Any advantages to cheap copper coated steel/alloy wire? - EEVblog

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kalel

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Any advantages to cheap copper coated steel/alloy wire?

« on: September 01, , 09:06:02 am » I know that there are many disadvantages (more resistance, for one), those being cheap replacements for the real thing.
However, are there any advantages to steel or aluminum copper coated wires? Maybe there's some niche use out there where it might work better.

Just seems like an interesting topic to enquire about. « Last Edit: September 01, , 09:10:30 am by kalel »

Ian.M

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Re: Any advantages to cheap copper coated steel/alloy wire?

« Reply #1 on: September 01, , 09:19:33 am » Well you can MIG weld with the steel stuff! 

Seriously, for longer HF suspended cables, where the frequency can be high enough to keep >90% of the current in the copper skin, solid core CCS (for strength) or CCA (for light weight) wire can be useful.

Any stranded cable smaller than 1/0 AWG made from Aluminum isn't fit for purpose for electrical supply, and neither are fit for purpose for data cabling. The following users thanked this post: kalel

kalel

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Re: Any advantages to cheap copper coated steel/alloy wire?

« Reply #2 on: September 01, , 02:32:38 pm »

Well you can MIG weld with the steel stuff! 

Seriously, for longer HF suspended cables, where the frequency can be high enough to keep >90% of the current in the copper skin, solid core CCS (for strength) or CCA (for light weight) wire can be useful.

Any stranded cable smaller than 1/0 AWG made from Aluminum isn't fit for purpose for electrical supply, and neither are fit for purpose for data cabling.

Since steel is magnetic, how does that impact the functionality of a coil made from such a wire? They are usually not of course, just curious.

Nauris

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Re: Any advantages to cheap copper coated steel/alloy wire?

« Reply #3 on: September 01, , 08:02:20 pm » Around here overhead cables use copper clad steel cable. Like this MHBU: http://www.nestorcables.com/copper-telecom-cable/mhbu The following users thanked this post: kalel

CatalinaWOW

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Re: Any advantages to cheap copper coated steel/alloy wire?

« Reply #4 on: September 01, , 08:27:38 pm » Your title identifies the number one advantage, with broad applicability.  The second is anywhere that strength is required.  Antennas, telephony, balloon tethers and the like. 

Copper coating such wires would help in corrosion resistance and possibly in making the connections.

Conductivity is not the be-all and end-all of properties for electrical wire.  If it were all wire would be silver. The following users thanked this post: kalel

calexanian

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Re: Any advantages to cheap copper coated steel/alloy wire?

« Reply #5 on: September 03, , 11:56:57 pm » Most hams are familiar with coper clad steel wire as antenna wire. Electrical properties of the copper because of skin effect, and mechanical strength of the steel to keep the antenna from stretching. For general power distribution use I see no advantage to it. Only the higher impedance of the steel which of course is not a good thing in power circuits.  Charles Alexanian
Alex-Tronix Control Systems

T3sl4co1l

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Re: Any advantages to cheap copper coated steel/alloy wire?

« Reply #6 on: September 04, , 01:34:17 am » I recently realized my RG-174 has copper clad steel core.  Probably for strength, or, just because it doesn't matter?

RG-174 is so lossy to begin with, at high frequencies, it doesn't much matter that it's got steel inside.  At low frequencies, where the steel will give excess AC resistance, the current rating is still only an ampere or so, so who cares.

Tim Seven Transistor Labs, LLC
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floobydust

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Re: Any advantages to cheap copper coated steel/alloy wire?

« Reply #7 on: September 04, , 01:39:05 am » Lately through-hole resistor leads are magnetic, I think it's lower cost and spot-welding ease for wirewound parts.

stj

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Re: Any advantages to cheap copper coated steel/alloy wire?

« Reply #8 on: September 04, , 02:15:24 am » i suspect that's the tin plating the magnet is finding.

T3sl4co1l

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Re: Any advantages to cheap copper coated steel/alloy wire?

« Reply #9 on: September 04, , 02:17:42 am » "Lately" as in the last half a century or so.   Tinned steel (sometimes with copper clad / underplate) is not unusual, or harmful, in most applications.  If anything, it's completely beneficial: resistors benefit from the reduced thermal conductivity and increased strength and elastic modulus, without worrying about the increased resistance, because, they're already resistors and the couple extra microohms in the leads don't matter.  (Current sense resistors often are copper leaded, for thermal dissipation keeping the leads cool, and for minimizing excess resistance, so that the low-tempco resistive element dominates.)

