solda apostila cswip welding inspection notes and questions[1]

Download Solda Apostila CSWIP Welding Inspection Notes and Questions[1]

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    WELDING INSPECTION - STEELS CONTENTS PAGE TERMINOLOGY 3 THE DUTIES OF A WELDING INSPECTOR 9 CODES AND STANDARDS 12 THE WELDING PROCEDURE 14 DESTRUCTIVE TESTING 20 SYMBOLS 27 MATERIALS 32 FOUR FACTORS FOR ESTABLISHING A WELD 37 WELDABILITY 38 RESIDUAL STRESS AND DISTORTION 44 HEAT TREATMENT 47 CALIBRATION 49 DEFECTS DETECTED BY SURFACE INSPECTION 50 INTERNAL DEFECTS 54 MACRO EXAMINATION 58 NON-DESTRUCTIVE TESTING 61 REPAIR BY WELDING 66 CONSUMABLES 70 WELDING POSITIONS 75

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    WELDING PROCESSES

    MANUAL METAL ARC WELDING 78

    TUNGSTEN INERT GAS WELDING 83 METAL INERT GAS WELDING 88 SUBMERGED ARC WELDING 94 AUTOMATIC METAL ARC WELDING 101 ELECTRON BEAM WELDING 103 ELECTRO-SLAG WELDING 105

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    TERMINOLOGY

    Use of the correct terminology is important. CSWIP uses BS 499 standard. Frequently the terms weld and joint are used incorrectly. Exact definitions are given in BS 499 PT 1 1983 - Welding terminology and BS 499 Pt 2: 1980 Weld symbols. TYPES OF WELD Butt Weld Fillet Weld Edge Weld small indentations at each weld Spot Weld (Illustration depicts resistance weld. Spot welds can be made with MIG or TIG processes.) The four basic welds can be used to join various types of joints.

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    TYPES OF JOINT The following are some typical joints: BUTT ----------------------------------------------------------------------------------------------------------- TEE ----------------------------------------------------------------------------------------------------------- CORNER ----------------------------------------------------------------------------------------------------------- LAP

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    PLATE EDGE PREPARATION FOR BUTT WELDS The illustrations show standard terminology for the various features of plate edge preparations. Square edged closed butt Square edged open butt with backing strip < 3 mm sheet, > 3 mm - plate (considerations - penetration control, backing strip of the same material and usually removed) Backing bar - ceramic or copper Fusible insert - electric bolt (e.b) (copper can cause loquation cracking) (uses TIG process) Single V Single bevel Double V Double bevel Single J Single U Double J Double U

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    included angle bevel angle bevel angle width sidewall face radius root face root gap land FEATURES OF A COMPLETED WELD A butt weld in plate, made by welding from both sides, has two weld faces and four toes. In a full penetration weld made from one side, the protruding weld on the underside is called the penetration bead, which also has two toes. The root is defined (BS 499) as the zone on the side of the first run farthest from the welder. toe face toe root toe face toe If a weld is sectioned, polished and etched, the fusion boundary can be established. Metal lying between the two fusion boundaries is weld metal - a mixture of deposited metal and plate metal that has been melted. The fusion zone is the area of highest dilution between filler metal and parent plate. Adjacent to the fusion boundary is the heat affected zone (HAZ), in which the plate material has had its metallurgical structure modified by the heat of welding. excess weld metal fusion zone throat fusion boundary / line HAZ Excess weld metal is the correct term, not weld reinforcement. Excess weld metal lying outside the plane joining the toes of the weld. Fillet welds have similar features.

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    toes face fusion boundary root HAZ The shape of a fillet in cross-section is described in three terms. Mitre fillet Convex fillet Concave fillet A convex fillet has a poor toe blend - greater notch effect and sharper angle at toe, not used in fatigue situations. A concave fillet has a better toe blend for fatigue situations, however a reduced throat. The concave weld may be made by welding alone or by subsequent grinding. SIZE OF WELDS Full Penetration Butt Welds. The general rules are: design throat thickness = thickness of the thinner part joined. cap width = prep width + 10% either side (for open prep, not specified in BS 499) Partial Penetration Butt Welds. The term partial penetration strictly implies butt welds that are designed to have less than full penetration. Failure to achieve full penetration when it is wanted should be listed as the defect incomplete penetration. The design throat thickness of a partial penetration weld is t1 and the actual throat thickness is t2. With a partial penetration weld made from both sides, the design throat thickness is t1 + t1 and the actual throat thickness is t2 + t2. Note that the degree of penetration must be known. t1 t2 t1 t2 t1 t2 t1 t2 t1 t2 t1 t2 Fillet Welds. Fillet weld sizes are calculated by reference to allowable shear stress on the throat area, i.e.

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    throat area = design throat thickness x length of weld. The size required is specified on drawings in terms of leg length (l). For fillet welds with equal leg lengths l = 1.4 t1. This does not apply to concave fillet welds. l l t1 = t2 t1 t1 t1 t1 t2 t2 If an asymmetrical weld is required, both leg lengths are specified and t1 is taken as the minimum throat dimension. l1 l2 t1 Deep penetration fillet weld. With high current density processes, e.g. submerged arc and MIG (spray), penetration along the joint line can be produced. This gives an increase in throat thickness with no change in leg length. l l t1 t1

    THE DUTIES OF THE WELDING INSPECTOR VISUAL INSPECTION

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    At any point in the course of welding, i.e. tacking, root pass, filler pass or capping pass, but particularly for the root and cap, a detailed inspection may be required. British Standard 5289: 1976 gives guidance on tools and responsibilities together with sketches of typical defects. The inspector at this point must - a) observe, identify and perhaps record (measure) the features of the weld. b) decide whether the weld is acceptable in terms of the particular levels that are permitted; defect levels may be in-house or national codes of practice. When the defect size is in excess of the permitted level then either a concession must be applied for (from a competent person), or the weld rejected. AIDS OF VISUAL INSPECTION Illumination: Good lighting is essential. Inspection Lenses: The magnification should not exceed 2 - 2.5 diameters. If higher magnification is required use a binocular microscope. Optical viewing can progressively develop from eyesight, to use of a hand torch and mirror, to the addition of a magnifier and light source. In order to achieve accessibility, remote probe units are available which must have the following properties. a) Large field of vision b) Freedom from distortion of image c) Accurate preservation of colour values d) Adequacy of illumination CODE OF PRACTICE A code of practice for an inspection department should take the form outlined below. It is appreciated that full implementation of the code would be extremely costly and therefore it may be necessary to reduce the amount of inspection to less than is theoretically required. The inspector should be familiar with the following: a) All applicable documents b) Workmanship standards c) All phases of good workshop practice d) Tools and measuring devices INSPECTION BEFORE WELDING Before Assembly: Check * All applicable documents. * Quality plan is authorised and endorsed with signature, date and company stamp. * Application standard is up to date with the latest edition, revision or amendment. * The drawings are clear, the issue number is marked and the latest revision is used.

    * Welding procedure sheets (specifications) are available, have been approved and are employed in pro

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