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Am I blackening steel correctly?

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vintagengineer02/01/2017 18:26:54
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When you send a car to the scrapyard it goes whole( engine, gearbox & back axle) into a frag machine that is a large shredder. A lot of modern cars are now made of boron high tensile steel to keep the weight down. Also the springs, camshafts, driveshafts and anti roll bars are all made of high carbon steel which all goes into the pot for black mild steel.

From my own experience as a blacksmith, I can assure you that I have forged black mild steel and it has become as hard as glass in places due to poor quality control.

The only steel you can rely on is structural beams and new steel made to a specific steel grade. I only use black mild steel for non structural decorative work.

Posted by Tony Pratt 1 on 02/01/2017 13:18:36:

Posted by Michael-w on 02/01/2017 12:59:05:
Posted by vintagengineer on 02/01/2017 12:44:36:

Be careful if using black mill scale steel as this is now made from recylced cars and can contain all sorts of crap, including boron and tool steel. and can be hardened to the point of shattering. Structural steel beams are made from new steel.

Hi,

Is there any evidence to back that up?

Michael W

I'm also waiting with bated breath for justification from 'vintagengineer' for his original staementfrown

Michael-w02/01/2017 18:39:41
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2018 forum posts
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Posted by vintagengineer on 02/01/2017 18:26:54:

When you send a car to the scrapyard it goes whole( engine, gearbox & back axle) into a frag machine that is a large shredder. A lot of modern cars are now made of boron high tensile steel to keep the weight down. Also the springs, camshafts, driveshafts and anti roll bars are all made of high carbon steel which all goes into the pot for black mild steel.

From my own experience as a blacksmith, I can assure you that I have forged black mild steel and it has become as hard as glass in places due to poor quality control.

The only steel you can rely on is structural beams and new steel made to a specific steel grade. I only use black mild steel for non structural decorative work

 

Then you are using it for the right purpose, it is not intended for structural work, this applies to both BMS and black steel. Here is a quote of a typical chemical analysis for 070M20 (EN3A), the bright version is EN3B.

**LINK**

It should conform at least roughly to that analysis, I don't see a mention of boron in there, I know it's hard to test this, but if it isn't conforming to these numbers, it isn't mild steel by definition. And i'd imagine it certainly wouldn't be what the common stockists will be offering. If you go to a scrap yard or recycling plant for steel, you can expect the lottery that comes with it.

Michael W

Edited By Michael-w on 02/01/2017 18:41:38

vintagengineer02/01/2017 19:52:35
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459 forum posts
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Any mild steel containing ANY recycled steel will not meet any standard steel specification, also the majority of black steel is imported. I cannot vouch for BMS but I will ask my supplier tomorrow where this is new steel or recycled steel.

Posted by Michael-w on 02/01/2017 18:39:41:

Posted by vintagengineer on 02/01/2017 18:26:54:

When you send a car to the scrapyard it goes whole( engine, gearbox & back axle) into a frag machine that is a large shredder. A lot of modern cars are now made of boron high tensile steel to keep the weight down. Also the springs, camshafts, driveshafts and anti roll bars are all made of high carbon steel which all goes into the pot for black mild steel.

From my own experience as a blacksmith, I can assure you that I have forged black mild steel and it has become as hard as glass in places due to poor quality control.

The only steel you can rely on is structural beams and new steel made to a specific steel grade. I only use black mild steel for non structural decorative work

Then you are using it for the right purpose, it is not intended for structural work, this applies to both BMS and black steel. Here is a quote of a typical chemical analysis for 070M20 (EN3A), the bright version is EN3B.

**LINK**

It should conform at least roughly to that analysis, I don't see a mention of boron in there, I know it's hard to test this, but if it isn't conforming to these numbers, it isn't mild steel by definition. And i'd imagine it certainly wouldn't be what the common stockists will be offering. If you go to a scrap yard or recycling plant for steel, you can expect the lottery that comes with it.

