L.N.V.M. Society Group of Institutes, Palam Extn., Part-1, Sec.-7, Dwarka, New Delhi - 45 1 Aircraft Metallurgy (According to the Syllabus Prescribed by Director General of Civil Aviation, Govt. of India) 2 Aircraft Metallurgy L.N.V.M. Society Group of Institutes, Palam Extn., Part-1, Sec.-7, Dwarka, New Delhi - 45 3 FIRST EDITION AIRCRAFT METALLURGY Prepared by L.N.V.M. Society Group o f Institutes * School of Aeronautics ( Approved by Director General of Civil Aviation, Govt. of India) * School of Engineering & Technology ( Approved by Director General of Civil Aviation, Govt. of India) Author Arjun Singh Published By L.N.V.M. Society Group of Institutes H-974, Palam Extn., Part-1, Sec-7, Dwarka, New Delhi-45 4 Aircraft Metallurgy Published By L.N.V.M. Society Group of Institutes, Palam Extn., Part-1, Sec.-7, Dwarka, New Delhi - 45 First Edition 2007 All rights reserved; no part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the publishers. Price : Rs. 250/- Type Setting Anita Gupta Cover Designed by Abdul Aziz Printed at Graphic Syndicate, Naraina, New Delhi L.N.V.M. Society Group of Institutes, Palam Extn., Part-1, Sec.-7, Dwarka, New Delhi - 45 5 Dedicated To Shri. Laxmi Narain Verma [ Who Lived An Honest Life ] 6 Aircraft Metallurgy Preface Material” is the word which is associated with every object existing in the universe. The knowledge of material enhances our understanding of physical world. The aircraft design is based on the suitability of material considering the various factors such as weight, strength, cost, reliability and easy availability. The knowledge of aircraft material is essential for aspirant of Aircraft maintenance engineering to get through their DGCA Licence papers and translate this knowledge on their day to day work in aviation field. This book is prepared by L.N.V.M. Society Group of Institute, with the dedicated efforts by it’s experienced faculty and staff with the view to sumup the vast material details under single cover to impart the essential knowledge to AME trainees to succeed in their aspired carrier. My thanks are due to those who helped me to bring out this valuable edition. I would very much appreciate criticism, suggestions and detection of errors from the readers which will be grate fully acknowledged. Arjun Singh Senior Instructor L.N.V.M. Society Group of Institutes Dated : Aug. 2006 L.N.V.M. Society Group of Institutes, Palam Extn., Part-1, Sec.-7, Dwarka, New Delhi - 45 7 CONTENTS 1. TERMS AND DEFINITIONS 7 2. FERROUS METALS : PRODUCTION OF IRONS AND THEIR PROPERTIES 10 3. FERROUS METALS : PRODUCTION OF STEELS AND ALLOY STEELS 19 4. NON-FERROUS METALS AND ALLOYS 33 5. NICKEL ALLOYS 41 6. COPPER AND ITS ALLOYS 51 7. WROUGH ALUMINIUM ALLOYS 59 8. MAGNESIUM ALLOYS 85 9. HEAT TREATMENT OF STEELS 110 10. SURFACE (CASE) HARDENING OF STEELS 125 11. HEAT TREATMENT OF NON-FERROUS METALS AND ALLOYS 133 12. IDENTIFICATION OF METALS 140 13. MECHANICAL TESTING OF METALS 143 14. MATERIAL CORROSION : IT’S NATURE AND CONTROL 159 15. CORROSION : REMOVAL AND RECTIFICATION 167 16. CORROSION : METHODS OF PROTECTION 175 17. MERCURY CONTAMINATION OF AIRCRAFT STRUCTURES 183 18. NDE : OIL AND CHALK PROCESSES 186 19. NDE : PENETRANT DYE PROCESSES 188 20. NDE : MAGNETIC FLAW DETECTION 193 21. NDE : FLUORESCENT PENETRANT PROCESSES 203 22. NDE : ENDOSCOPE INSPECTIONS 208 23. NDE : ULTRASONIC FLAW DETECTION AND THICKNESS MEASUREMENT 215 24. NDE : RADIOLOGICAL EXAMINATION OF AIRCRAFT STRUCTURE 225 25. NDE : EDDY CURRENT METHODS 236 26. SELECTION OF MATERIALS 247 27. SOFT SOLDERING 254 28. BRAZING 263 29. OXY ACETYLENE WELDING 275 30. ARC WELDING 284 31. WOODS & GLUES 299 32. FABRICS AND DOPES 317 33. PLASTICS 323 8 Aircraft Metallurgy 34. TRANSPARENT MATERIALS 331 35. NATURAL AND SYNTHETIC RUBBERS 336 36. ADVANCED COMPOSITES MATERIALS 341 37. COMPOSITE SAFETY 364 38. METHODS OF APPLYING PRESSURE DURING CURING OF COMPOSITES 372 39. METHODS OF CURING OF COMPOSITES 380 40. TYPES OF DAMAGES OF COMPOSITES AND THE METHODS OF INSPECTION 388 41. LIGHTENING PROTECTION OF COMPOSITE STRUCTURES 392 42. COMPOSITE TERMINOLOGY 394 L.N.V.M. Society Group of Institutes, Palam Extn., Part-1, Sec.