One annoying use I can think of offhand: Orange Drop (Vishay/Sprague 715P) caps have tinned steel leads, which sucks for high RMS current applications.  The cap itself is quality polypropylene film and heavy metallizing, or foil (I forget which), so capable of quite a lot of peak current.  Alas, they don't even put an RMS rating on them.  With heavy copper leads, they could assign a quite generous RMS spec, I think.  And then they'd actually be worth paying for, for those applications where you need that much current.

Tim Seven Transistor Labs, LLC
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nanofrog

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Re: Any advantages to cheap copper coated steel/alloy wire?

« Reply #10 on: September 04, , 02:49:18 am »

Lately through-hole resistor leads are magnetic, I think it's lower cost and spot-welding ease for wirewound parts.

I've only noticed it in the really cheap/nasty stuff, which can really suck for use in a breadboard (thinner than tinned copper & bend far easier as well).

But this probably has to do with the fact I've switched to SMD on proto-boards and/or SMD adapter boards for IC's, and I just buy decent thru-hole stuff on an as-needed basis (i.e. high power dissipation). Both methods happen to reduce necessary on-hand stock as well as reduces component storage space.

Tinned copper leads are still available, and don't have to cost an arm + leg either. Take Royal Ohm for example; Tayda sells them for $0.012 per for Q=10 min. (both companies are located in Thailand).

Not much different from other sources either, such as TME ($0.011 per for Q=100 min.). These larger suppliers can also offer more products than Tayda, particularly in the SMD realm and a greater selection in values overall (SMD or thru-hole), and faster delivery (Tayda is slow; they initially ship their orders by container IIRC).

i suspect that's the tin plating the magnet is finding.

Tin is a paramagnetic substance from a technical standpoint, but it's so weak that it's effectively non-magnetic for all practical purposes.

So using a magnet is a good way to check to see if your component leads are steel.  The following users thanked this post: kalel

kalel

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Re: Any advantages to cheap copper coated steel/alloy wire?

« Reply #11 on: September 04, , 05:57:01 am »

So using a magnet is a good way to check to see if your component leads are steel. 

Yes, I have used a simple small magnet recently to find out some wires I thought were copper had steel (or something magnetic) also. Cheap dupont jumper cables. It might make them more durable however and for the price and type of projects I generally work with, it might not be important to have a bit more resistance.

I even made a little coil (0.22 uH) with this type of wire for a Joule Thief test. It's definitely not easy to wrap it around things, and I'm not sure how the steel affects the magnetic field in operation.

T3sl4co1l

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Re: Any advantages to cheap copper coated steel/alloy wire?

« Reply #12 on: September 04, , 07:28:02 am » Mind that you'll occasionally see nickel plated wire, or nickel underplate.  This is mildly magnetic, much like [work hardened 304 and 316] stainless steel is, but mild because the layer is thin.

An example is mil spec Teflon wire, when it is nickel rather than silver plated.

Tim Seven Transistor Labs, LLC
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Bringing a project to life?  Send me a message! The following users thanked this post: kalel

CatalinaWOW

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Re: Any advantages to cheap copper coated steel/alloy wire?

« Reply #13 on: September 04, , 04:56:34 pm »

Cheap dupont jumper cables. It might make them more durable however and for the price and type of projects I generally work with, it might not be important to have a bit more resistance.

Numbers are appropriate.  The conductivity of "copper" and "steel" can vary pretty widely depending on the specific alloy and condition.  The copper used in wires is less likely to vary widely and is likely to be approximately 1.8E-8 ohm-m, though some alloys and conditions can be two or three times higher or lower than that.   "Steels" vary much more widely ranging from 9.6E-8 ohm-m for pure iron clear up to 2E-6 for the worst alloys.  The most likely alloys for wires run around 1.7E-7 or roughly 10 times worse than copper.

Sounds horrible, but in reality for a test lead in copper that is 20 gauge, two feet long you are talking 0.02 ohm.  In "steel" that might become 0.2 ohm.  Even if you are pushing an amp through that test lead it is only 0.2V drop.  Not always negligible, but it will be in many cases.  The following users thanked this post: kalel

floobydust

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Re: Any advantages to cheap copper coated steel/alloy wire?

« Reply #14 on: September 04, , 08:48:12 pm » excerpt from Audio Power Amplifier Design Handbook. – 5th ed. Self, Douglas  ISBN:  978-0-240--6

Distortion 9: Magnetic Distortion

"This arises when a signal at amplifier output level is passed through a ferromagnetic conductor. Ferromagnetic materials have a nonlinear relationship between the current passing through them and the magnetic flux it creates, and this induces voltages that add distortion to the signal. The effect has been found in some types of output relays where the signal being switched passes through the soft-iron frame that makes up part of the magnetic circuit. That particular manifestation is dealt with in detail in Chapter 17, where output relays are examined.

