1、 I AWS C5.1 73 m 07842b5 0002i23 5 m .- - AWS C5.1-73 RECOMMENDED PRACTICES FOR PLASMA-ARC WELDING Prepared by AWS Arc Welding and Arc Cutting Committee Under the Direction of AWS TechnicaI Activities Committee Jay Bland Technical Director AMERICAN WELDING SOCIETY, INC. 2501 N.W. 7th Street, Miami,
2、Florida 33125 I I t I Library of Congress Number: 73-88838 International Standard Book Number: 0-87 17 I - 107-9 American Welding Society, 2501 N.W. 7th Street, Miami, FL 33125 1973 by American Welding Society. All rights reserved. Note: By publication of these recommended practices, the American We
3、lding Society does not insure anyone utilizing these recommended practices against liability arising from the use of such recommended practices. A publication of a code. standard, or recommended practices by the American Welding Society does not carry with it the right to make, use, or sell patented
4、 items. Each prospective user should make an independent investigation. Printed in the United States of America 9. t . AWS C5.1 73 M 0784265 0002425 _ 7 - W _ Contents Foreri*osd . v Pei-soiincl . . . . . . . . . . . . . . . . . . . , . . . . . . . , . . . . . . . . . . . . . . . . . . . . , . . . ,
5、 vi 1. Scope 1 2. Definitions of Terms, . . , . , . . . , . , . . . . . . , . . . . . . . . . . . . . . . . . . . . . . 1 3. Fundamentals . 3 3 6 1 1 11 11 13 14 3.1 3.2 Process Description . . . , . . . . . . . , . . . . . . . . . . . . . . . . , . . . . . . . . . Principles of Operation . . . . .
6、, , . . . . , . . , . . . . . . . , . . . . , . . . . . . . 3. Equipment and Apparatus Requirements . . . . . . . . , . . . . . , . , . , , . . . . . Manual Welding . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . Mechanized Welding . , . . , , . , . . . . , . . . . . .
7、. . . . . . . . . . . . . . . . Powder Surfacing . . . . . , . . . . . , , . . . . . . . . . . . , . . , . . . . . . , . . , Hot Wire Surfacing . . . . . . . . . . . . . . . . . . . . , . . . . . . . , . . . , . . . . 4.1 4.2 4.3 3.4 5. Application of the Plasma-Arc WeIding Process to Metal Joining
8、, . . . . , . . , , . , . , . . . . . . I . . . . . . . . . . . . . . . . 15 5.1 General Areas of Application . , . , . . . . . , . , . . . . . . . . . . . . . . . , . 15 5.2 Base Metals . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . 16 5.3 Filler Metal Additio
9、n. , . . . . . , . , . . , . , . . . . , . . . . . . . . . . . . . . . . 16 5.3 Gases 17 5.5 Auxiliary Weld Shielding . . . . . . . , . . . . , . . , . . . . , . . . . . . . . . . . 18 5.6 Joint Design,. . , . . . . . . . :. . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . 19 5.7 Tooling
10、Practices,. . . . , . . . . . . . . . . , . , , . , . . , . , . , , . . . . . , . , . 20 5.8 Manual Welding . . . . , . . , . . . . . . . . . . . . . , . . . . . . , . . . . . . . . . . Li- 5.9 Mechanized Welding,. , . , . . . . . , . . . . , . . . . . . . . . . . . . . . . . . . . 22 5.10 Multipass
11、 Welding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . 42 5.1 I Reverse Polarity Welding . . . , , . . . . . , . , . . . . . . . . . . . . . . . . . , . 42 5.12 Reconmended Practices , . , . . , , . . . . . , . , . . . . . . . . . . . . . . . . . 42 5.13 Advantages and Liin
12、itations . . . . , . . . . . . . , . . . . . . , . . . . . . . . , . 42 39 6. Application of the Plasma-Arc Welding Process to Surfacing . , . . , . . . . . . . . . . . . . . . . , . . . , . . . . , . . . , . . . . . . 6. I General Considerations . . . . . . . . . . , . , . . . . . . . . . , . . , .
13、 . . . . . . . 6.2 Powder Surfacing . . . . . . . . , . . . . . . , . . . . . . . . . . . . . . . . . . . . . . 6.3 Hot-wire Surfacing , . . . . . , . , . . . . . . . . . , . , . . . . . . . . , . . . . . . . 46 46 46 52 7. Process Control . , . . . . , . , . . . . , . . . . , . . . . , . . . . , .
