ºF and solid at 640ºF When used for butt joints in copper tube, joint has tensile strength of 2,600 p.s.i. at temperatures up to 425ºF

16 Cadmium-zinc Solders Used to join aluminum with joints of wide clearance Provide strong, corrosive-resistant joint Melting range of 509 to 750ºF Solidify at 509ºF Solders containing 90% zinc have wide pasty range of 241ºF

17 Zinc-aluminum Solder Common has 95% zinc and 5% aluminum
High temperature solder that melts at 720ºF High resistance to corrosion due to high zinc content

18 Paste Solders Composed of finely granulated solder
Generally lead-tin in suspension in paste flux Flux paste make cleaning copper unnecessary Care must be taken making vertical joint Solder and flux tend to run down tube

19 Forms of Solders Solid wire form Other forms for special applications
General use for soldering copper tubing Commercially available Diameters of to 0.30 inch on spools weighing 1, 5, 10, 20, 25, and 50 pounds Flux may be incorporated in single or multiple hollows or external parallel grooves Other forms for special applications Pig, slabs, cakes, bars, paste, tape, ingots, creams, ribbon, preforms, powder, foil, and sheet (unlimited sizes and shapes)

20 Fluxes Liquid, solid, or gaseous material that when heated, improves wetting of metals with solder Does not clean base metal Removes tarnish films and oxides from both metal and solder (if base metal cleaned)

21 Flux Functions When applied to properly cleaned surface, flux:
Protects surface from oxidation during heating Permits easy displacement by filler metal so it flows into joint Floats out remaining oxides ahead of molten solder Increases wetting action of molten solder by lowering surface tension

22 Flux Classification Based on ability to remove metal tarnishes
Classified into three groups: Inorganic fluxes Most active – highly corrosive Organic fluxes Moderately active – intermediate Rosin fluxes Least active – noncorrosive

23 Highly Corrosive Fluxes
Consist of inorganic acids and salts Zinc chloride, ammonium chloride, sodium chloride, potassium chloride, hydrochloric acid, and hydrofluoric acid Available as liquids, pastes, and dry salts Recommended for metals requiring rapid and highly active fluxing action Leave chemically active residue after soldering Will cause severe corrosion at joint if not removed

24 Intermediate Fluxes Weaker than inorganic salt types
Consists of mild organic acids and bases Citric acid, lactic acid, and benzoic acid Very active at soldering temperatures, but activity short-lived Also highly volatile at soldering temperatures Useful for quick soldering operations Residue does not remain active after joint soldered Removed readily with materials requiring mild flux

25 Noncorrosive Fluxes Composed of water and white resin dissolved in organic solvent (abietic acid or benzoic acid) Electrical industry large user Residue does not cause corrosion Effective on copper, brass, bronze, nickel, and silver

26 Paste Fluxes Many types ranging from noncorrosive to corrosive
Can be localized at joint and will not spread to other parts of work Body composed of petroleum jelly, tallow, lanolin, and glycerin, or other moisture-retaining substances

27 Joint Design Examples from Figure 10-3
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

28 Joint Design Depends on service requirements of assembly Other factors
Heating method Assembly requirements before soldering Number of items to be soldered Method of applying solder Severe conditions mean design such that strength of joint equal to or greater than load-carrying capacity of weakest member

29 Joint Design Joint must be accessible
Solder normally face-fed into joint Clearance between parts being joined should be such that solder can be drawn into space between by capillary action No greater than inch 0.003 to inch recommended Joint's tensile strength reduced as clearance increases beyond recommended amount

30 Heating Methods Heat necessary to carry out soldering
Solder must melt while surface heated to permit molten solder to flow over surface Applied in one of several ways Soldering irons, dip soldering, induction heating, resistance heating, oven heating, spray gun heating, and flame heating

