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OXY-ACETYLENE WELDING AND CUTTING
OXY-ACETYLENE WELDING AND CUTTING HAROLD P. MANLY PREFACE
In the preparation of this work the object has been to cover not only the
several processes of welding but also those other processes which are so
closely allied in method and results as to make them a part of the whole
subject of joining metal to metal with the aid of heat.
The workman who wishes to handle his trade from start to finish finds that
it is necessary to become familiar with certain other operations which
precede or follow the actual joining of the metal parts the purpose of
these operations being to add or retain certain desirable qualities in the
materials being handled. For this reason the following subjects have been
included: Annealing tempering hardening heat treatment and the
restoration of steel.
In order that the user may understand the underlying principles and the
materials employed in this work much practical information is given on the
uses and characteristics of the various metals; on the production handling
and use of the gases and other materials which are a part of the equipment;
and on the tools and accessories for the production and handling of these
materials.
An examination will show that the greatest usefulness of this book lies in
the fact that all necessary information and data has been included in one
volume making it possible for the workman to use one source for securing a
knowledge of both principle and practice preparation and finishing of the
work and both large and small repair work as well as manufacturing methods
used in metal working.
An effort has been made to eliminate all matter which is not of direct
usefulness in practical work while including all that those engaged in
this trade find necessary. To this end the descriptions have been limited
to those methods and accessories which are found in actual use today. For
the same reason the work includes the application of the rules laid down
by the insurance underwriters which govern this work as well as
instructions for the proper care and handling of the generators torches
and materials found in the shop.
Special attention has been given to definite directions for handling the
different metals and alloys which must be handled. The instructions have
been arranged to form rules which are placed in the order of their use
during the work described and the work has been subdivided in such a way
that it will be found possible to secure information on any one point
desired without the necessity of spending time in other fields.
The facts which the expert welder and metalworker finds it most necessary
to have readily available have been secured and prepared especially for
this work and those of most general use have been combined with the
chapter on welding practice to which they apply.
The size of this volume has been kept as small as possible but an
examination of the alphabetical index will show that the range of subjects
and details covered is complete in all respects. This has been accomplished
through careful classification of the contents and the elimination of all
repetition and all theoretical historical and similar matter that is not
absolutely necessary.
Free use has been made of the information given by those manufacturers who
are recognized as the 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 2400 degrees in practice is
about one-eighth as good an electrical conductor as copper and has a
tensile strength of 13000 to 30000 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
25000 to 45000 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 40000 to 60000 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
and the metal is found to be hard and brittle. When the iron is slowly
cooled and then broken the fracture is gray and the iron is more malleable
and less brittle. If cast iron contains sulphur or phosphorus it will show
a white fracture regardless of the rapidity of cooling being brittle and
less desirable for general work.
_Steel._--Steel is composed of extremely minute particles of iron and
carbon forming a network of layers and bands. This carbon is a smaller
proportion of the metal than found in cast iron the percentage being from
3/10 to 2-1/2 per cent.
Carbon steel is specified according to the number of "points" of carbon a
point being one one-hundredth of one per cent of the weight of the steel.
Steel may contain anywhere from 30 to 250 points which is equivalent to
saying anywhere from 3/10 to 2-1/2 per cent as above. A 70-point steel
would contain 70/100 of one per cent or 7/10 of one per cent of carbon by
weight. The percentage of carbon determines the hardness of the steel also
many other qualities and its suitability for various kinds of work. The
more carbon contained in the steel the harder the metal will be and of
course its brittleness increases with the hardness. The smaller the grains
or particles of iron which are separated by the carbon the stronger the
steel will be and the control of the size of these particles is the object
of the science of heat treatment.
In addition to the carbon steel may contain the following:
Silicon which increases the hardness brittleness strength and difficulty
of working if from 2 to 3 per cent is present.
Phosphorus which hardens and weakens the metal but makes it easier to
cast. Three-tenths per cent of phosphorus serves as a hardening agent and
may be present in good steel if the percentage of carbon is low. More
than this weakens the metal.
Sulphur which tends to make the metal hard and filled with small holes.
Manganese which makes the steel so hard and tough that it can with
difficulty be cut with steel tools. Its hardness is not lessened by
annealing and it has great tensile strength.
