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Wilbur Wright
Introduction
Soldering has been used for thousands of years, but a solid theoretical understanding has come only in the last one hundred. Brazing is similar to soldering but performed at higher temperatures. It has come into use more recently as higher temperature torches became available. Although soldering and brazing do not make joints as strong as welded ones, they are widely used in making and repairing a wide range of products from airplanes to computers to household plumbing to jewelry. Soldering and brazing processes can be as simple as using a soldering iron, a propane torch or as complex as using radio frequency energy in a vacuum to join parts. We will discuss the theory, materials, fluxes, and common industrial processes. These processes have some advantages over welding and we will present them. There are safety issues too. Because soldering copper water pipe is so useful and something every welder should know how to do, we cover step-by-step instructions in Chapter 15.
Process Names
What is the AWS designation for brazing?
The AWS designation for brazing is B.
What common names are sometimes used for brazing?
Silver soldering, silfloss, and hard soldering are non-preferred names for brazing. Silver brazing filler metals are not solders; they have melting points above 840°F (450°C).
How are brazing processes classified and what are the commercially significant ones?
Brazing processes are classified by heat-source type. Commercially important ones are:
•Dip Brazing (DB)
•Furnace Brazing (FB)
•Induction Brazing (IB)
•Infrared Brazing (IB)
•Resistance Brazing (RB)
•Torch Brazing (TB)
What is the AWS designation for soldering?
The AWS designation for soldering is S.
What are the commercially important soldering processes?
•Dip Soldering (DS)
•Furnace Soldering (FS)
•Induction Soldering (IS)
•Infrared Soldering (IRS)
•Iron Soldering (INS)
•Resistance Soldering (RS)
•Torch Soldering (TS)
•Wave Soldering (WS)
Note that with the exception of iron soldering and wave soldering both brazing and soldering share most common processes.
Process
In general terms how does the brazing process work?
Brazing joins materials that have been heated to the brazing temperature followed by adding a brazing filler metal having a melting point above 840°F (450°C). This temperature will be below the melting point of the base metals joined by this joining process. The non-ferrous filler metal is drawn into and fills the closely fitted mating or faying surfaces of the joint by capillary attraction. The filler material, usually aided by fluxes, wets the base metal surfaces allowing the brazing material to flow or capillary more readily through and between the two surfaces. When the filler metal cools and solidifies, the base materials are joined. See Figure 3–1.
Figure 3–1Capillary forces draw molten filler metal into brazed joint
How does soldering differ from brazing?
Brazing takes place above 840°F (450°C) and soldering below 840°F (450°C), otherwise, the processes are quite similar. They both depend on capillary attraction to draw filler metal or solder into the joint. In general brazed joints are stronger than soldered ones because of the strength of the alloys used.
What is the difference between brazing and braze welding?
Brazing depends on capillary attraction to draw the filler metal into the mating joint, while in braze welding the filler metal is deposited in grooves or fillets at the points where needed for joint strength. Capillary attraction is not a factor in distributing the filler metal, as the joints are open to the welder. Braze welding is not a brazing process, but welding with brazing filler metal. Braze welding is frequently used to repair cracked or broken cast iron parts. Joint design is similar to those for OAW: V-groove butt joints, lap joints, T-joints, fillets, and plug joints.
What advantage does braze welding have over welding?
Because braze welding does not melt the base metal and is performed at a lower temperature than welding, there is less distortion of the part. Also, the process of braze welding is performed only on a small area of the part, so the entire part does not need to be brought up to braze temperature all at once.
How does a brazed joint hold the base metals together?
Filler metal atoms have a stronger attraction to the base metal’s atoms than to their own. This force between two surfaces is called adhesion. This preference for atoms other than its own causes the wetting action of the base metal. When wetting action takes place in a small diameter tube or between closely spaced parallel plates as in a joint, capillary action occurs. Capillary attraction is so strong it readily opposes gravity and works to the welder’s advantage by bringing filler material into the joint and distributing it evenly. A soldered joint’s strength comes from the same forces. See Figure 3–2.
Figure 3–2Capillary attraction
On what metals can brazing be performed?
Most common metals can be brazed or soldered including:
•Aluminum
•Bronze
•Brass
•Cast iron
•Copper
•Stainless Steel
•Steel
•Titanium
•Tool steels (some)
•Tungsten carbide (tool bits)
What metals can be soldered?
Most metals may be soldered.