31 Flame Heating Type of torch depends upon size, mass, and design of assembly Time important factor Fast: high temperature flame and large tip size Slow: low temperature and small tip size Highest temperatures reached with acetylene Care taken to avoid sooty flame

32 Air-acetylene Torch Various tip sizes Thermadyne Industries, Inc
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

33 Joint Preparation of Copper Tubing
End of tub to be soldered should be square and free from burrs Outer surface round and within to inch of specified diameter for distance of 1 inch Use hacksaw or bandsaw to cut ends off Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

34 Joint Preparation of Copper Tubing
Pipe cutter may be used, but care taken to not put too much pressure on tube (deforms) Makes reaming necessary to remove burrs on outside and inside of tubing Stanley G. Flagg & Co Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

35 Precleaning and Surface Preparation
Essential surface is clean Dirty surface impairs wetting and alloying action Prevents solder from flowing as thin film All foreign materials must be removed Examples: oil, paint, pencil marks, lubricants Strength and adherence of solder function of surface contact area of solder to base metal Contact improved by roughening surface of base

36 Two Methods of Surface Cleaning: Mechanical
More widely used in soldering and brazing of tube or pipe Methods include: Grit- or shot-blasting Mechanical sanding or grinding Cleaning with stainless-steel wool Filing Hand sanding Wire brushing Scraping Stanley G. Flagg & Co Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

37 Mechanical Cleaning Sandcloth most widely used method for copper, brass, and softer metals End of tube cleaned for distance slightly more than required for full insertion of tube into cup of fitting Cup of fitting should also be cleaned Cleaning beyond these areas wastes filler metal and may permit solder to flow out of area Excessive cleaning may reduce outer diameter of tubing

38 Two Methods of Surface Cleaning: Chemical
Usually done for production operations Either solvent or alkaline degreasing recommended Vapor condensation type solvents leave least residual film on surface Acid cleaning (pickling) removes rust, scale, oxides, and sulfides Inorganic acids used singly or mixed Hydrochloric and sulfuric acid most used

39 Practice Jobs: Soldering Job 10-J54
Cut tubing into 12 inch lengths. Remove burrs and straighten up ends of tubing; clean surface thoroughly. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

40 Practice Jobs: Soldering Job 10-J54
Flux tube and fitting surfaces immediately after cleaning. Preferred flux is mildly corrosive and contains zinc and ammonium chlorides in petrolatum base. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

41 Practice Jobs: Soldering Job 10-J54
Assemble joint by inserting tub into fitting. Small twist helps spread flux over two surfaces. Adjust flame to get reducing flame. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

42 Practice Jobs: Soldering Job 10-J54
When joint correct temperature, touch end of solder wire to joint. Never apply flame directly on solder. Should melt on contact with surface of base metal and drawn into joint by capillary attraction While joint still hot, remove surplus solder and flux with rag or brush. Allow to cool naturally before applying water. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

43 Check Test: Surface Inspection
Select 1-inch T-connection and solder length of tubing 12 inches long into each opening of connection. After joints cooled and excess flux cleaned off, cut tubing at each end. Cut three joints lengthwise along center line with hacksaw. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

44 Surface Inspection Place half tube and fitting in vise, tube end down and face of fitting cut flush against jaws of vise. Tighten vise until tub end flattened. Pull pipe away from fitting. Inspect soldered surfaces. Perfect joint will have entire cup area of fitting completely covered with solder. Defects: unsoldered areas and flux inclusions

45 Unsoldered Areas Bare spots running circumferentially many not leak, but weaken joint Bare spot same size running lengthwise may leak May be result of improper fluxing, heating, or improper cleaning if surface does not have glassy appearance of dried flux May be flux inclusion if unsoldered area covered with flux

46 Flux Inclusions Indicates flux had no chance to flow ahead of solder
May be caused by feeding solder into joint improperly On small tubing, solder should be fed at one point Shiny areas indicate metal tinned on both surfaces, but flux inclusion between them Serious – as if no solder at all on those areas Cause may be fitting too loose on tube

47 Check Test: Water Pressure
Make up closed-line assembly composed of joints made in all positions. Solder connections with both silver alloys and copper-phosphorus alloys Braze male-to-female fitting into line to introduce water under pressure into tubing. If flux sealed any pinholes, water dissolves it. Pump water into assembly at line pressure and observe for leaks.

