What is T6?

[Mac66]

In adverts for aluminium bike frames I often see something like "7005-T6" frame.

I think the T6 bit is about a heat treatment process, but can anyone explain what it actually involves. Is there a T scale?

Thanks

 

[alecstilleyedye]

t6 is indeed another way of saying heat treated. i've seen it on 6061 alu (my bike is that, but it says heat-treated, rather than t6). afaik t6 is not part of a scale, just another name for the process.

 

[Elmer Fudd]

T0 is as extruded.
T4 is solution treated and naturally aged.
T6 is solution treated and artificially aged.
Solution treated is where the alloy is extruded and cooled either by air or water to give a rapid temperature drop, this changes the grain structure to give a harder alloy.
Alloy gets "harder" the older it gets (ageing) so by cooking the alloy in ovens for a predetermined time (different temps and times for different alloys) you can make the alloy even stiffer.
1050 / 1070 is virtually pure alloy and as soft as poop.
6063 is the standard stuff you tend to see everywhere.
6061 is a slightly harder mix than 6063
7005 we are now getting into aerospace alloys.
3X04 A company specific alloy that is tough as old boots.

 

[LLB]

T0 is as extruded.
T4 is solution treated and naturally aged.
T6 is solution treated and artificially aged.
Solution treated is where the alloy is extruded and cooled either by air or water to give a rapid temperature drop, this changes the grain structure to give a harder alloy.
Alloy gets "harder" the older it gets (ageing) so by cooking the alloy in ovens for a predetermined time (different temps and times for different alloys) you can make the alloy even stiffer.
1050 / 1070 is virtually pure alloy and as soft as poop.
6063 is the standard stuff you tend to see everywhere.
6061 is a slightly harder mix than 6063
7005 we are now getting into aerospace alloys.
3X04 A company specific alloy that is tough as old boots.

You forgot 6082. Most extruders in the UK use either 6063 or 6082

 

[Elmer Fudd]

You forgot 6082

And Btre6, And 6005, 1024, etc etc
I wouldn't want a bike made out of '82 though, 1st pebble and you got a snapped frame !! **

**depending how its treated though.
You're right though, '63 is your glazing, decorative trim etc. '82 more architectural.

 

[LLB]

I worked on tooling which extruded solid bar out of 6082 (HDA Workington).

Boeing was the customer and it was used as a stiffener in the wings.

It was all controlled stretch stuff to work out he elasticity and get the temper grades IIRC

6082 is the ally of choice for many high stress situations and is used by all of the ally ladder companies like ABRU.

 

[LLB]

I'm not involved in the extrusion process directly (only if the dies don't run properly), but IIRC the temper grades are achieved by running presses up to a specific speed to give an extrusion speed through a water curtain or air blowers which give the correct temperature drop to achieve the desired temper.

One of our customers in Sweden has managed to achieve an extrusion speed of 50 metres a minute down the tables on 2 cavity 50mm dia (2mm WT)

 

[yenrod]

I'll have to look what mine is...

Frame, that is...

 

[alecstilleyedye]

7005 seems to be the most popular these days on mid range bikes, merida still use 6061 (it's how you can spot a merida frame with a carrera badge on), as do some other other makes. colnago have some 600 series alu frames too.

 

[Elmer Fudd]

I'm not involved in the extrusion process directly (only if the dies don't run properly), but IIRC the temper grades are achieved by running presses up to a specific speed to give an extrusion speed through a water curtain or air blowers which give the correct temperature drop to achieve the desired temper.

One of our customers in Sweden has managed to achieve an extrusion speed of 50 metres a minute down the tables on 2 cavity 50mm dia (2mm WT)

Spent my life correcting dies of all sorts, and the last place was totally responsible for one of the presses (Fielding) Do ya know of any jobs ???
Workington at one stage was part of BA (or was that Warrington)
'82 has to have an exit temp of 500c and drop by 200c within I think 30secs to get the correct properties 2mm WT ? that's big !! 50m/min is not that hard, just the crappy handling gear can't keep up with the press i.e. billet heaters, pullers, stretchers, the poor old sawmen !!

 

[LLB]

Spent my life correcting dies of all sorts, and the last place was totally responsible for one of the presses (Fielding) Do ya know of any jobs ???
Workington at one stage was part of BA (or was that Warrington)
'82 has to have an exit temp of 500c and drop by 200c within I think 30secs to get the correct properties 2mm WT ? that's big !! 50m/min is not that hard, just the crappy handling gear can't keep up with the press i.e. billet heaters, pullers, stretchers, the poor old sawmen !!

Plenty in China if you know your onions. Boss went out there and one company had 30 presses all working flat out. Workington gone, HDA Warington & Almetex gone, Latchford gone, Banbury going soon now Alcoa has been taken over by SAPA

Definitely a shrinking market. Who do you work for Hydro Birtley ?

 

[Tim Bennet.]

These are the typical increases in properties we see to the 6000 series when T6 treated:
Yield Strength (MPa): 55 increased to 241
Tensile Strength (MPa): 125 increased to 290
Elongation A5 (%): 27 decreased to 10
Hardness Vickers (HV): 5 increased to 100

However it is a process that is applied to the raw material and unfortunately welding the frames together destroys much (2/3rds) of this increase in its properties at the very place that is subject to the most stress. This is in direct contrast to say the 853 (and its family) type steels that actually increase their strength with welding. I think some very high end Al frames (Colnago?) did have some form of post weld treatment. Unless you know which are post treated, its impossible to compare 6061-T6 frames on the criteria of the raw material alone.

There the minimum wall thickness and size of the tubing to form a satisfactory weldment is one of the design constraints of aluminium in bikes.

7005 has slightly better properties, but its real advantage is it only looses about half its T6 enhanced properties when welded. This is why it's used for mid range frames as you can get an okay frame without the hassle of any post weld treatment. Cheap 6061-T6 frames just make sure they have lots of material in the welded region. And then add fillet pieces, etc, etc.

 

[simonali]

1050 / 1070 is virtually pure alloy

Pure alloy?

 

[Elmer Fudd]

Definitely a shrinking market. Who do you work for Hydro Birtley ?

Worked there on contract a few years back, how I met the woman I'm with now.
Started off at BA Redditch** many moons ago and I've "been around a bit" since then. I heard about Banbury being taken over but didn't know that their days may be numbered.

** Was back their for 2 or 3 years just before moving up here. They only do tubes these days. Very boring from a Correctors point of view although you could have some fun

 

[Elmer Fudd]

Pure alloy?

Ok, Ok, pure ally ! (Well 99.5% and 99.7% p.a.)