Bolt is externally helical threaded fastener requiring matching nut. Whitworth proposed standardization in 1841, Crystal Palace construction enabled it. British standard adopted in 1905
Tempering increases toughness by reducing hardness of iron-based alloys. Process performed after hardening by heating below critical point. Temperature determines amount of hardness reduction and alloy composition
Alloy is a mixture of elements, usually metallic, with controlled properties. Alloys show good electrical conductivity, ductility, and luster. Atoms join by metallic bonding rather than covalent bonds. Alloys can be classified as substitutional or interstitial based on atomic arrangement
Austenite is a non-magnetic metallic iron allotrope or solid iron-alloy solution. Forms above 1000 K (727 °C) in plain-carbon steel. Named after Sir William Chandler Roberts-Austen. Forms from alpha iron between 912-1,394 °C
Steel is an alloy of iron and carbon with improved strength and fracture resistance. Carbon content in steel ranges from 0.02% to 2.14% by weight. Steel is denser than pure iron, with density between 7,750 and 8,050 kg/m³
Metal is a naturally occurring chemical element found in Earth's crust. Steel is an alloy of iron with varying carbon content (0.5-1.5%). Steel is not a pure metal but a variation on one