48 Torch Brazing (TB) Copper-zinc alloys (spelter) developed for joining iron and steel at beginning of Iron Age Alloys strong and easily melted Vigorous wetting action on clean fluxed ferrous metals Early silver solder survive today as silver-base brazing alloys Used extensively in brazing joints in copper tubing

49 Torch Brazing (TB) Differences between brazing and soldering
Higher melting temperatures of brazing filler metals Special fluxes used for brazing Solidus temperature Highest temperature where brazing material solid Liquidus temperature Temperature where brazing material melted Melting range is difference between solidus and liquidus temperatures

50 Advantages of Brazing Brazed joints stronger than threaded joints
Vibration does not loosen brazed joints Brazed joints do not leak Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

51 Advantages of Brazing Silver alloy filler metal used for brazing as resistant to attack as metals themselves Streamlined design Accurate assemblies Cut to exact dimensions Temporary piping assembled rapidly Can be taken apart and pieces reused Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

52 Factors in Selecting Brazing Filler Metal
Compatibility with base metal and joint design Service requirements for brazed assembly Brazing temperature required Method of heating

53 American Welding Society’s Classifications of Brazing Filler Metals
Bag—silver base BAlSi—aluminum BAu—gold base BCu—copper BCuP—copper phosphorus RBCuZn—copper zinc BMg—magnesium base BNi—nickel base The composition and melting ranges of filler metals in these classifications are given in Table 10-4 in the textbook.

54 Aluminum-silicon Filler Metals (BAlSi)
Used exclusively for brazing aluminum Require flux Type 2 Used as cladding and applied with dip and furnace brazing Type 3 General-purpose metal for dip and furnace application Type 4 Used for torch brazing and dip and furnace brazing Highly corrosion resistant Type 5 Used for dip and furnace brazing at temps lower than type 2

55 Copper-phosphorus Filler Metals (BCuP)
Used primarily for joining copper and copper alloys May be used for joining other nonferrous metals Self-fluxing, but fluxes recommended Type 1 used for preplacing in joints and suited for resistance and furnace brazing Types 2, 3, and 4 highly fluid filler metals suited for close clearance Type 5 used for joins where clearance is less

56 Gold Filler Metals (BAu)
Gold alloys used to join parts in electron tube assemblies and missile components Suitable for induction, furnace, and resistance brazing Require a flux

57 Copper (BCu) and Copper-zinc (RBCuZn) Filler Metals
Used for joining both ferrous and nonferrous metals with borax-boric acid flux Extremely fluid so require close fits Overheating will cause volatilization of zinc Should NOT be used to join copper alloys or stainless steels because of interior corrosion resistance Used for joining ferrous metals, nickel, and copper-nickel alloys

58 Magnesium Filler Metals (BMg)
Used for joining magnesium with Torch brazing processes Dip brazing processes Furnace brazing processes

59 Nickel Filler Metals (BNi)
Used when extreme heat and corrosion resistance required Nickel alloys very strong and may have high or low ductility depending on brazing method Filler metal supplied as powder, paste, or sheet or formed with binder materials into wire and strip

60 Nickel Filler Metals (BNi)
Type 1 – highly corrosive, cannot use with thin sheets Type 2 – lowest melting point and is least corrosive Type 3 – chromium-free alloy with narrow melting range and free-flowing characteristics Type 4 – similar to type 3 Type 5 – resists oxidation up to 2000ºF and used for high strength joints Type 6 – free-flowing filler metal, minimum corrosion Type 7 – makes strong leak-proof joint at low temps

