Tool-steel: a concise handbook on tool-steel in general, its treatment in the operations of forging, annealing, hardening, tempering, etc. and the appliances therefor

Front matter

Class _JIiia_0 Book TfSG

GopghtN^

COPYRIGHT DEPOSIT.

Preface

The changes which tool-steel undergoes by the various operations of forging, annealing, hardening, tempering, etc., have theoretically been established by Ledebur, Wedding, Reiser, Osmond, and others.

The rules, which have been deduced from theory, of what has to be observed in the above-mentioned operations are in themselves of a simple nature and readily comprehended, and a more universal knowledge of them has been diffused by the scientific publications of the above-mentioned writers, as well as by the so-called " directions for the treatment " of the steel, which nearly every manufacturer of tool-steel furnishes to his customers.

The almost sole object of these directions is to promote a more intimate knowledge of steel and its treatment in the manufacture of tools among those who are especially entrusted with it, but, as a rule, an explanation of " how and by what means " their observance is to be effected is wanting.

The steel recommended by them is not seldom invested with mysterious properties, and encouragement is frequently given to the continuance of primitive appliances, but little suitable for the purpose and difficult to attend.

In these directions the pith of the matter is very seldom treated of, or only in a very brief way, so that the changes which the steel undergoes in the various operations of the manufacture of tools remain, as a rule, not understood, and there is no probability of the mind being directed towards the necessity of suitable working appliances.

Publications on this subject derived from practice are also scarce, because experiences gathered in this line are preferably kept secret.

VI PREFACE.

•

These conditions apparently explain the limited general diffusion of a knowledge of practically approved appliances and working processes, in consequence of which master-workman and manufacturer are frequently placed in the disagreeable j)Osition of having to desist from making the most of the highest efficiencies attainable in tools, or are forced to work with a greater expense of time, money and material than would otherwise be necessary.

The master-workman and the workmen entrusted with the manufacture of tools are under the necessity of gathering experience from their own practice, and it is largely left to themselves to devise appliances required for successful working without having at their disposal anything that will give them a clue to liow it is to be done.

It was especially the latter condition that induced me to write this small work.

It is chiefly intended as a guide to the master-workman and the intelligent tool-maker, and, in accordance with this object, is exclusively adapted to practical needs.

As sources of the explanations derived from theory, which have been incorporated into the book, the scientific works and separate publications of the previously mentioned authors have served.

The general arrangement of the material has been modeled after the excellent work by F. Reiser : " Das Harten des Stables in Theorie und Praxis " (" Hardening of Steel in Theory and Practice").

The directions and working appliances collected in the book have throughout been taken from practice, and are intended to assist master-workmen and workmen employed in the practical execution of the various operations in the manufacture of tools, in their occupation, which demands varied knowledge and experience.

The Author.

BiSMARCKHUETTE ON SaALE.

Introduction

PAGE

Products of iron -works used in the manufacture of tools; Tool-steel and various designations of it 1

Crucible steel the most noble product of the manufacture of tool-steel; Weld steel and the product brought into commerce under this name ... 2

I

Composition of Tool-Steel and its Classification According to It.

Definition of steel; Various forms in which carbon occurs in iron; Hardening carbon 3

Carbide; Graphitic carbon; Accidental admixtures in steel; On what the quality of steel depends , 4

Quantity of injurious admixtures in steel; Silicon in crucible steel; Intentionally added admixtures 5

Manganese : Manganese steel ; Properties of actual manganese steel ; Tungsten 6

Properties of steel to which tungsten has been added; Chromium 7

Nickel; Molybdenum, titanium and vanadium 8

II

Classification of Tool-Steel According to the Degree of Hardness AND the Purpose for which It is to be Used.

Groups of commercial tool-steel; Tool-steel which acquires its hardness exclusively from a content of carbon; Tool-steel which in addition to carbon contains admixtures increasing the hardness, also called special steel 9

Modes of labeling tool-steel; Designations for the degree of hardness 10

Selection of tool-steel for a determined purpose; Standard in practice for the useful effect of the finished tool; Less attention required in working

soft steel 11

(Vii)

Vni CONTENTS.

