Low carbon steel / soft iron (not steel) CONFUSION

[RobGer]

"Low carbon steels."
"annealed steel"
"soft iron (not steel)"
"A nice cold rolled carbon steel [e.g. 1006, 1008] "
"material is Si-Fe alloy."
"high permeablility low Hc materials "

These are all descriptions of recomended materials with suitable properties for electromagnets etc. as described on this forum.

I'm seriously confused.
I'm looking for a suitable steel/iron core for a DC Electromagnet. Sorry for my ignorance.
Could someone please clarify difference between "Low carbon steel" and "soft iron" for me?
Also, why anealed and low carbon?

Explanations appreciated.

RobGer

 

[EdStainless]

OK, you need to decide which properties you really need.
In truth there are two, Saturation (B) and core loss (related to H and construction details).
In a DC application the second one doesn't matter.
Since we are not concerned with resistivity and hysteresis, only saturation, then we can lump a lot of things together. One catch is that permeability may matter if you are not magnetizing to high field strengths.
In Fe, any trace impurity will decrease the Bmax and perm. At low levels almost every type of impurity will have a similar effect. The effect of cold work and strain will harm the properties also.
In paractice, availability often drives these decisions. Only for special applications can you afford to select the optimum material. Usually a well annealed, low carbon steel is good enough. The lower the carbon the better, so 1002 would usually be better than 1008 for this application.
The effect of Si is to imcrease the resistivity and reduce eddy currents in AC applications. Si gives the most improvement in resistivity with the least harm to other properties.

I think that there are Bmax vs concentration curves for various impurities in Fe in Bozorth. I'll have to look.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[israelkk]

Just to add to EdStainless, even in DC applications residual magnetism (when the current is zero) can be an issue esspecially in electromagnets. The purer the metal the lower the residual magnetism.

 

[RobGer]

Thanks for your helpfull replies EdStainless & israelkk.

I will now approach my local steel suppliers in search for an annealed, 1002 low carbon steel for testing.

Regards,

RobGer

 

[dgallup]

Depending on the sensitivity of your application, you may be able to tolerate a lot more carbon than 1002. A lot of solenoid & relay manufactures get away with un-annealed 12L14 which has pretty rotten magnetic properties but has great cost, availability and machinability benefits.

 

[RobGer]

Thanks for considering my requirements dgallup.
I cant fing Australian supplier of low carbon steel.
The lowest readily available is 1214 as you suggest.
I'll give it a try!

Best Regards.

RobG