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...cast irons. Incorrect heat treatment can lead to oxidation or decarburisation. Long heat treatment times at high temperatures can lead to grain growth of the core, necessitating core “refining” before quenching. Carbonitriding Carried out on a similar range of steels as carburising, although carbon contents can be as high as 0.4–0.5% when a reasonably tough,...

...aluminium or zinc utensils; they will react with the sodium hydroxide solution. Have a large bowl of clean, cold water handy, for use in the event of an accident. Remove all food and drink from your work area, and keep children and animals well away from your workspace and chemicals. Always work in a well-ventilated area (if possible, outside), and avoid working on your...

...slabs of frozen carbon dioxide scooting downhill. Some gullies start near the tops of sand dunes where an underground reservoir of water is very improbable. In 2008 the lander Phoenix actually saw water on Mars. When it scraped away at the dirt, it found water-ice a few centimetres down, but more excitingly droplets that could hardly be anything other than water were seen to form on the lander’s legs. It was suggested that ......