Welding Cast Iron

[corrosionman]

We propose to repair some arms from old cast iron signposts and are amazed at the cost of weld electrodes for C I work. Roughly six time more than I expected, at £3.50 per rod of 3.25 mm size Please can anyone suggest why they cost so much.
Thanks in advance
Corrosion man

 

[metengr]

Most electrodes for cast iron contain significant Nickel content. It is the price of Nickel and other alloy elements in weld electrodes that set price. You might want to investigate actual weld electrodes for cast iron, they would be in AWS SFA 5.15.

 

[chicopee]

An alternative may be brazing.

 

[0707]

I agree with metengr

but what is your cast iron spec?

lm

 

[swall]

corrosionman--if you go with Ni-Rod (the high nickel content stuff metengr mentioned) you should be aware of the cosmetic issue of the color mismatch. Ditto for brazing.You didn't say so in your post, but weld repair of old sign posts suggests that appearance might be an issue for you.

 

[berkshire]

If you are repairing just the arms of old cast iron sign posts, and matching the weld area is a problem, if you can remove the arms then:
Maybe you should use Oxy Acetylene welding with preheat and a sand box for cooling, using cast iron welding rods for the weld.
Your difficulty these days may be finding a qualified welder to do this.
B.E.

 

[stanweld]

I would be really concerned that the "old" sign posts are gray cast iron. If so I would not suggest welding repair. The repair will no doubt be subject to fatigue; your repair will only be temporary.

 

[corrosionman]

Gentlemen
The cast iron repair job is the 100 year old arms of old Yorkshire Signposts. My painting Team are shotblasting and painting them but a good number are cracked or broken due to vehical damage and have been repaired many yrs ago by mechanical straps or even very primitive weldingthat has failed. , but, yes, it is gray !!WE don't have a spec for the CI.
On advice from chicopee we braized a couple today - - (We have a very skilled welder in our W/S ) Our test is very non scientific. We lay the arm flat across two bricks then jump on it, hard. So far we are 100% sucessfull - - no breaks. My fear is that one day a heavy arm might break and fall on someones head !! We paint the arms so visual is of no importance and I guess paint keeps joint dry from rain so dissimilar metal corrosion will be no bother (I hope)
Gents, I greatly appreciate all your comments- - I guess its the Learning Curve again.
Please feel free to shout at me if I am doing anything daft
Corrosionman

 

[MintJulep]

Are all the cracks in the same general area?

Are you doing any sort of NDT to look for cracks that haven't yet resulted in anything falling off?

I would be suspicious of arms that haven't developed a visible crack yet.

 

[0707]

On this welding subject please go to

http://www.controlledproductsgroup.com/technical/cwafall2005.pdf

http://www.lincolnelectric.com/knowledge/articles/content/castironpreheat.asp

http://www.welding-technology-machines.info/welding-of-cast-iron/welding-of-cast-iron.htm

lm

 

[tomwalz]

Dear Corrosionman:

Actually, in my experience, the jumping up and down is a pretty good test. The test for brazed carbide saw mill saws is to hit them with a stick about eighteen inches long. Officially (sort of) a good man or woman takes a piece of red oak eighteen inches long and just beat the heck out of the carbide tips.

Bad brazes fail pretty easily. Good brazes hold.

Brazing can be thought of as a ‘go / no go’ process rather than one with grades of quality.

Of, course some good brazes are better than others but I would bet that your test is very good for the application. It is easy, simple, cheap, amusing, provides exercise for the staff and is pretty well repeatable.

Tom


Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.

 

[vesselfab]

furnace brazing is the way to go. High preheat & heat maintained good flow of brazing consumable into the pours of the cast iron.

works on 24" thick cast iron repairs for high tension load cast iron for us