Citric soak

[A. G. Maisey]

Why did the springs become brittle?

Difference between a spring and other ferric material is that the spring has been hardened and then the temper has been drawn.

A weapon is heat-treated in the same way, that is, it has been heat treated and often the temper that it has been drawn to is the same as a spring.

A keris is also heat treated, but with a keris, because of the laminate construction probably only the hardened edges of the core will react in the same way as a spring, ie, they must become brittle.

After reading this I would hesitate to use electric rust removal on any keris except perhaps the old junky corroded ones that have lost any hardened material long ago. I would not use this treatment on any keris that I valued.

[GIO]

[QUOTE=A. G. Maisey]Why did the springs become brittle?

QUOTE]

Good question, Alan
I am not in a position to answer. I only report what is indicated in the book I mentioned.
In my very humble opinion, the heat treatment ("temper") of a keris is far from the procedure needed to harden a spring, both for what the heat needed and for the partial section of the blade which is interested. In fact a keris blade can be easily bent, and this should not happen easily in case the steel iron core is tempered. It is true that also Japanese katanas can be bent, and this could be due to the fact that different types of steel are layered to form the blade, and different percentages of carbon should be differently treated (different temperature of the heating and of the water), and the keris is made in a similar way as the katanas.
Always in my very humble opinion the heat treatment of a keris is intended more to eliminate tensions in the metal due to the hammering than to harden the blade.
I repeat that I know nothing about these matters and should be very grateful if some more prepared friend would contribute and give a competent opinion.

[Emanuel]

Originally Posted by A. G. Maisey

Why did the springs become brittle?

Rust removal through electrolysis is subject to hydrogen embrittlement: http://en.wikipedia.org/wiki/Hydrogen_embrittlement

Hydrogen evolved from the water through the electrolytic process can fuze with the object and induce cracking. Low-alloy, medium/high carbon steels like spring steels are apparently very susceptible to this.

Reversing the hydrogen absorption is done through heating.

There's never any quick solution I guess.

Emanuel

[A. G. Maisey]

Re heat treat.

For simple forge heat treat, the heat treatment of a spring and a blade is the same, the only variation is the colour to which it may be drawn, and even that does not always vary.

In simple terms, after annealing, you heat the object to be hardened to critical, which can be most easily detected by testing with a magnet:- when the magnet does not grip the object it is at critical temperature.

The object, either blade or spring is then plunged into the cooling medium, which may be water, or oil, or brine, dependent upon the steel to be hardened.

After the hardening the temper is drawn. There are a number of various indicators used by traditional blacksmiths to gauge the correct temperature, for a spring, some old timers would run a piece of hardwood down the object and gauge the temperature by the colour and character of the sparks thrown off.

The usual textbook method is to clean off the surface to be drawn, and re-heat the object until the correct colour for intended hardness shows, then cool the object again in the cooling medium.Different levels of hardness are required for different purposes.

As noted, a keris blade, and many other blades, are laminated, and in the case of a keris, only the projecting edges of the blade core are homogenous steel, the laminations that sandwich the core are irons of various qualities, or iron + nickelous material. This is the reason I wrote:-

A keris is also heat treated, but with a keris, because of the laminate construction probably only the hardened edges of the core will react in the same way as a spring, ie, they must become brittle.

The heat treat of a keris blade is not done to relieve any tensions.

The blade would be annealed to relieve tensions, not subjected to a heat-treat to relieve tensions.

However, a keris blade is carved from a forged blank (bakalan):- most of what we see in the blade is produced by stock removal, and during this process the blade may have been returned to the forge several times prior to heat-treat. By the time it actually gets to heat-treat stage there is probably not much, if any, tension to relieve. Put it another way:- I've made a few keris and a whole heap of damascus and plain carbon steel blades. I always annealed the damascus and the carbon steel, I never annealed any of the keris I made.

Some keris blades can be bent, but not necessarily all --- or more precisely, not necessarily all blades can be bent in the hardened section of blade; since hardening of a keris is only for part of the length of the blade, they can all be bent in the unhardened section.

The temper is not drawn in a keris blade, it is simply plunged point first into the cooling medium. End of story. If the laminations are the traditional irons or iron and nickel, yes, you can bend the hardened section of the blade a little without too many concerns, however, if steel has been used as a laminate material it may or may not bend.

In the damascus blades that I made I did not draw the temper in small blades, like trout/bird blades, but in other larger blades that could conceivably be used for chopping I did draw the temper. The reason I did this was because the small blades were intended only to cut, and if the temper was not drawn the edge would last longer, but the bigger blades that might be used to chop could gap if the temper was not drawn, and that edge would not hold as long as the small blade edge.

Emanuel has given us a link to additional information as to exactly why this cracking can occur. I do not fully understand what I've read, but I think it comes down to :- ferric material that is hard is susceptible to cracking. Ferric material that is not hard is not susceptible to cracking. But I am unclear as to whether it is the quality of hardness, or the content of carbon that leads to this susceptibility.

In any case, it seems that an old, degraded keris would be quite safe to de-rust using electricity, but a well preserved good quality keris would be at high risk.

[A. G. Maisey]

It has occurred to me that some of what I have written in the preceding post could be clarified.

The photos are of my desk knife. It is 01 damascus, I made it about 30 years ago --- in fact, it was the first piece of damascus I made, it was intended to be a 10inch bowie, but it was full of faults that I kept on removing until I finished up with a desk knife.

It has been given a spring temper, that is, it was hardened and drawn to a full blue. This means that it is pretty hard, holds an edge very well and will bend and return to dead straight.

The link will take you to a page that explains the colours that we use as a guide for drawing a temper.

http://www.anvilfire.com/article.php...s_hardness.htm

[kulbuntet]

oxalic acid is a mild acid that work really good for removing rust.