61 Silver Filler Metals (BAg)
Used for joining virtually all ferrous and nonferrous metals Exception of aluminum, magnesium and other metals with low melting points Generally free-flowing Best results when clearance between tube and bore of fitting held between and inch Flux required

62 Silver Filler Metals (BAg)
Types 1 and 1a are general-purpose metals Free-flowing and have low melting points Type 2 Suitable for general purposes at higher temperatures Type 3 Used for brazing carbide tool tips to shanks and for corrosion-resistant joints in stainless steel Type 4 Carbide tip brazing, but at higher temperatures

63 Silver Filler Metals (BAg)
Types 5 and 6 General-purpose for higher brazing temperatures Type 7 Cadmium-free filler metal with low melting point used for furnace brazing Type 8 Silver-copper eutectic used for vacuum tube parts Free-flowing, but does not wet well on ferrous metals

64 Silver Filler Metals (BAg)
Type 8a Resembles type 8, but addition of lithium makes it self-fluxing on ferrous metals and alloys in dry protective atmosphere Type 13 Filler metal with high melting point Type 18 Sterling silver with lithium added to promote self-fluxing Low melting point

65 Unclassified Filler Metals
Based on uncommon metals as gold, platinum, and palladium Used in brazing vacuum tube components Evolving fields of jet and rocket propulsion and nuclear energy continues to push development of new filler metals

66 Forms of Filler Metals Most ductile so they can be rolled or drawn to wire or strip in various standard forms May also be supplied as powders Nickel filler metals available only as powder Powders can be bonded into wire or strip with plastic binder materials

67 Fluxes Same responsibility in brazing process
Important to use right flux Has to stay on tube without blowing or washing away while being heated Prevents oxidation from spoiling clean metal surfaces As brazing allow flows in, flux flows out of joint Clean flux off parts by washing off with water

68 Forms of Fluxes Paste or liquid Powder
Solid coating preapplied on brazing filler metal Vapor

69 Fluxes Act as temperature indicator At 212ºF, water in paste boils off
At about 600 to 700ºF, flux begin to work (bubble) At 800ºF, flux begins to melt At 1,100ºF, flux clear, waterlike fluid At 1,150 to 1,300ºF, brazing temp has been reached At 1,600ºF, loses protective qualities Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

70 Brazing Flux Materials
Borates Sodium, potassium, and lithium borate compounds Used in high temperature fluxes Melting range is 1,400ºF Oxide-dissolving characteristics good Fused borax Used as active flux at high temperatures

71 Brazing Flux Materials
Fluoroborates Compounds of fluorine, boron, and active metals such as sodium and potassium Better flow properties and oxide removal properties than borates Protection against oxidation is short duration Boric acid Commonly used base for brazing fluxes Used principally as cleaning agent

72 Brazing Flux Materials
Fluorides Contain sodium, potassium, lithium, and other elements For active fluxes and react readily with even the most stable oxides at high temperatures Work well dissolving refractory metal oxides Assist in brazing with silver filler metals Increase capillary flow of brazing filler metals Chlorides Similar in fluxing to fluorides (less effective)

73 Brazing Flux Materials
Alkalies Hydroxides of sodium and potassium Elevate temperature at which fluxes effective Have ability to absorb moisture from air Limits usefulness Wetting agents Used in paste and liquid fluxes to improve contact between flux and metal interfaces Water Present in all fluxes Study Table 10-5 for the correct use of commercially available brazing fluxes.

