For added strength, the R60 rod designation contains higher carbon, manganese, and some silicon.
In addition to meeting minimum chemical requirements, a weld must be made as defined in AWS A5.2 specification and produce a minimum of 60-ksi tensile strength. An even stronger alloy is available that contains other alloying elements and meets a minimum tensile strength of 65 ksi.
A note of interest is that R45 has very little alloy, which is probably similar to that of a coat hanger. For oxyacetylene welding, where only a low strength is needed a coat hanger could work. However, its chemistry may not be consistent and if you try it, be sure all of the paint or clear coating is removed.
Oxyacetylene is often more useful than other welding processes for braze welding. Unlike fusion welding, braze welding does not melt the base metal, so the melting point of the filler rod is below the melting point of the material being welded. When joining cast iron, for example, the joint does not have to deal with a mixture of the very high carbon-based material.
Fig. 3.10. One area in which oxyacetylene can be very useful over other welding processes is when braze welding. The melting point of 60-percent copper and 40-percent zinc filler rod is about 1,630 degrees F, well below that of cast iron, for example. This allows a quality joint to be made without having to melt the very-high-carbon cast iron.
A common brazing alloy with 60-percent copper 40-percent zinc has a melting point of about 1,630 degrees F, which is well below that of cast iron. Weld strength typically exceeds 45 ksi. The rod melts and wets the surface but does not melt the cast iron. A flux ensures a very clean surface and assists in the wetting process.
The other advantage of braze welding cast iron is that the high heat input and inherent slow cooling reduces the shrinkage stresses in the cast iron and avoids cracks. Braze welding is a preferred method of repairing cracks in cast-iron parts, particularly some types that are very difficult to fusion weld.
Welding equipment can be purchased from many sources, including the Internet. However, welding equipment operates in a difficult environment and sometimes requires repair, so make sure businesses are available to repair the product if it fails.
Oxyfuel equipment is unique; it is essential to match the torches, regulators, and hose with the fuel gas. With the increasing cost of acetylene, alternative fuel gases may be best for you, and you should discuss the available options with your gas supplier. Some equipment is sold with two cylinders, but determine if your gas supplier is willing to fill them or swap them with filled cylinders instead. If you are braze welding, heating, and cutting rather than truly welding, a gas distributor may recommend a system that uses propane, propalyene, or another alternative to acetylene.
Safety
These general safety guidelines should be followed, but the following short overview of general safety issues is not meant to replace the instructions supplied with the oxyfuel welding and cutting outfit or other equipment. Read and understand the manufacturer’s instructions for safe use of the product.
General Precautions
• Do not use oil. Oil, grease, coal dust, and other organic ingredients are easily ignited and burn violently in the presence of oxygen. Never allow such materials to come in contact with oxygen or oxygen-fuel gas equipment. Oxygen-fuel gas equipment does not require lubrication.
• A serious accident can occur if oxygen is used as a substitute for compressed air. Oxygen must never be used to power pneumatic tools, to blow out pipelines, to dust clothing, or for pressure testing.
• Never use acetylene at pressures above 15 psi.
• Never use torches, regulators, or other equipment in need of repair. If a regulator creeps up in pressure, it has a seat leak and should be repaired or replaced.
• Do not connect an oxygen regulator to a cylinder unless it has a filter on the inlet. If it is on the input nipple, check to see it is installed every time the regulator is put on a cylinder.
• Always use the equipment manufacturer’s recommended operating pressures. Using pressures higher than recommended not only makes flame adjustment difficult, but it can cause a flashback fire inside the torch.
• Always used fully enclosed goggles or a full-face helmet when working with a lighted torch. Goggles with a number-4 shade are generally satisfactory for oxyacetylene welding and oxyfuel cutting.
• Do not use matches to light a torch. Always use a friction lighter to avoid having your hands near the flame when lighting.
• Wear suitable clothing: fire resistant gauntlet gloves and long-sleeved shirts. Wool is more fire resistant than cotton or synthetic fabric.
• Before starting to weld or cut, check the area to make sure sparks, flames, hot metal, or slag will not start a fire.
• Never weld or cut without adequate ventilation.
• Use particular caution when welding and cutting in dusty or gassy locations. These atmospheres necessitate extra precautions to avoid explosions or fires from sparks, matches, or open flames of any type.
• Never weld or cut on containers that have held flammable or toxic substances until the container has been thoroughly cleaned and flammable gases have been neutralized.
Precautions for Containers with Flammable Substances
• Assume the container may contain residue.
• Wash with a strong solution of caustic soda to remove heavy oil.
• If possible, fill the container with water to within a few inches of the working area before welding. When impractical to fill with water, an inert gas such as nitrogen or carbon dioxide can be used to purge the container of oxygen and flammable vapors. Maintain the gas purge during welding.
Other Precautions
• Make sure that jacketed or hollow parts are sufficiently vented before heating, welding, or cutting. Air, gas, or liquid confined inside a hollow container expands when heated. The pressure created can cause a violent rupture.
Fig. 3.11. The American Welding Society classifies oxyacetylene welding filler rods based on their chemical composition. A common alloy has an AWS specification A5.2 designation of R45. The rod contains little alloy having low carbon and manganese additions. The rod produces an all weld tensile strength of about 45 ksi.
• Remove or securely fasten in place any bushings in a casting before heating the casting. Bronze bushings expand more than cast iron when heated to the same temperature. If a bushing is left in place, the casting may be damaged or expansion may cause the bushing to fly out. If it cannot be removed, bolting large washers or plates over the ends may be possible.
• Protect cylinders, hoses, and your legs and feet when cutting. Do not cut material in such as position that allows sparks, hot metal, or a cut part to fall against a gas cylinder, the hoses, or your legs and feet.
• Take special care to make certain that a flame, sparks, hot slag, or hot metal do not reach combustible material and start a fire. This is particularly important in cutting operations. Have someone stand by to watch the sparks and give warning if sparks are going into an area that could cause fire problems.
• An appropriate fire extinguisher, a pail of water, a water hose, or a sand bucket should be located and