B-H curve variations for low carbon alloys 1

[israelkk]

Looking for documented data of the magnetic properties variation (tolerances) of the B-H curve for commercial low carbon alloys such as AISI 1010, 1018, 1020 and AISI 12L14, 1113, 1117 etc.

 

[cesaredu13]

I foun this 1018 Steel here on the forum.
Steel 1018 (Low carbo steel)
H (amp/m) B (Tesla)
0 0
238.73 0.250
795.78 0.925
1591.55 1.250
2387.33 1.390
3978.88 1.525
7957.75 1.710
15915.5 1.870
23873.25 1.955
39788.75 2.020
79577.5 2.110
159155 2.225
318310 2.430

And the 1008 & 1010 are from the Maxwell SV Software.

Steel 1008( Low Carbon steel)
H (A/m))B (Tesla)
0 0
159.2 0.2402
318.3 0.8654
477.5 1.1106
636.6 1.2458
795.8 1.331
1591.5 1.5
3183.1 1.6
4774.6 1.683
6366.2 1.741
7957.7 1.78
15915.5 1.905
31831 2.025
47746.5 2.085
63662 2.13
79577.5 2.165
159155 2.28
318310 2.485
397887 2.585

Steel 1010 (Low Carbon Steel)
H(A/m) B (Tesla)
0 0
238.7 0.2003
318.3 0.3204
358.1 0.40045
437.7 0.50055
477.5 0.5606
636.6 0.7908
795.8 0.931
1114.1 1.1014
1273.2 1.2016
1591.5 1.302
2228.2 1.4028
3183.1 1.524
4774.6 1.626
6366.2 1.698
7957.7 1.73
15915.5 1.87
31831 1.99
47746.5 2.04
63662 2.07
79577.5 2.095
159155 2.2
318310 2.4

Hope this help.

 

[israelkk]

cesaredu13

Thank you for the post. However, those are fixed values where it is not clear if those are minimum, typical or maximum properties. I am looking for the variations from those values too.

AISI 1008, 1010 and 1018 are not defined as electrical steels therefore there is no magnetic properties requirements from the metal founder according to metal spec (ASTM). Therefore, to correctly design solenoids with a minimum factor of safety for the solenoid forces, those variations are required.

 

[MJR2]

One thing I do when there is a concern about the quality of steel affecting the design is to run a sensitivity analysis. Run your design through FEA using a range of the steel properties. Then you will know just how much of a concern it really is. Maybe to cover the variability you'll need to spec a better grade.

Mike

 

[israelkk]

MJR2

Electrical steels (better grade) are difficult to machine and they are a must when you use AC electricity. I am using DC electricity supply and has all the knowledge and tools to analyse magnetic circuits (solenoids, valves etc.) using FEA and analytical tools. FEA programs and data in books give the properties of the commercial grades of low carbon steels as a single curve. I know for fact that real life different batches of materials vary considerably from the typical documented curves. I just look for any work done by anyone to map the properties for variety of batches and how much it deviates from the typical curves used in FEA programs or given in books.

 

[MJR2]

israelkk

If I had been a bit more motivated I would have a 12L14 curve handy. So I just sent out a sample. I'm getting into machined parts where the vendor wants to use it.

I plotted up all of my curve data including the three above. I've got a nice .pdf file of seven similar/different steels that help illustrate what you are talking about. Except I don't know how to post it. A .jpeg just will not make it for resolution.

The short answer is with data from three sources for 1018 steel I have three curves. I live with the the data I have measured. Looking at the curves I find that I try to design in the area where it minimizes the differences from steel to steel. In other words 1.6 to 1.8 tesla.

Your purchasing people will be constantly asking if you really mean 1010 or 1020. I was asked that this morning. And yes the spec says 1010 for a reason.

Get samples and send them to KJS as I have this morning. I have provided B-H curves on occassion to steel suppliers and told them I expect the steel to make that spec.

I drives one a bit crazy to think about how much all the stuff we use in the designs varies. Steel, permanent magnets, wire resistance, winding technique, machining and fab tolerances, ambient temperature, temperature cycles, and measurment techniques to mention a few. All of this and they think we can design to plus/minus five percent or less. They think I'm good as often as it happens. I'm surprised every time.

Mike

 

[dgallup]

For critical applications you can specify minimum magnetic properties if you are buying specialty magnetic alloys. Expect to pay for it. Commodity alloys like 1010 & 12L14 are never tested by the mills. You would have to do it in house or send out to a lab like KJS. It will take a lot of samples to find the real production spread. I always hear horror stories about the "one lot of steel" that would just never work despite the chemistry being in spec, re-annealing, etc. I've never experienced it in 25 years.