sheet silver cracked apart - any idea why?
I've a piece of silver sheet 0.8mm thickness. I've annealed it a couple of times before with no problems but when I annealed it today - it cracked.
I did everything as normal, moved the flame slowly across the surface, didnt even get it to glowing red and then waited a couple of seconds before putting into the quench. The quench was room temperature water. Everything just as I've done it before.
Photo below shows what has happened - its fractured in several places but one is huge and completely ruined the sheet.
any ideas? Its never happened to me before
anybody have this happen to them?
Did I do something wrong?
Was the silver faulty?
Oh dear...that looks nasty I can't offer much advice but very interested to see what other people say. When exactly did the crack appear...before or after you quenched it?
after quenching but it didnt happen the second it went into the quench - it was n thewater a couple of seconds and then went!
I am not a metallurgist, but this is how I understand it. I have tried to use non-technical language so as hopefully not to get it wrong. But there are members more expert than I am in this subject.
Silver should only be annealed if it has been thoroughly hardened by hammering, rolling or drawing. The reason for annealing is to allow the crystalline structure to return to the state where the metal is soft enough to work with again. By repeatedly annealing the sheet when it did not need it , the structure of the alloy has been disrupted, so finally it just cracked.
Kind regards, Dennis.
Dennis is correct as far as i can see, im unsure why you have annealed a sheet that hasn't been worked. it only needs it once worked like dennis states.
I'm just a beginner so would you explain to me why this doesn't happen when you reticulate silver, I'm curious to know
Thanks for your replies.
Dennis and Stu,
I have actually worked the silver - as can be seen from the photo, it has had a number of discs punched from it and each time it came out of the disc cutter it was buckled slightly so I hammered it to straighten it again, thus hardening it up. If it had been soft enough to use in the disc cutter, I wouldnt have annealed it again but I am not an expert so please correct me if I am wrong in that. In total I dont think it has been annealed more than 4 times, including this last time and each time it has been because it was too hard and unyielding to be put into the disc cutter.
WhenI use my disc cutter it normally takes a couple of blows with a hefty hammer to cut through the sheet and as I understood it, this process alone has a ripple effect on the rest of the sheet, thus tightening the structure of the metal. Is this not right?
I've done that before when reticulating - it usually means I've either overheated the metal while annealing or (more often!) quenched it too quickly.
Thanks for all your replies - its all a learning process for me - albeit a rather expensive one in this case!
I will phone Cooksons and ask them about it, thats where I got the sheet silver from. No doubt they will tell me I've done something wrong !
I'll dig out Brepohl this evening and put together a slightly more technical post - short form is down to crystal growth and grain boundaries forming.