Oxy-acetylene welding manual

by Lorn Campbell

Part Three.—ALUMINUM WELDING

(131) Many times aluminum crank cases which have large holes punched in them and parts missing are brought to a welder for repairs. A question arises as to whether it is best to back up these holes and fill in the missing parts with a filler-rod as the welding progresses, or whether these parts should be cast separately or cut out of another crank case. It will generally depend upon the size of the hole, as to the desirable procedure in a case of this kind. It must be remembered that if the casting and welding are to be done at one and the same time each additional layer of metal must be fused to the last layer and that in reality a great deal of welding is necessary. In addition this added metal must be fused to the crank case. On small holes, perhaps two or three inches in diameter, this method is recommended, but if the hole is much larger, it is best to cast a piece and then weld it in, for in this instance there is only one line of weld to look after.

(132) On aluminum work it is proper to weld from the closed end of a crack toward the open, whether the piece has or has not been preheated. This is true also of all other metals, for if the weld were to be started at the open end and worked backwards there would certainly be internal strains set up, which would be undesirable. If it is not clear which end is the open one, the operator should stop a moment and figure it out.

(133) Were a suspension arm of the U type on an aluminum crank case to break about three or four inches from the body of the case, it could be welded in place without dismantling the motor, if handled properly. Free access must be had to the line of break, so that the operator can manipulate his flame at whatever angle he thinks best. Due to the contraction and expansion, which may throw the piece being welded out of alignment slightly, it is best to blank the bolt hole at the end of this suspension arm and face it off, before the piece is welded in position. Later a new hole can be drilled which will line up accurately with the frame, and the welder will not then have to worry or attempt to return it exactly to its former position. In order to keep the case itself as cool as possible, wet asbestos should be packed around it, near the broken arm, so that too much heat will not be absorbed by it. The broken end is then tacked in position at two or three places and the weld started. On such a problem the puddle system will be found best, for both horizontal and vertical welding are to be done, as well as some overhead. As flux causes the metal to flow, it is rather difficult for the beginner to apply it to vertical and overhead work. The puddle stick should work through the metal its full thickness and eliminate every possible trace of the break, digging out the old metal where dirt is found, and adding new metal for reinforcing. When one side has been welded and reinforced it should not be allowed to cool while the other side is being worked. The torch should be played upon it every now and then, in order that the whole line of weld will be at approximately the same temperature; otherwise, the weld may break in cooling. The ease with which aluminum is puddled together, which many welders have likened to the children’s method of making mud pies, seems so simple to the beginner that he cannot see where the strength comes from when cooled. On account of this, he invariably works his aluminum too long. After welding a few test bars of this metal and breaking them in the line of weld, many old welders will gain confidence upon seeing the results of their own efforts.

CHAPTER X
WELDING OF MALLEABLE IRON

(134) The welding of malleable iron, so far as the actual fusion of the metal is concerned, is not practiced except in very few instances, where the parts are very thin and have been completely annealed. This is on account of its being what might be termed a heat-treated metal. To begin with, malleable iron is cast iron, and becomes malleable only after it has been heated to the proper condition in the presence of material which will absorb much of its carbon content, and kept in this state until a suitable depth of its exterior has been annealed. It has been changed from a brittle casting to one which will bend to some extent without breaking, and its surface, by the withdrawal of the carbon, has been converted into steel. The interior remains cast iron. The depth of penetration will depend entirely upon the number of hours the work is treated. Usually it runs from one-sixty-fourth to one-eighth of an inch, depending upon the type of work. An idea may be gained of how a cross-section of this metal will appear, by noting [Fig. 79].

Fig. 79.—Illustrating Cross-section of Malleable Iron.

(135) A machinist would not think of destroying the temper in his tools and then attempting to use them without retempering them. So the welder will not attempt to melt malleable iron, for he realizes that if he were to attempt fusing this metal that its character would be entirely destroyed. If he should make a fusion, the weld itself and in the vicinity thereof the metal would be very brittle and retain none of its ductile qualities. When a weld of this kind is attempted, first, a few steel sparks are given off from the surface of the metal, which quickly diminish and the surface seems to recede from the flame. A white foam appears as the steel surface is burned and many small blow holes then make their appearance. The casting resembles a steel casting which contains much sand and impurities. The welding of malleable iron, in its broadest sense, is therefore not recommended, although as it has been stated there are occasions when it can be successfully accomplished. The best manner of bonding malleable iron is by the use of a bronze filler-rod, and this process will hereafter be referred to, for convenience, as welding, although it may resemble brazing in some respects.

