Recommendation for cast iron casting repairers…

[noel shelleyParticipant @noelshelley55608]

I’m not sure it helps much but it does illustrate the point as Robert has said – When melting brass fittings for casting some will have bits of copper pipe in them, though the temperature of the molten brass is below the melting point of the copper it will slowly disappear  as it is dissolved in the molten brass NOT melted.

Mercury will amalgamate/dissolve many metals.

Galvanising is a 3 layer process.  Noel.

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

The handwheel is much thinner and lighter than the bracket. I wonder much penetration you will get with a MIG welder on the bracket.

Robert.

I think you lack practical understanding, the thickness of the part makes no difference,  even if microscopic surface fusion is happening between the filler and base it’s exactly that, microscopic, a thick part like that is probably going to have better success at repair.

How would the thickness make any difference on the understanding brazing has microscopic surface fusion with the filler?

Have you ever repaired cast iron with any type bronze brazing? Can we see the results?

[Pete.]

On Pete. Said:

On Robert Atkinson 2 Said:

The handwheel is much thinner and lighter than the bracket. I wonder much penetration you will get with a MIG welder on the bracket.

Robert.

I think you lack practical understanding, the thickness of the part makes no difference,  even if microscopic surface fusion is happening between the filler and base it’s exactly that, microscopic, a thick part like that is probably going to have better success at repair.

How would the thickness make any difference on the understanding brazing has microscopic surface fusion with the filler?

Have you ever repaired cast iron with any type bronze brazing? Can we see the results?

Penetration for brazing has nothing to do with the surface fusion, it is about how far the braze penetrates into the joint, be it engineered or a crack. This is mainly by capillary action and thus how long the braze remains liquid as it moves into the joint. This is not an issue with traditional brazing where the base metal is heated to the melting temperature of of the braze. But with MIG brazing the heating is only local to the arc. Hence my question as to how far the braze would penetrate the fracture a relatively massive casting. Note that brazing normally requires a gap of 1 to 5 thou to allow capillary action. This has to be included in a joint designed for brazing.

No, I have never repaired a cast iron part by brazing. That does not mean I don’t understand the principles behind brazing and soldering of which I have done a lot. This includes specifying surface finishes and plating.

Robert.

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

But with MIG brazing the heating is only local to the arc. Hence my question as to how far the braze would penetrate the fracture a relatively massive casting.

This is why you Vee the joint out. You can then get the arc as far in as you want so it will still be local even if you cut a Vee 50mm deep or however deep the casting is. Though as Pete says going half way from each side will be better at keeping the two parts lined up. You will get that microscopic bond along the whole of the ground surface of the vee.

In effect you are then applying beads of braze to the ground sides of the Vee and subsequent filling beads will be braze on braze. The Mig is likely to make the filling of a deep Vee easier, if doing it with a torch you run more risk of heating the previous braze and having the lot drop out on the floor. The mig is more local heating so the whole lot of braze does not get upto melting point.

It’s a bit like welding. Say you had two plates 50mm thick and wanted to weld them together to get a joint as strong as the metal. You would not grind a 3mm chamfer on the corners and run a single bead of weld hoping it would penitrate 47mm beyond the bottom of the small Vee, couple of mm if lucky depending on the power of the welder. You cut a deep well prep and build it up with a number of passes which all penitrate into the root, sides of teh vee and other passes.

[Pete.Participant @pete-2]

<p style=”text-align: left;”>Bronze brazing with gas does not flow a low viscosity liquid like silver solder in to a close fitting gap, regardless if gas or electric a cast repair would always be V’d out throughout the thickness of the part, it simply wouldn’t flow, as a cracked casting will fit together so tightly you’re unable to barely see the crack, if you tried using epoxy as you originally mentioned you wouldn’t physically be able to fit the parts together properly.</p>

[JasonBModerator @jasonb]

This is the full size original cylinder of an engine I’m currently working on at 1/3rd scale. Original is just over 12″ long and you can see how the frost cracks have been deeply ground out in preperation for repair, somewhat bigger than the gap you nee dfor silver solder(braze) but the filler material will get right to the bottom of the cracks as they have been ground out to allow for that.

