30. Why Diamond cannot cut steel
CNC – Why you cannot cut steel with diamond
PCD (Poly Crystalline Diamond) tools are made of diamond, and diamond is essentially pure carbon, with atoms arranged in a cubic crystal arrangement that makes it very strong. At higher temperatures (more than 700 deg. C), the Carbon atoms react with Iron to form Iron Carbide (Fe3C). They basically divorce their old Carbon partners in the crystal structure, get hitched to some new Iron partners, and the crystal structure collapses.
Structure of diamond
Each carbon atom is covalently bonded to four other carbon atoms. A lot of energy is needed to separate the atoms in diamond. This is because covalent bonds are strong, and diamond contains many covalent bonds. This also makes diamond’s melting point and boiling point very high. There are no free electrons or ions in diamond, so it does not conduct electricity. (This extra bit of knowledge is for those of you with kids in high school, who had to dig up some of your long-buried chemistry knowledge so you can clear their doubts. I went through this phase just a couple of years ago, and hence still remember the covalent bond and other chemistry stuff. Thankfully my kid is in college doing law now, of which I know nothing and hence cannot help her in any way.)
With this sad exception of steel (sad because most of our metal cutting is on steel) and Titanium, PCD does not bond with work piece materials. Because of this the built-up edge too is minimal.
Text source: CADEM NCyclopedia multimedia CNC training software.
Lunch in Sandur, Karnataka
Lunch in the hostel mess in my old school. A group of us old students landed up unannounced, and the cook made something in a hurry. Seriously simple stuff, North Karnataka style. Dry Jowar roti and a palya (sabzi). The yucky looking thing that looks like a dead animal is actually a whole brinjal cooked in a style peculiar to North Karnakata, and is very tasty.
Sandur is in the heart of the mining area in Bellary, in North Karnakata. I did a few years of schooling there (the rest being in Chattisgarh, Jharkhand, AP, TN and Orissa). When you read about Karnataka’s mining scandals in newspapers, this is the place they are talking about.
Sandur, before mining
Sandur, after mining
Sandur used to be a very green area, with thick forests, streams and lots of wildlife. It’s now a brown wasteland because of the illegal iron ore mining (which has thankfully stopped because of courts’ intervention).