What are the advantages of the brazing and soldering processes over other joining methods?
•Ability to join dissimilar metals—Steel is easily joined to copper, cast iron to stainless steel, and brass to aluminum. Many combinations of metals are readily joined.
•Ability to join nonmetals to metals—Ceramics are easily joined to metals, or each other.
•Ability to join parts of widely different thicknesses—either thin-to-thin or thin-to-thick parts may be joined without burn-through or overheating.
•Excellent stress distribution—Many of the distortion problems of fusion welding are eliminated because of the lower process temperature and the even distribution of heat with more gradual temperature changes.
•Low temperature process—the components being joined like semiconductors are less likely to be damaged, since the base metals are not subjected to melting temperatures.
•Economical for complex assemblies—many parts can be joined in a single process step.
•Joins precision parts well—with proper jigs and fixtures, parts may be very accurately positioned.
•Parts may be temporarily joined, subjected to other manufacturing processes, and then separated without damage.
•Parts can be assembled rapidly—processes are readily adaptable to batch and automatic assembly operations.
•Mistakes are readily fixed—a misaligned part can be repositioned without damage.
•Ability to make leak-proof and vacuum-tight joints—many tanks are soldered or brazed; high-power radio transmitter vacuum tubes and integrated circuits with metal to ceramic joints are brazed.
•Joints require little or no finishing—with proper process design the brazed or soldered joint can be nearly invisible.
•Combined brazing and heat treatment cycles—when protective atmosphere brazing is used, the brazing process may be incorporated into the heat treatment cycle.
What are some disadvantages of the brazing process?
•While brazing processes can produce high-strength joints, they are rarely as strong as a fusion-welded joint.
•The brazed parts and the filler metal may lack a color match.
Important Processes Detailed
How do each of the commercially important brazing and soldering processes work and what are their advantages and applications?
Dip Brazing
There are two types. Molten-metal bath dip brazing uses a pot of molten filler metal, usually temperature controlled and heated by electricity, oil, or gas. The cleaned, fluxed parts are immersed into the molten filler metal that enters the joints by capillary attraction. When the assembly is withdrawn and cooled, the brazing is complete. The parts are usually self-jigging. A layer of flux usually covers the molten metal to retard oxidation.
The other method is molten chemical bath dip brazing. Here the parts are cleaned, filler metal is placed between the joints, the parts to be joined are then assembled with filler in place, preheated, then dipped into a pot of molten chemicals serving as a flux.
The advantage of dip brazing over torch brazing is that even heating of the part reduces distortion. Dip brazing may be manual or automated; it is used on small to medium parts. See Figure 3–3.
Dip soldering very much resembles molten metal dip brazing using a molten metal bath but at a lower temperature.
Figure 3–3Chemical bath dip brazing or soldering
Furnace Brazing
The parts are cleaned, brazing filler metal is placed inside the joints, and the parts assembled using fixtures to hold them in proper position. The pre-placed brazing filler metal can be in the form of filings, foil, paste, powder, tape, or special shapes called preforms that fit the joint. Both batch and continuous conveyor furnaces are used. Furnaces may have multiple heat zones for preheat, brazing, and cool-down.
Flux is used in furnaces with an air atmosphere, but air can be eliminated by using a special atmosphere (argon or helium) or a vacuum. If flux is not used in the brazing process, it will not have to be removed in a later step—a significant advantage. Furnace brazing offers lower distortion than torch brazing, and may also perform heat-treating. See Figure 3–4.
Figure 3–4Furnace brazing
Furnace soldering is similar to furnace brazing, but at a lower temperature and normally in an air atmosphere.
Induction Brazing
This process depends on inducing an alternating current in the part. As this induced current flows around inside the part, it generates heat from the resistance of the part itself, and brings it up to brazing temperature. A solid-state, or vacuum-tube oscillator generates alternating current from 10 to 500 kHz. This current is fed to a coil of copper tubing that usually surrounds the part. This copper coil acts as the primary of a transformer and the parts themselves act as the secondary. The copper tubing coil itself is kept from melting by cooling water flowing through the tubing’s interior. Power from one to several hundred kilowatts is used. Induction coils are designed in shapes that maximize the transfer of current to the assembly being brazed and take many shapes and sizes. See Figures 3–5 and 3–6.