-7, Dwarka, New Delhi - 45 7 CHAPTER-1 TERMS AND DEFINITIONS VARIOUS PHYSICAL TERMS USED IN WORKSHOP TECHNOLOGY Terms used in describing the properties of materials should be clearly understood by the reader. Many of these terms have acquired popular meanings which are not necessarily corrects, while others are very hazy in the minds of a majority of people. It is the author’s intention to define these terms in the following pages so that a firm foundation may be established from the equation point of view. Hardness Hardness is the property of resisting penetration or permanent distortion. The hardness of a piece of metal can usually be increased by hammering, rolling, or otherwise working on it. In the case of steel, some aluminium alloys, and a few other metals, hardness can also be increased by a heat treatment. A modified heat treatment known as annealing will soften metals. Increased hardness and strength go hand by hand. Testing apparatus has been developed for testing hardness rapidly by without destroying or harming the tested metal or part. The principle usually employed in this type of apparatus is to sink a hardened steel ball under a definite load into the material being tested. The impression made by the ball is to be measured and recorded; the smaller the impression, the harder the material. For each type of material there is a fairly definite relationship between the depth of penetration (which is represented by a Hardness Number for convenience) and the ultimate strength of the material. Tables have been worked up for different materials based on this relationship. By means of a simple hardness test and the use of such a table, the approximate tensile strength of a piece of material or finished part can be obtained without cutting out tensile test specimens or mutilating the part. Brittleness Brittleness is the property of resisting a change in the relative position of molecules, or the tendency to fracture without change of shape. Brittleness and hardness are very closely associated. Hard material is invariably more brittle than soft material. In aircraft construction the use of too brittle material must be avoided or failure will be caused by the shock loads to which it will be subjected. Malleability Malleability is the property of metals which allows them to be bent or permanently distorted without rupture. It is this property that permits the manufacture of sheets, bar stock, forging, and fabrication by bending and hammering. It is obviously the direct opposite of brittleness. Ductility Ductility is the property of metals which allows them to be drawn out without breaking. This property is essential in the manufacture of wire and tubing by drawing. It is very similar to malleability and, in fact, is generally used in place of that term to describe any material that can be easily deformed without breaking. Thus in aircraft work a material is usually referred to as soft or hard, or else is ductile or brittle. Ductile material is greatly preferred because of its ease of forming and its resistance to failure under shock loads. In order to obtain the required strength it is often necessary, however, to use a hard material. Elasticity Elasticity is the property of returning to the original shape when the force causing the change of shape is removed. All aircraft structural design is based on this property since it would not be desirable to have any member remain permanently distorted after it had been subjected to a load. Each material has a point known as the elastic limit beyond which it cannot be loaded without causing permanent distortion. In aircraft construction, members and parts are so designed that the maximum applied loads to which the airplane may be subjected will bear stress above their elastic limit. Density Density is the weight of a unit volume of the material. In aircraft work the actual weight of a material per cubic inch is preferred since this figure can be used in calculating the weight of a part before actual manufacture. The density of a material is an important consideration in deciding which material to use in the design of a part. Fusibility Fusibility is the property of being liquefied by heat. Metals are fused in welding. Steels fuse around 25000 F, aluminium alloys around 11000 F. 8 Aircraft Metallurgy Conductivity Conductivity is the property of transmitting heat or electricity. The conductivity of metals is of interest to the welder as it affects the amount of heat he must use and, to a certain extent, the design of his welding jig. Electrical conductivity is also important in connection with the bonding of airplanes to eliminate radio interference. Contraction and Expansion Contraction and expansion are caused by the cooling or heating of metals. These properties affect the design of welding jigs, castings, and the tolerances necessary for hot rolled material. HEAT-TREATMENT TERMS Critical Range Critical range , applied to steel, refer to the range of temperature between 13000 F. and 16000F. When steel passes through this temperature range, its internal structure is altered. Rapid cooling of the metal through this range of temperature will prevent the normal change of the structure, and unusual properties will be possessed by the material so treated. The heat treatment of steel is based on this phenomenon. Annealing Annealing is the process of heating steel above the critical range, holding it at that temperature until it is uniformly heated and the grain is refined, and then cooling it very slowly.