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Up Topic Welding Industry / Technical Discussions / Preheating method
- - By zambrota (**) Date 03-25-2011 01:04
Your prompt answer would be much appreciated.
I have to repair gray cast iron by welding through 100mm thick wall section. Client supplied the welding procedure. It says: "Preheating of casting to be done in such a way as to place the resulting weld in compression". What does it mean? Any idea or reference link? What method of preheating is it? Has anybody used that method in practice? Please help.

Thanks guys
Parent - By tigerlee Date 03-25-2011 02:13
You can see the AWS D11.2.
Various kind of cast steel repair method and sample procedure shown on AWS D11.2.
Parent - By MBSims (****) Date 03-25-2011 02:37
Good luck.  Welding gray cast iron is rarely successful, especially groove welds in thick sections.  Mechanical repairs, such as Metalock or Lock 'n Stitch type, are a better choice.
Parent - - By welderbrent (*****) Date 03-25-2011 02:52
Better you than me.

I can think of one possibility...under a clamping or restraining force, as you apply the pre-heat and the part attempts to expand with the increasing heat it will be under compression.

Good Luck.

Have a Great Day,  Brent
Parent - - By zambrota (**) Date 03-25-2011 05:22
Thanks Brent,

The problem is the completed weld will be under tension due to the shrinkage stresses during welding pool solidification. Weld is anyway under compression while still hot because of high restraint. Question is how to get compression in weld after cooling?

Thanks
Parent - - By DaveBoyer (*****) Date 03-26-2011 01:51
You would have to heat the part where it is NOT broken to expand that material a greater ammount then the welded area will contract.

This is easier in theory than in practice.
Parent - - By MBSims (****) Date 03-26-2011 21:23
"The only difference between theory and practice is that, in theory, there's no difference between theory and practice."
:lol:
Parent - By welderbrent (*****) Date 03-27-2011 03:20
I have to remember that one. 

Have a Great Day,  Brent
Parent - By Joseph P. Kane (****) Date 03-27-2011 19:00
OK Then!  Why not just say ..." It is easier to talk about, than to put in practice!"
Up Topic Welding Industry / Technical Discussions / Preheating method

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