Welding Craft Practice Oxy-Acetylene And Arc 361pages 1975

361 Pages·1975·11.66 MB·English

A project of Volunteers
in Asia

Welding
Cr
Pract&es
Volumes
1 and 2

by: N. Parkin
and C. R. Flood

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by;
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WELDIMG
CRAFT PRACTICE
-

Part 1, Volume 1: _

Oxyacetylene
Gas Welding

and Related Studies

N. FARKIN
Lecturer in Welding and Plumbing
cllanterbury
Twhnical
College
and
C. R. FLOOD
Let turer in Welding and Metal Plate Work
Chterbury
Technical Co&p

CONTENTS

OXV-ACETYLENE
GA!5 WELDlNG

B-AsIc WELDS AND‘TECHNUJE

~XVGEN qmNG
OF STEELS

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WELDING
CRAFT
PRACTICE
PART I

I
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WELDING
CRAFT
PRACTICE
PART
I

VOLUME
7: Oxy-acetylene
Gas Welding
and
Related
Studies

BY

N. PARKIN,
M.I.P., M.R.S.H., M.R.P.A.

Lecturer
in Welding
and Plumbing

Canterbury
Technical
College

AND

c. R. FLOOD,
A.M.1NST.W.

Lecturer
in Welding
and Metal Plate Work

Canterbury
Technical
College

PERGAMON
PRESS

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Copyright @ Pergamon Press 1969
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First edition 1969
Reprinted 1975
Library of Congress Catalog Card No. 68-3 1344

Printed in Great Britain by A. Wheaton & Co., Exeter
ISBN 0 08 012980 3

.-,.a--,..
_

7

P~BL~ER's
FOREWORD

INTRODUCTION

Chapter 1 Oxy-acetylene Gas Welding
-:
The Gases
1. I
‘” ,,p,
Sys terns and Equipment
,a <
Safety Precautions and Fire Prevention

2 Basic Welds and Technique

Basic Welds
Leftward Technique
Rightward Technique
Fusion Welding of Cast Iron
Bronzewelding and Brazing
Building up Worn Parts

3 Oxygen Cutting of Steels

Machine
Templates
Stack Cutting

4 Inspection and Testing of Welds

Visual Inspection of Welds

5 Related Studies

Metals and Alloys Commonly Welded
. Meclianical Properties of Metals
The Structure of Metals
The State and Structure of Matter

V

CONTENTS

Appendix 1 Glossary of Welding and General Terms and
Abbreviaths

&4ppendix 2 Revision Questions

INDEX

147

152

153

u blisher’s
Foreword

THE Industrial Training Act has resulted in an increase in the
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ROBERT MAXWELL
Publisher

vii

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and Commercial
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Introduction

IN A rapidly developing welding industry there is a constant
demand for skilled craftsmen capable of producing high-quality
work with first-class equipment. The wide range of modern welding
work makes it necessary for the operator to be as capable of
controlling expensive automatic machines as he is of performing
skilful manual welding. The need is for adequately trained person-
nel with a sound understanding of the various processes and
materials to be used, a keen appreciation 0; the importance of the
correct, careful use of equipment and a completely “safety-
conscious” outlook.
The two volumes of this book cover the gr
’ necessary for
the acquisition of the essential basic skills
,afe working
methods, sufficient technology and related studies being included
to provide a suitable background to the practical work and form a
basis for further, more advanced studies. It is intended for all who
wish to learn to weld and the ground covered will enable the
beginner to obtain a sound knowledge of the equipment, a keen
appreciation of safety and, by means of a graduated series of
practical exercises, a good standard of skill.
The intention has been to cover the requirements of the syllabus
of the City and Guilds of London Institute, Course 323, Welding
Craft Practice (Part I), the relevant information being given for the
production and testing of the specimen welds required in this
course, and it is hoped that all would-be welders will aim at
obtaining a suitable qualification.
Volume 1 deals with Oxygen-Acetylene Processes and Weld
Defects, Testing of Welds and Welding Science, Volume 2 with
Electric Arc Processes and Elementary Electricity, Classification of