The problem has also been experienced with loudspeaker terminals. The terminal pair in question was a classy-looking Chinese item with all its metal parts gold-plated, and had proved wholly satisfactory at the prototype stage. Once again the product involved was trembling on the brink of mass production, and once again the pre-production batch showed more distortion than expected. The THD residual showed third-harmonic distortion that had certainly not been there before. Some rapid investigation revealed the hitherto unknown concept of nonlinear loudspeaker terminals. The metal parts of the terminals appeared to be made of gold-plated brass (as they were in all the prototype samples) but were actually gold-plated steel, which is of course a cheaper material   –  brass has copper in it, and copper is expensive. Although the amplifier output currents were only passing through about 10 mm of steel (the current went through that length twice, on go and return), the nonlinear magnetic effects were sufficient to increase the output distortion from 0.% to 0.% at 100W into 8R at 1kHz.  In  other words distortion nearly doubled. It is, however, highly likely that if the offending terminals had been used with a non-Blameless amplifier having rather more distortion of its own the extra nonlinearity would have gone completely unnoticed, and I can only presume that this was what the manufacturer hoped and expected. Parts incorrectly made from steel can of course be readily detected by the application of a small magnet. " The following users thanked this post: kalel

CatalinaWOW

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Re: Any advantages to cheap copper coated steel/alloy wire?

« Reply #15 on: September 05, , 12:08:02 am »

excerpt from Audio Power Amplifier Design Handbook. – 5th ed. Self, Douglas  ISBN:  978-0-240--6

Distortion 9: Magnetic Distortion

"This arises when a signal at amplifier output level is passed through a ferromagnetic conductor. Ferromagnetic materials have a nonlinear relationship between the current passing through them and the magnetic flux it creates, and this induces voltages that add distortion to the signal. The effect has been found in some types of output relays where the signal being switched passes through the soft-iron frame that makes up part of the magnetic circuit. That particular manifestation is dealt with in detail in Chapter 17, where output relays are examined.

The problem has also been experienced with loudspeaker terminals. The terminal pair in question was a classy-looking Chinese item with all its metal parts gold-plated, and had proved wholly satisfactory at the prototype stage. Once again the product involved was trembling on the brink of mass production, and once again the pre-production batch showed more distortion than expected. The THD residual showed third-harmonic distortion that had certainly not been there before. Some rapid investigation revealed the hitherto unknown concept of nonlinear loudspeaker terminals. The metal parts of the terminals appeared to be made of gold-plated brass (as they were in all the prototype samples) but were actually gold-plated steel, which is of course a cheaper material   –  brass has copper in it, and copper is expensive. Although the amplifier output currents were only passing through about 10 mm of steel (the current went through that length twice, on go and return), the nonlinear magnetic effects were sufficient to increase the output distortion from 0.% to 0.% at 100W into 8R at 1kHz.  In  other words distortion nearly doubled. It is, however, highly likely that if the offending terminals had been used with a non-Blameless amplifier having rather more distortion of its own the extra nonlinearity would have gone completely unnoticed, and I can only presume that this was what the manufacturer hoped and expected. Parts incorrectly made from steel can of course be readily detected by the application of a small magnet. "

Again, horses for courses.  As I recall many commercial amplifiers have distortion in the .02% class. Won't make the audiophiles happy, but is apparently good enough for most people.   As you say, the speakers extra .% distortion will go totally unnoticed in those amplifiers.   If you are trying for the very best you will need to watch for these small effects, but in many cases they won't matter.  Same thing for test leads.  If you are trying for 6, 7 or 8 digits of accuracy you will not want these in your test leads.  But if you are using a count meter you will often not notice the impact.

The art of engineering is making things "good enough" without taking more time or money than necessary.  The scientists and dilettantes can endlessly pursue more digits of perfection.  Scientists with good reason - and the others are just making themselves happy so that is ok too.

Back to numbers.  Ratio of steel conductivity to copper conductivity is relatively constant.  The ratio of steel price to copper prices varies a lot.  At the moment the cost of conductivity is lower in steel than it is for copper, by my memory by roughly a factor of two.  Over the past few decades that has reversed more than once and at one point I remember the cost was lower for copper by roughly the same factor of two.  But if your application can stand the extra weight, magnetic affects and stiffness the price might make you choose steel over copper.

These economic things mean that few engineering answers are static.  The best solution in one decade may be foolish in the next. The following users thanked this post: kalel