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Oxy acetylene welding practice
OXY ACETYLENE WELDING PRACTICE
A practical presentation of the modern processes of welding, cutting, and lead burning, with special attention to welding technique for steel, cast iron, aluminum, copper, and brass.
BY ROBERT KEHL
AMERICAN TECHNICAL SOCIETY, CHICAGO, 1918
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Oxy acetylene welding practice
INTRODUCTION
High temperature flames, such as the oxy-hydrogen flame, were known for many years, but the oxy-acetylene flame was first used experimentally in 1901 by Fouche and Picard. The same experimenters also developed the first welding blowpipes, used industrially in 1903, and started the developments in oxy-acetylene welding which were destined to become so important in the modem manufacturing and repair fields. Cutting by means of oxygen was first made commercially possible in 1905 by Jottrand, who took out his basic patent in that year.
Many difficulties were encountered in the early development, owing to imperfect knowledge of the character of the flame and of the technique of the method of application, but notwithstanding these difficulties, the oxy-acetylene welding and cutting processes have developed wonderfully, especially during the last ten years, during which time they have replaced old methods and have made possible operations which hitherto could not be accomplished. The discovery of liquid air greatly decreased the cost of oxygen, and the increase in the number of oxygen supply points throughout the country has removed the last obstacle to the rapid advance of the art. Everywhere manufacturers are very willing to supplant their old methods by the oxy-acetylene process.
Their rapid increase in the number of plants using the process has produced an active demand for skilled operators, a demand which unfortunately has been always much greater than the supply. However, now that the apparatus on the market has become standardized and our knowledge of good oxy-acetylene practice has reached a point where methods can be carefully outlined, the publishers of this little volume feel that an authoritative article on this subject will be appreciated by the many persons interested in the welding field. The material has been written for the welding operator as well as for the superintendent and manager. The examples have been taken from the automobile industry because in that field almost every phase or class of welding is covered, and while the instructions and data deal with automobile welding in particular, the repairman and manufacturer will find no difficulty in applying this information to their own particular needs. The publishers will be very glad to give special information to any reader, either through their own experts or through the help of the author himself.
Many difficulties were encountered in the early development, owing to imperfect knowledge of the character of the flame and of the technique of the method of application, but notwithstanding these difficulties, the oxy-acetylene welding and cutting processes have developed wonderfully, especially during the last ten years, during which time they have replaced old methods and have made possible operations which hitherto could not be accomplished. The discovery of liquid air greatly decreased the cost of oxygen, and the increase in the number of oxygen supply points throughout the country has removed the last obstacle to the rapid advance of the art. Everywhere manufacturers are very willing to supplant their old methods by the oxy-acetylene process.
Their rapid increase in the number of plants using the process has produced an active demand for skilled operators, a demand which unfortunately has been always much greater than the supply. However, now that the apparatus on the market has become standardized and our knowledge of good oxy-acetylene practice has reached a point where methods can be carefully outlined, the publishers of this little volume feel that an authoritative article on this subject will be appreciated by the many persons interested in the welding field. The material has been written for the welding operator as well as for the superintendent and manager. The examples have been taken from the automobile industry because in that field almost every phase or class of welding is covered, and while the instructions and data deal with automobile welding in particular, the repairman and manufacturer will find no difficulty in applying this information to their own particular needs. The publishers will be very glad to give special information to any reader, either through their own experts or through the help of the author himself.