FAOB

Classification of steel according to the degree of hardness and the purposes for which it is to be employed as in use in Bismarck huette; Special steels 12

Natural hard steel; Special turning steel; Magnet steel; Composition of self-hardened steel and of very hard special turning steel 13

Composition of magnet steel; Tool steel for definite purposes 14

Soft-centred or mild-centred steel, and mode of producing it 15

III. Observations on the Exteknai, Appearance of Commercial Tool,-Steel

Defects which the surface of the steel may show, Scales; Cracks; Seams. 16 Edge cracks; Appearance of the fracture; Structure of soft and of hard

steel 17

Defects which may be observed on the surfaces of the fractures of tool-steel; Flaws or blisters; Spots due to liquation; Flaws in the centre of the steel and their cause 18

IV

Observations on the Fracture of Steel, with Regard to the Structure IN THE Hardened and Non-Hardened States.

Difference in the appearance of the structure of steel according to how it has been worked 19

Conditions on which the appearance of the fracture of unhardened steel may depend 20

Conditions on which the appearance of the fracture of hardened steel is dependent; Tables showing the influence of the various degrees of temperature upon hardened and unhardened steel, and their general application in practice 21

V. Practice of the Fire-Treatment of Steel

Purpose of the repeated heating of steel in the manufacture of tools 22

Proper adaptation of the appliances for heating; Choice of fuel; Disadvantages which may result from the use of certain fuels 23

Hard coke and furnace for heating the steel 24

Smith-coal or forge coal 26

Effect produced by a content of sulphur in the coal; Coke dust 26

CONTENTS. IX

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Location of the highest degree of heat developed in an open fire; Difficulties encountered in heating in an open fire 27

Conversion of an open fire into a provisional furnace 28

Disagreeable feature in heating cutters; Construction of a unifHe in the open fire 29

Unsuitableness of mild soft coke for forging and hardening from open fires; Advantages of charcoal for open fires 30

Disadvantages resulting from the action of the blast upon tool-steel or the finished tool 31

Mode of protecting the steel from the action of the blast; Weakening the effect of the blast; Eemedy for the attacks of the air upon the surface of the steel 32

Disadvantages of open fires in making or repairing a large number of tools; Importance of the influence of light in judging the degree of temperature of the steel 33

Location in the works of the devices for forging and hardening tools; Avoidance of drawbacks due to heating the steel in an open fire 34

Most simple type of furnace; Construction of a furnace to be operated with coke 35

Construction of a furnace to be operated with charcoal 38

Furnace for heating long articles 39

Construction of furnaces to be fitted for coal 40

Conversion of a furnace into a regular niufHe furnace 41

Construction of a muffle furnace to be worked with charcoal 42

Muffle furnaces, the muffles of which are heated by gas; Heating muffles

of refractory clay 43

Ordinary forging reverberatory furnace 44

Small reverberatory furnace for forging and hardening operations on a

small scale; Reverberatory furnace with two hearths 45

Small reverberatory furnace with step-grate and two hearths; Reverberatory furnace with a fire-place patented by Gasteiger, of Vienna 47

Reverberatory furnace with muffle 48

VL

Appliances for Annealing Steel.

Changes in the properties of strength of steel; Forging strains and their removal by annealing; General rule applying to annealing; Protection of tool-steel from the air by annealing it in vessels 49

X CONTENTS.

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Hints for tlie jiraotical execution of annealing; Annealing in boxes; Construction of an annealing furnace for forged pieces 50

Furnace for annealing steel in an annealing pot or in annealing boxes 52

Control of the result of the annealing operation 54

Annealing furnace for annealing long articles 55

VII. Appliances por Hardening Steel

Importance of thoroughly uniform heating; Disadvantages of imperfect heating appliances 55

Hints for liie choice of suitable appliances; Furnaces suitable for hardening 56

Methods for hardening tools in a bath of molten metal or in a bath of fused salts; Possibility of overheating of the melted mass 57