ix

1

INTRODUCTION

Electrodes, Welding Symbols, Engineering Drawing, Metal Plate
Surface Development and Workshop Calculations.
We wish to express our appreciation to Messrs. Hancock and
Company (Engineers) Ltd., Air Products Ltd., Lincoln Electric
Company Ltd., Murex Welding Processes Ltd., for allowing the
reproduction of photographs and diagrams of their welding
equipment.
Material from B.S. 1295; 1959 : Tests.for Use in the Training of
Welders, B.S. 1719; Part 1, 1963 : Classlpcation Coding and
Marking of Covered Electrodes for Metal-Arc Welding and B.S.
499 ; Part 2, 1965 : Welding Terms and Symbols, is reproduced by
permission of the British Standards Institution, 2 Park Street,
London, W. 1, from whom copies of the complete standards can be
obtained.
The student is advised to make a further study of the British
Standards referred to.

N. PARKIN

C.R. FLOOD

X

I

CHAPTER
7

cetylene
as VVellding

THIS is a process in which welding heat is produced by the combus-
tion of an acetylene/oxygen gas mixture in a blowpipe which
directs the heat in the form of a concentrated flame to the required
point causing melting of ,a.he parent metal. It is widely used in the
welding of most metals and alloys.

The Gases

Acetylene

Acetylene is an inflammable, comparatively heavy gas with a
distinctive smell, and it gives the highest flame temperature
(3200°C approx.) of any fuel gas. It is unstable and is liable to
decompose or detonate at elevated temperatures or at pres-
sures above 15 p.s.i. When mixed with air it forms explosive
mixtures in all proportions between 2% and 82%, and when in
contact with copper or alloys containing ‘70% copper, e.g. pipes
and valves, it can form violently explosive compounds known as
acetylides.
To make it possible for acetylene to be generated and used with
safety a comprehensive set of safety regulations is essential and a
thorough study must be made of the Memorandum on Safety
Measures Required in the Use oj- Acetylene Gas and in Oxy-
acetylene Processes in Factories (H.M.S.O., Form 1704) and the
recommendations of the British Acetylene Association and the
suppliers of gas and carbide.
7

WELDING
CRAFT
PRACTICE-PART
1, VOL.
1

Acetylene is a “hydrocarbon”,
or a chemical compound of
carbon and hydrogen (C,H,), and is prepared by the interaction
between calcium carbide and water.
Calcium carbide is made by smelting quicklime and coke in a
furnace. The result is the formation of a hard grey solid, calcium
carbide (CaC,) and carbon monoxide (CO) gas:
Quicklime + carbon =z calcium carbide + carbon monoxide
(heated)
CaO
+
3c
=
CaC,
+
CO
Calcium carbide reacts chemically in contact with water to
generate acetylene gas :
Calcium carbide + water = acetylene + slaked lime
(heat given out)
CaC,
+ H,O = C,H,
+
Ca(OH),
One pound of calcium carbide produces approximately 4+ ftS of
acetylene gas.

GENERATION
OF ACETYLENE

There are two types of generator:
(a) Water
to carbide,
used when small gas yields or portability
are required and ranging in capacity from a calcium carbide charge
of several pounds up to 1 cwt.
Generation is brought about by allowing a controlled flow of
water to have access to calcium carbide placed in charging trays.
The gas is cooled and “washed” by allowing it to pass through the
body of water in the container, the washing removing some of the
impurities (ammonia and sulphuretted hydrogen). The flow of
water to the calcium carbide is controlled by the pressure of genera-
ted gas.
hrethod
of operation
(see Fig. 1.1). The flow of water from the
outer container (1) to the calcium carbide trays (2) is regulated by
the water control valve (3). As gas is generated it passes through
the main body of water into the rising gas bell (4) and the pressure
of gas gradually lifts the rising bell, allowing the water control
valve to close owing to the upward movement of the valve control
2