(136) The art of welding malleable iron with bronze is not very difficult to learn. Possibly, the greatest trouble will be experienced by the beginner in distinguishing malleable iron from other castings. By again referring to [Fig. 43] and carefully noting the various methods outlined, this trouble should be overcome. Many times, too, if the welder has had any mechanical experience, he can probably determine where the casting has been used and can ofttimes satisfy himself whether it is malleable or not. Malleable castings are very seldom used as a wearing surface, and are generally employed where there is strain, to replace steel castings and forgings, which are much more expensive. If it has been determined that the metal is malleable iron, half the battle has been won.

(137) In preparing malleable iron, a clean surface is necessary in the vicinity of the weld. No “V-ing” out is necessary unless the piece is greater than one-quarter inch in thickness, and then the surface of the “V” should be as rough as possible. The ends are placed as close together as possible, the same as in brazing, and a welding tip which is one size smaller than would be used on the same thickness of cast iron is then used, with a slightly carbonizing flame. See [Fig. 23]. The work is heated, the same as in cast iron and steel. This flame is played directly on the work in a vertical position, similar to that used in preheating the weld in cast iron and steel, until heated to a cherry red, back about one-half inch on each side of the weld. As soon as this heat is obtained, the bronze filler-rod carries a quantity of bronze flux to the weld and this further tends to clean the surface. With the end of the filler-rod directly in contact with the work nearest the operator, the neutral flame melts the end of the rod, which immediately should run over the adjoining surface and through the crack. When this occurs the flame is abruptly twisted away from that portion of the weld to avoid burning the bronze. This is repeated along the line of the weld until the entire surface is covered with a thin coating of bronze. With this as a foundation more bronze is added, but during this process the torch is turned so that the neutral flame will not bear down directly on the bronze, which has already been added. It should rather strike it at an angle and radiate enough heat from the side of the neutral flame to permit a fusion between the filler-rod and the bronze already added. Much more surface should be covered and more of a reinforcement made than in either cast iron or steel, in order to warrant enough strength for this class of work.

(138) A good bronze for welding purposes should work easily under the influence of the oxy-acetylene flame and have sufficient alloys present to take care of those destroyed by the action of the flame. It is not thought advisable to work over welds of bronze, for fear of making them porous, unless more filler-rod is added whenever the flame is brought in contact with the weld.

(139) Welds of malleable iron can be made which will be even stronger than the surrounding metal, and at times they can be reinforced by adding small strips of steel. These can be entirely covered, to make them inconspicuous. Contrary to custom it is recommended that plenty of flux be used, for best results have been found when a surplus rather than a sparing amount has been employed.

(140) The matter of heat in malleable iron is of considerable importance. If not enough heat is used there will be no fusion between the bronze and the iron, whereas on the other hand, if too much heat is used, the bronze will not adhere, but will seem to boil on the surface and form in small globules rather than spread over the whole metal. In addition the character of the piece being worked on will be changed when heated too much. This matter of heat should be given great attention and the beginner should learn and have emphasized the fact that the proper heat is one which will permit the bronze to run like water over the surface, and this will form a good foundation to work upon.

(141) In general, malleable iron work is seldom preheated, for this is not necessary if the pieces have been fitted together as closely as possible before the weld is started. Once the student has learned the flow of metal and how to reinforce his weld, he will be in a position to handle most any kind of malleable iron properly. It is well to remember, however, that malleable iron is allowed to cool slowly and is not immersed in water, as has been suggested when working on brass, for here we have one metal in the piece itself and another in the weld, and too great a strain would set up if they were cooled abruptly.

