Autogenous welding and cutting
AUTOGENOUS WELDING AND CUTTINGBY THEODORE KAUTNY AND JAMES F. WHITEFORD
McGRAW-HILL BOOK COMPANY, NEW YORK, 1915
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Autogenous welding and cutting
AUTHOR'S PREFACE
The literature of autogenous welding technique has been enriched lately in many valuable ways, and there exist a large number of works which cover this field.
Autogenous welding is a process intended for general introduction both in small workshops and in large factories. The range of welding technique is so wide that a thorough study of the process requires extensive research which makes great demands on the time of the reader.
A pocket book of brief compass will be welcome to the works engineer, to the works foreman, and to the practical autogenous welder; in which the most important elements of the process are placed together in an easily available manner, and which shall be a faithful companion and a reliable adviser in connection with the various questions arising in practice.
The object of the present work is to meet these requirements and I pass it on to the general public in the hope that it will be favorably received and fulfil its task.
CONTENTS
- AUTOGENOUS WELDING FLAMES
- ACETYLENE MANUFACTURE AND APPARATUS
- OXYGEN MANUFACTURE AND APPARATUS
- GAS MAINS AND FITTINGS
- AUTOGENOUS WELDING BURNERS
- AUTOGENOUS CUTTING BURNERS
- AUTOGENOUS WELDING OF IRON
- REPAIRS OF GREY CAST IRON
- WELDING OF SHEET IRON
- MANUFACTURE AND REPAIRS OP BOILERS
- MANUFACTURE OF CYLINDRICAL VESSELS
- MANUFACTURE OF RECTANGULAR VESSELS AND MISCELLANEOUS ARTICLES
- MANUFACTURE AND INSTALLATION OP LARGE PIPES AND CONDUITS
- MANUFACTURE AND INSTALLATION OF GAS AND WATER PIPE
- CONSTRUCTION OF PIPE-SHAPED APPARATUS
- WELDING OF COPPER
- WELDING OF ALUMINUM
- WELDING OF NICKEL AND OTHER METALS
- CONCLUSION
AUTOGENOUS WELDING AND CUTTING
AUTOGENOUS WELDING FLAMES
Autogenous welding is a process by which, through the use of a hot blow pipe flame, the edges of metal parts, placed against each other, are heated to their melting point so they will flow' into one another. After the welding and cooling the parts form one body of almost the same physical properties.
The applications of the process in industry are both numerous and varied and its already wide field of practical uses is being rapidly extended. It is used to replace the seaming, riveting and hard soldering of metal sheets and for the installation of permanent plumbing fixtures and gas and water pipe.
In the manufacture, from strips of sheet metal, of piping and tubing of various kinds and dimensions, which are used for gas, water and steam conduits and also for the construction of different parts of bicycles, automobiles and aeroplanes.
The process is also used in the building trades, for making numerous parts out of rolled metal, as metal door and window frames, for the reinforcing of concrete, and for decorative metal work.
In the construction of internal combustion motors, to make various fittings and connections as well as for manufacturing the jacket of water-cooled cylinders. In the shipbuilding industry, for the construction and erection of pipes, as well as for boiler repairs. In the machine shop and foundry, to repair worn and defective castings of all kinds.
It is also extensively used to replace hard soldering in the finer metals and to manufacture metal furniture and sundry household articles of copper, aluminum and nickel.
Combustible Gases - For autogenous welding various combustible gases are used in conjunction with oxygen, to secure a flame of sufficient temperature to fuse metallic parts.
These gases are hydrogen, Blau or liquid gas, illuminating gas, benzine or benzol vapors, and acetylene.
Hydrogen - Hydrogen gas is a chemical element which exists in nature, in great quantities, in various chemical combinations. Of these, the most common is water, its combination with oxygen (H2O), and as a consequence water is used as a basis for the manufacture of hydrogen.
Inasmuch as the separation of water into its elements means the destruction of a chemical combination, considerable mechanical power is required.