CONTENTS
- WELDING PROCESSES
- OXY-ACETYLENE PROCESS
- ELECTRIC PROCESSES
- TECHNIQUE OF OXY-ACETYLENE WELDING
- SIMPLE WELDING JOB
- OPERATION AND CARE OF WELDING APPARATUS
- WELDING DIFFERENT METALS
- MISCELLANEOUS OXY-ACETYLENE PROCESSES
- CUTTING
- LEAD BURNING
- CARBON REMOVING BY USE OF OXYGEN
- EXAMPLES OF AUTOMOBILE REPAIR
- COSTS
TECHNIQUE OF OXY-ACETYLENE WELDING
SIMPLE WELDING JOB
Apparatus Required. The material in the following paragraphs must not be considered as instructions for welding but merely as a brief discussion of the various steps in making a simple weld. Complete instructions for connecting and operating the equipment are given in detail later. In general, the following equipment is needed for every welding job, no matter how small:
(a) A welding blowpipe
(b) A supply of oxygen
(c) An oxygen regulator
(d) A supply of acetylene
(e) An acetylene regulator
(f) Hose to connect blowpipe to oxygen and acetylene supplies
Preparing the Metal. First, the edges of the two pieces of metal to be welded are chamfered or beveled, so that when they are placed together the two beveled edges form a V, the width of the V being about equal to the thickness of the metal.
Next, the two pieces are placed together on a flat surface of fire brick, or other nonconductor of heat, so that the edges just touch at the bottom of the groove. This gives the line of the weld. The two pieces are then ready to be welded as soon as the apparatus is connected.
Connecting the Apparatus. To connect the apparatus, the following steps should be taken:
(1) The oxygen regulator is connected to the oxygen cylinder.
(2) The acetylene regulator is connected to the acetylene cylinder.
(3) The one hose is connected to the oxygen regulator and to the blowpipe.
(4) The other hose is connected to the acetylene regulator and to the blowpipe.
(5) A welding head is selected and attached to the blowpipe.
(6) The oxygen and acetylene are turned on and the blowpipe is lighted.
Welding. The operator is now ready to weld. He takes the lighted blowpipe in his right hand. Fig. 14, and plays the flame upon the beveled edges of the two pieces of metal to be welded. The intense heat of the flame melts the edges and they flow together. As the edges flow together, the operator melts in new metal from a rod which he holds in his left hand, so that the entire goove is filled up, producing a perfect union or weld.
When the entire groove has been filled in this manner, the operator turns out the blowpipe, and allows the metal to cool. The foregoing is a brief outline of the steps taken by an operator in performing a simple operation of welding two small pieces of steel. We will now take up these different steps and will give more specific and detailed descriptions of the welding apparatus and complete instructions in its operation and use.
Necessity for Care. It is proper that in the operation of the welding apparatus we should lay stress upon the importance of careful and orderly methods in the handling of such apparatus. It should be borne in mind that the regulators and gages are sensitive measuring devices, that in the blowpipe the orifices are carefully designed and accurately machined to permit the passage of a definite quantity of gas and, therefore, that rough usage and abuse will certainly decrease their efficiency. It is not necessary in this place to give detailed instructions for the operation and care of the various makes of apparatus, because these are invariably furnished by the manufacturers with their equipment.
Because of the fact that dissolved acetylene is most generally used in garages and small job shops, we will confine our explanations to the use of, apparatus with cylinder equipment. Owing to the greater simplicity of handling, however, the operator will have no difficulty in making use of generated acetylene when the opportunity arises.
Welding Blowpipe. The two types of welding blowpipes were described on pages 7 and 8, and need no further explanation as to the principles of operation. They are furnished by the manufacturers in various lengths to take care of various classes of work, from short light-weight blowpipes less than a foot long for light sheet-metal work up to blowpipes several feet long, which allow the operator to stay away from the intense heat as far as possible when working on heavy jobs.
Welding Heads and Tips. About ten sizes of welding heads, of tips, are supplied for use on different thicknesses of metal and various classes of work, each giving its own special size flame. The oxygen consumption of the various size heads ranges from about 4 to 70 cubic feet per hour. In some makes the heads are made of one piece, while in others they consist of a brass or bronze body and a copper tip, which can be easily and cheaply replaced when necessary.
