Welding ppt pdf

Embed Size px. Start on. Show related SlideShares at end. WordPress Shortcode. Share Email. Top clipped slide. Download Now Download Download to read offline. Welding ppt Nov. Welding defects. Oxy acetylene welding.

Heating ppt. Welding and types. Solar industrial heating system ppt. Welding, Cutting, and Brazing Techniques. Welding for engineers chapter 1. General Welding Safety Practices. Belt drive. Related Books Free with a 30 day trial from Scribd. Related Audiobooks Free with a 30 day trial from Scribd. Outstanding Leadership Stan Toler. Welding ppt 1. WELDING — Welding is a materials joining process which produces coalescence of materials by heating them to suitable temperatures with or without the application of pressure or by the application of pressure alone, and with or without the use of filler material.

Avoid long arcs. Slow are travel speed. Long arc. Tool large a diameter electrode. Correct arc travel speed. Correct arc length. Correct diameter electrode as per metal thickness. Proper manipulation of electrode. Porosity Blow hole or gas pocket Or Group of pine holes on the surface of the weld caused by gas entrapment. Porosity Porosity is the presence of cavities in the weld metal caused by the freezing in of gas released from the weld pool as it solidifies Porosity Spatter Small metal particles which are thrown out of the arc during welding along the weld.

Wrong polarity in DC. Use of long arc. Arc blow. Uneven flux coated electrode. Use good flux-coated electrode. Edge of plate melted off Edge of plate melted off in lap and corner joints only. Use of excessive current. Wrong manipulation of the electrode. Set correct current. Ensure correct manipulation of electrode. Deposit additional weld metal to increase throat thickness.

Crack A hairline separation exhibits in the root or middle or surface of the weld metal or parent metal. Crack Hydrogen Crack Crack: It is a discontinuity produced either by tearing of the weld metal when it is in plastic stage and is solidifying from the molten state and is still above degree C which is called hot crack, or by fracture when cold when it is termed as cold crack.

Crack which is visible on the surface is called a surface crack and a crack which can only be detected by radiography or fracturing, say by nick break test, is called Internal crack. Cracks in fusion welded joints may occur either in weld metal or in parent metal, e. Weld metal crack can generally be classified as longitudinal, transverse, crater and "hairline" which are usually associated with slag inclusions. Sometimes longitudinal crack in a weld seam may emanate from crater cracks.

Parent metal crack usually means crack within the blackish HAZ, which may be longitudinal, or transverse to seam or sometimes just under the run. Transverse crack in Parent metal may also originate from crack in the weld metal. Fast cooling. Improper welding techniques. Poor ductility, Absence of preheating and post-heating on high carbon steels. Cool slowly. Use fewer passes. Use proper welding technique. Internal defects Incomplete penetration Failure of weld metal to reach the root of the joint.

Welding speed too much. Less current. Use of larger dia. Inadequate cleaning or gouging before depositing sealing run. Wrong angle of electrode.

Insufficient root gap. Ensure correct angle of bevel and required root gap. Use correct size of electrode. Correct welding speed required.

Correct current setting required. Wrong size and type of electrode. Excessive current. Long are length. Improper welding technique. Inadequate cleaning of each run in multi-run welding. Use correct type of electrode. Use correct arc length. Use correct welding technique. Ensure thorough cleaning of each run in multi-run welding. Slag Inclusions Effects of faults Thickness of base metal reduced. Weakens the strength of weld. Reduces the throat thickness. Consumes more electrode.

Change in base metal properties. Poor weld appearance. Waste of labour and materials. Failure of joints will lead to accidents. The job can be used after the test.

The test to be carried out on welded specimens by destruction is called destructive test. The job cannot be used after the test. Visual inspection non-destructive test This is one of the important inspection methods without much expense.

This method of inspection needs a magnifying glass, a steel footrule, try square and welding gauges. Visual inspection is made in three stages namely: - before welding - during welding - after welding Visual inspection before welding The operator must be familiar with the type of work, electrode and welding machine.

