Hi,

Quite a technical question here.

For the Early Santa cruz bullit’s that are made in the USA from 2002/2003 that are made with 7005 aluminium before they changed frame material to 6061.

Does any one know if the 7005 frame is heat treated or non heat treated when its built?

Cheers for reading!

Are you sure they were ever 7005?

I dunno what they did post welding but to get the best properties a typical heat treatment regime for 7005 would be like this (its t53 which applies to extrusions but the tube treatment would be broadly similar) from ASM handbook.

Fabrication Characteristics
Annealing temperature. 345 °C (650 °F)
Solution temperature. 400 °C (750 °F)
Heat treatment. T53: Press quench from hot working temperature, naturally age 72 h at room temperature, then two-
stage artificially age 8 h at 100 to 110 °C (212 to 230 °F) plus 16 h at 145 to 155 °C (290 to 310 °F)

But in lots of cases 7005 isn’t heat treated as it retains ok ish properties after welding (whereas 6061 is pretty dreadful after welding). You see lots of lower end bikes made of 7005 these days and it wouldn’t surprise me if they keep them cheap by not heat treating them.

I do know that the 6061 frames are/were heat treated post weld as I’ve had a few long telecons with some guys at SC USA 5 years ago.

7005 can be precipiation hardened at room temperature (naturally aged) to the T6 condition over a period of 2 or 3 weeks.
To weld 6061 if it is already in the T6 condition and then artificially age it would take it to the T7 condition (which can happen when a frame is powder coated, similar time and temperatures are involved). T7 = overaged.
http://www.alcotec.com/us/en/solutions/-Understanding-the-Aluminum-Alloy-Designation-System.cfm

To weld 6061 if it is already in the T6 condition and then artificially age it would take it to the T7 condition (which can happen when a frame is powder coated, similar time and temperatures are involved). T7 = overaged.

Normally if planning to heat treat post fabrication you would start with 6061-O. Do your forming and welding and then solution/quench/age.

The only issue with natural ageing is that it can lead to unstable microstructure which may over age itself, whereas if you artificially age it tends to make it stable.

Even more complexity now is that the simple solution quench age processes are being replaced by 2/3/4 stage process which lead to very specific strength or corrosion resistance microstructures that are becoming very difficult to know about as the manufacturers tend to keep their cards close to their chests..

FATBOYSLIM – Why the question?

PS Macavity don’t mention the powder coating thing, whilst you and I know this to be true we will still get flamed to hell and back for even daring to mention it.

IIRC, historically, US built frames were generally made of 6061 and Far East frames of 7005 simply because that’s what the native aluminium mills made the most of in each region…..

FATBOYSLIM – Why the question?

+1

IIRC, historically, US built frames were generally made of 6061 and Far East frames of 7005 simply because that’s what the native aluminium mills made the most of in each region…..

This is interesting. I used to work in the Aluminium industry, and I heard some funny stories of US mills (ie ALCOA) trying to push their customers around, forcing them to only take certain materials etc. Until they bumped into Boeing..

OK – the reason for my question is I just bought a Santa cruz Bullit, it’s a 2002 version, ( i know this because its with out the extra headtube gusseting and a bend in the seatpost tube and a different head angle which only allows a 5 inch fork).

So this makes it an early version of the bullit. The frame states it’s made in the USA.

The later versions of the bullit were made in Taiwan from 6061.

By having a read on the internet, 7005 is stronger than 6061, but is more difficult to make stronger bike frames. So cheap 7005 frames use more material making it a heaver frame. More expensive 7005 frames have to be heat treated for its strength, they use less material and are therefore stronger and lighter than a 6061.

So I’m trying to figure out if Santa Cruz went for the expensive heat treatment for building their bikes, or is they went for the cheaper option!

Phew!

Cheers for the replies.

I dunno if this is correct as I have a 2005 model which is made in USA and SC USA told me it is 6061 pwht to T6.

Toys19, you have the later version of the bullit, with more plates, welding, a straight seat post tube and a slacker head angle allowing you to go upto 6 inches of travel on the front, it’s defo 6061.

I just read that the frames are made in Taiwan, but everything is assembled in Santa cruz, or elsewhere in the USA, so it’s allowed to have the Made in the USA sticker on it!

OK toys19
got that.

I just read that the frames are made in Taiwan, but everything is assembled in Santa cruz, or elsewhere in the USA, so it’s allowed to have the Made in the USA sticker on it!

Ahhh crafty.

My memory of reading the catalogues (generally, not SC) was that 7000 series was used as there was no need to heat-treat it.

For those people who posted and maybe interested, I emailed santa cruz and asked them the question about 7005 frames and whether they were heat treated or not.
They replied that the frames were indeed heat treated first, allowing a lighter and strong frame to be produced.

Cheers for all the replies.