74 Factors Influencing Joint Design
Composition of base and filler metals May be similar or dissimilar materials Types of joints (consider) Brazing process to be used Fabrication or manufacturing techniques required Quantity of production Method of applying filler metal Service requirements Pressure, temperature, corrosion, and tightness

75 Factors Influencing Joint Design
Two basic types of brazed joints are butt joint and lap joint Strength of butt joints less than lap joints Typical joints for brazing Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

76 Factors Influencing Joint Design
Service requirements Service part expected to provide Characteristics of material to be carried: temperature, pressure ranges, corrosiveness Properties of base metal and filler metal: tensile strength, resistance to impact, fatigue, and extremes of temperature and pressure Stress distribution Should be designed to avoid stress concentrations at brazed area that may cause tearing

77 Factors Influencing Joint Design
Placement of brazing filler metal Most torch-brazed joints have filler metal face-fed Mass factory production require preplacement Preplacement of brazing filler metal in shim form Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

78 Factors Influencing Joint Design
Preinserted silver alloy in groove Methods of preplacing brazing filler metal in wire form Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

79 Factors Influencing Joint Design
Electric conductivity Consider resistance set up by brazed joint Brazing filler materials have lower electrical conductivity than copper Pressure tightness Lap joint should be used in fabrication of pressure-tight assemblies Entire surface to me joined must have uniform coverage Provide outlet for air or gases enclosed when brazing closed assembly (provide vent)

80 Heating Methods Several methods of heating Selection factors:
Heat requirements of joint Materials being brazed Accessibility to joint Production quotas Compactness and lightness of design Mass of component

81 Torch Brazing (TB) Four different kinds of torches used for brazing process, depending on fuel-gas mixtures Mixtures include: Air-gas, air-acetylene, oxyacetylene, oxyhydrogen, city gas, natural gas, propane, propylene, butane Air-gas torches Provide lowest flame temperatures and least heat Air-gas and air-acetylene torches Used to advantage on small parts and thin sections

82 Torch Brazing (TB) Oxygen-gas torches Oxyhydrogen
Gases: city, natural, propane, propylene, or butane Provide higher flame temperature Oxyhydrogen Used for brazing aluminum and other nonferrous alloys Temperature higher than air-gas but lower than oxyacetylene Danger of overheating reduced Provide joint with additional cleaning during brazing

83 Torch Brazing (TB) Oxyacetylene torches
Provide widest range of heat control and highest temperature of all torches Used in variety of situations and with most fillers Torch heating limited to brazing filler metals that may be used with flux or are self-fluxing Aluminum-silicon, silver, copper-phosphorus, and copper-zinc classifications

84 Furnace Brazing (FB) Used when:
Parts to be brazed can be preassembled or jigged to hold them in position Brazing filler metals can be preformed and preplaced Exacting atmosphere control is necessary Method of heating varies according to application and relative cost of fuel Flame does not make direct contact with parts

85 Induction Brazing (IB)
Used on parts that are self-jugging or that can be fixtured so effective heating not reduced by fixture Parts to be brazed act as short-circuited resistance unit in electric circuit and heated as result Most of heat generated relatively near surface Interior heated by thermal conduction from hot surface

86 Resistance Brazing (RB)
Process used when small areas are to be brazed and material high in electrical conductivity Heat provided by resistance of parts to flow of high current Supplied by transformer Conductors made of carbon, molybdenum, tungsten, or steel Application is brazing of conductors into commutator slots in large electric motors

87 Dip Brazing (DB) Two methods in common use: Molten metal dip brazing
Limited to brazing of small assemblies Wire connections and metal strips Filler metal melted in graphite crucible (heated) Cover of flux maintained over molten filler metal Clean parts immersed into molten metal Take care that mass does not lower temperature below that necessary for brazing

88 Dip Brazing (DB) Molten chemical dip process
Limited to small assemblies that can be dipped Flux heated in metal or ceramic container to fluid Heat applied externally or by resistance heating of flux Parts cleaned, assembled, and held in jigs before dipping Brazing filler metal preplaced on base metal Rings, washers, slugs, or cladding

89 Infrared Brazing (IRB)
Used mostly for brazing small parts Heat source is high intensity quartz lamp Radiant heat Produce up to 5,000 watts

