Assembly Line

Heat treating

Controlled heating and cooling rearrange a material's internal structure without changing its shape, making it harder, tougher or less brittle.

53 lines that use it

Aluminum ladder 7 stations · 10 raw sources Aluminum window frame 9 stations · 24 raw sources Ball bearing 9 stations · 13 raw sources Balloon 8 stations · 3 raw sources Barbed wire 7 stations · 13 raw sources Billiard ball 9 stations · 21 raw sources Bolt 6 stations · 13 raw sources Button 8 stations · 8 raw sources Carbon fiber 6 stations · 4 raw sources Chocolate 8 stations · 7 raw sources Coil spring 7 stations · 21 raw sources Coin 6 stations · 9 raw sources Condom 9 stations · 13 raw sources Copper wire 6 stations · 4 raw sources Corn flakes 8 stations · 19 raw sources Drill bit 7 stations · 15 raw sources Eraser 6 stations · 19 raw sources Flag 6 stations · 21 raw sources Gas cylinder 10 stations · 25 raw sources Glass 5 stations · 10 raw sources Glass bottle 8 stations · 11 raw sources Glass jar 5 stations · 10 raw sources Guitar string 6 stations · 18 raw sources Hammer 8 stations · 21 raw sources Hook-and-loop fastener 5 stations · 5 raw sources Kitchen knife 6 stations · 16 raw sources LED light bulb 7 stations · 20 raw sources Memory chip 7 stations · 10 raw sources Microchip 8 stations · 15 raw sources Neodymium magnet 8 stations · 6 raw sources Nichrome 8 stations · 15 raw sources Nitrile glove 8 stations · 17 raw sources Nonstick pan 7 stations · 10 raw sources Padlock 7 stations · 25 raw sources Railroad rail 9 stations · 12 raw sources Razor blade 6 stations · 16 raw sources Rebar 6 stations · 14 raw sources Rubber band 6 stations · 2 raw sources Rubber boots 6 stations · 9 raw sources Saw blade 7 stations · 17 raw sources Scissors 8 stations · 22 raw sources Sewing needle 8 stations · 16 raw sources Sheet steel 7 stations · 13 raw sources Socks 6 stations · 11 raw sources Steel chain 7 stations · 12 raw sources Steel I-beam 6 stations · 12 raw sources Steel wire 7 stations · 12 raw sources Synthetic graphite 6 stations · 2 raw sources Tinplate 6 stations · 13 raw sources Window glass 7 stations · 13 raw sources Windshield 8 stations · 20 raw sources Wrench 9 stations · 20 raw sources Yoga mat 6 stations · 9 raw sources

What it looks like on the line

  • Razor bladeHarden the strip. The ribbon runs through a hardening furnace and an abrupt quench, then a tempering furnace that adds toughness.
  • EraserHeat to vulcanize. Heat makes the sulfur cross-link the rubber molecules, which turns a sticky gum into a durable rubber. Charles Goodyear discovered the process in 1839 and patented it in 1844.
  • Steel chainTemper for toughness. A second coil reheats the chain to a lower temperature before another water cooling, giving back some elasticity.
  • Hook-and-loop fastenerHeat-set the loops. Heat fixes the shape of the woven monofilament, often under infrared light. The nylon remembers the shape, so the loops stand up and stay open.
  • Billiard ballHarden the surface. More heating hardens the outer layer. That patent packs its balls in sawdust for three days. Aramith says its better grades go through several hardening steps that leave a translucent vitrified surface.
  • Rubber bandCure the rubber. Heat links the rubber molecules together so the band springs back after stretching. Before this step the tube is soft and would stay stretched.
  • Sewing needleHarden in oil. The needles are heated, quenched in oil and slowly cooled, which adds strength and reduces brittleness. A deep freeze makes them more elastic.
  • Coil springHeat treat the coil. Coils go straight onto a conveyor through an oven. Wire that was already hard only needs its winding stress relieved, so it keeps its shape and springs back. Springs wound from soft steel are hardened and then tempered.
  • Saw bladeHarden and temper. Discs go into the heat at 860 °C to 1100 °C, depending on the steel, then get quenched. Clamped in packs, they warm slowly again to 350 °C to 560 °C, which gives up some hardness for toughness.
  • Sheet steelAnneal it soft again. Cold rolling leaves the steel hard and stiff. Heating it in a controlled furnace restores its ductility, so it can later be pressed into a car door or folded into a duct.
  • Ball bearingHarden everything. Rings and balls are heated, cooled in oil and tempered in a second oven, so they carry loads without denting.
  • Carbon fiberStabilize it in air. Filaments pass slowly through ovens full of hot air. The chains rearrange into a heat-proof form, and the fiber turns from white to black.