CHAPTER XI
OXY-ACETYLENE CUTTING

(142) By heating a bar of wrought iron or steel to a welding heat and holding it in a stream of compressed air, or a strong blast, it will at once begin to melt and sizzle, emitting an incandescent and scintillating light. This light is dangerous to observe at close range without colored glasses. The burning of the metal can be maintained for hours, without any other source of heat except that caused by the combustion of the iron. The oxy-acetylene cutting process is based upon this principle, in that a neutral flame is applied in order to heat the part being cut to the desired temperature. Once the melting-point is reached, pure oxygen under pressure is applied to maintain oxidation and force out the burned portion.

(143) The apparatus used for cutting does not differ to any great extent from that of the welding class, except that a different torch is employed. There are combination regulators and torches manufactured, but a combination tool is always regarded by most authorities as a loss in efficiency, either on one side or another. While a low-pressure welding regulator may be used on the oxygen line for cutting, yet its use upon large work, where the pressure is high and the regulator must pass a great deal of gas very freely without freezing up, this low-pressure regulator will be a serious handicap and cause much trouble, if used.

Fig. 80.—The Cutting Torch Eats its Way through Steel of any Size with Remarkable Ease, Leaving a Clean-cut Edge. This View Shows a Cutting Torch in Operation at the Ordnance Welding School, U. S. Army.

(144) An ideal arrangement on the oxygen line for cutting is to have a double or “twin” regulator attached to the oxygen drum, one side of which will do for welding and the other, being high-pressure type, will produce a constant flow of high-pressure gas, suitable for the cutting jet. Then when cutting is done a three-hose torch should be employed. One of its oxygen connections which governs the neutral flame can be connected to the low-pressure regulator, while the oxygen jet should be controlled by the high-pressure regulator, the third connection will furnish the acetylene gas for the preheating flame. However, in place of this three-hose arrangement, most cutting is accomplished by means of a two-hose apparatus, wherein only one hose is used to convey the oxygen from a single regulator to the torch. On such apparatus much trouble is usually experienced in cutting old metals where a great deal of scale is present or in a close place where the torch is apt to get hot.

(145) Many times part of the scale or metal will pop up against the tip and cause the oxygen jet to flicker. This slight variation may cause an excessive pressure of oxygen to be introduced into the preheating flame momentarily, by backing up the oxygen in the cutting jet. This lean mixture of gas will generally flash back instantaneously and will deposit a layer of carbon on the inside of the tip, which causes much annoyance to the operator. This condition is to be found where there is but one oxygen line. In the two-hose arrangement this is entirely overcome, due to the independence of the pressure on each line.

(146) The high-pressure regulator differs from the low-pressure regulator in these respects: The diaphragm, see [Fig. 16], is much smaller in diameter, which makes it less sensitive, and of course much stronger. The diaphragm springs are usually much heavier; the nozzle contains a larger opening for passing gas freely without freezing; and to take care of the increased pressure on the line, usually a higher pressure working gauge is added to the regulator. Such a regulator is capable of passing much more gas than the low-pressure type, but as far as being as sensitive and maintaining a constant, absolute flow of gas, its design will not permit it to do so. In cutting, these requisites are not necessary. In welding, however, the delicate adjustment of the flame demands a very sensitive regulator and usually the larger the diameter of the diaphragm the more sensitive the adjustment.

Fig. 81.—End Views of Cutting Tips, Showing Possible Arrangements of Preheating Flames in Regard to Oxygen Jet. The Black Circles Represent the Preheating Flames, which Vary in Number and Arrangement According to the Nature of the Work, the Possible Limit being a Continuous Circle, as Shown. The White Circles Illustrates the Oxygen Jet, which, too, Varies in Size According to the Work.

(147) The cutting torch differs from the welding torch in many respects. The tip itself, when looking at its end, may resemble any one of the views shown in [Fig. 81]. In the welding torch, but one hole is to be found in the tip; in the cutting tips, two or more holes are to be found. In all cases the center hole passes pure oxygen, whereas in the surrounding holes, both oxygen and acetylene mix and when lighted give a neutral flame. This will hereafter be called the preheating flame. The gases issuing from these openings are controlled by three valves, one of which may have a trigger or lever arrangement for quick action, and it will control the center jet of oxygen which really does the cutting. This is under much higher pressure than the preheating flame. The other two valves will control the oxygen and acetylene gases used for the preheating flame. In lighting such a torch, the acetylene is turned on in the same manner as has been taught when welding, until it just leaves the end of the tip. Then the oxygen valve is opened, which controls the preheating flame, and enough is permitted to pass to produce a neutral flame. As soon as this has been accomplished, the third valve should be quickly opened and held so a moment, to see if the neutral flame has been changed. Generally this operation will deprive the neutral flame of some of its oxygen, and a feather flame, showing too much acetylene and not enough oxygen gas, can be noticed. This will necessitate turning on slightly more oxygen at the torch valve. The third valve is then shut off and the torch is ready to start cutting.