The following factors are to be ensured. The material to be welded is of weldable quality. The edges have been properly prepared for welding as per thickness of the plate. Setting of root gap. Proper procedure to be followed to control distortion. Polarity of the electrodes in the case of DC welding current.

Current setting according to the size of the electrode and position of welding. Whether any jigs and fixtures are necessary to ensure proper alignment. Proper facilities should exist for storing and drying of the electrodes. Visual inspection during welding The following points are to be checked. Studying the sequence of weld deposit.

Examining whether each weld is cleaned adequately before making the next run in multi-run welding. Shape of the bead, angle of electrode during welding, amperage, speed of travel, arc length, correct manipulation of the electrode and control of spatters.

Inspection after welding Surface defects in and around the welds, such as cracks, longitudinal and transverse , undercut, overlap, excessive convexity of contour, the weld surface smoothness of the run and penetration and control of distortion are to be inspected. Check points for inspection Shape of profile shall be checked by measuring the dimensions of the weld. In butt welds the surface should be slightly convex.

In fillet welds the contour may be convex or concave. Uniformity of surface height and spacing of the ripples are an indication of the quality of workmanship.

Degree of undercut. Smoothness of joint where welding is recommended. Freedom from surface cavities and trapped slag. Deposition of runs, single or multiple. Penetration bead in butt weld. Quality of the weld metal. The various tests to be conducted on welded joints are determined mainly by the service conditions to which the welded components will be subjected to. It is also necessary to draw samples on a scientific basis and test them not only to control the quality of the weld, but also to assess the skill and ability of the welder.

Non-destructive testing Destructive testing Non-destructive testing NDT In this method the test to be carried out is done on the job itself without destroying it and after the test, the job can still be used. Destructive testing In this method the tests are carried out on welded specimens by destruction. The specimen will be spoiled during the test and cannot be reused. In general the above mechanical tests are the least expensive and most reliable for assessing the weld quality.

Therefore, these tests are most widely carried out. Non-destructive testing methods are classified as common testing and special testing methods. The weld surface and joint are examined visually with naked yes preferably with the help of a magnifying with naked eyes preferably with the help of a magnifying lens. Visual examination can help in detecting the following defects on the surface of the weld. Porosity Surface defects Undercut Improper profile and dimensional accuracy Poor weld appearance Incomplete penetration.

Leak or pressure test This test is used to test welded pressure vessels, tanks and pipelines to determine if leaks are present. The welded vessel, after closing all its outlets, is subjected to internal pressure using water, air or kerosene. The internal pressure depends upon the working pressure in the welded joint. The internal pressure may be raised to two times the working pressure of the vessel.

The weld may be tested as follows. The pressure on the gauge may be noted immediately after applying the internal pressure and again after, say, 12 to 24 hours. Any drop in pressure reading indicates a leak. After generating air pressure in the vessel, soap solution may be applied on the weld seam and carefully inspected for bubbles which would indicate leak.

Stethoscopic sound test The principle of this test is that defect-free weld metal gives a good ringing sound when struck with a hammer whereas a weld metal containing defects give a flat sound. An ordinary physicians stethoscope and a hammer may be used to magnify and identify the sound. Structural welds and welds in pressure vessels have been successfully tested using this method.

Dye is applied on cleaned test surface After hold time, surface is cleaned using cleaner. A liquid developer white in colour is then sprayed on the weld. The coloured dye comes out in the shape of surface defects into the white developer coating. The defect can be seen in normal light with naked eyes. Stages of LPI Following steps are involved in penetrant inspection : Surface preparation Application of the penetrant Controlling time for penetration.

Removal of excess penetrant. Application of developer. Enter the email address you signed up with and we'll email you a reset link. Need an account? Click here to sign up. Download Free PDF. Lecture -2 Classification of Welding Processes I. Social Mufti. A short summary of this paper. Download Download PDF.

Translate PDF. Lecture - 2 Classification of Welding Processes I Welding is a process of joining metallic components with or without application of heat, with or without pressure and with or without filler metal.

A range of welding processes have been developed so far using single or a combination above factors namely heat, pressure and filler. Thus, the composition of the autogenous weld metal corresponds to the base metal only.