Forge-practice and heat treatment of steel

Front matter

• • •

AND

HEAT TREATMENT OF STEEL

Preface To The Third Edition

Modern demands on the finished products of steel have necessitated rapid strides in the art of heat treatment of the metal. As the subjects of forging, hardening, tempering and annealing are so closely correlated it has seemed wise to add to "Forge Practice" a certain amount of material devoted to the other branches of the art.

The introduction of heat measuring and hardness testing instruments, together with various other modern appliances, and up to date systems of doing work have made necessary a broader knowledge of heat-treating methods than was formerly the case: for after all the most important factor is the man doing the work.

It is the earnest wish of the writers of this volume that it may be instrumental in helping men engaged in heat treating steel to be of greater value to themselves and others.

Preface To The Second Edition

The author believes that the text book should be used to explain principles and give examples, not to give minute explicit directions for making a set of exercises.

This necesitates an independent set of drawings for the work to be done.

It is for this purpose that the set of drawings is given.

The author has felt the need and lack of such drawings in the text-book as used before, and it is to remedy this defect that the addition has been made.

The exercises are such as have been found useful in the shop, and an effort has also been made to give drawings of such tools as are ordinarily used in the forge and machine shops.

J. L. B.

vi

Preface To The First Edition

This little volume is the outgrowth of a series of notes given to the students at Lewis Institute from time to time in connection with shop work of the character described.

It is not the author's purpose to attempt to put forth anytliing which will in any way take the place of actual shop work, but rather to give some explanation which will aid in the production of work in an intelligent manner.

The examples cited are not necessarily given in the order in which they could most advantageously be made as a series of exercises, but are grouped under general headings in such a way as to be more convenient for reference.

The original drawings from which the engravings were made were drawn by L. S. B.

Chapter I. General Description Of Forge And Tools

Forge. — The principal part of the forge as generahy made now is simply a cast-iron hearth with a bowl, or depression, in the center for the fire. In the bottom of this bowl is an opening through which the blast is forced. This blast-opening is known as the tuyere. Tuyeres are made in various shapes; but the object is the same in all, that is, to provide an opening, or a number of openings, of such a shape as to easily allow the blast to pass through, and at the same time, as much as possible, to prevent the cinders from dropping into the blast-pipe.

There should be some means of opening the blast-pipe beneath the tuyere and cleaning out the cinders which work through the tuyere-openings, as some cinders are bound to do this no matter how carefully the tuyere is designed.

When a long fire is wanted, sometimes several tuyeres are placed in a line; and for some special work the tuyeres take the form of nozzles projecting inwardly from the side of the forge.

Coal. — The coal used for forge-work should be of the best quality bituminous, or soft, coal. It should coke easily; that is, when dampened and put on the fire it should cake up, form coke, and not break into small pieces. It should be as free from sulphur as possible, and make very little clinker when burned.

Good forge-coal should be of even structure through the lumps, and the lumps should crumble easily in the hand. The lumps should crumble rather than split up into layers, and the broken pieces should look bright and glossy on all faces, almost like black glass, and show no dull-looking streaks.

Ordinary soft coal, such as is used for "steaming-coal," makes a dirty fire with much clinker. " Steaming-coal " when broken is liable to split into layers, some of which are bright and glossy, while others are dull and slaty-looking.

Fire. — On the fire, to a very great extent, depends the success or failure of all forging operations, particularly work with tool-steel and welding.

In building a new fire the ashes, cinders, etc., should be cleaned away from the center of the forge down to the tuyere. Do not clean out the whole top of the forge, but only the part where the new fire is wanted, leaving, after the old material has been taken out, a clean hole in which to start the fresh fire.

The hearth of the forge is genei^ally kept filled with cinders, etc., even with the top of the rim.

Shavings, oily waste, or some other easily lighted material should be placed on top of the tuyere and set on fire.

As soon as the shavings are well lighted, the blast should be turned on and coke (more or less of which is always left over from the last fire) put on top and outside of the burning shavings. Over this the "green coal" should be spread.

Green coal is fresh coal dampened with water. Before using the forge-coal it should be broken into small pieces and thoroughly wet with water. This is necessary, as it holds together better when coking, making better coke and keeping in the heat of the fire better. It is also easier to prevent the fire from spreading out too much, as this dampened coal can be packed down hard around the edges, keeping the blast from blowing through.

The fire should not be used until all the coal on top has been coked. As the fire burns out in the center, the coke, which has been forming around the edge, is pushed into the middle, and more green coal added around the outside.

