Manual Peening

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I've heard about people manually peening their hot passes by hand with a ball-peen hammer, but never thought it did much as I am only personally familiar with shot-peening methods in the past.I _did_ do a search, but didn't find all the answers I was looking for.I was wondering what the method of manual peening is.  How hard, often, and how far do you space your hits?Also, I read that you don't want to do this on a root pass because it can conceil or start cracks.  Since it is common to get cracking on an open root with 60XX rods would a light peening help prevent this?  I imagine it would relieve the stress, allow the weld to stretch instead of the base metal pulling the weld apart and possibly letting you leave the 60XX pass without cutting it out from the back.  Everything I read says against peening the root.  Any details why?Thanks
Reply:"Peening may be used on intermediate weld layers for control of shrinkage stresses in thick welds to prevent cracking or distortion, or both. No peening shall be done on the root or surface layer of the weld or the base metal at the edges of the weld except as provided in 2.20.6.6(3). Care should be taken to prevent overlapping or cracking of the weld or base metal."5.27 D1.1 {2006}"The use of manual slag hammers, chisels, and lightweight vibrating tools for the removal of slag and spatter is allowed and shall not be considered peening."5.27.1 D1.1 {2006}~~~~~~~~~~~~"The toe of the weld may be peened with a blunt instrument, so as to produce local plastic deformation which smooths the transition between weld and base metal, while inducing a compressive residual stress. Such peening shall always be done after visual inspection, and be followed by MT as described below. Consideration should be given to the possibility of locally degraded notch toughness due to peening. In order to qualify fatigue categories X1 and K1, representative welds (all welds for non redundant structures or where peening has been applied) shall recieve MT for surface and near-surface discontinuities. Any indications which cannot be resolved by light grinding shall be repaired in conformance with 5.26.1.4."2.20.6.6(3) D1.1 {2006}Last edited by tanglediver; 08-12-2007 at 05:08 PM.City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:Cracking should not be common on 6010 open root passes. If you are experiencing cracking on the root pass, you need to identify what is causing the cracks and correct. Often times it is from indequate throat size that are unable to support stresses until a hot pass can be laid in.Last edited by reddoggoose; 08-12-2007 at 05:15 PM.Arguing with a Welding Engineer is like wrestling with a pig... after a while you realize the pig likes it
Reply:The only thing I ever peened is cast iron with a slag hammer after every pass to  help stress relieve it.  Only on  a cold weld.  I preheat cast iron to almost red when I can. It welds much better.  When I am done, I put it in a bucket of speedi dry and leave it.  My dad had a forge, it was great for stuff like that.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:I have one of those needle scalers, they are a handy tool, leaves lots of dents in a hot weld for stress relive. great for cleaning slag, not the best for a capNothing Ever Got Done By Quitting, Never Give Up.