flyingbrick Posted October 5, 2013 Share Posted October 5, 2013 Hi all. Paranoia Is on the rise. I'm ready to blaze my sump together but need to know if there is any reason why I shouldn't use this scrap Ali tread plate of unknown constitution. I know it will look daft but don't care. I'll say its for added surface area and cooling or something It will be welded to the cast flanges with aluminium rods which are are also unknown ( I'll check the code on them in morning) It's obviously a important part and it will be subjected to heat cycling and vibration. Quote Link to comment Share on other sites More sharing options...
Guypie Posted October 5, 2013 Share Posted October 5, 2013 A lot of manufacturers use cast alloy, i cant imagine there being a problem as long as its all thick enough to cope with the stress. Probably just anneal it after welding to relieve hardness. This page has some info on ali motorbike tank construction that may be relevant http://www.eurospares.com/frame7.htm Quote Link to comment Share on other sites More sharing options...
flyingbrick Posted October 5, 2013 Author Share Posted October 5, 2013 It's not the cast I'm worried about really. It's the cast mixed with tread plate mixed with heat cycling . I have NO experience with this sort of thing. I did a shit tone of reading last night which helped with regards to temps, pre heating, removing contaminates etc. I guess worst case is that it cracks and I have to replace it/ who cares Quote Link to comment Share on other sites More sharing options...
eke_zetec_RWD Posted October 5, 2013 Share Posted October 5, 2013 Basically if it welds nice then it should be sweet. The tread plate will be 5000 series normally and very weldable. The cast will either weld nice or it will crack while cooling. Depending one the pile of scrap alloy the put in the melting pot to make it in the first place lol. 1 Quote Link to comment Share on other sites More sharing options...
flyingbrick Posted October 6, 2013 Author Share Posted October 6, 2013 Thanks man. If it doesn't crack while cooling should I have it annealed afterward to remove stresses? Quote Link to comment Share on other sites More sharing options...
flyingbrick Posted October 6, 2013 Author Share Posted October 6, 2013 So I tacked the main bits together and couldn't help but have a play on the front edge ( where I'm guessing it won't cause too much war page while not bolted down) Basically my first pass was terrible. It was popping and cracking and melting away in spots to reveal huge craters. I used copious amounts of filler and worked quickly at 150A. The filler seemed to flush all the shit out. I was left with a very big bulbus weld covered in black flecks like I'd thrown black sand at wet silver paint. I then ground all of the weld off and started again- then just had a few spots to grind out and fill in afterward. I did second run at 100A and i was able to go at a much nicer speed- but material was stinking hot by then. This pic shows the impurities that have popped to the surface when I got a bit off track on the second pass. And overall. I'm pretty happy with that! And it hasn't cracked. It's lumpy because I'm using 3mm filler rods as that's all I have. More dabs of 2mm rod be nicer. Is there any harm is running back over the weld to tidy it up? Any advice much appreciated. I must be on the right track? Quote Link to comment Share on other sites More sharing options...
downtrail Posted October 7, 2013 Share Posted October 7, 2013 The big craters will be more than likely the material was not clean enough to start with. You have to get rid of the layer that oxidixes on alloy before welding as its melting point is higher than the actual alloy so as it melts away it'll crater the alloy as you have over heated it. Aluminium needs to be super clean. inside and out when welding. even if you have cleaned the outside where the bead will be if you havent cleaned the inside or the other side of the plate the impurities will rise and cause those black specs you describe. Cleanliness is godliness when welding anything. Best way is to mechanically clean it first to get rid of the oxide layer. Use either sand paper or simmiler but not cutting / grinding discs. wire wheel is ok as long as it has not been used for steel as it'll impregnate the alloy with bits of steel and you may be worse off. then chemically clean it with a solvent I use acetone. Good luck and keep it up weld dosen't look too bad from photos Quote Link to comment Share on other sites More sharing options...
flyingbrick Posted October 7, 2013 Author Share Posted October 7, 2013 Cheers man. I did clean it with a stainless wire wheel but it wasn't new and I didn't go far enough away from the weld. When I do the sides I 'll use a new stainless wheel etc and solvents as you say. Cheers! Quote Link to comment Share on other sites More sharing options...
Mitch.W Posted October 7, 2013 Share Posted October 7, 2013 yeah, if that stainless wire wheel had been used on mild steel it would have left shit on it the aluminium , you need separate tools for aluminium and steel and whatnot Quote Link to comment Share on other sites More sharing options...
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