Furnace and crucible for melting the metals or salts; Advantages of the use of a pyrometer; Disadvantages which may arise from heating steel in melted lead 58

Mode of preventing melted lead from adhering to some portions of the tool; Heating steel in fused salts; Mixture of salts 59

Fusion of the salts; Addition of yellow prussiate of potash; Preparation of the articles to be heated; Suspension of the articles in the melt 60

Unequal heating of the melt and its detection; Advantages of heating tools in melted salt 61

VIII. Hardening of Tool-Steel in General

What is understood by hardening; Hardening temperature; Definition of temper color; Appearance of the temper colors 62

General custom of tempering finished tools; Requirements for the appearance of the temper colors; Conditions to which the changes steel undergoes in hardening are chiefly due 63

Changes in the dimensions of the steel, illustrated 64

Strains in the steel before it is hardened not removed by simply heating in hardening; Practical utilization of the property of steel of assuming fixed dimensions in hardening operations succeeding one another 65

Observations on the fractures of tool-steel of the same degree of hardness notched at various distances from each other, and then hardened and broken on the notched places 66

CONTENTS. XI

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Illustration of the cross-section of steel not hardened and of the cross-section of the same steel hardened 67

Cause of cracking; Cracking from the interior 68

Observations on the fracture of hardened steel of a larger cross-section;

Severance of the corners of a cube, illustrated 69

Examples of the force of the strain in forming cracks, illustrated 70

Distortions of the steel caused by strains, illustrated 71

■Change in the cross-section of tools by hardening; Prevention of cracking; Influence of manganese upon the change in volume of the steel in hardening 72

IX

Hardening of Tools Which Are to be Hardened in Their Entirety.

Cause of cracking and means of avoiding it; Prevention of cracking by

letting-down ; Portions of tools especially subject to snapping oflT;

Cracking from the interior 73

Effect of letting-down; Cause of the snapping off of the teeth of a cutter... 74 Avoidance of superficial scale-like separations on tools; Prevention against

a tool completely losing its hardness 75

Reheating in hot sand or in hot water 76

Process of allowing the hardened tool to remain in the hardening bath

until it is entirely cold; Practical application of this process 77

Division of tools into several sections 78

Diminution of strains by boring out a tool; Main points to be considered

in the construction of a tool 79

X

Hardening of Tools which are only to be Partially Hardened.

Division of partial hardening into three groups 80

Mode of heating; Overheating of broad cutters; Powder for cooling off... 81 Heating tools all over which are to be partially hardened; Experiment

with a bar of steel 82

Hardening tools so that there is a gradual transition of the hardened into

the luihardened portions 83

Xll CONTENTS.

PAGE

XI

Cooling of Tooi^ in Hardening and Dkvicek for this Purpose.

General rule for heating tools for hardening; Formation of steam in the hardening bath, and its effect 83

Hardening of especially large and heavy tools; Uneven cooling before hardening, and its effect 84

Formation of cracks by catching the red-hot tool with cold tongs, illustrated by an example 85

Correct and incorrect forms of tongs; Covering portions not to be hardened 86

Intentional uneven cooling by covering portions of the tool, illustrated by examples 87

Cooling of tools which have to be heated in their entirety; Mode of using running water for hardening 89

Use of falling water for hardening and device for this purpose 90

Equalization of strains formed by hardening, and device for this purpose. 91

Device for hardening if a water conduit or running water is not available. 92

Object of hardening in an ascending water jet; Simultaneous use of a falling and ascending water jet; Device for hardening in an ascending water jet 93

Method of hardening by means of a jet if the operation of hardening is to be effected in a large reservoir; Hardening of hollow bodies, and devices for that purpose 95

XII. Liquids Used in Quenching Steel

Pure water; Most suitable temperature of the hardening water; Composition of water; Increase in the heat-conducting power of water by salts and acids 97

Means for les.sening the too intense hardening effect of well or spring water; Favorable effiect of hardening water which has been used for sometime; Hardening water mixed with soluble constituents 98

Common salt; Soda (carbonate of soda); Acids; Use of acidulated water. 99

Alcohol; Soap; Effects of soluble admixtures of organic nature; Hardening water mixed with insoluble constituents 100

Hardening water mixed with oils or fats 101

CONTENTS. Xlll

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Oils and fats; Precaution in using fat or oil for hardening; Metals; Mercury 102

Tin, zinc and lead; Change in the properties of steel cooled in melted metals 103

Gaseous cooling agents; Solid bodies as cooling agents 104

Results obtained in Bismarckhuette by experiments regarding the cutting power of medium hard tool-steel hardened in various cooling agents... 105

XIII

Tempering of Hardened Steel, and Devices for this Purpose.

