Many thanks for the answer, my research confirms your reply - I have used high silver content rods and thus used oxy-propane equipment to melt it, but I have now found some lead free 5% silver/tin/copper solder with a melting point of 200degrees. I have a range of 200 to 1000degrees to consider and I think I will look for something about 300 degrees. Not too hot but strong emough for the job.