Solid State Welding - Oxidation

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Hello all. Firstly I'd like to say what a great forum. I don't do any welding myself, but trawling through previous posts I have learned some useful information which will help with a materials exam I have tomorrow. I'm hoping somebody may be able to help in regards to the followin question which is likely to come up in my exam:The following solid state welding processes could all be used for fabrication of low carbon steelResistance Welding    Friction Welding    Ultrasonic Welding    Flash Butt WeldingWith the aid of suitable sketched, briefly describe the principe of the 4 above cases with particular reference to how each of these welding processes deals with oxidation of the welded area.I am aware of what each process involves, although I have no idea how each deals with oxidation. (I am aware of inert gas used in MIG / TIG etc). I've looked online and can only find limited info. I only need a brief idea for each - If anyone could help or point me in the right direction it would be much appreciated. Thanks in advance for any replies. Jordan
Reply:.....and I suppose  that you don't have enough time to do any searching on your own?Blackbird
Reply:Originally Posted by jordan_bHello all. Firstly I'd like to say what a great forum. I don't do any welding myself, but trawling through previous posts I have learned some useful information which will help with a materials exam I have tomorrow. I'm hoping somebody may be able to help in regards to the followin question which is likely to come up in my exam:The following solid state welding processes could all be used for fabrication of low carbon steelResistance Welding    Friction Welding    Ultrasonic Welding    Flash Butt WeldingWith the aid of suitable sketched, briefly describe the principe of the 4 above cases with particular reference to how each of these welding processes deals with oxidation of the welded area.I am aware of what each process involves, although I have no idea how each deals with oxidation. (I am aware of inert gas used in MIG / TIG etc). I've looked online and can only find limited info. I only need a brief idea for each - If anyone could help or point me in the right direction it would be much appreciated. Thanks in advance for any replies. Jordan
Reply:Dave - I don't really understand the need for the manor of your. I've trawled through the internet for hours, and have yet to find anything that specifically mentions oxidation. Hence why I went through the effort of joinin a welding forum. Oldiron2 - Thanks for your reply:As I say, I understand the main aspect of the process, just not how oxidation in particular is avoided. From what I've read the process is fairly simple: It just involves moving one component relative to the other and applying pressure. Obviously the heat at the iterface and pressure applied to the components create the weld. Typically used to join pipes, and can be used to weld disimilar metals. All I can think of is that some type of gas shield is created by the metal moving outwards at the interface?I have no idea how oxide is avoided in resistance welding. I just realise that both surfaces need to be clean and oxide free before the weld takes place.
Reply:OK, suppose you're joining a heavy crankshaft to a flywheel. The crank is held in a lathe and spun at very high speed. The stationary flywheel is suddenly pushed into the end of the spinning crank which quickly slows down.Where and how is the heat produced? Where does the weld occur? Why is oxidation not a problem, meaning why does air not react with the weld metal?Your turn.
Reply:You just answered your own question. Start with clean material and clean tongs, set heat correctly, and voila.People who write tests don't necessarily PHRASE questions well, so when writing answers instead of "multiple guess" type tests, cover the bases.
Reply:Both - Thank you very much for your replies. Oldiron - Now starting to make sense. I suppose the fact that the weld takes place below a layer of metal (Which then gets removed) also stops air reacting with the weld. Farmall - I agree, most questions aren't phrased well. Thanks for your adviceLast edited by jordan_b; 05-31-2012 at 04:39 PM.
Reply:Originally Posted by jordan_bIf anyone would be decent enough to just give a one liner on each, specifically in regards to oxidation avoidance it would genuinely be much appreciated. I am from Wales Uk and about to go to bed, so I will reply in around 8 hours if anyone is able to provide an answer in the meantime. Thanks
Reply:Originally Posted by jordan_bBoth - Thank you very much for your replies. Oldiron - Now starting to make sense. I suppose the fact that the weld takes place below a layer of metal (Which then gets removed) also stops air reacting with the weld. Farmall - I agree, most questions aren't phrased well. Thanks for your advice
Reply:Originally Posted by Oldiron2How does that old saying go about "give a man a fish"....OK, here's another one liner:  "Teach a man (how to) think...."I often need to coordinate with someone in N.Z. and then must get by on 4 or 5 hours sleep.....Life ain't fair, but it's the only game being run right now.
Reply:Sounds like the OP is in a "welding school".Don't welding schools have libraries anymore or is "everything" on the net.When I studied engineering (many moons ago) it was as much about learning how to find relevant information/tables/formulas, etc as it was about the actual information taught.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Originally Posted by SundownIIISounds like the OP is in a "welding school".Don't welding schools have libraries anymore or is "everything" on the net.When I studied engineering (many moons ago) it was as much about learning how to find relevant information/tables/formulas, etc as it was about the actual information taught.
Reply:Originally Posted by Oldiron2Jordan;Thought you'd quit already. Guess not. Yes, the kinetic energy is converted by the friction to heat at the point of contact, which is not contacted by the air. Probably have a gradation from plastic state 'outermore' to a small area which is truly molten. I don't know the details of ultrasonic welding but the principle is the same;  the details should be available online to figure that one out as you did with the first.Need to get back to work. Good luck.
Reply:When you wake up, you might have time to read the following articles about a few of the processes you listed above. Being fairly detailed, they should help you figure out the answers you want. I have no idea how good or fast your system is, but my search for the three sites below took only a few minutes to complete. Now I need to read them all myself, just to see if there's anything I should but don't already know! Understanding Ultrasonic Welding Basics of Flash Butt WeldingRotary Friction Forge Welding
Reply:Oxidation is a time/temperature solution, with iron based materials in solid state oxidation is slow, from Ac1 - Ac3 it is increasing rapidly, when liquidus to homogeneous it is reactive.With friction and flash/upset welding surface oxides flow to the outside and are removed after welding. With resistance and ultrasonic any oxides not removed from the surface before welding will remain in the nugget. Joining with these processes occur in the plastic(flow) state between solidus and liquidus. There is some argument about the upset flash weld parameters consisting of some liquidus to homogeneous sections (never mind IMO).I do not consider resistance, ultrasound or friction welding in quite the same league re: joining as friction and flash. They are joining but so are fastening and chemical bonding. Originally Posted by jordan_bI definitely wish I had joined a British forum. By far the most unfriendly forum I've ever visited.I don't need to explain myself, but I will. I am currently studying a mechanical and manufacturing engineering degree part time. I work 9 hour days monday to friday, and my local library closes  at 6pm (The same time I finish work)I have been looking over a large quantity of learning material, and came about this particular question a few hours ago. I have an exam in 15 hours, and therefore cannot go the library. I don't believe that everything can be found on the internet!. You say about finding techniques to learn information - Asking on forums is one technique I have used to great effect in the past. Welding is about 1% of what we have been told to learn. You know nothing about me, so don't go making assumptions until you know the facts.
Reply:Originally Posted by Oldiron2When you wake up, you might have time to read the following articles about a few of the processes you listed above. Being fairly detailed, they should help you figure out the answers you want. I have no idea how good or fast your system is, but my search for the three sites below took only a few minutes to complete. Now I need to read them all myself, just to see if there's anything I should but don't already know! Understanding Ultrasonic Welding Basics of Flash Butt WeldingRotary Friction Forge Welding