and maintenance where one type of equipment can perform many different repairs
•Welding of thin sheet, tubing, and small diameter pipe
•In field operations for natural gas distribution systems up to four inch diameter schedule forty pipes
For what type jobs are OAW definitely not a good choice?
OAW welds of thick sections are not economical when compared with shielded metal arc welding, flux-cored arc welding, or gas metal arc welding.
What disadvantages does OAW have over other welding processes?
In general most other processes are faster: they can apply more weld filler metal in a given time.
What metals can the OAW process readily weld?
•Copper
•Bronze
•Lead
•Low alloy steels
•Wrought Iron
•Cast steel
What materials can be welded by the OAW process if additional steps are taken?
Aluminum and stainless steel may be welded, provided one or more of the following steps are taken—preheat, postheat, use of fluxes, or special welding techniques.
What are three major problems associated with welding aluminum?
•Does not change color prior to melting, so it requires extra welder skill to control heat input.
•Has hot shortness—lacks strength at high temperatures.
•Exposed aluminum has a very thin oxide layer that requires the use of flux and also the oxide surface does not let the welder see a wet-looking molten weld pool.
Besides welding, what other processes can an oxyacetylene welding assembly perform?
With minor additional equipment, it may perform:
•Brazing and soldering
•Case hardening
•Descaling
•Post-heating
•Pre-heating
•Stress relieving
•Oxyacetylene cutting
•Flame hardening
•Flame straightening
•Shrink-to-fit parts assembly
•Surface treatment
•Forging
•Heating for bending and forming
•Tempering and annealing
Why is the carbon content of steel important to the welder?
Carbon content determines its weldability and controls the steel’s tendency to harden upon rapid cooling. The greater the carbon content, the harder it may become.
Why should clothes hangers not be used as welding rod?
Both safety and quality suggest clothes hangars should not be used for welding. Hangers are usually painted and may release toxic fumes, as they burn; they may also be plated, also possibly toxic. From a quality standpoint, their metal content is unknown, variable and unlikely to provide a good weld.
What factors are important in the selection of filler metal (welding rod)?
Usually the filler metal is a close match to the base metal. Sometimes the filler metal will have deoxidizers added which will improve the weld more than just a base metal match. Rod diameters vary from
Table 1–3 Oxyacetylene steel welding rods
What procedures should be followed in welding common metals and what welding rods would make a good starting point?
For all metals, begin by removing all surface dirt, scale, oxide, grease, and paint. Refer to Table 1–4 for technique, flux, flame, and suggested method.
Table 1–4 Information for welding various metals
Weld Preparation
What joint preparation is used for OAW butt welds?
See Figure 1–19.
Figure 1–19Preparation for OAW butt welds
Figure 1–20Correct and defective butt weld profiles
Weld Profiles
On a butt weld, what do the following weld profiles look like: correct weld, poor penetration, excessive reinforcement, undercutting, and excessive root reinforcement?
See Figure 1–20.
Safety
What essential pieces of safety equipment are needed to begin OAW?
See Figure 1–21.
•Non-synthetic fabric (cotton or wool) long-sleeved shirt buttoned to the top to prevent sparks from entering.
•Tinted welding goggles with minimum of number 5 shade lenses.
•Leather gloves.
•Spark igniter.
•Pliers for moving hot metal.
Figure 1–21Oxyacetylene safety equipment
What are the main hazards of OFW and what safety equipment can prevent these injuries?
•External eye injuries from welding or grinding sparks are prevented using welding goggles, safety glasses, or safety shields.
•Internal (retinal) eye damage from viewing hot metal and the radiation being emitted during welding and while cooling (until the metal is no longer red), prevented by using a number 5 tinted lens.
•Burns from weld sparks and hot metal prevented by leather or heavy cotton welding gloves, fire retardant clothing, leathers or specially treated welding jacket or cape-sleeves and bibs when working overhead, cuffless pants, high-top leather shoes.
•Fume hazards from the vapors of metals and flux, must be avoided by proper ventilation, fume filters, and welder air supplies to