(Courtesy of the General Welding & Equipment Co.)

Fig. 82.—Cutting a Heavy Shaft.

Fig. 83.—Position to Hold Torch in when Cutting Metal.

(148) On small cutting jobs, about as much acetylene pressure is used on the line as there would be if it were a welding job. The oxygen pressure, however, is generally much greater, and a pressure anywhere from ten to two hundred pounds should be used, depending upon the thickness of the metal and the conditions which must be met. In extreme cases where very heavy cuts are to be made, a much higher pressure than has been mentioned should be used, but the limitations given will cover a wide range of work. To start a cut it is necessary to bring the preheating flame in contact with one edge of the metal to be cut and play it there until the metal is red hot. As soon as this condition is reached the torch is held steady—the neutral flame just touching the metal; then the third valve controlling the cutting jet of oxygen is opened. This oxygen, under high pressure, quickly acts upon the hot metal and severs it instantaneously, melting and oxidizing the metal so that it will not flow together, in one and the same operation. As soon as this occurs the torch should be advanced as rapidly as possible in the direction the metal is to be cut. The more rapid the advancement and the steadier the torch is held the cleaner the cut will be; and incidentally, less gas consumed in the execution of the job. In cutting, as in welding, it is always well to give the torch a chance, and when the operator sees much molten metal splashing directly back on the torch, he should change the angle slightly to avoid his apparatus becoming overheated. It has been found that if the cutting torch is held at the angle shown in [Fig. 83], the most satisfactory results can be expected.

(149) At the present time only such metals as steel and wrought iron can be successfully cut. When it comes to cast iron no method has yet been discovered to cut it with any degree of success by the oxy-acetylene flame, on account of the high melting-point of the oxide and various other matters. The day is looked forward to, however, when after sufficient time and study has been devoted to this subject, that cast iron can be as successfully cut as any other metal, by introducing another gas or agent to destroy some of the reactions which retard its application at the present time.

(150) The use of the cutting torch in preparing steel work, for welding of large size, plays an important part, in quickly and efficiently “V-ing” out and getting it ready for use. Care should be taken, after its use, to see that the heavy oxide which it leaves is largely destroyed, before any more metal is added.

Fig. 84.—Method of Cutting with Two Welding Torches. Torch A is Adjusted so that a Neutral Flame will do the Preheating, while a Fork in the Oxygen Line Supplies Oxygen only to Torch B, and it does the Cutting.

(151) Frequently the welder has a call for a cutting torch, where none is available, yet an extra welding torch or two may be on hand. If this is the case, two welding torches may be fastened together in such a manner that a temporary job of cutting may be handled. The arrangement shown in [Fig. 84] illustrates this point. If no extra welding torch is available, a carbon burning torch or any piece of copper tubing which has a valve in one end, suitable for taking a hose connection, and the other end free to have a welding tip brazed on, can be used in the same manner. The welding torch will give the neutral flame and the extra line of oxygen will do the cutting. It is well to remember that oxygen, no matter under what pressure, cannot be expected to act upon cold metal. A red heat is absolutely necessary. There are various short cuts, it is true, in obtaining this heat, and where a large shaft is to be cut, the operator would not think of playing his torch upon such a piece of metal until it was red hot in the locality in which he wished to start his cut. This would consume too much time and gas. Generally a hammer and cold chisel are brought into play and a slight curl on the metal is obtained as shown in [Fig. 85]. The moment this becomes red hot, the oxygen jet may be turned on, and the cut commenced. As soon as started, the operator is able to “carry-on” at will.