We might say the fire is made up of three parts: the center where the coke is forming and the iron heating; a ring around and next to this center where coke is forming; and, outside of this, a ring of green coal.

This is . the ordinary method of making a small fire.

This sort of fire is suitable for smaller kinds of work. It can be used for about an hour or two, at the end of which time it should be cleaned. When welding, the cleaning should be done much oftener.

Large Fires. — Larger fires are sometimes made as follows : Enough coke is first made to last for several hours by mounding up green coal over the newly started fire and letting it burn slowly to coke thoroughly. This coke is then shoveled to one side and the fire again started in the following way: A large block, the size of the intended fire, is placed on top of the tuyere and green coal is packed down hard on each side, forming two mounds of closely packed coal. The block is taken out and the fire started in the hole between the two mounds, coke being added as necessary. This sort of a fire is sometimes called a stock fire, and will last for some time. The mounds keep the fire together and help to hold in the heat.

For larger work, or where a great many pieces are to be heated at once, or when a very even or long-continued heat is wanted, a furnace is used. For furnace use, and often for large forgefires, the coke is bought ready-made.

Banking Fires. — When a forge-fire is left it should always be banked. The coke should be well raked up together into a mound and then covered with green coal. This will keep the fire alive for some time and insure plenty of good coke for starting anew when it does die out. A still better method to follow, when it is desired to keep the fire for some time, is to bury a block

GENER.\L DESCRIPTION OF FORGE AND TOOLS. 5

of wood in the center of the fire when banking it.

Oxidizing Fire. — When the blast is supplied from a power fan, or blower, the beginner generally tries to use too much air and blow the fire too hard.

Coal requires a certain amount of air to burn properly, and as it burns it consumes the oxygen from the air. When too much blast is used the oxygen is not all burned out of the air and will affect the heated iron in the fire. Whenever a piece of hot iron comes in contact with the air the oxygen of the air attacks the iron and forms oxide. This oxide is the scale which is seen on the outside of iron. The higher the temperature to which the iron is heated, the more easily the oxide is formed. When welding, particularly, there should be as little scale, or oxide, as possible, and to prevent its formation the iron should not be heated in contact with any more air than necessary. Even on an ordinary forging this scale is a disadvantage, to say the least, as it must be cleaned orf, and even then is liable to leave the surface of the work pitted and rough. If it were possible to keep air away from the iron entirely, no trace of scale would be formed, even at a high heat.

If just enough air is blown into the fire to make it burn properly, all the ox^^gen will be burned out, and very little, if any, scale will be formed while heating. On the other hand, if too much air is used, the ox3^gen will not all be consumed and this unburned oxygen will attack the iron and form scale. This is known as "oxidizing";

that is, when too much air is admitted to the fire the surplus oxygen will attack the iron, forming "oxide," or scale. This sort of a fire is known as an "oxidizing" fire and has a tendency to "oxidize" anything heated in it.

Anvil. — The ordinary anvil, Fig. i, has a body of cast iron, wrought iron, or soft steel, with a tool-steel face welded on and hardened. The hardened steel covers jus^ the top face, leaving the horn and the small block next the horn of the softer material.

Fig. I.

The anvil should be so placed that as the workman faces it the horn will point toward his left.

The square hardie-hole in the right-hand end of the face is to receive and hold the stems of hardies, swages, etc.

For small work the anvil should weigh about 150 lbs.

Hot and Cold Chisels. — Two kinds of chisels are commonly used in the forge-shop: one for cutting cold stock, and the other for cutting red-hot metah These are called cold and hot chisels.

The cold chisel is generally made a little thicker in the blade than the hot chisel, which is forged down to a thin edge.

Fig. 2 shows common shapes for cold and hot chisels, as well as a hardie, another tool used for cutting.

Fig. 2.

Both chisels should be tempered alike when made.

The cold chisel holds its temper; but, from contact with hot metal, the hot chisel soon has its edge softened. For these reasons the two chisels should never be used in place of each other, for by using the cold chisel on hot work the temper is drawn and the edge left too soft for cutting cold metal, while the hot chisel soon becomes so soft that if used in place of the cold it will have its edge turned and ruined.

It would seem that it is useless to temper a hot chisel, as the heated work, with which the chisel

FORGE- PRACTICE.

comes in contact, so soon draws the temper. When the chisel is tempered, however, the steel is left in a much better condition even after being affected by hot metal on which it is used than it would be if the chisel were made untempered.

