EN24 To Mild Steel

[craigthewelder]

Hi guys, I've got a job coming into the workshop tomorrow which involves welding some EN24 to mild steel. Now i really can't find out that much info about this,so far I've read that the joint should be heated to around 200c before welding and thats it.
Has anyone have any knowledge of this such as preheat,cooling rates, ect, any help will be greatly appreciated. I'm going to be using metrode 29.9 Super R rods which I'm pretty certain are the right rods for the job.

Cheers for any help.

 

[busa]

Craig.

I did a job a few years ago, EN24 - Mild, if I remember correctly the preheat was around 250c and we welded with 312 stainless. EN24 is a bitch for cracking, needs to be cooled very slowly, good luck with it, let us know how you get on.
.

 

[craigthewelder]

Thanks for the help. From what I've managed to find out on the web it does sound like its very prone to cracking. I've no idea about the size of the job yet so trying to keep the cooling rate nice and slow might be the biggest challenge. Anyway I'll give it a blast tomorrow and see how we get on.

 

[TechnicAl]

To weld En24 to MS the best way is to preheat the En24 to 250 oC, weld 2 layers of E312 weld metal to the face being welded, pack it in sand and allow to cool slowly. Then weld the "buttered" face to the MS without preheat.
This is the belt and braces method
In most cases you are OK welding straight in with 312 (250 oC preheat) but if its an awkward joint or highly restrained it may still crack.

 

[craigthewelder]

Thanks for that TechnicAl, I'll keep it in mind. The job has been put back a couple of weeks. I haven't had a real good look at the drawing but apparently the job has to be stress relived within 1 hour of welding, does that sound right to anyone?

 

[TechnicAl]

Dont stress relieve 312 weld metal, you will embrittle it. 312 weld metal is prone to forming sigma phase when heated in the region of 500-900 oC (actually when cooled through through these temps). Sigma phase is hard and brittle, if enough forms it can leterally fall apart. The same will occur with 309, 307, 308Mo, in fact any Duplex Austenite / Ferrite microstructure.

Therefore if you want to SR (I assume 600 oC) you can only use mild or low alloy steel. As you are welding the En24 to MS I would use a 7018 welding rod. Make sure its baked before use and kept in a warm oven until needed. The risk of cracking is increased but you can SR.

 

[craigthewelder]

Thanks again, you've probably just saved me a major headache. My gaffer will be pleased as we've got about 100 boxes of 7018 rods in storage.

From what I've seen of the drawing the EN24 is just a key way that fits in a fabricated tube.

 

[Welderpaul]

Hell, Technical, you are a fountain of knowledge.

 

[craigthewelder]

To weld En24 to MS the best way is to preheat the En24 to 250 oC, weld 2 layers of E312 weld metal to the face being welded, pack it in sand and allow to cool slowly. Then weld the "buttered" face to the MS without preheat.
This is the belt and braces method
In most cases you are OK welding straight in with 312 (250 oC preheat) but if its an awkward joint or highly restrained it may still crack.

I case anyone is interested this is pretty much the method that i followed. I left everything to cool down slowly over night, dye pen the joint this morning and everything looked good. I hope the next 3 joints go just as well!

 

[cookie munsta]

sounds good, what is en24 by the way, sounds like a ****** to weld.

 

[Mad Mick]

Hi all,had similar job about 1 year ago with 130mm dia. kingpins.Al gave me similar advice on UK welder site ref sigma phase embrittlement, preheat etc. Job went fine,took an age to cool!Regards ,Mick.PS am I the only one who appears unable to register on UKW these days?Have tried everything in the book and more.

 

[mohanvishal@indiatimes.co]

weld strength of en24 to ms

hi all, can some one guide me , asto , whether, weld joint of en24 to ms, have more strength that parent material???
vishal