Just as the separation of the chemical parts of water requires a considerable amount of power, so the combination of these elements - which takes place in the burning of such mixture known as oxy-hydrogen gas - develops aconsiderable amount of heat. Therefore the flame caused by the burning of oxy-hydrogen gas can be used for autogenous welding.
The burning of a molecular equivalent mixture of oxygen and hydrogen results in the forming of water. Water, however, when superheated at a high temperature, as under the influence of a blow pipe flame, dissociates again into its elements.
In using this flame for autogenous welding the danger exists that, during the formation of oxygen and hydrogen within the flame, the oxygen will unite with the metal, i.e. the metal will burn, or, what corresponds to lower degree of burning, the metal will become overheated.
The temperature of a hydrogen-oxygen flame can never go higher than the dissociation temperature of water which is estimated at 2000°C. (3632°F.).
To prevent the burning or overheating of metals in welding with hydrogen-oxygen, it becomes necessary to use a supercharge of hydrogen; in order that the oxygen liberated within the flame combines again with the free hydrogen, and thus making it harmless for the iron. This practice, however, increases the size and decreases the temperature, of the flame. Hydrogen is handled commercially in steel cylinders under a pressure of 150 atmospheres.
A hydrogen-oxygen welding outfit consists of 2 steel cylinders; one containing compressed hydrogen and the other compressed oxygen. Each cylinder is supplied with a pressure reducing valve connected with the welding burner by means of flexible tubes.
In the operation of a hydrogen-oxygen welding apparatus, if the burner is brought too near to the metal, a black spot can be observed in the middle of the glowing metal. This is due to the metal being cooled by the unburnt gas mixture and such a condition must be avoided.
For the welding of thin metal sheets, the use of oxy-hydrogen is practical, although the quality of the welding seam decreases as the thickness of the metal increases.
Oxy-hydrogen welding was the first autogenous welding system employed and was used extensively until the more advantageous system of welding with acetylene was introduced, which latter system has now almost entirely replaced the welding with the oxy-hydrogen flame.
Blau or Liquid Gas - Blau or liquid gas is manufactured by vaporizing liquid hydrocarbons in closed retorts and superheating the vapors. This is not a chemical combination but a mechanical mixture of various gases and vapors.
When this gas is used for welding, the free hydrogen contained in the products of combustion is absorbed by the iron. In working heavier sheets, necessitating a prolonged use of the flame, an extensive absorption of the hydrogen by the metal occurs. As the metal solidifies, the absorbed hydrogen is expelled producing a porous welding seam.
For the welding of certain metals, as aluminum, and for welding thin metal sheets, the employment of Blau gas is practical, but such operation is very expensive on account of the high cost of compressing and transporting the gas.
Illuminating Gas - Illuminating gas (coal gas and water gas) can only be used for welding very thin metal sheets, owing to the low temperature of the flame. On account of the great loss of heat caused by the absorbing and conductive qualities of the metal, it is impossible, with a flame of low temperature, to heat thick metal sheets locally to the melting point.
Benzine or Benzol Vapors - In autogenous welding, the vapors of liquid hydrocarbons have the same properties as Blau or liquid gas. The temperature of a Benzol welding flame at about 2700°C. (5000°F.) is higher than the illuminating gas welding flame, but is considerably lower than that of the oxygen-acetylene flame.
This gas derives its name from that of the inventor, a chemist, Blau of Augsburg, Germany. Numerous tests have proved that Benzol welding is less advantageous from an economical and qualitative standpoint than the oxy-acetylene or the oxy- hydrogen welding, but the process may be used to advantage for many purposes, especially for the welding of light pieces. Further, the apparatus used for such welding is capable of being moved easily from place to place.
Acetylene - The use of acetylene in autogenous welding has rapidly extended since its first introduction. This is due to the peculiar conditions resulting from the burning of acetylene in a stream of oxygen.
Acetylene is a chemical combination of carbon and hydrogen (C2H2) and the burning, i.e. its combination with oxygen, takes place in two phases, with a well defined zone formed of the first phase.
This zone consists of the products of combustion of the first phase, i.e. carbon monoxyde and hydrogen, which products combine with the oxygen of the air, in an exterior envelope of the flame, to the final products of combustion, i.e. carbonic acid and water.
