Oxy-Acetylene Welding and Cutting | Page 2

leaders in their respective fields, thus insuring that the work is thoroughly practical and that it represents present day methods and practice.
THE AUTHOR.

CONTENTS
CHAPTER I
METALS AND ALLOYS--HEAT TREATMENT:--The Use and Characteristics of the Industrial Alloys and Metal Elements--Annealing, Hardening, Tempering and Case Hardening of Steel
CHAPTER II
WELDING MATERIALS:--Production, Handling and Use of the Gases, Oxygen and Acetylene--Welding Rods--Fluxes--Supplies and Fixtures
CHAPTER III
ACETYLENE GENERATORS:--Generator Requirements and Types--Construction--Care and Operation of Generators.
CHAPTER IV
WELDING INSTRUMENTS:--Tank and Regulating Valves and Gauges--High, Low and Medium Pressure Torches--Cutting Torches--Acetylene-Air Torches
CHAPTER V
OXY-ACETYLENE WELDING PRACTICE:--Preparation of Work--Torch Practice-- Control of the Flame--Welding Various Metals and Alloys--Tables of Information Required in Welding Operations
CHAPTER VI
ELECTRIC WELDING:--Resistance Method--Butt, Spot and Lap Welding--Troubles and Remedies--Electric Arc Welding
CHAPTER VII
HAND FORGING AND WELDING:--Blacksmithing, Forging and Bending--Forge Welding Methods
CHAPTER VIII
SOLDERING, BRAZING AND THERMIT WELDING:--Soldering Materials and Practice-- Brazing--Thermit Welding
CHAPTER IX
OXYGEN PROCESS FOR REMOVAL OF CARBON
INDEX

OXY-ACETYLENE WELDING AND CUTTING, ELECTRIC AND THERMIT WELDING

CHAPTER I
METALS AND THEIR ALLOYS--HEAT TREATMENT
THE METALS
_Iron._--Iron, in its pure state, is a soft, white, easily worked metal. It is the most important of all the metallic elements, and is, next to aluminum, the commonest metal found in the earth.
Mechanically speaking, we have three kinds of iron: wrought iron, cast iron and steel. Wrought iron is very nearly pure iron; cast iron contains carbon and silicon, also chemical impurities; and steel contains a definite proportion of carbon, but in smaller quantities than cast iron.
Pure iron is never obtained commercially, the metal always being mixed with various proportions of carbon, silicon, sulphur, phosphorus, and other elements, making it more or less suitable for different purposes. Iron is magnetic to the extent that it is attracted by magnets, but it does not retain magnetism itself, as does steel. Iron forms, with other elements, many important combinations, such as its alloys, oxides, and sulphates.
[Illustration: Figure 1.--Section Through a Blast Furnace]
_Cast Iron._--Metallic iron is separated from iron ore in the blast furnace (Figure 1), and when allowed to run into moulds is called cast iron. This form is used for engine cylinders and pistons, for brackets, covers, housings and at any point where its brittleness is not objectionable. Good cast iron breaks with a gray fracture, is free from blowholes or roughness, and is easily machined, drilled, etc. Cast iron is slightly lighter than steel, melts at about 2,400 degrees in practice, is about one-eighth as good an electrical conductor as copper and has a tensile strength of 13,000 to 30,000 pounds per square inch. Its compressive strength, or resistance to crushing, is very great. It has excellent wearing qualities and is not easily warped and deformed by heat. Chilled iron is cast into a metal mould so that the outside is cooled quickly, making the surface very hard and difficult to cut and giving great resistance to wear. It is used for making cheap gear wheels and parts that must withstand surface friction.
_Malleable Cast Iron._--This is often called simply malleable iron. It is a form of cast iron obtained by removing much of the carbon from cast iron, making it softer and less brittle. It has a tensile strength of 25,000 to 45,000 pounds per square inch, is easily machined, will stand a small amount of bending at a low red heat and is used chiefly in making brackets, fittings and supports where low cost is of considerable importance. It is often used in cheap constructions in place of steel forgings. The greatest strength of a malleable casting, like a steel forging, is in the surface, therefore but little machining should be done.
_Wrought Iron._--This grade is made by treating the cast iron to remove almost all of the carbon, silicon, phosphorus, sulphur, manganese and other impurities. This process leaves a small amount of the slag from the ore mixed with the wrought iron.
Wrought iron is used for making bars to be machined into various parts. If drawn through the rolls at the mill once, while being made, it is called "muck bar;" if rolled twice, it is called "merchant bar" (the commonest kind), and a still better grade is made by rolling a third time. Wrought iron is being gradually replaced in use by mild rolled steels.
Wrought iron is slightly heavier than cast iron, is a much better electrical conductor than either cast iron or steel, has a tensile strength of 40,000 to 60,000 pounds per square inch and costs slightly more than steel. Unlike either steel or cast iron, wrought iron does not harden when cooled suddenly from a red heat.
_Grades of Irons._--The mechanical properties of cast iron differ greatly according to the amount of other materials it contains. The most important of these contained elements is carbon, which is present to a degree varying from 2 to 5-1/2 per cent. When iron containing much carbon is quickly cooled and then broken, the fracture is nearly white in color