Grinding Chisels. — It is very important to have the chisels, particularly cold chisels, ground correctly, and the following directions should be carefully followed.

The sides of a cold chisel shoiild be ground to form an angle of about 60° with ^^ach other, as shown in Fig. 3. This makes an angle blunt

Fig. 3.

enough to wear well, and also sharp enough to cut well.

The cutting edge should be ground convex, or curving outward, as at B. This prevents the comers from breaking off. AVhen the edge of the chisel is in this shape, the strain of cutting tends to force the corners back against the solid metal

GENERAL DESCRIPTION OF FORGE AND TOOLS. Q

in the central part of the tool. If the edge were made concave, like C, the strain would tend to force the corners outward and snap them off. The arrows on B and C indicate the direction of these forces.

Hot chisels should be ground sharper. The sides should be ground at an angle of about 30° instead of 60°.

Another tool used for cutting is the hardie. This takes the place of the cold or hot chisel. It has a stem fitted to the square hole in the right-hand end of the anvil face, this stem holding the hardie in place when in use.

Cutting Stock. — When soft steel and wrought -iron bars are cut with a cold chisel the method should be about as follows: First cut about one-fourth of the way through the bar on one side; then make a cut across each edge at the ends of the first cut; turn the bar over and cut across the second side about one-fourth the wa}^ through; tilt the bar slightly, with the cut resting on the outside corner of the anvil, and by striking a sharp blow with the sledge on the projecting end, the piece can generally be easity broken off.

Chisels should alwa3^s be kept carefully ground and sharp.

A much easier way of cutting stock is to use bar shears, but these are not always at hand.

The edge of a cJiisel should never under any circumstances he driven clear through the stock and allowed to come in contact with the hard face of the anvil.

Sometimes when trimming thin stock it is conlO FORGE-PRACTICE.

venient to cut clear through the piece; in this case the cutting should be done either on the horn, the soft block next the horn, or the stock to be cut should be backed up with some soft metal. An easy way to do this is to cut a wide strip of stock about two inches longer than the width of the face of the anvil, and bend the ends down to fit over the sides of the anvil. The cutting may be done on this without injury to the edge of the chisel. It is very convenient to have one of these strips always at hand for use when trimming thin work with a hot chisel.

The author has seen a copper block used for this same purpose. The block was formed like Fig. 4, the stem being shaped to fit into the hardie-hole of the anvil. This block was designed for use principall)^ when Fig. 4. trimming thin parts of heated

work with a hot chisel.

Care should always be taken to see that the work rests fiat on the anvil or block when cutting. The work should be supported directly underneath the point where the cutting is to be done; and the solider the support, the easier the cutting.

Hammers. — Various shapes and sizes of hammers are used, but the commonest, and most convenient for ordinary use, is the ball pene-hammer shown in

Fig. 5-

The large end is used for ordinary work, and the small ball end, or pene, for riveting, scarfing,

GENERAL DESCRIPTION OF FORGE AND TOOLS.

etc. These hammers vary in weight from a few ounces up to several pounds. For ordinary use about a i^- or 2 -pound hammer is used.

Several other types in ordinary use are illustrated

Fig. 5.

Fig. 6.

in Fig. 6, A is a straight-pene ; B, a cross-pene; and C, a riveting-hammer.

Sledges. — Very light sledges are sometimes made the same shape as ball-pene hammers. They are used for light tool-work and boiler- work.

Fig. 7 illustrates a common shape for sledges. This is a double-faced sledge.

V

A

Fig. 7.

Fig. 8.

Sledges are also made with a cross-pene or straight-pene, as shown in Fig. 8.

12 FORGE-PRACTTCE.

For ordinary work a sledge should weigh about lo or 12 lbs.; for heavy work, from i6 to 20.

Sledges for light work weigh about 5 or 6 lbs.

Tongs. — Tongs are made in a wide variety of shapes and sizes, depending upon the work they are intended to hold. Three of the more ordinary shapes are illustrated.

The ordinary straight- jawed tongs are shown in Fig. 9. They are used for holding flat iron. For holding round iron the jaws are grooved or bent to the shape of the piece to be held.

Fig. 10 shows a pair of bolt-tongs. These tongs are used for holding bolts or pieces which are larger on the end than through the body, and are so shaped that the tongs do not touch the enlarged end when the jaws grip the body of the work.

Fig. 9.

Fig. II.

