Build materials

[nightmare]

According to the "Thatcham vehicle description" of the carlton

 "High strength steels" are NOT used in the production of this vehicle.

So WHAT did they use....



Dagenham rustbins rejects.

Cardboard and sticky back plastic?

Or some other substance that is and forever will remain a trade secret.

[Catho]

I think mine (before I started restoration) was constructed from pure Iron Oxide.....

[melinx]

The metallurgists on the forum will probably correct me but I believe that the 'high strength steels' means high carbon steel which is more prone to corrosion than medium or low carbon steel.

I think that it has something to do with the way corrosion penetrates more easily into the grain boundaries of high carbon steel.

It just means that a slightly thicker gauge of steel is required to achieve the required strength.

[Pedro]

The metallurgists on the forum will probably correct me but I believe that the 'high strength steels' means high carbon steel which is more prone to corrosion than medium or low carbon steel.

I don't think there's a difference that is all too noticaeble. High carbon = less iron oxide = less rust. In theory!

It just means that a slightly thicker gauge of steel is required to achieve the required strength.

Actually, the opposite applies.
Professional roll cages are made from something called T45 tubing. 3 times lighter than CDS m(cold drawn steel), twice as strong as CDS and 3 times the price! It distorts less when welded (bonus!) too. The equivalent sheet steel (spec name eludes me at the mo) used on chassis mods and strengthening has the same qualities.
The obvious difference is that the higher grade steel is stringer, so less is needed to achieve the desired effect compared to cheap-sh1t steel.
The carbon content is considerably higher than the cheap-sh1t steel used to build 95% of all cars (excluding the likes of Aston Martin, Ferrari, mid to  high end Mercedes, BMW, Audi, SAAB etc).
That's one reason why 'premium' brands cost more. They rust less and stay stronger for longer, ergo, you're in a safer 'cage'.

[melinx]

I've had a good look on the Internet and you're right of course; there is no real evidence to support the statement that high carbon steels rust faster than low carbon.

It would seem that many years ago I was fed some 'urban mythology' by someone who I believed knew what he was talking about.

The specification for the T45 that you mention is, I believe : -

T45 is a carbon manganese cold drawn seamless tube. The full spec is BS 4T45:1972.

Weight %:
C: 0.17 - 0.25
Si: 0.10 - 0.35
Mn: 1.30 - 1.70
Cr: 0.25 max
Ni: 0.40 max
Mo: 0.10
P+S: 0.040 max

Typical Mechanical Properties:
Treatment: Hardened and Tempered
Tensile Strength (Rm, N/MM2): 700 / 900
Proof Stress (Rp 0.2, N/MM2): 620
Hardness HB: 201 / 262

The various alloying elements make it considerably stronger and less corrosion prone than mild steel;  the inclusion of manganese makes it pretty tough (it makes railway lines very hard wearing)

[Pedro]

I've had a good look on the Internet and you're right of course; there is no real evidence to support the statement that high carbon steels rust faster than low carbon.

Carbon doesn't corrode like iron or steel (which contains alot of iron), iron ore most definitely does!

More carbon content = less rust.

QED

BTW, when people talk about wheels being 'alloys' and meaning aluminium alloy wheels, then yes they are right.
But steel is an alloy. So you can have steel wheels AND call them 'alloys' and be correct - and very smug -  on both counts!

[melinx]

More carbon content = less rust.

Err, I have to say that my search didn't show anything to back that up either !

More nickel = less corrosion, but not carbon

[Pedro]

Is the internet always the definitive answer to life, the universe and everything?

If the carbon takes up the 'space' in the steel alloy that would normally be occupied by iron ore and other ferrous composites, then there HAS to be less rust!
Doesn't there?

I don't know how carbon or (nickel for that matter) deteriorates, or what it's called when it corrodes, or even how it corrodes - assuming it does corrode. Which I'm not sure that it does - then again, they both disappear when the rest of the steel corrodes (rusts) and eventually turns to dust..........so I guess they must do.