[FulmenParticipant @fulmen]

Re: Metallurgy of brazing: Robert is right, if the metals can form alloys, they will. Metals behave like “solid liquids” far below their melting point, meaning they behave physically like a solid while allowing for significant diffusion within that solid. This is not a fringe concept but a core tenet of modern metallurgy.

As I understand it this can be experienced when reheating silver soldered parts where old joint have a higher melting point than fresh solder?

[Dave HalfordParticipant @davehalford22513]

As Jason says, Mig Brazing is the same as any other welding process in that it needs a vee notch, except similar to stick welding with nickel rods the temperature is somewhat lower hence Mig brazing is used for boron steel found in modern cars.

Nickel rods run some 20A less current than a similar rod for steel needs.

I’ve done nickel welding on a cast iron exhaust manifold- preheat was just running the engine for 15 minutes to my knowledge the repair did not fail.

Using the same rods on a lathe bull wheel produced a weld that was un-machinable except with an angle grinder. Apparently you need 99% nickel as in the expensive ones for machining.

[Robert Atkinson 2Participant @robertatkinson2]

We are going around in circles here.
I never said the bronze mig repair would not work. I was questioning the amount of penetration of the braze into a relatively massive casting with only local heating.
This lead to some statements about a repair based on built up silicon bronze using the MIG wire. That is neither brazing or welding its a form of additive manufacturing. It would probably work for the OP’s repair but would be a lot of work especially in the thick section of the boss. You would have to jig the parts together, V grind a few spots and apply filler to hold it together and then progressively grind out other sections and fill. Interestingly theis would be very difficult with traditional brazing particuarly with an eutectic alloy

Yes, I’m being pedantic but others are using teminology incorrectly.  Welding does not have to use filler. Building up metal with a welder is not welding. Soldering and brazing always use a filler that is different to the base metal and “mixes” with it at a molecular level.

Robert.

 

[Paul KempParticipant @paulkemp46892]

“Building up metal with a welder is not welding”. Really?  Are you sure about that?  If that is true then any weld process that uses a filler material is not welding.  If that is true then the majority of structural assemblies from ships to bridges and anything in between is not welded.  So we have no need for weld inspectors, weld procedures, welder codings and in fact they are all wrongly termed and they should perhaps be metallic bond inspections, metallic bond procedures etc?  What a load of tosh.

Paul.

[Robert Atkinson 2Participant @robertatkinson2]

No need to be rude. Welding is the the joining of two similar base materials (metal in this context) by melting them and causing them to fuse together. Use of additional material similar to the base material is optional. Gaps, V notches etc are optional in welding and are not fundamental to the process. The building up of filler material to fill a gap, as opposed to a bead that contacts the base material, is not fundamentally a weld as it does not involve the base material.  A common use for built up filler is when the heating method does not have enough energy to melt the full thickness of the base material and allow it to fuse. Yes, it is commonly called welding but metalurgically speaking the built up layers are not a weld they are filler. Where I work the people who check welded and brazed joints (among other things) are called NDT inspectors (Non Destructive Test).

The same applies to the built up MIG brazing that was discussed as a repair option. I got into more detailed discussion because it was suggested the the method relied on adhesion like action of the braze on the metal surface rather than mixing of the base metal and braze by dissolution or diffusion. and the definition of penetration, which is different for welding and brazing. Hence the pedantic differentation of welding, soldering, brazing and gluing. That does not affect common usage of the terms.

Robert.

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

The handwheel is much thinner and lighter than the bracket. I wonder much penetration you will get with a MIG welder on the bracket.

Robert.

So to answer the original question. If you ran a single bead of MIG braze over the outside of the bracket centred on the crack you would only have a skin deep bond which would not be very strong. Same would apply to tig and gas Brazing and stick, mig & tig welding.

 

Similar to if you just spread some Epoxy adhesive over the outside of the crack, again it would not go deep and be quite weak.