Working Pressures. The necessary pressures of the gas that are required by the different size welding heads are given by the manufacturers, and it is very important that the operator use only the pressures recommended if he wishes to get the best economy and the strongest weld possible. Some operators believe that by increasing the pressure above that specified by the maker of the apparatus that they are able to do the work more quickly and easily. This idea is wrong, because when the pressure is increased, the larger volumes of oxygen and acetylene cannot mix as well, so that oxide forms in the weld and has to be removed. This takes more time and is very likely to leave a slightly oxidized and weak weld.
It is equally bad to use a pressure that is too low. If this is done, continual back-firing will result.
Care of Blowpipe. If the blowpipe is handled properly there will be very little deterioration. It should only be necessary to clean the replaceable and working parts and occasionally ream out the tips. The tips should never be
reamed out with any instrument other than a copper or brass wire having a long taper. Care should be taken that the orifices of the tips are not enlarged by reaming. If they become enlarged, they may be closed slightly by placing a conical swag over the end and tapping lightly with a hammer. The end of the tip should then be dressed off square by means of an extra fine file, and the orifice trued round by reaming with a twist drill of the proper size.
The blowpipe may be cleaned by removing both the acetylene and the oxygen hose and connecting the tip to the oxygen hose. Fig. 16, and turning on the oxygen to a pressure of about 20 pounds per square inch, having the acetylene needle valve open and the oxygen needle valve closed, so as to drive any obstructions through the larger acetylene passages of the blowpipe. Then close the acetylene valve and open the oxygen valve to clean out the oxygen passages.
Regulators. There are various types of regulators on the market today, but the most successful ones are very similar in design and construction. The principal parts of a constant-pressure regulator, Fig. 17, consist of the body proper, regulator valve, diaphragm, pressure-adjusting spring, safety-relief valve, and gages,
Operation of the Regulator. Gas passes from the cylinder valve through the passageway to the regulator valve. The pressure over- comes the tension of the inner spring and moves the sleeve-piece toward the back of the regulator, opening the valve. This allows gas to pass into the diaphragm chamber and out of the regulator by way of the hose connection. As the pressure in the diaphragm chamber increases, the tension of the pressing-adjusting spring is overcome, the diaphragm deflects, the sleeve-piece moves forward, and the valve closes partly or all the way. Then, as gas passes out of the regulator and the pressure in the diaphragm chamber decreases, the tension of the pressure-adjusting spring and the pressure of the gas entering the regulator move the sleeve-piece backward, admitting more oxygen to the regulator. The pressure in the diaphragm chamber builds up as before, the diaphragm deflects, the sleeve-piece moves outward, and the valve closes.
Oxygen Welding Regulator. This is an automatic regulator which is especially designed for welding operations. It is connected to the oxygen cylinder and is designed to deliver oxygen to the blowpipe at any uniform pressure at which the regulator is set. To do successful welding, the oxygen regulator must be as nearly perfect as it is possible to construct it. This device is required to reduce a pressure which may be as high as 1800 pounds per square inch in the cylinder and which is constantly varying, down to a pressure from 10 to 30 pounds per square inch; at the same time the regulator must keep the lower pressure constant.
Oxygen regulators are usually equipped with two gages. The high-pressure gage shows the pressure of the gas in the cylinder and may be used to determine the amount of oxygen in the cylinder (see under Measuring Oxygen, page 99). The low-pressure gage shows the operating pressure at which the oxygen is being supplied to the blowpipe.
Acetylene Regulator. The acetylene regulator is used with acetylene supplied in cylinders. It is connected to the acetylene cylinder adapter, and this to the acetylene cylinder. The acetylene regulator is designed to deliver acetylene at a uniform pressure, as needed by the blowpipe.
Acetylene regulators are usually equipped with a large gage that shows the pressure in the cylinder, but which cannot be used to accurately determine the contents of the cylinder (see Measuring Acetylene, page 102). A small gage is not necessary with the low-pressure, or injector, blowpipe, because the acetylene pressure required by this type of blowpipe is very low — only a few ounces. With the pressure blowpipe, however, a small gage is necessary, because it is important to know that the acetylene pressure, which ranges from 2 to 13 pounds per square inch, is supplied to the blowpipe at the required pressure for the tip used.
