|
Spockie-Tech
Site Admin
Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia
|
On a vaguely related note, there has been some interesting discussion over on the RFL forum recently about "Hardox" (the wonder steel that all the Europeans seem so taken with).
Some Scandinavian/Belgian guy said that he had a limited quantity of some super-secret not-yet-released alloy of Hardox that he would sell pieces of at a special price, and the some of the more metallurgically-aware Yanks proceeded to rip into him, basically pointing out that Hardox is just a fairly ordinary steel alloy that is surface hardened to a high degree for use as wear-plates in excavators and things, and that its nothing you couldnt achieve yourself with a good alloy and the right heat-treating.
(Steven Nelson of Team-SLAM fame said something like "So Hardox is basically "Farm Steel" - He's renowned for making low-tech indestructible brick-bots out of farming equipment)
It seems to me that the company that makes "Hardox" has done a good job of marketing on the European market and convinced them that this is some super-steel that no-one else can do.. So this guy making out like he had pieces of "Unobtanium" for the lucky ones to buy really pissed a few of them off..
back to the point though..
quote:
When they change to this hotter crystal structure I beleive they become one big grain. When it cools down different points cool quicker, forming grains first, causing all those little grains to form again. Depending on how fast you cool you end up with different size grains.
ah, This explains why the "quenching" (cooling) process is just as important in heat-treating as the getting-it-hot bit. Thanks. I'd heard of oil-quenching, air-quenching and so on, but didnt really undertstand why it does what it does.
I suppose oil will have a higher heat capacity than air, so will suck heat out of a hot bit of metal quicker and alter this crystal formation process as the cooling happens more rapidly. It sounds to me like slower quenching would promote even crystal growth and result in a harder final product than fast quenching would (which would probably vreate more unjoined crystals throughout the metal) ? _________________ Great minds discuss ideas. Average minds discuss events. Small minds discuss people
|
Thu Dec 02, 2004 10:12 am |
|
|
Knightrous
Site Admin
Joined: 15 Jun 2004
Posts: 8511
Location: NSW
|
I know the person your talking about Brett, he managed to wangle a small piece of prototype Hardox 650. Hardox is no wonder metal, i'm not sure there is a wonder metal, but in comparison with Titanium, Aluminium and regular steel, it above them all.
Tough As Nails is a robot that is made completely out of Hardox 400 4mm with some 6mm in places. After a few years of battle, it had gained a few dint's from large spinners(I believe SuperNova was one of them), but no robot to date has put a hole in this 4mm armour. But we look at robots that use 1/2 inch titanium and they are still getting holes put in them. SuperNova has managed to put a hole through 16mm aluminium.
On another side note, Hardox makes great weapon teeth, Typhoon 2 (UK Wars 7 Winner) uses Hardox for there teeth and went the whole UK champs, World Championships 3 and only had to sharpen the teeth a slight bit at the end of the WC3. But I've heard numerous stories of 30lbers bluntening tool steel in just single battles.
Hardox is just so cheap and so strong, I can't see why anyone would want Titanium..... _________________ https://www.halfdonethings.com/
|
Thu Dec 02, 2004 11:40 am |
|
|
|
|
|
|
|
|
mytqik
Joined: 26 Jun 2004
Posts: 127
|
Yeah, thanks Nick, it is nice to be back. I am off again soon though I am going to need a new passport soon, & I have only had this one a couple of years now
If you have a look at the Kkeerroo's excellent post on grain structure (He/they paid more attention in Materials Tech, than I did) in the other thread, you will understand why welding is bad. Every time you weld, yu are apling heat to the Hardox, the longer the run, the larger the HAZ (heat affected zone). That is why the short run method is suggested, however, the weld & the parent metal directly besides is still tempered back to it original soft form.
You can try to use a cooling method, I have seen it welded with water flowing across the plate to keep the metal cool. The downside is you need ALOT more amps to make the weld, as the water prevents the weld from forming. Other things could be to clamp a strip of aluminium along the weld. The alu will act as a heat just like in electronics.
Personally, I would silver solder/braze it. Silver solding can provide some extremely strong joints & has the benifit of not harming the parent metal to the same extent welding does. The down side it that every joint needs to be designed as a lap joint, as but joints are weak when soldering. It can also look very attractive when polished.
The drama with post weld heat treating or using a softer material & then heat treating it, is that every joint needs to be designed with the heat treatment in mind. Imagine a cube that is welded along each edge, now when it is heat treated every weld in the cube will need to be under shear & tensile stress as the cude expands with heat. This means the weld metal would have to be of similar composion as the parent metal. If not, the welds will crack either during the heating or the quenching of the metal.
It is an extremely interesting & detailed area of engineering. There are people that devote their entire life to this sort of thing, but I would rather build things using their technology
|
Tue Dec 07, 2004 7:26 pm |
|
|
|
|
|
|
|
|
|