9 002
西红柿炒鸡蛋做法
NICKEL
TABLE OF CONTENTS FOR THE WELDING HANDBOOK INTRODUCTION (2)
STAINLESS STEEL WELDING CHARACTERISTICS (3)
AUSTENITIC STAINLESS STEELS (3)
PRESERVATION OF CORROSION RESISTANCE (5)
Carbide Precipitation (5)
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Stress-Corrosion Cracking (5)
WELDING PREHEATING (5)
MARTENSITIC STAINLESS STEELS (5)
WELDING PREHEATING (6)
FERRITIC STAINLESS STEELS (7)
PRESERVATION OF CORROSION RESISTANCE (7)
WELDING PREHEATING (7)
PRECIPITATION HARDENING STAINLESS STEELS (7)
WELD ROD SELECTION (7)
AUSTENITIC STAINLESS STEELS (8)
MARTENSITIC STAINLESS STEELS (8)
新乡凤凰山FERRITIC STAINLESS STEELS (8)
PRECIPITATION HARDENING STAINLESS STEELS (8)
WELDING PROCESSES FOR STAINLESS STEELS (10)
WELDING DISSIMILAR METALS (10)
AUSTENITIC STAINLESS STEELS TO LOW CARBON STEELS (10)
PROCEDURES FOR WELDING TRANSITION JOINTS (10)
FERRITIC AND MARTENSITIC STAINLESS STEELS TO
CARBON OR LOW-ALLOY STEELS (11)
USE OF CHILL BARS (11)
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JOINT DESIGN (11)
PREPARATION (11)
POST/WELD CLEANING AND FINISHING (12)
WELD SPATTER (12)
FLUX REMOVAL (12)
FINISHING WELDS (12)
SOFT SOLDERING (13)
PROPER CLEANING A MUST (13)
SELECTION OF THE PROPER FLUX (13)
SELECTION OF THE PROPER SOLDER (14)
CLEANING AFTER SOLDERING (14)
随笔600
BRAZING (14)
T he information prented in this ction was originally produced by the Committee of Stainless Steel Producers, American Iron and Steel Institute. The original Handbook also contained data from ASM International publication Joining of Stainless Steels. The Committee of Stainless Steel Producers no longer exists. The Nickel Development Institute () has reprints of this handbook titled “Welding of Stainless Steels and Other Joining Methods” (A designer handbooks ries No. 9 002).
It should be noted that the data are typical or average values. Materials specifically suggested for applications described herein are made solely for the purpo of illustration to enable the reader to make his own evaluation.
The Nickel Development Institute reprinted it for distribution in August 1988. Material prented in the hand-book has been prepared for the general information of the reader and should not be ud or relied on for specific applications without first curing competent advice.Introduction
Stainless steels are iron-ba alloys containing 10.5% or more chromium. They have been ud for many industrial, architectural, chemical, and consumer applications for over a half century.
Reference is often made to stainless steel in the singular n as if it were one material. Actually there are well over
100 stainless steel alloys. Three general classifications are
ud to identify stainless steels. They are: 1. Metallurgical Structure; 2. The AlSl numbering system: namely 200, 300,
and 400 Series numbers; 3. The Unified Numbering System, which was developed by American Society for Testing Materials (ASTM) and Society of Automotive Engineers (SAE)
to apply to all commercial metals and alloys.
Stainless steels are engineering materials capable of meeting a broad range of design criteria. They exhibit
excellent corrosion resistance, strength at elevated temperature, toughness at cryogenic temperature, and fabrication characteristics and they are lected for a broad range of consumer, commercial, and industrial applications. They are ud for the demanding requirements of chemical processing to the delicate handling of food and pharmaceuticals. They are preferred over many othe
r
materials becau of their performance in even the most aggressive environments, and they are fabricated by methods common to most manufacturers.
In the fabrication of stainless steel products, components, or equipment, manufacturers employ welding as the principal joining method. Stainless steels are welded materials, and a welded joint can provide optimum corrosion resistance, strength, and fabrication economy. However, designers should recognize that any metal, including stainless steels, may undergo certain changes during welding. It is necessary, therefore, to exerci a reasonable degree of care during welding to minimize or prevent any deleterious effects that may occur, and to prerve the same degree of corrosion resistance and strength in the weld zone that is an inherent
part of the ba metal.