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(a) A welding blowpipe
(b) A supply of oxygen
(c) An oxygen regulator
(d) A supply of acetylene
(e) An acetylene regulator
(f) Hose to connect blowpipe to oxygen and acetylene supplies
Preparing the Metal. First, the edges of the two pieces of metal to be welded are chamfered or beveled, so that when they are placed together the two beveled edges form a V, the width of the V being about equal to the thickness of the metal.
Next, the two pieces are placed together on a flat surface of fire brick, or other nonconductor of heat, so that the edges just touch at the bottom of the groove. This gives the line of the weld. The two pieces are then ready to be welded as soon as the apparatus is connected.
Connecting the Apparatus. To connect the apparatus, the following steps should be taken:
(1) The oxygen regulator is connected to the oxygen cylinder.
(2) The acetylene regulator is connected to the acetylene cylinder.
(3) The one hose is connected to the oxygen regulator and to the blowpipe.
(4) The other hose is connected to the acetylene regulator and to the blowpipe.
(5) A welding head is selected and attached to the blowpipe.
(6) The oxygen and acetylene are turned on and the blowpipe is lighted.
Welding. The operator is now ready to weld. He takes the lighted blowpipe in his right hand. Fig. 14, and plays the flame upon the beveled edges of the two pieces of metal to be welded. The intense heat of the flame melts the edges and they flow together. As the edges flow together, the operator melts in new metal from a rod which he holds in his left hand, so that the entire goove is filled up, producing a perfect union or weld.
When the entire groove has been filled in this manner, the operator turns out the blowpipe, and allows the metal to cool. The foregoing is a brief outline of the steps taken by an operator in performing a simple operation of welding two small pieces of steel. We will now take up these different steps and will give more specific and detailed descriptions of the welding apparatus and complete instructions in its operation and use.
Necessity for Care. It is proper that in the operation of the welding apparatus we should lay stress upon the importance of careful and orderly methods in the handling of such apparatus. It should be borne in mind that the regulators and gages are sensitive measuring devices, that in the blowpipe the orifices are carefully designed and accurately machined to permit the passage of a definite quantity of gas and, therefore, that rough usage and abuse will certainly decrease their efficiency. It is not necessary in this place to give detailed instructions for the operation and care of the various makes of apparatus, because these are invariably furnished by the manufacturers with their equipment.
Because of the fact that dissolved acetylene is most generally used in garages and small job shops, we will confine our explanations to the use of, apparatus with cylinder equipment. Owing to the greater simplicity of handling, however, the operator will have no difficulty in making use of generated acetylene when the opportunity arises.
Welding Blowpipe. The two types of welding blowpipes were described on pages 7 and 8, and need no further explanation as to the principles of operation. They are furnished by the manufacturers in various lengths to take care of various classes of work, from short light-weight blowpipes less than a foot long for light sheet-metal work up to blowpipes several feet long, which allow the operator to stay away from the intense heat as far as possible when working on heavy jobs.
Welding Heads and Tips. About ten sizes of welding heads, of tips, are supplied for use on different thicknesses of metal and various classes of work, each giving its own special size flame. The oxygen consumption of the various size heads ranges from about 4 to 70 cubic feet per hour. In some makes the heads are made of one piece, while in others they consist of a brass or bronze body and a copper tip, which can be easily and cheaply replaced when necessary.
Working Pressures. The necessary pressures of the gas that are required by the different size welding heads are given by the manufacturers, and it is very important that the operator use only the pressures recommended if he wishes to get the best economy and the strongest weld possible. Some operators believe that by increasing the pressure above that specified by the maker of the apparatus that they are able to do the work more quickly and easily. This idea is wrong, because when the pressure is increased, the larger volumes of oxygen and acetylene cannot mix as well, so that oxide forms in the weld and has to be removed. This takes more time and is very likely to leave a slightly oxidized and weak weld.