 

So what to do pull the two halves apart so you can apply adhesive to the whole of the fractured surface. But run into problems pushing them tightly back together

The same is done for the braze repair the crack is opened up in this case by grinding away material so the available bonding surface that is accessible becomes far greater hence a stronger joint. Bonus is there is no material between the fractured faces to stop them going back together in the right position

The advantage with the grinding out and brazing method it can be used with parts that have not completely come apart like that cylinder casting I have shown. If you only had adhesive and could not open up the joint at best you would have a weak patch on the outside.

[noel shelleyParticipant @noelshelley55608]

All of this is getting away from the original question. The finer points of joining metal and their terminology for most is not needed – if it works that’s fine ! I often join stainless without a filler ?

How is the process of joining/repairing Mazak or aluminium with a low temperature rod to start the process defined ?

Noel.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, I agree with Paul Kemp, and is the last I’m saying on this.

Regards Nick.

[Paul KempParticipant @paulkemp46892]

“Gaps, V notches etc are optional in welding and are not fundamental to the process. The building up of filler material to fill a gap, as opposed to a bead that contacts the base material, is not fundamentally a weld as it does not involve the base material.”

Unfortunately that statement only holds true for thin ‘plate’ where a full penetration fusion weld can be achieved by heat alone, Noel referenced this, common for thin stainless and even mild steel using TIG but consideration needs to be given to back purging (gas) to prevent contamination of the reverse side of the weld where shielding gas may not reach if it is a critical application.  For anything thicker than very thin ‘plate’ a weld prep (normally a vee or j) is absolutely fundamental to a successful, homogeneous full penetration weld, end of.

The type of prep used for a particular weld will consider access and distortion, a single vee prep will cause more distortion than a double (both sides) when the weld sequence must be considered.

Consider a simple 3 pass single vee prep weld.  The root pass melts and fuses the filler to the parent material on both sides of the prep.  The second pass melts and fuses the parent metal on one side of the prep and the filler material from the first pass.  The third pass melts and fuses the parent metal on the other side of the prep and filler material from the root pass and the second pass.  In all three passes to varying degrees the filler material in your words contacts the base material.  So this must by your definition constitute a weld?  There is a problem though with the back side of the root weld which was unprotected by shield gas or flux, the solution to which is varied dependant on access.

The composition of the filler material be it rod or wire is chosen to be as close as possible to match the parent metal taking account of any alloying elements that may be ‘lost’ in the weld pool and during solidification.  The objective being the properties of the completed weld are as closely matched as possible to the parent metal.

In my world, the weld inspector is employed within the NDT department and outside his physical inspection duties he will also sign off weld procedures which include the detail of the prep to be applied and the sequencing of the individual passes.  NDT is a broad collective of non destructive techniques the application of those techniques to the inspection of welds is a specialised branch of the NDT tree.

Brazing / silver soldering / soft soldering are all related to the principle of the E word you quoted.  Preps for brazing are as valid as those for welding in creating access for a proper joint area.  The argument here seems to be the thickness / width of the filler in the gap created

This thread is a fantastic example of often how a simple question generates responses far beyond the level required by the original question!  Hopefully the OP will return at some point and report on the solution chosen and its success or otherwise.

Paul.

[Robert Atkinson 2Participant @robertatkinson2]

Have you read what you wrote?
Your descripion of a 3 pass weld completely matches my description of a weld “…a bead that contacts the base material..”

Thanks for agreeing with me.

Robert.

[FulmenParticipant @fulmen]

Differentiating between filler and base material on subsequent passes seems like splitting hairs to me. For all practical purposes these are the same material, so previously deposited filler becomes the base on the next pass.

Although: That would mean that multiple passes of “MIG braze” could constitute both brazing and welding (of braze material) in different areas of the same melt pool. Sometimes you just have to accept that no single category fits perfectly.

[JasonB]

On JasonB Said:

It could be made from two pieces of bright mild steel flat screwed together

The repair is still work in progress but the more regular club attendees put their heads together and have decided to do something similar to JasonB’s suggestions.

The two sections of the original part with mounting faces are going to be retained (I.e. the top of the bracket that clamps to the table and the round boss, which the wheel is mounted to) and a thick plate of mild steel will be used to attach the two, with suitable machining to retain the original dimension between the faces. Assuming it all goes well I’ll add some photos once it’s all back together!

[Author]

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