WELDING OPERATIONS I

SUBCOURSE NO. OD1651

United States Army Combined Arms support Command, Fort Lee, Virginia
 

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GENERAL

The purpose of this course is to introduce the basic requirements involved in metal-arc welding operations. The scope of this subcourse consists of describing the classification of electrodes and their intended uses; describing automotive welding processes, materials and identification processes; describing the methods of destructive and nondestructive testing of welds and troubleshooting procedures; describing the type and techniques of joint design; and describing the theory, principles, and procedures of welding armor plate. Six credit hours are awarded for successful completion of this subcourse.

Lesson 1: ELECTRODES CLASSIFICATION AND INTENDED USES; AUTOMOTIVE WELDING PROCESSES, MATERIALS, AND IDENTIFICATION PROCESSES; METHODS OF DESTRUCTIVE AND NONDESTRUCTIVE TESTING OF WELDS AND TROUBLESHOOTING PROCEDURES; TYPES AND TECHNIQUES OF JOINT DESIGN; AND THE THEORY, PRINCIPLES, AND PROCEDURES OF WELDING ARMOR PLATE


1.    INTRODUCTION

Welding is one of the most important functions performed in both an intermediate direct support (IDS) and intermediate general support (IGS) maintenance company. Experience gained during the second world war revealed that many broken parts can be welded and put back into service, thus often saving the expense of fabricating or purchasing a new piece of equipment. As a result of this experience, a service section containing a metalworking shop with welding capabilities is now established within these maintenance organizations.

The first task of this lesson is designed to assist you in learning the processes for identifying electrodes by classification, and intended uses; the automotive welding processes, materials, and identification processes, and the techniques of joint design as they pertain to electric arc welding.


2.    IDENTIFICATION AND USES OF ELECTRODES

a. General. During electric arc welding operations, when molten metal is exposed to the atmosphere, it will absorb oxygen and nitrogen from the air and will become brittle. To protect it from this damaging reaction, a slag cover over the molten or solidifying metal must be provided. This cover is made by coating the electrode with a substance that will vaporize and defuse in the arc stream to form a protective cover that will stabilize the arc and protect the metal. Because there are several different types of metals used in Army equipment, it is necessary to use the correct electrode whenever welding this equipment. The following subparagraphs describe the classification of electrodes, their intended uses, and the factors to be considered when selecting electrodes.

b. Factors in Selecting an Electrode. The purpose of selecting the correct type electrode is to provide arc stability, smoothness of the weld bead, easy slag removal, and minimum spatter that are essential to top quality welding. Factors to be considered when selecting electrodes are:
(1) Specific metal properties required in the weld such as corrosion resistance, ductility, or high tensile strength.
(2) Type of base metal to be welded.
(3) Position of the weld, such as flat or vertical.
(4) The type of electrical current that is available.
(5) Electric current polarity (straight or reverse) which is available.
(6) Dimensions of the section to be welded.
(7) The type of fit that the work permits.

c. Classification of Electrodes.
(1) Metal-arc electrodes may be grouped and classified as bare electrodes, thinly coated electrodes, and shielded-arc or heavy coated electrodes. A classification number series, (formulated by the American Welding Society), has been adopted by the welding industry for the identification of electrodes. By means of this numbering system, the following characteristics of a given electrode can be identified:
(a) Whether the electrode has a light or heavy coating.
(b) The composition of the coating.
(c) The recommended welding position.
(d) The type of electric current (direct or alternating current) and the polarity for which the electrode is intended.
(e) The base metal for which the electrode is recommended.
(2) The identification system for steel arc welding electrodes is a four digit number series preceded by a letter as described below:
(a) The symbol E indicates that the electrode is intended for use in electrical welding.
(b) The first two (or three) digits of the number indicate the tensile strength (the resistance of the material to forces trying to pull it apart), in thousands of pounds per square inch, of the deposited metal.
(c) The third (or fourth) digit indicates the position of the weld. The number 0 in either one of these positions indicates the classification is not used. The number 1 indicates the electrode may be used for all welding positions. The number 2 indicates that the electrode may be used only in the flat and horizontal positions. The number 3 indicates the electrode is to be used only in the flat welding position.
(d) The fourth (or last) digit indicates the type of coating on the electrode, and the power supply (either alternating current
(ac) or direct current (dc), straight polarity (sp), or reverse polarity (rp)) to be used with the pertinent electrode.
(e) A listing of the types of coatings, welding currents, and polarity requirements of the fourth (or last) identifying digit of the electrode is listed below.
(f) The number E6010 identifies an electric welding electrode with a minimum stress relieved tensile strength of 60,000 psi (pounds per square inch). It can be used to weld in all positions, preferably using direct current reverse polarity electricity. However, alternating current and direct current straight polarity can also be used.


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