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Steel, cuts like butter!

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Alan Worland10/03/2011 22:40:21
247 forum posts
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I am making a steam engine from castings and materials supplied by Stuart Turner and have just made the piston rod with integral crosshead, and it machined beautifully - it is the best bit of bar I have ever turned!
I realise that there are many grades, and I am largely unable to identify them (unless it is silver steel or a piece of gauge plate)
What grade might this have been? It turned to a wonderfull surface (ideal for going through a gland) It milled like a piece of hard cheese and screwcut with the smoothest thread ever!
I only ask because I would like to make this my standard turning steel!
Andrew Binning10/03/2011 23:15:08
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You were probably turning a bit of leaded steel EN1A. The lead gives it it's free machining properties. Not so good for welding though I have never had a problem with this, I think it can affect strength of the weld. Won't affect you here, you will not want to weld it!
 
EN1A is the old designation although still widely used and recognised by suppliers. The current BS970/1972 ( British Standard ) uses different coding and the equivalent material is 230M07 Pb.
Identifying unknown materials is always a problem but one way is with what Tubal Cain in his Model Engineers Handbook ( Page 7.5 in the 3rd edition ) calls the spark test. The type of sparks generated when you grind a sample of the material give an indication of it's chemical content. If you haven't got the above book it is a valuable source of advice on all aspects of Model Engineering, I refer to my copy at least once a week!
Good luck with the engine!
 
Nicholas Farr11/03/2011 06:56:30
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3988 forum posts
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Hi, welding free cutting steels don't really affect the weld that much, but does affect the HAZ, (heat affected zone) this may cause a shaft for example to snap off under load when you least expect it to around the edge of the weld, the weld will often remain intact.
 
This usually happens on larger sections (40 mm +) and both preheating and post heating is very often required and is also reduced when using low hydrogen electrodes. Smaller sections will often have enough heat input by the welding process, but a little preheat and low hydrogen electrodes will reduce the chance of a failure.
 
It is best to aviod welding free cutting steels, and use a normal steel for parts that you know are going to be welded.
 
Regards Nick.
Weldsol11/03/2011 08:15:15
74 forum posts
Hi Nick what you are describing sounds more like Hydrogen cracking and the pre and post heating will help
Lead bearing free cutting steel will give rise to porosity.
Sulphur bearing free cutting steel will give rise to cracking
Both of these are not limited to thickness
Pre heating will in fact make matters worse as this will give rise to more dilution of the base material.
EN 3b is the material that is weldable and will give a good finish when machining
 
Paul
David Clark 111/03/2011 10:57:20
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3357 forum posts
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Hi There
EN1A leaded and EN1A tend to crack when welding especially when in thin sections.
regards david
Andrew Binning11/03/2011 11:11:42
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I wish I hadn't mentioned welding leaded steels!!! It was not on the topic of the original thread.
 
However thank you for all the information, I have had my knowledge extended by the replies to this thread. Hopefully Alan Worland has not been too confused by it all!
 
Regards to everyone,
 
Andrew Binning
 
 
Nicholas Farr11/03/2011 11:20:20
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3988 forum posts
1799 photos
Hi Paul, yes it is like you say Hydrogen cracking but is often refered to as "Cold Cracking". In Leaded steel atomic Hydrogen is drawn into the HAZ, but Hydrogen is insoluble in ferrite (iron) so on cooling molecular Hydrogen is rejected and forms high pressure pockets, crystal voids, Hydrogen entrapment. These Hydrogen voids reduce the strength and cracks form, and lead to sudden failure some days after it has been welded.
 
No they are not limited to thickness, but a smaller section will achieve enough heat for this effect not to occur so readily. In my old company I used to work for, we used to weld shafts up to 4" in diameter into conveyor belt drums. At one piont the turner who used to make them started to use leaded free cutting steel, and the problems of them snapping off at the weld started. Pre heating and post heating prevented this, but was more costly and time consuming, nor was very practical to implament. Such shafts were subsequently made from non free cutting steels and the problems no longer occured.
 
Sulphur in steels is very prone to "Hot cracking" due to iron sulphide forming in steels above 0.04%. Most steels are made with less than this, but it can be imported into the weld from a variety of sources. Iron sulphide melts at about 1000 C, if the steel is cooled below 980 C the Iron sulphide solidifies. Due to high contraction rates and the weak nature of iron sulphide, fracture occurs on solidification of the weld. Thankfully I haven't had the pleasure of welding sulphur steels.
 
MIG welding is regarded as low Hydrogen. But as I've said, its best to aviod welding free cutting steels, especially leaded or sulphur ones.
 
Regards Nick.
 
P.S. Andrew may not be OT, but I feel it is related. Can be disheartening turning something up nicely and then welding it into somrthing else only to find it failing later on.

Edited By Nicholas Farr on 11/03/2011 11:33:10

mgj11/03/2011 17:41:25
1017 forum posts
14 photos
You are absolutely right, but again a lot depends on the job, and unless the job is for critical applications you'll get away with MIg welding 230M07 pb quite happily in our sorts of sizes. (define critical! Also depends on the loading and whether changes in section close to welds have been properly radiused
 
If the application is critical, then one is possibly better off silver soldering, and thats is usually better because distortion is less likely to be a problem.
Alan Worland11/03/2011 17:44:37
247 forum posts
21 photos
Well! Thanks for all the info on welding EN1A, I wasn't planning on welding it but it seems it may not have been totally succesfull
May be worth getting hold of Tubals book as my 'metal drawer' is full of all sorts, although I haven't come across anything which cuts and finishes so well.
 
Alan

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