In autogenous welding this zone within the flame is active while the outer envelope serves to protect the metal against oxidation. The formula of the chemical changes is as follows:
C2H2 + 20 = 2C0 + H2 and
2C0 + H2 + 30 = 2CO2 + H2O
Acetylene consists of a chemical combination of 2 atoms of carbon and 2 atoms of hydrogen (C2H2). Inasmuch as the carbon is two-atomic, the acetylene forms a non-saturated compound and there exists therefore, in the acetylene molecule, a certain interior tension.
This causes the gas to form other combinations belonging to the acetylene group at the comparatively low temperature of 480°C. (896°F.) which phenomena is called Polymerisation. Such higher combinations of the acetylene are Benzin, Benzol, Styrolin, Naphthalin, etc.
Benzol, like the balance of these combinations, has physical properties different from acetylene and this is the reason why Benzol vapors used in place of acetylene do not give the expected results in autogenous welding.
Furthermore, such polymeres of acetylene are liable to condense part of their carbon in the form of tar products under circumstances existing in an acetylene generator.
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Autogenous welding and cutting
The applications of the process in industry are both numerous and varied and its already wide field of practical uses is being rapidly extended. It is used to replace the seaming, riveting and hard soldering of metal sheets and for the installation of permanent plumbing fixtures and gas and water pipe.
In the manufacture, from strips of sheet metal, of piping and tubing of various kinds and dimensions, which are used for gas, water and steam conduits and also for the construction of different parts of bicycles, automobiles and aeroplanes.
The process is also used in the building trades, for making numerous parts out of rolled metal, as metal door and window frames, for the reinforcing of concrete, and for decorative metal work.
In the construction of internal combustion motors, to make various fittings and connections as well as for manufacturing the jacket of water-cooled cylinders. In the shipbuilding industry, for the construction and erection of pipes, as well as for boiler repairs. In the machine shop and foundry, to repair worn and defective castings of all kinds.
It is also extensively used to replace hard soldering in the finer metals and to manufacture metal furniture and sundry household articles of copper, aluminum and nickel.
Combustible Gases - For autogenous welding various combustible gases are used in conjunction with oxygen, to secure a flame of sufficient temperature to fuse metallic parts.
These gases are hydrogen, Blau or liquid gas, illuminating gas, benzine or benzol vapors, and acetylene.
Hydrogen - Hydrogen gas is a chemical element which exists in nature, in great quantities, in various chemical combinations. Of these, the most common is water, its combination with oxygen (H2O), and as a consequence water is used as a basis for the manufacture of hydrogen.
Inasmuch as the separation of water into its elements means the destruction of a chemical combination, considerable mechanical power is required.
Just as the separation of the chemical parts of water requires a considerable amount of power, so the combination of these elements - which takes place in the burning of such mixture known as oxy-hydrogen gas - develops aconsiderable amount of heat. Therefore the flame caused by the burning of oxy-hydrogen gas can be used for autogenous welding.
The burning of a molecular equivalent mixture of oxygen and hydrogen results in the forming of water. Water, however, when superheated at a high temperature, as under the influence of a blow pipe flame, dissociates again into its elements.
In using this flame for autogenous welding the danger exists that, during the formation of oxygen and hydrogen within the flame, the oxygen will unite with the metal, i.e. the metal will burn, or, what corresponds to lower degree of burning, the metal will become overheated.
The temperature of a hydrogen-oxygen flame can never go higher than the dissociation temperature of water which is estimated at 2000°C. (3632°F.).
To prevent the burning or overheating of metals in welding with hydrogen-oxygen, it becomes necessary to use a supercharge of hydrogen; in order that the oxygen liberated within the flame combines again with the free hydrogen, and thus making it harmless for the iron. This practice, however, increases the size and decreases the temperature, of the flame. Hydrogen is handled commercially in steel cylinders under a pressure of 150 atmospheres.
