I am in the middle of modifying a diecast model landrover and would like to use solder to reassemble it. Does anyone know what sort of alloys are used in the manufacture of metal diecast toys/models in general, and what kind of solders will stick to them?
Because of the low melting temp and high content of aluminum, basically nothing. Your best pick is still a CA glue. Or, if you can find some, there are special low-temp soldering wires designed for aluminum alloys, but your problem will be to heat the parts enough for the melted metal to adhere, while at the same time staying below the meltin temp of zamac.
There are "cold" salders. Check the local hardware store. I used some on a broken router years ago and it is stil together. I used it another time, but cannot remember the application. The stuff if amazing. It also grinds and sands like metal once hard.
Try looking for low power soldering irons. For white metal soldering the model train guys often used to use their train controllers to power a 12V iron, achieving good temperature control. My iron (picked up at a model show many years ago) is an 8W 12V tool, and I use it with my drill controller. You also need suitable solder (electrical solder will *not* do - it's for copper or tin) and a liquid flux to clean and prepare the joint surfaces.
This swiss site has some interesting (if erratically translated) tips.
I quote from the first paragraph (cleaned up a bit):
There are various types of white metal. According to the kind of use, its composition will be : tin / antimony / lead or, tin / antimony / lead / bismuth or, tin / bismuth / lead / bismuth. The melting point will vary between 140 to 240 °C.
The solder used for this material is made up of tin, lead, cadmium and bismuth. It melts at a temperature of 70°C.
Googling for "soldering zamac" provides little hope:
general opinion seems to be that it rarely works, and even when it does the join is weak.
Soldering works by alloying the solder and workpiece metals at the join, hence the need for different solders for white metal compared to tin/copper. I am told it is possible to solder white metal to tin/copper/whatever if you prepare each surface and tin it with its own solder first - the join is then solder - solder.
Carrs make a 70 degree solder and a suitable flux for joining whitemetal. It's made in England so you should be able to find it there (I can get it in New Zealand). I use a fine 240 volt soldering iron controlled with a variac, but most of the people I know use a light dimmer.
Yes, it looks like I will have to make do with the best superglue I can find. Sigh.