Fig. 85.—When no Edge is Available to Start the Cut on Large Work, Much Time may be Saved by Making a Curl with a Cold Chisel, as Shown.

(152) An armored hose is generally used on the oxygen line for cutting, as well as on the acetylene line, as there is much more pressure used in cutting than in welding. This type of hose wears much longer and does not kink to the extent that the unprotected hose does. The armor protects both lines from being burned by the melted metal, which is very apt to come in contact with the rubber, were it not protected in some manner.

(153) The question often arises in welding circles, as to why, since the cutting torch contains a series of neutral flames, it would not be just as well to use such a method in welding, as no doubt more heat could be obtained and a greater surface handled. The answer to such a question would be, that the opportunity for oxidation is so great that successful welding could not be expected, although if this were the last means at a welder’s disposal, he would certainly be justified in making a weld in this manner. He should be very careful, however, to see that his extra oxygen supply is completely shut off and that there is no possible chance for that gas leaking into the weld.

(154) To plunge a flame, such as is used in the cutting torch, under water and see it continue to burn while submerged, looks quite marvelous to the average layman. Yet in cutting piling along water fronts this is continually being done. Not only does the torch stay lighted, but it retains much of its efficiency as a cutting tool, and some instances have been recorded where cutting has been accomplished at a depth of thirty feet under the sea. It is true that the water conducts a large part of the heat away very rapidly, but to facilitate such operations, an air line is brought down which ejects air under the torch and clears the water away to some extent, but this is not necessary. In order to explain this phenomenon in a very simple way, it will be stated that nothing will burn unless oxygen is present, and the more oxygen used, up to a certain point, the more rapidly will the burning take place. When submerging the cutting torch, it is presumed that the flame obtains what added oxygen is necessary from the cutting jet and this together with the velocity of the flame and its hydrogen enveloping flame permits the neutral flame to continue burning.

CHAPTER XII
CARBON BURNING

(155) Those who are familiar with gasoline engines will know that after being used for some time, the impurities in the lubrication oil and in the gasoline, which is continually being burned, will form around the top of the piston and cylinder head in the motor. When enough has been deposited and a few high points become overheated through long running, there will be a metallic knock distinctly heard when an extra strain is being exerted by the motor. This layer of impurities is called carbon and its presence means loss of power. Owing to the construction of most cylinder blocks, it is a very difficult matter to reach this portion of the block without dismantling. This requires skilled labor and means much delay. A method of removing this carbon by the oxygen process has been devised, which will save much time and trouble.

Fig. 86.—Removing Carbon from U. S. Army Truck, by the Oxygen Process, at the Ordnance Welding School.

Fig. 87.—Carbon Burning Apparatus. The Small Copper Tube A is Flexible and can be Bent in any Shape Desired.

(156) To remove carbon from a gasoline engine, first shut off the gasoline in the line and allow the engine to run until all gas has been removed from the carburetor. This is merely a safety measure. If a vacuum feed is used, the vacuum tank is drained, as it would require much time for the engine to consume this amount of gas. The hood of the car is then removed and all parts of the motor on the side where the burning is to be done are covered with asbestos paper or by a heavy piece of canvas which has previously been dampened. This is to keep the sparks from dropping into the apron or oily parts of the machine. Remove the spark plugs and see from the condition of these spark plugs whether the cylinder is dry or oily. An oily cylinder will burn out much more rapidly than when dry. This can be detected very easily from the condition of the spark plugs. It is recommended that only the spark plugs be removed as the removal of the bonnet or any larger portion will require much more oxygen and will not produce as satisfactory results as when the oxygen is introduced through a small opening.