Michael W

Edited By Michael-w on 02/01/2017 18:41:38

not done it yet02/01/2017 20:29:27
1900 forum posts
11 photos

I would suggest that the problem that vintage engineer refers to is one of cheapo recycling. Poor homogenisation of the constituents while in the melting pot? Certainly there would be variations between batches but that should, with quality control, be minimised.

The problems could be avoided, but at a price as usual.

Dave Halford02/01/2017 20:32:52
201 forum posts

I have some old 1935 C section steel used for telecoms racking some parts cut / drill well and some spots are hard.

So mixed scrap in steel is nothing new.

I remember old 60's/70's jap cars rusting rather badly.

Nick Hulme02/01/2017 21:47:53
523 forum posts
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Don't type your post here!
Posted by vintagengineer on 02/01/2017 19:52:35:Any mild steel containing ANY recycled steel will not meet any standard steel specification

Type below your quoted text to avoid your text being displayed by the system as part of what you're quoting.

:D

Neil Wyatt02/01/2017 22:30:01
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13606 forum posts
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Or click on the top line then mouse click on the red arrow to insert a plain text line before the quote.

Posted by Nick Hulme on 02/01/2017 21:47:53:
Don't type your post here!
Posted by vintagengineer on 02/01/2017 19:52:35:Any mild steel containing ANY recycled steel will not meet any standard steel specification

Type below your quoted text to avoid your text being displayed by the system as part of what you're quoting.

:D

vintagengineer02/01/2017 22:47:44
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459 forum posts
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Thank you for your polite response.

Posted by Neil Wyatt on 02/01/2017 22:30:01:

Or click on the top line then mouse click on the red arrow to insert a plain text line before the quote.

Posted by Nick Hulme on 02/01/2017 21:47:53:
Don't type your post here!
Posted by vintagengineer on 02/01/2017 19:52:35:Any mild steel containing ANY recycled steel will not meet any standard steel specification

Type below your quoted text to avoid your text being displayed by the system as part of what you're quoting.

:D

Neil Lickfold02/01/2017 22:51:07
435 forum posts
85 photos

There is a hot process that takes place at about 140deg C, you can buy the stuff from heat treatment supply companies. It has caustic soda in it, and other salts. I consider it safe to use if you take the appropriate precautions.

They will also give you the instructions for it's proper use. It does not work on stainless steels or steels with a high chrome content. But us great for MS or heat treated A2 tool steel and P20 that I know of, does not effect a steels temper as the 140C is below the steels tempering range.

Neil

Ajohnw02/01/2017 23:01:16
3631 forum posts
160 photos
Posted by Dave Halford on 02/01/2017 20:32:52:

I have some old 1935 C section steel used for telecoms racking some parts cut / drill well and some spots are hard.

So mixed scrap in steel is nothing new.

I remember old 60's/70's jap cars rusting rather badly.

60's 70's ? There were hardly any around then. There were a few about in the 80's but serious numbers came later. That's when they had steel supply limitations. Also near the start of oil technology getting well ahead of car engines and as far as the manufacturers were concerned lasting far to long.

There was a lot of crap mild steel around during wwII. My father told me that they had a name for it in toolrooms - park railings. As they were collecting them and resmelting them. There can still be crap pieces of steel about but sorry I don't think that has anything to do with recycling the stuff.

John

-

John

-

Michael Gilligan02/01/2017 23:22:15
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11244 forum posts
477 photos

I'm surprised no-one has mentioned the FIAT story [myth?] discussed here: **LINK**

http://message.snopes.com/showthread.php?t=30479

See post #13 if you can't be bothered reading the whole page.

MichaelG.

PaulR05/01/2017 21:41:11
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123 forum posts
21 photos

Off topic to the OP but on topic as far as recycled steel goes...

The most free cutting mild steel I've ever used came from some 're-purposed' plastic coated rods from a 1990s vintage clothes airer (and I still have about half a dozen 3ft lengths)!

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