can steel/cast iron be silver soldered

firebird · Apr 26, 2012

Hi

I need to fabricate some parts for my portable engine, a cylinder block and axles etc. Having had some success using a brake cylinder on my beam engine ( albeit an aluminium one ) I have been looking at some cast iron ones but need to build them up with saddles and valve chests. Does cast iron and steel silver solder, if so any tips would be really useful.

Cheers

Rich

Jasonb · Apr 26, 2012

Rich, it can be silver soldered but is not the easiest thing to do. You need to bring the heat of the iron up to about 500degC over a few minuets. You can then come in with your torch and bring the job upto soldering temp then let cool very slowly. You will need Tenacity No5 or CuP alloys equivalent flux due to the longer heating time. Do a few tests first before committing to your cylinder.

You could make the curved saddle by bending 1/8" steel and then solder a bit of steel with a suitable curve on the underside and a flat top. The CI cylinder and valve chest can be machined from one solid block and bolted to the steel base, some full size engines used this method.

http://img.photobucket.com/albums/v115/escortmad79/steam/Africa/BotshabeloPort.jpg

J

firebird · Apr 26, 2012

Hi Jason

A couple of good ideas there. I will sort through my scrap box at the weekend and see what turns up.

Cheers

Rich

Jasonb · Apr 26, 2012

Should have said it can help to preheat the iron which draws the carbon to the surface, allow to cool, clean off carbon with a wire brush then treat as I said above.

Link added to pic in my post above you may have missed.

J

kwoodhands · Apr 26, 2012

firebird said:
Hi

I need to fabricate some parts for my portable engine, a cylinder block and axles etc. Having had some success using a brake cylinder on my beam engine ( albeit an aluminium one ) I have been looking at some cast iron ones but need to build them up with saddles and valve chests. Does cast iron and steel silver solder, if so any tips would be really useful.

Cheers

Rich

Not sure about cast iron but you can hard solder steel. I have hard soldered 1018 and some other steels, except stainless.I use a 10% solution of hydrocloric acid for a pickling solution and standard white flux for ferros metal.The steel has to get red hot,more like orange to my eyes. Then the silver solder will flow.
Make sure there is a slight gap ,.002/.004 between the pieces so the solder will flow thru.A few dimples with a center punch will suffice for the gap.
When the stock has cooled down ,place the steel back in the pickle for ten minutes .
Then thoroughly wash and brush with a steel brush until the flux is cleaned off.
Wash thoroughly several times and then dry .The acid promotes rust, if you do not clean the pickle adequately you will know it the next day.
I imagine you can dispel the acid pickling if the parts are very clean. I use the pickle for added ease in cleaning the steel.
You could try this with cast iron if you have any scrap.
There are other pickling solutions that may work, possibly sulphuric acid or even citric acid.I did try citric acid once but on brass not steel or iron.I left the parts in the acid over night, worked fine.
mike

Jasonb · Apr 27, 2012

Rich, I just thought do you have access to ME as their series on teh portable has just covered making up the cylinder, its a poor article but may give you some ideas. Used a bent steel saddle then the cyl was cut from CI bar with a curved botton and bolt on valve chest. Let me know if you want more details.

I just had another thought, looking at the photo I posted above, you could make the platform that the cylinder sits on out of copper or cut from bronze and solder that to the boiler during construction, Bronze would be better as you could leave it a shade oversize and then skim true to the barrel and it would have enough meat in in to take studs.

Mike the steel is not the problem to solder its the carbon in the CI which stops the solder wetting the surface the flux or pickle will have no effect on this. MEB had avery good article early on about hard soldering CI.