Magnesium

[atreyu]

Hi All,

I need to do a repair on a magnesium side cover off a motorcycle. I don't know the grade used (It's a 70's Honda item).

I'm not too bad at alloy so I expect there shouldn’t be an issue in the small repair I need to do (welding a blanking plug in)

Could someone give me any pointers that they think would be helpful?

The main thing is what filler wire to use? and where can I get it? I don’t need alot and can’t see any on ebay.

(out of interest is it possible to weld a alloy, say 6000 grade to magnesium)

 

[hotrodder]

Unfortunatly you get a brittle mess if you try to weld ally to/with magnesium or visa versa.

Welding mag is kinda similar to 'dirty', cast ally... warm, clean, the arc will dance around a bit (keep the arc length v.short) and glow green. The weld pool is poorly defined. Typically very dirty/sooty (one of the few times i always avoid using a gas lens) so keep a carbide burr and stainless brush to hand.

Clean ALL the swarf/chips up as while a chunk of the stuff is hard to ignite little bits aren't- melt a blob of filler wire off by mistake and you don't want it landing in your lap!

The only source i'm aware of that sells in smaller quanties than by the kg is SIF who also offer 12 rod packs. It's spendy stuff so have a stiff drink before clicking the link... http://www.rapidwelding.com/dynamic/Category.aspx?c=TIGAZ61A&o=0&zl=3&sq=10. If you want one or two lengths of wire (probably cut in half for postage reasons) then i can probably be persuaded to suffer the local PO





Alloy is not an abbreviation for aluminium. Steel is an alloy (of iron and carbon), stainless is an alloy as are bronzes, brass etc. Aluminium can be an alloy but isn't always. Ally or ali are acceptable abbreviations. This has been a pedantic service anouncement

 

[piman]

Hello Atreyu,

are you sure it is magnesium, as it is an expensive material when a cheaper aluminium casting would normally be the commercial choice for a manufacturer?

Alec

 

[pedrobedro]

As above, it's probably not magnesium on a 70's Honda unless it's an exotic race bike. The heads on Fireblades were the first I remember Honda using magnesium and Kawasaki started with the ZX6/9R using it for casings. Could you use the aluminium brazing kit like Durafix or something ?

 

[Windy Miller]

As Pedro says, maybe Durafix would do it? I'd be interested to know how it turns out.

 

[brightspark]

As Pedro says, maybe Durafix would do it? I'd be interested to know how it turns out.

it would work verry well

 

[Windy Miller]

it would work verry well

Shame. Just the wrong stuff for the job?

 

[astro_al]

I think I have some magnesium filler kicking around, let me know if you need some and I'll have a look.

Al

 

[rtbcomp]

How come it doesn't catch fire? I tried to cast some once and it went up in (very bright) flames!

 

[Hitch]

Dont drop hydrochloric acid on it either.... it makes Hydrogen

 

[atreyu]

Thank you for all the quick replies.

It does sound like it should be possible for me to do what I need then, but I think it will be a good idea to see if there’s another cover made of aluminium (I applogise for saying alloy in the first post, I'm aware of the basic mistake there) before I attempt to weld the current cover.
The cover is defiantly some kind of magnesium (see pictures below).
To go into more detail, I am wanting to convert the bike to have the gear change on the RH side. I have the required splined gear change/selector shaft in order to do this but it requires a hole to be made in the RH engine cover, with a boss welded on in order to take an oil seal. I’ll also plug and weld or glue the kickstart shaft hole currently there. I’m using a previously repaired cover for the conversion so it’s “ripe” for experimenting.
I appreciate the offers of a few mag rods, If I go ahead I will be in touch (very generous!)

Thanks Dave

 

[langy]

It only catches alight if you get it too hot, It needs to be welded with magnesium rod and have a bucket of sand handy.

We just had to repair this Mag wheel as someone had repaired it with aluminium rod and when the tyre was inflated the piece just popped off.

How come it doesn't catch fire? I tried to cast some once and it went up in (very bright) flames!

 

[hotrodder]

Mmmmm, Torq thrust spindle mounts

Durafix themselves say do not use on magnesium You can also test with a drop of vinegar if you suspect a piece is magnesium... the acetic acid in vinegar will react with mag (bubbling/fizzing away producing hydrogen) but not with ally

The ignition point of mag is close to it's melting point unless the surface area to volume ratio is large. Same deal with anything, you can burn steel wool with a lighter and custard powder is explosive. Large chunks of mag need to be surrounded with heat to get a proper blaze, you can even gas weld it if the flux is still available. Magnesium myth vid... http://www.youtube.com/watch?v=k017ZD8rpDQ

 

[tigler]

Mag is surprisingly common on many Jap bikes from 70's on. Particularly dirt bikes.
For a good mag fire have a look at the dreadful accident that happened at the '55 Lemans 24h. A Merc 300 SLR crashed into the crowd killing many spectators, the burning engine and other mag parts are a awful sight.

 

[KemppiFrog]

Mag was used for VW gearboxes a while back. Friend managed to use his as an earth while welding the structure of his auto-cross racer. Had the presance of mind to chuck sand over it in time. (Turbo Volvo powered, class winner)
KF

Mag dust and iron filings make Thermite. Favoured material in incendiary bombs. Will burn through almost anything.

 

[langy]

We used preheat and weld a bit then clean then weld a bit more then clean and so on and so forth. A lot of Mag rods disappeared in this repair.

Mmmmm, Torq thrust spindle mounts

Durafix themselves say do not use on magnesium You can also test with a drop of vinegar if you suspect a piece is magnesium... the acetic acid in vinegar will react with mag (bubbling/fizzing away producing hydrogen) but not with ally

The ignition point of mag is close to it's melting point unless the surface area to volume ratio is large. Same deal with anything, you can burn steel wool with a lighter and custard powder is explosive. Large chunks of mag need to be surrounded with heat to get a proper blaze, you can even gas weld it if the flux is still available. Magnesium myth vid... http://www.youtube.com/watch?v=k017ZD8rpDQ

 

[tigler]

Mag was used for VW gearboxes a while back. Friend managed to use his as an earth while welding the structure of his auto-cross racer. Had the presance of mind to chuck sand over it in time. (Turbo Volvo powered, class winner)
KF

Mag dust and iron filings make Thermite. Favoured material in incendiary bombs. Will burn through almost anything.

Was also used for the crankcases of late 70's Porsche 911's. Caused problems with the seats for the oil drain tubes corroding through salt attack then leaking.

 

[langy]

I thought i would post this here as there are doubters about welding magnesium, It has also been sent for crack testing and they gave me a certificate to prove its ok.

Before

After

 

[Wozzaaah]

Thread tidied, off-topic posts are here.