Figure 3–5Different shapes of induction brazing coils
Figure 3–6Coils in place on brazing work
Cleaning the parts, inserting brazing filler metal and flux into the joints, assembling the parts and heating them with an induction coil, perform induction brazing. The process is very fast, usually measured in seconds, and used to make consumer and military parts. It is often automated. Some processes utilize a vacuum and use no flux. Induction Soldering is similar to induction brazing, but at a lower temperature.
Infrared Brazing
Infrared brazing is a form of furnace brazing. High-intensity quartz lamps supply long-wave heat of up to 5 kW each. Concentrating reflectors focus heat on the parts. This process is sometimes performed in a vacuum and is usually employed in a conveyor-fed production process. Infrared Soldering is similar to infrared brazing, but at a lower temperature.
Resistance Brazing
Electric current flowing through the joint to be brazed provides heat for this process. The joint is cleaned, fluxed, and braze filler material is placed inside the joint in the form of wire, washers, shims, powder, or paste. Then the joint is placed between two electrodes, squeezed together, and electricity is applied. The source of electricity is usually a step-down transformer providing from 2 to 25 volts. Current runs from 50 amperes for small jobs to thousands of amperes for large ones. The electrodes are high-resistance electrical conductors like carbon or graphite blocks, or tungsten or molybdenum rods. Most of the heat is produced in the electrodes raising them to incandescence. This heat flows into the joint completing the braze joint. The resistance of the joint alone is not usually an adequate heat source. The cycle time varies from one second to several minutes depending on part size. See Figure 3–7.
Figure 3–7Resistance brazing or soldering method
Torch Brazing
Heating is done with one or more gas torches. Depending on the size of the parts and the melting point of the filler metal, a variety of torch fuels (acetylene, propane, methylacetylene-propadiene stabilized, or natural gas) may be burned in oxygen, compressed air, or atmospheric air. A neutral or oxidizing flame will usually produce excellent results.
Flux is required with most braze filler metals and can usually be applied to the joint ahead of brazing. The filler metal can be preplaced in the joint or face fed. Manual torch brazing is successfully used on assemblies involving components of unequal mass. It is frequently used in the repair of castings in the field and is often automated for high-production of small and medium-sized parts. It is a versatile process and probably the most popular brazing technique.
Torch Soldering
This is very much like torch brazing but at a lower temperature. Usually propane, methylacetylene-propadiene gas, or natural gas burning in air supplies the heat.
The joint is cleaned to shiny metal with emery cloth, wire brushes, steel wool, or commercial abrasive pads. The flux (used for wetting the joining surfaces) is usually applied in liquid or paste form, or may be alloyed inside the solder wire.
While widely used in manufacturing and maintenance, it is also used in plumbing to join copper tubing for potable water. See Chapter 15 for a detailed procedure for the torch soldering of copper tubing.
Iron Soldering
Traditional soldering irons contain a copper tip on a heat-resistant handle. They are heated electrically or in a gas, oil, or coke furnace. The copper tip stores and carries heat to the solder joint. This transfer is made possible by heat being transferred from the heated tip of the iron to the part to be soldered; when the joint is raised to soldering temperature, solder is applied to the joint itself, and wets the entire joint. Flux core solder is used for electronic work. This solder has been formed concentrically around a core of one or more strands of flux. In sheet metal and other non-electrical work, the flux may also be in the solder core, or applied as a paste or a liquid.
Today most soldering irons are heated electrically and are available from just a few watts for electronic work to 1250 watts for roofing and heavy sheet- metal work. Many irons for electronic work have temperature-controlled tips to avoid damage to the sensitive components. See Figure 3–8.
Figure 3–8Electrically-heated soldering irons
Wave Soldering
This process is used to solder electronic components onto printed circuit boards. A conveyor belt draws a printed circuit board with components over a fountain (or wave) of solder. This solders all the components in place in a single step. Wave soldering machines are available which can flux, dry, preheat, solder, and clean the flux off a finished board on a single conveyor line. See Figure 3–9.
Figure 3–9Wave soldering
Joint Design for Brazing
Why is joint design an important part of brazing process design?
Well-designed braze joints start with fundamental butt and lap joints. Figures 3–10A shows a butt joint angled to provide more surface area for the brazed or soldered material to bond; this angles joint is called a scarf joint. Figure 3-10B shows both a lap joint and a square edged butt joint. Good joint design insures a reliable, repeatable production brazing process that will provide a strong joint.