Pick-up tongs, Fig. 11, are used for handling small pieces, tempering, etc., but are very seldom used for holding work while forging.

Fitting Tongs to Work. — Tongs should always be carefully fitted to the work they are intended to hold.

Tongs which fit the work in the manner shown in Fig. 12 should not be used until more carefully fitted. In the first case shown, the jaws are too close together; and in the second case, too far apart.

When properly fitted, the jaws should touch the work the entire length, as illustrated in Fig. 13. With properly fitted tongs the work may be held firmly, but if fitted as shown in Fig. 12 there is always a very ' ' wobbly ' ' action between the jaws and the work.

To fit a pair of tongs to a piece of work, the jaws should be heated red-hot, the piece to be held placed between them, and the jaws closed down tight around the piece with a hammer. To prevent the handles from being brought too close together while the tongs are being fitted, a short piece of stock should be held between them just back of the jaws. If the handles are too far apart,

a few blows just back of the eye will close them up.

Flatter — Set-hammer — Swage — Fuller — Swage-block.

— Among the commonest tools used in forge-work are the ones mentioned above.

The flatter, Fig. 14, as its name implies, is used for flattening and smoothing straight surfaces.

The face of the flatter is generally from 2 inches to 3 inches square, and should be kept perfectly smooth with the edges slightly rounding.

Fig. 15 shows a set-hammer. This is used for finishing parts which cannot be reached with the flatter, up into corners, and work of that character. The face of this tool also should be smooth and flat, with the corners more or less rounded, depending on the work it is intended to do.

Set-hammers for small work should be about I or i^ inches square on the face.

' ' Set-hammer " is a name which is sometimes given to almost any tool provided with a handle, which tool in use is held in place and struck with another hammer. Thus, flatters, swages, fullers, etc., are sometimes classed under the general name of set-hammers.

GENERAL DESCRIPTION OF FORGE AND TOOLS.

IS

Fullers, Fig. i6, are used for finishing up filleted corners, forming grooves, and for numerous purposes which will be given more in detail later.

They are made in a variety of sizes, the size being determined by the shape of the edge A. On a ^ inch fuller this edge would be a half-circle ^ inch in diameter ; on a f inch it would be f inch in diameter, etc.

Fullers are made "top" and "bottom." The one shown with a handle is a " top ' ' fuller, and the lower one in the illustration is a "bottom" fuller and has the stem forged to fit into the square hardie-hole of the anvil. This stem should be a loose fit in the hardie-hole. Tools of this character should never be used on an anvil where they fit so tightly that it is necessary to drive them into place.

A top and bottom swage is shown in Fig. 17. The swages shown here are for finishing round work; but swages are made to be used for other shapes as well.

Swages are sized according to the shape they are made to fit. A i-inch round swage, for instance, is made to fit a circle i inch in diameter, and would be used for finishing work of that size.

All of the above tools are made of low-carbon tool steel.

A swage-block is shown in Fig. i8. These blocks are made in a variety of shapes; the illustration showing a common form for general use. This block is made of cast iron and is about 3^ inches thick. It has a wide range of uses and is very convenient for general work, where it takes the place of a good many special tools.

Chapter II. Welding

Welding-heat. — A piece of wrought iron or mild steel, when heated, as the temperature increases becomes softer and softer until at last a heat is reached at which the iron is so soft that if another piece of iron heated to the same point touches it, the two will stick together. The heat at which the two pieces will stick together is know^n as the welding-heat. If the iron is heated much beyond this point, it will bum. All metals cannot be welded (in the sense in which the term is ordinarily used). Some, when heated, remain very dense and retain almost their initial hardness until a certain heat is reached, when a very slight rise of temperature will cause them to either crumble or melt. Only those metals which, as the temperature is increased, become gradually softer, passing slowly from the solid to the liquid state, can be welded easily. Metals of this kind just before melting become soft and more or less pasty, and it is in this condition that they are most weldable. The greater the range of temperature through which the metal remains pasty the more easily may it be welded.

In nearly all welding the greatest trouble is in heating the metal properly. The fire must be clean and bright or the result will be a "dirty" heat; that is, small pieces of cinder and other dirt will stick to the metal, get in between the two pieces, and make a bad weld.

Too much care cannot be used in welding ; if the pieces are too cold they will not stick, and no amount of hammering will weld them. On the other hand, if they are kept in the fire too long and heated to too high a temperature they will be burned, and burned iron is absolutely worthless.

