Chapter 28 Oxyfuel Welding Cutting and Brazing Chapter

Chapter 28 Oxyfuel Welding, Cutting, and Brazing

Chapter Outcomes • Explain the processes of oxyfuel welding and oxyfuel cutting • Identify the characteristics of gases used with oxyfuel torches • Safely handle and store gas cylinders • Safely work with oxyfuel equipment • Properly light and shut down an oxyfuel torch gyn 9037/Shutterstock. com Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Chapter Outcomes • Differentiate between types of oxyacetylene flames and their applications • Use a cutting torch • Weld with an oxyacetylene torch • Compare and contrast brazing and braze welding • Use a multiflame heating tip Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Welding • The process of joining metals through the introduction of heat generated by burning gases – Fuel gas is mixed with correct proportions of oxygen – Produces a flame of over 5700°F (3149°C) – Produces CO 2 which shields weld – Filler metal may be added to weld Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Cutting • Uses acetylene and oxygen to preheat metal to a bright orange color (kindling temperature) – Kindling temperature is the point at which the metal readily reacts with oxygen – Pressurized oxygen blows through the melted metal • Can be used on metals from less than 1/8” up to 12” thick Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Gases Used in Oxyfuel Torches • Gases used in oxyfuel torches include – Oxygen (O 2) – Acetylene (C 2 H 2) – Propane (C 3 H 8) – Propylene (C 3 H 6) – Butane (C 4 H 10) – MAPP gas (C 3 H 4) – Compressed natural gas (CH 4) or CNG Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Gases Used in Oxyfuel Torches • Oxygen (O 2) – Naturally occurring – Approximately 21% of the atmosphere – Not flammable but needed to support any burning process; considered an accelerant – Used to increase combustion rate and temperature of the flame • About 2 1/2 parts oxygen per one part acetylene (2. 5: 1) required for complete combustion of acetylene Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Gases Used in Oxyfuel Torches • Acetylene (C 2 H 2) – Colorless gas with garlic-like odor – Produced by submerging calcium carbide in water – Can be used for heating, cutting, and brazing – Burns at higher temperatures than most other gases Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Gases Used in Oxyfuel Torches • Propane (C 3 H 8) – Produces very high heat but the inner flame is not as hot as acetylene – Used for heating and cutting – Often mixed with similar gases – Mixes sold as liquefied petroleum gas (LPG) • Oxygen-to-fuel ratio of 4. 3: 1 Anthony Di. Chello/Shutterstock. com Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment • Basic acetylene setup – Pressurized cylinder of acetylene – Pressurized cylinder of oxygen – Pressure regulators for both tanks – Gas hoses – Torch handle – Torch head attachment – Cylinder valves – Cylinder caps Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment • Pressurized oxygen cylinders Oxygen regulator – Wall thickness at least 1/4” – 250 ft 2 of oxygen at 2200 psi – Pressure relief valve vents excess pressure – The valve has two seats and should always be turned fully open or fully closed – Available in variety of sizes Oxygen cylinder Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment • Pressurized acetylene cylinders – Explosively unstable when pressurized over 15 psi – Cylinder is filled with uniformly porous mass saturated with acetone – Acetylene dissolves in acetone and is prevented from forming large pressurized concentrations Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment • Pressurized acetylene cylinders Acetylene regulator – Pressurized to 250 psi – Must be kept upright – Must be fastened securely – Valves should be opened no more than 3/4 of a turn – Includes emergency pressure release device Acetylene cylinder Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment • Propane and LPG cylinders – Strong, light-gauge steel – Steel ring around valve for protection – Must be kept vertical to prevent compression Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment • Pressure regulators – Control pressure of gas flowing to the torch – Soft brass or bronze – Two gauges measure tank pressure and working pressure – Provide constant pressure even as tank pressure falls – Gas-specific and should not be interchanged Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment—Hoses • Hoses – Gas- and pressure-specific – Color-coded – Three grades – Four types Photo Love/Shutterstock. com Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment—Hoses • Color-coded – Red for acetylene and other gases – Green for oxygen – Black reserved for inert gases Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment—Hoses • Grade R – Neither internal nor external flame protection – Less costly than grade T hoses • Grade RM – Acetylene only – Inside tube is neither flame-resistant nor oil-resistant – Outside cover is flame- and oil-resistant • Grade T – Used for most fuel gases – Inside tube and outside cover are flame-resistant and