Figure 3–10AButt joint prepared at an angle and called a scarf joint
Figure 3–10BLap and butt joints
What design changes can be made in butt and lap joints to increase their strength?
See Figures 3–11 through 3–13.
Figure 3–11Progressive design changes to increase butt joint strength
Figure 3–12Progressive design changes to increase lap joint strength
In Figure 3–12, the maximum strength of a simple lap joint appears in B, an overlap of 3 times the thickness of the base metal (3T). More overlap without additional refinements will not improve strength.
Figure 3–13Progressive design changes to increase butt joint strength against torsional (twisting) forces
What factors influence joint good design?
•Base metal selection—differences in base metal thermal expansion coefficients may lead to poor joint fit at brazing temperature with too much or too little clearance.
•Effect of flux on clearance—flux must enter the joint ahead of the braze filler metal and then be displaced by it, but when joint clearance is too small the flux may be held in the joint by capillary forces. This prevents proper braze filler entry and leaves voids.
•Effect of base metal to filler metal combinations on clearance.
•Effect of brazing metal filler on clearance.
•Effect of joint length and geometry on clearance.
•Dissimilar base metals form a cell that leads to electrolytic corrosion.
What are typical clearances used in brazed joints?
Joint clearances range from 0.002 to 0.010 inches (0.05 to 0.25 mm). Assuming that the joint clearance is adequate to admit braze filler material, the lower the joint clearance, the stronger the joint. Too much clearance will reduce joint strength, too little will permit voids in the joint.
Joint Preparation
How parts to be joined usually cleaned for brazing?
There are two classes of cleaning: chemical and mechanical. There are many different processes in use. Some common chemical ones are:
•Solvent cleaning with petroleum solvents or chlorinated hydrocarbons.
•Vapor degreasing with perchlorethylene or other solvents.
•Alkaline cleaning with mixtures of phosphates, silicates, carbonates, detergents, hydroxides, and wetting agents.
•Electrolytic cleaning.
•Salt baths.
•Ultrasonic cleaning.
•Mechanical cleaning processes include:
•Grinding
•Filing
•Machining
•Blasting
•Wire brushing
Wire brushes must be free of contaminating materials and selected so none of the wire wheel material is transferred to the part being cleaned. A stainless steel wire brush is a good choice for most materials.
Blasting media must be chosen so it does not embed in the base metal and is easily removed after blasting. For this reason, blasting media like alumina, zirconia, and silicon-carbide should be avoided. These processes are used to remove all dirt, paint and grease so the flux and braze filler metal can readily and completely wet the base metal surface.
How are joints prepared for soldering?
Many of the same processes used in brazing are used for soldering. However, in a non-production situation, mechanical cleaning especially with emery cloth, steel wool, or commercial abrasive pads or by filing will be effective. Getting down to fresh, bare metal is the objective. Complete the soldering immediately, before the base metals have a chance to re-oxidize.
Brazing and Soldering Fluxes
What is the purpose of flux in soldering and brazing?
•Further cleaning the base metal surface after the initial chemical or mechanical cleaning.
•Preventing the base metal from oxidizing while heating.
•Promoting the wetting of the joint material by the braze filler material or solder by lowering surface tension and to aid capillary attraction.
How do fluxes promote wetting of the base metals?
Flux covers and wets the base metal preventing oxidization until the braze filler material or solder reaches the joint surfaces. Since the flux has a lower attraction to the base metal’s atoms than the filler or solder, when the filler metal or solder melts, it slides under the flux and adheres to the clean, unoxidized base metal surface ready to receive it. Fluxes will not remove oil, dirt, paint or heavy oxides, so the joint surface must already be clean for them to work.
What are the main categories of brazing fluxes?
Brazing fluxes usually contain fluorides, chlorides, borax, borates, fluoroborates, alkalis, wetting agents, and water. A traditional and still common flux is 75% borax and 25% boric acid (borax plus water) mixed into a paste.
The AWS Brazing Manual provides specifications for brazing and brazing fluxes. This specification has 15 classifications of fluxes. Many manufacturers supply proprietary flux mixtures meeting these specifications. See Table 3–1 for abbreviated AWS flux categories and applications.
Table 3–1 Representative brazing flux categories
In working with brazing flux, what precautions must be observed?
Many fluxes contain powerful poisons with long-term and short-term actions. See the Safety section for details.
If water must be added to turn a powdered flux into a paste or to thin an existing paste, what precautions must be followed?
Distilled water must be used, since tap water may contain chemicals that would damage the joint.
