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tures, but with slow cooling rates another factor comes into play, namely grain size. Common engineering metals consist of grains of the metal that all have different crystal orientations relative to each other. Smaller grain sizes lead to higher strength as well as toughness; certain alloying elements contribute to inhibiting grains from growing during the quenching procedure. A slower cooling rate will result in larger grain sizes. Different heat treatments can also be employed and some of the foremost reasons to heat treat a steel are:

Relieving residual stresses, which might lead to cracking;

l Making sure the alloying elements are spread evenly throughout the metal (normalising);

l Ensuring a specific microstructure or grain size.

Precipitation hardening also happens during heat treatment and leads to little clusters of other elements forming in the steel, altering the properties once more. Minute adjustments to composition, cooling rates, heat treatment and casting procedures can have profound effects on the properties and the suitability of steels for specific applications. This is exactly what makes the recreation of the T1 locomotive such a feat of engineering.