What is melting point of white Metal?

[6029 King Stephen]

I am trying to reduce a K's GWR railcar to its component parts and assumed that it had been assembled with 70 degree solder but after placing it in a pot of boiling water, this clearly is not the case. My next option is to use the oven but before I do, what is the melting point for white Metal, as I only want to melt the solder and not the castings?

 

Regards,

 

Steve

[great central]

To me that sounds a risky option, I'm no expert but have built a good few white metal kits. I think the next step up from low melt solder at around 70C is 130C, but I fear that is close to WM melting point. Is it possible to salvage the kit without dismantling or has it been badly assembled? I'm sure others may well have better advice

[bbishop]

Depends on the composition of the white metal.

 

A white metal alloy may include antimony, tin, lead, cadmium, bismuth, and zinc. Not all of these metals are found in all white metal alloys. Metals are mixed to achieve a desired goal or need. A base metal for jewellery needs to be castable, polishable, have good flow characteristics, have the ability to cast fine detail without an excessive amount of porosity and cast at between 230C and 300C.

 

Bill

[Pebbles]

This issue has been highlighted before by, I believe, Richard Jones. It appears that after a period of time some interaction between the low point solder and the white metal occurs. This prevents the subsequent re-melting of the low point joint in boiling water. 

[Titan]

Possibly daft suggestion...

 

Could cooking oil be substituted for water? You would be able to very carefully and incrementally be able to raise the temperature gradually above 100C.

 

However I make no claims for the safety of this method or how easy it will be to clean the parts afterwards...

[t-b-g]

Having played around with my temperature controlled soldering iron to establish the same thing, I can confirm that the whitemetal used in the kits I tried it on melts with the iron set at around 200 degrees C.

 

I would allow a decent safety margin as I am not sure how accurate the temperature on an oven is or how much variation there is in the metals used (there is certainly some variation in the composition).

 

If it was me, I would experiment on some spare bits/sprues first, just in case!

[bertiedog]

200C is far to high for traditional white metal,it will melt at about 170c if it was made by K's, the low melt solder should fail at about 100c, with it's melt at about 80c, the eutectic point where it bonds is about 90c.

 

It would therefore need more heat to break the bonds, and risks getting to the plastic state just before going liquid. The remelt temperature does go up with age, and not all casting metal is the same. Pewter is used nowadays to minimise lead in the mixture. So very modern kits melt at a far higher temperature, nearer 220c, or more

 

To take apart the kit will be difficult, but not impossible, use a temperature controlled iron, with  knife edge soldering tip. This can be run along the joint till continuous pressure starts to break it apart. Other tip shapes may help release other parts.

 

Don't worry about slight bends in the castings as force is applied, white metal is easily bent back true afterwards.

 

It may be that the assembler was skilled at using ordinary solder with white metal, it works if you know how to do it. But it renders the joints totally permanent like a weld.

 

With the railcar there are small parts that may melt to easily, so the best plan would be to razor saw the joints. Go carefully at each end and scribe the middle section, and the flex gently till it breaks. Some joints may be able to be sawn in a straight line. Do not worry about the missing metal, it will all be adjustable in the re-assembly, when further real low melt can be used. A thin wire can be soldered to one side of the joint to help make up the missing sawn off material.

 

A Scalpel used backwards can be used as a scraping cutter around awkward parts to establish a break line.

If you need very thin saw blades, and have access to a grindstone, then grind some ordinary junior hacksaw blades down on  each side, with skill you can get them to about 3 thou thick. It only needs a section about 10mm long, and use it as a pull saw.

 

Stephen

[t-b-g]

200C is far to high for traditional white metal,it will melt at about 170c if it was made by K's, the low melt solder should fail at about 100c, with it's melt at about 80c, the eutectic point where it bonds is about 90c.

 

It would therefore need more heat to break the bonds, and risks getting to the plastic state just before going liquid. The remelt temperature does go up with age, and not all casting metal is the same. Pewter is used nowadays to minimise lead in the mixture. So very modern kits melt at a far higher temperature, nearer 220c, or more

 

To take apart the kit will be difficult, but not impossible, use a temperature controlled iron, with  knife edge soldering tip. This can be run along the joint till continuous pressure starts to break it apart. Other tip shapes may help release other parts.

 

Don't worry about slight bends in the castings as force is applied, white metal is easily bent back true afterwards.

 

It may be that the assembler was skilled at using ordinary solder with white metal, it works if you know how to do it. But it renders the joints totally permanent like a weld.

 

With the railcar there are small parts that may melt to easily, so the best plan would be to razor saw the joints. Go carefully at each end and scribe the middle section, and the flex gently till it breaks. Some joints may be able to be sawn in a straight line. Do not worry about the missing metal, it will all be adjustable in the re-assembly, when further real low melt can be used. A thin wire can be soldered to one side of the joint to help make up the missing sawn off material.

 

A Scalpel used backwards can be used as a scraping cutter around awkward parts to establish a break line.

If you need very thin saw blades, and have access to a grindstone, then grind some ordinary junior hacksaw blades down on  each side, with skill you can get them to about 3 thou thick. It only needs a section about 10mm long, and use it as a pull saw.

 

Stephen

 

I have been soldering all sorts of whitemetal with my iron set at 180 degrees with no problems.  I have managed to melt small whitemetal items at 200degrees but any larger items, that act as heat sinks, have been quite successfully soldered using 145 degree solder with the iron set at 200 degrees with never any damage.

 

Of course not all that temperature will transfer from the iron to the whitemetal, which may account for the difference.