What are the main types of soldering fluxes?
•Organic fluxes—consisting of organic acids and bases, after soldering they can be removed with water and are widely used in electronics.
•Inorganic fluxes—containing no carbon compounds, so they do not char or burn easily and are used in torch, oven, resistance, and induction soldering. They are not used for soldering electrical joints.
•Rosin-based fluxes—easily cleaned from parts after soldering. They are usually non-corrosive; available as powders, pastes, liquids, and as a core within soldering wire. They are used in electrical and electronics applications.
How are brazing fluxes applied?
•Flux can be applied by spraying, brushing, or dipping.
•Flux is adhered to the end of a brazing rod by heating of the rod’s end with the torch and dipping it into the flux. The flux is a dry powder.
•Some brazing (and braze welding) rod comes from the factory with flux already applied to the outside.
•Sheets, rings, and washers of flux can be inserted in the joint before assembly.
•Special guns can inject flux (or mixtures of flux and filler metal) directly into the joint.
•Flux can be dissolved in alcohol and supplied within the fuel gas stream directly to the brazing joint eliminating the manual operation of adding flux. This process automatically controls the amount applied. See Figure 3–14.
Figure 3–14Gas fluxing unit for oxyfuel brazing
How are soldering fluxes applied?
Soldering fluxes are brushed, rolled, or sprayed. Many solders have flux cores, so no separate fluxing step is needed.
Brazing Filler Materials and Soldering Alloys
What properties must brazing filler materials have?
They must have the ability to make joints with mechanical and chemical properties for the application.
•Melting point below that of the base metals being joined and with the right flow properties to wet the base metals and fill joints by capillary attraction. See Figure 3–15.
•Composition that will not allow it to separate into its components (liquation) during brazing.
Figure 3–15Melting points of braze filler metals and solders fall well below most base metals
What do the terms solidus and liquidus mean?
Solidus is the highest temperature at which a metal is completely solid. Liquidus is the lowest temperature at which a metal is completely liquid.
In general what can be said about the solidus and liquidus temperatures of pure metal? What can be said of alloys of two metals?
Because pure metals have an abrupt melting point, their solidus and liquidus temperatures are the same. However, in an alloy of two metals there is both a range of temperatures and a range of compositions at which both solid and liquid phases of the alloy can exist.
What is the best way to show how the melting and freezing properties of an alloy of two metals changes as its composition changes from all one base metal to all of the other base metal?
A constitutional diagram shows how the changing alloy’s mix of composition affects its melt properties. See silver-copper constitutional diagram in Figure 3–16.
Figure 3–16Silver-Copper constitutional diagram
What does the above constitutional diagram show?
•The solidus line ADEB indicates the temperature at which the alloy begins to melt for compositions of copper and silver.
•The liquidus line ACB indicates the temperature above which the alloy is completely melted.
•For a particular mix of the two metals, the melting point is lower than the melting point of either pure metal making up the alloy, or of any other mixture of the alloy. For a silver-copper alloy, the minimum melting point is 1435°F (779°C) and occurs at 72% silver - 28% copper (point C). This is called the eutectic temperature and eutectic composition. Note that copper melts at 1481°F (805°C) and silver at 1761°F (961°C), both well above the 1435°F eutectic temperature.
•For alloy mixtures other than the eutectic, there is a range of temperatures in which both solid and liquid phases of the alloy can exist together (area ADC and area CEB). In these areas of temperature and composition the alloy is mushy or slushy, while at the eutectic it has a sharp melting point and is as fluid as a pure metal.
How can the information in a constitutional diagram suggest brazing and soldering alloys for specific applications?
•By using a eutectic alloy, we can minimize the temperature at which we perform the brazing (or soldering in the case of tin-lead or tin-antimony alloys) and still have a fluid composition that can easily make its way into the brazing joints.
•By using a non-eutectic alloy, we can achieve an alloy that is slushy or less fluid than at the eutectic. The wider the difference between the solidus and liquidus lines in the constitutional diagram, the more sluggish the alloy is in this temperature range. This would be helpful where too fluid an alloy would not stay in place in an inverted joint and where we want capillary attraction to prevail over gravity. A good example of this is soldering a fitting or seam upside down.
Do other soldering and brazing two-metal alloys have the same general pattern as the silver-copper constitutional diagram?
Yes, see the tin-lead constitutional diagram in Figure 3–17.
