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Forge practice and heat treatment of steel
Forge practice and heat treatment of steel
BY JOHN LORD BACON
Member American Society of Mechanical Engineers
Sometime Instructor in Forge Practice and Machine Design,Lewis Institute, Chicago
NEW YORK: JOHN WILEY & SONS, INC., 1919
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Forge practice 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 them- selves and others.
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 them- selves and others.
CONTENTS
- GENERAL DESCRIPTION OF FORGE AND TOOLS
- WELDING
- CALCULATION or STOCK FOR BENT SHAPES
- UPSETTING, DRAWING OUT, AND BENDING
- SIMPLE FORGED WORK
- CALCULATION OF STOCK; AND MAKING OF GENERAL FORCINGS
- STEAM-HAMMER WORK
- DUPLICATE WORK
- TOOL FORGING AND TEMPERING
- MISCELLANEOUS WORK
- TABLES
- COURSE OF EXERCISES IN FORGE WORK
CHAPTER I - GENERAL DESCRIPTION OF FORGE AND TOOLS
Forge. The principal part of the forge as generally 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.
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 generally 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.
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 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.
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 f the top face, leaving the horn and the small block next the horn of the softer material.
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.
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 metal. 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.
DOWNLOAD FREE BLACKSMITHING BOOK:
Forge practice and heat treatment of steel
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.
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 generally 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.
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 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.
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 f the top face, leaving the horn and the small block next the horn of the softer material.
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.
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 metal. 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.
DOWNLOAD FREE BLACKSMITHING BOOK:
Forge practice and heat treatment of steel
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