90 Diffusion Brazing (DFB)
General term for many special processes developed by the demands of nuclear and aerospace industries Employs filler metal that diffuses into base metal under specific set of conditions of time, temperature, and pressure Provides joint with high melting point than normal brazing Permits high service temperatures

91 Brazeable Metals: Aluminum and Aluminum Alloys
Aluminum alloys with high magnesium content difficult to braze Poor fluxing and wetting Contain silicon Belong to BAlSi group Flux usually required

92 Brazeable Metals: Magnesium and Magnesium Alloys
Most forms brazed with filler metals of BMg group Torch and furnace brazing have limited applications Dip brazing used for all Corrosion resistance depends upon thoroughness of flux removal

93 Brazeable Metals: Copper
Two types of copper for industrial use Oxygen-bearing copper Contains small percentage of oxygen as cuprous oxide Oxide active at temperatures above 1,680ºF Reduces ductility of brazing materials Tensile strength not affected by heating Oxygen-free copper Not subject to oxygen migration or hydrogen embrittlement during brazing Filler metals: BAg and BCuP groupings used

94 Low Carbon and Low Alloy Steel
Can be brazed without difficulty All processes may be used Best suited filler metals BAg, BCu, and BCuZn Flux necessary

95 Brazeable Metals: Stainless Steel
Wide range of base metals Most of BAg, BCu, and BCuZn filler metals may be used BAg grades with nickel best for corrosion resistance Fillers containing phosphorus should be avoided Brittle nickel and iron phosphides may be formed BNi filler materials used for all applications above 800ºF to obtain maximum corrosion resistance Flux necessary

96 Brazeable Metals: High Carbon and High Speed Tool Steels
Best accomplished prior to or at same time as hardening Hardening temperatures range from 1,400 to 1,500ºF, so filler metals used that have brazing temperatures above 1,500ºF used after hardening At same time, filler metals having solidus at or below hardening temperature used Flux is necessary

97 Brazeable Metals: Nickel and High Nickel Alloys
Brazed by standard processes Subject to embrittlement when mixed with sulfur and metals with low melting points Subject to stress corrosion cracking Anneal before brazing BAg groups used when high corrosion resistance desired BNi filler metals offer greatest corrosion and oxidation resistance and elevated-temperature strength

98 Brazeable Metals: Cast Iron
Somewhat difficult Requires thorough cleaning with electrochemical flame, grit-blasting, or chemical methods Percentage of silicon and graphitic carbon high, wetting difficult High temperature filler metals BCu used Has high carbon content with low melting point

99 Brazeable Metals: Other Metals
Many metals brought into use by aircraft and missile development Include: tungsten, tantalum, molybdenum, niobium, beryllium, titanium, and zirconium Most can be brazed with silver-based filler metals May apply to certain types of ceramics May join graphite to graphite and graphite to metals Growing application – brazing dissimilar metals

100 Practice Job: Brazing Brazing materials for joining copper tubing divided into two classes Silver alloys Copper-phosphorous alloy Wide differences in melting and flowing characteristics Provides needed strength and tightness

101 Brazing Copper Tubing and Pipe: Practice Job 10-J55
Select copper tubing with diameters ranging from 1/2 to 1-1/2 inches and copper fittings to match diameters. Clean tube ends and sockets and make them free of burrs. Choose and apply flux immediately after cleaning to prevent oxidation. Use flux with consistency of honey.

102 Brazing Copper Tubing and Pipe: Practice Job 10-J55
Assemble joint, support so lined up true and square. Strength of joint depends on maintaining proper clearance between outside of tube and socket of fitting. As clearance increases, tensile strength reduced. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

103 Brazing Copper Tubing and Pipe: Practice Job 10-J55
Brush additional flux at joint around chamfer of fitting. Use oxyacetylene torch for brazing and adjust flame to slight excess acetylene. Heat tube, beginning 1 inch from edge of fitting; sweep flame around tube in short strokes, up and down, at right angles to run of tube (constant motion). Continue until flux bubbles, then becomes quiet and transparent (tube has reached brazing temperature).