Figure 3–17Tin-lead constitutional diagram
What are the most common brazing filler metals?
Filler materials covered by AWS specifications are grouped as:
•Aluminum-silicone
•Copper
•Copper-phosphorus
•Copper-zinc
•Heat-resisting material
•Magnesium
•Nickel-gold
•Silver
What determines the choice of braze filler metal?
The filler choice is determined by base materials or metals.
What is the purpose of shims or washers of filler metal preplaced in the work?
Preplacing filler metal permits the parts to be brazed or soldered in an oven or by other means without need of human attention to feed in the filler metal at the right time and place. See Figure 3–18.
Figure 3–18Method of preplacing brazing filler metal
What is stop-off used for?
Stop-off is used to outline the area not to be brazed. It prevents the flux from entering that area.
What are the most common solders?
Tin-lead alloys are the most common solders. It is customary to indicate the tin percentage first, then the lead content and the same with other two-metal alloys. A 40/60 tin-lead solder is 40% tin and 60% lead.
Tin-lead solders 35%/65%, 40%/60% and 50%/50% are popular because of their low liquidus temperatures. Tin-lead solders 60%/40% and the 63%/37% eutectic are used when low-processing temperatures are needed. Tin-silver, tin-copper-silver, and tin-antimony alloys are used where lead must be eliminated for health reasons as in stainless steel fabrication for kitchens, food processing equipment, and copper potable water systems. Never use lead-containing solder on potable water systems.
What are some other less common solders?
•Bismuth-containing solders provide alloys with very low melting temperatures for sprinkler heads and heat detectors for alarms.
•Indium alloys with liquidus temperatures as low as 230°F (138°C) are used for glass-to-glass and glass-to-metal seals in electronics.
Troubleshooting Brazing & Soldering Processes
Problem: No flow or no wetting.
Causes:
•Wrong braze filler
•Temperature too low
•Time at temperature too short
•Parts not properly cleaned
•Parts fit poorly
•Heat source in wrong location
Problem: Excess flow or wetting causes hole plugging or brazing wrong joints.
Causes:
•Temperature too high
•Time at temperature too long
•Too much filler material
•No stop-off used
Problem: Erosion—Braze filler material eats away parent metal.
Causes:
•Temperature too high
•Time at temperature too long
•Excessive braze filler metal
•Cold worked parts
Safety
What special chemical hazards do brazing and soldering present and what precautions must be taken?
Base metals and filler metals may contain toxic materials such as: antimony, arsenic, barium, beryllium, cadmium, chromium, cobalt, mercury, nickel, selenium, silver, vanadium, or zinc. These will be vaporized during brazing or soldering and cause skin, eye, breathing, or serious nervous system problems. Some of these toxic materials are cumulative such as lead and may be absorbed through the skin. The following precautions are essential:
•Keep your head out of the brazing or soldering plume.
•Perform brazing or soldering in a well ventilated area.
•On failure of normal ventilating equipment, use respiratory equipment.
Many brazing and soldering fluxes and heating bath salts contain fluorides. Others contain acids and aluminum salts. The following precautions apply:
•Avoid direct contact with skin.
•Do not eat or keep food near these materials.
•Do not smoke around these materials.
•Insure MSDSs are affixed to containers of these materials and major equipment using them so they are visible to you and others.
What is an excellent source of information about these hazards in addition to the MSDSs?
See the AWS booklet Z49.1, Safety in Welding, Cutting and Allied Processes.
What eye protection is needed for brazing and soldering?
•For soldering, wear safety glasses or face shields to protect the eyes from external injuries caused by sparks, flying metal, or solder splashes.
•For brazing, using a number 5 tinted lenses will protect against internal (retinal) eye damage caused by viewing the radiation coming off hot metal. Some brazing requires darker lens shades of up to number 8.
What other safety precautions must be taken while soldering or welding?
•Skin protection from sparks and hot metal prevented by gloves and nonflammable clothing.
•Fires from the welding process can be prevented by moving flammables away from the weld zone and having water or fire extinguishers close at hand.
•Use adequate ventilation when using cleaning solvents to prepare the joints; chlorinated hydrocarbons are toxic and may create phosgene gas when heated.
•Always wear chemical-type eye goggles or face shields, rubber gloves, and long sleeves while using cleaning solutions, pickling solutions, or acids. Note that chemical-type goggles do not have ventilation holes above the eyes where splashes could enter.