The heating must be done slowly enough to insure the work heating evenly all the way through. If heated too rapidly, the outside may be at the proper heat while the interior metal is much colder ; and, as soon as taken from the fire, this cooler metal on the inside and the air almost instantly cool the surface to be welded below the welding temperature, and it will be too cold to weld by the time any work can be done on it.

If the pieces are properly heated (when welding wrought iron or mild steel), they will feel sticky when brought in contact.

When welding, it is best to be sure that everything is ready before the iron is taken from the fire. All the tools should be so placed that they may be picked up without looking to see where they are. The face of the anvil should be perfectly clean, and the hammer in such a position that it will not be knocked out of the way when the work is placed on the anvil for welding.

All the tools being in place, and the iron brought to the proper heat, the tongs should be held in such a way that the pieces can be easily placed in position for welding without changing the grip or letting go of them ; then, when everything is ready, the blast should be shut off, the pieces taken from the fire, placed together on the anvil, and welded together with rapid blows of the hammer, welding (after the pieces are once stuck together) the thin parts first, as these are the parts which naturally cool the quickest.

Burning Iron or Steel. — The statement that iron can be burned seems to the beginner to be rather exaggerated. The truth of this can, however, be very easily shown. If a bar of iron be heated in the forge and considerable blast turned on, the bar will grow hotter and hotter, until at last sparks will be seen coming from the fire. These sparks, which are quite unlike the ordinary ones from the fire, are white and seem to explode and form little white stars.

These sparks are small particles of burning iron which have been blown upward out of the fire.

The same sparks may be made by dropping fine iron-filings into a gas-flame, or by burning a piece of oily waste which has been used for wiping up iron-filings.

If the bar of iron be taken from the fire at the time these sparks appear, the end of the bar will seem white and sparkling, with sparks, like stars similar to those in the fire, coming from it. If the heating be continued long enough, the end of the bar will be partly consumed, forming lumps similar to the "clinkers" taken from a coal fire.

FORGE-PRACTICE.

To burn iron two things are necessary: a high enough heat, and the presence of oxygen.

As noted before, when welding, care must be taken not to have too much air going through the fire; in other words, not to have an oxidizing fire.

If the fire is not an oxidizing one, there is not so much danger of injury to the iron by burning and the forming of scale.

Iron which has been overheated and partially burned has a rough, spongy appearance and is brittle and crumbly.

Use of Fluxes in Welding, — AVhen a piece of iron or steel is heated for welding under ordinary conditions the outside is oxidized; that is, a thin film of iron oxide is formed. This oxide is the black scale which is continually falling from heated iron and is formed when heated iron is brought in contact with the air. This oxide of iron is not fluid except at a very high heat, and, if allowed to stay on the iron, will prevent a good weld.

When welding without a flux the iron is brought to a high enough heat to melt the oxide, which is forced from between the welding pieces by the blows of the hammer.

This heat may easily be taken when welding ordinary iron; but when working with some machine-steel, and particularly tool-steel, the metal cannot be heated to a high enough temperature to melt the oxide without burning the steel.

From the above it would seem imipossible to weld steel, as it cannot be heated under ordinary conditions without oxidizing, but by the use of a flux this difficulty may be overcome and the oxide mehed at a lower temperature.

The flux (sand and borax are the most common) should be sprinkled on the part of the piece to be welded when it has reached about a yellow heat, and the heating continued until the metal is at a proper temperature to be soft enough to weld, but care should be taken to see that the flux covers the parts to be welded together.

The flxtix has a double action; in the first place, as it melts it flows over the piece and forms a protecting covering which prevents oxidation, and also when raised to the proper heat dissolves the oxide that has already formed.

The oxide melts at a much lower heat when combined with the flux than without it, and to melt the oxide is the principal use of the fliix. The metal when heated in contact with the flux becomes soft and "weldable" at a lower temperature than when without it.

Ordinary borax contains water which causes it to bubble up when heated. If the heating is continued at a high temperature, the borax melts and runs like water; this melted borax, when cooled, is called borax-glass.

Borax for welding is sometimes fused as above and then powdered for use.

Sal ammoniac mixed with borax seems to clean the surface better than borax alone. A flux made of one part of sal ammoniac and four parts borax works well, particularly when welding tool-steel, and is a little better than borax alone.

Most patented welding compounds have borax as a basis, and are very little, if any, better than the ordinary mixture given above.

The flux does not in any way stick the pieces together or act as a cement or glue. Its use is principally to help melt the oxide already formed and to prevent the formation of more.