104 Brazing Copper Tubing and Pipe: Practice Job 10-J55
Switch flame to fitting at base of cup. Heat uniformly by sweeping flame from fitting to tube until flux on fitting stops bubbling. When flux liquid and transparent, start sweeping flame back and forth along axis of joint to maintain heat on parts to be joined. Flame must keep moving to avoid burning tube or fitting.

105 Brazing Copper Tubing and Pipe: Practice Job 10-J55
Apply brazing rod at point where tub enters socket of fitting. Keep both fitting and tub heated as alloy drawn into joint. When proper temperature reached, alloy will flow readily into space by capillary attraction. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

106 feeding as soon as joint is filled.
Brazing Copper Tubing and Pipe: Practice Job 10-J55 Capillary attraction draws alloy into space between tube outer wall and fitting socket Continuous fillet of brazing alloy will be visible completely around joint. Stop feeding as soon as joint is filled. Allow to cool naturally and clean off remaining flux. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

107 Brazing Pipe Difficult to bring tube or pipe 1 inch or larger in diameter up to proper temperature at same time Double-tip torch maintains proper temperature over larger areas Mild preheating of whole assembly recommended Can heat portion of joint to brazing temperature and alloy applied

108 Brazing Pipe Joint divided into sectors and each given individual treatment until have completed fillet Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

109 Horizontal and Vertical Joints
Horizontal and vertical positions same as flat Material drawn into joint by capillary attraction, not action of gravity Major problem is overheating Start applying filler at top then two sides and finally bottom (overlap filler) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

110 Brazed Joints Torch can be formed to reach hard-to-braze joints
Direct flame where you want it Keep torch in generally horizontal position Torch flame illumination Protect surfaces around joint Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

111 Fittings That Can Be Brazed: Special Techniques
Couplings, Ls, Ts, and crosses Variety of sizes and types Cups must be cleaned thoroughly and well-fluxed Fittings with both brazed and threaded ends Do not braze next to screwed joint Make up brazed end first and then threaded end Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

112 Fittings That Can Be Brazed: Special Techniques
Unions Protect ground sealing surfaces with generous supply of flux; do not play torch flame directly on ground surfaces Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

113 Fittings That Can Be Brazed: Special Techniques
Flanges Heat should be applied to hub of flange Large flanges may need Preheating from another source in order to make sure flange is evenly Heated all over Entire assembly must be cooled slowly Return bends Must be free at one end while brazing operation carried on to provide for expansion Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

114 Fittings That Can Be Brazed: Special Techniques
Valves Do not remove valve bonnet Valve should be opened wide and backed off just a little Wrap wet cloth around bonnet to protect it Light coat of flux on valve seat on plug Most of heat should be at base of cup Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

115 Review Aids to Good Brazing: Fluxing
Flux reduces oxidation and soaks up few oxides that may form Surface must be cleaned prior to using flux High pressure joints require thicker coating of flux Appearance tells when to solder Clear, still, water look at 1,100ºF Overheating destroys effectiveness of flux

116 Support Poor Capillary Action
Keep assembly well-supported so no strains Allow for expansion from heating joint Poor capillary action Joint may be too hot Surfaces may not be cleaned Joint clearance too great Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

117 Timing Brazing speedy operation
Flux applied right after surface cleaned Begin heating, when flux shows hot enough, start feeding filler alloy – work rapidly! Remember: Flux immediately after cleaning Do not heat assembly any longer than necessary

118 Aftercare and Disassembly
Remove flux after finishing brazing Scrub joints with water and flush inside of piping systems Disassembly Brush flux around area of fillet at edge of cup Put pipe in vise and heat joint; when up to brazing heat, pull tubing out of fitting Wipe molten alloy off pipe and cup before it sets Parts can be used again

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