|Ni||Melting point 1455 °C||Nickel|
With structural steels produces significant increase in notch toughness, even in the low temperature range, and is therefore alloyed for increasing toughness in case-hardening, heat-treatable and subzero toughness steels. All transformation points (A1 - A4) are lowered by Ni; it is not a carbide former. As result of pronounced extension of the γ-phase, Ni in contents of > 7% imparts austenitic structure to chemically resistant steels down to well below room temperature. Ni on its own only makes the steel rust resistant, even in high percentages, but in austenitic Cr-Ni steels results in resistance to the effect of reducing chemicals. Resistance of these steels in oxidizing substances is achieved by means of Cr. At temperatures above 600 °C, austenitic steels have greater high temperature strength, as their recrystallization temperature is high. They are practically unmagnetizable. Thermal and electrical conductivity are significantly reduced. High Ni contents in precisely defined alloying ranges lead to steels with certain physical properties, low thermal expansion (Invar types).