Alloy steel has a varying but small percentage of other elements mixed with
it to give certain desired qualities. Silicon steel and manganese steel are
sometimes classed as alloy steels. This subject is taken up in the latter
part of this chapter under _Alloys_ where the various combinations
and their characteristics are given consideration.
Steel has a tensile strength varying from 50000 to 300000 pounds per
square inch depending on the carbon percentage and the other alloys
present as well as upon the texture of the grain. Steel is heavier than
cast iron and weighs about the same as wrought iron. It is about one-ninth
as good a conductor of electricity as copper.
Steel is made from cast iron by three principal processes: the crucible
Bessemer and open hearth.
_Crucible steel_ is made by placing pieces of iron in a clay or
graphite crucible mixed with charcoal and a small amount of any desired
alloy. The crucible is then heated with coal oil or gas fires until the
iron melts and by absorbing the desired elements and giving up or
changing its percentage of carbon becomes steel. The molten steel is then
poured from the crucible into moulds or bars for use. Crucible steel may
also be made by placing crude steel in the crucibles in place of the iron.
This last method gives the finest grade of metal and the crucible process
in general gives the best grades of steel for mechanical use.
[Illustration: Figure 2.--A Bessemer Converter]
_Bessemer steel_ is made by heating iron until all the undesirable
elements are burned out by air blasts which furnish the necessary oxygen.
The iron is placed in a large retort called a converter being poured
while at a melting heat directly from the blast furnace into the
converter. While the iron in the converter is molten blasts of air are
forced through the liquid making it still hotter and burning out the
impurities together with the carbon and manganese. These two elements are
then restored to the iron by adding spiegeleisen (an alloy of iron carbon
and manganese). A converter holds from 5 to 25 tons of metal and requires
about 20 minutes to finish a charge. This makes the cheapest steel.
[Illustration: Figure 3.--An Open Hearth Furnace]
_Open hearth steel_ is made by placing the molten iron in a receptacle
while currents of air pass over it this air having itself been highly
heated by just passing over white hot brick (Figure. 3). Open hearth steel
is considered more uniform and reliable than Bessemer and is used for
springs bar steel tool steel steel plates etc.
_Aluminum_ is one of the commonest industrial metals. It is used for
gear cases engine crank cases covers fittings and wherever lightness
and moderate strength are desirable.
Aluminum is about one-third the weight of iron and about the same weight as
glass and porcelain; it is a good electrical conductor (about one-half as
good as copper); is fairly strong itself and gives great strength to other
metals when alloyed with them. One of the greatest advantages of aluminum
is that it will not rust or corrode under ordinary conditions. The granular
formation of aluminum makes its strength very unreliable and it is too soft
to resist wear.
_Copper_ is one of the most important metals used in the trades and
the best commercial conductor of electricity being exceeded in this
respect only by silver which is but slightly better. Copper is very
malleable and ductile when cold and in this state may be easily worked
under the hammer. Working in this way makes the copper stronger and harder
but less ductile. Copper is not affected by air but acids cause the
formation of a green deposit called verdigris.
Copper is one of the best conductors of heat as well as electricity being
used for kettles boilers stills and wherever this quality is desirable.
Copper is also used in alloys with other metals forming an important part
of brass bronze german silver bell metal and gun metal. It is about
one-eighth heavier than steel and has a tensile strength of about 25000 to
50000 pounds per square inch.
_Lead._--The peculiar properties of lead and especially its quality
of showing but little action or chemical change in the presence of other
elements makes it valuable under certain conditions of use. Its principal
use is in pipes for water and gas coverings for roofs and linings for vats
and tanks. It is also used to coat sheet iron for similar uses and as an
important part of ordinary solder.
Lead is the softest and weakest of all the commercial metals being very
pliable and inelastic. It should be remembered that lead and all its
compounds are poisonous when received into the system. Lead is more than
one-third heavier than steel has a tensile strength of only about 2000
pounds per square inch and is only about one-tenth as good a conductor of
electricity as copper.
_Zinc._--This is a bluish-white metal of crystalline form. It is
brittle at ordinary temperatures and becomes malleable at about 250 to 300
degrees Fahrenheit but beyond this point becomes even more brittle than at
ordinary temperatures. Zinc is practically unaffected by air or moisture
through becoming covered with one of its own compounds which immediately
resists further action. Zinc melts at low temperatures and when heated
beyond the melting point gives off very poisonous fumes.