14、. . . . . . . . . . . . . . . 7.1 7.2 Joint Preparatiw and 54 . 54 54 General . . . . , . . . . . , . . . . . . . . , . . . . . . . . . . Tolerances . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . ! CON TENTS 7.3 Considerations for Welding Thin Metal Sections 55 7.4 Controlling the Opera
15、tion 58 7.5 Maintenance . 58 7.6 Inspection and Testing Methods,. . 61 7.7 Design Data and Test Results . 61 7.8 Applicable Specifications 62 8. Training and Qualification of Welders and Welding Operators 63 9. Safety Recommendations . 63 10. Practical Applications . 64 10.1 General 64 10.2 Manual a
16、nd Low-Current Plasma-Arc Welding Applications 64 10.3 Mechanized High-Current Plasma-Arc Welding Applications 65 10.4 Surfacing with the Plasma-.4rc Welding Process 65 Appendix: Occupational Noise Exposure 66 Bibliography 68 iv Foreword Plasma-arc welding was introduced as a practical fabricating p
17、rocess approximately fifteen years ago. Early applications involved melting, cutting, and spray-coating metallic materials. In the past several years, rapid advances have been made in the development of this technique, and plasma-arc welding has now achieved acceptance as an efficient metal joining
18、process. During the recent period of progress, sufficient data have been gathered and organized to yield an authoritative source of technical information on plasma-arc welding. Accordingly, the AWS Arc Welding and Arc Cutting Committee has prepared these recommended practices through the work of the
19、 Subcommittee on Plasma-Arc Welding. These recommended practices are based on a survey of plasma-arc welding as used in the metal fabricating industry. The description of plasma-arc welding and its salient features is presented here as clearly and concisely as possible. Because the plasma-arc proces
20、s is similar to gas tungsten-arc welding, similarities in the processes are not described in detail, to keep the text as brief as possible. The plasma-arc welding process, however, does have unique features in operation and equipment that are advantageous for a certain range of metal thicknesses. Th
21、ese features are fully explored in the text. The Committee developed these guidelines in the hope that they would lead to further development of the plasma-arc welding process and thus to higher quality and performance standards. Comments on this publication will be most welcome. They should be addr
22、essed to the Secretary, AWS Arc Welding and Arc Cutting Committee, American Welding Society, 2501 N. W. 7th Street, Miami. Florida 3312.5. L -E Person ne1 AWS Arc Welding and Arc Cutting Committee R. D. Ilciriri D. H. Mtrr-liri J. MI. Mir(-hell R. L. Orivi E. R. Picwc L. J. Priiwmik Hobart Brothers
23、Company A mer ican We Id in g Society Kaiser Aluminum iIoiT. I 2 / PLASMA-ARC WELDING PRACTICES Electrode , Shieldin Outer Gas Throat Length Torch Standoff g Gas P1 enum CUP Chamber Electro Setback 7-4- nmcir VI II lb Fig. I - Plusaiu-arc torch rerniitiokogy. de e Diam 2.8 Electrode setback. The dis
24、tance the electrode is recessed behind the constricting orifice measured from the outer face of the nozzle. 2.9 Keyhole. A condition in which the plasma column penetrates completely through the workpiece at the leading edge of the weld puddle. As the torch progresses, the molten metal, supported by
25、surface tension, flows in behind the keyhole to form the weld bead. 2.10 Lack of fill. Slight and blending reduction of thickness at the toe(s) of the weld generally associated with keyhole-type welds. 2.11 Multiport nozzle. A constricting nozzle containing two or more orifices located in a configur
26、ation to achieve a degree of control over the arc shape. 2.12 Nontransferred arc. An arc established between the electrode and the constricting nozzle. The workpiece is not in the electrical circuit. 2.13 Orifice gas. The gas directed through the plenum chamber and constricting orifice to form the p
27、lasma column. 2.14 Pilot arc. A low-current arc established between the electrode and the nozzle to ionize the orifice gas and facilitate starting the main welding arc. 2.15 Plenum or plenum chamber. The space between the inside wall of the constricting nozzle and the electrode. 2.16 Shielding gas.
28、A protective gas provided at the outer periphery of the arc to prevent air contamination of the weld and/or base metal. 2.17 Single port nozzle. A constricting nozzle containing one orifice, located below and concentric with the electrode. 2.18 Throat length. The length of the constricting orifice.
