Making a welded Damascus Knife

John Neeman Tools have posted a beautiful video of manufacturing a welded Damascus patterned knife.

5 layers of 3 different steels were forge-welded, folded, and forged. With each step being repeated 8 times. This produces a patterned with 320 layers. Finally twisting and forging the steel produces a more complex pattern.

Just checking the number of layers, I get their total to be different. My calculation of the number of layers is 5 × 28 = 1280, that is 4 times more than claimed (320 layers should be the result of folding 6 times (6 folds 5 × 26).

With 1280 folds, if we assume the thickness of the knife is 2 mm, that means each layer is 1.6 μm, 320 folds would be 6 μm layers. These are both lower than what can be resolved using the naked eye. It’s very close to the wavelength of visble light — if the metal were folded one more time, or the final thickness of the knife is less than 1 mm you would be there.

Effect of tempering upon the tensile properties of a nanostructured bainitic steel

This paper is now available at for those with access by science direct. I made final proof corrections last Saturday, so when the final version is released the conclusions will change… in that “hard–nanostructured–bainitic steels” will become “hard nanostructured bainitic steels”.

Periodic Video of Speculum

Prof. Martyn Poliakoff has made a video showing Isaac Newton’s first telescope, which is kept at the Royal Society, in London. As we learned in physics, Isaac Newton used a mirror in his telescope to minimise chromatic aberrations which can occur when using lenses. The mirror was therefore a critical part of the telescope, a special alloy of one-third tin and two-thirds copper and a small amount of arsenic was used, called Speculum.

Adventures in Physical Metallurgy of Steels

During July 2013 I attended Adventures in Physical Metallurgy of Steels hosted by the Phase Transformations and Complex Properties research group of the Department of Materials Science and Metallurgy.

The programme looked like this, videos are appearing on bhadeshia123’s channel on youtube (links). There is also a playlist available.

Introduction to Adventure. H. Bhadeshia

Architectured Steels, T. Koseki

Magneto-structural coupling. I. Abrikosov

Quench and partitioning. J. Speer

Crystallographic variant selection. S. Kundu

Secondary hardened bainite, J. R. Yang

Welding of high carbon steel, K. Fang

Isotropy and Fatigue: P. Ölund

Atoms in bainite, atomic mechanisms. F. Caballero

Pulsed steels, R. Qin

Fullerenes & buckyballs in steel: I. V. Shchetinin

Boron: Type IV cracking, F. Abe

Low-density steel, H-L. Yi

Friction stirring of steel, T. Debroy

Flash Processing, G. Cola

Reliable first principles calculations for iron: A. Paxton

Steels composites for energy applications, C. Capdevila-Montes

Microstructures without contact, C. Davis

Pop-in deformation, H. N. Han

Plausibility of fine bainite, C. García-Mateo

Reduced Activation, K. Wu

Architectured microstructures, G. Anand

Flash microstructure, S. Babu

Energetic TWIP, D. Dye

Mass production of fine bainite: A. Rose

Voids and 30000 atoms, S. Munetoh

Soft Particles, T. Tsuchiyama

Mechanochemistry, F. Miani

Simplex and Kappa steels, I. Gutierrez-Urrutia

Innoculated high-speed steel, A. Chaus

Non-cubic ferrite, D-W. Suh

Montage of events


Structure of superbainite. Inset is a same-scale image of a carbon nanotube. [1]

Structure of superbainite. Inset is a same-scale image of a carbon nanotube. [1]

According to archaeologists, the Iron Age began in 1300 BC and lasted for around two millennia. Today, steels (alloys of iron and carbon) comprise 95% of global metal consumption and this trend shows no sign of declining.

Glancing at the media, however, one would be forgiven for assuming that steel is now a has-been. We are bombarded with stories of novel materials: carbon nanotubes, metallic glasses, graphene, carbon fibre, nickel superalloys. . . all of which are “stronger than steel”.

“Now we can construct space elevators!” claim the articles. “Let’s build a climbing frame to the moon! We’ll use this stuff to make everything!”

The observant among us, however, will note that most cars, trains and buildings still don’t feature superalloys, metallic glass or magic nanotubes. Neither are they invisible; nor do they fly; nor do they do any of the other things that journalists tend to ‘predict’.

Instead, steels somehow remain the best — and cheapest — materials for the job. Also, they are stronger than steel. This is because ‘steel’ is a vague construct used by sensationalists, with an unspecified strength guaranteed to be less than that of a novel material. Metallurgists rarely refer to ‘steel’, just as the Inuit have fifty words for snow, not one of which is ‘snow’.

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Audi’s audacious aluminium advertising artifice

Audi’s advert for their A6 is really beautifully made…

Suppose you could make metal do anything you wanted,
use it in ways no one thought possible,
at Audi that’s what we do,
the new Audi A6 with Aluminium-hybrid body,
engineered for a lighter touch.

The way the metal forming is done in the advert is really nice, just shaping the parts by hand, just like the clay model can be formed when producing models of the car.

The technology is interesting, and challenging, a combination of aluminium and steel parts are used to make the car body. About 20% of aluminium by weight of the car body is aluminium, that means about 40% by volume. Non-load bearing parts such as body panels are aluminium (which benefit from good stiffness/weight ratio). All of the car body is made from cold formed and warm formed steels as in conventional car body. Interesting, aluminium sections seem to be present as side impact bars and bumper. From the advert you might be left with the impression that the whole body is aluminium, or that this is something that would be desirable, especially confusing since ‘hybrid’ is also now commonly used to refer to automobiles which use combinations of different power sources for the engine.

This video shows which parts of the car body are aluminium and steel.

However these cars overall are not much lighter due to the use of aluminium. From the previous model of A6 the weight saving is 30 kg, the weight if the total car is 1575 kg unladen or 2,155 kg gross weight (figures for 4 door 2.0 diesel). I want to look up the weight of Audio A6 since they are first introduced, that’s because in all cars there has been a trends towards increasing weight, despite all the advances in decreasing the weight of the car body.

Japanese Swords are medieval nanotechnology

During Japanese sword making the steel is folded repeatedly. Each time the steel is folded the structure is refined.

The folding is a key process in sword making. Folding and striking the metal forges the surfaces back together. This process of folding, then forge welding, can be repeated as many as 16 times. The process removes impurities and helps even out the carbon content, and controls the scale of chemical segregation, and it is this which results in alternating layers of hard and ductile material.

So how can folding the steel result in a nanoscale structure?

When the steel is folded the number of layers obviously increases geometrically. 1 fold result in 2 layers, 2 folds results in 22 = 4 layers, 3 folds results in 23 = 8 layers. By the time we get to 15 or 16 layers we have 32768 layers or 65536 layers. After that the sword is forged out to have a width of around half a centimetre.

5 mm divided by 65536 = 76 nm.

So each layer is 76 nm. So we can legitimately argue that Japanese Swords are bulk nano materials, with structure controlled on the ‘nano’ level, for metallurgists this is just routine stuff.

Edo period Forge Scene

Edo period Forge Scene

Of course Japanese swords are not true examples of nanotechnology, despite the validity of the maths the folding doesn’t really result in a controlled structure on the nanoscale due to the changes that occur during the welding process… I plan to talk more about that in a later post.

As you can see below, the laminations are typically visible on the millimetre scale.

Lamination on Japanese Sword

Lamination on Japanese Sword