oil-resistant Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment—Hoses • Type L – Single-line, designed for light-duty service • Type S – Single-line, used for standard-duty service • Type H – Single-line, used for heavy-duty service • Type VD – Bonded double-line (used most often) Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment—Hoses • Gas line connectors – Left-hand threaded brass nuts for fuel hoses – Right-hand threaded for oxygen hoses – Hose barbs are tapered, ringed nipples which are inserted into the ends of the hose and secured by ferrules Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment—Torches • Torches – Fuel gases and oxygen are mixed inside the torch – Mix ratio controlled by adjusting the torch valves – Flame shape and intensity can be adjusted – Torch assemblies vary in size and function Photo Love/Shutterstock. com Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment—Torches • Single-piece – Strictly for cutting – Few moving parts – Range from compact to over 6′ long Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment—Torches • Two-piece – Torch body, or handle – Cutting, welding, heating attachments Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment—Torches • Torch bodies – Textured handle – Fuel control valve – Oxygen control valve • Oxygen and fuel hose attachments – Screwed onto the torch body – Mixing of gases takes place in the attachment Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment • Welding and brazing tips – Simple angled tubes with specifically shaped and sized orifices in the tip – The mixing chamber is built into the base of the attachment – Single orifice in the tip – Tip sizes vary to create larger, stronger flames Photo Love/Shutterstock. com Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment • Cutting attachments – A single, center outlet pushes pure oxygen – A ring of orifices supplies the oxyfuel mix – Have adjustments for oxygen and a lever to force pure oxygen through the tip – Allow torch to burn through ferrous metals Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment • Cutting tips – Solid pieces of copper alloy – Replaceable – Available in many sizes – Multiple orifices – More, larger orifices provide more heat for thicker metal Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment • Cutting tips – Use a tip selection chart to determine tip sizes – Center orifice supplies a cutting jet of pure oxygen – Outer orifices supply the oxyfuel mix • Propane uses a two-piece tip with a solid brass core Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment • Multiflame heating tips – Often called rosebuds – Use large volumes of fuel and oxygen – Large rosebuds may exceed the withdraw rate of a cylinder – Propane may need to be used – Two acetylene tanks may be connected in a manifold system Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment • Multiflame heating tips – Allows for adjustment of heating tip to fit the thickness of metal needed – If too small, heating takes too long or metal cools before sufficiently heated – Too large and too much acetylene can be withdrawn or heating is inefficient Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment • Cutting table – Dedicated table for cutting metal – Steel with a grated top – Funnel bottom collects the stream of dross Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Safety Devices • Flashback – Recession of flame back into the tip or mixing chamber – May hiss or squeal – Most likely in the fuel line – Can travel all the way back and start a fire at the tank – Shut off gas immediately – Starving the torch will cause the flame to be insufficient or flashback Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Safety Devices • Reverse flow check valves – Keep gas flowing in one direction only • Flashback arrestors – Stops flashback in the gas passages Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Clothing and PPE • Always use proper equipment and clothing – Safety goggles, glasses, and face shield – Heavy, leather welding gloves – Cotton clothing • Do not saturate clothing in fuel gas or oxygen before use My best art/Shutterstock. com Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Storing Oxyfuel • No smoking around torch assembly • Store oxygen cylinders separate from gas cylinders • Chain cylinders securely • Remove regulators and use steel cap • Secure upright for travel • Release pressure from cylinder valves and hoses before leaving • Inform instructor of any leaks Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Equipment • Report damaged equipment • Ensure reverse flow check valves and flash arrestors are in place • Do not mix torch parts • Never use petroleum lubricants in torches • Check for gas leaks at connections • Attach regulators carefully – Release regulator pressure before disconnecting – Replace damaged hoses when necessary – Use only brass and bronze fittings for repairs Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Checking for Leaks • Check for leaks each time part of the torch system is connected or reconnected – Apply a nonpetroleum-based soapy solution to torch connections – The solution bubbles when a leak is present Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Using the Torch • Work in a well-ventilated area • Keep a fire extinguisher nearby • Open acetylene valve minimally and oxygen valve fully • Never stand in front or stare down the regulator • In case of a flashback, kill the oxygen immediately • Keep acetylene below 15 psi • Keep heat and flame away from cylinders • Never leave a torch unattended • Never weld or cut containers containing flammables Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Equipment—Setting Up 1. 