Part 5 (1/2)

A flux is used to float off physical i coating around the weld; to assist in the re handled; to lower the temperature at which the materials flow; to make a cleaner weld and to produce a better quality of metal in the finished work

The flux must be of such composition that it will acco new difficulties They may be prepared by the operator inapparatus, the sa the welding rods, that is, only the best should be considered

The flux used for cast iron should have a softening effect and should prevent burning of the metal In many cases it is possible and even preferable to weld cast iron without the use of a flux, and in any event the smaller the quantity used the better the result should be Flux should not be added just before the completion of the work because the heat will not have time to drive the added elements out of the metal or to incorporate them with the metal properly

Alu a flux because of the oxide formed This oxide, called alumina, does not melt until a heat of 5,000 Fahrenheit is reached, four times the heat needed to melt the aluminum itself It is necessary that this oxide be broken down or dissolved so that the aluether Copper is another metal that requires a flux because of its rapid oxidation under heat

While the flux is often thrown or sprinkled along the break while welding,the hot end of the welding rod into the flux whenever the work needs it Sufficient poill stick on the end of the rod for all purposes, and with some fluxes too much will adhere Care should always be used to avoid the application of excessive flux, as this is usually worse than using too little

SUPPLIES AND FIXTURES

_Goggles_--The oxy-acetylene torch should not be used without the protection to the eyes afforded by goggles These not only relieve unnecessary strain, but ress of the ith the ht while welding is even greater than when cutting ht which is nearest to sunlight of any artificial illuives a little reen and less blue in its composition, it would be the saht fro lost with the addition of the extra oxygen needed to produce the welding heat The light that is dangerous comes froht white heat

Goggles for protection against this light and the heat that goes with itfor welding and the lighter for cutting Those having frames in which the metal parts do not touch the flesh directly are h temperature reached by these parts

_Gloves_--While not as necessary as are the goggles, gloves are a convenience in many cases Those in which leather touches the hands directly are really of little value as the heat that protection is desired against ained in comfort Gloves are made with asbestos cloth, which are not open to this objection in so great a degree

[Illustration: Figure 9--Fra Stand]

_Tables and Stands_--Tables for holding hile being welded (Figure 9) are usually ether

The top should be rectangular, about two feet wide and two and one-half feet long The legs should support the working surface at a height of thirty-two to thirty-six inches from the floor Metal lattice work may be fastened or laid in the top fraether with a mixture of one-third ce welded is braced and supported on this table with pieces of firebrick so that it will re the operation

Holders for supporting the tanks of gas may be made or purchased in forms that rest directly on the floor or that are mounted on wheels These holders are quite useful where the floor or ground is very uneven

_Hose_--All perenerators to the torches are idly supported, but the short distance from the end of the pipe line to the torch itself is completed with a flexible hose so that the operator h which the gases nited will burst this part of the equip it For that reason it is well to use hose with great enough strength to withstand excessive pressure

A poor grade of hose will also break down inside and clog the flow of gas, both through itself and through the parts of the torch To avoid outside dae and cuts this hose is sometimes encased with coiled sheet th of more than 1,000 pounds to the square inch Many operators prefer to distinguish between the oxygen and acetylene lines by their color and to allow this, red is used for the oxygen and black for acetylene

_Other Materials_--Sheet asbestos and asbestos fibre in flakes are used to cover parts of the hile preparing the the operation itself The flakes and se sheets are thrown into a bin where the co while protected by the asbestos

Asbestos fibre and also ordinary fireclay are often used toor mould into a form that may be placed behind aluminum and some other ly difficult to handle under ordinary methods This forms a solid mould into which the metal is practically cast as melted by the torch so that the desired shape is secured without danger of the walls ofaway

Carbon blocks and rods are made in various shapes and sizes so that they may be used to fill threaded holes and other places that it is desired to protect during welding These may be secured in rods of various diameters up to one inch and in blocks of several different dimensions

CHAPTER III

ACETYLENE GENERATORS

Acetylene generators used for producing the gas from the action of water on calcium carbide are divided into three principal classes according to the pressure under which they operate