The principal use of zinc is as an alloy with other metals to form brass
bronze german silver and bearing metals. It is also used to cover the
surface of steel and iron plates the plates being then called galvanized.
Zinc weighs slightly less than steel has a tensile strength of 5000
pounds per square inch and is not quite half as good as copper in
conducting electricity.
_Tin_ resembles silver in color and luster. Tin is ductile and
malleable and slightly crystalline in form almost as heavy as steel and
has a tensile strength of 4500 pounds per square inch.
The principal use of tin is for protective platings on household utensils
and in wrappings of tin-foil. Tin forms an important part of many alloys
such as babbitt Britannia metal bronze gun metal and bearing metals.
_Nickel_ is important in mechanics because of its combinations with
other metals as alloys. Pure nickel is grayish-white malleable ductile
and tenacious. It weighs almost as much as steel and next to manganese is
the hardest of metals. Nickel is one of the three magnetic metals the
others being iron and cobalt. The commonest alloy containing nickel is
german silver although one of its most important alloys is found in nickel
steel. Nickel is about ten per cent heavier than steel and has a tensile
strength of 90000 pounds per square inch.
_Platinum._--This metal is valuable for two reasons: it is not
affected by the air or moisture or any ordinary acid or salt and in
addition to this property it melts only at the highest temperatures. It is
a fairly good electrical conductor being better than iron or steel. It is
nearly three times as heavy as steel and its tensile strength is 25000
pounds per square inch.
ALLOYS
An alloy is formed by the union of a metal with some other material either
metal or non-metallic this union being composed of two or more elements
and usually brought about by heating the substances together until they
melt and unite. Metals are alloyed with materials which have been found to
give to the metal certain characteristics which are desired according to
the use the metal will be put to.
The alloys of metals are almost without exception more important from an
industrial standpoint than the metals themselves. There are innumerable
possible combinations the most useful of which are here classed under the
head of the principal metal entering into their composition.
_Steel._--Steel may be alloyed with almost any of the metals or
elements the combinations that have proven valuable numbering more than a
score. The principal ones are given in alphabetical order as follows:
Aluminum is added to steel in very small amounts for the purpose of
preventing blow holes in castings.
Boron increases the density and toughness of the metal.
Bronze added by alloying copper tin and iron is used for gun metal.
Carbon has already been considered under the head of steel in the section
devoted to the metals. Carbon while increasing the strength and hardness
decreases the ease of forging and bending and decreases the magnetism and
electrical conductivity. High carbon steel can be welded only with
difficulty. When the percentage of carbon is low the steel is called "low
carbon" or "mild" steel. This is used for rods and shafts and called
"machine" steel. When the carbon percentage is high the steel is called
"high carbon" steel and it is used in the shop as tool steel. One-tenth
per cent of carbon gives steel a tensile strength of 50000 to 65000
pounds per square inch; two-tenths per cent gives from 60000 to 80000;
four-tenths per cent gives 70000 to 100000 and six-tenths per cent
gives 90000 to 120000.
Chromium forms chrome steel and with the further addition of nickel is
called chrome nickel steel. This increases the hardness to a high degree
and adds strength without much decrease in ductility. Chrome steels are
used for high-speed cutting tools armor plate files springs safes
dies etc.
Manganese has been mentioned under _Steel_. Its alloy is much used for
high-speed cutting tools the steel hardening when cooled in the air and
being called self-hardening.
Molybdenum is used to increase the hardness to a high degree and makes the
steel suitable for high-speed cutting and gives it self-hardening
properties.
Nickel with which is often combined chromium increases the strength
springiness and toughness and helps to prevent corrosion.
Silicon has already been described. It suits the metal for use in
high-speed tools.
Silver added to steel has many of the properties of nickel.
Tungsten increases the hardness without making the steel brittle. This
makes the steel well suited for gas engine valves as it resists corrosion
and pitting. Chromium and manganese are often used in combination with
tungsten when high-speed cutting tools are made.
Vanadium as an alloy increases the elastic limit making the steel
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