 

As often the case in soldering, there is a difference between heat and temperature. A tiny tip turned up high will not necessarily be as effective as a bigger tip at a lower temperature at heating up the metal and the solder at the joint.

 

Likewise an oven. Set at, say, 180degrees, it will be hotter at the top than the bottom.

 

So I stand by my suggestion that testing with a bit of scrap is the way forward!

 

I have never had to resort to putting whitemetal models into an oven to dismantle them but I would want to make sure that the model wouldn't end up a blob if I was going to try it.

 

I would keep turning the oven up until the scrap melted, then turn it down by around 30% before I put anything worth keeping in. 

[34theletterbetweenB&D]

...It may be that the assembler was skilled at using ordinary solder with white metal, it works if you know how to do it. But it renders the joints totally permanent like a weld...

The 'sign peculiar' of assembly with electrical solder is that the soldered joint is brighter than the whitemetal. (I did all my whitemetal kits that way until I had work that paid properly. Hell's bells, the kits cost enough, without spending nearly as much again on a temp. controllable iron, solder and flux; when my Pa's array of irons and electrical solder were free and always available - he was an electronics enthusiast -  and my teenage fingers were quick and nimble.)

[RexAshton]

Having stripped down several white metal kits over the years I now have 100% success using a chef's blowlamp with the air hole closed to reduce the flame temperature. I would suggest removing the small components - steps etc with a temp controlled iron and then gently waft the larger parts with the blowlamp bringing the temperature up gently an evenly until the solder melts.

 Gently warming the model will mean that as soon as the heat is removed there will be no heat soak but the model will reduce to its component parts. Remember though that there will be a lot of cleaning up to do afterwards. When necessary I re-heat the castings until the solder melts then shake the part into an empty box. Centrifugal force removes most of the still liquid solder.

It might sound like a  disaster waiting to happen but a bit of practice on something that doesn't matter will provide the experience to tackle a loco.

[6029 King Stephen]

Thanks for all the comments and suggestions.  A few weeks back I had built a whitemetal bus kit and after washing it in Cif to get it ready for painting, I used a hairdryer to dry it.  I was shocked to discover that the heat of the hairdryer was sufficient to melt the solder.  I have tried the hairdryer on the railcar but to no avail.  I suspect that it has been soldered with ordinary solder as the solder is might brighter than low melt solder seems to be on other kits I have.

 

Going forward, I think I will try to melt the solder in the oven by setting the oven at 100 degrees C and putting a waste piece of K's whitemetal in and then slowly raising the temperature until the bit melts.  Then I will return to 100 degrees and raise the temperature slowly until the solder melts and the model falls apart.  I will have to be careful with fumes as whoever built it has used some find of padding/filler in the cab roof areas.

 

I wanted to dismantle the kit because it is a bit lopsided and tighter in the centre than at the ends.  Whitemetal dummy bogie has been built using the same solder, so that hasn't come apart either.  The motor bogie appears to be one of the old Triang ones with steamroller wheels to match.  I won't be reusing either bogie.

 

Regards,

 

Steve

[MarcD]

I hope I'm not going to get shouted at for saying this. I'm not brave enough to bring a soldiering iron anywhere near white metal. If I'm using white metal as I have no idea what temp it melts at, I used a super glue to grab and fix the parts and back fill any gaps with 2 part epoxy

 

Marc 

[DCB]

Sounds the solder might melt at the same temp as the white metal so you might have to resort to selective surgery / bodgery with razor saw and drills to separate the ends so you can true it and spread the floor.

I have soldered white metal kits with electrical solder for years, actually welded white metal by melting edges together at times and the results wont come apart, which is a shame as they aren't exactly brilliantly square...

The upside is if a kit has been soldered with electrical solder it will be robust and of course if you source some similar solder you can build up any gaps rather like welding new metal into an old motorbike engine.  I once lengthened a K's 44XX bunker to make a 1930 s style 44XX by adding  electrical solder to fill the resulting gap after cutting.

Edited June 1, 2017 by DavidCBroad

[bertiedog]

Admissions, admissions,...... so there are people who are owning up to using normal solder on whitemetal the bane of repairers everywhere. I admit I did it, but only on parts that were totally in line and checked carefully before committing it to 60/40 solder.

A lot of the time, due to shortages of Woods Alloy, I used whitemetal itself as the solder, gives the same welded joint.

 

I think that in particular with the window sections etc that general heating may be dangerous to the whitemetal.

Doe it really need to come apart is the other general question, how much can be borne as out of line etc , and may be recoverable with body filler or Milliput filler. K's were major offenders in things not lining up well anyway, and you have to balance the risk to the castings against the accuracy that you are seeking, which might not be there anyway.

 

Stephen

[hayfield]

If it is low melt it could be either 70 or 100 degrees, the larger pieces of whitemetal act as a heat sink. with 70 degree solder just hold over the steam of a kettle (with grips or pliers), if its 100 degree may need a tad over 100 degree to melt it. I would not put it in the oven

 

It could be normal solder, which could be a problem

 

I use an Antex 25 watt iron, so with care a little more heat on the larger pieces is fine

 

On a joint consisting of large castings, put some flux on it and carefully dab the joint with a soldering iron, you will soon tel if its low melt solder

 

You could try and file off excess solder, or carefully use a rotary drill

[6029 King Stephen]

I think I will try using my temperature controlled soldering iron on some of the joints to determine what kind of solder has been used. I will start at the setting for white metal and move up. Obviously I will be very careful when approaching the higher setting for ordinary solder. If it proves to be ordinary solder, the I will sell it on eBay when I return to U.K. At the end of August.

 

Regards,

 

Steve