Monday

A very hard question

Hard enough for a die to draw tungsten filaments.

Hard enough bits and blades too.

Developed by Osram.

Monday Answer

Bill is a major general this week.

The company is OSRAM. OSRAM is one of the two largest lighting manufacturers in the world and is a subsidiary of Siemens AG. The name is derived from Osmium and Wolfram (German for tungsten), as both these elements were commonly used for lighting filaments at the time the company was founded. The company was founded in year 1906. Osram is part of the Industry sector of Siemens and one of the two leading lighting manufacturers in the world. Sales for the OSRAM group worldwide in the year ending September 30, 2007 totaled 4.7 billion euros, 88 percent of which came from outside Germany. Around 60 percent of sales come from energy-efficient products. This global player employs more than 41,000 people worldwide, supplies customers in some 150 countries and has 48 production facilities in 17 countries. Most of us probably never heard of them--China, India, and Africa has though!!

The product they applied (which had been around since the late 1800s) in the 1920s was tungsten carbide which they used to draw filaments for light bulbs. In the early days of incandescent lamp manufacturing, a carbon filament (core) was coated with tungsten hexachloride. This carbon wire was later heated to incandescence in an atmosphere of pure hydrogen. The carbon filament completely dissolves and leaves a "pure" tungsten carbide filament. This was then further heated in a stream of of hydrogen (I believe at sub

incandescence), which reduced the filament to pure tungsten. This results in a tubular shaped form. The reason this was done, is because tungsten is not very ductile. This means you can�t just wind a filament from a piece of tungsten wire, because it will break.

Through the years they developed and used powder and something called melting base. Tungsten carbide was easier to get, faster to machine, less expensive, and hard enough to do the work. Previous to tungsten carbide a diamond die was used to make filaments.

Tungsten is used today for high speed steel and tungsten carbide for blade tips and bits. It is also heavily used as a shield in the nuclear industry, and in sporting goods where a metal item hits something or needs to be weighted. Roller ski pole tips and mountaineering tools use it. The commercial uses of tungsten fall into two categories; Those that exploit its high strength at high temperatures, and those that exploit its density. Tungsten is not as strong as any number of other metals at normal temperatures, but once you get into very high temperatures (yellow or white hot), the others start melting or dropping dramatically in strength, while tungsten keeps up a relatively high strength. This is the main reason it is used for incandescent light bulb filaments.

Tungsten is also by far the most dense element you can buy for less than precious metal prices. It's exactly the same density as gold, but something like a hundred or more times cheaper. Lead is cheaper still, but tungsten is almost twice as dense-thus used for nuclear applications, and in applications where size counts, tungsten is used.

May 8, 2008 OSRAM sold their tungsten carbide business to an Austrian firm.

Re: Monday Answer- Adenda

Gary, Here in the states they are known as Osram Sylvania. Yup, GTE sold Sylvania to Osram abut 15-20 years ago so there's a good chance most folks have heard of their North American operations.