2. 3. 4. 5. 6. 7. Ensure cylinders are secured properly Quickly purge valves before attaching regulators Install flashback arrestors and check valves Install hoses and tighten connections Connect torch body to hoses Assemble remaining torch components Check for leaks Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Lighting Safety • Never use a butane lighter or a match to light a torch • Use a flint or electronic striker designed for the task Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Lighting the Torch 1. 2. 3. 4. 5. 6. 7. 8. Set regulators are at zero pressure Open cylinder valves slowly Adjust regulators to recommended pressure Crack torch fuel valve to allow a small amount of flow Quickly ignite fuel tip with striker Increase gas flow until flame separates from the tip Slowly open oxygen torch valve creating an intermediate flame with a blue inner cone Add oxygen as needed for a neutral flame Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Types of Flames • Flame type is determined by the ratio of oxygen to acetylene in the mixture produced by the torch • Preheating the flame brings metal to kindling temperature • Three distinct types of oxyacetylene flames – Neutral flame – Carburizing flame – Oxidizing flame Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Neutral Flame • Acetylene to oxygen ratio is almost 1: 1 • Enough for a complete burn • Does not chemically react with metal being welded • Required for most torch operations Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Carburizing Flame • Acetylene to oxygen ratio is higher than in neutral flame • Feather of white-hot unburned carbon around inner core • Increases carbon content of a weld metal • Hardfacing is done with a carburizing flame Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxidizing Flame • Oxygen-rich fuel mixture at tip • Excess oxygen combines with or burns some of the metal being welded • Sharp tip with distinct hissing noise • Welding cast iron and brazing steel Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Torch Shut-Down Procedure 1. 2. 3. 4. Quickly close the torch fuel gas valve Close the oxygen control valve Close both cylinder valves Purge the system by opening both torch valves to release all pressure from the torch, hoses, and regulators 5. Check all of the gauges on the regulators; each should be at 0 6. Back out the pressure-adjusting screws of both regulators until there is no tension on them 7. Close all torch valves Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Oxyfuel Cutting Torch • Versatile – Cuts metals – Loosens damaged or stuck fasteners – Can be used to help bend metal Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Burning Steel • The cutting process is accomplished by burning or oxidizing the steel • When melted, iron combines with gases in process to form dross – Dross is the waste material Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Steps in the Cutting Process 1. 2. 3. 4. 5. 6. 7. Select appropriate tip for the job Clean the base metal Mark your cutting path or cut line Position your workpiece to be cut Adjust pressure regulators as needed Light the torch and set to a neutral flame Brace against a table or stable surface (continued) Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Steps in the Cutting Process 8. Hold torch flame inner cone approximately 1/8” above metal 9. Maintain the preheat of the base metal 10. Hold torch at 90° to metal and depress cutting lever 11. Move at a steady pace to maintain cut and preheat 12. When complete, release cutting lever and close torch control valves Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Welding with Oxyfuel • Useful in areas without electricity or in emergencies • Requires great deal of manual manipulation and is time-consuming • Mild steel is welded fairly easily by fusion welding with an oxyfuel setup • No filler metal or flux is needed for the process Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Braze Welding and Brazing • Melt a filler metal to join two pieces of metal • Braze welding – Melts above 800°F but below melting point of the base metal • Brazing – Similar but uses capillary action to draw in filler metal • Both use a brass or bronze filler material Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Braze Welding and Brazing • • • Does not fuse two base metals Stronger than solder Can bond dissimilar metals Good choice where high heat can damage material Bronze filler flexes with movement Flux is required on brass and bronze filler metals Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.