Weld-preparation
where Quality starts
Weld-preparation includes many activities.
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All of them are important for correct performance of welding operations.
This presentation could be used as a check list, for assuring that no important steps were overlooked.
Check list for Weld-preparation
Drawings provided for production should be current and updated.
The welder and the supervisor should be assured that this is the case.
For correct Weld-preparation, a suitable Welding Procedure Specification (WPS) should be ready and approved for work.
In case it is not ready it should be written and approved by the person in charge.
Weld-preparation requires that all tools and measuring instruments needed for the job be fetched and brought to the welding area, and inspected as being in good working condition. In particular fixtures and positioners need special attention.
Materials for the job, cleared by receiving inspection, should be made available in the workplace.
If heavy, suitable hoisting and manipulating accessories should be ready for use.
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Consumables as designated in the WPS, in the quantity needed for the work shift, should be kept in their original container.
Unidentified consumables should not be used.
Covered electrodes should be kept in the hot oven to avoid humidity absorption.
Consumables should meet specifications. But if special brands demonstrated in the past exceptional performance those should be preferred for improved productivity.
Welding Equipment should be subject to periodic inspection and maintenance. The welder should be instructed to check if the torch elements need replacement.
Personal Protection Equipment should be weared by all workers engaged in handling the materials or in actual welding.
Adequate Weld-preparation requires that Fume exhausters be in place and operating. Shielding screens should be deployed to protect passers by.
Personnel Qualification if required, should be verified as valid and applicable to the process involved.
Cutting, if performed as a preparatory stage, should be specified and controlled per applicable document.
(See: Cutting, Abrasive Water Jet Cutting, Electrical Discharge Cutting, Laser Beam Cutting).
Both the process and the cut parts should be inspected for conformance to requirements.
Sawing leaves generally a clean surface, but abrasive wheel cutting risks heating or burning unless performed under water cooling.
All flame or arc cutting processes may leave slag or oxidation which must be removed before welding.
Aluminum alloys, stainless steels and titanium develop oxidized surfaces to be removed with special attention before welding.
Rust, paint or lubricant may cover surfaces from manufacturing, shipping or storing.
Cleaning, (See Abrasive Blast Cleaning, Solvent Cleaning, Ultrasonic Cleaning, Alkaline Cleaning), Degreasing ( See Vapor Degreasing), Pickling (See Pickling) and Brushing must be performed as specified, to provide the cleanest surfaces for welding.
If porosity is detected in the weld, the first culprit to be investigated may be insufficient cleaning.
Once the parts to be welded are assembled in preparation for welding, Tack-welding is usually performed to keep the joints in place. See Tack Welds.
Weld Preheating shall be applied as directed in the WPS (Welding Procedure Specification), or in cool weather to remove condensation of water vapor on the metal surfaces.
Welding proper will come only after the preparatory stages listed above.
Good weld quality depends heavily on the quality of Weld-preparation.
The first Inspection of the weld is to be done by the welder, whose pride should be in the quality of the work performed.
A Resources page, listing Online Sources publishing articles on Weld-preparation, was recently added to our Website.
Click on Bulletin_113.
Click on PWL#146.
An Article on Hand Grinding was published (3) in Issue 153 of Practical Welding Letter for May 2016.
Click on PWL#153.
An Article on Selecting Wire Brushes for Weld Cleaning was published (3) in Issue 169 of Practical Welding Letter for September 2017.
Click on PWL#169.
If you did not yet find what you need, why not typing your question in the following Search Box?
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To reach a Guide to the collection of the most important Articles from Past Issues of Practical Welding Letter, click on Welding Topics.
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Processes
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We used to remind to our readers titles and links to our informative pages on:
- welding basics,
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- welding materials and
- other welding related subjects.
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