Various ways in which tempering may be effected; Tempering from the

interior 105

Recognition of the advance of the heat by the progression of the temper colors; To impart special toughness to a tool which in use is exposed

to shock and blow 106

Progression of cracks, illustrated by an example; Tempering from the

interior 107

Tempering from the interior assisted by simultaneous heating from the

outside; An error frequently committed in cooling 108

Precaution in tempering from the outside; Requisite for tempering tools. 109 Effect of the duration of time in tempering, and its practical utilization;

Blazing off with oil 110

Tempering small tools in oil, and device for that purpose Ill

Tempering in an open fire, upon red-hot iron and by means of a gas flame. 112

Tempering by means of hot sand, and devices for that purpose 113

Tempering of long knives and furnace for that purpose 114

Ck)oling tempered tools 115

Error frequently committed in tempering partially hardened tools 116

XIV. Straightening Tools

Methods by means of which straightening may be effected; Cause of distortion of tools during hardening; Straightening claws and their use . . 117

Tools required for straightening; Straightening of tools by uneven heating and cooling in tempering 118

XIV CONTENTS.

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XV

Case-Hardening and Preventatives a<;ainst Superficial Decabbonization and overheating.

Object of case-hardening; Effect on the structure of iron or steel when

heating with carbon is effected at a high temperature 119

Method pursued in the operation of case-hardening; Application of case-hardening in practice 120

Manner of packing a spindle which is to be iiard in two places, illustrated. 121

Burning in, and mode of effecting this operation 122

Hardening paste and its preparation 123

Dry hardening powder and its composition; Agents for cooling tools 124

Cooling of unevenly heated tools; Compositions of suitable powders;

Mode of applying the powder 125

Mixtures which are to be applied in a pasty condition 126

Carbon compounds in a gaseous form for case-hardening; Use of pig-iron for case-hardening 127

XVI. Welding of Steel

Heating steel for welding 127

Agents which assist in the formation of a soft layer on the surface of the steel; Operation of welding 128

XVII

Regeneration of Steel which has been Spoiled in the Fire.

Steel burnt and overheated 129

Mode of restoring the fine structure of the steel when tools have been overheated; Definitions of roasted or baked steel, and of dead steel 130

XVIII

Investigations of Defects of Hardened Tools. What experience in hardening includes; Test operation with one piece... 131 Overheating; Severance of corners and edges of larger tools; Uncertainty

and timidity in hardening; Hints for the inspection of tools 132

Observations on the fracture of the tool; What curved cracks on flat tools indicate 133

CONTENTS. XV

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Failure due to incorrect cooling; Tools cracked from the interior; Cracks or separation of corners; Edge cracks; Uneven degree of hardness 134

Cause of uniform degree of insuflBcient hardness; Soft spots; Soft skin on the surface of a hardened tool; Tools roasted or baked 135

Defects noticed in using tools; Experiments at Bismarckhuette as to the efficiency of tools 136

Increase in efficiency by a suitable process of cooling; Defect very frequently observed on very hard cutting tools caused by grinding upon hard, rapidly-revolving emery wheels 137

Defects of tools with engraved surfaces; Notching of tools and prevention. 138

Examination of tools which prove defective in use 139

XIX. Improving the Pbopkkties of Strength of Steel

Object of improving the properties of strength of steel; Properties of steel rolled or forged at a high temperature; Efl'ects of the operations of hardening and tempering 140

Most useful methods for improving and regulating the properties of strength of steel 141