It is equally bad to use a pressure that is too low. If this is done, continual back-firing will result.
Care of Blowpipe. If the blowpipe is handled properly there will be very little deterioration. It should only be necessary to clean the replaceable and working parts and occasionally ream out the tips. The tips should never be
reamed out with any instrument other than a copper or brass wire having a long taper. Care should be taken that the orifices of the tips are not enlarged by reaming. If they become enlarged, they may be closed slightly by placing a conical swag over the end and tapping lightly with a hammer. The end of the tip should then be dressed off square by means of an extra fine file, and the orifice trued round by reaming with a twist drill of the proper size.
The blowpipe may be cleaned by removing both the acetylene and the oxygen hose and connecting the tip to the oxygen hose. Fig. 16, and turning on the oxygen to a pressure of about 20 pounds per square inch, having the acetylene needle valve open and the oxygen needle valve closed, so as to drive any obstructions through the larger acetylene passages of the blowpipe. Then close the acetylene valve and open the oxygen valve to clean out the oxygen passages.
Regulators. There are various types of regulators on the market today, but the most successful ones are very similar in design and construction. The principal parts of a constant-pressure regulator, Fig. 17, consist of the body proper, regulator valve, diaphragm, pressure-adjusting spring, safety-relief valve, and gages,
Operation of the Regulator. Gas passes from the cylinder valve through the passageway to the regulator valve. The pressure over- comes the tension of the inner spring and moves the sleeve-piece toward the back of the regulator, opening the valve. This allows gas to pass into the diaphragm chamber and out of the regulator by way of the hose connection. As the pressure in the diaphragm chamber increases, the tension of the pressing-adjusting spring is overcome, the diaphragm deflects, the sleeve-piece moves forward, and the valve closes partly or all the way. Then, as gas passes out of the regulator and the pressure in the diaphragm chamber decreases, the tension of the pressure-adjusting spring and the pressure of the gas entering the regulator move the sleeve-piece backward, admitting more oxygen to the regulator. The pressure in the diaphragm chamber builds up as before, the diaphragm deflects, the sleeve-piece moves outward, and the valve closes.
Oxygen Welding Regulator. This is an automatic regulator which is especially designed for welding operations. It is connected to the oxygen cylinder and is designed to deliver oxygen to the blowpipe at any uniform pressure at which the regulator is set. To do successful welding, the oxygen regulator must be as nearly perfect as it is possible to construct it. This device is required to reduce a pressure which may be as high as 1800 pounds per square inch in the cylinder and which is constantly varying, down to a pressure from 10 to 30 pounds per square inch; at the same time the regulator must keep the lower pressure constant.
Oxygen regulators are usually equipped with two gages. The high-pressure gage shows the pressure of the gas in the cylinder and may be used to determine the amount of oxygen in the cylinder (see under Measuring Oxygen, page 99). The low-pressure gage shows the operating pressure at which the oxygen is being supplied to the blowpipe.
Acetylene Regulator. The acetylene regulator is used with acetylene supplied in cylinders. It is connected to the acetylene cylinder adapter, and this to the acetylene cylinder. The acetylene regulator is designed to deliver acetylene at a uniform pressure, as needed by the blowpipe.
Acetylene regulators are usually equipped with a large gage that shows the pressure in the cylinder, but which cannot be used to accurately determine the contents of the cylinder (see Measuring Acetylene, page 102). A small gage is not necessary with the low-pressure, or injector, blowpipe, because the acetylene pressure required by this type of blowpipe is very low — only a few ounces. With the pressure blowpipe, however, a small gage is necessary, because it is important to know that the acetylene pressure, which ranges from 2 to 13 pounds per square inch, is supplied to the blowpipe at the required pressure for the tip used.
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