A hydrogen-oxygen welding outfit consists of 2 steel cylinders; one containing compressed hydrogen and the other compressed oxygen. Each cylinder is supplied with a pressure reducing valve connected with the welding burner by means of flexible tubes.
In the operation of a hydrogen-oxygen welding apparatus, if the burner is brought too near to the metal, a black spot can be observed in the middle of the glowing metal. This is due to the metal being cooled by the unburnt gas mixture and such a condition must be avoided.
For the welding of thin metal sheets, the use of oxy-hydrogen is practical, although the quality of the welding seam decreases as the thickness of the metal increases.
Oxy-hydrogen welding was the first autogenous welding system employed and was used extensively until the more advantageous system of welding with acetylene was introduced, which latter system has now almost entirely replaced the welding with the oxy-hydrogen flame.
Blau or Liquid Gas - Blau or liquid gas is manufactured by vaporizing liquid hydrocarbons in closed retorts and superheating the vapors. This is not a chemical combination but a mechanical mixture of various gases and vapors.
When this gas is used for welding, the free hydrogen contained in the products of combustion is absorbed by the iron. In working heavier sheets, necessitating a prolonged use of the flame, an extensive absorption of the hydrogen by the metal occurs. As the metal solidifies, the absorbed hydrogen is expelled producing a porous welding seam.
For the welding of certain metals, as aluminum, and for welding thin metal sheets, the employment of Blau gas is practical, but such operation is very expensive on account of the high cost of compressing and transporting the gas.
Illuminating Gas - Illuminating gas (coal gas and water gas) can only be used for welding very thin metal sheets, owing to the low temperature of the flame. On account of the great loss of heat caused by the absorbing and conductive qualities of the metal, it is impossible, with a flame of low temperature, to heat thick metal sheets locally to the melting point.
Benzine or Benzol Vapors - In autogenous welding, the vapors of liquid hydrocarbons have the same properties as Blau or liquid gas. The temperature of a Benzol welding flame at about 2700°C. (5000°F.) is higher than the illuminating gas welding flame, but is considerably lower than that of the oxygen-acetylene flame.
This gas derives its name from that of the inventor, a chemist, Blau of Augsburg, Germany. Numerous tests have proved that Benzol welding is less advantageous from an economical and qualitative standpoint than the oxy-acetylene or the oxy- hydrogen welding, but the process may be used to advantage for many purposes, especially for the welding of light pieces. Further, the apparatus used for such welding is capable of being moved easily from place to place.
Acetylene - The use of acetylene in autogenous welding has rapidly extended since its first introduction. This is due to the peculiar conditions resulting from the burning of acetylene in a stream of oxygen.
Acetylene is a chemical combination of carbon and hydrogen (C2H2) and the burning, i.e. its combination with oxygen, takes place in two phases, with a well defined zone formed of the first phase.
This zone consists of the products of combustion of the first phase, i.e. carbon monoxyde and hydrogen, which products combine with the oxygen of the air, in an exterior envelope of the flame, to the final products of combustion, i.e. carbonic acid and water.
In autogenous welding this zone within the flame is active while the outer envelope serves to protect the metal against oxidation. The formula of the chemical changes is as follows:
C2H2 + 20 = 2C0 + H2 and
2C0 + H2 + 30 = 2CO2 + H2O
Acetylene consists of a chemical combination of 2 atoms of carbon and 2 atoms of hydrogen (C2H2). Inasmuch as the carbon is two-atomic, the acetylene forms a non-saturated compound and there exists therefore, in the acetylene molecule, a certain interior tension.
This causes the gas to form other combinations belonging to the acetylene group at the comparatively low temperature of 480°C. (896°F.) which phenomena is called Polymerisation. Such higher combinations of the acetylene are Benzin, Benzol, Styrolin, Naphthalin, etc.
Benzol, like the balance of these combinations, has physical properties different from acetylene and this is the reason why Benzol vapors used in place of acetylene do not give the expected results in autogenous welding.
Furthermore, such polymeres of acetylene are liable to condense part of their carbon in the form of tar products under circumstances existing in an acetylene generator.
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Autogenous welding and cutting