(157) Place the carbon removing apparatus, which consists of the oxygen drum, regulator, a length of hose and carbon burning torch, the latter being made up principally of a shut-off valve and a long length of small copper tubing as shown at A in [Fig. 87]. Turn on not over twenty-five pounds oxygen pressure as far as the torch, and the apparatus is then ready to use. With the torch inserted through the spark plug hole in number one cylinder, that is, the one nearest the radiator, guide the rise of the piston until it is at the top of the stroke. This means that both intake and exhaust valves are closed. On automobiles where a self starter is used, it will be necessary to use a crank for turning over the motor. With the piston at the top of the stroke and both valves closed, there is only a small portion of the cylinder head to be worked upon and this is the part which has the carbon deposit upon it. All machined surfaces and valve seats are fully protected and will not be subjected to any exposure during the burning. If the cylinder seems very dry, a teaspoon of alcohol or kerosene may be sprayed into it through the spark plug port, to facilitate the clearing of the carbon. If the cylinder is somewhat oily, this is not necessary. A match or burning taper is then held over the hole and a stream of oxygen will carry the flame down into the cylinder and ignite the carbon. As soon as this occurs, a small cracking noise can be heard and the carbon will run around the inside of the cylinder in a heated condition. The part around the valves should be cleaned off first, before going to the inner chamber, as this process does not seem to work very well if performed the other way. A roaring noise will be in evidence and the popping of the carbon from the surface as it frees itself may frighten the operator when attempting his first job, but there is absolutely no danger.

(158) It must be remembered that oxygen itself does not burn, but merely assists the other inflammable material in burning, therefore it is only the carbon which is contained in the cylinder that in this case does the burning. As soon as this is all consumed, there will be nothing else to burn and the sparks will die of their own accord. When this occurs, the operator will shut off his torch, blow the cylinder out with compressed air and replace the spark plug and then proceed with the next cylinder, which he will treat in the same manner. He must be sure, however, that the piston in cylinder number two, or whatever cylinder he is working on, is moved to the top of its stroke and that both valves in that particular cylinder are closed before he starts his burning. After all cylinders have been treated like number one and the spark plugs are in position, the gasoline is turned on (if the vacuum tank has been drained, it is best to fill this), and the motor started, with the exhaust “cut off” open, in order that any loose particles of carbon may be blown out.

(159) While this process is in very common use, and seems to be very simple, there are many who go through the steps without obtaining satisfactory results. It is considered best, if possible, in attempting carbon burning for the first time, to try it on some motor which is about to be overhauled, in order that the results may be studied so that the operator will not go blindly on, without showing some improvement. Many times only the high points are burned out, which will free the motor temporarily of some of its knocks, but within a week or so they will become evident again. He who will become proficient in learning carbon burning should apply himself and study his results.

(160) There are those who consider carbon burning injurious to the motor on account of the high temperature flame which they think is introduced. But it is ignorance as to the working principle of this process that makes them think this. When it is considered that a gasoline motor depends upon a rapid succession of internal explosions for its power, the folly of condemning a process of this nature, where absolutely no actual flame is used, will be seen. It is only the incandescent particles of carbon flying about that give any heat at all. After a cylinder has been burned or decarbonized, the hand can be placed upon it immediately, without any fear of being burned. Those motors equipped with aluminum pistons may be handled in the same way as those of cast iron, and when properly used this method of decarbonization is very satisfactory.

(161) Many times it is asked how often carbon burning is to be recommended. This will all depend upon the type of motor, its condition, and to some extent, upon the lubricating oil and gasoline used, as well as the mileage of the car. If a machine is being run continually, it may be necessary to have the carbon removed about every two months, but conditions will tend to lengthen or shorten this time as the case may be. When the knocks are in evidence, and the loss of power is noticed, it is time for the carbon to be removed, and whether this is one month or two it is an error to continue running the car which is filled with carbon. Invariably the carbon burner is asked by his customer whether carbon burning will regrind valves; this and many other questions can be intelligently answered and explained to the questioner’s satisfaction if a careful study of the process is made.

(Courtesy of the British Oxygen Co.)

Fig. 88.—Photograph Showing Square Piece Cut Out of a Steel Block 9 Inches Thick.

(Courtesy of the Davis-Bournonville Co.)

Fig. 89.—This is an Electrically Driven Oxy-acetylene Cutting Machine for Making Duplicate Cuts on Steel from a Drawing. Dies and many Irregular Forms may be Produced at Low Cost by it.

(Courtesy of the Davis-Bournonville Co.)

Fig. 90.—This Shows a Motor-driven Oxy-acetylene Device Particularly Adapted to Cutting Plates or Sheets into Round, Oval, or Irregular Forms with either Straight or Beveled Edges.