Casting-Repair,
back to service from scrap
Casting-Repair is an essential economic necessity.
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Casting-Repair is a complex of knowledge, technology and skills.
Castings whose standing or function is compromised need Casting Repair.
Casting affected by wear, corrosion, breakage or other weakened state must be restored to acceptable working condition.
Castings are metal bodies built by pouring molten metal in suitable molds, containing a hollow cavity of the desired shape, and letting it solidify as the temperature comes back to ambient while heat is dissipated to the environment.
Casting is also the process by which these metal bodies are manufactured. It was mastered in ancient times by artists who produced cast art work still looked at for inspiration and studied at present.
Most common metals can be shaped in cast form. The basic processes are long known from the dawn of civilization. Several old bronze castings from Greek and Roman artists are displayed in Museums for being admired as proof of antique skill.
Cast artworks from China are famous and inspiring to these days.
The study of ancient technological prowess and the reconstruction of old techniques is a matter of interest to historians and technologists of all times.
A new list of online Resources on Weld Repair of Castings is now available by clicking on the link to Bulletin_105.
Casting-Repair techniques
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As casting is still a most important modern manufacturing process, techniques were developed to salvage and repair by welding occasional casting defects, machining errors or broken or fractured features of cast parts.
When approaching Casting-Repair one should do whatever is needed to know exactly which are the material and the condition of the object. By trying any welding procedure without sufficient previous information one may damage the body beyond repair.
General information on weldability of various materials can be found in several specific pages in our website. One should remark that definite properties of the same material may be quite different depending on the manufacturing processes employed in the given case.
If a welding process is sought for Casting-Repair of a certain metal, the weldability of the cast metal involved should be ascertained beforehand. One should know that the so called white cast iron has no weldability, meaning that one should never try to weld it.
For other cast irons the weldability may depend on special techniques. Widely applied is some form of preheating before welding to prevent cracking due to thermal stresses and to reduce residual stresses, distortion and hardness.
A special section providing information on Repairing a crack in Cast Iron is included in our page on Cast Iron Welding, with the warning that it refers to Gray Cast Iron without special strength requirements.
Besides cast iron, most other cast metals, like cast steel, stainless steels, aluminum, magnesium, titanium, copper alloys can in principle be subject to Casting-Repair, but attention must be paid to the specific weldability of the material in cause.
While the most common oxy-fuel flame and electric arc processes are used commonly, special processes involving high energy beam (laser beam or electron beam) can be used sometimes to take advantage of the fact that these may easily reach the bottom of cavities from a distance.
If welding is deemed dangerous for any reason for a certain material, alternative Casting-Repair procedures like braze-welding or brazing may be more suitable.
The Chapter 8 of the ninth edition of the AWS Welding Handbook, Volume 4 is a most informative resource for welding of Cast Irons.
See AWS WHB-4.9.
A Chapter titled Repair Welding of Castings (4 pages) from the
ASM Handbook, Volume 15: Casting is downloadable from ASM (RWC).
Even in simple cases, the development of suitable welding Casting-Repair techniques should be thoroughly studied in advance, and applied first on scraps for selecting proper parameters before issuing the Welding Procedure Specification.
Also the manual skill of the welders may be important such that training efforts must be usually taken before tackling a sensitive job. Welder qualification may be a requirement of applicable codes.
Click on PWL#155.
Watch the following Video on
Cast Iron Weld Repair |
Any questions or comments or feedback? Write them down and send them to us by e-mail. Click on the Contact Us button in the NavBar at top left of every page.
Let us remind you that, if you are interested, we offer a no cost subscription to our Practical Welding Letter and a bonus book in pdf format to be made available for download to your computer on the subject of
PRACTICAL HARDNESS TESTING MADE SIMPLE. Click on Subscription.
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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