铸钢及高合金铸钢焊接.pdf

STEEL
CASTINGS
HANDBOOK
Supplement 7
Welding of High Alloy Castings
Steel Founders Society of America
2004
Welding of high alloy steel castings
E. A. Schoefer
Consultant
Steel Founders Society of America
Edited by M. Blair
Steel Founders Society of America
1 Introduction
Iron-base and nickel-base high alloys-by definition those containing eight percent or
more of another element -are widely used for construction of industrial process
equipment that must resist the deteriorating effect of a corrosive of high temperature
environment. Both wrought and cast forms of such alloys may be welded during the
manufacture of finished components so the weldability of the alloys often is a matter of
concern to the user. The same welding processes are applied to wrought and cast
products and, in general, similar techniques and practices are employed. Differences
between wrought and cast alloys in chemical composition and microstructure, however
influence the welding characteristics of each form and must be given consideration. In
addition, the high alloys differ markedly from carbon and low alloy steels in physical
properties such as electrical resistance, thermal expansion and thermal conductivity. It
is essential, therefore, to employ procedures allowing for all these factors when welding
high alloy castings
1.1 All the casting alloys have equal or better weldability than the corresponding
wrought alloys, but there are variations from grade to grade in the ease with which
satisfactory welds are obtained. The low-carbon, austenitic grades usually are
considered easier to weld than high-carbon austenitic or straight-chromium ferritic or
martensitic types. Nevertheless, each of the standard alloy compositions can be
welded successfully in the foundry. Using information derived from the extensive
research of Alloy Casting Institute and Steel Founders Society of America, the
foundryman often is able to tailor the composition balance especially to provide the
optimum weldability. Accordingly, castings are readily welded into fabricated structures
and welding is considered a regular part of the foundry production process
1. 2 Welding is used a procedure for upgrading casting quality during the course of
manufacture through improvement of surface conditions, or by elimination of shrinkage
voids. It is also used for producing large or complex assemblies where the size of the
completed structure precludes production as a one-piece castings, or where total quality
will be improved by dividing the structure into simpler components which can later be
welded int an integral assembly
1.3 Welds properly made do not impair high alloy castings with respect to their corrosion
resistance or their mechanical properties from sub-zero to elevated temperatures