i have a large conrtact involving the laying of 6mm intermittent fillet welds. 100mm hit, 100mm miss. For various reasons the only two process that I can use are SMAW and SSFCAW. In theory the latter process should offer productivity benefits over the former. However, in trials using a 1.8mm dia. Lincoln NR203MP wire we have experienced difficulties in keeping the weld size to a 6mm leg and stop/start cracking, this after spending time training the operators. When the time taken to repair the crater cracks is taken into account, SSFCAW is slower than SMAW and is also producing oversized welds. Perhaps the SSFCAW process is unsuitable for intermittent welding! I would welcome comment and/or suggestions on where the theory is going wrong.
Many thanks in hope of useful replies.
A couple of things come to mind that may help.
Since you have a large contract, you may want to look at some machines to do your welding.
Bug-o makes a unit that can be programmed to make stitch welds. I'm not sure, but I think it can be set to pause its travel briefly at the end of each weld so that your craters will be filled. That should reduce/eliminate crater cracking. This would mean that you will need to run the FCAW process in order to use the machine.
If you can, you may want to try a gas shielded wire, there are many combinations available. We use Lincoln Outershield 71M with 100% CO2 shielding for nearly all our welding and dont have any real problem with crater cracking. When we do it usually means the welder needs to correct their technique.
Hope this helps.
CHGuilford
I would suggest that you use a smaller dia. wire such as .045" or .035". This will allow your operators to pause long enough at the start and stop of each weld to fill the crater and thus eliminate cracking, without causing excess weld size. You may want to try the .045" first as the .035" is more expensive.
By -
Date 11-29-2000 09:22
Hello,
referring to the posting of CHGuilford I would also propose to think about some portable equipment. I have attached a link to
a German company, which is producing such type of equipment. The max. welding length normally is 45 mm, but the also produce some special types. Mail me, if you wish to get some additional information.
Link: http://www.slv-halle.de/produkte/geraete/KKS2.htm
Best regards
Joerg
