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Hardox
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Spockie-Tech
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Joined: 31 May 2004
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Location: Melbourne, Australia


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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" Laughing - 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.. Laughing

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) ?
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Post Thu Dec 02, 2004 10:12 am 
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Knightrous
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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.....
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Post Thu Dec 02, 2004 11:40 am 
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Philip
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quote:
Originally posted by Spockie-Tech:
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).


Christian is a good guy.

The Americans appear to be scarred of new ideas. I noticed that someone wanted to change the amount of fuel a flame thrower could carry but was knocked back.

Post Thu Dec 02, 2004 1:28 pm 
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Knightrous
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I can afford a sheet of Hardox 450 3.25mm x 6000mm x 1500mm. It's only $660 roughly from Brisbane. I'd like to see you get a sheet of your magically tempered/heat treated Aluminium or Titanium in that size for that price Smile
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Post Fri Dec 03, 2004 12:24 am 
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Nick
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That's 9 square metres for $660? Not bad, but I still prefer lighter / cheaper / cut-to-size materials. Isn't Hardox also highly heat treated? I'm not saying Hardox is crap, I'm just saying it's way off topic.
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Post Fri Dec 03, 2004 6:21 am 
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mytqik



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The thing to remember about the Hardox is that it needs to be kept cool when cutting. Ie water jet cutting instead of oxy. If you oxy/abrasive/weld hardox, you have just re-tempered your expensive piece of steel into a much lower quality steel. the only way around this would be to re-heat treat the entire robot, once it is fabricated, which would be a very tricky thing.

So ideally hardox need to be water cut & then bolted together, to maintain its properties.

Post Tue Dec 07, 2004 8:33 am 
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Nick
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Back in the country for Christmas? Nice to hear from you again Smile

I take it that would mean that welding Hardox would be right out unless I got it heat treated afterwards?

Have you seen anything about that laminated Fedur & Tridur I posted earlier? I suspect its expensive and not available in small pieces, but it could be versatile material for bot building.
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Post Tue Dec 07, 2004 8:53 am 
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Knightrous
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Welding any heat treat metal (Hardox/Aluminium/Titanium/Unobtanium?) will lost it properties alone the welding seems. I've been told the best thing to do with hardox is to use stainless steel welding wire in the mig and stitch weld the panels together, then stitch weld again inbetween the previous stitches until it is completely welded. Only doing short stitches doesn't get the Hardox as hot as doing full run welds, so you take less of the temper out.

On a slightly off/on topic thing, has anybody considered using spring tempered steel for armour?
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Post Tue Dec 07, 2004 10:15 am 
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mytqik



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Yeah, thanks Nick, it is nice to be back. I am off again soon though Sad I am going to need a new passport soon, & I have only had this one a couple of years now Smile

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 Very Happy

Post Tue Dec 07, 2004 7:26 pm 
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3Faze



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Typing with several pulled muscles in my shoulders here, so I'll keep it brief.

Hardox really does work, assuming you can stand the weight (no worse than steel), and can work it effectively.

Post Tue Dec 07, 2004 7:46 pm 
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dyrodium
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Just wondering... Can anyone calculate the cost of creating a small feather chassis with Hardox? Can it be drilled using a drill press? If you had the EXACT dimensions and design of a bot, would you be able to have the parts water-jet cut and then bolt it all together? (I am guessing that would be a pretty strong amour). (though I am not going to use such technology on my first bot, I will soon get $500 for my old 3 foot fish tank set up... Very Happy
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Post Tue Dec 07, 2004 8:03 pm 
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Nick
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Since Hardox is, err, HARD, you will have trouble drilling it. It's not impossible, but you would need cobalt steel or even tunsten drills, a low speed and coolant. It would also take much longer than drilling mild steel.

Waterjetting and bolting would be far easier, as long as your CAD work is accurate.
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Post Tue Dec 07, 2004 8:33 pm 
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Woody



Joined: 07 Oct 2004
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Hardox

As far as weight is concerned it's much the same as mild steel.

3mm is the thinnest plate you can get.

Welded construction appears to be the norm over here in the U.K.

This utility should help in your calculations.

http://www.metalsuppliersonline.com/research/FreeWeightCalc.asp
Plus another handy utility...... http://www.joshmadison.com/software/convert/

Post Tue Dec 07, 2004 8:36 pm 
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dyrodium
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Hmm A little out of my league for the moment...
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Post Tue Dec 07, 2004 8:41 pm 
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Philip
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The wear plate is welded on to my loader bucket. It was not heat treated after this welding.

It is hard to argue against Hardox when many roboteers use it and say that they have good results. What bennefit would they receive by lying to us?

Daniel K or Nick Mytiqik should talk directly to the tech at SSAB and discuss the product. Thomas was more than happy to tell me all about its properties. The information was over my head but you guys can speak his language, tech not Swedish.

Post Wed Dec 08, 2004 10:33 am 
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