ARC-Slag Remelting of Steel and Alloys

323 Pages·1997·3.89 MB·English

by  B I Medovar

title: Arc-slag Remelting of Steel and Alloys
author: Medovar, B. I.
publisher: Cambridge International Science Publishing
isbn10 | asin: 1898326215
print isbn13: 9781898326212
ebook isbn13: 9780585173719
language: English
subject Steel--Electrometallurgy, Electric furnaces.
publication date: 1996
lcc: TN706.A73X 1996eb
ddc: 669/.142
subject: Steel--Electrometallurgy, Electric furnaces.
Page i
Arc-Slag Remelting of Steel and Alloys
B I Medovar
V Ya Saenko
G M Grigorenko
Yu M Pomarin
V I Kumysh
E O Paton Electric Welding Institute National Academy of Sciences,
Kiev, Ukraine
CAMBRIDGE INTERNATIONAL SCIENCE PUBLISHING
Page ii
Published by Cambridge International Science Publishing
7 Meadow Walk, Great Abington, Cambridge CB1 6AZ, England
First published March 1996
© Russian original B I Medovar, V Ya Saenko, G M Grigorenko, Yu
M Pomarin and V I Kumysh
© 1996 Cambridge International Science Publishing
Conditions of sale
All rights reserved. No part of this publication may be reproduced or
transmitted in any form or by any means, electronic or mechanical,
including photocopy, recording, or any information storage and
retrieval system, without permission in writing from the publisher
British Library Cataloguing in Publication Data
A catalogue record for this book is available from the British Library
ISBN 1898326215
Translated from the Russian by V E Riecansky
Production Irina Stupak
Printed by St Edmundsbury Press, Bury St Edmunds, Suffolk,
England
Page iii
Contents
1 1
Phenomenological description of arc-slag remelting
2 9
Characteristics of the ASR process
2.1 Electric characteristics of arc discharge in ASR 9
2.2 Special features of electrode melting and 13
solidification of the ingot in ASR
2.3 Physico-chemical processes of interaction of gases 17
with metal in arc slag remelting
2.4 Electrical and energy parameters of arc-slag 26
remelting
3 34
Special features of nitrogen alloying steels in ASR
3.1 Solubility of nitrogen in ASR fluxes 34
3.2 Solubility of nitrogen in steels and alloys at an 39
excess pressure of up to 1.1 MPa
3.3 Effect of the composition of fluxes and gas 49
atmosphere on absorption of nitrogen by steels and
alloys in conventional and arc melting
3.4 Absorption of nitrogen in ASR 56
4 69
Equipment for arc slag remelting
4.1 Special features of the design of melting furnaces 69
4.2 Flux gates 77
5 80
Melting of ingots of structural steels by the ASR method
in industrial ESR furnaces
6 86
Technology of arc-slag remelting high-nitrogen steels
6.1 Electroslag and plasma-arc technologies in 86
production of high-nitrogen steels
6.2 Melting of ingots of nitrogen-containing steels by 105
the ASR method
6.3 Nitriding the metal during crucible melting 115
7 118
Arc slag remelting titanium and its alloys
7.1 Producing ingots of titanium and its alloys by VAR, 118
EBR, PAR and ESR methods
7.2 Melting ingots of titanium and its alloys by ASR 126
7.3 Methods of melting slab ingots by ASR of titanium 138
and its alloys
7.4 Producing cast titanium nitride by ASR 143
Conclusions 150
References 153
Index 159

Page 1
1
Phenomenological Description of Arc-Slag Remelting
Special electrometallurgy is one of branches of industry concerned
with the production of metals, alloys and steels of the highest quality
and reliability.
The leading position in the problem of special electrometallurgy
processes is occupied by refining remelting. The first of these
processes was vacuum arc remelting (VAR), in which the electric arc
is used as the heat source. The E O Paton Electric Welding Institute
have developed and applied widely electroslag remelting (ESR), in
which the metal is melted as a result of the heat generated during
passage of current through a slag pool. This was followed by the
development of electron beam (EBR) and plasma arc (PAR) remelting
processes, in which the electron beam and low-temperature plasma
respectively are used as heat sources.
Figures 1-5 show the diagrams of VAR, ESR, EBR and PAR
processes in the main variants and, for comparison, the diagram of
consumable plasma torch remelting (CPTR) - a variety of plasma arc
remelting which combines several features of PAR and VAR.
Comparison of the remelting methods shows clearly that they have a
number of common features and also large differences. The common
feature of all these processes is the droplet nature of melting of metal
and gradual melting of remelting metal in water-cooled moulds
(crystallizers). This droplet melting and forced solidification of liquid
metal with constant one-sided (from the top) heat supply is the main
advantage of all these remelting processes and also their main
advantage in comparison with other existing methods of producing
and solidifying liquid metal.
The remelting processes solve two tasks at the same time - remelting
liquid metal and its directional solidification.
In VAR, vacuum is the refining agent. Vacuum treatment of the flow
of droplets and the surface of the metal bath is accompanied by the
removal of not only the gases dissolved in liquid metal (hydrogen,
oxygen, nitrogen) but also of gases combined with the metal in the
form of oxides, nitrides and dissociating in the conditions of
rarefaction and high temperatures. Naturally, VAR may also be
accompanied by vacuum-carbon deoxidation. In vacuum, the so-
called nonferrous impurities evaporate from the metal, i.e. impurities
of low-melting metals having a high vapour tension (tin, lead,
antimony,
Page 2
arsenic, bismuth, etc.). The removal of low-melting impurities greatly
increases the quality, endurance and reliability of components made
from the so-called superalloys, i.e. creep-resisting alloys, and high-
strength alloyed structural steels.
Fig.1
Diagram of vacuum-arc remelting (VAR). 1)
electrode feed mechanism; 2) current supply;
3) rod; 4) vacuum chamber; 5) electrode;
6) anode; 7) water-cooled crystallizer;
8) ingot; 9) water-cooled stool.
Fig.2
(right) Electron beam remelting with an intermediate
container. 1) ingot withdrawal mechanism;
2) ingot; 3) electron beam guns; 4) vacuum
chamber; 5) water-cooled crystallizer;
6) ingot; 7) ingot withdrawal mechanism;
8) water-cooled container; 9) slag skin.
Fig.3
Plasma-arc remelting (PAR). 1) ingot feed
mechanism; 2) ingot; 3) chamber; 4) plasma torch;
5) water-cooled crystallizer; 6) ingot;
7) ingot withdrawal mechanism.
Fig.4
(right) Plasma-arc remelting a consumable
plasma torch (CPTR). 1) electrode feed mechanism;
2) chamber; 3) hollow electrode; 4) water-cooled
crystallizer; 5) ingot; 6) water-cooled stool.