The purpo of this booklet is to help designers and manufacturing engineers achieve a better understanding of
the welding characteristics of stainless steels, so they may exerci better control over the finished products with respect蛋挞如何做
to welding. In addition to welding, other ancillary joining methods are discusd, including soldering and brazing.
The Specialty Steel Industry of North America
(SSINA) and the individual companies it
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reprents have made every effort to ensure that
the information prented in this handbook is
technically correct. However, neither the SSINA
nor its member companies warrants the accuracy
of the information contained in this handbook or
its suitability for any general and specific u,
and assumes no liability or responsibility of any
kind in connection with the u of this information.
The reader is advid that the material contained
herein should not be ud or relied on for any
specific or general applications without first
curing competent advice.
2
Stainless Steel Welding Characteristics
During the welding of stainless steels, the temperatures of the ba metal adjacent to the weld reach levels at which microstructural transformations occur. The degree to which the changes occur, and their effect on the finished weldment — in terms of resistance to corrosion and mechanical properties — depends upon alloy content, thickness, filler metal, joint design, weld method, and welder skill. Regardless of the changes that take place, the principal objective in welding stainless steels is to provide a sound joint with qualities equal to or better than tho of the ba metal, allowing for any metallurgical changes that take place in the ba metal adjacent to the weld and any differences in the weld filler metal.
趣味性
For purpos of discussion, in welding there are three zones of principal concern: 1) The solidified weld metal, compod of either ba metal or ba metal and filler metal; 2) the heat-affected zone (HAZ) in which the ba metal is heated to high temperatures but less than the melting temperature; and 3) the ba metal which is only moderately warmed or not warmed at all. The three zones are illustrated by the drawing in Figure 1. Although risking over-simplification, the following discussion will be helpful in understanding the metallurgical characteristics of stainless steels and how their microstructures can change during welding.
AUSTENITIC STAINLESS STEELS
Austenitic stainless steels (Table 1) containing chromium and nickel as the principal alloying elements (in addition to iron) are identified as 300 Series (UNS designated S3xxxx). Tho containing chromium, nickel, and mangane (in addition to iron) are identified as 200 Series (UNS designated S2xxxx).
The stainless steels in the austenitic group have different compositions and properties but many common characteristics. They can be hardened by cold working, but not by heat treatment. In the annealed condition, all are nonmagnetic, although some may become slightly magnetic by cold worki
ng. At room temperature the 300 and 200 Series stainless steels retain an austenitic microstructure.
While resistance to corrosion is their principal attribute, they are also lected for their excellent strength properties at high or extremely low temperatures. They are considered to be the most weldable of the high-alloy steels and can be welded by all fusion and resistance welding process. Comparatively little trouble is experienced in making satisfactory welded joints if their inherent physical characteristics and mechanical properties are given proper consideration.
In comparison with mild steel, for example, the austenitic stainless steels have veral characteristics that require some revision of welding procedures that are considered standard for mild steel. As illustrated in Table 2, the melting point of the austenitic grades is lower, so less heat is required to produce fusion. Their electrical resistance is higher than that of mild steel so less electrical current (lower heat ttings) is required for welding. The stainless steels also have a lower coefficient of thermal conductivity, which caus a tendency for heat to concentrate in a small zone adjacent to the weld. The austenitic stainless steels also have coefficients of thermal expansion approximately 50% greater than mild steel, which calls for
more attention to the control of warpage and distortion.
Table 2
Comparison of Welding Characteristics of 304 Stainless Steel with Carbon Steel
304
304 at 212 F has a
304 results in the generation of more heat for the
304.
304 conducts heat much more slowly than carbon steel thus 304 requires less heat to produce fusion, which means faster 304 expands and contracts at a faster rate than carbon steel,
3
4
An important part of successful welding of the austenitic grades, therefore, requires proper lection of alloy (for both the ba metal and filler rod), and correct welding procedures.For the stainless steels more complex in composition, heavier in ctions or the end-u conditions more demanding (which narrows the choice of a ba metal), a greater knowledge of stainless steel metallurgy is desirable.
Two important objectives in making weld joints in austenitic stainless steels are: (1) prervation of corrosion resistance,
and (2) prevention or cracking.