29、AWS C5.L 73 m 0784265 0002432 b W Fundainetituls I 3 f 2.19 Torch standoff. The distance from the bottom of the constricting nozzle to the workpiece. 2.20 Transferred arc. An arc established between the electrode and the workpiece. 3. , Fundamentals 3.1 Process Description 3.1 1 General Description
30、3.1.1.1 The distinguishing feature of the plasma-arc welding process lies in the use of a constricting orifice. Arc constriction by a nozzle brings about several changes in arc characteristics. The most important of these is that the arc can be projected as a stream of ionized gas similar to a water
31、 stream from a hose nozzle, with strong directional stability. 3.1.2 Arc-Constricting Nozzle 3.1.2.1 A wide variety of nozzles has been made and evaluated. These include the single port nozzles and multiport nozzles with holes arranged in Single Port Nozzle ific Gas Multiport Nozzle e- - AWS C5-L 73
32、 W 0784265 0002433 8 - - - 4 / PLASMA-ARC WELDING PRACTICES circles. rows, and other geometric patterns. The single port nozzles are most widely used. Among the multiport nozzles, the most widely used design is the one in which the center orifice is bracketed by two smaller ports, with a common cent
33、erline for all three openings. These more common nozzle types are shown in Fig., 2. 3.1.2.2 The electrode in the plasma-arc torch is recessed in the arc-constricting nozzle. As the arc passes through the nozzle, it is collimated and focused so that the arc heat is concentrated on a relatively small
34、area of the workpiece. This increased heat concentration. coupled with the characteristically more forceful plasma stream, can produce a narrower weld fusion zone in a certain range of metal thicknesses. 3.1.2.3 With the single port nozzles, the arc and all of the orifice gas pass through the single
35、 orifice. With the multiport nozzle shown in Fig. 2. the arc and some of the orifice gas pass through the larser center orifice, while the remainder of the orifice gas is discharged through the two smaller ports that bracket the center orifice. The effect of the gas flou from the side ports is to sq
36、ueeze the cross section of the circular plasma-arc column into an oval or elongated shape. This is particularly desirable in keyhole-mode Lvelding. 3.1.3 Keyhole-Mode Welding 3.1.3.1 In plasma-arc ivelding of certain nietal thicknesses special combinations of plasma-gas flou arc current. and veld tr
37、avel speed will produce a relatively small weld puddle with a hole penetrating completely through the base metal at the leading edge of the veld puddle (called the keyhole). The plasma-arc process is the only gas-shielded ivelding process with this unusual characteristic. 3.1.3.2 In a stable keyhole
38、-mode operation. molten metal is displaced to the top bead surface by the plasma stream (in penetrating the plate) to form the characteristic keyhole. As the plasma-arc torch is mechanically inoved along the weld joint. metal melted by the arc is forced to tlow around the plasma stream, along the mo
39、lten side surfaces of the keyhole and to the rear where the weld puddle is formed and solidified. This niotion of molten metal. and the complete penetration of the metal thickness by the keyhole allow gases and impurities to flow to the surface or be expelled more readily before solidification. This
40、 action is similar to “magnetic stirring“ developed for gas tungsten-arc welding. The maximum iveld puddle voluine and the resultant root surface profile are largely determined by the effects of a force balance between the molten weld metal surface tension and the plasma stream velocity characterist
41、ics. The bead appearance for a butt weld made in the keyhole mode is pictured in Fig. 3. 3.1.3.3 With appropriately designed weld joints, the multiport nozzle shown in Fig. 2 can be used to advantage. When the multiport nozzle is aligned to place the common centerline of the side ports perpendicular
42、 to the weld groove. the arc is elongated in line with the joint. This allovs an increase of keyhole-mode welding speeds of from 30 to 50% over those obtained with single port nozzles, without undercutting and with welds having narrower fusion and heat-affected zones. 3.1.4 Comparison of Nonconstric
43、ted and Constricted Arcs 3.1.4.1 Typical electrical and thermal differences between constricted and nonconstricted arcs are shown in Fig. 4. The schematic representation of a AWS C5-L 73 87892b5 0002434 T - - Fundamentals I 5 F,q- 2 20 10 Plasma-arc length = 0.25 in. (0.030in. diam nozzle) Gas tungs
44、ten-arc length = 0.05 in. - 0.040 in. diam electrode O 2 4 6 8 10 .+: 1- Frrtidutzrerituls 1 9 I I I I I I l l I I I l I I I 1 I I I I l 1 I l l Cu Co r n rent trol I I l 4 Contactor I I I I Electrode l I I I I Orifice r Shield lu ter !Nozzle I I I I Nozzle I (-) Ga s ing Gas 1 (+I I I 1 Electrode (
45、-1 1 ,- Orifice Gas Cool in9 Water Shielding Gas Outer Gas Nozzle AWS C5.L 73 W - 0789265 0002437 7 W 10 / PLASMA-ARC WELDING PRACTICES I GTungsten Electrode I 111 Orifice Gas 3.2.4 Hot-wire Surfacing 3.2.4.1 In the application of the plasma-arc welding process to hot-wire surfacing. filler nieta1 i
46、n wire form is resistance heated and deposited on the workpiece in the puddle formed by a pIasnia-arc torch. This application is shown schematically in Fig, 10. 3.2.4.2 The electrical circuit and apparatus used for plasma-arc surfacing are similar to the requirements for plasma-arc welding. D-C Plas
47、ma-Arc Power Supply 1 Plasm-arc Fi 11 er, Metal ma-Arc PPlY 4. Equipment and Apparatus Requirements 4.1 Manual Welding 4.1.1 General Requirements 4.1.1.1 A complete system for manual plasma-arc welding consists of a torch, control. power supply, orifice- and shielding-gas supplies, source of cooling
48、 water. and accessories such as foot switch. rheostat, timers, and remote current controls. Apparatus is presently available for operation with low welding current of O. i and high of 100 amperes. Development of higher range torches and power supplies has begun. 4.1.2 Power Supply 4.1.2.1 Transferre
49、d Arc Power Supply. Rectifier type power supplies ivith a drooping VA characteristic are generally used for plasma-arc welding. 4.1.2.2 Pilot Arc Power Supply. Pilot arc supplies are preset to deliver approximately 5 A continuously to provide a stream of ionized gas for instant ignition of the main welding current. 4.1.3 Control Unit 4.1,3.1 Incorporated in the control unit are the main power supply, pilot arc supply. flowmeters, solenoid valves for controlling orifice and shielding gases, and vater flow. Indicating current meters. cont
